JP2003147270A - Bright aluminum pigment composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum pigment composition that has high brightness and floppiness and can realize a coating film having a uniform and beautiful appearance, and obtain coating material using the composition. SOLUTION: An aluminum pigment is controlled in its average particle size, ratio of average particle size to average thickness and average surface roughness are controlled individually in specific ranges whereby the excellent optical properties of high brightness and high floppiness can be achieved. In addition, the total amount of specific alteration products includes in the usual aluminum pigment composition is reduced lower than a certain level whereby the uneven coating that is critical in a higher brightness coating film can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aluminum pigment used in the field of high-grade metallic paints such as high-grade metallic paints for automobile bodies and parts, metallic paints for automobile repairs, metallic paints for home appliances, and metallic paints for industrial use. It relates to the paint used.

More specifically, the present invention relates to an aluminum pigment capable of suppressing unevenness in reflection while having an extremely high light brightness which is excellent in design property, and a coating using the same. Is.

[0003]

2. Description of the Related Art In general, aluminum pigments are widely used in the above-mentioned fields as a pigment having a unique metallic feeling which other pigments do not have and an excellent hiding power for the base.

In recent years, in particular, the fashionability of automobile body painting has come to be evaluated with the same or more values as the function originally possessed by the automobile.

Looking at the trend of fashionability of automobile body painting in recent years, in particular, the high whiteness type and the glaring monotonous silver metallic tone, which have been strong in the past, have decreased, the light brightness is strong, and the coating is dependent on the viewing angle. There is an increasing demand for a coating film having a strong optical anisotropy (flop property) whose appearance changes.

[0006] So far, as an aluminum pigment for the purpose of obtaining a high light reflectance, Japanese Patent No. 25755
No. 16 is an aluminum pigment having both a high hiding power and a high light reflectance, and in JP-A-49-14358, the surface of aluminum powder is polished by a wet ball mill method to provide a high reflectance. To obtain a good aluminum pigment,
Japanese Patent Publication No. 54-36607 discloses a method for forming a metallic coating film having an excellent sparkling effect. Further, JP-A-8-170034 describes an aluminum pigment which gives a coating film a strong glittering feeling and an excellent appearance.

[0007]

However, even the above-mentioned aluminum pigments have not reached the level of satisfying the currently desired high light brightness and high flop property. In addition to this, in a coating film having high light brightness, a slight disturbance in the alignment state of aluminum particles causes a disturbance in the reflection of light, resulting in unevenness that significantly impairs the appearance of the coating film, thus improving the orientation. Is desired. This problem is remarkable in automobile line coating, in which the orientation of aluminum particles tends to be sacrificed in order to give priority to coating efficiency, and the present situation is that the design limit cannot be raised due to unevenness.

The present invention provides an aluminum pigment composition having high optical properties, which are not obtained in the prior art, in particular, high glitter and flop properties, and which realizes a uniform and beautiful coating film appearance, And a coating material using the same.

[0009]

In order to solve the above problems, the inventors of the present invention have earnestly studied the relationship between the basic physical properties and optical characteristics of aluminum pigments and the manufacturing conditions. By controlling the average particle size of aluminum, the ratio of the average particle size to the average thickness of the aluminum pigment, and the average surface roughness within a specific range, we have found a phenomenon in which high optical brightness and high flop optical characteristics can be exhibited. . Furthermore, it has been found that coating unevenness can be improved by making the total amount of the specific deteriorated substances usually contained in the aluminum pigment composition less than a certain amount.

That is, the present invention provides (1) an aluminum pigment composition containing an aluminum pigment and a solvent,
The aluminum pigment has an average particle diameter d50 of 5 to 35 μ.
m, average thickness t (μm), average particle size d50 (μ
The ratio of m) is 30 to 90, the average surface roughness Ra is 20 nm or less, and the total amount of the modified substances having polar groups contained in the composition is 0.20 parts by mass with respect to 100 parts by mass of aluminum. Parts or less, (2) the modified product having the polar group contained in the aluminum pigment composition is a fatty acid having a carbon number of C1-10, an aliphatic alcohol having a carbon number of C1-10. , Carbon number C1
To 10 aliphatic aldehydes, and substances selected from aromatic carboxylic acids, aromatic aldehydes and aromatic phenols, the aluminum pigment composition according to (1) above, (3) above (1) ) Or (2), the coating composition containing the aluminum pigment composition according to (2) and having excellent orientation of aluminum particles during coating.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the average particle diameter d50 (μm), the average thickness t (μm), and the average surface roughness Ra (nm) of the aluminum pigment are defined as follows.

