JPH04187557A - Binder composition for powder forming, powder-formed article produced by using the same and production of powder-formed article - Google Patents

Abstract

PURPOSE:To improve the decreasing degree of a powder-formed article by mixing a specific skeleton-forming organic material and a void-forming organic material, mixing the obtained binder composition for powder-forming with powder and forming the mixture to a prescribed form. CONSTITUTION:A binder composition for powder-forming is produced by mixing (A) 20-70vol.% of a skeleton-forming organic material such as diallyl isophthalate prepolymer having a molecular weight of >=1,000, (B) a compatible 1st void-forming organic material such as dibutyl phthalate, (C) an incompatible 2nd void-forming organic material such as n-paraffin and (D) a polymerization initiator such as dicumyl peroxide at specific ratios. The powder-forming binder composition is added to the powder of Si3N4, etc., in an amount of 40-60vol.% based on the powder-formed article, the mixture is kneaded and a powder-formed article is produced by a plasticizing molding such as injection molding of the kneaded material. The powder-formed article is heated to a degreasing temperature in N2 gas flow at a prescribed rate of heating to effect the degreasing treatment and obtain a powder-formed article free from defects of cracks and bubbles.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a binder composition for powder molding that imparts a predetermined shape to powders of ceramics, metals, etc., and an excellent degreasing property using the binder composition. The present invention relates to a powder compact and a method for producing the powder compact.

(Conventional technology) Molding of powders such as ceramics and metals is performed using the mold press method,
Molding methods such as a slip casting method, a doctor blade method, an extrusion molding method, and an injection molding method are used to mold the material into a desired shape.

Among these, the mold press method is limited to simple shapes and does not give a flexible shape, and there are limits to the shapes that can be applied. In addition, the slip cast method
Is it suitable for complex shapes, and does it have some drawbacks in terms of molding efficiency and product dimensional accuracy? The doctor blade method is limited to forming thin sheets, and also does not have the ability to give shapes freely.

On the other hand, plasticization molding methods such as injection molding and extrusion molding have flexible shape-forming properties and high-efficiency, high-precision molding capabilities. On the other hand, however, in order to impart fluidity to the powder, it is necessary to add a large amount of a binder component as a fluidity-imparting material, which makes it difficult to remove the binder component.

That is, in order to impart fluidity to the powder as described above, a binder amount of approximately 40% by volume to 60% by volume is required for boat fishing. In this way, since a large amount of binder is added, it becomes difficult to remove unnecessary binder components after giving the desired shape, and defects such as cracks and foaming are likely to occur when removing the binder. It has become extremely difficult to form a molded product in a sound manner.

Normally, it is said that it is difficult to degrease (remove the binder) a molded body with a wall thickness of 10+e+* or more, and in order to obtain a molded body with a wall thickness greater than that, extremely controlled gas flow,
Degreasing must be accomplished using a degreasing furnace with a temperature pattern and an extremely long heating schedule. However, even so, defects such as cracks often occur after degreasing, and the present situation is that this method is not a practical industrial manufacturing method.

In contrast to the above-mentioned plasticization molding, conventional binder systems impart fluidity by heating thermoplastic resins, etc., and solidify in a mold at a low temperature, making it possible to remove the resin from the mold. types of substances have been used.

In general, molding methods that impart fluidity by heating use a type of material that solidifies at low temperatures and softens when exposed to high temperatures, exhibiting fluidity. , the mixture of powder and binder has almost no strength. Under these circumstances, degreasing at high temperatures generates gas pressure of decomposed and volatile components, and in order to suppress defects such as cracks under these conditions, The structure must be able to withstand the gas pressure generated.

However, as mentioned above, with conventional binder systems,
It is thought that the binder has no strength at all under high temperatures, and its strength is maintained only by the entanglement of the powder particles and the acting force between the particles, so if the wall thickness of the compact exceeds 10 mm, normal degreasing will suddenly fail. It becomes difficult.

(Problem to be solved by the invention) As mentioned above, with conventional binder systems, no strength can be obtained at high temperatures (temperatures at which degreasing is substantially carried out), so molding with a wall thickness exceeding 10 mm cannot be achieved. When degreasing the body, there is a problem in that defects such as cracks and foaming are extremely likely to occur.

