JP2008285522A - Water-based ink for ink-jet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water dispersion water-based ink for ink-jet recording having excellent dispersion stability and providing a printed material having high print density and to provide polymer particles useful for the water dispersion water-based ink. <P>SOLUTION: Provided are (1) polymer particles for ink-jet recording which are polymer particles containing a colorant, in which the polymer is a mixture comprising a phenol resin and a vinyl-based polymer, (2) a water dispersion comprising the polymer particles, and (3) a water-based ink for ink-jet recording comprising the water dispersion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water dispersion / water-based ink for ink jet recording, and polymer particles used in the water dispersion / water-based 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.
In particular, from the viewpoint of weather resistance and water resistance of printed matter, those using pigment-based ink as a colorant have become mainstream.

Patent Document 1 discloses (1) a water-soluble organic solvent having a vapor pressure lower than that of water, (2) a hydrophobic colorant that is soluble in a water-soluble organic solvent, and (3) An aqueous dispersion ink containing a hydrophobic resin (maleic acid resin, phenol resin, styrene acrylic resin, etc.) soluble in a water-soluble organic solvent and having the hydrophobic resin dispersed therein is disclosed.
Patent Document 2 discloses (1) a water-soluble organic solvent having a vapor pressure lower than that of water, (2) a hydrophobic colorant, and (3) a water-soluble organic solvent as an ink excellent in preventing ink adhesion to the nozzle plate. An aqueous ink containing a hydrophobic resin that is soluble in water, wherein the resin contains an acidic resin (phenol resin, styrene-acrylic acid resin, etc.) and has a pH of 7 or more.
Patent Document 3 discloses a microcapsule pigment in which at least one color ink is composed of two or more types of inks having different color material concentrations, and an ink having a low color material concentration is coated with an organic polymer compound having an ionic group. An ink set for ink jet recording using a dye for an ink having a high colorant concentration is disclosed.
However, conventional inkjet recording inks are not satisfactory in terms of dispersion stability and print density.

JP-A-8-269374 Japanese Patent Laid-Open No. 9-241552 Japanese Patent Laid-Open No. 2002-226741

  An object of the present invention is to provide an aqueous dispersion / aqueous ink for ink-jet recording which is excellent in dispersion stability and obtains a printed matter having a high printing density, and polymer particles used in the aqueous dispersion / aqueous ink.

By using a mixture containing a phenolic resin and a vinyl polymer as a polymer of polymer particles containing a colorant, the present inventors suppress the penetration of water-based ink in the thickness direction of the recording medium, and As a result of being able to remain on the surface layer of the recording medium and disperse, it has been found that a high printing density can be achieved.
That is, the present invention provides the following (1) to (3).
(1) Polymer particles for ink jet recording, which are polymer particles containing a colorant, wherein the polymer is a mixture containing (A) a phenol resin and (B) a vinyl polymer.
(2) An aqueous dispersion for inkjet recording containing the polymer particles of (1).
(3) A water-based ink for ink-jet recording containing the water dispersion of (2).

  According to the polymer particles for inkjet recording of the present invention, the aqueous dispersion containing the same, and the aqueous ink, a printed matter having excellent ink dispersion stability and high print density can be obtained.

The aqueous dispersion for ink jet recording and the aqueous ink of the present invention are polymer particles containing a colorant from the viewpoint of increasing dispersion stability and printing density, and the polymer comprises (A) a phenol resin and (B). It contains polymer particles which are a mixture containing a vinyl polymer.
Hereinafter, each component used for this invention is demonstrated. The polymer particles containing the colorant may be simply referred to as “colorant-containing polymer particles”.

[Colorant]
The colorant is not particularly limited, and pigments, hydrophobic dyes, water-soluble dyes (acid dyes, reactive dyes, direct dyes, etc.) can be used, but from the viewpoint of water resistance, dispersion stability, and scratch resistance. Pigments and hydrophobic dyes are preferred. Among them, it is preferable to use a pigment in order to develop the high weather resistance which has been demanded in recent years.
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 viewpoint 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 CI Pigment Green are included, and solid solutions thereof are also included. For example, as a solid solution of a magenta pigment, C.I. I. Pigment violet and C.I. I. Pigment Red solid solution is preferred, and C.I. I. Pigment violet 19 and C.I. I. A solid solution of Pigment Red 202 is preferred.
Examples of extender pigments include silica, calcium carbonate, and talc.

