Water-in-oil emulsion ink

Abstract

To provide a water-in-oil emulsion ink that enables the formation of a printed material with superior fixation performance, even when the ink is fully dried, when printed onto plain paper, and a method for producing the water-in-oil emulsion ink.SOLUTION: The present invention provides a water-in-oil emulsion ink having an aqueous phase within an oil phase, wherein the aqueous phase comprises a colorant, polymer A, and water, and the oil phase comprises an olefin, as well as a method for producing the water-in-oil emulsion ink.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a water-in-oil emulsion ink and a method for producing the water-in-oil emulsion ink. [Background technology]

[0002] Inkjet recording is a method of ejecting ink droplets from minute nozzles and depositing them directly onto a printing medium to obtain a printed matter on which characters and images are recorded. This method has the advantages of being easy to produce full color, being inexpensive, and not contacting the printed matter, so it is no longer limited to consumer printing, and in recent years it has begun to be applied to commercial and industrial printing fields. In the fields of commercial and industrial printing, high-speed printing is required, and in order to meet this demand, printers using a line head type inkjet recording method have been developed and oil-based pigment inks are used. When printing on plain paper using oil-based pigment inks, there is a problem that the oil-based ink penetrates into the interior of the printed matter, resulting in low print density. Therefore, the use of water-in-oil (W / O) emulsion inks has been investigated.

[0003] For example, Patent Document 1 discloses a water-in-oil emulsion ink having a water phase in an oil phase, the water phase containing a pigment dispersed with a polymer having an acid group, the oil phase containing a water-insoluble organic solvent and an emulsifier, the acid value of the polymer being 120 mgKOH / g or more and at least a portion of the acid groups of the polymer being neutralized, and the water content in the water-in-oil emulsion ink being within a predetermined range, for the purpose of providing a water-in-oil emulsion ink which has excellent storage stability and which, when printed on plain paper, can give a printed matter which has high print density and is less deformed after printing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-024982 Summary of the Invention [Problem to be solved by the invention]

[0005] With the technology of Patent Document 1, when printing on plain paper, the components in the aqueous phase remain on the surface layer of the plain paper, allowing for high print density to be achieved; however, it was found that this technology does not ensure the fixation of the printed matter when the ink is sufficiently dry. An object of the present invention is to provide a water-in-oil emulsion ink which, when printed on plain paper, can give a printed item with excellent fixation even when the ink is sufficiently dried, and a method for producing the water-in-oil emulsion ink. [Means for solving the problem]

[0006] The present inventors have discovered that the above problems can be solved by a water-in-oil emulsion ink having an aqueous phase containing a colorant, a polymer, and water, and an oil phase, wherein the oil phase contains an olefin. That is, the present invention provides the following [1] and [2]. [1] A water-in-oil emulsion ink having a water phase in an oil phase, the aqueous phase contains a colorant, polymer A, and water; A water-in-oil emulsion ink, wherein the oil phase contains an olefin. [2] A method for producing the water-in-oil emulsion ink described in [1] above, comprising a step of mixing and emulsifying an aqueous phase component containing an aqueous pigment dispersion obtained by dispersing the pigment in an aqueous medium with the polymer A, and an oil phase component. Effect of the Invention

[0007] The present invention can provide a water-in-oil emulsion ink that can provide a printed item with excellent fixation when printed on plain paper even when the ink is sufficiently dried, and a method for producing the water-in-oil emulsion ink. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Water-in-oil emulsion ink] The water-in-oil emulsion ink of the present invention (hereinafter also referred to as "emulsion ink") is a water-in-oil emulsion ink having an aqueous phase in an oil phase, the aqueous phase containing a colorant, polymer A, and water, and the oil phase containing an olefin. In the present invention, the term "olefin" refers to an olefin having the general formula C n H 2n It means an aliphatic chain unsaturated hydrocarbon having one carbon-carbon double bond represented by the following formula:

[0009] According to the present invention, when printing on plain paper, it is possible to obtain a printed matter having excellent fixability even when the ink is sufficiently dried. Although the reason for this is not clear, it is thought to be as follows. In the emulsion ink of the present invention, the aqueous phase contains a colorant, a polymer, and water, and the oil phase contains an olefin. The olefin has a certain degree of polarity due to the carbon-carbon double bond in the molecule, and therefore exhibits an interaction with the colorant and the polymer. Therefore, when printing is performed on plain paper using the emulsion ink of the present invention, when the water in the aqueous phase of the emulsion ink is absorbed by the plain paper and the colorant in the aqueous phase is bound to the surface of the plain paper, the polymer is plasticized by the interaction with the olefin, and it is considered that this plasticized polymer has the effect of increasing the fusion strength between the colorant and the plain paper. In addition, the olefin, which is a hydrocarbon solvent, has a weaker interaction with the cellulose fibers that constitute the plain paper compared to ester-based solvents, and is less likely to remain on the plain paper. Therefore, when the ink is sufficiently dried, the plasticizing effect of the polymer by the olefin disappears, and the colorant fused to the plain paper by the polymer is less likely to peel off even when rubbed, and it is considered that the fixation of the printed matter can be improved.

[0010] <Aqueous phase> The water phase of the emulsion ink of the present invention contains a colorant, polymer A, and water.

[0011] [Coloring material] The coloring material according to the present invention is preferably a pigment or a dye. Among these, a pigment is more preferable. The pigment may be either an inorganic pigment or an organic pigment, and a lake pigment or a fluorescent pigment may also be used. If necessary, they may be used in combination with an extender pigment. Examples of inorganic pigments include carbon black, metal oxides such as titanium oxide, iron oxide, red iron oxide, and chromium oxide, and pearlescent pigments. Carbon black is particularly preferred as an inorganic pigment for use in black ink. The type of carbon black is not particularly limited, and examples thereof include furnace black, lamp black, acetylene black, and channel black. The DBP oil absorption of the carbon black is preferably 20 mL / 100 g or more and 200 mL / 100 g or less from the viewpoints of improving the dispersion stability of the pigment in the aqueous phase and improving the storage stability and print density. Here, the DBP oil absorption refers to the oil absorption measured by the DBP method, specifically, a value based on ASTM D2414-65T.

[0012] Examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, and chelate azo pigments; and polycyclic pigments such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, and threne pigments. In the achromatic ink, achromatic pigments such as white, black, and gray can be used, while in the chromatic ink, chromatic pigments such as yellow, magenta, cyan, blue, red, orange, and green can be used. Specific examples of preferred organic pigments include one or more product numbers selected from the group consisting of CI Pigment Yellow, CI Pigment Red, CI Pigment Orange, CI Pigment Violet, CI Pigment Blue, and CI Pigment Green. Examples of the extender pigment include silica, calcium carbonate, and talc. The pigments can be used alone or in combination of two or more kinds.

[0013] When the colorant according to the present invention is a pigment, the content of the pigment in the components constituting the aqueous phase of the emulsion ink of the present invention (hereinafter also referred to as "aqueous phase components") is preferably 10% by mass or more, more preferably 13% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of improving print density, and is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of improving the fixation of the printed matter.

[0014] When the colorant according to the present invention is a pigment, the pigment's presence in the aqueous phase of the emulsion ink of the present invention is preferably in a state where the pigment is dispersed in the aqueous phase without a dispersant (i.e., in a state where the pigment is dispersed in the aqueous phase as a self-dispersing pigment), in a state where the pigment is dispersed in the aqueous phase with a low molecular surfactant, or in a state where the pigment is dispersed in the aqueous phase with polymer A. When the pigment is dispersed in the aqueous phase with polymer A, the polymer A may be either a water-soluble polymer or a water-insoluble polymer. Among these, the pigment's presence is more preferably one or more selected from the group consisting of a state where the pigment is dispersed in the aqueous phase as a self-dispersing pigment and a state where the pigment is dispersed in the aqueous phase with polymer A, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and the fixing property of the printed matter, and even more preferably a state where the pigment is dispersed in the aqueous phase with polymer A. Examples of the state in which the pigment is dispersed in the aqueous phase by the polymer A include a form in which the pigment is encapsulated by the polymer A and a form in which the polymer A is attached to a part of the pigment. Among these, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixation of the printed matter, the form in which the pigment is encapsulated by the polymer A is more preferable.

