JPH0747118B2 - Manufacturing method of composite powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composite powder in which the surface of one kind of core powder is substantially completely covered with the outer wall powder of another kind in order to improve the surface characteristics of the powder. A method of manufacturing a body. More specifically, the average diameter is 5 mm
By mixing and compressing using a continuous type or discontinuous type mixer such as a ball mill filled with the following ball-shaped mixed medium, a certain organic or inorganic powder is used as the core powder, and the average particle size of the core powder is The present invention relates to a method for producing a composite powder which has an average particle diameter of 1/5 or less of the diameter and which has an organic, inorganic or metal powder as an outer wall powder and which is substantially completely covered with a core powder. In addition,
In the present specification, the “substantially complete coating” means a state in which the core powder is uniformly and densely covered with the outer wall powder,
At this time, it is preferable that the core powder is substantially covered with the outer wall powder by a single particle layer of the outer wall powder. However, when the composite powder obtained by substantially completely covering the core powder with the outer wall powder is viewed microscopically, there is an extremely narrow gap between the particles of the outer wall powder.

Conventional technology Conventionally, using a ball mill, a crusher, an automatic mortar, etc., organic powder such as nylon powder, polymethylmethacrylate powder and various other plastic powders, and inorganic powder such as titanium dioxide and red iron oxide It is known to produce composite powders by wet or dry milling.

Problems to be Solved by the Invention However, in the conventional methods as described above, coating non-uniformity, core powder deformation, outer wall powder detachment, that is, stability of composite powder, etc. There were many unsolved drawbacks such as lack of. In view of these circumstances, the present inventors have
As a result of intensive studies to solve the drawbacks of the conventional method, to substantially completely coat the surface of the core powder with the outer wall powder, and to obtain a composite powder in which the deformation of the core powder was suppressed as much as possible, the average diameter was 5 mm or less. By using a mixer such as a ball mill filled with the above ball-shaped mixed medium, it was found that a composite powder having the above characteristics can be produced, and the present invention has been completed based on this finding.

Means for Solving Problems and Actions Thereof According to the present invention, a particle diameter of 30 μm constituting the core powder is obtained by using a mixer filled with a ball-shaped mixed medium having an average diameter of 5 mm or less.
The following organic or inorganic powder and one or more of organic, inorganic or metal powder having an average particle diameter of 1/5 or less of the core powder and constituting the outer wall powder A method for producing a composite powder is provided which produces a composite powder in which the core powder is substantially completely coated with the outer wall powder by mixing and compression, the particle size and the coating are uniform, and the deformation is extremely small.

Hereinafter, the structure of the present invention will be described in more detail.

In the manufacturing technique of the composite powder according to the present invention, it is most effective when a substantially spherical powder is used as the core powder.
This means that by reducing the size of the mixing medium of the device (mixing machine) that has been used for the mixing and grinding of solid materials and powder particles, the compression effect of mixing can be effectively utilized, and the conventional spherical shape can be used. It was unthinkable to those skilled in the art that things could be mixed and ground to retain their spherical shape, but according to the method of the present invention, such prior art did not have it. Using spherical powder as core powder,
Without substantially impairing the spherical shape, it is possible to substantially completely coat the surface with an outer wall powder having an average particle size of 1/5 or less of the average particle size of the core powder, which is conventionally From the common sense of, it is an epoch-making thing.

Any organic or inorganic powder can be used as the core powder and the outer wall powder constituting the composite powder of the present invention. Typical examples are polyamide resin, polyethylene resin,
Organic powder such as acrylic resin, polyester resin, fluororesin and cellulosic resin, titanium dioxide, talc, kaolin, zinc white, barium sulfate, magnesium carbonate, calcium carbonate, silica, dicalcium phosphate,
A core powder is any one of inorganic powders such as iron oxide, chromium oxide, chromium hydroxide, ultramarine blue, navy blue, and hydroxyapatite, or their treated powders such as silicon-treated, activator-treated, and wax-treated powders. The above-mentioned organic or inorganic powder, or one or more kinds of metal powder such as aluminum powder, gold powder, silver powder and iron powder are used as the outer wall powder. There is no particular limitation on the combination of the core powder and the outer wall powder, and organic powder-organic powder, organic powder-inorganic powder, organic powder-metal powder, inorganic powder-organic powder, inorganic powder Any of powder-inorganic powder and inorganic powder-metal powder may be used. However,
The average particle size of the outer wall powder needs to be 1/5 or less, preferably 1/10 or less with respect to the average particle size of the core powder. When the average particle diameter of the outer wall powder is larger than 1/5 of that of the core powder, the detachment stability of the outer wall powder becomes extremely poor, which is not preferable.

