JP4972394B2 - Method for producing dispersion of crosslinked core-shell polymer particles - Google Patents

Description

  The present invention relates to a water-based ink for ink jet recording and a method for producing a dispersion for ink jet recording used in the ink.

The ink jet recording system is a recording system in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle and attaching them to a recording member. This method is widely spread because it is easy to make full color and is inexpensive, and has many advantages such as the ability to use plain paper as a recording member and non-contact with the object to be printed.
Patent Document 1 discloses a water-based ink in which a pigment is contained in a vinyl polymer.
Patent Document 2 discloses an aqueous pigment dispersion in which a pigment is dispersed with a carboxy group-containing thermoplastic resin, the aqueous pigment dispersion having a carboxy group-containing thermoplastic resin crosslinked after the pigment is dispersed, It is said to be excellent in light resistance, water resistance, solvent resistance, stability over time, and the like.
Patent Document 3 discloses a method for producing an aqueous pigment dispersion in which a pigment and a resin having a carboxy group and a crosslinkable functional group are used, and the crosslinkable functional group of the resin is reacted with a crosslinker to crosslink. The obtained aqueous pigment dispersion is said to have good storage stability and form a coating film excellent in water resistance and the like.
However, these water dispersions and inks are insufficient in improving glossiness and improving bronzing.

International Publication No. 00/39226 Pamphlet International Publication No. 99/52966 Pamphlet Japanese Patent Laid-Open No. 9-104834

  An object of the present invention is to provide a water-based ink excellent in improving printing density and glossiness and suppressing bronzing, and a method for producing a dispersion for inkjet recording used in the ink.

The present invention provides the following (1) and (2).
(1) A method for producing a dispersion of crosslinked core-shell polymer particles containing a colorant, comprising the following steps I to III.
Step I: A step of polymerizing a hydrophobic monomer and a crosslinkable monomer having two or more reactive unsaturated groups in the presence of water, an organic solvent and a polymer having a salt-forming group to obtain a dispersion of core-shell polymer particles. Step II: Step of dispersing the mixture containing the core-shell polymer particle dispersion obtained in Step I and the colorant to obtain a core-shell polymer particle dispersion containing the colorant Step III: obtained in Step II (2) Step (2) for obtaining a dispersion of crosslinked core-shell polymer particles containing a colorant by crosslinking the core-shell polymer particles containing the colorant using a crosslinking agent having two or more reactive functional groups. A water-based ink for ink-jet recording, comprising a dispersion of crosslinked core-shell polymer particles containing a colorant, obtained by the method (1).

The water-based ink for ink-jet recording of the present invention is excellent in print density when printed on plain paper, and can give a printed matter with improved gloss and suppression of bronze phenomenon when printed on special paper. .
Moreover, according to the method of the present invention, a dispersion of crosslinked core-shell polymer particles containing a colorant to be contained in an aqueous ink for inkjet recording can be efficiently produced.

First, each component used for the manufacturing method of the dispersion of this invention is demonstrated.
The cross-linked core-shell polymer particles containing the colorant are sometimes referred to as “colorant-containing cross-linked core-shell polymer particles”, and the cross-linkable monomer having two or more reactive unsaturated groups is simply referred to as “cross-linkable monomer”. The crosslinking agent having two or more reactive functional groups is sometimes simply referred to as “crosslinking agent”.

There are no particular limitations on the colorant colorants, pigments, hydrophobic dyes, water-soluble dyes (acid dyes, reactive dyes, direct dyes, etc.) or the like can be used, water resistance, dispersion stability and abrasion resistance From the viewpoint, pigments and hydrophobic dyes are preferred. Among them, it is preferable to use a pigment in order to express the high weather resistance which has been recently demanded.
When the pigment and the hydrophobic dye are used in an aqueous ink, it is necessary to use a surfactant and a polymer to form fine particles that are stable in the ink. In particular, from the viewpoints of bleeding resistance, water resistance, and the like, it is preferable to include a pigment and / or a hydrophobic dye in the polymer particles.
The pigment may be either an inorganic pigment or an organic pigment. If necessary, they can be used in combination with extender pigments.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Of these, carbon black is preferred particularly for black aqueous inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments.
Preferred examples of organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed.
Examples of extender pigments include silica, calcium carbonate, and talc.

The hydrophobic dye should just be what can be contained in the particle | grains of a crosslinked polymer (A), and there is no restriction | limiting in particular in the kind. The hydrophobic dye is dissolved in an amount of 2 g / L or more, preferably 20 to 500 g / L (25 ° C.) with respect to the organic solvent (preferably methyl ethyl ketone) used in the production of the polymer from the viewpoint of efficiently containing the dye in the polymer. What to do is desirable.
Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes. Among these, oil-soluble dyes are preferable. Examples of the oil-soluble dye include C.I. I. Solvent Black, C.I. I. Solvent Yellow, C.I. I. Solvent Red, C.I. I. Solvent Violet, C.I. I. Solvent Blue, C.I. I. Solvent Green, and C.I. I. One or more types of products selected from the group consisting of Solvent Orange are listed, which are commercially available from Orient Chemical Co., Ltd., BASF Corp. and others.
Among these, from the viewpoint of enhancing the effect of reducing the bronzing phenomenon, it is preferable to use a cyan pigment, and a phthalocyanine pigment is more preferable. Specifically, a copper phthalocyanine pigment is preferable. I. One or more selected from the group consisting of CI Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 16 and 60 are preferred. The above colorants can be used alone or in admixture of two or more at any ratio.
The weight ratio of the colorant to the crosslinked core-shell polymer [(colorant weight / weight of crosslinked core-shell polymer particles containing colorant) × 100] is preferably 25 to 75, more preferably 30 to 70, and particularly preferably. Is 40-65. When the weight ratio is within the above range, when the crosslinked core-shell polymer is blended with the inkjet recording dispersion or the water-based ink, the printing density and glossiness are improved, and the bronzing phenomenon is more excellent.