The present invention was made to address such problems, and the purpose of the present invention is to
Another object of the present invention is to provide a binder composition for powder molding that can increase the strength at degreasing temperatures, and another object is to provide a powder molded product that significantly suppresses the occurrence of defects such as cracks and foaming. Furthermore, it is an object of the present invention to provide a method for producing a powder molded body, which makes it possible to obtain such a powder molded body by a plasticization molding method such as an injection molding method or an extrusion molding method.

[Configuration of the Invention (Means and Effects for Solving the Problems) The binder composition for powder molding of the present invention is a binder composition for powder molding that imparts a predetermined shape to powder,
An organic material for forming a skeleton that connects the powders by chemical or physical bonding, and an organic material for forming voids that can be removed in a substantial portion in a temperature range where the organic material retains substantial strength. The structure is characterized in that the organic material for skeleton formation is contained in a range of 96 to 70% by volume.

Further, the powder compact of the present invention is a powder compact in which a predetermined shape is imparted to powder with a binder composition, in which the binder composition for powder compacting according to claim 1 is added to the powder compact as the binder composition. 40% by volume to 6
A skeleton-forming organic material is placed in the vicinity of the powder, and the two organic materials are bonded to each other to form a skeleton structure containing the powder, and the gaps between the skeleton structure are It is characterized by having a structure in which a void-forming organic material is arranged on the inside.

Furthermore, the method for producing a powder compact of the present invention uses the binder composition for powder compacting according to claim 1 as the binder composition when shaping a mixture of powder and a binder composition into a predetermined shape, and A skeleton-forming organic material is dissolved in a first void-forming organic material, and an appropriate amount of a second void-forming organic material, which is a non-solvent for the skeleton-forming organic material, is added to the solution. The method is characterized by precipitating the organic material for forming voids from the organic material for forming voids, and molding the mixture of the binder composition and powder in this state into a predetermined shape.

That is, the present invention addresses the above-mentioned problems by using the above-mentioned organic material for forming a skeleton, which chemically or physically bonds powders together, as a strength-maintaining component during degreasing of a thick-walled molded body. By using it, the strength of the molded product at high temperatures during degreasing is improved and the occurrence of molded product defects such as cracks is suppressed. In other words, by using the organic material for forming the skeleton, a structure that can withstand the gas pressure of decomposition and volatile components generated during degreasing can be obtained. In addition to the above-mentioned strength-maintaining component, the organic material for skeleton formation as an easily degreasable component can decompose, volatilize, or
By using a void-forming organic material that can be easily removed from the system through phenomena such as evaporation and seepage, the necessary path for degreasing can be created in advance within the molded body while maintaining its strength. This makes it possible to maintain the healthy state of the molded body when the organic material for forming the skeleton is removed (degreased).

Furthermore, the powder compact of the present invention described above has been discovered as a compact structure that facilitates the degreasing process as described above.

Although it is possible to obtain the structure described above using thermoplastic resin as the organic material for forming the skeleton in the present invention, it is difficult to achieve the structure described above by using a thermosetting organic material as the main component. It becomes a product.

Examples of the thermosetting organic substance include diarylphthalate prepolymers, unsaturated polyesters, oligoester acrylates (oligomers of acrylic esters), and low molecular weight polybutadiene, which may be used alone or in combination. Further, from the viewpoint of strength retention effect, it is preferable to use an organic substance having a number average molecular weight of 1000 or more as the thermosetting organic substance. Furthermore, in order to obtain a molded article having the structure as described above, it is preferable to use a polar organic substance. This makes it easy to arrange it near the powder.

In addition, the strength-maintaining component may be a polymerizable organic monomer that is compatible with or has an affinity for these thermosetting organic substances, such as acrylic acid, methacrylic acid, etc. , and these esters may be used in combination with vinyl monomers, butadiene monomers, etc.

The organic material for forming voids in the present invention has physical properties that allow a substantial portion to be easily degreased in the temperature range where the organic material for forming a skeleton maintains its strength, and has a strength-maintaining component. It is necessary to select by considering affinity, compatibility, etc. Examples of such organic materials for forming voids include paraffin waxes, liquid paraffin, fatty acids such as stearic acid, various solvents, etc., and these may be used alone or in combination. Furthermore, it is also possible to use substances that are compatible with or have an affinity for these substances. Furthermore, in order to obtain a molded article having the above structure, it is preferable to use a non-polar organic material.

