JP2005263533A - Method for producing titanium oxide-based fine wire-like product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a titanium oxide-based fine wire-like product which is obtained at a low cost and has a long size. <P>SOLUTION: The titanium oxide-based fine wire-like product is produced by a production method comprising a raw material vessel closing process for charging a coarsely crushed natural rutile coarse powder having particle diameters of >75 to <300 μm into a raw material vessel in which a sodium hydroxide aqueous solution is accommodated and closing the vessel with a cap, a hydrothermal synthesis process for synthesizing the fine wire-like product by keeping the raw material solution in the closed raw material vessel at a prescribed temperature for a prescribed time, a solution neutralization process for neutralizing the solution containing the product after opening the raw material vessel, a washing process for washing the obtained product, a product separation process for separating the washed product into a gray product and a white product with a separation means, and an adsorbed water- and crystallization water-removing process for removing adsorbed water and crystallization water of the separated white product. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a titanium oxide-based fine wire product, a titanium oxide-based fine wire product and an apparatus for producing the same, and more specifically, using a coarsely pulverized natural rutile crude powder as a raw material, which is inexpensive and long. The present invention relates to a method for producing a titanium oxide fine wire product for producing a long titanium oxide fine wire product, a titanium oxide fine wire product, and an apparatus for producing the same.

Since titanium oxide (TiO ₂ ) has excellent properties such as ultraviolet absorption and adsorption, it has been conventionally used for pigments, paints, cosmetics, ultraviolet shielding materials, catalysts, catalyst carriers, and various electronic materials. Etc. Furthermore, in recent years, there has been great interest in the photocatalytic activity of titanium oxide itself. The excellent photocatalytic activity of titanium oxide has been put to practical use for the purpose of environmental purification, more specifically, decomposition of harmful organic substances, removal of air pollutants, sterilization, and antibacterial. Regarding the photocatalytic activity of such titanium oxide, it is known that the tetragonal anatase structure is also higher than the tetragonal rutile structure. Further, increasing the specific surface area of titanium oxide has been studied as a method for improving the photocatalytic activity of titanium oxide. For example, many attempts have been made such as making titanium oxide into a nanoscale tube or fiber.

As a nanoscale tube-shaped titanium oxide, for example, a titanium oxide crystal having a nanotube shape is known. In the nanotube body according to this conventional example, titanium oxide powder is placed in an aqueous solution of sodium hydroxide having a concentration of 13 to 65 outer wt% (preferably 18 to 55 wt%), and a temperature of 18 to 160 ° C. (preferably, 30 to 120 ° C.) for 1 to 50 hours (preferably 2 to 20 hours).
Further, this nanotube body is usually produced using titanium oxide powder having a particle size of 2 to 100 nm, desirably 2 to 30 nm, and has a thickness of 2 to 10 nm and a length of 50 to 150 nm. The titanium oxide powder used as a raw material for the nanotube body is produced by any one of the “liquid phase method”, “gas phase method”, and “sol-gel method”.

The “liquid phase method” is a method for producing titanium oxide by calcining hydrous titanium oxide obtained by heating and hydrolyzing titanium ore with a strong acid such as sulfuric acid at a temperature of 800 to 850 ° C. . The “gas phase method” is a method for producing titanium oxide by bringing O ₂ and H ₂ into contact with ТiCl ₄ . The “sol-gel method” means that a titanium alkoxide containing Тi (OR) ₄ or the like is hydrolyzed in an aqueous alcohol solution to form a sol, and a hydrolysis catalyst is added to the sol and left to stand. This is a method for producing a titanium oxide by gelling and firing the gelled product (see, for example, Patent Document 1 and Patent Document 2).

Hereinafter, the steps of the “liquid phase method”, the “gas phase method”, and the “sol / gel method” will be described in more detail. "Liquid phase method (also called sulfuric acid method)" is a raw material that uses ilmenite ore (ore containing FeТiO ₃ as a main component) and dissolves this raw material in sulfuric acid to produce titanium sulfate and iron sulfate. Titanium oxide is obtained through a dissolution step, a titanium sulfate separation step for separating the produced titanium sulfate and iron sulfate, a hydrolysis, drying and firing step for hydrolyzing the separated titanium sulfate and drying and firing. (For example, refer nonpatent literature 1.).

The “gas phase method (also referred to as chlorine method)” is a synthesis containing 95% or more of TiO ₂ obtained by removing iron from rutile or ilmenite ore containing TiO ₂ as a main component. A raw material chlorination process in which rutile or the like is used as a raw material to produce crude ТiCl ₄ by chlorinating this raw material with chlorine gas, and titanium oxide is obtained through a reduction / distillation process in which the obtained crude ТiCl ₄ is purified by distillation together with a reducing agent. (For example, see Non-Patent Document 1).

The “sol-gel method” refers to a hydrolysis process in which titanium alkoxide containing Тi (OR) ₄ or the like is used as a raw material, and this raw material is hydrolyzed in an aqueous alcohol solution to form a sol. A titanium oxide is obtained through a gelling step of adding a decomposition catalyst and allowing it to stand to gel, and a baking step of baking the obtained gelled product.
Japanese Patent Laid-Open No. 10-152323 JP 2002-241129 A Fine Ceramics Encyclopedia, Gihodo Publishing, 1987

In the nanotube body according to the above conventional example, the manufacturing process is not so simple when including the manufacturing process for manufacturing the fine titanium oxide powder as the raw material.
In other words, in order to obtain fine titanium oxide powder as a raw material for the nanotube body, as described above, any one of the “liquid phase method”, “gas phase method”, or “sol-gel method” must be used. I must. Therefore, in order to obtain the nanotube body which is the final product, many processes have to be performed, and there is a problem that the manufacturing process is complicated and the manufacturing cost increases.

  Also, in the production of the nanotube body according to the conventional example, as described above, a very fine titanium oxide powder having a particle size of 2 to 100 nm, desirably 2 to 30 nm is used as a raw material. Only a nanotube body of about 150 nm can be obtained. Therefore, for example, there is a problem that the length is insufficient for use in a non-woven structure having a large specific surface area that can be deformed flexibly or a semiconductor wire for electronic devices.

  Accordingly, an object of the present invention is to produce a titanium oxide fine wire product that is inexpensive and has a long length using a natural rutile crude powder obtained by coarsely pulverizing natural rutile as a raw material. It is to provide a titanium oxide-based fine wire product and a production apparatus thereof.

  In order to solve the above-mentioned problems, the means adopted by the method for producing a titanium oxide-based fine wire product according to claim 1 of the present invention is that a coarsely pulverized natural rutile crude powder is placed in a raw material container containing an alkaline aqueous solution. Including a raw material container sealing step for sealing and sealing, a hydrothermal synthesis step for maintaining the sealed raw material container at a predetermined temperature, and maintaining hydrothermal synthesis for a predetermined time, and a product obtained by hydrothermal synthesis A liquid neutralization step for neutralizing the alkaline aqueous solution, a water washing step for washing the product obtained thereby, and a product obtained in this water washing step into a gray product and a white product by separation means. It is characterized by comprising a product separation step to be separated, and an adsorption water / crystallization water removal step for removing adsorbed water and crystallization water of the white product separated in this product separation step.

  The means adopted by the method for producing a titanium oxide-based fine wire product according to claim 2 of the present invention is the method for producing a titanium oxide-based fine wire product according to claim 1, wherein the particle size of the natural rutile coarse powder is as follows. Is more than 75 μm and less than 300 μm, and the raw material liquid in the raw material container is held at 110 to 180 ° C. for 24 to 72 hours in the hydrothermal synthesis step.

  The means adopted by the method for producing a titanium oxide thin wire product according to claim 3 of the present invention is the method for producing a titanium oxide thin wire product according to any one of claims 1 and 2. In the adsorbed water / crystal water removal step, the white product is heated at 180 to 400 ° C. for 1 to 50 hours.

  The constitution of the titanium oxide thin wire product according to claim 4 of the present invention is characterized by being produced by the method for producing a titanium oxide thin wire product according to claim 1.

  The constitution of the titanium oxide thin wire product according to claim 5 of the present invention is characterized by being manufactured by the method for producing a titanium oxide thin wire product according to claim 2.

  The constitution of the titanium oxide thin wire product according to claim 6 of the present invention is characterized by being produced by the method for producing a titanium oxide thin wire product according to claim 3.

  The means employed by the apparatus for producing a titanium oxide-based fine wire product according to claim 7 of the present invention is a raw material container sealing step in which coarsely pulverized natural rutile crude powder is placed in a raw material container containing an alkaline aqueous solution and sealed. And a hydrothermal synthesis step of holding the sealed raw material container at a predetermined temperature and holding it for a predetermined time for hydrothermal synthesis, and a liquid for neutralizing an aqueous alkaline solution containing a product obtained by hydrothermal synthesis A water washing step of washing the product obtained thereby, and a product separation step of separating the product obtained in this water washing step into a gray product and a white product by a separating means, It is characterized by comprising an adsorbed water / crystal water removal step for removing adsorbed water and crystal water of the white product separated in the product separation step.

