JP6855790B2 - Granulation powder, manufacturing method of granulated powder and manufacturing method of sintered body - Google Patents

Description

The present invention relates to a granulated powder, a method for producing a granulated powder, and a method for producing a sintered body.

As a method for molding a metal powder, a compression molding method is known in which a granulated powder containing a metal powder and an organic binder is filled in a predetermined molding mold and compressed to obtain a molded body having a predetermined shape. There is. The obtained molded product undergoes a degreasing treatment for removing an organic binder and a firing treatment for sintering a metal powder to become a metal sintered body. Such a technique is one of powder metallurgy techniques, and has become widespread in many industrial fields in recent years because it is possible to mass-produce metal sintered bodies having complicated shapes depending on the shape of the molding die.

For example, Patent Document 1 discloses a granulated powder obtained by granulating a metal powder and an organic binder containing polyvinyl alcohol or a derivative thereof, waxes and a nonionic surfactant. Further, Patent Document 2 discloses a granulated powder obtained by granulating a metal powder, a graphite powder, and a binder composed of at least one of cellulose, a higher fatty acid and a wax. In the compression molding method, it is first necessary to fill the molding die with these granulated powders as closely as possible. Therefore, the fluidity is improved by granulating the mixture of the metal powder and the binder into particles larger than the metal powder.

Japanese Unexamined Patent Publication No. 2011-190475 Japanese Unexamined Patent Publication No. 2008-189993

By the way, such a granulated powder has a problem that characteristics such as fluidity are changed by absorbing moisture from the binder. When such a change occurs, it is not possible to produce a high quality metal sintered body.

Further, when the granulated powder is molded and fired to obtain a metal sintered body, there is also a problem that a large amount of binder-derived substances that cannot be completely removed remain. Such a residue also causes a deterioration in the quality of the metal sintered body.

An object of the present invention is a granulated powder capable of producing a high-quality sintered body, a method for producing a granulated powder capable of efficiently producing such a granulated powder, and baking capable of producing a high-quality sintered body. The purpose is to provide a method for producing a body.

The above object is achieved by the following invention.
The granulated powder of the present invention is a metal powder and
Polyvinyl alcohol and at least one in which moisture absorbing resin of polyvinyl pyrrolidone, and the hygroscopic melting point than low and the hygroscopicity resin hygroscopic than resin rather high, and a binder containing a high melting point component forming a fibrous, the ,
Have,
The hygroscopicity of the high melting point component is 20% or less of the hygroscopicity of the hygroscopic resin.
The content of the hygroscopic resin with respect to the content of the melting point component is 0.2 or more and 4 or less in terms of mass ratio.
The mass ratio of the binder to the metal powder Ri der 0.5 mass% 0.01 mass% or more,
The average particle size is 20 μm or more and 100 μm or less .

As a result, the amount of the binder used can be reduced, so that the fluidity of the granulated powder due to the binder absorbing moisture is lowered, the quality of the sintered body is lowered due to the residue derived from the binder, and the shrinkage rate of the molded body is reduced. A granulated powder that can be kept to a minimum and can produce a high quality sintered body is obtained.
Further, this makes it possible to further enhance the binding force between the particles of the metal powder by the binder. That is, the fibrous melting point component straddles the adjacent particles of the metal powder, so that the particles of the granulated powder are more strongly reinforced. Therefore, even if the amount of the binder used is particularly small, the particles of the granulated powder are less likely to collapse and have high fluidity.

In the granulated powder of the present invention, the apparent density is preferably 30% or more of the true density of the material constituting the metal powder.

As a result, it is possible to suppress the occurrence of problems due to the large amount of binder. That is, the decrease in the fluidity of the granulated powder due to the moisture absorption of the binder, the decrease in the dimensional accuracy of the molded product and the sintered body, and the decrease in the quality of the sintered body due to the residue derived from the binder should be minimized. Can be done.

In the granulated powder of the present invention, the average diameter of the fibrous melting point component is preferably 1 nm or more and 300 nm or less.

In the granulated powder of the present invention, the average length of the fibrous melting point component is preferably 50 nm or more and 500 μm or less.

As a result, even if the total amount of the binder is small, the particles of the metal powder can be firmly bonded to each other. As a result, the total amount of the binder can be reduced, and the degree of defects due to the large amount of the binder can be reduced.

In the granulated powder of the present invention, the melting point component is preferably cellulose.
As a result, the high melting point component has a high tensile strength, so that a binder capable of firmly binding the particles of the metal powder to each other can be obtained even in a small amount. As a result, the amount of binder used can be effectively reduced.

In the granulated powder of the present invention, the melting point component is preferably derived from a plant.
As a result, the high melting point component can be extracted from the plant, which is a sustainable resource, so that the environmental load in the production of the granulated powder can be reduced.

In the granulated powder of the present invention, the average particle size of the granulated powder is preferably 3 times or more and 10 times or less the average particle size of the metal powder.

The granulated powder of the present invention is preferably subjected to a firing treatment for sintering the metal powder.

Method for producing a granulated powder of the present invention, polyvinyl alcohol and at least one in which moisture absorbing resin of polyvinyl pyrrolidone, and than said hygroscopic resin rather high melting point than and the moisture absorbing resin has a low hygroscopic property, fiber high melting point component forming the Jo, a step of preparing a binder, the binder solution containing containing,
A step of obtaining a granulated powder in which the mass ratio of the binder to the metal particles is 0.01% by mass or more and 0.5% by mass or less by binding the metal particles to each other using the binder solution.
Have a,
The hygroscopicity of the high melting point component is 20% or less of the hygroscopicity of the hygroscopic resin.
The content of the hygroscopic resin with respect to the content of the melting point component is 0.2 or more and 4 or less in terms of mass ratio.
The average particle size of the granulated powder is 20 μm or more and 100 μm or less .
Thereby, the granulated powder of the present invention can be efficiently produced.

The method for producing a sintered body of the present invention includes a step of molding the granulated powder of the present invention to obtain a molded body.
The step of firing the molded product to obtain a sintered body and
It is characterized by having.
As a result, a high-quality sintered body can be produced.

It is sectional drawing which shows one granulated particle included in the embodiment of the granulated powder of this invention.

Hereinafter, the granulated powder of the present invention, the method for producing the granulated powder, and the method for producing the sintered body will be described in detail based on a preferred embodiment based on the accompanying drawings.

<Granulated powder>
First, an embodiment of the granulated powder of the present invention will be described.

FIG. 1 is a cross-sectional view showing one granulated particle included in the embodiment of the granulated powder of the present invention.
The granulated particles 1 shown in FIG. 1 include a plurality of metal particles 51, and the binder 52 is interposed between the metal particles 51 to form a spherical shape as a whole. In the present specification, an aggregate of a plurality of metal particles 51 is referred to as a "metal powder", and an aggregate of a plurality of granulated particles 1 is referred to as a "granulated powder".

In the granulated particles 1 shown in FIG. 1, the binder 52 is interposed between the metal particles 51 and binds to each other, and is present so as to cover at least a part of the surface of each metal particle 51. As a result, each metal particle 51 is in a state of being dispersed in the matrix of the binder 52.

