Magnesium oxide powder for tablets and method for producing the same

Abstract

To provide a production method for magnesium oxide powder for tablets that has suppressed bulk density and excellent compression moldability during tableting.SOLUTION: The method includes the steps of (1) preparing a slurry containing magnesium hydroxide and magnesium carbonate, (2) drying the slurry of (1), and (3) calcining the dried product of (2). The ratio of magnesium hydroxide to the total amount of magnesium hydroxide and magnesium carbonate in the slurry of the step (1) is 5 to 70% in mass ratio based on magnesium oxide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to magnesium oxide powder for tablets and a method for producing the same. [Background technology]

[0002] Tablets containing magnesium oxide as the main active ingredient are widely used for various purposes such as antacids, laxatives, magnesium supplementation, and anti-hypomasemia. Such tablets are manufactured by combining magnesium oxide powder with additives such as binders and disintegrants and then compressing the mixture into tablets.

[0003] Conventionally, methods for producing magnesium oxide powder include burning metallic magnesium to oxidize it, or calcining magnesium salts to thermally decompose them. Examples of magnesium salts used as raw materials include magnesium hydroxide and magnesium carbonate (Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2016 / 147862 [Overview of the project] [Problems that the invention aims to solve]

[0005] One of the objectives of the present invention is to provide magnesium oxide powder for tablets that has a low bulk density and excellent compression moldability during tableting, as well as a method for producing the same. [Means for solving the problem]

[0006] As a result of diligent research, the inventors have discovered that by preparing a mixed slurry containing magnesium hydroxide and magnesium carbonate in a predetermined ratio, and then drying and calcining it, a magnesium oxide powder for tablets can be obtained that has reduced bulk density and excellent compression moldability during tableting, thus completing the present invention.

[0007] In other words, the purpose of this invention relates, for example, to the following: [1] A method for producing magnesium oxide powder for tablets. The above method includes a preparation step, a production step, and a calcination step. The preparation step prepares a slurry containing magnesium hydroxide and magnesium carbonate. The production step produces a dried product by drying the slurry. The calcination step calcines the dried product. In the above method, the ratio of magnesium hydroxide to the total amount of magnesium hydroxide and magnesium carbonate in the slurry is 5 to 75% by mass ratio in terms of magnesium oxide. In the manufacturing method described in [2][1], the magnesium hydroxide in the slurry is magnesium hydroxide produced by the seawater method or the bittern method. In the manufacturing method described in [3] [1] or [2], the slurry is prepared by preparing a first slurry and a second slurry, respectively. The first slurry contains the magnesium hydroxide. The second slurry contains the magnesium carbonate. The slurry is prepared by mixing and stirring the first slurry and the second slurry. In the manufacturing method described in any one of items [4][1] to [3], the firing step is carried out at a temperature of 600 to 1000°C. [5] Magnesium oxide powder for tablets. The above magnesium oxide powder for tablets is manufactured by the manufacturing method described in any one of items [1] to [4]. The magnesium oxide powder for tablets described in [6][5] has a BET specific surface area of ​​39 m². 2 It is less than / g. The magnesium oxide powder for tablets described in [7], [5], or [6] has a bulk density of 85 mL / 10 g or less. [8] Magnesium oxide powder for tablets. The above magnesium oxide powder for tablets contains hexagonal prismatic magnesium oxide and needle-shaped magnesium oxide. The above magnesium oxide powder for tablets has a BET specific surface area of ​​39 m². 2 The value is less than / g. The magnesium oxide powder for tablets has a bulk density of 85 mL / 10 g or less. [9] Magnesium oxide tablets. The above magnesium oxide tablets contain the magnesium oxide powder for tablets described in any one of items [5] to [8]. In the magnesium oxide tablets described in

[10] [9], the hardness is 30N or higher. In the magnesium oxide tablets described in

[11] [9] or

[10] , the tensile strength is 1.3 N / mm 2 That's all. [Effects of the Invention]