  The means employed by the apparatus for producing a titanium oxide fine wire product according to claim 8 of the present invention is the titanium oxide fine wire product producing apparatus according to claim 7, wherein the natural rutile coarse powder has a particle size. Is more than 75 μm and less than 300 μm, and the raw material liquid in the raw material container is held at 110 to 180 ° C. for 24 to 72 hours in the hydrothermal synthesis step.

  Means employed by the apparatus for producing a titanium oxide thin wire product according to claim 9 of the present invention is the apparatus for producing a titanium oxide thin wire product according to any one of claims 7 and 8. In the adsorbed water / crystal water removal step, the white product is heated at 180 to 400 ° C. for 1 to 50 hours.

  According to the method for producing a titanium oxide thin wire product according to claims 1 to 3 or the apparatus for producing a titanium oxide thin wire product according to claims 7 to 9 of the present invention, Rather than using titanium oxide produced using any of the `` method '', `` gas phase method '', or `` sol-gel method '', hydrothermal synthesis using coarsely pulverized natural rutile crude powder, A titanium oxide thin wire product (white product) can be produced at a lower cost than the conventional example. In addition, since the natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used, the length of the titanium oxide-based fine wire product is an oxidation that the surface layer peels off and is generated by crystal growth by a hydrothermal synthesis process. The titanium oxide system is much longer than the conventional example using fine titanium oxide having a particle size of 2 to 30 nm because the length corresponding to the particle size of the titanium-containing coarse powder raw material is obtained from the production mechanism of the titanium-based fine wire product. Fine line products can be produced. Therefore, when this titanium oxide thin wire product is used for the purpose of removing air pollutants, a special effect, for example, a non-woven structure, can be deformed flexibly and has a large specific surface area and improved reliability against breakage. An excellent effect can be obtained. That is, a titanium oxide nanowire product obtained by a low-cost process itself functions as a catalyst and also functions as a highly reliable porous structure, or a conventional titanium oxide nanoparticle fired body or It is possible to realize functions that could not be realized with the titanium oxide-based nanoparticle coated body.

  The titanium oxide thin wire product according to claims 4 to 6 of the present invention is produced by the method for producing a titanium oxide thin wire product according to any one of claims 1 to 3. It is. Therefore, according to the titanium oxide thin wire product according to claims 4 to 6 of the present invention, any one of the “liquid phase method”, “gas phase method”, and “sol-gel method” as in the conventional example is used. Instead of using the titanium oxide produced by the method, a natural rutile coarse powder obtained by roughly crushing natural rutile is used, so that the titanium oxide-based fine wire product (white product) is less expensive than the conventional example. Since the raw material is natural rutile crude powder having a particle size of more than 75 μm and less than 300 μm, the length of the titanium oxide-based fine wire product is generated by crystal growth by the hydrothermal synthesis process after peeling off the surface layer. From the production mechanism of the titanium oxide-based fine wire product, the length corresponding to the particle size of the titanium-containing coarse powder raw material, much more than the conventional example manufactured from fine titanium oxide with a particle size of 2 to 30 nm It's long. Therefore, when this titanium oxide thin wire product is used for the purpose of removing air pollutants, a special effect, for example, a non-woven structure, can be deformed flexibly and has a large specific surface area and improved reliability against breakage. An excellent effect can be obtained. That is, a titanium oxide nanowire product obtained by a low-cost process itself functions as a catalyst and also functions as a highly reliable porous structure, or a conventional titanium oxide nanoparticle fired body or It is possible to realize functions that could not be realized with the titanium oxide-based nanoparticle coated body.

  Hereinafter, the manufacturing method of a titanium oxide type | system | group thin wire | line product which manufactures a titanium oxide type | system | group thin wire | line product according to the form of this invention, and its manufacturing apparatus are demonstrated. That is, the present invention does not use titanium oxide produced by any of the “liquid phase method”, “gas phase method”, and “sol-gel method” as a raw material as in the conventional example, but a titanium oxide type. Natural rutile crude powder is used as a raw material for the fine linear product. 99,3 wt% of the natural rutile coarse powder has a particle size of more than 75 μm and less than 300 μm obtained by coarsely pulverizing natural rutile.

  In the present invention, natural rutile coarse powder having a particle size in the above range is dispersed in an alkaline aqueous solution in a raw material container, specifically, an aqueous sodium hydroxide solution, and the raw material container is closed and sealed (raw material) Container sealing step). Then, while maintaining the raw material liquid in the sealed raw material container at a predetermined temperature, the thin line product is hydrothermally synthesized (hydrothermal synthesis step) while being held for a predetermined time. Next, the raw material container is opened and the liquid containing the product is neutralized with an acid, for example, dilute hydrochloric acid aqueous solution (liquid neutralization step). Further, the obtained product is washed with distilled water (water washing step), and the product washed with water is separated into a gray product and a white product (product separation step) by the separating means. At the same time, the adsorbed water and crystal water of the separated white product are removed (adsorbed water / crystal water removal step). Through the above steps, nanotubes and nanofibers, or nanofibers, which are titanium oxide-based fine wire products (white products), are produced from natural rutile crude powder. In the present invention, a sodium hydroxide (NaOH) aqueous solution is used as described above, but other alkaline aqueous solutions such as a potassium hydroxide (KOH) aqueous solution and a calcium hydroxide (CaOH) aqueous solution are used. Can do.

  As described above, in the present invention, a titanium oxide-based fine wire product is produced using any one of the “liquid phase method”, “gas phase method”, and “sol / gel method” as in the conventional example. Instead of using fine titanium oxide powder, it is produced by hydrothermal synthesis using natural rutile crude powder. In other words, a process for producing a titanium oxide fine wire product from natural rutile crude powder in the method for producing a titanium oxide fine wire product according to an embodiment of the present invention, and a “liquid phase method” and a “gas phase method” The process according to the conventional example of manufacturing a nanotube body using titanium oxide manufactured by any one of the “sol-gel method” is almost the same.

  That is, according to this invention, the titanium oxide manufacturing process which manufactures a fine titanium oxide powder is unnecessary, and the process of the chemicals used by this titanium oxide manufacturing process is also unnecessary. Therefore, it can be said that the titanium oxide thin wire product can be produced at a lower cost than the conventional example, and that the production method is friendly to the global environment. The cost of natural rutile crude powder is much lower than that of titanium oxide produced by any one of the “liquid phase method”, “gas phase method”, and “sol-gel method”. This can greatly contribute to the cost reduction of the system fine wire product.

  In the present invention, as described above, a natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used to produce a titanium oxide thin wire product. Therefore, the length of the titanium oxide fine wire product is determined by the particle size of the natural rutile coarse powder from the production mechanism of the titanium oxide fine wire product, which is formed by the surface peeling and crystal growth by the hydrothermal synthesis process. Therefore, it is possible to produce a titanium oxide fine wire product that is much longer than the conventional example using fine titanium oxide powder having a particle diameter of 2 to 30 nm.

  In the present invention, as described above, natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used, and therefore the length of the titanium oxide-based fine wire product varies. However, if natural rutile coarse powder whose particle size is adjusted by sieving is used, for example, a titanium oxide fine wire product with high uniformity in length can be produced. Although particles larger than 300 μm can be used, it is not necessarily effective because the amount of unreacted rutile particles increases. On the other hand, it is of course possible to use particles smaller than 75 μm, but there is an increase in cost due to an increase in crushing time and an influence on the length of the final product, the titanium oxide-based fine wire product.

By the way, a titanium oxide-based fine line product approximated by a composition of H ₂ Ti ₃ O ₇ · 3H ₂ O by hydrothermal synthesis, that is, titanium oxide containing water-containing structure titanium oxide containing moisture such as adsorbed water and crystal water. Although a fine line product can be obtained, the titanium oxide fine line product can be made thick and solid by increasing the hydrothermal synthesis temperature and increasing the hydrothermal synthesis holding time. The content ratio of nanofibers can be increased. Conversely, the content ratio of nanotubes can be increased by lowering the hydrothermal synthesis temperature and shortening the hydrothermal synthesis holding time. Furthermore, the nanotubes or nanofibers thus obtained are heated at, for example, 200 ° C. for 1 hour (adsorbed water / crystal water removal step) to remove adsorbed water and crystal water, thereby removing H ₂ Ti ₃ O. Nanotubes or nanofibers having a composition of ₇ can be produced.

  By the way, in this example, as described above, the nanotube or nanofiber was heated at 200 ° C. in the process of removing adsorbed water / crystal water. It is preferable to heat with. In addition, about the upper limit of heating temperature, since the structure of a titanium oxide type fine wire-like product will change when it exceeds 400 degreeC, it is set to 400 degreeC. The heating time may be 1 to 50 hours. In addition, the reason why the lower limit of the heating time is set to 1 hour is that a short time is desirable in engineering, and the upper limit of the heating time is set to 50 hours, there is almost no change even if it exceeds 50 hours. Because.

  When such a titanium oxide thin wire product is used for the removal of air pollutants, a special effect, for example, a non-woven structure, can be flexibly deformed, has a large specific surface area, and is reliable for destruction. An excellent effect of improvement can be obtained. That is, the titanium oxide nanowire product obtained by a low-cost process itself functions as a catalyst and also functions as a highly reliable porous structure, or a conventional titanium oxide nanoparticle fired body or oxide. It is possible to realize functions that could not be realized with a titanium-based nanoparticle coated body.

