JP2016010753A - Method for producing powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily acquire particulates by treatment different from treatment using a grinding aid.SOLUTION: Dry grinding treatment is applied to a substance including a crystal of a metallic compound so that an easy-to-dissolve area and a hard-to-dissolve area, relatively different in easiness of dissolution into a solvent from each other, can be produced in each particle in a ground product after grinding (S1). The solvent is adjusted so that a specific surface area of finally obtained powder can become large (S2). The solvent after adjustment is added to the ground product after the dry grinding treatment (S3). The powder is acquired from the inside of the solvent (S4).

Description

  The present invention is a method for producing a powder by subjecting a substance containing a crystal of a metal compound to a dry pulverization treatment.

  A dry pulverization method is widely used as a method for pulverizing metal compounds. However, when the dry pulverization method is used, it is usually very difficult to obtain fine particles having a size of less than 1 micrometer, that is, nanometer size (hereinafter also referred to as nanoparticles). This is because, if the dry pulverization process is continued, the pulverized and mixed particles are aggregated to increase the particle size, and a phenomenon called reverse pulverization occurs.

  In order to compensate for the drawbacks of such dry pulverization methods, a technique of adding a pulverization aid during pulverization is used. In Patent Document 1, alcohols such as methanol and ethanol, and liquids that volatilize at low temperatures such as hexane, toluene, and acetone are used as grinding aids. It is considered that a grinding aid that is liquid at the time of addition is easier to handle than a grinding aid that is a gas at the time of addition. Moreover, since it volatilizes after addition, it is thought that it is excellent in the dispersibility compared with the solid or liquid auxiliary agent.

JP 2003-305378 A

  However, even if a highly volatile grinding aid is used, it is liquid when added. For this reason, dispersibility is low compared with the case where a gaseous auxiliary agent is added. On the other hand, gaseous auxiliaries are more difficult to handle than liquid or solid pulverization auxiliaries. Thus, no matter what form of grinding aid is used, there are problems in terms of dispersibility and ease of handling. For this reason, even if a grinding aid is used, there is a limit to a method for obtaining fine particles (particularly nanoparticles).

  An object of the present invention is to provide a method for producing a powder that makes it easy to obtain fine particles by a treatment different from that using a grinding aid.

  As a result of intensive studies on the reason why nanoparticles cannot be obtained by the dry pulverization method, the present inventors have reached the following findings. In the pulverized substance, relatively large particles composed of two regions having different properties are formed. From various experimental results, it is considered that one of the two regions is a region made of a crystalline part and the other is a region made of an amorphous part. The crystalline part is mainly composed of single crystal or polycrystal. On the other hand, the amorphous part is mainly composed of a region having no crystal structure. Even if the crystalline part becomes a fine particle to some extent by pulverization, the crystalline part aggregates with each other through a region composed of an amorphous part, so that a large particle is formed as a whole. For this reason, it is considered that the reason why it is difficult to finally obtain nanoparticles by the dry pulverization method is as follows.

  On the other hand, since the amorphous part is mainly composed of a region having no crystal structure, it is more easily dissolved in a solvent such as water than the crystalline part. For this reason, each particle | grain of the pulverized material which arises after a grinding | pulverization contains two area | regions where the easiness to melt | dissolve in a solvent differs relatively.

  Based on the above findings, the present inventor has reached the following powder production method that makes it easy to obtain fine particle powder while using the dry pulverization method. That is, a powder manufacturing method for obtaining a powder of a substance containing a crystal of a metal compound, wherein an easily soluble region and a hardly soluble region that are relatively different in solubility in a solvent are in a pulverized product after pulverization. A pulverizing step for subjecting the substance to a dry pulverization process so as to occur in each of the particles, an adjusting step for adjusting a solvent, an adding step for adding the adjusted solvent to the pulverized product after the dry pulverizing treatment, An acquisition step of acquiring the powder of the substance from the solvent. In the adjustment step, the solvent is adjusted so that a specific surface area of the powder acquired in the acquisition step is increased.

  According to the present invention, first, each particle in the pulverized product after pulverization is caused by dry pulverization to generate an easily soluble region that is easy to dissolve in a solvent and a hardly soluble region that is difficult to dissolve. And an easy-dissolution area | region is dissolved in a solvent by adding a solvent to the ground material after grinding. At this time, the solvent is adjusted so that the specific surface area of the finally obtained powder becomes large. As a method of adjustment, you may adjust so that an easily melt | dissolution area | region may become easy to melt | dissolve. This adjustment relates to temperature and pH, for example. As the easily soluble region dissolves in the solvent, the hardly soluble region mainly remains in each particle. For this reason, fine particles mainly consisting of a hardly soluble region are easily generated in the powder. In the solvent adjustment step, since the specific surface area of the finally obtained powder is adjusted to be large, a powder having a large specific surface area can be obtained.

