JP7279360B2 - Method for producing scale-like zinc dust - Google Patents

Description

The present invention relates to a method for producing scale-like zinc dust. More particularly, it relates to a method for producing scale-like zinc dust that is useful for anticorrosion undercoatings for cars, ships, steel structures, and the like.

Zinc dust is suitably used in anticorrosive undercoat paints and the like for protecting large-scale steel structures such as bridges, factory plants, tanks, and steel towers from corrosion, as well as cars, ships, and small and medium-sized steel structures. The resin layer containing zinc dust works as an anti-corrosion layer that protects the steel material from rust by sacrificing zinc due to its electrochemical properties. Furthermore, by adding flakes of zinc dust to the anticorrosion layer, the so-called labyrinth effect of extending the reach of the steel sheet from the rust generating source such as water and enhancing the initial anticorrosion performance is exhibited. As a method for scaly zinc dust, for example, a dry ball mill treatment or a wet bead mill treatment with linear higher fatty acid mixed as a lubricant has been developed (see Patent Documents 1 to 4).
In recent years, anti-corrosion paints are required not only to have excellent anti-corrosion performance, but also to be lead-free and chromium-free from the viewpoint of global environmental conservation. There is also a demand for design properties such as texture and lamé (glitter).
Among these, various studies have been made on techniques for improving designability. Conventional anti-corrosion coatings containing flaky zinc powder do not provide sufficient design properties, so techniques have been developed to improve the metallic and lame appearances by mixing metallic aluminum or aluminum flakes.

JP-A-51-103932 JP-A-54-60329 JP-A-55-122807 Japanese Patent No. 3124830

As described above, various methods for producing scale-like zinc dust by flaking zinc and methods for improving design properties have been developed. However, for example, the method of mixing metal aluminum or aluminum flakes with zinc dust to improve the design has a problem that the proportion of zinc in the paint is reduced, resulting in a decrease in anticorrosion performance. In addition, the methods of mixing straight-chain higher fatty acids as a lubricant disclosed in Patent Documents 1 to 4 for scaly treatment have the problem that the scaly processing takes too long and is inefficient. In order to further improve this, if an operation is performed to increase the strength of the treatment, the zinc flakes are shredded to become finer than the zinc by spreading. There is a problem that the metal luster of the flake-like zinc powder is lowered due to the increase in the number of small pieces. Therefore, there is room for improvement in developing a technique for efficiently producing scale-like zinc dust that achieves both anticorrosion performance and design.

The present invention has been made in view of the above-mentioned current situation, and it is an object of the present invention to provide a method for efficiently producing flaky zinc powder which is excellent in anticorrosion performance and excellent in design. aim.

The present inventors have made various studies on a method for producing flaky zinc dust, and found that a step of obtaining a slurry containing zinc dust and at least one selected from the group consisting of fatty acids having branched chains and salts thereof; It was found that scaly zinc powder that achieves both anticorrosion performance and design property can be efficiently produced by performing the step of scalyizing the zinc powder, and the above problems can be solved successfully. The present invention has been arrived at.

That is, the present invention includes a step A of obtaining a slurry containing zinc dust and at least one selected from the group consisting of fatty acids having branched chains and salts thereof, and a step B of scalying the zinc dust in the slurry. A method for producing scale-like zinc powder characterized by:

The fatty acid and its salt preferably have 8 to 24 carbon atoms.

It is preferable that the amount of the fatty acid and its salt used is 0.01 to 5.0% by mass with respect to 100% by mass of the zinc powder.

In the above step B, the scaly treatment can be performed for 25% or more and 200% or less of the scaly treatment time at which the median diameter (D50) of the obtained scaly zinc dust is maximized. preferable.

In the production method described above, the median diameter (D50) of the flake-like zinc powder to be obtained is preferably 1 to 120 μm.

The present invention also provides scaly zinc powder, the scaly zinc powder contains at least one selected from the group consisting of fatty acids having branched chains and salts thereof, and the scaly zinc powder is When used as a paint containing zinc dust and a binder at a mass ratio (zinc dust/binder) of 1.2, the coating film has a 60° gloss value of 20 or more.

The present invention further provides a paint containing the zinc flake powder and a binder.

The content of the scale-like zinc dust is preferably 15 to 95% by mass with respect to 100% by mass of the solid content in the paint.

The paint is preferably used for anticorrosion purposes.

