JP2020093968A - Snow crystal-like zinc carbonate salt particle, snow crystal-like composite particle and method for producing the same - Google Patents

Abstract

To provide a novel particle containing a zinc component and having excellent soft focus properties.SOLUTION: A snow crystal-like zinc carbonate salt particle has a median diameter of 5-100 μm.SELECTED DRAWING: Figure 2

Description

The present invention relates to snow crystal-like zinc carbonate particles, snow crystal-like composite particles and a method for producing them.

Particles containing a zinc component have characteristics such as ultraviolet ray shielding effect (ultraviolet ray absorbing ability), near infrared ray reflecting effect, photocatalytic effect, etc. It is useful for various applications such as heat dissipation materials.

In addition, for the purpose of imparting soft focus to particles containing a zinc component, the shape thereof is made into a star shape, multi-needle shape, columnar shape, scooping shape, petal shape, hexagonal plate shape, plate shape, radial shape, etc. Is proposed.

For example, Patent Document 1 discloses a cosmetic composition having a star shape and containing at least star-shaped zinc oxide particles whose main component is zinc oxide.

Patent Document 2 discloses multi-needle zinc oxide particles having a particle diameter of 0.1 to 100 μm and a multi-needle shape.

JP, 2010-241763, A JP, 2013-155070, A

An object of the present invention is to provide a novel particle containing a zinc component, which particle has excellent soft focus properties.

As a result of various studies, the present inventors have found that the snow crystal-like zinc carbonate particles having a median diameter of 5 to 100 μm and the snow crystal-like composite particles containing zinc oxide and phosphate have excellent soft focus properties. The inventors have found that the above can be exhibited and have completed the present invention.

That is, the present invention relates to the following <1> to <11>.
<1> Snow crystal-like zinc carbonate particles having a median diameter of 5 to 100 μm.
<2> Snow crystal-like zinc carbonate particles according to <1>, which contains a phosphorus component.
<3> When light is projected onto the surface coated with the snow crystal zinc carbonate particles at an incident angle of −45°, the original stimulus Y value of the light reflected at a reflection angle of 45° is Y _45° , when the original stimulus Y value of the light reflected at the corner -25 ° was _{Y -25 °,} the value of _{Y 45 °} / _{Y -25 °} is 1.0 to 3.0, <1> or <2> 2. Snow crystal-like zinc carbonate particles described in.
<4> The snow crystal according to any one of <1> to <3>, which is produced by dissolving pyrophosphate in a metal bicarbonate aqueous solution and adding a zinc salt aqueous solution to the obtained aqueous solution. Zinc carbonate particles.
<5> Snow crystal-like composite particles containing zinc oxide and a phosphate.
<6> The snow crystal-like composite particles according to <5>, having a median diameter of 5 to 100 μm.
<7> The phosphate is Ca ₅ (PO ₄ ) ₃ (OH), Ca ₃ (PO ₄ ) ₂ , NaCaPO ₄ , Na ₉ Zn ₃ (PO ₄ ) ₅ , NaZnPO ₄ , and Ca ₉ NaZn(PO). ₄ ) The snow crystal-like composite particles according to <5> or <6>, which is at least one selected from the group consisting of ₇ ).
<8> When light is projected onto the surface coated with the snow crystal-like composite particles at an incident angle of −45°, the original stimulus Y value of the light reflected at a reflection angle of 45° is Y _45° , the reflection angle − when the original stimulus Y value of the light reflected by the 25 ° and the _{Y -25 °,} the value of _{Y 45 °} / _{Y -25 °} is 1.0 to 3.0, any <5> to <7> The snow crystal-like composite particle as described in 1 above.
<9> The snow crystal-like composite particles according to any one of <6> to <8>, which are produced by firing the snow crystal-like zinc carbonate particles according to <4>.
<10> Snow crystal zinc carbonate having a step (A) of dissolving pyrophosphate in an aqueous solution of a metal bicarbonate and a step (B) of adding an aqueous zinc salt solution to the aqueous solution obtained in the step (A). A method for producing salt particles.
<11> A method for producing snow crystal-like composite particles, which comprises a step (C) of firing the snow crystal-like zinc carbonate particles obtained by the method according to <10>.