[0015] [Polymer A] The polymer A according to the present invention (hereinafter, simply referred to as "polymer A") preferably has a function of stably dispersing a colorant in an aqueous phase and a function of increasing the fixation of the resulting printed matter. From the viewpoint of achieving both a function of stably dispersing a colorant in an aqueous phase and a function of increasing the fixation of the resulting printed matter, the polymer A is preferably a water-insoluble polymer (a) (hereinafter, simply referred to as "polymer (a)"). Here, a polymer is judged to be "water-insoluble" if, when a polymer that has reached a constant weight after drying at 105°C for 2 hours is dissolved in 100 g of water at 25°C until saturation is reached, the amount of dissolution is 10 g or less. In addition, when the water-insoluble polymer (a) has acid groups and the acid groups are neutralized with a neutralizing agent when the polymer is contained in the emulsion ink of the present invention, the polymer is judged to be "water-insoluble" based on the amount of dissolution measured in the presence of a neutralizing agent such that the mass ratio of the polymer (a) to the neutralizing agent when the polymer is contained in the emulsion ink of the present invention is the same. In addition, when the water-insoluble polymer (a) has acid groups, which are neutralized with a neutralizing agent and further crosslinked with a crosslinking agent (hereinafter also referred to as crosslinked polymer (a')), the solubility is determined based on the amount of dissolution measured under conditions in which the mass ratio of the crosslinked polymer (a') to the neutralizing agent and the state of the crosslinked structure when contained in the emulsion ink of the present invention are the same.

[0016] From the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixability of the printed matter, the polymer A is preferably contained in the aqueous phase as a polymer dispersant that disperses the pigment or as polymer particles that do not contain a pigment, and more preferably contained in the aqueous phase as a polymer dispersant. When the pigment is present in the aqueous phase as a self-dispersing pigment dispersed in the aqueous phase, the polymer A is preferably contained in the aqueous phase as polymer particles that do not contain a pigment.

[0017] Examples of the water-insoluble polymer (a) include polyester resins, polyurethane resins, and vinyl resins. When the colorant according to the present invention is a pigment, among these, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixability of the printed matter, a vinyl resin having an acid group is preferred, and a vinyl resin containing a constituent unit derived from a carboxyl group-containing monomer and a constituent unit derived from a hydrophobic monomer is more preferred. In this specification, a "hydrophobic" monomer means that the amount of the monomer dissolved is less than 10 g when the monomer is dissolved to saturation in 100 g of ion-exchanged water at 25° C. From the viewpoint of the adsorption of the polymer to the pigment, the amount of the hydrophobic monomer dissolved is preferably 5 g or less, more preferably 1 g or less.

[0018] Preferred examples of the carboxy group-containing monomer include one or more selected from the group consisting of (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethylsuccinic acid, with (meth)acrylic acid being more preferred and acrylic acid being even more preferred. In this specification, "(meth)acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid. The carboxyl group-containing monomers can be used alone or in combination of two or more kinds.

[0019] The hydrophobic monomer is preferably at least one selected from the group consisting of aromatic group-containing monomers, (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol, and hydrophobic macromonomers. In this specification, the term "(meth)acrylate" refers to at least one selected from the group consisting of acrylates and methacrylates. The hydrophobic monomers can be used alone or in combination of two or more. Examples of aromatic group-containing monomers, (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol, and hydrophobic macromonomers include those described in paragraph 1 of JP 2022-102920 A.

[0020] ~

[0022] Among these, from the viewpoints of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability, and improving the fixation of the printed matter, the hydrophobic monomer is more preferably one or more selected from the group consisting of aromatic group-containing monomers and (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol, even more preferably an aromatic group-containing monomer, and even more preferably one or more selected from the group consisting of styrene-based monomers and aromatic group-containing (meth)acrylates.

[0020] The vinyl resin may further contain a constituent unit derived from a nonionic monomer in addition to the constituent unit derived from a carboxy group-containing monomer and the constituent unit derived from a hydrophobic monomer. Examples of the nonionic monomer include those described in paragraph

[0024] of JP-A-2022-102920.

[0021] Among these, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixation property of the printed matter, the water-insoluble polymer (a) is preferably a vinyl-based resin containing one or more structural units derived from a carboxyl group-containing monomer selected from the group consisting of acrylic acid and methacrylic acid, and one or more structural units derived from a hydrophobic monomer selected from the group consisting of an aromatic group-containing monomer, a (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol, and an aromatic group-containing monomeric macromonomer, and may also be a vinyl-based resin containing a structural unit derived from a nonionic monomer. From the viewpoints of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability, and improving the fixation of the printed matter, the water-insoluble polymer (a) is more preferably a vinyl-based resin containing structural units derived from one or more carboxy-containing monomers selected from the group consisting of acrylic acid and methacrylic acid, and structural units derived from one or more hydrophobic monomers selected from the group consisting of aromatic group-containing monomers and (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol, and even more preferably a vinyl-based resin containing structural units derived from one or more carboxy-containing monomers selected from the group consisting of acrylic acid and methacrylic acid, and structural units derived from one or more hydrophobic monomers selected from the group consisting of styrene-based monomers and aromatic group-containing (meth)acrylates.

[0022] The content of the constituent units derived from each monomer in the water-insoluble polymer (a) is as follows, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and from the viewpoint of improving the fixation of the printed matter. The content of structural units derived from carboxy group-containing monomers in the water-insoluble polymer (a) is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, still more preferably 30% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less. The content of structural units derived from hydrophobic monomers in the water-insoluble polymer (a) is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less. When the water-insoluble polymer (a) is a vinyl resin containing a structural unit derived from a macromonomer, the content of the structural unit derived from the macromonomer in the polymer (a) is preferably 5 mass% or more, more preferably 10 mass% or more, even more preferably 15 mass% or more, and preferably 35 mass% or less, more preferably 30 mass% or less, even more preferably 25 mass% or less. When the water-insoluble polymer (a) is a vinyl resin containing a structural unit derived from a nonionic monomer, the content of the structural unit derived from a nonionic monomer in the polymer (a) is preferably 3 mass% or more, more preferably 5 mass% or more, even more preferably 8 mass% or more, and preferably 20 mass% or less, more preferably 15 mass% or less, even more preferably 12 mass% or less. The content of the constituent units derived from each monomer in the above polymer (a) can be measured by analysis such as NMR, etc. In addition, the preferred range of the content of each monomer (content as unneutralized amount) in the raw material monomers during the production of the above polymer (a) can be considered to be the same as the preferred range of the content of the constituent units derived from each monomer in the above polymer (a).

[0023] The weight average molecular weight of the water-insoluble polymer (a) is preferably at least 2,000, more preferably at least 5,000, even more preferably at least 7,000, and is preferably at most 100,000, more preferably at most 50,000, even more preferably at most 30,000, and even more preferably at most 20,000. When the weight average molecular weight of the polymer (a) is within the above range, the adsorptivity to the pigment is sufficient, the pigment exhibits dispersion stability, and the fixability of the printed matter can be improved. The weight average molecular weight of the polymer (a) can be measured by the method described in the Examples.