The method for producing flaky zinc powder of the present invention comprises the above-described structure, and the obtained flaky zinc powder has excellent anticorrosion performance and excellent design properties. It can be suitably used for paints and the like.

1 is an SEM photograph (magnification: 1000 times) of flake-like zinc powder of Example 1. FIG. 2 is an SEM photograph (magnification: 1000 times) of the scale-like zinc powder of Example 2. FIG. 10 is an SEM photograph (magnification: 1000 times) of flake-like zinc powder of Example 3. FIG. 10 is an SEM photograph (magnification: 1000 times) of the scale-like zinc powder of Example 4. FIG. 10 is an SEM photograph (magnification: 1000 times) of flake-like zinc powder of Example 5. FIG. 10 is an SEM photograph (magnification: 1000 times) of flake-like zinc powder of Example 6. FIG. 10 is an SEM photograph (magnification: 1000 times) of the scale-like zinc dust of Example 7. FIG. 10 is an SEM photograph (magnification: 1000 times) of flake zinc powder of Example 8. FIG.

Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to the following description, and can be appropriately modified and applied without changing the gist of the present invention. In addition, the form which combined 2 or 3 or more of each preferable form of this invention described below also corresponds to the preferable form of this invention.

<Method for producing scale-like zinc dust>
1. Process A
Step A is a step of obtaining a slurry containing at least one selected from the group consisting of fatty acids having branched chains and salts thereof (hereinafter also referred to as fatty acids having branched chains (salts)) and zinc dust. By using a fatty acid (salt) having a chain as a lubricant, the branched chain of the fatty acid (salt) can sufficiently suppress sticking of the zinc powder to each other due to steric hindrance, and as a result, the step B can be performed efficiently. It is believed that scaly zinc dust can be obtained, and as a result, scaly zinc dust that sufficiently exhibits both anticorrosion performance and design properties can be obtained. In addition, it is considered that the use of a fatty acid (salt) having a branched chain promotes scaly formation of zinc dust while the fatty acid (salt) having a branched chain is supported on the zinc dust surface. As a result, it is possible to effectively suppress the approach of the zinc dust that is scaly, so when beads are used in the scaly process, the collision energy of the beads is used to cause the zinc dust to adhere to each other, or to cause the zinc dust to adhere to each other. It is considered that the energy for breaking the adhesion can be effectively used as the energy for flaking each zinc powder without being wasted. Therefore, by using a fatty acid (salt) having a branched chain, it becomes possible to produce scale-like zinc powder with less energy than conventionally.

The fatty acid having a branched chain may be one having a hydrocarbon group having a branched structure and a carboxyl group. Further, examples of salts thereof include alkali metal salts such as sodium and potassium; alkaline earth metal salts such as calcium and magnesium; salts such as zinc and aluminum; and the like. Among these, fatty acids having branched chains are preferred.

The number of carbon atoms in the branched fatty acid (salt) is preferably 8-24. Thereby, the slipperiness as a lubricant is further enhanced, and the scaly formation can be performed more efficiently. The number of carbon atoms is more preferably 10-22, still more preferably 12-20.

As the hydrocarbon group having a branched structure, an alkyl group having a branched structure is preferred.
The number of carbon atoms in the alkyl group having a branched structure is preferably 7-23, more preferably 9-21, still more preferably 11-19.

