JP2017141315A - Hydrophilic carbon black aqueous dispersion, hydrophilic carbon black aqueous dispersion and manufacturing method of hydrophilic carbon black aqueous dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrophilic carbon black capable of suitably used for an inkjet printer ink by exhibiting excellent dispersibility in an aqueous medium, a hydrophilic carbon black dispersion and a manufacturing method of the hydrophilic carbon black dispersion.SOLUTION: There is provided hydrophilic carbon black having spin-spin relaxation time ofH nuclear T2, measured by a CPMG method of pulse NMR at a state dispersed in water of 500 ms or less and average particle diameter Dupaof agglomerates at the state dispersed in water of 70 to 200 nm. There is provided a hydrophilic carbon black aqueous dispersion containing the hydrophilic carbon black. There is provided a manufacturing method of the hydrophilic carbon black aqueous dispersion which is a method for hydrophilic treatment of carbon black by using an oxidant, an azotization, a surfactant and a hydrophilic agent such as microcapsule or the like and preferably by oxidizing by an oxidant.SELECTED DRAWING: None

Description

  The present invention relates to a hydrophilic carbon black aqueous dispersion, a hydrophilic carbon black aqueous dispersion, and a method for producing a hydrophilic carbon black aqueous dispersion.

  In recent years, water-based inks have become widespread replacing organic solvent-based inks in a wide range of fields because of their safety and low environmental impact. Especially for business use, water-based color materials that do not smell are essential as inks used for various printing in offices, and for industrial use, organic solvents are used due to problems in the working environment, safety of ink and paint handling, and waste liquid treatment. There is an increasing tendency to use as little as possible. In addition, water-based colorants are also more popular than organic solvent-type colorants because they do not require special equipment such as explosion-proof equipment, exhaust equipment, and organic solvent recovery equipment during production. .

  As the water-based coloring material, two dyes and pigments are mainly used depending on the application. The dye has excellent gradation and easily forms a high-resolution image, but has low light resistance and has a practical problem. On the other hand, since pigments are extremely excellent in water resistance and light resistance, many pigment inks are now provided.

  Gravure inks that are printed via printing plate making and water-based liquid inks for offset printing have been developed, but the most popular recording method for offices that uses water-based inks is the ink jet recording method.

  The ink jet recording method is a method in which ink droplets are ejected from a fine nozzle head and characters and images are recorded on the surface of a recording medium such as paper. Since it can be easily printed on demand without making a full color printing plate on a simple recording medium, it has begun to spread widely.

  An ink jet printer that employs an ink jet recording method is a method in which ink droplets are ejected from a fine nozzle head and characters and images are recorded on the surface of a recording medium such as paper. (Registered trademark) method and piezo method. The former is a recording method that instantaneously heats the ink guided to the nozzle head with a heater to generate bubbles, and the ink expansion is intermittently ejected by volume expansion due to the bubbles, the latter is an electrostrictive element (piezoelectric element) Is a recording system that converts electrical signals into mechanical signals and intermittently ejects ink droplets stored in the nozzle head portion, and various pigments corresponding to such recording methods have been proposed. (For example, refer to Patent Document 1 (Japanese Patent Laid-Open No. 2000-319572)).

JP 2000-319572 A

  As such an ink jet printer ink, an aqueous dispersion of carbon black has been used, but since the surface of carbon black has very few functional groups having high affinity with water molecules, it is hydrophobic. It is extremely difficult to stably disperse in water at a high concentration because of low wettability with water. For this reason, when used in an aqueous black ink such as an ink jet printer ink in which carbon black is dispersed in water as a black pigment, it is necessary to improve the water dispersibility by modifying the surface properties of the carbon black.

  As such a modification method, there is known a method for improving the dispersion performance of carbon black in water by forming a hydrophilic functional group on the surface by oxidizing carbon black. A method of oxidizing with an aqueous solution of hypohalite and a method of oxidizing carbon black with low-temperature oxygen plasma are known.

  On the other hand, the above-mentioned oxidation treatment improves the dispersibility of carbon black in water to a certain extent, but as an aqueous dispersion used for ink jet printer ink, it is further excellent in dispersibility (stability in water). Is now required.

  Examples of a method for evaluating the dispersibility of carbon black in an aqueous carbon black dispersion used in an ink jet printer ink include a method for measuring the amount of hydrophilic functional groups bonded to the surface described in Patent Document 1. It is done.

  However, according to the inventor's study, the method for measuring the amount of the hydrophilic functional group is to simultaneously measure the amount of hydroxyl groups that contribute to the dispersibility of carbon black in water. It was found that the amount of the hydrophilic functional group to be measured does not necessarily correlate with the dispersibility of carbon black.

  Under such circumstances, the present invention provides a hydrophilic carbon black, a hydrophilic carbon black aqueous dispersion, and a hydrophilic carbon that exhibit excellent dispersibility in an aqueous medium and can be suitably used for ink jet printer inks. It aims at providing the manufacturing method of a black aqueous dispersion.

