JP2008266595A - Pigment dispersion and aqueous ink for ink jet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous ink for inkjet recording excellent in the discharge property in a thermal method, and is excellent in wear resistance. <P>SOLUTION: The pigment dispersion comprises water, an aqueous polymer and a pigment as essential components, wherein the aqueous polymer is carboxy group-containing polyurethane obtained by reacting a reaction product comprising, as a main ingredient, a compound expressed by general formula (1) prepared by reacting a diol compound (A) having one or two carboxyl groups in one molecule and a diisocyanate compound (B) and having isocyanate reaction rate in a range of 0.45-0.55; a diol compound; and a diisocyanate compound. An aqueous ink for ink jet recording is obtained by using the pigment dispersion. In general formula (1), R<SP>1</SP>and R<SP>3</SP>represent a partial structure excluding the isocyanate group of the compound (B) and R<SP>2</SP>represent a partial structure excluding the hydroxyl of the compound (A). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water-based ink for inkjet recording using a pigment as a coloring material.

  Conventionally, a dye ink using a dye as a coloring material has been used as a water-based ink for inkjet recording. Dye inks have many advantages such as excellent storage stability, hardly clogging the nozzles of inkjet printers, and the printed matter obtained has excellent gloss. However, it has been pointed out that there are defects derived from dyes such as inability to store printed matter for a long time due to poor weather resistance, and poor water resistance and light resistance. In recent years, it has been pointed out that weather resistance, water resistance and light resistance are poor. Development of a water-based ink for ink-jet recording (hereinafter abbreviated as water-based pigment ink) using an excellent pigment is underway.

The aqueous pigment ink is usually a pigment dispersion in which pigment particles are uniformly dispersed in an aqueous solvent such as water. After recording, an ink film containing the pigment particles is formed on the recording medium. The image quality of the recorded matter with the aqueous pigment ink is greatly influenced by the color development and gloss of the pigment particles themselves in the ink film, and when using a recording medium with a smooth recording surface such as glossy paper, There has been a problem that the color developability and glossiness of the recording portion are impaired due to irregular reflection of light by pigment particles in the ink film. There is also a problem that the fixing property to the recording medium is insufficient and the formed image has poor abrasion resistance.
In contrast to normal printing, ink jet printing is performed by ejecting ink droplets from a printer head. There are piezo and thermal methods for this ejection method. In particular, the thermal method boils the ink in the nozzle with the heater of the heating resistor arranged in the printer head and blows ink droplets. Due to the rapid temperature change, a phenomenon called kogation occurs in the heater portion, which causes a problem that liquid does not discharge (non-ejection) during long-time printing. Therefore, ejection stability is also required for the ink used.

At present, water-based pigment inks containing a resin component are being studied in order to improve fixability and gloss on recording media, and water-based inks for ink-jet recording to which water-based polyurethane is added are known to satisfy the physical properties to some extent. It has been. Specifically, an inkjet recording liquid containing an acetylene glycol type hydrophobic diol known as a surfactant and a polyurethane using a carboxy group-containing diol as a raw material (see, for example, Patent Document 1), a urethane-modified polyester resin An ink composition for ink jet recording (for example, refer to Patent Document 2) and an ink composition for ink jet recording including a self-dispersing pigment and a polyurethane dispersion (for example, refer to Patent Document 3) are known.
However, the ink jet recording liquid described in Patent Document 1 has a problem that the gloss and printing durability of a printed matter are inferior particularly when glossy paper is used as a recording medium. Moreover, the ink composition for inkjet recording described in Patent Document 2 has low ejection stability, and the printed matter obtained has poor scratching properties. The ink composition for inkjet recording described in Patent Document 3 has ejection stability. There was a problem that was inferior.
Japanese Patent Laid-Open No. 06-279718 Japanese Patent Laid-Open No. 2004-300393 JP 2005-515289 A

  The problem to be solved by the present invention is that ink droplets can be stably ejected even during long-time printing in a thermal ink jet printer, and a printed image having excellent weather resistance, particularly abrasion resistance can be obtained. The object is to provide a water-based ink for ink-jet recording.

The present inventors have found that the above problem can be solved by using a carboxy group-containing polyurethane designed so that the carboxy group is uniformly introduced into the polymer chain of the polyurethane.
In conventional carboxy group-containing polyurethanes, introduction of carboxy groups is not controlled at all, and most of the carboxy groups are randomly introduced into the polyurethane chain.
Patent Document 1 describes a block-type urethane oligomer, but the position of the carboxy group is not specified for the purpose of controlling the oligomer segment. Patent Document 3 discloses an aqueous polyurethane dispersion synthesized through an adduct of an acid group-containing diol containing a carboxy group-containing diol and a diisocyanate compound, but there is no description of a method for synthesizing the adduct.

The present inventors have found that the carboxy group introduced at random in this way has a great influence on the discharge property.
In the case of random polymerization, the amount of carboxy groups introduced into the molecular chain that occurs during polymerization is non-uniform. In particular, when the polymerization design is performed so as to control the molecular weight of the obtained polyurethane to be low, the amount of carboxy groups introduced per molecular chain is theoretically reduced, and thus a molecular chain in which no carboxy group is introduced may occur. That is, even if the degree of aqueousity is predicted in advance and the amount of raw material monomer charged is determined, some molecular chains of the resulting polyurethane become water-insoluble, so that the solubility partially decreases. In addition, an isocyanate group and a part of the carboxy group undergo a crosslinking reaction during polymerization to produce an unnecessary gel component in water, the molecular weight becomes larger than expected, or the crosslinked carboxy group does not function as a water dispersion stable group. Water solubility with respect to the charged amount is reduced. The present inventors have also found that these phenomena, and the ink ejection stability and printability are greatly reduced by these phenomena.

That is, the present invention is a pigment dispersion containing water, an aqueous polymer, and a pigment as essential components, wherein the aqueous polymer is
A diol compound (A) having 1 or 2 carboxy groups in one molecule is reacted with a diisocyanate compound (B), the compound represented by the general formula (1) as a main component, and an isocyanato group reaction rate. Provided is a pigment dispersion which is a carboxy group-containing polyurethane obtained by reacting a reaction product in the range of 0.45 to 0.55, a diol compound, and a diisocyanate compound.

