Titanium phosphate compound-containing powder and method for producing the same

Abstract

To provide a highly useful titanium phosphate compound-containing powder and a method for producing the same.SOLUTION: Provided is a titanium phosphate compound-containing powder having a titanium phosphate compound as a main component. The titanium phosphate compound is one or more selected from the group consisting of a compound represented by chemical formula TiP2O7, a compound represented by chemical formula Ti(HPO4)2, and a compound represented by chemical formula Ti(HPO4)2 H2O, has an aspect ratio represented by the ratio (planar direction length DPL50 of primary particles / thickness DPT50 of primary particles) of the planar direction length DPL50 of primary particles at which the cumulative frequency from the small particle size side becomes 50% in the volume-based cumulative planar direction length distribution to the thickness DPT50 of primary particles at which the cumulative frequency from the small particle size side becomes 50% in the volume-based cumulative thickness distribution, the aspect ratio being 5 or more and 10 or less, and has a specific surface area of 20 m2 / g or more and 50 m2 / g or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a titanium phosphate compound-containing powder and a method for producing the same.

Background Art

[0002] There are two types of titanium phosphate compounds: crystalline and amorphous. Crystalline titanium phosphate generally has a layered structure and is being studied for applications in various fields such as raw materials for lithium ion conductors, raw materials for fertilizers, additives, and pigments added to cosmetics and paints. Several hydrates of this crystalline titanium phosphate are known. Also, titanium pyrophosphate, which is one of the titanium phosphate compounds, is known to be usable for the same applications as crystalline titanium phosphate.

[0003] Regarding crystalline titanium phosphate and titanium pyrophosphate, Patent Document 1 discloses a method for producing insoluble layered titanium phosphate and that when the reaction conditions are changed by a method similar to the production of insoluble layered titanium phosphate, titanium pyrophosphate is produced. Also, Patent Document 2 discloses a method for producing twin particles of crystalline titanium phosphate and a method for producing titanium pyrophosphate using the twin particles as a raw material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the titanium phosphate compound has a desirable shape depending on its use, and it is required that the shape has a certain degree of uniformity. However, since the titanium pyrophosphate obtained by the production method of titanium pyrophosphate described in Patent Document 1 does not use a titanium phosphate having a specific shape as a raw material, its shape is considered to be non-uniform. Further, in the production method of Patent Document 2, since titanium pyrophosphate is produced using titanium phosphate having a pseudo-spherical particle shape as a raw material, it is difficult to produce titanium pyrophosphate having a particle shape other than spherical or pseudo-spherical. Therefore, there is room for improvement in the titanium phosphate compound in terms of obtaining a powder having a uniform shape.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide a powder containing a titanium phosphate compound in which the particles have a plate shape and high usefulness is expected.

Means for Solving the Problems

[0007] The present inventors conducted intensive studies to solve the above problems. As a result, it was found that the above problems are solved by a plate-shaped titanium phosphate-based compound having a predetermined aspect ratio and a further predetermined specific surface area, and the present invention was completed.

[0008] That is, the above various objects can be achieved by the present invention having the following configuration, and the present invention includes the following aspects and forms.

[0009] One aspect of the present invention is 1. A titanium phosphate compound-containing powder mainly composed of a titanium phosphate compound, wherein the titanium phosphate compound is at least one selected from the group consisting of a compound represented by the chemical formula TiP2O7, a compound represented by the chemical formula Ti(HPO4)2, and a compound represented by the chemical formula Ti(HPO4)2·H2O, the thickness D of the primary particle at which the cumulative frequency from the small particle size side is 50% in the cumulative thickness distribution based on volume PTThe aspect ratio represented by the ratio (the planar direction length D of the primary particle PL PL 50) of the planar direction length D of the primary particle at which the cumulative frequency from the small particle size side in the cumulative planar direction length distribution based on volume with respect to 50 reaches 50% is 5 or more and 10 or less, and PL the ratio (the planar direction length D of the primary particle PT PT 50 / the thickness D of the primary particle) is 5 or more and 10 or less, and the specific surface area is 20 m 2 / g or more and 50 m 2 / g or less, and it is a titanium phosphate compound-containing powder.

[0010] 2. In the titanium phosphate compound-containing powder according to 1. above, it is preferable that the D PL PL 50 is 0.1 μm or more and less than 1 μm.

[0011] 3. In the titanium phosphate compound-containing powder according to 1. or 2. above, it is preferable that the pH of the aqueous dispersion with a solid content concentration of 1 mass% is 4.0 or less.

[0012] 4. In the titanium phosphate compound-containing powder according to any one of 1. to 3. above, it is preferable that the electrical conductivity of the aqueous dispersion with a solid content concentration of 1 mass% is 0.2 mS / cm or more.

[0013] 5. In the titanium phosphate compound-containing powder according to any one of 1. to 4. above, it is preferable that the titanium phosphate compound is at least one selected from the group consisting of a compound represented by the chemical formula TiP2O7 and a compound represented by the chemical formula Ti(HPO4)2.

[0014] 6. In the titanium phosphate compound-containing powder according to any one of 1. to 5. above, it is preferable that the compound represented by the chemical formula TiP2O7 is non-cubic TiP2O7.

[0015] 7. One aspect of the present invention is a method for producing the titanium phosphate compound-containing powder according to any one of 1. to 6. above, which has a synthesis step of synthesizing a raw material containing titanium and phosphorus to obtain a reaction solution, A production method in which the reaction temperature in the synthesis step is 80°C or higher and lower than 130°C, and the reaction time is 1 hour or longer and 72 hours or shorter.

[0016] 8. The production method according to 7. above preferably has a firing step of firing the solid separated from the reaction solution at a temperature of 200°C or higher and 850°C or lower.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a titanium phosphate compound-containing powder having a plate-like particle shape and expected to have high utility.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited only to the following embodiments. Also, in this specification, unless otherwise specified, measurements of operations and physical properties are performed under conditions of room temperature (20°C or higher and 25°C or lower) / relative humidity of 40% RH or higher and 50% RH or lower.

[0020] [Titanium Phosphate Compound-Containing Powder] The titanium phosphate compound-containing powder according to one embodiment of the present invention is a titanium phosphate compound-containing powder mainly composed of a titanium phosphate compound, wherein the titanium phosphate compound is at least one selected from the group consisting of a compound represented by the chemical formula TiP2O7, a compound represented by the chemical formula Ti(HPO4)2, and a compound represented by the chemical formula Ti(HPO4)2·H2O, and the thickness D of the primary particle at which the cumulative frequency from the small particle size side is 50% in the cumulative thickness distribution based on volume PT with respect to 50, the in-plane length D of the primary particle at which the cumulative frequency from the small particle size side is 50% in the cumulative in-plane length distribution based on volume PL 50 of the ratio (the in-plane length D of the primary particle PL 50 / the thickness D of the primary particle PT 50) represented by the aspect ratio is 5 or more and 10 or less, and the specific surface area is 20 m 2 / g or more and 50 m 2 / g or less. According to this embodiment, a titanium phosphate compound-containing powder having a plate-like shape with a certain degree of particle shape uniformity and high utility can be provided.

[0021] The inventors of the present invention presume the mechanism by which the above problems can be solved by the present invention as follows.

[0022] The titanium phosphate compound-containing powder according to the present invention has an aspect ratio (also simply referred to as "aspect ratio" in this specification) represented by the in-plane length D of the primary particle PL 50 / the thickness D of the primary particle PT 50 of 5 or more and 10 or less. That is, since one particle has a large plane, when adding a titanium phosphate compound-containing powder to an object in an application where a plate-like particle shape is particularly advantageous, it becomes possible to more efficiently impart the characteristics derived from the titanium phosphate compound. Further, the titanium phosphate compound-containing powder according to the present invention, in addition to the above-described aspect ratio of 5 or more and 10 or less, has a specific surface area of 20 m 2 / g or more and 50 m 2It is in the range of less than / g. With this configuration, the titanium phosphate compound-containing powder according to the present invention has excellent electrical conductivity, so its usefulness is further improved. In addition, by having this configuration, the titanium phosphate compound-containing powder has a low pH and is easily decomposed (in other words, it has high activity). From this point as well, the usefulness of the titanium phosphate compound-containing powder is improved. It should be noted that the above mechanism is based on speculation, and the present invention is not limited to the above mechanism at all.

[0023] (Titanium phosphate compound) The titanium phosphate compound-containing powder according to the present invention contains a titanium phosphate compound as a main component. Here, the main component means that the titanium phosphate compound is contained in an amount of 60% by mass or more in the total amount of the titanium phosphate compound-containing powder. In one embodiment of the present invention, the titanium phosphate compound-containing powder may contain the titanium phosphate compound in an amount of 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more in the total amount of the titanium phosphate compound-containing powder.

