Resin-coated metal pigments

Abstract

To provide an aluminum pigment that maintains excellent gloss and design as the aluminum pigment but yet gives a metallic coat having excellent metallic feeling and design as well as excellent adhesion and storage stability when used as a coating or a pigment for print ink, and a method for producing the same.SOLUTION: A resin-coated aluminum pigment has a resin deposited over the entire surface of flaky metal aluminum powder. The resin has an average thickness of 2-30 nm. When measured by XPS, the proportion of aluminum is 15 atom% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a novel aluminum pigment. More specifically, when used as a pigment for paints, it provides an aluminum pigment that gives a metallic coating film with excellent metallic luster, design, adhesion, and storage stability, and a method for producing the same. Further, the present invention relates to a novel metallic paint comprising the above aluminum pigment, a paint resin, and a diluent, and also to a paint and a metallic ink that give a metallic coating film with excellent adhesion while maintaining an unprecedented excellent metallic luster and design.

Background Art

[0002] Conventionally, aluminum pigments have been used for metallic paints, printing inks, plastic kneading, etc. for the purpose of obtaining a cosmetic effect that emphasizes metallic feeling. However, an aluminum pigment with no surface treatment has high metallic feeling and design, but has a drawback that when a adhesion test by cellophane tape peeling is performed, a large amount of peeling occurs because the adhesion with the resin in the coating film is inferior depending on the resin system of the paint and the printing ink. <{

[0003] This is considered to be due to insufficient compatibility and wettability between the surface of the aluminum pigment and the paint and printing ink resin, and as a countermeasure, a method of surface-treating the aluminum pigment has been proposed.

[0004] A method has been proposed in which a paste of flaky aluminum powder, which is bronze powder, iron powder, and an aluminum pigment, is dispersed in an organic solvent, first adsorbed with a radically polymerizable unsaturated carboxylic acid or the like, and then surface-coated with a polymer formed from a monomer having a radically polymerizable double bond (Japanese Patent Laid-Open No. 62-81460). However, although this method improves the adhesion, since the main purpose is to achieve stain resistance and chemical resistance of the metallic coating film, the film thickness of the resin to be coated becomes thick, resulting in a decrease in metallic feeling and a significant decrease in design.

[0005] A method has been proposed to impart adhesion to aluminum pigments while maintaining their aesthetic appeal by adding lower fatty acids with 1 to 5 carbon atoms (Japanese Patent Publication No. 4684429). However, aluminum pigments obtained by this method have the problem of having poor storage stability, which is insufficient. As a method for imparting adhesion to aluminum pigments while maintaining their aesthetic appeal, a method has been proposed that specifies the amount of monomer having radical polymerizable double bonds used (Japanese Patent Publication No. 4684429). However, the thickness of the resin film formed on the aluminum surface is not uniquely determined by the amount of monomer having radical polymerizable double bonds used, but also varies greatly depending on the surface area of ​​the raw material powder used. Aluminum pigments obtained by this method have a resin layer that is too thin, resulting in a large proportion of uncoated aluminum. Therefore, they have the problem of being more susceptible to corrosion due to increased contact with moisture in the air and having poor storage stability.

[0006] A method has been proposed in which external effects such as ultrasonic irradiation are added during the resin coating process (Japanese Patent Publication No. 5224561). However, this method has the problem that the metallic feel and design quality are reduced because the ultrasonic irradiation causes fine scratches on the surface of the aluminum pigment. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 62-81460 [Patent Document 2] Patent No. 4684429 [Patent Document 3] Patent No. 5224561 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to provide an aluminum pigment and a method for producing the same, which, while maintaining the excellent gloss and design properties of aluminum pigments, can provide a metallic coating film with excellent metallic feel, design properties, adhesion, and storage stability when used as a pigment for paints and printing inks. [Means for solving the problem]

[0009] The inventors diligently continued their research to solve the problems of conventional aluminum pigments as described above. As a result, they produced a resin-coated aluminum pigment in which a resin adheres to the entire surface of flake-shaped metallic aluminum powder, the average film thickness of the resin is 2 to 30 nm, and the aluminum content measured by XPS is 15 atomic percent or less. They discovered that the resulting aluminum pigment could achieve the above objectives, leading to the present invention.

[0010] In other words, the present invention is as follows (1) to (6).

[0011] (1) A resin-coated aluminum pigment in which a resin is attached to the entire surface of flake-shaped metallic aluminum powder, wherein the average film thickness of the resin is 2 to 30 nm, and the proportion of aluminum measured by XPS is 15 atomic percent or less. (2) The resin-coated aluminum pigment described in (1), wherein the average particle length of the flake-shaped metallic aluminum powder is 1 to 100 μm and the average thickness is 0.3 μm or less. (3) The surface diffusion area of ​​flake-shaped aluminum metal powder in water is 2.5 m². 2 The aluminum pigment described in (1) or (2) is 1 / g or more. (4) An aluminum pigment according to any of (1) to (3), wherein the flake-shaped aluminum metal powder has an average surface roughness Ra of 20 nm or less, or an average height Rc of the irregularities in the average surface roughness curve of 80 nm or less. (5) The resin-coated aluminum pigment according to any one of (1) to (4), wherein the resin is a (co)polymer formed from a monomer containing at least one monomer having four or more radically polymerizable double bonds.

[0012] (6) Step of dissociating flaky metallic aluminum powder into primary particles (kneading step); Step of dispersing the metallic aluminum particles obtained in the kneading step in an organic solvent (dispersion step); Thereafter, while heating and stirring, at least one selected from a radically polymerizable unsaturated carboxylic acid, a phosphoric acid or phosphonic acid mono- or diester having a radically polymerizable double bond, and a coupling agent having a radically polymerizable double bond is added and mixed (first step); then A monomer having two or more radically polymerizable double bonds and a polymerization initiator are added, and the component adsorbed on the surface of the flaky metallic aluminum powder in the first step and the monomer having two or more radically polymerizable double bonds are polymerized to form a resin layer (second step), A method for producing a resin-coated aluminum pigment, comprising:

Effect of the Invention

[0013] According to the present invention, it is possible to provide an aluminum pigment having excellent adhesion and storage stability while maintaining metallic luster and design properties.

