JPH044975B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a reduced alkali metal titanate. In recent years, the need for conductive materials has been increasing, and materials that can be used as static electricity removal materials, antistatic materials, and conductive materials are being developed or researched. These conductive materials include gold, silver, platinum,
Conductive metals such as copper and nickel, carbon materials such as carbon black, metal oxides such as tin oxide and antimony oxide, and organic conductive compounds such as polypyrrole and polyacetylene are known.
These conductive materials are processed into conductive paints, adhesives, inks, fabrics, fibers, molded bodies, sintered bodies, etc., and used for various purposes. (Prior art) Generally, methods for imparting conductivity to titanates include coating the surface of the titanate with a conductive substance, reducing the titanate to form a titanate made of lower oxides, etc. There are known ways to obtain it. In the former coating method, a conductive substance is deposited on the surface of the titanate by a physical or chemical method to obtain a titanate coated with the conductive substance.The conductive substances include silver, copper, etc. , nickel, tin, antimony, etc., and it is easy to operate, so it is convenient to apply electroless plating-related technology. However, although this method is superior in that it imparts conductivity to the titanate substrate without altering its properties, the titanate material used as a raw material is generally provided in the form of fine powder and has a specific surface area of 5 to 100 m2. ² /g
In order to uniformly coat the powder surface and exhibit conductivity, 1 to 5 g of the conductive substance to be coated is required per 1 g of the raw material titanate. This means that the weight composition of the coating material is equal to or greater than that of the titanate, making it difficult to utilize the inherent properties of the titanate and making it expensive, reducing its industrial applicability. In the latter reduction method, titanate is calcined in a reducing atmosphere or titanate is produced in a reducing atmosphere to reduce M ₂ O・nTiO _2-X (M is an alkali metal, n is 2 to 12 A titanate consisting of a lower order oxide is obtained which exhibits conductivity expressed as an integer of 0<x≦1, and x is a number of 0<x≦1. The conductive titanate obtained by this reduction method is extremely useful in that the conductivity can be controlled by controlling the reduction conditions to obtain a titanate made of any low-dimensional oxide. However, depending on the type of titanate, it is difficult to reduce, and reduction must be carried out at high temperatures or for a long time, which may cause the titanate to melt and form a sintered body, or the crystal state to change. There were times when I admitted that. (Problems to be Solved by the Invention) The purpose of the present invention is to reduce the alkali metal titanate to produce a conductive alkali metal titanate in a temperature range in which the salt does not melt or change its crystalline state. The object of the present invention is to provide a manufacturing method that can obtain the desired product by reduction in the oxidation process and by short-time calcination. Another object of the present invention is to provide a method for producing a reduced alkali metal titanate in which the physical properties of the conductive alkali metal titanate produced by reduction calcination do not lose any of the physical properties of the raw material, other than conductive performance. A further object of the present invention is to provide a method for producing a reduced alkali metal titanate salt having uniform conductivity. (Means for Solving the Problems) The present invention provides an alkali metal titanate having a composition represented by the general formula M ₂ O·nTiO ₂ (wherein M is an alkali metal and n is an integer from 2 to 12). It relates to a method for producing a reduced alkali metal titanate salt, which is characterized by adding boron or one or more boron compounds to the compound, and firing at a temperature of 500 to 1000° C. in an inert gas atmosphere or a reducing atmosphere. The alkali metal titanate of the present invention has the general formula
M ₂ O・nTiO ₂ (in the formula, M is an alkali metal, n is 2 to
(an integer of 12), preferably in the form of fine powder or fibers. Specific examples include lithium titanate, sodium titanate, potassium titanate, etc. Taking potassium titanate as an example, potassium dititanate, potassium tetratitanate, potassium hexatitanate, etc. are industrially produced. In the case of potassium tetratitanate, it is a fibrous body with a layered structure, and in the case of potassium hexatitanate, it is a fibrous body with a tunnel structure. In the present invention, especially potassium hexatitanate represented by the formula K ₂ O.6TiO ₂ has the advantage of excellent fire resistance, heat insulation, and mechanical strength, and also has excellent surface smoothness when used as a filler. It is. As the alkali metal titanate used in the present invention, fibrous substances are particularly preferable, and generally fibrous potassium titanate is practically preferable.
Those with an aspect ratio of 5 μm or more and an aspect ratio of 20 or more, especially 100 or more are suitable as reinforcing fillers. The boron or boron compound used in the present invention is as follows. That is, boron is preferably in the form of crystal or amorphous powder. Examples of boron compounds include boron oxide, alkali metal borate salts, boron halides such as boron chloride, boron alcoholates, and preferably boron oxide anhydrides. In the present invention, in the case of powder, the particle size is preferably as small as possible;
When dissolving in a solvent such as water or alcohol, a solution can be applied to the raw material, but even if the raw material is in powder form, it is preferable to add some water etc. to dissolve the raw material, alkali metal titanate. It is preferable to prepare a homogeneous mixture by mixing, slurrying, and spray drying. Even in the case of a solution, it is preferable to mix the alkali metal titanate salt as a raw material into the solution to form a slurry, and then spray dry it to obtain a uniform mixture. There are no particular restrictions on the amount of boron or boron compounds added, but alkali metal titanate is usually used.