Polymer having a salt-forming group A polymer having a salt-forming group (hereinafter also simply referred to as “polymer”) is crosslinked with a crosslinking agent to form a crosslinked polymer. Here, as the polymer, when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the amount dissolved is preferably 10 g or less, more preferably 5 g or less, and even more preferably 1 g. The following water-insoluble polymers are preferred from the viewpoint of ease of production of the core-shell polymer particles. The dissolution amount is the dissolution amount when the polymer salt-forming groups are neutralized 100% with acetic acid or sodium hydroxide according to the kind of the salt-forming groups. Examples of the salt-forming group include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group, and a carboxy group is particularly preferable from the viewpoint of reactivity with a crosslinking agent.
Examples of the polymer to be used include polyester, polyurethane, and vinyl polymer. From the viewpoint of dispersion stability, a vinyl polymer obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound) is preferable.

(Vinyl polymer)
As the vinyl polymer, (a) a salt-forming group-containing monomer (hereinafter sometimes referred to as “(a) component”), (b) a macromer (hereinafter sometimes referred to as “(b) component”) and / or (c ) A vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to as “monomer mixture A”) containing a hydrophobic monomer (hereinafter also referred to as “component (c)”) is preferable. This vinyl polymer has a structural unit derived from the component (a), a structural unit derived from the component (b) and / or a structural unit derived from the component (c). A more preferable vinyl polymer has a structural unit derived from the component (a) or a structural unit derived from the components (a) and (c) as a main chain, and a graft having a structural unit derived from the component (b) as a side chain. It is a polymer.

(A) The salt-forming group-containing monomer is used from the viewpoint of enhancing the dispersion stability of the resulting dispersion.
Examples of the salt-forming group-containing monomer include cationic monomers and anionic monomers described in JP-A-9-286939, paragraph [0022].
Representative examples of the cationic monomer include unsaturated amine-containing monomers and unsaturated ammonium salt-containing monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N′-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferable.
Representative examples of anionic monomers include unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, and the like.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxy Examples thereof include ethyl phosphate.
Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

(B) The macromer is used from the viewpoint of enhancing the dispersion stability of the colorant-containing crosslinked core-shell polymer particles. The macromer includes a macromer which is a monomer having a polymerizable unsaturated group having a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000. In addition, the number average molecular weight of (b) macromer is measured using polystyrene as a standard substance by gel chromatography using chloroform containing 1 mmol / L of dodecyldimethylamine as a solvent.
Among (b) macromers, from the viewpoint of dispersion stability of the colorant-containing crosslinked core-shell polymer particles, styrene-based macromers and aromatic group-containing (meth) acrylate-based macromers having a polymerizable functional group at one end are preferable. .
Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. Examples of the styrene monomer include styrene, 2-methylstyrene, vinyl toluene, ethyl vinyl benzene, vinyl naphthalene, chlorostyrene, and the like.

Examples of the aromatic group-containing (meth) acrylate-based macromer include a homopolymer of an aromatic group-containing (meth) acrylate or a copolymer thereof with another monomer. As an aromatic group-containing (meth) acrylate, an arylalkyl having 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably 7 to 12 carbon atoms, which may have a substituent containing a hetero atom. (Meth) acrylate having an aryl group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a group or a substituent containing a hetero atom In addition, examples of the substituent containing a hetero atom include a halogen atom, an ester group, an ether group, and a hydroxy group. Examples include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, and benzyl (meth) acrylate is particularly preferable.
The polymerizable functional group present at one end of the macromer is preferably an acryloyloxy group or a methacryloyloxy group, and the other monomer to be copolymerized is preferably acrylonitrile.
The content of the styrene monomer in the styrene macromer or the aromatic group-containing (meth) acrylate in the aromatic group-containing (meth) acrylate macromer is preferably 50% by weight from the viewpoint of increasing the affinity with the pigment. Above, more preferably 70% by weight or more.

(B) The macromer may have a side chain composed of another structural unit such as an organopolysiloxane. This side chain can be obtained, for example, by copolymerizing a silicone macromer having a polymerizable functional group at one end represented by the following formula (1).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} O] _{t -Si (CH 3) 3 (} 1)
(In the formula, t represents a number of 8 to 40).
Examples of commercially available styrenic macromers as component (b) include Toa Gosei Co., Ltd. trade names, AS-6 (S), AN-6 (S), HS-6 (S), and the like. It is done.

(C) The hydrophobic monomer is used from the viewpoint of improving the printing density. Examples of the hydrophobic monomer include alkyl (meth) acrylates and aromatic group-containing monomers.
As the alkyl (meth) acrylate, those having an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms are preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meta) ) Acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) Examples include decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and (iso) stearyl (meth) acrylate.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present. Indicates. “(Meth) acrylate” indicates acrylate, methacrylate, or both.

The aromatic group-containing monomer has an aromatic group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a substituent containing a hetero atom. Vinyl monomers are preferable, and examples thereof include the styrene monomer (c-1 component) and the aromatic group-containing (meth) acrylate (c-2 component). The above-mentioned thing is mentioned as a substituent containing a hetero atom.
Among the components (c), a styrene monomer (c-1 component) is preferable from the viewpoint of improving printing density, and styrene and 2-methylstyrene are particularly preferable as the styrene monomer (c-1 component). The content of the component (c-1) in the component (c) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density.
Moreover, as an aromatic group containing (meth) acrylate (c-2) component, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. are preferable. The content of the component (c-2) in the component (c) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density and gloss.
Moreover, it is also preferable to use (c-1) component and (c-2) component together.

