JP2024169313A - Resin-bonded aluminum pigments, paints, and inks - Google Patents

Abstract

To provide a resin-coated aluminum pigment that offers superior designability and exhibits superior adhesion and chemical resistance.SOLUTION: A resin-coated aluminum pigment comprises aluminum particles whose surfaces are coated with a resin containing a polymer of a monomer and/or oligomer with one or more radical-polymerizable double bonds. In the resin-coated aluminum pigment, the resin layer surface has an average surface roughness Ra of 0.1-5.0 nm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a resin-attached aluminum pigment, and to paints and inks containing the resin-attached aluminum pigment.

Traditionally, aluminum pigments have been used in metallic paints, printing inks, plastic blends, etc., to achieve a cosmetic effect that emphasizes a metallic look. By coating these aluminum pigments with resin, it is possible to improve alkali resistance tests. In particular, thin-film aluminum with an average particle size of 20 μm or less and a particle thickness of 0.2 μm or less has excellent design properties.

As a method for improving the alkali resistance of aluminum pigments as described above, a method of subjecting the aluminum pigments to a specific surface treatment has been proposed.
For example, Patent Document 1 describes that by setting the ratio of the resin mass per unit mass of the resin-adhered aluminum pigment to the total surface area of the particles of the resin-adhered aluminum pigment within a predetermined range, the design tends to be excellent and the alkali resistance also tends to be excellent. However, there is no description of the contribution of the thickness of the resin layer to the design.

Patent Document 2 describes a method for producing a resin-coated metal pigment in which 0.1 to 50 parts by weight of resin per 100 parts by weight of the metal pigment is attached to the surface of the metal pigment, and describes how the desired resin-coated metal pigment can be obtained by promoting physical dispersion by applying an external action such as ultrasonic irradiation during the resin coating process. However, there is no mention of the contribution that the thickness of the resin layer can make to the design.

Patent Document 3 describes that by setting the ratio of the total area of resin particles with an equivalent circle diameter of 25 nm or more on the surface of the coating resin that coats the aluminum particle surface to a specific range, it is possible to provide a pigment with excellent chemical resistance to chemicals such as alkali. However, there is no description of the contribution that the thickness of the resin layer can make to the design.

Patent Document 4 describes an aluminum pigment that can give a metallic coating film that has excellent design and adhesion, and a method for producing the same. However, there is no mention of the contribution that the thickness of the resin layer can make to the design, nor is there any mention of alkali resistance.

JP 2018-135455 A JP 2012-162733 A International Publication No. 2018/047360 JP 2002-226733 A

The present invention aims to provide a resin-adhered aluminum pigment that has not necessarily been fully realized in the conventional techniques described above, and aims to provide a resin-adhered aluminum pigment that has excellent design properties, adhesion, and chemical resistance.

As a result of intensive research to solve the above-mentioned problems, the inventors have discovered that by setting the average surface roughness of the resin layer surface of a resin-adhered aluminum pigment and/or the thickness of the resin-adhered layer within a predetermined range, a resin-adhered aluminum pigment can be obtained that has excellent design properties, adhesion, and chemical resistance to chemicals such as alkalis, and have completed the present invention.
That is, the gist of the present invention is as follows.
[1] A resin-adhered aluminum pigment in which the surfaces of aluminum particles are coated with a resin containing a polymer of a monomer and/or oligomer having one or more radically polymerizable double bonds, and the average surface roughness Ra of the resin layer surface of the resin-adhered aluminum pigment is 0.1 to 5.0 nm.
[2] The resin-adhered aluminum pigment according to the above [1], wherein the thickness τ of the resin-adhered layer measured by cross-sectional observation is 10 nm to 20 nm.
[3] A resin-adhered aluminum pigment in which the surfaces of aluminum particles are coated with a resin containing a polymer of a monomer and/or oligomer having one or more radically polymerizable double bonds, and the thickness τ of the resin-adhered layer measured by cross-sectional observation is 10 nm to 20 nm.
[4] The resin-adhered aluminum pigment according to the above [1], wherein the ratio ((A)/(SSA)) of the resin mass per unit mass of the resin-adhered aluminum pigment (A(g/g)) to the total surface area per unit mass of the aluminum particles (SSA( ^m2 /g)) is 0.0077 g/ ^m2 to 0.025 g/ ^m2 .
[5] The resin-adhered aluminum pigment according to the above [1], wherein the average cross-sectional thickness τ' of the aluminum particles is 0.03 μm to 0.2 μm.
[6] The resin-adhered aluminum pigment according to the above [5], wherein the average particle diameter d50 of the aluminum particles is 5 μm to 15 μm.
[7] A paint containing the resin-adhered aluminum pigment according to any one of [1] to [6] above.
[8] An ink containing the resin-adhered aluminum pigment according to any one of [1] to [6] above.

The present invention makes it possible to provide resin-attached aluminum pigments that have not necessarily been fully realized with conventional technology, and makes it possible to provide resin-attached aluminum pigments that have excellent design properties, adhesion, and chemical resistance.

1 is an example of a TEM photograph of the resin-coated metal pigment of Example 1. 1 is an example of a TEM photograph of the resin-coated metal pigment of Comparative Example 1.

The following describes an example of a preferred embodiment of the present invention. However, the following embodiment is merely an example for explaining the present invention, and the present invention is not limited to the following embodiment.

