Method for producing magnesium hydroxide particles, method for increasing the particle size of magnesium hydroxide particles, magnesium hydroxide particles, and resin composition

Abstract

To provide a method for producing magnesium hydroxide particles, which can easily grow magnesium hydroxide particles using a magnesium hydroxide material containing a predetermined amount of silicon. [Solution] The present disclosure relates to a method for producing magnesium hydroxide particles. The production method according to the first disclosure includes a mixture formation step. In the mixture formation step, a mixture is formed by mixing a magnesium hydroxide material containing 100 ppm or more of silicon with a slurry containing magnesium hydroxide seed crystals. The production method according to the first disclosure also includes an aging step. In the aging method, the mixture is aged to grow the seed crystals and form the magnesium hydroxide particles having a particle size larger than that of the seed crystals.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing magnesium hydroxide particles, a method for increasing the particle size of magnesium hydroxide particles, magnesium hydroxide particles, and resin compositions containing magnesium hydroxide particles. [Background technology]

[0002] Various methods for producing magnesium hydroxide have been investigated. For example, Patent Document 1 discloses a method for producing a predetermined high-purity magnesium hydroxide. The specification of Patent Document 1 also discloses that "conventionally, magnesium hydroxide has been obtained by reacting seawater, which is used as a raw material, with milk of lime. However, such magnesium hydroxide contains relatively large amounts of boric acid, silica, alumina, iron, calcium, etc., which are contaminated from the milk of lime, etc., and is therefore unsuitable for use as a high-quality product as is." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 60-155529 Summary of the Invention [Problem to be solved by the invention]

[0004] In producing magnesium hydroxide, for example, producing magnesium hydroxide in the presence of an acceptable component or a component that is preferable to remain is preferable from the viewpoint of achieving the Sustainable Development Goals (SDGs). However, Patent Document 1 does not disclose such a method. Therefore, an object of the present disclosure is to provide a method for producing magnesium hydroxide particles, which can easily grow magnesium hydroxide particles using a magnesium hydroxide material containing a predetermined amount of silicon. [Means for solving the problem]

[0005] The present disclosure includes the following aspects. (First Disclosure) The present disclosure relates to a method for producing magnesium hydroxide particles. The production method according to the present disclosure includes a mixture formation step. In the mixture formation step, a magnesium hydroxide material containing 100 ppm or more of silicon is mixed with a slurry containing magnesium hydroxide seed crystals to form a mixture. The production method according to the present disclosure also includes an aging step. In the aging method, the mixture is aged to grow the seed crystals, thereby forming magnesium hydroxide particles having a particle size larger than that of the seed crystals.

[0006] (Second Disclosure) In the second disclosure, in the first disclosure, the magnesium hydroxide particles in the aging step contain 100 ppm or more of silicon. (Third Disclosure) In this third disclosure, in the first or second disclosure, the magnesium hydroxide particles in the aging step have a D50 of 0.6 to 5.0 μm.

[0007] (Fourth Disclosure) In the present fourth disclosure, the method of any one of the first to third disclosures further includes, before the mixture-forming step, a magnesium hydroxide material-forming step in which an alkaline substance containing 100 ppm or more of silicon is reacted with a water-soluble magnesium compound to form the magnesium hydroxide material.

[0008] (Fifth Disclosure) In this fifth disclosure, in the fourth disclosure, the alkaline substance is calcium hydroxide. (Sixth Disclosure) In this sixth disclosure, in the fourth or fifth disclosure, the alkaline substance is calcium hydroxide derived from limestone.

[0009] (7th Disclosure) In the present seventh disclosure, in any one of the first to sixth disclosures, the magnesium hydroxide seed crystals in the mixture forming step contain 100 ppm or more of silicon. (Eighth Disclosure) In the present eighth disclosure, in any of the first to seventh disclosures, the slurry containing the magnesium hydroxide seed crystals in the mixture formation step is formed by reacting an alkaline substance containing 100 ppm or more of silicon with a water-soluble magnesium compound, and aging the mixture at a predetermined aging temperature.

