JPH0688834B2 - Method for producing polycrystalline compact of fibrous alkali metal titanate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polycrystal comprising a fibrous alkali metal titanate salt. Fibrous alkali metal titanate has excellent mechanical properties such as high bending strength, as well as high electrical insulation, thermal or chemical stability, and negative thermal conductivity-temperature coefficient characteristics. It is a prepared material. Therefore, it is widely used for plastic reinforcing materials, antifriction materials, battery diaphragms, heat insulating structural materials, excess materials, adsorbent materials, catalysts and their supports, pigments and the like.

(Prior Art) A method for producing amorphous titanium oxide fibers has been reported by Kruczynski et al. [Naturs 291, 399 (1981)]. The method relates to producing a titanium oxide hydrogel by neutralizing an aqueous solution of titanium tetrachloride with potassium hydroxide, and producing a titanium oxide amorphous body composed of long fiber bundles by freeze-drying.

Various methods have already been proposed for producing crystalline alkali metal titanate fibers. That is, a firing method, a melting method, a hydrothermal method, a flux method and a melt method are known. Generally, in many cases, titanium oxide and a basic oxygen-containing alkali metal compound are used as the raw materials in any of the methods.

For example, in Japanese Examined Patent Publication No. 27264/1987, TiO ₂ products in a commercially available sulfate method for producing hydrous titania, anatase TiO ₂ , pigments, electronic material powders or catalysts as a titanium source, well refined anatase Pigments, ground rutile ores and commercial ilmenite are disclosed. Also disclosed are alkali metal hydroxides and alkali metal carbonates as basic oxygen-containing alkali metal compounds. 42-27
No. 264 is one for synthesizing fibrous alkali metal titanate by firing a non-liquid mixture of the titanium source and a basic oxygen-containing alkali metal compound at 200 to 1150 ° C. and having a diameter of 0.
200 to 8 to produce a colloid-rich product with a particle size of 005 to 0.1 micron and a length of at least 10 times the diameter
Fired at 50 ° C, diameter 0.1-0.6 microns and length 10
To produce a pigment-rich product with a particle size of ~ 100 times, fire at 850-975 ° C, and an insulation type with a particle size of 0.6-3 microns and a length of 100-1000 times the particle size. It is described that the desired fibrous alkali metal titanate can be obtained by calcination at 975 to 1150 ° C. in the case of producing a high-content material. Also disclosed is a manufacturing method in which an alkali metal halide is added to a non-liquid mixture of raw materials and then the mixture is fired.

By the way, the amorphous or crystalline fiber alkali titanate obtained by the above method is molded into a certain shape,
It is considered that it is very difficult to fire it to form a sintered body. That is, many of the fibrous alkali titanate is excellent in mechanical strength, for example, the fibers are broken in the molding step, or the fibers are entangled with each other even if they are not broken, and do not sinter unless pressure is applied, It is considered that there are many problems in the substantial manufacturing method, including the point that an appropriate sintering aid is required. In addition, a sintered body having a porous structure has not been established with a reproducible manufacturing method, although it has a wide range of applications as described above.

(Problems to be Solved by the Invention) An object of the present invention is to provide a polycrystalline compact of a fibrous alkali metal titanate having a large aspect ratio and a large mechanical strength such as bending strength and tensile strength. To provide a manufacturing method.

Further, the object of the present invention is to control the shape and size of the fibrous alkali metal titanate salt from the crystallization and sintering conditions of the amorphous material, and to produce the fibrous alkali metal salt having a predetermined fiber structure and porous structure. To do.

(Means for Solving the Problems) The present invention provides a mixture of a titanium source compound and an oxygen-containing alkali metal compound having a molar ratio of TiO ₂ / M ₂ O (M represents an alkali metal) of 0.4 or more and less than 1.5. After baking at a temperature of 600 to 1100 ℃ to make it amorphous, it is pressure molded and
The present invention relates to a method for producing a polycrystal compact of a fibrous alkali metal titanate salt, which comprises re-firing at 0 to 1350 ° C.

The titanium source compound of the present invention is a compound substantially containing TiO ₂ , and specific examples thereof include titanium oxide, rutile ore, titanium hydroxide wet cake, and hydrous titania. The particle shape is preferably fine particles as much as possible.
For example, in the case of titanium oxide, the anatase type fine particles were crushed by colliding the particles with high speed in the rutin ore.
So-called "jet crushed products" are preferred. A suitable particle size is in the range of 200 to 425 mesh.

