JP4759262B2 - Water-based ink for inkjet recording - Google Patents

Description

  The present invention relates to an aqueous dispersion for inkjet recording and an aqueous ink for inkjet recording containing the aqueous dispersion.

  The ink jet recording method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording member and attaching them. According to this method, not only has the advantage that the device to be used is low noise and good operability, but also has the advantage that colorization is easy and plain paper can be used as a recording member. Widely used in recent years. In recent years, pigments or hydrophobic dye-based inks (hereinafter simply referred to as “pigment-based inks”) are mainly used as colorants for inks used in inkjet printers in order to improve water resistance and light resistance.

However, when the pigment-based ink is used in the water-based ink, the pigment does not dissolve in the ink, so that there is a drawback that the storage stability of the ink is poor.
In order to improve water resistance, marker resistance and scratch resistance of ink, an ionic functional group containing a particulate material, a solvent, and a polymer having an ionic functional group, an acid residue or a base residue at its terminal A composition containing a polymer (Patent Document 1), a water-based ink (Patent Document 2) containing a colorant and a water-insoluble polymer having two or more hydroxyl groups at its ends, (A) a salt-forming group-containing monomer, And (B) a monomer mixture containing a macromer and a monomer capable of copolymerizing with (C) a salt-forming group-containing monomer and a macromer, and containing a water-insoluble polymer and a pigment having an ionic group at the terminal. A water-based ink (Patent Document 3) is proposed.
However, these water-based inks show some improvement in water resistance, marker resistance and scratch resistance, but are still not sufficient. In addition, when printed with an ink jet printer, the printed matter tends to be faint, there is a problem in the print density, and there is a problem in bleeding property (image quality deterioration phenomenon occurring at the boundary between different colors).

JP 2003-261738 A JP 2004-26988 A JP 2004-210951 A

  INDUSTRIAL APPLICABILITY The present invention is a water dispersion for ink jet recording having good dispersion stability and ejection properties, high print density, water resistance, bleed resistance (difficulty in image quality deterioration phenomenon at the boundary between different colors) and scratch resistance. It is an object to provide a body and water-based ink.

The present invention contains a water-insoluble polymer having a weight average molecular weight of 1000 to 15000, a structural unit derived from a hydrophobic monomer of 100 % by weight, and having an ionic group only at both ends and a colorant. A water dispersion for inkjet recording , wherein the ionic group has a polymerization initiator (A) having an ionic group, a chain transfer agent (B) having an ionic group, and a function of the polymerization initiator and the chain transfer agent. An aqueous dispersion for inkjet recording, which is derived from one or more compounds selected from the group consisting of iniferters (C) having water , and an aqueous ink for inkjet recording using the aqueous dispersion.

  The water-based ink of the present invention has excellent dispersion stability, excellent dischargeability when printing with an ink jet printer, and good high print density, water resistance, bleed resistance, and scratch resistance. .

BEST MODE FOR CARRYING OUT THE INVENTION

<Colorant>
As the colorant, pigments and hydrophobic dyes are preferable from the viewpoint of water resistance. Among them, it is preferable to use a pigment in order to express the high weather resistance which has been demanded in recent years. The pigment may be either an organic pigment or an inorganic pigment. If necessary, extender pigments can be used in combination.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
Specific examples of preferred organic pigments include CI Pigment Yellow 13, 17, 74, 83, 93, 97, 109, 110, 120, 128, 139, 151, 154, 155, 174, 180; CI Pigment Red 48 57: 1, 122, 146, 176, 184, 185, 188, 202; CI pigment violet 19, 23; CI pigment blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 16 60; CI Pigment Green 7, 36 and the like.

  Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Among these, carbon black is particularly preferable for black water-based inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black. Of these, furnace black and channel black are preferable. 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. Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes. Among these, oil-soluble dyes are preferable.
From the viewpoint of efficiently incorporating the hydrophobic dye into the water-insoluble polymer particles, the hydrophobic dye has a solubility in an organic solvent used in the production of the aqueous dispersion of preferably 2 g / L or more, more preferably 20 to 500 g. Those that are / L are preferred.

The oil-soluble dye is not particularly limited, but from the viewpoint of water resistance, for example, CI Solvent Black 3, 7, 27, 29, 34, 45; CI Solvent Yellow 14, 16, 29, 56, 82 83: 1; CI Solvent Red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73; CI Solvent Violet 3; CI Solvent Blue 2, 4, 11, 44, 64 70; CI Solvent Green 3, 7, 7; CI Solvent Orange 2, and the like. In addition, a dye obtained by solubilizing a water-soluble dye may be used.
Among them, CI solvent yellow 29 and 30 as yellow, CI solvent blue 70 as cyan, CI solvent red 18 and 49 as magenta, CI solvent black 3 and 7 as black, and nigrosine black dye preferable. Said colorant can be used individually or in mixture of 2 or more types.

