JP2016196381A - Production method of surface-coated zinc oxide particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method capable of easily producing a surface-coated zinc oxide particle with sufficiently suppressed zinc elution and good in compatibility with an organic solvent, and also to provide a surface-coated zinc oxide particle obtained by the production method, and a zinc oxide particle dispersoid and cosmetic containing the same, and stable over time.SOLUTION: A production method is a method for producing a surface-coated zinc oxide particle with part or all of the surface of a zinc oxide coated with fatty acid salt. The production method of a surface-coated zinc oxide particle includes: a slurry preparation step of preparing slurry containing a zinc oxide and a fatty acid salt, with 110 g/L or less concentration of the zinc oxide; and an aging step of aging the slurry at 85°C or higher .SELECTED DRAWING: None

Description

The present invention relates to a method for producing surface-coated zinc oxide particles.

Zinc oxide is also referred to as zinc white and is widely used as a raw material for cosmetics because it has ultraviolet shielding performance. However, in zinc oxide, zinc ions elute over time, so when mixed with cosmetics, the emulsion system may be broken, and other components may be modified by the surface catalytic activity of zinc oxide. It was. Therefore, for the purpose of reducing zinc elution, suppressing catalytic activity, improving dispersibility, etc., zinc oxide is treated with an inorganic substance such as silica, titania, metal soap, etc. (for example, see Patent Documents 1 and 2) Organic processing with organic substances such as silicone and fatty acids (for example, see Patent Document 3) is performed.

JP 2008-94917 A JP 2003-411147 A JP-A-7-267894

As described above, inorganic treatment and organic treatment of zinc oxide are performed for the purpose of reducing zinc elution, suppressing catalyst activity, improving dispersibility, and the like. However, the conventional treatment is insufficient in suppressing zinc elution, and the surface of zinc oxide is not uniformly treated, so there is room for improvement in these respects. In addition, a dispersion containing a conventional zinc oxide may cause an increase in viscosity due to a change with time depending on the combination of a solvent, a dispersant, and the like. There was also a problem that it was easy to harden. Therefore, there has been a demand for zinc oxide and dispersions thereof that are stable in an organic solvent, particularly an ester solvent, and zinc elution is sufficiently suppressed.

In addition, cosmetics that do not contain silicone are demanded in the market from the viewpoint that it does not require strong cleansing and the environmental load is low, and silicone is not included as a cosmetic material (also referred to as a cosmetic raw material). What is needed is a non-silicone material.

An object of this invention is to provide the manufacturing method which can provide easily the surface covering zinc oxide particle with which zinc elution is fully suppressed and the familiarity with an organic solvent is favorable in view of the said present condition. Another object of the present invention is to provide surface-coated zinc oxide particles obtained by this production method, as well as zinc oxide particle dispersions and cosmetics containing the same, which are stable over time.

Among the various studies on zinc oxide with low zinc elution, the present inventors have focused on the fact that zinc elution is sufficiently suppressed if the surface of zinc oxide is partially or entirely coated with a fatty acid salt. In order to obtain such surface-coated zinc oxide particles, when a slurry containing zinc oxide and a fatty acid salt and having a zinc oxide concentration within a predetermined range is aged at 85 ° C. or more, zinc elution is remarkably suppressed. I found out. In general, it is known that when zinc oxide is used as a water slurry and the slurry is heated to a high temperature of 50 ° C. or higher, particles are likely to aggregate. As a result, the process was likely to be uneven. When the temperature exceeds 80 ° C., the amount of evaporated water on the liquid surface is large, so that coarse agglomerates resulting from drying of the slurry are likely to occur near the liquid surface of the reaction tank, and coarse particles are mixed into the product or uniform processing is performed. It is also known that it becomes difficult. However, contrary to the conventional common technical knowledge, the present inventors significantly suppressed zinc elution when the temperature of the aging process was set to 85 ° C. or higher and the zinc oxide concentration of the slurry used for the aging process was set within a predetermined range. It was found that the obtained zinc oxide particles can be obtained. Since these zinc oxide particles are uniformly coated with a fatty acid salt, they are well-familiar with organic solvents and are found to be uniformly and stably dispersed in organic solvents. As a result, the present invention has been completed.

