JPH10107479A - Radio wave absorbing gypsum board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent various kinds of radio interferences, etc., generated from the outside, without eliminating the conveniences of a gypsum board by covering the front and rear surfaces of a gypsum board containing conductive fiber with a base paper for gypsum board. SOLUTION: The front and rear surfaces of a gypsum core, using a beta-type calcined gypsum which contains a carbon fiber made of conductive coal tar pitch, oil pitch, coal liquefied substance, polyacrylonitrile, cellulose, etc., are covered with a base paper for gypsum board. To produce such a gypsum board, a specified quantity of calcined gypsum, water, additives, etc., are mixed to make a slurry, and it is formed by using a base paper for gypsum board, according to a conventional method in a normal gypsum board line and then is dried after curing. Thus, while keeping the conveniences of a gypsum board, the generation of various kinds of radio interferences from the outside can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gypsum board,
More specifically, the present invention relates to a radio wave absorbing gypsum board having excellent performance in radio wave absorbing properties.

[0002]

2. Description of the Related Art Due to recent remarkable advances in science and technology, advanced electronic equipment and electronic equipment have become widely used in various fields, and building components in which these are installed and used. Gypsum board is widely used because it is inexpensive in addition to remarkable performances such as fire resistance, sound insulation, heat insulation and workability.

With respect to electronic devices, the ambient temperature and humidity are set in order to operate the electronic devices and their systems normally provided in a computer room, a laboratory, a control room for various precision devices, a radio-related laboratory, and the like. In addition to taking into account the effects of vibrations and the like, ferrite tiles and copper wire mesh are applied to the interior and exterior of the building to prevent various types of radio interference. However, these ferrite tiles, copper wire mesh, and the like are very expensive, and their construction is complicated.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a radio-absorbing gypsum board for preventing the occurrence of various types of radio interference from the outside while utilizing the convenience of the gypsum board. With the goal.

[0005]

The above object is achieved by the present invention described below. That is, the present invention is a radio wave absorbing gypsum board in which the gypsum core contains conductive fibers in a gypsum board in which the front and back surfaces of the gypsum core are covered with gypsum board base paper.

The present inventors have conducted intensive studies on a method for solving the problems of the prior art, and found that a gypsum core should contain conductive fibers in order to easily give a gypsum board radio wave absorbability. The present inventors have found what should be done and completed the present invention.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to embodiments. Gypsum core constituting the radio-absorbing gypsum board of the present invention, as the gypsum, mainly use β-type calcined gypsum industrially, if necessary further, light aggregates such as perlite, vermiculite, Various foaming agents,
It is also possible to use a combination of known materials such as a gypsum water reducing agent, a gypsum setting accelerator, a gypsum setting retarder, a reinforcing fiber, and a water repellent. The addition of a water repellent is preferable because the radio wave absorption varies depending on the moisture.

[0008] The conductive fibers contained in the gypsum core include:
There is no particular limitation as long as the fiber has conductivity, for example,
Examples thereof include carbon fiber, copper fiber, and aluminum fiber, and carbon fiber is preferable from the viewpoint of light weight in consideration of reinforcement of a gypsum core. The carbon fiber may be either pitch-based or PAN-based, and includes, for example, carbon fibers made from coal tar pitch, petroleum pitch, coal liquefaction, polyacrylonitrile, cellulose, or the like.

The shape of the conductive fiber has a diameter of 1 to 50 μm.
m, a length of 1 to 40 mm can be used, but it is desirable to uniformly disperse and mix in the gypsum core in order to make the radio wave absorption uniform, so that the diameter is preferably 5 to
It is 20 μm long and 1-30 mm long.

[0010] By lowering the volume resistivity of the gypsum board and making the gypsum board conductive, incident radio waves are exchanged for electric current and further exchanged for heat to cause radio wave absorption. For this reason, the effect of radio wave absorption increases as the volume resistivity of the gypsum board is lower, but the volume resistivity is 80 Ω · cm.
If it is less than or equal to 30, an absorption shielding effect of 30 dB or more is exhibited. Generally, it is considered that an absorption / shielding effect of an average or more is obtained if the absorption is 30 dB or more.

The volume resistivity of the gypsum board is 80Ω · c.
m or less, the amount of the conductive fiber added is 0.5% by volume to 2% by volume of the gypsum board. If it is less than 0.5% by volume, the volume specific resistance becomes 80 Ω · cm or more, and the radio wave absorption performance is small. It is not preferable because the performance of the gypsum board varies.

As the base paper for gypsum board used in the present invention, generally used base paper is used. When producing the gypsum board, a predetermined amount of calcined gypsum, water, additives and the like are mixed to form a slurry. It is molded using a gypsum board base paper in a usual gypsum board line according to a conventional method, cured and dried. Also, if necessary, carbon fiber
Conductive fibers such as copper fibers and aluminum fibers may be mixed. The conductive fibers may be added to and mixed with calcined gypsum before the addition of water, or may be added to calcined gypsum slurry.

[0013]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following Examples and Comparative Examples unless it exceeds the gist thereof.

Examples 1 to 3 A slurry obtained by adding 80 parts by weight of water and a small amount of a foaming agent to 100 parts by weight of β-type calcined gypsum was mixed with a slurry having a diameter of 10 μm and a length of 20 μm.
mm of carbon fiber is 0.8, 1.2, 1.8 of β-type calcined gypsum.
The radio-absorbing gypsum board of the present invention having a thickness of 12.5 mm and a specific gravity of 0.65 was produced in a usual manner using an ordinary gypsum board line using gypsum board base paper on both sides in addition to the volume%.
For this gypsum board, the volume specific resistance was measured by the Wheatstone bridge method (JISH0505), and the radio wave absorption performance was measured by the Advantest method. The results are shown in Table 1.

Comparative Example 1 In the same manner as in Example 1, except that no carbon fiber was added.
A gypsum board of a comparative example having a thickness of 5 mm and a specific gravity of 0.65 was produced. With respect to this gypsum board, the volume specific resistance was measured by the Wheatstone bridge method (JIS H0505), and the radio wave absorption performance was measured by the Advantest method. The results are shown in Table 2.

Comparative Example 2 In the same manner as in Example 1, carbon fiber was replaced with β-type calcined gypsum.
By adding 4% by volume, a gypsum board of a comparative example having a thickness of 12.5 mm and a specific gravity of 0.65 was produced. About this gypsum board
The volume resistivity was measured by the Wheatstone bridge method (JIS H0505), and the radio wave absorption performance was measured by the Advantest method. The results are shown in Table 2.

[0017]

[Table 1] Volume specific resistance value and radio wave absorption performance of Examples

[0018]

[Table 2] Volume resistivity value and radio wave absorption performance of comparative example

[0019]

As described above, according to the present invention, it is possible to provide a radio-absorptive gypsum board which prevents the occurrence of various types of radio interference from the outside while utilizing the convenience of the gypsum board.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 14:38)

Claims (3)

[Claims] 1. A radio-absorbing gypsum board, wherein the gypsum core comprises conductive fibers, wherein the gypsum core comprises a gypsum board base paper coated on both sides thereof. 2. The conductive fiber according to claim 1, wherein the conductive fiber is a carbon fiber.
The radio-absorbing gypsum board according to the above. 3. The radio-absorbing gypsum board according to claim 1, wherein the volume specific value is 80 Ω · cm or less.