JP2014078698A - Electromagnetic wave-absorbing composition and electromagnetic wave absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave absorber which has a polymer component as a matrix, brings about a high electromagnetic wave absorption effect even with a small electromagnetic wave loss material content, allows an absorption wavelength band varying from an electromagnetic wave irradiation angle to another to be designed, and is flexible enough to offer a large degree of design freedom.SOLUTION: An electromagnetic wave-absorbing composition comprises (A) a polymer component of rubber resulting from the copolymerization of polyfunctional monomers; and (B) at least one kind of loss material selected from a group consisting of a dielectric loss material and a magnetic loss material, provided that the ratio L/D of a long-axis length L to a short-axis length D is 2-100.

Description

  The present invention relates to a composition that absorbs unnecessary electromagnetic noise generated from electronic components and the like, and an electromagnetic wave absorber that is a molded body thereof. More specifically, the present invention relates to an electromagnetic wave absorptive composition and an electromagnetic wave absorber that are capable of adjusting an electromagnetic wave absorption band and an absorption amount according to an irradiation angle of an electromagnetic wave and that are excellent in flexibility even when formed into a sheet shape. .

In recent years, the spread of small electronic devices such as mobile phones and wireless LANs, the wireless use of electronic devices such as the installation of ETC (Electronic Toll Collection System), and the installation of related devices are progressing. In these electronic devices and related devices, problems such as electromagnetic interference and electromagnetic interference are pointed out due to electromagnetic noise generated from electronic components and power supplies incorporated in the device. The body is being developed.
In order to absorb electromagnetic waves efficiently, the conventionally known electromagnetic wave absorbers need to have a high loss material content or be designed to be thick, and realize a lightweight and compact absorber. It was difficult to do.
As the electromagnetic wave absorber, an electromagnetic wave absorber made of a metal layer etched into a mesh shape, an electromagnetic wave absorber made of a composite material in which a conductive carbon material is dispersed and contained in a matrix made of a polymer component, and the like are known ( Regarding the latter, Patent Documents 1 and 2). Of these, an electromagnetic wave absorber having a polymer component as a matrix is advantageous because a lightweight and flexible electromagnetic wave absorber can be obtained.
The electromagnetic wave absorbing performance of the electromagnetic wave absorber is expressed by taking in the electromagnetic wave without reflecting it and changing to heat energy. For this reason, it is necessary to design the electromagnetic wave and the electromagnetic wave absorber so as to match the impedance.
In the case of an electromagnetic wave absorber having a polymer component as a matrix, it is designed to satisfy the following formula 1 by including an appropriate electromagnetic wave loss material.

When a dielectric loss material is used as the electromagnetic wave loss material, the complex relative permeability is approximated to 1 and the parameter d / λ is varied to satisfy the above formula (1) for each value of d / λ. Thus, when the imaginary component ε _r ″ of the complex dielectric constant is plotted against the real component ε _r ′, a non-reflection curve (curve of electromagnetic wave absorption rate = ∞ (dB)) as shown in FIG. 1 is obtained. FIG. 1 also shows a curve with an electromagnetic wave absorption rate of 20 dB.
As the relationship between the real component and the imaginary component of the complex relative permittivity is closer to the non-reflection curve, an electromagnetic wave absorber having better absorption characteristics can be manufactured. In general, it is considered that 20 dB or more is required as the electromagnetic wave absorption rate. Therefore, a material having a complex dielectric constant as close to a non-reflection curve as possible within the range of the 20 dB curve in FIG. 1 is searched.
As apparent from FIG. 1, in order to reduce the thickness of the electromagnetic wave absorber (that is, to reduce the value of the parameter d / λ), it is necessary to increase the complex relative dielectric constant. Therefore, in the case of a conventionally known electromagnetic wave absorber material, it is necessary to increase the content of the dielectric loss material (and filler) in the absorber, and thus a lightweight and small electromagnetic wave absorber cannot be obtained. There was a problem with. For example, according to the technique of Patent Document 1 described above, it is described that it is preferable to use 100 parts by weight or more of carbon material and 240 parts by weight or more of metal hydroxide with respect to 100 parts by weight of the polymer component.
When a magnetic loss material is used as the electromagnetic wave loss material, the dielectric loss material is approximated to a complex relative permittivity of 1 and between the real component u _r ′ and the imaginary component u _r ″ of the complex permeability. The same argument as in the case of.

JP 2010-192550 A Japanese Patent Laid-Open No. 04-297097

Enomae et al., Nordic Pull and Paper Research Journal, 21 (2), pp 253-259 (2006).

The present invention has been made by paying attention to the current situation as described above.
An object of the present invention is an electromagnetic wave absorber having a polymer component as a matrix,
Even if the content of the electromagnetic wave loss material is small, a high electromagnetic wave absorption effect is obtained,
To provide an electromagnetic wave absorber that can be designed to have different absorption wavelength bands depending on the irradiation angle of electromagnetic waves, and that is flexible and has a high degree of design freedom, and an electromagnetic wave absorbing composition therefor .

According to the present invention, the above objects and advantages of the present invention are as follows.
(A) Dielectric loss in which the ratio L / D of the polymer component which is a rubber obtained by copolymerizing a polyfunctional monomer and (B) the major axis length L and the minor axis length D is 2 to 100 Achieved by an electromagnetic wave absorbing composition, characterized in that it comprises at least one loss agent selected from materials and magnetic loss materials;
An electromagnetic wave comprising the molded body of the above-mentioned electromagnetic wave absorbing composition, wherein the (B) loss material in the molded body is oriented so that the orientation strength in the major axis direction is 1.2 or more. Achieved with an absorber.

The electromagnetic wave absorbing composition of the present invention can provide an electromagnetic wave absorber that effectively absorbs electromagnetic wave noise with a smaller content of the electromagnetic wave absorbing material while using the polymer component as a matrix. Therefore, the electromagnetic wave absorber of the present invention, which is a molded product of the electromagnetic wave absorbing composition of the present invention, is lightweight and flexible while having the above performance. Furthermore, the electromagnetic wave absorber of the present invention can be designed so that the absorption wavelength band differs depending on the irradiation angle of the electromagnetic wave.
The electromagnetic wave absorber of the present invention includes, for example, personal computers, mobile phones, digital cameras, televisions, etc .; antenna covers; ETC lanes, outer walls of highways, outer walls of high-rise buildings, steel towers, bullet trains, aircraft Structures; ship masts; IC cards such as RF-IDs; IC tags; readers / writers; devices compatible with wireless power feeding systems, etc. By applying the electromagnetic wave absorber of the present invention to these devices, it is possible to significantly reduce copying noise derived from circuit boards and to suppress noise disturbances due to reflected waves, and thus it is possible to increase the sensitivity of the devices. .

