JP4735403B2 - Method for producing granulated powder - Google Patents

Description

The present invention relates to the production how of the granulated powder.

There are many examples of using granulated powder obtained by granulating raw material particles in order to make use of powder characteristics. Since the granulated particles have high fluidity and are easy to handle, they are suitably used as, for example, a powder for forming a molded body.
There are various granulation methods for forming such a granulated powder from raw material particles, and the obtained powder characteristics are also characteristic. And it is necessary to select the granulation method according to the kind of raw material particle | grains, the use of granulated particle | grains, the required powder characteristic, etc.

For example, Patent Document 1 discloses a method of producing a granulated powder using water atomized metal particles as a raw material using a rolling fluidized granulator.
In the above method, the raw material particles are granulated while supplying a methanol solution (binder solution) of polyvinylpyrrolidone (binder) to obtain a granulated powder.
However, the fluidity of the binder solution tends to decrease due to the ratio of the solvent in the binder solution or the temperature of the binder solution, and it is difficult to spread the binder solution over the entire raw material powder.

In addition, if the ratio of the solvent in the binder solution is increased in order to ensure the fluidity of the binder solution, it takes a long time to volatilize and remove the solvent during or after granulation. There is also a problem that the decline in sex is inevitable.
Furthermore, since the specific gravity of the binder and the raw material particles are greatly different, uneven distribution occurs in the mixture of the raw material particles and the binder solution at the time of granulation, and the binder content becomes uneven between the granulated particles. There's a problem. The granulated particles obtained in this way tend to have a wide range of particle size distribution. That is, for example, there are many coarse particles that are hardly granulated and grown containing a large amount of binder.
For example, when such a granulated particle is filled in a molding die to obtain a molded body, characteristics of the obtained molded body, and consequently, characteristics of a sintered body obtained by firing the molded body vary.

JP-A-11-106804

An object of the present invention is to provide a method for producing efficiently manufacturable granulated powder granulated powder powder particle size distribution is controlled narrowly.

The above object is achieved by the present invention described below.
Method for producing a granulated powder of the present invention, by impinging the formed binder particles raw material particles and a binder, providing a plurality of binder-coated particles obtained by coating the surface of the raw material particles in the binder A first step;
The binder-coated particles are bonded to each other by rolling and / or flowing the plurality of binder-coated particles while applying a solvent capable of dissolving the binder to the plurality of binder-coated particles. It has the 2nd process of obtaining the granulated particle containing the said raw material particle, It is characterized by the above-mentioned.
Thereby, the granulated powder whose particle size distribution was controlled narrowly can be manufactured efficiently.

In the granulated powder manufacturing method of the present invention, the collision between the raw material particles and the binder particles is performed such that the collision energy is 2 × 10 ⁴ to 2 × 10 ⁵ J / kg per 1 kg of the raw material particles. It is preferable.
Thereby, it is possible to coat the surface of each raw material particle with the binder by deforming the binder while preventing the raw material particles from being destroyed.

In the granulated powder manufacturing method of the present invention, in the first step, the weight of the binder particles is preferably 0.5 to 30 g per kg of the raw material particles.
Thereby, it is possible to reliably prevent a large amount of the binder not contributing to the coating from remaining, while sufficiently covering almost the entire surface of the raw material powder with the binder.
In the manufacturing method of the granulated powder of this invention, it is preferable in the said 2nd process that the said solvent is provided so that it may become 5-100g per 1g of said binders.
Accordingly, the binder can be appropriately dissolved and reliable granulation can be achieved while preventing the binder in the binder-coated particles from being excessively dissolved.

In the manufacturing method of the granulated powder of this invention, it is preferable in the said 2nd process that the said solvent is provided by spraying.
Thereby, a solvent can be spread over the whole binder covering particle | grains uniformly. As a result, in the entire binder-coated particles put into the processing container, the degree of binder dissolution becomes uniform, and when a plurality of binder-coated particles aggregate to grow into granulated particles, the binder coating aggregates. The number of particles is made uniform. As a result, granulated particles having a uniform particle size can be obtained.

In the method for producing a granulated powder of the present invention, after the second step, the granulated particles are rolled and / or fluidized while a second solvent capable of dissolving the binder is applied to the granulated particles. It is preferable to have a third step of making the granulated particles more uniform in size and obtaining second granulated particles .
Thereby, the particle diameter of the granulated particles can be further uniformed, and second granulated particles having a uniform particle diameter can be obtained.

In the method for producing a granulated powder of the present invention, conditions for rolling and / or flowing the binder-coated particles in the second step, and rolling and / or flowing the granulated particles in the third step. It is preferable that the conditions are different.
Thereby, the conditions of the third step can be set according to the state of the granulated particles, that is, the particle size, particle size distribution, etc. of the granulated particles, and the second granulated particles having a sharper particle size distribution. Can be obtained.

In the method for producing a granulated powder of the present invention, the two conditions are the solubility of the solvent and the second solvent in the binder, the supply amount of the solvent and the second solvent, and the rolling, respectively. And / or at least one of the stirring forces when flowing.
Each of these conditions strongly contributes to the granulation process of the granulated particles and the second granulated particles, and by appropriately setting these, the particle size distribution of the second granulated particles is efficiently controlled. can do. As a result, the second granulated particles having a sharper particle size distribution can be efficiently obtained.

In the manufacturing method of the granulated powder of this invention, it is preferable to have the process of removing the said solvent from the said granulated particle between the said 2nd process and the said 3rd process.
Thereby, the unintentional deformation | transformation of the granulated particle in a 3rd process can be prevented, and the uniform shape of the 2nd granulated particle obtained can be aimed at.
In the granulated powder manufacturing method of the present invention, in the third step, the second solvent is preferably applied by spraying.
Thereby, a 2nd solvent can be spread uniformly to the whole granulated particle. Thereby, in the whole granulated particle put into the processing container, the degree of dissolution of the binder becomes uniform, and the homogenization of the granulated particle is further promoted. As a result, it is possible to obtain second granulated particles having a particularly uniform particle diameter.

In the manufacturing method of the granulated powder of this invention, it is preferable that the average particle diameter of said 2nd granulated particle is 40-180 micrometers.
Thereby, it is possible to more surely make the particle diameter of the obtained second granulated particles uniform.
In the manufacturing method of the granulated powder of this invention, it is preferable that the average particle diameter of the said granulated particle is 40-180 micrometers.
Thereby, for example, when forming a compact by filling the granulated powder into a molding die, the granulated powder has excellent fluidity and filling properties into the molding die.

In the manufacturing method of the granulated powder of this invention, it is preferable that the average particle diameter of the said raw material particle is 1-20 micrometers.
By using such raw material particles having a relatively small particle size, granulated particles (granulated powder) having a small particle size according to the particle size can be obtained. Such a granulated powder has a particularly high filling property in a mold, so that a high-density molded body and a sintered body can be produced. That is, the present invention can be applied particularly effectively when granulated particles are produced using such relatively small raw material particles.

