Sodium acetate anhydride particle group and method for producing the same

Abstract

To provide an anhydrous sodium acetate particle group, that has a large bulk density and furthermore the amount of fine particles is small, and resulting therefrom, that is useful for various applications, and to provide a method for producing the same.SOLUTION: Provided is an anhydrous sodium acetate particle group having an average of the value shown in the following formula (1) of 2.5% or less. {arithmetic average roughness Ra (μm) of anhydrous sodium acetate particle surface / thickness d (μm) of anhydrous sodium acetate particle)}×100 -- (1). (In the above formula (1), d represents the height when an anhydrous sodium acetate particle is placed in a most stable state on a flat surface.).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aggregate of sodium acetate anhydride particles, i.e., a group of sodium acetate anhydride particles, and a method for producing the same. Specifically, the present invention relates to a group of sodium acetate anhydride particles and a method for producing the same, which have a large bulk density due to the smoothness of the particle surface and are useful for various applications.

Background Art

[0002] Generally, the powder of sodium acetate anhydride is a food additive such as a preservative, an acidulant, a pH adjuster, etc., and a compound useful as a reagent. Furthermore, its use in pharmaceutical applications such as powder formulations of hemodialysis solutions has also been increasing in recent years.

[0003] Among the above applications, especially in the use as a food additive, it is common to use a mixture by combining a plurality of organic acids and organic salts with the powder of sodium acetate anhydride according to the purpose. In such a method of use, the proportion of the powder of sodium acetate anhydride in the mixture after mixing is often large. Therefore, the influence of the powder of sodium acetate anhydride on the volume of the above mixture is great, and a group of sodium acetate anhydride particles with a large bulk density is desired so that the volume of the above mixture can be reduced. Also, from the viewpoints of transportation, storage, management, etc., a group of sodium acetate anhydride particles with a large bulk density is advantageous.

[0004] Conventionally, as a method for producing a group of sodium acetate anhydride particles, a method is known in which a sodium compound such as sodium hydroxide or sodium carbonate is reacted with acetic acid to produce sodium acetate trihydrate, and this is dehydrated at 120°C or higher.

[0005] In addition to the above production method, a method of dehydrating an aqueous sodium acetate solution under a reduced pressure of 200 mmHg or less, a method of spray-drying an aqueous sodium acetate solution, etc. are also known (see, for example, Patent Documents 1 and 2).

[0006] However, the bulk density of the sodium acetate anhydride particle groups obtained by such a method is usually as low as around 0.70 g / mL. Therefore, the advantages of the sodium acetate anhydride particle groups with a large bulk density as described above are not obtained.

[0007] Under such circumstances, the applicant of the present application has already proposed a method for obtaining sodium acetate anhydride particle groups with a large bulk density by drying a mixture of powder particles of sodium acetate anhydride with a volatile fraction of 2.0% by weight or more and a bulk density of less than 0.75 g / mL and a solvent such as water at 50 to 140 °C until the volatile fraction becomes less than 2.0% by weight (see Patent Document 3).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] By the method described in Patent Document 3 above, it is possible to obtain sodium acetate anhydride particle groups with a larger bulk density more effectively than the conventional method. However, even with the method described in Patent Document 3 above, it is limited to increasing the bulk density of the sodium acetate anhydride particle groups to around 0.80 g / mL. Further, in the method described in Patent Document 3 above, in both the step of mixing the powder particles of sodium acetate anhydride and the solvent and the step of drying the mixture, the corners of the sodium acetate anhydride particles are shaved, and a large number of fine particles passing through a sieve with an opening of 150 μm are generated, resulting in a decrease in handleability. Therefore, the need for sodium acetate anhydride particle groups that achieve both an improvement in bulk density and a reduction in the amount of fine particles is high, and further improvement is required to meet this need.

[0010] The present invention has been made in view of such circumstances, and provides sodium acetate anhydride particle groups that have a high bulk density, a further small amount of fine particles, and are useful for various applications due to this, and a method for producing the same.