Electromagnetic wave reflection characteristics of electromagnetic wave absorber using dielectric loss material. Electromagnetic wave reflection characteristics of the electromagnetic wave absorber obtained in the preliminary experiment example.

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that modifications, improvements, and the like appropriately added to the embodiments described above fall within the scope of the present invention.
<< Electromagnetic wave absorbing composition >>
The electromagnetic wave absorbing composition of the present invention is
(A) A polymer component and (B) a loss agent are contained.

<(A) Polymer component>
The (A) polymer component in the present invention is a rubber obtained by copolymerizing a polyfunctional monomer. The term “copolymerization” as used herein is a concept including not only addition polymerization type copolymerization but also polycondensation type.
Examples of the rubber include rubber produced through an addition polymerization process such as acrylic rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber, fluorine rubber, styrene butadiene rubber; and heavy rubber such as silicone rubber and urethane rubber. Rubbers produced through the condensation process can be mentioned, and these main raw material monomers are copolymerized with a monomer mixture consisting of a polyfunctional monomer and optionally other monomers. It is preferable to use a rubber formed as described above. Specifically, each is as follows.

[Acrylic rubber]
The main raw material monomer of the acrylic rubber is (meth) acrylic acid ester. Examples of the (meth) acrylic acid ester include ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, and (meth) acrylic. An octyl acid, 2-ethylhexyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, etc. can be mentioned, It is preferable to use 1 or more types selected from these. As the (meth) acrylic acid ester, one or more selected from the group consisting of ethyl (meth) acrylate, propyl (meth) acrylate and butyl (meth) acrylate is more preferable.
Examples of the polyfunctional monomer used in the acrylic rubber include di (meth) acrylate esters of polyhydric alcohols, alkenyl esters of unsaturated carboxylic acids, polyalkenyl esters of polybasic acids, and di (unfunctional) polyhydric alcohols. In addition to saturated carboxylic acid esters, divinylbenzene and the like can be mentioned. Examples of the di (meth) acrylate ester of the unsaturated carboxylic acid include ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylolpropane triacrylate and the like;
Examples of unsaturated carboxylic acid alkenyl esters include allyl acrylate, allyl methacrylate, allyl cinnamate, and the like;
Examples of polyalkenyl esters of polybasic acids include diallyl phthalate, diallyl maleate, triallyl cyanurate, triallyl isocyanurate and the like;
Oligo (meth) acrylates such as polyester, epoxy resin, urethane resin, alkyd resin, silicone resin, and spirane resin;
Polymer di (meth) acrylates having hydroxyl groups at both ends, such as poly-1,3-butadiene having hydroxyl groups at both ends, polyisoprene having hydroxyl groups at both ends, polycaprolactone having hydroxyl groups at both ends, Each can be mentioned, and one or more selected from these can be used. Of these, one or more selected from the group consisting of trimethylolpropane triacrylate, divinylbenzene, and triallyl isocyanurate is more preferable.

  Other monomers optionally used in the acrylic rubber include, for example, unsaturated nitrile monomers such as (meth) acrylonitrile; olefin monomers such as ethylene and propylene; vinyl chloride, vinylidene chloride, fluorine And vinyl halide monomers such as vinylidene halide. (A) Appropriate flexibility is given to the polymer component, and (B) from the viewpoint of orienting the loss material to a desired degree in the obtained electromagnetic wave absorber, other monomers among the above are used. It is preferable to use (meth) acrylonitrile.

In the acrylic rubber as the polymer component (A) in the present invention, the structural unit derived from the acrylate ester is preferably 50 to 99.5 mol%, preferably 60 to 99 mol, based on the total structural unit. % Is more preferable;
The structural unit derived from the polyfunctional monomer is preferably 0.5 to 7 mol%, more preferably 0.5 to 5 mol%, more preferably 0. More preferably 5 to 3 mol%; and
The structural unit derived from the other monomer is preferably 49.5 mol% or less, and more preferably 30 mol% or less, based on all the structural units.
The structural unit derived from the polyfunctional monomer is preferably 0.5 mol% or more from the viewpoint of securing the orientation of the (B) loss material in the electromagnetic wave absorber, while at the time of preparing the composition. From the viewpoint of ensuring the workability of the above and preventing the electromagnetic wave absorber from becoming excessively brittle, this value is preferably 7 mol% or less. The lower limit value of the structural unit derived from the other monomer is not particularly limited, and for example, a numerical value of 3 mol% can be exemplified.

[NBR]
The main raw material monomers of the NBR are unsaturated nitrile compounds and conjugated dienes.
Examples of the unsaturated nitrile compound include (meth) acrylonitrile, ethacrylonitrile, α-chloroacrylonitrile, α-fluoroacrylonitrile and the like, and it is preferable to use one or more selected from these. .
Examples of the conjugated diene include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and chloroprene (2-chloro-1,3-butadiene). It is preferable to use one or more selected from these. As the conjugated diene, one or more selected from butadiene and isoprene are preferable, and butadiene is more preferable.
As a polyfunctional monomer used for NBR, the same thing as the above-mentioned as a polyfunctional monomer used for acrylic rubber can be used.
Other monomers optionally used in NBR include, for example, monomers having a carboxyl group such as (meth) acrylic acid, crotonic acid, cinnamic acid; glycidyl (meth) acrylate, (meth) acrylic Examples thereof include monomers having an epoxy group such as acid 3,4-oxycyclohexyl.
In the NBR as the polymer component (A) in the present invention, the structural unit derived from the unsaturated nitrile compound is preferably from 10 to 60 mol%, preferably from 20 to 55 mol%, based on all structural units. More preferably;
The structural unit derived from the conjugated diene is preferably 39.5 to 85 mol%, more preferably 45 to 80 mol%, based on all structural units;
The structural unit derived from the polyfunctional monomer is preferably 0.5 to 7 mol%, more preferably 1.0 to 6 mol%, based on all structural units; and
The structural unit derived from the other monomer is preferably 44.5 mol% or less, and more preferably 30 mol% or less, based on all structural units.

[Chloroprene rubber]
The main raw material monomer of the chloroprene rubber is 2-chloro-1,3-butadiene (chloroprene).
As the polyfunctional monomer used in the chloroprene rubber, the same ones as described above as the polyfunctional monomer used in the acrylic rubber can be used.
Other monomers optionally used in the chloroprene rubber include, for example, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, Examples thereof include butadiene.
In the chloroprene rubber as the polymer component (A) in the present invention, the structural unit derived from chloroprene is preferably 70 to 97 mol%, and preferably 80 to 97 mol%, based on all structural units. More preferred;
The structural unit derived from the polyfunctional monomer is preferably 0.5 to 7 mol%, more preferably 0.5 to 5 mol%, more preferably 0. More preferably from 5 to 2 mol%; and
The structural unit derived from the other monomer is preferably 30 mol% or less, and more preferably 20 mol% or less with respect to the total structural unit.