As a combination of the core powder and the outer wall powder constituting the composite powder according to the present invention, for example, nylon 12 spherical powder (average particle size 7 μm) is used as the core powder and titanium dioxide powder (average particle size 0.
2 μm) as outer wall powder, polyethylene powder (average particle size 15 μm) as core powder, polystyrene powder (average particle size 3 μm) as outer wall powder, spherical silica powder (average particle size 10 μm) as core A combination of powdered zinc white powder (average particle size 0.5 μm) as outer wall powder, dicalcium phosphate powder (average particle size 30 μm) as core powder, and spherical cellulose powder (average particle size 3 μm) as outer wall powder. The combination etc. It is needless to say that these are just examples and there are innumerable combinations depending on the purpose and application.

The minimum amount of outer wall powder required in the production of the composite powder according to the present invention is the amount by which the outer wall powder covers the surface of the core powder with the single particle layer.

The mixer used for producing the composite powder according to the present invention may be any mixer such as a rotary ball mill, a vibration ball mill, a planetary ball mill, a sand mill, an attritor, etc. It can be preferably used. However, as the mixed medium conventionally used in such a mixer, balls having an average diameter of 30 mm or more are generally used, and when such balls are used, the core powder and the outer wall powder are Crushed or deformed,
Moreover, since the number of times of contact with the powder is small, it may not be possible to manufacture the core powder in which the outer wall powder is completely covered. Therefore, as the ball-shaped mixed medium used for producing the composite powder of the present invention, it is necessary to use a mixed medium having an average diameter of 5 mm or less, preferably 2 mm to 5 mm with good workability.

As described above, if the average diameter of the mixed medium is larger than 5 mm, the core powder cannot be substantially completely covered or the powder may be deformed or crushed, which is not preferable. The material of the mixing medium of the mixer used in the present invention is not particularly limited, and for example, any of ceramic, metal or resin can be used.

There is no particular limitation between the amount of the powder and the amount of the mixing medium of the mixer when producing the composite powder according to the present invention, but generally speaking, the larger the amount of the mixing medium with respect to the amount of the powder, the greater the amount. The mixing and compression effect is great and the treatment is completed in a short time, but the composite powder is likely to be deformed. Further, the smaller the amount of the mixed medium is, the smaller the compression effect is and the longer the treatment is required, but the deformation of the composite powder is reduced. Therefore, it is preferable to use 300 to 700 parts by weight of the mixed medium with respect to 100 parts by weight of the total powder.

In carrying out the present invention, with the mixed medium filled,
It is a necessary condition that there is an upper space in the mixer, and it is preferable that the upper space is about 1/3 to 2/3.

The temperature during the mixer treatment is not particularly limited as long as the properties and shape of the powder used are not impaired.

In addition, the atmosphere of the upper space of the mixer during the treatment is not particularly limited. In addition, it is preferable to mix the core powder and the outer wall powder with a general powder mixer such as a Henschel mixer before the mixing and compression treatment. Further, in carrying out the present invention, liquid such as water or alcohol may be used in combination with the powder treated with the mixer.