Means for Solving the Problems

[0011] The inventors of the present invention have conducted intensive studies to solve the above problems. In the process of the research, from the viewpoint that in order to further increase the bulk density of the sodium acetate anhydride particle groups, it is important to suppress the surface roughness so that the surface of the sodium acetate anhydride particles becomes smooth, the inventors focused on the surface roughness ratio of the sodium acetate anhydride particles. Here, the surface roughness ratio of the sodium acetate anhydride particles refers to the value shown in the following formula (1).

[0012] {Arithmetic mean roughness Ra (μm) of the surface of sodium acetate anhydride particles / Thickness d (μm) of sodium acetate anhydride particles} × 100 ……(1)

[0013] In the above formula (1), d indicates the height when the sodium acetate anhydride particles are placed in the most stable state on a plane, and is an index correlated with the size of the sodium acetate anhydride particles. In addition, the surface roughness ratio of the sodium acetate anhydride particles shown in the above formula (1) takes into account the correlation between the surface roughness and the thickness of the sodium acetate anhydride particles. When the size of the particles becomes extremely large, the surface roughness ratio becomes relatively small. Therefore, it is the ratio of the surface roughness to the thickness that is calculated.

[0014] Then, the surface roughness ratio of the sodium acetate anhydride particles calculated as described above was measured for at least arbitrarily selected 5 sodium acetate anhydride particles, and the average value (average of the surface roughness ratios of the crystal particles) was found to be 2.5% or less, and the bulk density was increased well and the fine particle ratio was also reduced, thus completing the present invention.

[0015] That is, the first gist of the present invention is sodium acetate anhydride particle groups in which the average value of the value shown in the following formula (1) is 2.5% or less. {Arithmetic mean roughness Ra (μm) of the surface of sodium acetate anhydride particles / Thickness d (μm) of sodium acetate anhydride particles} × 100 ……(1) (In the above formula (1), d indicates the height when the sodium acetate anhydride particles are placed in the most stable state on a plane.)

[0016] Further, the present invention is a method for producing the sodium acetate anhydride particle groups of the first gist, a step of charging an aqueous sodium acetate solution as a raw material into a can of a horizontal stirring shaft type mixer, and a step of concentrating the aqueous sodium acetate solution in the can, The second gist is a method for producing sodium acetate anhydride particle groups in which the peripheral speed of the stirring blade of the horizontal stirring shaft type mixer in the concentration step is 1.0 to 6.0 m / s.

Advantages of the Invention

[0017] Thus, the average of the value shown in the above formula (1) of the sodium acetate anhydride particle groups of the present invention is 2.5% or less. Therefore, it is possible to obtain sodium acetate anhydride particle groups having a higher bulk density than before, which can contribute to reducing the volume of the product to which it is added. Further, since the bulk density can be increased as described above and the fine particle ratio is also small, the sodium acetate anhydride particle groups of the present invention are useful from the viewpoints of transportation, storage, management, etc. And the sodium acetate anhydride particle groups of the present invention are useful for pharmaceutical applications such as food additives such as shelf life improvers, acidulants, pH adjusters, reagents, and powder preparations of hemodialysis solutions.

[0018] In particular, when the bulk density of the above sodium acetate anhydride particle groups is 0.75 g / mL or more, since the bulk density is higher than that of conventional sodium acetate anhydride particle groups, it can further contribute to reducing the volume of the product to which it is added, and is further useful from the viewpoints of transportation, storage, management, etc.

[0019] Also, when the proportion of sodium acetate anhydride fine particle groups passing through a sieve with an opening size of 150 μm is 5% by weight or more and 25% by weight or less, the amount of fine powder that rises during the production of a preparation using the sodium acetate anhydride particle groups can be reduced while the bulk density can be favorably increased.

[0020] Furthermore, when the standard deviation of the particle size distribution in the above-mentioned sodium acetate anhydride particle groups is 300 μm or less, problems such as segregation occurring due to vibration during transportation can be solved.

[0021] Also, when the median diameter in the above-mentioned sodium acetate anhydride particle groups is 280 μm or more and 500 μm or less, since the particle diameter is close to that of other raw materials such as glycine used as a food additive preparation, the mixability is good, and the occurrence of segregation after making it into a food additive preparation can be suppressed.

