Method for producing titanium phosphate powder

Abstract

A method for reducing foreign matter in titanium phosphate powder is provided. A method for manufacturing titanium phosphate powder includes: mixing a titanium sulfate solution with a phosphoric acid solution to prepare a mixture, wherein the titanium sulfate solution is obtained by contacting a raw titanium sulfate solution with activated carbon and then filtering it through a filter.

Description

Technical Field

[0001] This invention relates to a method for manufacturing titanium phosphate powder. Background Technology

[0002] It is known that titanium phosphate can be formed into crystalline particles with the chemical formula Ti(HPO4)2·nH2O (n is an integer).

[0003] International Publication No. 2018 / 180797 discloses a method for manufacturing titanium phosphate powder, which is a method for producing titanium phosphate powder containing plate-shaped crystal particles of titanium phosphate by reacting raw materials containing titanium and phosphorus through a hydrothermal synthesis method. As the aforementioned raw materials, a mixture of titanium sulfate and phosphoric acid is used. Summary of the Invention

[0004] International Publication No. 2018 / 180797 describes the use of a mixture of titanium sulfate and phosphoric acid as a raw material containing titanium and phosphorus. Titanium sulfate is obtained by dissolving titanium-containing ore in sulfuric acid and removing impurities such as iron using an agglomerating agent, resulting in a titanium sulfate solution. This titanium sulfate solution contains dissolved organic carbon derived from the agglomerating agent. This dissolved organic carbon is not separated even during the washing (water washing) process in the manufacture of titanium phosphate powder and remains as foreign matter in the titanium phosphate powder. Therefore, it is desirable to further reduce the amount of foreign matter in the titanium phosphate powder during its manufacture.

[0005] Therefore, the present invention was made in view of the above circumstances, and its object is to provide a method for removing foreign matter from titanium phosphate powder.

[0006] The inventors conducted extensive research to address the aforementioned problems. As a result, they discovered that the problems were solved through the following method for manufacturing titanium phosphate powder, thus completing this invention. The method comprises: mixing a titanium sulfate solution with a phosphoric acid solution to prepare a mixed solution, wherein the titanium sulfate solution is obtained by contacting the raw titanium sulfate solution with activated carbon and then filtering it using a filter. Attached Figure Description

[0007] Figure 1 This is a graph showing the XRD results of the raw material titanium sulfate solution 1.

[0008] Figure 2 This is a graph representing the evaluation results of the transmittance of raw material titanium sulfate solution 1.

[0009] Figure 3 This is a graph showing the results of measuring the transmission spectrum of raw material titanium sulfate solution 1.

[0010] Figure 4 This is a graph representing the evaluation results of the transmittance of raw material titanium sulfate solution 1. Detailed Implementation

[0011] The following describes one embodiment of the present invention. The present invention is not limited to the following embodiment, and various modifications can be made within the scope of the claims. The embodiments described in this specification can be combined in any way to form other embodiments.

[0012] In this instruction manual, the range "X~Y" means "above X and below Y". Furthermore, unless otherwise specified, the operation and physical properties are measured at room temperature (20~25°C) and relative humidity 40~50%RH.

[0013] One aspect of the present invention relates to a method for manufacturing titanium phosphate powder, comprising: mixing a titanium sulfate solution with a phosphoric acid solution to prepare a mixture, wherein the titanium sulfate solution is obtained by contacting a raw titanium sulfate solution with activated carbon and then filtering it using a filter. According to the present invention, foreign matter (especially organic matter) in the titanium phosphate powder can be reduced.

[0014] In this specification, titanium phosphate is represented by the chemical formula Ti(HPO4)2·nH2O (0≤n≤1).

[0015] In this specification, titanium phosphate powder refers to titanium phosphate particulate powder or compositions comprising it. Titanium phosphate powder may contain impurities (especially organic matter) originating from manufacturing processes (e.g., agglomerants) as foreign matter. In this specification, powder includes not only powdered (dry) substances, but also substances that exist in a dispersion medium and can be obtained in powder form upon evaporation of the dispersion medium.

[0016] The method for manufacturing titanium phosphate powder in this manner includes: mixing a titanium sulfate solution with a phosphoric acid solution to prepare a mixed solution, wherein the titanium sulfate solution is obtained by contacting the raw titanium sulfate solution with activated carbon and then filtering it with a filter.

[0017] The titanium sulfate solution obtained in this method is obtained by contacting the raw titanium sulfate solution with activated carbon and then filtering it using a filter. There are no particular limitations on the method of contacting the raw titanium sulfate solution with activated carbon; it can be a method of mixing the raw titanium sulfate solution with activated carbon, or a method of passing the raw titanium sulfate solution through a column filled with activated carbon.

[0018] The titanium sulfate solution in contact with activated carbon contains titanium sulfate (Ti(SO4)2) as a titanium-containing substance. In this specification, titanium sulfate refers to a solution containing sulfate ions (SO4) in water. 2- ) and titanium ions (Ti 4+ ) solution.