  In addition, by heating such a titanium oxide thin wire product at a temperature of 500 ° C. or higher, the nanotube or nanofiber structure is destabilized, so that nano-sized fine particles made of titanium oxide can be obtained. However, although the nano-sized fine particles made of titanium oxide are shorter in length than the original fine line product, some of the one-dimensional structure in which the fine particles are bonded to each other remains, so that the titanium oxide according to the conventional example remains. It has different characteristics from titanium oxide fine particles produced from Therefore, in solar cell applications using a photoelectric conversion function, it is possible to contribute to highly efficient electron transfer.

Hereinafter, the Example regarding the manufacturing method of the titanium oxide type | system | group thin wire | line product of this invention which manufactures a titanium oxide type | system | group thin wire | line product is described. In this Example, natural rutile crude powder native to Australia, which was coarsely pulverized, was used as a raw material for producing a titanium oxide thin wire product. The chemical analysis values of this natural rutile crude powder were TiO ₂ ; 96.0 wt%, Fe ₂ O ₃ ; 0.95 wt%, ZrO ₂ ; 0.94 wt%, SiO ₂ (total); 0.60 wt%, Cr ₂ O ₃ ; 0.17 wt%, Al ₂ O ₃ ; 0.26 wt%, P; 0.025 wt% or less, MnO; 0.01 wt%, CaO; 0.02 wt% or less, MgO; 0.05 wt%, V ₂ O ₅ ; 0.46 wt%, Nb ₂ O ₅ ; 0.32 wt%, S; 0.01 wt% or less, SnO ₂ ; 0.015 wt%, U; 30 ppm, Th;

  The particle size distribution of this natural rutile coarse powder is as follows: natural rutile having a particle size of less than 75 μm; 0.2 wt%, particle size exceeding 75 μm, natural rutile having a particle size of less than 106 μm; 2.7 wt%, particle size exceeding 106 μm and less than 150 μm Natural rutile of 27.5 wt%, particle size greater than 150 μm and less than 180 μm; natural rutile less than 180 μm; 42.8 wt%, natural rutile greater than 180 μm and less than 212 μm; 19.8 wt%, particle size greater than 212 μm and 250 μm Natural rutile less than 5.2 wt%, particle size greater than 250 μm, natural rutile less than 300 μm; natural rutile greater than 1.6 wt%, particle size greater than 300 μm; 0.5 wt%. That is, in this example, a titanium oxide-based fine linear product was produced using natural rutile crude powder containing 96.0 wt% titanium oxide and having a particle size of 99.3 wt% of more than 75 μm and less than 300 μm as a raw material. To manufacture.

The main impurities of the natural rutile coarse powder are Fe ₂ O ₃ , ZrO ₂ and SiO ₂ as is apparent from the chemical analysis values. However, SiO ₂ does not have a significant effect on the photoelectric conversion function that is important for photocatalytic applications. In addition, the amount of natural radioisotope contained in natural rutile ore is 50 ppm or less for both U and Th. From the viewpoint of natural radioactive material management (NORM), which should be considered in the titanium ore industry, it is handled in a large amount. This natural rutile powder is a good quality raw material because there is no particular problem unless it is. The natural rutile coarse powder had a grayish brown color due to the impurities.

  300 mg of the above natural rutile crude powder was dispersed in 50 ml of a 10 mol / liter sodium hydroxide aqueous solution in a stainless steel raw material container lined with a fluororesin, and then closed and sealed. Then, the sealed raw material container was left in an oven heated to 130 ° C. for 50 hours to hydrothermally synthesize the titanium oxide nanowire product. By the way, in this example, the raw material container was allowed to stand in an oven for 50 hours, but when the raw material liquid was stirred, the hydrothermal synthesis rate of the titanium oxide-based nanowire product was promoted. It was possible to shorten the reaction time to about 24 hours by adding a magnetic stirrer that is rotated by magnetic force and stirring the raw material liquid. On the other hand, under the standing conditions of this example, although the reaction time is somewhat longer as about 50 hours, stable crystal growth occurs, so that a long titanium oxide thin wire product having excellent linearity can be obtained. The concentration of the sodium hydroxide aqueous solution is considered to be 5 to 15 mol from Patent Document 1 and various documents described above, but in this example, natural rutile containing a relatively large amount of impurities is used as a raw material. For this reason, a 10 molar aqueous sodium hydroxide solution is used for the time being.

After leaving it for 50 hours, the raw material container was taken out from the oven and cooled to room temperature to obtain a product described later. The product thus obtained is a gray product containing a large amount of impurity components such as iron (relatively large aggregated precipitate) and a floating white product (which precipitates when left for a long time). . Next, a liquid containing a product composed of the gray product and the white product is neutralized with a dilute hydrochloric acid aqueous solution, washed with distilled water, and then subjected to a well-known sedimentation method (required sedimentation time is 1). Time), the white product was separated and the separated white product was dried. The white product (floating matter) thus obtained is a titanium oxide-based nanowire product, more specifically, a nanotube and a nano-particle having a composition approximated by H ₂ Ti ₃ O ₇ · 3H ₂ O. It was a mixture with wire. The unreacted rutile crude powder can be removed by centrifugation or the like and used again as a raw material.

  By the way, in the method for producing a titanium oxide thin wire product according to this example, as described above, a gray product (aggregated precipitate) containing a large amount of impurity components such as iron and a floating white product are obtained. Although it isolate | separated by the sedimentation method, what is necessary is just to isolate | separate industrially with a centrifuge. In addition, although it is thought that the heating temperature should just be made into the range of 110-180 degreeC, for example from the patent document 1 mentioned above and various literature, in this Example, since natural rutile containing many impurities is a raw material, it is heating The temperature was 130 ° C. In addition, it is considered that the hydrothermal synthesis holding time may be in the range of, for example, 24 to 72 hours from Patent Document 1 and various documents described above. In this example, natural rutile containing a large amount of impurities is a raw material. Therefore, the hydrothermal synthesis holding time was set to 50 hours. However, the hydrothermal synthesis holding time is changed depending on the heating temperature and the ratio of nanotubes to nanofibers desired for the titanium oxide nanowire product. For example, it is possible to control the aspect of the titanium oxide thin wire product in which the proportion of nanofibers is increased by increasing the hydrothermal synthesis holding time, and most of them are nanofibers.

The titanium oxide nanowire product obtained as described above is heated at 200 ° C. for 1 hour using, for example, a resistance heating oven (adsorbed water / crystal water removal step), so that the composition becomes H ₂ Ti _3. A mixture of nanotubes and nanofibers made of highly pure water-containing titanium oxide of O ₇ was obtained. The mixture of nanotubes and nanofibers having the composition of H ₂ Ti ₃ O ₇ obtained in this way is as shown in FIG. 1 showing a thin line product taken with a scanning electron microscope. Incidentally, it is possible to prevent the absorption of moisture in the air by saving nanotubes and nanofibers having a composition of H ₂ Ti ₃ O ₇ obtained by heating, for example in a desiccator.

That is, as well understood from FIG. 1, a mixture of nanotubes and nanofibers (composition of nanotubes and nanofibers) composed of H ₂ Ti ₃ O ₇ obtained by hydrothermal synthesis of natural rutile coarse powder. The mixing ratio was about 1: 1) with a thickness of 20 nm or more and a length of 10 to 500 μm. By the way, in natural rutile coarse powder, as described above, Fe ₂ O ₃ , ZrO ₂ , and SiO ₂ were present in a relatively large amount as impurities. However, it was confirmed that most of these were removed by energy dispersive X-ray spectroscopy (EDS analysis) using a scanning electron microscope and a transmission electron microscope.

It is a figure which shows the fine wire-shaped product image | photographed with the scanning electron microscope in connection with the Example of this invention.

The present invention relates to the production how AND ITS apparatus for producing a titanium oxide thin line like product, and more particularly, a crude ground natural rutile coarse powder as a raw material, cheap, yet long titanium oxide length producing how the titanium oxide fine linear product to produce a fine line-like product relates aND iTS manufacturing apparatus.

Since titanium oxide (TiO ₂ ) has excellent properties such as ultraviolet absorption and adsorption, it has heretofore been used for pigments, paints, cosmetics, ultraviolet shielding materials, catalysts, catalyst carriers, and various electronic materials. Etc. Furthermore, in recent years, there has been great interest in the photocatalytic activity of titanium oxide itself. The excellent photocatalytic activity of titanium oxide has been put to practical use for the purpose of environmental purification, more specifically, decomposition of harmful organic substances, removal of air pollutants, sterilization, and antibacterial. Regarding the photocatalytic activity of such titanium oxide, it is known that the tetragonal anatase structure is also higher than the tetragonal rutile structure. Further, increasing the specific surface area of titanium oxide has been studied as a method for improving the photocatalytic activity of titanium oxide. For example, many attempts have been made such as making titanium oxide into a nanoscale tube or fiber.

