WO2014050594A1 - Pigment dispersion, ink, ink for inkjet printing, and method for producing pigment dispersion - Google Patents

Abstract

The present invention provides: a pigment dispersion which is characterized by containing a pigment and a compound (A) having a hydantoin structure; a method for producing this pigment dispersion; an ink which contains this pigment dispersion; and an ink for inkjet printing, which contains this pigment dispersion. This pigment dispersion enables the production of an ink, especially an ink for inkjet printing, which is capable of forming a sharp print image, while having excellent pigment dispersion stability. An ink for inkjet printing, which is obtained using this pigment dispersion, is capable of maintaining excellent ejection stability from an ink ejection nozzle for a long period of time.

Description

Pigment dispersion, ink, ink for inkjet printing, and method for producing pigment dispersion

The present invention relates to a pigment dispersion that can be used in the production of ink that can be used when printing is performed by various printing methods including the ink-jet printing method.

In recent years, in the industry related to ink-jet printing, which has been growing rapidly, the performance of ink-jet printers and the improvement of ink have progressed dramatically, making it possible to easily obtain high-gloss and high-definition images comparable to silver halide photographs even in ordinary households. It is becoming.

In particular, improvements have been made rapidly with the aim of improving image quality and reducing environmental impact, such as the transition from conventional dye inks to pigment inks and from solvent-based to water-based inks. Is actively developing inks based on water-based pigment inks.

The water-based pigment ink is generally obtained by mixing a pigment dispersion, which is a precursor thereof, with various additives and diluting with an aqueous medium. Examples of the pigment ink obtained using the pigment dispersion as the precursor include, for example, a pigment, 5 to 30 parts by weight of a (meth) acrylic acid alkyl ester compound having a long-chain alkyl group having 8 to 20 carbon atoms, α, 5 to 30 parts by weight of β-monoethylenically unsaturated carboxylic acid monomer and 40 to 90 parts by weight of other copolymerizable radical polymerizable monomer (however, the total of the above monomer components is 100 parts by weight) The ratio of the acrylic resin and the compound having an ether structure having a specific structure is mainly comprised of an acrylic resin obtained by copolymerization of the compound, a compound having an ether structure having a specific structure, a basic compound and an aqueous medium. Resin / compound having ether structure of specific structure] = 20/80 to 80/20 (weight ratio), and 100 parts by weight of pigment and the acrylic resin and the compound An ink composition for ink-jet recording is known which contains 8 to 300 parts by weight of the total amount of compounds having a specific ether structure (see, for example, Patent Document 1).

However, since the ink composition causes aggregation of pigment particles due to the influence of the organic solvent used in manufacturing the ink composition, when the printed image is formed using the ink composition, the sharpness of the printed image is reduced. There was a case. In addition, when trying to print the ink by the ink jet printing method, it may cause sedimentation of the pigment or clogging of the ink discharge nozzle due to aggregation of the pigment particles, and the dispersion stability and discharge stability of the pigment dispersion and ink. In some cases, it was not possible to improve the performance.

JP-A-10-158562

The problem to be solved by the present invention is to provide a pigment dispersion which is excellent in pigment dispersion stability and ink ejection stability and which is used for producing an ink capable of forming a clear printed image.

As a result of earnest research to solve the above problems, the present inventors have found that the above problems can be solved by using a pigment dispersant containing a compound having a hydantoin structure, and have completed the present invention.

That is, the present invention relates to a pigment dispersion characterized by containing a compound (A) having a hydantoin structure and a pigment, an ink containing the pigment dispersion, and an ink for inkjet printing.

The pigment dispersion of the present invention can produce an ink excellent in pigment dispersion stability and capable of forming a clear printed image, particularly an ink for inkjet printing. In particular, the ink for inkjet printing obtained using the pigment dispersion can maintain excellent ejection stability from the ink ejection nozzle for a long period of time.

The pigment dispersion of the present invention is characterized by containing a compound (A) having a hydantoin structure and a pigment.

The hydantoin structure possessed by the compound (A) specifically refers to a cyclic structure represented by the following general formula (1).

[R ¹ and R ^{2 in} General Formula (1) each independently represent a hydrogen atom or an alkyl group. ]

Examples of R ¹ and R ² in the general formula (1) include a hydrogen atom or an alkyl group such as a methyl group or an ethyl group. Among them, a methyl group or an ethyl group is preferable.

The hydantoin structure is an essential structure for producing an ink capable of improving the dispersion stability of the pigment and forming a clear printed image. The hydantoin structure is an essential structure for producing ink for ink jet printing excellent in ink ejection stability.

Among the hydantoin structures, the structure represented by the following general formula (1-1) is preferable because the hydantoin structure can be easily introduced into the compound (A).

[R ¹ and R ² in the general formula (1-1) each independently represent a hydrogen atom or an alkyl group, and R ³ and R ⁴ each independently represent an alkylene group. ]

Examples of R ¹ and R ² in the general formula (1-1) include a hydrogen atom or an alkyl group such as a methyl group or an ethyl group. Among them, a methyl group or an ethyl group is preferable. Examples of R ³ and R ⁴ in the general formula (1-1) include alkylene groups such as a methylene group, an ethylene group, a propylene group, and a butylene group, and a methylene group and an ethylene group are preferable.

The hydantoin structure represented by the general formula (1) is preferably present in the range of 1 to 30% by mass in the compound (A), and preferably present in the range of 3 to 20% by mass. It is more preferable for producing an ink having excellent stability and, as a result, further excellent ink ejection stability and storage stability. In the compound (A) having the general formula (1-1), the hydantoin structure represented by the general formula (1) in the general formula (1-1) is 1 to 30 masses in the compound (A). %, Preferably 3 to 20% by mass.

The compound (A) having a hydantoin structure has a weight average molecular weight in the range of 5,000 to 100,000 in order to further improve the dispersion stability of the pigment, and particularly to improve the ejection stability of the ink. It is preferable to use those having a weight average molecular weight in the range of 10,000 to 50,000.

Moreover, the said compound (A) uses what has hydrophilic groups, such as anionic group, a cationic group, a nonionic group, from a viewpoint which provides the outstanding dispersion stability in an aqueous medium (B), for example. It is preferable to use a compound having one or both of an anionic group and a cationic group.

As the anionic group, for example, a carboxyl group, a carboxylate group, a sulfonic acid group, a sulfonate group, and the like can be used. Among them, a part or all of the carboxyl group and the sulfonic acid group are basic compounds. It is preferable to use a carboxylate group or a sulfonate group neutralized by the above in order to impart good water dispersion stability. Moreover, as said cationic group, a tertiary amino group etc. can be used, for example. In addition, examples of the nonionic group include a polyoxyethylene structure.

The hydrophilic group is preferably present in the compound (A) in the range of 15 to 2,000 mmol / kg, and more preferably in the range of 500 to 1,000 mmol / kg. And more preferable for obtaining a pigment dispersion having ejection stability.

As the compound (A), it is preferable to use a compound having a urea bond in the range of 0 to 2% by mass in the compound (A) in order to further improve the dispersion stability of the pigment.