[0019] There are no particular limitations on the raw material titanium sulfate solution; for example, it can be produced using the sulfuric acid process or by dissolving titanium oxysulfate in water. In the sulfuric acid process, titanium-containing ore (such as ilmenite ore) is dissolved in sulfuric acid to remove the iron content, thereby obtaining the raw material titanium sulfate solution.

[0020] The titanium sulfate solution used as the raw material for contacting activated carbon can be a titanium sulfate solution obtained directly through the sulfuric acid process, a solution obtained by further purification of the titanium sulfate solution obtained through the sulfuric acid process, a solution obtained by dissolving titanium oxysulfate in water, or a commercially available product. From the viewpoint of simplifying the manufacturing process, it is preferable to use a titanium sulfate solution obtained directly through the sulfuric acid process or a commercially available product as the raw material for contacting activated carbon.

[0021] The concentration of sulfuric acid in the raw titanium sulfate solution is not particularly limited, but is preferably between 10 g / L and 700 g / L, and more preferably between 30 g / L and 600 g / L. When the sulfuric acid concentration is less than 10 g / L, the titanium component is not fully dissolved, and titanium hydroxide, titanium oxide, etc., precipitate out, thus making it impossible to stably synthesize titanium phosphate. When the sulfuric acid concentration exceeds 700 g / L, it hinders the synthesis of titanium phosphate, making it difficult to obtain titanium phosphate of arbitrary particle size. The sulfuric acid concentration can be determined, for example, by turbidimetry.

[0022] There are no particular restrictions on the titanium concentration in the raw titanium sulfate solution, but it should be, for example, 10 g / L or more and 300 g / L or less (converted to titanium dioxide), preferably 25 g / L or more and 200 g / L or less. When the titanium concentration is less than 10 g / L, the amount of titanium phosphate obtained during synthesis becomes low, leading to production problems. When the titanium concentration exceeds 300 g / L, titanium hydroxide, titanium oxide, etc., precipitate, making stable synthesis of titanium phosphate impossible. The titanium concentration can be determined as a titanium dioxide content using the method described in JIS K 5116:2004.

[0023] There is no particular limitation on the lower limit of the total organic carbon (TOC) in the raw titanium sulfate solution; for example, if it exceeds 3 mg / L, it can be 4 mg / L or higher, 5 mg / L or higher, 6 mg / L or higher, or 7 mg / L or higher. There is no particular limitation on the upper limit of the TOC in the raw titanium sulfate solution; for example, it can be 15 mg / L. The TOC in the raw titanium sulfate solution can be determined using a TOC meter, and details of the determination method are described in the examples.

[0024] The shape of the activated carbon that comes into contact with the raw titanium solution is not particularly limited; examples include powder, granules, fibers, and blocks. The preferred shape of the activated carbon is powder or granules. Activated carbon of the same shape can be used, or a combination of two or more shapes can be used.

[0025] When activated carbon is in powder or granular form, the particle size is, for example, 0.50 mm or more and 1.70 mm or less. The particle size of activated carbon can be determined by the method described in JIS K 1474:2014.

[0026] Activated carbon can be commercially available or manufactured using known methods.

[0027] In one embodiment, the method of contacting the raw material titanium sulfate solution with activated carbon includes a method of mixing the raw material titanium sulfate solution with activated carbon.

[0028] In the method of mixing a raw titanium sulfate solution and activated carbon, the raw titanium sulfate solution and activated carbon are mixed to prepare a liquid containing titanium sulfate and activated carbon. The method for manufacturing titanium phosphate powder according to this approach may include: mixing a raw titanium sulfate solution and activated carbon to prepare a liquid containing titanium sulfate and activated carbon.

[0029] In the method of mixing the raw material titanium sulfate solution and activated carbon, from the viewpoint of further maximizing the effects of the present invention, the mass ratio of activated carbon to titanium (converted to titanium dioxide) is preferably 0.003 or more, more preferably 0.005 or more. There is no particular upper limit to the mass ratio of activated carbon to titanium (converted to titanium dioxide), but from the viewpoint of productivity, it is preferably 0.03 or less, more preferably 0.02 or less. The mass ratio of activated carbon to titanium (converted to titanium dioxide) is preferably 0.003 or more and 0.03 or less, more preferably 0.005 or more and 0.02 or less.

[0030] There are no particular restrictions on the method of mixing the raw titanium sulfate solution with activated carbon. Activated carbon can be added to the raw titanium sulfate solution, or the raw titanium sulfate solution can be added to the activated carbon.

[0031] There are no particular restrictions on the temperature when mixing the raw material titanium sulfate solution with activated carbon, for example, it can be above 10°C and below 40°C.