The hydrophobic dye is not particularly limited as long as it can be contained in the polymer particles. The hydrophobic dye is preferably 2 g / L or more, more preferably 20 to 500 g / L (25 with respect to the organic solvent (preferably methyl ethyl ketone) used in the production of the polymer, from the viewpoint of efficiently incorporating the dye in the polymer. C.) It is desirable to dissolve.
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.
The above colorants can be used alone or in admixture of two or more at any ratio.

[(A) Phenolic resin)]
When (A) the phenol resin is combined with (B) the vinyl polymer, the aqueous ink is prevented from penetrating in the thickness direction of the recording medium, and the colorant is retained on the surface layer of the recording medium. As a result, a high print density is achieved. Conceivable.
The phenol resin is a general term for resins obtained from phenols (phenol, substituted phenol, cresol, xylenol, resorcin) and aldehydes (formaldehyde, acetaldehyde, furfural) and modified resins thereof.
Examples of the substituted phenol include alkylphenols having 1 to 12 carbon atoms, such as butylphenol, octylphenol, and nonylphenol.
Examples of the phenol resin include a phenol-formaldehyde resin and a phenol-furfural resin, depending on the combination of phenols and aldehydes.
Examples of the modified phenolic resin include rosin-modified phenolic resin (see JP-A-10-324727), alkoxy group-containing silane-modified phenolic resin (see JP-A-2001-2745 and JP-A-2001-294039), and the like. .
Among these, alkylphenol resins and / or rosin-modified phenolic resins are more preferable from the viewpoint of printing density.

As the alkylphenol resin, either a novolak type resin or a resole resin can be used.
The rosin-modified phenol resin can be obtained by a known method using rosins, phenols, polyols and the like.
Examples of rosins that can be used in the production of rosin-modified phenolic resins include gum rosin, wood rosin, tall oil rosin, disproportionated rosin, hydrogenated rosin, polymerized rosin, modified products thereof, and salts of these with metals. Is mentioned.
Phenols that can be used for the production of rosin-modified phenolic resins are preferably novolak-type, resol-type obtained from bisphenol, alkylphenol, or novolak and then resole, preferably 3-20 nuclei, more preferably 4- A phenol resin having a 10-nuclear number is exemplified.
Examples of polyols that can be used in the production of rosin-modified phenolic resins include pentaerythritol, glycerin, ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, trimethylol ethane, trimethylol propane, diethylene glycol, pentaerythritol, and dipentaerythritol. Etc.

(A) As a commercially available product suitable as a phenol resin, alkylphenol resins such as Tamanol 100S and 200N manufactured by Arakawa Chemical Industry Co., Ltd .; And rosin-modified phenolic resins; phenolic resins such as TAMANOL PA, TAMANOL 758, and TAMANOL 759.
(A) A phenol resin having the following physical properties (i) to (ii) is more preferable from the viewpoint of printing density.
(I) Softening point according to JISK-5902-1969: preferably 300 to 600K, more preferably 340 to 500K, particularly preferably 340 to 430K
(Ii) Weight average molecular weight (Mw): preferably 1000 to 150,000, more preferably 1,000 to 50,000, particularly preferably 1,500 to 15,000
In addition, the weight average molecular weight of the phenol resin is obtained by using a gel chromatography device “System-21” (filler: styrene divinylbenzene copolymer, column flow rate 1.0 ml / min, temperature: 40 ° C.) manufactured by Shodex, Can be measured.