（１）

(1)

(In General Formula (1), R ¹ and R ³ represent a partial structure excluding the isocyanate group of the diisocyanate compound (B), R ¹ and R ³ may be the same or different, and R ² is And represents a partial structure excluding the hydroxy group of the diol compound (A) having one or two carboxy groups in one molecule.

  The present invention also relates to a method for producing an aqueous polymer for use in a pigment dispersion containing water, an aqueous polymer, and a pigment as essential components, and the diol compound (A) having one or two carboxy groups in one molecule. A reaction product obtained by reacting the diisocyanate compound (B) with the compound represented by the general formula (1) as a main component and having an isocyanate reaction rate in the range of 0.45 to 0.55; Provided is a method for producing an aqueous polymer in which a diol compound is reacted with a diisocyanate compound.

  The present invention also provides a water-based ink for ink jet recording using the pigment dispersion described above.

According to the present invention, ink droplets can be stably ejected even during long-time printing in a thermal ink jet printer, an image can be formed without streak unevenness or ink bleeding, and weather resistance, particularly resistance A water-based ink for ink jet recording from which a printed image having excellent rubbing properties can be obtained.
In particular, when the weight average molecular weight of the carboxy group-containing polyurethane is in the range of 10,000 to 50,000, the thermal type ejection properties are particularly excellent.
Furthermore, when the acid value of the carboxy group-containing polyurethane is 20 to 70 mgKOH / g, the ejection stability is excellent.
When the diol compound (A) to be used is dimethylolpropionic acid or dimethylolbutanoic acid, a carboxy group can be introduced almost according to the charged amount.

(Pigment dispersion liquid polymer (carboxy group-containing polyurethane))
The aqueous polymer used in the present invention is a compound represented by the general formula (1) obtained by reacting a diol compound (A) having one or two carboxy groups in one molecule with a diisocyanate compound (B). A carboxy group-containing polyurethane obtained by reacting a reaction product having a main component and an isocyanate reaction rate within a range of 0.45 to 0.55, a diol compound, and a diisocyanate compound.

（１）

(1)

In the general formula (1), R ¹ and R ³ represent a partial structure excluding the isocyanate group of the diisocyanate compound (B) described later, and R ¹ and R ³ may be the same or different, and R ² Represents a partial structure excluding the hydroxy group of the diol compound (A) having 1 or 2 carboxy groups in one molecule described later.

  Examples of the diol compound (A) having 1 or 2 carboxy groups in one molecule used in the present invention include esters obtained by reaction of polyhydric alcohols and polybasic acid anhydrides, and 2,2-dimethylol. Examples thereof include dihydroxyalkanoic acids such as lactic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and 2,2-dimethylolvaleric acid. Preferable compounds include 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid. Among them, dimethylolpropionic acid or dimethylolbutanoic acid is preferable because it is easily available.

Examples of the diisocyanate compound (B) used in the present invention include aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4, Cycloaliphatic diisocyanate compounds such as 4-cyclohexylmethane diisocyanate, aromatic diisocyanate compounds such as xylylene diisocyanate and tetramethylxylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate Is mentioned.
Among these, an aliphatic diisocyanate compound or an alicyclic diisocyanate compound is preferable from the viewpoint that light discoloration of a printed image hardly occurs.

In the general formula (1), R ¹ and R ³ are

The partial structure represented by is preferable.

In the general formula (1), R ² is

The partial structure represented by is preferable.

The diol compound (A) and the diisocyanate compound (B) are reacted to have the compound represented by the general formula (1) as a main component and an isocyanate group reaction rate within a range of 0.45 to 0.55. In order to obtain a reaction product (hereinafter abbreviated as reaction product (1)), for example, the diol compound (A) and the diisocyanate compound (B) are charged into a solvent having no active hydrogen and reacted. The solution is kept at 60-80 ° C. for reaction. Preferred solvents here include dialkyl ethers, diesters, N-methylpyrrolidone, dimethylformamide, ketones, dioxane, acetic acid esters, halogenated aromatic compounds, and the like of glycol compounds.
During the reaction, the hydroxyl value of the reaction solution or the quantitative value of the isocyanate group is monitored, and when the reaction rate reaches a certain rate, that is, when the reaction rate of the isocyanate group falls within the range of 0.45 to 0.55. By stopping, the reaction product (1) is obtained. As a method for stopping the reaction, since it is necessary to further react the isocyanate group and the diol compound later, a method of lowering the reaction temperature to a temperature at which the isocyanate substantially does not react, for example, 30 ° C. or less is preferable.
Here, the quantitative value of the isocyanato group can be obtained by the method described in ISO 14896 (Testing method for isocyanate group content), and the reaction rate of the isocyanate group is the quantitative value of the isocyanate group of the reaction product before the reaction. It can be calculated from the value divided by the quantitative value.

In the present invention, the isocyanato group reaction rate refers to the reaction rate when the isocyanate group contained in the pre-reaction mixture of the diol compound (A) and the diisocyanate compound (B) is 1. That is, the ratio of the isocyanate group remaining in the reaction product (1) is a ratio obtained by dividing the isocyanate reaction ratio from 1.
That is, when the reaction rate of the isocyanato group is less than 0.45, a large amount of unreacted diisocyanate compound (B) and diol compound (A) remain, and react in the same system with the diol compound added in the next step. Therefore, the carboxy group cannot be uniformly introduced into the polyurethane. On the other hand, when the reaction rate of the isocyanato group exceeds 0.55, the crosslinking reaction between the isocyanato group and the carboxy group proceeds, and a water-soluble property is greatly lowered because a crosslinked structure is formed.
The isocyanato group reaction rate of 0.5 means that, for example, when the diol compound (A) and the diisocyanate compound (B) are reacted at a molar ratio of 1: 2, the diisocyanate compound (B) is present on both sides of the diol compound (A). Indicates that a half of the isocyanato group contained in the pre-reaction mixture is a bonding site of the diol compound (A) and the diisocyanate compound (B), and the other half remains as an isocyanato group.

  The molar ratio of the diol compound (A) and the diisocyanate compound (B) is preferably in the range of at least 1: 1.8 to 1: 2.2, particularly preferably 1: 2. When the molar ratio is less than 1.8, the content of the compound represented by the general formula (1) decreases, the monoisocyanate component in the reaction product (1) increases, and a carboxy group is introduced at the end of the polyurethane. The ratio may increase and water solubility may decrease. On the other hand, when the molar ratio exceeds 2.2, the diisocyanate compound (B) becomes excessive and the crosslinking reaction between the isocyanato group and the carboxy group easily proceeds.

