JP2000044852A - Aqueous-based ink for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject ink satisfying general ink properties and having excellent stability after preserving for a long period of time at a high temperature by including a specific betaine-based compound, etc., in an ink comprising an emulsion of colored polymer fine particles and suppressing a containing amount of a urea-based compound smaller than a specific amount. SOLUTION: This aqueous-based ink contains (A) an ink comprising (i) an ink colored with a coloring material such as an oil-soluble dye and (ii) an emulsion of polymer fine particles such as vinylic polymer fine particles, (B) a betaine-based compound of the formula (R1-R3 are each H or the like; R4 is a 1-5C alkylene) (e.g. N,N,N-trimethylglycine) and (C) a polyhydric alcohol such as diethylene glycol, and (D) preferably a content of a urea-based compound such as a urea is suppressed smaller than 6 wt.%. A preferable mixing ratio is 2-20 wt.% of the component A and 1.5-25 wt.% of the component A(i) is a solid based on whole of the ink, and 40-300 pts.wt. of the component B and 100-500 pts.wt. of the component C based on 100 pts.wt. of the component A(i).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording ink which satisfies general ink characteristics and has excellent stability after long-term storage at a high temperature of 60 ° C. or higher.

[0002]

BACKGROUND OF THE INVENTION The applicant of the present invention has previously disclosed in Japanese Patent Application Laid-Open Nos.
JP-A-286939 proposes an ink jet ink comprising a polymer emulsion in which polymer particles are impregnated with a coloring material for the purpose of improving water resistance and fixability on recording paper and preventing scorching of the ink to a printer head. . According to such an ink, the problems such as low water resistance of the conventional inkjet ink are solved. However, various performances required for ink-jet inks are becoming increasingly severe, and higher-performance inks are being demanded. In particular, if the ink comprising the polymer emulsion is stored at a high temperature of 60 ° C. or higher for a long period of time, the stability of the polymer fine particles may decrease. Therefore, further improvement in the high-temperature storage stability has been desired.

Accordingly, an object of the present invention is to provide an ink jet recording ink which satisfies general ink characteristics and has excellent stability after storage for a long time at a high temperature of 60 ° C. or higher.

[0004]

Means for Solving the Problems The inventors of the present invention have made an ink comprising a polymer emulsion contain a specific betaine compound and a polyhydric alcohol, and the content of the urea compound is not more than a specific amount. It has been found that the above object is achieved by the above.

The present invention has been made on the basis of the above findings, and is based on a water-based ink jet recording system containing a betaine compound represented by the following formula (1) and a polyhydric alcohol and containing not more than 6% by weight of a urea compound. The object has been achieved by providing an ink.

[0006]

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[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the water-based ink for ink-jet recording (hereinafter, simply referred to as "ink") of the present invention will be described. In the ink of the present invention,
A betaine compound represented by the above formula (1) is contained. By containing the betaine compound, the stability after long-term storage at a high temperature becomes extremely high, and a moisturizing effect is imparted to the ink, whereby the liquid stability is improved, and the ink ejection property is further improved.

In the above formula (1), as R ₁ , R ₂ and R ₃ , the same or different methyl, ethyl, propyl and isopropyl groups are preferably used. R
_{As 4} , a methylene group, an ethylene group, a propylene group and a butylene group are preferably used, and a methylene group is particularly preferably used. As the betaine-based compound, those having high solubility in water are particularly preferably used. Examples of such compounds include N, N, N-trimethylglycine, α-propiobetaine, γ-butyrobetaine, and the like. In particular, since N, N, N-trimethylglycine has good moisturizing property of the ink, the ejection property is improved and the clogging prevention property is good.

The betaine compound is preferably contained in an amount of 10 to 500 parts by weight, particularly 40 to 300 parts by weight, based on 100 parts by weight of the coloring material. When the content is within this range, sufficient high-temperature storage stability is exhibited.

The ink of the present invention contains a urea compound in an amount of 6% by weight or less, preferably 4% by weight or less. As a result of detailed studies by the present inventors, the use of the betaine-based compound represented by the above formula (1) and the urea-based compound gives the ink more moisture retention and further improves the liquid stability. It has been found that the ink ejection properties are further improved, but it has also been found that the storage stability of the ink at a high temperature of 60 ° C. or higher is reduced by the combined use of the betaine compound and the urea compound. As a result of a more detailed study, it has been found that the decrease in the high-temperature storage stability becomes practically practical if the content of the urea-based compound is 6% by weight or less. Therefore, in the present invention, the content of the urea-based compound is set to 6% by weight or less. A urea-based compound may not be contained in order not to be affected by the above combination at all. When two or more urea-based compounds are contained, the total content thereof is set to 6% by weight or less.

