JP2009149722A - Alcoholic carbon black dispersion and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alcoholic carbon black dispersion having an excellent dispersibility in an alcoholic dispersant, excellent in quick drying property and suitably used as a black ink for an inkjet printer, corresponding to a high speed machine. <P>SOLUTION: This alcoholic carbon black dispersion is characterized by chemically modifying carboxyl groups on the surface of the carbon black by the ring opening reaction of oxirane ring to form a hydroxyester, and dispersing such the carbon black as a main component in an alcoholic medium having alcoholic hydroxy groups. The method for producing the same is characterized by refluxing the oxidation-treated carbon black and an oxirane compound in a reaction solvent in the presence of a catalyst to perform the ring-opening reaction of the oxirane ring for hydroxy-esterifying and chemically modifying the carboxyl groups on the surface of the carbon black, and then dispersing the carbon black as a main component into the alcoholic medium having the alcoholic hydroxy groups. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used for black inks such as inkjet printers, and is particularly excellent in dispersion stability in a dispersion medium mainly composed of an alcohol-based solvent used in a high-speed machine corresponding to an increase in printing speed. The present invention relates to an alcoholic carbon black dispersion and a method for producing the same.

  Furthermore, the alcoholic carbon black dispersion of the present invention can be effectively used as a resin composition, coating composition, ink, thermal transfer ink, thermal transfer ink ribbon coating agent, various thermosetting ink compositions, and the like. it can.

  The recording method using an ink jet printer is a method in which ink droplets are ejected from a fine nozzle head and characters and figures are recorded on the surface of a recording medium such as paper. Since paper is not required, application fields such as office, personal and industrial use are expanding.

  As recording inks used in inkjet printers, pigment-based inks with high image reliability, such as water resistance and light resistance, are frequently used in place of dyes. An aqueous black ink is preferably used.

  However, carbon black is hydrophobic and has low water dispersibility, making it difficult to stably disperse in water at a high concentration. Therefore, techniques for applying various hydrophilization techniques to carbon black have been proposed. For example, Patent Document 1 discloses a method of oxidizing carbon black with an aqueous hypohalite solution, and Patent Document 2 discloses an aqueous pigment ink containing water and carbon black, in which the carbon black is 1.5 mmol / g. An aqueous pigment ink having the above surface active hydrogen content is disclosed.

  Patent Document 3 discloses a method for producing an aqueous pigment ink comprising a step of finely dispersing carbon black having an oil absorption of 100 ml / 100 g or less in an aqueous medium and a step of oxidizing the carbon black using hypohalite. Patent Document 4 discloses an aqueous pigment ink which is oxidized with a hypohalite and is an ammonium salt in which at least a part of acidic groups present on the surface of the oxidized carbon black is bonded to an amine compound. .

  In addition, a method of modifying the surface of carbon black with organic radicals has also been proposed. For example, Patent Document 5 discloses a structural formula (A1-N) in a recording ink in which a color material composed of carbon black is dispersed in an aqueous medium. = N-A2) There has been proposed a recording ink using as a coloring material carbon black in which a functional group generated by the decomposition of a radical generator composed of an azo compound is chemically bonded to the surface.

  An aqueous dispersion in which carbon black obtained by condensation polymerization of a terminal amine of polyethyleneimine on a carboxyl group generated by liquid-phase oxidation of carbon black is dispersed in water as a black pigment is also present in the present applicant. After confirming that the adhesion to the printing medium was improved and the water resistance of the printed matter was improved, it was proposed as Patent Document 6.

Further, Patent Document 7 discloses a step of adsorbing an organic dye derivative having a basic functional group or a triazine derivative having a basic functional group to carbon black in water to obtain an aqueous dispersion of carbon black, and this aqueous dispersion. There has been proposed a method for producing an alcohol dispersion of carbon black, which comprises a step of diluting an alcohol with alcohol.
JP-A-48-018186 Japanese Patent Laid-Open No. 08-003498 JP 08-319444 A JP 09-286938 A JP-A-11-323229 JP 2005-255705 A JP-A-2005-060512

  In general, the aqueous medium has a drawback that the paper tends to curl after printing, and the method using the special paper causes a problem of increasing the running cost. Furthermore, in recent years, the printing speed of printers has increased, and fixing and quick-drying have been emphasized in order to prevent the show-through prevention of images after printing and scratch resistance, and for printers more than conventional serial heads. The conversion to a line head system with a significantly faster printing speed is expected to increase, and there is a demand for the development of ink that can handle high-speed printing.