The average particle diameter d50 (μm) is a particle diameter at which the cumulative frequency of particle volume is 50%, and is a value measured by using a Laser Micron Sizer LMS-24 (manufactured by Seishin Enterprise Co., Ltd.).

The average particle diameter d50 is selected from among ultrafine, fine, medium, coarse and extra coarse according to the intended design, but the average particle diameter d50 is 5 to 35 μm and 7 to 30 μm.
More preferably m. If the average particle size is less than 5 μm, the orientation of the aluminum particles is likely to be disturbed in the coating film, and as a result, light scattering is likely to occur, so that the desired sense of light brightness cannot be obtained. On the other hand, when the particle size is larger than 35 μm, the size of the aluminum particles exceeds the film thickness of the coating film, so that part of the aluminum particles protrudes onto the surface of the coating film and deteriorates the finish of the coating film. It will be difficult.

The average thickness t (μm) is a value calculated by the following formula by measuring the water surface diffusion area WCA (m ² / g) per 1 g of the metal component. t (μm) = 0.4 / [WCA (m ² / g)]

The ratio of the average particle diameter d50 to the average thickness t in the present invention is given by d50 / t and is expressed as the so-called flatness of the aluminum pigment. The flatness gradually increases when aluminum powder is ground with a medium agitating mill or a ball mill, and when it is spread to a certain extent, the particles tend to bend. Generally, when it exceeds 200, the particles are easily cracked and easily bent. The flatness d50 / t in the present invention is 30 to 90, and 4
It is more preferably 0 to 80. Flatness of 30 or more,
The particles are sufficiently spread, and the hiding property required for the aluminum pigment is obtained. On the other hand, when the flatness is 90 or less, the spreading of the particles is not excessive, the smoothness of the particle surface is obtained, and the required high light brightness is obtained.

The average surface roughness Ra referred to in the present invention is measured by an atomic force microscope (hereinafter abbreviated as AFM).
The average surface roughness Ra of the aluminum pigment of the present invention is 20 n.
m or less, and more preferably 15 nm or less.

When the thickness is 20 nm or less, since the regular reflectance of light on the surface is large, extremely excellent light brightness is exhibited and the flop property is also good.

Further, the average height Rc of the unevenness of the surface roughness curve is
Is preferably 80 nm or less. Rc represents the magnitude of the surface irregularities, and is represented by the sum of the average absolute value of the peak heights of the surface roughness curve and the average absolute value of the depths of the valley bottoms of the surface roughness curve. , Rc is 80 nm or less,
It shows extremely high light brightness and good flop property.

The surface of the aluminum pigment of the present invention has few irregularities on the surface even when observed by a scanning electron microscope (SEM), and there is little adhesion of ultrafine powder to the surface, and the particles extend from the center to the end. It was found to contain significantly more aluminum pigment particles with a uniform thickness.

In the present invention, the altered substance contained in the aluminum pigment composition, the amount of which is to be limited, is derived from the higher fatty acids used as a grinding aid in the production process of the aluminum pigment composition. It is a substance having a polar group that is generated by chemical changes such as reduction during milling. In particular, it is a substance having a carboxyl group, an aldehyde group or a hydroxyl group as a polar group, and is an organic substance having these polar groups. More specifically, a C1-10 fatty acid, a C1-10 aliphatic alcohol, a C
1 to 10 aliphatic aldehydes, and aromatic carboxylic acids, aromatic aldehydes and aromatic phenols. The total amount of these substances having polar groups is 0.20 parts by mass or less with respect to 100 parts by mass of aluminum. These are alteration products produced by alteration of higher fatty acids used as a grinding aid as described above. Specific examples of the fatty acid having 1 to 10 carbon atoms include formic acid, acetic acid, propionic acid, butyric acid, kissic acid, caproic acid, caprylic acid, capric acid and the like. Examples of the aliphatic aldehydes and aliphatic alcohols include derivatives obtained by reducing the above fatty acids.