[(B) Vinyl polymer]
In the present invention, from the viewpoint of dispersion stability, a vinyl polymer (B) obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound) is used.
The vinyl polymer (B) used in the present invention is dissolved when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C. from the viewpoint of affinity with the phenol resin. A water-insoluble vinyl polymer having an amount of preferably 10 g or less, more preferably 5 g or less, and still more preferably 1 g or less is preferred. 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.
(B) 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 A polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to as “monomer mixture”) containing / c (c) a hydrophobic monomer (hereinafter also referred to as “component (c)”) is preferable. This 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 vinyl polymer has a structural unit derived from component (a), or a structural unit derived from component (a) and a structural unit derived from component (c) in the main chain, and a structural unit derived from component (b). In the side chain.

(A) The salt-forming group-containing monomer is used from the viewpoint of enhancing the dispersion stability of the obtained aqueous 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, and a carboxy group is particularly preferable.
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 polymer particles. The macromer includes a macromer which is a monomer having a polymerizable unsaturated group having a number average molecular weight of preferably 500 to 100,000, more 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, from the viewpoint of dispersion stability of the colorant-containing polymer particles, a styrene macromer and an aromatic group-containing (meth) acrylate macromer 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. The aromatic group-containing (meth) acrylate may have a substituent containing a hetero atom, preferably 7 to 22 carbon atoms, more preferably 7 to 18 carbon atoms, still more preferably 7 to 12 carbon atoms. Or an aryl group having 6 to 22 carbon atoms, more preferably 6 to 18 carbon atoms, and still more preferably 6 to 12 carbon atoms, which may have a substituent containing a hetero atom. Examples of the substituent having a (meth) acrylate having 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 may have a substituent containing a hetero atom, preferably an aromatic group having 6 to 22 carbon atoms, more preferably 6 to 18 carbon atoms, and still more preferably an aromatic group having 6 to 12 carbon atoms. The vinyl monomer which has group is preferable, for example, the said styrene-type monomer (c-1 component) and the said aromatic group containing (meth) acrylate (c-2 component) are mentioned. 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.
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 (2) (hereinafter sometimes 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, 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.

(B) The content of the components (a) to (e) in the monomer mixture at the time of production of the vinyl polymer (content as an unneutralized amount; the same applies hereinafter) or (a) to (a) in the polymer The content of the structural unit derived from the component e) 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, particularly preferably 0.03 to 0.50.

[(B) Production of vinyl polymer]
(B) The vinyl polymer 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 (B) vinyl polymer used in the present invention is preferably 5,000 to 500,000, more preferably 10,000 to 400,000, more preferably from the viewpoint of printing density and dispersion stability of the colorant. Is 10,000 to 300,000, particularly preferably 20,000 to 300,000. In addition, the weight average molecular weight of a vinyl-type polymer is measured by the method shown in an Example.
The (B) vinyl polymer used in the present invention is neutralized with a neutralizing agent when used (a) having a salt-forming group derived from a salt-forming group-containing monomer. 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.

(Production of aqueous dispersion of polymer particles containing colorant)
The method for producing an aqueous dispersion of polymer particles containing a colorant is not particularly limited, but can be efficiently produced by the method having the following steps I and II.
Step I: (A) Step of obtaining a dispersion of polymer particles containing a colorant by dispersing a mixture containing (A) a phenol resin, (B) a vinyl polymer, a colorant, an organic solvent, and water Step II: Step Step of removing organic solvent from the dispersion obtained in I

In step I, it is preferable to first dissolve (A) the phenol resin and (B) the vinyl polymer in an organic solvent. (A) Only the phenol resin may be dissolved in an organic solvent in advance. Next, after adding a colorant to the obtained organic solvent solution, water is added, and a neutralizing agent, a surfactant and the like are further added and mixed as necessary to obtain an oil-in-water dispersion. Is preferred. From the viewpoint of printing density in the mixture, the colorant is preferably 5 to 60% by weight, more preferably 10 to 40% by weight, and the organic solvent is preferably 10 to 70% by weight, more preferably 10 to 50% by weight. It is. The total amount of (A) phenolic resin and (B) vinyl polymer is preferably 2 to 40% by weight, more preferably 3 to 20% by weight, and water is preferably 1 to 70% by weight, more preferably 20 to 70% by weight.
(B) When the vinyl polymer has a salt-forming group, it is preferable to use a neutralizing agent, but the degree of neutralization is not particularly limited. 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 water-insoluble polymer. Examples of the neutralizing agent include those described above. Further, (B) the vinyl polymer may be neutralized in advance.
Examples of the organic solvent include alcohol solvents such as ethanol, isopropanol and isobutanol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and diethyl ketone, and ether solvents such as dibutyl ether, tetrahydrofuran and dioxane. The solubility in water is preferably 50% by weight or less and 20% by weight or more at 20 ° C., and methyl ethyl ketone and methyl isobutyl ketone are particularly preferable. From the viewpoint of dissolving the phenol resin and promoting the emulsification and dispersion of the pigment, an organic solvent that dissolves 20 g / L (25 ° C.) or more of the phenol resin used is preferable.

Next, there is no particular limitation on the method for dispersing the mixture in Step I. Although the average particle size of the polymer particles can be atomized only by the main dispersion until the desired particle size is reached, after pre-dispersion, the main dispersion is further performed by applying a shear stress to determine the average particle size of the polymer particles. It is preferable to control to obtain a desired particle size. In the main dispersion, two or more main dispersion means described later may be used in combination. The dispersion temperature in step I is preferably 5 to 50 ° C, and more preferably 10 to 35 ° C. In the middle of step I, water and an organic solvent may be appropriately added in order to adjust the viscosity.
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., Ltd., trade name], KD Mill [Kinetic Dispersion Co., Ltd., trade name] and the like are preferable.
As means for giving the shear stress of this dispersion, for example, a kneader such as a roll mill, a bead mill, a kneader, an extruder, a high-pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), a minilab 8.3H type (Rannie Co., trade name) Representative homo-valve type high-pressure homogenizer, microfluidizer (Microfluidics, trade name), nanomizer (Nanomizer, trade name), optimizer (Sugino Machine Co., trade name), Genus PY (Shiramizu Chemical Co., Ltd.) Product name], DeBEE2000 [Japan EE Co., Ltd., product name] and the like chamber type high-pressure homogenizer. Among these, when a pigment is used, a roll mill, a bead mill, a kneader, and a high-pressure homogenizer are preferable from the viewpoint of reducing the particle size of the pigment. A plurality of these devices can be combined.

In Step II, an aqueous dispersion of polymer particles containing a colorant can be obtained by distilling off the organic solvent from the obtained dispersion by a known method to form an aqueous system. The organic solvent in the aqueous dispersion containing the resulting polymer particles is substantially removed. The amount of residual organic solvent is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
The obtained aqueous dispersion of the colorant-containing polymer particles is one in which the solid content of the polymer containing the colorant is dispersed in water as the main medium. Here, the form of the polymer particles is not particularly limited as long as the particles are formed of a mixture containing at least a colorant, (A) a phenol resin, and (B) a vinyl polymer. For example, (A) a particle form in which a colorant is encapsulated in a mixture containing a phenol resin and (B) a vinyl polymer, and a colorant is uniformly dispersed in a mixture containing (A) a phenol resin and (B) a vinyl polymer. And (A) a particle form in which a colorant is exposed on the polymer particle surface of a mixture containing a phenol resin and (B) a vinyl polymer. Here, the mixture containing (A) the phenol resin and (B) the vinyl polymer does not need to be uniformly mixed, and may have a disproportionate distribution as long as both are integrated. For example, more (A) phenol resin may be present on the surface of the colorant-containing polymer particles. Other polymers may be included in the mixture as long as the present invention is not impaired.

(Polymer particles containing colorant)
In the polymer particles containing the colorant, the weight ratio of [(A) phenol resin / (B) vinyl polymer] is preferably 0.02 to 10, more preferably from the viewpoint of printing density and dispersion stability. Is 0.05 to 3, more preferably 0.1 to 1, more preferably 0.1 to 0.8, still more preferably 0.1 to 0.5, and particularly preferably 0.1 to 0.4. .
The total weight ratio of the colorant, (A) phenol resin, and (B) vinyl polymer [[(A) phenol resin + (B) vinyl polymer] / colorant] is from the viewpoint of dispersion stability of the polymer particles. The ratio is preferably 5/95 to 90/10, more preferably 10/90 to 75/25, and particularly preferably 15/85 to 50/50.
The weight ratio of the colorant to the (A) phenol resin [(A) phenol resin / colorant] is preferably 1/40 to 1/1, more preferably 1/30 to 1/3. (B) The weight ratio to the vinyl polymer [(B) vinyl polymer / colorant] is preferably 1/20 to 2/1, more preferably 1/10 to 1/1.

(Water dispersion for inkjet recording)
The content of each component in the aqueous dispersion for inkjet recording is as follows from the viewpoint of printing density and dispersion stability.
The content of the colorant is preferably 3 to 30% by weight, more preferably 5 to 20% by weight.
(A) Content (phenol conversion) of a phenol resin becomes like this. Preferably it is 0.1-20 weight%, More preferably, it is 0.1-15 weight%, Most preferably, it is 0.1-10 weight%.
The content (solid content) of the (B) vinyl polymer is preferably 0.5 to 20% by weight, more preferably 0.5 to 15% by weight, and particularly preferably 1 to 10% by weight.
(Water-based ink for inkjet recording)
The aqueous ink of the present invention contains the aqueous dispersion of the present invention, and additives such as a wetting agent, a dispersant, an antifoaming agent, an antifungal agent, and a chelating agent can be added as necessary. There is no restriction | limiting in particular in the mixing method of these additives.
The content of each component in the water-based ink for ink-jet recording is as follows from the viewpoint of reducing the print density and dispersion stability.
The content of the colorant is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight. (A) The content of the phenol resin (in terms of pure content) is preferably 0.05 to 15% by weight, more preferably 0.08 to 8% by weight, and particularly preferably 0.1 to 5% by weight. (B) The content (solid content) of the vinyl polymer is preferably 0.3 to 20% by weight, more preferably 0.5 to 10% by weight, and particularly preferably 0.8 to 8% by weight. is there.

The water content in the water dispersion for inkjet recording and the water-based ink is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.
From the viewpoint of dispersion stability, the average particle size of the polymer particles containing the colorant in the aqueous dispersion and aqueous ink is preferably 40 to 400 nm, more preferably 50 to 300 nm, and particularly preferably 60 to 200 nm. The average particle size is measured by the method described in the examples.
The viscosity (20 ° C.) at a solid content of 20% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, 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 viscosity of the aqueous dispersion and aqueous ink is measured by the method described in the examples.
The 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. It is 25-50 mN / m, More preferably, it is 25-45 mN / m. 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. In addition, the measuring method of the weight average molecular weight of a vinyl-type polymer, the viscosity of water-based ink, and the average particle diameter of a colorant containing polymer particle is as follows.
(1) Weight average molecular weight of vinyl polymer Gel chromatograph “HLC-8120GPC” manufactured by Tosoh Corporation (column used: Tosoh Corporation, TSK-GEL, α-M × 2, column flow rate: 1 mL / min, (Temperature: 20 ° C.), N, N-dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent, and polystyrene as a standard substance.
(2) Viscosity measurement Using an E-type viscometer “RE80” manufactured by Toki Sangyo Co., Ltd., using a standard rotor (1 ° 34 ′ × R24), measuring temperature 20 ° C., measuring time 1 minute, rotation speed The measurement was performed under the condition of 100 rpm.
(3) Measurement of average particle diameter of colorant-containing polymer particles Measurement was performed using a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by 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%.

Production Example 1
In a reaction vessel, 20 parts of MEK, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol) and 10% of 200 parts of the monomer mixture shown in Table 1 are mixed and mixed, and nitrogen gas replacement is sufficiently performed and mixed. A solution was obtained.
On the other hand, the remaining 90% of the monomer mixture shown in Table 1 was charged into a dropping funnel, and 0.27 part of the polymerization chain transfer agent, 60 parts of MEK, and a radical polymerization initiator (2,2′-azobis (2,4-dimethyl). 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 the dropping, a solution in which 0.3 part of the radical polymerization initiator was dissolved in 5 parts of MEK was added, and further aged at 65 ° C. for 2 hours and at 70 ° C. for 2 hours to obtain a vinyl polymer solution. Obtained. The weight average molecular weight of this polymer was 200,000.

The details of the monomers shown in Table 1 are as follows.
Styrene macromer: manufactured by Toa Gosei Co., Ltd., trade name: AS-6S, number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group / polyethylene glycol monomethacrylate (ethylene oxide average added mole number = 9): Shin-Nakamura Chemical Product name: NK ester M-90G
Polypropylene glycol monomethacrylate (propylene oxide average added mole number = 9): manufactured by NOF Corporation, trade name: BLEMMER PP-500

Example 1
10.6 parts of phenol resin “Tamanol 200N” [alkylphenol resin, Mw: 2300, acid value 50 to 110, softening point 398 to 418K, manufactured by Arakawa Chemical Industries, Ltd.] (50% MEK solution, pure content equivalent value 5.3) Part) and 25 parts of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure are mixed with 50 parts of MEK (methyl ethyl ketone), and quinacridone pigment (CI Pigment Violet 19, Clariant) is mixed therein. 100 parts by Japan Co., Ltd., trade name: Hostaperm Red E5B02) and mixed well. Further, 4.6 parts and 1.8 parts (neutralization degree 60%) of 5N aqueous sodium hydroxide and 25% aqueous ammonia, respectively. In addition, they were mixed for 30 minutes at 20 ° C. on a roll mill. The obtained mixture was diluted with ion-exchanged water so as to be a 20% aqueous solution, and it was subjected to 10-pass dispersion treatment at a pressure of 200 MPa with a microfluidizer (trade name, manufactured by Microfluidics).
After adding 250 parts of ion-exchanged water to the obtained dispersion and stirring, MEK was completely removed at 60 ° C. under reduced pressure, a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer Diameter: 2.5cm, manufactured by Fuji Photo Film Co., Ltd.) Filtered with a 25mL needleless syringe (Terumo Co., Ltd.) and removed coarse particles to remove pigment particles containing 20% solids. An aqueous dispersion of polymer particles was obtained.

To 40 parts of the resulting pigment-containing vinyl polymer particle aqueous dispersion, 7 parts of triethylene glycol monobutyl ether, 1 part of Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), Proxel XL2 (manufactured by Avicia Corporation) 3 parts and 36 parts of ion-exchanged water were mixed, and glycerin and water were added so that the viscosity at 20 ° C. was 4 mPa · s, and the total was adjusted to 100 parts. By filtering the obtained mixed solution with a syringe having a capacity of 25 mL equipped with a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.), and removing coarse particles. A water-based ink was obtained.
Comparative Example 1
A water-based ink was obtained in the same manner as in Example 1 except that the alkylphenol resin of Example 1 was not used.

Example 2
Instead of the phenol resin “Tamanol 200N” used in Example 1, phenol resin “KG-2212” [Rosin-modified phenol resin, Mw: 120,000, acid value of 22 or less, softening point 445 to 455 K, Arakawa Chemical Industries, Ltd. Manufactured] A water-based ink was obtained in the same manner as in Example 1 except that 10.6 parts (50% MEK solution, 5.3 parts pure conversion value) was used.
Example 3
In place of the Tamanol 200N of Example 1, “Tamanol 379” [rosin-modified phenolic resin, Mw: 11,000, acid value of 26 or less, softening point 433 to 443K, manufactured by Arakawa Chemical Industries, Ltd.] 10.6 parts ( A water-based ink was obtained in the same manner as in Example 1 except that a 50% MEK solution (5.3 parts pure conversion value) was used.

Example 4
Instead of the quinacridone pigment of Example 1, a quinacridone solid solution pigment (solid solution of CI Pigment Violet 19 and CI Pigment Red 202, manufactured by Ciba Specialty Chemicals Co., Ltd., trade name: CROMOPHTAL Jet Magenta 2BC ) Was used in the same manner as in Example 1 except that the water-based ink was obtained.
Example 5
A water-based ink was obtained in the same manner as in Example 1 except that a cyan pigment (CI Pigment Blue 15: 3, manufactured by Dainichi Seika Kogyo Co., Ltd.) was used in place of the quinacridone pigment of Example 1. .
Example 6
A water-based ink was obtained in the same manner as in Example 1, except that a yellow pigment (CI Pigment Yellow 74, manufactured by Sanyo Color Co., Ltd.) was used instead of the quinacridone pigment of Example 1.
Example 7
A water-based ink was obtained in the same manner as in Example 1 except that 10.6 parts of the phenol resin in Example 1 was changed to 21.2 parts.

Comparative Example 2
To 40 parts of the aqueous dispersion of pigment-containing vinyl polymer particles obtained in Comparative Example 1, 7 parts of triethylene glycol monobutyl ether, 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), phenol resin “Tamanol 200N” 0.68 part (50% MEK solution, 0.34 part pure value), 0.3 part of Proxel XL2 (manufactured by Avicia Co., Ltd.) and 36 parts of ion-exchanged water are mixed, and the viscosity at 20 ° C. is 4 mPa · s. Then, glycerin and water were added so that the total amount became 100 parts. By filtering the obtained mixed solution with a syringe having a capacity of 25 mL equipped with a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.), and removing coarse particles. A water-based ink was obtained.
Comparative Example 3
Instead of Tamanol 200N of Example 1, acrylic resin “JONCRYL 611” [JONCRYL RESIN type, Mw: 8100, acid value 53, softening point 385K, manufactured by BASF Japan Ltd.] 10.6 parts (50% MEK solution, pure A water-based ink was obtained in the same manner as in Example 1 except that the minute conversion value (5.3 parts) was used.

Next, the dispersion stability and the character density of the inks obtained in each Example and each Comparative Example were evaluated by the following methods. The results are shown in Table 2.
(Evaluation of dispersion stability)
The sealed ink described in Examples was allowed to stand at 70 ° C. for one week, and the change rate of the particle diameter and viscosity was measured. Evaluation was made according to the following criteria.
◎: Change rate of particle size and viscosity is within ± 10% ○: Change rate of particle size and viscosity is within ± 20% ×: Change rate of particle size and viscosity exceeds ± 20% (evaluation of printing density)
Using a printer (model number: EM-930C) manufactured by Seiko Epson Corporation, solid printing (printing condition = paper type: plain paper, mode setting) on commercially available high-quality plain paper (Xerox Corporation, trade name: XEROX 4024) Fine], and left at 25 ° C. for 24 hours, the print density was measured with a Macbeth densitometer (manufactured by Gretag Macbeth Co., product number: SpectroEye). The average value was measured.
Since the mode setting is fine and ink is not overprinted, the print density is preferably 0.92 or more for magenta pigments and 0.95 or more for cyan and yellow pigments.

From Table 2, it can be seen that the aqueous inks of Examples 1 to 7 are superior in dispersion stability and print density as compared with the aqueous inks of Comparative Examples 1 to 3.
A difference of 0.01 in print density is a sufficient difference that can be visually confirmed.

Claims (7)

  Polymer particles for inkjet recording, wherein the polymer particles contain a colorant, and the polymer is a mixture containing (A) a phenol resin and (B) a vinyl polymer.   The polymer particles for inkjet recording according to claim 1, wherein a weight ratio of ((A) phenol resin / (B) vinyl polymer) is 0.02 to 10.   (A) The polymer particle for inkjet recording of Claim 1 or 2 whose phenol resin is an alkylphenol resin and / or a rosin modified phenol resin.   (A) The polymer particle for inkjet recording in any one of Claims 1-3 whose weight average molecular weights of a phenol resin are 1000-150,000.   (B) The vinyl polymer has a structural unit derived from the salt-forming group-containing monomer (a) and a structural unit derived from the hydrophobic monomer (c) in the main chain, and the structural unit derived from the macromer (b) as the side chain. The polymer particles for ink-jet recording according to any one of claims 1 to 4, which is a graft polymer.   An aqueous dispersion for ink-jet recording, comprising the polymer particles according to claim 1.   An aqueous ink for inkjet recording, comprising the aqueous dispersion according to claim 6.