Examples of the urea compound include aliphatic urea and aromatic urea. Examples of the aliphatic urea include urea, methyl urea, dimethyl urea, trimethyl urea, tetramethyl urea, ethyl urea, and diethyl urea. Acetyl urea, biuret, allantoin, etc., and aromatic ureas include phenyl urea, benzyl urea, N-ethyl-
N'-phenylurea, ethoxyphenylurea, diphenylurea, tetraphenylurea, benzoylurea and the like. However, ethylene urea is excluded. In particular, it is preferable to use urea, methyl urea, dimethyl urea or ethyl urea together with the above-mentioned betaine compound in a specific amount or less from the viewpoint of ensuring high-temperature storage stability.

As the polymer emulsion, an emulsion of colored polymer fine particles colored with a coloring material is used, and particularly, an emulsion of polymer fine particles impregnated with a water-insoluble or poorly water-soluble coloring material is preferably used. In this specification, “impregnated with a coloring material” means one or both of a state in which the coloring material is sealed in the polymer fine particles and a state in which the coloring material is adsorbed on the surface of the polymer fine particles. In this case, it is not necessary that all the coloring materials to be incorporated in the ink of the present invention be encapsulated or adsorbed in the polymer fine particles, and the coloring materials are dispersed in the emulsion as long as the effects of the present invention are not impaired. Is also good. In a preferred embodiment of the present invention, the ink comprises an aqueous dispersion (emulsion) of polymer fine particles impregnated with a water-insoluble or poorly water-soluble coloring material, and contains the betaine-based compound and the urea-based compound in an amount of 6%. % Or less, and further contains a polyhydric alcohol described below.

The coloring material is not particularly limited as long as it is water-insoluble or hardly water-soluble and can be adsorbed by the polymer. In this specification,
The term “water-insoluble or poorly water-soluble” means that at least 10 parts by weight of a coloring material does not dissolve in 100 parts by weight of water at 20 ° C. It is not allowed. Examples of the coloring material include dyes such as oil-soluble dyes and disperse dyes, and pigments. In particular, oil-soluble dyes and disperse dyes are preferred from the viewpoint of good adsorption and encapsulation properties.

Each of the dyes used in the present invention is preferably an organic solvent,
For example, in a ketone-based solvent, 2 g / liter or more, especially 20 g / l
It is preferable to dissolve in an amount of up to 600 g / liter.

The above-mentioned coloring material is contained in the ink of the present invention in an amount of 1 to 30% by weight, particularly 1.5 to 25% by weight, from the viewpoints of ensuring a sufficient printing density and ensuring the stability of the polymer fine particles. Is preferred. Further, the content of the coloring material is preferably about 10 to 200% by weight, particularly about 25 to 150% by weight based on the weight of the polymer in relation to the content of the polymer.

As the polymer forming the polymer emulsion, for example, a vinyl polymer, a polyester polymer, a polyurethane polymer and the like can be used. Particularly preferably used polymers are vinyl polymers and polyester polymers. Less than,
Each of these polymers will be described.

The vinyl-based polymer includes a silicone macromer represented by the following formula (2) and at least one polymer selected from the group consisting of acrylamide and methacrylamide-based monomers (excluding those having a salt-forming group). Vinyl obtained by copolymerizing a reactive monomer (a), a polymerizable unsaturated monomer (b) having a salt-forming group, and a monomer (c) copolymerizable with these monomers in the presence of a radical polymerization initiator. It is preferable to use a system polymer in that scoring resistance is improved.

[0018]

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The silicone macro represented by the above formula (2)
In the mer, X represents a polymerizable unsaturated group;
CH_Two= CH- and CH_Two= C (CH_Three)-Group
Is mentioned. Y represents a divalent linking group, specifically-
COO-, -COOC_bH_2b-(Where b is a number from 1 to 5
And a phenylene group. _Three
H₆-Is preferred. R_FiveIs a hydrogen atom; methyl or ethyl
A lower alkyl group such as a group; an aryl group such as a phenyl group;
Indicates an alkoxy group such as a toxic group, and is a methyl group
Is preferred. Z is a number average molecular weight of at least about 500
[Gel permeation chromatography (hereinafter referred to as GP
C) and converted to polyethylene. Hereinafter the same)
Monovalent siloxane polymer portion, preferably several
Monovalent dimethyl siloxane having an average molecular weight of 800 to 5000
It is a polymer. n is 0 or 1, preferably 1.
is there. m is an integer of 1 to 3, and is preferably 1.

Preferred silicone macromers include:
Examples described in paragraphs [0016] of columns 5 to 6 of JP-A-9-286939 filed by the applicant of the present invention, etc., are particularly preferable, and particularly preferable ones are column 5 to column 6 of the same. The silicone macromer [FM-0711 (trade name) manufactured by Chisso Corporation] described in the paragraph number [0020] of the above.

