Metallic pigments, their uses, and methods for manufacturing metallic pigments

Abstract

Provided are 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. The problem is solved by a metal pigment containing metal particles and composite particles having one or more coating layers formed on surfaces of the metal particles, or the like, the metal pigment being characterized in that (1) the composite particles have a scale-like shape, (2) a volume-based diameter D50 is 0.1 to 30 μm when a particle size distribution of the composite particles is measured by a laser diffraction type particle size distribution meter, and (3) the composite particles have an average thickness of 15 to 300 nm.

Description

[Technical Field]

[0001] The present invention relates to a metal pigment containing novel composite particles. More specifically, in its first embodiment, the present invention relates to a metal pigment (including in the form of a composition) containing novel composite particles having low aggregation of individual particles and excellent opacity, color tone, etc. The first invention of this application relates, in its second embodiment, to a (composite) metal pigment comprising metal particles and composite particles having a metal oxide coating formed on their surface, and more specifically, to a (composite) metal pigment that effectively suppresses aggregation and deformation of composite particles and achieves a high level of balance in terms of excellent design, gloss, suppression of blemishes, and stability in water-based paints in the coating film. The present invention relates to a metal pigment comprising composite particles in which metal particles are coated with a polysiloxane layer. The present invention further relates to a metal pigment suitable for water-based paints, which includes composite particles coated with a polysiloxane layer, has a high degree of polysiloxane condensation, excellent mechanical stability, and high design properties, as well as a metal pigment composition, an aqueous paint composition, an aqueous ink composition, and a coating film containing the metal pigment. The third invention of this application relates to a method for producing a metal pigment. More specifically, the third invention of this application relates to a method for producing a metal pigment that includes composite particles having low aggregation of individual particles and excellent opacity, color tone, etc. [Background technology]

[0002] Traditionally, metallic pigments have been used in metallic paints, printing inks, and plastic compounding applications to achieve a metallic aesthetic effect. In recent years, in the paint industry, there has been a growing need to switch to water-based paints that use less organic solvents as a measure to conserve resources and reduce pollution. However, for metallic paints containing metal pigments, there are still not enough types of water-based paints that are practical for use. One reason for this is that metal pigments are prone to corrosion in water-based paints. When metal powder is present in water-based paints, corrosion by water occurs in one or more ranges of acidic, neutral, or basic conditions, depending on the properties of the various metals, and hydrogen gas is generated. This is an extremely serious safety issue in the manufacturing processes of paints and inks at paint and ink manufacturers, as well as in the painting and printing processes at automobile, home appliance, and printing manufacturers. Furthermore, color degradation is unavoidable because the smoothness of the metal surface is lost due to corrosion. The corrosion resistance of metal pigments in water, water-based paints, or water-based inks can be rephrased as "storage stability."

[0003] Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-147226) discloses an aluminum pigment having an inorganic molybdenum coating and further having a coating made of amorphous silica covering the coating. Patent Document 2 (International Publication No. 2004 / 096921) also discloses an aluminum pigment having an inorganic molybdenum coating and further having a coating made of amorphous silica and / or a coating formed from a silane coupling agent covering the coating. However, none of the methods described in these patent documents (such as methods for producing aluminum pigments) could avoid a decrease in the color tone of the metal pigments, and the processes were complicated.

[0004] Furthermore, Patent Document 3 (International Publication No. 2018 / 180936) discloses a coated pigment (metal pigment composition) containing a coating layer which is a metal particle and a silicon-containing compound layer, with a small proportion of aggregates formed by four or more particles adhering to each other, with the aim of providing a coated pigment (metal pigment composition) in which aggregates are dispersed in a relatively small state. However, other than the preference for adjusting the stirring Reynolds number to a predetermined range, Patent Document 3 does not provide any specific instructions on how to obtain a coated pigment with few aggregates. Furthermore, it has been found that even if the range of characteristic parameters specified in Patent Document 3 is satisfied, it is still difficult to obtain sufficiently satisfactory storage stability, low aggregation, opacity, and color tone.

[0005] Furthermore, to improve the stability of metal pigments in water-based paints, pigments using composite particles in which metal particles are coated with metal oxides such as amorphous silica have been proposed. However, after coating with amorphous silica, many of the pigment particles exist as aggregates, which can result in reduced opacity per unit mass and inferior brightness, thus creating a need for means to suppress aggregation.

[0006] For example, Patent Document 4 proposes a technology that can achieve a low percentage of aggregates in which four or more composite particles are bonded to each other, at 35% or less on a numerical basis. However, this technology allows for particles where two or three composite particles are aggregated, and there was a need for a technology that could more effectively suppress aggregation in order to realize high-gloss metallic coatings and the like. Furthermore, because these aggregated particles can have an effective particle thickness that is 2 to 3 times greater than that of non-aggregated primary particles, in thin paint films, the particles may not fit within the film, and the protruding particle heads can cause bumps and a decrease in gloss, thus hindering the reduction of paint film thickness. Furthermore, in the technology described in Patent Document 4, a large force must be applied during stirring of the coating reaction to prevent the composite particles from sticking together. As a result, particle deformation due to stirring is particularly significant for thin particles, which can reduce the aesthetic appeal of the metal particles after coating, and a solution to this problem was needed.

[0007] Furthermore, since the aforementioned corrosion occurs on the metal surface, it reduces surface smoothness and also diminishes the aesthetic appeal of the metallic pigment. Among metallic pigments, aluminum flake pigments in particular have a problem in water-based paints because, being amphoteric metals, aluminum reacts with water to generate gas. To counteract this, it is effective to coat the surface of the aluminum flake pigment with an oxide of a metal or metalloid, such as polysiloxane.

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

[0009] However, strong agitation and mixing during paint manufacturing, or prolonged circulation (paint circulation and agitation) during painting, can apply strong shear forces to the metal pigments, damaging the coating layer and leading to reduced storage stability, such as gas generation, and changes in color tone. In particular, if the aspect ratio of the metal pigment particles themselves increases, their mechanical stability decreases, and the particles deform due to circulation, resulting in a further decrease in storage stability, such as gas generation, and changes in color tone.

[0010] In Patent Document 5, the reaction rate (degree of crosslinking) of the polysiloxane is not controlled, and because the reaction rate is not sufficiently increased, it is thought that there are problems with mechanical stability, damage to the coating layer during paint formation and paint circulation, storage stability (gas generation), and deterioration of color tone.

[0011] Furthermore, in the silicon compound treatment, alkoxysilane, followed by water and a catalyst, is added to the aluminum pigment slurry in a stirred-tank reactor to promote hydrolysis and dehydration condensation reactions, thereby treating the aluminum flakes with silica. However, the condensate can cause the aluminum flakes to aggregate, resulting in a paint that does not exhibit the desired opacity or brightness. Additionally, untreated aluminum flakes may form on the surface of the treatment solution or in contact with the reaction tank, and their inclusion can cause gas generation or deterioration of color tone. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2003-147226 [Patent Document 2] International Publication No. 2004 / 096921 Pamphlet [Patent Document 3] International Publication No. 2018 / 180936 Brochure [Patent Document 4] Japanese Patent Publication No. 2018-172617 [Patent Document 5] Special Publication No. 2013-518948 [Overview of the project] [Problems that the invention aims to solve]

[0013] The object of the first invention of this application is to provide, in its first embodiment, a metal pigment (hereinafter also referred to as "metal pigment composition") containing novel composite particles not found in the prior art. A further object of the first invention of this application is to provide a metal pigment composition containing novel composite particles that have excellent storage stability, low aggregation of individual particles, and excellent opacity, color tone, etc., in a first embodiment thereof, while eliminating the disadvantages of the prior art.

[0014] Furthermore, in view of the limitations of the prior art described above, the object of the first invention of this application is, in its second embodiment, to provide a metal pigment (hereinafter also referred to as "composite metal pigment") that effectively suppresses aggregation and deformation of composite particles and achieves a high level of balance in terms of excellent design properties, gloss, suppression of imperfections in the coating film, and stability in water-based paints.

[0015] The present invention, part 2, aims to provide a novel metal pigment consisting of composite particles coated with a polysiloxane layer. Furthermore, in view of the above-mentioned prior art, the present invention aims to provide a metal pigment suitable for water-based paints that has a high reaction rate of polysiloxane constituting the coating layer of composite particles, excellent mechanical stability, and high design appeal. Furthermore, the present invention aims to provide a metal pigment composition, an aqueous paint composition, or an aqueous ink composition containing the said metal pigment. In this specification, the corrosion resistance of composite particles contained in metal pigments in water, water-based paints, or water-based inks is also referred to as "storage stability."

[0016] The object of the third invention of this application is to provide a method for producing a metal pigment with low aggregation (hereinafter also referred to as "metal pigment composition"). A further object of the third invention of this application is to provide a metal pigment composition containing composite particles that overcome the disadvantages of the prior art, namely, that have excellent storage stability, low aggregation of individual particles, and excellent opacity, color tone, etc. Furthermore, a further object of the third invention of this application is to provide a manufacturing apparatus for metal pigment compositions that exhibit less aggregation. [Means for solving the problem]

[0017] As a result of diligent research, the inventor has found a means to solve the problem of the first invention described above. More specifically, the inventors have diligently researched and found that in composite particles, the proportion of aggregates in which four or more particles are bonded to each other is small, and that D in the particle size distribution 50 In addition to controlling the above within a predetermined range, we have found that the objectives of the first aspect of this application can be achieved by controlling the average thickness of the composite particles, the proportion of bent composite particles (i.e., damaged composite particles), etc., within a predetermined range.

[0018] Furthermore, as a result of diligent research, the inventors have discovered that the above problem can be solved by controlling the average thickness of the composite particles, the particle size of the composite particles, etc., within a predetermined range in a composite metal pigment, and have completed the second aspect of the first invention of this application.

[0019] Furthermore, the inventors have discovered that by making the polysiloxane layer coating the metal pigment a strong structure with a specific chemical structure without damaging the metal pigment, the mechanical strength of the polysiloxane layer can be improved, thereby solving the problem of the second invention of this application. The inventors have also discovered that by appropriately setting the catalyst type, amount, timing of addition, temperature, etc., for obtaining the polysiloxane when coating the metal pigment with a polysiloxane layer, it is possible to increase the reaction rate of the polysiloxane while suppressing metal corrosion. More specifically, by adding a basic catalyst in two stages, starting the reaction under gentle conditions that are less likely to cause metal corrosion, and then carrying out the reaction under conditions that allow for a rapid reaction and a high reaction rate, the metal pigment of the second invention of this application, consisting of composite particles, has been completed.

[0020] Furthermore, as a result of diligent research, the inventors have discovered that when coating metal particles with a silicon compound using a stirred tank reactor, controlling the size of the stirred tank reactor and the stirring conditions (whisker blade conditions and linear velocity) within a predetermined range can prevent damage to the metal particles and suppress aggregation during condensation, thus completing the third invention of this application.

[0021] In other words, the inventions of this application and their various embodiments are as follows. [1] A metal pigment comprising metal particles and composite particles having one or more coating layers on their surface, (1) The shape of the composite particles is flaky, (2) When the particle size distribution of the composite particles is measured using a laser diffraction particle size analyzer, the volume-based D 50 The size is 0.1 to 30 μm. (3) A metallic pigment characterized in that the average thickness of the composite particles is 15 to 300 nm. [2] The metal pigment according to [1], wherein the proportion of the bent composite particles is 10% or less. [3] The metal pigment according to [1] or [2], wherein the proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less of the total number of composite particles. [4] The metal pigment according to any one of [1] to [3], wherein the metal particles contain aluminum or an aluminum alloy. [5] The metal pigment according to any one of [1] to [4], wherein the one or more coating layers include a metal oxide coating layer. [6] The metal pigment according to any one of [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 [1] to [6], wherein at least one layer of the coating layer is a polysiloxane layer. [8] The metal 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 metal pigment according to [7], wherein the proportion of Q4 structures having four -O-Si-bonds in the structure of the polysiloxane constituting the polysiloxane layer is 40-90%.

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

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

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

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

[13] A metal pigment according to any one of the following [1] to

[12] , wherein the hydrophilicity A, defined as the sum of (Q1 structure ratio with one Si atom having one -O-Si bond × 3) + (Q2 structure ratio with two Si atoms having two -O-Si bonds × 2) + (Q3 structure ratio with three Si atoms having three -O-Si bonds), is 10 to 80%.

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

[13] , further comprising a coating layer in which the composite particles comprises at least one of a metal, a metal oxide, a metal hydrate, and a resin.

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

[16] A metal pigment as described in any one of items [1] to

[15] , wherein when 200 g of an aqueous metallic paint containing 12 g of the metal pigment as nonvolatile content, 18 g of methoxypropanol, 110 g of aqueous acrylic resin, 18 g of melamine resin, and 12 g of water is taken into a flask and the amount of hydrogen gas generated is measured in a constant temperature water bath at 60°C for up to 24 hours, the amount of gas generated is 10 ml or less.

[17] A water-based metallic paint containing a metal pigment as described in any one of items [1] to

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

[18] A metal pigment composition containing a metal pigment as described in any one of items [1] to

[16] .

[19] A water-based paint composition containing a metal pigment as described in any one of items [1] to

[16] .

[20] A water-based ink composition containing a metal pigment as described in any one of items [1] to

[16] . [twenty one] A coating film containing a metal pigment as described in any one of items [1] to

[16] . [twenty two] A method for producing a metal pigment, 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 metal particles with a silicon compound, and (3) The process of filtering and washing, The aforementioned stirred tank type reactor, The volume of the reaction vessel is 100L 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 aforementioned stirring blade during stirring is 1 to 20 m / s. The aforementioned manufacturing method. [twenty three] The manufacturing method described in

[22] , 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), stir the mixture so as not to create any stagnant areas at the surface and 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 aforementioned manufacturing method. [twenty four] The manufacturing method according to

[22] or

[23] , wherein in step (1) and / or (2), the processed liquid withdrawn from near the bottom of the reaction vessel is returned to the reaction vessel from the top of the reaction vessel and circulated. [twenty five] The manufacturing method according to any one of

[22] to

[24] , wherein, after adding the silicon-containing raw material and catalyst in step (2), the inner wall of the reaction vessel near the wetted part of the reaction vessel and the mixed liquid is washed with the reaction liquid or solvent to reduce deposits or stagnant matter.

[26] A manufacturing method according to any one of items

[22] to

[25] , wherein step (2) is performed over a period of 2 hours or more.

[27] A manufacturing method according to any one of items

[22] to

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

[16] is produced.

[28] A metal pigment obtained by the manufacturing method described in any one of items

[22] to

[27] .

[29] A stirred-tank type reactor used in the manufacturing method described in any one of items

[22] to

[27] . [Effects of the Invention]

[0022] According to the first invention of this application, it is possible to obtain 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. According to a preferred embodiment of the first aspect of the present invention, a metal pigment composition can be obtained that has low aggregation of individual particles, excellent hiding power and color tone (such as brilliance), and generates little gas. Furthermore, according to a more preferred embodiment of the first aspect of the first invention of this application, a metal pigment composition can be obtained that has low aggregation of individual particles, excellent opacity and color tone, low gas generation, and good storage stability. The composite metal pigment according to the second aspect of the first invention of this application can effectively suppress aggregation and deformation of the composite particles constituting the composite metal pigment, thereby enabling a high level of balance in terms of excellent design, gloss, suppression of imperfections in coatings such as metallic coatings, and stability in water-based paints, exceeding the limitations of the prior art.

[0023] According to the second invention of this application, a novel metal pigment not found in the prior art is provided, comprising composite particles coated with a polysiloxane layer. Furthermore, according to the second invention of this application, the polysiloxane constituting the coating layer of the composite particles has a high reaction rate, and it is possible to provide a metal pigment with excellent mechanical stability, storage stability (gas generation), and color tone.

[0024] According to the third invention of this application, a method for producing a metal pigment composition with low aggregation can be provided. In one embodiment, a metal pigment composition can be obtained in which the aggregation of individual particles is small, and which has excellent opacity, color tone (luster, etc.) and low gas generation. In another embodiment, a stirred tank type reactor for producing the metal pigment composition can be provided. [Modes for carrying out the invention]

[0025] The present invention will be described below in accordance with typical or preferred embodiments, but the present invention is not limited to these embodiments. Unless otherwise expressly indicated, these embodiments may be freely combined within the scope of the present invention as defined in the appended claims.

[0026] First Invention The present invention, the first invention, A metal pigment comprising metal particles and composite particles having one or more coating layers on their surface, (1) The shape of the composite particles is flaky, (2) When the particle size distribution of the composite particles is measured using a laser diffraction particle size analyzer, the volume-based D 50 The size is 0.1 to 30 μm. (3) A metallic pigment characterized in that the average thickness of the composite particles is 15 to 300 nm.

[0027] In the present invention, it is preferable that the proportion of bent composite particles is 10% or less. In the present invention, it is preferable that the proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less of the total number of composite particles. In the first invention of this application, it is preferable that the metal particles contain aluminum or an aluminum alloy. In the present invention, it is preferable that the one or more coating layers include a metal oxide coating layer. In the present invention, it is preferable that at least one layer of the coating layer is a silicon compound-containing layer. In the first invention of this application, it is preferable that at least one layer of the coating layer is a polysiloxane layer. More preferably, the proportion of Q4 structures having four -O-Si-bonds among the Si atoms in the polysiloxane structure constituting the polysiloxane layer is 40 to 90%. Furthermore, it is more preferable that the average thickness of the polysiloxane layer is 5 to 100 nm. In the first invention of this application, it is preferable that the average particle thickness of the composite particles is 15 to 160 nm. In the present invention, it is preferable that the average aspect ratio of the composite particles is 20 to 400. In the present invention, it is preferable that 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. In the present invention, it is preferable that the hydrophilicity A, defined as the sum of (Q1 structure ratio having one -O-Si- bond per Si atom × 3) + (Q2 structure ratio having two -O-Si- bonds per Si atom × 2) + (Q3 structure ratio having three -O-Si- bonds per Si atom), is 10 to 80%. In the present invention, it is preferable that the composite particles further include a coating layer comprising at least one of a metal, a metal oxide, a metal hydrate, and a resin.

[0028] In the present invention, the metal pigment is preferably such 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 aqueous acrylic resin, 18 g of melamine resin, and 12 g of water is taken into a flask and the amount of hydrogen gas generated is measured in a constant temperature water bath at 60°C for up to 24 hours, the amount of gas generated is 10 ml or less. The metal pigment of the first invention of this application is preferably used in a metal pigment composition containing the metal pigment. The metal pigment of the first invention of this application is preferably used in an aqueous paint composition containing the metal pigment. The metal pigment of the first invention of this application is particularly preferably used in an aqueous metallic paint, and when 200 g of an aqueous metallic paint containing the metal pigment and 5% by mass or more of water is taken into 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 amount of gas generated is preferably 10 ml or less. The metal pigment of the first invention of this application is preferably used in an aqueous ink composition containing the metal pigment. The metal pigment of the first invention of this application is preferably used in a coating film containing the metal pigment.

[0029] Metal oxide coating layer In the first invention of this application, it is preferable that one or more coating layers constituting the composite particles include a metal oxide coating layer. The metal oxide coating that constitutes the metal oxide coating layer may be formed over the entire surface of the metal particles, or it may be formed only on a part of the surface. The metal oxide coating may be composed entirely of metal oxides, or it may be composed only of metal oxides and may contain components other than metal oxides. Details regarding the metal oxide coating layer and preferred forms of the metal oxide coating constituting it are the same as those described later in relation to the first and second embodiments of the first invention of this application. The one or more coating layers constituting the composite particles may have other coating layers (second coating layers) in addition to the metal oxide coating layer. Such second coating layers are the same as those described later in relation to the first and second embodiments of the first invention of this application.

[0030] Silicon compound-containing layer A silicon compound-containing layer is particularly preferred as the metal oxide coating layer. In other words, in the metal pigment of the first invention of this application, it is preferable that at least one 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 of the coating layers a silicon compound-containing layer, gas generation in the water-based paint can be suppressed, good storage stability can be obtained, and the water resistance when it is made into a coating film is excellent. Details such as preferred forms of the silicon-containing compound layer are the same as those described later in relation to the first and second embodiments of the first invention of this application.

[0031] Polysiloxane layer A polysiloxane layer is particularly preferred as the silicon compound-containing layer. Therefore, it is particularly preferable that the composite particles contained in the metal pigment of the first invention of this application have a structure in which metal particles are at the center and the metal particles are coated with polysiloxane. Polysiloxanes are composed of compounds containing siloxane bonds (Si-O-Si) consisting of silicon atoms (Si) and oxygen atoms (O). These compounds may be crystalline or amorphous, but amorphous is particularly preferred. Furthermore, polysiloxanes may be formed using organosilicon compounds (including silane coupling agents) as starting materials. In this case, organosilicon compounds or their derived components may be included to the extent that they do not impede the effects of the first invention of this application. In a typical example, polysiloxanes can be formed by hydrolyzing organosilicon compounds. The polysiloxane layer may contain additives, impurities, etc. other than silicon compounds, as long as they do not impair the properties of the first invention of this application. Details regarding the preferred form of the polysiloxane layer, etc., are the same as those described later in relation to the second invention of this application.

[0032] Particularly preferred embodiments of the present invention are the first and second embodiments, which are described in detail below. First aspect of the first invention The first aspect of the present invention is, A metal pigment (composition) comprising metal particles and composite particles having one or more coating layers on their surface, (1) The shape of the composite particles is flaky, (2) When the particle size distribution of the composite particles is measured using a laser diffraction particle size analyzer, the volume-based D 50 The size 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) A metal pigment (composition) characterized in that the proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less of the total number of composite particles. The following describes the components of the metal pigment (composition) of the first embodiment, as well as their details.

[0033] 1. Composite particles contained in the metal pigment composition The metal pigment composition according to the first aspect of the first invention of this application comprises composite particles including metal particles and one or more coating layers on their surfaces. In other words, in the description of the first aspect in this specification, the term "metal pigment composition" refers to a composition in which composite particles, including metal particles and one or more coating layers on their surfaces, are dispersed in a solvent containing water and / or a hydrophilic solvent, or in which the composite particles are accompanied by a solvent containing water and / or a hydrophilic solvent, and which may optionally contain other components. Furthermore, in the description of the first embodiment described herein, a composition obtained by adding a resin to a metal pigment composition may be referred to as a "resin composition" or a "resin composition containing a metal pigment composition" to distinguish it from the term "metal pigment composition."

[0034] metal particles The composite particles contained in the metal pigment composition according to the first aspect of the first invention of this application include metal particles and one or more coating layers formed on their surfaces. That is, one or more coating layers are formed on the surface of the metal particles that form 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 known or commercially available metal used as a metal pigment, such as aluminum, aluminum alloys, 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 elemental metals but also alloys and intermetallic compounds. Metal particles may be used individually or in combination of two or more types.

[0036] The average particle size of the metal particles is not particularly limited, but D in the particle size distribution of the composite particles described later. 50 The average particle size may be such that it can produce the following: That is, when the volume distribution is measured with a laser diffraction particle size analyzer in composite particles, D 50 The volume-average particle size (D) of the metal particles should be set to 0.1 to 30 μm. 50 You just need to set it to ). The average particle size of metal particles can be controlled in the process of grinding, sieving, and filtering atomized metal powder (e.g., aluminum powder) using a ball mill or the like, by appropriately adjusting the particle size of the atomized metal powder, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, and the degree of sieving and filtering.

[0037] The shape of the metal particles is not limited, but it is particularly desirable that they be flaky. This allows the composite particles contained in the metal pigment composition according to the first aspect of the first invention of this application to also have a flaky shape, resulting in a more reliable acquisition of high opacity and other properties. From this viewpoint, the aspect ratio (shape coefficient obtained by dividing the average particle size by the average thickness) of the flaky metal particles is preferably 1 to 1000, and more preferably 15 to 500. An aspect ratio of 1 or more of the metal particles allows for a higher degree of brilliance to be obtained. Furthermore, an aspect ratio of 1000 or less of the metal particles maintains the mechanical strength of the flakes and allows for a stable color tone to be obtained. Here, the average thickness of the metal particles used in the first aspect of the first invention of this application can be calculated from the water surface diffusion area and density of the metal particles.

[0038] Furthermore, the metal particles do not necessarily have to be composed solely of metal; as long as they do not hinder the effects of the first aspect of the first invention of this application, particles made of synthetic resin, or inorganic particles such as mica or glass whose surfaces are coated with metal can also be used. In the first aspect of the first invention of this application, it is particularly desirable that the particles be made of aluminum or an aluminum alloy, due to their high weather resistance, low specific gravity, and ease of availability.

[0039] Aluminum flakes, which are commonly used as metallic pigments, are particularly suitable as metal particles constituting the composite particles. Suitable aluminum flakes are those that possess the surface properties, particle size, and shape required for metallic pigments, such as surface gloss, whiteness, and brilliance. Aluminum flakes are usually commercially available in paste form. Paste-like aluminum flakes usually contain flaky aluminum powder, as well as residual mineral spirits (aliphatic hydrocarbons) and fatty acids used during pulverization, and organic solvents such as solvent naphtha and xylene. Paste-like aluminum flakes may be used as is, or the fatty acids on the surface may be removed beforehand with an organic solvent. Also, the volume average particle size (D 50So-called aluminum vapor-deposited foils having a diameter of 3 to 30 µm and an average thickness (t) of 5 to 50 nm can also be used.