  The content of the compound represented by the general formula (1) contained in the reaction product (1) is preferably at least 80% or more, particularly preferably 90% or more in terms of solid content ratio. When the content of the compound represented by the general formula (1) contained in the reaction product (1) is less than 80%, that is, it indicates that the monoisocyanate component is large, and a carboxy group is introduced into the polyurethane terminal. The ratio may increase and water solubility may decrease.

  When the reaction product (1) is allowed to stand for a long time, the crosslinking reaction between the isocyanato group and the carboxy group proceeds to form a crosslinked polymer. Therefore, it is preferable to immediately perform the next step, that is, the reaction between the reaction product (1), the diol compound and the diisocyanate compound.

The diol compound to be reacted with the reaction product (1) is not particularly limited and can be appropriately selected depending on the desired printability of the ink. For example, particularly when abrasion resistance is desired, it is preferable that a certain softness is imparted to the aqueous polymer to be used, and polyether polyol and polyester polyol are preferable. In addition, since the urethane bond in the carboxy group-containing polyurethane used in the present invention tends to increase the film hardness of the obtained printed matter, a high molecular weight diol compound should be used for the purpose of reducing the amount of urethane bond in one molecule. Is preferred. However, since the molecular weight of the diol compound is preferably in the range of 400 to 3000, more preferably in the range of 500 to 2500, because the molecular weight of the diol compound is converted to the number average molecular weight because it affects the ink ejection properties when the polymer is too high. (The number average molecular weight in the present invention is measured by gel permeation chromatography and expressed as a value in terms of polystyrene. Hereinafter, unless otherwise specified, abbreviated as Mn)
Examples of these diol compounds include polyester polyols, polyether polyols, polyhydroxy polycarbonates, polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy polyester amides and polyhydroxy polythioethers. Of these, polyester polyol, polyether polyol and polyhydroxy polycarbonate are preferred. One of these diol compounds may be reacted, or several may be mixed and reacted.
In addition to the high molecular diol compound, a low molecular weight diol compound may be used in combination as appropriate for the purpose of adjusting the film hardness of the printed matter. Examples include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and the like.

  Moreover, as a diisocyanate compound which reacts with the said reaction product (1), the diisocyanate compound used for the above-mentioned diisocyanate compound (B) can be used suitably.

  In the present invention, a chain extender can be used as necessary. Examples of the chain extender in this case include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6- Hexanediol, 1,9-nonanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-cyclohexanediol, diols such as xylylene glycol, ethylenediamine, propylenediamine, xylylenediamine, isophoronediamine, One or more diamines such as 4,4′-diaminodiphenylmethane, tolylenediamine, and 4,4′-diaminodicyclohexylmethane can be used.

In order to react the reaction product (1), the diol compound, and the diisocyanate compound, they may be reacted by a known method. For example, the reaction is performed in a solvent having no active hydrogen at 60 to 110 ° C. for 10 to 20 hours. At that time, a known urethanization catalyst such as dibutyltin dilaurate may be used. Thereafter, the obtained mixture of the carboxy group-containing polyurethane and the organic solvent is gradually phase-inverted from the oil phase to the water phase using water and a basic substance, and then the solvent is removed, whereby the aqueous polymer of the carboxy group-containing polyurethane and I can do it.
Examples of basic substances used for phase inversion include ammonia, ethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-phenyldiethanolamine, monoethanolamine, dimethylethanol. Organic amines such as amine, diethylethanolamine, morpholine, N-methylmorpholine, 2-amino-2-ethyl-1-propanol, alkali metals such as lithium, potassium and sodium, inorganic alkalis such as sodium hydroxide and potassium hydroxide And the like. The amount of the basic substance used is appropriately set according to the physical properties of the carboxy group-containing polyurethane, but the amount of the basic substance used is not particularly limited, but is usually 70 to 130% of the acid value of the polyurethane. The amount of basic material necessary to neutralize the is used.

The thus-obtained carboxy group-containing polyurethane has an acid value of 20 to 70 mgKOH / g, so that the prepared inkjet recording water-based ink has good ejection stability and good print quality such as abrasion resistance. Therefore, it is preferable.
Further, the weight average molecular weight of the carboxy group-containing polyurethane is preferably 10,000 to 50,000, more preferably 20,000 to 50,000. (The mass average molecular weight in the present invention is measured by gel permeation chromatography and expressed as a value in terms of polystyrene. Hereinafter, unless otherwise specified, it is abbreviated as Mw) When Mw is less than 10,000, There is a possibility that the fixing property of the pigment to the recording medium becomes poor and the abrasion resistance of the printed image is lowered. On the other hand, when Mw exceeds 50,000, the viscosity of the prepared water-based ink for inkjet recording becomes high, and the ejection stability may be lowered.

The aqueous polymer prepared from the carboxy group-containing polyurethane used in the present invention forms an aqueous dispersion. The particle size of the aqueous dispersion is preferably less than 50 nm. When the particle size is 50 nm or more, the dispersion stability of the aqueous dispersion is insufficient, and the carboxy group-containing polyurethane may precipitate from the ink and cause kogation when ink is ejected for a long time.
Here, the particle diameter can be measured by a known and common centrifugal sedimentation method, laser diffraction method (light scattering method), ESA method, capillary method, electron microscope method, or the like. Preferable is measurement by Microtrac UPA using a dynamic light scattering method.

  The amount of the carboxy group-containing polyurethane blended in the pigment dispersion of the present invention varies depending on the pigment blending ratio, but is preferably 20 to 200 parts by mass, more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the pigment. Part. In particular, when used as a water-based ink for inkjet recording, if the blending amount of the carboxy group-containing polyurethane is small, the print quality such as abrasion resistance is lowered, and if the blending amount is too large, the ink ejection stability is lowered. There is.

(Pigment)
Examples of pigments used for preparing the pigment dispersion of the present invention include inorganic pigments such as barium sulfate, lead sulfate, titanium oxide, yellow lead, bengara, chromium oxide, and carbon black, anthraquinone pigments, perylene pigments, disazo pigments, Examples include phthalocyanine pigments, isoindoline pigments, dioxazine pigments, quinacridone pigments, perinone pigments, and benzimidazolone pigments. These can be used alone or in combination.

  As the black pigment, it is preferable to use carbon black such as furnace black, lamp black, acetylene black, channel black, etc., which has excellent light resistance and high hiding power.

