JP2008088427A - Crosslinked core-shell polymer particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crosslinked core-shell polymer particle usable in a water-based ink for ink-jet printing and excellent in density of printing, in improving gloss, and in controlling bronzing phenomena, and to provide a water dispersion, a water-based ink containing the same, and a method for producing the crosslinked polymer particle. <P>SOLUTION: The crosslinked core-shell polymer particle contains a pigment, and a core portion and a shell portion of the crosslinked core-shell polymer particle are each crosslinked, and a weight ratio of the pigment and the crosslinked core-shell polymer [(weight of the pigment/weight of the pigment-containing crosslinked core-shell polymer particle)×100] is 25-75, the water dispersion and the water-based ink for ink-jet printing are prepared by using the crosslinked core-shell polymer particle, and the method for producing the crosslinked polymer particle is elucidated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crosslinked core-shell polymer particle, an aqueous dispersion and an aqueous ink containing the crosslinked core-shell polymer particle, and a method for producing the crosslinked polymer particle.

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.
Among them, from the viewpoint of weather resistance and water resistance of printed materials, those using pigment-based inks as colorants have become mainstream, but when pigments are used as colorants, reflected light depends on the observation angle of printed materials. A bronzing phenomenon may occur in which a color different from the original color of the pigment is observed. For example, a phthalocyanine pigment contained in cyan ink may cause the reflected light to be colored red, which may significantly deteriorate the image quality. The bronze phenomenon is described in detail in “Color Science Handbook” (University of Tokyo Press), page 777.
In order to improve this bronze phenomenon, an ink composition containing a polyether-modified polysiloxane and a sulfone group-containing (co) polymer emulsion (Patent Document 1), an ink containing a polycyclic aromatic heteroconjugated compound (Patent Document 2) ) Etc. have been proposed. However, in these methods, there are concerns about adverse effects on print image quality due to additives and pigment changes.

  On the other hand, an aqueous dispersion of colored fine particles having a core / shell structure and an aqueous ink are known. For example, in order to improve durability, an ink in which a colorant combined with a primer core / shell polymer is encapsulated with a durable core / shell polymer (Patent Document 3), in order to improve image peelability after recording, Ink in which colored resin particles having at least a core made of a colorant and a thermoplastic resin and a shell made of a resin having a three-dimensional crosslinked structure are present in a capsule emulsion state (Patent Document 4), improving ejection stability and light resistance In order to improve the solvent resistance, an aqueous dispersion having colored fine particles containing two or more kinds of resins and coloring materials as a core (Patent Document 5) has a core-shell structure with at least two layers of fine particles. A colored fine particle dispersion (Patent Document 6) in which two or more of the core and the shell have a crosslinked structure has been proposed. However, these water dispersions, inks, and additives have not improved the bronze phenomenon.

JP 2003-306620 A JP 2004-67903 A Special table 2003-520279 gazette Japanese Patent Laid-Open No. 2002-12802 JP 2003-206430 A JP 2004-269558 A

  The present invention relates to a crosslinked core-shell polymer particle excellent in printing density, glossiness improvement, and suppression of bronzing phenomenon, aqueous dispersion and aqueous ink containing the same, and production of crosslinked polymer particle, which can be used in an aqueous ink for inkjet recording It is an object to provide a method.

The present invention provides the following (1) to (5).
(1) A crosslinked core-shell polymer particle containing a pigment, wherein the core part and the shell part of the crosslinked core-shell polymer particle are both crosslinked, and the weight ratio of the pigment to the crosslinked core-shell polymer [(pigment of Weight / weight of crosslinked core-shell polymer particles containing pigment) x 100] is 25-75.
(2) The crosslinked core-shell polymer particles of (1) obtained by the following steps 1 to 3.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2: adding the pigment to the polymer particles containing the pigment Step 2: polymerizing the crosslinkable monomer and the hydrophobic monomer to obtain core-shell polymer particles having a core portion crosslinked Step 3: Step 2 (3) The step (1) or (3), wherein the core-shell polymer particle obtained by crosslinking the obtained core part is reacted with a crosslinking agent having a reactive functional group other than at least two reactive unsaturated groups in the molecule. (2) An aqueous dispersion containing the crosslinked core-shell polymer particles according to (2).
(4) A water-based ink for ink jet recording containing the water dispersion according to (3).
(5) A pigment containing a pigment having the following steps 1 to 3, wherein the weight ratio of pigment to crosslinked polymer [(weight of pigment / weight of crosslinked polymer particles containing pigment) × 100] is 25 to 75 A method for producing crosslinked polymer particles.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2 for inclusion in polymer particles containing the pigment Step 2: Polymerization of the crosslinkable monomer and the hydrophobic monomer to obtain polymer particles Step 3: Polymer particles obtained in Step 2 and molecules Reacting with a crosslinking agent having at least two reactive functional groups therein

  When the crosslinked core-shell polymer particles of the present invention are contained in a water-based ink for inkjet recording, the printed matter has excellent print density when printed on plain paper, and has excellent bronze suppression and gloss when printed on special paper. Can be given.

The crosslinked core-shell polymer particle containing the pigment of the present invention has a structure in which the core polymer is physically or chemically bonded to the core polymer, and the core polymer and the shell polymer are both crosslinked. Being done. Here, the polymer of the core part and the polymer of the shell part include, in addition to crosslinking, from the viewpoint of the required performance, the type of constituent unit (type of monomer as a raw material) and / or the weight ratio of constituent unit (monomer The weight ratio is different. That is, the polymer in the core part has a high affinity with the pigment, and the polymer in the shell part has a function of stability as an aqueous dispersion of the polymer particles.
The weight ratio of the pigment to the crosslinked core-shell polymer [(weight of pigment / weight of crosslinked core-shell polymer particles containing pigment) × 100] is 25 to 75, preferably 30 to 70, particularly preferably 40 to 65. . When the weight ratio is within the above range, when blended with an aqueous dispersion for ink jet recording or an aqueous ink, the printing density and glossiness are improved and the bronzing phenomenon is suppressed. When the weight ratio is less than 25, the printing density and glossiness are insufficient, and when it exceeds 75, the suppression of the bronze phenomenon is insufficient.
The core part of the core-shell polymer particles is preferably obtained by polymerizing a crosslinkable monomer having at least two reactive unsaturated groups in the molecule and (c) a hydrophobic monomer.
The shell part of the core-shell polymer particle has a polymer formed by copolymerizing a monomer mixture containing (a) a salt-forming group-containing monomer, (b) a macromer and / or (c) a hydrophobic monomer. It is preferably obtained by crosslinking with a crosslinking agent having a reactive functional group other than one unsaturated group.