[0024] The acid value of the water-insoluble polymer (a) is preferably 120 mgKOH / g or more, more preferably 180 mgKOH / g or more, and even more preferably 220 mgKOH / g or more from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, and is preferably 320 mgKOH / g or less, more preferably 300 mgKOH / g or less, and even more preferably 280 mgKOH / g or less from the viewpoint of improving the fixation of the printed matter. If the acid value is within the above range, the amount of acid groups and their neutralized acid groups is sufficient, and the dispersion stability of the pigment is ensured. It is also preferable from the viewpoint of the balance between the affinity of the polymer (a) with water and the interaction between the polymer (a) with the pigment. The acid value of the polymer (a) can be measured by the method described in the Examples, or calculated from the mass ratio of the constituent monomers.

[0025] At least a part of the acid groups of the water-insoluble polymer (a) is neutralized from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase. The neutralization is preferably carried out so that the pH is 7 or more and 11 or less. Examples of the neutralizing agent used for neutralizing the water-insoluble polymer (a) include alkali metal hydroxides and ammonia. Among them, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, alkali metal hydroxides are preferred, and more preferred are one or more selected from the group consisting of sodium hydroxide and potassium hydroxide. From the same viewpoint as above, the degree of neutralization is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, and preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 60 mol% or less. Specifically, the degree of neutralization (mol %) can be calculated by the following formula. Degree of neutralization (mol%)=[{weight of neutralizing agent added (g) / equivalent weight of neutralizing agent} / [{acid value of water-insoluble polymer (a) (mg KOH / g) × weight of water-insoluble polymer (a) (g)} / (56.1 × 1,000)]] × 100

[0026] From the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixability of the printed matter, the polymer A is preferably a crosslinked polymer (a') obtained by crosslinking the water-insoluble polymer (a) with a crosslinking agent. In this case, the crosslinked polymer (a') has a structure derived from the crosslinking agent in addition to the constituent units derived from the monomers constituting the polymer (a). From the viewpoint of improving the fixability of printed matter, the crosslinking agent preferably has a water solubility (mass ratio) of 50% or less, more preferably 40% or less, and even more preferably 35% or less. Here, the water solubility % (mass ratio) refers to the solubility (%) when 10 parts by mass of the crosslinking agent is dissolved in 90 parts by mass of water at room temperature of 25°C. Suitable examples of the crosslinking agent include those described in paragraphs

[0031] to

[0034] of JP 2022-102920 A. Among these, the crosslinking agent is preferably a polyfunctional epoxy compound having two or more epoxy groups in the molecule, more preferably a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group having from 3 to 8 carbon atoms, even more preferably one or more selected from the group consisting of trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and diethylene glycol diglycidyl ether, and even more preferably trimethylolpropane polyglycidyl ether. When the crosslinking agent is a polyfunctional epoxy compound, the epoxy equivalent of the crosslinking agent is preferably 90 or more, more preferably 100 or more, even more preferably 110 or more, and preferably 300 or less, more preferably 200 or less, even more preferably 150 or less.

[0027] From the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixation of the printed matter, the degree of crosslinking of the crosslinked polymer (a') is preferably 20 mol % or more, more preferably 30 mol % or more, even more preferably 40 mol % or more, still more preferably 45 mol % or more, and is preferably 80 mol % or less, more preferably 70 mol % or less, even more preferably 60 mol % or less, still more preferably 55 mol % or less. As described above, the degree of crosslinking of the crosslinked polymer (a') is calculated from the equivalent of the acid group of the water-insoluble polymer (a) and the equivalent of the crosslinkable functional group of the crosslinking agent when the water-insoluble polymer (a) is crosslinked with a crosslinking agent and contains an acid group, and is expressed as "the molar equivalent number of the crosslinkable functional group of the crosslinking agent / the molar equivalent number of the acid group of the polymer (a)". As described above, when a part of the acid groups of the water-insoluble polymer (a) is neutralized, the neutralized acid groups can also become crosslinking points. Therefore, when the sum of the neutralization degree and the crosslinking degree exceeds 100 mol%, the crosslinking degree of the crosslinked polymer (a') is expressed as "the molar equivalent number of the crosslinkable functional group of the crosslinking agent / the molar equivalent number of the acid group of the polymer (a)" as described above, and the neutralization degree of the crosslinked polymer (a') is the value obtained by subtracting the crosslinking degree from 100 mol%.

[0028] The acid value of the crosslinked polymer (a') is preferably 60 mgKOH / g or more, more preferably 80 mgKOH / g or more, and even more preferably 100 mgKOH / g or more from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, and is preferably 180 mgKOH / g or less, more preferably 160 mgKOH / g or less, and even more preferably 140 mgKOH / g or less from the viewpoint of improving the fixation of the printed matter. If the acid value is within the above range, the amount of acid groups and their neutralized acid groups is sufficient, and the fixation of the printed matter can be improved while ensuring the dispersion stability of the pigment. The acid value of the crosslinked polymer (a') can be measured by the method described in the Examples, and can also be calculated from the mass ratio of the constituent monomers and the degree of crosslinking.

[0029] At least a part of the acid groups of the crosslinked polymer (a') is preferably neutralized from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixability of the printed matter. Examples of the neutralizing agent used for neutralizing the crosslinked polymer (a') include the same ones as those exemplified above. From the viewpoint of improving the dispersion stability of the pigment, the counter ion of the neutralized acid group of the crosslinked polymer (a') is preferably an alkali metal cation, more preferably a sodium ion (Na + ) and potassium ion (K + ) is one or more selected from the group consisting of Regarding the degree of neutralization of the crosslinked polymer (a'), a part of the acid groups of the crosslinked polymer (a') may be neutralized, or all of the acid groups may be neutralized.

[0030] When the colorant according to the present invention is a pigment, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixability of the printed matter, the pigment is preferably dispersed in the aqueous phase by a crosslinked polymer (a') obtained by crosslinking a water-insoluble polymer (a) with a crosslinking agent as the polymer A. That is, the pigment is preferably dispersed by a crosslinked polymer (a') having a structure derived from the crosslinking agent in addition to the constituent units derived from the monomers constituting the polymer (a). In this case, the crosslinked polymer (a') functions as a polymer dispersant. When the pigment is dispersed by the crosslinked polymer (a'), the pigment is preferably present in the aqueous phase in a form in which the crosslinked polymer (a') encapsulates the pigment.

[0031] 〔water〕 The water contained in the aqueous phase of the emulsion ink of the present invention may be ultrapure water, ion-exchanged water, distilled water, or the like.

[0032] The water content in the aqueous phase component of the emulsion ink of the present invention is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and still more preferably 45% by mass or more, and from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, it is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0033] (Surfactant) In the emulsion ink of the present invention, a surfactant may be contained in the aqueous phase. It is considered that the surfactant can improve the dispersion stability of the pigment in the aqueous phase. From this viewpoint, the surfactant is preferably a nonionic surfactant, more preferably one or more selected from the group consisting of acetylene glycol surfactants, polyoxyalkylene alkyl ether surfactants, polyether-modified silicone surfactants, and fluorine-based surfactants, even more preferably one selected from the group consisting of acetylene glycol surfactants and polyether-modified silicone surfactants, and even more preferably an acetylene glycol surfactant. Preferred examples of the acetylene glycol surfactant and the polyether-modified silicone surfactant include those described in paragraphs

[0051] to

[0052] of JP-A-2022-102920. From the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, the HLB value of the nonionic surfactant is preferably 6 or more, more preferably 8 or more, even more preferably 10 or more, and still more preferably 12 or more, and is preferably 20 or less, more preferably 18 or less. The HLB value is a value indicating the affinity of a surfactant to water and oil as a hydrophilic-lipophilic balance, and in the present invention, the HLB value can be calculated by the Griffin method from the following formula: In the following formula, examples of the "hydrophilic group contained in the surfactant" include a hydroxyl group and an ethyleneoxy group. HLB value = 20 x [(total formula weight of hydrophilic groups contained in surfactant) / (molecular weight of surfactant)]

