JP6546717B2 - Electromagnetic wave absorbing composition and electromagnetic wave absorber - Google Patents

Description

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

2. Description of the Related Art In recent years, the spread of small electronic devices such as mobile phones and wireless LANs, the installation of ETC (Electronic Toll Collection System), and the like are progressing to wireless electronic devices and the related devices. In these electronic devices and their related devices, it is pointed out that electromagnetic interference, electromagnetic interference, etc. are generated due to electromagnetic noise generated from the electronic components, power source etc. incorporated inside. Body development is in progress.
In order to absorb electromagnetic waves efficiently, it is necessary to increase the content of the loss material or to design the electromagnetic wave absorber thickly, so that a conventionally known electromagnetic wave absorber realizes a lightweight, compact absorber. It was difficult to do.
Known electromagnetic wave absorbers include an electromagnetic wave absorber made of a metal layer etched in a mesh shape, an electromagnetic wave absorber made of a composite material in which a conductive carbon material is dispersed in a matrix made of a polymer component, and the like (see FIG. Regarding the latter, Patent Documents 1 and 2). Among them, an electromagnetic wave absorber having a polymer component as a matrix is advantageous since a lightweight and flexible electromagnetic wave absorber can be obtained.
The electromagnetic wave absorption performance of the electromagnetic wave absorber is exhibited by incorporating the electromagnetic wave into the interior without reflecting it and converting it into thermal energy. Therefore, it is necessary to design so that the impedance matching between the electromagnetic wave and the electromagnetic wave absorber can be achieved.
In the case of an electromagnetic wave absorber having a polymer component as a matrix, it is designed to satisfy the following equation 1 by containing 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 then the parameter d / λ is varied to satisfy the above equation (1) for each value of d / λ. Thus, when the imaginary component ε _r ′ ′ of the complex relative permittivity is plotted with respect to the real component ε _r ′, a non-reflection curve (curve of electromagnetic wave absorptivity = ∞ (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 dielectric constant is closer to the above-mentioned non-reflection curve, an electromagnetic wave absorber having better absorption characteristics can be manufactured. In general, it is considered that the electromagnetic wave absorptivity needs to be 20 dB or more, and therefore, a material exhibiting a complex dielectric constant as close as possible to the non-reflection curve within the range of the 20 dB curve in FIG.
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 the conventionally known electromagnetic wave absorber material, it is necessary to increase the content of the dielectric loss material (and the filler) in the absorber, so that it is not possible to obtain a lightweight and small electromagnetic wave absorber. And there was a problem. 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 a carbon material and 240 parts by weight or more of a metal hydroxide with respect to 100 parts by weight of a polymer component.
When a magnetic loss material is used as the electromagnetic wave loss material, the above-mentioned dielectric loss material is located between the real component u _r ′ of the complex permeability and the imaginary component u _r ′ ′ after approximating the complex relative permittivity to 1. The same arguments as in the above case apply.

JP, 2010-192550, A Unexamined-Japanese-Patent No. 04-297097

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

The present invention has been made focusing on the above-mentioned current situation.
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 can be obtained,
It is possible to design an absorption wavelength band so as to be different for each irradiation angle of electromagnetic waves, and to provide an electromagnetic wave absorber that is flexible and has a large degree of freedom in design, and an electromagnetic wave absorbing composition therefor. .

According to the invention, the above objects and advantages of the invention are, first of all:
(A) A polymer component obtained by copolymerizing a polyfunctional monomer and having a glass transition temperature of + 5 ° C. or less measured by a differential scanning calorimeter, and (B) major axis length L and minor axis Achieved by an electromagnetic wave absorbing composition characterized by containing a dielectric loss material of a carbon material having a ratio L / D to the length D of 2 to 100; second,
An electromagnetic wave comprising: a molded body of the above electromagnetic wave absorbing composition, wherein the (B) loss material in the molded body is oriented such that the alignment strength in the long axis direction is 1.2 or more. Achieved by the absorber.

The electromagnetic wave absorbing composition of the present invention can give an electromagnetic wave absorber which effectively absorbs electromagnetic wave noise with a smaller content of an electromagnetic wave absorbing material while using a polymer component as a matrix. Therefore, the electromagnetic wave absorber of the present invention, which is a molded article of the electromagnetic wave absorbing composition of the present invention, is lightweight and flexible while having the above-mentioned performance. Furthermore, in the electromagnetic wave absorber of the present invention, the absorption wavelength band can be designed to be different for each irradiation angle of the electromagnetic wave.
The electromagnetic wave absorber of the present invention is, for example, a case of a personal computer, a mobile phone, a digital camera, a television, etc .; antenna cover; ETC lane, outer wall of highway, outer wall of high-rise building, tower, bullet train, building etc. It can be preferably used as a structure; a ship mast; an IC card such as an RF-ID; an IC tag; a reader / writer; By applying the electromagnetic wave absorber of the present invention to these devices, it is possible to significantly reduce copying noise originating from the circuit board and suppress noise interference due to reflected waves, thus making it possible to increase the sensitivity of the device. .

