JPH05186704A - Surface-modified carbon black and production thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a surface-modified carbon black which can always obtain uniform dispersion stability regardless of an acidic compounding system and a basic compounding system, and a method for producing the same. [Structure] A surface-modified carbon black having a surface functional group composition in which a hydroxyl group having a molar ratio to a quinone group of at least 10 or more is introduced on the surface of carbon black. In the production method, carbon black is treated with an oxidizing agent or a sulfur-containing oxidizing agent to sulfonate the surface, and the filtered and dried residual carbon black is melt-reacted with a basic melting agent and cooled. Then, it is neutralized with an acid, washed with water and dried.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a surface-modified carbon black for improving dispersibility and a method for producing the same.

[0002]

2. Description of the Related Art Carbon black is widely used as a coloring pigment or an ultraviolet absorber in the fields of printing inks and paints. In order to improve the coloring property and the light absorption performance of these products, it is necessary to uniformly disperse carbon black in a solvent or a resin, but since carbon black has poor dispersibility, it is necessary to obtain a uniform dispersion system. A lot of energy is required in terms of process work. As a means for alleviating such problems, a method of adding various dispersants is generally performed. However, even if this method is used, satisfactory dispersibility is not obtained, and if the dispersibility of the dispersant and the vehicle component is poor, the performance of the ink or paint is deteriorated.

Generally, the relationship between the surface state of the carbon black to be dispersed and the vehicle resin is such that carbon black having a basic surface (electron donor property) strongly adsorbs with a polymer having an acidic functional group and has an acidic surface (electron-accepting property). A polymer having a basic functional group tends to be easily adsorbed on carbon black having a scepter property. Therefore, good dispersion stability can be obtained when the charge polarities of the carbon black to be mixed and the vehicle resin are different. A method for modifying the polarity of the particle surface has been proposed for a long time in order to enhance the dispersibility of carbon black without using a dispersant by utilizing such a propensity. For example, a method in which carbon black is subjected to a dry oxidation treatment with air, ozone, or nitrous acid gas to introduce an acidic group to the surface (Japanese Patent Publication No. 52-2874), carbon black is wet treated with aqueous ammonia to form a base on the surface. A typical surface modification method is a method of introducing a functional group (“Materials Technology”, Volume 2, No. 11, pp. 665 to 666).

[0004]

However, in the ink / paint industry that uses various pigments and additives having different surface charges, it may be difficult to control the surface charge of all pigments. In many cases, the process that prioritizes the affinity is selected even if the dispersion stability is sacrificed. Under such circumstances, a carbon black having a weakly acidic or neutral surface, which exhibits good dispersion stability regardless of whether it is an acidic compounding system or a basic compounding system, is desired.

As a result of intensive studies on the surface modification of carbon black satisfying the above-mentioned requirements, the present inventors have found that the sulfonic acid group is once fixed on the surface of carbon black, and then it is melted with an alkali to substitute it with a hydroxyl group. It was clarified that when the surface functional group composition was adjusted to adjust the molar ratio with the quinone group, it was converted into carbon black having a weakly acidic to neutral surface property showing good uniform dispersion in various compounding systems.

The present invention was developed on the basis of the above findings, and its object is to produce a surface-modified carbon black which can always obtain uniform dispersion stability regardless of an acidic compounding system or a basic compounding system. To provide an industrial method for doing so.

[0007]

The surface-modified carbon black according to the present invention for achieving the above-mentioned object has a surface functional group in which a hydroxyl group having a molar ratio to the quinone group of at least 10 or more is introduced on the surface of the carbon black. The composition is characterized by having a composition.

Carbon black produces functional groups such as carboxyl groups (-COOH) and quinone groups (C = O) on the surface of particles during the formation process. The surface functional group composition according to the present invention has a molar ratio (-) to quinone groups. OH / C = O) has at least 10 or more hydroxyl groups, and this composition has a weakly acidic to neutral surface property showing good uniform dispersibility in both acidic and basic compounding systems. Become.