Further, as the compound (A), the use of a compound having a primary amino group in the range of 0 to 5% by mass in the compound (A) prevents aggregation of pigment particles and provides a clear printed image. In order to further improve the dispersion stability and ejection stability, more preferably in the range of 0 to 1% by mass, still more preferably 0 to 0.1% by mass.

As the compound (A) having a hydantoin structure, for example, polyurethane (A-1), vinyl resin such as acrylic resin, polyester resin and the like can be used. Among them, as the compound (A), in order to further improve the compatibility with the pigment, it is preferable to use polyurethane (A-1) or vinyl resin (A-2). ) Is more preferable.

The polyurethane (A-1) can be produced, for example, by reacting a polyol (a1) containing a polyol having a hydantoin structure, a polyisocyanate (a2), and, if necessary, a chain extender. .

As the polyol having the hydantoin structure, those having the structure represented by the general formula (1) can be used. Specifically, a polyol represented by the following general formula (2) can be preferably used.

[R ¹ and R ^{2 in} General Formula (2) each independently represent a hydrogen atom or an alkyl group, and R ³ and R ⁴ each independently represent an alkylene group. ]

Examples of R ¹ and R ² in the general formula (2) include a hydrogen atom or an alkyl group such as a methyl group or an ethyl group. Among them, a methyl group or an ethyl group is preferable. Moreover, as R < ³ > and R < ⁴ > in General formula (2), alkylene groups, such as a methylene group, ethylene group, a propylene group, or a butylene group, are mentioned, A methylene group and ethylene group are preferable. More specifically, the polyol represented by the general formula (2) includes 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin), 1,3-bis (hydroxymethyl) -5,5. -Dimethylimidazolidine-2,4-dione, 1,3-bis (2-hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione, etc. are preferably used, and 1,3-bis (2 More preferably, -hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione is used.

As the polyol (a1), other polyols can be used as needed in addition to the polyol having the hydantoin structure.

As the other polyol, for example, a polyol having a hydrophilic group can be used from the viewpoint of imparting good water dispersion stability of the polyurethane (A-1).

As the polyol having a hydrophilic group, for example, a polyol having an anionic group, a polyol having a cationic group, and a polyol having a nonionic group can be used, and among them, a polyol or a cation having an anionic group. It is preferable to use a polyol having a functional group.

As the polyol having an anionic group, for example, a polyol having a carboxyl group or a polyol having a sulfonic acid group can be used.

Examples of the polyol having a carboxyl group include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, and the like. Of these, 2,2-dimethylolpropionic acid is preferably used. Moreover, the polyester polyol which has a carboxyl group obtained by making the polyol which has the said carboxyl group react with various polycarboxylic acids can also be used.

Examples of the polyol having a sulfonic acid group include dicarboxylic acids such as 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfophthalic acid, 5- (4-sulfophenoxy) isophthalic acid, and salts thereof, A polyester polyol obtained by reacting with a molecular weight polyol can be used.

The polyol having a carboxyl group or the polyol having a sulfonic acid group is preferably used in the range where the acid value of the polyurethane (A-1) is from 10 to 70, and preferably from 10 to 60. More preferably, it is particularly preferably used in the range of 30-50. The acid value referred to in the present invention is a theoretical value calculated based on the amount of a compound having an acid group such as a polyol having a carboxyl group used in the production of the polyurethane (A-1).

The anionic group is preferably partially or completely neutralized with a basic compound or the like in order to develop good water dispersibility.

Examples of basic compounds that can be used when neutralizing the anionic group include organic amines having a boiling point of 200 ° C. or higher, such as ammonia, triethylamine, morpholine, monoethanolamine, diethylethanolamine, sodium hydroxide, A metal hydroxide containing potassium hydroxide, lithium hydroxide or the like can be used. The basic compound is preferably used in the range of basic compound / anionic group = 0.5 to 3 (molar ratio) from the viewpoint of improving the water dispersion stability of the obtained ink. It is more preferable to use in the range of ˜2 (molar ratio).

As the polyol having a cationic group, for example, a polyol having a tertiary amino group can be used. Specifically, N-methyl-diethanolamine and a compound having two epoxies in one molecule can be used. A polyol obtained by reacting with a secondary amine can be used.

The cationic group is preferably partially or completely neutralized with an acidic compound such as formic acid, acetic acid, propionic acid, succinic acid, glutaric acid, tartaric acid, and adipic acid.

Further, the tertiary amino group that can be used as the cationic group is preferably partially or entirely quaternized. As the quaternizing agent, for example, dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride and the like can be used, and dimethyl sulfate is preferably used.

Also, as the polyol having a nonionic group, polyalkylene glycol having a structural unit derived from ethylene oxide can be used.

The polyol having a hydrophilic group is preferably used in the range of 1 to 45% by mass with respect to the total mass of raw materials used for the production of the polyurethane (A-1).

Further, as the other polyols, for example, polyether polyols, polyester polyols, polyester ether polyols, polycarbonate polyols and the like can be used other than those described above. Among these, it is preferable to use a polyether polyol in order to further improve the dispersion stability of the pigment.

As the polyether polyol, for example, one obtained by addition polymerization of alkylene oxide using one or more compounds having two or more active hydrogen atoms as an initiator can be used.

Examples of the initiator include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, glycerin, trimethylolethane. Trimethylolpropane and the like can be used.

Further, as the alkylene oxide, for example, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran and the like can be used.

Specifically, it is preferable to use polyoxytetramethylene glycol, polypropylene glycol, or polyethylene glycol as the polyether polyol in order to improve the ink ejection stability. In addition, it is more preferable to use a polyether polyol having a number average molecular weight of 1,000 to 3,000 in order to obtain a printed material that suppresses the tackiness of the printing surface and has excellent water resistance.

Examples of the polyester polyol include a ring-opening polymerization reaction of a cyclic ester compound such as an aliphatic polyester polyol, an aromatic polyester polyol, or ε-caprolactone obtained by esterifying a low molecular weight polyol and a polycarboxylic acid. Polyesters obtained by the above, copolymerized polyesters thereof, and the like can be used.

As the low molecular weight polyol, for example, ethylene glycol, propylene glycol and the like can be used.

Examples of the polycarboxylic acid include succinic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, and anhydrides or ester-forming derivatives thereof. .

In addition, as the polyester ether polyol, for example, a reaction product of a polyether polyol obtained by adding the alkylene oxide to the initiator and a polycarboxylic acid can be used. As the initiator and the alkylene oxide, the same ones exemplified as those usable when the polyether polyol is produced can be used. Moreover, as said polycarboxylic acid, the thing similar to what was illustrated as what can be used when manufacturing the said polyester polyol can be used.

Further, as the polycarbonate polyol, for example, those obtained by reacting a carbonic acid ester with a polyol, or those obtained by reacting phosgene with bisphenol A or the like can be used.

As the carbonate ester, methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, diphenyl carbonate and the like can be used.

