JP2024020773A - powder composition - Google Patents

Abstract

To provide a powder composition that is hardly solidified during transportation and storage.SOLUTION: A powder composition comprises a water-soluble powder that is powder of a water-soluble compound, and a water-insoluble powder that is powder of a water-insoluble compound. At a temperature of 30°C and a relative humidity of 90%, the water-insoluble powder has an amount of steam adsorbed W90 per 1 g of the powder composition, and at a temperature of 30°C and a relative humidity of 50%, the water-insoluble powder has an amount of steam adsorbed W50 per 1 g of the powder composition. The powder composition has a difference W90-W50 of 1.5 cm3/g or more.SELECTED DRAWING: None

Description

The present invention relates to powder compositions.

For example, water-soluble powders such as sodium hydrogen carbonate become difficult to handle when they solidify into lumps.
Patent Document 1 relates to an acidic component removing agent containing sodium hydrogen carbonate for removing acidic components in exhaust gas generated during waste incineration processing. Powdered acidic component remover is stored in a silo, from which it is transported using a gas flow and supplied into the exhaust gas, reacted with the acidic components in the exhaust gas, and then sent to the bag filter. An example of an acidic component remover is described in which a specific colloidal calcium carbonate and a specific hydrophobic fumed silica are added to sodium bicarbonate in order to improve the fluidity and pressure characteristics in bag filters.

International Publication No. 2018/012434

According to the findings of the present inventors, when an acidic component remover containing sodium bicarbonate is transported or stored in a powder transport vehicle equipped with a tank (loading container), there are problems when loading it into the tank. Even if it is not present, caking or sticking may occur inside the tank, making it difficult to extract it.
Patent Document 1 is intended to improve the fluidity of the acidic component removing agent in the flow path of exhaust gas treatment equipment, etc., and does not take into account the problem of state changes within the tank (loading container).
An object of the present invention is to provide a powder composition that is unlikely to cause caking or sticking during transportation or storage.

The present inventors focused on environmental changes after a powder composition is loaded into a loading container (hereinafter also referred to as "container").
For example, in a season of high temperatures, when a powder composition is loaded into a container under an open air atmosphere, the atmosphere inside the container immediately after loading contains a lot of moisture, but the relative humidity is low to some extent. However, when the environment changes during transportation or storage and the temperature inside the container decreases, the relative humidity of the atmosphere inside the container becomes high, and the moisture in the atmosphere condenses into water droplets, causing the powder composition to deteriorate. It is thought that the powder composition adheres to the powder composition, causing caking and adhesion of the powder composition, and adhesion between the powder composition and the inner surface of the tank of the powder transport vehicle, making it difficult to remove it from the tank of the powder transport vehicle. This phenomenon becomes more pronounced as the solubility of the powder composition in water increases.
On the other hand, if water-insoluble powder with high hygroscopicity is simply added, the water-insoluble powder will adsorb moisture in the atmosphere during loading, so the moisture absorption effect during transportation and storage will not be sufficient. I can't get it. Therefore, water-insoluble powder should be selected so that the amount of moisture absorbed by the powder composition is small in an atmosphere with medium relative humidity, and increases in the amount of moisture absorbed in an atmosphere with high relative humidity. The present invention was based on the discovery that caking caused by fluctuations in relative humidity within a closed container can be suppressed.

The present invention has the following aspects.
[1] A powder composition containing a water-soluble powder, which is a powder of a water-soluble compound, and a water-insoluble powder, which is a powder of a water-insoluble compound, at a temperature of 30°C and a relative humidity of 90%. From the water vapor adsorption amount W by the water-insoluble powder per 1 g of the powder composition in ₉₀ , the water-insoluble water vapor adsorption amount per 1 g of the powder composition at a temperature of 30 ° C. and a relative humidity of 50%. A powder composition in which W ₉₀ - W ₅₀ , which represents the difference after subtracting the amount of water vapor adsorption W ₅₀ by the powder, is 1.5 cm ³ /g or more.
[2] The powder composition according to [1], wherein the water-insoluble powder includes a porous substance having a pore volume of 1.0 mL/g or more.
[3] The powder composition according to [2], wherein the porous substance contains porous silica.
[4] The powder composition according to any one of [1] to [3], wherein the water-insoluble powder contains calcium carbonate.
[5] The powder composition according to any one of [1] to [4], wherein the content of the water-insoluble powder is 5% by mass or less with respect to the total mass of the powder composition. thing.
[6] The powder composition according to any one of [1] to [5], wherein the water-soluble powder contains a water-soluble salt.
[7] The powder composition according to [6], wherein the water-soluble salt contains an alkali metal carbonate.
[8] The powder composition according to [7], wherein the alkali metal carbonate contains sodium hydrogen carbonate.
[9] The powder composition according to any one of [1] to [8], wherein the powder composition has an average particle size of 3 to 20 μm.
[10] The powder composition according to any one of [1] to [9], wherein the water vapor adsorption amount W ₉₀ is 2.0 to 10.0 cm ³ /g.

