JP2974617B2 - Method for producing water-based ink for inkjet recording - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aqueous ink for ink jet recording, and more particularly to a method for producing an aqueous ink for ink jet recording in which the process of dispersing the ink can be easily controlled.

[0002]

2. Description of the Related Art A water-based ink for ink-jet recording generally comprises a dispersion obtained by pre-dispersing a dispersant such as a pigment and a water-soluble resin in an aqueous liquid medium such as water or alcohols. After the preparation, a dispersion step of dispersing the dispersion to a predetermined degree using a disperser such as a sand mill is performed, and then the dispersion is diluted to a predetermined concentration. The degree of dispersion of the dispersion in the dispersion step was based on the time during which the dispersion stayed in the disperser.

However, depending on the difference in the viscosity and viscoelasticity of the dispersion and the type of disperser used, the degree of dispersion of the dispersion is not always correlated with the time that the dispersion stays in the disperser. What did not do was actually. Therefore, experience and know-how are required for the management of the dispersion process, and it has been difficult to facilitate the process management.

Accordingly, an object of the present invention is to provide a method for producing a water-based ink for ink-jet recording, which is less dependent on the viscosity and viscoelasticity of the dispersion and the type of the disperser, and which can easily control the dispersion process of the ink. It is in.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the degree of dispersion of a dispersion is correlated with the integrated power per unit weight applied to the disperser,
As a result of further study, it was found that the above object can be achieved by controlling the dispersing step with the integrated power per unit weight being in a specific range.

The present invention has been made based on the above findings, and is applied to a sand mill when a pigment dispersion prepared by preliminarily dispersing at least a pigment and a polymer dispersant in an aqueous liquid medium is dispersed in the sand mill. The object has been achieved by providing a method for producing a water-based ink for ink-jet recording, characterized in that the integrated power per unit weight is 0.1 to 10 kWh / kg.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a method for producing a water-based ink for ink-jet recording according to the present invention will be described with reference to the drawings. Here, FIG. 1 is a flowchart showing a process of an embodiment of the method for producing a water-based ink for inkjet recording of the present invention.

In the manufacturing method of the embodiment shown in FIG. 1, at least a step of stirring a polymer dispersant and an aqueous liquid medium with a dissolver (1), a step of adding a pigment and further stirring (pre-dispersion) with a dissolver (2) (3) dispersing the pigment dispersion obtained by the preliminary dispersion using a Dyno mill with a predetermined integrated power per unit weight of the pigment dispersion, and diluting the pigment dispersion to a predetermined concentration. Step (4) is provided. Hereinafter, each of these steps will be described.

In the above step (1), the polymer dispersant and the aqueous liquid medium are stirred with a dissolver. in this case,
The blending weight ratio of the polymer dispersant and the aqueous liquid medium is such that the former: the latter = 1: 200 to 1: 1 from the viewpoint of the dispersibility at the time of preliminary dispersion and dispersion, and further, the handleability at the time of preliminary dispersion and dispersion. And more preferably 1: 100 to 1: 2. Further, the stirring time is preferably from 5 to 120 minutes, more preferably from 10 to 60 minutes, from the viewpoint of making the mixing of the polymer dispersant and the aqueous liquid medium uniform.

In the step (2), a pigment is added to a mixture of the polymer dispersant obtained in the step (1) and an aqueous liquid medium, and the mixture is further stirred with a dissolver (preliminary dispersion).
I do. In this case, from the viewpoint of the preliminary dispersion and the dispersibility at the time of dispersion, and further the handling at the time of preliminary dispersion and dispersion, the blending ratio of the pigment to the aqueous liquid medium is determined as follows. The ratio is preferably from 33 to 1: 1 and from 1:25 to
More preferably, the ratio is 1: 2. The stirring time is
In order to sufficiently wet the pigment with the mixture of the polymer dispersant and the aqueous liquid medium, the time is preferably 5 to 120 minutes, preferably 10 to 120 minutes.
More preferably, it is 60 minutes. The concentration of the pigment in the pigment dispersion obtained in this step is to sufficiently wet the pigment with the mixture of the polymer dispersant and the aqueous liquid medium,
Further, from the viewpoint of the preliminary dispersion and the handling at the time of dispersion, 3 to
It is preferably 50% by weight, more preferably 4 to 35% by weight.