The binder 52 contains a water-soluble resin 522 (water-soluble polymer material) and a melting point component 521. The water-soluble resin 522 is a water-soluble resin. Further, the high melting point component 521 is a component having a lower water solubility than the water-soluble resin 522 and a higher melting point than the water-soluble resin 522.

In the granulated particles 1, the mass ratio of the binder 52 to the metal powder is 0.01% by mass or more and 0.5% by mass or less.

In such granulated particles 1, the mass ratio of the binder 52 to the metal powder is sufficiently suppressed. Therefore, according to the granulated powder containing the granulated particles 1, it is possible to suppress the occurrence of defects due to the large amount of the binder 52. That is, the amount of the binder 52 that comes into contact with the outside air is reduced, and even if the binder 52 absorbs moisture, the amount of moisture absorbed is naturally reduced, so that it is possible to suppress the decrease in the fluidity of the granulated particles 1 due to the moisture absorption. At the same time, since the residue after firing of the granulated particles 1 is naturally reduced, the deterioration of the quality of the sintered body due to the residue derived from the binder 52 can be minimized. Therefore, a high-quality sintered body can be efficiently produced. Further, when the molded product obtained by molding the granulated particles 1 is degreased and fired, the shrinkage rate of the molded product can be minimized. From this point of view as well, it is possible to suppress a decrease in the dimensional accuracy of the sintered body and improve the quality.

Here, the binder 52 contains a water-soluble resin 522 and a high melting point component 521.

Of these, the water-soluble resin 522 dissolves in a solvent such as water when the granulated particles 1 are formed, and exhibits high binding properties. Therefore, even if the amount of the binder 52 used is small, the metal particles 51 are sufficiently bound to each other, which contributes to the efficient production of the granulated particles 1. In addition, since it has high thermal decomposability, the binder 52 can be more reliably decomposed and removed in a shorter time during degreasing or firing.

On the other hand, since the high melting point component 521 has a lower water solubility than the water-soluble resin 522, it is difficult to dissolve in the solvent even when the granulated particles 1 are formed. Therefore, it is taken into the granulated particles 1 while maintaining the solid state, and the high melting point component 521 reinforces the water-soluble resin 522 to more firmly fix the metal particles 51 to each other. As a result, the metal particles 51 can be more sufficiently bound to each other even if the amount of the binder 52 used is small. Then, it is possible to prevent the granulated particles 1 from being chipped and to improve the shape retention of the molded product.

Further, even if the amount of the binder 52 used is particularly small, the granulated particles 1 are less likely to collapse and have high fluidity. Further, the granulated particles 1 are less likely to be destroyed by an external force, an impact, or the like. As a result, the granulated particles 1 are less likely to have a decrease in apparent density, fluidity, and the like. As a result, the molded product has high shape retention, and it is possible to manufacture a high-quality sintered body with good dimensional accuracy and density.

Further, the high melting point component 521 is a component having a higher melting point than the water-soluble resin 522. Therefore, when the molded product obtained by molding the granulated particles 1 is degreased or fired, the water-soluble resin 522 and the high melting point component 521 are sequentially melted and thermally decomposed. That is, the high melting point component 521 is removed later than the water-soluble resin 522. As a result, deformation of the molded product during degreasing or firing is suppressed, and finally a high-quality sintered body with high dimensional accuracy can be obtained.

If the content of the binder 52 is less than the lower limit, the amount of the binder 52 may be too small depending on the particle size of the metal particles 51 and the like, and the shape retention of the granulated particles 1 may be lowered. On the other hand, when the content of the binder 52 exceeds the upper limit value, the amount of the binder 52 is too large depending on the particle size of the metal particles 51 and the like, and a problem occurs due to the large amount of the binder 52 as described above. There is a risk.

Hereinafter, the binder 52 and the metal particles 51 will be described in order.
(binder)
As described above, the binder 52 contained in the granulated particles 1 contains the high melting point component 521 and the water-soluble resin 522.

-High melting point component-
Of these, the high melting point component 521 may be contained in the granulated particles 1 in any form. Examples include granular, fibrous (long or short fibers), scaly and the like. Among these, the high melting point component 521 is preferably in the form of fibers as shown in FIG. By including the fibrous high melting point component 521, the binding force between the metal particles 51 by the binder 52 can be further enhanced. That is, the granulated particles 1 are more strongly reinforced by the fibrous melting point component 521 straddling the adjacent metal particles 51. Therefore, even if the amount of the binder 52 used is particularly small, the granulated particles 1 are less likely to collapse and have high fluidity. Further, the granulated particles 1 are more difficult to be destroyed by an external force, an impact, or the like. As a result, the apparent density, fluidity, and the like of the granulated particles 1 are unlikely to decrease. As a result, it becomes possible to produce a high-quality sintered body having particularly good dimensional accuracy and density.

Further, by reducing the amount of the binder 52 used, it is possible to reduce the residual amount of the substance derived from the binder 52 when the granulated particles 1 are molded and fired to obtain a sintered body. This makes it possible to manufacture a high-quality sintered body in which foreign matter is less likely to be mixed.

Further, by reducing the amount of the binder 52 used, it is possible to reduce the shrinkage rate when the molded product produced by using the granulated particles 1 is fired. Therefore, the dimensional accuracy of the finally obtained sintered body is less likely to decrease, and the time required for degreasing can be shortened.

The constituent material of the high melting point component 521 is not particularly limited as long as it is a material having a lower water solubility than the water-soluble resin 522 and a higher melting point than the water-soluble resin 522. As an example, polyolefins such as polyethylene, polypropylene and ethylene-vinyl acetate copolymer, acrylic resins such as polymethylmethacrylate and polybutylmethacrylate, styrene resins such as polystyrene, polyvinyl chloride, polyvinylidene chloride, polyamide and polyethylene terephthalate. , Polyester such as polybutylene terephthalate, cellulose, lignin, polyether, chitin, chitosan, and various resins such as copolymers thereof.

Of these, the melting point component 521 is preferably cellulose. Examples of the form of this cellulose include fibrous and granular forms. Cellulose solids have high tensile strength. Therefore, by using cellulose as the high melting point component 521, a binder 52 capable of particularly firmly binding the metal particles 51 to each other can be obtained even in a small amount. As a result, the amount of the binder 52 used can be effectively reduced. On the other hand, cellulose initiates thermal decomposition at a relatively low temperature. Therefore, when the molded product containing the binder 52 is subjected to the degreasing step or the firing step, the binder 52 is less likely to remain in the molded product.

Examples of the cellulose used for the high melting point component 521 include cellulose having a molecular formula of (C ₆ H ₁₀ O ₅ ) _n , methyl cellulose, ethyl cellulose, propyl cellulose, acetyl cellulose, nitro cellulose, carboxyl methyl cellulose, and hirodo. Examples thereof include cellulose derivatives such as xymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose, and those containing one or more of these are used.

In addition, the cellulose used exhibits viscosity when dispersed in water. Due to this viscosity, the shape retention of the granulated particles 1 can be improved while suppressing the amount of the binder 52 used.

