JP2003088996A - Forming method by rubber press - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming method by a rubber press by which a highly pure and flawless formed product having objective shape is surely manufactured because impurities and foreign matters are not mixed in the molding powder of a raw material in the forming process. SOLUTION: This method is a forming method by the rubber press for manufacturing the formed product having a three-dimensional shape by applying pressurization by hydrostatic pressure after filling the molding power a rubber case 11. By this forming method by the rubber press, in the state where a formed resin molded article 12 is set to the rubber case so that the great part of the foamed resin molded article 12 having a prescribed shape is brought into contact with the outside of the rubber case, the molding powder is filled into the rubber case and pressurization of the molding powder by hydrostatic pressure is performed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber press molding method for obtaining a green compact by hydrostatic pressing.

[0002]

2. Description of the Related Art Conventionally, a rubber press molding method has been widely used as a molding means for obtaining a powder compact having an isotropic structure. In this molding method, after molding a fine powder in a rubber case, a uniform hydrostatic pressure is applied from all directions through a liquid medium for molding.

As such a rubber press molding method, for example, in Japanese Patent Publication No. 7-108477, a molded article of an arbitrary shape made of an organic material which is plastically deformable and has a small springback amount is used as a core. A rubber press molding method is disclosed in which a crucible or a cylindrical green body is obtained by hydrostatically pressing in a state of being set in a case.

According to the rubber press molding method disclosed in the above-mentioned publication, the springback action of the rubber case generated at the step of lowering the pressure when the green compact is molded by hydrostatic pressure is mitigated by the molded article made of the above organic material. Therefore, the molded body to be molded hardly receives a large stress or interfacial friction force, and the molded body is cracked,
It is possible to prevent molding defects such as damage,
It was always possible to mold a desired green body with high molding efficiency.

However, in the rubber press molding method disclosed in the above publication, the molding powder as the raw material of the green body is
Since the molded article of an arbitrary shape made of an organic material was in direct contact, foreign matters such as impurities and organic material particles contained in the organic material constituting the molded article fell into the molding powder and were mixed, In some cases, it was not possible to mold a high-purity green compact.

If it is not possible to form a high-purity molded body in this way, for example, when the molded powder is a carbonaceous material, the molded powder is not The impurities such as impurities and foreign materials such as organic material particles burned and removed cause defects such as pinholes in the carbon product to be manufactured, and it is difficult to manufacture a product without defects. Further, in the rubber press molding method disclosed in the above publication, the molded product may move with respect to the rubber case during rubber pressing, and it is difficult to obtain a green molded body having a desired shape.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and since impurities and foreign matters are not mixed in the raw material molding powder during the molding process, it is of high purity and free from defects. An object of the present invention is to provide a rubber press molding method capable of reliably molding a green molded body having a desired shape.

[0008]

The rubber press molding method according to the first aspect of the present invention is a rubber press for producing a three-dimensional shaped green body by filling a rubber case with molding powder and applying hydrostatic pressure. A molding method, in a state where the resin molded product is set in the rubber case so that most of the resin molded product having a predetermined shape comes into contact with the outside of the rubber case,
The molding powder is filled in the rubber case, and the molding powder is hydrostatically pressurized.

In the rubber press molding method of the second aspect of the present invention, a recess is formed in the vicinity of the center of the lower surface of the rubber press molding, and the recess is provided in the rubber case having a space having a shape similar to that of the green body to be molded. Fit the bottom-tube-shaped foamed resin molded product with its opening facing downward, fill the rubber case with molding powder, and then place the rubber case in the liquid medium of the hydrostatic pressure device. It is characterized in that the inside of the foamed resin molded product is removed, the inside of the foamed resin molded product is filled with the liquid medium, and the molding powder is hydrostatically pressurized. Hereinafter, the present invention will be described in detail.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, the rubber press molding method of the first invention will be described. The first rubber press molding method of the present invention is a rubber press molding method for producing a three-dimensional shaped green body by filling molding powder into a rubber case and applying hydrostatic pressure. With the resin molded product set in the rubber case so that the majority of the resin molded product comes into contact with the outside of the rubber case, the molding powder is filled in the rubber case and the hydrostatic pressure of the molding powder is applied. It is characterized by performing pressure.

