JPH0677676B2 - Method for producing mixed powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a mixed powder in which two or more kinds of powders are mixed with each other.

[Conventional technology]

Various powders, such as metals, have been used in many industrial fields.
Abrasive material, cement raw material, glass raw material, refractory raw material, ceramic raw material, ceramics, synthetic resin, pigment, fertilizer, feed,
Various methods have been adopted for mixing powders of agricultural chemicals, pharmaceuticals, spices, etc., for example, a method of mixing the powders by mixing the powders with each other by rotating the container itself containing the powders to be mixed. A method of stirring the powder in it by rotating the blades and screws provided inside, a method of mixing by forming a fluidized bed of the powder by sending air into the container containing the powder, etc. And the wet method in which powders of metal, inorganic carbide, nitride, ceramics, and cermet are mixed in an organic solvent such as alcohol or hexane in a ball mill, for example.

[Problems to be solved by the invention]

However, the above method of rotating the container itself takes time, the method of stirring with a blade or a screw and the method of forming a fluidized bed with air have a mixing degree depending on the injection speed of air. In addition, all of these dry mixing methods result in powder agglomeration and generation of static electricity as the mixing time increases, resulting in backmixing and segregation, resulting in a completely homogeneous mixture. There is naturally a limit to obtaining it, and even in the above-mentioned wet method, segregation is inevitably involved because the specific gravity, shape, and size of each powder are different, and since it is not possible to completely eliminate agglomeration of particles, it is also homogeneous. It was difficult to obtain a proper mixture.

[Findings based on research]

Therefore, as a result of various studies to solve the above problems, the inventors of the present invention (1) do not substantially dissolve any of two or more kinds of powders to be mixed with each other, and 1 or 2 or more of the powders are respectively mixed with 2 or more liquids that are immiscible with each other to contain 1 or 2 or more of the powders.
After the above mixture has been formed, when these mixtures are combined and stirred and mixed together, the liquids that are immiscible with each other are divided into very fine droplets in the form of a discontinuous phase. The violent movement of the droplets at the interface repulsing each other causes the particles of each powder to be individually separated into fine particles to form a suspension in which the agglomeration of the particles is completely suppressed. ) By spray-drying this suspension, the liquid that wets the surface of the powder particles can be efficiently removed, and a mixed powder that is uniformly mixed with each other without causing agglomeration or segregation between the powders is obtained. In that case, a highly uniform mixed powder is produced in a short time. (3) By using two or more kinds of liquids that do not substantially dissolve any of the powders and are immiscible with each other. The physical and physical properties of each powder as well as each liquid Without degrading the chemical properties, the characteristics that are provided for each powder to produce a mixed powder as it can exhibit, found.

[Means for solving problems]

This invention was invented based on the above findings.
The purpose of the present invention is to provide a method for producing a mixed powder having high homogeneity, that is, a high degree of mixing, from two or more powders, and producing a mixed powder in which these powders are mixed with each other, from two or more powders. In which the powders do not substantially dissolve and are immiscible with each other.
One or more of the powders are mixed in one or more liquids, and one or more of the powders are mixed while being crushed, if necessary, to obtain one or more of the powders. After forming two or more mixtures containing, the mixture is stirred and mixed together to form a suspension, and then the suspension is spray dried.
It is characterized by forming a mixed powder in which the two or more kinds of powders are uniformly mixed.

[Specific Description of the Invention]

1. Raw material powder Examples of the raw material powder mixed according to the present invention include metals, abrasives, cement raw materials, glass raw materials, refractory raw materials, ceramic raw materials, ceramics, pigments, synthetic resins, fertilizers, feeds, agricultural chemicals, pharmaceuticals. , Powders such as spices and the like can be mentioned, but the present invention is particularly one in which powder particles are easily attached to each other and easily aggregate, for example, a fine powder having a very small particle size in general, or a particle surface having an adhesive property. It is particularly convenient in the case of mixing those having a particle shape, particles having a shape in which the particles are easily entangled with each other, those having a tendency to be magnetically or electrostatically charged, or the case where it is necessary to produce a mixed powder having particularly high uniformity. Used.