The above-mentioned surface-modified carbon black is treated by oxidizing the carbon black with an oxidizing agent or a sulfur-containing oxidizing agent to make the surface sulfone, and filtering and drying the residual carbon black to cause a melting reaction with a basic melting agent to cool. Then
Then, it can be produced by a method of neutralizing with an acid, washing with water and drying.

The carbon black as a raw material is not particularly limited by the type and production history, and various types such as oil furnace black, gas furnace black, channel black, thermal black, acetylene black can be used. The raw material carbon black is first subjected to an oxidation treatment for sulfonating the surface and fixing the sulfone groups.

For the carbon black containing a large amount of sulfur in the raw material such as oil furnace black, the oxidation treatment is carried out by a method of oxidizing the sulfur compound on the particle surface using an oxidizing agent. For carbon black with a low sulfur content in the raw material such as gas furnace black, channel black, and thermal black, a sulfonic acid group is added to the particle surface by a direct substitution reaction using a sulfur-containing oxidizing agent. The method of fixing is adopted. By controlling the oxidation conditions in this step, it becomes possible to adjust the molar ratio of hydroxyl groups to quinone groups on the finally obtained carbon black surface.

Examples of the oxidizing agent used in this case include hydrogen peroxide, nitric acid, bromine water, hypochlorite, hypobromite, permanganate, chromate and the like. As the sulfur-containing oxidizing agent, for example, sulfuric acid, fuming sulfuric acid,
Examples thereof include sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid and amidosulfuric acid. These oxidizers and sulfur-containing oxidizers are usually used in the state of an aqueous solution in which carbon black is dispersed or dipped, but the concentration thereof may be such that the oxidative action proceeds, and it is high enough to cause a rapid oxidative reaction. Concentrations should be avoided. Therefore, it is preferable that the treatment operation is also performed in a process in which the carbon black is allowed to stand for a predetermined time with the oxidizing agent or the sulfur oxidizing agent for a predetermined time to slowly progress the oxidation reaction.

After the oxidation treatment, the carbon black is diluted by adding water and filtered. After filtration, the residual carbon black is thoroughly washed with a saturated aqueous sodium chloride solution to remove the oxidant component and dried. Drying in this case is preferably carried out in a temperature range of 90 ° C. or lower, because if the drying is carried out at a high temperature, there is a slight influence of the remaining oxidant component, and the oxidation proceeds further. Further, in order to complete the dehydration in a short time, a means such as reduced pressure drying may be applied.

The dried residual carbon black is added with a basic melting agent and kept at a temperature of 200 ° C. or higher for 60 minutes or more with stirring to cause a melting reaction to convert the sulfonic acid groups on the surface into hydroxyl groups. As the basic melting agent, sodium or potassium hydroxide, carbonate or the like is used. The carbon black after the melting reaction treatment is immediately cooled, subsequently subjected to a neutralization treatment with an appropriate inorganic acid such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid, thoroughly washed with water and then dried to obtain the surface-modified carbon black of the present invention. To get

[0015]

[Function] The modified carbon black in which acidic groups are fixed on the surface of particles by the conventional technique does not exhibit good dispersibility unless the resin and the additive are all in a compounding system on the acidic side. The fixed modified carbon black can be uniformly dispersed only in a basic compounding system. However, the surface-modified carbon black provided by the present invention is substituted with a hydroxyl group having a molar ratio to the quinone group of at least 10 or more as a functional group composition of the surface, and exhibits a substantially weakly acidic to neutral surface property. ing. Therefore, even if the compounding target is a resin component containing various functional groups such as a hydroxyl group, a carboxyl group, an amino group, an imino group, a methylol group, an epoxy group, and an isocyanate group, good and stable uniform dispersibility can always be obtained.

Further, according to the production method of the present invention, carbon black surface is fixed with a sulfonic acid group and treated with a basic melting agent to substitute with a hydroxyl group by an industrial process. It becomes possible to efficiently produce a modified carbon black having a functional group structure. In particular, when an oil furnace carbon black containing a large amount of sulfur is used as a raw material, the sulfur content can be utilized for sulfonization, which is more advantageous for industrial production.

