JPH0741368A - Power-kneaded material for molding and kneading method therefor - Google Patents

Abstract

PURPOSE:To enhance the strength of an injection-or extrusion-molded body of metal or ceramic powder after dewaxing, facilitate the handling and enhance the yield of production. CONSTITUTION:A crystalline thermoplastic resin is used as least one component of a binder kneaded with ceramic or metal powder, this resin is first melted and the other component of the binder and the powder are kneaded in order. The resin is allowed to exist in a molded body after dewaxing in the form of fibers entangled with the particles of the powder.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention exhibits appropriate fluidity at the time of molding of ceramic powder or metal powder by injection molding, extrusion molding, and the like, and at the same time, has sufficient strength for handling the molded body after degreasing. The present invention relates to a kneaded material for molding a powder and a kneading method thereof.

[0002]

2. Description of the Related Art Generally, as a manufacturing method for molding a ceramic powder or a metal powder, degreasing and sintering it to obtain a sintered body, the powder and an organic binder are heated and kneaded to have fluidity. A method of forming a kneaded material, molding the kneaded material by an injection molding method, an extrusion molding method, or the like, then degreasing while gradually heating the obtained molded body to decompose and remove the binder, and then sintering Has been done.

As a more advanced degreasing method, Japanese Patent Publication Sho 59
-27743 uses a binder in which at least two kinds of resins are mixed, one resin is soluble in a solvent, the other resin is insoluble in a solvent, and a resin component soluble in a solvent after molding is dissolved in an organic solvent. A solvent degreasing method for extraction has been proposed.

Also, in the process of degreasing by heating, in order to prevent the binder from expanding and cracking in the molded body, the molded body is heated to a flow temperature of the binder or higher, and then the molded body is heated. Place in the vapor phase of the organic solvent, gradually introduce the solvent from the surface of the molded body to extract the binder (Japanese Patent Publication No. 57-40111), or two types to reduce the amount of carbon decomposed during firing. Using the above binders, a method of removing a part of the binder by solvent extraction, sublimation, or decomposition action before firing to reduce the amount of carbon in the molded body and then firing (Japanese Patent Application Laid-Open No. 57-26).
105) and the like have been proposed.

Further, Japanese Patent Publication No. 4-61826 proposes a method of extracting a resin as a binder component using a CO ₂ supercritical fluid.

However, in the degreasing method by heating, in order to obtain a degreased molded article free from defects such as cracking, swelling, and deformation, the heating rate of heating must be made extremely small and decomposition and removal must be carried out for a long time. For example, degreasing treatment requires several days. Further, there are many problems such as the difficulty of degreasing treatment increases in a molded body having a large wall thickness, and the defective rate increases in subsequent sintering.

Further, in the degreasing treatment for extracting a part of the resin as the binder component with a solvent or the like, it has been devised to use two or more kinds of binder components at the same time to control the extraction speed and the extraction amount, but the degreasing is performed. If a large amount of binder is left so that the strength of the molded body does not become too low to withstand handling, there is a problem that the defective product rate during firing increases and it is difficult to obtain a product with good dimensional accuracy.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves these problems in the prior art and is easy to handle even if the amount of binder component remaining after degreasing treatment by the extraction method is small, Furthermore, it is an object of the present invention to provide a kneaded material for molding a powder and a kneading method thereof, which can secure a sufficient strength that enables simple preliminary processing.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned objects, and a kneading material for molding a powder according to the present invention comprises at least one binder component kneaded with a ceramic powder or a metal powder. The component is characterized in that it has a fibrous form and remains after degreasing.

In the kneaded product for molding powder according to the present invention, one binder component can be degreased by an extraction method, and the other component contains two or more kinds of binder components having different properties that are not degreased by the extraction method. When used in a molding kneaded product of ceramic powder or metal powder, and the remaining component is in the form of fibers, the molded product has sufficient strength necessary for handling.

The kneaded material for molding a powder according to the present invention has a binder composed of components A, B, C and D, and when component A is heated and kneaded with component B, it is incompatible with component B and is crystalline, A component which is not extracted by the extraction degreasing method and has a fiber-like form after degreasing, a component B is a component which is selectively extracted by the extraction degreasing method, and a component C is a component A,
Component B is a plasticity imparting component that imparts flexibility and fluidity to the mixture, and component D is a lubricity imparting component that improves slippage between particles of ceramic powder or metal powder.

