JPH0573694B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in a method for producing alkali titanate. The alkali titanate produced according to the present invention is
Used as reinforcing material for composite materials, ion exchange material, ion adsorption material, molecular adsorption material, friction material, filtration material, catalyst carrier, etc. [Summary] The present invention is a method for producing alkali titanate in which raw materials including a titanium source and an alkali source are mixed and fired.The method of the present invention is to prepare alkali titanate in the form of fibers by adjusting the mixed raw materials into granules and then firing them. Along with gaining
This shortens the firing time. [Prior Art] So-called mineral fiber materials are considered important as core materials for various composite materials. In particular, alkali titanate fibers have been attracting attention as an alternative to conventional asbestos materials, and methods for producing alkali titanates have therefore been studied. The conventional method for producing alkali titanate is as follows:
The sintering method, melting method, hydrothermal method, flux method, and KDC method have been proposed. The calcination method is a method of calcination of a raw material mixture and synthesis by solid phase reaction. The melting method is a method in which a stoichiometrically blended mixture is mainly melted, and the melt is cooled and solidified to crystallize it. The hydrothermal method is a method of synthesizing using a solvent at a high temperature and pressure above the critical point of water. Currently, the flux method and KDC method are used industrially as synthesis methods. The flux method is a method in which alkali titanate is melted together with a flux, crystals of alkali titanate are grown in the melt, and after cooling, the flux is eluted and removed to obtain alkali titanate. The KDC method is a method in which raw materials are kneaded and made into a lump, which is then fired (Japanese Patent Application Laid-open Nos. 139826-1982 and 26719-1980). [Problems to be Solved by the Invention] However, each of the above conventional methods has the following problems. In the calcination method, the product is not sufficiently crystalline and the fiber length is only a few microns. In the melting method, since the crystals grow in close contact with each other, it is difficult to dissociate the crystals, and if the material is used as a reinforcing material without this treatment being performed insufficiently, there will be no reinforcing effect. The hydrothermal method is not suitable for synthesizing substances other than alkali hexatitanate, and furthermore, because the synthesis operation is performed in a highly alkaline solution under high pressure, equipment costs including safety equipment are expensive, and continuous operation is difficult. In the flux method, it may be difficult to dissociate potassium titanate crystals using a common flux, or harmful gases may be generated. A flux suitable for this method, such as potassium molybdate, has a high unit price and requires about 10 times the amount of the raw material mixture, which requires recovery equipment and increases the size of the equipment. Further, no matter which fluxing agent is used, a washing and drying process is required to remove the fluxing agent. Furthermore, since it is necessary to generate crystals by slow cooling operation, a long operation time of about 12 hours is required. In the KDC method, the firing time is long and the reaction tends to be non-uniform. For example, even if a substance is obtained in the form of fibers, there are portions that are not fibrous. Additionally, water is required to separate the fibers, which necessitates a drying step and an alkali treatment step. The present invention solves the problems of each of the above-mentioned methods, and provides a method for producing alkali titanate that can produce crystals of alkali titanate with high reaction uniformity and good dispersibility in an extremely short time and at low cost. The purpose is to provide [Means for Solving the Problems] The present invention provides a method for producing alkali titanate, which includes a step of mixing raw materials containing a titanium source and an alkali source, and a step of firing the mixed raw materials. The method is characterized in that a step of adjusting the mixed raw materials into granules having an average particle size of 3 mm or less is provided between the step and the firing step. In the firing step, it is preferable to maintain the shape of the granules. The firing step preferably includes a fluidized firing method or uses an external heating rotary kiln. Preferably, the mixing step includes a method of mixing raw materials with a liquid to form a slurry. The step of adjusting into granules includes a method of spraying and drying the mixed raw materials, or a method of applying and drying the mixed raw materials on the surface of the plate,