Examples of the polyol that can react with the carbonate ester include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3 -Butanediol, 1,2-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 2,5-hexanediol, 1,6-hexanediol, 1,7- Heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 3-methyl-1,5-pentanediol, 2 -Ethyl-1,3-hexanediol, 2-methyl-1,3-propyl Pandiol, 2-methyl-1,8-octanediol, 2-butyl-2-ethylpropanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, Relatively low molecular weight dihydroxy compounds such as hydroquinone, resorcin, bisphenol-A, bisphenol-F, 4,4'-biphenol, polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyhexamethylene adipate Polyester polyols such as polyhexamethylene succinate and polycaprolactone can be used.

Examples of the polyisocyanate (a2) include aromatics such as 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate. Polyisocyanates, aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, or polyisocyanates having an aliphatic cyclic structure thing It can be. Among them, it is preferable to use an aliphatic polyisocyanate from the viewpoint of preventing yellow discoloration. From the viewpoint of further improving the scratch resistance and alkali resistance in addition to the above-mentioned discoloration prevention, a polyisocyanate having an aliphatic cyclic structure is preferably used. Preference is given to using isocyanates.

The polyurethane (A-1) is obtained by, for example, reacting a polyol (a1) containing a polyol having a hydantoin structure with a polyisocyanate (a2) in the presence or absence of a solvent, and removing the solvent as necessary. Can be manufactured.

In the reaction of the polyol (a1) and the polyisocyanate (a2), for example, the equivalent ratio of the isocyanate group of the polyisocyanate (a2) to the hydroxyl group of the polyol (a1) is 0.8-2. 5 is preferable, and 1 to 1.5 is more preferable.

In addition, the reaction of the polyol (a1) and the polyisocyanate (a2) is preferably performed in the range of about 20 ° C. to 120 ° C. for about 30 minutes to 24 hours.

Solvents usable in the reaction of the polyol (a1) and the polyisocyanate (a2) include, for example, ketone compounds such as acetone and methyl ethyl ketone; ether compounds such as tetrahydrofuran and dioxane; acetate esters such as ethyl acetate and butyl acetate. Compounds: Nitrile compounds such as acetonitrile; amide compounds such as dimethylformamide and N-methylpyrrolidone can be used alone or in combination of two or more.

In order to introduce a hydantoin structure into the polyurethane (A-1), the polyol having the above hydantoin structure is used. After the polyisocyanate (a2) is excessively used to produce a polyurethane having an isocyanate, the following general structure is used. A hydantoin structure may be introduced into the polyurethane (A-1) by reacting the monool represented by the formula (3).

[R ¹ and R ^{2 in} General Formula (3) each independently represent a hydrogen atom or an alkyl group, and R ³ represents an alkylene group. ]

Examples of R ¹ and R ² in the general formula (3) include a hydrogen atom or an alkyl group such as a methyl group or an ethyl group, and a methyl group or an ethyl group is preferable.

Examples of the monool include 1-hydroxymethyl-5,5-dimethylhydantoin.

Further, when the polyurethane (A-1) is produced, a chain extender can be used as necessary. In particular, when a urea bond is introduced into the polyurethane (A-1), it is preferable to use polyamine or hydrazine as a chain extender.

Examples of the chain extender include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4′-dicyclohexylmethanediamine, 3,3. Diamine compounds such as' -dimethyl-4,4'-dicyclohexylmethanediamine and 1,4-cyclohexanediamine; N-hydroxymethylaminoethylamine, N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine, N-ethylamino Diamine compounds containing one primary amino group and one secondary amino group such as ethylamine and N-methylaminopropylamine; polyamine compounds such as diethylenetriamine, dipropylenetriamine and triethylenetetramine; Hydrazine compounds such as drazine, N, N′-dimethylhydrazine, 1,6-hexamethylenebishydrazine; dihydrazide compounds such as succinic acid dihydrazide, adipic acid dihydrazide, glutaric acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide; β-semicarbazide Semicarbazide compounds such as propionic acid hydrazide, 3-semicarbazide-propyl-carbazate, semicarbazide-3-semicarbazidemethyl-3,5,5-trimethylcyclohexane can be used.

For example, in the case of a polyamine, the chain extender is preferably used in the range where the equivalent ratio of the amino group it has and the isocyanate group it has is 1.9 or less (equivalent ratio). More preferably, it is used in the range of 5 to 1.5 (equivalent ratio).

The pigment dispersion of the present invention can be produced, for example, by kneading a compound (A) such as polyurethane (A-1) obtained by the above method with a pigment or the like. Moreover, you may mix the said kneaded material and an aqueous medium (B) as needed.

Also, examples of the aqueous medium (B) include water, organic solvents miscible with water, and mixtures thereof. Examples of the organic solvent miscible with water include alcohol compounds such as methanol, ethanol, n-propanol and isopropanol; ketone compounds such as acetone and methyl ethyl ketone; polyalkylene glycol compounds such as ethylene glycol, diethylene glycol and propylene glycol; And alkyl ether compounds such as N-methyl-2-pyrrolidone and the like. In the present invention, only water may be used, a mixture of water and an organic solvent miscible with water may be used, or only an organic solvent miscible with water may be used. From the viewpoint of safety and load on the environment, water alone or a mixture of water and an organic solvent miscible with water is preferable, and only water is particularly preferable.

As the vinyl resin (A-2) that can be used for the compound (A), those obtained by polymerizing a vinyl monomer mixture containing a vinyl monomer having a hydantoin structure can be used. .

Examples of the vinyl monomer having a hydantoin structure include 1-allylhydantoin, 3- (3-chlorophenyl) -5-methyl-5- (allyloxy) hydantoin, and 3- (3-chlorophenyl) -5-phenyl- 5- (allyloxy) hydantoin, 3-allyl-5,5-dimethylhydantoin, 1-benzyl-3-phenyl-5-allylhydantoin, 3-phenyl-5-allylhydantoin, 3′-allylspiro [tetralin-2,5 '-Hydantoin], 1-methyl-3-allyl-5-[(E) -benzylidene] thiohydantoin, 1-allyl-3-phenyl-5- [1- [2- (methoxycarbonyl) hydrazono] ethyl] hydantoin Etc., and 1-allylhydantoin is preferably used.

The vinyl monomer having a hydantoin structure is preferably used in the range of 1 to 30% by mass in the total amount of the vinyl monomer mixture.

The hydantoin structure possessed by the vinyl resin (A-2) is preferably a structure derived from the 1-allyl hydantoin, and specifically, one nitrogen in the structure represented by the general formula (1). A structure represented by the following general formula (1-2) in which an atom is bonded to a hydrogen atom is preferable.

[R ¹ and R ² in the general formula (1-2) each independently represent a hydrogen atom or an alkyl group. ]

Examples of R ¹ and R ² in the general formula (1-2) include a hydrogen atom or an alkyl group such as a methyl group or an ethyl group, and among them, a hydrogen atom is preferable.

The hydantoin structure represented by the general formula (1-2) is also preferably present in the range of 1 to 30% by mass in the compound (A), and preferably present in the range of 3 to 20% by mass. As a result, the dispersion stability of the pigment is excellent, and as a result, it is more preferable for producing an ink having further excellent ink ejection stability and storage stability.