As the acrylamide or methacrylamide monomer (hereinafter referred to as “(meth) acrylamide monomer”), those described in JP-A-9-286939, column 5, line 40 to column 7, line 22 are used. Acrylamide, N- (1,1-dimethyl-3-oxobutyl) acrylamide (diacetone acrylamide), N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-diisopropylacrylamide, N, N- Dibutyl acrylamide, N-t-butylacrylamide, N-t-hexylacrylamide, N-
Acrylamide monomers such as t-octylacrylamide, N-benzylacrylamide, N-isopropylacrylamide, N-methylolacrylamide, N-cyclohexylacrylamide, and methacrylamide, N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, N -T-butyl methacrylamide,
N-t-octyl methacrylamide, N-isopropyl methacrylamide, N-methylol methacrylamide,
It is preferable to use a methacrylamide monomer such as N-cyclohexyl methacrylamide.

As the polymerizable unsaturated monomer (b),
JP-A No. 9-286939, column 7, line 23 to column 8, line 29 and the like are used. In particular, as cationic monomers, unsaturated tertiary amine-containing monomers, unsaturated ammonium salt-containing monomers, and the like are used. Specific examples thereof include monovinylpyridines such as vinylpyridine, 2-methyl-5-vinylpyridine and 2-ethyl-5-vinylpyridine; N, N-dimethylaminostyrene, and N, N-dimethylaminomethylstyrene. Styrenes having a dialkylamino group such as N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N
Esters having a dialkylamino group of acrylic acid or methacrylic acid such as -dimethylaminopropyl acrylate and N, N-diethylaminopropyl methacrylate; vinyl ethers having a dialkylamino group such as 2-dimethylaminoethyl vinyl ether;
(N ', N'-dimethylaminoethyl) acrylamide, N
Having a dialkylamino group such as-(N ', N'-dimethylaminoethyl) methacrylamide, N- (N', N'-diethylaminoethyl) acrylamide, N- (N ', N'-diethylaminoethyl) methacrylamide Acrylamide or methacrylamide, or those obtained by quaternizing them with a known quaternizing agent such as an alkyl halide (alkyl group having 1 to 4 carbon atoms) and the like can be mentioned. Also,
Examples of the anionic monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.Specifically, as the unsaturated carboxylic acid monomer, acrylic acid, methacrylic acid, itaconic acid, There are maleic acid and the like, or anhydrides and salts thereof, and unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-
There are acrylamide-2-methylpropanesulfonic acid and the like and salts thereof, and other sulfuric acid monoesters of 2-hydroxyethyl (meth) acrylic acid and their salts. Examples of unsaturated phosphoric acid monomers include vinyl phosphate, diphenyl-2- and the like. It is preferable to use methacryloyloxyethyl phosphate or the like.

As the monomer (c) copolymerizable with the monomers (a) and (b), those described in JP-A-9-286939, column 8, line 30 to column 9, line 1 can be used. Especially methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, acrylic acid 2
-Acrylates such as ethylhexyl and dodecyl acrylate; methacrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate; styrene Styrene-based monomers such as styrene and 2-methylstyrene; hydroxyl-containing acrylates and methacrylates such as 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate and 3-hydroxypropyl methacrylate; polymerizable functional groups at one end A vinyl macromer composed of a vinyl polymer having a polymer, a polyester macromer composed of a polyester having a polymerizable functional group at one end, and a polyurethane having a polymerizable functional group at one end. Polyurethane macromer,
It is preferable to use a polyalkyl ether macromer composed of a polyalkyl ether having a polymerizable functional group at one end.

The monomer (c) is not limited to the above, and a commercially available radical copolymerizable monomer can also be used. In particular, it is preferable to use one or more monomers represented by the following formulas (3-1) to (3-4) from the viewpoint of storage stability of the emulsion.

[0025]

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As the monomers represented by the above formulas (3-1) to (3-4), commercially available products can also be used. For example, styrene and / or acrylonitrile copolymer macromer having a methacryloyloxy group at one end [AN-6, AS-6 (trade name) manufactured by Toagosei Co., Ltd.], methacrylic acid having a methacryloyloxy group at one end Methyl polymer macromer [Toa Gosei Co., Ltd., AA-6 (trade name)], polyoxyethylene macromer having a methacryloyloxy group at one end [Shin Nakamura Chemical Co., Ltd., NK ester M-90Gne
w, M-40Gnew and M-20Gnew (trade name)], polyester macromers having a methacryloyloxy group at one end [FM4DX (trade name) manufactured by Daicel Chemical Industries, Ltd.] and the like.

