WO2019044121A1

WO2019044121A1 - Highly dispersed basic magnesium carbonate powder, and method for producing same

Info

Publication number: WO2019044121A1
Application number: PCT/JP2018/022917
Authority: WO
Inventors: 将志中村
Original assignee: 神島化学工業株式会社
Priority date: 2017-08-28
Filing date: 2018-06-15
Publication date: 2019-03-07
Also published as: JP6976773B2; JP2019038724A

Abstract

Provided are: highly dispersed basic magnesium carbonate powder in which aggregation of primary particles is suppressed and which can be developed for various applications; and a method for producing the same. The highly dispersed basic magnesium carbonate powder has a sedimentation volume of 60 mL or more obtained by measurement under the following measurement conditions. (Measurement conditions of sedimentation volume) 5 g of the basic magnesium carbonate powder is put into a 100 mL measuring cylinder with a lid, then pure water is weighed up to 100 mL and mixed, the resultant mixture is left standing at 20°C for 2 hours, and thereafter, in a separation phase of a powder dispersed phase and a pure water phase, the volume occupied by the powder dispersed phase is measured as the sedimentation volume (mL).

Description

Highly dispersed basic magnesium carbonate powder and method for producing the same

The present invention relates to highly dispersed basic magnesium carbonate and a method of producing the same.

Basic magnesium carbonate has properties such as poor water solubility, oil absorption, and thickening properties, and is used in various fields as additives for paints, foods, medicines, cosmetics, rubber, paper, and the like. In general, basic magnesium carbonate powder is in the form of aggregates or aggregates of flaky primary particles, and the form of aggregation or aggregation is controlled depending on the use (eg, Patent Documents 1 and 2). With regard to natural basic magnesium carbonate, the size of primary particles is relatively large, and the variation in size is large, making it difficult to develop applications.

Japanese Patent Laid-Open No. 2000-16028 JP 2003-342894

As described above, since the basic magnesium carbonate powder has a form in which primary particles are aggregated, a decrease in properties due to the form may be observed when applied to each use. For example, when added as a thickener to a paint, the heat resistance and color of the paint deteriorate as the amount added increases, and when added to cosmetics, the smoothness decreases, and it is used for food, paint, medicine, etc. In this case, the particles settle with time in water to cause phase separation, which affects the handling and the uniformity of quality during production and use.

An object of the present invention is to provide a highly dispersed basic magnesium carbonate powder which can suppress the aggregation of primary particles and can be developed for various uses, and a method for producing the same.

As a result of intensive investigations, the inventor of the present invention has found that the problems described above can be solved by adopting the following configuration, and the present invention has been accomplished.

That is, in one embodiment, the present invention relates to a highly dispersed basic magnesium carbonate powder having a sedimentation volume of 60 mL or more obtained by measurement under the following measurement conditions.
(Measurement conditions of sedimentation volume)
5 g of the basic magnesium carbonate powder is put into a 100 mL measuring cylinder with a lid, and then the pure water is weighed to 100 mL, mixed, and allowed to stand for 2 hours at 20 ° C. The volume occupied by the powder dispersed phase in the phase is measured as settling volume (mL).

The present inventors have found that the sedimentation volume of a basic magnesium carbonate powder correlates well with the cohesion of primary particles, and completed the present invention. In the highly dispersed basic magnesium carbonate powder (hereinafter, also referred to as "highly dispersed powder"), since the sedimentation volume is in the above range, the aggregation of the primary particles is suppressed, in other words, the dispersion at the primary particle level is achieved. Thus, a highly dispersed powder suitable for various application development can be obtained. If the sedimentation volume is less than the above range, the degree of aggregation of primary particles may be increased, which may cause the problems observed in conventional low-dispersion basic magnesium carbonate powders.

In the highly dispersed powder, the degree of dispersion represented by the following formula is preferably 6 or more.
Degree of dispersion = (d _L / d ₅₀ ) × 100
(Wherein, d _L is the average major axis (μm) of primary particles obtained using a SEM photograph, and d ₅₀ is the cumulative 50% diameter (μm on a volume basis) in the particle size distribution obtained by a laser diffraction particle size distribution analyzer )))

According to the SEM photograph, the average particle size (average major axis d _L ) of the primary particles can be determined regardless of the presence or absence of aggregation of the primary particles. On the other hand, according to the laser diffraction type particle size distribution analyzer, a value (d ₅₀ ) including the particle diameter of any of primary particles and secondary particles which are aggregates of primary particles can be obtained, and generally d _L ₅₀ is a larger value. In other words, d ₅₀ can be treated as an index of secondary particle diameter. Therefore, if the primary particles are dispersed as they are without aggregation, d _L and d ₅₀ approximate each other, and the degree of dispersion represented by the above equation also increases. In the said highly dispersed powder, since the dispersion degree represented by the said Formula is made into the said range, aggregation (formation of secondary particle) of a primary particle is suppressed, and a primary particle can exhibit the state with high dispersibility. .