[0010] (Ninth Disclosure) In the present ninth disclosure, in the eighth disclosure, the aging temperature at which the mixture is aged in the aging step is higher than the predetermined aging temperature. (10th Disclosure) The present tenth disclosure is the method of any one of the first to ninth disclosures, further comprising a seed crystal formation step prior to the mixture formation step. In the seed crystal formation step, a slurry containing the magnesium hydroxide seed crystals is formed by aging a portion of the magnesium hydroxide material. In the mixture formation step, the remainder of the magnesium hydroxide material is mixed with the slurry containing the magnesium hydroxide seed crystals formed in the seed crystal formation step.

[0011] (Eleventh Disclosure) According to the present eleventh disclosure, in the tenth disclosure, the mass ratio of the part of the magnesium hydroxide material to the remainder of the magnesium hydroxide material is 1-90:10-99. (12th Disclosure) The twelfth disclosure relates to a method for increasing the particle size of particles containing magnesium hydroxide crystals. The method according to the twelfth disclosure includes a mixture formation step. In the mixture formation step, a magnesium hydroxide material containing 100 ppm or more of silicon is mixed with a slurry containing magnesium hydroxide seed crystals to form a mixture. The method according to the twelfth disclosure also includes an aging step. In the aging method, the mixture is aged to grow the seed crystals, thereby forming magnesium hydroxide particles having a particle size larger than that of the seed crystals.

[0012] (13th Disclosure) The present disclosure relates to magnesium hydroxide particles. The magnesium hydroxide particles contain 100 ppm or more and less than 1,000 ppm of silicon. The magnesium hydroxide particles have a D50 of 0.6 to 5.0 μm.

[0013] (14th Disclosure) In the present fourteenth disclosure, in the thirteenth disclosure, the magnesium hydroxide particles are surface-treated with a surface treatment agent, which is at least one selected from the group consisting of higher fatty acids, anionic surfactants, phosphate esters, coupling agents, and esters of polyhydric alcohols and fatty acids. (15th Disclosure) The present fifteenth disclosure relates to a resin composition. The resin composition contains magnesium hydroxide particles according to the thirteenth or fourteenth disclosure and a resin. [Effects of the Invention]

[0014] The method for producing particles containing magnesium hydroxide crystals according to the present disclosure allows magnesium hydroxide particles to be easily grown using a magnesium hydroxide material containing a predetermined amount of silicon. DETAILED DESCRIPTION OF THE INVENTION

[0015] The method for producing magnesium hydroxide particles, the method for increasing the particle size of magnesium hydroxide particles, the magnesium hydroxide particles, and the resin composition containing the magnesium hydroxide particles according to the present disclosure will be described in detail below. The method for producing magnesium hydroxide particles according to the present disclosure may be referred to hereinafter as the "production method according to the present disclosure." Furthermore, the method for increasing the particle size of magnesium oxide particles according to the present disclosure may be referred to hereinafter as the "method according to the present disclosure."

[0016] The manufacturing method according to the present disclosure and the method according to the present disclosure include the following steps. - A mixture forming step of forming a mixture by mixing a magnesium hydroxide material containing 100 ppm or more of silicon with a slurry containing magnesium hydroxide seed crystals. - Aging step of aging the mixture to grow the seed crystals and form magnesium hydroxide particles having a particle size larger than that of the seed crystals. Hereinafter, the above-mentioned mixture forming step may be simply referred to as the "mixture forming step", and the above-mentioned aging step may be simply referred to as the "aging step".

[0017] Producing magnesium hydroxide in the presence of components that are acceptable or that are preferred to remain is preferable from the perspective of achieving the Sustainable Development Goals (SDGs). The present inventors have found that magnesium hydroxide containing a predetermined amount of silicon is suitable for use, for example, as a flame retardant, and have conducted various studies to form particles containing magnesium hydroxide crystals. As a result, they have found that calcium hydroxide containing a predetermined amount of silicon is less likely to grow magnesium hydroxide crystals due to the high silicon content.

[0018] The production method and method according to the present disclosure use a magnesium hydroxide material containing 100 ppm or more of silicon. However, since the production method and method according to the present disclosure include a predetermined mixture formation step and a predetermined aging step, magnesium hydroxide particles having a particle size larger than that of the seed crystals can be easily formed. Magnesium hydroxide particles formed from a magnesium hydroxide material containing 100 ppm or more of silicon are useful in a variety of applications, including at least one of a flame retardant, an electric wire coating material, an additive, a resin filler, a high-performance material, a catalyst, a paper sizing agent, a filler, and an annealing separator for electrical steel sheets.

