JP2589554B2 - Manufacturing method of metal powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is suitable for imparting corrosion resistance and weather resistance by being mixed with paint, or imparting electromagnetic shielding properties by being mixed with plastic or rubber. The present invention relates to a method for producing a fine metal powder.

[Prior Art] Conventionally, as a paint used in a field requiring corrosion resistance and weather resistance, a mixture of powders made of glass, metal, or the like has been used. These powders, such as glass powder and stainless steel powder, themselves have corrosion resistance, and those that impart corrosion resistance by covering the coated surface with the powder, such as zinc powder, the powder becomes a sacrificial electrode This can be classified into those that prevent corrosion of the coated surface and those that improve the weather resistance by applying a metallic coating such as aluminum powder.

Among such powders, glass powder is used, such as a spherical piece obtained by breaking a glass balloon.

In addition, as stainless steel powder, a rolled material of stainless steel is subjected to grain boundary corrosion and physically pulverized, or a powder of molten stainless steel is atomized with water, and the powder is physically flattened by a stamp mill or the like. Things are used.

As the zinc powder, a spherical zinc powder made from a gas phase, or a powder obtained by physically flattening this powder with a ball mill or the like is used.

Further, as the aluminum powder, a powder obtained by physically flattening a spherical powder obtained by gas atomizing a molten aluminum with a stamp mill or the like is used.

In recent years, various amorphous alloys having excellent corrosion resistance have been developed, and attempts have been made to impart even better corrosion resistance by powdering and mixing these amorphous alloys with paints. I have.

As examples of such attempts, JP-A-60-252668 and JP-A-60-252669 disclose that the vertical and horizontal lengths are several tens to
It has been proposed to add an amorphous alloy powder containing scaly particles of several hundred μm and a thickness of 5 μm or less to a paint. This powder is obtained by dropping a powder alloyed by a method such as atomization or the like from above, and acetylene flame ejected from a concentrically arranged nozzle while the powder is falling,
It is manufactured by melting a powder with a heat source such as an oxygen-hydrogen flame or an oxygen-propane flame, and rapidly cooling the droplets simultaneously with rolling with twin rolls.

On the other hand, various types of plastics are known in which a conductive filler is added to impart an action such as an electromagnetic shield or a reinforcing filler is added to strengthen the plastic. In particular, metal fillers such as copper, nickel, and silver are used as the conductive filler.

As these metal fillers, fibrous or dendritic materials made by shaving metal by a chatter vibration method using a lathe are often used.

In addition, amorphous alloys are well known as soft magnetic materials, but a method for producing a plate-like powder directly from a molten metal has not been developed so far, and application development in such a field has been delayed.

"Problem to be Solved by the Invention" It is generally considered that a flaky powder is preferable as a powder for a paint. That is, when the powder is mixed with a paint resin and applied by brushing, spraying, or the like, the powder is laminated in parallel with the coating surface due to the surface tension generated when the resin is cured (this is referred to as a leafing phenomenon). This is because a coated film is formed, and the material is shielded from the outside air to provide better corrosion resistance and weather resistance. Further, when the thickness of the powder is increased, there is a problem that the smoothness of the coating film is deteriorated. Further, if the major axis is too large, cracks and peeling of the coating film tend to occur, and the strength of the coating film tends to decrease.

However, the glass powder made by breaking the glass balloon,
Since it was like a fragment of a spherical surface, it did not become a perfect plane, the above-mentioned leafing phenomenon could not be satisfactorily caused, and sufficient corrosion resistance could not be imparted.

In the case of stainless steel powder, which is obtained by physically grinding a rolled material by intergranular corrosion of a rolled material, or stainless steel, zinc, aluminum powder, etc., which is obtained by physically flattening a spherical powder made by atomization or the like with a stamp mill, etc. Was likely to be irregular, and a sufficiently thin flat product could not be obtained. Therefore, the above-mentioned leafing phenomenon could not be satisfactorily caused, and sufficient corrosion resistance could not be provided.