  Thus, according to the present invention, a method for producing a powder that makes it easy to obtain a fine particle powder by a process different from the use of a grinding aid is realized.

  In the present invention, it is preferable to adjust at least one of temperature and pH of the solvent in the adjustment step. According to this, for example, when the easy-dissolving region is easily dissolved according to the temperature change of the solvent, the temperature of the solvent is changed so that the easily-dissolving region is easily dissolved in the solvent. In addition, the solvent is adjusted to a pH that increases the specific surface area of the powder according to the acidity and basicity of the metal compound. By these, fine powder can be obtained.

  In the present invention, in the adjustment step, when the substance is a substance whose solubility in the solvent increases as the temperature rises, the solvent is heated, and the substance responds as the temperature rises. It is preferable to cool the solvent when the substance has low solubility in water. According to this, the easily soluble region can be easily dissolved in the solvent by changing the temperature of the solvent in accordance with the change in the solubility of the substance with respect to the temperature change of the solvent. It is known in advance for many substances how the solubility changes with temperature. For this reason, it is possible to adjust the solvent so that the easily soluble region can be easily dissolved based on the existing knowledge without actually examining the solubility of the easily soluble region with respect to the temperature change.

  In the present invention, the metal compound may contain at least one of an inorganic carbonate and a metal oxide.

  In the present invention, the main component of the solvent may be water. It has been confirmed that fine powder having a large specific surface area can be obtained when the solvent is water.

  Moreover, in this invention, when the said substance is a shell, it is preferable that the temperature of the said solvent is 5 to 60 degreeC. When the shell is pulverized, a large amount of fine powder can be obtained when the temperature of the water is in the range of 5 ° C to 60 ° C.

  Moreover, in this invention, when the said substance is a shell, it is preferable that the pH of the solvent after the said adjustment is the range to the value in 0.5-7.0. When the shell is crushed, as the pH condition, a large amount of fine particle powder can be obtained in the range of the pH value of water from 0.5 to 7.0.

  Moreover, in this invention, when the said metal compound is aluminum oxide in the said adjustment process, it is preferable to heat the temperature of the said solvent to 40 degreeC or more. When a substance containing aluminum oxide crystals is pulverized, a large amount of fine powder can be obtained when the temperature of the water is heated to 40 ° C. or higher.

FIG. 1 is a flow diagram of the powder production method of the present invention. FIG. 2 is a schematic diagram illustrating a model relating to a particle state of a substance including a crystal of a metal compound. FIG. 3 is a graph showing the results of measuring the specific surface area of the calcium carbonate powder in Example 1 and Comparative Example 1. FIG. 4 is a graph showing the results of measuring the specific surface area of the strontium carbonate powder in Example 2 and Comparative Example 2. FIG. 5 is a graph showing the results of measuring the specific surface area of the magnesium carbonate powder in Example 3 and Comparative Example 3. FIG. 6 is a graph showing the results of measuring the specific surface area of the aluminum oxide powder in Example 4. FIG. 7 is a graph showing the results of measuring the specific surface area of the calcium carbonate powder in Example 5. FIG. 8 is a graph showing the results of measuring the specific surface area of the calcium carbonate powder in Example 6.

  Hereinafter, a method for producing a powder according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. The method for producing the powder is a method for obtaining powder from a substance containing metal compound crystals. Substances to be crushed (hereinafter referred to as “target substances”) include substances existing in nature such as shells. Examples of the metal compound include inorganic carbonates such as calcium carbonate, magnesium carbonate, and strontium carbonate, and metal oxides such as aluminum oxide and titanium oxide.

The manufacturing method of this powder is performed according to the flow shown in FIG. First, in the dry pulverization step of S1, the target substance is dry pulverized. As long as the desired effect of the present invention is not impaired, a grinding aid can be appropriately added as necessary. For the dry pulverization, any conventionally known method such as a ball mill, a jet mill or a vibration mill can be used. For example, when adopting a ball mill, the material of the balls used in the ball mill (zirconia, stainless steel, etc.), size and diameter, and the rotation speed and grinding time of the ball mill are such that the specific surface area of the powder obtained by grinding is increased. It is desirable to adjust appropriately. The specific surface area is the surface area per unit mass of the particles contained in the powder (m ² / g). As the particles in the powder become smaller, the surface area of the particles per unit mass increases. For this reason, the specific surface area is an index of particle size.

