JPH06134917A - Expanded graphite laminated sheet, expanded graphite laminated composite material and production thereof - Google Patents

Abstract

PURPOSE:To provide an expanded graphite sheet composite material as a radiation and heat-barrier material excellent in drawing processability. CONSTITUTION:Plastic films 5, 5 are superposed on both surfaces of an expanded graphite sheet 4 and melted to be bonded to the sheet 4. Metal plates 6, 6 are further superposed on both surfaces of the plastic films 5, 5 to be bonded to the films 5, 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an expanded graphite laminate sheet and a method for producing the same, and an expanded graphite sheet composite material and a method for producing the same.

[0002]

[Prior art]

(Heat-resistant sealing material) Conventionally, asbestos-based sealing materials have been the mainstream as heat-resistant sealing materials such as packing and gaskets. However, due to their carcinogenicity, metal-based materials such as aluminum or stainless steel coated with rubber on a metal plate. It has changed to that of aramid fiber or aramid fiber.

On the other hand, in recent years, it has been confirmed that it is effective to use an expanded graphite sheet as the heat-resistant sealing material. However, it is difficult for the expanded graphite sheet to have low mechanical strength such as bending strength and tensile strength. Therefore, conventionally, as a first method for improving the mechanical strength of the expanded graphite sheet, a thin metal plate (copper foil, aluminum foil, stainless steel foil, hook plate, claw-finishing soft steel plate such as grommets, etc.) is expanded. There is a method of sandwiching between graphite sheets to form a composite. The second method is disclosed in Japanese Patent Laid-Open No. 62-62
As shown in Japanese Patent No. 273835, there is a method of impregnating an expanded graphite sheet with a resin.

On the other hand, the expanded graphite sheet, on the other hand, has excellent heat shielding properties in the plate thickness direction and heat diffusivity in the plate plane direction, which is several tens of times higher than those in the plate thickness direction. Suitable for use as a heat sink and heat shield by combining with a metal plate.

Heretofore, as the heat dissipation plate and heat shield plate of this type, for example, (a) asbestos products, (b) inorganic plates such as rock wool and glass wool, (c) metal plates,
(D) There are a composite material in which an inorganic plate is sandwiched between metal plates and bonded with an adhesive, and (e) a composite material in which an expanded graphite sheet is sandwiched between metal plates and bonded with an adhesive.

[0006]

[Problems to be Solved by the Invention]

(Problem of Measures for Improving Mechanical Strength of Expanded Graphite Sheet for Heat-Resistant Sealing Material) However, in the case of the first method for increasing the mechanical strength in obtaining a heat-resistant sealing material using expanded graphite as a base material, that is, When mechanically joining with tabbed mild steel plates, the mechanical strength is improved, but on the other hand, a large one cannot be obtained as the tabbed mild steel plates.
As a result, applicable products are limited to small products. Moreover, due to the presence of the claws, the sealing property often decreases with time, and rust is generated. In the first method, when a copper foil, an aluminum foil, or a stainless steel foil is used, the expanded graphite sheet is bonded with an adhesive, so that the heat resistance is not sufficient and the cost of the foil and the adhesive increases.
Furthermore, since all of this 1st method uses a metal thin plate, it is poor in flexibility.

The product obtained by the second method deteriorates the sealing property during the resin impregnation process and increases the amount of resin impregnated, which causes a high cost. Moreover, the impregnation with the resin lowers the flexibility and tends to cause non-uniformity in thickness.

(Problems for heat dissipation plate or heat shield plate)
Although the above (a) and (b) for obtaining a heat sink or heat shield, the heat shield effect is great, but it has poor heat dissipation and low mechanical strength, so it is difficult to use for the vibrating body and drive part. , (A) asbestos is a carcinogen, and (b)
Inorganic products also deteriorate the working environment.

