JP2001152026A - Electromagnetic wave absorbing paste including reactive inorganic composition and method of manufacturing for electromagnetic wave absorbing material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an electromagnetic wave absorbing paste for forming an electromagnetic wave absorbing material capable of machining, having a firm structure, high stiffness, durability and nonflammability and capable of changing its matching frequency to a predetermined value without changing main binder, thickness and kind of electromagnetic wave absorbing fillers. SOLUTION: This electromagnetic wave absorbing paste is a paste for forming an electromagnetic wave absorbing material principally comprising a thermosetting resin and a reactive inorganic compound produced from an element of the second group and/or the element of the third B group of the periodic system as the essential components and an electromagnetic wave absorbing filler, andmixing 5-80 pts.vol of the reactive inorganic compound based on the 100 pts.vol of the sum of the reactive inorganic compound and the electromagnetic wave absorbing filler and <=50 pts.vol of the thermosetting resin per 100 pts.vol of the sum of the reactive inorganic compound and the electromagnetic wave absorbing filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to at least one kind of reactive compound and at least one kind of electromagnetic wave absorbing filler.
TECHNICAL FIELD The present invention relates to a composite material containing a kind and used as an electromagnetic wave absorber capable of changing a matching frequency to a desired level, and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the increasing interest in electronic application products, global electronic pollution is increasing more than ever. Of the few available methods to overcome this pollution, shielding or absorbing electromagnetic waves seems to be promising in the future. Electromagnetic shielding protects the user from external electromagnetic interference, but impairs nearby by the reflection of electromagnetic waves. In view of this, electromagnetic wave absorption is the only method to be employed to prevent electromagnetic contamination.

In order to prevent the above-mentioned interference due to the reflection of electromagnetic waves, there is known an electromagnetic wave absorbing material prepared by dispersing ferrite or a mixture of ferrite and metal powder or ferrite and carbon powder in an organic polymer.
Commercially available electromagnetic wave absorbers for the UHF band are produced by using a rubber material containing magnetic powder or a resin containing magnetic powder such as ferrite and / or conductive powder such as carbon. Rubber-ferrite absorbers have low weather resistance and soften under warm and humid conditions. Further, the rubber ferrite absorbent is not suitable as a partition wall of a building or a member having sufficient strength due to low rigidity.

[0004] Japanese Patent Application Publication No. 299871/93
No. discloses a high-frequency electromagnetic wave absorbing resin composition made of a thermoplastic resin and a fibrous alkaline earth metal titanate, the molded product of which shows a strong tensile strength,
It also discloses that it has excellent absorption characteristics in a frequency band exceeding 500 MHz.

The above patent applications disclose a number of thermoplastics including PPS (polyphenylene sulfide), PBT (polybutadiene terephthalate) and PA-66 (polyamide). Since these thermoplastics are all flammable, these absorbers are not preferred as wall materials for buildings.

Japanese Patent Application Publication No. 12904/96 discloses an electromagnetic wave absorbing paste composed of ferrite and a resole type phenol resin. The technique of this patent application discloses a method of treating an electronic component by dipping the electronic component into a paste containing ferrite and a phenolic resin. The outermost ferrite / resin layer blocks and absorbs electromagnetic waves generated by the electronic device, thereby reducing electromagnetic interference. However, this prior art does not disclose any method for forming an electromagnetic wave absorbing sheet.

Japanese Patent Application Publication No. 235417/86
Discloses an electromagnetic wave absorbing material comprising a phenol formaldehyde oligomer, an isocyanate and a ferrite. Isocyanate is an essential component for achieving a predetermined mixing ratio that promotes generation of bubbles in the absorbent. This material can be used to reduce the side lobe noise of parabolic antennas.
Since this material contains many air bubbles, its mechanical strength was weak and it could not be used as a wall material. Further, isocyanates have a strong pungent odor and are harmful to the human body.

[0008] A thin and flat electromagnetic wave absorbing material for the UHF band is IEEE TRANSACTI in December 1994.
ONS ON BROADCASTING, 40th edition,
No. 4 is introduced. This multilayer type absorber is a wireless LA
It would be effective to use it on walls of ordinary homes and offices to protect the radio waves emitted from N and electronic devices. In this technique, a layer mainly composed of an epoxy resin containing carbonyl iron and ferrite has a thickness of 1.9 GHz, 2.45 GHz,
It has been found that it absorbs 80% or more of the 19 GHz electromagnetic wave. However, epoxy resins are very susceptible to fire, and the article did not disclose any useful manufacturing methods.

Japanese Patent No. 2704929 discloses a high-strength polymer cement material produced using a polymer precursor and hydraulic cement. Recently, the inventors have found that the polymer cement material disclosed in the above patent slightly absorbs electromagnetic waves. However, the frequency level and the electromagnetic wave reflection loss of the material are inadequate for absorbing electromagnetic waves generated from practical electronic devices in any way.

[0010] Electronic devices that are actually used generate various electromagnetic waves at various frequency levels, the magnitude of which varies from megahertz to gigahertz. The absorption characteristics of the electromagnetic wave absorber greatly depend on the frequency level. In the prior art, several methods have been used to change the matching frequency level. Such methods include: (a) changing the chemical structure of the electromagnetic wave absorbing filler (b) changing the ratio of the resin to the electromagnetic wave absorbing filler (c) the ratio of the complex magnetically permeable powder to the complex dielectric powder (D) changing the thickness of the absorbing material, and (e) changing the geometrical shape of the absorbing material.

However, in these methods, there is a problem in the manufacturing process of the absorber due to the difference in the fluidity of the paste, and there is a limitation in freely changing the matching frequency shift. Further, the prior art did not disclose a suitable and well-defined matrix material or manufacturing method capable of effectively manufacturing a thinner and flat electromagnetic wave absorbing material.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electromagnetic wave absorbing material which is machine-workable, structurally strong, highly rigid, durable, non-flammable and therefore easily producible as a long and wide sheet. To provide. Also, in the present invention, by replacing the reactive inorganic compound with a part of the electromagnetic wave absorbing filler, the content of the main binder, thickness, without changing the type of electromagnetic wave absorbing filler, the matching frequency. It can be changed to a desired level. Another object of the present invention is to improve the processability, durability, and mechanical strength of the absorbent by adding a reactive inorganic filler. Further, another object of the present invention is to provide an effective processing method for manufacturing an absorbent material, and a dome shape, a parabolic shape, a pyramid shape, a plate shape, an angle shape, a channel shape, a cylindrical shape, a spiral shape using the same. It is an object of the present invention to provide a manufacturing method of a complicated shape such as the above.