In the crosslinked core-shell polymer particles, the degree of crosslinking of the core part represented by the following formula (1) is preferably 0.5 to 15% by weight from the viewpoint of printing density and glossiness, more preferably 0.7 to It is 13% by weight, more preferably 1.0 to 11% by weight, and particularly preferably 1.5 to 9% by weight.
Crosslinking degree of core part (% by weight) = (Amount of crosslinkable monomer / Amount of polymer of crosslinked core part) × 100 (1)
In formula (1), the polymer amount of the crosslinked core portion is the amount of crosslinked polymer, and is the total amount (calculated value) of the crosslinking monomer and hydrophobic monomer used.
Moreover, the crosslinking degree of the shell part represented by the following formula (2) is preferably 0.5 to 15% by weight, more preferably 0.7 to 13% by weight, and still more preferably, from the viewpoint of printing density and gloss. Is 1.0 to 11% by weight, particularly preferably 1.5 to 9% by weight.
Crosslinking degree of shell portion (% by weight) = (Amount of crosslinking agent / Amount of polymer of shell portion) × 100 (2)
In (2), the polymer amount of the shell portion is the amount of polymer before crosslinking, and does not include the amount of crosslinking agent.

Although there is no restriction | limiting in particular in the manufacturing method of the bridge | crosslinking core-shell polymer particle of this invention, According to the method which has the following processes 1-3, it can manufacture efficiently.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2: adding the pigment to the polymer particles containing the pigment Step 2: polymerizing the crosslinkable monomer and the hydrophobic monomer to obtain core-shell polymer particles having a core portion crosslinked Step 3: Step 2 The step of reacting the obtained core-shell polymer particles obtained by crosslinking the core part with a crosslinking agent having at least two reactive functional groups in the molecule. The present invention also provides a method for producing the following crosslinked polymer particles. provide.
The crosslinked polymer particle containing a pigment having the following steps 1 to 3, wherein the weight ratio of the pigment to the crosslinked polymer [(weight of pigment / weight of crosslinked polymer particle containing pigment) × 100] is 25 to 75 Manufacturing method.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2 for inclusion in polymer particles containing the pigment Step 2: Polymerization of the crosslinkable monomer and the hydrophobic monomer to obtain polymer particles Step 3: Polymer particles obtained in Step 2 and molecules Step of reacting with a crosslinking agent having at least two reactive functional groups therein Each component will be described below.

(Pigment)
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.
Specific examples of preferred 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.
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.

(polymer)
The polymer used in the present invention is preferably a water-insoluble polymer. A water-insoluble polymer is a polymer having a dissolution amount of 10 g or less, preferably 5 g or less, more preferably 1 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C. Say. When the polymer has a salt-forming group, the dissolution amount is a dissolution amount when the salt-forming group of the polymer is neutralized 100% with acetic acid or sodium hydroxide according to the type.
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 water-insoluble vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to as “monomer mixture”) containing a hydrophobic monomer (hereinafter also referred to as “component (c)”) is preferable. This water-insoluble 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 preferred water-insoluble 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 structural unit derived from the component (b) as a side chain. It is a water-insoluble graft 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 include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group.
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 polymer particles containing the pigment. 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 the macromers, a styrene macromer and an aromatic group-containing (meth) acrylate macromer having a polymerizable functional group at one end are preferable from the viewpoint of dispersion stability of polymer particles containing a pigment.
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. As mentioned above, More preferably, it is 70 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 (3).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} O] _{t -Si (CH 3) 3 (} 3)
(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. 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 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 may further contain (e) a monomer represented by the following formula (4) (hereinafter sometimes referred to as “(e) component”).
CH ₂ = C (R ¹ ) COO (R ² O) _q R ³ (4)
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, or a phenyl group optionally having an alkyl group having 1 to 9 carbon atoms, q means the average number of moles added And a number of 1 to 60, preferably a number of 1 to 30.)
(E) component expresses the outstanding effect of improving discharge property.
In the formula (4), 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 an aliphatic alkyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, and Examples thereof include an alkyl group having 4 to 30 carbon atoms having a heterocycle and a phenyl group optionally having an alkyl group having 1 to 8 carbon atoms.

  Specific examples of the component (e) include methoxypolyethylene glycol (1 to 30: the value of q in the formula (4); hereinafter the same) (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, butoxypolyethylene 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 at the time of vinyl polymer production (content as an unneutralized amount; the same applies hereinafter) or derived from the components (a) to (e) in the vinyl polymer The content of the structural unit 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 [component (a) + component (d)] in the monomer mixture is preferably 6 to 60% by weight, more preferably 10 to 50% by weight, from the viewpoint of dispersion stability of the resulting dispersion. is there. 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 water-insoluble polymer)
The water-insoluble polymer used in the present invention is produced by copolymerizing a monomer mixture 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 mol of the monomer mixture.
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 vary depending on the type of radical polymerization initiator, monomer, and solvent used, 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 water-insoluble 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 gloss and dispersion stability of the colorant, and from 10,000 to 300,000. Is more preferable, and 20,000 to 300,000 is particularly preferable. In addition, the weight average molecular weight of the polymer was measured by the method shown in the Examples.
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 formula 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
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
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.

(Crosslinkable monomer having at least two reactive unsaturated groups in the molecule)
Examples of the crosslinkable monomer having at least two reactive unsaturated groups in the molecule (hereinafter, also simply referred to as “crosslinkable monomer”) 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, pentaerythrito (Meth) acrylic acid ester compounds of polyhydric alcohols such as rutetra (meth) acrylate; (2) acrylamides such as N-methylallylacrylamide, N-vinylacrylamide, N, N′-methylenebis (meth) acrylamide, bisacrylamide acetic acid Compound: (3) Divinyl compounds such as divinylbenzene, divinyl ether, divinylethyleneurea, etc .; (4) diallyl phthalate, diallyl malate, diallylamine, triallylamine, triallyl ammonium salt, allyl etherified pentaerythritol, in the molecule And polyallyl compounds such as allyl ethers of sucrose having at least two allyl ether units.
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 at least two reactive functional groups in the molecule)
A crosslinking agent having at least two reactive functional groups in the molecule (hereinafter, also simply referred to as “crosslinking agent”) is used for appropriately crosslinking the shell part of the core-shell polymer particle obtained by crosslinking the core part. The molecular weight of the crosslinking 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 crosslinked 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 other than a reactive unsaturated group, an epoxy group, an aldehyde group, an amino group, a carboxy group, and an oxazoline group.
From the viewpoint of efficiently crosslinking the surface of the polymer and enhancing the storage stability of the aqueous dispersion, the crosslinking agent preferably has a solubility in 100 g of water at 25 ° C. of 80 g or less, more preferably 50 g or less, and 30 g The following are more preferable.