The metal plate of (c) differs greatly depending on the material. For example, in the case of a copper plate or an aluminum plate, the heat dissipation is very good, but the heat dissipation in the plane direction of the plate (heat diffusion).
Is about the same as the plate thickness direction, and therefore the heat shield property is extremely poor.

The type (d) solves the above problems and is the most widely used at present, but it has many working steps and the product is expensive. As the product is used, the work environment is inevitable. In addition, workability such as drawing is poor.

On the other hand, in (e), as described above, the heat dissipation of the expanded graphite sheet in the plate plane direction is about 20 in the plate thickness direction.
Because it is double, it has better heat dissipation than others,
Although it is extremely useful as a heat sink or heat shield,
The adhesive strength varies due to reasons such as the difficulty of uniformly applying the adhesive to the adhesive, and when the heat sink or heat shield is drawn into a specified shape, the drawing force causes the adhesive layer to shear. In particular, there is a problem that floating portions are generated at corners or bent portions.

Therefore, a first object of the present invention is to have sufficient mechanical strength, high flexibility, and low cost for the purpose of a heat-resistant sealing material or the like.

A second problem is to provide a heat dissipation plate or heat shield plate with excellent heat dissipation and heat shield properties, high joint strength, and sufficient withstand drawing workability.

[0014]

The expansive graphite laminate sheet of the present invention which has solved the above-mentioned first problem is obtained by superposing a plastic film on both sides of the expansive graphite sheet and at least a part of the plastic film at these superposed surfaces. Is welded to the expanded graphite sheet.

In this production, plastic films are superposed on both sides of the expanded graphite sheet, and all or a part of these plastic films are heated to a temperature above the softening point temperature of the plastic film, and at least the heated part is in the plate thickness direction. It is possible to adopt a mode in which each plastic film is welded to and bonded to the expanded graphite sheet by pressurizing. In this case, it is preferable that the plastic film has a large number of through holes.

On the other hand, in the expanded graphite sheet composite material of the present invention which has solved the second problem, a plastic film is superposed on both surfaces of the expanded graphite sheet, and at least a part of the plastic film is superposed on the superposed surfaces of the expanded graphite sheet. And a metal plate is laminated on at least one surface of each plastic film, and at least a part of the plastic film is welded and bonded to the metal plate.

In this production, firstly, plastic films are superposed on both sides of the expanded graphite sheet, and all or a part of these plastic films are heated to a temperature not lower than the softening point temperature of the plastic film, and at least the heating part thereof. Is pressed in the plate thickness direction, each plastic film is welded to the expanded graphite sheet and joined, and then a metal plate is superposed on at least one of both surfaces of each plastic film, and the whole or part of each plastic film is It is possible to employ a method in which the plastic film is heated to a softening point temperature or higher, and at least the heated portion is pressed in the plate thickness direction to weld and join the plastic films to the metal plate.

Further, a plastic film is superposed on both sides of the expanded graphite sheet, and a metal plate is superposed on at least one of the outer surfaces of the expansive graphite sheet. It is also possible to heat the above and press at least the heated portion in the plate thickness direction so as to weld and join the respective plastic films to the expanded graphite sheet and the metal plate.

The expanded graphite sheet composite material obtained by any of the above methods is preferably subjected to spot welding subsequently from the viewpoint of improving properties such as drawability, heat dissipation and vibration damping performance.

[0020]

In the expansive graphite laminate sheet of the present invention, which is suitable for use as a heat-insulating sealant, a plastic film is welded to the expansive graphite sheet, either entirely or partially, and joined. Therefore, the plastic film compensates the bending strength and the tensile strength of the expanded graphite sheet, and since the plastic film is highly flexible, it does not hinder the flexibility of the expanded graphite sheet. In addition, since no adhesive is used for joining, the cost is reduced, and the variation in joining strength and thickness is small because of welding.

In the case of producing this expanded graphite laminate sheet, a plastic sheet is polymerized on both sides of the expanded graphite sheet, heated to a temperature not lower than the softening point temperature of the plastic film, and pressed to obtain the intended product. Since it can be obtained, the manufacturing equipment becomes simple and a wide product can be continuously manufactured.