The monomer mixture A may further contain (d) a hydroxyl group-containing monomer (hereinafter sometimes referred to as “component (d)”). (D) The hydroxyl group-containing monomer exhibits an excellent effect of enhancing dispersion stability.
As the component (d), for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of added moles of oxyalkylene group. The same)) (meth) acrylate, polypropylene glycol (n = 2-30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) (meth) acrylate, etc. Can be mentioned. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable.

The monomer mixture A may further contain (e) a monomer represented by the following formula (2) (hereinafter also referred to as “(e) component”).
CH ₂ = C (R ¹ ) COO (R ² O) _q R ³ (2)
Wherein R ¹ is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, R ² is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ is , A monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, q means an average number of added moles, and represents a number of 1 to 60, preferably 1 to 30. )
(E) component expresses the outstanding effect of improving discharge property.
In the formula (2), examples of the hetero atom include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.
Preferable examples of R ¹ include methyl group, ethyl group, (iso) propyl group and the like.
Preferred examples of the R ² O group include an oxyethylene group, an oxytrimethylene grave, an oxypropane-1,2-diyl group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, and two or more kinds thereof. Examples thereof include oxyalkanediyl groups having 2 to 7 carbon atoms (oxyalkylene groups).
Preferable examples of R ³ include aliphatic alkyl groups having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, alkyl groups having 7 to 30 carbon atoms having an aromatic ring, and 4 to 30 carbon atoms having a heterocyclic ring. Of the alkyl group.

  Specific examples of the component (e) include methoxypolyethylene glycol (1 to 30: the value of q in the formula (2), the same applies hereinafter) (meth) acrylate, methoxypolytetramethylene glycol (1 to 30) ( (Meth) acrylate, ethoxy polyethylene glycol (1-30) (meth) acrylate, octoxy polyethylene glycol (1-30) (meth) acrylate, polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether, (iso) Propoxy polyethylene glycol (1-30) (meth) acrylate, butoxy polyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol) Polymerization) (1 to 30, ethylene glycol therein: 1-29) (meth) acrylate. Among these, octoxypolyethylene glycol (1-30) (meth) acrylate and polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether are preferable.

Specific examples of commercially available (d) and (e) components include Shin-Nakamura Chemical Co., Ltd. polyfunctional acrylate monomer (NK ester) M-40G, 90G, 230G, and Nippon Oil & Fats Co., Ltd. BLEMMER series, PE-90, 200, 350, PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800 , 50PEP-300, 50POEP-800B, 43PAPE600B, and the like.
The components (a) to (e) can be used alone or in admixture of two or more.

The content of the components (a) to (e) in the monomer mixture A (content as an unneutralized amount; the same applies hereinafter) or (a) to (a) in the polymer at the time of producing the polymer having a salt-forming group (E) Content of the structural unit derived from a component is as follows.
The content of component (a) is preferably 2 to 40% by weight, more preferably 2 to 30% by weight, and particularly preferably 3 to 20% by weight from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (b) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, particularly from the viewpoint of enhancing the interaction with the colorant.
The content of the component (c) is preferably 5 to 98% by weight, more preferably 10 to 60% by weight, from the viewpoint of improving print density.
The content of component (d) is preferably 5 to 40% by weight, more preferably 7 to 20% by weight, from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (e) is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, from the viewpoint of improving dischargeability.
The total content of [(a) component + (d) component] in the monomer mixture A is preferably 6 to 60% by weight, more preferably 10 to 50% by weight, from the viewpoint of dispersion stability of the resulting dispersion. It is. The total content of [component (a) + component (e)] is preferably 6 to 75% by weight, more preferably 13 to 50% by weight, from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. . Moreover, the total content of [(a) component + (d) component + (e) component] is preferably 6 to 60% by weight, more preferably from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. 7 to 50% by weight.
The weight ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 to 1, more preferably from the viewpoint of dispersion stability and print density of the resulting dispersion. Is 0.02 to 0.67, more preferably 0.03 to 0.50.

(Production of polymer having a salt-forming group)
The polymer having a salt-forming group is produced by copolymerizing the monomer mixture A by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is not particularly limited, but a polar organic solvent is preferable. When the polar organic solvent is miscible with water, it can be used by mixing with water. Examples of the polar organic solvent include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol and propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate and the like. Among these, methanol, ethanol, acetone, methyl ethyl ketone, or a mixed solvent of one or more of these and water is preferable.
In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), t-butyl peroxyoctate, dibenzoyl oxide, etc. Known radical polymerization initiators such as organic peroxides can be used.
The amount of the radical polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per 1 mol of the monomer mixture A.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide may be further added.

Since the polymerization conditions of the monomer mixture A vary depending on the radical polymerization initiator, the monomer, the type of the solvent, and the like, it cannot be determined unconditionally. Usually, the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C, and the polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained polymer can be purified by repeating reprecipitation or by removing unreacted monomers and the like by membrane separation, chromatographic method, extraction method and the like.

The weight average molecular weight of the polymer used in the present invention is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, from the viewpoint of printing density, glossiness, and dispersion stability of the colorant, and preferably from 10,000 to 30 Is more preferable, and 20,000 to 300,000 is particularly preferable. In addition, the weight average molecular weight of a polymer is measured by the method shown in an Example.
When the water-insoluble vinyl polymer used in the present invention has (a) a salt-forming group derived from a salt-forming group-containing monomer, it is neutralized with a neutralizing agent. As the neutralizing agent, an acid or a base can be used depending on the type of the salt-forming group in the polymer. For example, hydrochloric acid, acetic acid, propionic acid, phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycolic acid, gluconic acid, glyceric acid and other acids, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine , Bases such as trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine.

