Metal pigment, application thereof, and method for manufacturing metal pigment

Abstract

To provide a metal pigment containing novel composite particles that have not been seen in conventional technologies, and a method for manufacturing a metal pigment having reduced flocculation.SOLUTION: The problem is solved by a metal pigment containing composite particles, each having a metal particle and one or more coating layers formed on its surface. The metal pigment is characterized in that (1) the composite particles have a flaky shape, (2) the volume-based diameter D50 is 0.1 to 30 μm when the particle size distribution of the composite particles is measured using a laser diffraction type particle size distribution meter, and (3) the composite particles have an average thickness of 15 to 300 nm.SELECTED DRAWING: None

Description

Technical Field

[0001] The first invention of the present application relates to a metallic pigment containing novel composite particles. More specifically, in the first aspect of the first invention of the present application, it relates to a metallic pigment (including the case where it is a composition) containing novel composite particles with low cohesiveness of individual particles and excellent hiding power, color tone, etc. In the second aspect of the first invention of the present application, it relates to a (composite) metallic pigment comprising metal particles and a metal oxide coating formed on the surface thereof. More specifically, it relates to a (composite) metallic pigment that effectively suppresses the aggregation and deformation of the composite particles and has a high level of balance in excellent design, gloss, suppression of defects, stability in water-based paints, etc. in the coating film. The second invention of the present application relates to a metallic pigment composed of composite particles in which the metal particles are coated with a layer of polysiloxane. The second invention of the present application further relates to a metallic pigment suitable for a water-based paint containing composite particles coated with a polysiloxane layer, having a high degree of condensation of polysiloxane, excellent mechanical stability, and high design, and also relates to a metallic pigment composition, a water-based paint composition, a water-based ink composition, and a coating film containing the metallic pigment. The third invention of the present application relates to a method for producing a metallic pigment. More specifically, the third invention of the present application relates to a method for producing a metallic pigment containing composite particles with low cohesiveness of individual particles and excellent hiding power, color tone, etc.

Background Art

[0002] Conventionally, metallic pigments have been used for metallic paints, printing inks, plastic compounding, etc. for the purpose of obtaining a cosmetic effect that emphasizes the metallic feeling. In recent years, in the paint field, as a measure for resource conservation and pollution-free, the need to convert to water-based paints with a small amount of organic solvent used has been increasing. However, in metallic paints containing metallic pigments, there are still not enough types of practical water-based paints. The reason for this is that metallic pigments are prone to corrosion in water-based paints. When metal powders are present in water-based paints, corrosion by water occurs in any one of acidic, neutral, or basic regions, or in multiple regions, based on the properties of various metals, and hydrogen gas is generated. This is an extremely serious safety issue in the manufacturing processes of paints and inks by paint manufacturers and ink manufacturers, as well as in the painting and printing processes by automobile manufacturers, home appliance manufacturers, printing manufacturers, etc. In addition, since the smoothness of the metal surface is lost due to corrosion, a decrease in color tone is inevitable. Note that the corrosion resistance of metallic pigments in water, water-based paints, or water-based inks can be paraphrased as "storage stability".

[0003] Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-147226) discloses an aluminum pigment having an inorganic molybdenum film and further having a film made of amorphous silica covering the film. Also, Patent Document 2 (International Publication No. 2004 / 096921 pamphlet) discloses an aluminum pigment having an inorganic molybdenum film and further having a film formed from a film made of amorphous silica covering the film and / or a silane coupling agent. However, in any of the methods (such as the manufacturing method of aluminum pigments) described in these patent documents, a decrease in the color tone of metallic pigments cannot be avoided, and the processes are complicated.

[0004] Also, Patent Document 3 (International Publication No. 2018 / 180936 pamphlet) discloses a coated pigment (metallic pigment composition) in which aggregates are dispersed in a relatively small amount, including metal particles and a coating layer that is a silicon-containing compound layer, and a coated pigment of composite particles in which the proportion of aggregates in which four or more particles are adhered to each other is small. However, in Patent Document 3, apart from the preference of adjusting the stirring Reynolds number within a predetermined range, no specific teaching can be found on how to obtain a coating pigment with a small number of target aggregates. Also, it has been found that even if the range of the characteristic parameters defined in Patent Document 3 is satisfied, it is still difficult to obtain sufficiently satisfactory storage stability, low aggregability, hiding power, and color tone solely by that.

[0005] In addition, in order to improve the stability of metal pigments in aqueous paints, pigments using composite particles in which metal particles are coated with a metal oxide such as amorphous silica have been proposed. As a result of many of the pigment particles existing as aggregates after being coated with amorphous silica or the like, the hiding power per unit mass may decrease or the lightness may be inferior, and means for suppressing aggregation have been demanded.

[0006] For example, Patent Document 4 proposes a technique capable of realizing a low value of 35% or less on a number basis for the ratio of aggregates in which four or more composite particles are fixed to each other. However, in this technique, particles in which two or three composite particles are aggregated are tolerated, and in order to realize a high-gloss metallic coating film or the like, a technique for more effectively suppressing aggregation has been demanded. In addition, since the substantial particle thickness of these aggregated particles can be 2 to 3 times that of primary particles without aggregation, in a coating film with a thin film thickness, the particles may not fit within the coating film, and the protrusion of the particles may cause bumps and a decrease in gloss, which has been an obstacle when reducing the film thickness of the coating film. Furthermore, in the technique described in Patent Document 4, in order to prevent the adhesion of composite particles to each other, it is necessary to apply a large force during the stirring of the coating treatment reaction. Therefore, especially for particles with a small thickness, particle deformation due to stirring is significant, which may reduce the designability of the metal particles after coating, and a solution to this has been demanded.

[0007] In addition, since the above-mentioned corrosion occurs from the surface of the metal, the surface smoothness decreases, leading to a decrease in the designability of the metal pigment. Among metal pigments, aluminum flake pigments in particular, being amphoteric metals, have the problem that in aqueous paints, aluminum reacts with water to generate gas. As a countermeasure, it is effective to coat the surface of aluminum flake pigments with oxides of metals or metalloids such as polysiloxane.

[0008] If the metal particles are coated with a certain amount or more of oxides of metals or metalloids, the generation of hydrogen gas is suppressed during the normal handling of the paint. In Patent Document 5, it is stated that by combining an acid catalyst and a base catalyst in the reaction process of alkoxysilane, a polysiloxane layer is coated on the metal pigment, providing a metallic effect pigment with excellent gas stability.

[0009] However, during strong stirring and mixing during paint production, or during long - term circulation (circulation and stirring of the paint) during painting, etc., when a strong shearing force is applied to the metal pigment, the coating layer is damaged, leading to a decrease in storage stability such as gas generation and a change in color tone. Especially when the aspect ratio of the metal pigment particles themselves is large, the mechanical stability decreases, and the particles are deformed by circulation, resulting in further deterioration of storage stability such as gas generation and color tone.

[0010] In Patent Document 5, the reaction rate (degree of cross - linking) of polysiloxane is not controlled, and since the reaction rate is not increased sufficiently, there is a problem that the coating layer is damaged during mechanical stability, paint formation, or paint circulation, resulting in a decrease in storage stability (gas generation) and color tone.

[0011] Furthermore, in the silicon compound treatment, in a stirring tank - type reactor, alkoxysilane, then water, and a catalyst are added to the aluminum pigment slurry to proceed with hydrolysis and dehydration condensation reactions to perform silica treatment on the aluminum flakes. At this time, the aluminum flakes aggregate with each other due to the condensate, and when made into a paint, the desired hiding power and brightness cannot be exhibited, or aluminum flakes that are not sufficiently treated are formed on the surface layer of the treatment liquid or the liquid - contacting part with the reaction tank, and the mixing of these may cause gas generation and deterioration of the color tone.

Prior Art Documents

Patent Document

[0012]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0013] An object of the first invention of the present application is, in its first aspect, to provide a metallic pigment (hereinafter, also referred to as "metallic pigment composition") containing novel composite particles not found in the prior art. A further object of the first invention of the present application is, in its first aspect, to provide a metallic pigment composition containing novel composite particles in which the disadvantages of the prior art are eliminated, that is, having excellent storage stability, low aggregability of individual particles, excellent hiding power, color tone, etc.

[0014] Furthermore, in view of the above limitations of the prior art, an object of the first invention of the present application is, in its second aspect, to effectively suppress aggregation and deformation of composite particles, and to provide a metallic pigment (hereinafter, also referred to as "composite metallic pigment") in which excellent designability, gloss, suppression of defects, stability in aqueous paints, etc. in a coating film are balanced at a high level.

[0015] An object of the second invention of the present application is to provide a novel metallic pigment composed of composite particles coated with a polysiloxane layer. Further, in view of the above prior art, the second invention of the present application aims to provide a metal pigment having a high reaction rate of polysiloxane constituting the coating layer of composite particles, excellent mechanical stability, and high designability, and being suitable for an aqueous paint. Furthermore, the second invention of the present application aims to provide a metal pigment composition, an aqueous paint composition, or an aqueous ink composition containing the metal pigment. In this specification, the corrosion resistance of the composite particles contained in the metal pigment in water, an aqueous paint, or an aqueous ink is also referred to as "storage stability".

[0016] An object of the third invention of the present application is to provide a method for producing a metal pigment with less aggregation (hereinafter, also referred to as a "metal pigment composition"). A further object of the third invention of the present application is to provide a metal pigment composition containing composite particles that eliminates the disadvantages of the prior art, that is, has excellent storage stability, low aggregability of individual particles, and excellent hiding power, color tone, etc. Furthermore, an even further object of the third invention of the present application is to provide an apparatus for producing a metal pigment composition with less aggregation.

Means for Solving the Problems

[0017] As a result of intensive research, the inventor of the present invention has found means for solving the problems of the first invention of the present application. More specifically, as a result of intensive research, the inventor of the present invention has found that in composite particles, the ratio of aggregates in which four or more particles are fixed to each other is small, and in addition to controlling D in the particle size distribution within a predetermined range, by controlling the average thickness of the composite particles, the ratio of bent composite particles (i.e., damaged composite particles), etc. within a predetermined range, the problems of the first aspect of the first invention of the present application can be achieved. 50 Also, as a result of intensive research, the inventor of the present invention has found that by controlling the average thickness of the composite particles, the particle size of the composite particles, etc. within a predetermined range in the composite metal pigment, the above problems can be achieved, and the second aspect of the first invention of the present application has been completed.

[0018] Also, as a result of intensive research, the inventor of the present invention has found that by controlling the average thickness of the composite particles, the particle size of the composite particles, etc. within a predetermined range in the composite metal pigment, the above problems can be achieved, and the second aspect of the first invention of the present application has been completed.

[0019] Furthermore, the inventors of the present invention have found that by making the polysiloxane coating layer, which coats the metal pigment without damaging it, into a strong structure having a specific chemical structure, the mechanical strength of the polysiloxane layer can be improved, and it is possible to solve the problem of the second invention of the present application. Then, when coating the metal pigment with a polysiloxane layer, the inventors of the present invention appropriately set the catalyst species, amount, addition time, temperature, etc. for obtaining the polysiloxane, thereby suppressing metal corrosion and increasing the reaction rate of the polysiloxane. More specifically, a basic catalyst is added in two steps, and the reaction is started under mild conditions where metal corrosion is less likely to occur. Then, the reaction is carried out under conditions where the reaction is fast and the reaction rate can be increased, thus completing the metal pigment of the second invention of the present application composed of composite particles.

[0020] In addition, as a result of intensive research, the inventors of the present invention have found that when coating metal particles with a silicon compound using a stirred tank reactor, by controlling the size of the stirred tank reactor and the stirring conditions (stirring blade conditions and linear velocity) within a predetermined range, the metal particles can be prevented from being damaged and the aggregation during condensation can be suppressed, thus completing the third invention of the present application.

[0021] That is, each invention of the present application and its various aspects are as follows. [1] A metal pigment comprising metal particles and composite particles having one or more coating layers on the surface thereof, (1) The shape of the composite particles is scaly, (2) When measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer, D 50 on a volume basis is 0.1 to 30 μm, (3) The average thickness of the composite particles is 15 to 300 nm. A metal pigment characterized by this. [2] The metal pigment according to [1], wherein the proportion of the bent composite particles is 10% or less. [3] The proportion of the number of aggregates in which four or more of the composite particles are fixed to each other is 35% or less with respect to the total number of the composite particles, the metallic pigment according to [1] or [2]. [4] The metallic pigment according to any one of [1] to [3], wherein the metal particles contain aluminum or an aluminum alloy. [5] The metallic pigment according to any one of [1] to [4], wherein the one or more coating layers include a metal oxide coating layer. [6] The metallic pigment according to any one of [1] to [5], wherein the one or more coating layers include a silicon compound-containing layer. [7] The metallic pigment according to any one of [1] to [6], wherein at least one of the coating layers is a layer of polysiloxane. [8] The metallic pigment according to any one of [1] to [7], wherein the average particle thickness of the composite particles is 15 to 160 nm. [9] The metallic pigment according to any one of [1] to [8], wherein the average aspect ratio of the composite particles is 20 to 400.

[10] The metallic pigment according to [7], wherein the proportion of the Q4 structure in which the Si atom in the structure of the polysiloxane constituting the polysiloxane layer has four -O-Si- bonds is 40 to 90%.

[11] The metallic pigment according to any one of [1] to

[10] , wherein the relative elemental concentration ((A / B)×100) of the elemental concentration A of the metal and the elemental concentration B of Si when the surface of the composite particles is evaluated by XPS is 10 mol% or less.

[12] The metallic pigment according to [7] or

[10] , wherein the average thickness of the polysiloxane layer is 5 to 100 nm.

[13] The hydrophilicity A defined by the sum of ((the ratio of the Q1 structure having one -O-Si- bond per Si atom) × 3) + ((the ratio of the Q2 structure having two -O-Si- bonds per Si atom) × 2) + (the ratio of the Q3 structure having three -O-Si- bonds per Si atom) is 10 to 80%, and the metallic pigment according to any one of [1] to

[12] .

[14] The metallic pigment according to any one of [1] to

[13] , wherein the composite particles further comprise a coating layer containing at least one of a metal, a metal oxide, a metal hydrate, and a resin.

[15] A metallic pigment composed of composite particles in which the metal particles are coated with a layer of polysiloxane, 1) The proportion of the Q4 structure in which the Si atom in the polysiloxane structure has four -O-Si- bonds is 40 to 90%, and 2) The relative elemental concentration ((A / B) × 100) of the elemental concentration A of the metal and the elemental concentration B of Si when the surface of the composite particles is evaluated by XPS is 10 mol% or less, The metallic pigment.

[16] A metallic pigment according to any one of [1] to

[15] , wherein 200 g of an aqueous metallic paint containing 12 g of the metallic pigment as a non-volatile component, 18 g of methoxypropanol, 110 g of an aqueous acrylic resin, 18 g of a melamine resin, and 12 g of water is taken in a flask, and the gas generation when measuring the cumulative hydrogen gas generation amount up to 24 hours in a constant temperature water bath at 60°C is 10 ml or less.

[17] An aqueous metallic paint containing a metallic pigment according to any one of [1] to

[15] and containing 5% by mass or more of water, wherein 200 g of the aqueous metallic paint is taken in a flask, and the gas generation when measuring the cumulative hydrogen gas generation amount up to 24 hours in a constant temperature water bath at 60°C is 10 ml or less.

[18] A metallic pigment composition containing a metallic pigment according to any one of [1] to

[16] .

[19] An aqueous paint composition containing a metallic pigment according to any one of [1] to

[16] .

[20] An aqueous ink composition containing the metal pigment according to any one of [1] to

[16] .

[21] A coating film containing the metal pigment according to any one of [1] to

[16] .

[22] A method for producing a metal pigment, wherein the production method includes the following steps (1) to (3) using a stirred tank reactor: (1) A step of dispersing metal particles in a solvent; (2) A step of coating the metal particles with a silicon compound; and (3) A step of filtering and washing. The stirred tank reactor is such that the volume of the reaction tank is 100 L or more, the ratio of the diameter of the reaction tank to the maximum diameter of the stirring blade is in the range of 0.2 to 1.0, and the shortest distance between the inner surface of the reaction tank and the tip of the stirring blade is 10 mm or more, and the tip speed of the stirring blade during stirring is 1 to 20 m / s. The production method.

[23] The production method according to

[22] , wherein in step (1), the average particle diameter of the metal particles in the dispersion liquid is 1.2 times or less of the average particle diameter of the metal particles as the raw material, and the metal particles in the dispersion liquid are uniformly dispersed in the solvent, in step (2), stirring is performed so as not to form a stagnant portion on the surface layer and the bottom, the average particle diameter of the composite particles contained in the metal pigment obtained after step (3) is 1.3 times or less of the average particle diameter of the metal particles as the raw material. The production method.

[24] The production method according to

[22] or

[23] , wherein in step (1) and / or (2), the treatment liquid withdrawn from near the bottom of the reaction tank is returned to the reaction tank from the upper part of the reaction tank and circulated.

[25] The production method according to any one of

[22] to

[24] , wherein in step (2), after introducing the silicon-containing raw material and the catalyst, the inner wall of the reaction tank near the liquid contact portion between the reaction tank and the mixed liquid is washed with the reaction liquid or the solvent to reduce the adherents or the stagnant substances.

[26] The production method according to any one of

[22] to

[25] , wherein step (2) is carried out over 2 hours or more.

[27] The production method according to any one of

[22] to

[26] , wherein the metal pigment according to any one of [1] to

[16] is produced.

[28] The metal pigment obtained by the production method according to any one of

[22] to

[27] .

[29] A stirring tank type reactor used in the production method according to any one of

[22] to

[27] .

Advantages of the Invention

[0022] According to the first invention of the present application, a metal pigment composition containing novel composite particles not found in the prior art and a novel composite metal pigment not found in the prior art can be obtained. According to a preferred embodiment of the first aspect of the first invention of the present application, a metal pigment composition with low cohesiveness of individual particles, excellent hiding power, color tone (such as glossiness), and little gas generation can be obtained. Furthermore, according to a more preferred embodiment of the first aspect of the first invention of the present application, a metal pigment composition with low cohesiveness of individual particles, excellent hiding power, color tone, little gas generation, and good storage stability can be obtained. The composite metal pigment of the second aspect of the first invention of the present application can effectively suppress the aggregation and deformation of the composite particles constituting the composite metal pigment. Therefore, excellent designability, gloss, suppression of defects, stability in water-based paints, etc. in coating films such as metallic coating films can be balanced at a high level beyond the limits of the prior art.

[0023] According to the second invention of the present application, a novel metal pigment not found in the prior art, which is composed of composite particles coated with a polysiloxane layer, is provided. Also, according to the second invention of the present application, a metal pigment with a high reaction rate of the polysiloxane constituting the coating layer of the composite particles, excellent mechanical stability, storage stability (gas generation), and color tone can be provided.

[0024] According to the third invention of the present application, a method for manufacturing a metal pigment composition with less aggregation can be provided. According to one aspect, a metal pigment composition can be obtained in which the aggregability of individual particles is small, having excellent hiding power and color tone (such as a sense of brilliance), and generating little gas. Further, according to one aspect, a stirring tank type reactor for manufacturing the metal pigment composition can be provided.

Embodiments for Carrying Out the Invention

[0025] Hereinafter, the present invention will be described along typical or preferred embodiments, but the present invention is not limited by these embodiments. Unless clearly indicated otherwise, these embodiments can be freely combined within the scope of the present invention defined in the appended claims.

[0026] First Invention The first invention of the present application is a metal pigment containing composite particles having metal particles and one or more coating layers on the surface thereof, (1) the shape of the composite particles is scaly, (2) D on a volume basis when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 0.1 to 30 μm, (3) the average thickness of the composite particles is 15 to 300 nm, characterized in that it is a metal pigment.

[0027] In the first invention of the present application, the proportion of the bent composite particles is preferably 10% or less. In the first invention of the present application, the number ratio of aggregates in which four or more of the composite particles are adhered to each other is preferably 35% or less with respect to the total number of the composite particles. In the first invention of the present application, it is preferable that the metal particles contain aluminum or an aluminum alloy. In the first invention of the present application, it is preferable that the one or more coating layers include a metal oxide coating layer. In the first invention of the present application, it is preferable that at least one layer of the coating layer is a silicon compound-containing layer. In the first invention of the present application, it is preferable that at least one layer of the coating layer is a polysiloxane layer. Here, it is more preferable that the proportion of the Q4 structure in which the Si atom in the structure of the polysiloxane constituting the polysiloxane layer has four -O-Si- bonds is 40 to 90%. Also, it is more preferable that the average thickness of the polysiloxane layer is 5 to 100 nm. In the first invention of the present application, it is preferable that the average particle thickness of the composite particles is 15 to 160 nm. In the first invention of the present application, it is preferable that the average aspect ratio of the composite particles is 20 to 400. In the first invention of the present application, when the surface of the composite particles is evaluated by XPS, it is preferable that the relative element concentration ((A / B)×100) of the metal element concentration A and the Si element concentration B is 10 mol% or less. In the first invention of the present application, it is preferable that the hydrophilicity A defined by the sum of (Q1 structure ratio in which the Si atom has one -O-Si- bond × 3)+(Q2 structure ratio in which the Si atom has two -O-Si- bonds × 2)+(Q3 structure ratio in which the Si atom has three -O-Si- bonds) is 10 to 80%. In the first invention of the present application, it is preferable that the composite particles further include a coating layer containing at least one of a metal, a metal oxide, a metal hydrate, and a resin.

[0028] Regarding the metal pigment of the first invention of the present application, when 200 g of an aqueous metallic paint containing 12 g of the metal pigment as a non-volatile component, 18 g of methoxypropanol, 110 g of an aqueous acrylic resin, 18 g of a melamine resin, and 12 g of water is taken in a flask and the cumulative hydrogen gas generation amount is measured in a constant temperature water bath at 60°C for up to 24 hours, it is preferable that the gas generation is 10 ml or less. The metal pigment of the first invention of the present application is preferably used in a metal pigment composition containing the metal pigment. The metal pigment of the first invention of the present application is preferably used in an aqueous paint composition containing the metal pigment. The metal pigment of the first invention of the present application is particularly preferably used in an aqueous metallic paint. When 200 g of an aqueous metallic paint containing the metal pigment and containing 5% by mass or more of water is collected in a flask and the cumulative amount of hydrogen gas generated is measured in a constant temperature water bath at 60 °C for up to 24 hours, the gas generation is preferably 10 ml or less. The metal pigment of the first invention of the present application is preferably used in an aqueous ink composition containing the metal pigment. The metal pigment of the first invention of the present application is preferably used in a coating film containing the metal pigment.

[0029] Metal Oxide Coating Layer It is preferable that one or more coating layers constituting the composite particles in the first invention of the present application include a metal oxide coating layer. The metal oxide coating constituting the metal oxide coating layer may be formed on the entire surface of the metal particles or only on a part of the surface. The metal oxide coating may be entirely composed of a metal oxide, or only a part thereof may be composed of a metal oxide and may contain components other than the metal oxide. Details such as the preferred forms of the metal oxide coating layer and the metal oxide coating constituting the same are the same as those described later in relation to the first and second aspects of the first invention of the present application. One or more coating layers constituting the composite particles may have another coating layer (second coating layer) in addition to the metal oxide coating layer. Such a second coating layer is the same as those described later in relation to the first and second aspects of the first invention of the present application.

[0030] Silicon Compound-Containing Layer As the above metal oxide coating layer, a silicon compound-containing layer is particularly preferably used. That is, in the metal pigment of the first invention of the present application, it is preferable that at least one layer of the one or more coating layers formed on the surface of the metal particles that form the core of the composite particles is a silicon compound-containing layer. By making at least one layer of the coating layers a silicon compound-containing layer, generation of gas in the aqueous paint can be suppressed, good storage stability can be obtained, and the water resistance when forming a coating film is excellent. Details such as the preferred form of the silicon-containing compound layer are the same as those described later in relation to the first and second aspects of the first invention of the present application.

[0031] Polysiloxane Layer As the above silicon compound-containing layer, a layer of polysiloxane is particularly preferably used. Therefore, it is particularly preferable that the composite particles contained in the metal pigment of the first invention of the present application have a structure in which the metal particles are centered and the metal particles are coated with polysiloxane. Polysiloxane is composed of a compound containing a siloxane bond (Si-O-Si) composed of a silicon atom (Si) and an oxygen atom (O). These compounds may be either crystalline or amorphous, but are particularly preferably amorphous. In addition, polysiloxane may be formed using an organosilicon compound (including a silane coupling agent) as a starting material. In this case, within a range that does not interfere with the effects of the first invention of the present application, it may contain an organosilicon compound or a component derived therefrom. In a typical example, polysiloxane can be formed by hydrolyzing an organosilicon compound. The layer of polysiloxane may contain additives, impurities, etc. other than the silicon compound within a range that does not impair the characteristics of the first invention of the present application. Details such as the preferred form of the layer of polysiloxane are the same as those described later in relation to the second invention of the present application.

[0032] Particularly preferred aspects of the first invention of the present application are the first aspect and the second aspect, which are described in detail below. First Aspect of the First Invention The first aspect of the first invention of the present application is A metallic pigment (composition) comprising composite particles having metal particles and one or more coating layers on the surface thereof, (1) The shape of the composite particles is scaly, (2) When measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer, D 50 on a volume basis is 0.1 to 30 μm, (3) The average thickness of the composite particles is 20 to 300 nm, (4) At least one layer of the coating layer is a metal oxide film layer, preferably a silicon compound-containing layer, (5) The proportion of the bent composite particles is 10% or less, (6) The number ratio of aggregates in which four or more of the composite particles are adhered to each other is 35% or less with respect to the total number of the composite particles. A metallic pigment (composition) characterized by being, Hereinafter, each component of the metallic pigment (composition) of the first aspect and its details will be described.

[0033] 1. Composite Particles Contained in a Metal Pigment Composition The metallic pigment composition according to the first aspect of the first invention of the present application includes composite particles including metal particles and one or more coating layers on the surface thereof. That is, in the description of the first aspect in this specification, the term "metallic pigment composition" means that composite particles including metal particles and one or more coating layers on the surface thereof are dispersed in a solvent containing water and / or a hydrophilic solvent, or the composite particles are accompanied by a solvent containing water and / or a hydrophilic solvent, and may optionally contain other components. Also, in the description of the first aspect in this specification, a composition obtained by adding a resin to the metallic pigment composition may be referred to as a "resin composition" or a "resin composition containing the metallic pigment composition" to distinguish it from the term "metallic pigment composition".

[0034] Metal Particles The composite particles contained in the metallic pigment composition according to the first aspect of the first invention of the present application include metal particles and one or more coating layers formed on the surface thereof. That is, one or more coating layers are formed on the surface of the metal particles that are the core of the composite particles.

[0035] The material of the metal particles (core particles) constituting the composite particles is not particularly limited, and may be any metal used as a known or commercially available metal pigment, such as aluminum, aluminum alloy, zinc, iron, magnesium, nickel, copper, silver, tin, chromium, stainless steel, etc. In this specification, the metal of the metal particles constituting the composite particles includes not only a single metal but also alloys and intermetallic compounds. Only one kind of metal particles may be used alone, or two or more kinds may be used in combination.

[0036] The average particle size of the metal particles is not particularly limited, but it may be an average particle size that can bring about D 50 as described later. That is, when the volume distribution is measured with a laser diffraction particle size distribution analyzer in the composite particles, D 50 is 0.1 to 30 μm, and the volume average particle size (D 50 ) of the metal particles may be set. The average particle size of the metal particles can be controlled by appropriately adjusting the particle size of the raw material atomized metal powder (for example, aluminum powder), the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc. in the process of grinding and sieving and filtering the raw material atomized metal powder using a ball mill or the like.

[0037] The shape of the metal particles is not limited, but it is particularly preferably flaky (flake-like). As a result, the composite particles contained in the metal pigment composition according to the first aspect of the first invention of the present application can also have a flaky shape, and thus high hiding power and the like can be obtained more reliably. From this perspective, the aspect ratio (shape coefficient obtained by dividing the average particle diameter by the average thickness) of the flaky metal particles is preferably from 1 to 1000, and more preferably from 15 to 500 in particular. When the aspect ratio of the metal particles is 1 or more, a higher sense of brilliance can be obtained. Further, when the aspect ratio of the metal particles is 1000 or less, the mechanical strength of the flakes is maintained and a stable color tone can be obtained. Here, the average thickness of the metal particles used in the first aspect of the first invention of the present application can be calculated from the water surface diffusion area and density of the metal particles.