[0013]

According to the present invention, there is provided an electromagnetic wave absorbing paste used to form an electromagnetic wave absorbing material capable of changing a matching frequency to a desired level. At least one reactive inorganic compound formed by using an element of group IIA and / or group IIIB as an essential component; (a) a complex magnetically permeable ceramic powder; (b) a high dielectric powder; and (c) a low conductive metal. Powder (d) low-conductivity carbon powder containing at least one kind of electromagnetic wave absorbing filler, and the reactive inorganic compound in a volume ratio of 100 parts by mass of the electromagnetic wave absorbing filler and the reactive inorganic compound. 5 to 80 parts by weight, and further, the thermosetting resin was mixed at a volume ratio of 50 parts or less based on 100 parts by weight of the total amount of the electromagnetic wave absorbing filler and the reactive inorganic compound. Features The electromagnetic wave absorbing paste (Claim 1) wherein the thermosetting resin is a formaldehyde resin, an unsaturated polyester resin, an epoxy resin, an alkyd resin, a vinyl ester resin, a polyurethane resin, a diallyl phthalate resin, a polyamideimide resin, and a polyimide resin. Any one of
The electromagnetic wave absorbing paste according to claim 1, wherein the formaldehyde resin comprises:
3. The electromagnetic wave absorbing paste according to claim 2, wherein the paste is one of a phenol resin precursor, a melamine resin precursor, and a urea resin precursor.
The reactive inorganic compound formed by using an element of Group A and / or Group IIIB as an essential component is magnesium, calcium, strontium, barium, aluminum,
2. An electromagnetic wave absorbing paste according to claim 1, characterized in that it is a compound mainly produced by one of gallium and indium, an element of group IIA and / or IIIB being essential. The electromagnetic wave absorbing paste according to claim 1, wherein the reactive inorganic compound formed as a component is a hydraulic cement, wherein the paste reacts without adding water. The electromagnetic wave absorbing paste according to claim 1 (claim 6), wherein the electromagnetic wave absorbing filler has an electric resistance of 10 ⁻⁷ Ω.
2. The electromagnetic wave absorbing paste according to claim 1, wherein the electric resistance of the complex magnetically permeable ceramic powder is 10 ³ Ωm or more. An electromagnetic wave absorbing paste (claim 8),
The electric resistance of the complex magnetically permeable ceramic powder is 10 ⁶ Ωm
The electromagnetic wave absorbing paste according to claim 1, wherein the complex magnetically permeable ceramic powder is ferrite. 11. The electromagnetic wave absorbing paste according to claim 1, wherein the complex magnetically permeable ceramic powder is ferrite. 10) A method for producing an electromagnetic wave absorbing material capable of changing a matching frequency to a desired level using the electromagnetic wave absorbing paste defined in claim 1 as a starting material, comprising: (a) a Banbury mixer, a pressure kneader or (B) mixing the raw materials at a shear rate of 50 s ^-1 with a roll mill; (b) supplying the paste obtained in the step (a) to an extruder or a calender roll to form a desired molded product; (C) heating and curing the molded article at a high temperature. (Claim 11) The method for producing an electromagnetic wave absorbing material, wherein the electromagnetic wave absorbing material is plate-shaped, dome-shaped, parabolic 12. The method for manufacturing an electromagnetic wave absorbing material according to claim 11, wherein the shape is any one of a shape, a pyramid, an angle, a channel, a cylinder, a spiral, a grid, and a honeycomb. 12).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The components of the composition of the present invention and the processing method will be described respectively.

(1) Polymer matrix material First, in the present invention, several mixing ratios of raw materials that can be used as an electromagnetic wave absorbing material after mixing, molding, heat curing, and then laminating this with a conductive metal layer are disclosed. I do. As a first example of the present invention, the inventor has paid considerable attention to the selection of a suitable resin as the primary binder of the electromagnetically active filler.

Examples of the above resins include thermosetting resins such as formaldehyde resin, unsaturated polyester resin, epoxy resin, alkyd resin, vinyl ester resin, polyurethane resin, silicone resin, diallyl phthalate resin, polyamideimide resin and polyimide resin. There is a resin. The type of these thermosetting resins is not particularly limited, but formaldehyde resins are preferred in view of fire resistance. Normal,
Thermosetting resins have excellent durability, electrical properties, dimensional stability, chemical resistance and heat resistance. In the present invention, one or a combination of two or more thermosetting resins can be used.

Among many thermosetting resins, formaldehyde resin is excellent in thermal stability, solvent resistance, abrasion resistance and fire resistance, and is inexpensive. As the formaldehyde resin, a phenol resin, a urea resin and a melamine resin are well known, and are used alone or in combination to form a molding material. One of the main features of phenolic resins is that they can withstand working temperatures in the range of 120-170 ° C without significant degradation over time. In addition, phenolic moldings may be inherently superior in refractory properties. Phenolic moldings are considered quasi-noncombustible materials because of their low fire spread and low smoke generation. This is a priority feature to be considered when obtaining approval in the construction field. Examples of phenol formaldehyde resins include phenol, resorcinol, o-cresol or p-cresol, m-cresol, pt
Phenols such as -butylphenol, p-octylphenol, p-nonylphenol, p-phenylphenol, mixed xylenol, cashew nut shell liquid; gashyas, formalin, paraformaldehyde,
There are reactants with formaldehydes such as trioxane and hexamethylenetetramine. In general, the use of other thermoplastic resins is not excluded, but the use of phenol formaldehyde resins is preferred.

The thermosetting resin is a solution of water or alcohol, preferably methanol, ethanol, propanol, butanol, methyl ethyl ketone, cyclohexanol, phenol, cresol, ethylene glycol,
An alcohol solution such as trimethylene glycol is preferred. If the resin is used in liquid form, the non-volatiles should not be less than 30% by weight of the resin solution.

Various other components, such as denaturing agents, hardeners, accelerators, plasticizers, solidifying agents or solidification accelerators, coupling agents, etc., may be added to the electromagnetic wave absorbing paste, but these are used here. It is not an essential component of the disclosed electromagnetic wave absorbing paste. The denaturing agent is a polymer having an acid amide bond such as polyamide or polyacrylamide, and examples thereof include N-methoxymethyl nylon, nylon 6, nylon 66, nylon 610, and nylon 12.
When this additive is used as a solvent, the polyamide is preferably dissolved in alcohol and the polyacrylamide is preferably dissolved in water. Typical plasticizers include glycerol, glycerol triacetate, phthalic anhydride, furfural, alkylphenol, zinc stearate, magnesium stearate, rosin and the like. Examples of the solidifying agent or solidifying accelerator include hexamethylenetetramine, acetic acid, citric acid, sulfuric acid, hydrochloric acid, sodium hydroxide, sodium carbonate and the like. Examples of the coupling agent include γ-aminopropyltriethoxysilane, γ-ureidopropyltriethoxysilane, and γ-glycidoxypropyltriethoxysilane. Examples of curing agents include methyl ethyl ketone peroxide, benzoyl peroxide, cumene hydroperoxide, tertiary butyl perbenzoate, dicumyl peroxide, and the like. Examples of the curing accelerator include cobalt naphthenate, manganese naphthenate, and dimethylaniline.