Here, the "state in which the resin molded product is set in the rubber case so that most of the resin molded product having a predetermined shape is in contact with the outside of the rubber case" is a bag-like and easily deformable rubber. The shape of the molded body to be molded is obtained by embedding a resin molded product of a predetermined shape from the outside of the rubber case to the inside without breaking the case so that a part of the resin molded product is exposed. It means a state of being transformed into a shape similar to. That is, according to the rubber press molding method of the first aspect of the present invention, it is possible to manufacture a green molded body in which a concave portion having substantially the same shape as the outer shape of the resin molded product is formed on at least a part of the surface thereof.

The rubber press molding method according to the first aspect of the present invention will be described below with reference to the drawings. 1 (a), 1 (b) and FIGS. 2 (a), 2 (b) are explanatory views schematically showing how a three-dimensional shaped molded body is produced by the rubber press molding method of the first present invention. Is.

In the rubber press molding method of the first invention,
First, as shown in FIGS. 1A and 1B, the resin molded product 12 is set in the rubber case 11 so that most of the resin molded product 12 having a predetermined shape contacts the outside of the rubber case 11.

The rubber case 11 is a container that can be filled with molding powder, has a predetermined shape, and is made of a material that is easily deformable. Further, it may be composed of a container and a lid and configured so that the lid can be easily attached and detached.
The material is not particularly limited, and examples thereof include synthetic rubber such as styrene / butadiene rubber, isoprene rubber, chloroprene rubber, and acrylonitrile / butadiene copolymer rubber. Further, the size thereof is not particularly limited, and is appropriately determined according to the size of the green body to be molded.

The rubber case 11 may be deformed by embedding the resin molded product 12 in a partially exposed form as shown in the drawing, but as described above, it has a predetermined shape. It is preferable that the resin molded article 12 is formed in such a manner that it can be embedded (fitted) in advance. When the rubber case 11 is deformed by the resin molded product 12, it is possible to easily produce molded products of various shapes by changing the shape of the resin molded product 12. However, the size of the resulting molded product is Easy to vary. On the other hand, when the rubber case 11 is preliminarily formed into a predetermined shape, it is possible to always produce a green body having a constant size, and there is almost no variation in size among the obtained green bodies.

The resin molded product 12 is not particularly limited, but is preferably a foamed resin molded product or a hollow rubber ball. When the resin molded product 12 is embedded from the outside of the rubber case 11, the rubber case 11 can be deformed without being damaged.

When the resin molded product 12 is the foamed resin molded product, its shape is not particularly limited and is appropriately determined in accordance with the shape of the molded product to be molded. When the molded body has a concave portion, the foamed resin molded product is preferably a tubular body.

Further, when the green body to be molded has a concave portion, it is desirable that the foamed resin molded article has a bottomed tubular shape. When a green molded body is produced by hydrostatic pressing, liquid enters the inside of the foamed resin molded product and pressure acts from the inside as well, so all surfaces including the inner wall of the recess formed in the green molded body In addition, a substantially uniform pressure can be applied, and a high degree of isotropicity and a dense structure can be imparted to the green body.

When the resin molded product 12 is a hollow rubber ball, it is desirable that the gas inside the hollow rubber ball be released by pressurization. This is to prevent the hollow rubber spheres from being damaged by the pressure applied when the green molded body is produced by hydrostatic pressing.

The raw material of the resin molded product 12 is not particularly limited. For example, when the resin molded product 12 is a hollow rubber ball, the same synthetic rubber as the rubber case 11 described above can be used. When the resin molded product 12 is a foamed resin molded product, examples thereof include foamed plastic. Specific examples thereof include styrofoam, foamed polyethylene, foamed polypropylene, and the like, and among these, styrene foam is preferable. This is because, although it is compressed and deformed, it is difficult to return to its original shape after being deformed, so that the springback property is small, and since blow molding is possible, it is possible to easily produce a desired shape. .

Next, as shown in FIG. 2A, the molding powder 13 is filled in the space of the rubber case 11. At this time, it is necessary to densely fill the molding powder 13 so that there is no gap between the rubber case 11 and the molding powder 13. If there is a gap between the rubber case 11 and the molding powder 13, the green molded body to be molded will have an irregular shape, and it will be difficult to manufacture a green molded body having a desired shape.

The molding powder 13 is not particularly limited, and examples thereof include a carbonaceous material and a ceramic material.

The carbonaceous material is not particularly limited,
For example, graphite powder, carbon black, coke powder, tar pitch, etc. can be mentioned. These may be used alone or in combination of a plurality of materials. The ceramic material is not particularly limited, and examples thereof include nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride, carbide ceramics such as silicon carbide and titanium carbide, and oxides such as alumina, silica, and zirconia. Ceramics etc. can be mentioned.