According to the present invention, it is possible to provide novel particles containing a zinc component and having excellent soft focus properties.

FIG. 1 is a schematic diagram showing the relationship between the incident angle and the reflection angle. FIG. 2 shows magnified images of the particles of Example 3, Example 5, Example 7 and Comparative Example 1 at magnifications of 500 times and 2000 times. FIG. 3 is a diagram showing the original stimulation Y value obtained from Examples 1 to 5 as polar coordinates. FIG. 4 is a diagram showing the original stimulation Y value obtained from Examples 6 to 7 and the zinc oxide reagent as polar coordinates.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below, but these are examples of preferred embodiments, and the present invention is not limited to these contents.

In the snow crystal-like zinc carbonate particles and the snow crystal-like composite particles of the present invention (hereinafter, may be collectively referred to as “particles of the present invention”), the snow-crystal shape means within a plane from the center of the particle. It means a shape having three, four, or six protrusions that spread radially substantially evenly. As the snowflake shape, for example, shapes as shown in Example 3, Example 5 and Example 7 of FIG. 2 are exemplified.

Since the particles of the present invention are in the form of snow crystals, the light reflecting surfaces are randomly arranged, and the reflected light is scattered in various directions. Therefore, the particles of the present invention have excellent soft focus properties.

[Snow crystal zinc carbonate particles]
The snow crystal-like zinc carbonate particles of the present invention have a median diameter of 5 to 100 μm.
When the median diameter is 5 μm or more, a sufficient light reflecting surface can be secured and the soft focus property is improved. When the median diameter is 100 μm or less, it is possible to suppress roughness when the snow crystal zinc carbonate particles of the present invention are used in products such as cosmetics.

The median diameter of the snow crystal-like zinc carbonate particles of the present invention is preferably 5 to 80 μm, more preferably 5 to 60 μm, and further preferably 5 to 40 μm from the viewpoint of improving the soft focus property.

In the present invention, the median diameter is a particle diameter corresponding to a cumulative percentage of 50% on a volume basis, and can be measured by a nanoparticle diameter distribution measuring device.

Examples of the zinc carbonate salt in the present invention include sodium zinc carbonate, potassium potassium carbonate, lithium zinc carbonate and hydrates thereof.

<Method for producing snow crystal-like zinc carbonate particles>
In the snow crystal zinc carbonate particles of the present invention, pyrophosphate is dissolved in a metal bicarbonate aqueous solution (step (A)), and the zinc salt aqueous solution is added to the aqueous solution obtained in step (A) (step ( B)) is obtained.

(Process (A))
Step (A) is a step of dissolving pyrophosphate in a metal bicarbonate aqueous solution.
By using pyrophosphate, the zinc carbonate salt particles obtained in the step (B) described below can be formed into snow crystals.

The basic crystal structure of zinc carbonate is a simple cubic lattice of cubic system. By using pyrophosphate, the phosphate plays a role of accelerating the crystal growth rate of the (111) plane of zinc carbonate, and its cubic simple cubic lattice has a tetrahedral-based shape. It is presumed that it will change to snowflakes.

Examples of the pyrophosphate include sodium pyrophosphate, potassium pyrophosphate, calcium pyrophosphate, and the like. Among these, sodium pyrophosphate is preferable from the viewpoint of easily forming snow crystal particles. The pyrophosphate salts may be used alone or in combination of two or more.

Examples of the metal bicarbonate in the metal bicarbonate aqueous solution include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate and the like. Among these, sodium hydrogen carbonate is preferable from the viewpoint of reactivity. The metal bicarbonate salts may be used alone or in combination of two or more.