The resin-adhered aluminum pigment of the present invention has excellent adhesion and chemical resistance while maintaining excellent design properties.

The resin-adhered aluminum pigment of the present invention has a structure in which the surfaces of aluminum particles are coated with a resin containing a polymer of a monomer and/or oligomer having one or more radically polymerizable double bonds.
The specific shapes of the aluminum particles that are the raw material for the resin-adhered aluminum pigment of the present invention will be described below.

The aluminum particles used in the present invention are not limited to a particular type, and may be any type commonly used as an aluminum pigment, and may have a flat shape such as a scaly, angular, or rounded shape. If high designability (e.g., characteristics such as brightness, brilliance, flip-flop feel, and hiding power) is to be maintained, the effect of the present invention will be more pronounced if high design grade (vapor deposition metallic paint or ink grade) aluminum particles (hereinafter sometimes referred to as flake aluminum powder) are used.

The method for producing aluminum particles is not particularly limited, but the aluminum particles can be obtained by grinding granular powder or small pieces of metallic aluminum together with a few percent of a grinding aid using a mechanical method such as a stamp mill method, a dry ball mill method, a wet ball mill method, an attritor method, or a vibrating ball mill method.
Examples of methods for producing highly decorative aluminum particles include the method described in WO 99/54074, and the flake-shaped aluminum powder obtained by this method, which has a smooth surface and uniform thickness, can be particularly preferably used as the raw material for the aluminum pigment of the present invention.

The particle size of the aluminum particles used as the raw material for the resin-adhered aluminum pigment of the present invention varies depending on the application. When the resin-adhered aluminum pigment of the present invention is used for paints and printing inks, aluminum particles with an average particle size d50 (μm) of about 1 to 100 μm can be suitably used. Recently, applications in which high designability of metal pigments is particularly required include automobiles, general home appliances, and information appliances such as mobile phones, and in these applications, metal pigments are used to paint metals such as iron and magnesium alloys or plastics. In order to ensure high designability, the preferred average particle size (d50) of the aluminum particles of the resin-adhered aluminum pigment of the present invention used for these applications is 5 to 35 μm, and more preferably 5 to 15 μm.

The average particle diameter d50 (μm) of the aluminum particles of the present invention can be measured using a general laser diffraction/scattering type particle size distribution measuring device, and can be measured, for example, as follows.
The average particle size (d50) of the particles of the flaky aluminum powder is measured using a laser diffraction/scattering type particle size distribution measuring device (LA-300/Horiba, Ltd.) Mineral spirits can be used as the measurement solvent.
It is preferable that the resin-adhered aluminum pigment sample is subjected to ultrasonic dispersion for 2 minutes as a pretreatment, and then charged into a dispersion tank and the measurement is started after confirming that the appropriate concentration has been reached.

The average cross-sectional thickness τ' (μm) of the aluminum particles can be determined by measuring an FE-SEM image of the cross section of the coating film using image analysis software.
Specifically, 100 particles are randomly selected from an FE-SEM image of the cross section of the coating film, the cross-sectional thickness of the particles is automatically measured, and the arithmetic average value of the 100 particles is calculated.
The average cross-sectional thickness τ' (μm) of the aluminum particles of this embodiment is preferably 0.03 μm to 0.2 μm.

The specific composition and shape of the resin attached to the surface of the resin-attached aluminum pigment of the present invention will be described below.

The resin attached to the resin-attached aluminum pigment of this embodiment is not particularly limited, but is preferably a polymer of a monomer and/or oligomer having one or more radically polymerizable double bonds.

The monomer having one or more radically polymerizable double bonds is not particularly limited, and conventionally known monomers can be used. Specific examples of the monomer having one or more radically polymerizable double bonds include, but are not limited to, unsaturated carboxylic acids (e.g., acrylic acid, methacrylic acid, itaconic acid, fumaric acid, citraconic acid, crotonic acid, maleic acid, or maleic anhydride), mono- or diesters of phosphorus or phosphonic acid (e.g., 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 ...octyl-2-acryloyloxyethyl phosphate, dioctyl-2-acryloyloxyethyl phosphate, dioctyl-2-acryloyloxyethyl phosphate, dioctyl-2-acryloyloxyethyl phosphate, dioctyl-2-acryloyloxyethyl phosphate, di phosphate, 2-methacryloyloxypropyl phosphate, bis(2-chloroethyl)vinyl phosphonate, diallyl dibutyl phosphonosuccinate, 2-methacryloyloxyethyl phosphate, 2-acryloyloxyethyl phosphate), coupling agents (e.g., γ-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyl tris(β-methoxyethoxy)silane, isopropyl isostearoyl diacryl titanate, acetoalkoxyaluminum diisopropylate, zircoaluminate), nitriles of unsaturated carboxylic acids (e.g., acrylonitrile, methacrylonitrile), or nitriles of unsaturated carboxylic acids Esters (e.g., methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, glycidyl acrylate, cyclohexyl acrylate, 1,6-hexanediol diacrylate, 1,4-butadiol diacrylate, triethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane triacrylate, tetramethylolpropane tetraacrylate, tetramethylolpropane methane triacrylate, trimethylolpropane ... Methylolpropane trimethacrylate, tetramethylolmethane trimethacrylate, di-trimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, di-pentaerythritol hexaacrylate, di-pentaerythritol pentaacrylate, di-pentaerythritol pentaacrylate monopropionate, triacrylformal, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methoxyethyl methacrylate, butoxyethyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, and the like can be suitably used.
Furthermore, cyclic unsaturated compounds (e.g., cyclohexene) and aromatic unsaturated compounds (e.g., styrene, α-methylstyrene, vinyltoluene, divinylbenzene, cyclohexene vinyl monoxide, divinylbenzene monoxide, vinyl acetate, vinyl propionate, allylbenzene, or diallylbenzene) can also be suitably used. The oligomer having one or more radically polymerizable double bonds can be a polymer of these monomers.

