Medium composition for flexographic printing ink and flexographic printing ink composition

Abstract

To provide a medium composition for flexographic printing ink and a flexographic printing ink composition which are excellent in defoaming property during production and printing, can suppress occurrence of pin holes in a printed matter, even if printing is performed using a flexographic printing ink composition immediately after production by a dispensing system, and can suppress occurrence of pinholes in a printed matter, even if printing is performed using a flexographic printing ink composition which is temporally stored after production by a dispensing system.SOLUTION: There are provided a medium composition for flexographic printing ink which contains a neutralized product of an acid group-containing resin, a defoaming agent, and an aqueous medium, wherein the defoaming agent contains either one or more of the following (i) to (iii): (i) an ethylene oxide / propylene oxide block copolymer having a cloud point of lower than 50°C; (ii) an ethylene oxide / propylene oxide block copolymer having an HLB value of less than 10.0; and (iii) an ethylene oxide / propylene oxide block copolymer having a number average molecular weight of less than 5,000, and a flexographic printing ink composition which contains the medium composition for flexographic printing ink and a coloring pigment.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a medium composition for flexographic printing ink and a flexographic printing ink composition. [Background technology]

[0002] Flexographic printing is widely used for printing on packaging containers for daily necessities, industrial materials, etc. Flexographic printing can be applied to printing on printing substrates such as paper such as corrugated cardboard and plastic films. In recent years, aesthetics have been required to give the contents a high-class impression, and high-definition, high-quality printed matter is in demand. Flexographic printing is a type of letterpress printing method in which ink is applied to a resin relief plate via an anilox roll, and then transferred from the relief plate to the printing substrate. Flexographic printing is excellent for high-speed printing, and can reproduce fine characters and sharp expressions even with a small amount of ink transferred. The formulation of flexographic printing ink compositions used in flexographic printing is different from ink compositions used in other different printing methods and must be a printing method-specific formulation.

[0003] In recent years, from the viewpoint of inventory management of printing inks in printing factories, a system that delivers the required amount in a short delivery time has become essential, and efforts are being made to shorten production processes, such as the dispersion process, which occupies most of the ink production time. Recently, printing companies have begun to use a dispensing system or the like to mix a previously prepared flexographic printing ink composition or pigment dispersion with a flexographic printing ink medium composition and various additives such as an aqueous medium, thereby producing a required amount of flexographic printing ink composition when needed. However, when conventional flexographic printing ink medium compositions, flexographic printing ink compositions, or pigment dispersions are applied to production systems such as dispensing systems, since they contain a large amount of defoaming agent, although they have excellent defoaming properties, they may cause frequent cissing on the printing surface, dripping of the ink onto the printing plate, or misting during flexographic printing.

[0004] Furthermore, in the field of flexographic printing, there is a demand for even higher speed printing, for example, 400 sheets / min. In order to suppress foaming during high speed printing, it is necessary to add a large amount of defoaming agent to the flexographic printing ink composition. Silicone-based compounds are generally used as defoaming agents in flexographic printing ink compositions, but when a large amount of defoaming agent is added, there is a risk that pinholes will occur on the printed surface due to the silicone. For this reason, it is necessary to suppress foaming as well as breaking foam so that foaming can be achieved even if the amount of silicone is reduced to an extent that pinholes do not appear on the printed surface. Furthermore, pinholes on the printed surface may not be observed in a printed matter printed using a flexographic printing ink composition immediately after production, but may be observed in a printed matter printed using an aged flexographic printing ink composition, and an improvement was required.

[0005] Cited Document 1 discloses an aqueous flexographic printing ink composition containing a pigment, a pigment dispersion resin, a styrene-acrylic resin emulsion having a core-shell structure, an antifoaming agent, and an aqueous solvent, in which the mass ratio of the core part to the shell part is shell part:core part=10:90 to 50:50, and the shell part and / or the core part contain structural units derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms as a hydrophobic group. This aqueous flexographic printing ink composition is said to solve the problems that, when a conventional flexographic printing ink composition is applied to a production system such as a dispensing system, the ink drips onto the printing plate and misting occurs during flexographic printing, although the ink has excellent antifoaming properties due to the large amount of antifoaming agent contained therein. Cited Document 2 discloses an aqueous flexographic printing ink composition containing a pigment, a pigment dispersion resin, a rosin resin having an acid value of 0 mgKOH / g and / or 0 to 350 mgKOH / g, a styrene-acrylic resin emulsion having a glass transition temperature of -30 to 60°C and an acid value of 30 to 80 mgKOH / g, and a solvent containing water. This aqueous flexographic printing ink composition is said to have excellent physical properties such as coating film properties and resolubility. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-190416 A [Patent Document 2] JP 2019-108530 A Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 does not describe or suggest a flexographic printing ink medium composition or a flexographic printing ink composition containing a specific ethylene oxide / propylene oxide block copolymer. Patent Document 2 discloses a flexographic printing ink composition containing a neutralized product of an acid group-containing resin and an ethylene oxide / propylene oxide block copolymer, but the ethylene oxide / propylene oxide block copolymer is used as a pigment dispersion resin and is not used as a defoaming agent. Furthermore, the cloud point, HLB value and number average molecular weight of the ethylene oxide / propylene oxide block copolymer are significantly different from those specified in the present application.

[0008] The inventors have discovered that a flexographic printing ink medium composition containing a neutralized product of an acid group-containing resin and a specific ethylene oxide / propylene oxide block copolymer, and a flexographic printing ink composition containing the flexographic printing ink medium composition and a coloring pigment, can improve defoaming properties during printing and suppress the occurrence of pinholes in printed matter, and further, can suppress the occurrence of pinholes in printed matter even when printing is performed using ink that has been stored over a long period of time.

[0009] The first problem to be solved by the present invention is to provide a flexographic printing ink medium composition and a flexographic printing ink composition which have excellent defoaming properties during production and printing, and which are capable of suppressing the occurrence of pinholes in printed matter even when printing is performed using a flexographic printing ink composition immediately after production using a dispensing system, and which are capable of suppressing the occurrence of pinholes in printed matter even when printing is performed using a flexographic printing ink composition that has been produced using a dispensing system and then stored over time.