  In other words, in order to support high-speed printing, it is effective to develop inks with excellent quick drying properties, and it is necessary to develop new dispersion technology for black pigments typified by carbon black in volatile organic solvents. It was.

  Therefore, the present inventor has eagerly studied to deal with these situations, and as a result has reached the development of the present invention, the purpose of which is excellent dispersion performance in an alcohol-based dispersion medium excellent in quick drying. It is an object of the present invention to provide an alcoholic carbon black dispersion that is suitably used as a black ink for an ink jet printer compatible with a high-speed machine and a method for producing the same.

  In order to achieve the above object, the alcoholic carbon black dispersion according to the present invention comprises a carbon black whose surface is carboxylated by a hydroxy ester by an oxirane ring-opening reaction and chemically modified. It is structurally characterized by being dispersed in an alcoholic medium having a functional hydroxyl group.

  The chemically modified hydroxyesterified structure specifically has at least one of the following structural formulas (1) to (5). R1 and R3 are alkyl groups, alkenyl groups, alkynyl groups, halogenated alkyl groups, and aryl groups, and R2 is hydrogen, alkyl groups, alkenyl groups, alkynyl groups, halogenated alkyl groups, and aryl groups.

  In addition, this alcoholic carbon black dispersion is produced by subjecting the oxidized carbon black and oxirane compound to reflux in the presence of a catalyst in the presence of a catalyst to cause the oxirane ring to undergo a ring-opening reaction. A structural feature is that the carboxyl group is chemically modified by hydroxyesterification, and the carbon black is dispersed in an alcoholic medium having an alcoholic hydroxyl group as a main component.

  The catalyst is preferably a halogenated quaternary ammonium compound represented by the following general formula (6).

但し、Ｒ₁ ,Ｒ₂ ,Ｒ₃ およびＲ₄は、全てが同一の低級アルキル基を表すか、またはその三つが同一の低級アルキル基を表し、かつ残りの一つがフェニル基またはベンジル基を表し、Ｘ^-はハロゲンイオン、ＯＨ⁻ 、またはＨＳＯ₄ ⁻ を表す。

Provided that R ₁ , R ₂ , R ₃ and R ₄ all represent the same lower alkyl group, or three of them represent the same lower alkyl group, and the remaining one represents a phenyl group or a benzyl group. , X ⁻ represents a halogen ion, OH ⁻ , or HSO ₄ ^— .

  According to the alcoholic carbon black dispersion of the present invention, it is possible to provide an alcoholic carbon black dispersion that is excellent in quick drying and is suitably used as a black ink for an inkjet printer compatible with a high-speed machine.

  Also, according to the production method, the carboxyl group on the surface of the oxidized carbon black is chemically modified by ring-opening reaction in the presence of a catalyst in the presence of a catalyst to form a hydroxy ester, in an alcoholic medium having an alcoholic hydroxyl group. By dispersing, a carbon black dispersion excellent in dispersion stability in an alcoholic medium can be produced.

  Carbon black used in the present invention may be any of furnace black, channel black, acetylene black, thermal black, and the like, and the type thereof is not particularly limited.

When used as an alcoholic black ink for ink jet printers, etc., colloidal properties such as nitrogen adsorption specific surface area (N ₂ SA) and DBP absorption of carbon black contribute to dispersion performance and ink performance in alcoholic media. greatly affects the nitrogen adsorption specific surface area as the carbon black characteristics (N ₂ SA) is 100 m ² / g or more, DBP absorption amount is preferably used more than 50 cm ^3/100 g.