<Water-insoluble polymer>
In the present invention, a water-insoluble polymer having a weight average molecular weight of 1000 to 15000, having 90% by weight or more of a structural unit derived from a hydrophobic monomer and an ionic group at both ends (hereinafter sometimes simply referred to as a water-insoluble polymer). ).
In order to stably disperse the colorant in the water-based ink, a surfactant, a water-soluble polymer, or a water-insoluble polymer can be used. In particular, in order to obtain a water-based ink excellent in water resistance, high printing density, bleed resistance, and scratch resistance, it is preferable to include a colorant in the polymer particles of the water-insoluble polymer.

  Examples of water-insoluble polymers include vinyl polymers, ester polymers, urethane polymers and the like. Of these polymers, water-insoluble vinyl polymers are preferred.

  The ionic groups at both ends of the water-insoluble polymer are a polymerization initiator (A) having an ionic group, a chain transfer agent (B) having an ionic group, and an iniferter having a function of a polymerization initiator and a chain transfer agent. It is preferably derived from one or more compounds selected from the group consisting of (C) (hereinafter sometimes simply referred to as “iniferter”). The terminal derived from a monomer may be sufficient as needed.

  As used herein, the term “ionic group” refers to both a functional group that is actually charged and in an ionic state, and a functional group that does not have a charge but has the ability to become an ion by an external action. means.

  As used herein, the “terminal” of the water-insoluble polymer means the terminal in the main chain of the water-insoluble polymer, and does not mean the terminal in the side chain. Therefore, when the water-insoluble polymer is a graft copolymer, the “end” of the water-insoluble polymer does not include the end of the graft chain.

  The water-insoluble polymer having ionic groups at both ends is selected from the group consisting of a polymerization initiator (A) having an ionic group and a chain transfer agent (B) or iniferter (C) having an ionic group. It can be obtained by polymerizing monomers in the presence of more than one species.

  Examples of the ionic group include a cationic group, an anionic group, and a betaine group. Different ionic groups may be used in combination.

Specific examples of the cationic group are represented by the formula: —NH _n R ¹⁰ _2-n (wherein n is an integer of 0 to 2, and R ¹⁰ independently represents an alkyl group or an aryl group). An phosphine group represented by an amine base, a pyridinium salt, an imidazolinium salt, a formula: —P (R ²⁰ ) ₂ (wherein R ²⁰ independently represents an alkyl or aryl group), and the like; These cationic groups may be used alone or in combination of two or more. Among these, an amine base is preferable from the viewpoint of achieving both ink dispersion stability, water resistance, and scratch resistance. The alkyl group is preferably an alkyl group having 1 to 8 carbon atoms, and the aryl group is preferably an aryl group having 6 to 12 carbon atoms.

Specific examples of the anionic group include a —COOM group (wherein M represents a hydrogen atom, an alkali metal atom, ammonia or an amine, the same applies hereinafter), a —SO ₃ M group, a —PO ₃ M ₂ group, and the like. These anionic groups may be used alone or in combination of two or more.

  Specific examples of the betaine group include a carbobetaine group, a sulfobetaine group, and a phosphobetaine group, such as those having an amino group and a carboxyl group in the molecule, such as those contained in amino acids. Can be used alone or in combination of two or more. Among these, those having an amino group and a carboxyl group in the molecule are preferable from the viewpoint of achieving both the dispersion stability of the ink and the water resistance and scratch resistance.

  Examples of the polymerization initiator having an ionic group include 2,2′-azobis (2-amidinopropane), dibasic acid, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis [2 -(5-Methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [ 2- (2-Imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride 2,2′-azobis [2- (1- (2-hydroxyethyl) -2-yl) propane] dihydrochloride and the like. These can be used alone or in admixture of two or more. Among these, 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamide] are more preferable.

  The chain transfer agent having an ionic group may be any one having a functional group that causes chain transfer and an ionic group. Examples of the functional group that causes chain transfer include a mercapto group and a disulfide group. Among them, a mercapto group is preferable. The number of ionic groups in the chain transfer agent having an ionic group is not limited, and the number may be 2 or more.

  Specific examples of the chain transfer agent having an ionic group include 1-amino-2-methyl-2-propanethiol, 2-aminoethanethiol, 2-diethylaminoethanethiol, 2-dimethylaminoethanethiol, 4-aminothio Chain transfer agents having cationic properties such as phenol, dithiodianiline, 3,4,5,6-tetrahydro-2-pyrimidinethiol, 2-mercaptothiazoline; thioglycolic acid, mercaptopropionic acid, mercaptosuccinic acid, thiolactic acid, Anionic chain transfer agents such as 4,4′-dithiobutyric acid, 3,3′-dithiopropionic acid, dithioglycolic acid; and DL-penicillamine, N- (2-mercaptopropionyl) glycine, DL-cysteine , DL-homocysteine, cystamine, DL-cystine, etc. Chain transfer agent having a betaine such as Le group-containing amino acids and derivatives thereof. These chain transfer agents can be used alone or in admixture of two or more.