The highly dispersed powder preferably has a cumulative 50% diameter (d ₅₀ ) on a volume basis of 7 μm or less in a particle size distribution obtained by a laser diffraction type particle size distribution analyzer. Generally, as the particle size of the powder decreases, it tends to agglomerate. In the high dispersion powder, despite the smaller the cumulative 50% diameter (d _50), since aggregation of the primary particles is suppressed, can be performed widely efficiently expansion into various applications .

The highly dispersed powder preferably has a BET specific surface area of 50 m ² / g or less. When the primary particles are compactly aggregated, the BET specific surface area of the aggregates tends to be high. By setting the BET specific surface area of the highly dispersed powder in the above range, the aggregation of primary particles is suppressed, and it is possible to achieve a state where primary particles are dispersed sparsely.

The present invention provides, in a further embodiment, a method of producing the highly dispersed basic magnesium carbonate powder, wherein
A preparation step of preparing a raw material dispersion in which a raw material basic magnesium carbonate powder having a sedimentation volume of less than 60 mL is dispersed in a dispersion medium, and hydrothermal treatment of the raw material dispersion at a temperature of 150 ° C. or less to obtain a treated dispersion. The present invention relates to a method for producing a highly dispersed basic magnesium carbonate powder including the steps.

In the said manufacturing method, it is relatively low temperature of 150 degrees C or less with respect to the dispersion liquid of the raw material basic magnesium carbonate powder (Hereafter, it is also called "raw material powder") with relatively large abundance of the aggregate of primary particles. A highly dispersed powder can be efficiently produced only by subjecting it to hydrothermal treatment. Although the reason for this is not clear, it is presumed as follows. By performing predetermined hydrothermal treatment, aggregation of primary particles in the raw material powder is gradually loosened while suppressing undesired decomposition reaction (described later) of the raw material powder, and a state in which the primary particles are dispersed individually is obtained. A high dispersion state at the primary particle level, which can not be obtained merely by pulverizing the dry powder, will be achieved by the destruction or separation of aggregates of primary particles that have undergone a predetermined hydrothermal treatment. However, when the hydrothermal treatment is carried out at a temperature exceeding 150 ° C., the decomposition reaction of the raw material powder proceeds and it becomes a mixed phase in which anhydrous magnesium carbonate and magnesium hydroxide coexist, and the target basic magnesium carbonate powder is obtained. It will not be possible.

In the said manufacturing method, it is preferable to perform the said hydrothermal treatment at the temperature of 100 degreeC or more and 150 degrees C or less. By performing the hydrothermal treatment in the above temperature range, it is possible to promote the destruction or separation of the aggregates of the primary particles, and it is possible to manufacture the target highly dispersed powder with high yield.

The manufacturing method may further include a drying step of filtering the treated dispersion after the hydrothermal step and drying the filtered powder. Thereby, the dried highly dispersed powder can be suitably manufactured.

The present invention relates, in one embodiment, to a powder suspension composition containing 0.1 to 100 parts by mass of the highly dispersed basic magnesium powder with respect to 100 parts by mass of a solvent.

The powder suspension composition is suitably used as a cosmetic, a food or a paint.

The present invention relates, in one embodiment, to a powdery cosmetic comprising the highly dispersed basic magnesium powder in a blending amount of 0.5% by weight or more and 80% by weight or less.

The present invention relates, in another embodiment, to a polymer composition in which 1 to 500 parts by mass of the highly dispersed basic magnesium powder is blended with 100 parts by mass of the polymer material.

It is preferable that the said polymeric material is resin, rubber | gum, or paper. Since the said highly dispersed powder has the above-mentioned characteristic, it can be used suitably as a reinforcing filler of the product using these polymeric materials.

3 is a SEM photograph of the basic magnesium carbonate of Example 1. 5 is a SEM photograph of the basic magnesium carbonate of Comparative Example 1;

<< Highly dispersed basic magnesium carbonate >>
In the highly dispersed basic magnesium carbonate powder of the present embodiment, the sedimentation volume obtained by measurement under the following measurement conditions is 60 mL or more.
(Measurement conditions of sedimentation volume)
Charge 5 g of basic magnesium carbonate powder into a 100 mL measuring cylinder with a lid, measure up to 100 mL of pure water, mix, and separate from the powder dispersed phase and the pure water phase after standing for 2 hours at 20 ° C. Measure the volume occupied by the powder dispersed phase in as the sedimentation volume (mL).

In the present embodiment, since the highly dispersed powder has a sedimentation volume in the above range, aggregation of primary particles can be suppressed to achieve a dispersed state at the primary particle level. Thereby, a highly dispersed powder suitable for various application development can be obtained. Although the sedimentation volume may be 60 mL or more, 70 mL or more is preferable, 80 mL or more is more preferable, and 85 mL or more is particularly preferable. On the other hand, the sedimentation volume may be approximately 100 mL or less when the powder dispersed phase is in the form of a colloid, or may be 98 mL or less in consideration of handling properties and the like. If the sedimentation volume is less than the above range, the degree of aggregation of primary particles may be increased, which may cause the problems observed in conventional low-dispersion basic magnesium carbonate powders. Although the pure water phase after mixing and leaving the powder and pure water contains substantially no basic magnesium carbonate powder, it contains a small amount of powder which is difficult to distinguish by ordinary visual inspection. It is also good. Even in this case, the distinction between the powder dispersed phase and the pure water phase can be easily made visually.

In the highly dispersed powder of the present embodiment, the degree of dispersion represented by the following formula is preferably 6 or more, more preferably 8 or more, further preferably 10 or more, and particularly preferably 15 or more.
Degree of dispersion = (d _L / d ₅₀ ) × 100
(Wherein, d _L is the average major axis (μm) of primary particles obtained using a SEM photograph, and d ₅₀ is the cumulative 50% diameter (μm on a volume basis) in the particle size distribution obtained by a laser diffraction particle size distribution analyzer )))

In the present embodiment, since the degree of dispersion of the highly dispersed powder is in the above range, the aggregation of primary particles (formation of secondary particles) is suppressed, and the primary particles can exhibit a highly dispersed state. The higher the degree of dispersion, the better, but from the viewpoint of simplification of the process of cohesive failure of primary particles and physical limitations, 90 or less is preferable, and 80 or less is more preferable.

The highly dispersed powder preferably has a cumulative 50% diameter (d ₅₀ ) on a volume basis of 7 μm or less, more preferably 5 μm or less, still more preferably 4 μm or less, in the particle size distribution obtained by a laser diffraction particle size distribution analyzer. Particularly preferred is 3.5 μm or less. In the highly dispersed powder according to the present embodiment, the aggregation of the primary particles is suppressed despite the fact that the 50% cumulative diameter (d ₅₀ ) is reduced, so the development for various applications can be widely and efficiently. It can be carried out. The cumulative 50% diameter (d ₅₀ ) is preferably 0.1 μm or more, more preferably 0.3 μm or more, and still more preferably 0.5 μm or more from the viewpoint of handling properties and the like.

In the highly dispersed powder according to the present embodiment, the standard deviation in the particle size distribution obtained by the laser diffraction particle size distribution analyzer is not particularly limited, but is preferably 9 μm or less, more preferably 8 μm or less, and 5 μm or less More preferably, 3 μm or less is particularly preferred. By setting the standard deviation to the above range, it is possible to obtain a homogeneous highly dispersed powder with a uniform particle size. The standard deviation is obtained by the following equation.
Standard deviation = (d _84- d ₁₆ ) / 2
(Wherein, d ₈₄ is the cumulative 84% diameter on a volume basis in the particle size distribution obtained by a laser diffraction particle size distribution analyzer, and d ₁₆ is the accumulation on a volume basis in the particle size distribution obtained by a laser diffraction particle size distribution analyzer 16% diameter)

In the present embodiment, BET specific surface area of the highly dispersed powder is preferably not more than ^{50 m} 2 / g, more preferably not more than ^{^{40m 2 / g, 30m 2 /}} g more preferably less, and particularly preferably less ^{20 m} 2 / g . The smaller the BET specific surface area, the larger the size of the plate-like primary particles, and the firmer the structure of the primary particles along with that, the water is easily held or fixed between the plate-like primary particles, and the high dispersion is achieved. The state can be achieved. On the other hand, 10 m ² / g or more is preferable, and 15 m ² / g or more of the BET specific surface area is more preferable. The BET specific surface area of anhydrous magnesium carbonate (magnesite) is low, and when anhydrous magnesium carbonate is produced as a by-product in the production of a highly dispersed powder, the BET specific surface area is lowered. Magnesite is a cubic particle, and since there is no void between primary particles such as basic magnesium carbonate, water can not be held or fixed between primary particles, and as a result, high dispersibility is achieved. It can not be done. Therefore, the BET specific surface area is preferably in the above range from the viewpoint of suppressing the formation of anhydrous magnesium carbonate.

In the present embodiment, the apparent specific gravity of the high dispersion powder is preferably 0.28 g / mL or less, more preferably 0.25 g / mL or less, still more preferably 0.22 g / mL or less, particularly 0.2 g / mL or less preferable. 0.15 g / mL or more is preferable and, as for the apparent specific gravity of highly dispersed powder, 0.16 g / mL or more is more preferable. By making the apparent specific gravity of the highly dispersed powder in the above range, the dispersibility and the handling property can be improved. The apparent specific gravity can be measured according to JIS K 6220-1: 2001.