[0024] The titanium phosphate compound according to the present invention is one or more selected from the group consisting of a compound represented by the chemical formula TiP2O7, a compound represented by the chemical formula Ti(HPO4)2, and a compound represented by the chemical formula Ti(HPO4)2·H2O. That is, the titanium phosphate compound-containing powder according to the present invention contains one or more titanium phosphate compounds selected from the group consisting of a compound represented by the chemical formula TiP2O7, a compound represented by the chemical formula Ti(HPO4)2, and a compound represented by the chemical formula Ti(HPO4)2·H2O. Therefore, the titanium phosphate compound-containing powder according to the present invention contains one or more titanium phosphate compounds selected from the group consisting of a compound represented by the chemical formula TiP2O7, a compound represented by the chemical formula Ti(HPO4)2, and a compound represented by the chemical formula Ti(HPO4)2·H2O in an amount of 60% by mass or more. In the titanium phosphate compound-containing powder according to the present invention, the titanium phosphate compound may be one of the above-described compounds or a mixture of two or more thereof. When two or more titanium phosphate compounds are mixed, the content of the titanium phosphate compound is the total amount thereof. Hereinafter, the compound represented by the chemical formula TiP2O7 is simply referred to as TiP2O7, the compound represented by the chemical formula Ti(HPO4)2 is simply referred to as Ti(HPO4)2, and the compound represented by the chemical formula Ti(HPO4)2·H2O is simply referred to as Ti(HPO4)2·H2O. In addition, the compound represented by the chemical formula TiP2O7 can also be referred to as titanium pyrophosphate, for example. Further, the compound represented by the chemical formula Ti(HPO4)2 can also be referred to as titanium hydrogen phosphate anhydride, for example. Further, the compound represented by the chemical formula Ti(HPO4)2·H2O can also be referred to as titanium hydrogen phosphate monohydrate, for example. Hereinafter, when referring to a titanium phosphate compound, it refers to all of the compound represented by the chemical formula TiP2O7, the compound represented by the chemical formula Ti(HPO4)2, and the compound represented by the chemical formula Ti(HPO4)2·H2O. In addition, in this specification, each physical property described as "titanium phosphate compound-containing powder" is also directly applicable as the physical property of the titanium phosphate compound.

[0025] The titanium phosphate compound according to one embodiment is preferably at least one selected from the group consisting of a compound represented by the chemical formula TiP2O7 and a compound represented by the chemical formula Ti(HPO4)2. Thereby, the usefulness of the titanium phosphate compound-containing powder is improved. For example, the specific surface area of the titanium phosphate compound-containing powder becomes more suitable, and the electrical conductivity also becomes more suitable. Further, since the pH of the titanium phosphate compound-containing powder is relatively low, it is suitable. In this case, the total amount of the content of the compound represented by the chemical formula TiP2O7 and the content of the compound represented by the chemical formula Ti(HPO4)2 in the titanium phosphate compound-containing powder is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 99% by mass or more. Here, the total amount of the content of the compound represented by the chemical formula TiP2O7 and the content of the compound represented by the chemical formula Ti(HPO4)2 in the titanium phosphate compound-containing powder represents the single content of the other compound when one of the compounds is not contained.

[0026] In addition, among the compounds represented by the chemical formula TiP2O7, there are those with a cubic crystal structure and those that are not cubic (those with an unknown crystal structure, referred to as non-cubic crystals). In the titanium phosphate compound-containing powder according to one embodiment, the compound represented by the chemical formula TiP2O7 is preferably a non-cubic crystal, that is, non-cubic TiP2O7. Thereby, the usefulness of the titanium phosphate compound-containing powder is further improved. For example, the specific surface area of the titanium phosphate compound-containing powder becomes more suitably sufficient, and the electrical conductivity and pH also become more suitably sufficient. As will be described in detail in the Examples section, in this specification, among the compounds represented by the chemical formula TiP2O7, those with a cubic crystal structure are referred to as cubic TiP2O7 or cubic titanium pyrophosphate. Also, among the compounds represented by the chemical formula TiP2O7, those that are non-cubic crystals are referred to as non-cubic TiP2O7 or non-cubic titanium pyrophosphate.

[0027] The titanium phosphate compound contained in the titanium phosphate compound-containing powder according to one embodiment is preferably at least one selected from the group consisting of a non-cubic crystal of a compound represented by the chemical formula TiP2O7 (non-cubic TiP2O7) and a compound represented by the chemical formula Ti(HPO4)2. Thereby, the usefulness of the titanium phosphate compound-containing powder is improved. For example, the specific surface area of the titanium phosphate compound-containing powder becomes more suitable, and the electrical conductivity also becomes more suitable. Further, since the pH of the titanium phosphate compound-containing powder also becomes lower, it is suitable. In this case, the total amount of the non-cubic crystal of the compound represented by the chemical formula TiP2O7 (non-cubic TiP2O7) and the compound represented by the chemical formula Ti(HPO4)2 in the titanium phosphate compound-containing powder is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 99% by mass or more. Here, the total amount of the non-cubic crystal of the compound represented by the chemical formula TiP2O7 (non-cubic TiP2O7) and the compound represented by the chemical formula Ti(HPO4)2 in the titanium phosphate compound-containing powder represents the single content of the other compound when one of the compounds is not contained.

[0028] Incidentally, whether the titanium phosphate compound in the titanium phosphate compound-containing powder is cubic TiP2O7, non-cubic TiP2O7, Ti(HPO4)2, or Ti(HPO4)2·H2O can be evaluated by X-ray diffraction (hereinafter, "XRD") measurement.

[0029] Specifically, in the spectrum obtained by XRD, when the top two peaks with high intensity are present around diffraction angle 2θ = 22.6° and around diffraction angle 2θ = 25.3° (regardless of the order of intensity), the titanium phosphate compound can be evaluated as cubic TiP2O7. Also, in the spectrum obtained by XRD, when the top two peaks with high intensity are present around diffraction angle 2θ = 12.7° and around diffraction angle 2θ = 20.9° (regardless of the order of intensity), the titanium phosphate compound can be evaluated as non-cubic TiP2O7. Further, in the spectrum obtained by XRD, when the top two peaks with high intensity are present around diffraction angle 2θ = 11.9° and around diffraction angle 2θ = 24.9° (regardless of the order of intensity), the titanium phosphate compound can be evaluated as Ti(HPO4)2. Additionally, in the spectrum obtained by XRD, when the top two peaks with high intensity are present around diffraction angle 2θ = 11.6° and around diffraction angle 2θ = 25.7° (regardless of the order of intensity), the titanium phosphate compound can be evaluated as Ti(HPO4)2·H2O. The details of the measurement method are described in the examples.

[0030] (Particle shape) The particle shape of the titanium phosphate compound contained in the titanium phosphate compound-containing powder according to the present invention is plate-like. The particle shape of the titanium phosphate compound (particle shape of primary particles) can be evaluated by visually checking the obtained SEM image using a scanning electron microscope (SEM) (SU8000, Hitachi High-Tech Corporation). The details of the measurement method are described in the examples.

[0031] For example, when the particle shape is disc-shaped (including cases where the shape of the plate surface is not a perfect circle, such as oval or gourd-shaped with a constriction) or polygonal plate-shaped (such as hexagonal plate-shaped or other polygonal plate-shaped), it is determined that the particle shape is plate-like.

[0032] The surface direction length D of the primary particle at which the cumulative frequency from the small particle size side becomes 50% in the volume-based cumulative particle size distribution (volume-based cumulative surface direction length distribution) of the titanium phosphate compound-containing powderPL 50 is not particularly limited. However, the length D in the plane direction of the primary particles of the titanium phosphate compound-containing powder PL 50 is preferably 0.1 μm or more, more preferably 0.15 μm or more, still more preferably 0.2 μm or more, and particularly preferably 0.25 μm or more. The length D in the plane direction of the primary particles of the titanium phosphate compound-containing powder PL 50 is preferably less than 1 μm, more preferably 0.8 μm or less, still more preferably 0.6 μm or less, particularly preferably 0.5 μm or less, and most preferably 0.4 μm or less. The length D in the plane direction of the primary particles of the titanium phosphate compound-containing powder PL Examples of the preferred range of 50 include, but are not limited to, 0.1 μm or more and less than 1 μm, 0.15 μm or more and 0.8 μm or less, 0.2 μm or more and 0.6 μm or less, 0.25 μm or more and 0.5 μm or less, 0.25 μm or more and 0.4 μm or less, etc. When the D PL 50 is within these ranges, in combination with other configurations, the pH and electrical conductivity of the titanium phosphate compound-containing powder become suitable, and the usefulness of the titanium phosphate compound-containing powder is further improved. Also, the production efficiency of the titanium phosphate compound-containing powder is further improved.

[0033] The thickness D of the primary particles at which the cumulative frequency from the small particle size side is 50% in the volume-based cumulative particle size distribution (volume-based cumulative thickness distribution) of the titanium phosphate compound-containing powder PT 50 is not particularly limited. However, the thickness D of the primary particles of the titanium phosphate compound-containing powder PT 50 is preferably 0.01 μm or more, more preferably 0.02 μm or more, still more preferably 0.03 μm or more. The thickness D of the primary particles of the titanium phosphate compound-containing powder PT 50 is preferably 0.5 μm or less, more preferably 0.25 μm or less, still more preferably 0.15 μm or less, particularly preferably 0.1 μm or less, and most preferably 0.05 μm or less. The thickness D of the primary particles of the titanium phosphate compound-containing powder PTExamples of the preferable range of 50 include, but are not limited to, 0.01 μm or more and 0.5 μm or less, 0.02 μm or more and 0.25 μm or less, 0.02 μm or more and 0.15 μm or less, 0.03 μm or more and 0.1 μm or less, 0.03 μm or more and 0.05 μm or less, etc. When the D PT When 50 is within these ranges, in combination with other configurations, the pH and electrical conductivity of the titanium phosphate compound-containing powder become suitable, and the usefulness of the titanium phosphate compound-containing powder is further improved. Also, the production efficiency of the titanium phosphate compound-containing powder is further improved.