  Next, in the solvent adjustment step of S2, the temperature, pH, etc. of the solvent added to the pulverized product after the step of S1 are adjusted. In this embodiment, water is used. However, water may not be the main component depending on the characteristics of the target substance. When adjusting the temperature, the solvent is heated when the target substance is a substance whose solubility in the solvent increases as the temperature rises. On the other hand, when the target substance is a substance whose solubility in the solvent decreases with increasing temperature, the solvent is cooled. The pH is adjusted by adding water such as nitric acid, acetic acid or hydrochloric acid, adding a base such as sodium hydroxide or potassium hydroxide, or preparing water to distilled water by desalting and purification. In the case of distilled water, the pH will be adjusted to around 7.0. When the target substance is a shell, the temperature of the solvent is preferably 5 ° C to 60 ° C. Moreover, it is preferable that pH of a solvent is the range of 0.5-7.0. When the metal compound contained in the target substance is aluminum oxide, it is preferable to heat the solvent to 40 ° C. or higher. In addition, the timing which performs the process of S2 is not restricted after S1. This step may be performed any time before the step of S3, for example, may be performed in parallel with S1.

  In the solvent addition step of S3, the solvent adjusted in the step S2 is added to the pulverized product obtained in the step S1. After the addition, depending on the type of the object, in order to dissolve the pulverized material, an appropriate time, standing or stirring may be performed. In the powder acquisition step of S4, powder is acquired from the mixture of the pulverized product and the solvent obtained in step S3. In step S4, the mixture may be subjected to solid-liquid separation such as centrifugation, filtration, and filter press, and then dried in a dryer, or the mixture may be directly dried in a dryer or naturally dried. Thus, various methods can be used for the process of S4. For example, when centrifugation is performed as solid-liquid separation, after centrifugation, the supernatant of the solvent is removed from the mixture, and the precipitate in the solvent is taken out. The number of rotations and the rotation time of the centrifugal separation are not particularly limited as long as the precipitate can be obtained from the mixture of the pulverized material and the solvent. When the precipitated substance taken out from the solvent is dried after centrifugation, the drying time and drying temperature can be appropriately changed depending on the target substance. Further, after centrifugation, the precipitate taken out from the solvent may be naturally dried. Centrifugation of the mixture can previously remove much of the solvent from the mixture. For this reason, when performing solid-liquid separation, the time required for subsequent drying may be shortened, and the energy input to drying may be reduced.

  Next, a model related to the particle state of the target substance in the steps S1, S3, and S4 will be described. A model as shown in FIG. 2 is estimated as a model that is consistent with the examples described later. From the target substance 1, a crystalline part 2 that is minute to some extent is generated by the dry pulverization step of S1. The crystalline part 2 is mainly composed of single crystal or polycrystal. However, even if the crystalline part 2 of the fine particles is generated, the fine particles are aggregated with each other through the region composed of the amorphous part 3, so that the pulverized product as a result of the pulverization is large as a whole. Particles are formed. The amorphous part 3 is mainly composed of a region having no crystal structure. This is the reason why it is difficult to finally obtain nanoparticle powder by the dry pulverization method.

  By the way, the amorphous part 3 is more soluble in the solvent than the crystalline part 2. That is, after the dry pulverization step of S1, two regions of an easily soluble region and a hardly soluble region that are relatively different in solubility in a solvent are generated in the object 1. The amorphous part 3 corresponds to a readily soluble region, and the crystalline part 2 corresponds to a hardly soluble region. In the present embodiment, the easily soluble region and the hardly soluble region are regions generated in each particle in the pulverized product immediately after pulverization, and the easiness of dissolution in a solvent is relatively different in the particles immediately after pulverization. An area.

  Therefore, in the present embodiment, the dry pulverization of S1 is performed until the crystalline part 2 considered to be the reason why it is difficult to form the nanoparticle powder by the dry pulverization method through the amorphous part 3. The object 1 is pulverized in the process. Furthermore, the solvent is adjusted so that the specific surface area of the finally obtained powder 5 is increased in the solvent adjustment step of S2. For example, the temperature of the solvent is adjusted so that the amorphous portion 3 that is an easily soluble region is easier to dissolve than before the adjustment. As a result, even if the metal compound contained in the substance is a hardly soluble substance such as calcium carbonate, the amorphous part 3 is dissolved in the solvent in the solvent addition step of S3, so that the hardly soluble region aggregated. The crystalline part 2 is dispersed as particles 4. In some cases, the pH and the like of the solvent may be adjusted so that the amorphous part 3 that is an easily soluble region is less soluble than before the adjustment. What is necessary is just to adjust a solvent so that the specific surface area of the powder 5 finally acquired may become large.