When the molding powder 13 is a carbonaceous material composed of coke powder and tar pitch, the compounding amount is 1 tar pitch per 100 parts by weight of coke.
It is preferably 0 to 80 parts by weight. Also, molding powder 1
In No. 3, the raw material powder was kneaded with a kneader or the like to give a lumpy raw material composition, which was then pulverized using a pulverizer or the like so that the average particle diameter was 20
It can be prepared by adjusting the thickness to about 30 μm.

Then, as shown in FIG. 2 (b), the rubber case 11 in which the molding powder 13 is sealed is attached to the hydrostatic pressure device 1.
5 is placed in the liquid medium 16 and the molding powder 13 is hydrostatically pressurized to produce a three-dimensional shaped green body.

The hydrostatic pressure device 15 is not particularly limited, and a hydrostatic pressure device commonly used in rubber press molding can be used. The liquid medium 16 is not particularly limited, and water can be used, for example.

Further, when the resin molded product 12 is formed into a bottomed tubular shape of the foamed resin molded product and a green molded body having a recess is produced, air inside the foamed resin molded product is removed and the molded product is placed inside the foamed resin molded product. It is desirable that the molding powder 13 is hydrostatically pressurized while being filled with the fluid (liquid medium 16). The pressure applied to the outer periphery of the rubber case 11 and the rubber case 1
The pressure applied inside 1 can be the same,
This is because it is possible to produce a green body having a high degree of isotropicity and a dense structure.

The above-mentioned hydrostatic pressure conditions are as follows:
Although it is appropriately determined in consideration of the material, composition, size of the green body, etc. of No. 3, it is usually desirable that the pressure is about 60 to 150 MPa. If the pressure is less than 60 MPa, the strength of the produced green body to be produced is insufficient and the shape stability is poor. On the other hand, if the pressure exceeds 150 MPa, the physical properties of the green formed body will no longer be improved, which is disadvantageous in terms of time and cost.

As described above, according to the rubber press molding method of the first aspect of the present invention, since the resin molding and the molding powder do not come into direct contact with each other, impurities contained in the resin molding and foreign matters such as foamed resin particles are not generated. A green molded body having a high purity and no defects can be produced without being mixed in the molding powder. Therefore, pin products and the like are not generated in a carbon product or the like manufactured by subjecting the green body manufactured by the rubber press molding method of the first invention to firing or the like, and a dense and defect-free product such as a crucible. Can be reliably manufactured. Further, since the resin molded product does not move with respect to the rubber case during the rubber press, it is possible to surely produce the green molded body having a desired shape.

Next, the rubber press molding method of the second invention will be described. According to the rubber press molding method of the second invention, a concave portion is formed near the center of the lower surface of the rubber case, and the concave portion of the rubber case having a space having a shape similar to that of the molded body to be molded has a cylindrical shape with a bottom. The resin molded product is fitted such that its opening faces downward, and after filling the rubber case with the molding powder, the rubber case is placed in the liquid medium of the hydrostatic pressure device, and the foamed resin is used. Air inside the molded product is removed, the liquid medium is filled into the foamed resin molded product, and the isostatic pressing of the molding powder is performed.

FIGS. 3 (a) and 3 (b) are explanatory views schematically showing how a green molded body is manufactured by the rubber press molding method of the second present invention.

As shown in FIG. 3A, in the rubber press molding method of the second aspect of the present invention, first, a concave portion 34 is formed in the vicinity of the center of the lower surface of the rubber press molding method, which has a shape similar to that of the green molding object to be molded. In the recess 34 of the rubber case 31 having a space,
The bottomed tubular foamed resin molded product 32 is fitted with the opening 37 thereof facing downward.

The rubber case 31 has a concave portion 34 formed in the vicinity of the center of the lower surface thereof. By using the rubber case 31 having such a shape, a bottomed cylindrical shaped molded body can be obtained. Further, as described in the rubber press molding method of the first aspect of the present invention, since the rubber case 31 is preliminarily formed into a predetermined shape, it is possible to always produce a green body having a constant size. The material and size of the rubber case 31 may be the same as the rubber case 11 described in the rubber press molding method of the first aspect of the present invention.