[Fluoro rubber]
The main raw material monomer of the fluororubber is an unsaturated monomer having a fluorine atom. Examples of the unsaturated monomer having a fluorine atom include vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, perfluoro (alkyl vinyl ether), chlorotrifluoroethylene, pentafluoropropene, and trifluoroethylene. One or more selected from these can be used.
As the polyfunctional monomer used in the fluororubber, the same ones as described above as the polyfunctional monomer used in the acrylic rubber can be used.
Examples of other monomers optionally used in the fluororubber include ethylene, propylene, styrene, α-methylstyrene, and the like. One or more selected from these can be used. it can.
In the fluororubber as the polymer component (A) in the present invention, the structural unit derived from the unsaturated monomer having a fluorine atom is preferably 70 to 99.5 mol% with respect to the total structural unit. 80 to 97 mol% is more preferable;
The structural unit derived from the polyfunctional monomer is preferably 0.5 to 7 mol%, more preferably 0.5 to 5 mol%, more preferably 0. More preferably 5 to 3 mol%; and
The structural unit derived from the other monomer is preferably 29.5 mol% or less, and more preferably 20 mol% or less with respect to all the structural units.

[Styrene butadiene rubber]
The main raw material monomers for the styrene-butadiene rubber are styrene and 1,3-butadiene.
As the polyfunctional monomer used in the styrene-butadiene rubber, the same ones as described above as the polyfunctional monomer used in the acrylic rubber can be used.
Other monomers optionally used in the styrene-butadiene rubber include, for example, conjugated dienes other than 1,3-butadiene, such as 1,3-pentadiene, isoprene, 1,3-hexadiene;
Examples include aromatic vinyl compounds other than styrene such as α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, and 2,2,6-tolylstyrene. One or more selected from these can be used.
In the styrene-butadiene rubber as the polymer component (A) in the present invention, the structural unit derived from 1,3-butadiene is preferably 40 to 85 mol% based on the total structural units, and is preferably 50 to 75%. More preferably mol%;
The structural unit derived from styrene is preferably 10 to 50 mol%, more preferably 15 to 40 mol%, based on all structural units;
The structural unit derived from the polyfunctional monomer is preferably 0.5 to 7 mol%, more preferably 0.5 to 5 mol%, more preferably 0. More preferably 5 to 3 mol; and
The structural unit derived from the other monomer is preferably 30 mol% or less, and more preferably 10 mol% or less, based on the total structural units.

[Method for producing rubber produced through addition polymerization step]
The acrylic rubber, acrylonitrile-butadiene rubber (NBR), chloroprene rubber, fluororubber and styrene-butadiene rubber can be produced by a known addition polymerization process.
Examples of the polymerization method include emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, and the like. From the viewpoint of ease of polymerization control, mass productivity, and the like, emulsion polymerization is preferable. Emulsion polymerization can be performed, for example, in the same manner as that described in Japanese Patent No. 5151202, or by a method with appropriate modifications added thereto.

[silicone rubber]
The main raw material monomer of the silicone rubber is a bifunctional hydrolyzable silane compound. Specific examples thereof include dimethylmethoxysilane, diphenyldimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, and the like, and one or more selected from these can be given. Can be used.
The polyfunctional monomer in the silicone rubber is a trifunctional or tetrafunctional hydrolyzable silane compound. Specific examples thereof include trifunctional hydrolyzable compounds such as methyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, vinyltrimethoxysilane, phenyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane. Γ-glycidoxypropyl triethoxysilane, etc .;
Examples of the tetrafunctional hydrolyzable compound include tetramethoxysilane, tetraethoxysilane, and the like, and one or more selected from these can be used.

[Urethane rubber]
The main raw materials of the urethane rubber are diisocyanate and dihydroxyl compound, and urethane rubber can be produced by chain growth of these with a chain extender. Specific examples thereof include diisocyanate such as diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate;
Examples of the dihydroxy compound include polytetramethylene glycol, polycaprolactone diol, polyethylene glycol, polypropylene glycol, polyethylene adipate polyol, polybutylene adipate polyol and the like;
Examples of the chain extender include ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, nonanediol, and the like, and one or more selected from these can be used. .
Examples of the polyfunctional monomer in the urethane rubber include a trifunctional hydroxyl-containing chain extender and a trifunctional isocyanate. Specific examples thereof include trifunctional hydroxyl-containing chain extenders such as glycerin, trimethylolethane, trimethylolpropane, hexanetriol and the like;
Examples of the trifunctional isocyanate include trimethylene diisocyanate and the like.

[Method for producing rubber produced through polycondensation step]
Said silicone rubber and urethane rubber can each be manufactured by a well-known method.
The polycondensation for producing these rubbers can be performed in any system such as a solution, suspension, or mass, but is preferably performed in bulk from the viewpoint of ease of control and mass productivity. .

[(A) Particle diameter of polymer component]
The average particle diameter of the (A) polymer component in the electromagnetic wave absorbing composition of the present invention is preferably 50 to 300 nm, more preferably 50 to 250 nm, and particularly preferably 50 to 200 nm. In order to ensure the orientation of the (B) lossy material in the obtained electromagnetic wave absorbing composition, the average particle diameter is preferably 50 nm or more. On the other hand, the viewpoint of the stability of the synthetic system when producing the polymerizability Therefore, it is preferable to keep the average particle diameter at 300 nm or less.
The above average particle size is a 50% particle size when the particle size distribution obtained by measuring the volume average particle size of polymer particles dispersed in a liquid medium by a dynamic light scattering method is expressed as a cumulative distribution. (D50 median diameter). This average particle diameter can be measured using, for example, a microtrack particle size analyzer, a nanotrack particle size analyzer (both manufactured by Nikkiso Co., Ltd.), or the like.