(2) Electromagnetic Wave Absorbing Filler The electromagnetic wave absorbing material used in the present invention comprises at least (a) a complex magnetically permeable ceramic powder, (b) a high dielectric powder, (c) a low conductive metal powder, and (d) a low conductive carbon. It is one selected from the group consisting of powder. In particular,
(A) Complex permeable ceramic powders are most preferred.

According to a first embodiment of the present invention, a complex magnetic permeability
The conductive ceramic powder is an essential component of the electromagnetic wave absorbing paste.
You. This complex permeable ceramic powder contains hematite
(Fe ₂O₃), Magnetite (Fe₃O₄), General formula
MO. Fe₂O₃Is a ferrite represented by However
And M is Mn, Co, Ni, Cu, Zn, Ba, M
g, Cd, Ba, Sr and the like. Absorbent material has excellent absorption
In order to demonstrate the performance, the complex permeable ceramic powder
Electric resistivity is 10³Ωm or more, more preferably 10⁶Ω
m or more. Generally, Mn-Zn ferrite
Resistance is 2 × 10³Ωm, while the Mg-Zn ferrite
And the electrical resistance of Ni-Zn ferrite is 10 ⁶Ωm or less
Above.

The high dielectric powder includes MO. Particles such as particles, fibers, and whiskers. TiO ₂ type titanate, MO.
ZrO ₂ type zirconates are included. Where M is B
a, La, Sr, Pb, Zr, and K. Further, it is silicon carbide, silicon nitride, or the like, and its shape is a particle, a fiber, a whisker shape, or the like.

The low conductive metal powder includes particles, fiber-like supermalloy, permalloy, sendust, ferromagnetic alloys such as carbonyl iron. In particular, one of Al, V, Co, Mo, Cr, Ni, Si, C, etc.
Iron alloys composed of one or more elements are preferred. However, the electric resistivity of the low conductive metal powder is preferably 10 ⁻⁷ Ωm or more, and the initial transmittance is preferably 200 or more. The carbon mixed with the resin is preferably low conductive carbon, carbon fiber or the like. The electric resistivity of the carbon powder or carbon fiber is preferably 10 ⁻⁷ Ωm or more. The above-mentioned electromagnetic wave absorbing fillers (a) to (d) may be used alone in a desired ratio.
You may mix and use two or more.

(3) Reactive inorganic compound The present invention also discloses a reactive inorganic compound as an important component of the present invention. The reactive inorganic compound is very useful for changing the matching frequency to a desired level, and also improves processing performance, durability, and mechanical strength. The metal ions of the reactive inorganic compound are effective in crosslinking the thermosetting resin through an ionic crosslinking reaction during processing. Therefore, this reactive inorganic compound serves to shorten the high-speed shear mixing time and plays an important role as a processing accelerator for improving mechanical strength and durability. This additive can be found in Groups IIA and / or III of the Periodic Table.
It is an inorganic compound mainly formed by a group B element such as magnesium, calcium, strontium, barium, aluminum, gallium, and indium. We believe that the oxides, hydroxides, sulfates, carbonates and other compounds of magnesium, calcium, barium, aluminum and gallium are the best inorganic powders because of their good affinity with organic binders. discovered. Such examples include aluminum, aluminum hydroxide, calcium oxide, calcium hydroxide,
Calcium carbonate, calcium sulfate, magnesium oxide,
There are many hydraulic cements made of barium aluminate, gallium hydroxide, as well as calcium and / or aluminum.

The term "hydraulic cement" means a material which contains calcium silicate, calcium aluminate and hardens in the presence of water. The hydraulic cement is, for example, calcium silicate cement such as Portland cement or calcium aluminate cement such as high alumina cement. However, hydraulic cements are most preferred because they are chemically stable and are available in larger quantities than other reactive compounds. In addition, high pH compounds with a pH above 9 and low pH compounds with a pH below 5 show good hardness in high-speed shear mixing. Generally, the pH of Portland cement and high alumina cement is higher than 11, while the pH of gallium hydroxide is 3. Furthermore, in order to shorten the high-speed shear mixing time and improve the mechanical strength and durability, the reactive inorganic compound is at least a volume part with respect to 100 parts of the total amount of the electromagnetic wave absorbing filler and the reactive inorganic compound. We have found that it must be 5 parts, preferably at least 10 parts, more preferably at least 30 parts. On the other hand, in order to effectively absorb electromagnetic waves, the content of the reactive inorganic compound must be 80 by volume ratio with respect to 100 parts of the total amount of the electromagnetic wave absorbing filler and the reactive inorganic compound.
Parts or less, preferably 70 parts or less, more preferably 60 parts or less.

(4) Manufacturing Method As a second specific example of the present invention, the inventor provides an inexpensive and effective processing method for manufacturing an electromagnetic wave absorbing material. For example, the composition is premixed with an open kneader, a planetary mixer or a blender to mix the inorganic component and the resin. This pre-mixing is usually simple and only serves as a partial mixing, which can be omitted in the next step if necessary as it can be carried out in the next step. The next step is high-speed shear mixing in a twin roll mill, which is the most important step. The premixed paste or individual ingredients are fed to rolls for high speed shear mixing. For high-speed shear mixing, the speed ratio between the front and rear rollers is preferably adjusted to 5: 4. During high speed shear mixing, as the solvent in the paste evaporates, the paste becomes entangled around the two rollers. After a few minutes of mixing, the paste becomes entangled around the faster roll. In low-speed shear mixing, the forward and backward roll speeds are equal. During this time, the paste can be peeled off from the roll, so this paste is collected from the roll,
Roll it several times until it becomes a sheet.

In calendering, the speeds of the front roll and the rear roll are both reduced to keep the speeds equal. Calendering can be divided into two parts: "fining" and "stretching". Fine and uniform sheet is created by reducing the layer thickness by fining. In this step, the sheet is folded several times until it is a fine and uniform sheet and rolled again. During "stretching", the sheet is fed to the roll several times without folding. The sheet is then stretched to remove any defects contained within the sheet. After the completion of the roll milling, the sheet is directly cured by heating in an oven at a temperature of 135 ° C. to 250 ° C. for several hours as shown in Route 1 of FIG.

The paste subjected to the high-speed shear mixing may be supplied to an extruder without performing the above-described calendering, and may be formed into a channel shape, an angle shape, a pipe shape, or the like. The molded body is cured by heating in the same manner as described above. Or,
The sheet is further densified by pressing between the impression cylinders of a hydraulic laminating press at the desired pressure and a temperature of 40 ° C. to 180 ° C. to remove lamination defects (see route 2 in FIG. 1). Further, the obtained sheet can be formed into a complicated shape such as a dome shape, a parabola shape, a pyramid shape, or a spiral shape after calendering. Then, the obtained sheet or molded body is heated and cured as described above.