[0038] Further, the metal particles do not necessarily have to be composed only of metal, and particles in which the surfaces of inorganic particles such as synthetic resin particles, mica, and glass are coated with metal can also be used as long as the effects of the first aspect of the first invention of the present application are not inhibited. In the first aspect of the first invention of the present application, particles formed from aluminum or an aluminum alloy are particularly desirable in terms of high weather resistance, low specific gravity, easy availability, and the like.

[0039] Particularly suitable as the metal particles constituting the composite particles are aluminum flakes that are generally widely used as metallic pigments. As the aluminum flakes, those having surface properties, particle diameters, and shapes required for metallic pigments, such as surface glossiness, whiteness, and brilliance, are suitable. Aluminum flakes are usually commercially available in a paste state. The paste-like aluminum flakes may usually contain flaky aluminum powder, as well as residual amounts of mineral spirits (aliphatic hydrocarbons), fatty acids, and organic solvents such as solvent naphtha and xylene used during pulverization. The paste-like aluminum flakes may be used as they are, or the fatty acids on the surface may be removed in advance with an organic solvent or the like before use. Also, the volume average particle diameter (D 50So-called aluminum vapor-deposited foils with a particle size (d) of 3 to 30 μm and an average thickness (t) of 5 to 50 nm can also be used.

[0040] Desirable Physical Properties of the Metal Pigment (Composition) The metal pigment (composition) according to the first aspect of the first invention of the present application is characterized by satisfying the following physical property requirements. (1) The shape of the composite particles is scaly. (2) When the particle size distribution of the composite particles is measured with a laser diffraction particle size distribution analyzer, D 50 by volume is 0.1 to 30 μm. (3) The average thickness of the composite particles is 20 to 300 nm. (4) At least one layer of the coating layer is a metal oxide film layer, preferably a silicon compound-containing layer. (5) The proportion of bent composite particles is 10% or less. (6) The number ratio of aggregates in which four or more composite particles are adhered to each other is 35% or less with respect to the total number of composite particles. Hereinafter, each of these physical property requirements will be described.

[0041] (1) The shape of the composite particles is scaly The shape of the composite particles of the metal pigment composition according to the first aspect of the first invention of the present application is scaly (flake-like). Thereby, the coating film formed using the metal pigment composition can exhibit high hiding power, luster, and the like. In this specification, the shape of the composite particles being "scaly" (flake-like) means that the average aspect ratio (shape coefficient obtained by dividing the average particle size by the average thickness) of the composite particles is 5 or more. From the viewpoint of obtaining high hiding power and luster, the average aspect ratio of the scaly composite particles is preferably 5 to 1000, and more preferably 15 to 500. When the average aspect ratio is 5 or more, sufficient luster can be achieved, while when the average aspect ratio is 1000 or less, the mechanical strength of the flakes is maintained and a stable color tone can be obtained. In this physical property requirement, the "composite particles" refer to the aggregate (collective) when a plurality of composite particles are aggregated and adhered. Here, the average particle size for calculating the average aspect ratio of the composite particles is the volume-based D called the median diameter 50 which will be described later for requirement (2). Also, the average thickness for calculating the average aspect ratio of the composite particles will be described later for requirement (3).

[0042] (2) D on a volume basis when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 0.1 to 30 μm D on a volume basis when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 0.1 to 30 μm. Thereby, the coating film formed using the metal pigment composition can exhibit high hiding power, brilliance, etc., and the aggregability of individual particles can be suppressed to be small. This D on a volume basis 50 is generally also called the median diameter. From the viewpoints of obtaining high hiding power, brilliance, and small aggregability, D on a volume basis when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 may preferably be 0.1 to 25 μm, more preferably 0.1 to 20 μm, still more preferably 0.1 to 15 μm, and particularly preferably 0.1 to 10 μm. Alternatively, from the same viewpoints, D on a volume basis when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 0.2 to 25 μm, more preferably 0.5 to 20 μm, still more preferably 1 to 20 μm, and even more preferably 3 to 20 μm. In this physical property requirement, the "composite particles" refer to the aggregate (collective) when a plurality of composite particles are aggregated and adhered. Here, D on a volume basis when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50refers to the particle diameter at a cumulative degree of 50% in the volume cumulative particle size distribution. The laser diffraction particle size analyzer is not particularly limited, and for example, "LA-300" (manufactured by Horiba, Ltd.) can be used. As the measurement solvent, isopropyl alcohol or mineral spirit can be used. For example, after subjecting a metal pigment composition containing composite particles of a sample to ultrasonic dispersion for 2 minutes as a pretreatment, it is put into a dispersion tank and after confirming that it is appropriately dispersed, D 50 can be measured. The particle diameter 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 photographing the composite particles in the resin composition from the coating film surface with an optical microscope, a laser microscope, etc., and obtaining the equivalent circle diameter distribution using commercially available image analysis software to determine the particle diameter can be adopted. The volume-based D 50 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), the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filtration, etc. in the step of grinding and sieving / filtering the raw material atomized metal powder using a ball mill or the like in the method for producing the metal pigment composition described later, and also by appropriately adjusting the type of the organosilicon compound used, the pH, concentration, stirring temperature, stirring time, type of stirring device, power / degree of stirring (type and diameter of the stirring blade, rotation speed, presence or absence of external stirring, etc.) in the step of coating with a metal oxide film layer, preferably a silicon compound-containing layer (and other coating layers as necessary).

[0043] (3) The average thickness of the composite particles is 20 to 300 nm The average thickness of the composite particles contained in the metal pigment composition according to the first aspect of the first invention of the present application is 20 to 300 nm. Thus, in combination with the fulfillment of the above requirement (2), the coating film formed using the metal pigment composition can exhibit higher hiding power, brilliance, etc., and the cohesiveness of individual particles can be more effectively suppressed. From the above viewpoints, the average thickness of the composite particles is preferably 20 to 300 nm, more preferably 20 to 250 nm, still more preferably 20 to 200 nm, and when hiding property and high brightness are desired, it is more preferably 30 to 150 nm. In this physical property requirement, the "composite particles" refer to the aggregates (aggregates) when a plurality of composite particles are aggregated and adhered. The average thickness of the composite particles here can be calculated from the water surface diffusion area and density of the composite particles. The water surface diffusion area refers to the area occupied by the dried composite particles per unit mass when the dried composite particles are uniformly diffused on the water surface and coated in a non-gapped state by utilizing the leafing phenomenon. The measurement of the water surface diffusion area can be carried out in accordance with the provisions of JIS K5906:1998. However, in the composite particles of the first aspect of the first invention of the present application, when the hydrophilicity of the surface is strong, it may be difficult to obtain the above water surface diffusion area. In this case, the average thickness of the composite particles can be measured according to the method described in the examples below. That is, a film (thin film) is formed using a metal pigment composition in which the composite particles are dispersed in a mixture of an alcohol-based solvent such as methoxypropanol and water, and the average thickness of the composite particles can be obtained by observing the thickness of the composite particles (30 or more, preferably 50 or more, particularly preferably 500 or more) with a scanning electron microscope (SEM). The average thickness of the composite particles contained in the metal pigment composition is based on volume D 50Similarly, in the method for producing a metal pigment composition described below, in the step of grinding and sieving / filtering the raw material atomized metal powder (for example, aluminum powder) using a ball mill or the like, by appropriately adjusting the particle diameter of the raw material atomized metal powder, the mass per grinding ball in the case of using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter press, etc., and in the step of coating an oxide metal film layer, preferably a silicon compound-containing layer (and other coating layers as necessary), by appropriately adjusting the type of organosilicon compound used, the pH, concentration, stirring temperature, stirring time, type of stirring device, power / degree of stirring (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) in the coating step (including the step when the organosilicon compound is hydrolyzed and used), it can be controlled.

[0044] (4) At least one layer of the coating layer is an oxide metal film layer, preferably a silicon compound-containing layer In the metal pigment composition according to the first aspect of the first invention of the present application, at least one layer of the one or more coating layers formed on the surface of the metal particles that are the core of the composite particles is an oxide metal film layer, preferably a silicon compound-containing layer. By making at least one layer of the coating layer an oxide metal coating layer, preferably a silicon compound-containing layer, gas generation in the aqueous paint can be suppressed, good storage stability can be obtained, and the water resistance when formed into a coating film is excellent. The coating layer of the composite particles may have another coating layer (second coating layer) in addition to the oxide metal film layer. Such a second coating layer will be described in more detail later. The oxide metal coating is a film composed of a layer containing an oxide metal, and may be formed on the entire surface of the metal particle or only on a part of the surface. The oxide metal coating may be entirely composed of an oxide metal, or only a part of it may be composed of an oxide metal and may contain components other than the oxide metal. The oxide metal constituting the oxide metal coating is a compound containing oxygen and at least one metal element as its constituent elements. Therefore, the metal oxide may be a metal oxide in the narrow sense that contains only oxygen and at least one metal element as its constituent elements. However, as long as it contains oxygen and at least one metal element as its constituent elements, it may contain elements other than the oxygen and metal elements as its constituent elements. For example, it may be a metal hydroxide, an oxide hydrate, a oxynitride, etc. It may also be a compound containing an organic group. The metal oxide may be a so-called simple oxide in which there is only one kind of metal element as a constituent element, or may be a composite oxide containing two or more kinds of metal elements as constituent elements. At least one of the metal elements that are the constituent elements of the metal oxide may be a typical metal, a transition metal, or even a so-called semi-metal element. Among them, the metal oxide containing silicon as a constituent element is particularly suitable as the metal oxide constituting the metal oxide coating layer (in this case, it also applies to the silicon compound-containing layer). Specific examples of suitable metal oxides constituting the metal oxide coating include silicon oxide, aluminum oxide, boron oxide, zirconium oxide, cerium oxide, iron oxide, titanium oxide, chromium oxide, tin oxide, molybdenum oxide, vanadium oxide, their oxide hydrates, their hydroxides, and their mixtures, etc. Among them, silicon oxide, aluminum oxide, and their mixtures, as well as their oxide hydrates and hydroxides, are preferably used. Particularly preferably, silicon oxides such as (also applicable to silicon compounds) silicon oxide, silicon hydroxide, and / or silicon oxide hydrate can be used.

[0045] The silicon compound-containing layer preferably used as the metal oxide film layer is desirably a layer composed of a compound containing particularly a Si-O bond (siloxane bond). Examples of such a layer include a layer containing at least one of a silane-based compound and a silicon oxide. Such compounds include silane-based compounds [H 3 SiO(H 2 SiO) n SiH 3 (where n represents an arbitrary positive integer). In addition to this, SiO 2 , SiO2 ·nH 2 Examples of the silicon oxide represented by O (where n represents any positive integer) and the like are given. These silane compounds and silicon oxides may be either crystalline or amorphous, but are particularly preferably amorphous. Therefore, as the layer containing silicon oxide (such as silica), for example, a layer containing amorphous silica can also be preferably employed.

[0046] Further, the layer composed of a compound containing an Si - O bond may be a layer formed using an organosilicon compound (including a silane coupling agent) as a starting material. In this case, the silicon compound - containing layer may contain an organosilicon compound or its derived components within a range that does not interfere with the effects of the first aspect of the first invention of the present application. In a typical example, the layer composed of a compound containing an Si - O bond can be formed by hydrolyzing an organosilicon compound.

[0047] The silicon compound - containing layer may contain additives, impurities, etc. other than the silicon compound within a range that does not impair the characteristics of the first aspect of the first invention of the present application.

[0048] The content of silicon contained in the silicon compound - containing layer is not particularly limited, but is preferably 1 to 30 parts by mass, and more preferably 2 to 20 parts by mass, relative to 100 parts by mass of the metal particles. When the silicon content of the silicon compound - containing layer is 1 part by mass or more relative to 100 parts by mass of the metal particles, the corrosion resistance, water dispersibility, stability, etc. of the metal pigment composition can be maintained at a high level. When the silicon content of the silicon compound - containing layer is 30 parts by mass or less relative to 100 parts by mass of the metal particles, aggregation of the composite particles and a decrease in color tone such as hiding power and metallic luster can be prevented.

[0049] The coating layer of the composite particles contained in the metal pigment composition according to the first aspect of the first invention of the present application is preferably particularly hydrophilic. The composite particles usually form a metal pigment composition in a dispersed form in an aqueous solvent (water or a mixed solvent containing water and an organic solvent). However, when the coating layer has a hydrophilic surface, the composite particles can be highly dispersed in such an aqueous solvent. Moreover, since silicon oxide (such as amorphous silica) is very stable in an aqueous solvent, a metal pigment composition containing highly stable composite particles in an aqueous solvent can be provided. From such a viewpoint, in the composite particles contained in the metal pigment composition according to the first aspect of the first invention of the present application, it is desirable that at least the outermost layer is a metal oxide film layer, preferably a silicon compound-containing layer (particularly a layer composed of a compound containing an Si-O bond). When the coating layer is composed of a plurality of layers, in addition to the outermost metal oxide film layer, preferably a silicon compound-containing layer, a metal oxide film layer, preferably a silicon compound-containing layer (particularly an Si-O-based coating layer) can be separately formed as a layer other than the outermost layer.

[0050] The thickness of the coating layer of each composite particle is not particularly limited as long as the average thickness of the composite particles is in the range of 20 to 300 nm as described above. The thickness of the coating layer is usually desirably in the range of about 1 to 50 nm (particularly 1 to 30 nm, and further 1 to 20 nm). When the thickness of the coating layer is 1 nm or more, a coating film having sufficient water resistance and suppressing the occurrence of corrosion or discoloration of metal particles in an aqueous paint can be obtained. On the other hand, when the thickness of the coating layer is about 50 nm or less, the brightness, distinctness of image, and hiding power of the coating film can be maintained at a high level.

[0051] The thickness of the metal oxide film layer, preferably the silicon compound-containing layer, contained in the coating layer of each composite particle is also not particularly limited as long as the average thickness of the composite particles is in the range of 20 to 300 nm as described above. From the viewpoint of the function of the layer, the thickness of the metal oxide film layer, preferably the silicon compound-containing layer, can usually be in the range of 1 to 20 nm, and particularly preferably in the range of 1 to 15 nm.

[0052] Specific examples of the organosilicon compound that can preferably be used in the first aspect of the first invention of the present application will be further described below, but the organosilicon compound is not necessarily limited to these specific examples. The organosilicon compound may contain at least one of the organosilicon compounds represented by the following general formula (1), a silane coupling agent represented by any one of the following general formulas (2), (3), and (4), and at least one selected from their partial condensates.

[0053] Si(OR 1 ) 4 ··· (1) (In the formula, R 1 is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and R 1 may all be the same, some may be the same, or all may be different.) R 2 m Si(OR 3 ) 4-m ··· (2) (In the formula, 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 there are two or more of R 2 or R 3 , they may all be the same, some may be the same, or all may be different. 1 ≦ m ≦ 3.) R 4 p R 5 q Si(OR 6 ) 4-p-q ··· (3) (In the formula, 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. R 4 , R 5 , or R6 When there are two or more, they may all be the same, some may be the same, or they may all be different. 1 ≦ p ≦ 3, 0 ≦ q ≦ 2, and 1 ≦ p + q ≦ 3.) R 7 r SiCl 4-r ··· (4) (In the formula, R 7 is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group. When there are two or more R 7 , they may all be the same, some may be the same, or they may all be different. 0 ≦ r ≦ 3.)

[0054] Examples of the hydrocarbon group in R 1 in formula (1) include methyl, ethyl, propyl, butyl, hexyl, octyl, etc., and these may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Also, the four R 1 may all be the same, some may be the same, or they may all be different. Preferred examples of such an organosilicon compound of formula (1) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, etc. Among these, tetraethoxysilane is particularly preferred.

[0055] Examples of the hydrocarbon group in R 2 in formula (2) include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., and these may be branched or linear and may contain a halogen group such as fluorine, chlorine, bromine, etc. Among these, hydrocarbon groups having 1 to 18 carbon atoms are particularly preferred. Also, when there are two or more R 2 , they may all be the same, some may be the same, or they may all be different. The number of R 2 in the molecule is 1 to 3, that is, 1 to 3 in formula (2) when m = 1 to 3, but it is more preferably m = 1 or 2. R in formula (2) 3 Examples of the hydrocarbon group in 3 include methyl, ethyl, propyl, butyl, hexyl, octyl, etc., and these may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Also, when there are two or more Rs 3 they may all be the same, some may be the same, or they may all be different. Preferred examples of such an organosilicon compound (silane coupling agent) of formula (2) include methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, trimethylmethoxysilane, trimethylethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltributoxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltributoxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, dibutyldibutoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, dihexyldimethoxysilane, dihexyldiethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dioctyldimethoxysilane, dioctyldiethoxysilane, dioctylethoxybutoxysilane, decyltrimethoxysilane, decyltriethoxysilane, didecyldimethoxysilane, didecyldiethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, dioctadecyldimethoxysilane, dioctadecyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropyltributoxysilane, etc.

[0056] R in formula (3) 4 Examples of reactive groups that can form a chemical bond with other functional groups in 4 include a vinyl group, an epoxy group, a styryl group, a methacryloxy group, an acryloxy group, an amino group, a ureido group, a mercapto group, a polysulfide group, an isocyanate group, and the like. Also, when there are two or more Rs 4 they may all be the same, some may be the same, or they may all be different. In the molecule, the number of Rs 4 in formula (3) is p = 1 to 3, that is, 1 to 3, but it is more preferable that p = 1. Examples of the hydrocarbon group of R in formula (3) 5 include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc. These may be branched or linear and may contain halogen groups such as fluorine, chlorine, and bromine. Among these, hydrocarbon groups having 1 to 18 carbon atoms are particularly preferable. Also, when there are two or more Rs 5 they may all be the same, some may be the same, or they may all be different. Examples of the hydrocarbon group of R in formula (3) 6 include methyl, ethyl, propyl, butyl, hexyl, octyl, etc. These may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferable. Also, when there are two or more Rs 6 they may all be the same, some may be the same, or they may all be different.

[0057] Preferred examples of such organosilicon compounds (silane coupling agents) of formula (3) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-methyl-3-aminopropyl-trimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyl-triethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane and the like.

[0058] R in formula (4) 7 Examples of the hydrocarbon group in include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl and the like. These may be branched or linear and may contain halogen groups such as fluorine, chlorine and bromine. Among these, hydrocarbon groups having 1 to 12 carbon atoms are particularly preferred. Also, R 7When there are two or more, they may all be the same, some may be the same, or all may be different. R in the molecule 7 The number of is, in formula (4), r = 0 to 3, that is, 0 to 3, but it is more preferably r = 1 to 3. Preferred examples of such an organosilicon compound (silane coupling agent) of formula (4) include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, octyldimethylchlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, tetrachlorosilane, and the like.

[0059] The organosilicon compound represented by the above general formula (1) may be used alone or in combination of two or more. Also, the silane coupling agent represented by any of the general formulas (2), (3), and (4) may be used alone or in combination of two or more. When used in combination of two or more, only the silane coupling agent represented by any of (2), (3), and (4) may be used in combination of two or more, or silane coupling agents represented by different two or more general formulas may be used in combination.

[0060] The hydrolyzate and / or the condensation reaction product of the organosilicon compound can be obtained by stirring and mixing the organosilicon compound, an amount of water necessary for performing the hydrolysis reaction, and a hydrolysis catalyst. At that time, a hydrophilic solvent can also be used as needed. The various conditions of the hydrolysis reaction (that is, the reaction for forming the silicon compound-containing layer) will be described later.

[0061] An oligomer that has been partially condensed in advance may be used as a raw material for the hydrolysis reaction and / or the condensation reaction for obtaining the hydrolyzate and / or the condensation reaction product of the organosilicon compound. The condensation reaction of the hydrolyzate of the organosilicon compound may be carried out simultaneously with the hydrolysis reaction of the organosilicon compound, or may be carried out in separate steps and, if necessary, with a change of catalyst. At that time, heating may be carried out as needed.

[0062] The coating layer of the composite particles contained in the metal pigment composition according to the first aspect of the first invention of the present application is not particularly limited except that at least one layer is a metal oxide film layer, preferably a silicon compound-containing layer. However, a coating layer other than the above metal oxide film layer, preferably a silicon compound-containing layer (hereinafter referred to as "second coating layer") can also be formed as needed. The second coating layer may be composed of, for example, at least one of a metal (such as an alkali metal; an alkaline earth metal; metals such as manganese, iron, cobalt, nickel, copper, silver, etc.), a metal oxide (such as titanium oxide, zirconium oxide, iron oxide, etc.), a metal hydrate, and a resin (such as a synthetic resin such as an acrylic resin, an alkyd resin, a polyester resin, a polyurethane resin, a polyvinyl acetate resin, a nitrocellulose resin, a fluororesin, etc.). As the second coating layer, for example, a molybdenum-containing film, a phosphate compound film, etc. can be formed. By providing the second coating layer, the corrosion resistance of the metal particles can be improved, and the formation of the metal oxide film layer, preferably the silicon compound-containing layer, can be promoted. The second coating layer is preferably formed (when formed) particularly between the metal particles and the metal oxide film layer, preferably the silicon compound-containing layer. Therefore, for example, a layer structure of "metal particles / second coating layer / metal oxide film layer, preferably silicon compound-containing layer" can be preferably adopted. Although not particularly limited, examples of the molybdenum-containing film include those disclosed in JP-A No. 2003-147226, WO 2004 / 096921 pamphlet, Patent No. 5979788, and JP-A No. 2019-151678. Examples of the phosphate compound film include those disclosed in Patent No. 4633239. A preferred example of the molybdenum-containing substance constituting the molybdenum-containing film is the mixed coordination type heteropolyanion compound disclosed in JP-A No. 2019-151678. In another variant, the second coating layer can be formed outside the metal particles and the metal oxide film layer, preferably the silicon compound-containing layer. In yet another variant, the components of the second coating layer (such as molybdenum-containing compounds and phosphate compounds) can be included together with the metal oxide, preferably the silicon compound, in the metal oxide film layer, preferably the silicon compound-containing layer.

[0063] The mixed coordination type heteropolyanion compound used in the aspect of forming the second coating layer (a typical example is a molybdenum-containing film) other than the metal oxide film layer, preferably the silicon compound-containing layer, of the composite particles contained in the metal pigment composition according to the first aspect of the first invention of the present application is not particularly limited, but specific examples are as follows.

[0064] The mixed coordination type heteropolyanion of the mixed coordination type heteropolyanion compound that can be used has a structure in which some of the heteroatoms of the heteropolyanion composed of one type of element are substituted with another element, and it exhibits physical properties different from those of a mixture of each heteropolyanion.

[0065] When represented by a chemical formula, if the mixed coordination type heteropolyanion is represented as [X p M q N r O s t then the heteropolyanion is [X p M q O s t and it is further distinguished from the isopolyanion [M q O s t Here, the heteroatom X represents an element of Group IIIB, IVB, or VB such as B, Si, Ge, P, or As, and among them, B, Si, and P are preferred. The polyatoms M and N represent transition metals such as Ti, Zr, V, Nb, Ta, Mo, or W, and Ti, Zr, V, Nb, Mo, and W are preferred. Also, p, q, r, and s represent the number of atoms, and t represents the oxidation number. ​​​Since heteropolyanion compounds have numerous structures, mixed coordination type heteropolyanion compounds can have even more structures. Representative and preferred mixed coordination type heteropolyanion compounds include the following mixed coordination type heteropolyacids: H 3 PW x Mo 12-x O 40 ·nH 2 O (phosphotungstomolybdic acid · n hydrate), H 3+x PV x Mo 12-x O 40 ·nH 2 O (phosphovanadomolybdic acid · n hydrate), H 4 SiW x Mo 12-x O 40 ·nH 2 O (silicotungstomolybdic acid · n hydrate), H 4+x SiV x Mo 12-x O 40 ·nH 2 O (silicovanadomolybdic acid · n hydrate), etc. are exemplified. (However, 1 ≦ x ≦ 11, n ≧ 0)

[0066] Among these heteropolyanion compounds, preferred specific examples include H 3 PW 3 Mo 9 O 40 ·nH 2 O, H 3 PW 6 Mo 6 O 40 ·nH 2 O, H 3 PW 9 Mo 3 O 40 ·nH 2 O, H 4 PV 1 Mo 11 O 40 ·nH 2 O, H 6 PV 3 Mo 9 O 40 ·nH 2 O, H 4 SiW 3 Mo 9O 40 ·nH 2 O, H 4 SiW 6 Mo 6 O 40 ·nH 2 O, H 4 SiW 9 Mo 3 O 40 ·nH 2 O, H 5 SiV 1 Mo 11 O 40 ·nH 2 O, H 7 SiV 3 Mo 9 O 40 ·nH 2 Examples of the mixed coordination type heteropolyacid include O etc. (However, n ≥ 0). The mixed coordination type heteropolyanion compound may be used in the form of an acid (so-called mixed coordination type heteropolyacid), or may be used in the form of a (partial or complete) salt having a specific cation as a counter ion.

[0067] When the mixed coordination type heteropolyanion compound is used in the form of a salt having a specific cation as a counter ion, examples of the counter cation source include 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 at least one selected from amine compounds which are organic components. Among the inorganic components, salts of alkali metals, alkaline earth metals, and ammonia are preferred. Furthermore, when at least one selected from these alkali metals, alkaline earth metals, and ammonia is used as the counter cation source, H 3 PW x Mo 12-x O 40 ·nH 2 O (phosphotungstomolybdic acid · n hydrate), H 3+x PV x Mo 12-x O 40 ·nH 2O(phosphovanadomolybdic acid·n hydrate), H 4 SiW x Mo 12-x O 40 ·nH 2 O(silicotungstomolybdic acid·n hydrate), H 4+x SiV x Mo 12-x O 40 ·nH 2 It is more preferably used in the form of a salt with at least one selected from O(carbovanadomolybdic acid·n hydrate).

[0068] Also, as the counter cation source of the mixed coordination type heteropolyanion compound, an amine compound which is an organic component is preferably used, and as a specific example, those represented by the following general formula (5) are preferable.

[0069] (R 8 -N(-R 10 )-) n -R 9 ··· (5) (In the formula, R 8 , R 9 and R 10 may be the same or different, and are a hydrogen atom, or a monovalent or divalent hydrocarbon group having 1 to 30 carbon atoms which may optionally contain an ether bond, an ester bond, a hydroxyl group, a carbonyl group, or a thiol group, and optionally R 8 and R 9 may together form a 5-membered or 6-membered cycloalkyl group, or may form a 5-membered or 6-membered ring which can additionally contain a nitrogen or oxygen atom as a crosslinking member, or optionally R 8 , R 9 and R 10 may together form a polycyclic polycycle which can contain one or more additional nitrogen atoms and / or oxygen atoms as crosslinking members. R 8 , R 9 and R 10 are not simultaneously hydrogen atoms. n represents an integer from 1 to 2.)