[0010] The second problem to be solved by the present invention is a composition for producing an aqueous dispersion liquid comprising a neutralized product of an acid group-containing resin, a defoaming agent, and an aqueous medium, the defoaming agent comprising the following (i) to (iii): (i) an ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C.; (ii) Ethylene oxide / propylene oxide block copolymers having an HLB value of less than 10.0; (iii) ethylene oxide / propylene oxide block copolymers having a number average molecular weight of less than 5,000; and a flexographic printing ink composition containing the flexographic printing ink medium composition and a color pigment. [Means for solving the problem]

[0011] As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by a flexographic printing ink medium composition and a flexographic printing ink composition having specific compositions, and have thus completed the present invention. Specifically, it is as follows: [Section 1] The composition contains a neutralized product of an acid group-containing resin, a defoamer, and an aqueous medium, The defoaming agent is selected from the following (i) to (iii): (i) an ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C.; (ii) Ethylene oxide / propylene oxide block copolymers having an HLB value of less than 10.0; (iii) ethylene oxide / propylene oxide block copolymers having a number average molecular weight of less than 5,000; Contains one or more of the following: A medium composition for flexographic printing inks. [Section 2] Item 2. The flexographic printing ink medium composition according to item 1, wherein the content of the neutralized product of the acid group-containing resin is 0.5% by mass or more based on the total amount of the flexographic printing ink medium composition. [Section 3] Item 3. The medium composition for flexographic printing ink according to item 1 or 2, wherein the acid group-containing resin constituting the neutralized product of the acid group-containing resin is at least one selected from the group consisting of acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, and styrene-maleic acid-acrylic resins. [Section 4] 4. The medium composition for flexographic printing ink according to any one of items 1 to 3, wherein a neutralization rate of the neutralized product of the acid group-containing resin is 80% or more and 120% or less. [Section 5] 5. The medium composition for flexographic printing ink according to any one of items 1 to 4, wherein the neutralizing alkali component in the neutralized product of the acid group-containing resin is one or more selected from ammonia, sodium hydroxide, potassium hydroxide, and alkanolamines. [Section 6] Item 6. A flexographic printing ink composition comprising the flexographic printing ink medium composition according to any one of Items 1 to 5 and a color pigment. Effect of the Invention

[0012] The present invention provides a flexographic printing ink medium composition and a flexographic printing ink composition which have excellent defoaming properties during production and printing, and which can suppress the occurrence of pinholes in printed matter even when printing is performed using a flexographic printing ink composition immediately after production using a dispensing system, and which can suppress the occurrence of pinholes in printed matter even when printing is performed using a flexographic printing ink composition that has been produced using a dispensing system and then stored over time.

[0013] According to the present invention, a neutralized product of an acid group-containing resin, a defoaming agent, and an aqueous medium are contained, and the defoaming agent is selected from the following (i) to (iii): (i) an ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C.; (ii) Ethylene oxide / propylene oxide block copolymers having an HLB value of less than 10.0; (iii) ethylene oxide / propylene oxide block copolymers having a number average molecular weight of less than 5,000; and a flexographic printing ink composition containing the flexographic printing ink medium composition and a color pigment.

[0014] The present inventors speculate as follows about the effects of the flexographic printing ink medium composition and the flexographic printing ink composition of the present invention, but the present invention is not limited to this speculation. A defoaming agent cannot exert a defoaming effect unless it has low solubility in the medium. Therefore, the ethylene oxide / propylene oxide block copolymer used in the flexographic printing ink composition so far does not exert a defoaming effect because it dissolves in the medium at room temperature (25°C ± 5°C) in terms of cloud point, HLB value and number average molecular weight, especially cloud point. On the other hand, the ethylene oxide / propylene oxide block copolymer used in the flexographic printing ink medium composition and the flexographic printing ink composition of the present invention is considered to have insufficient defoaming properties near room temperature in terms of cloud point, HLB value and number average molecular weight, especially cloud point. However, in a state where a neutralized aqueous resin with a high acid value exists in the medium, that is, in a state where the salt concentration is high, it has been found that the ethylene oxide / propylene oxide block copolymer used in the flexographic printing ink medium composition and the flexographic printing ink composition of the present invention does not dissolve in the medium even at near room temperature, and it is considered to exert a strong defoaming effect (foam suppression as well as foam breaking) near room temperature. In this specification, the "cloud point" refers to the cloud point when the compound is made into a 1% by mass aqueous solution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Medium composition for flexographic printing ink] The medium composition for flexographic printing ink of the present invention contains a neutralized product of an acid group-containing resin, a defoaming agent, and an aqueous medium, The defoaming agent is selected from the following (i) to (iii): (i) an ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C.; (ii) Ethylene oxide / propylene oxide block copolymers having an HLB value of less than 10.0; (iii) ethylene oxide / propylene oxide block copolymers having a number average molecular weight of less than 5,000; Contains one or more of the following: The flexographic printing ink medium composition of the present invention may contain other additives in addition to the neutralized product of the acid group-containing resin, the defoaming agent and the aqueous medium.

[0016] <Neutralized product of acid group-containing resin> The neutralized product of the acid group-containing resin, which is a component of the flexographic printing ink medium composition of the present invention, is obtained by neutralizing the acid group-containing resin with a neutralizing alkali component. By neutralizing the acid groups in the acid group-containing resin with the neutralizing alkali component, the neutralized product of the acid group-containing resin becomes soluble in water.

[0017] The acid group-containing resin constituting the neutralized product of the acid group-containing resin is not particularly limited as long as it is a resin having an acid group in the molecule. Examples of the acid group in the acid group-containing resin include a carboxyl group, a phosphoric acid group, and a sulfonic acid group, and among these, the carboxyl group is preferred. The acid group-containing resin constituting the neutralized product of the acid group-containing resin is not particularly limited. For example, acrylic resin, vinyl resin, urethane resin, polyester resin, etc. can be mentioned. Among these, it is preferable to use one or more selected from the group consisting of acrylic resin, styrene-acrylic resin, styrene-maleic acid resin, and styrene-maleic acid-acrylic resin. In the present invention, the neutralized product of the acid group-containing resin preferably functions as an alkali-soluble water-soluble resin.

[0018] In the present invention, the acid value of the acid group-containing resin constituting the neutralized product of the acid group-containing resin is not particularly limited, and is, for example, 5 mgKOH / g or more, preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, and is, for example, 250 mgKOH / g or less, preferably 200 mgKOH / g or less, more preferably 150 mgKOH / g or less.