Further, Japanese Patent Application Laid-Open Nos.
The powder described in -252669 is melted in the middle of dropping the powder as described above, and the droplets are manufactured by quenching simultaneously with rolling by twin rolls, so that the minimum thickness and Aspect ratio (ratio of major axis to thickness)
Also, it was difficult to obtain a powder having a shape with a limited ratio of the major axis / minor axis. Furthermore, in this method, since the powder is melted in the middle of dropping, the supply amount of the raw material powder cannot be increased, and the target powder cannot be industrially mass-produced.

On the other hand, most of conventional metal fillers for plastics are fibrous or dendritic, and when mixed with plastics, a large number of gaps are formed between the fillers, particularly electromagnetic shielding. In the case of the conductive filler used for the purpose of (1), the effect tends to be insufficient.

The present invention has been made in view of the above-described problems of the related art, and its object is to provide corrosion resistance, powder for paint added to impart weather resistance, and to impart electromagnetic shielding properties. Suitable as a powder for plastic added for thin thickness, circular, regular shape,
An object of the present invention is to provide a method for producing a metal powder having a smooth surface and good corrosion resistance.

"Means for solving the problem" In order to achieve the above object, the present invention provides a method for producing a metal powder to be added to paint, plastic or rubber,
An alloy capable of forming an amorphous phase is melted, discharged from a nozzle, and sprayed with a gas having an injection pressure of 40 kg / cm ² or more to generate droplets of the molten material. On the surface of a disk-shaped rotary cooling body that rotates at a rotation speed of 1000 to 20000 rpm arranged in the direction, the droplets collide and solidify by cooling before solidifying, and the metal powder thus obtained has a thickness of 0.5 to It is characterized in that particles having a diameter of 5 μm, a minor axis and a major axis of 5 to 500 μm, an aspect ratio (ratio of major axis to thickness) of 5 or more, and a major axis / minor axis ratio of 1 to 1.5 are collected.

In a preferred embodiment of the present invention, the following or the alloy described below is used as the metal.

General formula AxBy (where A is composed of at least one selected from Fe, Ni, Co, Cr, Mo, B is composed of at least one selected from P, C, B, S, and x, y are 60 ≦ x ≦ 90, 1 in atomic%
0 ≦ y ≦ 40. ).

General formula AlaMbNc (where M is at least one selected from Cr, Fe, Mn, Ni, Cu, Ca, and N is Y, La, Ce, Hf, Mm
[Misch metal] is composed of at least one selected from the group consisting of a, b, and c in atomic% of 50 ≦ a ≦ 95, 0.5 ≦ b ≦ 35, 0.5 ≦
c ≦ 25. ).

“Action” The present inventors spray droplets by spraying a gas onto a melt of glass, metal, etc., in order to obtain a powder suitable for adding to paints, plastics, rubbers, etc. for the above purpose. An experiment was conducted in which the droplets were formed, and the droplets collided with various types of rotating cooling bodies to be cooled and solidified. As a result, even if a droplet is made to collide with a cylindrical rotating cooling body conventionally used for producing an amorphous alloy or the like by a conventional method, a large amount of irregularly-shaped and irregular-shaped powder is formed. However, the desired flaky powder could not be obtained efficiently. However, the liquid of the melt of the alloy capable of forming an amorphous phase is sprayed with a high-pressure gas of 40 kg / cm ² or more, and the rotation speed is 100 to 200.
When colliding with a disk-shaped rotating cooling body rotating at 00 rpm,
It was found that a metal powder having a small thickness, a circular shape, a regular shape, a smooth surface, and good corrosion resistance can be obtained in a very high yield.

The reason for this is, for spraying at 40 kg / cm ² or more high pressure gas, the thickness becomes thinner droplets collide with the cooling body at a high speed, by using a disk-shaped rotary cooling member, the collided droplets At the same time, the impact force causes the heat to flatten, and at the same time, spreads in the rotational direction due to the rotational force of the cooling body, and further expands in the outer peripheral direction due to the centrifugal force. This is considered to be due to flakes. For this reason, in the present invention, the collision point when the droplet of the molten material collides with the disk-shaped rotary cooling body is a portion where the above-described rotational force and centrifugal force effectively act, that is, the disk-shaped rotary cooling body. It is preferable that the portion is slightly shifted in the circumferential direction from the rotation axis. Further, by using an alloy capable of forming an amorphous phase and spraying with a high-pressure gas, a metal powder having a regular shape, a smooth surface, and excellent corrosion resistance can be obtained.