The viscosity of the aqueous cellulose dispersion having a concentration of 2% by mass is preferably 200 mPa · s or more and 10000 mPa · s or less, and more preferably 500 mPa · s or more and 8000 mPa · s or less. By using cellulose having such a viscosity, when the binder 52 containing such cellulose is dissolved in a solvent, it is possible to obtain an appropriate binding force necessary for efficiently forming the granulated particles 1. Therefore, cellulose having such a viscosity is particularly useful as cellulose to be added to the binder 52.

If the viscosity is lower than the lower limit, the action of cellulose as the high melting point component 521 may decrease. On the other hand, if the viscosity exceeds the upper limit value, the viscosity becomes too high, which may make it difficult to produce the granulated particles 1 having high fluidity.

The viscosity of cellulose is measured at a rotation speed of 60 rpm by a rotary viscosity measuring method for an aqueous dispersion having a concentration of 2% by mass and 25 ° C.

The specific surface area of the cellulose used is not particularly limited ^{, but is preferably 30 m 2} / g or more and 500 m ² / g or less, ^{more preferably 50 m 2} / g or more and 300 m ² / g or less, and 70 m ^{2 or less.} It is more preferably / g or more and 200 m ² / g or less. By using cellulose having such a specific surface area, it becomes easy for the celluloses to form an appropriate three-dimensional network, and the cellulose exhibits sufficient viscosity in a solvent. Therefore, it is possible to obtain an appropriate binding force necessary for efficiently forming the granulated particles 1. Further, since the contact area between the cellulose and the water-soluble resin 522 is necessary and sufficient, the action of the water-soluble resin 522 is further enhanced.

If the specific surface area is less than the lower limit, the action of cellulose as the high melting point component 521 may decrease. On the other hand, if the specific surface area exceeds the upper limit, the viscosity becomes too high when the cellulose is dispersed in the solvent, which may make it difficult to produce the granulated particles 1 having high fluidity.
The specific surface area of cellulose is measured by the BET method.

The melting point component 521 may be artificially produced or derived from an animal, but is preferably derived from a plant. In addition, examples of the form include fibrous and granular forms. Since such a high melting point component 521 is extracted from a plant which is a sustainable resource, it is possible to reduce the environmental load in the production of the granulated particles 1.

Examples of plant-derived materials that can be used as the refractory component 521 include cellulose nanofibers, cellulose nanofibrils, fibrated cellulose, cellulose nanocrystals, cellulose nanopowder, lignin fiber, and lignin powder. Such a plant-derived high melting point component 521 is produced, for example, by subjecting wood or the like to a treatment such as mechanical defibration or acid hydrolysis.

When the form of the high melting point component 521 is fibrous or scaly, the average length thereof is not particularly limited, but is preferably 50 nm or more and 500 μm or less, and more preferably 100 nm or more and 300 μm or less. It is more preferably 1 μm or more and 200 μm or less. By setting the average length of the high melting point component 521 within the above range, the metal particles 51 can be more firmly bonded to each other even if the total amount of the binder 52 is small. That is, the length of the high melting point component 521 is a necessary and sufficient length for enhancing physical properties such as the tensile strength of the binder 52 and for binding the metal particles 51 to each other. As a result, the total amount of the binder 52 can be sufficiently reduced, and the degree of defects due to the large amount of the binder 52 as described above can be reduced.

If the average length of the high melting point component 521 is less than the lower limit, the length may not be sufficient to achieve the above effect depending on the particle size of the metal particles 51 and the like. Further, when the average length of the high melting point component 521 exceeds the upper limit value, the fluidity of the binder 52 decreases depending on the particle size of the metal particles 51 and the like, and the binder 52 is distributed between the metal particles 51. May be difficult.

The average length of the high melting point component 521 is obtained by taking out 100 or more high melting point components 521 contained in the granulated particles 1 and averaging the major axis lengths (the lengths of the axes having the maximum lengths). Is. In measuring the major axis length, a method of photographing 100 or more high melting point components 521 on a flat plate and measuring the major axis length on an image (on a projected image) may be adopted.

The average diameter of the high melting point component 521 is not particularly limited, but is preferably 1 nm or more and 300 nm or less, more preferably 2 nm or more and 200 nm or less, and further preferably 4 nm or more and 100 nm or less. By setting the average diameter of the high melting point component 521 within the above range, the metal particles 51 can be more firmly bonded to each other even if the total amount of the binder 52 is small. That is, the diameter of the high melting point component 521 is a necessary and sufficient diameter for enhancing physical properties such as the tensile length of the binder 52 and for binding the metal particles 51 to each other. As a result, the total amount of the binder 52 can be sufficiently reduced, and the degree of defects due to the large amount of the binder 52 as described above can be reduced.

If the average diameter of the high melting point component 521 is less than the lower limit value, the tensile strength of the high melting point component 521 may be insufficient to achieve the above effect depending on the constituent materials of the high melting point component 521 and the like. Further, when the average diameter of the high melting point component 521 exceeds the upper limit value, the fluidity of the binder 52 decreases depending on the length of the high melting point component 521, the constituent material, etc., and the binder 52 is distributed between the metal particles 51. It may be difficult to make it.

The average diameter of the high melting point component 521 is obtained by taking out 100 or more high melting point components 521 contained in the granulated particles 1 and averaging their minor axis lengths (maximum lengths in the direction orthogonal to the major axis). It is a thing. In measuring the length of the minor axis, a method of photographing 100 or more melting point components 521 on a flat plate and measuring the minor axis length on an image (on a projected image) may be adopted.

The average diameter of the high melting point component 521 is the average value of the maximum thickness when the morphology of the high melting point component 521 is scaly, and the average diameter when it is granular. In the latter case, a value measured by a particle size measuring method such as a laser diffraction method can also be adopted.

Further, the high melting point component 521 may be subjected to surface treatment such as coupling agent treatment, surfactant treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, plasma irradiation treatment and the like, if necessary.

The thermal decomposition temperature of the high melting point component 521 is not particularly limited, but is preferably 200 ° C. or higher and 600 ° C. or lower, and more preferably 250 ° C. or higher and 500 ° C. or lower. Since the thermal decomposition temperature of the high melting point component 521 is within the above range, when the molded product formed by using the granulated particles 1 is degreased and fired, the high melting point component 521 is decomposed at the initial stage of the temperature raising process. It can be suppressed. In addition, it is possible to prevent the high melting point component 521 from remaining without being decomposed when the temperature is raised to a temperature at which the metal particles 51 are sintered during degreasing and firing. As a result, it is possible to suppress the deterioration of the dimensional accuracy of the molded product due to the early decomposition of the high melting point component 521, and to suppress the generation of the residue derived from the high melting point component 521. High quality sintered body can be produced.

The thermal decomposition temperature of the high melting point component 521 is measured by a thermogravimetric / differential thermal measuring device (TG-DTA device).

The ratio of the high melting point component 521 in the binder 52 is not particularly limited, but is preferably 1% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 85% by mass or less, and 30% by mass or more and 70% by mass or more. It is more preferably mass% or less. By setting the ratio of the high melting point component 521 within the above range, the above-mentioned effect by adding the high melting point component 521 can be sufficiently exhibited.