[0034] The length D in the plane direction of the primary particles of the titanium phosphate compound-containing powder PL 50 and the thickness D of the primary particles PT 50 can be measured and calculated as follows. The titanium phosphate compound-containing powder is randomly measured with a scanning electron microscope (SEM). Then, for the obtained SEM image, using the image analysis software "Mac-View ver.4" manufactured by Mountech Co., Ltd., 100 or more (preferably 100 or more and 200 or less) primary particles (plate-like primary particles) are measured, and the longest diameter (μm) and thickness (μm) in the plane direction of each primary particle are obtained.

[0035] Here, the longest diameter (μm) and thickness (μm) in the plane direction of each primary particle are defined as follows. First, in the projection view in the vertical direction of a single primary particle placed on a horizontal plane in the most stable stationary state, the length of the straight line connecting two points existing on the outer peripheral line of the projection view when the distance of the straight line is the largest is defined as the longest diameter (μm). Also, when an image of a single primary particle taken from a direction substantially perpendicular to the thickness direction (projection view in the direction substantially perpendicular to the thickness direction) is sandwiched between two parallel lines in contact with the image (projection view), the interval (distance between the two parallel lines) when the interval between the two parallel lines is the largest is defined as the thickness (μm). And for the longest diameter (μm) in the plane direction of each primary particle, the value at which the cumulative frequency from the small particle size side in the volume-based cumulative particle size distribution (volume-based cumulative length distribution in the plane direction) is 50% is defined as the length D in the plane direction of the primary particles PLLet it be 50 (μm). Also, regarding the thickness (μm) of each primary particle, the value at which the cumulative frequency from the small particle size side becomes 50% in the volume-based cumulative particle size distribution (volume-based cumulative thickness distribution) is defined as the thickness D of the primary particle. PT Let it be 50 (μm). Note that the longest diameter (μm) in the plane direction, the thickness (μm), and D PL 50 (μm) and D PT Details of the measurement method of 50 (μm) will be described in the examples.

[0036] The length D in the plane direction of the primary particles of the titanium phosphate compound-containing powder PL 50 can be controlled by the synthesis conditions in the synthesis process described later. For example, by increasing the heating temperature or increasing the heating time in the synthesis process, the length D in the plane direction of the primary particles of the titanium phosphate compound to be synthesized PL 50 can be increased, and the length D in the plane direction of the primary particles of the titanium phosphate compound-containing powder PL 50 can be increased.

[0037] The thickness D of the primary particles of the titanium phosphate compound-containing powder PT 50 can be controlled by the conditions in the synthesis process described later. For example, by increasing the heating temperature or increasing the heating time in the synthesis process, the thickness D of the titanium phosphate compound to be synthesized PT 50 can be increased, and the thickness D of the primary particles of the titanium phosphate compound-containing powder PT 50 can be increased.

[0038] The titanium phosphate compound-containing powder according to the above aspect of the present invention has a length D in the plane direction of the primary particles PL 50 / the thickness D of the primary particles PTThe aspect ratio represented by 50 is 5 or more and 10 or less. If the aspect ratio of the titanium phosphate compound-containing powder is less than 5, higher usefulness than conventional particles cannot be obtained. Further, if the aspect ratio exceeds 10, for example, the particles are likely to break due to physical impact, and it may be difficult to use them stably, and high usefulness cannot be obtained. The lower limit value of the aspect ratio of the titanium phosphate compound-containing powder is 5 or more, preferably 6 or more, more preferably 6.5 or more, and particularly preferably 7 or more. Further, the upper limit of the aspect ratio is 10 or less, preferably 9 or less, more preferably 8.5 or less, and particularly preferably 8 or less. Examples of the preferable range of the aspect ratio of the titanium phosphate compound-containing powder include, but are not limited to, 5 or more and 9 or less, 6 or more and 10 or less, 6 or more and 9 or less, 6.5 or more and 8.5 or less, 7 or more and 8 or less, etc. When the aspect ratio is within these ranges, high usefulness is expected. Although not particularly limited, the titanium phosphate compound-containing powder having an aspect ratio within the above range is expected to have high usefulness in applications such as gas barrier fillers, solid lubricant fillers, or proton conductive fillers, for example.

[0039] In the calculation of the aspect ratio, the planar direction length D of the primary particle PL 50 and the thickness D of the primary particle PT 50 use the same unit (for example, μm).

[0040] The aspect ratio of the titanium phosphate compound-containing powder is the planar direction length D in the primary particles of the above titanium phosphate compound-containing powder PL 50 or the thickness D in the primary particles of the above titanium phosphate compound-containing powder PT 50 can be controlled by control. The aspect ratio of the titanium phosphate compound-containing powder is particularly preferably controlled by controlling the planar direction length D in the primary particles of the above titanium phosphate compound-containing powder PL 50.

[0041] (Specific surface area) The titanium phosphate compound-containing powder according to one embodiment of the present invention has a specific surface area of 20 m 2 / g or more and 50 m 2 / g or less. If the specific surface area of the titanium phosphate compound-containing powder is less than 20 m 2 / g, higher utility than conventional particles cannot be obtained. Further, if the specific surface area exceeds 50 m 2 / g, the titanium phosphate compound-containing powder tends to aggregate, and the titanium phosphate compound-containing powder becomes bulky, limiting its applications, so that high utility cannot be obtained. The lower limit of the specific surface area of the titanium phosphate compound-containing powder according to one embodiment is 20 m 2 / g or more, preferably 25 m 2 / g or more, more preferably 28 m 2 / g or more, even more preferably more than 28 m 2 / g, particularly preferably 30 m 2 / g or more, and most preferably 35 m 2 / g or more. Further, the upper limit value of the specific surface area of the titanium phosphate compound-containing powder according to one embodiment is 50 m 2 / g or less, preferably 48 m 2 / g or less, more preferably 47.5 m 2 / g or less, and even more preferably 45 m 2 / g or less. That is, the preferable range of the specific surface area of the titanium phosphate compound-containing powder is, for example, 20 m 2 / g or more and 48 m 2 / g or less, 20 m 2 / g or more and 47.5 m 2 / g or less, 20 m 2 / g or more and 45 m 2 / g or less, 25 m 2 / g or more and 50 m 2 / g or less, 25 m 2 / g or more and 48 m 2 / g or less, 25 m 2 / g or more and 47.5 m 2 / g or less, 25 m 2 / g or more and 45 m 2 / g or less, 28 m 2 / g or more and 50 m 2Below / g, 28 m 2 Above / g, 48 m 2 Below / g, 28 m 2 Above / g, 47.5 m 2 Below / g, 28 m 2 Above / g, 45 m 2 Below / g, 28 m 2 Above / g, over 50 m 2 Below / g, 28 m 2 Above / g, over 48 m 2 Below / g, 28 m 2 Above / g, over 47.5 m 2 Below / g, 28 m 2 Above / g, over 45 m 2 Below / g, 30 m 2 Above / g, 50 m 2 Below / g, 30 m 2 Above / g, 48 m 2 Below / g, 30 m 2 Above / g, 47.5 m 2 Below / g, 30 m 2 Above / g, 45 m 2 Below / g, 35 m 2 Above / g, 50 m 2 Below / g, 35 m 2 Above / g, 48 m 2 Below / g, 35 m 2 Above / g, 47.5 m 2 Below / g, 35 m 2 Above / g, 45 m 2 Examples thereof include, but are not limited to, below / g. When the specific surface area is within the above range, the usefulness of the titanium phosphate compound-containing powder is improved. In particular, since the electrical conductivity is improved, it can be suitably used, for example, as a raw material for a lithium ion conductor used in a lithium ion secondary battery or the like. Further, when the specific surface area is within the above range, the pH also becomes relatively low and it becomes easily decomposable. Therefore, the titanium phosphate compound-containing powder can be suitably used as a raw material for an agricultural fertilizer.

[0042] The specific surface area of the titanium phosphate compound-containing powder can be measured by the BET flow method. Details of the method for measuring the specific surface area are described in the examples.

[0043] The specific surface area of the titanium phosphate compound-containing powder can be controlled by the synthesis process and firing conditions described below. For example, by adjusting the heating temperature and heating time in the synthesis process (e.g., lowering the heating temperature and increasing the heating time), or by adjusting the firing temperature and firing time in the firing process (e.g., increasing the firing temperature and shortening the firing time), the specific surface area of the synthesized titanium phosphate compound can be controlled within the above range, and the specific surface area of the titanium phosphate compound-containing powder can be controlled within the above range.

[0044] The titanium phosphate compound-containing powder according to one embodiment of the present invention preferably has an uneven shape on the surface of the particles. That is, the titanium phosphate compound, which is the main component of the titanium phosphate compound-containing powder, preferably has unevenness on the particle surface (the surface of primary particles). Note that the unevenness may be pores.