In the above step (3), the pigment dispersion obtained in the preliminary dispersion in the above step (2) is dispersed using a dyno mill (a kind of sand mill). The degree of dispersion is adjusted based on the integrated power per unit weight of the pigment dispersion applied to the Dyno mill. As described above, it was not easy to control the degree of dispersion of the pigment dispersion by time, but according to the present invention, the management of the dispersion step of the pigment dispersion was performed by integrating power per unit weight of the pigment dispersion. By doing so, the dependence of the degree of dispersion on the type of mill is reduced, and the degree of dispersion can be easily managed. Further, the dispersion of the pigment in the obtained ink is very good, and the reproducibility of the particle size distribution of the pigment is excellent. In step (3), the integrated power applied to the Dyno mill per unit weight of the pigment dispersion (per kg of the pigment dispersion) is in the range of 0.1 to 10 kWh / kg. The integrated power per unit weight is 0.1 kWh / k
g, the dispersion is insufficient, coarse particles remain, and a good pigment dispersion cannot be obtained, and 10 kWh /
If the weight is more than kg, a good pigment dispersion cannot be obtained due to aggregation and / or thickening due to overdispersion, and / or a further significant improvement in dispersibility cannot be achieved. The cumulative power per unit weight of the pigment dispersion is 0.25 to 8 kWh /
kg, more preferably 0.5 to 5 kWh / kg. Incidentally, the integrated power per unit weight of the pigment dispersion is measured by an integrated wattmeter provided in a Dyno mill.

In the step (4), the pigment dispersion dispersed in the step (3) is diluted to a predetermined concentration to obtain an ink. By such dilution, the concentration of each component is set as the final ink concentration. The dilution is preferably performed by mixing a predetermined amount of the pigment dispersion with at least a predetermined amount of a polymer dispersant and an aqueous liquid medium.

The manufacturing method of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the manufacturing method of the embodiment, after the step (4), it is preferable that the ink is centrifuged by a centrifuge (for example, 2500 G, for 20 minutes). Such centrifugation is preferable because particles of preferably 2 μm or more, more preferably 1 μm or more are removed and an ink without clogging is obtained. In the manufacturing method of the above embodiment, a conventionally known device, for example, a disper or a homomixer may be used instead of using a dissolver in the steps (1) and (2). Further, in the manufacturing method of the above embodiment, in place of a dyno mill as a sand mill, a conventionally known device,
For example, a Glen mill, a super mill, a spike mill, a pearl mill, etc. may be used. Further, in the production method of the above embodiment, the processing amount (weight) of the pigment dispersion can be appropriately adjusted according to the scale of the dispersing apparatus used. Further, in the manufacturing method of the above-described embodiment, the ink may be manufactured by adding various components described below as necessary in addition to the above-described components. For example, in the above step (1), in addition to the polymer dispersant, a surfactant such as an anionic surfactant or a pH adjuster may be stirred together with the aqueous liquid medium.

Next, various components used in the ink produced by the production method of the present invention will be described.

As the aqueous liquid medium, water is mainly used. Also, a mixture of water and a water-soluble solvent can be used. Water is preferably incorporated in the ink in an amount of 70 to 98% by weight, more preferably 85 to 95% by weight. Further, the water-soluble solvent is preferably incorporated in an amount of 0.1 to 30% by weight, more preferably 0.1 to 15% by weight.

The type of the water-soluble solvent is not particularly limited as long as it has a function as a wetting agent or a humectant. For example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol,
Glycols such as tetraethylene glycol and polyethylene glycol; glycerin; diethylene glycol diethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, ethyl Ethers of polyhydric alcohols such as carbitol acetate, diethyl carbitol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and propylene glycol monomethyl ether; acetates; thiodiglycol; N-methyl-2-pyrrolidone; 1,3-dimethylimidazolidinone; triethanolamine; formua De; nitrogen-containing compounds such as dimethylformamide, may be used one or two or more of dimethyl sulfoxide.

The type of the above pigment is not particularly limited,
For example, carbon black; I. Pigment Yellow 1, 5, 12, 14, 17, 24, 42, 53, 8
3, 95, 97, 98 and 100; I. Pigment Red 1, 3, 4, 5, 17, 22, 31, 48, 4
9, 53, 63, 64, 81: 1, 88 and 101;
C. I. Pigment Blue 1, 15, 16, 27, 2
8, 29, 56, 60 and 63; I. Pigment Black 1 and 11 can be used, and carbon black is particularly preferable. The pigment is preferably incorporated in the ink in an amount of 1 to 15% by weight, more preferably 2 to 10% by weight.
If the amount of the pigment is less than 1% by weight, the print density is insufficient, and even if the amount exceeds 15% by weight, the print density cannot be significantly improved. . The average particle diameter of the pigment is preferably 0.05 to 3 μm, more preferably 0.05 to 1 μm, from the viewpoint of improving the storage stability of the ink.

