JPH0380724B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a reduced alkali metal titanate. Reduced alkali metal titanates have electrical conductivity and are useful as electrically conductive materials. (Conventional technology) With the development of science and technology and the diversification of needs, the development of high-performance, multifunctional materials has been actively conducted, and even in the plastics industry, various research efforts have been made on the development of conductive polymer materials. For example, polymer materials using carbon particles or fibers or metal powders such as copper, silver, and gold as conductive fillers have been proposed. However, carbon particles, carbon fibers, metal powders such as copper, silver, and gold are all black or have a color unique to the metal, and these conductive fillers are non-reinforcing fillers except for carbon fibers. It is a drug. Further, carbon fiber was initially developed as a high-performance reinforcing agent, but recently it has been actively researched as a conductivity imparting agent. However, since carbon fiber itself is expensive, it cannot be filled very highly from an economic standpoint, and therefore there is a limit to the effect of imparting electrical conductivity. The present inventor has focused on alkali metal titanates, especially fibrous alkali metal titanates, which exhibit well-balanced performance as plastic fillers, and has developed a conductive composition, a titanate with a metal coating, a method for producing the same, and a reduction method. We have developed an alkali metal titanate with electrical conductivity, including a manufacturing method for the alkali metal titanate, and are currently applying for a patent. However, these technologies of the earlier application are still far from being sufficient. That is, for example, in the technology of forming a conductive metal film on the surface of an alkali metal titanate, the same amount or 5 to 10 times as much metal material as the alkali metal titanate is required, making it difficult for industrial applicability. In addition, the technology that imparts conductivity to alkali metal titanate by reduction requires a high reduction temperature and long reduction time, so the size of the crystals may change and it may not be possible to achieve the desired result. It has been difficult to obtain an alkali metal titanate having conductivity. (Problems to be Solved by the Invention) An object of the present invention is to provide a method for producing a reduced alkali metal titanate having excellent conductivity by reducing an alkali metal titanate under mild reducing conditions. It is in. (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). The present invention relates to a method for producing a reduced alkali metal titanate salt, which is characterized by adding calcium carbide to the compound and sintering it in an inert gas atmosphere or a reducing atmosphere. In the present invention, the raw material alkali metal titanate is a known compound, which has conventionally been produced by a hydrothermal synthesis method, a flux method, a calcination method, etc. In the present invention, any known alkali metal titanate can be used as long as it is included in the above general formula, and examples thereof include sodium titanate, potassium titanate, lithium titanate, and the like. In particular, potassium titanate, which is represented by the formula K ₂ O (4-6) TiO ₂ , is advantageous in that it has excellent fire resistance, heat insulation, and mechanical strength, and also has excellent surface smoothness when used as a filler. be. Alkali metal titanate salts are generally in the form of powder or fibrous single crystals, but any of these forms can be used in the present invention. However, among these, fibrous substances are preferable, and fibrous potassium titanate is generally preferable for practical purposes.
As mentioned above, those having an aspect ratio of 20 or more, especially 100 or more are suitable as reinforcing fillers. As the calcium carbide used in the present invention, practically available industrial calcium carbide is sufficient. The smaller the particle size, the better, preferably 100 mesh or less, more preferably 200 mesh or less. The amount of calcium carbide added is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, per 100 parts by weight of the alkali metal titanate. In the present invention, an inert gas atmosphere means that the gas in the reactor does not react with the alkali metal titanate within the firing temperature range of the present invention,
Examples include argon gas and nitrogen gas. Further, the term "reducing atmosphere" means an atmosphere in which no reactor gas exists or is filled with hydrogen gas, ammonia gas, or the like. Various inert gases such as nitrogen gas, hydrogen gas, ammonia gas, etc. that can be used in the present invention are practically available industrial gases, and no special purification is necessary. The reduced alkali metal titanate of the present invention can be produced by firing a mixture of the above-mentioned alkali metal titanate and calcium carbide in an inert gas atmosphere or a reducing atmosphere. As will be described in detail later in Examples, for example, a mixture of alkali metal titanate and calcium carbide is placed in a closed high-temperature heating furnace, and then the air in the system is removed under reduced pressure, or the furnace is filled with inert gas such as nitrogen gas. Either a gas is introduced and the air is replaced with nitrogen, and then the temperature is raised for thermal reduction, or after the temperature has been raised, a reducing gas such as hydrogen gas is introduced and the reaction is carried out at a predetermined temperature to form an alkali titanate. It is preferable to provide conductivity by extracting oxygen from the metal salt crystal to generate oxygen defects. The firing temperature of the present invention is preferably about 500
-1000°C, more preferably about 600-900°C, and the firing time is usually about 10-180 minutes, preferably about 20-60 minutes. When the firing time is within the above range, it is particularly preferable because excellent conductivity is imparted without damaging the shape of the alkali metal titanate salt. (Effect of the invention) The reduced alkali metal titanate according to the present invention has various physical properties of the alkali metal titanate before reduction, especially heat resistance, reinforcing properties and surface smoothness when used as a composite material. without losing any of its features.