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

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and based on the ordinary knowledge of the person skilled in the art within the scope not departing from the spirit of the present invention. It is to be understood that those to which appropriate changes, improvements, etc. have been added to the embodiments of the present invention fall within the scope of the present invention.
<< Electromagnetic wave absorbing composition >>
The electromagnetic wave absorbing composition of the present invention is
(A) containing a dielectric loss material of the polymer component and (B) a carbon material.

<(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 encompassing not only addition type copolymerization but also polycondensation type.
Examples of the rubber include rubbers produced through an addition polymerization process such as acrylic rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber, fluororubber, styrene butadiene rubber, etc .; and heavy metals such as silicone rubber and urethane rubber The rubber etc. which are manufactured through a condensation process can be mentioned, The monomer mixture which consists of a polyfunctional monomer and the other monomer optionally used for these main raw material monomers is copolymerized It is preferable to use the resulting rubber. Specifically, they are as follows.

[Acrylic rubber]
The main raw material monomer of the said acrylic rubber is (meth) acrylic acid ester. Examples of this (meth) acrylic acid ester include ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate and (meth) acrylic acid. Examples thereof include octyl acid, 2-ethylhexyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate and the like, and it is preferable to use one or more selected from these. The (meth) acrylic acid ester is more preferably at least one selected from the group consisting of ethyl (meth) acrylate, propyl (meth) acrylate and butyl (meth) acrylate.
As a polyfunctional monomer used for acrylic rubber, for example, di (meth) acrylate ester of polyhydric alcohol, alkenyl ester of unsaturated carboxylic acid, polyalkenyl ester of polybasic acid, di (unsubstituted of polyhydric alcohol Other than saturated carboxylic acid) ester etc., divinylbenzene etc. can be mentioned. Examples of di (meth) acrylate esters of the above unsaturated carboxylic acids include ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethylolpropane triacrylate;
Examples of alkenyl esters of unsaturated carboxylic acids include allyl acrylate, allyl methacrylate, allyl cinnamate and the like;
Examples of polyalkenyl esters of polybasic acids such as 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, spilane resin and the like;
Polymeric 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 1 or more types selected from these can be used. Among these, one or more selected from the group consisting of trimethylolpropane triacrylate, divinylbenzene and triallyl isocyanurate is more preferable.

  Examples of other monomers optionally used for acrylic rubber include unsaturated nitrile monomers such as (meth) acrylonitrile; olefin monomers such as ethylene and propylene; vinyl chloride, vinylidene chloride, fluorine Examples thereof include halogenated vinyl monomers such as vinylidene fluoride. From the viewpoint of imparting appropriate flexibility to the polymer component (A) and orienting the (B) loss material to a desired degree in the resulting electromagnetic wave absorber, among the above monomers as other monomers It is preferred to use (meth) acrylonitrile.

In the acrylic rubber as the polymer component (A) in the present invention, the structural unit derived from the acrylic acid ester is preferably 50 to 99.5 mol%, more preferably 60 to 99 mol based on all structural units. It is more preferable to use%
It is preferable to make it 0.5-7 mol% with respect to all the structural units, and, as for the structural unit derived from the said polyfunctional monomer, it is more preferable to set it as 0.5-5 mol%, 0.. More preferably, it is 5 to 3 mol%;
The amount of structural units derived from the other monomers is preferably 49.5 mol% or less, more preferably 30 mol% or less, based on all 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, and on the other hand, in the preparation of the composition From the viewpoint of securing the workability of the above and preventing the electromagnetic wave absorber from becoming excessively brittle, it is preferable to set this value to 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 said NBR are an unsaturated nitrile compound and a conjugated diene.
Examples of this 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, chloroprene (2-chloro-1,3-butadiene) And the like, and it is preferable to use one or more selected from these. The conjugated diene is preferably at least one selected from butadiene and isoprene, and more preferably butadiene.
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.
Examples of other monomers optionally used in NBR include monomers having a carboxyl group such as (meth) acrylic acid, crotonic acid, cinnamic acid, etc .; glycidyl (meth) acrylate, (meth) acrylic acid The monomer etc. which have epoxy groups, such as acid 3,4- oxycyclohexyl, etc. can be mentioned.
In NBR as the polymer component (A) in the present invention, the structural unit derived from the unsaturated nitrile compound is preferably 10 to 60% by mole, and more preferably 20 to 55% by mole, based on all structural units. Is more preferred;
It is preferable to set it as 39.5-85 mol% with respect to all the structural units, and, as for the structural unit derived from the said conjugated diene, it is more preferable to set it as 45-80 mol%;
The structural unit derived from the polyfunctional monomer is preferably 0.5 to 7 mol%, more preferably 1.0 to 6 mol%, with respect to the total structural units.
The content of the structural units derived from the other monomers is preferably 44.5 mol% or less, more preferably 30 mol% or less, based on all structural units.