The aromatic carboxylic acids are mainly benzoic acid and a methyl group-substituted product thereof, and specific examples thereof include methylbenzoic acid, dimethylbenzoic acid, trimethylbenzoic acid and isomers thereof. Further, compounds in which a carboxyl group contained in these compounds is reduced to be an aldehyde group or a hydroxyl group are also included. Specific examples include benzaldehyde, methylbenzaldehyde, dimethylbenzaldehyde, trimethylbenzaldehyde, phenol, methylphenol, dimethylphenol, trimethylphenol and isomers thereof.

The aluminum pigment composition of the present invention is produced in the form of a paste by milling atomized aluminum powder as a raw material in a medium stirring mill or a ball mill in the presence of a milling solvent. At the time of grinding, the ratio of the mass of the grinding ball to the mass of aluminum of the aluminum powder is preferably 2 to 100. The specific gravity of the ground balls is preferably 6 or less. More preferably, the ratio of the mass of the grinding balls to the mass of aluminum of the aluminum powder is 6 to 65.

When the ratio of the mass of the ground powder to the mass of aluminum of the aluminum powder is 2 or more, an aluminum pigment having a small surface roughness can be obtained, and the one having high light brightness and high flop property can be obtained. On the other hand, when it is 100 or less, the grinding time is remarkably lengthened and the productivity is suppressed from being lowered, which is practical.

Furthermore, the ratio of the mass of the grinding solvent to the mass of aluminum of the aluminum powder is preferably 1.8 to 30. More preferably, it is 2.6-18.

When the ratio of the mass of the grinding solvent to the mass of aluminum is 1.8 or more, the aluminum particles are less in contact with each other during grinding, scratches on the particle surface are suppressed, and the reflectance is less lowered. Since the concentration of aluminum particles is low, the milling does not proceed rapidly, and it is easy to control the milling.

It is more preferable that the ground balls have a specific gravity of 1-6. More preferably, the specific gravity is 2 to 5
Is. When the specific gravity is 5 or less, the aluminum pigment having a small surface roughness of the present invention can be obtained, which is preferable. It is hard to have a rough surface like conventional pigments. Further, the specific gravity of the grinding balls is preferably larger than the specific gravity of the grinding solvent. In particular, if the specific gravity of the grinding balls is less than 1, the grinding balls float on the solvent and the shearing stress between the grinding balls cannot be obtained, and the grinding does not proceed. Therefore, the specific gravity is preferably 1 or more.

As the material of the grinding balls, glass balls, alumina balls, zirconia balls and the like can be used, but in the present invention, an appropriate ball can be selected depending on the specific gravity of the grinding balls. The surface roughness of the ground ball is JIS of steel balls for ball bearings.
Surface roughness Ra (maximum) of B 1501 is 0.08 μm
Those having a grade (G40) or less are preferable. More preferably, it is 0.04 μm (grade G20) or less.

The atomized aluminum powder used as a raw material is preferably one containing few impurities other than aluminum. Generally, 99.5% or more is used, but preferably 99.7% or more, more preferably
It is 99.8% or more.

The average particle size of the atomized aluminum powder is preferably 2 to 20 μm. Furthermore, 3 ~
It is more preferably 12 μm. When the particle size is 2 μm or more, the surface of the aluminum pigment and the particles are hard to be broken even if milled, which is preferable. Further, when it is 20 μm or less, the spreading time of the surface of the aluminum pigment due to grinding can be short, while the history of shear stress due to the grinding balls is small, and the undulation of the surface which increases with the spreading time is not remarkable. Is preferred.

The shape of the atomized aluminum powder is preferably spherical powder or teardrop powder.

The grinding solvent is not particularly limited, but conventionally used hydrocarbon solvents such as mineral spirit and solvent naphtha and alcohol-based, ether-based, ketone-based and ester-based solvents are used. it can.
Further, these solvents are also used as a paste forming solvent for aluminum pigments. The amount of the pasting solvent added is not particularly limited, but is usually adjusted so that the heating residue of the pasty aluminum pigment composition is about 50 to 80% by mass, preferably 60 to 78% by mass.

In the non-leafing type, a higher unsaturated fatty acid represented by oleic acid is used as the grinding aid. In the leafing type, higher saturated fatty acid typified by stearic acid is used. The amount of the grinding aid is preferably 1 to 50% by mass based on the mass of aluminum.