Alternatively, it is preferable to include a method of extruding the mixed raw materials through a mesh. In the step of preparing granules, it is preferable to adjust the raw material to a diameter of 3 mm or less, and the granules may be granulated. [Operation] A liquid phase coexists in the mixing of raw materials with a titanium source and an alkali source, but when the entire mixing system is divided into lumps by this liquid phase, the size and mixing state of each lump change. Not uniform. As a result, it was found that the reactions within individual clusters were complicated. It was also found that some of the fired products progressed to sintering and became difficult to crush. The inventor conducted an experiment based on the above findings. Looking microscopically at the calcination reaction for synthesizing alkali titanate, if there are uneven parts in the mixing state of the titanium source material and the alkali source material, local evaporation of the alkali will increase and the reaction will stall. It becomes uniform. Therefore, the initial products influence the reaction products produced by the reaction. In other words, it was found that the uniformity of the raw material mixture has a large influence on the uniformity of the reaction product. In particular, in the firing reaction between titanium dioxide (TiO ₂ ) and an alkali, a low alkali titanate with a low melting point is produced as an initial product. In this case, it is a reaction in which a liquid phase and a solid phase coexist, and it is clear that the liquid phase moves due to gravity and also due to capillarity in the pores of the solid phase, making the reaction likely to be non-uniform. Ivy. Therefore, the inventor of the present invention prevented the movement of the liquid phase by granulating the raw material so that the above phenomenon would not occur. This granulation operation, on the one hand, ensures homogeneity of raw material mixing and reaction, thus allowing molar ratio mixing of the products. That is, in the conventional method, an excess of alkali is added so that titanium and alkali react sufficiently, so that the fired product contains an excess of alkali in addition to the alkali titanate. Therefore, it was necessary to wash away the excess alkali binding the crystals with water to dissociate the crystals. This washing contained a large amount of alkali, and it was also necessary to treat the alkali and dry the alkali titanate. However, since the present invention does not use surplus alkali, it is possible to directly obtain alkali titanate simply by pulverizing it without contacting with water. Furthermore, it has been found that the alkali titanate produced on the surface of the fired product has a high infrared reflective ability and inhibits the passage of heat, thereby delaying the reaction, but this problem can also be prevented by granulating the product. the result,
The reaction can now be completed in a short time. The baked product thus produced is in the form of granules and has a large specific surface area, and it is possible to obtain a hydrate simply by leaving it in a humid place. Here, granules refer to particles of 3 mm or less. To prepare the granules, the titanium source material and the alkali source material are mixed, a granulating agent is added, and if necessary, a reaction control agent is added and mixed. The following method is best for making it into granules. (1) The above mixed raw materials are granulated using a spray dryer or the like. (2) Pour or coat the mixed raw materials onto a flat plate to form a plate, then dry and crush it to an appropriate size to make granules. (3) Extrude the mixed raw material through a mesh plate having a large number of pores of a predetermined diameter to form granules. The granules thus obtained are further granulated if necessary. As a method for firing without destroying the granules or granules, it is effective to use a fluidized firing method. If the granules are fired by a fluidized calcination method in which buoyancy is given to the granules and the granules are fired, this is effective in preventing the particles from sticking together, and also improves the passage of heat and accelerates the reaction. Further, even if an externally heated rotary kiln in which the granules are rotated is used, the thermal efficiency is good and the reaction can be promoted. Furthermore, the atmosphere of these furnaces can be easily controlled. Atmosphere adjustment is effective for crystal growth and is expected to impart new properties to alkali titanate. As the raw material used in the present invention, any compound containing titanium can be used as a titanium source, but titanium oxide or titanium hydroxide is preferably used as the main raw material. titanium chloride, to control granulation and reaction;
It is effective to use organic titanium compounds (titanium ethoxide, etc.), metallic titanium, etc. as auxiliary raw materials. As the alkali source, any compound containing an alkali can be used, but as the main raw material, carbonates, hydroxides, nitrates, sulfates, chlorides, etc. are preferable. A granulating agent or a reaction control agent may be added as an auxiliary raw material other than the titanium source and the alkali source. A granulating agent must be selected that does not inhibit the reaction. As the liquid for the granulating agent, in addition to water, there are many other liquids such as alcohols, fats and oils, and acetic acid. As the solid, organic polymers such as pulp and methylcellulose are effective. Preferred examples of the reaction controlling agent include ammonium salts such as ammonium chloride, ammonium