When the ratio of the high melting point component 521 is less than the lower limit value, the above-mentioned effect of adding the high melting point component 521, for example, the granulated particles 1, is sufficiently reinforced depending on the composition of the high melting point component 521 and the like. There is a risk that the effects of increasing the fluidity and increasing the shape retention of the molded product will not be exhibited. On the other hand, if the ratio of the high melting point component 521 exceeds the upper limit value, the ratio of the high melting point component 521 in the binder 52 becomes too high, so that the shape and constituent material of the high melting point component 521 and the components other than the high melting point component 521 may be affected. , The fluidity of the binder 52 is lowered, and it may be difficult to distribute the binder 52 between the metal particles 51. In this case, the fluidity of the granulated particles 1 may decrease, or the moldability of the granulated particles 1 may decrease.

Further, as described above, the high melting point component 521 is a component having a lower water solubility than the water-soluble resin 522 and a higher melting point than the water-soluble resin 522.

Whether or not the water solubility of the high melting point component 521 is lower than that of the water-soluble resin 522 can be evaluated as an alternative depending on the magnitude relationship of the hygroscopicity. Therefore, the fact that the water solubility of the high melting point component 521 is lower than that of the water-soluble resin 522 means that the hygroscopicity of the high melting point component 521 is lower than that of the water-soluble resin 522. At this time, the hygroscopicity of the high melting point component 521 and the hygroscopicity of the water-soluble resin 522 are obtained by methods based on the saturated salt method specified in JIS B 7920: 2000, respectively.

Further, in the hygroscopicity for 24 hours, the hygroscopicity of the high melting point component 521 is preferably 20% or less, more preferably 10% or less, and 5% or less of the hygroscopicity of the water-soluble resin 522. Is even more preferable. As a result, the water-soluble resin 522 is easily dissolved in water and easily develops binding properties, while the high melting point component 521 has sufficient mechanical strength to reinforce the granulated particles 1. Therefore, due to the actions of both, granulated particles 1 having good fluidity and which are hard to collapse even if the total amount of the binder 52 is reduced can be obtained.

Further, the melting point of the high melting point component 521 and the melting point of the water-soluble resin 522 are measured by a thermogravimetric / differential thermal measuring device (TG-DTA device), respectively.

When the high melting point component 521 and the water-soluble resin 522 are, for example, an amorphous resin and there is no melting point, a glass transition point can be adopted as the melting point. This glass transition point is also measured by a thermogravimetric / differential thermal measuring device (TG-DTA device).

The melting point of the high melting point component 521 is preferably 10 ° C. or higher and 170 ° C. or lower, and more preferably 30 ° C. or higher and 100 ° C. or lower, higher than the melting point of the water-soluble resin 522. By using such a high melting point component 521, when the molded product formed by using the granulated particles 1 is degreased and fired, the high melting point component 521 is considerably softened in the initial stage of the temperature rising process. The water-soluble resin 522 can be softened at an early stage. As a result, even if the water-soluble resin 522 is softened, the molded product is less likely to be deformed, and a sintered body having high dimensional accuracy can be finally produced. Further, when the melting point of the high melting point component 521 is too high, it is possible to prevent the residue derived from the high melting point component 521 from being completely removed and remaining.

-Water-soluble resin-
Next, the water-soluble resin 522 (water-soluble polymer material) will be described.

When the binder 52 contains such a water-soluble resin 522, the water-soluble resin 522 is interposed between the refractory component 521 and the metal particles 51, and the binding property between the metal particles 51 can be further enhanced. That is, since the water-soluble resin 522 dissolves in a solvent such as water and exhibits high binding properties as described above, it binds between the high melting point component 521 and the metal particles 51. As a result, the reinforcing function of the granulated particles 1 described above by the high melting point component 521 is enhanced. Then, it is possible to realize the granulated particles 1 that are more difficult to break even when an impact or the like is applied.

Examples of the water-soluble resin 522 include polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, polyacrylamide, poly (meth) acrylic acid, polyamide, polyethylene glycol, starch, gelatin, casein, and the like, and one of them. Alternatively, those containing two or more types are used.

Among these, as the water-soluble resin 522, a resin containing at least one of polyvinyl alcohol and polyvinylpyrrolidone is particularly preferably used. Since these have particularly high binding properties, the granulated particles 1 can be efficiently formed even in a relatively small amount. Therefore, the total amount of the binder 52 can be reduced, and the degree of failure due to the large amount of the binder 52 as described above can be further reduced. In addition, since it has high thermal decomposability, the binder 52 can be reliably decomposed and removed in a short time during degreasing and firing. Therefore, a high-quality sintered body with particularly little residue can be obtained.

Further, as the water-soluble resin 522, one containing polyvinyl alcohol is more preferably used. As a result, the above effect becomes more remarkable.

When polyvinyl alcohol is used, the saponification degree of polyvinyl alcohol is preferably 90 mol% or more and 99 mol% or less. When the saponification degree of polyvinyl alcohol is within the above range, the water-soluble resin 522 and the high melting point component 521 can be mixed more uniformly. As a result, the hygroscopicity of the water-soluble resin 522 is partially increased on a part of the surface of the granulated particles 1, and it is possible to suppress the decrease in the fluidity of the granulated particles 1. Further, since the variation in the characteristics of the granulated particles 1 among the particles is suppressed, the granulated particles 1 having the same characteristics can be obtained.

On the other hand, the degree of polymerization of polyvinyl alcohol is not particularly limited, but is preferably 300 or more and 3000 or less, and more preferably 500 or more and 2500 or less. When the degree of polymerization of polyvinyl alcohol is within the above range, the water-soluble resin 522 and the refractory component 521 can be mixed more uniformly. As a result, the above effect becomes more remarkable.

The total ratio of the content of the high melting point component 521 and the content of the water-soluble resin 522 in the binder 52 is not particularly limited, but is preferably 70% by mass or more, and more preferably 85% by mass or more. preferable. As a result, the actions of both the high melting point component 521 and the water-soluble resin 522 can be sufficiently exerted, and a high-quality sintered body can be finally obtained.

The ratio of the content of the water-soluble resin 522 to the content of the high melting point component 521 is not particularly limited, but is preferably 0.2 or more and 5 or less in terms of mass ratio, and is 0.5 or more and 3.5 or less. It is more preferable to have it, and it is more preferable to have 1 or more and 3 or less. As a result, the balance between the high melting point component 521 and the water-soluble resin 522 is optimized, so that a high-quality sintered body can be finally obtained.

If this ratio is less than the lower limit, the water-soluble resin 522 tends to be insufficient, so that the binding property of the binder 52 may decrease depending on the amount of the binder 52 used. On the other hand, if this ratio exceeds the upper limit value, the water-soluble resin 522 tends to be excessive, so that the ratio of the high melting point component 521 is reduced by that amount, and the effect of reducing the total amount of the binder 52 used is reduced. May be suppressed.

-Other ingredients-
Further, the binder 52 may contain a component (other components) other than the high melting point component 521 and the water-soluble resin 522. The content of other components in the binder 52 is preferably, for example, 10% by mass or less.