That is, the present invention includes a slurry preparation step for preparing a slurry containing zinc oxide and a fatty acid salt and having a zinc oxide concentration of 110 g / L or less, and an aging step for aging the slurry at 85 ° C. or higher. This is a method for producing surface-coated zinc oxide particles.

The fatty acid salt is preferably a metal salt and / or an amine salt. As a result, surface-coated zinc oxide particles with less zinc elution and better compatibility with organic solvents can be obtained.

The present invention is also surface-coated zinc oxide particles obtained by the above production method.

The present invention is also a zinc oxide particle dispersion comprising the surface-coated zinc oxide particles, an organic solvent and a dispersant. Since this dispersion is a state in which the surface-coated zinc oxide particles are uniformly and stably dispersed in an organic solvent without increasing the viscosity over time, physical properties derived from the surface-coated zinc oxide particles (for example, ultraviolet rays) The shielding performance and the like can be stably exhibited.

The dispersing agent preferably contains polyhydroxystearic acid. As a result, the surface-coated zinc oxide particles can be more uniformly dispersed.

The zinc oxide particle dispersion is preferably used as a cosmetic raw material. Thereby, cosmetics excellent in ultraviolet shielding performance etc. can be given.

The present invention is also a cosmetic containing the zinc oxide particle dispersion.

According to the method for producing surface-coated zinc oxide particles of the present invention, surface-coated zinc oxide particles that are sufficiently suppressed in zinc elution and have good compatibility with organic solvents can be easily provided. The surface-coated zinc oxide particles obtained by this production method are particles in which a part or all of the surface of zinc oxide is coated with a fatty acid salt, but since the familiarity with organic solvents, particularly ester solvents, is good, A stable dispersion can be provided with time. Such surface-coated zinc oxide particles and zinc oxide particle dispersions are particularly useful as a raw material for cosmetics, and are also useful as non-silicone materials that have recently been considered to have a good feeling in use.

FIG. 1 is a graph showing the change in viscosity over time of a dispersion obtained by adding each sample powder obtained in Examples or Comparative Examples to an alcohol solution of oleic acid. FIG. 2 is a graph showing changes in viscosity over time of a dispersion containing surface-coated zinc oxide particles, an organic solvent, and a dispersant obtained in Example 1 or 2.

Hereinafter, an example of the present invention will be described in detail. However, the present invention is not limited to the following description, and can be applied as appropriate without departing from the scope of the present invention.

[Method for producing surface-coated zinc oxide particles]
The production method of the present invention includes a slurry preparation step and an aging step, but may further include one or more other steps performed by a normal particle surface treatment or the like. Moreover, you may perform each process twice or more as needed.

(I) Slurry production process The slurry production process is a process for producing a slurry containing zinc oxide and a fatty acid salt and having a zinc oxide concentration of 110 g / L or less. The production method is not particularly limited, and it is preferable to stir so that the raw materials are uniformly mixed. The order of adding and mixing the raw materials is not particularly limited, and the temperature at the time of slurry production is not particularly limited. For example, it is preferable to prepare the slurry at 5 to 35 ° C. from the work surface.

Although the said slurry contains a zinc oxide, a fatty acid salt, and a dispersion medium, you may contain another component in the range which does not impair the effect of this invention. Other components will be described later.
Each component can be used alone or in combination of two or more.

Although the said zinc oxide is not specifically limited, For example, it is preferable that it is a particle | grain with an average primary particle diameter of 1-300 nm. Thereby, since ultraviolet shielding property and visible light transparency can be improved, the surface-coated zinc oxide particles obtained are more suitable for cosmetic raw material applications. The average primary particle diameter is more preferably 5 to 200 nm, still more preferably 10 to 100 nm, and particularly preferably 15 to 50 nm. The particle shape is not particularly limited.

