Method for producing alkali metal titanate and apparatus for producing alkali metal titanate

Abstract

To provide a method for producing an alkali metal titanate and an apparatus for producing the alkali metal titanate capable of reducing a production cost by recovering a flux.SOLUTION: A method for producing an alkali metal titanate of the present invention comprises a reaction step in which a raw material 51 containing a titanium compound and an alkali metal compound is heated in a flux 61 for the titanium compound to react with the alkali metal compound to produce a product 52 containing an alkali metal titanate, and a flux separation step in which the product 52 is separated from the flux 61. In the flux separation step, the product 52 is separated from the flux 61 by allowing the flux 61 to pass through a liquid permeability holding part 11 while the product 52 is held by the liquid permeability holding part 11.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a method and apparatus for producing alkali metal titanate, and in particular, proposes a technology that contributes to reducing manufacturing costs. [Background technology]

[0002] Alkali metal titanates possess high strength, heat resistance, wear resistance, high dielectric properties, and other excellent chemical and physical characteristics, and can be used in automotive wear materials, ceramic capacitors, and as reinforcing materials compounded into resin materials in engineering plastics.

[0003] Various methods are known for producing alkali metal titanates, including calcination, melting, and fluxing. In the fluxing method, the raw materials, a titanium compound and an alkali metal compound, are reacted by heating them to, for example, 900°C or higher in a flux, such as potassium chloride, to produce alkali metal titanates.

[0004] Related technologies include, for example, those described in Patent Documents 1 to 3. In particular, Patent Document 1 describes "heating a mixture of a titanium source compound and a compound that becomes a divalent ion metal oxide upon heating and / or a halide of said metal in the presence of a flux under atmospheric pressure and non-aqueous conditions." [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2-164800 [Patent Document 2] U.S. Patent No. 2841470 [Patent Document 3] U.S. Patent No. 3,328,117 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the flux process described above, a considerable amount of flux is used to heat the raw materials. However, after heating the raw materials, almost all of the flux is evaporated, and any remaining residue is removed by washing, without being recovered. Therefore, a relatively large amount of new flux is required each time alkali metal titanate is manufactured, which increases manufacturing costs.

[0007] This invention aims to solve these problems, and its objective is to provide a method for producing alkali metal titanate and an apparatus for producing alkali metal titanate that can recover flux and reduce manufacturing costs. [Means for solving the problem]

[0008] The present invention provides a method for producing alkali metal titanate, comprising a reaction step of heating raw materials containing a titanium compound and an alkali metal compound in a flux to react the titanium compound and the alkali metal compound to produce a product containing alkali metal titanate, and a flux separation step of separating the product from the flux, wherein in the flux separation step, the product is separated from the flux by allowing the flux to pass through the permeable retaining section while the product is held in the permeable retaining section.

[0009] The permeable retaining portion is preferably in the shape of a container having a permeable hole that allows flux to pass through but prevents the product from passing through.

[0010] More specifically, in the flux separation step, it is preferable to separate the product from the flux by lifting the permeable retaining part, together with the product held in the permeable retaining part, out of the flux.

[0011] In the reaction step, the titanium compound and the alkali metal compound can be reacted while the raw materials are held in the permeable holding section.

[0012] In this case, from the reaction step until at least the flux passes through the liquid-permeability holding portion in the flux separation step, the raw material or the product can be held by the liquid-permeability holding portion.

[0013] It is preferable that before the reaction step, a raw material forming step is further included in which a compacted powder as the raw material that can be held by the liquid-permeability holding portion is formed from a mixed powder containing a titanium compound and an alkali metal compound.

[0014] It is preferable that at least a portion of the liquid-permeability holding portion that contacts the product is made of aluminum oxide.

[0015] The reaction step is preferably carried out in a sealed state inside the reaction vessel in the reaction vessel.

[0016] In the flux separation step, after the flux passes through the liquid-permeability holding portion, it is preferable to heat the product in a reduced-pressure atmosphere to separate the flux remaining in the product.

[0017] [[ID=​​​​​​​​​​​The liquid-permeability maintaining part preferably has a container shape with liquid-permeating holes that allow the flux to pass through but do not allow the product to pass through.

[0021] The liquid-permeability maintaining part is configured to be able to hold the raw material, and in particular, it is preferably configured to be able to hold a compact of a mixed powder containing a titanium compound and an alkali metal compound as the raw material.

[0022] It is preferable that at least the part of the liquid-permeability maintaining part that contacts the product is made of aluminum oxide.

[0023] The reaction vessel preferably has a lid that can maintain the inside of the reaction Tank in a sealed state.

