JP7680286B2 - Metal pigment composition packaging - Google Patents

Description

The present invention relates to a package of a metal pigment composition containing novel composite particles, and a method for storing and transporting the package. More specifically, the present invention relates to a package of a metal pigment composition containing novel composite particles that have little aggregation of individual particles even when stored for a long period of time and can maintain excellent hiding power, color tone, etc., and a method for storing and transporting the package.

2. Description of the Related Art Metallic pigments have been used for metallic paints, printing inks, plastic blends, and the like, for the purpose of obtaining cosmetic effects that emphasize a metallic appearance.
In recent years, in the paint industry, the need to switch to water-based paints that use less organic solvents has increased as a resource-saving and pollution-free measure, but there are still not enough types of practical water-based paints for metallic paints that contain metal pigments. The reason for this is that metal pigments are easily corroded in water-based paints. When metal powder is present in water-based paints, corrosion by water occurs in either acidic, neutral, or alkaline regions or in multiple regions based on the properties of the various metals, and hydrogen gas is generated. This is an extremely serious safety issue in the manufacturing process of paints and inks at paint and ink manufacturers, and in the painting and printing processes at automobile, home appliance, and printing manufacturers. In addition, corrosion can cause the smoothness of the metal surface to be lost, pigment particles to aggregate with each other, or pigment particles to deform, resulting in an unavoidable decrease in color tone.

Patent Document 1 (JP 2003-147226 A) discloses an aluminum pigment having an inorganic molybdenum coating and a coating made of amorphous silica that covers the coating. Patent Document 2 (WO 2004/096921 A) discloses an aluminum pigment having an inorganic molybdenum coating and a coating made of amorphous silica that covers the coating and/or a coating formed from a silane coupling agent.
However, all of the methods described in these patent documents inevitably cause changes in the color tone of the metallic pigment, and these methods also have the problem that aggregation and color tone changes of the metallic pigment progress during long-term storage and/or transportation, particularly in uncontrolled environments such as high temperature and humidity.

Patent Document 3 (International Publication No. WO 2018/180936) discloses a composite particle coated pigment that includes metal particles and a coating layer that is a silicon-containing compound layer and has a small proportion of aggregates in which four or more particles are adhered to each other, for the purpose of providing a coated pigment (metal pigment composition) that is dispersed with relatively few aggregates.
However, in Patent Document 3, apart from the fact that it is preferable to adjust the stirring Reynolds number to a predetermined range, no specific teaching can be found on how to obtain the desired coated pigment with few aggregates. Moreover, even if the range of characteristic parameters specified in Patent Document 3 is satisfied, it is difficult to obtain a sufficiently satisfactory hydrogen gas generation suppression performance, low aggregation, hiding power, and color tone by itself. Moreover, even with the coated pigment, the problem of aggregation and color tone change during long-term storage and/or transportation in uncontrolled environments such as high temperature and high humidity cannot be solved.

JP 2003-147226 A International Publication No. 2004/096921 International Publication No. 2018/180936

An object of the present invention is to provide a package of a metal pigment composition containing novel composite particles not found in the prior art, as well as a method for storing and transporting the package.
A further object of the present invention is to provide a novel technology which overcomes the disadvantages of the conventional technology, i.e., which has excellent storage stability, small aggregation of individual particles, excellent hiding power, color tone, etc., and which can maintain these characteristics even when stored and/or transported for a long period of time in uncontrolled environments such as high temperature and high humidity.

As a result of intensive research by the inventors to solve the above problems, they discovered that in a package in which a metal pigment composition containing composite particles having metal particles and one or more coating layers on the surfaces of the metal particles is packed in a packaging container, by forming a specific protective layer on the portion of the packaging container that comes into contact with the metal pigment composition, it is possible to suppress the progression of aggregation and color change of the metal pigment composition in the package, and thus completed the present invention.

That is, the various aspects of the present invention are as follows.
[1]
A package in which a metal pigment composition containing composite particles having metal particles and one or more coating layers on the surfaces of the metal particles is packed in a packaging container, the package satisfying the following (1) to (4):
(1) The composite particles have a scale-like shape;
(2) The volume-based _D50 of the composite particles is 1 to 30 μm when the particle size distribution is measured using a laser diffraction particle size distribution analyzer;
(3) The average thickness of the composite particles is 20 to 400 nm;
(4) The packaging container has a base material containing at least a part of a metal, and one or more types of protective layers selected from the following a) and b) are formed on the portion of the packaging container that comes into contact with the metal pigment composition:
(a) a protective layer having a thickness of 1 to 200 μm, which is formed from a resin containing at least one selected from the group consisting of a glycidyl ether type epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, a cyclic oxirane type epoxy resin, a novolac phenolic resin, a resol type phenolic resin, a polyester resin, and an epoxy resin heat-cured with a phenolic resin;
(b) a protective layer formed from a metal phosphate and having a weight per unit area of 0.1 g/m ² to 10 g/m ² .
[2] The packaging body according to the above [1], wherein at least one of the coating layers is a silicon compound-containing layer.
[3] The package according to [1] or [2] above, wherein the metal particles are aluminum or an aluminum alloy.
[4] The package according to any one of [1] to [3] above, wherein the moisture content of the metal pigment composition in the package is 0 to 1000 ppm relative to the mass of the metal pigment composition.
[5] The package according to any one of the above [1] to [4], wherein the metal pigment composition has a pH in the range of 6 to 8.
[6] The package according to any one of [1] to [5] above, in which when the sealed package is stored in an indoor warehouse at 20°C for one year, the residue of the metal pigment composition after storage is 0.05% by weight or less.
[7] The package according to any one of [1] to [5] above, in which when the sealed package is stored in a heating room at 60°C for three months, the residue of the metal pigment composition after storage is 0.05% by weight or less.
[8] A method for storing a metal pigment composition at 0 to 50°C using the packaging material according to any one of [1] to [7] above.
[9] A method for transporting a metal pigment composition at 0 to 50°C using the package according to any one of [1] to [7] above.

According to the present invention, even if a metal pigment composition containing metal particles and composite particles having one or more coating layers on the surface thereof is stored and/or transported for a long period of time, the progression of particle aggregation and color change can be suppressed. Furthermore, a high-quality metal pigment composition in which the progression of particle aggregation and color change is suppressed in this manner can be suitably used as a raw material for water-based paints.

The following describes in detail the embodiments of the present invention. Note that the present invention is not limited to the following embodiments, and can be modified in various ways within the scope of the gist of the invention.

<Packaging>
The package according to the present invention is a package in which a metal pigment composition containing composite particles having metal particles and one or more coating layers on the surfaces of the metal particles is packed in a packaging container, and the package satisfies the following (1) to (4).
(1) The composite particles have a scale-like shape.
(2) The volume-based _D50 of the composite particles is 1 to 30 μm when the particle size distribution is measured using a laser diffraction particle size distribution analyzer.
(3) The average thickness of the composite particles is 20 to 400 nm.
(4) The packaging container has a substrate containing at least a part of a metal, and at least one type of protective layer selected from the following a) and b) is formed on the portion that comes into contact with the metal pigment composition:
a) a protective layer having a thickness of 1 to 200 μm, which is formed from a resin containing at least one selected from the group consisting of a glycidyl ether type epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, a cyclic oxirane type epoxy resin, a novolac phenolic resin, a resol type phenolic resin, a polyester resin, and an epoxy resin heat-cured with a phenolic resin;
b) A protective layer formed from a metal phosphate and having a weight per unit area of 0.1 g/m ² to 10 g/m ² .

1. Composite Particles Contained in the Metal Pigment Composition The metal pigment composition according to the present invention comprises composite particles having metal particles and one or more coating layers on the surfaces thereof.
As used herein, the term "metal pigment composition" refers to a composition in which composite particles comprising metal particles and one or more coating layers on the surfaces thereof are dispersed in a solvent comprising a hydrophilic solvent or are accompanied by a solvent comprising a hydrophilic solvent, and may optionally include other ingredients.

1) Metal Particles The composite particles contained in the metal pigment composition of the present invention include metal particles and one or more coating layers formed on the surfaces of the metal particles.

The material of the metal particles constituting the composite particles is not particularly limited, and may be any metal known or commercially available metal used as a metal pigment, such as aluminum, aluminum alloy, zinc, iron, magnesium, nickel, copper, silver, tin, chromium, stainless steel, etc. In this specification, the metal of the metal particles constituting the composite particles includes not only simple metals but also alloys and intermetallic compounds.
In this way, the metal particles may be made of a metal consisting of only one type of metal element, or may be made of a metal consisting of two or more types of metal elements.
The metal particles in the present invention are preferably a metal containing aluminum element as a main component, for example, aluminum or an aluminum alloy, and more preferably aluminum.

The metal particles are preferably scaly (flake-like). This allows the composite particles contained in the metal pigment composition of the present invention to have a scaly shape, making it easier to more reliably obtain high hiding power, etc. The aspect ratio of the scaly metal particles (shape coefficient obtained by dividing the average particle size by the average thickness) is preferably 20 to 400. By having an aspect ratio of the metal particles of 20 or more, a higher sense of brilliance can be obtained. In addition, by having an aspect ratio of the metal particles of 400 or less, mechanical strength can be maintained and a stable color tone can be obtained. Here, the average thickness of the metal particles used in the present invention can be determined by a known method, for example, by using a method of calculation from the water surface diffusion area and density of the metal particles.

The average particle size of the metal particles is not particularly limited as long as it is an average particle size that can provide _D50 in the particle size distribution of the composite particles described below. In other words, it is desirable to set the average particle size of the metal particles so that _D50 is 1 μm or more and 30 μm or less when the volume distribution of the composite particles is measured with a laser diffraction particle size distribution meter.
The average particle size of the metal particles can be controlled in the process of grinding, sieving and filtering the raw atomized metal powder (e.g., aluminum powder) using a ball mill or the like by appropriately adjusting the particle size of the raw atomized metal powder, the mass per grinding ball when a ball mill is used, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc.

The metal particles do not necessarily have to be composed of metal only, and as long as they do not impair the effects of the present invention, for example, synthetic resin particles, or inorganic particles such as mica or glass whose surfaces are coated with metal can also be used. In the present invention, it is particularly desirable for the particles to be made of aluminum or an aluminum alloy in terms of high weather resistance, low specific gravity, ease of availability, etc.

Particularly suitable as the metal particles constituting the composite particles are aluminum flakes, which are commonly used as metallic pigments. Aluminum flakes having the surface properties, particle size, and shape required for metallic pigments, such as surface gloss, whiteness, and brilliance, are suitable. Aluminum flakes are usually commercially available in a paste state. Paste-like aluminum flakes may usually contain scaly aluminum powder, mineral spirits (aliphatic hydrocarbons), residual fatty acids used during grinding, and organic solvents such as solvent naphtha and xylene. Paste-like aluminum flakes may be used as they are, or may be used after removing fatty acids and the like from the surface with an organic solvent or the like in advance.
Also usable as the metal particles are so-called aluminum vapor-deposited foils, which in the state of composite particles have a volume average particle size (D ₅₀ ) of 1 μm or more and 30 μm or less and an average thickness of 20 nm or more and 400 nm or less.

2) Metal Pigment Composition The metal pigment composition according to the present invention is characterized by further satisfying the following physical property requirements.
(1) The composite particles have a scale-like shape.
(2) When the particle size distribution of the composite particles is measured using a laser diffraction particle size distribution analyzer, the volume-based _D50 is 1 μm or more and 30 μm or less.
(3) The average thickness of the composite particles is 20 nm or more and 400 nm or less.

(1) The shape of the composite particles is scaly The shape of the composite particles of the metal pigment composition according to the present invention is scaly (flake-like). As a result, the coating film formed using the metal pigment composition can exhibit high luminance, high flip-flop feeling, high hiding power, etc. In this specification, the shape of the composite particles being "scaly" (flake-like) refers to the average aspect ratio of the composite particles (shape coefficient obtained by dividing the average particle diameter by the average thickness) being 20 or more. From the viewpoint of obtaining high luminance, flip-flop feeling, hiding power, etc., the average aspect ratio of the scaly composite particles is preferably 20 or more and 400 or less. By having an average aspect ratio of 20 or more, a sufficient luminance can be obtained, while by having an average aspect ratio of 400 or less, the mechanical strength of the flakes can be maintained and a stable color tone can be obtained. The aspect ratio is more preferably 25 or more, and even more preferably 30 or more. It is also more preferably 350 or less, and even more preferably 300 or less.
The "composite particle" in the requirement for genuine properties (1) refers to an aggregate (assembly) when a plurality of composite particles are aggregated or adhered to each other.