Further, when the vinyl resin (A-2) is produced, other vinyl monomers can be used as necessary in addition to the vinyl monomer having a hydantoin structure.

Examples of the other vinyl monomers include vinyl monomers having an acid group such as (meth) acrylic acid, allyl sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid, Amide groups such as (meth) acrylamide, diethyl (meth) acrylamide, N-vinylpyrrolidone, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N'-methylenebis (meth) acrylamide, etc. Vinyl monomer having, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl ( (Meth) acrylate, n-octyl (Meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, n-dodecyl ( (Meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, itaconimide, glycidyl (meth) acrylate, methylglycidyl (meth) acrylate, vinyl acetate, vinyl propionate, vinyl laurate Styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, N-methylaminoethyl (meth) acrylate, Nt-butylaminoethyl (meth) acrylate, aminomethyl acrylate Aminoethyl acrylate, aminopropyl (meth) acrylate, amino-n-butyl (meth) acrylate, and the like can be used.

The other vinyl monomers are preferably used in the range of 80 to 99% by mass in the total amount of the vinyl monomer mixture used for producing the vinyl resin (A-2).

The vinyl resin (A-2) can be produced, for example, by radical polymerization of a mixture of various vinyl monomers in the presence of a polymerization initiator and an aqueous medium.

The compound (A) is preferably included in the range of 5 to 200 parts by mass with respect to 100 parts by mass of the pigment described later, and included in the range of 20 to 100 parts by mass, the dispersion stability of the pigment and the ink This is more preferable for further improving the discharge performance.

In addition, as the pigment, known and commonly used inorganic pigments and organic pigments can be used.
Examples of the inorganic pigment that can be used include titanium oxide, antimony red, bengara, cadmium red, cadmium yellow, cobalt blue, bitumen, ultramarine, carbon black, and graphite.

Examples of the organic pigments include quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, ansanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, Organic pigments such as diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, and azo pigments can be used.

Among the organic pigments, examples of the black pigment include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black; copper oxide, iron oxide (C.I. Pigment black 11), metal oxides such as titanium oxide; aniline black (CI pigment black 1) and the like can be used.

Among the organic pigments, examples of color pigments include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow, C.I. I. Pigment Yellow 154, monoazo pigments such as C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 81, C.I. I. Pigment yellow 83, C.I. I. Pigment red 38, C.I. I. Disazo pigments such as C.I. Pigment Orange 13; I. Pigment red 53: 1, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 48: 2, C.I. I. Azo lake pigments such as CI Pigment Red 57: 1; I. Pigment red 150, C.I. I. Pigment red 185, C.I. I. Pigment red 213, C.I. I. Azo pigments such as C.I. Pigment Red 269, C.I. I. Pigment blue 16, C.I. I. Pigment blue 15: 3, C.I. I. Pigment green 7, C.I. I. Phthalocyanine pigments such as CI Pigment Green 36; I. Pigment violet 19, C.I. I. Pigment red 122, C.I. I. Pigment red 202, C.I. I. Quinacridone pigments such as CI Pigment Red 282 and solid solution pigments thereof; I. Pigment red 254, C.I. I. Pigment red 255, C.I. I. Pigment red 264, C.I. I. Pigment red 270, C.I. I. Diketopyrrolopyrrole pigments such as CI Pigment Red 272, solid solutions of quinacridone pigments and diketopyrrolopyrrole pigments, and the like can be used.

These pigments can be used in combination of two or more. These pigments may be surface-treated and have a self-dispersing ability with respect to the aqueous medium (B).

Examples of the method of kneading the compound (A) and the pigment include, for example, (i) a method of kneading the compound (A) and the pigment under a high shear force using a two-roll or a mixer, ii) The compound (A) and the pigment are mixed using a dispersing device such as a Henschel mixer, a pressure kneader, or a planetary mixer, and then the solubility of the compound (A) is controlled to control the compound (A). And the like, and a method of mixing them using a dispersing device.

Among them, the method of kneading by the method (i) is preferable for producing a pigment dispersion having further excellent pigment dispersion stability because the pigment can be finely pulverized.

The pigment is preferably contained in the pigment dispersion of the present invention in the range of 5 to 50% by mass, and more preferably in the range of 5 to 30% by mass.

When the compound (A) and the pigment are kneaded, the solid content concentration of the kneaded product is preferably 55 to 90% by mass. Thereby, sufficient shearing force can be applied to the compound (A) and the pigment, and a kneaded product in which the pigment is uniformly dispersed can be obtained. In the kneading, a solid content concentration of the kneaded product can be adjusted using a solvent such as polypropylene glycol, a wetting agent, or the like as necessary.

The kneading apparatus used in the kneading step may be any kneading apparatus that can generate a high shearing force with respect to a kneaded product having a high solid content ratio, and can be selected from known kneading apparatuses. However, it is preferable to use a kneading apparatus having a stirring tank and stirring blades and capable of sealing the stirring tank, rather than using an open kneader having no stirring tank such as a two-roll. It is preferable to use a kneading apparatus having a stirring tank and stirring blades. When the kneading apparatus having such a configuration is used, polypropylene glycol, a wetting agent, moisture and the like are not volatilized during kneading, and kneading of a kneaded material having a certain solid content ratio can be continued, thereby reducing coarse particles. It is effective. Moreover, the kneaded material that is solid at room temperature after kneading can be directly diluted with the aqueous medium (B) to shift to a step of producing a pigment dispersion.

Examples of such devices include Henschel mixers, pressure kneaders, Banbury mixers, planetary mixers, and the like, with planetary mixers being particularly preferred. In the present invention, kneading is preferably performed in a state where the pigment concentration and the solid content concentration of the pigment and the compound (A) are high, so that the viscosity of the kneaded material varies in a wide range depending on the kneaded state of the kneaded material. However, the planetary mixer can be kneaded in a wide range of viscosity compared to a two-roller, etc., and further can be added with an aqueous medium (B) and distilled off under reduced pressure. It is easy to adjust the load shear force.

When mixing a kneaded product containing the pigment and the compound (A) obtained by the above method and an aqueous medium (B) to produce a pigment dispersion, a kneader having a stirring tank as described above A method in which a solid kneaded material is produced using, then the aqueous medium (B) is added to and mixed in the stirring tank, and if necessary, stirred to dilute directly.

The pigment dispersion can also be produced by a method in which the kneaded product and the aqueous medium (B) are mixed and stirred as necessary using another stirrer equipped with a stirring blade.

The aqueous medium (B) may be mixed in a necessary amount with respect to the kneaded product. However, the aqueous medium (B) is preferably mixed continuously or intermittently. It is preferable because the dilution is efficiently performed and the pigment dispersion of the present invention can be produced in a shorter time.

The pigment dispersion obtained by the above method may be subjected to a dispersion treatment using a disperser as necessary.