[0008] The present invention provides magnesium oxide powder for tablets that has reduced bulk density and excellent compression moldability during tableting, as well as a method for producing the same. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a scanning electron microscope (SEM) image of a cross-section of a tablet obtained by compressing the magnesium oxide powder sample from Example 3. In the image, the region considered to correspond to magnesium carbonate is indicated by a bounding box. [Figure 2] Figure 2 is an SEM image of a cross-section of a tablet obtained by compressing the magnesium oxide powder sample of Comparative Example 4. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below with reference to specific embodiments. However, the present invention is not limited to the following embodiments and can be implemented in any form without departing from the spirit of the invention.

[0011] One embodiment of the present invention relates to a method for producing magnesium oxide powder for tablets. The manufacturing method of this embodiment is characterized by comprising the following steps. (1) A step of preparing a slurry containing magnesium hydroxide and magnesium carbonate. (2) A step of drying the slurry. (3) A step of firing the above dried material.

[0012] In step (1), a slurry containing magnesium hydroxide and magnesium carbonate is prepared. Such a slurry is formed by dispersing magnesium hydroxide and magnesium carbonate in water or an aqueous medium.

[0013] The method for producing magnesium hydroxide used in step (1) is not particularly limited. According to one embodiment, examples include the seawater method or the bittern method. Magnesium hydroxide produced by the seawater method or the bittern method has large particles and is an aggregate, so it has excellent handling properties.

[0014] When producing magnesium hydroxide (Mg(OH)₂) by the seawater method, the procedure is not limited, but for example, the following can be mentioned. As the magnesium raw material, seawater is used. As the alkali raw material, for example, slaked lime is used. These magnesium raw material and alkali raw material are continuously reacted. The reaction temperature is as it goes, and the residence time is, for example, 10 minutes or more. The product obtained by the reaction is concentrated, for example, to a solid content concentration of 5% by mass or more. The obtained concentrated product is washed to remove salts such as sodium, whereby a slurry of magnesium hydroxide can be obtained. Hereinafter, the magnesium hydroxide thus produced is also referred to as "seawater method magnesium hydroxide".

[0015] When producing magnesium hydroxide (Mg(OH)₂) by the bittern method, the procedure is not limited, but for example, the following can be mentioned. As the magnesium raw material, bittern is used. As the alkali raw material, for example, slaked lime is used. These magnesium raw material and alkali raw material are continuously reacted. The reaction temperature is as it goes, and the residence time is, for example, 10 minutes or more. The obtained product is washed to remove salts such as sodium, whereby a magnesium hydroxide slurry can be obtained. Hereinafter, the magnesium hydroxide thus produced is also referred to as "bittern method magnesium hydroxide".

[0016] As for magnesium hydroxide, one type of magnesium hydroxide may be used alone, or two or more types of magnesium hydroxide may be used in any ratio. The two or more types of magnesium hydroxide may be a combination of magnesium hydroxide produced by the seawater method and magnesium hydroxide produced by the brine method. Alternatively, the two or more types of magnesium hydroxide may be a combination of two or more types of magnesium hydroxide produced by the seawater method with different BET specific surface areas. Alternatively, the two or more types of magnesium hydroxide may be a combination of two or more types of magnesium hydroxide produced by the brine method with different BET specific surface areas.

[0017] Magnesium hydroxide obtained by the seawater process is finely divided and tends to become a powder suitable for tablet applications when converted to magnesium oxide. However, because the amount of magnesium in seawater is small, the manufacturing equipment may need to be large. Conversely, magnesium hydroxide obtained by the brine process tends to have somewhat larger particles, but the manufacturing equipment can be relatively compact.