The solvent contained in the aluminum pigment composition contains a deterioration product, in particular, as described above, a deterioration product derived from the process. In particular, a modified product having a polar group is also highly reactive and therefore has an action of eroding and degrading the surface oxide layer of aluminum particles during storage. Therefore, when a certain amount or more of the modified product having a polar group is contained in the aluminum pigment composition, the chemical stability of the paste-like aluminum pigment composition decreases. As a result, the aluminum particles tend to agglomerate during storage, making it difficult to uniformly disperse the aluminum particles during coating of the paint. Further, such aluminum particles are also weak against mechanical shear, and for example, during coating, a strong pressure is applied to the particles near the spray nozzle, so the particles may cause soft agglomeration, especially in a bell type coating machine. This tendency is remarkable. When the particles are not sufficiently dispersed in this manner, when the coating film is formed, the particles are not loosened and overlapping portions are generated, so that a density difference occurs in the distribution of aluminum particles in the coating film, Since the orientation state deteriorates, it causes unevenness.

Particularly, a substance having a carboxyl group, an aldehyde group or a hydroxyl group as the polar group, particularly an organic substance having such a polar group is not preferable because of the above effects.

In particular, the surface of aluminum particles is usually
Although it is protected by an oxide film and is chemically stable,
During the crushing process, the active aluminum surface is exposed. This active aluminum surface functions as a chemical catalyst, but various chemical reactions are likely to occur especially at high temperatures. Under such conditions, some of the higher fatty acids are decomposed into lower and intermediate fatty acids having a small number of carbon atoms, and these fatty acids are further reduced to form aliphatic aldehydes and aliphatic alcohols. To be done. Moreover, aromatic carboxylic acids are formed by the reaction of the lower fatty acids generated at this time with the aromatics in the grinding solvent. A portion of these is reduced to form aromatic aldehydes and aromatic alcohols. Deteriorated substances having these polar groups are particularly difficult to remove, which is not preferable.

The modified product having a polar group formed by the above reaction will be specifically described. The fatty acid formed by decomposing the higher fatty acid is a fatty acid having 1 to 10 carbon atoms, and more specifically. Examples thereof include formic acid, acetic acid, propionic acid, butyric acid, xanthic acid, caproic acid, caprylic acid, capric acid and the like. Further, aliphatic aldehydes and aliphatic alcohols formed by reducing these are also applicable.

The aromatic carboxylic acids are mainly benzoic acid and its methyl group-substituted product, and specific examples thereof include methylbenzoic acid, dimethylbenzoic acid, trimethylbenzoic acid and its isomers. Further, a compound in which a carboxyl group contained in these compounds is reduced to be an aldehyde group or a hydroxyl group is also applicable. Specifically, benzaldehyde,
Methylbenzaldehyde, dimethylbenzaldehyde,
Examples include trimethylbenzaldehyde, phenol, methylphenol, dimethylphenol, trimethylphenol and isomers thereof.

As a result of detailed investigation of the relationship between the amount of the substance having a polar group and the coating unevenness, the inventors have found that the coating unevenness can be improved by setting the total amount of the substance having the polar group to a certain amount or less. Specifically, the total amount of the substance having a polar group is preferably 0.20 parts by mass or less, more preferably 0.15 parts by mass with respect to 100 parts by mass of aluminum.
It is below the mass part.

Next, the amount of the above-mentioned substance having a polar group was adjusted to 0.
As a method of suppressing the amount to 20 or less, it is necessary to control the amount of heat generated during pulverization to a certain amount or less. Specifically, it is necessary to maintain the temperature in the crushing container at 50 ° C or lower, and more preferably 40 ° C or lower. In the pulverization generally performed, the amount of heat generated during the pulverization of aluminum particles is considerably large, and it was difficult to keep the temperature in the pulverization container at 60 ° C. or lower. However, in the present invention, it is possible to suppress the generation of a substance having a polar group which causes unevenness by suppressing the generation of heat. The method of suppressing the amount of heat generated during pulverization is not particularly limited, but it is desirable to strongly control the temperature inside the crushing container by suppressing the generation of friction energy during grinding by optimizing the grinding media and by the jacket cooling system of the ball mill.

In addition to this, as a method of suppressing the amount of the substance having a polar group, a method of removing the substance having a generated polar group by washing the filtered aluminum filter press cake after the pulverization by a solvent replacement method or the like is also considered. To be Since substances having these polar groups have high adsorptivity to aluminum particles, it is preferable to use a method in which the substances that do not generate are removed rather than removed.