[0019] In the present invention, the weight average molecular weight of the acid group-containing resin constituting the neutralized product of the acid group-containing resin is not particularly limited, and is, for example, 1000 or more, preferably 2000 or more, more preferably 3000 or more, and is, for example, 150000 or less, preferably 100000 or less, more preferably 80000 or less.

[0020] Among the acid group-containing resins, the acrylic resin is, for example, a resin obtained by polymerizing a monomer component containing (meth)acrylic acid and a (meth)acrylic acid alkyl ester. Among the acid group-containing resins, the styrene-acrylic resin is, for example, a resin obtained by polymerizing monomer components containing (meth)acrylic acid and a styrene monomer as essential components and, as necessary, an alkyl (meth)acrylate ester or the like. Among the acid group-containing resins, the styrene-maleic acid resin is, for example, a resin obtained by polymerizing monomer components containing maleic acid or maleic anhydride and a styrene-based monomer as essential components and, as necessary, containing an alkyl (meth)acrylate ester or the like. Among the acid group-containing resins, the styrene-maleic acid-acrylic resin is, for example, a resin obtained by polymerizing monomer components including maleic acid or maleic anhydride, a styrene monomer, and (meth)acrylic acid or a (meth)acrylic acid alkyl ester.

[0021] In the neutralized product of the acid group-containing resin, the neutralization rate is not particularly limited, and can be, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and can be, for example, 120% or less, preferably 115% or less, more preferably 110% or less. The neutralization rate of the acid group-containing resin can be calculated from the "equivalent number of acid groups in the acid group-containing resin before neutralization" and the "number of moles of the neutralizing alkali component" present in the composition according to the following formula. Neutralization rate = number of moles of neutralizing alkali component / number of equivalents of acid groups in acid group-containing resin before neutralization × 100 (%)

[0022] The neutralizing alkali component in the neutralized product of the acid group-containing resin is not particularly limited as long as it is a basic compound that reacts with the acid group of the acid group-containing resin. At least one of inorganic basic compounds and organic basic compounds can be used. In the present invention, it is preferable to use at least one of inorganic basic compounds such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, ammonia, and organic amines such as primary amines or secondary amines (alkylamines such as diethylamine, triethylamine, ethylenediamine, monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, triethanolamine, and other alkanolamines). In the present invention, it is preferable to use one or more neutralizing alkali components selected from ammonia, sodium hydroxide, potassium hydroxide, and alkanolamines as the neutralizing alkali components in the neutralized product of the acid group-containing resin. In particular, in order to improve drying properties, it is preferable to use amines with low boiling points and high volatility, and it is preferable to use those with boiling points of 150°C or less, more preferably 100°C or less, even more preferably 50°C or less, and particularly preferably 0°C or less such as ammonia.

[0023] The content of the neutralized product of the acid group-containing resin in the flexographic printing ink medium composition is not particularly limited, and is, for example, 0.1 mass% or more, preferably 0.3 mass% or more, more preferably 0.5 mass% or more, and for example, 50 mass% or less, preferably 40 mass% or less, more preferably 30 mass% or less, based on the total amount of the flexographic printing ink medium composition.

[0024] <Antifoaming agent> The defoaming agent which is a component of the medium composition for flexographic printing ink of the present invention is selected from the following (i) to (iii): (i) an ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C.; (ii) Ethylene oxide / propylene oxide block copolymers having an HLB value of less than 10.0; (iii) ethylene oxide / propylene oxide block copolymers having a number average molecular weight of less than 5,000; It contains one or more of the following:

[0025] Ethylene oxide / propylene oxide block copolymers contain two or more blocks, each block being composed of polyethylene oxide or polypropylene oxide. The ratio of the amount of polyethylene oxide to the amount of polypropylene oxide (copolymerization ratio) is not particularly limited. The total amount (molar amount) of polypropylene oxide and polyethylene oxide is 100%, and the amount of polyethylene oxide is, for example, 5 mol% or more, preferably 8 mol% or more, more preferably 10 mol% or more, and for example, 95 mol% or less, preferably 90 mol% or less, more preferably 80 mol% or less. In the present invention, the ratio of the amount of polyethylene oxide can be less than 50 mol%.

[0026] The ethylene oxide / propylene oxide block copolymer can be synthesized by a known method. For example, a polypropylene oxide / polyethylene oxide / polypropylene oxide block copolymer can be formed by reacting a polyethylene oxide polymer with propylene oxide. Also, for example, a polyethylene oxide / polypropylene oxide / polyethylene oxide block copolymer can be formed by reacting a polypropylene oxide polymer with ethylene oxide.

[0027] (i) The ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C. is not particularly limited as long as it has a cloud point of less than 50° C., preferably less than 45° C., more preferably less than 35° C., and even more preferably less than 30° C., contains two or more blocks, and each block is composed of polyethylene oxide or polypropylene oxide. The lower limit of the cloud point is not particularly limited, but is, for example, −30° C. or higher, preferably −25° C. or higher, more preferably −20° C. or higher, and even more preferably −15° C. or higher.

[0028] (i) The HLB value of the ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C. is not particularly limited, and is, for example, 0.5 or more, preferably 0.8 or more, more preferably 1.0 or more, and even more preferably 1.2 or more, and is, for example, less than 20.0, preferably less than 18.0, more preferably less than 15.0, and even more preferably less than 10.0. In this specification, the HLB value is used in the field of surfactants and indicates the balance between the hydrophilic and lipophilic parts of a molecule (hydrophile-lipophile balance). The HLB value can be calculated by applying the Griffin formula shown below (a formula based on the experimental value calculated from the measurement of the emulsification efficiency for a certain oil and the weight fraction of the hydrophilic part). [Griffin formula] HLB = (100 / 5) x hydrophilic group weight / (hydrophilic group weight + hydrophobic weight)

[0029] (i) The number average molecular weight of the ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C. is not particularly limited, and is, for example, 700 or more, preferably 1000 or more, more preferably 1200 or more, and even more preferably 1500 or more, and is, for example, less than 100000, preferably less than 70000, more preferably less than 50000, and even more preferably less than 35000.

[0030] (ii) The ethylene oxide / propylene oxide block copolymer having an HLB value of less than 10.0 is not particularly limited as long as it has an HLB value of less than 10.0, preferably less than 8.0, more preferably less than 6.0, and even more preferably less than 4.0, contains two or more blocks, and each block is composed of polyethylene oxide or polypropylene oxide. The lower limit of the HLB value is not particularly limited, but is, for example, 0.5 or more, preferably 0.8 or more, more preferably 1.0 or more, and even more preferably 1.2 or more.

