JPH05117722A - Production of aluminum pigment - Google Patents

Abstract

PURPOSE:To efficiently produce an aluminum pigment consisting of the aluminum fine flakes having a smooth discoid shape, having uniform thickness and grain diameter and excellent in such a quality as the development of a metallic luster. CONSTITUTION:A raw aluminum powder and an org. solvent are passed downward through a crushing vessel 10 and returned to the upper part of the vessel 10 from the lower part of the vessel 10 through the circulating lines 32 and 34 outside the vessel 10. In this case, the raw powder is circulated under the pressurized and closed conditions, agitated in the vessel 10 by a multistage agitating arm 14 rotating at the peripheral velocity of >=5m/sec along with a crushing medium and crushed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum pigment, and more particularly to a method for producing an aluminum pigment for metallic paint.

[0002]

2. Description of the Related Art Metallic paint having metallic luster is applied to paint automobiles and the like. In metallic coating, fine metal pieces or powder dispersed in the coating reflects light to develop a unique luster. Aluminum is usually used as the material of the metal pieces or powder. Aluminum pigments are said to be able to exhibit excellent luster for a long period of time and to be easily manufactured and processed. To produce aluminum pigments for metallic paints,
The aluminum powder raw material is finely crushed by using a crushing device such as a ball mill or an attritor to obtain an aluminum pigment having good gloss development in metallic paint.

As a concrete prior art, Japanese Patent Laid-Open No. 1-1 is known.
There are aluminum pigments disclosed in 19601 and Japanese Patent Laid-Open No. 64-54070, or a method for producing the same. In JP-A-1-119601, it is said that quality performance such as gloss is improved by defining the particle size and thickness of the aluminum fine pieces constituting the aluminum pigment within a certain range. Japanese Laid-Open Patent Publication No. 64-54070 also states that quality performance such as gloss is improved by defining the thickness, particle diameter, other shape of the aluminum fine pieces, or the particle size distribution thereof. In particular, it is said that a fine aluminum piece having a uniform thickness and no jagged outer peripheral edge and a rounded outer contour can form a coating film having good metallic luster.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The aluminum pigment having a specific shape, that is, a substantially circular plate shape and made of fine aluminum particles having a uniform particle size, as disclosed in Japanese Patent Publication No. 070, may not improve metallic luster and other quality performances as a metallic paint. However, there is a drawback in that it is very time-consuming to manufacture such aluminum fine pieces and the manufacturing efficiency is extremely low, resulting in high cost.

In the above prior art, the aluminum fine powder is crushed by the ball mill to obtain the desired aluminum fine pieces, but the processing time may be from several hours to 10 hours or more in some cases. .. This is because crushing with a ball mill is excellent in that it spreads the aluminum powder raw material flatly, spreads the outer contour, smoothes the surface, or obtains fine particles with a uniform particle size. However, this is because the pulverization efficiency is very low and the desired pulverized product cannot be obtained unless it takes a long time.

When an attritor, which is often used for pulverizing metal powder, is used, it is difficult to obtain the circular plate-shaped aluminum fine pieces as described above, and it takes a long processing time. Therefore, an object of the present invention is to provide an aluminum fine piece having a smooth outer circular plate shape capable of exhibiting excellent quality performance in terms of metallic luster and the like as an aluminum pigment for metallic paints, and having a uniform particle size. An object of the present invention is to provide a method capable of efficiently producing an aluminum pigment comprising

[0007]

The method for producing an aluminum pigment according to the present invention, which solves the above-mentioned problems, is to pass an aluminum powder raw material together with an organic solvent from the upper part to the lower part in the crushing tank to obtain the lower part of the crushing tank. From the crushing tank to the upper part of the crushing tank through the circulation path, and circulate in a pressure-sealed state while crushing in the crushing tank with a plurality of stirring arms rotating at a peripheral speed of 5 m / sec or more. Grind with stirring with medium.

As the aluminum powder raw material, the same atomized aluminum powder as that used in the production of conventional aluminum pigments can be used. Normal atomized aluminum powder is
The outer shape has irregularities, and the particle size has a relatively wide range.
The particle size of the aluminum powder raw material is about 0.1 to 50 μm, and preferably about 0.5 to 20 μm.

As the aluminum powder raw material, when the atomized aluminum powder is pulverized by a gas flow pulverization method or the like to have a spherical shape having a smooth outer shape and no unevenness, that is, a spheroidized atomized powder is finally used, The quality performance of the manufactured aluminum pigment is improved. The airflow type pulverization method is a method using a pulverizing device generally called a jet mill or the like, and is conventionally used as a fine pulverizing method for various pulverized materials. As a means for spheroidizing the aluminum powder raw material, an air flow type pulverizing method is preferable, but a mechanical type pulverizing method can also be used.

