JPH11189736A - Aqueous dispersion of carbon black - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject dispersion exhibiting excellent dispersibility and dispersion stability by including carbon black, an aqueous medium and a specific dispersant. SOLUTION: This dispersion comprises (A) carbon black, (B) an aqueous medium, and (C) a dispersant of the formula (R<1> and R<2> are each H or a 1-4C alkyl; R<3> is ethylene, phenylene residue or naphthalene residue; M is H, an alkali metal, ammonia or an amine; (n) is an integer of 1-3); wherein, for the component A, the amount of the whole surface functional group is pref. >=0.2 meq/g, more pref. 0.2-0.8 meq/g, the particle size being pref. 0.01-10 μm; the component C is pref. taurine sodium salt or α-anphthylaminesulfonic acid alkali metal salt (e.g. sodium 4-amino-1naphthalenesulfonate), its amount of the component C to be added being pref. 0.01-10 mmol per g of the component A.

Description

Detailed Description of the Invention

[0001]

This invention relates to an aqueous dispersion of carbon black.

[0002]

2. Description of the Related Art Carbon black is used in a wide range of fields such as printing inks, paints and plastic forming materials as color pigments and light shielding materials. In the past, it has been common to use carbon black dispersed in an organic medium in these applications, but recently, from the viewpoint of environmental problems and effects on the human body, conversion to water-based is progressing rapidly. is there. However, most carbon blacks are inherently lipophilic, and their suitability for pigment dispersion and the like is greatly inferior to the aqueous vehicle, and therefore, a satisfactory dispersion cannot be obtained by the ordinary dispersion method. Therefore, conventionally, various additives, for example, a method of modifying the surface of carbon black with a dispersant such as a surfactant or an aqueous pigment dispersion resin to impart dispersibility in water has been investigated. If the modification of the particle surface is insufficient, the particles easily re-aggregate and the dispersion stability is impaired, or if the compatibility of the dispersant and the dispersion resin is poor, the performance of the ink or paint may deteriorate. was there. Further, if the dispersant resin is changed depending on the application, the dispersant must be selected according to the change, and there is a problem in that it lacks versatility.

On the other hand, various attempts have been made to impart dispersibility in water to carbon black, and one of them is a hydrophilic treatment by oxidizing carbon black. As the oxidation treatment method, a vapor phase oxidation method such as ozone treatment and plasma treatment and a liquid phase oxidation method using nitric acid, hydrogen peroxide solution, sodium perchlorate, etc. have been devised. Comparing general oxidation treatment conditions, liquid-phase oxidation is more effective than gas-phase oxidation, and in liquid-phase oxidation, nitric acid increases surface acidity rather than hydrogen peroxide, and hydrophilicity improves. Are known. However, it has been pointed out that it is difficult to purify after the treatment by liquid phase oxidation, and that mutagenesis is caused particularly in carbon black obtained by nitric acid oxidation. Further, in the gas phase oxidation, there is an advantage that no purification step is required, but as mentioned above, there is a disadvantage that sufficient hydrophilicity cannot be obtained due to the low acidity.

As another method, a hydrophilization treatment method using fluorine gas has been devised, but it has a problem in performance stability during storage.

[0005]

An object of the present invention is to provide a carbon black aqueous dispersion having excellent dispersibility and dispersion stability without these drawbacks.

[0006]

[Wherein R ¹ and R ² each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ represents an ethylene group, a phenylene residue or a naphthylene residue, and M represents hydrogen, an alkali metal, ammonia or an amine. And n represents an integer of 1 to 3. ]

Further, the present invention is the above-mentioned carbon black aqueous dispersion, wherein the total amount of surface functional groups of carbon black is 0.2 meq/g or more.

Furthermore, the present invention is characterized in that the dispersant is a taurine sodium salt represented by the general formula (1) in which R ¹ and R ² are hydrogen, R ³ is an ethylene group, M is sodium and n is 1. And the above-mentioned carbon black aqueous dispersion. Furthermore, in the present invention, the dispersant is a sodium salt of α-naphthylamine sulfonic acid represented by formula (1), wherein R ¹ and R ² are hydrogen, R ³ is a naphthylene residue, M is sodium, and n is 1. The above-mentioned carbon black aqueous dispersion characterized in that.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The carbon black used in the present invention is not particularly limited by the type and production history, and various types such as commercially available oil furnace black, gas furnace black, thermal black, acetylene black, and channel black can be used. Further, carbon black which has been subjected to the usual ozone treatment, plasma treatment and liquid phase oxidation treatment can also be used. Generally, in the production process of carbon black, surface functional groups such as a carboxyl group (—COOH), a phenolic hydroxyl group (—OH), and a quinone group (>C═O) are generated on the particle surface.
The quantification of these functional groups was carried out by measuring the carboxyl group (-COO
H) and a phenolic hydroxyl group (—OH) can be determined by a titration method, and a quinone group (>C═O) can be determined by a sodium borohydride hydrogen absorption method.