In the present specification, the average particle diameter is the maximum inscribed circle of each of 100 particles that are drawn on a diagonal line on an image taken with a field emission scanning electron microscope (JSM-7000F, manufactured by JEOL Ltd.). Means the arithmetic average of diameters.
In addition, when measuring the average primary particle diameter of zinc oxide in the slurry, the slurry is filtered, washed with water, and then dried at 105 ° C. for 2 hours using a constant temperature dryer (manufactured by ASONE, SONW-450). Use the particles produced.

The concentration of zinc oxide in the slurry is 110 g / L or less. By subjecting the slurry in which the zinc oxide concentration is within this range to the aging step at a predetermined temperature, surface-coated zinc oxide particles that sufficiently suppress zinc elution and are well-familiar with the organic solvent can be obtained. Preferably it is 100 g / L or less, More preferably, it is 90 g / L or less, More preferably, it is 80 g / L or less. Moreover, although the minimum of the density | concentration of a zinc oxide is not specifically limited, For example, it is preferable that it is 30 g / L or more from viewpoints, such as an improvement of coating efficiency and production cost. More preferably, it is 40 g / L or more, More preferably, it is 50 g / L or more.
In the present specification, the concentration of zinc oxide means the content (g) of zinc oxide with respect to 1 L of the dispersion medium contained in the slurry.

Although the said fatty acid salt is not specifically limited, For example, it is preferable that it is a salt of C8-C30 fatty acid (monocarboxylic acid). The lower limit of the carbon number of the fatty acid is more preferably 10 or more, still more preferably 14 or more, whereby the irritation to the skin of the surface-coated zinc oxide particles obtained is further reduced, and the cosmetic raw material is used. Will be more useful. In consideration of solubility or dispersibility in the slurry, the upper limit of the carbon number is more preferably 24 or less, and still more preferably 20 or less.

Specific examples of the fatty acid constituting the fatty acid salt include caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, and montanic acid. Saturated fatty acids such as melicic acid; unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid; and the like, which further have a substituent (for example, a hydroxyl group, a carbonyl group, an epoxy group, etc.). May be. Of these, saturated fatty acids are preferred.

The fatty acid salt is preferably a metal salt and / or an amine salt. As a result, surface-coated zinc oxide particles with less zinc elution and better compatibility with organic solvents can be obtained. Of these, metal salts are preferred.

The metal constituting the metal salt is not particularly limited. For example, in addition to Group 1 metals such as sodium, lithium, potassium, rubidium and cesium, Group 2 metals such as magnesium, calcium, strontium and barium, manganese , Iron, copper, zinc, aluminum and the like, and one or more of these can be used. Among them, a periodic table Group 1 metal is preferable. More preferred are sodium, potassium and lithium. That is, the metal salt (fatty acid metal salt) is preferably a sodium salt, a potassium salt and / or a lithium salt.

The amine constituting the amine salt is not particularly limited, and any of primary amine, secondary amine, and tertiary amine may be used. Further, it may be a polyamine having two or more amino groups in one molecule. Specifically, alkylamine etc. are mentioned, for example.

The content of the fatty acid salt is preferably 1 to 50 parts by weight with respect to 100 parts by weight of zinc oxide in the slurry. By setting to this range, it becomes possible to coat the zinc oxide surface more uniformly with the fatty acid salt. More preferably, it is 5 parts by weight or more. Further, it is more preferably 40 parts by weight or less, still more preferably 30 parts by weight or less, and particularly preferably 15 parts by weight or less.

Although it does not specifically limit as said dispersion medium, For example, water, an organic solvent, or a mixture thereof etc. are mentioned. Examples of the organic solvent include alcohol, acetone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dioxane and the like. Examples of the alcohol include monovalent water-soluble alcohols such as methanol, ethanol and propanol; bivalent or more such as ethylene glycol and glycerin. Of water-soluble alcohols. The dispersion medium is preferably water, and more preferably ion-exchanged water.