When color printing is carried out by subtractive color mixing using the ink produced by the production method of the present invention, an aqueous pigment comprising four types of inks containing black, yellow, magenta and cyan pigments, respectively. It is preferable to use an ink set. In this case, carbon black is used as a black pigment, and C.I. I. Pigment Yellow 17 and 83, and C.I. I. Pigment Red 4
8: 3, 83 and 122, and C.I. I. Pigment Blue 15: 3 is preferred because color reproducibility is improved.

As the above-mentioned polymer dispersant, those which can improve the dispersibility of the pigment in the ink are used. Examples of the polymer dispersant include gelatin, proteins such as casein, natural gums such as gum arabic, glucoxides such as saponin, alkyl cellulose, carboxyalkyl cellulose, cellulose derivatives such as hydroxyalkyl cellulose, lignin sulfonate, shellac and the like. Natural polymer, polyacrylate, styrene-acrylic acid copolymer salt, vinylnaphthalene-acrylic acid copolymer salt, styrene-maleic acid copolymer salt, vinylnaphthalene-maleic acid copolymer salt, β-naphthalene Anionic polymers such as sodium salt of sulfonic acid formalin condensate and polyphosphoric acid, and nonionic polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyalkylene glycol can be used. These can be used alone or in combination of two or more.

In particular, when a copolymer of a (meth) acrylic acid derivative is used as the polymer dispersant, the step (3)
This is preferred because the dispersibility of the pigment in Example 1 further improves, the reproducibility of the particle size distribution of the pigment further improves, and the long-term storage stability of the ink further improves. The copolymer of the (meth) acrylic acid derivative may be one in which only acrylic acid or methacrylic acid or a derivative thereof is used as a copolymer component, or may be a copolymer of acrylic acid or methacrylic acid or a derivative thereof. And a polymerizable monomer may be used as a copolymerization component. As the derivatives of (meth) acrylic acid, alkali metal salts, alkaline earth metal salts, ammonium salts or amine salts and esters thereof, and hydrogen atoms bonded to the double bond carbon may have various functional groups (for example, carboxyl group and carboxyalkyl group). (For example, maleic acid, itaconic acid, citraconic acid, and fumaric acid). In particular, a derivative of (meth) acrylic acid capable of introducing a side chain having a chain length sufficient to exhibit steric hindrance into the copolymer is preferable.

Particularly preferred copolymers of the (meth) acrylic acid derivative include a monomer (a) represented by the following general formula (A) and a monomer (a) represented by the following general formula (B). And a copolymer obtained by polymerizing the monomer (b) [hereinafter, this copolymer is referred to as “copolymer (I)”].

[0022]

Embedded image

The copolymer (I) is described in detail below.
In the general formula (A), R ₁ and R ₂ represent a hydrogen atom or a lower alkyl group (preferably C 1 to C
3), which may be the same or different. In particular, it is preferred that both R ₁ and R ₂ are hydrogen atoms, or that R ₁ is a hydrogen atom and R ₂ is a methyl group. m ₁ is, 0-2
And preferably 0 or 1. AO represents an oxyalkylene group having 2 to 3 carbon atoms (that is, an oxyethylene group or an oxypropylene group), and is preferably an oxyethylene group. n represents an integer of 1 to 300, preferably an integer of 2 to 150, more preferably 4 to
It is an integer of 130. If n is 0, the dispersion stability cannot be sufficiently exhibited, and if n exceeds 300, the viscosity of the ink increases, which may adversely affect the ejection behavior, for example, when used in an ink jet printer. X represents a hydrogen atom or a lower alkyl group (preferably C1 to C5), and is preferably a hydrogen atom, a methyl group or an ethyl group.