Mode for Carrying Out the Invention

[0014] The aluminum pigment according to the present invention has excellent adhesion and storage stability while maintaining excellent metallic luster and design properties.

[0015] The flaky metallic aluminum powder used as a raw material for the aluminum pigment of the present invention is not particularly limited in its type, and may generally be those commonly used as aluminum pigments. Its shape is flat, such as scaly, angular, round, etc. The manufacturing method is not particularly limited either, but it can be obtained by grinding granular powder or flakes of metallic aluminum together with a few percent of a grinding aid by mechanical methods, such as the stamp mill method, dry ball mill method, wet ball mill method, attritor method, vibration ball mill method, etc.

[0016] The particle size of the flaky metallic aluminum powder used as a raw material varies depending on the application. For paints and printing inks, those with an average particle size (average particle major diameter) d50 of about 1 to 100 μm are suitable and can be applied to the present invention. Also, recently, applications that particularly require high design quality include those for automobiles, general household appliances, information household appliances typified by mobile phones, and printing. They are used for coating metals such as iron and magnesium alloys, or plastics, etc. The preferred particle size for use in these is 5 to 35 μm, and more preferably 5 to 25 μm. The flaky metallic aluminum powder used as a raw material may be commercially available in a paste state, and this can be used as it is, or the fatty acids, etc. on the surface may be removed in advance with an organic solvent, etc. and then used. Also, aluminum vapor-deposited foil (for example, average particle size (d50) of 3 to 30 μm, average thickness (t) of 5 to 50 nm) can also be used.

[0017] Regarding the design quality of the flaky metallic aluminum powder used as a raw material for the aluminum pigment of the present invention, it is not particularly limited. However, if one wishes to maintain a high level of design quality, using a high design quality grade (grade for high-class metallic paints or inks) will more effectively exhibit the effects of the present invention. Examples of manufacturing methods for flaky metallic aluminum powder with high design quality include, for example, the method described in International Publication WO99 / 54074. The flaky metallic aluminum powder obtained by this manufacturing method, with a smooth surface and uniform thickness, can be particularly preferably used as a raw material for the aluminum pigment of the present invention.

[0018] The specific shape of the flake-shaped metallic aluminum powder used as a raw material in the present invention is described below.

[0019] The preferred range for the average particle size (average particle diameter) d50 is 5 to 35 μm, and a more preferred range is 5 to 25 μm. Other preferred ranges for the defined shape are an average thickness t of 0.3 μm or less, more preferably 0.2 μm or less, a preferred ratio of average particle size d50 (μm) to average thickness t (μm) of 30 to 90, and an average surface roughness Ra of 20 nm or less. Furthermore, the average height Rc of the surface roughness curve is preferably 80 nm or less. And most preferably, the material satisfies all of these property ranges.

[0020] Average particle size d50 (μm), average thickness t (μm), and water surface diffusion area WCA (m²) of flake-shaped metallic aluminum powder. 2 The mean surface roughness ( / g), average surface roughness Ra (nm), and average height Rc of the surface roughness curve are defined as follows:

[0021] <Average particle size (average particle length) (d50)> The average particle size (average particle diameter) d50 (μm) is measured by the following method. Mineral spirits are used as the measurement solvent, and the flake-shaped metallic aluminum powder sample is subjected to ultrasonic dispersion for 2 minutes as a pretreatment before being measured using a laser micron sizer LMS-24 (manufactured by Seishin Corporation).

[0022] The average particle size d50 is preferably 5 to 35 μm. More preferably 5 to 25 μm. The average particle size d50 can be appropriately selected from extra-fine, fine, medium, coarse, and extra-coarse depending on the desired design. Particles with an average particle size of 5 μm or more tend to orient in a certain direction within the coating film, and light scattering is reduced, making it easier to achieve the desired brightness. On the other hand, particles with an average particle size of 35 μm or less are practical because the particle size does not exceed the thickness of the coating film, and some particles are less likely to protrude from the coating film surface, making it easier to obtain a fine metallic coating film.

[0023] <Average thickness (t)> The average thickness t (μm) of the metallic aluminum particles themselves is equal to the water surface diffusion area WCA (m²) per gram of metallic component. 2 The value was calculated by measuring ( / g) and using the following formula. t(μm) = 0.4 / [WCA(m 2 / g)]

[0024] The method for calculating the average thickness described above is found, for example, on pages 16-22 of "Aluminium Paint and Powder," by J. Ed-wards & RI Wray, 3rd edition, Reinhold Publishing Corp., New York (1955).

[0025] <Water surface diffusion area (WCA)> The water surface diffusion area (WCA) of aluminum particles is 2.5 m². 2 A value of 1 / g or more is preferred. The surface diffusion area is determined according to JIS K 5906-1991 after a certain pretreatment. Note that the method for measuring the surface diffusion area described in JIS is for the leafing type, whereas the method described in the aforementioned International Publication WO99 / 54074 is for the non-leafing type. However, the procedure is the same as for the leafing type, except for the pretreatment of the sample with a 5% stearic acid mineral spirit solution.

[0026] The preliminary treatment of the samples is described in the Journal of Paint Raw Materials, No. 156, pp. 2-16 (published September 1, 1980 by Asahi Kasei Corporation).

[0027] <Ratio of average particle size d50 to average thickness t (flatness)> In this invention, the ratio of the average particle size d50 to the average thickness t is given by d50 / t, and is the so-called flatness of the flake-shaped metallic aluminum powder (hereinafter sometimes referred to as flatness).

[0028] When metallic aluminum powder is ground in a medium-agitated mill or ball mill, the flatness gradually increases, and once it is spread to a certain extent, the particles become more prone to bending. Generally, when the flatness exceeds 200, the particles become more prone to cracking and bending. Therefore, a flatness d50 / t of 30 to 90 is preferable. When the flatness is 90 or less, the surface of the flake-like metallic aluminum powder is smooth, reducing light scattering on the surface and increasing specular reflectance, thereby improving light brightness and also increasing floppiness. Furthermore, when the flatness is 30 or more, the opacity, which is one of the important functions of aluminum pigments, is maintained, making it suitable for practical use.