The concentration of the metal bicarbonate salt in the aqueous metal bicarbonate solution is preferably 5.3 to 8.8% by mass, more preferably 7.0 to 8.3% by mass, and 7.2 to 8.0% by mass. Is more preferable. When the concentration of the metal bicarbonate is 5.3 mass% or more, the metal bicarbonate required for the reaction can be secured. Further, if the concentration of the metal bicarbonate salt is too high, the metal bicarbonate salt is saturated, so the concentration of the metal bicarbonate salt is preferably 8.8% by mass or less.
In the present invention, examples of water used as an aqueous solution include distilled water and ion-exchanged water.

As a method for dissolving the pyrophosphate in the metal bicarbonate aqueous solution, a known dissolution method can be adopted. For example, a method of adding pyrophosphate to an aqueous solution of metal bicarbonate and mixing them may be mentioned. Examples of the mixing method include a method of stirring for 10 to 120 minutes, preferably 30 to 60 minutes. At that time, the temperature of the aqueous metal bicarbonate solution may be, for example, 10 to 40° C., preferably 15 to 30° C.

The concentration of the pyrophosphate in the aqueous solution obtained by dissolving the pyrophosphate in the metal bicarbonate aqueous solution is 0.1 to 1.6% by mass from the viewpoint of easily forming snow crystal particles. It is preferably 0.1 to 1.3% by mass, more preferably 0.1 to 0.9% by mass.

(Process (B))
Step (B) is a step of adding a zinc salt aqueous solution to the aqueous solution obtained in step (A).
Examples of the zinc salt in the zinc salt aqueous solution include zinc acetate dihydrate, zinc acetate (anhydrous), zinc oxalate dihydrate, zinc nitrate, zinc sulfate, zinc chloride, zinc bromide and the like. Among these, zinc acetate dihydrate and zinc acetate (anhydrous) are preferable from the viewpoint of reactivity. The zinc salt may be used alone or in combination of two or more.

The concentration of the zinc salt in the aqueous zinc salt solution is preferably 13.0 to 23.1% by mass, more preferably 16.2 to 21.5% by mass, and further preferably 18.9 to 21.5% by mass. When the zinc salt concentration is 13.0 mass% or more, the zinc salt necessary for the reaction can be secured. If the zinc salt concentration is too high, the zinc salt will be saturated, so the zinc salt concentration is preferably 23.1% by mass or less.
In the present invention, examples of water used as an aqueous solution include distilled water and ion-exchanged water.

As a method of adding the zinc salt aqueous solution to the aqueous solution obtained in the step (A), a known addition method can be adopted. For example, an aqueous zinc salt solution is added to the aqueous solution obtained in step (A) at a rate of, for example, 25 to 100 g/min, preferably 40 to 80 g/min, for example, 1.3 to 6.0 minutes, preferably 1.7. The method of dripping for -3.8 minutes is mentioned. At that time, the temperature of the aqueous solution obtained in the step (A) may be, for example, 10 to 40° C., preferably 15 to 30° C.
The dropping may be performed while stirring the aqueous solution obtained in the step (A).

The snow crystal-like zinc carbonate particles thus obtained can be washed and dried if necessary.
The washing can be performed with a washing liquid such as water and ethanol. The cleaning time is, for example, 0 to 30 minutes, preferably 0 to 10 minutes. The amount of the cleaning liquid used is, for example, 0 to 1000 mL, preferably 0 to 300 mL, per 10 g of particles.

Drying may be performed at room temperature or by heating, and further may be performed under reduced pressure.
The temperature for heating and drying is, for example, 80 to 250°C, preferably 100 to 200°C. The drying time is, for example, 30 minutes to 24 hours, preferably 60 minutes to 12 hours.

In the present invention, the median diameter of the particles can be adjusted by appropriately adjusting the concentration, addition rate and addition time of the aqueous zinc salt solution in step (B).

If the reaction time of the metal bicarbonate and zinc salt is 24 hours or more, the particles collide with each other and disintegrate, resulting in the production of fine particles having a median diameter of less than 5 μm. In the present invention, the reaction of metal bicarbonate and zinc salt is usually completed within 3 to 240 minutes. Therefore, in producing the snow crystal-like zinc carbonate particles of the present invention, fine particles having a median diameter of less than 5 μm are not produced.

The snow crystal-like zinc carbonate particles of the present invention contain the phosphorus component derived from the pyrophosphate used in step (A).

The content of the phosphorus component in the snow crystal zinc carbonate particles of the present invention is preferably 0.5 to 10% by mass, more preferably 1 to 6% by mass. The amount of the phosphorus component contained in the particles can be measured by elemental analysis (wavelength dispersive X-ray fluorescence analyzer (ZSX-Primus II, manufactured by Rigaku Corporation)).

[Snow crystal composite particles]
The snow crystal-like composite particles of the present invention are obtained by firing (secondary heat treatment) the snow crystal-like zinc carbonate particles of the present invention, and contain zinc oxide and a phosphate.
Examples of the phosphate contained in the snow crystal-like composite particles of the present invention include Ca ₅ (PO ₄ ) ₃ (OH), Ca ₃ (PO ₄ ) ₂ , NaCaPO ₄ , Na ₉ Zn ₃ (PO ₄ ) ₅ , NaZnPO ₄ , Ca ₉ NaZn(PO ₄ ) _{7 and the} like. Among these, Ca ₅ (PO ₄ ) ₃ (OH) and Ca ₃ (PO ₄ ) ₂ are preferable from the viewpoint of safety when the snow crystal-like composite particles of the present invention are used in products such as cosmetics.
The phosphate contained in the snow crystal-like composite particles of the present invention can be confirmed by an X-ray diffractometer.

The content of zinc oxide is preferably 60 to 90 parts by mass when the total mass of the snow crystal-like composite particles of the present invention is 100 parts by mass.

The content of the phosphate is preferably 10 to 40 parts by mass, when the total mass of the snow crystal-like composite particles of the present invention is 100 parts by mass.
The content of zinc oxide or phosphate can be measured by X-ray diffraction.

The snow crystal-like composite particles of the present invention preferably have a median diameter of 5 to 100 μm.
When the median diameter is 5 μm or more, a sufficient light reflecting surface can be secured and the soft focus property is improved. When the median diameter is 100 μm or less, it is possible to suppress roughness when the snow crystal-like composite particles of the present invention are used in products such as cosmetics.

From the viewpoint of improving the soft focus property, the median diameter of the snow crystal-like composite particles of the present invention is more preferably 5 to 80 μm, further preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

<Method for producing snow crystal-like composite particles>
The snow crystal-like composite particles of the present invention are obtained by further firing (secondary heat treatment) the snow crystal-like zinc carbonate particles of the present invention (step (C)).

(Process (C))
Step (C) is a step of firing the snow crystal-like zinc carbonate particles of the present invention. By firing the snow crystal-like zinc carbonate particles of the present invention, the zinc carbonate salt containing a phosphorus component is thermally decomposed into zinc oxide containing sodium component, sodium carbonate, carbon dioxide gas and water, and zinc oxide and phosphorus are contained. Snow crystal-like composite particles containing an acid salt are obtained.

Firing of the snow crystal-like zinc carbonate particles of the present invention is carried out, for example, by heating in a stationary or rotary high temperature furnace. The temperature during firing is, for example, 500 to 800°C, preferably 500 to 650°C. The firing time is, for example, 60 to 600 minutes, preferably 60 to 180 minutes. By firing at a temperature and time within this range, as described above, the zinc carbonate salt containing a phosphorus component is thermally decomposed, and snow crystal-like composite particles containing zinc oxide and a phosphate can be obtained.

The snow crystal-like composite particles after firing can be washed and dried as necessary.
The washing can be performed with a washing liquid such as water and ethanol, and is preferably performed until the pH of the waste liquid becomes 9 or less. The cleaning time is, for example, 0 to 30 minutes, preferably 0 to 10 minutes.
The amount of the cleaning liquid used is, for example, 0 to 6000 mL, preferably 0 to 3000 mL, per 10 g of particles.

Drying may be performed at room temperature or by heating, and further may be performed under reduced pressure.
The temperature for heating and drying is, for example, 80 to 250°C, preferably 100 to 200°C. The drying time is, for example, 30 minutes to 24 hours, preferably 60 minutes to 12 hours.