[0034] (Water-soluble organic solvent) In the emulsion ink of the present invention, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and from the viewpoint of improving the fixation of the printed matter, it is preferable that the aqueous phase further contains a water-soluble organic solvent. In the present invention, the "water-soluble organic solvent" refers to an organic solvent that dissolves in 100 mL of water at 25°C in an amount of 10 mL or more. The water-soluble organic solvent is preferably one that can be mixed with water in any mass ratio. The water-soluble organic solvent is not particularly limited as long as it forms a single phase with water at any mass ratio when mixed with water, and examples thereof include alkanols having 1 to 4 carbon atoms, polyhydric alcohols, polyhydric alcohol alkyl ethers, ketones, cyclic ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. Among these, one or more selected from the group consisting of polyhydric alcohols and polyhydric alcohol alkyl ethers are more preferred, and polyhydric alcohols are even more preferred. As the polyhydric alcohol, glycerin is preferably used. The boiling point of the water-soluble organic solvent under atmospheric pressure is preferably 60°C or higher, more preferably 90°C or higher, even more preferably 150°C or higher, and preferably 350°C or lower, more preferably 330°C or lower, even more preferably 310°C or lower. The water-soluble organic solvents can be used alone or in combination of two or more kinds.

[0035] In the emulsion ink of the present invention, the aqueous phase may contain a viscosity modifier, an antifoaming agent, an antiseptic, an antifungal agent, an antirust agent, etc., to the extent that the effect of the present invention is not impaired.

[0036] <Oil phase> The oil phase of the emulsion inks of the present invention contains an olefin.

[0037] [Olefin] In the present invention, the term "olefin" refers to an olefin represented by the general formula C n H 2nIt means an aliphatic chain unsaturated hydrocarbon having one carbon-carbon double bond represented by the following formula: The olefin is preferably liquid at 25° C. and 1 atmosphere. From the viewpoint of appropriately controlling volatility and improving fixation of printed matter, the number of carbon atoms in the olefin is preferably 8 or more, more preferably 10 or more, even more preferably 12 or more, still more preferably 14 or more, and still more preferably 16 or more, and from the same viewpoints as above, the number of carbon atoms in the olefin is preferably 24 or less, more preferably 22 or less, still more preferably 20 or less, and still more preferably 18 or less. The molecular chain structure of the olefin may be either linear or branched, but is preferably linear from the viewpoints of appropriately controlling volatility and ensuring fixability.

[0038] From the viewpoint of reducing the impact on the environment, the olefin contained in the oil phase of the emulsion ink of the present invention can be preferably either an α-olefin in which the carbon-carbon double bond is at the end of the carbon chain, or an internal olefin in which the carbon-carbon double bond is located inside the carbon chain. However, from the viewpoint of improving the fixation of printed matter, internal olefins are more preferable. The position of the double bond in the olefin can be confirmed, for example, by a gas chromatograph mass spectrometer (GC-MS). Specifically, by accurately separating each component having a different carbon chain length and double bond position by a gas chromatograph (GC), the proportion of each olefin can be determined from the GC peak area, and further, the double bond position in the olefin can be identified by a mass spectrometer (MS). The olefin to be used may be a commercially available product, or may be one synthesized by a known method. Commercially available olefin products include, for example, the Linealene (trade name) series (manufactured by Idemitsu Kosan Co., Ltd.) and the Neoden (trade name) series (manufactured by Shell Chemical). An example of a method for synthesizing an olefin is the method for producing an internal olefin described in JP-A-2014-156462.

[0039] (Other non-water-soluble organic solvents) The oil phase of the emulsion ink of the present invention may contain other water-insoluble organic solvents in addition to the olefin. In the present invention, the term "water-insoluble organic solvent" refers to an organic solvent that dissolves in less than 10 mL of water at 25° C. in 100 mL of water.

[0040] As the other water-insoluble organic solvent, either a non-polar organic solvent or a polar organic solvent can be used. The other water-insoluble organic solvent may be used alone or in combination of two or more kinds as long as they form a single continuous phase in the oil phase.

[0041] Examples of non-polar organic solvents include aliphatic hydrocarbon solvents such as paraffin-based, isoparaffin-based, and naphthenic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. The initial boiling point of the non-polar organic solvent is preferably 90° C. or higher, more preferably 150° C. or higher, and preferably 300° C. or lower, more preferably 250° C. or lower. Commercially available non-polar organic solvents include, for example, the Isopar (trade name) series and Exxor (trade name) series (both manufactured by ExxonMobil Corporation); and the AF Solvent (trade name) series (manufactured by JXTG Nippon Oil & Energy Corporation).

[0042] Examples of polar organic solvents include fatty acid ester solvents and higher alcohol solvents. Examples of fatty acid ester solvents include fatty acid esters having 13 to 30 carbon atoms, such as isononyl isononanoate, isodecyl isononanoate, isotridecyl isononanoate, methyl laurate, isopropyl laurate, hexyl laurate, 2-ethylhexyl laurate, isopropyl myristate, isopropyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, isobutyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, 2-ethylhexyl stearate, isopropyl isostearate, methyl soybean oil, isobutyl soybean oil, methyl tall oil, isobutyl tall oil, propylene glycol monocaprate, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, trimethylolpropane tri-2-ethylhexanoate, and glyceryl tri-2-ethylhexanoate. Examples of higher alcohol solvents include higher alcohols having 12 to 20 carbon atoms, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, and oleyl alcohol.

[0043] From the viewpoint of improving the fixation of printed matter, the olefin content in the components constituting the oil phase of the emulsion ink of the present invention (hereinafter also referred to as "oil phase components") is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, still more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, and is preferably 97% by mass or less, more preferably 95% by mass or less, and still more preferably 90% by mass or less.

[0044] In the oil phase of the emulsion ink of the present invention, the content of olefins in the total content of olefins and other water-insoluble organic solvents (hereinafter also referred to as "total amount of water-insoluble organic solvents") is, from the viewpoint of improving the fixation of printed matter, preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and preferably 100% by mass or less.

[0045] (emulsifier) The oil phase of the emulsion ink of the present invention preferably contains an emulsifier. The emulsifier is not particularly limited as long as it can emulsify the aqueous phase in the oil phase to form a water-in-oil emulsion, but lipophilic emulsifiers such as surfactants and polymer dispersants are preferred. As the lipophilic surfactant, a nonionic surfactant having an HLB value of 6 or less is preferred. Examples of the nonionic surfactant include sorbitan fatty acid esters such as sorbitan monooleate, sorbitan sesquioleate, and sorbitan monostearate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate; glycerin fatty acid esters such as glycerol monostearate and glycerol monooleate; polyoxyethylene sorbit fatty acid esters; polyoxyethylene glycerin fatty acid esters such as polyoxyethylene glycerin vegetable oil fatty acid ester; sucrose fatty acid esters such as sucrose stearate, sucrose palmitate, sucrose oleate, sucrose erucate, and sucrose laurate; polyethylene glycol fatty acid esters; polyglycerin condensed ricinoleate; polyoxyethylene alkyl ethers; polyoxyethylene alkylphenyl ethers; polyoxyethylene alkylamines / fatty acid amides; and polyoxyethylene polyoxypropylene alkyl ethers. The lipophilic surfactants can be used alone or in combination of two or more kinds.

[0046] Examples of lipophilic polymer dispersants include polyester polyimines, polyester polyamines, polyalkylol aminoamides and their salts, polyether polyamines, hydroxyl group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, modified polyurethanes, modified poly(meth)acrylates, polyether ester-type anionic surfactants, naphthalene sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Among these, polyester polyimines, polyester polyamines, polyalkylol aminoamides and their salts, and polyether polyamines are preferred, and polyester polyimines are more preferred. These may be used alone or in combination of two or more.