In the method for producing a resin-deposited aluminum pigment of the present embodiment described below, it is preferable to use a polymerization initiator.
The polymerization initiator is generally known as a radical generator, and the type thereof is not particularly limited.
Examples of the polymerization initiator include, but are not limited to, peroxides such as benzoyl peroxide, lauoyl peroxide, and bis-(4-t-butylcyclohexyl)peroxydicarbonate, and azo compounds such as 2,2'-azobis-isobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, and 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile.
The amount of the polymerization initiator used is not particularly limited since it is adjusted depending on the reaction rate of each radically polymerizable monomer, but is preferably 0.1 to 25 parts by mass per 100 parts by mass of the aluminum pigment.

During the resin polymerization of the resin-attached aluminum pigment of this embodiment described below, it is preferable to add a reversible addition-fragmentation chain transfer agent (hereinafter referred to as a RAFT agent) together with the polymerization initiator to control the molecular weight of the reaction product, thereby performing living radical polymerization. This polymerization is superior in productivity compared to other living radical polymerizations in that (1) it can be applied to a variety of monomers, and (2) it can be applied to a wide range of reaction conditions. Examples of the RAFT agent used to obtain the resin layer of the resin-adhered aluminum pigment of the present invention include, but are not limited to, dithiocarbonates such as O-ethyl-S-(1-phenylethyl)dithiocarbonate, O-ethyl-S-(2-propoxyethyl)dithiocarbonate, and O-ethyl-S-(1-cyano-1-methylethyl)dithiocarbonate; dithioesters such as cyanoethyl dithiopropionate, benzyl dithiopropionate, benzyl dithiobenzoate, and acetoxyethyl dithiobenzoate; dithiocarbamates such as S-benzyl-N,N-dimethyldithiocarbamate and benzyl-1-pyrrolecarbodithioate; and trithiocarbonates such as dibenzyl trithiocarbonate and S-cyanomethyl-S-dodecyl trithiocarbonate. It is preferable to select the most suitable RAFT agent depending on the reactivity of the monomer, and in particular, dithiocarbamates and dithiocarbonates are suitable for the polymerization of acrylic esters, and dithioesters are suitable for the polymerization of methacrylic esters. The RAFT agent is preferably used in an amount of 0.1 to 30 parts by weight, more preferably 1.0 to 10 parts by weight, per 100 parts by weight of the total amount of resin. By using an amount of 0.1 part by weight or more, it is possible to suppress the tendency for the average molecular weight of the reaction product to become high, and by using an amount of 30 parts by weight or less, it is possible to suppress the tendency for the average molecular weight of the reaction product to become low.

The solvent is not limited to the following examples, but any organic solvent that is inactive to the metal pigment may be used to disperse the metal pigment in the organic solvent, and examples of the organic solvent 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, glycols such as propylene glycol and ethylene glycol, glycol ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether, and glycol esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and ethylene glycol monomethyl ether acetate. These organic solvents may be used alone or in combination of two or more.
The amount of the organic solvent used is preferably an amount that results in a solids concentration of the metal pigment of 1 to 40% by weight. In the present invention, the organic solvent is also used as a reaction solvent when forming a resin by polymerizing the monomer and/or oligomer having one or more double bonds in the molecule.

When producing resin-attached aluminum pigments, a combination of shear external action and vibration external action may be used as an external action. A shear external action refers to an action of promoting physical dispersion by applying high shear force when dispersing a metal pigment in an organic solvent and when adding a monomer to the dispersion. Methods for this include, for example, a method of dispersing a metal pigment or a monomer using an agitator, disperser, vibration generator, or ultrasonic generator. When a vibration generator or ultrasonic generator is used, the dispersion or the slurry liquid during the polymerization reaction is mechanically vibrated strongly, promoting physical dispersion. In particular, high-speed dispersion using an agitator is more preferable because it does not destroy the surface of the vapor-deposition-like aluminum pigment.

The resin-adhered aluminum pigment of the present invention is characterized by its high designability, due to the high smoothness of the resin-adhered layer and the thin film formation, compared to conventional thin film aluminum pigments. This is thought to be because the thin film aluminum pigment can be made into a monodisperse state under high speed stirring, and the molecular weight can be controlled at a low molecular weight state by RAFT polymerization, making it possible to achieve both high smoothness and thin film formation. This uniformity can be evaluated by measuring the thickness τ of the resin layer of the resin-coated pigment and the average surface roughness Ra.

