JPS62226856A - Manufacture of polycrystal body of fibrous alkali metal titanate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a polycrystalline body comprising a fibrous alkali metal titanate. Fibrous alkali metal titanates have excellent mechanical properties such as high bending strength, as well as high electrical insulation, thermal and chemical stability, and negative thermal conductivity and temperature coefficient characteristics. It is a material that has been prepared. Therefore, it is widely used in applications such as plastic reinforcement materials, anti-friction materials, battery diaphragms, heat-insulating drying materials, filtration materials, adsorption materials, catalysts and their carriers, and pigments.

(Prior art) Regarding the manufacturing method of amorphous titanium oxide fiber, K ruc
zynski et al. (Nazure, Vol. 291, p. 399)
(1981)). The method involves preparing a titanium oxide hydrodel by neutralizing an aqueous solution of titanium tetrachloride with potassium hydroxide, and producing an amorphous titanium oxide consisting of titanium oxide by freeze-drying.

Furthermore, various methods have already been proposed for producing crystalline alkali metal titanate fibers. Namely, the sintering method, the melting method, the hydrothermal method, the Brax method, the melting method, and the like are known. Generally, in any of the methods, titanium oxide and a basic oxygen-containing alkali metal compound are often used as raw materials.

For example, Japanese Patent Publication No. 42-27264 describes hydrous titania as a titanium source, sharp ffz: 1Tio□, 1"i02 product in a commercial sulfate process for producing pigments, electronic material powders, catalysts, etc., and well-purified sharp apertures. Stone pigments, crushed rutile ore, commercially available ilmenite, etc. are disclosed. Also, as basic oxygen-containing alkali metal compounds, alkali metal hydroxides, alkali metal carbonates, etc. are disclosed. The non-liquid mixture of the titanium source and the basic oxygen-containing alkali metal compound is fired at 2O0 to 1150°C to form a fibrous alkali metal titanate, and the diameter is 0.005 to 0.1 micron. 2O0-850°C when producing colloid-rich particles with particle dimensions whose length is at least 10 times the diameter.
■ If you want to produce pigment-rich pigments with a diameter of 0.1 to 0.6 microns and a quality of 10 to 100 times the diameter, calcining at 850 to 975°C; is 0
．． 975 when producing highly insulated particles with a particle size of 6 to 3 microns and a length of 100 to 1000 times the diameter.
It is described that the desired M&fibrous alkali metal titanate can be obtained by firing at ~1150°C. IWi also shows a 91 method in which an alkali metal halide is added to a non-liquid mixture of raw materials and fired.

By the way, it is considered that it is very difficult to form the amorphous or crystalline fiber titanium oxide obtained by the above method into a certain shape and fire it into a sintered body. In other words, #IA fibrous titanium oxide has excellent mechanical strength, so for example, the fibers may break during the molding process, or even if they do not break, the fibers become entangled with each other, resulting in sintering unless under pressure. It is thought that there are many problems with the actual manufacturing method, such as the need for a suitable sintering aid and the need for a suitable sintering aid.In addition, the sintered body with a porous structure is Despite its wide range of uses, no reproducible manufacturing method has been established.

(Problems to be Solved by the Invention) An object of the present invention is to produce a polycrystalline fibrous alkali metal titanate having a large aspect ratio and high mechanical strength such as bending strength and tensile strength. Our goal is to provide the following.

Another object of the present invention is to control the shape, thickness, etc. of fibrous alkali metal titanate from the crystallization and sintering conditions of the amorphous material, and to manufacture it with a predetermined fiber structure and porous structure. It's about doing.

(Means for Solving the Problems) The present invention involves firing a mixture of a titanium source compound and an oxygen-containing alkali metal compound at a temperature of about 600 to 1100°C to form an amorphous body, and then press-molding the mixture, About 900 to 1 more
The present invention relates to a method for producing a polycrystalline fibrous alkali metal titanate, which is characterized by re-firing at 350°C.

The titanium source compound of the present invention is a compound substantially containing TiO2, and specific examples include titanium oxide, rutile ore, titanium hydroxide wet cake, and hydrous titania. The particle shape is preferably fine particles.For example, for titanium oxide, 7-natase type fine particles are preferable, and for rutile ore, so-called "jet pulverized products" in which particles are pulverized by high-speed collision are preferable.The particle size is 2O0
A range of ~425 meshes is suitable.

The oxygen-containing alkali metal compound used in the present invention is a compound that generates M2O (M is an alkali metal) during firing, such as potassium, sodium, cesium, rubidium oxides, hydroxides, carbonates, bicarbonates, Examples include acid salts and nitrates. Examples of such compounds include 2O
．． KOH.

K2Co,,K HCo1,K2O,OiKNO,,N
a2O, Na0HSNa2CO=, NaHCO,, Na
2C2On, NaN0-1Cs, O, CsOH.

Cs z-CO:l, CsHCO2, C92C2O41
1CsN O,, Rb2C%Rb0Ir1Rb, Co,
, RbHCO, , Rb2C, O RbN0. etc. can be mentioned.