[(A) Stress relaxation rate of polymer component]
The (A) polymer component in the electromagnetic wave absorbing composition of the present invention has a stress relaxation rate R1 after 1 second defined by the following formula (R1) of 50 to 90% and is defined by the following formula (R2). The stress relaxation rate R2 after 1,000 seconds is preferably 25 to 60%.
R1 = τ (1) / τ (0) × 100 (%) (R1)
R2 = τ (1,000) / τ (0) × 100 (%) (R2)
(In the above formula, τ (0), τ (1) and τ (1,000) are respectively converted into the polymer (A) at a temperature Tp which is 40 ° C. higher than the flow start temperature Ts of the polymer (A). (The shear stress is 0 seconds, 1 second, and 1,000 seconds after the shearing force is applied and the shear strain reaches 30%.)
The stress relaxation ratios R1 and R2 can be calculated from the viscoelasticity data measured using a commercially available viscoelasticity measuring device using a polymer component processed into a predetermined shape as a sample, according to the above formulas R1 and R2. Specifically, at a measurement temperature Tp that is 40 ° C. higher than the flow start temperature Ts of the polymer component, while applying a force of 4.9 N from the top of the sample to the bottom in the vertical direction, 0.52 rad from the lateral direction of the sample. Shear force is applied at an angular velocity of / sec, and when the shear strain reaches 30%, the shear force is adjusted to maintain 30% shear strain. Here, the shear stresses τ (0), τ (1) and τ (1,000) after 0 seconds, 1 second and 1,000 seconds after the shear strain reached 30% were measured, and these By substituting the values into the above formulas (R1) and (R2), the stress relaxation rate R1 after 1 second and the stress relaxation rate R2 after 1,000 seconds can be obtained.

The reason why the stress relaxation rates R1 and R2 are measured at a temperature Tp that is 40 ° C. higher than the flow start temperature Ts of the polymer component (A) is that this temperature is the lower limit of the processable temperature. Further, the shearing force of 30% assumes the deformation behavior of the polymer component (A) during processing.
The stress relaxation rate R1 after 1 second is an index related to the ease of orientation of the (B) lossy material and the appearance of the molded body during molding of the electromagnetic wave absorber. When R1 is 50% or more, it is ensured that the lossy material is appropriately oriented by processing. On the other hand, when R1 is 90% or less, surface roughness, cracking and the like do not occur in the obtained molded body, and it is ensured that a good appearance is exhibited.
The stress relaxation rate R2 after 1,000 seconds is an index related to the maintenance of the orientation of the (B) lossy material in the obtained electromagnetic wave absorber and the reproducibility of the absorber size when the absorber is molded. When R2 is 25% or more, it is ensured that the initial orientation is maintained for a long time. On the other hand, when R2 is 60% or less, variations in the size of the obtained molded body are reduced.
Therefore, by using a polymer component satisfying both predetermined R1 and R2, it becomes easy to control the orientation of the (B) loss material in the obtained electromagnetic wave absorber, and the orientation is maintained for a long time. It will be done.
The stress relaxation rate R1 after 1 second is more preferably 70 to 90%, further preferably 75 to 90%;
The stress relaxation rate R2 after 1,000 seconds is more preferably 30 to 60%, and further preferably 35 to 60%.

[(A) Glass transition temperature of polymer component]
The glass transition temperature (Tg) of the polymer component (A) in the present invention is preferably + 5 ° C. or lower. This glass transition temperature is a numerical value determined from data measured by a differential scanning calorimeter (DSC) in accordance with JIS K7121. The lower limit of the glass transition temperature is not particularly limited, but for example, a value of −100 ° C. or higher can be exemplified.
In general, the lower the glass transition temperature of the polymer component (A) is, the more flexible and the electromagnetic wave absorber having high resistance to deformation can be obtained. On the other hand, when the glass transition temperature of the (A) polymer component is low, the stress relaxation becomes faster, so that the degree of maintaining the orientation of the (B) loss material in the absorber becomes low. Therefore, in order to obtain a suitable electromagnetic wave absorber in which (B) the lossy material is easily oriented and the imparted orientation is maintained for a long time, a polymer component having a low glass transition temperature but somewhat slow stress relaxation is used. Necessary. The present invention satisfies the above conflicting requirements by employing a rubber obtained by copolymerizing a polyfunctional monomer as the polymer component (A).

<(B) Loss material>
The (B) loss material in the present invention is at least one selected from dielectric loss materials and magnetic loss materials.
(B) The ratio L / D (aspect ratio) between the major axis length L and the minor axis length D of the lossy material is 2 to 100, and preferably 10 to 80.
(B) The size of the loss material is determined from the standpoint of balancing electromagnetic wave absorption performance, ease of kneading when preparing an electromagnetic wave absorbing composition, workability when manufacturing an electromagnetic wave absorber, and the like. The length L and the short axis length D are as follows.
Long axis length L: preferably 10 to 500 μm, more preferably 25 to 400 μm, mandala preferably 40 to 300 μm
Short axis length D: preferably 1 to 12 μm, more preferably 2 to 10 μm
(B) The major axis length L of the lossy material is preferably 10 μm or more when emphasizing that high electromagnetic wave absorbing performance is expressed with a small amount of addition. (A) Dispersibility in the polymer component and the electromagnetic wave absorber From the viewpoint of workability, the thickness is preferably 500 μm or less.

The dielectric loss material as the loss material (B) in the present invention is a material that performs conversion of electromagnetic wave energy into heat by dielectric loss ability. Examples of such dielectric loss materials include carbon materials, titanic acid compounds, titanium oxide, metals, and the like.
Examples of the carbon material include graphite, carbon fiber, carbon microcoil, carbon nanotube, and graphene.
The graphite can be obtained, for example, by a method of finely pulverizing and classifying coal coke. As the shape of graphite, scaly black smoke is preferable from the viewpoint of orientation when an electromagnetic wave absorber is used.
Examples of the carbon fibers include carbon fibers obtained by carbonizing organic fibers (for example, polyacrylonitrile) at high temperatures; carbon fibers obtained by carbonizing petroleum pitch, coal pitch, or coal tar pitch at high temperatures, and carbon nanofibers. There may be. This carbon nanofiber can be obtained by a known substrate growth method or vapor phase growth method.
The carbon microcoil is a kind of vapor-grown carbon fiber obtained mainly by a catalyst-activated pyrolysis method of acetylene, and is a material having a 3D-helical / helical structure with a coil diameter of the order of microns. The coil diameter is 1 to 10 μm, the carbon fiber diameter forming the coil is 0.1 to 1 μm, and the length of the coil is preferably 1 to 10 mm.
Specifically, the carbon nanotube can be obtained by a vapor phase growth method such as an arc discharge method, a laser evaporation method, or a thermal decomposition method. The carbon nanotubes in the present invention may be either single-walled or multi-walled.
The graphene can be obtained by, for example, a peeling transfer method, a SiC pyrolysis method, a chemical vapor deposition method, a method of cutting a carbon nanotube, or the like. As the graphene in the present invention, scale-shaped powdery graphene is preferably used from the viewpoint of easily obtaining the predetermined aspect ratio of the present invention and the orientation in the electromagnetic wave absorber.

