Granules of magnesium oxide, magnesium oxide tablets and fine granular preparations containing magnesium oxide granules, and methods for producing the same

Abstract

To provide magnesium oxide granules, and magnesium oxide tablets and fine granular preparations containing magnesium oxide granules for improving handling and suppressing blackening, and methods for producing the same.SOLUTION: Magnesium oxide granules having a degree of hydration of 35% or more, and magnesium oxide tablets and fine granular preparations containing the same.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to magnesium oxide granules, magnesium oxide tablets and fine granules containing the same, and methods for producing them. [Background technology]

[0002] Tablets and fine granules containing magnesium oxide granules are widely used for various purposes such as antacid, laxative, magnesium supplement, and antihypomagnesemia.

[0003] It is known that two types of magnesium oxide with different activities are mixed to improve the tableting properties of magnesium oxide tablets. For example, Patent Document 1 discloses magnesium oxide granules that are a mixture of low-activity magnesium oxide and medium- or high-activity magnesium oxide.

[0004] Furthermore, for example, Patent Document 2 discloses a configuration in which magnesium oxide granules are covered with a coating layer made of magnesium hydroxide and / or magnesium carbonate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6343338 [Patent Document 2] Patent No. 4833567 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to improve the handleability of magnesium oxide granules and to suppress the occurrence of blackening. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have succeeded in obtaining magnesium oxide granules with a high degree of hydration. Furthermore, the present inventors have discovered that use of magnesium oxide granules with a high degree of hydration can improve handling properties and suppress the occurrence of darkening, and have arrived at the present invention based on this finding.

[0008] That is, the present invention provides, for example, the following aspects. [1] Magnesium oxide granules with a degree of hydration of 35% or more. [2] The magnesium oxide granules according to [1], wherein the BET specific surface area is 15 to 150 m 2 / g. [3] The magnesium oxide granules according to [1] or [2] have a bulk density of 0.4 to 1.2 g / mL. [4] A magnesium oxide tablet containing the magnesium oxide granules described in any one of [1] to [3]. [5] A method for producing magnesium oxide tablets, comprising tableting a raw material containing the magnesium oxide granules according to any one of [1] to [3]. [6] A method for producing the magnesium oxide granules according to any one of [1] to [3], comprising obtaining magnesium oxide by calcining magnesium hydroxide, wherein the calcination is carried out only at a temperature of 1000°C or less. [7] Magnesium oxide fine granules containing the magnesium oxide granules according to any one of [1] to [3]. [8] A method for producing magnesium oxide fine granules, comprising re-granulating a raw material containing the magnesium oxide granules according to any one of [1] to [3]. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the handling properties of magnesium oxide granules and to suppress the occurrence of blackening. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a photograph showing the side surface of the tablets obtained in Examples 1 and 5 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the present invention will be described based on specific embodiments, but the present invention is not limited to these embodiments and can be implemented with any modifications as long as they do not deviate from the gist of the present invention.

[0012] [Magnesium oxide granules] Magnesium oxide granules can be difficult to handle. For example, magnesium oxide granules present a problem with their compactibility during tableting. Patent Document 1 reports mixing two types of magnesium oxide with different activities to improve tableting compactibility. However, mixing low-activity magnesium oxide results in blackening of the tablet surface during tableting. Patent Document 2 reports coating the surface of magnesium oxide granules to prevent blackening during tableting. However, the present inventors believed that coating the granules would reduce the purity of the magnesium oxide, leading to a decrease in the magnesium oxide content in the tablet, and conducted further investigations. Surprisingly, the present inventors were able to improve the handling of the granules and prevent blackening during tableting by adjusting the degree of hydration of magnesium oxide granules. The improved handleability of magnesium oxide granules also improves compactibility during tableting, facilitating tableting. According to the present invention, it is possible to produce tablets with an extremely low content of low-activity magnesium oxide and a high content of medium- to high-activity magnesium oxide. Furthermore, according to the present invention, it is possible to suppress the occurrence of darkening on the tablet surface without coating the magnesium oxide granules. Furthermore, according to the present invention, it is possible to produce fine granules with an extremely low content of low-activity magnesium oxide and an extremely high content of medium- to high-activity magnesium oxide. Darkening due to metal wear may occur during the granulation process in the production of fine granules, but the occurrence of such darkening can be suppressed by adjusting the degree of hydration. Note that the magnesium oxide granules disclosed in the present invention may contain low-activity magnesium oxide, as long as the degree of hydration is adjusted and the occurrence of darkening can be suppressed during the production of tablets and fine granules.