As an aluminum powder raw material, the particle size distribution is narrow,
The quality performance of the aluminum pigment is improved by using those having a uniform particle size. As a method of defining the particle size distribution, a classification accuracy index (κ = D _p90 / D _p10 ) can be applied. This classification accuracy index corresponds to a partial classification efficiency of 10% in the partial classification efficiency curve derived from the result of classifying the particle size into several sections for the powder whose particle size changes continuously. The particle size is defined as a value (κ) represented by the ratio of the particle size of 10% classified diameter (D _p10 ) to the 90% classified diameter (D _p90 ). The smaller the classification accuracy index κ, the narrower the particle size distribution and the more uniform the particle size. If the particle size is perfectly uniform, that is, the ideal classification accuracy index value is κ =
It is 1. As the aluminum powder raw material used in this invention,
The classification accuracy index κ = 1 to 3 is preferable. In order to obtain an aluminum powder raw material with a small classification accuracy index κ, use a raw material that has a narrow particle size distribution, and classify the powder raw material with a classifying device such as an air stream classifier and use only those with a prescribed particle size range. You may do it.

The above-mentioned spheroidized atomized powder,
Moreover, the use of the one having a classification accuracy index κ = 1 to 3 improves the quality performance of the aluminum pigment, which is the most preferable. The above aluminum powder raw material is processed into a flat flake shape by using a crushing device. As the crushing device, a crushing device having a cylindrical space having a sealable space and having a stirring arm rotatably driven by a driving means such as a motor is used inside the crushing device.

The stirring arm may have a cylindrical rod shape, a prismatic rod shape, or the structure of a stirring arm employed in a conventional stirring arm type crushing device or dispersing device. The stirring arm is attached to the rotating shaft in a plurality of stages at intervals in the axial direction. The number of stages of attachment of the stirring arm is set in consideration of the efficiency of stirring or crushing, the size of the device, and the like. A plurality of stirring arms are preferably attached in the radial direction of the rotating shaft. The higher the moving speed of the tip of the stirring arm, that is, the peripheral speed, the better the efficiency of crushing and processing the aluminum powder raw material. Specifically, it is necessary to operate at a peripheral speed of 5 m / sec or more, and preferably it is operated at a peripheral speed of about 5 to 10 m / sec.

The crushing tank has a supply port for the material to be crushed at the top and a discharge port for the material to be crushed at the bottom. It is preferable that the discharge port is provided with a variable clearance separating valve in which the opening / closing amount of the valve, that is, the clearance for separating the object to be crushed from the crushing medium and taking it out is changed by the pressure in the crushing tank. The discharge port and the supply port are connected to each other outside the crushing tank by a circulation path including pipes. The circulation path is preferably provided with a forced circulation means such as a pump for forcibly circulating the pulverized material. The pressure in the crushing tank can be set by adjusting the variable clearance separating valve or the like or adjusting the output of the pump. Specifically, the pressure in the crushing tank is usually set to about 1 to 4 kg / cm ² . Further, the crushing strength or the quality of the product is also affected by the flow rate or flow rate of the mixed liquid of the aluminum powder raw material and the organic solvent, which flows in the crushing tank and the circulation path.

The above-mentioned aluminum powder raw material is supplied to the crushing apparatus as described above together with the organic solvent and crushed. As the organic solvent, an organic solvent such as mineral spirit, toluene, xylene, or IPA (isopropylene alcohol) used for pulverizing a usual aluminum powder raw material can be used.

The crushing tank contains a crushing medium made of glass, metal, ceramics or the like, and the aluminum powder raw material is stirred together with the crushing medium by the rotation of the stirring arm to crush the aluminum powder raw material. The type and diameter of the grinding medium are appropriately selected and used according to the conditions such as the type of raw material and the intended use of the product. The mixed liquid of the aluminum fine particles and the organic solvent obtained by the pulverization can be used as it is as an aluminum pigment by adding it to the metallic paint.
However, if necessary, a concentration operation such as concentration by filtration or concentration by evaporation of an organic solvent, and other various treatment steps and additives can be added.

[0016]

It is known that when the powder raw material is crushed, the shape and particle size distribution of the crushed product obtained vary depending on the structure of the crushing device and the crushing mechanism thereof. The crushing mechanism includes impact shearing and grinding shearing. The impacting shearing spreads the object to be ground, and the grinding shearing causes the object to be ground to be ground. In order to grind the powder raw material into a desired shape, it is necessary to carry out grinding in which the above-mentioned impact shearing and grinding shearing are combined in an appropriate ratio.
However, it is difficult to theoretically elucidate the behavior and the crushing function of the object to be crushed in the crushing device, and the specific phenomenon of the crushing function in various crushing devices and crushing methods is not always known.