Specific examples of preferred compounds represented by the above general formula (A) include methoxy polyethylene glycol, methoxy polyethylene polypropylene glycol, ethoxy polyethylene glycol, ethoxy polyethylene polypropylene glycol, propoxy polyethylene glycol, and propoxy polyethylene polypropylene glycol. Ethylene oxide, propylene oxide to esterified product of dealkylated (oxidized) reactant of acrylic acid, methacrylic acid or fatty acid, or to dehydrogenated (oxidized) reactant of acrylic acid, methacrylic acid or fatty acid Adducts. In the compound represented by the general formula (A),
When both ethylene oxide and propylene oxide are added, any of random addition, block addition, alternate addition and the like can be used. In this case, the addition molar ratio of ethylene oxide to propylene oxide (former: latter) is preferably from 10:90 to 90:10, and more preferably from 10:90 to 60:40.

Examples of the compound represented by the general formula (B) include unsaturated monocarboxylic acids and salts thereof, and unsaturated dicarboxylic acids and salts thereof. Specifically, acrylic acid, methacrylic acid and crotonic acid and metal salts thereof, and maleic acid which is an unsaturated dicarboxylic acid monomer,
Examples include itaconic acid, citraconic acid and fumaric acid and their alkali metal salts, alkaline earth metal salts, ammonium salts and amine salts, and their acid anhydrides, maleic anhydride, itaconic anhydride and citraconic anhydride.

In the copolymer (I), the molar ratio of the monomers (a) and (b) [monomer (a) / monomer (b)] is 0.1 / 100-100. / 100, more preferably 1/100 to 70/100. If the ratio of the monomer (a) is smaller than this, the dispersion storage stability is impaired. If the ratio of the monomer (a) is larger than this, the solubility in water is reduced and the dispersibility is reduced. There is a risk of doing so. That is, it is preferable to set the molar ratio of the monomers (a) and (b) within such a range, since a polymer dispersant having excellent dispersibility and excellent storage stability can be obtained.

In the copolymer (I), another copolymerizable monomer may be further used as a copolymer component as long as its function as a polymer dispersant is not impaired. The monomer includes (meth) acrylonitrile, (meth)
Acrylamide, styrene, styrene sulfonic acid and the like can be mentioned.

The copolymerization mode of the above monomers (a) and (b) can be random copolymerization, block copolymerization, alternating copolymerization, or graft copolymerization. There is no particular limitation as long as the function of the polymer dispersant (I) is not impaired.

When the copolymer (I) has a high molecular weight, the viscosity of the copolymer (I) increases, and the handleability is poor. When the ink is used as an ink, the viscosity of the ink may increase and the performance of the ink may decrease. Weight average molecular weight of 5000 to 20
It is preferably 10,000, and more preferably 5000 to 70,000.

Particularly, in the copolymer (I), from the viewpoint of dispersibility and storage stability of the dispersion, preferably 1 to 300, more preferably 2 to 150 oxyalkylene groups per molecule are used. More preferably, 4 to 130 polyalkylene glycol monoester monomers (particularly, a polyalkylene glycol ester of (meth) acrylic acid or an alkoxypolyalkylene glycol ester) and a (meth) acrylic acid monomer are introduced. It is desirable to use a copolymer obtained by polymerization.

The method for preparing the copolymer (I) is not particularly limited as long as the function of the copolymer (I) as a polymer dispersant is not impaired, and a conventionally known preparation method is used.
Specific examples of the preparation method include the method described in JP-A-7-223852, column 4, line 42 to column 5, line 11.

It is unclear why the use of a copolymer of a (meth) acrylic acid derivative, particularly the above-mentioned copolymer (I), as the polymer dispersant particularly improves the dispersibility of the pigment in the step (3). No, but it is presumed to be as follows. That is, in the ink, the copolymer (I) is charged in a state where a charged site (for example, a carbonyl site) in the molecule is adsorbed on the pigment surface and a side chain polyoxyalkylene group is directed outward. Surrounds the surface of the pigment. Since the polyoxyalkylene group has a long chain length and high steric hindrance, aggregation between the pigments is inhibited by the polyoxyalkylene group. As a result, it is considered that the dispersibility and the storage stability of the pigment in the step (3) are improved. Since the steric hindrance caused by the polyoxyalkylene group is particularly noticeable when the pH of the ink is high, it is preferable to set the pH of the ink to a high region as described later.

The above polymer dispersant is added to the ink in an amount of 0.05%.
Preferably, it is blended in an amount of 10 to 10% by weight. If the compounding amount of the polymer dispersant is less than 0.05% by weight, the compounding amount does not reach a level sufficient to stabilize the pigment, so that storage stability may be lacking. In addition, the storage stability may not be further improved, and the viscosity of the ink may be increased. More preferably, the compounding amount of the polymer dispersant is 0.1 to 4% by weight.
More preferably, it is 5 to 3% by weight.