[0013] When the degree of hydration of magnesium oxide granules is calculated using the following formula, from the viewpoint of achieving the present invention, the lower limit should be 30% or more, preferably 32.5% or more, and more preferably 35% or more. On the other hand, the upper limit is not particularly limited, but since a too high degree of hydration means that the reaction from magnesium hydroxide to magnesium oxide has not progressed, the degree of hydration should generally be 70% or less, preferably 65% or less, and even more preferably 60% or less. The degree of hydration of magnesium oxide granules does not necessarily correlate with the degree of hydration of magnesium oxide powder. For example, even when the same magnesium oxide powder is used, the degree of hydration of magnesium oxide granules varies depending on the granule density and particle size. For example, the hydration degree of magnesium oxide granules tends to decrease as the granule density increases. By controlling the hydration degree of magnesium oxide granules in the granular state within the above range, the effects of the present invention can be significantly achieved.

[0014] In this specification, the "degree of hydration" is determined by the following method. Weigh 2 g of sample into a magnetic crucible of known mass, add 5 ml of water, mix well for 1 minute, and leave to stand at room temperature for 1 hour. After leaving to stand, dry for 2.5 hours in a constant temperature dryer at 105°C. After drying, place in a desiccator and allow to cool for 30-60 minutes before weighing. Heat in an electric furnace at 980°C for 1 hour. Then, place again in the desiccator and allow to cool for 30-60 minutes before weighing. The degree of hydration is calculated using the following formula: Formula 1: Degree of hydration = 100 x (weight of sample after drying (g) - weight of sample after heating (g)) / weight of sample after heating (g)

[0015] The BET specific surface area of magnesium oxide granules is controlled by the degree of crystal growth and impurity content of magnesium hydroxide before calcination, the steam atmosphere during calcination, etc. The higher the degree of crystal growth of magnesium hydroxide before calcination, the higher the BET of magnesium oxide granules tends to be. Also, the higher the impurity content of magnesium hydroxide before calcination, the lower the BET of magnesium oxide granules tends to be. Furthermore, the BET of magnesium oxide granules tends to be lower when magnesium oxide powder is calcined in an atmosphere with a higher amount of steam. It is preferable to adjust the above conditions appropriately so that the BET specific surface area of the magnesium oxide granules falls within the following lower and upper limits. The lower limit is 10 m 2 / g or more, especially 15m 2 / g or more, even 20m 2 / g or more is preferable. The upper limit is 150m 2 / g or less, 100m 2 / g or less, more preferably 60m 2 / g or less, especially 50m 2 / g or less, and even 40m 2 / g or less is preferable. By adjusting the BET specific surface area within this range, the water absorption of magnesium oxide can be suppressed. Furthermore, during tableting, tablets with high water resistance can be formed. In particular, 2 When the content is 0.01g or less, the storage stability is excellent when the tablet is made.

[0016] In this specification, the BET specific surface area means the specific surface area of magnesium oxide granules measured by the BET method. A specific method for measuring the BET specific surface area will be described in the examples below.

