JPS6241162B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fine black colored powder, and particularly to a colored powder suitable as a pigment, a conductive material, and a raw material for ceramics. Conventionally, carbon black powder and triiron tetroxide powder are known as black pigments. Carbon black powder is an excellent material not only in terms of colorability (i.e. blackness) as a black pigment but also in terms of conductivity as a conductive material (specific resistance 10 ^-2 to 10゜Ωcm). . However, because some resins are difficult to adapt and disperse, and because they contain a very small amount of carcinogenic 3,4-benzpyrene derived from manufacturing raw materials, their safety is being questioned in the cosmetics field. Furthermore, since it has a much larger specific surface area than other types of pigments, it is difficult to stably maintain a uniform dispersion state in a liquid medium even when used in combination with other pigments. On the other hand, triiron tetroxide powder has poor dispersibility due to its ferromagnetic nature, and also has low thermal stability (in the atmosphere
When heated above 150℃, it is oxidized to γ-Fe ₂ O ₃ ). On the other hand, it is a reduction product of titanium dioxide powder and is a substance called lower titanium oxide (general formula:
Ti _o O _2o-1 , n≧2) powder has excellent compatibility with resin, dispersibility in resin, and heat resistance (300 to 400
°C), and has excellent safety. The conductivity of this powder can be varied over a wide range from 10 ^-2 to ^{10 3} Ω・cm depending on the degree of reduction, and the color tone can be varied from gray-white, blue-gray, blue-black, purple-black, brown-black, and red-brown. It has the advantage of being possible. However, this low-order titanium oxide powder can be produced only by the conventional manufacturing method (reducing titanium dioxide using metallic titanium powder or hydrogen gas as a reducing agent), which results in coarse powder particles (average particle size of 1.0 μm or more, specific surface area of 1.5 m ² /g or less) was unavoidable. In other words, since these manufacturing methods require a processing temperature of 1000°C or higher, sintering and growth of particles occur. In this way, it is suitable as a pigment and conductive material.
It was virtually impossible to obtain a fine powder (specific surface area of 20 m ² /g or more). The purpose of the present invention is to eliminate the drawbacks of the various conventional colored powders and methods for producing them, and to develop an industrial method for producing fine colored powders that are compatible with resins, non-toxic, and highly safe. It is to provide. As a result of structural analysis by X-ray diffraction, the present inventors found that when titanium dioxide powder is heated in an ammonia atmosphere, even at a relatively low temperature of 500 to 950°C,
The reduction of titanium dioxide to titanium monoxide progresses,
A colored powder equivalent to the above-mentioned lower titanium oxide in terms of conductivity and color can be obtained, and in addition, sintering of powder particles,
It was found that almost no growth occurred. According to this method, titanium monoxide powder is obtained when the reduction is sufficiently advanced, and when the reduction is stopped at an appropriate stage, a composite powder consisting of titanium monoxide and titanium dioxide is obtained. In both cases, dry quantitative analysis revealed that 1 to 15% by weight of nitrogen (N) was solidly dissolved in titanium monoxide. That is, the composite powder is composed of titanium monoxide having a cubic NaCl structure in which oxygen is partially replaced with nitrogen and titanium dioxide having a tetragonal structure. The higher the reduction degree (corresponding to the ratio of TiO/TiO ₂ ), the higher the conductivity of the powder, and the specific resistance changes in the range of 10 ³ to ^{10 -2} Ω・cm, and the colors are green-gray, blue-gray, blue-black, and blue-black. It varies in color from black to purple-black to bronze. In addition, the higher the degree of reduction,
The nitrogen content in the produced TiO also increases. If the above method is carried out using a reactor in which raw materials are filled into a boat and left standing horizontally, the NH ₃ consumption rate will be 100 to 300 Kg NH ₃ /Kg of product in order to achieve a blackness L value of 19 or less.
However, when carried out using a reaction apparatus having a vertical cylindrical reaction tower devised by the present inventors and detailed below,
The NH ₃ basic unit becomes low at 5 to 25 Kg NH ₃ /Kg of product.
Therefore, in order to implement this method industrially, it is highly desirable to utilize a fluidized bed reactor in order to increase productivity and reduce production costs. but,
When using this vertical reactor reactor,
Sintering, which does not occur when using a static reactor, is likely to occur, and even if titanium dioxide powder with a specific surface area of 30 m ² /g or more is used, it is difficult to obtain a product powder with a specific surface area of 20 m ² /g or more. It turns out that it is. Therefore, the present inventors carried out the above method on an industrial scale and studied the various conditions of the method in order to obtain the desired fine colored powder with high productivity and good economic efficiency. This problem could be solved by using titanium dioxide powder produced by wet hydrolysis. That is, according to the present invention, titanium dioxide powder produced by wet hydrolysis has a specific surface area of 30
