JPS60216603A - Manufacture of electromagnetic wave reflecting body - Google Patents

Abstract

PURPOSE:To obtain a uniform electromagnetic wave reflecting characteristic by inserting a nonconductive nonwoven cloth between a sheet radical curing resin compound and a fiber conductor material and applying compression molding. CONSTITUTION:The fiber conductor material, the nonconductive nonwoven cloth and the sheeet form radical curing resin compound are laminated sequentially, and they are molded by compression at heating. In the heat compression molding, the side of the nonwoven cloth in contact with the resin compound is deformed smoothly together with said compound and the side in contact with the conductor material is hardly deformed, then a shear force due to the compound flow does not directly reach the conductor material because of a kind of cushion operation. Thus, the fracture of the fiber conductor material or the increase in the interval of fibers is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a resin electromagnetic wave reflector having uniform electromagnetic wave reflection characteristics.

In recent years, with the widespread use and advancement of electronic technology and communication technology, there has been a desire to develop inexpensive electromagnetic wave reflectors that can accommodate various shapes.

For example, electromagnetic wave reflectors with high efficiency and high reliability are strongly desired for shielding of electromagnetic waves generated from electronic equipment and reflectors of parabolic antennas used for reception of communication satellites and broadcasting satellites.

As is well known, metal materials have high electromagnetic wave reflectivity, but they have poor formability and are difficult to mold into arbitrary shapes easily and inexpensively.For example, in the case of reflective plates for parabolic antennas, etc.
It is difficult to obtain a precise curved surface of a reflector over a large area at low cost.

On the other hand, resin molding is an extremely useful technology for obtaining high surface precision at low cost, and can be applied to electromagnetic wave reflectors. It is necessary to mix or stack large amounts of
As one of the promising technologies, a technology to obtain an electromagnetic wave reflector by laminating a conductive layer made of conductive fibers and a sheet-like radical-curing resin compound and heating and compression molding has recently been attracting attention.

However, in the above method, the resin compound component flows during hot compression molding, and due to the shear force generated by this, the conductive fiber layer, which is the conductive layer, may break or the distance between the conductive fibers may partially increase. This has the serious disadvantage of creating a part that is transparent to electromagnetic waves.

An object of the present invention is to provide a novel method for manufacturing an electromagnetic wave reflector that solves the drawbacks of the conventional heat compression molding technique.

That is, the present invention provides an electromagnetic wave reflector having uniform electromagnetic wave reflection characteristics, which is produced by sequentially laminating (A) a fibrous conductive material, (B) a non-conductive nonwoven fabric, and (C) a sheet-like radical-curable resin compound and compression-molding the same under heating. The present invention will be described in detail below.

Examples of the fibrous conductive material (A) used in the present invention include nets of conductive fibers such as metal fibers, carbon fibers, metal-coated glass fibers, and metal-coated organic fibers;
Examples include materials such as cloth and mats. The type of metal is not particularly limited, but brass, aluminum, aluminum alloy, nickel, chromium, stainless steel, etc. are preferable from the viewpoint of cost and corrosion resistance.

The gap in the fibrous conductive material needs to be narrower as the frequency of the electromagnetic waves to be reflected increases, but the smaller the gap, the higher the frequency range can be reflected. The wavelength of high frequency waves is about 25°, so it is preferably 2.5° or less, especially 1°.
．． The number of birds is preferably 0 or less.

Moreover, it is of course possible to use the above-mentioned fibrous conductive material not only in one layer but also in multiple layers, but since fibrous conductive materials are relatively expensive, it is usually desired to obtain a high and uniform reflectance with a single layer.

The non-conductive non-woven fabric (B) in the present invention includes, for example, fabrics made from non-conductive organic or inorganic fibers such as rayon, polyester, acrino-nylon, glass, etc., without being woven on a loom, i.e., ordinary fabrics. Non-woven fabrics can be used. The thickness of this (B) non-conductive nonwoven fabric is usually 0.15 mm.
The above is preferable, and 0.3 to 5 is particularly preferable. Generally, if the thickness is less than 0.15 mm, the effect of preventing the opening of the fibrous conductive material as described below is reduced, which is not preferable.

Further, the above-mentioned nonwoven fabric may be impregnated in advance with a thermosetting resin that hardens during the molding process, such as unsaturated polyester resin or epoxy resin.

