Method for producing magnesium hydroxide

Abstract

The purpose of the present disclosure is to provide a novel method for producing magnesium hydroxide.　Provided is a method for producing magnesium hydroxide, the method including: mixing magnesium oxide, calcium chloride, hydrochloric acid, and water so as to obtain a mixed liquid; and subjecting the mixed liquid to a hydrothermal treatment so as to obtain magnesium hydroxide.

Description

Magnesium hydroxide manufacturing method

[0001] The present disclosure relates to a method for producing magnesium hydroxide.

[0002] As a method for producing magnesium hydroxide, Patent Document 1 discloses a method for producing magnesium hydroxide by adding lithium hydroxide or sodium hydroxide to an aqueous suspension of magnesium hydroxide or magnesium oxide in an amount of 100 mass % or more relative to 100 mass % of the solid content calculated as magnesium hydroxide, wet-pulverizing the mixture, and then hydrothermally treating the mixture at 180 to 230°C. The resulting magnesium hydroxide particles are then surface-treated with a Si compound and an Al compound to form a mixed coating layer of the Si compound and the Al compound on the surface of the magnesium hydroxide or magnesium oxide suspension. ２ and Al ２ O ３ The present invention describes a method for producing magnesium hydroxide, characterized in that the magnesium hydroxide is formed in a ratio of 0.2 to 10 mass% based on 100 mass% of magnesium hydroxide in terms of total converted amount.

[0003] Patent Document 2 describes a method for producing magnesium hydroxide, which includes adding water to magnesium oxide of a predetermined purity to prepare a suspension, reacting the suspension with stirring, removing magnesium hydroxide by filtration to prepare a filter cake, washing the filter cake, separating it into solid and liquid, and drying it.

[0004] Japanese Patent Application Laid-Open No. 2005-336472 U.S. Patent No. 5,286,285

[0005] The present disclosure aims to provide a new method for producing magnesium hydroxide.

[0006] A first embodiment of the present disclosure provides a method for producing magnesium hydroxide, including: mixing magnesium oxide, calcium chloride, hydrochloric acid, and water to obtain a mixed solution; and hydrothermally treating the mixed solution to obtain magnesium hydroxide.

[0007] A second embodiment of the present disclosure provides a method for producing magnesium hydroxide, including: mixing magnesium oxide, calcium chloride, and a dispersion medium to obtain a first mixed liquid; adjusting the pH of the first mixed liquid to obtain a second mixed liquid having a lower pH than the first mixed liquid; and hydrothermally treating the second mixed liquid to obtain magnesium hydroxide.

[0008] In a third embodiment of the present disclosure, in any one of the first to second embodiments, the amount of calcium contained in the calcium chloride may be 0.1 moles or more and 5 moles or less per mole of magnesium contained in the magnesium oxide.

[0009] In a fourth embodiment of the present disclosure, in any one of the first embodiment or the third embodiment, the amount of chlorine contained in the hydrochloric acid may be 0.01 mol or more and 0.5 mol or less per 1 mol of magnesium contained in the magnesium oxide.

[0010] In a fifth embodiment of the present disclosure, in any one of the first, third, and fourth embodiments, the pH of the mixed solution may be 8 or more and 12 or less.

[0011] In a sixth embodiment of the present disclosure, in any one of the first to fifth embodiments, the hydrothermal treatment can be carried out at 130°C or higher and 200°C or lower.

[0012] A seventh embodiment of the present disclosure provides a method for producing a resin composition, comprising mixing magnesium hydroxide produced by any one of the production methods described in the first to sixth embodiments with a resin to obtain a resin composition.

[0013] In the eighth embodiment of the present disclosure, a BET specific surface area of ​​1 m ２ / g or more 20m ２ / g or less, an average particle size of 0.1 μm or more and 3 μm or less, and a half-width of a peak derived from the (001) plane measured by X-ray diffraction of 0.1 or more and 0.5 or less.

[0014] According to the present disclosure, a new method for producing magnesium hydroxide can be provided.

[0015] FIG. 1 shows a scanning electron microscope image (20,000x magnification) of the calcium hydroxide obtained in Example 1-1. FIG. 2 shows a scanning electron microscope image (20,000x magnification) of the calcium hydroxide obtained in Example 2-4. FIG. 3 shows a scanning electron microscope image (20,000x magnification) of the calcium hydroxide obtained in Example 2-6. FIG. 4 shows a scanning electron microscope image (20,000x magnification) of the calcium hydroxide obtained in Example 2-8. FIG. 5 shows a scanning electron microscope image (20,000x magnification) of the calcium hydroxide obtained in Example 2-9. FIG. 6 shows a scanning electron microscope image (20,000x magnification) of the calcium hydroxide obtained in Comparative Example 1-1. FIG. 7 is a chart showing the results of a heat degradation test for Example 4 and Comparative Example 1.

