CN119684825A

CN119684825A - Metallic pigment composition

Info

Publication number: CN119684825A
Application number: CN202411897180.8A
Authority: CN
Inventors: 藤本克宏; 直井千纱; 杉本笃俊
Original assignee: Asahi Kasei Corp
Current assignee: Asahi Kasei Corp
Priority date: 2021-03-26
Filing date: 2022-03-25
Publication date: 2025-03-25
Also published as: JP7642416B2; CN115124863A; CN115124863B; KR20220134457A; JP2022150635A

Abstract

The present invention relates to metallic pigment compositions. Provided is a novel metal pigment composition comprising composite particles having metal particles and 1 or more coating layers on the surfaces thereof, (1) the composite particles having a scaly shape, (2) the composite particles having a volume-based D ₅₀ of 3 [ mu ] m or more and 30 [ mu ] m or less when the particle size distribution of the composite particles is measured by a laser diffraction type particle size distribution meter, (3) the composite particles having an average thickness of 20nm or more and 300nm or less, (4) at least 1 layer of the coating layers being a silicon-containing compound layer, (5) the ratio of the metal element content based on the metal particles to the silicon content based on the coating layers in the composite particles being 0.02 or more and 0.3 or less in terms of the ratio of the silicon content to the metal element content, and (6) the number ratio of the composite particles having a particle size of 0.1 [ mu ] m or more and 1 [ mu ] m or less being 10% or less relative to the total number of the composite particles in the metal pigment composition.

Description

Metal pigment composition

The present application is a divisional application of application number 2022, 3 and 25, application number 202210305519. X, and entitled "metallic pigment composition".

Technical Field

The present invention relates to novel metallic pigment compositions containing composite particles. More specifically, the present invention relates to a novel composite particle-containing metallic pigment composition having excellent paint stability, storage stability, paint color tone (specifically, brightness, flip flop feel, hiding), and paint adhesion.

Background

Conventionally, metallic pigments have been used for metallic paints, printing inks, plastic kneading, and the like in order to obtain metallic cosmetic effects.

In recent years, in the paint field, as a countermeasure for saving resources and making it harmless, there has been an increasing necessity for conversion of aqueous paints with a small amount of organic solvent, but the types of aqueous paints that can be practically used for metallic paints containing metallic pigments have been insufficient. The reason for this is that metallic pigments are easily corroded in aqueous paints. When metal powder is present in the aqueous paint or the aqueous ink, corrosion due to water and hydrogen gas are generated in any one or more of the acidic, neutral and alkaline ranges depending on the properties of various metals. Particularly, the production process of paints and inks by paint manufacturers and ink manufacturers, and the painting process and printing process by automobiles, home appliance manufacturers, printing manufacturers and the like are extremely serious problems in terms of safety.

Since the corrosiveness of the metallic pigment is a problem in terms of storage stability, the corrosion resistance of the metallic pigment can be modified as storage stability.

Further, since the smoothness of the metal surface is lost by corrosion, it is unavoidable that the color tone (specifically, the brightness, the flop feeling, and the concealing property) of the coating film, which is the color tone when used as the coating film, is lowered. In addition, in recent years, there has been a demand for metallic paint which gives a finished product having high brightness due to a variety of color designs, and therefore, there has been a demand for a high effect (i.e., a property of changing brightness depending on an observation angle, and a parameter depending on an orientation degree of metallic pigment) as a color tone of a coating film.

In addition, when a metallic pigment is used as a coating material, the pigment is required to have a small aggregation property (specifically, aggregation property of each particle constituting the pigment), that is, coating stability.

In addition, when forming a coating film by converting a metallic pigment paint, it is required that the adhesion to a substrate, that is, paint adhesion, is not reduced.

Patent document 1 (pamphlet of international publication No. 2020/21745) discloses a resin-coated metallic pigment having a fine average particle diameter, in which a predetermined copolymer is used as a coating resin, in order to solve the problem that adhesion to a resin in a coating film is low when a coating material or a printing ink is formed from an aluminum pigment which has not been subjected to a surface treatment.

Patent document 2 (pamphlet of international publication No. 2019/77904) discloses an aluminum flake pigment containing small-diameter aluminum flakes having a particle size of 1 μm or less, the ratio of the number of the small-diameter aluminum flakes to the total number of the aluminum flakes being 35% or less in a microscopic image when observed by a scanning electron microscope, from the viewpoint of providing new design and a high-grade metallic feeling.

However, it is difficult to provide the above-mentioned paint stability, storage stability, paint color (specifically, brightness, flop feel, concealing property), and paint adhesion, which are sufficiently satisfactory by any of the techniques disclosed in these patent documents, and it is desired to develop a novel composite particle-containing metallic pigment composition.

Prior art literature

Patent literature

Patent document 1 International publication No. 2020/21745 pamphlet

Patent document 2 International publication No. 2019/77904 pamphlet

Disclosure of Invention

Problems to be solved by the invention

The object of the present invention is to provide a novel composite particle-containing metallic pigment composition which is not known in the prior art.

It is a further object of the present invention to provide a novel composite particle-containing metallic pigment composition which is superior in paint stability, storage stability, paint color tone (specifically, brightness, flop feel, concealing property), and paint adhesion, which are problems of the prior art.

Solution for solving the problem

The present inventors have intensively studied and found that the above-mentioned problems can be solved by a metal pigment composition comprising composite particles having metal particles and a coating layer comprising 1 or more layers of a silicon-containing compound layer (i.e., a silica layer) on the surface thereof, the composite particles being formed into a scaly shape, performing a coating treatment so that the average thickness of the composite particles (specifically, the size (particle diameter) of the metal particles which become nuclei of the composite particles and the thickness of the silica layer which constitutes the coating layer on the surface thereof) falls within a certain range, controlling D ₅₀ of the volume basis in the particle size distribution of the composite particles to fall within a prescribed range, and controlling the ratio of the silicon content based on the silica layer to the metal element content based on the metal particles which are nuclei of the composite particles and the number ratio of composite particles having a prescribed minute particle diameter to fall within a prescribed range.

Further, the inventors have found that the above-mentioned problems can be solved by the above-mentioned metallic pigment composition, in which, in the composite particles contained in the metallic pigment composition, when a coating layer comprising 1 or more layers of a silicon compound-containing layer (that is, a silica layer) is formed on the surfaces of the metallic particles which are the cores of the composite particles, a silica layer having a certain thickness is required to exert corrosion resistance, and on the other hand, when the size (particle diameter) of the composite particles is small, the metallic particles which are the cores of the composite particles are also small, the thickness of the silica layer is relatively large, so that the orientation of the metallic pigment is inhibited, the original optical properties of the metallic particles are hardly exhibited, and when the size (particle diameter) of the composite particles is small, the adhesion between the substrate and the coating material is inhibited, and the adhesion of the coating resin substrate is lowered.

That is, various aspects of the present invention are as follows.

Mode 1

A metallic pigment composition comprising composite particles having metallic particles and 1 or more coating layers on the surface thereof,

(1) The composite particles are in the shape of scales,

(2) The composite particles have a volume-based D ₅₀ of 3-30 μm when measured by a laser diffraction particle size distribution meter,

(3) The composite particles have an average thickness of 20nm to 300nm,

(4) At least 1 of the cover layers is a silicon-containing compound layer,

(5) The ratio of the metal element content based on the metal particles to the silicon content based on the covering layer in the composite particles is 0.02 or more and 0.3 or less in terms of the ratio of the silicon content to the metal element content,

(6) The ratio of the number of the composite particles having a particle diameter of 0.1 μm or more and 1 μm or less to the total number of the composite particles in the metallic pigment composition is 10% or less.

Mode 2

The metallic pigment composition according to the above [ aspect 1], wherein the ratio of the number of the composite particles having a size of 3 times or more of the size D ₅₀ based on the volume when the particle size distribution of the composite particles is measured by the laser diffraction type particle size distribution meter to the total number of the composite particles in the metallic pigment composition is 3% or less.

Mode 3

The metal pigment composition according to the above [ mode 1] or [ mode 2], wherein the metal particles are aluminum or an aluminum alloy.

Mode 4

The metal pigment composition according to any one of the above [ 1] to [ 3], further comprising a coating layer containing at least one of a metal, a metal oxide, a metal hydrate and a resin.

Mode 5

The metal pigment composition according to any one of the above [1] to [ 4], wherein the silicon-containing compound layer is disposed at least as an outermost layer.

Mode 6

A water-based metallic paint comprising the metallic pigment composition according to any one of the above [ modes 1] to [ 5 ].

Mode 7

An aqueous metal coating film comprising the metal pigment composition according to any one of the above [ aspects 1] to [ 5 ].

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a novel composite particle-containing metallic pigment composition which is not available in the prior art can be provided.

According to a preferred embodiment of the present invention, there can be provided a metallic pigment composition excellent in paint stability (specifically, a characteristic that aggregation of particles constituting a pigment is small when the pigment is used as a paint), storage stability (specifically, a characteristic that generation of hydrogen gas due to corrosion can be suppressed), paint color tone (specifically, a characteristic that brightness, flop feel, concealing are high), and paint adhesion (specifically, a characteristic that adhesion to a substrate is high when a metallic pigment is painted to form a paint film).

Detailed Description

The present invention will be described below with reference to exemplary or preferred embodiments, but the present invention is not limited to these embodiments. These embodiments can be freely combined within the scope of the invention as defined in the appended claims, unless explicitly stated.

1. Composite particles contained in metallic pigment composition

The metallic pigment composition of the present invention comprises composite particles having metallic particles and 1 or more coating layers on the surface thereof.

In the present specification, the term "metallic pigment composition" refers to a composition in which composite particles including metallic particles and 1 or more coating layers on the surface thereof are dispersed in a solvent including water and/or a hydrophilic solvent, or the composite particles include water and/or a hydrophilic solvent together with a solvent, and optionally other components can be included.

In the present specification, a composition obtained by adding a resin to a metallic pigment composition may be referred to as a "resin composition" or a "resin composition containing a metallic pigment composition" in distinction from the term "metallic pigment composition".

Metal particles

The composite particles contained in the metallic pigment composition of the present invention comprise metallic particles and 1 or more coating layers formed on the surfaces thereof. That is, the metal particles serving as cores of the composite particles have 1 or more coating layers formed on the surfaces thereof.

The material of the metal particles (core particles) constituting the composite particles is not particularly limited, and may be any of metals used as known or commercially available metal pigments, such as aluminum, aluminum alloy, zinc, iron, magnesium, nickel, copper, silver, tin, chromium, stainless steel, and the like. In the present specification, the metal of the metal particles constituting the composite particles includes not only a simple metal but also an alloy or an intermetallic compound.

As such, the metal particles may be used alone with a metal formed of only 1 metal element or with a combination of 2 or more metals (i.e., a metal formed of 2 or more metal elements) to be formed of only 1 metal element.

The metal particles in the present invention are preferably metals containing aluminum as a main component, for example, aluminum or an aluminum alloy is preferable, and aluminum is more preferable.

The shape of the metal particles is not limited, but is particularly preferably a scaly (flake-like) shape. Thus, the composite particles contained in the metallic pigment composition of the present invention can have a scaly shape, and as a result, high hiding properties and the like can be obtained more reliably. From the above viewpoints, the ratio of the diameter to thickness of the flaky metal particles (the shape factor obtained by dividing the average particle diameter by the average thickness) is preferably 20 or more and 30 or less. By setting the ratio of the diameter to the thickness of the metal particles to 20 or more, a higher brightness can be obtained. In addition, the metal particles have a ratio of diameter to thickness of 3000 or less, so that the mechanical strength of the sheet is maintained, and a stable color tone can be obtained. The average thickness of the metal particles used in the present invention can be calculated from the water surface diffusion area and the density of the metal particles.

The average particle diameter of the metal particles is not particularly limited as long as the average particle diameter of D ₅₀ in the particle size distribution of the composite particles to be described later is formed. That is, the average particle diameter of the metal particles is preferably set so that the D ₅₀ of the composite particles when the volume distribution is measured by a laser diffraction particle size distribution meter is 3 μm or more and 30 μm or less.

The average particle diameter of the metal particles can be controlled by appropriately adjusting the particle diameter of the raw material atomized metal powder (for example, aluminum powder) in the step of grinding and sieving/filtering the raw material atomized metal powder using a ball mill or the like, the mass per 1 grinding ball when using a ball mill, the rotation speed of the grinding apparatus, the degree of sieving and filter press, and the like.

The metal particles do not necessarily need to be composed of only metal, and particles having surfaces covered with metal, such as particles of synthetic resin, inorganic particles of mica, glass, or the like, may be used as long as the effects of the present invention are not impaired. In the present invention, particles formed of aluminum or an aluminum alloy are preferable from the viewpoints of high weather resistance, small specific gravity, easiness of obtaining, and the like in particular.

The metal particles constituting the composite particles are particularly preferably aluminum flakes which are usually used as a metal pigment. Aluminum flakes having surface properties, particle diameters, and shapes required for metallic pigments, such as surface gloss, whiteness, and brightness, are suitable. Aluminum flakes are generally commercially available in the paste state. The paste-like aluminum flakes may generally contain scaly aluminum powder, mineral spirits (aliphatic hydrocarbons) used in pulverization, residual fatty acid components, and organic solvents such as solvent naphtha and xylene. The paste-like aluminum flakes may be used as they are or may be used by removing fatty acids from the surface thereof in advance with an organic solvent or the like.

In addition, a so-called aluminum vapor deposition foil having a volume average particle diameter (D ₅₀) of 3 μm or more and 30 μm or less and an average thickness of 20nm or more and 300nm or less in the state of composite particles can be used.

2. Preferred physical Properties of the metallic pigment composition

The metallic pigment composition of the present invention is characterized by satisfying the following physical properties.

(1) The shape of the composite particles is a scale shape,

(2) The D ₅₀ of the volume basis of the particle size distribution of the composite particles measured by a laser diffraction particle size distribution meter is 3 μm or more and 30 μm or less,

(3) The composite particles have an average thickness of 20nm to 300nm,

(4) At least 1 of the cover layers is a silicon-containing compound layer,

These physical properties are described below.

(1) The composite particles are in the shape of scales

The composite particles of the metallic pigment composition of the present invention have a scaly (flake-like) shape. Thus, the coating film formed using the metallic pigment composition can exhibit high brightness, high flop, high hiding, and the like. In the present specification, the shape of the composite particles being "scaly" (flaky) means that the average aspect ratio (the shape factor obtained by dividing the average particle diameter by the average thickness) of the composite particles is 10 or more. The average diameter-thickness ratio of the flaky composite particles is preferably 10 to 1500 from the viewpoint of obtaining high brightness, flop, concealing, and the like. The average aspect ratio of 10 or more can give a sufficient gloss, while the average aspect ratio of 1500 or less can maintain the mechanical strength of the sheet and can give a stable color tone.

The term "composite particles" in the physical property condition (1) refers to an aggregate (aggregate) of a plurality of composite particles when the composite particles are aggregated/adhered.

Here, the average particle diameter used for calculating the average diameter-thickness ratio of the composite particles is a volume reference D ₅₀ called a median particle diameter, and this will be described in detail in the description of the condition (2) below. The average thickness used to calculate the average aspect ratio of the composite particles is described in detail below in the description of condition (3).