When synthesizing the vinyl polymer, the monomer (a) is used in an amount of 1 to 40 with respect to the total amount of the monomers.
% By weight of the above monomer (b),
The copolymerization is preferably carried out using 25% by weight of the monomer (c) in a proportion of 35 to 96% by weight based on the total amount of the monomers.

The above-mentioned vinyl polymer is disclosed in JP-A-9-28.
No. 6,939, column 9, lines 10 to 23, and is particularly preferably produced by a solution polymerization method.

In the copolymerization, a radical polymerization initiator is used. Examples thereof include those described in JP-A-9-286939, column 9, lines 24 to 36.
2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), dimethyl- 2,2'-azobisbutyrate, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (1-
It is preferable to use an azo compound such as cyclohexanecarbonitrile). These radical polymerization initiators are used in an amount of 0.001 to 2.0 mol%, preferably 0.01 to 1.
It is preferable to use 0 mol%.

At the time of copolymerization, a polymerization chain transfer agent may be further added. Specific examples of the polymerization chain transfer agent include JP-A-9-286939, column 9, line 37 to column 10, column 1.
Examples thereof include those described in line 0; particularly, mercaptans such as mercaptoethanol, n-dodecylmercaptan, and t-dodecylmercaptan; xanthogen disulfides such as dimethylxanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide; tetrachloride Halogenated hydrocarbons such as carbon; hydrocarbons such as pentaphenylethane; and acrolein;
Unsaturated cyclic hydrocarbon compounds such as methacrolein, allyl alcohol, and α-methylstyrene dimer (preferably containing 50% by weight or more of 2,4-diphenyl-4-methyl-1-pentene); xanthene, 2,5- It is preferable to use an unsaturated heterocyclic compound such as dihydrofuran.

The weight-average molecular weight (converted to polyethylene by GPC; the same applies hereinafter) of the vinyl polymer thus obtained is preferably from 3,000 to 50,000.

As the polyester-based polymer, JIS
An acid value based on K0070 of 3 to 100 KOHmg /
g is preferably used. The acid value is 3 KOHm
g / g, a polymer emulsion in which a coloring material is stably impregnated may not be obtained.
If it exceeds g / g, the water resistance of the ink may be inferior. The acid value is more preferably 3 to 90 KOH mg / g, further preferably 30 to 80 KOH mg / g, particularly preferably 50 to 70 KOH mg / g.
A KOH mg / g yields good results in terms of improved emulsion formation and stability.

The polyester-based polymer has a number average molecular weight of preferably 500 to 100,000, more preferably 1,000 to 50,000, and still more preferably 1500.
~ 30000, even more preferably 2000-1500
A value of 0 is preferable from the viewpoints of scorching to the printer head, water resistance and scratch resistance of the printed ink, and emulsion formation.

Examples of the polyester-based polymer having the above preferable physical properties include, for example, those containing a unit derived from a diol component represented by the following formula (4) in a polyester chain. In particular, a diol component represented by the following formula (4) (hereinafter, referred to as component (a)) and a polycarboxylic acid and / or a derivative thereof (hereinafter, referred to as component (b)) are co-condensed and polymerized. Is preferred.

[0035]

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The diol component represented by the above formula (4), which is the component (a), is preferably an alkylene oxide adduct of bisphenol A, particularly an ethylene oxide or propylene oxide adduct of bisphenol A.

The polyvalent carboxylic acid and / or the component (b)
Alternatively, as the derivative thereof, for example, at least one selected from the group consisting of polyvalent carboxylic acids, acid anhydrides thereof, and lower alkyl esters thereof is used.

As the polyvalent carboxylic acid, a divalent or higher carboxylic acid is used. As the lower alkyl ester of these polyvalent carboxylic acids, an alkyl ester having 1 to 4 carbon atoms is used. In particular, as the polyvalent carboxylic acid, a divalent carboxylic acid such as maleic acid, fumaric acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, dimer acid, or 1,2,4-benzenetricarboxylic acid It is preferable to use an acid or trimellitic anhydride.

The polyester-based polymer is obtained by co-condensation polymerization of the diol component and a polycarboxylic acid and / or a derivative thereof. The copolycondensation method is not particularly limited, and a known method is used. The above (a) component and the above (b)
The molar ratio of the component (b) to the component (a)
The components are preferably used in an amount of 0.01 to 1.4 mol, particularly preferably 0.1 to 1.2 mol.

Of the above polyester polymers, a diol component represented by the above formula (4) (the component (a)), trimellitic anhydride (hereinafter also referred to as the component (b) ′), and trimellitic anhydride A polyester polymer (hereinafter, referred to as polyester A) obtained by copolycondensation of a polycarboxylic acid other than an acid and / or a derivative thereof (hereinafter, also referred to as "(b)") is preferable.