Specific examples of the alkyl group having a branched structure include isopropyl group, sec-butyl group, isobutyl group, tert-butyl group, 1-methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, isoamyl group, and neopentyl group. , 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, tert-amyl group, 1,3-dimethylbutyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, 2-ethyl-2-methyl propyl group, 1-methylheptyl group, 2-ethylhexyl group, 1,5-dimethylhexyl group, t-octyl group, isooctyl group, sec-nonyl group, tert-nonyl group, neononyl group, isodecyl group, sec-decyl group , tert-decyl group, neodecyl group, isoundecyl group, sec-undecyl group, tert-undecyl group, neoundecyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, neododecyl group, isotridecyl group, sec-tridecyl group, tert -tridecyl group, neotridecyl group, isotetradecyl group, sec-tetradecyl group, tert-tetradecyl group, neotetradecyl group, isopentadecyl group, sec-pentadecyl group, tert-pentadecyl group, neopentadecyl group, isohexadecyl group, sec-hexadecyl group, tert-hexadecyl group, neohexadecyl group, isoheptadecyl group, sec-heptadecyl group, tert-heptadecyl group, neoheptadecyl group, isooctadecyl (isostearyl) group, sec-octadecyl group, tert-octadecyl group , neo-octadecyl group, isononadecyl group, sec-nonadecyl group, tert-nonadecyl group, neo-nonadecyl group, isoicosyl group, sec-icosyl group, tert-icosyl group, neoicosyl group, isoheneicosyl group, sec-henicosyl group, tert-henicosyl group, neohenicosyl group, isodocosyl group, sec-docosyl group, tert-docosyl group, neodocosyl group, isotricosyl group, sec-tricosyl group, tert-tricosyl group, neotricosyl group, isotetracosyl group, sec-tetracosyl group, tert-tetracosyl group, neotetracosyl group , isopentacosyl group, sec-pentacosyl group, tert-pentacosyl group, neopentacosyl group, isohexacosyl group, sec-hexacosyl group, tert-hexacosyl group, neohexacosyl group, isoheptacosyl group, sec-heptacosyl group, tert-heptacosyl group, neoheptacosyl group, isooctacosyl group, sec-octacosyl group, tert-octacosyl group, neooctacosyl group, n-nonacocyl group, isononacosyl group, sec-nonacosyl group, tert-nonacosyl group, neononacosyl group, n-triacontyl group, isotriacontyl group, sec-triacontyl group group, tert-triacontyl group, and the like.

A preferred branched structure of the fatty acid (salt) having a branched chain is the following formula (1);

(In the formula, R ¹ , R ² and R ³ represent a hydrogen atom or an alkyl group having 1 to 22 carbon atoms, provided that at least two of R ¹ , R ² and R ³ have 1 to 22 alkyl group).
The alkyl groups for R ¹ , R ² and R ³ may have a straight chain structure or a branched structure.
Specific examples of the alkyl group having a branched structure include the alkyl groups described above.
Linear alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl (amyl), n-hexyl, n-heptyl, n-octyl and n-nonyl. group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group, n-henicosyl group, n-docosyl group and the like.

In the compound represented by the above formula (1), at least two alkyl groups of R ¹ , R ² and R ³ preferably have 1 to 18 carbon atoms. More preferably 2 to 16, still more preferably 4 to 14, even more preferably 5 to 12, particularly preferably 6 to 10.

Specific examples of fatty acids (salts) having a branched chain include isobutyric acid, isovaleric acid (isopentanoic acid), 2-ethylbutyric acid, ethylmethylacetic acid, isocaproic acid (isohexanoic acid), isoenanthic acid (isoheptanoic acid), and isocaprylic acid. (isooctanoic acid), isoperargonic acid (isononanoic acid), isocaric acid (isodecanoic acid), isoundecanoic acid, isolauric acid (isododecanoic acid), isotridecylic acid (isotridecanoic acid), isomyristic acid (isotetradecanoic acid), isopentadecyl Acid (Isopentadecanoic acid), Isopalmitic acid (Isohexadecanoic acid), Isomargaric acid (Isoheptadecanic acid), Isostearic acid (Isooctadecanoic acid, 2-heptylundecanoic acid), Isononadecylic acid (Isononadecanoic acid), Isoarachidic acid (Isoicosanoic acid) ), isodocosanoic acid, isohexacosanoic acid, 2-ethylhexanoic acid, 2-propylhexanoic acid, 2-butylhexanoic acid, 2-ethylheptanoic acid, 2-propylheptanoic acid, 2-butylheptanoic acid, 2-ethyloctanoic acid, 2-propyloctanoic acid, 2-butyloctanoic acid, 2-pentyldecanoic acid, 2-heptyloctanoic acid, 2-hexylnonanoic acid, 2-heptylnonanoic acid, 2-hexyldecanoic acid, 2-hexyldodecanoic acid, 2-octyl Decanoic acid, 2-hexyltridecanoic acid, 2-heptyldodecanoic acid, 2-octylundecanoic acid, 13-methyltetradecanoic acid, 12-methyltetradecanoic acid, 15-methylhexadecanoic acid, 14-methylhexadecanoic acid, 10-methylhexadecane acid, 18-methyleicosanoic acid, phytanic acid, salts thereof, and the like.
Among them, isoenanthic acid, isocaprylic acid, isopelargonic acid, isocapric acid, isoundecanoic acid, isolauric acid, isotridecylic acid, isomyristic acid, isopentadecylic acid, isopalmitic acid, isomargaric acid, isostearic acid, isononadecylic acid, isoarachine Acids and salts thereof, more preferably isolauric acid, isotridecylic acid, isomyristic acid, isopentadecylic acid, isopalmitic acid, isomagaric acid, isostearic acid, isononadecylic acid, isoarachidic acid, and particularly preferably isostearin is an acid.