[0022] And the method for producing the sodium acetate anhydride particle groups of the present invention includes a step of introducing an aqueous sodium acetate solution as a raw material into the tank of a horizontal stirring shaft type mixer, and a step of concentrating the aqueous sodium acetate solution in the tank, and in the step of concentrating, the peripheral speed of the stirring blade of the horizontal stirring shaft type mixer is set to 1.0 to 6.0 m / s. By such a production method, when producing the sodium acetate anhydride particle groups of the present invention having the excellent effects described above, the sodium acetate anhydride particle groups of the present invention can be efficiently produced.

Embodiments for Carrying Out the Invention

[0023] Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to this embodiment.

[0024] The average value of the value shown by the following formula (1) in the sodium acetate anhydride particle groups of the present invention is 2.5% or less. In the present invention, "particle group" means an aggregate of particles. Similarly, "fine particle group" means an aggregate of fine particles. From the perspective of the effects of the present invention, the average of the values shown in the following formula (1) is preferably 0.1 to 2.0%, more preferably 0.3 to 1.8%, and still more preferably 0.6 to 1.6%.

[0025] {Arithmetic mean roughness Ra (μm) of the surface of sodium acetate anhydride particles / Thickness d (μm) of sodium acetate anhydride particles} × 100 ……(1) (In the above formula (1), d represents the height when the sodium acetate anhydride particles are placed in the most stable state on a plane.)

[0026] Here, the “arithmetic mean roughness Ra of the surface of sodium acetate anhydride particles” is the arithmetic mean roughness Ra described in JIS B 0601:2001. For the surface of sodium acetate anhydride particles, within a range of 50 μm square, the surface roughness at 10 locations per sodium acetate anhydride particle is measured, and the average value is obtained. Also, the “thickness d of sodium acetate anhydride particles” indicates the height when the sodium acetate anhydride particles are placed in the most stable state (non-rolling state) on a plane as described above. When there are multiple surfaces with similar rolling stability on the sodium acetate anhydride particles, the lowest height measured as described above among them is taken as the above thickness d. And the smaller the value shown in the above formula (1), the smaller the voids present on the surface of the sodium acetate anhydride particles with respect to the thickness of the sodium acetate anhydride particles, indicating that the sodium acetate anhydride particles have a smoother surface.

[0027] The value shown in the above formula (1) takes into account the correlation between the size and thickness of the sodium acetate anhydride particles. When the size of the particles becomes extremely large, the surface roughness becomes relatively small. Therefore, it is the ratio of the surface roughness to the thickness calculated. Also, when making a comparison, if the size of the sodium acetate anhydride particles is extremely large, the value (surface roughness rate) shown in the above formula (1) will become relatively small. Therefore, as the size of the sodium acetate anhydride particles used in the above measurement, those with an average length of the major axis and minor axis of 400 to 900 μm are selected. The value shown in the above formula (1) is measured for at least 5 arbitrarily selected sodium acetate anhydride particles, and the average value of the measured values is taken.

[0028] The arithmetic mean roughness Ra of the surface of the sodium acetate anhydride particles can be measured, for example, using a shape measurement laser microscope (manufactured by Keyence Corporation, VX-9710 (measurement length: 1 mm, objective lens: 10x)) or the like. The thickness d of the sodium acetate anhydride particles can also be measured, for example, using a shape measurement laser microscope (manufactured by Keyence Corporation, VX-9710 (measurement length: 1 mm, objective lens: 10x)) or the like.

[0029] In the present invention, the arithmetic mean roughness Ra of the surface of the sodium acetate anhydride particles is preferably 0.01 to 10 μm, particularly preferably 0.1 to 5 μm, and even more preferably 1 to 3 μm. Furthermore, the thickness d of the sodium acetate anhydride particles is usually 10 to 500 μm, preferably 20 to 400 μm, and particularly preferably 50 to 300 μm.