[0070] Specific examples of the amine compound, which is the 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-ethylhexylamine, and branched tridecylamine; linear secondary amines such as dimethylamine, diethylamine, dipropylamine, dibutylamine, dihexylamine, dioctylamine, dilaurylamine, ditridecylamine, and distearylamine; branched secondary amines such as diisopropylamine, diisobutylamine, di-2-ethylhexylamine, and di-branched tridecylamine; asymmetric secondary amines such as N-methylbutylamine, N-ethylbutylamine, N-ethylhexylamine, N-ethyllaurylamine, N-ethylstearylamine, N-isopropyloctylamine, and N-isobutyl-2-ethylhexylamine; linear tertiary amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, trilaurylamine, tritridecylamine, and tristearylamine; branched tertiary amines such as triisopropylamine, triisobutylamine, tri-2-ethylhexylamine, and tri-branched tridecylamine; tertiary amines having mixed hydrocarbon groups such as N,N-dimethyloctylamine, N,N-dimethyllaurylamine, N,N-dimethylstearylamine, and N,N-diethyllaurylamine. In addition, there are amines having alkenyl groups such as allylamine, diallylamine, triallylamine, and N,N-dimethylallylamine; alicyclic primary amines such as cyclohexylamine and 2-methylcyclohexylamine; primary amines having aromatic ring substituents such as aniline, benzylamine, and 4-methylbenzylamine; alicyclic secondary amines such as N,N-dicyclohexylamine and N,N-di-2-methylcyclohexylamine; secondary amines having aromatic ring substituents such as dibenzylamine and N,N-di-4-methylbenzylamine;Asymmetric secondary amines such as N-cyclohexyl-2-ethylhexylamine, N-cyclohexylbenzylamine, N-stearylbenzylamine, N-2-ethylhexylbenzylamine; alicyclic tertiary amines such as N,N-dimethylbenzylamine, N,N-dimethylcyclohexylamine, tricyclohexylamine; tertiary amines having aromatic ring substituents such as tribenzylamine, tri-4-methylbenzylamine; amines having an ether bond such as morpholine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-butoxypropylamine, 3-decyloxypropylamine, 3-lauryl-oxypropylamine; alkanolamines such as monoethanolamine, diethanolamine, monoisopropanolamine, monopropanolamine, butanolamine, triethanolamine, N,N-dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, N-butylethanolamine, N-cyclohexyl-N-methylaminoethanol, N-benzyl-N-propylaminoethanol, or N-hydroxyethylpyrrolidine, N-hydroxyethylpiperazine, N-hydroxyethylmorpholine; 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; cyclic amines such as N,N'-dimethylpiperazine, N-methoxyphenylpiperazine, N-methylpiperidine, N-ethylpiperidine, quinuclidine, diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]-7-undecene; aromatic amines such as pyridine, quinoline, etc., or any arbitrary mixture thereof is exemplified.;

[0071] Among these amine compounds, preferred specific examples include at least one selected from primary, secondary, or tertiary amines of linear or branched alkyl having 4 to 20 carbon atoms, or alkanolamines. Examples include butylamine, hexylamine, cyclohexylamine, octylamine, tridecylamine, stearylamine, dihexylamine, di-2-ethylhexylamine, linear or branched ditridecylamine, distearylamine, tributylamine, trioctylamine, linear or branched tritridecylamine, tristearylamine, N,N-dimethylethanolamine, N-methyldiethanolamine, triethanolamine, morpholine, and the like. At least one selected from these amine compounds represented by the general formula (5), and H 3 PW x Mo 12-x O 40 ·nH 2 O (phosphotungstomolybdic acid · n hydrate), H 3+x PV x Mo 12-x O 40 ·nH 2 O (phosphovanadomolybdic acid · n hydrate), H 4 SiW x Mo 12-x O 40 ·nH 2 O (silicotungstomolybdic acid · n hydrate), H 4+x SiV x Mo 12-x O 40 ·nH 2 O (silicovanadomolybdic acid · n hydrate) is more preferably used in the form of a salt with at least one selected therefrom. Among the above mixed coordination type heteropolyanion compounds, H 3 PW x Mo 12-x O 40 ·nH 2 O (phosphotungstomolybdic acid · n hydrate), H 3+x PV x Mo 12-x O 40 ·nH 2 O (phosphovanadomolybdic acid · n hydrate), H 4SiW x Mo 12-x O 40 ·nH 2 O (mixed coordination type heteropolyacid of silicotungstomolybdic acid·n hydrate) or an organic amine salt of these mixed coordination type heteropolyacids is most preferred.

[0072] The metal oxide film layer of the composite particles contained in the metal pigment composition according to the first aspect of the first invention of the present application, preferably the second coating layer other than the silicon compound-containing layer, may be a layer containing other corrosion inhibitors in order to further improve the corrosion resistance of the core metal particles (preferably aluminum particles or aluminum alloy particles). The corrosion inhibitor to be added is not particularly limited, and any known corrosion inhibitor can be used. The amount used may be in a range that does not inhibit the desired effect of the first aspect of the first invention of the present application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organic phosphorus compounds, metal salts of molybdic acid, and the like.

[0073] From the viewpoints of adhesion and chemical resistance when forming a coating film, the metal oxide film layer of the composite particles contained in the metal pigment composition, preferably the silicon compound-containing layer and / or the second coating layer, or as a separate layer, may further contain an organic oligomer or polymer. Further, from the viewpoint of storage stability, at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (sub)phosphate esters and their salts may be contained in the metal oxide film layer of the composite particles, preferably the silicon compound-containing layer and / or the second coating layer, or as a separate layer. These compounds are not particularly limited, but for example, those disclosed in JP-A-2019-151678 can be used.

[0074] (5) The proportion of bent composite particles is 10% or less. In the metal pigment composition according to the first aspect of the first invention of the present application, the proportion of bent composite particles is 10% or less. As a result, in combination with the satisfaction of the above requirements, the coating film formed using the metal pigment composition exhibits even higher hiding power, brilliance, and the like. The proportion of bent composite particles is understood to be an index related to the degree of deformation or breakage of the composite particles. If the proportion of bent composite particles is 10% or less, the degree of deformation or breakage of the composite particles is small, whereby the projected area of the particles when formed into a coating film becomes large and it becomes easy to orient parallel to the coating film surface, so that high hiding power and excellent brilliance can be exhibited. Further, the proportion of the untreated surface on the surface of the coating film formed using the metal pigment composition is reduced, so that the water resistance of the coating film can be expected to be improved. In this physical property requirement, the "composite particles" refer to the aggregates (aggregates) when a plurality of composite particles are aggregated and fixed. In the metal pigment composition, the proportion of bent composite particles is preferably as small as possible. This proportion is preferably 9% or less, more preferably 8% or less, even more preferably 7% or less, and most preferably 6% or less. Specifically, the proportion of bent composite particles in the metal pigment composition can be measured according to the method described in the examples below. That is, a coating film (thin film) is formed using a metal pigment composition in which the composite particles are dispersed in a mixture of an alcohol-based solvent (hydrophilic solvent) such as methoxypropanol and water, and the degree of deformation of the particle cross-section can be observed with a scanning electron microscope (SEM). At that time, for each composite particle, when the shortest distance from both ends of the particle is 0.8 times or less of the length of the particle, it is determined that there is deformation. By observing 300 or more, preferably 500 or more particles, the proportion of particles with deformation can be calculated, and this can be used as the proportion of bent composite particles. In addition, in the observation, particles having a particle diameter in the range of 90% from the center when measuring the particle size distribution are targeted. The ratio of bent composite particles in the metal pigment composition can be mainly controlled by appropriately adjusting the stirring time, the type of stirring device, the power / degree of stirring (such as the type and diameter of the stirring blade, the rotation speed, the presence or absence of external stirring, etc.) in the step of coating the metal oxide film layer, preferably the silicon compound-containing layer (and other coating layers as required).

[0075] (6) The number ratio of aggregates in which four or more composite particles are adhered to each other is 35% or less based on the total number of composite particles In the metal pigment composition according to the first aspect of the first invention of the present application, the number ratio of aggregates in which four or more composite particles are adhered to each other is 35% or less based on the total number of composite particles. As a result, in combination with the satisfaction of the above-mentioned various requirements, the coating film formed using the metal pigment composition exhibits higher hiding power, brilliance, etc., and the aggregability of individual particles can be more effectively suppressed. The number ratio of aggregates in which four or more composite particles are adhered to each other is understood to be the degree of overlap of composite particles, that is, the degree of aggregability. If the number ratio of aggregates in which four or more composite particles are adhered to each other is 35% or less based on the total number of composite particles, the orientation of the composite particles in the coating film is orderly, and the ratio of composite particles arranged parallel to the coating film surface increases. As a result, the projected area of the composite particles in the coating film formed using the metal pigment composition increases, enhancing the hiding power and brilliance, and furthermore, it becomes easier to form a uniform and sufficient coating on individual particles, resulting in a further reduction in the aggregability of individual particles. Furthermore, since the number ratio of aggregates in which four or more composite particles are adhered to each other is small, aggregates of composite particles once formed in the aqueous paint can collapse, exposing the untreated surface, and reacting with water, which is the solvent of the aqueous paint, to generate hydrogen gas can be effectively prevented. The number ratio of aggregates in which four or more composite particles are adhered to each other in the metal pigment composition is preferably 30% or less, more preferably 20% or less, even more preferably 15% or less, still more preferably 10% or less, and most preferably 5% or less. The smaller this ratio, the better, but it is not easy to make it exactly zero. The "composite particles" in these physical property requirements refer to individual composite particles, which is different from the physical property requirements of (1) to (3) and (5) above, even when multiple composite particles are aggregated and adhered. Also, the "aggregate" in these physical property requirements refers to a state where multiple composite particles are aggregated and adhered. The number ratio of aggregates in which four or more composite particles in the metal pigment composition are adhered to each other can be measured in detail according to the method described in the examples below. That is, a film (thin film) is formed using a metal pigment composition in which composite particles are dispersed in a mixture of an alcohol-based solvent such as methoxypropanol and water, and the degree of overlap of the composite particles can be observed with a scanning electron microscope (SEM). At this time, for each composite particle, a) when the minimum distance d between the surfaces of the base metals (metal particles) of the target composite particles is twice or more the average coating layer thickness t, they are not aggregated; or b) when the minimum distance d between the surfaces of the base metals (metal particles) of the target composite particles is less than the average coating layer thickness t, they are considered aggregated. According to this criterion, the presence or absence of aggregation is determined. By observing 300 or more, preferably 500 or more composite particles, the ratio of composite particles in which four or more are adhered to each other (aggregated) can be calculated, and this can be taken as the number ratio of aggregates in which four or more composite particles are adhered to each other. Here, the average coating layer thickness is the average coating layer thickness at arbitrary locations of 50, preferably 100, arbitrary particles. The number ratio of aggregates in which four or more composite particles in the metal pigment composition are adhered to each other with respect to the total number of composite particles in the metal pigment composition can be controlled mainly by appropriately adjusting the stirring time, the type of stirring device, the power / degree of stirring (such as the type and diameter of the stirring blade, the rotation speed, the presence or absence of external stirring, etc.) in the process of coating the metal oxide film layer, preferably the silicon compound-containing layer (and other coating layers as required).

[0076] 2. Method for Producing a Metal Pigment Composition The metal pigment composition according to the first aspect of the first invention of the present application is made into flaky metal particles, for example, by using a method commonly used in the pigment industry. After this step, the metal particles are produced through steps such as sieving (classification), filtration, washing, and mixing. Then, it can be preferably produced by a production method including a step of coating the metal particles with a metal oxide film layer, preferably a silicon compound-containing layer, under stirring using a solvent containing water and / or a hydrophilic solvent. More specifically, the following methods can be mentioned, but it is not limited thereto.

[0077] When the metal pigment composition according to the first aspect of the first invention of the present application has a metal oxide film layer that is a silicon compound-containing layer, for example, in a mixed liquid containing (a) metal particles, (b) a silicon-containing raw material containing at least one organic silicon compound, (c) a solvent (water and / or a hydrophilic solvent), and optionally other optional components, it can be preferably produced by a method including a step of forming a silicon compound-containing layer on the surface of the metal particles by subjecting the organic silicon compound to a hydrolysis / (partial) condensation reaction (silicon compound-containing layer formation step). This step can usually be carried out under stirring.

[0078] Grinding and Sieving / Filtration Process Here, the case of using aluminum powder as the metal particles will be described as an example. Aluminum powder is generally produced by using a method commonly used in the pigment industry, such as the atomized aluminum powder and / or aluminum foil, and grinding in the presence of a grinding aid or an inert solvent using methods such as the dry ball mill method, the wet ball mill method, the attritor method, and the stamp mill method to make it into a so-called flaky shape. After this step, it is obtained through the necessary steps such as sieving (classification), filtration, washing, and mixing. Examples of the grinding aids here include fatty acids, aliphatic amines, aliphatic amides, aliphatic alcohols, etc. Generally, oleic acid, stearic acid, stearylamine, etc. are preferred. Examples of the inert solvents include those showing hydrophobicity such as mineral spirits, solvent naphtha, LAWS, HAWS, toluene, xylene, etc., and these can be used alone or in combination. The grinding aids and inert solvents are not limited to these. From the viewpoint of preventing dust explosion and ensuring safety, grinding by the wet ball mill method is preferred as the grinding process.

[0079] When aluminum particles are employed as the metal particles in the production of the metal pigment composition according to the first aspect of the first invention of the present application, commercially available paste-like aluminum flakes obtained through such grinding, sieving, and filtration can be used. The paste-like aluminum flakes may be used as they are, or alternatively, the fatty acids, etc. on the surface may be removed in advance with an organic solvent or the like before use. Also, as the metal particles in the production of the metal pigment composition according to the first aspect of the first invention of the present application, so-called vapor-deposited aluminum pigments produced by peeling a metal layer vapor-deposited on a carrier material such as a resin film by physical vapor deposition (PVD) from the carrier material and then grinding can also be used.

[0080] Hereinafter, as a preferred example of the step of forming the metal oxide film layer, the step of forming a silicon compound-containing layer will be described. Process for Forming a Silicon Compound-Containing Layer The mixed liquid containing at least one of the above (a) metal particles, (b) a silicon-containing raw material containing at least one organic silicon compound, and (c) a solvent, and optionally other optional components can be prepared by mixing these components. The order of mixing is not particularly limited.

[0081] As the metal particles, the above-described metal particles can be used, and in particular, particles of aluminum or an aluminum alloy can be preferably used. Also, as for the particle shape, as described above, it is preferable to use flaky metal particles. As the metal particles, known or commercially available ones (typically paste-like aluminum flakes) can be used.

[0082] The content (solid content) of the metal particles in the above mixture is not particularly limited and can be appropriately set according to the type, particle size, etc. of the metal particles used.

[0083] As the silicon-containing raw material, an organosilicon compound is used. As the organosilicon compound, although not limited, preferably the above-described ones can be used. At least one of the organosilicon compound represented by the above formula (1) (a typical example is tetraalkoxysilane) and / or its condensate, and the silane coupling agent represented by any one of the above formulas (2) to (4) can be preferably used. Hereinafter, the case where tetraalkoxysilane is used as the organosilicon compound represented by the above formula (1) will be described as an example. In the following, tetraalkoxysilane and / or its condensate may be simply collectively referred to as "tetraalkoxysilane".

[0084] 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 of mixing and using both (referred to as the "first method") can be adopted. Alternatively, a method (referred to as the "second method") including a step of forming a first silicon compound-containing layer by treating with one and forming a second silicon compound-containing layer by treating with the other on the metal particles can also be adopted.

[0085] As a first method, for example, by appropriately adjusting the pH of a mixed solution containing metal particles, tetraalkoxysilane represented by the above formula (1), and a silane coupling agent represented by any one of the above formulas (2) to (4), a step of subjecting tetraalkoxysilane and the silane coupling agent to a hydrolysis / condensation reaction to form a silicon compound-containing layer is included.

[0086] As a second method, for example, by appropriately adjusting the pH of a mixed solution containing metal particles and tetraalkoxysilane represented by the above formula (1), tetraalkoxysilane is subjected to a hydrolysis / condensation reaction to form a first silicon compound-containing layer (for example, a silica film composed of amorphous silica) on the surface of the metal particles, and by adjusting the pH of a mixed solution containing metal particles and a silane coupling agent represented by any one of the above formulas (2) to (4), the silane coupling agent is subjected to a hydrolysis / condensation reaction to form a second silicon compound-containing layer on the surface of the first silicon compound-containing layer.

[0087] The usage amount of tetraalkoxysilane represented by the above formula (1) or its condensate can be appropriately set according to the type of tetraalkoxysilane used, etc. The usage amount may be, for example, 2 to 200 parts by mass, more preferably 5 to 100 parts by mass, based on 100 parts by mass of the metal particles (solid content), from the viewpoint of the coating treatment effect and from the viewpoint of suppressing aggregation of the metal particles or a decrease in the brilliance.

[0088] The usage amount of the silane coupling agent represented by any one of the above formulas (2) to (4) is not particularly limited, but is usually about 0.1 to 20 parts by mass, particularly preferably 1 to 10 parts by mass, based on 100 parts by mass of the metal particles (solid content). By the usage amount being about 0.1 to 20 parts by mass, a desired coating treatment effect and desirable coating film physical properties can be obtained.

[0089] As the solvent in the mixed solution, that is, the solvent for the hydrolysis reaction and / or condensation reaction of the organosilicon compound, it may be appropriately selected according to the type of silicon-containing raw material used, etc. Usually, water, a hydrophilic organic solvent, or a mixed solvent thereof can be used. By using these solvents, the uniformity of the reaction and the uniformity of the resulting hydrolyzate and / or condensate can be enhanced. In the mode of directly forming a silicon compound-containing layer on metal particles, from the viewpoint of avoiding the rapid progress of the reaction between the metal particles and water, it is particularly preferable that the solvent of the mixed solution contains a hydrophilic organic solvent. In the first aspect of the first invention of the present application, a mixed solvent of water and a hydrophilic organic solvent can be preferably used.

[0090] The hydrophilic organic solvent is not particularly limited. For example, 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 their esters; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols, etc. can be mentioned. These can be used alone or in combination of two or more.

[0091] Also, when using a mixed solvent of water and a hydrophilic organic solvent as the solvent, the ratio between the two is not particularly limited. In the mode of directly forming the silicon compound-containing layer on the metal particles, from the viewpoint of avoiding the rapid progress of the reaction between the metal particles and water, before introducing the silicon compound, it is preferable that the total of the two is 100% by mass and the water content is 20% by mass or less. The lower limit value of the water content in this case is not limited, but usually about 1% by mass is sufficient.

[0092] The amount of the solvent used in the step of forming the silicon compound-containing layer (excluding the amount of the solvent for pre-dispersing the metal particles if any) is not limited, but usually about 100 to 10,000 parts by mass with respect to 100 parts by mass of the metal particles (solid content), and particularly preferably 200 to 1,000 parts by mass. By the amount of the solvent being 100 parts by mass or more, an increase in the viscosity of the mixed solution (slurry) is suppressed, and appropriate stirring becomes possible. Also, by the amount of the solvent being 10,000 parts by mass or less, it is possible to prevent the recovery and regeneration costs of the treatment liquid from becoming high. Here, the amount of the solvent used refers to the total amount of the solvent used for forming the first silicon compound-containing layer and the second silicon compound-containing layer in the case of the above second method.

[0093] In the above mixed solution, other additives may be blended as necessary within a range that does not interfere with the effects of the first aspect of the first invention of the present application. For example, in addition to catalysts such as hydrolysis catalysts and dehydration condensation catalysts, surfactants, metal corrosion inhibitors, etc. can be mentioned.

[0094] Among these, a hydrolysis catalyst can be preferably used. By blending a hydrolysis catalyst, the pH of the mixed solution can be adjusted, and the organic silicon compound can be efficiently hydrolyzed and dehydrated and condensed. As a result, it becomes possible to efficiently and surely form a silicon compound-containing layer on the surface of the metal particles.

[0095] The hydrolysis catalyst may be a known or commercially available one and is not particularly limited. 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; phosphonic acids such as vinylphosphonic acid, 2-carboxyethanephosphonic acid, 2-aminoethanephosphonic acid, and octane phosphonic acid. These hydrolysis catalysts may be used alone or in combination of two or more. In addition, examples of the hydrolysis catalyst include inorganic alkalis such as ammonia, sodium hydroxide, and potassium hydroxide; inorganic alkali salts such as ammonium carbonate, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate; amines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, ethylenediamine, pyridine, aniline, choline, tetramethylammonium hydroxide, and guanidine; and salts of organic acids such as ammonium formate, ammonium acetate, monomethylamine formate, dimethylamine acetate, pyridine lactate, guanidinoacetic acid, and aniline acetate. These hydrolysis catalysts can be used singly or in combination of two or more.

[0096] The addition amount of the hydrolysis catalyst is not particularly limited, but usually it may be 0.01 to 20 parts by mass, particularly preferably 0.02 to 10 parts by mass, based on 100 parts by mass of the metal particles (solid content). When the addition amount is 0.01 part by mass or more, the precipitation amount of the silicon compound-containing layer can be sufficient. Also, when the addition amount is 20 parts by mass or less, the aggregation of the metal particles can be effectively suppressed.

[0097] When preparing the above-mentioned mixed solution, these components may be mixed so as to be uniform in the mixed solution, and the mixing order is not particularly limited. In the first aspect of the first invention of the present application, in the embodiment having a silicon compound-containing layer, the preparation of the above mixed solution is preferably carried out under stirring with an appropriate intensity.

[0098] The temperature of the mixed solution may be either normal temperature or under heating. Generally, the temperature of the mixed solution may be set to 20 to 90 °C, and particularly preferably controlled within the range of 30 to 80 °C. When the temperature is 20 °C or higher, the formation rate of the silicon compound-containing layer is increased, and the treatment time can be shortened. On the other hand, when the temperature is 90 °C or lower, the reaction can be easily controlled, and the probability of obtaining desired composite particles can be increased.

[0099] The stirrer for stirring the mixed solution is not particularly limited, and a known stirrer capable of efficiently and uniformly stirring the mixed solution containing aluminum particles and an organosilicon compound can be used. Specific examples include kneaders, mixers, rotary vessel stirrers, stirred reaction tanks, V-type stirrers, double cone-type stirrers, screw mixers, sigma mixers, flash mixers, air flow stirrers, ball mills, edge runners, etc. Further description of the stirrer will be given later.

[0100] The temperature of the mixed solution when stirring the mixed solution containing metal particles and an organosilicon compound is usually preferably about 10 to 100 °C, and particularly preferably 30 to 80 °C. When this temperature is 10 °C or higher, the reaction time for obtaining a sufficient treatment effect can be shortened. Also, when this temperature is 100 °C or lower, the control of the reaction for obtaining the desired metal pigment composition becomes easier.

[0101] The stirring time of the mixed solution is not particularly limited as long as it is sufficient for forming the desired silicon compound-containing layer. This stirring time is preferably, for example, 0.5 to 10 hours, and more preferably 1 to 5 hours. When the stirring time is 0.5 hours, a sufficient treatment effect can be obtained. Also, when the stirring time is 10 hours or less, an increase in treatment cost can be suppressed.

[0102] In the above mixture, a silicon compound-containing layer is formed on the surface of the metal particles (or via the second coating layer) by subjecting the silicon-containing raw material to a hydrolysis / condensation reaction. This hydrolysis / condensation reaction can be particularly carried out by adjusting the pH of the mixture, etc.

[0103] When adjusting the pH, particularly at the stage where the silicon compound-containing layer is formed on the surface of the metal particles (or via the second coating layer), since the pH value of the mixture changes, it is desirable to appropriately adjust so that the pH value can be maintained within a certain range. At that time, it is desirable to adjust the pH value by adding a hydrolysis catalyst. However, as long as the characteristics of the metal pigment composition according to the first aspect of the first invention of the present application having a silicon compound-containing layer are not impaired, the pH value may be adjusted using other acidic or alkaline compounds.

[0104] When using a basic hydrolysis catalyst as the hydrolysis catalyst, it is preferable that the pH value is 7 to 13, more preferably 7 to 11, and even more preferably 7.5 to 10. When the pH value is 7 or more, the silicon compound-containing layer can be formed rapidly. On the other hand, when the pH value is 13 or less, aggregation of the metal particles and reduction of the brilliance can be suppressed, and generation of hydrogen gas due to corrosion can be prevented.

[0105] When using an acidic hydrolysis catalyst as the hydrolysis catalyst, it is preferable that the pH value is 1.5 to 7, more preferably 1.5 to 6, even more preferably 2 to 4, and particularly preferably 2 to 3. When the pH value is 1.5 or more, the reaction can be appropriately controlled and it becomes easy to obtain a metal pigment composition containing desired composite particles. On the other hand, when the pH value is 7 or less, the precipitation rate of the silicon compound-containing layer can be kept high.

[0106] In any case of adopting either the above first method or the second method, the hydrolyzate and / or condensate of the organosilicon compound represented by the above general formula (1) is preferably added in an amount of 0.01 to 50 parts by mass, more preferably 1 to 30 parts by mass, in terms of the state where the hydrolysis and condensation reactions are completed, based on 100 parts by mass of the metal particles (solid content). Further, the silane coupling agent represented by any one of the above general formulas (2) to (4), and / or the hydrolyzate and / or condensate derived from their partial condensates are added in a total 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 where the hydrolysis and condensation reactions are completed, based on 100 parts by mass of the metal particles (solid content).

[0107] The addition amount of the hydrolyzate and / or condensate of the organosilicon compound represented by the general formula (1) 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 all of the organosilicon compound is hydrolyzed and condensed. For example, when tetraethoxysilane (TEOS) is used as the organosilicon compound represented by the general formula (1), the addition amount of the hydrolyzate and / or condensate of the organosilicon compound can be calculated using the following mass ratio before and after the hydrolysis and condensation reactions. (Hydrolysis) Si(OC 2 H 5 ) 4 (Molecular weight: 208) + 4H 2 O → Si(OH) 4 (Molecular weight: 96) + (C 2 H 5 OH) 4 (Condensation) Si(OH) 4 (Molecular weight: 96)+ Si(OH) 4 (Molecular weight: 96) → (SiO 2 ) 2 (Molecular weight: 60×2) + 4H 2 O Before and after the above hydrolysis and condensation reactions, the mass becomes 60 / 208 = 0.288 times. Therefore, for example, when 10 parts by mass of TEOS is used with respect to 100 parts by mass of metal particles (solid content), the addition amount of the hydrolyzate and / or its condensate is 0.288 times that, i.e., 2.88 parts by mass.

[0108] Similarly, the addition amount of the hydrolyzate and / or its condensate of a silane coupling agent represented by any of general formulas (2) to (4) can also be calculated by multiplying the mass of the silane coupling agent represented by any of general formulas (2) to (4) and / or its partial condensate used in the production of the metal pigment composition by the mass ratio before and after the reaction when all of the silane coupling agent and / or its partial condensate are hydrolyzed and undergo a condensation reaction. For example, when methyltrimethoxysilane is used as the silane coupling agent represented by general formula (2), the addition amount of the hydrolyzate and / or its condensate of the silane coupling agent can be calculated using the following mass ratio before and after the hydrolysis and condensation reactions. (Hydrolysis) CH 3 Si(OCH 3 ) 3 (Molecular weight: 136) + 3H 2 O → CH 3 Si(OH) 3 (Molecular weight: 94) + (CH 3 OH) 3 (Condensation) CH 3 Si(OH) 3 (Molecular weight: 94) + CH 3 Si(OH) 3 (Molecular weight: 94) → (SiCH 3 O1 .5 ) 2 (Molecular weight: 67×2) + 3H 2 O Before and after the above hydrolysis / condensation reaction, the mass becomes 67 / 136 = 0.49 times. For example, when 1.23 parts by mass of methyltrimethoxysilane is used with respect to 100 parts by mass of metal particles (solid content), the addition amount of its hydrolyzate and / or its condensate is 0.49 times that, i.e., 0.60 parts by mass.

[0109] Also, regardless of whether the first method or the second method is adopted above, before the metal particles are combined with the organosilicon compound which is the silicon compound source (or before being combined with the molybdenum compound when forming the second coating layer), it is preferable to sufficiently disperse them in water, a hydrophilic organic solvent, or a mixed solvent thereof. In this pre-dispersion (initial dispersion), preferably, a part of the dispersion (for example, 0.5 to 30% by mass, preferably 1 to 20% by mass, more preferably 1 to 15% by mass of the whole dispersion per minute) is taken out of the dispersion tank once and then returned to the dispersion tank again to perform external circulation, so that the degree of dispersion can be further enhanced. By performing ultrasonic treatment outside the dispersion tank in the middle of the external circulation flow path, the dispersibility can be further enhanced. The ultrasonic treatment is not particularly limited, but it can usually be carried out at 10 to 1000 W, preferably 50 to 800 W, and usually for 20 seconds to 10 minutes, preferably about 30 seconds to 5 minutes. Also, the amount of the solvent used for this pre-dispersion may be usually about 100 to 10000 parts by mass, preferably 200 to 5000 parts by mass, more preferably 300 to 1000 parts by mass, with respect to 100 parts by mass of the metal particles (solid content) from the viewpoint of appropriately adjusting the stirring intensity to obtain sufficient dispersion. Such pre-dispersion of the metal particles can usually be carried out at 10 to 80°C, preferably 15 to 60°C, most preferably around room temperature (about 20 to 30°C). Also, the pre-dispersion of the metal particles can be carried out for 5 minutes to 2 hours, preferably 10 minutes to 1 hour (including the ultrasonic treatment if performed).

