JP2006022270A - Carbon black and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide carbon black satisfying both properties of a jet black property and dispersibility and having a color tone tinged with blue and high safety. <P>SOLUTION: The carbon black has the following characteristics: (a) ≤30 ml/100 g difference (ΔDBP) between DBP absorption amount and 24M4DBP absorption amount, (b) ≥40nm and ≤50 nm modal diameter (Dmod) of an aggregate, (c) ≤10 nm absolute value of the difference between 25% integrated value (D25) of the aggregate and Dmod and (d) ≤20 nm absolute value of the difference between 75% integrated value (D75) and Dmod of the aggregate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to carbon black used for various uses such as a filling material, a reinforcing material, a conductive material and a coloring material, and a method for producing the same.

  Carbon black is widely used as a colorant in resin colorants, printing inks, paints, water-based inks, and the like, and as a reinforcing agent for rubber compositions such as automobile tires. There is a need for carbon black that exhibits excellent effects in dispersibility, blackness (blackness), color tone, gloss, coloring power, and the like in resin molded products and various inks. In addition, in the rubber composition, carbon black having an effect excellent in wear resistance is required in addition to these.

For example, various improvements have been made to carbon black for the purpose of improving the effects of both dispersibility and jetness. In application to various inks and the like, various improvement methods have been proposed by paying attention to the specific surface area of CB, the DBP absorption amount, and the correlation thereof (for example, see Patent Documents 1 to 5).
Carbon black is an agglomerate in which a plurality of primary particles are connected. Controlling the size (agglomerate diameter) and shape of the agglomerates, and the aggregate diameter distribution is a reinforcement for a rubber composition, for example. It is known that it is closely related to the blackness and dispersibility of the ink and the ink (for example, see Non-Patent Document 1). For example, in application to rubber compositions, it is known that the smaller the aggregate diameter of carbon black, the higher the blackness as a colorant and the better physical properties as a rubber composition (see, for example, Patent Document 1).

The bonds between the carbon black primary particles constituting the agglomerates include a strong bond part that is completely fused to the crystallite level of the primary particle, such as a chemical bond, and a physical bond or the like from the outside such as compression. There are weak bonds that are easily separated by pressure.
Usually, the compressed DBP absorption amount (24M4DBP absorption amount) is used as an indicator of the existence ratio of this strong bond portion in carbon black, and the DBP absorption amount is used for that of the weak bond portion. Until now, in order to obtain carbon black having both blackness and dispersibility in resin coloring applications and paint applications, the carbon black aggregate diameter, DBP absorption amount, 24M4DBP absorption amount, difference between DBP absorption amount and 24M4DBP absorption amount ( A physical property value such as ΔDBP) was controlled. For example, carbon blacks suitable for rubber compositions have been proposed with specific values (see, for example, Patent Document 6).

  In addition, in carbon black, the higher the DBP absorption, the lower the blackness and handling characteristics, and the higher the bulk density, the lower the transport efficiency. However, it is known that the higher the amount of 24M4DBP absorbed, the better the dispersibility and the carbon black also has a bluish tone. Therefore, in order to achieve a contradictory physical property (blackness / dispersibility), a proposal has been made to reduce ΔDBP (for example, see Patent Document 7).

In addition, in such a method for producing carbon black, the aggregate diameter distribution is narrowed by shortening the residence time of the raw material oil to achieve both carbon black characteristics (for example, see Patent Document 8). For example, in a method for producing carbon black having a small aggregate diameter, a method of adding an alkali metal salt or a solution thereof to a raw material oil or introducing it into a combustion zone or a reaction zone is known (for example, Patent Document 9). reference).
Carbon Black Handbook 3rd edition, I.I. Overview page 7 Japanese Patent Publication No. 50-68992 Japanese Patent Publication No. 52-13808 Japanese Patent Publication No.52-27632 Japanese Patent Publication No.52-41234 Japanese Patent No. 3373712 Japanese Patent Publication No. 6-104788 JP 2000-80302 A Japanese Patent No. 3185552 Japanese Patent No. 3419123

  When carbon black is applied to various inks and the like, considering the mixing of carbon black with a vehicle or resin, the carbon black having a small aggregate diameter has an advantage of high blackness. However, carbon black with such high blackness still has problems in both blackness and dispersibility, such as a decrease in dispersibility in ink and a decrease in fluidity when used as a resin composition. The characteristics were not improved sufficiently.