[0017]

[Example] With a sulfur content of 0.3% by weight, the composition of surface functional groups in 1 g of carbon black is 4 μl of carboxyl groups.
Oil furnace black of eq./g and quinone group 25 μeq / g was used as a raw material, and 12 g of this carbon black was subjected to oxidation treatment under various conditions using various oxidizing agents. After the oxidation treatment, 500 ml of water and 58 g of sodium chloride were added, and the mixture was stirred and mixed, followed by suction filtration, and the residue was thoroughly washed with saturated aqueous sodium chloride solution. The residual carbon black was dried for 48 hours in a constant temperature oven maintained at 80 ° C, and 5 g of this was heated to 250 ° C.
The mixture was placed in a mixture of 100 g of the basic melting agent and 10 ml of water heated at 0 ° C., and the reaction was carried out while stirring for 90 minutes, then the temperature was kept at 325 ° C. for 5 minutes, and the reaction product was immediately put into 1 kg of crushed ice. Quenched. When the ice was completely melted and the reaction product was in a cooled state, dilute sulfuric acid was injected to neutralize the reaction product, and the reaction product was suction-filtered, and then the residue was washed with water until no sulfate ion was observed, and the temperature was kept at 90 ° C. Dried at temperature.

The surface functional groups of each of the carbon blacks surface-modified in this way were measured, and the results are shown in Table 1 in comparison with the varying conditions during production. The measurement of each functional group was carried out by the following method. (1) Measurement of carboxyl group (-COOH) content 5 g of dry carbon black was weighed in 1 mg units, reacted with 50 ml of 0.1 N sodium hydrogen carbonate aqueous solution by shaking for 6 hours, filtered, and the supernatant of the filtrate was filtered. Collect 20 ml and
Titrate with a 05N hydrochloric acid solution. Carboxyl groups are
Calculate as the microequivalent (μeq. / G) in 1 g of carbon black by the following formula.

(2) Measurement of hydroxyl (-OH) content 0.1 to 0.3 g of dried carbon black was weighed in units of 1 mg, and 5 × 10 ^-4 / l of 2,2-diphenyl-1-picrylhydrazyl ( After reacting with 25 ml of a carbon tetrachloride solution (DPPH) at 60 ° C. for 6 hours, the supernatant is collected by centrifugation and the absorbance is measured at a wavelength of 520 nm. The hydroxyl content was applied to a calibration curve prepared separately, and the microequivalent (μ
eq / g) is calculated from the following formula.

(3) Measurement of quinone (C = O) content 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 with 50 ml for 2 hours. After that, the supernatant after the reaction is centrifuged to collect 10 ml, and the amount of hydrogen gas generated when 0.3 ml of 12N sulfuric acid aqueous solution is added is measured. The quinone group content is calculated from the following formula as microequivalent (μeq. / G) in 1 g of carbon black.

[0021]

[Table 1]

From the results shown in Table 1, the surface-modified carbon blacks obtained in RUN Nos. 1 to 4 have a large molar ratio of the hydroxyl group content to the quinone group content. It has a surface texture close to neutrality. On the other hand, under the changing conditions of RUN Nos. 5 to 6, many hydroxyl groups are not formed.

[0023]

As described above, according to the present invention, a surface-modified carbon black capable of always providing good dispersibility and stability without being affected by the charge polarity of the compounding component system A manufacturing method for efficiently obtaining the same is provided. Therefore, it is extremely useful as a coloring pigment for inks and paints and an ultraviolet absorber.

Claims (2)

[Claims] 1. A surface-modified carbon black having a surface functional group composition in which a hydroxyl group having a molar ratio with respect to a quinone group of at least 10 is introduced on the surface of the carbon black. 2. A carbon black is treated with an oxidant or a sulfur-containing oxidant to make the surface sulfone, and the filtered and dried residual carbon black is melt-reacted with a basic melting agent and cooled, and then neutralized with an acid. Treated and washed with water,
A method for producing a surface-modified carbon black, which comprises drying.