Other components include, for example, polyolefins such as polyethylene, polypropylene and ethylene-vinyl acetate copolymer, acrylic resins such as polymethylmethacrylate and polybutylmethacrylate, styrene resins such as polystyrene, polyvinyl chloride and polyvinylidene chloride. , Polyester, Polyethylene terephthalate, Polybutylene terephthalate and other polyesters, polyethers or copolymers thereof, waxes, alcohols, higher fatty acids, fatty acid metals, higher fatty acid esters, higher fatty acid amides, nonionic Examples thereof include surfactants and silicone-based lubricants, and one or a mixture of two or more of these is used.

Among these, as waxes, for example, candelilla wax, carnauba wax, rice wax, wood wax, vegetable wax such as jojoba oil, honey wax, lanolin, animal wax such as whale wax, montane wax, ozokelite, etc. Like mineral waxes such as selecin, paraffin waxes, microcrystallin waxes, natural waxes such as petroleum waxes such as petrolatum, synthetic hydrocarbons such as polyethylene waxes, montan wax derivatives, paraffin wax derivatives, microcrystallin wax derivatives. Examples include synthetic waxes such as modified waxes, hardened waxes, hydrogenated waxes such as hardened castor oil derivatives, fatty acids such as 12-hydroxystearic acid, acid amides such as stearic acid amides, and esters such as phthalate anhydride. Be done.

Examples of alcohols include polyhydric alcohols, polyglycols, polyglycerols and the like, and in particular, cetyl alcohols, stearyl alcohols, oleyl alcohols, mannitol and the like are preferably used.

Examples of higher fatty acids include stearic acid, oleic acid, linoleic acid and the like, and in particular, saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid are preferably used.

Examples of fatty acid metals include lauric acid, stearic acid, succinic acid, stearyl lactic acid, lactic acid, phthalic acid, benzoic acid, hydroxystearic acid, ricinolic acid, naphthenic acid, oleic acid, palmitic acid, and erucic acid. Examples of compounds of higher fatty acids and metals such as Li, Na, Mg, Ca, Sr, Ba, Zn, Cd, Al, Sn, Pb, and Cd include magnesium stearate, calcium stearate, and sodium stearate. , Zinc stearate, calcium oleate, zinc oleate, magnesium oleate and the like are preferably used.

Examples of the nonionic surfactant-based lubricant include electrostripper-TS-2 and electrostripper-TS-3 (both manufactured by Kao Corporation).

Examples of silicone-based lubricants include dimethylpolysiloxane and its modified products, carboxyl-modified silicone, α-methylstyrene-modified silicone, α-olefin-modified silicone, polyether-modified silicone, fluorine-modified silicone, hydrophilic special-modified silicone, and olefin poly. Examples thereof include ether-modified silicone, epoxy-modified silicone, amino-modified silicone, amide-modified silicone, and alcohol-modified silicone.

The mass ratio of the binder 52 to the metal particles 51 is appropriately set according to the constituent materials of the metal particles 51, the components contained in the binder 52, and the like, but is 0.01% by mass or more and 0.5% by mass or less. It is more preferable that it is 0.1% by mass or more and 0.3% by mass or less, and further preferably 0.12% by mass or more and 0.25% by mass or less. By setting the mass ratio of the binder 52 to the metal particles 51 within the above range, the granulated particles 1 in which the total amount of the binder 52 is sufficiently suppressed can be obtained. According to the granulated particles 1, the degree of defects due to the large amount of the binder 52 as described above can be reduced.

If the content of the binder 52 is less than the lower limit, the amount of the binder 52 may be too small depending on the particle size of the metal particles 51 and the like, and the shape retention of the granulated particles 1 may be lowered. As a result, the granulated particles 1 are likely to be chipped, the fluidity of the granulated particles 1 may be lowered, and the shape retention of the molded product may be lowered. On the other hand, when the content of the binder 52 exceeds the upper limit value, the amount of the binder 52 is too large depending on the particle size of the metal particles 51 and the like, and a problem occurs due to the large amount of the binder 52 as described above. There is a risk. That is, the hygroscopicity of the granulated particles 1 is increased to reduce the fluidity, the shrinkage rate of the molded product is increased to reduce the dimensional accuracy of the sintered body, and a large amount of residue derived from the binder 52 remains. There is a risk of

(Metal particles)
The metal particles 51 contained in the granulated particles 1 are not particularly limited, and may be any kind of metal particles 51. Examples of the constituent material of the metal particles 51 include sinterable metal materials used for powder metallurgy, and examples thereof include Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Y. , Zr, Nb, Mo, Pd, Ag, In, Sn, Ta, W and the like, or alloys and intermetallic compounds containing at least one of these.

Further, the metal powder containing the metal particles 51 may be a mixed powder formed by mixing two or more kinds of powders having different compositions from each other, such as metal powder and ceramics (metal oxide, metal nitride, metal carbide, etc.). Metal compound) It may be a mixed powder with a powder.

Among these, examples of the Fe-based alloy include stainless steel, low carbon steel, carbon steel, heat-resistant steel, die steel, high-speed tool steel, Fe-Ni alloy, Fe-Ni-Co alloy and the like.

Examples of Ni-based alloys include Ni-Cr-Fe-based alloys, Ni-Cr-Mo-based alloys, and Ni-Fe-based alloys.

Examples of Co-based alloys include Co-Cr-based alloys, Co-Cr-Mo-based alloys, and Co-Al-W-based alloys.

Examples of Ti-based alloys include alloys of Ti with metal elements such as Al, V, Nb, Zr, Ta, and Mo. Specifically, Ti-6Al-4V and Ti-6Al- 7Nb and the like can be mentioned.

Examples of Al-based alloys include duralumin and the like.
Further, as the ceramic material constituting the ceramic powder, for example, oxide-based materials such as alumina, magnesia, berylia, zirconia, itria, forsterite, steatite, wallastenite, mulite, carbide, ferrite, sialone, and cerium oxide. Examples thereof include ceramic materials, non-oxide ceramic materials such as silicon nitride, aluminum nitride, boron nitride, titanium nitride, silicon carbide, boron carbide, titanium carbide, and tungsten carbide.

The average particle size of the metal powder is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 20 μm or less, and further preferably 3 μm or more and 10 μm or less. A metal powder having such a particle size has a sufficiently high fluidity of the granulated powder while avoiding a decrease in compressibility during molding, so that a sufficiently dense sintered body can be finally produced. Become.

If the average particle size is less than the lower limit, the metal powder tends to aggregate before granulation, the content of the metal powder varies among the particles of the granulated powder, and the compressibility during molding becomes high. It may decrease significantly. On the other hand, if the average particle size exceeds the upper limit, the gaps between the particles of the granulated powder may become too large during molding, resulting in insufficient densification of the finally obtained sintered body. is there.

The average particle size of the metal powder is the particle size when the cumulative mass-based particle size is 50% from the small diameter side in the particle size distribution obtained by the laser diffraction method.

The maximum particle size of the metal powder is preferably about 10 μm or more and 100 μm or less, and more preferably about 10 μm or more and 50 μm or less. By using the metal powder having such a maximum particle size, the fluidity of the granulated powder when molding the granulated powder can be particularly enhanced. As a result, it is finally possible to produce a sintered body having high dimensional accuracy and excellent mechanical properties. That is, the maximum particle size of the metal powder has a great influence on the fluidity of the granulated powder and also has a great influence on the filling property of the metal powder at the time of molding. Therefore, by setting the maximum particle size within the above range, a sintered body having high dimensional accuracy and excellent mechanical properties can be finally obtained.