[0045] The presence or absence of the uneven shape on the surface of the titanium phosphate compound can be evaluated by visually checking the obtained SEM image using a scanning electron microscope (SEM) (SU8000, Hitachi High-Tech Corporation) for the titanium phosphate compound, which is the main component of the titanium phosphate compound-containing powder.

[0046] (pH) The titanium phosphate compound-containing powder according to one embodiment of the present invention preferably has a pH of 4.0 or less in an aqueous dispersion having a solid content concentration of 1% by mass. More specifically, it is preferable that the pH at 25°C of an aqueous dispersion obtained by mixing the titanium phosphate compound-containing powder and pure water so that the solid content concentration is 1% by mass is 4.0 or less. Details of the pH measurement method are described in the examples. When the pH is 4.0 or less, the usefulness of the titanium phosphate compound-containing powder is improved. For example, when the pH is 4.0 or less, the titanium phosphate compound-containing powder has high activity and is easily decomposed, so it can be suitably used, for example, as a raw material for a lithium ion conductor or as a raw material for an agricultural fertilizer.

[0047] Further, in the titanium phosphate compound-containing powder according to one embodiment of the present invention, the pH of the aqueous dispersion with a solid content concentration of 1% by mass is preferably 4.0 or less, more preferably 3.5 or less, still more preferably less than 3.5, particularly preferably 3.25 or less, and most preferably 3.0 or less. The lower limit of the pH of the aqueous dispersion is not particularly limited, but is preferably 1.0 or more, more preferably 1.5 or more, and particularly preferably 2.0 or more. That is, examples of the preferable range of the pH of the aqueous dispersion include 1.0 or more and 4.0 or less, 1.5 or more and 3.5 or less, 1.5 or more and less than 3.5, 2.0 or more and 3.25 or less, 2.0 or more and 3.0 or less, and the like. When the pH of the aqueous dispersion with a solid content concentration of 1% by mass is within the above range, the titanium phosphate compound-containing powder has higher activity and is more easily decomposed, and thus can be more preferably used, for example, as a raw material for a lithium ion conductor or a raw material for an agricultural fertilizer.

[0048] (Electrical conductivity) In the titanium phosphate compound-containing powder according to one embodiment of the present invention, the electrical conductivity of the aqueous dispersion with a solid content concentration of 1% by mass is preferably 0.2 mS / cm or more. More specifically, it is preferable that the electrical conductivity of the aqueous dispersion obtained by mixing the titanium phosphate compound-containing powder and pure water so that the solid content concentration is 1% by mass is 0.2 mS / cm or more. Details of the method for measuring the electrical conductivity are described in the examples. When the electrical conductivity is 0.2 mS / cm or more, the usefulness of the titanium phosphate compound-containing powder is improved. For example, the titanium phosphate compound-containing powder can be suitably used as a proton conductor as a raw material for a fuel cell or a sensor.

[0049] Further, for the titanium phosphate compound-containing powder according to an embodiment of the present invention, the electric conductivity of the aqueous dispersion with a solid content concentration of 1% by mass is preferably 0.2 mS / cm or more, more preferably 0.25 mS / cm or more, still more preferably 0.3 mS / cm or more, and particularly preferably 0.35 mS / cm or more. Also, the upper limit of the electric conductivity of the aqueous dispersion is not particularly limited, but is preferably 5 mS / cm or less, more preferably 2.5 mS / cm or less, still more preferably 1 mS / cm or less, and particularly preferably 0.5 mS / cm or less. That is, as a preferable range of the electric conductivity of the aqueous dispersion, for example, 0.2 mS / cm or more and 5 mS / cm or less, 0.2 mS / cm or more and 2.5 mS / cm or less, 0.2 mS / cm or more and 1 mS / cm or less, 0.2 mS / cm or more and 0.5 mS / cm or less, 0.25 mS / cm or more and 5 mS / cm or less, 0.25 mS / cm or more and 2.5 mS / cm or less, 0.25 mS / cm or more and 1 mS / cm or less, 0.25 mS / cm or more and 0.5 mS / cm or less, 0.3 mS / cm or more and 5 mS / cm or less, 0.3 mS / cm or more and 2.5 mS / cm or less, 0.3 mS / cm or more and 1 mS / cm or less, 0.3 mS / cm or more and 0.5 mS / cm or less, 0.35 mS / cm or more and 5 mS / cm or less, 0.35 mS / cm or more and 2.5 mS / cm or less, 0.35 mS / cm or more and 1 mS / cm or less, 0.35 mS / cm or more and 0.5 mS / cm or less, etc. can be mentioned. When the electric conductivity of the aqueous dispersion with a solid content concentration of 1% by mass is within the above range, the usefulness of the titanium phosphate compound-containing powder is further improved. Specifically, for example, it becomes more suitably used as a raw material for a proton conductor used in a fuel cell or a sensor, a lithium ion conductor used in a lithium ion secondary battery, etc.

[0050] [Method for producing titanium phosphate compound-containing powder] The method for producing the titanium phosphate compound-containing powder described above is not particularly limited as long as it is a method capable of producing the titanium phosphate compound-containing powder according to the present invention.

[0051] Another form of the present invention is a method for producing a titanium phosphate compound-containing powder. The production method includes a synthesis step of synthesizing a raw material containing titanium and phosphorus to obtain a reaction solution. In the synthesis step, the reaction temperature is 80°C or higher and less than 130°C, and the reaction time is 1 hour or longer and 72 hours or shorter.

[0052] According to the production method, a titanium phosphate compound-containing powder mainly composed of a titanium phosphate compound, wherein the titanium phosphate compound is at least one selected from the group consisting of a compound represented by the chemical formula TiP2O7, a compound represented by the chemical formula Ti(HPO4)2, and a compound represented by the chemical formula Ti(HPO4)2·H2O, and the thickness D of the primary particle at which the cumulative frequency from the small particle size side is 50% in the cumulative thickness distribution based on volume PT with respect to D50, the surface direction length D of the primary particle at which the cumulative frequency from the small particle size side is 50% in the cumulative surface direction length distribution based on volume PL 50 of the ratio (the surface direction length D of the primary particle PL 50 / the thickness D of the primary particle PT 50) represented by the aspect ratio is 5 or more and 10 or less, and the specific surface area is 20 m 2 / g or more and 50 m 2 / g or less, a titanium phosphate compound-containing powder can be obtained.

[0053] From the above, it can be said that the production method according to this aspect is a preferable production method of the above titanium phosphate compound-containing powder. The details of the titanium phosphate compound-containing powder produced by the production method according to an embodiment of the present invention are as described above.

[0054] (Synthesis step) The synthesis step is a step of synthesizing a raw material containing titanium and phosphorus to obtain a reaction solution. Here, the synthesis is carried out in the presence of water, particularly in the presence of high-temperature water. By this step, a raw material containing titanium and phosphorus is synthesized, and further, the crystals obtained as a result of the synthesis grow.

[0055] The raw materials containing titanium and phosphorus are not particularly limited, and may be compounds containing titanium and phosphorus, or may be a mixture of a compound containing titanium and a compound containing phosphorus. The raw materials containing titanium and phosphorus may be, for example, a mixture of titanium(IV) sulfate (Ti(SO4)2) and / or titanyl sulfate (TiOSO4) and phosphoric acid (H3PO4). By using titanium(IV) sulfate and / or titanyl sulfate as the titanium source, it becomes easier to obtain titanium phosphate having a desired aspect ratio. The compounds containing titanium and phosphorus, the compounds containing titanium, and the compounds containing phosphorus may each be used alone or in combination of two or more kinds.

[0056] Here, in the synthesis step, the raw materials containing titanium and phosphorus may be obtained by a mixing step of mixing an aqueous phosphoric acid solution, a titanium sulfate solution, and water. At this time, the concentration of the aqueous phosphoric acid solution is preferably 50% by mass or more and 95% by mass or less, and more preferably 70% by mass or more and 90% by mass. The titanium sulfate solution is preferably 80 g / L or more and 150 g / L or less in terms of TiO2, and more preferably 90 g / L or more and 130 g / L or less. The sulfuric acid concentration of the titanium sulfate solution is preferably 300 g / L or more and 700 g / L or less, and preferably 400 g / L or more and 600 g / L or less. Water is not particularly limited, but pure water is preferred.

[0057] The mixing ratio of the aqueous phosphoric acid solution, the titanium sulfate solution, and water is not particularly limited. However, the ratio of the mass of the titanium sulfate solution to the mass of the aqueous phosphoric acid solution (mass of titanium sulfate solution / mass of aqueous phosphoric acid solution) is preferably 0.25 or more and 2 or less, more preferably 0.5 or more and 1.5 or less, and even more preferably 0.6 or more and 1 or less. Also, the ratio of the mass of water to the mass of the aqueous phosphoric acid solution (mass of water / mass of aqueous phosphoric acid solution) is preferably 0.5 or more and 2.5 or less, more preferably 0.75 or more and 2 or less, and even more preferably 1 or more and 1.5 or less.

