JPH1036726A - Aqueous pigment ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition excellent in water resistance and weather resistance of a recorded material, not causing nozzle clogging when used for ink-jet recording, comprising a specific oxidized carbon black. SOLUTION: This composition contains (A) an oxidized carbon black obtained by oxidizing (i) carbon black with (ii) a hypohalous acid and/or its salt in a wet state and (B) a water-soluble cationic polymer or oligomer in an aqueous liquid medium. The component A is obtained by oxidizing component (i) finely dispersed in water by using the component (ii). Preferably, the oxygen content is >=5.0wt.%, the average particle diameter is <=300nm and the content of the component A is 0.1-50wt.% based on the whole ink. The component B has <=50,000 number-average molecular weight. To be concrete, a polyallylamine, a polyethyleneimine, a polyvinylamine or a polyvinyl pyrrolidone is used as the component B. The content of the component B is preferably 0.1-20wt.% based on the whole ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment ink composition, and more particularly to an aqueous pigment ink composition containing, as a colorant, oxidized carbon black having improved water dispersibility and a water-soluble cationic polymer or oligomer.

[0002]

2. Description of the Related Art Conventionally, aqueous dye inks containing a black dye have been mainly used as recording liquids for writing instruments and ink jet printers. In recent years, water-based pigment inks using pigments such as carbon black to give light resistance and water resistance to recorded images have attracted attention.

For this type of pigment ink, various brands of carbon black which are commercially available for colorants (for color) are used. It is considered that acidic carbon black has an acidic group such as a carboxyl group on its surface. These are generally gas or liquid phase oxidation methods using conventional oxidizing agents such as ozone, nitric acid, hydrogen peroxide, and nitrogen oxides, or surface modification methods such as plasma treatment, such as furnace black. It is obtained by appropriately oxidizing carbon black for color.

[0004] Such a conventional acidic carbon black,
Alternatively, channel black exhibits a certain degree of hydrophilicity, but has insufficient affinity for an aqueous medium and dispersion stability, and is difficult to disperse alone in water. Therefore, when these are used as a colorant of an aqueous pigment ink, they are dispersed in an aqueous medium using a disperser in the presence of a so-called pigment dispersant such as various water-soluble synthetic polymers and a surfactant, Need to stabilize.

For example, JP-A-64-6074 and JP-A-4-149286 disclose an aqueous pigment ink containing acidic carbon black, a dispersant (anionic surfactant or polymer dispersant) and a buffer. Have been described. JP-A-3-210373 discloses an inkjet ink containing an acidic carbon black having a volatile content of 3.5 to 8% by weight and a water-soluble anionic polymer.
JP-A-3-134073 describes an inkjet recording liquid containing neutral or basic carbon black and a water-soluble resin.

In general, ink is solidified by an orifice of an ink jet recording head or a ballpoint pen tip in order to generate droplets stably from a fine tip of an ink jet recording head or to write smoothly with a thin pen tip of an aqueous ballpoint pen. It is necessary to prevent that.

However, when a commercially available carbon black is used as in the case of a conventional water-based pigment ink, the resin forming the dispersant does not redissolve after adhering to the orifice or the like, causing clogging and non-ejection of droplets. Etc. are likely to occur. Further, since the aqueous pigment ink containing a dispersant has a viscous tone, resistance is caused in the path to the nozzle tip when continuous ejection and high-speed printing are performed for a long time, and the ejection becomes unstable, and smooth recording becomes difficult. Further, the conventional aqueous pigment ink has a disadvantage that the pigment concentration cannot be sufficiently increased in order to secure ejection stability, and the print density is insufficient compared with the aqueous dye ink (recording liquid).

To solve these drawbacks, the present inventors have disclosed an aqueous pigment ink containing no dispersant in Japanese Patent Application No. 8-98436. In the water-based pigment ink described herein, the water dispersibility of carbon black used as a colorant is significantly improved, and does not contain a resin component such as a dispersant. Therefore, this water-based pigment ink does not cause clogging of nozzles when used for ink-jet recording, can be written smoothly from a fine pen tip, and has a sufficient density.

However, in this aqueous pigment ink,
It is desired to improve the water resistance and light resistance of a recorded matter after recording.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to prevent clogging of a nozzle when used for ink-jet recording and to prevent a thin pen tip from being used. Another object of the present invention is to provide a water-based pigment ink which can be written smoothly, has a sufficient density, and is excellent in water resistance and light resistance of a recorded matter.

[0011]

According to the present invention, there is provided an aqueous liquid medium comprising carbon black obtained by wet oxidation of carbon black with hypohalous acid and / or a salt thereof and a water-soluble cationic polymer or An aqueous pigment ink composition comprising an oligomer and an oligomer is provided, whereby the above object is achieved.