(2) The D ₅₀ of the volume basis is 3 μm or more and 30 μm or less when the particle size distribution of the composite particles is measured by a laser diffraction type particle size distribution meter

The D ₅₀ of the volume basis of the particle size distribution of the composite particles measured by a laser diffraction particle size distribution meter is 3 μm or more and 30 μm or less. Thus, a coating film formed using the metallic pigment composition exhibits high brightness, high flop, high hiding, and the like, and aggregation of particles constituting the metallic pigment composition is suppressed and aggregation performance thereof can be reduced. This volume-based D ₅₀ is also commonly referred to as median particle size.

From the viewpoint of obtaining such high brightness, high flop, high concealing property, and small aggregation property of each particle, D ₅₀, which is a volume reference when the particle size distribution of the composite particles is measured by a laser diffraction particle size distribution meter, is 3 μm or more as a lower limit value, and 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less as an upper limit value.

The term "composite particles" in the physical property condition (2) refers to an aggregate (aggregate) of a plurality of composite particles when the composite particles are aggregated/adhered.

Here, D ₅₀, which is a volume basis when the particle size distribution of the composite particles is measured by a laser diffraction particle size distribution meter, refers to a particle diameter having a cumulative degree of 50% in the volume cumulative particle size distribution. The laser diffraction particle size distribution meter is not particularly limited, and may be, for example, "LA-300" (manufactured by horiba, inc.). As the measuring solvent, isopropyl alcohol and mineral spirits can be used. For example, the metal pigment composition containing the composite particles of the sample was subjected to ultrasonic dispersion for 2 minutes as a pretreatment, and then placed in a dispersion tank, and after confirming that the dispersion was proper, D ₅₀ was measured.

The particle size of the composite particles in the resin composition described later cannot be measured by this method. Therefore, as an alternative method in this case, for example, a method of capturing composite particles in a resin composition from the surface of a coating film by an optical microscope, a laser microscope, or the like, and obtaining a distribution of equivalent circle diameters by using commercially available image analysis software, thereby obtaining particle diameters, may be employed.

The D ₅₀ of the volume basis of the composite particles contained in the metal pigment composition can be controlled by appropriately adjusting the particle diameter of the raw material atomized metal powder (for example, aluminum powder) in the step of grinding and sieving/filtering the raw material atomized metal powder using a ball mill or the like, the mass per 1 grinding ball in the case of using the ball mill, the rotation speed of the grinding apparatus, the degree of sieving and the filter press, and the like, and by appropriately adjusting the type of the organosilicon compound used in the step of covering the silicon compound layer (and other covering layers as needed), the pH, the concentration, the stirring temperature, the stirring time, the type of stirring apparatus, the stirring power/degree (the type and diameter of stirring wings, the rotation speed, the presence or absence of external stirring, and the like) in the covering step (in the case of hydrolyzing the organosilicon compound, including the step) in the metal pigment composition to be described later.

(3) The composite particles have an average thickness of 20nm to 300nm

The average thickness of the composite particles containing the metal particles and the coating layer having 1 or more silicon compound-containing layers (i.e., silica layers) on the surface thereof in the metallic pigment composition of the present invention is preferably 20nm to 300 nm. Thus, in combination with satisfying the above conditions (1) to (2), the coating film formed using the metallic pigment composition exhibits further high brightness, high flop, high hiding, and the like, and aggregation of the composite particles constituting the metallic pigment composition is suppressed and aggregation thereof can be reduced.

In addition, the combination of the above-described components (4) to (6) satisfies the following conditions, and exhibits high corrosiveness even when used in aqueous metallic paint, metallic coating film, or the like, and also exhibits excellent adhesion even when used in coating film such as metallic coating film.

The average thickness of the composite particles is 20nm or more as a lower limit and 300nm or less, preferably 250nm or less, and more preferably 200nm or less as an upper limit from the above point of view.

The term "composite particles" in the physical property condition (3) refers to an aggregate (aggregate) of a plurality of composite particles when the composite particles are aggregated and adhered.

The average thickness of the composite particles herein can be calculated from the water surface diffusion area and the density of the composite particles. The water surface diffusion area refers to an area occupied by dry composite particles per unit mass when the dry composite particles are uniformly diffused on the water surface by using a floating phenomenon and covered in a state of no gap. The water surface diffusion area can be measured according to JIS K5906:1998.

However, in the composite particles of the present invention, when the surface hydrophilicity is high, 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 examples described later. That is, the average thickness of the composite particles can be obtained by forming a coating film (thin film) using a metallic pigment composition in which the composite particles are dispersed in a mixture of an alcohol solvent such as methoxypropanol and water, and observing the thickness of the composite particles (500 or more) by a Scanning Electron Microscope (SEM).

The average thickness of the composite particles contained in the metal pigment composition can be controlled by appropriately adjusting the particle diameter of the raw material atomized metal powder (for example, aluminum powder) in the step of grinding and sieving/filtering the raw material atomized metal powder using a ball mill or the like, the mass per 1 grinding ball when using a ball mill, the rotation speed of the grinding apparatus, the degree of sieving and the filter press, and the like, as in the volume reference D ₅₀, and can be controlled by appropriately adjusting the type of the organosilicon compound used in the step of covering the silicon-containing compound layer (and other covering layers as needed), the pH, the concentration, the stirring temperature, the stirring time, the type of stirring apparatus, the stirring power/degree (for example, the type and diameter of stirring wings, the rotation speed, the presence or absence of external stirring), and the like in the covering step (in the case of hydrolyzing the organosilicon compound, also including the step) in the metal pigment composition to be described later.

(4) At least 1 layer of the covering layer is a silicon-containing compound layer

In the metallic pigment composition of the present invention, at least 1 layer of the coating layers formed on 1 or more layers of the surfaces of the metallic particles which become the cores of the composite particles is a silicon-containing compound layer. This can suppress the generation of gas in the aqueous coating material, provide good storage stability (i.e., corrosion resistance), and provide excellent water resistance when forming a coating film.

In addition, when the aqueous metal coating composition is used to form a metal coating film or the like, the aqueous metal coating composition satisfies the above-described conditions (1) to (3) and the following conditions (5) to (6), and the aqueous metal coating composition exhibits excellent coating color tone achieved by high brightness, high flop and high hiding, and also exhibits excellent adhesion even when used in a coating film such as a metal coating film.

The coating layer of the composite particles may have other coating layers (2 nd coating layer) in addition to the silicon compound-containing layer. Such a2 nd cover layer is further described below.

The silicon-containing compound layer is particularly preferably a layer composed of a compound containing si—o-bonds (siloxane bonds). Examples of such a layer include a layer containing at least one of a silane compound and a silicon oxide. As such a compound, in addition to a silane compound [ H ₃SiO(H₂SiO)_nSiH₃ ] (where n represents an arbitrary positive integer), a silicon oxide represented by SiO ₂、SiO₂·nH₂ O (where n represents an arbitrary positive integer) or the like can be exemplified. These silane compounds and silicon oxides may be either crystalline or amorphous, but are particularly preferably amorphous. Therefore, as the layer containing silicon oxide (silicon dioxide or the like), for example, a layer containing amorphous silicon dioxide can also be suitably used.

The layer composed of the compound containing a si—o bond may be a layer formed using an organosilicon compound (containing a silane coupling agent) as a starting material. In this case, the silicon-containing compound layer may contain an organic silicon compound or a component derived therefrom within a range that does not hinder the effect of the present invention. In a typical example, the layer composed of a compound containing an si—o bond can be formed by hydrolyzing an organosilicon compound.

The silicon-containing compound layer may contain additives, impurities, and the like other than the silicon compound within a range that does not impair the characteristics of the present invention.

The silicon content in the silicon-containing compound layer is not particularly limited as long as it is an amount that can satisfy the condition (5) described later.

The coating layer of the composite particles contained in the metallic pigment composition of the present invention is particularly preferably hydrophilic. The composite particles generally form a metallic pigment composition in a form dispersed in an aqueous solvent (water or a mixed solvent containing water and an organic solvent), and in the case where the coating layer has a hydrophilic surface, the composite particles can be highly dispersed in such an aqueous solvent. Further, since the silicon oxide (amorphous silica or the like) is very stable in an aqueous solvent, a metal pigment composition containing highly stable composite particles in an aqueous solvent can be provided. From this viewpoint, it is preferable that at least the outermost layer of the composite particles contained in the metallic pigment composition of the present invention is a silicon-containing compound layer (particularly, a layer composed of a compound containing si—o bond). When the coating layer is formed of a plurality of layers, a silicon-containing compound layer (particularly, a si—o-based coating layer) may be formed as a layer other than the outermost layer, in addition to the silicon-containing compound 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 20nm to 300nm, as described above, but is generally preferably in the range of about 5 to 50nm (particularly 10nm to 40nm, further 15nm to 30 nm). When the thickness of the coating layer is 1nm or more, a coating film having sufficient water resistance and suppressed corrosion or discoloration of the metal particles in the aqueous coating material can be obtained. On the other hand, the thickness of the coating layer is about 50nm or less, whereby the brightness, the distinctness of image and the concealing ability of the coating film can be maintained at a high level.

The thickness of the silicon-containing compound layer contained in 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 20nm to 300nm as described in the above-mentioned condition (3), but may be in the range of usually 5nm to 50nm, particularly preferably 10nm to 40nm from the viewpoint of the function of the layer.

Specific examples of the organosilicon compound usable in the present invention are further described below, but the organosilicon compound is not limited to these specific examples.

The organosilicon compound may contain at least one of organosilicon compounds represented by the following general formula (1), and at least one selected from silane coupling agents represented by any one of the following general formulae (2), (3) and (4), and partial condensates thereof.

Si(OR¹)₄(1)

(Wherein R ¹ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and R ¹ may be the same, partially the same, or different from each other.)

R² _mSi(OR³)_4-m(2)

( Wherein R ² is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms which may optionally contain a halogen group, and R ³ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. R ² and R ³ may be the same or different, and when R ² or R ³ are 2 or more, they may be all the same, some of them may be the same, or all of them may be different. M is more than or equal to 1 and less than or equal to 3. )

R⁴ _pR⁵ _qSi(OR⁶)_4-p-q(3)

( Wherein R ⁴ is a group containing a reactive group capable of chemically bonding to 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 R ⁴、R⁵ or R ⁶ is 2 or more, they may be all the same, some of them may be the same, or all of them may be different. P is more than or equal to 1 and less than or equal to 3 q is more than or equal to 0 and less than or equal to 2 p+q is more than or equal to 1 and less than or equal to 3. )

R⁷ _rSiCl_4-r(4)

( Wherein R ⁷ is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms and optionally containing a halogen group, and R ⁷ is 2 or more, all of them may be the same, some of them may be the same, or all of them may be different. R is more than or equal to 0 and less than or equal to 3. )

Examples of the hydrocarbon group in R ¹ of the formula (1) include methyl, ethyl, propyl, butyl, hexyl, octyl, and the like, and these groups may be branched or straight. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. In addition, the 4R ¹ groups may all be the same, some of the same, or all different.

Preferable examples of the organosilicon compound of the formula (1) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and the like. Among them, tetraethoxysilane is particularly preferable.

Examples of the hydrocarbon group in R ² of the formula (2) include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, and naphthyl groups, which may be branched or straight-chain and may contain halogen groups such as fluorine, chlorine, and bromine. Of these, a hydrocarbon group having 1 to 18 carbon atoms is particularly preferable. In the case where R ² is 2 or more, they may be all the same, some of them may be the same, or all of them may be different. The number of R ² in the molecule is 1 to 3 in the formula (2), m=1 to 3, but more preferably m=1 or 2.

Examples of the hydrocarbon group in R ³ of the formula (2) include methyl, ethyl, propyl, butyl, hexyl, octyl, and the like, and these groups may be branched or straight. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. In the case where R ³ is 2 or more, they may be all the same, some of them may be the same, or all of them may be different.

As a preferable example of the organosilicon compound (silane coupling agent) of the formula (2), examples thereof include methyltrimethoxysilane, methyltriethoxysilane, methylttributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, trimethylmethoxysilane, trimethylethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltributoxysilane, butyltrimethoxysilane, butyl triethoxysilane, butyl tributoxysilane, dibutyl dimethoxy silane, dibutyl diethoxy silane, dibutyl dibutoxy silane, isobutyl trimethoxy silane, isobutyl triethoxy silane, hexyl trimethoxy silane, hexyl triethoxy silane, dihexyl dimethoxy silane, dihexyl diethoxy silane, octyl trimethoxy silane, butyl triethoxysilane, butyl tributoxysilane, dibutyl dimethoxy silane, dibutyl diethoxy silane, dibutyl dibutoxy silane, isobutyl trimethoxy silane isobutyl triethoxysilane, hexyl trimethoxysilane, hexyl triethoxysilane, dihexyl dimethoxy silane, dihexyl diethoxy silane, octyl trimethoxy silane, 3-chloropropyl tributoxy silane, and the like.

Examples of the reactive group capable of chemically bonding to other functional groups in R ⁴ of the 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 (polysulfide) group, an isocyanate group, and the like.

In the case where R ⁴ is 2 or more, they may be all the same, some of them may be the same, or all of them may be different. The number of R ⁴ in the molecule is 1 to 3 in formula (3), p=1 to 3, but more preferably p=1.

Examples of the hydrocarbon group of R ⁵ in the formula (3) include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, and naphthyl groups, which may be branched or straight-chain and may contain halogen groups such as fluorine, chlorine, and bromine. Of these, a hydrocarbon group having 1 to 18 carbon atoms is particularly preferable. In the case where R ⁵ is 2 or more, they may be all the same, some of them may be the same, or all of them may be different.

Examples of the hydrocarbon group in R ⁶ of the formula (3) include methyl, ethyl, propyl, butyl, hexyl, octyl, and the like, and these groups may be branched or straight. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. In the case where R ⁶ is 2 or more, they may be all the same, some of them may be the same, or all of them may be different.

As preferable examples of the organosilicon compound (silane coupling agent) of the formula (3), vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyl methyldimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyldiethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-acryloxypropyl trimethoxysilane, N-methyl-3-aminopropyl-trimethoxysilane, N-2- (aminoethyl) -3-aminopropyl methyldimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldiethoxysilane, 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, 3-aminopropyl-triethoxysilane, N-3-aminopropyl-2- (aminopropyl) -amino-trimethoxysilane, N-2-aminopropyl-triethoxysilane, N-2-aminopropyl-3-aminopropyl-ethoxysilane, N-aminopropyl-2-aminopropylsilane, N-glycidoxylsilane, 3-glycidoxypropylsilane, and the following examples mentioned 3-triethoxysilyl-N- (1, 3-dimethyl-butylidene) propylamine, 3-ureidopropyltriethoxysilane, 3-mercaptopropyl methyldimethoxysilane, 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl-triethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyl triethoxysilane, and the like.

Examples of the hydrocarbon group in R ⁷ of the formula (4) include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, and naphthyl groups, which may be branched or straight-chain and may contain halogen groups such as fluorine, chlorine, and bromine. Of these, a hydrocarbon group having 1 to 12 carbon atoms is particularly preferable. In the case where R ⁷ is 2 or more, they may be all the same, some of them may be the same, or all of them may be different. The number of R ⁷ in the molecule is 0 to 3 in the formula (4), r=0 to 3, but more preferably r=1 to 3.