Next, in the coating composition, the aluminum pigment composition according to the present invention needs to be compounded in an amount of 2 to 40 parts by mass, more preferably 4 to 30 parts by mass, per 100 parts by mass (solid content) of the resin component. .

The aluminum pigment composition according to the present invention comprises
The dispersibility of the particles when formed into a paint is extremely good. In addition, the aluminum particles do not softly aggregate due to the shear applied to the particles during coating. Therefore, in the coating film after coating, the aluminum particles are distributed in a uniform state with no difference in shade, and the scaly particles can be oriented parallel to the coating film. As a result, the intensity of the reflected light becomes uniform at any part of the coated plate, and it becomes possible to suppress the occurrence of unevenness. Therefore, the aluminum pigment composition of the present invention, and the appearance of the coating film obtained by the coating material using this aluminum pigment composition, the brightness of light is very high, and even unevenness is well suppressed, high texture not seen in the past. Is obtained.

Typical examples of the present invention will be shown below. The various measuring methods used in Examples and Comparative Examples are as follows.

The average particle diameter d50 was measured by a laser micron sizer LMS-24 (manufactured by Seishin Enterprise Co., Ltd.). Mineral spirit was used as the measurement solvent, and ultrasonic dispersion (2 minutes) was performed as the preliminary dispersion of the aluminum pigment.

Average thickness t The average thickness t was calculated by measuring the water surface diffusion area WCA and using the above equation. As a pretreatment for WCA measurement, 1 g of aluminum pigment, 1 to 2 ml of mineral spirit solution of 5% by mass stearic acid was added and predispersed, 50 ml of petroleum benzine was added and mixed, and the mixture was heated at 40 to 45 ° C. for 2 hours and then filtered. It was suction-filtered with and powdered. The measurements other than the pretreatment were performed by the method according to JIS K5906.

Average surface roughness Ra The arithmetic average surface roughness was obtained from the line profile (300 scans) of 5 μm square in one visual field measured by an atomic force microscope (AFM), and the arithmetic average value was calculated for four or more visual fields, Ra (nm).

50 g of chloroform was added to 3 g of the aluminum pigment composition having a polar group derived from the higher fatty acid and contained in the aluminum pigment composition to form a slurry, and the mixture was stirred at 50 ° C. for 1 hour. After the completion of stirring, filtration is carried out and the filtrate is analyzed by gas chromatography to quantify the total amount of fatty acids and aromatic compounds produced by the alteration of the higher fatty acids contained in the aluminum pigment composition. Here, the amount of the modified substance having a polar group contained in the aluminum pigment composition is shown as a ratio to 100 parts by mass of aluminum.

Evaluation of Light Luminance and Flop Property (1) Preparation of Paint / Coating Film The base coat paint was an aluminum pigment composition (heating residue 75% by mass) 10.0 parts by mass, Acridic 47-
712 (acrylic resin, Dainippon Ink and Chemicals, Inc.) 80.
0 parts by mass, Super Beckamine J-820 (melamine resin, manufactured by Dainippon Ink and Chemicals, Inc.) 20 parts by mass, thinner (toluene / ethyl acetate / butyl cellosolve = 7/2/1)
(Mass ratio)) 178.5 parts by mass were blended. Further, as a top coat paint, 80.0 parts by mass of Acridic 44-179 (acrylic resin, manufactured by Dainippon Ink Co., Ltd.), 20 parts by mass of Super Beckamine J-820 (melamine resin, manufactured by Dainippon Ink Co., Ltd.), Thinner (toluene) 17
8.5 parts by mass were compounded.

Using the above paint, air pressure of 4 with an air spray gun (Wider77 / made by Iwata Coating Machine Co., Ltd.)
2C1B (2 coat 1 bake) coating was performed so that the film thickness of the base coat was about 20 μm at × 10 ⁵ Pa. The baking conditions were 140 ° C. × 30 minutes.