The shape and size of the recess 34 are not particularly limited, and are appropriately determined according to the size of the green body to be molded. The bottomed tubular foamed resin molded body 32 is fitted into such a recess 34 so that the opening 37 faces downward. This is because when the hydrostatic pressure is applied, the inside of the opening 37 is also filled with the liquid, and the pressure is applied from the inside of the foamed resin molded product 32 to the rubber case 11 filled with the molding powder.

The outer diameter and height of the bottomed tubular foamed resin molded article 32 are such that they can be fitted into the recesses 34, but the inner diameter thereof is foamed resin molded upon hydrostatic pressing. The size is appropriately adjusted so that the object 32 is not deformed or destroyed. Specifically, the thickness of the foamed resin molded product 32 is preferably about 1 to 10% of the outer diameter of the rubber case 31. When it exceeds 10%, the foamed resin molded product 32 becomes too thick, and it becomes difficult to separate the foamed resin molded product 32 from the rubber case 31 after rubber press molding. On the other hand, when it is less than 1%, the strength of the foamed resin molded product 32 itself is lowered,
It can be easily damaged.

The material of the foamed resin molded article 32 is not particularly limited, and the same material as the foamed resin molded article which is an example of the resin molded article 12 explained in the rubber press molding method of the first present invention is used. Can be mentioned.

Next, the molding powder 3 is placed inside the rubber case 31.
Fill 3. When filling the molding powder 33 into the rubber case 31, the space of the rubber case 31 and the molding powder 3
Forming powder 33 so that there is no gap between
Need to be packed closely. This is as described in the first rubber press molding method of the present invention. In addition, the raw material forming the molding powder 33 and the preparation method thereof are the same as the above-mentioned molding powder 1
The same raw material and preparation method as those in No. 3 can be mentioned.

Next, as shown in FIG. 3B, the rubber case 31 having the molding powder 33 filled therein is placed in the liquid medium 36 of the hydrostatic pressure device 35. By arranging the rubber case 31 in the liquid medium 36 in this way, air remains inside the foamed resin molded product 32, and when the foamed resin molded product 32 is arranged in the liquid medium 36 due to the buoyancy of the air. ,
The foamed resin molding 32 does not separate from the rubber case 31.

Next, the air inside the foamed resin molded product 32 is removed and the inside of the foamed resin molded product 32 is filled with the liquid medium 36. Inside of the foamed resin molding 32 and the rubber case 31
The same pressure is applied to the surroundings of the product to give the produced green body a high degree of isotropy and a dense structure, and the foamed resin molded product 32 is prevented from being deformed or damaged during hydrostatic pressure application. This is because

The method of removing the air inside the foamed resin molded product 32 is not particularly limited, and examples thereof include a method of sucking air by a pump such as a suction pump. By removing the air inside the foamed resin molded article 32, the foamed resin molded article 32 cannot obtain the buoyancy of the air, but the rubber case 31 is already placed in the liquid medium 36.
Since it is arranged inside, the foamed resin molded product 32 does not separate from the rubber case 31 due to the pressure applied from the liquid medium 36.

Then, the molding powder 33 filled in the rubber case 31 is hydrostatically pressurized to produce a three-dimensional green molded body. The isostatic pressing of the molding powder 33 can be performed under the same conditions as those described in the rubber press molding method of the first present invention described above.

As described above, according to the rubber press molding method of the second aspect of the present invention, since the foamed resin molded product and the molding powder do not come into direct contact with each other, impurities and foamed resin contained in the foamed resin molded product are obtained. A foreign material such as particles is not mixed in the molding powder, and a three-dimensional green molded body having high purity and no defects can be produced. Therefore, pinholes and the like do not occur in carbon products and the like manufactured by subjecting the green compact molded by the rubber press molding method of the second invention to firing and the like, and products such as crucibles that are dense and have no defects Can be reliably manufactured. Further, since the foamed resin molded product does not move with respect to the rubber case during the rubber press, it is possible to reliably produce the green molded body having the desired shape. Even in the rubber pressing method according to the first and second aspects of the present invention, the springback action or the like does not occur, and the green body does not crack or the like.

[0043]

EXAMPLES The present invention will be described below based on examples.

Example 1 A cylindrical rubber case (thickness 10 mm) having a diameter of 500 mm and a height of 1000 mm was provided on the lower surface with a diameter of 300 mm and a height of 7 mm.
A 00 mm recess was provided. Then, the outer diameter 3
A bottomed cylindrical foamed resin molded product made of expanded polystyrene having a diameter of 00 mm, an inner diameter of 250 mm and a height of 700 mm was fitted so that its opening faced downward.