[0032] In the resulting liquid containing titanium sulfate and activated carbon, activated carbon-based adsorption begins. The adsorption time is not particularly limited, but is preferably 3 hours to 24 hours, and more preferably 4 hours to 12 hours. Activated carbon-based adsorption can be carried out while the liquid containing titanium sulfate and activated carbon is standing, or it can be carried out with stirring.

[0033] In one embodiment, the method of contacting the raw titanium sulfate solution with activated carbon includes a method of circulating the raw titanium sulfate solution through a column filled with activated carbon.

[0034] In the method of passing a raw titanium sulfate solution through a column filled with activated carbon, a raw titanium sulfate solution that has undergone activated carbon treatment is prepared.

[0035] As for the column filled with activated carbon, conventionally known columns can be used.

[0036] When passing a titanium sulfate solution through a column filled with activated carbon, there are no particular restrictions on the contact temperature, contact time, or flow rate. The contact temperature can be, for example, above 10°C and below 40°C. The contact time can be, for example, above 3 hours.

[0037] Titanium sulfate solution is obtained by contacting raw titanium sulfate solution with activated carbon and then filtering it through a filter.

[0038] There are no particular restrictions on the materials used for the filters. Examples include: cellulose mixed esters, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer, polycarbonate, polyethersulfone, cellulose acetate, nitrocellulose, regenerated cellulose, polyamide, triacetyl cellulose, polypropylene, polyvinyl chloride (PVC), nylon, nylon 66, polysulfone, polyester, polypropylene / polyethylene, acrylic copolymers, polycarbonate, polylactic acid, polycaprolactone, polyglycolic acid, polydioxanone, polyhydroxybutyrate, polybutadiene, polyurethane, polystyrene (PS), polymethyl methacrylate, polycarbonate resins, glass, metals, etc.

[0039] There are no particular restrictions on the structure of the filters used; for example, deep structures, pleated structures, membrane structures, etc., can be used.

[0040] The filtration precision of the filter can be appropriately selected based on the activated carbon used. The lower limit of the filter's filtration precision is, for example, 0.1 μm or more, 0.6 μm or more, or 1.2 μm or more. The upper limit of the filter's filtration precision is, for example, 2.5 μm or less, 2.0 μm or less, 1.5 μm or less, or 1.0 μm or less. The filter's filtration precision is, for example, 0.1 μm or more and 2.5 μm or less, preferably 0.6 μm or more and 2.0 μm or less, more preferably 1.2 μm or more and 1.5 μm or less. The filter's filtration precision can be 1.2 μm or more and 2.5 μm or less, 0.6 μm or more and 2.0 μm or less, or 0.1 μm or more and 1.0 μm or less.

[0041] The filters used can be commercially available products.

[0042] There are no particular restrictions on the filtration method; it can be any of the following: natural filtration, vacuum filtration, pressure filtration, or centrifugal filtration, all performed under normal pressure.

[0043] The filtration process in the filter can be repeated more than once.

[0044] By filtering a liquid containing titanium sulfate and activated carbon, or a raw titanium sulfate solution that has undergone activated carbon treatment, it is possible to effectively remove impurities (especially organic matter) from the activated carbon and from the raw titanium sulfate solution.

[0045] As described above, in the raw titanium sulfate solution, an agglomerating agent is used to remove impurities such as iron from titanium-containing ore. The dissolved organic carbon from the agglomerating agent is contained in the raw titanium sulfate solution as total organic carbon (TOC). This organic carbon remains even after a washing (water washing) process following the synthesis of titanium phosphate powder, and is not separated as a component. It may appear as black or gray foreign matter in the titanium phosphate powder after the drying process, or contribute to a decrease in the whiteness of the titanium phosphate powder.

[0046] In this method, the total organic carbon content in the titanium sulfate solution is less than 3 mg / L, preferably more than 1 mg / L and less than 3 mg / L. The total organic carbon content in the titanium sulfate solution can be more than 1 mg / L and less than 2 mg / L. To achieve a total organic carbon content of less than 1 mg / L in the titanium sulfate solution, a large amount of activated carbon and a long adsorption time are required, which is not preferred from a productivity point of view. When the total organic carbon content in the titanium sulfate solution exceeds 3 mg / L, the whiteness of the titanium phosphate powder decreases (whiteness: less than 95), or a large number of colored impurities such as black and gray are observed on the surface of the titanium phosphate powder slurry. Therefore, in the evaluation of the formation of coatings containing titanium phosphate powder, poor appearance results from changes in the hue of transmitted light and the presence of foreign matter in the coating.

[0047] The total organic carbon content in the titanium sulfate solution is a value obtained by measuring the total organic carbon content in the titanium sulfate solution immediately after preparation (within 24 hours). The total organic carbon content in the titanium sulfate solution can be measured using a total organic carbon meter, and details of the measurement method are described in the examples.