As a nanoscale tube-shaped titanium oxide, for example, a titanium oxide crystal having a nanotube shape is known. In the nanotube body according to this conventional example, titanium oxide powder is placed in an aqueous solution of sodium hydroxide having a concentration of 13 to 65 outer wt% (preferably 18 to 55 wt%), and a temperature of 18 to 160 ° C. (preferably, 30 to 120 ° C.) for 1 to 50 hours (preferably 2 to 20 hours).
Further, this nanotube body is usually produced using titanium oxide powder having a particle size of 2 to 100 nm, desirably 2 to 30 nm, and has a thickness of 2 to 10 nm and a length of 50 to 150 nm. The titanium oxide powder used as a raw material for the nanotube body is produced by any one of the “liquid phase method”, “gas phase method”, and “sol-gel method”.

The “liquid phase method” is a method for producing titanium oxide by calcining hydrous titanium oxide obtained by heating and hydrolyzing titanium ore with a strong acid such as sulfuric acid at a temperature of 800 to 850 ° C. . The “gas phase method” is a method for producing titanium oxide by bringing O ₂ and H ₂ into contact with ТiCl ₄ . The “sol-gel method” means that a titanium alkoxide containing Тi (OR) ₄ or the like is hydrolyzed in an aqueous alcohol solution to form a sol, and a hydrolysis catalyst is added to the sol and left to stand. This is a method for producing a titanium oxide by gelling and firing the gelled product (see, for example, Patent Document 1 and Patent Document 2).

Hereinafter, the steps of the “liquid phase method”, the “gas phase method”, and the “sol / gel method” will be described in more detail. "Liquid phase method (also called sulfuric acid method)" is a raw material that uses ilmenite ore (ore containing FeТiO ₃ as a main component) and dissolves this raw material in sulfuric acid to produce titanium sulfate and iron sulfate. Titanium oxide is obtained through a dissolution step, a titanium sulfate separation step for separating the produced titanium sulfate and iron sulfate, a hydrolysis, drying and firing step for hydrolyzing the separated titanium sulfate and drying and firing. (For example, refer nonpatent literature 1.).

The “gas phase method (also referred to as chlorine method)” is a synthesis containing 95% or more of TiO ₂ obtained by removing iron from rutile or ilmenite ore containing TiO ₂ as a main component. A raw material chlorination process in which rutile or the like is used as a raw material to produce crude ТiCl ₄ by chlorinating this raw material with chlorine gas, and titanium oxide is obtained through a reduction / distillation process in which the obtained crude ТiCl ₄ is purified by distillation together with a reducing agent. (For example, see Non-Patent Document 1).

The “sol-gel method” refers to a hydrolysis process in which titanium alkoxide containing Тi (OR) ₄ or the like is used as a raw material, and this raw material is hydrolyzed in an aqueous alcohol solution to form a sol. A titanium oxide is obtained through a gelling step of adding a decomposition catalyst and allowing it to stand to gel, and a baking step of baking the obtained gelled product.
Japanese Patent Laid-Open No. 10-152323 JP 2002-241129 A Fine Ceramics Encyclopedia, Gihodo Publishing, 1987

In the nanotube body according to the above conventional example, the manufacturing process is not so simple when including the manufacturing process for manufacturing the fine titanium oxide powder as the raw material.
In other words, in order to obtain fine titanium oxide powder as a raw material for the nanotube body, as described above, any one of the “liquid phase method”, “gas phase method”, or “sol-gel method” must be used. I must. Therefore, in order to obtain the nanotube body which is the final product, many processes have to be performed, and there is a problem that the manufacturing process is complicated and the manufacturing cost increases.

  Also, in the production of the nanotube body according to the conventional example, as described above, a very fine titanium oxide powder having a particle size of 2 to 100 nm, desirably 2 to 30 nm is used as a raw material. Only a nanotube body of about 150 nm can be obtained. Therefore, for example, there is a problem that the length is insufficient for use in a non-woven structure having a large specific surface area that can be deformed flexibly or a semiconductor wire for electronic devices.

Accordingly, an object of the present invention is to produce a titanium oxide thin wire product that is inexpensive and has a long length using a natural rutile crude powder obtained by coarsely pulverizing natural rutile as a raw material. it is to provide a law you and the manufacturing equipment.

In order to solve the above-mentioned problems, the means adopted by the method for producing a titanium oxide-based fine wire product according to claim 1 of the present invention is that a coarsely pulverized natural rutile crude powder is placed in a raw material container containing an alkaline aqueous solution. A raw material container sealing step for sealing and sealing, a hydrothermal synthesis step for heating a raw material liquid composed of natural rutile coarse powder and an alkaline aqueous solution in the sealed raw material container , and an alkali containing a product obtained by hydrothermal synthesis A liquid neutralization step for neutralizing the aqueous solution, a water washing step for washing the product obtained thereby, and a product obtained in this water washing step are separated into a gray product and a white product by a separating means. And a water removal process for removing adsorbed water and crystallization water of the white product separated in the product separation process.

  The means adopted by the method for producing a titanium oxide-based fine wire product according to claim 2 of the present invention is the method for producing a titanium oxide-based fine wire product according to claim 1, wherein the particle size of the natural rutile coarse powder is as follows. Is more than 75 μm and less than 300 μm, and the raw material liquid in the raw material container is held at 110 to 180 ° C. for 24 to 72 hours in the hydrothermal synthesis step.

The means adopted by the method for producing a titanium oxide thin wire product according to claim 3 of the present invention is the method for producing a titanium oxide thin wire product according to any one of claims 1 and 2. In the adsorbed water / crystal water removal step, the white product is held at 180 to 400 ° C. for 1 to 50 hours.

The means employed by the apparatus for producing a titanium oxide fine wire product according to claim 4 of the present invention is a raw material container sealing step in which coarsely pulverized natural rutile crude powder is placed in a raw material container containing an alkaline aqueous solution and sealed. A hydrothermal synthesis step of hydrothermal synthesis of the natural rutile coarse powder and the alkaline aqueous solution in the sealed raw material container, a liquid neutralization step of neutralizing the alkaline aqueous solution containing the product obtained by hydrothermal synthesis, A water washing step for washing the product thus obtained, a product separation step for separating the product obtained in this water washing step into a gray product and a white product by a separating means, and this product separation It is characterized by comprising an adsorbed water / crystal water removal step for removing adsorbed water and crystal water of the white product separated in the process.

The means adopted by the apparatus for producing a titanium oxide fine wire product according to claim 5 of the present invention is the titanium oxide fine wire product producing apparatus according to claim 4 , wherein the natural rutile coarse powder has a particle size of It is more than 75 μm and less than 300 μm, and the raw material liquid in the raw material container is held at 110 to 180 ° C. for 24 to 72 hours in the hydrothermal synthesis step.

Means employed by the apparatus for producing a titanium oxide thin wire product according to claim 6 of the present invention is the apparatus for producing a titanium oxide thin wire product according to any one of claims 4 and 5. In the adsorbed water / crystal water removal step, the white product is held at 180 to 400 ° C. for 1 to 50 hours.

According to the method for producing a titanium oxide thin wire product according to claims 1 to 3 or the apparatus for producing a titanium oxide thin wire product according to claims 4 to 6 of the present invention, Rather than using titanium oxide produced using any of the `` method '', `` gas phase method '', or `` sol-gel method '', hydrothermal synthesis using coarsely pulverized natural rutile crude powder, A titanium oxide thin wire product (white product) can be produced at a lower cost than the conventional example. In addition, since the natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used, the length of the titanium oxide-based fine wire product is an oxidation that the surface layer peels off and is generated by crystal growth by a hydrothermal synthesis process. The titanium oxide system is much longer than the conventional example using fine titanium oxide having a particle size of 2 to 30 nm because the length corresponding to the particle size of the titanium-containing coarse powder raw material is obtained from the production mechanism of the titanium-based fine wire product. Fine line products can be produced. Therefore, when this titanium oxide thin wire product is used for the purpose of removing air pollutants, a special effect, for example, a non-woven structure, can be deformed flexibly and has a large specific surface area and improved reliability against breakage. An excellent effect can be obtained. That is, a titanium oxide nanowire product obtained by a low-cost process itself functions as a catalyst and also functions as a highly reliable porous structure, or a conventional titanium oxide nanoparticle fired body or It is possible to realize functions that could not be realized with the titanium oxide-based nanoparticle coated body.

  Hereinafter, the manufacturing method of a titanium oxide type | system | group thin wire | line product which manufactures a titanium oxide type | system | group thin wire | line product according to the form of this invention, and its manufacturing apparatus are demonstrated. That is, the present invention does not use titanium oxide produced by any of the “liquid phase method”, “gas phase method”, and “sol-gel method” as a raw material as in the conventional example, but a titanium oxide type. Natural rutile crude powder is used as a raw material for the fine linear product. 99,3 wt% of the natural rutile coarse powder has a particle size of more than 75 μm and less than 300 μm obtained by coarsely pulverizing natural rutile.

