JP5005414B2 - Zinc oxide, method for producing the same, and cosmetics using the same - Google Patents

Description

  The present invention relates to zinc oxide, a method for producing the same, and a cosmetic using the same.

Zinc oxide is a white pigment, UV shielding material, filler, adsorbent, photocatalyst, catalyst, ceramic raw material, conductive material, piezoelectric material, gas sensor, electrophotographic photosensitive material, varistor, phosphor, emitter, electronic device, etc. It is used for applications, and is used in cosmetics, external preparations, paints, resin compositions and the like.
In order to produce zinc oxide, for example, a method of producing zinc oxide directly in a liquid by neutralizing a solution containing a zinc salt with an alkali neutralizer is known (see Patent Document 1). Further, in Patent Document 2, an aqueous solution containing a zinc salt and a precipitating agent are mixed in 1 second to 15 minutes while stirring with a Reynolds number of 30 or more when directly producing the zinc oxide, and the pH is 11 or more. To produce a flaky zinc oxide powder having an average particle size of 0.1 to 0.88 μm, an average particle thickness of 0.01 to 0.2 μm, and an average plate ratio of 3 or more It is also disclosed that water-soluble organic substances such as citric acid and ethanolamine are allowed to coexist in the precipitation. Furthermore, in Patent Document 3, an alkali is added to an aqueous zinc salt solution to obtain a precipitate of zinc hydroxide [Zn (OH) ₂ ], and then an alkali is further added until the precipitate of zinc hydroxide is completely dissolved. Uniform tetrahydroxyzincate ions [Zn (OH) ₄ ²⁻ ] are generated, and then heated at 30 ° C. or higher and lower than 100 ° C. to produce zinc oxide particles and films having a size of 0.01 μm to 10 μm. The method of doing is disclosed.

JP-A-53-116296 Japanese Patent No. 2683389 JP 2004-149367 A

In the prior art, zinc oxide having a flake-like or needle-like particle shape is obtained by neutralizing a solution containing a zinc salt with an alkali neutralizing agent such as sodium hydroxide or ammonia and directly depositing zinc oxide. Although it can be manufactured, the zinc oxide of Patent Document 1 has problems such as large variations in particle diameter and shape and low crystallinity. The flaky zinc oxide of Patent Document 2 has problems such as high bulk density and low filling properties. Moreover, the acicular zinc oxide of patent document 3 tends to be aggregated particles, and has a problem that the bulk density is high and the filling property is low.
For this reason, zinc oxide is required to be controlled in shape, size, crystallinity and the like according to each application. For example, when used for fillers, ceramic raw materials, etc., since the bulk density of flaky or needle-like particles is high, zinc oxide having a low bulk density and good fillability is required. In addition, when used as a photocatalyst, a catalyst, a ceramic raw material, a conductive material, a piezoelectric material, etc., zinc oxide having good crystallinity in addition to filling properties is required. In addition, zinc oxide with good dispersibility is required for use in cosmetics, external preparations, paints, resin compositions and the like.

  As a result of searching for a method for controlling the particle shape, particle diameter, etc. of zinc oxide, the present inventor added an amine compound to an aqueous solution in which a zinc compound and a carboxylic acid and / or a salt thereof were mixed, and the pH of the aqueous solution was 7 or more. As a result, it was found that, when the aqueous solution was heated to 40 ° C. or higher, the particle shape of zinc oxide could be controlled to a hexagonal column, particularly a shape similar to a drum, and the present invention was completed.

  That is, the present invention has (1) a hexagonal column shape, the average minor axis diameter of the column is 0.5 to 5.0 μm, the average major axis diameter is 0.5 to 10.0 μm, Zinc oxide in which the minor axis diameter of the central portion of the hexagonal column is smaller than both ends thereof, in particular, zinc oxide having a shape similar to a drum, (2) a zinc compound, and a mole of the zinc compound with respect to zinc atoms Expressed as a ratio, an amine compound is added to an aqueous solution mixed with an amount of carboxylic acid and / or a salt thereof in the range of 0.001 to 0.01 to precipitate the precipitate with an aqueous solution having a pH of 7 or more, A method for producing zinc oxide, wherein the aqueous solution is heated to 40 ° C. or higher, and (3) a cosmetic containing the zinc oxide.