[0048] The transmittance of the titanium sulfate solution at a wavelength of 550 nm in this method is the value of the transmittance measured immediately after preparation (within 24 hours) with the transmittance of pure water at a wavelength of 550 nm set to 100%. The transmittance of the titanium sulfate solution at a wavelength of 550 nm can be measured using a spectrophotometer, and the details of the measurement method are described in the examples.

[0049] The transmittance of the titanium sulfate solution at a wavelength of 550 nm in this method is, for example, 70% or more and 100% or less, preferably 90% or more and 100% or less, and more preferably 95% or more and 100% or less. When the transmittance of the titanium sulfate solution at a wavelength of 550 nm is less than 70%, the presence of particles in the titanium sulfate solution leads to impurities and uneven shape of the synthesized product during the synthesis of titanium phosphate powder.

[0050] The titanium sulfate solution of this method can suppress the decrease in transmittance at a wavelength of 550 nm even after long-term storage. Higher storage temperatures promote particle precipitation, thus reducing the transmittance of the titanium sulfate solution at 550 nm. When stored at 43°C for 3 weeks, the transmittance of the titanium sulfate solution at 550 nm is, for example, 70% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more (up to 100%). Preferably, even when stored at 43°C for 4 weeks or more (e.g., 9 weeks), the transmittance of the titanium sulfate solution at 550 nm remains at 90% or more, more preferably 95% or more.

[0051] The titanium sulfate solution of this method effectively removes impurities (especially organic matter) and can suppress changes in transmittance over time (decreased transmittance). Therefore, one aspect of the present invention relates to a titanium sulfate solution with a total organic carbon content of less than 3 mg / L. Preferably, the titanium sulfate solution of this method has a transmittance of 95% or more at a wavelength of 550 nm. One aspect of the present invention relates to a method for purifying a titanium sulfate solution, comprising: contacting the raw titanium sulfate solution with activated carbon and then filtering it using a filter. The purification method of this method may further include: mixing the raw titanium sulfate solution with activated carbon to prepare a liquid containing titanium sulfate and activated carbon; or passing the raw titanium sulfate solution through a column filled with activated carbon to prepare a raw titanium sulfate solution treated with activated carbon. In the case where the purification method of this method includes mixing the raw titanium sulfate solution with activated carbon to prepare a liquid containing titanium sulfate and activated carbon, the mass ratio of the activated carbon to titanium (converted from titanium dioxide) in the raw titanium sulfate solution is preferably 0.005 or more.

[0052] The method for manufacturing titanium phosphate powder in this manner includes: mixing the titanium sulfate solution obtained above with a phosphoric acid solution to prepare a mixture.

[0053] Phosphoric acid solution contains phosphoric acid as a phosphorus-containing substance.

[0054] The concentration of phosphoric acid in the phosphoric acid solution is, for example, 50% by mass or more and less than 100% by mass, preferably 80% by mass or more and less than 100% by mass.

[0055] The phosphoric acid solution may further contain phosphates. There are no particular limitations on the type of salt; examples include metal salts (e.g., alkali metal salts, Group II element salts, etc.), amine salts, etc. A single type of salt may be used, or two or more may be used in combination. A single type of phosphate may be used, or two or more may be used in combination. When the phosphoric acid solution contains phosphates, the concentration of the phosphates is, for example, 50% by mass or more and less than 100% by mass, preferably 80% by mass or more and less than 100% by mass. In one embodiment, the phosphoric acid solution preferably does not contain phosphates.

[0056] The phosphoric acid solution contains water. The concentration of water in the phosphoric acid solution is, for example, greater than 0% by mass and less than 50% by mass, preferably greater than 0% by mass and less than 20% by mass. In one embodiment, the phosphoric acid solution contains phosphoric acid and water.

[0057] The mixture in this method is prepared by mixing titanium sulfate solution, phosphoric acid solution, and other ingredients as needed.

[0058] There are no particular limitations on the method of mixing titanium sulfate solution, phosphoric acid solution, and other components as needed. The mixing method, mixing order, mixing conditions, etc., can appropriately adopt well-known methods.

[0059] The concentration of phosphoric acid in the mixture is, for example, 20% by mass or more and 40% by mass or less relative to the total mass of the mixture, preferably 21% by mass or more and 35% by mass or less.

[0060] The concentration of sulfuric acid in the mixture is, for example, 2% by mass or more and 15% by mass or less relative to the total mass of the mixture, preferably 3% by mass or more and 12% by mass or less.

[0061] The concentration of titanium in the mixture, calculated as titanium dioxide relative to the total mass of the mixture, is, for example, 1% by mass or more and 10% by mass or less, preferably 2% by mass or more and 5% by mass or less.