Examples of the titanate compound include potassium titanate, barium titanate, calcium titanate, strontium titanate, magnesium titanate, zirconium titanate, lanthanum titanate, and bismuth titanate. Of these, barium titanate is preferable from the viewpoints of availability and electromagnetic wave absorption characteristics.
Examples of the metal include copper, aluminum, and stainless steel.
The dielectric loss material as described above may be used after being treated with an appropriate surface treatment agent from the viewpoint of improving the dispersibility in the polymer component (A). Examples of the surface treatment agent used here include coupling agents such as a silane coupling agent, a titanate coupling agent, and an aluminum coupling agent;
A block copolymer having a nonpolar segment and a polar segment or a graph and a copolymer can be exemplified.

The magnetic loss material as the loss material (B) in the present invention is a material that performs conversion of electromagnetic wave energy into heat by magnetic loss ability. Examples of such a magnetic loss material include ferrite, carbonyl iron, magnetite (Fe ₃ O ₄ ), iron alloy, and pure iron particles.
The ferrite may be either soft ferrite or hard ferrite (permanent magnet material). Specific examples of these include soft ferrite such as Mn—Zn ferrite, Ni—Zn ferrite, Mn—Mg ferrite, Mn ferrite, Cu—Zn ferrite, Cu—Mg—Zn ferrite and the like;
Examples of the hard ferrite include M type (Magnet Blumbite type) ferrite, W type ferrite, X type ferrite, Y type ferrite, and Z type ferrite.
The carbonyl iron is a fine powder obtained by pyrolyzing carbonylated iron, which is an organic intermetallic compound, and examples thereof include pentacarbonyliron (Fe (CO) ₅ ).
Examples of the iron alloy include magnetic stainless steel (Fe—Cr—Al—Si alloy), sendust (Fe—Si—Al alloy), perm alloy (Fe—Ni alloy), silicon copper (Fe—Si alloy), Fe— Si-B (-Cu-Nb) alloy etc. can be mentioned.
Preferred examples of the pure iron particles include those produced by a method in which iron oxide such as hematite is reduced with hydrogen gas or the like and then the surface is oxidized as necessary.
Among the magnetic loss materials as described above, it is preferable to select a magnetic loss material that is light in weight, has a small environmental load, and has a low frequency dependency of the magnetic loss, and specifically, Mn—Zn ferrite, magnetite, It is preferable to use a magnetic loss material selected from Sendust and Permalloy.

The preferable content of the (B) loss material in the electromagnetic wave absorbing composition of the present invention differs between the case of the dielectric loss material and the case of the magnetic loss material, and (A) with respect to 100 parts by weight of the polymer component, respectively. It is as follows.
In the case of a dielectric loss material: Preferably it is 5-100 weight part, More preferably, it is 10-80 weight part, More preferably, it is 20-70 weight part In the case of a magnetic loss material: Preferably it is 10-2,000 weight part, More preferably Is 50 to 900 parts by weight, more preferably 100 to 800 parts by weight

<Other ingredients>
The electromagnetic wave absorbing composition of the present invention contains the above-mentioned (A) polymer component and (B) loss material as essential components, but may contain other components besides these. Other components that can be used here include, for example, flame retardants, crosslinking agents, crosslinking aids, inorganic fillers, solid lubricants, antioxidants, thermal stabilizers, light stabilizers, UV absorbers, neutralizers. Agents, lubricants, compatibilizers, anti-fogging agents, anti-blocking agents, slip agents, dispersants, colorants, antibacterial agents, fluorescent brighteners, softeners, resins, rubbers other than (A) polymer components, etc. Can be mentioned.

Examples of the flame retardant include magnesium hydroxide and aluminum hydroxide. The content ratio of the flame retardant in the electromagnetic wave absorbing composition of the present invention is preferably 30% by weight or less, more preferably 1 to 10% by weight with respect to the entire electromagnetic wave absorbing composition.
As said crosslinking agent, a peroxide, sulfur, etc. can be mentioned, for example. The content of the crosslinking agent in the electromagnetic wave absorbing composition of the present invention is preferably 10% by weight or less, more preferably 0.1 to 3% by weight, based on the entire electromagnetic wave absorbing composition.
Examples of the crosslinking aid include polyfunctional monomers such as triallyl isocyanurate and trimethylolpropane triacrylate;
Examples of the inorganic filler include talc, calcium carbonate, mica, glass powder, glass balloon and the like;
Examples of the solid lubricant include fluororesin powder and molybdenum disulfide.

<Method for Producing Electromagnetic Wave Absorbing Composition and Electromagnetic Wave Absorber>
The electromagnetic wave absorbing composition of the present invention is a composition comprising a mixture of the above components, and the electromagnetic wave absorber of the present invention is a molded body of the electromagnetic wave absorbing composition.
From the above components, the electromagnetic wave absorbing composition may be collectively manufactured through the electromagnetic wave absorbing composition; alternatively, an electromagnetic wave absorbing composition is first manufactured from the above components, and the electromagnetic wave absorption from the composition in a separate step. It is good also as manufacturing a body.
In the former case, the electromagnetic wave absorber can be obtained by putting all of the above components all together or sequentially into a suitable kneading / molding apparatus and performing kneading and molding. Here, at the time of kneading or molding, it is preferable to use an apparatus in which the raw material mixture takes a share in a certain direction, thereby forming (B) a molded body in which the loss agent is oriented. Examples of such kneading and forming methods include roll forming, calender roll forming, kneading extrusion forming (single axis or biaxial) and the like;
For example, injection molding, blow molding, vacuum molding, and the like performed by arranging an appropriate mold at the outlet of the kneading extruder can be exemplified.
In the latter case, in at least one of the step of manufacturing the composition and the step of manufacturing the electromagnetic wave absorber, an apparatus in which the raw material mixture or the composition has a share in a certain direction is adopted, and finally (B ) It is preferable to form a molded body in which the loss agent is oriented.
Examples of the kneading apparatus in which the raw material mixture has a share in a certain direction include a roll, a calender roll, a kneading extruder (single screw or twin screw), etc .;
Examples of the kneading apparatus in which the raw material mixture does not take a share in a certain direction can include a Banbury mixer, a brabender, a kneader, and the like. The shape of the electromagnetic wave absorbing composition obtained after kneading can be, for example, a lump shape (indefinite shape), a sheet shape, a pellet shape, a powder shape, a granular shape, or the like depending on the properties of the kneading apparatus.