The inks produced by the production method of the present invention may contain the following components in addition to the above components, if necessary.

In the ink, it is preferable to use a dispersibility improver together with the polymer dispersant from the viewpoint of improving the dispersibility of the pigment in the step (3). As the dispersibility improver, various surfactants such as an anionic surfactant, a cationic surfactant, a nonionic surfactant and an amphoteric surfactant can be used. The surfactant is preferably incorporated in the ink as a whole in an amount of 0.01 to 10% by weight, more preferably 0.05 to 5% by weight.

Examples of the above anionic surfactant include alkyl benzene sulfonate, alkyl naphthalene sulfonate, alkane or olefin sulfonate, alkyl sulfate, polyoxyethylene alkyl or alkyl aryl ether sulfate, and alkyl phosphate. , An alkyl diphenyl ether disulfonate, an ether carboxylate, an alkyl sulfosuccinate, an α-sulfofatty acid ester, and a surfactant selected from the group consisting of a fatty acid salt, a condensate of a higher fatty acid and an amino acid, a naphthenate, etc. Can be used. Anionic surfactants preferably used include alkyl benzene sulfonates (especially linear alkyl), alkanes or olefin sulfonates (especially secondary alkane sulfonates, α-olefin sulfonates), alkyl sulfates Polyoxyethylene alkyl or alkyl aryl ether sulfate (especially polyoxyethylene alkyl ether sulfate), alkyl phosphate (especially monoalkyl), ether carboxylate, alkyl sulfosuccinate, α-sulfofatty acid ester And surfactants selected from the group consisting of fatty acid salts, and particularly preferred are alkylbenzene sulfonates (especially those of linear alkyl), polyoxyethylene alkyl or alkylaryl ether sulfates Ester salts (especially polyoxyethylene alkyl ether sulfate salts), and alkyl sulfate salts. These can be used alone or in combination of two or more.

As the above-mentioned cationic surfactant, aliphatic amine salts, quaternary ammonium salts, sulfonium salts, phosphonium salts and the like can be used. These can be used alone or in combination of two or more.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, sorbitan fatty acid ester,
A surfactant selected from the group consisting of polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester and alkyl (poly) glycoxide can be used. Nonionic surfactants preferably used are surfactants selected from polyoxyethylene alkyl ethers and polyoxyethylene alkyl aryl ethers. These can be used alone or in combination of two or more.

As the amphoteric surfactant, amino acid type compounds, betaine type compounds and the like can be used.

In particular, when the above surfactant is used,
Either an anionic surfactant or a combination of an anionic surfactant and a nonionic surfactant is used, and the amount of each is 0.01 to 5% by weight (particularly 0.01 to 3% by weight,
In particular, 0.05 to 2% by weight), and the mixing ratio of both is anionic surfactant: nonionic surfactant = 10
It can be used in a weight ratio of 0: 1 to 1: 100 (especially 90: 1 to 1:70, especially 70: 1 to 1:50), and the print density of the printed image and the long-term storage It is preferable from the viewpoint of improving dispersion stability.

When an anionic surfactant is used as the surfactant, the mixing ratio of the polymer dispersant and the anionic surfactant is such that the polymer dispersant and the anionic surfactant are mixed. = 1: 2 to 30: 1 by weight. If the amount of the polymer dispersant exceeds the above range, the wettability of the polymer dispersant with the pigment may be insufficient, and the dispersibility may be reduced. On the other hand, if the amount of the anionic surfactant is more than the above range, the foaming property of the ink is increased and the handleability may be poor. The compounding ratio of the two is more preferably the polymer dispersant: the anionic surfactant = 1: 1 to 15: 1, and further preferably 1: 1 to 10: 1.

In the above ink, polypropylene glycol may be blended to improve the permeability of the ink into the recording paper and to prevent strikethrough (ink seepage to the back side of the recording paper). preferable. The molecular weight of the polypropylene glycol is preferably from 400 to 3,000, and more preferably from 400 to 2,000. The polypropylene glycol is preferably incorporated in the ink in an amount of 0.01 to 3% by weight,
It is more preferred that the content be 1 to 1% by weight.