[0110] Process for Forming a Second Coating Layer The composite particles constituting the composite metal pigment according to the first aspect of the first invention of the present application preferably further have, in addition to the metal oxide coating layer, another coating layer (second coating layer), preferably a coating layer containing at least one selected from metals, metal oxides, metal hydrates, and resins. The second coating layer is preferably formed (when formed) particularly between the metal particles and the metal oxide coating layer, preferably the silicon compound-containing layer. Therefore, a layer structure of "metal particles / second coating layer / metal oxide coating layer, preferably silicon compound-containing layer" can be preferably adopted. The second coating layer is not particularly limited, and may be a molybdenum-containing film, a phosphate compound film, or the like. Preferred examples of the molybdenum-containing substance constituting the molybdenum-containing film include the mixed coordination type heteropolyanion compound disclosed in JP-A-2019-151678. Examples of the constituent components of the second coating layer, including the mixed coordination type heteropolyanion compound, are as described above. Hereinafter, a mode of forming a molybdenum-containing film as the second coating layer between the metal particles and the metal oxide coating layer, preferably the silicon compound-containing layer, will be described by way of example.

[0111] When forming a molybdenum-containing film as the second coating layer between the metal particles and the metal oxide coating layer, preferably the silicon compound-containing layer, prior to the formation of the metal oxide coating layer, preferably the silicon compound-containing layer, a mixed solution containing the metal particles and a molybdenum compound (typically a mixed coordination type heteropolyanion compound) is stirred to form a molybdenum-containing film on the surface of the metal particles.

[0112] The method for forming a molybdenum-containing film on the surface of the metal particles is not particularly limited, and any method capable of uniformly stirring a mixed solution containing the metal particles and the molybdenum compound in an aqueous solvent may be used. For example, a molybdenum-containing 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.

[0113] In addition, the stirrer for stirring the mixed liquid containing metal particles and a molybdenum compound is not particularly limited, and a known stirrer capable of efficiently and uniformly stirring the mixed liquid containing aluminum particles and a molybdenum compound can be used. Specific examples include kneaders, mixers, rotary vessel stirrers, stirred reaction tanks, V-type stirrers, double cone-type stirrers, screw mixers, sigma mixers, flash mixers, air current stirrers, ball mills, edge runners, and the like. Examples of the stirring blades of the stirrer are not particularly limited, and include anchor blades, paddle blades, propeller blades, turbine blades, and the like.

[0114] The amount of the molybdenum compound used can be appropriately set according to the type of the molybdenum compound used and the like. Generally, this amount may be 0.02 to 20 parts by mass, particularly preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the metal particles (solid content). When the content is 0.02 parts by mass or more, a sufficient treatment effect can be obtained. Further, when the content is 20 parts by mass or less, the brilliance of the obtained metal pigment composition can be maintained at a high level.

[0115] As the solvent used for mixing the metal particles and the molybdenum compound, usually water, a hydrophilic organic solvent, or a mixed solvent thereof can be used.

[0116] 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, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether, and their esters; glycols such as ethylene glycol, propylene glycol, 1,3 - butanediol, 1,4 - butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. One or more of these can be used.

[0117] The amount of the solvent used in the step of forming the second coating layer (excluding the amount of the solvent for pre - dispersing the metal particles if any) is not particularly limited, but is usually preferably 50 to 5000 parts by mass, and more preferably 100 to 2000 parts by mass with respect to 100 parts by mass of the metal particles (solid content). By the amount of the solvent being 50 parts by mass or more, uneven distribution of the molybdenum compound and aggregation of the metal particles can be suppressed. Also, by the amount of the solvent being 5000 parts by mass or less, a sufficient treatment effect by the molybdenum compound on the metal particles can be obtained.

[0118] When stirring the mixed solution containing the metal particles and the molybdenum compound, the temperature of the mixed solution is usually preferably about 10 to 100°C, and particularly preferably 30 to 80°C. By this temperature being 10°C or more, the reaction time for obtaining a sufficient treatment effect can be shortened. Also, by this temperature being 100°C or less, the control of the reaction for obtaining the desired metal pigment composition becomes easier.

[0119] The stirring time of the mixed solution is not particularly limited as long as it is sufficient time for forming a desired molybdenum-containing film. This stirring time is preferably, for example, 0.5 to 10 hours, and more preferably 1 to 5 hours. By setting the stirring time to 0.5 hours, a sufficient treatment effect can be obtained. Also, by setting the stirring time to 10 hours or less, an increase in treatment cost can be suppressed.

[0120] After completion of stirring of the mixed solution containing metal particles and a molybdenum compound, the particles having the second coating layer formed thereon can be recovered. In this case, known washing, solid-liquid separation, etc. can be appropriately carried out as necessary. For example, after washing the mixed solution with a hydrophilic organic solvent, it is preferable to filter using a filter or the like to remove water and unreacted substances from the cake containing the metal particles having a molybdenum-containing film. In this way, a molybdenum-containing film which is the second coating layer can be formed. When forming other second coating layers, it can be carried out according to the above method.

[0121] In an embodiment of forming an oxide metal coating layer, preferably a silicon compound-containing layer, on the second coating layer (molybdenum-containing film) on the metal particles, after completion of stirring of the mixed solution containing metal particles and a molybdenum compound, without recovering the particles having the second coating layer formed thereon, a dispersion of a metal oxide coating source, preferably a silicon compound source (typically, at least one of the organosilicon compounds represented by the above formula (1), such as tetraalkoxysilane and / or its condensate, and the silane coupling agents represented by any of the above formulas (2) to (4)) in water and / or a hydrophilic organic solvent may be directly added and stirred. At this time, a dispersion of the organosilicon compound represented by the above formula (1), such as tetraalkoxysilane and / or its condensate, may be added to the system containing the particles having the second coating layer formed thereon, and then a dispersion of at least one of the silane coupling agents represented by any of the above formulas (2) to (4) may be added and stirred (see the second method in the above-mentioned "formation step of the silicon compound-containing layer").

[0122] Stirring Conditions In the production of the metal pigment composition according to the first aspect of the first invention of the present application, it is necessary to carry out at least the step of forming the metal oxide coating layer, preferably the silicon compound-containing layer, under stirring. Further, in the production of the metal pigment composition according to the first aspect of the first invention of the present application, not only the step of forming the metal oxide coating layer, preferably the silicon compound-containing layer, but also the step of forming the second coating layer are preferably carried out under stirring. In the mode of pre-dispersing the above-mentioned metal particles, it is more preferably carried out under stirring. Further, in the production of the metal pigment composition according to the first aspect of the first invention of the present application, it is even more preferable to carry out the entire process including the pre-dispersion of the metal particles, the step of forming the second coating layer, and the step of forming the metal oxide coating layer, preferably the silicon compound-containing layer, under stirring. In the production of the metal pigment composition according to the first aspect of the first invention of the present application, by carrying out at least the step of forming the metal oxide coating layer, preferably the silicon compound-containing layer, under appropriately controlled stirring, it is possible to effectively suppress or prevent the phenomenon that composite particles adhere to each other through the metal oxide coating layer, preferably the silicon compound-containing layer, or that agglomerated particles composed of metal particles are entirely coated with the metal oxide coating layer, preferably the silicon compound-containing layer. Further, by carrying out the entire process including the pre-dispersion of the metal particles, the step of forming the second coating layer, and the step of forming the metal oxide coating layer, preferably the silicon compound-containing layer (until all the layers to be formed on the metal particle surface are completely formed), it becomes possible to more easily obtain the metal pigment composition according to the first aspect of the first invention of the present application that satisfies all of the physical property requirements (1) to (6) above. The following description of the stirring conditions is applicable to any step in the production of the metal pigment composition according to the first aspect of the first invention of the present application.

[0123] Stirring can be carried out by a known or commercially available stirring device. For example, at least one of a kneader, a mixer, a rotary vessel stirrer, a stirred reaction tank, a V-type stirrer, a double cone-type stirrer, a screw mixer, a sigma mixer, a flash mixer, an air flow stirrer, a ball mill, an edge runner, etc. can be used.

[0124] Among these stirrers, it is preferable to use a stirring tank type apparatus that is stirred by a stirring blade (impeller). As a result of the pressure shearing action together with the circulation action of flowing the entire reaction system including the liquid phase by the stirring blade, it is possible to more effectively suppress the generation of aggregation of composite particles.

[0125] The shape of the stirring blade is not particularly limited. For example, an anchor type, propeller type, turbine type, inclined turbine type, fan turbine type, paddle type, inclined paddle type, or gate type can be used. A Max Blend blade (manufactured by Sumitomo Heavy Industries, Ltd.) or a full zone blade (manufactured by Kobe Steel, Ltd.) is also suitable. Further, these shaped stirring blades can be combined in multiple stages.

[0126] The stirring speed is preferably such that the stirring blade is not exposed by the vortex generated by the stirring. Further, in order to suppress the vortex generated by the stirring, a cylindrical tank, a rectangular tank, or a tank provided with a baffle plate can be preferably used.

[0127] In the production of a metallic pigment composition containing composite particles according to the first aspect of the first invention of the present application, it is desirable to set the size of the optimal stirring tank and stirring blades and the speed of the stirring blades in relation to the amount of the mixed solution and physical properties (density, viscosity, etc.). The size of the stirring tank is preferably selected such that the maximum amount of the mixed solution used in a series of processes is 20 to 80% of the stirring tank. Preferably, in the case of a cylindrical stirring tank with an internal volume of 100 liters or more, the ratio of the height (L) to the inner diameter (D) of the stirring tank is generally in the range of L / D = 0.5 to 3.0, usually in the range of 1 to 2. Also, the size of the stirring blades is generally such that the maximum diameter is in the range of 0.2 to 0.9 of the inner diameter of the stirring tank, preferably about 0.4 to 0.6. The shape of the stirring blades (including the length) is preferably appropriately selected according to the physical properties of the mixed solution, and it is important that the entire stirring tank is stirred throughout the process. In particular, it is preferable to combine multiple stages of an inclined paddle type, an inclined turbine type, or a propeller type that are likely to generate upstream and downstream flows so that there are no stagnant parts near the liquid surface or the bottom surface of the stirring tank that are not stirred, or to use a max blend blade or a full zone blade. At this time, it is desirable to keep a distance of 5 mm or more between the stirring blades and the inner surface of the stirring tank (including baffle plates). By doing so, it becomes easier to suppress damage and deformation of the metal particles. The speed of the stirring blades is preferably such that the tip speed is 0.5 to 50 m / s, more preferably 1 to 20 m / s, and even more preferably 2 to 10 m / s. When the tip speed of the stirring blades is within the range of 0.5 to 50 m / s, the dispersibility of the composite particles in the produced metallic pigment composition can be enhanced, and as a result, it becomes easier to obtain a metallic pigment composition in which the aggregability of individual particles is small, which has excellent hiding power and color tone, and generates little gas. Also, when the linear speed of stirring is within the above range, damage to metal particles (for example, flaky aluminum powder) is prevented, the rate of the hydrolysis / condensation reaction is appropriately controlled, and aggregation of the composite particles can be effectively suppressed. As an index representing the stirring state, there is the stirring Reynolds number (hereinafter abbreviated as "stirring Re number"). The stirring Re number does not reflect the sizes other than the shapes and diameters of the stirring tank and the stirring blade. Therefore, the stirring Re number is only a guide and is not particularly limited, but it is preferably 3000 or more, and more preferably 5000 or more. The upper limit of the stirring Re number may vary depending on the type, scale, etc. of the stirring device. The upper limit of the stirring Re number may be about 100,000 in the case of a normal laboratory scale, but when using a scaled-up large device, it may exceed 100,000 as long as the desired effect of the first aspect of the first invention of the present application is not hindered. This upper limit is also acceptable when it is about 1 million, for example.

[0128] The stirring Re number here is calculated by the following formula. Stirring Re number = (ρ × n × d 2 ) / μ (In the formula, ρ is the density (kg / m 3 ) of the mixed liquid to be stirred at 25°C, n is the stirring rotation speed (rps), d is the diameter of the stirring blade (m), and μ is the viscosity (Pa·s) of the mixed liquid to be stirred at 25°C, respectively.)

[0129] Process for Recovering Composite Particles After the step of forming an oxide metal coating layer, preferably a silicon compound-containing layer (and optionally a second coating layer) on the metal particles is completed, the obtained composite particles can be recovered. In the recovery, known treatments such as washing and solid-liquid separation can be carried out as necessary. For example, after washing the dispersion with an organic solvent, it is preferably filtered using a filter to remove water and unreacted substances from the cake containing the composite particles. Further, thereafter, if necessary, the cake containing the composite particles may be heat-treated at a temperature in the range of, for example, 100 to 500°C. The composite particles recovered in this way can constitute a metal pigment composition usually containing a small amount of a solvent containing water / hydrophilic solvent remaining and accompanied in the manufacturing process, as described later.

[0130] 3. Metal Pigment Composition The metal pigment composition of the first aspect of the first invention of the present application obtained as described above includes composite particles containing metal particles and one or more coating layers on the surface thereof, and is regarded as constituting a metal pigment composition containing a solvent such as water / hydrophilic solvent used in the manufacturing process as the remaining solid content (non-volatile content). When the metal particles in the metal pigment composition have a silicon compound layer, usually, a hydrolyzate and / or a condensate of a silicon compound which is at least one selected from organosilicon compounds (for example, at least one of the organosilicon compounds represented by the above general formula (1), silane coupling agents represented by any of the above general formulas (2), (3) and (4), and partial condensates thereof) may be present in an amount of 0.02 to 50 parts by mass in terms of the state where the hydrolysis / condensation reaction is completed, based on 100 parts by mass of the metal particles. In the metal pigment composition, a compound for forming an optional second coating layer (a molybdenum-containing compound in an optional embodiment for forming a molybdenum-containing film as the second coating layer, for example, a mixed coordination type heteropolyanion compound) may be present in an amount of 0.01 to 10 parts by mass based on 100 parts by mass of the metal particles. In the metal pigment composition, an optional organic oligomer or polymer may be present in an amount of 0.01 to 50 parts by mass based on 100 parts by mass of the metal particles. In the metal pigment composition, at least one selected from the group consisting of optional inorganic phosphoric acids and their salts, and acidic organic (sub)phosphoric esters and their salts may be present in an amount of 0.01 to 20 parts by mass based on 100 parts by mass of the metal particles. In the metal pigment composition, as the remaining content of the above components (non-volatile content), there may be present a water / hydrophilic solvent used in the manufacturing process and / or a hydrophilic organic solvent newly added to adjust the composition of the composition. The amount of the solvent containing water / hydrophilic solvent may be, for example, 0.5 to 95% by mass of the metal pigment composition. Alternatively, the amount of the solvent containing water / hydrophilic solvent may be 1 to 90% by mass, or 2 to 80% by mass, or 5 to 70% by mass of the metal pigment composition.

[0131] The metallic pigment composition may optionally contain any components other than those described above. Examples of the optional components include at least one of non-hydrophilic organic solvents, grinding aids, antioxidants, light stabilizers, polymerization inhibitors, and surfactants.

[0132] Examples of the non-hydrophilic organic solvents include those showing hydrophobicity such as mineral spirits, solvent naphtha, toluene, and xylene, which are also used in the manufacturing process of metallic pigments. Examples of the grinding aids include fatty acids, aliphatic amines, aliphatic amides, and aliphatic alcohols. As the antioxidants, those typified by phenolic compounds, phosphorus compounds, and sulfur compounds can be used.

[0133] As the light stabilizers, those used as the aforementioned antioxidants can also be used, but those typified by benzotriazole compounds, benzophenone compounds, salicylate compounds, cyanoacrylate-based, oxalic acid derivatives, hindered amine-based compounds (HALS), and hindered phenolic compounds can be used.

[0134] 4. Use of the Metal Pigment Composition Such metallic pigment compositions can be used in organic solvent-based paints, inks, etc. Further, by adding this metallic pigment composition to an aqueous paint or aqueous ink in which resins, which are film-forming components (binders), are dissolved or dispersed in a water-based medium, a metallic aqueous paint or metallic aqueous ink, which is a resin composition, can be obtained. Further, the metallic pigment composition can also be used as a water-resistant binder and filler by kneading with resins, etc. Antioxidants, light stabilizers, polymerization inhibitors, and surfactants may be added when the metallic pigment composition is blended into an aqueous paint or aqueous ink, or resins, etc. As a modified form, it is also possible to obtain a molded body from a kneaded product of the metallic pigment composition and resins, etc.

[0135] When used in paints or inks, the metallic pigment composition may be added directly to (aqueous) paint or (aqueous) ink as it is, but it is preferably added after being dispersed in a solvent in advance. Examples of solvents to be used include water, texanol, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, etc. Also, examples of these resins include acrylic resins, polyester resins, polyether resins, epoxy resins, fluororesins, rosin resins, etc. Further, examples of binders for paints or inks include rubber in addition to resins. These resins are preferably emulsified, dispersed or dissolved in water. Therefore, carboxyl groups, sulfone groups, etc. contained in the resins can be neutralized.

[0136] Preferred resins are acrylic resins and polyester resins. If necessary, resins such as melamine-based curing agents, isocyanate-based curing agents, and urethane dispersions can be used in combination. Furthermore, it may be combined with coloring pigments such as inorganic pigments, organic pigments, extender pigments, etc. generally added to paints, silane coupling agents, titanium coupling agents, dispersants, anti-settling agents, leveling agents, thickeners, defoamers. In order to improve the dispersibility in paint, a surfactant may be further added, or in order to improve the storage stability of the paint, an antioxidant, a light stabilizer, and a polymerization inhibitor may be further added.

[0137] Examples of coloring pigments include phthalocyanine, quinacridone, isoindolinone, perylene, azo lake, iron oxide, lead yellow, carbon black, titanium oxide, pearl mica, etc.

[0138] The content of the metal pigment composition according to the first aspect of the first invention of the present application in the above aqueous paint or aqueous ink (resin composition) is not limited, but usually may be 0.1 to 50% by mass, and particularly preferably 1 to 30% by mass. When this content is 0.1% by mass or more, a high decorative (metallic) effect can be obtained. Further, when this content is 50% by mass or less, it is possible to prevent the properties of the aqueous paint or aqueous ink, such as weather resistance, corrosion resistance, mechanical strength, etc., from being impaired.

[0139] The content of the solvent is not particularly limited, but may be 20 to 200% by mass with respect to the binder content. When the content of the solvent is within this range, the viscosity of the paint and ink can be adjusted to an appropriate range, and handling and film formation can be facilitated.

[0140] The coating method or printing method of the aqueous paint or the like is not particularly limited. For example, various coating methods or printing methods can be appropriately adopted in consideration of the form of the aqueous paint or the like, the surface shape of the material to be coated, etc. Examples of the coating method include a spray method, a roll coater method, a brush coating method, a doctor blade method, etc. Examples of the printing method include gravure printing, screen printing, etc.

[0141] The coating film formed by the aqueous paint or the like may be formed on the undercoat layer or the intermediate coat layer by electrodeposition coating or the like. Further, if necessary, a top coat layer or the like may be formed on the coating film formed by the aqueous paint or the like.

[0142] In the case of these layer structures, each coating film layer may be coated, and after curing or drying, the next coating film layer may be coated, or after each coating film layer is coated by so-called wet-on-wet coating, the next coating film layer may be coated without curing or drying. The aqueous paint or the like containing the metal pigment composition according to the first aspect of the first invention of the present application preferably adopts a method including a step of forming a coating film layer with an aqueous paint or the like after coating and curing or drying the undercoat film layer, in that a coating film having good mirror-like glossiness can be obtained. The curing method of the paint composition in each coating layer may be heat curing or room temperature curing. Also, the drying method of the paint composition of each coating layer may be, for example, using hot air or natural drying at room temperature.

[0143] The thickness of the coating layer formed by an aqueous paint or the like is not particularly limited, but may usually be about 2 to 100 μm. When the thickness of the coating layer is 2 μm or more, a sufficient hiding effect of the substrate by the ink or paint can be obtained. Also, when the thickness of the coating layer is 100 μm or less, drying becomes easy, and the occurrence of defects such as running and sagging can be suppressed.

[0144] Second Aspect of the First Invention The second aspect of the first invention of the present application is a (composite) metal pigment comprising composite particles having metal particles and a metal oxide coating formed on the surface thereof, (1) The volume-based average particle diameter D when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 3 to 20 μm, (2) The average particle thickness of the composite particles is 15 to 160 nm, (3) The proportion of non-aggregated primary particles in the composite particles is 35% or more on a number basis, (4) The proportion of bent composite particles in the composite particles is 10% or less on a number basis, and the above (composite) metal pigment. Hereinafter, the details of each component of the (composite) metal pigment of the second aspect will be described.

[0145] 1. Composite Particles Constituting a Composite Metal Pigment The composite metal pigment according to the second aspect of the first invention of the present application comprises composite particles having metal particles and a metal oxide coating formed on the surface thereof. That is, in the description of the second aspect in this specification, the term "composite metal pigment" includes, as essential components, composite particles having metal particles and a metal oxide coating formed on the surface thereof, and may contain other components, for example, an organic treating agent, water and / or a solvent containing a hydrophilic solvent.

[0146] Metal Particles The composite particles constituting the composite metal pigment according to the second aspect of the first invention of the present application include metal particles and a metal oxide coating formed on the surface thereof. That is, one or more metal oxide coatings are formed on the surface of the metal particles serving as the core of the composite particles. The metal oxide coating usually has a layered structure.

[0147] The material of the metal particles (core particles) constituting the composite particles is not particularly limited, and may be any of the metals used as known or commercially available metal pigments, such as aluminum, aluminum alloy, zinc, iron, magnesium, nickel, copper, silver, tin, chromium, stainless steel, etc. In this specification, the metal of the metal particles constituting the composite particles includes not only a single metal but also an alloy and an intermetallic compound. Only one kind of metal particles may be used alone, or two or more kinds may be used in combination. The metal particles in the second aspect of the first invention of the present application preferably contain aluminum or an aluminum alloy.

[0148] The average particle size of the metal particles is not particularly limited, but it is preferably an average particle size that can bring about D 50 in the particle size distribution of the composite particles described later. That is, when the volume distribution is measured with a laser diffraction particle size distribution analyzer in the composite particles, D 50 is 3 to 20 μm, or the volume average particle size (D 50 ) of the metal particles is preferably set so as to facilitate this. The average particle size of the metal particles can be controlled by appropriately adjusting the particle size of the raw material atomized metal powder (such as aluminum powder), the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc. in the process of grinding and sieving and filtering the raw material atomized metal powder using a ball mill or the like.

[0149] Although the thickness and shape of the metal particles are not particularly limited, it is desirable that the average particle thickness is 10 - 110 nm and the particles are scaly (flake-like). As a result, the composite particles constituting the composite metal pigment according to the second aspect of the first invention of the present application can also have a scaly shape, and thus high hiding power and the like can be obtained more reliably. The average thickness of the metal particles is preferably such that it can result in the average thickness of the composite particles described later, and specifically, it is preferably 10 - 110 nm. Thereby, aggregation and deformation of the composite particles are effectively suppressed, and it becomes easy to realize excellent design properties, gloss, suppression of roughness, stability in aqueous paints, etc. in the coating film. From the above viewpoints, the average thickness of the metal particles is preferably 15 - 100 nm, and more preferably 20 - 80 nm.

[0150] Here, the average particle thickness of the metal particles can be measured by a method known in the art. For example, a coating film is formed using a metal pigment comprising metal particles and composite particles having a metal oxide coating on the surface thereof, and the average particle thickness can be measured by obtaining a FE-SEM image (field emission scanning electron microscope image) of the cross section and performing image analysis. More specifically, it can be measured by the method described in the examples of the present application.

[0151] The aspect ratio (shape coefficient obtained by dividing the average particle diameter by the average thickness) of the scaly metal particles is preferably 30 - 700, more preferably 50 - 600, and particularly preferably 80 - 500. When the aspect ratio of the metal particles is 30 or more, a higher sense of brilliance can be obtained. Also, when the aspect ratio of the metal particles is 700 or less, the mechanical strength of the flakes is maintained, and a stable color tone can be obtained. The average thickness of the metal particles, similar to the volume-based D50, can be controlled by appropriately adjusting the particle diameter of the raw material atomized metal powder (e.g., aluminum powder), the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filtering, etc. in the process of grinding and sieving / filtering the raw material atomized metal powder using a ball mill or the like in the method for producing the composite metal pigment described later.

[0152] Also, the metal particles do not necessarily have to be composed only of metal. As long as the effects of the second aspect of the first invention of the present application are not inhibited, particles such as those in which the surfaces of inorganic particles such as synthetic resin particles, mica, and glass are coated with metal can also be used. In the second aspect of the first invention of the present application, particles containing aluminum or an aluminum alloy are particularly desirable in terms of high weather resistance, low specific gravity, easy availability, etc.

[0153] Particularly suitable as the metal particles constituting the composite particles is aluminum flake, which is generally widely used as a metallic pigment. As the aluminum flake, those having surface properties, particle size, and shape required for metallic pigments such as surface glossiness, whiteness, and brilliance are suitable. Aluminum flakes are usually commercially available in a paste state. The paste-like aluminum flakes may be used as they are, or the fatty acids on the surface may be removed in advance with an organic solvent or the like before use. Also, so-called aluminum vapor-deposited foils with a volume average particle diameter (D 50 ) of 3 to 20 μm and an average thickness (t) of 10 to 110 nm can also be used.

[0154] Metal Oxide Coating The composite particles constituting the composite metal pigment of the second aspect of the first invention of the present application have a metal oxide coating formed on the surface of the metal particles. The metal oxide coating is a film composed of a layer containing a metal oxide, and may be formed over the entire surface of the metal particle or only on a part of the surface. The metal oxide coating may be entirely composed of a metal oxide, or only a part thereof may be composed of a metal oxide and may contain components other than the metal oxide.

[0155] The metal oxide constituting the metal oxide coating is a compound containing oxygen and at least one metal element as its constituent elements. Therefore, the metal oxide may be a metal oxide in the narrow sense having only oxygen and at least one metal element as its constituent elements, but as long as it contains oxygen and at least one metal element as its constituent elements, it may contain elements other than the oxygen and the metal element as its constituent elements. For example, it may be a metal hydroxide, an oxide hydrate, an oxynitride, etc. It may also be a compound containing an organic group. The metal oxide may be a so-called single oxide having only one kind of metal element as a constituent element, or a composite oxide having two or more metal elements as constituent elements. At least one metal element that is a constituent element of the metal oxide may be a typical metal, a transition metal, or even a so-called semi-metal element. Among them, a metal oxide having silicon as a constituent element is particularly suitable as the metal oxide constituting the metal oxide coating.

[0156] Specific examples of suitable metal oxides constituting the metal oxide coating include silicon oxide, aluminum oxide, boron oxide, zirconium oxide, cerium oxide, iron oxide, titanium oxide, chromium oxide, tin oxide, molybdenum oxide, vanadium oxide, their oxide hydrates, their hydroxides, and mixtures thereof. Among them, silicon oxide, aluminum oxide, and mixtures thereof, as well as their oxide hydrates and hydroxides, are preferably used. Particularly preferably, silicon oxides such as silicon oxide, silicon hydroxide, and / or silicon oxide hydrate can be used.