[0019] In the mixture forming step, a magnesium hydroxide material containing 100 ppm or more of silicon is mixed with a slurry containing magnesium hydroxide seed crystals to form a mixture.

[0020] The magnesium hydroxide material containing 100 ppm or more of silicon and the slurry containing magnesium hydroxide seed crystals are mixed for a pouring time of preferably 1 minute or more, more preferably 3 minutes or more, and even more preferably 5 minutes or more. The mixing is also preferably carried out for a pouring time of 120 minutes or less, more preferably 100 minutes or less, and even more preferably 90 minutes or less. By setting the pouring time within the above range, it becomes easier to set D50 within the specified range, and by extending the pouring time, D50 can be increased.

[0021] The magnesium hydroxide material contains, in a dry state, 100 ppm or more, preferably 120 ppm or more, and more preferably 130 ppm or more of silicon. Also, the magnesium hydroxide material contains, in a dry state, preferably 1,000 ppm or less, more preferably 800 ppm or less, and even more preferably 700 ppm or less of silicon. This makes it easier for the magnesium hydroxide particles produced to contain a predetermined amount of silicon, making them suitable for use as, for example, a flame retardant. The silicon includes not only silicon atoms but also silicon-containing compounds such as silicon dioxide.

[0022] In the present disclosure, the amount of silicon in a sample in a dry state can be measured using a scanning X-ray fluorescence analyzer ZSX Primus IV manufactured by Rigaku Corporation. The sample in the dry state can be obtained by drying the sample at 105°C for 24 hours. Examples of the sample include magnesium hydroxide material, alkaline substances, magnesium hydroxide seed crystals, and magnesium hydroxide particles.

[0023] The magnesium hydroxide material is not particularly limited as long as it contains 100 ppm or more of silicon, and can be formed by a method known in the art, and any material known in the art can be used. The magnesium hydroxide material can be formed by reacting an alkaline substance containing 100 ppm or more of silicon with a water-soluble magnesium compound.

[0024] The alkaline substance may be, for example, at least one of calcium hydroxide, sodium hydroxide, and aqueous ammonia, preferably calcium hydroxide, and more preferably calcium hydroxide derived from limestone, which makes it easier for the magnesium hydroxide particles produced to contain a predetermined amount of silicon.

[0025] When the alkaline substance is calcium hydroxide derived from limestone, the calcium hydroxide can be formed, for example, as follows. Limestone is calcined at 900°C to 1300°C to obtain calcium oxide. The obtained calcium oxide is added to ion-exchanged water to a concentration of, for example, 200 g / L, and the calcium oxide and water are reacted at, for example, 90°C to obtain a reaction product. The reaction product is passed through a 50-mesh sieve to remove impurities such as unreacted calcium oxide and / or calcium carbonate, to obtain calcium hydroxide slurry. The concentration of silicon in the calcium hydroxide in the resulting calcium hydroxide slurry varies depending on the limestone used as the raw material, but is, for example, 120 to 220 ppm.

[0026] The water-soluble magnesium compound may include, for example, at least one of magnesium chloride, magnesium nitrate, and seawater. The reaction of the alkaline substance and the water-soluble magnesium compound can be carried out at a temperature of preferably 1° C. or higher, more preferably 10° C. or higher, and even more preferably 20° C. or higher. The reaction of the alkaline substance and the water-soluble magnesium compound can be carried out at a temperature of preferably 80° C. or lower, more preferably 60° C. or lower, and even more preferably 40° C. or lower. This can prevent the medium from freezing and the magnesium hydroxide material from agglomerating. The reaction between the alkaline substance and the water-soluble magnesium compound is preferably carried out under conditions of pH 8.5 to 10.0.

[0027] In the production method and method according to the present disclosure, the "magnesium hydroxide material containing 100 ppm or more of silicon" in the mixture-forming step may be formed by reacting an alkaline substance containing 100 ppm or more of silicon with a water-soluble magnesium compound. Furthermore, the production method and method according to the present disclosure may further include, before the mixture-forming step, a magnesium hydroxide material-forming step of reacting an alkaline substance containing 100 ppm or more of silicon with a water-soluble magnesium compound to form the magnesium hydroxide material.