Furthermore, among the representative organic pigments of cyan, magenta, and yellow, which are the three primary colors, pigments that can be suitably used in the present invention are exemplified below.
Examples of cyan pigments include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment blue 3, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15:34, C.I. I. Pigment blue 16, C.I. I. Pigment blue 22, C.I. I. Pigment blue 60, and the like.

  Examples of magenta pigments include C.I. I. Pigment red 5, C.I. I. Pigment red 7, C.I. I. Pigment red 12, C.I. I. Pigment red 48, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57, C.I. I. Pigment red 112, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 146, C.I. I. Pigment red 168, C.I. I. Pigment red 184, C.I. I. Pigment red 202, and the like.

  Examples of yellow pigments include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 2, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 75, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 98, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, and the like.

  As for the particle diameter of the pigment, the primary particle diameter is preferably in the range of 1 to 500 nm, and more preferably in the range of 20 to 200 nm. The particle diameter of the pigment after being dispersed in the medium is preferably in the range of 10 to 300 nm, and more preferably in the range of 50 to 150 nm. The primary particle diameter of the pigment can be measured by an electron microscope, a gas or solute adsorption method, an air flow method, an X-ray small angle scattering method, and the like. The pigment particle diameter after dispersion can be measured by a known and common centrifugal sedimentation method, laser diffraction method (light scattering method), ESA method, capillary method, electron microscope method, or the like. Preferable is measurement by Microtrac UPA using a dynamic light scattering method.

(water)
The water used in the present invention may be water alone or a mixed solvent composed of a water-soluble organic solvent having compatibility between water and water. Examples of the water-soluble organic solvent include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone, and methyl isobutyl ketone; methanol, ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, and 2-methoxyethanol. Alcohols such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc .; amides such as dimethylformamide, N-methylpyrrolidone, etc., and especially those having 3 to 6 carbon atoms It is preferable to use a compound selected from the group consisting of a ketone and an alcohol having 1 to 5 carbon atoms.

(Other components Pigment dispersing resin)
Since the carboxy group-containing polyurethane used in the present invention has the ability to disperse pigments, it may be used alone as a pigment-dispersing resin, or a resin used as a general-purpose pigment dispersant (hereinafter referred to as pigment dispersing agent). (Abbreviated as resin) can be used in combination. Alternatively, it can be used for vehicle purposes. When using together, there is no limitation in particular in the addition order of the carboxy group containing polyurethane and resin for pigment dispersion to be used, and it can change suitably according to the objective. For example, the pigment dispersion of the present invention in which a pigment is dispersed with a carboxy group-containing polyurethane can be diluted with a solvent as it is to be used as an ink, or the pigment dispersion dispersed with a general-purpose pigment dispersion resin The carboxy group-containing polyurethane used in the invention may be added later to obtain the pigment dispersion of the present invention.

The general-purpose pigment dispersion resin is preferably an aqueous resin suitable for preparing a pigment dispersion. Preferred examples include acrylic resins such as polyvinyl alcohols, polyvinyl pyrrolidones, and acrylic acid-acrylic acid ester copolymers. Resin, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene A styrene-acrylic resin such as an acrylic acid-acrylic acid ester copolymer, a styrene-maleic acid copolymer, a styrene-maleic anhydride copolymer, a vinylnaphthalene-acrylic acid copolymer, and a salt of the aqueous resin. Can be mentioned.
Examples of the compound for forming the salt of the copolymer include diethylamine, ammonia, ethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, triethanolamine, diethanolamine, aminomethylpropanol, morpholine and the like. Of the salt. The amount of the compound used to form these salts is preferably equal to or greater than the neutralization equivalent of the copolymer.
These aqueous resins can be used alone or in admixture of two or more. In addition, there is no restriction | limiting in particular in the form of the aqueous resin used here, such as a random copolymer and a block copolymer.

  In particular, when preparing a water-based ink for ink-jet recording, the Mw of the pigment-dispersing resin is 6,000 to 20,000 in order to obtain a water-based ink that suppresses kogation in the heater portion and has excellent ejection stability. It is preferable that it exists in the range. If Mw is 6,000 or less, the dispersion stability of the water-based ink itself may be lowered. On the other hand, if it exceeds 20,000, the viscosity of the water-based ink tends to be high and the dispersion stability tends to be lowered. Further, kogation on the heater portion becomes severe, which may cause non-ejection of ink droplets from the nozzle tip of the thermal ink jet printer.

  The compounding amount of the pigment dispersing resin is preferably 1 to 100 parts by mass, more preferably 2 to 70 parts by mass with respect to 100 parts by mass of the pigment. The acid value of the pigment dispersing resin is preferably 50 to 300 mgKOH / g.

  In particular, when preparing a water-based ink for ink-jet recording, it is preferable to use a salt of a styrene- (meth) acrylic acid copolymer from the viewpoint of more preferable dispersion stability and the like, and the styrene- (meth) acrylic pigment is previously used. When the carboxy group-containing polyurethane is added and adjusted to an aqueous dispersion dispersed in water with an acid copolymer salt, a print image having particularly excellent ink ejection properties and excellent abrasion resistance can be obtained. it can.

  The method for obtaining the pigment dispersion of the present invention is not particularly limited and can be carried out by a known method. For example, the pigment dispersion of the present invention in which the pigment is dispersed with water or an aqueous solvent containing water with the carboxy group-containing polyurethane can be diluted with the solvent as it is and used as an ink. The carboxy group-containing polyurethane used in the present invention may be added later to the pigment dispersion dispersed in step (1), and the concentration may be adjusted with a solvent as necessary to obtain the pigment dispersion of the present invention.

  As a stirring / dispersing device for dispersing the pigment, for example, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a dyno mill, a dispermat, an SC mill, a nanomizer, and the like, various commonly known dispersions are used. You can use the machine.

(Water-based ink for inkjet recording)
In the aqueous inkjet recording ink of the present invention, the pigment dispersion of the present invention is diluted with water or an aqueous solvent containing water, and a drying inhibitor, a penetrating agent, or other additives are added thereto as necessary. Prepare.