Further, in the aqueous pigment ink containing the aqueous liquid medium, the oxidized carbon black and the water-soluble cationic polymer or oligomer according to the present invention, the oxidized carbon black comprises (a) finely dispersing the carbon black in water. (B) oxidizing using hypohalous acid and / or a salt thereof; and (c) performing the steps (a) and
After (b), purification and concentration are performed, and the pigment concentration is 10 to 30% by weight.
And a step of obtaining a water dispersion of the above. Alternatively, after the steps (a) and (b), a step of neutralizing a part of the acidic groups present on the surface of the carbon black with a volatile basic compound may be used. preferable.

Furthermore, in the aqueous pigment ink containing the aqueous liquid medium, the oxidized carbon black and the water-soluble cationic polymer or oligomer according to the present invention, the water-soluble cationic polymer or oligomer has a weight average molecular weight of 100,000 or less, or Polyallylamine, polyethyleneimine, polyvinyl which is a cationic polymer or oligomer having a number average molecular weight of 50,000 or less and having a cationic group such as an amino group, an imino group, a tertiary amine group, or a quaternary ammonium group in the molecular structure. It is preferably selected from the group of amines and polyvinylpyrrolidone.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The oxidized carbon black contained in the aqueous pigment ink of the present invention can be obtained by subjecting carbon black to a wet oxidation treatment with hypohalous acid and / or a salt thereof. Carbon black, which is a raw material of oxidized carbon black, is generally a carbon powder obtained by thermally decomposing or incompletely burning natural gas or liquid hydrocarbon (such as heavy oil or tar). These are classified into channel black, furnace black, lamp black and the like according to the manufacturing method, and are commercially available.

The type of carbon black used as a raw material is not particularly limited. Any of the above-mentioned acidic carbon black, neutral carbon black and alkaline carbon black can be used.

Specific examples of carbon black include # 10B, # 20B, # 30, # 33, # 40, and # 10B manufactured by Mitsubishi Chemical Corporation.
# 44, # 45, # 45L, # 50, # 55, # 95,
# 260, # 900, # 1000, # 2200B, # 2
300, # 2350, # 2400B, # 2650, # 2
700, # 4000B, CF9, MA8, MA11, M
A77, MA100, MA220, MA230, MA6
00 and MCF88, etc .; Monarch 12 manufactured by Cabot Corporation
0, Monarch 700, Monarch 800, Monarch 88
0, Monarch 1000, Monarch 1100, Monarch 1
300, Monarch 1400, Mogal L, Legal 99
R, Legal 250R, Legal 300R, Legal 3
30R, Legal 400R, Legal 500R, Legal 660R, etc .; Detexa's PRINTEX A, PRINTEX G, PRINTEX U, PRINTEX V,
PRINTEX 55, PRINTEX 140U, PRINTEX 140V, Special Black 4, Special Black 4A, Special Black 5, Special Black 6, Special Black 100, Special Black 250, Color Black FW1, Color Black FW
2, color black FW2V, color black FW1
8, color black FW200, color black S15
0, color black S160 and color black S17
0 and the like.

Since acidic carbon black has an acidic group such as a phenolic hydroxyl group and a carboxyl group on the surface of the particles, it is preferable to use it as a raw material. Acidic carbon black generally has a pH of 6 or less, especially 4 or less.

The acidic carbon black is, for example, MA8, MA100, 2200B, 240 from Mitsubishi Kasei.
0B under the trade name of Color Cabon Black F from Tegusa
W200, color black FW18, color black
S150, color black S160, color black
S170, PRINTEX U, PRINTEX 140
0, Monarch 1300, Mogar L, Regal 400R from Cabot Corporation, Raven 1200, Raven 1220 from Columbian Carbon, Inc.
It is commercially available under the trade name Raven 1225.

Neutral or basic carbon black is, for example, # 33, # 45, # 45L, # 45 from Mitsubishi Kasei.
10B, # 4000B, # 2300, # 2400, # 9
Under the trade name of 000
5. PRINTEX 60, PRINTEX 300, PRINTEX A, etc. are brand names of color furnaces, etc. from Cabot Corporation, Legal 330R, Legal 300R,
Under the trade name of oil furnace such as Regal SR, Raven 40, CONDUCTE from Columbian Carbon
XSC, commercially available under the trade name MOLACCO LS.

The carbon black is wet-oxidized in water using hypohalous acid and / or a salt thereof. Specific examples of the hypohalous acid and / or its salt include sodium hypochlorite and potassium hypochlorite, and sodium hypochlorite is particularly preferred from the viewpoint of reactivity.

In the oxidation reaction, carbon black and a hypohalite (eg, sodium hypochlorite) are charged into an appropriate amount of water, and the reaction is carried out for 5 hours or more, preferably for about 10 to 15 hours.
It is carried out by stirring at 50 ° C. or higher, preferably 95 to 105 ° C. At that time, it is preferable that the carbon black is oxidized in a finely dispersed state.