[Chloroprene rubber]
The main raw material monomer of the said chloroprene rubber is 2-chloro- 1, 3- butadiene (chloroprene).
As a polyfunctional monomer used for chloroprene rubber, the same thing as the above-mentioned as a polyfunctional monomer used for acrylic rubber can be used.
Other monomers optionally used for chloroprene rubber include, for example, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, and the like. Butadiene etc. can be mentioned.
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%, preferably 80 to 97 mol%, based on all structural units. More preferred;
It is preferable to make it 0.5-7 mol% with respect to all the structural units, and, as for the structural unit derived from the said polyfunctional monomer, it is more preferable to set it as 0.5-5 mol%, 0.. More preferably, it is 5 to 2 mol%;
The amount of structural units derived from the other monomers is preferably 30 mol% or less, more preferably 20 mol% or less, based on all structural units.

[Fluorine rubber]
The main raw material monomer of the said fluororubber is the unsaturated monomer which has a fluorine atom. Examples of the unsaturated monomer having a fluorine atom include vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, perfluoro (alkyl vinyl ether), chlorotrifluoroethylene, pentafluoropropene, trifluoroethylene and the like. One or more selected from these can be used.
As a polyfunctional monomer used for fluorine rubber, the same thing as the above-mentioned as a polyfunctional monomer used for acrylic rubber can be used.
Examples of other monomers optionally used for the fluororubber include ethylene, propylene, styrene, α-methylstyrene and the like, and one or more selected from these may 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% by mole based on all structural units. And 80 to 97 mol% are more preferable;
It is preferable to make it 0.5-7 mol% with respect to all the structural units, and, as for the structural unit derived from the said polyfunctional monomer, it is more preferable to set it as 0.5-5 mol%, 0.. More preferably, it is 5 to 3 mol%;
It is preferable to set it as 29.5 mol% or less with respect to all the structural units, and, as for the structural unit originating in the said other monomer, it is more preferable to set it as 20 mol% or less.

[Styrene butadiene rubber]
The main raw material monomers of the said styrene butadiene rubber are styrene and 1, 3- butadiene.
As a polyfunctional monomer used for a styrene butadiene rubber, the same thing as the above-mentioned as a polyfunctional monomer used for acrylic rubber can be used.
Other monomers optionally used in styrene butadiene rubber include, for example, conjugated dienes other than 1,3-butadiene such as 1,3-pentadiene, isoprene, 1,3-hexadiene, etc.
Examples of aromatic vinyl compounds other than styrene include α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,2,6-tolylstyrene and the like. 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% by mole with respect to all structural units, and 50 to 75 It is more preferable to use mol%;
The structural unit derived from styrene is preferably 10 to 50 mol%, more preferably 15 to 40 mol%, based on all structural units.
It is preferable to make it 0.5-7 mol% with respect to all the structural units, and, as for the structural unit derived from the said polyfunctional monomer, it is more preferable to set it as 0.5-5 mol%, 0.. More preferably, 5 to 3 moles; and
The amount of structural units derived from the other monomers is preferably 30 mol% or less, more preferably 10 mol% or less, based on all structural units.

[Method of producing rubber produced through addition polymerization step]
The above-mentioned acrylic rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber, fluororubber and styrene butadiene rubber can each 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, but in view of easiness of polymerization control, mass productivity and the like, emulsion polymerization is preferable. The emulsion polymerization can be carried out, for example, in the same manner as the method described in Japanese Patent No. 5151206 or by a method with an appropriate modification.

