JP7320401B2 - Water-in-oil emulsion ink - Google Patents

Description

The present invention relates to a water-in-oil emulsion ink and a method for producing the water-in-oil emulsion ink.

The inkjet recording method is a recording method in which ink droplets are directly ejected from fine nozzles and adhered to a printing medium to obtain a printed material on which characters and images are recorded. This method has the advantages of easy and inexpensive full-color printing and non-contact printing. Therefore, in recent years, it has begun to be applied not only to consumer printing for general consumers, but also to commercial and industrial printing fields. there is
Conventionally, water-based inks using pigments or dyes as colorants have been used as inks for inkjet recording. However, when printing on plain paper using a water-based ink, the print density is high because the water-absorbing nature of the plain paper is high, but on the other hand, the water contained in the water-based ink causes the fibers of the plain paper to swell, causing the printed matter to curl. There is a problem that it is deformed by
In addition, high-speed printing is required in the fields of commercial printing and industrial printing, and in order to cope with this high-speed printing, a printing machine adopting a line head type inkjet recording system has been developed, and an oil-based pigment ink is used. When the oil-based pigment ink is used for printing on plain paper, deformation of the printed matter can be reduced, but there is a problem that the ink penetrates into the inside of the printed matter and the printing density of the printed matter becomes low.
Therefore, the use of water-in-oil (W/O) emulsion ink is being studied.

For example, Patent Literature 1 discloses that a W/O type ink jet emulsion ink having a high concentration of 55% by mass or more is capable of obtaining a sufficient image optical density for recording on plain paper. A W/O type ink jet emulsion ink comprising an oil phase of 90% by mass or less and an aqueous phase of 45% by mass or less and 10% by mass or more, wherein the aqueous phase contains water, an aqueous solvent, a colorant and a resin. disclosed.
In Patent Document 2, for the purpose of providing an ink-jet emulsion ink capable of obtaining a sufficient optical density of an image and reducing paper deformation when recorded on plain paper, Disclosed is an ink-jet emulsion ink in which the aqueous phase contains water and a colorant, and the colorant is a modified pigment containing a polymer.

JP 2013-194111 A JP 2015-189859 A

A water-in-oil emulsion ink has an oil phase as a continuous phase and an aqueous phase emulsified in the oil phase. When a pigment is contained as a coloring agent in the aqueous phase, the oil phase and the aqueous phase are easily separated, and thus an improvement in storage stability is also required. However, the techniques of Patent Documents 1 and 2 do not provide sufficient storage stability when the emulsion ink is stored for a long period of time at high temperatures.
Further, in the techniques of Patent Documents 1 and 2, the print density of the printed matter is not sufficient, and the deformation of the printed matter cannot be sufficiently reduced.
The present invention provides a water-in-oil emulsion ink which is excellent in storage stability and which, when printed on plain paper, gives printed matter with high print density and little deformation after printing, and the water-in-oil emulsion ink. An object of the present invention is to provide a method for producing the

The present inventors have developed a water-in-oil emulsion ink having an aqueous phase containing water and a colorant and an oil phase containing a water-insoluble organic solvent, wherein the colorant is a pigment and a polymer dispersant having an acid group. The polymer dispersant has an acid value of 120 mgKOH/g or more, at least part of the acid groups of the polymer dispersant are neutralized, and the water content in the emulsion ink is adjusted to a predetermined amount. It has been found that the above problem can be solved by setting the range.
That is, the present invention provides the following [1] and [2].
[1] A water-in-oil emulsion ink having an aqueous phase in an oil phase,
the aqueous phase contains a pigment dispersed with a polymer (a) having an acid group;
The oil phase contains a water-insoluble organic solvent and an emulsifier,
The polymer (a) has an acid value of 120 mgKOH/g or more, and at least part of the acid groups of the polymer (a) are neutralized,
A water-in-oil emulsion ink, wherein the content of water in the water-in-oil emulsion ink is 5% by mass or more and 40% by mass or less.
[2] The method for producing a water-in-oil emulsion ink according to [1] above, which comprises emulsifying, in an oil phase, an aqueous pigment dispersion obtained by dispersing a pigment with the polymer (a) in an aqueous medium.

The present invention provides a water-in-oil emulsion ink which is excellent in storage stability and which, when printed on plain paper, gives printed matter with high print density and little deformation after printing, and the water-in-oil emulsion ink. can provide a manufacturing method of

[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, wherein the aqueous phase is a polymer having an acid group ( a) (hereinafter also referred to as "polymer (a)") contains a pigment dispersed therein, the oil phase contains a water-insoluble organic solvent and an emulsifier, and the polymer (a) has an acid value of 120 mgKOH /g, at least part of the acid groups of the polymer (a) are neutralized, and the water content in the water-in-oil emulsion ink is 5% by mass or more and 40% by mass or less.

The water-in-oil emulsion ink of the present invention is excellent in storage stability, and when printed on plain paper, can improve print density and reduce deformation of printed matter. Although the reason is not clear, it is considered as follows.
In the present invention, the pigment is dispersed in the aqueous phase, which is the dispersed phase, with the polymer (a) having an acid group. The acid value of the polymer (a) is 120 mgKOH/g or more, and at least part of the acid groups of the polymer (a) are neutralized, so that the pigment in the aqueous phase is removed by the action of electrostatic repulsion. stabilized. By suppressing the interaction of the pigment particles between the droplet particles of the dispersed phase and suppressing the coalescence of the droplet particles of the dispersed phase, the entire emulsion ink system is stabilized, and as a result, a water-in-oil emulsion It is thought that the storage stability is improved when the ink is stored at high temperature for a long period of time.
Further, in the present invention, since the content of water in the emulsion ink is 5% by mass or more and 40% by mass or less, it is considered possible to achieve high print density and reduce deformation of printed matter.

<Aqueous phase>
The aqueous phase contains a pigment dispersed with a polymer (a) having acid groups.
[Pigment]
Pigments used in the present invention may be either inorganic pigments or organic pigments, and lake pigments and fluorescent pigments may also be used. In addition, if necessary, they can be used in combination with an extender pigment.
Specific examples of inorganic pigments include metal oxides such as carbon black, titanium oxide, iron oxide, red iron oxide and chromium oxide, and pearl luster pigments. Carbon black is particularly preferred for black ink.
The type of carbon black is not particularly limited and includes furnace black, thermal lamp black, acetylene black, channel black and the like.
The DBP oil absorption of carbon black is preferably 20 mL/100 g or more and 200 mL/100 g or less from the viewpoint 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, and specifically, it is a value based on ASTM D2414-65T.

Specific examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, and chelate azo pigments; Examples include polycyclic pigments such as linone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, and threne pigments.
The hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, blue, red, orange and green can be used.
Specific examples of preferred organic pigments include C.I. I. Pigment Yellow, C.I. I. Pigment Red, C.I. I. pigment orange, C.I. I. pigment violet, C.I. I. pigment blue, and C.I. I. One or more types of each product number selected from Pigment Green.
Examples of extender pigments include silica, calcium carbonate, and talc.
The pigments may be used singly or in combination of two or more.