[0047] The polyester polyimine is preferably an amide or salt formed by reacting a polyalkyleneimine such as polyethyleneimine with a polyester having a carboxy group, such as a polymer of hydroxystearic acid or a polymer of a cyclic ester, and includes a dispersant having a graft structure in which two or more polyester chains are bonded as branches to a polyalkyleneimine chain as a backbone. Commercially available lipophilic polymer dispersants include, for example, the Solsperse (product name) series manufactured by Lubrizol Japan Co., Ltd.; the Efka (product name) series manufactured by BASF; the Disparlon (product name) series manufactured by Kusumoto Chemicals Co., Ltd.; and the Ajisper (product name) series manufactured by Ajinomoto Co., Inc.

[0048] In the emulsion ink of the present invention, from the viewpoint of improving the fixation of printed matter, it is preferable that the oil phase does not contain a colorant such as a pigment.

[0049] [Manufacturing method of water-in-oil emulsion ink] The emulsion ink of the present invention can be produced by mixing and emulsifying the aqueous phase component and the oil phase component. When the colorant according to the present invention is a pigment, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixation of the printed matter, it is preferable that the emulsion ink of the present invention is obtained by a manufacturing method including a step of mixing and emulsifying an aqueous phase component containing an aqueous pigment dispersion with an oil phase component (hereinafter also referred to as "Step I"). The aqueous pigment dispersion may be one in which a pigment is dispersed in an aqueous medium with a polymer A, or one in which a self-dispersing pigment is dispersed in an aqueous medium. From the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the fixation of the printed matter, it is more preferable that the emulsion ink of the present invention is obtained by a manufacturing method including a step of mixing and emulsifying an aqueous phase component containing an aqueous pigment dispersion in which a pigment is dispersed in an aqueous medium with a polymer A with an oil phase component. Here, the term "aqueous" in the aqueous pigment dispersion means that water accounts for the largest proportion, by mass, of the medium in which the pigment is dispersed.

[0050] [Preparation of Water-Based Pigment Dispersion] In the present invention, when the pigment is dispersed in a water-insoluble polymer (a) that does not have a crosslinked structure as the polymer A, the water-based pigment dispersion is preferably produced by a method including the following step 1. Step 1: A step of dispersing a pigment mixture containing a pigment, a water-insoluble polymer (a), and water to obtain an aqueous pigment dispersion in which the pigment is dispersed in an aqueous medium by the water-insoluble polymer (a).

[0051] (Process 1) Step 1 is preferably carried out, for example, by a method (i) of dispersing a pigment mixture obtained by mixing a previously prepared aqueous dispersion of polymer (a) with a pigment, or a method (ii) of dispersing a pigment mixture containing a pigment, polymer (a), an organic solvent, water, and, if necessary, a neutralizer, a surfactant, etc., to obtain a dispersion, and then removing the organic solvent from the dispersion. Among these, method (i) is preferred from the viewpoint of improving the fixability of the printed matter.

[0052] In the case of the method (i), it is preferable to include the following step 1-1 before step 1. Step 1-1: A step of neutralizing a part of the acid groups of the water-insoluble polymer (a) with a neutralizing agent to obtain an aqueous dispersion of the water-insoluble polymer (a)

[0053] In the dispersion treatment in step 1, the pigment particles can be atomized to a desired particle size only by main dispersion using shear stress. However, from the viewpoint of obtaining a uniform aqueous pigment dispersion, it is preferable to pre-disperse the pigment mixture and then further carry out main dispersion. As a dispersing machine used for preliminary dispersion, a commonly used mixing and stirring device such as an anchor blade or a dispersing blade can be used. Examples of means for applying shear stress used in the present dispersion include kneaders such as roll mills and kneaders, high-pressure homogenizers such as microfluidizers, and media-type dispersers such as paint shakers and bead mills. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the pigment. When the dispersion treatment is performed using a high-pressure homogenizer, the pigment can be controlled to have a desired particle size by controlling the treatment pressure and the number of passes, and the cumulant average particle size of the aqueous pigment dispersion described below can also be adjusted. From the viewpoints of productivity and economy, the treatment pressure is preferably 60 MPa or more and 300 MPa or less. The number of passes is preferably 3 or more, more preferably 7 or more, from the viewpoint of reducing the particle size of the pigment, and is preferably 30 or less, more preferably 20 or less, from the viewpoint of the dispersion stability of the pigment.

[0054] When the pigment mixture contains an organic solvent, the organic solvent can be removed by a known method to obtain an aqueous pigment dispersion. It is preferable that the organic solvent in the obtained aqueous pigment dispersion is substantially removed, but it may remain as long as it does not impair the object of the present invention. The amount of the residual organic solvent is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.

[0055] (Process 2) In the present invention, when the pigment is dispersed in a crosslinked polymer (a') as the polymer A, the aqueous pigment dispersion is preferably produced by a method that further includes the following step 2 after step 1. Step 2: A step of adding a crosslinking agent to the aqueous pigment dispersion obtained in step 1, and reacting the water-insoluble polymer (a) with the crosslinking agent to obtain an aqueous pigment dispersion dispersed with the crosslinked polymer (a').

[0056] In step 2, the polymer (a) obtained by dispersing the pigment in the aqueous pigment dispersion obtained in step 1 is crosslinked with a crosslinking agent to obtain an aqueous pigment dispersion in which the pigment is dispersed in a crosslinked polymer (a') having a structure derived from the polymer (a) and a structure derived from the crosslinking agent. In step 2, the preferred crosslinking agent and degree of crosslinking are as described above.

[0057] The temperature of the crosslinking treatment is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher, and is preferably 95°C or lower, more preferably 85°C or lower, and even more preferably 75°C or lower. From the viewpoints of completion of the crosslinking reaction and economic efficiency, the time for the crosslinking treatment is preferably 0.5 hours or more, more preferably 1 hour or more, even more preferably 3 hours or more, and is preferably 12 hours or less, more preferably 10 hours or less, even more preferably 8 hours or less.

[0058] From the viewpoint of improving dispersion stability and facilitating production of the ink, the non-volatile component concentration (solid content concentration) of the aqueous pigment dispersion is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and is preferably 65% ​​by mass or less, more preferably 60% by mass or less, even more preferably 55% by mass or less. The solid content concentration of the aqueous pigment dispersion can be measured by the method described in the Examples.

[0059] From the viewpoints of reducing coarse particles and improving storage stability and print density, the cumulant average particle size of the aqueous pigment dispersion is preferably 50 nm or more, more preferably 60 nm or more, and even more preferably 70 nm or more, and is preferably 200 nm or less, more preferably 160 nm or less, and even more preferably 150 nm or less. The cumulant average particle size of the aqueous pigment dispersion can be measured by the method described in the Examples.

[0060] The aqueous pigment dispersion is preferably a dispersion in which polymer particles containing a pigment are dispersed in an aqueous medium mainly made of water. Here, the form of the polymer particles containing a pigment is not particularly limited as long as the particles are formed by at least the pigment and the polymer (a) or the crosslinked polymer (a'), but as described above, it is preferable that the polymer (a) or the crosslinked polymer (a') is in a form in which the pigment is encapsulated therein.

[0061] When polymer A is contained in the aqueous phase as polymer particles not containing a pigment, polymer A is preferably incorporated in the emulsion ink of the present invention as an aqueous dispersion of water-insoluble polymer (a) or crosslinked polymer (a'). The aqueous dispersion of the polymer (a) is preferably produced by a method including the above-mentioned step 1-1. The aqueous dispersion of the crosslinked polymer (a') is preferably produced by a method including the following step 1-1' after step 1-1. Step 1-1': A step of adding a crosslinking agent to the aqueous dispersion of the water-insoluble polymer (a) obtained in step 1-1, and reacting the water-insoluble polymer (a) with the crosslinking agent to obtain an aqueous dispersion of the crosslinked polymer (a').