Preferable examples of the organosilicon compound (silane coupling agent) of the 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 1 or more than 2. The silane coupling agent represented by any one of the general formulae (2), (3) and (4) may be used alone or in combination of 2 or more. When 2 or more kinds of silane coupling agents are used in combination, only 2 or more kinds of silane coupling agents represented by any one of (2), (3) and (4) may be used in combination, or different 2 or more kinds of silane coupling agents represented by the general formula may be used in combination.

The hydrolysate of the organosilicon compound and/or the condensate thereof is obtained by stirring and mixing the organosilicon compound and water in an amount necessary for the hydrolysis reaction with a hydrolysis catalyst. In this case, a hydrophilic solvent may be used as needed. Various conditions for the hydrolysis reaction (i.e., the reaction for forming the silicon-containing compound layer) are described later.

As a raw material for hydrolysis reaction and/or condensation reaction of a hydrolysate and/or condensation reactant of an organosilicon compound, an oligomer partially condensed in advance may be used.

The condensation reaction of the hydrolysate of the organosilicon compound may be carried out simultaneously with the hydrolysis reaction of the organosilicon compound, or may be carried out by a separate process and replacing the catalyst as needed. In this case, the temperature may be raised as needed.

The coating layer of the composite particles contained in the metallic pigment composition of the present invention is not particularly limited except that at least 1 layer is a silicon compound-containing layer, and a coating layer other than the silicon compound-containing layer (hereinafter referred to as "2 nd coating layer") may be formed as required.

The 2 nd coating layer may contain at least one of a metal (alkali metal; alkaline earth metal; metal such as manganese, iron, cobalt, nickel, copper, silver, etc.), a metal oxide (titanium oxide, zirconium oxide, oxide of iron, etc.), a metal hydrate, and a resin (synthetic resin such as acrylic resin, alkyd resin, polyester resin, polyurethane resin, polyvinyl acetate resin, nitrocellulose resin, fluorine resin, etc.), for example. As the 2 nd coating layer, for example, a molybdenum-containing coating film, a phosphoric acid compound coating film, or the like can be formed. By providing the 2 nd coating layer, the formation of the silicon compound-containing layer can be promoted while improving the corrosion resistance of the metal particles.

The 2 nd capping layer (where formed) is particularly preferably formed between the metal particles and the silicon-containing compound layer. Thus, for example, a layer structure of "metal particles/2 nd cap layer/silicon-containing compound layer" can be suitably employed. Examples of the molybdenum-containing coating film include, but are not particularly limited to, those disclosed in Japanese patent application laid-open No. 2003-147226, WO 2004/096921, japanese patent application laid-open No. 5979788, and Japanese patent application laid-open No. 2019-151678. As an example of the phosphate compound coating film, a phosphate compound coating film disclosed in japanese patent No. 4633239 is given. As a preferable example of the molybdenum-containing substance constituting the molybdenum-containing coating film, there is mentioned a mixed coordination type heteropolyanion compound disclosed in Japanese patent application laid-open No. 2019-151678.

In another modification, the 2 nd coating layer may be formed outside the metal particles and the silicon-containing compound layer. In still another modification, the constituent components (molybdenum-containing compound, phosphoric acid compound, etc.) of the 2 nd coating layer may be contained in the silicon-containing compound layer together with the silicon compound.

The mixed coordination type heteropolyanion compound used for forming the 2 nd coating layer (typical example, molybdenum-containing coating film) other than the silicon-containing compound layer of the composite particles contained in the metallic pigment composition of the present invention is not particularly limited, and specifically, the following examples are given.

The mixed coordination type heteropolyanion of the mixed coordination type heteropolyanion compound that can be used has a structure in which a plurality of polyatoms of the heteropolyanion formed of one element are replaced with other elements, and exhibits physical properties different from those of the mixture of the heteropolyanions.

When the mixed coordination type heteropolyanion is represented by [ X _pM_qN_rO_s]^t ] in the case of the chemical formula, the heteropolyanion is [ X _pM_qO_s]^t ] and is further distinguished from the heteropolyanion [ M _qO_s]^t ]. Among them, X as a hetero atom represents a IIIB, IVB, VB group element such as B, si, ge, P, as, and among them, B, si, and P are preferable. The polyatomic M, N represents a transition metal such as Ti, zr, V, nb, ta, mo, W, and is preferably Ti, zr, V, nb, mo, W.

Further, p, q, r, s represents the number of atoms, and t represents the oxidation number.

The heteropoly anion compound has many structures, and the mixed coordination type heteropoly anion compound can have many structures, but as a typical and preferable mixed coordination type heteropoly anion compound, a mixed coordination type heteropoly acid such as H ₃PW_xMo_12-xO₄₀·nH₂ O (phosphotungstic acid. N hydrate), H _3+xPV_xMo_12-xO₄₀·nH₂ O (phosphovanadic acid. N hydrate), H ₄SiW_xMo_12-xO₄₀·nH₂ O (silicotungstic acid. N hydrate), H _4+xSiV_xMo_12-xO₄₀·nH₂ O (silicovanadic acid. N hydrate) and the like can be exemplified. (wherein, x is more than or equal to 1 and less than or equal to 11 n is greater than or equal to 0)

Among these heteropoly anion compounds, preferable specific examples include mixed coordination type heteropoly acids such as H₃PW₃Mo₉O₄₀·nH₂O、H₃PW₆Mo₆O₄₀·nH₂O、H₃PW₉Mo₃O₄₀·nH₂O、H₄PV₁Mo₁₁O₄₀·nH₂O、H₆PV₃Mo₉O₄₀·nH₂O、H₄SiW₃Mo₉O₄₀·nH₂O、H₄SiW₆Mo₆O₄₀·nH₂O、H₄SiW₉Mo₃O₄₀·nH₂O、H₅SiV₁Mo₁₁O₄₀·nH₂O、H₇SiV₃Mo₉O₄₀·nH₂O. (wherein n.gtoreq.0)

The mixed coordination type heteropoly anion compound may be used as an acid (so-called mixed coordination type heteropoly acid), or may be used as a (partial or complete) salt using a specific cation as a counter ion.

Examples of the counter cation source in the case of using a mixed coordination type heteropolyanion compound as a salt of a specific cation as a counter ion include at least one selected from alkali metals such as lithium, sodium, potassium, rubidium and cesium, alkaline earth metals such as magnesium, calcium, strontium and barium, metals such as manganese, iron, cobalt, nickel, copper, zinc, silver, cadmium, lead and aluminum, inorganic components such as ammonia, and amine compounds as organic components. Among the inorganic components, salts of alkali metals, alkaline earth metals, and ammonia are preferable.

Further, when at least one of these alkali metal, alkaline earth metal, and ammonia is used as a counter cation source, it is more preferable to use a salt with at least one member selected from the group consisting of H ₃PW_xMo_12-xO₄₀·nH₂ O (phosphotungstopolybdic acid n hydrate), H _3+xPV_xMo_12-xO₄₀·nH₂ O (phosphovanadomolybdic acid n hydrate), H ₄SiW_xMo_12-xO₄₀·nH₂ O (silicotungstopolybdic acid n hydrate), and H _4+xSiV_xMo_12-xO₄₀·nH₂ O (silicovanadomolybdic acid n hydrate).

Further, as the counter cation source of the mixed coordination type heteropolyanion compound, an amine compound as an organic component is also preferably used, and as a specific example, an amine compound represented by the following general formula (5) is preferable.

(R⁸-N(-R¹⁰)-)_n-R⁹(5)

( Wherein R ⁸、R⁹ and R ¹⁰ may be the same or different and each is a hydrogen atom, or a hydrocarbon group of 1 to 30 carbon atoms and optionally containing an ether bond, an ester bond, a hydroxyl group, a carbonyl group, or a mercapto group, R ⁸ and R ⁹ may be optionally combined 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 crosslinking group, or R ⁸、R⁹ and R ¹⁰ may be optionally combined to form a multiple ring which may contain 1 or more additional nitrogen and/or oxygen atoms as a crosslinking group. R ⁸、R⁹ and R ¹⁰ do not simultaneously form a hydrogen atom. n represents an integer of 1 to 2. )

Specific examples of the amine compound as a counter cation source of the mixed coordination type heteropolyanion compound include linear primary amines such as ethylamine, propylamine, butylamine, hexylamine, octylamine, laurylamine, tridecylamine, and stearylamine; branched primary amines such as isopropylamine, isobutylamine, 2-ethylhexyl amine, and branched tridecyl amine, linear secondary amines such as dimethylamine, diethylamine, dipropylamine, dibutylamine, dihexylamine, dioctylamine, dilaurylamine, ditridecyl amine, distearyl amine, branched secondary amines such as diisopropylamine, diisobutylamine, di-2-ethylhexyl amine, and di-branched tridecyl amine, N-methylbutylamine, Asymmetric secondary amines such as N-ethylbutylamine, N-ethylhexyl amine, N-ethyllaurylamine, N-ethylstearyl amine, N-isopropyloctylamine, N-isobutyl-2-ethylhexyl amine, straight-chain tertiary amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, trilaurylamine, tridecyl amine, tristearylamine, branched tertiary amines such as triisobutylamine, tri-2-ethylhexyl amine, and tri-branched tridecyl amine, tertiary amines having a mixed hydrocarbon group such as N, N-dimethyloctylamine, N-dimethyllaurylamine, N-dimethylstearyl amine, N-diethyllaurylamine, tertiary amines having an allyl amine, and the like, alkenyl-containing amines such as diallylamine, triallylamine and N, N-dimethylallylamine, alicyclic primary amines such as cyclohexylamine and 2-methylcyclohexylamine, aromatic-ring-substituted primary amines such as aniline, benzylamine and 4-methylbenzylamine, alicyclic secondary amines such as N, N-dicyclohexylamine and N, N-di-2-methylcyclohexylamine, aromatic-ring-substituted secondary amines such as dibenzylamine and N, N-di-4-methylbenzylamine, asymmetric secondary amines such as N-cyclohexyl-2-ethylhexyl amine, N-cyclohexylbenzyl amine, N-stearyl benzyl amine and N-2-ethylhexyl benzyl amine, N-dimethylbenzylamine, Alicyclic tertiary amines such as N, N-dimethylcyclohexylamine and tricyclohexylamine, tertiary amines having an aromatic ring substituent such as tribenzylamine and tri-4-methylbenzylamine, amines having an ether bond such as morpholine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-butoxypropylamine, 3-decyloxypropylamine and 3-lauryloxypropylamine, amines having an ether bond such as monoethanolamine, diethanolamine, monoisopropanolamine, monopropanolamine, butanolamine, triethanolamine, N-dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, N-butylethanolamine, N-cyclohexyl-N-methylaminoethanol, and the like, Alkanolamines such as N-benzyl-N-propylaminoethanol, N-hydroxyethyl pyrrolidine, N-hydroxyethyl piperazine, N-hydroxyethyl morpholine, diamines such as ethylenediamine, N-methylethylenediamine, N, N '-dimethylethylenediamine, N, N, N', N '-tetramethylethylenediamine, 1, 2-propanediamine, 1, 3-propanediamine, N, N-dimethyl-1, 3-propanediamine, N-cyclohexyl-1, 3-propanediamine, N-decyl-1, 3-propanediamine, N-isotridecyl-1, 3-propanediamine, N, N' -dimethylpiperazine, N-methoxyphenylpiperazine, N-methylpiperidine, cyclic amines such as N-ethylpiperidine, quinuclidine, diazabicyclo [2, 2] octane, 1, 8-diazabicyclo [5,4,0] -7-undecene, aromatic amines such as pyridine and quinoline, or any mixture thereof.

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

More preferably, the amine compound represented by the general formula (5) is used as a salt with at least one compound selected from the group consisting of H ₃PW_xMo_12-xO₄₀·nH₂ O (phosphotungstopolybdic acid n-hydrate), H _3+xPV_xMo_12-xO₄₀·nH₂ O (phosphovanadomolybdic acid n-hydrate), H ₄SiW_xMo_12-xO₄₀·nH₂ O (silicotungstopolybdic acid n-hydrate) and H _4+xSiV_xMo_12-xO₄₀·nH₂ O (silicovanadomolybdic acid n-hydrate).

Among the above mixed coordination type heteropoly anion compounds, most preferred are mixed coordination type heteropoly acids of H ₃PW_xMo_12-xO₄₀·nH₂ O (phosphotungstopolybdic acid. N-hydrate), H _3+xPV_xMo_12-xO₄₀·nH₂ O (phosphovanadyl molybdic acid. N-hydrate), H ₄SiW_xMo_12-xO₄₀·nH₂ O (silicotungstopolybdic acid. N-hydrate), or organic amine salts of these mixed coordination type heteropoly acids.

The 2 nd coating layer other than the silicon compound-containing layer of the composite particles contained in the metallic pigment composition of the present invention may be a layer containing another corrosion inhibitor in order to further improve the corrosion resistance of the metal particles (preferably aluminum particles or aluminum alloy particles) serving as nuclei. The corrosion inhibitor to be added is not particularly limited, and any known corrosion inhibitor may be used. The amount thereof may be within a range that does not hinder the desired effect of the present invention. Examples of such corrosion inhibitors include acid phosphate esters, dimer acids, organic phosphorus compounds, and metal salts of molybdic acid.

The silicon compound-containing layer and/or the 2 nd coating layer of the composite particles contained in the metallic pigment composition may further contain an organic oligomer or polymer as another layer from the viewpoints of adhesion and chemical resistance at the time of forming a coating film.

The silicon-containing compound layer and/or the 2 nd coating layer of the composite particle may contain at least one member selected from the group consisting of inorganic phosphoric acids and salts thereof, and acidic organic (phosphorous) acid esters and salts thereof, from the viewpoint of storage stability, or may be contained as another layer.

These compounds are not particularly limited, and for example, those disclosed in Japanese patent application laid-open No. 2019-151678 can be used.

(5) The ratio of the metal element content based on the metal particles to the silicon content based on the covering layer in the composite particles is 0.02 or more and 0.3 or less in terms of the ratio of the silicon content to the metal element content

The composite particles contained in the metallic pigment composition of the present invention have metallic particles serving as nuclei thereof and 1 or more coating layers on the surfaces of the metallic particles. As described in detail in the above description of the condition (4), at least 1 layer of the cover layer is a silicon compound-containing layer (so-called silicon dioxide layer). Therefore, the composite particle of the metallic pigment composition of the present invention has, as constituent components, a metal element constituting the metallic particle that becomes the core of the composite particle, and a silicon element derived from a silicon-containing compound layer (so-called silica layer) constituting the coating layer on the surface of the metallic particle.

In the composite particles contained in the metallic pigment composition of the present invention, the ratio of the silicon element content to the metallic element content is preferably 0.02 or more and 0.3 or less. The content of each element in the composite particles can be determined by, for example, dissolving the metal pigment composition, and analyzing the content of the metal element and the content of the silicon element in the composite particles contained therein by using a high-frequency Inductively Coupled Plasma (ICP) emission spectrometry.

The content of the metal element constituting the metal particles which become the core of the composite particle is proportional to the size (i.e., particle diameter) of the metal particles, and the content of the silicon element originating from the silicon-containing compound layer (so-called silica layer) constituting the covering layer on the surface of the metal particles is proportional to the thickness of the silicon-containing compound layer (so-called silica layer).