Subsequently, the electromagnetic wave absorber of the present invention can be obtained by supplying such a composition to an appropriate molding apparatus and molding it.
Examples of molding apparatuses that require a certain share of the composition include rolls, calender rolls, kneading extruders (single or biaxial), injection molding machines, blow molding machines, vacuum molding machines, slit die coating machines. Etc .;
Examples of the molding apparatus in which the composition does not take a share in a certain direction include a press apparatus.
Kneading and molding can be carried out at any temperature, but each component is well dispersed, and (B) a viewpoint that a lossy material can quickly obtain a composition or molded body oriented in the predetermined range of the present invention. To 30 to 200 ° C. More preferably, it is between 0-100 ° C higher than the flow start temperature Ts (° C) of the polymer component (A) used, more preferably 20-80 ° C higher, still more preferably It is between 30-60 degreeC high temperature. Among the kneading and molding processes, the processing temperature at the stage of applying a share in a certain direction to the raw material mixture or composition is set to a temperature 20 to 60 ° C. higher than Ts (° C.) (B ) Preferred in terms of the orientation of the lossy material.
As the shape of the electromagnetic wave absorber obtained as described above, for example, a sheet shape, a plate shape, a film shape, a rod shape, a rectangular parallelepiped shape, a cylindrical shape, a polygonal column shape (particularly a triangular column, a quadrangular column or a hexagonal column), a polygonal pyramid shape ( In particular, (B) a shape that can utilize the orientation of the lossy material in an assumed application such as a triangular pyramid or a square pyramid) is preferable.
The size of the electromagnetic wave absorber is arbitrary. For example, when the electromagnetic wave absorber is formed into a sheet shape, the thickness d is, for example, in the range of 0.1 to 10 mm, and the parameter d / λ when the wavelength of the target electromagnetic wave is λ is not shown in FIG. It is preferable to set it as close as possible to the reflection curve.

  In the electromagnetic wave absorber of the present invention, (B) the lossy material is oriented so that the orientation strength in the major axis direction is 1.2 or more. The long-axis orientation strength means the degree of alignment of the (B) orientation agent in the electromagnetic wave absorber, and the larger this value, the higher the electromagnetic wave absorption effect. More specifically, the electromagnetic wave absorber sample cut out into a sheet shape is photographed with an electron microscope, and the angle distribution of (B) lossy material in the field of view is examined. The axial orientation strength is evaluated. Specific approximation methods and calculation procedures are described in Non-Patent Document 1 (Enomae et al., Nordic Pull and Paper Research Journal, 21 (2), pp 253-259 (2006)). The maximum value of the long-axis orientation strength is theoretically 2.5, but 1.6 or less is sufficient in relation to the present invention. The long axis direction orientation strength of the (B) loss material in the electromagnetic wave absorber of the present invention is preferably 1.3 to 1.6.

<Usage of electromagnetic wave absorber>
The electromagnetic wave absorber of the present invention may be used alone or in combination with a plurality of electromagnetic wave absorbers having different electromagnetic wave absorption characteristics. In this case, for example, a plurality of electromagnetic wave absorbers having different complex relative dielectric constants are each formed into a sheet shape and laminated to form a laminated absorber;
Preferable examples include (B) a laminated absorbent body in which a plurality of sheets having the same or different complex relative dielectric constants are laminated so that the orientation direction of the lossy material is different between layers. Examples of the method for producing a laminated absorbent body include multilayer laminate extrusion molding, insert injection molding, multicolor injection molding (core back molding, rotational mold molding, etc.) and the like.
You may use the electromagnetic wave absorber of this invention with a metal layer or a metal oxide layer, for example. In this case, the metal layer is preferably provided on at least one of the surfaces of the electromagnetic wave absorber. Examples of the metal species include copper, nickel, iron, zinc, titanium, silver and the like. Examples of the metal oxide include oxides of these metals. The thickness of the metal layer or metal oxide layer is preferably 0.1 to 20 mm, and more preferably 0.5 to 10 mm. As the most preferred embodiment when used with a metal layer,
The metal layer can be formed by, for example, a method of attaching a separately manufactured metal plate, laminating, metal film in-mold molding, plating, vacuum deposition, sputtering, or the like.

<Evaluation method>
Various evaluations in the following preliminary experimental examples, examples, and comparative examples were performed by the following methods.
(1) Flow start temperature of polymer component The flow start temperature Ts of the polymer component is manufactured by Shimadzu Corporation in accordance with “Thermal Plastic Flow Test Method” described in JIS-K7210 (1999). It calculated | required by the constant-speed temperature increase test using the thermal-fluid evaluation apparatus "CFT-500D".
The measurement conditions were as follows.
Temperature increase rate: 5 ° C / min Load: 100kgf
Capillary die size: 1.00mm inner diameter and 1.00mm length
(2) Stress relaxation rate of polymer component The stress relaxation rate of the polymer component was processed into a cylindrical shape having a height of 2 mm and a diameter of 20 mm using a viscoelasticity measuring device “MR-500” manufactured by UBM Co., Ltd. Each polymer sample was determined by a shear stress relaxation test using a parallel plate having a diameter of 19.96 mm.
At the measurement temperature Tp that is 40 ° C. higher than the flow start temperature Ts, the rotation angle is adjusted so that the vertical load at the start of measurement is 4.9 N and the shear strain is 30% at the measurement temperature Tp, The shear stress with respect to the elapsed time was measured. Then, after 0 second, 1 second and 1,000 seconds after the shear strain reached 30%, the shear stresses τ (0), τ (1) and τ (1,000) were examined. Substituting into the above formulas (R1) and (R2), the stress relaxation rate R1 after 1 second and the stress relaxation rate R2 after 1,000 seconds were determined.
(3) Glass transition temperature of polymer component The glass transition temperature of the polymer component was measured according to JIS K 7121 (1987) using a differential scanning calorimeter (Model “DSC 204 F1” manufactured by NETZSCH). It was measured by differential scanning calorimetry (DSC).

(4) Orientation of Loss Material in Electromagnetic Wave Absorber Non-Patent Document 1 (Enomae et al., Nordic Pull and Paper Research Journal, 21 (2), pp 253-259 (2006) )) Was evaluated according to the analysis method described.
The electromagnetic wave absorber sheet obtained in each example and comparative example was cut into a size of 5 mm × 2 mm, and used as a sample for photographing. Here, the cross section was cut so that the observation surface was parallel to the orientation axis. Using a field emission scanning electron microscope (product name: S-4300) manufactured by Hitachi High-Technologies Corporation, the above-described imaging sample is arranged so that the orientation axis of the lossy material in the cross section is in the horizontal direction. did.
For the obtained image, a 1024 × 1024 pixel portion was trimmed, 8-bit gray scale processing was performed, and the orientation strength calculated using the analysis software “Fiber-Orientation-Analysis-8.13” was determined as the major axis orientation mirror strength. did.