[0024] The apparatus for producing an alkali metal titanate of this invention preferably further includes a reduced-pressure heating furnace that heats the product in a reduced-pressure atmosphere to separate the flux remaining in the product. [[ID=id19]]

Advantages of the Invention

[0025] According to the method for producing an alkali metal titanate and the apparatus for producing an alkali metal titanate of this invention, the flux can be recovered, and the production cost can be reduced.

Brief Description of the Drawings

[0026] [Figure 1] It is a cross-sectional view along the depth direction of a reaction vessel, schematically showing the reaction vessel and the liquid-permeability maintaining part of a production apparatus that can be used in the method for producing an alkali metal titanate according to one embodiment of this invention. [Figure 2] It is a cross-sectional view schematically showing a state in which a product is separated from a flux using a liquid-permeability maintaining part in the production apparatus of FIG. 1. [Figure 3] It is a cross-sectional view schematically showing the reaction vessel and the liquid-permeability maintaining part of another production apparatus. [Figure 4]Figure 3 is a schematic cross-sectional view showing how the product is separated from the flux using a permeable holding section in the manufacturing apparatus. [Figure 5] Furthermore, this is a schematic cross-sectional view showing the reaction tank and liquid permeability retaining section of other manufacturing equipment. [Figure 6] This is a schematic cross-sectional view showing a vacuum heating furnace that can be equipped in the manufacturing apparatus shown in Figure 1. [Figure 7] This is an SEM image of the powder obtained in Example 1. [Figure 8] This is an SEM image of the powder obtained in Example 2. [Figure 9] This is an SEM image of the powder obtained in Reference Example 1. [Figure 10] This is an SEM image of the powder obtained in Reference Example 2. [Modes for carrying out the invention]

[0027] Embodiments of this invention will be described below. A method for producing alkali metal titanate according to one embodiment of this invention includes a reaction step of heating raw materials containing a titanium compound and an alkali metal compound in a flux to react the titanium compound and the alkali metal compound to produce a product containing alkali metal titanate, and a flux separation step of separating the product from the flux. In the flux separation step, the product is separated from the flux by allowing the flux to pass through the permeable retaining section while the product is retained in the permeable retaining section. As a result, the flux, which was previously removed, can be recovered and reused, thereby reducing manufacturing costs.

[0028] (Alkali metal titanate) The alkali metal titanate to be produced here is a type of titanate compound, represented by the general formula: M2O·nTiO2 (wherein M is an alkali metal element and n is an integer from 1 to 12). Specifically, alkali metals included in the alkali metal titanate include lithium, sodium, potassium, rubidium, cesium, francium, etc., and it is particularly preferable to use at least one selected from the group consisting of potassium, sodium, and lithium.

[0029] Alkali metal titanates include sodium hexa-titanate (Na2Ti6O 13 ), sodium titanate (Na2Ti8O 17 ), potassium tetratitanate (K2Ti4O9), potassium hexatitanate (K2Ti6O 13 ), potassium titanate (K2Ti8O 17 ), lithium titanate (Li4Ti5O 12 ) and others. Among them, potassium hexatinate (K2Ti6O 13 Potassium hexatinate (K2Ti6O) has high strength, high rigidity, chemical resistance, and wear resistance, and is used in a wide range of applications such as friction materials for automobile brake pads, insulating materials, gaskets, and plastic reinforcing materials. Therefore, in the method of this embodiment, potassium hexatinate (K2Ti6O) is mainly used. 13 It is preferable to manufacture ).

[0030] The alkali metal titanate-containing product obtained by the method of this embodiment may contain silicon, for example, from ore, but even if silicon is present, the silicon content is, for example, 3% by mass or less, preferably 2% by mass or less. The product may further contain at least one element selected from the group consisting of iron (Fe), magnesium (Mg), aluminum (Al), and vanadium (V), for example, from ore. The total content of these elements is, for example, 4% by mass or less, typically 3% by mass or less.

[0031] Preferably, the alkali metal titanate contains 0.1% by mass or less of chlorine, which can degrade the resin material of engineering plastics.

[0032] The alkali metal titanate is preferably in the form of fibrous particles. Such fibrous alkali metal titanate particles are thought to function effectively to strengthen the resin material when used as a reinforcing material for engineering plastics. In this embodiment, the flux method is employed, and the alkali metal titanate particles produced by this method tend to be fibrous.