By using the component (b) ′, the formability and stability of the emulsion and the amount of colorant adsorbed are improved.
The bonding form of trimellitic anhydride in the polyester A is such that the cyclic anhydride site in trimellitic anhydride is opened,
It is in a state of being incorporated in the polyester chain. It is preferable to use the acid anhydride instead of the trimellitic acid itself, particularly since the effects of high reactivity during the synthesis of the polyester and high formation of the emulsion are exhibited.

The above (b) "used for the above polyester A
It is preferable to use a component obtained by removing trimellitic anhydride from the above-mentioned component (b) used in the above-mentioned polyester.

The molar ratio of the component (a), the component (b) ′, and the component (b) ″, which is a copolycondensation component in the polyester A, is as follows: b) The component is 0.
It is preferably from 0.5 to 0.7 mol, particularly preferably from 0.1 to 0.5 mol. The component (b) "is present in an amount of 0.3 to 1.2 mol, especially 0.5 to 1.2 mol.
1.1 mole is preferred.

A polyester polymer obtained by adding a dimer acid to the above-mentioned polyester A component and subjecting it to copolycondensation is also preferable. The dimer acid is a substance synthesized by a polymerization reaction of two unsaturated fatty acids, and includes, for example, an acyclic dimer acid, a monocyclic dimer acid, and a bicyclic dimer acid. Used. Commercially available products include Unidim 22 (trade name, manufactured by Union Cap Co., Ltd.) and Haridima (trade name, manufactured by Harima Kasei Co., Ltd.). By using the above dimer acid, the formability and stability of the emulsion are improved, and the coloring material is easily impregnated. Acyclic dimer acids are particularly preferred from the viewpoint of further improving the formability and stability of the emulsion.

The dimer acid is used in an amount of 0.001 to 0.7 mol, preferably 0.01 to 0.5 mol, per 1 mol of the component (a).
Molar is preferred. Other preferred component ratios are as described above.

The above polyester-based polymer preferably has a glass transition point (hereinafter, referred to as Tg) of 20 ° C. or higher, and particularly preferably 50 to 150 ° C. The temperature is preferably 20 ° C. or higher for an ink jet system using a piezoelectric element, and 30 ° C. or higher for an ink jet recording system using thermal energy. Outside of these preferred ranges, the polyester-based polymer tends to solidify at the nozzle of the printer, and the nozzle may be clogged. In addition, when the printed papers are overlapped, paper reflection of the ink may occur. In addition, Tg is measured by a differential scanning calorimeter (hereinafter, referred to as DSC).

The above-mentioned various polymers are used as solid components in the ink of the present invention from the viewpoint of securing a sufficient print density and preventing the printer head from being clogged due to thickening of the ink due to evaporation and aggregation of the polymer fine particles. 1 to 30% by weight,
In particular, it is preferably contained in an amount of 2 to 20% by weight.

The ink of the present invention contains a polyhydric alcohol. This polyhydric alcohol is used as a wetting agent, for example, ethylene glycol,
Examples include propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, and ethers thereof. These polyhydric alcohols are preferably contained in an amount of 50 to 1000 parts by weight, particularly 100 to 500 parts by weight, based on 100 parts by weight of the coloring material, from the viewpoint of improving moisture retention and initial ejection stability.

The ink of the present invention uses water (preferably ion-exchanged water) as a medium, and its amount is preferably 50 to 50%.
It is 98% by weight, more preferably 55-95% by weight, and even more preferably 60-90% by weight.

The ink of the present invention contains, in addition to the above-mentioned components, an alkyl phosphate in order to prevent ink ejection failure due to stains on the face surface of the print head and to improve the accuracy of the landing position of ink droplets. And a phosphate salt such as polyoxyethylene alkyl ether phosphate. These phosphoric ester salts are preferably monoester salts or diester salts, and particularly preferably diester salts. The alkyl group in the above alkyl phosphate preferably has 8 to 18 carbon atoms. Similarly, the number of carbon atoms of the alkyl group in the polyoxyethylene alkyl ether phosphate is preferably 8 to 18, and the number of moles of the oxyethylene group added is preferably 0 to 20 mol. The content of the phosphoric acid ester salt is 0.01 to 50 parts by weight with respect to 100 parts by weight of the coloring material from the viewpoint of preventing ink ejection failure due to scorching of the coloring material on the head and improving the accuracy of the landing position of the ink droplet. Parts, especially 0.1 to 40 parts by weight.