[0058] The reaction temperature (also referred to as the aging temperature) in the synthesis process is preferably 80°C or higher and less than 130°C, more preferably 80°C or higher and 120°C or lower, still more preferably 80°C or higher and 110°C or lower, particularly preferably 80°C or higher and 100°C or lower, and most preferably 80°C or higher and less than 100°C. According to one embodiment, the reaction temperature in the synthesis process is 85°C or higher and 98°C or lower. If the reaction temperature is within this range, a titanium phosphate compound having a plate-like shape and a relatively small particle size can be obtained. Also, if the reaction temperature is within this range, when manufacturing titanium phosphate powder, it can be manufactured with general-purpose equipment, so the manufacturing cost can be suppressed.

[0059] The rate of temperature increase in the synthesis process is not particularly limited. For example, it may be 0.1°C / min or higher, or 0.2°C / min or higher. Also, the rate of temperature increase during heat treatment is not particularly limited. For example, it may be 5°C / min or lower, 3°C / min or lower, or 1°C / min or lower. Examples of the range of the rate of temperature increase in the synthesis process include, but are not limited to, 0.1°C / min or higher and 5°C / min or lower, 0.2°C / min or higher and 3°C / min or lower, 0.2°C / min or higher and 1°C / min or lower, etc.

[0060] Also, in the synthesis process, the reaction time for allowing the reaction to proceed by maintaining the reaction temperature is preferably 1 hour or longer and 72 hours or shorter, more preferably 2 hours or longer and 36 hours or shorter, still more preferably 3 hours or longer and 18 hours or shorter, and particularly preferably 4 hours or longer and 9 hours or shorter. When the reaction time is within the above range, a powder containing a titanium phosphate compound having a plate-like shape and a relatively small particle size can be manufactured more efficiently.

[0061] In the synthesis process according to one embodiment, the ratio [P] / [Ti] of the molar concentration [P] of phosphorus to the molar concentration [Ti] of titanium in the raw material is not particularly limited, but is preferably 3 or more, more preferably 5 or more, and particularly preferably 9 or more. Also, [P] / [Ti] is not particularly limited, but is preferably 20 or less, more preferably 15 or less. When within these ranges, titanium phosphate in a plate-like shape can be produced more efficiently. Examples of the preferred range of [P] / [Ti] include, but are not limited to, 3 or more and 20 or less, 5 or more and 20 or less, 9 or more and 20 or less, 9 or more and 15 or less, etc.

[0062] In the synthesis process according to one embodiment, the molar concentration of titanium in the raw material is not particularly limited, but is preferably 0.05 mol / L or more, more preferably 0.2 mol / L or more. Also, the molar concentration of titanium in the raw material for titanium phosphate is not particularly limited, but is preferably 1 mol / L or less, more preferably 0.6 mol / L or less. When within these ranges, titanium phosphate in a plate-like shape can be produced more efficiently.

[0063] The molar concentrations of titanium and phosphorus in the raw material containing titanium and phosphorus can be confirmed by calculating from the addition amounts, respectively.

[0064] In the synthesis process according to one embodiment, it is preferable that the synthesis reaction is heated under a predetermined pressure. Here, the predetermined pressure is not particularly limited, but is preferably atmospheric pressure (0.1 MPa) or more. When within this range, a powder containing a titanium phosphate compound in a plate-like shape can be produced more efficiently. Also, the pressure is not particularly limited, but is preferably 0.3 MPa or less. When within this range, production with general-purpose equipment becomes possible, and further, the time required for synthesis is shortened, so productivity is further improved.

[0065] The apparatus used in the synthesis process is not particularly limited, and examples include a reaction vessel made of a glass-lining material, an autoclave, etc.

[0066] The reaction solution obtained by the synthesis step according to one embodiment may be in a slurry state (dispersed state). Further, in the production method according to one embodiment, after the synthesis step, a substitution step of substituting the solution portion of the reaction solution in the slurry state with pure water may be included.

[0067] [Drying step] The production method according to one embodiment may include a drying step of drying the reaction solution obtained in the synthesis step to obtain a powdery solid. In one embodiment, the powdery solid obtained by the drying step may be a titanium phosphate compound-containing powder.

[0068] The reaction solution to be dried in the drying step is preferably in a slurry state, that is, a titanium phosphate compound-containing slurry (titanium phosphate compound-containing dispersion). Further, the slurry-like reaction solution is preferably replaced with pure water by the above-described substitution step.

[0069] In the drying step, the method of drying the reaction solution is not particularly limited, and it is sufficient that the liquid component in the reaction solution can be evaporated so that it becomes 2% by mass or less after the drying step. However, from the viewpoint of production efficiency, it is preferable to dry the reaction solution by heat treatment. The temperature of the heat treatment is not particularly limited, but it is preferably 80°C or higher and lower than 150°C, more preferably 90°C or higher and 140°C or lower, still more preferably 95°C or higher and 130°C or lower, and particularly preferably 100°C or higher and 120°C or lower. Also, the time of the heat treatment is not particularly limited, but it is preferably 1 hour or more and 48 hours or less, more preferably 4 hours or more and 32 hours or less, and particularly preferably 8 hours or more and 28 hours or less. By having the heating temperature and heating time during drying within the above ranges, it is possible to prevent aggregation of the titanium phosphate compound-containing powder by the drying treatment while improving production efficiency.

[0070] The solid obtained by drying the reaction solution obtained by synthesizing the above-described raw material containing titanium and phosphorus is a compound represented by the chemical formula Ti(HPO4)2·H2O (titanium phosphate monohydrate). The compound represented by the chemical formula Ti(HPO4)2·H2O thus obtained has the following composition of the titanium phosphate compound-containing powder (the length D in the plane direction of the primary particles PL 50 / the thickness D of the primary particle PT The aspect ratio represented by 50 is 5 or more and 10 or less; and the specific surface area is 20 m 2 / g or more and 50 m 2 / g or less).

[0071] (Firing step) The method for producing the titanium phosphate compound-containing powder according to one embodiment may have a firing step of firing the solid separated from the reaction solution at a temperature of 200°C or higher and 850°C or lower. When the method for producing the titanium phosphate compound-containing powder has a firing step, the powdery solid obtained by the firing step can be used as the titanium phosphate compound-containing powder.

[0072] By having the firing step, the usefulness of the titanium phosphate compound-containing powder can be further improved. More specifically, by firing at 200°C or higher, the specific surface area of the titanium phosphate compound-containing powder increases and the electrical conductivity improves. Therefore, for example, it becomes more suitable as a raw material for a lithium ion conductor used in a lithium ion secondary battery or the like. In addition, since the pH when mixed with water or the like becomes lower, the phosphorus component is more likely to elute. Therefore, for example, it becomes more suitable as a fertilizer for agriculture. Further, by firing at a temperature of 850°C or lower, deformation of the titanium phosphate compound-containing powder due to firing can be prevented, a plate-like titanium phosphate compound-containing powder can be more easily obtained, and a titanium phosphate compound-containing powder having an aspect ratio of 5 or more can be more easily obtained.

[0073] The firing method is not particularly limited, and examples thereof include a method capable of performing a firing treatment in an air atmosphere.

[0074] The heating rate during the firing process is not particularly limited, but for example, it can be 1 °C / min or more. Also, the heating rate during the heat treatment is not particularly limited, but for example, it can be 10 °C / min or less. Examples of the preferable range of the heating rate during the heat treatment include, but are not limited to, 1 °C / min or more and 10 °C / min or less.

[0075] The firing temperature (heating temperature) during the firing process is preferably, for example, 200 °C or more, and examples include 225 °C or more, 250 °C or more, 275 °C or more, etc. Also, the upper limit of the firing temperature is preferably 850 °C or less, and examples include 825 °C or less, 800 °C or less, 790 °C or less, 780 °C or less, 770 °C, 760 °C or less, etc. Examples of the preferable range of the firing temperature (heating temperature) during the firing process include 200 °C or more and 825 °C or less, 200 °C or more and 800 °C or less, 200 °C or more and 790 °C or less, 200 °C or more and 780 °C or less, 200 °C or more and 770 °C or less, 200 °C or more and 760 °C or less, 225 °C or more and 850 °C or less, 225 °C or more and 825 °C or less, 225 °C or more and 800 °C or less, 225 °C or more and 790 °C or less, 225 °C or more and 780 °C or less, 225 °C or more and 770 °C or less, 225 °C or more and 760 °C or less, 250 °C or more and 850 °C or less, 225 °C or more and 825 °C or less, 250 °C or more and 800 °C or less, 250 °C or more and 790 °C or less, 250 °C or more and 780 °C or less, 250 °C or more and 770 °C or less, 250 °C or more and 760 °C or less, 275 °C or more and 850 °C or less, 275 °C or more and 825 °C or less, 275 °C or more and 800 °C or less, 275 °C or more and 790 °C or less, 275 °C or more and 780 °C or less, 275 °C or more and 770 °C or less, 275 °C or more and 760 °C or less. When the firing temperature is within this range, the production of the titanium phosphate-containing powder can be carried out more sufficiently, the collapse of the plate-like shape and the progress of sintering between particles are suppressed, and the production of the titanium phosphate-containing powder can be carried out more sufficiently.