Here, the average particle size for calculating the average aspect ratio of the composite particles is the volume-based _D50 , which is called the median diameter, and this point will be described in detail in the explanation of requirement (2) below. Also, the average thickness for calculating the average aspect ratio of the composite particles will be described in detail in the explanation of requirement (3) below.

(2) When the particle size distribution of the composite particles is measured by a laser diffraction particle size distribution meter, the volume-based _D50 is 1 μm or more and 30 μm or less When the particle size distribution of the composite particles is measured by a laser diffraction particle size distribution meter, the volume-based _D50 is 1 μm or more and 30 μm or less. This allows the coating film formed using the metal pigment composition to exhibit high luminance, high flip-flop feeling, high hiding power, etc., and the aggregation of the individual particles constituting the metal pigment composition is suppressed, so that the aggregation property can be reduced. This volume-based _D50 is generally also called the median diameter.

From the viewpoint of obtaining such high light luminance, high flip-flop feeling, high hiding power, and small aggregation of individual particles, the volume-based _D50 when the particle size distribution of the composite particles is measured with a laser diffraction particle size distribution meter has a lower limit of 1 μm or more, preferably 2 μm or more, and more preferably 3 μm or more, and an upper limit of 30 μm or less, preferably 25 μm or less, and more preferably 20 μm or less.
The "composite particle" in the requirement for genuine properties (2) refers to an aggregate (assembly) when a plurality of composite particles are aggregated or adhered to each other.

Here, when the particle size distribution of the composite particles is measured by a laser diffraction particle size distribution analyzer, the volume-based _D50 refers to the particle size at a cumulative degree of 50% in the volume cumulative particle size distribution. The laser diffraction particle size distribution analyzer is not particularly limited, but for example, an "LA-300" (manufactured by Horiba, Ltd.) can be used. Mineral spirits can be used as the measurement solvent. For example, a metal pigment composition containing a sample composite particle can be subjected to ultrasonic dispersion for 2 minutes as a pretreatment, and then placed in a dispersion tank to confirm that it has been properly dispersed, after which _D50 can be measured.
The particle size of the composite particles in the resin composition obtained by adding a resin to the metal pigment composition cannot be measured by this method, so as an alternative method in this case, a method can be adopted in which the composite particles in the resin composition are photographed from the coating surface using, for example, an optical microscope or a laser microscope, and the particle size is obtained by obtaining the distribution of the circle equivalent diameter using commercially available image analysis software.

The volumetric _D50 of the composite particles contained in the metal pigment composition can be controlled by appropriately adjusting the particle size of the raw atomized metal powder, the mass per grinding ball when a ball mill is used, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc. in the process of grinding, sieving and filtering the raw atomized metal powder (e.g., aluminum powder) using a ball mill or the like in the manufacturing method of the metal pigment composition described later, and by appropriately adjusting the type of organosilicon compound used in the process of coating with a silicon compound-containing layer (and other coating layers as necessary), the pH, concentration, stirring temperature, stirring time, type of stirring device, and stirring power/degree (type and diameter of stirring blade, rotation speed, presence or absence of external stirring, etc.) in the coating process (including the case where the organosilicon compound is hydrolyzed and used).

(3) Average thickness of composite particles is 20 nm to 400 nm The average thickness of composite particles having metal particles and one or more coating layers on the surfaces thereof, which are contained in the metal pigment composition according to the present invention, is 20 nm to 400 nm. This, together with the satisfaction of the above requirements (1) and (2), allows a coating film formed using the metal pigment composition to exhibit high luminance, high flip-flop feeling, high hiding power, etc.

From the above viewpoints, the average thickness of the composite particles has a lower limit of 20 nm or more, preferably 25 nm or more, and more preferably 30 nm or more, and an upper limit of 400 nm or less, preferably 350 nm or less, and more preferably 300 nm or less.
In the real property requirements, the "composite particle" refers to an aggregate (aggregate) of multiple composite particles that are aggregated or adhered to each other.

The average thickness of the composite particles can be calculated from the water surface diffusion area and density of the composite particles. The water surface diffusion area refers to the area occupied by the dry composite particles per unit mass when the dried composite particles are uniformly diffused on the water surface by utilizing the leafing phenomenon and coated without gaps. The water surface diffusion area can be measured according to the provisions of JIS K5906:1998.
However, in the case of the composite particles of the present invention, if the surface is highly hydrophilic, it may be difficult to determine the water surface diffusion area. In this case, the average thickness of the composite particles can be measured according to the method described in the examples described below. That is, a coating (thin film) is formed using a metal pigment composition in which the composite particles are dispersed in a mixture of an alcoholic solvent such as methoxypropanol and water, and the average thickness of the composite particles (100 or more) is observed with a scanning electron microscope (SEM) to determine the average thickness of the composite particles.

The average thickness of the composite particles contained in the metal pigment composition, like the volumetric D ₅₀ , can be controlled by appropriately adjusting the particle size of the raw atomized metal powder, the mass per grinding ball when a ball mill is used, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc. in the process of grinding, sieving and filtering the raw atomized metal powder (e.g., aluminum powder) using a ball mill or the like in the manufacturing method of the metal pigment composition described later, and by appropriately adjusting the type of organosilicon compound used in the process of coating with a silicon compound-containing layer (and other coating layers as necessary), the pH, concentration, stirring temperature, stirring time, type of stirring device, and stirring power/degree (e.g., type and diameter of stirring blades, rotation speed, presence or absence of external stirring), etc.

3) Coating layer The metal pigment composition according to the present invention must have one or more coating layers formed on the surface of the metal particles that are the core of the composite particles. Examples of the coating layer include those containing at least one of silicon compounds, metals (alkali metals; alkaline earth metals; manganese, iron, cobalt, nickel, copper, silver, etc.), metal oxides (titanium oxide, zirconium oxide, iron oxide, etc.), metal hydrates, and resins (acrylic resins, alkyd resins, polyester resins, polyurethane resins, polyvinyl acetate resins, nitrocellulose resins, fluororesins, and other synthetic resins), and among these, it is desirable for the coating layer to contain a silicon compound-containing layer, particularly a layer made of a structure containing Si-O bonds. This makes it possible to suppress gas generation in the water-based paint, and to obtain good storage stability (i.e., corrosion resistance), and also to obtain excellent water resistance when formed into a coating film. The coating layer may be formed in two or more layers, and in this case, it is preferable that at least one layer is a silicon compound-containing layer.

The silicon compound-containing layer is preferably a layer composed of a compound containing a Si-O- bond (siloxane bond). Examples of such layers include layers containing at least one of polysiloxane, silane-based compounds, and silicon oxides formed by hydrolysis and condensation of an organosilicon compound. Examples of such compounds include, in addition to polysiloxane, silane-based compounds [H ₃ SiO(H ₂ SiO) _n SiH ₃ ] (where n is any positive integer), and silicon oxides represented by SiO ₂ , SiO _{2.nH 2} O (where n is any positive integer). These silane-based compounds and silicon oxides may be either crystalline or amorphous, but are particularly preferably amorphous. Therefore, as a layer containing a silicon oxide (silica, etc.), a layer containing, for example, amorphous silica can also be suitably adopted.

The layer composed of a compound containing an Si-O bond may be a layer formed using an organosilicon compound (including a silane coupling agent) as a starting material. In this case, the silicon compound-containing layer may contain an organosilicon compound or a component derived therefrom within a range that does not impair the effects of the present invention. In a typical example, the layer composed of a compound containing an Si-O bond may be formed by hydrolyzing an organosilicon compound.
The silicon compound-containing layer may contain additives, impurities, etc. other than the silicon compound, as long as the properties of the present invention are not impaired.

The coating layer of the composite particles contained in the metal pigment composition according to the present invention is preferably particularly hydrophilic. The composite particles usually form a metal pigment composition in the form of being dispersed in an aqueous solvent (water or a mixed solvent containing water and an organic solvent), but if the coating layer has a hydrophilic surface, the composite particles can be highly dispersed in such an aqueous solvent. Moreover, since compounds containing Si-O bonds (polysiloxane, amorphous silica, etc.) are very stable in aqueous solvents, a metal pigment composition containing composite particles that are highly stable in aqueous solvents can be provided. From this perspective, it is desirable that at least the outermost layer of the composite particles contained in the metal pigment composition according to the present invention is a silicon compound-containing layer (particularly a layer composed of a compound containing Si-O bonds). When the coating layer is composed of multiple layers, in addition to the outermost silicon compound-containing layer, a silicon compound-containing layer (particularly a Si-O coating layer) may be separately formed as a layer other than the outermost layer.

The thickness of the coating layer of each composite particle is not particularly limited as long as the average thickness of the composite particles is in the range of 20 nm to 400 nm as described above, but is usually preferably in the range of about 10 to 80 nm, particularly 15 nm to 70 nm, and further 20 nm to 60 nm. By making the coating layer thicker than 10 nm, it is possible to obtain a coating film that has sufficient water resistance and suppresses the occurrence of corrosion or discoloration of metal particles in water-based paint. On the other hand, by making the coating layer thicker than about 80 nm, the brightness, clarity, and hiding power of the coating film can be maintained at a high level.

When the coating layer of each composite particle includes a silicon compound-containing layer, the thickness of the layer is not particularly limited as long as the average thickness of the composite particles is in the range of 20 nm to 400 nm, but from the viewpoint of the layer's function, it may usually be in the range of 10 nm to 80 nm, and is particularly preferably in the range of 15 nm to 70 nm.

Specific examples of the organosilicon compound that can be used in the present invention are described below, but the organosilicon compound is not limited to these specific examples.
The organosilicon compound may contain at least one organosilicon compound represented by the following general formula (1) and at least one selected from the group consisting of silane coupling agents represented by any of the following general formulas (2), (3) and (4) and partial condensates thereof:
Si(OR ¹ ) ₄ ... (1)
(In the formula, R ¹ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and all of the R ¹ may be the same, some of the R 1 may be the same, or all of the R 1 may be different.)
R ² _m Si(OR ³ ) _4-m ... (2)
(In the formula, ^R2 is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms which may optionally contain a halogen group, and R3 is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. ^R2 and ^R3 may be the same or different, and when there are two or more ^R2s or ^R3s , they may all be the same, some may be the same, or all may be different. 1≦m≦3.)
R ⁴ _p R ⁵ _q Si(OR ⁶ ) _4-pq ... (3)
(In the formula, R ⁴ is a group containing a reactive group capable of chemically bonding with another functional group, R ⁵ is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms which may optionally contain a halogen group, and R ⁶ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. When there are two or more R ^{4 s} , R ^{5 s} , or R ^{6 s} , they may all be the same, some may be the same, or all may be different. 1≦p≦3, 0≦q≦2, and 1≦p+q≦3.)
R ⁷ _r SiCl _4-r ... (4)
(In the formula, ^R7 is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms which may optionally contain a halogen group, and when there are two or more ^R7s , all of them may be the same, some of them may be the same, or all of them may be different. 0≦r≦3.)

Examples of the hydrocarbon group in R ¹ of formula (1) include methyl, ethyl, propyl, butyl, hexyl, octyl, etc., which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. In addition, the four R ¹ may all be the same, some may be the same, or all may be different.

Preferred examples of such organosilicon compounds of formula (1) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, etc. Among these, tetraethoxysilane is particularly preferred.

Examples of the hydrocarbon group in ^R2 in formula (2) include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear, and may contain halogen groups such as fluorine, chlorine, and bromine. Among these, hydrocarbon groups having 1 to 18 carbon atoms are particularly preferred. In addition, when there are two or more ^R2s , they may all be the same, some may be the same, or all may be different. The number of ^R2s in the molecule in formula (2) is m=1 to 3, that is, 1 to 3, but it is more preferable that m=1 or 2.

Examples of the hydrocarbon group in ^R3 in formula (2) include methyl, ethyl, propyl, butyl, hexyl, octyl, etc., which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. In addition, when there are two or more ^R3s , they may all be the same, some may be the same, or all may be different.

Preferred examples of such organosilicon compounds (silane coupling agents) of formula (2) include methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, trimethylmethoxysilane, trimethylethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltributoxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltributoxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, dibutyldibutoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, dihexyldimethoxysilane, dihexyldiethoxysilane, octyltrimethoxysilane, octyltrimethoxysilane, octyltriethoxy ... Examples of the silane include isethoxysilane, dioctyldimethoxysilane, dioctyldiethoxysilane, dioctylethoxybutoxysilane, decyltrimethoxysilane, decyltriethoxysilane, didecyldimethoxysilane, didecyldiethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, dioctadecyldimethoxysilane, dioctadecyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropyltributoxysilane, and the like.