[0017] The bulk density of magnesium oxide granules can be controlled by the degree of crystal growth of magnesium hydroxide before calcination and the mechanism and type of mill used in the milling process described below. The bulk density of magnesium oxide granules tends to be higher when the degree of crystal growth of magnesium hydroxide before calcination is higher. It is preferable to adjust the above conditions appropriately to set the bulk density of the magnesium oxide granules within the following lower and upper limits. The lower limit is 0.3 g / mL or more, preferably 0.35 g / mL or more, and even more preferably 0.4 g / mL or more. The upper limit is 1.0 g / mL or less, preferably 1.1 g / mL or less, and even more preferably 1.2 g / mL or less. Adjusting the bulk density within this range allows for the production of magnesium oxide with even better handleability.

[0018] Bulk density can be measured in accordance with the Japanese Pharmacopoeia General Test Method 3.01 Bulk Density and Tapped Density Measurement Method. For example, bulk density can be measured using a 100 mL stainless steel cup (actual measured mass (g) / 100 (mL)).

[0019] In one embodiment, the magnesium oxide granules do not contain low-activity magnesium oxide. Not containing low-activity magnesium oxide is preferred from the viewpoint of suppressing the occurrence of darkening during tablet molding. Not containing low-activity magnesium oxide is preferred from the viewpoint of suppressing the occurrence of darkening during the production of fine granules. In one embodiment, the magnesium oxide granules are composed of medium- to high-activity magnesium oxide.

[0020] In this specification, the term "low activity magnesium oxide" may refer to magnesium oxide obtained by calcining magnesium hydroxide at an average calcination temperature of 1000°C to 2000°C. For example, to obtain "low activity magnesium oxide," any average calcination temperature can be used, such as 1000°C to 1100°C, 1100°C to 1200°C, 1200°C to 1500°C, 1500°C to 1700°C, or 1700°C to 2000°C. The term "medium-high activity magnesium oxide" may refer to magnesium oxide obtained by calcining magnesium hydroxide at an average calcination temperature of 500°C to 900°C. For example, to obtain "medium-high activity magnesium oxide," any average calcination temperature can be used, such as 700°C to 800°C, 800°C to 900°C, or 900°C to 1000°C. However, the activity of magnesium oxide may also be determined by an index commonly used in the field. For example, the CAA value described in Patent Document 1 can be used.

[0021] The magnesium hydroxide is not limited, and may be natural or synthetic, or may be commercially available. For example, magnesium hydroxide can be obtained by the reaction process described below.

[0022] The particle size of the magnesium oxide granules is not limited. The upper limit of the average particle size can be, for example, 1000 μm or less, particularly 750 μm or less, or even 500 μm or less. The lower limit can be, for example, 250 μm or more, particularly 200 μm or more, or even 150 μm or more.

[0023] The darkening of magnesium oxide tablets and magnesium oxide granules can be measured by any method, such as using image analysis software such as ImageJ (NIH) or visually inspecting using a digital microscope (Hirox, KH-8700).

[0024] [Manufacturing method of magnesium oxide granules] The present embodiment relates to a method for producing magnesium oxide granules.

[0025] In one embodiment, the production method includes a reaction step of calcining magnesium hydroxide. In the reaction step, magnesium hydroxide can be obtained by carrying out the following reaction using a magnesium raw material and an alkali raw material. As the magnesium raw material, for example, seawater can be used. It is preferable to remove impurities from the seawater in advance. For example, purified seawater can be used. As the alkali raw material, for example, slaked lime (Ca(OH)2) and caustic soda (NaOH) can be mentioned. Although the alkali raw material is not limited, caustic soda is preferred from the viewpoint of reducing the amount of heavy metals in the magnesium oxide granules. MgCl2+1.8NaOH→0.9Mg(OH)2+1.8NaCl+0.1MgCl2

[0026] When synthesizing magnesium hydroxide, the reaction rate can be increased by employing a seed crystal reaction in which the magnesium hydroxide slurry obtained in the synthesis is re-added. During the seed crystal reaction, the magnesium hydroxide slurry is re-added to the reaction vessel in an amount two to four times the reaction amount. The seed crystal reaction is also preferred from the viewpoint of achieving a desirable bulk density for the magnesium oxide granules. Furthermore, the seed crystal reaction can improve the handleability of the resulting magnesium oxide granules.