It does not specifically limit as said other component, For example, a dispersing agent etc. are mentioned. Although content of another component is not specifically limited, For example, it is preferable to set it as 10 weight% or less in 100 weight% of slurry.

(Ii) Aging step The aging step is a step of aging the slurry obtained in the slurry preparation step at 85 ° C or higher. By setting the aging temperature of the slurry having a zinc oxide concentration within a predetermined range to 85 ° C. or more, surface-coated zinc oxide particles that sufficiently suppress zinc elution and are well-familiar with the organic solvent can be obtained. The aging temperature is preferably 87 ° C or higher, more preferably 90 ° C or higher. The upper limit of the aging temperature is not particularly limited, but is preferably 200 ° C. or less for the convenience of facilities, for example. More preferably, it is 150 degrees C or less, More preferably, it is 120 degrees C or less.

In the aging step, the aging time is not particularly limited, but is preferably 1 minute or more. More preferably, it is 5 minutes or more, More preferably, it is 10 minutes or more. The upper limit of the aging time is not particularly limited, but is preferably 10 hours or less from the viewpoint of improving production efficiency, for example. More preferably, it is 5 hours or less, More preferably, it is 2 hours or less.
In the present specification, the aging temperature means the maximum temperature during aging. The aging time means a holding time of the maximum temperature (aging temperature) at the time of aging, and does not include a temperature raising time until the maximum temperature is reached. The temperature raising time is not particularly limited, but is preferably as short as possible.

The surface-coated zinc oxide particles can be obtained through the above steps, but the following steps may be performed as necessary.

(Iii) Neutralization step After the aging step, the slurry (also referred to as aging slurry) may be neutralized as necessary. In the neutralization step, the pH of the ripening slurry is preferably adjusted to 7 to 10, more preferably 7 to 8, and still more preferably 7 to 7.5.

In the neutralization step, a zinc salt such as zinc chloride is preferably used as a neutralizing agent. Thereby, surface-coated zinc oxide particles in which zinc elution is more sufficiently suppressed can be obtained. Moreover, you may use the acid and alkali which are generally used normally as a pH adjuster.
In order to sufficiently perform the neutralization reaction, the slurry may be aged after adding the neutralizing agent. The temperature and time of the subsequent aging step are not particularly limited.

(Iv) A washing step and, if necessary, an aging slurry (including those obtained through other steps such as a neutralization step and a post-ageing step) may be washed. Although the washing method is not particularly limited, for example, it is preferable to wash the ripened slurry with water and / or an organic solvent until the electric conductivity of the filtrate becomes 100 μS / cm or less after filtration.

(V) Grinding step It is preferable to refine the particles by wet pulverization or dry pulverization after the aging step (may be performed after another step). Of these, dry pulverization is preferred. In dry pulverization, a high-speed rotary pulverizer, an edge runner by the action of compression, friction, or shear can be used. Examples of the high-speed rotary pulverizer include an atomizer.

[Surface coated zinc oxide particles]
Since the surface-coated zinc oxide particles obtained by the production method of the present invention have little zinc elution and good compatibility with organic solvents, the surface-coated zinc oxide particles are stably dispersed in the organic solvent. Therefore, it is particularly suitable for applications that are often stored or used in a dispersed state. Among these, it is particularly preferably used as a cosmetic raw material.

The particle shape of the surface-coated zinc oxide particles is not particularly limited, and examples thereof include a needle shape, a rod shape, a plate shape, and a spherical shape. Moreover, it is preferable that an average particle diameter is 1-100 nm. Thereby, since ultraviolet-ray shielding property and visible light transparency can be improved, it becomes a thing more suitable for cosmetics raw material use. More preferably, it is 5-80 nm, More preferably, it is 10-50 nm.