[0029] <Average surface roughness (Ra)> The average surface roughness Ra is calculated by the following method. For observing the surface morphology of aluminum pigments, an atomic force microscope (hereinafter abbreviated as AFM) TMX-2010 (manufactured by Topometrix) is used. As a pretreatment, the aluminum pigment sample is ultrasonically cleaned with excess methanol and chloroform, then vacuum dried, dispersed again in acetone, dropped onto a Si wafer, and air dried. For quantitative determination of surface roughness by AFM, for flake-shaped metallic aluminum powder that does not overlap with other flake-shaped metallic aluminum powder, the surface roughness curve (line profile of surface irregularities) is measured over 300 scans in a 5 μm square field of view, and the arithmetic mean roughness of the roughness curve (arithmetic mean of the absolute values ​​of elevation within a reference length of 5 μm) is calculated.

[0030] The reference length is determined by the average particle size d50, with 5 μm being used as the standard. The arithmetic mean roughness is measured in three or more fields of view, and the arithmetic mean value obtained from these measurements is defined as the "average surface roughness Ra (nm)". The term "surface roughness" is based on JIS B0660:1998. The average surface roughness Ra is preferably 20 nm or less, and more preferably 15 nm. When it is 20 nm or less, the specular reflectance of light on the surface is large, resulting in extremely excellent luminosity and good flop properties.

[0031] <Average height (Rc) of surface roughness curve> The average height Rc of the surface roughness curve of flake-shaped metallic aluminum powder is expressed as the sum of the average absolute value of the peak heights of the surface roughness curve and the average absolute value of the trough depths of the surface roughness curve, as measured above. Specifically, it refers to the value obtained by arithmetic mean of the surface roughness curve measured in three or more fields of view and then taking the arithmetic mean of these values. Rc is preferably 80 nm or less. When the average height Rc is 80 nm or less, it exhibits extremely excellent high brightness and good flop properties.

[0032] The surface of flake-shaped metallic aluminum powder that satisfies all the conditions described above shows, upon scanning electron microscopy (SEM) observation, that there are few surface irregularities, little adhesion of extremely fine powders, and that it contains a considerable amount of aluminum pigment particles with a uniform thickness from the center to the edges of the particle.

[0033] <Method for manufacturing resin-coated aluminum pigment> The manufacturing method of the present invention is as follows. A process (mixing process) to break down flake-shaped metallic aluminum powder into primary particles; A step (dispersion step) in which the metallic aluminum particles obtained in the above mixing step are dispersed in an organic solvent; Subsequently, while heating and stirring, at least one selected from radically polymerizable unsaturated carboxylic acids, phosphoric acid or phosphonic acid mono or diester having a radically polymerizable double bond, and coupling agents having a radically polymerizable double bond is added and mixed (first step); then The second step involves adding a monomer having two or more radically polymerizable double bonds and a polymerization initiator to polymerize the components adsorbed on the surface of the flake-shaped metallic aluminum powder in the first step with the monomer having two or more radically polymerizable double bonds, thereby forming a resin layer. A method for producing resin-coated aluminum pigments, including the pigment itself. The resin-coated aluminum pigment of the present invention can be produced by the manufacturing method of the present invention. Preferably, the resin-coated aluminum pigment of the present invention is obtained by, in a kneading step, breaking down the untreated flake-shaped metallic aluminum powder into primary particles using a kneader mixer; in a dispersion step, dispersing it in an organic solvent; then, while heating and stirring, adding at least one selected from a radically polymerizable unsaturated carboxylic acid, a phosphoric acid or phosphonic acid mono or diester having a radically polymerizable double bond, and a coupling agent having a radically polymerizable double bond to treat the surface of the flake-shaped metallic aluminum powder; and then, in a second step, adding a monomer having two or more radically polymerizable double bonds and a polymerization initiator to polymerize the components adsorbed on the surface of the flake-shaped metallic aluminum powder in the first step with the monomer having two or more radically polymerizable double bonds to form a resin layer. Next, we will describe the details of each process.

[0034] <Regarding the mixing process for flake-shaped metallic aluminum powder> Untreated flake-shaped metallic aluminum powder is kneaded in a kneader mixer. In this kneading process, the softly aggregated aluminum particles are broken down into primary particles beforehand, allowing the metallic aluminum surface to be uniformly coated with resin, thereby improving storage stability. This kneading process breaks down the soft aggregate before the resin coating process, and allows the primary particles to be coated with resin, resulting in excellent storage stability. The rotation speed during kneading with a kneader mixer is preferably 10 rpm to 100 rpm, and more preferably 20 rpm to 70 rpm. From the viewpoint of kneadability, a rotation speed of 10 rpm or more is preferred, and from the viewpoint of preventing bending, a rotation speed of 70 rpm or less is preferred. The mixing time is preferably 30 minutes to 2 hours, and more preferably 40 minutes to 1 hour. From the viewpoint of breaking down into primary particles, the mixing time is preferably 30 minutes or more, and from the viewpoint of preventing bending, it is preferably 2 hours or less. The mixing temperature is preferably 30°C to 60°C, and more preferably 40°C to 50°C. From the viewpoint of breaking down into primary particles, a mixing temperature of 40°C or higher is preferred, and from the viewpoint of suppressing deterioration of aluminum particles, a temperature of 60°C or lower is preferred. The blade shape is not particularly limited, but a sigma shape is preferred from the viewpoint of uniformly mixing the aluminum particles and breaking them down into primary particles.

[0035] <Regarding the dispersion process of flake-shaped metallic aluminum powder> Flake-shaped metallic aluminum powder is dispersed in an organic solvent. The organic solvent used can be any solvent that is inert to the flaked metallic aluminum powder. Examples include aliphatic hydrocarbons such as hexane, heptane, octane, and mineral spirits; aromatic hydrocarbons such as benzene, toluene, xylene, and solvent naphtha; ethers such as tetrahydrofuran and diethyl ether; alcohols such as ethanol, 2-propanol, and butanol; esters such as ethyl acetate and butyl acetate; and cellosolves such as ethylene glycol monoethyl ether.