When the flaky powder thus obtained is mixed with a paint, a leafing phenomenon occurs in which the paint is arranged in parallel with the coated surface during the drying of the coated film, and the coated surface is covered without gaps, and good corrosion resistance and weather resistance are obtained. Can be granted. In addition, since the thickness is sufficiently thin, the smoothness of the coating film is improved, and cracks are less likely to occur due to stress such as surface distortion.

Further, when the flaky powder thus obtained is mixed with plastic or rubber, for example, when plastic or rubber is press-formed, the powder tends to be oriented so as to be parallel to each other due to the pressure of the press. as a result,
The planes of the powders are arranged so as to face in the same direction, and the powders are arranged in a specific direction without gaps. Therefore, as compared with the case where a conventional fibrous or dendritic filler is used, characteristics such as an electromagnetic shield can be improved. Even when the powders are not arranged so that their planes face in the same direction, the powder obtained by the present invention can provide better electromagnetic shielding properties than conventional fillers because of its large surface area.

In the present invention, the thickness of the solidified powder is 0.5 to 5 μm.
m, minor axis and major axis are 5 to 500 μm, aspect ratio (ratio of major axis to thickness) is 5 or more, and major / minor axis ratio is 1 to 1.5. More suitable powder is obtained as the powder to be added. In particular, when used as an additive powder for paints, if the thickness is less than 0.5 μm, there is a problem in maintaining corrosion resistance over a long period of time, and if the thickness exceeds 5 μm, the smoothness of the coating film deteriorates. When the minor axis is 5 μm or less, the powders overlap non-uniformly, and when the major axis exceeds 500 μm, the strength of the coating film deteriorates. If the aspect ratio is less than 5, the leafing phenomenon is less likely to occur. Further, when the ratio of the major axis / minor axis exceeds 1.5, gaps are likely to be formed between the powders, and the desired properties cannot be effectively provided.

Further, by using the above-mentioned or the above-mentioned raw materials, powders corresponding to the respective purposes of use can be obtained.

That is, a metal powder having an amorphous structure manufactured using the alloy represented by the general formula AxBy is suitable for use in adding to a paint for the purpose of imparting corrosion resistance. The metal powder itself has excellent corrosion resistance, and imparts corrosion resistance by covering the surface to be coated with the powder. In addition, some of the alloys represented by the general formula AxBy have excellent electromagnetic shielding properties, and are also suitable for use in adding to plastics and rubbers for the purpose of imparting electromagnetic shielding properties.

Further, a metal powder having an amorphous structure produced using an alloy represented by the general formula AlaMbNc, for example, reflection of heat rays, such as prevention of moisture transmission, mainly for the purpose of adding to the paint for the purpose of imparting weather resistance. It is suitable, especially for metallic coating and outdoor silver paint. In addition, since this metal powder has an amorphous structure, excellent corrosion resistance can be imparted.

When the powder obtained in the present invention is used as an additive powder for paint, the mixing amount of the powder in the paint is 2 to 30 vo.
About 1% is preferable, and about 5 to 20vo1% is more preferable. If the content of the powder is less than 2% by volume, the portion of only the base material paint in the coating film at the time of application increases, and the effect of mixing the powder is not sufficient. On the other hand, when it exceeds 30 vo1%, the strength of the coating film is weakened, cracks and peeling are likely to occur, and processing adhesion tends to be poor. However, this amount is appropriately changed depending on the type of powder or paint used.

As the binder component of the paint, various synthetic resins used for the paint can be used freely, and for example, vinyl resin, acrylic resin, polyurethane resin, epoxy resin and the like are preferably used. However, the binder component for coating here, when cured after application,
It is meant to include monomers and oligomers of those resins.

A solvent, a curing agent, a pigment, a thickener, a dispersant, a stabilizer, and the like can be freely added to the paint, if necessary, in addition to the powder and the paint binder component. The solvent is appropriately selected according to the resin to be used, and for example, xylene, toluene, alcohol, acetone, ethyl acetate, water and the like are used. Also, as a form of paint,
Various types such as a solvent type, an emulsion type, a non-solvent type, and a powder type can be adopted.