  Specific examples of these carbon blacks include Talker Black # 8500, Talker Black # 8500F, Talker Black # 7550SB, Talker Black # 7550F (above manufactured by Tokai Carbon Co., Ltd.), # 650, # 750, MA600, # 44B, # 44, # 45B, MA7, MA11, # 47, # 45, # 33, # 45L, # 47, # 50, # 52, MA77, MA8 (manufactured by Mitsubishi Chemical Corporation), FW200, FW2V, FWI, FW18PS, NIpex180IQ, FW1, Special Black6, S160, S170 (manufactured by Degussa), Black Pearls 1000M, Black Pearls 800, Black Pearls 880, Monarch 1300, Monarch 1300 ch 880, CRX 1444, Regal 330R, Regal 660R, Regal 660, Regal 415R, Regal 415, Black Pearls 4630, Monarch 4630 (above Cabot), Raven 7000, Raven 3500, Raven 3500, Raven 3500, Raven 3500, Raven 3500, Raven 3500, Raven 3500, Raven 3500, Raven 3500, Raven 3500 3396, Raven 1255, Raven 1250, Raven 1190, Raven 1000, Raven 1020, Raven 1035, Raven 1100ULTRA, Raven 1170, Raven 1200 (above made by Columbia, Inc.), 7 , 720, 725, 00, 305, 320, 325, X25, X45 (above Asahi Carbon Co., Ltd.), N220, N110, N234, N121 (above Sid Richardson Co., Ltd.), Niteron # 300 (above Nisshin Carbon Co., Ltd.) Show black N134, N110, N220, N234, N219 (manufactured by Showa Cabot Co., Ltd.).

  These carbon blacks must have a carboxyl group on the surface, and the carboxyl group is chemically modified by hydroxyl esterification by a ring-opening reaction of the oxirane ring.

  In this case, those chemically modified to at least one of the following structural formulas via a carboxyl group (COO-group) on the surface of carbon black are preferable.

(1) A carboxyl group (COO— group) on the surface of carbon black (CB) is bonded to a —CH ₂ CH (OH) — structure or —CH ₂ CH (OH) —CH ₂ —O— structure, Chemically modified with an alkyl group, alkenyl group, alkynyl group, halogenated alkyl group or aryl group (Chemical Formula 1, Chemical Formula 2).

(2) Carbon black (CB) having a carboxyl group (COO-group) modified with —C ₆ H ₁₀ OH (Chemical Formula 4).

(3) a carboxyl group of the carbon black (CB) surface (COO- group) is _-C 6 _{H 9} (OH) - bound to the structure or _{-C 6 H 9 (OH) -CH} 2 -O- structure, the terminal Modified with hydrogen, alkyl group, alkenyl group, alkynyl group, halogenated alkyl group or aryl group (Chemical Formula 3, Chemical Formula 5).

  The surface-modified carbon black according to the present invention has the structure described above. However, in order to have self-dispersibility in the dispersion, the amount of hydrosyl groups is 35 to 150 μmol / g, and the number of molecules bonded to carboxyl groups is small. It is preferably in the range of 200 to 1000 μmol / g.

  The molecular structure bonded to the carboxyl group functions to improve the affinity with the solvent and the dispersion stability in the compound having the alcoholic hydroxyl group as the main component of the solvent, and the hydrosyl group has the alcohol as the main component of the solvent. In a compound having a functional hydroxyl group, it functions to improve the affinity with a solvent.

  The affinity with the solvent is mainly influenced by the intermolecular force derived from the functional group and chemical composition of the dispersion medium, and the molecular structure bonded to the carboxyl group of the present invention is an alcoholic hydroxyl group generated by the opening of the oxirane ring. It is possible to produce dispersions suitable for various alcoholic media by promoting the interaction with the intermolecular force of the alcoholic solvent of the dispersion medium and selecting the substituent structure.

  Although a hydroxyl group is present together with a carboxyl group on the surface of carbon black, since the hydroxyl group does not participate in these reactions, the chemical structural formulas of the carbon black surface thus chemically modified are illustrated in Chemical Formulas 7 to 11. did. In the formula, CB represents carbon black, R1 and R3 are alkyl groups, alkenyl groups, alkynyl groups, halogenated alkyl groups, aryl groups, and R2 is hydrogen, alkyl groups, alkenyl groups, alkynyl groups, halogenated alkyl groups. , An aryl group.

  The alcoholic carbon black dispersion of the present invention is obtained by dispersing carbon black thus modified in an alcoholic medium having an alcoholic hydroxyl group as a main component, and the carbon black concentration is 1 to 20 wt. Adjust to about%.

  The alcoholic medium having an alcoholic hydroxyl group used as a main component in the dispersion medium of the alcoholic carbon black dispersion of the present invention is in the range of 50 to 100 wt% in the entire dispersion medium (the remaining 0 to 50 wt% is a secondary solvent). Are preferably included. As the type of alcohol, lower alcohols and higher alcohols as general-purpose solvents, glycol solvents and their monoethers, etc. can be used, and alcohols with a low boiling point and alcohols with a high boiling point may be used in combination. Selection according to the type of pigment is possible.