[Polymer (a) having an acid group]
The polymer (a) used in the present invention is not particularly limited as long as it has an acid group and at least pigment dispersibility.
Acid groups of the polymer (a) include carboxy groups (--COOM), sulfonic acid groups (--SO ₃ M), phosphoric acid groups (--OPO ₃ M ₂ ), etc., which are dissociated to release hydrogen ions. Groups exhibiting acidity, or their dissociated ionic forms (-COO ^- , -SO ₃ ^- , -OPO ₃ ^2- , -OPO ₃ ^- M) and the like can be mentioned. In the above chemical formula, M represents a hydrogen atom, alkali metal, ammonium or organic ammonium. Among these, a carboxy group (--COOM) is preferable from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase and improving the storage stability and print density.

The acid value of the polymer (a) is 120 mgKOH/g or more from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and print density, and reducing the deformation of the printed matter. , preferably 140 mgKOH/g or more, more preferably 160 mgKOH/g or more, still more preferably 180 mgKOH/g or more, still more preferably 200 mgKOH/g or more, still more preferably 220 mgKOH/g or more, and preferably 320 mgKOH/g g or less, more preferably 300 mgKOH/g or less, still more preferably 280 mgKOH/g or less. When the acid value is within the above range, the amount of acid groups and their neutralized acid groups is sufficient to ensure the dispersion stability of the pigment. It is also preferable from the viewpoint of the balance between the affinity between the polymer (a) and water and the interaction between the polymer (a) and the pigment.
The acid value of polymer (a) can be measured by the method described in Examples. Moreover, it can be calculated from the mass ratio of the constituent monomers.

At least part of the acid groups of the polymer (a) are neutralized from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and print density, and reducing the deformation of the printed matter. become.
Neutralization is preferably carried out so that the pH becomes 7 or more and 11 or less.
Examples of the neutralizing agent used for neutralizing the 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, improving the storage stability and printing density, and reducing the deformation of the printed matter, alkali metal hydroxides are preferred, and more preferred. It is one or more selected from 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, still more preferably 35 mol% or more, and preferably 80 mol% or less, more preferably 70 mol% or more. mol % or less, more preferably 60 mol % or less.
Here, the degree of neutralization (mol%) can be specifically determined by the following formula.
Degree of neutralization (mol%) = [{additional mass of neutralizing agent (g) / equivalent of neutralizing agent} / [{acid value of polymer (a) (mgKOH/g) x mass of polymer (a) (g )}/(56×1,000)]]×100

Examples of the polymer (a) include polyester-based resins, polyurethane-based resins, vinyl-based resins, and the like. Among them, vinyl-based resins are preferable, and vinyl-based resins containing a structural unit derived from a carboxy group-containing monomer and a structural unit derived from a hydrophobic monomer are more preferable. The vinyl resin may further contain structural units derived from at least one monomer selected from macromonomers and nonionic monomers.

(Carboxy group-containing monomer)
A carboxy group-containing monomer is used as a monomer component of the vinyl resin from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and print density, and reducing the deformation of the printed matter. preferably.
Carboxy group-containing monomers include (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, 2-methacryloyloxymethylsuccinic acid and the like, preferably (meth)acrylic acid. , more preferably acrylic acid.
As used herein, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid.
The carboxy group-containing monomers may be used alone or in combination of two or more.

(Hydrophobic monomer)
The hydrophobic monomer improves the adsorption of the polymer to the pigment, improves the dispersion stability of the pigment in the aqueous phase, improves storage stability and print density, and reduces deformation of printed matter. , is preferably used as a monomer component of the vinyl resin.
As used herein, the term "hydrophobic" means that the amount of the monomer dissolved in 100 g of deionized water at 25° C. until saturation is less than 10 g. The dissolved amount of the hydrophobic monomer is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of the adsorption of the polymer to the pigment.
The hydrophobic monomer is preferably at least one selected from aromatic group-containing monomers and (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol.
As used herein, "(meth)acrylate" is at least one selected from acrylate and methacrylate.
The hydrophobic monomers may be used singly or in combination of two or more.

The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having 6 to 22 carbon atoms, which may have a substituent containing a hetero atom, more preferably a styrene-based monomer and an aromatic It is at least one selected from group-containing (meth)acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500.
The styrenic monomer is preferably at least one selected from styrene, α-methylstyrene, 2-methylstyrene, vinyltoluene, and divinylbenzene, more preferably at least one selected from styrene and α-methylstyrene. is.
Aromatic group-containing (meth)acrylate is preferably at least one selected from phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate, more preferably benzyl (meth)acrylate .

The (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having 1 to 22 carbon atoms. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, (meth)acrylates having a linear alkyl group such as stearyl (meth)acrylate; isopropyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylates having a branched chain alkyl group such as isodecyl (meth)acrylate, isododecyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate; alicyclic alkyl such as cyclohexyl (meth)acrylate group-containing (meth)acrylates, and the like.

(Macromonomer)
The macromonomer is a compound having a polymerizable functional group at one end and a number average molecular weight of 500 or more and 100,000 or less. can be used as The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, more preferably a methacryloyloxy group.
The number average molecular weight of the macromonomer is preferably 1,000 or more and 10,000 or less. The number average molecular weight is measured by gel permeation chromatography using chloroform containing 1 mmol/L of dodecyldimethylamine as a solvent, using polystyrene as a standard substance.
From the viewpoint of the dispersion stability of the pigment in the aqueous phase, the macromonomer is preferably an aromatic group-containing monomer-based macromonomer or a silicone-based macromonomer, more preferably an aromatic group-containing monomer-based macromonomer.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing monomer-based macromonomer include the aromatic group-containing monomers described in the hydrophobic monomer above, preferably styrene and benzyl (meth)acrylate, more preferably styrene. .
Macromonomers can be used alone or in combination of two or more.
Specific examples of commercially available styrenic macromonomers include AS-6(S), AN-6(S), HS-6(S) (trade name of Toagosei Co., Ltd.) and the like.
Examples of silicone-based macromonomers include organopolysiloxanes having a polymerizable functional group at one end.

(Nonionic monomer)
A nonionic monomer can be used as a monomer component of the vinyl-based resin from the viewpoint of the dispersion stability of the pigment in the aqueous phase.
Nonionic monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; polypropylene glycol (n = 2 to 30, n is the average addition mole of oxypropylene groups The following n indicates the average added mole number of the oxyalkylene group.) Polyalkylene glycol (meth)acrylate such as (meth)acrylate, polyethylene glycol (n = 2 to 30) (meth)acrylate; methoxy Alkoxypolyalkylene glycol (meth)acrylate such as polyethylene glycol (n=1 to 30) (meth)acrylate; 29) (meth)acrylates and the like. Among them, polypropylene glycol (n=2 to 30) (meth)acrylates, alkoxypolyalkylene glycol (meth)acrylates, and phenoxy (ethylene glycol/propylene glycol copolymerization) (meth)acrylates are preferred.
A nonionic monomer can be used individually by 1 type or in combination of 2 or more types.
Specific examples of commercially available nonionic monomers include NK Ester M-20G, 40G, 90G, 230G, etc. of Shin-Nakamura Chemical Co., Ltd., Blenmer PE-90 and 200 of NOF Corporation. , 350, etc., PME-100, 200, 400, etc., PP-500, 800, 1000, etc., AP-150, 400, 550, etc., 50PEP-300, 50POEP-800B, 43PAPE-600B, etc. is mentioned.