[0040] Desired physical properties of metal pigments (compositions) 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, the volume-based D 50 is 0.1 to 30 µm. (3) The average thickness of the composite particles is 20 to 300 nm. (4) At least one of the coating layers 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 proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less relative to the total number of composite particles. Each of these physical property requirements will be described below.

[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-shaped). This allows a coating film formed using the metal pigment composition to exhibit high hiding power, brilliant luster, and the like. In the present specification, the statement that the shape of composite particles is "scaly" (flake-shaped) means that the average aspect ratio of the composite particles (a shape factor obtained by dividing the average particle diameter by the average thickness) is 5 or more. From the viewpoint of obtaining high hiding power and brilliant luster, the average aspect ratio of the scaly composite particles is preferably from 5 to 1000, and more preferably from 15 to 500. When the average aspect ratio is 5 or more, sufficient brilliant 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 these physical property requirements, "composite particles" refers to aggregates (assemblies) of multiple composite particles when they are aggregated and fixed together. Here, the average particle size used to calculate the average aspect ratio of the composite particles is the median diameter, which is a volume-based value D. 50 The requirements (2) will be discussed later. The average thickness used to calculate the average aspect ratio of the composite particles will be discussed later in relation to requirement (3).

[0042] (2) Volume-based D when measuring the particle size distribution of composite particles using a laser diffraction particle size analyzer 50 The size must be between 0.1 and 30 μm. Volume-based D when measuring the particle size distribution of composite particles using a laser diffraction particle size analyzer 50 The thickness is 0.1 to 30 μm. This allows the coating film formed using the metal pigment composition to exhibit high opacity and gloss, while also suppressing the aggregation of individual particles. This volume-based D 50 This is also commonly referred to as the median diameter. From the viewpoint of obtaining high concealment, glossiness, and low cohesiveness, the volume-based D when measuring the particle size distribution of composite particles with a laser diffraction particle size analyzer is used. 50 The particle size may preferably be 0.1 to 25 μm, more preferably 0.1 to 20 μm, even more preferably 0.1 to 15 μm, and particularly preferably 0.1 to 10 μm. Alternatively, from a similar viewpoint, the volume-based D when the particle size distribution of composite particles is measured using a laser diffraction particle size analyzer. 50 The particle size is 0.2 to 25 μm, more preferably 0.5 to 20 μm, even more preferably 1 to 20 μm, and even more preferably 3 to 20 μm. In these physical property requirements, "composite particles" refers to aggregates (assemblies) of multiple composite particles when they are aggregated and fixed together. Here, when the particle size distribution of composite particles is measured using a laser diffraction particle size analyzer, the volume-based D 50This refers to the particle size at which the cumulative percentage in the volume cumulative particle size distribution reaches 50%. While not particularly limited, the laser diffraction particle size analyzer can be used, such as the "LA-300" (manufactured by Horiba, Ltd.). Isopropyl alcohol or mineral spirits can be used as the measurement solvent. For example, a metal pigment composition containing composite particles of the sample is subjected to ultrasonic dispersion for 2 minutes as a pretreatment, then placed in a dispersion tank, and after confirming that it is properly dispersed, D 50 It can be measured. The particle size of composite particles in the resin composition described later cannot be measured by this method. Therefore, as an alternative method in this case, one can adopt a method in which composite particles in the resin composition are photographed from the surface of the coating film using an optical microscope, laser microscope, etc., and the particle size is determined by obtaining the distribution of equivalent circle diameters using commercially available image analysis software. Volume-based D of composite particles contained in the metal pigment composition 50 This can be controlled in the method for producing a metal pigment composition described later, by appropriately adjusting the particle size of the atomized metal powder raw material, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc. in the step of grinding and sieving / filtering the atomized metal powder raw material (e.g., aluminum powder) using a ball mill, etc., and by appropriately adjusting the type of organosilicon compound used, the pH, concentration, stirring temperature, stirring time, type of stirring device, and the power / degree of stirring (type and diameter of stirring blades, 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 needed).

[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 this application is 20 to 300 nm. This, combined with satisfying requirement (2) above, allows the coating film formed using the metal pigment composition to exhibit even higher opacity and gloss, and to further suppress the aggregation of individual particles. From the above viewpoint, the average thickness of the composite particles is preferably 20 to 300 nm, more preferably 20 to 250 nm, even more preferably 20 to 200 nm, and even more preferably 30 to 150 nm if opacity and high brightness are desired. In these physical property requirements, "composite particles" refers to aggregates (assemblies) of multiple composite particles when they are aggregated and fixed together. 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 a unit mass of dry composite particles when they are uniformly diffused on the water surface using the leafing phenomenon, covering it without any gaps. The water surface diffusion area can be measured according to the provisions of JIS K5906:1998. However, in the case of composite particles according to the first aspect of the first invention of this application, it may be difficult to determine the water surface diffusion area if the surface hydrophilicity is strong. 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) can be 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 average thickness of the composite particles can be determined 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 later, the process of grinding and sieving / filtering the raw material atomized metal powder (e.g., aluminum powder) using a ball mill or the like can be controlled by appropriately adjusting the particle size of the raw material atomized metal powder, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, and in the process of coating with a metal oxide film layer, preferably a silicon compound-containing layer (and other coating layers as needed), the type of organosilicon compound used, the pH, concentration, stirring temperature, stirring time, type of stirring device, and the power / degree of stirring (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) in the coating process (including the process of hydrolyzing the organosilicon compound if used).

[0044] (4) At least one layer of the coating layer is a metal oxide film layer, preferably a silicon compound-containing layer. In the metal pigment composition according to the first aspect of the first invention of this application, at least one 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 metal oxide film layer, preferably a silicon compound-containing layer. By making at least one of the coating layers a metal oxide film layer, preferably a silicon compound-containing layer, gas generation in the water-based paint can be suppressed, good storage stability can be obtained, and the resulting coating film has excellent water resistance. The coating layer of the composite particles may have other coating layers (second coating layers) in addition to the metal oxide film layer. Such second coating layers will be described further later. The metal oxide coating is a film composed of a layer containing metal oxide, and may be formed over the entire surface of the metal particles or on only a portion of the surface. The metal oxide coating may be composed entirely of metal oxides, or it may be composed only of metal oxides and may contain components other than metal oxides. The metal oxides that make up a metal oxide coating are compounds that contain oxygen and at least one metallic element as their constituent elements. Therefore, metal oxides may be metal oxides in the narrow sense, consisting only of oxygen and at least one metallic element as constituent elements. However, as long as they contain oxygen and at least one metallic element as constituent elements, they may also contain elements other than oxygen and the metallic element, such as metal hydroxides, oxide hydrates, or oxynitrides. They may also be compounds containing organic groups. Furthermore, the metal oxide may be a so-called single oxide, which consists of only one type of metal element, or it may be a composite oxide, which consists of two or more types of metal elements. The constituent elements of the metal oxide may be at least one metallic element, which may be a typical metal, a transition metal, or even a so-called metalloid. Among these, metal oxides with silicon as a constituent element are particularly suitable as metal oxides constituting the metal oxide coating layer (in this case, also corresponding to a silicon compound-containing layer). Suitable metal oxides for 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 these, 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 (which also fall under silicon compounds) can be used.

[0045] The silicon compound-containing layer, which is preferably used as a metal oxide film layer, is more preferably composed of a compound containing a Si-O bond (siloxane bond). Examples of such layers include a layer containing at least one silane compound and a silicon oxide. Examples of such compounds include silane compounds [H3SiO(H2SiO)] nExamples of silicon oxides include SiH3 (where n is any positive integer), SiO2, SiO2·nH2O (where n is any positive integer), and others. These silane compounds and silicon oxides may be crystalline or amorphous, but amorphous is particularly preferred. Therefore, as a layer containing silicon oxide (silica, etc.), a layer containing amorphous silica, for example, can also be suitably adopted.

[0046] Furthermore, the layer composed of a compound containing a 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, to the extent that it does not impede the effects of the first embodiment of the first invention of this application. In a typical example, the layer composed of a compound containing a Si-O bond can be formed by hydrolysis of an organosilicon compound.

[0047] The silicon compound-containing layer may also contain additives, impurities, etc. other than silicon compounds, as long as they do not impair the properties of the first embodiment of the first invention of this application.

[0048] The silicon content in the silicon compound-containing layer is not particularly limited, but is preferably 1 to 30 parts by mass per 100 parts by mass of metal particles, and more preferably 2 to 20 parts by mass. A silicon content of 1 part by mass or more per 100 parts by mass of metal particles can maintain high corrosion resistance, water dispersibility, and stability of the metal pigment composition. A silicon content of 30 parts by mass or less per 100 parts by mass of metal particles can prevent aggregation of composite particles and a decrease in color tone, such as opacity and metallic luster.

[0049] The coating layer of the composite particles contained in the metal pigment composition according to the first aspect of the first invention of this application is preferably hydrophilic. The composite particles usually form a metal pigment composition in which they are dispersed in an aqueous solvent (water or a mixed solvent containing water and an organic solvent), but if the coating layer has a hydrophilic surface, the composite particles can be highly dispersed in such an aqueous solvent. Moreover, since silicon oxides (such as amorphous silica) are very stable in aqueous solvents, it is possible to provide a metal pigment composition containing composite particles that are highly stable in an aqueous solvent. From this viewpoint, in the composite particles contained in the metal pigment composition according to the first aspect of the first invention of this 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 Si-O bonds). When the coating layer is composed of multiple 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 a Si-O-based coating layer) may be formed separately as a layer other than the outermost layer.

[0050] The thickness of the coating layer for individual composite particles 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. It is generally desirable that the thickness of the coating layer be in the range of approximately 1 to 50 nm (especially 1 to 30 nm, and even 1 to 20 nm). A coating layer thickness of 1 nm or more provides sufficient water resistance, and a coating film can be obtained in which corrosion or discoloration of metal particles in water-based paints is suppressed. On the other hand, a coating layer thickness of approximately 50 nm or less allows for the maintenance of high levels of brightness, clarity, and opacity of the coating film.

[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 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, may usually be in the range of 1 to 20 nm, and is particularly preferably in the range of 1 to 15 nm.

[0052] Specific examples of organosilicon compounds that can be preferably used in the first aspect of the first invention of this application will be further described below, but organosilicon compounds are not limited to these specific examples. The organosilicon compound may contain at least one organosilicon compound represented by the following general formula (1), a silane coupling agent represented by any 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 R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 1 (They may be entirely identical, partially identical, or entirely different.) R 2 m Si(OR 3 ) 4-m ... (2) (In the formula, R 2 R is a hydrogen atom, or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group. 3 R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 2 and R 3 They may be the same or different, R 2 , or R 3 If there are two or more of these, they may be all identical, partially identical, or all different. (1 ≤ m ≤ 3.) R 4 p R 5 q Si(OR 6 ) 4-p-q ... (3) (In the formula, R 4 R is a group containing a reactive group that can chemically bond with other functional groups, 5 R is a hydrogen atom, or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group. 6 R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 4 , R 5 , or R 6If there are two or more of these, they may all be identical, partially identical, or all different. (1 ≤ p ≤ 3, 0 ≤ q ≤ 2, and 1 ≤ p + q ≤ 3.) R 7 r SiCl 4-r ... (4) (In the formula, R 7 R is a hydrogen atom, or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group. 7 If there are two or more of these, they may all be identical, partially identical, or completely different. (0 ≤ r ≤ 3.)

[0054] R in equation (1) 1 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, and octyl, which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Also, four R 1 They may be entirely identical, partially identical, or entirely different. Preferred examples of organosilicon compounds of formula (1) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane. Among these, tetraethoxysilane is particularly preferred.

[0055] R in equation (2) 2 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear, and may contain halogen groups such as fluorine, chlorine, and bromine. Among these, hydrocarbon groups having 1 to 18 carbon atoms are particularly preferred. Also, R 2 If there are two or more of them, they may all be identical, partially identical, or all different. R in the molecule 2 In equation (2), the number of elements is m = 1 to 3, i.e., 1 to 3, but it is more preferable that m = 1 or 2. R in equation (2)3 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, and octyl, which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Also, R 3 If there are two or more of them, they may all be identical, partially identical, or completely different. Preferred examples of organosilicon compounds of formula (2) (silane coupling agents) 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, octyl Examples include riethoxysilane, dioctyldimethoxysilane, dioctyldiethoxysilane, dioctylethoxybutoxysilane, decyltrimethoxysilane, decyltriethoxysilane, didecyldimethoxysilane, didecyldiethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, dioctadecyldimethoxysilane, dioctadecyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, and 3-chloropropyltributoxysilane.

[0056] R in equation (3)4 Examples of reactive groups that can chemically bond with other functional groups include vinyl groups, epoxy groups, styryl groups, methacryloxy groups, acryloxy groups, amino groups, ureido groups, mercapto groups, polysulfide groups, and isocyanate groups. Also, R 4 If there are two or more of them, they may all be identical, partially identical, or all different. R in the molecule 4 The number of elements in equation (3) is from p=1 to 3, i.e., 1 to 3, but it is more preferable that p=1. R in equation (3) 5 Examples of hydrocarbon groups include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear, and may contain halogen groups such as fluorine, chlorine, or bromine. Among these, hydrocarbon groups with 1 to 18 carbon atoms are particularly preferred. Also, R 5 If there are two or more of them, they may all be identical, partially identical, or completely different. R in equation (3) 6 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, and octyl, which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Also, R 6 If there are two or more of them, they may all be identical, partially identical, or completely different.

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

[0058] R in equation (4) 7 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear, and may contain halogen groups such as fluorine, chlorine, and bromine. Among these, hydrocarbon groups having 1 to 12 carbon atoms are particularly preferred. Also, R 7If there are two or more of them, they may all be identical, partially identical, or all different. R in the molecule 7 In equation (4), the number of elements is r = 0 to 3, i.e., 0 to 3, but it is more preferable that r = 1 to 3. Preferred examples of organosilicon compounds (silane coupling agents) of formula (4) include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, octyldimethylchlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, and tetrachlorosilane.

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

[0060] Hydrolyzed products of organosilicon compounds and / or condensed products thereof are obtained by stirring and mixing the organosilicon compound with the amount of water necessary for the hydrolysis reaction and a hydrolysis catalyst. A hydrophilic solvent may also be used as needed. The conditions for the hydrolysis reaction (i.e., the reaction for forming the silicon compound-containing layer) will be described later.

[0061] For hydrolysis and / or condensation reactions to obtain hydrolysates and / or condensation products of organosilicon compounds, partially condensed oligomers may be used as raw materials. The condensation reaction of the hydrolyzed product of the organosilicon compound may be carried out simultaneously with the hydrolysis reaction of the organosilicon compound, or it may be carried out in separate steps, with the catalyst changed if necessary. In this case, heating may be added 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 this application is not particularly limited except that at least one layer is a metal oxide film layer, preferably a silicon compound-containing layer, but a coating layer other than the aforementioned metal oxide film layer, preferably a silicon compound-containing layer (hereinafter referred to as the "second coating layer") may be formed as needed. The second coating layer may consist of at least one of the following: metals (alkali metals; alkaline earth metals; such as manganese, iron, cobalt, nickel, copper, silver, etc.), metal oxides (such as titanium oxide, zirconium oxide, iron oxide, etc.), metal hydrates, and resins (such as synthetic resins like acrylic resin, alkyd resin, polyester resin, polyurethane resin, polyvinyl acetate resin, nitrocellulose resin, and fluororesin). For example, a molybdenum-containing film or a phosphate compound film can be formed as the second coating layer. By providing the second coating layer, the corrosion resistance of the metal particles can be improved, and the formation of a metal oxide film layer, preferably a silicon compound-containing layer, can be promoted. The second coating layer is preferably formed (if formed) between the metal particles and the metal oxide film layer, preferably the silicon compound-containing layer. Therefore, for example, a layer configuration of "metal particles / second coating layer / metal oxide film layer, preferably the silicon compound-containing layer" can be suitably adopted. While not particularly limited, examples of molybdenum-containing coatings include those disclosed in Japanese Patent Application Publication No. 2003-147226, International Publication No. 2004 / 096921, Japanese Patent No. 5979788, and Japanese Patent Application Publication No. 2019-151678. An example of a phosphate compound coating is the one disclosed in Japanese Patent Application Publication No. 4633239. A preferred example of a molybdenum-containing substance constituting the molybdenum-containing coating is the mixed-coordination type heteropolyanion compound disclosed in Japanese Patent Application Publication No. 2019-151678. In another variant, the second coating layer may be formed outside the metal particles and 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 or phosphate compounds) may be incorporated together with the metal oxide, preferably the silicon compound, within the metal oxide film layer, preferably the silicon compound-containing layer.

[0063] The mixed-coordinate heteropolyanion compounds used in the manner in which a second coating layer (typically a molybdenum-containing coating) 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 this application are formed are not particularly limited, but the following are specific examples.

[0064] Mixed-coordinate heteropolyanion compounds that can be used have a structure in which some of the poly atoms of a heteropolyanion composed of one element are substituted with other elements, and exhibit different physical properties from a mixture of each heteropolyanion.

[0065] When expressed using a chemical formula, mixed-coordinate heteropolyanions are represented as [X p M q N r O s ] t If expressed as such, the heteropolyanion is [X p M q O s ] t And further, isopolyanion [M q O s ] t It is also distinguished as such. However, the heteroatom X represents elements of the IIIB, IVB, and VB groups such as B, Si, Ge, P, and As, with B, Si, and P being preferred among them. The polyatoms M and N represent transition metals such as Ti, Zr, V, Nb, Ta, Mo, and W, with Ti, Zr, V, Nb, Mo, and W being preferred. Furthermore, p, q, r, and s represent the number of atoms, and t represents the oxidation number. Since heteropolyanion compounds have numerous structures, mixed-coordination type heteropolyanion compounds can have even more structures. Representative and preferred mixed-coordination type heteropolyanion compounds include the following mixed-coordination type heteropolyacid: H3PW x Mo 12-x O 40 ·nH2O (phosphotungstomolybdic acid n-hydrate), H 3+x PV x Mo 12-x O 40 ·nH2O (phosphovanadomolybdic acid n-hydrate), H4SiW x Mo 12-x O 40 ·nH2O (silicotungstomolybdic acid n-hydrate), H 4+x SiV x Mo 12-x O 40 ·nH2O (silicovanadomolybdic acid n-hydrate), etc. are exemplified. (provided that 1≤x≤11, n≥0)

[0066] As preferred specific examples among these heteropolyanion compounds, H3PW3Mo9O 40 ·nH2O, H3PW6Mo6O 40 ·nH2O, H3PW9Mo3O 40 ·nH2O, H4PV1Mo 11 O 40 ·nH2O, H6PV3Mo9O 40 ·nH2O, H4SiW3Mo9O 40 ·nH2O, H4SiW6Mo6O 40 ·nH2O, H4SiW9Mo3O 40 ·nH2O, H5SiV1Mo 11 O 40 ·nH2O, H7SiV3Mo9O 40 ·nH2O, and other mixed-coordination type heteropolyacids are exemplified. (provided that 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 using mixed-coordinate heteropolyanionic compounds in the form of salts with a specific cation as a counterion, the counter-cation source can be at least one selected from, for example, 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 organic components such as amine compounds. Among the inorganic components, salts of alkali metals, alkaline earth metals, and ammonia are preferred. Furthermore, when at least one selected from these alkali metals, alkaline earth metals, and ammonia is used as the countercation source, H3PW x Mo 12-x O 40 nH2O (phosphotungstomolybdic acid n-hydrate), H 3+x PV x Mo 12-x O 40 nH2O (Limvanadomolybdate n-hydrate), H4SiW x Mo 12-x O 40 • nH2O (silicic acid gustomolybdic acid n-hydrate), H 4+x SIV x Mo 12-x O 40 It is more preferable to use it in the form of a salt with at least one selected from nH2O (silica domolybdate n-hydrate).

[0068] Furthermore, amine compounds, which are organic components, are also preferably used as countercation sources for mixed-coordinate heteropolyanion compounds, and a specific example is one represented by the following general formula (5).

[0069] (R 8 -N(-R 10 )-) n -R 9 ... (5) (In the formula, R 8 , R 9 and R 10The hydrogen atoms may be the same or different, and are monovalent or divalent hydrocarbon groups having 1 to 30 carbon atoms, which may optionally contain ether bonds, ester bonds, hydroxyl groups, carbonyl groups, or thiol groups, and optionally R 8 and R 9 They may together form a 5-membered or 6-membered cycloalkyl group, or form a 5-membered or 6-membered ring that can additionally contain nitrogen or oxygen atoms as a bridging member, or optionally R 8 , R 9 and R 10 They may come together to form a multi-membered polyring that may contain one or more additional nitrogen and / or oxygen atoms as bridging members. 8 , R 9 and R 10 (They cannot simultaneously become hydrogen atoms. n represents an integer between 1 and 2.)

[0070] The above amine compounds that serve as countercation sources for mixed-coordinate heteropolyanion compounds include, specifically, 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 dibranched tridecylamine; asymmetric secondary amines such as N-methylbutylamine, N-ethylbutylamine, N-ethylhexylamine, N-ethyllaurylamine, N-ethylstearylamine, N-isopropyloctylamine, and N-isobutyl-2-ethylhexylamine; and trimethylamine and triethylamine. In addition to linear tertiary amines such as tripropylamine, tributylamine, trioctylamine, trilaurylamine, tritridecylamine, and tristearylamine; branched tertiary amines such as triisopropylamine, triisobutylamine, tri-2-ethylhexylamine, and tribranched tridecylamine; and tertiary amines having mixed hydrocarbon groups such as N,N-dimethyloctylamine, N,N-dimethyllaurylamine, N,N-dimethylstearylamine, and N,N-diethyllaurylamine, allyl Amines, including alkenyl amines such as diallylamine, triallylamine, and N,N-dimethylallylamine; alicyclic primary amines such as cyclohexylamine and 2-methylcyclohexylamine; primary amines with aromatic ring substituents such as aniline, benzylamine, and 4-methylbenzylamine; alicyclic secondary amines such as N,N-dicyclohexylamine and N,N-di-2-methylcyclohexylamine; and secondary amines with 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, and N-2-ethylhexylbenzylamine; alicyclic tertiary amines such as N,N-dimethylbenzylamine, N,N-dimethylcyclohexylamine, and tricyclohexylamine; tertiary amines with aromatic ring substituents such as tribenzylamine and tri-4-methylbenzylamine; amines with ether linkages such as morpholine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-butoxypropylamine, 3-decyloxypropylamine, and 3-lauryloxypropylamine; monoethanolamine, diethanolamine, monoisopropanolamine, monopropanolamine, butanolamine, triethanolamine, N,N-dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, and N-butylethanol Alkanolamines such as amines, N-cyclohexyl-N-methylaminoethanol, N-benzyl-N-propylaminoethanol, or N-hydroxyethylpyrrolidine, N-hydroxyethylpiperazine, N-hydroxyethylmorpholine; ethylenediamine, N-methylethylenediamine, N,N'-dimethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, 1,2-propanediamine, 1,3-propanediamine, N,N-dimethyl-1,3-propanediamine, N- Examples include diamines such as cyclohexyl-1,3-propanediamine, N-decyl-1,3-propanediamine, and N-isotridecyl-1,3-propanediamine; cyclic amines such as N,N'-dimethylpiperazine, N-methoxyphenylpiperazine, N-methylpiperidine, N-ethylpiperidine, quinuclidine, diazabicyclo[2,2,2]octane, and 1,8-diazabicyclo[5,4,0]-7-undecene; aromatic amines such as pyridine and quinoline, or any mixture thereof.

[0071] Preferred specific examples among these amine compounds include at least one selected from primary, secondary, or tertiary linear or branched alkyl amines or alkanolamines having 4 to 20 carbon atoms, such as 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 the amine compounds represented by these general formulas (5), and H3PW x Mo 12-x O 40 nH2O (phosphotungstomolybdic acid n-hydrate), H 3+x PV x Mo 12-x O 40 nH2O (Limvanadomolybdate n-hydrate), H4SiW x Mo 12-x O 40 • nH2O (silicic acid gustomolybdic acid n-hydrate), H 4+x SIV x Mo 12-x O 40 It is more preferable to use it in the form of a salt with at least one selected from nH2O (silica domolybdate n-hydrate). Among the mixed-coordinate heteropolyanion compounds mentioned above, H3PW x Mo 12-x O 40 nH2O (phosphotungstomolybdic acid n-hydrate), H 3+x PV x Mo 12-x O 40 nH2O (Limvanadomolybdate n-hydrate), H4SiW x Mo 12-x O 40 Mixed-coordinate heteropoly acids of nH2O (silicon gustomolybdic acid n-hydrate), or organic amine salts of these mixed-coordinate heteropoly acids, are most preferred.

