JPH10316918A - Water-base ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink which has improved stability as a liquid and can give printed matter improved in water resistance and printing density by including a water-insoluble or difficultly water-soluble colorant adsorbed by a polyester and a specified benzenecarboxylic acid ester compound. SOLUTION: A neutralizing agent such as sodium hydroxide or potassium hydroxide is added to a mixture obtained by adding 5-50 pts.wt. polyester having an acid value of 3-100 KOHmg/g and a glass transition point of 30 deg.C or above, 0.05-20 pts.wt. benzenecarboxylic acid ester compound of the formula (wherein Ra is a 6-15 C hydrocarbon group; and n is 2-4) and a water-insoluble or difficultly water-soluble colorant to 100 pts.wt. solvent to ionize the carboxyl groups of the polyester. 100-300 pts.wt. water is added to 100 pts.wt. resultant mixture to effect its phase reversion and to thereby form a polyestercontaining suspension in the water phase. The mixture is heated to remove the solvent and the water to obtain an ink containing a suspension containing the colorant adsorbed by the polyester and the benzenecarboxylic acid ester compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink which is excellent in water resistance of printed matter and has improved print density and liquid stability, and is particularly useful as an ink for ink jet recording.

[0002]

2. Description of the Related Art Water-based inks are often used for printing and writing implements from the viewpoint of manufacturing and handling. For example, printer devices have become widespread due to the recent development and widespread use of computers, and water-based inks are used for these printers.

[0003] Ink used in an ink jet printer is usually a water-soluble dye which dissolves in water in order to prevent the nozzle from being clogged with the ink, but has a problem in the water resistance of the printed matter. Therefore, in order to improve the water resistance of the printed matter, the composition of the ink is important.

In order to improve the water resistance of the ink,
(A) using a pigment (Japanese Patent Laid-Open No. 4-28776,
JP-A-4-189876, JP-A-4-359907, JP-A-4-359907, etc.), (B) using a non-aqueous liquid medium (JP-A-4-261478),
(C) Using a water-resistant dye (US Pat. No. 4,963,318)
No. 9), and (D) those using emulsion-polymerized or dispersed-polymerized particles dyed with a dye (Japanese Patent Application Laid-Open No. Hei 3-250069,
6-340835) and the like.

[0005] However, when the pigment (A) is used, the saturation of printed matter may be reduced and clogging in the nozzle may occur. In addition, the fixability to paper or an OHP sheet is insufficient, and the recording preservation property is poor. Had a problem. In the case of (D) dyed polymer particles, it is difficult to dye at a high concentration,
When left for a long period of time, the dye was precipitated, and the liquid stability was poor. In addition, even in the proposals of (B) and (C), an ink which sufficiently satisfies all required characteristics such as water resistance and print density of a printed matter has not been obtained.

Accordingly, an object of the present invention is to provide a water-based ink which is excellent in water resistance of a printed matter and has improved print density and liquid stability.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and found that a water-based ink containing a water-insoluble or hardly water-soluble coloring material and a specific compound improves the water resistance of printed matter. It was also found that printing density and liquid stability were improved.

The present invention provides an aqueous ink comprising a suspension containing a polyester having a water-insoluble or poorly water-soluble coloring material adsorbed thereon and a benzene carboxylate compound represented by the following formula (1). By doing so, the above object has been achieved.

[0009]

Embedded image (In the formula, _Ra represents the same or different hydrocarbon group having 6 to 15 carbon atoms, and n represents 2 to 4.)

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water-based ink of the present invention contains a suspension containing a polyester to which a water-insoluble or poorly water-soluble coloring material is adsorbed and a benzenecarboxylic acid ester compound represented by the above formula (1). It is assumed that. That is, the water-insoluble or poorly water-soluble colorant is at least partially adsorbed by the micelle formed by the polyester or is enclosed in the micelle. The water-based ink of the present invention is a water-based ink in which micelles containing the polyester adsorbed with the water-insoluble or poorly water-soluble colorant and the benzenecarboxylic acid ester compound represented by the formula (1) exist as suspensions in water. It is.

The polyester according to the present invention preferably contains a unit derived from a diol component represented by the following formula (2) in a polyester chain.

[0012] The above polyester is JIS K007
Those having an acid value based on 0 of 3 to 100 KOH mg / g are preferred. If the acid value is less than 3 KOH mg / g, a suspension in which the coloring material is stably adsorbed may not be obtained. If the acid value exceeds 100 KOH mg / g, the water resistance may be poor. . More preferably, the acid value is from 3 to 70 KOH mg / g, further preferably from 10 to 60 KOH mg / g, and still more preferably from 15 to 70 KOH mg / g.
55KOHmg / g, more preferably 20-50KOH
mg / g, more preferably 25 to 50 KOH mg / g, is favorable in terms of suspension formability and stability.