In the manufacturing method of the granulated powder of this invention, it is preferable that the said raw material particle is a metal particle.
The granulated powder containing metal powder can be used, for example, as a raw material for producing molded bodies and sintered metal bodies .

Hereinafter, the manufacturing method and granulated powder of the granulated powder of this invention are demonstrated in detail, referring an accompanying drawing.
First, the granulating apparatus used in the method for producing the granulated powder of the present invention will be described.
FIG. 1 is a schematic diagram showing the configuration of a granulating apparatus used in the method for producing a granulated powder of the present invention. In the following description, the upper side of FIG. 1 is referred to as “upper” and the lower side is referred to as “lower”.

A rolling granulator 1 shown in FIG. 1 includes a processing container 10 for performing granulation, a blade 20 and a cross screw 30 disposed in the processing container 10, and a spray nozzle 40.
As shown in FIG. 1A, the processing container 10 has a bottom part 11 and a side wall part 12 erected from the bottom part 11, and the side wall part 12 has an inner diameter and an outer diameter from the upper side to the lower side. It has a gradually increasing weight shape (for example, a truncated cone shape). Since the processing container 10 (side wall portion 12) has such a shape, the powder blown up on the outer peripheral side of the processing container 10 by the blade 20 in the processing container 10 falls to the center side of the processing container 10. An air current can be formed. As a result, the powder can be processed without unevenness, and a granulated powder having a sharp particle size distribution can be efficiently produced.

Further, the processing container 10 has an opening on the upper side, and a lid portion 13 is mounted so as to close the opening.
The blade 20 includes a base 23 and three rotary blades 21, 21, 21 having one end fixed to the base 23 and provided radially at substantially equal intervals.
A through hole 110 is provided at the center of the bottom 11 of the processing container 10, and the rotation drive shaft 22 is inserted through the through hole 110.

The upper end of the rotational drive shaft 22 is fixed to the base 23, and the lower end is connected to a rotational drive source (not shown). Then, the rotational drive shaft 22 is rotationally driven in the forward and reverse directions by the rotational drive source, whereby the blade 20 rotates.
Further, the rotary blades 21, 21, and 21 are respectively fixed to be inclined with respect to the rotary drive shaft 22 so that the front side in the rotation direction of the blade 20 is a downward slope. Thereby, with rotation of the blade 20, the powder can be effectively jumped up and the airflow as described above can be formed.

A through hole 130 is provided in the side wall portion 12 of the processing container 10, and the rotation drive shaft 31 is inserted into the through hole 130.
One end of the rotation drive shaft 31 is fixed to the cross screw 30 and the other end is connected to a rotation drive source (not shown). Then, the rotational screw 31 is rotated in the forward and reverse directions by the rotational driving source, whereby the cross screw 30 is rotated.

The spray nozzle 40 is provided through the lid portion 13 attached to the processing container 10, and the supply port is located in the processing container 10. Thereby, it is comprised so that a solvent can be sprayed in the processing container 10. FIG. By spraying the solvent from the spray nozzle 40, a downward air flow is generated in the vicinity of the spray nozzle 40.
Here, the operation of the rolling granulator 1 as described above, that is, a method for producing a granulated powder using the rolling granulator 1 will be described. The granulated powder production method using the rolling granulator 1 is an example of the granulated powder production method of the present invention, and it goes without saying that the granulated powder production method of the present invention is not limited thereto. .

In the present invention, first, a plurality of binder-coated particles obtained by coating the surface of raw material particles with a binder are prepared, and then a plurality of binder-coated particles are rolled while applying a solvent capable of dissolving the binder. By flowing, binder-coated particles are bonded to each other to obtain granulated particles formed by coating a plurality of raw material particles with a binder.
The granulated powder manufacturing method in this embodiment includes a first step of obtaining a plurality of binder-coated particles obtained by coating the surface of raw material particles with a binder, and a binder coating while applying a solvent capable of dissolving the binder. And a second step of obtaining granulated particles obtained by combining particles and combining a plurality of raw material particles with a binder. In the following, “a plurality of raw material particles” is also referred to as “raw material powder”, and “a plurality of binder-coated particles” is also referred to as “binder-coated powder”. Further, “a plurality of granulated particles” is also referred to as “granulated powder”.

Hereinafter, these steps will be sequentially described in detail.
[1] First, the surface of the raw material powder is coated with a binder. Thereby, a binder coating powder is obtained (first step).
Examples of the method of coating the surface of the raw material powder with the binder include a method of colliding the raw material powder and a binder powder (binder particles) composed of the binder, a method of bringing the raw material powder into contact with a liquid containing the binder, and the like. .

Among these, it is preferable to use a method in which the raw material powder and the binder powder collide. Thereby, a binder can be reliably adhered to the surface of the raw material powder, and a binder-coated powder obtained by uniformly coating the raw material powder with the binder can be obtained.
In this case, when the binder powder and the raw material powder collide, the shape of the binder changes into a film shape covering each raw material particle by the collision energy. Thereby, each raw material particle will be coat | covered with a binder, and uneven distribution of the raw material particle and binder in binder coating | coated powder can be prevented or suppressed. As a result, granulated particles (granulated powder) in which the raw material particles and the binder are uniformly distributed can be obtained in the second step described later.

Such collision between the raw material powder and the binder can be efficiently performed by applying mechanical energy to the mixture of the raw material powder and the binder.
Specifically, the application of the energy can be performed by, for example, a method of causing the mixture to collide with a blade or a casing, a method of applying a compressive force and a shearing force to the mixture, and the like. Depending on the energy application method, various mixers or various pulverizations such as hybridization, mechano-fusion, sheeter composer, roll crusher, colloid mill, rotor mill, roller mill, vibration mill, jet mill, mechanical vortex pulverizer, etc. A machine or the like can be used.

In this case, the mechanical energy due to the collision is preferably about 2 × 10 ⁴ to 2 × 10 ⁵ J / kg per 1 kg of the raw material powder (raw material particles), and 4 × 10 ⁴ to 1 × 10 ⁵ J / kg. More preferred is the degree. Thereby, it is possible to coat the surface of each raw material particle with the binder by deforming the binder while preventing the raw material particles from being destroyed.
In addition, the weight of the binder used in this step is preferably about 0.5 to 30 g, more preferably about 1 to 20 g, per 1 kg of the raw material powder (raw material particles). Thereby, it is possible to reliably prevent a large amount of the binder not contributing to the coating from remaining, while sufficiently covering almost the entire surface of the raw material powder with the binder.

In addition, the shape of the binder which collides with the raw material powder in this step is not limited to the powdery shape (granular shape) as described above, and may be a lump shape, a block shape or the like.
The raw material powder is not particularly limited, and powders composed mainly of various inorganic materials can be used. For example, metal materials such as steel, iron nickel alloy, iron cobalt alloy, iron silicon alloy, and stainless steel can be used. The metal powder comprised by these can be used suitably. These metal powders may be used alone or in combination of two or more. Thus, the granulated powder containing a metal powder can be used as a manufacturing raw material of a molded object and a metal sintered compact, for example so that it may mention later.