Examples of the reactive group capable of chemically bonding with another functional group in ^R4 of formula (3) include a vinyl group, an epoxy group, a styryl group, a methacryloxy group, an acryloxy group, an amino group, a ureido group, a mercapto group, a polysulfide group, and an isocyanate group.
In addition, when there are two or more ^R4s , they may all be the same, some may be the same, or all may be different. The number of ^R4s in the molecule is p=1 to 3 in formula (3), that is, 1 to 3, and more preferably p=1.

Examples of the hydrocarbon group of ^R5 in formula (3) include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear and may contain a halogen group such as fluorine, chlorine, or bromine. Among these, a hydrocarbon group having 1 to 18 carbon atoms is particularly preferred. When there are two or more ^R5s , they may all be the same, some may be the same, or all may be different.

Examples of the hydrocarbon group in R ⁶ of formula (3) include methyl, ethyl, propyl, butyl, hexyl, octyl, etc., which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. In addition, when there are two or more R ^6s , they may all be the same, some may be the same, or all may be different.

Preferred examples of such organosilicon compounds (silane coupling agents) of formula (3) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-methyl-3-aminopropyl-trimethoxysilane, N-2-(aminoethyl)-3-amino Propylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatepropyltriethoxysilane, etc.

Examples of the hydrocarbon group in R ⁷ in formula (4) include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear, and may contain halogen groups such as fluorine, chlorine, and bromine. Among these, hydrocarbon groups having 1 to 12 carbon atoms are particularly preferred. In addition, when there are two or more R ^7s , they may all be the same, some may be the same, or all may be different. The number of R ^7s in the molecule in formula (4) is r=0 to 3, that is, 0 to 3, but it is more preferable that r=1 to 3.

Preferred examples of such organosilicon compounds (silane coupling agents) of formula (4) include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, octyldimethylchlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, and tetrachlorosilane.

The organosilicon compound represented by the above general formula (1) may be used alone or in combination of two or more. The silane coupling agent represented by any of the general formulas (2), (3), and (4) may be used alone or in combination of two or more. When using two or more in combination, only the silane coupling agent represented by any of the general formulas (2), (3), and (4) may be used in combination of two or more, or silane coupling agents represented by two or more different general formulas may be used in combination.

The hydrolysis product of the organosilicon compound and/or its condensation reaction product can be obtained by stirring and mixing the organosilicon compound with the amount of water required for the hydrolysis reaction and a hydrolysis catalyst. In this case, a hydrophilic solvent can also be used if necessary. The conditions for the hydrolysis reaction (i.e., the reaction for forming the silicon compound-containing layer) will be described later.

As a raw material for the hydrolysis and/or condensation reaction to obtain a hydrolysate of an organosilicon compound and/or a condensation product thereof, a partially condensed oligomer may be used.
The condensation reaction of the hydrolyzate of the organosilicon compound may be carried out simultaneously with the hydrolysis reaction of the organosilicon compound, or may be carried out in separate steps, and if necessary, using a different catalyst. In this case, heating may be performed as necessary.

It is preferable that at least one of the coating layers of the composite particles contained in the metal pigment composition of the present invention is a silicon compound-containing layer, but coating layers other than the silicon compound-containing layer (hereinafter referred to as "other coating layers") may be formed alone or together with the silicon compound-containing layer.
The other coating layer may contain at least one of metals (alkali metals; alkaline earth metals; manganese, iron, cobalt, nickel, copper, silver, etc.), metal oxides (titanium oxide, zirconium oxide, iron oxide, etc.), metal hydrates, and resins (acrylic resins, alkyd resins, polyester resins, polyurethane resins, polyvinyl acetate resins, nitrocellulose resins, fluororesins, and other synthetic resins). As the other coating layer, for example, a molybdenum-containing coating, a phosphate compound coating, etc. can be formed. By providing the other coating layer, the corrosion resistance of the metal particles can be improved.

When other coating layers are formed, they are preferably formed between the metal particles and the silicon compound-containing layer. Therefore, for example, a layer structure of "metal particles/other coating layers/silicon compound-containing layer" can be preferably adopted. Although not particularly limited, examples of molybdenum-containing coatings include those disclosed in JP 2003-147226 A, WO 2004/096921 A, Japanese Patent No. 5979788, and Japanese Patent No. 2019-151678 A. Examples of phosphate compound coatings include those disclosed in Japanese Patent No. 4633239. A preferred example of a molybdenum-containing material constituting the molybdenum-containing coating is the mixed coordination type heteropolyanion compound disclosed in JP 2019-151678 A.

In another variation, other coating layers can be formed on the outside of the metal particles and the silicon compound-containing layer. In yet another variation, components of the silicon compound-containing layer (such as molybdenum-containing compounds and phosphate compounds) can be included in the silicon compound-containing layer along with the silicon compound.

The mixed coordination heteropolyanion compound used in the embodiment for forming a coating layer other than the silicon compound-containing layer of the composite particle contained in the metal pigment composition according to the present invention (a typical example is a molybdenum-containing coating) is not particularly limited, but specific examples include the following.
The mixed coordination heteropolyanion of the mixed coordination heteropolyanion compound that can be used has a structure in which some of the polyatoms of a heteropolyanion consisting of one type of element are replaced with another element, and exhibits physical properties different from those of a mixture of the individual heteropolyanions.

When expressed by a _chemical formula, the mixed coordination heteropolyanion is expressed as _{[ XpMqNrOs} ] ^t , and the heteropolyanion is expressed as [ _XpMqOs ] ^t , and is further distinguished from _the isopolyanion [ _MqOs ] ^t . However, the heteroatom X represents an element of _the IIIB, IVB, or _VB group, such as B, Si, or As, and among them, B, Si, or P is preferable. The polyatoms _M and N represent transition metals such as Ti, Zr, V, Nb, Ta, Mo, or W, and Ti, Zr, V, Nb, Mo, or W is preferable.
Furthermore, p, q, r, and s represent the number of atoms, and t represents the oxidation number.

Since heteropolyanion compounds have numerous structures, mixed coordination type heteropolyanion compounds can have even more numerous structures. Representative and preferred mixed coordination type heteropolyanion compounds include the following mixed coordination type heteropolyacids: H ₃ PW _x Mo _12-x O _{40.nH 2} O (phosphotungstomolybdic acid, n-hydrate), H _3+x PV _x Mo _12-x O _{40.nH 2} O (phosphovanadomolybdic acid, n-hydrate), H ₄ SiW _x Mo _12-x O _{40.nH 2} O (silicotungstomolybdic acid, n-hydrate), H _4+x SiV _x Mo _12-x O _{40.nH 2} O (silicovanadomolybdic acid, n-hydrate), etc. (where 1≦x≦11, n≧0)

Specific preferred examples of these heteropolyanion compounds include H ₃ PW ₃ Mo ₉ O _{40.nH 2} O, H ₃ PW ₆ Mo ₆ O _{40.nH 2} O, H 3 PW 9 Mo ₃ O _40.nH 2 O, H ₄ PV ₁ Mo ₁₁ O _{40.nH 2} O, H ₆ PV ₃ Mo ₉ O _{40.nH 2} O, H ₄ SiW ₃ Mo ₉ O _{40.nH 2} O, H ₄ SiW ₆ Mo ₆ O _{40.nH 2 O} , _{H 4 SiW 9} Mo _{3 O 40.nH 2} O, and H ₅ SiV ₁ Mo ₁₁ O _{40.nH 2} O, H ₇ SiV ₃ Mo ₉ O _{40.nH 2} O, and other mixed coordination heteropolyacids (where n≧0).

The mixed coordination heteropolyanion compound may be used in the form of an acid (so-called mixed coordination heteropolyacid) or in the form of a (partial or complete) salt having a specific cation as a counter ion.
When the mixed coordination heteropolyanion compound is used in the form of a salt having a specific cation as a counter ion, the counter cation source may be at least one selected from alkali metals such as lithium, sodium, potassium, rubidium, cesium, etc., alkaline earth metals such as magnesium, calcium, strontium, barium, etc., metals such as manganese, iron, cobalt, nickel, copper, zinc, silver, cadmium, lead, aluminum, etc., inorganic components such as ammonia, and organic components such as amine compounds. Among the inorganic components, salts of alkali metals, alkaline earth metals, and ammonia are preferred.

Furthermore, when at least one selected from these alkali metals, alkaline earth metals, and ammonia is used as the counter cation source, it is _more preferable to use it in the form of a salt with at least one selected from H ₃ PW _x Mo 12 _{- x} O _{40.nH 2 O} (phosphotungstomolybdic acid, n-hydrate), H _3+x PV _x Mo _12-x O _{40.nH 2} O (phosphovanadomolybdic acid, n-hydrate), H ₄ SiW _x Mo 12-x O _{40.nH 2} O (silicotungstomolybdic acid, n-hydrate), and H _4+x SiV _x Mo 12 _-x O 40.nH 2 O (silicovanadomolybdic acid, n-hydrate).

Furthermore, amine compounds, which are organic components, are also preferably used as the counter cation source for the mixed coordination heteropolyanion compound. Specific examples thereof include those represented by the following general formula (5).
(R ⁸ -N(-R ¹⁰ )-) _n -R ⁹ ... (5)
(wherein R ⁸ , R ⁹ and R ¹⁰ may be the same or different and are a hydrogen atom or a monovalent or divalent hydrocarbon group having 1 to 30 carbon atoms and optionally containing an ether bond, an ester bond, a hydroxyl group, a carbonyl group or a thiol group; optionally R ⁸ and R ⁹ may join together to form a 5- or 6-membered cycloalkyl group or a 5- or 6-membered ring which may additionally contain a nitrogen or oxygen atom as a bridging member; or optionally R ⁸ , R ⁹ and R ¹⁰ may join together to form a multi-membered multiple ring which may contain one or more additional nitrogen and/or oxygen atoms as bridging members. R ⁸ , R ⁹ and R ¹⁰ are not hydrogen atoms at the same time; and n represents an integer of 1 to 2.)

Examples of the amine compound that is a counter cation source for the mixed coordination heteropolyanion compound include linear or branched primary amines, linear, branched, or asymmetric secondary amines, linear, branched, or tertiary amines having mixed hydrocarbon groups, as well as alicyclic primary amines, primary amines having aromatic ring substituents, alicyclic secondary amines, secondary amines having aromatic ring substituents, alicyclic asymmetric secondary amines, alicyclic tertiary amines, tertiary amines having aromatic ring substituents, amines having ether bonds, alkanolamines, diamines, cyclic amines, aromatic amines, and the like, or any mixtures thereof.

Among these amine compounds, preferred examples include at least one selected from primary, secondary, or tertiary amines or alkanolamines having linear or branched alkyl groups having 4 to 20 carbon atoms. Specific examples include butylamine, hexylamine, cyclohexylamine, octylamine, tridecylamine, stearylamine, dihexylamine, di-2-ethylhexylamine, linear or branched ditridecylamine, distearylamine, tributylamine, trioctylamine, linear or branched tritridecylamine, tristearylamine, N,N-dimethylethanolamine, N-methyldiethanolamine, triethanolamine, morpholine, etc.

It is more preferable to use at least one selected from the amine compounds represented by the general formula (5) in the form of a salt of at least one selected from H ₃ PW _x Mo _12-x O _{40.nH 2} O (phosphotungstomolybdic acid, n-hydrate), H _3+x PV _x Mo _12-x O _{40.nH 2} O (phosphovanadomolybdic acid, n-hydrate), H ₄ SiW _x Mo _12-x O _{40.nH 2} O (silicotungstomolybdic acid, n-hydrate), and H _4+x SiV _x Mo _12-x O _{40.nH 2} O (silicadomolybdic acid, n-hydrate).

Of the above mixed coordination type heteropolyanion compounds, the most preferred are mixed coordination type heteropolyacids such as H ₃ PW _x Mo _12-x O _{40.nH 2} O (phosphotungstomolybdic acid, n-hydrate), H _3+x PV _x Mo _12-x O _{40.nH 2} O (phosphovanadomolybdic acid, n-hydrate), and H ₄ SiW _x Mo _12-x O _{40.nH 2} O (silicotungstomolybdic acid, n-hydrate), or organic amine salts of these mixed coordination type heteropolyacids.

The coating layer other than the silicon compound-containing layer of the composite particle contained in the metal pigment composition according to the present invention (if formed) may be a layer containing another corrosion inhibitor in order to further improve the corrosion resistance of the core metal particle (preferably an aluminum particle or an aluminum alloy particle). The corrosion inhibitor to be added is not particularly limited, and any known corrosion inhibitor can be used. The amount of the corrosion inhibitor used may be within a range that does not inhibit the desired effect of the present invention. Examples of such corrosion inhibitors include acid phosphate esters, dimer acids, organic phosphorus compounds, metal salts of molybdic acid, etc.