The average surface roughness Ra of the resin layer surface of the resin-adhered aluminum pigment of the present invention is preferably 0.1 to 5.0 nm, more preferably 0.1 to 4.5 nm, even more preferably 0.1 to 2.6 nm, and most preferably 0.1 to 2.5 nm. Of these, the upper limit of the average surface roughness Ra is preferably the upper limit described above, more preferably 2.5 nm, even more preferably 2.2 nm, and most preferably 2.0 nm. In addition, the lower limit of the average surface roughness Ra may be 0.3 nm, 0.5 nm, 0.7 nm, or 0.9 nm in some cases. When the average surface roughness Ra is equal to or less than the upper limit, the regular reflectance of light on the surface of the coating film using the resin-adhered aluminum pigment is high, and therefore the coating film shows extremely excellent light brightness and has good flop properties.
The average surface roughness Ra referred to in the present invention can be calculated by a surface morphology observation method using a general atomic force microscope. Specifically, it is calculated, for example, by the following method.
As a method for observing the surface morphology of metal pigments, an atomic force microscope (hereinafter abbreviated as AFM) (for example, Dimension Icon (manufactured by Bruker)) can be used. As a pretreatment, for example, a resin-attached aluminum pigment sample is ultrasonically cleaned with excess methanol and chloroform, vacuum dried, dispersed again in acetone, dropped onto a Si wafer, and naturally dried. The quantification of surface roughness by AFM is performed for resin-coated metal pigments that do not overlap with other resin-coated metal pigments, with a measurement field of view of 2 μm and 512 pixels, the measurement field of view is divided into 16 sections, and a third-order tilt correction (Plane Fit) is performed on each section, and the calculated average value is defined as the "average surface roughness Ra (nm)". The terminology of surface roughness is based on JIS-B-0601:2013.

In the resin-adhered aluminum pigment of the present invention, the thickness τ of the resin-adhered layer measured by cross-sectional observation of the resin-adhered aluminum pigment is preferably 5 to 30 nm, and more preferably 10 nm to 20 nm. The upper limit of the thickness τ of the resin-adhered layer is even more preferably 18 nm, and most preferably 16 nm. When the thickness τ of the resin-adhered layer is within the above range, it exhibits extremely excellent design properties, and also has good adhesion and chemical resistance.

The average film thickness τ of the resin layer in the present invention is calculated, for example, as follows. First, as a pretreatment, the resin-adhered aluminum pigment is ultrasonically cleaned with excess methanol and chloroform, then vacuum dried, dispersed and washed again in acetone, and then naturally dried. Then, it is embedded in epoxy resin and completely cured, after which it is trimmed and cut into pieces, and the cross section is observed with a transmission electron microscope (hereinafter abbreviated as TEM) to observe the interface between the resin coating layer and the aluminum pigment. Observations are performed in four fields of view at 200,000 times magnification per field, and the area of the coating layer is measured from the outline of the entire resin layer using known image analysis software (for example, Image-ProPLUS ver. 7.0 (manufactured by Media Cybernetics)), and the arithmetic average value of these four fields of view is defined as the [arithmetic average film thickness τ].

(I) The ratio ((A)/(SSA)) of the mass of resin per unit mass of the resin-adhered aluminum pigment (A (g/g)) to the total surface area of aluminum particles per unit mass of the resin-adhered aluminum pigment (SSA (m ² /g))
(1) Resin mass (A (g/g))
The resin mass per unit mass of the resin-adhered aluminum pigment (A (g/g)) is the calculated mass (g) of resin adhering to 1 g of the resin-adhered aluminum pigment.
The total particle surface area per unit mass (SSA (m ² /g)) of the resin-adhered aluminum pigment is the total area (m ² ) of 1 g of aluminum particles.
The ratio (A)/(SSA) in the resin-adhered aluminum pigment of the present invention is preferably 0.0077 g/ ^m2 to 0.025 g/ ^m2 . When the ratio (A)/(SSA) is within the above range, the amount of resin relative to the aluminum particles is appropriate. By making the ratio (A)/(SSA) equal to or greater than the lower limit of the above range, a decrease in alkali resistance is suppressed, and by making it equal to or less than the upper limit of the above range, the resin layer is easily controlled and a decrease in color tone is suppressed.

In the present invention, A (g/g) and SSA (m ² /g) can be measured, for example, by the following method.
1 g of the resin-adhered aluminum pigment of the present invention is weighed into a 100 ml beaker, 50 ml of petroleum benzene is added and thoroughly dispersed, and then the pigment is heated in a thermostatic water bath at 40°C for 1 hour. The heated dispersion is filtered and thoroughly washed with acetone before being collected. The solid sample obtained after filtration is dried in a desiccator for 90 minutes or more. A portion of the dried sample is analyzed by thermogravimetry and differential thermal TG-DTA to determine the resin mass per unit mass of the resin-adhered aluminum pigment (A (g/g)).

The SSA (m ² /g) of the aluminum particles means the total surface area per 1 g of the aluminum particles, and is a value calculated by the following formula.
SSA (m ² /g) = 2 x (0.4/τ' (μm))

The method for calculating the above-mentioned SSA (m ² /g) is described, for example, in Aluminum Paint and Powder, J. D. Edwards & R. I. Wray, 3rd Edition, Reinhold Publishing Corp., New York (1955), pp. 16-22.