[0157] Using silicon oxide for the metal oxide coating is particularly advantageous from the viewpoints of realizing good storage stability in an aqueous paint, improving the water resistance when forming a coating film, and suppressing gas generation. By using silicon oxide for the metal oxide coating, the metal oxide coating usually becomes 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 silicon oxide. Examples of such compounds include silane compounds [H 3 SiO(H 2 SiO) n SiH 3 (where n represents an arbitrary positive integer). In addition to this, silicon oxides represented by SiO 2 、SiO 2 ·nH 2 O(where n represents an arbitrary positive integer) etc. are exemplified. These silane compounds and silicon oxides may be either crystalline or amorphous, but are particularly preferably amorphous. Therefore, as a layer containing silicon oxide (such as silica), for example, a layer containing amorphous silica can also be preferably employed.

[0158] Moreover, the metal oxide coating using silicon oxide may be a layer formed using an organosilicon compound (including a silane coupling agent) as a starting material. In this case, the metal oxide coating may contain an unreacted organosilicon compound or a component derived therefrom within a range that does not interfere with the effects of the second aspect of the first invention of the present application. In a typical example in this case, the metal oxide coating can be formed by hydrolyzing an organosilicon compound.

[0159] The mass of the metal oxide coating layer when using silicon oxide is not particularly limited, but is preferably 1 to 20 parts by mass, and more preferably 2 to 15 parts by mass, based on 100 parts by mass of the metal particles. When the silicon content of the metal oxide coating is 1 part by mass or more based on 100 parts by mass of the metal particles, the corrosion resistance, water dispersibility, stability, etc. of the composite metal pigment can be maintained at a high level. When the silicon content of the metal oxide coating is 20 parts by mass or less based on 100 parts by mass of the metal particles, aggregation of the composite particles and a decrease in color tone such as hiding power and metallic luster can be prevented.

[0160] The metal oxide coating of the composite particles contained in the composite metal pigment according to the second aspect of the first invention of the present application is preferably particularly hydrophilic. The composite particles usually form a composite metal pigment in a form dispersed in an aqueous solvent (water or a mixed solvent containing water and an organic solvent). However, when the metal oxide coating has a hydrophilic surface, the composite particles can be highly dispersed in such an aqueous solvent. Moreover, since metal oxides such as silicon oxides (amorphous silica, etc.) are very stable in an aqueous solvent, a composite metal pigment containing composite particles highly stable in an aqueous solvent can be provided. From such a viewpoint, in the composite particles contained in the composite metal pigment according to the second aspect of the first invention of the present application, it is desirable that at least the outermost layer is a metal oxide film, and particularly preferably a silicon compound-containing layer (a layer composed of a compound containing an Si-O bond). Since the metal oxide also has excellent affinity with the metal particles, when the composite particles have a coating layer composed of a plurality of layers, in addition to the outermost metal oxide coating, layers other than the outermost layer, particularly preferably the layer in contact with the metal particles, may be separately formed as a metal oxide layer, particularly preferably a silicon compound-containing layer (particularly an Si-O-based coating layer).

[0161] The thickness of the metal oxide coating of each composite particle is not particularly limited as long as the average thickness of the composite particles is in the range of 15 to 160 nm as described later. The thickness of the metal oxide coating is usually desirably in the range of about 1 to 70 nm (particularly 2 to 50 nm, and further 5 to 40 nm). When the thickness of the metal oxide coating is 1 nm or more, a coating film having sufficient water resistance and suppressing the corrosion or discoloration of the metal particles in the aqueous paint can be obtained. On the other hand, when the thickness of the metal oxide coating is about 70 nm or less, the brightness, distinctness of image, and hiding power of the coating film can be maintained at a high level.

[0162] When the silicon compound-containing layer is included in the metal oxide coating of each composite particle, the thickness of the silicon compound-containing layer is also not particularly limited as long as the average thickness of the composite particles is in the range of 15 to 160 nm as described later. From the viewpoint of the function of the layer, the thickness of the silicon compound-containing layer may usually be in the range of 1 to 70 nm, and particularly preferably in the range of 2 to 50 nm.

[0163] Details such as the preferred form of the organosilicon compound that can be used in this embodiment are the same as those described above in relation to the first aspect.

[0164] Physical Properties of the Composite Metal Pigment The composite metal pigment according to the second aspect of the first invention of the present application is characterized in that the metal particles and composite particles constituting the same satisfy the following physical property requirements. (1) The volume-based average particle diameter D when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 3 to 20 μm. (2) The average particle thickness of the composite particles is 15 to 160 nm. (3) The ratio of primary particles without aggregation in the composite particles is 35% or more based on the number. (4) The ratio of bent composite particles in the composite particles is 10% or less based on the number. Hereinafter, each of these physical property requirements will be described.

[0165] (1) The volume-based average particle diameter D when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 3 to 20 μm The volume-based average particle diameter D when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is 3 to 20 μm. Thereby, aggregation and deformation of the particles are effectively suppressed, and a coating film formed using the composite metal pigment or a metal pigment composition containing the same can achieve excellent design properties, gloss, suppression of roughness, stability in aqueous paints, etc. This volume-based D 50 is generally also referred to as the median diameter. From the viewpoint of obtaining excellent design properties, gloss, suppression of roughness, stability in aqueous paints, etc., the volume-based D when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer 50 is preferably 4 to 15 μm, more preferably 5 to 12 μm. In this physical property requirement, the "composite particles" refers to the aggregate (aggregate) when a plurality of composite particles are aggregated and fixed. Here, when measuring the particle size distribution of composite particles with a laser diffraction particle size distribution analyzer, D on a volume basis 50 refers to the particle diameter at a cumulative degree of 50% in the volume cumulative particle size distribution. The laser diffraction particle size distribution analyzer is not particularly limited, but for example, "LA-300" (manufactured by Horiba, Ltd.) can be used. As the measurement solvent, hydrophilic solvents such as water, isopropanol, and methoxypropanol can be used. For example, for a composite metal pigment containing composite particles of a sample, after performing ultrasonic dispersion for about 2 minutes as a pretreatment, it is put into a dispersion tank and after confirming that it is appropriately dispersed, D 50 can be measured. D on a volume basis of the composite particles constituting the composite metal pigment 50 In the method for producing a composite metal pigment described later, in the step of grinding and sieving / filtering the raw material atomized metal powder (for example, aluminum powder) using a ball mill or the like, the particle diameter and charged amount of the raw material atomized metal powder, the amount of grinding solvent such as mineral spirit, the type and amount of grinding aid, the mass per grinding ball and the charged amount when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter press, etc. are appropriately adjusted, and in the step of coating the metal oxide coating (and other coating layers as necessary), the pH, concentration, stirring temperature, stirring time, type of stirring device, power / degree of stirring (type and diameter of stirring blade, rotation speed, presence or absence of external stirring, etc.) during hydrolysis of raw materials such as organosilicon compounds are appropriately adjusted, it can be controlled. Also, there is a tendency for the particle diameter to increase due to aggregation during the metal oxide coating treatment. Since particle enlargement causes a decrease in color tone, hiding power, and the appearance of the coating film, it is effective to prevent particle enlargement particularly by pretreating the raw material aluminum paste used in the treatment.

[0166] (2) The average particle thickness of the composite particles is 15 to 160 nm The average thickness of the composite particles contained in the composite metal pigment according to the second aspect of the first invention of the present application is 15 to 160 nm. Thus, in combination with the satisfaction of the above requirements (1) and (2), aggregation and deformation of the composite particles can be effectively suppressed, and excellent designability, gloss, suppression of roughness, stability in aqueous paints, etc. in the coating film can be realized. From the above viewpoints, the average thickness of the composite particles is preferably 20 to 130 nm, more preferably 25 to 110 nm, and even more preferably 30 to 90 nm. In this physical property requirement, "composite particles" refers to an aggregate (aggregate) when a plurality of composite particles are aggregated and fixed. Here, the average thickness of the composite particles can be measured by measuring the average particle thickness of the metal particles and the thickness of the metal oxide coating respectively, and calculated according to the following formula from these. Average particle thickness of composite particles = Average particle thickness of metal particles + Thickness of metal oxide coating × 2 The average particle thickness of the metal particles can be measured by the method described in the above (2). The thickness of the metal oxide coating can be measured by a method known in the art, for example, by STEM (scanning transmission electron microscope). More specifically, it can be measured by the method described in the examples of the present application. The average thickness of the composite particles contained in the composite metal pigment is volume-based D 50 Similarly, in the method for producing a composite metal pigment described later, and in the step of coating a metal oxide coating such as a silicon compound-containing layer (and other coating layers as necessary), the pretreatment of the raw material aluminum paste, and the pH, concentration, stirring temperature, stirring time, type of stirring device, power / degree of stirring (type and diameter of stirring blade, rotation speed, presence or absence of external stirring, etc.) of the raw materials such as organosilicon compounds during hydrolysis are appropriately adjusted, it can be controlled. Also, although the particle diameter tends to increase due to aggregation during the metal oxide coating treatment, since particle enlargement causes a decrease in color tone, hiding power, and coating film appearance, it is effective to prevent particle enlargement particularly by the pretreatment of the raw material aluminum paste used in the treatment. The composite particles contained in the composite metal pigment according to the second aspect of the first invention of the present application preferably have an aspect ratio (shape factor obtained by dividing the average particle size by the average thickness) of 30 to 700. When the aspect ratio of the composite particles is 30 or more, it becomes easier to obtain a higher sense of gloss. Also, when the aspect ratio of the composite particles is 700 or less, the mechanical strength of the composite particles is maintained, and it becomes easier to obtain a stable color tone. The aspect ratio is preferably 50 to 600, and more preferably 80 to 500.

[0167] (3) The proportion of primary particles without aggregation in the composite particles is 35% or more on a number basis In the composite metal pigment according to the second aspect of the first invention of the present application, the proportion of primary particles without aggregation in the total composite particles contained in the composite metal pigment is 35% or more on a number basis. The fact that the proportion of primary particles is 35% or more means that the aggregability of individual particles is suppressed, and not only for primary particles but also for aggregated particles, the degree of aggregation is smaller. As a result, the coating film formed using the composite metal pigment exhibits excellent design, gloss, and suppression of roughness, and can improve stability in water-based paints and the like. Also, by suppressing the aggregability of individual particles in this way, the stirring for dispersion can be mild enough, and the deformation of the particles due to stirring can be significantly reduced.

[0168] From the viewpoint of promoting the above effects, the proportion of primary particles without aggregation in the aggregate of composite particles is preferably 40% or more on a number basis, more preferably 50% or more, even more preferably 60% or more, and particularly preferably 70% or more. The proportion of primary particles without aggregation in the aggregate of composite particles is generally preferably higher, and there is no particular upper limit, and it is ideal to reach 100%. The proportion of primary particles without aggregation in the aggregate of composite particles can be measured by methods known in the art. For example, a coating film is formed using a metal pigment composed of an aggregate of composite particles having metal particles and a metal oxide coating on the surface thereof, and an FE-SEM image (field emission scanning electron microscope image) of the cross-section is obtained and subjected to image analysis, or the proportion can be measured by an evaluator counting the number of primary particles and aggregated particles in the FE-SEM image. More specifically, it can be measured by the method described in the examples of the present application.

[0169] The proportion of primary particles without aggregation in the aggregate of composite particles can be controlled by appropriately setting the selection and treatment of the metal particles constituting the composite particles, the type and production conditions of the metal oxide coating formed on the metal particles. As an existing technique, attempts have been made to enhance mechanical dispersion by increasing the stirring rotation speed during the coating treatment so that the Reynolds number is above a certain value. However, this method has limitations in dispersing fine particles as handled in the present application, and there is a problem that scaly thin particles are broken or deformed due to strong stress during stirring. On the other hand, before performing the coating treatment of the metal particles with a metal oxide, it is possible to suppress the aggregation of particles during the coating treatment by performing a pretreatment for improving the dispersibility of the metal particles, thereby significantly increasing the proportion of primary particles without aggregation. For example, when the raw material metal particles are dispersed and supplied in a solvent, by replacing the solvent with the same solvent used in the coating treatment and, if desired, performing a heating treatment for a certain period of time to sufficiently familiarize the solvent with the surface of the metal particles, the aggregation generated during the coating treatment can be significantly suppressed. Furthermore, adding a small amount of surfactant at this time is also effective in suppressing aggregation.

[0170] These treatments improve the dispersibility of the metal particles themselves. Therefore, it is not necessary to perform vigorous stirring during the coating process, and primary particles without aggregation can be produced even with mild stirring. As a result, it becomes possible to significantly reduce the deformation of the particles during the coating process, and it becomes easier to achieve excellent design, gloss, suppression of defects, stability in water-based paints, etc. in the coating film.

[0171] In addition to the above, factors that affect the ratio of primary particles without aggregation include the particle size of raw material atomized metal powder (such as aluminum powder) etc. in the process of grinding and sieving / filtering using a ball mill etc., the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter press, and in the process of coating an oxide metal coating such as a silicon compound-containing layer (and other coating layers if necessary), the pH, concentration, stirring temperature, stirring time, type of stirring device, power / degree of stirring (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) during hydrolysis of raw materials such as organosilicon compounds, etc. can be mentioned, and by appropriately adjusting these, the ratio of primary particles without aggregation can also be controlled.

[0172] In the composite metal pigment according to the second aspect of the first invention of the present application, it is preferable that the ratio of the number of aggregates in which four or more composite particles are fixed to each other is 15% or less with respect to the total number of composite particles. As a result, in combination with the fulfillment of the above various requirements, the coating film formed using the composite metal pigment exhibits higher hiding power, luster, etc., and the aggregability of individual particles can be more effectively suppressed. The ratio of the number of aggregates in which four or more composite particles are fixed to each other is understood to be the degree of overlap of the composite particles, that is, the degree of aggregability. If the ratio of the number of aggregates in which four or more composite particles are fixed to each other is 15% or less with respect to the total number of composite particles, the orientation of the composite particles in the coating film is orderly, and the ratio of the composite particles arranged parallel to the coating film surface increases. As a result, the projected area of the composite particles in the coating film formed using the metal pigment composition becomes larger, the hiding power and luster are enhanced, and furthermore, it becomes easier to form a uniform and sufficient coating on individual particles, so it is considered that the aggregability of individual particles becomes even smaller. Furthermore, since the ratio of the number of aggregates in which four or more composite particles are fixed to each other is small, aggregates of composite particles once formed in the aqueous paint collapse, exposing the untreated surface, and reacting with water, which is the solvent of the aqueous paint, to generate hydrogen gas can be effectively prevented. In the composite metal pigment, the ratio of the number of aggregates in which four or more composite particles are fixed to each other is preferably 10% or less, more preferably 6% or less, and even more preferably 3% or less. The smaller this ratio is, the better, but it is not easy to make it exactly zero.

[0173] (4) The proportion of bent composite particles in the composite particles is 10% or less on a number basis. In the composite metal pigment according to the second aspect of the first invention of the present application, the ratio of bent composite particles in the total composite particles contained in the composite metal pigment is 10% or less. As a result, in combination with the fulfillment of the above requirements (1) to (3), the coating film formed using the composite metal pigment exhibits excellent design, gloss, and suppression of defects, and can improve stability, etc. in the aqueous paint.

[0174] In the coating treatment of aluminum particles, particle aggregation is likely to occur. To avoid this, a technique has been conventionally known in which the stirring during the reaction is intensified to apply shear to the particles and prevent aggregation. Although particle aggregation can be suppressed to a certain extent by this technique, on the other hand, there is a problem that the flaky aluminum particles are deformed by the shear and the coating film performance deteriorates. The ratio of the bent composite particles is understood to be an index related to the degree of deformation or breakage of the composite particles. If the ratio of the bent composite particles is 10% or less, the degree of deformation or breakage of the composite particles is small, and as a result, the ratio of the untreated surface (the surface on which the metal oxide film is not formed) of each composite particle becomes small, improving the stability in the aqueous paint. Furthermore, since it becomes easier to form a uniform and sufficient coating on each individual particle, the aggregability of each individual particle becomes even smaller, so that a coating film exhibiting excellent design, gloss, and suppression of defects can be obtained on the surface of the coating film formed using the composite metal pigment. The smaller the ratio of the bent composite particles in the aggregate of the composite particles, the better. This ratio is preferably 6% or less, more preferably 3% or less. Since the lower the ratio of the bent composite particles, the more preferable, there is no particular lower limit, but ideally it is 0%.

[0175] The ratio of the bent composite particles in the composite metal pigment can be measured by a method known in the art. For example, a coating film is formed using a metal pigment composed of an aggregate of metal particles and composite particles having a metal oxide coating on the surface thereof, and the ratio can be measured by obtaining a FE-SEM image (field emission scanning electron microscope image) of the cross section thereof and performing image analysis. More specifically, particles having a ratio of the straight-line distance between both ends of the cross section of the metal particles in the FE-SEM image to the path length between both ends along the cross section of the metal particles of 1.2 or more are determined as bent particles, and the ratio of the number thereof is obtained to perform the measurement. More specifically, for example, it can be measured by the method described in the examples of the present application. The proportion of bent composite particles in the composite metal pigment can be mainly controlled by appropriately adjusting the pretreatment for improving the dispersibility of the raw material aluminum paste, stirring time, type of stirring device, power / degree of stirring (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) in the process of coating the metal oxide coating (and other coating layers if necessary). Furthermore, by improving the dispersibility of the particles themselves during the reaction through the pretreatment of the raw material aluminum paste, the stirring for dispersion can be mild enough, and thus the deformation of the particles due to stirring can be significantly reduced.

[0176] Second Coating Layer Regarding the coating layer of the composite particles contained in the composite metal pigment according to the second aspect of the first invention of the present application, it is not particularly limited except that it has at least one layer of metal oxide coating, but a coating layer other than the metal oxide coating (hereinafter referred to as the "second coating layer") can also be formed if necessary. The second coating layer preferably comprises at least one of, for example, metals (alkali metals; alkaline earth metals; metals such as manganese, iron, cobalt, nickel, copper, silver, etc.), metal oxides (titanium oxide, zirconium oxide, iron oxide, etc.), metal hydrates, and resins (synthetic resins such as acrylic resin, alkyd resin, polyester resin, polyurethane resin, polyvinyl acetate resin, nitrocellulose resin, fluororesin, etc.). As the second coating layer, for example, a molybdenum-containing film, a phosphate compound film, etc. can be formed. By providing the second coating layer, the corrosion resistance of the metal particles can be improved, and the formation of the metal oxide coating such as the silicon compound-containing layer can be promoted.

[0177] The second coating layer is preferably formed (when formed) particularly between metal particles and a metal oxide coating such as a silicon compound-containing layer. Therefore, for example, a layer structure such as "metal particles / second coating layer / metal oxide coating" can be preferably adopted. Although not particularly limited, examples of the molybdenum-containing coating include those disclosed in JP-A-2003-147226, WO 2004 / 096921 pamphlet, Patent No. 5979788, and JP-A-2019-151678. Examples of the phosphate compound coating include those disclosed in Patent No. 4633239. A preferred example of the molybdenum-containing substance constituting the molybdenum-containing coating is the mixed coordination type heteropolyanion compound disclosed in JP-A-2019-151678. In another modified form, the second coating layer can be formed outside a metal oxide coating such as metal particles and a silicon compound-containing layer. In yet another modified form, the constituent components (such as molybdenum-containing compounds and phosphate compounds) of the second coating layer can be included together with a silicon compound or the like in a metal oxide coating such as a silicon compound-containing layer.

[0178] The mixed coordination type heteropolyanion compound preferably used in the mode of forming a second coating layer (a typical example is a molybdenum-containing coating) other than the metal oxide coating of the composite particles contained in the composite metal pigment according to the second aspect of the first invention of the present application is not particularly limited, but the details such as its preferred form are the same as those described above in relation to the first aspect.

[0179] The second coating layer other than the metal oxide coating of the composite particles contained in the composite metal pigment according to the present embodiment may be a layer containing other corrosion inhibitors in order to further improve the corrosion resistance of the core metal particles (preferably aluminum particles or aluminum alloy particles). The corrosion inhibitor to be added is not particularly limited, and any known corrosion inhibitor can be used. The amount of use thereof may be in a range that does not inhibit the desired effect of the second aspect of the first invention of the present application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organic phosphorus compounds, metal salts of molybdic acid, and the like.

[0180] In the metal oxide coating and / or the second coating layer of the composite particles contained in the composite metal pigment, or as a separate layer, an organic oligomer or polymer can be further contained from the viewpoints of adhesion and chemical resistance when forming a coating film. Also, in the metal oxide coating and / or the second coating layer of the composite particles, or as a separate layer, at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (sub)phosphoric acid esters and their salts may be contained from the viewpoint of storage stability. These compounds are not particularly limited, and for example, those disclosed in JP-A-2019-151678 can be used.

[0181] 2. Method for Producing a Composite Metal Pigment The composite metal pigment according to the second aspect of the first invention of the present application can be suitably produced, for example, by a production method including a step of forming a metal oxide coating on metal particles under stirring using a solvent containing water and / or a hydrophilic solvent. Hereinafter, a specific method will be described by taking the case where the metal oxide coating is a silicon compound-containing layer as an example, but the method for producing the composite metal pigment according to the second aspect of the first invention of the present application is not limited thereto. Those skilled in the art can appropriately form a metal oxide coating other than the silicon compound-containing layer with reference to the following description. In producing the composite metal pigment according to the second aspect of the first invention of the present application, it is preferable to perform a pretreatment described later.

[0182] The composite metal pigment in which the metal oxide coating is a silicon compound-containing layer can be suitably produced, for example, by a method including a step of forming a silicon compound-containing layer on the surface of metal particles by subjecting an organosilicon compound to a hydrolysis / (partial)condensation reaction in a mixed solution containing (a) metal particles, (b) a silicon-containing raw material containing at least one organosilicon compound, (c) a solvent (water and / or a hydrophilic solvent), and optionally other optional components (silicon compound-containing layer forming step). This step can usually be carried out under stirring.

[0183] Grinding and Sieving / Filtration Process Here, the case of using aluminum powder as the metal particles will be described as an example. Aluminum powder is generally obtained by using atomized aluminum powder and / or aluminum foil and pulverizing them using methods commonly used in the pigment industry such as the dry ball mill method, wet ball mill method, attritor method, stamp mill method, etc. in the presence of a grinding aid and an inert solvent, making it into a so-called scaly shape. Further, after this step, it is obtained through steps such as sieving (classification), filtration, washing, and mixing as required. Examples of the grinding aid here include fatty acids, aliphatic amines, aliphatic amides, aliphatic alcohols, etc. Generally, oleic acid, stearic acid, stearylamine, etc. are preferred. Also, examples of the inert solvent include those showing hydrophobicity such as mineral spirit, solvent naphtha, toluene, xylene, etc., and these can be used alone or in combination. The grinding aid and the inert solvent are not limited to these. From the viewpoint of preventing dust explosion and ensuring safety, grinding by the wet ball mill method is preferred as the grinding step.

[0184] When aluminum particles are employed as the metal particles in the production of the composite metal pigment according to the second aspect of the first invention of the present application, commercially available paste-like aluminum flakes obtained through such grinding and sieving / filtration can be used. The paste-like aluminum flakes may be used as they are, or may be used after previously removing fatty acids, etc. on the surface with an organic solvent or the like.

[0185] Pretreatment Process The composite metal pigment according to the second aspect of the first invention of the present application can be preferably produced by a production method including a step of forming a metal oxide coating on the metal particles as described above. However, prior to the step of forming the metal oxide coating, it is preferable to perform a pretreatment in order to improve the dispersibility of the particles in this step. Thereby, it is possible to suppress the aggregation of the particles during the coating treatment. As a result, the dispersibility of the obtained composite particles is also good, and the proportion of primary particles without aggregation can be significantly increased. As a more specific pretreatment, when the metal particles as raw materials are dispersed in an inert solvent and supplied, the solvent can be replaced with the same solvent used in the coating treatment. Further, if desired, a heating treatment can be performed for a certain period of time to sufficiently allow the solvent to adhere to the surface of the metal particles, thereby significantly suppressing aggregation during the coating treatment. The heat treatment temperature is preferably about 30 to 60 °C, and the treatment time is preferably optimized within the range of 3 hours to 7 days. In the step of performing the coating treatment, hydrophilic solvents such as ethanol, isopropanol, and methoxypropanol are preferably used, so the same hydrophilic solvent used in the reaction is preferably used in the pretreatment as well. Furthermore, adding a small amount of surfactant at this time is also effective in suppressing aggregation by the pretreatment. The surfactant is not particularly limited, but nonionic surfactants and anionic surfactants are preferred, and it is particularly preferred to use nonionic surfactants.

[0186] In the pretreatment, the dispersibility can be further enhanced by performing ultrasonic treatment. The ultrasonic treatment is not particularly limited, but is usually 10 to 1000 W, preferably 50 to 800 W, and can usually be performed for 20 seconds to 10 minutes, preferably about 30 seconds to 5 minutes. Such preliminary dispersion of the metal particles can usually be carried out at 10 to 80 °C, preferably 15 to 60 °C, and most preferably around room temperature (about 20 to 40 °C). Also, the preliminary dispersion of the metal particles can be carried out for 5 minutes to 2 hours, preferably 10 minutes to 1 hour (including ultrasonic treatment if performed).

[0187] Process for Forming a Silicon Compound-Containing Layer Subsequently, the step of forming a silicon compound-containing layer can be carried out. Details such as the preferred form of the step of forming the silicon compound-containing layer are the same as those described above in relation to the first aspect.

[0188] Process for Forming a Second Coating Layer The composite particles constituting the composite metal pigment according to the second aspect of the first invention of the present application preferably further have, in addition to the metal oxide coating, preferably a silicon compound-containing layer, another coating layer (second coating layer), preferably a coating layer containing at least one selected from metals, metal oxides, metal hydrates, and resins. Details of preferred forms such as the formation process of the second coating layer are as described above in relation to the first aspect.

[0189] Process for Recovering Composite Particles After the step of forming a metal oxide coating such as a silicon compound-containing layer (and optionally a second coating layer) on the metal particles is completed, the obtained composite particles can be recovered. In the recovery, known treatments such as washing and solid-liquid separation can be carried out as necessary. For example, it is preferable to wash the dispersion with an organic solvent and then filter it using a filter to remove water and unreacted substances from the cake containing the composite particles. Further, thereafter, if necessary, the cake containing the composite particles may be heat-treated at a temperature in the range of, for example, 100 to 500°C. The composite particles recovered in this way can constitute a composite metal pigment (hereinafter also referred to as a "metal pigment composition") that usually contains a small amount of water / hydrophilic solvent remaining and accompanying the solvent used in the manufacturing process, as described below.

[0190] 3. Metal Pigment Composition The composite metal pigment obtained as described above includes metal particles and composite particles including one or more metal oxide coatings on the surface thereof, and may also include, as the remaining portion of the solid content (non-volatile content), unreacted organosilicon compounds, compounds forming the second coating layer, oligomers or polymers derived therefrom, etc., and is generally considered to form a metal pigment composition that usually contains solvents such as water / hydrophilic solvents used in the manufacturing process. In the metal pigment composition, usually, a hydrolyzate and / or a condensate of a silicon compound, which is at least one selected from organosilicon compounds (for example, at least one of the organosilicon compounds represented by the above general formula (1), a silane coupling agent represented by any one of the above general formulas (2), (3), and (4), and a partial condensate thereof), may be present in an amount of 0.02 to 50 parts by mass in terms of the state where the hydrolysis / condensation reaction is completed, based on 100 parts by mass of the metal particles. In the metal pigment composition, a compound for forming an optional second coating layer (in an optional embodiment of forming a molybdenum-containing film as the second coating layer, a molybdenum-containing compound, for example, a mixed coordination type heteropolyanion compound) may be present in an amount of 0.01 to 10 parts by mass based on 100 parts by mass of the metal particles. In the metal pigment composition, an optional organic oligomer or polymer may be present in an amount of 0.01 to 50 parts by mass based on 100 parts by mass of the metal particles. In the metal pigment composition, at least one selected from the group consisting of optional inorganic phosphoric acids and their salts, and acidic organic (sub)phosphoric acid esters and their salts may be present in an amount of 0.01 to 20 parts by mass based on 100 parts by mass of the metal particles. In the metal pigment composition, a solvent containing water / hydrophilic solvent used in the production process may be present. The amount of the solvent containing water / hydrophilic solvent may be, for example, 0.5 to 95% by mass of the metal pigment composition. Alternatively, the amount of the solvent containing water / hydrophilic solvent may be 1 to 90% by mass, or 2 to 80% by mass, or 5 to 70% by mass of the metal pigment composition.