It is also preferable that the ink of the present invention contains an alkoxypropanediol represented by the following formula (5), an oxyalkylene derivative thereof, or glyceryl ether. Particularly preferred is glyceryl ether (having an alkyl group having 1 to 10 carbon atoms). It is also preferable to include a monohydric alcohol. Particularly, methanol, ethanol, isopropyl alcohol, n-butyl alcohol, octyl alcohol and the like are preferable. Further, these monohydric alcohols may be used in combination with the above-mentioned alkoxypropanediol or its oxyalkylene derivative. The content of each of these components is 0.00 parts by weight with respect to 100 parts by weight of the coloring material in order to prevent the face of the print head from being stained and to promote the penetration of the ink into the paper.
It is preferably 1 to 50 parts by weight, particularly preferably 0.1 to 40 parts by weight.

[0052]

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Further, various known additives such as dispersants, silicone-based antifoaming agents, surface tension regulators, benzotriazole, benzophenone, and the like may be added to the ink of the present invention.
UV absorbers such as salicylic acid ester and cyanoacrylate, fungicides such as chloromethylphenol, EDT
A chelating agent such as A and an oxygen absorbent such as a sulfite may be blended.

The dispersant is preferably contained in the ink of the present invention in an amount of usually 0.01 to 10% by weight, from the viewpoint of reducing the particle size of the polymer fine particles and the stability of the emulsion. -5% by weight, more preferably 0.1-1% by weight.

The antifoaming agent is used in the ink of the present invention in an amount of from 0 to 2;
% By weight, especially 0.001-2% by weight, especially 0.00
It is preferred that the content be 5 to 0.5% by weight. When the amount of the defoamer exceeds 2% by weight, the generation of foam is suppressed,
In printing, repelling may occur in the ink, and the printing quality may be degraded.

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, the use of a silicone-based antifoaming agent, an ethylene oxide compound of an alkyl phenol, or an ethylene oxide adduct of acetylene glycol suppresses the generation of bubbles, facilitates adjustment of the surface tension of the ink, and causes ink ejection and bleeding. This is preferable in that there is little unevenness in print density. These surface tension adjusters are desirably contained in the ink of the present invention in an amount of 0.005 to 15% by weight from the viewpoints of printing quality and ink stability.

The ink of the present invention has a surface tension at 20 ° C. of 25 to 65 mN / m, particularly 28 to 50 mN, in order to prevent bleeding of the ink and deterioration of print quality and to prevent ink leakage from the print head nozzles. / M. The surface tension can be measured by an automatic surface tensiometer (CBVP-Z type) manufactured by Kyowa Interface Science Co., Ltd.

The ink of the present invention has a viscosity at 20 ° C. of 0.5 to 8 mPa · sec, particularly 1 to 5 from the viewpoint of ejection stability when used in an ink jet printer.
It is preferably mPa · sec. The above viscosity is
E-type viscometer (VISCONIC E) manufactured by Tokyo Keiki Co., Ltd.
LD) or a rotational vibration type viscometer (Viscomate VM-100) manufactured by Nikkato Tokyo Branch.

Next, a preferred method for producing the ink of the present invention will be described. First, the polymer and the coloring material are added to an organic solvent. Next, a neutralizing agent and, if necessary, a surfactant are added to the obtained solution or dispersion to ionize the salt-forming groups in the polymer. Next, when water is added to the obtained mixture, emulsification is performed using a known emulsification method. Examples of the emulsification method include a method using an emulsifier such as a microfluidizer and a phase inversion emulsification method.
Thereafter, the organic solvent is distilled off from the emulsion by heating the system under reduced pressure. Thus, an emulsion of polymer fine particles impregnated with the coloring material is obtained.

By dissolving various hydrophobic stabilizers together with the coloring material in the water-insoluble organic solvent at the time of preparing the emulsion, the stabilizers can be encapsulated in the polymer. Examples of the stabilizer include, but are not particularly limited to, ultraviolet absorbers such as benzotriazole, benzophenone, salicylate, and cyanoacrylate described above; primary antioxidants such as hindered phenol-based and amine-based agents; Secondary antioxidants, such as phosphorus and sulfur, and ultraviolet stabilizers, such as hindered amine, can be used.

The emulsion of the polymer particles impregnated with the coloring material contains the above-mentioned betaine-based compound and further contains the above-mentioned urea-based compound in an amount of 6% by weight or less, or does not contain the urea-based compound. Further, by adding and dispersing other components as necessary, the ink of the present invention can be obtained.

In preparing the ink of the present invention, it is preferable to remove coarse particles. For example, the prepared ink is subjected to pressure filtration by a filter or treatment by a centrifugal separator, and is preferably 2000 nm or more, more preferably 10 nm or more.
By removing particles having a size of 00 nm or more, more preferably 500 nm or more, an ink without clogging can be obtained.

The pH of the polymer emulsion thus obtained and the final ink are preferably 5 to 12, preferably 5.5 to 10, in order to ensure the stability of the emulsion.

The ink of the present invention is used as an ink for ink-jet recording, but may be used as other inks, for example, as ink for writing implements such as general fountain pens, ball-point pens, and felt-tip pens.

