JPS6378702A - Method of molding ceramics - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a molding method that can efficiently produce three-dimensional shaped ceramic molded products.

[Prior art and its problems] Conventionally, slurry casting, powder press molding, injection molding, and the like have been used as methods for molding ceramics.

However, although the slurry casting method can produce molded products with complex shapes at low cost, it is not suitable for mass production because of the long molding cycle.

Further, although the powder press molding method has high productivity, it tends to cause non-uniformity in the packing density of the powder between the inside and the surface of the molded product.

Furthermore, although the injection molding method has excellent molding accuracy and can produce molded products with uniform density, when manufacturing molded products that require a smooth surface such as crushed balls, it is necessary to post-process the protrusions remaining on the gate part. This caused the problem of reduced productivity. In addition, this injection molding method has problems such as a defect called lamination in which the surface of the molded product peels off thinly, and welding in the molded product, which reduces the strength of the molded product.

"Means for Solving the Problems" Therefore, in the present invention, a kneaded material of inorganic powder and a thermoplastic binder is hot extruded, and then this material is formed into a cavity of a predetermined shape while it is still flexible. We attempted to solve the above problem by cutting out the material with a mold and molding it at the same time.

The method for molding ceramics of the present invention will be explained in detail below.

Various inorganic powders that are ceramic raw materials can be used in the molding method of the present invention. As such inorganic powder,
Examples include pulverized oxide-based inorganic substances such as alumina, zirconia, mullite, forsterite, and cordierite, and non-oxide-based inorganic substances such as silicon nitride and silicon carbide. The size of the inorganic powder is 0.1~
The thickness is preferably about 50.0 μm. These inorganic powders may be used alone or in combination.

Furthermore, as the thermoplastic binder used in the molding method of the present invention, various kinds of thermoplastic binders are used.
In particular, binders used in ceramic raw materials for injection molding are preferably used. Such binders include polyethylene, polystyrene, polypropylene, acrylic resins,
Examples include thermoplastic resins such as ethyl cellulose, wax, and the like. These binders may be used alone or in combination.

When carrying out the molding method of the present invention, in addition to the thermoplastic binder described above, various additives commonly used in ceramic molding can be used. Examples of such additives include plasticizers such as diethyl phthalate, dibutyl phthalate, and dioctyl phthalate, and lubricants such as stearic acid and mineral oil.

The above-mentioned inorganic powder, thermoplastic binder, and additives are thoroughly kneaded in a temperature range in which the binder appropriately melts. Although this kneaded material can be directly subjected to extrusion molding as described below, it is usually first processed into pellets. A pressure kneader, a hot extruder, etc. can be used to mix and purify these raw materials. In addition, when pelletizing, the size is 10 mm.
The following is desirable. If the pellet is too large,
When this is heated and plasticized, a problem arises in that it cannot be uniformly plasticized.

As shown in FIG. 1, the molding material thus prepared is then heated and plasticized using an extrusion molding machine equipped with a heating tube, and then extruded into a predetermined shape. In this extrusion step, the molding material is heated (usually to about 50 to 200°C) depending on the type of binder used. Further, in this step, it is desirable to extrude the molding material downward. For horizontal extrusion, suitable holding means are required to hold the extruded material.

The cross-sectional shape of this extruded material is determined depending on the desired shape of the molded product. First, the width of the material to be extruded is set to be approximately equal to or larger than the width of the cavity of the mold, which will be described later.

Further, the thickness of the material to be extruded is determined so that when the material is sandwiched between the molds, a sufficient amount of the material is filled into the cavity as described later.

The cross-sectional shape of the material to be extruded is desirably formed so that the part where a large amount of material needs to be supplied is thick and the part where a small amount of material needs to be supplied is thin. That is, it is desirable that the cross-sectional shape of the material to be extruded be thick at a position corresponding to the deep part of the cavity of the mating mold. For example, when producing a spherical molded product, it is desirable that the cross-sectional shape of the extruded material be circular with a thick center.

Next, as shown in FIGS. 2 and 3, the material thus extruded is quickly sandwiched between molds 3 while still being flexible. As the mold 3 used in this step, a mating mold in which a cutting edge is provided around the cavity is preferably used. In the mating mold 3, the sandwiched material is removed with a cutting blade to remove the excess part around the cavity.
The cavity is filled with the necessary and sufficient amount of material.

Thereafter, when the mold 3 is opened as shown in FIG. 4, a molded product 4 having a desired shape is obtained.

When the material extruded in this way is sandwiched between the molds 3, the material may be sandwiched from both sides, but the mold 3
Alternatively, one side may be fixed and the other side may be moved to sandwich the material.

The molded product manufactured in this manner is appropriately subjected to degreasing treatment and sintering treatment to obtain a ceramic molded product.

"Operation" When a kneaded mixture of inorganic powder and thermoplastic binder, which is a molding material, is hot extruded, the material is extruded in a viscous and flexible state. This extruded material has good shape transferability and is easy to transmit pressure. When this material is sandwiched between the molds 3, the cavity of the molds 3 is filled with the material. At this time, excess material is cut off and removed.

Since the material is filled into the cavity of the mold 3 from the parting surface of the mold 3, which has the widest opening, defects such as welds and laminations do not occur, unlike injection molding methods that inject material through a narrow gate. . Further, in this molding method, since the material is filled into the mold from the parting surface, there is no need to provide a gate in the mold, and therefore, gate treatment of the obtained molded product is unnecessary.

"Example" Hereinafter, the method for molding ceramics of the present invention will be described in detail with reference to Examples.