The sheet-like radical-curable resin compound (C) used in the present invention is compression molded in a heated state, shaped and cured.

Usually, a material consisting of a resin such as unsaturated polyester, a reactive diluent, a reinforcing fiber filler, a radical initiator, and various auxiliary agents is pressed with a roll and molded into one piece to form a fluidity sheet (plate shape). ) is plastically deformed under pressure in a heated mold, fluidized, and molded into any desired shape.This material is generally known as SMC (Sheet Molding Compound). It is.

As for the resin component (C), as mentioned above, unsaturated polyester resin is the most common, and usually α,β-unsaturated unsaturated acid-base acids such as fumaric acid, maleic anhydride, and itaconic acid; or saturated polybasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrahydrophthalic anhydride, cyclohexanedicarboxylic acid, trimellitic anhydride, dimethylterental acid; for example, ethylene glycol , propylene glycol, diethylene glycol, cyfropylene glycol, phthanediol, hexanediol, neopentyl glycol, trimethylbentanediol, dimethylolcyclohexane, hydrogenated bisphenol A, alkylene oxide adducts to bisphenol, glycerin, trimethylolethane, trimethylolpropane, It can be obtained by a condensation reaction with polyhydric alcohols such as pentaerythritol and trishydroxyethyl in cyanurate, and further by using a monobasic acid such as a fatty acid, dicyclopentadiene, etc. as a modified raw material if necessary, but it can also be obtained by a reaction with polyhydric alcohols such as pentaerythritol and trishydroxyethyl in cyanurate, but it can also be obtained by reacting with polyhydric alcohols such as pentaerythritol and trishydroxyethyl incyanurate, using monobasic acids such as fatty acids, dicyclopentadiene, etc. as modified raw materials, but also bisphenol. Polyhydric epoxy resin having a plurality of 7 epoxy groups in the molecule such as diglycidyl ether of A, resin having an unsaturated group which is an adduct of unsaturated carboxylic acid, polyhydric alcohol and unsaturated carboxylic acid are condensed together. For example, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, allyl alcohol, etc. can be hydroxylated with resins having unsaturated groups such as resins having isocyanate groups at the molecular ends. Among these, it is the cheapest,
Particular preference is given to unsaturated polyester resins with high crosslink density.

The reactive diluent used in (C) above imparts appropriate plasticity to the resin compound during molding and reacts with the unsaturated resin component to develop the strength of the molded product. Styrene, vinyltoluene, paramethylstyrene, α-methylstyrene, methyl methacrylate,
Radically polymerizable monomers such as ethyl methacrylate, butyl methacrylate, divinylbenzene, and ethylene glycol dimethacrylate are used.

The reinforcing material contained in the above (C) is one that improves the mechanical strength of the molded product, and is made of high-strength organic fibers such as glass fiber, carbon fiber, and Kepler (trademark) with a length of 3 to 5 mm.
Glass fibers cut to 0 mm are used, but inexpensive glass fibers are particularly preferred.

The filler used in (C) has functions such as reducing shrinkage and coloring, and includes, for example, calcium carbonate, alumina,
Silica, talc, barium sulfate, mica powder, aluminum hydroxide, clay, etc. are used.

Further, in the resin compound (C) above, a radical initiator that causes a radical curing reaction of the resin and the reactive diluent is used, and examples of the radical initiator include benzoyl peroxide, lauroyl peroxide, and tert-butyl hydroperoxide. organic peroxides such as oxide, tert-butyl peroxybenzoate, cumene hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, methyl ethyl ketone peroxide, etc., such as azobisisobutyronitrile, azobisvaleronitrile, etc. Azo radical initiators are preferably used, and one or more of them are appropriately selected and used depending on the temperature during compression molding.

In addition, a plurality of auxiliaries are usually used in the resin compound (C) above.

One of the auxiliary agents is a thickening agent that adjusts the viscosity and plasticity of the resin compound, such as metal oxides or metal salts such as magnesium oxide, magnesium hydroxide, zinc oxide, and tolylene diisocyanate, diphenylmethane diiso7, etc.
Diisocyanates such as anates or reactants with polyhydric alcohols are used. - In addition, in order to reduce molding shrinkage that occurs during compression molding, heat treatment of polyacrylic resin, polymethyl methacrylate resin, polystyrene resin, polyethylene resin, linear polyester resin, styrene-butadiene block copolymer resin, polyvinyl acetate resin, etc. A plastic resin is used as one of the auxiliary agents.