[0028] The manufacturing method and the method according to the present disclosure may further include a silicon concentration adjustment step of adjusting the silicon concentration contained in the magnesium hydroxide material before the mixture formation step. In the silicon concentration adjustment step, the silicon concentration can be adjusted to be higher or lower. In the silicon concentration adjusting step, for example, the silicon concentration can be adjusted to a high level by adding a silicon compound to the magnesium hydroxide material, or by mixing multiple alkaline substances with different silicon concentrations.

[0029] Examples of the silicon compound include alkali silicates and water glass. Examples of the alkali silicate include sodium silicate, sodium metasilicate, sodium orthosilicate, and potassium silicate. Examples of the water glass include No. 3 water glass. As the silicon compound, No. 3 water glass is preferred.

[0030] In the production method and method according to the present disclosure, the slurry containing magnesium hydroxide seed crystals can be obtained by a seed crystal formation step. Furthermore, the production method and method according to the present disclosure may include the seed crystal formation step before the mixture formation step. The seed crystal formation step can be carried out by a method known in the art. The seed crystal formation step can be carried out, for example, by reacting an alkaline substance with a water-soluble magnesium compound and aging the mixture.

[0031] Preferable examples of the "alkaline substance" and the "magnesium hydroxide compound" in the seed crystal formation step are the same as the "alkaline substance" and the "magnesium hydroxide compound" exemplified in the description of the mixture formation step, respectively.

[0032] The aging in the seed crystal formation step can be carried out at a predetermined aging temperature for a predetermined aging time. The predetermined aging temperature in the seed crystal formation step is preferably 100°C or higher, more preferably 115°C or higher, and even more preferably 120°C or higher. The predetermined temperature is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower. This makes it easier to keep the particle size of the magnesium hydroxide particles formed within the predetermined range. Furthermore, increasing the aging temperature makes it easier to increase the particle size of the magnesium hydroxide particles and also reduces the BET specific surface area.

[0033] By reducing the BET specific surface area, for example, it is possible to prevent magnesium hydroxide from changing into magnesium carbonate. The ripening temperature in the seed crystal formation step can be lower than the ripening temperature in the ripening step described below. Details will be explained in the section describing the ripening step.

[0034] The predetermined aging time in the seed crystal formation step is preferably 30 minutes or more, more preferably 45 minutes or more, and even more preferably 60 minutes or more. The predetermined aging time is preferably 300 minutes or less, more preferably 270 minutes or less, and even more preferably 240 minutes or less. This allows the magnesium hydroxide seed crystals to grow efficiently. As a result, the magnesium hydroxide particles formed tend to have a predetermined particle size, and the magnesium hydroxide particles exhibit excellent dispersibility when mixed with a resin.

[0035] In the seed crystal formation step, a slurry containing the magnesium hydroxide seed crystals may be formed by aging a portion of the magnesium hydroxide material. Furthermore, in the mixture formation step, the remainder of the magnesium hydroxide material can be mixed with the slurry containing the magnesium hydroxide seed crystals derived from a portion of the magnesium hydroxide material formed in the seed crystal formation step. This can improve production efficiency. Examples of the improvement in production efficiency include omitting the step of transferring a portion of the magnesium hydroxide material to a separate container and omitting the step of adjusting the temperature of a portion of the magnesium hydroxide material.

[0036] Specifically, when the production method and method according to the present disclosure include the seed crystal formation step, a single magnesium hydroxide material, for example, magnesium hydroxide material produced in the same lot, can be divided into a first fraction and a second fraction. A slurry containing the magnesium hydroxide seed crystals can then be formed from the first fraction. Then, in the mixture formation step, the magnesium hydroxide material containing 100 ppm or more of silicon (second fraction) can be mixed with the slurry containing the magnesium hydroxide seed crystals (first fraction).

[0037] Alternatively, the magnesium hydroxide material containing 100 ppm or more of silicon (second fraction) may be further divided into a plurality of fractions, and the mixture-forming step and the aging step may be repeated. For example, a magnesium hydroxide material containing 100 ppm or more of silicon (second fraction) can be divided into two fractions, fraction 2A and fraction 2B. Then, in a first mixture formation step (first mixture formation step), a slurry containing magnesium hydroxide seed crystals (first fraction) and the magnesium hydroxide material containing 100 ppm or more of silicon (fraction 2A) can be mixed to form a first mixture (first mixture). Then, in a first aging step (first aging step), the first mixture can be aged to form first particles of magnesium hydroxide (first particles).