The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 50 to 150%.
Here, the degree of neutralization can be determined by the following formulas (3) and (4) when the salt-forming group is an anionic group.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100 (3)
When the salt-forming group is a cationic group, it can be determined by the following formula.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]} × 100 (4)
The acid value and amine value can be calculated from the structural unit of the polymer. Alternatively, it can also be determined by a method in which a polymer is dissolved in an appropriate solvent (for example, methyl ethyl ketone) and titrated.

Hydrophobic monomer The hydrophobic monomer is the same as the hydrophobic monomer (c) described in the section of the polymer having a salt-forming group. Examples of the hydrophobic monomer include the styrene monomer (c-1 component) and the aromatic group-containing (meth) acrylate (c-2 component). Among these, from the viewpoint of improving printing density, styrene monomers (c-1 component) are preferable, and styrene and 2-methylstyrene are particularly preferable.

Crosslinkable monomers having two or more reactive unsaturated groups Crosslinkable monomers having two or more reactive unsaturated groups include (1) ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (Meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,2-butylene glycol di (meth) acrylate, 1,3-butylene glycol di ( (Meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra ( And (meth) acrylic acid ester compounds of polyhydric alcohols such as acrylate; (2) acrylamide compounds such as N-methylallylacrylamide, N-vinylacrylamide, N, N′-methylenebis (meth) acrylamide, bisacrylamide acetic acid (3) Divinyl compounds such as divinylbenzene, divinyl ether, divinylethyleneurea; (4) diallyl phthalate, diallyl malate, diallylamine, triallylamine, triallyl ammonium salt, allyl etherified pentaerythritol, at least 2 in the molecule And polyallyl compounds such as allyl ethers of sucrose having one allyl ether unit.
Among these, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, divinylbenzene, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, and methylenebisacrylamide are particularly preferable.

Crosslinking agent having two or more reactive functional groups A crosslinking agent having two or more reactive functional groups is used to moderately crosslink a polymer having a salt-forming group. The molecular weight of the cross-linking agent is preferably 120 to 2000, more preferably 150 to 1500, and particularly preferably 150 to 1000, from the viewpoint of easy reaction and storage stability of the resulting cross-linked polymer particles.
The number of reactive functional groups is preferably 2 to 4 and most preferably 2 from the viewpoint of improving the gloss by controlling the molecular weight. The reactive functional group is preferably at least one selected from the group consisting of a hydroxyl group, an epoxy group, an aldehyde group, an amino group, and a carboxy group.
Specific examples of the crosslinking agent include the following (a) to (e).
(A) Compound having two or more hydroxyl groups in the molecule:
For example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl alcohol, diethanolamine, Polyhydric alcohols such as tridiethanolamine, polypropylene glycol, polyvinyl alcohol, pentaerythritol, sorbit, sorbitan, glucose, mannitol, mannitan, sucrose, and glucose.

(B) Compound having two or more epoxy groups in the molecule:
For example, polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether.
(C) Compound having two or more aldehyde groups in the molecule:
For example, polyaldehydes such as glutaraldehyde and glyoxal.
(D) Compound having two or more amino groups in the molecule:
For example, polyamines such as ethylenediamine and polyethyleneimine.
(E) Compound having two or more carboxy groups in the molecule:
For example, polyvalent carboxylic acids such as oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid and adipic acid.
Among these, (b) a compound having two or more epoxy groups in the molecule is preferable, and trimethylolpropane polyglycidyl ether is particularly preferable.

The polymer having a salt-forming group has a reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent. Preferred examples of the combination of both are as follows.
When the reactive group of the polymer is an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, the crosslinking agent is preferably the compounds (a), (b), and (d).
Moreover, when the reactive group of a polymer is an amino group and a hydroxyl group, the said (b), (c) and (e) compound are preferable for a crosslinking agent.
When the reactive group of the polymer is an isocyanate group or an epoxy group, the crosslinking agent is preferably the compounds (a), (d) and (e).
Among the above combinations, from the viewpoint of controlling the polymer so as to give an appropriate cross-linked structure, at least one selected from an acidic group (carboxy group, sulfonic acid group, phosphoric acid group, etc.), amino group and hydroxyl group. A combination of a polymer having a reactive group and (b) a compound having two or more epoxy groups in the molecule is particularly preferred.

Polymers having an acidic group such as a carboxy group, a sulfonic acid group, and a phosphoric acid group, an amino group, a hydroxyl group, an isocyanate group, and an epoxy group as the reactive group (crosslinkable functional group) that can react with the crosslinking agent are described above. In the production of a polymer, it can be produced by copolymerizing a polymerizable monomer composition containing a monomer having the reactive group.
As the polymer having a reactive group capable of reacting with a crosslinking agent, the polymer having a salt-forming group such as an acidic group or amino group may be a polymer obtained by copolymerization of the above-mentioned salt-forming group-containing monomer. As a polymer to have, the polymer which copolymerized the above-mentioned hydroxyl-containing monomer can be used.
As the polymer having an epoxy group, a monomer having an epoxy group, specifically, a polymer obtained by copolymerizing glycidyl (meth) acrylate can be used. As the polymer having an isocyanate group, (i) a monomer having an isocyanate group, for example, a polymer copolymerized with isocyanate ethyl (meth) acrylate, (ii) an isocyanate-terminated prepolymer obtained from an unsaturated polyester polyol and isocyanate was copolymerized. A polymer or the like can be used.