[0016] A first method for producing magnesium hydroxide according to the present disclosure includes mixing magnesium oxide, calcium chloride, hydrochloric acid, and water to obtain a mixed solution, and subjecting the mixed solution to hydrothermal treatment to obtain magnesium hydroxide.

[0017] The present disclosure can provide a new method for producing magnesium hydroxide. In a preferred embodiment, the first production method allows magnesium hydroxide to be produced simply and easily, and production costs can be reduced. For example, the first production method can lower the pH during hydrothermal treatment, preventing deterioration of equipment used in the hydrothermal treatment and expanding the usability of the equipment. Furthermore, the first production method allows calcium chloride, a raw material used, to be reused, reducing production costs. Furthermore, the first production method allows magnesium hydroxide to grow crystals at a relatively low temperature. Good crystal growth makes it easy to obtain magnesium hydroxide with good dispersibility in resin.

[0018] Although the present disclosure should not be interpreted as being limited to a particular theory, the reason why the above-mentioned effects are obtained by the first production method is thought to be as follows: In the first production method, magnesium oxide and calcium chloride are mixed and then subjected to hydrothermal treatment in the presence of hydrochloric acid. Therefore, it is thought that it is easy to lower the pH during the hydrothermal treatment and that this can promote crystal growth of magnesium hydroxide.

[0019] In the present disclosure, "magnesium hydroxide," "magnesium oxide," "calcium chloride," and "magnesium carbonate" each refer to the compound magnesium hydroxide (Mg(OH) ２ ), magnesium oxide (MgO), calcium chloride (CaCl ２ ) and magnesium carbonate (Mg(CO ３ ) ２ ), and may contain elements such as Ca, Si, Cl, S, Al, and Fe as impurities. Also, "calcium chloride" refers to the compound calcium chloride (CaCl ２ ) hydrates. Such hydrates include calcium chloride dihydrate (CaCl ２ ・2H ２ O) and the like.

[0020] In the present disclosure, magnesium hydroxide, magnesium oxide, calcium chloride, and magnesium carbonate may preferably be magnesium hydroxide particles, magnesium oxide particles, calcium chloride particles, and magnesium carbonate particles, respectively. In the present disclosure, "particles" refers to an aggregate of particulate materials that are independent of each other. The shape of each particle may be spherical, irregular, or the like. When the particle shape is spherical, "spherical" is not limited to "true spherical."

[0021] The magnesium oxide may be any material containing 80% by mass or more of magnesium oxide (MgO) as a compound. In the magnesium oxide, the content of magnesium oxide (MgO) as a compound may be preferably 80% by mass or more and 100% by mass or less, more preferably 85% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, based on 100% by mass of the total amount of magnesium oxide. In the present disclosure, the content of elements in a material can be measured by wavelength dispersive X-ray fluorescence spectroscopy.

[0022] The average particle size of the magnesium oxide may be preferably 0.5 μm or more and 50 μm or less, more preferably 1.0 μm or more and 40 μm or less, and even more preferably 1.5 μm or more and 30 μm or less.

[0023] In the present disclosure, the average particle size can be measured by a microtrack method in accordance with JIS Z 8830, and can be the volume-based median size (D50).

[0024] The specific surface area of ​​the magnesium oxide is preferably 0.01 m ２ / g or more 500m ２ / g or less, more preferably 0.05m ２ / g or more 150m ２ / g or less, more preferably 0.1m ２ / g or more 40m ２ / g or less.

[0025] In the present disclosure, the specific surface area can be measured by the BET method, and specifically, can be measured in accordance with JIS Z 8830.

[0026] The magnesium oxide may be a commercially available product or may be produced by firing a magnesium compound.

[0027] Examples of the magnesium compound include magnesium salts such as magnesium carbonate, magnesium chloride, magnesium nitrate, and magnesium sulfate; magnesium hydroxide; and the like.

[0028] The temperature at which the magnesium compound is fired may be preferably 500° C. or higher and 1500° C. or lower, more preferably 700° C. or higher and 1400° C. or lower, and even more preferably 800° C. or higher and 1000° C. The higher the firing temperature, the easier it is to obtain magnesium oxide with higher purity, and the lower the firing temperature, the easier it is to reduce production costs.