[0033] More specifically, the minor axis of the alkali metal titanate particles is preferably 0.05 μm to 1.00 μm, more preferably 0.10 μm to 0.50 μm, and the major axis is preferably 1.00 μm to 100.00 μm, more preferably 5.00 μm to 50.00 μm. If the minor axis of the alkali metal titanate particles is too short, the fibrous particles will easily break, affecting the resin strengthening ability, and there is a risk that the crushed alkali metal titanate fine powder will disperse into the air. Also, if the minor axis of the alkali metal titanate particles is too long, it becomes difficult to maintain the shape of the fibrous particles. If the major axis of the alkali metal titanate particles is too short, the resin strengthening ability may be inferior, and if it is too long, the bulk increases, making it difficult to handle.

[0034] The short and long diameters of alkali metal titanate particles are determined using a particle size and shape distribution analyzer, as the average values ​​of the short diameter d and long diameter L of 10,000 or more alkali metal titanate particles. Here, the long diameter L represents the maximum length between any two points on the contour line of the projected image of the alkali metal titanate particle, and the short diameter d represents the minimum length in the direction perpendicular to the long diameter L. A PITA-3 model manufactured by Seishin Corporation can be used as the particle size and shape distribution analyzer.

[0035] Specifically, using a particle size and shape distribution analyzer (PITA-3 model, manufactured by Seishin Corporation), fibrous particles are identified by taking projection images of more than 10,000 particles of each alkali metal titanate, defining the longest distance between any two points on the contour line of the projection image as the major axis L, and the shortest distance perpendicular to the major axis as the minor axis d. Here, particles satisfying L / d ≥ 3 are defined as fibrous particles. Then, using the particle size and shape distribution analyzer, the circumference of the projection image of the fibrous particles identified as described above is measured, and the mass of each fibrous particle is determined from the volume of a sphere with a cross-section of a circle having the same circumference as the measured fibrous particle, and the theoretical value of the true density of the alkali metal titanate (potassium titanate, etc.). Subsequently, the masses of each fibrous particle are accumulated to calculate the total mass of the fibrous particles, and the ratio of this total mass of fibrous particles to the total mass of the alkali metal titanate particles used in the measurement is defined as the fibrous particle content.

[0036] When alkali metal titanate is added to water to form an aqueous slurry, it is desirable that the slurry have a pH close to neutral. This is because, when alkali metal titanate is used as a reinforcing material for engineering plastics, the degradation of the resin material by the alkali metal titanate is suppressed. Specifically, the pH of the aqueous slurry is preferably between 5.5 and 8.5.

[0037] (raw materials) The raw materials used in the method of this embodiment include titanium compounds and alkali metal compounds.

[0038] As titanium compounds, one or more selected from the group consisting of titanium dioxide, titanium dioxide, orthotitanic acid or its salts, metatitanic acid or its salts, titanium hydroxide, and peroxotitanic acid or its salts can be used. Among these, titanium dioxide is preferred. This is because titanium dioxide has excellent miscibility and reactivity with alkali metal compounds, and is relatively inexpensive. When using titanium dioxide, its rutile or anatase crystal form is preferred.

[0039] Titanium compounds are generally used in particulate form, particularly in the form of aggregates or granules containing granules. These aggregates refer to those formed from secondary particles (primary particles aggregated), tertiary particles (secondary particles aggregated), and other coarse particles of higher order. Aggregates or granules of titanium dioxide are particularly preferred. The average particle size of the titanium compound is preferably 0.1 mm or more, more preferably 0.5 mm to 10.0 mm, and even more preferably 0.5 mm to 1.0 mm, in order to efficiently achieve uniform mixing with the alkali metal compound. However, even if the aggregate or granules have a large average particle size exceeding 10.0 mm, it is possible to use them after crushing or grinding to reduce the average particle size to 10.0 mm or less. Here, the average particle size refers to the value measured according to the sieving test method for chemical products of JIS K0069. The same applies to the average particle size of the alkali metal compound described later.

[0040] As aggregates of titanium compounds, titanium oxide produced by the sulfuric acid method from titanium sulfate or titanyl sulfate, titanium oxide produced by the gas phase oxidation or hydrolysis of titanium tetrachloride, or titanium oxide produced by neutralizing or hydrolyzing an aqueous solution of titanium tetrachloride or alkoxytitanium can be used. Alternatively, granulated titanium compounds can be used instead of aggregates of titanium compounds. Granulated titanium compounds can be obtained by spray-drying commercially available fine titanium oxide or by adding a binder and kneading the mixture.