[0062] In step 1-1', the preferred crosslinking agent and the degree of crosslinking are as described above. The preferred temperature and time for the crosslinking treatment in step 1-1' are the same as those in step 2 described above.

[0063] When the aqueous phase of the emulsion ink of the present invention contains the above-mentioned pigment-free polymer particles, a surfactant, a water-soluble organic solvent, or an optional component, step I is preferably a step of mixing the aqueous pigment dispersion with, as necessary, an aqueous dispersion of the water-insoluble polymer (a) or the crosslinked polymer (a'), a surfactant, a water-soluble organic solvent, or an optional component, or adjusting the water content to prepare an aqueous phase component, and then mixing and emulsifying the aqueous phase component with an oil phase component.

[0064] The stirring means used for mixing and emulsification in step I is not particularly limited as long as it can apply shear force, but high-speed stirring and mixing devices such as a homogenizer (e.g., "Ultra Turrax" from IKA Japan Co., Ltd.), a homomixer, or a disper (e.g., "Ultra Disper" from Asada Iron Works Co., Ltd.) are preferred. For example, when using a homogenizer, when dropping the aqueous phase component into the oil phase component, it is preferable to adjust the homogenizer rotation speed to preferably 500 rpm or more, more preferably 1,000 rpm or more, even more preferably 1,500 rpm or more, and preferably 8,000 rpm or less, more preferably 7,000 rpm or less, and even more preferably 6,000 rpm or less. After the aqueous phase component is dropped, it is preferable to adjust the homogenizer rotation speed to preferably 5,000 rpm or more, more preferably 7,000 rpm or more, even more preferably 10,000 rpm or more, and preferably 20,000 rpm or less, more preferably 17,000 rpm or less, and even more preferably 15,000 rpm or less. In step I, the amount of the aqueous phase component per 100 parts by mass of the oil phase component is, from the viewpoints of productivity and of obtaining a stable emulsion, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 17 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and more preferably 30 parts by mass or less.

[0065] If necessary, the emulsion ink of the present invention may further contain various additives commonly used in water-in-oil emulsion inks, such as a humectant, wetting agent, penetrating agent, dispersant, surfactant, viscosity modifier, defoamer, preservative, antifungal agent and rust inhibitor, and may further be subjected to filtration treatment using a filter or the like.

[0066] (Content of each component in emulsion ink) The content of the colorant in the emulsion ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more from the viewpoint of improving the print density, and is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 7% by mass or less, from the viewpoint of improving the fixation of the printed matter.

[0067] When the colorant according to the present invention is a pigment, the total content of the pigment and polymer A in the emulsion ink of the present invention is, from the viewpoints of improving the dispersion stability of the pigment in the aqueous phase and improving fixation, preferably at least 3 mass%, more preferably at least 5 mass%, and even more preferably at least 6 mass%, and from the same viewpoints as above, is preferably at most 18 mass%, more preferably at most 13 mass%, and even more preferably at most 10 mass%.

[0068] When the colorant according to the present invention is a pigment, the mass ratio of the pigment content to the polymer A content in the emulsion ink of the present invention [pigment / polymer A] is, from the viewpoint of improving print density, preferably 10 / 90 or more, more preferably 30 / 70 or more, even more preferably 50 / 50 or more, and still more preferably 60 / 40 or more, and from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving fixation, is preferably 97 / 3 or less, more preferably 95 / 5 or less, and even more preferably 90 / 10 or less.

[0069] The water content in the emulsion ink of the present invention is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more, from the viewpoints described above, and is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.

[0070] When a surfactant is contained in the aqueous phase of the emulsion ink of the present invention, the content of the surfactant in the emulsion ink of the present invention is, from the viewpoint of adjusting the viscosity of the emulsion ink and improving the fixation of printed matter, preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, and is preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less, and still more preferably 3% by mass or less.

[0071] When the aqueous phase of the emulsion ink of the present invention contains a water-soluble organic solvent, the content of the water-soluble organic solvent in the emulsion ink of the present invention is, from the viewpoint of adjusting the viscosity of the emulsion ink and improving the fixation of printed matter, preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more, and from the viewpoint of improving print density, preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0072] From the viewpoint of improving the fixation of printed matter, the content of the oil phase component in the emulsion ink of the present invention is preferably more than 50% by mass, more preferably 55% by mass or more, and more preferably 60% by mass or more, and from the same viewpoints as above, it is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0073] The combined content of the olefin and other water-insoluble organic solvents in the emulsion ink of the present invention (total amount of water-insoluble organic solvents) is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, from the viewpoint of adjusting the viscosity of the emulsion ink and improving the fixation of printed matter, and is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of improving print density.

[0074] From the viewpoint of improving the fixation of printed matter, the olefin content in the emulsion ink of the present invention is preferably 10% by mass or more, more preferably 30% by mass or more, and more preferably 50% by mass or more, and from the same viewpoints as above, it is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0075] The content of the lipophilic emulsifier in the emulsion ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of improving the storage stability, and is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of adjusting the viscosity of the emulsion ink.

[0076] (Emulsion ink viscosity) The viscosity of the emulsion ink of the present invention at 25°C is preferably 2 mPa s or more, more preferably 3 mPa s or more, and even more preferably 4 mPa s or more, and from the viewpoint of improving storage stability and jetting properties when the emulsion ink is used for inkjet recording, is preferably 30 mPa s or less, more preferably 25 mPa s or less, and even more preferably 20 mPa s or less. The viscosity is measured by the method described in the examples.

[0077] The emulsion ink of the present invention is preferably used for inkjet recording. In this case, the emulsion ink of the present invention is loaded into a known inkjet recording device and ejected as ink droplets onto a printing medium to record an image or the like. The inkjet recording apparatus may be of any type, such as a thermal type or a piezoelectric type, but it is preferable to use a piezoelectric type inkjet recording apparatus. Examples of the printing medium include highly absorbent plain paper, low absorbent coated paper, and non-absorbent resin film. Examples of the coated paper include general-purpose glossy paper and multicolor foam gloss paper. The resin film is preferably at least one selected from the group consisting of polyester film, polyvinyl chloride film, polypropylene film, and polyethylene film. The resin film may be a corona-treated substrate. Among these, plain paper is preferred because when the emulsion ink of the present invention is printed on plain paper, a print having excellent fixability can be obtained even when the ink is sufficiently dried. EXAMPLES

[0078] In the following Preparation Examples, Production Examples, Examples and Comparative Examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. Various physical properties were measured by the following methods.

[0079] (1) Measurement of weight-average molecular weight of water-insoluble polymer (a) The measurement was performed by gel permeation chromatography under the following conditions. GPC equipment: Tosoh Corporation "HLC-8320GPC" Columns: Tosoh Corporation's "TSKgel SuperAWM-H", "TSKgel SuperAW3000", and "TSKgel guardcolumn Super AW-H" Eluent: N,N-dimethylformamide with phosphoric acid and lithium bromide dissolved at concentrations of 60mmol / L and 50mmol / L, respectively. Flow rate: 0.5mL / min Standard material: Monodisperse polystyrene kit with known molecular weight [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)] (manufactured by Tosoh Corporation) Measurement sample: 0.1 g of polymer (a) was mixed with 10 mL of the eluent in a glass vial, stirred with a magnetic stirrer at 25°C for 10 hours, and filtered with a syringe filter (membrane filter material: hydrophilic PTFE, pore size 0.2 µm, "DISMIC-13HP" manufactured by Advantech Co., Ltd.) and used.