  Although the average particle diameter of the raw material particles is not particularly limited, for example, it is preferably 1 to 20 μm, more preferably 2 to 17 μm, and further preferably 3 to 15 μm. By using such raw material particles having a relatively small particle size, granulated particles (granulated powder) having a small particle size according to the particle size can be obtained. Such a granulated powder has a particularly high filling property in a mold, so that a high-density molded body and a sintered body can be produced. That is, the present invention can be applied particularly effectively when granulated particles are produced using such relatively small raw material particles.

In addition, although the average particle diameter of the raw material particles may be lower than the lower limit value, the shape action of the raw material particles becomes strong, the raw material particles are easily aggregated, and the aggregate may be mixed in the raw material powder.
Also, the true density of the raw material powder is not particularly limited, for example, is preferably from 6~14g / cm ^3, more preferably from 6 to 12 g / cm ^3, in the range of 7~10g / cm ³ Is more preferable. When the true density of the raw material powder is within the above range, the raw material powder can efficiently reach the spray zone in the second step described later. As a result, it is possible to efficiently perform granulation and obtain a granulated powder having a narrow particle size distribution width. Moreover, when the true density of the raw material powder is a value within the above range, the obtained granulated powder is heavy and has good fluidity and is suitable for manufacturing a molded body.

  Among such raw material powders, as the metal powder, for example, those manufactured by an atomizing method (for example, a water atomizing method, a gas atomizing method, a high-speed rotating water atomizing method, etc.), a reduction method, a carbonyl method, or a pulverization method are used. However, it is preferable to use those produced by the atomizing method. Since the metal powder produced by the atomizing method has a spherical shape close to a true sphere, excellent dispersibility and fluidity are imparted to the granulated powder obtained from the metal powder. For this reason, when the granulated powder is filled in the mold, the filling property can be improved, and a molded body having a complicated shape can be easily formed.

  By the way, in the water atomization method, a metal powder is produced by bringing a molten metal obtained by melting a metal into contact with water, so that a metal oxide is easily formed on the surface. When the raw material powder is a metal powder having a metal oxide on such a surface, the binder of the binder-coated particles produced in this step preferably contains a reducing agent capable of reducing the metal oxide. . The granulated powder produced using such binder-coated particles undergoes a treatment that causes the metal oxide and the reducing agent to react, thereby causing the metal oxide and the reducing agent to react with each other. The rate will be low.

Examples of the treatment for reacting the metal oxide with the reducing agent include a method of heating them.
In addition, as will be described in detail later, when a granulated powder produced using the binder-coated particles containing the reducing agent as described above is molded to obtain a molded body, and this molded body is fired to obtain a sintered body. The metal oxide and the reducing agent can be reacted by heat applied during the firing process. As a result, the sintered body finally obtained has a high quality with a low content of metal oxide.

In addition, since the reducing agent is included in the binder that coats the metal particles, the reducing agent can be reliably held near the surface of the metal particles, and the reducing agent can be reliably removed from the vicinity of the surface of the metal particles. Can be prevented.
The binder-coated particles containing such a reducing agent can be obtained by colliding the raw material powder and the binder powder as described above. At this time, by dispersing the reducing agent in the binder powder, the shape of the binder is changed to a film shape covering each metal particle by collision energy. Accordingly, the reducing agent also covers each metal particle. Will be distributed as follows. As a result, the metal oxide and the reducing agent can be present in extremely close positions, and these can be reliably reacted. As a result, almost no metal oxide remains in the finally obtained sintered body.

Examples of the binder include polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), zinc stearate, lithium stearate, calcium stearate, ethylene bisstearamide, ethylene vinyl copolymer, paraffin, wax, sodium alginate, agar, Gum arabic, resin, sucrose, etc. can be used. Among these, polyvinyl alcohol and polyvinyl pyrrolidone are preferable from the viewpoints of strength of bonding, high binder removal property by heating, and low cost. Such a binder may be used individually by 1 type, and 2 or more types may be mixed and used for it.
The binder used in the present invention is not limited to those described above, and any binder that functions as a binder between the raw material particles may be selected as appropriate according to the degree of saponification and the degree of polymerization. Can be used.

[2] Next, the binder-coated powder is rolled and / or fluidized while a solvent capable of dissolving the binder is applied to the obtained binder-coated powder. Thereby, the binder-coated particles are bonded to each other to obtain granulated particles formed by bonding a plurality of raw material particles with the binder (second step).
In the present embodiment, in the second step, first, the binder-coated powder is housed in the processing container 10 of the rolling granulator 1 as described above, and the binder-coated powder is stirred by the blade 20. Roll. In such a state, the solvent in the mist state is supplied by spraying from the spray nozzle 40. As a result, the binder on the surface of the binder-coated particles is once dissolved, and the aggregation of the binder-coated particles is promoted during rolling to obtain granulated particles.

Production of granulated powder by such rolling has been conventionally performed as one of granulation methods.
In a conventional method, a granulated powder is obtained by rolling a raw material powder while applying a binder solution obtained by dissolving a binder in a solvent to the raw material powder.
However, although it depends on the binder composition and the temperature of the solution, generally, the binder solution tends to have high viscosity and low fluidity. For this reason, when the binder solution is applied to the raw material powder, it is difficult to spread the binder solution over the entire raw material powder.

The granulated powder obtained in such a state has a variation in the particle size and apparent density of each granulated particle. For example, the granulated powder is obtained when the molded powder is obtained by filling the granulated powder into a mold. There was a problem that the characteristics of the compacts and the sintered bodies obtained by firing the compacts varied.
In addition, a granulated powder with a wide particle size distribution, that is, a non-uniform particle size, has low fluidity, so it tends to cause uneven filling when filled in a mold, and increases the size variation of the sintered body. I was invited.

On the other hand, in order to ensure the fluidity of the binder solution, the ratio of the solvent in the binder solution was also increased. As a result, the fluidity of the binder solution is improved, but it takes a long time to volatilize and remove the solvent during granulation, resulting in a decrease in the productivity of the granulated powder.
In addition to the method of applying the binder solution to the raw material powder as described above, the mixture of the raw material powder and the powdery binder is put into a rolling granulator, and the mixture is rolled while applying the solvent. Thus, a method of obtaining a granulated powder has also been performed.

  However, since the specific gravity of the binder and the raw material powder are greatly different, uneven distribution occurs in the mixture of the raw material particles and the binder solution at the time of granulation, and the binder content becomes uneven between the granulated particles. There was a problem. For this reason, the obtained granulated powder includes particles that are excessively granulated by aggregation of many raw material particles and particles that are hardly granulated, and the particle size distribution width tends to be widened. there were.

  On the other hand, in the present invention, the surface of the raw material particles is previously coated with a binder before granulation. And the granulated powder is obtained by granulating the binder covering particle | grains obtained in this way by the granulation method accompanied by rolling and a flow, providing the solvent which can melt | dissolve a binder. According to such a method, a granulated powder having a narrow particle size distribution can be efficiently produced.

That is, since the raw material particles are previously coated with the binder, the raw material particles and the binder are dispersed very uniformly. When the binder-coated particles are rolled in this state, granulation is uniformly performed while reliably preventing excessive granulation and non-granulation, and granulated particles having a uniform particle diameter can be obtained.
This is considered to be due to the following reason (phenomenon).