  From the viewpoint of obtaining a water-based ink having excellent dischargeability, 2-aminoethanethiol and 2-diethylaminoethanethiol are preferable among the chain transfer agents having cationic properties, and among the chain transfer agents having anionic properties. Thioglycolic acid, mercaptosuccinic acid and mercaptopropionic acid are preferable, and among the chain transfer agents having betaine properties, DL-cysteine is preferable. Among these, thioglycolic acid, mercaptopropionic acid, and mercaptosuccinic acid are more preferable. Alternatively, mercaptosuccinic acid, which is a chain transfer agent that gives two ionic groups at the ends, may be used.

  Iniferter (C) includes 1,2-biscarboxymethyl-1,1,2,2-tetraphenylethane, 1,2-bis (2-carboxyethyl) -1,1,2,2-tetraphenyl Ethane and the like can be mentioned. These can be used alone or in admixture of two or more.

  Among the chain transfer agent (A) having an ionic group, the polymerization initiator (B) having an ionic group, and the iniferter (C), a chain transfer agent having an ionic group and a polymerization initiation having an ionic group The agent is preferable because its use is simple.

  When a chain transfer agent having a functional group that has no charge but has an ability to become an ion by an external action is used, all or a part of the functional group is ionized before preparing the water-based ink. In the ionization, the functional group of the chain transfer agent may be ionized by adding a compound to be ionized to the chain transfer agent, or the functional group is present in the molecule by the functional group present in the water-insoluble polymer. It may be ionized.

  For example, when a monomer is polymerized in the presence of thioglycolic acid as a chain transfer agent, an alkaline compound that can neutralize active hydrogen of thioglycolic acid, such as sodium hydroxide, is obtained in the resulting polymerization reaction mixture. Alkaline compounds such as potassium hydroxide and aqueous ammonia may be added. However, even in this case, when a monomer having an amino group is included in the monomers constituting the polymer, the carboxyl group at the terminal of the produced polymer is already ionized. There is no need to add an alkaline compound.

  When a chain transfer agent having a cationic group is used as the chain transfer agent, a compound having an opposite charge, that is, a compound having an anionic property may be used.

From the viewpoint of obtaining a water-insoluble polymer having a weight average molecular weight of 1000 to 15000 and from the viewpoint of obtaining a water-based ink excellent in dispersion stability, water resistance, scratch resistance and bleed resistance, a polymerization initiator (A) having an ionic group The total amount of the chain transfer agent (B) having an ionic group is preferably 5 to 40 parts by weight, more preferably 10 to 40 parts by weight, particularly 100 parts by weight of the total monomers to be subjected to polymerization. The amount of the polymerization initiator (A) having an ionic group is preferably 20 to 35 parts by weight, and preferably 1 to 30 parts by weight, more preferably 100 parts by weight of all monomers to be subjected to polymerization. Is 5 to 25 parts by weight, particularly preferably 7 to 20 parts by weight. The amount of the chain transfer agent (B) having an ionic group is preferably 100 parts by weight based on the total amount of monomers to be subjected to polymerization. 1 to 0 parts by weight, more preferably 5 to 25 parts by weight, particularly preferably 7 to 20 parts by weight.
Further, the amount of the iniferter (C) is preferably 5 with respect to 100 parts by weight of all monomers to be polymerized from the viewpoint of obtaining a water-based ink excellent in dispersion stability, scratch resistance and bleed resistance. -30 parts by weight, more preferably 5-20 parts by weight, particularly preferably 7-20 parts by weight.

  In the present specification, “water-insoluble” in the water-insoluble polymer means that the polymer is dissolved in an organic solvent, and when it has an ionic group and its salt-forming group is neutralized 100%, at 105 ° C. for 2 hours. After drying, when dissolved in 100 g of water at 25 ° C., it means that the dissolved amount is less than 2 g. “Water-soluble” means other than “water-insoluble”.