[0029] The time for calcining the magnesium compound may be preferably 0.5 hours to 10 hours, more preferably 1 hour to 5 hours, and even more preferably 1 hour to 3 hours. The longer the calcination time, the easier it is to obtain magnesium oxide with a higher purity, and the lower the calcination temperature, the easier it is to reduce production costs.

[0030] In the mixed solution, the amount of magnesium oxide per 1 L of the mixed solution may be preferably 1 g or more and 500 g or less, more preferably 10 g or more and 300 g or less, and even more preferably 30 g or more and 200 g or less.

[0031] In this disclosure, the "solids content" of a material means the residue after heating the material at 105°C for 1 hour.

[0032] The calcium chloride is a compound of calcium chloride (CaCl ２ The calcium chloride may be a material containing 80% by mass or more of calcium chloride (CaCl ２ The content of the magnesium oxide (a) may be preferably 80% by mass or more and 100% by mass or less, more preferably 85% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, based on 100% by mass of the total amount of magnesium oxide.

[0033] The calcium chloride may remain unconsumed in the production of magnesium hydroxide. Therefore, after producing magnesium hydroxide by the first production method, the calcium chloride may be recovered and reused in the production of magnesium hydroxide of the present disclosure. Such calcium chloride recovery may be carried out by subjecting the solvent to solid-liquid separation from the mixed solution after the hydrothermal treatment. The number of times calcium chloride is reused may be preferably 0 to 5 times, more preferably 1 to 3 times.

[0034] The amount of calcium contained in the calcium chloride is preferably 0.1 mol to 5 mol, more preferably 0.2 mol to 3 mol, and even more preferably 0.4 mol to 2 mol, per mol of the total amount of magnesium contained in the magnesium oxide. The greater the amount of calcium chloride, the easier it is to promote crystal growth of magnesium hydroxide, and the smaller the amount of calcium chloride, the easier it is to suppress costs.

[0035] The concentration of the hydrochloric acid may be preferably 0.01 mol / L or more and 12 mol / L or less, more preferably 0.1 mol / L or more and 10 mol / L or less, and even more preferably 1 mol / L or more and 5 mol / L or less.

[0036] The amount of chlorine contained in the hydrochloric acid may be preferably 0.01 mol or more and 0.5 mol or less, more preferably 0.02 mol or more and 0.4 mol or less, and even more preferably 0.05 mol or more and 0.2 mol or less, relative to 1 mol of the total amount of magnesium contained in the magnesium oxide. The larger the amount of hydrochloric acid, the easier it is to promote the crystal growth of magnesium hydroxide, and the smaller the amount of hydrochloric acid, the easier it is to suppress costs.

[0037] The order of mixing magnesium oxide, calcium chloride, hydrochloric acid, and water is not particularly limited. For example, a mixed solution may be prepared by mixing calcium chloride and water to prepare an aqueous calcium chloride solution, mixing the aqueous calcium chloride solution with magnesium oxide to prepare a suspension, and then mixing the suspension with hydrochloric acid to prepare the mixed solution.

[0038] In this embodiment, the calcium chloride concentration in the aqueous calcium chloride solution may be preferably 5 g / L or more and 250 g / L or less, more preferably 10 g / L or more and 150 g / L or less, and even more preferably 20 g / L or more and 100 g / L or less.

[0039] When mixing the calcium chloride aqueous solution and magnesium oxide, a wet pulverization treatment may be carried out using a homogenizer or the like.

[0040] The temperature at which the magnesium oxide, calcium chloride, hydrochloric acid, and water are mixed is not particularly limited. In one embodiment, the mixing is preferably carried out at a temperature of 5°C or higher and 50°C or lower, more preferably 10°C or higher and 45°C or lower, and even more preferably 10°C or higher and 40°C or lower.

[0041] The pH of the mixed solution before the hydrothermal treatment may be preferably 8 or more and 12 or less, more preferably 8.5 or more and 11 or less, and even more preferably 9 or more and 10.5 or less. The lower the pH, the easier it is to promote the crystal growth of magnesium hydroxide, and the higher the pH, the easier it is to suppress costs.

[0042] In the mixed solution, the concentration of magnesium oxide per 1 L of the mixed solution may be preferably 1 g or more and 500 g or less, more preferably 10 g or more and 300 g or less, and even more preferably 30 g or more and 200 g or less.

[0043] The mixed solution is subjected to hydrothermal treatment to obtain magnesium hydroxide. The hydrothermal treatment can be typically carried out by maintaining the mixed solution at 100° C. or higher under pressure.