According to the present invention, it is possible to obtain a powder composition that is unlikely to cause caking during transportation or storage.

FIG. 2 is a perspective view for explaining a moisture resistance test according to an example.

The following definitions of terms apply throughout the specification and claims.
The numerical range represented by "~" means a numerical range whose lower and upper limits are the numbers before and after ~.
A water-soluble compound is a compound whose concentration in a saturated solution at 20° C. is 1 g/L or more using water as a solvent.
A water-insoluble compound is a compound whose concentration in a saturated solution at 20° C. is less than 1 g/L when water is used as a solvent.
The pore volume of the porous material is a value measured by a nitrogen adsorption method. The pore volume can be measured by the nitrogen adsorption method using a specific surface area/pore distribution measuring device (for example, "Tristar II" manufactured by Micromeritic Co., Ltd.).
The average particle size of the powder composition is a volume-based average particle size measured using a laser diffraction scattering particle size distribution analyzer (for example, Microtrac FRA9220, manufactured by Nikkiso Co., Ltd.).

The powder composition of this embodiment includes a water-soluble powder that is a powder of a water-soluble compound, and a water-insoluble powder that is a powder of a water-insoluble compound.
The average particle size of the powder composition is preferably 3 to 20 μm, more preferably 5 to 18 μm, and even more preferably 8 to 15 μm. If it is below the upper limit of the above range, caking is more likely to occur due to fluctuations in relative humidity within the closed container, which is preferable since the effect of the present invention is large. Furthermore, when the powder composition of the present invention is used for reacting with a gas such as an acidic component removing agent, it is preferable that the average particle size is equal to or less than the upper limit value of the average particle size in terms of high reaction efficiency with the gas. When it is at least the lower limit of the above range, good fluidity is likely to be obtained.

<Water-soluble powder>
The water-soluble compound used as the water-soluble powder may be any compound that is solid at room temperature and can exist as a powder. It can be selected depending on the use of the powder composition.
Examples of water-soluble compounds include water-soluble salts and water-soluble organic substances. Water-soluble salts are preferred in terms of high reactivity with acidic gases in exhaust gas and storage stability.
Examples of water-soluble salts include alkali metal carbonates, alkali metal hydrogen carbonates, and alkaline earth metal hydroxides.
Examples of alkali metal carbonates, alkali metal hydrogen carbonates, and alkaline earth metal hydroxides include sodium carbonate (Na ₂ CO ₃ ), sodium carbonate hydrate, sodium hydrogen carbonate (NaHCO ₃ ), and double salts of these and water. sodium sesquicarbonate (Na ₂ CO ₃ .NaHCO ₃ .2H ₂ O), Wegscheider salt (Na ₂ CO ₃ .3NaHCO ₃ ) which is an anhydrous double salt, calcium hydroxide (Ca(OH) ₂ ) and water. An example is oxidized dolomite.
One type of water-soluble compound may be used as the water-soluble powder, or two or more types may be used in combination.

For example, when the powder composition is used as an agent for removing acidic components from exhaust gas, it is preferable that the water-soluble powder contains an alkali metal carbonate.
In particular, from the viewpoint of high reactivity with exhaust gas, it is preferable that the water-soluble powder contains sodium hydrogen carbonate.