[Zinc oxide particle dispersion]
The zinc oxide particle dispersion of the present invention (also simply referred to as “dispersion”) includes surface-coated zinc oxide particles obtained by the production method of the present invention, an organic solvent, and a dispersant. As described above, since the surface-coated zinc oxide particles are well-familiar with the organic solvent, the dispersion of the present invention is in a state where the surface-coated zinc oxide particles are uniformly and stably dispersed in the organic solvent. Therefore, the viscosity does not increase over time, and even if sedimentation occurs during storage or use, the particles can be easily redispersed with simple stirring, so that various applications such as cosmetics can be used. Useful for applications.
In addition, each content component can use 1 type (s) or 2 or more types, respectively.

In the dispersion, the content of the surface-coated zinc oxide particles is preferably 10 to 80% by weight with respect to 100% by weight of the total amount of the surface-coated zinc oxide particles, the organic solvent and the dispersant, for example. As a result, the performance derived from the surface-coated zinc oxide particles can be fully exhibited, and the particles are more uniformly and stably dispersed. More preferably, it is 30-70 weight%, More preferably, it is 50-60 weight%.

The organic solvent is not particularly limited, and examples thereof include ester oils such as ethylhexyl palmitate and triisodecyl isononanoate; alcohols; liquid paraffins such as hydrogenated polyisobutene; silicone oils such as decamethylcyclopentasiloxane; Among these, since the surface-coated zinc oxide particles are particularly well-familiar with ester oil, it is preferable to use ester oil.

In the dispersion, the content of the organic solvent is preferably, for example, 10 to 80% by weight with respect to 100% by weight of the total amount of the surface-coated zinc oxide particles, the organic solvent, and the dispersant. More preferably, it is 30-70 weight%, More preferably, it is 35-49 weight%.

The dispersant is not particularly limited, and a compound used in a normal dispersion may be used, and polyhydroxy stearic acid is particularly preferable.

In the dispersion, the content of the dispersant is preferably 0.01 to 20 parts by weight with respect to 100 parts by weight of the surface-coated zinc oxide particles, for example. Thereby, the surface-coated zinc oxide particles can be uniformly dispersed in the organic solvent. More preferably, it is 0.1-8 weight part, More preferably, it is 1-5 weight part.

The dispersion may further include one or more other components as necessary.

The method for producing the dispersion is not particularly limited, and can be produced by a usual method of mixing and stirring each raw material. For example, a bead mill, a ball mill, a high-pressure homogenizer, a stirring homogenizer, an ultrasonic homogenizer, a wet jet It is preferable to manufacture using an apparatus such as a mill. These devices may be appropriately selected from the viewpoint of the degree of dispersion, production efficiency, and the like.

[Cosmetics]
Since the dispersion of the present invention is in a state where the surface-coated zinc oxide particles are uniformly and stably dispersed in an organic solvent, it can be used for various applications. Among them, it is particularly useful as a cosmetic raw material. The applied cosmetic is not particularly limited, and examples thereof include foundations, makeup bases, sunscreens, eye shadows, blushers, mascara, lipsticks, sunscreen agents, and the like. Thus, a cosmetic comprising the dispersion of the present invention is also one aspect of the present invention.
In addition, since the dispersion of this invention does not require silicone, it can also be used as a non-silicone material which has attracted attention in recent years as a material that gives cosmetics with excellent usability.

The cosmetic may contain one or more other components in addition to the dispersion of the present invention, as necessary. Other components are not particularly limited, and examples thereof include any aqueous component and oily component that are usually used in the cosmetic field. Specifically, oils, surfactants, humectants, higher alcohols, sequestering agents, natural and synthetic polymers, water-soluble and oil-soluble polymers, UV screening agents, various extracts, inorganic and organic pigments, inorganic And various powders such as organic clay minerals, inorganic and organic pigments treated with metal soap or silicone, colorants such as organic dyes, preservatives, antioxidants, pigments, thickeners, pH adjusters, fragrances, A cooling sensation agent, an antiperspirant, a disinfectant, a skin activator, etc. are mentioned. The content of these components is not particularly limited as long as the effects of the present invention are not impaired.

In order to describe the present invention in detail, examples will be given below, but the present invention is not limited to these examples. Unless otherwise specified, “%” means “wt% (mass%)”.