[0038] Then, in a second mixture formation step (second mixture formation step), the first particles of magnesium hydroxide can be mixed as a slurry containing magnesium hydroxide seed crystals with a magnesium hydroxide material containing 100 ppm or more of silicon (fraction 2B) to form a second mixture (second mixture). Then, in a second aging step (second aging step), the second mixture can be aged to form second particles of magnesium hydroxide (second particles). The same applies when the magnesium hydroxide material (second fraction) containing 100 ppm or more of silicon is divided into three or more fractions.

[0039] The ratio of the part of the magnesium hydroxide material to the remainder of the magnesium hydroxide material can be any ratio, preferably 1-90:10-99, more preferably 5-70:30-95, even more preferably 10-50:50-90, and even more preferably 20-40:60-80. This makes it easier to adjust the particle size of the formed magnesium hydroxide particles to within a predetermined range.

[0040] The example of repeating the mixture-forming step and the aging step using a single magnesium hydroxide material has been described above. In the manufacturing method and method according to the present disclosure, the mixture-forming step and the aging step can be performed using different magnesium hydroxide materials, and the mixture-forming step and the aging step can be repeated multiple times. By repeating the mixture-forming step and the aging step multiple times, the particle size of the magnesium hydroxide particles can be made larger.

[0041] For example, when the mixture formation step and the aging step are repeated twice, the procedure can be as follows. In the first mixture formation step (first mixture formation step), a slurry containing magnesium hydroxide seed crystals and a magnesium hydroxide material containing 100 ppm or more of silicon can be mixed to form a first mixture (first mixture). Then, in the first aging step (first aging step), the first mixture can be aged to form first particles (first particles) of magnesium hydroxide.

[0042] Next, in a second mixture formation step (second mixture formation step), the first particles of magnesium hydroxide can be mixed as a slurry containing magnesium hydroxide seed crystals with a magnesium hydroxide material containing 100 ppm or more of silicon to form a second mixture (second mixture). Next, in a second aging step (second aging step), the second mixture can be aged to form second particles of magnesium hydroxide (second particles). The same applies when the mixture-forming step and the aging step are repeated three or more times.

[0043] The magnesium hydroxide seed crystals preferably contain a predetermined amount of silicon in a dry state. The predetermined amount of silicon is preferably 100 ppm or more, more preferably 120 ppm or more, and even more preferably 130 ppm or more. The predetermined amount of silicon is preferably 1,000 ppm or less, more preferably 800 ppm or less, and even more preferably 700 ppm or less. This makes it easier for the magnesium hydroxide particles that are the product to contain the predetermined amount of silicon, making them suitable for use as, for example, a flame retardant.

[0044] In the aging step, the mixture is aged to grow the seed crystals, thereby forming magnesium hydroxide particles having a particle size larger than that of the seed crystals. It is generally known that carrying out an aging step can grow magnesium hydroxide crystals and increase the primary particle size. The inventors of the present application have found that when a certain amount of silicon is contained in the system, the growth of magnesium hydroxide crystals is inhibited, and even when the aging step is carried out, the primary particles of magnesium hydroxide do not easily grow. In the production method and the method according to the present disclosure, by including a predetermined aging step, magnesium hydroxide particles having a larger particle size can be obtained.

[0045] The aging in the aging step can be carried out at a predetermined aging temperature for a predetermined aging time. The predetermined aging temperature in the aging step is preferably 100° C. or higher, more preferably 115° C. or higher, and even more preferably 120° C. or higher. The predetermined temperature is preferably 200° C. or lower, more preferably 190° C. or lower, and even more preferably 180° C. or lower.

