JPH06104354B2 - Method for manufacturing flexible graphite sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is a flexible material that is used as an electromagnetic wave shield material by being attached to the surface of packing material or gasket material, covering electric wires, lining electric equipment cases, and the like. The present invention relates to a method for manufacturing a graphite sheet.

(Prior Art) As an electromagnetic wave shielding material, a flexible graphite sheet is used for sticking to the surface of packing material or gasket material, covering electric wires, lining electric equipment cases, and the like. And
As a method for producing this type of sheet, the technique described in Japanese Patent Publication No. 44-23966 is known.

That is, a conventional flexible graphite sheet is manufactured by compressing expanded graphite into a sheet shape in the absence of an adhesive.

(Problems to be solved by the invention) However, since expanded graphite does not have high adhesiveness, when an excessive compression force is applied to the expanded graphite particles, a fragmentation phenomenon occurs in the particles themselves, and The adhesion between particles is lost.

Therefore, in the method of producing an expanded graphite sheet by repeatedly compressing expanded graphite in the absence of an adhesive as in the above-mentioned conventional technique, even if the compressive force is increased to reduce the sheet thickness, the particles themselves are The lower limit of the thickness dimension of the sheet is limited to a relatively high value due to the phenomenon of division and the loss of adhesion between particles.

Moreover, when the expanded graphite sheet is rolled by the rolling roll group, the difference in rotation caused between the rolling rolls, that is, the variation in the moving speed due to the dimensional change of the expanded graphite sheet and the uneven rotation of the rolling rolls causes a tensile force to the expanded graphite sheet. This will result in a loss of adhesion between the particles. Therefore, it has been impossible to manufacture a continuous expanded graphite sheet having a thickness of less than 0.25 mm by the conventional method.

By the way, the shielding effect of the expanded graphite sheet affects the thickness of the sheet, and the expanded graphite sheet having a thickness of 0.25 mm and a density of 1.0 g / cm ³ has a shielding effect of 70 dB at a frequency of 500 MHz.

On the other hand, in addition to the above-mentioned material having a high shielding effect of about 70 dB, an electromagnetic wave shielding material having a shielding effect of about 30 dB to 40 dB or about 20 dB lower than that is required. That is, the thin expanded graphite sheet having a thickness of less than 0.25 mm is required.

However, according to the conventional method, it was not possible to produce an expanded graphite sheet having a thickness dimension of less than 0.25 mm thickness, that is, a sheet having a shield effect lower than 70 dB, and therefore, it is more than the design allowable value. A sheet with a significantly high shielding effect is used as an electromagnetic wave shielding material.

However, since expanded graphite sheets are relatively expensive, it is economically wasteful to use sheets with a thickness that is significantly larger than the thickness that allows design tolerance. In particular, there is a problem in that it is restricted in use in a field where a low seated effect is required.

The present invention has been made in view of the background of the above-mentioned prior art, in order to secure a shield effect of moderate or less, thickness 0.25mm
It is an object of the present invention to provide a method for producing a flexible graphite sheet that can be easily formed even with a flexible graphite sheet of less than less than.

(Means for Solving the Problems) In the method for producing a flexible graphite sheet according to the present invention, an expanded graphite is supplied and adhered onto the adhesive layer while moving the sheet material on which the adhesive layer is formed. After that, the expanded graphite is rolled to a predetermined thickness and density by rolling means.

(Function) In the present invention, since the expanded graphite sheet adhered to the adhesive layer on the sheet material is rolled by the rolling means, the phenomenon of separation of the expanded graphite particles themselves and the separation between the particles are suppressed, and by the rolling means. Even if tensile force acts on the expanded graphite, no separation occurs between the particles.

Therefore, the sheet material can be manufactured by the strong rolling process.

(Embodiment) FIG. 1 is a schematic explanatory view showing an example of an apparatus for carrying out the present invention. In the drawing, 1 is a storage hopper, 2 is a vibration supply means, 3 is a sheet material, and 4 is a rolling means.

In the storage hopper 1, graphite particles in the form of flakes, powder, slices or particles are subjected to interlayer treatment with, for example, an oxidizing medium, and then rapidly heated or a temperature of 100 ° C. or more is applied to cause almost instantaneous graphite A caterpillar-like graphite material obtained by a well-known treatment method in which the particles are sufficiently expanded in the direction perpendicular to the carbon layer, and water rinsing or exposing treatment is performed as necessary.
That is, the expanded graphite 5 is stored, and the expanded graphite 5 dropped from the lower end opening of the storage hopper 1 onto the vibration supply means 2 is in accordance with supply conditions such as the vibration frequency of the vibration supply means 2 and the inclination of the chute 2a. Is supplied to the upper surface of.

The sheet material 3 is made of synthetic resin such as polyester resin and acrylic resin, metal foil such as aluminum foil and copper foil, and paper tape made from paper. The sheet material 3 is fed from the feeding drum 6 and wound on the winding drum 7 and is used in the tunnel. It moves alongside the endless conveyor 9 in 8 and moves at a speed synchronized with the endless conveyor 9.

As shown in FIG. 2, the sheet material 3 has an adhesive layer 10 formed on the front surface thereof and a release agent layer 21 formed on the rear surface thereof.