2. Liquid As the liquid to be mixed with the raw material powder, various liquids can be used as long as they do not substantially dissolve any of the raw material powders and are two or more liquids which are immiscible with each other. However, it is desirable that these liquids have excellent wettability as described above, because the better the wettability to the powder, the greater the force for separating the powder loss into individual liquids, and the low viscosity and thermal stability. Of course, those which easily volatilize are preferable.

As such a liquid, various inorganic liquids and organic liquids can be used, for example, water, acetone, ethylene glycol, ethylene glycol diacetate, 1,
1,1-Trichloroethane, hexane, carbon tetrachloride and the like are preferably used.

These liquids, when combined together, must be in the form of discontinuous phases, as described above, when stirred and mixed together, unless they completely dissolve and form a homogeneous continuous phase. It is possible to create droplets that are very finely divided and that move violently while repelling each other at the interface,
Although various kinds of liquids can be used in various combinations as the liquid used in the present invention, very fine droplets in the form of the above discontinuous phase can be efficiently formed during stirring and mixing. It is preferable to use a combination of liquids that do not dissolve in each other as much as possible.

3. Mixing of powder and liquid When mixing the above-mentioned raw material powder with a liquid, it is preferable to stir them sufficiently so that the powders are separated into individual particles as much as possible, for which, for example, a mixing tank equipped with a stirring device is used. In this case, if the powder is pulverized and mixed with the liquid, the agglomeration of the powder particles is further prevented, the surface of the powder is activated, or the particle size and particle size distribution of the powder are adjusted. Then, the powder is mixed with the liquid while being crushed by a crusher such as an attritor or a ball mill.

The liquid-powder mixture thus obtained generally becomes a suspension having a relatively high fluidity or a mud-like suspension having a low fluidity, that is, a slurry, depending on the mixing ratio of the liquid and the powder. .

4. Formation of Suspension Combined in One To combine the mixture of the liquid and powder into one, and to stir, mix to form a suspension, for example, in a stirring tank into which the mixture flows respectively, These mixtures are combined into one, and by stirring and mixing with a stirring blade that rotates at high speed, the agglomeration of each powder particle is released and segregation is avoided, and it has a uniform composition, usually in the form of a slurry. A suspension forms.

In addition, in forming the suspension by combining the mixture of the liquid and the powder into one, the smaller the difference in the specific gravity of the mixture, the more the mixture, and thus the powder, were uniformly mixed. When the specific gravities of the two or more powders to be mixed are considerably different from each other because the suspension is easily formed, the liquid having an appropriate specific gravity is selected for each powder. It is preferable to make the difference in specific gravity of the mixture as small as possible.

5. Spray drying It is important that the suspension is spray dried before coalescence of droplets or segregation of powder particles occurs as much as possible. For that purpose, the suspension is dispersed in sufficiently fine droplets. It is necessary to quickly introduce the liquid through a sprayer into the drying chamber, for example by dropping the suspension directly from the stirred tank into the sprayer at the top of the spray drier or from the stirred tank to the spray dryer. The suspension is stirred in a vessel in which the liquid droplets and the powder particles are uniformly dispersed without causing agglomeration by, for example, applying ultrasonic vibrations to the pipeline through which the suspension liquid is sent. It is important to supply from the spray dryer to the spray dryer.

The product produced by spray-drying, i.e. the mixed powder, is removed from the bottom of the drying chamber and from a device for collecting and separating dry particles, such as a cyclone dust collector, while the evaporated liquid passes through the cyclone and then into a scrubber condenser. Where each liquid is recovered by phase separation. Air is usually used as the hot air used for drying, but when handling a raw material powder or liquid that cannot be exposed to this air, an inert gas such as nitrogen is used.

As a spray dryer, the diameter of droplets can be reduced,
For example, a jet spray dryer is preferably used.

〔Example〕

Next, the present invention is applied to a tungsten carbide (hereinafter referred to as WC) powder, a solid solution powder of TiC and WC (TiC / WC weight ratio = 3 /
The production of a mixed powder of 7) and Co powder will be described as an example in comparison with a comparative example.

First, as a raw material powder, a WC powder having an average particle size of 4.0 μm, a solid solution powder of TiC and WC having an average particle size of 1.0 μm, and
Prepare Co powder with 4.0μm, 140g of this WC powder and Co
20 g of the powder was added to 160 ml of hexane and mixed with the hexane for 1 hour while crushing the powder with a ball mill rotating at 600 rpm to form a mixed slurry of WC powder and Co powder, while TiC and WC were mixed. Solid solution powder with 1
Add 60 g to 160 ml ethylene glycol and add this mixture.
A slurry of the solid solution was formed by mixing with the ethylene glycol for 1 hour while grinding with a ball mill rotating at 600 rpm.