  The binder-coated particles 80 introduced into the processing container 10 gradually move (roll) to the outer peripheral side (side wall 12 side) of the processing container 10 as the blade 20 rotates, and are moved upward by the rotary blade 21. Be jumped up to. The splashed particles descend on the central portion side of the processing container 10 and are rolled by the blade 20 again. When such a series of processes is repeated, a plurality of binder-coated particles 80 are aggregated to form granulated particles.

  In such a granulation process, the binder-coated particles 80 are wetted with a mist solvent sprayed from the spray nozzle 40, and the binder in the binder-coated particles 80 is dissolved to form a plurality of binders. The coated particles 80 aggregate and grow to particles having a predetermined diameter. At this time, since the surface of the raw material particles is previously coated with the binder in the binder-coated particles 80, it is ensured that the binder is unevenly distributed during granulation even if there is a large difference in specific gravity between the raw material particles and the binder. Can be prevented. For this reason, an approximately equal number of binder-coated particles 80 aggregate and grow into particles having an approximately equal particle diameter. Thereby, the granulated powder with which the particle size was equal can be obtained reliably.

Further, in the process of granulation, when the particles being granulated come into contact with the rotating cross screw 30, particles having a large particle size (powder having a high degree of granulation) are crushed. Thereby, excessive granulation is suppressed and the particle size distribution of the granulated powder is controlled to a narrow width.
Moreover, since the surface of the raw material particles is coated with a binder in advance, contact between the raw material particles and air (oxygen) can be prevented during granulation. Thereby, for example, when the raw material particles are made of a metal material, oxidation of the metal material can be prevented, and the composition of the raw material particles in the granulated particles can be prevented from changing unintentionally.

  In the rolling granulator 1 shown in FIG. 1, since the solvent is sprayed and supplied as described above, the solvent can be uniformly distributed throughout the binder-coated particles 80. As a result, the degree of dissolution of the binder becomes uniform in the entire binder-coated particles 80 charged into the processing container 10, and agglomeration occurs when the plurality of binder-coated particles 80 aggregate to grow into granulated particles. The number of binder-coated particles 80 to be made uniform is achieved. As a result, granulated particles having a uniform particle size can be obtained.

In addition, the supply method of a solvent is not limited to the above methods, You may supply by what kind of method.
The solvent may be supplied continuously from the start to the end of the second step, but may be supplied intermittently. Specifically, for example, the solvent may be supplied in the first half of the second step, and the supply of the solvent may be stopped in the second half.
Further, by spraying the solvent from the upper part of the processing container 10, the gas in the processing container 10 forms a swirling flow by the rotating action of the blade 20, and the rise of the binder-coated powder is moderately suppressed. As a result, the opportunity for bonding (collision) between the binder-coated powder and the solvent increases, and the resulting granulated powder has a particularly sharp particle size distribution.

  Examples of the solvent capable of dissolving the binder include inorganic solvents such as water, carbon disulfide, and carbon tetrachloride, methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), Ketone solvents such as cyclohexanone, 3-heptanone, 4-heptanone, methanol, ethanol, n-propanol, isopropanol, n-butanol, i-butanol, t-butanol, 3-methyl-1-butanol, 1-pentanol, Alcohol solvents such as 2-pentanol, n-hexanol, cyclohexanol, 1-heptanol, 1-octanol, 2-octanol, 2-methoxyethanol, allyl alcohol, furfuryl alcohol, phenol, diethyl ether, dipropiol Ethers such as ether, diisopropyl ether, dibutyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), 2-methoxyethanol Solvents, cellosolve solvents such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, aliphatic hydrocarbon solvents such as hexane, pentane, heptane, cyclohexane, methylcyclohexane, octane, didecane, methylcyclohexene, isoprene, toluene, xylene, benzene , Aromatic hydrocarbon solvents such as ethylbenzene and naphthalene, pyridine, pyrazine, furan, pyrrole, thiophene, 2-methylpyridine, 3-methylpyridine Aromatic heterocyclic compounds such as 4-methylpyridine and furfuryl alcohol, amide solvents such as N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), dichloromethane, chloroform, 1,2 -Halogenated solvents such as dichloroethane, trichloroethylene, chlorobenzene, acetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, isobutyl acetate, isopentyl acetate, ethyl chloroacetate, butyl chloroacetate, isobutyl chloroacetate, ethyl formate, isobutyl formate, acrylic acid Ester solvents such as ethyl, methyl methacrylate and ethyl benzoate, amine solvents such as trimethylamine, hexylamine, triethylamine and aniline, nitrile solvents such as acrylonitrile and acetonitrile, nitro Examples include nitro solvents such as rhomethane and nitroethane, and organic solvents such as aldehyde solvents such as acetaldehyde, propionaldehyde, butyraldehyde, pentanal, and acrylic aldehyde, and a mixture of one or more selected from these. Can be used.

The solvent may contain a binder to the extent that the fluidity is not lowered.
The number of rotations per unit time of the blade 20 in the second step (hereinafter simply referred to as “the number of rotations”) is not particularly limited as long as the minimum rolling of the binder-coated powder can be ensured, for example, 50 to 500 rpm. Is preferably about 100 to 300 rpm. When the rotational speed of the blade 20 is a value within the above range, the binder-coated powder can be efficiently rolled and granulated efficiently. Moreover, since a moderate compaction state is obtained, it can be set as the granulated powder with a high apparent density. As a result, it is possible to obtain a granulated powder that is denser and has a particularly narrow particle size distribution width.

  On the other hand, when the rotation speed of the blade 20 is less than the lower limit, rolling and jumping up of the binder coating powder becomes insufficient, which may cause uneven granulation. In addition, the compaction is insufficient, and there is a possibility that the granulated powder has a low apparent density, and the granulated powder does not have a spherical shape and has an irregular shape and poor fluidity. On the other hand, when the rotation speed of the blade 20 exceeds the upper limit, the granulated particles are crushed by the blade 20 and there is a possibility that the amount of powder that does not progress is increased.

Moreover, the rotation speed per unit time of the cross screw 30 in a 2nd process is although it does not specifically limit, For example, it is preferable that it is about 50-3500 rpm, and it is more preferable that it is about 100-3000 rpm. Thereby, particle | grains with a big particle diameter can be crushed and particle diameter can be equalize | homogenized, preventing excessive crushing.
The supply weight of the solvent in the second step is preferably about 5 to 100 g, more preferably about 7 to 70 g, per 1 g of binder in the binder-coated powder (binder-coated particles). Accordingly, the binder in the binder-coated particles 80 can be appropriately dissolved while preventing the binder from being excessively dissolved, and reliable granulation can be achieved.