[0030] Incidentally, the bulk density of the sodium acetate anhydride particle group of the present invention is preferably 0.75 g / mL or more, more preferably in the range of 0.80 to 1.5 g / mL, and even more preferably in the range of 0.85 to 1.0 g / mL. That is, when the bulk density is large in this way, it can contribute to reducing the volume of the product to which it is added, and further, it is more useful from the viewpoints of transportation, storage, management, etc.

[0031] In the present invention, the bulk density is measured using an apparent bulk density measuring device as shown in JIS K 6891. For example, using a bulk density measuring instrument (manufactured by Kuramochi Scientific Instruments Co., Ltd.), the sodium acetate anhydride particle group is dropped from above into a 100 mL container, the overflowing powder is leveled off, and the bulk density can be calculated from the weight of the contents.

[0032] In addition, in the sodium acetate anhydride particle group of the present invention, when the ratio (fine particle ratio) of the sodium acetate anhydride fine particle group passing through a sieve with an opening of 150 μm is 5% by weight or more and 25% by weight or less, it is possible to reduce the amount of fine particles that fly up during the production of a preparation using the sodium acetate anhydride particle group while favorably increasing the bulk density, which is preferable. The ratio of the sodium acetate anhydride fine particle group passing through the opening of 150 μm is more preferably 6 to 20% by weight, and even more preferably 7 to 15% by weight.

[0033] In addition, the index of the variation in the particle size in the sodium acetate anhydride particle group can be represented by the standard deviation of the particle size distribution. And in the sodium acetate anhydride particle group of the present invention, the standard deviation of the particle size distribution is preferably 300 μm or less, more preferably 50 to 280 μm, even more preferably 70 μm to 260 μm, and particularly preferably 90 to 230 μm. That is, if the standard deviation of the particle size distribution is too large, segregation tends to occur due to differences in particle size, for example, due to vibration during transportation. In addition, if the standard deviation of the particle size distribution is too small, the bulk density tends to be small.

[0034] The standard deviation of the particle size distribution is a value obtained by first obtaining the particle diameter (μm) at which the cumulative frequency is 16% and the particle diameter (μm) at which the cumulative frequency is 84% from the data representing the particle size distribution as a cumulative distribution, and applying these values to the following formula (2).

[0035] {(Particle diameter at which cumulative frequency is 16%) - (Particle diameter at which cumulative frequency is 84%)} / 2 ……(2)

[0036] The above particle size distribution is determined by vibrating and classifying 100 g of a sample (sodium acetate anhydride particle group) for 9 minutes using an electromagnetic sieve shaker (model: AS-200; manufactured by Retsch). The electromagnetic sieve shaker uses sieves with mesh openings of 1000 μm, 500 μm, 355 μm, 250 μm, 150 μm, 106 μm, and 75 μm (the diameter of each sieve is 200 mm), vibrates and classifies as described above, and from the weight of the sample remaining on each sieve, data representing the particle size distribution as a cumulative distribution is obtained.

[0037] In addition, when the median diameter of the sodium acetate anhydride particle group of the present invention is 280 μm or more and 500 μm or less, for example, it has good mixability because it has a particle size close to that of other raw materials such as glycine used as a food additive preparation, and can suppress the occurrence of segregation after being made into a food additive preparation, so it is preferable. The median diameter of the above sodium acetate anhydride particle group is more preferably 270 to 400 μm, and even more preferably 290 to 350 μm. The above median diameter is the particle diameter (μm) at which the cumulative frequency becomes 50% when data representing the above particle size distribution as a cumulative distribution is created.

[0038] Examples of the method for producing the sodium acetate anhydride particle group of the present invention include (i) a method of producing using a horizontal stirring shaft type mixer, (ii) a method of producing by impact pulverization of sodium acetate anhydride obtained by a conventional method in a dry state, and (iii) a method of producing by adding an abrasive in the step of stirring and concentrating a sodium acetate solution. Among them, the method (i) is preferable because the surface roughness of the sodium acetate anhydride particles is reduced.