[0191] The metal pigment composition may optionally contain any components other than the above. Examples of the optional components include at least one of an antioxidant, a light stabilizer, and a surfactant.

[0192] As the antioxidant, those typified by phenolic compounds, phosphorus compounds, and sulfur compounds can be used.

[0193] As the light stabilizer, those used as the antioxidants described above can also be used, but those typified by benzotriazole compounds, benzophenone compounds, salicylate compounds, cyanoacrylate, oxalic acid derivatives, hindered amine compounds (HALS), and hindered phenol compounds can be used.

[0194] Examples of surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyalkylene alkyl phenyl ethers such as polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyalkylene alkyl amino ethers such as polyoxyethylene lauryl amino ether, polyoxyethylene stearyl amino ether, sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate; polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate; polyalkylene glycol fatty acid esters such as polyethylene glycol monolaurate, polyethylene glycol monooleate, polyethylene glycol monostearate, polyethylene glycol dilaurate, polyethylene glycol distearate; nonionic surfactants typified by glycerin fatty acid esters such as monoglycerin laurate, monoglycerin stearate, monoglycerin oleate, sulfate esters such as sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene octyl phenyl ether sulfate, sodium polyoxyethylene nonyl phenyl ether sulfate, triethanolamine lauryl sulfate, sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate; sulfonates such as sodium dodecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate;Examples of anionic surfactants include phosphate esters salts such as potassium alkyl phosphate, and examples of cationic surfactants include quaternary ammonium salts such as lauryl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, and stearyl trimethyl ammonium chloride. One or more selected from these can be used. Particularly preferred examples among these include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, or a mixture thereof.;

[0195] 4. Use of the Composite Metal Pigment The composite metal pigment of the second aspect of the first invention of the present application can be used in organic solvent-based paints, inks, etc. Further, by adding this composite metal pigment to an aqueous paint or aqueous ink in which resins, which are film-forming components (binders), are dissolved or dispersed in a water-based medium, a metallic aqueous paint or metallic aqueous ink can be obtained. Further, the composite metal pigment can also be kneaded with a resin or the like and used as a water-resistant binder and filler. Antioxidants, light stabilizers, and surfactants may be added when the composite metal pigment is blended into an aqueous paint or aqueous ink, or a resin or the like.

[0196] When the composite metal pigment is used in paints or inks, it may be added directly to (aqueous) paints or (aqueous) inks, but it is preferably dispersed in a solvent in advance and then added. Examples of the solvent to be used include water, texanol, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and the like. Examples of these resins include acrylic resins, polyester resins, polyether resins, epoxy resins, fluorine resins, rosin resins, and the like. Examples of the binder for paints or inks include rubber in addition to resins. These resins are preferably emulsified, dispersed, or dissolved in water. Therefore, carboxyl groups, sulfone groups, etc. contained in the resins can be neutralized.

[0197] Preferred resins include acrylic resins and polyester resins. If necessary, resins such as melamine-based curing agents, isocyanate-based curing agents, and urethane dispersions can be used in combination. Furthermore, coloring pigments such as inorganic pigments, organic pigments, and extender pigments generally added to paints, silane coupling agents, titanium coupling agents, dispersants, anti-settling agents, leveling agents, thickeners, and defoamers may be combined. In order to improve the dispersibility in the paint, a surfactant may be further added, and in order to improve the storage stability of the paint, an antioxidant, a light stabilizer, and a polymerization inhibitor may be further added.

[0198] Examples of coloring pigments include phthalocyanine, quinacridone, isoindolinone, perylene, azo lake, iron oxide, lead yellow, carbon black, titanium oxide, pearl mica, and the like.

[0199] The content of the composite metal pigment according to the second aspect of the first invention of the present application in the above aqueous paint or aqueous ink (resin composition) is not limited, but is usually preferably 0.1 to 30% by mass, particularly preferably 1 to 20% by mass. When the content is 0.1% by mass or more, a high decorative (metallic) effect can be obtained. Also, when the content is 30% by mass or less, it is possible to prevent the properties of the aqueous paint or aqueous ink, such as weather resistance, corrosion resistance, and mechanical strength, from being impaired.

[0200] The content of the solvent is not particularly limited, but may be 20 to 200% by mass with respect to the binder content. When the content of the solvent is within this range, the viscosities of the paint and ink can be adjusted to an appropriate range, and handling and film formation can be facilitated.

[0201] The coating method or printing method of water-based paints and the like is not particularly limited. For example, various coating methods or printing methods can be appropriately adopted in consideration of the form of water-based paints 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, a doctor blade method, and the like. Examples of the printing method include gravure printing, screen printing, and the like.

[0202] The coating film formed by water-based paints and the like may be formed on the undercoat layer or the intermediate coat layer by electrodeposition coating or the like. Further, if necessary, a top coat layer or the like may be formed on the coating film formed by water-based paints and the like.

[0203] In the case of these layer structures, each coating film layer may be coated, and after curing or drying, the next coating film layer may be coated, or each coating film layer may be coated by so-called wet-on-wet coating and then the next coating film layer may be coated without curing or drying. The water-based paint and the like containing the composite metal pigment according to the second aspect of the first invention of the present application preferably adopt a method including a step of forming a coating film layer with a water-based paint or the like after coating and curing or drying the base coating film layer in that a coating film having good mirror-like glossiness can be obtained. The curing method of the paint composition in each coating film layer may be heat curing or room temperature curing. Further, as the drying method of the paint composition of each coating film layer, for example, hot air may be used, or natural drying at room temperature may be used.

[0204] The thickness of the coating film layer formed by water-based paints and the like is not particularly limited, but is usually preferably about 0.5 to 100 μm, and more preferably about 1 to 50 μm. When the thickness of the coating film layer is 0.5 μm or more, a sufficient concealing effect of the base with ink or paint can be obtained. Further, when the thickness of the coating film layer is 100 μm or less, drying becomes easy, and the occurrence of defects such as sagging and running can be suppressed.

[0205] The composite metal pigment of the second aspect of the first invention of the present application and the coating film and the like obtained using the same have excellent design properties, gloss, suppression of roughness, stability in aqueous paints, etc. at a high level, so they can be used in various applications where metal pigments have been conventionally used, such as paints, inks, resin kneading agents, etc. More specifically, they can be suitably used in automotive bodies, automotive repair materials, automotive parts, home appliances, etc., plastic parts, paints for PCM, high weather resistance paints, heat resistant paints, anticorrosive paints, paints for ship bottoms, offset printing inks, gravure printing inks, screen printing inks, etc.

[0206] Second Invention The second invention of the present application is a (composite) metal pigment composed of composite particles in which metal particles are coated with a layer of polysiloxane, 1) The proportion of the Q4 structure in which Si atoms in the structure of polysiloxane have four -O-Si- bonds is 40 to 90%, and 2) The relative elemental concentration ((A / B)×100) of the elemental concentration A of metal and the elemental concentration B of Si when the surface of the composite particles is evaluated by XPS is 10 mol% or less, is the above - mentioned (composite) metal pigment. Regarding the metal pigment of the second invention of the present application, it is preferable that when 200 g of an aqueous metallic paint containing 12 g of the metal pigment as a non - volatile component, 18 g of methoxypropanol, 110 g of an aqueous acrylic resin, 18 g of a melamine resin, and 12 g of water is collected in a flask and the cumulative hydrogen gas generation amount is measured in a constant temperature water bath at 60°C for up to 24 hours, the gas generation is 10 ml or less. The metal pigment of the second invention of the present application is preferably used in a metal pigment composition containing the metal pigment. The metal pigment of the second invention of the present application is preferably used in an aqueous paint composition containing the metal pigment. The metal pigment of the second invention of the present application is particularly preferably used in an aqueous metallic paint. When 200 g of an aqueous metallic paint containing the metal pigment is collected in a flask and the cumulative hydrogen gas generation amount is measured in a constant temperature water bath at 60°C for up to 24 hours, it is preferable that the gas generation is 10 ml or less. The metal pigment of the second invention of the present application is preferably used in an aqueous ink composition containing the metal pigment. The metal pigment of the second invention of the present application is preferably used in a coating film containing the metal pigment. Hereinafter, the details of the second invention will be described.

[0207] The second invention of the present application is a composite metal pigment composed of composite particles in which metal particles are coated with polysiloxane, and satisfies the following requirements. 1) The proportion of the Q4 structure in which the Si atom in the structure of polysiloxane has four -O-Si- bonds is 40 to 90%. 2) The relative element concentration ((A / B)×100) of the metal element concentration A and the Si element concentration B when the surface of the composite particles is evaluated by XPS is 10 mol% or less.

[0208] Metal Particles The composite particles constituting the metal pigment of the second invention of the present application include metal particles and a polysiloxane layer formed on the surface thereof.

[0209] The material of the metal particles (core particles) constituting the composite particles is not particularly limited, and may be any metal used as a known or commercially available metal pigment, such as aluminum, aluminum alloy, zinc, iron, magnesium, nickel, copper, silver, tin, chromium, stainless steel, etc. In this specification, the metal of the metal particles constituting the composite particles includes not only simple metals but also alloys and intermetallic compounds. Only one kind of metal particles may be used alone, or two or more kinds may be used in combination. The metal particles in the second invention of the present application preferably contain aluminum or an aluminum alloy, and more preferably those composed of 95% by mass or more of aluminum element.

[0210] The average particle size of the metal particles is not particularly limited, but it is preferably an average particle size that can bring about D 50 in the particle size distribution of the composite particles described later. That is, when the volume distribution is measured with a laser diffraction particle size distribution analyzer in the composite particles, D 50The volume average particle diameter (D 50 ) of the metal particles is preferably set to be 1 to 30 μm, or to facilitate this. The average particle diameter of the metal particles can be controlled by appropriately adjusting the particle diameter of the raw material atomized metal powder (such as aluminum powder), the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc. in the process of grinding and sieving and filtering the raw material atomized metal powder using a ball mill or the like. The thickness and shape of the metal particles are not particularly limited, but it is desirable that the average particle thickness is 10 - 400 nm, more preferably 10 - 300 nm, and in a flaky shape. As a result, the composite particles constituting the composite metal pigment according to the second invention of the present application can also easily have a flaky shape, and thus a high hiding power and the like can be obtained more reliably. The average thickness of the metal particles is preferably a thickness that can result in the average thickness of the composite particles described later, and specifically, it is preferably 20 - 400 nm. Thereby, aggregation and deformation of the composite particles are effectively suppressed, and it becomes easy to realize excellent design properties, gloss, suppression of defects, stability in aqueous paints, etc. in the coating film. From the above viewpoints, the average thickness of the metal particles is preferably 25 - 350 nm, more preferably 30 - 300 nm.

[0211] Here, the average particle thickness of the metal particles can be measured by a method known in the art. For example, a coating film is formed using a metal pigment comprising the metal particles and composite particles having a metal oxide coating on its surface, and the average particle thickness can be measured by obtaining an FE-SEM image (field emission scanning electron microscope image) of the cross section and performing image analysis. More specifically, it can be measured by the method described in the examples of the present application. The aspect ratio of the metal particles (the shape coefficient obtained by dividing the average particle diameter by the average thickness) is preferably from 20 to 400, more preferably from 30 to 350, and particularly preferably from 40 to 300. When the aspect ratio of the metal particles is 20 or more, a higher sense of brilliance can be obtained. Further, when the aspect ratio of the metal particles is 400 or less, the mechanical strength of the flakes is maintained and a stable color tone can be obtained. The average thickness of the metal particles is volume-based D 50 Similarly, in the step of grinding and sieving / filtering the raw material atomized metal powder (for example, aluminum powder) using a ball mill or the like, the particle diameter of the raw material atomized metal powder, the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter press, etc. can be appropriately adjusted to control.

[0212] Further, the metal particles do not necessarily have to be composed only of metal, and particles in which the surfaces of inorganic particles such as synthetic resin particles, mica, and glass are coated with metal can also be used as long as the effects of the second invention of the present application are not inhibited. In the present invention, particles containing aluminum or an aluminum alloy are desirable particularly in terms of high weather resistance, low specific gravity, and easy availability.

[0213] Particularly suitable as the metal particles is aluminum flakes which are generally widely used as metallic pigments. As the aluminum flakes, those having surface properties, particle diameters, and shapes required for metallic pigments such as surface glossiness, whiteness, and brilliance are suitable. Aluminum flakes are usually commercially available in a paste state. The paste-like aluminum flakes may be used as they are, or may be used after previously removing fatty acids on the surface with an organic solvent or the like. Further, so-called aluminum vapor-deposited foils having a volume average particle diameter (D 50 ) of 3 to 20 μm and an average thickness (t) of 10 to 110 nm can also be used.

[0214] Composite Particles The composite particles contained in the metal pigment of the second invention of the present application have a structure in which metal particles are centered and the metal particles are coated with polysiloxane.

[0215] Polysiloxane is composed of compounds containing a siloxane bond (Si-O-Si) consisting of silicon atoms (Si) and oxygen atoms (O). These compounds may be either crystalline or amorphous, but are particularly preferably amorphous. Further, polysiloxane may be formed using an organosilicon compound (including a silane coupling agent) as a starting material. In this case, within a range that does not prevent the effects of the second invention of the present application, it may contain an organosilicon compound or a component derived therefrom. In a typical example, polysiloxane can be formed by hydrolyzing an organosilicon compound. The layer of polysiloxane may contain additives, impurities, etc. other than silicon compounds within a range that does not impair the characteristics of the second invention of the present application.

[0216] Specific examples of polysiloxane that can be used in the second invention of the present application will be further described below, but polysiloxane is not limited to these specific examples. Details such as preferred examples of the polysiloxane of the second invention of the present application are the same as those of the compounds having a siloxane bond described as the preferred form of the "organosilicon compound" in the first aspect of the first invention.

[0217] The polysiloxane layer may contain additives, impurities, etc. other than polysiloxane within a range that does not impair the characteristics of the second invention of the present application.

[0218] <Structure of the polysiloxane layer> In the prior art, the structure of polysiloxane in the polysiloxane layer constituting the coating layer of composite particles has not been controlled, and it is assumed that Q4 structures in which Si atoms have four -O-Si- bonds, Q3 structures having three bonds, Q2 structures having two bonds, and Q1 structures having one bond randomly exist. For this reason, the mechanical stability of the composite particles contained in the metal pigment is not sufficient.

[0219] In the second invention of the present application, in the structure of the polysiloxane layer of the composite particles, the ratio of the Q4 structure should be 40 to 90%. By setting the ratio of the Q4 structure to 40% or more, sufficient mechanical strength of the composite particles contained in the metal pigment in the polysiloxane layer can be obtained. The upper limit of the Q4 structure is very difficult to be 90% or more from the three-dimensional structure, and by setting the ratio to 90% or less, the flexibility of the polysiloxane layer can be ensured, and the mechanical strength of the composite particles contained in the metal pigment can be increased.

[0220] In addition, in the second invention of the present application, the hydrophilicity A defined by the sum of the Q1 structure ratio × 3 + the Q2 structure ratio × 2 + the Q3 structure ratio is preferably 10 to 80%. This is because the bonding site has a hydrophobic structure of -Si-O-Si- (silanol bond), while the unreacted site (terminal) has a silanol structure of -Si-OH, with 3 silanol groups in the Q1 structure, 2 silanol groups in the Q2 structure, and 1 silanol group in the Q3 structure. Therefore, the above calculation formula is an index indicating the total amount of silanol groups. By setting this total to 10% or more, the hydrophilicity of the polysiloxane layer surface is high, and sufficient dispersibility in the aqueous paint can be achieved. Also, by setting this total to 80% or less, excessive hydrophilicity can be suppressed, and deterioration of water resistance and weather resistance when the metal pigment is made into a coating film can be prevented.

[0221] In the second invention of the present application, the average thickness of the polysiloxane layer can be 5 to 100 nm, preferably 15 to 80 nm. When this average thickness is 5 nm or more, sufficient storage stability such as prevention of gas generation can be obtained when made into a paint, and when it is 100 nm or less, a decrease in light reflectance can be suppressed. Also, since the polysiloxane in the composite particles is excellent in mechanical strength, there is an effect of further improving the mechanical strength of the composite particles coated thereby.

[0222] In the second invention of the present application, the amount of polysiloxane in the composite particles only needs to be the above-mentioned thickness and is not particularly limited, but it is preferably 0.1 to 50 parts by mass, more preferably 1 to 40 parts by mass, based on 100 parts by mass of the metal particles.

[0223] When the relative elemental concentration of the metal to silicon on the particle surface of the composite particles contained in the metal pigment of the second invention of the present application is measured by XPS (X-ray Photoelectron Spectroscopy), the elemental concentration of the metal is 10 mol% or less with respect to silicon. This numerical value can be calculated from the formula ((A / B)×100), where A is the elemental concentration of the metal and B is the elemental concentration of silicon.

[0224] In XPS, the ratio of elements present in a layer up to a certain depth from the surface can be determined. Therefore, when the value of the relative elemental concentration of the metal to silicon on the surface of the composite particles is 10 mol% or less, which is the upper limit value, it means that the exposure of the metal pigment is small and it is sufficiently covered with the polysiloxane layer. That is, the polysiloxane layer has a sufficient thickness and there are few parts not covered with the polysiloxane layer. As a result, a decrease in the storage stability of the pigment and a decrease in stability when used as an aqueous paint can be effectively suppressed. The value of the relative elemental concentration of the metal to silicon is preferably 8 mol% or less, more preferably 6 mol% or less, and the lower the better. In order to form such a polysiloxane layer, it is important to form an appropriate amount of polysiloxane as a coating layer under appropriate conditions, as described later.

[0225] <XPS Analysis Method> Regarding the method for confirming the composition of the composite particles contained in the metal pigment of the second invention of the present application by XPS, the method will be described taking the case where aluminum is used as the metal particles as an example. When aluminum is used as the metal particles, silicon and aluminum (aluminum compounds such as oxides included) that constitute the polysiloxane are present on or in the vicinity of several nm from the surface of the composite metal powder particles of the second invention of the present application. The ratio of these two elements can be confirmed by measuring the relative elemental concentration by XPS.

[0226] XPS is an analytical method that excites the solid surface with X-rays under high vacuum and measures the photoelectrons emitted from the surface. By this analytical method, information on the types, oxidation states, and concentrations of elements present in the vicinity of the surface within several nanometers can be obtained, and the relative concentrations of aluminum present as silicon, aluminum metal, or aluminum oxide on the surface can be determined.

[0227] In the second invention of the present application, the total amount of aluminum / relative elemental concentration of silicon on the surface of composite particles coated with a polysiloxane layer is measured.

[0228] For example, when aluminum is used as the metal particles, the above silicon concentration and aluminum concentration can be measured under the following conditions. In XPS, one type of element may be detected as being divided into multiple states such as oxides, but in the second invention of the present application, the total value of the multiple states is defined as the concentration of the element. · Measuring device: ULVAC-PHI Versa probeII · Excitation source: mono.AlKα 20 kV × 5 mA 100 W · Analysis size: 100 μmφ × 1.4 mm. The X-ray beam with a diameter of 100 μm oscillates with a width of 1.4 mm. · Photoelectron extraction angle: 45° · Acquisition region Survey scan: 0~1100 eV Narrow scan: Al 2p, Si 2p, O 1s, C 1s · Pass energy Survey scan: 117.4 eV Narrow scan: 46.95 eV

[0229] The shape of the composite particles contained in the metal pigment according to the second invention of the present application is preferably scaly (flake-like). Thereby, the coating film formed using the metal pigment can exhibit high brightness, a high flip-flop feeling, high hiding power, and the like. In this specification, that the shape of the composite particles is "scaly" (flake-like) means that the average aspect ratio (shape coefficient obtained by dividing the average particle diameter by the average thickness) of the composite particles is 20 or more. From the viewpoint of obtaining high brightness, flip-flop feeling, hiding power, etc., the average aspect ratio of the scaly composite particles is preferably 20 or more and 400 or less. When the average aspect ratio is 20 or more, a sufficient luster can be exhibited, while when the average aspect ratio is 400 or less, the mechanical strength of the flakes is maintained and a stable color tone can be obtained. The aspect ratio is more preferably 25 or more, and even more preferably 30 or more. Also, it is more preferably 350 or less, and even more preferably 300 or less. In the "composite particles" of the second invention of the present application, when a plurality of composite particles are aggregated and fixed, it refers to the aggregate (aggregate). Here, the average particle diameter for calculating the average aspect ratio of the composite particles is the volume-based D called the median diameter 50 and the explanation regarding this point and the average thickness for calculating the average aspect ratio of the composite particles will be described later.

[0230] The composite particles of the second invention of the present application have a volume-based D when the particle size distribution of the composite particles is measured with a laser diffraction particle size distribution analyzer 50 and is preferably 1 μm or more and 30 μm or less. Thereby, the coating film formed using the metal pigment exhibits high brightness, a high flip-flop feeling, high hiding power, etc., and the aggregation of the individual particles constituting the metal pigment is suppressed and its aggregability can be reduced. This volume-based D 50 is generally also called the median diameter. From the viewpoint of obtaining such high brightness, high flip-flop feeling, high hiding power, and small aggregability of individual particles, the volume-based D when the particle size distribution of the composite particles is measured with a laser diffraction particle size distribution analyzer 50Preferably, the lower limit is 1 μm or more, more preferably 2 μm or more, still more preferably 3 μm or more, and the upper limit is preferably 30 μm or less, more preferably 25 μm or less, still more preferably 20 μm or less. In the second invention of the present application, the "composite particles" refer to the aggregate (aggregate) when a plurality of composite particles are aggregated and fixed. Here, when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer, D on a volume basis 50 refers to the particle size at a cumulative degree of 50% in the volume cumulative particle size distribution. The laser diffraction particle size distribution analyzer is not particularly limited, but for example, "LA-300" (manufactured by Horiba, Ltd.) can be used. As the measurement solvent, isopropanol or mineral spirit can be used. For example, after performing ultrasonic dispersion for 2 minutes as a pretreatment on the metal pigment containing the composite particles of the sample, it is put into the dispersion tank and after confirming that it is appropriately dispersed, D 50 can be measured.

[0231] 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 photographing the composite particles in the resin composition from the coating film surface with an optical microscope, a laser microscope, etc., and obtaining the particle size by obtaining the distribution of the equivalent circle diameter using commercially available image analysis software can be adopted.

[0232] D on a volume basis of the composite particles contained in the metal pigment 50In the manufacturing method described below, in the step of grinding and sieving / filtering the raw material atomized metal powder (for example, aluminum powder) using a ball mill or the like, the particle size of the raw material atomized metal powder, the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter press, etc. are appropriately adjusted, and in the step of coating the polysiloxane layer (and other coating layers as necessary), the type of polysiloxane used, the pH, concentration, stirring temperature, stirring time, type of stirring device, stirring power / degree (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) in the coating process (including the process when hydrolyzing and using an organosilicon compound) are appropriately adjusted, it can be controlled.

[0233] The average thickness of the composite particles having metal particles and one or more coating layers on their surfaces contained in the metal pigment of the second invention of the present application is desirably 20 nm or more and 400 nm or less. Thereby, in combination with the satisfaction of the above requirements (1) to (2), the coating film formed using the metal pigment exhibits high brightness, high flip-flop feeling, high hiding power, etc.

[0234] From the above viewpoints, the lower limit of the average thickness of the composite particles is 20 nm or more, preferably 25 nm or more, more preferably 30 nm or more. The upper limit is 400 nm or less, preferably 350 nm or less, more preferably 300 nm or less.

[0235] In the second invention of the present application, the "composite particles" refer to the aggregate (aggregate) when a plurality of composite particles are aggregated and adhered. Here, the average thickness of the composite particles can be calculated from the water surface diffusion area and density of the composite particles. The water surface diffusion area refers to the area occupied by the dried composite particles per unit mass when the dried composite particles are uniformly diffused on the water surface using the leaching phenomenon and covered in a non-gapped state. The measurement of the water surface diffusion area can be performed according to the provisions of JIS K5906:1998. However, in the case of the composite particles of the second invention of the present application, when the hydrophilicity of the surface is strong, it may be difficult to obtain the above-mentioned water surface diffusion area. In this case, the average thickness of the composite particles can be measured according to the method described in the examples below. That is, a film (thin film) is formed using a metal pigment in which the composite particles are dispersed in a mixture of an alcohol-based solvent such as methoxypropanol and water, and the average thickness of the composite particles can be obtained by observing the thickness of the composite particles (50 or more, preferably 100 or more) with a scanning electron microscope (SEM). The average thickness of the composite particles contained in the metal pigment is D on a volume basis 50 Similarly, in the method for producing a metal pigment described below, in the step of grinding and sieving / filtering the raw material atomized metal powder (for example, aluminum powder) using a ball mill or the like, the particle size of the raw material atomized metal powder, the mass per grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter press, etc. are appropriately adjusted, and in the step of coating the polysiloxane layer (and other coating layers as necessary), the type of the organosilicon compound used, the pH, concentration, stirring temperature, stirring time, type of stirring device, stirring power / degree (for example, type and diameter of the stirring blade, rotation speed, presence or absence of external stirring), etc. are appropriately adjusted, whereby it can be controlled.

[0236] At least one of the coating layers of the composite particles contained in the metal pigment according to the second invention of the present application is a polysiloxane layer, but a coating layer other than the above-mentioned polysiloxane layer (hereinafter referred to as "other coating layer") may be formed alone or together with the polysiloxane layer. Examples of the other coating layer may include at least one of a metal (alkali metal; alkaline earth metal; metals such as manganese, iron, cobalt, nickel, copper, and silver), a metal oxide (titanium oxide, zirconium oxide, iron oxide, etc.), a metal hydrate, and a resin (synthetic resins such as acrylic resin, alkyd resin, polyester resin, polyurethane resin, polyvinyl acetate resin, nitrocellulose resin, and fluororesin). As the other coating layer, for example, a molybdenum-containing film, a phosphate compound film, etc. can be formed. By providing the other coating layer, the corrosion resistance of the metal particles can be improved. The other coating layer is preferably formed between the metal particles and the polysiloxane layer. Therefore, for example, a layer structure such as "metal particles / other coating layer / polysiloxane layer" can be preferably adopted. Although not particularly limited, examples of the molybdenum-containing film include those disclosed in JP 2003-147226 A, WO 2004 / 096921 pamphlet, Patent No. 5979788, and JP 2019-151678 A. Examples of the phosphate compound film include those disclosed in Patent No. 4633239. A preferred example of the molybdenum-containing substance constituting the molybdenum-containing film is the mixed coordination type heteropolyanion compound disclosed in JP 2019-151678 A. In another modified form, the other coating layer can be formed outside the metal particles and the polysiloxane layer. In yet another modified form, the constituent components (such as molybdenum-containing compounds and phosphate compounds) of the polysiloxane layer can be included together with the silicon compound in the polysiloxane layer.

[0237] The mixed coordination type heteropolyanion compound used in the aspect of forming the other coating layer (a typical example is a molybdenum-containing film) other than the polysiloxane layer of the composite particles contained in the metal pigment according to the second invention of the present application is not particularly limited, but the details such as its preferred form are the same as those described above in relation to the first aspect of the first invention of the present application.

[0238] For the other coating layers of the composite particles contained in the metal pigment according to the second invention of the present application, other than the polysiloxane layer, they may be layers containing other corrosion inhibitors in order to further improve the corrosion resistance of the core metal particles (preferably aluminum particles or aluminum alloy particles). The corrosion inhibitor to be added is not particularly limited, and any known corrosion inhibitor can be used. The amount of use may be within a range that does not inhibit the desired effects of the second invention of the present application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organic phosphorus compounds, metal salts of molybdic acid, and the like.

[0239] From the viewpoints of adhesion and chemical resistance when forming a coating film, the polysiloxane layer and / or other coating layers of the composite particles contained in the metal pigment, or as a separate layer, may further contain an organic oligomer or polymer. Also, from the viewpoint of storage stability, at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (sub)phosphate esters and their salts may be contained in the polysiloxane layer and / or other coating layers of the composite particles, or as a separate layer. These compounds are not particularly limited, but for example, those disclosed in JP-A-2019-151678 can be used.