The above polyester has a Tg (glass transition point) measured by DSC (differential scanning calorimetry) of 20 ° C. or more in an ink jet system using a piezoelectric element.
In an ink jet system using thermal energy, the temperature is preferably 30 ° C. or higher, and especially 40 ° C. or higher, regardless of both types.
50 ° C. or lower, more preferably 50 to 150 ° C. If the Tg is less than the above condition, the polyester may solidify in the nozzle of the ink jet printer and clogging may occur.

The polyester is preferably a polyester capable of forming micelles capable of adsorbing a water-insoluble or poorly water-soluble coloring material (hereinafter, also simply referred to as a "coloring material").

The above-mentioned polyester is not particularly restricted but includes, for example, a diol component represented by the following formula (2) [hereinafter referred to as component (a)] and a polycarboxylic acid derivative [hereinafter referred to as component (b)]. Is preferable [hereinafter, referred to as polyester (A)]. still,
In the present specification, the “polycarboxylic acid derivative” refers to a polycarboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof.

[0016]

Embedded image (Wherein, R represents an alkyl group having 1 to 4 carbon atoms, A represents an alkylene group having 2 to 4 carbon atoms, for example, an ethylene or propylene group, and x and y are the same or different one or more integers. And the average value of x + y is 2 to 10.)

As to the component (a), the diol component is not particularly limited, but is an alkylene oxide adduct of bisphenol A, preferably an ethylene oxide or propylene oxide adduct of bisphenol A. Is polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl)
Propane, polyoxypropylene (3.3) -2,2-
Bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0)-
Polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane and the like can be preferably used.

The polycarboxylic acid derivative as the component (b) is not particularly limited. For example, at least one selected from the group consisting of polycarboxylic acids, acid anhydrides and lower alkyl esters thereof Is used.

As the polyvalent carboxylic acid, divalent carboxylic acids and trivalent or higher carboxylic acids are used. Also,
As the lower alkyl ester of these polycarboxylic acids, an alkyl ester having 1 to 4 carbon atoms is used. Particularly, as the polycarboxylic acid, maleic acid, fumaric acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, n-dodecenyl succinic acid, divalent carboxylic acid such as dimer acid, or 1, 2,4-benzenetricarboxylic acid and trimellitic anhydride are preferred.

Further, the above polyester is represented by the above formula (2)
A diol component (that is, the component (a));
A copolymer obtained by co-condensation of a dimer acid (hereinafter, referred to as a component (b) ′) and a polycarboxylic acid derivative other than the dimer acid (hereinafter, referred to as a “component (b)”) is also preferable (hereinafter, referred to as a polyester (B)). ].

The component (a) used in the polyester (B) includes the same ones as those used in the polyester (A). Further, the component (b) ′ will be described.
The term “substance” refers to a substance synthesized by a polymerization reaction of two molecules of unsaturated fatty acids. As the dimer acid, for example, acyclic dimer acid, monocyclic dimer acid and bicyclic dimer acid are used. By using the above dimer acid, the formability and stability of the suspension and the adsorption amount of the coloring material are improved. The dimer acids may be used alone or in combination of two or more. As the dimer acid, commercially available products can also be used. Examples thereof include Unidim 22 (trade name, acyclic rich type) manufactured by Union Cap, Haridimmer 250K (trade name, monocyclic / bicyclic rich type) manufactured by Harima Kasei, and the like. In particular, those whose main component is an acyclic dimer acid are preferable from the viewpoint of suspension formability and stability.

The component (b) "used in the polyester (B) may be the same as the component (b) used in the polyester (A) except for dimer acid.

In the polyester (B), the molar ratio of the component (a) to the component (b) ′ and the component (b) ″ is determined by the acid value, number average molecular weight and Tg of the polyester (B). The above components may be freely combined within a range where the Tg is 20 ° C. or higher, depending on the value of the component (b) ′ and the component (b) ′ is preferably 1 mole of the component (a). , 0.001 to 0.7 mol, especially 0.01 to 0.1 mol.
5 moles are preferred. On the other hand, the amount of the component (b) ″ is preferably from 0.3 to 1.2 mol, particularly preferably from 0.5 to 1.1 mol, per 1 mol of the component (a).

Further, the above polyester is represented by the above formula (2)
A diol component (that is, the component (a));
Dimer acid [that is, the above (b) ′ component], trimellitic anhydride [hereinafter, referred to as the (b) ^* component], and a polyvalent carboxylic acid other than these acids [(b) ′ and (b) ^* component]. Those obtained by copolycondensation with an acid derivative (hereinafter, referred to as (b) ^** component) are also preferable (hereinafter, referred to as polyester (C)).

The component (a) used in the polyester (C) includes the same components as those used in the polyester (A). The component (b) ′ may be the same as that used for the polyester (B). The use of the trimellitic anhydride, which is the component (b) ^* , improves the suspension formability, stability, and color material adsorption amount. The trimellitic anhydride may be used alone or in combination of two or more.