The zinc oxide of the present invention is a hexagonal column having a specific size, and the minor axis diameter of the central part of the column of the hexagonal column is smaller than both end portions, particularly an oxidation having a shape similar to a drum. Zinc, which has better filling properties than flakes and needles, and is used as a filler, white pigment, etc. in cosmetics, external preparations, paints, resin compositions, etc., or as a ceramic raw material and conductive material When used for the above, the high filling property can be secured, so that the characteristics of zinc oxide can be fully utilized. Moreover, when it mix | blends with cosmetics from having a specific magnitude | size, a dispersibility is good and the feeling of sliding to skin improves.
Moreover, since the manufacturing method of the zinc oxide of this invention can precipitate zinc oxide from aqueous solution, it can manufacture with sufficient productivity.

  The zinc oxide of the present invention contains at least 50% by weight of ZnO exhibiting an X-ray diffraction pattern of any one of hexagonal, cubic and cubic face-centered structures. Zinc hydroxide and zinc sulfate used in production Zinc compounds such as zinc nitrate, zinc chloride, and zinc acetate may be contained. It may also contain sulfate radicals, nitrate radicals, chlorine, acetic acid, etc. that comprised the zinc compound used in the production, and also contains materials such as carboxylic acids, their salts, and amine compounds. May be. Furthermore, the surface of the zinc oxide particles may be coated with a surface treatment agent of an inorganic compound such as silica or alumina or an organic compound such as siloxane.

Zinc oxide has a hexagonal surface and has a hexagonal column shape extending in a direction perpendicular to the surface, and the average minor axis diameter of the column is 0.5 to 5.0 μm. It is 0-4.0 micrometers. Moreover, the average major axis diameter of a column is 0.5-10.0 micrometers, Preferably it is 1.0-8.0 micrometers. The particle shape of zinc oxide can be observed with an electron microscope. The average minor axis diameter and average major axis diameter of zinc oxide are the major axis diameter of at least 20 particles (referred to as the length of the longest axis), the minor axis diameter (the axis most perpendicular to the midpoint of the longest axis). Measured from the electron micrograph, and the weight-average major axis calculated by the following formula, assuming that the particles are prismatic equivalents. Based on diameter and weight average minor axis diameter.
Weight average major axis diameter = Σ (Ln · Ln · Dn ² ) / Σ (Ln · Dn ² )
Weight average minor axis diameter = Σ (Dn · Ln · Dn ² ) / Σ (Ln · Dn ² )
In the above formula, n represents the number of each measured particle, Ln represents the major axis diameter of the nth particle, and Dn represents the minor axis diameter of the nth particle.
Moreover, when an electron micrograph is observed in detail, there is a constriction at the center of the hexagonal column, and there are zinc oxide particles whose minor axis diameter is smaller than at both ends. A shape in which the minor axis diameters of the both end portions and the central portion of the hexagonal column are smaller than the both end portions is referred to as a shape similar to a drum (drum shape) in the present invention. The (short axis diameter at the center) / (short axis diameter at both ends) is preferably about 0.5 to 0.99, and more preferably about 0.7 to 0.99. Such a drum shape has a shape in which a growth twin crystal having a hexagonal plate nuclei existing in the constricted portion at the center as a symmetry plane occurs.

  The method for producing zinc oxide of the present invention comprises mixing a zinc compound and a carboxylic acid and / or a salt thereof in an amount ranging from 0.001 to 0.01, expressed as a molar ratio of the zinc compound to zinc atoms. An amine compound is added to the aqueous solution to adjust the pH of the aqueous solution to 7 or higher to precipitate a precipitate, and then the aqueous solution is heated to 40 ° C. or higher. Any zinc compound can be used as long as it is water-soluble. For example, zinc sulfate, zinc nitrate, zinc chloride, zinc acetate, and the like can be used. Zinc sulfate is preferred because it is easy to obtain hexagonal columnar, particularly drum-shaped zinc oxide. Moreover, even if it does not melt | dissolve in neutral water, such as metallic zinc, a zinc oxide, and zinc hydroxide, if it is a compound which melt | dissolves in an acid and an alkali, it can be used similarly to said zinc compound.