On the other hand, when obtaining a heat dissipation plate or a heat shield plate, it is preferable to use a metal plate as the outermost surface material as described above. However, by using the expanded graphite laminate sheet described above and welding at least a part of the plastic film, it is possible to join the metal plate.

According to this welding and joining, compared with the case of using an adhesive, it is possible to join more uniformly and firmly, so that it is possible to prevent a phenomenon such as floating at the interface when drawing is performed. In this case, the plastic film also plays a role of fusion bonding with the expanded graphite sheet, and since both have flexibility, they exhibit a processing flow to some extent when drawn, and have excellent followability, thus exhibiting excellent formability.

In the production of such an expanded graphite sheet composite, the same advantages as in the case of producing an expanded graphite laminated sheet are brought about.

The expanded graphite sheet in the present invention is, for example, one manufactured as follows. That is,
An intercalation compound is obtained by treating natural graphite, pyrolytic graphite, quiche graphite, etc. with sulfuric acid, sodium nitrate, potassium permanganate, bromine, or the like. By heat-treating this at a high temperature, gas is generated from the intercalation compound, whereby the intercalation between the graphite layers is expanded by about 200 times in the direction perpendicular to the carbon plane. The expanded graphite is expanded graphite, and the expanded graphite is compression-pressed with a press, a belt, a roll, etc. to form an expanded graphite sheet. The thickness of the expanded graphite sheet used in the present invention is not particularly limited, but normally about 0.1 to 2 mm is suitable.

On the other hand, the plastic film used in the present invention may be of any kind as long as it is a thermoplastic resin such as polypropylene, polyethylene, styrene, polyvinyl chloride, etc., but excluding fluorine resin which is difficult to weld, for example. . The thickness is preferably as thin as possible, but normally about 10 to 100 μm is suitable. The plastic film may be a thin flat plate, but the one having a large number of through holes provided at a certain interval or the mesh-like one is more advantageous in terms of conductivity, and spot welding is easier. At the same time, air is released between the laminated sheets, which is desirable in that the adhesion is improved.

On the other hand, the welding method includes electric heating using a heat roll, a linear heater, a planar heater, high frequency heating,
The heating can be carried out by electric heating or other method, and after heating the plastic film at a temperature above its softening point, the heated portion is pressed in the plate thickness direction by, for example, a rolling mill or a press. In this case, the pressurizing pressure of about 1 to 10 kg / cm ² is sufficient, preferably ^{2 to} 8 kg / cm ² , and more preferably 4
~ 6kg / cm ²

The expanded graphite laminate sheet thus obtained has increased mechanical strength such as bending strength and tensile strength and has flexibility, and is cut into a predetermined shape or punched to form a packing. It can be used as a heat-resistant sealing material such as a gasket.

On the other hand, this expanded graphite laminate sheet can be suitably used as a base material for the expanded graphite sheet composite material described below.

On the other hand, the expanded graphite sheet composite material of the present invention is
The expanded graphite laminated sheet is used as a base material, and metal plates are laminated on both sides thereof, and the whole or a part of the plastic films on both sides of the laminated sheet are welded and joined together. In other words, expanded graphite laminated as a core material. The sheet and each metal plate as a skin material are joined by two uniform plastic films.

In this production, after obtaining the above-mentioned expanded graphite laminated sheet, metal plates are laminated on both outer surfaces thereof, and at least a part of the plastic film is heated and pressure-bonded to perform the joining. You can

In this case, the number of steps is two over time,
When continuously obtaining the desired expanded graphite sheet composite material from the beginning, both surfaces of the expanded graphite sheet are overlaid with a plastic film, and further a metal plate is overlaid on the outside thereof, and then the respective plastic films are welded and It can also be manufactured by pressure bonding.