[0072] The second coating layer, other than the metal oxide film layer, preferably the silicon compound-containing layer, of the composite particles in the metal pigment composition according to the first aspect of the first invention of this application, 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 added corrosion inhibitor is not particularly limited, and any known corrosion inhibitor can be used. The amount used should be within a range that does not hinder the desired effect of the first aspect of the first invention of this application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organophosphorus compounds, and metal salts of molybdic acid.

[0073] From the viewpoint of adhesion and chemical resistance when a coating film is formed, organic oligomers or polymers may be further contained in 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. Furthermore, the composite particles may contain, from the viewpoint of storage stability, at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (or phosphate) esters and their salts, in the metal oxide film layer, 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 Japanese Patent Application Publication No. 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 this application, the proportion of bent composite particles is 10% or less. This, combined with the satisfaction of the above requirements, allows the coating film formed using the metal pigment composition to exhibit even higher opacity and gloss. The proportion of bent composite particles is understood to be an indicator related to the degree of deformation or damage of the composite particles. If the proportion of bent composite particles is 10% or less, the degree of deformation or damage of the composite particles is small, which increases the projected area of ​​the particles when formed into a coating film and makes it easier for them to orient parallel to the coating film surface, thereby enabling high opacity and excellent gloss. Furthermore, by reducing the proportion of untreated surface on the coating film surface formed using the metal pigment composition, an improvement in the water resistance of the coating film can also be expected. In these physical property requirements, "composite particles" refers to aggregates (assemblies) of multiple composite particles when they are aggregated and fixed together. The proportion of bent composite particles in the metal pigment composition should be as low 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. The proportion of bent composite particles in a metal pigment composition can be measured in detail according to the method described in the examples below. Specifically, a film (thin film) can be formed using a metal pigment composition in which 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 using a scanning electron microscope (SEM). In this case, for each composite particle, deformation is judged to exist if the shortest distance to both ends of the particle is 0.8 times or less of the particle length, and the proportion of deformed particles is calculated by observing 300 or more, preferably 500 or more, and this can be taken as the proportion of bent composite particles. When observing, particles with a particle diameter in the range of 90% from the center when the particle size distribution is measured should be targeted. The proportion of bent composite particles in a metal pigment composition can be controlled mainly by appropriately adjusting the stirring time, type of stirring device, stirring power / degree (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) during the process of coating a metal oxide film layer, preferably a silicon compound-containing layer (and other coating layers as needed).

[0075] (6) The proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less of the total number of composite particles. In the metal pigment composition according to the first aspect of the first invention of this application, the proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less of the total number of composite particles. As a result, in conjunction with satisfying the above requirements, the coating film formed using the metal pigment composition can exhibit even higher opacity and luster, and the aggregation of individual particles can be further suppressed. The proportion 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, i.e., the degree of aggregation. If the proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less of the total number of composite particles, the orientation of the composite particles in the coating film is orderly, and the proportion of composite particles that are aligned parallel to the surface of the coating film increases. As a result, the projected area of ​​the composite particles in the coating film formed using the metal pigment composition increases, improving opacity and luster, and it is thought that the aggregation of individual particles is further reduced as it becomes easier to form a uniform and sufficient coating on individual particles. Furthermore, by reducing the proportion of aggregates where four or more composite particles are bonded together, it is possible to effectively prevent the collapse of aggregates of composite particles once formed in the water-based paint, exposing the untreated surface and reacting with water, the solvent of the water-based paint, to generate hydrogen gas. The proportion of aggregates in a metal pigment composition where four or more composite particles are fixed to each other is preferably 30% or less, more preferably 20% or less, even more preferably 15% or less, even more preferably 10% or less, and most preferably 5% or less. The lower this proportion is, the better, but it is not easy to make it completely zero. In this physical property requirement, "composite particle" refers to individual composite particles, unlike the physical property requirements (1) to (3) and (5) above, even when multiple composite particles are aggregated and fixed together. Furthermore, in this physical property requirement, "aggregate" refers to a state in which multiple composite particles are aggregated and fixed together. The proportion of aggregates in a metal pigment composition where four or more composite particles are bonded to each other can be measured in detail according to the method described in the examples below. Specifically, a film (thin film) can be 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 using a scanning electron microscope (SEM). At that time, for each composite particle, the presence or absence of aggregation can be determined according to the following criteria: a) if the minimum distance d between the surfaces of the base metal (metal particles) of the composite particle in question is 2 times or more the average thickness t of the coating layer, then aggregation has occurred; or b) if the minimum distance d between the surfaces of the base metal (metal particles) of the composite particle in question is less than 2 times the average thickness t of the coating layer, then aggregation has occurred. By observing 300 or more, preferably 500 or more, composite particles, the proportion of composite particles in which four or more are bonded to each other (aggregated) can be calculated and this can be taken as the proportion of aggregates in which four or more composite particles are bonded to each other. The average thickness of the coating layer here refers to the average thickness of the coating layer at any arbitrary location of 50 particles, preferably 100 particles. The ratio of aggregates in which four or more composite particles are fixed to each other to the total number of composite particles in a metal pigment composition can be controlled mainly by appropriately adjusting the stirring time, type of stirring device, stirring power / degree (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) during the process of coating with a metal oxide film layer, preferably a silicon compound-containing layer (and other coating layers as needed).

[0076] 2. Method for producing a metal pigment composition A metal pigment composition according to the first aspect of the first invention of this application can be suitably produced by a manufacturing method that includes, for example, forming flake-shaped metal particles using a method commonly used in the pigment industry, producing metal particles through processes such as sieving (classification), filtration, washing, and mixing, and then 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 are listed, but are not limited thereto.

[0077] A metal pigment composition according to the first aspect of the first invention of this application can be suitably produced, for example, when the metal oxide film layer is a silicon compound-containing layer, by a method including a step of forming a silicon compound-containing layer on the surface of metal particles by hydrolyzing / (partially) condensing the organosilicon compound in a mixture 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 other optional components as needed. This step can usually be carried out under stirring.

[0078] Grinding and sieving / filtration process Here, we will explain using the case where aluminum powder is used as the metal particle. Aluminum powder is generally obtained by grinding atomized aluminum powder and / or aluminum foil using methods commonly used in the pigment industry, such as the dry ball mill method, wet ball mill method, attritor method, and stamp mill method, in the presence of grinding aids and inert solvents to form so-called flakes. After this process, it is further obtained by performing necessary steps such as sieving (classification), filtration, washing, and mixing. Examples of grinding aids used here include fatty acids, aliphatic amines, aliphatic amides, and aliphatic alcohols. Generally, oleic acid, stearic acid, and stearylamine are preferred. Examples of inert solvents include hydrophobic substances such as mineral spirits, solvent naphtha, LAWS, HAWS, toluene, and xylene, which can be used alone or in combination. The grinding aids and inert solvents are not limited to these. As for the grinding process, from the viewpoint of preventing dust explosions and ensuring safety, grinding by the wet ball mill method is preferred.

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

[0080] Below, as a preferred example of the process for forming the metal oxide film layer, the process for forming the silicon compound-containing layer will be described. Process for forming a silicon compound-containing layer The mixture containing (a) metal particles, (b) a silicon-containing raw material comprising at least one organosilicon compound, and (c) a solvent, as well as other optional components as needed, can be prepared by mixing these components. The order of mixing is not particularly limited.

[0081] As the metal particles, the metal particles described above can be used, but aluminum or aluminum alloy particles are particularly suitable. Furthermore, as described above, it is preferable to use flaky metal particles. Known or commercially available metal particles (typically paste-like aluminum flakes) can be used.

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

[0083] As the silicon-containing raw material, organosilicon compounds are used. While not limited to specific types, those described above are preferably used as organosilicon compounds. An organosilicon compound represented by formula (1) above (typically tetraalkoxysilane) and / or its condensate, and at least one of the silane coupling agents represented by any of the formulas (2) to (4) above can be suitably used. In the following, we will explain using the case where tetraalkoxysilane is used as the organosilicon compound represented by formula (1) above as an example. In the following, tetraalkoxysilane and / or its condensates may be collectively referred to simply as "tetraalkoxysilane."

[0084] When using a tetraalkoxysilane represented by formula (1) above and a silane coupling agent represented by any of formulas (2) to (4) above in combination, a method of mixing the two (referred to as the "first method") can be adopted. Alternatively, a method (referred to as the "second method") can be adopted, which includes the step of treating metal particles with one of the agents to form a first silicon compound-containing layer, and then treating them with the other agent to form a second silicon compound-containing layer.

[0085] One first method is a method that includes the step of forming a silicon compound-containing layer by appropriately adjusting the pH of a mixed solution containing metal particles, a tetraalkoxysilane represented by formula (1) above, and a silane coupling agent represented by any of the formulas (2) to (4) above, thereby causing a hydrolysis / condensation reaction of the tetraalkoxysilane and the silane coupling agent.

[0086] As a second method, for example, a method is provided that includes the steps of: adjusting the pH of a mixture containing metal particles and a tetraalkoxysilane represented by formula (1) above to hydrolyze / condense the tetraalkoxysilane, thereby forming a first silicon compound-containing layer (for example, a silica film made of amorphous silica) on the surface of the metal particles; and adjusting the pH of a mixture containing metal particles and a silane coupling agent represented by any of the formulas (2) to (4) above to hydrolyze / condense the silane coupling agent, thereby forming a second silicon compound-containing layer on the surface of the first silicon compound-containing layer.

[0087] The amount of tetraalkoxysilane or its condensate represented by formula (1) above can be appropriately set depending on the type of tetraalkoxysilane used. The amount used may be 2 to 200 parts by mass, and more preferably 5 to 100 parts by mass, per 100 parts by mass of metal particles (solid content), from the viewpoint of coating effect and from the viewpoint of suppressing aggregation of metal particles or reduction of glossiness.

[0088] The amount of silane coupling agent represented by any of the above formulas (2) to (4) is not particularly limited, but is usually about 0.1 to 20 parts by mass per 100 parts by mass of metal particles (solids), and is particularly preferably 1 to 10 parts by mass. By using an amount of about 0.1 to 20 parts by mass, the desired coating effect and desirable coating film properties can be obtained.

[0089] The solvent in the mixture, i.e., the solvent for the hydrolysis and / or condensation reaction of the organosilicon compound, can be appropriately selected depending on the type of silicon-containing raw material used, but usually water, a hydrophilic organic solvent, or a mixture thereof can be used. By using these solvents, the uniformity of the reaction and the uniformity of the resulting hydrolysate and / or condensation product can be improved. In embodiments in which the silicon compound-containing layer is formed directly on metal particles, it is particularly preferable that the solvent in the mixture contains a hydrophilic organic solvent from the viewpoint of avoiding the rapid reaction between the metal particles and water. In the first aspect of the first invention of this application, a mixture of water and a hydrophilic organic solvent can be suitably used.

[0090] Examples of hydrophilic organic solvents are not particularly limited, but include alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol; ether alcohols and their esters such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. These can be used individually or in combination of two or more.

[0091] Furthermore, when a mixed solvent of water and a hydrophilic organic solvent is used as the solvent, the ratio of the two is not particularly limited. In embodiments in which a silicon compound-containing layer is formed directly on metal particles, from the viewpoint of avoiding a rapid reaction between the metal particles and water, it is preferable that the water content be 20% by mass or less, with the total of the two being 100% by mass, before adding the silicon compound. In this case, there is no lower limit to the water content, but it is usually sufficient to set it to about 1% by mass.

[0092] The amount of solvent used in the silicon compound-containing layer formation process (excluding the amount of solvent used for pre-dispersion of metal particles, if applicable) is not limited, but is usually sufficient to be around 100 to 10,000 parts by mass per 100 parts by mass of metal particles (solid content), and is particularly preferable to be 200 to 1,000 parts by mass. Using 100 parts by mass or more of solvent suppresses the increase in viscosity of the mixture (slurry) and allows for appropriate stirring. Using 10,000 parts by mass or less of solvent can prevent high costs for recovering and regenerating the processed liquid. Note that, in the case of the second method described above, the amount of solvent used refers to the total amount of solvent used for forming the first silicon compound-containing layer and the second silicon compound-containing layer.

[0093] In the above-mentioned mixture, other additives may be added as needed, within the limits that do not impede the effects of the first embodiment of the first invention of this application. Examples include catalysts such as hydrolysis catalysts and dehydration condensation catalysts, as well as surfactants, metal corrosion inhibitors, and the like.

[0094] Among these, hydrolysis catalysts can be suitably used. By incorporating a hydrolysis catalyst, the pH of the mixture can be adjusted, and the organosilicon compounds can be efficiently hydrolyzed and dehydrated, resulting in the efficient and reliable formation of a silicon compound-containing layer on the surface of the metal particles.

[0095] The hydrolysis catalyst can be any known or commercially available one and is not particularly limited. Examples of hydrolysis catalysts include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; organic acids such as benzoic acid, acetic acid, chloroacetic acid, salicylic acid, oxalic acid, picric acid, phthalic acid, and malonic acid; and phosphonic acids such as vinylphosphonic acid, 2-carboxyethanephosphonic acid, 2-aminoethanephosphonic acid, and octanephosphonic acid. These hydrolysis catalysts may be used individually or in combination of two or more. Furthermore, as hydrolysis catalysts, examples of 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 can also be used. These hydrolysis catalysts can be used individually or in combination of two or more.

[0096] The amount of hydrolysis catalyst added is not particularly limited, but is usually 0.01 to 20 parts by mass per 100 parts by mass of metal particles (solid content), and is particularly preferably 0.02 to 10 parts by mass. An amount of 0.01 parts by mass or more ensures sufficient deposition of the silicon compound-containing layer. An amount of 20 parts by mass or less effectively suppresses aggregation of metal particles.

[0097] When preparing the above mixture, it is sufficient to mix each of these components uniformly in the mixture, and there are no particular restrictions on the order in which they are added. In the production of a metal pigment composition according to the first aspect of the first invention of this application, which has a silicon compound-containing layer, it is preferable that the preparation of the above-mentioned mixture be carried out under stirring of a moderate intensity.

[0098] The temperature of the mixture can be at room temperature or under heating. Generally, the temperature of the mixture should be between 20 and 90°C, and it is particularly preferable to control it within the range of 30 to 80°C. A temperature of 20°C or higher increases the formation rate of the silicon compound-containing layer, thereby shortening the processing time. On the other hand, a temperature of 90°C or lower makes it easier to control the reaction, thereby increasing the probability of obtaining the desired composite particles.

[0099] The stirrer used to agitate the mixture is not particularly limited, and any known stirrer capable of efficiently and uniformly agitating a mixture containing aluminum particles and organosilicon compounds can be used. Specific examples include kneaders, mixing machines, rotary vessel stirrers, agitated reaction vessels, V-type stirrers, double-cone stirrers, screw mixers, sigma mixers, flash mixers, airflow stirrers, ball mills, edge runners, etc. Further explanation of stirrers will be given later.

[0100] When stirring a mixture containing metal particles and organosilicon compounds, the temperature of the mixture should generally be around 10 to 100°C, and preferably 30 to 80°C. A temperature of 10°C or higher allows for a shorter reaction time to obtain sufficient processing effect. Furthermore, a temperature of 100°C or lower makes it easier to control the reaction to obtain the desired metal pigment composition.

[0101] The stirring time of the mixture is not particularly limited, as long as it is sufficient time for the desired silicon compound-containing layer to form. This stirring time is preferably, for example, 0.5 to 10 hours, and more preferably 1 to 5 hours. A stirring time of 0.5 hours is sufficient to obtain the desired treatment effect. Furthermore, a stirring time of 10 hours or less can suppress an increase in treatment costs.

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

[0103] When adjusting the pH, the pH value of the mixture changes, especially when the silicon compound-containing layer is formed on the surface of the metal particles (or via the second coating layer). Therefore, it is desirable to adjust the pH appropriately so that it can be maintained within a certain range. In this case, it is desirable to adjust the pH value by adding a hydrolysis catalyst, but the pH value may also be adjusted using other acidic or alkaline compounds, as long as the properties of the metal pigment composition in the first embodiment of the first invention of this application, which has a silicon compound-containing layer, are not impaired.

[0104] When using a basic hydrolysis catalyst, the pH value is preferably 7 to 13, more preferably 7 to 11, and even more preferably 7.5 to 10. A pH value of 7 or higher allows for the rapid formation of a silicon compound-containing layer. On the other hand, a pH value of 13 or lower can suppress the aggregation of metal particles and the decrease in luster, and can also prevent the generation of hydrogen gas due to corrosion.

[0105] When an acidic hydrolysis catalyst is used as the hydrolysis catalyst, the pH value is preferably 1.5 to 7, more preferably 1.5 to 6, even more preferably 2 to 4, and particularly preferably 2 to 3. A pH value of 1.5 or higher allows for appropriate control of the reaction, making it easy to obtain a metal pigment composition containing the desired composite particles. On the other hand, a pH value of 7 or lower allows for maintaining a high deposition rate of the silicon compound-containing layer.

[0106] Regardless of whether the first method or the second method described above is employed, 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, and more preferably 1 to 30 parts by mass, based on 100 parts by mass of metal particles (solid content), in terms of the equivalent weight after completion of the hydrolysis and condensation reactions. Further, the silane coupling agent represented by any one of the above general formulas (2) to (4), and / or the hydrolyzate derived from a partial condensate thereof and / or the condensate thereof, 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, based on 100 parts by mass of metal particles (solid content), in terms of the equivalent weight after completion of the hydrolysis and condensation reactions.

[0107] The added amount of the hydrolyzate and / or condensate of the organosilicon compound represented by general formula (1) can be calculated by multiplying the mass of the organosilicon compound represented by general formula (1) used in producing the metal pigment composition by the mass ratio before and after the reaction when all of the organosilicon compound undergoes hydrolysis and condensation reaction. For example, when tetraethoxysilane (TEOS) is used as the organosilicon compound represented by general formula (1), the added amount of the hydrolyzate and / or condensate of the organosilicon compound can be calculated using the mass ratio before and after the following hydrolysis and condensation reactions. (Hydrolysis) Si(OC2H5)4 (molecular weight: 208) + 4H2O → Si(OH)4 (molecular weight: 96) + (C2H5OH)4 (Condensation) Si(OH)4 (molecular weight: 96) + Si(OH)4 (molecular weight: 96) → (SiO2)2 (molecular weight: 60×2) + 4H2O Before and after the above hydrolysis and condensation reactions, the mass becomes 60 / 208 = 0.288 times the original mass. Therefore, for example, when 10 parts by mass of TEOS is used relative to 100 parts by mass of metal particles (solid content), the added amount of the hydrolyzate and / or condensate thereof is 0.288 times that amount, that is, 2.88 parts by mass.

[0108] Similarly, the added amount of the hydrolyzate and / or condensate thereof of the silane coupling agent represented by any one of general formulas (2) to (4) can also be calculated by multiplying the mass of the silane coupling agent represented by any one of general formulas (2) to (4) and / or the partial condensate thereof used in the production of the metal pigment composition by the mass ratio before and after the reaction when all of said silane coupling agent and / or said partial condensate thereof undergo hydrolysis and condensation reaction. For example, when methyltrimethoxysilane is used as the silane coupling agent represented by general formula (2), the added amount of the hydrolyzate and / or condensate thereof of the silane coupling agent can be calculated by using the following mass ratio before and after the hydrolysis and condensation reaction. (Hydrolysis) CH3Si(OCH3)3 (molecular weight: 136) + 3H2O → CH3Si(OH)3 (molecular weight: 94) + (CH3OH)3 (Condensation) CH3Si(OH)3 (molecular weight: 94) + CH3Si(OH)3 (molecular weight: 94) → (SiCH3O1 .5 )2 (molecular weight: 67×2) + 3H2O Before and after the above hydrolysis / condensation reaction, the mass becomes 67 / 136 = 0.49 times. Therefore, for example, when 1.23 parts by mass of methyltrimethoxysilane is used relative to 100 parts by mass of metal particles (solid content), the added amount of the hydrolyzate and / or condensate thereof is 0.49 times of that, that is, 0.60 parts by mass.

[0109] Furthermore, regardless of whether the first or second method described above is adopted, it is preferable that the metal particles be thoroughly dispersed in water, a hydrophilic organic solvent, or a mixture thereof before being combined with the organosilicon compound which is the silicon compound source (or, if forming a second coating layer, before being combined with the molybdenum compound). In this pre-dispersion (initial dispersion), it is preferable to perform external circulation, in which a portion 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 total dispersion per minute) is temporarily withdrawn from the dispersion tank and then returned to the dispersion tank. Dispersibility can be further improved by performing ultrasonic treatment outside the dispersion tank in the middle of the external circulation flow path. The ultrasonic treatment is not particularly limited, but can usually be performed at 10 to 1000 W, preferably 50 to 800 W, for 20 seconds to 10 minutes, preferably 30 seconds to 5 minutes. Furthermore, the amount of solvent used for this pre-dispersion can usually be about 100 to 10000 parts by mass per 100 parts by mass of metal particles (solids), preferably 200 to 5000 parts by mass, and more preferably 300 to 1000 parts by mass, from the viewpoint of obtaining sufficient dispersion by appropriately adjusting the stirring intensity. Such pre-dispersion of metal particles can usually be carried out at 10-80°C, preferably 15-60°C, and most preferably around room temperature (around 20-30°C). Furthermore, the pre-dispersion of metal particles (including ultrasonic treatment if applicable) can be carried out for 5 minutes to 2 hours, preferably 10 minutes to 1 hour.

[0110] Second coating layer formation process The composite particles constituting the composite metal pigment of the first aspect of the first invention of this application preferably further have, in addition to the metal oxide coating layer, a coating layer other than the metal oxide coating layer (second coating layer), preferably comprising at least one selected from metals, metal oxides, metal hydrates, and resins. The second coating layer is preferably formed (if formed) between the metal particles and the metal oxide coating layer, preferably the silicon compound-containing layer. Therefore, a layer configuration of "metal particles / second coating layer / metal oxide coating layer, preferably the silicon compound-containing layer" can be suitably adopted. The second coating layer is not particularly limited, but may be a molybdenum-containing coating, a phosphate compound coating, etc. A preferred example of a molybdenum-containing substance constituting the molybdenum-containing coating is the mixed-coordinate heteropolyanion compound disclosed in Japanese Patent Application Publication No. 2019-151678. Examples of components of the second coating layer, including the mixed-coordinate heteropolyanion compound, are as described above. In the following, an example will be given of a method in which a molybdenum-containing coating is formed as a second coating layer between metal particles and a metal oxide coating layer, preferably a silicon compound-containing layer.

[0111] When forming a molybdenum-containing coating as a second coating layer between metal particles and a metal oxide coating layer, preferably a silicon compound-containing layer, the molybdenum-containing coating can be formed on the surface of the metal particles by stirring a mixture containing the metal particles and a molybdenum compound (typically a mixed-coordinate heteropolyanionic compound) prior to the formation of the metal oxide coating layer, preferably the silicon compound-containing layer.

[0112] The method for forming a molybdenum-containing film on the surface of metal particles is not particularly limited, and any method that allows for uniform stirring of a mixture containing metal particles and a molybdenum compound in an aqueous solvent is acceptable. For example, a molybdenum-containing film can be formed on the surface of metal particles by stirring or kneading a mixture containing metal particles and a molybdenum compound in a slurry or paste state. In the mixture, the molybdenum compound may be dissolved or dispersed.

[0113] Furthermore, the stirrer used to agitate the mixture containing metal particles and molybdenum compounds is not particularly limited, and any known stirrer capable of efficiently and uniformly agitating the mixture containing aluminum particles and molybdenum compounds can be used. Specific examples include kneaders, mixing machines, rotary vessel stirrers, agitated reaction vessels, V-type stirrers, double-cone stirrers, screw mixers, sigma mixers, flash mixers, airflow stirrers, ball mills, edge runners, etc. The stirring blades of the stirrer are not particularly limited, but examples include anchor blades, paddle blades, propeller blades, turbine blades, etc.

[0114] The amount of molybdenum compound used can be appropriately set depending on the type of molybdenum compound used. Generally, this amount should be 0.02 to 20 parts by mass per 100 parts by mass of metal particles (solids), and is particularly preferably 0.1 to 10 parts by mass. A content of 0.02 parts by mass or more allows for sufficient treatment effect to be obtained. Furthermore, a content of 20 parts by mass or less allows for high brilliance to be maintained in the resulting metal pigment composition.

[0115] Typically, water, hydrophilic organic solvents, or mixtures thereof can be used as solvents for mixing metal particles with molybdenum compounds.

[0116] Examples of hydrophilic organic solvents include alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol; ether alcohols and their esters such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. One or more of these can be used.

[0117] The amount of solvent used in the second coating layer formation step (excluding the amount of solvent used for pre-dispersion of metal particles, if applicable) is not particularly limited, but is usually preferably 50 to 5000 parts by mass, and more preferably 100 to 2000 parts by mass, per 100 parts by mass of metal particles (solid content). Using 50 parts by mass or more of solvent can suppress the uneven distribution of molybdenum compounds and the aggregation of metal particles. Using 5000 parts by mass or less of solvent can provide a sufficient treatment effect of the molybdenum compound on the metal particles.