[0041] The alkali metal compound is preferably at least one selected from the group consisting of potassium compounds, sodium compounds, and lithium compounds, depending on the target alkali metal titanate. More specifically, it can be an oxide, carbonate, hydroxide, or oxalate of potassium, sodium, and / or lithium. For example, if the target alkali metal titanate is potassium titanate, potassium carbonate is particularly preferred as the alkali metal compound.

[0042] Alkali metal compounds can be in particulate form. The average particle size of the alkali metal compound is preferably 0.1 mm to 10.0 mm, more preferably 0.5 mm to 10.0 mm, and even more preferably 0.5 mm to 1.0 mm, for ease of handling.

[0043] Regarding the ratio of titanium compound to alkali metal compound to be included in the raw materials, for example, if the alkali metal titanate to be synthesized is potassium titanate, it is preferable to have a molar ratio of 2.4 to 3.6, or even 2.6 to 3.4, of the number of moles of titanium atoms in the raw materials to the number of moles of potassium atoms in the raw materials.

[0044] Furthermore, the raw materials may, if necessary, contain powdered metallic titanium and / or titanium hydride, for example, 0.01 to 0.20 moles per mole of titanium atoms in the titanium compound. In this case, the number of moles of titanium atoms in the ratio of the titanium compound to the alkali metal compound described above should be adjusted to include the number of moles of titanium atoms in such metallic titanium or titanium hydride. The raw materials may also contain alkaline earth metal compounds such as magnesium compounds and barium compounds. In addition, the raw materials may contain trace amounts of inorganic oxides and other compounds such as Fe2O3, Al2O3, SiO2, CeO2, WO3, ZrO2, Zr(CO3)2, CaCO3, etc., in amounts that do not affect the formation of alkali metal titanate. The raw materials preferably contain titanium compounds and potassium compounds in amounts of 85% to 100% by mass, and more preferably 90% to 100% by mass, when calculated on a solid content basis.

[0045] (Raw material forming process) In the raw material molding process, the mixed powder containing the above-mentioned titanium compound and alkali metal compound is molded to form compacts such as pellets. This makes it easier to hold the raw materials as compacts and the products generated from them in the permeable holding section during the reaction process and flux separation process described later, and makes it even easier to separate the products from the flux.

[0046] However, if the raw materials mentioned above can be held in the permeable retaining section during the reaction process described later, the raw materials can be used directly in the reaction process without performing the raw material molding process. In this case, the raw material molding process can be omitted.

[0047] In the raw material molding process, a mixed powder containing titanium compound powder and alkali metal compound powder is formed into a compact using a press or extrusion molding machine. The compact can be of a size that is held in the liquid-permeable holding section without passing through the liquid-permeable holes, etc., described later, and its shape is not particularly limited.

[0048] (Reaction process) In the reaction process, for example, in the reaction vessel 1 of an alkali metal titanate manufacturing apparatus (hereinafter also simply referred to as the "manufacturing apparatus") as shown in Figure 1, the raw material 51 is heated in flux 61 to react the titanium compound and alkali metal compound contained in the raw material 51. This produces a product 52 containing alkali metal titanate (see Figure 2).

[0049] The reaction vessel 1 illustrated in Figure 1 comprises a bottomed, cylindrical or similar vessel body 2 capable of storing molten flux 61 inside, a lid 3 covering the opening of the vessel body 2, and a heater 4 provided around the vessel body 2 that can heat the inside of the reaction vessel 1. While the reaction process can be carried out using such a reaction vessel 1, the configuration of the reaction vessel is not limited to that shown in the figure.

[0050] In the reaction process, it is preferable to heat the raw material 51 in the flux 61 at a temperature of 800°C to 1150°C for 1 to 48 hours. If the heating temperature is too low, the reaction may not proceed, and if the heating temperature is too high, there is a concern that the flux will volatilize excessively. If the heating time is too short, sufficient crystal growth may not be expected. If the heating time is too long, sufficient crystal growth can be achieved, but from a cost perspective, prolonged heating is not industrially desirable.

[0051] The lid 3 of the reaction vessel 1 is preferably constructed in such a way that it can be closed to maintain a sealed state inside the reaction vessel 1. In this case, the reaction process can be carried out in a sealed state inside the reaction vessel 1. This suppresses the evaporation of the flux 61 heated by the heater 4 during the reaction process and the resulting loss of flux 61, so that more flux 61 can be recovered after the reaction process for reuse. During the reaction process, the atmosphere inside the reaction vessel 1 is not particularly limited as long as it does not affect the flux 61 or other raw materials, and for example, air or an inert gas can be applied.