[0039] And, in particular, a method for producing anhydrous sodium acetate particle groups includes a step of charging an aqueous sodium acetate solution as a raw material into a can of a horizontal stirring shaft type mixer, and a step of concentrating the aqueous sodium acetate solution in the can, and in the concentrating step, the stirring blades of the horizontal stirring shaft type mixer are driven so that the peripheral speed thereof is 1.0 to 6.0 m / s. This method is more effective in producing the anhydrous sodium acetate particle groups of the present invention. The peripheral speed of the stirring blades is more preferably 1.5 to 5.0 m / s, and even more preferably 2.0 to 4.5 m / s.

[0040] Here, the "horizontal stirring shaft type mixer" means a mixer in which the stirring shaft used for stirring the raw materials and the obtained products charged into the can is arranged in the horizontal direction, and stirring blades for stirring are installed in the vertical direction with respect to the stirring shaft, and it is characterized by having a horizontal drum shape and supporting the stirring shaft at two points at both ends. Therefore, although the drum itself may be tilted, considering the mechanical load on the stirring shaft, usually, the drum and the stirring shaft are installed horizontally. Specific examples of the horizontal stirring shaft type mixer include, for example, the "Lödige Mixer" manufactured by Lödige, the "Pau Mixer·Conical Horizontal Type" manufactured by Tsukasa Kogyo Co., Ltd., the "Pum Apex Mixer" manufactured by Pacific Machinery Co., Ltd., the "Ribbon Mixer" manufactured by Aisin Industry Co., Ltd., etc. In addition, the "Paddle Dryer" manufactured by Nara Machinery Co., Ltd., which is classified as a dryer, also has the same function and can be used as the horizontal stirring shaft type mixer. As the stirring blades of the horizontal stirring shaft type mixer, stirring blades such as anchor blades, turbine blades, paddle blades, pitched paddles, ribbon blades, scoop shovels, serrated shovels, and Becker shovels are used. Among them, a horizontal stirring shaft type mixer equipped with a scoop shovel or a Becker shovel is preferably used from the viewpoint of efficiently producing the anhydrous sodium acetate particle groups of the present invention.

[0041] As the raw material to be charged into the can of the above horizontal stirring shaft type mixer, an aqueous sodium acetate solution is used. Here, the above aqueous sodium acetate solution is a mixture of sodium acetate (or sodium acetate trihydrate) in water. Note that instead of the above aqueous sodium acetate solution, sodium acetate or sodium acetate trihydrate and water may be individually charged into the above can.

[0042] The above aqueous sodium acetate solution can also contain other solvents in addition to water. Examples of such solvents include aqueous solvents such as alcohols having 1 to 5 carbon atoms and acetic acid from the viewpoint of use as a food additive.

[0043] The initial concentration of the aqueous sodium acetate solution obtained as described above is in a range where sodium acetate does not precipitate from the solvent. Also, from the viewpoint of performing concentration, the higher the concentration of the above aqueous sodium acetate solution, the shorter the production time until such anhydrous sodium acetate particle groups are obtained, which is desirable. Therefore, the concentration of the above aqueous sodium acetate solution is usually 30% by weight or more, preferably 30 to 65% by weight, more preferably 40 to 60% by weight.

[0044] Note that, in order to adjust the pH of the above aqueous sodium acetate solution, acetic acid, sodium hydroxide, sodium diacetate, etc., or their aqueous solutions may be added as necessary.

[0045] The concentration step of the aqueous sodium acetate solution in the above can is, for example, (1) a method of concentrating a sodium acetate solution (for example, an aqueous sodium acetate solution) by performing operations such as heating or reduced pressure, and drying the crystallized anhydrous sodium acetate, (2) a method of shaking off the solvent after crystallizing anhydrous sodium acetate, (3) a method of heating a sodium acetate hydrate powder such as sodium acetate trihydrate above its melting point to volatilize a solvent such as water, etc. In particular, since the step of obtaining anhydrous sodium acetate particle groups can be performed in one step, (1) is preferable.

[0046] In the above concentration step, it is preferably carried out at a temperature of 80 to 200 °C, particularly 90 to 180 °C, and more preferably 100 to 160 °C. If the temperature is too low, sodium acetate trihydrate tends to precipitate, and the production tends to take a long time. On the other hand, if the temperature is too high, sodium acetate may decompose.