[0018] The method for producing magnesium carbonate used in step (1) is not particularly limited, but one method is to react magnesium hydroxide with carbon dioxide. The procedure is not limited, but for example, the following procedure can be used: Contact magnesium hydroxide with carbon dioxide gas and allow the reaction to proceed until the pH reaches 7-9. Then, heat the reaction mixture to 80°C or higher and hold for 30 minutes or more. By cooling the reaction mixture, magnesium carbonate can be obtained. The magnesium carbonate may be not just one type of magnesium carbonate, but two or more types of magnesium carbonate with different BET specific surface areas. The magnesium carbonate may be natural or synthetic. Synthetic magnesium carbonate is more preferable because it is easier to control the impurity concentration. Heavy magnesium carbonate as defined in the Japanese Pharmacopoeia is more preferable. In the case of light magnesium carbonate, the bulk density becomes very high, making it difficult to use for tablet applications.

[0019] The concentrations of magnesium hydroxide and magnesium carbonate in the slurry of step (1) are not particularly limited. In one embodiment, the total concentration of magnesium hydroxide and magnesium carbonate in the slurry can be, for example, 5% by mass or more, or 10% by mass or more, or for example, 50% by mass or less, or 40% by mass or less, or 30% by mass or less.

[0020] The slurry in step (1) preferably has the characteristic of containing magnesium hydroxide and magnesium carbonate in a predetermined ratio. Specifically, the ratio of magnesium hydroxide to the total amount of magnesium hydroxide and magnesium carbonate is preferably 5% by mass or more, more preferably 10% by mass or more, or 15% by mass or more, in terms of magnesium oxide by mass ratio, and preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less. By setting the ratio of magnesium hydroxide above the lower limit, the compressibility of the resulting magnesium oxide powder during tableting is improved, and the hardness and / or tensile strength of the resulting tablets can be increased. On the other hand, by setting the ratio of magnesium hydroxide below the upper limit, the bulk density of the resulting magnesium oxide powder can be reduced, and the manufacturing efficiency of the tablets can be improved.

[0021] The equivalent magnesium oxide mass of magnesium hydroxide and magnesium carbonate can be calculated from the molecular mass of magnesium hydroxide (Mg(OH)2) (approximately 58.320 g / mol), magnesium carbonate (MgCO3) (approximately 84.3139 g / mol), and magnesium oxide (MgO) (approximately 40.3044 g / mol). For example, the equivalent magnesium oxide mass of 100 g of magnesium hydroxide is 100 g × (40.3044 / 58.320) = approximately 69.11 g, and the equivalent magnesium oxide mass of 100 g of magnesium carbonate is 100 g × (40.3044 / 84.3139) = approximately 47.80 g.

[0022] The slurry in step (1) may contain water or an aqueous medium, magnesium hydroxide, and magnesium carbonate, as well as one or more other components. These other components are not limited to magnesium hydroxide and magnesium carbonate, but include other magnesium salts. Examples of these other magnesium salts are not limited to magnesium chloride, magnesium nitrate, and magnesium sulfate. However, from the viewpoint of increasing the purity of the resulting magnesium oxide and ensuring its uniform physical properties and characteristics, it is preferable to use as few other components as possible.

[0023] The method for preparing the slurry in step (1) is not particularly limited. In one embodiment, the slurry can be obtained by dispersing magnesium hydroxide and magnesium carbonate in water or an aqueous medium to form a slurry. In another embodiment, the slurry can be obtained by preparing a first slurry by dispersing magnesium hydroxide in water or an aqueous medium to form a slurry, and a second slurry by dispersing magnesium carbonate in water or an aqueous medium to form a slurry, and then mixing these first and second slurries.

[0024] During the preparation of the slurry in step (1), stirring may be added. The stirring method is not particularly limited, but one example is stirring with a rotor. The stirring speed is not particularly limited, but can be, for example, 5 to 1000 rpm. The stirring time is not particularly limited, but can be, for example, 10 minutes or more, or 20 minutes or more, or 30 minutes or more.

[0025] In step (2), the slurry from (1) is dried. The drying method is not limited. Examples include natural drying, heat drying, forced-air drying, and reduced-pressure drying, as well as combinations thereof, and any of these may be used.

[0026] Dehydration treatment may be added before or simultaneously with drying in step (2). The dehydration method is not limited. Examples include pressing, water absorption, and volatilization, as well as combinations thereof.