[0027] However, magnesium hydroxide can be obtained by any method as described above, and the method of obtaining it is not limited.

[0028] In one embodiment, the production method includes a washing step of washing the magnesium hydroxide. In the washing step, the magnesium hydroxide obtained in the reaction step may be washed. Washing can be performed by a method commonly used in the art. For example, washing can be performed using a washer. An example of the washer is a vacuum filter. By performing the washing step, excess salts can be removed from the magnesium hydroxide. An example of the excess salts is sodium salt.

[0029] In one embodiment, the production method includes a drying step of drying the magnesium hydroxide. The magnesium hydroxide obtained in the drying step can be subjected to a calcination step to rapidly perform calcination. Drying can be performed by a method commonly used in the art. For example, drying can be performed using hot air. The upper limit of the hot air temperature is 500°C or less, preferably 400°C or less, and more preferably 300°C or less. The lower limit is 80°C or more, preferably 90°C or more, and more preferably 100°C or more. The drying time varies depending on the drying temperature and is not limited, but the upper limit is 200 minutes or less, preferably 150 minutes or less, and more preferably 100 minutes or less. The lower limit is 10 minutes or more, preferably 20 minutes or more, and more preferably 30 minutes or more.

[0030] In one embodiment, the production method includes a calcination step of calcining magnesium hydroxide. Magnesium oxide is obtained by the calcination step. Calcination can be performed by a method commonly used in the art. For example, calcination can be performed using a calciner. Examples of calciners include rotary kilns. Furthermore, although not limited thereto, the use of indirect hot air in calcination can result in more active magnesium oxide.

[0031] The upper limit of the firing temperature is preferably 1000°C or less, particularly 950°C or less, and even more preferably 900°C or less, as the average firing temperature. Setting the upper limit as described above makes it possible to obtain a raw material for magnesium oxide granules with high activity. By setting the temperature within the above range, the obtained magnesium oxide does not contain low-activity magnesium oxide, thereby suppressing the occurrence of blackening. Furthermore, firing at high temperatures increases the hardness of the particles due to sintering. Increased particle hardness increases metal abrasion. However, by setting the temperature within the above range, such metal abrasion can be suppressed. The lower limit of the firing temperature is not particularly limited, but from the viewpoint of firing time, it is preferably 450°C or more, particularly 470°C or more, and even more preferably 500°C or more.

[0032] By calcining magnesium hydroxide within the above temperature range, it is possible to obtain magnesium oxide having a degree of hydration and bulk density that satisfy the above ranges. Furthermore, the magnesium oxide obtained by calcining within the above temperature range can suppress sintering. Furthermore, the use of magnesium oxide obtained by calcining within the above temperature range can suppress the occurrence of blackening.

[0033] The degree of hydration and bulk density of magnesium oxide can be controlled by appropriately adjusting the thermal history when calcining magnesium hydroxide. Specific examples of the thermal history include calcination conditions or calcination equipment such as the temperature rise time, holding temperature, holding time, and temperature drop time when calcining magnesium hydroxide. Examples of calcination equipment include rotary kilns, tunnel kilns, and shuttle kilns. In the case of a rotary kiln, conditions such as the kiln rotation speed, kiln installation angle, kiln overall length, and kiln diameter during calcination can be adjusted. Since various conditions vary depending on the equipment, the degree of hydration and bulk density can be adjusted by appropriately adjusting them within the scope of the embodiment.

[0034] Here, in this specification, the meanings of the terms relating to the calcination of magnesium hydroxide are as follows. Heating time: When calcining magnesium hydroxide, this refers to the time it takes to heat from room temperature to reach the maximum target temperature. Holding temperature: This refers to the target average temperature when calcining magnesium hydroxide. It is also called the calcination temperature. Holding time: This refers to the time for which the holding temperature is maintained when calcining magnesium hydroxide. Cooling time: When calcining magnesium hydroxide, this refers to the time it takes to cool from the holding temperature to room temperature after the holding time has elapsed. Note that cooling includes active cooling using a cooling means as well as gradual cooling such as natural cooling.