In addition, in consideration of the manufacturing method of the powder compact, which will be described in detail later, the above-mentioned easily degreasable component is the first component that can dissolve the strength-retaining component.
It is preferable to consist of an easily degreasable component and a second easily degreasable component that is compatible with this solution and has a non-solvent relationship with respect to the main component of the strength maintaining component.

The proportions of the organic material for forming the skeleton and the organic material for forming the voids described above are preferably adjusted so that the organic material for forming the skeleton is contained in the entire composition in a range of 20% by volume to 70% by volume. In addition, when using other components, it is preferable to adjust the content of the void-forming organic material to 20% by volume or more. 2 organic materials for skeleton formation
If it is less than 0% by volume, a sufficient strength retention effect during degreasing cannot be obtained, and if it exceeds 70% by volume, healthy degreasing becomes difficult due to the presence of easily degreased components.

In addition, when using a thermoplastic resin as a strength-maintaining component, use a resin with a high softening temperature, such as polystyrene, high-melting point polyethylene, etc., and use a low-melting point wax, low-melting point fatty acid, liquid paraffin, etc. as an easily degreasable component. Is it appropriate to do so?

The constituent components of the binder composition for powder molding of the present invention are not limited to the strength-retaining component and easily degreasable component described above. It is sufficient for these materials to fulfill their original functions, and the addition of inorganic or organic materials that do not have either of these functions is not equally excluded as long as these functions are not significantly interfered with. For example, the addition of thermoplastic resins, thermosetting substances, plasticizers, mold release agents, surfactants, polymerization accelerators, stabilizers, polymerization initiators, etc. in amounts that do not impair the aforementioned functions is specifically excluded. It's not something you can do. Furthermore, it is also effective to blend a component that improves the affinity between the strength-retaining component and the easily degreasable component, depending on the materials used.

A powder molded body using the binder composition for powder molding of the present invention is molded, for example, by a plasticization molding method such as an injection molding method or an extrusion molding method. Here, the ratio of the binder composition to the molding powder is not limited, but the binder composition may be contained in a large amount such that the binder composition is contained in the molded article at about 40% to 60% by volume. The present invention is particularly effective when using Moreover, various ceramic powders, metal powders, etc. are exemplified as the target molding powder.

Moreover, as the structure of the powder compact after hardening obtained using the binder composition for powder compaction of the present invention, the three types of structures shown in FIG. 1 can be cited as typical examples. Here, although the structure is referred to as after curing, the structure of the mixed wire or molded object before curing is the same except for whether or not it is cured.

That is, the structure (1) shown in FIG.
This is a structure in which component 2, in which a strength-retaining component and an easily degreasable component are uniformly dispersed or dissolved, exists between the two. Figure 1 (
In the structure (It) shown in b), strength-retaining component 3 is powder 1
At the same time, the strength-retaining components 3 are chemically or physically combined with each other to form a skeleton structure in the molded body together with the powder 1, and the easily degreasable component 4 is present between the skeletons. It has a structure that Structure (m) shown in FIG. 1(C) is an intermediate structure between structure (1) and structure (II), in which the strength-retaining component 3 is present near the powder 1, and This structure has a structure in which a component 2 in which a strength retaining component and an easily degreasable component are uniformly dispersed or dissolved exists between the strength retaining components 3.

Here, as an evaluation result of the above-described structures (1) to (m) as molded bodies, the results of measuring the bending strength at high temperature are shown in FIG. This comparison of high-temperature strength will help you understand the characteristics of the molded product. The bending test was conducted at a temperature range from room temperature to 200° C. using 25 mm x 5 dragon x 2 mm t molded bodies corresponding to each structural model.

As is clear from FIG. 2, structure (II) has high strength at high temperatures and is most suitable for the purpose of the present invention. Furthermore, as a result of molding and degreasing these kneaded products, good degreasing results can be obtained for compositions with high strength. As is clear from the above, the thermosetting component exists near the powder,
This and the powder come together to form a skeleton structure in the molded body, and it can be determined whether it is an easily removable component or is contained between the skeletons, and whether it is optimal as a plasticized molded body.

However, in structures (1) and (III), it is possible to improve the strength at high temperatures compared to molded products using conventional thermoplastic organic materials, so the binder composition of the present invention The above does not exclude molded bodies of structures (1) and (III).

Next, a method for manufacturing the powder compact having the above structure (II) will be described.