[0062] As other components, phosphorus-free and titanium-free acids can be mentioned. There are no particular limitations on the phosphorus-free and titanium-free acids; known organic acids, known inorganic acids, etc., can be mentioned. Examples of phosphorus-free and titanium-free acids include hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, acetic acid, citric acid, and formic acid. A single phosphorus-free and titanium-free acid can be used alone, or two or more can be used in combination. Preferably, the phosphorus-free and titanium-free acid includes at least one acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, acetic acid, citric acid, and formic acid, and more preferably, sulfuric acid. The content of these acids (preferably sulfuric acid) (total content if two or more are included) relative to the total mass of the phosphorus-free and titanium-free acid is preferably 50% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass (up to 100% by mass).

[0063] Titanium phosphate can be manufactured by reacting the mixture obtained above using a hydrothermal synthesis method. The method for manufacturing titanium phosphate powder in this manner may include: preparing a liquid containing titanium phosphate powder by reacting the mixture obtained above using a hydrothermal synthesis method.

[0064] There are no particular restrictions on the conditions for hydrothermal synthesis; conventionally known conditions can be appropriately adopted. The reaction temperature is, for example, 50°C or higher and 140°C or lower, preferably 80°C or higher and 130°C or lower. The reaction time is, for example, 1 hour or higher and 100 hours or lower, preferably 3 hours or higher and 72 hours or lower.

[0065] The method for manufacturing titanium phosphate powder in this manner may include: washing (preferably with pure water) and / or drying the liquid containing titanium phosphate powder obtained above. There are no particular limitations on the washing and drying methods; conventionally known methods may be appropriately employed.

[0066] The obtained powder is a titanium phosphate powder with the chemical formula Ti(HPO4)2·nH2O (0≤n≤1), which shows the crystalline nature of titanium phosphate. This can be confirmed by powder X-ray diffraction.

[0067] In the method for manufacturing titanium phosphate powder according to this approach, foreign matter (especially organic matter) other than titanium phosphate can be reduced. Therefore, one aspect of the present invention relates to titanium phosphate powder having a carbon content of 0.005% by mass or less per unit mass. There is no particular limitation on the lower limit of the carbon content per unit mass of titanium phosphate powder, for example, it is 0.001% by mass or more. The carbon content per unit mass of titanium phosphate powder is preferably 0.001% by mass or more and 0.005% by mass or less, but may also be 0.002% by mass or more and 0.004% by mass or 0.003% by mass or more and 0.004% by mass or less. The carbon content per unit mass of titanium phosphate powder can be measured using a carbon / sulfur measuring device, and details of the measurement method are described in the examples.

[0068] The applications of the obtained titanium phosphate powder are not particularly limited and can be used for various purposes. Examples of applications for titanium phosphate powder include: inorganic particles for light scattering, specifically inorganic particles or materials used in light-diffusing films, light-diffusing plates, cosmetics, etc.; white pigments, functional fillers, lubricants, etc. From the viewpoint of improving the sliding properties between particles, the shape of the titanium phosphate particles contained in the titanium phosphate powder is preferably a thin plate shape. Regarding the shape of the titanium phosphate particles contained in the titanium phosphate powder, from the viewpoint that the surface direction of the particles in a coating film obtained by dispersing or suspending titanium phosphate powder in a solvent (e.g., ink containing titanium phosphate powder, coating containing titanium phosphate powder) and drying the solvent is parallel to the coated substrate, it is easy to obtain a uniform thickness, has high dispersibility, and is less prone to aggregation, a thin plate shape is preferred.

[0069] Furthermore, titanium phosphate has a refractive index of 1.79, which is higher than that of commonly used inorganic particles such as silica particles and acrylic beads as polymer particles, but lower than that of titanium oxide used in white pigments. Therefore, coating films containing titanium phosphate powder and polymer binders exhibit good light scattering and transmission properties, making them suitable for use as inorganic particles for light scattering in light-diffusing films, light-diffusing plates, and the like.

[0070] In order to prevent changes in the hue of the scattered and transmitted light, the inorganic particles used for light scattering are preferably highly white and preferably free of impurities formed by colored substances other than white, such as black and gray.

[0071] The present invention includes the following methods and forms.

[0072] [1] A method for manufacturing titanium phosphate powder, comprising: mixing titanium sulfate solution and phosphoric acid solution to prepare a mixture, wherein the titanium sulfate solution is obtained by contacting the raw titanium sulfate solution with activated carbon and then filtering it with a filter.

[0073] [2] A method for purifying a titanium sulfate solution, comprising: contacting the raw titanium sulfate solution with activated carbon and then filtering it with a filter.

[0074] [3] According to the purification method of titanium sulfate solution described in [2], wherein the mass ratio of activated carbon to titanium (converted to titanium dioxide) in the raw material titanium sulfate solution is 0.005 or more.

[0075] [4] A titanium phosphate powder having a carbon content of less than 0.005% by mass per unit mass.

[0076] [5] A titanium sulfate solution having a total organic carbon content of less than 3 mg / L.

[0077] [6] The titanium sulfate solution according to [5] has a transmittance of more than 95% at a wavelength of 550 nm.