[0031] (ii) The cloud point of the ethylene oxide / propylene oxide block copolymer having an HLB value of less than 10.0 is not particularly limited, and is, for example, −30° C. or higher, preferably −25° C. or higher, more preferably −20° C. or higher, and even more preferably −15° C. or higher, and is, for example, less than 170° C., preferably less than 150° C., more preferably less than 130° C., and even more preferably less than 100° C.

[0032] (ii) The number average molecular weight of the ethylene oxide / propylene oxide block copolymer having an HLB value of less than 10.0 is not particularly limited, and is, for example, 700 or more, preferably 1000 or more, more preferably 1200 or more, and even more preferably 1500 or more, and is, for example, less than 100000, preferably less than 70000, more preferably less than 50000, and even more preferably less than 35000.

[0033] (iii) The ethylene oxide / propylene oxide block copolymer having a number average molecular weight of less than 5,000 is not particularly limited as long as it has a number average molecular weight of less than 5,000, preferably less than 4500, more preferably less than 4000, and even more preferably less than 3500, contains two or more blocks, and each block is composed of polyethylene oxide or polypropylene oxide. The lower limit of the number average molecular weight is not particularly limited, but is, for example, 700 or more, preferably 1000 or more, more preferably 1200 or more, and even more preferably 1500 or more.

[0034] (iii) The cloud point of the ethylene oxide / propylene oxide block copolymer having a number average molecular weight of less than 5,000 is not particularly limited, and is, for example, −30° C. or higher, preferably −25° C. or higher, more preferably −20° C. or higher, and even more preferably −15° C. or higher, and is, for example, less than 170° C., preferably less than 150° C., more preferably less than 130° C., and even more preferably less than 100° C.

[0035] (iii) The HLB value of the ethylene oxide / propylene oxide block copolymer having a number average molecular weight of less than 5,000 is not particularly limited, and is, for example, 0.5 or more, preferably 0.8 or more, more preferably 1.0 or more, and even more preferably 1.2 or more, and is, for example, less than 20.0, preferably less than 18.0, more preferably less than 15.0, and even more preferably less than 10.0.

[0036] The medium composition for flexographic printing ink of the present invention preferably contains one or more ethylene oxide / propylene oxide block copolymers having a cloud point of less than 50° C., an HLB value of less than 10.0, and a number average molecular weight of less than 5,000. More preferably, the medium composition contains one or more ethylene oxide / propylene oxide block copolymers having a cloud point of less than 35° C., an HLB value of less than 5.0, and a number average molecular weight of less than 3,500.

[0037] The defoaming agent, which is a component of the medium composition for flexographic printing ink of the present invention, may contain a defoaming agent other than the ethylene oxide / propylene oxide block copolymers (i) to (iii). For example, one or more selected from the group consisting of silicone-based defoaming agents, fluorine-based defoaming agents, silica-based defoaming agents, polyether-based defoaming agents, oil-based defoaming agents, metal soap-based defoaming agents, amide wax-based defoaming agents, alcohol-based defoaming agents, sorbitan ester-based defoaming agents, etc. are included. Among these, one or more selected from the group consisting of silicone-based defoaming agents, fluorine-based defoaming agents, silica-based defoaming agents, and polyether-based defoaming agents are preferred because of their excellent foam breaking and foam suppressing effects, and one or more silicone-based defoaming agents and silica-based defoaming agents are more preferred.

[0038] Examples of such defoamers include the Antifoam series manufactured by Dow Corning Toray, the Roadsil series and Roadsil Antifoam series manufactured by Rhodia NICCA, the TSA series and YMA series manufactured by Toshiba Silicones, and the FluoWet series manufactured by Clariant.

[0039] The content of the defoaming agent in the flexographic printing ink medium composition is not particularly limited, and is, for example, 0.005% by mass or more, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and for example, 5.0% by mass or less, preferably 3.0% by mass or less, more preferably 2.0% by mass or less, based on the total amount of the flexographic printing ink medium composition.

[0040] The content of the ethylene oxide / propylene oxide block copolymer (i) to (iii) in the flexographic printing ink medium composition is not particularly limited, and is, for example, 0.001 mass% or more, preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and for example, 3.0 mass% or less, preferably 2.0 mass% or less, more preferably 1.5 mass% or less, based on the total amount of the flexographic printing ink medium composition.

[0041] The medium composition for flexographic printing ink of the present invention contains one or more of the ethylene oxide / propylene oxide block copolymers (i) to (iii) in addition to a neutralized product of an acid group-containing resin, and thus can improve defoaming properties during printing and suppress the occurrence of pinholes in printed matter. Furthermore, even when printing is performed using ink that has been stored over a long period of time, the occurrence of pinholes in printed matter can be suppressed.

[0042] <Aqueous medium> The aqueous medium which is a component of the medium composition for flexographic printing ink of the present invention may be, for example, water alone or a mixture of water and a water-soluble organic solvent.

[0043] The water is not particularly limited, and examples thereof include ion-exchanged water, ultrafiltered water, reverse osmosis water, tap water, industrial water, distilled water, pure water, and ultrapure water. Among these, it is preferable to remove ionic impurities as much as possible. Furthermore, when water is used that has been sterilized by ultraviolet irradiation or addition of hydrogen peroxide, the growth of bacteria and fungi can be prevented during long-term storage.

[0044] The water-soluble organic solvent is not particularly limited as long as it has a solubility in water at 25° C. of 1 g / L or more, preferably 10 g / L or more, more preferably 100 g / L or more, and further preferably is an organic solvent that can be uniformly mixed in any ratio. Examples of the water-soluble organic solvent include monoalcohol-based organic solvents, polyhydric alcohol-based organic solvents, polyhydric alcohol alkyl ether-based organic solvents, ketone-based organic solvents, ether-based organic solvents, ester-based organic solvents, and nitrogen-containing compound-based organic solvents. These can be used alone or in combination of two or more.

[0045] Examples of the water-soluble organic solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, t-butanol, 2-methyl-2-propanol, hexanol, octanol, decanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monooctyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol Cholesterol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, glycerin, etc. These can be used alone or in combination of two or more.

[0046] The aqueous medium may be water alone. The aqueous medium may contain, in addition to water, a water-soluble organic solvent in an amount that does not cause a decrease in the performance of the flexographic printing ink composition.