Among the conventional crushing methods, when the crushing is carried out for a long time using a ball mill, the above-mentioned ratio of impact shearing and grinding shearing is appropriate. It is considered that fine aluminum pieces having a smooth outer plate shape and a uniform grain size were obtained.
In the method of the present invention, the aluminum powder raw material is passed together with the organic solvent from the upper part to the lower part in the crushing tank, and is returned from the lower part of the crushing tank to the upper part of the crushing tank through the circulation path outside the crushing tank, and the pressure is applied. While being circulated in a closed state, the above-mentioned impact shearing and grinding shearing are good by agitating with the pulverizing medium by the multi-stage stirring arm rotating at a peripheral speed of 5 m / sec or more in the pulverizing tank. The fine aluminum pieces suitable for the aluminum pigment are obtained. However,
It is not known in detail what kind of phenomenon occurs when grinding is performed under such conditions, or the theoretical mechanism of grinding. However, it is considered that the following actions are occurring.

Since the aluminum powder raw material is pulverized while being circulated, the pulverizing action on the aluminum powder raw material is uniformly performed, and aluminum fine particles having a uniform particle size are obtained. As the aluminum powder raw material moves from the upper part to the lower part of the crushing tank while being agitated and pulverized, the natural movement and pulverization of the aluminum powder raw material proceed smoothly, and the progress of pulverization and the distribution of the pulverizing medium depending on the position Appropriate and good grinding occurs.

Since the aluminum powder raw material is crushed in a pressure-sealed state, H ₂ gas or the like generated from the aluminum powder raw material during the crushing is not released to the surroundings. Moreover, since the stirring arm is rotated in the crushing tank in a closed state, the stirring arm can be rotated at high speed. For this reason, compared with, for example, crushing with an attritor, the safety is high, and the crushing efficiency is much higher than that of an attritor or a ball mill, and crushing can be performed in a short time.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a manufacturing apparatus for carrying out the manufacturing method of the present invention. Crushing tank 1
0 has a cylindrical shape, and a plurality of stages of stirring arms 14 are attached to a rotating shaft 12 passing through the center. The rotary shaft 12 is
Mechanical seal 1 attached to the wall of crushing tank 10
After that, it protrudes to the outside, is connected to the motor 20, and is driven to rotate. A pipe 32 for supplying a mixed liquid of an aluminum powder raw material and an organic solvent is connected to the upper portion of the crushing tank 10, and the pipe 32 is connected to a raw material tank 42 via a raw material supply pump 40. The pipe 34 is also connected to the lower portion of the crushing tank 10 via the variable gap separation valve 50, and the pipe 34 is
It is connected to the raw material tank 42. Therefore, the mixed liquid of the aluminum powder raw material and the organic solvent passes from the upper part to the lower part of the crushing tank 10, and the variable gap separation valve 50 and the pipe 3 are connected.
4, the raw material tank 42, the raw material supply pump 40, and the piping 32 circulate through the circulation path. A branch valve 36 is attached in the middle of the pipe 34 so that the pulverized aluminum powder raw material can be collected together with the organic solvent. In the crushing tank 10, a pipe 62 for supplying sealing water to the mechanical seal, a piping system 60 including a pipe 64 for the cooling jacket 18 for cooling the crushing tank 10, and the like, and other similar crushing devices as in a normal crushing device. Various mechanisms are provided.

FIG. 2 shows the detailed structure of the crushing tank 10 portion. A supply port 10a connected to the pipe 32 is arranged on the ceiling surface of the crushing tank 10, and a discharge port 10b connected to the constant pressure separation valve 50 is arranged on the bottom surface of the crushing tank 10.
The stirring arm 14 projects in all directions of the rotary shaft 12 and faces the inner wall of the crushing tank 10 with a slight gap. The cross-sectional shape of the stirring arm 14 is roughly rectangular, but it may be circular or other shapes. The stirring arm 14
A plurality of stages are arranged side by side along the axial direction of the rotary shaft 12. Although not shown, the grinding tank 10 contains a grinding medium made of steel balls or the like.