(5) Electromagnetic wave absorption performance of the electromagnetic wave absorber The electromagnetic wave absorption performance of the electromagnetic wave absorber is measured by using a vector network analyzer (VNA, product name: N5227 PNA) manufactured by Agilent Technologies, and (B) loss material as a measurement frequency band. Is a dielectric loss material, 1-10 GHz band and 18-26 GHz band,
(B) When the loss material is a magnetic loss material, 1-10 GHz band,
Each measurement frequency band was measured by the free space method.
As an evaluation sample,
300mm x 300mm for 1-10GHz band,
For the 18-26 GHz band, 100 mm x 100 mm,
Thickness 0.5-2.0mm (The optimum value was set in this range according to the result of the following preliminary experiment)
The sheet was prepared, and the back of the sample was lined with an aluminum plate having a thickness of 0.2 mm. And it measured so that it might arrange | position so that the flow direction (MD direction) of the composition in this sample might become equilibrium with respect to the electric field direction of electromagnetic waves.
(6) Elongation at break The elongation at break was measured at a tensile speed of 500 mm / min in accordance with JIS 6251 with respect to a test piece obtained by punching the electromagnetic wave absorber sheet obtained in each Example and Comparative Example into a No. 3 dumbbell shape. did.
When the elongation at break was 180% or more, the elongation at break was evaluated as “good”, and when it was less than 180%, the elongation at break was evaluated as “bad”.

<Production example of (A) polymer component>
Production Example 1
In an aqueous solution obtained by dissolving 5 parts by weight of sodium dodecylbenzenesulfonate as an emulsifier in 200 parts by weight of distilled water, 85 parts by weight of ethyl acrylate, 12 parts by weight of acrylonitrile and 3 parts by weight of trimethylolpropane triacrylate were charged and cooled to 10 ° C. Thereafter, 0.02 part by weight of paramentane hydroperoxide was added, and a polymerization reaction was performed at 10 ° C. After the polymerization conversion reached about 90% by weight, 0.5 part by weight of N, N-diethylhydroxylamine was added to the reaction system to stop the copolymerization reaction, and a copolymer latex was obtained (reaction time). 6 hours). The obtained latex was added to a large excess of 0.25 wt% calcium chloride aqueous solution to coagulate the copolymer rubber. The coagulated product was recovered, washed thoroughly with water, and dried at about 90 ° C. for 3 hours to obtain a copolymer 1.
Further, a part of the obtained latex was diluted 10 times by volume with a chloroform / toluene mixed solvent (volume ratio 4: 1), and a dynamic light scattering nanotrack particle size analyzer (form “UPA-EX150”, The volume average particle diameter was calculated using Nikkiso Co., Ltd. and found to be 189 nm. Moreover, the glass transition temperature of the copolymer 1 was 0 degreeC.

Production Example 2
In an aqueous solution in which 5 parts by weight of sodium dodecylbenzenesulfonate as an emulsifier is dissolved in 200 parts by weight of distilled water, 79 parts by weight of butyl acrylate and 21 parts by weight of acrylonitrile are charged and cooled to 10 ° C. 02 parts by weight were added and the polymerization reaction was carried out at 15 ° C. After the polymerization conversion reached about 95%, 0.5 parts by weight of N, N-diethylhydroxylamine was added to the reaction system to stop the copolymerization reaction, and a copolymer latex was obtained (reaction time 4). time). The obtained latex was added to a large excess of 0.25 wt% calcium chloride aqueous solution to coagulate the copolymer rubber. The coagulated product was collected, sufficiently washed with water, and then dried at about 90 ° C. for 3 hours to obtain a copolymer 2.
Using the obtained latex, the volume average particle size of the copolymer 2 was calculated in the same manner as in Production Example 1, and it was 178 nm. Moreover, the glass transition temperature of the copolymer 2 was -11 degreeC.

Production Example 3
In the above Production Example 1, the copolymer 3 was prepared by operating in the same manner as in Production Example 1 except that 77 parts by weight of ethyl acrylate, 6 parts by weight of acrylonitrile and 17 parts by weight of trimethylolpropane triacrylate were used. Obtained.
The volume average particle size of the copolymer 3 was calculated in the same manner as in Production Example 1 using the obtained latex, and it was 170 nm. Moreover, the glass transition temperature of the copolymer 3 was -9 degreeC.

Production Example 4
An aqueous solution prepared by dissolving 5 parts by weight of sodium dodecylbenzenesulfonate as an emulsifier in 200 parts of distilled water, 66 parts by weight of butadiene, 28 parts by weight of acrylonitrile and 6 parts by weight of divinylbenzene as raw materials, and a redox catalyst were charged into an autoclave at 10 ° C. After adjusting the temperature to 0.01 parts of paramentane hydroxide as a polymerization initiator, emulsion polymerization was carried out to a polymerization conversion rate of 95%. Next, a reaction terminator N, N-diethylhydroxylamine was added to synthesize a copolymer emulsion. Then, water vapor is blown into this solution to remove unreacted raw material monomers, and then this solution is added to a 5% calcium chloride aqueous solution, and the precipitated copolymer is dried by a blow dryer set at 80 ° C. As a result, a copolymer 4 was obtained.
The volume average particle size of the copolymer 4 was calculated in the same manner as in Production Example 1 using the obtained latex, and it was 191 nm. Moreover, the glass transition temperature of the copolymer 4 was -40 degreeC.

Comparative production example 1
Mixing roll manufactured by Kansai Roll Co., Ltd., which was a mixture of 100 parts by weight of vinyl chloride (product name: TH-1400) manufactured by Taiyo PVC Co., Ltd. and 400 parts by weight of dioctyl phthalate as a plasticizer at 100 ° C. Was used for kneading for 1 minute at a roll speed of 20 rpm and a back of 22 rpm to obtain a soft polyvinyl chloride composition.

<Manufacture of magnetic loss material>
Production Example 5
A soft magnetic iron powder with an average particle size of 4 μm and an aspect ratio of 1 coated with magnetite (Fe ₃ O ₄ ) having a thickness of 10 nm is plastically deformed by processing for 2 minutes using an attritor and processed into a flat shape As a result, soft magnetic iron powder 2 having an aspect ratio of 20 was obtained.