In the present specification, the term "finely dispersed" means that at least secondary particles of carbon black are finely ground in water to make them finer to primary particles or to a degree close to primary particles.
The average particle size of the finely dispersed carbon black is generally 3
It is at most 00 nm, preferably at most 150 nm, more preferably at most 100 nm.

In general, fine dispersion is performed by an operation of wet grinding in an aqueous medium for 3 to 10 hours using a mill medium and a grinding apparatus. As a mill medium, glass beads, zirconia beads, magnetic beads, stainless steel beads and the like are used. Examples of the pulverizer include a ball mill, an attritor, a Fouro jet mixer, an impeller mill, a colloidal mill, and a sand mill [for example, a bead mill, a sand glider, a super mill, an agitator mill, a Dyno mill (trade name)] and the like.

However, depending on the type of carbon black used as a raw material, the carbon black may be finely dispersed only by high-speed stirring in a water solvent using a homogenizer (homomixer) or the like.

The fine dispersion is not necessarily performed before the oxidation treatment. The fine dispersion treatment may be performed simultaneously with the oxidation treatment by stirring or pulverizing in an aqueous solvent such as hypohalite.

The amount of the hypohalite used varies depending on the type thereof, but is generally 1.5 to 150% by weight, preferably 4 to 75% by weight in terms of 100%, based on the weight of carbon black. .

The obtained oxidized carbon black contains about 3
It has an oxygen content of at least about 5% by weight, preferably at least about 5% by weight, more preferably at least 10% by weight. As a result of the oxidation treatment by the method of the present invention, the oxygen content increases several times to several tens times the oxygen content of the carbon black before the treatment.

The oxygen content is measured by the "inert gas-infrared absorption method". In this method, a sample is heated in a stream of an inert gas such as helium, oxygen is extracted as carbon monoxide, and measurement is performed by an infrared absorption method.

The characteristics of the water-based pigment ink of the present invention are as follows.
It is not just the oxygen content of the oxidized carbon black contained. Although the reason is not clear, the oxidized carbon black of the present invention forms a stable aqueous dispersion as compared with a commercially available acidic carbon black even if the oxygen content is 3 to 10% by weight.

In general, it is said that in the reaction between carbon black and hypohalite, various functional groups present on the surface of carbon black are oxidized to form carboxyl groups and hydroxyl groups. These polar groups have active hydrogen, and the amount of this active hydrogen can be measured, for example, by the Tweil method.

The oxidized carbon black used in the aqueous pigment ink of the present invention has a high surface active hydrogen content (mmol / g).
It is preferable to have This is because such oxidized carbon black exhibits particularly good water dispersibility. The surface active hydrogen content of the oxidized carbon black contained in the aqueous pigment ink of the present invention is not particularly limited, but is preferably at least about 0.3 mmol / g or more, and is preferably at least about 1.3 mmol / g.
More preferably, it is 0 mmol / g or more.

In general, carbon black having a high surface active hydrogen content has many hydroxyl groups and carboxyl groups having active hydrogen on its surface, so that the hydrophilicity of the carbon black itself is improved. At the same time, the surface area also increases, and it is thought that the water dispersibility is improved as if the surface of carbon black had chemical properties such as acid dyes.

The characteristics of the aqueous pigment ink of the present invention are as follows:
It is not only the surface active hydrogen content of the oxidized carbon black contained. That is, carbon black having an active hydrogen content of about 0.1 to about 1.0 mmol / g does not always achieve the object of the present invention.

Next, the dispersion of the oxidized carbon black after the oxidation treatment is filtered (when hot), the obtained wet cake is redispersed in water, and then beads and coarse particles are removed using a mesh wire mesh. . Alternatively, after removing the beads and coarse particles, the wet cake may be washed with water to remove by-product salts. Alternatively, the slurry from which beads and coarse particles have been removed may be diluted with a large amount of water, and the membrane may be purified and concentrated as it is.

If necessary, the wet cake of oxidized carbon black is preferably dispersed again in water and acid-treated with a mineral acid (for example, hydrochloric acid or sulfuric acid). The acid treatment is performed by adding hydrochloric acid to the aqueous dispersion to adjust the pH to 3 or less,
It is preferable to heat and stir for 1 to 5 hours as described above. This is because the acid treatment is advantageous for ammonium chloride or amine chloride by aqueous ammonia or an amine compound in the next step, and for adsorbing a water-soluble cationic polymer or oligomer. Thereafter, the dispersion is filtered, washed with water, and the obtained wet cake is dispersed in water.

If necessary, the dispersion of oxidized carbon black is then neutralized with a basic compound, preferably an amine compound. Since an acidic group is present on the surface of the oxidized carbon black, at least a part of the acidic group is (ion) bonded to an amine compound to form an ammonium salt or an amine salt. As described above, by aminating the oxidized carbon black, the dispersion stability of the aqueous pigment ink, the prevention of nozzle clogging, and the water resistance when recording on paper are improved.

Preferred amine compounds include water-soluble volatile amines and alkanolamines. Specifically, ammonia, a volatile amine substituted with an alkyl group having 1 to 3 carbon atoms (eg, methylamine, trimethylamine, diethylamine, propylamine);
(E.g., ethanolamine, diethanolamine, triethanolamine); alkyl alkanolamines substituted with an alkyl group having 1 to 3 carbon atoms and an alkanol group having 1 to 3 carbon atoms. . A particularly preferred amine compound is ammonia. However, not all acidic groups need to be ammonium or amine salts. Rather, it is necessary to partially form an acidic group so that the water-soluble cationic polymer or oligomer used for ink formation can be adsorbed on the surface of carbon black.

These can be used in combination of two or more.
Further, in order to adjust the affinity and dispersion stability for an aqueous medium, and to prevent metal corrosion, some acidic groups on the surface of the oxidized carbon black may be converted into alkali metal salts. Sodium oxide, potassium hydroxide, lithium hydroxide and the like are used in combination with the amine compound.

Thereafter, a dispersion of the oxidized carbon black subjected to aminification is added to a 0.01 osmosis membrane or an ultrafiltration membrane.
Purify and concentrate using a separation membrane with a pore size of less than μm. The concentration is generally performed such that the pigment dispersion is a concentrated pigment dispersion having a carbon black content of about 10 to 30% by weight based on water. The pigment dispersion thus obtained can be used as it is as an aqueous pigment ink. In this case, the concentration of carbon black is preferably adjusted to 1 to 20% by weight. The concentrated pigment dispersion may be further dried to obtain a powdery pigment, or may be further concentrated to obtain a pigment dispersion having a pigment concentration of about 50% by weight. Thereafter, these are dispersed in an aqueous medium described below, and a water-soluble cationic polymer or oligomer is added to adjust the concentration to an appropriate value, whereby the aqueous pigment ink of the present invention is obtained.

The oxidized carbon black according to the present invention generally contains 1 to 50% by weight based on the total amount of the aqueous pigment ink.
Preferably, it is contained in the range of 2 to 20% by weight. If the carbon black content is less than 1% by weight, the printing or writing density becomes insufficient, and if it exceeds 20% by weight, the carbon black tends to agglomerate and precipitate during long-term storage, or the ejection stability is deteriorated. It is.

The average particle size of carbon black in the aqueous pigment ink of the present invention is 300 nm or less, particularly 150 nm.
Hereinafter, it is more preferably 100 nm or less. If the average particle size of the carbon black exceeds 300 nm, sedimentation of the pigment is likely to occur.

The aqueous pigment ink composition of the present invention preferably further contains a water-soluble cationic polymer or oligomer. This is for improving the water resistance and light resistance of the recorded matter after recording with the aqueous pigment ink composition.

Unlike the commonly used pigment dispersants, the water-soluble cationic polymer or oligomer does not require much performance for dispersing the pigment. This is because the oxidized carbon black itself has good dispersibility and redispersibility in an aqueous medium.

Generally, when lipophilic carbon black is dispersed in an aqueous solvent, a hydrophilic group and a lipophilic group must be arranged in a well-balanced manner in the dispersant. Must strongly adhere to the surface. However, since the water-soluble cationic polymer or oligomer used in the present invention does not need to be adsorbed on the carbon black surface, the lipophilic group may be weaker than a general dispersant.

However, the addition of a water-soluble cationic polymer or oligomer must not impair the dispersion stability and ejection stability of the aqueous pigment ink composition.
Therefore, in order to avoid solidification of the ink at the orifice or nozzle and to quickly re-dissolve it, water-soluble is easily wrapped and re-dissolved in the form of fine carbon black particles without forming carbon black into large aggregates during drying. It is necessary to use a cationic polymer or oligomer.

Such water-soluble cationic polymers or oligomers include cationic polymers having a weight average molecular weight of 100,000 or less, preferably about 50,000 or less. In addition, polymers or oligomers having a number average molecular weight of 50,000 or less, preferably in the range of 20,000 to 1,000, are included.

If the average molecular weight of the polymer is 100,000 or more, the viscosity of the ink and the particle size of the dispersion become large, so that good ejection stability cannot be obtained. The amine value varies depending on the type of the cationic polymer, and is not particularly limited. Generally, the amine value is preferably about 5 to 30 (mg eq / g-polymer solid).

The water-soluble cationic polymer or oligomer used in the present invention includes a compound represented by the formula

[0049]

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A polyallylamine represented by the formula:

[0051]

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A polyvinylamine represented by the formula:

[0053]

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Polyethyleneimine represented by the formula:

[0055]

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Polyvinylpyrrolidone represented by the formula:

[0057]

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A polyamidine (hydrochloride) represented by the formula:

[0059]

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A polyamine sulfone represented by the formula:

[0061]

Embedded image

And the like.
m and n are positive integers).

In addition, cationically modified polyacrylamide, copolymer of acrylamide and cationic monomer, hydroxypropylated polyethyleneimine, polyamide-epichlorohydrin resin, quaternized polyvinylpyridinium, alkylated polyvinylpyrrolidone, etc .;
Vinylpyrrolidone-based monomers, oxazoline-based monomers, vinyloxazolidone-based monomers, homopolymers of vinylimidazole-based monomers, and these monomers and acrylamide, methacrylamide, acrylate,
Copolymers with common monomers such as methacrylate, tert-butyl acrylate, vinyl ether, acrylonitrile, vinyl acetate, ethylene, styrene and the like can be mentioned.

Polyallylamine, polyvinylamine, polyethyleneimine, polyvinylpyrrolidone and the like can be preferably used.

Further, an amine-added epoxy resin, an amine-added polybutadiene resin, an acrylamine copolymer resin,
Amine-added acrylic resin, amine-added methacrylic resin,
Acrylamide resin, copolymer of acrylamide and cationic monomer, resin having oxazoline group, methacrylamide resin having cationic group, methacrylamine copolymer having cationic group, cation-modified polyvinyl alcohol, cation-modified cellulose, cation A copolymer of a vinyl monomer having a functional group and a vinyl monomer exhibiting water solubility, a cationic urea resin, a cationic sizing agent, and the like can be used within the technical scope of the present invention. Further, if necessary, a nonionic polymer can be added within a range not to impair the effects of the present invention.

Specific examples of the water-soluble cationic polymer or oligomer include polyallylamine (PAA) and polyallylamine hydrochloride (PAA-HC) manufactured by Nitto Boseki Co., Ltd.
l), Polyvinylamine (PVAM 0, manufactured by Mitsubishi Chemical Corporation)
595B) and polyethyleneimine (Epomin PS-012, PS-200, P-1000) manufactured by Nippon Shokubai Co., Ltd.

These water-soluble cationic polymers or oligomers are used with respect to the total amount of the aqueous pigment ink of the present invention.
It is preferable to add 0.1 to 20% by weight, about 1 to 1/10 times the weight of the oxidized carbon black contained in the ink of the present invention.

The aqueous pigment ink of the present invention may contain a water-miscible organic solvent, if necessary. In addition, water, a water-miscible organic solvent, and a mixture thereof are referred to as an aqueous medium in this specification.

Examples of the water-miscible organic solvent include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
C1-C4 alkyl alcohols such as sec-butyl alcohol and isobutyl alcohol; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran (THF) and dioxane; ethylene glycol, propylene glycol, diethylene glycol And polyalkylene glycols such as polyethylene glycol and polypropylene glycol; polyhydric alcohols such as ethylene glycol monoethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether and triethylene glycol monoethyl ether. Lower alkyl ether; polyethylene glycol monomethyl ether Lower alkyl ether acetates such as Seteto; glycerol; and 2-pyrrolidone, 2
Pyrrolidone such as -methylpyrrolidone and N-methyl-2-pyrrolidone; The use amount of these organic solvents is not particularly limited, but generally ranges from 3 to 50% by weight.

Since the water-based pigment ink of the present invention has been sufficiently desalted and purified, corrosion of writing instruments, ink jet printers and the like does not occur. Furthermore, since part of the carboxyl groups on the surface of the carbon black is an ammonium salt or the like, there is no need to particularly adjust the pH. In addition, a part of the carboxyl group is an alkali metal of hypohalous acid (N
a, K) It may be an alkali metal salt derived from a salt.

Further, in the aqueous pigment ink of the present invention, additives such as a viscosity modifier, a fungicide and a rust inhibitor, which are usually used for this kind of ink, can be appropriately selected and used in an appropriate amount.

According to the present invention, there is provided a carbon black-containing ink having a very high degree of oxidation as compared with a commercially available (acidic) carbon black as a colorant and having excellent water dispersibility. It is considered that the amount of polar groups (for example, hydroxyl group, carboxyl group, and carbonyl group) on the surface of the carbon black is increased, and at the same time, the surface area is increased.

Further, by adding a water-soluble cationic polymer or oligomer to the aqueous pigment ink of the present invention, the fixability to recording paper, the print density and the gloss are improved. Further, the resolubility and redispersibility of the recording liquid are improved. Alternatively, long-term dispersion stability is excellent even without mechanical dispersion treatment, and re-aggregation of oxidized carbon black does not occur. Alternatively, the carbon black does not settle in the ink reservoir.