The silicon compound-containing layer and/or other coating layer of the composite particles contained in the metal pigment composition, or as a separate layer, may further contain an organic oligomer or polymer from the viewpoint of adhesion and chemical resistance when a coating film is formed.
In addition, from the viewpoint of storage stability, at least one selected from the group consisting of inorganic phosphoric acids and salts thereof, and acidic organic (or acidic) phosphorous esters and salts thereof may be contained in the silicon compound-containing layer and/or other coating layer of the composite particle, or as a separate layer.
These compounds are not particularly limited, but for example, those disclosed in JP-A-2019-151678 can be used.

2. Method for Producing Metal Pigment Composition The metal pigment composition of the present invention can be suitably produced by a production method including a step of preparing scaly metal particles using a method commonly used in the pigment industry, followed by steps of sieving (classifying), filtering, washing, mixing, etc. to produce the metal particles, and then forming a coating layer under stirring using a solvent containing water and/or a hydrophilic solvent. More specifically, the following methods can be mentioned, but are not limited to these.
In the following, as a typical example, a case will be described in which at least one coating layer of the composite particle contained in the metal pigment composition is a silicon compound-containing layer.

The metal pigment composition according to the present invention can be suitably produced, for example, by a method including a step of forming a silicon compound-containing layer on the surface of the metal particles (silicon compound-containing layer forming step) by subjecting the organosilicon compound to a hydrolysis/(partial) condensation reaction in a mixed liquid containing (a) metal particles, (b) at least one silicon-containing raw material containing an organosilicon compound, (c) a solvent (water and/or a hydrophilic solvent), and, if necessary, other optional components. This step can usually be carried out under stirring.

Crushing and Sieving/Filtering Steps Here, an example will be described in which aluminum powder is used as the metal particles.
The aluminum powder is generally obtained by pulverizing atomized aluminum powder and/or aluminum foil in the presence of a grinding aid or an inert solvent into a so-called flake-like form using a method commonly used in the pigment industry, such as a dry ball mill method, a wet ball mill method, an attritor method, or a stamp mill method, and then passing through any necessary steps, such as sieving (classification), filtration, washing, and mixing.

Examples of the grinding aid include fatty acids, fatty amines, fatty amides, and fatty alcohols. In general, oleic acid, stearic acid, and stearylamine are preferred. Examples of the inert solvent include hydrophobic solvents such as mineral spirits, solvent naphtha, LAWS, HAWS, toluene, and xylene, which can be used alone or in combination. The grinding aid and the inert solvent are not limited to these.
As the pulverization step, pulverization by a wet ball mill method is preferred from the viewpoint of preventing dust explosions and ensuring safety.

When aluminum particles are used as the metal particles in the production of the metal pigment composition according to the present invention, commercially available paste-like aluminum flakes obtained through such pulverization, sieving, and filtration can be used. The paste-like aluminum flakes may be used as is, or may be used after removing fatty acids and the like from the surface with an organic solvent or the like in advance.

In addition, the metal particles used in producing the metal pigment composition of the present invention can be so-called vapor-deposited aluminum foil pigments, which are produced by peeling off a metal layer that has been vapor-deposited on a carrier material such as a resin film by physical vapor deposition (PVD) from the carrier material and pulverizing it.

Formation process of silicon compound-containing layer The mixed solution containing the above-mentioned (a) metal particles, (b) silicon-containing raw material containing at least one kind of organosilicon compound, and (c) solvent, and other optional components as necessary, can be prepared by mixing these components.The order of mixing is not particularly limited.

The metal particles may be any of the above-mentioned metal particles, and aluminum or aluminum alloy particles may be preferably used. As described above, flake-like metal particles may be used. Known or commercially available metal particles (typically paste-like aluminum flakes) may be used.
The content (solid content) of the metal particles in the mixed liquid is not particularly limited, and can be appropriately set depending on the type, particle size, etc. of the metal particles used.

As the silicon-containing raw material, an organosilicon compound is used. The organosilicon compound is not limited, but preferably, the above-mentioned compounds can be used.
At least one of the organosilicon compounds represented by the above formula (1) (a typical example is tetraalkoxysilane) and/or their condensates, and the silane coupling agents represented by any of the above formulas (2) to (4) can be suitably used.
Hereinafter, an example will be described in which tetraalkoxysilane is used as the organosilicon compound represented by the above formula (1). In the following, tetraalkoxysilane and/or its condensate may be collectively referred to simply as "tetraalkoxysilane".

When using a tetraalkoxysilane represented by the above formula (1) in combination with a silane coupling agent represented by any one of the above formulas (2) to (4), a method of using a mixture of the two (referred to as "method 1") can be adopted. Alternatively, a method including a step of treating metal particles with one agent to form a first silicon compound-containing layer, and treating the metal particles with the other agent to form a second silicon compound-containing layer (referred to as "method 2") can also be adopted.

The first method includes, for example, a method including a step of forming a silicon compound-containing layer by appropriately adjusting the pH of a mixture containing metal particles, a tetraalkoxysilane represented by the above formula (1), and a silane coupling agent represented by any one of the above formulas (2) to (4), thereby causing a hydrolysis/condensation reaction of the tetraalkoxysilane and the silane coupling agent.

The second method includes, for example, a step of forming a first silicon compound-containing layer (e.g., a silica coating made of amorphous silica) on the surface of the metal particles by appropriately adjusting the pH of a mixed solution containing metal particles and a tetraalkoxysilane represented by the above formula (1) to cause a hydrolysis/condensation reaction of the tetraalkoxysilane, and a step of forming a second silicon compound-containing layer on the surface of the first silicon compound-containing layer by adjusting the pH of a mixed solution containing metal particles and a silane coupling agent represented by any one of the above formulas (2) to (4) to cause a hydrolysis/condensation reaction of the silane coupling agent.

The amount of the tetraalkoxysilane or condensate thereof represented by the above formula (1) used can be appropriately set depending on the type of tetraalkoxysilane used. For example, from the viewpoint of the coating treatment effect and from the viewpoint of suppressing aggregation of metal particles or reduction in brilliance, the amount used may be 2 to 200 parts by mass, and more preferably 5 to 100 parts by mass, per 100 parts by mass of metal particles (solid content).

The amount of the silane coupling agent represented by any of the above formulas (2) to (4) used is not particularly limited, but may usually be about 0.1 to 20 parts by mass per 100 parts by mass of metal particles (solid content), and is preferably 1 to 10 parts by mass. By using an amount of about 0.1 to 20 parts by mass, it is possible to obtain the desired coating treatment effect and desirable coating film properties.

The solvent in the mixed solution, i.e., the solvent for the hydrolysis reaction and/or condensation reaction of the organosilicon compound, may be appropriately selected depending on the type of silicon-containing raw material used, but typically water, a hydrophilic organic solvent, or a mixed solvent thereof can be used. By using these solvents, the uniformity of the reaction and the uniformity of the resulting hydrolysis product and/or condensation reaction product can be improved. In the embodiment in which the silicon compound-containing layer is formed directly on the metal particles, it is particularly preferable that the solvent of the mixed solution contains a hydrophilic organic solvent from the viewpoint of avoiding the reaction between the metal particles and water from proceeding too rapidly. In the present invention, a mixed solvent of water and a hydrophilic organic solvent can be preferably used.

Examples of hydrophilic organic solvents include, but are not limited to, alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol; ether alcohols and esters thereof such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. These can be used alone or in combination of two or more.

When a mixed solvent of water and a hydrophilic organic solvent is used as the solvent, the ratio of the two is not particularly limited. In an embodiment in which a silicon compound-containing layer is formed directly on metal particles, it is preferable that the water content is 20 mass% or less, with the total of the two being 100 mass%, before the silicon compound is added, in order to avoid the reaction between the metal particles and water proceeding too quickly. In this case, the lower limit of the water content is not limited.

The amount of solvent used in the silicon compound-containing layer formation process (excluding the amount of solvent used when pre-dispersing metal particles) is not limited, but is usually about 100 to 10,000 parts by mass per 100 parts by mass of metal particles (solid content), and is preferably 200 to 1,000 parts by mass. By using 100 parts by mass or more of solvent, the increase in viscosity of the mixed liquid (slurry) is suppressed, and appropriate stirring is possible. In addition, by using 10,000 parts by mass or less of solvent, the recovery and regeneration costs of the treatment liquid can be prevented from becoming high. In addition, the amount of solvent used here refers to the total amount of solvent used for forming the first silicon compound-containing layer and the second silicon compound-containing layer in the case of the second method described above.

The above-mentioned mixed solution may contain other additives as necessary within the range that does not impair the effects of the present invention. For example, in addition to catalysts such as a hydrolysis catalyst and a dehydration condensation catalyst, surfactants, metal corrosion inhibitors, etc. may be mentioned.
Among these, a hydrolysis catalyst can be preferably used. By adding a hydrolysis catalyst, the pH of the mixed solution can be adjusted and the organosilicon compound can be efficiently hydrolyzed and dehydrated and condensed, so that a silicon compound-containing layer can be efficiently and reliably formed on the surface of the metal particles.

The hydrolysis catalyst may be any known or commercially available one, and is not particularly limited. Examples of hydrolysis catalysts that can be used include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; organic acids such as benzoic acid, acetic acid, chloroacetic acid, salicylic acid, oxalic acid, picric acid, phthalic acid, and malonic acid; and phosphonic acids such as vinylphosphonic acid, 2-carboxyethanephosphonic acid, 2-aminoethanephosphonic acid, and octanephosphonic acid. These hydrolysis catalysts may be used alone or in combination of two or more.

Examples of hydrolysis catalysts that can be used include inorganic alkalis such as ammonia, sodium hydroxide, and potassium hydroxide; inorganic alkali salts such as ammonium carbonate, ammonium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate; amines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, ethylenediamine, pyridine, aniline, choline, tetramethylammonium hydroxide, and guanidine; and salts of organic acids such as ammonium formate, ammonium acetate, monomethylamine formate, dimethylamine acetate, pyridine lactate, guanidinoacetic acid, and aniline acetate. These hydrolysis catalysts can be used alone or in combination of two or more.

The amount of hydrolysis catalyst added is not particularly limited, but is usually 0.01 to 20 parts by mass per 100 parts by mass of metal particles (solid content), and is preferably 0.02 to 10 parts by mass. When the amount added is 0.01 parts by mass or more, the amount of deposition of the silicon compound-containing layer can be sufficient. Also, when the amount added is 20 parts by mass or less, aggregation of the metal particles can be effectively suppressed.

In preparing the above-mentioned mixture, the components may be mixed uniformly in the mixture, and the order of mixing is not particularly limited.
In the production of the metal pigment composition according to the present invention, the preparation of the above-mentioned mixed liquid is preferably carried out under appropriate stirring.

The agitator for agitating the mixture is not particularly limited, and any known agitator capable of efficiently and uniformly agitating the mixture containing aluminum particles and an organosilicon compound can be used. Specific examples include kneaders, mixers, rotary vessel agitators, stirred reaction tanks, V-shaped agitators, double cone agitators, screw mixers, sigma mixers, flash mixers, airflow agitators, ball mills, edge runners, etc. A further explanation of the agitator will be given later.

The temperature of the mixed liquid containing the metal particles and the organosilicon compound when stirring is usually about 10 to 80°C, and preferably 20 to 70°C. By keeping this temperature at 10°C or higher, the reaction time required to obtain a sufficient treatment effect can be shortened. Also, by keeping this temperature at 80°C or lower, it becomes easier to control the reaction to obtain the desired metal pigment composition.

The stirring time of the mixed solution is not particularly limited as long as it is sufficient to form the desired silicon compound-containing layer. For example, this stirring time is preferably 0.5 to 20 hours, and more preferably 1 to 10 hours. By setting the stirring time to 0.5 hours or more, a sufficient treatment effect can be obtained. Furthermore, by setting the stirring time to 20 hours or less, an increase in treatment costs can be suppressed.

In the above-mentioned mixed solution, the silicon-containing raw material is subjected to a hydrolysis/condensation reaction to form a silicon compound-containing layer on the surface of the metal particles (or via another coating layer). This hydrolysis/condensation reaction can be carried out by, in particular, adjusting the pH of the mixed solution.
In adjusting the pH, since the pH value of the mixed solution changes, particularly at the stage where the silicon compound-containing layer is formed on the surface of the metal particles (or via other coating layers), it is desirable to appropriately adjust the pH value so that the pH value can be maintained within a certain range. In this case, it is desirable to adjust the pH value by adding a hydrolysis catalyst, but the pH value may also be adjusted using other acidic or alkaline compounds as long as the properties of the metal pigment composition according to the present invention are not impaired.