[0027] The drying time in step (2) is not particularly limited and will vary depending on the drying method and whether or not dewatering is performed and the method used. For example, it should be carried out until the moisture content in the slurry (moisture content of the dried product) is 10% by mass or less, and more particularly until it is 3% by mass or less.

[0028] In step (3), the dried material from (2) is fired. The firing conditions are not particularly limited, but for example they can be as follows:

[0029] The firing temperature in step (3) is not limited, but can be, for example, 500°C or higher, 600°C or higher, or 700°C or higher, or it can be, for example, 1300°C or lower, 1200°C or lower, or 1100°C or lower.

[0030] The baking time in step (3) is not limited, but can be, for example, 30 minutes or more, 60 minutes or more, or 90 minutes or more, or can be, for example, within 5 hours, within 3 hours, or within 2 hours.

[0031] Furthermore, the firing temperature and firing time in step (3) can be adjusted as appropriate so that the BET specific surface area or other physical properties and characteristics of the final magnesium oxide satisfy the range described later.

[0032] The manufacturing method of the embodiment described above makes it possible to obtain magnesium oxide powder for tablets that has a reduced bulk density and excellent compression moldability during tableting. The reason for this is not entirely clear, but it is presumed that magnesium oxide derived from magnesium hydroxide contributes to the reduction of bulk density, while magnesium oxide derived from magnesium carbonate contributes to the improvement of compression moldability during tableting. Furthermore, it is presumed that by drying and calcining the magnesium hydroxide and magnesium carbonate in a uniformly slurryed state, the desirable properties of both magnesium hydroxide-derived magnesium oxide and magnesium carbonate-derived magnesium oxide are exhibited in a well-balanced manner, resulting in magnesium oxide powder that possesses both properties. In this specification, "excellent compression moldability" during tableting means that when tablets are compressed, tablets with excellent hardness and / or tensile strength are obtained.

[0033] One embodiment of the present invention relates to magnesium oxide powder for tablets produced by the manufacturing method of the embodiment. Such magnesium oxide powder has a low bulk density and excellent compression moldability during tableting, and can be suitably used in the manufacture of tablets.

[0034] One embodiment of the present invention relates to a magnesium oxide powder for tablets that satisfies the following characteristics. Such magnesium oxide powder for tablets can be manufactured, for example, by the manufacturing method of the embodiment, but is not limited thereto.

[0035] The magnesium oxide powder of this embodiment, when observed with a scanning electron microscope (SEM), contains hexagonal prismatic magnesium oxide and needle-shaped magnesium oxide. In one embodiment, the hexagonal prismatic magnesium oxide originates from magnesium hydroxide, and the needle-shaped magnesium oxide originates from magnesium carbonate. Although not bound by theory, it is presumed that the magnesium oxide powder of this embodiment has an appropriate amount of needle-shaped magnesium oxide derived from magnesium carbonate within the hexagonal prismatic magnesium oxide derived from magnesium hydroxide, which allows for improved hardness and tensile strength of tablets during tableting while suppressing bulk density.

[0036] The BET specific surface area of the magnesium oxide powder of this embodiment is not limited, but its upper limit value is, for example, 39 m 2 / g or less, or 38 m 2 / g or less, or 37 m 2 / g or less, which is preferable. By setting the BET specific surface area of the magnesium oxide powder to be below the upper limit, the bulk density of the magnesium oxide powder can be suppressed, and the manufacturing capacity during tablet production is likely to be improved. On the other hand, although not limited, its lower limit value is, for example, 15 m 2 / g or more, or 20 m 2 / g or more, or 25 m 2 / g or more. The method for measuring the BET specific surface area of the magnesium oxide powder is not particularly limited. For example, it can be measured by the gas adsorption method using a specific surface area measuring device.