[0065]

EXAMPLES In the examples, "%" is based on weight unless otherwise specified.

[Production Example 1] In a reactor equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, 20 g of methyl ethyl ketone as a polymerization solvent, and monomers initially charged as shown in Table 1 as a polymerizable unsaturated monomer Was charged, and the nitrogen gas was sufficiently replaced. On the other hand, in the dropping funnel, the monomers and polymerization chain transfer agents described in the column of dropped monomers in Table 1, 60 g of methyl ethyl ketone, and 0.2 g of 2,2′-azobis (2,4-dimethylvaleronitrile) were added. It was charged after sufficient nitrogen substitution. Under a nitrogen atmosphere, the temperature of the mixture in the reaction vessel was raised to 65 ° C. while stirring, and the mixture in the dropping funnel was gradually added dropwise over 3 hours. Two hours after the completion of the dropwise addition, a solution prepared by dissolving 0.1 g of 2,2′-azobis (2,4-dimethylvaleronitrile) in 5 g of methyl ethyl ketone was added thereto, and further added at 70 ° C. for 2 hours at 65 ° C.
After aging at 2 ° C. for 2 hours, a vinyl polymer solution was obtained.

A part of the obtained vinyl polymer solution was
It was dried at 105 ° C. under reduced pressure for 2 hours and isolated by completely removing the solvent. The weight average molecular weight and Tg of this vinyl polymer were measured using GPC (solvent: tetrahydrofuran) and DSC, respectively.
Approximately 10,000 and 180 ° C.

The vinyl polymer solution obtained above was dried under reduced pressure. To 5 g of the vinyl polymer obtained, 25 g of toluene and 5 g of Vail Fast Blue 2606 (manufactured by Orient Chemical Co., Ltd.) were added and completely dissolved. 2 g of an aqueous sodium hydroxide solution was added to partially neutralize the salt-forming groups of the vinyl polymer. Next, 300 g of ion-exchanged water was added,
After stirring, the mixture was emulsified at 8500 psi for 30 minutes using a microfluidizer (manufactured by Microfluidizer). The obtained emulsion was completely removed by removing toluene at 60 ° C. under reduced pressure, and further concentrated by removing a part of water to obtain an emulsion of vinyl polymer fine particles impregnated with a hydrophobic dye (average particle size: 98 nm). , Solid concentration; 10
%).

[0069]

[Table 1]

[Examples 1 and 2 and Comparative Example 1] The emulsion of the vinyl polymer fine particles obtained in Production Example 1 was mixed with each component according to the following formulation, and the resulting dispersion was mixed with 0.2 μm.
The resulting mixture was filtered through a filter of m to remove dust and coarse particles to obtain water-based inks.

[Formulation of Example 1] 12 g of the emulsion (solid content) obtained in Production Example 1 10 g of N, N, N-trimethylglycine 5 g of diethylene glycol Electrostripper F [trade name, manufactured by Kao Corporation] 1 g (potassium polyoxyethylene alkyl ether phosphate), ion-exchanged water 72 g

[Blending of Example 2] 10 g of the emulsion (solid content) obtained in Production Example 1 10 g of α-propiobetaine 10 g of urea 4 g of diethylene glycol 5 g of dialkyl phosphate sodium salt (alkyl group having 8 carbon atoms) 1g ・ Ion exchange water 70g

[Compound of Comparative Example 1] 10 g of the emulsion (solid content) obtained in Production Example 1 8 g of urea 5 g of diethylene glycol 2 g of n-butyl alcohol 1 g of acetylenol EH 1 g of ion-exchanged water