In order to solve the above technical problem, the present inventors have further studied. The spin-spin relaxation time T2 of ¹ H nuclei measured by the CPMG (Carr-Purcell-Meiboom-Gill) method of pulsed NMR in a state dispersed in water. Is 500 ms or less, and the hydrophilized carbon black having an agglomerate average particle size Dupa _50% of 70 to 200 nm in a state of being dispersed in water exhibits extremely excellent dispersibility and is suitably used for ink jet printer inks, etc. As a result, the present invention has been completed.

That is, the present invention
(1) The spin-spin relaxation time T2 of ¹ H nucleus measured by the CPMG method of pulse NMR in a state dispersed in water is 500 ms or less,
Hydrophilized carbon black characterized in that the average particle diameter Dupa _50% of agglomerates in a state dispersed in water is 70 nm to 200 nm,
(2) A hydrophilized carbon black aqueous dispersion comprising the hydrophilized carbon black described in (1) above,
(3) The hydrophilized carbon black aqueous dispersion according to (2), wherein the solid content concentration is 3% by mass to 25% by mass,
(4) The aqueous hydrophilized carbon black dispersion according to the above (2) or (3) having a pH of 6.0 to 9.0,
(5) The hydrophilized carbon black aqueous dispersion according to any one of (2) to (4), wherein the electrical conductivity at a solid content concentration of 15% by mass is 3 mS / cm or less,
(6) The aqueous hydrophilized carbon black dispersion according to any one of (2) to (5) above, which is for inkjet printer ink,
(7) In an aqueous medium, with respect to 100 parts by mass of carbon black, 30 to 500 parts by mass of a hydrophilizing agent is sequentially added in small amounts to obtain a hydrophilized product,
Centrifuge the resulting hydrophilized product,
The spin-spin relaxation time T2 of ¹ H nucleus measured by the CPMG method of pulse NMR in a state dispersed in water is 500 ms or less,
A method for producing an aqueous dispersion of hydrophilized carbon black, characterized in that an aqueous dispersion of hydrophilized carbon black having an average particle diameter Dupa _50% of agglomerates in a state dispersed in water of 70 nm to 200 nm is obtained,
Is to provide.

  According to the present invention, hydrophilized carbon black, hydrophilized carbon black aqueous dispersion, and hydrophilized carbon black aqueous dispersion that exhibit excellent dispersibility in an aqueous medium and can be suitably used for inkjet printer inks The manufacturing method of can be provided.

First, the hydrophilic carbon black according to the present invention will be described.
The hydrophilized carbon black according to the present invention has a ¹ H nucleus spin-spin relaxation time T2 of 500 ms or less as measured by a pulsed NMR CPMG method in a state of being dispersed in water, and an average particle diameter of agglomerates in a state of being dispersed in water. Dupa _50% is 70 nm to 200 nm.

  Examples of the hydrophilic carbon black according to the present invention include oxidized carbon black having an acidic group on the surface.

The present inventor has intensively studied to develop a hydrophilic carbon black excellent in dispersibility in an aqueous medium, and has come to focus on the molecular mobility of oxidized carbon black in an aqueous medium. In addition, the molecular mobility can be measured by the spin-spin relaxation time T2 of ¹ H nucleus measured by the CPMG method of pulsed NMR in a state of being dispersed in water, and it is found that it correlates with dispersibility in an aqueous medium. Thus, the present invention has been completed.

Unlike high-resolution NMR, pulsed NMR does not give chemical shift information, but instead, relaxation times of ¹ H nuclei (spin-lattice relaxation time T1 and spin-spin relaxation time) that are closely related to molecular mobility. This is a technique capable of quickly measuring T2).
In recent years, the use of pulsed NMR has been rapidly expanding. Examples of measuring methods in pulsed NMR include the Hahn echo method, the solid echo method, the CPMG method, and the 90 ° pulse method. However, the relaxation time T2 in the present invention means the spin-spin relaxation time T2 of ¹ H nucleus measured by the CPMG method.

In the hydrophilized carbon black according to the present invention, the spin-spin relaxation time T2 of ¹ H nuclei measured by the pulsed NMR CPMG method in a state dispersed in water is in the state of water molecules bound to the surface of the hydrophilized carbon black particles. The smaller the value, the more water molecules bound to the particle surface (because the hydration layer is thick), which improves the water dispersibility of hydrophilized carbon black and improves filtration performance. It will be easier.

In the hydrophilized carbon black according to the present invention, the spin-spin relaxation time T2 of ¹ H nuclei measured by the pulsed NMR CPMG method in a state dispersed in water is 500 ms or less, preferably 450 ms or less, preferably 400 ms or less. More preferably.
The lower limit value of the relaxation time T2 is not particularly limited, but the relaxation time T2 is usually 0.01 ms or longer.

  When the spin-spin relaxation time T2 is 500 ms or less, the hydrophilic carbon black can exhibit particularly excellent dispersibility in an aqueous medium, and when the spin-spin relaxation time T2 exceeds 500 ms, Since the number of water molecules constrained is small (because the hydration layer is thin), the surface tends to aggregate and the dispersibility of the hydrophilized carbon black is lowered, and the filtration performance is easily lowered.

