JP2518261B2 - Method for producing black powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a black powder suitable as a black pigment.

[Prior Art and Problems] Conventionally, it has been known that black powder is made of various raw materials. Among them, titanium oxide-based black powder is well compatible with resins, and also has dispersibility, heat resistance, and safety. It has excellent advantages and is in high demand.

Conventionally, as a method of producing a titanium oxynitride-based black powder, a method of heating and reducing a mixture of titanium dioxide powder and metallic titanium powder in a vacuum, and a method of heating and reducing titanium dioxide powder with hydrogen gas have been tried. However, any of the methods has a problem that the raw material particles are sintered during heating and the produced particles become coarse and non-uniform, and the obtained black powder is unsuitable as a black pigment. Therefore, instead of the above-mentioned conventional method, a method of reducing the titanium dioxide powder using ammonia gas has been developed. Generally, in order to reduce titanium dioxide powder with ammonia gas, (a) a method of contacting titanium dioxide powder charged in a boat with an ammonia stream, (b) a method of contacting titanium dioxide powder with an ammonia stream in a rotary furnace, etc. However, all of these methods have a problem that ammonia gas is difficult to penetrate into the inside of the powder layer and the reaction efficiency is extremely low, and a method using a fluidized bed has been developed instead of the above method. (For example, Japanese Patent Publication No. 61-25414). An outline of the method of using the fluidized bed is as follows.The bottom of a vertical cylindrical reaction vessel is conically inclined downward, and a stirring means is provided at the bottom, while an ammonia gas inlet is provided at the center of the bottom. Further, a means for heating the bottom portion is provided, and the titanium dioxide powder charged into the conical bottom portion by ejecting ammonia gas is kept in a fluid state and is heated and reduced while being stirred by the stirring means. The method has the advantage that the reaction efficiency is superior to the conventional methods, and is highly practical. However, when a fine titanium dioxide powder or titanium hydroxide powder having a specific surface area of 15 m ² / g or less is used as a raw material, the amount carried away from the reaction system by the ammonia gas introduced increases, and the recovery rate decreases, There is also a problem that control of the reaction is difficult.

[Knowledge for Solving Problems] Generally, in the above reaction system, if the raw material powder charged into the reaction furnace is too large, unreacted portions are generated, and fine powder cannot be obtained. I am using. However, the present inventors have found that in order to prevent coarsening due to sintering during heating, it is rather preferable that the raw material powder be granulated to some extent in advance. It was also found to be advantageous in terms of control.

The present inventors, based on the above findings, in the heating reduction reaction of the titanium dioxide powder with ammonia gas, pursuing the optimum particle size range of the raw material powder, the reaction efficiency by adjusting the particle size to a grain size of 0.1 ~ 5 mm or less. It was also confirmed that the recovery rate of raw materials was remarkably improved and the reactor was simplified.

[Structure of the Invention] According to the present invention, a raw material made of titanium dioxide or titanium hydroxide is charged into a vertical cylindrical reaction vessel, and ammonia gas is blown from the bottom of the reaction vessel through a gas dispersion plate and simultaneously stirred. While in the method of heating and reducing the raw material while keeping it in a fluidized state, the titanium dioxide or titanium hydroxide powder is adjusted to a particle size of 0.1 to 5 mm or less and then charged into a reaction vessel to obtain the maximum temperature in the furnace. Is maintained at 700 to 950 ° C. for reduction, and the obtained black titanium oxynitride granules are crushed to provide a method for producing a black powder.

Further, as a preferred embodiment thereof, titanium dioxide powder or titanium hydroxide powder having a specific surface area of 4 m ² / g or more, water or water containing a water-soluble organic binder is kneaded and granulated,
There is provided a method for producing fruit-shaped particles in the above particle size range.

In the present invention, a raw material powder of titanium dioxide or titanium hydroxide is used which has been adjusted to a grain size of 0.1 to 5 mm or less. In this case, the raw material titanium dioxide or titanium hydroxide is preferably a powder having a specific surface area of 4 m ² / g or more. If the raw material powder is less than 4 m ² / g, the strength is small when it is made into a granular shape, and it easily disintegrates and pulverizes during heating and reduction. To form the raw material powder into a granular shape, water or water containing a water-soluble organic binder may be added to the powder, kneaded, granulated, and dried. Water may be added to the titanium dioxide powder, kneaded and dried to form a cake, which may be crushed, sieved and adjusted to the above particle size. As the water-soluble organic binder, a resin composition such as polyvinyl alcohol or polyvinyl methyl ether can be used. When the grain size of the fruit grains is less than 0.1 mm, the amount of carryover to the outside of the system increases when charged into a reaction vessel and brought into contact with ammonia gas, resulting in a decrease in yield. If the grain size exceeds 5 mm, the reaction inside the grain is difficult to proceed, and unreacted substances may remain.