In addition, when the snow crystal-like composite particles of the present invention contain Ca ₅ (PO ₄ ) ₃ (OH) which is preferable as a phosphate, for example, the snow crystal-like zinc carbonate particles of the present invention may be added before firing. It is preferable to heat (primary heat treatment), cool, and immerse in a calcium salt aqueous solution that is a supply source of calcium in Ca ₅ (PO ₄ ) ₃ (OH). When the snow crystal-like zinc carbonate particles of the present invention are immersed in an aqueous calcium salt solution after firing, the particles will be significantly disintegrated, but they should be heated at a temperature lower than the firing temperature (primary heat treatment) before firing. Thus, the disintegration of particles can be prevented.

The heating temperature is, for example, 250 to 500°C, preferably 350 to 450°C. The heating time is, for example, 60 to 300 minutes, preferably 60 to 180 minutes.

Examples of the calcium salt in the calcium salt aqueous solution include calcium chloride, calcium hydroxide, calcium acetate, calcium carbonate, calcium bromide, calcium iodide, calcium nitrate and the like. Among these, calcium chloride is preferable from the viewpoint of solubility. The calcium salts may be used alone or in combination of two or more.

The concentration of the calcium salt in the aqueous calcium salt solution is preferably 5 to 40 g/L, more preferably 5 to 20 g/L, even more preferably 5 to 10 g/L. When the concentration of calcium salt is 5 g/L or more, the calcium salt necessary for the reaction can be secured. If the concentration of calcium salt is too high, the amount of calcium salt necessary for the reaction will be saturated, so the concentration of calcium salt is preferably 40 g/L or less.
The immersion time may be, for example, 1 to 30 minutes, preferably 1 to 10 minutes.

After that, washing and drying can be performed as necessary.
The washing can be performed with a washing liquid such as water and ethanol. The amount of the cleaning liquid used is, for example, 1 to 10 L, preferably 3 to 5 L per 20 g of particles.

Drying may be performed at room temperature or by heating, and further may be performed under reduced pressure.
The temperature for heating and drying is, for example, 80 to 250°C, preferably 100 to 200°C. The drying time is, for example, 30 minutes to 24 hours, preferably 60 minutes to 12 hours.

In the present invention, the distance from the center of the snow crystal-like zinc carbonate particles and the snow crystal-like composite particles (particles of the present invention) to the tip of the protrusion is 5 to 60 μm from the viewpoint of keeping the median diameter within a preferable range. Is preferred, 5-40 μm is more preferred, and 5-20 μm is even more preferred. The distance from the center of the particle of the present invention to the tip of the protrusion can be measured from an enlarged image by a scanning electron microscope.

The thickness of the particles of the present invention with respect to the diameter in plan view is preferably 1 to 20 μm, more preferably 1 to 10 μm, and even more preferably 1 to 5 μm from the viewpoint of suppressing roughness when used in products such as cosmetics. The thickness of the particles of the present invention with respect to the diameter in plan view can be measured from an enlarged image by a scanning electron microscope.

When light is projected onto the surface coated with the particles of the present invention at an incident angle of −45°, the original stimulus Y value of the light reflected at a reflection angle of 45° is Y _45° and the reflection angle is −25°. When the original stimulus Y value of the reflected light is Y _-25° , the value of Y _45° /Y _-25° is preferably 1.0 to 3.0.

When the value of Y _45° /Y _−25° is in the above range, the difference between Y _45° and Y _−25° is small, so that the particles have sufficient soft focus property. The value of Y _45° /Y _−25° is more preferably 1.0 to 2.7, further preferably 1.0 to 2.5, from the viewpoint of improving the soft focus property.