[0035] The thermal history is not particularly limited as long as the average firing temperature is within the above temperature range. As a firing condition, a temperature rise time may or may not be required. However, if a temperature rise time is required, it may be set within a range of 0.5 to 3 hours, for example, 0.5 to 2 hours. The holding temperature is preferably 350 to 900°C, more preferably 400 to 800°C. Furthermore, the holding time is preferably 0 to 3 hours, more preferably 0 to 2 hours. Furthermore, the temperature drop time is preferably 10 to 40 hours, more preferably 15 to 30 hours.

[0036] The kiln rotation speed, kiln installation angle, kiln overall length, and kiln diameter are not particularly limited. For example, the kiln rotation speed is preferably 40 to 60 seconds per rotation, more preferably 45 to 55 seconds per rotation. The kiln installation angle preferably has a gradient of 1 to 4%, more preferably a gradient of 2 to 3%. The kiln overall length is preferably 10 to 30 m, more preferably 20 to 25 m. The kiln diameter is preferably 1 to 2 m, more preferably 1.1 to 1.4 m.

[0037] In one embodiment, the production method includes a pulverization step of pulverizing magnesium oxide. The pulverization can be performed by a method commonly used in the art. For example, the pulverization can be performed using a pulverizer. Examples of the pulverizer include an impact pulverizer.

[0038] In one embodiment, the production method includes a classification step of classifying magnesium oxide. The classification step produces a magnesium oxide product with a certain particle size. The upper limit of the average particle size of the classified product is not limited, but can be, for example, 50 μm or less, particularly 30 μm or less, or even 20 μm or less. The lower limit can be, for example, 1 μm or more, particularly 3 μm or more, or even 5 μm or more. The classification can be carried out using a classifier commonly used in this field. Examples of classifiers include air classifiers.

[0039] In one embodiment, the production method includes a granulation step of granulating magnesium oxide. Magnesium oxide granules having a certain particle size are obtained by the granulation step. The average particle size of the magnesium oxide granules is as described above. In one embodiment, the granulation step includes compression molding of the magnesium oxide. The compression molding can be performed by a method commonly used in the art. For example, a commercially available granulator or roller compactor can be used. Examples of granulators include dry granulators. The roller pressure is not limited, but can be, for example, 10 to 20 MPa. In one embodiment, the granulation step may include pulverizing the compression-molded magnesium oxide. The pulverization is as described above. In one embodiment, the granulation step includes sizing the magnesium oxide. Compression-molded magnesium oxide may be used for sizing. Sizing can be performed by a method commonly used in the art. For example, sizing can be performed using a vibrating sieve. In this case, magnesium oxide granules having the above-described average particle size can be obtained by adjusting the sizes of the upper and lower screens of the vibrating sieve. By setting the average particle size within the above range, it is possible to obtain magnesium oxide having a degree of hydration and bulk density that satisfy the above ranges.

[0040] [Magnesium oxide tablets] The present embodiment relates to a tablet containing magnesium oxide granules. In one aspect, the tablet contains magnesium oxide granules as a main component.

[0041] The content of magnesium oxide granules contained in the magnesium oxide tablet is not limited. For example, the upper limit can be, for example, 100% by mass or less, 95% by mass or less, or 90% by mass or less, based on the entire tablet. For example, the lower limit can be, for example, 70% by mass or more, 80% by mass or more, or 85% by mass or more, based on the entire tablet. Additives may be used in the tablet as needed. Examples of additives include, but are not limited to, various pharmaceutically acceptable pharmaceutical additives, such as excipients, binders, disintegrants, lubricants, colorants, and flavoring agents. These components may be used alone or in any combination of two or more.

[0042] [Magnesium oxide tablet manufacturing method] The present embodiment relates to a method for producing magnesium oxide tablets. In one aspect, the production method includes a tableting step of tableting a raw material containing magnesium oxide granules. In one aspect, the raw material containing magnesium oxide granules contains magnesium oxide granules as a main component. As described above, the content of magnesium oxide granules in the raw material is not particularly limited, and any content can be adopted.