[0046] When the production method of the present disclosure includes the above-mentioned seed crystal formation step, the predetermined aging temperature in the aging step can be higher than the predetermined aging temperature in the seed crystal formation step. In this case, the temperature difference between the predetermined aging temperature in the aging step and the predetermined aging temperature in the seed crystal formation step is preferably 70°C or less, more preferably 40°C or less, and even more preferably 20°C or less. Furthermore, the temperature difference is preferably 10°C or more. This makes it possible to precisely control the growth rate of the magnesium hydroxide particles to be formed while maintaining production efficiency, and to obtain magnesium hydroxide particles having the desired shape, particle size, and BET specific surface area.

[0047] The predetermined aging time in the aging step is preferably 20 minutes or more, more preferably 30 minutes or more, and even more preferably 40 minutes or more. The predetermined aging time in the aging step is preferably 300 minutes or less, more preferably 240 minutes or less, and even more preferably 210 minutes or less. This makes it easier for the formed magnesium hydroxide particles to have the predetermined particle size, and the magnesium hydroxide has excellent dispersibility when mixed with a resin.

[0048] The suspension containing magnesium hydroxide particles obtained in the aging step can be dehydrated and then washed with a large amount of deionized water, for example, 20 times the amount of the magnesium hydroxide particles, thereby removing impurities such as sodium and suppressing aggregation of the magnesium hydroxide primary particles.

[0049] The magnesium hydroxide particles preferably contain a predetermined amount of silicon in a dry state. The predetermined amount of silicon is preferably 100 ppm or more, more preferably 120 ppm or more, and even more preferably 130 ppm or more. The predetermined amount of silicon is preferably 1,000 ppm or less, more preferably 600 ppm or less, even more preferably 400 ppm or less, and even more preferably 300 ppm or less. This makes it possible to make the resin composition flame-retardant when the magnesium hydroxide particles are mixed with a resin to form a resin composition. As a result, the magnesium hydroxide particles are suitable for use as, for example, a flame retardant.

[0050] The magnesium hydroxide particles preferably have a D50 of 0.6 μm or more, more preferably 0.7 μm or more, and even more preferably 0.8 μm or more. The magnesium hydroxide particles also preferably have a D50 of 5.0 μm or less, more preferably 3.0 μm or less, even more preferably 2.0 μm or less, and even more preferably 1.5 μm or less. This ensures excellent dispersibility of the magnesium hydroxide when mixed with a resin.

[0051] As used herein, the D50 of a particle means the 50% particle size on a volume basis, and is measured as follows. (1) 0.7 g of particles are weighed into a 100 mL beaker, and 70 mL of a 2.0 g / L aqueous solution of sodium hexametaphosphate is added to the beaker, followed by ultrasonic treatment for 3 minutes to obtain a particle dispersion. (2) The D50 of the dispersion is measured using a particle size distribution analyzer MT3300ExII manufactured by Microtrac Bell Corporation.

[0052] The magnesium hydroxide particles are preferably 1.0 m 2 / g or more, more preferably 1.5m 2 / g or more, and more preferably 2.0m 2 The magnesium hydroxide particles preferably have a BET specific surface area of ​​8.5 m / g or more. 2 / g or less, more preferably 8.0m 2 / g or less, and more preferably 7.5m 2 / g or less, which can prevent magnesium hydroxide from changing into, for example, magnesium carbonate in a resin composition mixed with the magnesium hydroxide.

[0053] The BET specific surface area is measured, for example, by a high-precision specific surface area / pore distribution measuring device BELsorp-mini manufactured by Microtrac BEL Corporation.

[0054] The magnesium hydroxide particles may be surface-treated with a surface treatment agent. The surface treatment agent may be selected from those known in the art. Examples of the surface treatment agent include higher fatty acids, anionic surfactants, phosphate esters, coupling agents, and esters of polyhydric alcohols and fatty acids.

[0055] The resin composition contains the magnesium hydroxide and a resin. Examples of the resin include acrylic resin, urethane resin, fluororesin, epoxy resin, alkyd resin, silicone resin, phenolic resin, melamine resin, unsaturated polyester resin, polyethylene, copolymers of ethylene and other α-olefins, copolymers of ethylene and vinyl acetate, ethyl acrylate, or methyl acrylate, polypropylene, copolymers of propylene and other α-olefins, polybutene-1, poly-4-methylpentene-1, polystyrene, copolymers of styrene and acrylonitrile, copolymers of ethylene and propylene diene rubber or butadiene, and any combination thereof.