The rolling means 4 shown in FIG.
It is configured by arranging. 15,16,1 in the figure
Denoted at 7 and 18 are embossing rolls for embossing or marking on at least one of the sheet material 3 and the expanded graphite 5 that is adhesively rolled on the adhesive layer 10 of the sheet material 3. is there.

Next, the operation of the above configuration will be described.

The expanded graphite 5 dropped from the lower end opening of the storage hopper 1 onto the vibration supply means 2 is supplied onto the sheet material 3 according to the supply conditions such as the vibration frequency of the vibration supply means 2 and the inclination of the chute 2a.

The sheet material 3 is wound by the winding drum 7, placed on the endless conveyor 9, and is moved in the arrow direction at the same speed as the endless conveyor 9 in a horizontal state in which the downward bending is suppressed. The expanded graphite 5 supplied onto the sheet material 3 is placed on the sheet material 3 with a thickness determined by the relationship between the supply amount from the vibration supply means 2 and the moving speed of the sheet material 3, and particularly the expanded graphite 5 Particles located in the lower layer of the sheet material 3
Quantitative supply rolls 13, 14 as a thick layer 5A of continuous expanded graphite particles adhered to the adhesive layer 10 formed on the upper surface of
Pass through.

At this point, the distance between the constant quantity supply roll 13 and the sheet material 3, that is, the layer thickness of the thick layer 5A is such that the expanded graphite 5 has a predetermined thickness and density by the rolling means 4 arranged on the downstream side. The size is set to be suitable for rolling into a state.

That is, expanded graphite 5 obtained by rolling by rolling means 4
Having a density that is somewhat larger and slightly smaller than the thickness of
The size is set to form 5A.

With the movement of the sheet material 3, the expanded graphite 5 forming the thick layer 5A is the rolling roll group 4A which constitutes the rolling means 4.
And go through 4B and 4C and 4D. These rolling roll groups 4A and 4B
The distance between 4C and 4D is set to a size such that the thick layer 5A can be rolled to have a predetermined thickness and density. Therefore, when the thick layer 5A passes through the rolling means 4, the expanded graphite sheet 5B rolled to a predetermined thickness and density is formed on the sheet material 3.

The rolling of the thick layer 5A by the rolling means 4 causes the expanded graphite particles in the upper part of the thick layer 5A to adhere to the adhesive layer 10 on the sheet material 3.
Since the expanded graphite sheet 5B is formed by compressing the expanded graphite sheet while adhering to each other, the phenomenon of separation of the expanded graphite particles themselves which occurs during rolling and the separation between the particles are suppressed by the adhesive force of the adhesive layer 10. .

Moreover, even if tensile force acts on the expanded graphite 5 due to uneven rotation occurring among the rolling roll groups 4A, 4B, 4C, 4D, no separation occurs between the expanded graphite particles.

Therefore, the strong rolling treatment by the rolling means 4 becomes possible, and the expanded graphite sheet 5B having a thickness of 0.01 mm can be obtained.

FIG. 3 is a three-dimensional graph showing the shielding effect at a frequency of 500 MHz in terms of the density of the expanded graphite 5 and the thickness of the expanded graphite sheet 5B. In this figure, the shielding effect of about 30 dB to 40 dB is 0.1 mm to It can be seen that an expanded graphite sheet with a pressure of 0.14 mm is used, and a shielding effect of about 20 dB is obtained with an expanded graphite sheet with a thickness of 0.06 mm.

In the above embodiment, the sheet material 3 having the adhesive layer 10 formed on only one side thereof is moved to supply the expansive graphite 5 on the adhesive layer 10 to adhere the sheet material 3. The so-called double-sided tape formed with the agent layer is used as the sheet material 3
You may use as.

In this case, expanded graphite is supplied and adhered onto the adhesive layer on one side, and after rolling treatment, the release paper covering the adhesive layer on the other side is removed to form the adhesive layer. The exposed graphite is supplied, expanded graphite is supplied onto the adhesive layer, and the expanded graphite is adhered to the adhesive layer, followed by rolling.

(Effects of the Invention) As described above, according to the present invention, while moving the sheet material on which the adhesive layer is formed, the expanded graphite is supplied and adhered onto the adhesive, and then the expansion is performed by the rolling means. Since graphite is rolled to a predetermined thickness and density, a movable graphite sheet having a thickness of less than 0.25 mm, which has hitherto been impossible, can be easily formed.

Therefore, since an expanded graphite sheet having a shielding effect close to a desired value can be used as an electromagnetic wave shielding material, economical waste can be eliminated and the range of use can be expanded.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of an apparatus for carrying out the present invention, FIG. 2 is an enlarged cross-sectional view showing an example of a sheet material, and FIG. 3 shows a shielding property of a flexible graphite sheet obtained by the present invention. It is a three-dimensional graph shown. 3 ... Sheet material 4 ... Rolling means 5 ... Expanded graphite 10 ... Adhesive layer

Claims (1)

[Claims] 1. An expanded graphite is supplied and adhered onto the adhesive layer while moving a sheet material on which the adhesive layer is formed, and then the expanded graphite is rolled to a predetermined thickness and density by a rolling means. A method for producing a flexible graphite sheet, comprising: