JP4004112B2 - Carbon black, carbon black dispersion liquid and production method thereof - Google Patents

Description

【００３９】
【表２】
表−１ 表面処理カーボンブラックの分散結果と印字評価（続き）

註）略号：４−ＨＢＡ ＝４−ヒドロキシ安息香酸
４−ＰＳＡ ＝４−フェノールスルホン酸
ＥＧ ＝エチレングリコール
ＮＭＰ ＝Ｎ−メチル−２−ピロリドン
【００４０】
【発明の効果】
本発明により、インクジェット用インク組成物として有用なカーボンブラック水性分散液を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous dispersion of carbon black, and more specifically, an aqueous dispersion of carbon black formed by adding a phenol compound having a hydrophilic functional group in order to disperse hydrophobic carbon black particles in an aqueous medium. And a manufacturing method thereof. The carbon black aqueous dispersion obtained by the present invention is useful as various recording water-based inks including ink jet printing.
[0002]
[Prior art]
Ink jet printers are widely used in offices and homes as inexpensive printing machines, but with the recent demand for higher printing quality, the required characteristics of ink to be used are becoming more severe. Particularly for black inks that are used in large quantities, low solution viscosity and surface tension are required for stable printing while maintaining high optical density. Also, during thermal jet printing, the ink is heated at a temperature of about 280 ° C or higher, so when using a colorant, resin, or solvent with low thermal stability, the thermal decomposition products may cause defective printing or nozzle clogging. Cause.
[0003]
Carbon black is considered to be optimal as a black colorant having a high optical density and excellent thermal stability. However, carbon black particles are hydrophobic aggregates and are usually difficult to disperse in an aqueous medium. As a method of dispersing carbon black in water, a method using various dispersants, a method of graft polymerization of a hydrophilic monomer, a method of adding an organic compound having a hydrophilic functional group to the surface, a method of directly oxidizing the surface, etc. have been devised. ing.
[0004]
As a method for dispersing carbon black in an aqueous medium using a dispersant, there are water-soluble methods described in JP-B-1-28304, JP-B-2-230271, JP-A-8-41394, JP-A-8-113741, and the like. Describes a method of using a functional vinyl polymer as a dispersant. In these methods, since the dispersant is a high-viscosity polymer, the ink ejection properties are likely to deteriorate, and the dispersant may be thermally deteriorated.
[0005]
As a method for graft polymerization of a hydrophilic monomer on the surface of carbon black, grafting using a vinyl monomer or an epoxy compound in JP-B-1-4936, JP-A-4-234467, JP-A-6-128517, etc. A method of polymerizing is described. In these methods, it is difficult to remove the ungrafted polymer as a by-product, and it is difficult to keep the composition of the product constant.
[0006]
As a method of adding an organic compound having a hydrophilic functional group to the surface of carbon black, USP 5,571,311 describes a method of adding sulfanilic acid or anthranilic acid using a diazo coupling reaction. Diazonium salts are susceptible to decomposition and have many losses and side reactions. Further, the diazotization reaction has a risk of runaway / explosion and is not preferable when handling a large amount.
[0007]
As a method for directly oxidizing the surface of carbon black, JP-A-8-3498 discloses a method for oxidizing using hypochlorite. In this method, the hydrophobicity of the carbon black itself is lost, and there is a problem in that the water resistance of the printing is reduced and bleeding occurs.
[0008]
[Problems to be solved by the invention]
The inventors of the present invention have solved the above-mentioned problems in the prior art, and have earnestly devised a method for significantly improving the dispersibility in an aqueous medium while maintaining the excellent characteristics of carbon black such as blackness, heat resistance and water resistance. investigated.
[0009]
[Means for Solving the Problems]
As a result of intensive studies by the present inventors in view of the above problems, it is possible to provide a carbon black dispersion liquid having excellent characteristics that can provide an ink for inkjet printing that enables high-density and high-quality printing. Successfully achieved the present invention. That is, the present invention resides in a carbon black to which a phenol compound having a hydrophilic functional group is added, a carbon black dispersion containing the carbon black, and a production method thereof.
[0010]
Carbon black having excellent affinity with the surface of carbon black and having a phenolic compound having a hydrophilic functional group capable of improving dispersibility in an aqueous medium added to the surface, and carbon containing the same Black aqueous dispersions can provide inks for inkjet printing having excellent characteristics, and these can be obtained by reacting carbon black and the phenol compound with a radical initiator in an aqueous solvent. The present inventors have found that this can be done.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
Carbon black that can be used in the present invention is not particularly limited, and furnace black, channel black, lamp black, and the like that are usually available can be used. Those previously oxidized by various methods may be used.
[0012]
The phenol compound added to carbon black in the present invention is a phenol compound having a hydrophilic functional group. Here, the phenol compound means a compound in which various functional groups are added to C ₆ H ₅ OH, and a compound in which the OH portion of such a compound is a salt. The position and number of functional groups are not limited, but have at least one hydrophilic functional group.
[0013]
The kind of the hydrophilic functional group is not particularly limited, but for example, a sulfonic acid group, a carboxyl group, or a salt thereof is particularly preferable.
Specific examples of the phenol compound having a hydrophilic functional group include 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2-hydroxybenzenesulfonic acid, 3-hydroxybenzenesulfonic acid, 4 -Hydroxybenzenesulfonic acid, 2-aminophenol, 3-aminophenol, 4-aminophenol, 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, catechol, resorcinol, hydroquinone, 3-hydroxy-2-naphthoic acid 2-hydroxy-1-naphthoic acid, 6-hydroxy-2-naphthalenesulfonic acid, 4-hydroxy-1-naphthalenesulfonic acid and the like. Of these, hydroxybenzoic acids and hydroxybenzenesulfonic acids are preferred from the viewpoint of reactivity with carbon black and dispersibility.
[0014]
In order to produce the carbon black or the carbon black dispersion of the present invention, the above carbon black and a phenol compound may be reacted in an aqueous solvent.
The reaction may be initiated by using a radical initiator together with heating, light irradiation, or a reducing agent.
[0015]
The degree of heating is 50 ° C or higher, preferably 70 ° C or higher.
Examples of the reducing agent include low oxidation state transition metals such as FeCl ₂ and FeBr, and amines such as tetramethylethylenediamine.
As a result, the present inventors have found that a reaction between the phenol compound and carbon black occurs on the surface of carbon black.
[0016]
As the radical initiator, a water-soluble peroxide is suitable.
For example, persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, perphosphate, perborate, hydrogen peroxide, peracetic acid and its salts, benzoyl peroxide, alkali metal peroxide, etc. . Among these, it is preferable to use persulfates and perphosphates whose reaction is easily controlled. The amount of radical initiator used depends on the amounts of carbon black and phenolic compound used, and it is appropriate to use an oxide in an amount of 0.1 to 5 times the combined weight. However, the initiator may be used in excess of this amount.
[0017]
In addition, the mixture ratio of a phenol compound and carbon black is not specifically limited, Preferably it is 20-300 weight part of phenol compounds with respect to 100 weight part of carbon black, Most preferably, it is 50-100 weight part.
The ratio to be added to the carbon black is not particularly limited, but preferably 2 to 50% by weight, particularly preferably about 4 to 15% by weight of the phenol compound is added to the carbon black to which the phenol compound is added. Fully effective.
[0018]
In the production method of the present invention, the above reaction is carried out in an aqueous solvent. As used herein, the aqueous solvent refers to water or a mixture of water and a water-soluble organic solvent. Usually, water may be used, but a water-soluble organic solvent is appropriately mixed when the phenol compound to be used does not dissolve. Can be used. For example, alcohols such as methanol and ethanol, aliphatic polyols such as ethylene glycol, glycerin and low molecular weight polyethylene glycol, nitriles such as acetonitrile, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, N -Lactams such as methylpyrrolidone, sulfur-containing solvents such as dimethyl sulfoxide, dimethyl sulfone and sulfolane, and phosphorus-containing solvents such as hexamethylphosphoric triamide.
[0019]
The aqueous dispersion of carbon black obtained by the above method can be used as it is as a black ink composition such as an inkjet ink, but is separated and washed to remove unreacted phenolic compounds and excess salts. It is preferable. As the separation method, methods such as filtration and centrifugation are used. As the filter medium, a membrane filter of about 0.1 μm is convenient with little separation loss. Although demineralized water is usually used for washing, a water-soluble organic solvent can be mixed as appropriate so that the remaining organic compounds such as phenols can be easily removed. In order to adjust pH, various salts may be dissolved and used.
[0020]
In order to suppress reaggregation of carbon black, the pH of the dispersion is preferably in the range of 3-10. This is because in the case of a strong acid or strong base liquid, the negative charge on the surface of the carbon black is neutralized by hydrogen ions or metal cations and the dispersion stability due to charge repulsion is inhibited. Particularly preferably, the pH is 7 to 10, and the dispersion stability is very excellent.
[0021]
Examples of pH regulators include monohydrogen phosphate, dihydrogen phosphate, hydrogen carbonate, carbonate, hydroxide, and the like, and alkali metal salts, alkaline earth metal salts, ammonium salts, and the like may be used. it can. Among these, phosphates and carbonates such as 1 ammonium dihydrogen phosphate and 1 potassium dihydrogen phosphate are preferable, and reaggregation of carbon black hardly occurs.
[0022]
In order to finely disperse the carbon black added with the phenol compound thus obtained in an aqueous medium, a commonly used means such as a mill disperser or ultrasonic irradiation may be used. As the mill disperser, a bead mill using glass beads having a particle size of 1 mm or less is suitable. In order to realize high-quality ink jet printing, it is preferable to disperse to a volume average particle size of 0.2 μm and a maximum particle size of 1 μm or less. More preferably, it is dispersed to a volume average particle size of 0.1 μm and a maximum particle size of about 0.5 μm. Here, the volume average particle size and the maximum particle size are values measured by a dynamic light scattering method.
[0023]
In order to realize ink jet printing with stable ejection properties, it is necessary to keep the ink solution viscosity low and the surface tension high. The solution viscosity is preferably 1 to 3 mPa · s, and the surface tension is preferably 50 mN / m or more. More preferably, the solution viscosity is adjusted to 1 to 2 mPa · s, and the surface tension is adjusted to 60 mN / m or more.
When used as an inkjet ink composition, the solid content concentration of carbon black in the dispersion is preferably 20 wt% or less, particularly preferably 5 to 10 wt%.
[0024]
The black ink composition thus obtained is suitable as an ink for ink jet printing and can be used for many other purposes as an aqueous ink. Examples include writing instrument ink, printing ink, and transfer ink.
[Example]
Hereinafter, the present invention will be described specifically by way of examples.
[0025]
The volume average particle size and the maximum particle size of carbon black dispersed in the carbon black dispersion in the present invention are measured at 23 ° C. using “MICROTRAC-UPA150” (MODEL 9230) by a dynamic light scattering method. It was. The presence or absence of aggregates was confirmed by magnifying and observing 400 times using an optical microscope (manufactured by Shimadzu Corporation). The solution viscosity was measured at 25 ° C. and 50 rpm using “RE-80L” manufactured by TOKI Sangyo. The surface tension was measured at room temperature using “CBVP-A13” manufactured by Kyowa Interface Science. The pH was measured at room temperature using Toa Denpa Kogyo "HM-20".
[0026]
The residual amount of the phenol compound during the reaction was measured by LC analysis using a liquid chromatograph “LC-9A” manufactured by Shimadzu Corporation. “MCIgel ODS1HU” (4.6φ × 150 L) manufactured by Mitsubishi Chemical Corporation was used for the column, and the eluent was dissolved in 10 vol% acetonitrile aqueous solution as a buffer with 0.05M potassium dihydrogen phosphate as a buffer, and the flow rate was 1 ml / min. Used in. The detector used was “SPD-10A” manufactured by Shimadzu Corporation, and the absorbance at a wavelength of 250 nm was measured. The thermal stability of the carbon black treated with the obtained phenol compound and the addition amount of the organic component were measured by measuring TG / DTA at 100 to 1000 ° C. using “SSC-5000” manufactured by SEIKO ELECTRONICS.
[0027]
For printing evaluation, a thermal jet printer “PICTY200” (PR-101 / J200) manufactured by NEC Corporation was used, and the ink of the ink cartridge “HP51629A” was refilled. As printing paper, neutral paper for copying and Xerox “4024” paper were used. The print density was measured using a “Macbeth densitometer RD914”.
[0028]
Example 1
2 g of carbon black ("MA7" manufactured by Mitsubishi Chemical Corporation), acidic functional group 0.13 meq / g, BET specific surface area 137 m ² / g, DBP oil absorption 65 ml in a 200 ml round bottom flask equipped with a stirring blade and a cooling tube / 100 g) and 1 g (7 mmol) of 4-hydroxybenzoic acid, 5 g (18 mmol) of potassium persulfate are added, and the mixture is immersed in an oil bath at 90 ° C. while stirring at 600 rpm in 100 ml of 50 vol% aqueous methanol solvent, and heated. Reflux for a period of time. After completion of the reaction, the solid content was filtered off using a 0.1 μm membrane filter, washed twice with 150 ml of demineralized water, and then washed once with 100 ml of methanol. When the first filtrate was analyzed by LC, 80% of 4-hydroxybenzoic acid had disappeared. Thereby, it turns out that 80% of the prepared benzoic acid is contained in said solid content.
[0029]
The solid content was dried at 100 ° C. under reduced pressure of 50 mmHg for 2 hours with a vacuum dryer to obtain 2.2 g of black powder. When TG / DTA was measured, the weight loss at 100 to 1000 ° C. was about 9 wt%, and no sudden weight or heat change was observed. From the above, it can be seen that 4-hydroxybenzoic acid, an organic compound, remains in the solid content and is not simply present as a mixture with carbon black but is chemically bonded to carbon black. Recognize.
[0030]
(Example 2)
In the same manner as in Example 1, carbon black was refluxed for 10 hours instead of Degussa “FW200” (acid functional group 1.4 meq / g, BET specific surface area 550 m ² / g, DBP oil absorption 154 ml / 100 g). And reacted. In order to adjust the pH, washing was performed with 150 ml of 1N aqueous sodium hydroxide solution, and then with demineralized water and methanol. LC analysis of the first filtrate revealed that 77% of 4-hydroxybenzoic acid had disappeared. After drying under reduced pressure, 2.2 g of black powder was obtained.
[0031]
(Example 3)
The reaction was carried out in the same manner as in Example 1, except that 1 g (6 mmol) of 4-phenolsulfonic acid was used instead of 4-hydroxybenzoic acid as the phenol compound. LC analysis of the filtrate revealed that 82% of 4-phenolsulfonic acid had disappeared. In order to adjust the pH, washing was performed with 150 ml of 1N aqueous sodium hydroxide solution, and then with demineralized water and methanol. After drying under reduced pressure, 2.2 g of black powder was obtained.
[0032]
(Comparative Example 1)
In Example 1, the reaction was carried out without using carbon black. After completion of the reaction, the filtrate was subjected to LC analysis. As a result, 68% of 4-hydroxybenzoic acid disappeared, and about 60% of the filtrate produced a dimer.
[0033]
(Example 4)
0.3 g of carbon black added with the phenol compound obtained in Example 1 was weighed in a 20 ml glass container, and 0.4 g of ethylene glycol, 0.35 g of glycerin, 3.95 g of demineralized water, and 7 glass beads of 0.8φ were used. .2 g was added and sealed. After shaking for 30 minutes at 350 spm with a shaker, ultrasonic waves of 40 kHz were irradiated for 2 hours using an ultrasonic cleaner (Branson 1210). After removing the glass beads with a 5C qualitative filter paper, the glass beads were magnified 400 times with an optical microscope, but no agglomerates were observed. When the particle size distribution was measured, the volume average particle size (mv) was 0.147 μm, and the maximum particle size counted by Microtrac was 0.48 μm. The solution viscosity at 25 ° C. was 1.75 mPa · s, the surface tension was 67.4 mN / m, and the pH was 6.4.
[0034]
(Example 5)
Dispersion was carried out in the same manner as in Example 4 except that carbon black added with the phenol compound obtained as black powder in Example 2 was used. The particle size distribution was mv 0.044 μm, maximum particle size 0.20 μm, and pH 9.0.
[0035]
(Example 6)
Dispersion was carried out in the same manner as in Example 4 except that carbon black added with the phenol compound obtained as black powder in Example 3 was used. The particle size distribution was mv 0.134 μm, the maximum particle size 0.58 μm, and pH 8.5.
[0036]
(Example 7)
The same operation as in Example 4 was performed except that 0.75 g of N-methylpyrrolidone was used instead of ethylene glycol and glycerin. The particle size distribution was mv 0.146 μm, the maximum particle size was 0.41 μm, the solution viscosity was 1.42 mPa · s, the surface tension was 56.4 mN / m, and the pH was 4.8.
[0037]
(Examples 8 to 11)
The carbon black dispersions obtained in Examples 4 to 7 were printed with an ink jet printer, and the presence or absence of blurring or bleeding of characters, shading or unevenness of solid coating portions, and streaks were confirmed. The results are summarized in Table 1.
[0038]
[Table 1]
Table 1 Dispersion results and print evaluation of surface-treated carbon black

[0039]
[Table 2]
Table 1 Dispersion results and print evaluation of surface-treated carbon black (continued)

I) Abbreviation: 4-HBA = 4-hydroxybenzoic acid 4-PSA = 4-phenolsulfonic acid EG = ethylene glycol NMP = N-methyl-2-pyrrolidone
【The invention's effect】
According to the present invention, an aqueous carbon black dispersion useful as an inkjet ink composition can be obtained.

Claims (12)

Carbon black to which a phenol compound having a hydrophilic functional group is added. The carbon black according to claim 1, wherein the hydrophilic functional group of the phenol compound is at least one of a sulfonic acid group, a carboxyl group, and a salt thereof. A method for producing carbon black to which a phenol compound is added, comprising reacting carbon black, a phenol compound having a hydrophilic functional group, and a radical initiator in an aqueous solvent. A carbon black dispersion comprising carbon black to which a phenol compound having a hydrophilic functional group is added. A method for producing a carbon black dispersion, comprising reacting carbon black, a phenol compound having a hydrophilic functional group, and a radical initiator in an aqueous solvent. The carbon black dispersion according to claim 4, wherein the hydrophilic functional group of the phenol compound is a sulfonic acid group and / or a salt thereof. The carbon black dispersion according to claim 4 or 6, wherein the hydrophilic functional group of the phenol compound is a carboxyl group and / or a salt thereof. The method for producing a carbon black dispersion according to claim 5, wherein the radical initiator is at least one of persulfate, perphosphate, organic peroxide and hydrogen peroxide. The carbon black dispersion according to claim 4, 6 or 7, wherein carbon black is dispersed in an aqueous solvent so that the maximum particle size is 1 µm or less and the volume average particle size is 0.2 µm or less. The carbon black dispersion according to claim 4, 6, 7 or 9, wherein the solid content concentration of the carbon black is 20 wt% or less and is in a range of pH 3 to 10. An ink composition comprising carbon black to which a phenol compound having a hydrophilic functional group is added. An ink-jet ink composition comprising carbon black to which a phenol compound having a hydrophilic functional group is added.