The amount of the fatty acid (salt) having a branched chain is not particularly limited, but it is preferably 0.01 to 5.0% by mass based on 100% by mass of the zinc dust. By using a fatty acid (salt) having a branched chain, it is possible to exert its effect as a lubricant with a smaller amount than in the case of using a straight-chain fatty acid. It is more preferably 0.05 to 3.5% by mass, still more preferably 0.1 to 2.8% by mass, and particularly preferably 0.2 to 2.3% by mass.

The zinc dust is not particularly limited, but preferably has an average particle size of 0.1 to 80 μm. It is more preferably 0.5 to 60 μm, still more preferably 1 to 50 μm.
The average particle diameter can be measured by the particle size distribution analyzer described in the Examples.

The amount of water used in step A is preferably 10% by mass or less with respect to 100% by mass of zinc dust. As a result, the adhesion of the flake-like zinc dust to each other is sufficiently suppressed, and the flake-like zinc dust having excellent design properties can be obtained. The amount of water used is more preferably 5% by mass or less, still more preferably 1% by mass or less, and most preferably 0% by mass.

In the above step A, it is preferable to prepare the slurry using a solvent other than water.
As the solvent, commonly used solvents can be used, for example, hydrocarbons such as pentane, hexane, heptane, octane, toluene, xylene, mineral turpentine, mineral spirit, solvent naphtha; methanol, ethanol, isopropanol, 2- Alcohols such as methyl-2-propanol, butanol, hexanol, methoxybutanol, methoxymethylbutanol, capryl alcohol, lauryl alcohol, myristyl alcohol, oleyl alcohol, stearyl alcohol, isopalmityl alcohol, isostearyl alcohol, and these alcohols Esters such as acetate and propionate, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, octylene glycol, and neopentyl glycol, glycerin , glycol ethers such as dipropylene glycol monomethyl ether, diethylene glycol methyl ether, and ethylene glycol hexyl ether; and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. Hydrocarbons are preferred, and xylene is more preferred.
The amount of solvent other than water is preferably 10 to 600% by mass based on 100% by mass of zinc powder. More preferably 50 to 400% by mass, still more preferably 100 to 250% by mass.

The slurry obtained in the step A may contain components other than the fatty acid (salt) having a branched chain, zinc powder and the solvent.
Other components include, for example, lubricants (grinding aids) other than branched chain fatty acids (salts), dispersants, and the like.
The content of other components is preferably 0 to 1.0% by mass with respect to 100% by mass of zinc dust. More preferably 0.05 to 0.5% by mass, still more preferably 0.1 to 0.3% by mass.

Examples of other lubricants include solid paraffin, polyethylene wax, aliphatic amines, aliphatic amides, aliphatic esters, aliphatic alcohols, graphite, silica powder, talc, zinc phosphate, talc, and mica.
The content of other lubricants is preferably 0 to 1.0% by mass with respect to 100% by mass of zinc powder. It is more preferably 0 to 0.5% by mass, still more preferably 0 to 0.3% by mass, and most preferably 0% by mass.

2. Process B
Step B is a step of flaking the zinc dust in the slurry obtained in Step A.
The scaly treatment method is not particularly limited and can be carried out by a commonly used method.
For example, planetary mills, bead mills, vibration mills, medialess pulverizers and the like can be used. Among these, the method using a bead mill is preferable.

As the beads used in the bead mill, any of glass beads, alumina beads, zirconia beads, titania beads, silicon nitride beads and the like may be used. Zirconia beads and alumina beads are preferred.
When using a bead mill, it is preferable to use beads having a diameter of 0.03 to 0.5 mm.
Although the amount of beads used in a bead mill is not particularly limited, it is 10 to 1000% by mass with respect to 100% by mass of zinc powder used. Thereby, the zinc dust and the beads sufficiently collide with each other, and the median diameter (D50) of the obtained zinc dust can be set in a more suitable range. The amount of beads used is more preferably 20 to 950% by mass, still more preferably 30 to 900% by mass.
When using a bead mill, it is preferable to use a rotating disk, and the rotation speed of the rotating disk is preferably 100 to 10000 rpm. It is more preferably 200 to 6000 rpm, still more preferably 250 to 4000 rpm, and particularly preferably 300 to 3500 rpm.
The peripheral speed of the rotating disk is preferably 4 to 50 m/s. It is more preferably 6 to 40 m/s, still more preferably 8 to 30 m/s, and particularly preferably 8 to 20 m/s.