The most important issue here is the compatibility between the organic material for forming the skeleton and the organic material for forming the voids. If the skeleton-forming substance is completely dissolved in the void-forming substance, structure (II) will not be obtained. However, if these are completely separated and have no mutual affinity, it will not be possible to knead them uniformly.

Therefore, it is necessary to establish a relationship that is as familiar as possible and that is substantially separate. As means for achieving such a state, the following methods are exemplified.

■ Use of the solvent-nonsolvent relationship, that is, dissolve the skeleton-forming substance (A) in the pore-forming substance B or one of its components (first pore-forming substance: B1), and add a non-solvent to the solution for A. A second void-forming substance (B2) is added. As a result, when a certain amount of B2 is added, A starts to precipitate from B. When the addition of B2 is stopped when the entire amount of A has been precipitated, this state or the state where A and B, +82, are extremely familiar, and the state where A is gathered around the powder, that is, the structure (I
The state t) is obtained.

■ Adding a familiar intermediate layer to both A and B.
A substance that has the same or similar group as the functional group that gives rise to the unique characteristics of B, and also has the same or similar group as the functional group unique to B, is placed between the two. . Surfactants are typical substances that have this function. However, it is important to note here that since this intermediate layer is inserted between A, the bond between A is likely to be inhibited, and as a result, the strength of the kneaded product with powder (in case of hardening, after hardening) ) or may decline. Therefore, in the present invention, it is preferable that such an intermediate layer itself has the role of bonding A to each other.

Next, in the case of using a thermosetting substance, curing (curing to maintain the shape of the molded object) is as follows: (a) Hardening is performed in the mold immediately after molding.

(b) After being molded and removed from the mold, a curing treatment such as heating is performed.

(e) Curing is carried out at the same time as degreasing using a method such as heating during degreasing.

There are other methods. Although these are examples of injection molding methods, similar steps can be considered with other plasticization molding methods, and any of these can be used as the curing method of the present invention.

Further, as a curing method, for example, when a thermosetting organic substance is used, radical polymerization, ionic polymerization, addition polymerization, polycondensation, polyaddition, etc. can be used. In this,
Radical polymerization is considered to have the widest control range and is preferred. Regarding this radical polymerization, various types of polymerization initiators are known, and it is preferable to optimize the initiators depending on molding conditions and the like. As the polymerization initiator, peroxide, inorganic peroxide, azo compound, etc. are used.

Examples of the peroxides include 1,1-bis-tert-butylperoxy-3,3.5-1-limethylcyclohexane, 1,1-bis-tert-butyl, ? -oxydicyclohexane, 2,2-bis tert-butyl peroxyoctane, n-butyl 4,4-bis tert-butyl peroxyvalerate, 2,2-bis tert-butyl peroxybutane, etc. Peroxyketals; tertiary-butyl hydroperoxide,
Hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, bara-menthane hydroperoxide, 2,5-dimethylhexane/2,5-hydroperoxide, and 1,1,13-tetramethylbutyl hydroperoxide. Dialkyl peroxides such as ditertiary-butyl peroxide, tertiary-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl/2,5-ditertiary-butylperoxyhexane; acetyl peroxide, isobutyryl peroxide diacyl peroxides such as oxide, octane peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, m-toluoyl peroxide; carbonate, peroxydicarbonates such as di-n-propyl peroxydicarbonate, diallyl peroxydicarbonate; tert-butyl peroxyacetate,
Tert-butyl peroxyisobutyrate, Tert-butyl peroxyisobutyrate, Tert-butyl peroxybenzonide, 2,5-dimethyl-2,5
Examples include peroxy esters such as -dibenzoyl peroxyhexane.

These peroxides are selected depending on the conditions of plasticization molding such as injection molding, taking into consideration the temperature at which radical generation starts, half-life, activation energy, etc.

In addition, as substances that promote radical generation of these polymerization initiators, C0% Mn5Cu, Ni, Fe, Zn
Compounds containing ions such as, or dimethylaniline,
Aromatic tertiary amines such as dimethyl para-toluidine may also be added. Furthermore, it is also possible to add promoters of polymerization promoters. By adding these polymerization accelerators, the polymerization temperature can be significantly lowered, and curing at room temperature is also possible.

(Example> Next, examples of the present invention will be described.