[0076] The holding time of the firing temperature during the heat treatment is not particularly limited, but is preferably 30 minutes or more, more preferably 60 minutes or more, and still more preferably 100 minutes or more. Also, the holding time during the heat treatment is not particularly limited, but is preferably 1200 minutes or less, more preferably 600 minutes or less, and still more preferably 300 minutes or less. When the holding time is within these ranges, a titanium phosphate compound-containing powder having a suitable specific surface area can be obtained. Also, the production efficiency is further improved. Here, examples of the preferable range of the holding time during the heat treatment include, but are not limited to, 30 minutes or more and 1200 minutes or less, 60 minutes or more and 600 minutes or less, 100 minutes or more and 300 minutes or less, etc.

[0077] The apparatus for performing the firing treatment is not particularly limited, and for example, a general-purpose firing furnace can be used. Examples of commercially available products include the electric muffle furnace KM-420 manufactured by Advantec Toyo Co., Ltd. Also, the titanium phosphate compound-containing powder may be heat-treated in a state filled in a heat-resistant container. The heat-resistant container is not particularly limited, and examples thereof include crucibles. Examples of crucibles include alumina crucibles.

[0078] Here, the structure of the titanium phosphate compound contained in the titanium phosphate compound-containing powder according to the present invention may change depending on the firing temperature.

[0079] For example, when fired at a temperature of 200°C or more and 350°C or less, a compound represented by the chemical formula Ti(HPO4)2 (titanium phosphate anhydride) is obtained. The compound represented by the chemical formula Ti(HPO4)2 thus obtained has the above-described composition of the titanium phosphate compound-containing powder (the aspect ratio represented by the length D PL 50 of the primary particle in the plane direction / the thickness D PT 50 is 5 or more and 10 or less; and the specific surface area is 20 m 2 / g or more and 50 m 2 / g or less).

[0080] For example, when fired at a temperature exceeding 350°C, a compound represented by the chemical formula TiP2O7 (titanium pyrophosphate) is obtained. Among them, for example, when fired at a temperature exceeding 350°C and not exceeding 780°C, preferably at a temperature of 400°C or higher and 780°C or lower, a non-cubic crystal (non-cubic crystal TiP2O7) of the compound represented by the chemical formula TiP2O7 is obtained. The non-cubic crystal TiP2O7 thus obtained has the following composition of the titanium phosphate compound-containing powder (the aspect ratio represented by the length D PL 50 in the plane direction of the primary particle / the thickness D of the primary particle PT 50 is 5 or more and 10 or less; and the specific surface area is 20 m 2 / g or more and 50 m 2 / g or less). Further, the firing temperature for obtaining the non-cubic crystal (non-cubic crystal TiP2O7) of the compound represented by the chemical formula TiP2O7 is more preferably 500°C or higher and 780°C or lower, still more preferably 600°C or higher and 780°C or lower, particularly preferably 650°C or higher and 780°C or lower, and most preferably 700°C or higher and 780°C or lower.

[0081] Also, for example, when fired at a temperature exceeding 780°C, a cubic crystal (cubic crystal TiP2O7) of the compound represented by the chemical formula TiP2O7 is obtained. In this case, the upper limit of the firing temperature is preferably 850°C or lower, more preferably 825°C or lower, and still more preferably 800°C or lower. By the firing temperature being within the above range, the obtained cubic crystal TiP2O7 has the following composition of the titanium phosphate compound-containing powder (the aspect ratio represented by the length D PL 50 in the plane direction of the primary particle / the thickness D of the primary particle PT 50 is 5 or more and 10 or less; and the specific surface area is 20 m 2 / g or more and 50 m 2 / g or less).

[0082] [Other processes] The manufacturing method according to an embodiment of the present invention may further include other steps. For example, it may include a first cooling step of cooling the reaction solution to a predetermined temperature after the synthesis step, or a second cooling step of cooling the titanium phosphate compound-containing powder after the firing step to a predetermined temperature. On the other hand, the manufacturing method according to an embodiment of the present invention preferably does not include a pulverization step of pulverizing the titanium phosphate compound-containing powder. By not including the pulverization step, the production efficiency can be improved, the possibility of a decrease in the aspect ratio due to unintentional destruction of primary particles in the pulverization step can be eliminated, and the possibility of an expansion of the particle size distribution can also be eliminated.

[0083] Although the embodiments of the present invention have been described in detail, these are illustrative and exemplary and not restrictive, and it is clear that the scope of the present invention should be interpreted by the appended claims.

[0084] [Use] The titanium phosphate compound-containing powder according to the present invention can be suitably applied to various uses such as additives and pigments used by adding to cosmetics, paints, etc., raw materials such as lithium ion conductors used in lithium ion secondary batteries, etc., raw materials for agricultural fertilizers, gas barrier fillers, solid lubricant fillers, fillers such as proton conductive fillers.

Examples

[0085] The effects of the present invention will be described using the following examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following production examples and examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the technical scope of the present invention is not limited only to the following examples. The quantitative ratios (unit: "parts by mass", "mass%") of the raw materials used as solutions or dispersions are all values in terms of solid content. Unless otherwise specified, each operation was carried out at room temperature (hereinafter, room temperature is taken as 25 °C).

[0086] [Production of Titanium Phosphate Compound-Containing Powder] [Example 1] A mixed solution was obtained by mixing 34% by mass of an aqueous phosphoric acid solution with a concentration of 85%, 29% by mass of a titanium sulfate solution with a concentration of 120 g / L in terms of TiO₂ and a sulfuric acid concentration of 500 g / L, and 37% by mass of pure water. The molar ratio of phosphorus to titanium in the mixed solution was [P] / [Ti] = 11.2. Next, 200 L of this mixed solution was filled into an autoclave (a heat-resistant and pressure-resistant sealed container), heated at a rate of 0.3 °C / min with stirring, and after reaching the aging temperature of 90 °C, it was heated at the aging temperature (90 °C) and a pressure of about 0.11 MPa for 5 hours. After the heating was completed, it was naturally cooled to room temperature with stirring, and then a slurry (dispersion) was taken out from the autoclave. The solution in the slurry was replaced with pure water and dried at 105 °C for 24 hours to obtain a powder (solid).

[0087] Subsequently, the powder was filled into an alumina crucible and heated at a rate of 3 °C / min using an electric muffle furnace KM-420 (manufactured by Advantec Toyo Co., Ltd.). After reaching the firing temperature of 300 °C, the firing temperature was maintained for 180 minutes, and then it was naturally cooled to room temperature to obtain the titanium phosphate compound-containing powder of Example 1.

[0088] [Example 2] The titanium phosphate compound-containing powder of Example 2 was obtained in the same manner as in Example 1, except that the firing temperature was 600 °C.

[0089] [Example 3] The titanium phosphate compound-containing powder of Example 3 was obtained in the same manner as in Example 1, except that the firing temperature was 756 °C.

[0090] [Comparative Example 1] The powder of Comparative Example 1 was obtained in the same manner as in Example 1, except that the firing temperature was 895 °C.

[0091] [Comparative Example 2] An aqueous phosphoric acid solution with a concentration of 85% was 25% by mass, a titanium sulfate solution with a TiO₂ equivalent of 120 g / L and a sulfuric acid concentration of 500 g / L was 29% by mass, and pure water was 46% by mass. They were mixed to obtain a mixed solution. 200 L of the mixed solution was filled into an autoclave (a heat-resistant and pressure-resistant sealed container), and while stirring, the temperature was raised at a rate of 0.3 °C / min. After reaching 130 °C, it was heated at the aging temperature (130 °C) and a pressure of about 0.13 MPa for 5 hours. Otherwise, in the same manner as in Example 1, the powder (solid) of Comparative Example 2 was obtained. The molar ratio of phosphorus to titanium in the mixed solution was [P] / [Ti] = 8.2.

[0092] [Comparative Example 3] The powder obtained in Comparative Example 2 was filled into an alumina crucible and heated using an electric muffle furnace KM-420 (manufactured by Advantec Toyo Co., Ltd.) at a heating rate of 3 °C / min. After reaching the firing temperature of 300 °C, the firing temperature was maintained for 180 minutes, and then it was naturally cooled to room temperature to obtain the fired powder of Comparative Example 3.

[0093] [Comparative Example 4] Except that the firing temperature was 756 °C, in the same manner as in Comparative Example 3, the fired powder of Comparative Example 4 was obtained.

[0094] [Comparative Example 5] Except that the firing temperature was 787 °C, in the same manner as in Comparative Example 3, the fired powder of Comparative Example 5 was obtained.

[0095] [Comparative Example 6] Except that the firing temperature was 895 °C, in the same manner as in Comparative Example 3, the fired powder of Comparative Example 6 was obtained.

[0096] Regarding the titanium phosphate compound-containing powders of each example and the powders of each comparative example obtained above, various measurements and evaluations were carried out according to the following procedures. The results of these measurements and evaluations are shown in Table 1. Among the SEM images obtained by observation with a scanning electron microscope, those of Example 1 are shown in Fig. 2(a) and those of Example 2 are shown in Fig. 2(b).

[0097] <Regarding the particle shape of the powder> [D PT 50 and D PL Measurement of 50 and calculation of aspect ratio For each of the titanium phosphate compound-containing powders of the respective examples obtained above and the powders of the respective comparative examples, measurements were randomly performed using a scanning electron microscope (SEM). The SEM images for measuring the maximum diameter (μm) in the plane direction of the primary particles and the thickness (μm) of the primary particles were specifically taken as follows.