On the other hand, when the supply weight of the solvent is less than the lower limit, the binder in the binder-coated powder is not sufficiently dissolved, which may cause granulation unevenness. On the other hand, if the supply weight of the solvent exceeds the upper limit value, the binder in the binder-coated powder may be excessively dissolved and the binder may be unevenly distributed.
Although the supply rate of the solvent in the second step is not particularly limited, for example, it is preferably 30 to 1000 g / min, more preferably 50 to 800 g / min, and 100 to 600 g / min. Further preferred. When the supply rate of the solvent is a value within the above range, the particle size distribution of the obtained granulated powder can be made sharper while the binding (granulation) of the binder-coated powder by the binder proceeds evenly. .

On the other hand, when the supply rate of the solvent is less than the lower limit, granulation unevenness may be caused. On the other hand, when the supply rate of the solvent exceeds the upper limit, the binder is excessively dissolved and is likely to be unevenly distributed, and granulation may proceed excessively. As a result, the obtained granulated powder may have a wide particle size distribution.
The treatment time (stirring time) of the second step as described above is not particularly limited, but is preferably 1 to 90 minutes, more preferably 2 to 85 minutes, and 3 to 80 minutes. Is more preferable. Residue of the ungranulated binder-coated powder can be suppressed, and the particle size distribution of the obtained granulated powder can be made sufficiently sharp.

  On the other hand, if the treatment time of the second step is less than the lower limit, a relatively large amount of small particle size powder (such as ungranulated raw material powder) may remain. Even if the process is performed, it may be difficult to make the particle size distribution of the obtained granulated powder sufficiently sharp. On the other hand, when the processing time of the second step exceeds the upper limit, a solvent is directly applied to a powder having a relatively large particle size (a lump of non-flowing powder), which may cause granulation unevenness. is there.

By the first step and the second step as described above, a granulated powder having a narrow particle size distribution can be efficiently produced.
In addition, in this embodiment, although the 2nd process was performed using the rolling granulation apparatus, the fluidized bed granulation apparatus which granulates by a fluid action, and the rolling flow which granulates by a rolling fluid action A granulator may be used.

The granulated powder thus obtained is mainly composed of granulated particles formed by bonding a plurality of raw material particles with a binder. The granulated powder may contain particles other than the granulated particles as described above, such as various additives and ungranulated particles.
The average particle diameter of the granulated particles in the obtained granulated powder is preferably about 40 to 180 μm, more preferably about 45 to 140 μm, and still more preferably about 50 to 100 μm. Thereby, for example, when forming a compact by filling the granulated powder into a molding die, the granulated powder has excellent fluidity and filling properties into the molding die. When the average particle size is less than the lower limit, when the molded product is produced using the granulated powder, the fluidity of the powder is not stable, and the dimensional variation of the sintered product (molded product) may increase. There is sex. On the other hand, when the average particle size exceeds the upper limit, when a molded product is produced using granulated powder, filling unevenness is likely to occur particularly in the production of a small molded product, and the size of the sintered product (molded product). There may be large variations.

By the way, you may make it perform the following 3rd processes with respect to the obtained granulated powder as needed.
In addition, you may have the process of removing a solvent from the obtained granulated powder prior to the 3rd process mentioned later as needed. In this case, unintentional deformation of the granulated particles in the third step described later can be prevented, and the shape of the obtained second granulated particles can be made uniform.
As a method for removing the solvent, for example, a method of volatilizing and removing the solvent by heating the granulated powder, a method of volatilizing and removing the solvent by reducing the pressure around the granulated powder, and the like can be used.

[3] The granulated powder is tumbled and / or fluidized as described above while applying a second solvent capable of dissolving the binder again to the obtained granulated powder. Thereby, the particle size of the granulated particles can be made more uniform. As a result, second granulated particles having a uniform particle size are obtained (third step).
In the present embodiment, in the third step, first, the granulated particles 80a are charged into the processing container 10 of the rolling granulator 1. At this time, you may make it use the same apparatus as the rolling granulation apparatus used at the 2nd process. In this case, after the second step is completed, it is possible to proceed to this step without taking out the obtained granulated particles, so that it is possible to simplify the step by omitting the trouble of replacing the particles. it can.

  The granulated particles 80 a charged into the processing container 10 gradually move (roll) to the outer peripheral side of the processing container 10 as the blade 20 rotates, and are sprung upward by the rotary blade 21. The splashed particles descend on the central portion side of the processing container 10 and are rolled by the blade 20 again. In such a rolling process, the granulated particles 80a are wetted with the second solvent in the mist state sprayed from the spray nozzle 40, and a part of the binder contained in the granulated particles 80a. It dissolves and granulation proceeds again with respect to the granulated powder.

At this time, for example, the granulated particles 80a having a relatively small particle diameter are aggregated and grown. On the other hand, a part of the binder (particularly near the outer surface) melts out of the granulated particles 80a having a relatively large particle size due to the above-mentioned wetting, and a part of the binder-coated particles 80 (raw material particles) are also produced. The particles are separated from the particle 80a and the particle size is reduced. In addition, the granulated particles 80a having a relatively large binder content (small amount of raw material particles) even when the particle size is relatively large are positively moistened to elute the binder solution, and the granulated particles having a relatively small particle size. Aggregates with 80a to grow.
In this way, the granulated particles 80a are further uniformized in particle size and become second granulated particles.

  In the rolling granulator 1 shown in FIG. 1, since the second solvent is sprayed and supplied as described above, the second solvent can be evenly distributed throughout the granulated particles 80a. . Thereby, in the whole granulated particle 80a thrown in in the processing container 10, the extent of a binder melt | dissolves becomes uniform, and the uniformization of the granulated particle 80a will be promoted further. As a result, it is possible to obtain second granulated particles having a particularly uniform particle diameter.

Note that the method of supplying the second solvent is not limited to the method described above, and any method may be used.
The second solvent may be supplied continuously from the start to the end of the third step, but may be supplied intermittently. Specifically, for example, the second solvent may be supplied in the first half of the third step, and the supply of the second solvent may be stopped in the second half.

  Further, by spraying the second solvent from the upper part of the processing container 10, the gas in the processing container 10 forms a swirling flow by the rotating action of the blade 20, and the rise of the granulated particles 80 a is moderately suppressed. . As a result, the opportunity for the granulated particles 80a to come into contact with the second solvent is increased, the particle size of the granulated particles 80a is actively made uniform, and the resulting second granulated powder has a particle size distribution. Is particularly sharp.

  Here, the conditions for rolling and / or flowing the granulated particles 80a in the third step (hereinafter also simply referred to as “conditions of the third step”) are the same as the binder-coated particles 80 in the second step. It is preferably different from the conditions for rolling and / or flowing (hereinafter also simply referred to as “conditions for the second step”). Thus, the conditions of the third step can be set according to the state of the granulated particles 80a, that is, the particle size, the particle size distribution, etc. of the granulated particles 80a, and the second granulation with a sharper particle size distribution. Grain particles can be obtained.

  The conditions of the second step and the third step are the solubility of each solvent (solvent and second solvent) in the binder, the supply amount of each solvent, and each particle (binder-coated particle 80). And at least one of the stirring force (for example, the rotational speed of the blade 20, the stirring time, etc.) when rolling and / or flowing the granulated particles 80a). Each of these conditions strongly contributes to the granulation process of the granulated particles and the second granulated particles, and by appropriately setting these, the particle size distribution of the second granulated particles is efficiently controlled. can do. As a result, the second granulated particles having a sharper particle size distribution can be efficiently obtained.