[0078] Example

[0079] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. It should be noted that, unless otherwise specified, "%" and "parts" refer to "mass %" and "parts by mass," respectively. In addition, in the following examples, unless otherwise specified, the operation is carried out at room temperature (25°C).

[0080] <Preparation of Titanium Sulfate Solution>

[0081] [Preparation of Titanium Sulfate Solution 1]

[0082] A titanium sulfate solution 1 (containing 118 g / L titanium (converted to titanium dioxide), 500 g / L sulfuric acid, and 4 mg / L total organic carbon in an aqueous solution) was mixed with activated carbon (particle size: 1.70 mm ~ 0.50 mm, Kuraray Co., Ltd. GW10 / 32) at a mass ratio of activated carbon to titanium (converted to titanium dioxide) of 0.01 to prepare a liquid 1 containing titanium sulfate and activated carbon. After standing for 12 hours, the solution was filtered using a filter (filtration accuracy 0.65 μm, ROKITECHNO CO., LTD. CES-006) to produce titanium sulfate solution 1.

[0083] [Preparation of Titanium Sulfate Solution 2]

[0084] A titanium sulfate solution 2 (containing 190 g / L titanium and 290 g / L sulfuric acid, with a total organic carbon content of 7 mg / L) was mixed with activated carbon (particle size: 1.70 mm to 0.50 mm, Kuraray Co., Ltd. GW10 / 32) at a mass ratio of activated carbon to titanium (converted from titanium dioxide) of 0.01 to prepare a liquid 2 containing titanium sulfate and activated carbon. After standing for 12 hours, the solution was filtered using a filter (filtration accuracy 0.65 μm, ROKITECHNO CO., LTD. CES-006) to produce titanium sulfate solution 2.

[0085] <Evaluation>

[0086] [Long-term storage test 1 (XRD determination)]

[0087] The raw titanium sulfate solution 1, within 14 days of manufacturing and after being stored at 43°C for 4 weeks, was filtered using a filter (0.6 μm pore size, Whatman nuclepore membrane filter) to recover the solid components. XRD analysis of each solid component was performed. The results are presented below. Figure 1 . Figure 1 The upper paragraph represents the test results of raw material titanium sulfate solution 1 within 14 days after manufacturing. Figure 1 The following section presents the measurement results of raw material titanium sulfate solution 1 after being stored at 43°C for 4 weeks.

[0088] The details of the XRD measurements are as follows:

[0089] Measurement Apparatus: Ultima IV sample horizontal multi-object X-ray diffractometer manufactured by Rigaku Corporation

[0090] X-Ray: 20kV / 10mA

[0091] Diverging slit: 1°

[0092] Longitudinal diverging slit: 10mm

[0093] Scattering slit: 2°

[0094] Light-receiving slit: 0.05mm

[0095] kβ filter

[0096] Start: 10

[0097] Stop: 70

[0098] Step size: 0.01

[0099] Standard card: 01-075-2544 or 00-014-053.

[0100] like Figure 1 As shown, the raw material titanium sulfate solution 1 contained titanium oxide within 14 days after manufacturing, and titanium oxysulfate precipitated in the raw material titanium sulfate solution 1 after being stored at 43°C for 4 weeks.

[0101] [Long-term storage test 2 (evaluation of transmittance)]

[0102] As the test samples, raw titanium sulfate solution 1 was used within 14 days after manufacturing, after being stored at 20°C for 7 days, 14 days, 21 days, 28 days, 42 days, and 43 days, and after being stored at 43°C for 7 days, 14 days, and 21 days.

[0103] The transmittance of the test sample at a wavelength of 550 nm was measured using a UV-Vis spectrophotometer (manufactured by Shimadzu Corporation, UV-2450). The transmittance of the test sample was evaluated when the transmittance of pure water at a wavelength of 550 nm was set to 100%.

[0104] The results are shown in Figure 2 .like Figure 2 As shown, the stability of raw material titanium sulfate solution 1 is low, and the transmittance deteriorates due to storage.

[0105] [Long-term storage test 3 (determination of transmission spectrum and evaluation of transmittance)]

[0106] As the test sample, titanium sulfate solution 1 was used immediately after manufacturing (within 24 hours after preparation) and after being stored at 43°C for 1 to 9 weeks (except for the first week and the fourth week).

[0107] The transmission spectrum of the test sample (baseline (Tt=100%): pure water) was measured using a UV-Vis spectrophotometer (Shimadzu Corporation, UV-2450). The results are shown below. Figure 3 .

[0108] The transmittance of the test sample at a wavelength of 550 nm was measured using a UV-Vis spectrophotometer (Shimadzu Corporation, UV-2450). The transmittance of the test sample was evaluated when the transmittance of pure water at a wavelength of 550 nm was set to 100%. The results are shown below. Figure 4 .

[0109] like Figure 3 and Figure 4 As shown, after activated carbon treatment and filtration, the raw material titanium sulfate solution 1 ( Figure 2 Compared to the previous method, titanium sulfate solution 1 showed improved storage stability.