Example 1 First, a binder composition was added at 50% by volume to silicon nitride powder (manufactured by Denki Kagaku Kogyo). The components and proportions of this binder composition include diallylisophthalate,
Prepolymer (molecular weight 8000, manufactured by Osaka Soda) 40% by volume, n-paraffin (melting point 60°C) 17% by volume,
dibutyl phthale) (DBP) 39.9% by volume,
and dicumyl peroxide (DC) as a polymerization initiator.
P) 3.0% by volume.

Here, the diallyl isophthalate fist prepolymer is
It is soluble in dibutyl phthalate, insoluble in n-paraffin, and is soluble in dibutyl phthalate and n-paraffin.
It is compatible with paraffin.

Next, a binder composition was added to the silicon nitride powder and kneaded for 60 minutes in a pressure kneader while heating at 80°C. This kneaded material corresponds to the structure (II) described above.

After that, the above kneaded material was 3CI+n+s x 5mm x
The desired powder molded body was obtained by injection molding to a size of 5 mm. When the bending strength at 200°C of the thus obtained powder molded body was measured, it was found to be 50
A good value of kgf'/cJ was obtained.

In addition, the same kneaded material was injection molded into a shape of 30 mm φ x 20 mm, heated to 250°C in a nitrogen stream at a rate of 10°C/hour, held at 250°C for 20 hours, and then heated to 500°C at 10°C for 7 hours. Degreasing was carried out by raising the temperature at a rapid rate. The molded product after degreasing was in good condition with no defects observed.

Furthermore, when the degreased body was sintered and evaluated, the density was 3.
2g/cm', room temperature strength 105kg r 7mm 2
Good results were obtained.

Example 2 Alumina powder was mixed with 48.0% by volume of diallyl isophthalate prepolymer (molecular ffi 8000, manufactured by Osaka Soda) and 1.1% of diisodecyl phthalate (DIDP) and butylphthalylbutyl glycolate (BPBG).
volume ratio) mixture 34.2% by volume, paraffin (melting point 50
°C) 15.0 volume ffi 9 to 5DCP 2.0 volume
A binder composition prepared at 9ci was added so that the total amount of the binder composition added to the powder was 45% by volume, and kneaded for 60 minutes in a pressure kneader while heating at 70'C. This kneaded material corresponds to the above-mentioned structure (II).

Next, the above kneaded material was injection molded into a pellet shape of 30 mmφ
After increasing the temperature at ℃/hour and holding it at 250℃ for 10 hours,
When the temperature was raised to 600°C at a rate of 0°C/hour, a degreased body without defects was obtained.

Example 3 Add diallyl phthalate prepolymer (molecule = Ioooo, manufactured by Osaka Soda) to stainless steel powder 46.0 volume q6
, mixture of dioctyl phthalate (DIDP) and butylphthalyl butyl glycolate (BPBG) (volume ratio) 342% by volume, paraffin (melting point 50°C) 150% by volume, dipentaerythritol hexaacrylate 3.
A binder composition prepared by adding 8% by volume and 2.0% by volume of DCP was added so that the total amount of the binder composition added to the powder was 40% by volume, and the mixture was heated in a pressure kneader at 7°C. The mixture was kneaded for 60 minutes.

This kneaded material corresponds to the above-mentioned structure (n).

Next, the above mixed wire was injection molded into a pellet shape of 30 mmφ x 20 mats, and then the temperature was raised from room temperature at 20°C/hour in an argon stream, held at 250°C for 10 hours, and then heated to 600°C at 50°C/hour. When the temperature was raised to ℃, a defatted body without defects was obtained.

Example 4 Alumina powder was mixed with 25.9% by volume of diallyl isophthalate prepolymer (molecular weight 8000, manufactured by Osaka Soda) and polyethylene terephthalate (PET) (molecular ffi 4
000) 16.1% by volume, paraffin (melting point 60°C)
16.5% by volume, DBP 38.5% by volume, DCP 3
．． The binder composition adjusted to 0% by volume was added so that the total amount of the binder composition added to the powder was 45% by volume, and kneaded for 60 minutes in a pressure kneader under heating at 70°C.

This is a thermosetting resin called diallylisophthalate.
The structure (I
This is a kneaded material that falls under I).

Next, the above kneaded material was injection molded into a pellet shape of 30 + n + nφ
/ hour, held at 250℃ for 10 hours, then heated to 50℃/hour.
When the temperature was raised to 600° C. for an hour, a degreased body with no defects was obtained.