FIG. 3 shows the detailed structure of the variable clearance separating valve 50. One end of a tubular tubular body 52 is connected to the discharge port 10b of the crushing tank 10, and the other end of the tubular body 52 is connected to the pipe 3
4 is connected. Inside the tube portion 52, the tip of a truncated cone-shaped valve body 54 is in contact with the discharge port 10b, and the valve body 54 closes the discharge port 10b. Disc 54
Is attached to a support shaft 55 penetrating the inside of the support body 56, and is movable in the vertical direction in the figure.
A spring 57 that constantly urges the support shaft 55 upward is provided inside the support body 56. Therefore, the valve body 54
Is always pressed against the discharge port 10b.

The operation of the variable clearance separating valve 50 will be briefly described. With the conventional structure of a simple slit-shaped outlet or mesh-shaped outlet, for example, if a dispersion medium or unpulverized powder raw material is clogged in the outlet, the outlet becomes narrow and a sufficient circulation amount cannot be secured. However, the crushing performance will also decrease. However, in the variable clearance separation valve 50, the valve body 54 and the discharge port 10b
When the pressure inside the crushing tank 10 is increased due to the clogging of the gap with the dispersion medium or the like, the valve body 54 is pushed away by this pressure, and the gap between the valve body 54 and the discharge port 10b expands. As a result, when the clogging is cleared, the pressure in the crushing tank 10 is reduced, and the valve body 54 is restored by the biasing force of the spring 57, and the gap between the valve body 54 and the discharge port 10b is also restored. Therefore, by mounting the variable gap separation valve 50, the discharge port is not clogged, and good pulverization can always be performed. If the valve body 54 of the variable clearance separating valve 50 is vibrated or rotated, clogging becomes more difficult. further,
As described above, even when H ₂ gas or the like is generated in the crushing tank 10 and the internal pressure becomes high, the variable gap separation valve 50 operates to release the pressure, which is safe.

As for the structure of the variable clearance separating valve 50 described above, the structure of the pressure control valve disclosed in JP-A-63-229158 can be applied. A concrete example in which the aluminum powder raw material is crushed by the crushing device having the above structure will be described. First, a normal atomized aluminum powder was used as the aluminum powder raw material. Figure 4
The grain shape is shown in a micrograph. Magnification is 10
It was shot at 00 times. It can be seen that the individual powders are of various sizes and shapes with small irregularities. When the particle size distribution was measured, the classification accuracy index κ =
It was about 4.3 to 5.0. In Example 1 and Comparative Example, this atomized aluminum powder was used as it was.

In Example 2, the atomized aluminum powder was pulverized by the following air flow pulverizer to be spheroidized. The grain shape is shown in FIG. Magnification is 1
I'm shooting at 500x. The outer shape of the powder was almost spherical, with no small irregularities. The classification accuracy index κ = 3.5. Airflow pulverizer: Jet mill PJM-I type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) Operating conditions: Atomized aluminum powder throughput 1-1.
2 kg / Hr N ₂ gas pressure 3 kg / cm ² N ₂ gas was used instead of air to prevent the aluminum powder from bursting.

In Example 3, spheroidizing was performed by the same airflow crusher as in Example 2, and the powder raw material was classified to
The classification accuracy index κ was adjusted to 2.5 to 3.0 before use. The grain shape was the same as in Example 2. To these aluminum powder raw materials, an appropriate amount of mineral spirit was added as an organic solvent, and in Examples 1 to 3, pulverization was performed by the method of the present invention using the pulverizing device.

Crusher: Wet fine crusher "Apex mill" (manufactured by Kotobuki Giken Kogyo Co., Ltd.) Operating conditions: Dispersion medium Zirconia 3 mmφ Medium filling rate 80% Stirring arm peripheral speed 8 m / sec Flow rate 150 kg / Hr Grinding capacity 1 liter Grinding Mixing of raw materials: Aluminum powder raw material 6 parts by weight Mineral spirit 93 parts by weight Oleic acid 1 part by weight In the comparative example, a conventional crushing method was carried out by using an attritor under the following conditions.

Crusher: Attritor MA-D type (manufactured by Mitsui Miike Machinery Co., Ltd.) Operating condition: Dispersion medium Steel ball 5 mm φ Medium filling rate 60% Stirring arm peripheral speed 4 m / sec Crushing capacity 5 liter Charge amount 2.5 kg Operation Time 6 hours Blending of pulverized raw material: Aluminum powder raw material 6 parts by weight Mineral spirit 93 parts by weight Oleic acid 1 part by weight Table 1 shows the characteristics of the obtained aluminum pigment.

The product shape is shown in a photograph of the result of observation with a microscope. The magnification is 2000 times. The classification accuracy index κ is represented by κ = D _p90 / D _p10 as described above.
The coating film quality was evaluated by the brightness of the coating film when the metallic paint was produced using an aluminum pigment and the metallic paint was applied, that is, the L value. The larger the L value, the better the appearance as metallic coating.