As described above, the polymer (a) according to the present invention preferably includes structural units derived from one or more carboxy group-containing monomers selected from acrylic acid and methacrylic acid, and aromatic group-containing monomers and aliphatic alcohol-derived a structural unit derived from one or more hydrophobic monomers selected from (meth)acrylates having a hydrocarbon group, and a constitution derived from at least one monomer selected from macromonomers and nonionic monomers. It may be a vinyl resin containing units.

(Content of Structural Units Derived from Each Monomer in Vinyl Resin)
The content of the structural unit derived from each monomer in the vinyl resin improves the dispersion stability of the pigment in the aqueous phase, improves storage stability and print density, and reduces deformation of the printed matter. From, it is as follows.
The content of structural units derived from a carboxy group-containing monomer in the vinyl resin is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 70% by mass. % or less, more preferably 60 mass % or less, and still more preferably 50 mass % or less.
The content of the structural unit derived from the hydrophobic monomer in the vinyl resin is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and preferably 95% by mass. Below, more preferably 90% by mass or less, still more preferably 85% by mass or less.
When the vinyl resin contains a structural unit derived from a macromonomer, the content of the structural unit derived from the macromonomer in the vinyl resin is preferably 5% by mass or more, more preferably 10% by mass or more, and further It is preferably 15% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.
When the vinyl resin contains a structural unit derived from a nonionic monomer, the content of the structural unit derived from the nonionic monomer in the vinyl resin is preferably 3% by mass or more, more preferably 5% by mass or more. , more preferably 7% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.
The content of the structural unit derived from each monomer in the vinyl-based resin can be measured by analysis. In addition, the preferable range of the content of each monomer in the raw material monomers (content as unneutralized amount) in the production of the vinyl resin is the content of the structural unit derived from each monomer in the vinyl resin. It can be considered the same as the preferred range.

The total content of structural units derived from a carboxy group-containing monomer and structural units derived from a hydrophobic monomer in the vinyl resin is preferably 60% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more. and preferably 100% by mass or less.
The mass ratio of the content of structural units derived from carboxy group-containing monomers to the content of structural units derived from hydrophobic monomers in the vinyl resin [content of structural units derived from carboxy group-containing monomers/structure derived from hydrophobic monomers Unit content] is preferably 0.1 or more, more preferably 0.15 or more, still more preferably 0.2 or more, and preferably 2 or less, more preferably 1.5 or less, still more preferably It is 1 or less, more preferably 0.7 or less, and even more preferably 0.5 or less.

The vinyl resin is produced by copolymerizing the raw material monomers by known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these polymerization methods, the solution polymerization method is preferred. Moreover, there is no restriction on the chain mode of the polymerization monomers, and any polymerization mode such as random, block, or graft may be used.

The weight average molecular weight of polymer (a) is preferably 2,000 or more, more preferably 5,000 or more, still more preferably 7,000 or more, and preferably 100,000 or less, more preferably 50,000. Below, more preferably 30,000 or less, still more preferably 20,000 or less. When the weight-average molecular weight of the polymer (a) is within the above range, it has sufficient adsorptive power to pigments and can exhibit dispersion stability.
The weight average molecular weight is measured by the method described in Examples.

(crosslinking agent)
In the present invention, the polymer (a) is crosslinked with a crosslinking agent from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and print density, and reducing the deformation of the printed matter. It is preferable to be As a result, the polymer (a) is strongly adsorbed or immobilized on the surface of the pigment, the aggregation of the pigment in the aqueous phase is suppressed, the dispersion stability of the pigment is improved, and the swelling of the polymer is also suppressed. It is believed that the storage stability is improved.
From the viewpoint of reacting with the acid groups of the polymer (a), the cross-linking agent has a water solubility (mass ratio) of preferably 50% or less, more preferably 40% or less, and even more preferably 35% or less. be. Here, the water solubility % (mass ratio) refers to the dissolution rate (%) when 10 parts by mass of the cross-linking agent is dissolved in 90 parts by mass of water at room temperature of 25°C.

The cross-linking agent is a polyfunctional compound, and the cross-linkable functional group of the polyfunctional compound preferably reacts with the acid group of the polymer (a) to form a covalent bond. The covalent bond is preferably one or more selected from ester bond, thioester bond, amide bond, amino bond, ether bond, thioether bond, carbonyl bond, thiocarbonyl bond and sulfonyl bond, more preferably ester bond, It is one or more selected from a thioester bond and an amide bond. The crosslinkable functional group of the polyfunctional compound is not particularly limited as long as it can form the covalent bond described above.
The crosslinkable functional group is preferably one or more selected from an epoxy group, an isocyanate group, an aziridino group, an amino group and an oxazoline group, more preferably an epoxy group. In addition, the concept of an epoxy group includes a glycidyl group.

As a polyfunctional compound having an epoxy group, that is, a polyfunctional epoxy compound, from the viewpoint of crosslinking efficiency, preferably a compound having two or more epoxy groups in the molecule, more preferably a compound having two or more glycidyl ether groups, still more preferably It is a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group with 3 or more and 8 or less carbon atoms.
The molecular weight of the cross-linking agent is preferably 120 or more from the viewpoints of easiness of reaction, improvement of dispersion stability of the pigment in the aqueous phase, improvement of storage stability and print density, and reduction of deformation of the printed matter. It is more preferably 150 or more, still more preferably 200 or more, and preferably 2,000 or less, more preferably 1,500 or less, still more preferably 1,000 or less.
When the cross-linking agent is a polyfunctional epoxy compound, the epoxy equivalent of the cross-linking agent is preferably 90 or more, more preferably 100 or more, still more preferably 110 or more, and preferably 300 or less, more preferably 200 or less. , more preferably 150 or less.
When the cross-linking agent is a polyfunctional epoxy compound, the number of epoxy groups in the cross-linking agent is such that the cross-linking reaction is efficiently performed to improve the dispersion stability of the pigment in the aqueous phase, and improve the storage stability and print density. and from the viewpoint of reducing deformation of the printed matter, it is 2 or more per molecule, and preferably 6 or less per molecule, more preferably 4 or less, further preferably 3 or less from the viewpoint of market availability. be.

Specific examples of cross-linking agents include polypropylene glycol diglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, and neopentyl. Polyglycidyl ethers such as glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A type diglycidyl ether and the like are included. Among these, one or more selected from trimethylolpropane polyglycidyl ether and pentaerythritol polyglycidyl ether are preferred, and trimethylolpropane polyglycidyl ether is more preferred.

The degree of crosslinking is preferably 10 mol% or more, more preferably 30, from the viewpoints of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and print density, and reducing deformation of the printed matter. mol % or more, and preferably 80 mol % or less, more preferably 70 mol % or less, even more preferably 60 mol % or less, and even more preferably 50 mol % or less.
The degree of crosslinking is the degree of crosslinking calculated from the equivalent weight of the acid group of the polymer (a) and the equivalent weight of the crosslinkable functional group of the crosslinking agent, and is expressed as "number of molar equivalents of the crosslinkable functional group of the crosslinking agent/polymer (a) is represented by the number of molar equivalents of acid groups possessed by ".