It is to be noted that the composite material after welding should be fixed by applying a compressive force in the plate thickness direction by spot welding.
In addition to improving properties such as drawability, heat dissipation, and vibration damping performance, it is a necessary measure when used above the softening point temperature of the plastic film. Here, the spot welding is a kind of resistance welding, in which pressure is applied in the plate thickness direction from the upper and lower sides of the object to be welded by an electrode, a large current is caused to flow, and the heat generated by the resistance melts and welds. .

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically below with reference to the drawings. FIG. 1 is a perspective view of an expanded graphite laminate sheet of the present invention, and FIG. 2 is a perspective view of an expanded graphite sheet composite material using the same as a base material.

The expanded graphite laminate sheet 1 of the present invention comprises
As shown in FIG. 1, plastic films 5 and 5 are superposed on both surfaces of an expanded graphite sheet 4, and these plastic films 5 and 5 are welded and joined.

The expanded graphite sheet composite material 2 shown in FIG. 2 has the expanded graphite laminate sheet 1 as a base material and has both surfaces
Steel plates 6 and 6 are superposed, and the plastic films 5 and 5 are welded and joined to each other.

Expanded graphite laminate sheet 1 shown in FIG.
Can be manufactured, for example, in the manner shown in FIG.
That is, chemical-treated graphite, in which an acid and a peroxide are placed between graphite crystal layers, is expanded by about 200 times by heating with electricity or gas. Subsequently, the expanded graphite 3 is continuously compression-compressed by the compressors 10, 10 ... to manufacture the expanded graphite sheet 4. On the other hand, the unwinders 11 and 11 deliver the plastic films 5 and 5 at the same feed rate as the expanded graphite sheet 4, and the welding machines 12 and 12 deposit the plastic films 5 and 5 on the upper and lower surfaces of the expanded graphite sheet 4. While overlapping, the plastic films 5 and 5 are softened and welded. Furthermore, in order to increase the welding strength, the film is cooled by the coolers 13 and 13 and then wound by the winder 14,
The coiled expanded graphite laminate sheet 1 is obtained.

When the plastic films 5 and 5 are welded, the entire surface of the expanded graphite sheet 4 is uniformly welded as shown in FIG. 6, and only the both ends of the expanded graphite sheet 4 in the line direction are linearly welded. 7 (see FIG. 7), linearly weld 7 at an appropriate pitch in the line direction of the expanded graphite sheet 4 (see FIG. 8), or linearly weld at an appropriate pitch in the width direction of the expanded graphite sheet 4. It is also possible to weld 7 (see FIG. 9). By the way, the pitch is usually 1
A range of 00 to 1000 mm is suitable.

Further, as the plastic film 5,
In addition to the non-hole type, for example, as shown in FIG.
Those with through holes of φ2 to 50 mm for every 100 mm pitch,
Alternatively, for example, a mesh shape as shown in FIG. 11 may be used, and as described above, these are extremely effective.

On the other hand, the expanded graphite sheet composite material 2 shown in FIG.
Can be manufactured, for example, in the manner shown in FIG.
That is, while the expanded graphite laminate sheet 1 manufactured in the mode shown in FIG. 3 is conveyed on the line, the steel plates 6 and 6 are supplied from above and below at the same feed speed to set (polymerization) device 15, After setting 3 layers at 15,
The plastic films 5 and 5 are softened and welded by the welding machines 12 and 12. Further, in order to enhance the welding strength, the pressurizing machines 16, 16 and the cooling machine 17 are passed. Then, the expanded graphite sheet composite material 2 is obtained by cutting into a predetermined size with a cutting machine 18.

On the other hand, FIG. 5 shows an example of using steel plates 6'and 6'preliminarily cut into a predetermined shape. The steel plates 6'and 6'are set at the same position above and below the expanded graphite laminate sheet 1, and the heating furnace is set. After heating at 19, 19, the welding machine 12, 12
To soften and weld the plastic films 5 and 5.