In addition, the carbon black of this small aggregate diameter has a reddish color due to unreacted oil and polycyclic aromatic hydrocarbons (PAH) remaining in the carbon black due to the production method. There was a problem that the color tone and safety were lowered.
For example, in the carbon black described in Patent Document 6, the influence on the aggregate diameter and application characteristics, in particular, the influence of the carbon black of the small aggregate and the carbon black of the large aggregate is not considered. There was a problem that it was not designed with safety in mind. Furthermore, in the manufacturing method, a method is described in which about 50 to 80% of the total feedstock and the remaining about 50 to 20% are divided and introduced into the high-temperature combustion gas stream. In production on a scale, there is a problem that it is difficult to control the aggregate diameter, and it is difficult to reduce small aggregates and large aggregates that affect the application characteristics of carbon black.

In addition, in the production method described in Patent Document 9, in order to add an alkali metal salt or a solution thereof to a raw material oil or introduce it into a combustion zone or a reaction zone, the alkali metal remains in carbon black as ash, and the coating vehicle. In addition, when blended with a resin, there is a problem that it becomes a binder and causes deterioration of dispersibility and fluidity.
The present invention achieves both high blackness and good dispersibility, both of which are considered to be in a trade-off relationship as described above, in the relationship between the characteristics of carbon black and the physical properties of a carbon black-containing composition such as a resin composition. Furthermore, the present invention provides a carbon black having a bluish tone and high safety and a method for producing the same.

The present inventors have analyzed the factors affecting the dispersibility and blackness of carbon black, and are diligent in order to obtain carbon black that exhibits higher blackness and better dispersibility than the conventional one, and has a bluish tone and high safety. investigated. As a result, it was found that it is important to satisfy both of the following (1) and (2).
(1) Dispersibility and color tone were improved when there were many strong bonds such as chemical bonds among the primary particles forming the aggregate. Therefore, it is preferable that the difference (ΔDBP) between the DBP absorption amount and the 24M4 DBP absorption amount is a certain value or less.
(2) Since it was confirmed that the small-diameter aggregate is involved in the reduction of dispersibility and color tone, and the large-diameter aggregate is involved in the reduction in blackness, there is an optimum range for the maximum frequency diameter of the aggregate diameter. .

  That is, the carbon black primary particles constituting the aggregate are chemically strongly bonded, and the maximum frequency diameter of the aggregate is within a preferable range, and excessively small aggregates and excessively large aggregates are reduced. Thus, the present invention has been completed by discovering that carbon black having both high blackness and dispersibility, which has been considered to be a trade-off, has a bluish color tone and high safety.

  In the method for producing carbon black by the furnace method, the oxygen concentration at the raw material hydrocarbon compound introduction position in the production furnace is increased, and the residence time until the carbon black production reaction of the raw material hydrocarbon compound is stopped within a specific range. As a result, the bond between the carbon black primary particles is strengthened so that the maximum frequency diameter of the aggregate is adjusted to a preferable range and the distribution of the aggregate diameter is narrow, and such carbon black has the characteristics described above. As a result, the present invention was completed.

That is, the gist of the present invention resides in carbon black having the following characteristics (a) to (d).
(A) The difference (ΔDBP) between the DBP absorption amount and the 24M4 DBP absorption amount is 30 ml / 100 g or less.
(B) The most frequent diameter (Dmod) of the aggregate is 40 nm or more and 55 nm or less.
(C) The absolute value of the difference between the aggregate 25% value of aggregates (D25) and Dmod is 10 nm or less.
(D) The absolute value of the difference between the aggregate 75% value (D75) and Dmod is 20 nm or less.