[0044] The pressure (gauge pressure) during the hydrothermal treatment may be preferably 0.1 MPa or more and 4.0 MPa or less, more preferably 0.2 MPa or more and 1.5 MPa or less, and even more preferably 0.4 MPa or more and 1.0 MPa or less.

[0045] The temperature during the hydrothermal treatment may be preferably 100° C. or higher and 250° C. or lower, more preferably 140° C. or higher and 200° C. or lower, and even more preferably 150° C. or higher and 180° C. The higher the temperature of the hydrothermal treatment, the more likely it is that crystal growth of magnesium hydroxide will be promoted, and the lower the temperature of the hydrothermal treatment, the easier it will be to suppress costs.

[0046] The hydrothermal treatment time may be preferably 0.5 hours or more and 8 hours or less, more preferably 1 hour or more and 6 hours or less, and even more preferably 2 hours or more and 4 hours or less. The longer the hydrothermal treatment time, the more sustained the crystal growth of magnesium hydroxide can be, and the shorter the hydrothermal treatment time, the easier it is to suppress costs.

[0047] The pH of the mixed solution after the hydrothermal treatment may be preferably from 8 to 12, more preferably from 8.5 to 11, and even more preferably from 9 to 10.5. The lower the pH, the easier it is to promote the crystal growth of magnesium hydroxide, and the higher the pH, the easier it is to suppress costs.

[0048] The mixed liquid after the hydrothermal treatment may be subjected to treatments such as solid-liquid separation, washing, drying, etc., thereby obtaining a dried magnesium hydroxide.

[0049] The method of solid-liquid separation is not particularly limited and may be, for example, filtration. The filtration may be performed under normal pressure, elevated pressure, or reduced pressure. The temperature during the filtration may be preferably 5°C or higher and 50°C or lower, more preferably 10°C or higher and 40°C or lower, and even more preferably 10°C or higher and 35°C or lower.

[0050] The washing can be carried out using a washing solvent such as water. In one embodiment, the washing can be carried out by mixing the filtered magnesium hydroxide with a washing solvent and performing solid-liquid separation. The amount of the washing solvent can be preferably 1 part by mass or more and 100 parts by mass or less, more preferably 5 parts by mass or more and 50 parts by mass or less, and even more preferably 10 parts by mass or more and 30 parts by mass or less, per part by mass of the obtained magnesium hydroxide. The solid-liquid separation can be carried out by the same method as the solid-liquid separation of the mixed liquid after the hydrothermal treatment.

[0051] The number of times of washing is not particularly limited, and may be preferably from 1 to 10 times, more preferably from 1 to 5 times, and even more preferably from 1 to 3 times.

[0052] The drying can typically be carried out after solid-liquid separation of the mixed solution or the washed mixture. The drying temperature can be preferably 60°C or higher and 300°C or lower, more preferably 80°C or higher and 200°C or lower, and even more preferably 100°C or higher and 150°C or lower. The drying time can be preferably 1 hour or higher and 100 hours or lower, more preferably 2 hours or higher and 50 hours or lower, and even more preferably 8 hours or higher and 24 hours or lower.

[0053] The dried product may be further pulverized. This pulverization can facilitate control of the particle size of the magnesium hydroxide. The pulverization is typically carried out by dry pulverization.

[0054] The second method for producing magnesium hydroxide of the present disclosure includes: mixing magnesium oxide, calcium chloride, and a dispersion medium to obtain a first mixed liquid; adjusting the pH of the first mixed liquid to obtain a second mixed liquid having a lower pH than the first mixed liquid; and hydrothermally treating the second mixed liquid to obtain magnesium hydroxide.

[0055] The present disclosure can provide a new method for producing magnesium hydroxide. In a preferred embodiment, the above-described production method allows magnesium hydroxide to be produced easily, and production costs can be easily reduced. The production method of the present disclosure has a low pH during hydrothermal treatment, which prevents deterioration of equipment used in the hydrothermal treatment and increases the usability of the equipment. Furthermore, the production method of the present disclosure allows magnesium hydroxide to grow crystals at relatively low temperatures.

[0056] Although the present disclosure should not be interpreted as being limited to a particular theory, the reason why the above-mentioned effects are obtained by the above-mentioned production method is thought to be as follows: In other words, in the production method of the present disclosure, magnesium oxide, calcium chloride, and a dispersion medium are mixed, and then the pH is lowered and hydrothermal treatment is carried out. This is thought to prevent deterioration of the equipment and promote crystal growth of magnesium hydroxide.

[0057] Magnesium hydroxide, magnesium oxide, calcium chloride and magnesium carbonate have the same meanings as those in the first production method.