Next, the raw material composition obtained by mixing 50 parts by weight of tar pitch with 100 parts by weight of fine petroleum coke powder was kneaded with a kneader to form a lump, and then pulverized by using a pulverizer. A carbonaceous molding powder finely pulverized to an average particle size of 25 μm was filled in the above rubber case, and hydrostatically pressurized at a pressure of 100 MPa by a hydrostatic pressure (CIP) device according to a conventional method, an outer diameter of 420 mm, an inner diameter of 250 mm, Height 82
A 0 mm bottomed cylindrical shaped feature was made. No cracks or damages were observed in the obtained green body, and
It was possible to produce a green body having the desired shape.

Then, the green compact is heated in a reducing atmosphere to 1000 ° C. under a temperature rising condition of 1.5 ° C./hour and fired, and then the obtained sintered body is placed in a reducing atmosphere. Then, it was heated to 3000 ° C. under a temperature rising condition of 50 ° C./hour for graphitization treatment to produce a crucible made of graphite.

Comparative Example 1 Inside a cylindrical rubber case (thickness 10 mm) having a diameter of 500 mm and a height of 1000 mm, a cylindrical container made of expanded polystyrene having an outer diameter of 300 mm, an inner diameter of 250 mm and a height of 700 mm was formed at the center thereof. , Particle size 0.3-1.0m
A molded product filled with m coke grains was set as a core.

Next, after the carbonaceous molding powder was filled in the space of the rubber case so as to cover the above-mentioned molded product with the same carbonaceous molding powder as in Example 1, the hydrostatic pressure was applied under the same conditions as in Example 1. Pressurization was applied to produce a green form. No cracks, damages, etc. were found in the obtained green body, but the molded product set in the rubber case as the above core moved and the green body of the desired shape could be produced. There wasn't.

Then, firing and graphitization were performed under the same conditions as in Example 1 to produce a crucible made of graphite.

When the crucibles produced in Example 1 and Comparative Example 1 were checked for the presence of pinholes,
No pinhole was confirmed in the crucible according to Example 1,
Although it was sintered very densely, a plurality of pinholes were confirmed in the crucible according to Comparative Example 1, and there were defects.

As described above, according to the rubber press molding method of the first and second aspects of the present invention, impurities and foreign matters are not mixed in the raw material molding powder during the molding process. In this way, it is possible to surely produce a green molded body having a target shape without defects, and a carbon product or the like obtained thereafter does not have pinholes and the like, and a dense and defect-free product can be manufactured.

[Brief description of drawings]

1 (a) and 1 (b) are explanatory views schematically showing how a green molded body is molded by the rubber press molding method of the first present invention.

2 (a) and 2 (b) are explanatory views schematically showing how a green molded body is molded by the rubber press molding method of the first present invention.

FIGS. 3 (a) and 3 (b) are explanatory views schematically showing how a green molded body is molded by the rubber press molding method of the second invention.

[Explanation of symbols]

11,31 rubber case 12 Resin molding 13,33 Molding powder 15,35 Hydrostatic pressure device 16, 36 Liquid medium 32 Foamed resin molding 34 rubber case 37 opening

Claims (6)

[Claims] 1. A rubber press molding method for producing a three-dimensional green molded body by filling a rubber case with molding powder and applying hydrostatic pressure. With the resin molded product set in the rubber case so as to come into contact with the outside of the rubber case,
A rubber press molding method characterized in that the molding powder is filled in the rubber case and the molding powder is hydrostatically pressurized. 2. The rubber press molding method according to claim 1, wherein the resin molded product is a foamed resin molded product or a hollow rubber ball. 3. The rubber press molding method according to claim 2, wherein the foamed resin molded product has a bottomed tubular shape. 4. The rubber press molding method according to claim 2, wherein the gas inside the hollow rubber ball is released by pressurization. 5. The hydrostatic pressurization of the molding powder in a state where the air in the space formed by the inner wall of the resin molded product is removed and the inside of the resin molded product is filled with a fluid. The rubber press molding method described in 1. 6. A recess is formed near the center of the lower surface,
Inside the rubber case, a bottomed tubular foamed resin molded product is fitted into the recess of the rubber case having a space similar to the molded body to be molded, with its opening facing downward. After filling the molded product with molding powder, the rubber case is placed in the liquid medium of the hydrostatic pressure device, the air inside the foamed resin molded product is removed, and the liquid medium is packed inside the foamed resin molded product. And pressurizing the molding powder with hydrostatic pressure.