  Another aspect of the present invention is at least a first reaction zone for forming a high-temperature combustion gas stream and a downstream of the first reaction zone, and the raw material hydrocarbon compound is brought into contact with the high-temperature combustion gas stream from the first reaction zone. In the method for producing carbon black using the carbon black production apparatus, the second reaction zone for producing carbon black and the third reaction zone downstream of the second reaction zone and stopping the carbon black production reaction. The raw material hydrocarbon compound is supplied into the high-temperature combustion gas stream having a content of 4% by volume to 6% by volume, and the residence time of the raw material hydrocarbon compound in the second reaction zone is 10 ms to 25 ms. The feature lies in a method for producing carbon black.

  The novel carbon black whose aggregate distribution is controlled within a suitable range of the present invention exhibits good blackness and dispersibility when applied to rubber, various inks, etc., and also has a good bluish tone and high color tone. It has safety.

Hereinafter, the present invention will be described in detail.
The carbon black of the present invention has a difference between the DBP absorption amount and the 24M4DBP absorption amount (DBP absorption amount−24M4DBP absorption amount), that is, ΔDBP is 30 ml / 100 g or less, the most frequent diameter Dmod of the aggregate is 40 nm to 55 nm, The absolute value of the difference between D25 and Dmod, which is an integrated 25% value, is 10 nm or less, and the absolute value of the difference between D75 and Dmod, which is an aggregate 75% value, is 20 nm or less.

  In the carbon black of the present invention, when ΔDBP exceeds 30 ml / 100 g, blackness and handling properties when used as a black pigment are lowered. ΔDBP is not particularly limited as long as it is 30 ml / 100 g or less, but carbon black that is too small may be difficult to produce in chemical industry, and is generally 5 ml / 100 g or more, especially 10 ml / 100 g or more. It is preferably 25 ml / 100 g or less.

In the carbon black of the present invention, if Dmod is too small, the dispersibility may be lowered. Conversely, if the Dmod is too large, the blackness may not be sufficient. Therefore, Dmod is 40 nm or more, preferably 55 nm or less, particularly 53 nm or less, more preferably 50 nm or less, and particularly preferably 45 nm or less.
In the carbon black of the present invention, the absolute value of the difference between D25 and Dmod, which is 25% of the aggregate, is 10 nm or less, and the absolute value of the difference between D75 and Dmod, which is the 75% of the aggregate. Is 20 nm or less. D25 is a Stokes in which the integrated value of the volume sum from the smaller Stokes diameter is 25% in the histogram drawn when the Stokes equivalent diameter of carbon black and the relative occurrence frequency thereof are taken on the X axis and the Y axis, respectively. D75 means the Stokes diameter (nm) at which the integrated value of the volume sum from the smaller Stokes diameter is 75% in this histogram.

  In the carbon black of the present invention, if the absolute value of the difference between D25 and Dmod is too large, the dispersibility may decrease. In the carbon black of the present invention, there is no particular limitation as long as the difference in absolute value is 10 nm or less. However, carbon black having this difference that is too small may be difficult to manufacture in the chemical industry. Specifically, it is preferably 1 nm or more, particularly 3 nm or more, and preferably 10 nm or less, especially 8 nm or less, particularly 5 nm or less.

  Further, if the absolute value of the difference between D75 and Dmod is too large, the blackness may decrease. In the carbon black of the present invention, there is no particular limitation as long as the difference in absolute value is 20 nm or less. However, carbon black having this difference that is too small may be difficult to manufacture in the chemical industry. Specifically, it is preferably 1 nm or more, particularly 5 nm or more, particularly 10 nm or more, and 20 nm or less, particularly 18 nm or less, particularly 15 nm or less.