[0056] The resin composition is suitable for use in at least one of flame retardants, electric wire coating materials, additives, resin fillers, high-performance materials, catalysts, paper sizing agents, fillers, and annealing separators for electrical steel sheets, for example. [Example]

[0057] The present disclosure will be described below using examples, but the present disclosure is not limited to these examples. [Manufacturing Example 1] Limestone was calcined at 900°C to obtain calcium oxide. The obtained calcium oxide was added to ion-exchanged water to a concentration of 200 g / L, and the liquid temperature was adjusted to 90°C to obtain a suspension containing calcium hydroxide. The obtained suspension containing calcium hydroxide was passed through a 50-mesh sieve, and ion-exchanged water was added to adjust the concentration, obtaining a 2.2 mol / L calcium hydroxide slurry. The silicon content in the calcium hydroxide was 198 ppm.

[0058] [Example 1] 410 mL of a 1.7 mol / L aqueous magnesium chloride solution was placed in a stainless steel reaction vessel, and the temperature of the aqueous solution was adjusted to 35° C. while stirring at 200 rpm using a chemical stirrer. 290 mL of 2.2 mol / L calcium hydroxide slurry produced in Production Example 1, adjusted to 35° C., was poured into the stainless steel reaction vessel over 5 minutes to obtain magnesium hydroxide material No. 1.

[0059] A portion (10% by mass) of magnesium hydroxide material No. 1 was transferred to an autoclave and aged for 2 hours (120 minutes) at 170°C while stirring at 500 rpm, yielding magnesium hydroxide seed crystal slurry No. 1. Subsequently, the remainder (90% by mass) of magnesium hydroxide material No. 1 was poured over a 30-minute pouring time into magnesium hydroxide seed crystal slurry No. 1, which was maintained at 170°C while stirring at 500 rpm, to yield mixture No. 1. After the pouring was completed, mixture No. 1 was aged for 1.5 hours (90 minutes) at 170°C, yielding aged product No. 1.

[0060] The aged product No. 1 was filtered under suction and washed with deionized water in an amount 20 times the mass of the magnesium hydroxide to obtain a magnesium hydroxide cake, which was then dried at 105°C for 24 hours to obtain magnesium hydroxide particles No. 1. The silicon content [Si (ppm)], D50 [D50 (μm)] and BET specific surface area [BET (m 2 / g)] are shown in Table 1.

[0061] [Example 2] Magnesium hydroxide particles No. 2 were obtained in the same manner as in Example 1, except that magnesium hydroxide seed crystal slurry No. 2 was formed from a portion (30% by mass) of magnesium hydroxide material No. 1, and the magnesium hydroxide seed crystal slurry No. 2 (30% by mass) was mixed with the remainder (70% by mass) of magnesium hydroxide material No. 1 to obtain mixture No. 2. The results are summarized in Table 1.

[0062] [Example 3] Magnesium hydroxide particles No. 3 were obtained in the same manner as in Example 1, except that magnesium hydroxide seed crystal slurry No. 3 was formed from a portion (50% by mass) of magnesium hydroxide material No. 1, and the magnesium hydroxide seed crystal slurry No. 3 (50% by mass) was mixed with the remainder (50% by mass) of magnesium hydroxide material No. 1 to obtain mixture No. 3. The results are summarized in Table 1.

[0063] [Example 4] Magnesium hydroxide particles No. 4 were obtained in the same manner as in Example 1, except that magnesium hydroxide seed crystal slurry No. 4 was formed from a portion (70% by mass) of magnesium hydroxide material No. 1, and the magnesium hydroxide seed crystal slurry No. 4 (70% by mass) was mixed with the remainder (30% by mass) of magnesium hydroxide material No. 1 to obtain mixture No. 4. The results are summarized in Table 1.

[0064] [Examples 5 to 8] Magnesium hydroxide particles No. 5 to No. 8 were obtained in the same manner as in Example 2, except that the aging temperature of the seed crystals was changed as shown in Tables 1 and 2. The results are summarized in Tables 1 and 2. [Examples 9 to 11] Magnesium hydroxide particles Nos. 9 to 11 were obtained in the same manner as in Example 4, except that the maturation time of the seed crystals, the time of pouring onto the seed crystals, and the maturation time in the maturation step were changed as shown in Table 2. The results are summarized in Table 2.