Specific examples of such a crosslinking agent include the following (a) to (f).
(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-pentane Polyhydric alcohols such as diol, 1,6-hexanediol, neopentyl alcohol, diethanolamine, 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, polyglycol such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether Glycidyl ether.
(C) Compounds having two or more aldehyde groups in the molecule: for example, polyaldehydes such as glutaraldehyde and glyoxal.
(D) Compounds having two or more amino groups in the molecule: for example, polyamines such as ethylenediamine and polyethyleneimine.
(E) Compounds 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.
(F) Compound having two or more oxazoline groups in the molecule: for example, a compound in which 2 or more, preferably 2 to 3 oxazoline groups are bonded to an aliphatic group or an aromatic group, more specifically 2 , 2′-bis (2-oxazoline), 1,3-phenylenebisoxazoline, bisoxazoline compounds such as 1,3-benzobisoxazoline, and terminal oxazoline groups obtained by reacting the compound with a polybasic carboxylic acid A compound having
Among these, (b) a compound having two or more epoxy groups in the molecule is preferable, and trimethylolpropane polyglycidyl ether is particularly preferable.

The core-shell polymer particles obtained by crosslinking the core part have a reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent in the polymer constituting the shell part. It is as follows.
When the reactive group of the polymer in the shell part is an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, the above-mentioned compounds (a), (b), (d), and (f) are preferable as the crosslinking agent.
Moreover, when the reactive group of the polymer of a shell part is an amino group and a hydroxyl group, the said (b), (c) and (e) compound is preferable for a crosslinking agent.
When the reactive group of the polymer of the shell part 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 to give an appropriate cross-linked structure to the polymer of the shell part of the core-shell polymer particle, an acidic group (carboxy group, sulfonic acid group, phosphoric acid group, etc.), amino group and hydroxyl group A combination of a polymer having one or more reactive groups selected from (b) and a compound having two or more epoxy groups in the molecule is particularly preferred.

As the reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent, a polymer having an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, an amino group, a hydroxyl group, an isocyanate group, an epoxy group, etc. In the production of the polymer, it can be produced by copolymerizing a polymerizable monomer composition containing the monomer having the reactive group.
As the polymer having a reactive group capable of reacting with the crosslinking agent, the polymer having a salt-forming group such as an acidic group or an amino group can be a polymer obtained by copolymerizing the aforementioned salt-forming group-containing monomer. As the polymer having, a polymer obtained by copolymerizing the above-mentioned hydroxyl group-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.

(Water-insoluble organic compound)
In the present invention, it is possible to use a water-insoluble organic compound from the viewpoint of improving the flexibility of the crosslinked core-shell polymer particle and improving the gloss of the printed matter by containing the water-insoluble organic compound in the crosslinked core-shell polymer particle. it can. The water-insoluble organic compound can be added during or after the production process of the polymer particles containing the pigment, or during or after the production process of the crosslinked core-shell polymer particles described later.
From the viewpoint of improving the glossiness of the water-based ink, the water-insoluble organic compound preferably has a molecular weight of 100 to 2,000, more preferably a molecular weight of 100 to 1,200.
The amount of the water-insoluble organic compound dissolved in 100 g of water (20 ° C.) is preferably 5 g or less, more preferably 3 g or less, still more preferably 1 g or less, and particularly preferably 0.5 g or less.
The water-insoluble organic compound improves the glossiness of the printed matter when printed on special paper and also improves the storage stability of the aqueous dispersion from its LogP value (water-insoluble organic compound 1-octanol / water). The logarithmic value of the distribution coefficient is preferably 4 to 16, more preferably 5 to 16, and particularly preferably 6 to 15.
By using a water-insoluble organic compound, a secondary color printed matter obtained with an ink set having a water-based ink containing cross-linked core-shell polymer particles having different colors is particularly excellent in gloss.

The water-insoluble organic compound is preferably an ester compound, an ether compound, or a sulfonic acid amide compound so as to be easily contained in the (crosslinked) polymer particle, and an ester having two or more ester or ether bonds in the molecule. Or selected from the group consisting of an ether compound (x) and / or one or more ester or ether bonds in the molecule and a carboxy group, a sulfonic acid group, a phosphoric acid residue, a carbonyl group, an epoxy group and a hydroxyl group. An ester or ether compound (y) having one or more, preferably 1 to 3 functional groups, is more preferred. The number of ester or ether bonds in the compound (x) is preferably 2 to 3. The number of ester or ether bonds in the compound (y) is preferably 1 to 3.
Among the ester compounds, esters obtained from monovalent carboxylic acids or salts thereof and polyhydric alcohols, polyacids (polycarboxylic acids, phosphoric acids) or esters obtained from salts thereof and monohydric alcohols are preferred, and ether compounds Of these, polyhydric alcohol ethers are preferred. Examples of the salt include alkali metal salts, alkanolamine salts, ammonium salts and the like.

Examples of monovalent carboxylic acids include linear or branched aliphatic carboxylic acids having 1 to 18 carbon atoms, preferably 2 to 10 carbon atoms, and aromatic carboxylic acids having 6 to 12 carbon atoms (for example, benzoic acid). Can be mentioned. Examples of the polyvalent acid include aliphatic carboxylic acids having 2 to 12 carbon atoms such as maleic acid, fumaric acid, itaconic acid, succinic acid, adipic acid and sebacic acid, and 6 to 12 carbon atoms such as phthalic acid and trimellitic acid. Aromatic carboxylic acid, phosphoric acid and the like can be mentioned.
As the monohydric alcohol, a linear or branched aliphatic alcohol having 1 to 18 carbon atoms, preferably 2 to 10 carbon atoms (for example, ethyl alcohol, butyl alcohol, hexyl alcohol, octyl alcohol, dodecyl alcohol), carbon number 6-12 aromatic alcohol (for example, phenol), these alkylene oxide compounds, etc. are mentioned.
Examples of the polyhydric alcohol include polyhydric alcohols having 2 to 12 carbon atoms such as ethylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, and glycerin, and alkylene oxide compounds thereof. A saturated or unsaturated fatty acid or alcohol can be used.

Specific examples of the water-insoluble organic compound include (1) aliphatic carboxylic acid ester, (2) aromatic carboxylic acid ester, (3) cycloalkane (ken) carboxylic acid ester obtained from the above carboxylic acid, alcohol and the like. (4) Phosphate ester, (5) Oxy acid ester, (6) Glycol ester, (7) Epoxy ester, (8) Sulfonamide, (9) Polyester, (10) Glyceryl alkyl ether, (11) Glyceryl alkyl Examples include esters and (12) glycol alkyl ethers.
Among these, from the viewpoint of improving glossiness, the compounds of (1) to (5), (8) and (10) are preferable, (1) aliphatic carboxylic acid ester, (2) aromatic carboxylic acid ester. , (3) one or more selected from the group consisting of cycloalkane (ken) carboxylic acid ester and (4) phosphoric acid ester, and more preferably aliphatic dicarboxylic acid ester, aromatic di- or tricarboxylic acid ester, cyclohexane It is especially preferable that it is 1 or more types chosen from the group which consists of alkane (ken) dicarboxylic acid ester and phosphoric acid di or triester.

(Polymer particles containing pigment)
The polymer particles containing the pigment are used for suppressing the bronzing phenomenon, improving the dispersion stability of the colorant and the printing density. The production method of polymer particles containing a pigment (hereinafter sometimes referred to as “pigment-containing polymer particles”) can be performed, for example, by the following steps.
Step: Dispersing a mixture containing a polymer, an organic solvent, a pigment, water and, if necessary, a neutralizing agent

  In the step, first, the polymer is dissolved in an organic solvent, and then a pigment, water, and if necessary, a neutralizing agent, a surfactant, and the like are added to the organic solvent and mixed to obtain an oil-in-water dispersion. It is preferable to obtain a body. In the mixture, the pigment 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. When the polymer has a salt-forming group, it is preferable to use a neutralizing agent, but the polymer may be previously neutralized with a neutralizing agent. There is no particular limitation on the degree of neutralization. Usually, it is preferable that the liquid dispersion of the finally obtained water dispersion is neutral, for example, pH is 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the vinyl polymer.

Examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents. 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.
The organic solvent has a solubility in 100 g of water of 20 ° C., preferably 5 g or more, more preferably 10 g or more, more specifically 5 to 80 g, and even more preferably 10 to 50 g. . In particular, methyl ethyl ketone and methyl isobutyl ketone are preferable. These solvents can be used alone or in admixture of two or more.
As the neutralizing agent, an acid or a base can be used according to the kind of the salt-forming group in the polymer, and examples thereof include those mentioned above.

There is no restriction | limiting in particular in the dispersion method of the mixture in the said process. It is preferable to carry out the main dispersion by applying a shear stress after preliminarily dispersing. In the process, atomization is performed so that polymer particles having a desired average particle diameter are obtained.
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 apparatuses, Ultra Disper [Asada Tekko Co., Ltd., trade name], Ebara Milder [Ebara Manufacturing Co., Ltd., trade name], TK homomixer, TK pipeline mixer, TK homojetter, 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., Ltd., trade name], KD Mill [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 of pigment-containing polymer particles obtained in this step can be used for producing the crosslinked core-shell polymer particles of the present invention.

(Crosslinked core-shell polymer particles containing pigment (hereinafter also simply referred to as “pigment-containing crosslinked core-shell polymer particles”))
As described above, the crosslinked core-shell polymer particles of the present invention are preferably produced by a method having the following steps 1 to 3.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2: adding the pigment to the polymer particles containing the pigment Step 2: polymerizing the crosslinkable monomer and the hydrophobic monomer to obtain core-shell polymer particles having a core portion crosslinked Step 3: Step 2 A step of reacting the obtained core-shell polymer particles obtained by crosslinking the core part with a crosslinking agent having at least two reactive functional groups in the molecule.

In Step 1, first, a dispersion of polymer particles containing the above-mentioned pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, a hydrophobic monomer, water, and optionally surface active By adding and mixing an agent or the like, at least a part of the crosslinkable monomer and the hydrophobic monomer is permeated and contained in the polymer particles. There is no restriction | limiting in particular in the dispersion method of the obtained mixture. The dispersion in step 1 is preferably performed at 5 to 50 ° C, more preferably 10 to 35 ° C.
As a mixing and stirring device for dispersing the mixture and a means for giving a shear stress, the same ones as described in the polymer particle column containing the pigment can be used.
The amount of the hydrophobic monomer used is such that the weight ratio of the hydrophobic monomer and the polymer particle containing the pigment (polymer particle containing the hydrophobic monomer / pigment) is 0 from the viewpoint of improving the printing density, glossiness and suppressing the bronze phenomenon. .1 to 1 is preferable, and 0.2 to 0.5 is more preferable.
The amount of the crosslinkable monomer having at least two reactive unsaturated groups in the molecule is a total amount of 100 of the hydrophobic monomer and the crosslinkable monomer from the viewpoint of improving the printing density, glossiness and suppressing the bronze phenomenon. 0.5 to 15 parts by weight, more preferably 0.7 to 13 parts by weight, still more preferably 1.0 to 11 parts by weight, particularly preferably 1.5 to 9 parts by weight with respect to parts by weight. preferable.

In step 2, the crosslinkable monomer and the hydrophobic monomer in the obtained dispersion are polymerized to obtain a dispersion of core-shell polymer particles having a core portion crosslinked. The initiator for polymerization may be added in Step 1 or after Step 1. The initiators 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 core-shell polymer particles obtained in Step 2 have a core part in which a polymer having a structural unit derived from a hydrophobic monomer is cross-linked by a cross-linkable monomer, and a shell part made of a polymer derived from a polymer containing a pigment. As described above, the polymer constituting the shell part may be a polymer obtained by copolymerizing a monomer mixture containing (a) a salt-forming group-containing monomer, (b) a macromer and / or (c) a hydrophobic monomer. preferable.
An aqueous dispersion of core-shell polymer particles in which the core part containing a pigment having a desired average particle diameter is crosslinked can be obtained by distilling off the organic solvent from the obtained dispersion to form an aqueous system. The organic solvent in the aqueous dispersion containing the obtained polymer particles is preferably substantially removed, but may remain as long as the object of the present invention is not impaired. The organic solvent contained in the aqueous dispersion can be removed by a general method such as distillation under reduced pressure. The amount of residual organic solvent is preferably 0.1% by weight or less, more preferably 0.01% by weight or less. The organic solvent may be removed after Step 2 or may be removed in Step 3.

In step 3, the core-shell polymer particles obtained by crosslinking the core part obtained in step 2 are reacted with a crosslinking agent having at least two reactive functional groups in the molecule to obtain crosslinked core-shell polymer particles. In this step 3, the polymer that is the shell part is crosslinked by a crosslinking agent having at least two reactive functional groups in the molecule, thereby obtaining a crosslinked core-shell polymer particle in which both the core part and the shell part are crosslinked. It is done.
From the viewpoint of crosslinking efficiency, an aqueous dispersion of core-shell polymer particles obtained by crosslinking the core part obtained in step 2 and a crosslinking agent having at least two reactive functional groups in the molecule are mixed to form a polymer. A method of obtaining a water dispersion of crosslinked core-shell polymer particles is preferable. At that time, it is preferable from the viewpoint of crosslinking efficiency and storage stability due to surface crosslinking that the polymer is water-insoluble and the amount of the crosslinking agent dissolved in water is as described above.
The catalyst, solvent, temperature, and time in the crosslinking 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 cross-linking agent having at least two reactive functional groups in the molecule is selected from the viewpoint of improving gloss and suppressing bronze phenomenon, ie, the polymer of the shell part of the core-shell polymer particle in which the core part is crosslinked, that is, the process 0.5 to 15 parts by weight is preferable, 0.7 to 13 parts by weight is more preferable, and 1.0 to 11 parts by weight is even more preferable with respect to 100 parts by weight of the polymer of the polymer particles containing the pigment in 1. 1.5 to 9 parts by weight is particularly preferable.
From the same viewpoint, the crosslinking agent is preferably 0.1 to 10 parts by weight, and 0.3 to 8 parts by weight with respect to 100 parts by weight of the core-shell polymer particles obtained by crosslinking the core part containing the pigment. More preferred is 0.5 to 5 parts by weight.

The crosslinking rate (mol%) of the shell part of the crosslinked core-shell polymer particles is preferably 1 to 80%, more preferably 3 to 60%, and particularly preferably 5 to 50% from the viewpoint of gloss. Here, the crosslinking rate (mol%) of the shell portion refers to a value determined by the following formula.
Cross-linking rate (mol%) = [(number of moles of cross-linking agent reacted with 1 mol of polymer in shell portion / number of moles of reactive group capable of reacting with cross-linking agent possessed by 1 mol of polymer in shell portion) × 100]
It is preferable to remove coarse particles by filtering the aqueous dispersion containing the obtained pigment-containing crosslinked core-shell polymer particles. The aqueous dispersion of the pigment-containing crosslinked core-shell polymer particles is obtained by dispersing the solid content of the pigment-containing crosslinked core-shell polymer in water as a main medium. Here, the form of the pigment-containing crosslinked core-shell polymer particles is not particularly limited, as long as the particles are formed of at least the pigment and the crosslinked core-shell polymer. For example, a particle form in which a pigment is encapsulated in a crosslinked core-shell polymer, a particle form in which the pigment is uniformly dispersed in the crosslinked core-shell polymer, and a particle form in which the pigment is exposed on the surface of the crosslinked core-shell polymer particle are included.

(Method for producing pigment-containing crosslinked polymer particles (hereinafter also simply referred to as “pigment-containing crosslinked polymer particles”))
The present invention provides the following method for producing crosslinked polymer particles.
Production of pigment-containing crosslinked polymer particles having the following steps 1 to 3, wherein the weight ratio of pigment to crosslinked polymer [(weight of pigment / weight of crosslinked polymer particle containing pigment) × 100] is 25 to 75 Method.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2 for inclusion in polymer particles containing the pigment Step 2: Polymerization of the crosslinkable monomer and the hydrophobic monomer to obtain polymer particles Step 3: Polymer particles obtained in Step 2 and molecules The step of reacting a crosslinking agent having at least two reactive functional groups therein The weight ratio of pigment to crosslinked polymer [(weight of pigment / weight of crosslinked polymer particles containing pigment) × 100] The preferred range is the same as that of the crosslinked core-shell polymer particles containing the pigment. Steps 1 to 3 are the same as the above-described method for producing a crosslinked core-shell polymer particle containing a pigment, and the preferred range is also the same.

(Aqueous dispersion containing pigment-containing crosslinked core-shell polymer particles or pigment-containing crosslinked polymer particles (hereinafter referred to as pigment-containing crosslinked core-shell polymer particles) and water-based ink)
The aqueous dispersion of the present invention can be obtained by incorporating the pigment-containing crosslinked core-shell polymer particles obtained by the above method.
The water-based ink of the present invention is an ink containing the water dispersion of the present invention and containing water as a main medium. If necessary, additives such as a wetting agent, a dispersant, an antifoaming agent, an antifungal agent, and a chelating agent. Can be added. There is no restriction | limiting in particular in the mixing method of each of these components.
The water-insoluble organic compound and the water content such as the pigment-containing crosslinked core-shell polymer particles in the aqueous dispersion for inkjet recording and the water-based ink are as follows from the viewpoint of improving the glossiness and suppressing the bronze phenomenon.
The content of the pigment-containing crosslinked core-shell polymer particles and the like 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 pigment-containing crosslinked core-shell polymer particles is preferably 0.3 to 3, more preferably 0.3 to 2, from the viewpoint of printing density and gloss. More preferably, it is 0.5 to 1.5, and particularly preferably 0.7 to 1.3. The calculation of the weight ratio between the core part and the shell part includes the amount of the crosslinking agent.
The content of the water-insoluble organic compound is preferably 0.1 to 5% by weight, more preferably 0.2 to 4% by weight, and particularly preferably 0.3 to 3% by weight.
The water content is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.

The average particle size of the pigment-containing crosslinked core-shell polymer particles and the like in the obtained water dispersion and water-based ink is preferably 40 to 150 nm, more preferably 45 to 120 nm, and particularly preferably 50 to 50 from the viewpoint of glossiness and bronzing phenomenon suppression. 100 nm. The average particle diameter is determined by the method described in the examples.
The preferred surface tension (20 ° C.) of the aqueous dispersion and aqueous ink of the present invention is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m as the aqueous dispersion, and preferably as the aqueous ink. Is 25-50 mN / m, more preferably 27-45 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.

The water-based ink for ink-jet recording of the present invention can obtain a highly glossy printed matter when printed on special paper. Examples of the special paper include ink jet photographic paper having a void type glossy medium having a 60 ° glossiness of preferably 10 to 45. Here, the glossiness is a value measured by the method described in the examples. Such photographic paper is commercially available, and a preferred example is Seiko Epson Corporation trade name: KA450PSK.
The ink jet method to which the water-based ink of the present invention is applied is not limited, but is particularly suitable for a piezo ink jet printer.

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 water-insoluble polymer)
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)) 1.2 parts were added and mixed, and nitrogen gas substitution was sufficiently performed 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 dropped over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution obtained by dissolving 0.3 part of the radical polymerization initiator in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and 70 ° C. for 2 hours to obtain a polymer solution. It was.
The weight average molecular weight of the obtained polymer was measured by the above method. The results are shown in Table 1.

The details of the compounds shown in Table 1 are as follows.
-Styrene macromer: manufactured by Toa Gosei Co., Ltd., trade name: AS-6 (S) (50% toluene solution, solid content 15 parts), number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group, polyethylene glycol monomethacrylate ( Ethylene oxide average added mole number = 9, terminal: methyl group): Shin-Nakamura Chemical Co., Ltd., trade name: NK ester M-90G
Polypropylene glycol monomethacrylate (propylene oxide average added mole number = 9, terminal: hydroxyl group): manufactured by NOF Corporation, trade name: BLEMMER PP-500

Example 1 (Preparation of dispersion 1 of crosslinked core-shell polymer particles containing pigment)
<Preparation of base dispersion 1>
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 at a pressure of 150 MPa with a microfluidizer (trade name, manufactured by Microfluidics).
<Reaction of cross-linked core>
To 200 parts of the obtained dispersion (solid content: 14%), 9.3 parts of styrene, 0.49 parts of divinylbenzene (purity 81%: trade name: DVB-810: manufactured by Nippon Steel Chemical Co., Ltd.), radical polymerization A solution in which 0.2 part of initiator (2,2′-azobis (2,4-dimethylvaleronitrile)) was mixed was added and mixed with a disper blade for 1 hour at 20 ° C. The resulting mixture was mixed with a microfluidizer (Microfluidics). The product was a 5-pass dispersion treatment at a pressure of 150 MPa.
The obtained dispersion was put into a reaction vessel under a nitrogen atmosphere and reacted at 77 ° C. for 3 hours with stirring to obtain a dispersion containing a pigment and having a cross-linked site in the core.
<Dispersion treatment>
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Film Co., Ltd.) was attached. Then, the mixture was filtered with a 25 mL needle-free syringe (manufactured by Terumo Corporation) to remove coarse particles, thereby obtaining an aqueous dispersion of pigment-containing water-insoluble polymer particles having a solid content concentration of 22%.
<Crosslinking reaction of shell part>
200 parts of the obtained aqueous dispersion (9.8 parts of polymer in the shell part) was put into a reaction vessel under a nitrogen atmosphere, and further, a crosslinking agent (trimethylolpropane polyglycidyl ether, manufactured by Nagase ChemteX Corporation, Denacol). Add 0.40 parts of EX-321, epoxy equivalent 140, amount of about 27 g dissolved in 100 g of water (25 ° C)) and 47.4 parts of ion-exchanged water, and react at 90 ° C for 1.5 hours with stirring. Then, the concentration was adjusted with ion-exchanged water to obtain a pigment-containing polymer particle dispersion having a shell part crosslinked (crosslinking ratio: 17.8 mol%) at a concentration of 20%.
<Preparation of ink>
To 31.26 parts of the resulting pigment-containing vinyl polymer particle aqueous dispersion, 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), Proxel XL2 0.3 parts (produced by Avicia Co., Ltd.) and 50.44 parts of ion-exchanged water were mixed, and the resulting liquid mixture was filtered through a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, Fuji Film Co., Ltd.). The aqueous ink shown in Table 2 was obtained by filtering with a syringe without a needle having a capacity of 25 mL, and removing coarse particles.

The average particle diameter was measured and the crosslinking rate was calculated as follows.
(1) Average particle diameter It measured with the 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%.
(2) Calculation of crosslinking rate The crosslinking rate (mol%) of a shell part is represented by the following formula.
Cross-linking rate (mol%) = [(number of moles of cross-linking agent reacted with 1 mol of polymer in shell portion / number of moles of reactive group capable of reacting with cross-linking agent possessed by 1 mol of polymer in shell portion) × 100]
In Example 1, 9.8 parts of the polymer in the shell part is reacted with 0.40 part of Denacol EX-321 (epoxy equivalent 140). Therefore, the number of molar equivalents of the crosslinking agent reacted with 1 mole of polymer having a weight average molecular weight of 180,000 is
(0.40 / 140) / (9.8 / 18000) = 52.4.
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-500, molecular weight 612).
180000 × 0.12 / 86 + 18000 × 0.15 / 612 = 295 mol Therefore, the crosslinking rate of the shell portion is 52.4 × 100/295 = 17.8 (mol%).

Example 2 (Preparation of dispersion 2 of crosslinked core-shell polymer particles containing pigment)
<Preparation of base dispersion 2>
After 58 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, 10.6 parts of neutralizer 1 (5N aqueous sodium hydroxide solution) (neutralization degree 55%) ) And neutralizing agent 2 (25% aqueous ammonia solution) 5.6 parts (neutralization degree 100%) and ion-exchanged water 978 parts to neutralize the salt-forming groups, and further copper phthalocyanine pigment (Pigment Blue 15: 3) 167 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 at a pressure of 150 MPa with a microfluidizer (trade name, manufactured by Microfluidics).
<Reaction of cross-linked core>
200 parts of the obtained dispersion (solid content: 14%), 6.15 parts of styrene, 0.32 parts of divinylbenzene (purity 81%: trade name: DVB-810: manufactured by Nippon Steel Chemical Co., Ltd.), radical polymerization A solution in which 0.13 part of initiator (2,2′-azobis (2,4-dimethylvaleronitrile)) was mixed was added and mixed with a disper blade for 1 hour at 20 ° C. The resulting mixture was mixed with a microfluidizer (Microfluidics The product was a 5-pass dispersion treatment at a pressure of 150 MPa.
The obtained dispersion was put into a reaction vessel under a nitrogen atmosphere and reacted at 77 ° C. for 3 hours with stirring to obtain a dispersion having a cross-linked site in the core together with the pigment.
<Dispersion treatment>
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Film Co., Ltd.) was attached. The mixture was filtered with a 25 mL needle-free syringe (manufactured by Terumo Corporation) to remove coarse particles, thereby obtaining an aqueous dispersion of pigment-containing graft polymer particles having a solid content concentration of 21%.
<Crosslinking reaction of shell part>
200 parts of the obtained aqueous dispersion (8.9 parts of the polymer in the shell part) was put into a reaction vessel under a nitrogen atmosphere, and further a crosslinking agent (trimethylolpropane polyglycidyl ether, manufactured by Nagase ChemteX Corporation, Denacol). EX-321, epoxy equivalent 140) 0.69 parts and ion-exchanged water 34.1 parts are added, the reaction is carried out at 90 ° C. for 1.5 hours with stirring, and the shell part is adjusted by adjusting the concentration with ion-exchanged water. A crosslinked pigment-containing polymer particle dispersion was obtained at a concentration of 20%.
The crosslinking rate (mol%) of the shell part was calculated in the same manner as in Example 1.
<Ink formulation>
27.07 parts of an aqueous dispersion of pigment-containing vinyl polymer particles obtained by crosslinking the obtained shell part, 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part, 0.3 part of Proxel XL2 (manufactured by Avicia Co., Ltd.) and 54.63 parts of ion-exchanged water were mixed, and the resulting liquid mixture was filtered with a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm The water-based ink shown in Table 2 was obtained by filtering with a 25 mL needleless syringe equipped with Fujifilm Co., Ltd. and removing coarse particles.

Example 3 (Preparation of Dispersion 3 of Crosslinked Core-Shell Polymer Particles Containing Pigment)
Except for changing the amount of the crosslinking agent for the crosslinking reaction of the shell part, the same procedure as in Example 2 was performed to obtain an aqueous dispersion of pigment-containing vinyl polymer particles having a crosslinked shell part at a concentration of 20%.
The aqueous dispersion 26.86 parts of the pigment-containing vinyl polymer particles obtained by crosslinking the shell part was mixed with 0.30 part of a water-insoluble organic compound and stirred to obtain a water-insoluble organic compound [(i) phthalic acid and 2- Ethylene oxide adduct of ethylhexyl alcohol (average addition mole number 4, Nippon Emulsifier Co., Ltd., trade name: New Coal 1004) 25 parts diester and (ii) ethylene oxide adduct of trimellitic acid and lauryl alcohol (average addition) It consists of 75 parts of a triester with 4 moles, manufactured by Nippon Emulsifier Co., Ltd.). In this mixed solution, 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), 0.3 part of Proxel XL2 (manufactured by Avicia Corporation), and ions 54.54 parts of exchange water was mixed, and the resulting mixture was filtered with a 25 mL needleless syringe equipped with a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Film Co., Ltd.). Then, by removing coarse particles, water-based inks shown in Table 2 were obtained.

Example 4 (Preparation of dispersion 4 of pigment-containing crosslinked core-shell polymer particles)
Using the base dispersion 1 used in Example 1, 200 parts of the base dispersion 1 (solid content 14%), 7.0 parts of styrene and 0.37 parts of divinylbenzene (purity 81%: trade name: DVB- 810: manufactured by Nippon Steel Chemical Co., Ltd.) was added and mixed with a disper blade at 20 ° C. for 1 hour. 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.
The obtained dispersion was put into a reaction vessel under a nitrogen atmosphere, 0.15 part of a radical polymerization initiator (potassium persulfate) was added, and the mixture was reacted at 77 ° C. for 3 hours with stirring to contain a pigment. A dispersion having a cross-linked site in the core was obtained.
<Dispersion treatment>
In the same manner as in Example 1, an aqueous dispersion of pigment-containing water-insoluble polymer particles having a solid content concentration of 22% was obtained.
<Crosslinking reaction of shell part>
200 parts of the obtained aqueous dispersion (10.4 parts of polymer in the shell part) was put into a reaction vessel under a nitrogen atmosphere, and further a crosslinking agent (trimethylolpropane polyglycidyl ether, manufactured by Nagase ChemteX Corporation, Denacol). 0.43 parts of EX-321, epoxy equivalent 140) and 43.5 parts of ion-exchanged water were added, the reaction was carried out at 90 ° C. for 1.5 hours with stirring, the concentration was adjusted with ion-exchanged water, and the shell part was adjusted. A pigment-containing polymer particle dispersion crosslinked (crosslinking rate: 17.8 mol%) was obtained at a concentration of 20%.
<Preparation of ink>
To 29.28 parts of the pigment-containing vinyl polymer particle aqueous dispersion obtained, 0.30 part of a water-insoluble organic compound was mixed and stirred to obtain a water-insoluble organic compound [(i) ethylene oxide of phthalic acid and 2-ethylhexyl alcohol. 25 parts of diester with adduct (average number of moles 4; Nippon Emulsifier Co., Ltd., trade name: New Coal 1004) and (ii) ethylene oxide adduct of trimellitic acid and lauryl alcohol (average number of moles 4) Made of 75 parts of triester with Emulsifier Co., Ltd.) in the polymer particles. In this mixed solution, 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), 0.3 part of Proxel XL2 (manufactured by Avicia Corporation), and ions The mixture was mixed with 52.12 parts of the exchanged water, and the resulting mixture was filtered with a 25 mL needleless syringe equipped with a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by FUJIFILM Corporation). Then, by removing coarse particles, water-based inks shown in Table 2 were obtained.