[0098] (Taking SEM images for measuring the maximum diameter) A commercially available aluminum foil was fixed to the SEM substrate with a double-sided conductive carbon tape. Next, the powders of each example and each comparative example were mixed with methanol, respectively, and each solution was dropped onto the surface of the aluminum foil. Subsequently, by drying the solution, samples for SEM imaging of each example and each comparative example were prepared. The magnification of SEM imaging was set to 50,000 times, and samples for SEM imaging were prepared such that there were 10 or more and 50 or fewer primary particles with confirmable shapes in one field of view. Also, the imaging was performed from a direction perpendicular to the surface of the SEM substrate to which the aluminum foil was fixed, and the imaging positions were random.

[0099] (Taking SEM images for measuring the thickness) A double-sided conductive carbon tape was fixed to the surface of the SEM substrate, and the powders of each example and each comparative example were attached to the adhesive surface on the side opposite to the SEM substrate of the double-sided conductive carbon tape. Subsequently, compressed air was blown onto the adhesive surface to which the powder was attached to remove excess powder, thereby preparing samples for SEM imaging of each example and each comparative example. The magnification of SEM imaging was set to 50,000 times, and samples for SEM imaging were prepared such that there was 1 or more and 10 or fewer primary particles with confirmable shapes in one field of view. Also, the imaging was performed from a direction perpendicular to the surface of the SEM substrate to which the conductive carbon tape was fixed, and the imaging positions were random.

[0100] Next, for the obtained SEM images, using the image analysis software "Mac-View ver.4" manufactured by Mounttech Co., Ltd., primary particles (plate-like primary particles) with 100 or more and 200 or less points were measured, and the longest diameter (μm) in the plane direction of each primary particle, the planar length D of the primary particle PL 50 (μm), the thickness (μm), and the thickness D of the primary particle PT 50 (μm) were determined.

[0101] Here, the longest diameter (μm) in the plane direction of each primary particle, the planar length D of the primary particle PL 50 (μm), the thickness (μm), and the thickness D of the primary particle PT 50 (μm) were specifically measured as follows.

[0102] (Measurement of the longest diameter and the planar length D PL 50 (μm)) First, from the SEM images of each particle taken to measure the longest diameter, the SEM image of the primary particle (corresponding to the projection view in the vertical direction) that is assumed to be placed on the aluminum foil corresponding to the horizontal plane in the most stable stationary state was selected. Specifically, the SEM image of the primary particle where the upper or lower surface of the plate-like particle is observable was assumed to be the SEM image of the primary particle placed on the horizontal plane in the most stable stationary state and selected. Subsequently, the length of the straight line when the distance between two points existing on the outer peripheral line of the image of the SEM image of the primary particle is maximized was measured as the longest diameter (μm). And for the longest diameter (μm) in the plane direction of each primary particle, the value at which the cumulative frequency from the small particle size side in the volume-based cumulative particle size distribution becomes 50% was defined as the planar length D of the primary particle PL 50 (μm).

[0103] (Measurement of the longest diameter and the thickness D PT 50 (μm)) First, among the SEM images of each primary particle taken to measure the thickness, an SEM image in which the thickness direction of the plate-shaped primary particle can be observed was assumed to be an image taken from a direction substantially perpendicular to the thickness direction and selected. Subsequently, the image of the SEM image of the selected primary particle was sandwiched between two parallel lines, and the distance between the two parallel lines (the distance between the two parallel lines) when the distance between the two was the largest was taken as the thickness (μm). Also, for the thickness (μm) of each primary particle, the value at which the cumulative frequency from the small particle size side in the volume-based cumulative particle size distribution becomes 50% was defined as the thickness D PT 50 (μm).

[0104] (Calculation of aspect ratio) Then, the in-plane length D PL 50 (μm) of the primary particle calculated above and the thickness D PT 50 (μm) of the primary particle were used to calculate the aspect ratio represented by the ratio of the in-plane length D PT 50 of the primary particle to the thickness D PL 50 of the primary particle (in-plane length D PL 50 / thickness D PT 50 of the primary particle). If the aspect ratio was 5 or more and 10 or less, it was determined that the titanium phosphate compound-containing powder had a desired plate shape and sufficient usefulness was exhibited. D PL 50 and D PT 50, as well as the calculation results of the aspect ratio, are shown in Table 1. For Comparative Example 1, sintering due to firing progressed and D PT 50 exceeded 1 μm, so the measurement of D PT 50 was terminated. Therefore, for Comparative Example 1, neither D PL 50 was measured nor the aspect ratio was calculated.

[0105] [Specific surface area] For each of the titanium phosphate compound-containing powders of the respective examples obtained above and the powders of the respective comparative examples, the specific surface area was determined. Specifically, the specific surface area was measured by the BET flow method using a fully automatic specific surface area measuring device Macsorb (registered trademark) HM Model-1210 Series manufactured by Mountech Co., Ltd. The results are shown in Table 1.

[0106] [Visual confirmation of particle shape] The above "D PT 50 and D PL 50 measurement, and calculation of aspect ratio", the particle shape of the powder was visually confirmed using the SEM images of the respective examples and comparative examples. As a result, in all examples and in all comparative examples except Comparative Example 1, it was confirmed that the particle shape was plate-like. The SEM images used were those with a magnification at which 10 or more particles could be confirmed in one field of view.

[0107] <Regarding the properties of particles> [XRD analysis] For each of the titanium phosphate compound-containing powders of the respective examples obtained above and the powders of the respective comparative examples, X-ray diffraction (XRD) measurement was carried out, and the type of the titanium phosphate compound as the main component of each powder was determined based on the following criteria. The results are shown in Table 1. The conditions for XRD measurement and the criteria for determining the type of the titanium phosphate compound as the main component are as follows.

[0108] 〈XRD measurement conditions〉 Apparatus name: Sample horizontal type multi-purpose X-ray diffractometer Ultima IV (manufactured by Rigaku Corporation) Tube target: Cu Tube voltage: 20 kV Tube current: 10 mA Divergence slit: 1.0° Scattering slit: 2.0° Receiving slit: 0.15 mm Step width: 0.01° / step.

[0109] The criteria for determining the type of titanium phosphate compound that is the main component of each powder are shown below.

[0110] ≪Cubic TiP2O7 (Cubic titanium pyrophosphate)≫ The determination was made using the standard data ICDD (The International Center for Dffraction Data) PDF (Powder Diffraction File) of 038 - 1468 for TiP2O7. The TiP2O7 assigned to the said standard data (ICDD PDF of 038 - 1468) has a cubic crystal structure. In this specification, the titanium phosphate compound assigned to the said standard data is referred to as cubic TiP2O7, or cubic titanium pyrophosphate.

[0111] The specific determination method when the main component titanium phosphate compound is cubic TiP2O7 is as follows. In the comparison between the standard data (ICDD PDF of 038 - 1468) of cubic TiP2O7 and the spectrum data obtained from XRD measurement, if the top two peaks with high intensity that are specific to the said standard data are present in the spectrum data at around diffraction angle 2θ = 22.6° and around diffraction angle 2θ = 25.3° (regardless of the order of intensity), it is determined that cubic TiP2O7 is the main phase, and it is judged that cubic TiP2O7 has been generated. That is, the main component titanium phosphate compound contained in the titanium phosphate compound - containing powder is judged to be cubic TiP2O7.

[0112] ≪Non - cubic TiP2O7 (Non - cubic titanium pyrophosphate)≫ The determination was made using the standard data (ICDD PDF of 045 - 0037) of TiP2O7. The TiP2O7 assigned to the said standard data (ICDD PDF of 045 - 0037) has an unknown crystal structure. In this specification, the titanium phosphate compound assigned to the said standard data is referred to as non - cubic TiP2O7, or non - cubic titanium pyrophosphate.

[0113] When the main component titanium phosphate compound is non-cubic TiP2O7, the specific determination method is as follows. In the comparison between the standard data of non-cubic TiP2O7 (ICDD PDF 045-0037) and the spectral data obtained from XRD measurement, similar to the two peaks with high intensity uniquely found in the standard data, when the two peaks with high intensity in the spectral data are present around diffraction angle 2θ = 12.7° and around diffraction angle 2θ = 20.9° (regardless of the order of intensity), it is determined that non-cubic TiP2O7 is the main phase and it is judged that non-cubic TiP2O7 has been generated. That is, it is judged that the main component titanium phosphate compound contained in the titanium phosphate compound-containing powder is non-cubic TiP2O7.

[0114] ≪Ti(HPO4)2 (anhydrous titanium hydrogen phosphate)≫ In the comparison between the standard data of Ti(HPO4)2 (ICDD PDF 032-1369) and the spectral data obtained from XRD measurement, similar to the two peaks with high intensity uniquely found in the standard data, when the two peaks with high intensity in the spectral data are present around diffraction angle 2θ = 11.9° and around diffraction angle 2θ = 24.9° (regardless of the order of intensity), it is determined that Ti(HPO4)2 is the main phase and it is judged that Ti(HPO4)2 has been generated. That is, it is judged that the main component titanium phosphate compound contained in the titanium phosphate compound-containing powder is Ti(HPO4)2.