Example 1
An 80 g / L water slurry of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., FINEX-30, average particle size 35 nm) was prepared.
Subsequently, sodium stearate (manufactured by Nippon Color Industry Co., Ltd., KS-3) is added to the water slurry so as to be 10% with respect to the weight of zinc oxide, and the mixture is heated to 90 ° C. Aged.
An aqueous solution of zinc chloride in the same molar amount as the added sodium stearate was added to the slurry over 30 minutes, neutralized to pH 7.0-7.5, and then aged for 1 hour.
Filtration, washing with water until the filtrate has a conductivity of 100 μS / cm or less, the cake obtained was dried at 85 ° C. for 16 hours, and then pulverized with an atomizer to obtain the surface-coated zinc oxide particles (1) of the present invention. Obtained.

Example 2
Surface-coated zinc oxide particles (2) of the present invention were obtained in the same manner as in Example 1 except that the aging time after reaching 90 ° C. was 10 minutes.

Comparative Example 1
A comparative product (C1) was obtained in the same manner as in Example 1 except that the concentration of zinc oxide during preparation of the water slurry was 140 g / L.

Comparative Example 2
A comparative product (C2) was obtained in the same manner as in Example 1 except that the aging temperature after adding sodium stearate to the water slurry was 80 ° C.

Comparative Example 3
In a high-speed stirrer, methylhydride polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., KF-9901) so that it becomes 5% with respect to zinc oxide (FINEX Co., Ltd., FINEX-30, average particle size 35 nm) and zinc oxide. ) Was added and stirred for 10 minutes.
The obtained treated powder was heated in a dryer at 120 ° C. for 16 hours.
The heated powder was pulverized using a jet mill to obtain a comparative product (C3).

1. Zinc elution suppression effect In order to evaluate the zinc elution suppression effect, each of the surface-coated zinc oxide particles obtained in the examples or the comparative product obtained in the comparative example (sample powder) was added to an alcohol solution of oleic acid, The viscosity of this dispersion (test solution) was measured over time. When zinc elutes over time, the viscosity of the solution increases. Therefore, the zinc elution suppression effect by the added zinc oxide can be evaluated based on the degree of the viscosity increase. Details of the test method are shown below. The results are shown in FIG. For reference, FIG. 1 also shows a case where no sample powder is contained (blank).
<Test method>
(1) Add oleic acid in isopropyl alcohol to 20 wt% to prepare a test solution.
(2) Take the solution in a sample tube, add 10% by weight of sample powder to the test solution, shake the sample tube, and mix the test solution and powder.
(3) The viscosity of the test solution immediately after mixing is measured with a B-type viscometer (rotor No. 3, 12 rpm, 1 minute later). Thereafter, the sample tube is allowed to stand at room temperature (25 ° C.), and the viscosity is measured over time.

From FIG. 1, the following was confirmed.
Example 1 and Comparative Example 1 differ only in the zinc oxide concentration of the slurry subjected to the aging process, and Example 1 and Comparative Example 2 differ only in the aging temperature. In addition, Example 2 is an example in which only the aging time is different from Example 1. Under these differences, when the changes in viscosity of the obtained dispersions containing zinc oxide over time were compared, it was found from FIG. 1 that when the comparative products obtained in Comparative Examples 1 and 2 were used, On the other hand, when the surface-coated zinc oxide particles obtained in Examples 1 and 2 were used, the viscosity hardly increased. From this, it was found that surface-coated zinc oxide particles that are remarkably excellent in zinc elution suppression effect can be obtained only by subjecting a slurry having a zinc oxide concentration in a predetermined range to an aging step at a predetermined temperature.
Comparative Example 3 is an example in which conventional organic treatment was performed on zinc oxide. As in Comparative Examples 1 and 2, the viscosity of the test solution significantly increased over time. Therefore, it was found that the surface-coated zinc oxide particles obtained by the production method of the present invention have an excellent zinc elution suppressing effect even with respect to zinc oxide subjected to conventional organic treatment.