m ² /g or more, it is a vertical cylindrical reaction tower whose lower part is narrowed in the shape of an inverted truncated cone, and has a means at the bottom to disperse ammonia gas upward, and the ammonia gas stagnates inside. a means for stirring titanium dioxide powder; an ammonia gas supply path communicating with the ammonia gas dispersion means; a cooling means for the supply path; and a means for externally heating the reaction tower. There is provided a method for producing a fine colored powder having a specific surface area of 20 m ² /g or more, which comprises heating the powder at 500° to 950° C. in an ammonia gas atmosphere while stirring with the stirring means using an apparatus. Fine titanium dioxide powder is currently produced in two ways. 1 Dry method Titanium tetrachloride is hydrolyzed in an oxyhydrogen flame. 2. Wet method An aqueous solution of titanium sulfate or titanium tetrachloride is hydrolyzed by boiling and alkali neutralization, and the resulting titanium hydroxide is dehydrated and calcined in the atmosphere. TiO ²⁺ (aq) + 2H ₂ O (l)
→TiO(OH) ₂ (s) + 2H ⁺ (aq) TiO(OH) ₂ (s) → TiO ₂ (s) + H ₂ O(g) The reduction of these two types of powders was carried out in an NH ₃ atmosphere.
When carried out at 500° to 950°C, it was found that the dry method
TiO ₂ powder (specific surface area 50m ² /g (average particle size 0.03
µm)), the sintering was significant, and even if the reduction conditions were varied, the specific surface area of the reduced powder was around 10 m ² /g (average particle size 0.2 µm), and the desired fine product could not be obtained. Ta. On the other hand, the powder produced by the wet method (40 m ² /g (average particle size 0.04 μm)) has a specific surface area of 20 m ² /g or more (average particle size 0.08 μm).
It was found that sintering during reduction was small. The method of the invention is carried out at temperatures of 500-950°C.
At temperatures below 500°C, reduction is difficult to proceed, and at temperatures above 950°C, sintering becomes so pronounced that it cannot be ignored. 600~850℃
is particularly preferred. During processing, ammonia gas has a linear velocity of 0.5cm/sec.
It is preferable to supply the air with the above air flow. 0.5cm/
If it is less than sec, reduction of the powder tends to be uneven.
The time required for the treatment is approximately 3 to 8 hours. The reactor used in the method of the invention is equipped with stirring means in the reaction zone to ensure good contact between the NH ₃ gas and the powder. The color of the colored powder obtained by the method of the present invention changes with the degree of reduction as described above, and the larger the specific surface area of the black titanium oxide powder, the more
It is known that blackness (L value) (measured with Suga Test Instruments Color Computer SM-3) and tinting power increase. Therefore, as a pigment, the specific surface area is 20
A powder having a particle size of m ² /g or more is desirable, and can be easily produced by the method of the present invention. As described above, the black colored powder of the present invention has a high degree of blackness and excellent tinting power, so when it is added to plastics as a pigment, a small amount is effective. Also, since it does not contain harmful substances, it can be used as a material for cosmetics, etc. In addition, the specific resistance is 10 ^-2 to ^{10 3} Ω・cm (10Kg/cm ²
Since it is a compacted powder, it can be used as a conductive material for antistatic purposes and as a resistance paste. Furthermore, when a ceramic sintered body is produced using the colored powder obtained by the method of the present invention as a raw material, it exhibits a golden color and can be used for decorative purposes. The apparatus used in the present invention will be specifically described with reference to the accompanying drawings. The illustrated apparatus comprises a reaction tower 1, an ammonia gas supply line 2 equipped with cooling means 4, and means 17 for heating the reaction tower 1.
A titanium dioxide inlet 8 is provided in the upper part of the reaction tower, and the lower end is narrowed in the shape of an inverted truncated cone.
The bottom is closed by a gas distribution plate 3. The gas distribution plate may be something like a perforated plate. The gas distribution plate 3 is supported by a support rod 15 and held on the bottom surface of the inverted truncated cone, and the reacted titanium oxide can be taken out by lowering the support rod. The reaction tower has a stirring blade 6 fixed to a rotating shaft.
6', 6'' are provided and rotated by a motor 5 outside the tower. A gas discharge pipe 10 is provided at the top of the tower, and this discharge pipe communicates with a cyclone 11 to agitate the gas. The incoming dust is separated, the powder is returned to the reaction tower by the screw conveyor 12, and the gas is discharged from the conduit 16.The stirring blades are preferably made of three stacked bamboo dragonfly wings with a large pitch. That is, in the drawing, the right half and the left half of the upper end wing 6 and the lower end wing 6' are inclined at opposite pitches, and the front half and the opposite half of the middle wing 6'' are inclined at opposite pitches. Furthermore, it is preferable to provide the blade with a large number of holes through which titanium oxide can pass. An ammonia supply pipe 2, which also serves as a product discharge path, is provided below the reaction tower. This ammonia supply pipe 2 has a cooling means 4 (which may be a water jacket). In the illustrated embodiment, the upper end is not directly connected to the reaction tower and a space is formed between it and the reaction tower, but it may be in contact with the inverted conical portion so as not to interfere with the operation of the gas distribution plate. In that case, a preheating zone must be provided near the gas distribution plate. Further, in the illustrated embodiment, the support rod 15 of the gas distribution plate 3