In the present specification, there is no limitation on the type of monomer constituting the polymer. However, in order to maximize the expression of good water resistance, scratch resistance, high print density and good bleed resistance, the polymer is water-soluble. An insoluble vinyl polymer is preferred. As a water-insoluble vinyl polymer, it is 90% by weight or more in the presence of a polymerization initiator (A) having an ionic group and a chain transfer agent (B) having an ionic group, or in the presence of an iniferter (C). A polymer obtained by polymerizing a monomer containing a hydrophobic monomer is preferred.
It is preferable that essentially no ionic group is present except at both ends of the water-insoluble polymer. Moreover, it is preferable that it is a structural unit derived from a hydrophobic monomer other than the both ends of a water-insoluble polymer. Thereby, the interaction between the colorant and the water-insoluble polymer can be enhanced.
Therefore, in the monomer to be polymerized, in the hydrophobic monomer or water-insoluble polymer described later, the constituent unit derived from the hydrophobic monomer is preferably 90 to 100% by weight, more preferably 95 to 100% by weight, and 98 to 100%. Weight percent is particularly preferred.
Further, in the monomer to be polymerized, in the salt-forming group-containing monomer or water-insoluble polymer described later, the constituent unit derived from the salt-forming group is preferably 0 to 5% by weight, more preferably 0 to 3% by weight, and 0 ˜2% by weight is particularly preferred.

The hydrophobic monomer is preferably one or more monomers selected from the group consisting of monomers represented by formula (I) and / or formula (II).
CH ₂ = C (R ¹ ) COOR ² (I)
(Wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ² is a hydrocarbon group having 1 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a cyclic group having 3 to 30 carbon atoms. (Indicates hydrocarbon.)
CH ₂ = C (R ³ ) R ⁴ (II)
(In the formula, R ³ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁴ represents an aryl group having 6 to 22 carbon atoms.)
Monomers (I) and / or (II) are preferably contained in one or more types from the viewpoint of printing density and bleed resistance. These can be used alone or in admixture of two or more.

R ¹ in formula (I) is preferably a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or cyclic carbonization having 3 to 30 carbon atoms. A hydrogen group is preferred.
Monomers having an alkyl group of formula (I) include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (Meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, Preference is given to (meth) acrylates in which the ester moiety such as heryl (meth) acrylate is an alkyl group having 1 to 22 carbon atoms. These can be used in combination of two or more.

  As used herein, “(meth) acryl” means “acryl”, “methacryl”, or a mixture thereof. In addition, (iso or tertiary) and (iso) mean both the case where these groups are present and the case where these groups are not present. When these groups are not present, they indicate normal. (Meth) acrylate means both methacrylate and acrylate. The same applies to the following.

  Monomers having an aryl group of formula (I) include phenyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 1-naphthalyl acrylate, 2-naphthalyl. (Meth) acrylate, phthalimidomethyl (meth) acrylate, p-nitrophenyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-acrylic Preferable examples include aryl groups having 6 to 22 carbon atoms such as leuoxyethyl phthalic acid. These can be used alone or in admixture of two or more. The aryl group includes an alkylaryl group and an arylalkyl group.

  Preferred examples of the monomer having a cyclic hydrocarbon group of the formula (I) include monocyclic, bicyclic and tricyclic or higher polycyclic (meth) acrylates having 6 to 22 carbon atoms. Specifically, as monocyclic (meth) acrylate having 6 or more carbon atoms, cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) Examples include acrylate, cyclooctyl (meth) acrylate, cyclononyl (meth) acrylate, cyclodecyl (meth) acrylate, and examples of bicyclic (meth) acrylate include isobornyl (meth) acrylate and norbornyl (meth) acrylate. Examples of the tricyclic (meth) acrylate include adamantyl (meth) acrylate. Among these, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and adamantyl (meth) acrylate are preferable from the viewpoint of storage stability. These can be used in combination of two or more.

R ³ in the formula (II) is preferably a hydrogen atom or a methyl group, and R ⁴ is preferably an aryl group having 6 to 22 carbon atoms.
The monomer represented by formula (II) is selected from styrene, vinylnaphthalene, α-methylstyrene, vinyltoluene, ethylvinylbenzene, 4-vinylbiphenyl, and 1,1-diphenylethylene from the viewpoint of water resistance. More than species are preferred. Among these, at least one selected from styrene, α-methylstyrene, vinyl toluene, and vinyl naphthalene is more preferable from the viewpoint of printing density and bleeding resistance. The aryl group includes an alkylaryl group and an arylalkyl group.

  If necessary, it may be a water-insoluble vinyl polymer obtained by polymerizing a monomer mixture containing the hydrophobic monomer and a copolymerizable monomer. Examples of the copolymerizable monomer include a salt-forming group-containing monomer, a macromer, a hydroxyl group-containing monomer, and a hydrophilic nonionic monomer.

  Examples of the salt-forming group-containing monomer include an anionic monomer and a cationic monomer. You may use an anionic monomer and a cationic monomer individually or in mixture of 2 or more types, respectively.

  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. In these, unsaturated carboxylic acid monomers, such as acrylic acid and methacrylic acid, are preferable.

  Examples of the macromer include macromers having a polymerizable unsaturated group having a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000. Among them, a styrenic macromer having a polymerizable functional group at one end is preferable because of its high affinity with the colorant.

  Examples of the styrenic macromer include a styrene homopolymer having a polymerizable functional group at one end or a copolymer of styrene and another monomer. Among these, those having an acryloyl group or a methacryloyl group as a polymerizable functional group at one end are preferable. Examples of other monomers include acrylonitrile.