For 100 parts by weight, it is sufficient to add about 2 to 15 parts by weight of boron, and for boron compounds, it is sufficient to add about 2 to 15 parts by weight in terms of boron to achieve the object of the present invention. The reduced alkali metal titanate of the present invention is prepared by mixing an alkali metal titanate with one or more substances selected from the above-mentioned boron or boron compounds in an inert gas atmosphere or a reducing atmosphere.
It can be manufactured by firing at a temperature of °C. As will be described in detail later in Examples, for example, after placing an alkali metal titanate in a closed high-temperature heating furnace, the air in the system is removed under reduced pressure, or nitrogen gas is introduced into the furnace and the air is replaced with nitrogen. Oxygen is removed from the crystals of alkali metal titanate by first substituting, then raising the temperature to 500-1000°C and allowing the reaction to proceed, or by introducing hydrogen gas into the furnace to carry out the reaction. By pulling it out, a reduced alkali metal titanate salt imparted with electrical conductivity is obtained. In a system containing boron, when heated to 500 to 1000°C, the oxygen atoms that make up the lattice of the alkali metal titanate react with active boron and are pulled out, resulting in the formation of boron oxide. Although a portion of the alkali metal titanate is solid-dissolved in the reduced alkali metal titanate, most of it evaporates and essentially does not significantly modify the physical properties of the alkali metal titanate. When hydrogen gas is introduced, oxygen is further removed by the hydrogen, and the reduced alkali metal titanate can be obtained in a short time. In this case, better results can be obtained if the container is made of carbon material. When a boron compound is mixed, the atmosphere inside the furnace
When the temperature exceeds 500℃, the boron-based compound decomposes or melts, and boron oxide diffuses into the alkali metal titanate as a solid solution.Hydrogen gas is then introduced, which removes oxygen and simultaneously generates boron ions with different ionic valences. By introducing , a reduced alkali metal titanate salt having remarkable electrical conductivity can be obtained. In this case as well, good results can be obtained when a carbon-based material is used for the container. This is because the atmosphere in the furnace becomes a reducing atmosphere by using carbon-based materials. In the case of boron, a preferable combination is an inert gas atmosphere such as nitrogen gas or argon gas, or a reducing atmosphere such as hydrogen gas, and in the case of boron-based compounds, a combination of an inert gas and a carbon-based material with hydrogen gas is preferable. Firing in a reducing atmosphere may be used. The firing temperature of the present invention is usually 500 to 1000°C,
Preferably the temperature is in the range of 600 to 900°C, and the firing time is usually in the range of 15 to 120 minutes, preferably 20 to 70 minutes. The reduced alkali metal titanate obtained by the production method of the present invention is a conductive material having a shape of fine powder, fine fiber, fine layer, etc., and when sintered, a conductive sintered body and a binder. Conductive paints, inks, and adhesives can be obtained by kneading with resin, conductive compounds, sheets, etc. can be obtained by kneading with resin, and conductive fabrics, fibers, and papers can be obtained by papermaking or blending. This is extremely advantageous in providing a conductive composite material as a reinforcing conductive material without impairing the heat resistance, which is a characteristic of inorganic conductive materials. In addition, the properties of alkali metal titanates, which have high industrial applicability as materials for composite materials that provide heat resistance, dimensional stability, surface smoothness, reinforcing properties, etc., are not reduced, and conductivity is further added. It is a reduced alkali metal titanate salt having properties suitable as a material for composite materials. (Example) Examples will be described below. Example 1 Potassium titanate [manufactured by Otsuka Chemical Co., Ltd., trade name, Teismo D] 5 g and boron [manufactured by Wako Pure Chemical Industries, Ltd.]
Add water to 0.5 g and mix, make a slurry, and spray dry to create a mixture. Fill the resulting mixture in a 30 ml graphite crucible container, transfer it to a siliconite tubular electric furnace, and seal it. , Nitrogen gas was flowed at a flow rate of 150 ml/min for about 1 hour at room temperature, and after adjusting the atmosphere, the temperature was raised to 500° C. while introducing nitrogen gas. Next, the introduced gas was changed to hydrogen gas, hydrogen gas was introduced at a flow rate of 120 ml/min, and the temperature was maintained at 850°C for about 1 hour.The electric furnace was then turned off, and the hydrogen gas was allowed to cool while flowing, and the introduced gas was heated to 200°C. After switching to nitrogen gas, it was taken out of the furnace. By carrying out the reduction treatment using the method described above, a blue-colored reduced potassium titanate was obtained. Example 2 Water was added to 5 g of potassium titanate (Teismo D) and 1 g of boric anhydride and mixed to form a slurry,
The mixture was prepared by spray drying. The mixture was placed in a 30 ml alloy container, transferred to a siliconite tubular electric furnace, and nitrogen gas was added at room temperature to 150 ml/h.
