JPS646128B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an expanded graphite molded body suitable as a gasket, a packing, or a molding material thereof.

Conventional expanded graphite molded bodies of this type, such as expanded graphite sheets, are made from crystal grains such as scale-like natural graphite.
Usually, caterpillar-shaped expanded graphite particles that have been expanded 80 times or more in the axial direction are compressed into a desired amount of sheet form using a roll or a platen.

This expanded graphite sheet is mainly used as a molding material for high-performance gaskets and packings, and due to the inherent properties of expanded graphite, gaskets and packings made of expanded graphite have excellent heat resistance, occlusion resistance,
Although it has excellent chemical resistance and sealing properties, it also has the following drawbacks.

Namely, first, it is difficult to handle due to lack of strength, second, it easily adheres to the mating material and is easily destroyed between layers, and third, it tends to cause electrochemical corrosion to the mating material at the contact area. has.

Therefore, although various efforts have been made to overcome these drawbacks, they have not been sufficient.

That is, regarding the first drawback, in order to compensate for the lack of strength, reinforcing materials such as organic and inorganic polymer materials (for example, synthetic resins, water glass, phosphates, etc.) are used when forming expanded graphite sheets, that is, expanded graphite particles. It is common practice to add it during compression molding. However, as mentioned above, since the crystal grains of expanded graphite particles have been expanded by more than 80 times, it is impossible to expect the reinforcing material to be uniformly dispersed and mixed, and it is extremely difficult to obtain a homogeneous product. This is difficult, and furthermore, the addition of the reinforcing material impairs the properties of expanded graphite, such as chemical resistance and heat resistance. Therefore, the reality is that such a method is rarely used.

Further, as methods for eliminating the second drawback, surface treatment by impregnation with oil, plating treatment with metal, application of inorganic and organic solid lubricants, etc. are known. However, this method impairs the processability of expanded graphite sheets as molding materials for gaskets, etc., and is therefore often applied to final products, resulting in poor versatility. . Moreover, as described above, properties such as chemical resistance and heat resistance may be impaired.

Furthermore, in order to eliminate the third drawback, there are methods of adding sacrificial metals such as zinc, impregnation with inorganic corrosion inhibitors such as sodium nitrite and permanganate, or organic corrosion inhibitors such as amines and oils. Methods are known. However, according to the former method, strength properties such as flexibility are significantly impaired by mixing solid substances such as zinc, and according to the latter method, inorganic or organic corrosion inhibitors are mixed. Impregnation deteriorates heat resistance, making it difficult to maintain the desired effect at temperatures above 200°C.

Therefore, in view of the above-mentioned circumstances, it is considered that there is still no product that is sufficient to eliminate the above-mentioned drawbacks of expanded graphite molded bodies.

Therefore, the present invention provides an expanded graphite molded article in which a metal or metal oxide is vapor-deposited on the surface of expanded graphite particles, and the expanded graphite particles are compression-molded into a desired shape, thereby maintaining the original characteristics of expanded graphite. This is intended to eliminate the above-mentioned disadvantages that are inevitable in molded products made of expanded graphite alone, while maintaining the product as it is without any damage.

That is, according to the present invention, during compression molding (including roll molding) of expanded graphite particles, metals or metal oxides (hereinafter both are collectively referred to as "metals, etc.") deposited on the surface of expanded graphite particles. ) The cohesive force inherent in the fine powder increases the bonding force between the expanded graphite particles, making it possible to obtain an expanded graphite molded body with excellent strength. Here, as the metal etc. deposited on the surface of the expanded graphite particles, metals such as zinc, lead, aluminum, copper, antimony, magnesium, etc., or metal oxides thereof are used.

Therefore, even when such an expanded graphite molded body is used as a gasket or packing, there will be no drawbacks such as poor handling due to insufficient strength, seizure or destruction due to adhesion to the mating material. Furthermore, if the metal deposited on the surface of the expanded graphite particles is a sacrificial metal such as magnesium, aluminum, or zinc, or an oxide of these metals, electrochemical corrosion to the other material can be even more reliably prevented. be done. Moreover, since the expanded graphite particles are compression-molded using fine powder such as metal vapor-deposited on the surface, the shape of the expanded graphite particles themselves is not changed by additives, etc., and the original characteristics of expanded graphite are retained. is not harmed in any way.