  The number average molecular weight of the macromer is measured using polystyrene as a standard substance by gel permeation chromatography using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and the like. Among them, 2-hydroxyethyl (meth) acrylate is preferable.

Hydrophilic nonionic monomers include those of formula (III)
CH ₂ C═C (R ⁵ ) COO (R ⁶ O) _p R ⁷ (III)
(In the formula, R ⁵ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁶ is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ⁷ is a hydrogen atom or C1-C30 monovalent hydrocarbon group which may have a hetero atom, p is an average addition mole number, and shows the number of 1-60.
One or more types of monomers selected from the group consisting of monomers represented by R ⁶ O is preferably an oxyalkylene group having 2 to 3 carbon atoms, and R ⁷ is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

  Polyethylene glycol (1-30: p in formula (III) is shown. The same applies hereinafter) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) ( (Meth) acrylate, methoxypolyethylene glycol (1-30) (meth) acrylate, methoxypolytetramethylene glycol (1-30) (meth) acrylate, ethoxypolyethylene glycol (1-30) (meth) acrylate, butoxypolyethylene glycol (1 -30) (meth) acrylate, octoxypolyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (1-30, In it Chi glycol: 1-29) (meth) acrylate, and the like. These may be used alone, or two or more thereof. Among these, methoxypolyethylene glycol (1-30) (meth) acrylate and octoxypolyethylene glycol (1-30) (meth) acrylate are preferable.

  The hydrophobic monomer in the water-insoluble vinyl polymer is preferably a monomer of the formula (II) from the viewpoint of improving the discharge stability of the water-based ink, the printing density, and the bleeding resistance.

The total amount of the macromer, the hydroxyl group-containing monomer and the hydrophilic nonionic monomer among all the monomers subjected to polymerization is preferably 0 from the viewpoint of improving the stability of the water-insoluble polymer in water and the water resistance of the water-based ink. It is 10 to 10 weight%, More preferably, it is 0 to 5 weight%, Preferably it is 0 to 10 weight part with respect to 100 weight part of hydrophobic monomers, More preferably, it is 0 to 5 weight part.
The weight average molecular weight (measured by the method described in Examples) of the water-insoluble vinyl polymer is 1,000 to 15,000, preferably 1,000 from the viewpoint of water resistance, scratch resistance and dispersion stability after printing. To 10,000, more preferably 3,000 to 10,000. Since it is preferable that essentially no ionic group is present at both ends of the water-insoluble polymer, this range is preferable in order to ensure dispersion stability.
The acid value (KOHmg / g) of the polymer is preferably 7 to 120, or the amine value (HCLmg / g) is preferably 5 to 80.

  The water-insoluble vinyl polymer is produced by copolymerizing monomers 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. The polar organic solvent 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, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate. Among these, ethanol, acetone, methyl ethyl ketone, isobutyl methyl ketone, or a mixture of these with water is preferable. If necessary, toluene may be used in combination.

  The polymerization conditions of the monomer vary depending on the radical polymerization initiator having an ionic group to be used, the chain transfer agent, the monomer, the type of the solvent, etc., but the polymerization temperature is usually 30 to 100 ° C., preferably 50 to 90 ° C. The polymerization time is 1 to 24 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas.

  After completion of the polymerization reaction, the water-insoluble vinyl polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. The obtained water-insoluble vinyl polymer can be purified by repeating reprecipitation or removing unreacted monomers by membrane separation, chromatographic methods, extraction methods, and the like.

  As a neutralizing agent for the water-insoluble vinyl polymer, an acid or a base can be used depending on the kind of the salt-forming group of the polymer. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid, propionic acid, lactic acid, succinic acid, glycolic acid, gluconic acid, and glyceric acid. Examples of the base include amines such as trimethylamine, triethylamine, diethanolamine, N-methyldiethanolamine, and triethanolamine, and alkali metal hydroxides such as ammonia, sodium hydroxide, and potassium hydroxide.

  There is no particular limitation on the degree of neutralization of the water-insoluble vinyl polymer. Usually, it is preferable that the obtained aqueous dispersion is neutral, for example, pH is 4 to 11.

  After neutralization of the water-insoluble vinyl polymer, the water-insoluble vinyl polymer may be contained alone in the ink, or polymer particles of a water-insoluble vinyl polymer containing a colorant may be contained in the ink. Among these, water-insoluble vinyl polymer polymer particles containing a colorant are preferable from the viewpoint of satisfying dispersion stability, scratch resistance, dischargeability, and bleed resistance.