[0080] (2) Measurement of the acid value of the water-insoluble polymer (a) or the crosslinked polymer (a') The measurements were performed in accordance with JIS K0070:1992, except that the measurement solvent was changed from a mixed solvent of ethanol and ether to a mixed solvent of ethanol and toluene [ethanol:toluene=1:1 (volume ratio)].

[0081] (3) Measurement of solids concentration 10.0 g of sodium sulfate, which had been kept constant in a desiccator, was weighed out into a 30 mL polypropylene container (φ=40 mm, height=30 mm), and about 1.0 g of the sample was added thereto and mixed, then accurately weighed, and kept at 105°C for 2 hours to remove volatile matter, and left in the desiccator at room temperature (25°C) for 15 minutes, after which the mass was measured. The mass of the sample after removing the volatile matter was taken as the solid content, and divided by the mass of the sample added to obtain the solid content concentration (%).

[0082] (4) Measurement of cumulant average particle size of water-based pigment dispersion Cumulant analysis was performed using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.) to measure the cumulant average particle size. The measurement conditions were a temperature of 25°C, an angle between the incident light and the detector of 90°, and 100 integrations. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The concentration of the measurement sample was 5×10 -3% (converted into solids concentration).

[0083] (5) Viscosity of water-in-oil emulsion ink The viscosity was measured at 25°C using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., using a standard cone rotor 1°34'×R24, rotation speed 50 rpm).

[0084] <Preparation of Water-Insoluble Polymer (a)> Preparation Example 1 A raw monomer mixture was prepared by mixing 30.8 parts of acrylic acid, 59.2 parts of styrene, and 10.0 parts of α-methylstyrene. In a reaction vessel, 10 parts of methyl ethyl ketone (hereinafter referred to as "MEK"), 0.3 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the raw monomer mixture were mixed and thoroughly purged with nitrogen gas. Meanwhile, a mixture of the remaining raw monomer mixture, 0.27 parts of the polymerization chain transfer agent, 40 parts of MEK, and 1.1 parts of an azo-based radical polymerization initiator (FUJIFILM Wako Pure Chemical Industries, Ltd. "V-65", 2,2'-azobis(2,4-dimethylvaleronitrile)) (hereinafter referred to as "V-65") was placed in a dropping funnel, and the raw monomers in the reaction vessel were heated to 65°C while stirring under a nitrogen atmosphere, and the mixture in the dropping funnel was dropped over 3 hours. After stirring for 2 hours from the end of the dropping while maintaining the contents in the reaction vessel at 65°C, a solution in which 0.15 parts of the polymerization initiator was dissolved in 2.5 parts of MEK was added, and the mixture was further aged at 65°C for 2 hours and 70°C for 2 hours to obtain a solution of a polymer (a1) having a carboxy group (weight average molecular weight: 11,800, acid value: 240mgKOH / g).

[0085] Preparation Example 2 37.0 parts of methacrylic acid, 33.0 parts of benzyl acrylate, 40.0 parts of styrene macromer ("AS-6S" manufactured by Toagosei Co., Ltd., number average molecular weight: 6,000, solid content concentration 50%) (hereinafter referred to as "styrene macromer") (20.0 parts as solid content), and 10.0 parts of polypropylene glycol monomethacrylate ("Blenmer PP-800" manufactured by NOF Corporation, average number of propylene oxide added moles: 13, terminal: hydroxyl group) (hereinafter referred to as "PP-800") were mixed to prepare a raw material monomer mixture. 10 parts of MEK, 0.3 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the raw material monomer mixture were added and mixed in a reaction vessel, and nitrogen gas replacement was performed sufficiently. Meanwhile, a mixture of the remaining raw monomer mixture, 0.27 parts of the polymerization chain transfer agent, 40 parts of MEK, and 1.1 parts of the azo-based radical polymerization initiator (V-65) was placed in a dropping funnel, and the subsequent steps were carried out in the same manner as in Preparation Example 1 to obtain a solution of a polymer (a2) having a carboxy group (weight average molecular weight: 14,000, acid value: 240 mgKOH / g).

[0086] [Table 1]

[0087] <Preparation of Water Dispersion of Water-Insoluble Polymer (a)> Manufacturing Example 1-1 As shown in Table 2, 313.7 parts of ion-exchanged water and 40.5 parts of 5N aqueous sodium hydroxide solution were added to 80.0 parts of polymer (a1) obtained by drying the polymer solution obtained in Preparation Example 1 under reduced pressure, and the ratio of the number of moles of sodium hydroxide to the number of moles of carboxyl groups in polymer (a1) was 50 mol% (neutralization degree 50 mol%). The aqueous solution was heated at 90°C for 5 hours while stirring at 150 rpm to obtain an aqueous dispersion D1 of polymer (a1) (solid concentration 20.0%).

[0088] Manufacturing Example 1-2 An aqueous dispersion D2 (solid content concentration 20.0%) of polymer (a2) was obtained in the same manner as in Production Example 1-1, except that the type of polymer (a) in Production Example 1-1 was changed to polymer (a2) as shown in Table 2.

[0089] [Table 2]

[0090] <Production of Water-Based Pigment Dispersion> Manufacturing Example 2-1 (Process 1) 400.0 parts of ion-exchanged water and 100.0 parts of black pigment (carbon black, Cabot Corporation's "MONARCH717", DBP oil absorption: 55mL / 100g) were added to 60.3 parts of the aqueous dispersion D1 of the polymer (a1) obtained in Production Example 1-1, and the mixture was stirred for 60 minutes using a disperser (Asada Iron Works Co., Ltd.'s "Ultra Disperser") at 20°C and rotating the disperser blade at 7,000 rpm. The resulting mixture was subjected to 10 pass dispersion treatment at a pressure of 200MPa using a Microfluidizer (trade name, Microfluidics Co., Ltd.) to obtain a dispersion treatment product. The obtained dispersion was filtered using a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a cellulose acetate membrane filter ("Minisart" manufactured by Sartorius) having a pore size of 5 μm to remove coarse particles, and then ion-exchanged water was added to obtain an aqueous pigment dispersion (i-1) having a solids concentration of 20.0% (mass ratio [pigment / polymer (a1)]=89 / 11). (Process 2) 100.0 parts (solid content concentration 20.0%) of the aqueous pigment dispersion (i-1) obtained in step 1 was placed in a screw-capped glass bottle, and 0.65 parts of trimethylolpropane polyglycidyl ether ("Denacol EX-321" manufactured by Nagase ChemteX Corporation, epoxy equivalent: 139, water solubility: 27%) (hereinafter referred to as "EX-321") was added as a crosslinking agent so that 50 mol % of the total carboxy groups in the polymer (a1) were crosslinked (crosslinking degree 50 mol %). The bottle was then sealed and heated at 70°C for 5 hours while stirring with a stirrer. Thereafter, the temperature was lowered to room temperature, and the mixture was filtered using the membrane filter and syringe. The mixture was then concentrated under reduced pressure so that the pigment content in the resulting aqueous pigment dispersion was 36.0%, thereby obtaining an aqueous black pigment dispersion (hereinafter also referred to as "black pigment dispersion") Bk-I shown in Table 3 (mass ratio [pigment / crosslinked polymer (a1')] = 86 / 14, pigment content 36.0%, solids concentration 41.9%, cumulant average particle size 94 nm).

[0091] Manufacturing Examples 2-2 to 2-3 In step 1 of Production Example 2-1, the type or amount of the aqueous dispersion of polymer (a) was changed as shown in Table 3, and the same procedure was repeated to obtain water-based pigment dispersions (i-2) to (i-3), respectively. Then, in step 2 of Production Example 2-1, the type or amount of the aqueous dispersion of polymer (a) was changed as shown in Table 3, and the same procedure was repeated to obtain black pigment dispersions Bk-II and Bk-III, respectively, shown in Table 3.