[0052] The flux 61 used in the reaction step can be selected from alkali metal chlorides, alkali metal carbonates, alkali metal fluorides, as well as molybdenum oxide, alkali metal molybdates, tungsten oxides, alkali metal tungstates, alkali metal oxides, lead fluoride, lead oxide, boron oxide, vanadium oxide, etc., or a mixture of two or more of these, depending on the alkali metal titanate obtained. For example, when obtaining potassium titanate, the flux 61 can contain potassium chloride (KCl) and / or potassium molybdate (K2MoO4).

[0053] The illustrated manufacturing apparatus further comprises, in addition to the reaction tank 1 described above, a permeable holding section 11 that allows molten flux 61 to pass through while retaining the product 52. Preferably, the permeable holding section 11 is configured to also retain the raw materials 51. The illustrated permeable holding section 11 is connected to a support rod 12 that extends inside and outside the reaction tank 1. This support rod 12 is mainly used to lift the permeable holding section 11 out of the flux 61 during the flux separation process.

[0054] In this embodiment, the raw material 51 is held in the permeable holding section 11 and immersed together with the permeable holding section 11 in the flux 61 to carry out the reaction process. In the reaction process, the titanium compound and alkali metal compound in the raw material 51 are reacted while the raw material 51 is held in the permeable holding section 11. The resulting product, which contains alkali metal titanate, is then held in the permeable holding section 11 and the flux separation process described below is carried out.

[0055] (Flux separation process) After the reaction step, a flux separation step is performed to separate the product 52, which contains alkali metal titanate generated in the reaction step, from the flux 61.

[0056] At this time, the permeable retaining section 11 is used to hold the product 52 in the permeable retaining section 11 while allowing the flux 61 to pass through the permeable retaining section 11. As a result, most of the flux 61 is separated from the product 52, and the flux 61 can be recovered. The recovered flux 61 can be used again in the production of alkali metal titanate. As a result, the increase in manufacturing costs caused by the need for new flux each time alkali metal titanate is produced can be suppressed.

[0057] The permeable retaining section 11 can be used in the flux separation process as shown in Figure 2, for example. That is, after the reaction process is completed, the lid 3 of the reaction vessel 1 is opened, and the permeable retaining section 11 is lifted from the flux 61 to the outside of the reaction vessel 1 using the support rod 12, as indicated by the arrow in Figure 2. As a result of the reaction process, the material held in the permeable retaining section 11 has changed from the raw material 51 to the product 52. When the permeable retaining section 11 is lifted, the product 52 held in it is also lifted to the outside of the reaction vessel 1. Meanwhile, the flux 61 passes through the permeable retaining section 11 and remains inside the reaction vessel 1. This makes it easy to separate the product 52 from the flux 61. The flux 61 that remains inside the reaction vessel 1 can be stored inside the reaction vessel 1 or recovered from inside the reaction vessel 1 and reused. By maintaining the storage of flux 61 inside reaction vessel 1 and proceeding with the next production, the addition of flux to reaction vessel 1 becomes unnecessary, thus simplifying the production process.

[0058] The permeable holding section 11 is preferably in the shape of a basket, bag, dish, or other container, with multiple, especially many, permeable holes formed at the bottom, etc., as shown in Figures 1 and 2. The permeable holding section 11 shown has multiple or multiple layers of container sections, each with permeable holes at the bottom, and multiple raw materials 51 or products 52 are held within each of these container sections. The permeable holes provided in the permeable holding section 11 can be sized or shaped to allow flux 61 to pass through but not the products 52 or raw materials 51.

[0059] However, the permeable retaining section is not limited to a container shape, as long as it can hold the product 52 and through which the flux 61 can pass. For example, in the other manufacturing apparatus shown in Figures 3 and 4, a permeable retaining section 11a, such as a plate, sheet, mesh, or other net-like structure with permeable holes, is fixedly attached to the inner surface of the reaction tank 21, midway along its depth. In addition, a flux storage tank 25 is provided at the bottom of the reaction tank 21, and the inside of the reaction tank 21 and the inside of the flux storage tank 25 are connected via an openable and closable communication hole 26 provided at the bottom of the reaction tank 21. The other configurations can be substantially the same as those shown in Figures 1 and 2, and further explanation is omitted here.

[0060] In the manufacturing apparatus shown in Figures 3 and 4, the reaction process is carried out with the communication hole 26 at the bottom of the reaction vessel 21 closed. Then, in the flux separation process, the communication hole 26 is opened, and as shown by the arrow in Figure 4, the flux 61 is moved from inside the reaction vessel 21 to inside the flux storage tank 25 by its own weight through the communication hole 26. At this time, the product 52 on the permeable holding section 11a is held in the permeable holding section 11a, but the flux 61 passes through the permeable holding section 11a and flows out from inside the reaction vessel 21 through the communication hole 26. In this manufacturing apparatus as well, the product 52 can be effectively separated from the flux 61.