The maximum particle size of the metal powder is the particle size when the cumulative mass-based particle size is 99.9% from the small diameter side in the particle size distribution obtained by the laser diffraction method.

Further, the average particle size of the metal powder is set to D50, and the particle size when the cumulative particle size based on the mass is 10% from the small diameter side in the particle size distribution obtained by the laser diffraction method for the metal powder is set to D10, and similarly, the small diameter side. When the particle size is D90, (D90-D10) / D50 is preferably 0.5 or more and 5 or less, and more preferably 1.0 or more and 3.5 or less. A metal powder satisfying such conditions makes it possible to make the shape of the granulated powder closer to a true sphere. Therefore, the obtained granulated powder has particularly high fluidity, and the dimensional accuracy and mechanical properties of the finally obtained sintered body are particularly good. Further, since the particle size distribution is optimized, the variation in density during molding can be suppressed, and the variation in residual stress during molding can be suppressed to be small. As a result, the amount of deformation of the molded body due to stress release is suppressed, and finally the dimensional accuracy of the sintered body becomes particularly good.

Such a metal powder may be produced by any method, and for example, by a method such as an atomizing method (water atomizing method, gas atomizing method, high-speed rotating water flow atomizing method, etc.), a reduction method, a carbonyl method, a pulverization method, or the like. The manufactured one can be used.

Of these, as the metal powder, it is preferable to use one produced by the atomizing method. According to the atomizing method, a metal powder having an extremely fine average particle size as described above can be efficiently produced. In addition, it is possible to obtain a metal powder having a uniform particle size with little variation in particle size. Therefore, by using such a metal powder, it is possible to prevent the formation of pores in the sintered body and improve the density.

Further, since the metal powder produced by the atomizing method has a spherical shape relatively close to a true sphere, it is excellent in filling property at the time of molding and also excellent in dispersibility in a binder. Therefore, when the granulated powder is filled in a molding die and molded, the filling property and uniformity can be improved, and a more dense sintered body can be finally obtained.

The use of such granulated particles 1 is not particularly limited, but is preferably used, for example, in the production of a molded product obtained by molding the granulated powder, particularly in the production of a molded product for producing a sintered body.

In addition to the above, the granulated particles 1 may contain various additives such as a solvent (dispersion medium), a rust preventive, an antioxidant, a surfactant, and an antifoaming agent.

(Powder characteristics of granulated powder)
Further, such a granulated powder has a high apparent density (bulk density) because the total amount of the binder 52 is small and the fluidity is high.

Specifically, the ratio of the apparent density of the granulated particles 1 (granulated powder) to the true density of the material constituting the metal particles 51 (metal powder) (hereinafter, abbreviated as "ratio of apparent density". ) Is preferably 30% or more, more preferably 30.5% or more and 45% or less, and further preferably 31% or more and 40% or less. When the ratio of the apparent density is within the above range, it is possible to suppress the occurrence of defects due to the large amount of the binder 52. Therefore, it is possible to prevent the fluidity and the like of the granulated particles 1 from being lowered due to the moisture absorption of the binder 52, and the dimensional accuracy of the molded product and the sintered body being lowered. At the same time, the deterioration of the quality of the sintered body due to the residue derived from the binder 52 can be minimized.

If the ratio of the apparent density is less than the lower limit value, the amount of the binder 52 is large, so that there is a possibility that problems associated therewith may easily occur. On the other hand, when the ratio of the apparent density exceeds the upper limit value, the amount of the binder 52 is small, so that the granulated particles 1 are easily chipped, the filling property of the granulated particles 1 at the time of molding is lowered, and the baking is performed. The quality of the body may deteriorate.

The apparent density of the granulated powder (granulated particles 1) is measured in accordance with the method for measuring the apparent density of metal powder specified in JIS Z 2504: 2012.

Further, the true density of the material constituting the metal particles 51 is calculated based on the elements constituting the metal particles 51 and the composition ratio.

The fluidity of the granulated powder is 15 [seconds / 50 g] or more and 28 [seconds / 50 g] or less, but preferably 18 [seconds / 50 g] or more and 25 [seconds / 50 g] or less, more preferably. Is 20 [seconds / 50g] or more and 24 [seconds / 50g] or less. If the fluidity exceeds the upper limit, the filling property of the granulated powder may not be sufficiently improved when a molded product is obtained using the granulated powder. On the other hand, when the fluidity is lower than the lower limit, when a molded product is obtained using the granulated powder, the frictional force between the granulated particles 1 is reduced, and the shape retention of the molded product is likely to be lowered. There is a risk. As a result, the dimensional accuracy of the sintered body may decrease.

The fluidity of the granulated powder is measured according to the fluidity test method of the metal powder specified in JIS Z 2502: 2012.

The average particle size of the granulated powder is not particularly limited, but is preferably 20 μm or more and 100 μm or less, and more preferably 30 μm or more and 60 μm or less. When the average particle size of the granulated powder is smaller than the lower limit, the fluidity may not be sufficiently increased. On the other hand, when the average particle size of the granulated powder is larger than the upper limit value, the gap between the granulated particles 1 tends to be large, so that the relative density of the sintered body may not be sufficiently increased.

The average particle size of the granulated particles 1 is the particle size when the cumulative mass standard is 50% from the small diameter side in the particle size distribution obtained by the laser diffraction method.

On the other hand, the average particle size of the granulated particles 1 is preferably 3 times or more and 10 times or less the average particle size of the metal particles 51. By setting the average particle size of the granulated particles 1 within the above range, the balance of the particle sizes of the granulated particles 1 and the metal particles 51 is optimized, so that the fluidity of the granulated particles 1 and the metal particles 51 It is possible to achieve both the sinterability of the particles. In addition, the granulated particles 1 are likely to collapse appropriately, and the metal particles 51 are likely to be rearranged at a higher density. As a result, when a molded product is obtained using the granulated particles 1, the shape retention of the molded product becomes better, and a sintered body with high dimensional accuracy can be obtained.

<Manufacturing method of granulated powder>
Next, an embodiment of the method for producing a granulated powder of the present invention will be described.

The method for producing the granulated powder according to the present embodiment includes a step of preparing a binder solution containing a binder 52 containing a water-soluble resin 522 and a high melting point component having a lower water solubility and a higher melting point, and the binder solution. A step of binding the metal particles 51 to each other and granulating the binder 52 so that the content of the binder 52 is 0.01% by mass or more and 0.5% by mass or less. According to such a production method, the above-mentioned granulated particles 1 (granulated powder) can be efficiently produced. Hereinafter, each step will be described in sequence.

[1] First, a binder solution containing a binder 52 containing a water-soluble resin 522 and a melting point component 521 is prepared.

The binder solution is prepared using the binder 52 and a solvent (dispersion medium) for dissolving or dispersing the binder 52. Examples of the solvent include water, alcohols and the like.

[2] Next, the obtained binder solution is used to bind the metal particles 51 to each other for granulation. At this time, if a binder solution is first prepared and then the metal particles 51 are bound to each other using the binder solution, the binder solution can be evenly distributed between the metal particles 51. Therefore, the binder solution is uniformly distributed, and granulated powder having a uniform particle size can be produced. That is, it is possible to efficiently produce granulated powder capable of producing a high-quality sintered body.