In the present invention, natural rutile coarse powder having a particle size in the above range is dispersed in an alkaline aqueous solution in a raw material container, specifically, an aqueous sodium hydroxide solution, and the raw material container is closed and sealed (raw material) Container sealing step). And the natural rutile coarse powder and alkaline aqueous solution in the sealed raw material container are hydrothermally synthesized (hydrothermal synthesis step). Next, the raw material container is opened, and the liquid containing the product is neutralized with an acid, for example, dilute hydrochloric acid aqueous solution (liquid neutralization step). Further, the obtained product is washed with distilled water (water washing step), and the product washed with water is separated into a gray product and a white product (product separation step) by the separating means. At the same time, the adsorbed water and crystal water of the separated white product are removed (adsorbed water / crystal water removal step). Through the above steps, nanotubes and nanofibers, or nanofibers, which are titanium oxide-based fine wire products (white products), are produced from natural rutile crude powder. In the case of the present invention, as described above, but using sodium hydroxide (NaOH) aqueous solution, for example other alkali aqueous solution such as potassium hydroxide (KOH) aqueous solution may be used.

  As described above, in the present invention, a titanium oxide-based fine wire product is produced using any one of the “liquid phase method”, “gas phase method”, and “sol / gel method” as in the conventional example. Instead of using fine titanium oxide powder, it is produced by hydrothermal synthesis using natural rutile crude powder. In other words, a process for producing a titanium oxide fine wire product from natural rutile crude powder in the method for producing a titanium oxide fine wire product according to an embodiment of the present invention, and a “liquid phase method” and a “gas phase method” The process according to the conventional example of manufacturing a nanotube body using titanium oxide manufactured by any one of the “sol-gel method” is almost the same.

  That is, according to this invention, the titanium oxide manufacturing process which manufactures a fine titanium oxide powder is unnecessary, and the process of the chemicals used by this titanium oxide manufacturing process is also unnecessary. Therefore, it can be said that the titanium oxide thin wire product can be produced at a lower cost than the conventional example, and that the production method is friendly to the global environment. The cost of natural rutile crude powder is much lower than that of titanium oxide produced by any one of the “liquid phase method”, “gas phase method”, and “sol-gel method”. This can greatly contribute to the cost reduction of the system fine wire product.

  In the present invention, as described above, a natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used to produce a titanium oxide thin wire product. Therefore, the length of the titanium oxide fine wire product is determined by the particle size of the natural rutile coarse powder from the production mechanism of the titanium oxide fine wire product, which is formed by the surface peeling and crystal growth by the hydrothermal synthesis process. Therefore, it is possible to produce a titanium oxide fine wire product that is much longer than the conventional example using fine titanium oxide powder having a particle diameter of 2 to 30 nm.

  In the present invention, as described above, natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used, and therefore the length of the titanium oxide-based fine wire product varies. However, if natural rutile coarse powder whose particle size is adjusted by sieving is used, for example, a titanium oxide fine wire product with high uniformity in length can be produced. Although particles larger than 300 μm can be used, it is not necessarily effective because the amount of unreacted rutile particles increases. On the other hand, it is of course possible to use particles smaller than 75 μm, but there is an increase in cost due to an increase in crushing time and an influence on the length of the final product, the titanium oxide-based fine wire product.

By the way, a titanium oxide-based fine line product approximated by a composition of H ₂ Ti ₃ O ₇ · 3H ₂ O by hydrothermal synthesis, that is, titanium oxide containing water-containing structure titanium oxide containing moisture such as adsorbed water and crystal water. Although a fine line product can be obtained, the titanium oxide fine line product can be made thick and solid by increasing the hydrothermal synthesis temperature and increasing the hydrothermal synthesis holding time. The content ratio of nanofibers can be increased. Conversely, the content ratio of nanotubes can be increased by lowering the hydrothermal synthesis temperature and shortening the hydrothermal synthesis holding time. Furthermore, the nanotubes or nanofibers thus obtained are retained at, for example, 200 ° C. for 1 hour (adsorbed water / crystal water removal step) to remove adsorbed water and crystal water, thereby removing H ₂ Ti ₃ O. Nanotubes or nanofibers having a composition of ₇ can be produced.

  By the way, in this example, as described above, the nanotube or nanofiber was heated at 200 ° C. in the process of removing adsorbed water / crystal water. It is preferable to heat with. In addition, about the upper limit of heating temperature, since the structure of a titanium oxide type fine wire-like product will change when it exceeds 400 degreeC, it is set to 400 degreeC. The heating time may be 1 to 50 hours. In addition, the reason why the lower limit of the heating time is set to 1 hour is that a short time is desirable in engineering, and the upper limit of the heating time is set to 50 hours, there is almost no change even if it exceeds 50 hours. Because.

  When such a titanium oxide thin wire product is used for the removal of air pollutants, a special effect, for example, a non-woven structure, can be flexibly deformed and has a large specific surface area and improved reliability against breakage. An excellent effect can be obtained. That is, the titanium oxide nanowire product obtained by a low-cost process itself functions as a catalyst and also functions as a highly reliable porous structure, or a conventional titanium oxide nanoparticle fired body or oxide. It is possible to realize functions that could not be realized with a titanium-based nanoparticle coated body.

  In addition, by heating such a titanium oxide thin wire product at a temperature of 500 ° C. or higher, the nanotube or nanofiber structure is destabilized, so that nano-sized fine particles made of titanium oxide can be obtained. However, although the nano-sized fine particles made of titanium oxide are shorter in length than the original fine line product, some of the one-dimensional structure in which the fine particles are bonded to each other remains, so that the titanium oxide according to the conventional example remains. It has different characteristics from titanium oxide fine particles produced from Therefore, in solar cell applications using a photoelectric conversion function, it is possible to contribute to highly efficient electron transfer.

Hereinafter, the Example regarding the manufacturing method of the titanium oxide type | system | group thin wire | line product of this invention which manufactures a titanium oxide type | system | group thin wire | line product is described. In this Example, natural rutile crude powder native to Australia, which was coarsely pulverized, was used as a raw material for producing a titanium oxide thin wire product. The chemical analysis values of this natural rutile crude powder were TiO ₂ ; 96.0 wt%, Fe ₂ O ₃ ; 0.95 wt%, ZrO ₂ ; 0.94 wt%, SiO ₂ (total); 0.60 wt%, Cr ₂ O ₃ ; 0.17 wt%, Al ₂ O ₃ ; 0.26 wt%, P; 0.025 wt% or less, MnO; 0.01 wt%, CaO; 0.02 wt% or less, MgO; 0.05 wt%, V ₂ O ₅ ; 0.46 wt%, Nb ₂ O ₅ ; 0.32 wt%, S; 0.01 wt% or less, SnO ₂ ; 0.015 wt%, U; 30 ppm, Th;

  The particle size distribution of this natural rutile coarse powder is as follows: natural rutile having a particle size of less than 75 μm; 0.2 wt%, particle size exceeding 75 μm, natural rutile having a particle size of less than 106 μm; 2.7 wt%, particle size exceeding 106 μm and less than 150 μm Natural rutile of 27.5 wt%, particle size greater than 150 μm and less than 180 μm; natural rutile less than 180 μm; 42.8 wt%, natural rutile greater than 180 μm and less than 212 μm; 19.8 wt%, particle size greater than 212 μm and 250 μm Natural rutile less than 5.2 wt%, particle size greater than 250 μm, natural rutile less than 300 μm; natural rutile greater than 1.6 wt%, particle size greater than 300 μm; 0.5 wt%. That is, in this example, a titanium oxide-based fine linear product was produced using natural rutile crude powder containing 96.0 wt% titanium oxide and having a particle size of 99,3 wt% exceeding 75 μm and less than 300 μm as a raw material. To manufacture.

The main impurities of the natural rutile coarse powder are Fe ₂ O ₃ , ZrO ₂ and SiO ₂ as is apparent from the chemical analysis values. However, SiO ₂ does not have a significant effect on the photoelectric conversion function that is important for photocatalytic applications. In addition, the amount of natural radioisotope contained in natural rutile ore is 50 ppm or less for both U and Th. From the viewpoint of natural radioactive material management (NORM), which should be considered in the titanium ore industry, it is handled in a large amount. As long as there is no particular problem, this natural rutile coarse powder is a good quality raw material. The natural rutile coarse powder had a grayish brown color due to the impurities.

  300 mg of the above natural rutile crude powder was dispersed in 50 ml of a 10 mol / liter sodium hydroxide aqueous solution in a stainless steel raw material container lined with a fluororesin, and then closed and sealed. Then, the sealed raw material container was left in an oven heated to 130 ° C. for 50 hours to hydrothermally synthesize the titanium oxide nanowire product. By the way, in this example, the raw material container was allowed to stand in an oven for 50 hours, but when the raw material liquid was stirred, the hydrothermal synthesis rate of the titanium oxide-based nanowire product was promoted. It was possible to shorten the reaction time to about 24 hours by adding a magnetic stirrer that is rotated by magnetic force and stirring the raw material liquid. On the other hand, under the standing conditions of this example, although the reaction time is somewhat longer as about 50 hours, stable crystal growth occurs, so that a long titanium oxide thin wire product having excellent linearity can be obtained. The concentration of the sodium hydroxide aqueous solution is considered to be 5 to 15 mol from Patent Document 1 and various documents described above, but in this example, natural rutile containing a relatively large amount of impurities is used as a raw material. For this reason, a 10 molar aqueous sodium hydroxide solution is used for the time being.