2. Evaluation of familiarity with organic solvent In order to evaluate the familiarity with organic solvent, the oil absorption of each (sample) of the surface-coated zinc oxide particles obtained in Examples or the comparative product obtained in Comparative Examples was measured. The smaller the value of the oil absorption, the better the familiarity with the measurement oil (organic solvent). Details of the test method are shown below. The results are shown in Table 1.
<Test method>
(1) About 0.5 g of a sample is precisely weighed on a medicine wrapping paper.
(2) Place the sample on the center of the glass plate and the 10 cm ground glass part.
(3) Put measurement oil into a microburette, add 0.2 mL dropwise to the sample, and knead with a gold spatula.
(4) Thereafter, 1 to 2 drops of measurement oil are added, and the whole is kneaded with a gold spatula for each addition.
(5) The end point is when the whole becomes a hard putty-like lump for the first time.
(6) The oil absorption is calculated by the following formula.
Oil absorption (ml / 100 g) = V (mL) ÷ sample weight (g) × 100
In the formula, V represents the amount (mL) of the measurement oil added dropwise.

The details of the measurement oil used are shown below.
Isopropyl myristate: EXOPARL IPM manufactured by Kao Corporation
Hydrogenated polyisobutene: NOF Corporation, Pearl Ream 3
Triisodecyl isononanoate: Nisshin Oilio Group, Salacos 913

From Table 1, the following was confirmed.
Comparing the oil absorption amount of each sample, each surface-coated zinc oxide particle obtained in Examples 1 and 2 has a large oil absorption amount for each measured oil compared to each comparative product obtained in Comparative Examples 1 to 3. Reduced (Table 1). Therefore, it was found that the surface-coated zinc oxide particles obtained by the production method of the present invention have very good compatibility with the organic solvent.

3. Evaluation of the stability of the dispersion In order to evaluate the stability of the dispersion, the surface-coated zinc oxide particles (test powder) obtained in Example 1 or 2, an organic solvent, and a dispersion containing the dispersant The change in viscosity with time was observed. Details of the test method are shown below. The results are shown in FIG.
<Test method>
(1) A 140 ml mayonnaise bottle is charged with 50 g of test powder, 4 g of polyhydroxystearic acid, 46 g of ethylhexyl palmitate, and 100 g of φ0.5 mm zirconia (ZrO ₂ ) beads.
(2) Seal tightly with an inner lid and disperse with a paint shaker for 1 hour, then separate the beads to obtain an organic solvent dispersion of zinc oxide.
(3) Take this dispersion in a sample tube, store in a dryer at 40 ° C., and observe the change in viscosity over time (B-type viscometer: rotor No. M3, 60 rpm, 1 minute).

From FIG. 2, the following was confirmed.
The surface-coated zinc oxide particles obtained in Examples 1 and 2 were all obtained by the production method of the present invention. From FIG. 2, the dispersion containing any of these showed an increase in viscosity over time. It turns out that it hardly occurred. Accordingly, it was found that the zinc oxide dispersion containing the surface-coated zinc oxide particles, the organic solvent and the dispersant obtained by the production method of the present invention was stable over time.

Claims (7)

A slurry preparation step of preparing a slurry containing zinc oxide and a fatty acid salt and having a concentration of the zinc oxide of 110 g / L or less;
And a maturing step of maturing the slurry at 85 ° C. or higher. The method for producing surface-coated zinc oxide particles according to claim 1, wherein the fatty acid salt is a metal salt and / or an amine salt. A surface-coated zinc oxide particle obtained by the production method according to claim 1. A zinc oxide particle dispersion comprising the surface-coated zinc oxide particles according to claim 3, an organic solvent, and a dispersant. The zinc oxide particle dispersion according to claim 4, wherein the dispersant contains polyhydroxystearic acid. The zinc oxide particle dispersion according to claim 4 or 5, wherein the zinc oxide particle dispersion is used as a cosmetic raw material. A cosmetic comprising the zinc oxide particle dispersion according to any one of claims 4 to 6.

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