Here, the incident angle and the reflection angle in the present invention will be described with reference to FIG.
The incident angle −α° means that when the incident light L1 is projected, the angle formed by the traveling direction of the incident light L1 and the normal line n of the incident surface is α°.
The reflection angle β ₂ ° means that the angle formed by the traveling direction of the reflected light L2 and the normal line n of the reflection surface is β ₂ °. The reflection angle-beta ₃ °, the traveling direction of the reflected light L3 is located on the light source side of the incident light 1 is taken as the reference normal n, it makes with the traveling direction of the reflected light beam L3 and the normal n of the reflecting surface This means that the angle is β ₃ °.

The original stimulus value Y _β2° of the light reflected at the reflection angle β ₂ ° is the value observed at the observation point P2, and the original stimulation value Y _β3° of the light reflected at the reflection angle −β _{3 °} is the observation point P3. It is the value observed in.

The values of Y _45° and Y _−25° can be measured using a color meter “VC-2” (manufactured by Suga Test Instruments Co., Ltd.), and specifically, by the method described in Examples. be able to.

In addition, the particles of the present invention are used in cosmetics such as foundation, nail polish, hair color cosmetics, hair mist cosmetics, facial cleansing foam cosmetics, lotion cosmetics, emulsion cosmetics, moisturizing gel cosmetics, and whitening serum cosmetics. Can be used.

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

[Materials used]
The following materials were used as raw materials for the zinc carbonate particles or the composite particles.
Zinc acetate dihydrate: Special grade reagent (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.)
Sodium bicarbonate: Special grade reagent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
Sodium pyrophosphate (anhydrous): Genuine special grade (Junsei Kagaku Co., Ltd.)
Calcium chloride: Special grade reagent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
Sodium polyphosphate: Food additive (Fujifilm Wako Pure Chemical Industries, Ltd.)

[Example 1]
64.0 g of sodium hydrogen carbonate was dissolved in 758.0 g of distilled water to prepare a 7.8 mass% sodium hydrogen carbonate aqueous solution. 0.9 g (0.1 mass%) of sodium pyrophosphate (anhydrous) was added to the prepared sodium hydrogen carbonate aqueous solution, and the mixture was stirred at 300 rpm for 60 minutes using a stirring blade to dissolve sodium pyrophosphate (anhydrous).

Next, 27.1 g of zinc acetate dihydrate was dissolved in 116.0 g of water to prepare a 18.9 mass% zinc acetate aqueous solution. The prepared zinc acetate aqueous solution was added dropwise to an aqueous solution in which sodium pyrophosphate (anhydrous) was dissolved at a rate of 50 g/min using a tubing pump, and the mixture was held for 30 minutes to obtain zinc sodium carbonate trihydrate particles.

The obtained sodium zinc carbonate trihydrate particles were filtered using Whatman 40 Ashless filter paper (mesh size 8 μm), washed with 300 mL of deionized water on a funnel, and dried in an oven at 110° C. for 2 hours. did. The dried sodium zinc carbonate trihydrate particles were crushed in an agate mortar to obtain zinc sodium carbonate trihydrate particles of Example 1.

[Example 2]
Sodium zinc carbonate trihydrate particles of Example 2 were obtained in the same manner as in Example 1 except that the amount of sodium pyrophosphate (anhydrous) charged was 1.8 g (0.2% by mass).

[Example 3]
Sodium zinc carbonate trihydrate particles of Example 3 were obtained in the same manner as in Example 1, except that the amount of sodium pyrophosphate (anhydrous) was changed to 3.6 g (0.4% by mass).

[Example 4]
Sodium zinc carbonate trihydrate particles of Example 4 were obtained in the same manner as in Example 1 except that the amount of sodium pyrophosphate (anhydrous) was changed to 5.4 g (0.7% by mass).

[Example 5]
Sodium zinc carbonate trihydrate particles of Example 5 were obtained in the same manner as in Example 1 except that the amount of sodium pyrophosphate (anhydrous) charged was 7.2 g (0.9% by mass).

[Example 6]
The sodium zinc carbonate trihydrate particles of Example 2 were heated in a high temperature furnace “SSFT-1520” (manufactured by Yamada Denki Co., Ltd.) at 400° C. for 3 hours and then cooled. The cooled particles were immersed in 1000 g of an 11.1 g/L calcium chloride aqueous solution for 1 minute, filtered, washed, and dried in an oven at 110° C. for 2 hours.