In the highly dispersed powder according to the present embodiment, the average major axis of the primary particles obtained in the SEM photograph is preferably 0.1 μm or more, more preferably 0.2 μm or more, and 0.3 μm or more. Is more preferable, and 0.4 μm or more is particularly preferable. The average major axis of the primary particles is preferably 2 μm or less, more preferably 2.5 μm or less, and still more preferably 2 μm or less. By setting the average major axis of the primary particles in the above range, the dispersibility, the handling property and the like can be further improved.

In the highly dispersed powder according to the present embodiment, the average thickness of the primary particles obtained in the SEM photograph is preferably 0.001 μm or more, more preferably 0.005 μm or more, and 0.01 μm or more. Is more preferable, and particularly preferably 0.015 μm or more. The average thickness of the primary particles is preferably 0.5 μm or less, more preferably 0.3 μm or less, and still more preferably 0.2 μm or less. By setting the average thickness of the primary particles in the above range, the dispersibility, the handling property, and the like can be further improved.

In the highly dispersed powder according to the present embodiment, the aspect ratio of primary particles represented by the following formula is preferably 5 or more, more preferably 6 or more, still more preferably 7 or more, and particularly preferably 8 or more. The aspect ratio is preferably 30 or less, more preferably 25 or less, and still more preferably 20 or less.
Ask ratio = average major diameter of primary particles (μm) / average thickness of primary particles (μm)
By setting the aspect ratio of the primary particles in the above range, the dispersibility and thickening property of the highly dispersed powder can be improved.

In the highly dispersed powder according to the present embodiment, the average crystallite diameter of the primary particles obtained by X-ray diffraction is not particularly limited, but is preferably 110 Å to 200 Å, more preferably 120 Å to 190 Å, and more preferably 130 Å to 180 Å. More preferably, 140 Å or more and 180 Å or less are particularly preferable. When the average crystallite diameter of the primary particles is in the above range, the heat resistance of the highly dispersed powder can be improved.

Basic magnesium carbonate is a compound represented by the following chemical formula.
x MgCO ₃ · Mg (OH) ₂ · yH ₂ O
(Wherein, x is an integer of 3 to 5 and y is an integer of 3 to 8)

The highly dispersed powder of the present embodiment contains basic magnesium carbonate as a main component. 95% or more is preferable, as for the ratio of basic magnesium carbonate, 98% or more is more preferable, and 99% or more is more preferable. In addition, highly dispersed powder may contain the unavoidable impurity component originating in a raw material, a manufacturing method, etc. The impurity component is, for example, Ca, S, Si or the like. The content of these impurities is preferably 0.3% by mass or less in the highly dispersed powder in terms of each element.

The shape of the primary particles of the highly dispersed powder of the present embodiment is mainly plate-like, but may be cubic, indeterminate, needle-like or the like in part.

The application of the highly dispersed powder of the present embodiment is not particularly limited. For example, fillers and reinforcing materials for rubber products, insulating materials, fire and heat insulating materials requiring characteristics such as high temperature resistance, glass products, magnesium salts, magnesium Single body, printing oil, ink, china, resin filler (warp preventing material, reinforcing material such as battery separator), paper making filler (reinforcing material), white inorganic filler, paint, heat insulating material, heat insulating material, sound absorbing material, Filters, building materials, pharmaceuticals and carriers thereof, peptizer production, pesticides and carriers thereof, cosmetics and carriers thereof, catalyst carriers, microbial carriers, biological carriers, fertilizers, absorbents, oil absorbents, desiccants, thickeners, Air Freshener, Deodorant, Sealant, Rust Inhibitor, Food Additive, Filter Material, Filter Aid, Abrasive, Color Protecting Agent, Desiccant, Column Filler, Daily Use Chemical Products, Gas Barrier Agent, Thermal Conductivity Filler etc. It is. Moreover, highly dispersed powder can be used as a raw material of magnesium oxide. A publicly known method can be adopted as a method of converting basic magnesium carbonate to magnesium oxide, and examples thereof include a heat treatment of basic magnesium carbonate and the like.

As a specific example of the application of the highly dispersed powder of the present embodiment, a powder suspension in which 0.1 to 100 parts by mass, preferably 1 to 50 parts by mass of the highly dispersed basic magnesium powder of the present embodiment is blended with 100 parts by mass of a solvent. A turbid composition can be suitably employed. As a solvent, it can select suitably according to the use of a powder suspension composition, For example, organic solvents, such as water and alcohol (for example, ethanol etc.), acetone, toluene, etc. are mentioned. The use of this powder suspension composition is not particularly limited, but it is suitable as a cosmetic, food or paint because the highly dispersed powder is plate-like and has hiding power, oil absorption, thickening properties and high smoothness. Used. Furthermore, since the highly dispersed powder of the present embodiment has excellent smoothness, it can also be used as a base material for powdery cosmetics. When using for powdery cosmetics, 0.5 weight%-80 weight% are preferable, and, as for the compounding quantity of highly dispersed powder, 1 weight%-50 weight% is more preferable.