[0118] When stirring a mixture containing metal particles and a molybdenum compound, the temperature of the mixture should generally be around 10 to 100°C, and preferably 30 to 80°C. A temperature of 10°C or higher allows for a shorter reaction time to obtain sufficient processing effect. Furthermore, a temperature of 100°C or lower makes it easier to control the reaction to obtain the desired metal pigment composition.

[0119] The stirring time of the mixture is not particularly limited, as long as it is sufficient time for the desired molybdenum-containing coating to form. This stirring time is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours. A stirring time of 0.5 hours is sufficient to obtain the desired treatment effect. Furthermore, a stirring time of 10 hours or less can suppress an increase in treatment costs.

[0120] After stirring of the mixture containing metal particles and molybdenum compound is complete, the particles with the second coating layer can be recovered. In this case, known washing, solid-liquid separation, etc., can be carried out as appropriate as needed. For example, it is preferable to wash the mixture with a hydrophilic organic solvent and then filter it using a filter or the like to remove water and unreacted substances from the cake containing metal particles with a molybdenum-containing coating. In this way, the molybdenum-containing coating, which is the second coating layer, can be formed. The method described above can also be used to form other second coating layers.

[0121] In an embodiment in which a second coating layer (molybdenum-containing coating) is formed on metal particles, followed by a metal oxide coating layer, preferably a silicon compound-containing layer, after stirring of the mixture containing the metal particles and the molybdenum compound is completed, a dispersion of water and / or a hydrophilic organic solvent (typically an organosilicon compound represented by formula (1), such as tetraalkoxysilane and / or its condensates, and at least one silane coupling agent represented by any of formulas (2) to (4) above) may be directly added and stirred into the system without recovering the particles on which the second coating layer has been formed. At this time, a dispersion of an organosilicon compound represented by formula (1), such as tetraalkoxysilane and / or its condensates, may be added to the system containing the particles on which the second coating layer has been formed, and then a dispersion of at least one silane coupling agent represented by any of formulas (2) to (4) above may be added and stirred (see the second method in the "Step for Forming a Silicon Compound-Containing Layer" described above).

[0122] Stirring conditions In the production of a metal pigment composition according to the first aspect of the first invention of this application, it is necessary to carry out the step of forming at least a metal oxide coating layer, preferably a silicon compound-containing layer, under stirring. Furthermore, in the production of a metal pigment composition according to the first aspect of the first invention of this application, it is preferable to carry out not only the step of forming a metal oxide coating layer, preferably a silicon compound-containing layer, but also the step of forming a second coating layer, under stirring. In the embodiment in which the metal particles are pre-dispersed as described above, it is even more preferable to carry out this step under stirring as well. Furthermore, in the production of a metal pigment composition according to the first aspect of the first invention of this application, it is even more preferable to carry out the entire process, including the pre-dispersion of metal particles, the step of forming a second coating layer, and the step of forming a metal oxide coating layer, preferably a silicon compound-containing layer, under stirring. In the production of a metal pigment composition according to the first aspect of the first invention of this application, by carrying out the process of forming at least a metal oxide coating layer, preferably a silicon compound-containing layer, under appropriately controlled stirring, it is possible to effectively suppress or prevent the phenomenon of composite particles adhering to each other via the metal oxide coating layer, preferably a silicon compound-containing layer, or of aggregated particles consisting of metal particles being coated with the metal oxide coating layer, preferably a silicon compound-containing layer. Furthermore, by carrying out the entire process, including the pre-dispersion of metal particles, the process of forming the second coating layer, and the process of forming the metal oxide coating layer, preferably a silicon compound-containing layer (until all the layers to be formed on the surface of the metal particles have been formed), under stirring, it becomes possible to more easily obtain a metal pigment composition according to the first aspect of the first invention of this application that satisfies all of the above physical property requirements (1) to (6). The following description of stirring conditions may apply to any step in the production of the metal pigment composition according to the first aspect of the first invention of this application.

[0123] Agitation can be carried out using known or commercially available agitation devices. For example, at least one of the following can be used: a kneader, a mixing machine, a rotary vessel agitator, agitated reaction vessel, a V-type agitator, a double-cone agitator, a screw mixer, a sigma mixer, a flash mixer, an airflow agitator, a ball mill, an edge runner, etc.

[0124] Among these stirrers, it is preferable to use a stirred tank type apparatus that performs stirring by a stirring blade (impeller). By virtue of the stirring blade, a pressure shearing effect is exerted together with a circulation effect that causes the entire reaction system including a liquid phase to flow; as a result, the formation of agglomeration of composite particles can be more effectively suppressed.

[0125] The shape of the stirring blade is not particularly limited, and 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. Maxblend blades (manufactured by Sumitomo Heavy Industries Process Equipment Co., Ltd.) and Fullzone blades (manufactured by Shinko Environmental Solution Co., Ltd.) are also suitable. Further, stirring blades of these shapes can also be combined in multiple stages.

[0126] It is preferable that stirring is performed at a stirring speed such that the stirring blade is not exposed by a vortex generated by stirring. In addition, in order to suppress the vortex generated by stirring, a cylindrical tank, a square tank, a tank provided with a baffle, or the like can be suitably used.

[0127] In the production of a metal pigment composition containing composite particles according to the first aspect of the first invention of this application, it is desirable to set the optimal size of the stirring tank and stirring blades, and the speed of the stirring blades in relation to the volume and physical properties (density, viscosity, etc.) of the mixed liquid. The size of the stirring tank should be selected so that the maximum volume of the mixed liquid used in the series of steps is 20 to 80% of the stirring tank's capacity. 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, L / D, is generally in the range of 0.5 to 3.0, and is usually in the range of 1 to 2. 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 is preferably around 0.4 to 0.6. The shape (including length) of the stirring blades should be appropriately selected according to the physical properties of the mixed liquid, and it is important that the entire stirring tank is stirred throughout the entire process. In particular, to prevent the formation of unmixed stagnant areas near the liquid surface or the bottom of the agitator, it is preferable to combine multiple stages of inclined paddle, inclined turbine, or propeller type agitators, which easily generate upstream and downstream currents, or to use MaxBlend or FullZone blades. In this case, it is desirable to maintain a distance of 5 mm or more between the agitator blades and the inner surface of the agitator (including baffles). Doing so makes it easier to suppress damage and deformation of metal particles. The speed of the stirring blade tip is preferably 0.5 to 50 m / s, more preferably 1 to 20 m / s, and even more preferably 2 to 10 m / s. By having the speed of the stirring blade tip in the range of 0.5 to 50 m / s, the dispersibility of the composite particles in the resulting metal pigment composition can be improved, and consequently, it becomes easier to obtain a metal pigment composition with low aggregation of individual particles, excellent opacity and color tone, and low gas generation. Furthermore, by having the stirring linear speed within the above range, damage to the metal particles (e.g., flaky aluminum powder) is prevented, and the rate of the hydrolysis / condensation reaction can be appropriately controlled, effectively suppressing aggregation of composite particles. The stirring Reynolds number (hereinafter abbreviated as "stirring Re number") is an indicator that represents the state of stirring. The stirring Re number does not reflect the size other than the shape and diameter of the stirring tank and impeller. Therefore, the stirring Re number is only a guideline and is not particularly limited, but it is preferably 3000 or higher, and more preferably 5000 or higher. 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 around 100,000 in a typical laboratory scale, but when using a large-scale device that has been scaled up, it may exceed 100,000 as long as the desired effect of the first aspect of the first invention of this application is not hindered. This upper limit may also be acceptable, for example, around 1 million.

[0128] The stirring number Re here is calculated using the following formula. Stirring Re number = (ρ×n×d 2 ) / μ (In the formula, ρ is the density of the mixed liquid being stirred at 25°C (kg / m³) 3 ) where n is the stirring speed (rps), d is the impeller diameter (m), and μ is the viscosity of the mixed liquid being stirred at 25°C (Pa·s).

[0129] Composite particle recovery process After the step of forming a metal oxide coating layer, preferably a silicon compound-containing layer (and optionally a second coating layer) on the metal particles is completed, the resulting composite particles can be recovered. Known treatments such as washing and solid-liquid separation can be performed as needed during recovery. 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. Alternatively, the cake containing the composite particles may then be heat-treated at a temperature in the range of, for example, 100 to 500°C, as needed. The recovered composite particles, as described later, may constitute a metal pigment composition containing a small amount of water / hydrophilic solvent that was typically used in the manufacturing process.

[0130] 3. Metal Pigment Compositions The metal pigment composition according to the first aspect of the first invention of this application, obtained as described above, is considered to consist of composite particles including metal particles and one or more coating layers on their surfaces, and the residual solid content (non-volatile content) includes a solvent such as water / hydrophilic solvent used in the manufacturing process. In a metal pigment composition, if the metal particles have a silicon compound layer, a silicon compound which is a hydrolysate and / or condensate thereof of an organosilicon compound (for example, at least one organosilicon compound represented by the above general formula (1), a silane coupling agent represented by any of the above general formulas (2), (3), and (4), and their partial condensates) may be present in an amount of 0.02 to 50 parts by mass per 100 parts by mass of metal particles, calculated as the state after the hydrolysis / condensation reaction is completed. The metal pigment composition may contain, in an optional manner, a compound that forms a second coating layer (in an optional embodiment where a molybdenum-containing film is formed as the second coating layer, a molybdenum-containing compound, such as a mixed-coordination heteropolyanionic compound), in an amount of 0.01 to 10 parts by mass per 100 parts by mass of metal particles. The metal pigment composition may contain 0.01 to 50 parts by mass of an optional organic oligomer or polymer per 100 parts by mass of metal particles. The metal pigment composition may contain at least one selected from the group consisting of any choice of inorganic phosphoric acids and their salts, and acidic organic (or phosphate) esters and their salts, in amounts of 0.01 to 20 parts by mass per 100 parts by mass of metal particles. The metal pigment composition may contain, as a residue of the above-mentioned components (non-volatile matter), water / hydrophilic solvent used in the manufacturing process and / or hydrophilic organic solvent newly added to adjust the composition of the composition. The amount of solvent containing water / hydrophilic solvent may be, for example, 0.5 to 95% by mass of the metal pigment composition. Alternatively, the amount of 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 metal pigment composition may optionally contain any other components not listed above. Examples of optional components include at least one of a nonhydrophilic organic solvent, grinding aid, antioxidant, light stabilizer, polymerization inhibitor, or surfactant.

[0132] Examples of non-hydrophilic organic solvents include mineral spirits, solvent naphtha, toluene, and xylene, which are also used in the manufacturing process of metal pigments and exhibit hydrophobic properties. Examples of grinding aids include fatty acids, aliphatic amines, aliphatic amides, and aliphatic alcohols. Antioxidants that can be used include phenolic compounds, phosphorus compounds, and sulfur compounds.

[0133] As light stabilizers, those used as antioxidants as mentioned above can be used, but those represented by benzotriazole compounds, benzophenone compounds, salicylate compounds, cyanoacrylate compounds, oxalic acid derivatives, hindered amine compounds (HALS), and hindered phenol compounds can also be used.

[0134] 4. Uses of Metal Pigment Compositions Such metal pigment compositions can be used in organic solvent-based paints, inks, etc. Furthermore, by adding this metal pigment composition to an aqueous paint or 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 produced. The metal pigment composition can also be kneaded with resins, etc., to be used as a water-resistant binder or filler. Antioxidants, light stabilizers, polymerization inhibitors, and surfactants may be added when compounding the metal pigment composition with aqueous paints, aqueous inks, or resins, etc. As a modified form, it is also possible to obtain a molded article from a mixture of the metal pigment composition and resins, etc.

[0135] When metal pigment compositions are used in paints or inks, they may be added directly to (water-based) paints or inks, but it is preferable to disperse them in a solvent beforehand. Examples of solvents that can be used include water, texanol, diethylene glycol monobutyl ether, and propylene glycol monomethyl ether. Examples of resins include acrylic resins, polyester resins, polyether resins, epoxy resins, fluororesins, and rosin resins. In addition to resins, rubber can also be used as a binder in paints or inks. These resins are preferably emulsified, dispersed, or dissolved in water. This allows for the neutralization of carboxyl groups, sulfone groups, and other components contained in the resins.

[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, and extender pigments that are commonly added to paints, as well as silane coupling agents, titanium coupling agents, dispersants, anti-settling agents, leveling agents, thickeners, and defoaming agents. To improve dispersibility in the paint, surfactants may be added, and to improve the storage stability of the paint, antioxidants, light stabilizers, and polymerization inhibitors may be added.

[0137] Examples of coloring pigments include phthalocyanine, quinacridone, isoindolinone, perylene, azolake, iron oxide, lead yellow, carbon black, titanium dioxide, and pearl mica.

[0138] The content of the metal pigment composition according to the first aspect of the first invention of the present application in the above-mentioned aqueous paint or aqueous ink (resin composition) is not limited, but is normally 0.1 to 50% by mass, and particularly preferably 1 to 30% by mass. When the content is 0.1% by mass or more, a high decorative (metallic) effect can be obtained. Further, when the 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 and the like, from being impaired.

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

[0140] There are no particular limitations on the coating method or printing method for aqueous paints and the like. For example, various coating methods or printing methods can be appropriately adopted in consideration of the form of the aqueous paint, the surface shape of the material to be coated, and the like. Examples of coating methods include a spray method, a roll coater method, a brush coating method, a doctor blade method, and the like. Examples of printing methods include gravure printing, screen printing, and the like.

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

[0142] In the case of these layer configurations, after each coating layer is applied and cured or dried, the next coating layer may be applied, or after each coating layer is applied by so-called wet-on-wet coating, the next coating layer may be applied without curing or drying. For aqueous paints and the like containing the metal pigment composition according to the first aspect of the first invention of the present application, it is preferable to adopt a method including the step of forming a coating layer with the aqueous paint or the like after coating the base coating layer and curing or drying the same, from the viewpoint that a coating film having good mirror-like luster can be obtained. The curing method for the paint composition in each coating layer may be thermal curing or room temperature curing. Furthermore, the drying method for the paint composition in each coating layer may be, for example, using hot air or natural drying at room temperature.

[0143] The thickness of the coating layer made by water-based paints, etc., is not particularly limited, but is usually around 2 to 100 μm. A coating layer thickness of 2 μm or more provides sufficient concealment of the substrate by the ink or paint. On the other hand, a coating layer thickness of 100 μm or less facilitates drying and can suppress the occurrence of defects such as blotches and sagging.

[0144] First invention, second aspect The second aspect of the first invention of this application is, A (composite) metal pigment comprising metal particles and composite particles having a metal oxide coating formed on their surface, (1) When the particle size distribution of the composite particles is measured using a laser diffraction particle size analyzer, the average particle diameter D is determined by volume. 50 The size is 3-20 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 by number, (4) The above-mentioned (composite) metal pigment, wherein the proportion of bent composite particles among the composite particles is 10% or less by number. The details of each component of the (composite) metal pigment of the second embodiment will be described below.

[0145] 1. Composite particles constituting composite metal pigments The composite metal pigment according to the second aspect of the first invention of this application comprises composite particles having metal particles and a metal oxide coating formed on their surface. In other words, in the description of the second embodiment in this specification, the term "composite metal pigment" includes, as an essential component, composite particles having metal particles and a metal oxide coating formed on their surface, and may also include other components, such as organic treatment agents, water and / or solvents including hydrophilic solvents.

[0146] metal particles The composite particles constituting the composite metal pigment according to the second aspect of the first invention of this application include metal particles and a metal oxide coating formed on their surface. That is, one or more layers of metal oxide coating are formed on the surface of the metal particles that form 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 known or commercially available metal used as a metal pigment, such as aluminum, aluminum alloys, 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 elemental metals but also alloys and intermetallic compounds. Metal particles may be used individually or in combination of two or more types. In the second aspect of the first invention of this application, the metal particles preferably contain aluminum or an aluminum alloy.

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

[0149] While there are no particular restrictions on the thickness or shape of the metal particles, it is desirable that their average particle thickness be 10-110 nm and that they be flake-shaped. As a result, the composite particles constituting the composite metal pigment according to the second aspect of the first invention of this application can also have a flake-like shape, thereby more reliably obtaining high opacity and other properties. The average thickness of the metal particles is preferably such that it results in the average thickness of the composite particles described later, and is preferably 10-110 nm. This effectively suppresses aggregation and deformation of the composite particles, making it easier to achieve excellent design properties, gloss, suppression of imperfections, and stability in water-based paints in the coating film. From the above viewpoint, 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 methods known in the industry. For example, it can be measured by forming a coating film using a metal pigment comprising metal particles and composite particles having a metal oxide coating on their surface, obtaining an FE-SEM (field emission scanning electron microscope) image of its cross-section, and performing image analysis. More specifically, it can be measured by the method described in the embodiment of this application.

[0151] The aspect ratio (shape factor obtained by dividing the average particle size by the average thickness) of the flaky metal particles is preferably 30 to 700, more preferably 50 to 600, and particularly desirable to be 80 to 500. An aspect ratio of 30 or higher for the metal particles allows for a higher degree of luster. Furthermore, an aspect ratio of 700 or lower for the metal particles maintains the mechanical strength of the flakes and allows for a stable color tone. The average thickness of the metal particles can be controlled, similar to the volume standard D50, in the manufacturing method of composite metal pigments described later, by appropriately adjusting the particle size of the atomized metal powder, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, and the degree of sieving and filtering during the grinding, sieving, and filtering process of the atomized metal powder (e.g., aluminum powder) using a ball mill or the like.

[0152] Furthermore, the metal particles do not necessarily have to be composed solely of metal; as long as they do not hinder the effects of the second aspect of the first invention of this application, particles of synthetic resin, particles in which the surface of inorganic particles such as mica or glass is coated with metal can also be used. In the second aspect of the first invention of this application, it is particularly desirable that the particles contain aluminum or an aluminum alloy, in terms of high weather resistance, low specific gravity, and ease of availability.

[0153] Aluminum flakes, which are commonly used as metallic pigments, are particularly suitable as metal particles constituting the composite particles. Suitable aluminum flakes are those that possess the surface properties, particle size, and shape required for metallic pigments, such as surface gloss, whiteness, and brilliance. Aluminum flakes are usually commercially available in paste form. Paste-like aluminum flakes may be used as is, or the surface fatty acids may be removed beforehand with an organic solvent or the like. Also, the volume average particle size (D 50 So-called aluminum vapor-deposited foils with a thickness of 3-20 μm and an average thickness (t) of 10-110 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 this 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 metal oxide, and may be formed over the entire surface of the metal particles or on only a portion of the surface. The metal oxide coating may be composed entirely of metal oxides, or it may be composed only of metal oxides and may contain components other than metal oxides.

[0155] The metal oxides that make up a metal oxide coating are compounds that contain oxygen and at least one metallic element as their constituent elements. Therefore, metal oxides may be metal oxides in the narrow sense, consisting only of oxygen and at least one metallic element as constituent elements. However, as long as they contain oxygen and at least one metallic element as constituent elements, they may also contain elements other than oxygen and the metallic element, such as metal hydroxides, oxide hydrates, or oxynitrides. They may also be compounds containing organic groups. Furthermore, the metal oxide may be a so-called single oxide, which consists of only one type of metal element, or it may be a composite oxide, which consists of two or more types of metal elements. The constituent elements of the metal oxide, at least one of which is a metallic element, may be a typical metal, a transition metal, or even a so-called metalloid. Among these, metal oxides with silicon as a constituent element are particularly suitable as metal oxides constituting a metal oxide coating.

[0156] Specific examples of suitable metal oxides for 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 these, 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 metal oxide coatings offers particular advantages in terms of achieving good storage stability in water-based paints, improving water resistance when applied to a coating film, and suppressing gas generation. By using silicon oxide for the metal oxide coating, the metal oxide coating typically becomes a layer composed of compounds containing Si-O- bonds (siloxane bonds). Examples of such layers include layers containing at least one silane compound and silicon oxide. Such compounds include silane compounds [H3SiO(H2SiO)]. n Examples of silicon oxides include SiH3 (where n is any positive integer), SiO2, SiO2·nH2O (where n is any positive integer), and others. These silane compounds and silicon oxides may be crystalline or amorphous, but amorphous is particularly preferred. Therefore, as a layer containing silicon oxide (silica, etc.), a layer containing amorphous silica, for example, can also be suitably adopted.

[0158] Furthermore, 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 unreacted organosilicon compounds or their derived components, to the extent that it does not impede the effects of the second aspect of the first invention of this application. In a typical example in this case, the metal oxide coating can be formed by hydrolysis of the organosilicon compound.

[0159] When silicon oxide is used, the mass of the metal oxide coating layer is not particularly limited, but it is preferably 1 to 20 parts by mass per 100 parts by mass of metal particles, and more preferably 2 to 15 parts by mass. By having a silicon content of 1 part by mass or more per 100 parts by mass of metal particles, the corrosion resistance, water dispersibility, stability, etc. of the composite metal pigment can be maintained at a high level. By having a silicon content of 20 parts by mass or less per 100 parts by mass of metal particles, aggregation of composite particles and a decrease in color tone such as opacity 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 this application is preferably hydrophilic. The composite particles usually form a composite metal pigment in the form dispersed in an aqueous solvent (water or a mixed solvent containing water and an organic solvent), but if 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 oxide (amorphous silica, etc.) are very stable in aqueous solvents, it is possible to provide a composite metal pigment containing composite particles that are highly stable in aqueous solvents. From this viewpoint, in the composite particles contained in the composite metal pigment according to the second aspect of the first invention of this application, it is desirable that at least the outermost layer is a metal oxide film, and it is particularly desirable that it be a silicon compound-containing layer (especially a layer composed of compounds containing Si-O bonds). Since metal oxides have excellent affinity for metal particles, when composite particles have a coating layer composed of multiple layers, in addition to the outermost metal oxide coating, layers other than the outermost layer, particularly preferably layers in contact with the metal particles, may be formed separately, such as metal oxide layers, and especially preferably silicon compound-containing layers (particularly Si-O-based coating layers).

[0161] The thickness of the metal oxide coating on individual composite particles is not particularly limited, as long as the average thickness of the composite particles is in the range of 15 to 160 nm, as will be described later. It is generally desirable that the thickness of the metal oxide coating be in the range of approximately 1 to 70 nm (especially 2 to 50 nm, and even 5 to 40 nm). A metal oxide coating thickness of 1 nm or more provides sufficient water resistance, and a coating film can be obtained in which corrosion or discoloration of metal particles in water-based paints is suppressed. On the other hand, a metal oxide coating thickness of approximately 70 nm or less allows the brightness, clarity, and opacity of the coating film to be maintained at a high level.

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

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

[0164] Physical properties of composite metal pigments The composite metal pigment according to the second aspect of the first invention of this application is characterized in that the metal particles and composite particles constituting it satisfy the following physical property requirements. (1) When measuring the particle size distribution of composite particles using a laser diffraction particle size analyzer, the average particle diameter D is determined by volume. 50 The size should be between 3 and 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 by number. (4) The proportion of bent composite particles among the composite particles is 10% or less by number. The following describes each of these physical property requirements.