Production of Dispersion of Colorant-Containing Crosslinked Core-Shell Polymer Particles A dispersion of crosslinked core-shell polymer particles containing the colorant of the present invention is produced by a method having the following steps I to III.
Step I: A step of polymerizing a hydrophobic monomer and a crosslinkable monomer having two or more reactive unsaturated groups in the presence of water, an organic solvent and a polymer having a salt-forming group to obtain a dispersion of core-shell polymer particles. Step II: Step of dispersing the mixture containing the core-shell polymer particle dispersion obtained in Step I and the colorant to obtain a core-shell polymer particle dispersion containing the colorant Step III: obtained in Step II Cross-linking the core-shell polymer particles containing the colorant using a cross-linking agent having two or more reactive functional groups to obtain a dispersion of the cross-linked core-shell polymer particles containing the colorant

In step I, first, a polymer having the above-mentioned salt-forming group dissolved in an organic solvent, a hydrophobic monomer and a crosslinkable monomer (hereinafter referred to as monomer mixture B) are added to an aqueous medium and emulsified and dispersed. It is preferable to polymerize in the state. At this time, it is preferable to use a neutralizing agent to neutralize the polymer having a salt-forming group, but the polymer may be previously neutralized with a neutralizing agent. There is no particular limitation on the degree of neutralization of the polymer. Usually, it is preferable to neutralize so that the finally obtained dispersion has neutral liquidity, for example, pH of 4.5 to 10 (20 ° C.). The pH can also be determined by the desired degree of neutralization of the polymer.
Examples of the organic solvent include one or more selected from the group consisting of alcohol solvents, ketone solvents, and ether solvents. The organic solvent has a solubility in 100 g of water at 20 ° C., preferably 5 g or more, more preferably 10 g or more, more specifically preferably 5 to 80 g, more preferably 10 to 50 g, Methyl ethyl ketone is preferred. Examples of the alcohol solvent include ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Among these solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable. These solvents can be used alone or in admixture of two or more.
Although there is no restriction | limiting in particular in the emulsification method in the process I, It is preferable to fully emulsify the monomer mixture B by the ultrasonic dispersion method etc. The ultrasonic disperser preferably has a frequency of 20 to 2000 kHz and a wattage per liter of the total reaction liquid amount of preferably 20 to 1000 W, more preferably 50 to 800 W. It is commercially available from companies such as Nippon Seiki Seisakusho and Alex. As for the emulsification conditions of Step I, the temperature is preferably 5 to 50 ° C., and the time is preferably about 0.5 to 3 hours.

The weight ratio of [crosslinkable monomer having two or more reactive unsaturated groups / hydrophobic monomer] is preferably 1/100 to 20/100, more preferably 2/100 to 10/100.
The weight ratio of [total amount of hydrophobic monomer and crosslinkable monomer having two or more reactive unsaturated groups / polymer amount having a salt-forming group] is preferably 2/10 to 10/2, and preferably 3/10 to 10 10/3 is more preferable.
As the polymerization initiator, those described above can be used. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C.
The obtained core-shell polymer particle dispersion comprises a core-shell polymer particle in which a cross-linked polymer particle obtained by polymerizing a hydrophobic monomer and a cross-linkable monomer is contained in a shell portion made of a polymer having a salt-forming group as a core portion. However, it is dispersed in water as the main medium.

In Step II, the obtained dispersion of core-shell polymer particles and the colorant are mixed and dispersed. If necessary, an organic solvent and water can be further added.
In the dispersion, the colorant is preferably 5 to 50% by weight, the organic solvent is preferably 10 to 70% by weight, the polymer is preferably 2 to 40% by weight, and the water is preferably 10 to 70% by weight.
The temperature during dispersion is preferably 5 to 50 ° C, more preferably 10 to 35 ° C.
There is no restriction | limiting in particular in the dispersion method of the mixture in process II. Preferably, after pre-dispersion, this dispersion is further performed by applying a shear stress, and the particles are atomized so as to obtain polymer particles having a desired average particle diameter.
When preliminarily dispersing the mixture, a commonly used mixing and stirring device such as an anchor blade can be used. Among the mixing and stirring devices, Ultra Disper [Asada Steel Co., Ltd., trade name], Ebara Milder [Ebara Manufacturing Co., Ltd., trade name], TK homomixer, TK pipeline mixer, TK homo jetter, TK homomic line flow, High-speed agitating and mixing devices such as Filmix [Special Machine Industry Co., Ltd., trade name], Clear Mix [M Technique Co., trade name], K-Dymill [Kinetic Dispersion Co., Ltd., trade name] and the like are preferable.

  Examples of means for applying the shear stress of this dispersion include a kneader such as a roll mill, a bead mill, a kneader, and an extruder, a high-pressure homogenizer [Izumi Food Machinery Co., Ltd., trade name], Minilab 8.3H type (Rannie, trade name). Homovalve type high pressure homogenizers, microfluidizers (Microfluidics, trade name), Nanomizers (Nanomizer Co., trade names), Ultimateizers (Sugino Machine Co., trade names), Genus PY (Shiramizu Chemical Co., Ltd.) , Product name], DeBEE2000 [Nippon BEE Co., Ltd., product name] and the like, chamber type high pressure homogenizers and the like. Among these, a high-pressure homogenizer is preferable from the viewpoint of reducing the particle size of the pigment contained in the mixture.