In addition, the resin-attached aluminum pigment of the present invention has a more dense and uniform coating of resin on the surface of the aluminum particles than conventional aluminum pigments, improving the chemical resistance in the coating film. When the color difference ΔE is calculated according to 6.3.19 of JIS-Z-8781 (2017) to evaluate chemical resistance, it is preferable that ΔE is less than 1.0.

The resin-adhered aluminum pigments of the present invention can be used in paints and inks.
Paints containing the resin-adhered aluminum pigment of the present invention can be suitably used for automobiles, general home appliances, information appliances such as mobile phones, printing, and for coating substrates such as metals such as iron and magnesium alloys, and plastics, and can exhibit high design properties. Inks containing the resin-adhered aluminum pigment of the present invention can be suitably used for metallic paints, printing inks, paints for kneading into plastics, and can exhibit high design properties.

Additives commonly used in the paint industry, such as pigments, dyes, wetting agents, dispersants, color separation inhibitors, leveling agents, slip agents, rheology control agents, viscosity modifiers, anti-skinning agents, anti-gelling agents, defoamers, thickeners, anti-sagging agents, mildew inhibitors, UV absorbers, film-forming aids, and surfactants, may also be added as appropriate to paints or inks containing the novel resin-attached aluminum pigment of the present invention.

Next, the present invention will be described in detail with reference to examples. In the following description, "%" indicates % by weight.

Example 1
100 g of commercially available aluminum paste (manufactured by Asahi Kasei Corporation, SB-10 "average particle size 10 μm, non-volatile content 74 mass%"; aluminum particles of the present invention) was placed in a 1-liter four-neck flask, 500 g of mineral spirits was added, and the mixture was stirred for 3 hours while bubbling nitrogen gas, and the temperature in the system was raised to 70° C. Next, 1.11 g of acrylic acid was added, and stirring was continued at 70° C. for 30 minutes. Next, 7.83 g of trimethylolpropane trimethacrylate, 0.87 g of di-trimethylolpropane tetraacrylate, 2.0 g of 2,2'-azobis-2,4-dimethylvaleronitrile (polymerization initiator), 0.5 g of bis(dodecylsulfonylthiocarbonyl) disulfide (RAFT agent), and 50 g of mineral spirits were added dropwise over 1 hour (i.e., the addition method was dropwise, and the drop time was 1 hour), and polymerization was carried out for a total of 8 hours while maintaining the temperature in the system at 70°C. When the unreacted amounts of trimethylolpropane trimethacrylate and di-trimethylolpropane tetraacrylate in the filtrate sampled at this point were analyzed by gas chromatography, it was found that 99% or more of the added amounts had reacted. After the polymerization was completed, the treated slurry was filtered to obtain a resin-adhered aluminum pigment. The heating residue of the aluminum pigment (according to JIS-K-5910) was 56.1% by weight.

Example 2
A resin-adhered aluminum pigment was obtained in the same manner as in Example 1, except that the amounts of trimethylolpropane trimethacrylate and di-trimethylolpropane tetraacrylate were changed to 12.6 g and 0.14 g, respectively.

Example 3
A resin-adhered aluminum pigment was obtained in the same manner as in Example 1, except that the mineral spirit was changed to 150 g.

Example 4
An ultrasonic disperser was attached directly to the outside of the 1-liter four-neck flask used in Example 1, and ultrasonic waves were applied to the slurry liquid inside. A resin-coated aluminum paste was obtained in the same manner as in Example 1, except that ultrasonic waves with a frequency of 40 kHz and an output of 12 W were irradiated during polymerization using this ultrasonic disperser. The non-volatile content of this paste according to JIS-K-5910 was 50.1% by weight.

Example 5
A resin-adhered aluminum pigment was obtained in the same manner as in Example 1, except that the amount of aluminum paste used in Example 1 was changed to 100 g (manufactured by Asahi Kasei Corporation, FD-5060 "average particle size 6 μm, non-volatile content 72 mass%"; aluminum particles of the present invention), 5.31 g of trimethylolpropane trimethacrylate, and 0.59 g of di-trimethylolpropane tetraacrylate.

Example 6
A resin-adhered aluminum pigment was obtained in the same manner as in Example 1, except that in Example 3, 10.62 g of trimethylolpropane trimethacrylate and 1.18 g of di-trimethylolpropane tetraacrylate were used.

Example 7
A resin-adhered aluminum pigment was obtained in the same manner as in Example 1, except that the amount of aluminum paste used was changed to 100 g (manufactured by Asahi Kasei Corporation, BS-120 "average particle size 13 μm, non-volatile content 65 mass%"; aluminum particles of the present invention), 4.95 g of trimethylolpropane trimethacrylate, and 0.55 g of di-trimethylolpropane tetraacrylate.

Example 8
A resin-adhered aluminum pigment was obtained in the same manner as in Example 5, except that the amounts of trimethylolpropane trimethacrylate and di-trimethylolpropane tetraacrylate were changed to 7.2 g and 0.8 g, respectively.

Example 9
A resin-adhered aluminum pigment was obtained in the same manner as in Example 1, except that the amounts of trimethylolpropane trimethacrylate, di-trimethylolpropane tetraacrylate, and divinylbenzene were changed to 6.83 g, 0.87 g, and 1.0 g, respectively.

Example 10
A resin-adhered aluminum pigment was obtained in the same manner as in Example 2, except that the dropping time was changed to 0.5 hours.