Although not shown, setting devices 6 and 6 are provided on the downstream side of the setting (polymerization) devices 15 and 15 in the process of FIG. 3, and after laminating into a five-layer structure, welding, pressurization and cooling are performed. You can also do

Next, the effects of the present invention will be clarified by examples. (Example 1) The expanded graphite sheet has a thickness of 0.25 mm and a width of 1300 mm.
The thickness of the plastic film is 3
0 μm ethylene-vinyl acetate copolymer (EVA) 5%
As the filled polyethylene, as shown in FIG. 10, there were used staggered holes having φ2 mm for every 50 mm pitch. Then, in synchronism with the expanded graphite sheet at a speed of about 2 m / min, the plastic films are superposed on the upper and lower surfaces of the expanded graphite sheet, and are continuously welded as shown in FIG. I took it.

As a result of measuring the tensile strength of this expanded graphite laminate sheet, it was found to be 60 to 70 kg / cm ² , which was 20% higher than the strength of the expanded graphite sheet alone.
On the other hand, the flexibility was not so different from that of the expanded graphite sheet alone.

(Example 2) The expanded graphite laminate sheet produced in Example 1 was sandwiched between steel plates,
In the embodiment of FIG. 4, the expanded graphite sheet composite material of the present invention was obtained by thermocompression bonding above the softening point temperature of the plastic film. When the thermal conductivities of this product of the present invention and other materials are compared, as shown in Table 1 below, the product of the present invention has thermal conductivity comparable to that of a metal in the plate plane direction and carbon brick in the plate thickness direction. It was found to be of moderate thermal conductivity.

[0046]

[Table 1]

(Example 3) The product of the present invention manufactured in Example 2 and the preceding Example 1 were deep-drawn, and the occurrence frequency of deviation during processing was investigated. As a result, in the case of the prior art example 1, 24 of the processed products 100 were displaced, whereas in the case of the product of the present invention, the displacement was only 3.

Example 4 The expanded graphite sheet composite material produced in Example 2 was deep-drawn and spot-welded to prepare a heat insulator for an automobile shown in FIG. This product of the present invention takes advantage of the effects of vibration absorption and noise prevention, and this was compared with a steel plate alone and a conventional product. As the conventional product, a product obtained by stacking two steel plates was used. The results are shown in FIGS.

13 to 15 show the shock wave attenuation waveforms,
It can be seen that the impact noise of the product of the present invention is obviously attenuated in a short time when compared with the steel plate alone and the conventional product. On the other hand, FIG. 16 shows the results of frequency analysis of impact sound. The product of the present invention has a lower sound pressure level over the entire frequency when compared with the steel plate alone and the conventional product. On the other hand, FIG. 17 is a comparison diagram of sound pressure levels at normal temperature and high temperature, and it can be confirmed that the product of the present invention maintains the vibration damping performance even at high temperatures.

Example 5 As shown in FIG. 18, the expanded graphite laminate sheet a produced in Example 1 was sandwiched between the brake lining b of the brake pad and the back surface steel plate c and welded, and then Was actually used as a brake pad, and the thermal change in each of the above parts was investigated.
The survey results are shown in FIG.

Referring to FIG. 19, the expanded graphite laminate sheet a reduces heat conduction to the brake pad fixing surface (direction c) and diffuses heat from the brake lining b in the plane direction (direction a). Therefore, it can be seen that the deterioration of brake operation is reduced. By the way, the thermal conductivity from the brake lining b in the plane direction of the expanded graphite laminate sheet a is 80 to 120 kcal / m.
On the other hand, the thermal conductivity from the expanded graphite laminate sheet a to the steel sheet c was 3 to 4 kcal / m · Hr · ° C.

[0052]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to provide an expanded graphite laminate sheet having high mechanical strength and flexibility, and using this as a base material, for heat dissipation excellent in drawability. It is also possible to provide an expanded graphite sheet composite material that is effective as a heat shield composite material.