[0058] In the second production method, the amount of magnesium oxide in 1 L of the first mixed solution may be preferably 1 g or more and 500 g or less, more preferably 10 g or more and 300 g or less, and even more preferably 30 g or more and 200 g or less.

[0059] The calcium chloride may remain unconsumed in the production of magnesium hydroxide. Therefore, after producing magnesium hydroxide by the second production method, the calcium chloride may be recovered and reused in the production of magnesium hydroxide of the present disclosure. Such calcium chloride recovery may be carried out by subjecting the solvent to solid-liquid separation from the mixed solution after the hydrothermal treatment. The number of times calcium chloride is reused may be preferably 0 to 5 times, more preferably 1 to 3 times.

[0060] The amount of calcium contained in the calcium chloride is preferably 0.1 mol to 5 mol, more preferably 0.2 mol to 3 mol, and even more preferably 0.4 mol to 2 mol, per mol of the total amount of magnesium contained in the magnesium oxide. The greater the amount of calcium chloride, the easier it is to promote crystal growth of magnesium hydroxide, and the smaller the amount of calcium chloride, the easier it is to suppress costs.

[0061] The dispersion medium includes water and a mixture of water and a hydrophilic medium. Examples of the hydrophilic medium include alcohol solvents such as methanol, ethanol, propanol, isopropyl alcohol, and butanol; and ketone solvents such as acetone. Water is preferred as the dispersion medium.

[0062] The amount of the dispersion medium may be preferably 100 parts by mass or more and 1,000 parts by mass or less, more preferably 200 parts by mass or more and 700 parts by mass or less, and even more preferably 300 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the total of the magnesium oxide and calcium chloride.

[0063] The order of mixing the magnesium oxide, calcium chloride, and dispersion medium is not particularly limited. For example, calcium chloride and a dispersion medium may be mixed to prepare a calcium chloride solution, and the calcium chloride solution may be mixed with magnesium oxide to prepare a suspension.

[0064] In this embodiment, the calcium chloride concentration in the aqueous calcium chloride solution may be preferably 5 g / L or more and 250 g / L or less, more preferably 10 g / L or more and 150 g / L or less, and even more preferably 20 g / L or more and 100 g / L or less.

[0065] The temperature at which the magnesium oxide, calcium chloride, and dispersion medium are mixed is not particularly limited. In one embodiment, the mixing is preferably carried out at a temperature of 5° C. or higher and 50° C. or lower, more preferably 10° C. or higher and 45° C. or lower, and even more preferably 10° C. or higher and 40° C. or lower.

[0066] When mixing the calcium chloride aqueous solution and magnesium oxide, a wet pulverization treatment may be carried out using a homogenizer or the like.

[0067] After preparing the first mixture, the pH of the first mixture is adjusted to obtain a second mixture having a lower pH than the first mixture, preferably in the range of 8 to 12, more preferably 8.5 to 11, and even more preferably 9 to 10.5.

[0068] The difference in pH between the first mixed liquid and the second mixed liquid is more than 0, and may be preferably 0.1 to 1.5, more preferably 0.3 to 1, and even more preferably 0.4 to 0.9.

[0069] The pH adjustment can be typically carried out by mixing an acid with the first mixed solution. Examples of the acid include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid; and organic acids such as acetic acid. The acid is preferably an inorganic acid, and more preferably hydrochloric acid.

[0070] H contained in the above acid ＋ The amount of acid is preferably 0.01 mol or more and 0.5 mol or less, more preferably 0.02 mol or more and 0.4 mol or less, and even more preferably 0.02 mol or more and 0.4 mol or less, relative to 1 mol of the total amount of magnesium contained in the magnesium oxide. The greater the amount of acid, the easier it is to promote crystal growth of magnesium hydroxide, and the smaller the amount of acid, the easier it is to suppress costs.

[0071] In the second mixed solution, the concentration of magnesium oxide per 1 L of the mixed solution may be preferably 1 g or more and 500 g or less, more preferably 10 g or more and 300 g or less, and even more preferably 30 g or more and 200 g or less.

[0072] The temperature at which the pH is adjusted is not particularly limited. In one embodiment, the pH adjustment is preferably performed at a temperature of 5°C or higher and 50°C or lower, more preferably 10°C or higher and 45°C or lower, and even more preferably 10°C or higher and 40°C or lower.

[0073] The second mixed solution is subjected to a hydrothermal treatment to obtain magnesium hydroxide. The hydrothermal treatment can be typically carried out by maintaining the second mixed solution at 100° C. or higher under pressure.