The polymer (a) exists in the aqueous phase of the emulsion ink of the present invention in a state of being adsorbed to the pigment, a state of containing the pigment (a particle form encapsulating (encapsulating) the pigment, (including particle morphology with uniformly dispersed pigment) and morphology without adsorbed pigment. From the viewpoint of the dispersion stability of the pigment, in the present invention, the form of particles in which the polymer (a) contains the pigment (hereinafter also referred to as "pigment-containing polymer particles") is preferable, and the form of particles encapsulating the pigment is preferably more preferred.

[Surfactant]
The emulsion ink of the present invention preferably contains a surfactant in the aqueous phase. Surfactants improve the dispersion stability of pigments in the aqueous phase, reduce the energy of the interface between the aqueous phase and the oil phase, contribute to the formation of a fine and stable dispersed phase, and further improve storage stability and printability. It is believed to improve concentration.
The surfactant is preferably a nonionic surfactant, more preferably an acetylene glycol-based surfactant, a polyoxyalkylene alkyl ether-type surfactant, a polyether-modified silicone-based surfactant, and a fluorine-based surfactant. It is one or more selected from surfactants, more preferably one selected from acetylene glycol-based surfactants and polyether-modified silicone-based surfactants, and still more preferably acetylene glycol-based surfactants.
The HLB (hydrophilic-lipophilic balance) value of the nonionic surfactant is preferably 6 or more, more preferably 8 or more, still more preferably 10 or more, still more preferably 12 or more, and preferably 20 or less, It is more preferably 18 or less.
Here, the HLB value is a value that indicates the affinity of a surfactant for water and oil, and can be obtained from the following equation according to Griffin's method. In the following formula, the "hydrophilic group contained in the surfactant" includes, for example, a hydroxyl group and an ethyleneoxy group.
HLB = 20 x [(sum of formula weights of hydrophilic groups contained in surfactant)/(molecular weight of surfactant)]

The acetylene glycol-based surfactant is preferably an ethylene oxide (hereinafter also referred to as "EO") adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl- EO adduct of 4-octyne-3,6-diol, EO adduct of 2,5-dimethyl-3-hexyne-2,5-diol, 2,5,8,11-tetramethyl-6-dodecine-5 EO adduct of ,8-diol and EO adduct of 3,5-dimethyl-1-hexyn-3-ol, more preferably 2,4,7,9-tetramethyl- EO adduct of 5-decyne-4,7-diol, EO adduct of 3,6-dimethyl-4-octyne-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol and more preferably an EO adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol.
The average EO addition mole number of the EO adduct used as the acetylene glycol-based surfactant is preferably 5 or more, more preferably 6 or more, still more preferably 7 or more, and even more preferably 8 or more, and preferably is 40 or less, more preferably 36 or less, still more preferably 32 or less.

Commercially available acetylene glycol-based surfactants include Surfynol 465 (2,4,7,9-tetramethyl-5-decyne-4,7-diol EO average 10 mol adduct, HLB : 13), same 485 (2,4,7,9-tetramethyl-5-decyne-4,7-diol EO average 30 mol adduct, HLB: 17), acetylenol E81 manufactured by Kawaken Fine Chemicals Co., Ltd. ( EO average 8.1 mol adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, HLB: 13.0), E100 (2,4,7,9-tetramethyl EO average 10 mol adduct of 5-decyne-4,7-diol, HLB: 13.9), the same E200 (EO of 2,4,7,9-tetramethyl-5-decyne-4,7-diol average 20 mol adduct, HLB: 16.4) and the like.

As polyether-modified silicone-based surfactants, those having a structure in which side chains and/or terminal hydrocarbon groups of silicone oil are substituted with polyether groups are preferred. As the polyether group, a polyethyleneoxy group, a polypropyleneoxy group, an ethyleneoxy group (EO) and a propyleneoxy group (trimethyleneoxy group or propane-1,2-diyloxy group; PO) are added blockwise or randomly. A polyalkyleneoxy group is preferable, and a compound in which a polyether group is grafted to a silicone main chain, a compound in which a silicone and a polyether group are bonded in a block form, or the like can be used.
Commercially available polyether-modified silicone surfactants include KF-353, KF-355A, KF-642, etc. manufactured by Shin-Etsu Chemical Co., Ltd.; Silface SAG005, etc. manufactured by Nisshin Chemical Co., Ltd.; and BYK-348 manufactured by BYK-Chemie Japan.

[Water-soluble organic solvent]
The aqueous phase of the emulsion ink of the present invention further includes a water-soluble organic solvent from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and printing density, and reducing the deformation of printed matter. It is preferable to contain
A water-soluble organic solvent is 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 not particularly limited as long as it is commonly used in the aqueous phase of water-in-oil emulsion inks and forms a single phase with water. alcohols, polyhydric alcohol alkyl ethers, ketones, cyclic ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, and the like. Among these, one or more selected from polyhydric alcohols and polyhydric alcohol alkyl ethers are preferred.
The boiling point of the water-soluble organic solvent is preferably 60°C or higher, more preferably 90°C or higher, still more preferably 150°C or higher, and preferably 350°C or lower, more preferably 330°C or lower, still more preferably 310°C. It is below.
The water-soluble organic solvents may be used singly or in combination of two or more as long as they form a single phase with water.

In the present invention, the aqueous phase may contain an oil-in-water polymer emulsion, a viscosity modifier, an antifoaming agent, an antiseptic, an antifungal agent, an anticorrosive, etc., as long as the effects of the present invention are not impaired.

<Oil phase>
The oil phase of the emulsion ink of the invention contains a water-insoluble organic solvent and an emulsifier.

[Water-insoluble organic solvent]
The water-insoluble organic solvent refers to an organic solvent that dissolves less than 10 mL in 100 mL of water at 25°C.
Both non-polar organic solvents and polar organic solvents can be used as the water-insoluble organic solvent. These may be used singly or in combination of two or more as long as they form a single continuous phase.

Examples of the non-polar organic solvent include petroleum hydrocarbon solvents such as paraffinic, isoparaffinic and naphthenic hydrocarbon solvents, alicyclic hydrocarbon solvents and aromatic hydrocarbon solvents.
The initial boiling point of the nonpolar 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.
Examples of commercially available non-polar organic solvents include Isopar (trade name) series, Exol (trade name) series (both manufactured by ExxonMobil); AF Solvent (trade name) series (manufactured by JXTG Nippon Oil & Energy Corporation), and the like. mentioned.

Examples of the polar organic solvent include fatty acid ester-based solvents and higher alcohol-based solvents.
Fatty acid ester solvents include isononyl isononanoate, isodecyl isononanoate, isotridecyl isononanoate, methyl laurate, isopropyl 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, C13-30 fatty acid esters such as tall oil isobutyl, propylene glycol monocaprate, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, trimethylolpropane tri-2-ethylhexanoate, glyceryl tri-2-ethylhexanoate is mentioned.
Higher alcohol-based solvents include higher alcohols having 12 to 20 carbon atoms, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, and oleyl alcohol.