Another processing method includes a step of mixing with a Banbury mixer or a pressure kneader, which will be described below. For example, send the composition to a Banbury mixer or a pressure kneader,
Mix with the above static load. Mixing may use a pair of rotors rotating in opposite directions. The high speed rotor is rotated clockwise at a speed 1.5 times faster than the low speed rotor. The mixing time can be reduced by increasing the rotor speed, and the rotor speed is preferably kept above 10 rpm.
The composition is mixed until the highest net torque level is at least 1.5 times the lowest net torque, at which point the paste is removed from the mixer. The paste can then be fed to an extruder, preferably a single or twin screw extruder, and extruded as sheets or into any number of desired shapes, such as channels, pipes, and the like. Preferably, the screw speed is adjusted to give the desired feel and quality to the extruded material, and the extruder chamber temperature is controlled to be above room temperature. When the extrusion is completed, the extruded material is directly cured by heating in an oven at a temperature of 135 ° C. to 250 ° C. for several hours, as shown by route 1 in FIG. Alternatively, if the extruded material is a sheet, it is further densified by pressing between the impression cylinders of a hydraulic laminating press at the desired pressure and a temperature of 40 ° C. to 180 ° C. to remove lamination defects (route in FIG. 2). 2). Also, after extrusion, the sheet can be shaped into a desired shape. Alternatively, the paste may be subjected to high-speed shear mixing in a Banbury mixer or a pressure kneader and then calendered with a twin-screw roll mill.

The load torque during mixing can be measured by the method described below. The motor of the pressure kneader is connected via a load sensor to a computer and an analog / digital transducer that measures the power required by a pair of rotors rotating in opposite directions at a constant mixing speed. Torque can be calculated using the following equation: T =
(P. 9550) / n where T is torque and the unit is N.
m and P are powers and are units of kW, and n is a rotation speed of the rotor and units are rpm. Mixing torque and paste temperature
Enable continuous monitoring during operation.

As described above, in the present invention, the inventor has adopted the necessary special mixing method and molding technique in order to produce a member with a higher filler content. It is desirable that the content of the non-volatile organic substance in the electromagnetic wave absorbing composition is suppressed to a minimum level of 30% by volume of the electromagnetic wave absorbing filler. The reason for this is to improve the electromagnetic characteristics of the material. The transmittance, the dielectric constant, the electrical conductivity or the electrical resistance depends on the content of the electromagnetic wave absorbing filler in the resin.

When these fillers are increased to a necessary amount sufficient to keep the particles in contact with each other, the electromagnetic properties of the material are similar to solids consisting solely of electromagnetic wave absorbing fillers. For example, if the ferrite content of the ferrite resin composite material is very large, the ferrite resin composite material is almost the same as a fired ferrite tile in terms of electromagnetic wave absorption characteristics. However, when the content of the electromagnetic wave absorbing filler is large, the production becomes difficult and the mechanical strength is reduced, so that the content has an upper limit. Further, problems arise with the prior art, which does not disclose an accurate or specific manufacturing method to achieve this purpose.

Various methods are known for producing thermosetting plastics. Normally, these plastics contain very high amounts of resin, exceeding 50% by volume of the total volume of the final product. When the resin volume is high, molding by methods such as hand lay-up, spray-up, pressure bag, autoclave molding, cold pressing, pressure molding, resin injection, pultrusion, filament winding, injection molding, etc. Becomes easier.

The extrusion and calendering rings used in the present invention are very widely used in thermoplastic resin processing because thermoplastic resins usually have appropriate fluidity and thermal properties. Surprisingly, we mainly add to the thermoplastic composition by adding reactive inorganic compounds formed by elements of group IIA and / or IIIB,
It has been found that such fluidity can be obtained.
The metal ions of the reactive inorganic compound are effectively crosslinked with the thermosetting resin by an ionic crosslinking reaction during processing. Therefore, the reactive inorganic compound plays an important role as a processing accelerator for shortening high-speed shear mixing time and improving mechanical strength and durability. Further, another major requirement of the present invention is that the present invention discloses a specified shear rate applied to the paste during high shear mixing. We have a minimum shear rate of about 50 s ^-1
It was discovered that. In other words, at this level of shear rate, the energy required for the chemical reaction between the thermosetting resin and the electromagnetic wave absorbing filler is minimized. This energy is used for Banbury mixing, as disclosed in the present invention,
It can be provided only by a pressure kneader or roll milling.

Although the present invention discloses a reactive inorganic compound, it is very useful for changing the matching frequency to a desired level with or without changing the binder content. It is. If the binder content is kept equal at any mixing ratio, the fluidity of the paste can be kept at the same level in all cases. As a result, experience has shown that the production of many types of electromagnetic wave absorbers requires only one processing line. Further, when the resin content is increased, the absorbent becomes flammable and expensive, and dimensional stability is reduced due to shrinkage of the resin upon curing.

As shown in the following examples, the electromagnetic wave absorbing material of the present invention comprises three main members. That is, they are an electromagnetic wave absorbing filler, a reactive inorganic compound, and a thermosetting resin. In order to obtain a high dielectric constant of the reactive inorganic compound and the thermosetting resin (that is, a composition excluding the electromagnetic wave absorbing filler) and to obtain better absorption characteristics, the dielectric constant needs to be independent of frequency. Typically, the dielectric constant of most ceramics is higher than that of polymers, i.e., many ceramics have dielectric constants in the range of 6-10, while the dielectric constant of polymers is 2-10.
~ 5. In view of this point, it is desirable to increase the content of the reactive inorganic compound in the absorbent than the content of the thermosetting resin. Surprisingly, we have found that the dielectric constant of cement is frequency independent in the frequency range of 0.1-20 GHz. Therefore, it is preferable to use cement as the reactive inorganic compound, although this does not preclude the use of other reactive inorganic compounds.

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. In this example, “part” means “part in volume ratio”. The volume of a liquid type substance was calculated by dividing the mass of the liquid by the density. The density of the liquid type substance was measured according to JIS K5400-4.6.2. The volume of the solid type material was calculated by dividing the mass of the solid by the density. The density is calculated from the specific gravity measurement data, and the specific gravity is JIS K 7112-6.2.
4 was measured. In all Examples and Comparative Examples except Comparative Example 6, the cumulative amount of the electromagnetic wave absorbing filler and the reactive inorganic compound was kept at 100 parts by volume.