When the ratio is 0.02 or more, the thickness of the silicon-containing compound layer (so-called silica layer) in the coating layer on the surface of the metal particles with respect to the particle diameter of the metal particles becomes a thickness capable of effectively exhibiting corrosion resistance. When the ratio is 0.3 or less, the thickness is a thickness that can effectively exhibit the optical performance of the metal particles. The lower limit of the above ratio is 0.02 or more, preferably 0.03 or more, and more preferably 0.04 or more. The upper limit is 0.3 or less, preferably 0.2 or less, and more preferably 0.15 or less. That is, the composite particles of the metallic pigment composition of the present invention can effectively exhibit both corrosion resistance based on the silicon compound layer (so-called silica layer) in the coating layer of the composite particles and optical properties based on the characteristics possessed by the metallic particles that become the nuclei of the composite particles (for example, excellent coating color tone achieved by high brightness, high flop, high hiding property) by the ratio of the above-mentioned metallic element content to the above-mentioned silicon element content. Specifically, by effectively exhibiting the corrosion resistance of the silica layer, even when used as an aqueous coating material such as an aqueous metallic coating material, an aqueous ink, or the like, the gas generation is suppressed to obtain good storage stability, and the water resistance when used as a coating film is excellent.

In addition, when the above-described conditions (1) to (4) and the following condition (6) are satisfied, excellent coating color tone such as high hiding property and brightness is further exhibited, and even when the coating composition is used for a coating film such as a metal coating film, excellent adhesion can be exhibited.

The term "composite particles" in the physical property condition (5) refers to an aggregate (aggregate) of a plurality of composite particles when the composite particles are aggregated and adhered.

As for the metal particles, as described above, a metal formed of only 1 metal element, or a combination of 2 or more metals to be formed of only 1 metal element (i.e., a metal formed of 2 or more metal elements) may be used alone. For example, in the case where the metal particles forming the core of the composite particle are composed of a metal formed of 1 metal element, "the metal element constituting the aforementioned metal particles" in the present condition (5) refers to the 1 metal element, and in the case where the metal particles forming the core of the composite particle are composed of a metal formed of 2 metal elements, the "metal element constituting the aforementioned metal particles" in the present condition (5) refers to the 2 metal elements. That is, if the metal particles forming the core of the composite particle are aluminum metal particles formed only of aluminum element, "the metal element constituting the metal particles" in the present condition (5) refers to aluminum metal element, and if the metal particles forming the core of the composite particle are metal particles formed of 2 metal elements of aluminum element and other metal element, the metal particles forming the core of the composite particle refer to aluminum metal element and other metal element.

As for the metal particles, as described above, the metal particles in the present invention are preferably aluminum or an aluminum alloy, more preferably aluminum. The amount of the metal particles contained in the composite particles and the silicon content contained in the silicon-containing compound layer constituting the coating layer on the surface of the metal particles are not particularly limited as long as the above ratio (i.e., the present condition (5)) can be satisfied.

(6) The ratio of the number of the composite particles having a particle diameter of 0.1 μm or more and 1 μm or less to the total number of the composite particles in the metallic pigment composition is 10% or less

The number ratio of composite particles having a particle diameter of 0.1 μm or more and 1 μm or less (hereinafter also referred to as fine composite particles) to the total number of composite particles (i.e., total number) contained in the metallic pigment composition of the present invention is 10% or less.

As described in the above condition (4), excellent corrosion resistance can be obtained by forming at least 1 layer of the coating layer on the surface of the metal particles which are nuclei of the composite particles contained in the metal pigment composition of the present invention, as a silicon-containing compound layer (so-called silica layer). The silica layer has a certain thickness that satisfies the condition (5) in order to obtain excellent corrosion resistance. However, in the case of fine composite particles having a particle diameter of 1 μm or less (specifically, in the case of composite particles having a particle diameter of 0.1 μm or more (i.e., fine composite particles) except that the composite particles having a particle diameter of less than 0.1 μm are considered to be composite particles because the effect on the performance of the present invention is negligible due to the undersize, the ratio of the thickness of the oxide layer to the particle diameter of the metal particles forming the core of the composite particles increases, and the ratio of the metal itself to the composite particles decreases). Therefore, if the number ratio of the fine composite particles in the metallic pigment composition is increased, the original optical properties of the metallic particles (for example, excellent coating color tone achieved by high brightness, high flop, and high hiding) cannot be exhibited. Further, since such fine composite particles are relatively thick with respect to the thickness of the particle diameter, orientation of the fine composite particles is difficult, and the orientation of the whole metallic pigment is hindered, and the original optical properties of the metallic particles cannot be exhibited.

Further, since the fine composite particles having a particle diameter of 1 μm or less inhibit adhesion between the substrate and the coating material, adhesion between the coating resin and the substrate is easily reduced when the fine composite particles are used as the coating material in the case where many fine composite particles are present in the metallic pigment composition.

In the metallic pigment composition of the present invention, the number ratio of the fine composite particles to the total number of the composite particles in the metallic pigment composition is 10% or less. Accordingly, the number of composite particles having a small particle diameter in the total composite particles contained in the metallic pigment composition is suppressed, and thus the original optical properties (for example, high brightness, high flop, and high hiding property) of the metallic particles can be exhibited.

In addition, by combining the above-mentioned conditions (1) to (5), the excellent coating color tone achieved by high brightness, high flop and high hiding property is further exhibited, and at the same time, aggregation of the composite particles constituting the metallic pigment composition is suppressed, and further, the corrosion resistance by the silica layer is effectively exhibited, whereby gas generation can be suppressed even when used as an aqueous coating material such as an aqueous metallic coating material, an aqueous ink and the like, and good storage stability is obtained, and the water resistance when used as a coating film is excellent.

The number ratio of the fine composite particles is preferably as low as possible from the standpoint of 10% or less, preferably 5% or less, more preferably 3% or less, of the total number of composite particles in the metallic pigment composition.

The term "composite particles" in the physical property condition (6) refers to an aggregate (aggregate) of a plurality of composite particles when the composite particles are aggregated and adhered.

The method for measuring the number ratio of composite particles (i.e., fine composite particles) having a particle diameter of 0.1 μm or more and 1 μm or less is not particularly limited, and may be, for example, by preparing a coating film using the metal pigment composition of the present invention, photographing the coating film with a digital microscope (for example, manufactured by HiROX: KH-3000) at a magnification in the range of approximately 500 or more of the total number of particles (i.e., the total number of total composite particles), and extracting particles having an equivalent circle diameter of 0.1 μm or more and 1 μm or less from the total particles contained therein using Image analysis software (for example, manufactured by Media Cybernetics: image-ProPLUS ver.7.0), and measuring the number as the number relative to the total number of particles, thereby obtaining the number ratio of fine composite particles. Here, the equivalent circle diameter refers to a diameter of a circle having the same area as the projected area of the particle image, and is generally referred to as a Heywood diameter. For example, even if particles having a shape other than a circular shape and a shape of a shape are present, if the area thereof is 78.5nm ² (corresponding to the area of a circle having a particle diameter=10 nm), the particle diameter is regarded as 10nm. In the case where particles are aggregated and adhered to each other and the boundary cannot be visually confirmed, the equivalent circle diameter may be obtained from the cross-sectional area of the shape of the aggregated and adhered state, and in the case where the boundary can be visually confirmed at this magnification even if aggregation and adhesion occur to some extent, the particle diameter (equivalent circle diameter) of each particle may be measured.

In the "composite particles" in the present physical property condition (6), as described above, the effect on the performance of the present invention can be ignored, except that very small composite particles having a particle diameter of less than 0.1 μm (specifically, composite particles having an equivalent circle diameter of less than 0.1 μm) are considered as composite particles because of the undersize.

The number ratio of the composite particles having a particle diameter of 3 times or more the size D ₅₀ of the volume standard when the volume distribution of the composite particles is measured by a laser diffraction particle size distribution meter (hereinafter also referred to as coarse composite particles) is preferably 3% or less of the number (i.e., total number) of the total composite particles in the metallic pigment composition.

Thus, when a coating film is formed, a metal coating film having a dense feel can be formed, and further, roughness of the surface at the time of forming the coating film can be suppressed.

In addition, in combination with the above-mentioned conditions (1) to (6), the metallic pigment composition can further exhibit excellent coating color tone such as high hiding property and brightness, and at the same time, aggregation of the composite particles constituting the metallic pigment composition can be suppressed, and further, even when used as an aqueous coating material such as an aqueous metallic coating material, an aqueous ink, and the like, gas generation can be suppressed, and good storage stability can be obtained, and further, when used as a coating film, excellent water resistance can be obtained, and even when used as a coating film such as a metallic coating film, excellent adhesion can be exhibited.

The number ratio of the coarse composite particles is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less, based on the total amount of the composite particles in the metallic pigment composition.

The term "composite particles" in the present physical property condition refers to an aggregate (aggregate) of a plurality of composite particles when the composite particles are aggregated/adhered.

The method for measuring the coarse composite particles is not particularly limited, and may be obtained by, for example, a method of observing the coating film with a digital microscope, a laser diffraction type particle size distribution meter, or the like, as in the measurement of the fine composite particles.

The number ratio of the fine composite particles and the coarse composite particles contained in the metallic pigment composition of the present invention can be controlled mainly by appropriately selecting the particle diameter of the metallic particles to be used, and appropriately adjusting the stirring time, the type of stirring device, the power/degree of stirring (the type and diameter of stirring wings, the rotation speed, the presence or absence of external stirring, etc.) in the step of covering the silicon-containing compound layer (and other covering layers as needed), and the like. In particular, as described later, the ratio of the number of fine composite particles contained in the metallic pigment composition of the present invention is preferably controlled by removal (grinding and classification under mild conditions) of the metallic particles having a small particle diameter before the step of covering the silicon-containing compound layer (and, if necessary, the other covering layer) and stirring under mild conditions in the step of covering the silicon-containing compound layer (and, if necessary, the other covering layer).

3. Process for producing metallic pigment composition

The metallic pigment composition of the present invention can be suitably produced, for example, by a production method comprising the steps of producing predetermined flaky (flake-like) metallic particles from a slurry of metallic powder by grinding, washing, sieving (classifying), filtering, concentrating, etc., followed by the step of covering the metallic particles with a silicon-containing compound layer under stirring using a solvent containing water and/or a hydrophilic solvent. More specifically, the following methods are exemplified, but are not limited thereto.

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

(1) Crushing, sieving (classifying) and filtering

Here, a case where aluminum particles are used as the metal particles will be exemplified and described.

The aluminum particles are usually pulverized in the presence of a pulverizing aid or an inert solvent by 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 triturator method, to form so-called flaky (flake) aluminum particles, and after this step, coarse aluminum particles are removed by sieving (classification), and the paste-like aluminum particle pigment is obtained by performing the necessary steps such as filtration, washing, and mixing. In this specification, this is also referred to as "paste-like aluminum flake pigment".

Here, the coarse scale-like (flake-like) aluminum particles refer to aluminum particles that cannot pass through the metal mesh #300 to # 800.

In the present invention, when the atomized aluminum powder and/or aluminum foil are pulverized, it is preferable to conduct the pulverization under mild conditions. This is because, among composite particles obtained by forming a coating layer containing a silicon compound layer of at least 1 layer on the surface of aluminum particles, the generation of composite particles having a minute particle diameter of 1 μm or less (specifically, composite particles having a particle diameter of 0.1 μm or more are not considered as composite particles except that the composite particles having a particle diameter of 0.1 μm or less are considered as composite particles because the composite particles are too small in size, and therefore refer to composite particles having a particle diameter of 0.1 μm or more and 1 μm or less) can be effectively suppressed.

Here, the mild conditions mean that conditions such as reduction of the mass per 1 grinding ball and reduction of the rotation speed of the grinding device are appropriately adjusted and combined.

In addition to the above operations, the grinding conditions are preferably determined in consideration of adjusting the average particle diameter (D ₅₀) of the flaky (flake-like) aluminum particles to be within the range of the present embodiment and improving productivity.

In view of the fact that the average particle diameter (D ₅₀) of the flaky (or flaky) aluminum particles is in the range of 3 μm or more and 30 μm or less, particularly preferable grinding conditions are a combination of conditions in which atomized aluminum powder having a particle diameter of 1 to 30 μm is preferably used as a raw material, the mass of each 1 grinding ball used in the grinding apparatus is preferably 0.08 to 11mg, and the rotational speed of the grinding apparatus is 33% to 78%, more preferably 36% to 57%, relative to the critical rotational speed (Nc).

The specific gravity of the grinding balls used in the ball mill or the like is preferably 8 or less, more preferably 7.5 or less, and still more preferably 7 or less from the viewpoint of easily reducing the ratio of the fine particles and from the viewpoint of improving the surface smoothness of the aluminum particles.

The specific gravity of the grinding ball is preferably greater than the specific gravity of the grinding solvent. By making the specific gravity of the grinding balls larger than that of the grinding solvent, the grinding balls can be prevented from floating in the solvent, and the shearing stress between the grinding balls can be sufficiently obtained, so that grinding tends to be sufficiently performed.

As the grinding balls used in the method for producing an aluminum pigment according to the present embodiment, grinding balls having high surface smoothness such as steel balls, stainless steel balls, zirconia balls, and glass balls are preferable from the viewpoints of adjustment of surface smoothness of aluminum particles and durability of the grinding balls.

On the other hand, steel balls, alumina balls, and the like having low surface smoothness are not preferable from the viewpoints of adjustment of surface smoothness of aluminum particles and durability of the grinding balls.

Therefore, for example, in the case of steel balls, it is preferable to use steel balls whose surface smoothness is improved by mechanical polishing and chemical polishing.

The mass of each 1 grinding ball is preferably 0.08-11 mg as described above.

By using the grinding balls having a mass of 0.08 mg/or more, it is possible to prevent the occurrence of a phenomenon that the grinding balls cannot be ground due to a reduction in shearing stress between the grinding balls because the grinding balls do not move individually and move in clusters or blocks, so-called group motion.

Further, by using the grinding balls having a mass of 11 mg/or less, excessive impact force applied to the aluminum powder can be prevented, and generation of warpage, deformation, cracks, and the like can be prevented.

The atomized aluminum powder as the raw material is preferably one having less impurities other than aluminum.

The purity of the atomized aluminum powder is preferably 99% or more, more preferably 99.5% or more, and still more preferably 99.7% or more.

The average particle diameter of the atomized aluminum powder as the raw material is preferably 2 to 25 μm.

The atomized aluminum powder as the raw material is preferably spherical powder, teardrop powder, or the like. By using these, the shape of the aluminum pigment during grinding tends to be less likely to be lost. On the other hand, needle-like powder and amorphous powder are not preferable because the shape of the aluminum pigment during grinding tends to be lost.

In the case of producing the aluminum pigment according to the present embodiment by a milling apparatus equipped with a ball mill, a milling solvent is preferably used.

The type of the milling solvent is not limited to the following, and examples thereof include conventionally used hydrocarbon solvents such as mineral spirits and solvent naphtha, and low-viscosity solvents such as alcohols, ethers, ketones and esters.