The dried particles were disintegrated in an agate mortar and fired at 650° C. for 2 hours in a high temperature furnace “SSFT-1520” (manufactured by Yamada Denki Co., Ltd.). The particles after calcination were cooled, washed with ion-exchanged water, and filtered using a filter paper of Whatman 40 Ashless. Then, the particles were dried in an oven at 110° C. for 2 hours and crushed in an agate mortar to obtain composite particles of Example 6.

[Example 7]
Composite particles of Example 7 were obtained in the same manner as in Example 6 except that the sodium zinc carbonate trihydrate particles of Example 2 were changed to the zinc sodium carbonate trihydrate particles of Example 3.

[Comparative Example 1]
Comparative example as in Example 1 except that 3.6 g (0.4% by mass) of sodium polyphosphate was added instead of 0.9 g (0.1% by mass) of sodium pyrophosphate (anhydrous). Sodium zinc carbonate trihydrate particles 1 were obtained.

<Observation>
The particles of Examples 1 to 7 and Comparative Example 1 were observed with a scanning electron microscope "JCM-6000PLUS type neoscope" (manufactured by JEOL Ltd.). The particles of Examples 1 to 7 were all in the form of snow crystals. FIG. 2 shows magnified images of the particles of Example 3, Example 5, Example 7 and Comparative Example 1 at 500 times and 2000 times.

In addition, the distance from the center of the particles of Examples 1 to 7 to the tip of the protrusion was measured from the enlarged image obtained with the above-mentioned microscope. The results are shown in Tables 2-3.

<Median diameter>
The median diameter of particles of Examples 1 to 7 and Comparative Example 1 (particle diameter corresponding to a cumulative percentage of 50% on a volume basis) was calculated with a nanoparticle diameter distribution measuring device (trade name: SALD-7100, manufactured by Shimadzu Corporation). did. The results are shown in Tables 2-3.

<Composition analysis>
The compositions of the particles of Examples 1 to 7 and Comparative Example 1 were analyzed under the following conditions using an X-ray diffractometer "XRD-6000" (manufactured by Shimadzu Corporation). The results are shown in Tables 2-3.

voltage; 40kV
drive axis; θ-2θ
scan range; 10-80°
scan speed; 0.2 deg/min
sampling pitch;0.02deg

In addition, elemental analysis of the particles of Example 3 was performed with a wavelength dispersive X-ray fluorescence analyzer "ZSX-Primus II" (manufactured by Rigaku Corporation). The results are shown in Table 4.

<Light reflection characteristics>
The particles of Examples 1 to 7 and Comparative Example 1 and the zinc oxide reagent “zinc oxide, −5 μm, 99.9%” (Fuji Film Wako Pure Chemical Industries, Ltd.) were used as an electronic balance “HM-200” (A Co., Ltd.).・About 50 mg was weighed using a product made by And Day) and the value was recorded.

An adhesive tape "Scotch 313" (manufactured by 3M Japan Co., Ltd.) was cut into a length of about 6 cm and placed on a Teflon (registered trademark) sheet with the adhesive surface facing upward. The measured amount of particles and the total amount of the zinc oxide reagent were placed on the adhesive surface of the adhesive tape, and spread over the entire adhesive surface using a dry brush.

The particles and the zinc oxide reagent which did not adhere to the adhesive surface were dropped to the surroundings so that the particles and the zinc oxide reagent were evenly spread over the adhesive surface of the adhesive tape. When particles and zinc oxide reagent adhered to the back surface of the adhesive surface, they were knocked off. The mass of the particles and the zinc oxide reagent dropped on the Teflon (registered trademark) sheet without adhering to the adhesive surface was measured using an electronic balance, and the mass of the particles and zinc oxide reagent adhered on the adhesive tape were recorded. .. It was confirmed that the mass of the particles attached to the adhesive tape and the zinc oxide reagent was 19 mg±5 mg.