Further, various auxiliary agents such as an auxiliary agent that imparts mold releasability, an auxiliary agent that prevents color unevenness, and an auxiliary agent that improves the adhesion between a reinforcing material such as glass fiber and a resin may be mixed and used as appropriate.

The resin compound (C) above is usually used in the form of a sheet having a thickness of 0.5 to 7 mm.

In the present invention, (A) a fibrous conductive material, (B) a non-conductive nonwoven fabric, and (C) a sheet-like radical-curing resin compound are sequentially laminated in a mold and compression-molded under heating to produce an electromagnetic wave. Manufacture reflectors. At this time, consideration is given so that the side of the fibrous conductive material (A) during use is directed toward the incident electromagnetic waves. Therefore, (A) above,
(B) and (C) are sequentially laminated in the order of (A) → (B) → (C) on a lower mold installed in a press machine, and then the mold is tightened and compression molding is performed. Furthermore, in the case where an electromagnetic wave reflecting layer is formed on the upper mold surface, it is of course possible to layer the electromagnetic wave reflecting layer on the lower mold in the order of (C) → (B) → (A) and then compression molding.

The mold is usually heated to 120 to 170°C, and the pressure during compression molding is usually 10 to 200 kg/cyi, especially 1
Conditions of 35 to 155°C and 70 to tookg/ffl are preferable. The compression molding time is usually 1 to 30 minutes, and of course there is no particular adverse effect even if the compression molding time is long, but from the viewpoint of productivity, 1 to 5 minutes is preferable.

In the method of the present invention, a non-conductive nonwoven fabric is interposed between a fibrous conductive material and a sheet-like radical-curing resin compound and compression molded, so that the electromagnetic wave reflector obtained is uniform in each part of the molded product. It has excellent electromagnetic wave reflection characteristics and is characterized by extremely high quality and reliability.

This is because when hot compression molding is performed, shearing force is generated by the flow of the lower layer (C) radical-curing resin compound, but the nonwoven fabric effectively absorbs the shearing force (in other words, the nonwoven fabric (C) The side in contact with the resin compound deforms smoothly together with the compound,
On the other hand, (A) the side in contact with the conductive material hardly deforms, so the shearing force caused by the flow of the compound does not directly reach the conductive material due to a type of oxidation effect.)
.

Therefore, it is assumed that (A) breakage of the fibrous conductive material or increase in the fiber spacing (opening) is prevented, and the uniform reflection characteristics inherent to the fibrous conductive material are maintained.

At the same time, during hot compression molding, the lower layer radical curing resin gradually seeped out through the nonwoven fabric layer (A
) It cures between and on the surface of the fibrous conductive material to form a strong resin layer, which has the effect of effectively protecting the conductive material from the external environment.

The electromagnetic wave reflector of the present invention obtained as described above has uniform and excellent electromagnetic wave reflection characteristics in each part, regardless of whether the mold surface is flat or curved, resulting in extremely high product reliability. shows.

EXAMPLES The present invention will be specifically explained below with reference to Examples.

Example 1 First, a sheet-shaped resin compound (SMC) was manufactured as follows. That is, phthalic acid-based unsaturated polyester resin (Nister ML3101 manufactured by Mitsui Toatsu Chemical Co., Ltd.) 6
0 parts, polyvinyl acetate-based low shrinkage agent (Mitsui Toatsu Chemical Co., Ltd.)
Nistar EM 128) 40 parts, curing catalyst tert-butyl peroxybenzoate 1.2 parts, internal mold release agent zinc stearate 3.0 parts, colorant 10.0 parts (TR9301Gray manufactured by Toyo Ink Manufacturing Co., Ltd.), filling After mixing 150 parts of Calcrum Carbonate (NS≠200 manufactured by Nitto Funka Kogyo), add 1.5 parts of magnesium oxide as a thickener.
Glass roving cut into 1 inch pieces (PB5 manufactured by Nitto Boseki) was added to the prepared unsaturated polyester composition as a reinforcing material.
Containing 30% by weight of 49), the SMC impregnation machine was set so that the thickness was 2.5 mm and the unit weight was 400 to 450 g/m, and the sheet was formed into a sheet with a width of 1000 mm, and was aged at 40°C for 16 hours. did.