By the way, as mentioned above, the reason why the bonding force between expanded graphite particles is increased by the cohesive force of fine powder such as metal is that fine powder such as metal is deposited on the surface of expanded graphite particles. , the specific surface area increases, and the surface energy increases. Therefore, it is desirable that the fine powder of metal or the like deposited on the surface of the expanded graphite particles be as fine as possible.

Further, various metals can be selected as the metal to be deposited on the surface of the expanded graphite particles, as described above, but lead or lead oxide is particularly suitable at high temperatures, as they have the best lubricity at high temperatures.

Furthermore, even if the final product such as a gasket is manufactured (compression molded) using an expanded graphite sheet obtained by compression molding expanded graphite particles on the surface of which a metal or the like is vapor-deposited, Alternatively, even if the above-mentioned expanded graphite particles are used and compression-molded into the final product shape, the above-mentioned advantages will still be obtained.

Next, the present invention will be specifically explained based on the drawings.

FIG. 1 shows an example of a vacuum evaporation apparatus for vacuum evaporating metal or the like onto the surface of expanded graphite particles.

That is, in the illustrated vacuum evaporation apparatus, 1 is a vacuum container, a supply pipe 2 for supplying an inert gas such as argon, and a vacuum suction pump (not shown).
The exhaust pipes 3 are connected to the exhaust pipes 3, respectively.

In the upper part of this vacuum container 1, there are shutters 4, respectively.
A hopper 4 is provided with a pair of drop ports 4b, 4b which are opened and closed at the same time as the hopper 4, and a suitable amount of expanded graphite particles 10 are stored in the hopper 4.

By the way, the expanded graphite particles 10 are generally obtained as follows.

In other words, a material with large crystal grains with well-developed crystals, such as flaky natural graphite, is oxidized mainly with concentrated sulfuric acid and concentrated nitric acid to generate a sulfuric acid compound between the crystal layers in the C-axis direction, and this is washed with water. The water is replaced by water. Then, after drying to appropriately remove surface water, it is placed in an atmosphere of 350° C. or higher, and water, etc. existing between crystal layers is vaporized by rapid heating. By doing so, expanded graphite particles in which the crystal grains are expanded 80 times or more in the C-axis direction can be obtained. The morphology of the expanded graphite particles is
As shown in the figure, it has a caterpillar shape with numerous wedge-shaped fracture grooves 10a, 10a, . . . that are discontinuous and parallel to the C-axis direction.

Further, in the lower part of the vacuum container 1, a pair of storage tanks 5, 5 are provided, which are located directly below each of the drop ports 4b, and are also located between the storage tanks 5, 5, for evaporation. A source crucible 6 is provided.
The evaporation source crucible 6 contains metals such as lead or lead oxide to be vapor-deposited onto the expanded graphite particles 10. The evaporation source crucible 6 is heated by a heating element 7 to evaporate the metal, etc., and its heating temperature, that is, the evaporation source temperature, can be adjusted as appropriate by a thermocouple 8. Note that 9 is a heating power source.

According to the vacuum evaporation apparatus as described above,
The inside of the vacuum container 1 is maintained at an atmosphere of 10 ^-2 to ^{10 -3} torr, and expanded graphite particles 10, 10, . 50 Å to 0.1 μm on the surface
Expanded graphite particles 10 are obtained in which ultrafine powder of metal or the like is uniformly and firmly deposited. The thickness of this vapor deposition layer can be set arbitrarily by appropriately adjusting the vapor deposition time, that is, the falling distance of the expanded graphite particles 10, and the evaporation source temperature, but is preferably 100 Å to 1 μm. Since it is quite difficult to measure the thickness of the vapor deposited layer and adjust it based on this, the thickness of the vapor deposited layer is adjusted by measuring the weight increase of expanded graphite particles due to vapor deposition, but this weight increase is 0.1 to 1. % weight increase is desirable.

In addition, according to the above vapor deposition method using the vacuum vapor deposition apparatus shown in FIG. In cases where the deposition rate is extremely slow, it is more effective to use a vacuum deposition apparatus as shown in FIG.