nitrate, ammonium carbonate, and urea, and organic acids. The product of the invention after calcination can be further ground into a form suitable for use. In this case, it is preferable to leave the fired product in an atmosphere containing steam for a while and then crush it. [Example] Next, an example of the present invention will be described. The present invention is not limited to the following examples. (Example 1) Potassium or sodium was used as the alkaline raw material in the raw material blend used in this example. Approximately 10 times the amount of water was added to each raw material mixture shown in Table 1 to form a slurry, and granules were prepared using a spray dryer. Of these, No. 9 is made into a slurry with methyl alcohol. The obtained granules were observed using a scanning electron microscope and chemically analyzed to determine their size and TiO ₂ /R ₂ O
The composition was determined in terms of (molar ratio). Firing was performed in an electric furnace under the conditions shown in Table 1. The product was determined by X-ray diffraction. In addition, the shape of the product was observed using a scanning electron microscope. In particular, the calcined granules of alkali titanate obtained in the form of fibers were observed as aggregates in which fibers were entangled in a cage shape. When lightly crushed in a urethane ball mill, the fiber diameter was 0.1 to 105 μm in bulk and the fiber length was 30 to 105 μm. The results obtained are shown in Table 1. (Example 2) Methyl alcohol was added to the raw material mixture shown in Table 2 and mixed, applied on a flat plate, dried, crushed and fired in an electric furnace. Evaluation of each of the granules and products thus obtained was carried out in the same manner as in Example 1, and the results shown in Table 2 were obtained. (Example 3) Water was added to the raw material mixture shown in Table 3, mixed and extruded through a mesh plate, dried, and then fired in an electric furnace. Evaluation of each granule and product was performed in the same manner as in Example 1, and the results shown in Table 3 were obtained. (Example 4) The raw material mixture shown in Table 4 was spray-dried, and the obtained granules were fired in a fluidized fluidized furnace and an externally heated rotary kiln. The granules and products were evaluated in the same manner as in Example 1, and the results shown in Table 4 were obtained. (Example 5) The raw material mixture shown in Table 5 was spray-dried and fired in an externally heated rotary kiln while flowing carbon dioxide gas. The granules and products were evaluated in the same manner as in Example 1, and the results shown in Table 5 were obtained. (Example 6) The raw material compounds shown in Table 6 were spray-dried to prepare granules. Furthermore, after firing in an electric furnace, it was left in a humidified room. The No. 1 specimen was left on a gridiron dripping with water, and the No. 2 specimen was left in a room humidified by ultrasonic waves. After standing, both were easily separated into fibers using a urethane ball mill. X
When the product was examined by line diffraction, it was found to be hydrated potassium titanate (X _I phase) (Kagaku Kogyo, Vol. 31)
(See p. 503, 1980). The results obtained are shown in Table 6.

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〔Effect of the invention〕

As is clear from the above Examples, the significance of the present invention is to complete the synthesis of alkali titanate in a short time by granulating the mixed raw materials before firing. Further, according to the present invention, the equipment cost and manufacturing cost required for production can be significantly reduced compared to those of conventional production methods, and therefore, there is a great effect on the production of alkali titanate.

Claims (1)

[Scope of Claims] 1. A method for producing an alkali titanate comprising a step of mixing raw materials containing a titanium source and an alkali source, and a step of firing the mixed raw materials, wherein the mixing step and the firing step are performed. A method for producing alkali titanate, comprising a step of adjusting the mixed raw materials into granules with an average particle size of 3 mm or less. 2. The method for producing an alkali titanate according to claim 1, wherein in the firing step, the shape of the granules is maintained. 3. The method for producing an alkali titanate according to claim 2, wherein the firing step includes a fluidized firing method. 4. The method for producing an alkali titanate according to claim 2, in which an external heating rotary kiln is used in the firing step. 5. The method for producing alkali titanate according to claim 1, wherein the mixing step includes a method of mixing raw materials with a liquid to form a slurry. 6. The method for producing alkali titanate according to claim 5, wherein the step of preparing the granules includes a method of spraying and drying the mixed raw materials. 7. The method for producing alkali titanate according to claim 5, wherein the step of preparing the granules includes applying the mixed raw materials to the surface of a plate and drying them. 8. The method for producing alkali titanate according to claim 1, wherein the step of preparing the granules includes extruding the mixed raw materials through a mesh.