When a basic hydrolysis catalyst is used as the hydrolysis catalyst, the pH value is preferably 7 to 11, and more preferably 7.5 to 10. A pH value of 7 or more allows the silicon compound-containing layer to be formed quickly. On the other hand, a pH value of 11 or less can suppress the aggregation of metal particles and the decrease in brilliance, and can prevent the generation of hydrogen gas due to corrosion.

When an acidic hydrolysis catalyst is used as the hydrolysis catalyst, the pH value is preferably 1.5 to 4, and more preferably 2 to 3. By setting the pH value to 1.5 or more, the reaction can be appropriately controlled, making it easier to obtain a metal pigment composition containing the desired composite particles. On the other hand, by setting the pH value to 4 or less, the deposition rate of the silicon compound-containing layer can be maintained high.

Regardless of whether the first or second method is used, the hydrolyzate and/or condensate of the organosilicon compound represented by the general formula (1) is preferably added in an amount of 0.01 to 50 parts by mass, more preferably 1 to 30 parts by mass, based on the state after the hydrolysis and condensation reaction is completed, based on 100 parts by mass of the metal particles (solid content). In addition, the hydrolyzate and/or condensate derived from the silane coupling agent represented by any of the general formulas (2) to (4) and/or their partial condensates is added in an amount of 0.01 to 0.8 parts by mass, more preferably 0.01 to 0.7 parts by mass, based on the state after the hydrolysis and condensation reaction is completed, based on 100 parts by mass of the metal particles (solid content).

The amount of hydrolyzate and/or condensate of the organosilicon compound represented by general formula (1) to be added can be calculated by multiplying the mass of the organosilicon compound represented by general formula (1) used in the production of the metal pigment composition by the mass ratio before and after the reaction when the organosilicon compound is completely hydrolyzed and undergoes a condensation reaction.

For example, when tetraethoxysilane (TEOS) is used as the organosilicon compound represented by general formula (1), the amount of hydrolyzate of the organosilicon compound and/or its condensate to be added can be calculated using the mass ratio before and after the hydrolysis and condensation reactions described below.
(Hydrolysis)
Si(OC ₂ H ₅ ) ₄ (molecular weight: 208) + 4H ₂ O
→ Si(OH) ₄ (molecular weight: 96) + (C ₂ H ₅ OH) ₄
(condensation)
Si(OH) ₄ (molecular weight: 96) + Si(OH) ₄ (molecular weight: 96)
→ (SiO ₂ ) ₂ (molecular weight: 60×2) + 4H ₂ O
The mass before and after the above hydrolysis and condensation reactions is 60/208 = 0.288 times, so for example, when 10 parts by mass of TEOS is used per 100 parts by mass of metal particles (solid content), the amount of the hydrolysate and/or condensate added will be 0.288 times that amount, or 2.88 parts by mass.

Similarly, the amount of hydrolyzate and/or condensate thereof of a silane coupling agent represented by any one of general formulas (2) to (4) added can be calculated by multiplying the mass of the silane coupling agent represented by any one of general formulas (2) to (4) and/or its partial condensate used in the production of the metal pigment composition by the mass ratio before and after the reaction when the silane coupling agent and/or its partial condensate are completely hydrolyzed and undergo a condensation reaction.

For example, when methyltrimethoxysilane is used as the silane coupling agent represented by the general formula (2), the amount of the hydrolysate of the silane coupling agent and/or its condensate to be added can be calculated using the mass ratio before and after the hydrolysis and condensation reactions described below.
(Hydrolysis)
_CH3Si ( _OCH3 ) ₃ (molecular weight: 136) + _3H2O
→ CH ₃ Si(OH) ₃ (molecular weight: 94) + (CH ₃ OH) ₃
(condensation)
_CH3Si (OH) ₃ (molecular weight: 94) + _CH3Si (OH) ₃ (molecular weight: 94)
→ (SiCH ₃ O _1.5 ) ₂ (molecular weight: 67×2) + 3H ₂ O
The mass before and after the above hydrolysis/condensation reaction is 67/136 = 0.49 times. Therefore, for example, if 1.23 parts by mass of methyltrimethoxysilane is used per 100 parts by mass of metal particles (solid content), the amount of the hydrolyzate and/or condensate added will be 0.49 times that amount, or 0.60 parts by mass.

In addition, whether the first method or the second method is adopted, it is preferable to thoroughly disperse the metal particles in water, a hydrophilic organic solvent, or a mixed solvent thereof before combining with the organosilicon compound that is the silicon compound source (or, in the case of forming another coating layer, typically before combining with the molybdenum compound). In this pre-dispersion (initial dispersion), preferably, a part of the dispersion liquid (for example, 0.5 to 30 mass %, preferably 1 to 20 mass %, more preferably 1 to 15 mass % of the total dispersion liquid per minute) is once withdrawn outside the dispersion tank and then returned to the dispersion tank by performing external circulation, thereby further increasing the degree of dispersion. Dispersibility can be further increased by performing ultrasonic treatment outside the dispersion tank midway through the external circulation flow path.

The ultrasonic treatment is not particularly limited, but can be carried out for usually 20 seconds to 10 minutes, preferably 30 seconds to 5 minutes, at usually 10 to 1000 W, preferably 50 to 800 W. The amount of the solvent used for this pre-dispersion may be usually about 100 to 10,000 parts by mass, preferably 200 to 5,000 parts by mass, and more preferably 300 to 1,000 parts by mass, per 100 parts by mass of the metal particles (solid content), from the viewpoint of obtaining sufficient dispersion by appropriately adjusting the intensity of stirring.
Such pre-dispersion of metal particles can be carried out usually at 10 to 80° C., preferably 15 to 60° C., and most preferably at about room temperature (about 20 to 40° C.) The pre-dispersion of metal particles can be carried out for 5 minutes to 10 hours, preferably 10 minutes to 5 hours (including ultrasonic treatment if performed).

As described above, the other coating layer is preferably formed between the metal particles and the silicon compound-containing layer (if any). Therefore, the layer structure of "metal particles/other coating layer/silicon compound-containing layer" can be preferably adopted.
The other coating layer is not particularly limited, but may be a molybdenum-containing coating, a phosphate compound coating, etc. A preferred example of a molybdenum-containing material constituting the molybdenum-containing coating is the mixed coordination heteropolyanion compound disclosed in JP 2019-151678 A. Examples of the components of the other coating layers, including the mixed coordination heteropolyanion compound, are as described above.
Hereinafter, an embodiment in which a molybdenum-containing coating is formed as another coating layer between metal particles and a silicon compound-containing layer will be described as an example.

When a molybdenum-containing coating is formed as another coating layer between the metal particles and the silicon compound-containing layer, the molybdenum-containing coating can be formed on the surface of the metal particles by stirring a mixed liquid containing the metal particles and a molybdenum compound (typically a mixed coordination type heteropolyanion compound) prior to the formation of the silicon compound-containing layer.
The method for forming a molybdenum-containing coating on the surface of metal particles is not particularly limited, and any method can be used as long as it can uniformly stir a mixture containing metal particles and a molybdenum compound in an aqueous solvent. For example, a molybdenum-containing coating can be formed on the surface of metal particles by stirring or kneading a mixture containing metal particles and a molybdenum compound in a slurry or paste state. In the mixture, the molybdenum compound may be dissolved or dispersed.

The agitator for agitating the mixture containing the metal particles and the molybdenum compound is not particularly limited, and any known agitator capable of efficiently and uniformly agitating the mixture containing the aluminum particles and the molybdenum compound can be used. Specific examples include kneaders, mixers, rotary vessel agitators, agitation reaction tanks, V-type agitators, double cone agitators, screw mixers, sigma mixers, flash mixers, airflow agitators, ball mills, edge runners, etc. Examples of the agitator blades include, but are not limited to, anchor blades, paddle blades, propeller blades, turbine blades, etc.

When forming a molybdenum-containing coating as the other coating layer, the amount of the molybdenum compound used can be appropriately set depending on the type of molybdenum compound used. This amount is generally 0.02 to 20 parts by mass per 100 parts by mass of metal particles (solid content), and is preferably 0.1 to 10 parts by mass. By setting the content to 0.02 parts by mass or more, a sufficient treatment effect can be obtained. Furthermore, by setting the content to 20 parts by mass or less, the brilliance of the resulting metal pigment composition can be maintained at a high level.

The solvent used to mix the metal particles and the molybdenum compound is usually water, a hydrophilic organic solvent, or a mixture of these.

Examples of hydrophilic organic solvents include alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol; ether alcohols and esters thereof such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. These can be used alone or in combination of two or more.

The amount of solvent used in the other coating layer formation process (excluding the amount of solvent used when pre-dispersing metal particles) is not particularly limited, but is usually preferably 50 to 5,000 parts by mass, and more preferably 100 to 2,000 parts by mass, per 100 parts by mass of metal particles (solid content). By using 50 parts by mass or more of solvent, uneven distribution of molybdenum compounds and aggregation of metal particles can be suppressed. Also, by using 5,000 parts by mass or less of solvent, a sufficient treatment effect of the molybdenum compound on the metal particles can be obtained.

The temperature of the mixed liquid containing the metal particles and the molybdenum compound when stirring is usually about 10 to 80°C, and preferably 30 to 70°C. By keeping this temperature at 10°C or higher, the reaction time required to obtain a sufficient treatment effect can be shortened. Also, by keeping this temperature at 80°C or lower, it becomes easier to control the reaction to obtain the desired metal pigment composition.

The stirring time of the mixed solution is not particularly limited as long as it is sufficient to form the desired molybdenum-containing coating. For example, this stirring time is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours. By setting the stirring time to 0.5 hours or more, a sufficient treatment effect can be obtained. Furthermore, by setting the stirring time to 10 hours or less, an increase in treatment costs can be suppressed.

After the stirring of the mixed solution containing the metal particles and the molybdenum compound is completed, the particles on which the other coating layer is formed can be collected. In this case, known washing, solid-liquid separation, etc. can be appropriately performed as necessary. For example, it is preferable to wash the mixed solution using a hydrophilic organic solvent, and then filter it using a filter or the like to remove water and unreacted substances from the cake containing the metal particles with the molybdenum-containing coating. In this way, the molybdenum-containing coating, which is the other coating layer, can be formed. When other coating layers are formed, they can also be formed in accordance with the above method.

In the embodiment in which a silicon compound-containing layer is formed on metal particles after the other coating layer (molybdenum-containing coating), after stirring of the mixture containing the metal particles and the molybdenum compound is completed, a dispersion of a silicon compound source (typically an organosilicon compound represented by the above formula (1), such as tetraalkoxysilane and/or its condensate, and at least one silane coupling agent represented by any one of the above formulas (2) to (4)) in water and/or a hydrophilic organic solvent may be directly added and stirred into the system without recovering the particles on which the other coating layer is formed. In this case, a dispersion of an organosilicon compound represented by the above formula (1), such as tetraalkoxysilane and/or its condensate, may be added to the system containing the particles on which the other coating layer is formed, and then a dispersion of at least one silane coupling agent represented by any one of the above formulas (2) to (4) may be added and stirred (see the second method in the above "Silicon compound-containing layer formation process").

Stirring conditions In the production of the metal pigment composition of the present invention, it is necessary to carry out at least the step of forming the coating layer of the composite particle, typically the step of forming the silicon compound-containing layer, under stirring. In addition, in the production of the metal pigment composition of the present invention, it is preferable to carry out not only the step of forming the silicon compound-containing layer, but also the step of forming other coating layers under stirring. In the embodiment in which the above-mentioned metal particles are pre-dispersed, it is more preferable to carry out this step under stirring. In addition, in the production of the metal pigment composition of the present invention, it is even more preferable to carry out all steps, including the pre-dispersion of the metal particles, the step of forming other coating layers, and the step of forming the silicon compound-containing layer, under stirring.

In the manufacture of the metal pigment composition of the present invention, at least the process of forming the coating layer of the composite particle, typically the silicon compound-containing layer, is carried out under appropriately controlled stirring, so that it is possible to effectively suppress or prevent the phenomenon that the composite particles adhere to each other through the silicon compound-containing layer, or that the aggregate particles of metal particles are covered with the silicon compound-containing layer.In addition, by carrying out all steps under stirring, including the pre-dispersion of metal particles, the process of forming other coating layers, and the process of forming the silicon compound-containing layer (until the time when all layers to be formed on the metal particle surface are formed), it is possible to more easily obtain the metal pigment composition of the present invention that satisfies all of the above physical property requirements.
The following explanation of the stirring conditions can be applied to any step in the production of the metal pigment composition according to the present invention.