In this application document, the spin-spin relaxation time T2 of ¹ H nuclei is measured by the CPMG (Carr-Purcell-Meiboom-Gill) method of pulsed NMR using “Acron Area” manufactured by XiGo Nanotools, in a state dispersed in water. Value.

In the hydrophilized carbon black according to the present invention, the average particle size Dupa _50% of the agglomerate in a state dispersed in water is 70 nm to 200 nm, preferably 90 nm to 160 nm, and more preferably 100 nm to 150 nm. .

In this application document, the average particle diameter Dupa _50% of the above-mentioned hydrophilized carbon black agglomerate is irradiated with laser light using a laser diffraction / scattering particle size distribution measuring device in the state of an aqueous dispersion, and the scattered light In the cumulative frequency distribution curve of the agglomerate particle diameter obtained from the frequency modulation degree, a value of 50% cumulative frequency is meant.

If the above-mentioned average particle diameter Dupa _{50% of} the agglomerate is within the above range, it can be suitably dispersed in an aqueous medium and used suitably for an aqueous black ink such as an aqueous inkjet printer ink.
The average particle diameter Dupa _50% of the agglomerate is considered to be a characteristic related to the size of the aggregate of the hydrophilic carbon black particles dispersed in the aqueous medium. When the average particle diameter Dupa _50% of the agglomerate of the above-mentioned hydrophilic carbon black is less than 70 nm, when used for aqueous black ink such as ink jet printer ink, the particle diameter is small, and the print density is settled between paper fibers. When the average particle size Dupa _50% of the carbon black agglomerate exceeds 200 nm, the probability of contact of the agglomerate of the hydrophilic carbon black in the aqueous medium increases, and the hydrophilic carbon black in the aqueous dispersion increases. Therefore, when used for water-based black ink such as ink jet printer ink, it is difficult to discharge from the head of the ink jet printer during printing, and ink clogging such as nozzle clogging is likely to occur.

  ADVANTAGE OF THE INVENTION According to this invention, the hydrophilic carbon black which exhibits the outstanding dispersibility in an aqueous medium and can be used conveniently for inkjet printer ink can be provided.

Next, the aqueous hydrophilized carbon black dispersion according to the present invention will be described.
The aqueous hydrophilized carbon black dispersion according to the present invention is characterized by including the hydrophilized carbon black according to the present invention.

  The aqueous hydrophilized carbon black dispersion according to the present invention preferably has a solid content concentration of 3 to 25% by mass, more preferably 5 to 20% by mass, and 6 to 15% by mass. More preferably it is.

  The hydrophilized carbon black aqueous dispersion according to the present invention can easily exhibit suitable dispersibility when used in water-based inks such as ink jet printer ink because the solid content concentration is in the above range. it can.

  In the present application documents, the solid content concentration of the hydrophilic carbon black in the aqueous medium means a value measured at a maximum absorption wavelength of 500 nm using an absorptiometer.

In the aqueous hydrophilized carbon black dispersion according to the present invention, examples of the aqueous medium include water and those containing water as a main component and further containing a water-soluble organic solvent, and those containing only water are preferable.
Examples of water constituting the aqueous medium include purified water such as ion exchange water (deionized water) and distilled water.

  The hydrophilized carbon black aqueous dispersion according to the present invention preferably has a pH of 6.0 to 9.0, more preferably 6.5 to 8.5, and 7.0 to 8. More preferred is 0.

The aqueous hydrophilized carbon black dispersion according to the present invention can be suitably used for aqueous inks such as inkjet printer inks because the pH is within the above range.
When the pH of the aqueous hydrophilized carbon black dispersion is less than 6.0, dissociation of acidic functional groups imparted to the hydrophilized carbon black surface is hindered, and the electric repulsive action on the particle surface is lost and aggregation tends to occur. At the same time, when used in water-based inks such as ink jet printer ink, the acidity of the ink is high, so that the heads of the printing press are easily worn out.
Further, when the pH of the hydrophilic carbon black aqueous dispersion exceeds 9.0, the ion concentration in the dispersion becomes excessive, and it becomes easy to aggregate due to salting out, and it is easy to suck carbon dioxide in the air, The pH of the dispersion tends to become unstable.

The aqueous hydrophilized carbon black dispersion according to the present invention preferably has an electrical conductivity of 3 mS / cm or less, more preferably 2 mS / cm or less, and more preferably 1 mS / cm or less at a solid content concentration of 15% by mass. Is more preferred.
In the hydrophilic carbon black aqueous dispersion according to the present invention, the lower limit of the electric conductivity at a solid content concentration of 15% by mass is not particularly limited, but is usually 0.5 mS / cm or more.

