JPS608203B2 - Pressure molding method for graphite compacts - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for forming a graphite compact.

More specifically, the present invention provides a method for uniformly pressurizing and crimp-bonding a graphite sheet stack made up of a plurality of graphite sheets stacked together to obtain a graphite molded body with almost no blisters or residual stress due to residual air. Regarding. Graphite has excellent heat resistance, chemical resistance, and lubricity, and sheet-like products are used in various mechanical devices,
It is widely used as gaskets and packing in automobiles.

However, due to its excellent physical properties, there is a strong demand for trough-shaped or other irregularly shaped products, and various fields have desired the development of a molding method to make this possible. Conventionally, when trying to obtain a gutter-like shape like a cylinder split vertically from a sheet of graphite, deforming a single sheet under pressure would result in cracks, cracks, etc. because graphite's crystal structure has extremely low plasticity. It is known that wrinkles etc. occur.

For example, a willow sheet with a density of 1.02/ground and 0.5 to the naked eye will wrinkle when bent into a curved surface with a radius of less than 1.
A sheet with 5 ribs will wrinkle if bent into a curved surface with a radius of curvature of 50 ribs or less, and will break if the radius of curvature is less than 3 ribs.
Similarly, as can be easily inferred from its crystal structure, a graphite sheet has a small degree of stress relaxation, and it is impossible to maintain the desired shape when an external force is removed. Therefore,
Instead of pressing and molding a relatively thick graphite sheet, a method of stacking and pressing a plurality of relatively thin graphite sheets may be considered.

In other words, this method prevents wrinkles, cracks, etc. from occurring by crimping and molding multiple graphite sheets into one, and maintains the desired shape due to the adhesion between the sheets even when external forces are removed. However, when pressure forming multiple graphite sheets using the conventionally known mold press method, the gas permeability of the graphite sheets is extremely low, so air remains between the graphite sheets, causing blisters. It appears. In addition, in this case, as can be inferred from the fact that the graphite structure is a layered lattice made up of successive layers of L6 carbon atoms, the crimping of each sheet does not necessarily occur at truly corresponding points; Stress remains in the body. Therefore, after being removed from the mold, it cannot maintain the same shape as the mold. or,
In severe cases, the sheets have the disadvantage of peeling off from each other. Conventionally, in the rubber extrusion molding method in which a material is interposed between a rubber pad and a mold and pressure is applied from the rubber pad side to form the material, "mahome" uses a rubber pad with a high hardness on the material side and a low hardness on the pressure side. A method called ``Method'' is disclosed in Taru Kosho 53-13471. However, when pressurizing and molding a graphite sheet stack consisting of several stacked graphite sheets, the density of the molded body must be increased by 0.2 degrees or more than the density of the graphite sheets, which is extremely difficult. A large molding load is required, and the thick rubber used in the conventional method is significantly disadvantageous because the pressure is weakened. As a result of repeated research into easily obtaining gutter-shaped or other irregularly shaped graphite molded bodies with good heat resistance and almost no swelling or residual stress due to residual air, the present inventors found that the purpose of simple pressure molding was to Instead of applying pressure using a thick rubber sub-chamber as is used in A graphite molded body with uniform density and almost no residual air or residual stress can be obtained by applying pressure using a rubber plate that is thick enough to efficiently transmit enough pressure to crimp and integrate the bodies. The present invention was developed based on this knowledge.

Accordingly, an object of the present invention is to provide a method for easily obtaining a gutter-shaped or other irregularly shaped graphite molded body that has good heat resistance and has almost no swelling or residual stress due to residual air.

According to the present invention, a sheet that is non-adhesive and has a low coefficient of friction and high mechanical strength is re-laid on a rubber plate that is fixed via a fixing means to the upper part of a female mold having a concave surface of a predetermined shape. Using a female mold assembly made of A method for press-molding a graphite molded body is provided, which is characterized in that the entire graphite sheet stack is press-fitted and integrated by applying pressure with a mold.