The milling conditions for the atomized aluminum powder are preferably such that the volume of the milling solvent is 1.5 to 16.0 times, more preferably 2.0 to 12.0 times, the mass of aluminum in the atomized aluminum powder. The volume of the milled solvent is preferably 1.5 times or more the mass of aluminum in the atomized aluminum powder, because warpage, deformation, cracking, and the like associated with long-term milling of the atomized aluminum powder can be prevented.

In addition, since the volume of the milling solvent is 16.0 times or less the mass of aluminum in the atomized aluminum powder, uniformity in the mill during milling is improved, and the atomized aluminum powder and the milling medium are effectively brought into contact with each other, so that milling tends to be suitably performed.

The volume of the milled sphere is preferably 0.5 to 3.5 times, more preferably 0.8 to 2.5 times, the volume of the milled solvent (volume of the milled sphere/volume of the milled solvent).

By the volume of the grinding balls being 0.5 times or more the volume of the grinding solvent, uniformity of the grinding balls in the mill at the time of grinding is improved, and there is a tendency that grinding is suitably performed.

Further, since the ratio of the volume of the grinding balls to the volume of the grinding solvent is 3.5 times or less, the ratio of the grinding balls in the mill is preferably in a suitable range, and the stacking of balls is not excessively high, the problem of deterioration in shape such as warpage, deformation, and cracking of particles due to grinding stress is prevented, and the reduction in brightness and the enhancement of scattered light can be prevented.

In the case of producing the aluminum pigment according to the present embodiment by a milling apparatus equipped with a ball mill, it is preferable to use a milling aid in addition to the above-mentioned milling solvent.

Examples of the pulverizing aids include fatty acids, fatty amines, fatty amides, and fatty alcohols. Oleic acid, stearic acid, stearyl amine and the like are generally preferred. Examples of the inert solvents include mineral spirits, solvent naphthas, LAWS, HAWS, toluene, xylene, and other inert solvents exhibiting hydrophobicity, which may be used alone or in combination. The pulverizing aid and the inactive solvent are not limited to them.

The grinding aid is preferably used in an amount of 0.2 to 30 mass% based on the mass of the atomized aluminum powder.

The grinding balls used for grinding the atomized aluminum powder preferably have a diameter of 0.6 to 2.4mm.

By using the grinding balls having a diameter of 0.6mm or more, the lamination of the grinding balls is not excessively low, and the pressure applied to the aluminum particles during grinding is in a suitable range, so that grinding tends to be suitably performed.

In addition, the use of the grinding balls having a diameter of 2.4mm or less is preferable because the stacking of the grinding balls is not excessively high, and problems of shape deterioration such as warping, deformation, and cracking of the particles due to the weight of the balls are prevented, and reduction in brightness and enhancement of scattered light can be prevented.

The rotational speed of the ball mill during grinding of the atomized aluminum powder is preferably 33% to 78% with respect to the critical rotational speed (Nc) as described above.

The ratio of the rotation speed to the critical rotation speed is preferably 33% or more, since uniformity of movement of the aluminum slurry and balls in the ball mill is maintained.

Further, when the ratio of the rotational speed to the critical rotational speed is 78% or less, the grinding ball is prevented from being stirred up or falling down by its own weight, and the impact force applied to the aluminum particles by the grinding ball is not excessively high, so that the problem of shape deterioration such as warping, deformation, and cracking of the particles is prevented.

The aluminum pigment according to the present embodiment may be produced by a vacuum vapor deposition method, in addition to the above-described production method having a step of grinding atomized aluminum powder.

The pulverization step is preferably pulverization by a wet ball mill method from the viewpoint of preventing dust explosion and ensuring safety.

In the present invention, it is preferable that aluminum particles having a small particle diameter among the aluminum particles are removed in advance by classification before forming a coating layer containing at least 1 layer of a silicon compound layer on the surfaces of the scaly (flaky) aluminum particles. This is because, among composite particles obtained by forming a coating layer containing a silicon compound layer of at least 1 layer on the surface of aluminum particles, the generation of composite particles having a minute particle diameter of 1 μm or less (specifically, composite particles having a particle diameter of 0.1 μm or less, except for composite particles having a particle diameter of less than 0.1 μm, since the size is too small, the influence on the performance of the present invention can be ignored and not recognized as composite particles, and therefore, composite particles having a particle diameter of 0.1 μm or more and 1 μm or less can be referred to as composite particles) can be effectively suppressed thereafter. Specifically, the number ratio of composite particles having a particle diameter of 0.1 μm or more and 1 μm or less in the aluminum pigment can be suppressed to 10% or less relative to the total number of composite particles in the aluminum pigment. This classification is used in combination with the above-mentioned milling under mild conditions. The generation inhibition of the minute composite particles can be further improved.

However, the above-mentioned grinding step under mild conditions and classification for removing the above-mentioned scaly (flaky) aluminum particles having a small particle diameter do not necessarily need to be performed in both steps, and only one of them may be performed as needed. That is, the grinding step under the above-described mild conditions may be omitted, and only the step of removing the scaly (flaky) aluminum particles having a minute particle diameter by classification after the normal grinding step may be performed, or the grinding step under the above-described mild conditions may be performed, and the subsequent classification may not be performed.

As the classification step for removing the scaly (flaky) aluminum particles having a small particle diameter, wet classification is preferable from the viewpoint of securing safety and the like, and there is a method using a machine such as a gravity classifier (sedimentation classifier), a pyramid classifier, a hydraulic classifier, a siphon classifier, a centrifugal classifier, a hydrocyclone, a jet classifier, a rake classifier, an ajus classifier, a spiral classifier, a classification tank, a hydraulic separator, a decanter centrifuge, or the like, for example.

As the metal particles in the production of the metal pigment composition of the present invention, so-called vapor-deposited aluminum pigments produced by peeling and pulverizing a metal layer deposited on a carrier material such as a resin film by Physical Vapor Deposition (PVD) from the carrier material can also be used. In this case, it is also important to appropriately adjust the pulverizing conditions to suppress the generation of fine particles or to remove fine particles by classification.

(2) Process for forming silicon-containing compound layer

The mixed solution containing the above-mentioned (a) metal particles, (b) a silicon-containing raw material containing at least one of the organic silicon compounds, and (c) a solvent, and, if necessary, other optional components can be produced by mixing these components. The order of mixing is not particularly limited.

As the above-mentioned (a) metal particles, particles of aluminum or aluminum alloy can be particularly suitably used. In addition, as described above, as for the particle shape thereof, metal particles in a scale shape (flake shape) can be suitably used.

The content (solid content) of the metal particles in the mixed liquid is not particularly limited as long as the metal pigment composition of the present invention is obtained, and may be appropriately set according to the kind, particle size, and the like of the metal particles used.

As the silicon-containing raw material, an organosilicon compound is used. The organosilicon compound is not limited, but the aforementioned organosilicon compound can be preferably used.

At least one of the organosilicon compound represented by the above formula (1) (typically, tetraalkoxysilane) and/or a condensate thereof, and the silane coupling agent represented by any one of the above formulas (2) to (4) can be suitably used.

Hereinafter, a case where tetraalkoxysilane is used as the organosilicon compound represented by the above formula (1) will be described as an example. In the following, the tetraalkoxysilane and/or the condensate thereof may be referred to simply as "tetraalkoxysilane".

When the tetraalkoxysilane represented by the above formula (1) and the silane coupling agent represented by any one of the above formulas (2) to (4) are used in combination, a method (referred to as "method 1") in which both are used in combination may be employed. Alternatively, a method including a step of forming the 1 st silicon-containing compound layer by treating the metal particles with one of them and forming the 2 nd silicon-containing compound layer by treating the metal particles with the other of them (referred to as "method 2") may be employed.

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

The method 2 includes, for example, a step of forming a1 st silicon-containing compound layer (e.g., a silica coating film formed of amorphous silica) on the surface of the metal particles by hydrolyzing/condensing the tetraalkoxysilane by appropriately adjusting the pH of a mixture containing the metal particles and the tetraalkoxysilane represented by the above formula (1), and a step of forming a 2 nd silicon-containing compound layer on the surface of the 1 st silicon-containing compound layer by hydrolyzing/condensing the silane coupling agent by appropriately adjusting the pH of a mixture containing the metal particles and the silane coupling agent represented by any one of the above formulas (2) to (4).

The amount of the tetraalkoxysilane represented by the above formula (1) or the condensate thereof can be appropriately set depending on the kind of the tetraalkoxysilane used and the like. For example, from the viewpoint of the effect of the coating treatment and from the viewpoint of suppressing aggregation of metal particles, a reduction in the brightness, and the like, the amount thereof is preferably 2 parts by mass or more and 200 parts by mass or less, more preferably 3 parts by mass or more and 100 parts by mass or less, and still more preferably 5 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the metal particles (solid content).

The amount of the silane coupling agent represented by any one of the above formulas (2) to (4) is not particularly limited, but is preferably 0.1 part by mass or more and 20 parts by mass or less, more preferably 0.5 part by mass or more and 15 parts by mass or less, still more preferably 1 part by mass or more and 10 parts by mass or less, per 100 parts by mass of the metal particles (solid content), from the viewpoint of a desired effect of the covering treatment or the like.

The solvent in the mixed solution, that is, the solvent used for the hydrolysis reaction and/or condensation reaction of the organosilicon compound may be appropriately selected depending on the kind of the silicon-containing raw material used, and water, a hydrophilic organic solvent, or a mixed solvent thereof may be generally used. By means of these solvents, the uniformity of the reaction, the uniformity of the resulting hydrolysates and/or condensation reactants can be improved. In the method of directly forming the silicon-containing compound layer 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 rapid reaction between the metal particles and water. In the present invention, a mixed solvent of water and a hydrophilic organic solvent can be suitably used.

Examples of the hydrophilic organic solvent include, but are not particularly limited to, alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol, ether alcohols 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, and esters thereof, glycols such as ethylene glycol, propylene glycol, 1, 3-butanediol, 1, 4-butanediol, polyethylene glycol, polypropylene glycol, and ethylene propylene glycol, and ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. They may be used in an amount of 1 or 2 or more.

In the case of using a mixed solvent of water and a hydrophilic organic solvent as the solvent, the ratio of the two is not particularly limited as long as the metallic pigment composition of the present invention is obtained.

The amount of the solvent used in the step of forming the silicon-containing compound layer (in the case of performing the preliminary dispersion of the metal particles, the amount of the solvent used is not limited, and is usually about 100 to 10000 parts by mass, and particularly preferably 200 to 1000 parts by mass based on 100 parts by mass of the metal particles (solid content). The use amount of the solvent is 100 parts by mass or more, whereby the increase in viscosity of the mixed solution (slurry) is suppressed, and appropriate stirring can be performed. In addition, the use amount of the solvent is 10000 parts by mass or less, whereby the recovery and regeneration costs of the treatment solution can be prevented from increasing. In the case of the method 2, the amount of the solvent used herein refers to the total amount of the solvent used for the formation of the 1 st silicon-containing compound layer and the formation of the 2 nd silicon-containing compound layer.

Other additives may be blended as necessary in the above-mentioned mixed solution within a range that does not inhibit the effect of the present invention. Examples of the catalyst include a catalyst such as a hydrolysis catalyst and a dehydration condensation catalyst, a surfactant, a metal corrosion inhibitor, and the like.

Among them, a hydrolysis catalyst can be suitably used. By blending the hydrolysis catalyst, the pH of the mixed solution is adjusted, and the organic silicon compound can be efficiently hydrolyzed and dehydrated and condensed, and as a result, a silicon compound-containing layer can be efficiently and reliably formed on the surface of the metal particles.

The hydrolysis catalyst is not particularly limited as long as it is a known or commercially available hydrolysis catalyst. Examples of the hydrolysis catalyst 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-carboxyethane phosphonic acid, 2-aminoethane phosphonic acid, and octane phosphonic acid. These hydrolysis catalysts may be used singly or in combination of 2 or more.

Examples of the hydrolysis catalyst include inorganic bases such as ammonia, sodium hydroxide and potassium hydroxide, inorganic base salts such as ammonium carbonate, ammonium bicarbonate, sodium carbonate and sodium bicarbonate, and salts of organic acids such as monomethyl amine, dimethyl amine, trimethyl amine, monoethyl amine, diethyl amine, triethyl amine, monoethanolamine, diethanolamine, triethanolamine, N-dimethylethanolamine, ethylenediamine, pyridine, aniline, choline, tetramethylammonium hydroxide and guanidine, and ammonium formate, ammonium acetate, monomethyl ammonium formate, dimethyl ammonium acetate, pyridine lactate, guanidinoacetic acid and aniline acetate. These hydrolysis catalysts may be used in an amount of 1 or 2 or more.

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

In the production of the above-described mixed solution, the mixing order is not particularly limited as long as the components are uniformly mixed in the mixed solution.

The metallic pigment composition of the present invention is preferably produced by stirring the mixture with a proper strength.

The temperature of the mixed solution may be either normal temperature or under heating. In general, the temperature of the mixed solution is not less than 20 ℃ and not more than 90 ℃, and is particularly preferably controlled within a range of not less than 30 ℃ and not more than 80 ℃. By setting the temperature to 20 ℃ or higher, the formation rate of the silicon-containing compound layer increases, and the treatment time can be shortened. On the other hand, when the temperature is 90 ℃ or lower, the reaction can be easily controlled, and the probability of obtaining desired composite particles can be improved.

The stirrer for stirring the mixed solution is not particularly limited, and a known stirrer that can effectively and uniformly stir the mixed solution containing aluminum particles and the organosilicon compound can be used. Specific examples thereof include kneaders, rotary vessel mixers, stirred tanks, V-type mixers, double cone mixers, screw mixers, sigma mixers, flash mixers, air mixers, ball mills, and wheel mills. Further description of the mixer is described below.

The temperature of the mixed solution when the mixed solution containing the metal particles and the organosilicon compound is stirred is usually about 10 to 100 ℃, and particularly preferably 30 to 80 ℃. By setting the temperature to 10 ℃ or higher, the reaction time for obtaining a sufficient treatment effect can be shortened. In addition, by setting the temperature to 100 ℃ or lower, the reaction for obtaining the desired metallic pigment composition can be more easily controlled.

The stirring time of the mixed solution is not particularly limited as long as it is a time sufficient for forming the desired silicon-containing compound layer. The stirring time is, for example, preferably 0.5 to 10 hours, more preferably 1 to 5 hours. By setting the stirring time to 0.5 hours or longer, a sufficient treatment effect can be obtained. In addition, by setting the stirring time to 10 hours or less, an increase in the processing cost can be suppressed.

In the above mixed solution, the silicon-containing raw material is subjected to hydrolysis/condensation reaction to form a silicon-containing compound layer on the surface of the metal particles (or via the 2 nd coating layer). The hydrolysis/condensation reaction can be carried out, in particular, by adjusting the pH of the mixed solution.

In the step of adjusting the pH, particularly in the step of forming the silicon-containing compound layer on the surface of the metal particles (or via the 2 nd coating layer), the pH of the mixed solution is preferably adjusted appropriately so that the pH can be maintained within a constant range. In this case, the pH is preferably adjusted by adding a hydrolysis catalyst, but other acidic or basic compounds may be used as long as the characteristics of the metallic pigment composition of the present invention are not impaired.