In addition, an inorganic binder can be used as a binder component for paint. For example, a paint is used in which a solution obtained by adding a small amount of sodium bicarbonate to an aqueous solution of sodium silicate is used as a binder.

This paint can be applied by various methods such as a brush coating method and a spray method. In this case, in order to disperse the powder and make it adhere well, surface treatment using a surface treatment agent such as a surfactant and a covering agent or a surface modifier may be performed prior to the application.

When the powder obtained in the present invention is used as an additive powder for plastics and rubber, the mixing amount of the powder in the plastic and rubber is preferably 10 to 60% by weight. If the amount is less than 10% by weight, the effect of mixing the powder cannot be sufficiently obtained, and if it exceeds 60% by weight, the appearance and strength of plastics and rubber tend to be adversely affected.

As plastic and rubber, for example, polyethylene,
Thermoplastic resins such as polypropylene, polystyrene, and polyvinyl chloride; thermosetting resins such as phenolic resins, epoxy resins, unsaturated polyester resins, and polyurethanes; and various resins such as natural rubber and synthetic rubber can be used freely. . Further, if necessary, a reinforcing material such as glass fiber, a plasticizer, a stabilizer, a coloring agent, and the like can be freely added.

Press molding is most preferred as a method for molding plastic and rubber because the powder is oriented in the same direction, but other molding methods such as injection molding and extrusion molding can also be employed. In order to improve the electromagnetic shielding properties, it is preferable to orient the powders in the same direction.However, even if the powders are randomly arranged, the powder obtained by the present invention is flaky and has a large surface area. Can provide more excellent properties than the fibrous or dendritic filler.

FIG. 1 shows an example of an apparatus for carrying out the present invention.

The material to be powdered is melted using a device such as a high-frequency melting furnace or a resistance furnace. The melting temperature is the melting point of the material +
The temperature may be about 50 to 300 ° C. A nozzle 2 for flowing out the melt 1 is provided, and an atomizing nozzle 3 for blowing a high-pressure injection gas to the falling melt 1 is provided. The atomizing nozzle 3 is arranged, for example, in a circular shape so as to surround the nozzle 2, and has a structure in which high-speed gas is ejected from a number of ejection ports toward the flow of the molten metal 1. Below the nozzle 2, a disk-shaped rotary cooling body 4 is arranged with its rotation axis shifted slightly laterally from directly below the nozzle 2.

Therefore, a high-pressure jet gas is blown from the atomizing nozzle 3 to the flow of the melt 1 flowing out of the nozzle 2 and falling, thereby forming droplets 5 of the melt 1. The droplets 5 scatter while spreading downward,
The powder collides with the disk surface of the rotary cooling body 4 to be cooled and solidified to form a circular flaky powder 6.

The pressure of the gas injected from the atomizing nozzle 3 is 40 kg / cm ²
That is all. Further, as the injection gas, various types such as argon, helium, nitrogen, air, or a mixed gas can be used. Further, the rotary cooling body 4 is cooled to 50 ° C. or less by, for example, water cooling, and the number of rotations is set to 1000 to 20,000 rpm.

Example 1 Using the apparatus shown in FIG. 1, 200 g of an aluminum alloy ingot having a composition of Al ₈₅ Ni _7.5 Mm _7.5 was set in a graphite crucible and melted at 900 ° C. to obtain a melt 1. The melt 1 was dropped from the nozzle 2 and sprayed with nitrogen gas from the atomizing nozzle 3 at a pressure of 80 kg / cm ² to form a droplet 5. This droplet 5 is 300m in diameter
m, and a disk-shaped rotary cooling body having a rotation speed of 7200 rpm, and rapidly solidified to obtain a disk-shaped flaky powder.

This powder was classified, and those having shape characteristics of 0.5 to 5 μm in thickness, 5 to 500 μm in minor axis and major axis, aspect ratio of 5 or more, and ratio of major axis / minor axis of 1 to 1.5 were collected. The yield of the resulting powder was 76%. In addition, this powder is X-ra
As a result of y diffraction, it was confirmed that the film had an amorphous structure.