The aqueous hydrophilized carbon black dispersion according to the present invention can exhibit suitable dispersibility even when the electric conductivity at a solid content concentration of 15% by mass is within the above range.
In the hydrophilized carbon black aqueous dispersion according to the present invention, the electrical conductivity is considered to be a property related to the ion concentration in the dispersion in a state dispersed in the aqueous medium, and the hydrophilized carbon according to the present invention. When the black aqueous dispersion has an electric conductivity of more than 3 mS / cm at a solid concentration of 15% by mass, the ionic concentration in the dispersion becomes excessive, and the flocs caused by salting out are affected by the salt that coexists in the dispersion. It becomes easy to form (aggregate).

  The aqueous hydrophilized carbon black dispersion according to the present invention can be suitably used for ink jet printer ink applications.

  ADVANTAGE OF THE INVENTION According to this invention, the aqueous dispersion of the hydrophilic carbon black which exhibits the outstanding dispersibility in an aqueous medium and can be used conveniently for an inkjet printer ink can be provided.

Next, the manufacturing method of the hydrophilic carbon black aqueous dispersion which concerns on this invention is demonstrated.
The method for producing an aqueous dispersion of hydrophilized carbon black according to the present invention comprises hydrophilizing treatment by sequentially adding 30 to 500 parts by mass of a hydrophilizing agent in small amounts to 100 parts by mass of carbon black in an aqueous medium. The obtained hydrophilized product is centrifuged, and the spin-spin relaxation time T2 of ¹ H nuclei measured by the CPMG method of pulsed NMR in a state dispersed in water is 500 ms or less. In addition, an aqueous dispersion of hydrophilized carbon black having an agglomerate average particle diameter Dupa _50% in a state dispersed in water of 70 nm to 200 nm is obtained.

In the method for producing a hydrophilized carbon black aqueous dispersion according to the present invention, the carbon black to be hydrophilized is not particularly limited.
For example, Toast Carbon Co., Ltd. Seest 5H, 3H, NH, 116HM, 116, Talker Black # 5500, # 4500, # 4400, Asahi Carbon Co., Ltd. F-200, SUNBLACK 270, Mitsubishi Chemical Corporation Diamond Black SA, N234, II (IISAF), N (N339), SH (HAF), MA600, # 20, # 3050, # 3230, Cabot Show Black N234, N339, MAF, VULCAN XC 72, BLACK PEARLS 480, Nihon Kasei Carbon Corporation Niteron # 200IS, # 10, Denka Corporation Denka Black FX-35, HS-100, Evonik Degussa Color Black FW200, FW2, FW285, FW1, FW18, S170, S160, Sp Cial Black 6, 5, 4, 4A, Printex U, V, 140U, 140V, L6, 3, HIBLACK 40B1, 40B2, 420B, 150B, Colax HP1107, HP130, N234, N339, N351, MAF, N550, Purex HS55, One or more types selected from HS45, Columbian Raven 820, Conductex 7055ULTRA and the like can be mentioned.

  The method for hydrophilizing carbon black is not particularly limited, and examples of the hydrophilizing agent include a method using an oxidizing agent, an azotizing agent, a surfactant, or microcapsules.

For example, carbon black is added to an aqueous solution of an oxidizing agent such as an alkali metal salt or ammonium salt such as hypochlorite, chlorite, chlorate, persulfate, perborate or percarbonate. The method of oxidizing can be mentioned.
Moreover, as a hydrophilic treatment method of carbon black, a method of treating with an oxidizing agent such as hydrogen peroxide, ozone, ozone water or M ₂ O ₂ (M is an alkali metal), dichromate, permanganate, etc. Can be mentioned.
Furthermore, examples of the hydrophilic treatment method of carbon black include a method of performing a diazo coupling treatment. For example, p-nitrobenzoic acid is azotized with nitrous acid and azotized on the surface of carbon black. And a method using an azotating agent to be bonded.
In addition, as a method for hydrophilizing carbon black, a method using a surfactant that treats carbon black with a surfactant or a microcapsule in which a polymer is microencapsulated on the surface of carbon black and dispersed in water are used. And the like.
The hydrophilic treatment method of carbon black may be any hydrophilic method as long as the resulting hydrophilized product can be satisfactorily dispersed in an aqueous medium, and a method of oxidizing with an oxidizing agent is preferred.

Examples of the aqueous medium include water and those containing water as a main component and further containing a water-soluble organic solvent, and those consisting only of water are preferable.
Examples of water constituting the aqueous medium include purified water such as ion exchange water (deionized water) and distilled water.

Moreover, in order to improve dispersibility, you may add surfactant to an aqueous medium as needed.
As the surfactant, any of anionic, nonionic, and cationic surfactants can be used.

  The hydrophilization treatment of carbon black is preferably performed by stirring and mixing a hydrophilizing solution obtained by stirring and mixing a hydrophilizing agent and an aqueous medium with a disperser to form a slurry.

  Examples of the disperser include a high-pressure homogenizer, a sand mill, a dyno mill, a ball mill, a paint shaker, an ultrasonic disperser, and a disperser that disperses by a cavitation effect in a high-pressure chamber. Further, the dispersion treatment may be performed by a stirrer using a normal stirring blade, a high-speed disperser, an emulsifier, or the like.