[0037] The bulk density of the magnesium oxide powder of this embodiment is not limited, but its upper limit value is preferably, for example, 85 mL / 10 g or less, or 80 mL / 10 g or less, or 70 mL / 10 g or less. By setting the bulk density of the magnesium oxide powder to be below the upper limit, the manufacturing capacity during tablet production using the magnesium oxide powder is likely to be improved. On the other hand, although not limited, its lower limit value can be, for example, 20 mL / 10 g or more, or 25 mL / 10 g or more, or 30 mL / 10 g or more. The method for measuring the bulk density of the magnesium oxide powder is not particularly limited, but it can be obtained, for example, by measuring the volume and mass of the magnesium oxide powder and calculating the volume per 10 g.

[0038] One embodiment of the present invention relates to a tablet containing magnesium oxide powder. According to one aspect, such a magnesium oxide tablet contains, as a main component, the magnesium oxide powder for tablets of the above-described embodiment.

[0039] The magnesium oxide tablets of this embodiment preferably have a hardness and / or tensile strength above a predetermined value. Specifically, the hardness of the magnesium oxide tablets of this embodiment is not limited, but its lower limit is preferably, for example, 30 N or more, or 35 N or more, or 40 N or more. On the other hand, although not limited, its upper limit is, for example, 98 N or less. Furthermore, the tensile strength of the magnesium oxide tablets of this embodiment is not limited, but its lower limit is, for example, 1.3 N / mm². 2 Above or above, or 1.5 N / mm² 2 Above or above, or 1.7 N / mm² 2 It is preferable that the above is true. On the other hand, although not limited to this, the upper limit of the tensile strength is, for example, 5.0 N / mm². 2 The following applies. While there are no particular limitations on the method for measuring the hardness and tensile strength of magnesium oxide tablets, they can be determined, for example, by the method described in the examples below.

[0040] The content of magnesium oxide powder for tablets in the magnesium oxide tablets of this embodiment is not limited, but as an upper limit, it can be, for example, 100% by mass or less, 95% by mass or less, or 90% by mass or less, relative to the entire tablet. On the other hand, although not limited, as a lower limit, it can be, for example, 70% by mass or more, 80% by mass or more, or 85% by mass or more, relative to the entire tablet.

[0041] The magnesium oxide tablets of this embodiment may contain additives as needed. The additives are not limited to any particular type, but may include various pharmaceutically acceptable pharmaceutical additives, such as excipients, binders, disintegrants, lubricants, colorants, and flavorings. These components may be used individually or in any combination of two or more.

[0042] One embodiment of the present invention relates to a method for manufacturing magnesium oxide tablets. According to one embodiment, the manufacturing method includes a tableting step of compressing a raw material containing magnesium oxide powder into tablets. According to one embodiment, the raw material containing magnesium oxide powder mainly contains the magnesium oxide powder for tablets of the above embodiment. The content of magnesium oxide powder in the raw material is not particularly limited, and any content can be adopted.

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

[0044] According to one embodiment, the manufacturing method of this embodiment includes a mixing step in which raw materials containing magnesium oxide powder are mixed before the tableting step. In the mixing step, the raw materials containing magnesium oxide powder are mixed by any method.

[0045] This embodiment relates to a fine granule preparation containing magnesium oxide powder. In one embodiment, the fine granule preparation contains magnesium oxide powder as its main component. The content of magnesium oxide powder in the magnesium oxide fine granule preparation is not particularly limited, as in the case of magnesium oxide tablets, and any content can be adopted.

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

[0047] One embodiment of the present invention relates to a method for producing magnesium oxide granules. According to one embodiment, such a method includes a granulation step of granulating a raw material containing magnesium oxide powder. In one embodiment, the raw material containing magnesium oxide powder mainly contains the magnesium oxide powder for tablets of the above embodiment. As described above, the content of magnesium oxide powder in the raw material is not particularly limited and any content can be adopted.

[0048] The granulation process can be carried out by granulating the raw material containing magnesium oxide powder, for example, by a fluidized bed granulation method or a dry granulation method. Among these, the fluidized bed granulation method is preferred from the viewpoint of being easy to adjust to have the desired average particle size and bulk density. The granulation process yields a magnesium oxide granule having the desired average particle size as described above.