When a surfactant is contained in the aqueous phase and an acetylene glycol-based surfactant is used as the surfactant, the water-insoluble organic solvent is preferably a fatty acid ester from the viewpoint of storage stability. system solvent.
When a surfactant is contained in the aqueous phase, and when a polyether-modified silicone-based surfactant is used as the surfactant, the water-insoluble organic solvent is preferably It is a petroleum hydrocarbon solvent.

〔emulsifier〕
The emulsifier according to the present invention is not particularly limited as long as it is contained in the oil phase and can emulsify the water phase to form a water-in-oil emulsion, but lipophilic emulsifiers such as surfactants and polymer dispersants. is 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 acids such as polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate; Ester; Glycerin fatty acid ester such as glycerol monostearate and glycerol monooleate; Polyoxyethylene glycerin fatty acid ester such as polyoxyethylene sorbitol fatty acid ester and polyoxyethylene glycerin vegetable oil fatty acid ester; Sucrose stearate, sucrose palmitic acid Ester, sucrose fatty acid ester such as sucrose oleate, sucrose erucate, sucrose laurate; polyethylene glycol fatty acid ester; polyglycerol condensed ricinoleate; polyoxyethylene alkyl ether; polyoxyethylene alkylphenyl ether polyoxyethylene alkylamine/fatty acid amide; polyoxyethylene polyoxypropylene alkyl ether, and the like.
The lipophilic surfactants may be used singly or in combination of two or more.

Lipophilic polymer dispersants include polyester polyimines, polyester polyamines, polyalkylolaminoamides and their salts, polyether polyamines, hydroxyl group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high-molecular-weight acid esters, high-molecular-weight poly Carboxylic acid salt, long-chain polyaminoamide and polar acid ester salt, high molecular weight unsaturated acid ester, modified polyurethane, modified poly(meth)acrylate, polyether ester type anionic surfactant, naphthalenesulfonic acid formalin condensate salt, Examples include polyoxyethylene alkyl phosphate, polyoxyethylene nonylphenyl ether, stearylamine acetate, and the like. Among these, one or more selected from polyester polyimine, polyester polyamine, polyalkylolaminoamide and its salt, and polyether polyamine are preferable, and polyester polyimine is more preferable. You may use these individually by 1 type or in combination of 2 or more types.

The polyester polyimine preferably comprises an amide or salt formed by reacting a polyalkyleneimine, such as polyethyleneimine, with a polyester having carboxyl groups, such as a polymer of hydroxystearic acid or a polymer of cyclic esters. , dispersants having two or more polyester chains attached to a polyalkyleneimine backbone.
Examples of commercially available lipophilic polymer dispersants include Solsperse (trade name) series manufactured by Nippon Lubrizol; Efka (trade name) series manufactured by Efka CHEMICALS; ) series; Ajinomoto Co., Inc. Ajisper (trade name) series and the like.

In the present invention, the oil phase does not contain a colorant such as a pigment from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and print density, and reducing the deformation of the printed matter. is preferred.

[Method for producing water-in-oil emulsion ink]
The water-in-oil emulsion ink of the present invention can be produced by mixing an oil phase component and an aqueous phase component and emulsifying the aqueous phase. Among them, from the viewpoint of improving the dispersion stability of the pigment in the aqueous phase, improving the storage stability and print density, and reducing the deformation of the printed matter, the pigment is dispersed in the aqueous medium with the polymer (a). It is preferably obtained by a method including a step of emulsifying an aqueous pigment dispersion (hereinafter also referred to as "aqueous pigment dispersion") in an oil phase.
The "aqueous medium" in the water-based pigment dispersion means a medium in which water accounts for the largest proportion of the medium in which the pigment is dispersed.

[Production of aqueous pigment dispersion]
More preferably, the water-based pigment dispersion is efficiently produced by a method including step 1 below.
Step 1: A step of dispersing a pigment mixture containing a pigment, a polymer (a) and water to obtain an aqueous pigment dispersion in which the pigment is dispersed in an aqueous medium with the polymer (a).

(Step 1)
Specifically, step 1 is a method (1) of dispersing a pigment mixture obtained by mixing a previously prepared aqueous dispersion of the polymer (a) and a pigment; pigment, polymer (a), organic solvent, water and, if necessary, a neutralizing agent, a surfactant, etc., after obtaining a dispersion by dispersing the pigment mixture, and then removing the organic solvent from the dispersion by the method (2) or the like. . Among them, the method (1) is preferable from the viewpoint of improving storage stability and print density.

In the case of method (1), it is preferable to have the following step 1-1 before step 1.
Step 1-1: Part of the acid groups of the polymer (a) are neutralized with a neutralizing agent to obtain an aqueous dispersion of the polymer (a) (hereinafter also referred to as "aqueous polymer dispersion (D)"). Step Preferable neutralizing agent used for neutralization in Step 1-1 and the degree of neutralization of the polymer (a) are as described above.
The neutralizing agent is preferably used as an aqueous solution from the viewpoint of sufficiently and uniformly promoting neutralization.

In the dispersion treatment in step 1, the pigment particles can be atomized to a desired particle size only by the main dispersion by shearing stress. , and preferably further dispersed.
As a dispersing machine used for pre-dispersion, generally used mixing and stirring devices such as anchor blades and disper blades can be used.
Means for imparting shear stress used for this dispersion include, for example, 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 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 later is also adjusted. be able to.
The treatment pressure is preferably 60 MPa or more and 300 MPa or less from the viewpoint of productivity and economy.
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. .

When the pigment mixture contains an organic solvent, the aqueous pigment dispersion can be obtained by removing the organic solvent by a known method. The organic solvent in the resulting aqueous pigment dispersion is preferably substantially removed, but may remain as long as the object of the present invention is not impaired. The amount of residual organic solvent is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.

(Step 2)
When the polymer (a) is crosslinked with a crosslinking agent, the aqueous pigment dispersion is preferably obtained by a method including 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 to obtain an aqueous pigment dispersion in which the polymer (a) is crosslinked.

In step 2, the polymer (a) in which the pigment is dispersed in the water-based pigment dispersion obtained in step 1 is crosslinked with a cross-linking agent. A water-based pigment dispersion dispersed in a medium can be obtained.
Preferred cross-linking agents and degrees of cross-linking are as described above.

The temperature of the cross-linking treatment is preferably 40° C. or higher, more preferably 50° C. or higher, still more preferably 60° C. or higher, and is preferably 95° C. or lower, more preferably 85° C. or lower, and still more preferably 75° C. or lower. is.
The time for the cross-linking treatment is preferably 0.5 hours or more, more preferably 1 hour or more, still more preferably 3 hours or more, and preferably 12 hours or less, from the viewpoint of completion of the cross-linking reaction and economic efficiency. It is preferably 10 hours or less, more preferably 8 hours or less.

The non-volatile component concentration (solid content concentration) of the water-based pigment dispersion is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably from the viewpoint of improving dispersion stability and facilitating ink production. is 40% by mass or more, and preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. The solid content concentration of the aqueous pigment dispersion is measured by the method described in Examples.