Among these, alkali metal nitrates are particularly preferred.

The mixing ratio of the titanium source compound and the oxygen-containing alkali metal compound is T i O2/M 2O (M is an alkali metal)
The molar ratio of dew is preferably in the range of 0.4 to 1.5.

In the present invention, the titanium source compound and the oxygen alkali metal compound may be mixed as they are, or they may be mixed with water to form a slurry and then spray-dried. Although the manufacturing method of the (raw material) U compound is not limited to the above, the raw material mixture obtained by spray-drying the slurry raw material has an oxygen-containing alkali metal uniformly distributed on the particle surface of the titanium source compound. In addition, finely adhered granules are formed, and this granule has extremely high reactivity, which is particularly preferable.

In the present invention, these mixed raw materials are about 600.
The amorphous alkali metal titanate is obtained by firing at a temperature of 00° C., preferably about 850° C. to about 850° C., usually for about 2 to 20 hours.

Since the obtained amorphous alkali titanate is a lump, it is poured into cold water, and the individual particles are dispersed, for example, by ultrasonication for about 30 minutes. Through this operation, it is possible to confirm that an excessive amount of alkali has oozed out. However, this operation should not be carried out using acids, even though the time required for dispersion may be reduced. In other words, it is clear that even if it is weakly acidic, the structure and composition of the amorphous alkali metal titanate will change as a result.

Furthermore, it is preferable to wash and dry with distilled water. In order to shape the amorphous product obtained in this step, press molding is typically performed under pressure conditions of 10 to 200 MPa.

It is also possible to freely change the bulk density after molding by adding some organic sizing agent, surfactant, etc. to the above-mentioned product at this manufacturing stage.

Next, by firing the above molded body in a wide temperature range of about 900 to 1350°C, the general formula M2O・nTioz (
M is an alkali metal, n is an integer of 4, 6.8, or a mixture thereof), and a fibrous polycrystalline body can be obtained by gradually crystallizing the amorphous body.

The fiber structure within the polycrystalline body is affected by the temperature rise rate, temperature fall rate, firing time, etc. To obtain an oriented crystal structure, deep control is required at the nucleation stage. Therefore, it has become clear that a method of adding a small amount of an oxygen-containing iron compound in the 11th 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 molded article, crystallization from the surface is likely to occur due to a temperature gradient formed at the surface. Therefore, W throughout the amorphous body
In order to precipitate steel crystals, it is preferable to maintain the temperature at a predetermined temperature for 45 minutes to 10 hours at a heating rate of 10° C./min to 20° C./min. Furthermore, temperatures of 2 to b are preferred up to around 600°C. In particular, when unidirectional crystallization is performed using the temperature gradient method, a cooling rate within an appropriate time is required while relaxing thermal stress strain. A difference in the aspect ratio, which is the ratio of average fiber length/diameter, is observed in am-shaped crystals produced by rapid cooling compared to those produced by slow cooling.

The present invention is characterized in that the amorphous alkali metal titanate obtained in the first firing reaction is re-fired to produce a fibrous polycrystalline body made of crystalline alkali metal titanate. . Furthermore, depending on the firing temperature, the composition of the alkali metal titanate obtained can be determined by the general formula M2O.
Produce a sintered body represented by nTiO2 (M is an alkali metal, mouth is 4.G, a real number of 8 or a mixture thereof) and has a porous structure with a porosity of up to about 45%. It is also possible.

(Example) Hereinafter, this will be explained in detail with reference to Examples.

Example 1 Commercially available reagents titanium oxide (anatase type) and potassium nitrate were weighed so that the molar ratio of TiO□/2O was 1.3, and mechanically pulverized and mixed for a sufficient period of time.

Next, this raw material powder was filled into an alumina crucible and placed in a heating furnace. The heating rate was 10°C/min, and 10
The temperature was maintained at 00°C for 6 hours. After that, it is slowly cooled in the furnace. The resulting nodules were crushed, immersed in water overnight, and then dried separately to obtain amorphous potassium titanate. The product thus obtained was molded in a mold with a diameter of 60+au+ under a pressure of 75 MPa. Next, it was placed in an alumina crucible again and held at 1050°C for 10 hours in a Matsufuru furnace at a temperature increase rate of 10°C/min. The mixture was gradually cooled down to about 600''C at a cooling rate of 10°C/min to obtain a fibrous polycrystalline potassium hexatitanate.

The relative density of this polycrystal is 95%, and the average diameter is 1 to 3μ.
It was found by density measurements, stereoscopic microscopy, and scanning electron microscopy that it was a crystalline i-fiber with a length of 2 to 8 g+- and a maximum aspect ratio of nearly 600.