Examples of the granulation method include a spray drying method, a rolling granulation method, a fluidized bed granulation method, and a rolling fluidized granulation method.

Of these, in the spray drying method, a slurry (suspension) formed by mixing metal particles 51 and a binder solution is used. Then, the granulated particles 1 are obtained by spray-drying this slurry.

If necessary, any additive such as a rust preventive, an antioxidant, a surfactant, and an antifoaming agent may be added to the slurry.

As described above, granulated particles 1 formed by binding a plurality of metal particles 51 with a binder 52 can be obtained.

Further, the granulated particles 1 thus obtained may be heat-treated, if necessary. As a result, the hygroscopicity of the binder 52 is slightly lowered, so that the granulated particles 1 are less likely to absorb moisture.

The heating temperature at this time is appropriately set according to the composition of the binder 52, and is, for example, about 150 ° C. or higher and 250 ° C. or lower.
The heating time is, for example, about 0.1 hour or more and 3 hours or less.

<Manufacturing method of sintered body>
Next, a method for producing a sintered body using granulated powder (the embodiment of the method for producing a sintered body of the present invention) will be described.

The method for producing a sintered body according to the present embodiment includes a step of molding granulated particles 1 (granulated powder) to obtain a molded body and a step of firing the molded body to obtain a sintered body. According to such a manufacturing method, a high-quality sintered body can be manufactured. Hereinafter, each step will be described in sequence.

(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 product having a desired shape and size. Since the granulated powder of the present invention uses a small amount of binder, it is possible to obtain a molded product having a high filling property of the metal powder. Further, since the filling amount in the molding die is stable, the dimensional accuracy of the molded body can be improved. As a result, a molded product having a high density and high dimensional accuracy can be manufactured, and finally, a sintered body having a high density and high dimensional accuracy can be obtained.

The shape and dimensions of the manufactured molded product are determined in consideration of the amount of shrinkage due to subsequent degreasing and sintering. Further, the molding method is not limited to press molding, and may be extrusion molding, injection molding, hydrostatic pressure molding, or the like.
In addition, the obtained molded product may be subjected to secondary processing as needed.

(Solvent degreasing)
The molded product obtained in the above-mentioned molding step is subjected to a degreasing treatment (degreasing treatment) as necessary to obtain a degreased body. The degreasing treatment is not particularly limited, but is performed in a non-oxidizing atmosphere, for example, under a vacuum or reduced pressure state (for example, 1 × 10 ^-1 to 1 × ^10-6 Torr), or nitrogen gas, argon gas, hydrogen gas, and ammonia decomposition. It is performed by performing heat treatment in a gas such as gas. In this case, the heat treatment conditions are slightly different depending on the decomposition start temperature of the binder and the like, but preferably the temperature is 100 ° C. or higher and 750 ° C. or lower, 0.5 hours or more and 40 hours or lower, and more preferably the temperature is 150 ° C. or higher and 700 ° C. or lower. It is about 1 hour or more and 24 hours or less.
The obtained degreased body may be subjected to secondary processing as needed.

(Baking)
The degreased body obtained in the above-mentioned degreasing step is fired in a baking furnace and sintered to obtain a desired sintered body. By this firing, the metal powder constituting the granulated powder is diffused and granulated, and a dense sintered body having a high density and a low porosity is obtained as a whole.

The firing temperature at the time of firing differs slightly depending on the composition of the granulated powder and the like, but for example, when Fe-based alloy powder is used, it is preferably 1100 ° C. or higher and lower than 1400 ° C., and is 1200 ° C. or higher and 1350 ° C. or lower. Is more preferable.

The maximum temperature holding time during firing is preferably 0.5 hours or more and 5 hours or less, and more preferably 0.75 hours or more and 3 hours or less.

In particular, the granulated powder of the present invention has a low binder content. Therefore, a high-quality sintered body having a small residual amount of the substance derived from the binder, high density, and high dimensional accuracy can be obtained.

The firing atmosphere is not particularly limited, but is preferably a reduced pressure (vacuum) or non-oxidizing atmosphere. As a result, deterioration of characteristics due to oxidation of the metal can be prevented.

The sintered body obtained as described above may be used for any purpose, and examples of its use include various mechanical parts and the like.

If necessary, the obtained sintered body may be subjected to surface machining such as grinding and cutting, and secondary processing such as film forming treatment such as vapor phase plating or liquid phase plating.

Although the present invention has been described above based on preferred embodiments, the present invention is not limited thereto.

For example, in the method for producing granulated powder and the method for producing a sintered body, arbitrary steps can be added as needed.
Further, any element may be added to the granulated powder of the present invention, if necessary.

Next, specific examples of the present invention will be described.
1. 1. Production of granulated powder (Sample No. 1)
<1> First, as a metal powder, a precipitation hardening stainless steel powder (17-4PH) having an average particle size of 8 μm produced by a water atomizing method was prepared.

<2> On the other hand, cellulose nanofibers (CeNF) were prepared as the refractory component contained in the binder, and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA-117) was prepared as the water-soluble resin contained in the binder. The average length of the cellulose nanofibers was 10 μm, the average diameter was 10 nm, the melting point was 260 ° C., the thermal decomposition temperature was 300 ° C., and the hygroscopicity for 24 hours was 0%. The melting point of polyvinyl alcohol was 200 ° C., and the hygroscopicity for 24 hours was 30%.

Then, ion-exchanged water was prepared as a solvent, the above-mentioned binder components were added, and then the mixture was cooled to room temperature to prepare a binder solution. Table 1 shows the compounding ratio of the components of the binder, the mass ratio of the solid content of the binder to the metal powder, and the like.

<3> Next, the metal powder and the binder solution were mixed to prepare a slurry. The ratio of the metal powder in the slurry was 70% by mass.

<4> Next, the slurry was put into a spray dryer to granulate, and a granulated powder having an average particle size of 60 μm was obtained.

(Sample No. 2-44)
Except that the metal powder, the binder, the amount of the binder added, and the like were changed as shown in Tables 1 to 4, each sample No. Granulated powder was obtained in the same manner as in 1.

The abbreviations in Tables 1 to 4 refer to the following.
17-4PH: Precipitation hardening stainless steel 17-4PH
SKD-11: Alloy Tool Steel SKD-11
SUS316L: Austenitic stainless steel SUS316L
SKH-57: High-speed tool steel SKH-57
PVA: Polyvinyl alcohol (melting point 200 ° C, moisture absorption rate 30% for 24 hours)
PVP: Polyvinylpyrrolidone (melting point 160 ° C., moisture absorption rate 25% for 24 hours)
PP: Polypropylene (melting point 168 ° C, moisture absorption rate 0% for 24 hours)
PW: Paraffin wax (melting point 51 ° C., moisture absorption rate 0% for 24 hours)
CeNF: Cellulose nanofiber (melting point 270 ° C., moisture absorption rate 0% for 24 hours)
CeNC: Cellulose nanocrystal (melting point 260 ° C, moisture absorption rate 0% for 24 hours)
CeNP: Cellulose nanopowder (melting point 250 ° C, moisture absorption rate 0% for 24 hours)
LigP: Lignin powder (melting point 280 ° C or higher, moisture absorption rate 0% for 24 hours)

The average length of the cellulose nanofibers was 5 μm or more and 100 μm or less, and the average diameter was 5 nm or more and 60 nm or less.