<Water-insoluble powder>
The water-insoluble compound used as the water-insoluble powder may be any compound that is solid at room temperature, can exist as a powder, and does not react with the water-soluble powder. It can be selected depending on the use of the powder composition.
One type of water-insoluble compound may be used as the water-insoluble powder, or two or more types may be used in combination. It is preferable to use two or more types in combination because it is easy to adjust the balance of performance of the powder composition.

For example, when the powder composition is used as an acidic component remover for exhaust gas, a known water-insoluble compound to be included in the acidic component remover can be used. Specific examples include calcium carbonate, silica, zeolite, activated carbon, basic magnesium carbonate, diatomaceous earth, metallic fatty acids, and talc.
Examples of calcium carbonate include colloidal calcium carbonate, surface-hydrophobized calcium carbonate, light calcium carbonate, and heavy calcium carbonate described in Patent Document 1. Colloidal calcium carbonate is preferred from the viewpoint of imparting fluidity.
Examples of silica include porous silica, hydrophobic fumed silica described in Patent Document 1, hydrophilic fumed silica, and fused silica.

The water-insoluble powder preferably includes a porous substance having a pore volume of 1.0 mL/g or more. The porous material contributes to the hygroscopicity of the powder composition and helps prevent caking and sticking.
When the pore volume is 1.0 mL/g or more, the amount of moisture absorbed can be increased even with a small amount, so the amount of water-insoluble powder added can be kept low. Therefore, it is possible to increase the concentration of the water-soluble powder that exhibits the original function in the powder composition.
The pore volume is preferably 1.3 mL/g or more, more preferably 1.5 mL/g or more, and even more preferably 2.0 mL/g or more. The upper limit is not particularly limited, but from the viewpoint of suppressing disintegration and generation of fine powder due to reduction in particle strength, it is preferably 3.5 mL/g or less, more preferably 3.0 mL/g or less, and even more preferably 2.5 mL/g or less. .
Examples of porous substances include porous silica, diatomaceous earth, zeolite, and aerogel. Porous silica is preferred because it is easily available and has a large pore volume.

Preferably, the water-insoluble powder contains calcium carbonate. Calcium carbonate contributes to the flowability of the powder composition.
The water-insoluble powder preferably contains both the porous substance and calcium carbonate, and more preferably contains both the porous silica and calcium carbonate.

The total content of water-insoluble powders based on the total mass of the powder composition is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. When it is below the above upper limit, the effect of the water-soluble powder is excellent. The lower limit of the content of the water-insoluble powder is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more.
The total mass of the powder composition is the sum of the content of water-soluble powder and the content of water-insoluble powder.

<Powder composition>
In the powder composition of the present embodiment, W _{90 −W} 50, which represents the difference obtained by subtracting the following W ₅₀ from the following W ₉₀ , is 1.5 cm ³ /g or more.
W ₉₀ is the amount of water vapor adsorbed by the water-insoluble powder per 1 g of the powder composition at a temperature of 30° C. and a relative humidity of 90%. In other words, it is the amount of water that can be adsorbed by the total amount of water-insoluble powder present in 1 g of the powder composition at a temperature of 30° C. and a relative humidity of 90%.
W ₅₀ is the amount of water vapor adsorbed by the water-insoluble powder per 1 g of the powder composition at a temperature of 30° C. and a relative humidity of 50%. In other words, it is the amount of water that can be adsorbed by the total amount of water-insoluble powder present in 1 g of the powder composition at a temperature of 30° C. and a relative humidity of 50%.
A large value of W ₉₀ - W ₅₀ means that the amount of moisture absorbed by the powder composition is small in an atmosphere with medium relative humidity, and the amount of moisture absorbed by the powder composition increases in an atmosphere with high relative humidity. represents something.
When the W ₉₀ −W ₅₀ is 1.5 cm ³ /g or more, the effect of suppressing caking caused by fluctuations in relative humidity within a closed container is excellent.
The W ₉₀ −W ₅₀ is preferably 1.7 cm ³ /g or more, more preferably 2.0 cm ³ /g or more, and even more preferably 2.5 cm ³ /g or more. The higher the value of W ₉₀ - W ₅₀ , the better, so the upper limit is not particularly limited, but considering the ease of obtaining and handling of the compound used as the water-insoluble powder, In order to make the addition amount appropriate, the amount is preferably 7 cm ³ /g or less, more preferably 6 cm ³ /g or less, and even more preferably 5 cm ³ /g or less.