Next, the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an example of the shape of a graphite molded body obtained by the method of the present invention. FIG. 2 is a schematic diagram of conventional male and female molds. 3 and 4 show schematic cross-sectional views of an apparatus for carrying out the method of the invention. FIG. 3 shows the state before pressurization, and the rubber plate 6 is generally attached to the female mold 4 by the rubber plate fixing frame 6, but if the female mold is deep, it may be made loose. The rubber plate used in the present invention has a hardness of 8
Urethane rubber with a rating of 0 to 90 is preferable, and the thickness of the rubber is 5 to 90.
15 side is appropriate. Figure 4 shows the pressurized state, but the spacing between the male and female molds must be designed in consideration of the thickness of the rubber plate so that the molding load is sufficiently transmitted to the graphite sheet stack. Do not. Further, the sheet 7 on which the rubber slope is layered is made of a material having non-adhesive properties, a low coefficient of friction, and high mechanical strength, such as a reinforced Teflon sheet such as Chukoflo G type (manufactured by Chuko Kasei). The density of the graphite sheet 8 used in the method of the present invention is 0.2 or more times higher than the density of the intended molded product, preferably 0.
The smaller the size, the better. However, the density is 0.7#
Graphite sheets below the surface are easily cut and difficult to handle.
For graphite sheets with a density of 1.3 mm or higher, the skin layer on the surface is hard, so the peeling strength of the graphite molded product after being crimped and integrated becomes weak, so generally it is 0.7 to 1.3 mm. It is preferable to use a graphite sheet having a thickness of 0.9 to 1.1 ta. On the other hand, the thickness of the graphite sheet 8 is generally preferably on the 0.2 to 0.4 side. However, depending on the density, shape, and thickness of the intended molded object, a graphite sheet having a density and thickness outside the above range may be preferable.
In the present invention, a forming load (k9
Table 1 shows the relationship between the density of the molded body and the density of the molded body.

For the rubber plate 5, urethane rubber (hardness: 90, thickness: 1 mm) was used. Table 1 Using the method of the present invention, it is also possible to mold a molded article having a curvature in the longitudinal direction as shown in FIG.

In this case, a male mold of the desired shape is created, and a female mold is created parallel to it. The rubber plate fixing frame also has a curvature in order to attach the rubber according to the longitudinal curvature of the mold.
It is also possible to produce a molded body whose cross-sectional shape changes in the longitudinal direction as shown in FIG. According to the present invention, the precision of the female mold is not so strictly required as compared to conventional molds, so the mold as described above can be manufactured easily. FIGS. 7a and 7b show a part of a mold for obtaining a molded article having the shape shown in FIG. 6. FIG. 7a is a plan view thereof, and FIG. 7b is a side view thereof, in which 9 is a rubber plate fixing frame, 10 is a rubber plate, 11
is a female mold. Of course, the graphite molded body obtained using the method of the present invention can also be further pressed using a conventional mold as shown in FIG. FIG. 8 shows a schematic diagram of the hydrostatic pressing method. 12 is a liquid as a pressure medium, 13 is a rubber plate, 14 is a graphite sheet, and 15 is a male mold.

By this hydrostatic pressing method, the figures 1, 5 and 6
Although it is possible to obtain a molded body as shown in the figure, this method is not economical because the equipment is expensive. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited to the Examples.

Example 1 A graphite sheet with a density of 0.9 mm/sakaki and a thickness of 0.35 mm was cut into a rectangle with a width of 11 mm and a length of 7 mm, and 4 sheets were stacked and set in a mold.

Further, as a sheet to be layered on the rubber plate, Chuko Flow G type (Teflon sheet manufactured by Chukoh Kasei Co., Ltd.) was used. The rubber plates were made of urethane rubber with a hardness of 80 and used by stacking two pieces with a thickness of 5 and one with a thickness of 3 skin. 1
It was pressurized with 200 kg' ground to 1800 kg9' ground to give an average density of about 1.5 kg/ground.

Results of measuring the peel strength between the second and third sheets of the resulting gutter-shaped molded body with a bottom radius of curvature of 23.8 ribs (Figure 9a) using Shimadzu Autograph IS-2000. , No. 9
A peel strength chart as shown in Figure b was obtained. A, A
' indicates both ends of the trough-like molded body, B and B' indicate the transition from a curved surface to a flat surface, and C indicates the position of the lowest part of the molded body.
From this figure, the peel strength is determined over the entire surface of the molded product (A→B→C→B'
→ A'), it is approximately 30 ta' skin, and it can be seen that it is almost constant. Also, no air remained and no blistering occurred. Example 2 Pressure molding was carried out in the same manner as in Example 1, except that one sheet of urethane rubber having a hardness of 90 and a thickness of one piece was used as the rubber plate.