[0165] (1) When measuring the particle size distribution of composite particles using a laser diffraction particle size analyzer, the average particle diameter D is determined by volume. 50 The size is 3-20 μm. The average particle diameter D, based on volume, when measuring the particle size distribution of composite particles using a laser diffraction particle size analyzer. 50 The particle size is 3-20 μm. This effectively suppresses particle aggregation and deformation, and allows coating films formed using composite metal pigments or metal pigment compositions containing them to achieve excellent design, gloss, suppression of imperfections, and stability in water-based paints. This volume-based D 50 This is also commonly referred to as the median diameter. From the viewpoint of obtaining excellent design, gloss, suppression of imperfections, and stability in water-based paints, the volume-based D of the particle size distribution of composite particles when measured using a laser diffraction particle size analyzer is considered. 50 The particle size is preferably 4 to 15 μm, and more preferably 5 to 12 μm. In these physical property requirements, "composite particles" refers to aggregates (assemblies) of multiple composite particles when they are aggregated and fixed together. Here, when the particle size distribution of composite particles is measured using a laser diffraction particle size analyzer, the volume-based D 50 This refers to the particle size at which the cumulative percentage in the volume cumulative particle size distribution reaches 50%. While not particularly limited, laser diffraction particle size analyzers such as the "LA-300" (manufactured by Horiba, Ltd.) can be used. Hydrophilic solvents such as water, isopropanol, and methoxypropanol can be used as measurement solvents. For example, for a composite metal pigment containing composite particles of a sample, after ultrasonic dispersion for about 2 minutes as a pretreatment, the sample is placed in a dispersion tank, and after confirming that it is properly dispersed, D 50 It can be measured. Volume-based D of the composite particles constituting the composite metal pigment 50 This can be controlled in the manufacturing method of composite metal pigments described later, by appropriately adjusting the particle size and amount of atomized metal powder (e.g., aluminum powder) used as raw material in the step of grinding, sieving, and filtering the atomized metal powder using a ball mill, etc., by adjusting the amount of grinding solvent such as mineral spirits, the type and amount of grinding aid, the mass and amount of each grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc., and also by appropriately adjusting the pH, concentration, stirring temperature, stirring time, type of stirring device, and stirring power / degree (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) during the hydrolysis of raw materials such as organosilicon compounds in the step of coating with a metal oxide coating (and other coating layers as needed). Furthermore, particle size tends to increase due to aggregation during metal oxide coating treatment. Since particle enlargement leads to a decrease in color tone, opacity, and appearance of the coating film, it is particularly effective to prevent particle enlargement by pre-treating the aluminum paste used as a raw material 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 this application is 15 to 160 nm. This, combined with satisfying requirements (1) and (2) above, effectively suppresses aggregation and deformation of the composite particles, thereby achieving excellent design properties, gloss, suppression of blemishes, and stability in water-based paints in the coating film. From the above viewpoint, 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 these physical property requirements, "composite particles" refers to aggregates (assemblies) of multiple composite particles when they are aggregated and fixed together. The average thickness of the composite particles here can be calculated by measuring the average particle thickness of the metal particles and the thickness of the metal oxide coating, respectively, and using the following formula. 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 using the method described in (2) above. The thickness of the metal oxide coating can be measured by methods known in the industry, for example, by a scanning transmission electron microscope (STEM). More specifically, it can be measured by the method described in the embodiments of this application. The average thickness of the composite particles contained in the composite metal pigment is based on volume D. 50 Similarly, in the method for producing composite metal pigments described later, and in the process of coating with a metal oxide coating such as a silicon compound-containing layer (and other coating layers as needed), this can be controlled by appropriately adjusting the pretreatment of the raw material aluminum paste and the pH, concentration, stirring temperature, stirring time, type of stirring device, and stirring power / degree (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) during the hydrolysis of raw materials such as organosilicon compounds. Furthermore, particle size tends to increase due to aggregation during the metal oxide coating treatment, but particle enlargement leads to a decrease in color tone, a decrease in opacity, and a decrease in the appearance of the coating film. Therefore, it is particularly effective to prevent particle enlargement by 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 this application preferably have an aspect ratio (shape factor obtained by dividing the average particle size by the average thickness) of 30 to 700. An aspect ratio of 30 or more of the composite particles makes it easier to obtain a higher level of luster. Furthermore, an aspect ratio of 700 or less of the composite particles maintains the mechanical strength of the composite particles, making it easier to obtain a stable color tone. An aspect ratio of 50 to 600 is preferred, and 80 to 500 is more preferred.

[0167] (3) The proportion of non-aggregated primary particles in the composite particles is 35% or more by number. In the composite metal pigment according to the second aspect of the first invention of this application, the proportion of non-aggregated primary particles to the total composite particles contained in the composite metal pigment is 35% or more on a numerical basis. A proportion of primary particles of 35% or more means that the aggregation of individual particles is suppressed, and not only the primary particles but also the aggregated particles exhibit a smaller degree of aggregation. As a result, the coating film formed using the composite metal pigment exhibits excellent design properties, gloss, and suppression of imperfections, and the stability of water-based paints can be improved. Furthermore, because the aggregation of individual particles is suppressed in this way, only mild stirring is required for dispersion, thus significantly reducing particle deformation caused by stirring.

[0168] From the viewpoint of promoting the above effects, the proportion of non-aggregated primary particles in the aggregate of composite particles is preferably 40% or more on a numerical basis, more preferably 50% or more, even more preferably 60% or more, and particularly preferably 70% or more. The proportion of non-aggregated primary particles in an aggregate of composite particles is generally preferable as it is, with no particular upper limit, and ideally it should be 100%. The proportion of non-aggregated primary particles in an aggregate of composite particles can be measured by methods known in the industry. For example, it can be measured by forming a coating film using a metal pigment consisting of an aggregate of metal particles and composite particles having a metal oxide coating on their surface, obtaining an FE-SEM (field emission scanning electron microscope) image of the cross-section, and performing image analysis, or by having an evaluator count 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 embodiment of this application.

[0169] The proportion of non-aggregated primary particles in a composite particle aggregate can be controlled by appropriately setting the selection and treatment of the metal particles constituting the composite particles, as well as the type and manufacturing conditions of the metal oxide coating formed on the metal particles. Existing techniques have attempted to enhance mechanical dispersion by increasing the stirring speed during coating and raising the Reynolds number above a certain value. However, this method has limitations in dispersing fine particles like those dealt with in this application, and there is a problem that thin, flaky particles may break or deform due to the strong stress during stirring. On the other hand, by pre-treating the metal particles to improve their dispersibility before coating them with metal oxide, it is possible to suppress particle aggregation during the coating process, thereby significantly increasing the proportion of primary particles that do not aggregate. For example, if the raw material metal particles are supplied dispersed in a solvent, the aggregation that occurs during the coating process can be significantly suppressed by replacing the solvent with the same solvent used for the coating process, and further, optionally, by heating for a certain period of time to allow the solvent to thoroughly penetrate the surface of the metal particles. Furthermore, adding a small amount of surfactant at this time is also effective in suppressing aggregation.

[0170] These processes improve the dispersibility of the metal particles themselves, eliminating the need for excessive stirring during the coating process. This allows for the production of primary particles without aggregation, even with mild stirring. Consequently, particle deformation during the coating process is significantly reduced, making it easier to achieve superior aesthetics, gloss, suppression of imperfections, and stability in water-based paints.

[0171] In addition to the above, factors that affect the proportion of primary particles without aggregation include the particle size of the atomized metal powder (e.g., aluminum powder) used in the process of grinding, sieving, and filtering the raw material atomized metal powder using a ball mill, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, and the pH, concentration, stirring temperature, stirring time, type of stirring device, and stirring power / degree (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) of the raw material during hydrolysis of the silicon compound-containing metal coating (and other coating layers as needed) in the process of coating with a silicon compound-containing metal coating. The proportion of primary particles without aggregation can also be controlled by appropriately adjusting these factors.

[0172] In the composite metal pigment according to the second aspect of the first invention of this application, it is preferable that the proportion of aggregates in which four or more composite particles are fixed to each other is 15% or less of the total number of composite particles. This, in conjunction with satisfying the above requirements, allows the coating film formed using the composite metal pigment to exhibit even higher opacity and luster, and further suppress the aggregation of individual particles. The proportion 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, i.e., the degree of aggregation. If the proportion of aggregates in which four or more composite particles are fixed to each other is 15% or less of the total number of composite particles, the orientation of the composite particles in the coating film is orderly, and the proportion of composite particles aligned parallel to the surface of the coating film increases. As a result, the projected area of ​​the composite particles in the coating film formed using the metal pigment composition increases, improving opacity and luster, and furthermore, it is considered that the aggregation of individual particles is further reduced as it becomes easier to form a uniform and sufficient coating on individual particles. Furthermore, by reducing the proportion of aggregates where four or more composite particles are bonded together, it is possible to effectively prevent the collapse of aggregates of composite particles once formed in the water-based paint, exposing the untreated surface and reacting with water, the solvent of the water-based paint, to generate hydrogen gas. In composite metal pigments, the proportion 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 lower this proportion, the better, but it is not easy to make it completely zero.

[0173] (4) The proportion of bent composite particles among the composite particles is 10% or less by number. In the composite metal pigment according to the second aspect of the first invention of this application, the proportion of bent composite particles to the total composite particles contained in the composite metal pigment is 10% or less. As a result, in conjunction with satisfying the above requirements (1) to (3), the coating film formed using the composite metal pigment exhibits excellent design properties, gloss, and suppression of imperfections, as well as improved stability in water-based paints.

[0174] In the coating treatment of aluminum particles, particle aggregation is prone to occur. Conventionally, a method has been known to prevent aggregation by strongly stirring the particles during the reaction to apply shear. While this method can suppress particle aggregation to some extent, it has the problem that flake-shaped aluminum particles deform due to shear, reducing the performance of the coating film. The proportion of bent composite particles is understood to be an indicator related to the degree of deformation or damage of the composite particles. If the proportion of bent composite particles is 10% or less, the degree of deformation or damage of the composite particles is small, and as a result the proportion of the untreated surface (surface where the metal oxide film has not been formed) of each composite particle is small, the stability in the water-based paint is improved, and furthermore, it becomes easier to form a uniform and sufficient coating on each particle, so the aggregation of individual particles is further reduced, and a coating film that shows excellent design, gloss, and suppression of blemishes on the surface of the coating film formed using composite metal pigments can be obtained. The proportion of bent composite particles in an aggregate of composite particles should be as low as possible. This proportion is preferably 6% or less, and more preferably 3% or less. Since a lower proportion of bent composite particles is preferable, there is no particular lower limit, but ideally it is 0%.

[0175] The proportion of bent composite particles in a composite metal pigment can be measured by methods known in the industry. For example, it can be measured by forming a coating film using a metal pigment consisting of a collection of composite particles having metal particles and a metal oxide coating on their surface, acquiring an FE-SEM (field emission scanning electron microscope) image of its cross-section, and performing image analysis. More specifically, particles in which the ratio of the straight-line distance between the two ends of the cross-section of the metal particle in the FE-SEM image to the path length between the two ends along the cross-section of the metal particle is 1.2 or more are determined to be bent particles, and the proportion of such particles can be calculated. Even more specifically, it can be measured by the method described in the embodiment of this application. The proportion of bent composite particles in a composite metal pigment can be controlled mainly by appropriately adjusting the pretreatment to improve the dispersibility of the raw material aluminum paste, the stirring time, the type of stirring device, and the power / degree of stirring (type and diameter of the stirring blades, rotation speed, presence or absence of external stirring, etc.) during the process of coating with a metal oxide coating (and other coating layers as needed). Furthermore, by pre-treating the raw material aluminum paste, the dispersibility of the particles themselves during the reaction is improved, so only mild stirring is needed for dispersion, and thus particle deformation due to stirring can be greatly reduced.

[0176] 2nd coating layer The coating layer of the composite particles contained in the composite metal pigment according to the second aspect of the first invention of this application is not particularly limited except that it has at least one metal oxide coating, but a coating layer other than the metal oxide coating (hereinafter referred to as the "second coating layer") may be formed as needed. The second coating layer preferably comprises at least one of the following: metals (alkali metals; alkaline earth metals; such as manganese, iron, cobalt, nickel, copper, silver, etc.), metal oxides (such as titanium oxide, zirconium oxide, iron oxide, etc.), metal hydrates, and resins (such as synthetic resins like acrylic resin, alkyd resin, polyester resin, polyurethane resin, polyvinyl acetate resin, nitrocellulose resin, and fluororesin). For example, a molybdenum-containing coating or a phosphate compound coating can be formed as the second coating layer. By providing the second coating layer, the corrosion resistance of the metal particles can be improved, and the formation of an oxide metal coating such as a silicon compound-containing layer can be promoted.

[0177] The second coating layer is preferably formed (if formed) between the metal particles and the metal oxide coating, such as the silicon compound-containing layer. Therefore, a layer configuration such as "metal particles / second coating layer / metal oxide coating" can be suitably adopted. While not particularly limited, examples of molybdenum-containing coatings include those disclosed in Japanese Patent Application Publication No. 2003-147226, International Publication No. 2004 / 096921, Japanese Patent No. 5979788, and Japanese Patent Application Publication No. 2019-151678. An example of a phosphate compound coating is the one disclosed in Japanese Patent Application Publication No. 4633239. A preferred example of a molybdenum-containing substance constituting the molybdenum-containing coating is the mixed-coordination type heteropolyanion compound disclosed in Japanese Patent Application Publication No. 2019-151678. In another variant, the second coating layer may be formed outside the metal oxide coating, such as a layer containing metal particles and silicon compounds. In yet another variant, the components of the second coating layer (such as molybdenum-containing compounds or phosphate compounds) may be incorporated together with silicon compounds within the metal oxide coating, such as a layer containing silicon compounds.

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

[0179] The second coating layer, other than the metal oxide coating of the composite particles in the composite metal pigment according to this 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 added corrosion inhibitor is not particularly limited, and any known corrosion inhibitor can be used. The amount used should be within a range that does not hinder the desired effect of the second aspect of the first invention of this application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organophosphorus compounds, and metal salts of molybdic acid.

[0180] Organic oligomers or polymers may be further included in the metal oxide coating and / or second coating layer of the composite particles contained in the composite metal pigment, or as a separate layer, from the viewpoint of adhesion and chemical resistance when a coating film is formed. Furthermore, the composite particles may contain, from the viewpoint of storage stability, at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (or phosphate) esters and their salts, in the metal oxide coating and / or the second coating layer, or as a separate layer. These compounds are not particularly limited, but for example, those disclosed in Japanese Patent Application Publication No. 2019-151678 can be used.

[0181] 2. Method for producing composite metal pigments The composite metal pigment according to the second aspect of the first invention of this application can be suitably produced by a manufacturing method that includes, for example, a step of forming a metal oxide coating on metal particles under stirring using a solvent containing water and / or a hydrophilic solvent. The following describes a specific method using the case where the metal oxide coating is a silicon compound-containing layer as an example, but the method for producing a composite metal pigment according to the second aspect of the first invention of this application is not limited thereto. Those skilled in the art can appropriately form metal oxide coatings other than silicon compound-containing layers by referring to the following description. Furthermore, when manufacturing a composite metal pigment according to the second aspect of the first invention of this application, it is preferable to perform the pretreatment described later.

[0182] A composite metal pigment in which the metal oxide coating is a silicon compound-containing layer can be suitably produced, for example, by a method comprising the step of forming a silicon compound-containing layer on the surface of the metal particles by hydrolyzing / (partially) condensing the organosilicon compound in a mixture 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 formation step). This step can usually be carried out under stirring.

[0183] Grinding and sieving / filtration process Here, we will explain using (a) the case in which aluminum powder is used as the metal particles as an example. Aluminum powder is generally obtained by grinding atomized aluminum powder and / or aluminum foil using methods commonly used in the pigment industry, such as the dry ball mill method, wet ball mill method, attritor method, and stamp mill method, in the presence of grinding aids and inert solvents to form so-called flakes. After this process, it is further obtained by performing necessary steps such as sieving (classification), filtration, washing, and mixing. Examples of grinding aids used here include fatty acids, aliphatic amines, aliphatic amides, and aliphatic alcohols. Generally, oleic acid, stearic acid, and stearylamine are preferred. Examples of inert solvents include hydrophobic substances such as mineral spirits, solvent naphtha, toluene, and xylene, which can be used alone or in combination. The grinding aids and inert solvents are not limited to these. As for the grinding process, from the viewpoint of preventing dust explosions and ensuring safety, grinding by the wet ball mill method is preferred.

[0184] When aluminum particles are used as metal particles in the production of a composite metal pigment according to the second aspect of the first invention of this application, commercially available paste-like aluminum flakes obtained through such crushing and sieving / filtration can be used. The paste-like aluminum flakes may be used as is, or the fatty acids etc. on the surface may be removed in advance with an organic solvent or the like before use.

[0185] Pre-treatment process The composite metal pigment according to the second aspect of the first invention of this application can be suitably manufactured by a manufacturing method that includes a step of forming a metal oxide coating on metal particles as described above, but it is preferable to perform a pretreatment prior to the step of forming the metal oxide coating in order to improve the dispersibility of the particles in that step. This makes it possible to suppress particle aggregation during the coating process, resulting in good dispersibility of the resulting composite particles and a significant increase in the proportion of non-aggregated primary particles. More specifically, as a pretreatment, if the raw material metal particles are supplied dispersed in an inert solvent, the solvent can be replaced with the same solvent used in the coating process. Furthermore, if desired, heating for a certain period of time is performed to allow the solvent to thoroughly penetrate the surface of the metal particles, which can significantly suppress aggregation that occurs during the coating process. The heating temperature is preferably around 30 to 60°C, and the treatment time is preferably optimized between 3 hours and 7 days. Since hydrophilic solvents such as ethanol, isopropanol, and methoxypropanol are preferably used in the coating process, the same hydrophilic solvent used in the reaction is also preferably used in the pretreatment. Furthermore, adding a small amount of surfactant at this stage is also effective in suppressing aggregation caused by pretreatment. While there are no particular restrictions on the surfactant used, nonionic surfactants and anionic surfactants are preferred, and nonionic surfactants are particularly preferred.

[0186] During the pretreatment process, ultrasonic treatment can further enhance dispersibility. Ultrasonic treatment is not particularly limited, but can usually be performed at 10 to 1000 W, preferably 50 to 800 W, for 20 seconds to 10 minutes, preferably 30 seconds to 5 minutes. Such pre-dispersion of metal particles can usually be carried out at 10-80°C, preferably 15-60°C, and most preferably around room temperature (approximately 20-40°C). Furthermore, the pre-dispersion of metal particles (including ultrasonic treatment if applicable) can be carried out for 5 minutes to 2 hours, preferably 10 minutes to 1 hour.

[0187] Process for forming a silicon compound-containing layer Next, a step of forming a silicon compound-containing layer can be carried out. Details of the preferred form of the silicon compound-containing layer formation step are the same as those described above in relation to the first embodiment.

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

[0189] Composite particle recovery process After the step of forming a metal oxide coating (and optionally a second coating layer) such as a silicon compound-containing layer on the metal particles is completed, the obtained composite particles can be recovered. During recovery, known treatments such as washing and solid-liquid separation can be performed as needed. 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. Furthermore, if necessary, the cake containing the composite particles may then be heat-treated at a temperature in the range of, for example, 100 to 500°C. The recovered composite particles, as described later, can constitute a composite metal pigment (hereinafter also referred to as a "metal pigment composition") that typically contains a small amount of water / hydrophilic solvent remaining in the solvent used during the manufacturing process.

[0190] 3. Metal Pigment Compositions The composite metal pigment obtained as described above is considered to constitute a metal pigment composition that includes composite particles containing metal particles and one or more layers of metal oxide coating on their surface, and may also contain unreacted organosilicon compounds, compounds that form a second coating layer, oligomers or polymers derived therefrom as solid content (non-volatile content), and usually also contains solvents such as water / hydrophilic solvents used in the manufacturing process. The metal pigment composition may typically contain a silicon compound that is a hydrolysate and / or condensate thereof of an organosilicon compound (for example, at least one organosilicon compound represented by the above general formula (1), a silane coupling agent represented by any of the above general formulas (2), (3), and (4), and at least one of them selected from their partial condensates), in an amount of 0.02 to 50 parts by mass per 100 parts by mass of metal particles, calculated based on the state after the hydrolysis / condensation reaction is complete. The metal pigment composition may contain, in an optional manner, a compound that forms a second coating layer (in an optional embodiment where a molybdenum-containing film is formed as the second coating layer, a molybdenum-containing compound, such as a mixed-coordination heteropolyanionic compound), in an amount of 0.01 to 10 parts by mass per 100 parts by mass of metal particles. The metal pigment composition may contain 0.01 to 50 parts by mass of an optional organic oligomer or polymer per 100 parts by mass of metal particles. The metal pigment composition may contain at least one selected from the group consisting of any choice of inorganic phosphoric acids and their salts, and acidic organic (or phosphate) esters and their salts, in amounts of 0.01 to 20 parts by mass per 100 parts by mass of metal particles. The metal pigment composition may contain a solvent, including water / hydrophilic solvent, used in the manufacturing process. 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 other components not listed above. Examples of optional components include at least one of antioxidants, light stabilizers, and surfactants.

[0192] Antioxidants that can be used include phenolic compounds, phosphorus compounds, and sulfur compounds.

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

[0194] Examples of surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyalkylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; polyoxyalkylene alkylamino ethers such as polyoxyethylene lauryl amino ether and polyoxyethylene stearyl amino ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monooleate; and polyoxyalkylene sorbitas such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, and polyoxyethylene sorbitan monooleate. Examples of nonionic surfactants include polyalkylene glycol fatty acid esters such as polyethylene glycol monolaurate, polyethylene glycol monooleate, polyethylene glycol monostearate, polyethylene glycol dilaurate, and polyethylene glycol distearate; glycerin fatty acid esters such as laurate monoglyceride, stearate monoglyceride, and oleate monoglyceride; sulfate ester salts such as polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene octylphenyl ether sodium sulfate, polyoxyethylene nonylphenyl ether sodium sulfate, lauryl sulfate triethanolamine, lauryl sulfate sodium, lauryl sulfate potassium sulfate, and lauryl sulfate ammonium; and sulfonates such as dodecylbenzenesulfonate sodium, alkylnaphthalenesulfonate sodium, and dialkylsulfosuccinate sodium.Examples include anionic surfactants such as phosphate ester salts like potassium alkyl phosphate, and cationic surfactants such as quaternary ammonium salts like lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, and stearyltrimethylammonium chloride. One or more of these can be used. Particularly preferred examples include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, or mixtures thereof.

[0195] 4. Applications of composite metal pigments The composite metal pigment according to the second aspect of the first invention of this application can be used in organic solvent-based paints, inks, etc. Furthermore, 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 produced. The composite metal pigment can also be kneaded with resins, etc., and used as a water-resistant binder or filler. Antioxidants, light stabilizers, and surfactants may be added when compounding the composite metal pigment with aqueous paints, aqueous inks, or resins, etc.

[0196] When composite metal pigments are used in paints or inks, they may be added directly to (water-based) paints or inks, but it is preferable to disperse them in a solvent beforehand. Suitable solvents include water, texanol, diethylene glycol monobutyl ether, and propylene glycol monomethyl ether. Examples of suitable resins include acrylic resins, polyester resins, polyether resins, epoxy resins, fluororesins, and rosin resins. In addition to resins, rubber can also be used as a binder in paints or inks. These resins are preferably emulsified, dispersed, or dissolved in water. This allows for the neutralization of carboxyl groups, sulfone groups, and other components contained in the resins.

[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, it may be combined with coloring pigments such as inorganic pigments, organic pigments, and extender pigments that are commonly added to paints, as well as silane coupling agents, titanium coupling agents, dispersants, anti-settling agents, leveling agents, thickeners, and defoaming agents. To improve dispersibility in the paint, surfactants may be added, and to improve the storage stability of the paint, antioxidants, light stabilizers, and polymerization inhibitors may be added.

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

[0199] The content of the composite metal pigment according to the second aspect of the first invention of this application in the above-mentioned water-based paint or water-based ink (resin composition) is not limited, but is usually 0.1 to 30% by mass, and is particularly preferably 1 to 20% by mass. A content of 0.1% by mass or more allows for a high decorative (metallic) effect to be obtained. Furthermore, a content of 30% by mass or less prevents the properties of the water-based paint or water-based ink, such as weather resistance, corrosion resistance, and mechanical strength, from being impaired.

[0200] The solvent content is not particularly limited, but may be 20 to 200% by mass relative to the binder content. Having the solvent content within this range allows the viscosity of the paint or ink to be adjusted to an appropriate range, making handling and film formation easier.

[0201] The painting method or printing method for water-based paints, etc., is not particularly limited. For example, various painting or printing methods can be appropriately adopted considering the form of the water-based paint, the surface shape of the material to be painted, etc. Examples of painting methods include spray painting, roll coating, brush painting, and doctor blade painting. Examples of printing methods include gravure printing and screen printing.

[0202] The coating film formed by water-based paints, etc., may be formed on top of a primer or intermediate coat layer formed by electrodeposition coating, etc. Furthermore, if necessary, a topcoat layer or the like may be formed on top of the coating film formed by water-based paints, etc.

[0203] In these layer configurations, each coating layer may be painted, and after curing or drying, the next coating layer may be painted; or, after painting each coating layer using so-called wet-on-wet painting, the next coating layer may be painted without curing or drying. In the case of the water-based paint containing a composite metal pigment according to the second aspect of the first invention of this application, it is preferable to employ a method that includes the step of painting a base coating layer, curing or drying it, and then forming a coating layer with the water-based paint, etc., in order to obtain a coating film with good mirror-like gloss. The curing method for the paint composition in each coating layer may be thermal curing or room temperature curing. Furthermore, the drying method for the paint composition in each coating layer may be, for example, using hot air or natural drying at room temperature.

[0204] The thickness of the coating layer made by water-based paints, etc., is not particularly limited, but is usually preferably around 0.5 to 100 μm, and more preferably around 1 to 50 μm. A coating layer thickness of 0.5 μm or more ensures sufficient concealment of the substrate by the ink or paint. Furthermore, a coating layer thickness of 100 μm or less facilitates drying and can suppress the occurrence of defects such as blotches and sagging.

[0205] The composite metal pigment according to the second aspect of the first invention of this application and the coating film obtained using it possess excellent design properties, gloss, suppression of imperfections, and stability in water-based paints at a high level, and can therefore be suitably used in various applications where metal pigments have traditionally been used, such as paints, inks, and resin compounding agents, more specifically in automobile bodies, automobile repair materials, automobile parts, home appliances, plastic parts, PCM coatings, high-weather-resistant coatings, heat-resistant coatings, anticorrosion coatings, bottom coatings for ships, offset printing inks, gravure printing inks, and screen printing inks.

