JPS58222157A - Purification of carbon black - Google Patents

Abstract

PURPOSE:To purify carbon black by removing impurities such as metallic compds. or sulfides from it, by heat-treating at a specific temp. range in an atmosphere contg. hydrogen gas. CONSTITUTION:Carbon black is heat-treated at 500-1,500 deg.C in an atmosphere contg. hydrogen gas. By such an easy treatment, sulfides or metallic compds. in carbon black, which have been comparatively difficult to remove, are substantially reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying carbon black, and its purpose is to remove impurities such as metal compounds and sulfur-containing compounds contained in carbon black.

In addition to being used for rubber and coloring, carbon black is used in various ways as an electrical material, and such uses often require highly pure carbon black.

Foreign substances contained in carbon black include metal salts,
Contains metal oxides, sulfur, etc. Of these, sulfur has the largest content and is primarily derived from feedstock oil, but its form is complex and it is not easily soluble in organic solvents such as carbon disulfide and toluene, which are highly soluble in free sulfur. Will not be extracted, will not be eluted by inorganic acids or water, and will not survive at 1000°C in an inert gas or vacuum.

Even after some high-temperature heat treatment, it was not removed at all, and purification was not easy.

The present invention applies not only to metal compounds in carbon black, but also to
It provides an extremely effective method for removing sulfur content, and the gist is that 600 to 16
The purpose is to perform heat treatment at a temperature of 00'C. During this treatment, the sulfur content in the carbon black undergoes a chemical reaction with hydrogen gas to form hydrogen sulfide, which is effectively removed. In this case, temperatures below 500"C are inappropriate because the reaction rate is slow. At temperatures above 0"C, the rate is determined by the hydrogen gas supply rate rather than the reaction rate, so heat treatment is There is no special benefit even if the temperature is raised above IE500'C, which exceeds the carbon black formation temperature and the properties of the black itself may change. Considering this as the upper limit, the optimum temperature kl: 800°C to 16oO°C.

Next, as a method of removing metal salts and the like contained in carbon black, the temperature above their melting point is
There is a method of keeping it in a high vacuum to evaporate metal salts.

The feature of this method is that it is a dry refining method, so there is no risk of significantly changing the properties of the carbon blank, and if it is performed subsequent to the heat treatment in hydrogen gas described above, extremely efficient refining treatment is possible. This method targets compounds such as those shown in Table 1, such as chlorides, some sulfates, and oxides that have a relatively low melting point and high vapor pressure. In this case, heat treatment 57:-; For the compounds of Table 1, the purification objective can be achieved at a temperature of 800-1500°C.

Another method for removing metal salts and the like contained in carbon black is to wash and elute carbon black with water or an inorganic acid. Carbon black usually contains about 0.3 to 3% ash. These are caused by various causes such as the raw oil 2 reactor, additives, cooling water, and granulating agents, but a high proportion is caused by cooling water. Salt in ash is water.

In particular, many carbon blacks dissolve in hot water, and some carbon blacks can remove 80% or more of their ash content. When an aqueous solution of an inorganic acid is used, some of the oxides that are difficult to dissolve in water are dissolved, so the ash content is further reduced, and some carbon blacks have an ash content of 96 or more removed.

Inorganic acids that can be used include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and hydrofluoric acid, but the first two are recommended in terms of effectiveness and cost.

After cleaning with an inorganic acid, acid may remain if the cleaning is not done thoroughly with water. After washing with water or inorganic acid, the carbon black is heated to a temperature above 60°C and dried, but during this process, oxygen bonds to the surface of the carbon black, causing the pH value to become extremely acidic. However, in the present invention, such a problem is solved because the wet cleaning and drying are followed by heat treatment in a hydrogen gas-containing atmosphere.

That is, heat treatment in an atmosphere containing hydrogen gas not only has the effect of removing the sulfur content in the black, but also has the effect of removing residual chlorine ions and surface oxygen compounds.

Next, a more detailed explanation will be given with reference to examples.

(Example 1) Free Ness Black (product name: Ke
tjen E C) 4 Put F into a porcelain boat and H
Heat treatment was carried out for 2 hours at different heat treatment temperatures using a tubular furnace in which a mixed gas of 210% and 90% N2 was flowed for 60 mm. Table 2 shows the results of analysis of the main foreign elements contained in the black using heat treatment temperature and fluorescent X-ray analysis.

7 be.