The water-based pigment ink of the present invention has good recording / writing characteristics and can be printed at high speed, and can be used for short-time printing even when used as an ink for recording by an ink jet system or as a writing ink for a water-based ballpoint pen. Even the letters do not fade.

Further, the robustness (light fastness and water fastness) of characters and figures recorded on plain paper and non-absorbent coated paper is excellent, and even if immersed again in water, the carbon black does not flow out, and the water fastness is low. It has excellent light resistance without discoloration unlike dye ink even when exposed to sunlight.

Furthermore, since carbon black can be contained at a high concentration, the density of printed matter is excellent, and an optical density equal to or higher than that of a water-soluble black dye is provided.

[0077]

EXAMPLE 1 Commercially available acidic carbon black "MA-100" (pH 3.
5) [Mitsubishi Chemical Corporation] 300 g was thoroughly mixed and finely dispersed in 1000 ml of water, and then 450 g of sodium hypochlorite (effective chlorine concentration: 12%) was added dropwise to the mixture.
For 10 hours. The obtained slurry is applied to Toyo
o.2 (manufactured by Advantis), and washed with water until pigment particles leaked. This pigment wet cake is 3,000
The solution was re-dispersed in 100 ml and desalted with a reverse osmosis membrane until the electric conductivity was 0.2 mS. Further, this pigment dispersion was concentrated to a pigment concentration of 10% by weight.

Separately, a part of the obtained pigment dispersion was treated with an acid (acidified with hydrochloric acid, preferably adjusted to pH 2 and purified again), further concentrated, dried and pulverized to obtain a fine powder of carbon black. . The oxygen content (% by weight) of the obtained carbon black was 8%.

The oxygen content (% by weight) of the (oxidized) carbon black is determined by the method of melting an inert gas with an infrared ray absorption method (JISZ261).
3-1976 method) under the conditions shown in Table 1.

[0080]

TABLE 1 Analysis conditions Analysis instrument HERAEUS CHN-O RAPIO full automatic elemental analyzer sample decomposition furnace temperature 1140 ° C. fractionating tube temperature 1140 ° C. using gas _{N 2 / H 2 = 95%} / 5% of mixed gas flow rate 70 ml / min detector Non-dispersive spectrometer (Binos)

Example 2 To 50 g of the pigment dispersion obtained in Example 1 was added ethanol 5
g, 2-methylpyrrolidone 5 g, water 25.0 g and PA
15 g of A-L [polyallylamine manufactured by Nitto Boseki Co., Ltd .: 20% aqueous solution having a weight average molecular weight of about 10,000] was added and dissolved to obtain an aqueous pigment ink.

The viscosity of this ink is 3.4 cps / 25 ° C.
Below, the average particle size of the carbon black is 150 nm
Met.

The average particle size of the oxidized carbon black was measured using a laser light diffusion type particle size distribution analyzer (trade name: LPA3000 / 3100, manufactured by Otsuka Electronics Co., Ltd.).

Next, when this pigment ink was set in an ink jet recording apparatus [trade name: HG5130 (manufactured by Epson Corporation)] and printed on plain paper, the ink ejection was stable, and printing was performed promptly. Was glossy, the pigment did not flow even when immersed in water after drying, and the water resistance was good. The nozzle used was for a general aqueous dye ink, but the ink did not solidify, and there was no ejection failure in a printing test several hours later. Even if this ink is stored at 50 ° C. for one month, no sediment is generated, the average particle diameter and the viscosity are not changed, and the ink ejection is stable even if the printing test is performed again. Was. The optical density of the solid printed portion was measured using a Macbeth densitometer TR-927 (manufactured by Colmorgen) and was found to be 1.34, which was satisfactory.

1 g of this ink was placed in a petri dish and
After drying with a dryer at 12 ° C. for 12 hours, 2 g of the original ink was added and shaken gently. The solid was completely dissolved within 30 seconds.

Example 3 To 50 g of the 10% pigment dispersion obtained in Example 1 were added 5 g of ethanol, 5 g of 2-methylpyrrolidone, 22 g of water and P
A water-based pigment ink was obtained by adding 18 g of VAM0595B [polyvinylamine hydrochloride manufactured by Mitsubishi Chemical Corporation: an aqueous solution having an amine value of 12 to 13 mg eq / g. Solid and a polymer concentration of 17% with a weight average molecular weight of 60,000] and dissolving it. .

When the obtained water-based pigment ink was evaluated in the same manner as in Example 2, the same results as in Example 2 were obtained.