[0206] Second Invention The second invention of this application is a (composite) metal pigment comprising composite particles in which metal particles are coated with a layer of polysiloxane, 1) The proportion of Q4 structures in the polysiloxane structure, in which Si atoms have four -O-Si- bonds, is 40-90%, and 2) The relative elemental concentration ((A / B) × 100) of the elemental concentration A of the metal and the elemental concentration B of Si, as evaluated by XPS on the surface of the composite particle, is 10 mol% or less. The aforementioned (composite) metal pigment. In the present invention, the metal pigment is preferably such 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 aqueous acrylic resin, 18 g of melamine resin, and 12 g of water is taken into a flask and the amount of hydrogen gas generated is measured in a constant temperature water bath at 60°C for up to 24 hours, the amount of gas generated is 10 ml or less. The metal pigment of the second invention of this application is preferably used in a metal pigment composition containing the metal pigment. The metal pigment of the second invention of this application is preferably used in an aqueous paint composition containing the metal pigment. The metal pigment of the second invention of this application is particularly preferably used in aqueous metallic paints, and when 200 g of the aqueous metallic paint containing the metal pigment is taken into 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 amount of gas generated is preferably 10 ml or less. The metal pigment of the second invention of this application is preferably used in an aqueous ink composition containing the metal pigment. The metal pigment of the second invention of this application is preferably used in a coating film containing the metal pigment. The details of the second invention will be described below.

[0207] The second invention of this application is a composite metal pigment comprising composite particles in which metal particles are coated with polysiloxane, and satisfies the following requirements. 1) The proportion of Q4 structures, in which Si atoms have four -O-Si- bonds, in the polysiloxane structure is 40-90%. 2) The relative elemental concentration ((A / B) × 100) of the elemental concentration A of the metal and the elemental concentration B of Si, as evaluated by XPS on the surface of the composite particles, is 10 mol% or less.

[0208] metal particles The composite particles constituting the metal pigment of the second invention of this application include metal particles and a polysiloxane layer formed on their surface.

[0209] The material of the metal particles (core particles) constituting the composite particles is not particularly limited and may be any known or commercially available metal used as a metal pigment, such as aluminum, aluminum alloys, 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 elemental metals but also alloys and intermetallic compounds. Metal particles may be used individually or in combination of two or more types. The metal particles in the second invention of this application preferably contain aluminum or an aluminum alloy, and more preferably consist of 95% by mass or more of aluminum elements.

[0210] The average particle size of the metal particles is not particularly limited, but D in the particle size distribution of the composite particles described later. 50 It is preferable that the average particle size is such that it can produce D. That is, when the volume distribution is measured with a laser diffraction particle size analyzer in composite particles, D 50The volume-average particle size (D) of the metal particles should be such that it is 1 to 30 μm, or to facilitate this. 50 It is preferable to set ). The average particle size of metal particles can be controlled in the process of grinding, sieving, and filtering raw material atomized metal powder (e.g., aluminum powder) using a ball mill or the like, by appropriately adjusting the particle size of the raw material atomized metal powder, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, and the degree of sieving and filtering. While there are no particular restrictions on the thickness or shape of the metal particles, it is desirable that they have an average particle thickness of 10-400 nm, more preferably 10-300 nm, and be in a flake-like shape. As a result, the composite particles constituting the composite metal pigment according to the second invention of this application can easily have a flake-like shape, thereby more reliably obtaining high opacity and other properties. The average thickness of the metal particles is preferably such that it results in the average thickness of the composite particles described later, and is preferably 20-400 nm. This effectively suppresses aggregation and deformation of the composite particles, making it easier to achieve excellent design properties, gloss, suppression of imperfections, and stability in water-based paints in the coating film. From the above viewpoint, the average thickness of the metal particles is preferably 25-350 nm, and more preferably 30-300 nm.

[0211] Here, the average particle thickness of the metal particles can be measured by methods known in the industry. For example, it can be measured by forming a coating film using a metal pigment comprising metal particles and composite particles having a metal oxide coating on their surface, obtaining an FE-SEM (field emission scanning electron microscope) image of its cross-section, and performing image analysis. More specifically, it can be measured by the method described in the embodiment of this application. The aspect ratio of the metal particles (shape factor obtained by dividing the average particle size by the average thickness) is preferably 20 to 400, more preferably 30 to 350, and particularly preferably 40 to 300. An aspect ratio of 20 or higher for the metal particles allows for a higher degree of luster. Furthermore, an aspect ratio of 400 or lower for the metal particles maintains the mechanical strength of the flakes and allows for a stable color tone. The average thickness of metal particles is based on volume D. 50 Similarly, in the process of grinding, sieving, and filtering raw atomized metal powder (e.g., aluminum powder) using a ball mill or the like, the process can be controlled by appropriately adjusting the particle size of the raw atomized metal powder, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, and the degree of sieving and filtering.

[0212] Furthermore, the metal particles do not necessarily have to be composed solely of metal; as long as they do not hinder the effects of the second invention of this application, particles of synthetic resin, particles in which the surface of inorganic particles such as mica or glass is coated with metal can also be used. In the present invention, it is particularly desirable that the particles contain aluminum or an aluminum alloy in terms of high weather resistance, low specific gravity, and ease of availability.

[0213] Aluminum flakes, which are commonly used as metallic pigments, are particularly suitable as metal particles. Suitable aluminum flakes have the surface properties, particle size, and shape required for metallic pigments, such as surface gloss, whiteness, and brilliance. Aluminum flakes are usually sold in paste form. Paste-like aluminum flakes can be used as is, or the surface fatty acids, etc., may be removed beforehand with an organic solvent. Also, the volume average particle size (D 50 So-called aluminum vapor-deposited foils with a thickness of 3-20 μm and an average thickness (t) of 10-110 nm can also be used.

[0214] composite particles The composite particles contained in the metal pigment of the second invention of this application have a structure in which metal particles are at the center and the metal particles are coated with polysiloxane.

[0215] Polysiloxanes are composed of compounds containing siloxane bonds (Si-O-Si) consisting of silicon atoms (Si) and oxygen atoms (O). These compounds may be crystalline or amorphous, but amorphous is particularly preferred. Furthermore, polysiloxanes may be formed using organosilicon compounds (including silane coupling agents) as starting materials. In this case, organosilicon compounds or their derived components may be included to the extent that they do not impede the effects of the second invention of this application. In a typical example, polysiloxanes can be formed by hydrolyzing organosilicon compounds. The polysiloxane layer may contain additives, impurities, etc. other than silicon compounds, as long as they do not impair the properties of the second invention of this application.

[0216] Specific examples of polysiloxanes that can be used in the present invention II will be further described below, but polysiloxanes are not limited to these specific examples. Details such as preferred examples of polysiloxanes in the second invention of this application are the same as those of compounds having siloxane bonds described as preferred forms of "organosilicon compounds" in the first aspect of the first invention.

[0217] The polysiloxane layer may contain additives, impurities, etc. other than polysiloxane, as long as they do not impair the properties of the second invention of this application.

[0218] <Structure of the polysiloxane layer> Conventional technology does not control the structure of the polysiloxane in the polysiloxane layer that constitutes the coating layer of composite particles. It is assumed that the Si atoms randomly exist as Q4 structures with four -O-Si- bonds, Q3 structures with three bonds, Q2 structures with two bonds, and Q1 structures with one bond. For this reason, the mechanical stability of the composite particles contained in the metal pigment is insufficient.

[0219] In the present invention, the proportion of Q4 structures in the polysiloxane layer structure of the composite particles must be 40-90%. By setting the proportion of Q4 structures to 40% or more, sufficient mechanical strength of the composite particles contained in the metal pigment of the polysiloxane layer can be obtained. The upper limit of the Q4 structures is extremely difficult to set to 90% or more due to the three-dimensional structure, while setting the proportion to 90% or less ensures the flexibility of the polysiloxane layer and increases the mechanical strength of the composite particles contained in the metal pigment.

[0220] Furthermore, in the second invention of this application, it is preferable that the hydrophilicity A, defined as the sum of the ratio of Q1 structure × 3 + the ratio of Q2 structure × 2 + the ratio of Q3 structure, be between 10% and 80%. This is because the bonding sites have a hydrophobic structure of -Si-O-Si- (silanol bond), while the unreacted sites (terminals) have a silanol structure of -Si-OH, and the Q1 structure has 3 silanol groups, the Q2 structure has 2, and the Q3 structure has 1. Therefore, the above calculation formula serves as an indicator of the total amount of silanol groups. By setting this total to 10% or more, the hydrophilicity of the polysiloxane layer surface is high, and the dispersibility in water-based paints is sufficient. Also, by setting this total to 80% or less, it is possible to suppress excessively high hydrophilicity and prevent deterioration of water resistance and weather resistance when metal pigments are used as coating films.

[0221] In the second invention of this application, the average thickness of the polysiloxane layer can be 5 to 100 nm, and preferably 15 to 80 nm. If the average thickness is 5 nm or more, sufficient storage stability, such as prevention of gas generation, can be obtained when it is used as a coating, and if it is 100 nm or less, a decrease in light reflectance can be suppressed. Furthermore, since polysiloxane in composite particles has excellent mechanical strength, this has the effect of further improving the mechanical strength of the coated composite particles.

[0222] In the present invention, the amount of polysiloxane in the composite particles is not particularly limited, as long as it is equal to the thickness described above, but it is preferably 0.1 to 50 parts by mass, and more preferably 1 to 40 parts by mass, per 100 parts by mass of metal particles.

[0223] In the composite particles contained in the metal pigment of the second invention of the present application, when the relative elemental concentration of the metal to silicon on the particle surface is measured by XPS (X-ray Photoelectron Spectroscopy, also known as ESCA), the elemental concentration of the metal is 10 mol% or less relative to silicon. This 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] XPS can determine the proportion of elements present in a layer from the surface to a certain depth. Therefore, when the value of the relative elemental concentration of metal to silicon on the surface of the composite particles is not more than the upper limit of 10 mol%, it indicates that there is little exposure of the metal pigment and the particle is sufficiently covered with the polysiloxane layer, that is, the polysiloxane layer has a sufficient thickness and there are few portions not covered by the polysiloxane layer. As a result, a decrease in the storage stability of the pigment and a decrease in the stability when used in a water-based paint can be effectively suppressed. The value of the relative elemental concentration of metal to silicon is preferably 8 mol% or less, more preferably 6 mol% or less, and a lower value is more favorable. 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 will be 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 by taking the case where aluminum is used as the metal particle as an example. When aluminum is used as the metal particle, silicon constituting polysiloxane and aluminum (including aluminum compounds such as oxides) are present on the surface of the composite metal powder particle of the second invention of the present application or within a few nanometers from the surface. The ratio of these two elements can be confirmed by measuring the relative elemental concentration via XPS.

[0226] XPS is an analytical method that excites a solid surface with X-rays under high vacuum and measures the photoelectrons emitted from the surface. This method provides information on the types, oxidation states, and concentrations of elements present in the vicinity of the surface (a few nanometers), and allows for the determination of the relative concentrations of silicon, aluminum metal, and aluminum oxide present on the surface.

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

[0228] For example, when aluminum is used as the metal particle, the silicon concentration and aluminum concentration can be measured under the following conditions. Note that in XPS, one element may be detected in multiple states such as oxides, but in the second invention of this application, the sum of the values ​​of multiple states is used as the element concentration. • Measuring device: ULVAC-FI Versa probeII • Excitation source: mono.AlKα 20kV × 5mA 100W • Analysis size: 100 μmφ × 1.4 mm. A 100 μmφ X-ray beam is vibrated with a width of 1.4 mm. • Photoelectron extraction angle: 45° • Capture area Survey scan: 0-1100 eV Narrow scan:Al 2p、Si 2p、O 1s、C 1s • Pass energy Survey scan: 117.4 eV Narrow scan: 46.95eV

[0229] The shape of the composite particles contained in the metal pigment according to the second invention of this application is preferably flaky. As a result, the coating film formed using the metal pigment can exhibit high luminosity, high flip-flop effect, high opacity, etc. In this specification, the shape of the composite particles is "flaky" (flake-like) and refers to the average aspect ratio (shape coefficient obtained by dividing the average particle size by the average thickness) of the composite particles being 20 or more. From the viewpoint of obtaining high luminosity, flip-flop effect, opacity, etc., the average aspect ratio of the flaky composite particles is preferably 20 or more and 400 or less. An average aspect ratio of 20 or more allows for sufficient luminosity, while an average aspect ratio of 400 or less maintains the mechanical strength of the flakes and allows for a stable color tone. An aspect ratio of 25 or more is more preferable, and 30 or more is even more preferable. Furthermore, an aspect ratio of 350 or less is even more preferable, and 300 or less is even more preferable. In the present invention, the term "composite particle" refers to an aggregate (assembly) of multiple composite particles when they are aggregated and fixed together. Here, the average particle size used to calculate the average aspect ratio of the composite particles is the median diameter, which is a volume-based value D. 50 This point, as well as the explanation regarding the average thickness for calculating the average aspect ratio of composite particles, will be discussed later.

[0230] The composite particles of the second invention of this application have a volume-based D when the particle size distribution of the composite particles is measured using a laser diffraction particle size distribution analyzer. 50 However, it is preferable that the thickness is between 1 μm and 30 μm. This allows the coating film formed using the metal pigment to exhibit high brightness, high flip-flop effect, and high opacity, while suppressing the aggregation of individual particles constituting the metal pigment, thus reducing its cohesiveness. This volume-based D 50 This is also commonly referred to as the median diameter. From the viewpoint of obtaining such high luminosity, high flip-flop sensitivity, high opacity, and small aggregation of individual particles, the volume-based D when measuring the particle size distribution of composite particles with a laser diffraction particle size analyzer is considered. 50The lower limit is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, and the upper limit is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. In the present invention, the term "composite particle" refers to an aggregate (assembly) of multiple composite particles when they are aggregated and fixed together. Here, when the particle size distribution of composite particles is measured using a laser diffraction particle size analyzer, the volume-based D 50 This refers to the particle size at which the cumulative percentage in the volume cumulative particle size distribution reaches 50%. While there are no particular limitations on the laser diffraction particle size analyzer, for example, the "LA-300" (manufactured by Horiba, Ltd.) can be used. Isopropanol or mineral spirits can be used as the measurement solvent. For example, for a metal pigment containing composite particles of a sample, after ultrasonic dispersion for 2 minutes as a pretreatment, the sample is placed in a dispersion tank, and after confirming that it is properly dispersed, D 50 It can be measured.

[0231] The particle size of composite particles in the resin composition described later cannot be measured by this method. Therefore, as an alternative in this case, a method can be adopted in which composite particles in the resin composition are photographed from the surface of the coating film using an optical microscope, laser microscope, etc., and the particle size is determined by obtaining the distribution of equivalent circle diameters using commercially available image analysis software.

[0232] Volume-based D of composite particles contained in metal pigments 50This can be controlled in the manufacturing method described later by appropriately adjusting the particle size of the atomized metal powder, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc. in the step of grinding and sieving / filtering the raw material atomized metal powder (e.g., aluminum powder) using a ball mill, etc., and by appropriately adjusting the type of polysiloxane used, the pH, concentration, stirring temperature, stirring time, type of stirring device, and the power / degree of stirring (type and diameter of stirring blades, rotation speed, presence or absence of external stirring, etc.) in the step of coating with a polysiloxane layer (and other coating layers as needed).

[0233] The average thickness of the composite particles, which include metal particles and one or more coating layers on their surfaces, contained in the metal pigment of the second invention of this application is preferably 20 nm to 400 nm. This, combined with the satisfaction of the above requirements (1) to (2), results in a coating film formed using the metal pigment exhibiting high brightness, high flip-flop effect, high opacity, and so on.

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

[0235] In the present invention, the term "composite particle" refers to an aggregate (assembly) of multiple composite particles when they are aggregated and fixed together. 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 a unit mass of dry composite particles when they are uniformly diffused on the water surface using the leafing phenomenon, covering it without any gaps. The water surface diffusion area can be measured according to the provisions of JIS K5906:1998. However, in the case of composite particles of the second invention of this application, it may be difficult to determine the water surface diffusion area if the surface hydrophilicity is strong. 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) can be formed using a metal pigment dispersed in a mixture of an alcohol-based solvent such as methoxypropanol and water, and the average thickness of the composite particles can be determined 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 composite particles contained in metal pigments is based on volume D. 50 Similarly, in the method for producing metal pigments described later, the process of grinding and sieving / filtering the atomized metal powder raw material (e.g., aluminum powder) using a ball mill or the like can be controlled by appropriately adjusting the particle size of the atomized metal powder raw material, the mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, the degree of sieving and filter pressing, etc., and in the process of coating with a polysiloxane layer (and other coating layers as needed) can be controlled by appropriately adjusting the type of organosilicon compound used, the pH, concentration, stirring temperature, stirring time, type of stirring device, and the power / degree of stirring (e.g., type and diameter of the stirring blade, rotation speed, presence or absence of external stirring), etc., in the process of coating with a polysiloxane layer (and other coating layers as needed).

[0236] The coating layer of the composite particles contained in the metal pigment according to the second invention of this application is a polysiloxane layer, but a coating layer other than the polysiloxane layer (hereinafter referred to as "other coating layer") may be formed alone or together with the polysiloxane layer. Other coating layers may include, for example, at least one of the following: metals (alkali metals; alkaline earth metals; metals such as manganese, iron, cobalt, nickel, copper, and silver), 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, and fluororesin). Other coating layers can include, for example, molybdenum-containing coatings and phosphate compound coatings. By providing other coating layers, the corrosion resistance of 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 configuration of "metal particles / other coating layer / polysiloxane layer" can be suitably adopted. Although not particularly limited, examples of molybdenum-containing coatings include those disclosed in Japanese Patent Application Publication No. 2003-147226, International Publication No. 2004 / 096921, Japanese Patent No. 5979788, and Japanese Patent Application Publication No. 2019-151678. An example of a phosphate compound coating is the one disclosed in Japanese Patent Application Publication No. 4633239. A preferred example of a molybdenum-containing substance constituting a molybdenum-containing coating is the mixed-coordination type heteropolyanion compound disclosed in Japanese Patent Application Publication No. 2019-151678. In another variant, the other coating layers may be formed outside the metal particles and polysiloxane layers. In yet another variant, the components of the polysiloxane layer (such as molybdenum-containing compounds or phosphate compounds) may be incorporated within the polysiloxane layer together with the silicon compounds.

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

[0238] Other coating layers of the composite particles contained in the metal pigment according to the second invention of this application, other than the polysiloxane layer, 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 added corrosion inhibitor is not particularly limited, and any known corrosion inhibitor can be used. The amount used should be within a range that does not hinder the desired effect of the second invention of this application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organophosphorus compounds, and metal salts of molybdic acid.

[0239] Organic oligomers or polymers may be further included in the polysiloxane layer and / or other coating layer of the composite particles contained in the metal pigment, or as a separate layer, from the viewpoint of adhesion and chemical resistance when a coating film is formed. Furthermore, the polysiloxane layer and / or other coating layer of the composite particles, or a separate layer, may contain at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (or phosphate) esters and their salts, from the viewpoint of storage stability. These compounds are not particularly limited, but for example, those disclosed in Japanese Patent Application Publication No. 2019-151678 can be used.

[0240] In the second invention of this application, it is preferable that the metal pigment is an aqueous metallic paint, and when 200 g of the paint is taken into a flask and kept in a constant temperature water bath at 60°C for 24 hours, the cumulative amount of hydrogen gas generated is 10 ml or less. A gas generation of 10 ml means that the metal pigment is well covered with a polysiloxane layer, and as a result, the storage stability of the paint is good and the mechanical stability is improved. The amount of gas generated 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 amount of gas generated will be described in detail in the examples.

[0241] Method for manufacturing metal pigments The metal pigment according to the second invention of this application can be suitably manufactured by a manufacturing method that includes, for example, forming flake-shaped metal particles using a method commonly used in the pigment industry, followed by processes such as sieving (classification), filtration, washing, and mixing to produce the metal particles, and then forming a coating layer under stirring with a solvent containing water and / or a hydrophilic solvent. More specifically, the following methods are listed, but are not limited thereto. The metal pigment according to the second invention of this application can be suitably produced, for example, by a method comprising the step of forming a polysiloxane layer on the surface of the metal particles by hydrolyzing / (partially) condensing the organosilicon compound in a mixture containing (a) metal particles, (b) a silicon-containing raw material comprising at least one organosilicon compound, (c) a solvent (water and / or a hydrophilic solvent), and optionally other optional components (polysiloxane layer formation step). This step can usually be carried out under stirring.

[0242] <Grinding, sieving, and filtration processes> Here, we will explain using the case where aluminum powder is used as the metal particle. Aluminum powder is generally obtained by grinding atomized aluminum powder and / or aluminum foil using methods commonly used in the pigment industry, such as the dry ball mill method, wet ball mill method, attritor method, and stamp mill method, in the presence of grinding aids and inert solvents to form so-called flakes. After this process, it is further obtained by performing necessary steps such as sieving (classification), filtration, washing, and mixing. Examples of grinding aids used here include fatty acids, aliphatic amines, aliphatic amides, and aliphatic alcohols. Generally, oleic acid, stearic acid, and stearylamine are preferred. Examples of inert solvents include hydrophobic substances such as mineral spirits, solvent naphtha, LAWS, HAWS, toluene, and xylene, which can be used alone or in combination. The grinding aids and inert solvents are not limited to these. As for the grinding process, from the viewpoint of preventing dust explosions and ensuring safety, grinding by the wet ball mill method is preferred.

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

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

[0245] <Process for forming a polysiloxane layer> The mixture containing (a) metal particles, (b) a silicon-containing raw material comprising at least one organosilicon compound, and (c) a solvent, as well as other optional components as needed, can be prepared by mixing these components. The order of mixing is not particularly limited.

[0246] As the metal particles, the metal particles described above can be used, but aluminum or aluminum alloy particles are particularly suitable. Furthermore, as described above, it is preferable to use flaky metal particles. Known or commercially available metal particles (typically paste-like aluminum flakes) can be used.

[0247] The amount of metal particles (solid content) in the above mixture is not particularly limited and can be set appropriately depending on the type and particle size of the metal particles used.

[0248] As the silicon-containing raw material, organosilicon compounds are used. While not limited to specific types, those described above are preferably used as organosilicon compounds. An organosilicon compound represented by formula (1) above (typically tetraalkoxysilane) and / or its condensate, and at least one of the silane coupling agents represented by any of the formulas (2) to (4) above can be suitably used. In the following, we will explain using the case where tetraalkoxysilane is used as the organosilicon compound represented by formula (1) above as an example. In the following, tetraalkoxysilane and / or its condensates may be collectively referred to simply as "tetraalkoxysilane."

[0249] When using a tetraalkoxysilane represented by formula (1) above and a silane coupling agent represented by any of formulas (2) to (4) above in combination, a method of mixing the two (referred to as the "first method") can be adopted. Alternatively, a method (referred to as the "second method") can be adopted that includes the step of treating metal particles with one to form a layer of first polysiloxane, and then treating them with the other to form a layer of second polysiloxane.

[0250] One first method is a method that includes the step of forming a polysiloxane layer by appropriately adjusting the pH of a mixture containing metal particles, a tetraalkoxysilane represented by formula (1) above, and a silane coupling agent represented by any of formulas (2) to (4) above, thereby causing a hydrolysis / condensation reaction between the tetraalkoxysilane and the silane coupling agent.

[0251] As a second method, for example, a method is provided that includes the steps of: adjusting the pH of a mixture containing metal particles and a tetraalkoxysilane represented by formula (1) above to hydrolyze / condense the tetraalkoxysilane, thereby forming a layer of first polysiloxane (for example, a silica film made of amorphous silica) on the surface of the metal particles; and adjusting the pH of a mixture containing metal particles and a silane coupling agent represented by any of the formulas (2) to (4) above to hydrolyze / condense the silane coupling agent, thereby forming a layer of second polysiloxane on the surface of the first polysiloxane layer.

[0252] The amount of tetraalkoxysilane or its condensate represented by formula (1) above can be appropriately set depending on the type of tetraalkoxysilane used. The amount used may be 2 to 200 parts by mass, and more preferably 5 to 100 parts by mass, per 100 parts by mass of metal particles (solid content), from the viewpoint of coating effect and from the viewpoint of suppressing aggregation of metal particles or reduction of glossiness.

[0253] The amount of silane coupling agent represented by any of the above formulas (2) to (4) is not particularly limited, but is usually about 0.1 to 20 parts by mass per 100 parts by mass of metal particles (solids), and is particularly preferably 1 to 10 parts by mass. By using an amount of about 0.1 to 20 parts by mass, the desired coating effect and desirable coating film properties can be obtained.

[0254] The solvent in the mixture, i.e., the solvent for the hydrolysis and / or condensation reaction of the organosilicon compound, can be appropriately selected depending on the type of silicon-containing raw material used, but usually water, a hydrophilic organic solvent, or a mixture thereof can be used. By using these solvents, the uniformity of the reaction and the uniformity of the resulting hydrolysate and / or condensation product can be improved. In embodiments in which a polysiloxane layer is formed directly on metal particles, it is particularly preferable that the solvent in the mixture contains a hydrophilic organic solvent from the viewpoint of avoiding a rapid reaction between the metal particles and water. In the second invention of this application, a mixture of water and a hydrophilic organic solvent can be suitably used.