The dispersion obtained in step II is in the form of particles in which a colorant is encapsulated in the core-shell polymer particles, in the form of particles in which the colorant is uniformly dispersed in the core-shell polymer particles, or on the surface of the core-shell polymer particles. It is considered that the particle form in which the agent is exposed is dispersed in water and an organic solvent as a dispersion medium.
An aqueous dispersion can be obtained by distilling off the organic solvent from the resulting dispersion of the colorant-containing core-shell polymer particles to form an aqueous system. The removal of the organic solvent can be performed by a general method such as vacuum distillation. It is preferable that the organic solvent in the obtained aqueous dispersion is substantially removed, preferably 0.1% by weight or less. The organic solvent may be removed after step II and / or after step III, but from the viewpoint of controlling bronzing, a method of removing the organic solvent between steps II and III is preferred.

In Step III, the obtained core-shell polymer particles containing a colorant are reacted with a crosslinking agent to obtain a dispersion of the colorant-containing crosslinked core-shell polymer particles.
The catalyst, solvent, temperature, and time in the above reaction can be appropriately determined in consideration of the crosslinking agent to be used. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C.
The amount of the crosslinking agent used is 0.5 with respect to 100 parts by weight of the polymer having a salt-forming group constituting the shell part of the core-shell polymer particle containing the colorant, from the viewpoint of improving glossiness and improving the print density. -15 parts by weight is preferred, 0.7-13 parts by weight is more preferred, 1.0-11 parts by weight is even more preferred, and 1.5-9 parts by weight is particularly preferred.

The crosslinking rate (mol%) of the shell portion determined by the following formula (5) is preferably 1 to 80%, more preferably 3 to 60%, and particularly preferably 5 to 60% from the viewpoint of printing density and gloss. 50%.
Cross-linking ratio of shell part (mol%) = [number of molar equivalents of cross-linking agent to be reacted with 1 mol of polymer constituting shell part × 100 / reactive group capable of reacting with cross-linking agent possessed by 1 mol of polymer constituting shell part Number of moles] (5)
In the formula (5), “the number of molar equivalents of the crosslinking agent reacted with 1 mol of the polymer constituting the shell portion” means the number of moles of the crosslinking agent reacted with 1 mol of the polymer constituting the shell portion in one molecule of the crosslinking agent. It is a value multiplied by the number of reactive groups.
The polymer particles obtained by crosslinking in Step III are considered to be polymer particles obtained by crosslinking a polymer having a salt-forming group constituting the shell portion of the core-shell polymer particle containing the colorant.
It is preferable to remove coarse particles by filtering the resulting dispersion containing the colorant-containing crosslinked core-shell polymer particles.

Aqueous dispersion for inkjet recording and aqueous ink The aqueous ink of the present invention contains the dispersion or aqueous dispersion of the present invention, and if necessary, addition of a wetting agent, a dispersant, an antifoaming agent, an antifungal agent, a chelating agent, etc. An agent can be added. There is no restriction | limiting in particular in the mixing method of these additives.
The content of the colorant-containing crosslinked core-shell polymer particles in the water-based ink for ink-jet recording is as follows from the viewpoint of improving the gloss and suppressing the bronze phenomenon.
The content of the colorant-containing crosslinked core-shell polymer particles is preferably 1 to 15% by weight, more preferably 2 to 12% by weight, and particularly preferably 2 to 10% by weight.
The weight ratio of the core part to the shell part (core part / shell part) of the colorant-containing crosslinked core-shell polymer particles is preferably 0.3 to 3, more preferably 0.3 to, from the viewpoint of printing density and gloss. 2, More preferably, it is 0.5-1.5, Most preferably, it is 0.7-1.3. The calculation of the weight ratio between the core part and the shell part includes the amount of the crosslinking agent.
The water content is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.

The average particle diameter of the colorant-containing crosslinked core-shell polymer particles in the obtained water dispersion and water-based ink is preferably 40 to 150 nm, more preferably 45 to 130 nm, and particularly preferably 50 to 50 from the viewpoint of glossiness and bronzing phenomenon suppression. 120 nm. In addition, an average particle diameter is performed by the method of an Example description.
The preferable surface tension (20 ° C.) of the aqueous dispersion and the aqueous ink is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m as the aqueous dispersion, and preferably 25 to 68 as the aqueous ink. 50 mN / m, more preferably 27 to 45 mN / m.
The viscosity (20 ° C.) at a solid content of 10% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s, in order to obtain a good viscosity when used as a water-based ink. Further, the viscosity (20 ° C.) of the water-based ink is preferably 2 to 12 mPa · s, and more preferably 2.5 to 10 mPa · s, in order to maintain good ejection properties. The pH of the water-based ink is preferably 4-10.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
Production Example 1 (Production of a polymer having a salt-forming group)
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol), and 10% of 200 parts of each monomer shown in Table 1 were mixed and thoroughly replaced with nitrogen gas. A mixed solution was obtained.
On the other hand, the remaining 90% of the monomers shown in Table 1 were charged into a dropping funnel, and 0.27 part of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone and a radical polymerization initiator (2,2′-azobis (2,4-dimethyl) were added. Valeronitrile), trade name: V-65) 1.2 parts were added and mixed, and the gas was sufficiently replaced with nitrogen gas to obtain a mixed solution.
Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually added dropwise over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution in which 0.3 part of the radical polymerization initiator was dissolved in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and then at 70 ° C. for 2 hours. Further, a polymer solution having a polymer concentration adjusted to 35% by weight with methyl ethyl ketone was obtained.
The weight average molecular weight of the obtained polymer was measured by gel chromatography using dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent using polystyrene as a standard substance. The column used was Tosoh Corporation HLC-8120GPC. The results are shown in Table 1.