[0036] The weight concentration of the flake-shaped metallic aluminum powder in the organic solvent varies depending on the type and characteristics of the flake-shaped metallic aluminum powder used, particularly its WCA, but is preferably 0.1 to 40%, and more preferably 1 to 35%. A concentration of 0.1% or more is preferable from the viewpoint of the dispersibility of the flake-shaped metallic aluminum powder, as it does not require an excessive amount of solvent to handle and thus does not require effort to remove it later. A concentration of 40% or less is preferable from the viewpoint of the dispersibility of the flake-shaped metallic aluminum powder.

[0037] If the WCA of the metallic aluminum powder differs, it is necessary to appropriately adjust the weight concentration of the flake-shaped metallic aluminum powder in the organic solvent according to the WCA. As the WCA increases, the flake-shaped metallic aluminum powder in the organic solvent tends to aggregate. By lowering the weight concentration of the flake-shaped metallic aluminum powder in the organic solvent and maintaining a uniform dispersion, the surface of the metallic aluminum can be uniformly coated with resin, thereby improving the storage stability, which is an effect of the present invention. <Regarding the first step> In the first step, at least one selected from a radically polymerizable unsaturated carboxylic acid, a mono or diester of phosphoric acid or phosphonic acid having a radically polymerizable double bond, and a coupling agent having a radically polymerizable double bond is added to an organic solvent in which flake-shaped metallic aluminum powder is dispersed.

[0038] Examples of radically polymerizable unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, and fumaric acid, and one or more of these can be used in combination. The amount used varies depending on the type and characteristics of the flake-shaped metallic aluminum powder, particularly its WCA and the weight concentration of the flake-shaped metallic aluminum powder in the organic solvent. In this invention, the amount is between 0.1 and 5.0 parts by weight per 100 parts by weight of flake-shaped metallic aluminum powder, and more preferably between 0.2 and 3.0 parts by weight. At 0.1 parts by weight or more, a resin layer is sufficiently formed on the surface of the flake-shaped metallic aluminum powder, and the adhesion and storage stability, which are the effects of this invention, can be fully satisfied. At 5.0 parts by weight or less, the reduction in metallic feel and design, which are the effects of this invention, can be suppressed, which is preferable. If the WCA of the metallic aluminum powder differs, the amount of radically polymerizable unsaturated carboxylic acid used must be appropriately adjusted according to the WCA. When the WCA is high, increasing the amount of radically polymerizable unsaturated carboxylic acid used ensures sufficient formation of a resin layer on the surface of the flake-shaped metallic aluminum powder. As a result, the metallic aluminum powder is less likely to come into direct contact with moisture in the air, thus reducing corrosion and providing excellent storage stability, thus realizing the effects of the present invention. When the weight concentration of flake-shaped metallic aluminum powder in the organic solvent is high, a small amount of radically polymerizable unsaturated carboxylic acid is sufficient. However, when the weight concentration of flake-shaped metallic aluminum powder in the organic solvent is low, increasing the amount of radically polymerizable unsaturated carboxylic acid allows for sufficient adsorption of the radically polymerizable unsaturated carboxylic acid onto the surface of the flake-shaped metallic aluminum powder. As a result, a sufficient resin layer is formed on the surface of the flake-shaped metallic aluminum powder, achieving the adhesion and storage stability that are the effects of the present invention.

[0039] Examples of mono- or diesters of phosphoric acid or phosphonic acid having a radically polymerizable double bond include 2-methacryloyloxyethyl phosphate, di-2-methacryloyloxyethyl phosphate, tri-2-methacryloyloxyethyl phosphate, 2-acryloyloxyethyl phosphate, di-2-acryloyloxyethyl phosphate, tri-2-acryloyloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dioctyl-2-acryloyloxyethyl phosphate, 2-methacryloyloxypropyl phosphate, bis(2-chloroethyl) vinyl phosphonate, diallyl dibutyl phosphonosuccinate, and others, and one or more of these can be used in combination.

[0040] A preferred example is a phosphate monoester. This is presumably because the phosphate group has two OH groups, which allows it to be more firmly fixed to the surface of the flake-shaped metallic aluminum powder.

[0041] More preferred phosphate monoesters include monoesters having methacryloyloxy groups and acroyloxy groups, such as 2-methacryloyloxyethyl phosphate and 2-acroyloxyethyl phosphate. The amount used varies depending on the type and characteristics of the flake-shaped metallic aluminum powder, particularly its surface area, but in the present invention, it is between 0.1 and 2.0 parts by weight per 100 parts by weight of flake-shaped metallic aluminum powder, and more preferably between 0.2 and 1.5 parts by weight. At 0.1 parts by weight or more, a resin layer is sufficiently formed on the surface of the flake-shaped metallic aluminum powder, and the adhesion and storage stability, which are effects of the present invention, can be fully satisfied. At 2.0 parts by weight or less, the reduction in metallic feel and design, which are effects of the present invention, can be suppressed, which is preferable.

[0042] Examples of coupling agents having radically polymerizable double bonds include silane coupling agents, titanate coupling agents, and aluminum coupling agents.

[0043] Examples of silane coupling agents include γ-methacryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(β-methoxyethoxy)silane.

[0044] Examples of titanate-based coupling agents include isopropyl isostearoyl diacrylic titanate.

[0045] Examples of aluminum-based coupling agents include acetalkoxyaluminum diisopropylate and zircoaluminate.

[0046] The amount of coupling agent having a radically polymerizable double bond used varies depending on the type and characteristics of the flake-shaped metallic aluminum powder, particularly its surface area. In this invention, however, the amount is between 0.1 and 2.0 parts by weight per 100 parts by weight of flake-shaped metallic aluminum powder, and more preferably between 0.2 and 1.5 parts by weight. An amount of 0.1 parts by weight or more is sufficient to form a resin layer on the surface of the flake-shaped metallic aluminum powder, fully satisfying the adhesion and storage stability that are the effects of this invention. An amount of 2.0 parts by weight or less is preferable because it suppresses the reduction in metallic feel and aesthetic appeal that are the effects of this invention.