As the disperser for carrying out the dispersion treatment, known and commonly used equipment can be used, for example, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a dyno mill, a dispar mat, a nano mill, an SC mill, Nanomizer etc. can be mentioned, One of these may be used independently and may be used in combination of 2 or more types of apparatuses. In the present invention, the disperser and the disperser are devices that are used exclusively for the dispersion process, and do not include general-purpose mixers and stirrers that are widely used for normal mixing and stirring. And

In addition to the pigment, other additives can be used as necessary as the pigment dispersion.

As the additive, for example, a polymer dispersant or a wetting agent can be used.

As the polymer dispersant, for example, an acrylic resin or a styrene-acrylic resin can be used, and any of a random type, a block type, and a graft type can be used.

As the acrylic resin, for example, those obtained by polymerizing a (meth) acrylic monomer containing acrylic acid or methacrylic acid can be used.

Further, as the styrene-acrylic resin, those obtained by polymerizing the (meth) acrylic monomer and styrene as described above can be used.

The acrylic resin and styrene-acrylic resin can be produced by polymerizing a monomer having a polymerizable unsaturated double bond by, for example, a solution polymerization method or a suspension polymerization method.

Examples of the monomer having a polymerizable unsaturated double bond include styrene, α-styrene, β-styrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, α-hexylstyrene, Chlorostyrene, bromostyrene, nitrostyrene, methoxystyrene, vinyltoluene, (meth) acrylic acid, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec -Butyl (meth) acrylate, rt-butyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, 1,3-dimethylbutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. Can be used.

When using the polymer dispersant, a basic compound may be used to neutralize acid groups such as carboxyl groups of the polymer dispersant.

As the polymer dispersant, those having a weight average molecular weight in the range of 1,000 to 50,000 are preferably used, and those having a weight average molecular weight of 1,000 to 20,000 are preferably used. More preferred.

In addition, as the polymer dispersant, one having an acid value of 100 to 500 is preferably used, and one having an acid value of 100 to 200 is more preferably used.

Examples of the wetting agent that can be used when producing the pigment dispersion of the present invention include alcohol solvents, ketone solvents, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, halogens, and the like. Aliphatic hydrocarbon solvents are preferred, and glycol solvents are particularly preferred. For example, glycerin, polyoxyalkylene adduct of glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,4-butanediol, , 5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, trimethylolpropane, pentaerythritol and other polyol compounds, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, etc. Polyhydric alcohol alkyl ether compound, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether Polyhydric alcohol aryl ether compounds and polyhydric alcohol aralkyl ether compounds, lactam compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and ε-caprolactam, 1,3-dimethylimidazolidinone, and the like can be used. .

Examples of the alcohol solvent include methanol, ethanol, isopropanol, n -butanol, tertiary tert-butanol, isobutanol, diacetone alcohol, and the like. As the ketone solvent, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, or the like can be used.

As the ether solvent, dibutyl ether, tetrahydrofuran, dioxane or the like can be used.

Benzene, toluene or the like can be used as the aromatic hydrocarbon solvent.

As the aliphatic hydrocarbon solvent, heptane, hexane, cyclohexane or the like can be used.

As the halogenated aliphatic hydrocarbon solvent, methylene chloride, 1,1,1-trichloroethane, chloroform, carbon tetrachloride, 1,2-dichloroethane and the like can be used.

It is preferable to use diethylene glycol or triethylene glycol glycol as the wetting agent.

It is preferable to use the wetting agent in the pigment in the range of 20 to 50% by mass because the effect of reducing the coarse particles of the pigment is obtained.

The pigment dispersion of the present invention obtained by the above method can be suitably used as a precursor when producing various inks.

In general, various inks can be produced by mixing the pigment dispersion, the aqueous medium (B), and a binder resin as necessary.

Specifically, (1) the pigment dispersion, the aqueous medium (B), and, if necessary, a binder resin such as polyurethane are collectively mixed using various dispersing devices, and (2) the above-mentioned The pigment dispersion and the aqueous medium (B) are mixed using various dispersing devices, and then the mixture, the binder resin and the additive are further mixed using various dispersing devices. Ink can be prepared.

As the dispersing device, for example, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a dyno mill, a disperse mat, an SC mill, a nanomizer, or the like may be used alone or in combination of two or more. Can do.

Also, as the binder resin that can be used when manufacturing the ink, urethane resin or acrylic resin can be used.

The binder resin is preferably used in the range of 0.1 to 5% by mass in the total amount of the ink.

Examples of additives that can be used when producing the ink include viscosity modifiers, wetting agents, antifoaming agents, surfactants, preservatives, penetrating agents, pH adjusting agents, chelating agents, and plasticizers. UV absorbers, antioxidants, and the like can be used.

In the ink obtained by the above method, coarse particles having a particle diameter of approximately 250 nm or more may exist. The coarse particles may cause clogging of printer nozzles and the like, and may deteriorate ink discharge characteristics. Therefore, the coarse particles may be coarsened by a method such as centrifugation or filtration after the preparation of the aqueous dispersion of the pigment or after the preparation of the ink. It is preferred to remove the particles.

The ink obtained above preferably has a volume average particle diameter of 200 nm or less, and particularly in the case of forming a higher gloss image such as photographic image quality, it is in the range of 80 to 150 nm. Is more preferable.

In the ink obtained in the present invention, the total amount of the compound (A) such as polyurethane (A-1) is 0.2 to 10% by mass, the aqueous medium (B) is 50 to 95% by mass, and the pigment is 0%. It is preferably contained in the range of 5 to 15% by mass.

The ink of the present invention obtained by the above method can be used exclusively when printing by an ink jet printing method using an ink jet printer, for example, ink jet printing on a substrate such as paper, plastic film, metal film or sheet. Can be used for The ink jet printing method is not particularly limited, but a known method such as a continuous jet type (charge control type, spray type, etc.) or an on-demand type (piezo type, thermal type, electrostatic suction type, etc.) should be applied. Can do.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

[Example 1]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 412 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid and isophorone diisocyanate 357 Part by mass is reacted for 10 hours at 80 ° C. in the presence of 300 parts by mass of methyl ethyl ketone, which is an organic solvent, and then 1,3-bis (2-hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione is added. Hydantoin in which R ¹ and R ² in the general formula (1-1) are methyl groups and R ³ and R ⁴ are ethylene groups by supplying and reacting 100 parts by mass and then reacting 11 parts by mass of butanol An organic solvent solution of polyurethane (I) having a structure was obtained.

Next, 666 parts by mass of diethylene glycol is added to the organic solvent solution of the polyurethane (I) having the hydantoin structure and sufficiently stirred, and then the organic solvent solution of the polyurethane (I) having the hydantoin structure is desolvated. The mixture (I-1) of polyurethane (I) and diethylene glycol was obtained by adding and adjusting diethylene glycol so as to be 60% by mass.

417 parts by mass of the polyurethane (I-1), 500 parts by mass of Pigment Yellow 74 (manufactured by Sanyo Dye Co., Ltd., Fast® Yellow 7413), and 37 parts by mass of an 8N aqueous potassium hydroxide solution (solid content concentration = 34% by mass). The mixture was charged in a planetary mixer (PLM-V-50V manufactured by Inoue Seisakusho Co., Ltd.) kept at 60 ° C. and kneaded for 1 hour.