[Brief description of drawings]

FIG. 1 is a perspective view of an expanded graphite laminate sheet of the present invention.

FIG. 2 is a perspective view of an expanded graphite sheet composite material of the present invention.

FIG. 3 is a schematic view showing a production line for an expanded graphite laminate sheet.

FIG. 4 is a schematic view showing a production line of an expanded graphite sheet composite material.

FIG. 5 is a schematic view showing a production line of an expanded graphite sheet composite material.

FIG. 6 is a perspective view showing an example of welding.

FIG. 7 is a perspective view showing an example of welding.

FIG. 8 is a perspective view showing an example of welding.

FIG. 9 is a perspective view showing an example of welding.

FIG. 10 is a perspective view showing the shape of a plastic film.

FIG. 11 is a perspective view showing the shape of a plastic film.

FIG. 12 is a perspective view of a heat insulator using an expanded graphite sheet composite material.

FIG. 13 is a diagram showing a shock noise attenuation state of the product of the present invention.

FIG. 14 is a diagram showing a shock noise attenuation state of a conventional product.

FIG. 15 is a diagram showing a shock noise attenuation state of a single steel plate.

FIG. 16 is a frequency analysis diagram of an impact sound.

FIG. 17 is a comparison diagram of sound pressure levels at room temperature and high temperature.

FIG. 18 is a cross-sectional view of a brake pad using an expanded graphite sheet composite material.

FIG. 19 is a heat change diagram of the brake pad of FIG. 18.

[Explanation of symbols]

1 ... Expanded graphite laminate sheet, 2 ... Expanded graphite sheet composite material, 3 ... Expanded graphite, 4 ... Expanded graphite sheet, 5 ... Plastic film, 6 ... Metal plate (steel plate).

Claims (7)

[Claims] 1. An expanded graphite laminate sheet characterized in that a plastic film is superposed on both sides of an expanded graphite sheet, and at least a part of the plastic film is welded and bonded to the expanded graphite sheet on these superposed surfaces. 2. A plastic film is superposed on both sides of an expanded graphite sheet, and all or part of these plastic films are heated to a temperature above the softening point temperature of the plastic film, and at least the heated part is pressed in the plate thickness direction. And a method for producing an expanded graphite laminate sheet, which comprises welding and joining each plastic film to the expanded graphite sheet. 3. The method for producing an expanded graphite laminate sheet according to claim 2, wherein the plastic film has a large number of through holes. 4. A plastic film is superposed on both sides of an expanded graphite sheet, and at least a part of the plastic film is welded and bonded to the expanded graphite sheet on these superposed surfaces, and a metal plate is laminated on at least one surface of each plastic film. An expanded graphite sheet composite material, wherein at least a part of the plastic film is welded and bonded to a metal plate. 5. A plastic film is superposed on both sides of an expanded graphite sheet, and all or part of these plastic films are heated to a temperature above the softening point temperature of the plastic film, and at least the heated part is pressed in the plate thickness direction. After welding and joining each plastic film to the expanded graphite sheet, a metal plate is superposed on at least one of both surfaces of each plastic film, and the whole or a part of each plastic film is at a softening point temperature of the plastic film or more. A method for producing an expanded graphite sheet composite material, which comprises heating at least the heated portion in a plate thickness direction and welding and bonding the respective plastic films to a metal plate. 6. A plastic film is superposed on both sides of an expanded graphite sheet, and a metal plate is superposed on at least one of the outer surfaces of the expansive graphite sheet. Then, the whole or part of each plastic film is softened to the softening temperature. A method for producing an expanded graphite sheet composite material, comprising the steps of heating as described above, pressing at least the heated portion in the plate thickness direction, and welding and joining the plastic films to the expanded graphite sheet and the metal plate. 7. The method for producing an expanded graphite sheet composite material according to claim 5, further comprising spot welding after welding and joining by the method according to claim 5 or 6, and further joining.