[0047] The content of the aqueous medium in the flexographic printing ink medium composition is not particularly limited, and is, for example, 50.0% by mass or more, preferably 70.0% by mass or more, more preferably 75.0% by mass or more, and for example, 99.0% by mass or less, preferably 98.5% by mass or less, more preferably 98.0% by mass or less, based on the total amount of the flexographic printing ink medium composition. When a mixture of water and a water-soluble organic solvent is used as the aqueous medium, the content of the water-soluble organic solvent is not particularly limited, and is preferably, for example, less than 5.0% by mass in the total amount of the medium composition for flexographic printing ink.

[0048] <Wax> The flexographic printing ink medium composition of the present invention may contain a wax. By incorporating wax into a medium composition for flexographic printing ink, it is possible to obtain effects such as improved abrasion resistance of the ink film, improved blocking resistance of the ink film, and improved drying properties of the ink film when the flexographic printing ink composition is prepared and printed.

[0049] The average particle size of the wax, as measured by the Coulter Counter method, is, for example, 0.5 μm or more, preferably 1 μm or more, more preferably 2 μm or more, and for example, 10 μm or less, preferably 8 μm or less, more preferably 5 μm or less. In the present invention, the resin constituting the wax is not particularly limited. For example, polyolefin wax is preferable, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, paraffin wax, microcrystalline wax, etc. are more preferable, and polyethylene wax is even more preferable. The wax may be in the form of a wax fine particle dispersion.

[0050] The content of the wax in the flexographic printing ink medium composition is not particularly limited, and is, for example, 0% by mass or more, for example, 0.1% by mass or more, for example, 0.3% by mass or more, and is, for example, 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less, based on the total amount of the flexographic printing ink medium composition.

[0051] <Surfactant> The flexographic printing ink medium composition of the present invention may contain a surfactant. The surfactant may be any of a nonionic surfactant, a cationic surfactant, an anionic surfactant, and a betaine surfactant. The surfactant preferably includes an acetylene-based surfactant, a silicone-based surfactant, a fluorine-based surfactant, etc. These can be used alone or in combination of two or more.

[0052] The acetylene-based surfactant is a surfactant having an acetylene bond in the molecule, and examples thereof include acetylene alcohol-based surfactants and acetylene glycol-based surfactants. Specific examples of the acetylene surfactant include Dynol 607, Dynol 609, Olfin E1004, Olfin E1010, Olfin E1020, Olfin PD-001, Olfin PD-002W, Olfin PD-004, Olfin PD-005, Olfin EXP.4001, Olfin EXP.4200, Olfin EXP.4123, Olfin EXP.4300 (Nissin Chemical Industry Co., Ltd.), Surfynol 104E, Surfynol 104H, Surfynol 104A, Surfynol 104BC, Surfynol 104DPM, Surfynol 104PA, Surfynol 104PG-50, Surfynol 420, Surfynol 440, Surfynol 465 (EVONIK), and the like. These can be used alone or in combination of two or more.

[0053] Examples of silicone surfactants include dimethylpolysiloxane, methylphenylpolysiloxane, alkyl-modified polysiloxane, alkyl-aralkyl-modified polysiloxane, alkyl-polyether-modified polysiloxane, polyether-modified polysiloxane, polyester-modified polysiloxane, alkyl-polyester-modified polysiloxane, higher fatty acid ester-modified polysiloxane, and the like. Specific examples of silicone surfactants include BYK-307, BYK-315N, BYK-331, BYK-333, BYK-347, BYK-348, BYK-349, BYK-345, BYK-377, BYK-378, BYK-3455, BYK-UV3500 (BYK-Chemie), and the like. These can be used alone or in combination of two or more.

[0054] Examples of fluorine-based surfactants include perfluoro butyl sulfonates, perfluoro carboxylates, perfluoro phosphates, perfluoro phosphate-type compounds, perfluoro alkyl ethylene oxide adducts, perfluoro / hydrophilic / lipophilic group-containing oligomers, perfluoro / hydrophilic group-containing oligomers, perfluoro alkyl ethylene oxide adduct ... Examples of suitable perfluoroalkyl groups include perfluoroalkyl group-containing oligomers, perfluoroalkyl betaine and perfluoroalkyl amine oxide compounds. Specific examples of fluorine-based surfactants include F-410, F-444, F-553 (DIC), FS-65, FS-34, FS-35, FS-31, and FS-30 (DuPont). These can be used alone or in combination of two or more.

[0055] The content of the surfactant in the flexographic printing ink medium composition is not particularly limited, and is, for example, 0% by mass or more, for example, 0.05% by mass or more, for example, 0.1% by mass or more, and is, for example, 4% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less, based on the total amount of the flexographic printing ink medium composition.

[0056] <Other additives> The flexographic printing ink medium composition of the present invention may contain other additives, if necessary, in addition to the neutralized product of the acid group-containing resin, the defoaming agent, the aqueous medium, the wax, and the surfactant, within the range that does not impair the properties of the flexographic printing ink medium composition. Examples of other additives include rheology control agents, resin emulsions, pigment dispersants, extender pigments (calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay, talc, etc.), adhesive resins (acrylic resins, vinyl acetate resins, rosin resins, etc.), leveling agents, basic compounds (alkali metal hydroxides, ammonia, organic amines, etc.), etc. These other additives may be used alone or in combination of two or more.

[0057] (Rheology control agent) The rheology control agent that may be contained in the medium composition for flexographic printing ink of the present invention is not particularly limited. For example, one or more of an association type rheology control agent, a polymer type rheology control agent having a weight average molecular weight of 100,000 to 3,000,000, etc. may be used. For example, it is preferable to use an association type rheology control agent and a polymer type rheology control agent having a weight average molecular weight of 100,000 to 3,000,000 in combination.

[0058] Examples of the associative rheology control agent include acrylic swelling associative rheology control agents and / or urethane associative rheology control agents, such as RM-5, TT-615, TT-935, RM-8, RM-825, RM-1020, SCT-275, RM-2020, RM-SW, RM-2020NPR, RM-R, RM-12W, DR-1, DR-72, DR-300, RM-7, RM-50000, RM-60000, RM-845, RM-995 (manufactured by Rohm and Haas), Adekanol VF, UH-462, UH-752, UH-140S, UH-420, UH-438, UH-472, UH-450, UH-540, UH-550, and UH-541V. F, UH-526, UH-530 (ADEKA), Cognis 3220, Rheovis PE1332, PU1190, PU1191, PU1214, PU1215, PU1250, PU1251, PU1256, PU1270, PU1280, PU1291, PU1331 (BASF), RHEOLATE 266, 288, 244, 255, 278 (RHEOX), SN Thickener A-803, A-804, A-807, A-812, A-814 (SAN NOPCO), etc. Among these, urethane-modified ether association type rheology control agents are preferred.