That is, as shown in FIG. 3, this vacuum evaporation apparatus includes a hopper 11 for storing expanded graphite particles that is provided with a shutter 11a and an opening/closing shutter 11b in a vacuum container 1, and a hopper 11 for storing expanded graphite particles that is provided with a shutter 11a of the hopper 11 from directly below the shutter 11a. A transfer body 12 that is inclined downwardly and faces directly above the storage tank 5, and a shutter 13a and an opening/closing shutter 13b that are located below the transfer body 12 and extend in a downwardly inclined manner directly above the evaporation source crucible 6. A hopper 13 for storing fine powder such as metal or the like is provided in each case. The transfer body 12 is formed by integrally connecting guide bodies 12b and 12c at both ends of a net-like body 12a such as a wire mesh, and the transfer body 12 and hoppers 11 and 13 are equipped with appropriate vibrators 12d and 11c, respectively. 13c. Note that 14 is a vacuum gauge terminal. In FIG. 3, the same parts as in FIG. 1 are given the same reference numerals.

Therefore, in order to vapor-deposit the expanded graphite particles 10 using such a vacuum evaporation apparatus, first, the vacuum container 1 is
The crucible 6 was heated to about 1500°C while evacuating from the exhaust pipe 3 so that the internal pressure was about 10 ^-4 torr, and supplying argon from the supply pipe 2 until the pressure reached 10 ^-2 to ^{10 -3} torr.
Let it heat to. Then, while supplying an appropriate amount of powder such as metal in the hopper 13 from the shooter 13a to the crucible 6 by vibration by the vibrator 13c, the expanded graphite particles 10 in the popper 11 are caused to vibrate by the vibrator 11c. Therefore, an appropriate amount is supplied from the shooter 11a onto the transfer body 12. In this way, the expanded graphite particles 10 supplied onto the transfer body 12 are transferred to the transfer body 12, that is, the mesh body 1.
2a is rolled and transferred downward by its inclination and vibration by the biplate 12d, and during this time, ultrafine powder such as metal is uniformly and firmly deposited on the surface. Thereafter, the expanded graphite particles 10 fall from the transfer body 12, that is, the guide body 12c, and are stored in the storage tank 5.

Therefore, according to the vacuum evaporation apparatus shown in FIG. 3, the evaporation time can be arbitrarily set by appropriately adjusting the inclination of the transfer body 12 and the vibration by the vibrator 12d, so the amount of evaporation can be freely determined. It is possible to perform a good vapor deposition process even when the vapor deposition rate is extremely slow. Moreover, since the expanded graphite particles 10 are transferred by rolling on the transfer body 12 and are deposited during this time, the vapor deposition can be performed more uniformly.

Then, by using a desired amount of the expanded graphite particles obtained as described above and compression molding them into a desired shape such as a sheet, the expanded graphite molded article of the present invention can be obtained. In addition, by vapor deposition using the vacuum vapor deposition apparatus as illustrated in FIGS. 1 and 3, the caterpillar shape of the expanded graphite particles 10 as shown in FIG. ,10a...
is maintained as it is, the mutual anchoring effect between the expanded graphite particles that occurs during compression molding is not impaired in any way, and the bonding force between the expanded graphite particles due to the cohesive force of ultrafine powder such as metal is effectively increased.

Expanded graphite sheets used as molding materials for gaskets, etc. may be made by compression molding expanded graphite particles on which no metal, etc. is vapor-deposited into a sheet shape, and then vapor-depositing metal, etc. on the surface of the expanded graphite particles, or by laminating such sheets. When a gasket or the like is manufactured by compression molding, the same effect can be obtained when the expanded graphite sheet obtained according to the present invention is used.

This is also based on the cohesive force of fine powder such as metal deposited on the sheet surface.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a vacuum evaporation device, FIG. 2 is an enlarged view of expanded graphite particles, and FIG. 3 is a schematic diagram showing another example of a vacuum evaporation device. 10...Expanded graphite particles.

Claims (1)

[Claims] 1. An expanded graphite molded body obtained by compression molding expanded graphite particles having a desired amount of metal or metal oxide deposited on the surface into a desired shape.