JPS5948729B2 - How to feed expanded graphite to a mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of supplying expanded graphite to a molding die.

More specifically, the present invention relates to a method for smoothly and uniformly supplying expanded graphite, which is difficult to fill during molding because it becomes lumpy even under slight pressure, into a mold.

Conventionally, graphite is treated with acid to generate a graphite intercalation compound, which is rapidly heated at high temperatures to expand in a direction perpendicular to the plane of the graphite layer, that is, in the C-axis direction, resulting in a lightweight caterpillar-shaped flexible expansion. It is known that graphite has excellent compression moldability and can be easily formed into sheet-like or block-like molded products by pressurizing it alone or in combination with a binder.

However, in general, flexible expanded graphite particles have a bulk specific gravity of 0.
．． Since they are lightweight caterpillar-like particles with a size of less than O117/cc, they have extremely poor fluidity and become lumpy even under slight pressure, making it difficult to fill with material during molding and easily resulting in non-uniform molded products.

Therefore, in the past, the only method commonly used for forming expanded graphite was simply pressurizing and compressing the expanded graphite as it was, and with this forming method, it was possible to form only a sheet of about 1 size. First, it was impossible to mold rod-shaped objects, pipes, and other irregularly shaped products.

On the other hand, graphite has excellent heat resistance, chemical resistance, and lubricity, and sheet products formed using conventional methods are widely used as gaskets and backings for various mechanical devices, automobiles, etc. There is a great demand for rod-shaped objects, pipes, and other irregularly shaped objects due to their excellent physical properties, and the development of molding methods to make them possible has been desired from all walks of life.

By the way, the biggest obstacle to obtaining graphite molded products with shapes other than sheets is that there is no supply method for uniformly conveying and press-fitting expanded graphite particles as a raw material into a mold. That's what happened.

As mentioned above, the bulk specific gravity of expanded graphite particles is 0.01g.
Although it is extremely lightweight (less than /CC), the volume required for one molding is enormous, and it is extremely difficult to handle as it becomes lumpy even under the slightest pressure.

Therefore, even if you try to feed or fill it directly into a mold for molding rod-shaped objects, pipes, or other irregularly shaped products, it is impossible to feed it uniformly, and the obtained product becomes lumpy with slight pressure. Molded products have fatal disadvantages such as extremely nonuniform density, brittleness, and easy breakage.

Therefore, the inventors of the present invention have developed a method of forming graphite molded products from expanded graphite, which is extremely difficult to handle, into rod-shaped, pipe-shaped, or other irregularly shaped graphite products that have unprecedented mechanical strength and can be used in a wide variety of applications. In this method, as mentioned above, we focused on the importance of the method of feeding the raw material, expanded graphite particles, which have extremely low bulk density and become agglomerated under slight pressure, to the mold, and as a result of intensive research, we developed a method for feeding them into the mold. The present invention was achieved based on the finding that conveyance and supply using the equipped screw is suitable for smoothly and uniformly supplying expanded graphite particles to a mold.

Therefore, one object of the present invention is to provide a method for smoothly and uniformly supplying expanded graphite particles as a raw material to a molding die in order to obtain rod-shaped, pipe-shaped, or other irregularly shaped graphite molded products. be.

Another object of the present invention is to provide a method which can be carried out at low cost and is suitable for mass production of target products.

These and other features, features and benefits will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.

According to the present invention, expanded graphite is introduced from a hopper into a part of the screw of a cylinder that is directly connected to the hopper and is equipped with a screw having a predetermined compression ratio, and at the same time, the expanded graphite is extruded by rotating the screw, and the expanded graphite is directly or A method for supplying expanded graphite to a molding die is provided, which comprises compressing and supplying expanded graphite to a molding die that is indirectly and removably attached.

The invention will now be described with reference to the accompanying drawings.

FIG. 1 a, b, and C are cross-sectional views of a molded body obtained by compression-molding expanded graphite compressed and supplied into a mold by the method of one embodiment of the present invention. show.

These molded products can be obtained by an apparatus 1 as shown in FIG.