[0061] Another manufacturing apparatus shown in Figure 5 has a configuration almost identical to that shown in Figures 3 and 4, except that the permeable retaining section 11b, which serves as the bottom of the tank body 32, has an inclined surface that gradually deepens as it moves towards the central communication hole 36 inside the reaction vessel 31, and the communication hole 36 functions as a liquid passage hole with dimensions that do not allow the passage of the product 52. In the permeable retaining section 11b that constitutes the bottom of the tank body 32, the product 52 is retained, but the flux 61 flows along the inclined surface of the permeable retaining section 11b and passes through the communication hole 36, which corresponds to the central liquid passage hole at the deepest position.

[0062] Among the manufacturing apparatuses including the liquid-permeability maintaining parts 11, 11a, or 11b described above, here, the manufacturing apparatus mainly including the liquid-permeability maintaining part 11 shown in FIGS. 1 and 2 will be described. However, the configurations described for this manufacturing apparatus may be applicable to other manufacturing apparatuses either alone or in combination of a plurality of them.

[0063] The liquid-permeability maintaining part 11 can be made of at least a material with low reactivity with the flux 61. Specifically, the liquid-permeability maintaining part 11 made of nickel (Ni) or aluminum oxide (Al2O3) is preferably used. Among them, aluminum oxide has low reactivity not only with the flux 61 but also with the titanium compound and alkali metal compound of the raw material 51 and the alkali metal titanate of the product 52. Therefore, at least the part of the liquid-permeability maintaining part 11 that contacts the product 52 and the raw material 51 preferably consists of aluminum oxide. Thereby, instead of yellow to dark green compounds (K 0.8 Ni 0.4 Ti 3.6 O8, etc.) caused by the reaction with nickel, white potassium titanate can be generated.

[0064] On the other hand, the material of at least the inner surface part of the tank main body part 2 and the lid body 3 that does not contact the raw material 51 and the product 52 only needs to have low reactivity with the flux 61. Such an inner surface part may be made of nickel (Ni), aluminum oxide (Al2O3), or the like.

[0065] By the way, in the flux separation step, after allowing the flux 61 to pass through the liquid-permeability maintaining part 11 while holding the product 52 by the liquid-permeability maintaining part 11, the flux may adhere to and remain on the product 52. The flux remaining on the product 52 can also be removed by taking out the product 52 from the liquid-permeability maintaining part 11 and washing it. In this case, from the reaction step until the flux passes through the liquid-permeability maintaining part 11 in the flux separation step, the raw material 51 or the product 52 will be held by the liquid-permeability maintaining part 11.

[0066] On the other hand, the flux remaining in product 52 is preferably separated and recovered by heating product 52 under reduced pressure, as illustrated in Figure 6. This is explained in detail below.

[0067] As shown in Figure 2, after the permeable holding part 11 is lifted out of the flux 61 together with the product 52, the permeable holding part 11 and the product 52 are transferred from the reaction vessel 1 to the vacuum heating furnace 41 shown in Figure 6, while the product 52 is further held in the permeable holding part 11. The vacuum heating furnace 41 has, for example, a bottomed cylindrical furnace body 42 in which the product 52 and the permeable holding part 11 are housed, a lid 43 that can seal and cover the opening of the furnace body 42, and a heater 44 that heats the inside of the vacuum heating furnace 41. The permeable holding part 11 and the product 52 transferred from the reaction vessel 1 are placed inside the furnace body 42 through the opening of the furnace body 42 with the lid 43 of the vacuum heating furnace 41 open, and housed inside the vacuum heating furnace 41 when the lid 43 is closed and the furnace is sealed.

[0068] Here, a condenser 45, which serves as a cooler or condenser, is provided near the vacuum heating furnace 41, and the inside of the vacuum heating furnace 41 and the inside of the condenser 45 are connected by a connecting pipe 46. The condenser 45 is also connected to a vacuum pump (not shown) by a suction pipe 47.

[0069] In this type of vacuum heating furnace 41, to separate the flux remaining in the product 52 from the product 52, the product 52 inside is heated by a heater 44, while a vacuum pump is used to evacuate the inside of the vacuum heating furnace 41 through the suction tube 47, condenser 45, and connecting tube 46. As a result, the flux evaporated by heating reaches the inside of the condenser 45 via the connecting tube 46, where it is cooled and collected. The flux collected in the condenser 45 can be recovered and reused.