The component (b) ^** used in the polyester (C) is the same as the component (b) used in the polyester (A) except for dimer acid and trimellitic anhydride. Can be used.

In the polyester (C), the component (a)
Minute and the component (b) 'and the component (b) ^*Ingredients and (b) above
^**The molar ratio to the components is determined by the acid value, the number, and the like of the polyester (C).
Although it depends on the average molecular weight and the value of Tg, etc.
The above components may be freely combined within the above range.
The preferred component ratio is that the component (b) 'is the component (a)
0.001 to 0.7 mol, especially 0.1 to 1 mol per minute.
It is preferably from 0.01 to 0.5 mol. The above (b)^*component
Is 0.05 to 0.7 with respect to 1 mol of the component (a).
Mole, especially 0.1 to 0.5 mole is preferred. Also,
(B)^**The component is added in an amount of 0.1 to 1 mol of the component (a).
The amount is preferably from 3 to 1.2 mol, particularly preferably from 0.5 to 1.1 mol.

For example, each co-condensation polymerization component at the time of co-condensation polymerization [the above components (a), (b), (b) ′, (b) ″,
The acid value, Tg, number average molecular weight, etc., by changing the addition ratio of (b) ^* and (b) ^** ], using a carboxylic acid ester, or blocking the acid with a monohydric alcohol. Can be adjusted. The method of the copolycondensation is not particularly limited, and a known method is used.

Further, the above polyester has a number average molecular weight (converted to polystyrene by gel permeation chromatography) of 500 to 100,000, and more preferably 1 to 100,000.
000 to 50,000, preferably 1500 to 30000, and more preferably 2000 to 15000, from the viewpoints of scorching to the printer head, water resistance of the ink after printing, and suspension formability.

The above polyester is used in an aqueous ink in an amount of 1 to
A blend of 50% by weight, especially 2 to 30% by weight is preferred. If the amount is less than 1% by weight, the print density is insufficient. If the amount is more than 50% by weight, the storage stability is deteriorated, and particularly, the amount of ink produced by ink evaporation at the nozzle tip of an inkjet printer is reduced. The above range is preferable because the printer head may be clogged due to thickening or suspension aggregation.

Next, the benzene carboxylate compound represented by the formula (1) according to the present invention will be described. The benzene carboxylate compound is compatible with the coloring material, and by the compatibility with the coloring material adsorbed on the suspension, prevents crystallization of the coloring material and improves the adsorption amount of the coloring material. In the above formula (1), _Ra is a hydrocarbon group having 6 to 15 carbon atoms, preferably 8 to 13 carbon atoms, and n is 2 to 4. Examples of the hydrocarbon group represented by R _a include 2-exylhexyl, isononyl, normal octyl, normal decyl, isodecyl,
And alkyl groups such as normal undecyl, normal dodecyl, and tridecyl. Here, as the benzene carboxylate compound, dialkyl benzenedicarboxylate (n = 2), trialkyl benzenetricarboxylate (n = 3) or tetraalkyl benzenetetracarboxylate (n = 4) is preferably used.

The dialkyl benzenedicarboxylate (n
= 2) include, for example, dialkyl phthalate, dialkyl isophthalate, and dialkyl terephthalate, with dialkyl phthalate being particularly preferred. Particularly, from the viewpoint of compatibility with the colorant, a compound in which both R _a in the above formula (1) are both 2-ethylhexyl groups, that is, benzenedicarboxylic acid-di-2-ethylhexyl, especially phthalic acid-di-2. -Ethylhexyl is preferred. As the dialkyl benzenedicarboxylate, commercially available products can also be used. For example, a vinylizer 80 manufactured by Kao Corporation,
Vinicizer 90, Vinicizer 85, Vinicizer 1
05, a vinylizer 124, and a vinylizer 20 (trade name).

Examples of the trialkyl benzenetricarboxylate (n = 3) include, for example, trialkyl trimellitate, trialkyl hemimellitate, and trialkyl trimesate. The trialkyl trimellitate represented is preferred.

[0034]

Embedded image (In the formula, R ₁ , R ₂ and R ₃ represent the same or different hydrocarbon groups having 6 to 15 carbon atoms.)

R ₁ , R ₂ and R ₃ in the trialkyl trimellitate represented by the above formula (1) ′ are the same or different and represent a hydrocarbon group having 6 to 15, preferably 8 to 13 carbon atoms. , and the examples of these include the same as the examples of R _a formula (1) described above. Especially in view of the compatibility of the colorant, the formula (1) three R _a are both in are also 2-ethylhexyl group compounds, namely benzene tricarboxylic acid - tri-2-ethylhexyl, especially trimellitic acid - tri - 2-Ethylhexyl is preferred. Commercial products can also be used as the trialkyl benzenetricarboxylate. For example, Kao Corporation's Talkyl
-08, T-09, T-10, N-08, NSK (trade name) and the like.