[0038]

EXAMPLES (Example 1) Preparation of electromagnetic wave absorbing material 90 parts of Ni-Zn ferrite, 10 parts of calcium aluminate cement, 31.5 parts of phenol resin, solvent 31.
Five parts were subjected to high-speed shear mixing with a pressure kneader to form a paste. Static load 0.5Mpa and rotor speed 64r
pm. The rotor diameter was 148 mm and the average spacing between the rotor and the kneader wall was 2 mm. Composition 2
After mixing for 20 minutes, the highest net torque level reached 3.0 times the lowest net torque (a plot of net torque versus mixing time for this step is shown as curve A in FIG. 3). The paste was subsequently removed from the press kneader. Thereafter, the paste was supplied to a single screw extruder to extrude a sheet having a thickness of 5 mm. After the extrusion was completed, the sheet was heated and cured in an oven at 200 ° C. for 18 hours to obtain an electromagnetic wave absorbing material. The procedure described in this example is an outline including quantitative data, and the reader wants the reader to follow the processing method and the flowchart in FIG. 2 (route 1) for accurate details.

Note: The phenolic resin used in this example is Shaunol BRS330 (trade name), an alcohol-soluble phenolic resin precursor manufactured by Showa Polymer Co., Ltd.
Shaunol BRS330 is available in liquid form as a solution of methanol and free phenol. The amount of the solvent in the mixture ratio is calculated by subtracting the amount of the non-volatile substance from the total amount of Shaunol BRS330. The amount of resin in the mixing ratio is Shaunol BRS330
Of non-volatile substances.

Shear rate Shear rate applied to the paste during mixing (γ)
Was calculated using the following known equation:

Γmax = (πDR) / t where D is the diameter of the rotor, R is the rotation speed, and t is the distance between the rotor and the wall of the kneader. This gave a shear rate of 248 s ^{- 1} for the paste being mixed.

(Example 2) Preparation of electromagnetic wave absorbing material 50 parts of Ni-Zn ferrite, 50 parts of calcium aluminate cement, 31.5 parts of phenol resin, solvent 31.
Five parts were subjected to high-speed shear mixing with a pressure kneader to form a paste. Static load 0.5Mpa and rotor speed 64r
pm. The rotor diameter was 148 mm and the average spacing between the rotor and the kneader wall was 2 mm. After mixing this composition for 59 minutes, the highest net torque level reached 2.8 times the lowest net torque (a plot of net torque versus mixing time for this step is shown in curve B of FIG. 3). Thereafter, the paste was removed from the press kneader. Next, this paste was supplied to a single screw extruder to extrude a sheet having a thickness of 5 mm. After the extrusion was completed, the sheet was heated and cured in an oven at 200 ° C. for 18 hours to obtain an electromagnetic wave absorbing material. The procedure described in this example is an outline including quantitative data, and the reader wants the reader to follow the processing method and the flowchart in FIG. 2 (route 1) for accurate details.

Note: The phenolic resin used in this example is Shonor BRS330 (trade name), an alcohol-soluble phenolic resin precursor manufactured by Showa Polymer Co., Ltd.
Shaunol BRS330 is available in liquid form as a solution of methanol and free phenol. The amount of the solvent in the mixing ratio is Shaunol BRS330.
Is calculated by subtracting the amount of non-volatile substance from the total amount of. The amount of resin in the mixing ratio is Shaunol BRS33
Equivalent to a nonvolatile content of 0.

Shear rate Shear rate applied to the paste during mixing (γ)
Was calculated using the following known equation:

Γmax = (πDR) / t where D is the diameter of the rotor, R is the rotation speed, and t is the distance between the rotor and the wall of the kneader. This gave a shear rate of 248 s ^-1 for the paste being mixed.

(Example 3) Preparation of electromagnetic wave absorbing material 60 parts of Ni-Zn ferrite, 40 parts of calcium aluminate cement, 31.5 parts of phenol resin, solvent 31.
5 parts and 4.5 parts of N-methoxymethyl 6-nylon (trade name, trade resin, manufactured by Teikoku Chemical Industry Co., Ltd.) were mixed with an open kneader to form a paste. Thereafter, this paste was supplied to a twin roll mill and subjected to high-speed shear mixing. For high speed shear mixing, the forward and backward roll speeds were 250 and 200 mm / s, respectively, and the nip spacing between the rolls was 3 mm. After a few minutes of high-speed shear mixing, the paste was slowly converted into a rubbery, viscous sheet in low-speed shear mixing to a strength sufficiently suitable for subsequent processing. The sheet was then peeled off, folded, and rolled again several times at the desired nip interval until a fine-grained, uniform sheet was obtained. When the calendering was completed, the sheet was heated and cured in an oven at 200 ° C. for 18 hours to obtain an electromagnetic wave absorbing material. It should be noted that the procedure described in this example is an outline including quantitative data, and the reader is required to provide accurate details in FIG.
I would like you to follow the (route 1) processing method and flowchart.

Note: The phenolic resin used in this example is Shaunol BRS330 (trade name), an alcohol-soluble phenolic resin precursor manufactured by Showa Polymer Co., Ltd.
Shaunol BRS330 is available in liquid form as a solution of methanol and free phenol. The amount of solvent in the mixing ratio is therefore: Shaunol BRS33
It is calculated by subtracting the amount of non-volatile substance from the total amount of zero. The amount of resin in the mixing ratio is Shaunol BRS
Equivalent to a non-volatile content of 330.

Shear rate Shear rate (γ) given to the paste during mixing
Was calculated using the following known equation:

Γmax = [6U ₀ / h ₀ ]. [0.22
6+ (U ₁ −U ₂ ) / 6U ₀ ] where U ₁ and U ₂ are the speeds of the two rollers, U ₀ is the average speed, and h ₀ is the nip interval between the rollers. This results in a shear rate of 118 s applied to the paste being mixed.
^-1 .

Example 4 Preparation of Electromagnetic Wave Absorbing Material 70 parts of Ni-Zn ferrite, 30 parts of calcium aluminate cement, 31.5 parts of phenolic resin, 31.
A composition containing 4.5 parts of N-methoxymethyl 6-nylon (trade name: Toresin, manufactured by Teikoku Chemical Industry Co., Ltd.) was used as an electromagnetic wave absorbing material according to the method shown in Example 3 using 4.5 parts of the composition.

Note: The phenolic resin used in this example is Shaunol BRS330 (trade name), an alcohol-soluble phenolic resin precursor manufactured by Showa Polymer Co., Ltd.
Shaunol BRS330 is available in liquid form as a solution of methanol and free phenol. The amount of solvent in the mixing ratio is thus calculated by subtracting the amount of non-volatile substances from the total amount of Shaunol BRS330. The amount of resin in the mixing ratio is Shaunol BRS330
Of non-volatile substances.

(Example 5) Preparation of electromagnetic wave absorbing material 50 parts of Ni-Zn ferrite, 24 parts of ferros alloy,
Composition containing 13 parts of barium titanate, 13 parts of calcium aluminate cement, 36 parts of phenolic resin, 36 parts of solvent, and 4.5 parts of N-methoxymethyl 6-nylon (trade name: Toresin, manufactured by Teikoku Chemical Industry Co., Ltd.) Was prepared as an electromagnetic wave absorbing material according to the method described in Example 3.