The ammonia supply pipe, which also serves as a product discharge pipe, is bent diagonally to support the process. The product discharge pipe ends in a receiver 13, and the product stored there is sequentially discharged by a rotary valve 14. The heating means 17 are conveniently electrical resistance heat. In the embodiment shown, a heat insulating material 7 is provided between the cooling means 4 and the heating device 17, but depending on the design this heat insulating material is not required. For this device, it is best to use a material that does not easily nitride the high-temperature part of the furnace core tube, and Ni-based Inconel is the best, but SUS310S can also be used satisfactorily.
It is not necessary to describe the details of the design and manufacture since it can be easily manufactured by someone with ordinary knowledge of chemical engineering. When carrying out the method of the invention, the rotational speed of the stirring blades is important. The appropriate speed depends on the specific shape and dimensions of the blade, but if the rotation speed is too slow, it will be difficult to obtain the desired fine particles. The titanium dioxide powder 16 retained in the reaction tower 1 is stirred by the stirring blades 6, 6', 6'' and is simultaneously brought into contact with NH ₃ from the gas distribution plate 3. At this time, the titanium dioxide powder 16 is heated by the heating means 17. 〓〓〓
Reduction progresses with heat. Examples In the following examples, a vertical reactor having a configuration as shown in the attached drawings was used, which was equipped with a reaction column having an inner diameter of 30 cm and a height of 13 cm. They are stacked alternately in three tiers. The rotor blades each have a longitudinal width of 75 mm, are propeller-shaped and inclined at 60 degrees to the vertical, and are long enough to provide a gap of 1.5 cm between each blade and the wall of the reaction column. Example (1) Titanium dioxide fine powder (manufactured by Teikoku Kako Co., Ltd., trade name) with a comparative area of 40 m ² /g (average particle size 0.04 μm)
3 kg of MT500B (wet method) was charged into the reaction tower, ammonia gas was flowed through the dispersion plate at a linear velocity of 2 cm/sec, and the stirring blade was rotated at 15 rpm to stir the powder. I gave back my time. The recovered powder weighs 2.3 kg, exhibits a blue-black color, has an L value of 10, and a specific surface area of 29 m ² /g (average particle size of 0.05 μm).
m), specific resistance 2×10 ^-1 Ω・cm (10Kg/cm ² compacted powder)
It was hot. Also, according to X-ray diffraction, TiO ₂ /TiO
The ratio of (N) is 1/10. Examples (2) to (5) Using the titanium dioxide powder of Example (1), reduction was carried out using the same reaction apparatus and changing the reduction conditions.
Table 1 shows the reaction conditions and results. In addition, in the case of the reaction apparatus used in these examples, the rotation of the stirring blade is preferably 10 rpm or more, and especially
A speed of 20 rpm or more was preferable. Comparative example (1) Fine titanium dioxide powder with a specific surface area of 50 m ² /gr (average particle size 0.03 μm) (manufactured by Dexa, Germany, trade name: P-)
25, produced by a dry method) was charged into the reactor used in Example (1), ammonia gas was flowed at a linear velocity of 2 cm/sec in the furnace, and the stirring blade was rotated at 15 rpm to stir the powder. Reduction was carried out at a furnace temperature of 700°C for 5 hours. The specific surface area of the recovered powder was 10 m ² /g (average particle size 0.15 μm), and sintering was considerably observed. Comparative Examples (2) to (3) Using the titanium dioxide powder of Comparative Example (1), reduction was carried out using the same reaction apparatus but under different reduction conditions. Table 1 shows the conditions and results.

[Table] 〓〓〓〓

【table】 [Brief explanation of the drawing]

The accompanying drawings are conceptual diagrams showing examples of devices used in the present invention. In the figure, 1: reaction tower, 2: ammonia gas supply pipe, 3: gas distribution plate, 4: cooling means, 17:
heating means. 〓〓〓〓

Claims (1)

[Scope of Claims] 1. Titanium dioxide powder produced by wet hydrolysis and having a specific surface area of 30 m ² /g or more is grown in a vertical cylindrical reaction tower, the lower part of which is shaped like an inverted truncated cone. an ammonia gas supply path communicating with the ammonia gas dispersion means; Using a reaction apparatus comprising a means for cooling the supply path; and a means for heating the reaction tower from the outside, the reaction tower is heated at 500 to 950°C in an ammonia gas atmosphere while being stirred by the stirring means. A method for producing fine colored powder with a specific surface area of 20 m ² /g or more.