Example 5 (Preparation of dispersion 5 of crosslinked core-shell polymer particles containing pigment)
Using the base dispersion 1 used in Example 1, 220 parts of the base dispersion 1 (solid content 14%), 9.86 parts of styrene, 1.10 parts of divinylbenzene, a radical polymerization initiator (2, 2 ′ -A solution in which 0.22 part of azobis (2,4-dimethylvaleronitrile) was mixed was added and mixed with a disper blade for 1 hour at 20 ° C. The resulting mixture was mixed with a microfluidizer (trade name, manufactured by Microfluidics). Five-pass dispersion treatment was performed at a pressure of 150 MPa.
The obtained dispersion was put into a reaction vessel under a nitrogen atmosphere and reacted at 77 ° C. for 3 hours with stirring to obtain a dispersion containing a pigment and having a cross-linked site in the core.
<Dispersion treatment>
In the same manner as in Example 1, an aqueous dispersion of pigment-containing water-insoluble polymer particles having a solid content concentration of 22% was obtained.
<Crosslinking reaction of shell part>
200 parts of the resulting aqueous dispersion was put into a reaction vessel under a nitrogen atmosphere, and further a crosslinking agent (trimethylolpropane polyglycidyl ether, manufactured by Nagase ChemteX Corporation, Denacol EX-321, epoxy equivalent 140) was 0. 20 parts and 47.4 parts of ion-exchanged water were added, and the mixture was reacted at 90 ° C. for 1.5 hours with stirring. % Concentration was obtained.
<Preparation of ink>
29.3 parts of the obtained pigment-containing vinyl polymer particle aqueous dispersion was mixed with 0.30 part of a water-insoluble organic compound and stirred to obtain a water-insoluble organic compound [(i) ethylene oxide of phthalic acid and 2-ethylhexyl alcohol. 25 parts of diester with adduct (average number of moles 4; Nippon Emulsifier Co., Ltd., trade name: New Coal 1004) and (ii) ethylene oxide adduct of trimellitic acid and lauryl alcohol (average number of moles 4) Made of 75 parts of triester with Emulsifier Co., Ltd.) in the polymer particles. In this mixed solution, 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), 0.3 part of Proxel XL2 (manufactured by Avicia Corporation), and ions The mixture was mixed with 52.12 parts of the exchanged water, and the resulting mixture was filtered with a 25 mL needleless syringe equipped with a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by FUJIFILM Corporation). Then, by removing coarse particles, water-based inks shown in Table 2 were obtained.

Comparative Example 1
In Example 1, it carried out like Example 1 except not having used a core part.
Comparative Example 2
In Example 1, it carried out similarly to Example 1 except not having used divinylbenzene of a crosslinking agent by the crosslinking reaction of a core part.
Comparative Example 3
In Example 1, it carried out like Example 1 except not having performed crosslinking reaction of a shell part.

The water-based inks obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated by performing the following glossiness test and bronze 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.
Glossiness of 50 or more 〇 (High gloss)
Glossiness of 40 or more and less than 50 △ (slightly high)
Glossiness less than 40 x (low gloss)
(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.
Δ: Redness is not easily recognized even when a photograph or the like is printed.
X: The fluorescent light reflected on the printing surface and the reflected light of sunlight appear reddish.
(3) Printing density Using the printer, solid printing (printing condition = paper type: plain paper, mode setting: super fine) on commercially available plain paper (XEROX, trade name: 4024) at 25 ° C. After being left for 24 hours, the print density was measured 5 times with a Macbeth densitometer (manufactured by Gretag Macbeth, product number: RD914), and an average value was obtained. The higher the value, the higher the print density.

  From Table 2, it can be seen that the aqueous inks of Examples 1 to 5 are superior in the printing density and glossiness, the suppression of the bronze phenomenon, and the balance thereof as compared with the aqueous inks of Comparative Examples 1 to 3.

Claims (12)

  A crosslinked core-shell polymer particle containing a pigment, wherein the core part and the shell part of the crosslinked core-shell polymer particle are both crosslinked, and the weight ratio of the pigment to the crosslinked core-shell polymer [(pigment weight / pigment The weight of the crosslinked core-shell polymer particles containing x)] is 25-75.   The crosslinked core-shell polymer particle according to claim 1, wherein the degree of crosslinking of the shell part of the crosslinked core-shell polymer particle is 0.5 to 15% by weight.   The crosslinked core-shell polymer particle according to claim 1 or 2, wherein the degree of crosslinking of the core part of the crosslinked core-shell polymer particle is 0.5 to 15% by weight.   The crosslinked core-shell polymer particles according to any one of claims 1 to 3, wherein a weight ratio of the core part to the shell part (core part / shell part) of the crosslinked core-shell polymer particle is 0.3 to 3.   The crosslinked core-shell polymer particles according to any one of claims 1 to 4, wherein the pigment is a cyan pigment.   The core part of a crosslinked core-shell polymer particle is a polymer obtained by polymerizing a crosslinking monomer and a hydrophobic monomer having at least two reactive unsaturated groups in the molecule. Cross-linked core-shell polymer particles.   The shell part of the cross-linked core-shell polymer particles has at least two polymers in the molecule formed by copolymerizing a monomer mixture containing (a) a salt-forming group-containing monomer, (b) a macromer and / or (c) a hydrophobic monomer. The crosslinked core-shell polymer particles according to claim 1, which is a polymer obtained by crosslinking with a crosslinking agent having a reactive functional group. The crosslinked core-shell polymer particles according to any one of claims 1 to 7, which are obtained by the following steps 1 to 3.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2: adding the pigment to the polymer particles containing the pigment Step 2: polymerizing the crosslinkable monomer and the hydrophobic monomer to obtain core-shell polymer particles having a core portion crosslinked Step 3: Step 2 A step of reacting the obtained core-shell polymer particles obtained by crosslinking the core part with a crosslinking agent having at least two reactive functional groups in the molecule.   An aqueous dispersion comprising the crosslinked core-shell polymer particles according to claim 1.   The aqueous dispersion according to claim 9, further comprising a water-insoluble organic compound.   An aqueous ink for ink-jet recording comprising the aqueous dispersion according to claim 9 or 10. The crosslinked polymer particle containing a pigment having the following steps 1 to 3, wherein the weight ratio of the pigment to the crosslinked polymer [(weight of pigment / weight of crosslinked polymer particle containing pigment) × 100] is 25 to 75 Manufacturing method.
Step 1: Polymer particles containing a pigment, a crosslinkable monomer having at least two reactive unsaturated groups in the molecule, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is mixed. Step 2 for inclusion in polymer particles containing the pigment Step 2: Polymerization of the crosslinkable monomer and the hydrophobic monomer to obtain polymer particles Step 3: Polymer particles obtained in Step 2 and molecules Reacting with a crosslinking agent having at least two reactive functional groups therein