The tetraalkyl benzenetetracarboxylate (n = 4) includes, for example, tetraalkyl pyromellitate, tetraalkyl prenitate, tetraalkyl melophanate and the like. Particularly, the following formula (1) ″ Are preferred.

[0037]

Embedded image (In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent the same or different hydrocarbon groups having 6 to 15 carbon atoms.)

R _{1 to} R ₄ in the tetraalkyl pyromellitate represented by the above formula (1) ”are the same or different hydrocarbon groups having 6 to 15, preferably 8 to 13 carbon atoms, examples of these include the same as examples of R _a formula (1) described above. in particular in terms of compatibility with the color material, any four R _a in the formula (1) is 2 Preferred is a compound which is a -ethylhexyl group, that is, benzenetetracarboxylic acid-tetra-2-ethylhexyl, particularly pyromellitic acid-tetra-2-ethylhexyl. As the tetraalkyl benzenetetracarboxylate, a commercially available product can be used. For example, PN-08 series (trade name) manufactured by Kao Corporation and the like can be mentioned.

The above-mentioned benzenecarboxylic acid ester compounds may be used in combination so as to optimize the compatibility with the coloring material.

The benzenecarboxylic acid ester compound is contained in the water-based ink in an amount of 0.05 to 20% by weight, particularly 0.1% by weight.
Preferred is a blend of 10 to 10% by weight. If the amount is less than 0.05% by weight, the coloring material may not be stably adsorbed at a high concentration. If the amount exceeds 20% by weight, the stability of the suspension may decrease and the particle size of the suspension may increase. The above range is preferable.

Next, the color material will be described. The coloring material is not particularly limited as long as it is a water-insoluble or poorly water-soluble coloring material and can be adsorbed to the polyester.
Examples thereof include dyes such as oil-soluble dyes and disperse dyes, and pigments. Oil-soluble dyes and disperse dyes are particularly preferred from the viewpoint of good adsorption and encapsulation properties.

In the present specification, “pigment” means
The term "dye" refers to a substance which is dyed in a state of being dissolved in water or a solvent [Color Chemical Encyclopedia, March 1988]
Monthly First Press, CMC Corporation, Synthetic Organic Chemistry Association,
See page 45 and later].

The disperse dye is not limited, but
Preferred specific examples include C.I. I. Disperse Yellow series and the like.

The oil-soluble dye is not limited, but preferred specific examples thereof include C.I. I. Solvent Black 3 series.

From the viewpoint that the dye is efficiently adsorbed to the polyester by phase inversion emulsification described below, a solvent,
For example, 20 g / l or more, particularly 60 to 6
A dissolution of 00 g / l is preferred.

On the other hand, the pigment is not particularly limited, but it is particularly preferable to use azo pigments, phthalocyanine pigments, anthraquinone pigments, and carbon black pigments. In the present invention, a water-soluble dye such as an acid or basic dye may be directly used in combination.

The above-mentioned coloring material is preferably contained in the aqueous ink in an amount of 1 to 30% by weight, particularly 1.5 to 25% by weight. If the amount is less than 1% by weight, the print density is insufficient,
Even if the content exceeds 30% by weight, the print density cannot be significantly improved.
In addition, the stability over time of the particle diameter of the suspension decreases,
Since the average particle diameter increases, the dispersion stability of the suspension itself tends to decrease, and the above range is preferable.

The average particle diameter of the suspension containing the polyester to which a coloring material is adsorbed as a recording agent in the aqueous ink of the present invention and the above-mentioned benzenecarboxylic acid ester compound is as follows:
0.5 to 500 nm is preferred. When the average particle size is 0.
If it is less than 5 nm, ink bleeding may occur, and if it is more than 500 nm, the dispersion stability of the suspension itself may decrease, so the above range is preferable. The average particle diameter is 0.5 to 300 nm, more preferably 1 to 300 nm.
A thickness of 200 nm, more preferably 10 to 100 nm, is favorable in terms of suspension formability and stability. The average particle diameter can be adjusted, for example, by the conditions of phase inversion emulsification described below. The average particle diameter is measured by a conventionally known measuring method.

The water-based ink of the present invention uses water (preferably ion-exchanged water) as a medium and contains a suspension containing the above-mentioned colorant-adsorbed polyester and the above-mentioned benzenecarboxylic acid ester compound, and also contains a substantial amount of a suspension. Water-soluble alkyl glycine, conventionally known various additives, for example, wetting agents such as polyhydric alcohols, dispersants, silicone-based antifoaming agents, cationic, anionic or nonionic various surfactants Agent such as chloromethylphenol and / or chelating agent such as EDTA, oxygen absorber such as sulfite, benzotriazole, benzophenone, hydroxybenzoate, salsylate and cyanoacrylate It may contain an ultraviolet absorber such as a system.