[0255] Examples of hydrophilic organic solvents are not particularly limited, but include alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol; ether alcohols and their esters such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. These can be used individually or in combination of two or more.

[0256] Furthermore, when a mixed solvent of water and a hydrophilic organic solvent is used as the solvent, the ratio of the two is not particularly limited. In embodiments in which a polysiloxane layer is directly formed on metal particles, from the viewpoint of avoiding a rapid reaction between the metal particles and water, it is preferable that the water content be 20% by mass or less, with the total of the two being 100% by mass, before adding the silicon compound. In this case, the lower limit of the water content is not limited.

[0257] The amount of solvent used in the polysiloxane layer formation process (excluding the amount of solvent used for pre-dispersion of metal particles, if applicable) is not limited, but is usually sufficient to be around 100 to 10,000 parts by mass per 100 parts by mass of metal particles (solids), and is particularly preferable to be 200 to 1,000 parts by mass. Using 100 parts by mass or more of solvent suppresses the increase in viscosity of the mixture (slurry) and allows for appropriate stirring. Using 10,000 parts by mass or less of solvent can prevent high costs for recovering and regenerating the processed liquid. Note that, in the case of the second method described above, the amount of solvent used here refers to the total amount of solvent used for forming the first polysiloxane layer and the second polysiloxane layer.

[0258] In the above-mentioned mixture, other additives may be added as needed, within the limits that do not impede the effects of the second invention of this application. Examples include catalysts such as hydrolysis catalysts and dehydration condensation catalysts, as well as surfactants, metal corrosion inhibitors, and the like.

[0259] Among these, hydrolysis catalysts can be suitably used. By incorporating a hydrolysis catalyst, the pH of the mixture can be adjusted, and the organosilicon compounds can be efficiently hydrolyzed and dehydrated, resulting in the efficient and reliable formation of a polysiloxane layer on the surface of the metal particles.

[0260] In the second invention of this application, it is preferable to use a catalyst with high catalytic activity, that is, a catalyst with a pH far from the neutral range, or to raise the temperature in order to strengthen the polysiloxane layer. However, under such conditions, there is a risk of corrosion of the metal particles. For this reason, by first covering the surface of the metal particles with a polysiloxane layer by a reaction under mild conditions, and then carrying out the reaction under conditions that allow for a higher reaction rate, a strong structure can be formed, thereby suppressing metal corrosion and preventing a decrease in storage stability and color degradation during circulation.

[0261] In the initial mild reaction, which coats the surface of metal particles with a polysiloxane layer without corrosion, it is preferable to use a known weak base compound such as ammonia as a catalyst in an amount of 0.1 mol% to 100 mol% relative to the silicon-containing compound, and to carry out the reaction at a temperature in the range of 10 to 55°C. More preferably, the catalyst amount is 1 mol% to 80 mol%, 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] The catalyst can be any known or commercially available one and is not particularly limited. Examples of hydrolysis catalysts include inorganic alkalis such as ammonia; and amines such as monomethylamine, dimethylamine, trimethylamine, pyridine, and aniline. These catalysts can be used individually or in combination of two or more.

[0263] Alternatively, a preferred method involves using a compound composed of a weak acid-weak base pair as a catalyst. Preferably, such a catalyst is 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 using a compound whose pKa and / or pKb of the acid and base constituting the compound are 3.5 or higher, which is the lower limit of these ranges, the hydrolysis and condensation reactions of the silicon-containing compound can proceed by a mechanism similar to that under acidic or basic conditions, corrosion of metal particles can be suppressed, and high catalytic activity can be observed. On the other hand, by using a compound whose pKa and / or pKb of the acid and base constituting the compound are 5.5 or lower, which is the upper limit of these ranges, sufficient catalytic activity can be obtained, and a decrease in color tone due to particle aggregation and enlargement caused by prolonged contact of uncoated metal particles with water can be avoided.

[0264] Preferred examples of compounds composed of these weak acid-weak base pairs include ammonium benzoate, ammonium p-tolulate, ammonium m-tolulate, ammonium o-tolulate, 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 bicarbonate, ammonium carbamate, and ammonium lactate. Among these, ammonium benzoate, ammonium p-tolulate, ammonium m-tolulate, and ammonium o-tolulate derived from aromatic carboxylic acids, and ammonium acetate, ammonium propionate, ammonium carbonate, ammonium bicarbonate, and ammonium carbamate, which have short carbon chains, are particularly preferred.

[0265] Such catalysts are preferably used in amounts of 1 mol% to 200 mol% relative to the silicon compound, and more preferably in amounts of 2 mol% to 150 mol%. 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. Even under the conditions described above, it is desirable to appropriately adjust the reaction time, in addition to the amount of catalyst and temperature, so that corrosion does not occur depending on the type of metal particle and an appropriate coating state is achieved.

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

[0267] Furthermore, it is preferable to carry out the reaction under neutral to weakly basic conditions with a pH of 6 to 9. A pH above the lower limit of this range can inhibit the hydrolysis and condensation reactions from proceeding through acidic conditions. Conversely, a pH below the upper limit of this range can inhibit the same reaction from proceeding through basic conditions, as in the prior art. This pH range is more preferably 6.5 to 9, and even more preferably 7 to 8.5.

[0268] In the reaction to form a strong structure, which follows the reaction under the mild conditions described above, it is preferable to use a known weak base compound such as ammonia as a catalyst in an amount of 100 mol% to 1000 mol% relative to the silicon-containing compound, and in an amount 2 to 10 times the amount used in the mild reaction, and to carry out the reaction at a temperature in the range of 40 to 80°C. It is more preferable to use an amount of catalyst of 110 mol% to 5000 mol%, and in an amount 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, even 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; and phosphonic acids such as vinylphosphonic acid, 2-carboxyethanephosphonic acid, 2-aminoethanephosphonic acid, and octanephosphonic acid can be used. These hydrolysis catalysts may be used individually or in combination of two or more.

[0270] Furthermore, catalysts such as inorganic alkalis including ammonia, sodium hydroxide, and potassium hydroxide; inorganic alkali salts including ammonium carbonate, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate; amines including monomethylamine, dimethylamine, trimethylamine, pyridine, and aniline; and salts of organic acids including ammonium formate, ammonium acetate, monomethylamine formate, and aniline acetate can also be used. These hydrolysis catalysts can be used individually or in combination of two or more.

[0271] In reactions aimed at forming robust structures, using compounds composed of a weak acid-weak base pair is also a preferred method.

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

[0273] Specific methods to suppress corrosion of metal particles and increase the reaction rate include first adding a small amount of NH3 catalyst and reacting at a low temperature, then adding a sufficient amount of NH3 catalyst and raising the temperature to continue the reaction. Furthermore, to increase the reaction rate, it is preferable to use two or more catalysts with different basicities in combination. In particular, in the initial stages of the reaction, a weakly basic catalyst can be used to keep the pH low and promote the hydrolysis and dehydration condensation of silane. Once the reaction has progressed to a certain extent, a stronger catalyst can be used to raise the pH and promote the remaining hydrolysis and dehydration condensation reactions. As a result, a higher reaction rate can be obtained compared to conventional polysiloxane formation techniques, and a robust polysiloxane layer can be formed.

[0274] A combination of weak acids and weak bases satisfying the aforementioned pKa and pKb values ​​may be used, and the compound generated in situ may be used as a catalyst. For example, to generate the preferred catalyst compounds in situ, one can add benzoic acid, p-toluic acid, m-toluic acid, o-toluic acid, acetic acid, propionic acid, or carbamic acid to ammonia, respectively. Alternatively, acidic or basic salts may be used in combination, such as sodium benzoate and ammonium chloride, or sodium acetate and ammonium chloride.

[0275] <Other coating layer formation processes> As described above, the other coating layer is preferably formed (if any) between the metal particles and the polysiloxane layer. Therefore, a layer configuration of "metal particles / other coating layer / polysiloxane layer" can be suitably adopted. Other coating layers are not particularly limited, but may include molybdenum-containing coatings, phosphate compound coatings, and the like. A preferred example of a molybdenum-containing substance constituting a molybdenum-containing coating is the mixed-coordinate heteropolyanion compound disclosed in Japanese Patent Application Publication No. 2019-151678. Examples of other coating layer components, including the mixed-coordinate heteropolyanion compound, are as described above. In the following sections, we will explain an example in which a molybdenum-containing coating is formed as another coating layer between the metal particles and the polysiloxane layer.

[0276] When forming a molybdenum-containing coating as an additional coating layer between metal particles and a polysiloxane layer, the molybdenum-containing coating can be formed on the surface of the metal particles by stirring a mixture containing metal particles and a molybdenum compound (typically a mixed-coordinate heteropolyanionic compound) prior to the formation of the polysiloxane layer. The method for forming a molybdenum-containing film on the surface of metal particles is not particularly limited, and any method that allows for uniform stirring of a mixture containing metal particles and a molybdenum compound in an aqueous solvent is acceptable. For example, a molybdenum-containing film can be formed on the surface of metal particles by stirring or kneading a mixture containing metal particles and a molybdenum compound in a slurry or paste state. In the mixture, the molybdenum compound may be dissolved or dispersed.

[0277] Furthermore, the stirrer used to agitate the mixture containing metal particles and molybdenum compounds is not particularly limited, and any known stirrer capable of efficiently and uniformly agitating the mixture containing aluminum particles and molybdenum compounds can be used. Specific examples include kneaders, mixing machines, rotary vessel stirrers, agitated reaction vessels, V-type stirrers, double-cone stirrers, screw mixers, sigma mixers, flash mixers, airflow stirrers, ball mills, edge runners, etc. The stirring blades of the stirrer are not particularly limited, but examples include anchor blades, paddle blades, propeller blades, turbine blades, etc.

[0278] When forming a molybdenum-containing coating as another coating layer, the amount of molybdenum compound used can be appropriately set depending on the type of molybdenum compound used. Generally, this amount should be 0.02 to 20 parts by mass per 100 parts by mass of metal particles (solids), and is particularly preferably 0.1 to 10 parts by mass. A content of 0.02 parts by mass or more allows for sufficient treatment effect to be obtained. Furthermore, a content of 20 parts by mass or less allows for high brilliance to be maintained in the resulting metal pigment.

[0279] Typically, water, hydrophilic organic solvents, or mixtures thereof can be used as solvents for mixing metal particles with molybdenum compounds.

[0280] Examples of hydrophilic organic solvents include alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol; ether alcohols and their esters such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. One or more of these can be used.

[0281] The amount of solvent used in the other coating layer formation steps (excluding the amount of solvent used for pre-dispersion of metal particles, if applicable) is not particularly limited, but is usually preferably 50 to 5000 parts by mass, and more preferably 100 to 2000 parts by mass, per 100 parts by mass of metal particles (solid content). Using 50 parts by mass or more of solvent can suppress the uneven distribution of molybdenum compounds and the aggregation of metal particles. Using 5000 parts by mass or less of solvent can provide a sufficient treatment effect of the molybdenum compound on the metal particles.

[0282] When stirring a mixture containing metal particles and a molybdenum compound, the temperature of the mixture should generally be around 10-80°C, and preferably 30-70°C. A temperature of 10°C or higher allows for a shorter reaction time to obtain sufficient processing effect. Furthermore, a temperature of 80°C or lower makes it easier to control the reaction to obtain the desired metal pigment.

[0283] The stirring time of the mixture is not particularly limited, as long as it is sufficient time for the desired molybdenum-containing coating to form. This stirring time is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours. A stirring time of 0.5 hours or more allows for sufficient treatment effect. Furthermore, a stirring time of 10 hours or less can suppress an increase in treatment costs.

[0284] After stirring of the mixture containing metal particles and molybdenum compound is complete, the particles with the other coating layer can be recovered. In this case, known washing, solid-liquid separation, etc., can be carried out as appropriate as needed. For example, it is preferable to wash the mixture with a hydrophilic organic solvent and then filter it using a filter or the like to remove water and unreacted substances from the cake containing metal particles with the molybdenum-containing coating. In this way, the molybdenum-containing coating, which is the other coating layer, can be formed. The formation of other coating layers can also be carried out in accordance with the above method.

[0285] In an embodiment in which a polysiloxane layer is formed on metal particles following another coating layer (molybdenum-containing coating), after stirring of the mixture containing the metal particles and the molybdenum compound is completed, the particles on which the other coating layer has been formed may be recovered, and a dispersion of water and / or a hydrophilic organic solvent of a silicon compound source (typically, an organosilicon compound represented by formula (1) above, such as tetraalkoxysilane and / or its condensates, and at least one silane coupling agent represented by any of formulas (2) to (4) above) may be directly added and stirred into the system. At this time, a dispersion of an organosilicon compound represented by formula (1) above, such as tetraalkoxysilane and / or its condensates, may be added to the system containing the particles on which the other coating layer has been formed, and then a dispersion of at least one silane coupling agent represented by any of formulas (2) to (4) above may be added and stirred (see the second method in the "Polysiloxane Layer Formation Step" described above).

[0286] <Stirring conditions> In the production of the metal pigment according to the second invention of this application, it is desirable to carry out at least the process of forming the coating layer of the composite particles, typically a polysiloxane layer, under stirring. Furthermore, in the production of the metal pigment according to the second invention of this application, it is preferable to carry out not only the process of forming the polysiloxane layer but also the process of forming other coating layers under stirring. In the embodiment in which the metal particles are pre-dispersed as described above, it is even more preferable to carry out this process under stirring. Moreover, in the production of the metal pigment according to the second invention of this application, it is even more preferable to carry out the entire process, including the pre-dispersion of the metal particles, the process of forming other coating layers, and the process of forming the polysiloxane layer, under stirring.

[0287] In the production of the metal pigment according to the second invention of this application, by carrying out at least the process of forming a coating layer on the composite particles, typically a polysiloxane layer, under appropriately controlled stirring, it is possible to effectively suppress or prevent the phenomenon of composite particles adhering to each other via the polysiloxane layer, or of aggregated particles consisting of metal particles being coated with the polysiloxane layer. Furthermore, by carrying out the entire process, including the pre-dispersion of metal particles, the formation of other coating layers, and the formation of the polysiloxane layer (until all the layers to be formed on the surface of the metal particles have been formed), under stirring, it becomes possible to more easily obtain the metal pigment according to the second invention of this application that satisfies all of the above physical property requirements. The following description of stirring conditions may apply to any step in the production of the metal pigment according to the second invention of this application.

[0288] Agitation can be carried out using known or commercially available agitation devices. For example, at least one of the following can be used: a kneader, a mixing machine, a rotary vessel agitator, agitated reaction vessel, a V-type agitator, a double-cone agitator, a screw mixer, a sigma mixer, a flash mixer, an airflow agitator, a ball mill, an edge runner, etc. Among these agitators, it is preferable to use a stirred tank type device that stirs using impeller blades. The impeller blades exert a circulating action that causes the entire reaction system, including the liquid phase, to flow, as well as a pressure shearing action, which can more effectively suppress the formation of aggregates of composite particles.

[0289] The shape of the impeller blade is not particularly limited, and for example, anchor type, propeller type, turbine type, inclined turbine type, fan turbine type, paddle type, inclined paddle type, and gate type can be used. Maxblend blades (manufactured by Sumitomo Heavy Industries Process Equipment Co., Ltd.) and Fullzone blades (manufactured by Kobe Steel Environmental Solutions Co., Ltd.) are also suitable. Furthermore, multiple stages of these shaped impeller blades can be combined. The stirring speed should preferably be such that the stirring blades are not exposed by the vortex generated by the stirring. Furthermore, cylindrical tanks, rectangular tanks, or tanks equipped with baffles can be suitably used to suppress the vortex generated by the stirring.

[0290] In the production of metal pigments containing composite particles according to the second invention of this application, it is desirable to set the optimal size of the stirring tank and impellers, and the speed of the impellers, in relation to the volume and physical properties (density, viscosity, etc.) of the mixed liquid. The size of the stirring tank should be selected so that the maximum volume of the mixed liquid used in the series of processes is 20-80% of the stirring tank's capacity. In the case of a cylindrical stirring tank, the ratio of the height (L) to the inner diameter (D) of the stirring tank, L / D, is generally in the range of 0.5-3.0, and is usually in the range of 1-2. The size of the impellers is generally such that the maximum diameter is in the range of 0.2-0.9 of the inner diameter of the stirring tank, and is preferably around 0.4-0.6. The shape (including length) of the impellers should be 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, to prevent stagnant areas that are not stirred from forming near the liquid surface or the bottom of the stirring tank, it is preferable to combine inclined paddle type, inclined turbine type, or propeller type impellers in multiple stages, or to use max blend impellers or full zone impellers, as these easily generate upstream and downstream flow. In this case, it is desirable to maintain a distance of 5 mm or more between the stirring blade and the inner surface of the stirring tank (including the baffle plate). Doing so makes it easier to suppress damage and deformation of the metal particles.

[0291] The speed of the stirring blade tip is preferably 0.5 to 50 m / s, more preferably 1 to 20 m / s, and even more preferably 2 to 10 m / s. By having the speed of the stirring blade tip within the range of 0.5 to 50 m / s, the dispersibility of the composite particles in the resulting metal pigment can be improved, and consequently, it becomes easier to obtain a metal pigment with low aggregation of individual particles, excellent opacity and color tone, and low gas generation. Furthermore, by having the stirring linear speed within the above range, damage to the metal particles (e.g., flaky aluminum powder) is prevented, and the rate of the hydrolysis / condensation reaction can be appropriately controlled, effectively suppressing aggregation of composite particles.

[0292] <Recovery of composite particles> After the surface coating process with polysiloxane is completed, the composite particles can be recovered. During recovery, known treatments such as washing and solid-liquid separation can be performed as needed. For example, it is preferable to wash the obtained slurry with water / organic solvent (preferably a hydrophilic solvent) and then filter it using a filter to remove water and unreacted substances from the slurry containing the coated composite particles. Alternatively, the filtered slurry may then be heat-treated at a temperature in the range of, for example, 100 to 500°C, as needed. The recovered composite particles, as described later, typically contain residual and entrained solvents, including water / organic solvent, used in the manufacturing process, constituting a metal pigment.

[0293] Metal pigment composition The metal pigment of the second invention obtained as described above is obtained in the form of a metal pigment composition comprising composite particles including metal particles (and a surface modifier if present) and a polysiloxane coating on their surface, and a solvent such as water / organic solvent (preferably a hydrophilic solvent) used in the manufacturing process as the residue of the solid content (non-volatile content). The metal pigment composition may typically contain a silicon compound that is a hydrolysate and / or condensate thereof of an organosilicon compound (for example, at least one organosilicon compound represented by the above general formula (1), a silane coupling agent represented by any of the above general formulas (2), (3), and (4), and at least one of them selected from their partial condensates), in an amount of 0.02 to 50 parts by mass per 100 parts by mass of metal particles, calculated based on the state after the hydrolysis / condensation reaction is complete.

[0294] The metal pigment composition may contain, in an optional manner, 0.01 to 10 parts by mass of a compound that forms an optional other coating layer (in an optional manner in which a molybdenum-containing film is formed as the other coating layer, a molybdenum-containing compound, such as a mixed-coordination heteropolyanionic compound) per 100 parts by mass of metal particles. The metal pigment composition may contain 0.01 to 50 parts by mass of an optional organic oligomer or polymer per 100 parts by mass of metal particles. The metal pigment composition may contain at least one selected from the group consisting of any choice of inorganic phosphoric acids and their salts, and acidic organic (or phosphate) esters and their salts, in amounts of 0.01 to 20 parts by mass per 100 parts by mass of metal particles. The metal pigment composition may contain a solvent, including water / hydrophilic solvent, as a residue of the above-mentioned components (non-volatile matter), which was used in the manufacturing process. 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 other components not listed above. Examples of optional components include at least one of the following: antioxidants, light stabilizers, polymerization inhibitors, and surfactants. Antioxidants that can be used include phenolic compounds, phosphorus compounds, and sulfur compounds. As light stabilizers, those used as antioxidants as mentioned above can be used, but those represented by benzotriazole compounds, benzophenone compounds, salicylate compounds, cyanoacrylate compounds, oxalic acid derivatives, hindered amine compounds (HALS), and hindered phenol compounds can also be used.

[0296] Examples of surfactants include nonionic surfactants such as polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, oxyalkylene alkylamino ethers, sorbitan fatty acid esters, polyalkylene glycol fatty acid esters, and glycerin fatty acid esters; anionic surfactants such as sulfate ester salts, sulfonates, and phosphate ester salts; and cationic surfactants such as quaternary ammonium salts. One or more of these can be used. Particularly preferred examples among these include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, or mixtures thereof.

[0297] (Moisture percentage) The moisture content of the metal pigment composition of the second invention of this application is preferably 0 ppm or more and 2000 ppm or less by mass relative to the metal pigment composition. By having such a moisture content, aggregation of the composite particles of the metal pigment composition and the progression of color changes in a package, such as a metal container in which the metal pigment composition is sealed, can be further suppressed. The moisture content is more preferably 1000 ppm or less, even more preferably 500 ppm or less, and particularly preferably 300 ppm or less. There is no lower limit for the moisture content; the lower the better.

[0298] To achieve such a moisture content, in the process of manufacturing the metal pigment, after the step of forming a polysiloxane layer (and / or, optionally, other coating layers) on the metal particles is completed, known treatments such as washing and solid-liquid separation are performed. In this process, it is preferable to wash the dispersion with an organic solvent with a moisture content of 2000 ppm or less, then filter it using a filter, and if necessary, repeat this operation multiple times to remove water and unreacted substances from the composition containing the composite particles. After that, if necessary, the cake containing the composite particles may be subjected to heat dehydration treatment in a gaseous atmosphere such as nitrogen with a low moisture content at a temperature in the range of 100 to 500°C. The composite particles recovered in this way may constitute a metal pigment composition that typically contains a small amount of water / hydrophilic solvent remaining in the solvent used in the manufacturing process.

[0299] Furthermore, when adjusting the solid content ratio of the composition, it is desirable to use an organic solvent with a water content of 2000 ppm or less (for example, the hydrophilic solvent mentioned above). The water content of the organic solvents used for these washing and solid content adjustments is preferably 2000 ppm or less, more preferably 1000 ppm or less, even more preferably 500 ppm or less, and particularly preferably 300 ppm or less.

[0300] (pH) The metal pigment composition of the second invention of this application preferably has a pH in the range of 5 to 9. By setting the pH within this range, aggregation of composite particles of the metal pigment composition in the packaging and the progression of color changes can be suppressed. The pH of the metal pigment composition is more preferably in the range of 6 to 8, and even more preferably in the range of 6.5 to 7.5. To achieve the pH of such a metal pigment composition, it is desirable to repeatedly perform known treatments such as washing and solid-liquid separation with a sufficient amount of organic solvent after the step of forming a polysiloxane layer (and / or, optionally, other coating layers) on the metal particles is completed, thereby thoroughly washing and removing polar compounds such as catalysts used in forming the coating layers.

[0301] The metal pigment of the second invention of this application can be used in organic solvent-based paints, inks, etc. In this case, by adding the metal pigment of the second invention of this application to an aqueous paint or aqueous ink in which the resins that form the film are dissolved or dispersed in a medium mainly composed of water, a metallic aqueous paint or metallic aqueous ink can be obtained. Furthermore, the metal pigment of the second invention of this application can also be kneaded with resins, etc., and used as a water-resistant binder or filler. For example, any additives such as antioxidants, light stabilizers, polymerization inhibitors, surfactants, etc., may be added when blending the metal pigment with aqueous paints, aqueous inks, or resins, etc.

[0302] When the metal pigment of the second invention of this application is used in paints or inks, it may be added directly to the (water-based) paint or (water-based) ink, but it is preferable to disperse it in a solvent beforehand. Examples of solvents that can be used in this case include water, texanol, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, etc. Examples of the resins mentioned above include acrylic resins, polyester resins, polyether resins, epoxy resins, fluororesins, rosin resins, etc.

[0303] The content of the metal pigment of the second invention of this application in the above-mentioned aqueous paint composition or aqueous ink composition is not limited, but is usually 0.1 to 50% by mass, and is particularly preferably 1 to 30% by mass. A content of 0.1% by mass or more allows for a high decorative (metallic) effect to be obtained. Furthermore, a content of 50% by mass or less prevents the properties of the aqueous paint composition or aqueous ink composition, such as weather resistance, corrosion resistance, and mechanical strength, from being impaired. The solvent content in this case is not particularly limited, but may be 20 to 200% by mass relative to the resin binder content. A solvent content within this range allows the viscosity of the paint or ink to be adjusted to an appropriate range, making handling and film formation easier.

[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 may be used in combination. Furthermore, these resins may be combined with inorganic pigments, organic pigments, extender pigments, silane coupling agents, titanium coupling agents, dispersants, anti-settling agents, leveling agents, thickeners, and defoaming agents that are commonly added to paints. Surfactants may be added to further improve the dispersibility of resins in the paint. Antioxidants, light stabilizers, and polymerization inhibitors may be added to further improve the storage stability of the paint.