[0047] The anhydrous sodium acetate particle group of the present invention thus obtained has a higher bulk density than the conventional anhydrous sodium acetate particle group, and therefore can contribute to reducing the volume of the product to which it is added. In addition, since the bulk density can be increased as described above, the anhydrous sodium acetate particle group of the present invention is also useful from the viewpoints of transportation, storage, management, etc. The anhydrous sodium acetate particle group of the present invention is useful as food additives such as a freshness improver, a sour agent, a pH adjuster, and pharmaceuticals such as reagents and powder preparations for hemodialysis solutions. In particular, its use as food additives such as a freshness improver, a sour agent, and a pH adjuster is highly expected.

Examples

[0048] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0049] [Example 1] 70 kg of sodium acetate trihydrate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 4.1 kg of water were charged into the tank of a horizontal stirring shaft type mixer (model FM130D; manufactured by Matsubo Co., Ltd. (manufacturer: Lödige Co., Ltd.)), heated and dissolved, and after preparing an aqueous sodium acetate solution having a concentration of 57% by weight, 0.084 kg of disodium acetate was added to adjust the pH of the above aqueous solution to 7.6. Subsequently, the temperature was adjusted so that the steam temperature in the tank was 110 °C and the temperature of the aqueous sodium acetate solution in the tank was maintained at 90 to 110 °C, and the peripheral speed (stirring peripheral speed) of the stirring blade of the horizontal stirring shaft type mixer was set to 4.2 m / s, and concentration and drying were carried out. Thus, an anhydrous sodium acetate particle group was obtained.

[0050] [Example 2] In Example 1, the circumferential speed (stirring circumferential speed) of the stirring blade of the horizontal stirring shaft type mixer during concentration and drying was set to 2.9 m / s, and concentration and drying were performed. Otherwise, in the same manner as in Example 1, sodium acetate anhydride particle groups were obtained.

[0051] [Example 3] In Example 1, the vapor temperature inside the can during concentration and drying was set to 130 °C, and concentration and drying were performed. Otherwise, in the same manner as in Example 1, sodium acetate anhydride particle groups were obtained.

[0052] [Comparative Example 1] An aqueous solution of sodium acetate with a concentration of 57% by weight heated to 70 °C was charged into the can of a vertical stirring shaft type crystallizer (DP type: model φ250DP crystallizer; manufactured by Tsukishima Kikai Co., Ltd.). The temperature and pressure were adjusted so that the stirring circumferential speed was 3.9 m / s, the temperature inside the can was about 80 °C, and the pressure inside the can was about 24 kPaG to concentrate and precipitate crystals. Then, the raw material was continuously charged so that the residence time was about 1.5 hours and the slurry concentration was 30% by weight, and the slurry containing crystallized sodium acetate anhydride particles was withdrawn. The withdrawn slurry was separated into a solid content and a solution by a centrifuge to obtain a mixture of sodium acetate anhydride particle groups and water (volatile fraction 4.2% by weight). The obtained mixture of sodium acetate anhydride particle groups and water was statically dried in a vacuum dryer (model DP-32; manufactured by Yamato Scientific Co., Ltd.) at a heating temperature of 80 °C and a vacuum degree of 1 Pa or less to obtain sodium acetate anhydride particle groups.

[0053] [Comparative Example 2] In the same manner as in Comparative Example 1, a mixture of sodium acetate anhydride particle groups and water (volatile fraction 3.3% by weight) was obtained. 6.8 kg of the obtained mixture of sodium acetate anhydride particle groups and water was charged into a horizontal stirring shaft type dryer (paddle dryer: model NPD-1.6W-12L; manufactured by Nara Machinery Co., Ltd.), and dried for 50 minutes at a stirring circumferential speed of 0.3 m / s, a heating temperature of 65 °C, and a gas flow rate of 6 L / min·kg to obtain sodium acetate anhydride particle groups.