The carbon black used in the present invention has a total amount of these surface functional groups, that is, a total surface functional group amount of 0.2.
~8.0 meq/g is preferable, and 1.0~
It is particularly preferably 6.0 meq/g. If the total amount of functional groups on the surface is less than 0.2 meq/g, the adsorption or reaction points of the dispersant are small and a sufficient dispersion effect cannot be obtained. On the other hand, there is no particular problem even if carbon black having a total amount of functional groups on the surface of more than 8.0 meq/g is used, but no significant improvement in dispersion effect is observed. The ratio of each functional group to the total amount of surface functional groups is not particularly limited, but it is preferable that the content of carboxyl groups is large.

The particle size of carbon black used in the present invention is the same as the particle size range of carbon black used in ordinary inks and paints, but it is preferably 0.01 to 10 μm, and 0.01 to 0. Particularly preferably, it is 5 μm. However, the particle size referred to here means an average primary particle size measured by an electron microscope or the like which is generally used to show the physical properties of carbon black. The dispersant used in the present invention is represented by the general formula (1) and has an amino group and a sulfonic acid (salt) group in the molecule. R ¹ R ² N—R ³ —(SO ₃ M) _n (1) [wherein R ¹ and R ² are each a hydrogen atom or a carbon number 1 to
4 represents an alkyl group, R ³ represents an ethylene group, a phenylene residue or a naphthylene residue, M represents hydrogen, an alkali metal, ammonia or an amine, and n represents an integer of 1 to 3. Examples of the amino group in the general formula (1) include a primary amino group (—NH ₂ ), a secondary amino group such as methylamine, ethylamine and butylamine, and a tertiary amino group such as dimethylamine, diethylamine and dibutylamine. it can. These amino groups are adsorbed by acid-base interaction to a carboxyl group (-COOH) and a phenolic hydroxyl group (-OH) which are acidic among the surface functional groups of carbon black, and particularly, a primary amino group. (-N
For H ₂ ), in addition to the acid-base interaction, a quinone group (>
It is known to form a Schiff base (>C=N-) with C=O), and such an action can provide a high dispersion effect.

The sulfonic acid (salt) group in the general formula (1) means a sulfonic acid when M is hydrogen and a sulfonate when M is an alkali metal, ammonia or amine. When M in the general formula (1) is a hydrogen atom, that is, sulfonic acid, it interacts with an amino group contained in the dispersant, and the dispersants undergo intermolecular association to form an amino group on the surface functional group of carbon black. In some cases, the adsorption or reaction of is inhibited and a sufficient dispersion effect cannot be obtained. In such a case, the target carbon black aqueous dispersion can be obtained by neutralizing the sulfonic acid with an alkali metal, ammonia or an amine before or during the surface treatment step before use. The sulfonic acid (salt) group in the general formula (1) is an ionic group and can impart hydrophilicity to carbon black.

Specific examples of the dispersant used in the present invention include:
Taurine, sphanic acid, orthanilic acid, methanilic acid,
Dimethylaniline-m-sulfonic acid, diethylaniline-m-sulfonic acid, anilinedisulfonic acid, aminophenolsulfonic acid, aminosulfobenzoic acid, aminonitrophenolsulfonic acid, aminonaphtholsulfonic acid, aminonaphtholdisulfonic acid, α-naphthylaminesulfonic acid , Β-naphthylamine sulfonic acid, α-naphthylamine disulfonic acid, β-naphthylamine disulfonic acid, naphthylamine trisulfonic acid, or their alkali metal salts, ammonium salts, amine salts and the like, but among them, taurine sodium salt or α -One of the alkali metal salts of naphthylamine sulfonic acid
It is particularly preferred to use the seed 4-amino-1-naphthalenesulfonic acid sodium salt. These dispersants may be used alone or in combination of two or more.