Example 3 Polyoxypropylene (2.
2) 90 g of a dimer acid mixture containing 1050 g of 2,2-bis (4-hydroxyphenyl) propane, 30% of an acyclic dimer acid compound and 10% of a monocyclic dimer acid compound, 270 g of fumaric acid, and trimellitic anhydride 12
0 g and hydroquinone 1.5 g were placed in a glass 2-liter four-necked flask, and a thermometer, a stainless steel stirring rod,
A falling condenser and a nitrogen inlet tube were attached to this. The reaction was carried out while stirring at 210 ° C. under a nitrogen stream in a mantle heater. The degree of polymerization is ASTM E28
Tracking is performed from the softening point according to −67, and the softening point is 100
The reaction was terminated when the temperature reached ° C. The obtained polyester was a pale yellow solid, and the Tg by DSC was 58 ° C. The acid value of the polyester based on JIS K0070 is 53 KOH mg / g, and the number average molecular weight (G
(In terms of polystyrene by PC) was 5,500. Next, the polyester 150 g, an oil-soluble dye (Orient Chemical Industries, OIL BLACK 860) to 70g and tetrahydrofuran 500g placed in a separable flask, the flask after N ₂ substitution and stirred in tetrahydrofuran said polyester and an oil-soluble dye Completely dissolved. Subsequently, 13.90 g of dimethylethanolamine and 1.13 g of sodium hydroxide were added to ionize the carboxyl groups in the polyester. Further, a mixed aqueous solution composed of 960 g of ion-exchanged water, 3 g of a formalin condensate of naphthalenesulfonic acid (HLB value 8.51) and 50 g of N, N, N-trimethylglycine was added dropwise, and the mixture was stirred under reduced pressure. And heated to 40 ° C. to remove tetrahydrofuran, and an emulsion of polyester fine particles containing 8% of N, N, N-trimethylglycine and impregnated with a coloring material (oil-soluble dye) (average particle size: 20 nm, solid Partial concentration;
20%). Using the emulsion, the following components were mixed with each other, and the resulting dispersion was filtered with a 0.2 μm filter to remove dust and coarse particles to obtain an aqueous ink. -20 g of the above-mentioned emulsion (solid content) (containing 8 g of N, N, N-trimethylglycine)-5 g of diethylene glycol-2 g of glycerin-1 g of sodium dialkylphosphate (carbon number of alkyl group 8) 1 g-72 g of ion-exchanged water

Example 4 and Comparative Example 2 In Example 3, 50 g of γ-propiobetaine and 4 g of urea were used instead of 50 g of N, N, N-trimethylglycine (Example 4). An ink was obtained in the same manner as in Example 1 except that 50 g of N, N, N-trimethylglycine and 8 g of urea were used (Comparative Example 2).

[Evaluation of Performance] The inks obtained in Examples and Comparative Examples were evaluated for water resistance, print density and high-temperature storage stability by the following methods. Table 2 shows the results.

<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 light density of the white portion where no printing was performed was measured with a Macbeth densitometer RD918 (manufactured by Macbeth), and the water resistance was evaluated according to the following criteria. ：: The optical density of the white portion is 96% or more before immersion. ：: The optical density of the white portion is 90% or more and less than 96% before immersion. X: The optical density of the white portion is less than 90% before immersion.

<Print Density> Solid printing was carried out on recycled paper for PPC [manufactured by Nippon Kaishi Paper Co., Ltd.], and after natural drying in a room for 24 hours, the optical density was measured using a Macbeth densitometer RD918.
(Manufactured by Macbeth) and evaluated according to the following criteria. ◎: reflection density of 1.2 or more ○: reflection density of 1.0 or more and less than 1.2 ×: reflection density of less than 1.0

<High Temperature Storage Stability> The ink was placed in a constant temperature chamber at 60 ° C. for 3 months, and the particle size distribution of the polymer particles before and after that was measured by a Coulter counter to evaluate the high temperature storage stability. ◎: No change in particle size distribution at all, average particle size of 100 nm or less in monodispersed system ○: Subtle change in particle size distribution, but average particle size of 100 nm or less in monodispersed system △: Particle size distribution Changed, polydisperse system having distribution of 2 peaks or more, average particle size of 200 nm or less.

[0080]

[Table 2]

As is clear from the results shown in Table 2, the inks of Examples 1 to 4 (products of the present invention) have high water resistance, high print density, and excellent storage stability at high temperatures. In particular, it can be seen that the inks of Examples 1 and 3 containing no urea are extremely excellent in high-temperature storage stability.
In contrast, the inks of Comparative Examples 1 and 2 are inferior in high-temperature storage stability.

[0082]

According to the present invention, there is provided an ink jet recording ink which satisfies general ink characteristics and has excellent stability after storage at a high temperature of 60 ° C. or higher for a long period of time.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Aida 2606 Akabane, Kaigamachi, Haga-gun, Tochigi Prefecture F-term in the Kao Corporation Research Laboratories (reference) 4J039 AD05 AD09 AD10 AD12 AD23 AE04 AE06 AE07 AE11 BC10 BC11 BC13 BC32 BC37 BE01 BE22 CA06 EA42 EA44 EA46 GA24

Claims (4)

[Claims] 1. A polymer emulsion of colored polymer fine particles colored with a coloring material, which contains a betaine compound represented by the following formula (1) and a polyhydric alcohol and contains a urea compound at 6% by weight or less. Water-based ink for inkjet recording. Embedded image 2. The aqueous ink for ink-jet recording according to claim 1, further comprising a phosphate ester salt. 3. The water-based ink for ink-jet recording according to claim 1, further comprising at least one of a glyceryl ether compound and a monohydric alcohol. 4. The urea-based compound is urea, methyl urea,
The aqueous ink for inkjet recording according to any one of claims 1 to 3, which is dimethyl urea or ethyl urea.