By adding ion-exchanged water heated to 60 ° C. in a total amount of 1200 parts by mass for 2 hours, a colored resin composition having a nonvolatile content of 35.3% by mass and a pigment concentration of 22.6% by mass is added to the kneaded product. Obtained.

By adding 233 parts by mass of diethylene glycol and 840 parts by mass of ion-exchanged water to the colored resin composition obtained by the above method, the mixture is stirred with a dispersion stirrer to obtain a precursor of a pigment dispersion (dispersion before dispersion treatment). )

Next, the precursor of the pigment dispersion was passed through a continuous centrifuge (Kokusan Co., Ltd., Sakai H-600S, 2 L capacity) and centrifuged at a centrifugal force of 18900 G and a residence time of 10 minutes. A pigment dispersion (I-2) was obtained by performing filtration through a 5 μm filter. The pigment concentration of this pigment dispersion (I-2) was 14.5% by mass.

By using the pigment dispersion (I-2) obtained above and mixing the following components, an ink for inkjet printing having a pigment concentration of 4% by mass was prepared.
Pigment dispersion (I-2) (pigment concentration 14.5% by mass); 28 g
・ 2-Pyrrolidinone; 8g
・ Triethylene glycol monobutyl ether; 8g
・ Glycerin; 3g
・ Surfactant (Surfinol 440, manufactured by Air Products); 0.5 g
・ Ion exchange water: 52.5 g

[Example 2]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 800 parts by mass of methyl ethyl ketone was charged, and then 500 parts by mass of methyl methacrylate, 77 parts by mass of methacrylic acid, 323 parts by mass of styrene, 1-allyl. A monomer liquid consisting of 100 parts by weight of hydantoin and a catalyst liquid consisting of 20 parts by weight of azobisisobutyronitrile and 200 parts by weight of methyl ethyl ketone are added dropwise at 80 ° C. over 10 hours, whereby the general formula (1-2) Thus, an organic solvent solution of vinyl resin (II) having a hydantoin structure in which R ¹ and R ² are hydrogen atoms was obtained.

A pigment dispersion (II-2) having a pigment concentration of 14.5% by mass was obtained in the same manner as in Example 1 except that the vinyl resin (II) was used instead of the polyurethane (I). It was. An ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (II-2) was used instead of the pigment dispersion (I-2).

[Example 3]
515 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid and isophorone diisocyanate 305 in a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube and a stirrer The reaction is carried out at 80 ° C. for 10 hours in the presence of 300 parts by weight of methyl ethyl ketone, which is an organic solvent, and then 50 parts by weight of 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin) is supplied and reacted. Then, 10 parts by mass of butanol was reacted to obtain an organic solvent solution of polyurethane (III) having a hydantoin structure represented by the general formula (1).

A pigment dispersion (III-2) having a pigment concentration of 14.5% by mass was obtained in the same manner as in Example 1, except that the polyurethane (III) was used instead of the polyurethane (I). . Further, an ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (III-2) was used instead of the pigment dispersion (I-2).

[Example 4]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 267 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 1,3-bis (2-hydroxyethyl) -5,5 327 parts by mass of a polyester polyol (number average molecular weight 2000) consisting of dimethylimidazolidine-2,4-dione and adipic acid, 120 parts by mass of 2,2-dimethylolpropionic acid and 277 parts by mass of isophorone diisocyanate are methyl ethyl ketone as an organic solvent. In the presence of 300 parts by mass, the reaction is carried out at 80 ° C. for 10 hours and then 9 parts by mass of butanol, whereby R ¹ and R ² in the general formula (1-1) are methyl groups, R ³ and R An organic solvent solution of polyurethane (IV) having a hydantoin structure in which ⁴ is an ethylene group was obtained.

A pigment dispersion (IV-2) having a pigment concentration of 14.5% by mass was obtained in the same manner as in Example 1, except that the polyurethane (IV) was used instead of the polyurethane (I). . Further, an ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (IV-2) was used instead of the pigment dispersion (I-2).

[Example 5]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube, and a stirrer, 310 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid and isophorone diisocyanate 394 Part by mass is reacted for 10 hours at 80 ° C. in the presence of 300 parts by mass of methyl ethyl ketone, which is an organic solvent, and then 1,3-bis (2-hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione is added. By supplying 100 parts by mass and reacting, and then reacting 76 parts by mass of dibutylamine, R ¹ and R ² in the general formula (1-1) are methyl groups, and R ³ and R ⁴ are ethylene groups. An organic solvent solution of polyurethane (V) having a hydantoin structure was obtained.

A pigment dispersion (V-2) having a pigment concentration of 14.5% by mass was obtained in the same manner as in Example 1, except that the polyurethane (V) was used instead of the polyurethane (I). . Further, an ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (V-2) was used instead of the pigment dispersion (I-2).

[Example 6]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube, and a stirrer, 540 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid and isophorone diisocyanate 301 Part by mass is reacted for 10 hours at 80 ° C. in the presence of 300 parts by mass of methyl ethyl ketone, which is an organic solvent, and then 1,3-bis (2-hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione is added. By supplying 30 parts by mass and reacting, and then supplying and reacting 10 parts by mass of butanol, R ¹ and R ² in the general formula (1-1) are methyl groups, and R ³ and R ⁴ are ethylene groups. An organic solvent solution of polyurethane (VI) having a certain hydantoin structure was obtained.

A pigment dispersion (VI-2) having a pigment concentration of 14.5% by mass was obtained in the same manner as in Example 1, except that the polyurethane (VI) was used instead of the polyurethane (I). . Further, an ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (VI-2) was used instead of the pigment dispersion (I-2).

[Example 7]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 558 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid and isophorone diisocyanate 293 Part by mass is reacted for 10 hours at 80 ° C. in the presence of 300 parts by mass of methyl ethyl ketone, which is an organic solvent, and then 1,3-bis (2-hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione is added. By supplying 20 parts by mass and reacting, and then supplying and reacting 9 parts by mass of butanol, R ¹ and R ² in the general formula (1-1) are methyl groups, and R ³ and R ⁴ are ethylene groups. An organic solvent solution of polyurethane (VII) having a certain hydantoin structure was obtained.

A pigment dispersion (VII-2) having a pigment concentration of 14.5% by mass was obtained in the same manner as in Example 1 except that the polyurethane (VII) was used instead of the polyurethane (I). . Further, an ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (VII-2) was used instead of the pigment dispersion (I-2).

[Example 8]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 412 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid and isophorone diisocyanate 357 Part by mass is reacted for 10 hours at 80 ° C. in the presence of 300 parts by mass of methyl ethyl ketone, which is an organic solvent, and then 1,3-bis (2-hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione is added. Hydantoin in which R ¹ and R ² in the general formula (1-1) are methyl groups and R ³ and R ⁴ are ethylene groups by supplying and reacting 100 parts by mass and then reacting 11 parts by mass of butanol An organic solvent solution of polyurethane (VIII) having a structure was obtained.