In addition, as another application, a polymer composition in which 1 to 500 parts by mass, preferably 5 to 300 parts by mass of the highly dispersed basic magnesium powder of the present embodiment is blended with 100 parts by mass of the polymer material is preferably listed. be able to. The polymeric material may be either a natural polymeric material or a synthetic polymeric material, and is preferably a resin, rubber or paper (pulp). The highly dispersed powder is in the form of a plate, and has heat resistance and smoothness, so it can be suitably used as a reinforcing filler for products using these polymer materials.

<< Production Method of Highly Dispersed Basic Magnesium Carbonate >>
In the method for producing highly dispersed basic magnesium carbonate powder of the present embodiment, a preparation step of preparing a raw material dispersion in which raw material basic magnesium carbonate powder having a sedimentation volume of less than 60 mL is dispersed in a dispersion medium, and 150 of the raw material dispersion Including a hydrothermal process to obtain a treated dispersion by hydrothermal treatment at a temperature not higher than ° C. Furthermore, it is preferable to include a drying step of filtering the treated dispersion liquid and drying the filtered powder after the hydrothermal step. Each step will be described below.

(Preparation process)
As raw material powder, basic magnesium carbonate obtained by a well-known method can be used widely. Moreover, a commercial item can also be used. The sedimentation volume of basic magnesium carbonate obtained by the conventional method, including commercial products, is often less than 60 mL, and the degree of aggregation of primary particles is high. As a method of producing the raw material powder, a known method can be adopted as described above, for example, a gas method utilizing reaction of magnesium hydroxide and carbon dioxide gas, reaction of magnesium salt and sodium carbonate is utilized Examples include the soda method and the anthracite method utilizing the reaction between magnesium salt and ammonium carbonate.

The gas method will be described as a representative example. The magnesium hydroxide powder is dispersed in water to prepare a slurry. The slurry concentration may be set in consideration of the reaction efficiency with the carbon dioxide gas in the next step, etc., and is about 10 to 80 g / L, preferably about 20 to 60 g / L as the MgO concentration. This slurry is heated to about 50 to 100 ° C., preferably about 60 to 80 ° C., carbon dioxide gas is blown into the slurry, and basic magnesium carbonate is obtained by carbonation reaction of magnesium hydroxide and carbon dioxide gas. it can. The flow rate of carbon dioxide gas may be appropriately set in consideration of reaction efficiency and the like, and is generally 10 to 50 L / min, preferably about 20 to 40 L / min. After completion of the carbonation reaction, the raw material powder can be obtained by dehydration and drying.

In the preparation step, the raw material powder is dispersed in a dispersion medium to prepare a raw material dispersion. Water is preferred as the dispersion medium. The concentration of the raw material powder can be set according to the efficiency, yield, etc. of the hydrothermal reaction in the next step, and is preferably 15 to 70 g / L, more preferably 20 to 60 g / L, and more preferably 25 to 50 g in terms of MgO concentration. / L is more preferable. For dispersing the raw material powder, a known mixer equipped with a stirring blade can be used. A raw material dispersion is obtained by sufficiently stirring and mixing water and raw material powder in a mixer. The temperature during dispersion may be room temperature or may be heated at a temperature of 100 ° C. or less. When preparation of a raw material dispersion liquid is continuously performed from manufacture of raw material powder, the slurry after carbonation reaction of magnesium hydroxide can be used as a raw material dispersion liquid as it is. At that time, the concentration of the raw material powder may be adjusted to a predetermined range by increasing or decreasing the water content.

(Hydrothermal process)
In the present hydrothermal process, the raw material dispersion is hydrothermally treated at a temperature of 150 ° C. or less to obtain a treated dispersion. By performing the hydrothermal treatment, the aggregation of the primary particles in the raw material powder is gradually loosened while the undesirable decomposition reaction (decomposition to anhydrous magnesium carbonate and magnesium hydroxide) of the raw material powder is suppressed, and the primary particles are dispersed individually Can be obtained. Furthermore, through the hydrothermal treatment, crystal growth in primary particles can be promoted, and the crystallite diameter can be increased.

The hydrothermal treatment can be carried out by stirring the raw material dispersion under heating conditions in a known pressure resistant heating vessel such as an autoclave. The heating temperature is 150 ° C. or less. Preferably, the heating temperature is 100 ° C. to 150 ° C., more preferably 120 ° C. to 150 ° C., still more preferably 130 ° C. to 150 ° C., particularly preferably 140 ° C. to 150 ° C. is there. When the temperature of the hydrothermal treatment exceeds 150 ° C., the decomposition reaction of the raw material powder proceeds to become a mixed phase in which anhydrous magnesium carbonate and magnesium hydroxide co-exist, and the target basic magnesium carbonate powder can not be obtained. The time of the hydrothermal treatment is set in a range to sufficiently advance the cohesive failure of the primary particles and to suppress the decomposition reaction of the raw material powder due to the long time treatment, and is about 1 to 12 hours, preferably about 2 to 8 hours, Preferably, it is about 2.5 to 6 hours. Through the hydrothermal process, a treated dispersion in which the highly dispersed powder is dispersed is obtained.