The nitrogen specific surface area (hereinafter sometimes referred to as “SN2”) in the carbon black of the present invention is not particularly limited, but if it is too small, the blackness may be lowered. May decrease. Therefore, SN2 is 150 m ² / g or more, especially 180 m ² / g or more, more preferably 200 m ² / g or more, particularly preferably 230 m ² / g or more, and 300 m ² / g or less, particularly 240 m ² / g or less. It is preferable.

  In the carbon black of the present invention, the size of the aggregate is not particularly limited, but if it is too small, the dispersibility may decrease, and conversely if too large, the blackness may decrease. Therefore, the DBP absorption amount as an index of the size of the aggregate is preferably 90 ml / 100 g or more, particularly preferably 110 ml / 100 g or more, more preferably 130 ml / 100 g or less, and particularly preferably 120 ml / 100 g or less. Further, the absorption amount of 24M4DBP is 85 ml / 100 g or more, preferably 90 ml / 100 g or more, more preferably 105 ml / 100 g or less, and particularly preferably 100 ml / 100 g or less.

The ash content in the carbon black of the present invention is arbitrary and is not particularly limited. However, if the ash content is too high, the dispersibility may be lowered. In general, it is preferably 0.05% by weight or less, more preferably 0.03% by weight or less, and particularly preferably 0.02% by weight or less.
The carbon black of the present invention is excellent in all of blackness, dispersibility, color tone and safety. In particular, the blackness index is preferably 11 or more and 14 or less. The dispersion area index indicating dispersibility is preferably 50 or less, particularly 40 or less, and particularly preferably 35 or less. The chromaticity (b value) of the ABS compound by the colorimeter is preferably −0.9 or less. The amount of PAH is preferably as small as possible, and is preferably 50 ppm or less.

The production method of the carbon black of the present invention is arbitrary and is not limited to a specific production method. Among them, the production method by the furnace method is preferable because a desired carbon black can be obtained efficiently. The method for producing carbon black of the present invention will be described below by taking the furnace method as an example.
As an example of a furnace for producing carbon black by the furnace method, a longitudinal sectional schematic view of the main part is shown in FIG. The furnace has a first reaction zone 1 for forming a high-temperature combustion gas flow in the longitudinal direction, and a raw material hydrocarbon compound is mixed with the high-temperature combustion gas flow generated in the first reaction zone to produce carbon black. A second reaction zone 2 having a portion and a third reaction zone that is downstream of the second reaction zone and stops the carbon black production reaction.

  In the first reaction zone, fuel hydrocarbons and oxygen-containing gas are generally introduced from the combustion burner 4 and burned to generate a high-temperature combustion gas stream. As the oxygen-containing gas, air, oxygen or a mixture thereof is generally used, and as the fuel hydrocarbon, hydrogen, carbon monoxide, natural gas, petroleum gas and petroleum-based liquid fuel such as heavy oil, and coal-based such as creosote oil are generally used. Liquid fuel is used.

  In the second reaction zone, the raw material hydrocarbon compound is introduced by spraying or the like from the raw material hydrocarbon compound introduction nozzle 5 provided in the flow of the high-temperature combustion gas generated in the first reaction zone in a cocurrent or substantially vertical direction. Is thermally decomposed to produce carbon black. The hydrocarbon compounds used as raw materials for carbon black are generally aromatic hydrocarbons such as benzene, toluene, xylene, naphthalene and anthracene; coal-based hydrocarbons such as creosote oil and carboxylic acid oil; ethylene heavy end oil, FCC Petroleum heavy oils such as oil; acetylenic unsaturated hydrocarbons; ethylene hydrocarbons; aliphatic saturated hydrocarbons such as pentane and hexane are preferably used.