The stirring can be carried out by using a known or commercially available stirring device, for example, at least one of a kneader, a kneading machine, a rotary vessel stirrer, a stirred reaction tank, a V-type stirrer, a double cone stirrer, a screw mixer, a sigma mixer, a flash mixer, an airflow stirrer, a ball mill, an edge runner, and the like can be used.
Among these agitators, it is preferable to use an agitation tank type device that uses an impeller for agitation. The impeller exerts a circulation effect for fluidizing the entire reaction system including the liquid phase as well as a pressure shear effect, so that the formation of agglomerates of composite particles can be more effectively suppressed.

The shape of the impeller is not particularly limited, and for example, anchor type, propeller type, turbine type, tilted turbine type, fan turbine type, paddle type, tilted paddle type, and gate type can be used. Max Blend impeller (manufactured by Sumitomo Heavy Industries Process Equipment Co., Ltd.) and Full Zone impeller (manufactured by Kobelco Eco-Solutions Co., Ltd.) are also suitable. In addition, impellers of these shapes can be combined in multiple stages.
The stirring speed is preferably set to such a level that the stirring blades are not exposed due to vortexes generated by stirring. In order to suppress vortexes generated by stirring, a cylindrical tank, a square tank, or a tank equipped with a baffle plate can be suitably used.

In the manufacture of the metal pigment composition containing the composite particles according to the present invention, it is desirable to set the optimal size of the stirring vessel, the stirring blade, and the stirring blade speed in relation to the amount of the mixed liquid and the physical properties (density, viscosity, etc.). The size of the stirring vessel should be selected so that the maximum amount of the mixed liquid used in the series of processes is 20 to 80% of the stirring vessel. In the case of a cylindrical stirring vessel, the ratio of the height (L) of the stirring vessel to the inner diameter (D) is generally set to a range of 0.5 to 3.0, and is usually set to a range of 1 to 2. In addition, the size of the stirring blade is generally set so that the maximum diameter is set to a range of 0.2 to 0.9 of the inner diameter of the stirring vessel, and it is preferable to set it to about 0.4 to 0.6. It is desirable to appropriately select the shape (including the length) of the stirring blade depending on the physical properties of the mixed liquid, and it is important that the entire stirring vessel is stirred throughout the entire process. In particular, it is preferable to combine inclined paddle type, inclined turbine type, and propeller type, which are prone to upstream and downstream flows, in multiple stages to prevent the formation of unstirred stagnation areas near the liquid surface or the bottom of the stirring vessel, or to use max blend blades or full zone blades. In this case, it is desirable to keep the distance between the stirring blades and the inner surface of the stirring vessel (including the baffle plate) at least 5 mm. This makes it easier to prevent damage and deformation of the metal particles.

The tip speed of the stirring blade is preferably 0.5 to 50 m/s, more preferably 1 to 20 m/s, and even more preferably 2 to 10 m/s. By having the tip speed of the stirring blade within the range of 0.5 to 50 m/s, the dispersibility of the composite particles in the resulting metal pigment composition can be increased, and it becomes easier to obtain a metal pigment composition in which the individual particles have low agglomeration, excellent hiding power, color tone, and little gas generation. In addition, by having the linear stirring speed within the above range, damage to the metal particles (e.g., scaly aluminum powder) can be prevented, and the rate of the hydrolysis/condensation reaction can be appropriately controlled, effectively suppressing the aggregation of the composite particles.

Composite Particle Recovery Process After the process of forming the silicon compound-containing layer (and optionally other coating layers) on the metal particles is completed, the obtained composite particles can be recovered. In the recovery, known treatments such as washing and solid-liquid separation can be carried out as necessary. For example, it is preferable to wash the dispersion with an organic solvent and then filter it using a filter to remove water and unreacted materials from the cake containing the composite particles. In addition, the cake containing the composite particles may then be heat-treated at a temperature in the range of, for example, 100 to 500°C as necessary. The composite particles thus recovered may constitute a metal pigment composition that usually contains a trace amount of water/hydrophilic solvent-containing solvent used in the manufacturing process.

3. Metal Pigment Composition The metal pigment composition of the present invention obtained as described above can be considered to be a metal pigment composition that contains composite particles including metal particles and one or more coating layers on the surfaces of the metal particles, and also contains a solvent such as water/hydrophilic solvent used in the production process as the residual solid content (non-volatile content).
The metal pigment composition may typically contain 0.02 to 50 parts by mass of a silicon compound which is a hydrolysate and/or condensate of an organosilicon compound (for example, at least one organosilicon compound represented by the above general formula (1), at least one silane coupling agent represented by any of the above general formulas (2), (3) and (4), and at least one partial condensate thereof) per 100 parts by mass of the metal particles, calculated as the state after the hydrolysis/condensation reaction is completed.

The metal pigment composition may contain 0.01 to 10 parts by weight of a compound forming an optional other coating layer (in the optional embodiment in which a molybdenum-containing coating is formed as the other coating layer, a molybdenum-containing compound, for example a mixed coordination heteropolyanion compound) per 100 parts by weight of the metal particles.
The optional organic oligomer or polymer may be present in the metal pigment composition in an amount of from 0.01 to 50 parts by weight per 100 parts by weight of the metal particles.
The metal pigment composition may contain at least one member selected from the group consisting of optional inorganic phosphoric acids and their salts, and acidic organic (or hypo)phosphates and their salts, in an amount of 0.01 to 20 parts by weight per 100 parts by weight of the metal particles.
The metal pigment composition may contain a solvent containing water/hydrophilic solvent used in the manufacturing process as a remainder of the above components (non-volatile content). The amount of the solvent containing water/hydrophilic solvent may be, for example, 0.5 to 95% by mass of the metal pigment composition. Alternatively, the amount of the solvent containing water/hydrophilic solvent may be 1 to 90% by mass, or 2 to 80% by mass, or 5 to 70% by mass of the metal pigment composition.

The metal pigment composition may optionally contain optional components other than those described above. Examples of the optional components include at least one of an antioxidant, a light stabilizer, a polymerization inhibitor, and a surfactant.
As the antioxidant, phenol-based compounds, phosphorus-based compounds, and sulfur-based compounds can be used.
As the light stabilizer, those used as the antioxidants described above can be used, but representative ones such as benzotriazole-based compounds, benzophenone-based compounds, salicylate-based compounds, cyanoacrylate-based compounds, oxalic acid derivatives, hindered amine-based compounds (HALS), and hindered phenol-based compounds can also be used.

Examples of surfactants include nonionic surfactants such as polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, oxyalkylene alkylamino ethers, sorbitan fatty acid esters, polyalkylene glycol fatty acid esters, and glycerin fatty acid esters; anionic surfactants such as sulfate ester salts, sulfonate salts, and phosphate ester salts; and cationic surfactants such as quaternary ammonium salts. One or more of these surfactants can be used. Particularly preferred examples of these surfactants include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, or mixtures thereof.

4. Packaging Container The packaging container of the present invention is used to pack a metal pigment composition, and has one or more protective layers selected from a) and b) formed on the portion that comes into contact with the metal pigment composition.
a) A protective layer having a thickness of 1 to 200 μm, which is formed from a resin containing at least one selected from the group consisting of a glycidyl ether type epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, a cyclic oxirane type epoxy resin, a novolac phenolic resin, a resol type phenolic resin, a polyester resin, and an epoxy resin heat-cured with a phenolic resin.
b) A protective layer formed from a metal phosphate and having a weight per unit area of 0.1 g/m ² to 10 g/m ² .

The base material of the packaging container of the present invention (the base portion protected by the protective layer) at least partially contains metal, and is more preferably formed substantially from metal. If the base material of the packaging container is metal, it has the advantages of being resistant to impact, less susceptible to leakage and contact with the outside air during transportation, and the internal temperature changes during storage are gradual. The packaging container of the present invention also includes a case in which the main components such as the base material are made of metal, and a part such as the seal part of the lid (accessories other than the base material and its protective layer, etc.) is made of a resin other than metal.
The metal constituting the substrate is preferably iron, stainless steel, or aluminum, more preferably iron or stainless steel, and even more preferably iron.
The thickness of the substrate is not particularly limited, but may be generally about 500 μm to 50 mm, and more typically about 800 μm to 20 mm. The thickness of the substrate is preferably generally constant throughout, but may be thicker at the top, bottom, or surrounding areas thereof than at other locations.

In the package of the present invention, if a protective layer as described above is formed on the portion of the packaging container that comes into contact with the metal pigment composition, the aggregation and color change of the composite particles contained in the metal pigment composition in the package can be further suppressed.

The epoxy resins in a) are not particularly limited, but examples thereof include glycidyl ether types such as bisphenol A type, bisphenol F type, hydrogenated bisphenol A type, and phenol novolac type, glycidyl ester types such as hexahydrophthalic acid glycidyl ester and glycidyl methacrylate copolymer, glycidyl amine types such as tetraglycidyldiaminodiphenylmethane, and cyclic oxirane types such as 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate. These may be used alone or in combination of two or more. These epoxy resins are used as paints in a commonly known manner, such as by being modified with fatty acids to cure at room temperature, by being heat cured using a curing agent such as melamine resin or amine, or by being made into a powder paint or emulsified to make a cationic electrodeposition type.

The phenolic resin is not particularly limited, but examples thereof include novolac phenolic resin and resol type phenolic resin. These phenolic resins are used as paints by curing with an amine-based curing agent or by curing with heat. These resins may be used alone or in combination of two or more types.

The resin containing an epoxy resin and a phenol resin is not particularly limited, but may be, for example, a resin obtained by heat curing using a phenol resin as a curing agent for the epoxy resin. The resin is used as it is as a coating material.
The polyester resin is not particularly limited, but examples thereof include polyethylene terephthalate resin, polyethylene isophthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, and copolymerized resins thereof. These polyester resins may be used in the form of a film laminated on a metal, or may be used as a powder coating. These may be used alone or in combination of two or more.

More preferably, the resin contains an epoxy resin, and even more preferably, a phenolic resin.

The resin layer a) has a coating thickness of 1 μm to 200 μm. When the resin coating thickness is 1 μm or more, defects in the coating are easily prevented, and the coloring prevention effect tends to be more suitably exhibited. From the viewpoints of cost and productivity, it is preferable that the resin coating thickness is 100 μm or less. The resin coating thickness is more preferably 2 μm to 50 μm, and even more preferably 3 μm to 40 μm.
The film thickness here refers to the average value of thicknesses at any five points, including slight variations due to the actual application process, for example.

The metal phosphate of b) is preferably iron phosphate or zinc phosphate.
The layer formed from the metal phosphate of b) has a weight per area of 0.1 g/m ² to 10 g/m ^2. When the coating amount of the metal phosphate is 0.1 g/m ² or more, defects in the coating are easily prevented, and the coloring prevention effect tends to be more suitably exhibited. When the coating amount of the metal phosphate is 10 g/m ² or less, it is preferable from the viewpoint of cost and productivity. The coating amount of the metal phosphate is more preferably 0.2 to 7 g/m ² , and even more preferably 0.3 to 5 g/m ² .

The protective layer may be one or more types selected from a) and b), and a) and b) may be used in combination. In the case of combination, it is preferable that b) contacts the base material of the packaging container (typically made of metal) and a layer of the resin of a) is formed thereon.
The resin layer of a) can be formed, for example, by applying various solvent-based resin coating agents to a metal plate, drying the applied resin, and baking the applied resin at a predetermined temperature for a predetermined time (for example, for epoxy phenol resin, at 210° C. for 10 minutes). When a pail can is used as a packaging container, the metal plate on which the resin layer is formed can be molded to obtain a pail can.

In the package of the present invention, it is preferable that the packaging container is sealable. If the packaging container is sealable, the aggregation of the metal pigment in the package and the progression of color changes can be further suppressed. Usually, the package is sealed when the metal pigment composition is stored or transported for a long period of time, for example, for one hour or more or one day or more.

The shape of the packaging container of the present invention is not particularly limited, but may be, for example, a roughly rectangular prism or a roughly cylindrical shape, and is preferably a roughly cylindrical shape. Among the roughly cylindrical shapes, the packaging container is preferably one called a pail or drum. When the packaging container is a pail or drum, it has the characteristic of being a general container that is convenient in terms of logistics and space saving during storage, and easy to take in and out of a warehouse, while still allowing the contents to be stably stored.