(Drying process)
After the hydrothermal process, the treatment dispersion containing the highly dispersed powder may be filtered, and the dried powder may be dried. At the time of filtration, filtration and dehydration may be performed while pressurizing with a known filter press. The pressure at the time of dehydration can be set appropriately, and is generally about 0.5 to 10 MPa, preferably 1 to 6 MPa, and more preferably 1.5 to 4 MPa. The filtered powder is then dried in a dryer. A well-known thing can be used for a dryer, for example, a hot-air dryer, an infrared dryer, a vacuum dryer etc. are mentioned. The drying temperature is preferably 50 to 150 ° C., more preferably 70 to 140 ° C., still more preferably 80 to 130 ° C., and particularly preferably 90 to 120 ° C. The drying time is about 1 to 20 hours, preferably 3 to 18 hours, more preferably 6 to 15 hours. After the drying step, pulverization may be carried out, if necessary. The state of primary particles can be stably maintained by performing the pulverization treatment after the hydrothermal treatment, as compared with the conventional pulverization treatment which does not undergo the hydrothermal treatment. Through the above steps, highly dispersed basic magnesium carbonate in which aggregation of primary particles is suppressed can be produced.

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

Example 1
In a reaction container equipped with a stirring blade, 80 L of magnesium hydroxide slurry with an MgO concentration of 40 g / L was heated to 70 ° C., and carbon dioxide gas was blown at a gas flow rate of 30 L / min while stirring to carry out a carbonation reaction. Phenolphthalein was added to the slurry, and the reaction was terminated when the color changed from pink to colorless. When the end was reached, the carbon dioxide gas blowing was stopped. Thereby, a slurry of raw material basic magnesium carbonate powder was obtained. Thereafter, water was added to adjust the concentration of basic magnesium carbonate to 35 g / L in terms of MgO concentration to obtain a raw material dispersion.

70 L of the raw material dispersion liquid with an MgO concentration of 35 g / L was placed in a stirrer-equipped autoclave with a capacity of 100 L, and subjected to hydrothermal treatment at a temperature of 150 ° C. for 4 hours while stirring to obtain a treated dispersion. The treated dispersion was then transferred to a filter press and dewatered by applying a pressure of 2.5 MPa for 3 minutes. The dewatered powder was allowed to stand and dried for 12 hours in a dryer set at 105 ° C. to obtain a highly dispersed basic magnesium carbonate powder.

(Example 2)
A highly dispersed basic magnesium carbonate powder was produced in the same manner as in Example 1 except that the temperature of the hydrothermal treatment was 140 ° C.

(Example 3)
A highly dispersed basic magnesium carbonate powder was produced in the same manner as in Example 1 except that the temperature of the hydrothermal treatment was set to 120 ° C.

(Example 4)
A highly dispersed basic magnesium carbonate powder was produced in the same manner as in Example 1 except that the temperature of the hydrothermal treatment was set to 100 ° C.

(Comparative example 1)
A basic magnesium carbonate powder was produced in the same manner as in Example 1 except that the raw material dispersion was dewatered and dried, and the hydrothermal treatment was not performed.

(Comparative example 2)
A basic magnesium carbonate powder was produced in the same manner as in Example 1 except that the temperature of the hydrothermal treatment was set to 80 ° C.

<Evaluation of basic magnesium carbonate powder>
The following analysis was performed about the basic magnesium carbonate powder obtained by the Example and the comparative example. Each evaluation result is shown in Table 1.

(1) Sedimentation Volume 5 g of basic magnesium carbonate powder was charged into a 100 mL measuring cylinder with a lid, and pure water was poured in to make up 100 mL. The lid of the measuring cylinder was closed and shaken for about 1 minute with a swing width of about 20 cm for uniform mixing, to prepare a dispersion. Thereafter, it was allowed to stand at 20 ° C. for 2 hours. The volume occupied by the powder dispersed phase in the separated phase of the powder dispersed phase and the pure water phase was read, and this was measured as a settling volume (mL).

(2) Scanning electron microscope (SEM photograph; average major diameter and average thickness of primary particles)
A double-sided tape was attached on an aluminum sample stand, and a sample powder was applied thereon so as to be traced with a spatula spatula. After gold deposition, the particle image of the sample powder was photographed at a magnification of 5000 using a scanning electron microscope (FE-SEM: S-4700 manufactured by Hitachi, Ltd.). The SEM photograph of the basic magnesium carbonate powder of Example 1 and the comparative example 1 is respectively shown by FIG. 1 and FIG.