In order to improve the drying property of the ink, it is preferable to add an aliphatic monohydric alcohol.
As the aliphatic monohydric alcohol, ethyl alcohol,
Preferably, one or two or more of 1-propyl alcohol and 2-propyl alcohol are used.
It is particularly preferred to use -propyl alcohol. The aliphatic monohydric alcohol is preferably contained in the ink at 0.0
The content is 1 to 10% by weight, and more preferably 0.1 to 8% by weight. In particular, when the blending amount of the aliphatic monohydric alcohol is related to the blending amount of the polymer dispersant, the blending ratio of both is such that the polymer dispersant: the aliphatic monohydric alcohol = 1: 10 to 1: By adjusting to be 1,
The drying property of the ink is further improved.

Further, in order to improve the intermittent ejection property of the ink, the molecular weight is 400 to 3500 (particularly 400 to 20).
(00) can also be blended. The polyethylene glycol disulfate salt is preferably incorporated in the ink at 0.01 to 3% by weight, more preferably 0.01 to 1% by weight.

Similarly, in order to improve the intermittent ejection property,
Sugars can be added to the ink. As the saccharide, one or more of D-glucose, fructose, maltose and saccharose are preferably used, and saccharose is particularly preferably used. The saccharide is preferably contained in the ink in an amount of 0.1 to 5% by weight, more preferably 0.1 to 3% by weight. In particular, the compounding amount of the saccharide is adjusted so that the compounding ratio of the two is 20: 1 to 1: 5 in relation to the compounding amount of the polymer dispersant. By
Intermittent ejection is further improved.

Similarly, a nitrogen-containing heterocyclic compound such as N-methyl-2-pyrrolidone or 1,3-dimethyl-2-imidazolidinone can be blended with the ink to improve the intermittent ejection property. . The nitrogen-containing heterocyclic compound is preferably incorporated in the ink in an amount of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight.

Similarly, in order to improve the intermittent ejection property, an aprotic polar solvent can be mixed with the ink. As the aprotic polar solvent, it is preferable to use one or more of dimethyl sulfoxide and sulfolane. The aprotic polar solvent is preferably incorporated in the ink in an amount of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight.

The polyethylene glycol disulfate salt, saccharide, nitrogen-containing heterocyclic compound, and aprotic polar solvent capable of improving the intermittent ejection property are used in combination with the above pigment having an average particle size of 0.05 to 3 μm. Thereby, the intermittent ejection property is further improved.

Further, in order to improve the fixability of the ink, it is preferable to incorporate an emulsion of acrylic type, aqueous urethane type, styrene-butadiene type or polyester type. In particular, it is preferable to mix an acrylic-urethane copolymer emulsion. As the emulsion, it is preferable to use an acryl-urethane block copolymer (a copolymer obtained by adding a polyurethane polymer to a polyacrylic acid polymer). The weight average molecular weight of the copolymer in the emulsion is 10,000
~ 300000, preferably 20000-2
More preferably, it is 50,000. The emulsion is preferably incorporated in the ink at a solid concentration of 0.01 to 10% by weight, more preferably 0.05 to 5% by weight.

Similarly, polyethyleneimine having a weight average molecular weight of 800 to 300,000 can be blended in order to improve the fixability of the ink. As the polyethyleneimine, it is preferable to use one or more of polyethyleneimine grafted to the side chain of the main chain composed of an acrylic chain, polyethyleneimine subjected to hydroxylation treatment, and polyethyleneimine zwitterionized. It is particularly preferable to use hydroxylated polyethyleneimine. The polyethyleneimine is preferably incorporated in the ink in an amount of 0.01 to 10% by weight.
It is more preferable that the content is from 0.5 to 5% by weight.

Further, if necessary, an antifoaming agent such as a silicone compound, a fungicide such as a chloromethylphenol compound, a chelating agent such as EDTA, and an oxygen absorbing agent such as a sulfite are added to the ink. You can also.

The above-mentioned ink has a pH of 9.5 from the viewpoint that it can improve the print density of a printed image, particularly the black print density.
１３13.0, preferably 10.0-12.0
Is more preferable. In order to keep the pH within the above range, a pH adjuster, for example, an amino alcohol may be added to the ink. Examples of the amino alcohol include monoethanolamine (for example, 2-aminoethanol),
It is preferable to use triethanolamine or the like.

The ink produced by the production method of the present invention can be used in any printer as long as it uses an ink jet recording system. For example, a thermal jet recording type printer that performs recording using thermal energy from a heater or the like of a heating resistance element disposed in a printer head, and a piezoelectric element recording that performs recording using a piezoelectric element disposed in the printer head Any type of printer can be used.