In the above step B, as the scalyization of the zinc dust progresses, the median diameter of the zinc dust (the D50 value of the particle size distribution) increases and reaches a peak.
The inventors have found that by increasing the median diameter (D50) of the zinc flakes to be obtained, the metallic effect is more excellent. That is, it is preferable to carry out the scaly treatment for 25% or more and 200% or less of the scaly treatment time at which the median diameter (D50) of zinc dust is maximized as 100%. More preferably 30 to 180% of the time, still more preferably 40 to 160% of the time, still more preferably 50 to 150% of the time, even more preferably 60 to 130% of the time, especially Preferred is 70-120% of the time, and even more preferred is 80-110% of the time.
The median diameter (D50) of the particle size distribution of the flake-like zinc dust can be determined by the method described in Examples.

The temperature at which step B is performed is not particularly limited, but it can be performed at a temperature of 5 to 60°C.

The median diameter (D50) of the scale-like zinc dust obtained in step B is preferably 1 to 120 μm. It is more preferably 3 to 100 μm, still more preferably 6 to 80 μm, and particularly preferably 10 to 50 μm.
The thickness of the scale-like zinc powder obtained in step B is preferably 0.1 to 10 μm. It is more preferably 0.1 to 8 μm, still more preferably 0.1 to 6 μm, and particularly preferably 0.1 to 4 μm.

The method for producing scale-like zinc dust of the present invention may include steps other than steps A and B. Other steps include a step of removing the solvent and the like contained in the slurry obtained in steps A and/or B, a step of washing and drying, and the like.

<Scale-like zinc powder>
The scale-like zinc powder obtained by the production method of the present invention is used to protect steel structures such as cars, ships, roads, railroads, harbors, buildings, elevated structures, bridges, factory equipment, plants, pipelines, and steel towers from corrosion. It can be suitably used for anticorrosion undercoat paints, anticorrosion paints, and the like.
The present invention also provides scaly zinc powder, the scaly zinc powder contains at least one selected from the group consisting of fatty acids having branched chains and salts thereof, and the scaly zinc powder is When used as a paint containing zinc dust and a binder at a mass ratio (zinc dust/binder) of 1.2, the coating film has a 60° gloss value of 20 or more. The 60° gloss value of the coating film is more preferably 40 or more, still more preferably 55 or more, and particularly preferably 60 or more.
The 60° gloss value of the coating film can be measured by the method described in Examples.
Examples of the above resin include resins contained in paints to be described later.

The flake-like zinc powder of the present invention may contain a fatty acid (salt) having a branched chain, but the fatty acid (salt) having a branched chain is preferably carried on the flake-like zinc powder. In this specification, the term "loading" means that a fatty acid (salt) having a branched chain is chemically, physically, electrically, van der Waals force or any other force bound to the surface of zinc dust. For example, it indicates a state in which branched chain fatty acids are chemically bonded or physically adsorbed to the zinc dust surface.

The content of the fatty acid (salt) having a branched chain is not particularly limited, but is preferably 0.01 to 5.0% by mass with respect to 100% by mass of the zinc powder. By using a fatty acid having a branched chain, it is possible to exert its effect as a lubricant with a smaller amount than in the case of using a straight-chain fatty acid. It is more preferably 0.05 to 3.5% by mass, still more preferably 0.1 to 2.8% by mass, and particularly preferably 0.2 to 2.3% by mass.

<Paint>
The present invention is also a paint containing the scale-like zinc dust of the present invention and a binder (hereinafter also referred to as resin).
The paint is preferably used for undercoating and anticorrosion purposes.
It is preferable that the content of flaky zinc dust in the paint is 15 to 95% by mass based on 100% by mass of the solid content in the paint. More preferably 20 to 95% by mass, still more preferably 25 to 95% by mass, particularly preferably 30 to 95% by mass.
In the present specification, the term "solid content" means solid or liquid residue at normal temperature excluding volatile components such as solvent and water, so-called non-volatile content, and dried at 150 ° C. for 1 hour. The solid content can be calculated by measuring the evaporation residue obtained.