A large value of W ₉₀ indicates that the powder composition absorbs a large amount of moisture in an atmosphere with high relative humidity.
The W ₉₀ is preferably 2.0 to 10.0 cm ³ /g, more preferably 2.2 to 9.0 cm ³ /g, even more preferably 2.5 to 8.0 cm ³ /g. If it is at least the lower limit of the above range, it will exhibit its effectiveness even when the environment changes from a state where the humidity is higher than 50%. If the humidity is below the upper limit, it will be vulnerable to changes in the environment from a state where the humidity is higher than 50%.

The content of water-soluble powder is preferably 95 to 99.5% by mass, more preferably 96 to 99% by mass, and the content of water-insoluble powder is preferably 95 to 99.5% by mass, based on the total mass of the powder composition of the present invention. The amount is preferably 0.5 to 5% by weight, more preferably 1 to 4% by weight.
The total content of water-soluble powder and water-insoluble powder in the powder composition is 100% by mass.

<Method of designing powder composition>
The value of W ₉₀ −W ₅₀ and the value of W ₉₀ can be adjusted depending on the type and amount of the water-insoluble powder.
To design the composition of the powder composition, in advance, for each water-insoluble powder, at a temperature of 30°C, the relative pressure (P/P ₀ ) to the saturated vapor pressure (P ₀ ) of water is 0.9. The water vapor adsorption amount V (standard state conversion) per 1 g of the water-insoluble powder is determined and set as V _0.9 (unit: cm ³ (STP)/g). V _0.9 represents the amount of water that can be adsorbed by 1 g of water-insoluble powder at a temperature of 30° C. and a relative humidity of 90%.
In addition, for each water-insoluble powder, at a temperature of 30°C, the water vapor per 1 g of the water-insoluble powder when the relative pressure (P/P ₀ ) to the saturated vapor pressure (P ₀ ) of water is 0.5. The adsorption amount V (standard state conversion) is determined and set as V _0.5 (unit: cm ³ (STP)/g). V _0.5 represents the amount of water that can be adsorbed by 1 g of water-insoluble powder at a temperature of 30° C. and a relative humidity of 50%.

V _0.9 and V _0.5 can be measured by the following method.
The water-insoluble powder to be measured was dried under vacuum at 200°C for 3 hours as a sample, and using a vapor adsorption measurement device, the adsorbed gas was H ₂ O and the adsorption temperature was 30°C, and P/P was measured. ₀ and the water vapor adsorption amount V (standard state conversion, unit: cm ³ (STP)/g) is measured. In the obtained water vapor adsorption isotherm, V when (P/P ₀ ) is 0.9 is read and defined as V _0.9 . Read V when (P/P ₀ ) is 0.5 and set it as V _0.5 .

The composition of the powder composition is more preferably such that W ₉₀ -W ₅₀ is 1.5 cm ³ /g or more based on the value of V _0.9 - V _0.5 of each water-insoluble powder. can be designed by selecting the type and amount of water-insoluble powder to be added so that W ₉₀ is 2.0 to 10.0 cm ³ /g.

For example, when the powder composition contains a mass % of the first water-insoluble powder and b mass % of the second water-insoluble powder, W ₉₀ −W ₅₀ and W ₉₀ are , are determined by the following formulas (I) and (II), respectively.
W ₉₀ - W ₅₀ = (V _0.9 ¹ - V _0.5 ¹ ) x (a/100) + (V _0.9 ^{2 -} V _0.5 ² ) x (b/100)... (I )
W ₉₀ = (V _0.9 ¹ ) x (a/100) + (V _0.9 ² ) x (b/100)... (II)
In the above formulas (I) and (II), the following is represented.
V _0.9 ¹ : V _0.9 of the first water-insoluble powder
V _0.9 ² :V _0.9 of the second water-insoluble powder
V _0.5 ¹ : V _0.5 of the first water-insoluble powder
V _0.5 ² : V _0.5 of the second water-insoluble powder
^{The type of water-insoluble powder (V 0.9 1} _, ^V _{0.5 1 ,} V ⁰ _{. 9} ² , V _0.5 ² ) and the addition amounts (a, b) to design the composition of the powder composition.
A similar design can be performed when there are three or more types of water-insoluble powders.