After leaving it for 50 hours, the raw material container was taken out from the oven and cooled to room temperature to obtain a product described later. The product thus obtained is a gray product containing a large amount of impurity components such as iron (relatively large aggregated precipitate) and a floating white product (which precipitates when left for a long time). . Next, a liquid containing a product composed of the gray product and the white product is neutralized with a dilute hydrochloric acid aqueous solution, washed with distilled water, and then subjected to a well-known sedimentation method (required sedimentation time is 1). Time), the white product was separated and the separated white product was dried. The white product (floating matter) thus obtained is a titanium oxide-based nanowire product, more specifically, a nanotube and a nano-particle having a composition approximated by H ₂ Ti ₃ O ₇ · 3H ₂ O. It was a mixture with wire. The unreacted rutile crude powder can be removed by centrifugation or the like and used again as a raw material.

  By the way, in the method for producing a titanium oxide thin wire product according to this example, as described above, a gray product (aggregated precipitate) containing a large amount of impurity components such as iron and a floating white product are obtained. Although it isolate | separated by the sedimentation method, what is necessary is just to isolate | separate industrially with a centrifuge. In addition, although it is thought that the heating temperature should just be made into the range of 110-180 degreeC, for example from the patent document 1 mentioned above and various literature, in this Example, since natural rutile containing many impurities is a raw material, it is heating The temperature was 130 ° C. In addition, it is considered that the hydrothermal synthesis holding time may be in the range of, for example, 24 to 72 hours from Patent Document 1 and various documents described above. In this example, natural rutile containing a large amount of impurities is a raw material. Therefore, the hydrothermal synthesis holding time was set to 50 hours. However, the hydrothermal synthesis holding time is changed depending on the heating temperature and the ratio of nanotubes to nanofibers desired for the titanium oxide nanowire product. For example, it is possible to control the aspect of the titanium oxide thin wire product in which the proportion of nanofibers is increased by increasing the hydrothermal synthesis holding time, and most of them are nanofibers.

The titanium oxide nanowire product obtained as described above is heated at 200 ° C. for 1 hour using, for example, a resistance heating oven (adsorbed water / crystal water removal step), so that the composition becomes H ₂ Ti _3. A mixture of nanotubes and nanofibers made of highly pure water-containing titanium oxide of O ₇ was obtained. The mixture of nanotubes and nanofibers having the composition of H ₂ Ti ₃ O ₇ obtained in this way is as shown in FIG. 1 showing a thin line product taken with a scanning electron microscope. Incidentally, it is possible to prevent the absorption of moisture in the air by saving nanotubes and nanofibers having a composition of H ₂ Ti ₃ O ₇ obtained by heating, for example in a desiccator.

That is, as well understood from FIG. 1, the mixture of nanotubes and nanofibers composed of H ₂ Ti ₃ O ₇ obtained by hydrothermal synthesis of natural rutile crude powder has a thickness of 20 nm. The length was 10 to 500 μm. By the way, in natural rutile coarse powder, as described above, Fe ₂ O ₃ , ZrO ₂ , and SiO ₂ were present in a relatively large amount as impurities. However, it was confirmed that most of them were removed by energy dispersive X-ray spectroscopy (EDS analysis) using a scanning electron microscope and a transmission electron microscope.

It is a figure which shows the fine wire-shaped product image | photographed with the scanning electron microscope in connection with the Example of this invention.

The present invention relates to the production how the titanium oxide thin line like product, and more particularly, a crude ground natural rutile coarse powder as raw materials, inexpensive and, moreover long titanium oxide thin line product length a manufacturing how the titanium oxide fine linear product to be produced.

Since titanium oxide (TiO ₂ ) has excellent properties such as ultraviolet absorption and adsorption, it has heretofore been used for pigments, paints, cosmetics, ultraviolet shielding materials, catalysts, catalyst carriers, and various electronic materials. Etc. Furthermore, in recent years, there has been great interest in the photocatalytic activity of titanium oxide itself. The excellent photocatalytic activity of titanium oxide has been put to practical use for the purpose of environmental purification, more specifically, decomposition of harmful organic substances, removal of air pollutants, sterilization, and antibacterial. Regarding the photocatalytic activity of such titanium oxide, it is known that the tetragonal anatase structure is also higher than the tetragonal rutile structure. Further, increasing the specific surface area of titanium oxide has been studied as a method for improving the photocatalytic activity of titanium oxide. For example, many attempts have been made such as making titanium oxide into a nanoscale tube or fiber.

As a nanoscale tube-shaped titanium oxide, for example, a titanium oxide crystal having a nanotube shape is known. In the nanotube body according to this conventional example, titanium oxide powder is placed in an aqueous solution of sodium hydroxide having a concentration of 13 to 65 outer wt% (preferably 18 to 55 wt%), and a temperature of 18 to 160 ° C. (preferably, 30 to 120 ° C.) for 1 to 50 hours (preferably 2 to 20 hours).
Further, this nanotube body is usually produced using titanium oxide powder having a particle size of 2 to 100 nm, desirably 2 to 30 nm, and has a thickness of 2 to 10 nm and a length of 50 to 150 nm. The titanium oxide powder used as a raw material for the nanotube body is produced by any one of the “liquid phase method”, “gas phase method”, and “sol-gel method”.

The “liquid phase method” is a method for producing titanium oxide by calcining hydrous titanium oxide obtained by heating and hydrolyzing titanium ore with a strong acid such as sulfuric acid at a temperature of 800 to 850 ° C. . The “gas phase method” is a method for producing titanium oxide by bringing O ₂ and H ₂ into contact with ТiCl ₄ . The “sol-gel method” means that a titanium alkoxide containing Тi (OR) ₄ or the like is hydrolyzed in an aqueous alcohol solution to form a sol, and a hydrolysis catalyst is added to the sol and left to stand. This is a method for producing a titanium oxide by gelling and firing the gelled product (see, for example, Patent Document 1 and Patent Document 2).

Hereinafter, the steps of the “liquid phase method”, the “gas phase method”, and the “sol / gel method” will be described in more detail. "Liquid phase method (also called sulfuric acid method)" is a raw material that uses ilmenite ore (ore containing FeТiO ₃ as a main component) and dissolves this raw material in sulfuric acid to produce titanium sulfate and iron sulfate. Titanium oxide is obtained through a dissolution step, a titanium sulfate separation step for separating the produced titanium sulfate and iron sulfate, a hydrolysis, drying and firing step for hydrolyzing the separated titanium sulfate and drying and firing. (For example, refer nonpatent literature 1.).

The “gas phase method (also referred to as chlorine method)” is a synthesis containing 95% or more of TiO ₂ obtained by removing iron from rutile or ilmenite ore containing TiO ₂ as a main component. A raw material chlorination process in which rutile or the like is used as a raw material to produce crude ТiCl ₄ by chlorinating this raw material with chlorine gas, and titanium oxide is obtained through a reduction / distillation process in which the obtained crude ТiCl ₄ is purified by distillation together with a reducing agent. (For example, see Non-Patent Document 1).

The “sol-gel method” refers to a hydrolysis process in which titanium alkoxide containing Тi (OR) ₄ or the like is used as a raw material, and this raw material is hydrolyzed in an aqueous alcohol solution to form a sol. A titanium oxide is obtained through a gelling step of adding a decomposition catalyst and allowing it to stand to gel, and a baking step of baking the obtained gelled product.
Japanese Patent Laid-Open No. 10-152323 JP 2002-241129 A Fine Ceramics Encyclopedia, Gihodo Publishing, 1987

In the nanotube body according to the above conventional example, the manufacturing process is not so simple when including the manufacturing process for manufacturing the fine titanium oxide powder as the raw material.
In other words, in order to obtain fine titanium oxide powder as a raw material for the nanotube body, as described above, any one of the “liquid phase method”, “gas phase method”, or “sol-gel method” must be used. I must. Therefore, in order to obtain the nanotube body which is the final product, many processes have to be performed, and there is a problem that the manufacturing process is complicated and the manufacturing cost increases.

  Also, in the production of the nanotube body according to the conventional example, as described above, a very fine titanium oxide powder having a particle size of 2 to 100 nm, desirably 2 to 30 nm is used as a raw material. Only a nanotube body of about 150 nm can be obtained. Therefore, for example, there is a problem that the length is insufficient for use in a non-woven structure having a large specific surface area that can be deformed flexibly or a semiconductor wire for electronic devices.

Accordingly, an object of the present invention is to produce a titanium oxide thin wire product that is inexpensive and has a long length using a natural rutile crude powder obtained by coarsely pulverizing natural rutile as a raw material. Is to provide the law .

In order to solve the above-mentioned problems, the means adopted by the method for producing a titanium oxide-based fine wire product according to claim 1 of the present invention is that a coarsely pulverized natural rutile crude powder is placed in a raw material container containing an alkaline aqueous solution. medium placed a raw material container sealing step of sealing the a hydrothermal synthesis step of the natural rutile coarse powder and aqueous alkaline solution of sealed material container hydrothermal synthesis, an alkaline aqueous solution containing a product obtained by hydrothermal synthesis A liquid neutralization step, a water washing step for washing the product obtained thereby, and a product for separating the product obtained in this water washing step into a gray product and a white product by separation means It is characterized by comprising a separation step and an adsorption water / crystallization water removal step for removing adsorbed water and crystallization water of the white product separated in this product separation step.