(Example 1) Figures 1 to 4 show a first example of the molding method of the present invention. In this example, first, the particle size o
, it, oμ A binder mainly composed of polystyrene is added to the shoulder alumina powder as a thermoplastic binder, heated and kneaded at 150°C for 2 hours using a heating kneader, and this is processed into pellets with a particle size of 10 mm or less. did.

This pellet is heated and plasticized again using an extrusion molding machine,
It was extruded into a cylindrical shape with a diameter of 10 mm. The material temperature during extrusion was 180°C. This extruded material was immediately sandwiched between mating molds 3.

The matching mold 3 consisted of a left mold and a right mold each having a hemisphere of 10 mm in diameter, and was designed to sandwich the material extruded from the extrusion molding machine 1 from the left and right sides.

The molded product removed from this mating mold 3 has a diameter of 10 m5.
It was a precise spherical shape. There was a slight crease in the center of this molded product along the parting line, but it was very thin and disappeared during the degreasing process described below.

This demolded molded product is sent to a debinding furnace at 20℃/
After raising the temperature with H, 500°C x 1. OH degreased. Thereafter, it was fired at 1600° C. for 2 to 4 hours to obtain an alumina ball as a ceramic molded product.

This alumina ball was immersed in red ink to examine the presence or absence of cracks and welds, but it was confirmed that there were no cracks or welds. Then, when the alumina ball was crushed and the fractured surface was observed, it was confirmed that the inside as well as the surface part had an extremely dense structure.

(Example 2) A mixture of silicon nitride powder and a binder (binding material) mainly composed of polystyrene was extruded into a cylindrical shape with a diameter of 13 mm. Immediately after extruding this product, it was sandwiched between mating molds 3 having a spherical cavity with a diameter of 13 mm to obtain a molded product. This material was degreased and fired to produce silicon nitride balls.

When the compressive strength of this silicon nitride ball was measured, it was found to have a strength equal to or higher than that of a silicon nitride ball manufactured by injection molding.

Furthermore, when the dimensions of the manufactured balls were examined, it was found that they were molded with an accuracy equal to or higher than that achieved by injection molding.

Furthermore, when the ball was crushed and the inside was observed, it was confirmed that the ball was formed with uniform density throughout.

(Example 3) As shown in FIGS. 5 to 8, a mixture consisting of a binder (binding material) mainly composed of silicon nitride and polystyrene is extruded into a plate shape of 711Iff+×70111ffl, and this is inserted into a spherical cavity with a diameter of 7 mm. are sandwiched between the lO cutting mold 3, which has 10 consecutively placed horizontally, and 10 pieces are placed at a time.
Balls 5... were manufactured.

When the molding cycle was gradually shortened, molding was possible even at a high speed cycle of 5 seconds per cycle, confirming that the molding method of the present invention achieves high productivity.

(Example 4) A disk-shaped molded product provided with two through holes was manufactured as shown in FIGS. 9 to 12.

First, a mixture consisting of a binder (binding material) mainly composed of silicon nitride and boris dylene was extruded into a plate shape, and molded using a mold 6. The mold 6 consists of a male mold 6a and a female mold 6b, and the female mold 6b has a cylindrical cavity 6c.
is formed. Further, slide bins 6d, 6d are inserted into the female mold 6b from the side. male type 6a
is formed into a cylindrical shape having an outer diameter that tightly fits into the cavity 6c of the female mold 6b.

In order to perform molding with this mold 6, first, the female mold 6b is pressed so that it is almost in contact with the back surface of the material to be extruded from the extruder.
Set. When the male die 6a approaches the material to be extruded from the surface side, the plate-shaped material is separated into the male die 6a and the female die 6.
b, and the cavity 6c is filled with material. The filled material is removed from the mold after pulling out the slide pins 6d, 6d. As shown in FIG. 12, the obtained molded product 7 was disc-shaped with two through holes. When this molded article 7 was degreased and fired, a ceramic molded article could be obtained without any cracks.

As a result, it was found that according to the molding method of the present invention, not only ball-shaped ceramic molded products but also complex-shaped ceramic molded products can be manufactured.

"Effects of the Invention" According to the ceramic molding method of the present invention described above, the mold is filled with the extruded material in a viscous and flexible state, so the molding pressure is uniformly transmitted to the entire material,
The material is molded to a uniform density. Therefore, according to this molding method, a homogeneous ceramic molded article can be manufactured.

Furthermore, according to the molding method of the present invention, there is no need to provide a gate in the mold, so there is no need to perform gate treatment on the demolded molded product. Moreover, the molding method of the present invention molds the material into a predetermined shape by sequentially filling the mold with the continuously extruded material, so that a molded product can be obtained in a short cycle. Therefore, according to the present invention, a molding method with high productivity can be provided.

Furthermore, according to the molding method of the present invention, the material is filled into the mold cavity from the parting surface, and the material is plastically deformed. (The flow of materials does not overlap in the cavity as shown in FIG. can do.

[Brief explanation of the drawing]

Figures 1 to 4 are schematic process diagrams for explaining one embodiment of the ceramic forming method of the present invention, and Figures 5 to 8 are
The figure is a schematic process diagram for explaining the ceramic molding method performed in Example 3, and Figures 9 to 12 are Example 4.
FIG. 3 is a schematic process diagram for explaining the molding method carried out in FIG. l...Extrusion molding machine, 3.6...Mold, 4.7...
- Molded product, 5 poles.

Claims (1)

[Claims] A ceramic molding method characterized by simultaneously molding a hot extruded kneaded material of inorganic powder and a thermoplastic binder by sandwiching it between molds having cavities of a predetermined shape while it is still flexible. .