The content of the water-insoluble polymer in the aqueous dispersion for ink jet recording or the water-based ink of the present invention is preferably 0.05 to 30% by weight from the viewpoints of dispersion stability, scratch resistance, dischargeability and bleed resistance. More preferably, it is 1 to 15% by weight.
The content of the colorant in the aqueous dispersion for ink jet recording or the aqueous ink of the present invention is preferably 1 to 40% by weight, more preferably 2 to 20% by weight, from the viewpoint of imparting sufficient stability and printing density. is there.

As a method of obtaining an aqueous dispersion of polymer particles of a water-insoluble polymer having an ionic group at both ends containing a pigment (hereinafter referred to as “both ends ionic polymer aqueous dispersion”), a water-insoluble polymer is used as an organic solvent. Preferably, a step of dissolving the mixture, adding a pigment, water, a neutralizing agent and, if necessary, a surfactant and mixing the mixture, then dispersing the mixture, and removing the organic solvent from the mixture are preferable.
In the mixture, the colorant is preferably 5 to 50% by weight, the organic solvent is preferably 10 to 70% by weight, the water-insoluble polymer is preferably 2 to 40% by weight, and the water is preferably 10 to 70% by weight. . 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 4-11. The above-mentioned neutralizing agent can be used.
Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents, and those having a water solubility at 20 ° C. of 50% by weight or less are preferable, and 10% by weight or more are preferable. For the dispersion treatment, a high-speed stirring mixer, a high-pressure homogenizer, or the like can be used.
The removal of the organic solvent can be performed by a general method such as vacuum distillation. The organic solvent in the aqueous dispersion of the obtained water-insoluble polymer particles is substantially removed, and the amount of the organic solvent is 0.1% by weight or less, preferably 0.01% by weight or less. The aqueous dispersion of water-insoluble polymer particles containing a colorant is a dispersion in which a solid content of a water-insoluble graft polymer containing a colorant is dispersed in water as a main solvent.
The water-insoluble polymer particles containing the colorant are not particularly limited as long as the particles are formed by at least the colorant and the water-insoluble polymer. For example, the water-insoluble polymer includes the colorant in the water-insoluble polymer. Particle form in which a colorant is uniformly dispersed in a water-insoluble polymer, a particle form in which a colorant is encapsulated in a water-insoluble polymer, but a part of the colorant is exposed on the particle surface, etc. It is.
The aqueous dispersion of water-insoluble graft polymer particles may be used as it is as an aqueous ink, but a wetting agent, a penetrating agent, a dispersant, a viscosity modifier, an antifoaming agent, an antifungal agent, and the like that are usually used in aqueous inks for inkjet recording. A rust inhibitor or the like may be added.

  The weight ratio of the water-insoluble polymer polymer particles to the colorant increases the printing density, facilitates the inclusion of the colorant in the polymer particles, and improves the water resistance, scratch resistance and marker resistance. Preferably it is 20-1000 weight part with respect to 1000 weight part of solid content, More preferably, it is 40-800 weight part.

  The average particle diameter of the water-insoluble polymer polymer particles in the obtained water dispersion and water-based ink is measured by the method described in the following production examples. The average particle size is 10 to 500 nm, preferably 20 to 250 nm, from the viewpoint of dispersion stability.

The content (solid content) of the water-insoluble polymer particles containing the colorant in the aqueous dispersion and the water-based ink is usually preferably 1 to 30% by weight, more preferably 3 from the viewpoint of printing density and ejection stability. It is desirable to adjust so that it may become -25 weight%.
The neutralization degree of the ionic group is preferably 50 to 200%, more preferably 60 to 150%, and particularly preferably 70 to 150%. Here, the degree of neutralization can be determined by the following formula when the ionic group is an anionic group.
[Weight of neutralizer (g) / equivalent of neutralizer] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)] × 100
Moreover, when an ionic group is a cationic group, it can obtain | require by a following formula.
[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [Amine number of polymer (HCL mg / g) × Weight of polymer (g) / (36.5 × 1000)] × 100
The acid value and amine value can be calculated from the structural unit of the polymer, but can also be determined by a method of titrating by dissolving the polymer in an appropriate solvent (for example, methyl ethyl ketone).

  The water content in the aqueous dispersion and aqueous ink of the present invention is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.

The preferred surface tension (20 ° C.) of the aqueous dispersion and aqueous ink of the present invention is 30 to 65 mN / m, more preferably 35 to 60 mN / m as the aqueous dispersion, and 25 to 50 mN / m as the aqueous ink. m, more preferably 27 to 45 mN / m.
The viscosity (20 ° C.) of the 10% by weight concentration of the aqueous dispersion of the present invention is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s, in order to obtain a preferable viscosity when used as an aqueous ink. In addition, the viscosity (20 ° C.) of the water-based ink of the present invention is preferably 2 to 12 mPa · s, and more preferably 2.5 to 10 mPa · s in order to maintain good ejection properties.