Since the component A remaining after degreasing is a crystalline thermoplastic polymer, when the binder component A is kneaded with the component B, the component A takes a fibrous form due to the stringing phenomenon and performs extraction degreasing. And component B is extracted, and component A remains in the form of fibers.

The binder component is preferably 10 to 40% by weight of component A, 30 to 70% by weight of component B, and component C.
In the proportion of 10 to 20% by weight and the component D in the proportion of 1 to 10% by weight. With the binder having such a structure, it is possible to obtain a molded product having a relatively small proportion of the binder and a small shrinkage during sintering. In particular, the components C and D serve to reduce the proportion of the binder component in the kneaded product and increase the packing density of the powder.

Since the binder component A is incompatible with the component B, the binder component A and the component B are separated from each other in the molded body, which allows the molded body to be extracted when extracted with a solvent, for example. Degreasing proceeds without swelling.

In the molded article of the present invention having a high strength after degreasing formed by molding, the fracture surface of the degreased molded article was observed by a scanning electron microscope to find binder component A.
As shown in the scanning electron micrograph shown in FIG.
This is considered to maintain sufficient strength.

Since the binder component A remains after degreasing to secure the strength of the molded body, the binder component A is contained in the binder in an amount of 10% by weight or more, although it varies to some extent depending on the type of resin used. If it is contained too much, the amount of decomposition gas generated at the time of firing increases, and the molded product is cracked, swelled, or deformed, increasing the defective product rate and causing the inside of the furnace to become dirty. In addition, since it becomes difficult to secure the dimensional accuracy of the sintered body, the content is preferably 40% by weight or less.

Since the component B plays a role as an original extractable binder main component, it is preferable that the component B is contained in an amount of 30% by weight or more. If the content is smaller than this, fluidity occurs when kneading with the ceramic particles. Lacks in properties, making molding difficult.

Further, since the component B is a component which is removed by extraction, the solvent or the like reaches the inside of the molded body through the gap where the component B is extracted, and it is necessary to remove the component B to the inside. It is preferable that the content is 30% by weight or more in order to secure a gap serving as a passage. Further, when the content of the component B is too large, the content of the component A becomes small and the strength that can be secured becomes small, so that it is preferably 70% by weight or less.

The component C is a plasticity-imparting component mainly for the component B, and is preferably contained in an amount of 10% by weight or more in order to secure the moldability required for the binder, that is, sufficient fluidity and plasticity. However, if it is contained too much, it is a low molecular weight substance in most cases, so the strength of the molded body decreases, and it tends to foam and form bubbles.
The following is preferable.

Further, since it is possible to obtain the effect of improving the lubricity between the particles of the powder and reducing the proportion of the binder in the molded body, it is preferable that the content be 1% by weight or more, and the content is too large. However, the effect is not further improved, and in most cases, since it is a low molecular weight substance, if it is contained too much, foaming easily occurs, and the strength of the molded body becomes small, so it is preferably 10% by weight or less.

The kneaded product for molding the powder of the present invention is a molding material suitable for injection molding and extrusion molding.
When a kneaded material for molding a powder and a binder consisting of B, C and D is kneaded by heating to form a molded article by injection molding or extrusion molding, the component A takes the form of a fiber entangled with powder particles. Since the strength retained during and after extraction is sufficiently high, the defective rate when degreasing is performed by extraction is small, and even if the residual amount of binder in the molded body after degreasing is small, it can withstand subsequent handling sufficiently. The effect of reducing the defective product rate during sintering can be obtained.

As the component A, it is preferable to use a crystalline resin selected from polyolefins such as polypropylene and polyethylene and polyamides, which is easily made into a fiber.

As the binder component B, a thermoplastic polymer substance which is selectively extracted under degreasing conditions in which the component A is not extracted is selected. As the component B, polystyrene,
It is preferable to use one or more selected from polymethylmethacrylate, polycarbonate, polyacetal, higher alcohol and wax. When a polymer resin compatible with the component B and a non-crystalline polymer substance are used as the component A, the component A is unlikely to be in a fibrous form after kneading, and has a high strength even after degreasing. It's hard to be.

The binder component C is a plasticity imparting component that imparts flexibility and fluidity to the mixture of components A and B, and the binder component D is a lubricity imparting component that improves the slippage of the ceramic powder. The inclusion of the components makes it possible to knead a relatively small amount of binder with the powder to form a kneaded product.