Next, 666 parts by mass of diethylene glycol is added to the organic solvent solution of polyurethane (VIII) and sufficiently stirred, and then the organic solvent solution of polyurethane (VIII) is desolvated, and diethylene glycol is added so that the nonvolatile content becomes 60% by mass. By addition and adjustment, a mixture (VIII-1) of the polyurethane (VIII) and diethylene glycol was obtained.

On the other hand, a powdery vinyl polymer having a weight average molecular weight of 11000 and an acid value of 156 obtained by polymerizing a vinyl monomer mixture containing 77 parts by mass of styrene, 10 parts by mass of acrylic acid and 13 parts by mass of methacrylic acid. Got.

150 parts by mass of the vinyl polymer, 167 parts by mass of the mixture (VIII-1), 500 parts by mass of Pigment Yellow 74 (manufactured by Sanyo Dye Co., Ltd., FastｅｌｌYellow 7413), 193 parts by mass of diethylene glycol, and 8N 84 parts by mass of an aqueous potassium hydroxide solution (solid concentration = 34% by mass) was charged into a planetary mixer (PLM-V-50V manufactured by Inoue Seisakusho Co., Ltd.) kept at 60 ° C. and kneaded for 1 hour.

The ion-exchanged water heated to 60 ° C. in a total amount of 1200 parts by mass for 2 hours was added to the kneaded product to obtain a colored resin composition having a nonvolatile content of 34% by mass and a pigment concentration of 21.7% by mass.

While adding 140 parts by mass of diethylene glycol and 840 parts by mass of ion-exchanged water to the colored resin composition obtained by the above method, the mixture is stirred with a dispersion stirrer to prepare a pigment dispersion precursor (dispersion before dispersion treatment). Obtained.

Next, the precursor of the pigment dispersion was passed through a continuous centrifuge (Kokusan Co., Ltd., Sakai H-600S, 2 L capacity) and centrifuged at a centrifugal force of 18900 G and a residence time of 10 minutes. A pigment dispersion (VIII-2) was obtained by filtration through a 5 μm filter. The pigment concentration of this pigment dispersion (VIII-2) was 14.2% by mass.

By using the pigment dispersion (VIII-2) obtained above and mixing the following components, an ink for inkjet printing having a pigment concentration of 4% by mass was prepared.
Pigment dispersion (VIII-2) (pigment concentration 14.2% by mass); 28.5 g
・ 2-Pyrrolidinone; 8g
・ Triethylene glycol monobutyl ether; 8g
・ Glycerin; 3g
・ Surfactant (Surfinol 440, manufactured by Air Products); 0.5 g
・ Ion exchange water; 52.0 g

[Example 9]
482 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid, and tolylene diisocyanate in a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube, and a stirrer 287 parts by mass are reacted at 80 ° C. for 10 hours in the presence of 300 parts by mass of methyl ethyl ketone as an organic solvent, and then 1,3-bis (2-hydroxyethyl) -5,5 dimethylimidazolidine-2,4-dione In the general formula (1-1), R ¹ and R ² are methyl groups, and R ³ and R ⁴ are ethylene groups. A polyurethane (IX) organic solvent solution having a hydantoin structure was obtained.

Next, 400 parts by mass of diethylene glycol is added to the organic solvent solution of polyurethane (IX) and sufficiently stirred, and then the organic solvent solution of polyurethane (IX) is desolvated, and diethylene glycol is added so that the nonvolatile content becomes 60% by mass. By addition and adjustment, a mixture (IX-1) of the polyurethane (IX) and diethylene glycol was obtained.

A pigment dispersion (IX-2) having a pigment concentration of 14.5% by mass in the same manner as in Example 1 except that the mixture (IX-1) is used instead of the mixture (I-1). Got.

Ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (IX-2) was used instead of the pigment dispersion (I-2).

[Example 10]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 412 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 1,3-bis (2-hydroxyethyl) -5,5 Reaction of 100 parts by mass of dimethylimidazolidine-2,4-dione, 120 parts by mass of 2,2-dimethylolpropionic acid and 357 parts by mass of isophorone diisocyanate at 80 ° C. for 20 hours in the presence of 300 parts by mass of methyl ethyl ketone as an organic solvent. And then reacting 11 parts by weight of butanol to give a polyurethane having a hydantoin structure in which R ¹ and R ² in the general formula (1-1) are methyl groups and R ³ and R ⁴ are ethylene groups (X ) Was obtained.

A pigment dispersion (X-2) having a pigment concentration of 14.5% by mass was obtained in the same manner as in Example 1 except that the polyurethane (X) was used instead of the polyurethane (I). . Further, an ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (X-2) was used instead of the pigment dispersion (I-2).

[Comparative Example 1]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 594 parts by mass of polyoxypropylene glycol (number average molecular weight 2000), 120 parts by mass of 2,2-dimethylolpropionic acid and isophorone diisocyanate 277 By reacting 10 parts by mass with 80 parts by mass of methyl ethyl ketone as an organic solvent for 10 hours and then reacting 9 parts by mass of butanol, R ¹ and R ^{2 in the} general formula (1-1) An organic solvent solution of polyurethane (I ′) having a hydantoin structure in which is a methyl group and R ³ and R ⁴ are ethylene groups was obtained.

A pigment dispersion (I′-2) having a pigment concentration of 14.5% by mass was prepared in the same manner as in Example 1 except that the polyurethane (I ′) was used instead of the polyurethane (I). Obtained. Further, an ink for inkjet printing was prepared in the same manner as in Example 1 except that the pigment dispersion (I′-2) was used instead of the pigment dispersion (I-2).

[Comparative Example 2]
Instead of the polyurethane (I), a weight average molecular weight of 11000 and an acid value of 156 obtained by polymerizing a vinyl monomer mixture containing 77 parts by mass of styrene, 10 parts by mass of acrylic acid and 13 parts by mass of methacrylic acid 250 parts by weight of a certain powdery vinyl polymer, 500 parts by weight of Pigment Yellow 74 (manufactured by Sanyo Dye Co., Ltd., Fast Yellow 7413), 260 parts by weight of diethylene glycol, 8N potassium hydroxide aqueous solution (solid content concentration = 34) (Mass%) 115 parts by mass was charged into a planetary mixer (PLM-V-50V manufactured by Inoue Seisakusho Co., Ltd.) kept at 60 ° C. and kneaded for 1 hour.

By adding ion exchange water heated to 60 ° C. in a total amount of 1200 parts by mass in 2 hours, a colored resin composition having a nonvolatile content of 33.9% by mass and a pigment concentration of 21.5% by mass is added to the kneaded product. Obtained.

By adding 140 parts by mass of diethylene glycol and 840 parts by mass of ion exchange water to the colored resin composition obtained by the above method in small amounts, the mixture was stirred with a dispersion stirrer to obtain a pigment dispersion precursor (dispersion before dispersion treatment). )

Next, the precursor of the pigment dispersion was passed through a continuous centrifuge (Kokusan Co., Ltd., Sakai H-600S, 2 L capacity) and centrifuged at a centrifugal force of 18900 G and a residence time of 10 minutes. A pigment dispersion (II′-2) was obtained by filtration through a 5 μm filter. The pigment concentration of this pigment dispersion (II′-2) was 14.2% by mass.