The drying inhibitor gives an effect of inhibiting drying of the water-based ink for inkjet recording at the ink jet nozzle opening of the inkjet printer head. Usually, a water-soluble organic solvent having a boiling point equal to or higher than that of water is used.
Examples of water-soluble organic solvents that can be used as drying inhibitors include polyhydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, and glycerol, pyrrolidones such as N-methyl-2-pyrrolidone and 2-pyrrolidone, amides, and dimethyl sulfoxide. And imidazolidinone. When the solvent is water, the amount of the drying inhibitor used is preferably in the range of 1 to 150 parts with respect to 100 parts of water.

The penetrating agent is used for facilitating penetration of the water-based ink for ink jet recording, which is ejected from the ink ejecting nozzle of the ink jet printer head and adheres to the recording medium, into the recording medium. By using the penetrating agent, it is possible to obtain a recorded matter in which the aqueous solvent quickly penetrates into the recording medium and the image does not blur.
Examples of penetrants used in the present invention include polyhydric alcohols such as ethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol, diols such as pentanediol and hexanediol, and laurin. Glycol ethers such as propylene glycol, lower alkyl ethers of polyhydric alcohols such as diethylene glycol ethyl ether and triethylene glycol monoethyl ether, lower alcohols such as ethanol and isopropyl alcohol, glycol ethers such as diethylene glycol-N-butyl ether, propylene And water-soluble organic solvents such as glycol derivatives. These can be used alone or in admixture of two or more. More preferable permeability may be obtained by using a mixture of two or more.

The water-based ink for ink-jet recording of the present invention may contain a slight amount of a surfactant for the purpose of adjusting physical properties such as the surface tension of the ink. The surfactant is not particularly limited, and anionic surfactants such as alkylbenzene sulfonates and higher fatty acid salts, nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene fatty acid esters, and other cationic surfactants. The surfactant may be appropriately selected from known and commonly used surfactants such as amphoteric surfactants. These surfactants can be used alone or in combination of two or more.
Examples of other additives include antiseptics, antifungal agents, and chelating agents for preventing nozzle clogging.

  If coarse particles are present in the water-based ink for ink jet recording, the ink jet nozzles of the ink jet printer may become clogged. Therefore, it is preferable to remove the coarse particles by centrifugal separation or filtration after the dispersion treatment.

  The water-based ink for ink-jet recording of the present invention thus obtained is excellent in dischargeability from the ink jet nozzles of the ink-jet printer head, and the ink film formed on the recording medium using the ink has a density and gloss. And high in abrasion resistance.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, these Examples demonstrate this invention concretely and an aspect is not limited by this.
In the synthesis examples, examples, and comparative examples, “parts” and “%” are all in terms of mass.

<Quantification of isocyanate group>
0.1 g of the sample solution was dissolved in 40 ml of a 0.01 N di-n-butylamine dimethylformamide solution, and then neutralized with 0.01 N hydrochloric acid in methanol using bromophenol blue as an indicator. And quantified.

<Quantification of acid value>
1.0 g of the sample solution is added to and dissolved in 40 ml of a mixed solvent of toluene and methanol (toluene: methanol = 7: 3), and phenolphthalein is used as an indicator with a methanol solution of 0.1 N potassium hydroxide. Quantification was performed using neutralization titration.

(Determination of pigment particle size in water-based ink for inkjet recording)
After adding water to the sample ink and diluting it 1000 times, the particle size of the pigment dispersed in the sample ink is measured using a particle size analyzer (“Microtrac UPA150” manufactured by Leeds & Northrup). It was measured.

<Synthesis Example 1> (Synthesis of reaction product (1-1))
In a four-necked flask equipped with a thermometer, stirrer, nitrogen introduction tube, and cooling tube, 290 g of methyl ethyl ketone (hereinafter abbreviated as MEK), 67 g of dimethylolpropionic acid (hereinafter abbreviated as DMPA), and isophorone diisocyanate (hereinafter abbreviated as IPDI) ) Was charged and reacted at 70 ° C. for 2 hours under a nitrogen gas atmosphere to obtain a reaction product (1-1). The isocyanato group quantitative value of the reaction product (1-1) was 7.3, and the reaction rate of the isocyanato group was 0.499.

<Synthesis Example 2> (Synthesis of reaction product (1-2))
A four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube was charged with 330 g of MEK, 67 g of DMPA, and 262 g of 4,4-cyclohexylmethane diisocyanate (hereinafter abbreviated as H2MDI) under a nitrogen gas atmosphere. The reaction was carried out at ° C for 1.5 hours to obtain a reaction product (1-2). The isocyanato group quantitative value of the reaction product (1-2) was 6.5, and the reaction rate of the isocyanato group was 0.49.

<Synthesis Example 3> (Synthesis of reaction product (1-3))
A four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube was charged with 268 g of MEK, 67 g of DMPA, and 201 g of IPDI, and reacted at 70 ° C. for 2 hours in a nitrogen gas atmosphere. -3) was obtained. The isocyanato group quantitative value of the reaction product (1-3) was 6.5, and the reaction rate of the isocyanato group was 0.54.

<Synthesis Example 4> (Synthesis of reaction product (1-4))
A four-necked flask equipped with a thermometer, stirrer, nitrogen introduction tube, and cooling tube was charged with 290 g of MEK, 73.7 g of DMPA, and 222 g of IPDI, and reacted at 70 ° C. for 2 hours in a nitrogen gas atmosphere. (1-4) was obtained. The isocyanato group quantitative value of the reaction product (1-4) was 6.5, and the reaction rate of the isocyanato group was 0.45.

<Comparative Synthesis Example 1> Synthesis of reaction product (ratio 1-1)
A four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and cooling tube was charged with 290 g of MEK, 67 g of DMPA, and 222 g of IPDI, and reacted at 70 ° C. for 1 hour in a nitrogen gas atmosphere. 1-1) was obtained. The isocyanato group quantitative value of the reaction product (ratio 1-1) was 9.0, and the reaction rate of the isocyanato group was 0.38.

<Comparative Synthesis Example 2> Synthesis of reaction product (ratio 1-2)
A four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and cooling tube was charged with 290 g of MEK, 67 g of DMPA, and 222 g of IPDI, and reacted at 70 ° C. for 6 hours in a nitrogen gas atmosphere. 1-2) was obtained. The isocyanato group quantitative value of the reaction product (ratio 1-2) was 6.2, and the reaction rate of the isocyanato group was 0.57.