Thus, in the kneaded material for molding a powder according to the present invention, the defective rate at the time of degreasing, handling after degreasing and at the time of firing and firing, which has been a problem in the related art, is greatly reduced, and the degreasing time is shortened to improve the production efficiency. In addition to the above, there is an effect that a sintered body with high dimensional accuracy can be obtained with good yield.

In the kneaded product for molding a powder according to the present invention, the order of kneading the binder component and the powder is important. First, the binder component A is melted by heating, and then the other binder component and the powder are added in this order and kneaded by heating. As a result, the binder component A becomes fibrous and becomes entangled with the powder particles, and handling is performed even after degreasing the molded body.
Further, a molded product having a sufficient strength that allows pre-processing can be obtained.

That is, first, the binder component A is put into a kneading machine and is heated and melted at a temperature higher than the melting point by 10 to 20 ° C., and then the components B and C are added to obtain a uniform opaque kneaded product. Knead for about 1 to 2 hours.

Next, the ceramic powder or metal powder and the binder component D are added to the sufficiently kneaded mixture of the binder components A, B and C, and the mixture is further kneaded for 1 to 3 hours. By continuously kneading these components, the component A becomes a fiber and a fine structure entangled with the particles of the powder is formed. After kneading with the powder, a pellet-shaped powder kneading material that can be put into the next molding machine is obtained.

The pelletized powder kneaded product for molding is molded into a desired product shape by an injection molding machine or an extrusion molding machine. At this time, depending on the type and composition of the binder component,
Select appropriate molding conditions.

Next, a powder compact containing the binder is
The degreasing treatment is performed under the condition that the binder component A does not dissolve and the components B, C and D are extracted. As a result, only the component A in the binder remains, so by adjusting the amount of the component A, the residual amount of the binder after degreasing can be easily controlled.

For this degreasing treatment, it is preferable to adopt an extraction method using a solvent, gas or supercritical fluid. In these degreasing treatments, the volume change of the binder is unlikely to occur, and as in the case of degreasing treatment by heating, the binder component It is possible to avoid that the heat-decomposes and causes defects such as cracking, swelling, and deformation of the molded body.

As a result, a small amount of the fibrous binder component A remains in the state of being entangled with the ceramic particles,
The strength of the degreased molded body is increased, and the degreasing treatment and the handling after the degreasing and at the time of firing become very easy. Further, in order to secure the dimensional accuracy of the sintered body, it is preferable that the amount of the binder remaining after degreasing is as small as possible, and in this respect also, the kneaded product for molding of the present invention is an excellent molding material.

When the degreased molded body, in which only the binder component A remains, is fired, the component A is decomposed while the temperature is raised to about 500.degree. Therefore, the temperature is raised up to 500 ° C. at a relatively slow rate of 50 ° C./hr. At this time, most of the binder has already been extracted,
Since the passage through which the decomposed gas is released is secured, and because the binder component A remains in the form of fibers, the decomposed gas of the component A is easily released outside the molded body.

Thus, even if the temperature is raised at a much higher rate than in the case of degreasing by heating, the number of defective products due to cracking, swelling, deformation, etc. is small, and heating at 500 ° C. or higher causes sintering. Since it is possible to fire the powder under the normal conditions,
The sintering process can be completed quickly.

[0035]

In the kneaded product for molding the powder of the present invention, two kinds of binder components having different properties are used during injection molding or extrusion molding of ceramic or metal powder, and the two kinds of binder components are mutually It utilizes a phenomenon in which one binder, which is not compatible and remains after degreasing, is kneaded into fibers and becomes entangled with powder particles and imparts relatively large strength after degreasing.

The behavior of the fibrous binder component at the time of degreasing and firing is not clear so far, but since the fibrous binder component remains in a tangled state after degreasing, the fibrous binder is degreased. It is believed that this contributes to ensuring the strength of the formed compact, and that the escape path for the decomposed gas is sufficiently secured during firing, so that a sintered body of ceramic powder or metal powder can be obtained with good yield.

In injection molding of plastics, it is rare that two or more kinds of resin components are kneaded and molded, but in molding of ceramics or metal powder, plastics are required as a binder at the time of molding, but are sintered. Since the binder does not remain in the final product obtained, there is no problem in mixing a plurality of types of plastics having different properties and using them as a binder component.