The same graphite sheet as in Example 1 was also used. The peel strength of the obtained molded product (Figure 10a) was measured using Shimadzu Autograph IS-2000 in the same manner as in Example 1, and as a result, a peel strength chart as shown in Figure 10b was obtained. Ta. From this figure, it can be seen that the peel strength varies over the entire surface of the molded product (A→B→
It can be seen that it is approximately 35 ta' over C→B→A) and is almost constant. Also, there was no residual air and no swelling. Example 3 Pressure molding was carried out in the same manner as in Example 1 except that one sheet of neoprene rubber having a hardness of 6 and a thickness of 1 mm was used as the rubber plate.

The same graphite sheet as in Example 1 was also used. The peel strength of the obtained molded article (FIG. 11a) was measured in the same manner as in Example 1, and as a result, a peel strength chart as shown in FIG. 11B was obtained. From this figure, it can be seen that the peel strength is approximately constant over the entire surface of the molded article (A→B→C→B→A') at approximately 25/skin. Comparative example 1,
Four graphite sheets of the same machine as in Example 1 were stacked and pressure-molded using a conventional mold consisting of a male mold 1 and a female mold 2 as shown in FIG.

The peel strength of the resulting molded article (FIG. 12a) was measured in the same manner as in Example 1, and as a result, a peel strength chart as shown in FIG. 12B' was obtained. As can be seen from this figure, an extremely non-uniform molded article was obtained in which the peel strength was maximum at A and A' and minimum at C. Non-uniform peel strength indicates non-uniform density of the compact. In this comparative example, stress remained and the shape was not completely maintained after being removed from the mold. Also, air remained. Naturally, the peel strength shows a minimum value in areas where air remains, but this is not shown because it is not quantitatively reproducible. Comparative Example 2 Four graphite sheets similar to those used in Example 1 were stacked and pressure-molded at a pressure of 800k9' using a hydrostatic press method (FIG. 8).

The peel strength of the resulting molded article (FIG. 13a) was measured in the same manner as in Example 1, and as a result, a peel strength chart as shown in FIG. 13B was obtained. As a result, it was found that the same tendency as the present invention was exhibited.

[Brief explanation of drawings]

FIG. 1 is an example of a graphite molded body obtained by the present invention,
Figure 2 is an overall view of a conventional mold consisting of a male mold and a female mold.
Figure 3 is a cross-sectional view of a mold for carrying out the method of the present invention, showing the state before pressurization, and Figure 4 shows the state of the mold being pressurized for carrying out the method of the present invention. 5 and 6 are cross-sectional views, and FIGS. 5 and 6 are examples of a graphite molded body having longitudinal curvature obtained by the method of the present invention, and FIG. 7a is a graphite molded body used to obtain a molded body having the shape shown in FIG. FIG. 7b is a plan view of a mold for carrying out the present invention, FIG. 7b is a side view of the mold, FIG. 8 is a schematic sectional view of an apparatus for hydrostatic pressing, FIGS. Fig. 11a is a cross-sectional view of a graphite molded body obtained by the method of the present invention with different types of rubber plates, Fig. 9b, Fig. 10b
and Fig. 11b is a peel strength chart of graphite molded bodies obtained by the method of the present invention with different types of rubber plates, and Fig. 12a is a cross-sectional view of graphite molded bodies obtained using a conventional mold. "First
Figure 2b is a peel strength chart of a graphite molded body obtained using a conventional mold, Figure 13a is a cross-sectional view of a graphite molded body obtained by isostatic pressing, and Figure 13b is a graphite molded body obtained by isostatic pressing. 1 is a peel strength chart of a graphite molded body obtained by the method. 3...Kawao mold, 4...Female mold, 5...Rubber plate, 0
6...Rubber plate fixing frame, 7...Sheet having non-adhesion, low coefficient of friction, and high mechanical strength, 8...
...Graphite sheet stacked body in which graphite sheets, which are molding materials, are stacked in layers, 9...Rubber plate fixing frame, 10...Com board, 11...Female mold. Figure 1 Figure 2 Figure 4 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13

Claims (1)

[Claims] 1 A female mold made by placing a non-adhesive sheet having a low coefficient of friction and high mechanical strength on a rubber plate fixed horizontally on the upper part of a female mold having a concave surface of a predetermined shape via a fixing means. Using a mold assembly, place a stacked graphite sheet body in which a plurality of flexible graphite sheets are stacked on top of the sheet, and process the stacked graphite sheet body with a male mold having a convex surface having a shape corresponding to the concave surface. 1. A method for pressure-molding a graphite molded body, which comprises pressing the graphite sheet stack to integrate the entire graphite sheet stack.