In the third reaction zone, the high-temperature reaction gas is cooled to, for example, about 1000 to 800 ° C. Specifically, for example, a liquid or gaseous cooling medium such as water is introduced from the reaction stop fluid introduction nozzle 6 into the furnace by spraying or the like. The cooled carbon black is separated and recovered from the gas flow by a collection bag filter or the like (not shown) further downstream of the third reaction zone.
When the carbon black of the present invention is produced by such a carbon black production furnace, the position where the raw material hydrocarbon compound is introduced, the composition and flow rate of the high-temperature combustion gas flow are adjusted, and the high temperature for supplying the raw material hydrocarbon compound It is important that the oxygen content in the combustion gas stream and the residence time of the raw hydrocarbon compound in the second reaction zone be within a specific range.

  In the method for producing carbon black of the present invention, it is important that the oxygen content of the high-temperature combustion gas stream at the feed hydrocarbon introduction position is relatively high, specifically, 4 vol% or more and 6 vol% or less. If the oxygen content is too low, ΔDBP may increase and the blackness may decrease. On the other hand, if the oxygen content is too high, the introduced raw material oil may burn and productivity may decrease. It is preferable to set it as volume% or more and 5 volume% or less. Further, the residence time of the raw material hydrocarbon compound in the second reaction zone, that is, the time from the introduction of the raw material hydrocarbon compound into the furnace to the third reaction zone which is the reaction stop region is set to 10 ms or more and 25 ms or less. This is very important. If this residence time is too short, Dmod may be reduced and dispersibility may be reduced. On the other hand, if it is too long, Dmod may be increased and blackness may be reduced. preferable.

  There are no particular limitations on the method for measuring the oxygen content and the residence time of the raw material hydrocarbon compound described above. For example, the oxygen content is calculated by a conventionally known method from the amount of air introduced into the production furnace and the amount of fuel introduced, or analyzed by gas chromatography after collecting combustion gas from the raw hydrocarbon compound introduction site. You may ask for it. In such an analysis, water generated by combustion is not taken into account. The residence time may be calculated by a conventionally known method from the high-temperature combustion gas flow rate and the cross-sectional area of the production furnace, or may be calculated by a fluid simulation.

  Further, in the present invention, the furnace temperature at the introduction site of the raw material hydrocarbon compound is desirably sufficiently high so that the raw material hydrocarbon compound is uniformly vaporized and thermally decomposed. It is preferably not lower than 2000C, more preferably not lower than 2000, and generally not higher than 2400 ° C. By setting this temperature range, the carbon black primary particles are chemically strongly bonded to each other, the maximum frequency diameter of the aggregate is set to a preferable range, and excessively small aggregates and excessively large aggregates are reduced. Carbon black with a narrow distribution of aggregates.

In order to make the temperature of the raw material hydrocarbon compound introduction site within the above range, for example, when forming a high-temperature combustion gas flow in the first reaction zone, a method of adding oxygen to air or a method of preheating the air is performed. Just do it. What is necessary is just to measure the temperature in a furnace with a radiation thermometer etc., for example.
The choke portion in the second reaction zone is a portion where the cross-sectional area in the furnace is abruptly narrowed. In the production furnace used in the present invention, if the choke portion is too short, the aggregate diameter is not likely to be sufficiently large. Conversely, if the choke portion is too long, the aggregate diameter distribution may be too wide, or excessively large aggregates may increase. is there. Therefore, in the present invention, for example, when the diameter of the choke portion in the furnace is 30 to 170 mm, the length is preferably set to 800 mm or more and 3000 mm or less.

  Further, in the production method of the present invention, in the second reaction zone, in order to suppress the formation of carbon black having a large aggregate diameter, the high disturbance field of the high-temperature combustion gas flow accompanying the change in the furnace inner diameter due to the choke portion or the like is reduced as much as possible. It is preferable to do. For example, in the present invention, the start portion and the end portion of the choke portion include the narrowest portion of the flow path, and a portion where the angle with respect to the axial direction in which the flow path is reduced changes from a value exceeding 5 ° to 5 ° or less is a start portion A region where the angle of the flow channel with respect to the expanding axial direction exceeds 5 ° is defined as the end. The diameter of the choke portion is arbitrary depending on the size of the furnace, but generally 170 mm or less is preferable. Particularly preferably, it is 30 mm or more, particularly preferably 50 mm or more, and is preferably 170 mm or less, and particularly preferably 150 mm or less. By setting it within this range, carbon black having a narrow aggregate distribution can be easily obtained.