[0054] [Comparative Example 3] A mixture of sodium acetate anhydride particles and water (volatile fraction: 3.3% by weight) was obtained in the same manner as in Comparative Example 1, except that the stirring peripheral speed was 5.7 m / s and the residence time was 3 hours. Then, the drying process of the obtained mixture of sodium acetate anhydride particles and water was carried out under the same conditions as in Comparative Example 2, except that the heating temperature was changed to 70 °C, the gas flow rate was changed to 9 L / min·kg, and the drying time was changed to 30 minutes, to obtain sodium acetate anhydride particles.

[0055] [Comparative Example 4] 135 kg of sodium acetate trihydrate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 7.8 kg of water were charged into the tank of a vertical stirring shaft type mixer (ribocone: model RM-100VD; manufactured by Okawara Seisakusho Co., Ltd.), and 0.16 kg of sodium diacetate was added to adjust the pH. Then, by stirring and mixing the inside of the tank at a vapor temperature of 120 °C, a stirring peripheral speed of 1.5 m / s at the center of the height in the inverted cone shape, and a gas flow rate of 0.5 L / min·kg, concentration and drying were carried out to obtain sodium acetate anhydride particles.

[0056] The sodium acetate anhydride particles of the examples and comparative examples thus obtained were measured and evaluated according to the following criteria. And their results are shown together in Table 1 below.

[0057] <Surface roughness ratio> The value (surface roughness ratio (%)) shown in the following formula (1) was measured for arbitrarily selected 5 sodium acetate anhydride particles with a particle diameter of 400 to 900 μm. And the average of the values was calculated. In addition, the measurement of the arithmetic mean roughness Ra of the surface of the following sodium acetate anhydride particles was carried out using a shape measurement laser microscope (manufactured by Keyence Corporation, VX-9710 (measurement length: 1 mm, objective lens: 10 times)). For the surface of the sodium acetate anhydride particles, in a range of 50 μm square, the surface roughness at 10 locations per sodium acetate anhydride particle was measured, and the average value was obtained. In addition, the thickness of the sodium acetate anhydride particles described below was also measured using a shape measurement laser microscope (manufactured by Keyence Corporation, VX-9710 (measurement length: 1 mm, objective lens: 10x)).

[0058] {Arithmetic mean roughness Ra (μm) of the surface of sodium acetate anhydride particles / Thickness d (μm) of sodium acetate anhydride particles} × 100 ……(1) (In the above formula (1), d indicates the height when the sodium acetate anhydride particles are placed in the most stable state on a plane.)

[0059] <Median diameter> Using sieves with mesh openings of 1000 μm, 500 μm, 355 μm, 250 μm, 150 μm, 106 μm, and 75 μm (the diameter of each sieve is 200 mm), about 100 g of the sample was sieved for 9 minutes using an electromagnetic sieve shaker (model: AS-200; manufactured by Retsch), and data representing the particle size distribution as a cumulative distribution was obtained from the weight of the sample remaining on each sieve. The particle diameter at which the cumulative frequency becomes 50% was defined as the median diameter (μm).

[0060] <Fine particle ratio> At the time of measuring the above median diameter, the weight percentage (wt%) of the total weight of the sample that passed through the sieve with a mesh opening of 150 μm with respect to the weight of the sample before classification was calculated and defined as the fine particle ratio.

[0061] <Standard deviation of particle size distribution> At the time of measuring the above median diameter, from the data representing the particle size distribution as a cumulative distribution, the particle diameter (μm) at which the cumulative frequency becomes 16% and the particle diameter (μm) at which the cumulative frequency becomes 84% were determined, and the standard deviation (μm) of the above particle size distribution was determined by applying these values to the following formula (2).

[0062] {(Particle diameter at which the cumulative frequency becomes 16%) - (Particle diameter at which the cumulative frequency becomes 84%)} / 2 ……(2)

[0063] <Bulk density> Using a bulk density meter (manufactured by Kuramochi Scientific Instruments Co., Ltd.), sodium acetate anhydride particle groups were dropped from above into a 100 mL container, the overflowing sodium acetate anhydride was ground, and the bulk density (g / mL) was calculated from the weight of the contents.