  Specific examples of the alcoholic medium having an alcoholic hydroxyl group include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3 -Pentanol, tert-amyl alcohol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5 , 5-trimethylhexanol, nonanol, n-decanol, undecanol, trimethylnonyl alcohol, tetradecanol, hebutadecanol, cyclohexanol, 2-methylcyclohexanol, Jill alcohol, and other such various higher alcohols and the like.

  Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, isopentyl diol, triethylene glycol, 3-methyl-1,3 butane diol, 1,3 propane diol, 1 , 3-butanediol, 1,5-pentanediol, hexylene glycol, and octylene glycol.

  Examples of glycol monoether solvents include ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol mono-2-ethylbutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1- Butanol, 3-methoxy-1-butanol, propylene glycol Ether monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol funnyl ether, propylene glycol-tert-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene Examples include glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, and tetrapropylene glycol monobutyl ether.

  In addition, as a secondary component solvent, a monoether acetate solvent may be used in combination with a main alcohol solvent, and specific examples include ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monoethyl ether acetate and the like. It is done.

  Thus, the carbon black surface carboxyl group has a structure in which a hydroxy ester is formed by a ring-opening reaction of the oxirane ring, so that it is stably dispersed in an alcoholic medium having an alcoholic hydroxyl group as a main component. When the dispersion is used for black ink such as an ink jet printer, it functions to maintain and improve the leveling property of the ink.

  Leveling means that the discharged ink droplets flow on the recording medium simultaneously with landing and form a uniform and smooth image in the landed area. In the ink jet method, in the process of placing ink on the recording medium, Since the leveling stress other than gravity does not work, it is necessary to adjust the viscosity and optimize the ink composition (leveling agent, etc.) to obtain a uniform image. When leveling is poor (the image forming surface has irregularities), the causes of image density unevenness and glossiness decrease overlap, leading to a decrease in image density.

  This alcoholic carbon black dispersion is obtained by refluxing an oxidized carbon black and an oxirane compound in a reaction solvent in the presence of a catalyst to cause a ring-opening reaction of the oxirane ring, whereby the carboxyl group on the surface of the carbon black is hydroxylated. It is produced by esterification, chemical modification, and dispersion in an alcoholic medium having an alcoholic hydroxyl group with the carbon black as a main component.

  Carbon black that has been oxidized to form carboxyl groups on the surface of carbon black is used, and gas phase methods such as ozone oxidation and air oxidation, or hydrogen peroxide, nitric acid, sulfuric acid, chlorate, persulfate, hydrogen peroxide, Oxidation is performed by a liquid phase method in which carbon black is placed in an aqueous solution of an oxidizing agent such as carbonate and stirred. In addition, when oxidizing by a vapor phase method, there is an advantage that the drying cost is not required and the operation is easier than the liquid phase method.

When oxidation treatment is performed by the liquid phase method, for example, the following procedure is performed.
Carbon black is placed in an aqueous oxidizing agent solution having an appropriate concentration, and is sufficiently stirred and mixed at an appropriate temperature, for example, a temperature of room temperature to 90 ° C., in a mixing and stirring tank to prepare an aqueous dispersion (slurry). In addition, a surfactant can be added in order to uniformly disperse carbon black in the slurry.

  There may be large undispersed lumps or coarse particles in the slurry. Centrifugation is used to prevent yield loss due to clogging of the membrane during purification and clogging of nozzles for inkjet printers when converted to ink. Classification and removal by methods such as filtration.

  Moreover, the reduced salt produced | generated by oxidation process becomes a factor which inhibits subsequent graft reaction, and removes it in order to suppress the re-simulation of carbon black. The reduction salt is removed using a separation membrane such as an ultrafiltration membrane (UF), a reverse osmosis membrane (RO), and an electrodialysis membrane.

  The oxidized carbon black is refluxed in the presence of a catalyst in the reaction solvent with the oxirane compound, and the oxirane ring is subjected to a ring-opening reaction, whereby the carboxyl group on the surface of the carbon black is hydroxyesterified and chemically modified. This reaction is shown in Chemical Formula 12 by taking the case of Chemical Formula 1 as an example. In the formula, CB represents carbon black, and R1 represents an alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, or an aryl group.