The cumulant average particle diameter of the water-based pigment dispersion is preferably 50 nm or more, more preferably 60 nm or more, and still more preferably 70 nm or more, from the viewpoint of reducing coarse particles and improving storage stability and print density. It is preferably 200 nm or less, more preferably 160 nm or less, still more preferably 150 nm or less.
The cumulant average particle size of the water-based pigment dispersion is measured by the method described in Examples.

The aqueous pigment dispersion is preferably one in which pigment-containing polymer particles are dispersed in an aqueous medium containing water as the main medium. Here, the form of the pigment-containing polymer particles is not particularly limited as long as the particles are formed from at least the pigment and the polymer (a). is preferably
The water-based pigment dispersion may contain 1% by mass or more and 10% by mass or less of glycerin, polyethylene glycol, or the like as a humectant to prevent drying, and may also contain additives such as antifungal agents.
The above additives may be blended when dispersing the pigment in the polymer (a), or may be blended after dispersing the pigment or after crosslinking.

In the present invention, when the aqueous phase of the emulsion ink contains the aforementioned surfactant, water-soluble organic solvent, or optional component, the water-based pigment dispersion and, if necessary, the surfactant, water-soluble organic solvent, Alternatively, an emulsion ink can be prepared by mixing optional components or adjusting the water content to prepare an aqueous phase component, and then mixing and emulsifying the aqueous phase component and the oil phase component.
The emulsion ink of the present invention may further contain humectants, humectants, penetrants, dispersants, surfactants, viscosity modifiers, antifoaming agents, preservatives, and other commonly used water-in-oil emulsion inks. Various additives such as an antifungal agent and an anticorrosive agent can be added, and further filtration treatment using a filter or the like can be performed.
The content of each component of the emulsion ink of the present invention and the physical properties of the ink are as follows.

The pigment content in the emulsion ink 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 print density. From the viewpoint of lowering viscosity and improving storage stability, the content is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 7% by mass or less.
The content of the pigment in the aqueous phase of the emulsion ink is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more, from the viewpoint of improving print density. From the viewpoint of lowering the viscosity of the ink and improving storage stability, the content is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less.

The total content of the pigment and polymer (a) in the emulsion ink is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and preferably 18% by mass or less. , more preferably 13% by mass or less, and still more preferably 10% by mass or less.

The mass ratio of the content of the pigment to the content of the polymer (a) in the emulsion ink [pigment/polymer (a)] improves the dispersion stability of the pigment in the aqueous phase, and improves storage stability and print density. From the viewpoint of improving the is 85/15 or less, more preferably 80/20 or less.

The water content in the emulsion ink is 5% by mass or more, preferably 7% by mass or more, from the viewpoint of improving print density, and from the viewpoint of improving storage stability and reducing deformation of printed matter. from the viewpoint of increasing the content, it is 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 12% by mass or less.

When the water phase of the emulsion ink contains a surfactant, the content of the surfactant in the emulsion ink is preferably 0.5% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of improving storage stability and printing density. is 1.0% by mass or more, more preferably 1.5% by mass or more, and 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.

The content of the water-soluble organic solvent in the emulsion ink is preferably 0.5% by mass or more from the viewpoint of adjusting the viscosity of the emulsion ink, improving the storage stability, and reducing deformation of the printed matter. More preferably 1.0% by mass or more, still 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, and still more preferably 5% by mass or less, more preferably 3% by mass or less.

The content of the water-insoluble organic solvent in the emulsion ink is preferably 10% by mass or more, more preferably 10% by mass or more, from the viewpoints of adjusting the viscosity of the emulsion ink, improving storage stability, and reducing deformation of printed matter. is 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, and from the viewpoint of improving print density, preferably 90% by mass or less, more preferably 80% by mass or less, More preferably, it is 75% by mass or less.

The content of the oil-soluble emulsifier in the emulsion ink is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more, from the viewpoint of improving storage stability. From the viewpoint of adjusting the viscosity of the ink, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

(Viscosity of emulsion ink)
The viscosity of the emulsion ink of the present invention at 25° C. is preferably 2 mPa·s or more, more preferably 5 mPa·s or more, and still more preferably 7 mPa·s or more. From the viewpoint of using the ink for inkjet recording, it is preferably 20 mPa·s or less, more preferably 17 mPa·s or less, and even more preferably 15 mPa·s or less. The viscosity is measured by the method described in Examples.

The emulsion ink of the present invention is preferably used for inkjet recording. An image or the like can be recorded by loading the emulsion ink into a known inkjet recording apparatus and ejecting the ink as ink droplets onto a printing medium.
The inkjet recording apparatus can be of any type such as a thermal type or a piezo type.
The print media to be used include highly water-absorbing plain paper, low water-absorbing coated paper, and non-water-absorbing resin film. Examples of coated paper include general-purpose glossy paper, multicolor foam gloss paper, and the like. The resin film is preferably at least one selected from polyester film, polyvinyl chloride film, polypropylene film and polyethylene film. A corona-treated substrate may be used for the resin film.
Among these, plain paper is preferable from the viewpoint of print density and deformation of printed matter.

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

(1) Measurement of weight-average molecular weight of polymer (a) A gel was prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol/L and 50 mmol/L, respectively, as an eluent. Permeation chromatography method [GPC device (model: HLC-8320GPC, manufactured by Tosoh Corporation), columns (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H, above, trade names manufactured by Tosoh Corporation), flow rate: 0.5 mL/min], monodisperse polystyrene kits with known molecular weights [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500), above, trade names manufactured by Tosoh Corporation].
A sample to be measured was obtained by mixing 0.1 g of polymer (a) with 10 mL of the eluent in a glass vial, stirring with a magnetic stirrer at 25° C. for 10 hours, and applying a syringe filter (trade name: DISMIC-13HP, membrane filter material : Hydrophilic PTFE, pore size 0.2 μm, manufactured by Advantech).

(2) Measurement of acid value of polymer (a) In JIS K0070, 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)]. Except for this, measurements were made according to JIS K0070.

(3) Measurement of Cumulant Average Particle Size A cumulant analysis was performed using a laser particle analysis system (model: 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 integration times, and 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 to solid concentration).

(4) Measurement of solid content concentration 10.0 g of sodium sulfate that has been made constant in a desiccator is weighed into a 30 mL polypropylene container (φ = 40 mm, height = 30 mm), and about 1.0 g of a sample is added thereto. After mixing, the mixture was accurately weighed, maintained at 105° C. for 2 hours to remove volatile matter, allowed to stand in a desiccator at room temperature (25° C.) for 15 minutes, and weighed. The mass of the sample after removing the volatile matter was defined as the solid content, and the mass of the added sample was divided to obtain the solid content concentration.

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

<Preparation of polymer (a)>
Preparation example 1
A raw material monomer was prepared by mixing 19.2 parts of acrylic acid, 70.8 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 material monomer are added and mixed, and the nitrogen gas is sufficiently replaced. went to
On the other hand, in the dropping funnel, the rest of the raw material monomer, 0.27 parts of the polymerization chain transfer agent, 40 parts of MEK and an azo radical polymerization initiator (trade name: V-65, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 2, 2′-Azobis(2,4-dimethylvaleronitrile)) (hereinafter referred to as “V-65”) 1.1 parts mixed solution was added, and under a nitrogen atmosphere, the raw material monomers in the reaction vessel were stirred to 65 C., and the mixture in the dropping funnel was added dropwise over 3 hours. After stirring for 2 hours from the end of the dropwise addition while maintaining the contents in the reaction vessel at 65° C., a solution of 0.15 parts of the polymerization initiator dissolved in 2.5 parts of MEK was added, and the mixture was further heated at 65° C. for 2 hours and 70°C. C. for 2 hours to obtain a solution of polymer (a1) having a carboxy group (weight average molecular weight: 11,000, acid value: 150 mgKOH/g).