[0074] The pressure (gauge pressure) during the hydrothermal treatment may be preferably 0.1 MPa or more and 4.0 MPa or less, more preferably 0.2 MPa or more and 1.5 MPa or less, and even more preferably 0.4 MPa or more and 1.0 MPa or less.

[0075] The temperature during the hydrothermal treatment may be preferably 100° C. or higher and 150° C. or lower, more preferably 140° C. or higher and 200° C. or lower, and even more preferably 150° C. or higher and 180° C. The higher the hydrothermal treatment temperature, the more likely it is that crystal growth of magnesium hydroxide will be promoted, and the lower the hydrothermal treatment temperature, the easier it will be to suppress costs.

[0076] The hydrothermal treatment time may be preferably 0.5 hours or more and 8 hours or less, more preferably 1 hour or more and 6 hours or less, and even more preferably 2 hours or more and 4 hours or less. The longer the hydrothermal treatment time, the more sustained the crystal growth of magnesium hydroxide can be, and the shorter the hydrothermal treatment time, the easier it is to suppress costs.

[0077] The pH of the mixed solution after the hydrothermal treatment may be preferably from 8 to 12, more preferably from 8.5 to 11, and even more preferably from 9 to 10.5. The lower the pH, the easier it is to promote the crystal growth of magnesium hydroxide, and the higher the pH, the easier it is to suppress costs.

[0078] The mixed liquid after the hydrothermal treatment may be subjected to treatments such as solid-liquid separation, washing, drying, etc., thereby obtaining a dried magnesium hydroxide product. The solid-liquid separation, washing, and drying may be performed by the method and under the conditions described in the first production method.

[0079] Magnesium hydroxide obtained by the manufacturing method of the present disclosure is also within the technical scope of the present disclosure. According to the manufacturing method of the present disclosure, magnesium hydroxide with good crystal growth can be easily obtained, and such magnesium hydroxide can have good dispersibility in resin and easily exhibit good flame retardancy.

[0080] The specific surface area of ​​the magnesium hydroxide is preferably 0.1 m ２ / g or more 100m ２ / g or less, more preferably 1m ２ / g or more 20m ２ / g or less, more preferably 3m ２ / g or more 10m ２When the specific surface area of ​​magnesium hydroxide is in this range, the dispersibility of magnesium hydroxide in the resin can be good, and it is easy to exhibit good flame retardancy.

[0081] The average particle size of the magnesium hydroxide is preferably 0.1 μm or more and 5 μm or less, more preferably 0.3 μm or more and 3 μm or less, and even more preferably 0.5 μm or more and 2 μm or less. When the average particle size of the magnesium hydroxide is in this range, the magnesium hydroxide can be well dispersed in the resin, and good flame retardancy can be easily exhibited.

[0082] The half-width of the peak derived from the (001) plane of the magnesium hydroxide measured by X-ray diffraction is preferably 0.1 to 0.5, more preferably 0.13 to 0.4, and even more preferably 0.15 to 0.3. When the crystallinity of the magnesium hydroxide is within the range evaluated by the half-width, the dispersibility of the magnesium hydroxide in the resin can be good, and it is easy to exhibit good flame retardancy. An Empyrean manufactured by Panalytical can be used as the X-ray diffraction measurement device.

[0083] In the magnesium hydroxide, magnesium hydroxide (Mg(OH) ２ The content of the magnesium hydroxide hydroxyl group 1) may be preferably 80% by mass or more and 100% by mass or less, more preferably 85% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, based on 100% by mass of the total amount of magnesium hydroxide.

[0084] The loose bulk density of the magnesium hydroxide may be preferably 1 mL / 10 g or more and 500 mL / 10 g or less, more preferably 10 mL / 10 g or more and 100 mL / 10 g or less, and even more preferably 30 mL / 10 g or more and 80 mL / 10 g or less.

[0085] The tapped bulk density of the magnesium hydroxide may be preferably 1 mL / 10 g or more and 500 mL / 10 g or less, more preferably 10 mL / 10 g or more and 100 mL / 10 g or less, and even more preferably 30 mL / 10 g or more and 80 mL / 10 g or less.

[0086] In the present disclosure, loose bulk density can be measured by the following method. [Method for measuring loose bulk density] 10 g of a sample is placed in a 100 mL measuring cylinder and its volume is measured. The loose bulk density is calculated by dividing the measured volume by the sample weight (10 g).

[0087] In the present disclosure, tapped bulk density can be measured by the following method. [Method for measuring tapped bulk density] 10 g of a sample is placed in a 100 mL measuring cylinder, and after shaking it by hand 20 times, its volume is measured. The tapped bulk density is calculated by dividing the measured volume by the sample weight (10 g).