Production Examples 1 to 6 (Preparation of polymer solution)
Into the reaction vessel, the kind and amount of monomers, solvent, and chain transfer agent having an ionic group shown in the column of “initially charged monomer” in Table 1 were charged, and after sufficiently replacing with nitrogen gas, the temperature was raised to 75 ° C. Warm up. When the iniferter of Production Example 4 was used, the temperature was raised to 90 ° C.
On the other hand, the monomers and solvents shown in the column of “Drip monomer” in Table 1 were added to the dropping funnel, the solvent, the chain transfer agent, the initiator, and the like, and polymerization was carried out while dropping into the reaction vessel over 5 hours. Thereafter, after further aging for 2 hours, methyl ethyl ketone was appropriately added to obtain a polymer solution having a polymer solid concentration of 50% by weight.

  The polymers obtained in Production Examples 1 to 3 and 6 have an ionic group derived from a polymerization initiator and a chain transfer agent at both ends, and the polymer obtained in Production Example 4 is an ion derived from an iniferter. The polymer obtained in Production Example 5 has an ionic group at both ends, and one end does not have an ionic group.

A portion of the resulting polymer solution was dried at 105 ° C. under reduced pressure for 2 hours and isolated by removing the solvent. Using polystyrene as the standard substance and chloroform containing 1 mmol / L dodecyldimethylamine as the solvent. When the weight average molecular weight was measured by gel permeation chromatography, the obtained polymer had the weight average molecular weight shown in Table 1.
In addition, it can confirm by the nuclear magnetic resonance method etc. that the obtained polymer has an ionic group in the terminal.

Each name shown in Table 1 means the following.
-2-ethylhexyl methacrylate: manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acryester EH
・ Styrene monomer: Nippon Steel Chemical Co., Ltd., trade name: Styrene monomer

Production Examples 7 to 16 (Preparation of pigment-containing water-insoluble polymer particle aqueous dispersion)
The pigment, methyl ethyl ketone, ion-exchange water and neutralizing agent shown in Table 2 were added to 28 parts by weight of the polymer solutions obtained in Production Examples 1 to 6 (polymer solid content: 50% by weight), and the mixture was sufficiently stirred. Using this roll [manufactured by Noritake Co., Ltd., trade name: NR-84A], the paste was kneaded for about 0.5 to 1 hour.

  The obtained paste was put into 250 parts by weight of ion-exchanged water and stirred sufficiently, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain a pigment-containing water-insoluble polymer particle aqueous dispersion having a solid content of 20% by weight. Obtained. The average particle size of the polymer particles of the obtained water-insoluble polymer was determined according to the following method. The results are shown in Table 2.

[Measurement method of average particle diameter]
Measurement was performed using ELS-8000 (cumulant method) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions were a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 200. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent.

In addition, each name described in Table 2 means the following.
・ Carbon black: manufactured by Cabot, product name: Monarch 880
・ Cyan Pigment: Dainippon Ink Industries, Ltd., trade name: Fastogen Blue TGR-SD
・ Oil-soluble cyan dye: BASF, trade name: Neozapon Blau 807

Examples 1-7
37.5 parts by weight of the colorant-containing water-insoluble polymer particle dispersion obtained in Production Examples 7 to 13, 10 parts by weight of glycerin, 5 parts by weight of diethylene glycol, 2- {2- (2-butoxyethoxy) ethoxy} ethanol 5 Parts by weight, 0.2 part by weight of EO adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (n = 10) and 42.3 parts by weight of ion-exchanged water, The obtained mixed solution was filtered through a 5 μm membrane filter (manufactured by Fuji Photo Film Co., Ltd., trade name: Disc Capsule CALC500 2.5CMD 50) to obtain aqueous inks of Examples 1 to 7, respectively. These water-based inks contained a water-insoluble polymer containing ionic groups at both ends.

Comparative Examples 1 and 2
Comparative Example 1 was carried out in the same manner as in Example 1 except that the pigment-containing water-insoluble polymer particle aqueous dispersion was changed to the pigment-containing water-insoluble polymer particle aqueous dispersion obtained in Production Examples 14 and 15, respectively. And 2 aqueous inks were obtained. These water-based inks are water-insoluble polymers containing hydroxyl groups and ionic groups at their ends.

  Next, the physical properties of the water-based inks obtained in each Example and each Comparative Example were measured based on the following method. The results are shown in Table 3.

(1) Ejectability Using a commercially available printer (registered trademark) manufactured by Epson Corporation (Part No .: EM930C), after continuous printing of 2000 characters / sheet on plain paper XEROX4024, characters, solid patterns and ruled lines are printed. A test document including this was printed, and the ejection property was evaluated based on the following evaluation criteria.