Therefore, two or more kinds of incompatible plastics having different properties are combined and kneaded to be used as a binder for molding powder such as ceramics. In particular, the present invention utilizes that one of the crystalline plastics forms a fine fiber-like structure and is entangled in the particles of powder such as ceramics and works excellently as a binder. The manufacturing process such as handling and firing becomes very easy.

Further, the amount of binder remaining after degreasing can be easily controlled, and the amount of binder remaining after degreasing can be reduced to facilitate the sintering of the molded body and more accurately predict the amount of shrinkage due to sintering. In addition to this, the defective product rate associated with the production of a powder sintered body is significantly reduced, which is suitable for the production of a sintered body having a complicated shape.

[0040]

【Example】

Example 1 20% by weight of polyethylene as component A of the binder was first melted by heating, then 60% by weight of polyoxymethylene as component B, 18% by weight of phthalic acid ester as component C and 2% by weight of stearic acid ester as component D.
Was kneaded to obtain a kneaded product of the binder. 50% by volume of alumina powder to 50% by volume of the kneaded material of this binder
And further kneaded to obtain a kneaded material for molding ceramic powder.

This kneaded product was injection-molded to obtain 60 mm ×
Forty plates of 50 mm × 5 mm in thickness were molded, and the molded body was placed in nitric acid vapor. By this degreasing treatment, polyoxymethylene was oxidatively decomposed and extracted, and only polyethylene remained in the degreased molded body. The degreased molded body was transferred to an electric furnace and fired at 1550 ° C. for 2 hours to obtain an alumina sintered body.

Example 2 15% by weight of polypropylene as the component A of the binder was first melted by heating and then polystyrene 70 was used as the component B.
By weight, 13% by weight of phthalic acid ester as component C and 2% by weight of stearyl alcohol as component D were kneaded to obtain a kneaded product of a binder. Silicon nitride powder (sintering aid Y ₂
(Including O ₃ ) was added at a ratio of 50% by volume and kneaded to obtain a kneaded material for molding ceramic powder.

60 m of this kneaded material for molding was obtained by injection molding.
20 pieces of m × 50 mm × 5 mm thick plate were formed, and the formed body was immersed in methylene chloride. Polystyrene was extracted by dissolving in methylene chloride and degreased, and only polypropylene remained in the degreased molded body. The degreased compact was fired in an electric furnace in a nitrogen atmosphere at 1750 ° C. for 5 hours to obtain a silicon nitride sintered body.

COMPARATIVE EXAMPLE 1 A molding kneaded product of the same alumina powder as that used in Example 1 was prepared by mixing 25% by weight of wax as a binder.
Twenty plates of 30 mm × 30 mm × thickness 5 mm were molded by injection molding. Next, in order to heat and degrease the binder, 500 ° C. at 3 ° C./hr for about 1 week
The temperature was raised to ° C. Since it is difficult to maintain the shape of the degreased molded body, in the case of a molded body having a complicated shape, it was necessary to take care such as burying it in sand to degrease it. Next, the degreased molded body is transferred into an electric furnace and baked at 1550 ° C. for 2 hours,
An alumina sintered body was obtained.

Comparative Example 2 Binder A was the same as in Example 2 except that binder A,
B, C and D were put into the kneading machine at once to obtain a kneaded product of the binder. The same silicon nitride powder as in Example 2 was added to this mixture in an amount of 50% by volume, and injection molding was performed to obtain 0 mm × 50 mm ×.
Twenty 5 mm plates were molded and similarly degreased and fired to obtain a sintered body of silicon nitride. The results of these tests are summarized in Table 1.

From the results shown in Table 1, in the molded body of the kneaded material for powder molding of the present invention, the time required for degreasing is short and
It can be seen that the useful effect that the strength after degreasing is large enough to withstand handling, the baking is easy, and the defective product rate due to the baking is small is obtained.

[0047]

[Table 1]

The fractured surfaces of the molded bodies obtained by degreasing the molded bodies obtained in Example 2 and Comparative Example 2 were examined by a scanning electron microscope. That is, FIG. 1 and FIG. 2 are enlarged photographs of the fracture surface after degreasing of the molded bodies obtained in Example 2 and Comparative Example 2, respectively (the length of the bar in the photograph is 1 μm). In this, a structure was observed in which the binder component became fibrous and was entangled in the particles of the silicon nitride powder. On the other hand, such a fibrous structure was not observed in FIG. From this observation result, it is considered that the strength of the molded body of Example 2 after degreasing and the baking yield are high because of the presence of the fibrous binder structure.