[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, it is also possible to extract any other aspects of the present invention from the above detailed description and the examples described below. [Examples]

[0050] The present invention will be described in more detail below with reference to examples, but these examples are merely illustrative examples for explanatory purposes, and the present invention is not limited in any sense to these examples.

[0051] [1. Sample Preparation] ·material: As magnesium hydroxide (Mg(OH)2), we used magnesium hydroxide produced by the seawater method (hereinafter referred to as "seawater method magnesium hydroxide" as appropriate) and magnesium hydroxide produced by the brine method (hereinafter referred to as "brine method magnesium hydroxide" as appropriate).

[0052] Magnesium hydroxide produced by the seawater method was prepared using the following procedure. Seawater was used as the magnesium raw material. Lime milk was used as the alkali raw material. The reaction temperature was left to chance, and the magnesium and alkali raw materials were reacted continuously with a residence time of 10 minutes or more. The resulting product was concentrated until the solid content concentration reached 5% by mass or more. The concentrated product was washed to remove salts such as sodium, thereby producing a slurry of 10-30% by mass of magnesium hydroxide produced by the seawater method (hereinafter referred to as "magnesium hydroxide slurry by the seawater method").

[0053] Magnesium hydroxide produced by the brine method was prepared using the following procedure. Brine was used as the magnesium raw material. Lime milk was used as the alkali raw material. The reaction temperature was left to chance, and the magnesium and alkali raw materials were reacted continuously with a residence time of 10 minutes or more. The resulting product was washed to remove salts such as sodium, thereby producing a slurry of 10-30% by mass of brine-processed magnesium hydroxide (hereinafter referred to as "brine-processed magnesium hydroxide slurry" as appropriate).

[0054] Magnesium carbonate (MgCO3) was produced by the gas absorption method. Specifically, magnesium hydroxide was brought into contact with carbon dioxide gas and reacted until the pH reached 7-9. The product was then heated to over 80°C and held for at least 30 minutes. After that, the product was cooled to prepare a slurry of 5-10% by mass of magnesium carbonate (hereinafter referred to as "magnesium carbonate slurry" as appropriate).

[0055] • Example 1: The above-mentioned magnesium hydroxide slurry using the seawater method and the above-mentioned magnesium carbonate slurry were mixed in a mass ratio of 8:2 in terms of magnesium oxide and stirred for 30 minutes. The resulting mixed slurry was dewatered using an Ishigaki filter press at a compression pressure of 0.5 MPa or higher, and then dried using a hot air dryer. The resulting dried material was fired using an Iwasa Machinery Industry Co., Ltd. rotary kiln at a feed rate of 400 kg / hour and a firing temperature of 600°C or higher, resulting in a specific surface area (BET) of 20-60 m². 2The material was calcined until it reached a range of / g. The calcination time was approximately 30 to 120 hours. The resulting calcined material was then pulverized using an impact pulverizer to obtain the magnesium oxide powder sample of Example 1.

[0056] Example 2: In Example 1, the mixing ratio of the seawater-based magnesium hydroxide slurry and the magnesium carbonate slurry was changed to a 5:5 mass ratio in terms of magnesium oxide; otherwise, the same procedure as in Example 1 was followed to obtain the magnesium oxide powder sample of Example 2.

[0057] • Comparative Example 1: Comparative Example 1 was obtained by performing the same procedure as in Example 1, except that the magnesium hydroxide slurry produced by the seawater method was used alone instead of the mixed slurry of magnesium hydroxide slurry produced by the seawater method and magnesium carbonate slurry produced in Example 1.

[0058] Comparison Example 2: In Comparative Example 2, a sample of magnesium oxide powder was obtained by performing the same procedure as in Example 1, except that the mixing ratio of the seawater-based magnesium hydroxide slurry and the magnesium carbonate slurry was changed to a mass ratio of 2:8 in terms of magnesium oxide.