<Synthesis Example 4> (Synthesis of carboxy group-containing polyurethane A)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 289 g of the reaction product (1-1) obtained in Synthesis Example 1 and poly (oxytetramethylene) glycol (OH group) of Mn650 Equivalent 173) 243 g, dibutyltin dilaurate (hereinafter abbreviated as DBTDL) 0.001 g and MEK 243 g were charged and reacted in a nitrogen gas atmosphere at 80 ° C. for 16 hours. Then, 5 g of methanol was added to stop the reaction. 36. A MEK solution of carboxy group-containing polyurethane A having a mass average molecular weight of 12,000 in terms of polystyrene was obtained. The obtained solution was neutralized with the same amount of sodium hydroxide as the charged amount of DMPA, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and the mass equivalent solid content 20 % Aqueous solution. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

<Synthesis Example 5> (Synthesis of carboxy group-containing polyurethane B)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 289 g of the reaction product (1-1) obtained in Synthesis Example 1 and poly (oxytetramethylene) glycol (OH group) of Mn650 Equivalent 173) (170 g), DBTDL (0.001 g), MEK (170 g) were charged and reacted at 80 ° C. for 16 hours in a nitrogen gas atmosphere. Then, 5 g of methanol was added to stop the reaction, and the carboxy group having an acid value of 46 and Mw of 50,000 was obtained. Containing polyurethane B was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

<Synthesis Example 6> (Synthesis of carboxy group-containing polyurethane C)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 330 g of the reaction product (1-2) obtained in Synthesis Example 2 and poly (oxytetramethylene) glycol (OH group) of Mn650 Equivalent 173) 178 g, DBTDL 0.001 g and MEK 180 g were charged and reacted at 80 ° C. for 16 hours in a nitrogen gas atmosphere. Then, 5 g of methanol was added to stop the reaction, and the carboxy group having an acid value of 42 and Mw 30,000 was obtained. Containing polyurethane C was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

<Synthesis Example 7> (Synthesis of carboxy group-containing polyurethane D)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 330 g of the reaction product (1-2) obtained in Synthesis Example 2 and 169 g of a polyester polyol (OH group equivalent 173) of Mn650 were obtained. Then, 0.001 g of DBTDL and 170 g of MEK were charged and reacted at 80 ° C. for 20 hours in a nitrogen gas atmosphere. Then, 5 g of methanol was added to stop the reaction, and a carboxyl group-containing polyurethane D having an acid value of 42 and Mw of 60,000 was obtained. It was. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

<Synthesis Example 8> (Synthesis of carboxy group-containing polyurethane E)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 289 g of the reaction product (1-1) obtained in Synthesis Example 1 and poly (oxytetramethylene) glycol (OH group) of Mn650 Equivalent 173) 270 g, DBTDL 0.001 g and MEK 270 g were charged and reacted at 80 ° C. for 10 hours in a nitrogen gas atmosphere. Then, 5 g of methanol was added to stop the reaction, and the carboxy group having an acid value of 34 and Mw 8,000 was obtained. Containing polyurethane E was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

<Synthesis Example 9> (Synthesis of carboxy group-containing polyurethane F)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 289 g of the reaction product (1-1) obtained in Synthesis Example 1 and poly (oxytetramethylene) glycol (OH group) of Mn2000 Equivalent 56) 667 g, IPDI 12.3 g, DBTDL 0.001 g and MEK 680 g were charged and reacted at 80 ° C. for 16 hours in a nitrogen gas atmosphere. Then, the reaction was stopped by adding 5 g of methanol, A carboxy group-containing polyurethane F having an Mw of 31,000 was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was a fluorescent transparent solution, and the particle size was 80 nm.

<Synthesis Example 10> (Synthesis of carboxy group-containing polyurethane G)
In a four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and cooling tube, 268 g of the reaction product (1-3) obtained in Synthesis Example 3 and 45 g of polypropylene glycol (OH group equivalent 281) of Mn400 Then, 7.2 g of ethylene glycol, 0.001 g of DBTDL, and 320 g of MEK were charged and reacted at 80 ° C. for 16 hours in a nitrogen gas atmosphere. Then, the reaction was stopped by adding 5 g of methanol, and the acid value was 75 and the Mw was 30,000. Carboxy group-containing polyurethane G was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

<Synthesis Example 11> (Synthesis of carboxy group-containing polyurethane H)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a cooling tube, 293 g of the reaction product (1-4) obtained in Synthesis Example 4 and poly (oxytetramethylene) glycol (OH group) of Mn2000 Equivalent 56) 450 g, DBTDL 0.001 g and MEK 450 g were charged and reacted at 80 ° C. for 16 hours in a nitrogen gas atmosphere. Then, 5 g of methanol was added to stop the reaction, and the carboxy group having an acid value of 28 and Mw 40,000 was obtained. Containing polyurethane H was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

<Comparative Synthesis Example 3> (Synthesis of carboxy group-containing polyurethane HH)
A four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube is charged with 266 g of IPDI, 67 g of DMPA, 325 g of polyester polyol (OH group equivalent 173) of Mn650, 0.001 g of DBTDL, and 646 g of MEK. After reacting at 80 ° C. for 10 hours in a nitrogen gas atmosphere, 15 g of ethylenediamine was added as a chain extender to stop the reaction, and a carboxyl group-containing polyurethane HH having an acid value of 45 and Mw of 80,000 was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was milky white and the particle size was 200 nm.

<Comparative Synthesis Example 4> (Synthesis of carboxy group-containing polyurethane HI)
A 4-neck flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube was charged with 105 g of IPDI, 67 g of DMPA and 172 g of MEK, and reacted at 70 ° C. for 4 hours in a nitrogen gas atmosphere to obtain urethane oligomer I1. . A 4-necked flask was charged with 117 g of IPDI, 357 g of poly (oxytetramethylene) glycol (OH group equivalent 173) of Mn650, 0.001 g of DBTDL, and 474 g of MEK, and reacted at 80 ° C. for 6 hours in a nitrogen gas atmosphere. Oligomer I2 was obtained. 948 g of the urethane oligomer I2 solution was charged with 344 g of urethane oligomer I1 and reacted at 80 ° C. for 10 hours under a nitrogen gas atmosphere. Then, 5 g of methanol was added to stop the reaction, and the carboxy group containing an acid value of 45 and Mw 12,000 was contained. Polyurethane HI was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was milky white and the particle size was 100 nm.