[0043] In the tableting process, the raw materials are tableted by a method commonly used in the art. For example, tableting can be performed using a tablet press. The tableting pressure is also not limited. For example, the upper limit of the punch pressure per tablet can be 20 kN or less, or 18 kN or less, or 16 kN or less. For example, the lower limit can be 2 kN or more, or 3 kN or more, or 4 kN or more. The shape of the punch is also not limited. For example, shapes include a standard R, a two-stage R, a sugar-coated R, a corner R, a corner flat, and a rounded corner flat.

[0044] In one embodiment, the manufacturing method includes a mixing step of mixing raw materials containing magnesium oxide granules prior to the tableting step, wherein the raw materials containing magnesium oxide granules are mixed by a method commonly used in the art.

[0045] [Magnesium oxide granules] This embodiment relates to fine granules containing magnesium oxide granules. In one aspect, the fine granules contain magnesium oxide granules as a main component. As with magnesium oxide tablets, the content of magnesium oxide granules in the magnesium oxide fine granules is not particularly limited and any content can be used.

[0046] The upper limit of the average particle size of the magnesium oxide granules is not limited, but may be, for example, typically 850 μm or less, 700 μm or less, or 500 μm or less.The lower limit of the particle size is not limited, but may be, for example, typically 100 μm or more, 200 μm or more, or 300 μm or more.

[0047] [Manufacturing method of magnesium oxide granules] The present embodiment relates to a method for producing magnesium oxide fine granules. In one aspect, the production method includes a granulation step of granulating a raw material containing magnesium oxide granules. In one aspect, the raw material containing magnesium oxide granules contains magnesium oxide granules as a main component. As described above, the content of the magnesium oxide granules in the raw material is not particularly limited, and any content can be adopted.

[0048] In the granulation step, the raw materials are granulated by a method commonly used in the art. For example, granulation can be performed by a fluidized bed granulation method or a dry granulation method. Among these, the fluidized bed granulation method is preferred from the viewpoint of ease of adjustment to a desired average particle size and bulk density. By the granulation step, magnesium oxide fine granules having the desired average particle size as described above can be obtained.

[0049] Although various aspects of the present invention have been described above, the present invention is not limited to these aspects. As will be apparent to those skilled in the art, any other aspect of the present invention may be extracted from the above detailed description and the following description of the examples. [Example]

[0050] The present invention will be described in more detail below with reference to examples. However, these examples are merely examples shown for the convenience of explanation, and the present invention is not limited to these examples in any sense.

[0051] [Magnesium oxide granules manufacturing ] Example 1 The magnesium oxide granules of Example 1 were produced by the following steps. 1.Reaction process Purified seawater was used as the magnesium raw material, and caustic soda (manufactured by Tokuyama Corporation) was used as the alkaline raw material. The following reaction was carried out using these magnesium raw materials and alkaline raw materials. MgCl2+1.8NaOH→0.9Mg(OH)2+1.8NaCl+0.1MgCl2 When synthesizing magnesium hydroxide, a seed crystal reaction was employed in which the magnesium hydroxide slurry obtained during synthesis was re-added. During the seed crystal reaction, magnesium hydroxide slurry was re-added to the reaction vessel in an amount 2 to 4 times the reaction volume. The reaction temperature was not specifically controlled, and the reaction was carried out continuously with a residence time of 30 minutes or more. A suspension containing magnesium hydroxide was obtained from the reaction process. 2. Cleaning process The magnesium hydroxide suspension obtained in the reaction step was washed with softened water treated with a water softener (manufactured by Kurita Technical Services Co., Ltd.) to remove salts including sodium. 3.Drying process The washed magnesium hydroxide obtained in the washing step was dried with hot air at 100°C to 300°C for 40 minutes. 4. Firing process The dried magnesium hydroxide obtained in the drying process was calcined in a rotary kiln (Iwasa Machinery Co., Ltd.) at an average calcination temperature of 720°C for 90 minutes. No heating time was set, and the holding temperature was the same as the average calcination temperature, 720°C, and the holding time was the same as the calcination time, 90 minutes. After calcination, the magnesium oxide was cooled through a crushing process and a classification process, and the temperature drop time was 20 hours. 5. Crushing process The magnesium oxide baked product obtained in the baking step was pulverized using an impact pulverizer (Nara Machinery Manufacturing Co., Ltd., Jiyuu Pulverizer). 6.Classification process The magnesium oxide pulverized product obtained in the pulverization step was classified using an air classifier (Hosokawa Micron Corporation, Micron Separator) to obtain magnesium oxide particles with a particle size of 10 μm. 7. Granulation process The magnesium oxide particles obtained in the classification step were compression-molded at a roll pressure of 10 MPa using a laboratory granulator (TF-MINI manufactured by Freund Corporation) and then crushed. The crushed magnesium oxide was then sized using a vibrating sieve with an upper mesh of approximately 500 μm and a lower mesh of approximately 160 μm. The granules between the upper and lower meshes were used as the magnesium oxide granules of Example 1.