[0070] The heating temperature in the vacuum heating furnace 41 in this case may be, for example, 30°C to 3000°C, and the vacuum level inside the vacuum heating furnace 41 is 10 -12 Pa~105 It can be expressed as Pa.

[0071] Furthermore, in the manufacturing apparatus shown in Figures 3 and 4, and in Figure 5, the reaction vessels 21 and 31 themselves can be used as vacuum heating furnaces as described above. In this case, after transferring the flux 61 from the reaction vessels 21 and 31 to the flux storage tanks 25 and 35, the communication holes 26 and 36 are closed, and although not shown in the figures, the reaction vessels 21 and 31 are connected to a condenser, and the product 52 inside the reaction vessels 21 and 31 is heated under a reduced pressure atmosphere. In this case as well, the flux remaining in the product 52 is collected and recovered by the condenser.

[0072] As described above, by performing the flux separation process, it becomes possible to effectively recover the flux used in the reaction process, thereby significantly reducing the manufacturing cost of alkali metal titanate. [Examples]

[0073] The present invention will be described in more detail below with reference to examples, but these are merely illustrative and not intended to limit the present invention.

[0074] (Example 1) 46.12 g of titanium dioxide (manufactured by Cosmo Chemical, average particle size 0.6 μm) as a titanium compound and 13.89 g of potassium carbonate (manufactured by Unid) as an alkali metal compound were weighed out and ground and mixed in an alumina mortar for more than 10 minutes to obtain the raw material mixture. The raw material thus obtained was filled into a powder molding die (φ20 mm) and 1 ton of pressure was applied to produce 6 pellets (compacted powder).

[0075] The pellets were placed in a permeable retaining section, which was a cylindrical alumina cage (manufactured by Shinagawa Fine Ceramics Co., Ltd.) equipped with support rods. The permeable retaining section containing the pellets was then inserted into a reaction vessel, a cylindrical alumina container (capacity 5 liters) that had been set up in a heating device and dried. 3000g of potassium chloride (flux) was then poured in from above. The support rods of the permeable retaining section were fixed to the lid of the reaction vessel, positioned so that the section was sufficiently submerged in potassium chloride and not in contact with the permeable retaining section. A thermocouple in an alumina protective tube was placed near the pellets, and after evacuating the reaction vessel, the atmosphere was replaced with an argon atmosphere. Next, the reaction vessel was heated to 1060°C at a rate of 1°C / min, and this temperature was maintained for 8 hours. After that, it was allowed to cool naturally to 800°C. When it reached 800°C, the permeable retaining section was lifted out of the heating container using the support rods, and the pellets were removed and separated from the reaction vessel filled with potassium chloride, along with the permeable retaining section. Afterward, the pellets were allowed to cool naturally, washed with water, and then crushed to obtain a white powder.

[0076] The obtained white powder was subjected to compositional analysis using a powder X-ray diffractometer (X-ray source: CuKα rays, manufactured by Panalytical, model number: X'Part-ProMPD), and the white powder was found to be potassium titanate (K2Ti6O 13 ) was confirmed to be the case.

[0077] Furthermore, using a particle size and shape distribution analyzer (PITA-3 model, manufactured by Seishin Corporation), the maximum length between any two points on the contour line of the projection image (major axis L) and the minimum length in the direction perpendicular to the major axis (minor axis d) were measured for the obtained white powder, using projection images of more than 10,000 particles. The average values ​​of major axis L and minor axis d are shown in Table 1. Furthermore, Figure 7 shows the results of scanning electron microscopy (SEM) observation of the obtained white powder. These results confirmed that the particles of the white powder were fibrous.

[0078] Furthermore, the pH of an aqueous slurry obtained by adding 3 g of the obtained white powder to 100 mL of water was measured, and the results are shown in Table 1.

[0079] (Example 2) A yellow to dark green powder was obtained in the same manner as in Example 1, except that a nickel cage was used instead of an alumina cage as the liquid-permeable retaining part of the substrate used.

[0080] The resulting yellow to dark green powder was subjected to compositional analysis in the same manner as in Example 1, and it was determined that the powder contained potassium titanate (K2Ti6O 13 ) and potassium titanate (K) containing nickel 0.8 Ni 0.4 Ti 3.6 It was confirmed to be a mixture with O8). Furthermore, the physical properties of the obtained powder were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0081] [Table 1]

[0082] Reference Examples 1 and 2 in Table 1 show the known physical properties of commercially available potassium titanate (both manufactured by Toho Titanium Co., Ltd.).