[0115] ≪Ti(HPO4)2·H2O (monohydrate titanium hydrogen phosphate)≫ In the comparison between the standard data of Ti(HPO4)2·H2O (ICDD PDF No. 083-0109) and the spectral data obtained from XRD measurement, when the top two peaks with high intensity, which are peculiar to the standard data, and the top two peaks with high intensity in the spectral data are present near diffraction angle 2θ = 11.6° and near diffraction angle 2θ = 25.7° (regardless of the order of intensity), it was determined that Ti(HPO4)2·H2O is the main phase and it was judged that Ti(HPO4)2·H2O was generated. That is, the titanium phosphate compound as the main component contained in the titanium phosphate compound-containing powder was judged to be Ti(HPO4)2·H2O.

[0116] Figure 1 shows the spectra of the titanium phosphate compound-containing powder of Example 1 (i in Figure 1), the spectra of the titanium phosphate compound-containing powder of Example 2 (iii in Figure 1), and the spectra of the powder of Comparative Example 1 (v in Figure 1) in the XRD measurement. Also shown in Figure 1 are the spectra of the standard data (standard chart) of Ti(HPO4)2 (ii in Figure 1), the spectra of the standard data of non-cubic TiP2O7 (iv in Figure 1), and the spectra of the standard data of cubic TiP2O7 (vi in Figure 1).

[0117] As shown in Figure 1, in the spectrum of Example 1, the top two peaks with high intensity were found at the positions of the peaks peculiar to the standard data of Ti(HPO4)2 described above (near diffraction angle 2θ = 11.9° and near diffraction angle 2θ = 24.9°). On the other hand, in the spectrum of Example 1, no peaks peculiar to the standard data of other titanium phosphate compounds (in this case, cubic TiP2O7, non-cubic TiP2O7, and Ti(HPO4)2·H2O) were found. Therefore, it was judged that the titanium phosphate compound as the main component contained in the titanium phosphate compound-containing powder of Example 1 is Ti(HPO4)2 as the main phase, and the content of Ti(HPO4)2 in the titanium phosphate compound-containing powder is 80% or more.

[0118] As shown in Fig. 1, in the spectrum of Example 2, the top two peaks with high intensity were found at the peak positions (near 2θ = 12.7° and near diffraction angle 2θ = 20.9°) specific to the standard data of the above-mentioned non-cubic TiP2O7. On the other hand, in the spectrum of Example 2, no peaks specific to the standard data of other titanium phosphate compounds (in this case, cubic TiP2O7, Ti(HPO4)2, and Ti(HPO4)2·H2O) were found. Therefore, it was determined that the main component titanium phosphate compound contained in the titanium phosphate compound-containing powder of Example 2 is non-cubic TiP2O7 as the main phase, and the content of non-cubic TiP2O7 in the titanium phosphate compound-containing powder is 80% or more.

[0119] In the spectrum of Example 3 (not shown), similar to Example 2, the top two peaks with high intensity were found at the peak positions (near 2θ = 12.7° and near diffraction angle 2θ = 20.9°) specific to the standard data of the above-mentioned non-cubic TiP2O7, and no peaks specific to the standard data of other titanium phosphate compounds were found. Therefore, it was determined that the main component titanium phosphate compound contained in the titanium phosphate compound-containing powder of Example 3 is non-cubic TiP2O7 as the main phase, and the content of non-cubic TiP2O7 in the titanium phosphate compound-containing powder is 80% or more.

[0120] As shown in Fig. 1, in the spectrum of Comparative Example 1, the top two peaks with high intensity were found at the peak positions (near diffraction angle 2θ = 22.6° and near diffraction angle 2θ = 25.3°) specific to the standard data of the above-mentioned cubic TiP2O7. On the other hand, in the spectrum of Comparative Example 1, no peaks specific to the standard data of other titanium phosphate compounds (in this case, non-cubic TiP2O7, Ti(HPO4)2, and Ti(HPO4)2·H2O) were found. Therefore, it was determined that the main component titanium phosphate compound contained in the titanium phosphate compound-containing powder of Comparative Example 1 is cubic TiP2O7 as the main phase, and the content of cubic TiP2O7 in the titanium phosphate compound-containing powder is 80% or more.

[0121] Similarly to the above, for Comparative Examples 2 to 6, the types of the main phases of the titanium phosphate compounds, which are the main components of each powder, were also determined. The results are shown in Table 1. In each of the powders of Comparative Examples 2 to 6, the content of the titanium phosphate compound forming the main phase in the powder was 80% or more. For example, in the powder of Comparative Example 2, the main component titanium phosphate compound was Ti(HPO4)2·H2O as the main phase, and it was determined that the content of Ti(HPO4)2·H2O in the titanium phosphate compound-containing powder was 80% or more.

[0122] <Measurement of pH> For each of the titanium phosphate compound-containing powders of the respective Examples obtained above and the powders of the respective Comparative Examples, an aqueous dispersion was prepared, and the pH of the aqueous dispersion was measured. More specifically, the titanium phosphate compound-containing powder or powder was mixed with pure water to obtain an aqueous dispersion having a solid content concentration of 1% by mass, and the pH of the aqueous dispersion was measured at 25°C. The pH was measured using a pH meter (model number: F-51, manufactured by Horiba, Ltd.). When the pH was 3.5 or less, it was determined as ○, and when the pH exceeded 3.5, it was determined as ×. The results are shown in Table 1.

[0123] <Measurement of Electrical Conductivity> For each of the titanium phosphate compound-containing powders of the respective Examples obtained above and the powders of the respective Comparative Examples, an aqueous dispersion was prepared, and the electrical conductivity (mS / cm) of the aqueous dispersion was measured. More specifically, the titanium phosphate compound-containing powder or powder was mixed with pure water to obtain an aqueous dispersion having a solid content concentration of 1% by mass, and the electrical conductivity of the aqueous dispersion was measured at 25°C. The electrical conductivity was measured using a desktop electrical conductivity meter (model number: DS-71, manufactured by Horiba, Ltd.). When the electrical conductivity was 0.20 mS / cm or more, it was determined as ○, and when the electrical conductivity was less than 0.20 mS / cm, it was determined as ×. The results are shown in Table 1.

[0124]

Table 1

[0125] From the results shown in Table 1, the titanium phosphate compound-containing powders of Examples 1 to 3 had a larger specific surface area than the comparative examples. In addition, the titanium phosphate compound-containing powders of Examples 1 to 3 showed the results that, in addition to having a low pH, they had good electrical conductivity. Thus, the titanium phosphate compound-containing powders of Examples 1 to 3 are considered to have high utility. For example, they can be suitably used as raw materials for lithium ion conductors used in lithium ion secondary batteries and the like, or as raw materials for agricultural fertilizers.

Claims

1. A titanium phosphate compound-containing powder mainly composed of a titanium phosphate compound, wherein the titanium phosphate compound is one or more selected from the group consisting of a compound represented by the chemical formula TiPO ２ O ７ , a compound represented by the chemical formula Ti(HPO ４ ) ２ , and a compound represented by the chemical formula Ti(HPO ４ ) ２ ·H ２ O; the aspect ratio represented by the ratio (primary particle surface direction length D ＰＴ 50 / primary particle thickness D ＰＬ 50) of the primary particle surface direction length D ＰＬ 50 at which the cumulative frequency from the small particle size side is 50% in the cumulative thickness distribution based on volume to the primary particle thickness D ＰＴ 50 at which the cumulative frequency from the small particle size side is 50% in the cumulative surface direction length distribution based on volume is 5 or more and 10 or less; and the specific surface area is 20 m ２ / g or more and 50 m ２ / g or less. Titanium phosphate compound-containing powder.

2. The titanium phosphate compound-containing powder according to claim 1, wherein D ＰＬ 50 is 0.1 μm or more and less than 1 μm.

3. The titanium phosphate compound-containing powder according to claim 1 or 2, wherein the pH of the aqueous dispersion having a solid content concentration of 1% by mass is 4.0 or less.

4. The titanium phosphate compound-containing powder according to claim 1 or 2, wherein the electric conductivity of the aqueous dispersion having a solid content concentration of 1% by mass is 0.2 mS / cm or more.

5. The titanium phosphate compound-containing powder according to claim 1 or 2, wherein the titanium phosphate compound is one or more selected from the group consisting of a compound represented by the chemical formula TiPO ２ O ７ and a compound represented by the chemical formula Ti(HPO ４ ) ２ .

6. The compound represented by the chemical formula TiP ２ O ７ is a non-cubic TiP ２ O ７ The titanium phosphate compound-containing powder according to claim 1 or 2.

7. A method for producing the titanium phosphate compound-containing powder according to claim 1, comprising a synthesis step of synthesizing a raw material containing titanium and phosphorus to obtain a reaction solution, wherein the reaction temperature in the synthesis step is 80°C or higher and lower than 130°C, and the reaction time is 1 hour or longer and 72 hours or shorter.

8. The production method according to claim 7, having a firing step of firing the solid separated from the reaction solution at a temperature of 200°C or higher and 850°C or lower.

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