As described above, in the present invention, the pulverizing effect of the powder is suppressed as much as possible by using a mixed medium having an average diameter of 5 mm or less for the mixer treatment, and the number of contacts is dramatically increased, and the nuclear powder surface due to friction static electricity etc. It is now possible to produce a composite powder with excellent desorption stability, in which the outer wall powder adhering to is strongly pressed and the particle size is uniform and the core powder is substantially completely covered with the outer wall powder. It was

EFFECTS OF THE INVENTION According to the present invention, the surface characteristics of the core powder can be improved by substantially completely covering the surface of the core powder with the powder to be the outer wall powder as described above. . For example, by coating the surface of a spherical core powder with an outer wall powder having a hiding power, a spherical composite powder having a good slip property and a hiding power can be obtained, and a hydrophobic outer wall powder on the surface of a hydrophilic core powder. It is possible to coat the body to make it hydrophobic, and conversely, to coat the surface of the hydrophobic core powder with hydrophilic outer wall powder to make it hydrophilic, and to make the surface of the core powder with low specific gravity high outer wall powder. It is possible to coat the body into a powder with a low specific gravity, and to coat the surface of a spherical core powder with a colored outer wall powder with poor slippage to form a colored composite powder with good slippage. A magnetic composite powder can be obtained by coating the body surface with a magnetic outer wall powder, which has the outstanding effect of improving the surface characteristics of all powders.

Examples Next, the present invention will be described in more detail with reference to Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples. In the following examples, "part" means part by weight.

Example 1 65.0 parts of spherical nylon 12 powder (average particle size 6.6 μm) was mixed with 35.0 parts of titanium dioxide powder (average particle size 0.2 μm) in a Henschel type mixer (FM10B manufactured by Mitsui Miike Seisakusho) for 5 minutes, Next, the obtained mixed powder was mixed and compressed for 14 hours in a rotary ball mill (Universal Ball Mill manufactured by Yamato Scientific Co., Ltd.) filled with alumina balls (Nippon Kagaku Sangyo HD alumina balls 3 mmφ). Observation with a scanning electron microscope (S-510 scanning electron microscope manufactured by Hitachi) confirmed that a composite powder having the particle structure shown in FIG. 1 was obtained.
This composite powder had a spherical shape, and the nylon 12 spherical powder was substantially completely covered with the titanium dioxide powder, and showed appropriate hiding power and hydrophilicity, and also had good slipperiness. Further, the detachment stability of the outer wall powder due to shearing force was also excellent.

The slip was evaluated by measuring the dynamic friction coefficient with a powder friction tester. In addition, powder friction tester (Journal of Powder Engineering)
Vol.21, No.9, p565 (1984)) is a custom-made product, which is made by attaching a double-sided adhesive tape to a horizontally installed iron plate, placing a sample on it, and then applying a load (5 to 5) to an aluminum attachment. 70 g / cm ² ), the strain stress when the attachment was moved left and right at a speed of 10 mm per second was measured with a strain gauge, and the dynamic friction coefficient was calculated from the relationship between the load and the shear stress.

The dynamic friction coefficient of the obtained composite powder was 0.38, which was considerably smaller than 0.60 of titanium dioxide, and was about the same as 0.39 of nylon 12 spherical powder, showing good slipperiness. Further, the hiding power was measured by a cryptometer, and the hiding power of this composite powder was as high as 30% of the titanium dioxide powder. Also, as a desorption stability test for the outer wall powder,
The obtained composite powder was dispersed in liquid paraffin to form a slurry, which was then treated with a colloid mill. The fact that the outer wall powder was not detached by such treatment is shown in the result of observing the particle structure of the powder after the test with a scanning electron microscope (S-510 scanning electron microscope manufactured by Hitachi) (Fig. 2). On the street.

Comparative Example 1 Nylon 12 spherical powder (average particle size 6.6 μm) as in Example 1
m) 63.0 parts titanium dioxide powder (average particle size 0.2 μm) 37.
Henschel type mixer with 0 parts (Mitsui Miike Seisakusho FM10
The mixture was mixed in B) for 5 minutes, and then the mixed powder was placed in a rotary ball mill (Universal Ball Mill manufactured by Yamato Scientific Co., Ltd.) filled with alumina balls (Nippon Kagaku Sangyo HD alumina balls 20 mmφ) and mixed and compressed for 14 hours.