(Moisture percentage)
The moisture content of the metal pigment composition in the package of the present invention is preferably 0 ppm or more and 2000 ppm or less (by mass) relative to the metal pigment composition. By setting the moisture content at such a level, the aggregation of the composite particles of the metal pigment composition in the package and the progression of color tone changes can be further suppressed. The moisture content is more preferably 1000 ppm or less, even more preferably 500 ppm or less, and particularly preferably 300 ppm or less. There is no lower limit for the moisture content, and the lower the better.

In order to achieve such a moisture content, in the process of producing the metal pigment composition, after the process of forming a silicon compound-containing layer (and/or other optional coating layers) on the metal particles is completed, known processes such as washing and solid-liquid separation are performed. In this case, for example, it is preferable to wash the dispersion using an organic solvent with a moisture content of 2000 ppm or less, and then filter it using a filter, and in some cases to repeat this operation multiple times to remove water and unreacted substances from the composition containing the composite particles. In addition, if necessary, the cake containing the composite particles may then be subjected to a heat dehydration treatment at a temperature in the range of, for example, 100 to 500°C in a gas atmosphere with a low moisture content, such as nitrogen. The composite particles thus recovered may, as described above, generally constitute a metal pigment composition that is accompanied by a small amount of solvent, including water/hydrophilic solvent, used in the production process.

Also, when adjusting the solid content of the composition, it is desirable to use an organic solvent (such as the above-mentioned hydrophilic solvent) having a moisture content of 2000 ppm or less.
The moisture content of the organic solvent used for washing or adjusting the solid content is preferably 2000 ppm or less, more preferably 1000 ppm or less, further preferably 500 ppm or less, and particularly preferably 300 ppm or less.

In addition, moisture may also be contained in the gas phase of the package. The moisture in the gas phase of the package originates from the moisture contained in the metal pigment composition packed in the packaging container, and from the moisture in the air in the volume of the packaging container other than the metal pigment composition. If there is a lot of moisture in the gas phase, the metal pigment composition will absorb this moisture and the moisture content will increase. For this reason, it is preferable to use dry air when putting the metal pigment composition into the packaging container. It is also a preferable method to replace the gas phase with dry air before closing the lid on the packaging container. When dry air is used when putting the metal pigment composition into the packaging container, or the gas phase is replaced with dry air before closing the lid on the packaging container and simultaneously sealed, the moisture content in the package is substantially equal to the moisture content in the metal pigment composition, and the moisture content in the metal pigment composition does not increase significantly during storage. The moisture content in the metal pigment composition can be measured by the method described later in the examples.

(pH)
The metal pigment composition in the package of the present invention preferably has a pH in the range of 5 to 9. By setting the pH in this range, it is possible to further suppress the aggregation of composite particles of the metal pigment composition in the package and the progression of color change. The pH of the metal pigment composition is more preferably in the range of 6 to 8, and even more preferably in the range of 6.5 to 7.5.
In order to achieve such a pH for the metal pigment composition, after completing the process of forming a silicon compound-containing layer (and/or, optionally, other coating layers) on the metal particles, it is desirable to repeatedly carry out known processes such as washing with a sufficient amount of organic solvent and solid-liquid separation, thereby thoroughly washing away and removing polar compounds such as catalysts used when forming the coating layer.

(residue)
When the package of the present invention is stored in a sealed indoor warehouse at 20° C. for one year, the residue of the metal pigment composition after storage is preferably 0.05% by weight or less (based on the total weight of the metal pigment composition at that time). In addition, even when the package of the present invention is stored in a sealed indoor warehouse at 20±10° C., preferably 20±20° C. for one year (i.e., even when stored in an indoor warehouse at a constant temperature within this temperature range, or in an indoor warehouse at a temperature that is manually or naturally changed within this temperature range for one year), the residue of the metal pigment composition after storage is more preferably 0.05% by weight or less. By setting the residual amount of the metal pigment composition to such an amount, it becomes easy to obtain a paint that can form a good coating film without bumps. The residual amount of the metal pigment composition is affected by the coating state of the metal particles in the composite particles, the moisture content in the metal pigment composition, etc., so by setting the coating that satisfies the above-mentioned specified requirements and the moisture content in the package within a specified range, it becomes easy to control the residual amount to the above-mentioned amount. The amount of residue is more preferably 0.02% by weight or less, and even more preferably 0.01% by weight or less.
The term "residue" used herein refers to the residue obtained by the measurement method described in the Examples below.

In addition, when the package of the present invention is stored in a sealed state in a heating chamber at 60°C for three months, the residue of the metal pigment composition after storage is preferably 0.05% by weight or less. In addition, when the package of the present invention is stored in a sealed state in a heating chamber at 60°C ± 10°C for three months (i.e., when stored in a heating chamber at a constant temperature within this temperature range or in a heating chamber at a temperature manually changed appropriately within this temperature range for three months), the residue of the metal pigment composition after storage is preferably 0.05% by weight or less. By setting the residual amount of the metal pigment composition to such an amount, it becomes easy to obtain a paint that can form a good coating film without bumps. The residual amount of the metal pigment composition is affected by the coating state of the metal particles in the composite particles, the moisture content in the metal pigment composition, etc., so by setting the coating that satisfies the above-mentioned specified requirements and the moisture content of the metal pigment composition in the package within a specified range, it becomes easy to control the residual amount to the above-mentioned amount. The amount of residue is preferably 0.02% by weight or less, and even more preferably 0.01% by weight or less.

(Storage and transportation methods)
The preservation method of the present invention is a method for preserving a metal pigment composition using the above-mentioned packaging material.
In the storage method of the present invention, the temperature inside the packaging container during storage of the metal pigment composition is preferably 0 to 50°C, more preferably 10 to 40°C, and even more preferably 15 to 25°C.

In one embodiment of the storage method, the metal pigment composition is preferably stored for 5 years or less, more preferably 2 years or less, and even more preferably 1 year or less.

In one embodiment of the preservation method, the warehouse in which the product is stored is preferably one that can be controlled to a range of 0 to 50°C or 10 to 40°C, and more preferably a constant temperature warehouse that can be controlled to a range of 15 to 25°C. It is preferable that the temperature of the warehouse can be controlled to a constant temperature throughout the entire storage period.

The transportation method of the present invention is a method for transporting a metal pigment composition using the above-mentioned package.
In one embodiment of the transportation method, the temperature inside the packaging container when transporting the metal pigment composition is preferably 0 to 50°C, more preferably 10 to 40°C, and even more preferably 15 to 25°C.

In one embodiment of the transportation method, the container or cargo space to be transported is preferably capable of being controlled within a range of 0 to 50°C or 10 to 40°C, and more preferably is a constant-temperature container or cargo space that can be controlled within a range of 15 to 25°C. It is preferable that the temperature of the warehouse can be controlled to a constant temperature throughout the entire transportation period.

In addition, whether in storage or transportation, it is advisable to keep the package out of direct sunlight. This is to prevent the possibility of the temperature of parts of the package increasing due to exposure to direct sunlight.

Next, the present invention will be specifically described with reference to examples and comparative examples.
The following examples are provided to illustrate the present invention and are not intended to limit the scope of the invention in any way.

Reference Example 1 Metal Pigment Composition In a 0.75 ^m2 reaction tank with a diameter of 0.8 m and a paddle-type stirring blade with a blade diameter of 0.5 m, 67 kg of commercially available aluminum paste (manufactured by Asahi Kasei Corporation, product name "GX-3100 (average particle size 11 μm, volatile content 74%)") was added 230 kg of methoxypropanol (hereinafter abbreviated as "PM"), and the mixture was stirred at 100 rpm with the stirring blade. At the same time, 10 L/min of the dispersion liquid withdrawn from the bottom was externally circulated from the top of the reaction tank to return to the reaction tank, and the aluminum paste was uniformly dispersed in the PM.
Next, a solution of 0.5 kg of tungstomolybdic acid hydrate (H ₃ PW ₆ Mo ₆ O ₄₀ ) dissolved in 2.5 kg of methoxypropanol was gradually added, and the slurry was stirred for 1 hour while maintaining the temperature at 40°C.
After that, 5 kg of tetraethoxysilane was added as an organic silicon compound, and then 5 kg of 25% ammonia water and 100 kg of purified water were added over 3 hours. Then, 0.7 kg of methyltrimethoxysilane was added as a silane coupling agent, and the mixture was stirred for 2 hours. After the reaction was completed, the mixture was cooled and the slurry was filtered.
The filtered slurry was washed five times (i.e. thoroughly) with PM having a moisture content of 200 ppm to reduce the moisture content, and the raw materials and catalysts used in forming the coating layer were thoroughly removed, and the slurry was again pressure filtered to obtain an aluminum pigment composition having a non-volatile content of 60%. Here, dry air with a dew point of -40°C was used when handling the slurry, such as during pressure filtration.

Reference Example 2 Metal Pigment Composition The same procedure as in Reference Example 1 was carried out except that an aluminum paste (manufactured by Asahi Kasei Corporation, product name "FD-5090 (average particle size 9 μm, volatile content 7%)") was used, to obtain an aluminum pigment composition with a non-volatile content of 60%.

[Example 1]
A steel pail can (20-liter straight pail can, manufactured by Shinbo Kogyo Co., Ltd.) with a capacity of 20 liters was prepared as a packaging container for packaging the metal pigment composition. A layer of epoxy phenol resin (Daitron #5301, manufactured by Dai Nippon Toryo Co., Ltd.) with an average thickness of 7 μm was formed on the portion of the packaging container that was in contact with the metal pigment composition. The epoxy phenol resin was applied as a coating agent made by mixing 20 mass % epoxy resin, 30 mass % phenol resin, and 50 mass % solvent, and after the solvent was evaporated at room temperature, the coating was baked at 210°C for 10 minutes to form a resin layer. 15 kg of the metal pigment composition prepared in Reference Example 1 was charged into the packaging container and sealed to obtain a package. At this time, the gas phase of the pail can was filled with the same dry air (dew point: -40°C) as used in Reference Example. The "average thickness" of the protective layer here refers to the average thickness of any five points.

[Comparative Example 1]
A package was obtained in the same manner as in Example 1, except that an untreated steel pail can in which no resin-containing layer was formed on the part that would come into contact with the metal pigment composition was used as a packaging container for packaging the metal pigment composition.

[Example 2]
A package was obtained in the same manner as in Example 1, except that the metal pigment composition prepared in Reference Example 2 was used.

[Comparative Example 2]
A package was obtained in the same manner as in Comparative Example 1, except that the metal pigment composition prepared in Reference Example 2 was used.

[Example 3]
A package was obtained in the same manner as in Example 1, except that a packaging container having an epoxy phenol resin layer with an average thickness of 50 μm was used.

[Example 4]
A package was obtained in the same manner as in Example 1, except that a packaging container having an epoxy phenol resin layer with an average thickness of 3 μm was used.

[Example 5]
A package was obtained in the same manner as in Example 1, except that PM with a moisture content of 2000 ppm was used to wash the filtered slurry.

[ Comparative Example 3 ]
A package was obtained in the same manner as in Example 1, except that the number of times the filtered slurry was washed was reduced to one time.

[Comparative Example 4 ]
A package was obtained in the same manner as in Example 5, except that an untreated steel pail can in which no resin-containing layer was formed on the part that would come into contact with the metal pigment composition was used as a packaging container for packaging the metal pigment composition.

[Example 6 ]
A package was obtained in the same manner as in Example 1, except that a 20-liter steel pail (special pail PS-20, manufactured by Shinbo Kogyo Co., Ltd.) on which a polyethylene resin layer having an average thickness of 100 μm was formed was used. The polyethylene resin layer was formed by blow molding and heat-sealed to the inner surface of the metal can.

[Example 7 ]
A package was obtained in the same manner as in Example 1, except that 10 kg of the metal pigment composition was charged into a 13-liter steel pail (13-liter white pail, manufactured by Takamura Shokai Co., Ltd.) having an epoxy resin layer with an average thickness of 7 μm.

[Comparative Example 5 ]
A package was obtained in the same manner as in Example 5, except that a steel pail can in which a layer of epoxy phenolic resin having an average thickness of 0.5 μm was formed on the portion in contact with the metal pigment composition was used as a packaging container for packaging the metal pigment composition.

[Example 8 ]
A package was obtained in the same manner as in Example 1, except that 150 kg of the metal pigment composition was charged into a 200-liter steel drum (open-head drum, manufactured by JFE Container) on which a 3 g/ ^m2 layer of iron phosphate had been formed.

[Example 9 ]
A package was obtained in the same manner as in Example 1, except that 150 kg of the metal pigment composition was placed in a steel drum (manufactured by JFE Container) on which a 3 g/ ^m2 layer of zinc phosphate had been formed.