[0065] [Examples 12 and 13] Magnesium hydroxide particles No. 12 and No. 13 were obtained in the same manner as in Example 3, except that the time of addition to the seed crystals and the aging time in the aging step were changed as shown in Tables 2 and 3. The results are summarized in Tables 2 and 3. [Example 14] Magnesium hydroxide particles No. 14 were obtained in the same manner as in Example 2, except that the aging temperature of the seed crystals was set as shown in Table 3. The results are summarized in Table 3.

[0066] [Comparative Example 1] Magnesium hydroxide particles No. 15 were obtained in the same manner as in Example 1, except that a slurry of magnesium hydroxide seed crystals was not formed and the entire amount of magnesium hydroxide material No. 1 was transferred to an autoclave and aged for 4 hours at 170° C. The results are summarized in Table 3.

[0067] Comparative Example 2 Magnesium hydroxide particles No. 16 were obtained in the same manner as in Comparative Example 1, except that "410 mL of 1.7 mol / L magnesium chloride aqueous solution" was changed to "353 mL of 1.7 mol / L magnesium chloride aqueous solution," "290 mL of 2.2 mol / L calcium hydroxide slurry" was changed to "547 mL of 2.1 mol / L sodium hydroxide aqueous solution," and "total amount of magnesium hydroxide material No. 1" was changed to "700 mL of the obtained magnesium hydroxide material." The results are summarized in Table 3.

[0068] [Table 1]

[0069] [Table 2]

[0070] Table 3

Claims

1. A method for producing magnesium hydroxide particles, A mixture formation step in which a mixture is formed by mixing a magnesium hydroxide material containing 100 ppm or more of silicon with a slurry containing magnesium hydroxide seed crystals. A maturation step in which the seed crystal is grown by maturing the mixture, thereby forming magnesium hydroxide particles that have a larger particle size than the seed crystal. Includes, The seed crystal of magnesium hydroxide in the mixture formation step contains 100 ppm or more of silicon. A method characterized by the following features.

2. The method according to claim 1, wherein the magnesium hydroxide particles in the aging process contain 100 ppm or more of silicon.

3. The method according to claim 1, wherein the slurry containing the magnesium hydroxide seed crystal in the mixture formation step is formed by reacting an alkaline substance containing 100 ppm or more of silicon with a water-soluble magnesium compound and aging it at a predetermined aging temperature of 100°C or higher and 200°C or lower.

4. The method according to claim 3, wherein the maturation temperature for maturing the mixture in the maturation step is higher than the predetermined maturation temperature.

5. Prior to the mixture formation step, the method further includes a seed crystal formation step in which a portion of the magnesium hydroxide material is matured to form a slurry containing seed crystals of magnesium hydroxide, In the mixture formation step, the remainder of the magnesium hydroxide material is mixed with a slurry containing the magnesium hydroxide seed crystal formed in the seed crystal formation step. The method according to claim 1.

6. The method according to claim 5, wherein the mass ratio of a portion of the magnesium hydroxide material to the remainder of the magnesium hydroxide material is 1 to 90:10 to 99.

7. A method for increasing the particle size of particles containing magnesium hydroxide crystals, A mixture formation step in which a mixture is formed by mixing a magnesium hydroxide material containing 100 ppm or more of silicon with a slurry containing magnesium hydroxide seed crystals. A maturation step in which the seed crystal is grown by maturing the mixture, thereby forming magnesium hydroxide particles that have a larger particle size than the seed crystal. Includes, The seed crystal of magnesium hydroxide in the mixture formation step contains 100 ppm or more of silicon. A method characterized by the following features.

8. It contains 100 ppm to 182 ppm of silicon. It has a D50 of 0.6 to 5.0 μm, Having a BET specific surface area of ​​1.0 to 7.5 m² / g, Magnesium hydroxide particles characterized by the following features.

9. The magnesium hydroxide particles according to claim 8, wherein the magnesium hydroxide particles are surface-treated with at least one surface treatment agent selected from the group consisting of higher fatty acids, anionic surfactants, phosphate esters, coupling agents, and polyhydric alcohols and fatty acid esters.

10. A resin comprising magnesium hydroxide particles as described in claim 8, A resin composition characterized by the following features.