When an alkaline hydrolysis catalyst is used as the hydrolysis catalyst, the pH is preferably 7 or more and 11 or less, and particularly preferably 7.5 or more and 10 or less. By having a pH of 7 or more, the silicon-containing compound layer can be formed rapidly. On the other hand, when the pH is 11 or less, aggregation of metal particles and a decrease in brightness can be suppressed, and further, generation of hydrogen gas due to corrosion can be prevented.

When an acidic hydrolysis catalyst is used as the hydrolysis catalyst, the pH is preferably 1.5 or more and 4 or less, and particularly preferably 2 or more and 3 or less. By properly controlling the reaction at a pH of 1.5 or more, a metallic pigment composition containing desired composite particles can be easily obtained. On the other hand, when the pH is 4 or less, the precipitation rate of the silicon-containing compound layer can be kept high.

In the case of using either of the above methods 1 and 2, it is preferable to add 0.01 to 50 parts by mass, more preferably 1 to 30 parts by mass, in terms of the state of completion of the hydrolysis and condensation reaction, to 100 parts by mass of the metal particles (solid content) of the hydrolysate of the organosilicon compound represented by the general formula (1) and/or the condensate thereof. Further, the hydrolysate and/or condensate derived from the silane coupling agent represented by any one of the above general formulae (2) to (4) and/or a partial condensate thereof is added in an amount of 0.01 to 0.8 parts by mass, more preferably 0.01 to 0.7 parts by mass in terms of the state of completion of the hydrolysis and condensation reaction, per 100 parts by mass of the metal particles (solid component).

The amount of the hydrolysate and/or condensate of the organosilicon compound represented by the general formula (1) to be added can be calculated by multiplying the mass of the organosilicon compound represented by the 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 subjected to the hydrolysis and condensation reaction.

For example, when Tetraethoxysilane (TEOS) is used as the organosilicon compound represented by the general formula (1), the addition amount of the hydrolysate of the organosilicon compound and/or the condensate thereof can be calculated using the following mass ratio before and after the hydrolysis and condensation reaction.

(Hydrolysis)

Si (OC ₂H₅)₄ (molecular weight: 208) +4H ₂O→Si(OH)₄ (molecular weight: 96) + (C) ₂H₅OH)₄

(Condensation)

Si (OH) ₄ (molecular weight: 96) +Si (OH) ₄ (molecular weight: 96) → (SiO ₂)₂ (molecular weight: 60X 2) +4H ₂ O)

Since the mass of the above is 60/208=0.288 times before and after the hydrolysis and condensation reaction, for example, when TEOS10 parts by mass is used per 100 parts by mass of the metal particles (solid content), the amount of the hydrolysate and/or condensate thereof added is 0.288 times, that is, 2.88 parts by mass.

Similarly, the amount of the hydrolysate and/or condensate of the silane coupling agent represented by any one of the general formulae (2) to (4) to be added may be calculated by multiplying the mass of the silane coupling agent represented by any one of the general formulae (2) to (4) and/or partial condensate thereof by the mass ratio before and after the reaction when the silane coupling agent and/or partial condensate thereof is completely hydrolyzed and condensed.

For example, when methyltrimethoxysilane is used as the silane coupling agent represented by the general formula (2), the following mass ratio before and after the hydrolysis and condensation reaction can be used to calculate the addition amount of the hydrolysate of the silane coupling agent and/or the condensate thereof.

(Hydrolysis)

CH ₃Si(OCH₃)₃ (molecular weight: 136) +3H ₂O→CH₃Si(OH)₃ (molecular weight: 94) + (CH) ₃OH)₃

(Condensation)

CH ₃Si(OH)₃ (molecular weight: 94) +CH ₃Si(OH)₃ (molecular weight: 94) → (SiCH ₃O_1.5)₂ (molecular weight: 67×2) +3H ₂ O)

Since the mass of the above is 67/136=0.49 times before and after the hydrolysis/condensation reaction, for example, when 1.23 parts by mass of methyltrimethoxysilane is used per 100 parts by mass of the metal particles (solid content), the amount of the hydrolysate and/or condensate thereof to be added is 0.49 times, that is, 0.60 parts by mass.

In the case of using either of the above methods 1 and 2, it is preferable that the metal particles are sufficiently dispersed in water, a hydrophilic organic solvent, or a mixed solvent thereof before being combined with the organic silicon compound as the silicon compound source (or before being combined with the molybdenum compound in the case of forming the 2 nd coating layer). In such preliminary dispersion (initial dispersion), it is preferable to perform an external circulation in which a part of the dispersion (for example, 0.5 mass% or more and 30 mass% or less, preferably 1 mass% or more and 20 mass% or less, more preferably 1 mass% or more and 15 mass% or less of the total dispersion per 1 part) is once drawn out of the dispersion tank and returned to the dispersion tank again, whereby the degree of dispersion can be further improved. By performing ultrasonic treatment outside the dispersion tank in the middle of the flow path of the external circulation, dispersibility can be further improved.

The ultrasonic treatment is not particularly limited, and may be performed at a temperature of usually 10W to 1000W, preferably 50W to 800W, usually 20 seconds to 10 minutes, preferably 30 seconds to 5 minutes. The amount of the solvent used for such preliminary dispersion may be generally about 100 to 10000 parts by mass, preferably 200 to 5000 parts by mass, more preferably 300 to 1000 parts by mass, based on 100 parts by mass of the metal particles (solid content), from the viewpoint of appropriately adjusting the stirring strength to obtain sufficient dispersion.

The preliminary dispersion of the metal particles may be carried out at a temperature of usually 10 ℃ to 80 ℃, preferably 15 ℃ to 60 ℃, and most preferably about room temperature (about 20 to 30 ℃). The preliminary dispersion of the metal particles (the ultrasonic treatment is also included in the case of performing the ultrasonic treatment) may be performed for 5 minutes to 10 hours, preferably 10 minutes to 5 hours.

(3) Step2 of Forming the coating layer

As described above, the 2 nd capping layer (where formed) is particularly preferably formed between the metal particles and the silicon-containing compound layer. Thus, a layer structure of "metal particles/2 nd cap layer/silicon-containing compound layer" can be suitably employed.

The 2 nd coating layer is not particularly limited, and may be a molybdenum-containing coating film, a phosphoric acid compound coating film, or the like. As a preferable example of the molybdenum-containing substance constituting the molybdenum-containing coating film, there is mentioned a mixed coordination type heteropolyanion compound disclosed in Japanese patent application laid-open No. 2019-151678. Examples of the constituent components of the 2 nd coating layer including the mixed coordination type heteropolyanion compound are as described above.

Hereinafter, a method of forming a molybdenum-containing coating film between metal particles and a silicon-containing compound layer as the 2 nd coating layer will be described by way of example.

In the case where a molybdenum-containing coating film is formed between the metal particles and the silicon-containing compound layer as the 2 nd coating layer, the molybdenum-containing coating film can be formed on the surfaces of the metal particles by stirring a mixed solution containing the metal particles and a molybdenum compound (typically, a mixed coordination type heteropolyanion compound) before the silicon-containing compound layer is formed.

The method for forming the molybdenum-containing coating film on the surface of the metal particles is not particularly limited as long as the method is a method capable of uniformly stirring a mixed solution containing the metal particles and the molybdenum compound in an aqueous solvent. For example, a molybdenum-containing coating film can be formed on the surface of the metal particles by stirring or kneading a mixed solution containing the metal particles and the molybdenum compound in a slurry state or a paste state. In the mixed solution, the molybdenum compound may be dissolved or dispersed.

The stirrer for stirring the mixed solution containing the metal particles and the molybdenum compound is not particularly limited, and a known stirrer that can effectively and uniformly stir the mixed solution containing the aluminum particles and the molybdenum compound can be used. Specific examples thereof include kneaders, rotary vessel mixers, stirred tanks, V-type mixers, double cone mixers, screw mixers, sigma mixers, flash mixers, air mixers, ball mills, and wheel mills. Examples of the stirring blade of the stirrer are not particularly limited, and include an anchor blade, a propeller blade, a turbine blade, and the like.

The amount of the molybdenum compound to be used may be appropriately set depending on the kind of the molybdenum compound to be used and the like. The amount is usually 0.02 parts by mass or more and 20 parts by mass or less, and particularly preferably 0.1 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of the metal particles (solid component). The content of 0.02 parts by mass or more can provide a sufficient treatment effect. In addition, the brightness of the obtained metallic pigment composition can be kept high by the content of 20 parts by mass or less.

As the solvent used in the mixing of the metal particles and the molybdenum compound, water, a hydrophilic organic solvent, or a mixed solvent thereof can be generally used.

Examples of the hydrophilic organic solvent include alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol, ether alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether, and esters thereof, glycols such as ethylene glycol, propylene glycol, 1, 3-butanediol, 1, 4-butanediol, polyethylene oxide glycol, polypropylene oxide glycol, and ethylene propylene glycol, and ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. They may be used in an amount of 1 or 2 or more.

The amount of the solvent used in the step of forming the 2 nd coating layer (in the case of performing the preliminary dispersion of the metal particles, the amount of the solvent used is not particularly limited, but is usually 50 parts by mass or more and 5000 parts by mass or less, more preferably 100 parts by mass or more and 2000 parts by mass or less, relative to 100 parts by mass of the metal particles (solid content). The use of the solvent in an amount of 50 parts by mass or more can suppress the segregation of the molybdenum compound and the aggregation of the metal particles. In addition, the amount of the solvent used is 5000 parts by mass or less, whereby a sufficient treatment effect with the molybdenum compound on the metal particles can be obtained.

The temperature of the mixed solution when the mixed solution containing the metal particles and the molybdenum compound is stirred is usually about 10 to 100 ℃, and particularly preferably 30 to 80 ℃. By setting the temperature to 10 ℃ or higher, the reaction time for obtaining a sufficient treatment effect can be shortened. In addition, by setting the temperature to 100 ℃ or lower, the reaction for obtaining the desired metallic pigment composition can be more easily controlled.

The stirring time of the mixed solution is not particularly limited as long as it is a time sufficient for forming a desired molybdenum-containing coating film. The stirring time is, for example, preferably 0.5 to 10 hours, more preferably 1 to 5 hours. By setting the stirring time to 0.5 hours or longer, a sufficient treatment effect can be obtained. In addition, by setting the stirring time to 10 hours or less, an increase in the processing cost can be suppressed.

After the stirring of the mixed solution containing the metal particles and the molybdenum compound is completed, the particles having the 2 nd coating layer formed thereon can be recovered. In this case, if necessary, known washing, solid-liquid separation, and the like can be appropriately performed. For example, it is preferable to remove water and unreacted substances from a cake containing metal particles having a molybdenum-containing coating film by washing the mixed solution with a hydrophilic organic solvent and then filtering the washed solution with a filter or the like. Thus, a molybdenum-containing coating film as the 2 nd coating layer can be formed. In the case of forming the other 2 nd cover layer, the method may be performed as described above.

In the method of forming the 2 nd coating layer (molybdenum-containing coating film) on the metal particles and then forming the silicon-containing compound layer, after the stirring of the mixed solution containing the metal particles and the molybdenum compound is completed, the particles having the 2 nd coating layer formed may not be recovered, but in this system, a silicon compound source (typically, at least one of the organic silicon compounds represented by the above formula (1), for example, tetraalkoxysilane and/or condensate thereof, and the silane coupling agent represented by any one of the above formulas (2) to (4)) may be directly added/stirred. In this case, a dispersion of an organic silicon compound represented by the above formula (1), for example, a tetraalkoxysilane and/or a condensate thereof may be added to a system including particles having a coating layer of the 2 nd, and then a dispersion of at least one of the silane coupling agents represented by any one of the above formulas (2) to (4) may be added and stirred (refer to the 2 nd method in the "step of forming a silicon-containing compound layer").

(4) Stirring conditions

In the production of the metallic pigment composition of the present invention, at least the step of forming the silicon-containing compound layer needs to be performed under stirring. In the production of the metallic pigment composition of the present invention, it is preferable that not only the step of forming the silicon compound-containing layer is performed under stirring, but also the step of forming the 2 nd coating layer is performed under stirring. In the manner of performing the above-described preliminary dispersion of the metal particles, it is more preferable that it is also performed under stirring. In the production of the metallic pigment composition of the present invention, it is further preferable that all the steps including the preliminary dispersion of the metallic particles, the step of forming the 2 nd coating layer, and the step of forming the silicon-containing compound layer are carried out with stirring.

In the production of the metallic pigment composition of the present invention, by performing at least the step of forming the silicon-containing compound layer with stirring properly controlled, the adhesion of the composite particles to each other via the silicon-containing compound layer or the coverage of the composite particles including the aggregated particles formed of the metallic particles with the silicon-containing compound layer can be effectively suppressed or prevented. The entire steps including the preliminary dispersion of the metal particles, the step of forming the 2 nd coating layer, and the step of forming the silicon-containing compound layer (until the end of forming all layers to be formed on the surfaces of the metal particles) are performed with stirring. The metallic pigment composition of the present invention satisfying all of the physical properties of the above-mentioned (1) to (6) can be more easily obtained.

The following description of the stirring conditions can be applied to any process in the production of the metallic pigment composition of the present invention.

The stirring can be performed by a known or commercially available stirring device. For example, at least one of a kneader, a mixer, a rotary vessel mixer, a stirred tank reactor, a V-type mixer, a double cone mixer, a screw mixer, a sigma mixer, a flash mixer, an air flow mixer, a ball mill, an edge mill, and the like can be used.

Stirring is particularly preferably carried out under mild conditions.

Here, the mild conditions mean that, in the case of performing the step of forming the silicon-containing compound layer by using the stirring reaction tank, stirring is performed at a low speed in which the tip speed of the stirring blade is 0.5 m/sec or more and 20 m/sec or less.

This is because, by performing such stirring at a low speed, the generation of composite particles having a minute particle diameter (specifically, composite particles having a particle diameter of less than 0.1 μm, since the size is too small, the influence on the performance of the present invention can be neglected, irrespective of the composite particles, among composite particles obtained by forming a coating layer containing at least 1 layer of a silicon-containing compound layer on the surface of metal particles, and therefore, it means composite particles having a particle diameter of 0.1 μm or more and 1 μm or less) can be effectively suppressed. Specifically, the number ratio of composite particles having a particle diameter of 0.1 μm or more and 1 μm or less in the metallic pigment composition can be suppressed to 10% or less relative to the total number of composite particles in the metallic pigment composition. The stirring under the mild condition can more effectively reduce the ratio of the composite particles of the minute particle diameter by using in combination with the above-mentioned grinding under the mild condition.

Among the above-mentioned agitators, an agitation tank type apparatus for agitating with an agitating blade is preferably used. The stirring blade plays a cyclic role of flowing the entire liquid-phase-containing reaction system and plays a pressure shearing role, so that the generation of composite particles can be more effectively suppressed.

The shape of the stirring vane is not particularly limited, and for example, an anchor shape, a propeller shape, a turbine shape, an inclined turbine shape, a fan turbine shape, a blade shape, an inclined blade shape, or a gate shape may be used. MAXBLEND wings (Sumitomo Heavy Industries Process Equipment co., ltd.) and FULLZONE wings (Kobelco Eco-Solutions co., ltd.) are also suitable. The stirring vanes of these shapes may be combined in a plurality of stages.