When it is given conductivity and used as a composite material, its suitability for antistatic, static electricity removal, and conductive material needs is improved compared to conventional reduced alkali metal titanate salts, etc., and it is especially suitable for sheets, paper, and fabrics. Regarding its compatibility with conductive materials such as films, it has high industrial applicability as a processing agent that can add conductivity without losing reinforcing properties and surface smoothness. The conductive alkali metal titanate of the present invention can be widely used in various applications such as reinforcing materials for plastics, fillers for conductive papers, and conductive inks. (Example) Examples will be described below. Example 1 Fibrous potassium titanate [fiber length 15-20 μm, fiber diameter 0.2-0.3 μm, Otsuka Chemical Co., Ltd., trade name Teismo]
5 g and 0.5 g of crushed calcium carbide [manufactured by Toyo Denka Kogyo Co., Ltd.] were mixed well, and the mixture was heated to 30 g.
ml in a platinum container, transferred to a siliconite tubular electric furnace, and after adjusting the atmosphere by flowing nitrogen gas at a flow rate of 150 ml/min at room temperature for about 1 hour, the temperature was raised while continuing to introduce nitrogen gas, and the temperature was raised to about 900 ml. The mixture was heated and baked at ℃ for 60 minutes. After that, turn off the power to the electric furnace and let it cool down to 200
After cooling to ℃, the container was taken out of the furnace. The fired product was taken out of the container, dispersed in a large amount of water, and then filtered and dried to obtain reduced potassium titanate. While the raw material fibrous potassium titanate was a white substance, the obtained reduced potassium titanate was blue-black in color. Example 2 5 g of fibrous potassium titanate (same as in Example 1) and 0.5 g of calcium carbide (manufactured by Toyo Denka Kogyo Co., Ltd.) ground to 325 mesh size were thoroughly mixed, and the mixture was poured into a 30 ml platinum tube. The mixture was poured into a container, transferred to a siliconite tubular electric furnace, and nitrogen gas was flowed at a flow rate of 150 ml/min at room temperature for about 1 hour.
After adjusting the atmosphere, the temperature was raised to 500°C while introducing nitrogen gas. Next, switch the introduced gas to hydrogen gas,
At 850℃ while introducing hydrogen gas at a flow rate of 120ml/min.
It was held for 40 minutes and fired. After that, the power to the electric furnace was turned off, and the furnace was allowed to cool with hydrogen gas flowing through it. After the temperature was at 200°C, the introduced gas was switched to nitrogen gas, and the platinum container was taken out of the furnace. The fired product was taken out from the container, dispersed in a large amount of water, and then filtered and dried to obtain reduced potassium titanate. While the raw material fibrous potassium titanate was a white substance, the obtained reduced potassium titanate was black with a bluish tinge. Example 3 A slurry was prepared by mixing 500 g of fibrous potassium titanate (same as in Example 1), 50 g of calcium carbide (manufactured by Toyo Denka Kogyo Co., Ltd.) ground to 325 mesh paste, 50 g of polyethylene glycol, and 2000 ml of water. None, spray-dried using a spray-drying device to obtain powder. Fill a 30 ml platinum container with 5 g of this powder, transfer it 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. After adjusting the atmosphere, place the inside of the furnace under nitrogen gas introduction. The temperature was raised to 500°C. Thereafter, the introduced gas was switched to ammonia gas, and the temperature was further increased to 800°C, and this temperature was maintained for 45 minutes to perform firing. Then turn off the electric furnace,
After cooling while introducing ammonia gas and switching the introduced gas to nitrogen gas at 200°C, the platinum container was taken out of the furnace. Put the baked product into water,
After thorough washing and drying, reduced potassium titanate was obtained. The obtained reduced potassium titanate was black in color. Example 4 5 g of sodium titanate [manufactured by Otsuka Chemical Co., Ltd.] and 0.3 g of calcium carbide [325 mesh pass, manufactured by Toyo Denka Kogyo Co., Ltd.] were thoroughly mixed, and the mixture was poured into a 30 ml platinum container. , transferred to a siliconite tubular electric furnace, and heated with 150 ml of nitrogen gas at room temperature.
Flow for about 1 hour at a flow rate of 100 mL to adjust the atmosphere in the furnace. After this, after raising the temperature inside the furnace to 500℃,
120ml/120ml of argon/hydrogen (1:1) mixed gas
Raise the temperature inside the furnace to 850℃ while flowing for 60 minutes.
Maintain this temperature for several minutes to perform baking. Next, the power to the electric furnace was turned off, the furnace was allowed to cool naturally to 200°C, the introduced gas was changed to nitrogen, and the platinum container was taken out of the furnace to complete the reaction. The following operations were carried out in the same manner as in Example 2 to obtain a ring-based sodium titanate having a blue-black color. Test Example 1 90 parts of each reduced alkali metal titanate salt obtained above and 10 parts of liquid paraffin were mixed well in a mortar, and then mixed at 50 kg/cm ² in a mold with an inner diameter of 10 mm and a length of 20 mm.
After press molding for 1 minute, silver paste was applied to both sides of the molded body, conductivity was measured using a digital multimeter (manufactured by Takeda Riken Co., Ltd.), and the volume resistivity was calculated using the following formula. The results are shown in Table 1. Volume resistivity (Ω・cm) = Measured resistance (Ω) x Electrode area (cm ² )/Distance between electrodes (cm) [Table]

Claims (1)

[Claims] 1 General formula M ₂ O・nTiO ₂ (wherein M is an alkali metal,
A reduced alkali metal titanate, which is produced by adding calcium carbide to an alkali metal titanate having a composition represented by (n means an integer from 2 to 12) and firing the mixture in an inert gas atmosphere or a reducing atmosphere. Salt manufacturing method. 2. The manufacturing method according to claim 1, wherein the firing temperature is 500 to 1000°C. 3. The manufacturing method according to claim 1, wherein the alkali metal titanate is fibrous.