Note: The phenolic resin used in this example is Shaunol BRS330 (trade name), an alcohol-soluble phenolic resin precursor manufactured by Showa Polymer Co., Ltd.
Shaunol BRS330 is available in liquid form as a solution of methanol and free phenol. The amount of solvent in the mixing ratio is thus calculated by subtracting the amount of non-volatile substances from the total amount of Shaunol BRS330. The amount of resin in the mixing ratio is Shaunol BRS330
Of non-volatile substances.

(Example 6) Preparation of electromagnetic wave absorbing material 50 parts of Mg-Zn ferrite, 50 parts of aluminum hydroxide
Parts, vinyl ester 48 parts, sodium carbonate 0.09
And a composition containing 0.3 part of methyl ethyl ketone peroxide as an electromagnetic wave absorber according to Example 1.

(Comparative Example 1) Preparation of electromagnetic wave absorbing material 100 parts of Ni-Zn ferrite, phenol resin 31.
Five parts and 31.5 parts of a solvent were mixed at high speed by a press kneader to form a paste. The static load was 0.5 Mpa and the rotor speed was 64 rpm. The rotor diameter is 148
mm, the average spacing between the rotor and the kneader wall was 2 mm. When this composition was mixed for 220 minutes, the highest net torque level was 1.
A factor of 4 was reached (a plot of net torque versus mixing time for this step is shown in curve C of FIG. 3). Thereafter, the paste was removed from the press kneader. The paste was then fed to a single screw extruder and extruded into a 5 mm thick sheet. The extruded sheet had many cracks in the direction perpendicular to the direction of extrusion and was not strong enough to be processed. The desired electromagnetic wave absorbing material could not be obtained.
It should be noted that the procedure described in this example is an outline including quantitative data, and the reader is required to refer to FIG. 2 (route 1) for accurate details.
I would like you to follow the processing method and flowchart.

Note: The phenolic resin used in this example is Shaunol BRS330 (trade name), an alcohol-soluble phenolic resin precursor manufactured by Showa Polymer Co., Ltd.
Shaunol BRS330 is available in liquid form as a solution of methanol and free phenol. The amount of solvent in the mixing ratio is therefore Shaunol BRS330
Is calculated by subtracting the amount of non-volatile substance from the total amount of. The amount of resin in the mixing ratio is Shaunol BRS33
Equivalent to a nonvolatile content of 0.

Shear rate Shear rate (γ) given to the paste during mixing
Was calculated using the following known equation:

Γmax = (πDR) / t where D is the diameter of the rotor, R is the rotation speed, and t is the distance between the rotor and the wall of the kneader. This gave a shear rate of 248 s ^-1 for the paste being mixed.

Comparative Example 2 Preparation of Electromagnetic Wave Absorber The composition of Example 6 of Japanese Patent No. 2704929 was prepared as a plate according to the method described in Example 3.

(Comparative Example 3) Preparation of electromagnetic wave absorbing material 18 parts of Ni-Zn ferrite, 82 parts of calcium aluminate cement, 31.5 parts of phenol resin, solvent 31.
A composition containing 5 parts, 4.5 parts of N-methoxymethyl 6-nylon (trade name: Toresin, manufactured by Teikoku Chemical Industry Co., Ltd.) and 5.5 parts of glycerol was prepared as a plate according to the method described in Example 3. .

Note: The phenolic resin used in this example is Shaunol BRS330 (trade name), an alcohol-soluble phenolic resin precursor manufactured by Showa Polymer Co., Ltd.
Shaunol BRS330 is available in liquid form as a solution of methanol and free phenol. The amount of solvent in the mixing ratio is thus calculated by subtracting the amount of non-volatile substances from the total amount of Shaunol BRS330. The amount of resin in the mixing ratio is Shaunol BRS330
Of non-volatile substances.

(Comparative Example 4) Preparation of electromagnetic wave absorbing material 100 parts of Mg-Zn ferrite, vinyl ester resin 1
A composition containing 96 parts, 0.36 part of sodium carbonate, and 1.2 parts of methyl ethyl ketone peroxide was used as an electromagnetic wave absorbing material according to the method shown in Example 1.

Comparative Example 5 Preparation of Electromagnetic Wave Absorber 20 parts of Ni-Zn ferrite, 80 parts of calcium aluminate cement and 40 parts of water were mixed for 4 minutes with a paddle mixer. Thereafter, the paste was poured into a mold having a thickness of 5 mm and compressed using a table vibrator. The molded material was placed in a humid room for 7 days at 20.degree. H. To obtain an electromagnetic wave absorbing material.

Note: 20 parts Ni-Zn ferrite is the maximum filler content that can be added to the composition. If the filler content exceeds 20 parts, the mechanical strength of the product becomes so weak that it cannot be removed from the mold.

Comparative Example 6 Preparation of Electromagnetic Wave Absorbing Material 65 parts of Ni—Zn ferrite and 100 parts of epoxy-modified urethane rubber were mixed in an open kneader to form a paste. Thereafter, the paste was supplied to a twin-roll mill to perform high-speed shear mixing. For high-speed shear mixing, the forward and backward roll speeds are 250 and 200 mm / s, respectively.
The nip interval between the rolls was 3 mm. After a few minutes of high shear mixing, the paste was gradually turned into a sheet in low shear mixing. Thereafter, the sheet was peeled off several times at a desired nip interval until it became a uniform sheet having a fine surface, folded, and repeatedly rolled. When the calendering was completed, it was hot-pressed at 60 ° C. between the impression cylinders of a hydraulic laminate press to obtain an electromagnetic wave absorbing material.

Shear rate Shear rate (γ) given to the paste during mixing
Was calculated using the following known equation:

Γmax = [6U ₀ / h ₀ ]. [0.22
6+ (U ₁ −U ₂ ) / 6U ₀ ] where U ₁ and U ₂ are the speeds of the two rollers, U ₀ is the average speed, and h ₀ is the nip interval between the rolls. This gives a shear rate of 118 s ^{-1 for} the paste being mixed.
Met.

Comparative Example 7 The composition given in Example 3 was mixed with an open kneader to form a paste. Thereafter, the paste was fed into a pair of rollers of a manual noodle machine having the same rotation ratio of the rollers. Maximum speed is 80m
At m / s, the nip spacing between the rollers was 3 mm. After high and low shear mixing, the stiffness of the paste did not increase. Therefore, the paste did not become a sheet, and a desired electromagnetic wave absorbing material could not be obtained.

Shear Rate The shear rate (γ) imparted to the paste during mixing was calculated using the following known equation:

Γmax = [6U ₀ / h ₀ ]. [0.22
6+ (U ₁ −U ₂ ) / 6U ₀ ] where U ₁ and U ₂ are the speeds of the two rollers, U ₀ is the average speed, and h ₀ is the nip interval between the rollers. This gave a shear rate of 36 s ^-1 for the paste being mixed.

