JPS59169199A - Radio wave absorber and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a styrene foam radio wave absorber suitable for use in a radio anechoic chamber (anechoic chamber), and a method for manufacturing the same.

(Background Art) Conventionally, radio wave absorbers used in anechoic chambers and the like have been made by coating the interface of polystyrene foam with carbon paint in order to improve radio wave absorption characteristics. This radio wave absorber is made by heating styrene beads to form beads with an expansion ratio of about 10 to 20 times, mixing and stirring these beads with carbon powder and an adhesive, and then mixing the mixture with carbon powder and an adhesive. Put it in a mold and heat it to foam about 40 times.
It is manufactured by secondary foaming and molding.

However, since the radio wave absorber described above uses carbon powder and adhesive, it takes time to mold it. For example, the molding time is about 5 to 6 times that of a radio wave absorber that is not coated with carbon powder. I needed it. Another disadvantage is that the manufacturing cost is high due to the use of carbon powder and adhesives, as well as the time required for molding. Furthermore, if your hands touch this radio wave absorber, your hands will become dirty due to the carbon powder, so at present, a coating is formed on the surface of the molded product before use.

(Problems to be solved by the invention) The present invention has been made to solve the above-mentioned problems, and by dispersing conductive fibers in expanded polystyrene, it is possible to reduce the cost and time required for molding. An object of the present invention is to provide a radio wave absorber with improved radio wave absorption characteristics and a method for manufacturing the same.

(Structure and operation of the invention) The radio wave absorber according to the present invention is characterized in that it is constructed by dispersing conductive fibers in expanded polystyrene. The conductive fibers used in the present invention include, for example, acrylic fibers coated with iron sulfide on the surface, carbon fibers, etc., but are not limited thereto, and various other fibers can be used. As a method for dispersing conductive fibers in expanded polystyrene, a method is used in which foaming is carried out in two stages. In detail, first, styrene beads are heated to about 1
Primary foaming is performed at a foaming ratio of 0 to 20 times. Then, the styrene beads, which have become beads due to secondary foaming, are mixed and stirred with conductive fibers and water, and the mixture is placed in a mold of a predetermined shape and heated to cause secondary foaming. Note that adding a small amount of surfactant to the mixture can improve the dispersibility of the conductive fibers and further shorten the molding time. The secondary foaming is performed at a foaming ratio of, for example, about 40 times. Through this secondary foaming, the styrene beads, which were shaped like beads, self-fuse with heat to form a molded body, but at this time, the conductive fibers are dispersed and fixed at the interface of each bead. .

The radio wave absorber 1 of the present invention manufactured by the method described above preferably has a shape as shown in FIG.

That is, radio wave introducing portions (wave type) 3 having a substantially triangular prism shape are arranged on the substrate 2. The bottom surface of the base 2 is, for example, 300 mm x 600 mm, and when installed on the wall of an anechoic chamber or the like, a large number of unit blocks as shown in FIG. 1 are pasted.

Next, the present invention will be explained in detail.

Example Styrene beads (specific gravity 0.025) were first foamed by heating, and then acrylic fibers (length 0.5 mm, diameter 100 denier) with secondary foam and iron sulfide (Fed) attached to the surface 52.5 g (unit of thread thickness)), 30 g of water, and Ig of surfactant (neutral detergent) are mixed and stirred, and the mixture is put into a mold with a volume of 1751 cm, heated with steam, and then heated with steam. Next, foaming was performed to produce a radio wave absorber made of expanded polystyrene having the shape shown in FIG.

Comparative Example Styrene beads (specific gravity 0.025) were heated to form a primary (foamed) material, then a secondary foam and carbon powder 105
g and adhesive (epoxy emulsion) 262.5 g
The mixture was mixed and stirred, put into a mold having a volume of 1,751 cm, and then heated to cause secondary foaming to produce a radio wave absorber having the same shape as the above example.

Results The return loss vs. frequency characteristics of the radio wave absorbers of the above examples and comparative examples are shown in FIG. 2, respectively. In the figure, the solid line shows the results of this example, and the dotted line shows the results of the comparative example (conventional example). As is clear from FIG. 2, the absorption characteristics of this example are superior to those of the comparative example over a wide range of frequencies. In addition, the molding time of the radio wave absorber of the comparative example was approximately 3
While it took about 0 minutes, in the case of this example, it took about 5 minutes.

As a result, the radio wave absorber of this example has superior radio wave absorption properties compared to the conventional carbon-containing radio wave absorber (comparative example).
It turned out that the molding time could also be significantly shortened.

(Effects of the Invention) As described above, the radio wave absorber of the present invention has excellent absorption characteristics over a wide range of frequencies compared to conventional radio wave absorbers coated with carbon powder, and the molding time is also significantly shortened. I can do it. In addition, since no carbon or adhesive is used, the molding time can be shortened and manufacturing costs can be reduced. Furthermore, there is no need to cover the surface of the molded product because there is no need to worry about getting your hands dirty even if you touch the radio wave absorber. Further, according to the present invention, it is easy to automatically supply each material when manufacturing the radio wave absorber, which has the advantage of facilitating mass production.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a radio wave absorber according to an embodiment of the present invention;
FIG. 2 is a graph showing a comparison of the absorption characteristics (reflection loss - frequency) of a radio wave absorber produced according to the method of the present invention and a conventional radio wave absorber. 1...Radio wave absorber 2...Base 3...Radio wave introduction part (/& type) Patent applicant TK Co., Ltd. Patent application agent Patent attorney Yama Megumi Moto −

Claims (2)

[Claims] (1) A radio wave absorber made of expanded polystyrene comprising a plurality of approximately triangular prism-shaped radio wave introducing portions arranged on a base, characterized in that conductive fibers are dispersed in the expanded polystyrene. (2) A process of heating the styrene beads to cause primary foaming, a process of mixing and stirring the secondary foamed styrene beads, conductive fibers, and water, and placing these mixtures in a mold and applying force. A method for manufacturing a radio wave absorber made of expanded polystyrene in which conductive fibers are dispersed, which comprises a step of performing secondary foaming by heat and molding.