The amount of the dispersant added in the present invention is
0.01 to 10 mmol per 1 g of carbon black
Is preferable, and 0.1 to 5 mmol is particularly preferable. If the addition amount is less than 0.01 mmol, the amount of the dispersant adsorbed on the surface of the carbon black particles or the amount of reaction thereof is small, and a satisfactory dispersion effect cannot be obtained. On the other hand, if the added amount is more than 10 mmol, there is no particular problem, but no significant improvement in the dispersion effect is observed. As the aqueous medium used in the present invention, a medium containing various aqueous solvents and aqueous resins can be used. Here, the aqueous solvent represents water or a mixed liquid of water and an organic solvent compatible with water. Examples of the organic solvent include lower alcohols such as methanol, ethanol and propanol, amides such as dimethylformamide and dimethylacetamide, ketones such as acetone and diacetone alcohol, ethers such as tetrahydrofuran and dioxane, and N-methyl. 2-pyrrolidone and the like can be mentioned, and these can be used alone or in combination of two or more kinds.
As the water-based resin, an acrylic resin, a urethane resin, a polyoxyalkylene resin, a vinyl resin, an epoxy resin, an amino resin, a polyvinyl acetal resin, a polyvinyl butyral resin, a styrene resin, a phenoxy resin, which are usually used for water-based paints, Examples thereof include polyester resins, which may be used alone or in combination of two or more. The form of these resins such as an aqueous solution type and an emulsion type is not particularly limited. Further, conventionally used surfactants may be used in combination for the purpose of improving dispersion stability, and various additives such as antifoaming agents and preservatives may be used.

The carbon black aqueous dispersion of the present invention comprises:
It is obtained by mixing and stirring carbon black with the above-mentioned dispersant and aqueous medium. The method of mixing and stirring is not particularly limited, but it is preferable to disperse carbon black in an aqueous medium containing a dispersant by shear stress by a pulverizer or a disperser or by impact force by the medium. Examples of such a pulverizer or disperser include a three-roll mill or a two-roll mill in which carbon black particles are finely dispersed by shear stress, a ball mill in which carbon black particles are finely dispersed by the impact force of media such as glass beads or zirconia beads, and an attritor , Sand mills, co-ball mills, basket mills, vibration mills, paint conditioners, etc., dispersers, homogenizers, clear mix (trade name), etc. that are finely dispersed by rotating blades that generate shear stress, cavitation, collision force, potential core, etc. Examples include a kneader, an extruder, and a jet mill that finely disperse carbon black particles with each other or with the collision force and shearing force of a vehicle or a disperser wall surface, and an ultrasonic disperser that finely disperses with ultrasonic waves. it can. Further, heat treatment may be performed during or before the process of mixing and stirring the carbon black, the dispersant and the aqueous medium. The heat treatment temperature is not particularly limited, but is preferably 40°C to 100°C.

The carbon black aqueous dispersion of the present invention comprises:
The amino group of the dispersant is adsorbed to the functional group on the surface of the carbon black particles by an acid-base interaction, and the primary amino group (-NH ₂ ) is a quinone group (>C in addition to the acid-base interaction). =O) and a Schiff base (>C=N-) are formed, the sulfonic acid (salt) group portion of the dispersant is coordinated on the surface of the carbon black particles, and the dispersibility in an aqueous medium is improved. Conceivable. Further, the carbon black aqueous dispersion of the present invention has excellent dispersion stability and jet blackness, and can provide a coating film with high gloss and high concentration.
The carbon black aqueous dispersion of the present invention is a printing ink,
It can be used in a wide range of fields such as paints, cosmetics, writing inks, toners, electrophotographic materials, recording materials such as inkjet, and coloring agents such as plastics.

[0016]

EXAMPLES The present invention will be described with reference to examples. In the example,
"Parts" and "%" are "parts by weight" and "% by weight", respectively. The amount of each surface functional group of the carbon black used in the examples was measured by the following method, and they were summed to obtain the total amount of surface functional groups. The results are shown in Table 1. (1) Measurement of carboxyl group (—COOH) amount 1 g of dry carbon black was weighed in units of 1 mg and adjusted to 0.
The mixture was shaken in 50 ml of 1N aqueous sodium hydrogencarbonate solution for 4 hours to cause a reaction, then filtered, and the supernatant of the filtrate was filtered.
Collect ml and titrate with 0.01 N hydrochloric acid aqueous solution.
The amount of carboxyl groups is calculated by the following formula as milliequivalent (meq./g) in 1 g of carbon black. Amount of carboxyl group=(50/20×0.01×(titration amount−vacuum titration))/carbon black sample weight (2) Measurement of hydroxyl group (—OH) amount 1 g of dry carbon black was weighed in 1 mg unit and adjusted to 0.
After reacting by shaking in 50 ml of 1N aqueous sodium hydroxide solution for 4 hours, the mixture was filtered and the supernatant of the filtrate was 20 m.
1 is taken and titrated with a 0.01 N hydrochloric acid aqueous solution. From this, the total amount of the amount of hydroxyl groups and the amount of carboxyl groups was determined by the following formula as milliequivalent (meq./g) in 1 g of carbon black. (Carboxyl group+hydroxyl group) amount=(50/20×0.01×(titration amount−empty titration amount))/carbon black sample weight The amount of the hydroxyl group was determined by subtracting the previously determined amount of the carboxyl group from this total amount. (3) Amount of quinone group (>C=O) 3 g of dry carbon black was weighed in units of 1 mg, and 100 mg of sodium borohydride dissolved in 0.1 N sodium hydroxide aqueous solution was reacted in 50 ml for 2 hours. Then, the amount of hydrogen gas generated when 6N sulfuric acid aqueous solution is added is measured. Perform a blank test to determine the amount of hydrogen gas generated. The quinone group amount is calculated by the following formula as a milliequivalent (meq./g) in 1 g of carbon black. Quinone group amount=reacted sodium borohydride amount/carbon black sample weight