  The means adopted by the method for producing a titanium oxide-based fine wire product according to claim 2 of the present invention is the method for producing a titanium oxide-based fine wire product according to claim 1, wherein the particle size of the natural rutile coarse powder is as follows. Is more than 75 μm and less than 300 μm, and the raw material liquid in the raw material container is held at 110 to 180 ° C. for 24 to 72 hours in the hydrothermal synthesis step.

  The means adopted by the method for producing a titanium oxide thin wire product according to claim 3 of the present invention is the method for producing a titanium oxide thin wire product according to any one of claims 1 and 2. In the adsorbed water / crystal water removal step, the white product is held at 180 to 400 ° C. for 1 to 50 hours.

According to the manufacturing how the titanium oxide thin line like product according to claims 1 to 3 of the present invention, "liquid phase", "gas phase process" as in the conventional example, any of the "sol-gel method" Rather than using titanium oxide produced by this method, hydrothermal synthesis is performed using coarsely pulverized natural rutile crude powder, so that the titanium oxide thin wire product (white Product) can be produced. In addition, since the natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used, the length of the titanium oxide-based fine wire product is an oxidation that the surface layer peels off and is generated by crystal growth by a hydrothermal synthesis process. The titanium oxide system is much longer than the conventional example using fine titanium oxide having a particle size of 2 to 30 nm because the length corresponding to the particle size of the titanium-containing coarse powder raw material is obtained from the production mechanism of the titanium-based fine wire product. Fine line products can be produced. Therefore, when this titanium oxide thin wire product is used for the purpose of removing air pollutants, a special effect, for example, a non-woven structure, can be deformed flexibly and has a large specific surface area and improved reliability against breakage. An excellent effect can be obtained. That is, a titanium oxide nanowire product obtained by a low-cost process itself functions as a catalyst and also functions as a highly reliable porous structure, or a conventional titanium oxide nanoparticle fired body or It is possible to realize functions that could not be realized with the titanium oxide-based nanoparticle coated body.

The following relates to the embodiment of the present invention will be described with the manufacturing how the titanium oxide fine linear product to produce a titanium oxide thin wire products. That is, the present invention does not use titanium oxide produced by any of the “liquid phase method”, “gas phase method”, and “sol-gel method” as a raw material as in the conventional example, but a titanium oxide type. Natural rutile crude powder is used as a raw material for the fine linear product. 99,3 wt% of the natural rutile coarse powder has a particle size of more than 75 μm and less than 300 μm obtained by coarsely pulverizing natural rutile.

  In the present invention, natural rutile coarse powder having a particle size in the above range is dispersed in an alkaline aqueous solution in a raw material container, specifically, an aqueous sodium hydroxide solution, and the raw material container is closed and sealed (raw material) Container sealing step). And the natural rutile coarse powder and alkaline aqueous solution in the sealed raw material container are hydrothermally synthesized (hydrothermal synthesis step). Next, the raw material container is opened, and the liquid containing the product is neutralized with an acid, for example, dilute hydrochloric acid aqueous solution (liquid neutralization step). Further, the obtained product is washed with distilled water (water washing step), and the product washed with water is separated into a gray product and a white product (product separation step) by the separating means. At the same time, the adsorbed water and crystal water of the separated white product are removed (adsorbed water / crystal water removal step). Through the above steps, nanotubes and nanofibers, or nanofibers, which are titanium oxide-based fine wire products (white products), are produced from natural rutile crude powder. In the present invention, as described above, the sodium hydroxide (NaOH) aqueous solution is used, but other alkaline aqueous solutions such as a potassium hydroxide (KOH) aqueous solution can be used.

  As described above, in the present invention, a titanium oxide-based fine wire product is produced using any one of the “liquid phase method”, “gas phase method”, and “sol / gel method” as in the conventional example. Instead of using fine titanium oxide powder, it is produced by hydrothermal synthesis using natural rutile crude powder. In other words, a process for producing a titanium oxide fine wire product from natural rutile crude powder in the method for producing a titanium oxide fine wire product according to an embodiment of the present invention, and a “liquid phase method” and a “gas phase method” The process according to the conventional example of manufacturing a nanotube body using titanium oxide manufactured by any one of the “sol-gel method” is almost the same.

  That is, according to this invention, the titanium oxide manufacturing process which manufactures a fine titanium oxide powder is unnecessary, and the process of the chemicals used by this titanium oxide manufacturing process is also unnecessary. Therefore, it can be said that the titanium oxide thin wire product can be produced at a lower cost than the conventional example, and that the production method is friendly to the global environment. The cost of natural rutile crude powder is much lower than that of titanium oxide produced by any one of the “liquid phase method”, “gas phase method”, and “sol-gel method”. This can greatly contribute to the cost reduction of the system fine wire product.

  In the present invention, as described above, a natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used to produce a titanium oxide thin wire product. Therefore, the length of the titanium oxide fine wire product is determined by the particle size of the natural rutile coarse powder from the production mechanism of the titanium oxide fine wire product, which is formed by the surface peeling and crystal growth by the hydrothermal synthesis process. Therefore, it is possible to produce a titanium oxide fine wire product that is much longer than the conventional example using fine titanium oxide powder having a particle diameter of 2 to 30 nm.

  In the present invention, as described above, natural rutile coarse powder having a particle size of more than 75 μm and less than 300 μm is used, and therefore the length of the titanium oxide-based fine wire product varies. However, if natural rutile coarse powder whose particle size is adjusted by sieving is used, for example, a titanium oxide fine wire product with high uniformity in length can be produced. Although particles larger than 300 μm can be used, it is not necessarily effective because the amount of unreacted rutile particles increases. On the other hand, it is of course possible to use particles smaller than 75 μm, but there is an increase in cost due to an increase in crushing time and an influence on the length of the final product, the titanium oxide-based fine wire product.

By the way, a titanium oxide-based fine line product approximated by a composition of H ₂ Ti ₃ O ₇ · 3H ₂ O by hydrothermal synthesis, that is, titanium oxide containing water-containing structure titanium oxide containing moisture such as adsorbed water and crystal water. Although a fine line product can be obtained, the titanium oxide fine line product can be made thick and solid by increasing the hydrothermal synthesis temperature and increasing the hydrothermal synthesis holding time. The content ratio of nanofibers can be increased. Conversely, the content ratio of nanotubes can be increased by lowering the hydrothermal synthesis temperature and shortening the hydrothermal synthesis holding time. Furthermore, the nanotubes or nanofibers thus obtained are retained at, for example, 200 ° C. for 1 hour (adsorbed water / crystal water removal step) to remove adsorbed water and crystal water, thereby removing H ₂ Ti ₃ O. Nanotubes or nanofibers having a composition of ₇ can be produced.

  By the way, in this example, as described above, the nanotube or nanofiber was heated at 200 ° C. in the process of removing adsorbed water / crystal water. It is preferable to heat with. In addition, about the upper limit of heating temperature, since the structure of a titanium oxide type fine wire-like product will change when it exceeds 400 degreeC, it is set to 400 degreeC. The heating time may be 1 to 50 hours. In addition, the reason why the lower limit of the heating time is set to 1 hour is that a short time is desirable in engineering, and the upper limit of the heating time is set to 50 hours, there is almost no change even if it exceeds 50 hours. Because.

  When such a titanium oxide thin wire product is used for the removal of air pollutants, a special effect, for example, a non-woven structure, can be flexibly deformed and has a large specific surface area and improved reliability against breakage. An excellent effect can be obtained. That is, the titanium oxide nanowire product obtained by a low-cost process itself functions as a catalyst and also functions as a highly reliable porous structure, or a conventional titanium oxide nanoparticle fired body or oxide. It is possible to realize functions that could not be realized with a titanium-based nanoparticle coated body.

  In addition, by heating such a titanium oxide thin wire product at a temperature of 500 ° C. or higher, the nanotube or nanofiber structure is destabilized, so that nano-sized fine particles made of titanium oxide can be obtained. However, although the nano-sized fine particles made of titanium oxide are shorter in length than the original fine line product, some of the one-dimensional structure in which the fine particles are bonded to each other remains, so that the titanium oxide according to the conventional example remains. It has different characteristics from titanium oxide fine particles produced from Therefore, in solar cell applications using a photoelectric conversion function, it is possible to contribute to highly efficient electron transfer.