Next, an example of an apparatus configuration most suitable for carrying out the method of the present invention is shown in the drawing.

As shown, the apparatus has a vertical cylindrical reaction vessel 10, and the reaction vessel 10 is installed in a heating furnace 11. An ammonia gas introducing chamber 12 is formed at the bottom of the reaction vessel, and an ammonia gas introducing passage 13 is connected to the introducing chamber 12. A preheating means 14 is attached to the introduction path 13. The introduction chamber 12 and the interior of the reaction container 10 are partitioned by a gas dispersion plate 15, and ammonia gas is blown up into the reaction container through the dispersion plate 15. A receiver 16 for collecting the product is provided on the side of the introduction chamber 12.
The receiver 16 is provided with cooling means 17. On the other hand, a raw material inlet 18 and an exhaust port 19 are provided at the top of the reaction vessel 10, and an exhaust passage 21 having a baffle plate 20 is connected to the exhaust port 19. Further, inside the reaction vessel 10, a stirrer 23 having rotary vanes 22 is provided near the upper part of the dispersion plate 15.

The raw material whose grain size is adjusted on the berries is charged into the reaction vessel through the charging port 18, while the ammonia gas is supplied to the introduction chamber 12 through the preheating means 14 and uniformly dispersed in the reaction vessel through the dispersion plate 15. And the granular material is blown up. The fruit-shaped raw material powder is kept in a fluid state by the ammonia gas introduced into the reaction vessel, and is further uniformly stirred by the stirrer 23. At this time, since the raw material is granular, it is difficult to carry over by the ammonia gas, and the reaction efficiency and the recovery rate are improved. Further, the reaction can be easily controlled.
Generally, the finer the raw material powder, the higher the reaction rate, but if it is too fine, the gas introduced may cause carryover, so the gas flow rate must be limited. There is a limit to the reaction rate. In the present invention, since the raw material powder is adjusted into a granular shape, carryover of the raw material powder is unlikely to occur, and a relatively large amount of ammonia gas can be introduced, so that the reaction rate is also improved. In addition, stirring is 2
It may be 3 revolutions / minute or more, and may be intermittently performed.

The reaction vessel 10 is heated by the heating furnace 11 to a maximum temperature inside the fluidized bed of 700 to 950 ° C, preferably 750 to 900 ° C. If the temperature is lower than 700 ° C, the reaction is difficult to proceed and the raw material is not blackened. If the temperature is higher than 950 ° C, the fruit granules are likely to sinter and become dark brown. The temperature inside the reaction vessel can be measured by installing a thermometer inside the stirrer 23 around the rotation axis. The heating temperature is the flow rate of ammonia gas,
The amount is appropriately adjusted within the above range depending on the charging amount of the raw material and the like, and this can be easily controlled by the heating furnace 11 and the preheating means 14. The preheating of the ammonia gas may be at a high temperature at a temperature at which the ammonia gas does not decompose and the reaction efficiency is not lowered, and specifically, it may be 600 ° C. or less.

In addition, it is preferable to use a material that is resistant to nitriding in the high temperature portion of the device so as to withstand the above reaction temperature.

After the reduction reaction is completed, while rotating the stirrer 23, the produced particles are stored in the cooled receiver 16, and the raw materials are charged again to carry out the reduction reaction.

Fruit-shaped titanium oxynitride particles can be obtained by the heating reduction reaction, but since the heating reduction reaction of the present invention is at a relatively low temperature, the particles are not sintered inside and easily converted into the original fine powder. Can be crushed. In this respect, in the method of reducing the titanium dioxide powder with hydrogen, the heating temperature is as high as 950 ° C. or more and the raw material powder is sintered, so that the particle size adjustment as in the present invention cannot be performed.

Further, the fruit-shaped titanium oxynitride particles are uniformly reduced to the inside of the particles, and a uniform titanium oxynitride powder can be obtained even if the particle size of the original raw material powder is crushed. For the crushing, a hammer method by a dry method, a jet mill, a ball mill by a wet method, or a sand mill method can be applied.

[Effects of the Invention] According to the production method of the present invention, black powder of titanium oxynitride can be produced with a high recovery rate even when using fine titanium dioxide powder or titanium hydroxide powder.