For the electromagnetic wave absorbing material, an electromagnetic wave absorbing effect test (Example 1-6 and Comparative Example 2-6), a bending strength test (Example 1-6 and Comparative Example 5-6), and a combustion test (Execution Example 1,
2, 5, and 6 and Comparative Example 6) were performed. The test method and its results are described below.

Electromagnetic wave absorption effect measuring method Using an HP 8722D network analyzer, 5
Μ and ε were evaluated by measuring S parameters in a frequency band of 0 MHz to 4 GHz. 2 measurement samples
The sample was placed on a 0D coaxial sample holder, and the constants μ and ε of the material were measured. Table 1 shows the effect of adding the reactive inorganic powder when shifting the effective frequency band to a desired region. The matching frequency, the reflection loss at the matching frequency, the effective absorption frequency band, and the bandwidth at the reflection loss of 15 dB of the samples performed according to Examples 1 to 6 and Comparative Examples 2 to 5 were calculated using the material constants. The return loss in Example 1 and Comparative Example 6 at five different frequencies commonly used in mobile telephones and wireless LAN systems was calculated using material constants. The results are shown in Table 2.

[0073]

[Table 1]

[0074]

[Table 2]

Method for Measuring Bending Strength of Electromagnetic Wave Absorbing Material The electromagnetic wave absorbing sheet was cut into sheet pieces having a width of 20 mm and a length of 120 mm. The sample was subjected to a three-point bending test using the thickness of the plate as the beam depth. The test is JIS K
6911 (Test method for thermosetting plastics). Table 3 shows the results of Examples 1 to 6 and Comparative Examples 5 to 6.

[0076]

[Table 3]

Method for Measuring Flammability of Electromagnetic Wave Absorbing Material The flammability of an electromagnetic wave absorbing material was measured according to ASTM D1692-6.
8 was measured. Dimension 152x50x12.5
mm sample was placed horizontally on top of a standard wire gauge. A propane gas flame having a width of 50 mm was applied to one end of the sample for 60 seconds to measure flammability, burning rate, and burning time. If the flame tip did not reach the mark 127 mm along the sample, it was classified as "self-extinguishing" in this test. Otherwise, it was classified as "flammable" in this test. Table 4
Shows the results of Examples 1, 2, 5, and 6 and Comparative Example 6.

[0078]

[Table 4]

As is clear from the results of Examples 1 to 6,
The electromagnetic wave absorbing material of the present invention has a high reflection loss at a matching frequency and a wide effective absorption band. As is clear from the results of Comparative Examples 2 to 5, only the narrow effective absorption band of these Comparative Examples is shown. The electromagnetic wave absorbing material described in Comparative Example 6 is flammable and does not have sufficient rigidity to be used as a wall material or the like. Comparative Example 7 shows that the composition used in Example 3 was molded using a manual noodle-making machine, and it was impossible to mold this paste as a sheet. As is evident from Comparative Example 7, there is a minimum energy level that must be substantially imparted to the paste by high speed shear mixing to form a molded sheet.

As is apparent from the results of Comparative Example 1, the reactive inorganic compound is an essential component of the mixture for processing the paste into a sheet. As is evident from Examples 1 and 2, the high shear time decreases as the content of reactive inorganic compound increases. FIG. 3 shows the relationship between the torque and the mixing time in Examples 1 and 2 and Comparative Example 1. further,
The reactive inorganic compound improves the bending strength of the absorbent material as shown in Examples 1-4 in Table 3. As the content of the reactive inorganic compound increases, the bending strength also increases.

On the other hand, Japanese Patent No. 27049 of the prior art patent
In Comparative Example 2 in which the material was produced according to No. 29 without adding the electromagnetic wave absorbing filler, the effective absorption band was very narrow. Similarly, in Comparative Example 3 in which the content of the electromagnetic wave absorbing filler was reduced by 18 parts, the matching frequency was almost equal to Comparative Example 2, and the effective absorption band was narrow. Therefore, to effectively absorb electromagnetic waves, there is a minimum content of electromagnetic wave absorbing filler to be added to the composition.

In Comparative Example 5 in which no resin was used, the bending strength was very low and the effective absorption band was narrow. Therefore, the material is not suitable for use as a wall material or the like.

As is clear from the results of Examples 1 to 4,
The reactive inorganic compound helps to shift the matching frequency to a desired level without changing the content of the main binder, the thickness and type of the electromagnetic wave absorbing filler. Example 6
When the results of Comparative Example 4 and Comparative Example 4 are compared, the effect of the inorganic compound on electromagnetic wave absorption becomes clear. The ratio of the content of the electromagnetic wave absorbing filler to the content of the reactive inorganic compound + the content of the main binder is equal in Example 6 and Comparative Example 4, that is, 0.51. However, Comparative Example 4 has lower absorption and a narrower bandwidth than Example 6. This indicates a clear effect of the reactive inorganic compound on the electromagnetic wave absorption characteristics.

From the above results, it can be seen that the electromagnetic wave absorbing material is superior in mutual electromagnetic interference or radio wave energy attenuation beyond mutual expectation due to the combination of the electromagnetic wave absorbing filler and the reactive inorganic compound. It is thought to bring about an electromagnetic wave absorption effect.

The electromagnetic wave absorption effect in a frequency band of 50 MHz to 4 GHz was measured. However, if the effective frequency band is 5
It is not limited to 0 MHz to 4 GHz. By adjusting the mixing ratio within the limits of the present invention, 4GH
Obviously, the material can be modified to absorb electromagnetic waves in the frequency band higher than z.

According to the test results, the radio wave absorber of the present invention is sufficient for use as a radio wave absorption material for radio LAN systems, UHF level television radio waves, radio waves generated from mobile telephones and walls of anechoic chambers. It has radio wave absorption characteristics. Further, it can be used as a fireproof electromagnetic wave absorbing case for any combustible absorber. This material is indispensable to prevent the malfunction of the radar of the automobile collision warning system. In particular, since it has a high degree of freedom in forming a desired shape, it can be easily used as an outer plate of a military stealth aircraft that absorbs radar radio waves in order to hinder enemy search operations.

It will be understood by those skilled in the art that the above embodiments can be modified without departing from the broad inventive concept thereof. Therefore, it is to be understood that this invention is not limited to the particular embodiments disclosed, but that it encompasses variations within the spirit and scope of the invention as defined by the appended claims.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method of manufacturing an electromagnetic wave absorbing material according to one embodiment of the present invention.

FIG. 2 is a flowchart illustrating a method of manufacturing an electromagnetic wave absorbing material according to another embodiment of the present invention.

FIG. 3 is a graph plotting a relationship between a mixing time and a pure torque (N · m).