[0049]

EFFECTS OF THE INVENTION When a powder molded body is molded by injection molding or the like with the powder-molding kneaded material of the present invention, a part of the binder component becomes fiber-like during kneading and becomes entangled with the powder particles, and remains after degreasing. Since the strength of the molded body sufficient for handling and the like can be secured, it is possible to prevent the degreased molded body from being cracked, swollen, or deformed to cause defective products. Further, the degreasing time can be remarkably shortened, and the binder remaining during firing can be easily decomposed and removed.

Further, when a molded body is produced by injection molding or extrusion molding using the powdered kneaded material according to the present invention, and the molded body is degreased by an extraction method to produce a sintered body,
The defective rate in degreasing is small, the degreasing time is significantly shortened, the defective rate due to firing is significantly reduced, and the shrinkage amount due to sintering can be accurately estimated. Since it is suitable for producing a sintered body, its industrial utility value is great.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph of a fractured surface obtained by degreasing a ceramic molded body obtained by injection-molding a powdery kneaded material, which is an example of the present invention.

FIG. 2 is a scanning electron microscope photograph of a fractured surface obtained by degreasing a ceramics molded body obtained by injection molding a powder molding kneaded material according to the prior art.

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[Procedure amendment]

[Submission date] December 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph of a fractured surface showing the structure of a ceramic material obtained by degreasing a ceramics molded body obtained by injection molding a powdery kneaded material as an example of the present invention.

FIG. 2 is a scanning electron microscope photograph of a fractured surface showing the structure of a ceramic material obtained by degreasing a ceramic compact formed by injection molding a powder molding kneaded material according to the prior art.

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Claims (7)

[Claims] 1. A kneaded product for molding a powder, characterized in that at least one component of a binder component kneaded with a ceramic powder or a metal powder is in a fiber form and remains after degreasing. 2. The binder is composed of components A, B, C and D, and when component A is heated and kneaded with component B, it is incompatible with component B, is crystalline, and is not extracted by the extraction degreasing method. A component that remains in a fibrous form after degreasing, a component B is a component that is selectively extracted by an extraction degreasing method, and a component C is a plasticizing component that imparts flexibility and fluidity to a mixture of components A and B. And component D is a lubricity imparting component that improves slippage between particles of ceramic powder or metal powder, and component A is added in an amount of 10 to 4 in the binder component.
0% by weight, component B 30-70% by weight, component C 10-
The kneaded material for molding a powder according to claim 1, which comprises 20% by weight and Component D in a ratio of 1 to 10% by weight. 3. A molding kneaded product comprising a binder composed of the components A, B, C and D and a powder is kneaded by heating to form a molded product by an injection molding method or an extrusion molding method. The powder-form kneaded product according to claim 1 or 2, which has a fiber-like form in which powder particles are entangled with each other. 4. The kneaded product for molding a powder according to claim 1, wherein an extraction method using a solvent, steam or a supercritical fluid is adopted for the degreasing treatment. 5. The powdery kneaded product according to claim 1, wherein the component A is at least one selected from polyolefins such as polypropylene and polyethylene, and polyamides. 6. The kneaded material for molding a powder according to claim 1, wherein the component B is one or more selected from polystyrene, polymethylmethacrylate, polycarbonate, polyacetal, higher alcohol and wax. . 7. A method of kneading a binder and powder molding compound, wherein the binder comprises components A, B, C and D, and the compatibility of component A with component B when heated and kneaded. It is a non-existent, crystalline, component that is not extracted by the extraction degreasing method, component B is a component that is selectively extracted by the extraction degreasing method, and component C is a mixture of components A and B that is flexible and fluid. Component D, which is a plasticizing component that gives
Is a lubricity-imparting component that improves sliding between particles of ceramic powder or metal powder, and the binder is component A
0-40% by weight, 30-70% by weight of component B, 10-20% by weight of component C, 1-10% by weight of component D. A method for kneading a powder-forming kneaded product, which comprises adding a binder component and kneading, and then adding and kneading ceramic powder or metal powder.