The stirring speed is preferably such that the stirring wings are not exposed by a vortex (vortex) generated by stirring. In order to suppress the vortex generated by stirring, a cylindrical tank, a square tank, a tank provided with a baffle, or the like may be suitably used.

In the production of the composite particle-containing metallic pigment composition of the present invention, it is preferable to set the most suitable stirring vessel, the size of the stirring blade, and the speed of the stirring blade in relation to the amount of the mixed liquid and the physical properties (density, viscosity, etc.). The size of the stirring tank is preferably selected so that the maximum amount of the mixed liquid used in the series of steps is 20% to 80% of the stirring tank. In the case of a cylindrical stirring tank, the ratio of the height (L) to the inner diameter (D) of the stirring tank is usually in the range of 0.5 to 3.0, and L/D is usually in the range of 1 to 2. In addition, the size of the stirring vane is preferably in the range of 0.4 to 0.6 inclusive, in which the maximum diameter is usually in the range of 0.2 to 0.9 inclusive of the inner diameter of the stirring vessel. The shape (including length) of the stirring blade is preferably selected appropriately according to the physical properties of the mixed solution, and it is important that the entire stirring tank be stirred in all the steps. In particular, it is preferable to use a combination of a plurality of stages of a tilt blade type, a tilt turbine type, and a propeller type, or to use MAXBLEND wings or FULLZONE wings, in which a non-stirred stay is not formed near the liquid surface or the bottom surface of the stirring tank. In this case, the stirring blade is preferably spaced apart from the inner surface of the stirring tank (including the baffle plate) by at least 5 mm. Thus, breakage and deformation of the metal particles can be easily suppressed.

The speed of the stirring blade is preferably 0.5m/s to 20m/s, more preferably 1m/s to 15m/s, still more preferably 2m/s to 10 m/s. When the speed of the tip of the stirring blade is in the range of 0.5m/s to 20m/s, the dispersibility of the composite particles in the produced metallic pigment composition can be improved, and a metallic pigment composition having small aggregation of the particles, excellent concealing properties, color tone, and less generation of gas can be easily obtained. In addition, when the linear velocity of stirring is within the above range, breakage of metal particles (for example, scaly aluminum powder) is prevented, and at the same time, the velocity of hydrolysis/condensation reaction is appropriately controlled, so that aggregation of composite particles can be effectively suppressed.

(5) Recovery process of composite particles

After the step of forming the silicon-containing compound layer (and optionally the 2 nd capping layer) of the metal particles is completed, the resulting composite particles may be recovered. In the recovery, if necessary, known treatments such as washing and solid-liquid separation may be performed. For example, it is preferable to remove water and unreacted substances from a cake containing composite particles by washing the dispersion with an organic solvent and then filtering the dispersion with a filter. Further, the filter cake containing the composite particles may be subjected to a heat treatment at a temperature in the range of, for example, 100 to 500 ℃ as needed. The composite particles thus recovered can generally constitute a metal pigment composition containing a small amount of solvent residue of water/hydrophilic solvent used in the production process, as will be described later.

4. Metal pigment composition

The metallic pigment composition of the present invention obtained as described above is known to be a metallic pigment composition comprising composite particles including metallic particles and 1 or more coating layers on the surface thereof, and further comprising a solvent such as water or a hydrophilic solvent used in the production process as a residual part of a solid component (non-volatile component).

In general, the metal pigment composition may contain 0.02 to 50 parts by mass of a hydrolysate of an organosilicon compound (for example, at least one of the organosilicon compounds represented by the general formula (1), a silane coupling agent selected from the group consisting of the silane coupling agents represented by the general formulae (2), (3) and (4), and at least one of partial condensates thereof) and/or a silicon compound of a condensate thereof, based on 100 parts by mass of the metal particles, in terms of the state in which the hydrolysis/condensation reaction is completed.

In the metallic pigment composition, the compound forming the optional 2 nd coating layer (molybdenum-containing compound, for example, mixed coordination type heteropolyanion compound, is an optional mode of forming a molybdenum-containing coating film as the 2 nd coating layer) may be present in an amount of 0.01 to 10 parts by mass relative to 100 parts by mass of the metallic particles.

The organic oligomer or polymer optionally selected in the metal pigment composition may be present in an amount of 0.01 to 50 parts by mass based on 100 parts by mass of the metal particles.

The metal pigment composition may contain 0.01 to 20 parts by mass of at least one selected from the group consisting of an inorganic phosphoric acid compound and a salt thereof, and an acidic organic (phosphorous) acid ester and a salt thereof, based on 100 parts by mass of the metal particles.

In the metallic pigment composition, as a residual part of the above-mentioned component (non-volatile component), there may be a solvent containing water/hydrophilic solvent used in the production process. The amount of the solvent containing water/hydrophilic solvent may be, for example, 0.5% by mass or more and 95% by mass or less of the metallic pigment composition. Or the amount of the solvent containing water/hydrophilic solvent may be 1% by mass or more and 90% by mass or less, or 2% by mass or more and 80% by mass or less, or 5% by mass or more and 70% by mass or less of the metallic pigment composition.

The metallic pigment composition may contain any component other than the above-mentioned components, which are arbitrarily selected. Examples of the optional component include at least one of an antioxidant, a light stabilizer, a polymerization inhibitor, and a surfactant.

As the antioxidant, antioxidants typified by phenol compounds, phosphorus compounds, and sulfur compounds can be used.

As the light stabilizer, a light stabilizer used as the antioxidant described above may be used, and light stabilizers typified by 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 may be used.

5. Use of metallic pigment compositions

The metallic pigment composition can be used for aqueous paints, inks and the like. The metallic pigment composition can be added to an aqueous paint or an aqueous ink in which a resin as a coating film forming component (binder) is dissolved or dispersed in a medium mainly containing water, to thereby form a metallic aqueous paint or a metallic aqueous ink. The metallic pigment composition may be kneaded with a resin or the like to be used as a water-resistant binder or filler. The antioxidant, light stabilizer, and surfactant may be added when the metallic pigment composition is blended into an aqueous paint, aqueous ink, resin, or the like.

In the case where the metallic pigment composition is used for a coating material or an ink, the metallic pigment composition may be directly added to a (aqueous) coating material or a (aqueous) ink, but is preferably added after being dispersed in a solvent in advance. Examples of the solvent used include water, dodecanol ester, diethylene glycol monobutyl ether, and propylene glycol monomethyl ether. Examples of these resins include acrylic resins, polyester resins, polyether resins, epoxy resins, fluorine resins, rosin resins, and the like. In addition, as an example of the binder for the paint or ink, rubber is mentioned in addition to resin.

These resins are preferably emulsified, dispersed or dissolved in water. For this purpose, carboxyl groups, sulfonic acid groups, and the like contained in the resins can be neutralized.

Preferred resins are acrylic resins, polyester resins.

If necessary, a resin such as a melamine-based curing agent, an isocyanate-based curing agent, or a urethane dispersion may be used in combination. Further, the pigment may be combined with a coloring pigment such as an inorganic pigment, an organic pigment, or an extender which is usually added to a paint, a silane coupling agent, a titanium coupling agent, a dispersant, a sedimentation inhibitor, a leveling agent, a thickener, or a defoaming agent. In order to improve dispersibility in the paint, a surfactant may be further added. In order to improve the storage stability of the paint, an antioxidant, a light stabilizer, and a polymerization inhibitor may be further added.

Examples of the coloring pigment include phthalocyanine, quinacridone, isoindolinone, perylene, azo lake, iron oxide, chrome yellow, carbon black, titanium oxide, and pearlescent mica.

The content of the metallic pigment composition of the present invention in the aqueous paint or aqueous ink (resin composition) is not limited, but is usually 0.1 mass% or more and 50 mass% or less, and particularly preferably 1 mass% or more and 30 mass% or less. When the content is 0.1 mass% or more, a high decorative (metallic) effect can be obtained. Further, the content of 50 mass% or less can prevent deterioration of the properties of the aqueous paint or the aqueous ink, such as weather resistance, corrosion resistance, mechanical strength, and the like.

The content of the solvent is not particularly limited, and may be 20% by mass or more and 200% by mass or less with respect to the binder content. By the content of the solvent being within this range, the viscosity of the paint, ink is adjusted to be within an appropriate range, and handling and film formation can be facilitated.

The method of applying or printing the aqueous paint and the like is not particularly limited. For example, various coating methods and printing methods can be appropriately employed in consideration of the form of the aqueous paint and the like, the surface shape of the material to be coated, and the like. Examples of the coating method include a spray method, a roll coater method, a brush coating method, and a doctor blade coating method. Examples of the printing method include gravure printing and screen printing.

The coating film formed by the aqueous coating material or the like may be formed on the undercoat layer or the intermediate coating layer formed by the electrodeposition coating or the like. In addition, a surface coating layer or the like may be formed on a coating film formed by an aqueous paint or the like as required.

In the case of these layer structures, each coating layer may be coated, or the next coating layer may be coated after curing or drying, or the next coating layer may be coated after each coating layer is coated by so-called wet-on-wet coating, without curing or drying. From the viewpoint of obtaining a coating film having good mirror-like brightness, the aqueous coating material or the like containing the metallic pigment composition of the present invention preferably employs a method comprising a step of forming a coating film layer by using an aqueous coating material or the like after applying an undercoat film layer and curing or drying.

The method of curing the coating composition in each coating layer may be either thermal curing or normal temperature curing. The method for drying the coating composition of each coating layer may be, for example, hot air or natural drying at ordinary temperature.

The thickness of the coating film layer formed by the aqueous paint is not particularly limited, and is usually preferably 0.5 μm or more and 100 μm or less. The thickness of the coating layer is 0.5 μm or more, whereby the hiding effect of the substrate by the ink or paint can be sufficiently obtained. In addition, the thickness of the coating layer is 100 μm or less, whereby drying becomes easy, and occurrence of defects such as wrinkles and sagging can be suppressed.

Examples

The present invention will be described more specifically with reference to the following examples, but it should be noted that these examples are merely illustrative, and the present invention is not limited by the description of these examples.

1. Method for evaluating physical Properties used in examples and comparative examples

The evaluation methods of the physical properties used in examples and comparative examples are as follows.

(1) Determination of the average particle diameter D ₅₀

The aluminum pigment compositions obtained in the examples and comparative examples were used as samples, and D ₅₀, which is a volume reference of composite particles contained therein, was measured using a laser diffraction particle size distribution meter "LA-300" (manufactured by horiba, inc.).

As the measuring solvent, mineral spirits were used.

The metal pigment composition containing composite particles as a sample was subjected to ultrasonic dispersion for 2 minutes as a pretreatment, and then placed in a dispersion tank, and after confirming that a proper concentration was formed, D ₅₀ was measured.

(2) Determination of the ratio of Si element to Al element

The contents of aluminum element and silicon element in the composite particles contained in the aluminum pigment compositions obtained in the examples and comparative examples were measured by a high-frequency Inductively Coupled Plasma (ICP) emission spectrometry.

(3) Determination of the composite particle count ratio

The number of composite particles (fine composite particles) having a particle diameter of 0.1 μm or more and 1 μm or less and the number of composite particles (coarse composite particles) having a particle diameter of 3 times or more the size of D ₅₀ based on the volume of the composite particles obtained by the above measurement in the aluminum pigment compositions obtained in the examples and comparative examples were measured by producing a coating film by producing a metal coating material and measuring the number of composite particles contained in the coating film. Specifically as described below.

First, a metallic paint having the following composition was produced.

Aluminum pigment composition as a nonvolatile matter of 0.25g

18.0G of isopropanol

Acrylic resin (1): 24g

Melamine resin (2): 5g

The product of DIC Co., ltd., ACRYDIC 47712 for the respective purposes of the present invention

2, Manufactured by DIC Co., ltd., AMIDIR J-820-60

The aluminum pigment compositions obtained in the examples and comparative examples were used as the aluminum pigment compositions.

To prepare a test piece for observation, a metal coating material prepared by the above formulation was first coated on a polyethylene terephthalate film (PET film) using a 1 mil applicator, left to stand at room temperature for 20 minutes, and then sintered at 140 ℃ for 20 minutes, to prepare a coated sheet.

Then, the coating film of the resulting coated sheet was photographed at a magnification of 700 times by a microscope (HiROX: KH-3000), and particles having an equivalent circle diameter of 0.1 μm or more and 1 μm or less and particles having an equivalent circle diameter exceeding 3 times the volume reference of D ₅₀ of the composite particles measured by the aforementioned laser diffraction particle size distribution analyzer "LA-300" (manufactured by Horiko Co., ltd.) were extracted by using Image analysis software (Media Cybernetics: image-ProPLUS ver.7.0), and the number of particles was measured for each of them relative to the total number of particles. Then, the former is the number ratio (%) of the composite particles having a particle diameter of 0.1 μm or more and 1 μm or less, and the latter is the number ratio (%) of the composite particles having a particle diameter of 3 times or more of the volume reference D ₅₀ when the volume distribution of the composite particles is measured by a laser diffraction particle size distribution meter.

The number of particles in the imaging range is approximately 500.

In addition, since the size of the particles having an equivalent circle diameter of less than 0.1 μm is too small, the influence on the performance of the present invention can be neglected, and the particles are not the object of measurement and are excluded.

2. Manufacture of aluminum pigment compositions

Reference example 1

A ball mill having an inner diameter of 2m and a length of 30cm was charged with a compound containing 50kg of atomized aluminum powder (average particle diameter: 25 μm), 82.2kg of mineral spirits, and 1.5kg of oleic acid, and the mixture was pulverized using 900kg of steel balls having a diameter of 1.6mm and a specific gravity of 7.8.

A steel ball having a surface roughness of 0.08 μm or less (grade G40) in terms of JIS B1501 (maximum) of the steel ball for ball bearing is used. The ball mill was rotated at 27rpm and was subjected to grinding for 6 hours.

After completion of grinding, the slurry in the mill was washed out with mineral oil, and then applied to a 400-mesh vibrating screen, and the fine-grained aluminum pigment was removed to 2% from the slurry by using a hydrocyclone classification device (manufactured by village Tian Gongye, model T-10, SUPERCLONE).

The obtained slurry was filtered through a filter, concentrated, and recovered as an aluminum pigment cake, and the nonvolatile component was adjusted to obtain an aluminum pigment paste (i.e., paste-like aluminum flake pigment) having a nonvolatile component of 80 mass%.

Reference example 2

An aluminum pigment paste having a nonvolatile content of 80 mass% was obtained in the same manner as in reference example 1, except that atomized aluminum powder (average particle diameter: 20 μm) was used as a raw material.

Reference example 3

The same procedure as in reference example 1 was conducted except that the fine-particle aluminum pigment was removed to 9% by using a hydrocyclone classification apparatus (manufactured by village Tian Gongye, model T-10, SUPERCLONE), to obtain an aluminum pigment paste having a nonvolatile content of 80% by mass.

Example 1

To 135kg of the aluminum pigment paste (average particle diameter 16 μm, nonvolatile matter 80 mass%) obtained in referential example 1 was added 465kg of methoxypropanol (hereinafter also referred to as "PM") in a reaction vessel having 2 inclined blade-type stirring blades having a blade diameter of 0.5m and an internal volume of 1m ² at positions 0.3m and 0.6m from the bottom surface, respectively, and the mixture was stirred at 100rpm (tip speed of the stirring blades 2.6 m/sec) by means of the stirring blades, and an external circulation was performed to return 40L/min of the dispersion liquid drawn out from the bottom from the upper portion of the reaction vessel to the reaction vessel, while uniformly dispersing the aluminum paste in the PM. In the external circulation, ultrasonic waves with the frequency of 20kHz and the output power of 500W are irradiated for 1 minute in the middle of the flow path, so that the dispersibility of particles is improved.