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 30, 2001 (2001.1.3)
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

[0013]

According to the present invention, there is provided an electromagnetic wave absorbing paste used to form an electromagnetic wave absorbing material capable of changing a matching frequency to a desired level. At least one reactive inorganic compound formed by using an element of group IIA and / or group IIIB as an essential component; (a) a complex magnetically permeable ceramic powder; (b) a high dielectric powder; and (c) a low conductive metal. Powder (d) low-conductivity carbon powder containing at least one kind of electromagnetic wave absorbing filler, and the reactive inorganic compound in a volume ratio of 100 parts by mass of the electromagnetic wave absorbing filler and the reactive inorganic compound. 5 to 80 parts by weight, and further, the thermosetting resin was mixed at a volume ratio of 50 parts or less based on 100 parts by weight of the total amount of the electromagnetic wave absorbing filler and the reactive inorganic compound. Features The electromagnetic wave absorbing paste (Claim 1), wherein the thermosetting resin is a formaldehyde resin, unsaturated polyester resin, epoxy resin, alkyd resin, vinyl ester resin, polyurethane resin, diallyl phthalate resin, polyamideimide resin and polyimide resin Any one of
The electromagnetic wave absorbing paste according to claim 1 (claim 2), wherein the formaldehyde resin is:
3. The electromagnetic wave absorbing paste according to claim 2, wherein the paste is one of a phenol resin precursor, a melamine resin precursor, and a urea resin precursor.
The reactive inorganic compound formed by using an element of Group A and / or Group IIIB as an essential component is magnesium, calcium, strontium, barium, aluminum,
2. An electromagnetic wave absorbing paste according to claim 1, characterized in that it is a compound mainly produced by one of gallium and indium, an element of group IIA and / or IIIB being essential. The electromagnetic wave absorbing paste according to claim 1, wherein the reactive inorganic compound formed as a component is a hydraulic cement, wherein the paste reacts without adding water. The electromagnetic wave absorbing paste according to claim 1 (claim 6), wherein the electromagnetic wave absorbing filler has an electric resistance of 10 ⁻⁷ Ω.
2. The electromagnetic wave absorbing paste according to claim 1, wherein the electric resistance of the complex magnetically permeable ceramic powder is 10 ³ Ωm or more. An electromagnetic wave absorbing paste (claim 8),
The electric resistance of the complex magnetically permeable ceramic powder is 10 ⁶ Ωm
The electromagnetic wave absorbing paste according to claim 1, wherein the complex magnetically permeable ceramic powder is ferrite. 11. The electromagnetic wave absorbing paste according to claim 1, wherein the complex magnetically permeable ceramic powder is ferrite. 10) A method for producing an electromagnetic wave absorbing material capable of changing a matching frequency to a desired level using the electromagnetic wave absorbing paste defined in claim 1 as a starting material, comprising: (a) a Banbury mixer, a pressure kneader or (B) mixing the raw materials at a shear rate of 50 s ^-1 or more with a roll mill; (b) supplying the paste obtained in the step (a) to an extruder or a calender roll to form a desired molded product; c) a step of heating and curing the molded article at a high temperature (claim 11). The method for producing an electromagnetic wave absorbing material according to claim 11, wherein the electromagnetic wave absorbing material has one of a shape of a bora, a pyramid, an angle, a channel, a cylinder, a spiral, a grid, and a honeycomb. Item 12).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 BF011 CC001 CC031 CC161 CC181 CD001 CF011 CF211 CK021 CM041 DA017 DA087 DA096 DA097 DA117 DE067 DE076 DE077 DE086 DE096 DE097 DE107 DE117 DE137 DE146 DE157 DE236 DG056 DJ006 FA007FA017FA

Claims (12)

[Claims] An electromagnetic wave absorbing paste used to form an electromagnetic wave absorbing material capable of changing a matching frequency to a desired level, the paste comprising a thermosetting resin, a Group IIA and / or a Group IIIB. (A) a complex magnetically permeable ceramic powder, (b) a high dielectric powder, (c) a low conductive metal powder, and (d) a low conductive carbon. Powder containing at least one of the electromagnetic wave absorbing fillers, and the reactive inorganic compound is contained in a volume ratio of 5 to 80 parts with respect to 100 parts of the total amount of the electromagnetic wave absorbing filler and the reactive inorganic compound. An electromagnetic wave absorbing paste, wherein the paste is mixed, and the thermosetting resin is further mixed at a volume ratio of 50 parts or less based on 100 parts of the total amount of the electromagnetic wave absorbing filler and the reactive inorganic compound. 2. The thermosetting resin is one of a formaldehyde resin, an unsaturated polyester resin, an epoxy resin, an alkyd resin, a vinyl ester resin, a polyurethane resin, a diallyl phthalate resin, a polyamideimide resin and a polyimide resin. The electromagnetic wave absorbing paste according to claim 1, wherein: 3. The electromagnetic wave absorbing paste according to claim 2, wherein the formaldehyde resin is any one of a phenol resin precursor, a melamine resin precursor, and a urea resin precursor. 4. The reactive inorganic compound produced as an essential component of a Group IIA and / or IIIB element, wherein the reactive inorganic compound is formed of one of magnesium, calcium, strontium, barium, aluminum, gallium and indium. The electromagnetic wave absorbing paste according to claim 1, which is a compound mainly produced. 5. The electromagnetic wave absorbing paste according to claim 1, wherein the reactive inorganic compound formed by using an element of Group IIA and / or Group IIIB as an essential component is a hydraulic cement. 6. The electromagnetic wave absorbing paste according to claim 1, wherein the paste reacts without adding water. 7. An electromagnetic wave absorbing filler having an electric resistivity of 1
0 ^-7 wave absorption paste according to claim 1, characterized in that at Ωm or more. 8. The method according to claim 1, wherein said complex magnetically permeable ceramic powder has an electric resistivity of 10 ³ Ωm or more.
The electromagnetic wave absorbing paste according to 1. 9. The composite magnetically permeable ceramic powder according to claim 1, wherein the electrical resistivity of the powder is 10 ⁶ Ωm or more.
The electromagnetic wave absorbing paste according to 1. 10. The electromagnetic wave absorbing paste according to claim 1, wherein the complex magnetically permeable ceramic powder is ferrite. 11. A method for producing an electromagnetic wave absorbing material capable of changing a matching frequency to a desired level by using the electromagnetic wave absorbing paste defined in claim 1 as a starting material, comprising: (a) a Banbury mixer; Mixing the raw materials with a kneader or a roll mill at a shear rate of 50 s ^-1 ; (b) supplying the paste obtained in the step (a) to an extruder or a calender roll to form a desired molded product; (C) a step of heating and curing the molded article at a high temperature. 12. The electromagnetic wave absorbing material has one of plate, dome, parabola, pyramid, angle, channel, cylinder, spiral, grid, and honeycomb shapes. The method for producing an electromagnetic wave absorbing material according to claim 11.