[0064]

Table 1

[0065] From the results in Table 1 above, the sodium acetate anhydride particle groups of the examples have an average surface roughness rate of the crystal particles of 2.5% or less. And the sodium acetate anhydride particle groups of the examples have a large bulk density and a small fine particle ratio. In contrast, the sodium acetate anhydride particle groups of Comparative Example 1 and Comparative Example 4 have an average surface roughness rate of the crystal particles exceeding 2.5%. And the sodium acetate anhydride particle groups of Comparative Example 1 and Comparative Example 4 have a smaller bulk density than the sodium acetate anhydride particle groups of the examples. Also, the sodium acetate anhydride particle groups of Comparative Example 2 and Comparative Example 3 also have an average surface roughness rate of the crystal particles exceeding 2.5%. And the sodium acetate anhydride particle groups of Comparative Example 2 and Comparative Example 3 have a bulk density similar to that of the sodium acetate anhydride particle groups of the examples, but have a high fine particle ratio and a large amount of fine powder. From these facts, it can be seen that the sodium acetate anhydride particle groups of the examples can contribute to reducing the volume of the product to which they are added compared to the sodium acetate anhydride particle groups of the comparative examples, and can further increase the bulk density while reducing the amount of fine powder that rises during the production of the preparation using the sodium acetate anhydride particle groups. Also, as described above, since the sodium acetate anhydride particle groups of the examples have a larger bulk density and a smaller fine particle ratio than the sodium acetate anhydride particle groups of the comparative examples, they are also useful from the viewpoints of transportation, storage, management, etc.

Industrial Applicability

[0066] The sodium acetate anhydride particle group of the present invention is useful as a food additive such as a freshness improver, an acidulant, a pH adjuster, a reagent, a pharmaceutical preparation such as a powder preparation of a hemodialysis solution, etc., and in particular, it is highly expected to be used as a food additive such as a freshness improver, an acidulant, a pH adjuster, etc.

Claims

1. A method for producing sodium acetate anhydride particle groups, wherein the value shown in the following formula (1) is 2.5% or less, the median diameter is 280 μm or more and 500 μm or less, and the bulk density is 0.75 g / mL or more, comprising a step of charging an aqueous sodium acetate solution as a raw material into a can of a horizontal stirring shaft type mixer, and a step of concentrating the aqueous sodium acetate solution in the can, wherein in the step of concentrating, the peripheral speed of the stirring blade of the horizontal stirring shaft type mixer is 1.0 to 6.0 m / s. {Arithmetic mean roughness Ra (μm) of the surface of sodium acetate anhydride particles / Thickness d (μm) of sodium acetate anhydride particles} × 100 …… (1) (In the above formula (1), d represents the height when the sodium acetate anhydride particles are placed in the most stable state on a plane. In the above formula (1), as the size of the sodium acetate anhydride particles used for measurement, those having an average length of the major axis and the minor axis of 400 to 900 μm are selected.)

2. A method for producing sodium acetate anhydride particle groups, comprising a step of charging an aqueous sodium acetate solution as a raw material into a can of a horizontal stirring shaft type mixer, and a step of concentrating the aqueous sodium acetate solution in the can, wherein the sodium acetate anhydride particle groups are produced by a method in which the peripheral speed of the stirring blade of the horizontal stirring shaft type mixer in the step of concentrating is 1.0 to 6.0 m / s, and the sodium acetate anhydride particle groups are characterized in that the value shown in the following formula (1) is 2.5% or less, the median diameter is 280 μm or more and 500 μm or less, and the bulk density is 0.75 g / mL or more. {Arithmetic mean roughness Ra (μm) of the surface of sodium acetate anhydride particles / Thickness d (μm) of sodium acetate anhydride particles} × 100 …… (1) (In the above formula (1), d represents the height when the sodium acetate anhydride particles are placed in the most stable state on a plane. In the above formula (1), as the size of the sodium acetate anhydride particles used for measurement, those having an average length of the major axis and the minor axis of 400 to 900 μm are selected.)

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