[0088] The magnesium hydroxide may have a surface treatment layer.

[0089] The magnesium hydroxide obtained by the production method of the present disclosure can be preferably used as a flame retardant, a neutralizing agent, a food additive (anti-caking agent, magnesium fortifying agent, etc.), an antacid, a laxative, a rubber reinforcing agent, a foam adjusting agent, a pigment, an anti-slip agent, etc.

[0090] In a preferred embodiment, the magnesium hydroxide used in the manufacturing method of the present disclosure has good dispersibility in resins and can be used as a flame retardant. When heated, magnesium hydroxide releases desorbed water through the following endothermic reaction, which is believed to result in a flame retardant effect: Mg(OH) ２ →MgO+H ２ Therefore, it is believed that if the crystallinity of magnesium hydroxide is good, it will have good dispersibility in the resin and the above reaction will proceed evenly in the resin, resulting in a good flame retardant effect.

[0091] A method for producing a resin composition, which includes mixing the magnesium hydroxide with a resin to obtain a resin composition, is also included within the technical scope of the present disclosure.

[0092] Examples of such resins include thermoplastic resins such as polyolefin resins, polyamide resins, and polyphenylene sulfide resins, and thermosetting resins such as epoxy resins, phenolic resins, silicone resins, urea resins, melamine resins, and unsaturated polyesters.

[0093] The magnesium hydroxide and the resin can be mixed as appropriate depending on the type of resin.

[0094] The present disclosure can provide a new method for producing magnesium hydroxide. In a preferred embodiment, the method can easily produce magnesium hydroxide, and the magnesium hydroxide obtained by the method has good dispersibility in resins, making it suitable for use as a flame retardant, neutralizing agent, food additive (anti-caking agent, magnesium reinforcing agent, etc.), antacid, laxative, rubber reinforcing agent, foam adjusting agent, pigment, anti-slip agent, etc.

[0095] The present disclosure will be explained in more detail with reference to the following examples, but the present disclosure is not limited thereto.

[0096] Production Examples 1 to 4 Magnesium carbonate was heated to the firing temperature at the heating rate shown in Table 1 using a firing furnace shown in Table 1, and fired at the firing temperature and for the holding time shown in Table 1 to obtain magnesium oxides (4) to (7).

[0097]

[0098] Examples 1-1 to 1-3, 2-1 to 2-9 102.9 g of calcium chloride dihydrate was mixed with 550 mL of water to prepare an aqueous solution, to which 35.0 g of magnesium oxide shown in Tables 2 and 3 was added, and the mixture was wet-pulverized using a homogenizer to obtain a slurry. Water was added to the obtained slurry, and the magnesium oxide concentration in the slurry was adjusted to 50 g / L. Hydrochloric acid was added to the slurry to obtain a mixed solution, which was then subjected to hydrothermal treatment at 170°C for 4 hours. The slurry after the hydrothermal treatment was then filtered, washed, dried, and pulverized to obtain a magnesium hydroxide powder. The above washing was performed once.

[0099] Production Example 5: The slurry after the hydrothermal treatment was filtered, and CaO powder was added to the filtrate in an amount equimolar to the magnesium in the filtrate, followed by stirring for 30 minutes to obtain a magnesium hydroxide slurry. ２ The aqueous solution was collected.

[0100] Examples 3-1 to 3-4: A mixed solution was obtained in the same manner as in Example 1, except that recovered calcium chloride was used, and magnesium hydroxide powder was obtained by performing hydrothermal treatment, followed by filtration, washing, drying, and pulverization. Recycling calcium chloride up to three times did not affect the magnesium hydroxide.

[0101] Comparative Examples 1-1 to 1-4 Magnesium hydroxide powder of Comparative Example 1 was obtained in the same manner as in Example 1, except that sodium chloride was used instead of calcium chloride.

[0102] The magnesium hydroxides obtained in the examples and comparative examples were evaluated by the following methods.

[0103] (Particle size measurement) The average particle size was measured using a laser diffraction / scattering particle size distribution analyzer MT3300EXII manufactured by Microtrac Bell Co., Ltd. An aqueous solution of sodium hexametaphosphate was used as the solvent. As a pretreatment before the measurement, the aqueous solution of sodium hexametaphosphate and the measurement sample were mixed, and the sample was dispersed in water by ultrasonic treatment.

[0104] (Measurement of Specific Surface Area) The BET specific surface area was measured by the BET method using a specific surface area and pore distribution measuring device BELsorp-max manufactured by Microtrac BEL Corporation.