  The oxirane compound is a compound having one oxirane ring at the molecular end, and is 0.5 to 5.0 times the amount of carboxy group (μmol / g) in consideration of the amount of carboxyl group on the surface of oxidized carbon black. It is preferable to set the ratio to the number of molecules. When the ratio is less than 0.5, the dispersion is poor, and when the ratio is more than 5.0, the deterioration of storage stability due to by-products is remarkable. Become. A more preferable range is 1.0 to 2.5.

  Further, the maximum molecular weight of the oxirane compound is preferably 9000. When exceeding 9000, there exists a malfunction that a reaction rate falls by the steric hindrance between the compound itself or a molecule | numerator. A more preferable range is 60 to 5000.

  Specific examples of the oxirane compound include propylene oxide, 1,2-epoxybutane, 1,2-epoxyhexane, 1,2-epoxyoctane, 1,2-epoxydecane, 1,2-epoxydodecane, and 1,2. -Epoxyoctadecane; 2,3-epoxybutane, 7,8-epoxy-2-methyloctadecane, 1-phenylpropylene oxide, stilbene oxide, 4-chlorostilbene oxide, 2-4-dichlorostilbene oxide, 1-methoxy-2 -Methylpropylene oxide, chlorooxirane, epichlorohydrin, chloroethyloxirane, hexafluoropropylene oxide, butadiene monooxyside; 1,2-epoxy-5-hexene, 1,2-epoxy-7-octene; glycidol (2 , 3-epoxy-1-propanol), 2-methyl Glycidol, 3-propyloxirane methanol; methyl glycidyl ether, stearyl glycidyl ether, 2-ethylhexyl glycidyl ether, pivaloyl glycidyl ether, phenyl glycidyl ether, tolyl glycidyl ether, xylyl glycidyl ether, nitrophenyl glycidyl ether, chlorophenyl glycidyl ether, Ethylphenyl glycidyl ether, tert-butylphenyl glycidyl ether; 4-methoxycarbonylphenyl glycidyl ether, allyl glycidyl ether, propargyl glycidyl ether, methoxycarbonyl oxirane, stearoxycarbonyl oxirane, glycidyl acetate, glycidyl stearate, glycidyl 2-ethylhexa Nart, glycidyl 2,2 Dimethylpropanate, glycidyl benzoate, glycidyl methyl benzoate, glycidyl nitrobenzoate, glycidyl chlorobenzoate, glycidyl ethyl benzoate, glycidyl tert-butyl benzoate, glycidyl methacrylate, glycidyl acrylate, styrene oxide, tolyloxirane, xylyloxirane, nitrophenyloxirane, chlorophenyl Oxirane, ethylphenyl oxirane, tert-butylphenyl oxirane, 4-methoxycarbonylphenyl oxirane, benzyl oxirane, furfuryl oxirane, cyclohexene oxide, cyclopentene oxide, cyclooctene oxide, cyclododecane epoxide, alpha pinene oxide, exo-2,3, -Epoxy norbornene, limo N'okishido; and the like.

  The reaction solvent is preferably an aprotic solvent, and dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, acetone, methylene chloride, toluene and the like can be used, and more preferably acetonitrile or tetrahydrofuran is preferable because of high reaction yield. .

  The catalyst is preferably a halogenated quaternary ammonium compound (R1R2R3R4N + X-), specifically, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetraethylammonium iodide, tetrapropylammonium bromide, tetrapropylammonium hydroxide. Side, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydroxide, tetrabutylammonium hydrogen sulfate, tetrabutylammonium iodide, trioctylmethylammonium chloride, trilaurylmethylammonium chloride, di-cured tallow alkyldimethylammonium acetate, Benzyltrimethylammonium chlora De, benzyltrimethylammonium hydroxide key side, benzyltriethylammonium chloride, benzyl tributyl ammonium bromide, benzyl tributyl ammonium chloride, phenyl trimethyl ammonium chloride, and the like, may be used alone or plural. In addition, the addition amount of a catalyst has the preferable range of 0.05-10 weight% with respect to carbon black.

  In this way, after the carboxyl group on the surface of carbon black is hydroxyesterified and chemically modified, the remaining oxirane compound and catalyst are removed by washing with a solvent such as ether or MEK after removing the reaction solvent.

  The alcoholic carbon black dispersion of the present invention contains a penetrant, a surfactant, a resin as a fixing aid, an ultraviolet absorber, an antioxidant, other various leveling agents, a water-soluble solvent, a water-insoluble solvent, and the like. To black ink including inkjet printers.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.