The wetting agent is not particularly restricted but includes, for example, glycols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol and polyethylene glycol; glycerin; ethers of polyhydric alcohols such as diethylene glycol monobutyl ether. Thiodiglycol; one or more amino acids such as glycine, methylglycine, leucine, proline, ε-amino-n-caproic acid, alanine and phenylalanine. The amount of these components is preferably 0.1 to 50% by weight, particularly preferably 0.1 to 30% by weight in the aqueous ink.

The dispersant is not particularly restricted but includes, for example, known anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, polymer dispersants and the like. One or two or more are used. Above all, β-naphthalenesulfonic acid formalin condensate is particularly preferable because the average particle diameter of the suspension can be reduced and the dispersion stability of the suspension can be improved. The β-naphthalenesulfonic acid formalin condensate salt preferably has an HLB value of 5 to 15 from the viewpoint of exhibiting a dispersing effect and suppressing an increase in the average particle diameter of the suspension.

Commercially available products can also be used as the β-naphthalenesulfonic acid formalin condensate salt. For example, Kao Corporation dispersant Demol SNB, MS, N, SSL,
ST, P, and C (product names).

The above dispersant is usually added to aqueous inks in an amount of 0.1.
It is blended in an amount of from 0.01 to 10% by weight. When the amount of the dispersant is 0.1.
If the content is less than 01% by weight, it is difficult to reduce the particle size of the suspension. If the content is more than 10% by weight, the average particle size of the suspension may increase, suspension stability may decrease, or gelation may occur. Is desirable. The compounding amount of the dispersant is 0.05 to 5% by weight, particularly 0.1 to 5% by weight.
1% by weight is more preferred.

The defoaming agent is not particularly limited, but a silicone compound is particularly preferable in terms of suppressing the generation of bubbles during the preparation of the ink and adjusting the surface tension of the ink.

As the silicone compound, a commercially available product can also be used. For example, Shin-Etsu Silicone KF
96 series (trade name) and the like.

The above-mentioned silicone compound is preferably incorporated in an amount of 0.001 to 2% by weight in the aqueous ink. If the amount is less than 0.001% by weight, bubbles are likely to be generated at the time of preparation, and it is difficult to remove small bubbles. If the amount exceeds 2% by weight, repelling occurs at the time of printing, and the printing quality is reduced. In some cases, the above range is preferable. A more preferred amount is 0.005 to 0.5% by weight.

As the surface tension adjusting agent, the above-mentioned silicone-based antifoaming agent and various cationic, anionic or nonionic surfactants can be used. In particular, ethylene oxide compounds of alkyl phenols and ethylene oxide adducts of acetylene glycol suppress the generation of bubbles, are easy to adjust the surface tension of ink, and have good ink ejection properties, little bleeding, and no uneven print density. Is preferred.

It is desirable that the above-mentioned surface tension adjusting agent is blended in an amount of 0.005 to 15% by weight in the aqueous ink. If the amount is less than 0.005%, the above characteristics may not be exhibited. If the amount is more than 15% by weight, bleeding, uneven printing density, etc. may occur, resulting in poor print quality or ink liquid. The above range is desirable because the stability decreases.

Surface tension of water-based ink of the present invention (20 ° C.)
Is preferably in the range of 25 to 50 dyne / cm. 2
If it is less than 5 dyne / cm, ink bleeding and deterioration of print quality may occur, and ink leakage may occur from the print head nozzle. If it exceeds 50 dyne / cm, the ink drying speed becomes too slow, and Occasionally, due to the occurrence of printhead contamination or the like, or the occurrence of defective ink supply to the printhead nozzles, defective ink ejection or reduced print quality may occur. The surface tension is 28 to 43
Dyne / cm is more preferred. In addition, the color tone is magenta,
28 to 40 dyne / cm for cyan and yellow,
Further, 28 to 36 dyne / cm is preferable, and when the color tone is black, 28 to 40 dyne / cm is preferable. In order to keep the surface tension within the above range, for example, the concentration of the coloring material is adjusted, the concentration and the molecular weight of the polyester are adjusted, additives such as surface tension adjusters such as various surfactants are added, and the wetting agent is added. Means such as selection may be used. The measurement of the surface tension is as follows.
Automatic surface tensiometer (CBVP-Z) manufactured by Kyowa Interface Science Co., Ltd.
Type).

The viscosity of the water-based ink of the present invention is 20
The temperature is preferably 0.5 to 8 cps, more preferably 1 to 5 cps, and further preferably 1 to 3 cps. If it is less than 0.5 cps, bleeding of the ink becomes remarkable, and ink leakage from the print head nozzle occurs, which is not preferable. Also, 8c
If it exceeds ps, the viscosity becomes too high, ink is not supplied to the print head, ejection failure occurs, and blurring or deterioration in print quality occurs.
In order to make the viscosity within the above range, for example, means for adjusting the concentration of the coloring material, adjusting the concentration and molecular weight of the polyester, adding various surfactants and the like, additives such as surface tension adjusters, selecting a wetting agent, etc. May be used. In addition, the measurement of the viscosity is performed by
E-type viscometer manufactured by Tokyo Keiki (VISCONIC ELD)
Alternatively, the measurement is performed by a rotary vibration type viscometer (Viscomate VM-100) manufactured by Nikkato Tokyo Branch.