For example, if a water-insoluble powder with a large value of V _0.9 - V _0.5 (unit: cm ³ (STP)/g), which is the difference obtained by subtracting V _0.5 from V _0.9 , is used, This is preferable because the amount of water-insoluble powder added to obtain the desired W ₉₀ -W ₅₀ can be small.
The water-insoluble powder having a large value of V _0.9 - V _0.5 is preferably a porous material having a pore volume of 1.0 mL/g or more.

For example, preferred embodiments include the following.
(Aspect 1)
The water-soluble powder contains sodium hydrogen carbonate, the water-insoluble powder contains calcium carbonate and porous silica having a pore volume of 1.0 mL/g or more,
The content of the sodium bicarbonate is 95 to 99.9% by mass, preferably 96 to 99% by mass, and the content of calcium carbonate is 0.5 to 4.9% by mass, based on the total mass of the powder composition. 5% by mass, preferably 1 to 4% by mass, the content of the porous silica is 0.1 to 4.5% by mass, preferably 0.1 to 4.5% by mass, and W ₉₀ -W A powder composition in which ₅₀ is 1.5 cm ³ /g or more.
In Embodiment 1, the total content of the sodium bicarbonate, calcium carbonate, and porous silica is preferably 97 to 100% by mass, more preferably 99 to 100% by mass.

<Method for producing powder composition>
The powder composition of this embodiment can be produced by mixing a water-soluble powder and a water-insoluble powder and then pulverizing them, or by mixing them simultaneously with pulverization.
It is preferable that the water-soluble powder and the water-insoluble powder coexist for most of the time during the grinding. For this reason, it is preferable to mix the two and supply the mixture to a pulverizer, or to supply the water-soluble powder and the water-insoluble powder to a pulverizer almost simultaneously and pulverize them.

Examples of the crushing means include an impact crusher (a crusher using blades rotating at high speed), a jet mill (a crusher using colliding airflow), and a ball mill. An impact pulverizer or jet mill is more preferable because fine particles can be easily obtained.

The pulverized material pulverized by the pulverizing means may be classified by the classifying means. The powder composition may be produced by a method in which particles having a particle size exceeding 50 μm that have been classified by the classification means are returned to the crushing means. The average particle size can also be adjusted to 3 to 20 μm by classifying the particles having a particle size exceeding 50 μm using a classifying means, returning the particles to the crushing means, and repeatedly crushing the particles.

As shown in the Examples below, the powder composition of this embodiment can suppress caking and sticking due to fluctuations in relative humidity within a closed container. Therefore, caking or sticking due to environmental changes during transportation or storage is unlikely to occur.

<Application>
Applications of the powder composition of this embodiment include, for example, when the water-soluble powder contains sodium hydrogen carbonate, as an acid component remover of exhaust gas, a foaming agent, a neutralizing agent, a bath agent, a fire extinguisher, and a food additive. , cleaning agents, and blasting materials.

The present invention will be explained in more detail below using Examples, but the present invention is not limited to these Examples.

<Measurement method/evaluation method>
[V _0.9 , V _0.5 of water-insoluble powder]
Using a vapor adsorption measurement device (BELSORP max II, manufactured by Microtrac Bell Co., Ltd.), the water vapor adsorption isotherm was measured by the method described above, and the results were V _0.9 , V _0.5 , V _0.9 - V _0.5 (Unit: cm ³ (STP)/g) was determined.