[0059] Example 3: In Example 1, magnesium hydroxide slurry produced by the bittern method was used instead of magnesium hydroxide slurry produced by the seawater method, and it was mixed with magnesium carbonate slurry in a mass ratio of 8:2 in terms of magnesium oxide equivalent. The same procedure as in Example 1 was followed to obtain the magnesium oxide powder sample of Example 3.

[0060] • Example 4: In Example 3, the magnesium oxide powder sample of Example 4 was obtained by performing the same procedure as in Example 3, except that the mixing ratio of the magnesium hydroxide slurry and the magnesium carbonate slurry was changed to a 5:5 mass ratio in terms of magnesium oxide.

[0061] • Comparative Example 3: In Comparative Example 3, a magnesium oxide powder sample was obtained by performing the same procedure as in Example 3, except that magnesium hydroxide slurry produced by the bittern method was used alone instead of a mixed slurry of magnesium hydroxide slurry produced by the bittern method and magnesium carbonate slurry.

[0062] • Comparative Example 4: In Example 3, the mixing ratio of magnesium hydroxide slurry and magnesium carbonate slurry was changed to a mass ratio of 2:8 in terms of magnesium oxide equivalent. The same procedure as in Example 3 was followed to obtain the magnesium oxide powder sample of Comparative Example 4.

[0063] Comparison Example 5: Comparative Example 5 was obtained by performing the same procedure as in Example 1, except that a magnesium carbonate slurry was used alone instead of a mixed slurry of seawater-based magnesium hydroxide slurry and magnesium carbonate slurry.

[0064] [2. Measurement and Evaluation of Physical Properties and Characteristics] The physical properties and characteristics of each magnesium oxide powder sample were measured and evaluated using the following procedure.

[0065] ·BET specific surface area: For each magnesium oxide powder sample, the BET specific surface area was measured by gas adsorption using a specific surface area analyzer (Belsorp MR6, manufactured by Microtrac BEL).

[0066] • Bulk density: For each magnesium oxide powder sample, the volume and mass were measured, and the volume per 10g of powder (mL / 10g) was calculated as the bulk density.

[0067] ·Adhesion (emission rate): 5.0 g of each calcined magnesium oxide sample was placed in a wide-mouthed bottle (manufactured by Nippon Yamamura Glass Co., Ltd., material: glass, mouth diameter: 3.3 cm, bottle height: 8 cm), the lid was closed, and the bottle was shaken 100 times. The lid of the bottle was opened, the bottle was inverted, and the magnesium oxide sample that did not adhere to the sides of the bottle was discharged and its mass was measured. The ratio of the obtained discharged amount to the initial amount (5.0 g) (discharge rate) was calculated and used as an indicator of the adhesion of each magnesium oxide sample. The closer the discharge rate is to 100%, the lower the proportion of magnesium oxide sample adhering to the sides of the bottle, indicating reduced adhesion and, consequently, a powder with improved handling properties.

[0068] • Tablet thickness, hardness, and tensile strength For each magnesium oxide powder sample, tablets were prepared using a manual tabletop tablet forming machine (HANDTAB-200, manufactured by Ichihashi Seiki Co., Ltd.) under the following conditions: sample amount 250 mg, flat punch 10 mmΦ, and tableting pressure 10 kN. The thickness of the obtained tablets was measured. In addition, the hardness of the tablets was measured using a tablet hardness tester (Tablet Tester 6D, manufactured by Dr. Schleuniger), and the tensile strength was determined based on the following formula. Tensile strength (N / mm 2 ) = Hardness / Fracture Area (Diameter × Thickness)

[0069] [3. Results] The preparation conditions for each magnesium oxide powder sample are shown in Table 1 below. Furthermore, the physical properties and characteristics of each magnesium oxide powder sample, as well as the measurement and evaluation results of the physical properties and characteristics of the tablets obtained by compressing each magnesium oxide powder sample, are shown in Table 2 below. Note that the powder in Comparative Example 5 was too bulky and could not be made into tablets.