Example 11
A resin-adhered aluminum pigment was obtained in the same manner as in Example 2, except that the addition method was changed from dropwise addition to lump-sum addition.

Comparative Example 1
100 g of commercially available aluminum paste (manufactured by Asahi Kasei Corporation, SB-10 "average particle size 10 μm, non-volatile content 74 mass%") was placed in a 1-liter four-neck flask, 500 g of mineral spirits was added, and the mixture was stirred for 1 hour while bubbling nitrogen gas, and the temperature in the system was raised to 70 ° C. Next, 1.11 g of acrylic acid was added and the mixture was stirred for 30 minutes at 70 ° C. Next, 12.6 g of trimethylolpropane trimethacrylate, 0.14 g of di-trimethylolpropane tetraacrylate, 2.0 g of 2,2'-azobis-2,4-dimethylvaleronitrile (polymerization initiator), and 50 g of mineral spirits were added dropwise with a metering pump over 1 hour (i.e., the addition method was dropwise, and the drop time was 1 hour), and the temperature in the system was kept at 70 ° C. while polymerization was continued for a total of 8 hours. During the polymerization reaction, ultrasonic waves with a frequency of 42 kHz and an output of 180 W were indirectly irradiated to the mixture in the four-neck flask for about 3 minutes every 15 minutes using a commercially available ultrasonic cleaner. The amount of unreacted trimethylolpropane trimethacrylate and di-trimethylolpropane tetraacrylate in the filtrate sampled at this point was analyzed by gas chromatography, and it was found that 99% or more of the added amount had reacted. After the polymerization was completed, the treated slurry was filtered to obtain a resin-adhered aluminum pigment. The heating residue of the aluminum pigment (according to JIS-K-5910) was 55.6% by weight.

Comparative Example 2
A resin-adhered aluminum pigment was obtained in the same manner as in Comparative Example 1, except that the amounts of trimethylolpropane trimethacrylate and di-trimethylolpropane tetraacrylate were changed to 7.83 g and 0.87 g, respectively.

Comparative Example 3
In Comparative Example 1, a resin-adhered aluminum pigment was obtained in the same manner as in Comparative Example 1, except that the aluminum paste was changed to 100 g (manufactured by Asahi Kasei Corporation, FD-5060 "average particle size 6 μm, non-volatile content 72 mass%"), 7.20 g of trimethylolpropane trimethacrylate, and 0.80 g of di-trimethylolpropane tetraacrylate.

Comparative Example 4
In Comparative Example 1, a resin-adhered aluminum pigment was obtained in the same manner as in Comparative Example 1, except that the aluminum paste was changed to 100 g (manufactured by Asahi Kasei Corporation, BS-120 "average particle size 13 μm, non-volatile content 65 mass%"), 4.95 g of trimethylolpropane trimethacrylate, and 0.55 g of di-trimethylolpropane tetraacrylate.

Comparative Example 5
A resin-adhered aluminum pigment was obtained in the same manner as in Comparative Example 1, except that the dropping time was changed to 0.5 hours.

Comparative Example 6
A resin-adhered aluminum pigment was obtained in the same manner as in Comparative Example 5, except that the addition method in Comparative Example 1 was changed from dropwise addition to lump-sum addition.

[Evaluation 1 (Ratio of Resin Mass (A (g/g)) to Total Surface Area (SSA (m ² /g)) ((A)/(SSA))]
(1) Resin mass (A (g/g))
1 g of the resin-adhered aluminum pigment obtained in the Examples and Comparative Examples was weighed into a 100 ml beaker, 50 ml of petroleum benzene was added and thoroughly dispersed, and then the pigment was heated for 1 hour in a thermostatic water bath at 40°C. The heated dispersion was filtered and thoroughly washed with acetone before being collected. The solid sample obtained after filtration was dried in a desiccator for 90 minutes or more. A portion of the dried sample was analyzed by thermogravimetry and differential thermal TG-DTA to determine the resin mass per unit mass of the resin-adhered aluminum pigment (A (g/g)).
(2) Total surface area of aluminum particles (SSA (m ² /g))
(The total surface area of the particles SSA (m ² /g) is defined as 2×(0.4/τ′ (μm)).
The average thickness τ' (μm) can be determined by measuring an FE-SEM image of the cross section of the coating film, which will be described later, using image analysis software.

[Evaluation 2 (measurement of average particle diameter d50 of aluminum particles)]
The average particle size (d50) of the aluminum particles was measured using a laser diffraction/scattering type particle size distribution measuring device (LA-300/HORIBA, Ltd.).
Mineral spirits was used as the measurement solvent.
The measurements were carried out in accordance with the equipment's instruction manual, but it should be noted that the aluminum particles used as samples were ultrasonically dispersed for 2 minutes as a pretreatment, and then placed in a dispersion tank. After confirming that the appropriate concentration had been achieved, the measurements were started.
After the measurement was completed, d50 was automatically displayed.