[Moisture resistance test (60°C)]
In the following process, the powder composition was exposed to an atmosphere of saturated steam at 60°C in a closed container, and then the whole sealed container was moved to an atmosphere at 5°C to simulate a state in which water vapor in the gas phase condensed. The state of solidification when exposed to this was investigated.
(Step 1) As shown in FIG. 1, 30.0 g of sample 2 of the powder composition was placed in a hollow cylindrical (inner diameter 146 mm, height 90 mm) polystyrene container 1 with a bottom. The sample 2 was placed in a donut shape on the bottom of the container 1, excluding the central circular part (about 40 mm in diameter). The thickness of donut-shaped sample 2 was approximately 5 mm.
The circular part at the center is where a beaker 3 containing distilled water is placed in step 3, which will be described later.
(Step 2: Initialization) A box-shaped desiccator (size: width 550 mm, depth 580 mm, height 700 mm) equipped with granular silica gel at the bottom was prepared. The container 1 containing the sample 2 was placed in the box desiccator in an open state without closing the opening, and was stored for 24 hours. The temperature inside the desiccator was 23° C. and the relative humidity was 20% RH.
(Step 3: Exposure to 60°C saturated steam atmosphere)
After being stored in the box desiccator for 24 hours, the container 1 was taken out from the box dessicator. As shown in FIG. 1, after placing a beaker 3 containing 5 mL of distilled water (outer diameter 34 mm, height 60 mm) in the center of the bottom of the container 1 where the sample 2 is not present, open the opening of the container 1. was covered and sealed with a lid 4 made of soft polyethylene. The container 1 sealed with the lid 4 was placed in a constant temperature bath at 60°C and stored for 1 hour.
(Step 4: Exposure to 5°C saturated steam atmosphere)
After being stored in the 60° C. constant temperature bath for 1 hour, the container 1 was taken out from the constant temperature bath while maintaining a sealed state, and then placed in a 5° C. refrigerator and stored for 30 minutes.
(Step 5: Evaluation of adhesion state)
After storing it in the refrigerator for 30 minutes, the container 1 sealed with the lid 4 was removed from the refrigerator, the lid 4 was removed, the beaker 3 was taken out, and the adhesion state of the sample 2 in the container 1 was visually observed. The state of adhesion was evaluated using the following criteria (evaluation values 1 to 4). Samples with an evaluation value of 3 or higher were determined to be good samples that were not easily affected by fluctuations in relative humidity within a closed container.
(Evaluation criteria)
Evaluation value 4: No sticking.
Evaluation value 3: Slight adhesion to the inner wall of the polystyrene container, no adhesion to the bottom surface.
Evaluation value 2: Adherence to the bottom of the polystyrene container.
Evaluation value 1: Severely stuck to the bottom of the polystyrene container.

[Flowability test: measurement of flow function (ffc)]
JIS Z 8835 (2016), “Measurement method of limit state line (CSL) and wall failure line (WYL) by one-plane shear test”, Annex A (reference) “Details and characteristics of one-plane shear test” The physical properties of the powder were measured and evaluated using a lower cell direct-acting type shear test.
Using a device capable of direct-acting lower cell measurement (Powder bed shear force measuring device NS-S500, manufactured by Nano Seeds Co., Ltd.), a load (indentation load) is applied from the top to the compressed powder bed in the horizontal direction. The changes in indentation load, bottom load, horizontal shear distance, and powder layer thickness were measured when a load was applied, and the correlation between vertical stress and shear stress was determined. Note that the load from above was set to 50N, 100N, 150N, 200N, or 250N, and measurements were performed under each condition. That is, one sample was measured five times under different conditions.
From the correlation between the normal stress and shear stress, the uniaxial collapse stress (σ _c ) and the maximum principal stress (σ ₁ ) were determined, and the flow function (ffc), which is the ratio of σ ₁ to σ _c , was determined. ffc is defined by the following equation (1). ffc=σ ₁ ÷σ _c ...(1)
The larger the value of ffc is, for example, the smaller σ _c is when σ ₁ is the same, the smaller the adhesion force of the powder particles, which makes the powder layer more likely to collapse and the powder to flow more easily. It can be evaluated.
In the example below, the value of ffc(100) was determined using the value of σ _c when σ ₁ =100 (kPa). Generally, the guidelines for liquidity are as follows.
1<ffc<2: Very difficult to flow.
2<ffc<4: Slightly difficult to flow.
4<ffc<10: Easy to flow.
ffc>10: Very easy to flow.
(Evaluation criteria)
Using the average value of ffc in Example 7 and ffc in Example 10 as a reference value, fluidity was evaluated based on the value of ffc (100) using the following criteria.
○: ffc(100) is equal to or greater than "reference value x 0.9". Equivalent to or higher than the standard value.
Δ: ffc(100) is greater than or equal to "reference value x 0.7" and less than "reference value x 0.9". Slightly inferior to the standard value.
x: ffc(100) is less than "reference value x 0.7". Inferior to standard value.