Light was projected onto the adhesive tape having the particles and the zinc oxide reagent attached thereto and a blank adhesive tape at an incident angle of −45°. The original stimulation Y value of light reflected at a reflection angle of −90° to 90° at that time was measured every 5° using a color meter “VC-2” (manufactured by Suga Test Instruments Co., Ltd.). The incident light was a C light source (halogen lamp), and the tilt angle was 0°.

From the value of the original stimulus Y value (Y- _25° ) of light reflected at a reflection angle of -25° and the value of the original stimulus Y value (Y _45° ) of light reflected at a reflection angle of 45°, Y _45° /Y ₋ The value at _25° was calculated and evaluated based on the following criteria. It shows in Tables 2-3.

Soft Focusing A: The value of Y _45° /Y _−25° was 3.0 or less.
Soft focus property x: The value of Y _45° /Y _−25° was larger than 3.0.

3 to 4 show the polar coordinates of the original stimulation Y value of the light reflected at the reflection angles of −90° to 90° for Examples 1 to 7 and the zinc oxide reagent.

From Tables 2 to 3, it was found that the particles of Examples 1 to 7 having a snow crystal shape had a good soft focus property.

From Table 4, it was confirmed that the particles of Example 3 having a snow crystal shape contained a phosphorus component.
3 to 4, it was found that the scattering of the light reflected from the particles of Examples 1 to 7 was more uniform than the scattering of the light reflected from the zinc oxide particles.

The particles of the present invention have a good soft focus property. Therefore, when the particles of the present invention are used in cosmetics or the like, by scattering light in various directions, it is possible to fill the irregularities of the skin to make it look smooth and to make wrinkles and the like less noticeable.

L1 incident light L2, L3 reflected light n normals P2, P3 observation points α, β ₂ , β ₃ angle

Claims (11)

Snow crystal-like zinc carbonate particles having a median diameter of 5 to 100 μm. The snow crystal-like zinc carbonate particle according to claim 1, which contains a phosphorus component. When light is projected onto the surface coated with the snow crystal-like zinc carbonate particles at an incident angle of −45°, the original stimulus Y value of the light reflected at a reflection angle of 45° is Y _45° and the reflection angle is −25. when the ° original stimulus Y value of the light reflected by the set to _{Y -25 °,} the value of _{Y 45 °} / _{Y -25 °} is 1.0 to 3.0, snow crystal according to claim 1 or 2 Zinc carbonate particles. Snow crystal-like zinc carbonate particles according to any one of claims 1 to 3, which are produced by dissolving pyrophosphate in a metal bicarbonate aqueous solution and adding an aqueous zinc salt solution to the obtained aqueous solution. .. Snow crystal-like composite particles containing zinc oxide and phosphate. The snow crystal-like composite particles according to claim 5, having a median diameter of 5 to 100 µm. The phosphate is Ca ₅ (PO ₄ ) ₃ (OH), Ca ₃ (PO ₄ ) ₂ , NaCaPO ₄ , Na ₉ Zn ₃ (PO ₄ ) ₅ , NaZnPO ₄ , and Ca ₉ NaZn(PO ₄ ) _7. The snow crystal-like composite particle according to claim 5 or 6, which is at least one selected from the group consisting of: When light is projected onto the surface coated with the snow crystal-like composite particles at an incident angle of −45°, the original stimulus Y value of the light reflected at a reflection angle of 45° is Y _45° and the reflection angle is −25°. The value of Y45 _° /Y- _25° is 1.0 to 3.0, where the original stimulation Y value of reflected light is Y- _25°. Snowflake composite particles. The snow crystal-like composite particles according to any one of claims 6 to 8, which are produced by firing the snow crystal-like zinc carbonate particles according to claim 4. A snow crystal-like zinc carbonate particle having a step (A) of dissolving a pyrophosphate in an aqueous solution of a metal bicarbonate and a step (B) of adding an aqueous solution of a zinc salt to the aqueous solution obtained in the step (A). Production method. A method for producing snow crystal-like composite particles, comprising a step (C) of firing the snow crystal-like zinc carbonate particles obtained by the method according to claim 10.