[0047] The addition of radically polymerizable unsaturated carboxylic acids, phosphoric acid or phosphonic acid mono or diester having radically polymerizable double bonds, or coupling agents having radically polymerizable double bonds (hereinafter referred to as "radically polymerizable unsaturated carboxylic acids, etc.") is preferably carried out while heating and stirring at a temperature of 40°C to 150°C. Above 40°C, the time required to raise the temperature to the polymerization temperature (second step) of monomers having two or more radically polymerizable double bonds and polymerization initiators is short, and below 150°C, the risk of ignition of organic solvent vapors is low, which is preferable. After the addition of radically polymerizable unsaturated carboxylic acids, etc. is complete, it is preferable to continue stirring at a temperature of 40°C to 150°C for about 5 minutes to 10 hours. This time allows for sufficient diffusion of radically polymerizable unsaturated carboxylic acids, etc. in the organic solvent and adsorption onto the surface of the flake-shaped metallic aluminum powder.

[0048] <Regarding the second step> In the second step, a monomer having two or more radical polymerizable double bonds and a polymerization initiator are added to the organic solvent that has undergone the first step.

[0049] Examples of monomers having two or more radically polymerizable double bonds include triethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetramethylolpropane tetraacrylate, di-trimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, di-pentaerythritol hexaacrylate, di-pentaerythritol pentaacrylate, and di-pentaerythritol pentaacrylate monopropionate. One or more of these can be used in combination. In particular, using monomers having four or more radically polymerizable double bonds results in a denser resin layer, reducing direct contact between the metallic aluminum powder and moisture in the air, thus preventing corrosion and providing excellent storage stability, thus realizing the effects of the present invention.

[0050] The amount of monomer having two or more radically polymerizable double bonds used varies depending on the type and characteristics of the flake-shaped metallic aluminum powder, particularly its WCA, but is between 1.5 and 14.0 parts by weight per 100 parts by weight of flake-shaped metallic aluminum powder, and more preferably between 1.5 and 10.0 parts by weight. At 1.5 parts by weight or more, a resin layer is sufficiently formed on the surface of the flake-shaped metallic aluminum powder, and the adhesion and storage stability, which are effects of the present invention, can be fully satisfied. At 14.0 parts by weight or less, the reduction in metallic feel and design, which are effects of the present invention, can be suppressed, which is preferable.

[0051] When the WCA of the metallic aluminum powder differs, it is necessary to appropriately adjust the amount of monomer having two or more radical polymerizable double bonds according to the WCA. When the WCA is high, increasing the amount of monomer having two or more radical polymerizable double bonds ensures sufficient formation of a resin layer on the surface of the flake-shaped metallic aluminum powder. As a result, the metallic aluminum powder is less likely to come into direct contact with moisture in the air, thus reducing corrosion and providing excellent storage stability, thus realizing the effects of the present invention. Polymerization initiators are generally known as radical generators, and their type is not particularly limited. Examples of polymerization initiators include peroxides such as benzoyl peroxide, lauroyl peroxide, and bis-(4-t-butylcyclohexyl) peroxydicarbonate, and azo compounds such as 2,2'-azobis-isobutyronitrile and 2,2'-azobis-2,4-dimethylvaleronitrile. The amount used is adjusted according to the reaction rate of the polymerizable monomer and, in particular, the weight concentration of the flake-shaped metallic aluminum powder in the organic solvent, and is approximately 0.1 to 25 parts by weight per 100 parts by weight of flake-shaped metallic aluminum powder. When the weight concentration of flake-shaped metallic aluminum powder in the organic solvent is high, a small amount of polymerization initiator is sufficient. However, when the weight concentration of flake-shaped metallic aluminum powder in the organic solvent is low, increasing the amount of polymerization initiator ensures sufficient polymerization between monomers having two or more radically polymerizable double bonds and polymerization to radically polymerizable unsaturated carboxylic acids adsorbed on the surface of the flake-shaped metallic aluminum powder in the first step, thereby achieving the adhesion and storage stability that are the effects of the present invention.

[0052] Various methods can be used to add monomers having two or more radically polymerizable double bonds and polymerization initiators, such as adding both simultaneously all at once, adding both simultaneously and gradually, or adding monomers having two or more radically polymerizable double bonds first and then gradually adding only the polymerization initiator. However, it is preferable to add monomers having two or more radically polymerizable double bonds all at once. By adding them all at once, the concentration in the organic solvent can be increased, and the polymerization efficiency of monomers having two or more radically polymerizable double bonds and polymerization to the radically polymerizable unsaturated carboxylic acid adsorbed on the surface of the flake-shaped metallic aluminum powder in the first step can be increased. As a result, resin coating can be performed with a smaller amount of monomers having two or more radically polymerizable double bonds, thereby achieving the effects of the present invention, which include suppressing a decrease in metallic feel and design aesthetics.

[0053] When adding monomers having two or more radically polymerizable double bonds and polymerization initiators, it is preferable to add them while stirring and under heating. The temperature at which addition occurs is not particularly limited, as long as polymerization takes place, but 60°C to 150°C is preferred. Furthermore, to increase polymerization efficiency, it is desirable to add and polymerize under an inert gas atmosphere such as nitrogen or helium.

[0054] Polymerization after adding monomers having two or more radically polymerizable double bonds and polymerization initiators should preferably be carried out at a temperature of 60°C to 150°C for 5 minutes to 10 hours while maintaining dispersion by continuous or intermittent stirring. This time allows for sufficient polymerization of monomers having two or more radically polymerizable double bonds and polymerization of radically polymerizable unsaturated carboxylic acids adsorbed on the surface of the flake-shaped metallic aluminum powder in the first step.

[0055] The polymerization time referred to herein is the time from the moment when the monomer having two or more radical polymerizable double bonds and the polymerization initiator are simultaneously present in the reaction system until the amount of unreacted monomer having two or more radical polymerizable double bonds falls below 1%.