In addition, after completion | finish of a 2nd process, the obtained granulated particle 80a is taken out, particle diameters, such as a particle size and a particle size distribution, of the granulated particle 80a are measured, Based on this measurement result, a 3rd process It is preferred to determine the conditions. Thereby, the 2nd granulated particle with a sharp particle size distribution can be obtained.
Specifically, for example, when obtaining the second granulated particle having a particle diameter smaller than that of the granulated particle, in the third step, the binder-coated particle 80 in the binder-coated particle 80 is more than the solvent used in the second step. Using the second solvent having a high solubility in the binder, supplying the second solvent in a larger amount than in the second step, or stirring force when rolling and / or flowing the granulated particles in the second step Larger than that.

On the other hand, when obtaining the second granulated particles having a particle size larger than that of the granulated particles, a second solvent having a lower solubility in the binder in the binder-coated particles 80 than the solvent used in the second step is used. Or, the second solvent may be supplied in a smaller amount than in the second step, or the stirring force for rolling and / or flowing the granulated particles may be smaller than in the second step.
In addition, as a 2nd solvent used at a 3rd process, the various solvent quoted at the said 2nd process can be used. The second solvent may contain a binder to the extent that the fluidity is not lowered.

  The number of rotations of the blade 20 in the specific third step is not particularly limited as long as it can ensure a minimum for the powder rolling operation, but is preferably about 100 to 700 rpm, for example, about 150 to 600 rpm. Is more preferable. When the rotational speed of the blade 20 is within the above range, the granulated powder can be efficiently rolled and granulated efficiently. Moreover, since a moderate compaction state is obtained, it can be set as the 2nd granulated powder with a high apparent density. As a result, it is possible to obtain a second granulated powder that is denser and has a particularly narrow particle size distribution width.

On the other hand, when the rotation speed of the blade 20 is less than the lower limit value, powder rolling and splashing are insufficient, which may cause granulation unevenness. On the other hand, when the rotation speed of the blade 20 exceeds the upper limit, the granulated particles are crushed by the blade 20 and there is a possibility that the amount of powder that does not progress is increased.
The supply weight of the second solvent in the third step is preferably about 5 to 200 g, more preferably about 10 to 150 g, per 1 g of binder in the granulated powder (granulated particles). Thereby, it is possible to achieve reliable granulation by appropriately dissolving the binder while preventing excessive dissolution of the binder in the granulated particles 80a.

On the other hand, when the supply weight of the second solvent is less than the lower limit, the binder in the granulated powder is not sufficiently dissolved, which may cause uneven granulation. On the other hand, when the supply weight of the second solvent exceeds the upper limit, the binder in the granulated powder is excessively dissolved, and the binder may be unevenly distributed.
Although the supply rate of the second solvent in the third step is not particularly limited, for example, it is preferably 3 to 300 g / min, more preferably 4 to 290 g / min, and 5 to 280 g / min. More preferably. When the supply rate of the second solvent is a value within the above range, the particle size distribution of the second granulated powder obtained while the homogenization of the particle size of the granulated particles 80a proceeds uniformly with the second solvent. Can be made sharper. That is, the particle diameter of the obtained second granulated particles can be made more uniform.

On the other hand, when the supply rate of the second solvent is less than the lower limit, the second solvent is not sufficiently supplied, and for example, a powder having a relatively small particle size may not be easily granulated. On the other hand, when the supply rate of the second solvent exceeds the upper limit, the second solvent is supplied excessively, and the shape of the obtained second granulated particles may become non-uniform.
Further, when obtaining the second granulated powder, it is preferable that the supply rate of the second solvent to the granulated powder is gradually changed as time passes. Thereby, the shape of the obtained second granulated particles can be made more uniform. In this case, the supply speed may be changed continuously or may be changed intermittently.

  The treatment time (stirring time) of the third step as described above is not particularly limited, but is preferably 5 to 180 minutes, more preferably 10 to 170 minutes, and 15 to 160 minutes. Is more preferable. When the treatment time of the third step is less than the lower limit value, it is not possible to sufficiently granulate the small particle size powder, and the particle size distribution of the obtained second granulated powder is sufficiently sharp. Can be difficult to do. On the other hand, if the processing time of the second step exceeds the upper limit, the effect of uniformizing the particle size of the granulated particles 80a by granulation cannot be obtained any more.

According to the third step as described above, in the rolling granulation method in which the width of the particle size distribution tends to be wide, a dense granulated powder (second granulated powder) having a narrow particle size distribution is obtained. Is possible. This granulated powder is heavy and fluid, and can be suitably used for the production of a molded body.
The average particle diameter of the second granulated particles in the obtained second granulated powder is not particularly limited, but when used for the production of a molded body as described later, it is preferably 40 to 180 μm, More preferably, it is 45-140 micrometers, and it is still more preferable that it is 50-100 micrometers. Thereby, it is possible to more surely make the particle diameter of the obtained second granulated particles uniform. When the average particle size is less than the lower limit, in the case of producing a molded body, the fluidity of the powder is not stable, and the dimensional variation of the sintered body (molded body) may increase. On the other hand, when the average particle diameter exceeds the upper limit, particularly in the production of a small molded article, filling unevenness is likely to occur, and the dimensional variation of the sintered body (molded article) may increase.

  In addition, the content of the binder in the second granulated powder is not particularly limited, but the second granulated powder (the finally obtained granulated powder) is used for the production of a molded body as described later. Is preferably 0.2 to 2.0% by weight, more preferably 0.3 to 1.8% by weight. Thereby, the 2nd granulated powder obtained has the outstanding characteristic. For example, if the content is less than the lower limit, when producing a molded body as described later, granulation is insufficient and the fluidity of the powder is not stable, and the dimensional variation of the sintered body (molded body). May become large. Moreover, there is a possibility that sufficient molded body strength cannot be obtained. On the other hand, if the content exceeds the upper limit, the porosity of the obtained sintered body (molded body) increases, and the mechanical strength and dimensional stability may be reduced.

Further, the density of the second granulated powder is not particularly limited, but when the second granulated powder (the finally obtained granulated powder) is used for the production of a molded body as described later, it is preferably an apparent density of 1.8~6.0g / cm ^3, and more preferably 2.0~5.5g / cm ³ or more. Thereby, the 2nd granulated powder obtained has the outstanding characteristic. For example, when the apparent density of the second granulated powder is a value within the above range, a molded body having a sufficiently high density and excellent mechanical properties such as tensile strength and hardness, corrosion resistance, and magnetic properties is obtained. Can be obtained. In addition, the molding density can be sufficiently increased, the dimensional change rate during sintering can be sufficiently reduced, and the dimensional accuracy of the molded body can be sufficiently increased.
The granulated powder of the present invention (second granulated powder) contains additives such as plasticizers, dispersants, surfactants, lubricants, etc. as other components depending on the application. It may be. In such a case, for example, the granulated powder can be suitably produced by including the above components in the raw material powder, the binder solution or the like.