The obtained powder is a scanning electron microscope (made by Hitachi
As is clear from the observation result with the S-510 scanning electron microscope), the coating of the titanium dioxide powder on the nylon 12 spherical powder was incomplete, and voids were conspicuous on the surface of the composite powder. In addition,
Even if the composite powder was mixed for a long time, the coating remained incomplete, and the nylon 12 spherical powder was deformed and broken. The composite powder shown in FIG. 3 has a hiding power and exhibits hydrophilicity, but the dynamic friction coefficient is as high as 0.45, and the slip is extremely poor. In addition, the desorption stability test of the outer wall powder was carried out by colloid milling in the same manner as in Example 1, and the particle structure was observed with a scanning electron microscope (Hitachi S-510 scanning electron microscope). As shown in FIG. 4, significant detachment of the outer wall powder was confirmed.

Example 2 Hydrophilic dicalcium phosphate powder (average particle size 30 μm)
60.0 parts of hydrophobic polystyrene powder (average particle size 3 μm)
Henschel type mixer with 40.0 parts (Mitsui Miike Seisakusho FM
10B) and mixed for 5 minutes, and then the resulting mixed powder is used for Amyruna balls (Nippon Kagaku Sangyo HD alumina balls 5 mm
Vibration type ball mill filled with φ (Japan spindle TKM
-2), and mixed and compressed for 2 hours.

In the obtained composite powder, the dicalcium phosphate powder was substantially completely covered with the polystyrene powder, showed a hydrophobic property, and had improved slippage as compared with the dicalcium phosphate core powder.

Example 3 Hydrophobic polyethylene powder (average particle size 15 μm) 65.0 parts was replaced with hydrophilic spherical silica powder (average particle size 2 μm) 35.0
A ball mill (made by Mitamura Riken Kogyo Co., Ltd.) filled with alumina balls (Nippon Kagaku Sangyo HD alumina balls 2 mmφ) after mixing for 1 minute in a small crusher (Kyoritsu Riko SK-M10) together with the parts. Centrifugal ball mill) and mixed and compressed for 1 hour.

The obtained composite powder was substantially completely covered and showed hydrophilicity.

Example 4 A rotary ball mill (Yamato Kagaku universal ball mill) in which 70.0 parts of spherical cellulose powder (average particle size 3 μm) and 30.0 parts of ultramarine (average particle size 0.3 μm) were filled with alumina balls (HD alumina balls 3 mmφ manufactured by Nippon Kagaku Sangyo Co., Ltd.) The mixture was mixed and compressed for 10 hours.

The obtained composite powder was substantially completely covered, and the slip was remarkably improved as compared with ultramarine.

Example 5 Non-magnetic polystyrene spherical powder (average particle size 8 μm) 72.0
The parts were placed in a vibrating ball mill (Nippon Spindle VKM-2) filled with 28.0 parts of magnetic iron oxide (average particle size 0.3 μm) and alumina balls (Ashizawa alumina balls 2 mmφ), and mixed and compressed for 3 hours.

The obtained composite powder was substantially completely covered, was magnetic, and was hydrophilic.

[Brief description of drawings]

FIG. 1 is an electron micrograph (10000 times) showing a particle structure of the composite powder obtained in Example 1, and FIG. 2 is a particle of the composite powder obtained in Example 1 after the colloid mill treatment. FIG. 3 is an electron micrograph (10000 times) showing the structure, FIG. 3 is an electron micrograph (10,000 times) showing the particle structure of the composite powder obtained in Comparative Example 1, and FIG. 4 is obtained in Comparative Example 1. It is an electron micrograph (10000 times) showing the particle structure of the obtained composite powder after colloid mill treatment.

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Claims (1)

[Claims] 1. A mixing machine filled with a ball-shaped mixed medium having an average diameter of 5 mm or less is used, and an organic or inorganic powder having a particle diameter of 30 μm or less constituting the core powder and an average particle diameter of the core powder The core powder is substantially completely covered with the outer wall powder by mixing and compressing 1/5 or less of the average particle size and one or more kinds of organic, inorganic or metal powders constituting the outer wall powder. A method for producing a composite powder, which comprises producing the composite powder described above.