By using the pigment dispersion (II′-2) obtained above and mixing the following components, an ink for inkjet printing having a pigment concentration of 4 mass% was prepared.
Pigment dispersion (II′-2) (pigment concentration: 14.2% by mass); 28.5 g
・ 2-Pyrrolidinone; 8g
・ Triethylene glycol monobutyl ether; 8g
・ Glycerin; 3g
・ Surfactant (Surfinol 440, manufactured by Air Products); 0.5 g
・ Ion exchange water; 52.0 g

[Measurement of weight average molecular weight]
The weight average molecular weight of the compound (A) such as polyurethane was measured by gel permeation chromatograph (GPC method). Specifically, polyurethane was coated on a glass plate with a 3 mil applicator and dried at room temperature for 1 hour to prepare a semi-dry coating film. The obtained coating film was peeled off from the glass plate, and 0.4 g was dissolved in 100 g of tetrahydrofuran to obtain a measurement sample.

Tetrahydrofuran was used as the eluent and sample solution, and the weight average molecular weight was measured using an RI detector with a flow rate of 1 mL / min, a sample injection amount of 500 μL, and a sample concentration of 0.4 mass%.
Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.

"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Standard sample: A calibration curve was prepared using the following standard polystyrene.
(Standard polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

[Evaluation of storage stability of ink for inkjet printing]
Evaluation was performed based on the viscosity of the ink for inkjet printing obtained above and the particle size of dispersed particles in the ink. The viscosity was measured using VISCOMETER TV-22 manufactured by Toki Sangyo Co., Ltd., and the particle diameter was measured using Microtrac UPA EX150 manufactured by Nikkiso Co., Ltd.

Next, after sealing the ink in a glass container such as a screw tube and performing a heating test for 4 weeks in a thermostat at 70 ° C., the viscosity of the ink and the particle diameter of the dispersed particles in the ink are as follows: It measured by the method similar to the above.

The changes in the viscosity and particle size after the heating test with respect to the viscosity and particle size of the ink before the heating test were calculated based on the following formulas, respectively, and the storage stability of the pigment ink was evaluated.

(Formula I)
[{(Particle size of dispersed particles in ink after heating test) − (Particle size of dispersed particles in ink before heating test)} / (Particle size of dispersed particles in ink before heating test)] × 100

[Criteria]
○: Change rate of particle size is less than 5% Δ: Change rate of particle size is 5% or more and less than 10% ×: Change rate of particle size is 10% or more

(Formula II)
[{(Ink viscosity after heating test) − (Ink viscosity before heating test)} / (Ink viscosity before heating test)] × 100

[Criteria]
○: Viscosity change rate is less than 2% Δ: Viscosity change rate is 2% or more and less than 5% ×: Viscosity change rate is 5% or more

[Evaluation of ink ejection stability]
A diagnostic page was printed and the state of the nozzle was confirmed with a Photomart D5360 (manufactured by Hewlett-Packard Company) in which a black ink cartridge was filled with the inkjet pigment ink. After continuously printing 20 pages of solid print with a print density setting of 100% in an area of 18 cm × 25 cm per page, a diagnostic page was printed again to check the state of the nozzles. The change in the state of the nozzles before and after continuous solid printing was evaluated as the ink ejection property. The evaluation criteria are described below.

[Criteria]
A: No change in the state of the nozzle and no abnormal discharge B: Some ink adhesion to the nozzle was confirmed, but no abnormal ink discharge direction C: Solid Abnormal ink ejection direction or non-ejection of ink after 50 pages were printed continuously D: Abnormal ink ejection direction or non-ejection of ink after solid printing 20 pages continuously E: An abnormality in the ink ejection direction or non-ejection of ink occurred during printing, and printing of 20 pages could not be completed continuously.

[Method for evaluating the sharpness of printed images]
(saturation)
Using the commercially available thermal jet type inkjet printer (Photomart D5360, manufactured by Hewlett-Packard Co., Ltd.) on the printing surface of photographic paper (glossy) [Pictrico Pro Photo Paper, manufactured by Pictorico Co., Ltd.], which is a dedicated paper for inkjet printing, the pigment The black ink cartridge was filled with ink, and solid printing with a print density setting of 100% was performed. The solid print image obtained above was used as a test print.

After leaving the test print obtained above at room temperature for 24 hours, the saturation (C * / L *) of the solid print image was calculated using “SpectroScan Transmission” (manufactured by X-Rite).

(Print density)
The test print obtained above was allowed to stand at room temperature for 24 hours, and then the print density of the solid print image was measured using “SpectroScan Transmission” (manufactured by X-Rite).

(Glossy)
After leaving the test printed matter obtained above at room temperature for 24 hours, the gloss of 60 parts of the gloss of arbitrary three places of the test printed matter was measured using Microhaze Plus (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the average value thereof Was calculated.

Claims (12)

1. A pigment dispersion comprising a compound (A) having a hydantoin structure and a pigment.
2. The pigment dispersion according to claim 1, wherein the compound (A) has a hydantoin structure represented by the following general formula (1).
   

   

   [R ¹ and R ^{2 in} General Formula (1) each independently represent a hydrogen atom or an alkyl group. ]
3. The pigment dispersion according to claim 1, wherein the compound (A) has a structure represented by the following general formula (1-1) including a hydantoin structure.
   

   

   [R ¹ and R ² in the general formula (1-1) each independently represent a hydrogen atom or an alkyl group, and R ³ and R ⁴ each independently represent an alkylene group. ]
4. The pigment dispersion according to claim 2, wherein the compound (A) has a hydantoin structure represented by the general formula (1) in the range of 1 to 30% by mass in the compound (A).
5. The pigment dispersion according to claim 1, wherein the compound (A) is the polyurethane (A-1) having the hydantoin structure.
6. The pigment dispersion according to claim 5, wherein the presence ratio of the urea bond in the compound (A) is in the range of 0 to 2% by mass.
7. The pigment dispersion according to claim 5, wherein the ratio of the primary amino group in the compound (A) is in the range of 0 to 5% by mass.
8. The pigment dispersion according to claim 1 or 5, further comprising an aqueous medium (B).
9. An ink containing the pigment dispersion according to any one of claims 1 to 8.
10. An ink for ink-jet printing containing the pigment dispersion according to any one of claims 1 to 8.
11. A method for producing a pigment dispersion, comprising kneading a compound (A) having a hydantoin structure and a pigment to produce a kneaded product thereof, and then mixing the kneaded product and an aqueous medium (B).
12. By reacting the polyol (a1) containing a polyol having a hydantoin structure with the polyisocyanate (a2) in the presence or absence of a solvent and removing the solvent as necessary, the polyurethane (A-1) is obtained. A hydantoin structure, characterized in that the polyurethane (A-1) and the pigment are kneaded to produce a kneaded product thereof, and then the kneaded product and the aqueous medium (B) are mixed. A process for producing a pigment dispersion containing polyurethane (A-1) having