The use of the granulated powder of the present invention is not particularly limited. For example, the production of a molded body containing the granulated powder, in particular, the sintered body obtained by sintering the molded body containing the granulated powder. It can use suitably for manufacture.
The manufacturing method of a molded object is not specifically limited, For example, it can carry out by various molding methods, such as a compacting (compression molding) method, a metal powder injection molding (MIM: Metal Injection Molding) method, and an extrusion molding method.

Hereinafter, as an example, production of a molded body (sintered body) by a compacting method will be described.
<Molding>
First, using the granulated powder of the present invention as described above, it is molded by a press molding machine to produce a molded body having a desired shape and size.
It should be noted that the shape and size of the molded body to be manufactured is determined in consideration of the shrinkage due to subsequent degreasing and sintering.

<Degreasing treatment>
The molded body obtained in the above-described molding process is subjected to a degreasing process (debinding process) to obtain a degreased body.
The degreasing treatment is not particularly limited, but it is a non-oxidizing atmosphere, for example, in a vacuum or under reduced pressure (for example, 1 × 10 ⁻¹ to 1 × 10 ⁻⁶ Torr), or nitrogen gas, argon gas, hydrogen gas, ammonia decomposition The heat treatment is performed in a gas such as a gas.

In this case, the heat treatment conditions vary slightly depending on the decomposition start temperature of the binder, etc., but are preferably about 100 to 750 ° C. for about 0.5 to 40 hours, more preferably about 150 to 700 ° C. for 1 to 24 hours. It is said to be about.
Further, degreasing by such heat treatment may be performed in a plurality of steps (stages) for various purposes (for example, for shortening the degreasing time). In this case, for example, a method in which the first half is degreased at a low temperature and the second half at a high temperature, a method in which low temperature and high temperature are repeated, and the like can be mentioned.
The binder may not be completely removed by the degreasing process. For example, a part of the binder may remain when the degreasing process is completed.

<Baking>
The degreased body obtained in the degreasing process described above is fired and sintered in a sintering furnace to obtain a desired sintered body.
By this firing, the metal powder constituting the granulated powder diffuses, grows grains, and becomes crystal grains. As a whole, a dense sintered body having a high density and a low porosity can be obtained.

  Although the firing temperature at the time of firing varies slightly depending on the composition of the granulated powder and the like, for example, it is preferably 900 to 1500 ° C., more preferably 1000 to 1450 ° C. When the firing temperature is less than the lower limit, the diffusion and granulation of the granulated powder do not proceed sufficiently, the porosity of the molded product finally obtained is increased, and sufficient mechanical strength cannot be obtained. there is a possibility. On the other hand, when the firing temperature exceeds the upper limit, thermal deformation tends to occur, and the dimensional accuracy of the finally obtained sintered body tends to decrease.

The firing time is preferably about 0.5 to 8 hours, and more preferably about 1 to 5 hours.
The firing atmosphere is not particularly limited, but is preferably a reduced pressure (vacuum) or non-oxidizing atmosphere. Thereby, characteristic deterioration due to metal oxidation can be prevented.
A preferable firing atmosphere is a reduced pressure (vacuum) of 1 Torr or less (more preferably 1 × 10 ⁻² to 1 × 10 ⁻⁶ Torr), or an inert gas atmosphere such as nitrogen gas or argon gas of 1 to 760 Torr, or A hydrogen gas atmosphere of 1 to 760 Torr is preferable.

Note that the firing atmosphere may change during firing. For example, first, the pressure is reduced to 1 × 10 ⁻² to 1 × 10 ⁻⁶ Torr (vacuum), and can be switched to the inert gas as described above.

Moreover, you may perform baking by two steps or more. For example, primary firing and secondary firing with different firing conditions can be performed. In this case, the firing temperature of the secondary firing can be higher than the firing temperature of the primary firing.
The sintered body obtained as described above may be used for any purpose.
The relative density of the sintered body obtained as described above varies depending on the application and the like, but is preferably 93% or more, and more preferably 95% or more.

Further, the porosity of the sintered body is not particularly limited, but is preferably 7% or less, and more preferably 5% or less. If the porosity exceeds 7%, the mechanical strength may decrease.
As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.

  For example, in the above-described embodiment, the processing for equalizing the particle size of the granulated powder has been described as having the third step. However, the same processing as the third step is performed once after the third step. This may be done. That is, as a process for equalizing the particle size of the granulated powder, the fourth, fifth,... Step may be included in addition to the third step. Thereby, the dispersion | variation in the particle size of the granulated powder obtained can be suppressed more. In this case, an arbitrary treatment is performed between the steps for homogenizing the particle diameter, such as between the third step and the fourth step or between the fourth step and the fifth step. It can be carried out.

Further, during the transition from the second process to the third process, changes in various conditions such as the processing temperature may be continuous or intermittent.
Moreover, in embodiment mentioned above, after manufacturing binder coating powder, this was processed and the granulated powder was obtained, However, Binder coating powder may be prepared previously.
Moreover, the apparatus used for the manufacturing method of the granulated powder of this invention is not limited to the thing of embodiment mentioned above.
For example, in the said embodiment, although the 3rd process was performed using the rolling granulation apparatus, the fluidized bed granulation apparatus which granulates by a fluid action, and the rolling flow which granulates by a rolling fluid action A granulator may be used.

1. Production of granulated powder (Example 1)
<1A> First, 25 kg of stainless steel SUS-316L powder (manufactured by Epson Atmix Co., Ltd., true density 7.98 g / cm ³ ) having an average particle diameter of 7.6 μm manufactured by a water atomizing method is prepared as a raw material powder. did.

<2A> On the other hand, as a binder, 150 g of polyvinylpyrrolidone (manufactured by BASF) powder was prepared and mixed with raw material powder to obtain a mixture.
<3A> Next, this mixture was put into a vibration mill and vibrated to obtain a binder-coated powder in which the surface of SUS-316L particles was coated with polyvinylpyrrolidone (first step). The energy imparted to the mixture by the vibration mill was 8.4 × 10 ⁴ J / kg per kg of SUS-316L powder.
<4A> Next, this binder-coated powder was put into a processing container of a tumbling granulator (manufactured by POWREC, VG-25). Then, while spraying ethanol (solvent) from the spray nozzle toward the binder coating powder in the processing container, the binder coating powder was rolled and granulated under the following granulation conditions to obtain a granulated powder (No. 1). Step 2).

<Granulation conditions>
・ Blade rotation speed: 200rpm
・ Cross screw speed: 250rpm
・ Supply weight of solvent: 3.75 kg (25 g per 1 g of binder)
・ Solvent supply rate: 535 g / min ・ Granulation time: 7 minutes

(Example 2)
A granulated powder was obtained in the same manner as in Example 1 except that a step of drying the granulated powder was provided between the step <3A> and the step <4A>.
In addition, the process of drying granulated powder was performed by operating a rolling granulation apparatus for 10 minutes in the state which stopped spraying of the solvent.