[0105] (Wavelength-dispersive X-ray fluorescence spectrometry) The content of each element in the sample was measured by wavelength-dispersive X-ray fluorescence spectrometry using a ZSX Primus IV manufactured by Rigaku Corporation.

[0106] (Measurement of loose bulk density) The loose bulk density was calculated by placing 10 g of a sample in a 100 mL measuring cylinder, measuring the volume, and dividing the volume by the sample weight (10 g).

[0107] (Measurement of tapped bulk density) The tapped bulk density was calculated by placing 10 g of a sample in a 100 mL measuring cylinder, manually shaking the cylinder 20 times, measuring the volume, and dividing the volume by the sample weight (10 g).

[0108] (Scanning Electron Microscope Observation) Using a scanning electron microscope (JSM-7600F manufactured by JEOL Ltd.), the structures of the calcium hydroxides obtained in Examples 1-1, 2-4, 2-6, 2-8, and 2-9 and Comparative Example 1-1 were observed at a magnification of 20,000. The results are shown in FIGS.

[0109]

[0110]

[0111] In Tables 2 and 3, magnesium oxide (1) represents MF150 manufactured by Kyowa Chemical Industry Co., Ltd., magnesium oxide (2) represents MF30 manufactured by Kyowa Chemical Industry Co., Ltd., and magnesium oxide (3) represents Pyroxema 5301 manufactured by Kyowa Chemical Industry Co., Ltd.

[0112] In Tables 2 and 3, the amount of calcium chloride dihydrate is the amount per mole of magnesium oxide, the amount of hydrogen chloride in hydrochloric acid is the amount per mole of magnesium oxide, and the amount of sodium chloride is the amount per mole of magnesium oxide. The amount of magnesium oxide was calculated by dividing the amount of magnesium oxide by the formula weight of magnesium oxide.

[0113] Example 4, Comparative Example 2 The magnesium oxide produced in Examples 1-3 was used as magnesium hydroxide for resin evaluation. 150 parts by weight of the magnesium hydroxide for resin evaluation was added to 100 parts by weight of polypropylene and kneaded to obtain a composition for resin evaluation. The composition for resin evaluation was maintained at 150°C in an air atmosphere, and the rate of weight change was measured to confirm the heat degradation of the magnesium oxide for resin evaluation. Natural magnesium hydroxide was also used as a comparative sample. As a result, as shown in Figure 7, it was confirmed that heat degradation was suppressed compared to natural magnesium hydroxide.

[0114] The present disclosure can provide a new method for producing magnesium hydroxide. In a preferred embodiment, the method can easily produce magnesium hydroxide, and the magnesium hydroxide obtained by the method has good dispersibility in resins, making it suitable for use as a flame retardant, neutralizing agent, food additive (anti-caking agent, magnesium reinforcing agent, etc.), antacid, laxative, rubber reinforcing agent, foam adjusting agent, pigment, anti-slip agent, etc.

Claims

1. A method for producing magnesium hydroxide, comprising: mixing magnesium oxide, calcium chloride, hydrochloric acid, and water to obtain a mixed solution; and subjecting the mixed solution to hydrothermal treatment to obtain magnesium hydroxide.

2. A method for producing magnesium hydroxide, comprising: mixing magnesium oxide, calcium chloride, and a dispersion medium to obtain a first mixed liquid; adjusting the pH of the first mixed liquid to obtain a second mixed liquid having a lower pH than the first mixed liquid; and hydrothermally treating the second mixed liquid to obtain magnesium hydroxide.

3. The manufacturing method according to claim 1 or 2, wherein the amount of calcium contained in the calcium chloride is 0.1 mole or more and 5 moles or less per mole of magnesium contained in the magnesium oxide.

4. The method of claim 1, wherein the amount of chlorine contained in the hydrochloric acid is 0.01 mole or more and 0.5 mole or less per mole of magnesium contained in the magnesium oxide.

5. The method of claim 1, wherein the pH of the mixture is 8 or more and 12 or less.

6. The method of claim 1 or 2, wherein the hydrothermal treatment is carried out at a temperature of 130°C or higher and 200°C or lower.

7. A method for producing a resin composition, comprising mixing the magnesium hydroxide produced by the method according to claim 1 or 2 with a resin to obtain a resin composition.

8. BET specific surface area is 1m ２ / g or more 20m ２ / g or less, an average particle size of 0.1 μm or more and 3 μm or less, and a half width of a peak derived from a (001) plane measured by X-ray diffraction is 0.1 or more and 0.5 or less.

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