In the method for producing a hydrophilized carbon black aqueous dispersion according to the present invention, an oxidizing treatment is carried out while sequentially adding 30 to 500 parts by mass of a hydrophilizing agent in small amounts to 100 parts by mass of carbon black in an aqueous medium. It is preferable to obtain an oxidized product.
The addition amount of the hydrophilizing agent with respect to 100 parts by mass of carbon black is 30 to 500 parts by mass, preferably 100 to 500 parts by mass, and more preferably 150 to 500 parts by mass.

  In the method for producing a hydrophilic carbon black aqueous dispersion according to the present invention, the amount of the hydrophilizing agent added to 100 parts by mass of the carbon black is within the above range, whereby the surface of the carbon black can be suitably hydrophilized. .

In the method for producing a hydrophilized carbon black aqueous dispersion according to the present invention, the hydrophilizing agent is sequentially added little by little to 100 parts by mass of carbon black.
The hydrophilizing agent may be added continuously in small amounts to the carbon black, or may be added in small portions at intervals (intermittently).
As described above, the hydrophilizing agent may be added continuously in small portions, but when added intermittently in small portions, it is preferable to add 1/10 to 1/2 of the total amount to be added. It is more preferable to add 1/10 to 1/3 each, and it is more preferable to add 1/10 to 1/5 each of the total amount to be added.

  In the method for producing a hydrophilic carbon black aqueous dispersion according to the present invention, as described above, the hydrophilizing agent may be added in small portions continuously (regardless of the number of times) to 100 parts by mass of carbon black. However, when intermittently adding a small amount, it is preferable to add the hydrophilic agent in 2 to 10 times, more preferably in 3 to 10 times, and more preferably in 5 to 10 times. More preferably, it is added.

In the method for producing a hydrophilized carbon black aqueous dispersion according to the present invention, the hydrophilizing agent is sequentially added little by little to 100 parts by mass of carbon black.
The hydrophilizing agent may be added continuously in small portions as described above, but when intermittently added in small portions, it is preferably added once every 5 to 90 minutes, for 5 to 60 minutes. More preferably, it is added once every time, and more preferably once every 5 to 30 minutes.

  In the method for producing a hydrophilized carbon black aqueous dispersion according to the present invention, as described above, the total amount of the hydrophilizing agent is added little by little to 100 parts by mass of carbon black at a time, thereby oxidizing the Exothermic runaway associated with the addition of the hydrophilizing agent can be suppressed, and the hydrophilizing agent can be effectively used to effectively hydrophilize. In addition, since the concentration of the hydrophilizing agent can be kept low, it is possible to slow down the hydrophilization reaction rate such as the oxidation reaction rate, and the hydrophilizing agent decomposes before contacting the carbon black surface or locally. Progress of the hydrophilization reaction can be suppressed.

  In the method for producing a hydrophilic carbon black aqueous dispersion according to the present invention, the temperature during the oxidation treatment is preferably 50 to 100 ° C, more preferably 60 to 90 ° C, and further preferably 60 to 80 ° C.

  In the method for producing a hydrophilic carbon black aqueous dispersion according to the present invention, the oxidation treatment time is preferably 2 to 24 hours, more preferably 3 to 12 hours, and further preferably 4 to 10 hours.

  In the method for producing a hydrophilic carbon black aqueous dispersion according to the present invention, after the oxidation treatment, the residual salt may be further separated using an ultrafiltration membrane.

  In the method for producing a hydrophilized carbon black aqueous dispersion according to the present invention, the hydrophilized product obtained by the above treatment is preferably sent at a flow rate of 3 kg / min to 8 kg / min and centrifuged. More preferably, the solution is fed at a flow rate of 3.5 kg / min to 7.5 kg / min and centrifuged, and further sent at a flow rate of 4.0 kg / min to 7.0 kg / min and further centrifuged. preferable.

  In the method for producing an aqueous dispersion of hydrophilized carbon black according to the present invention, particles other than carbon black called grit contained in carbon black are removed by feeding the hydrophilized product at the above flow rate and centrifuging. can do.

The supernatant obtained by the above centrifugation treatment may be used as the desired hydrophilized carbon black aqueous dispersion as it is, and further by treating with an ultrafiltration membrane to remove excess salts in the supernatant, The aqueous medium may be removed and a concentration treatment may be performed to a desired concentration.
In addition, the hydrophilic carbon black which concerns on this invention can also be isolated by performing a further concentration process.