  In the present invention, the flow rate of the high-temperature combustion gas flow in the choke is arbitrary, but a higher speed is preferable because carbon black having a narrow aggregate distribution can be easily obtained. After the raw material hydrocarbon compound is introduced into the production furnace, it is atomized by the motion and heat energy of the high-temperature combustion gas flow. In this case, the higher the speed of the high-temperature combustion gas flow, the better. s or more, preferably 300 m / s or more, and generally 500 m / s or less.

  Furthermore, in order to uniformly disperse the raw material hydrocarbon compound in the furnace, the raw material hydrocarbon compound is preferably divided into two or more and introduced into the production furnace. The feed position of the raw material hydrocarbon compound is preferably within a range that can move within 1 ms on the basis of the cross-sectional average flow velocity of the high-temperature combustion gas flow from the choke start portion even within the choke portion, and can move within 0.6 ms. It is preferable to be within the range. By introducing at this site, carbon black having a particularly narrow aggregate size distribution can be obtained.

  By preparing the coating composition, resin composition, and rubber composition containing the carbon black of the present invention described above, suitable characteristics can be exhibited in these various applications. When preparing the resin composition containing the carbon black of the present invention, applicable resins are not particularly limited, and various additives such as various thermoplastic resins or thermosetting resins, mixtures of these resins, or fillers are used. It may be added. Usually, what is used for preparing the resin composition may be appropriately selected according to the purpose. The carbon black of the present invention is added to these resin components and kneaded as necessary. At this time, what is usually used as a rubber kneader, for example, a roll mixer as a batch type open type, a Banbury type mixer as a batch type closed type, a single screw kneading extruder as a continuous screw type, a twin screw kneading extruder, a continuous rotor As a formula, a single screw kneader, a twin screw kneader, or the like can also be used. The carbon black content may also be determined by employing a known technique, and generally 1 to 60% by weight is preferable.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
The analysis method of each physical property value is as follows.
(1) Dmod
The maximum frequency Stokes diameter Dmod was determined as follows. Using a 20% ethanol solution as a spin liquid, a Stokes equivalent diameter was measured with a centrifugal sedimentation type particle size distribution analyzer (BI-DCP PARTICLE SIZER, manufactured by BROOKHAVEN INSTRUMENTS CORPORATION). A histogram of the frequency of occurrence (Figure 2) is created. A line (B) is drawn from the peak (A) of the histogram to the X axis parallel to the Y axis and ends at the point (C) on the X axis of the histogram. The Stokes diameter at point (C) is Dmod.

(2) D25, D75
D25 (volume 25% diameter) and D75 (volume 75% diameter) were determined as follows. In the above method for determining the maximum frequency Stokes diameter, the volume is obtained from the Stokes diameter and the frequency from the histogram of the Stokes equivalent diameter versus the relative occurrence frequency of the sample from FIG. Create a graph representing the sum (Figure 3). Therefore, the point (A) in FIG. 3 represents the sum of the volumes of all the samples. Here, a point (B) having a value of 25% of the total volume is determined, and a line is drawn from the point (B) to a point (C) that intersects the curve parallel to the X axis. A value is drawn from the point (C) in parallel to the Y axis, and the value at the point (D) intersecting the X axis is the 25% diameter (D25). The value of the point (E) obtained by the same method is 75% volume (D75).