Hereinafter, the Example regarding the manufacturing method of the titanium oxide type | system | group thin wire | line product of this invention which manufactures a titanium oxide type | system | group thin wire | line product is described. In this Example, natural rutile crude powder native to Australia, which was coarsely pulverized, was used as a raw material for producing a titanium oxide thin wire product. The chemical analysis values of this natural rutile crude powder were TiO ₂ ; 96.0 wt%, Fe ₂ O ₃ ; 0.95 wt%, ZrO ₂ ; 0.94 wt%, SiO ₂ (total); 0.60 wt%, Cr ₂ O ₃ ; 0.17 wt%, Al ₂ O ₃ ; 0.26 wt%, P; 0.025 wt% or less, MnO; 0.01 wt%, CaO; 0.02 wt% or less, MgO; 0.05 wt%, V ₂ O ₅ ; 0.46 wt%, Nb ₂ O ₅ ; 0.32 wt%, S; 0.01 wt% or less, SnO ₂ ; 0.015 wt%, U; 30 ppm, Th;

The particle size distribution of this natural rutile coarse powder is as follows: natural rutile having a particle size of less than 75 μm; 0.2 wt%, particle size exceeding 75 μm, natural rutile having a particle size of less than 106 μm; 2.7 wt%, particle size exceeding 106 μm and less than 150 μm Natural rutile of 27.5 wt%, particle size greater than 150 μm and less than 180 μm; natural rutile less than 180 μm; 42.8 wt%, natural rutile greater than 180 μm and less than 212 μm; 19.8 wt%, particle size greater than 212 μm and 250 μm Natural rutile less than 5.2 wt%, particle size greater than 250 μm, natural rutile less than 300 μm; natural rutile greater than 1.6 wt%, particle size greater than 300 μm; 0.5 wt%. That is, in this example, 96.0 wt% of titanium oxide was contained, and the particle size of 99 . A titanium oxide-based fine wire-like product is produced using a natural rutile coarse powder having a 3 wt% of more than 75 μm and less than 300 μm as a raw material.

The main impurities of the natural rutile crude powder are Fe ₂ O ₃ , ZrO ₂ and SiO ₂ as is apparent from the chemical analysis values. However, SiO ₂ does not have a significant effect on the photoelectric conversion function that is important for photocatalytic applications. In addition, the amount of natural radioisotope contained in natural rutile ore is 50 ppm or less for both U and Th. From the viewpoint of natural radioactive material management (NORM), which should be considered in the titanium ore industry, it is handled in a large amount. As long as there is no particular problem, this natural rutile coarse powder is a good quality raw material. The natural rutile coarse powder had a grayish brown color due to the impurities.

  300 mg of the above natural rutile crude powder was dispersed in 50 ml of a 10 mol / liter sodium hydroxide aqueous solution in a stainless steel raw material container lined with a fluororesin, and then closed and sealed. Then, the sealed raw material container was left in an oven heated to 130 ° C. for 50 hours to hydrothermally synthesize the titanium oxide nanowire product. By the way, in this example, the raw material container was allowed to stand in an oven for 50 hours, but when the raw material liquid was stirred, the hydrothermal synthesis rate of the titanium oxide-based nanowire product was promoted. It was possible to shorten the reaction time to about 24 hours by adding a magnetic stirrer that is rotated by magnetic force and stirring the raw material liquid. On the other hand, under the standing conditions of this example, although the reaction time is somewhat longer as about 50 hours, stable crystal growth occurs, so that a long titanium oxide thin wire product having excellent linearity can be obtained. The concentration of the sodium hydroxide aqueous solution is considered to be 5 to 15 mol from Patent Document 1 and various documents described above, but in this example, natural rutile containing a relatively large amount of impurities is used as a raw material. For this reason, a 10 molar aqueous sodium hydroxide solution is used for the time being.

After leaving it for 50 hours, the raw material container was taken out from the oven and cooled to room temperature to obtain a product described later. The product thus obtained is a gray product containing a large amount of impurity components such as iron (relatively large aggregated precipitate) and a floating white product (which precipitates when left for a long time). . Next, a liquid containing a product composed of the gray product and the white product is neutralized with a dilute hydrochloric acid aqueous solution, washed with distilled water, and then subjected to a well-known sedimentation method (required sedimentation time is 1). Time), the white product was separated and the separated white product was dried. The white product (floating matter) thus obtained is a titanium oxide-based nanowire product, more specifically, a nanotube and a nano-particle having a composition approximated by H ₂ Ti ₃ O ₇ · 3H ₂ O. It was a mixture with wire. The unreacted rutile crude powder can be removed by centrifugation or the like and used again as a raw material.

  By the way, in the method for producing a titanium oxide thin wire product according to this example, as described above, a gray product (aggregated precipitate) containing a large amount of impurity components such as iron and a floating white product are obtained. Although it isolate | separated by the sedimentation method, what is necessary is just to isolate | separate industrially with a centrifuge. In addition, although it is thought that the heating temperature should just be made into the range of 110-180 degreeC, for example from the patent document 1 mentioned above and various literature, in this Example, since natural rutile containing many impurities is a raw material, it is heating The temperature was 130 ° C. In addition, it is considered that the hydrothermal synthesis holding time may be in the range of, for example, 24 to 72 hours from Patent Document 1 and various documents described above. In this example, natural rutile containing a large amount of impurities is a raw material. Therefore, the hydrothermal synthesis holding time was set to 50 hours. However, the hydrothermal synthesis holding time is changed depending on the heating temperature and the ratio of nanotubes to nanofibers desired for the titanium oxide nanowire product. For example, it is possible to control the aspect of the titanium oxide thin wire product in which the proportion of nanofibers is increased by increasing the hydrothermal synthesis holding time, and most of them are nanofibers.

The titanium oxide nanowire product obtained as described above is heated at 200 ° C. for 1 hour using, for example, a resistance heating oven (adsorbed water / crystal water removal step), so that the composition becomes H ₂ Ti _3. A mixture of nanotubes and nanofibers made of highly pure water-containing titanium oxide of O ₇ was obtained. The mixture of nanotubes and nanofibers having the composition of H ₂ Ti ₃ O ₇ obtained in this way is as shown in FIG. 1 showing a thin line product taken with a scanning electron microscope. Incidentally, it is possible to prevent the absorption of moisture in the air by saving nanotubes and nanofibers having a composition of H ₂ Ti ₃ O ₇ obtained by heating, for example in a desiccator.

That is, as is well understood from FIG. 1, the mixture of nanotubes and nanofibers having a composition of H ₂ Ti ₃ O ₇ obtained by hydrothermal synthesis of natural rutile coarse powder has a thickness of 20 nm or more. And the length was 10 to 500 μm. By the way, in natural rutile coarse powder, as described above, Fe ₂ O ₃ , ZrO ₂ , and SiO ₂ were present in a relatively large amount as impurities. However, it was confirmed that most of them were removed by energy dispersive X-ray spectroscopy (EDS analysis) using a scanning electron microscope and a transmission electron microscope.

It is a figure which shows the fine wire-shaped product image | photographed with the scanning electron microscope in connection with the Example of this invention.

Claims (9)

  A raw material container sealing step of sealing coarsely pulverized natural rutile powder in a raw material container containing an alkaline aqueous solution, and maintaining the sealed raw material container at a predetermined temperature and holding for a predetermined time for hydrothermal synthesis Obtained by the hydrothermal synthesis step, the liquid neutralization step of neutralizing the alkaline aqueous solution containing the product obtained by hydrothermal synthesis, the water washing step of washing the product obtained thereby, and the water washing step. Product separation step of separating the separated product into a gray product and a white product by a separating means, and adsorption water for removing white water adsorbed water and crystal water separated in this product separation step -The manufacturing method of the titanium oxide type | system | group thin wire product characterized by consisting of a crystal water removal process.   2. The titanium oxide according to claim 1, wherein the natural rutile coarse powder has a particle size of more than 75 μm and less than 300 μm, and the raw material liquid in the raw material container is held at 110 to 180 ° C. for 24 to 72 hours in the hydrothermal synthesis step. A method for producing a fine line product.   The production of a titanium oxide-based fine wire product according to any one of claims 1 and 2, wherein the white product is heated at 180 to 400 ° C for 1 to 50 hours in the adsorbed water / crystal water removal step. Method.   A titanium oxide thin wire product produced by the method for producing a titanium oxide thin wire product according to claim 1.   A titanium oxide thin wire product produced by the method for producing a titanium oxide thin wire product according to claim 2.   A titanium oxide thin wire product produced by the method for producing a titanium oxide thin wire product according to claim 3.   A raw material container sealing step of sealing coarsely pulverized natural rutile powder in a raw material container containing an alkaline aqueous solution, and maintaining the sealed raw material container at a predetermined temperature and holding for a predetermined time for hydrothermal synthesis Obtained by the hydrothermal synthesis step, the liquid neutralization step of neutralizing the alkaline aqueous solution containing the product obtained by hydrothermal synthesis, the water washing step of washing the product obtained thereby, and the water washing step. Product separation step of separating the separated product into a gray product and a white product by a separating means, and adsorption water for removing white water adsorbed water and crystal water separated in this product separation step A production apparatus for a titanium oxide-based fine wire product composed of a crystal water removal step.   8. The oxidation according to claim 7, wherein the particle size of the natural rutile coarse powder is more than 75 μm and less than 300 μm, and the raw material liquid in the raw material container is held at 110 to 180 ° C. for 24 to 72 hours in the hydrothermal synthesis step. Production equipment for titanium-based fine wire products. The production of a titanium oxide-based fine wire product according to any one of claims 7 and 8, wherein the white product is heated at 180 to 400 ° C for 1 to 50 hours in the adsorbed water / crystal water removal step. apparatus.

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