(Evaluation of Metal Pigment Compositions)
(Average particle diameter: _D50 )
The average particle size (D ₅₀ ) of the composite particles in the metal pigment composition was measured using a laser diffraction/scattering type particle size distribution measuring device (LA-300/manufactured by Horiba, Ltd.).
Isopropanol was used as the measurement solvent.
The measurement was carried out according to the instruction manual of the instrument, but it should be noted that the composite particles to be used as samples were subjected to ultrasonic dispersion for 2 minutes as a pretreatment, then the particles were placed in a dispersion tank, and the measurement was started after confirming that the particles were dispersed to an appropriate concentration. After the measurement was completed, the _D50 was calculated by the instrument software and automatically displayed.

(Moisture percentage)
The moisture content in the metal pigment composition was measured by the Karl Fischer method in accordance with JIS K 0068.

(pH)
The pH of the metal pigment composition was measured at a temperature of 25° C. using a glass electrode type pH measuring device (PH METER F-15, manufactured by Horiba, Ltd.).

(Residual ratio of metal pigment composition after storage in package)
The packages of the metal pigment compositions obtained in each of the above Examples/Comparative Examples were stored for one year in a storage facility at 20±10°C (a temperature that naturally fluctuated due to the influence of the atmosphere surrounding the storage facility), and then 50 g of the metal pigment composition removed from the packages was dispersed in 1,000 ml of mineral spirits with a spatula, filtered through a 200 mesh nylon net (manufactured by NBC). The residue was thoroughly washed with acetone and dried at 105°C for 10 minutes. The mass was then measured, and this was used to calculate the mass of the residue and its proportion.

(Evaluation of coating film obtained from metal pigment composition before and after storage in package)
Before storage of the packages of the metal pigment compositions obtained in each of the above Examples and Comparative Examples, and after storing the packages for one year in a storage facility at 20±10°C (a temperature that naturally fluctuates due to the influence of the atmosphere surrounding the storage facility), water-based metallic paints were prepared using the metal pigment compositions removed from the packages with the following composition, and the paints and the coating films obtained from them were evaluated using the methods described below.
<Composition of water-based metallic paint>
Metal pigment composition: 12.0 g as non-volatile content
Methoxypropanol: 18.0 g
Polyoxyethylene lauryl ether (nonionic surfactant, Matsumoto Yushi Seiyaku Co., Ltd., product name "Marpon L5"): 6.0 g
・Purified water: 12.0g
- Water-soluble acrylic resin (※1): 110.0g
・Melamine resin (※2): 18.0g
*1: Alumatex WA911, manufactured by Mitsui Chemicals, Inc.
*2: Cymel 350, manufactured by Japan Cytec Industries Co., Ltd.
After mixing the above components, the pH was adjusted to 7.7 to 7.8 with dimethylethanolamine, and the viscosity was adjusted to 650 to 750 mPa·s (B-type viscometer, No. 3 rotor, 60 rpm, 2° C.) with a carboxylic acid-based thickener and purified water.

(Coating film evaluation)
The water-based metallic paint prepared according to the above formula was air spray painted onto a 12 cm x 6 cm steel plate (manufactured by Miki Coating Co., Ltd.) that had been coated with an undercoat paint so that the dry film thickness would be 6 μm, and after pre-drying at 90°C for 10 minutes, an organic solvent-based top coat paint having the following composition was dispersed with a spatula for 3 minutes, and then the paint viscosity was adjusted to 20.0 seconds using a Ford cup No. 4. The paint was air spray painted onto the plate so that the dry film thickness would be 20 μm, and the plate was dried at 140°C for 30 minutes to prepare a coated plate, which was then subjected to the following evaluations.
(Composition of organic solvent-based top coat paint)
Acrydic 44-179 (DIC Corporation, acrylic clear resin) 141g
・Super Beckamin J-820 (DIC, melamine resin) 35.3g
123.5g toluene

(Paint film)
The number of bumps on the entire surface of the topcoat film of the resulting coated plate was counted and evaluated according to the following criteria.
O: The item was not visible.
△: There were 10 or less lump.
×: There were more than 10 items.

(brightness)
The resulting coated panels were evaluated using a laser metallic feel measuring device Alcove LMR-200 manufactured by Kansai Paint Co., Ltd. The optical conditions were a laser light source with an incident angle of 45 degrees, and light receivers at receiving angles of 0 degrees and -35 degrees. The measured value was the IV value at a receiving angle of -35 degrees where the maximum light intensity was obtained from the reflected light of the laser, excluding the light in the specular reflection region reflected by the coating surface. The IV value is a parameter proportional to the intensity of the specularly reflected light from the coating, and represents the magnitude of the light brightness.
The obtained IV values were evaluated based on the following criteria.
◯: The decrease from the standard (before storage) was less than 20.
Δ: The decrease from the standard (before storage) was 20 or more and less than 40.
×: The decrease from the standard (before storage) was 40 or more.

(Concealment)
The prepared water-based metallic paint was applied to a polyethylene terephthalate sheet (PET sheet) using a 2 mil applicator so as to give a dry film thickness of 15 μm, and the coating film was dried at 140° C. for 30 minutes and visually evaluated.
○: The value was equal to or slightly lower than the standard (before storage).
△: Lower than the standard (before storage).
×: Significantly lower than the standard (before storage).

(Average thickness of composite particles, average thickness of coating layer)
In order to facilitate measurement of particle thickness, etc., the above water-based metallic paint was prepared under the same conditions as those used in the above "Coating Film Evaluation", except that the amount of metal pigment composition in the paint formulation used in the above "Coating Film Evaluation" was reduced to 1/10, using the metal pigment composition removed from the packaging before storage. Coated panels were then prepared under the conditions described in the above "Coating Film Evaluation".
The above coated plate was cut into 1 cm square pieces using a shearing machine.
The cross section of the obtained coating film was subjected to ion milling treatment using an ion milling device (IB-09010CP manufactured by JEOL Ltd.) set so as to be able to irradiate the ion beam up to a portion 20 μm away from the cross section of the coating film, and a precision-polished cross section sample was prepared by ion milling treatment.
The cross section of the resulting coating film (coated plate) was observed with an FE-SEM (S-4700, manufactured by HITACHI) to evaluate the thickness of the composite particles.
The conditions for FE-SEM observation and acquisition were such that the acceleration voltage was adjusted to 5.0 kV and the image magnification was 10,000 times.
Using the obtained FE-SEM image (10,000 times magnification), the thickness of 100 random particles in the cross section of the composite particle was measured using image analysis software Win Roof version 5.5 (manufactured by MITANI CORPORATION), and the average thickness was calculated. The thickness uniformity of the composite particle is high, and the difference in thickness due to the cut part of the particle is small. Therefore, the influence of the difference in the cut part of the particle on the average thickness measurement can be ignored.

For the coated plate prepared for obtaining the above FE-SEM image, an HR-STEM (high-resolution scanning transmission electron microscope, Hitachi S-5500) was used to adjust the acceleration voltage to 30 kV, obtain an image at a magnification of 200,000 times, and measure the thickness of the coating layer of the composite particle. If the surface of the coating layer is uneven, the area of the coating layer was measured using image analysis software Win Roof version 5.5, and the thickness of the coating layer was determined by dividing it by the perimeter of the coated particle. Furthermore, if the particle is large, it is not necessary to measure the area of the entire coating layer. The thickness of the coating layer can be obtained with sufficient accuracy by measuring the area of the coating layer in an area of about 1 μm along the particle surface and dividing it by the particle surface length. Furthermore, since the thickness of the coating layer is almost uniform regardless of the particle, the average value was calculated for 10 particles.

[Example 10 ]
The package of the metal pigment composition obtained in Example 1 was stored for three months in a storage facility (heated room) at 60°C (at a substantially constant temperature, including temporary fluctuations within ±10°C), and then the metal pigment composition was removed from the package and evaluated in the same manner as in Example 1, except for the storage conditions.

The evaluation results are shown in Table 1. It was found that the packaging body according to the present invention, which satisfies all of the requirements of items (1) to (4) obtained in each example, can suppress the progression of aggregation and coloring of the metal pigment composition in the packaging body.

The package according to the present invention, the metal pigment composition contained in the package after being stored and transported by the storage and transport method of the present invention, and the coating film obtained using them have excellent coating film properties such as low VOC, storage stability when used in water-based paints, suppression of bumps, design, and concealment at a high level beyond the limits of conventional technology. Therefore, these metal pigment compositions and coating films can be suitably used in various applications where metal pigments have been used conventionally, such as paints, inks, and resin kneading agents, more specifically, in automobile bodies, automobile repair materials, automobile parts, home appliances, plastic parts, PCM paints, highly weather-resistant paints, heat-resistant paints, anticorrosive paints, paints for ship bottoms, offset printing inks, gravure printing inks, screen printing inks, etc. Alternatively, these metal pigment compositions and coating films have high applicability in various industrial fields, such as the transportation machinery industry for automobiles, the electrical and electronic industry for home appliances, the paint industry, and the printing industry.

Claims (9)

A package in which a metal pigment composition is packed in a packaging container, the metal pigment composition including composite particles having metal particles and one or more coating layers on the surfaces thereof, the metal particles being aluminum or an aluminum alloy, at least one of the coating layers being a silicon compound-containing layer, the pH of the metal pigment composition in the package being in the range of 6 to 7.5, and the package satisfying the following (1) to (4):
(1) The composite particles have a scale-like shape;
(2) The composite particles have a volume-based _D50 of 1 to 30 μm when the particle size distribution is measured using a laser diffraction particle size distribution analyzer;
(3) The average thickness of the composite particles is 20 to 400 nm;
(4) At least one type of protective layer selected from the following a) and b) is formed on a portion of a packaging container having a substrate containing at least a metal, the portion being in contact with the metal pigment composition:
a) a protective layer having a thickness of 1 to 200 μm, which is formed from a resin containing at least one selected from the group consisting of a glycidyl ether type epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, a cyclic oxirane type epoxy resin, a novolac phenolic resin, a resol type phenolic resin, a polyester resin, and an epoxy resin heat-cured with a phenolic resin;
b) A protective layer formed from a metal phosphate and having a weight per unit area of 0.1 g/m ² to 10 g/m ² . The package according to claim 1, wherein the moisture content of the metal pigment composition in the package is 0 to 1000 ppm relative to the mass of the metal pigment composition. The package according to claim 1 or 2, in which when the sealed package is stored in an indoor warehouse at 20°C for one year, the residue of the metal pigment composition after storage is 0.05% by weight or less. The package according to claim 1 or 2, in which when the sealed package is stored in a heated room at 60°C for three months, the residue of the metal pigment composition after storage is 0.05% by weight or less. A method for storing a metal pigment composition at 0 to 50°C using a package according to any one of claims 1 to 4. A method for transporting a metal pigment composition at 0 to 50°C using a package according to any one of claims 1 to 4. a step of forming a silicon compound-containing layer on the surface of the metal particles by subjecting the organosilicon compound to a hydrolysis/(partial) condensation reaction in a mixed liquid containing metal particles, a silicon-containing raw material containing at least one organosilicon compound, a solvent selected from the group consisting of water, a hydrophilic organic solvent, and a mixed solvent thereof , and, if necessary, other optional components, thereby obtaining a metal pigment composition containing composite particles having metal particles and one or more coating layers on the surface of the metal particles, the coating layers including the silicon compound-containing layer;
adjusting the pH of the metal pigment composition containing the composite particles to a range of 6 to 8; and
A step of packaging the metal pigment composition containing the composite particles in a packaging container so as to satisfy the following (1) to (4):
A method for packaging a metal pigment composition comprising:
(1) The composite particles have a scale-like shape;
(2) The composite particles have a volume-based _D50 of 1 to 30 μm when the particle size distribution is measured using a laser diffraction particle size distribution analyzer;
(3) The average thickness of the composite particles is 20 to 400 nm;
(4) At least one type of protective layer selected from the following a) and b) is formed on a portion of a packaging container having a substrate containing at least a metal, the portion being in contact with the metal pigment composition:
a) a protective layer having a thickness of 1 to 200 μm, which is formed from a resin containing at least one selected from the group consisting of a glycidyl ether type epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, a cyclic oxirane type epoxy resin, a novolac phenolic resin, a resol type phenolic resin, a polyester resin, and an epoxy resin heat-cured with a phenolic resin;
b) A protective layer formed from a metal phosphate and having a weight per unit area of 0.1 g/m ² to 10 g/m ² . The packaging method according to claim 7, wherein a basic or acidic hydrolysis catalyst is used as the hydrolysis catalyst in the step of forming a silicon compound-containing layer on the surface of the metal particles. The packaging method according to claim 7 or claim 8, wherein the metal particles are aluminum or an aluminum alloy.