Conventionally, a hydrophilized carbon black aqueous dispersion is prepared once and then subjected to a filtration test, etc., and repeatedly prepared to a certain extent until a hydrophilized carbon black aqueous dispersion having an appropriate dispersibility is obtained, and suitable manufacturing conditions are determined. However, since a certain amount of time is required for the filtration test, it takes a certain amount of time to determine the manufacturing conditions. For example, when manufacturing a small lot of products, the overall manufacturing time is increased. It was easy to invite.
On the other hand, in the method for producing a hydrophilized carbon black aqueous dispersion according to the present invention, after the production, the dispersibility is improved by an apparatus using optical means such as pulse NMR and a laser diffraction / scattering particle size distribution measuring apparatus. It is possible to quickly and accurately measure the spin-spin relaxation time T2 of ¹ H nuclei and the agglomerate average particle size Dupa _50% , which are influential factors.
Therefore, according to the present invention, there is provided a method for easily and rapidly producing an oxidized carbon black aqueous dispersion that exhibits excellent dispersibility in an aqueous medium and can be suitably used for an ink jet printer ink. be able to.

  When preparing an inkjet printer ink using the hydrophilic carbon black aqueous dispersion according to the present invention, as additives to be added to the hydrophilic carbon black aqueous dispersion, wetting agents, preservatives, antifungal agents, rust preventives, A pH adjusting agent, a penetrating agent, a fixing agent, an antifoaming agent and the like can be mentioned.

Examples of the wetting agent include various water-soluble organic solvents. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, 1,3-butanediol, 1,3 -Propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 2 -Polyhydric alcohols such as ethyl-1,3-hexanediol, 1,2,4-butanol, 1,2,3-butanetriol, petriol, ethylene glycol monoethyl ether, ethylene glycol -Rumonobutyl ether, diethylene glycol monomethyl ether, diethyl Polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether Nitrogen-containing heterocyclic compounds such as monohydric alcohol aryl ethers, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, formamide Amides such as N-methylformamide, N, N-dimethylformamide, monoethanolamine, diethanolamine, triethanolamine, monoethylamine One or more selected from amines such as ethylene, diethylamine and triethylamine, sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol, propylene carbonate, ethylene carbonate, and γ-butyrolactone.
These water-soluble organic solvents can be used alone or in combination with water.

  As preservatives and antifungal agents, one or more selected from sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, isothiazoline compounds, sodium benzoate, sodium pentachlorophenol, proxel XL-2, etc. Can be mentioned.

  Examples of the rust inhibitor include one or more selected from acidic sulfites, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, benzotriazole, and the like.

  Examples of the pH adjuster include hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, lithium carbonate, Examples include one or more selected from alkali metal carbonates such as sodium carbonate and potassium carbonate, amines such as diethanolamine and triethanolamine, boric acid, hydrochloric acid, nitric acid, sulfuric acid, acetic acid and the like.

  As the penetrant, polyhydric alcohol alkyl ethers having low odor and low vapor pressure are preferably used, and among polyhydric alcohol alkyl ethers, the ink penetration rate into a recording material such as paper can be effectively increased. Therefore, it is preferable to select and use a material that improves the quick drying property of the ink on the recording material, prevents bleeding due to the slow drying property, and hardly causes bleeding due to penetration. Specific examples of such polyhydric alcohol alkyl ether include, for example, diethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol isopropyl ether, dipropylene glycol butyl ether, One or more selected from triethylene glycol methyl ether, triethylene glycol butyl ether, tripropylene glycol methyl ether, tripropylene glycol butyl ether and the like can be mentioned.

  When preparing an ink for an inkjet printer, for example, while stirring, adding a hydrophilic carbon black aqueous dispersion while stirring, a wetting agent, preservative, antifungal agent, rust preventive agent, pH adjuster, Add additives such as penetrating agent, fixing agent, antifoaming agent, etc., any known water-soluble resin, wax dispersed in water, resin emulsion, etc., stir, and if necessary with water, water-soluble organic solvent It can manufacture by adjusting a viscosity and filtering by the well-known arbitrary filtration methods.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

Example 1
To pure water 660 L, Tokai Carbon Co., Ltd. Carbon black (nitrogen adsorption specific surface area 135m ² / g, DBP absorption 140cm ^3/100 g) was 50kg charged, after stirring and mixing at a stirring speed of 100 rpm, the sodium persulfate 10 kg was added and heated to 65 ° C., and after reaching 65 ° C., 10 kg of sodium persulfate was added 10 times every 30 minutes while maintaining the temperature, and a total of 100 kg of sodium persulfate was added. Then, oxidation treatment was performed by holding at 65 ° C. for 6 hours.
The treatment solution subjected to the above oxidation treatment is subjected to residual salt separation treatment with an ultrafiltration membrane (AHP-1010, manufactured by Asahi Kasei Co., Ltd., molecular weight cut off 50000), and then an aqueous sodium hydroxide solution is added to adjust the pH to 10. It was adjusted.
In the treatment liquid adjusted to pH 10, the average particle size of the aggregates in the treatment liquid is adjusted at a flow rate of 3.0 kg / min to a centrifuge (manufactured by Mitsubishi Chemical Corporation, SJ-30F). The solution was sent and centrifuged, and the supernatant was collected.
In order to carry out concentration by removing and purifying excess salts in the resulting supernatant and removing water, the above ultrafiltration membrane was again treated to obtain a dispersion having a solid content (oxidized carbon black concentration) of 21% by mass. It was. Purified water was added to the resulting dispersion to adjust the solid content concentration to 20% by mass, thereby obtaining the target oxidized carbon black aqueous dispersion.