〔Evaluation criteria〕
○: When satisfying all three items of sharp and clear characters, uniform solid printing, and ruled line printing with no twist (no problem in practical use)
△: When all three items of sharp and clear characters, uniform solid printing, and creaseless ruled line printing are almost satisfied (no problem in actual use)
×: When one or more items are not satisfied among sharp and clear characters, uniform solid printing, and ruled line printing with no distortion (there is a problem in actual use)

(2) Print density (OD)
Solid printing was performed using the printer and plain paper, and after standing at 25 ° C. for 24 hours, the printing density was measured with a Macbeth densitometer (manufactured by Macbeth, product number: RD914), and evaluated according to the following evaluation criteria.
〔Evaluation criteria〕
○: Print density is 1.30 or more Δ: Print density is 1.20 or more and less than 1.30 ×: Print density is less than 1.20

(3) Water resistance Using the printer and paper, it was set on a 45 ° tilting table immediately after solid printing, and 1 ml of dropper water was dropped on the printed image. The print density was measured after natural drying at 25 ° C. Whether or not the non-printed portion was darkened was visually observed and evaluated according to the following criteria.
〔Evaluation criteria〕
○: The non-printing part is colorless. There is almost no color and there is no practical problem.
X: The non-printing part becomes dirty. It comes after dripping water.

(4) Bleed resistance Using the printer and paper, print an image with Yellow, Magenta, Cyan, and Black (4 colors) and visually observe the bleeding at the boundary between different colors. Based on the following evaluation criteria evaluated.
〔Evaluation criteria〕
○: There is no bleeding at the boundary between different colors. A level that is practically unnoticeable.
X: The blur of the boundary part between different colors generate | occur | produced and it is mixed.

(5) Scratch resistance Using the printer, solid printing was performed on glossy paper (manufactured by Epson Corporation, trade name: silky glossy paper), and after 24 hours, the printed surface was rubbed strongly with fingers. The degree of printing was evaluated based on the following evaluation criteria.
〔Evaluation criteria〕
○: The print is rubbed and the surroundings become slightly black, but there is no practical problem.
X: The print is rubbed considerably, the surroundings become extremely black, and the fingers are considerably stained.

From the results shown in Table 3, since the water-based inks obtained in Examples 1 to 7 use polymers having ionic groups at both ends, printing density, water resistance, bleed resistance, and scratch resistance It can be seen that, in addition to excellent properties, it has excellent ejection properties when printed by an ink jet printer.

Claims (7)

Water for ink jet recording comprising a water-insoluble polymer having a weight average molecular weight of 1000 to 15000, a structural unit derived from a hydrophobic monomer of 100 % by weight, and having an ionic group only at both ends and a colorant. A dispersion , wherein the ionic group has a function of a polymerization initiator (A) having an ionic group, a chain transfer agent (B) having an ionic group, and a polymerization initiator and a chain transfer agent An aqueous dispersion for inkjet recording, which is derived from one or more compounds selected from the group consisting of (C) . In the presence of the polymerization initiator (A) having an ionic group and the chain transfer agent (B) having an ionic group or the presence of an iniferter (C), the water-insoluble polymer contains 100 % by weight of a hydrophobic monomer. The aqueous dispersion for ink jet recording according to claim 1 , which is a polymer obtained by polymerizing a monomer to be contained. 3. The inkjet according to claim 2 , wherein the total usage amount of (A) and (B) is 5 to 40 parts by weight or the usage amount of (C) is 5 to 30 parts by weight with respect to 100 parts by weight of the monomer. Water dispersion for recording. The aqueous dispersion for inkjet recording according to any one of claims 1 to 3 , wherein the hydrophobic monomer is one or more monomers selected from the group consisting of monomers represented by formula (I) or formula (II).
CH ₂ = C (R ¹ ) COOR ² (I)
(Wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ² is a hydrocarbon group having 1 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a ring having 3 to 30 carbon atoms) Represents a hydrocarbon.)
CH ₂ = C (R ³ ) R ⁴ (II)
(In the formula, R ³ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁴ represents an aryl group having 6 to 22 carbon atoms.) The chain transfer agent having an ionic group is at least one selected from the group consisting of thioglycolic acid, mercaptopropionic acid and mercaptosuccinic acid, and the polymerization initiator having an ionic group is 4,4′-azobis. (4-cyanovaleric acid), 2,2'-azobis claim 1~ 4 [N- (2- carboxyethyl) -2-methylpropionamide] selected from the group consisting of at least one An aqueous dispersion for inkjet recording as described in 1. The ionic group is derived from 4,4′-azobis (4-cyanovaleric acid) which is a polymerization initiator (A) having an ionic group , or an ini having a function of a polymerization initiator and a chain transfer agent the water dispersion for inkjet printing according to claim 1 wherein Vater (C) 1,2' is derived from bis-carboxymethyl-1,1,2,2-phenylethane. A water-based ink for ink-jet recording comprising the water dispersion for ink-jet recording according to any one of claims 1 to 6 .