The oxygen-containing alkali metal compound used in the present invention is
It is a compound that produces M ₂ O (M is an alkali metal), and examples thereof include oxides, hydroxides, carbonates, bicarbonates, oxalates, and nitrates of potassium, sodium, cesium, and rubidium. Examples of such compounds include K ₂ O, KO
H, K ₂ CO ₃ , KHCO ₃ , K ₂ O ₂ O ₄ , KNO ₃ , Na ₂ O, NaOH, Na ₂ CO ₃ , NaHCO ₃ , Na ₂ C ₂ O ₄ , NaHO ₃ , Cs ₂ O, CsOH, _{Cs 2, CO 3, CsHCO 3} , Cs 2 C 2 O 4, CsNO 3, Rb 2 O, RbOH, Rb 2 CO 3, RbHCO 3, Rb 2 C 2 O 4, etc. RbNO ₃ can be mentioned. Of these, alkali metal nitrates are particularly preferable.

The mixing ratio of the titanium source compound and the oxygen-containing alkali metal compound is 0.4 in terms of the molar ratio in terms of TiO ₂ / M ₂ O (M is an alkali metal).
A range of not less than 1.5 and less than 1.5 is preferable. If the molar ratio is less than 0.4, it is difficult to obtain an alkali metal titanate, and if it is 1.5 or more, the amount of excess alkali is small and it is difficult to obtain a molded product.

In the present invention, the titanium source compound and the oxygen-containing alkali metal compound may be mixed as they are, or water-added slurry may be used and then spray-dried. Although the method for preparing the mixture of raw materials is not limited to the above, the raw material mixture obtained by spray-drying the slurry-like raw material has oxygen-containing alkali metal uniformly and finely adhered to the particle surface of the titanium source compound. It becomes a granulated body, and since this granulated body has extremely high reactivity, it is particularly preferable.

In the present invention, these mixed raw materials are heated to a temperature of about 600 to 1100 ° C, preferably about 850 to 1000 ° C, usually about 2 to 2
Baking for 0 hours gives an amorphous alkali metal titanate salt.

Since the obtained amorphous alkali titanate is a nodule, it is put into cold water, and individual particles are dispersed by, for example, performing ultrasonic treatment for about 30 minutes. By this operation, it is possible to confirm the protrusion of an excessive amount of alkali. But,
This operation should not be carried out with acid, because it will reduce the time required for dispersion. That is, it is clear that even if it is weakly acidic, the structure and composition of the amorphous alkali metal titanate salt will be changed as a result.

Furthermore, it is preferable to wash and dry with distilled water. In order to mold the amorphous product obtained in this step, press molding is usually performed under a pressure condition of about 10 to 200 MPa. At the stage of this operation, it is possible to freely change the bulk density after molding by adding a small amount of an organic sizing agent, a surfactant or the like to the above product. Thus, the polycrystalline molded body of the present invention obtained by press molding is a fiber reinforced plastic (FRP),
It is useful when making fiber reinforced metal (FRM) by the preform method. That is, the content of the fibers in the composite is increased by pouring the molten resin and the molten metal into the polycrystalline molded body of the present invention which is molded into a predetermined shape in advance, or the contact time between the metal and the fiber in the high temperature state is shortened. Therefore, it is possible to suppress problems such as deterioration and deterioration of the fiber due to the reaction.

Next, by firing the above-mentioned molded body in a wide temperature range of about 900 to 1350 ° C., M ₂ O · nTiO ₂ (M is an alkali metal, n is an integer of 4,6,8 or a mixture thereof) Is)
It can be obtained by gradually crystallizing the fibrous polycrystal represented by the above-mentioned amorphous form.

The fibrous structure in the polycrystalline body is affected by the temperature rising rate, the temperature falling rate, the firing time, and the like. In order to obtain an oriented crystal structure, careful control is required at the stage of nucleation. Therefore, it was revealed that a method of adding a small amount of an oxygen-containing iron compound in the first firing step for producing an amorphous material for the purpose of controlling nucleation is also effective. Examples of oxygen-containing iron compounds include iron nitrates, sulfates, chlorides, oxides and hydroxides.

In an amorphous compact, crystallization from the surface is likely to occur due to the temperature gradient formed on the surface. Therefore, in order to deposit fine crystals in the entire amorphous material, it is preferable to maintain the temperature at a predetermined temperature for 10 minutes / minute to 20 ° C / minute and for 45 minutes to 10 hours. Further, it is preferable to gradually cool to about 600 ° C. at a temperature decreasing rate of 2 to 10 ° C./min. In particular, in the case of unidirectional crystallization by the temperature gradient method, a cooling rate within an appropriate time is required while relaxing thermal stress strain. By quenching, the fibrous crystals show a difference in aspect ratio, which is the ratio of average fiber length / diameter, as compared with the slow cooling method.