[0059] Examples of polymer-type rheology control agents include rheology control agents of alkali-soluble polymers and / or polyethylene glycols having a weight-average molecular weight in the range of 100,000 to 3,000,000. For example, one or more selected from the group consisting of Primal ASE-60, TT-615, ASE-75, ASE-108, RM-5, ASE-95NP (manufactured by Rohm and Haas Company), Alkox R-1000, R-400, R-150, E-60, E-45, E-30, E-300, E-240, E-160, E-100, E-75 (manufactured by Myojo Chemical Industry Co., Ltd.), Rheovis AS1125, AS1130, AS1188, AS1956 (manufactured by BASF Corporation), Aron A-20L, A-7100, A-10H, A-7255, A-7185, A-7195, A-7075, A-7055, B-300K, B-500 (manufactured by Toagosei Co., Ltd.), and the like may be mentioned.

[0060] (Resin emulsion) The resin emulsion that may be contained in the medium composition for flexographic printing ink of the present invention is not particularly limited. For example, from the viewpoint of film-forming properties when the flexographic printing ink composition is constituted and printed, a resin emulsion containing a resin having a glass transition temperature of 10° C. or less is preferred. Examples of such resin emulsions include acrylic resin emulsions, water-soluble styrene-acrylic resin emulsions, water-soluble styrene-maleic acid resin emulsions, and water-soluble styrene-acrylic-maleic acid resin emulsions. The acid value of these resin emulsions can be, for example, 10 mgKOH / g or more and 200 mgKOH / g or less.

[0061] <Method of producing medium composition for flexographic printing ink> The method for producing the flexographic ink medium composition of the present invention is not particularly limited as long as it is a method capable of uniformly mixing the components of the flexographic ink medium composition. For example, the components of a medium composition for flexographic printing ink are placed in a container, and then mixed using various mixers such as a bead mill, pearl mill, sand mill, ball mill, jet mill, colloid mill, dyno mill, agitator mill, attritor, roll mill, ultrasonic homogenizer, high-pressure homogenizer, paint shaker, kneader, sand grinder, magnetic stirrer, disperser, dissolver, line mixer, homomixer, planetary mixer, Henschel mixer, intensive mixer, Banbury mixer, juice mixer, turbo mixer, Nanomizer, etc., and further additional components are added as necessary, and then mixed using various mixers to produce the composition.

[0062] <Applications of medium composition for flexographic printing ink> The flexographic printing ink medium composition of the present invention is used for producing a flexographic printing ink composition by blending a color pigment. In producing the flexographic printing ink composition, a pigment dispersion containing a color pigment can be used as the color pigment, and an aqueous medium can be blended as a dilution solvent, if necessary. When a flexographic printing ink composition is obtained using the flexographic printing ink medium composition of the present invention, a printing ink color matching and filling device (dispensing system) can be used. The color matching and filling device (dispensing system) is equipped with ink tanks for the desired number of colors, for example, 16 to 20 colors, and pumps, injection nozzles, measuring devices, stirrers, and computers connected to each of the tanks, and is an apparatus capable of producing ink and color matching at a blending ratio previously stored in the computer. For example, a flexographic printing ink composition can be produced by mixing (a) the medium composition for flexographic printing ink according to the present invention, (b) a pigment dispersion containing a color pigment, and (c) an aqueous medium as a dilution solvent, which is used as needed, using a color matching filling device (dispensing system) to obtain a compounding ratio stored in a computer.

[0063] [Flexographic printing ink composition] The flexographic printing ink composition of the present invention contains the above-mentioned flexographic printing ink medium composition and a color pigment. The flexographic printing ink composition of the present invention may contain other additives in addition to the flexographic printing ink medium composition and the color pigment.

[0064] <Medium composition for flexographic printing ink> The flexographic printing ink medium composition, which is a constituent of the flexographic printing ink composition of the present invention, is the above-mentioned [flexographic printing ink medium composition].

[0065] <Coloring pigments> The color pigment, which is a component of the flexographic printing ink composition of the present invention, is not particularly limited. Any pigment of any color tone listed as a CI pigment in the Color Index can be used, and may be either an organic pigment or an inorganic pigment.

[0066] Examples of organic pigments include azo-based, phthalocyanine-based, anthraquinone-based, perylene-based, perinone-based, quinacridone-based, thioindigo-based, dioxazine-based, isoindoline-based, quinophthalone-based, azomethine azo-based, diketopyrrolopyrrole-based, isoindoline-based, dye lake-based, benzimidazolone-based, indigo-based, thioindigo-based, nitro-based, nitroso-based, flavanthrone-based, quinophthalone-based, pyranthrone-based, indanthrone-based, and condensed polycyclic pigments. Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, mica, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine, iron black, and graphite. These pigments can be used alone or in combination of two or more.

[0067] The content of the color pigment in the flexographic printing ink composition is not particularly limited. It can be any content so as to obtain a desired color tone. In the total amount of the flexographic printing ink composition, the content is, for example, 0.01 mass% or more, for example, 0.1 mass% or more, for example, 1 mass% or more, and, for example, 70 mass% or less, for example, 50 mass% or less, for example, 40 mass% or less. In the case of organic pigments, the content is, for example, 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and can be, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 35% by mass or less. In the case of inorganic pigments, it can be, for example, 1 mass % or more, preferably 5 mass % or more, more preferably 10 mass % or more, and for example, 70 mass % or less, preferably 50 mass % or less, more preferably 40 mass % or less.

[0068] In the present invention, the color pigment is preferably used in the form of a pigment dispersion composition. The pigment dispersion composition contains, in addition to the color pigment, components such as a pigment dispersant, a rheology control agent, and an aqueous medium, and if necessary, a film-forming emulsion and other additives. The pigment dispersion composition can be obtained by mixing each component such as the color pigment using various mixers described in the manufacturing method of the medium composition for flexographic printing ink. The pigment concentration of the pigment dispersion composition is not particularly limited, but can be, for example, 10% by mass or more, preferably 15% by mass or more, and, for example, 65% by mass or less, preferably 60% by mass or less. The pigment dispersion composition may be a commercially available one. For example, a high pigment concentration water-based flexographic printing ink having a pigment concentration of 15 to 60 mass % may be used. For example, flexographic printing ink of each color of the "FK-FM" series manufactured by Sakata Inx Corporation may be used as the pigment dispersion composition.