Image analysis software (Image J) was used to randomly select 50 particles in the photograph, and the average major diameter (μm) and the average thickness (μm) of primary particles were determined. Here, the major axis of the primary particle is the size (that is, the longest diameter) of the particle in the direction in which the size of the particle becomes the largest by measuring the size of the measurement object particle from each direction.

(3) Cumulative 50% diameter and standard deviation Take 50 mL of ethanol into a beaker of 100 mL capacity, add about 0.2 g of sample powder, apply ultrasonication for 3 minutes (UD-201 manufactured by Tomy Seiko Co., Ltd.), and disperse it Was prepared. The dispersion was measured using a laser diffraction method-particle size distribution analyzer (Microtrac HRA Model 9320-X100 manufactured by Nikkiso Co., Ltd.), and the 50% cumulative diameter (d ₅₀ ) on a volume basis in the obtained particle size distribution (μm) Asked for).

Similarly, the cumulative 84% diameter (d ₈₄ ) (μm) and the cumulative 16% diameter (d ₁₆ ) (μm) on a volume basis in the obtained particle size distribution were determined, and the standard deviation was determined according to the following formula.
Standard deviation = (d _84- d ₁₆ ) / 2

(4) Degree of dispersion Average primary particle diameter (d _L ) (μm) obtained using SEM photographs and cumulative 50% diameter on a volume basis in particle size distribution obtained with a laser diffraction particle size distribution analyzer (d ₅₀₎ ) (Μm) was used to determine the degree of dispersion according to the following equation.
Degree of dispersion = (d _L / d ₅₀ ) × 100

(5) BET specific surface area A sample powder pretreated at about 130 ° C. for about 30 minutes in a nitrogen gas atmosphere using an 8-station preheating unit (manufactured by MOUNTECH) was used as a BET specific surface area measuring device Macsorb HM Model-1208 The BET specific surface area (m ² / g) was measured by a nitrogen gas adsorption method using (manufactured by MOUNTECH).

(6) Average Crystallite Size of Primary Particles The measurement of the average crystallite size of primary particles was carried out according to the following procedure. An X-ray diffraction pattern was obtained by measurement with an X-ray diffractometer (RINT-2500, manufactured by Rigaku Corporation) under the conditions of a Cu radiation source (40 kV, 30 mA). The crystallite diameter was calculated by the Scherrer method using the integrated powder X-ray analysis software "PDXL2".

(7) Apparent Specific Gravity The method of measuring the apparent specific gravity of the highly dispersed powder was measured according to JIS K 6220-1: 2001.

(8) Heat resistance (weight loss in thermogravimetric (TG) measurement)
The heat resistance of the highly dispersed powder was evaluated by measuring the weight loss in TG measurement. The smaller the weight loss in TG measurement, the higher the heat resistance. TG measurement was performed using “TG / DTA6300” manufactured by Seiko Instruments Inc. The measurement conditions were as follows. Temperature rising rate: 20 ° C./min, measurement atmosphere: Air 200 ml / min, reference: Al ₂ O ₃ , sample weight: 8.0 mg, measurement container: made of Pt, measurement temperature range: 40 to 300 ° C.

Next, the weight loss (%) at 200 ° C. and the weight loss (%) at 100 ° C. were determined according to the following formula.
Weight loss (%) = {(initial weight-weight at each temperature) / initial weight} x 100

Furthermore, a value obtained by subtracting the weight loss (%) at 100 ° C. from the weight loss (%) at 200 ° C. is obtained, and when this value is 2% or less, “◎”, more than 2% and 5% or less The heat resistance was evaluated on the basis of “○”, and the case of exceeding 5% as “×”.

(9) Measurement of average coefficient of friction (smoothness)
Using a friction tester KES-SE (manufactured by Kato Tech), spread 0.1 g of basic magnesium carbonate powder with a puff on a double-sided tape (15 mm wide) attached to the slide glass surface, load 25 g, moving speed H The average coefficient of friction was measured at (the predetermined moving speed in the tester). The sensor used 10 mm square silicon sensor. If the average coefficient of friction was 1.3 or more, it was judged to be smooth.

(10) Thickening property A 10 wt%, 20 ° C. water slurry was prepared using basic magnesium carbonate powder (mixed with a stir bar so that the solution becomes uniform). Rotor No. 1 was manufactured using a BL II viscometer (manufactured by Toki Sangyo Co., Ltd.). 3. The value of viscosity (cP) was calculated by reading the value one minute after the start of measurement under the condition of rotation speed 60 rpm. It was judged that the viscosity was good if the viscosity was 150 or more.