In Figure 2, one cylinder 2 has a compression ratio of 1.0 to 3.
．． A head 4 is attached to the end of the cylinder, and a mold 5 having slits 6 corresponding to the molded products a, b, and c illustrated in FIG. 1 is attached to the head. It is set to be detachable.

Further, the end of the slit 6 is closed by a removable lid.

When the compression ratio of the screw is 1.0, expanded graphite 8
Expanded graphite is extruded from the hopper 7 that supplies it without being compressed by the rotation of the screw, and
The expanded graphite enters the cavity of the head 4 and then is supplied and filled into the slit 6 of the mold 5 by the pressure of the expanded graphite that is continuously extruded from behind.

At this time, the expanded graphite is smoothly and uniformly compressed and supplied into the mold by the action of the rotating screw.

The mold 5 can be directly and detachably attached to the cylinder.

However, as shown in FIG.
It is preferable that the hollow part acts as a kind of buffer zone, and the expanded graphite can be supplied to the molding die 6 more smoothly and uniformly.

When the compression ratio of the screw 3 is 1 or more, the expanded graphite by the screw is compressed as it is conveyed and its density increases, and as a result, the length of the slit L1 of the mold 5 can be shortened.

However, if the compression ratio of the screw is 3.5 or more, the expanded graphite will become agglomerated due to compression, which is not preferable.

After uniformly supplying and filling expanded graphite into the slits 6 of the mold 5 in this way, the rotation of the screw 3 is stopped, the mold 5 is removed from the head 4, and as shown in FIG. By press-molding expanded graphite uniformly filled inside the slit 6 of the mold 5 to a length of L2 using the body 10, the intended graphite product can be obtained.

The product can be removed automatically and efficiently by uncapping the end of the slit and pushing it out, usually using hydraulic or pneumatic methods.

The expanded graphite particles used in the present invention are generally known natural graphite, quiche graphite, and pyrolytic graphite particles. Products soaked in mixtures of potassium acid, chromic acid, potassium dichromate, ammonium persulfate, etc., and mixtures of concentrated sulfuric acid and potassium chlorate, phosphoric acid, potassium permanganate, etc. are thoroughly washed with water and then dried. It is obtained by rapidly heating and expanding at a temperature of 600° C. or higher, preferably 800° C. or higher, and expands several tens to hundreds of times in the C-axis direction.

Next, a second embodiment will be described with reference to FIGS. 4 and 5.

This example is shown in Figures 4a and b. It is effective for obtaining a pipe-shaped hollow molded product as shown in C.

The apparatus is shown in FIG. The apparatus is substantially the same as that shown in FIG. 2, and each part is designated by the same number.

However, the mandrel 9 is provided directly at the end of the slit 6.

In this case, from the viewpoint of stability of the mandrel 9, it is preferable to connect the mold 5 directly to the cylinder 2, or to make the length of the head a little shorter.

The present invention was carried out using a screw with a compression ratio of 2.0, and then molded by pressure molding.

The results are shown in Table 1.

[Brief explanation of drawings]

Figures 1 a, b, and c are cross-sectional views illustrating the cross-sectional shape of the molded product, Figure 2 is an overall view of the supply press-fitting device, and Figure 3 shows the compression press fit into the mold. Cross-sectional view of main parts, No. 4
Figures a, b, and c are cross-sectional views showing other examples of molded products, and Figure 5 is an overall view of the supply press-fitting device for obtaining the product shown in Figure 4. 1... Screw extrusion device, 2... Cylinder, 3... Screw, 4...
Head, 5... Molding die, 6... Slit, 9... Mandrel.

Claims (1)

[Claims] 1. Expanded graphite with a bulk specific gravity of 0.01 g/cc or less is introduced from a hopper into a part of a cylinder directly connected to the hopper and equipped with a screw having a compression ratio of 1,0 to 3.5. At the same time, a screw is rotated to extrude the expanded graphite, and the expanded graphite is compressed and supplied to a molding mold that is removably attached directly or indirectly to the cylinder. Method. 2. A method according to claim 1, characterized in that the mold is fed via a head having a cavity and attached to the cylinder. 3. A method according to claim 1, characterized in that the mold is supplied directly from the cylinder.