Example 1
Tokai Carbon Co. Seast 9H carbon black (trade name) with (nitrogen adsorption specific surface area 142m ² / g, DBP absorption 130cm ³ /100g,pH6.8), ozone generator (manufactured by Yamato Scientific Co. CO-101) Was subjected to ozone oxidation for 8 hours under the conditions of pressure 0.02 MPa, flow rate 5 liters / minute, and room temperature. As a result of measuring the amount of carboxyl groups and the amount of hydroxyl groups of this oxidized carbon black by the following method, the amount of carboxyl groups was 480 μmol / g, and the amount of hydroxyl groups was 125 μmol / g.

(1) Measurement of the amount of carboxyl groups;
About 2 to 5 g of carbon black oxide was added to a sodium hydrogen carbonate aqueous solution having a concentration of 0.976 N and shaken for about 6 hours, followed by filtration and measurement by performing a titration test on the filtrate.
(2) measurement of the amount of hydroxyl groups;
2,2′-Diphenyl-1-picrylhydrazyl (DPPH) is dissolved in carbon tetrachloride to prepare a 5 × 10 ⁻⁴ mol / l solution. 0.1 to 0.6 g of oxidized carbon black was added to the solution, stirred for 6 hours in a thermostatic bath at 60 ° C., filtered, and the filtrate was measured with an ultraviolet absorptiometer and calculated from the absorbance.

  To 60 g of this oxidized carbon black, 740 g of anhydrous acetonitrile was added as a solvent, and the mixture was stirred for 0.5 hr at 2000 rpm at room temperature using a TK homomixer (manufactured by Primex) to obtain a uniform slurry.

While stirring this slurry at 200 rpm at room temperature, 5 g of glycidol (C ₃ H ₆ O ₂ , 3-hydroxypropylene oxide) was added, 0.6 g of tetrabutylammonium bromide was added as a catalyst, and the mixture was refluxed at 90 ° C. for 5 hours. After the reaction, the solvent was distilled off under reduced pressure, followed by vacuum drying at room temperature for 4 hrs to hydroxy esterify the carboxyl group on the surface of carbon black.

  340 g of 2-propanol as a dispersion medium is added to 60 g of carbon black chemically modified in this way, and the mixture is stirred for 0.5 hr with a TK homomixer (3000 rpm, room temperature) to obtain an alcoholic carbon black dispersion having a carbon black concentration of 15 wt%. Manufactured.

Example 2
Tokai Carbon Co. Seast 9H (trade name) (nitrogen adsorption specific surface area 142m ² / g, a DBP absorption 130cm ³ /100g,pH6.8)200g used as carbon black, ozone generator (manufactured by Yamato Scientific Co. CO-101 ) Was subjected to ozone oxidation for 7.5 hours under the conditions of a pressure of 0.02 Mpa and a flow rate of 5 liters / minute to obtain oxidized carbon black.

  To 60 g of this oxidized carbon black, 740 g of acetonitrile was added, and the mixture was stirred for 0.5 hr at 2000 rpm at room temperature using a TK homomixer to obtain a uniform slurry. While stirring this slurry at room temperature, 5 g of glycidol was added, and 0.6 g of tetrabutylammonium bromide was further added and refluxed for 5 hours. After the reaction, the solvent was distilled off under reduced pressure, vacuum dried at room temperature for 4 hours, 340 g of ethanol was added to the dried residue, and the mixture was stirred for 0.5 hr with a TK homomixer (3000 rpm, room temperature) to obtain an alcohol having a carbon black concentration of 15 wt%. Carbon black dispersion was produced.

Comparative Example 1
Tokai Carbon Co. Seast 9H (trade name) (nitrogen adsorption specific surface area 142m ² / g, a DBP absorption 130cm ³ /100g,pH6.8)200g used as carbon black, ozone generator (manufactured by Yamato Scientific Co. CO-101 ) Was subjected to ozone oxidation for 7.5 hours under conditions of a pressure of 0.02 MPa and a flow rate of 5 liters / minute. 340 g of 2-propanol was added to 60 g of this oxidized carbon black, and the mixture was stirred for 0.5 hr with a TK homomixer (3000 rpm, room temperature) to produce an alcoholic carbon black dispersion having a carbon black concentration of 15 wt%.