[0083] Furthermore, in Examples 1 and 2, the potassium chloride recovered from the reaction vessel could be reused as a flux. Therefore, it was found that the present invention can reduce the manufacturing cost of alkali metal titanate. [Explanation of symbols]

[0084] 1, 21, 31 Reaction vessels 2, 22, 32 Tank body 3, 23, 33 Lid 4, 24, 34 Heaters 11, 11a, 11b Liquid permeability holding part 12 Support rods 25, 35 Flux storage tanks 26, 36 communication hole 41. Vacuum heating furnace 42 Furnace body 43 Lid 44 Heater 45 Capacitors 46 Communication pipe 47 Suction tube 51 Raw materials 52 Product 61 Flux

Claims

1. A method for producing alkali metal titanate, A reaction step in which raw materials containing titanium compounds and alkali metal compounds are heated in a flux, and the titanium compounds and alkali metal compounds are reacted to produce a product containing alkali metal titanate, A flux separation step for separating the product from the flux, Includes, A method for producing alkali metal titanate, comprising the flux separation step, wherein the product is held in a permeable retaining section while the flux is allowed to pass through the permeable retaining section, thereby separating the product from the flux.

2. The method for producing alkali metal titanate according to claim 1, wherein the permeable retaining portion is in the shape of a container having permeable holes that allow flux to pass through but not the product to pass through.

3. The method for producing alkali metal titanate according to claim 1 or 2, wherein in the flux separation step, the permeable retaining part is lifted out of the flux together with the product held in the permeable retaining part, thereby separating the product from the flux.

4. A method for producing alkali metal titanate according to claim 1 or 2, wherein in the reaction step, the titanium compound and the alkali metal compound are reacted while the raw materials are held in the permeable retaining section.

5. The method for producing alkali metal titanate according to claim 4, wherein the raw material or the product is held in the permeable retaining section for at least the period from the reaction step until the flux passes through the permeable retaining section in the flux separation step.

6. A method for producing alkali metal titanate according to claim 1 or 2, further comprising a raw material molding step of forming a compacted raw material from a mixed powder containing a titanium compound and an alkali metal compound, which can be held in the liquid permeable retaining section, prior to the reaction step.

7. The method for producing alkali metal titanate according to claim 1 or 2, wherein at least the portion of the liquid permeable retaining portion that comes into contact with the product is made of aluminum oxide.

8. A method for producing alkali metal titanate according to claim 1 or 2, wherein the reaction step is carried out in a reaction vessel in a sealed state within the reaction vessel.

9. A method for producing alkali metal titanate according to claim 1 or 2, wherein in the flux separation step, after the flux has passed through the permeable retaining section, the product is heated under a reduced pressure atmosphere to separate the flux remaining in the product.

10. A method for producing alkali metal titanate according to claim 1 or 2, wherein the titanium compound contains titanium dioxide, the alkali metal compound contains potassium carbonate, and the alkali metal titanate contains potassium titanate.

11. The method for producing alkali metal titanate according to claim 1 or 2, wherein the flux comprises potassium chloride and / or potassium molybdate.

12. An apparatus for producing alkali metal titanate, A reaction vessel that stores flux internally and reacts titanium compounds and alkali metal compounds in the flux to produce a product containing alkali metal titanate, A permeable retaining section used for separating the product from the flux, through which the flux passes and which is capable of holding the product, A manufacturing apparatus for alkali metal titanate, equipped with the following features.

13. The apparatus for producing alkali metal titanate according to claim 12, wherein the permeable retaining portion is in the shape of a container having permeable holes that allow flux to pass through but not the product to pass through.

14. The apparatus for producing alkali metal titanate according to claim 12 or 13, wherein the permeable holding portion is configured to hold the raw material.

15. The apparatus for producing alkali metal titanate according to claim 14, wherein the permeable holding portion is configured to hold a compacted mixed powder containing a titanium compound and an alkali metal compound as raw materials.

16. The apparatus for producing alkali metal titanate according to claim 12 or 13, wherein at least the portion of the liquid-permeable retaining portion that comes into contact with the product is made of aluminum oxide.

17. The apparatus for producing alkali metal titanate according to claim 12 or 13, wherein the reaction vessel has a lid capable of maintaining a sealed state inside the reaction vessel.

18. The apparatus for producing alkali metal titanate according to claim 12 or 13, further comprising a vacuum heating furnace for heating the product under a reduced pressure atmosphere and separating the flux remaining in the product.

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