[0069] <Other additives> The flexographic printing ink composition of the present invention may contain other additives, if necessary, in addition to the flexographic printing ink medium composition and the color pigment, within a range that does not impair the properties of the flexographic printing ink composition. Examples of other additives include aqueous media, rheology control agents, basic compounds, film-forming emulsions, extender pigments (calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay, talc, etc.), adhesive resins (acrylic resins, vinyl acetate resins, rosin resins, etc.), pigment dispersants, leveling agents, etc. These other additives may be used alone or in combination of two or more. Of these, the aqueous medium, rheology control agent, basic compound, and film-forming emulsion may be, for example, the same as those described in the above section "Medium composition for flexographic printing ink."

[0070] The other additives may be contained in the flexographic printing ink medium composition beforehand, or may be contained in a pigment dispersion containing a color pigment beforehand, or may be added during or after mixing of the flexographic printing ink medium composition with the color pigment.

[0071] <Viscosity of flexographic printing ink composition> The viscosity of the flexographic printing ink composition of the present invention is not particularly limited, and may be, for example, in the range of 10 mPa s to 1000 mPa s (25° C. B-type viscometer) from the viewpoints of dispersibility and anti-settling property of the color pigment, and workability during production of the ink composition and printing.

[0072] <Method for producing flexographic printing ink composition> The flexographic printing ink composition of the present invention is preferably produced by mixing (a) the flexographic printing ink medium composition of the present invention, (b) a pigment dispersion containing a color pigment, and (c) an aqueous medium as a dilution solvent, which is used as necessary, in a mixing ratio stored in a computer using a printing ink color matching and filling device (dispensing system). As the aqueous medium as a dilution solvent (c), the same aqueous medium as in the above [Flexographic printing ink medium composition] can be used.

[0073] The blending ratio of (a) the medium composition for flexographic printing ink, (b) the pigment dispersion containing the color pigment, and (c) the aqueous medium as a dilution solvent can be adjusted as desired. For example, (b) can be 1 part by mass or more and 200 parts by mass or less, and (c) can be 0 part by mass or more and 500 parts by mass or less, per 100 parts by mass of (a).

[0074] <Applications of flexographic printing ink composition> The flexographic printing ink composition of the present invention is used for flexographic printing on various substrates with a flexographic printing machine using a flexographic plate. In flexographic printing, the anilox roll that supplies ink may be, for example, a ceramic anilox roll with cell engravings or a chrome-plated anilox roll. As the flexographic plate, for example, an ultraviolet-curing photosensitive resin plate or an elastomer plate produced by direct laser engraving can be used. As the flexographic printing machine, for example, a CI type multi-color flexographic printing machine or a unit type multi-color flexographic printing machine using an ink supply method such as a chamber method or a two-roll method can be used.

[0075] The various substrates on which flexographic printing is performed are not particularly limited, and examples thereof include plastic, paper, cloth, metal, glass, ceramic, wood, a laminate containing one or more of these, and a composition containing one or more of these.

[0076] Examples of plastics constituting the substrate include polyester resins (e.g., polyethylene terephthalate (PET), polyethylene naphthalate, polylactic acid, etc.), cellulose resins (e.g., diacetyl cellulose, triacetyl cellulose (TAC), etc.), polycarbonate resins, acrylic resins (e.g., polymethyl methacrylate, etc.), vinyl chloride resins, vinylidene chloride resins, polyolefin resins (e.g., polyethylene, polypropylene, polyolefin polymers having a cyclic or norbornene structure, ethylene-propylene copolymers, etc.), polya Examples of such materials include amide-based resins (e.g., nylon, aromatic polyamide polymers, etc.), polystyrene-based polymers (e.g., polystyrene, AS resin, ABS resin, etc.), polyimide-based resins, polyvinyl alcohol-based resins, polyvinyl butyral-based resins, vinyl acetate-based resins, polyether-based resins, epoxy-based resins, compositions containing one or more of these, composite materials such as laminates of one or more of these, composite materials in which an inorganic material such as a metal or a metal oxide is vapor-deposited on the surface of these, and composite materials in which the surface of these has been subjected to an easy-to-adhere treatment (corona discharge treatment, ultraviolet treatment, ozone treatment, plasma treatment, primer treatment, etc.).

[0077] The flexographic printing ink composition of the present invention can be suitably used for printing on the surface of paper or resin, for example, printing on cardboard cartons, paper containers (e.g., paper cups, paper plates, etc.), and paper containers whose surfaces are covered with a resin layer. EXAMPLES

[0078] The present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to the description of these examples. Unless otherwise specified, "parts" means "parts by mass." In addition, the numerical values ​​of the composition formulation of each component in Table 1 are parts by mass.

[0079] [Materials used] The materials used in preparing the flexographic printing ink medium composition and the flexographic printing ink composition are as follows:

[0080] <Acid group-containing resin neutralized product 1> Purified water was added to a styrene-maleic acid resin (acid value 199 mgKOH / g, glass transition temperature 88°C) and heated and stirred, and then the acid groups were neutralized with ammonia water (neutralization rate 100%) to obtain an acid group-containing neutralized resin 1. The acid group-containing neutralized resin 1 was a resin varnish with a solid content of 21.5 mass% and a pH of 7.5.