(3) Blackness index 30 g of PVC resin is masticated for 2 minutes with a slit width of 0.3 mm in a two-roll mill heated to 125 ° C., and 0.3 g of the sample is kneaded for 7 minutes to form a sheet. Using the same method, the blackness of the PVC black sheets of carbon black “# 45” and “# 990” manufactured by Mitsubishi Chemical Corporation was set at 10 and 14 points, respectively. The determined result is defined as the blackness index. A higher blackness index indicates a carbon black with better blackness.

(4) Dispersion area index The dispersion index was evaluated by the following method. The dispersion state in the ABS resin was observed, the number of undispersed aggregates was counted, and it was evaluated that the greater the number, that is, the greater the dispersion index, the worse the dispersibility. In a 250 cc Banbury mixer, 40% by weight of sample carbon black is blended with AS resin and kneaded at 165 ° C. for 10 minutes. The sheet is formed with a slit width of 0.3 mm, and the sheet is cut into chips and formed into a film of 65 ± 3 μm on a hot plate at 240 ° C. The diameter distribution of an undispersed mass having a diameter of 0.2 mm or more in a field of view of 3.6 mm × 4.7 mm is measured with an optical microscope with a magnification of 100 times, and the total area is calculated. This area is calculated as the number of reference particles by dividing the total area by the reference area based on the area of undispersed agglomerates having a diameter of 0.35 mm. This is observed over 25 fields of view, and the average value is taken as the dispersion index. The smaller the dispersion area index, the quicker dispersion occurs when making a paint.

<Condition conditions>
AS resin: 114.21 g
Irganox 1010: 1.14 g
Stearic acid Ca: 1.14 g
Sample carbon black: 77.66 g
<Dilution compound preparation conditions>
ABS resin: 97.50 g
Stearic acid Ca: 0.20 g
Carbon black 40% compound resin: 2.50 g

(5) b value 165 ° C., kneaded for 10 minutes and analyzed into a sheet with a slit width of 0.3 mm using a colorimeter (300A manufactured by Nippon Denshoku Co., Ltd.). Measurement is performed three times, and the average value is defined as b value. It shows that it is in a blue color tone, so that b value is small.
(6) DBP absorption amount This conforms to JIS K6221-1982.
(7) 24M4DBP absorption amount 25 g of a sample is put into a cylinder, a piston is inserted, and a pressure of 24,000 psi (1687 kg / cm ² ) is applied for 5 seconds with a hydraulic press. After the pressurization, the sample is taken out, transferred to a 1000 μm sieve, and the carbon mass is loosened and passed through the sieve. The DBP absorption amount is measured in accordance with JIS K6221-1982 for the sample processed by repeating the operation four times to obtain the CrDBP absorption amount.

(8) PAH amount 5 g of dried carbon black is put into a cylindrical glass filter paper, and Soxhlet extraction is performed for 48 hours using 180 cc of monochlorobenzene as a solvent. The extract was concentrated, and the amount of extraction was quantified by a liquid chromatogram, and the content was divided by the weight of carbon black. The conditions of the liquid chromatogram are as follows.

Liquid chromatogram analyzer: LC-6A manufactured by Shimadzu Corporation
Flow controller: SCL-6A manufactured by Shimadzu Corporation
Detector: Watari 490E type manufactured by Millipore Inc. Injection amount: 5 μL

Examples 1-3
A first reaction zone 1 having a combustion burner 4 shown in FIG. 1, a choke portion connected to the first reaction zone 1 and having an inner diameter of 150 mm and a length of 860 mm that penetrates a plurality of raw material hydrocarbon compound supply nozzles 5 from the periphery. A carbon black production furnace having a structure in which a second reaction zone 2 having a quenching apparatus and a third reaction zone 3 having an inner diameter of 400 mm and a length of 2700 mm were sequentially coupled together was used. Tables 1 and 2 show the compositions of the fuel and raw material hydrocarbon compound used. Table 3 shows manufacturing conditions and physical property values of the obtained carbon black.