[Evaluation 3 (Measurement of average cross-sectional thickness τ' of aluminum particles)]
(1) Preparation of Coated Plates Using the aluminum pigments obtained in the Examples and Comparative Examples, metallic base paints were prepared according to the following compositions.
Aluminum pigment: 2g
Thinner (Musashi Paint Co., Ltd., product name "Plaace Thinner No. 2726"): 50g
Acrylic resin (manufactured by Musashi Paint Co., Ltd., product name "Plaace No. 7160"): 33 g
The above paint was applied to an ABS resin plate using an air spray device so that the dry film thickness was 20 μm, and then dried in an oven at 60° C. for 30 minutes to obtain a metallic base-coated plate.
A top coat paint prepared according to the following composition was applied onto the metallic base coated plate using an air spray device.
・Hitaroid Varnish 3685S (Hitachi Chemical): 25g
Mixed thinner (solvent mixing ratio: toluene: 45% by mass, butyl acetate: 30% by mass, ethyl acetate: 20% by mass, 2-acetoxy-1-methoxypropane: 5% by mass): 20 g
・Duranate TPA100 (Asahi Kasei Chemicals): 5g
After the above coating, the plate was dried in an oven at 60° C. for 30 minutes to obtain a coated plate for evaluation.

(2) Preparation of Cross Section of Coating Film Using the coated plate for evaluation produced as described above, a cross section of the coating film was prepared according to the following procedure.
Using scissors, the coated plate for evaluation was cut into pieces measuring 2 cm square.
The cut 2 cm square coated evaluation panels were repeatedly cut along the cross section of the coating using a large rotary microtome (RV-240, manufactured by Yamato Koki Kogyo Co., Ltd.) to remove microscopic aluminum and acrylic resin protruding from the cross section.
The cross section of the coating film obtained as described above was subjected to ion milling treatment using an ion milling device (IB-09010CP manufactured by JEOL Ltd.) set so as to be able to irradiate the ion beam up to a portion 20 μm away from the cross section of the coating film, thereby preparing a cross section of the coating film for obtaining an FE-SEM image as described below.

(3) Obtaining particle cross section (FE-SEM image) The coating film cross section (coated plate) obtained in the above ((2) Preparation of coating film cross section) was attached parallel to an SEM sample stage, and an FE-SEM image of the coating film cross section was obtained using a field emission type FE-SEM (Hitachi/S-4700).
The conditions for FE-SEM observation and acquisition were such that the acceleration voltage was adjusted to 5.0 kV and the image magnification was 10,000 times.
In addition, before acquiring (capturing) the FE-SEM image, electronic axis alignment processing was performed to prevent distortion of the boundary between the aluminum particles and the acrylic resin in the FE-SEM image.

(4) Analysis (measurement of average thickness of particles on cross section)
Using the FE-SEM images (10,000 magnification) obtained in the procedure for obtaining particle cross sections (FE-SEM images) described above ((1)-(3)) and image analysis software Win Roof version 5.5 (manufactured by MITANI CORPORATION), the particle thicknesses at the cross sections of the aluminum particles were measured, and the average thickness was calculated.
An FE-SEM image for measuring the thickness of an aluminum particle in its cross section was displayed, and an ROI line was selected and aligned with the 5 μm scale of the image, and the length and unit were input and set using the register/change function.
Next, an image of the cross section of the aluminum particle on which thickness measurement was to be performed was displayed, a rectangular ROI was selected, and the rectangular ROI was aligned with the cross section of the particle and binary processing was performed.
Next, the subject was asked to select the measurement item of the vertical chord length, and then the measurement was carried out. The value (vertical chord length value) automatically measured by the image analysis software was displayed on the image.
In this manner, using the image analysis software Win Roof version 5.5, 100 particles having an average particle diameter within ±50% of d50 ((IV) Average particle diameter: d50) described below were selected, and the thickness of the cross section of the aluminum particles was automatically measured. The arithmetic mean value of the 100 particles was calculated, and the average cross-sectional thickness τ' of the particles was determined.

[Evaluation 4 (Measurement of average film thickness τ of resin-adhered aluminum pigment surface)]
First, 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 then naturally dried. Then, it was embedded in epoxy resin and completely cured, after which it was trimmed and cut into slices, and the cross section was observed with a transmission electron microscope (hereinafter abbreviated as TEM) to observe the surface irregularities of the resin coating layer. Observation was performed in four fields of view, each of which was 1 μm wide, and the area of the coating layer was detected using image analysis software Image-ProPLUS ver. 7.0 (manufactured by Media Cybernetics), the outline of the entire resin layer was detected, the area was measured, and the arithmetic average value of the four fields of view was calculated and defined as τ.

[Evaluation 5 (Measurement of average surface roughness Ra of resin-adhered aluminum pigment surface)]
Using an atomic force microscope (AFM), a line profile (300 scans) of one visual field of 4 μm square of the resin-coated metal pigment was obtained. This was divided into 16 sections, and a third-order tilt correction was performed to obtain the arithmetic average surface roughness. The same operation was performed for a total of four or more visual fields, and the arithmetic average value was obtained and designated as Ra.