Next, the method for producing the water-based ink of the present invention will be described by taking the case of the polyester (A) as an example. The aqueous ink of the present invention is preferably produced by so-called phase inversion emulsification.

Here, the phase inversion emulsification is a method in which the polyester (A) obtained by copolycondensation of the above-mentioned component (a) and the above-mentioned component (b), and the above-mentioned benzene carboxylate compound together with a coloring material in a solvent. After the addition, a neutralizing agent is added to ionize the carboxyl groups in the polyester (A), and then water is added. Then, the solvent is distilled off and the phase is changed to an aqueous phase.

First, the polyester (A) and the benzene carboxylate compound are added to a solvent together with a coloring material. In this case, it is preferable to add 5 to 50 parts by weight of the polyester (A) based on 100 parts by weight of the solvent from the viewpoint of forming a suspension. The addition of 0.05 to 20 parts by weight of the benzene carboxylate compound to 100 parts by weight of the solvent is preferable from the viewpoint of suspension formation and high-concentration adsorption of the coloring material. Although it does not specifically limit as said solvent, For example, methyl ethyl ketone and tetrahydrofuran are preferable.

Next, a neutralizing agent is added to a mixture of the polyester (A), the benzene carboxylate compound, the coloring material, and the solvent to form a carboxyl group in the polyester (A). Ionize. The neutralizing agent can be used without any particular limitation as long as it can ionize the carboxyl group in the polyester (A). In particular, sodium hydroxide, potassium hydroxide, triethylamine and dimethylethanolamine are used. In addition, the particle diameter of the suspension is further reduced, and the stability of the suspension is further improved. Of these, the use of sodium hydroxide and potassium hydroxide is more preferable because the heat resistance of the suspension is improved. The amount of the neutralizing agent used may be at least an amount capable of ionizing a carboxyl group in the polyester (A).

After the addition of the neutralizing agent, when water is added to the mixture to cause phase inversion, a suspension containing the polyester (A) is formed in the aqueous phase. The amount of water is preferably from 100 to 300 parts by weight based on 100 parts by weight of the mixed solution. In this case, it is preferable to add the above β-naphthalenesulfonic acid formalin condensate to the mixed solution, because the average particle diameter of the suspension can be reduced. Further, it is preferable to add the silicone-based antifoaming agent or the surface tension adjusting agent to the mixed solution, because the generation of bubbles can be suppressed and the surface tension can be adjusted.

After the phase inversion is completed, the system is heated under reduced pressure. The present invention comprising a suspension containing a polyester (A) having a desired concentration and adsorbing a coloring material, and a benzenecarboxylic acid ester compound having a desired concentration by removing the solvent and a predetermined amount of water from the mixed solution. Water-based ink is obtained.

In preparing the water-based ink of the present invention, it is preferable to remove coarse particles. For example, the mixed ink is subjected to pressure filtration using a filter or a centrifugal separator, and the ink is mixed.
By removing particles having a size of 00 nm or more, preferably 1000 nm or more, more preferably 500 nm or more, an ink without clogging can be obtained.

As described above, the preferred method of producing the aqueous ink of the present invention has been described by using the polyester (A) as an example. The same applies to the polyester (B) and the polyester (C). In addition, the p of the aqueous ink of the present invention
As H, p is used to ensure suspension stability.
It is preferable to adjust so that H = 5 to 12, particularly 5.5 to 10.

The water-based ink of the present invention is particularly useful as a water-based ink for ink-jet recording, but can also be used as an ink for writing implements such as general fountain pens, ball-point pens, and felt-tip pens.

[0070]

EXAMPLES Next, the effectiveness of the water-based ink of the present invention will be illustrated by examples. However, the invention is not limited to such an embodiment.