[0056] The metallic paints and metallic inks containing the aluminum pigment of the present invention can be used in any form, such as solvent-based or water-based. Furthermore, these metallic paints and metallic inks can be prepared by appropriately selecting from three basic components: (a) a paint resin, (b) an aluminum pigment, and (c) a diluent.

[0057] For solvent-based paints and inks, any resin from the conventional range of resins used in metallic paints and inks can be used as the paint resin. Examples of such resins include acrylic resins, alkyd resins, oil-free alkyd resins, polyvinyl chloride resins, urethane resins, melamine resins, unsaturated polyester resins, urea resins, cellulose resins, epoxy resins, and fluororesins, which may be used individually or in combination.

[0058] When used as a solvent-based paint or ink, the amount of aluminum pigment of the present invention used is preferably 0.1 to 300 parts by weight per 100 parts by weight of paint resin, and more preferably 0.2 to 200 parts by weight. At 0.1 parts by weight or more, sufficient metallic luster is obtained for metallic paints and metallic inks, and at 300 parts by weight or less, painting and printing workability is good, and the coating film is excellent and practical.

[0059] Examples of diluents that can be used in solvent-based paints and inks include aromatic compounds such as toluene and xylene, aliphatic compounds such as hexane, heptane, and octane, alcohols such as ethanol and butanol, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone, chlorine compounds such as trichloroethylene, and cellosolves such as ethylene glycol monoethyl ether. These diluents can be used individually or in mixtures of two or more. Their composition should be appropriately determined considering solubility in paint and ink resins, film formation characteristics, and painting workability.

[0060] Furthermore, metallic paints and metallic inks may contain additives commonly used in the paint industry, such as pigments, dyes, wetting agents, dispersants, color separation inhibitors, leveling agents, slip agents, anti-skinning agents, anti-gelling agents, and defoaming agents.

[0061] Furthermore, metallic paints and metallic inks can also be used as water-based paints by using water-based paint resins. However, if the aluminum pigment of the present invention reacts with water in water-based paints and inks, it is necessary to add a reaction inhibitor. Here, the resins for water-based paints and inks are water-soluble resins or water-dispersible resins, and may be used individually or in mixtures thereof. The types vary greatly depending on the purpose and application, and are not particularly limited, but for paints, water-based paint resins such as acrylic, acrylic-melamine, polyester, and polyurethane resins are generally used, with acrylic-melamine resins being the most commonly used among them.

[0062] The aluminum pigment of the present invention used in water-based paints and inks is 0.1 to 300 parts by weight, particularly preferably 0.2 to 200 parts by weight, based on 100 parts by weight of the resin for paints. When the amount is 0.1 part by weight or more, the metallic luster necessary for metallic paints and metallic inks is sufficient. When the amount is 300 parts by weight or less, the coating and printing workability is good, and the physical properties of the coating film are excellent and practical.

[0063] As various additives, for example, dispersants, thickeners, anti-sagging agents, fungicides, ultraviolet absorbers, film-forming aids, surfactants, other organic solvents, water, etc., those that can be usually used in the art and do not impair the effects of the present invention can be used, and as long as the amount does not impair the effects of the present invention, they can be added without any problem.

[0064] <Ratio of aluminum by XPS measurement> When the resin-coated aluminum pigment is measured by XPS, in addition to the detection of elements derived from the resin, aluminum elements are also detected. If the resin coating becomes too thin to maintain high design quality, defects in the thin resin coating occur and the proportion of exposed aluminum in the base material increases, resulting in poor storage stability. From the viewpoint of storage stability, the relative element concentration of aluminum is 15 atomic% or less, preferably 9 atomic% or less, more preferably 6 atomic% or less, and most preferably 3 atomic% or less. The lower limit of the aluminum ratio is preferably 0.1 atomic%. The ratio of aluminum can be made 15 atomic% or less by kneading before resin coating. That is, before resin coating, flaky metallic aluminum powder is kneaded, for example, with a kneader mixer, so that the agglomerated aluminum particles are previously loosened to become primary particles, whereby the surface of the metallic aluminum can be uniformly coated with resin and the ratio of aluminum can be lowered. If kneading is not performed before resin coating, the ratio of aluminum may exceed 15 atomic%.

[0065] The aluminum pigment of the present invention can be suitably used for coating and printing applications on metal substrates such as iron and magnesium alloys, or plastics, in automobiles, general home appliances, information appliances such as mobile phones, and printing applications, respectively, and exhibits high design quality. [Examples]

[0066] Next, embodiments of the present invention are shown. Furthermore, the test method and measurement method used in these embodiments are described in detail below.

[0067] [Preparation of metallic paint (I)] Using the aluminum pigment compositions (resin-coated aluminum pigments) prepared in Examples 1-3 and Comparative Examples 1-4, metallic paint (I) was prepared in the following proportions. Aluminum pigment composition: 5g as nonvolatile content, Thinner (manufactured by Musashi Paint Co., Ltd., product name "Plaace Thinner No. 2726"): 50g, Acrylic resin (manufactured by Musashi Paint Co., Ltd., product name "Plaace No. 7160"): 33g Then, the following evaluations were performed using the prepared metallic paint (I). The prepared metallic paint (I) was applied to an ABS resin plate using an air spray device to a dry film thickness of 10 μm, and then dried in a 60°C oven for 30 minutes to obtain an evaluation coated plate. Using the above-mentioned evaluation boards, the following evaluations (Evaluation 1 (Adhesion) and Evaluation 2 (Gloss Retention Rate)) were performed. [Evaluation 1 (Adhesion)] Cellophane tape (registered trademark: Nichiban Co., Ltd., CT-24) was applied to the coating on the evaluation plate described above, pulled at a 45-degree angle, and the degree of peeling of the aluminum pigment particles was visually observed. The evaluation method is as follows. ○: No peeling △: Slight peeling present ×: Peeling present