Example 2 Titanium hydroxide and potassium nitrate were weighed so that the molar ratio of TiO2/KzO was 1.0, and mechanically mixed thoroughly. As in Example 1, this was filled into an alumina crucible and placed in a heating furnace. The heating rate was 15°C/min, and 9
It was held at 50°C for 10 hours. Thereafter, the heating power was immediately turned off and a rapid cooling operation was performed to complete the reaction. Fibrous amorphous nodules were precipitated in the crucible taken out from the furnace. The nodules were immersed in warm water for about 2 hours, and then dispersed by ultrasonic waves for about 30 minutes.
I went for a minute. After thoroughly crushing the non-easy body in a mortar, 200M
It is press-formed into a disc with a diameter of 60 cm and a thickness of 301 II m under pressure conditions of Pa. Next, the molded body was reacted in a Matsufuru furnace at 900° C. for 7 hours. After performing a slow cooling operation to about 600° C. at a temperature decreasing rate of 5° C./min, the product was taken out of the furnace and cooled in air.

From the results of X-ray diffraction and chemical analysis, it was observed from the fracture surface that this am trade polycrystalline body 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
'io2/N a2O molar ratio of 1.4 and 1/
Weigh so that the molar ratio of F czo 3/Tie: is 0.5, and mix thoroughly mechanically. As in Example 1, this was filled into an alumina crucible and placed in a heating furnace.

The temperature increase rate was 7°C/min, and the temperature was maintained at 1000°C for 6 hours.

Thereafter, the heating power was immediately turned off, and a rapid cooling operation was performed to stop the reaction. The crucible taken out from the furnace contains amorphous 8
Sodium titanate had turned into a monster and was attached to the inner wall.

The amorphous product in the nodules was crushed and immersed in water, and then left in a heating bath for 2 hours to perform separate drying.

This was then molded at a pressure of 150 MPa to a diameter of 60
to +a, molded into a 30mm thick disk and heated to 1000℃
Bake for about 6 hours. After the reaction is completed, the temperature is approximately 5℃/
The mixture was gradually cooled to 650° C. at a cooling rate of 10 minutes, and then taken out from the furnace. The obtained fibrous polycrystalline body was a sintered body composed of sodium octitanate fibers and exhibited a relative density of 86%.

Example 4 Titanium hydroxide slurry (chemical analysis value TiO229.9%
, I-1260, 4,17%) in a container equipped with a high-speed stirrer, and the 112 contained in the titanium hydroxide slurry.
After adding 801 minutes of sodium hydroxide for neutralization, sodium nitrate was adjusted to a molar specific force of TiO2/Na2O, TI4, and thoroughly mixed and dissolved. Next, the slurry was applied to a spray dryer [Okawara Machining 8! (KK)
, OC-16 type] method to obtain a granular dry raw material with good fluidity. This raw material was placed in an alumina crucible, and an amorphous material was formed and the amorphous material was crystallized under the same conditions as in Example 3.

The obtained product was a polycrystalline body composed of sodium octitanate fibers, and was composed of crystals with an average fiber length of 4 to 6I. The relative density was 87%.

Example 5 Titanium oxide (anatase type), potassium cum nitrate, and ferric nitrate were each added to TiO□/ in a molar ratio of O of 1.2 and F
Weigh out so that the molar ratio of e2O-/Tio2 is 0.1, and wait for enough time 8! Perform mechanical grinding and mixing. Next, this raw material powder is filled into an alumina crucible and placed in a heating furnace. Temperature increase rate is 7℃/min, 900℃
It was held for 5 hours. Then, the heating power was turned off for rapid cooling. A pale yellow amorphous substance was observed in the crucible taken out from the furnace. Next, add about 20% polyvinyl alcohol.
5% by weight was added, and press molding was carried out under conditions of 100 MPa. This is baked at 1000°C for 15 hours. After the reaction is complete,
It was slowly cooled at a cooling rate of 5°C/min, and potassium 6 titanate and 8
A fibrous porous body made of a mixture of potassium titanate was obtained. It was revealed that this polycrystalline body had a porous structure with a porosity of about 33% and was composed of crystalline fibers of 4 to 71 $lI.

The same effect was also obtained by using synthetic polymers such as carboxymethylcellulose, sodium alginate, sodium polyacrylate, and polyacrylic ester instead of polyvinyl alcohol in order to obtain a similar porous structure.

(Effects of the Invention) The polycrystalline body produced according to the method of the present invention is composed of crystalline alkali titanate fibers with a long fiber length, and has a fiber length of 0 to 45
It has a porous structure with a porosity of %.

(that's all)

Claims (4)

[Claims] (1) After firing a mixture of a titanium source compound and an oxygen-containing alkali metal compound at a temperature of about 600 to 1100°C to form an amorphous body, this is pressure-molded and further
A method for producing a polycrystalline fibrous titanium alkali metal salt, which comprises re-firing at 50°C. (2) Claim 1, wherein the mixing ratio of the titanium source compound and the oxygen-containing alkali metal compound is a molar ratio of TiO_2/M_2O (M represents an alkali metal) of 0.4 to 1.5.
Manufacturing method described in section. (3) The production method according to claim 1, wherein the alkali metal compound containing alkali metal is an alkali metal nitrate. (4) The fibrous alkali metal titanate has the general formula M_2O
- The manufacturing method according to claim 1, which is a compound represented by nTiO_2 (M is an alkali metal, n is an integer of 4, 6, 8, or a mixture thereof).