Example 1 Polyoxypropylene (2.
2) 2 liters of 1050 g of 2,2-bis (4-hydroxyphenyl) propane, 90 g of an acyclic dimer acid mixture, 263 g of fumaric acid, 120 g of trimellitic anhydride, 0.8 g of hydroquinone and 2.3 g of dibutyltin oxide The flask was placed in a one-necked flask, and a thermometer, a stirring rod, a falling condenser, and a nitrogen inlet tube were attached. The reaction was carried out while stirring at 210 ° C. under a nitrogen stream in a mantle heater. The degree of polymerization was monitored from the softening point according to ASTM E28-67, and the reaction was terminated when the softening point reached 100 ° C. The obtained polyester (hereinafter, referred to as polyester) was a pale yellow solid, and the Tg by DSC was 60 ° C. Further, the acid value of the polyester based on JIS K 0070 was 42 KOH mg / g, and the number average molecular weight (in terms of polystyrene by gel permeation chromatography) was 4,100. Next, 150 g of the above polyester, 50 g of an oil-soluble dye (manufactured by Orient Chemical, OIL PINK 312), 6 g of di-2-ethylhexyl phthalate (manufactured by Kao Corporation, Vinicizer 80) and 500 g of methyl ethyl ketone were placed in a separable flask, and N ₂ was added. After the replacement, the mixture was stirred and completely dissolved. Subsequently, 11.11 g of dimethylethanolamine and 0.90 g of sodium hydroxide were added to ionize the carboxyl groups in the polyester. Furthermore, ion-exchanged water 9
After dropping 60 g, the suspension was heated to 40 ° C. under reduced pressure to remove methyl ethyl ketone, and a suspension containing polyester adsorbed with an oil-soluble dye and 0.5% by weight of di-2-ethylhexyl phthalate (average particle diameter: 20 nm, 20
% By weight) of an aqueous ink.

Example 2 The following polyester was used in place of the polyester used in Example 1,
By the same operation as in Example 1, a suspension containing polyester to which a coloring material was adsorbed and 0.5% by weight of di-2-ethylhexyl phthalate (average particle size: 40 nm, 20)
% By weight) of an aqueous ink. In an autoclave equipped with a polyester synthesis thermometer and a stirrer, 130 parts by weight of dimethyl terephthalate, 56 parts by weight of dimethyl isophthalate, 6 parts by weight of dimethyl sodium sulfoisophthalate, 159 parts by weight of ethylene glycol, and 30 parts by weight of tricyclodecane dimethanol 30 Parts by weight and 0.1 part by weight of tetrabutoxytitanate,
The ester exchange reaction was performed by heating at a temperature of 30 ° C. for 120 minutes. Thereafter, the temperature was raised to 240 ° C.
When the softening point reached 100 ° C. as 10 mmHg, the reaction was terminated, and a polyester was synthesized. The resulting polyester is a pale yellow-white solid, having a Tg of 50 ° C. and an acid value of 27.
KOH mg / g.

Example 3 The following polyester was used in place of the polyester used in Example 1, and trimellitic acid-tri-2-ethylhexyl [manufactured by Kao Corporation, T-Polymer, instead of di-2-ethylhexyl phthalate] 08 (trade name)] and an oil-soluble dye (Oient Chemical, OI
A suspension containing polyester adsorbed with a coloring material and tri-2-ethylhexyl trimellitate (average particle size: 23 nm, 20% by weight) was operated in the same manner as in Example 1 except that 60 g of L PINK 312) was used. ) Was obtained. Polyester synthetic polyoxypropylene (2.2) -2,2-bis (4-
1050 g of hydroxyphenyl) propane, 30% by weight of acyclic dimer acid compound and monocyclic dimer acid compound 1
90 g of a dimer acid mixture containing 0% by weight, 375 g of terephthalic acid, and 2.5 g of dibutyltin oxide were reacted with stirring at 210 ° C. for 8 hours under a nitrogen stream, and then 120 g of trimellitic anhydride was added to obtain an acid value. 48KOHmg
/ G was reached when the reaction was complete. The obtained polyester was a pale yellow solid, had a Tg of 52.5 ° C., a softening point of 98 ° C., and a number average molecular weight of 4,600.

Example 4 The following polyester was used in place of the polyester used in Example 1, and instead of di-2-ethylhexyl phthalate, pyromellitic acid-tetra-2-ethylhexyl [manufactured by Kao Corporation, PN- 08
(Trade name)], except that a suspension containing a polyester adsorbed with a coloring material and tetra-2-ethylhexyl pyromellitic acid (average particle size: 34 nm, 20% by weight) ) Was obtained. Polyester synthetic polyoxypropylene (2.2) -2,2-bis (4-
Hydroxyphenyl) propane 735 g, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 315 g, terephthalic acid 400 g, and trimellitic anhydride 130 g were used in the same manner as in the synthesis of polyester. The acid value is 52mg KO
When H / g was reached, the reaction was terminated and a polyester was obtained. Appearance is pale yellow solid, Tg is 65 ° C, softening point is 11
At 1 ° C., the number average molecular weight was 4,500.

Comparative Example 1 The same procedure as in Example 1 was repeated except that the polyester used in Example 1 was replaced with the polyester used in Example 2 and di-2-ethylhexyl phthalate used in Example 1 was not used. The same operation as in Example 1 was performed. However, most of the coloring materials used for the preparation precipitated and settled together with some of the polymers. Therefore, filtration is performed to remove sediment, and a suspension of polyester to which a coloring material is adsorbed (average particle size: 40 nm, 10% by weight)
Water-based ink was obtained.