[Evaluation 6 (Evaluation of adhesion and chemical resistance of coating film)]
Using the resin-adhered aluminum pigments obtained in Examples 1 to 9 and Comparative Examples 1 to 6, metallic paints were prepared according to the following compositions.
Resin-attached aluminum pigment: 1.3 g (solid mass)
Thinner (a mixture of 30 parts of butyl acetate, 45 parts of toluene, 20 parts of isopropyl alcohol, and 5 parts of ethyl cellosolve): (D) g (the total amount of the resin-adhered aluminum pigment and (D) was adjusted to 33 g).
Clear (a mixture of 29 parts of Acrydic A-166 (manufactured by DIC), 3 parts of nitrocellulose (industrial nitrocellulose 1/2 AS, manufactured by Companhia Nitro Qumica Brasileira), and 68 parts of the above thinner) (binder resin component): 42 g

The resulting coating composition was spray-coated onto an ABS resin plate to a film thickness of 15 μm, and then dried at 55° C. for 30 minutes to prepare a coated plate for evaluation.
Using the above-mentioned coating plates for evaluation, the adhesion, chemical resistance, and gloss retention were evaluated.

(Adhesion of coating film)
Using the coated plate prepared above, cellophane tape (registered trademark: CT405AP-18, manufactured by Nichiban Co., Ltd.) was attached to the coating film and pulled at a 45 degree angle, and the degree of peeling of the metal pigment particles was visually observed. Depending on the observation results, the following evaluation was made.
○ (Good): No peeling △ (Acceptable): Slight peeling × (Not acceptable): Peeling

(Chemical resistance of coating film)
The lower half of the coated plate prepared above was immersed in a beaker containing 2.5N NaOH aqueous solution and left at 23°C for 24 hours. After the test, the coated plate was washed with water and dried, and the immersed and unimmersed parts were color-measured according to condition d (8-d method) of JIS-Z-8722 (1982), and the color difference ΔE was calculated according to JIS-Z-8730 (1980) 6.3.2. Evaluation was made according to the value of the color difference ΔE as follows (the smaller the value, the better).
○ (Good): Less than 1.0 △ (Acceptable): 1.0 or more but less than 2.0 × (Unacceptable): 2.0 or more

[Evaluation 7: FF property (brightness, brilliance) and hiding power of coating film]
(1) Preparation of Coated Plates Using the resin-adhered aluminum pigments obtained in Examples 1 to 11 and Comparative Examples 1 to 6, metallic paints were prepared according to the following compositions.
Resin-attached aluminum pigment: 5.0 g
Thinner (product name "Acrydic 2000GL" manufactured by Kansai Paint Co., Ltd.): 13.0 g
Acrylic resin (product name "Acrydic 2000" manufactured by Kansai Paint Co., Ltd.): 97.0 g
Next, the metallic base paint was applied to a PET film using a 3 mil applicator and dried at room temperature for 30 minutes to obtain a metallic base-coated plate.

(2) Measurement of ΔF/F property (brightness, brilliance) The coating film formed by applying the above-prepared coating material to a PET sheet was evaluated for ΔF/F property using a variable angle colorimeter (manufactured by Suga Test Instruments Co., Ltd.). The incident angle was set to 45 degrees, and the light receiving angle of 15 degrees (L15) close to the regular reflection light and the light receiving angle of 60 degrees (L60) close to the base color were measured, excluding the light in the specular reflection area reflected by the coating film surface of the coating plate for evaluation. The ratio (L15/L60) was taken as FF property.

(3) Judgment of hiding power: hiding power The coating film formed by applying the above-prepared coating material to a PET sheet was judged visually. Specifically, the above-prepared coating material was prepared using the standard aluminum paste and the resin-coated aluminum paste, and two coated strips were drawn on a PET sheet, and a light was irradiated from the uncoated side to evaluate hiding power.
(The standard aluminum paste pigment is the aluminum pigment before it is resin-coated.)
⊚: Has the same hiding power as the standard aluminum paste pigment.
◯: The hiding power is slightly decreased compared to the standard aluminum paste pigment.
Δ: The hiding power is low compared to the standard aluminum paste pigment.
×: The hiding power is significantly reduced compared to the standard aluminum paste pigment.

The results of evaluations 1 to 7 are shown in Table 1.

Claims (8)

A resin-attached aluminum pigment in which the surfaces of aluminum particles are coated with a resin containing a polymer of a monomer and/or an oligomer having one or more radically polymerizable double bonds,
The resin-adhered aluminum pigment has a resin layer surface having an average surface roughness Ra of 0.1 to 5.0 nm. The resin-adhered aluminum pigment according to claim 1, in which the thickness τ of the resin-adhered layer measured by cross-sectional observation is 10 nm to 20 nm. A resin-attached aluminum pigment in which the surfaces of aluminum particles are coated with a resin containing a polymer of a monomer and/or an oligomer having one or more radically polymerizable double bonds,
A resin-adhered aluminum pigment, the thickness τ of a resin-adhered layer being 10 nm to 20 nm as measured by cross-sectional observation. 2. The resin-adhered aluminum pigment according to claim 1, wherein the ratio ((A)/(SSA)) of the resin mass per unit mass of the resin-adhered aluminum pigment (A(g/g)) to the total surface area per unit mass of the aluminum particles (SSA( ^m2 /g)) is 0.0077 g/ ^m2 to 0.025 g/ ^m2 . The resin-attached aluminum pigment according to claim 1, wherein the average cross-sectional thickness τ' of the aluminum particles is 0.03 μm to 0.2 μm. The resin-adhered aluminum pigment according to claim 5, wherein the average particle diameter d50 of the aluminum particles is 5 μm to 15 μm. A paint containing the resin-attached aluminum pigment according to any one of claims 1 to 6. An ink comprising the resin-adhered aluminum pigment according to any one of claims 1 to 6.

Images