It is preferable that the coating material has a resin content of 1 to 99% by mass as a solid component with respect to 100% by mass of the scale-like zinc dust. More preferably 3 to 90% by mass, still more preferably 5 to 80% by mass.

Examples of the binder (resin) include silicates such as sodium silicate, potassium silicate, and lithium silicate; alkali silicone, silicone, silicone emulsion, water-soluble silicone, acrylic resin, acrylic resin emulsion, epoxy resin emulsion, phenolic resin emulsion, silicone resin. , alkyl silicate, silane coupling agent, polystyrene resin, chlorinated rubber, epoxy resin, phenolic resin, polyurethane resin, polyester resin, phenol-modified alkyd resin, melamine resin, melamine/alkyd resin, alkyd resin, fluorine resin, aqueous urethane resin , water-based acrylic resins, water-based acrylic resin emulsions, water-based melamine resins, water-based modified epoxy resins, and water-based modified epoxy ester resins.
Among them, melamine/alkyd resins, epoxy resins, polyurethane resins, acrylic resins, polyester resins, alkyd resins, silicone resins, water-based urethane resins, water-based acrylic resins, water-based acrylic resin emulsions, water-based melamine resins, water-based modified epoxy resins, water-based modified Epoxy ester resins are preferred. More preferred are melamine/alkyd resins, epoxy resins, polyurethane resins, acrylic resins, silicone resins, water-based urethane resins, and water-based modified epoxy resins, and even more preferred are epoxy resins, polyurethane resins, water-based urethane resins, water-based modified epoxy resins, and melamine.・It is an alkyd resin.

The paint may contain other components than the scale-like zinc powder and the resin.
The total content of other components in the paint is preferably 0 to 5% by mass with respect to the total 100% by mass of the scale-like zinc powder and the resin. More preferably 0 to 1% by mass, still more preferably 0 to 0.5% by mass.

Examples of the other components include solvents, pigments, dispersants, wetting agents, leveling agents, thixotropic agents, thickeners, anti-sagging agents, antifungal agents, film-forming aids, stabilizers, and the like.
Solvents include those mentioned above.
Examples of pigments include aluminum powder, magnesium powder, nickel powder, cobalt powder, silicon oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium carbonate, zirconium oxide, barium sulfate, barium carbonate, silica, calcium carbonate, talc, mica, Clay, kaolin, bentonite, carbon black, aniline black, gunjo, watching red, cyanine blue, phthalocyanine green and the like.
Examples of dispersants include cationic surfactants such as octadecylamine acetate, alkyltrimethylammonium chloride, alkyldimethylbenzylammonium chloride; Examples include nonionic surfactants such as ethylene fatty acid esters.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited only to these examples. "%" means "% by mass" unless otherwise specified.

Various measurements (evaluations) were performed as follows.
<Median diameter of particle size distribution (D50)>
The median diameter (D50) of the particle size distribution was measured with a laser diffraction/scattering particle size distribution analyzer Microtrac MT-3300 EXII (manufactured by Nikkiso Co., Ltd.). Xylene was used as the solvent for the measurement, the refractive index of the scale-like zinc powder was 2.4, and the refractive index of the solvent was 1.5.

<60 ° gloss value evaluation of coating film>
The 60° gloss of the coating film was measured with a gloss meter VG 7000 (manufactured by Nippon Denshoku Industries Co., Ltd.).
10 g of scaly zinc powder obtained for each scaly treatment time in Examples and Comparative Examples described later, 9.47 g of thermosetting alkyd resin J-524-A (solid content concentration 50%, manufactured by DIC), butylated A paint was prepared by shaking 4.80 g of melamine resin J-820 (solid content concentration 75%, manufactured by DIC) and 2.67 g of xylene with a paint shaker, and a 6 mil applicator was used to form a coating film, followed by heating at room temperature for 30 minutes. After standing and drying, it was baked at 140° C. for 20 minutes, and the gloss of the coating film was measured with a gloss meter VG 7000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