In the production method of the present invention, the loss due to carry-over of raw materials is small, and a relatively large amount of ammonia gas can be introduced, so that the reaction rate is also improved. Incidentally, conventionally, it was difficult to recharge the raw material when the flow rate of the ammonia gas was 3 cm / sec or more in the furnace linear velocity, but in the present invention, the flow rate of the ammonia gas is set to 6 to 8 cm / sec in the furnace linear velocity. Can be increased.
As described above, the method of the present invention is suitable for implementation on an industrial scale because the loss of raw materials is small, the reaction can be easily controlled, and the reaction efficiency is good.

Further, according to the method of the present invention, titanium hydroxide such as orthotitanic acid or metatitanic acid, which has not been used in the conventional method utilizing a fluidized bed, can be used as a raw material.
Since these are cheaper than titanium dioxide powder, they are advantageous in reducing the manufacturing cost. Further, these titanium hydroxides are finer than the titanium dioxide powders that are usually used, and it is possible to manufacture finer titanium oxynitride than before.

Further, since the apparatus for carrying out the present invention uses the granular material, the supply system and the exhaust system of the ammonia gas can be greatly simplified as compared with the conventional apparatus using the powdered material. Specifically, conventionally, a cooling means for the introduction pipe of the ammonia gas is attached to suppress the thermal decomposition, but such a cooling means becomes unnecessary. Further, a mechanism for collecting the powder carried over to the outside of the furnace becomes unnecessary. Further, since the dispersion plate is installed outside the heating furnace, maintenance and the like are easy.

[Example 1] Using the above reaction apparatus (vessel inner diameter 30 cm, height 80 cm), titanium dioxide powder having a specific surface area of 40 m ² / g was kneaded with an aqueous solution of PVA 0.3% and dried to obtain a particle diameter of 1 mm or more and 4 mm or less. 15 kg of the granules were charged, ammonia gas was introduced at a rate of 6 cm / sec in the furnace, and the maximum temperature of the fluidized bed was controlled at 750 ° C. while rotating at 15 rpm to perform heat reduction for 8 hours. After the reaction, 12.
3 Kg of black granules were recovered. The fruit granules were wet-crushed with water using a ball mill and dried separately, and then ground with a hammer mill to obtain a bluish-black powder having a specific surface area of 28 m ² / g and an L value of 10.

[Examples 2 and 3] Using the titanium dioxide granules of Example 1, different reducing conditions were used in the same reaction apparatus to produce black powder. The crushing process after reduction is also the same. The reducing conditions and the product properties are shown in Table 1.

[Example 4] A titanium hydroxide slurry was washed with water, separately dried, and 15 kg of 2 mm or more and 4 mm or less fruit grains were charged and reduced under the same conditions as in Example 1, and the product was used with water. After wet crushing with a sand mill, it was separately dried and further crushed with a hammer mill and a git mill to obtain a purple black powder having a specific surface area of 32 m ² / g and an L value of 9.

[Comparative Example 1] [Execution encouragement] Using the titanium dioxide granules of Example 1, the furnace temperature was set to 500.
The reduction reaction was carried out under the same conditions as in Example 1 except that the temperature was maintained at 0 ° C. The obtained powder was whitish blue gray and black powder could not be obtained.

[Comparative Example 2] Using the titanium dioxide powder of Example 1 without granulation, the reduction reaction was carried out under the conditions shown in Table 1 by a conventional apparatus (JP-A-60-51616). As shown in Table 1, the characteristics of the obtained powder are almost the same as those of the powder of the present invention, but the yield is 1/2 or less, which is a significant decrease. This is because ammonia gas is introduced at a furnace linear velocity of 6 cm / sec, and it is difficult to reload the carry-over raw material powder.

[Brief description of drawings]

The figure is a schematic view showing an example of a suitable apparatus configuration for carrying out the method of the present invention. In the drawing, 10 ... reaction container, 11 ... heating furnace, 12 ... introduction chamber, 13 ... ammonia gas introduction path 15 ... dispersion plate, 16 ... receiver, 23 ... stirrer.

Claims (2)

(57) [Claims] 1. A vertical cylindrical reaction vessel is charged with a raw material made of titanium dioxide or titanium hydroxide, and ammonia gas is blown from the bottom of the reaction vessel through a gas dispersion plate while stirring to flow the raw material. In the method of heating and reducing while maintaining the state, after adjusting the powder of titanium dioxide or titanium hydroxide to a grain size of 0.1 to 5 mm or less, charged into a reaction vessel, the maximum temperature in the furnace is 700 to 950. A method for producing a black powder, which is characterized in that the black titanium oxynitride granules thus obtained are reduced by maintaining the temperature at ℃ and reduced. ^2. Titanium dioxide powder or titanium hydroxide powder having a specific surface area of 4 m ² / g or more is added and kneaded with water or water containing a water-soluble organic binder to form granules. The method according to claim 1, characterized in that