Example 5 Unsaturated polyester (molecular weight 3000
, isophthalic acid, tetrahydrophthalic acid, maleic anhydride, propylene glycol, etc.) 4
8.0% by volume, dioctyl phthalate (DOP) and DB
1=1 (volume ratio) mixture with P 34.2% by volume, paraffin (melting point 50°C) 15.082%, acrylic ester (manufactured by Toagosei Chemical Co., Ltd., trade name M-315)
) A binder composition prepared by adding 3.8% by volume and 1.0% by volume of DCP was added so that the total addition amount of the binder composition to the powder was 45% by volume, and the mixture was heated at 90°C.
The mixture was kneaded for 60 minutes in a pressure kneader under heating.

Next, the above-mentioned kneaded material was injection molded into a pellet shape of 30+n+nφ
/ hour, and after holding at 250℃ for 10 hours, 50℃
When the temperature was increased to 600° C./hour, a degreased body without defects was obtained.

Example 6 28.3% by volume of diallyl isophthalate prepolymer (Molecular JR8000, manufactured by Osaka Soda) was added to titania powder.
, DBP 46.5% by volume, liquid isoparaffinic hydrocarbon (manufactured by Idemitsu Petrochemical Co., Ltd.; trade name IP2835)
A binder composition prepared by adding 22.7% by volume and 2.5% by volume of ditertiary-butyl peroxide was added so that the total amount of binder composition added to the powder was 51% by volume, and kneaded with a pressure kneader. did.

In this kneaded product, phase separation occurs between a solution of diallylisophthalate prepolymer dissolved in DBP and a liquid isoparaffinic hydrocarbon solvent, and a liquid phase rich in DBP in which diallylisophthalate prepolymer is dissolved forms a liquid phase rich in DBP. It gathers around the powder, forms a strength-retaining component, and forms a structure (II
) to form.

Next, the above-mentioned kneaded product was injection molded into a pellet shape of 30 mmφ x 20 mmt, and was heated in the atmosphere from room temperature to IO”c /
After heating at 250℃ for 10 hours,
When the temperature was raised to 600°C at a rate of C/hour, a degreased body without defects was obtained.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a binder composition that has increased strength at the degreasing temperature and is capable of normal degreasing. Therefore, by the plasticization molding method using a large amount of binder composition,
It becomes possible to obtain a healthy thick-walled molded body.

[Brief explanation of the drawing]

Figures 1 (a) to (C) are diagrams each showing structural examples of molded bodies molded using the binder composition of the present invention, and Figure 2 is a graph showing the bending strength of the structure shown in Figure 1. It is. 1... Powder, 2... Component in which the strength-retaining component and easily degreasable component are uniformly dispersed or dissolved, 3...
...Strength retaining component, 4...Easy degreasing component. Applicant Toshiba Corporation Representative Patent Attorney Suyama Sa - N') ?

Claims (5)

[Claims] (1) In a powder molding binder composition that imparts a predetermined shape to powder, a skeleton-forming organic material that chemically or physically bonds the powders together, and this organic material has substantial strength. and a void-forming organic material that can be substantially removed in a temperature range where the structure is maintained, and the skeleton-forming organic material is contained in a range of 20% to 70% by volume. Binder composition for powder molding. (2) The binder composition for powder molding according to claim 1, wherein the organic material for forming a skeleton is composed mainly of a thermosetting organic substance. (3) The binder composition for powder molding according to claim 1, wherein the binder composition for powder molding is used for plasticization molding of powder. (4) In a powder molded body in which a predetermined shape is imparted to powder with a binder composition, the binder composition for powder molding according to claim 1 is added to the powder molded body in an amount of 40% by volume as the binder composition.
~60% by volume, the organic material for forming a skeleton is placed near the powder, the organic materials are bonded to each other to form a skeleton structure containing the powder, and the gaps between the skeleton structure are A powder compact characterized by having a structure in which a void-forming organic material is arranged on the inside. (5) When molding a mixture of a powder and a binder composition into a predetermined shape, the binder composition for powder molding according to claim 1 is used as the binder composition, and the organic material for forming a skeleton is used in the first cavity. A suitable amount of a second pore-forming organic material, which is a non-solvent for the skeleton-forming organic material, is added to the solution, and the skeleton-forming organic material is dissolved in the pore-forming organic material. 1. A method for producing a powder compact, which comprises precipitating the binder composition and molding the mixture of the powder into a predetermined shape.