[0305] Third Invention The third invention of this application is, A method for producing a metal 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 metal particles with a silicon compound, and (3) The process of filtering and washing, The aforementioned stirred tank type reactor, The volume of the reaction vessel is 100L 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 aforementioned stirring blade during stirring is 1 to 20 m / s. The manufacturing method described above. The details of the third invention of this application will be described below.

[0306] Reactor type reactor In the method for producing a metal pigment (also referred to as a "metal pigment composition") according to the third invention of this application, a stirred-tank reactor is used. A stirred-tank reactor is a device of the stirred-tank type that stirs using a stirring blade (impeller). The stirring blade exerts a circulating action that causes the entire reaction system, including the liquid phase, to flow, as well as a pressure shear action, which in turn can more effectively suppress the formation of aggregates of composite particles.

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

[0308] The stirring speed should preferably be such that the stirring blades are not exposed by the vortex generated by the stirring. Furthermore, cylindrical tanks, rectangular tanks, or tanks equipped with baffles can be suitably used to suppress the vortex generated by the stirring.

[0309] In the manufacturing method of the third invention of this application, it is desirable to set the optimal reaction vessel (sometimes called a "stirring vessel"), 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 liquid. The size of the reaction vessel is preferably selected so that the maximum amount of mixed liquid used in the series of steps is 20-80% of the reaction vessel's capacity, and the volume of the reaction vessel is preferably 100 L or more in order to prepare the industrially required amount of pigment with low quality variation. In one embodiment, it is sometimes desirable for the volume of the reaction vessel to be 150 L or more, or sometimes 200 L or more. The shape of the reaction vessel is preferably cylindrical in order to reduce stagnant areas and stir the entire vessel uniformly, and in the case of a cylindrical reaction vessel, the ratio of the height (L) to the inner diameter (D) of the reaction vessel, L / D, is generally in the range of 0.5 to 3.0, and is usually in the range of 1 to 2. In addition, the size of the stirring blade is preferably such that the ratio of the inner diameter of the reaction vessel to the maximum diameter of the stirring blade is in the range of 0.2 to 1.0, and is about 0.4 to 0.6. The shape (including length) of the stirring blades should be appropriately selected according to the physical properties of the mixed liquid, and it is important that the entire reaction vessel is stirred throughout the process. In particular, to prevent the formation of unmixed stagnant areas near the liquid surface or the bottom of the reaction vessel, it is preferable to combine inclined paddle type, inclined turbine type, or propeller type blades in multiple stages, or to use Maxblend blades or Fullzone blades, as these facilitate the generation of upstream and downstream currents. In this case, the shortest distance between the inner surface of the reaction vessel (including the baffles) and the stirring blades should preferably be 10 mm or more if the volume of the reaction vessel is 100 L or more. More preferably, the shortest distance between the inner surface of the reaction vessel (including the baffles) and the stirring blades should be 20 mm or more, even more preferably 40 mm or more, even more preferably 60 mm or more, and even more preferably 100 mm or more. Doing so makes it easier to suppress damage and deformation of metal particles.

[0310] When the volume of the reaction vessel is 100 L or more, the tip velocity (linear velocity) of the stirring blade is preferably 1 to 20 m / sec, more preferably 1.5 to 10 m / sec, and particularly preferably 2 to 8 m / sec. By keeping the tip velocity of the stirring blade within the range of 1 to 20 m / sec, the dispersibility of the composite particles in the resulting metal pigment composition can be improved, and consequently, it becomes easier to obtain a metal pigment composition with low aggregation of individual particles, excellent opacity and color tone, and low gas generation. Furthermore, by keeping the tip velocity (linear velocity) of the stirring within the above range, damage to the metal particles (e.g., flaky aluminum powder) is prevented, and the rate of the hydrolysis / condensation reaction can be appropriately controlled, effectively suppressing aggregation of composite particles.

[0311] The stirring Reynolds number (hereinafter abbreviated as "stirring Re number") is used as an indicator to represent the stirring state. The stirring Re number does not reflect the size other than the shape and diameter of the reaction vessel and impeller. Therefore, the stirring Re number is only a guideline and is not particularly limited, but it is preferably 3000 or higher, and more preferably 5000 or higher. 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 around 100,000 in a typical laboratory scale, but when using a large-scale device, it may exceed 100,000 as long as the desired effect of the third invention of this application is not hindered. For example, an upper limit of around 1 million is also acceptable.

[0312] The stirring number Re here is calculated using the following formula. Stirring Re number = (ρ×n×d 2 ) / μ (In the formula, ρ is the density of the mixed liquid being stirred at 25°C (kg / m³) 3 ) where n is the stirring speed (rps), d is the impeller diameter (m), and μ is the viscosity of the mixed liquid being stirred at 25°C (Pa·s).

[0313] Metal pigment composition The metal pigment composition produced according to the third invention of this application contains composite particles, the composite particles comprising metal particles and one or more coating layers formed on their surfaces. 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 may be any known or commercially available metal used as a metal pigment, such as aluminum, aluminum alloys, zinc, iron, magnesium, nickel, copper, silver, tin, chromium, stainless steel, etc. In this specification, the metal of the metal particles contained in the metal pigment composition includes not only elemental metals but also alloys and intermetallic compounds. The metal particles may be used individually or in combination of two or more types.

[0315] The average particle size of the metal particles is not particularly limited, but the D in the particle size distribution of the composite particles 50 The average particle size may be such that it can produce the following: That is, when the volume distribution is measured with a laser diffraction particle size analyzer in composite particles, D 50 The volume-average particle size (D) of the metal particles should be set to 0.1 to 30 μm. 50 ) should be set. Here, the volume-based D when measuring the particle size distribution of composite particles with a laser diffraction particle size analyzer 50 This refers to the particle size at which the cumulative percentage in the volume cumulative particle size distribution reaches 50%. While not particularly limited, the laser diffraction particle size analyzer can be used, such as the "LA-300" (manufactured by Horiba, Ltd.). Mineral spirits can be used as the measurement solvent. For example, a metal pigment composition containing composite particles of the sample is subjected to ultrasonic dispersion for 2 minutes as a pretreatment, then placed in a reaction vessel and, after confirming proper dispersion, D 50 It can be measured. The average particle size of metal particles can be controlled in the process of grinding, sieving, and filtering atomized metal powder (e.g., aluminum powder) using a ball mill or the like, by appropriately adjusting the particle size of the atomized metal powder, the specific gravity and mass of each grinding ball when using a ball mill, the rotation speed of the grinding device, and the degree of sieving and filter pressing.

[0316] The shape of the metal particles is not limited, but it is particularly desirable that they be flaky. This allows the composite particles contained in the metal pigment composition produced by the third invention of this application to also have a flaky shape, resulting in a more reliable acquisition of high opacity and other properties. From this viewpoint, the aspect ratio (shape coefficient obtained by dividing the average particle size by the average thickness) of the flaky metal particles is preferably 1 to 1000, and more preferably 15 to 500. An aspect ratio of 1 or more of the metal particles allows for a higher degree of brilliance to be obtained. Furthermore, an aspect ratio of 1000 or less of the metal particles maintains the mechanical strength of the flakes and allows for a stable color tone to be obtained. Here, the average thickness of the metal particles used in the third invention of this application can be calculated from the water surface diffusion area and density of the metal particles.

[0317] Furthermore, the metal particles do not necessarily have to be composed solely of metal; as long as they do not hinder the effects of the third invention of this application, particles made of synthetic resin, mica, glass, or other inorganic particles whose surfaces are coated with metal can also be used. In the third invention of this application, it is particularly desirable that the particles be made of aluminum or an aluminum alloy due to their high weather resistance, low specific gravity, and ease of availability.

[0318] Aluminum flakes, which are commonly used as metallic pigments, are particularly suitable as metal particles constituting the composite particles. Suitable aluminum flakes are those that possess the surface properties, particle size, and shape required for metallic pigments, such as surface gloss, whiteness, and brilliance. Aluminum flakes are usually commercially available in paste form. Paste-like aluminum flakes usually contain flaky aluminum powder, as well as residual mineral spirits (aliphatic hydrocarbons) and fatty acids used during pulverization, and organic solvents such as solvent naphtha and xylene. Paste-like aluminum flakes may be used as is, or the fatty acids on the surface may be removed beforehand with an organic solvent. Also, the volume average particle size (D 50 So-called aluminum vapor-deposited foils with a thickness of 3-30 μm and an average thickness (t) of 5-50 nm can also be used.

[0319] Covering layer The composite particles contained in the metal pigment composition manufactured according to the third invention of this application have one or more coating layers formed on the surface of the metal particles that form 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 it is made into a coating film is excellent. In addition to the silicon compound-containing layer, the coating layer of the composite particles may also have other coating layers (hereinafter referred to as the "second coating layer"). Such a second coating layer will be described further later.

[0320] Silicon compound-containing layer The silicon compound-containing layer is preferably composed of compounds containing Si-O bonds (siloxane bonds). Examples of such layers include those containing at least one silane compound and a silicon oxide. Examples of such compounds include silane compounds [H3SiO(H2SiO)] nExamples of silicon oxides include those represented by [SiH3] (where n is any positive integer), SiO2, SiO2·nH2O (where n is any positive integer), etc. These silane compounds and silicon oxides may be crystalline or amorphous, but amorphous is particularly preferred. Therefore, as a layer containing silicon oxide (silica, etc.), for example, a layer containing amorphous silica can also be suitably adopted.

[0321] Furthermore, the layer composed of a compound containing a 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, to the extent that it does not impede the effects of the third invention of this application. In a typical example, the layer composed of a compound containing a Si-O bond can be formed by hydrolysis of an organosilicon compound.

[0322] The silicon compound-containing layer may contain additives, impurities, etc. other than silicon compounds, as long as they do not impair the properties of the third invention of this application.

[0323] The silicon content in the silicon compound-containing layer is not particularly limited, but is preferably 1 to 30 parts by mass per 100 parts by mass of metal particles, and more preferably 2 to 20 parts by mass. A silicon content of 1 part by mass or more per 100 parts by mass of metal particles can maintain high corrosion resistance, water dispersibility, and stability of the metal pigment composition. A silicon content of 30 parts by mass or less per 100 parts by mass of metal particles can prevent aggregation of composite particles and a decrease in color tone, such as opacity and metallic luster.

[0324] The coating layer of the composite particles contained in the metal pigment composition manufactured according to the third invention of this application is preferably hydrophilic. The composite particles usually form a metal pigment composition in which they are dispersed in an aqueous solvent (water or a mixed solvent containing water and an organic solvent), but if the coating layer has a hydrophilic surface, the composite particles can be highly dispersed in such an aqueous solvent. Moreover, since silicon oxides (such as amorphous silica) are very stable in aqueous solvents, it is possible to provide a metal pigment composition containing composite particles that are highly stable in an aqueous solvent. From this viewpoint, it is desirable that the composite particles contained in the metal pigment composition manufactured according to the third invention of this application have at least the outermost layer be a silicon compound-containing layer (particularly a layer composed of a compound containing Si-O bonds). If the coating layer is composed of multiple layers, in addition to the outermost silicon compound-containing layer, a silicon compound-containing layer (particularly a Si-O-based coating layer) may be formed separately as a layer other than the outermost layer.

[0325] 2nd coating layer The coating layer of the composite particles contained in the metal pigment composition manufactured according to the third invention of this application is not particularly limited except that at least one layer is a silicon compound-containing layer, but coating layers other than the silicon compound-containing layer can also be formed as needed.

[0326] The second coating layer may consist of at least one of the following: metals (alkali metals; alkaline earth metals; metals such as manganese, iron, cobalt, nickel, copper, and silver), metal oxides (titanium oxide, zirconium oxide, iron oxide, etc.), metal hydrates, and resins (synthetic resins such as acrylic resins, alkyd resins, polyester resins, polyurethane resins, polyvinyl acetate resins, nitrocellulose resins, and fluororesins). For example, a molybdenum-containing coating or a phosphate compound coating can be formed as the second coating layer. 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 is preferably formed between the metal particles and the silicon compound-containing layer (if formed). Therefore, for example, a layer configuration of "metal particles / second coating layer / silicon compound-containing layer" can be suitably adopted. Examples of molybdenum-containing coatings, though not particularly limited, include those disclosed in Japanese Patent Application Publication No. 2003-147226, International Publication No. 2004 / 096921, Japanese Patent No. 5979788, and Japanese Patent Application Publication No. 2019-151678. An example of a phosphate compound coating is the one disclosed in Japanese Patent Application Publication No. 4633239. A preferred example of a molybdenum-containing substance constituting the molybdenum-containing coating is the mixed-coordination type heteropolyanion compound disclosed in Japanese Patent Application Publication No. 2019-151678.

[0328] Furthermore, the second coating layer may be formed on the outside of the metal particle and silicon compound-containing layer. Alternatively, the components of the second coating layer (such as molybdenum-containing compounds or phosphate compounds) may be incorporated together with the silicon compound within 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 added corrosion inhibitor is not particularly limited, and any known corrosion inhibitor can be used. The amount used should be within a range that does not hinder the desired effect of the third invention of this application. Examples of such corrosion inhibitors include acidic phosphate esters, dimer acids, organophosphorus compounds, and metal salts of molybdic acid.

[0330] From the viewpoint of adhesion and chemical resistance when a coating film is formed, organic oligomers or polymers may be further included in 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.

[0331] Furthermore, the silicon compound-containing layer and / or the second coating layer of the composite particles, or a separate layer, may contain at least one selected from the group consisting of inorganic phosphoric acids and their salts, and acidic organic (or phosphate) esters and their salts, from the viewpoint of storage stability. These compounds are not particularly limited, but for example, those disclosed in Japanese Patent Application Publication No. 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 this application includes the following steps (1) to (3). (1) A step of dispersing metal particles in a solvent, (2) A step of coating metal particles with a silicon compound, and (3) The filtration and washing process.

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

[0334] The solvent used in the manufacturing method of the third invention of this application, that is, the solvent for the hydrolysis and / or condensation reaction of the organosilicon compound, can be appropriately selected depending on the type of silicon-containing raw material used, but usually water, a hydrophilic organic solvent, or a mixture thereof can be used. By using these solvents, the uniformity of the reaction and the uniformity of the resulting hydrolysate and / or condensation reaction product can be improved. In the embodiment in which the silicon compound-containing layer is formed directly on metal particles, it is particularly preferable that the solvent in the mixture contains a hydrophilic organic solvent from the viewpoint of avoiding the rapid reaction between the metal particles and water. In the third invention of this application, a mixture of water and a hydrophilic organic solvent can be suitably used.

[0335] Examples of hydrophilic organic solvents are not particularly limited, but include alcohols such as methanol, ethanol, propanol, butanol, isopropanol, and octanol; ether alcohols and their esters such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; glycols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, polyoxyethylene glycol, polyoxypropylene glycol, and ethylene propylene glycol; ethyl cellosolve, butyl cellosolve, acetone, methoxypropanol, ethoxypropanol, and other alkoxy alcohols. These can be used individually or in combination of two or more.

[0336] Furthermore, when a mixed solvent of water and a hydrophilic organic solvent is used as the solvent, the ratio of the two is not particularly limited. In embodiments in which a silicon compound-containing layer is formed directly on metal particles, from the viewpoint of avoiding a rapid reaction between the metal particles and water, it is preferable that the water content be 20% by mass or less, with the total of the two being 100% by mass, before adding the silicon compound. In this case, there is no lower limit to the water content, but it is usually sufficient to set it to about 1% by mass.

[0337] The amount of solvent used in the manufacturing method of the third invention of this application (excluding the amount of solvent used for pre-dispersion of metal particles, if applicable) is not limited, but is usually sufficient to be around 100 to 10,000 parts by mass per 100 parts by mass of metal particles (solid content), and is particularly preferably 200 to 1,000 parts by mass. By using 100 parts by mass or more of solvent, the increase in viscosity of the mixed liquid (slurry) is suppressed, and appropriate stirring becomes possible. Furthermore, by using 10,000 parts by mass or less of solvent, it is possible to prevent high costs for recovering and regenerating the processed liquid.

[0338] In step (1), preferably, the degree of dispersion can be further enhanced by performing external circulation, in which a portion of the solvent to which the metal particles are added (hereinafter referred to as the "dispersion") (for example, 0.5 to 30% by mass of the total dispersion per minute, preferably 1 to 20% by mass, more preferably 1 to 15% by mass) is temporarily withdrawn from the reaction vessel and then returned to the reaction vessel. Dispersibility can be further enhanced by performing ultrasonic treatment outside the reaction vessel in the middle of the external circulation flow path.

[0339] The ultrasonic treatment is not particularly limited, but can usually be performed at 10 to 1000 W, preferably 50 to 800 W, for 20 seconds to 10 minutes, preferably 30 seconds to 5 minutes. Furthermore, the amount of solvent used for this pre-dispersion can usually be about 100 to 10000 parts by mass per 100 parts by mass of metal particles (solids), preferably 200 to 5000 parts by mass, and more preferably 300 to 1000 parts by mass, from the viewpoint of obtaining sufficient dispersion by appropriately adjusting the stirring intensity.

[0340] Such pre-dispersion of metal particles can usually be carried out at 10-80°C, preferably 15-60°C, and most preferably around room temperature (around 20-30°C). Furthermore, the pre-dispersion of metal particles (including ultrasonic treatment if applicable) can be carried out for 5 minutes to 2 hours, preferably 10 minutes to 1 hour.

[0341] Furthermore, in step (1), the average particle size (D) of the metal particles in the dispersion is 50 ) is the average particle size (D) of the raw material metal particles. 50 It is preferable that the average particle size is 1.2 times or less of the average particle size of the raw material metal particles. By keeping the average particle size 1.2 times or less of the average particle size of the raw material metal particles, the aggregation of individual particles is reduced and suppressed, making it easier to obtain a uniform silicon compound-containing layer, which in turn suppresses gas generation in the water-based paint and makes it easier to obtain good storage stability. Furthermore, the coating film formed using the metal pigment composition containing the final composite particles is also more likely to exhibit high opacity and gloss. This ratio is more preferably 1.1 times or less.

[0342] Process (2) Step (2) is a step in which metal particles are coated with a silicon compound by hydrolysis / (partial) condensation reaction of the organosilicon compound in a mixture of the dispersion from step (1), which is mixed with a silicon-containing raw material containing at least one organosilicon compound and other optional components as needed, under stirring.

[0343] As the silicon-containing raw material, organosilicon compounds can be used. While not limited to these, organosilicon compounds preferably include those represented by the following formula (1) (typically tetraalkoxysilane) and / or its condensates, as well as at least one of the following silane coupling agents represented by formulas (2) to (4). Details regarding preferred forms of these organosilicon compounds are the same as those described above in relation to the first aspect of the first invention of this application.

[0344] In the above-mentioned mixture, other additives may be added as needed, within the limits that do not impede the effects of the third invention of this application. Examples include catalysts such as hydrolysis catalysts and dehydration condensation catalysts, as well as surfactants, metal corrosion inhibitors, and the like.

[0345] Among these, hydrolysis catalysts can be suitably used. By incorporating a hydrolysis catalyst, the pH of the mixture can be adjusted, and the organosilicon compounds can be efficiently hydrolyzed and dehydrated, resulting in the efficient and reliable formation of a silicon compound-containing layer on the surface of the metal particles.

[0346] The hydrolysis catalyst can be any known or commercially available one and is not particularly limited. Examples of hydrolysis catalysts include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; organic acids such as benzoic acid, acetic acid, chloroacetic acid, salicylic acid, oxalic acid, picric acid, phthalic acid, and malonic acid; and phosphonic acids such as vinylphosphonic acid, 2-carboxyethanephosphonic acid, 2-aminoethanephosphonic acid, and octanephosphonic acid. These hydrolysis catalysts may be used individually or in combination of two or more.

[0347] Furthermore, hydrolysis catalysts can also be used, 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, 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 individually or in combination of two or more.

[0348] The amount of hydrolysis catalyst added is not particularly limited, but is usually 0.01 to 20 parts by mass per 100 parts by mass of metal particles (solid content), and is particularly preferably 0.02 to 10 parts by mass. An amount of 0.01 parts by mass or more ensures sufficient deposition of the silicon compound-containing layer. An amount of 20 parts by mass or less effectively suppresses aggregation of metal particles.

[0349] When preparing the above mixture, it is sufficient to mix each of these components uniformly in the mixture, and there are no particular restrictions on the order in which they are added.

[0350] The temperature of the mixture can be at room temperature or under heating. Generally, the temperature of the mixture should be between 20 and 90°C, and it is particularly preferable to control it within the range of 30 to 80°C. A temperature of 20°C or higher increases the formation rate of the silicon compound-containing layer, thereby shortening the processing time. On the other hand, a temperature of 90°C or lower makes it easier to control the reaction, thereby increasing the probability of obtaining the desired composite particles. ...

Claims

1. A metal pigment comprising metal particles and composite particles having one or more coating layers on their surface, (1) The composite particles have a flaky shape, (2) When the particle size distribution of the composite particles is measured using a laser diffraction particle size distribution analyzer, the volume-based D ５０ The size is 0.1 to 30 μm. (3) The average thickness of the composite particles is 15 to 230 nm, (4) The proportion of the bent composite particles is 10% or less, At least one layer of the coating is a polysiloxane layer, In the polysiloxane structure constituting the polysiloxane layer, the proportion of Q4 structures having four -O-Si- bonds among the Si atoms is 40-90%. A metallic pigment characterized in that the relative elemental concentration ((A / B) × 100) of the elemental concentration A of the metal and the elemental concentration B of Si, as evaluated on the surface of the composite particles by XPS, is 8 mol% or less.

2. The metal pigment according to claim 1, wherein the proportion of aggregates in which four or more composite particles are fixed to each other is 35% or less of the total number of composite particles.

3. The metal pigment according to claim 1 or 2, wherein the metal particles contain aluminum or an aluminum alloy.

4. The metal pigment according to any one of claims 1 to 3, wherein the one or more coating layers include a metal oxide coating layer.

5. The metal pigment according to any one of claims 1 to 4, wherein the one or more coating layers include a silicon compound-containing layer.

6. The metallic pigment according to any one of claims 1 to 5, wherein the average particle thickness of the composite particles is 15 to 160 nm.

7. The metallic pigment according to any one of claims 1 to 6, wherein the average aspect ratio of the composite particles is 20 to 400.

8. The metal pigment according to claim 1, wherein the average thickness of the polysiloxane layer is 5 to 100 nm.

9. A metal pigment according to any one of claims 1 to 8, wherein the hydrophilicity A, defined as the sum of (ratio of Q1 structures having one -O-Si- bond per Si atom × 3) + (ratio of Q2 structures having two -O-Si- bonds per Si atom × 2) + (ratio of Q3 structures having three -O-Si- bonds per Si atom), is 10 to 80%.

10. The metal pigment according to any one of claims 1 to 9, wherein the composite particles further comprise a coating layer comprising at least one of a metal, a metal oxide, a metal hydrate, and a resin.

11. A metal pigment according to any one of claims 1 to 10, wherein 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 aqueous acrylic resin, 18 g of melamine resin, and 12 g of water is taken into a flask and the amount of hydrogen gas generated is measured in a constant temperature water bath at 60°C for up to 24 hours, the amount of gas generated is 10 ml or less.

12. A water-based metallic paint containing a metal pigment according to any one of claims 1 to 10, and containing 5% by mass or more of water, wherein when 200 g of the water-based metallic paint is taken into 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 amount of gas generated is 10 ml or less.

13. A metal pigment composition containing the metal pigment described in any one of claims 1 to 11.

14. An aqueous paint composition containing a metallic pigment according to any one of claims 1 to 11.

15. An aqueous ink composition containing a metallic pigment according to any one of claims 1 to 11.

16. A coating film containing a metallic pigment according to any one of claims 1 to 11.

17. A method for producing a metal pigment, 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 metal particles with a silicon compound, and (3) Filtration and washing process, The aforementioned stirred tank type reactor, The volume of the reaction vessel 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 aforementioned stirring blade during stirring is 1 to 20 m / s. In step (2), stir the mixture so as not to create any stagnant areas at the surface and bottom. In step (2), after adding the silicon-containing raw material and catalyst, the inner wall of the reaction vessel near the wetted part of the reaction vessel and the mixed liquid is washed with the reaction liquid or solvent to reduce deposits or stagnant matter. The aforementioned manufacturing method.

18. A manufacturing method according to claim 17, 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. 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 aforementioned manufacturing method.

19. The manufacturing method according to claim 17 or 18, wherein in step (1) and / or (2), the processed liquid withdrawn from near the bottom of the reaction vessel is returned to the reaction vessel from the top of the reaction vessel and circulated.

20. The manufacturing method according to any one of claims 17 to 19, wherein step (2) is carried out over a period of two hours or more.

21. A manufacturing method according to any one of claims 17 to 20, wherein a metal pigment according to any one of claims 1 to 11 is produced.

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