Comparative Example 1 A commercially available aluminum flat powder was prepared. This powder consists of 99.9% pure aluminum and has a thickness of 0.5-2.0
μm, minor axis and major axis 5-50 μm, aspect ratio 10-10
It is 0.

Test Example 1 32% by weight of the aluminum alloy powder of Example 1 or the aluminum powder of Comparative Example 1 with respect to 42% by weight of coconut oil-modified short oil alkyd resin varnish, 15% by weight of butylated melamine resin varnish, and 11% by weight of solvent. Each paint was adjusted by mixing.

3.2mm thick, 200mm wide, 500mm high SPC-1 steel sheet, after a thin-film zinc phosphate conversion coating as a base treatment,
Brush with a coating thickness of 50 μm, 110-130 ° C
Was baked and painted.

A cross section of each of the coating films thus obtained was observed, and the orientation of the powder was examined. As a result, those containing the powder of Example 1 had good orientation, and those containing the powder of Comparative Example 1 had slightly poor orientation.

The specular reflectance of each coating film was measured. As a result, 90% or more contained the powder of Example 1 and about 85% contained the powder of Comparative Example 1.
Thus, the powder obtained by the present invention has excellent properties even in metallic coating. In addition, the aluminum alloy powder of Example 1 was amorphous and thus had good corrosion resistance and could be used for a water-soluble paint.

Example 2 Using an apparatus shown in FIG. 1, 500 g of an ingot of an alloy having a composition of CO ₇₀ Fe ₅ Si ₁₀ B ₁₅ was set in an alumina crucible and melted at 1250 ° C. to obtain a melt 1. . This melt 1
Was dropped from the nozzle 2, and argon gas was sprayed from the atomizing nozzle 3 onto the dropped melt 1 at a pressure of 100 kg / cm ² to form droplets 5. This droplet 5 is 300m in diameter
The resulting mixture was collided with a disk-shaped rotary cooling body having a rotation speed of 6000 rpm and rapidly cooled and solidified to obtain a disk-shaped flaky powder.

This powder was classified and fractionated to have a shape characteristic of a thickness of 0.5 to 5 μm, a minor axis and a major axis of 5 to 500 μm, an aspect ratio of 5 or more, and a major / minor axis ratio of 1 to 1.5. The yield of the resulting powder was 82%. This powder is an X-ray
As a result of diffraction, it was confirmed that the structure was an amorphous structure. A scanning electron micrograph of the powder at a magnification of 100 is shown in FIG.

Comparative Example 2 A powder of CO ₇₀ Fe ₅ Si ₁₀ B ₁₅ obtained by a gas atomization method was classified to obtain a spherical powder having an average diameter of 44 μm.

Test Example 2 Preparation of Electromagnetic Shield Sheet: Compounded silicon rubber was masticated with a roller to have appropriate plasticity. At this time, if the pressure is high, the elasticity of the rubber will be lost.
Not exceed 30 kg / cm ^2, also, because the vulcanization reaction with the roll temperature is high progresses, as the temperature inside the water cooled rollers of the roller does not exceed 40 ° C. in order to control it did. Kneading (mastication) was performed at a rotation speed of about 30 times / minute for 2 to 3 minutes. Thereafter, kneading was continued while small amounts of the respective alloy powders prepared so as to have the volume percentages shown in Table 6 were added to the silicone rubber. After the addition of the predetermined amount was completed, the mixture was set on a rubber molding machine having a mold size of 0.5 × 210 × 210 mm, and was subjected to a pressure of 70 kg / cm ^{2 at} a temperature of 120 to 130 ° C. for about 10 hours.
Pressurized for minutes. Thereafter, the mixture was cooled to 80 ° C. with the mixture set, and the sheet was taken out. The thickness of the sheet was 0.53 mm.

The following three types of alloy powders were used to produce three types of sheets.

Example 2 An alloy powder obtained by mixing the alloy powder obtained in Example 2 with 25% by volume.

Comparative Example 2-1: alloy powder obtained in Example 2 and Comparative Example 2
A mixture prepared by mixing 25 vol% of a mixed powder obtained by mixing the alloy powder (spherical powder) obtained in the above at a weight ratio of 1: 1.