The average length of the cellulose nanocrystals was 100 nm or more and 500 nm or less, and the average diameter was 10 nm or more and 50 nm or less.

The average particle size of the cellulose nanopowder was 100 nm.
The average particle size of the lignin powder was 40 μm.

In each table, the sample corresponding to the present invention is referred to as "Example", and the sample not corresponding to the present invention is referred to as "Comparative Example".

2. Evaluation of granulated powder and molded product 2.1 Evaluation of apparent density The granulated powder obtained in each Example and each Comparative Example was placed in a stainless steel box and vibrated for 1 minute.

Next, the apparent density of the granulated powder after the vibration was measured by the method for measuring the apparent density of the metal powder specified in JIS Z 2504: 2012.

In addition, the ratio of the apparent density to the true density was calculated based on the measured apparent density and the true density of the materials constituting the metal powder.
The measurement results and calculation results are shown in Tables 1 to 4.

2.2 Evaluation of fluidity The granulated powders obtained in each Example and each Comparative Example were placed in a stainless steel box and vibrated for 1 minute.

Next, the fluidity of the granulated powder after the vibration was measured by the fluidity test method of the metal powder specified in JIS Z 2502: 2012.

Then, the sample No. The fluidity of the granulated powder obtained in No. 7 was set to 1, and the relative value of the fluidity of the granulated powder obtained in each Example and each Comparative Example was calculated.

Subsequently, the calculated relative value was evaluated against the following evaluation criteria.
<Evaluation criteria for fluidity>
◯: Relative value of fluidity is more than 1 Δ: Relative value of fluidity is 1 or less The evaluation results are shown in Tables 1 to 4.

2.3 Evaluation of moisture absorption First, 10 g of the granulated powder obtained in each Example and each Comparative Example was weighed on a glass petri dish.

Next, a glass petri dish containing the granulated powder was left in a desiccator containing an aqueous sodium chloride solution and kept at 23 ° C. in order to obtain a condition of 75% relative humidity (saturated salt method, JIS B 7920: 2000). ).

Then, 240 minutes after the start of leaving, the mass of the granulated powder was measured. Then, the amount of moisture absorbed was measured according to the following equation.

Moisture absorption (mass%) = (W-W ₀ ) / W ₀ x 100
However, W is the mass at the time of measurement, and W ₀ is the initial mass.

Subsequently, the calculated moisture absorption amount was evaluated against the following evaluation criteria.
<Evaluation criteria for moisture absorption>
◯: Moisture absorption amount is 0.01% by mass or less Δ: Moisture absorption amount is more than 0.01% by mass and 0.04% by mass or less ×: Moisture absorption amount is more than 0.04% by mass Table 1 shows the measurement results. Shown in ~ 4.

2.4 Measurement of molding density First, the granulated powders obtained in each Example and each Comparative Example were molded under the molding conditions shown below.

<Molding conditions>
-Molding method: Press molding method-Molding shape: Columnar with a cross-sectional area of 1 cm ² and a height of 5 mm-Molding pressure: 300 MPa (3 t / cm ² )
-Molding environment: Room temperature 26 ° C, relative humidity 80%

Next, the molding density of the obtained molded product was measured.
The measurement results are shown in Tables 1 to 4.

2.5 Evaluation of ratra value Next, the molded body obtained in 2.4 was subjected to a ratra test according to the "Measuring method of ratra value of metal powder (JPMA P11-1992)" of the Japan Powder Metallurgy Industry Association standard. went. The rattra test is a test for evaluating the chipping resistance of the molded product.

Specifically, first, five molded bodies were put into a test wire mesh basket. Next, the wire mesh cage was rotated 1000 times at a rotation speed of 87 ± 10 rpm.

Then, the rattra value was calculated based on the following formula.
Rattra value (%) = {(mass of molded product before test-mass of molded product after test) / mass of molded product before test} x 100
The calculation results are shown in Tables 1 to 4.

As is clear from Tables 1 to 4, the granulated powders obtained in each example had high apparent density and fluidity, and had low hygroscopicity. Further, it was confirmed that the molded product obtained by using the granulated powder had good moldability and chipping resistance because the molding density was high and the rattra value was small. Therefore, it can be said that the granulated powder obtained in each example can finally produce a high-quality sintered body.

1 ... Granulated particles, 51 ... Metal particles, 52 ... Binder, 521 ... Melting point component, 522 ... Water-soluble resin

Claims (10)

With metal powder
Polyvinyl alcohol and at least one in which moisture absorbing resin of polyvinyl pyrrolidone, and the hygroscopic melting point than low and the hygroscopicity resin hygroscopic than resin rather high, and a binder containing a high melting point component forming a fibrous, the ,
Have,
The hygroscopicity of the high melting point component is 20% or less of the hygroscopicity of the hygroscopic resin.
The content of the hygroscopic resin with respect to the content of the melting point component is 0.2 or more and 4 or less in terms of mass ratio.
The mass ratio of the binder to the metal powder Ri der 0.5 mass% 0.01 mass% or more,
A granulated powder having an average particle size of 20 μm or more and 100 μm or less. The granulated powder according to claim 1, wherein the apparent density is 30% or more of the true density of the material constituting the metal powder. The granulated powder according to claim 1 or 2, wherein the fibrous melting point component has an average diameter of 1 nm or more and 300 nm or less. The granulated powder according to claim 3, wherein the fibrous melting point component has an average length of 50 nm or more and 500 μm or less. The granulated powder according to any one of claims 1 to 4, wherein the melting point component is cellulose. The granulated powder according to any one of claims 1 to 5, wherein the melting point component is derived from a plant. The granulated powder according to any one of claims 1 to 6, wherein the average particle size of the granulated powder is 3 times or more and 10 times or less the average particle size of the metal powder. The granulated powder according to any one of claims 1 to 7, which is subjected to a baking treatment for sintering the metal powder. Polyvinyl alcohol and at least one in which moisture absorbing resin of polyvinyl pyrrolidone, and binders that comprise high melting point component, which forms a melting point rather high, the fibrous than and the moisture absorbing resin has a low hygroscopic property than the hygroscopic resin, And the process of preparing a binder solution containing
A step of obtaining a granulated powder in which the mass ratio of the binder to the metal particles is 0.01% by mass or more and 0.5% by mass or less by binding the metal particles to each other using the binder solution.
Have a,
The hygroscopicity of the high melting point component is 20% or less of the hygroscopicity of the hygroscopic resin.
The content of the hygroscopic resin with respect to the content of the melting point component is 0.2 or more and 4 or less in terms of mass ratio.
A method for producing a granulated powder, wherein the average particle size of the granulated powder is 20 μm or more and 100 μm or less. A step of molding the granulated powder according to any one of claims 1 to 8 to obtain a molded product, and
The step of firing the molded product to obtain a sintered body and
A method for producing a sintered body, which comprises.

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