Preparation Example 2 and Comparative Preparation Example 1
A solution of polymers (a2) and (ac1) having carboxy groups was obtained in the same manner as in Preparation Example 1, except that the composition of the raw material monomers was changed as shown in Table 1. Table 1 shows the weight average molecular weight and acid value.

Preparation example 3
37.0 parts of methacrylic acid, 33.0 parts of benzyl acrylate, styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6S, number average molecular weight: 6,000, solid content concentration 50%) (hereinafter referred to as "styrene macromer ”) 20.0 parts (20.0 parts as solid content), polypropylene glycol monomethacrylate (manufactured by NOF Corporation, trade name: Blemmer PP-800, propylene oxide average added mole number 13, terminal: hydroxyl group) (hereinafter referred to as "PP-800") was mixed with 10.0 parts to prepare a raw material monomer. 10 parts of MEK, 0.3 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the raw material monomers were added and mixed in a reaction vessel, and nitrogen gas was sufficiently replaced.
On the other hand, a mixture of the rest of the raw material monomers, 0.27 parts of the polymerization chain transfer agent, 40 parts of MEK, and 1.1 parts of an azo radical polymerization initiator (V-65) is added to the dropping funnel, and thereafter prepared. In the same manner as in Example 1, a solution of polymer (a3) having carboxy groups (weight average molecular weight: 14,000, acid value: 240 mgKOH/g) was obtained.

<Production of aqueous polymer dispersion (D)>
Production Example 1-1
To 80.0 parts of polymer (a1) obtained by drying the polymer solution obtained in Preparation Example 1 under reduced pressure, 316.8 parts of ion-exchanged water and 20.2 parts of 5N sodium hydroxide aqueous solution were added to obtain polymer (a1). Neutralization was carried out so that the ratio of the number of moles of sodium hydroxide to the number of moles of the carboxyl group of was 40 mol % (degree of neutralization: 40 mol %). The aqueous solution was stirred at 150 rpm and heated at 90° C. for 5 hours to obtain an aqueous polymer dispersion (D1) (solid concentration: 20%).

Production Examples 1-2 to 1-3, Comparative Production Example 1-1
In Production Example 1-1, polymer water Dispersions (D2) to (D3) and (DC1) (all solid content: 20%) were obtained.

<Production of aqueous pigment dispersion (i)>
Production example 2-1
To 164.6 parts of the aqueous polymer dispersion (D1) obtained in Production Example 1-1, 313.3 parts of ion-exchanged water and 100.0 parts of a black pigment (carbon black, trade name: MONARCH717, manufactured by Cabot Corporation) were added. In addition, using a disper (manufactured by Asada Iron Works Co., Ltd., trade name: Ultra Disper), the mixture was stirred at 20° C. for 60 minutes under the condition of rotating the disper blade at 7,000 rpm. The resulting mixture was subjected to 10 passes of dispersion treatment with a microfluidizer (manufactured by Microfluidics, trade name) at a pressure of 200 MPa to obtain a dispersion treated product.
The obtained dispersed product was filtered with a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation) to remove coarse particles. After removal, ion-exchanged water was added to obtain an aqueous pigment dispersion (i-1) (mass ratio [pigment/polymer (a)]=76/24) with a solid content concentration of 20%.

Production Examples 2-2 to 2-11, Comparative Production Example 2-1
In Production Example 2-1, as shown in Tables 3 and 4, the water-based Pigment dispersions (i-2) to (i-11) and (i-C1) were obtained.
The pigments in Tables 3 and 4 are as follows.
Monarch717: black pigment (carbon black, trade name: MONARCH717, manufactured by Cabot Corporation, DBP oil absorption 53 mL/100 g)
Monarch880: black pigment (carbon black, trade name: MONARCH880, manufactured by Cabot Corporation, DBP oil absorption 105mL/100g)
Printex85: black pigment (carbon black, trade name: PRINTEX85, manufactured by Degussa, DBP oil absorption 48mL/100g)
PY74: Yellow pigment (C.I. Pigment Yellow 74, trade name: FastYellow FG, manufactured by Sanyo Color Co., Ltd.)
PR122: Magenta pigment (C.I. Pigment Red 122, trade name: Chromofine Magenta 6887, manufactured by Dainichiseika Kogyo Co., Ltd.)
PB15:3: Cyan pigment (CI Pigment Blue 15:3, trade name: TGR, manufactured by DIC Corporation)

<Production of crosslinked aqueous pigment dispersion>
Production Example 3-1
100.0 parts (solid content concentration 20%) of the aqueous pigment dispersion (i-1) obtained in Production Example 2-1 was placed in a glass bottle with a screw cap, and 38 mol of all carboxy groups possessed by the polymer (a1). % (crosslinking degree 38 mol%), trimethylolpropane polyglycidyl ether (trade name: Denacol EX-321, manufactured by Nagase ChemteX Corporation, epoxy equivalent: 139, water solubility: 27% ) (hereinafter referred to as “EX-321”) was added, and the mixture was sealed and heated at 70° C. for 5 hours while stirring with a stirrer. After 5 hours, the mixture was cooled to room temperature and filtered with a 25 mL needleless syringe (manufactured by Terumo Corporation) fitted with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation), Water-based black pigment dispersion (hereinafter also referred to as "black pigment dispersion") Bk-I (mass ratio [pigment/crosslinked polymer (a)] = 73.5/26.5, pigment content: 33.5. 6%, solid concentration: 45.7%, cumulant average particle size: 95 nm).

Production Examples 3-2 to 3-11, Comparative Production Example 3-1
In Production Example 3-1, in the same manner as in Production Example 3-1 except that the type of aqueous pigment dispersion (i) or the amount of cross-linking agent was changed as shown in Tables 5 and 6, Tables 5 and 6 Black pigment dispersions Bk-II to Bk-V and Bk-CI shown in , aqueous yellow pigment dispersions (hereinafter also referred to as "yellow pigment dispersions") YI to Y-II, aqueous magenta pigment dispersions (hereinafter , "magenta pigment dispersion") MI to M-II, and water-based cyan pigment dispersion (hereinafter also referred to as "cyan pigment dispersion") CI to C-II.

<Production of water-in-oil emulsion ink>
Example 1
An oil phase component was prepared by mixing 4.0 parts of Solsperse 11200 as an emulsifier, 28.5 parts of isopropyl myristate and 45.0 parts of methyl laurate as water-insoluble organic solvents.
Next, 17.9 parts of black pigment dispersion Bk-I, 2.0 parts of Surfynol 465 as a surfactant, 0.6 parts of deionized water, and 2.0 parts of glycerin as a water-soluble organic solvent are mixed. to prepare an aqueous phase component.
Using a homogenizer (trade name: ULTLRA-TURRAX, model: T25 digital, shaft generator (model: S25N-25F), both manufactured by IKA Japan Co., Ltd.), the oil phase component was stirred at 5,000 rpm. The aqueous phase components were added dropwise while stirring at . Thereafter, the mixture was stirred at 12,000 rpm for 3 minutes to obtain a water-in-oil (W/O) emulsion ink Bk-1 having a pigment content of 6.0%. The emulsion ink Bk-1 had a viscosity of 9.6 mPa·s.