[0068] [Rating 2 (Gloss Retention Rate)] The gloss at 60 degrees (both incident and reflected angles are 60 degrees) is measured using a gloss meter (Suga Test Instruments Co., Ltd., Digital Angle-Bending Gloss Meter UGV-5D). The measured value of the 60-degree gloss of the coated plate prepared above is denoted as G', and the measured value of the 60-degree gloss of a coated plate prepared similarly using untreated flake-shaped metallic aluminum powder is denoted as G. The gloss retention rate R is then calculated using the following formula. R = (G' / G) × 100 The determination method is as follows: ◎: 95 or higher 〇:90 or higher ×: Less than 90

[0069] [Preparation of metallic paint (II)] 240 g each of the aluminum pigment compositions (resin-coated aluminum pigments) prepared in Examples 1-3 and Comparative Examples 1-4 were placed into 300 ml metal cans, and the cans were sealed with lids and left to stand in a constant temperature room at 20°C for 90 days (A). The same preparations were left to stand in a drying oven at 50°C for 90 days (B). Metallic paint (II) was then prepared using these in the following proportions. Aluminum pigment composition: 5g, Thinner (manufactured by Kansai Paint Co., Ltd., product name "Acrylic No. 2000GL Thinner"): 8g Acrylic resin (manufactured by Kansai Paint Co., Ltd., product name "Acrylic No. 2026GL Clear"): 97g) Then, the following evaluation (Evaluation 3 (Storage Stability Evaluation)) was performed using the prepared metallic paint (II).

[0070] [Evaluation 3 (Storage Stability Evaluation)] Storage stability is determined by the magnitude of the difference in brightness between (A) and (B) above. Brightness was evaluated using the Alcove LMR-200 laser metallicity measuring device manufactured by Kansai Paint Co., Ltd. The optical conditions consisted of a laser light source with an incident angle of 45 degrees and receivers at receiving angles of 0 degrees and -35 degrees. For the measurement, the IV value was determined at the receiving angle of -35 degrees, where the maximum light intensity is obtained by excluding the light in the specular reflection region reflected from the paint film surface of the reflected laser light. The IV value is a parameter proportional to the specular reflection light intensity from the paint film and represents the magnitude of the light brightness. The determination method is as follows. ◎: The difference between (A) and (B) is less than 0.7 ○: The difference between (A) and (B) is less than 1.0 ×: The difference between (A) and (B) is 1.0 or greater.

[0071] [Evaluation 4 (Resin film thickness)] As a pretreatment, the resin-coated metal pigment was ultrasonically cleaned with excess methanol and chloroform, then vacuum-dried, dispersed and washed again in acetone, and air-dried. Approximately 2 nm of platinum was coated onto this, followed by embedding in epoxy resin and complete curing. Trimming and sectioning were performed using an ultramicrotome, and the cross-sections were observed using a scanning transmission electron microscope (STEM) to determine the thickness of the resin coating layer. Ten fields of view, each 1 μm wide, were observed, and the thickness was measured at 10 random points within each field of view. The average value was taken as the average thickness. The average thickness of the resin in the resin-coated aluminum pigment of the present invention is 2 to 30 nm, preferably 3 to 28 nm.

[0072] [Rating 5 (XPS: Aluminum percentage)] 0.1 g of the aluminum pigment of the present invention was placed in a 15 ml sample container and dispersed in hexane. This was then subjected to centrifugation (8,000 rpm × 3 min.) to settle the aluminum powder, and the supernatant was removed. This hexane dispersion, centrifugation, and supernatant removal process was repeated three times to wash the aluminum powder. After air drying, the aluminum powder was removed from the sample tube and placed on weighing paper. A piece of Si wafer (approximately 3 mm square) with double-sided tape attached was pressed onto the Si wafer to transfer the aluminum powder to the Si wafer, and XPS (ULVAC-PHY Versa probe II) measurement was performed.

[0073] Next, the present invention will be described in detail with reference to examples. Note that % in the following description refers to weight percentage. [Examples]

[0074] 700g of aluminum paste (containing flaked metallic aluminum powder) was placed in a kneader (Dalton KDH(J)-2) and kneaded at 25°C and 42 rpm for 60 minutes.

[0075] The aluminum paste used had a heating residue of 75% by weight, and the flake-like metallic aluminum particles it contained had an average particle size of 10 μm and a WCA of 2.5 m. 2 The ratio of average particle size d50 (μm) to average thickness t (μm) was 50, the average surface roughness Ra was 15 nm, and the average height Rc of the surface roughness curve was 60 nm.

[0076] 100 g of the mixed aluminum paste described above was placed in a 1-liter four-necked flask, 500 g of mineral spirits was added, and the mixture was stirred while introducing nitrogen gas, raising the temperature of the system to 70°C. Next, 0.37 g of acrylic acid was added and stirring was continued at 70°C for 30 minutes.

[0077] Next, 1.12 g of trimethylolpropane trimethacrylate and 2.0 g of 2,2'-azobis-2,4-dimethylvaleronitrile (polymerization initiator) were added together, and polymerization was carried out for a total of 6 hours while maintaining the temperature in the system at 70°C. At this point, the amount of unreacted trimethylolpropane trimethacrylate in the sampled filtrate was analyzed by gas chromatography, and it was found that more than 99% of the added amount had reacted. After the polymerization was completed, it was allowed to cool naturally to obtain a paste-like aluminum pigment of the present invention. The heating residue of this aluminum pigment (according to JIS-K-5910) was 74.1% by weight. [Examples]

[0078] 700g of aluminum paste (containing flaked metallic aluminum powder) was placed in a kneader (Dalton KDH(J)-2) and kneaded at 25°C and 42 rpm for 1 hour.

[0079] The aluminum paste used had a heating residue of 75% by weight, and the flake-like metallic aluminum particles it contained had an average particle size of 10 μm and a WCA of 3.5 m. 2 The ratio of average particle size d50 (μm) to average thickness t (μm) was 50, the average surface roughness Ra was 15 nm, and the average height Rc of the surface roughness curve was 60 nm.