The carboxylic acid is a compound having a carboxyl group and can be used without limitation. For example, the following can be used, and particularly when citric acid and / or a salt thereof is used, a drum-shaped zinc oxide is used. Is preferable because it can be manufactured.
(1) Polycarboxylic acids, particularly dicarboxylic acids and tricarboxylic acids such as oxalic acid and fumaric acid.
(2) Hydroxypolycarboxylic acids, especially hydroxydi- or hydroxytri-carboxylic acids such as malic acid, citric acid or tartronic acid.
(3) (Polyhydroxy) monocarboxylic acid, such as glucoheptonic acid or gluconic acid.
(4) Poly (hydroxycarboxylic acid) such as tartaric acid.
(5) Dicarboxyl amino acids and their corresponding amides, such as aspartic acid, asparagine or glutamic acid.
(6) A hydroxylated or non-hydroxylated monocarboxyl amino acid such as lysine, serine or threonine.
As the carboxylate, any salt can be used without limitation. For example, alkali metal salts such as sodium and potassium, ammonium salts and the like can be used. The amount of the carboxylic acid and its salt is expressed in terms of a molar ratio of the zinc compound to the zinc atom, preferably in the range of 0.001 to 0.01, and more preferably in the range of 0.001 to 0.005. If the amount of carboxylic acid is more than 0.01, hexagonal columnar, particularly drum-shaped zinc oxide is difficult to obtain, which is not preferable.

  The amine compound is a compound in which a hydrogen atom in ammonia is substituted with a hydrocarbon group, and includes a derivative in which the hydrocarbon group is substituted with a hydroxyl group, a carboxyl group, a phenyl group, a thiol group, or the like. Specifically, primary amines, secondary amines, tertiary amines and derivatives thereof which are water-soluble and exhibit alkalinity are preferable, and primary amines, secondary amines and derivatives thereof are more preferable. For example, alkylamines such as ethylamine, propylamine, butylamine and ethylenediamine, alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, N, N-dimethylethanolamine, monopropanolamine, dipropanolamine and tripropanolamine are preferred. Monoethanolamine and diethanolamine are more preferable. The addition amount of the amine compound can be appropriately adjusted according to the pH setting of the zinc compound aqueous solution described later, but is preferably in the range of 2 or more, expressed in terms of the molar ratio of the zinc compound to the zinc atom. An amount in the range of about 7 is more preferred. If the amount of the amine compound is more than 7, it is not preferable because the precipitate is easily complexed with the amine compound and redissolved, and the yield tends to decrease.

After keeping the aqueous solution in which the zinc compound and the carboxylic acid and / or salt thereof are dissolved at 40 ° C. or lower, the amine compound is added with stirring so that the pH of the aqueous solution becomes 7 or higher to precipitate the precipitate. . The generated precipitate is mainly composed of zinc hydroxide. If the temperature of the zinc compound solution is higher than 40 ° C., it is not preferable because zinc oxide is likely to be partially deposited due to the addition of the amine compound, resulting in a non-uniform state. ° C. Stirring can be carried out by using ordinary mixing and stirring means, for example, with a stirrer equipped with stirring blades. The operating conditions of the stirrer can be set as appropriate. For example, the rotational speed can be about 20 to 2000 rpm, and is preferably about 10 or more, more preferably about 10 to 50000, expressed by the following Reynolds coefficient.
Reynolds coefficient = (blade diameter) ² × stirring speed × solution density / solution viscosity The addition time of the amine compound can be set as appropriate, but is preferably about 1 second to 1 hour, and more preferably about 1 second to 30 minutes. Although pH is adjusted to 7 or more by addition of an amine compound, if it is lower than 7, desired zinc oxide cannot be obtained. The preferred pH is about 8 to 13, more preferably about 9 to 12, and still more preferably about 9 to 11. After adjusting to predetermined pH and depositing a deposit, you may hold | maintain the pH for about 10 minutes-5 hours as needed. Thereafter, while stirring, the aqueous solution is heated to 40 ° C. or higher, preferably about 60 to 250 ° C., more preferably about 80 to 110 ° C. to change the precipitate into zinc oxide. After heating to a predetermined temperature, the temperature may be maintained for about 10 minutes to 5 hours as necessary.

  Further mixed with an aqueous solution of a zinc compound and a carboxylic acid and / or a salt thereof and an amine compound is a salt such as sodium chloride, sodium sulfate, sodium nitrate, potassium chloride, potassium sulfate, potassium nitrate, ammonium chloride, ammonium sulfate, or ammonium nitrate. It is also possible to add salts to the aqueous zinc compound solution before mixing with the alkali compound. The amount of the salt added is preferably in the range of 0.0001 or more, and more preferably about 0.001 to 10 in terms of the molar ratio of the zinc compound to the zinc atom.