Hereinafter, the effectiveness of the present invention will be illustrated by way of examples. However, the scope of the present invention is not limited to such an embodiment. In the following examples, "parts" and "%" represent parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 First, the following components were stirred with a dissolver for 30 minutes. -4 parts of polymer dispersant A-4 parts of sodium lauryl sulfate-7 parts of diethylene glycol-1 part of monoethanolamine-64 parts of water Then, 20 parts of carbon black (primary particle diameter 20n)
m) was added to the above dissolver, and the mixture was further stirred for 50 minutes to pre-disperse the carbon black to obtain a pigment dispersion. The pigment dispersion was placed in a Dyno mill and dispersed until the cumulative power per unit weight of the pigment dispersion applied to the Dyno mill reached 1 kWh / kg. After the dispersion is completed, a predetermined amount of the polymer dispersant A, sodium lauryl sulfate, diethylene glycol, monoethanolamine, and water is added to the pigment dispersion so that the concentration of each component is as follows. The product was diluted, and the diluted solution was further centrifuged with a centrifuge (2500 G, 20 minutes) to remove coarse particles to obtain an aqueous ink for inkjet recording.・ Carbon black 5% ・ Polymer dispersant A 2% ・ Sodium lauryl sulfate 2% ・ Diethylene glycol 7% ・ Monoethanolamine 1% ・ Water 83% The above polymer dispersant A is methacrylic acid methoxypolyethylene glycol ( (EO addition number: 120 / molecule)
It is a copolymer of an ester and sodium methacrylate [molar ratio of monomers (former / latter) = 30/70].

In order to evaluate the dispersibility of the pigment in the obtained ink, the reproducibility of the particle size distribution of the pigment was evaluated by the following method. Table 2 shows the results.

[Reproducibility of Particle Size Distribution of Pigment] The particle size distribution of the pigment in the obtained ink was measured three times by a scattering intensity distribution measurement of DLS-7000AL (Otsuka Electronics Co., Ltd.). From the distribution, the peak top and its standard deviation were obtained.

[Examples 2 and 3 and Comparative Examples 1 and 2]
The types of the pigment and the polymer dispersant were as shown in Table 1, and the integrated power per unit weight of the pigment dispersion applied to the Dynomill was 2 kWh / kg (Example 2), 5
An ink was manufactured in the same manner as in Example 1 except that kWh / kg (Example 3), 0.08 kWh / kg (Comparative Example 1), and 12 kWh / kg (Comparative Example 2) were used. The same evaluation as in Example 1 was performed on the obtained ink. Table 2 shows the results.

[0059]

[Table 1]

[0060]

[Table 2]

As is clear from the results shown in Table 2, Example 1 was obtained by dispersing the pigment dispersion with the integrated power per unit weight of the pigment dispersion applied to the Dynomill being 0.1 to 10 kWh / kg. It can be seen that the inks Nos. 1 to 3 have excellent reproducibility of the particle size distribution of the pigment as compared with the inks obtained in Comparative Examples.

[0062]

According to the production method of the present invention, the dependence on the viscosity and viscoelasticity of the pigment dispersion and the type of the disperser is small,
The management of the ink dispersion process is facilitated. Further, according to the production method of the present invention, the dispersion of the pigment in the obtained ink is very good, and the reproducibility of the particle size distribution of the pigment is excellent.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a process of an embodiment of a method for producing a water-based ink for inkjet recording of the present invention.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideki Yanagi 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Prefecture, Japan Kao Co., Ltd. ) Inventor Shigemi Wakabayashi 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Pref. In the Kao Co., Ltd. JP, A) JP-A-6-306317 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09D 11/00-11/20

Claims (3)

(57) [Claims] When a pigment dispersion obtained by preliminarily dispersing at least a pigment and a polymer dispersant in an aqueous liquid medium is dispersed in a sand mill, the integrated power per unit weight applied to the sand mill is 0.1 to 0.1. A method for producing a water-based ink for ink-jet recording, comprising 10 kWh / kg. 2. The method for producing an aqueous ink for inkjet recording according to claim 1, wherein the polymer dispersant is a copolymer of a (meth) acrylic acid derivative. 3. The polymer dispersant according to the following general formula (A)
And a copolymer obtained by polymerizing a monomer (b) represented by the following general formula (B):
A method for producing the aqueous ink for inkjet recording according to claim 2. Embedded image