And the powder 5 which consists of microparticles | fine-particles with a large specific surface area mainly comprised from the crystalline part 2 can be acquired by the powder acquisition process of S4. According to this method, fine powder having a specific surface area of 12.4 to 26.4 m ² / g was obtained, for example, in Examples described later relating to calcium carbonate. A specific surface area of 12.4 to 26.4 m ² / g corresponds to an average particle diameter (specific surface area sphere equivalent diameter) of 82 to 175 nm. Therefore, according to this embodiment, it turns out that a nanoparticle is obtained.

[Example 1] (Specific surface area when water is added after dry grinding of calcium carbonate)
Calcium carbonate (specific surface area 0.55 m ² / g) and zirconia balls (diameter 3 mm) were previously dried at 60 ° C. for 12 hours. Next, 10.0 g of dried calcium carbonate and 100.0 g of zirconia balls were put into a stainless steel mill pot (80 cm ³ ), and dry pulverized using a planetary ball mill device (Premium line P-7 manufactured by FRITSCH) (S1). ). The number of rotations was 900 rpm, and pulverization was performed for 15 minutes to 240 minutes (15 minutes, 30 minutes, 60 minutes, 120 minutes, and 240 minutes).

  Next, desalting and purification by distillation (manufactured by Yamato Kagaku, WG250) was applied to water, distilled water was prepared, and the solvent was adjusted (S2). 40 mL of distilled water was added to the pulverized product after pulverization (S3). The collected mixture was centrifuged at a rotational speed of 3500 rpm for 15 minutes (Kubota Corp., universal cooling centrifuge 5800). The supernatant was removed from the centrifuged mixture, and the precipitate was immediately taken out and dried at 60 ° C. overnight to obtain calcium carbonate powder (S4). Thereafter, the specific surface area of the calcium carbonate powder was measured with a nitrogen adsorption amount measuring apparatus (Nisso, Adsotrac-DN-04).

[Comparative Example 1] (Specific surface area when water is not added after dry grinding of calcium carbonate)
The process up to the dry pulverization described in Example 1 was similarly performed, and then the specific surface area was measured in the same manner as in Example 1.

  When Example 1 and Comparative Example 1 were compared, Example 1 was able to obtain a powder having a larger specific surface area at all grinding times (FIG. 3). In FIG. 3, the black squares indicate the specific surface area of the raw material calcium carbonate.

[Example 2] (Specific surface area when water is added after dry pulverization of strontium carbonate)
The treatment was performed in the same manner as in Example 1 except that the calcium carbonate of Example 1 was changed to strontium carbonate (specific surface area of 5.9 m ² / g).

[Comparative Example 2] (Specific surface area when water is not added after dry pulverization of strontium carbonate)
The process up to the dry pulverization described in Example 2 was similarly performed, and then the specific surface area was measured in the same manner as in Example 2.

  When Example 2 and Comparative Example 2 were compared, Example 2 was able to obtain a powder having a larger specific surface area at all grinding times (FIG. 4). In FIG. 4, the black squares represent the specific surface area of the raw material strontium carbonate.

[Example 3] (Specific surface area when water is added after magnesium carbonate is dry-pulverized)
The treatment was performed in the same manner as in Example 1 except that the calcium carbonate of Example 1 was changed to magnesium carbonate (specific surface area of 1.4 m ² / g).

[Comparative Example 3] (Specific surface area when water is not added after dry pulverization of magnesium carbonate)
The process up to the dry pulverization described in Example 3 was similarly performed, and then the specific surface area was measured in the same manner as in Example 3.

  When Example 3 and Comparative Example 3 were compared, Example 3 was able to obtain a powder having a larger specific surface area at all grinding times (FIG. 5). In FIG. 5, the black squares indicate the specific surface area of the raw material magnesium carbonate.