  The zinc oxide obtained in this manner is filtered and washed as necessary to separate into solid and liquid, and dried and dry pulverized to obtain zinc oxide powder. For solid-liquid separation, a filter that is usually used industrially, such as a filter press or a roll press, can be used. Band-type heaters, batch-type heaters, spray dryers, etc. are used for drying. Impact-type crushers such as hammer mills and pin mills, roller mills, pulverizers, crushers, etc. For example, a compression pulverizer such as a jet mill or an airflow pulverizer such as a jet mill can be used. Although a drying temperature can be set suitably, about 80-200 degreeC is suitable. Moreover, the said zinc oxide powder may be baked at the temperature of about 200-800 degreeC as needed, and since crystallinity can be improved further, it is preferable. Firing can usually be performed in an atmosphere of air, oxygen, nitrogen, etc., and the firing time is suitably about 10 minutes to 10 hours.

  The zinc oxide of the present invention can be provided with a coating layer of an oxide such as silicon, titanium, aluminum, zirconium and tin or an inorganic compound such as a phosphate thereof on the particle surface as necessary. Further, for the purpose of imparting dispersibility to solvents, paints, plastics, and the like, an organic compound may be coated, or both the inorganic compound and the organic compound may be coated. Examples of organic compounds include (1) organosilicon compounds ((a) organopolysiloxanes (dimethylpolysiloxane, methylhydrogen polysiloxane, methylmethoxypolysiloxane, methylphenylpolysiloxane, dimethylpolysiloxanediol, dimethylpolysiloxanedi). Hydrogen or the like or copolymers thereof), (b) organosilanes (aminosilane, epoxysilane, methacrylsilane, vinylsilane, mercaptosilane, chloroalkylsilane, alkylsilane, fluoroalkylsilane, etc. or their hydrolysis products) (C) organosilazanes (hexamethylsilazane, hexamethylcyclotrisilazane, etc.), (2) organometallic compounds ((a) organotitanium compounds (aminoalkoxytitanium, phosphoric acid ester titanium) , Carboxylic acid ester titanium, sulfonic acid ester titanium, titanium chelate, phosphite titanium complex, etc.), (b) organoaluminum compound (aluminum chelate, etc.), (c) organozirconium compound (carboxylate ester zirconium, zirconium chelate) Etc.), (3) polyols (trimethylolpropane, trimethylolethane, pentaerythritol, etc.), (4) alkanolamines (monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, triol) Propanolamine etc.) or derivatives thereof (acetate, oxalate, tartrate, formate, benzoate, etc. organic acid salts), (5) higher fatty acids (stearic acid, lauric acid, oleic acid) ) Or a metal salt thereof (aluminum salt, zinc salt, magnesium salt, calcium salt, barium salt, etc.), (6) higher hydrocarbons (paraffin wax, polyethylene wax, etc.) or derivatives thereof (perfluorinated products, etc.). These organic compounds may be used singly or in combination of two or more, and when used in cosmetics, it is preferable to use organopolysiloxanes and higher fatty acids. The coating amount of the organic compound is preferably in the range of 0.1 to 50% by weight, more preferably in the range of 0.1 to 30% by weight with respect to zinc oxide. In order to coat the compound, it can be coated in an aqueous slurry of zinc oxide by adding an inorganic compound or an organic compound and neutralizing the organic compound. As another method for coating the compound, an organic compound can be added and mixed in the dry pulverization described above.

  The zinc oxide of the present invention is used by blending an appropriate amount in cosmetics such as sunscreen cosmetics and basic cosmetics. For example, in addition to the above-mentioned zinc oxide, known components commonly used in cosmetics, for example, (1) solvents (water, lower alcohols, etc.), (2) oil agents (higher fatty acids, higher alcohols, organopolysiloxanes) (Silicone oil), hydrocarbons, fats and oils), (3) surfactants (anionic, cationic, amphoteric, nonionic, etc.), (4) moisturizers (glycerins, polyols such as glycols) (5) Organic UV absorbers (benzophenone derivatives, paraaminobenzoic acid derivatives, salicylic acid derivatives, etc.), (6) antioxidants (phenolic, organic acids or salts thereof, acid amides) System, phosphate system, etc.), (7) thickener, (8) fragrance, (9) colorant (pigment, pigment, dye, etc.), (10) physiologically active ingredients (vitamins, hormones, Mino acids), (11) an antibacterial agent or the like may be blended. The form of the cosmetic is not particularly limited, such as solid, liquid, or gel. In the case of liquid or gel, the dispersion may be any of a water-in-oil emulsion, an oil-in-water emulsion, and an oil type. The blending amount of zinc oxide in the cosmetic is preferably in the range of 0.1 to 50% by weight.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1
Zinc sulfate 0.3 mol and citric acid 0.001 mol were dissolved in 150 cc of pure water. Next, 500 cc of pure water is put into a 2 L four-necked flask, and the aqueous zinc sulfate solution is added to the flask. A 350 cc aqueous solution containing 9.9 moles of monoethanolamine was added, the pH of the aqueous solution was adjusted to 10.0, and maintained for 30 minutes to precipitate a precipitate. Then, after heating up to 100 degreeC and ageing | curing | ripening for 1 hour, it cooled, filtered, washed with water, and dried, and obtained the zinc oxide powder (sample A) of this invention.
As a result of X-ray diffraction, this sample A was confirmed to be zinc oxide with good crystallinity. Further, from the electron micrographs (FIGS. 1 and 2), it has a hexagonal column shape (the drum shape), the average minor axis diameter of the column is 1.4 μm, and the average major axis diameter is 2.2 μm. It was.