[0240] In the second invention of the present application, it is preferable that the metal pigment is an aqueous metallic paint, and when 200 g of the paint is collected in a flask and held in a constant temperature water bath at 60°C for 24 hours, the cumulative amount of hydrogen gas generated is 10 ml or less. The fact that the gas generation is 10 ml means that the metal pigment is firmly covered with the polysiloxane layer. As a result, the storage stability of the paint is good and the mechanical stability is improved. The gas generation amount is preferably 10 ml or less, more preferably 5 ml or less, and particularly preferably 2 ml or less. There is no lower limit, and the less the better. The method for preparing the aqueous metallic paint and the method for measuring the gas generation amount will be described in detail in the examples.

[0241] Method for Producing a Metal Pigment The metal pigment according to the second invention of the present application is formed into flaky metal particles using, for example, a method commonly used in the pigment industry. After this step, the metal particles are produced through steps such as sieving (classification), filtration, washing, and mixing, and then can be preferably produced by a production method including a step of forming a coating layer under stirring using a solvent containing water and / or a hydrophilic solvent. More specifically, the following methods can be mentioned, but it is not limited thereto. The metal pigment according to the second invention of the present application can be preferably produced by a method including a step of forming a polysiloxane layer on the surface of metal particles by subjecting an organosilicon compound to a hydrolysis / (partial) condensation reaction in a mixed liquid containing, for example, (a) metal particles, (b) a silicon-containing raw material containing at least one kind of organosilicon compound, (c) a solvent (water and / or a hydrophilic solvent), and optionally other optional components (polysiloxane layer forming step). This step can usually be carried out under stirring.

[0242] <Crushing and Sieving / Filtration Step> Here, the case of using aluminum powder as the metal particles will be described as an example. Aluminum powder is generally produced by using atomized aluminum powder and / or aluminum foil and pulverizing them using a method commonly used in the pigment industry such as the dry ball mill method, wet ball mill method, attritor method, stamp mill method, etc. in the presence of a pulverization aid and an inert solvent to make them into a so-called flaky shape. Further, after this step, it is obtained through necessary steps such as sieving (classification), filtration, washing, and mixing. Examples of the pulverization aid here include fatty acids, aliphatic amines, aliphatic amides, aliphatic alcohols, etc. Generally, oleic acid, stearic acid, stearylamine, etc. are preferred. Examples of the inert solvent include those showing hydrophobicity such as mineral spirit, solvent naphtha, LAWS, HAWS, toluene, xylene, etc., and these can be used alone or in combination. The pulverization aid and the inert solvent are not limited to these. From the viewpoint of preventing dust explosion and ensuring safety, pulverization by the wet ball mill method is preferred as the pulverization step.

[0243] When aluminum particles are employed as the metal particles in the production of the metal pigment according to the second invention of the present application, commercially available paste-like aluminum flakes obtained through such pulverization, sieving, and filtration can be used. The paste-like aluminum flakes may be used as they are, or alternatively, the fatty acids on the surface may be removed in advance with an organic solvent or the like before use.

[0244] Also, as the metal particles in the production of the metal pigment of the second invention of the present application, so-called vapor-deposited aluminum pigments produced by peeling a metal layer vapor-deposited on a carrier material such as a resin film by physical vapor deposition (PVD) from the carrier material and pulverizing it can also be used.

[0245] <Step of forming a polysiloxane layer> The mixed liquid containing at least one of the above-mentioned (a) metal particles, (b) a silicon-containing raw material containing at least one kind of organosilicon compound, and (c) a solvent, and optionally other optional components, can be prepared by mixing these components. The order of mixing is not particularly limited.

[0246] As the metal particles, the above-mentioned metal particles can be used, but in particular, particles of aluminum or an aluminum alloy can be preferably used. Also, as described above, it is preferable to use flaky metal particles for the particle shape. As the metal particles, known or commercially available ones (typically paste-like aluminum flakes) can be used.

[0247] The content (solid content) of the metal particles in the above mixed liquid is not particularly limited and can be appropriately set according to the type, particle size, etc. of the metal particles used.

[0248] An organosilicon compound is used as the silicon-containing raw material. As the organosilicon compound, although not limited, preferably the above-mentioned ones can be used. At least one of the organosilicon compound represented by the above formula (1) (tetraalkoxysilane as a typical example) and / or its condensate, and the silane coupling agent represented by any one of the above formulas (2) to (4) can be preferably used. Hereinafter, the case of using tetraalkoxysilane as the organosilicon compound represented by the above formula (1) will be described as an example. In the following, tetraalkoxysilane and / or its condensate may be collectively referred to simply as "tetraalkoxysilane".

[0249] 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 of mixing and using both (referred to as the "first method") can be adopted. Alternatively, a method including a step of forming a first polysiloxane layer by treating metal particles with one and forming a second polysiloxane layer by treating with the other (referred to as the "second method") can also be adopted.

[0250] As the first method, for example, a method including a step of appropriately adjusting the pH of a mixed solution containing metal particles, tetraalkoxysilane represented by the above formula (1), and a silane coupling agent represented by any one of the above formulas (2) to (4), and subjecting tetraalkoxysilane and the silane coupling agent to a hydrolysis / condensation reaction to form a polysiloxane layer can be mentioned.

[0251] As the second method, for example, a step of appropriately adjusting the pH of a mixed solution containing metal particles and tetraalkoxysilane represented by the above formula (1) to subject tetraalkoxysilane to a hydrolysis / condensation reaction to form a first polysiloxane layer (for example, a silica film made of amorphous silica) on the surface of the metal particles, and a step of adjusting the pH of a mixed solution containing metal particles and a silane coupling agent represented by any one of the above formulas (2) to (4) to subject the silane coupling agent to a hydrolysis / condensation reaction to form a second polysiloxane layer on the surface of the first polysiloxane layer can be mentioned.

[0252] The amount of the tetraalkoxysilane represented by the above formula (1) or its condensate can be appropriately set according to the type of the tetraalkoxysilane used and the like. The amount can be, for example, 2 to 200 parts by mass, and more preferably 5 to 100 parts by mass, based on 100 parts by mass of the metal particles (solid content), from the viewpoint of the coating treatment effect and from the viewpoint of suppressing the aggregation of the metal particles or the decrease in the brilliance.

[0253] The amount of the silane coupling agent represented by any one of the above formulas (2) to (4) is not particularly limited, but is usually about 0.1 to 20 parts by mass, and particularly preferably 1 to 10 parts by mass, based on 100 parts by mass of the metal particles (solid content). By the amount being about 0.1 to 20 parts by mass, a desired coating treatment effect and desirable coating film physical properties can be obtained.

[0254] The solvent in the mixed solution, that is, the solvent for the hydrolysis reaction and / or the condensation reaction of the organosilicon compound, may be appropriately selected according to the type of the silicon-containing raw material used and the like. Usually, water, a hydrophilic organic solvent, or a mixed solvent thereof can be used. By using these solvents, the uniformity of the reaction and the uniformity of the obtained hydrolyzate and / or condensate can be enhanced. In the mode of directly forming a polysiloxane layer on the metal particles, from the viewpoint of avoiding the rapid progress of the reaction between the metal particles and water, it is particularly preferable that the solvent of the mixed solution contains a hydrophilic organic solvent. In the second invention of the present application, a mixed solvent of water and a hydrophilic organic solvent can be preferably used.

[0255] The hydrophilic organic solvent is not particularly limited. For example, 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 their esters; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. These can be used alone or in combination of two or more.

[0256] When a mixed solvent of water and a hydrophilic organic solvent is used as the solvent, the ratio between the two is not particularly limited. In the mode of directly forming a polysiloxane layer on metal particles, from the perspective of avoiding the rapid progress of the reaction between metal particles and water, before introducing the silicon compound, it is preferable that the total of the two is 100% by mass and the water content is 20% by mass or less. The lower limit value of the water content in this case is not limited.

[0257] The amount of the solvent used in the step of forming the polysiloxane layer (excluding the amount of the solvent for pre-dispersing the metal particles if any) is not limited, but is usually preferably about 100 to 10,000 parts by mass, particularly preferably 200 to 1,000 parts by mass, relative to 100 parts by mass of the metal particles (solid content). When the amount of the solvent used is 100 parts by mass or more, an increase in the viscosity of the mixed solution (slurry) is suppressed, and appropriate stirring becomes possible. Also, when the amount of the solvent used is 10,000 parts by mass or less, it is possible to prevent an increase in the cost of recovering and regenerating the treatment liquid. Here, the amount of the solvent used refers to the total amount of the solvent used for forming the first polysiloxane layer and the second polysiloxane layer in the case of the above-described second method.

[0258] In the above mixed solution, other additives may be blended as necessary within a range that does not interfere with the effects of the second invention of the present application. Examples include catalysts such as hydrolysis catalysts and dehydration condensation catalysts, surfactants, metal corrosion inhibitors, and the like.

[0259] Among these, a hydrolysis catalyst can be preferably used. By blending a hydrolysis catalyst, the pH of the mixed solution can be adjusted, and the organosilicon compound can be efficiently hydrolyzed and dehydrated and condensed. As a result, it becomes possible to efficiently and surely form a polysiloxane layer on the surface of the metal particles.

[0260] In the second invention of the present application, in order to strengthen the polysiloxane layer, it is preferable to use a catalyst having a high catalytic ability, that is, a catalyst whose pH is greatly deviated from the neutral range, or to increase the temperature. However, under such conditions, there is a risk that the metal particles may corrode. For this reason, after covering the surface of the metal particles with a polysiloxane layer by a reaction under mild conditions first, the reaction is carried out under conditions where the reaction rate can be increased to form a strong structure, thereby suppressing metal corrosion and suppressing a decrease in storage stability and a decrease in color tone during circulation.

[0261] In the initial gentle reaction of covering the surface with a polysiloxane layer without corroding the metal particles, it is preferable to use a known weak base compound such as ammonia as a catalyst in an amount of 0.1 mol% or more and 100 mol% or less based on the silicon-containing compound, and to carry out the reaction in the range of 10 to 55°C. The catalyst amount is more preferably 1 mol% or more and 80 mol% or less, the temperature is more preferably in the range of 15 to 50°C, and even more preferably in the range of 20 to 45°C.

[0262] As the catalyst, a known or commercially available one may be used, and it is not particularly limited. As the hydrolysis catalyst, for example, inorganic alkalis such as ammonia; amines such as monomethylamine, dimethylamine, trimethylamine, pyridine, aniline, etc. can also be used. These catalysts can be used alone or in combination of two or more.

[0263] Alternatively, it is also a preferable method to use a compound composed of a pair of a weak acid and a weak base as the catalyst. Such a catalyst is preferably a compound composed of a weak acid with a pKa of 3.5 to 5.5 and a weak base with a pKb of 3.5 to 5.5. By the pKa and / or pKb of the acid and base constituting the compound being 3.5 or more, which is the lower limit of these ranges, that is, by using a compound derived from other than a strong acid or a strong base, the hydrolysis and condensation reactions of the silicon-containing compound proceed by a mechanism similar to that under acidic or basic conditions, the corrosion of the metal particles is suppressed, and high catalytic activity can be exhibited. On the other hand, by the pKa and / or pKb of the acid and base constituting the compound being 5.5 or less, which is the upper limit of these ranges, sufficient catalytic activity can be obtained, and a decrease in color tone due to aggregation and growth of particles caused by the metal particles remaining in an uncovered state and continuously contacting water for a long time can be avoided.

[0264] Preferable examples of the compounds composed of these weak acid-weak base pairs include ammonium benzoate, ammonium p-toluate, ammonium m-toluate, ammonium o-toluate, ammonium phenylacetate, ammonium citrate, ammonium oxalate, ammonium acetate, ammonium propionate, ammonium acrylate, ammonium butyrate, ammonium isobutyrate, ammonium valerate, ammonium isovalerate, ammonium pivalate, ammonium carbonate, ammonium hydrogen carbonate, ammonium carbamate, and ammonium lactate. Among these, ammonium benzoate, ammonium p-toluate, ammonium m-toluate, ammonium o-toluate derived from aromatic carboxylic acids, and ammonium acetate, ammonium propionate, ammonium carbonate, ammonium hydrogen carbonate, ammonium carbamate with short carbon chains are particularly preferable.

[0265] Such a catalyst is preferably used in an amount of 1 mol% or more and 200 mol% or less, more preferably 2 mol% or more and 150 mol% or less, based on the silicon compound. The reaction temperature is preferably in the range of 10 to 55 °C, more preferably in the range of 15 to 50 °C, and even more preferably in the range of 20 to 45 °C. Among the above-described conditions, it is desirable to appropriately adjust the reaction time in addition to the catalyst amount and temperature so that corrosion does not occur depending on the type of metal particles and an appropriate coating state is achieved.

[0266] The reaction time may be, for example, from 10 minutes to 10 hours, preferably from 20 minutes to 5 hours, and even more preferably from 30 minutes to 3 hours.

[0267] Also, the reaction is preferably carried out under neutral to weakly basic conditions with a pH of 6 to 9. When the pH is at or above the lower limit of this range, hydrolysis and condensation reactions proceeding through the acidic condition pathway can be suppressed. Also, when the pH is at or below the upper limit of this range, the same reactions proceeding through the basic condition pathway as in the prior art can be suppressed. This pH range may be more preferably 6.5 to 9, and even more preferably 7 to 8.5.

[0268] In the reaction for forming a strong structure, which follows the reaction under the mild conditions described above, a known weak base compound such as ammonia is used as a catalyst in an amount of 100 mol% or more and 1000 mol% or less with respect to the silicon-containing compound, and 2 to 10 times the amount used in the mild reaction, and it is preferably carried out in the range of 40 to 80°C. The amount of the catalyst is more preferably 110 mol% or more and 5000 mol% or less, and 3 to 7 times the amount used in the mild reaction, and the temperature is more preferably in the range of 45 to 75°C, still more preferably in the range of 50 to 70°C, and particularly preferably in the range of 55 to 65°C.

[0269] The catalyst is not particularly limited. For example, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; organic acids such as benzoic acid, acetic acid, and chloroacetic acid; phosphonic acids such as vinylphosphonic acid, 2-carboxyethanephosphonic acid, 2-aminoethanephosphonic acid, and octanephosphonic acid can be used. These hydrolysis catalysts may be used alone or in combination of two or more.

[0270] Also, as the catalyst, for example, inorganic alkalis such as ammonia, sodium hydroxide, and potassium hydroxide; inorganic alkali salts such as ammonium carbonate, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate; amines such as monomethylamine, dimethylamine, trimethylamine, pyridine, and aniline; salts of organic acids such as ammonium formate, ammonium acetate, monomethylamine formate, and aniline acetate can be used. These hydrolysis catalysts can be used singly or in two or more.

[0271] It is also a preferred method to use a compound composed of a pair of a weak acid and a weak base even in the reaction for forming a strong structure.

[0272] The reaction time may be, for example, 30 minutes to 20 hours, preferably 40 minutes to 10 hours, and more preferably 60 to 5 hours.

[0273] As a specific method for suppressing the corrosion of metal particles and increasing the reaction rate, first, a small amount of NH 3 catalyst is added, and the reaction is carried out at a low temperature. Then, a sufficient amount of NH 3 catalyst is added, and the temperature is raised to carry out the reaction. In addition, in order to increase the reaction rate, it is also preferable to use two or more catalysts with different basicities in combination. In particular, at the initial stage of the reaction, a catalyst with a weak basicity is used to keep the pH low and promote the hydrolysis reaction and dehydration condensation of silane. When the reaction has proceeded to a certain extent, a catalyst with a stronger basicity is used to increase the pH and promote the remaining hydrolysis reaction and dehydration condensation reaction. As a result, a higher reaction rate can be obtained compared with the conventional polysiloxane formation technology, and a strong polysiloxane layer can be formed.

[0274] A weak acid and a weak base that satisfy the above-mentioned pKa and pKb may be combined and used, and the compound generated in the system may be used as a catalyst. For example, when generating a preferable compound as the above-mentioned catalyst in the system, any one of benzoic acid, p-toluic acid, m-toluic acid, o-toluic acid, acetic acid, propionic acid, and carbamic acid and ammonia may be added to the system respectively. In addition, acidic or basic salts may be used in combination, and examples include a combination of sodium benzoate and ammonium chloride and a combination of sodium acetate and ammonium chloride.

[0275] <Other coating layer formation steps> As described above, the other coating layer is preferably formed (when formed) particularly between the metal particles and the polysiloxane layer. Therefore, a layer structure of "metal particles / other coating layer / polysiloxane layer" can be preferably adopted. The other coating layer is not particularly limited, but may be a molybdenum-containing film, a phosphate compound film, or the like. Preferable examples of the molybdenum-containing substance constituting the molybdenum-containing film include the mixed coordination type heteropolyanion compound disclosed in JP-A-2019-151678. Examples of the constituent components of the other coating layer, including the mixed coordination type heteropolyanion compound, are as described above. Hereinafter, an embodiment in which a molybdenum-containing film is formed as another coating layer between the metal particles and the polysiloxane layer will be described as an example.

[0276] When forming a molybdenum-containing film as another coating layer between the metal particles and the polysiloxane layer, prior to the formation of the polysiloxane layer, a molybdenum-containing film can be formed on the surface of the metal particles by stirring a mixed solution containing the metal particles and a molybdenum compound (typically a mixed coordination type heteropolyanion compound). The method for forming a molybdenum-containing film on the surface of the metal particles is not particularly limited, and any method capable of uniformly stirring a mixed solution containing the metal particles and the molybdenum compound in an aqueous solvent may be used. For example, a molybdenum-containing 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.

[0277] In addition, the stirrer for stirring the mixed solution containing the metal particles and the molybdenum compound is not particularly limited, and a known stirrer capable of efficiently and uniformly stirring a mixed solution containing aluminum particles and the molybdenum compound can be used. Specific examples include kneaders, mixers, rotary vessel stirrers, stirred reactors, V-type stirrers, double cone-type stirrers, screw mixers, sigma mixers, flash mixers, air current stirrers, ball mills, edge runners, etc. Examples of the stirring blades of the stirrer are not particularly limited, and include anchor blades, paddle blades, propeller blades, turbine blades, etc.

[0278] When forming a molybdenum-containing film as another coating layer, the amount of the molybdenum compound used can be appropriately set according to the type of the molybdenum compound used and the like. Generally, this amount may be 0.02 to 20 parts by mass, particularly preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the metal particles (solid content). By the content being 0.02 parts by mass or more, a sufficient treatment effect can be obtained. Further, by the content being 20 parts by mass or less, the brightness of the obtained metal pigment can be highly maintained.

[0279] As the solvent used for mixing the metal particles and the molybdenum compound, usually, water, a hydrophilic organic solvent, or a mixed solvent thereof can be used.

[0280] 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, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether and their esters; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. These can be used alone or in combination of two or more.

[0281] The amount of the solvent used in the step of forming the other coating layer (excluding the amount of the solvent for pre-dispersing the metal particles) is not particularly limited, but is usually preferably 50 to 5000 parts by mass, more preferably 100 to 2000 parts by mass, based on 100 parts by mass of the metal particles (solid content). When the amount of the solvent used is 50 parts by mass or more, uneven distribution of the molybdenum compound and aggregation of the metal particles can be suppressed. Also, when the amount of the solvent used is 5000 parts by mass or less, a sufficient treatment effect by the molybdenum compound on the metal particles can be obtained.

[0282] When stirring the liquid mixture containing the metal particles and the molybdenum compound, the temperature of the liquid mixture is usually preferably about 10 to 80°C, particularly preferably 30 to 70°C. When this temperature is 10°C or higher, the reaction time for obtaining a sufficient treatment effect can be shortened. Also, when this temperature is 80°C or lower, the control of the reaction for obtaining the desired metal pigment becomes easier.

[0283] The stirring time of the liquid mixture is not particularly limited as long as it is sufficient for forming the desired molybdenum-containing film. This stirring time is preferably, for example, 0.5 to 10 hours, more preferably 1 to 5 hours. When the stirring time is 0.5 hours or more, a sufficient treatment effect can be obtained. Also, when the stirring time is 10 hours or less, an increase in the treatment cost can be suppressed.

[0284] After the stirring of the liquid mixture containing the metal particles and the molybdenum compound is completed, the particles having the other coating layer formed thereon can be recovered. In this case, known washing, solid-liquid separation, etc. can be appropriately carried out as necessary. For example, after washing the liquid mixture with a hydrophilic organic solvent, it is preferably filtered using a filter or the like to remove water and unreacted substances from the cake containing the metal particles having the molybdenum-containing film. In this way, a molybdenum-containing film as the other coating layer can be formed. When forming other coating layers, it can be carried out according to the above method.

[0285] In the mode of forming a polysiloxane layer on a metal particle subsequent to another coating layer (a molybdenum-containing film), after the stirring of the mixed solution containing the metal particle and the molybdenum compound is completed, without recovering the particles on which the other coating layer is formed, a dispersion of a silicon compound source (typically, at least one of an organosilicon compound represented by the above formula (1), such as tetraalkoxysilane and / or its condensate, and a silane coupling agent represented by any one of the above formulas (2) to (4)) in water and / or a hydrophilic organic solvent may be directly added and stirred into the system. At this time, a dispersion of an organosilicon compound represented by the above formula (1), such as tetraalkoxysilane and / or its condensate, may be added to the system containing the particles on which the other coating layer is formed, and then a dispersion of at least one of the silane coupling agents represented by any one of the above formulas (2) to (4) may be added and stirred (see the second method in the above-mentioned "polysiloxane layer forming step").

[0286] <Stirring conditions> In the production of the metal pigment according to the second invention of the present application, it is desirable to carry out at least the step of forming the coating layer of the composite particles, typically the polysiloxane layer, under stirring. Also, in the production of the metal pigment according to the second invention of the present application, it is preferable to carry out not only the step of forming the polysiloxane layer but also the step of forming the other coating layer under stirring. In the mode of performing the above-mentioned preliminary dispersion of the metal particles, it is more preferable to carry out this also under stirring. Further, in the production of the metal pigment according to the second invention of the present application, it is more preferable to carry out the entire process including the preliminary dispersion of the metal particles, the step of forming the other coating layer, and the step of forming the polysiloxane layer under stirring.

[0287] In the production of the metal pigment according to the second invention of the present application, by carrying out at least the step of forming the coating layer of the composite particles, typically the polysiloxane layer, under appropriately controlled stirring, it is possible to effectively suppress or prevent the phenomenon that the composite particles adhere to each other through the polysiloxane layer, or that the aggregated particles composed of metal particles are coated with the polysiloxane layer. Further, by carrying out the entire process under stirring including the pre-dispersion of the metal particles, the formation steps of the other coating layers, and the formation step of the polysiloxane layer (until all the layers to be formed on the metal particle surface are completely formed), it becomes possible to more easily obtain the metal pigment according to the second invention of the present application that satisfies all of the above physical property requirements. The following description of the stirring conditions can be applied to any step in the production of the metal pigment according to the second invention of the present application.

[0288] Stirring can be carried out by a known or commercially available stirring device. For example, at least one of a kneader, a mixer, a rotary vessel stirrer, a stirred reaction tank, a V-type stirrer, a double cone-type stirrer, a screw mixer, a sigma mixer, a flash mixer, an air flow stirrer, a ball mill, an edge runner, etc. can be used. Among these stirrers, it is preferable to use a stirring tank type device that stirs by a stirring blade (impeller). As a result of exerting a pressure shearing action together with a circulating action that causes the entire reaction system including the liquid phase to flow by the stirring blade, the generation of aggregation of the composite particles can be more effectively suppressed.

[0289] The shape of the stirring blade is not particularly limited, and for example, an anchor type, a propeller shape, a turbine shape, an inclined turbine shape, a fan turbine shape, a paddle shape, an inclined paddle shape, a gate shape can be used. A max blend blade (manufactured by Sumitomo Heavy Industries Process Equipment Co., Ltd.) or a full zone blade (manufactured by Kobe Steel Environmental Solutions Co., Ltd.) etc. are also suitable. Further, these shaped stirring blades can be combined in multiple stages. The stirring speed is preferably such that the stirring blades are not exposed by the vortices generated by the stirring. In addition, in order to suppress the vortices generated by the stirring, a cylindrical tank, a rectangular tank, a tank provided with a baffle plate, or the like can be preferably used.

[0290] In the production of the metal pigment containing the composite particles according to the second invention of the present application, it is desirable to set the optimum stirring tank, the size of the stirring blades, and the speed of the stirring blades 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 a 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 generally in the range of L / D = 0.5 to 3.0, and usually in the range of 1 to 2. In addition, the size of the stirring blades is generally such that the maximum diameter is in the range of 0.2 to 0.9 of the inner diameter of the stirring tank, and preferably about 0.4 to 0.6. The shape of the stirring blades (including the length) is preferably appropriately selected according to the physical properties of the mixed liquid, and it is important that the entire stirring tank is stirred throughout the process. In particular, it is preferable to combine a plurality of inclined paddle types, inclined turbine types, and propeller types that are likely to generate upstream and downstream flows so that there are no stagnant parts that are not stirred near the liquid surface or the bottom surface of the stirring tank, or to use a max blend blade or a full zone blade. At this time, the distance between the stirring blades and the inner surface of the stirring tank (including the baffle plate) is preferably set to be 5 mm or more. By doing so, it becomes easier to suppress the breakage and deformation of the metal particles.

[0291] The speed of the stirring blades is preferably such that the tip is 0.5 to 50 m / s, more preferably 1 to 20 m / s, and even more preferably 2 to 10 m / s. When the speed of the tip of the stirring blades is within the range of 0.5 to 50 m / s, the dispersibility of the composite particles in the produced metal pigment can be enhanced. As a result, it becomes easier to obtain a metal pigment having small aggregability of individual particles, excellent hiding power, color tone, and little gas generation. In addition, when the linear speed of the stirring is within the above range, breakage of metal particles (for example, flaky aluminum powder) is prevented, the speed of the hydrolysis / condensation reaction is appropriately controlled, and aggregation of the composite particles can be effectively suppressed.

[0292] <Recovery of Composite Particles> After the surface coating step with polysiloxane is completed, the composite particles can be recovered. In the recovery, known treatments such as washing and solid-liquid separation can be carried out as necessary. For example, it is preferable to wash the obtained slurry with water / organic solvent (preferably hydrophilic solvent) and then filter it using a filter to remove water and unreacted substances from the slurry containing the coated composite particles. Further, thereafter, if necessary, the filtered slurry may be heat-treated at a temperature in the range of, for example, 100 to 500°C. The composite particles recovered in this way can usually constitute a metal pigment containing a solvent such as water / organic solvent (preferably hydrophilic solvent) remaining and accompanying in the manufacturing process, as described later.

[0293] Metal Pigment Composition The metal pigment of the second invention of the present application obtained as described above includes composite particles containing metal particles (and a surface modifier if present) and a coating of polysiloxane on its surface, and is obtained in the form of a metal pigment composition containing a solvent such as water / organic solvent (preferably hydrophilic solvent) used in the manufacturing process as the remaining portion of the solid content (non-volatile content). In the metal pigment composition, usually, a hydrolyzate and / or a condensate of a silicon compound, which is at least one selected from hydrolyzates of organosilicon compounds (for example, at least one of the organosilicon compounds represented by the above general formula (1), silane coupling agents represented by any of the above general formulas (2), (3), and (4), and partial condensates thereof), may be present in an amount of 0.02 to 50 parts by mass in terms of the state where the hydrolysis / condensation reaction is completed, based on 100 parts by mass of the metal particles.

[0294] In the metal pigment composition, a compound for forming an optional other coating layer (in an optional embodiment for forming a molybdenum-containing film as the other coating layer, a molybdenum-containing compound, for example, a mixed coordination type heteropolyanion compound) may be present in an amount of 0.01 to 10 parts by mass based on 100 parts by mass of the metal particles. In the metal pigment composition, an optional organic oligomer or polymer may be present in an amount of 0.01 to 50 parts by mass per 100 parts by mass of the metal particles. In the metal pigment composition, at least one selected from the group consisting of optional inorganic phosphoric acids and their salts, and acidic organic (sub)phosphoric acid esters and their salts may be present in an amount of 0.01 to 20 parts by mass per 100 parts by mass of the metal particles. In the metal pigment composition, as the balance of the above components (non-volatile matter), a solvent containing water / hydrophilic solvent used in the production process may be present. The amount of the solvent containing water / hydrophilic solvent may be, for example, 0.5 to 95% by mass of the metal pigment composition. Alternatively, the amount of the solvent containing water / hydrophilic solvent may be 1 to 90% by mass, or 2 to 80% by mass, or 5 to 70% by mass of the metal pigment composition.