300 mu x 300 mm heated to 150°C (
D On top of the flat mold (lower mold), brass metal steel of 16 minosie (gap spacing 0.99 order) and thickness 0.5 mrt
A rayon nonwoven fabric (weight 70 g/rrl) of T was cut to the mold size and layered one after another, and then the sheet-like resin compound obtained as above was heated to 290 urn.
The pieces were cut to 290 mm x 290 mm and stacked, then the upper mold heated to 140°C was put down and compressed, and compression molded for 3 minutes at a pressure of 100 kg/c++t to obtain radio wave reflectors (I) of the present invention having two thicknesses.
I got it. The radio wave reflection performance of a radio wave reflector can be measured using a standing wave measuring device (
12.2.9 using a device manufactured by Shimada Rika Kogyo Co., Ltd.
．． The reflectance was measured at each point shown in FIG. 1 for electromagnetic waves of 3 and 4.0 GHz. The measurement results are shown in Table 1.

Example 2 Instead of the wire mesh used in Example 1, carbon fiber mat (3
0g/m), and polyester nonwoven fabric (thickness 0.46, weight 65g/7yL) was used instead of rayon nonwoven fabric.
An electromagnetic wave reflector (II) of the present invention was prepared using the sheet-like resin compound shown in Example 1 under the same conditions as in Example 1.

Table 1 shows the measurement results of electromagnetic wave reflection performance performed in the same manner as in Example 1.

Example 3 Polyester nonwoven fabric with 5 strips of thickness (435g/+nj)
unsaturated a IJ ester resin (Mitsui Toatsu Chemical ML
3101) 100 parts by weight, 10 parts by weight of calcium carbonate (N54200 manufactured by Nitto Funka Kogyo), 1.2 parts by weight of t-butylperoxybenzo/z-) as a polymerization initiator, and 4 parts by weight of magnesium oxide as a thickener. 1 part of the mixture
An electromagnetic wave reflector (G) of the present invention was obtained in exactly the same manner as in Example 2, except that a material impregnated with 17 g/m and aged at 40° C. for 16 hours was used. The measurement results of this electromagnetic wave reflection performance are listed in Table 1.

Example 4 The electromagnetic waves of the present invention were applied under exactly the same conditions as in Example 2, except that a thin polyester non-woven fabric with a thickness of 0.35 mm (40!i'/m'') was used instead of the polyester non-woven fabric in Example 2. A reflector (tV) was created.

The measurement results of this electromagnetic wave reflection performance are listed in Table 1.

Example 5 The electromagnetic wave reflector of the present invention was prepared under the same conditions as in Example 4, except that a thinner polyester nonwoven fabric with a thickness of 0.3 mm (35 mm/i) was used instead of the polyester nonwoven fabric in Example 4. (g) was prepared.The measurement results of this electromagnetic wave reflection performance are listed in Table 1.

Example 6 Electromagnetic wave reflection of the present invention was carried out under exactly the same conditions as in Example 2, except that an aluminum-coated glass fiber mat (55 l/m') was used instead of the carbon fiber mat used in Example 2. A body (Vl) was created. The measurement results of this electromagnetic wave reflection performance are listed in Table 1.

Comparative Example 1 Without using the rayon nonwoven fabric in Example 1, only the fibrous conductive material brass metal steel and sheet-like resin compound were compression molded under the same conditions as Example 1, and a comparative electromagnetic wave reflector ( A vID was created.The electromagnetic wave reflection performance was measured in a similar manner and is listed in Table 1.

Comparative Example 2 A comparative electromagnetic wave reflector was created by compression molding only the carbon fiber mat and sheet-like resin compound under the same conditions as in Example 2, without using the polyester nonwoven fabric in Example 2. The electromagnetic wave reflection performance was measured in a similar manner and is listed in Table 1.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the electromagnetic wave reflector of the present invention. In the figure, a9, a2, al, and a indicate measurement positions. 300 mrn, 17 = 1
50 mm ”'Q. Patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] (1) (A) Fibrous conductive material. A method for manufacturing an electromagnetic wave reflector having uniform electromagnetic wave reflection characteristics by sequentially laminating (B) a non-conductive nonwoven fabric and (C) a sheet-like radical-curable 41t fat compound and compression molding under heating.