[Example 4] (Specific surface area when water of different temperature is added to dry-milled aluminum oxide)
Aluminum oxide (specific surface area 0.8 m ² / g) and zirconia balls (diameter 3 mm) were previously dried at 60 ° C. for 12 hours. 100.0 g of zirconia balls were put into a stainless steel mill pot (80 cm ³ ), and dry pulverization treatment was performed for 30 minutes at a rotation speed of 1000 rpm using a planetary ball mill device (Premium line P-7 manufactured by FRITSCH) (S1 ). Demineralization purification by distillation (manufactured by Yamato Kagaku, WG250) was applied to water to prepare distilled water. And several types from which temperature differs by cooling or heating distilled water so that the temperature of distilled water may be 5 degreeC-70 degreeC (5 degreeC, 20 degreeC, 40 degreeC, 50 degreeC, 60 degreeC or 70 degreeC). Of distilled water was prepared (S2).

  Next, 10 mL of the solvent adjusted in the step S2 was added to 1.0 g of the aluminum oxide that had been pulverized, and the aluminum oxide was allowed to stand for 30 minutes in a thermostat set to the same temperature as the added solvent (S3). ). The mixture of pulverized aluminum oxide and solvent was centrifuged at a rotational speed of 3500 rpm for 15 minutes. The supernatant was removed from the centrifuged mixture, and the precipitate was immediately taken out and dried at 60 ° C. overnight to obtain an aluminum oxide powder (S4). Thereafter, the specific surface area of the aluminum oxide powder was measured with a nitrogen adsorption amount measuring apparatus (Nisso, Adsotrac-DN-04).

[Comparative Example 4] (Specific surface area when water of different temperature was added to aluminum oxide without dry pulverization)
It adjusted to 5 to 70 degreeC (5 degreeC, 20 degreeC, 40 degreeC, 50 degreeC, 60 degreeC or 70 degreeC) to 1.0g of aluminum oxide (specific surface area 0.8m < ² > / g) which has not performed the dry-type grinding | pulverization process. Distilled water 10mL was added and it left still for 30 minutes in the thermostat set to the same temperature as the added distilled water. The mixture of pulverized aluminum oxide and solvent was centrifuged at a rotational speed of 3500 rpm for 15 minutes. The supernatant was removed from the mixture, and the precipitate was immediately taken and dried at 60 ° C. overnight to obtain an aluminum oxide powder.

  When Example 4 and Comparative Example 4 are compared, the specific surface area of the aluminum oxide powder of Example 4 is greatly increased with distilled water of 40 ° C. or higher. That is, compared with the aluminum oxide powder added with distilled water of 40 ° C. or higher without performing the dry pulverization treatment, the aluminum oxide powder added with distilled water of 40 ° C. or higher after the dry pulverization processing is more specific. This means that the surface area is large. Based on the above comparison results and the fact that the higher the temperature, the higher the solubility of aluminum oxide, and the higher the temperature, the higher the temperature, the pulverized material after the pulverization treatment has an amorphous part that is an easily soluble region. Perceived to be dissolved in a solvent. On the other hand, the aluminum oxide powder of Comparative Example 4 that has not undergone the dry pulverization treatment and in which the easy dissolution region is not formed is considered to have a considerably smaller specific surface area than that of Example 4. (FIG. 6). In FIG. 6, the black squares indicate the specific surface area of the raw material aluminum oxide.

[Example 5] (Specific surface area when water with changed pH is added to scallop shell after dry pulverization)
Scallop shell coarse powder (manufactured by Tokoro Town Industrial Promotion Corporation, specific surface area 1.5 m ² / g, average particle size 20 μm) and zirconia balls (3 mm) at 80 ° C. 8 in advance with calcium carbonate and a small amount of organic compound as main components Dry for more than an hour. 60.0 g of zirconia balls and 5.00 g of coarse scallop shells are put into a stainless steel mill pot (45 cc), and dry pulverization treatment is performed at 400 rpm for 24 hours using a planetary ball mill device (Premium line P-7 manufactured by FRITSCH). Went (S1).

  Next, desalting purification by distillation (manufactured by Yamato Kagaku, WG250) is applied to water to prepare distilled water, and the pH of the obtained distilled water is adjusted to nitric acid (purity 60 to 61%, manufactured by Kanto Chemical). Then, by adjusting the pH to 0.5 to 7.0 (pH 0.5, pH 1.0, pH 3.0, pH 5.0 or pH 7.0), a plurality of types of solvents having different pHs were prepared (S2). 10 mL of each solvent adjusted in the step S2 was added to 1.00 g of scallop shell coarse powder subjected to the dry pulverization treatment, and the mixture was allowed to stand for 30 minutes (S3). Thereafter, using a micro high speed cooling centrifuge (MX-301 manufactured by Tommy Seiko Co., Ltd.), the mixture of the scallop shell coarse powder and the solvent was centrifuged at 20 ° C. and a rotational speed of 3500 rpm for 1 minute. The supernatant was removed from the mixture after centrifugation and vacuum dried for 12 hours or more to obtain calcium carbonate powder (S4).