After adjusting the atmosphere, the temperature was raised to 600℃ while nitrogen gas was introduced, and after maintaining the temperature at 600℃ for about 20 minutes, the introduced gas was switched to hydrogen gas, and hydrogen gas was introduced at a flow rate of 120ml/min. The temperature was increased while maintaining the temperature at 900°C for about 1 hour, and then the power to the electric furnace was turned off. Hydrogen gas continued to be introduced, and after cooling to 200°C, the introduced gas was switched to nitrogen gas, and then taken out of the furnace. A blue-colored reduced potassium titanate was obtained by reduction treatment using the above method. Example 3 In Example 1, the introduced gas was changed to hydrogen gas, and the temperature was increased to 750°C while introducing hydrogen gas at 120 ml/min.
By carrying out all the same operations as in Example 1 except that the mixture was held for about 1 hour, a blue-colored reduced potassium titanate was obtained. Example 4 After thoroughly mixing 5 g of sodium titanate (manufactured by Otsuka Chemical Co., Ltd.) and 0.5 g of boron (manufactured by Wako Pure Chemical Industries, Ltd.),
Pour into a 30 ml platinum crucible, transfer to a siliconite tubular electric furnace, and flow nitrogen gas at a flow rate of 150 ml/min at room temperature for about 1 hour to adjust the atmosphere, then raise the temperature to 500 °C while continuing to introduce nitrogen gas. I let it happen. Next, the introduced gas was switched to hydrogen gas, hydrogen gas was introduced at a flow rate of 120 ml/min, and the temperature was maintained at 900°C for 50 minutes.
After turning off the power to the electric furnace, the furnace was cooled to 200°C while hydrogen gas was introduced. The introduced gas was switched to nitrogen gas at 200°C and then taken out of the furnace. By carrying out the reduction treatment using the above method, a blue-colored reduced sodium titanate was obtained. Example 5 After adding 5 g of sodium titanate [manufactured by Otsuka Chemical Co., Ltd.], 1 g of anhydrous borax, and water to form a slurry,
A mixture was prepared by spray drying, placed in a graphite crucible, transferred to a siliconite tubular electric furnace, and after introducing nitrogen gas to adjust the atmosphere inside the furnace, nitrogen gas was introduced at a rate of 150 ml/min. At 500℃, switch to hydrogen gas, then at 850℃, about 1
After maintaining the firing temperature for an hour, the power was turned off, and the furnace was allowed to cool while flowing hydrogen gas, and after switching to nitrogen gas at 200°C, it was taken out of the furnace. A blue-colored reduced sodium titanate was obtained by reduction treatment using the above method. Example 6 90 parts by weight of each reduced alkali metal titanate obtained in Examples 1 to 5, 10 parts by weight of liquid paraffin
After mixing the weight parts well in a mortar, the inner diameter is 10 mm and the length is 20 mm.
After applying silver paste to ^both sides of the molded product, conductivity was measured using a digital multimeter [manufactured by Takeda Riken Co., Ltd.]. When the volume resistivity was calculated using the following formula, it was as shown in Table 1.

[Table] (Effects of the Invention) According to the production method of the present invention, a highly conductive reduced alkali metal titanate salt can be obtained by firing at a relatively low temperature and in a short time. Therefore, conductivity can be imparted to the alkali metal titanate without impairing its original physical properties, and the reduced alkali metal titanate obtained by the production method of the present invention has extremely high industrial applicability.

Claims (1)

[Claims] 1 General formula M ₂ O・nTiO ₂ (wherein M is an alkali metal,
boron or one or more boron compounds is added to an alkali metal titanate having the composition shown in (n means an integer from 2 to 12), and the mixture is heated at a temperature of 500 to 1000°C under an inert gas atmosphere or a reducing atmosphere. A method for producing a reduced alkali metal titanate salt, which is characterized by firing at 2. The manufacturing method according to claim 1, wherein the boron is crystalline boron or amorphous boron. 3. The manufacturing method according to claim 1, wherein the boron compound is boric acid, borax, or a boron-based organometallic compound. 4. The manufacturing method according to claim 1, wherein the inert gas atmosphere is N ₂ or Ar atmosphere. 5. The manufacturing method according to claim 1, wherein the reducing atmosphere is an H ₂ gas atmosphere or a carbon-filled atmosphere. 6 General formula M ₂ O・nTiO ₂ (In the formula, M is an alkali metal,
2. The method according to claim 1, wherein the alkali metal titanate having a composition represented by (n means an integer from 2 to 12) is in the form of fibers.