Examples 2-18, Comparative Examples 1-2
In Example 1, the content of the pigment was changed to 6.0 in the same manner as in Example 1, except that the types or amounts of the components constituting the oil phase component and the water phase component were changed as shown in Table 7 or Table 8. % water-in-oil (W/O) emulsion ink was obtained. Tables 7 and 8 show the viscosity of each emulsion ink.
In addition, each component of Table 7 and Table 8 is as follows.
Surfynol 465 (trade name, EO adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, average number of moles of EO added: 10, HLB: 13, Nissin Chemical Industry Co., Ltd. made)
Surfynol 485 (trade name, EO adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, average number of moles of EO added: 30, HLB: 17, Nissin Chemical Industry Co., Ltd. made)
Silface SAG005 (trade name, polyether-modified silicone, HLB: 7, manufactured by Nissin Chemical Industry Co., Ltd.)
Glycerin (concentrated glycerin for cosmetics, manufactured by Kao Corporation)
Solsperse 11200 (trade name, polymer dispersant, active ingredient 50%, manufactured by Lubrizol)
Solsperse 18000 (trade name, polymer dispersant, active ingredient 100%, manufactured by Lubrizol)
Isopropyl myristate (trade name: Excepar IPM, manufactured by Kao Corporation)
Methyl laurate (trade name: Excepar ML-85, manufactured by Kao Corporation)
Isopar M (trade name, isoparaffin-based solvent, manufactured by Ando Parachemie Co., Ltd.)

<Evaluation test of water-in-oil emulsion ink>
Using the emulsion inks obtained in Examples and Comparative Examples, storage stability, deformation of printed matters, and printing density were evaluated. The results are shown in Tables 7 and 8.

[Evaluation of storage stability]
The resulting emulsion ink was placed in a 100 mL screw-vial bottle and stored at 60° C. After standing, the emulsion ink was visually observed for separation of oil and water phases and aggregated sediment, and evaluated according to the following criteria. .
A: There was no separation of the oil phase and the water phase of the emulsion ink after storage for 1 week, and there was no aggregated sediment.
B: Separation of the oil phase and water phase of the emulsion ink or aggregation sediment was found after storage for one week.
C: There was separation of the oil phase and the water phase of the emulsion ink after storage for 1 day, or there was aggregation and sediment.

[Evaluation of deformation (curling amount) of printed matter]
An inkjet printer (trade name: Business Printer PX-105, manufactured by Seiko Epson Corporation) was filled with the obtained emulsion ink, and was printed on plain paper (trade name: Xerox Business 4200 copy paper, manufactured by Fuji Xerox Co., Ltd.) was printed with a solid image. The resulting printed material was placed on a horizontal table with the printed surface facing up, and left under the same conditions for one day. After being left for one day, the heights of the four corners of the printed matter from the horizontal table were measured, and the average value was calculated as the amount of curl to evaluate the deformation of the printed matter. A smaller curl amount indicates a smaller deformation of the printed matter.

[Evaluation of Print Density]
An inkjet printer (business printer PX-105) is filled with the obtained emulsion ink, and a solid image is printed on plain paper (Xerox business 4200 copy paper) under an environment of room temperature of 23° C. and relative humidity of 50% RH. The printed matter obtained was left under the same conditions for one day. The printing density of the printed material after being left for one day was measured using an optical densitometer (trade name: SpectroEye, manufactured by GretagMacbeth). The measurement was performed at arbitrary 10 locations by changing the measurement location of the printed matter, and the average value was taken as the print density.

As can be seen from Tables 7 and 8, in Examples 1 to 18, compared to Comparative Examples 1 and 2, the pigment contained in the water phase is dispersed with the polymer (a), and the water content in the emulsion ink is Since the content is 40% by mass or less, the storage stability is excellent, the print density is high, and the amount of curling is small. In addition, the viscosities of the emulsion inks of Examples 1 to 18 were all in the appropriate range for inkjet recording.

According to the emulsion ink and the method for producing the emulsion ink of the present invention, it is possible to obtain a printed matter which is excellent in storage stability, has a high printing density when printed on plain paper, and is less deformed after printing. Moreover, the emulsion ink of the present invention is useful for inkjet recording.

Claims (7)

A water-in-oil emulsion ink having an aqueous phase in an oil phase,
The aqueous phase contains a pigment dispersed with a polymer (a) having an acid group crosslinked with a crosslinking agent ,
The oil phase contains a water-insoluble organic solvent and an emulsifier,
The polymer (a) has an acid value of 120 mgKOH/g or more, and at least part of the acid groups of the polymer (a) are neutralized,
The degree of cross-linking represented by [the number of molar equivalents of crosslinkable functional groups of the cross-linking agent/the number of molar equivalents of acid groups possessed by the polymer (a) having acid groups] is 10 mol% or more and 80 mol% or less,
A water-in-oil emulsion ink, wherein the content of water in the water-in-oil emulsion ink is 5% by mass or more and 40% by mass or less . 2. The water-in-oil emulsion ink according to claim 1 , wherein the cross-linking agent is a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group with 3 to 8 carbon atoms. 3. The water-in-oil emulsion ink according to claim 1, wherein the content of the pigment in the water phase is 10% by mass or more and 35% by mass or less. The water-in-oil emulsion ink according to any one of claims 1 to 3 , wherein the degree of neutralization of the polymer (a) is 20 mol% or more and 80 mol% or less. 5. The water-in-oil emulsion ink according to any one of claims 1 to 4, further comprising a nonionic surfactant in the water phase and having an HLB value of 6 or more and 20 or less. The water-in-oil emulsion ink according to any one of claims 1 to 5, which is for inkjet recording. 7. The method according to any one of claims 1 to 6, comprising a step of emulsifying, in an oil phase, an aqueous pigment dispersion in which the polymer (a) having an acid group is crosslinked with a crosslinking agent and the pigment is dispersed in an aqueous medium. A method for producing a water-in-oil emulsion ink comprising:
The water-based pigment dispersion is
Step 1-1: A step of neutralizing a part of the acid groups of the acid group-containing polymer (a) with a neutralizing agent to obtain an aqueous dispersion of the acid group-containing polymer (a);
Step 1: A water-based pigment obtained by dispersing a pigment mixture obtained by mixing an aqueous dispersion of the polymer (a) having an acid group and a pigment, and dispersing the pigment in an aqueous medium with the polymer (a) having an acid group. obtaining a dispersion; and
Step 2: A step of adding a cross-linking agent to the aqueous pigment dispersion obtained in Step 1 to obtain an aqueous pigment dispersion in which the acid group-containing polymer (a) is cross-linked with the cross-linking agent. A method for producing a water-in-oil emulsion ink.