The present invention is characterized in that the amorphous alkali metal titanate salt obtained in the first firing reaction is re-fired to produce a fibrous polycrystal comprising a crystalline alkali metal titanate salt. . Further, depending on the firing temperature, the composition of the obtained alkali metal titanate has the general formula M ₂ O · nTi
It becomes a sintered body represented by O ₂ (M is an alkali metal, n is a real number of 4,6,8 or a mixture thereof) and has a porosity of 45.
It is also possible to manufacture a sintered body having a porous structure up to about%.

(Example) Hereinafter, it demonstrates in detail by an Example.

Example 1 A commercially available reagent titanium oxide (anatase type) and potassium nitrate were weighed so that the molar ratio of TiO ₂ / K ₂ O was 1.3, and mechanically ground and mixed for a sufficient time. Next, this raw material powder was filled in an alumina crucible and placed in a heating furnace. The temperature rising rate was 10 ° C./min, and the temperature was maintained at 1000 ° C. for 6 hours. After that, the furnace is gradually cooled. The obtained nodule was crushed, immersed in water overnight, and then dried separately to obtain amorphous potassium titanate. The thus obtained product is 75 MPa with a mold having a diameter of 60 mm.
Was molded under the pressure of. Next, it was put into the alumina pot again and the temperature rising rate was set to 10 ° C./minute in the pine furnace, and the temperature was maintained at 1050 ° C. for 10 hours. The mixture was gradually cooled to about 600 ° C. at a temperature decreasing rate of 10 ° C./min to obtain a fibrous potassium hexatitanate polycrystal.

This polycrystal has a relative density of 95% and an average diameter of 1 to 3 μ.
It was found from the density measurement, the stereoscopic microscope and the scanning electron microscope observation that the crystalline fiber had an m, a length of 2 to 8 mm and an aspect ratio of up to 600.

Example 2 Titanium hydroxide and potassium nitrate were added in a molar ratio of TiO ₂ / K ₂ O of 1.0.
And mix thoroughly mechanically. This was filled in an alumina crucible and placed in a heating furnace as in Example 1. The temperature rising rate was set to 15 ° C / min, and the temperature was maintained at 950 ° C for 10 hours. Immediately thereafter, the heating power source was turned off, and a rapid cooling operation was performed to complete the reaction. In the crucible taken out of the furnace,
Fibrous amorphous nodule was deposited. The nodule was immersed in warm water for about 2 hours, and ultrasonically dispersed for about 30 minutes. Approximately 60 mm under a pressure condition of 200 MPa after sufficiently crushing the amorphous material in a mortar.
Press-molded into a disc with a thickness of 30 mm. Next, the molded body was reacted in a pine oven at 900 ° C for 7 hours. After performing a slow cooling operation to about 600 ° C with a temperature decrease rate of 5 ° C / min,
Remove from furnace and air cool.

From the results of X-ray diffraction and chemical analysis, it was possible to observe from the fracture surface that this fibrous polycrystal was potassium tetratitanate with a relative density of 92% and unidirectional fibrous crystal growth.

Example 3 Titanium oxide, sodium nitrate and ferric nitrate were each added to TiO ₂
Weigh so that the molar ratio of / Na ₂ O is 1.4 and the molar ratio of Fe ₂ O ₃ / TiO ₂ is 0.5, and mix sufficiently mechanically. This was filled in an alumina crucible and placed in a heating furnace as in Example 1. The temperature rising rate was 7 ° C./minute, and the temperature was maintained at 1000 ° C. for 6 hours. Immediately thereafter, the heating power source was turned off and a rapid cooling operation was performed to stop the reaction. Amorphous sodium octatitanate was agglomerated and adhered to the inner wall of the crucible taken out of the furnace. After the amorphous product in the nodule was crushed and immersed in water, it was allowed to stand in a heating bath for 2 hours for another drying.

This is then molded at a pressure of 150MPa, diameter 60mm, thickness 30mm
It is molded into a circular plate and baked at 1000 ° C for about 6 hours. After the reaction is sintered, slowly cool to 650 ° C at a cooling rate of about 5 ° C / min,
It was taken out of the furnace. The obtained fibrous polycrystalline body was a sintered body composed of octasodium titanate fibers and had a relative density of 86%.