Example 4 300 g of commercially available carbon black “MA-8” (pH 3.5) [manufactured by Mitsubishi Chemical Corporation] was thoroughly mixed with 1000 ml of water, and 450 g of sodium hypochlorite (effective chlorine concentration: 12%) was added. The mixture was added dropwise and stirred at 100 to 105 ° C for 8 hours. further,
After adding 100 g of sodium hypochlorite to this reaction solution,
The mixture was dispersed at room temperature for 3 hours using a horizontal dispersing machine filled with beads, so that the average particle size of carbon black was about 100 nm. The resulting slurry was diluted 10-fold, and the pH was adjusted with aqueous hydrochloric acid.
The solution was adjusted to 2 and desalted with a reverse osmosis membrane until the electric conductivity was 0.2 mS. Further, the pigment dispersion was adjusted to pH 7.0 using monoethanolamine, and stirred for 1 hour. Further, this pigment dispersion was concentrated to a pigment concentration of 20% by weight.

Separately, a part of the desalted and purified pigment dispersion after the acid treatment was concentrated, dried and pulverized to obtain a fine powder of oxidized carbon black. When the oxygen content (% by weight) of the obtained carbon black was measured, it was 10%.

Example 5 To 25 g of the pigment dispersion obtained in Example 4, 62 g of water, 10 g of ethanol and SP-012 [polyethyleneimine manufactured by Nippon Shokubai Co., Ltd .: amine value 19 mg eq / g.Solid, number average average molecular weight 1200] 2.5 g and triethylamine 0.5
g was added and stirred sufficiently to obtain an aqueous pigment ink. The viscosity of this ink was 3.2 cps / 25 ° C. or less, and the average particle size of carbon black was 100 nm.

Next, this ink was set in an ink jet recording apparatus and printed on plain paper in the same manner as in Example 2.
The ink discharge was stable and promptly printed, the printed matter was glossy, the pigment did not flow even when immersed in water after drying, and the water resistance was good. The nozzle used was for a general aqueous dye ink. However, the ink did not solidify, and there was no ejection failure in a print test several hours later. Even if this ink is stored at 50 ° C. for one month, no sediment is generated, the average particle diameter and the viscosity are not changed, and the ink ejection is stable even if the printing test is performed again. Was.

1 g of this ink was placed in a petri dish, and
After drying with a dryer at 12 ° C. for 12 hours, 2 g of the original ink was added and shaken gently. The solid was completely dissolved within 30 seconds.

Example 6 To 25 g of the pigment dispersion obtained in Example 4 was added 49.5 of water.
g, ethanol 5 g, 2-methylpyrrolidone 5 g, PA
15 g of AL [polyallylamine manufactured by Nitto Boseki: 20% aqueous solution having a weight average molecular weight of about 10,000] and 0.5 g of triethylamine were added, and the mixture was sufficiently stirred to obtain an aqueous pigment ink.

When the obtained water-based pigment ink was evaluated in the same manner as in Example 5, the same results as in Example 5 were obtained.

Example 7 300 g of commercially available carbon black "# 45" (pH 8.0) (manufactured by Mitsubishi Chemical Corporation) was thoroughly mixed with 1000 ml of water, and 450 g of sodium hypochlorite (effective chlorine concentration: 12%) was added dropwise. And stirred at 100-105 ° C for 8 hours. further,
After 100 g of sodium hypochlorite was added to the reaction solution, the mixture was dispersed at room temperature for 3 hours using a horizontal disperser filled with beads to reduce the average particle size of carbon black to about 100 nm.
It was as follows. The obtained slurry was diluted 10-fold, adjusted to pH 2 with hydrochloric acid, and desalted with a reverse osmosis membrane until the conductivity became 0.2 mS. Further, the pH of the pigment dispersion was adjusted to 7.0 using aqueous ammonia, and the mixture was stirred for 1 hour. Further, this pigment dispersion was concentrated to a pigment concentration of 20% by weight.

A part of the obtained pigment dispersion was concentrated, dried,
Then, the powder was pulverized to obtain a fine powder of carbon black, and the oxygen content (% by weight) of the carbon black was measured to be about 10%.

Example 8 62 g of water, 5 g of ethanol, 5 g of 2-methylpyrrolidone, SP-01 were added to 25 g of the pigment dispersion obtained in Example 7.
2 [Polyethyleneimine manufactured by Nippon Shokubai Co., Ltd .: amine value 19
Solid, a number average molecular weight of 1200] (15 g) and diethyl ethanolamine (0.5 g) were sufficiently stirred to obtain an aqueous pigment ink.

When the obtained water-based pigment ink was evaluated in the same manner as in Example 5, the same results as in Example 5 were obtained.

Comparative Example 1 Acidic carbon black "MA-100" (pH 3.5)
[Mitsubishi Kasei Co., Ltd.] 500 g of Marquid 32-30WS
833 g of [30% aqueous solution of Marquid 32 (aqueous ammonia neutralizing agent)] and 300 g of water were added, and the mixture was dispersed using a disperser. Thereafter, the mixture was diluted with water to a pigment content of 20%. 5 g of ethanol, 5 g of 2-methylpyrrolidone and water were added to 25 g of this slurry to make the total amount 100 g, and the mixture was sufficiently stirred to obtain an aqueous pigment ink. The viscosity of this ink was 4.5 cps / 25 ° C. or less. The average particle size of the carbon black was 150 nm.