The details of the compounds shown in Table 1 are as follows.
NM-95: Styrene macromer: Japanese Patent Application Laid-Open No. 2005-54175, macromer described in Production Example 1, number average molecular weight: 3200, polymerizable functional group: methacryloyloxy group 43 PAPE600B: phenoxy polyethylene glycol polypropylene glycol monomethacrylate (ethylene oxide average) Addition mole number = 6, propylene oxide average addition mole number = 6), terminal: phenyl group, manufactured by NOF Corporation, trade name: BLEMMER 43PAPE600B
PP-800: Polypropylene glycol monomethacrylate (propylene oxide average added mole number = 13, terminal hydroxyl group), manufactured by NOF Corporation, trade name: BLEMMER PP-800

Example 1 (Preparation of aqueous dispersion of colorant-containing crosslinked core-shell polymer particles)
(Step I) Liquid A {12.86 parts of 5N aqueous sodium hydroxide and 25% aqueous ammonia 6. And ion-exchanged water 1198.86 parts} at room temperature with stirring (about 100 rpm) [styrene, divinylbenzene (6.4 parts relative to 100 parts of styrene, the pure content of divinylbenzene is 81 % By weight, trade name: DVB-810: manufactured by Nippon Steel Chemical Co., Ltd., radical polymerization initiator (2,2′-azobis (2,4-dimethylvaleronitrile), trade name: V-65, 100 parts of styrene After adding dropwise B liquid prepared by mixing 79.16 parts of 2.2 parts) and 352.4 methyl ethyl ketone solution of the polymer obtained in Production Example 1, ultrasonic dispersion (Nippon Seiki Co., Ltd.) Made by Seisakusho, Ultrasonic Generater Nissei Model USS-300T, 300μA) for 5 hours to emulsify, then heated to 75 ° C, polymerized with stirring for 3 hours, and styrene (hydrophobic monomer) A dispersion of core-shell polymer particles in which a crosslinked polymer particle obtained by polymerizing styrene and divinylbenzene (crosslinkable monomer) becomes a core portion, and a polymer having a salt-forming group obtained in Production Example 1 becomes a shell portion. Obtained.
(Step II) 271.34 parts of methyl ethyl ketone and 29.03 parts of ion-exchanged water were added to 1139.18 parts (solid content: 10%) of the obtained core-shell polymer particle dispersion, and a copper phthalocyanine pigment (CI pigment) was added. Blue 15: 3) 120 parts were added, and dispersion treatment was performed for 2 hours at a peripheral speed of 15 m / s using a pico mill manufactured by Asada Iron Works Co., Ltd. The obtained mixture was subjected to a 5-pass dispersion treatment with a microfluidizer (trade name, manufactured by Microfluidics) at a pressure of 150 MPa.
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, and a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) was used. An aqueous dispersion of pigment-containing polymer particles having a solid content concentration of 22% was obtained by filtering with an attached needleless syringe having a capacity of 25 mL (manufactured by Terumo Corporation) and removing coarse particles.

(Step III) Next, 200 parts of the obtained aqueous dispersion (21.3 parts of polymer) was put into a reaction vessel under a nitrogen atmosphere, and a crosslinking agent (trimethylolpropane polyglycidyl ether, trade name: Denacol). EX-321: Epoxy equivalent 140: manufactured by Nagase ChemteX Corporation) 0.41 part (crosslinking rate: 21 mol%) and 21.5 parts of ion-exchanged water were added and reacted at 90 ° C. for 1.5 hours with stirring. And the concentration was adjusted with ion-exchanged water to obtain an aqueous dispersion of crosslinked core-shell polymer particles containing a pigment having a solid content concentration of 20%.
The average particle size of this aqueous dispersion was measured by the following method and found to be 108 nm.
(Measurement method of average particle size)
The measurement was performed with a laser particle analysis system ELS-8000 (cumulant analysis) of Otsuka Electronics Co., Ltd. The measurement conditions are a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 100. The refractive index of water (1.333) is input as the refractive index of the dispersion solvent. The measurement concentration was usually about 5 × 10 ⁻³ wt%.

In addition, the crosslinking rate of the shell part was computed as follows based on the said Formula (5).
In the production of the core-shell polymer particles, 0.41 part (epoxy equivalent 140) of the crosslinking agent (Denacol EX-321) was reacted with 10 parts of the polymer of the shell part, so that 1 mol of the water-insoluble polymer (weight average molecular weight 160,000) The number of molar equivalents of the crosslinking agent to be reacted is
(0.41 / 140) / (10/160000) = 46.8.
Here, since the crosslinking agent (Denacol EX-321) reacts with a carboxy group and a hydroxyl group, the number of moles of the reactive group that can react with the crosslinking agent possessed by 1 mole of the water-insoluble polymer is methacrylic acid possessed by 1 mole of the water-insoluble polymer. It is the total number of moles of acid (molecular weight 86) and polypropylene glycol monomethacrylate (PP-800, molecular weight 840).
160000 × 0.12 / 86 + 16000 × 0.15 / 840 = 252 mol Therefore, the crosslinking ratio of the shell portion is 46.8 × 100/252 = 19 mol%.