<Evaluation of anticorrosion (rust prevention) performance>
10 g of flake-like zinc powder obtained in Examples described later, or 10 g of a sample of Comparative Example, thermosetting alkyd resin J-524-A (solid content concentration 50%, manufactured by DIC) 1.18 g, butylated melamine resin A paint having a dry zinc concentration of 92% was prepared by shaking 0.40 g of J-820 (75% solid content, manufactured by DIC) and 21.72 g of xylene with a paint shaker. Subsequently, the prepared paint is applied to one side of an SPCC-SB steel plate (0.8 t × 35 × 150 mm) using a hobby airbrush MX2370 (manufactured by Anest Iwata Co., Ltd.), and left to dry for 30 minutes at room temperature. A coating film was formed on a steel plate by baking at 140°C for 20 minutes, and a cross-cut was made from the coating film surface to the steel plate with a cutter blade, and an outdoor exposure test was conducted for 168 hours. The test was started on a rainy day, and after the start of the test, red rust generated from the cross-cut portion was visually observed over time, and qualitative evaluation of ◯, Δ, and × was performed. ○ means no red rust within 168 hours, △ means no red rust within 72 hours but red rust develops up to 168 hours, and x means red rust within 72 hours.

<Examples 1 to 8>
2.11 g (2 wt% to Zn) of isostearic acid (manufactured by Nissan Chemical Industries, Ltd., Fine Oxocol) was added to 136.5 g of xylene and dissolved, followed by 105.3 g of zinc powder #3 (manufactured by Sakai Chemical Industry Co., Ltd.). The slurry was repulped to form a slurry, and the slurry was scaly treated at 3000 rpm (peripheral speed 8.6 m/s) using a rotating disk and φ0.3 mm zirconia beads 567 g, filtered, dried, and scaly zinc. got the end The scaly treatment was performed at each time shown in Table 1.
The obtained flake-like zinc powder was subjected to the various measurements (evaluations) described above, and the results are shown in Table 1.

<Comparative Examples 1 to 6>
Stearic acid (manufactured by Kishida Chemical Co., Ltd.) 2.11 g (2 wt% to Zn) was added to and dissolved in 136.5 g of xylene, and then 105.3 g of zinc powder #3 (manufactured by Sakai Chemical Industry Co., Ltd.) was repulped to obtain a slurry. The slurry was scaly treated at 3000 rpm (peripheral speed 8.6 m/s) using a rotating disk and 567 g of φ0.3 mm zirconia beads, filtered and dried to obtain scaly zinc dust. The scaly treatment was performed at each time shown in Table 1.
The obtained flake-like zinc powder was subjected to the various measurements (evaluations) described above, and the results are shown in Table 1.

In the method of the example, by using a fatty acid (salt) having a branched chain, scales with a high 60 ° gloss value and excellent design in a shorter time than a comparative example that does not use such a fatty acid (salt) It was found that zinc dust in the form of zinc can be obtained. In a comparative example in which stearic acid, which is a fatty acid having no branched chain, was used to scaly zinc dust, as shown in Comparative Example 4, the median diameter (D50) value was the maximum and the 60 ° gloss was obtained. It took 240 minutes for the value to reach its highest value. D50) was maximized and the 60° gloss value was maximized in 120 minutes, which is half the time of Comparative Example 4.

Claims (8)

Step A of obtaining a slurry containing zinc dust and at least one selected from the group consisting of fatty acids having branched chains and salts thereof;
A step B of scaling the zinc dust in the slurry ,
The fatty acid and its salt have 8 to 24 carbon atoms
A method for producing scale-like zinc powder, characterized by: 2. The method for producing flaky zinc powder according to claim 1 , wherein the amount of the fatty acid and its salt used is 0.01 to 5.0% by mass with respect to 100% by mass of the zinc powder. In the step B, the scaly treatment is performed for 25% or more and 200% or less of the scaly treatment time at which the median diameter (D50) of the obtained scaly zinc dust is maximized. 3. The method for producing flaky zinc dust according to claim 1 or 2 . The method for producing flaky zinc powder according to any one of claims 1 to 3 , wherein the median diameter (D50) of the flaky zinc powder to be obtained is 1 to 120 µm. scaly zinc dust,
The flaky zinc powder contains at least one selected from the group consisting of fatty acids having branched chains and salts thereof,
The fatty acid and its salt have 8 to 24 carbon atoms,
When the flaky zinc dust is used as a paint containing the flaky zinc dust and the binder at a mass ratio (zinc dust/binder) of 1.2, the coating film has a 60° gloss value of 20 or more. Scaly zinc powder characterized by A paint comprising the scale-like zinc powder according to claim 5 and a binder. 7. The paint according to claim 6 , wherein the content of said scale-like zinc dust is 15 to 95% by weight with respect to 100% by weight of the solid content in the paint. 8. The paint according to claim 6 , wherein the paint is used for anticorrosion purposes.

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