<Comparative Synthesis Example 5> (Synthesis of carboxy group-containing polyurethane HJ)
A four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube was charged with 222 g of IPDI, 330 g of poly (oxytetramethylene) glycol (OH group equivalent 173) of Mn650, 0.001 g of DBTDL, and nitrogen. The reaction was performed at 100 ° C. for 2 hours in a gas atmosphere. Subsequently, 67 g of DMPA and 620 g of MEK were charged and reacted at 80 ° C. for 16 hours under a nitrogen gas atmosphere. Then, 5 g of methanol was added to stop the reaction, and the carboxyl group-containing polyurethane HJ having an acid value of 45 and Mw 50,000 was obtained. Got. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was milky white and the particle size was 150 nm.

<Comparative Synthesis Example 6> (Synthesis of carboxy group-containing polyurethane HK)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a cooling tube, 579 g of the reaction product (ratio 1-1) obtained in Comparative Synthesis Example 1 and Mn650 poly (oxytetramethylene) glycol (OH group equivalent 173) 357g, DBTDL 0.001g, MEK 357g were charged and reacted at 80 ° C for 16 hours in a nitrogen gas atmosphere. Then, 5g of methanol was added to stop the reaction, acid value 45, Mw 32,000. Of carboxy group-containing polyurethane HK was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was milky white and the particle size was 150 nm.

<Comparative Synthesis Example 7> (Synthesis of carboxy group-containing polyurethane HL)
In a four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube, 579 g of the reaction product (ratio 1-2) obtained in Comparative Synthesis Example 2 and poly (oxytetramethylene) glycol of Mn650 (OH group equivalent 173) 357g, DBTDL 0.001g, MEK 357g were charged and reacted at 80 ° C for 16 hours in a nitrogen gas atmosphere. Then, the reaction was stopped by adding 5g of methanol, acid value 41, Mw 42,000. Of carboxy group-containing polyurethane HL was obtained. The obtained resin solution was neutralized with the same amount of sodium hydroxide as DMPA in the charged amount, water was added for phase inversion emulsification, MEK was removed by desolvation under reduced pressure, water was added, and mass conversion solid content A 20% aqueous solution was obtained. The aqueous solution was milky white and the particle size was 200 nm.

<Example 1>
(Preparation of aqueous pigment dispersion (a))
6 parts of methyl ethyl ketone solution (acid value 130, mass average molecular weight 12:00) having a solid content of benzyl methacrylate-methacrylic acid copolymer 50%, 7.8 parts of 5% aqueous potassium hydroxide solution, phthalocyanine pigment “Fastogen” (Registered trademark) Blue TGR "(manufactured by Dainippon Ink & Chemicals, Inc.) 10 parts and 23.8 parts of water were charged into a 250 mL plastic bottle and mixed. (In this case, 10 parts of the copper phthalocyanine pigment, the amount of the resin is 30% by mass in terms of non-volatile content with respect to the pigment, and the 5% aqueous potassium hydroxide solution has a resin acid value of 100%. (The amount to be added, water is the amount necessary to make the non-volatile content of the mixed solution 30%.)
The mixed solution was dispersed for 2 hours with a paint conditioner (using zirconia beads having a diameter of 0.5 mm). After completion of the dispersion, the liquid obtained by removing the zirconia beads was distilled off the methyl ethyl ketone with an evaporator, centrifuged (8200 G, 30 minutes) to remove coarse particles, and then purified water was added to remove the non-volatile content. Thus, an aqueous pigment dispersion (a) having a nonvolatile content of 20% was obtained. The particle diameter of the obtained pigment dispersion was 110 nm.

Using the aqueous pigment dispersion (a) and the aqueous solution of the carboxy group-containing polyurethane A obtained in Synthesis Example 4, the water-based ink for thermal inkjet recording was prepared according to the following composition, filtered through a filter having a pore size of 6 μm. (A-A) was prepared.

Aqueous pigment dispersion (a) 19.9 parts Carboxy group-containing polyurethane aqueous solution A 7.5 parts Diethylene glycol monobutyl ether 10.0 parts Diethylene glycol 15.0 parts Surfinol 465 (manufactured by Air Products) 0.8 part Water 46.8 Part

<Examples 2 to 8>
The same operation as in Example 1 was carried out except that the same amount of the carboxy group-containing polyurethane aqueous solution B to H obtained in Synthesis Examples 5 to 11 was used in place of the carboxy group-containing polyurethane aqueous solution A blended in Example 1. Water-based inks for recording (a-B) to (a-H) were prepared.

<Example 9>
(Preparation of aqueous pigment dispersion (b))
10 parts of MEK solution of carboxy group-containing polyurethane A, 3.8 parts of 5% potassium hydroxide aqueous solution, 10 parts of phthalocyanine pigment “Fastogen (registered trademark) Blue TGR” (manufactured by Dainippon Ink & Chemicals, Inc.) , 26.8 parts of water was charged into a 250 mL polybin and mixed. (In this case, 10 parts of the copper phthalocyanine pigment, the amount of the resin is 50% by mass in terms of non-volatile content with respect to the pigment, and the 5% potassium hydroxide aqueous solution has a resin acid value of 100%. (The amount to be added, water is the amount necessary to make the non-volatile content of the mixed solution 30%.)
The mixed solution was dispersed for 2 hours with a paint conditioner (using zirconia beads having a diameter of 0.5 mm). After completion of the dispersion, the liquid obtained by removing the zirconia beads was distilled off the methyl ethyl ketone with an evaporator, centrifuged (8200 G, 30 minutes) to remove coarse particles, and then purified water was added to remove the non-volatile content. And an aqueous pigment dispersion (b) having a nonvolatile content of 20% was obtained. The particle diameter of the obtained pigment dispersion was 110 nm.
The aqueous pigment dispersion (b) was used, adjusted according to the following composition, and filtered through a filter having a pore diameter of 6 μm to prepare a thermal ink jet recording aqueous ink (b).

Aqueous pigment dispersion (b) 22.9 parts Diethylene glycol monobutyl ether 10.0 parts Diethylene glycol 15.0 parts Surfinol 465 (manufactured by Air Products) 0.8 parts Water 51.3 parts

<Example 10>
The same operation as in Example 8 was carried out except that the same amount of the MEK solution of carboxy group-containing polyurethane C obtained in Synthesis Example 6 was used instead of the MEK solution of carboxy group-containing polyurethane A obtained in Synthesis Example 4, and an aqueous pigment Dispersion C was obtained. The particle diameter of the obtained pigment dispersion was 120 nm. Using this aqueous pigment dispersion C, the same formulation as in Example 9 was carried out to prepare an aqueous inkjet recording ink (c).