(Example 2) Furnace black manufactured by Cabot (product name C3X-1)
60A2)'f: was used, and the same heat treatment and analysis as in Example 1 were performed. The results are shown in Table 3. (See the margin below.) (Tables 2 and 3 show that the sulfur in carbon black decreases markedly at temperatures above 60o'C in an atmosphere containing hydrogen gas. Chlorine and zinc, which are known to show a tendency to saturation at temperatures above 800°C, decrease significantly at temperatures above 800°C.The properties of Naori-bon black as a powder hardly changed due to heat treatment. (Example 3) In Example 2, carbon black was produced under heat treatment conditions of 1000° C.9 for -4 hours, and the influence of heat treatment time was compared with Example 2.

(Example 4) In Example 2, after the heat treatment for 2 hours at 1ooO'C was completed, the vacuum was immediately evacuated to 10 wtb Hf using a rotary pump, and the heat treatment was continued for an additional 10,002 hours to produce carbon black.

(Comparative Example 1) Using the carbon black of Example 2, 10
One was heat-treated for 2 hours, and the other was heat-treated for 4 hours.

Examples 3 and 4. In addition, the carbon black of Comparative Example 1 was analyzed in the same manner as in Example 1, and only elements with large changes are summarized in Table 4. :ppm) Table 4 shows that heat treatment in vacuum has a small effect on removing sulfur, but has a significant effect on removing sodium and potassium. Note that a longer heat treatment time is more effective, but the difference is not so large. It was also found that the properties of carbon black as a powder hardly change due to heat treatment in vacuum.

(Example 5) Page 11 Carbon black 8o used in Example 2! was dispersed in pure water 1.66 at 7o''C, stirred for 3o minutes, and subjected to suction P. To the obtained cake was added pure water 11 to re-disperse, filtered with suction, and this operation was repeated two more times. Water-soluble salts in the carbon black were removed repeatedly. When the cake-like carbon black was dried in air at 120° C. for 10 hours, a change in pH value was observed.

Using this washed and dried carbon black, Example 1
1000' in an atmosphere containing hydrogen gas by the same method as
After heat treatment for 02 hours, the different elements contained in the carbon black were analyzed and the pH value was measured according to JIS (Japanese Industrial Standards).

(Comparative Example 2) In Example 6, the same analysis and measurements were performed on the carbon black that was only washed and dried.

(Example 6) 8 oy of carbon black used in Example 2 was dispersed in 1.577 g of dilute hydrochloric acid (O, 2N) at 70°C, stirred for 30 minutes, filtered with suction, and then washed with 3 g of pure water. .

The operation of adding pure water 11 to the obtained cake, redispersing it, and filtering it by suction was repeated two more times.

This cake-like carbon black was dried in the same manner as in Example 5, and then heat-treated in an atmosphere containing hydrogen gas (Fl!).
After that, analysis and measurements were carried out.

(Comparative Example 3) The same analysis and measurements as in Example 6 were performed on carbon black that was only washed and dried.

Example 6, 6. Combining the results of Comparative Examples 2 and 3 (Example 7
) The carbon black used in Example 1 was washed with dilute hydrochloric acid and heat treated in an atmosphere containing hydrogen gas in the same manner as in Example 6, and then analyzed and measured.

(Comparative Example 4) Similar analyzes and measurements were performed on carbon black that was only washed and dried in Example 7.

The results of Example 7 and Comparative Example 4 are shown in Table 1), 2. 0. 0 As is clear from Tables 6 and 6, carbon black that has been washed with dilute hydrochloric acid over water and then heat-treated in an atmosphere containing hydrogen gas has a lower total amount of foreign elements than untreated carbon black. has decreased significantly,
It can be seen that it is refined. Furthermore, although dilute hydrochloric acid was more effective than washing with water, it has been found that using dilute sulfuric acid instead of dilute hydrochloric acid can provide almost the same effect. Furthermore, the pH value of carbon black often decreases significantly and becomes acidic at the end of washing and drying, but it is known that by heat treatment it can be restored to a value close to the initial value.

As is clear from the explanation in [2] above, the present invention is a purification method that can significantly reduce many foreign substances such as sulfur in carbon black, which were relatively difficult to remove in the past, through simple processing. It provides a processing method and is of great industrial value.

Claims (5)

[Claims] (1) Carbon black purification method 0 characterized by heat treating carbon black at a temperature of 600 to 1500"C in an atmosphere containing hydrogen gas (2) The method for purifying carbon black according to claim (1), wherein the heat treatment temperature is 800 to 1500'C. (3) After keeping carbon black at a temperature of 800 to 1600'C in an atmosphere containing hydrogen gas,
The method for purifying carbon black according to claim (1), characterized in that the heat treatment is further carried out in a vacuum atmosphere. (4) Claim No. 1, characterized in that the carbon black has been previously washed with water.
) or (3), the method for purifying carbon black. 2 pages (5) The method for purifying carbon black according to claim (1) or (3), wherein the carbon black has been previously washed with an inorganic acid and water.