(2) Laser-type metallic feeling measuring device Alcorp (manufactured by Kansai Paint Co., Ltd.) according to the method described in Research No. 117 of colorimetric paints, pages 67 to 72 (published by Kansai Paint Co., Ltd. in 1989). Was performed using. The optical condition is that the incident angle is 45
It has a laser light source of 0 degree and a light receiver at light receiving angles of 0 degree and -35 degree. The measured value is a light-receiving angle of -35 degrees, which is the maximum light intensity of the reflected light of the laser excluding the light in the specular reflection region reflected by the coating film surface, and is proportional to the intensity of specular reflection light from the aluminum pigment. The IV value as a parameter was determined. The IV value represents the magnitude of the light brightness, and if it is 350 or more, the light brightness is good.

(3) Evaluation of unevenness The unevenness of the coated plate was visually evaluated in the following three stages. ○: The unevenness is not noticeable △: The unevenness is slightly noticeable ×: The unevenness is noticeable

[0052]

Example 1 Atomized aluminum powder (average particle size 10 μm) was placed in a ball mill having an inner diameter of 10 cm and a length of 30 cm.
m) 50 g, 1 L of mineral spirits, and 10 g of oleic acid, and a diameter of 2 as grinding media.
2 kg of mm zirconia balls were filled. This ball mill keeps the crushing temperature at 30 ° C. and rotates at 72 rpm for 3
Milled for hours.

After pulverization, the slurry in the mill was washed out with mineral spirits, passed through a 400-mesh vibrating screen, and the slurry that passed through was filtered and concentrated to obtain a cake with a heating residue of 80% by mass. The obtained cake was transferred into a vertical mixer, a predetermined amount of solvent naphtha was added and mixed for 15 minutes to prepare an aluminum pigment having a heating residue of 75% by mass.

The above-mentioned measurement was carried out for the obtained aluminum pigment composition. The results are shown in Table 1.

[0055]

[Embodiment 2] The grinding media used in Embodiment 1 have a diameter of 2 m.
An aluminum pigment composition was prepared under the same conditions except that the crushing time was 6 hours.
The above measurement was performed on the obtained aluminum pigment composition. The results are shown in Table 1.

[0056]

Example 3 An aluminum pigment composition was prepared under the same conditions as in Example 1 except that the amount of oleic acid was 2 g. The above measurement was performed on the obtained aluminum pigment composition. The results are shown in Table 1.

[0057]

COMPARATIVE EXAMPLE 1 The grinding media used in Example 1 were the same as those used for steel balls having a diameter of 3.2 mm (2 kg) and a grinding time of 1.5.
Changed to time. The grinding temperature was 40 ° C. An aluminum pigment composition was produced under the same conditions except for this. The above measurement was performed on the obtained aluminum pigment composition. The results are shown in Table 1.

[0058]

[Comparative Example 2] The grinding media used in Example 1 were 4 kg of steel balls having a diameter of 1.0 mm and the rotation speed was 86 rpm.
And crushed for 2 hours. The grinding temperature was 60 ° C.
An aluminum pigment composition was produced under the same conditions except for this. The above measurement was performed on the obtained aluminum pigment composition. The results are shown in Table 1.

[0059]

[Table 1]

[0060]

As described above, according to the present invention, an aluminum pigment composition is obtained which has an unprecedentedly high light brightness and suppresses unevenness which is always a problem in a coating film having a high light brightness feeling. Can be provided. High-luminance designs that have been impossible to achieve due to unevenness are possible.

The aluminum pigment composition of the present invention can be utilized as an aluminum pigment for oil-based and water-based metallic paints for automobiles, etc. and an industrial-use industrial aluminum pigment mainly for plastic home appliances.

Claims (3)

[Claims] 1. An aluminum pigment composition comprising an aluminum pigment and a solvent, wherein the aluminum pigment comprises:
The average particle diameter d50 is 5 to 35 μm, the ratio of the average particle diameter d50 (μm) to the average thickness t (μm) is 30 to 90, the average surface roughness Ra is 20 nm or less, and it is contained in the composition. An aluminum pigment composition, wherein the total amount of the modified substance having a polar group is 0.20 parts by mass or less with respect to 100 parts by mass of aluminum. 2. The modified product having a polar group contained in the aluminum pigment composition is a C1-10 fatty acid, a C1-10 aliphatic alcohol, or a C1-10 carbon.
2. The aluminum pigment composition according to claim 1, which is a substance selected from the aliphatic aldehydes described above, and aromatic carboxylic acids, aromatic aldehydes, and aromatic phenols. 3. A coating material containing the aluminum pigment composition according to claim 1 or 2, which has excellent orientation of aluminum particles during coating.