Then, from each slurry thus formed, 140 ml of a mixed slurry of WC powder and Co powder, and TiC
35 ml of the solid solution powder slurry with WC was taken out, respectively, and both were mixed in a stirring tank by a stirring blade rotating at 300 rpm, and the mixed slurry was heated to a temperature of 350 ° C. as hot air for drying. Introduced into a jet spray dryer in which nitrogen was introduced, a mixed powder of the present invention composed of WC powder, solid solution powder, and Co powder was produced.

For comparison, by the conventional method, that is, using the above-mentioned WC powder, TiC and WC solid solution powder and Co powder as raw material powder, this WC powder: 156 g, TiC and WC solid solution powder: 35 g and Co powder : 20 g in 200 ml of ethanol, crushed by a ball mill rotating at 600 rpm for 1 hour and mixed, and the resulting slurry is dried in vacuum at a temperature of 150 ° C. to obtain WC powder, TiC and WC. A comparative mixed powder consisting of the solid solution powder and the Co powder was produced.

Next, in order to evaluate the homogeneity of mixing in these mixed powders, Chemical Engineering Progress (Chem.Eng.Prog), 51 [1] 27J-36J (1955), Wei.
Density shown by denbaum, SS, Bonilla, CF: X ² ex / X
² was measured and the results are shown in Table 1.

Further, using the above-mentioned mixed powder of the present invention and the comparative mixed powder as raw materials, both of them are press-molded at a pressure of 15 kg / mm ² to obtain a green compact, and these green compacts are subjected to a vacuum of 0.05 Torr and a temperature: A sintered body of the present invention and a comparative sintered body were produced by sintering under the conditions of 1380 ° C. and a holding time of 1 hour, and the WC powder and the solid solution powder of TiC and WC were bonded with the Co powder. Specific gravity, shrinkage ratio (%) of each sintered body obtained by
When the hardness (Rockwell hardness, A scale) and the transverse rupture strength (kg / mm ² ) were measured, the results shown in Table 1 were obtained.

[Effects of the Invention] From the results shown in Table 1, the mixed powder of the present invention has a significantly improved degree of mixing as compared with the comparative mixed powder, and regarding the sintered body using such mixed powder as a raw material, It can be seen that the sintered body of the present invention is particularly superior to the comparative sintered body manufactured by the conventional method, especially in its transverse rupture strength.

This difference in transverse rupture strength (strength) is due to the fact that in the comparative sintered body obtained from the comparative mixed powder, the TiC / WC solid solution phases agglomerate and cracks occur with the agglomerated portion as the starting point of fracture. On the other hand, in the sintered body of the present invention obtained from the mixed powder of the present invention, the TiC / WC solid solution phase is scattered in Co, and by being scattered uniformly, the above-mentioned agglomerated portion that easily breaks down is formed. It is considered to be based on the point that it does not form.

Incidentally, in the above-mentioned examples, as a specific example in the case of carrying out the present invention, WC powder, TiC / WC solid solution powder and Co powder production of mixed powder was explained, but also for other various powders, It is apparent that the same effect, that is, a mixed powder having a high degree of mixing can be obtained by the present invention.

As is apparent from the above description, according to the present invention, an extremely useful mixed powder can be obtained from two or more kinds of powders, and as a result, various materials having excellent characteristics can be provided, which is an industrially useful effect. Is obtained.

Claims (2)

[Claims] 1. A method for producing a mixed powder in which these powders are mixed with each other from two or more kinds of powders, in which none of said powders is substantially dissolved and which are immiscible with each other. After mixing one or more of the powders with two or more liquids respectively to form two or more mixtures containing one or more of the powders, the mixtures are combined together. By stirring, mixing to form a suspension and then spray drying the suspension,
The method for producing a mixed powder, which comprises forming a mixed powder in which the two or more kinds of powders are uniformly mixed. 2. When forming the mixture by mixing the powder with the liquid, one or more kinds of the powder are mixed with the liquid while being crushed. The manufacturing method according to claim (1).