[0092] [Table 3]

[0093] <Preparation of Aqueous Dispersion of Crosslinked Polymer (a')> Manufacturing Example 3-1 100.0 parts of the aqueous dispersion D1 of the polymer (a1) obtained in Production Example 1-1 (solid content concentration 20.0%) was taken into a screw-top glass bottle, and 5.95 parts of EX-321 was added as a crosslinking agent so that 50 mol% of the total carboxyl groups of the polymer (a1) were crosslinked (crosslinking degree 50 mol%), and the bottle was sealed and heated at 70 ° C. for 5 hours while stirring with a stirrer. After 5 hours, the temperature was lowered to room temperature, filtered with the membrane filter and syringe, and ion-exchanged water was added so that the solid content was 20.0 mass% to obtain the aqueous dispersion DX1 of the crosslinked polymer (a1') shown in Table 4.

[0094] [Table 4]

[0095] <Production of water-in-oil emulsion ink> Example 1 An oil phase component was prepared by mixing 10.0 parts (as is) of Solsperse 13940 (product name, manufactured by Lubrizol Corporation, polymer dispersant, active content 40%) (hereinafter referred to as "Solsperse 13940") as a lipophilic emulsifier and 65.0 parts of a C16 internal olefin. Next, 16.7 parts of black pigment dispersion Bk-I (pigment amount 6.0 parts), 2.0 parts of Surfynol 465 (trade name, manufactured by Nissin Chemical Industry Co., Ltd., EO adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, average EO added mole number: 10, HLB: 13) (hereinafter referred to as "Surfynol 465") as a surfactant, 2.0 parts of glycerin (manufactured by Kao Corporation, concentrated glycerin for cosmetics) as a water-soluble organic solvent, and 4.3 parts of ion-exchanged water were mixed to prepare an aqueous phase component. Using a homogenizer (product name: ULTLRA-TURRAX, model: T25 digital, shaft generator (model: S25N-25F), all manufactured by IKA Japan Co., Ltd.), the aqueous phase component was added dropwise while stirring the oil phase component at 5,000 rpm. The mixture was then stirred at 12,000 rpm for 3 minutes to obtain water-in-oil emulsion ink Bk-1, in which the pigment content in the emulsion ink was 6.0%. The viscosity of the emulsion ink Bk-1 was 10.6 mPa s. The C16 internal olefin used was produced according to Production Example 1 of JP 2022-160910 A.

[0096] Examples 2 to 11 and Comparative Examples 1 and 2 Water-in-oil emulsion inks with a pigment content of 6.0% were obtained in the same manner as in Example 1, except that the type or amount of each component was changed as shown in Table 5. The viscosity of each emulsion ink is shown in Table 5. The components other than those used in Example 1 shown in Table 5 are as follows. C18 internal olefin: Produced according to Production Example 2 of JP 2022-160910 A. C10 α-olefin: "Linearene 10" (1-decene) manufactured by Idemitsu Kosan Co., Ltd. C12 α-olefin: "Linearene 12" (1-dodecene) manufactured by Idemitsu Kosan Co., Ltd. C16 α-olefin: "Linearene 16" (1-hexadecene) manufactured by Idemitsu Kosan Co., Ltd. C18 α-olefin: "Linearene 18" (1-octadecene) manufactured by Idemitsu Kosan Co., Ltd. Isopar M: Product name, manufactured by Ando Parachemie Co., Ltd., isoparaffin-based solvent Isopropyl myristate: Kao Corporation's "Excepearl IPM" Methyl laurate: Kao Corporation "Excepearl ML-85"

[0097] Example 12 Self-dispersing carbon black (Senscient Technology's "SENSIJET Black SDP1000") was placed in a warm bath adjusted to 62°C using a reduced pressure distillation apparatus "N-1000S" (Tokyo Rikakikai Co., Ltd.), the pressure was reduced to 15 kPa, and the mixture was maintained for 4 hours to remove some of the water, thereby obtaining black pigment dispersion Bk-IV with a solids concentration adjusted to 36.0%. Next, water-in-oil emulsion ink Bk-12 was obtained in the same manner as in Example 3, except that black pigment dispersion Bk-IV was used instead of black pigment dispersion Bk-I, and further the amounts of water dispersion DX1 of crosslinked polymer (a1') obtained in Production Example 3-1 and ion-exchanged water were changed as shown in Table 5. The viscosity of the emulsion ink Bk-12 was 14.6 mPa s.

[0098] The fixing property of each of the emulsion inks of the examples and comparative examples was evaluated. The results are shown in Table 5. [Evaluation of Fixation] Each emulsion ink of the Examples and Comparative Examples was filled into an R&D piezo inkjet device (manufactured by Seiko Epson Corporation), and a 1 cm x 1 cm solid image was printed on plain paper ("Copy Plus" manufactured by Hammermill) in an environment of room temperature 23°C and relative humidity 50%. After leaving the paper to stand for one day at 40°C after printing, the bottom of the weight (bottom area 50 cm) was attached to a cellulose nonwoven fabric "Bencotto (registered trademark) M3-II" (manufactured by Asahi Kasei Corporation). 2 The printed surface was rubbed back and forth 100 times using a rubbing pad with a load of 700 gf. The fixability was evaluated based on the degree of staining of the ink transferred to the cellulose nonwoven fabric, according to the following criteria. (Evaluation Criteria) A: There was no dirt on the cellulose nonwoven fabric. B: The cellulose nonwoven fabric was almost free of stains. C: The cellulose nonwoven fabric was slightly soiled. D: The cellulose nonwoven fabric was soiled. E: The cellulose nonwoven fabric was significantly soiled.

[0099] [Table 5]

[0100] From Table 5, it can be seen that Examples 1 to 12 are superior to Comparative Examples 1 and 2 in fixing property. [Industrial Applicability]

[0101] According to the emulsion ink and the method for producing the emulsion ink of the present invention, a printed matter having excellent fixability can be obtained. Furthermore, the emulsion ink of the present invention is useful for inkjet recording.

Claims

1. A water-in-oil emulsion ink having a water phase in an oil phase, the aqueous phase contains a colorant, polymer A, and water; A water-in-oil emulsion ink, wherein the oil phase contains an olefin.

2. 2. The water-in-oil emulsion ink according to claim 1, wherein the content of an oil phase component in the water-in-oil emulsion ink is more than 50% by mass.

3. 3. The water-in-oil emulsion ink according to claim 1, wherein the content of the olefin in an oil phase component of the water-in-oil emulsion ink is 20% by mass or more.

4. 4. The water-in-oil emulsion ink according to claim 1, wherein the olefin has 8 or more and 20 or less carbon atoms.

5. The water-in-oil emulsion ink according to any one of claims 1 to 4, wherein the olefin is an internal olefin.

6. 6. The water-in-oil emulsion ink according to claim 1, wherein the colorant is a pigment, and a content of the pigment in an aqueous phase component of the water-in-oil emulsion ink is 10% by mass or more and 40% by mass or less.

7. 7. The water-in-oil emulsion ink according to claim 1, wherein the colorant is a pigment, the pigment is dispersed in the aqueous phase by the polymer A, and the polymer A is a crosslinked polymer (a') obtained by crosslinking a water-insoluble polymer (a) with a crosslinking agent.

8. 8. The water-in-oil emulsion ink according to claim 1, which is for ink-jet recording.

9. 9. The method for producing a water-in-oil emulsion ink according to claim 1, comprising a step of mixing and emulsifying an oil phase component and an aqueous phase component containing an aqueous pigment dispersion in which the colorant is a pigment and the pigment is dispersed in an aqueous medium with the polymer A.

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