[0017]

[Table 1]

The dispersibility of the carbon black aqueous dispersions obtained in the examples was evaluated by a laser particle size analyzer (MICROTRAC UPA Nikkiso Co., Ltd.).
The dispersed average particle diameter measured by The results are shown in Table 2. Example 1 Carbon black A 5.0 parts, 4-amino-1-naphthalenesulfonic acid sodium salt 1.2 parts, purified water 93.
Zirconia beads were added to the composition of 8 parts and dispersed for 90 minutes with a paint shaker (manufactured by Red Devil Co.) to obtain a carbon black aqueous dispersion.

Example 2 Zirconia beads were added to a composition consisting of 12.0 parts of carbon black A, 1.6 parts of sodium taurine salt, and 86.4 parts of purified water, dispersed with a paint shaker for 90 minutes, and at 24° C. at 70° C. Heat treatment was carried out for an hour to obtain an aqueous dispersion of carbon black. Example 3 Carbon black A 12.0 parts, 6-amino-1,3
-Zirconia beads were added to a composition consisting of 4.8 parts of naphthalenedisulfonic acid disodium salt and 83.2 parts of purified water, dispersed for 90 minutes with a paint shaker, and then at 24°C at 70°C.
Heat treatment was carried out for an hour to obtain an aqueous dispersion of carbon black.

Example 4 Carbon black B 5.0 parts, 4-amino-1-naphthalene sulfonic acid sodium salt 0.6 part, purified water 94.
Zirconia beads were added to the composition of 4 parts and dispersed for 90 minutes with a paint shaker to obtain an aqueous carbon black dispersion. Comparative Example 1 Zirconia beads were added to a composition consisting of 5.0 parts of carbon black A and 95.0 parts of purified water, and the mixture was dispersed for 90 minutes with a paint shaker to obtain a carbon black aqueous dispersion. Comparative Example 2 Zirconia beads were added to a composition consisting of 5.0 parts of carbon black B and 95.0 parts of purified water, and the mixture was dispersed for 90 minutes with a paint shaker to obtain a carbon black aqueous dispersion.

Comparing Examples 1, 2, and 3 with Comparative Example 1,
It can be seen that the dispersibility of carbon black is remarkably improved in the examples in which the dispersant is used. Similar effects can be confirmed by comparing Example 4 and Comparative Example 2.

[0022]

[Table 2]

[0023]

The carbon black aqueous dispersion of the present invention can obtain excellent dispersibility in an aqueous medium and dispersion stability by using a dispersion having an amino group and a sulfonic acid (salt) group. It was

Claims (4)

[Claims] 1. An aqueous carbon black dispersion comprising carbon black, an aqueous medium and a dispersant represented by the following general formula (1). R ¹ R ² N—R ³ —(SO ₃ M) _n (1) [wherein R ¹ and R ² are each a hydrogen atom or a carbon number 1 to
4 represents an alkyl group, R ³ represents an ethylene group, a phenylene residue or a naphthylene residue, M represents hydrogen, an alkali metal, ammonia or an amine, and n represents an integer of 1 to 3. ] 2. The carbon black aqueous dispersion according to claim 1, wherein the total amount of surface functional groups of carbon black is 0.2 meq/g or more. 3. A dispersant represented by the general formula (1) is R ¹ or R ¹ .
² is hydrogen, R ³ is ethylene group, M is sodium, n is 1
The aqueous dispersion of carbon black according to claim 1 or 2, which is a sodium salt of taurine represented by: 4. The dispersant used in the general formula (1) is R ¹ or R ¹ .
² is hydrogen, R ³ is naphthylene residue, M is sodium, n
Is an α-naphthylamine sulfonic acid sodium salt represented by 1. 4. The carbon black aqueous dispersion according to claim 1, wherein