Example 4 Titanium hydroxide slurry (chemical analysis value TiO ₂ 29.9%, T ₂ SO
₄ 4.17%) into a container equipped with a high-speed stirrer, and after adding sodium hydroxide for neutralization of H ₂ SO ₄ contained in the titanium hydroxide slurry, sodium nitrate was added to TiO ₂ / Na ₂ O. The mixture was adjusted so that the molar ratio was 1.0, and mixed and dissolved sufficiently.
Then, the slurry was dried by a spray dryer [Okawara Koki Co., Ltd., OC-16 type] to obtain a granular dry raw material having good fluidity. This raw material was placed in an alumina crucible, and under the same conditions as in Example 3, formation of an amorphous substance and crystallization treatment from the amorphous substance were performed. The product obtained was a polycrystalline body composed of sodium octatitanate fibers and was composed of crystals having an average fiber length of 4 to 6 mm. 87% relative density
It was.

Example 5 Titanium oxide (anatase type), potassium nitrate and ferric nitrate were weighed so that the molar ratio of TiO ₂ / K ₂ O was 1.2 and the molar ratio of Fe ₂ O ₃ / TiO ₂ was 0.1, and they were sufficiently Mechanical grinding and mixing is performed for a long time. Next, this raw material powder is filled in an alumina crucible and placed in a heating furnace. Temperature rising rate is 7 ° C /
Minutes, and kept at 900 ° C. for 5 hours. After that, the heating power source was turned off for rapid cooling. A light-colored amorphous substance was observed in the crucible taken out of the furnace. Then, about 25% by weight of polyvinyl alcohol was added, and press molding was performed under the condition of 100 MPa. This is baked at 1000 ° C. for 15 hours. After completion of reaction, 5
The mixture was gradually cooled at a temperature decreasing rate of ° C / min to obtain a fibrous porous body composed of a mixture of potassium hexatitanate and potassium octatitanate.
It was revealed that this polycrystal had a porous structure composed of crystalline fibers of 4 to 7 mm and having a porosity of about 33%.

In order to obtain a similar porous structure, the same effect was obtained even when synthetic polymers such as carboxymethyl cellulose, sodium alginate, sodium polyacrylate, and polyacrylate were used in place of polyvinyl alcohol.

Example 6 Titanium oxide and potassium nitrate were weighed so that the molar ratio of TiO ₂ / K ₂ O was 0.4 and mechanically mixed sufficiently. This was filled in an alumina crucible and placed in a heating furnace as in Example 1. Thereafter, in the same manner as in Example 1, the average diameter is 2 to 3 μ.
A polycrystal having m, a length of 5 to 10 mm, and a porosity of 75% made of fibrous potassium tetratitanate was obtained.

Example 7 Titanium oxide and potassium nitrate were weighed so that the molar ratio of TiO ₂ / K ₂ O was 0.8 and mechanically mixed sufficiently. This was filled in an alumina crucible and placed in a heating furnace as in Example 1. Thereafter, in the same manner as in Example 1, the average diameter is 1 to 3 μm.
A polycrystal having m, a length of 2 to 9 mm and fibrous potassium tetratitanate and potassium hexatitanate having a porosity of 85% was obtained.

(Effect of the Invention) The polycrystalline compact formed by the method of the present invention is composed of crystalline alkali titanate fibers having a long fiber length, and
It has a porous structure with a porosity of ~ 45%.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayoshi Suzue 463 Kagasuno, Kawauchi-cho, Tokushima City, Tokushima Prefecture, Tokushima Plant, Otsuka Chemical Co., Ltd. (56) Reference JP 61-21915 (JP, A)

Claims (3)

[Claims] 1. A mixture of a titanium source compound and an oxygen-containing alkali metal compound having a molar ratio of TiO ₂ / M ₂ O (M represents an alcal metal) of 0.4 or more and less than 1.5 at a temperature of about 600 to 1100 ° C. A method for producing a polycrystalline compact of a fibrous alkali metal titanate, which comprises firing to form an amorphous substance, press-molding the amorphous substance, and re-calcining at about 900 to 1350 ° C. 2. The method according to claim 1, wherein the oxygen-containing alkali metal compound is an alkali metal nitrate. 3. A fibrous alkali metal titanate is represented by the general formula M ₂
The method according to claim 1, which is a compound represented by O · nTiO ₂ (M is an alkali metal, n is an integer of 4,6,8 or a mixture thereof).