[0080] 100g of the mixed aluminum paste described above was placed in a 2-liter four-necked flask, 1475g of mineral spirits was added, and the mixture was stirred while introducing nitrogen gas, raising the temperature of the system to 70°C. Next, 1.5g of acrylic acid was added and stirring was continued at 70°C for 30 minutes. Next, 3.75 g of trimethylolpropane trimethacrylate and 3.0 g of 2,2'-azobis-2,4-dimethylvaleronitrile (polymerization initiator) were added together, and polymerization was carried out for a total of 6 hours while maintaining the temperature in the system at 70°C. At this point, the amount of unreacted trimethylolpropane trimethacrylate in the sampled filtrate was analyzed by gas chromatography, and it was found that more than 99% of the added amount had reacted. After polymerization was completed, the mixture was allowed to cool naturally to obtain a paste-like aluminum pigment of the present invention. The heating residue of this aluminum pigment (according to JIS-K-5910) was 73.6% by weight. [Examples]

[0081] An aluminum pigment was prepared in the same manner as in Example 2, except that the monomers used were 2.25 g of trimethylolpropane trimethacrylate and 1.5 g of ditrimethylolpropane tetraacrylate. The heating residue of this aluminum pigment (according to JIS-K-5910) was 74.1% by weight. [Examples]

[0082] An aluminum pigment was prepared in the same manner as in Example 2, except that the amount of trimethylolpropane trimethacrylate added was 9.75 g. The heat residue of this aluminum pigment (according to JIS-K-5910) was 74.2% by weight.

[0083] [Comparative Example 1] An aluminum pigment was prepared in the same manner as in Example 1, except that kneading with a kneader was not performed. The heating residue of this aluminum pigment (according to JIS-K-5910) was 73.9% by weight.

[0084] [Comparative Example 2] 100 g of flake-shaped metallic aluminum particles (heating residue 75% by weight, average particle size 10 μm, WCA: 2.5 m² / g, ratio of average particle size d50 (μm) to average thickness t (μm) is 50, average surface roughness Ra: 15 nm, average height Rc of surface roughness curve irregularities: 60 nm) were placed in a 1 liter four-necked flask, 500 g of mineral spirits were added, and the mixture was stirred while introducing nitrogen gas to raise the temperature of the system to 70°C. Next, 0.3 g of acrylic acid was added and stirring was continued at 70°C for 30 minutes.

[0085] Next, a solution was prepared consisting of 11.2 g of trimethylolpropane trimethacrylate, 2.0 g of 2,2'-azobis-2,4-dimethylvaleronitrile (polymerization initiator), and 85 g of mineral spirits. This solution was added to the reaction vessel at a rate of approximately 0.55 g / min using a metering pump, and polymerization was carried out for a total of 6 hours while maintaining the system temperature at 70°C. At this point, the amount of unreacted trimethylolpropane trimethacrylate in the sampled filtrate was analyzed by gas chromatography, and it was found that more than 99% of the added amount had reacted. After polymerization was completed, the mixture was allowed to cool naturally to obtain a paste-like aluminum pigment of the present invention. The heating residue of this aluminum pigment (according to JIS-K-5910) was 74.0% by weight.

[0086] [Comparative Example 3] An aluminum pigment was prepared in the same manner as in Example 1, except that the kneading time using the kneader was set to 10 minutes. The heat residue of this aluminum pigment (according to JIS-K-5910) was 73.9% by weight.

[0087] [Comparative Example 4] An aluminum pigment was prepared in the same manner as in Example 2, except that the amount of trimethylolpropane trimethacrylate added was 1.12 g. The heat residue of this aluminum pigment (according to JIS-K-5910) was 74.2% by weight.

[0088] Table 1 shows the results of performance evaluation based on the above-described test and measurement methods.

[0089] Table 1

Claims

1. A resin-coated aluminum pigment in which a resin adheres to the entire surface of flake-shaped metallic aluminum powder, wherein the average film thickness of the resin is 3 to 30 nm, and the aluminum content measured by XPS is 13 atomic percent or less. The resin is a (co)polymer formed from monomers containing at least one monomer having four or more radically polymerizable double bonds. A resin-coated aluminum pigment, wherein the amount of monomer added, which includes at least one monomer having four or more radical polymerizable double bonds, is 1.5 to 14.0 parts by weight per 100 parts by weight of flake-shaped aluminum powder.

2. The resin-coated aluminum pigment according to claim 1, wherein the average particle length of the flake-shaped metallic aluminum powder is 1 to 100 μm and the average thickness is 0.3 μm or less.

3. The surface diffusion area of ​​flake-shaped aluminum metal powder in water is 2.5 m². ２ The aluminum pigment according to claim 1, wherein the amount is 1 / g or more.

4. The aluminum pigment according to claim 1, wherein the flake-shaped aluminum metal powder has an average surface roughness Ra of 20 nm or less, or an average height Rc of the irregularities in the average surface roughness curve of 80 nm or less.

5. A process (mixing process) in which flake-shaped metallic aluminum powder is broken down into primary particles, wherein the mixing time is 30 minutes or more and 2 hours or less, the temperature during the mixing process is 40 to 50°C, and the rotation speed of the mixer during mixing is 10 to 100 rpm; A step (dispersion step) in which the metallic aluminum particles obtained in the above mixing step are dispersed in an organic solvent; The process then involves heating and stirring while adding and mixing at least one selected from a radically polymerizable unsaturated carboxylic acid, a phosphoric acid or phosphonic acid mono or diester having a radically polymerizable double bond, and a coupling agent having a radically polymerizable double bond (first step); followed by A second step involves adding a monomer having four or more radical polymerizable double bonds and a polymerization initiator to polymerize the components adsorbed on the surface of the flake-shaped metallic aluminum powder in the first step with the monomer having four or more radical polymerizable double bonds to form a resin layer, wherein the amount of monomer containing at least one type of monomer having four or more radical polymerizable double bonds added is 1.5 to 14.0 parts by weight per 100 parts by weight of the flake-shaped metallic aluminum powder. A method for producing a resin-coated aluminum pigment according to claim 1, including the method described in claim 1.

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