[0110] [Long-term storage test 4 (evaluation of transmittance)]

[0111] As test samples, liquid 1 containing titanium sulfate and activated carbon that was just manufactured (after adsorption by activated carbon), titanium sulfate solution 1 and titanium sulfate solution 2 that were just manufactured (within 24 hours after preparation) and stored at 43°C for 3 weeks, and raw titanium sulfate solution 1 and raw titanium sulfate solution 2 that were within 14 days after manufacturing and stored at 43°C for 3 weeks were used.

[0112] The transmittance of the test sample at a wavelength of 550 nm was measured using a UV-Vis spectrophotometer (manufactured by Shimadzu Corporation, UV-2450). The transmittance of the test sample was evaluated when the transmittance of pure water at a wavelength of 550 nm was set to 100%.

[0113] The results are shown in Table 1, “Transmittance (λ=550nm)”. In Table 1, “Before Storage” indicates the evaluation results of the test samples immediately after manufacturing and within 14 days after manufacturing, and “After Storage at 43°C for 3 Weeks” indicates the evaluation results of the test samples after storage at 43°C for 3 weeks.

[0114] [Determination of Total Organic Carbon]

[0115] The total organic carbon content of titanium sulfate solution 1, titanium sulfate solution 2, raw material titanium sulfate solution 1, and raw material titanium sulfate solution 2 was determined using a total organic carbon meter (manufactured by Shimadzu Corporation, TOC-L).

[0116] As test samples, freshly manufactured titanium sulfate solution 1 and titanium sulfate solution 2, as well as raw titanium sulfate solution 1 and raw titanium sulfate solution 2 within 14 days of manufacture, were used.

[0117] The results are shown in Table 1, “TOC content of titanium sulfate solution (mg / L)”.

[0118] <Manufacturing of Titanium Phosphate Powder 1>

[0119] [Manufacturing of Titanium Phosphate Powder 1]

[0120] Titanium sulfate solution 1 and pure water were added to an 85% (w / w) aqueous solution of phosphoric acid while stirring to obtain a mixture. The mixture was then placed in an autoclave (sealed container) and heated to 130°C for hydrothermal treatment. The hydrothermal treatment was carried out under natural pressure for 5 hours. After hydrothermal treatment, the mixture was washed with pure water (water washing treatment) and dried in a crucible at 105°C for 24 hours (drying treatment) to obtain titanium phosphate powder 1. Titanium phosphate powder 1 is white in appearance, and no gray or black impurities can be visually identified.

[0121] [Manufacturing of Titanium Phosphate Powder 2]

[0122] Titanium sulfate solution 2 is used instead of titanium sulfate solution 1, and titanium phosphate powder 2 is obtained in the same manner as titanium phosphate powder 1. Titanium phosphate powder 2 is white in appearance, and no gray or black impurities can be identified by visual inspection.

[0123] [Manufacturing of Titanium Phosphate Powder 3]

[0124] Titanium sulfate solution 1 was used instead of titanium sulfate solution 1, and titanium phosphate powder 3 was obtained in the same manner as titanium phosphate powder 1. Titanium phosphate powder 3 is white in appearance, but gray or black impurities can be observed by visual inspection.

[0125] [Manufacturing of Titanium Phosphate Powder 4]

[0126] Titanium sulfate solution 2 is used instead of titanium sulfate solution 1, and titanium phosphate powder 4 is obtained in the same manner as titanium phosphate powder 1. Titanium phosphate powder 4 is white in appearance, but gray or black impurities can be observed by visual inspection.

[0127] <Evaluation>

[0128] [Determination of carbon content]

[0129] The carbon content per unit mass of titanium phosphate powder 1 to 4 was determined using a carbon / sulfur measuring device (EMIA-320V2 type manufactured by Horiba Manufacturing Co., Ltd.).

[0130] If the carbon content per unit mass is less than 0.005% by mass, it is judged as good; if the carbon content per unit mass exceeds 0.005% by mass, it is judged as poor.

[0131] The results are shown in Table 2.

[0132] Evaluation of foreign matter in titanium phosphate powder

[0133] Water was added to 50g of each of titanium phosphate powders 1-4 to prepare a slurry, with the concentration of titanium phosphate powder being 10% by mass. After shaking the slurry by hand, the presence of foreign matter on the liquid surface was visually confirmed.

[0134] Record the case where the foreign object is less than 5 points as "〇" and the case where the foreign object is more than 6 points as "×".

[0135] The results are shown in Table 2.

[0136] [Table 1]

[0137]

[0138] [Table 2]

[0139]

[0140] As shown in Table 1, the titanium sulfate solution of the embodiment, after being treated with activated carbon and filtered, exhibited a transmittance of 100% immediately after preparation (before storage), which is higher than that of the raw titanium sulfate solution. Furthermore, the titanium sulfate solution of the embodiment maintained a transmittance of 100% after being stored at 43°C for 3 weeks, with no observed decrease in transmittance due to storage, demonstrating high storage stability. Moreover, the total organic carbon content of the titanium sulfate solution of the embodiment is below 3 mg / L, indicating a reduction in impurities.