The unit processing time is the processing time Hr per 1 kg of aluminum powder raw material.

[0031]

[Table 1] The product shape will be described. In the comparative example (FIG. 9), the outer shape is very complicated and has irregularities with acute angles, and the overall shape also has various shapes, and there is a great variation in size.
In Example 1 (FIG. 6), the unevenness of the outer shape is considerably reduced, and moreover, it has a roundness. There are some variations in the overall shape or particle size. In Example 2 (FIG. 7), the outer shape was very smooth with almost no unevenness. The variation in particle size is also small. In Example 3 (FIG. 8), the outer shape is smooth and the particle sizes are almost uniform.

As a result of the above measurement, in the embodiment of the present invention,
It was proved that an aluminum fine piece having a good product shape as an aluminum pigment can be obtained in a much shorter time than the comparative example showing the conventional technique. Further, it can be seen that the quality when the aluminum pigment is used in the metallic paint can exhibit more excellent appearance.

[0033]

As described above, according to the method for producing an aluminum pigment of the present invention, the aluminum powder raw material is pulverized by the pulverizing apparatus and the pulverizing conditions having the above-mentioned structure, so that the conventional ball mill can be used for a long time. The aluminum pigment having excellent quality performance, which could not be obtained without pulverizing for a long time, can be manufactured extremely efficiently. As a result, the manufacturing cost of aluminum pigments can be significantly reduced, and it can greatly contribute to the expansion of demand for metallic paints.

[Brief description of drawings]

FIG. 1 is an overall structural diagram of a manufacturing apparatus used in an embodiment of the present invention.

FIG. 2 is a sectional view of the entire structure of the crusher.

FIG. 3 is an enlarged structural sectional view of a separation valve portion.

FIG. 4 A micrograph of atomized aluminum powder (magnification 1
(000 times)

FIG. 5: Micrograph of spheroidized aluminum powder raw material (magnification 1
500 times)

FIG. 6 is a micrograph of the aluminum pigment obtained in Example 1 (magnification: 2000 times).

7 is a photomicrograph of the aluminum pigment obtained in Example 2 (magnification: 2000 times).

FIG. 8 is a micrograph of the aluminum pigment obtained in Example 3 (magnification: 2000 times).

FIG. 9 is a micrograph of the aluminum pigment obtained in Comparative Example (magnification: 2000 times).

[Explanation of symbols]

 10 Grinding tank 14 Stirring arm 32, 34 Piping (circulation path) 40 Raw material supply pump 50 Variable gap separation valve

[Procedure amendment]

[Submission date] September 25, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is an overall structural diagram of a manufacturing apparatus used in an embodiment of the present invention.

FIG. 2 is a sectional view of the entire structure of the crusher.

FIG. 3 is an enlarged structural sectional view of a separation valve portion.

FIG. 4 is a microscopic photograph showing the particle structure of atomized aluminum powder (magnification: 1000 times).

FIG. 5 is a microscopic photograph showing the particle structure of spheroidized aluminum powder raw material (magnification: 1500 times).

FIG. 6 shows the particle structure of the aluminum pigment obtained in Example 1.
Microscope photograph showing (magnification 2000 times)

FIG. 7 shows the particle structure of the aluminum pigment obtained in Example 2.
Microscope photograph showing (magnification 2000 times)

FIG. 8 shows the particle structure of the aluminum pigment obtained in Example 3.
Microscope photograph showing (magnification 2000 times)

FIG. 9 shows a particle structure of the aluminum pigment obtained in Comparative Example.
Be micrograph (magnification 2000 times)

[Explanation of Codes] 10 Grinding tank 14 Stirring arms 32, 34 Piping (circulation path) 40 Raw material supply pump 50 Variable gap separation valve

Claims (3)

[Claims] 1. An aluminum powder raw material, together with an organic solvent,
Pass the inside of the crushing tank from the upper part to the lower part, and return it from the lower part of the crushing tank to the upper part of the crushing tank through the circulation path outside the crushing tank.
A method for producing an aluminum pigment, which comprises pulverizing by stirring together with a pulverizing medium by a plurality of stages of stirring arms rotating at a peripheral speed of 5 m / sec or more in a pulverizing tank while circulating under pressure and airtightness. 2. The method for producing an aluminum pigment according to claim 1, wherein an aluminum powder raw material which has been previously pulverized by an airflow pulverization method to be spheroidized is used. 3. The method for producing an aluminum pigment according to claim 2, wherein a spheroidized aluminum powder raw material having a particle size distribution with a classification accuracy index κ (D _p90 / D _p10 ) = 1 to 3 is used.