[0052] Example 2 In the reaction step, slaked lime was used as the alkali raw material. In the calcination step, an indirect rotary kiln was used instead of a rotary kiln, and calcination was performed using indirect hot air at an average calcination temperature of 720°C. Other than that, the same procedure as in Example 1 was carried out.

[0053] Example 3 The average firing temperature in the firing step was changed to 750° C. Except for this, the same procedure as in Example 1 was carried out.

[0054] Example 4 In the granulation step, a roller compactor (manufactured by Freund-Turbo) was used instead of the laboratory granulator, and compression molding was performed at a roll pressure of 20 MPa. Except for this, the same procedure as in Example 1 was carried out.

[0055] Example 5 The average firing temperature in the firing step was changed to 900°C. In the granulation step, a roller compactor (manufactured by Freund-Turbo) was used instead of the laboratory granulator, and compression molding was performed at a roll pressure of 20 MPa. Other than that, the same procedure as in Example 1 was carried out.

[0056] Comparative Example 1 Magnesium oxide granules were obtained according to the procedure of Example 1 described in Patent Document 1. More specifically, magnesium oxide was obtained by calcining at an average calcination temperature of 750°C in the calcination step, and magnesium oxide was obtained by calcining at an average calcination temperature of 1100°C. These magnesium oxides were mixed in a 1:1 ratio and subjected to a granulation step. Other than that, the same procedure as in Example 1 was carried out.

[0057] Comparative Example 2 Magnesium oxide granules were obtained according to the procedure of Example 1 described in Patent Document 1. More specifically, in the reaction step, slaked lime was used as the alkaline raw material. In the calcination step, magnesium oxide calcined at an average calcination temperature of 770°C and magnesium oxide calcined at an average calcination temperature of 1150°C were obtained. These magnesium oxides were mixed in a 1:1 ratio and subjected to the granulation step. In the granulation step, a roller compactor (manufactured by Freund Turbo) was used instead of a laboratory granulator, and compression molding was performed at a roll pressure of 20 MPa. Other than that, the same procedure as in Example 1 was carried out.

[0058] Comparative Example 3 In the reaction process, slaked lime was used as the alkaline raw material. The average firing temperature in the firing process was changed to 1200°C. In the granulation process, a roller compactor (manufactured by Freund Turbo) was used instead of an experimental granulator, and compression molding was attempted at a roll pressure of 20 MPa, but granulation was not possible, and tablets could not be formed.