[0295] The metal pigment composition may optionally contain any components other than the above. Examples of the optional components include at least one of an antioxidant, a light stabilizer, a polymerization inhibitor, and a surfactant. As the antioxidant, those represented by phenolic compounds, phosphorus compounds, and sulfur compounds can be used. As the light stabilizer, those used as the above-mentioned antioxidant can also be used, but those represented by benzotriazole compounds, benzophenone compounds, salicylate compounds, cyanoacrylate-based, oxalic acid derivatives, hindered amine-based compounds (HALS), and hindered phenolic compounds can be used.

[0296] Examples of surfactants include nonionic surfactants typified by polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl phenyl ethers, oxyalkylene alkyl amino ethers, sorbitan fatty acid esters, polyalkylene glycol fatty acid esters, and glycerin fatty acid esters; anionic surfactants typified by sulfate esters, sulfonates, and phosphate esters; cationic surfactants typified by quaternary ammonium salts; and one or more selected from these can be used. Particularly preferred examples among these include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, or a mixture thereof.

[0297] (Water content) The water content of the metal pigment composition of the second invention of the present application is desirably 0 ppm or more and 2000 ppm or less based on the mass of the metal pigment composition. By setting the water content in this way, it is possible to further suppress the aggregation of composite particles and the progress of color tone change of the metal pigment composition in a package such as a metal container filled with and sealed with the metal pigment composition. The water content is more preferably 1000 ppm or less, still more preferably 500 ppm or less, and particularly preferably 300 ppm or less. There is no lower limit for the water content, and the lower the better.

[0298] To achieve such a moisture content, after the step of forming a polysiloxane layer (and / or, optionally, other coating layers) on the metal particles in the process of manufacturing the metal pigment, known treatments such as washing and solid-liquid separation are performed. At this time, for example, the dispersion is washed with an organic solvent having a moisture content of 2000 ppm or less and then filtered using a filter. In some cases, this operation is repeated multiple times to remove water and unreacted substances from the composition containing the composite particles. Further, thereafter, if necessary, the cake containing the composite particles may be subjected to heat dehydration treatment in an atmosphere of a gas such as nitrogen having a low moisture content at a temperature in the range of, for example, 100 to 500°C. The composite particles recovered in this way can constitute a metal pigment composition in which a small amount of water / hydrophilic solvent used in the manufacturing process remains and is accompanied as described above.

[0299] Also, when adjusting the solid content ratio of the composition, it is desirable to use an organic solvent having a moisture content of 2000 ppm or less (for example, the hydrophilic solvent described above). The moisture content of the organic solvent used for these washings and solid content adjustments is preferably 2000 ppm or less, more preferably 1000 ppm or less, still more preferably 500 ppm or less, and particularly preferably 300 ppm or less.

[0300] (pH) The metal pigment composition of the second invention of the present application preferably has a pH in the range of 5 to 9. By setting the pH within this range, aggregation of the composite particles of the metal pigment composition in the package and progress of color tone change can be suppressed. The pH of the metal pigment composition is more preferably in the range of 6 to 8, and still more preferably in the range of 6.5 to 7.5. To achieve such a pH of the metal pigment composition, after the step of forming a layer of polysiloxane (and / or, optionally, other coating layers) on the metal particles is completed, known treatments such as washing and solid-liquid separation are repeatedly performed with a sufficient amount of an organic solvent to sufficiently wash and remove polar compounds such as the catalyst used when forming the coating layer.

[0301] The metal pigment of the second invention of the present application can be used in organic solvent-based paints, inks, etc. At this time, by adding the metal pigment of the second invention of the present application to an aqueous paint or aqueous ink in which resins, which are film-forming components, are dissolved or dispersed in a water-based medium, a metallic aqueous paint or metallic aqueous ink can be obtained. Further, the metal pigment of the second invention of the present application can also be kneaded with a resin or the like and used as a water-resistant binder and filler. For example, optional additives such as antioxidants, light stabilizers, polymerization inhibitors, surfactants, etc. may be added when the metal pigment is incorporated into an aqueous paint or aqueous ink, or a resin or the like.

[0302] When the metal pigment of the second invention of the present application is used in paints or inks, it may be added directly to the (aqueous) paint or (aqueous) ink as it is, but it is preferably added after being dispersed in a solvent in advance. Examples of the solvent used in this case include water, texanol, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, etc. Examples of the above resins include acrylic resins, polyester resins, polyether resins, epoxy resins, fluorine resins, rosin resins, etc.

[0303] The content of the metal pigment of the second invention of the present application in the above aqueous paint composition or aqueous ink composition is not limited, but usually it may be 0.1 to 50% by mass, and particularly preferably 1 to 30% by mass. By the content being 0.1% by mass or more, a high decorative (metallic) effect can be obtained. Also, by the content being 50% by mass or less, it can be prevented that the properties of the aqueous paint composition or aqueous ink composition, such as weather resistance, corrosion resistance, mechanical strength, etc., are impaired. The content of the solvent at this time is not particularly limited, but it may be 20 to 200% by mass with respect to the resin binder content. By the content of the solvent being within this range, the viscosities of the paint and ink can be adjusted to an appropriate range, and handling and film formation can be facilitated.

[0304] Preferred resins are acrylic resins and polyester resins. If necessary, resins such as melamine-based curing agents, isocyanate-based curing agents, and urethane dispersions can be used in combination. Furthermore, these resins can be combined with inorganic pigments, organic pigments, extender pigments, silane coupling agents, titanium coupling agents, dispersants, anti-settling agents, leveling agents, thickeners, and defoamers that are generally added to paints. In order to improve the dispersibility of the resins 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.

[0305] Third Invention The third invention of the present application is A method for producing a metallic pigment (composition), wherein the production method includes the following steps (1) to (3) using a stirred tank type reactor, (1) A step of dispersing metal particles in a solvent, (2) A step of coating the metal particles with a silicon compound, and (3) A step of filtering and washing, The stirred tank type reactor is The volume of the reaction tank is 100 L or more, The ratio of the diameter of the reaction tank to the maximum diameter of the stirring blade is in the range of 0.2 to 1.0, and the shortest distance between the inner surface of the reaction tank and the tip of the stirring blade is 10 mm or more, and The tip speed of the stirring blade during stirring is 1 to 20 m / second, The production method, as described above. Hereinafter, the details of the third invention of the present application will be described.

[0306] Reaction Tank-Type Reactor In the method for producing a metallic pigment (also referred to as "metallic pigment composition") of the third invention of the present application, a stirred tank type reactor is used. A stirred tank type reactor is a stirred tank type device that is stirred by a stirring blade (impeller). As a result of the circulation action of flowing the entire reaction system including the liquid phase and the pressure shearing action by the stirring blade, the generation of aggregation of composite particles can be more effectively suppressed.

[0307] The shape of the stirring blade is not particularly limited, and for example, an anchor type, a propeller type, a turbine type, an inclined turbine type, a fan turbine type, a paddle type, an inclined paddle type, or a gate type can be used. Max blend blades (manufactured by Sumitomo Heavy Industries, Ltd., Process Equipment Division) and full zone blades (manufactured by Kobe Steel, Ltd., Environmental Solutions Division) are also suitable. Further, stirring blades of these shapes can be combined in multiple stages.

[0308]

[0309] ​In the manufacturing method of the third invention of the present application, it is desirable to set the optimal reaction tank (sometimes referred to as a "stirring tank"), the size of the stirring blade, and the speed of the stirring blade in relation to the amount and physical properties (density, viscosity, etc.) of the mixed solution. The size of the reaction tank is preferably selected such that the maximum amount of the mixed solution used in a series of processes is 20 to 80% of the reaction tank. The volume of the reaction tank is desirably 100 L or more in order to prepare a pigment with a small quality variation of the industrially required amount. In one embodiment, the volume of the reaction tank may desirably be 150 or more, or may desirably be 200 L or more. The shape of the reaction tank is preferably cylindrical in order to reduce the stagnant part and stir the whole uniformly. In the case of a cylindrical reaction tank, the ratio of the height (L) to the inner diameter (D) of the reaction tank, L / D, generally ranges from 0.5 to 3.0, usually in the range of 1 to 2. Also, the size of the stirring blade is such that the ratio of the inner diameter of the reaction tank to the maximum diameter of the stirring blade ranges from 0.2 to 1.0, preferably about 0.4 to 0.6. The shape (including the length) of the stirring blade is desirably appropriately selected according to the physical properties of the mixed solution, and it is important that the entire reaction tank is stirred throughout the process. In particular, it is preferable to combine multiple stages of an inclined paddle type, an inclined turbine type, or a propeller type that easily generate upstream and downstream flows so that there are no stagnant parts that are not stirred near the liquid surface or the bottom surface of the reaction tank, or to use a max blend blade or a full zone blade. At this time, the shortest distance between the inner surface of the reaction tank (including the baffle plate) and the stirring blade is desirably kept 10 mm or more when the volume of the reaction tank is 100 L or more. The shortest distance between the inner surface of the reaction tank (including the baffle plate) and the stirring blade is more preferably 20 mm or more, further preferably 40 mm or more, even more preferably 60 mm or more, and even more preferably 100 mm or more. By doing so, it becomes easy to suppress damage and deformation of the metal particles.

[0310] When the volume of the reaction tank is 100 L or more, the tip speed (linear speed) of the stirring blade is preferably 1 to 20 m / s, more preferably 1.5 to 10 m / s, and particularly preferably 2 to 8 m / s. When the tip speed of the stirring blade is within the range of 1 to 20 m / s, the dispersibility of the composite particles in the produced metal pigment composition can be enhanced. As a result, it becomes easier to obtain a metal pigment composition in which the cohesiveness of individual particles is small, which has excellent hiding power and color tone and generates little gas. Further, when the tip speed (linear speed) of the stirring is within the above range, breakage of metal particles (for example, flaky aluminum powder) is prevented, and the rate of the hydrolysis / condensation reaction is appropriately controlled, so that aggregation of the composite particles can be effectively suppressed.

[0311] As an index representing the stirring state, the stirring Reynolds number (hereinafter abbreviated as "stirring Re number") is used. The stirring Re number does not reflect the sizes other than the shapes and diameters of the reaction tank and the stirring blade. Therefore, the stirring Re number is only a guide and is not particularly limited, but it is preferably 3000 or more, and more preferably 5000 or more. The upper limit of the stirring Re number may vary depending on the type and scale of the stirring device. The upper limit of the stirring Re number may be about 100,000 in a normal laboratory scale, but when using a scaled-up large-scale device, it may exceed 100,000 as long as the desired effect of the third invention of the present application is not hindered. This upper limit is acceptable, for example, when it is about 1 million.

[0312] The stirring Re number here is calculated by the following formula. Stirring Re number = (ρ × n × d 2 ) / μ (In the formula, ρ represents the density (kg / m 3 ) of the mixed liquid to be stirred at 25°C, n represents the stirring rotation speed (rps), d represents the diameter (m) of the stirring blade, and μ represents the viscosity (Pa·s) of the mixed liquid to be stirred at 25°C, respectively.)

[0313] Metal Pigment Composition The metal pigment composition produced according to the third invention of the present application contains composite particles, and the composite particles include metal particles and one or more coating layers formed on the surface thereof. That is, one or more coating layers are formed on the surface of the core metal particles.

[0314] Metal Particles The material of the metal particles (core particles) is not particularly limited, and for example, any metal used as a known or commercially available metal pigment such as aluminum, aluminum alloy, zinc, iron, magnesium, nickel, copper, silver, tin, chromium, stainless steel, etc. may be used. In this specification, the metal of the metal particles contained in the metal pigment composition includes not only a single metal but also an alloy and an intermetallic compound. The metal particles may be used alone or in combination of two or more.

[0315] The average particle size of the metal particles is not particularly limited, but it may be an average particle size that can bring about D 50 in the particle size distribution of the composite particles. That is, when measuring the volume distribution of the composite particles with a laser diffraction particle size distribution analyzer, the volume average particle size (D 50 ) of the metal particles may be set so that D 50 is 0.1 to 30 μm. Here, D 50 on a volume basis when measuring the particle size distribution of the composite particles with a laser diffraction particle size distribution analyzer refers to the particle size at a cumulative degree of 50% in the volume cumulative particle size distribution. The laser diffraction particle size distribution analyzer is not particularly limited, but "LA-300" (manufactured by Horiba, Ltd.) etc. can be used. Mineral spirit can be used as the measurement solvent. For example, after performing ultrasonic dispersion for 2 minutes as a pretreatment on the metal pigment composition containing the composite particles of the sample, after putting it into the reaction tank and confirming that it is appropriately dispersed, D 50 can be measured. The average particle size of the metal particles can be controlled by appropriately adjusting, in the process of grinding and sieving / filtering raw atomized metal powder (for example, aluminum powder) using a ball mill or the like, the particle size of the raw atomized metal powder, the specific gravity per grinding ball when using a ball mill, the mass, the rotation speed of the grinding device, the degree of sieving and filter press, and the like.

[0316] The shape of the metal particles is not limited, but it is particularly preferably flaky (flake-shaped). As a result, the composite particles contained in the metal pigment composition produced by the third invention of the present application can also have a flaky shape, and thus a high hiding power and the like can be obtained more reliably. From this perspective, the aspect ratio (shape coefficient obtained by dividing the average particle size by the average thickness) of the flaky metal particles is preferably from 1 to 1000, and more preferably particularly from 15 to 500. When the aspect ratio of the metal particles is 1 or more, a higher sense of brilliance can be obtained. Further, when the aspect ratio of the metal particles is 1000 or less, the mechanical strength of the flakes is maintained and a stable color tone can be obtained. Here, the average thickness of the metal particles used in the third invention of the present application can be calculated from the water surface diffusion area and density of the metal particles.

[0317] Also, the metal particles do not necessarily have to be composed only of metal, and particles in which the surfaces of inorganic particles such as synthetic resin particles, mica, and glass are coated with metal can also be used as long as the effects of the third invention of the present application are not inhibited. In the third invention of the present application, particles formed from aluminum or an aluminum alloy are desirable particularly in terms of high weather resistance, low specific gravity, and easy availability.

[0318] Particularly suitable as the metal particles constituting the composite particles is aluminum flakes, which are generally widely used as metallic pigments. As aluminum flakes, those having surface properties, particle size, and shape required for metallic pigments, such as surface gloss, whiteness, and brilliance, are suitable. Aluminum flakes are usually commercially available in a paste state. The paste-like aluminum flakes usually contain scaly aluminum powder, as well as residual amounts of mineral spirits (aliphatic hydrocarbons), fatty acids, and organic solvents such as solvent naphtha and xylene used during pulverization. The paste-like aluminum flakes may be used as they are, or the fatty acids on the surface may be removed in advance with an organic solvent or the like before use. Also, so-called aluminum vapor-deposited foils with a volume average particle size (D 50 ) of 3 to 30 μm and an average thickness (t) of 5 to 50 nm can also be used.

[0319] Coating Layer The composite particles contained in the metal pigment composition produced according to the third invention of the present application have one or more coating layers formed on the surface of the metal particles serving as the core of the composite particles. At least one of the coating layers is a silicon compound-containing layer. By making at least one of the coating layers a silicon compound-containing layer, gas generation in the aqueous paint can be suppressed, good storage stability can be obtained, and the water resistance when forming a coating film is excellent. The coating layer of the composite particles may have another coating layer (hereinafter referred to as the "second coating layer") in addition to the silicon compound-containing layer. Such a second coating layer will be described in more detail later.

[0320] Silicon Compound-Containing Layer The silicon compound-containing layer is preferably a layer composed of a compound containing a Si-O bond (siloxane bond) in particular. Examples of such a layer include a layer containing at least one of a silane-based compound and silicon oxide. Examples of such compounds include silane-based compounds [H 3 SiO(H 2 SiO) n SiH 3(However, n represents any positive integer), in addition to this, SiO 2 SiO 2 ·nH 2 O (However, n represents any positive integer), etc., silicon oxides represented by these are exemplified. These silane-based compounds and silicon oxides may be either crystalline or amorphous, but are particularly preferably amorphous. Therefore, as a layer containing a silicon oxide (such as silica), for example, a layer containing amorphous silica can also be preferably employed.

[0321] Also, the layer composed of a compound containing an Si - O bond may be a layer formed using an organosilicon compound (including a silane coupling agent) as a starting material. In this case, the silicon compound-containing layer may contain an organosilicon compound or its derived components within a range that does not prevent the effects of the third invention of the present application. In a typical example, the layer composed of a compound containing an Si - O bond can be formed by hydrolyzing an organosilicon compound.

[0322] The silicon compound-containing layer may contain additives, impurities, etc. other than the silicon compound within a range that does not impair the characteristics of the third invention of the present application.

[0323] The content of silicon contained in the silicon compound-containing layer is not particularly limited, but is preferably 1 to 30 parts by mass, and more preferably 2 to 20 parts by mass, based on 100 parts by mass of the metal particles. When the silicon content of the silicon compound-containing layer is 1 part by mass or more based on 100 parts by mass of the metal particles, the corrosion resistance, water dispersibility, stability, etc. of the metal pigment composition can be maintained at a high level. When the silicon content of the silicon compound-containing layer is 30 parts by mass or less based on 100 parts by mass of the metal particles, aggregation of the composite particles and a decrease in color tone such as hiding power and metallic luster can be prevented.

[0324] The coating layer of the composite particles contained in the metal pigment composition produced according to the third invention of the present application is preferably particularly hydrophilic. The composite particles usually form a metal pigment composition in a dispersed form in an aqueous solvent (water or a mixed solvent containing water and an organic solvent). However, when the coating layer has a hydrophilic surface, the composite particles can be highly dispersed in such an aqueous solvent. Moreover, since silicon oxide (such as amorphous silica) is very stable in an aqueous solvent, a metal pigment composition containing highly stable composite particles in an aqueous solvent can be provided. From such a viewpoint, in the composite particles contained in the metal pigment composition produced according to the third invention of the present application, it is desirable that at least the outermost layer is a silicon compound-containing layer (particularly a layer composed of a compound containing an Si—O bond). When the coating layer is composed of a plurality of layers, in addition to the outermost silicon compound-containing layer, a silicon compound-containing layer (particularly an Si—O-based coating layer) may be separately formed as a layer other than the outermost layer.

[0325] Second Coating Layer The coating layer of the composite particles contained in the metal pigment composition produced according to the third invention of the present application is not particularly limited except that at least one layer is a silicon compound-containing layer, but a coating layer other than the above-mentioned silicon compound-containing layer can also be formed as needed.

[0326] The second coating layer may, for example, comprise at least one of a metal (an alkali metal; an alkaline earth metal; a metal such as manganese, iron, cobalt, nickel, copper, silver, etc.), a metal oxide (titanium oxide, zirconium oxide, iron oxide, etc.), a metal hydrate, and a resin (a synthetic resin such as an acrylic resin, an alkyd resin, a polyester resin, a polyurethane resin, a polyvinyl acetate resin, a nitrocellulose resin, a fluororesin, etc.). As the second coating layer, for example, a molybdenum-containing film, a phosphoric acid compound film, etc. can be formed. By providing the second coating layer, the corrosion resistance of the metal particles can be improved and the formation of the silicon compound-containing layer can be promoted.

[0327] The second coating layer, when formed, is preferably formed particularly between the metal particles and the silicon compound-containing layer. Therefore, for example, a layer structure such as "metal particles / second coating layer / silicon compound-containing layer" can be preferably adopted. Although not particularly limited, examples of the molybdenum-containing film include those disclosed in JP-A-2003-147226, WO 2004 / 096921 pamphlet, Patent No. 5979788, and JP-A-2019-151678. Examples of the phosphate compound film include those disclosed in Patent No. 4633239. A preferred example of the molybdenum-containing substance constituting the molybdenum-containing film is the mixed coordination type heteropolyanion compound disclosed in JP-A-2019-151678.

[0328] Also, the second coating layer may be formed outside the metal particles and the silicon compound-containing layer. Alternatively, the constituent components (such as molybdenum-containing compounds and phosphate compounds) of the second coating layer may be included together with the silicon compound in the silicon compound-containing layer.

[0329] The second coating layer may be a layer containing other corrosion inhibitors in order to further improve the corrosion resistance of the core metal particles (preferably aluminum particles or aluminum alloy particles). The corrosion inhibitor to be added is not particularly limited, and any known corrosion inhibitor can be used. The amount of use may be in a range that does not inhibit the desired effects of the third invention of the present application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organic phosphorus compounds, metal salts of molybdic acid, and the like.

[0330] From the viewpoints of adhesion and chemical resistance when forming a coating film, the silicon compound-containing layer and / or the second coating layer of the composite particles contained in the metal pigment composition, or as a separate layer, may further contain an organic oligomer or polymer.

[0331] Further, from the viewpoint of storage stability, at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (sub)phosphoric esters and their salts may be contained in the silicon compound-containing layer and / or the second coating layer of the composite particles, or as a separate layer. These compounds are not particularly limited, and for example, those disclosed in JP-A-2019-151678 can be used.

[0332] Method for Producing a Metal Pigment Composition The method for producing the metal pigment composition of the third invention of the present application includes the following steps (1) to (3). (1) A step of dispersing metal particles in a solvent, (2) A step of coating the metal particles with a silicon compound, and (3) A step of filtering and washing.

[0333] Step (1) Step (1) is a step of dispersing metal particles in a solvent. In order to obtain a metal pigment composition with less aggregation, in this step, the metal particles and the solvent are stirred to sufficiently disperse the metal particles in the solvent. Further, ultrasonic treatment described later may be performed.

[0334] The solvent used in the production method of the third invention of the present application, that is, the solvent for the hydrolysis reaction and / or condensation reaction of the organosilicon compound, may be appropriately selected according to the type of the silicon-containing raw material used, etc., but usually, water, a hydrophilic organic solvent, or a mixed solvent thereof can be used. By using these solvents, the uniformity of the reaction and the uniformity of the obtained hydrolys...

Claims

1. 1. A metallic pigment comprising a composite particle having a metal particle and one or more coating layers on a surface thereof, (1) The composite particles have a scale-like shape, (2) The volume-based D when the particle size distribution of the composite particles is measured using a laser diffraction particle size distribution analyzer ５０ is 0.1 to 30 μm, (3) A metallic pigment characterized in that the composite particles have an average thickness of 15 to 300 nm.

2. The metallic pigment according to claim 1 , wherein the proportion of said bent composite particles is 10% or less.

3. 3. The metal pigment according to claim 1, wherein the number of aggregates in which four or more of the composite particles are adhered to one another is 35% or less of the total number of the composite particles.

4. The metallic pigment according to any one of claims 1 to 3, wherein the metallic particles contain aluminum or an aluminum alloy.

5. The metallic pigment according to any one of claims 1 to 4, wherein the one or more coating layers comprises a metal oxide coating layer.

6. The metallic pigment according to any one of claims 1 to 5, wherein the one or more coating layers include a silicon compound-containing layer.

7. The metal pigment according to any one of claims 1 to 6, wherein at least one of the coating layers is a polysiloxane layer.

8. The metal pigment according to any one of claims 1 to 7, wherein the composite particles have an average particle thickness of 15 to 160 nm.

9. The metallic pigment according to any one of claims 1 to 8, wherein the composite particles have an average aspect ratio of 20 to 400.

10. 8. The metal pigment according to claim 7, wherein the proportion of a Q4 structure in which a Si atom has four --O--Si- bonds in the structure of the polysiloxane constituting the polysiloxane layer is 40 to 90%.

11. The metallic pigment according to any one of claims 1 to 10, wherein the relative element concentration ((A / B) x 100) of the metal element concentration A and the Si element concentration B when the surface of the composite particle is evaluated by XPS is 10 mol% or less.

12. 11. The metal pigment according to claim 7 or 10, wherein the average thickness of the polysiloxane layer is 5 to 100 nm.

13. 13. The metal pigment according to claim 1, wherein a hydrophilicity A defined as the sum of (a ratio of Q1 structures in which Si atoms have one —O—Si- bond×3)+(a ratio of Q2 structures in which Si atoms have two —O—Si- bonds×2)+(a ratio of Q3 structures in which Si atoms have three —O—Si- bonds) is 10 to 80%.

14. The metallic pigment according to any one of claims 1 to 13, wherein the composite particle further comprises a coating layer comprising at least one of a metal, a metal oxide, a metal hydrate, and a resin.

15. A metallic pigment comprising composite particles in which metal particles are coated with a layer of polysiloxane, 1) The proportion of Q4 structures in which Si atoms in the polysiloxane structure have four -O-Si- bonds is 40 to 90%, and 2) When the surface of the composite particle is evaluated by XPS, the relative element concentration ((A / B)×100) of the metal element concentration A and the Si element concentration B is 10 mol % or less. The metallic pigment.

16. 16. The metallic pigment according to claim 1, wherein 200 g of an aqueous metallic paint containing 12 g of the metallic pigment as a nonvolatile content, 18 g of methoxypropanol, 110 g of an aqueous acrylic resin, 18 g of melamine resin, and 12 g of water is placed in a flask, and the cumulative amount of hydrogen gas generated is measured in a constant temperature water bath at 60°C for up to 24 hours. The metallic pigment has a gas generation of 10 ml or less.

17. A water-based metallic paint containing the metal pigment according to any one of claims 1 to 15 and 5 mass% or more of water, wherein 200 g of the water-based metallic paint is collected in a flask and a cumulative amount of hydrogen gas generated is measured in a constant temperature water bath at 60°C for up to 24 hours, and the amount of gas generated is 10 ml or less.

18. A metal pigment composition comprising the metal pigment according to any one of claims 1 to 16.

19. An aqueous coating composition comprising the metal pigment according to any one of claims 1 to 16.

20. An aqueous ink composition comprising the metallic pigment according to any one of claims 1 to 16.

21. A coating film containing the metal pigment according to any one of claims 1 to 16.

22. A method for producing a metallic pigment, the method comprising the steps of: (1) dispersing metal particles in a solvent; (2) coating the metal particles with a silicon compound; and (3) filtering and washing; The stirred tank reactor is The volume of the reaction tank is 100 L or more, The ratio of the diameter of the reaction vessel to the maximum diameter of the stirring blade is in the range of 0.2 to 1.0, and the shortest distance between the inner surface of the reaction vessel and the tip of the stirring blade is 10 mm or more; and The tip speed of the stirring blade during stirring is 1 to 20 m / sec. The manufacturing method.

23. 23. The method of claim 22, further comprising the steps of: In step (1), the average particle size of the metal particles in the dispersion is 1.2 times or less the average particle size of the raw material metal particles, and the metal particles in the dispersion are uniformly dispersed in the solvent; In step (2), the mixture is stirred so as not to form any stagnation areas on the surface or bottom. the average particle size of the composite particles contained in the metal pigment obtained after step (3) is 1.3 times or less the average particle size of the raw material metal particles; The manufacturing method.

24. The method according to claim 22 or 23, wherein in the steps (1) and / or (2), the treated liquid withdrawn from near the bottom of the reaction vessel is returned to the reaction vessel from the upper part of the reaction vessel for circulation.

25. The method according to any one of claims 22 to 24, wherein in step (2), after the silicon-containing raw material and the catalyst are charged, the inner wall of the reaction vessel near the liquid-contacting portion between the reaction vessel and the mixed liquid is washed with the reaction liquid or a solvent to reduce deposits or retained materials.

26. The method according to any one of claims 22 to 25, wherein step (2) is carried out for 2 hours or more.

27. The method according to any one of claims 22 to 26, in which the metallic pigment according to any one of claims 1 to 16 is produced.

28. A metallic pigment obtained by the method according to any one of claims 22 to 27.

29. A stirred tank type reactor used in the production method according to any one of claims 22 to 27.

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