<Raw materials>
[Water-soluble powder]
- Sodium hydrogen carbonate (average particle size: 9 μm).
[Water-insoluble powder]
- Calcium carbonate A (colloidal calcium carbonate, Shiraishi Calcium Co. product name "Callite KT").
- Calcium carbonate B (colloid calcium carbonate, Takehara Chemical Co. product name "Neolite VT").
- Silica A (porous silica, Mizusawa Chemical Co., Ltd. product name "Mizukasil P-78D", pore volume 2.2 mL/g).
- Silica B (hydrophobic fumed silica, Tokuyama product name "REOLOSIL CP-102").
For each water-insoluble powder, V _0.9 , V _0.5 , and V _0.9 -V _0.5 were determined by the above method. The results are shown in Table 1.

(Examples 1 to 11)
Examples 1 to 6 are examples, and Examples 7 to 11 are comparative examples.
Note that Examples 7 and 10 have the same formulation as Example 5 in Table 4 of Patent Document 1, in that they are mixtures of 97.5% by mass of sodium hydrogen carbonate and 2.5% by mass of colloidal calcium carbonate. Example 9 has the same formulation as Example 1 in Table 4 of Patent Document 1 above in that it is a mixture of 97.7% by mass of sodium hydrogen carbonate, 2% by mass of colloidal calcium carbonate, and 0.3% by mass of hydrophobic fumed silica. .

After mixing water-soluble powder and water-insoluble powder with the composition shown in Table 2, using an impact crusher equipped with a wind classifier (Hosokawa Micron's product name "ACM Pulverizer ACM-10A type"), the average A powder composition having a particle size of 9 μm was obtained.
Using the above formulas (I) and (II) and the measured values in Table 1, W ₉₀ -W ₅₀ and W ₉₀ of the powder composition were determined. The results are shown in Table 2.
The obtained powder composition was subjected to a moisture resistance test (60° C.) and a fluidity test using the methods described above. The results are shown in Table 2.

The above moisture resistance test is a severe test in which the product is housed in a closed space and condensation is likely to occur due to a drop in temperature.
As shown in the results in Table 2, Examples 1 to 6 in which W ₉₀ -W ₅₀ is 1.5 cm ³ /g or more have an evaluation value of 3 or more in the moisture resistance test and are excellent in anti-caking properties.
Among Examples 1 to 6, especially Examples 1 to 4 and Example 6 containing calcium carbonate A or B and silica A had good fluidity comparable to the standard value (Examples 7 and 9). .

1 Polystyrene container (container)
2 Sample 3 Beaker containing distilled water 4 Lid

Claims (10)

A powder composition comprising a water-soluble powder that is a powder of a water-soluble compound and a water-insoluble powder that is a powder of a water-insoluble compound,
From the water vapor adsorption amount W ₉₀ by the water-insoluble powder per 1 g of the powder composition at a temperature of 30 ° C. and a relative humidity of 90%,
At a temperature of 30° C. and a relative humidity of 50%, W ₉₀ −W ₅₀ , which represents the difference obtained by subtracting the water vapor adsorption amount W ₅₀ by the water-insoluble powder per 1 g of the powder composition, is 1.5 cm ³ / A powder composition having a weight of at least 100 g. The powder composition according to claim 1, wherein the water-insoluble powder includes a porous material having a pore volume of 1.0 mL/g or more. The powder composition according to claim 2, wherein the porous material includes porous silica. The powder composition according to any one of claims 1 to 3, wherein the water-insoluble powder contains calcium carbonate. The powder composition according to claim 1, wherein the content of the water-insoluble powder is 5% by mass or less based on the total mass of the powder composition. The powder composition according to claim 1, wherein the water-soluble powder contains a water-soluble salt. The powder composition according to claim 6, wherein the water-soluble salt comprises an alkali metal carbonate. The powder composition according to claim 7, wherein the alkali metal carbonate comprises sodium bicarbonate. The powder composition according to claim 1, wherein the powder composition has an average particle size of 3 to 20 μm. The powder composition according to claim 1, wherein the water vapor adsorption amount W ₉₀ is 2.0 to 10.0 cm ³ /g.

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