Then, 1kg of phosphotungstic molybdic acid (H ₃PW₆Mo₆O₄₀) hydrate was slowly added to 5kg of methoxypropanol, and the mixture was stirred for 1 hour under the same conditions as above while maintaining the slurry temperature at 40 ℃.

Then, as the organosilicon compound, 10kg of tetraethoxysilane was added, and then 10kg of 25% aqueous ammonia and 200kg of purified water were added over 3 hours. Then, 1.3kg of methyltrimethoxysilane was further added as a silane coupling agent, and stirred for 2 hours under the same conditions as described above. After the reaction was completed, the slurry was filtered after cooling.

Thus, an aluminum pigment composition containing 60% of the nonvolatile component of composite particles having metal particles of aluminum and a coating layer containing a silicon compound-containing layer on the surface thereof was obtained. In the reaction, the external circulation was continued while the ultrasonic wave was irradiated.

Example 2

An aluminum pigment composition containing 60% of a nonvolatile component of composite particles having metal particles of aluminum and a coating layer containing a silicon compound layer on the surface thereof was obtained in the same manner as in example 1 except that the aluminum pigment paste (average particle diameter: 20 μm, nonvolatile component: 80 mass%) obtained in referential example 2 was changed.

Example 3

An aluminum pigment composition containing 60% of nonvolatile components of composite particles including metal particles of aluminum and a coating layer containing a silicon compound layer on the surface thereof was obtained in the same manner as in example 1 except that 3kg of tetraethoxysilane, 3kg of 25% aqueous ammonia, 70kg of purified water, and 0.5kg of methyltrimethoxysilane were changed.

Example 4

An aluminum pigment composition containing 60% of nonvolatile components of composite particles including metal particles of aluminum and a coating layer containing a silicon compound layer on the surface thereof was obtained in the same manner as in example 1 except that 50kg of tetraethoxysilane, 50kg of 25% aqueous ammonia, 500kg of purified water, 6.5kg of methyltrimethoxysilane and 5 hours of addition time of aqueous ammonia and purified water were changed.

Example 5

An aluminum pigment composition containing 60% of a nonvolatile component of composite particles having metal particles of aluminum and a coating layer containing a silicon compound layer on the surface thereof was obtained in the same manner as in example 1 except that the aluminum pigment paste (average particle diameter: 20 μm, nonvolatile component: 80 mass%) obtained in referential example 3 was changed.

Comparative example 1

An aluminum pigment composition having a nonvolatile content of 60% was obtained in the same manner as in example 1, except that the reaction with the organosilicon compound and the silane coupling agent was not performed.

Comparative example 2

An aluminum pigment composition having a nonvolatile content of 60% was obtained in the same manner as in example 1, except that fine particles were not removed by using a hydrocyclone classification device.

Comparative example 3

An aluminum pigment composition having a nonvolatile content of 60% was obtained in the same manner as in example 1, except that 1 inclined blade type stirring blade having a blade diameter of 0.35m was disposed at a position of 0.3m from the bottom surface, and the rotation speed was set at 1500rpm, whereby no external circulation was performed.

Comparative example 4

An aluminum pigment composition having a nonvolatile content of 60% was obtained in the same manner as in example 1 except that tetraethoxysilane was changed to 1.5kg, 25% ammonia water was changed to 1.5kg, purified water was changed to 35kg, and methyltrimethoxysilane was changed to 0.25 kg.

Comparative example 5

An aluminum pigment composition having a nonvolatile content of 60% was obtained in the same manner as in example 1 except that 100kg of tetraethoxysilane, 100kg of 25% aqueous ammonia, 1000kg of purified water, 13kg of methyltrimethoxysilane and 7 hours of addition time of aqueous ammonia and purified water were used.

The compositions and production conditions of the above examples and comparative examples are summarized in Table 1.

The following paint was produced using the aluminum pigment compositions obtained in the examples and comparative examples, and the evaluation as paint was performed by the following method. The results are also shown in Table 1.

TABLE 1

3. Production of paint and coating film

(1) Production of a coating

An aqueous metallic paint having the following composition was produced.

Aluminum pigment composition as a nonvolatile matter of 12.0g

Methoxy propanol 18.0g

Polyoxyethylene lauryl ether (nonionic surfactant, trade name "ACTINOL L" manufactured by Songben oil and fat Co., ltd.)

Purified Water 12.0g

Water-soluble acrylic resin (alternatively 1): 110.0g

Melamine resin (2) 18.0g

GmbH 1, sanjing Chemie Co., ltd., almatex WA911

Gnaphal 2:Nihon Cytec Industries Inc, manufactured by Cymel 350

The above components are mixed, the pH is adjusted to 7.7 to 7.8 with dimethylethanolamine, and the viscosity is adjusted to 650 to 750 mPas (measured by a type B viscometer, no.3Low, at 60 rpm, at 25 ℃) with a carboxylic acid thickener and purified water. Thus, an aqueous metallic paint was produced and used for evaluation.

(2) Production of coating film

The aqueous metallic paint produced by the above formulation was air-spray-coated on a 12cm×6cm steel sheet having a dry film thickness of 4 μm, pre-dried at 90 ℃ for 10 minutes, and then air-spray-coated with an organic solvent type surface coating paint having a dry film thickness of 20 μm, and dried at 140 ℃ for 30 minutes to produce a coated sheet as a coating film for evaluation.

4. Evaluation method

(1) Evaluation 1 (paint stability)

The change in the state of the aqueous metallic paint for evaluation manufactured by the above formulation after being left at 23 ℃ for 24 hours was evaluated by naked eyes as follows.

No particular change was found.

Delta. Aggregation of several aluminum pigments was found.

Aggregation of aluminum pigment was found.

(2) Evaluation 2 (evaluation of storage stability (gas production))

200G of the aqueous metallic paint prepared by the above formulation was collected in a flask, and the cumulative hydrogen generation was observed in a constant temperature water tank at 60 ℃ until 24 hours. The amount of gas generated was evaluated as follows, and used as an index of storage stability in the paint.

O is less than 5ml

Delta is more than 5ml and less than 20ml

X is more than 20ml

(3) Evaluation 3 (evaluation of color tone of coating film)

The brightness, the flop (FF), and the concealing property were evaluated by using the coating film for evaluation.

The organic solvent type surface coating paint is prepared by mixing the following components, dispersing the mixture for 3-4 minutes by a spatula, and adjusting the viscosity of the paint to 20.0 seconds by a Ford cup No. 4.

A345 (acrylic transparent resin manufactured by DIC Co., ltd.) 420g

L-117-60 (melamine resin manufactured by DIC Co., ltd.) 165g

SOLVESSO 100 (Exon Chemical Co., ltd., aromatic solvent) 228g

Brightness of

The brightness of the coating film was evaluated by using a KANSAIPAINT co., ltd. Laser metal sensor Alcope (line コ) LMR-200. As an optical condition, a laser light source having an incident angle of 45 degrees and a light receiver having a light receiving angle of 0 degrees and-35 degrees were provided. As a measurement value, the IV value was obtained at a light receiving angle of-35 degrees, which gives the maximum light intensity, in addition to the light of the specular reflection region reflected on the surface of the coating film, among the reflected light of the laser light. IV is a parameter proportional to the intensity of the specular reflection light from the coating film, and indicates the magnitude of the brightness. The determination method is as follows.

The reduction from the reference (comparative example 1) was less than 20.

The delta is a decrease from the reference (comparative example 1) of 20 or more and less than 40.

The reduction from the reference (comparative example 1) was 40 or more.

Different color sense with angle (FF)

Evaluation was performed using a goniometer manufactured by Suga Test Instruments co. The FF value was obtained from the slope of the logarithm of the reflected light intensity (L value) at an observation angle (light receiving angle) of 30 degrees and 80 degrees with respect to the light source having an incident angle of 45 degrees. The FF value is a parameter proportional to the degree of orientation of the metallic pigment, and represents the magnitude of the flop of the pigment. The determination method is as follows.

O is 0.05 or more higher than the reference (comparative example 1)

Delta is less than + -0.05 from the baseline (comparative example 1)

X0.05 or more lower than the reference (comparative example 1)

Concealment of

The aqueous metallic coating material thus produced was applied to a polyethylene terephthalate sheet (PET sheet) with a 2 mil applicator so as to form a dried film thickness of 15 μm, and the coated film was visually determined to have been dried at 140 ℃ for 30 minutes.

The ratio was slightly lower than the reference (comparative example 1).

Delta was reduced from the baseline (comparative example 1).

X is significantly lower than the reference (comparative example 1).

(4) Evaluation 4 (paint adhesion/checkerboard grid test)

Cellotate (registered trademark: nichiban Co., ltd., manufactured by CT-24) was adhered to the above-mentioned evaluation coating film formed on the coated plate, and the degree of peeling of the coating film was observed by pulling at an angle of 45 degrees and visually. The decision criteria are as follows.

No peeling off

Delta: there is slight peeling

X presence of peeling

The evaluation results are shown in Table 1. The composite metal pigment of the present invention satisfying all of the above physical properties (1) to (6) obtained in each example was confirmed to have good stability as a coating material, to be less in gas generation (i.e., to have good storage stability), to exhibit high brightness, high flop and high hiding (i.e., to have good coating color), and to be excellent in adhesion as a coating film.

Industrial applicability

The composite metal pigment and the coating film obtained by using the same of the present invention are excellent in design, gloss, suppression of mottle, stability in aqueous paint, etc. at a high level beyond the limit of the prior art, and therefore can be suitably used for various applications in which metal pigments have been conventionally used, such as paints, inks, resin binders, etc., more specifically, automobile bodies, automobile repair materials, automobile parts, home appliances, etc., 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., and have high availability in various fields of industries such as the transportation machinery industry of automobiles, the electrical and electronic industry of home appliances, the paint industry, the printing industry, etc.

Claims

1. A method of making a metallic pigment composition comprising:

grinding a slurry of metal powder to produce metal particles, and

A step of covering the metal particles with a silicon-containing compound layer,

The metallic pigment composition contains composite particles having metallic particles and 1 or more coating layers on the surface thereof,

(1) The composite particles are in the shape of scales,

(2) The D ₅₀ of the volume basis of the particle size distribution of the composite particles is 3 μm or more and 30 μm or less as measured by a laser diffraction type particle size distribution meter,

(3) The composite particles have an average thickness of 20nm to 300nm,

(4) At least 1 layer of the covering layer is a silicon-containing compound layer,

(6) The ratio of the number of the composite particles having a particle diameter of 0.1 μm or more and 1 μm or less relative to the total number of the composite particles in the metallic pigment composition is 10% or less,

The method for producing the metallic pigment composition implements at least any one of the following:

in the grinding step, grinding balls with the mass of 11 mg/or less are used;

in the grinding step, the ratio of the rotational speed of the grinding device to the critical rotational speed is 78% or less, and

Before the covering step, metal particles with small particle diameters in the metal particles are removed in advance by classification.

2. The method for producing a metallic pigment composition according to claim 1, wherein in the grinding step, 0.08 to 11 mg/mass of grinding balls are used and the ratio of the rotational speed of the grinding device to the critical rotational speed is 33 to 78%.

3. The method for producing a metallic pigment composition according to claim 1 or 2, further comprising a step of removing in advance fine metallic particles of the metallic particles by classification before the covering step.

4. The method for producing a metallic pigment composition according to claim 1 or 2, wherein the metal powder is atomized aluminum powder having a particle diameter of 1 to 30 μm.

5. The method for producing a metallic pigment composition according to claim 1 or 2, wherein in the grinding step, grinding balls having a specific gravity of 8 or less are used.

6. The method for producing a metallic pigment composition according to claim 1 or 2, wherein the composite particles have a shape factor of 10 or more and 1500 or less, which is an average particle diameter divided by an average thickness.

7. The method for producing a metallic pigment composition according to claim 1 or 2, wherein D ₅₀ of the volume basis when the particle size distribution of the composite particles is measured by a laser diffraction particle size distribution meter is 3 μm or more and 25 μm or less.

8. The method for producing a metallic pigment composition according to claim 1 or 2, wherein D ₅₀ of the volume basis when the particle size distribution of the composite particles is measured by a laser diffraction particle size distribution meter is 3 μm or more and 20 μm or less.

9. The method for producing a metallic pigment composition according to claim 1 or 2, wherein the composite particles have an average thickness of 20nm or more and 250nm or less.

10. The method for producing a metallic pigment composition according to claim 1 or 2, wherein the composite particles have an average thickness of 20nm or more and 200nm or less.

11. The production method of the metallic pigment composition according to claim 1 or 2, wherein a ratio of a metal element content based on the metallic particles to a silicon content based on the covering layer in the composite particles is 0.03 or more and 0.2 or less in terms of a ratio of the silicon content to the metal element content.

12. The production method of the metallic pigment composition according to claim 1 or 2, wherein a ratio of a metal element content based on the metallic particles to a silicon content based on the covering layer in the composite particles is 0.04 or more and 0.15 or less in terms of a ratio of the silicon content to the metal element content.

13. The method for producing a metallic pigment composition according to claim 1 or 2, wherein a ratio of the number of the composite particles having a particle diameter of 0.1 μm or more and 1 μm or less in the composite particles to a total number of the composite particles in the metallic pigment composition is 5% or less.

14. The method for producing a metallic pigment composition according to claim 1 or 2, wherein a ratio of the number of the composite particles having a particle diameter of 0.1 μm or more and 1 μm or less in the composite particles to a total number of the composite particles in the metallic pigment composition is 3% or less.

15. The method for producing a metallic pigment composition according to claim 1 or 2, wherein a ratio of the number of the composite particles having a particle diameter of 3 times or more of a size D ₅₀ based on a volume of the composite particles measured by a laser diffraction particle size distribution meter to a total number of the composite particles in the metallic pigment composition is 3% or less.

16. The method for producing a metallic pigment composition according to claim 1 or 2, wherein a ratio of the number of the composite particles having a particle diameter of 3 times or more the size D ₅₀ based on the volume of the composite particles measured by a laser diffraction particle size distribution meter to the total number of the composite particles in the metallic pigment composition is 1% or less.

17. The method for producing a metallic pigment composition according to claim 1 or 2, wherein the metallic particles are aluminum or an aluminum alloy.

18. The method for producing a metallic pigment composition according to claim 1 or 2, further comprising a cover layer containing at least one of a metal, a metal oxide, a metal hydrate and a resin.

19. The production method of a metallic pigment composition according to claim 1 or 2, wherein the silicon-containing compound layer is configured as at least an outermost layer.

20. A method for producing an aqueous metallic paint, comprising the step of adding the metallic pigment composition produced by the production method according to any one of claims 1 to 19 to an aqueous paint or an aqueous ink in which a resin as a coating film-forming component is dissolved or dispersed in a medium mainly comprising water.

21. A method for producing a metal coating film comprising the step of applying an aqueous paint containing the metal pigment composition produced by the production method according to any one of claims 1 to 19.