Further, when this ink was set in an ink jet recording apparatus and printed on plain paper in the same manner as in Example 2, the amount of ink discharged gradually decreased, and the density gradually disappeared. Further, in a print test several hours later, the nozzles were not clogged and returned.

1 g of this ink was placed in a petri dish, and
After drying in a dryer at 12 ° C. for 12 hours, 2 g of the original ink was added and shaken gently. After 5 minutes, the undissolved portion remained without completely dissolving.

Comparative Example 2 5 g of ethanol was added to 50 g of the pigment dispersion obtained in Example 1.
Then, 5 g of 2-methylpyrrolidone, 0.5 g of triethanolamine and water were added to obtain 100 g of an aqueous pigment ink.

The viscosity of this ink is 1.5 cps / 25 ° C.
Below, the average particle size of the carbon black is 150 nm
Met.

Further, when this ink was set in an ink jet recording apparatus and printed on non-absorbent coated paper in the same manner as in Example 2, the ink ejection was stable and printing was performed promptly. There was no luster, and the pigment flowed out when immersed in water after drying, and there was no water resistance.

Comparative Example 3 Polyethyleneimine used in Example 5: SP-012
Was replaced with SAM1000A [styrene maleic acid resin manufactured by Elphatochem Japan Ltd .: acid value 480, number average molecular weight 1600], and a pigment ink was prepared according to the composition shown in Table 2 below.

[0106]

Table 2 20% pigment dispersion obtained in Example 2 25.0 g SAM1000A 5.0 g Water 57.5 g Ethanol 5.0 g 2-Methylpyrrolidone 5.0 g 28% aqueous ammonia 2.0 g Triethanolamine 0.0 5g

The viscosity of this ink is 2.0 cps / 25 ° C.
And the average particle size of the carbon black is 100 nm
Met.

Further, when this ink was set in an ink jet recording apparatus and printed on plain paper in the same manner as in Example 2, the ink discharge was stable, and the ink was printed quickly.
The printed matter was glossy, but when immersed in water after drying, the pigment flowed out and bleeding was observed.

[0109]

According to the present invention, when recorded on plain paper, a water-resistant recorded image having sufficient print density and good gloss can be obtained. Even when printed on non-absorbent coated paper, it has fixability and water resistance. Even after the ink has dried and solidified in the orifice or ballpoint pen of the recording head, it has excellent re-dissolvability and re-dispersibility, and quickly returns when new ink flows. Further, even with a high-concentration pigment ink, the viscosity of the ink can be controlled to be low, the resistance in the path to the recording head is small, the ejection stability is good, and long-time printing and high-speed printing can be performed.

Claims (11)

[Claims] 1. An aqueous pigment comprising, in an aqueous liquid medium, oxidized carbon black obtained by wet-oxidizing carbon black with hypohalous acid and / or a salt thereof, and a water-soluble cationic polymer or oligomer. Ink composition. 2. The method according to claim 1, wherein the oxidized carbon black is obtained by converting carbon black finely dispersed in water to hypohalous acid and / or
Or a material obtained by wet oxidation using a salt thereof.
The aqueous pigment ink composition as described in the above. 3. The aqueous pigment ink composition according to claim 1, wherein the oxidized carbon black has an oxygen content of 5.0% by weight or more. 4. The aqueous pigment ink composition according to claim 1, wherein the average particle size of the oxidized carbon black is 300 nm or less. 5. The aqueous pigment ink composition according to claim 1, wherein the content of the oxidized carbon black is 0.1 to 50% by weight based on the total amount of the aqueous pigment ink. 6. The aqueous pigment ink composition according to claim 1, wherein the weight-average molecular weight of the water-soluble cationic polymer or oligomer is 100,000 or less. 7. The aqueous pigment ink composition according to claim 1, wherein the number average molecular weight of the water-soluble cationic polymer or oligomer is 50,000 or less. 8. The method according to claim 1, wherein the water-soluble cationic polymer or oligomer is polyallylamine, polyethyleneimine,
The aqueous pigment ink composition according to claim 1, which is selected from the group consisting of polyvinylamine and polyvinylpyrrolidone. 9. The content of the water-soluble cationic polymer or oligomer is based on the total amount of the aqueous pigment ink.
The aqueous pigment ink composition according to claim 1, wherein the amount is 0.1 to 20% by weight. 10. An ink jet recording liquid containing the aqueous pigment ink composition. 11. An ink for writing implements containing the aqueous pigment ink composition.