Comparative Example 2-2: Alloy powder (spherical powder) obtained in Comparative Example 2
Prepared by mixing 25vo1%.

Method of measuring electromagnetic shielding characteristics: Advantech method (10
Electromagnetic shielding characteristics were measured by a method of generating a low-impedance magnetic field and a high-impedance magnetic field at 00 MHz or lower and measuring the shielding effect from the magnetic field and electric field).

Table 1 shows the results. From Table 1, it can be seen that a sheet produced by mixing only the alloy powder obtained in Example 2 at 25% by volume has excellent electromagnetic shielding properties as compared with other sheets.

[Effects of the Invention] As described above, according to the present invention, droplets are formed by spraying a high-pressure gas onto a melt of a metal capable of forming an amorphous phase, and the droplets are formed into a disc-like shape. By causing the solid to cool and solidify by colliding with the rotating cooling body, a metal powder having a small thickness, a regular shape, a smooth surface, and excellent corrosion resistance can be obtained in a high yield. When this powder is added to a paint, a leafing phenomenon in which the powder is arranged in parallel with the coated surface during drying of the coating film occurs favorably, and the coated surface can be covered without gaps to provide good corrosion resistance and weather resistance. Also, when this powder is added to plastic or rubber, good electromagnetic shielding characteristics can be obtained. Furthermore, from coagulated powder,
0.5 to 5 μm in thickness, minor axis and major axis of 5 to 500 μm, aspect ratio of 5 or more, and major / major axis ratio of 1 to 1.5 are collected. Things are obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus for carrying out the present invention, FIG. 2 is a schematic view showing glass powder obtained by the method of the present invention, and FIG. 2 is obtained by the method of the present invention. 4 is a scanning electron micrograph of 100 times showing the particle shape of the obtained alloy powder. In the figure, 1 is a melt, 2 is a nozzle, 3 is an atomizing nozzle, 4
Is a rotary cooling body, 5 is a droplet, and 6 is a powder.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Masumoto 3-8-22 Uesugi, Sendai City, Miyagi Prefecture (72) Inventor Akihisa Inoue No.1, Kawauchi, Sendai City, Miyagi Prefecture Kawauchi Housing 11-806 (72) Inventor Oguchi Masahiro 1-9-9 Yaesu, Chuo-ku, Tokyo Imperial Piston Ring Co., Ltd. (72) Inventor Yoshio Harakawa 1-9-9 Yaesu, Chuo-ku, Tokyo Imperial Piston Ring Co., Ltd. (56) References Special JP-A-57-70206 (JP, A) JP-A-63-114901 (JP, A) JP-A-64-75607 (JP, A)

Claims (2)

(57) [Claims] In a method for producing a metal powder to be added to paints, plastics or rubbers, an alloy capable of forming an amorphous phase is melted and discharged from a nozzle, and a spray pressure of 40 kg / cm ² is applied to the melt. By spraying the above gas, droplets of the melt are generated, and the number of rotations 1000
On the surface of a disk-shaped rotary cooling body rotating at 220,000 rpm, the droplets collide and solidify by cooling before solidifying, and the metal powder thus obtained has a thickness of 0.5 to 5 μm, a minor axis and a major axis of 5 to 5 μm. A method for producing metal powder, comprising: collecting particles having a length of 500 μm, an aspect ratio (ratio of major axis to thickness) of 5 or more, and a major axis / minor axis ratio of 1 to 1.5. 2. The method for producing a metal powder according to claim 1, wherein said alloy capable of forming said amorphous phase is an alloy described below or described below. General formula AxBy (where A is composed of at least one selected from Fe, Ni, Co, Cr, Mo, B is composed of at least one selected from P, C, B, S, and x, y are 60 ≦ x ≦ 90, 1 in atomic%
0 ≦ y ≦ 40. ). General formula AlaMbNc (where M is at least one selected from Cr, Fe, Mn, Ni, Cu, Ca, and N is Y, La, Ce, Hf, Mm
[Misch metal] is composed of at least one selected from the group consisting of a, b, and c in atomic% of 50 ≦ a ≦ 95, 0.5 ≦ b ≦ 35, 0.5 ≦
c ≦ 25. ).