[0081] <Ethylene oxide / propylene oxide block copolymer> EO / PO block copolymer 1: Ethylene oxide / propylene oxide block copolymer (cloud point 20° C., number average molecular weight 2,200, HLB 1.8 to 2.0) (manufactured by Sanyo Chemical Industries, Ltd., product name "Newpol PE-71") EO / PO block copolymer 2: Ethylene oxide / propylene oxide block copolymer (cloud point 113° C., number average molecular weight 8,300, HLB 15.5 to 15.7) (manufactured by Sanyo Chemical Industries, Ltd., product name "Newpol PE-68") EO / PO block copolymer 3: Ethylene oxide / propylene oxide block copolymer (cloud point 105° C., number average molecular weight 16,000, HLB 15.5) (manufactured by Sanyo Chemical Industries, Ltd., product name "Newpol PE-108") EO / PO block copolymer 4: Ethylene oxide / propylene oxide block copolymer (cloud point 109° C., number average molecular weight 25,000, HLB 15.6) (manufactured by Sanyo Chemical Industries, Ltd., product name "Newpol PE-128")

[0082] <Silicone-based defoaming agent> Si-based defoamer 1: Silica / octamethylcyclotetrasiloxane / polyoxyalkylene alkyl ether (manufactured by Toray Dow Corning Co., Ltd., product name "FS Antifoam 013")

[0083] <Other additives> Wax 1: Polyethylene wax (solid content 40% by mass) Surfactant 1: Acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name "Surfynol 104E") Aqueous medium 1: Ion-exchanged water

[0084] <Pigment dispersion composition> PD-1: Indigo pigment dispersion composition (manufactured by Sakata Inx Corporation, "FK-FM Indigo 312") PD-2: Yellow pigment dispersion composition (manufactured by Sakata Inx Corporation, "FK-FM Yellow 305") PD-3: Red pigment dispersion composition (manufactured by Sakata Inx Corporation, "FK-FM Red 308") PD-4: Red pigment dispersion composition (manufactured by Sakata Inx Corporation, "FK-FM Red 309") PD-5: Green pigment dispersion composition (manufactured by Sakata Inx Corporation, "FK-FM Kusa 311") PD-6: Purple pigment dispersion composition (manufactured by Sakata Inx Corporation, "FK-FM Purple 313")

[0085] [evaluation] The flexographic printing ink medium compositions and flexographic printing ink compositions obtained in the respective Examples and Comparative Examples were evaluated for the following items, and the evaluation results are shown in Tables 1 and 2.

[0086] <Antifoaming evaluation> After preparing the flexographic printing ink medium composition and the flexographic printing ink composition, each was diluted with water and the viscosity of each was adjusted to 8 seconds at 25° C. using a Rigaud Zahn Cup No. 4. 800 parts by mass of the flexographic printing ink medium composition or the flexographic printing ink composition was added to a beaker (inner diameter 9.3 cm, height 16 cm), and circulated with a pump (circulation speed 1800 cc / min) while stirring with a stirrer (2400 rpm), and after 300 seconds, the liquid level and foam height in the container were measured, and the defoaming property was evaluated according to the following evaluation criteria. In the present invention, A is pass, and C is fail. (Evaluation Criteria) A: The height of the bubble-air interface is less than 100 mm. C: The height to the interface between the foam and air is 100 mm or more.

[0087] <Pinhole evaluation during manufacturing> After preparing the flexographic printing ink medium composition and the flexographic printing ink composition, each was left to stand until the liquid temperature reached 20°C. Then, using a marrow bar (0.15 mm), each was spread on a treated surface of a polypropylene film (manufactured by Toyobo Co., Ltd., product name "P2161"). The presence or absence of pinholes on the spread surface was visually confirmed, and pinhole evaluation during production was performed according to the following evaluation criteria. In the present invention, A is pass, and C is fail. (Evaluation Criteria) A: Pinholes are found on the applied surface. C: No pinholes are found on the applied surface.

[0088] <Evaluation of pinholes over time> After preparing the flexographic printing ink medium composition and the flexographic printing ink composition, each was kept at 60°C for 14 days, and then left to stand until the liquid temperature reached 20°C. Then, using a marrow bar (0.15 mm), each was spread on a treated surface of a polypropylene film (manufactured by Toyobo Co., Ltd., product name "P2161"). The presence or absence of pinholes on the spread surface was visually confirmed, and pinhole evaluation over time was performed according to the following evaluation criteria. In the present invention, A is pass, and C is fail. (Evaluation Criteria) A: Pinholes are found on the applied surface. C: No pinholes are found on the applied surface.

[0089] [Table 1]

[0090] [Table 2]

[0091] As shown in Table 1, the flexographic printing ink medium composition of the present invention was found to be excellent in all of the evaluation of defoaming properties, pinholes during production, and pinholes over time. On the other hand, the flexographic printing ink medium composition containing only a Si-based defoaming agent (Comparative Example A1) was found to have pinholes in the pinhole over time evaluation, and the flexographic printing ink medium compositions containing ethylene oxide / propylene oxide block copolymers not falling under any of (i) to (iii) (Comparative Examples A2 to A4) were found to have insufficient defoaming ability in the defoaming properties evaluation.

[0092] As shown in Table 2, it was found that the flexographic printing ink composition obtained from the flexographic printing ink medium composition of the present invention was excellent in the evaluation of defoaming property, evaluation of pinholes during production, and evaluation of pinholes over time. On the other hand, the flexographic printing ink composition obtained from the flexographic printing ink medium composition of Comparative Example A1, which is not the flexographic printing ink medium composition of the present invention, was confirmed to have pinholes in the evaluation of pinholes over time.

Claims

1. The composition contains a neutralized product of an acid group-containing resin, a defoamer, and an aqueous medium, The defoaming agent is selected from the following (i) to (iii); (i) an ethylene oxide / propylene oxide block copolymer having a cloud point of less than 50° C.; (ii) an ethylene oxide / propylene oxide block copolymer having an HLB value of less than 10.0; (iii) an ethylene oxide / propylene oxide block copolymer having a number average molecular weight of less than 5,000; Contains one or more of the following: A medium composition for flexographic printing inks.

2. 2. The flexographic printing ink medium composition according to claim 1, wherein the content of the neutralized product of the acid group-containing resin is 0.5% by mass or more based on the total amount of the flexographic printing ink medium composition.

3. 3. The medium composition for flexographic printing ink according to claim 1, wherein the acid group-containing resin constituting the neutralized product of the acid group-containing resin is at least one selected from the group consisting of acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, and styrene-maleic acid-acrylic resins.

4. 3. The medium composition for flexographic printing ink according to claim 1, wherein the neutralization rate of the neutralized product of the acid group-containing resin is 80% or more and 120% or less.

5. 3. The medium composition for flexographic printing ink according to claim 1, wherein the neutralizing alkali component in the neutralized product of the acid group-containing resin is at least one selected from the group consisting of ammonia, sodium hydroxide, potassium hydroxide, and alkanolamines.

6. 3. A flexographic printing ink composition comprising the flexographic printing ink medium composition according to claim 1 or 2 and a color pigment.

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