  Table 4 shows the physical property values of the carbon black obtained under the production conditions shown in Table 3. The carbon blacks of Examples 1 to 3 have excellent blackness of 11 to 14, and the dispersion area index is 50 or less, indicating very good dispersibility. Further, the b value is -0.9 or less, showing an excellent bluish color tone, and the PAH is 50 ppm or less, indicating that the carbon black is excellent in safety.

Comparative Examples 1 and 2
Comparative Example 1 is an example in which | Dmod-D25 | and | Dmod-D75 | were made small in order to obtain blackness equivalent to that of Examples 1, 2, and 3. The blackness is certainly good at 13.7, but since the ΔDBP is high, the dispersion area index is high, and the b value is −0.72, which is a reddish color tone. Since Comparative Example 2 also has a high ΔDBP, the dispersion area index is high.

Comparative Example 3
Comparative Example 3 is an example manufactured by reducing Dmod in order to obtain blackness equivalent to that of Examples 1, 2, and 3. Certainly, the blackness is 13.3 and ΔDBP is as good as 18, but since the Dmod is as small as 38, the dispersion area index is high and the b value is −0.84. Furthermore, the amount of PAH is very high at 240 ppm.

Comparative Example 4
Comparative Example 4 is an example in which ΔDBP was made small in order to obtain the same dispersibility as in Examples 1, 2, and 3. Certainly, the dispersion area index is as good as 30, but Dmod is large, | Dmod-D25 | is high, and | Dmod-D75 | is high, so the blackness is low. From the above, by controlling ΔDBP, Dmod, | Dmod-D25 |, | Dmod-D75 | within a suitable range as described above, both blackness and dispersibility are achieved, and a blue tone is obtained. It can also be seen that carbon black having good safety can be obtained.

  The carbon black of the present invention, when used as a black pigment in a resin colorant, paint, etc., can satisfy the blackness and dispersibility that have been considered to be difficult due to the contradictory relationship. Furthermore, it has a bluish color tone and is excellent in safety. Therefore, it is very useful in the preparation of resin colorants and paints.

The principal part longitudinal cross-section schematic which shows an example of the manufacturing furnace which can be used for manufacture of the carbon black of this invention. The figure which shows how to obtain | require the maximum frequency Stokes equivalent diameter Dmod. The figure which shows how to obtain | require a volume 25% diameter and a volume 75% diameter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st combustion zone 2 2nd combustion zone 3 3rd combustion zone 4 Combustion burner 5 Raw material hydrocarbon compound supply nozzle 6 Nozzle for reaction stop fluid introduction

Claims (4)

Carbon black having the following characteristics (a) to (d).
(A) The difference (ΔDBP) between the DBP absorption amount and the 24M4 DBP absorption amount is 30 ml / 100 g or less.
(B) The most frequent diameter (Dmod) of the aggregate is 40 nm or more and 55 nm or less.
(C) The absolute value of the difference between the aggregate 25% value of aggregates (D25) and Dmod is 10 nm or less.
(D) The absolute value of the difference between the aggregate 75% value (D75) and Dmod is 20 nm or less. The carbon black according to claim 1, wherein the ash content is 0.05% by weight or less. The carbon black according to claim 1 or 2, wherein the polycyclic aromatic hydrocarbon content is 50 ppm or less. At least a first reaction zone for forming a high-temperature combustion gas stream, and a second downstream of the first reaction zone for generating carbon black by contacting a raw material hydrocarbon compound with the high-temperature combustion gas stream from the first reaction zone. In a carbon black production method using a carbon black production apparatus including a reaction zone and a third reaction zone downstream of the second reaction zone and stopping the carbon black production reaction, the oxygen content is 4% by volume or more and 6% by volume. %. A method for producing carbon black, wherein a raw material hydrocarbon compound is supplied into a high-temperature combustion gas stream that is not more than%, and the residence time of the raw material hydrocarbon compound in the second reaction zone is 10 ms or more and 25 ms or less.

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