<Preliminary experiment>
Each of the following examples and comparative examples employs the optimum composition determined by the following preliminary experiment.
Several types of preliminary samples were prepared by varying the loss material with respect to 100 parts by weight of the polymer component. For each sample
When the loss material is a dielectric loss material, the real component ε _r ′ and the imaginary component ε _r ″ of the complex relative dielectric constant are
When the loss material is a magnetic loss material, the real component μ _r ′ and the imaginary component μ _r ″ of the complex permeability were respectively obtained, and a composition in which the relationship between the real component and the imaginary component was closest to the non-reflection curve was adopted. As the λ / d value in Examples and Comparative Examples, in the plot of the imaginary number component (vertical axis) vs. the real number component (horizontal axis), the point where the line parallel to the vertical axis originating from the plotted point intersects the antireflection curve The λ / d value was adopted.
The preliminary sample was prepared according to the following method.
Using a mixing roll manufactured by Kansai Roll Co., Ltd. adjusted to a predetermined temperature, the roll rotation speed is 20 rpm before and 22 rpm after that, 100 parts by weight of the polymer component is masticated for 1 minute, and then a predetermined amount of lost material And kneaded for another 3 minutes. A preliminary sample was obtained by forming the kneaded material into a sheet having a width of 500 mm and a thickness of 2 mm.
Table 1 and FIG. 2 show some of the preliminary experiments conducted to determine the compositions of Example E1 and Comparative Example e1. As the composition of Example E1, among the preliminary experimental examples 1 to 3, the composition of the preliminary experimental example 2 in which the relationship between the real component ε _r ′ and the imaginary component ε _r ″ of the complex dielectric constant is the closest to the non-reflection curve,
As a composition of the comparative example e1, among the preliminary experimental examples 4 to 6, the composition of the preliminary experimental example 6 in which the relationship between the real component ε _r ′ and the imaginary component ε _r ″ of the complex relative dielectric constant is closest to the non-reflection curve is
Each was adopted.

The abbreviations of the components in Table 1 have the following meanings.
[Polymer component]
Copolymer 1: “Copolymer 1” produced in Production Example 1 above
EPDM: Ethylene / propylene / diene rubber, manufactured by JSR Corporation, trade name “EP51”
[Loss material]
Carbon fiber 20: Carbon fiber, aspect ratio 20, manufactured by Mitsubishi Plastics, Inc., trade name “DIALEAD K223HM”

<Examples and comparative examples using dielectric loss materials>
Examples E1-E7 and Comparative Examples e1-e4
Each experiment was conducted using the types and amounts (parts by weight) of polymer components and loss materials listed in Table 2. The composition ratio and λ / d ratio of the polymer component and the loss material were determined by a preliminary experiment performed by the same method as described above.
Using a mixing roll manufactured by Kansai Roll Co., Ltd., adjusted to the temperature shown in Table 2, with a roll rotation speed of 20 rpm and a back of 22 rpm, a predetermined amount of polymer components were masticated for 1 minute. A fixed amount of lost material was added and kneaded for an additional 3 minutes. In Example E6, the flame retardant was added before the addition of the (B) loss material, and the crosslinking agent was added after the addition of the (B) loss material.
Subsequently, the kneaded material was pressure-molded using a 300 ton press machine manufactured by Kansai Roll Co., Ltd., and two sheets having different thicknesses were obtained for each frequency band. The thicknesses of these sheets are determined by substituting the frequencies 5.8 GHz and 22 GHz for the λ / d ratio obtained in the preliminary experiment. And each sheet | seat was cut out to the magnitude | size for each frequency band, and the electromagnetic wave absorption performance was evaluated.
The evaluation results are shown in Table 2.

The abbreviations of the components in Table 2 have the following meanings.
[Polymer component]
Copolymer 1: “Copolymer 1” produced in Production Example 1 above
Copolymer 2: “Copolymer 2” produced in Production Example 2 above
Soft PVC: “soft polyvinyl chloride composition” produced in Comparative Production Example 1 above
Copolymer 3: “Copolymer 3” produced in Production Example 3 above
Copolymer 4: “Copolymer 4” produced in Production Example 4 above
CEBC: Olefin Crystal / Ethylene Butylene / Olefin Crystal Block Copolymer, manufactured by JSR Corporation, product name “DR6100”
EPDM: ethylene / propylene / diene rubber, manufactured by JSR Corporation, product name “EP51”
[Loss material]
Carbon fiber: manufactured by Mitsubishi Plastics Co., Ltd., product name “DIALEAD K223HM”, aspect ratio 20
Graphite: manufactured by Chuetsu Graphite Industry Co., Ltd., product name “SB # 1”, aspect ratio 3
Spherical graphite: manufactured by Chuetsu Graphite Industry Co., Ltd., product name “WF-15C”, aspect ratio 1

<Examples and comparative examples using magnetic loss materials>
Example M1 and comparative examples m1 and m2
In the same manner as in Example E1 and the like, kneading was performed using the polymer components and loss materials of the types and amounts (parts by weight) listed in Table 3.
Subsequently, the kneaded material was pressure-molded using a 300 ton press manufactured by Kansai Roll Co., Ltd. to obtain a sheet. The thickness of the sheet is determined by substituting the frequency of 5.8 GHz for the λ / d ratio obtained in the preliminary experiment. And this sheet | seat was cut out to the magnitude | size of 300 mm x 300 mm, and electromagnetic wave absorption performance was evaluated.
The evaluation results are shown in Table 3.

The abbreviations of the components in Table 3 have the following meanings.
[Polymer component]
Copolymer 1: “Copolymer 1” produced in Production Example 1 above
EPDM: ethylene / propylene / diene rubber, manufactured by JSR Corporation, product name “EP51”
[Loss material]
Soft magnetic iron powder 1: aspect ratio 1
Soft magnetic iron powder 2: “soft magnetic iron powder 2” produced in Production Example 5 above, aspect ratio 20

Claims (6)

(A) Dielectric loss in which the ratio L / D of the polymer component which is a rubber obtained by copolymerizing a polyfunctional monomer and (B) the major axis length L and the minor axis length D is 2 to 100 An electromagnetic wave absorptive composition comprising at least one loss agent selected from a material and a magnetic loss material.   The polymer component (A) is selected from acrylic rubber, acrylonitrile-butadiene rubber (NBR), chloroprene rubber, fluorine rubber, and styrene-butadiene rubber, provided that a polyfunctional monomer is copolymerized. The electromagnetic wave absorbing composition according to claim 1.   The electromagnetic wave absorptive composition of Claim 2 whose copolymerization ratio of the polyfunctional monomer in the said (A) polymer component is 0.5-7 mol%.   The electromagnetic wave absorptive composition of Claim 1 or 2 whose glass transition temperature measured with the differential scanning calorimeter about the said (A) polymer component is +5 degrees C or less.   It consists of the molded object of the electromagnetic wave absorptive composition as described in any one of Claims 1-4, and (B) loss material in this molded object is set so that the major axis direction intensity | strength may be 1.2 or more. An electromagnetic wave absorber characterized by being oriented.   An electronic apparatus comprising the electromagnetic wave absorber according to claim 5.

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