  According to the results of Example 5, the specific surface area of the calcium carbonate powder is maximized when the solvent having pH 7.0 is added, and the specific surface area decreases as the acidity of the added solvent increases (FIG. 7). ). It is considered that the specific surface area was reduced by the bonding of the fine particles when the eluted calcium carbonate precipitated. Calcium carbonate is easily dissolved in a highly acidic solvent. For this reason, when preparing distilled water of pH 7.0 from water with low pH, it is thought that an easily soluble area | region becomes difficult to melt | dissolve. On the other hand, Example 5 leads to an increase in the specific surface area of the finally obtained powder by adjusting the pH to 7.0. Thus, it is preferable to adjust a solvent so that the specific surface area of the powder finally acquired may become large even if it is adjustment which becomes easy to melt | dissolve an easily melt | dissolving area | region.

[Example 6] (Specific surface area when distilled water whose temperature has been changed is added to scallop shells after dry grinding)
The water was subjected to desalting purification by distillation (manufactured by Yamato Kagaku, WG250) to prepare distilled water. And distilled water was cooled or heated so that the temperature of distilled water might be 5 to 90 degreeC (5 degreeC, 20 degreeC, 40 degreeC, 60 degreeC, 70 degreeC or 90 degreeC), and the solvent was adjusted (S2). . Then, the adjusted solvent was added to the pulverized product dry-pulverized by the method of Example 5, and the scallop shell coarse powder pulverized product in a thermostatic bath (LTB-125 manufactured by AS ONE) set to the same temperature as the solvent. The solvent mixture was allowed to stand for 30 minutes (S3). Other processes are the same as those in the fifth embodiment.

  According to the result of Example 6, the non-surface area of the calcium carbonate powder is reduced when the solvent is at a high temperature of 70 ° C. or higher (FIG. 8). This is because calcium carbonate becomes difficult to dissolve when the temperature rises, so as the solubility of calcium carbonate decreases, the amount of dissolution in the easy-dissolving region of each particle in the calcium carbonate pulverized product decreases, and the specific surface area increases. It is thought that it did not increase.

The above is a description of a preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the means for solving the problem. It is possible.

  According to the present invention, an adsorbent capable of adsorbing formaldehyde can be developed using scallop shell powder pulverized into nanoparticles. In addition, it can be used in various fields to which nanoparticles can be applied, such as cosmetics having an excellent ultraviolet shielding effect.

Claims (8)

A method for producing a powder for obtaining a powder of a substance containing a crystal of a metal compound,
A pulverization step of subjecting the substance to a dry pulverization treatment such that an easily soluble region and a hardly soluble region that are relatively easily dissolved in a solvent are generated in each particle in the pulverized product after pulverization;
An adjustment step of adjusting the solvent;
An addition step of adding the adjusted solvent to the pulverized product after the dry pulverization treatment;
An acquisition step of acquiring the powder of the substance from the solvent,
The said adjustment process WHEREIN: The said solvent is adjusted so that the specific surface area of the said powder acquired at the said acquisition process may become large, The manufacturing method of the powder characterized by the above-mentioned.   The method for producing a powder according to claim 1, wherein in the adjusting step, at least one of a temperature and a pH of the solvent is adjusted.   In the adjusting step, when the substance is a substance whose solubility in the solvent increases with an increase in temperature, the solvent is heated, and the substance becomes less soluble in the solvent with an increase in temperature. The method for producing a powder according to claim 2, wherein the solvent is cooled in the case of.   The said metal compound contains at least any one of inorganic carbonate and a metal oxide, The manufacturing method of the powder of any one of Claims 1-3 characterized by the above-mentioned.   The method for producing a powder according to any one of claims 1 to 4, wherein a main component of the solvent is water.   The method for producing a powder according to claim 5, wherein the temperature of the solvent is 5 ° C. to 60 ° C. when the substance is a shell.   The method for producing a powder according to claim 5, wherein when the substance is a shell, the pH of the solvent after the adjustment is in the range of 0.5 to 7.0.   In the said adjustment process, when the said metal compound is aluminum oxide, the temperature of the said solvent is heated to 40 degreeC or more, The manufacturing method of the powder of Claim 5 characterized by the above-mentioned.