[0070] [Table 1]

[0071] [Table 2]

[0072] From the above results, it can be seen that the magnesium oxide powders of Comparative Examples 1 and 3, obtained by calcining magnesium hydroxide without using magnesium carbonate, did not have sufficient hardness or tensile strength when compressed into tablets. On the other hand, the magnesium oxide powders of Comparative Examples 2 and 4, obtained by calcining magnesium carbonate as the main raw material with only a small amount of magnesium hydroxide, had a high bulk density and poor tablet manufacturing efficiency. In particular, the magnesium oxide powder of Comparative Example 5, obtained by calcining only magnesium hydroxide without using magnesium hydroxide, had too high a bulk density and could not be made into tablets.

[0073] In contrast, the magnesium oxide powders of Examples 1 to 4, obtained by calcining a material mixed with magnesium hydroxide and magnesium carbonate in a predetermined ratio, exhibited a moderately suppressed bulk density, as well as excellent hardness and tensile strength of tablets during compression. This demonstrates a well-balanced combination of the properties required for magnesium oxide powder for tablets.

[0074] Furthermore, cross-sections of the tablets obtained by compressing each magnesium oxide powder sample from Example 3 and Comparative Example 4 were observed and imaged using a scanning electron microscope (SEM). Figure 1 shows an SEM image of the tablet using the magnesium oxide powder sample from Example 3, and Figure 2 shows an SEM image of the tablet using the magnesium oxide powder sample from Comparative Example 4. As is clear from these SEM images, the magnesium oxide powder from Example 3 contains a moderate amount of needle-shaped magnesium oxide, indicated by the box in the image, within the hexagonal prismatic magnesium oxide. The hexagonal prismatic magnesium oxide is thought to originate from magnesium hydroxide, and the needle-shaped magnesium oxide is thought to originate from magnesium carbonate. Although not bound by theory, it is presumed that the moderate presence of needle-shaped magnesium oxide derived from magnesium carbonate within the hexagonal prismatic magnesium oxide derived from magnesium hydroxide makes it possible to improve the hardness and tensile strength of the tablets during compression while suppressing bulk density. On the other hand, the magnesium oxide powder from Comparative Example 4 has a very high proportion of needle-shaped magnesium oxide derived from magnesium carbonate, which is presumed to be the cause of the increased bulk density. [Industrial applicability]

[0075] This invention can be widely applied to magnesium oxide powder for tablets, and its utility is extremely high.

Claims

1. A method for producing magnesium oxide powder for tablets, (1) Preparation step of preparing a slurry containing magnesium hydroxide and magnesium carbonate, (2) A production step to produce a dried product by drying the slurry, (3) A firing process for firing the dried material, Includes, The slurry is prepared by preparing a first slurry containing magnesium hydroxide and a second slurry containing magnesium carbonate, respectively, and then mixing and stirring the first slurry and the second slurry. A method for producing magnesium hydroxide, wherein the ratio of magnesium hydroxide to the total amount of magnesium hydroxide and magnesium carbonate in the slurry is 5 to 75% by mass ratio in terms of magnesium oxide.

2. The manufacturing method according to claim 1, wherein the magnesium hydroxide in the slurry is magnesium hydroxide produced by the seawater method or the bittern method.

3. The manufacturing method according to claim 1, wherein the firing step is carried out at a temperature of 600 to 1000°C.

4. It contains hexagonal prismatic magnesium oxide and needle-shaped magnesium oxide, and has a BET specific surface area of ​​39 m². ２ Magnesium oxide powder for tablets, having a concentration of 85 mL / 10 g or less and a bulk density of 85 mL / 10 g or less.

5. A magnesium oxide tablet comprising the magnesium oxide powder for tablets described in claim 4.

6. A magnesium oxide tablet according to claim 5, having a hardness of 30 N or more.

7. Tensile strength of 1.3 N / mm ２ The magnesium oxide tablet according to claim 5.

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