Comparative Example 1 (Preparation of dispersion of crosslinked polymer particles containing colorant)
68 parts of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 281 parts of methyl ethyl ketone, and then 12.4 parts of neutralizer 1 (5N aqueous sodium hydroxide solution) (neutralization degree 55%) ) And neutralizing agent 2 (25% aqueous ammonia solution) 6.5 parts (neutralization degree 100%) and ion-exchanged water 975 parts to neutralize the salt-forming groups, and copper phthalocyanine pigment (Pigment Blue 15: 3) 157 parts were added, and dispersion treatment was performed for 2 hours at a peripheral speed of 15 m / s using a pico mill manufactured by Asada Tekko Co., Ltd. The obtained mixture was subjected to a 5-pass dispersion treatment with a microfluidizer (trade name, manufactured by Microfluidics) at a pressure of 150 MPa.
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, and a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 Dm, manufactured by Fuji Photo Film Co., Ltd.) was used. An aqueous dispersion of pigment-containing water-insoluble polymer particles having a solid content concentration of 22% was obtained by filtering with an attached needleless syringe having a capacity of 25 mL (manufactured by Terumo Corporation) to remove coarse particles.
Next, 200 parts of the obtained aqueous dispersion (13.2 parts of water-insoluble polymer) was put into a reaction vessel under a nitrogen atmosphere, and further a crosslinking agent (trimethylolpropane polyglycidyl ether, trade name: Denacol EX- 321: Epoxy equivalent 140: manufactured by Nagase ChemteX Corporation) 0.40 part (crosslinking rate: 14 mol%) and 47.4 parts of ion-exchanged water were added and reacted at 90 ° C. for 1.5 hours with stirring. The aqueous dispersion of crosslinked polymer particles containing a pigment having a solid content concentration of 20% was obtained by adjusting the concentration with ion-exchanged water.
The average particle size of the aqueous dispersion was measured by the above method and found to be 78 nm.

Ink Preparation Example 1
To 20.6 parts of an aqueous dispersion of crosslinked core-shell polymer particles containing a pigment having a solid content concentration of 20% obtained in Example 1, 16 parts of glycerin, 7 parts of triethylene glycol monobutyl ether, Surfynol 465 (Nissin) 1 part of Chemical Industry Co., Ltd.), 0.3 part of Proxel XL2 (Avisia Co., Ltd.) and 55.1 parts of ion-exchanged water were mixed, and the resulting mixture was filtered with a 1.2 μm filter (acetylcellulose membrane, An aqueous ink was obtained by filtering with a 25 mL needleless syringe with an outer diameter of 2.5 cm, manufactured by Fuji Photo Film Co., Ltd., and removing coarse particles.
Ink Preparation Example 2
In Preparation Example 1, instead of the aqueous dispersion of the crosslinked core-shell polymer particles containing the pigment having a solid content concentration of 20% obtained in Example 2, the pigment having a solid content concentration of 20% obtained in Comparative Example 1 was used. This was carried out in the same manner as in Example 1 except that the crosslinked polymer particles containing was used.

The water-based inks obtained in Examples and Comparative Examples were evaluated by performing the following glossiness test, bronze test, and print density test. The results are shown in Table 2.
(1) Glossiness test Using a commercially available inkjet printer [Seiko Epson Corporation, model number: PX-A650, piezo method], solid printing on commercially available special paper [photo paper <glossy>, manufactured by Seiko Epson Corporation]] [Printing condition = paper type: EPSON photographic paper, print quality: photo, color setting: no color correction] After leaving at 25 ° C. for 24 hours, a glossiness of 20 ° (manufactured by Nippon Denshoku Industries Co., Ltd.) The product name: HANDY GLOSSMETER PG-1) was measured five times, and the average value was obtained. The higher the value, the higher the glossiness.
(2) Bronze test Solid printing was performed under the same conditions as in (1) above, and after standing at 25 ° C for 24 hours, the bronze obtained was visually evaluated by the following method.
◯: Most preferable because red is hardly recognized even in solid printing.
(Triangle | delta): Even if it prints a photograph etc., redness is hard to be recognized.
X: The fluorescent light reflected on the printing surface and the reflected light of sunlight appear reddish.
(3) Printing density test Using the printer, solid printing on commercially available high-quality plain paper (trade name: KA4250NT, manufactured by Seiko Epson Corporation) [printing condition = paper type: plain paper, mode setting: fine, number of printing passes 1 time], and left for 24 hours at 25 ° C., the print density was measured 5 times with a Macbeth densitometer (product number: RD914, manufactured by Gretag Macbeth Co.), and the average value was obtained. The higher the value, the higher the print density.

  From Table 2, it can be seen that the water-based ink of Example 1 is superior to the water-based ink of Comparative Example 1 in terms of print density and bronze suppression, and is also excellent in the balance of print density, glossiness, and bronze suppression.

Claims (5)

A method for producing a dispersion of crosslinked core-shell polymer particles containing a colorant, comprising the following steps I to III.
Step I: A step of polymerizing a hydrophobic monomer and a crosslinkable monomer having two or more reactive unsaturated groups in the presence of water, an organic solvent and a polymer having a salt-forming group to obtain a dispersion of core-shell polymer particles. Step II: A step of mixing a dispersion of core-shell polymer particles obtained in Step I and a colorant and dispersing to obtain a dispersion of core-shell polymer particles containing a colorant Step III: obtained in Step II A step of obtaining a dispersion of crosslinked core-shell polymer particles containing a colorant by crosslinking the core-shell polymer particles containing a colorant with a crosslinking agent having two or more reactive functional groups.   The method for producing a dispersion according to claim 1, wherein the weight ratio of [crosslinkable monomer / hydrophobic monomer having two or more reactive unsaturated groups] is 1/100 to 20/100.   The weight ratio of [total amount of hydrophobic monomer and crosslinkable monomer having two or more reactive unsaturated groups / polymer amount having a salt-forming group] is 2/10 to 10/2. A method for producing the dispersion described in 1.   The dispersion according to any one of claims 1 to 3, wherein the amount of the crosslinking agent having two or more reactive functional groups is 0.5 to 15 parts by weight with respect to 100 parts by weight of the polymer having a salt-forming group. Body manufacturing method. The manufacturing method of the dispersion in any one of Claims 1-4 whose polymer which has a salt formation group is a graft polymer .