[0059] The physical properties of the magnesium oxide granules obtained in this example were measured by the following methods. [Degree of hydration] 2 g of sample was weighed into a magnetic crucible of known mass, 5 ml of water was added, and the mixture was mixed thoroughly for 1 minute and allowed to stand at room temperature for 1 hour. After standing, the sample was dried for 2.5 hours in a constant temperature dryer (Yamato Scientific Co., Ltd., low-temperature dryer DS-44) at 105°C. After drying, the sample was placed in a desiccator and allowed to cool for 30 to 60 minutes before being weighed. The sample was heated at 980°C for 1 hour in an electric furnace (Advantec Toyo Co., Ltd., electric muffle furnace FUW230PA). After that, the sample was placed in the desiccator again and allowed to cool for 30 to 60 minutes before being weighed. The degree of hydration was calculated using the above formula 1.

[0060] [Bulk density] The bulk density was measured using a stainless steel cup (actual mass (g) / 100 (mL)). The BET specific surface area was measured using a fully automatic surface area measuring device (manufacturer: Microtrack Bell).

[0061] [Magnesium oxide tablet manufacturing] The magnesium oxide granules of Examples 1 to 5 and Comparative Examples 1 to 3 were tableted using a tablet press (a small high-speed rotary tablet press, VIRG, manufactured by Kikusui Seisakusho Co., Ltd.) under the following conditions. Pestle...φ9 Number of pestles: 2 Rotating disc speed: 50 rpm Tablet weight: 370 mg Locking pressure: 10kN Tablet thickness: Free due to constant tableting pressure

[0062] The obtained tablets were photographed using a scanning electron microscope (manufactured by Keyence Corporation), and the presence or absence of blackening was visually confirmed.

[0063] [result] The results are shown in the table below and in FIG. [Table 1] [Table 2]

[0064] As shown in Table 1, when medium- to high-activity magnesium oxide was fired at a low temperature of 1000°C or less, magnesium oxide granules with a degree of hydration of 35% or more and a bulk density in the range of 0.4 to 1.2 g / mL were obtained. In addition, the BET specific surface area was also 15 to 50 m 2 / g, which was within a good range. Furthermore, as shown in Table 1, when the magnesium oxide granules of Examples 1 to 5 were used, no darkening was observed during tableting. Figure 1 shows the tablets obtained in Examples 1 and 5. Similarly to Examples 1 and 5, no darkening was observed during tableting in Examples 2 to 4. On the other hand, in the case of a mixture of medium-high activity magnesium oxide and low activity magnesium oxide calcined at a high temperature exceeding 1000°C, although the bulk density and BET specific surface area of Comparative Examples 1 and 2 were within the above ranges, the degree of hydration of the magnesium oxide granules was less than 35%. Furthermore, as shown in Table 2 and Figure 1, darkening was observed during tableting. This is thought to be due to the addition of low activity magnesium oxide. Therefore, the use of the magnesium granules of the present invention enables improved handleability and suppression of darkening. [Industrial Applicability]

[0065] The present invention has extremely high applicability in industrial fields where improved handling properties and reduced occurrence of blackening of magnesium oxide granules are required, particularly in the fields of pharmaceutical production and distribution.

Claims

1. A method for producing magnesium oxide tablets, comprising: The method includes tableting a raw material containing magnesium oxide granules having a degree of hydration of 35% or more and 60% or less and a bulk density of 0.3 to 1.2 g / mL without coating the magnesium oxide granules, at a punch pressure of 2 kN or more and 20 kN or less per tablet; The content of the magnesium oxide granules is 70% by mass or more relative to the tablet, The magnesium oxide granules used in the method include: A method for producing magnesium oxide tablets, which are obtained by calcining magnesium hydroxide to produce magnesium oxide, classifying the resulting magnesium oxide into particles of 1 μm or more and 50 μm or less, and dry granulating the resulting particles.

2. The content of the magnesium oxide granules in the tablet is 100% by mass or less, The method for producing magnesium oxide tablets according to claim 1, wherein the calcination is carried out in a rotary kiln at a temperature of 1000°C or less.

3. A method for producing magnesium oxide tablets as described in claim 1 or claim 2, wherein the punch pressure is 4 kN or more and 16 kN or less.

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