<Comparative Examples 1-5>
It is the same as that of Example 1 except using the same amount of the carboxy group-containing polyurethane aqueous solution HH to HL obtained in Comparative Synthesis Examples 3 to 7 instead of the carboxy group-containing polyurethane aqueous solution A blended in Example 1. The operation was performed to prepare water-based inks (aHH) to (aHL) for inkjet recording.

<Performance tests and evaluation criteria>

(Inkjet recording test (print density, gloss value))
Using a thermal inkjet printer BJ F300 type (manufactured by Canon Inc.) equipped with a bubble jet (registered trademark) recording head (BC-30E, manufactured by Canon Inc.), drawing with sample ink on the recording medium, An ejection stability test, a print density test, a gloss value test, and an abrasion resistance test were performed. As the recording medium, “Canon PB paper” manufactured by Canon Co., Ltd. or “Xerox 4024” manufactured by Xerox Co., Ltd. was used as plain paper, and “photographic paper gloss” manufactured by Seiko Epson Co., Ltd. was used as a dedicated paper for inkjet.

(Discharge stability)
The character pattern is continuously printed on plain paper. The more the number of continuous printed items (the number of sheets that can be printed without ejection) is judged to be better, and the following three criteria are used. Judged.
○ Number of printed materials 500 or more △ Number of printed materials 300 or more and less than 500 × Printed number of printed materials less than 300

(Print density)
Print a solid image on inkjet paper, use a print density measuring machine “GRETAG (registered trademark) D196 Gretag Macbeth Co., Ltd.”, measure the color image density for 5 points of a single sample, and average the values. The printing density was used. The larger the numerical value, the better the print density, and the determination was made based on the following three levels.
○ Printing density is 2.5 or more.
Δ: Print density is 2.0 or more and less than 2.5.
× Print density less than 2.0.

(Measure gloss value of image)
A solid image was printed on a special paper, and the gloss of the colored image was measured at a measurement angle of 20 degrees using a haze gloss meter “BYK Gardner” as a gloss value measuring machine. Three points of a single sample were measured, and a value obtained by averaging them was defined as a gloss value. The larger the value, the better the gloss, and the determination was made according to the following four levels of criteria.
◎ Gloss value 25 or more ○ Gloss value 20 or more.
Δ: Gloss value of 10 or more and less than 20.
X Gloss value less than 10.

(Abrasion resistance)
A solid image was printed on ink jet dedicated paper, and rubbed 5 times with a load of 200 g using plain paper as a contact paper, using a Gakushin type anti-friction tester. The gloss value of the printed matter before and after the test was measured, and the smaller the change rate of the gloss value, the better the rub resistance, and the determination was made according to the following four criteria.
◎ Gloss change rate is less than 5%.
○ Gloss change rate is 5% or more and less than 10%.
△ Gloss change rate is 10% or more and less than 15%.
X Gloss change rate of 15% or more.

  The performance test results of the aqueous pigment dispersion of the present invention and the aqueous ink for inkjet recording are collectively shown in the table.

From the results shown in Table 1, the water-based ink for inkjet recording using the carboxy group-containing polyurethane of the present invention is excellent in ejection stability, and the obtained inkjet print is excellent in gloss and has a high color image density, It can be seen that it has high printing durability. In particular, Examples 1-3, 8, and 9, in which the molecular weight of the carboxy group-containing polyurethane is in the range of 10,000 to 50,000 and the acid value is in the range of 20 to 70, the ejection stability is 500 sheets or more, and the gloss The value was 25 or more, indicating a very excellent value.
In Example 4, since the molecular weight was as high as 60000, the rub resistance was excellent, but the dischargeability was slightly lowered. Further, since the molecular weight of Example 5 was as low as 8000, the ejection property was good, but the abrasion resistance was slightly inferior. In Example 6, since the acid value was low, the particle size was slightly increased to 80 nm, and the dischargeability was slightly decreased. Moreover, since Example 7 had a high acid value, it was a little inferior to abrasion resistance.
On the other hand, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are all examples of a carboxy group-containing polyurethane that does not contain the reaction product (1), but this is low in both ejection stability and abrasion resistance. . Comparative Example 4 is an example in which the reaction rate of isocyanato groups is low, and Comparative Example 5 is an example in which the reaction rate of isocyanato groups is high, but this is very poor in ejection stability.

Claims (6)

A pigment dispersion mainly comprising water, an aqueous polymer, and a pigment, wherein the aqueous polymer is
A diol compound (A) having 1 or 2 carboxy groups in one molecule is reacted with a diisocyanate compound (B), the compound represented by the general formula (1) as a main component, and an isocyanato group reaction rate. A pigment dispersion, which is a carboxy group-containing polyurethane obtained by reacting a reaction product within a range of 0.45 to 0.55, a diol compound, and a diisocyanate compound.

(1)
(In General Formula (1), R ¹ and R ³ represent a partial structure excluding the isocyanate group of the diisocyanate compound (B), R ¹ and R ³ may be the same or different, and R ² is And represents a partial structure excluding the hydroxy group of the diol compound (A) having one or two carboxy groups in one molecule. The pigment dispersion according to claim 1, wherein the carboxy group-containing polyurethane has a mass average molecular weight in the range of 10,000 to 50,000. The pigment dispersion according to claim 1 or 2, wherein the acid value of the carboxy group-containing polyurethane is 20 to 70 mgKOH / g. The pigment dispersion according to any one of claims 1 to 3, wherein the diol compound (A) is dimethylolpropionic acid or dimethylolbutanoic acid. A method for producing an aqueous polymer for use in a pigment dispersion containing water, an aqueous polymer, and a pigment as essential components, and a diol compound (A) having one or two carboxy groups in one molecule and a diisocyanate compound (B ), A reaction product having a compound represented by the general formula (1) as a main component and an isocyanato group reaction rate in the range of 0.45 to 0.55, a diol compound, and a diisocyanate compound And a method for producing an aqueous polymer.

(1)
(In General Formula (1), R ¹ and R ³ represent a partial structure excluding the isocyanate group of the diisocyanate compound (B), R ¹ and R ³ may be the same or different, and R ² is And represents a partial structure excluding the hydroxy group of the diol compound (A) having one or two carboxy groups in one molecule. A water-based ink for ink-jet recording using the pigment dispersion according to any one of claims 1 to 4.