Example 5 Using the aqueous ink obtained in Example 1, the following components were mixed in the following composition, and the obtained dispersion was filtered with a 1000 nm filter to remove coarse particles, and ink jet recording was performed. A water-based ink was obtained. Using this ink, printing was carried out using a commercially available color bubble jet printer manufactured by Canon (model number BJC-430J), and the water resistance, fixability and scratch resistance were evaluated by the following methods. as a result,
The ink of Example 5 was found to be excellent in water resistance, fixability, and abrasion resistance. Further, the amount of introduced coloring material, printing density and liquid stability were evaluated by the following methods. Table 1 shows the results. [Formulation] 60 g of the water-based ink obtained in Example 1 10 g of diethylene glycol 2 g of glycerin 1 g of acetylenol EH 27 g of ion-exchanged water

<Water resistance> Solid printing was carried out on recycled paper for PPC (manufactured by Nippon Kabushiki Kaisha, Ltd.), and after standing for 1 hour or more, it was immersed vertically in still water for 10 seconds and pulled up vertically as it was. After air drying in a room, the optical density of the white portion where no printing was performed was measured with a Macbeth densitometer RD918 (manufactured by Macbeth). <Fixing property> OHP sheet exclusively for inkjet (MJOH
A solid print was made on PSIN Epson), an eraser (width 18.5 mm) was fixed at an inclination of 45 °, a load of 1 kg was placed thereon, and rubbed five times back and forth, and the state of the print surface was visually observed. <Scratch resistance> Printing was performed on plain paper and an OHP sheet containing boehmite, and when the paper was rubbed with a nail, the lack of a printed image and the surrounding stain were examined. <Color material introduction amount>
It was dissolved in 40 g of toluene, the absorbance of the solution was measured, and the value of the coloring material was determined. It should be noted that the color material introduction amount can also be calculated from the color material / polymer amount at the time of producing the suspension. <Print Density> Printing was performed using solid printed paper using recycled paper for PPC [manufactured by Nippon Kaishi Paper Co., Ltd.], allowed to dry naturally in a room for 24 hours, and then using a Macbeth densitometer RD918 (manufactured by Macbeth). It was measured. <Liquid stability> The evaluation ink was placed in a constant temperature room at 50 ° C. for one month, and the particle size distribution before and after that was measured by a Coulter counter. ：: No change in particle size distribution at all, average particle size of 100 nm or less in monodispersed system ：: Fine change in particle size distribution, but average particle size of 100 nm or less in monodispersed system ×: Aggregation at liquid bottom Precipitation occurs

[Examples 6 to 8] A water-based ink for ink-jet recording was prepared in the same manner as in Example 5, except that the water-based ink obtained in Example 1 was replaced with the water-based ink obtained in Examples 2 to 4. Got each. Using this ink, the amount of the coloring material introduced was evaluated in the same manner as in Example 5. Table 1 shows the results.

Comparative Example 2 A water-based ink for inkjet recording was obtained in the same manner as in Example 5, except that the water-based ink obtained in Example 1 was replaced with the water-based ink obtained in Comparative Example 1. Using this ink, the amount of the coloring material introduced was evaluated in the same manner as in Example 5. Table 1 shows the results.

[0080]

[Table 1]

In the inks of Examples 5 to 8 containing the suspension containing the polyester to which the coloring material was adsorbed and the benzenecarboxylic acid ester compound, the print density of the printed matter was higher than that of the ink of the conventional formulation (Comparative Example 2). It can be seen that the liquid stability is improved. In addition, although not shown in Table 1, the inks of Examples 5 to 8 also had good evaluations on the fixability, water resistance, and rub resistance. Furthermore, there was no problem with the bleeding in the inks of Examples 5 to 8. As described above, the inks of Examples are excellent in print density and liquid stability of printed matter, and in particular, the inks of Examples 7 and 8 are all excellent, and a printed matter with high print density is obtained. I understand.

[0082]

According to the water-based ink of the present invention, the printed matter is excellent in water resistance and the print density and liquid stability are improved. Further, by performing the above-mentioned adsorption by phase inversion emulsification, the adsorption of the coloring material can be easily and efficiently performed, the bleeding of the ink is further prevented, and the water resistance and the fixing property are further improved. The water-based ink can be used as ink for writing implements such as general fountain pens, ballpoint pens, and felt-tip pens.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Kuniyasu Kawabe 1334 Minato, Wakayama-shi, Wakayama

Claims (2)

[Claims] 1. A water-based ink comprising a suspension containing a polyester to which a water-insoluble or poorly water-soluble coloring material is adsorbed and a benzenecarboxylic acid ester compound represented by the following formula (1). Embedded image (In the formula, _Ra represents the same or different hydrocarbon group having 6 to 15 carbon atoms, and n represents 2 to 4.) 2. A water-based ink for ink-jet recording, wherein the water-based ink according to claim 1 is used.