(Example 2)
An oxidized carbon black aqueous dispersion was obtained in the same manner as in Example 1, except that the amount of liquid fed to the centrifuge was changed from 3.0 kg / min to 5.0 kg / min.

(Example 3)
Instead of adding 10 kg of sodium persulfate 10 times in total, sodium persulfate was added 10 times in total 15 kg of sodium persulfate in the same manner as in Example 1 except that 150 kg of sodium persulfate was added in total. An oxidized carbon black aqueous dispersion was obtained.

Example 4
An oxidized carbon black aqueous dispersion was obtained in the same manner as in Example 3 except that the amount fed to the centrifuge was changed from 3.0 kg / min to 5.0 kg / min.

(Example 5)
Instead of adding 10 kg of sodium persulfate a total of 10 times, 12.5 kg of sodium persulfate was added a total of 10 times, a total of 125 kg of sodium persulfate was added, and the solution was sent to the centrifuge A carbon black water dispersion was obtained in the same manner as in Example 1 except that the amount was changed from 3.0 kg / min to 4.0 kg / min.

  The production conditions in Examples 1 to 5 are shown in Table 1.

(Comparative Example 1)
To pure water 660 L, after Tokai Carbon Co., Ltd. Carbon black (nitrogen adsorption specific surface area 135m ² / g, DBP absorption 140cm ^3/100 g) was 50kg charged, and stirred and mixed at a stirring rate of 100 rpm, peroxide as an oxidizing agent 100 kg of sodium sulfate was added and the mixture was heated to 65 ° C. and held at 65 ° C. for 6 hours for oxidation treatment.
The treatment solution subjected to the above oxidation treatment is subjected to residual salt separation treatment with an ultrafiltration membrane (AHP-1010, manufactured by Asahi Kasei Co., Ltd., molecular weight cut off 50000), and then an aqueous sodium hydroxide solution is added to adjust the pH to 10. It was adjusted.
In the treatment liquid adjusted to pH 10, the average particle size of aggregates in the treatment liquid is adjusted at a flow rate of 3.0 kg / min to a centrifuge (manufactured by Mitsubishi Chemical Corporation, SJ-30F). The solution was sent and centrifuged, and the supernatant was collected.
In order to carry out concentration by removing and purifying excess salts in the resulting supernatant and removing water, the above ultrafiltration membrane was again treated to obtain a dispersion having a solid content (oxidized carbon black concentration) of 21% by mass. It was. Purified water was added to the resulting dispersion to adjust the solid content concentration to 20% by mass, thereby obtaining the target oxidized carbon black aqueous dispersion.

(Comparative Example 2)
An oxidized carbon black water dispersion was obtained in the same manner as in Comparative Example 1, except that the amount of liquid fed to the centrifuge was changed from 3.0 kg / min to 5.0 kg / min.

(Comparative Example 3)
An oxidized carbon black water dispersion was obtained in the same manner as in Comparative Example 1, except that the amount of liquid fed to the centrifuge was changed from 3.0 kg / min to 5.5 kg / min.

(Comparative Example 4)
The carbon oxide was oxidized in the same manner as in Comparative Example 1 except that the amount of sodium persulfate input was changed from 100 kg to 50 kg and the amount of liquid fed to the centrifuge was changed from 3.0 kg / min to 2.0 kg / min. A black water dispersion was obtained.

  The production conditions in Comparative Examples 1 to 4 are shown in Table 2.

Using the oxidized carbon black aqueous dispersions obtained in Examples 1 to 5 and Comparative Examples 1 to 4, respectively, measured by the CPMG method of pulse NMR in the state of being dispersed in water by the following method ¹ The spin-spin relaxation time T2 of H nuclei, the average particle diameter Dupa _50% , electrical conductivity, pH, filterability, and print density were measured. The results are shown in Table 4 and Table 5.

<Spin-spin relaxation time T2 of ¹ H nucleus measured by CPMG method of pulse NMR>
A predetermined amount is collected as a measurement sample from each of the obtained oxidized carbon black aqueous dispersions, and using “Acron Area” manufactured by XiGo Nanotools, the measurement nucleus is a hydrogen nucleus, under measurement conditions of a measurement temperature of 30 ° C. and a frequency of 13 MHz. The spin-spin relaxation time T2 was determined from the CPMG method.

<Average Agglomerate Particle Size Dupa _{50% of} Oxidized Carbon Black Particles>
In each oxidized carbon black aqueous dispersion, a heterodyne laser Doppler type particle size distribution measuring device "UPA model 9340, manufactured by Microtrac Co., Ltd." is used to measure the particle size of the carbon black particle aggregate to create a cumulative frequency distribution curve. From this cumulative frequency distribution curve, the value of 50% cumulative frequency was determined as the average particle size (D50) of the carbon black particle aggregates.