(Example 3)
A granulated powder was obtained in the same manner as in Example 1 except that the following step <5A> was added after the step <4A>.
<5A> Next, the obtained granulated powder was again put into a processing container of a rolling granulator. Then, under the following granulation conditions, the granulated powder was rolled while spraying ethanol (second solvent) in the same manner as in the above step <4A> to obtain a granulated powder.

<Granulation conditions>
・ Blade rotation speed: 200rpm
・ Cross screw speed: 250rpm
-Supply weight of second solvent: 2.25 kg (15 g per 1 g of binder)
-Feed rate of the second solvent: 225 g / min-Granulation time: 10 minutes (Example 4)
Same as Example 3 except that the second solvent supply weight, the second solvent supply rate, and the granulation time in step <5A> were the same as in step <4A>. Thus, a granulated powder was obtained.

(Comparative Example 1)
The step <3A> is omitted, and the mixture of the SUS-316L powder and the polyvinylpyrrolidone powder obtained in the step <2A> is directly used in the step <4A>, and the granulation conditions are changed as follows. A granulated powder was obtained in the same manner as in Example 1 except that.
<Granulation conditions>
・ Blade rotation speed: 150rpm
・ Cross screw speed: 3000rpm
・ Supply weight of solvent: 3.75 kg (25 g per 1 g of binder)
Solvent supply rate: 535 g / min Granulation time: 12 minutes (including 5 minutes drying time)

(Comparative Example 2)
A granulated powder was obtained in the same manner as in Comparative Example 1 except that the blade rotation speed was 450 rpm.
(Comparative Example 3)
<1B> First, the same raw material powder as in the above step <1A> was prepared.
<2B> On the other hand, a binder solution was prepared as follows. First, polyvinylpyrrolidone (manufactured by BASF Corp.) was prepared as a binder, and ethanol was prepared as a solvent. And 150 g of polyvinyl pyrrolidone was dissolved in 3.75 kg of solvent to obtain a binder solution.

<3B> Next, the raw material powder obtained in the step <1B> was put into a processing container of a tumbling granulator (manufactured by Paulec Co., Ltd., VG-25). Then, the raw material powder is rolled and granulated under the following granulation conditions while spraying the binder solution obtained in the step <2B> from the spray nozzle toward the raw material powder in the processing container, and the granulated powder Got.
<Granulation conditions>
・ Blade rotation speed: 150rpm
・ Cross screw speed: 3000rpm
・ Granulation time: 58 minutes (including drying time of 5 minutes)

2. Evaluation The particle size of the granulated powder obtained in each Example and each Comparative Example was measured with a shaker (vibrating sieving machine). The particle size distribution of the obtained granulated powder is shown in FIG. In addition, in FIG. 2, the particle size distribution of Example 2 and Comparative Examples 1-3 is shown as a representative.
As is clear from FIG. 2, the granulated powder of Example 2 had a very narrow particle size distribution.
Further, from the measurement results of the particle size, the granulated powder obtained in each Example and each Comparative Example has (1) a particle size of less than 40 μm, (2) a particle size of 40 μm or more and less than 180 μm, and (3) a particle size of 180 μm or more. The occupancy at three levels was calculated.
And the calculation result was evaluated in accordance with the following criteria.

<Evaluation criteria>
(Double-circle): The occupation rate of the level of (2) is 90% or more.
○: The occupation ratio at the level of (2) is 75% or more and less than 90%.
(Triangle | delta): The occupation rate of the level of (2) is 60% or more and less than 75%.
X: The occupation ratio of the level of (2) is less than 60%.
The results of calculation and evaluation are shown in Table 1.

As is clear from Table 1, each of the granulated powders of each Example had a high occupation ratio at the level (2) and a narrow particle size distribution width, that is, a uniform particle size. In particular, the tendency is remarkable in Examples 2 to 4.
On the other hand, the granulated powder of each comparative example had a wide particle size distribution and nonuniform particle size.

It is a schematic diagram which shows the structure of the granulation apparatus used in the manufacturing method of the granulated powder of this invention. It is a graph which shows the particle size distribution of Example 2 and Comparative Examples 1-3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rolling granulator 10 ... Processing container 11 ... Bottom part 110 ... Through hole 12 ... Side wall part 13 ... Cover part 130 ... Through hole 20 ... Blade 21 ... Rotary blade 22 ... Rotation Drive shaft 23 …… Base 30 …… Cross screw 31 …… Rotation drive shaft 40 …… Spray nozzle 80 …… Binder coated particles 80a …… Granulated particles

Claims (14)

A first step of preparing a plurality of binder-coated particles formed by coating the surface of the raw material particles with the binder by colliding the raw material particles with binder particles composed of the binder;
The binder-coated particles are bonded to each other by rolling and / or flowing the plurality of binder-coated particles while applying a solvent capable of dissolving the binder to the plurality of binder-coated particles. It has a 2nd process of obtaining the granulated particle containing the said raw material particle, The manufacturing method of the granulated powder characterized by the above-mentioned. The granulated powder production according to claim 1, wherein the collision between the raw material particles and the binder particles is performed so that a collision energy is 2 × 10 ⁴ to 2 × 10 ⁵ J / kg per kg of the raw material particles. Method.   The method for producing a granulated powder according to claim 1 or 2, wherein in the first step, the weight of the binder particles is 0.5 to 30 g per kg of the raw material particles.   In the said 2nd process, the said solvent is a manufacturing method of the granulated powder in any one of Claim 1 thru | or 3 provided so that it may become 5-100g per 1g of said binders.   In the said 2nd process, the said solvent is a manufacturing method of the granulated powder in any one of Claim 1 thru | or 4 provided by spraying.   After the second step, the granulated particles are rolled and / or flowed while applying a second solvent capable of dissolving the binder to the granulated particles, whereby the particle size of the granulated particles The method for producing a granulated powder according to claim 1, further comprising a third step of obtaining a second granulated particle by homogenizing the particles.   The structure according to claim 6, wherein a condition for rolling and / or flowing the binder-coated particles in the second step is different from a condition for rolling and / or flowing the granulated particles in the third step. A method for producing granular powder.   The two conditions are the solubility of the solvent and the second solvent in the binder, the supply amount of the solvent and the second solvent, and the stirring force when rolling and / or flowing, respectively. The method for producing a granulated powder according to claim 7, which is at least one of the following.   The method for producing a granulated powder according to any one of claims 6 to 8, further comprising a step of removing the solvent from the granulated particles between the second step and the third step.   The method for producing a granulated powder according to any one of claims 6 to 9, wherein in the third step, the second solvent is applied by spraying.   11. The method for producing a granulated powder according to claim 6, wherein an average particle diameter of the second granulated particles is 40 to 180 μm.   The method for producing a granulated powder according to any one of claims 1 to 11, wherein an average particle diameter of the granulated particles is 40 to 180 µm.   The method for producing a granulated powder according to any one of claims 1 to 12, wherein an average particle diameter of the raw material particles is 1 to 20 µm.   The method for producing a granulated powder according to any one of claims 1 to 13, wherein the raw material particles are metal particles.

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