Example 2
A zinc oxide powder (sample B) of the present invention was obtained in the same manner as in Example 1 except that 0.001 mol of sodium citrate was used in place of the citric acid used in Example 1.
As a result of X-ray diffraction, this sample B was confirmed to be zinc oxide with good crystallinity. Moreover, from the electron micrograph (FIG. 3), it had the shape of a hexagonal column (the drum shape), the average minor axis diameter of the column was 2.2 μm, and the average major axis diameter was 5.3 μm.

Comparative Example 1
In the same manner as in Example 1 except that citric acid is not used and pH is adjusted to 13.0 using 0.7 mol of sodium hydroxide instead of monoethanolamine, zinc oxide powder ( Sample C) was obtained.
Sample C was flaky zinc oxide having a large variation in shape and particle size from electron micrographs (FIGS. 4 and 5).

Comparing the X-ray diffraction intensities (FIG. 6) of the sample A of Example 1, the sample B of Example 2, and the sample C of Comparative Example 1, the samples of Examples 1 and 2 are about twice as large as the samples of the comparative example. To some extent, the zinc oxide of the present invention was zinc oxide with good crystallinity.
Moreover, when the sample B of Example 2 and the sample C of the comparative example 1 were each grind | pulverized with a hammer mill and the bulk density was measured, the bulk density of the sample B was 1 ml / g, but the sample C was 7 ml / g. Thus, it was found that the zinc oxide of the present invention has a low bulk density and good filling properties.
Moreover, when the feel when the sample A of Example 1 was directly rubbed on the skin was evaluated, the spread was good, and it was found that when blended in cosmetics, the dispersibility was good and the feeling of slipping on the skin was improved. It was.

  The present invention is zinc oxide having a hexagonal column shape having a specific size, in particular, a shape similar to a drum, and can be used for various applications.

2 is an electron micrograph of zinc oxide (sample A) obtained in Example 1. 2 is an electron micrograph of zinc oxide (sample A) obtained in Example 1. 4 is an electron micrograph of zinc oxide (sample B) obtained in Example 2. 2 is an electron micrograph of zinc oxide (Sample C) obtained in Comparative Example 1. 2 is an electron micrograph of zinc oxide (Sample C) obtained in Comparative Example 1. 2 is an X-ray diffraction chart of zinc oxide (samples A, B, and C) obtained in Example 1, Example 2, and Comparative Example 1. FIG.

Claims (8)

  It has a hexagonal column shape, the average minor axis diameter of the column is 0.5 to 5.0 μm, the average major axis diameter is 0.5 to 10.0 μm, and is short at the center of the hexagonal column. Zinc oxide whose shaft diameter is smaller than both ends.   The zinc oxide according to claim 1, wherein the hexagonal column has a shape similar to a drum.   The amine compound is added to an aqueous solution obtained by mixing a zinc compound and a molar ratio of the zinc compound to zinc atoms in an amount ranging from 0.001 to 0.01, and / or a salt thereof. A method for producing zinc oxide, comprising depositing a precipitate at a temperature of 7 or higher and then heating the aqueous solution to 40 ° C. or higher.   4. The method for producing zinc oxide according to claim 3, wherein the amount of the amine compound is in the range of 2.01 to 7 in terms of a molar ratio of the zinc compound to the zinc atom.   The said carboxylic acid and / or its salt are a citric acid and / or its salt, The manufacturing method of the zinc oxide of Claim 3 characterized by the above-mentioned.   The method for producing zinc oxide according to claim 3, wherein the zinc compound is zinc sulfate.   A method for producing zinc oxide, comprising firing the zinc oxide obtained by the production method according to claim 3 at a temperature of 200 to 800 ° C.   Cosmetics containing the zinc oxide as described in any one of Claims 1-2.

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