(11) Evaluation of reinforcement a. Preparation of Molded Body for Measurement of Flexural Modulus After blending 10 parts by mass of basic magnesium carbonate powder with 100 parts by mass of polypropylene resin (PP, manufactured by Nippon Polypropylene Corporation, BC6D), Labo Plastomill (Toyo Seiki Co., Ltd.) After melt-kneading at 180 ° C. for 5 minutes at a rotation speed of 50 rpm, the melt-kneaded product was cut to a diameter of about 5 mm or less with a shredder to produce pellets. The pellets were injection molded at an outlet temperature of 210 ° C. using an injection molding machine (J-50E2 manufactured by Japan Steel Works, Ltd.) to obtain 80 × 10 × 4 mm test pieces.
b. Measurement of Flexural Modulus The flexural modulus (GPa) of the obtained test piece was measured based on JIS K7171. Specifically, using Method 3382 manufactured by Instron Co., Ltd., method A is used as a test method without changing the strain rate, and the test piece has a length of 80 mm × width 10 mm × thickness 4 mm, distance between supporting points 64 mm, test speed 2 mm / It carried out on the conditions of min, radius R1 of indenter = 5 mm, and radius R2 of support stand = 5 mm. It was judged that the reinforcing property was good if the flexural modulus was 1.33 GPa or more.

From Table 1, in the highly dispersed basic magnesium carbonate powder obtained in the examples, the sedimentation volume and the degree of dispersion become high values, aggregation of primary particles was suppressed, and high dispersibility was obtained. Moreover, since it was a powder of low aggregation while heat resistance was favorable, both smoothness and thickening property were favorable. Furthermore, the flexural modulus of the resin composition containing the highly dispersed powder was also improved, and the reinforcing property was also good. On the other hand, in the basic magnesium carbonate powder of the comparative example, the sedimentation volume and the degree of dispersion had low values, and the primary particles were aggregated to result in low dispersibility. Along with this, the smoothness and the thickening property are also inferior. From the above, the highly dispersed basic magnesium carbonate powder of the present invention is a cosmetic (liquid cosmetic or powdery cosmetic), a food and a paint, and a resin, a rubber, and a rubber, which are required to have heat resistance and reinforcement. In addition to paper reinforcing materials and the like, development to various applications can be suitably achieved.

Claims

Highly dispersed basic magnesium carbonate powder having a sedimentation volume of 60 mL or more obtained by measurement under the following measurement conditions.
(Measurement conditions of sedimentation volume)
5 g of the basic magnesium carbonate powder is put into a 100 mL measuring cylinder with a lid, and then the pure water is weighed to 100 mL, mixed, and allowed to stand for 2 hours at 20 ° C. The volume occupied by the powder dispersed phase in the phase is measured as settling volume (mL).
The highly dispersed basic magnesium carbonate powder according to claim 1, wherein the degree of dispersion represented by the following formula is 6 or more.
Degree of dispersion = (d L / d 50 ) × 100
(Wherein, d L is the average major axis (μm) of primary particles obtained using a SEM photograph, and d 50 is the cumulative 50% diameter (μm on a volume basis) in the particle size distribution obtained by a laser diffraction particle size distribution analyzer )))
The highly dispersed basic magnesium carbonate powder according to claim 1 or 2, wherein a cumulative 50% diameter (d 50 ) on a volume basis in a particle size distribution obtained by a laser diffraction type particle size distribution analyzer is 7 μm or less.
The highly dispersed basic magnesium carbonate powder according to any one of claims 1 to 3, which has a BET specific surface area of 50 m 2 / g or less.
A method of producing the highly dispersed basic magnesium carbonate powder according to any one of claims 1 to 4,
A preparation step of preparing a raw material dispersion in which a raw material basic magnesium carbonate powder having a sedimentation volume of less than 60 mL is dispersed in a dispersion medium, and hydrothermal treatment of the raw material dispersion at a temperature of 150 ° C. or less to obtain a treated dispersion. A method of producing a highly dispersed basic magnesium carbonate powder comprising the steps of
The method for producing a highly dispersed basic magnesium carbonate powder according to claim 6, wherein the hydrothermal treatment is performed at a temperature of 100 ° C to 150 ° C.
The method for producing highly dispersed basic magnesium carbonate powder according to claim 6, further comprising a drying step of filtering the treated dispersion liquid and drying the filtered powder after the hydrothermal step.
A powder suspension composition containing 0.1 to 100 parts by mass of the highly dispersed basic magnesium powder according to any one of claims 1 to 4 with respect to 100 parts by mass of a solvent.
The powder suspension composition according to claim 8, wherein the powder suspension composition is used as a cosmetic, a food or a paint.
A powdery cosmetic product comprising the highly dispersed basic magnesium powder according to any one of claims 1 to 4 in a blending amount of 0.5% by weight or more and 80% by weight or less.
A polymer composition comprising 1 to 500 parts by mass of the highly dispersed basic magnesium powder according to any one of claims 1 to 4 with respect to 100 parts by mass of the polymer material.
The polymer composition according to claim 11, wherein the polymer material is a resin, rubber or paper.