<Electrical conductivity>
The liquid temperature of each oxidized carbon black aqueous dispersion was kept at 25 ° C., and the electric conductivity was measured using “Electric conductivity meter CM-30G” manufactured by Toa DKK Co., Ltd.

<PH>
The liquid temperature of each oxidized carbon black aqueous dispersion was kept at 25 ° C., and the pH was measured using “pH Meter HM-30G” manufactured by Toa DKK Corporation.

<Filterability>
Using 100 g of each oxidized carbon black aqueous dispersion as a measurement sample, a filtration test was conducted under a reduced pressure of 2666.4 Pa using a cellulose mixed ester membrane filter (membrane pore diameter: 1 μm) having a diameter of 25 mm, and the amount of filtration passing was measured.

<Print density>
In order to achieve the content ratio shown in Table 3, glycerin, diethylene glycol monobutyl ether, acetyl glycol, benzotriazole, preservative (Proxel XL-2 manufactured by Avicia Co., Ltd.) and triethanolamine are further added to each oxidized carbon black. By adding each, the water-based ink for inkjet printers was prepared, it filled in the cartridge for "EM-930C" by an inkjet printer Epson company, and the printing test was done. Plain paper (Xerox 4024) was used as the print medium.
After printing, each print density was measured for reflection optical density (OD value) using a Macbeth densitometer “RD-927, manufactured by Colemorgen”.

From Table 4, in Examples 1 to 5, the average of agglomerates in a state where the spin-spin relaxation time T2 of ¹ H nuclei measured by the pulsed NMR CPMG method of oxidized carbon black is 500 ms or less and dispersed in water. When the particle size Dupa _50% is 70 nm to 200 nm, the total amount of each oxidized carbon black aqueous dispersion 100 g is excellent in filterability (dispersibility) that can pass through a filter having a membrane pore diameter of 1 μm. It can be seen that the ink jet printer ink prepared using oxidized carbon black can exhibit excellent print density.

On the other hand, from Table 5, when the spin-spin relaxation time T2 of ¹ H nucleus measured by CPMG method of pulsed NMR of oxidized carbon black is more than 500 ms (Comparative Example 1 to Comparative Example 4), each oxidized carbon black aqueous dispersion It can be seen that only a part of 100 g can pass through a filter having a membrane pore diameter of 1 μm and the filterability (dispersibility) is poor.
Further, from Table 5, when the average particle diameter Dupa _50% of the agglomerate in the state dispersed in water is out of the range of 70 nm to 200 nm (Comparative Example 3 and Comparative Example 4), the printing itself is impossible ( Comparative Example 3) shows that the print density is very low (Comparative Example 4).
From Table 2 and Table 5, in Comparative Examples 1 to 4, since the oxidizing agent was added to the carbon black at a time, the reaction temperature increased rapidly, and the amount of self-decomposition before oxidizing the carbon black was mostly It is considered that the acidic functional group could not be uniformly imparted to the carbon black surface, and the relaxation time was over 500 ms.
From Tables 2 and 5, it is considered that in Comparative Example 3 and Comparative Example 4, Dupa _50% was out of the range of 70 to 200 nm because classification conditions were strict.

  According to the present invention, hydrophilized carbon black, hydrophilized carbon black aqueous dispersion, and method for producing hydrophilized carbon black that exhibit excellent dispersibility in an aqueous medium and can be suitably used for inkjet printer inks Can be provided.

Claims (7)

The spin-spin relaxation time T2 of ¹ H nucleus measured by the CPMG method of pulse NMR in a state dispersed in water is 500 ms or less,
Hydrophilic carbon black characterized in that the average particle diameter Dupa _50% of agglomerates in a state dispersed in water is 70 nm to 200 nm.   A hydrophilized carbon black aqueous dispersion comprising the hydrophilized carbon black according to claim 1.   The aqueous hydrophilized carbon black dispersion according to claim 2, wherein the solid content concentration is 3% by mass to 25% by mass.   The hydrophilized carbon black aqueous dispersion according to claim 2 or 3, wherein the pH is 6.0 to 9.0.   The hydrophilized carbon black aqueous dispersion according to any one of claims 2 to 4, wherein the electrical conductivity at a solid content concentration of 15% by mass is 3 mS / cm or less.   The hydrophilized carbon black aqueous dispersion according to any one of claims 2 to 5, which is used for ink jet printer ink. In an aqueous medium, with respect to 100 parts by mass of carbon black, a hydrophilization treatment was performed by sequentially adding 30 to 500 parts by mass of a hydrophilizing agent little by little.
Centrifuge the resulting hydrophilized product,
The spin-spin relaxation time T2 of ¹ H nucleus measured by the CPMG method of pulse NMR in a state dispersed in water is 500 ms or less,
A method for producing an aqueous dispersion of hydrophilized carbon black, characterized in that an aqueous dispersion of hydrophilized carbon black having an average particle size Dupa _50% of agglomerates in a state of being dispersed in water of 70 nm to 200 nm is obtained.