[0141] As shown in Table 2, it can be seen that for the titanium phosphate powder of the embodiment, by using a titanium sulfate solution with a total organic carbon content of less than 3 mg / L (refer to Table 1), the carbon content of the titanium phosphate powder is reduced to less than 0.005% by mass. It can be seen that this can effectively remove foreign matter (organic carbon) from the slurry of the titanium phosphate powder of the embodiment.

[0142] <Manufacturing of Titanium Phosphate Powder 2>

[0143] [Manufacturing of Titanium Phosphate Powder 5]

[0144] A titanium sulfate solution 2 (containing 190 g / L titanium and 290 g / L sulfuric acid, with a total organic carbon content of 7 mg / L) was mixed with activated carbon (particle size: 1.70 mm~0.50 mm, Kuraray Co., Ltd. GW10 / 32) at a mass ratio of activated carbon to titanium (converted from titanium dioxide) of 0.01 to prepare a liquid 2 containing titanium sulfate and activated carbon. After standing for 12 hours, the solution was filtered using a filter (filtration accuracy 1.2 μm, ROKITECHNO CO., LTD. CES-012) to produce a titanium sulfate solution 3. The total organic carbon content of the titanium sulfate solution 3 was 1 mg / L.

[0145] Titanium sulfate solution 3 and pure water were added to an 85% (w / w) aqueous solution of phosphoric acid while stirring to obtain a mixture. The mixture was then placed in an autoclave (sealed container) and heated to 130°C for hydrothermal treatment. The hydrothermal treatment was carried out under natural pressure for 5 hours. After hydrothermal treatment, the mixture was washed with pure water and dried in a crucible at 105°C for 24 hours to obtain titanium phosphate powder 5. Titanium phosphate powder 5 is white in appearance, and no gray or black impurities can be visually identified.

[0146] [Manufacturing of Titanium Phosphate Powder 6]

[0147] A titanium sulfate solution 2 (containing 190 g / L titanium and 290 g / L sulfuric acid, with a total organic carbon content of 7 mg / L) was mixed with activated carbon (particle size: 1.70 mm ~ 0.50 mm, Kuraray Co., Ltd. GW10 / 32) at a mass ratio of activated carbon to titanium (converted from titanium dioxide) of 0.01 to prepare a liquid 2 containing titanium sulfate and activated carbon. After standing for 12 hours, the solution was filtered using a filter (filtration accuracy 0.65 μm, ROKITECHNO CO., LTD. CES-006) to produce a titanium sulfate solution 4. The total organic carbon content of the titanium sulfate solution 4 was 1 mg / L.

[0148] Titanium sulfate solution 4 and pure water were added to an 85% (w / w) aqueous solution of phosphoric acid while stirring to obtain a mixture. The mixture was then placed in an autoclave (sealed container) and heated to 130°C for hydrothermal treatment. The hydrothermal treatment was carried out under natural pressure for 5 hours. After hydrothermal treatment, the mixture was washed with pure water and dried in a crucible at 105°C for 24 hours to obtain titanium phosphate powder 6. Titanium phosphate powder 6 is white in appearance, and no gray or black impurities can be visually identified.

[0149] <Evaluation>

[0150] [Evaluation of foreign objects]

[0151] In the mixture of hydrothermal treatment and water washing treatment, the presence of foreign matter on the liquid surface is visually confirmed.

[0152] In the manufacture of titanium phosphate powder 5, trace amounts of foreign matter originating from activated carbon were observed, but it was determined that this would not pose a practical problem. In the manufacture of titanium phosphate powder 6, no foreign matter originating from activated carbon was observed.

[0153] This application is based on Japanese Patent Application No. 2023-188363, filed on November 2, 2023, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A method for manufacturing titanium phosphate powder, comprising: A mixture is prepared by mixing a titanium sulfate solution with a phosphoric acid solution. The titanium sulfate solution is obtained by contacting the raw titanium sulfate solution with activated carbon and then filtering it through a filter.

2. A method for purifying titanium sulfate solution, comprising: After the raw material titanium sulfate solution comes into contact with activated carbon, it is filtered using a filter.

3. The purification method for titanium sulfate solution according to claim 2, wherein, The mass ratio of the activated carbon to the titanium in the raw material titanium sulfate solution, calculated as titanium dioxide, is 0.005 or more.

4. A titanium phosphate powder having a carbon content of less than 0.005% by mass per unit mass.

5. A titanium sulfate solution having a total organic carbon content of less than 3 mg / L.

6. The titanium sulfate solution according to claim 5 has a transmittance of 95% or more at a wavelength of 550 nm.

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