Comparative Example 2
Tokai Carbon Co. Seast 9H carbon black (trade name) with (nitrogen adsorption specific surface area 142m ² / g, DBP absorption 130cm ³ /100g,pH6.8), ozone generator (manufactured by Yamato Scientific Co. CO-101) Was subjected to ozone oxidation for 7.5 hours under the conditions of a pressure of 0.02 Mpa and a flow rate of 5 liters / minute.

  340 g of ethanol and 1 g of Surfynol 104E (surfactant) were added to 60 g of this oxidized carbon black, and the mixture was stirred for 0.5 hr with a TK homomixer (3000 rpm, room temperature) to obtain an alcoholic carbon black dispersion having a carbon black concentration of 15 wt%. Manufactured.

Comparative Example 3
Seast manufactured by Tokai Carbon Co., Ltd. as carbon black 9H (trade name) (nitrogen adsorption specific surface area 142m ² / g, a DBP absorption 130cm ³ /100g,pH6.8)60g, ethanol 340g and Surfynol 104E (the surfactant) 1 g was added, and the mixture was stirred for 0.5 hr (3,000 rpm, room temperature) with a TK homomixer to produce an alcoholic carbon black dispersion having a carbon black concentration of 15 wt%.

  Using these carbon black dispersions, diethylene glycol monomethyl ether (DEGME) / water = 7/3, a surfactant (Surfinol 104E, manufactured by Nissin Chemical Co., Ltd.) of 0.3%, and a carbon black concentration of 4 wt. % Ink was prepared.

For these inks, a line-head type piezo recording head arranged in an array so that the nozzle diameter is 25 μm, the number of nozzles is 512, and the nozzle resolution is 600 dpi (dpi is the number of dots per 2.54 cm) is mounted. Using a line head printer, the ink adhesion amount is 10 ml / m ^{2 under} the condition of recording resolution 600 × 600 dpi, and each ink is 5 mm from each side on J paper (64 g / m ² , A4 size) manufactured by Konica Minolta Business Technology. A solid image was printed so as to leave a margin.

The image density of the solid printed part was measured with a Macbeth densitometer, and the obtained results were evaluated according to the following criteria.
A: Black ink OD value: 1.4 or more
B: OD value of black ink: 1.3 or more and less than 1.4
C: OD value of black ink: less than 1.3

Further, the carbon black particle size and the viscosity of the dispersion were measured after storing these carbon black dispersions at 60 ° C. for 4 weeks.
Particle size: Measured at room temperature using UPA (laser diffraction method) manufactured by Microtrack.
Viscosity: Measured at 25 ° C. with an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE-80L).

  The obtained results are shown in Table 1.

  It can be seen that the alcoholic carbon black dispersions of the examples are superior in image density and dispersion stability as compared with the comparative examples.

Claims (4)

  An alcohol characterized in that a carboxyl group on the surface of carbon black is hydroxy-esterified by a ring-opening reaction of an oxirane ring and chemically modified, and the carbon black is dispersed in an alcoholic medium having an alcoholic hydroxyl group as a main component Carbon black dispersion. The alcoholic carbon black dispersion according to claim 1, wherein the chemically modified hydroxyesterified structure has at least one of the following structural formulas (1) to (5).
R1 and R3 are alkyl groups, alkenyl groups, alkynyl groups, halogenated alkyl groups, and aryl groups, and R2 is hydrogen, alkyl groups, alkenyl groups, alkynyl groups, halogenated alkyl groups, and aryl groups.

  The oxidized carbon black and the oxirane compound are refluxed in the reaction solvent in the presence of a catalyst to cause the oxirane ring to undergo a ring-opening reaction, whereby the carboxyl group on the carbon black surface is hydroxyesterified to chemically modify the carbon. A method for producing an alcoholic carbon black dispersion, comprising dispersing black in an alcoholic medium having an alcoholic hydroxyl group as a main component. The method for producing an alcoholic carbon black dispersion according to claim 3, wherein the catalyst is a halogenated quaternary ammonium compound represented by the following general formula (6).

Provided that R ₁ , R ₂ , R ₃ and R ₄ all represent the same lower alkyl group, or three of them represent the same lower alkyl group, and the remaining one represents a phenyl group or a benzyl group. , X ⁻ represents a halogen ion, OH ⁻ , or HSO ₄ ^— .