[silicone rubber]
The main raw material monomer of the said silicone rubber is a bifunctional hydrolysable silane compound. Specific examples thereof include, for example, dimethylmethoxysilane, diphenyldimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane and the like, and one or more selected from among these 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, γ-glycidoxypropyltrimethoxysilane Γ-glycidoxypropyltriethoxysilane etc .;
Examples of tetrafunctional hydrolyzable compounds include tetramethoxysilane and tetraethoxysilane, and one or more selected from these can be used.

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

[Method of producing rubber produced through polycondensation process]
The above-mentioned silicone rubber and urethane rubber can each be manufactured by a publicly known method.
The polycondensation for producing these rubbers can be carried out, for example, in any system such as solution, suspension, bulk and the like, but bulk polymerization is preferable from the viewpoint of controllability and mass productivity. .

[Particle size of (A) 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) loss material in the obtained electromagnetic wave absorbing composition, the average particle diameter is preferably 50 nm or more, and on the other hand, the viewpoint of the stability of the synthesis system in producing the polymerizability From this point, it is preferable to keep the average particle size 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 the particles of the polymer dispersed in the liquid medium by the dynamic light scattering method is represented by the cumulative distribution It means (d50 median diameter). This average particle size can be measured, for example, using a microtrack particle size analyzer, a nanotrack particle size analyzer (both manufactured by Nikkiso Co., Ltd.) or the like.

[Stress relaxation rate of (A) polymer component]
The polymer component (A) 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-mentioned formula, τ (0), τ (1) and τ (1,000) respectively represent the polymer (A) at a temperature Tp 40 ° C. higher than the flow start temperature Ts of the polymer (A) The shear stress applied is 0 seconds, 1 second and 1,000 seconds after the shear strain reaches 30%.)
The stress relaxation rates R1 and R2 described above can be calculated from the visco-elasticity data measured using a commercially available visco-elasticity measuring device with the polymer component processed into a predetermined shape as a sample, using the above formulas R1 and R2. 0 More specifically, at 40 ° C. higher measured temperature Tp than the flow initiation temperature Ts of the polymer component, the force of 4.9N directed from above the sample in the vertically downward with indicia pressure, from the side of the sample. The shear force is applied at an angular velocity of 52 rad / sec, and when the shear strain reaches 30%, the shear force is adjusted to maintain the shear strain of 30%. Here, shear stress τ (0), τ (1) and τ (1,000) were measured after 0 seconds, 1 second and 1,000 seconds after the shear strain reached 30%, The stress relaxation rate R1 after 1 second and the stress relaxation rate R2 after 1,000 seconds can be determined by substituting the values into the above formulas (R1) and (R2).

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 (A) polymer component because this temperature is the lower limit value of the processable temperature. Moreover, 30% of shear force assumes the deformation | transformation behavior of the (A) polymer component at the time of processing.
The stress relaxation rate R1 after 1 second is an index related to the ease of orientation of the (B) loss material when molding the electromagnetic wave absorber and the appearance of the molded body. When R1 is 50% or more, it is ensured that the loss material is properly 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 product, 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) loss material in the obtained electromagnetic wave absorber and the reproducibility of the absorber size at the time of absorber formation. By setting this R2 to 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, the variation in the size of the obtained molded article is reduced.
Therefore, by using a polymer component that satisfies both of R 1 and R 2, 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
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 still more preferably 35 to 60%.

[Glass transition temperature of (A) polymer component]
The glass transition temperature of the polymer (A) component in the present invention (Tg) of, + 5 ° C. Ru der less. The glass transition temperature is a numerical value determined from data measured by a differential scanning calorimeter (DSC) in accordance with JIS K 7121. The lower limit of the glass transition temperature is not particularly limited, but may be, for example, -100 ° C or more.
In general, as the glass transition temperature of the polymer component (A) is lower, an electromagnetic wave absorber that is soft and has 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 fast, and 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 the (B) loss material is easy to be oriented and the applied orientation is maintained for a long time, the polymer component is low in glass transition temperature but slow in stress relaxation to some extent. It will be necessary. The present invention satisfies the above contradictory requirements by employing a rubber obtained by copolymerizing a polyfunctional monomer as the polymer component (A).

<(B) Loss material>
(B) in the present invention the loss material is the ratio of the major axis length L and minor axis D L / D (aspect ratio) is from 2 to 100, is preferably from 10 to 80.
(B) The size of the loss material is a long axis from the viewpoint of balance such as electromagnetic wave absorption performance, ease of kneading when preparing an electromagnetic wave absorbing composition, and processability when manufacturing an electromagnetic wave absorber. The length L and the short axis length D are respectively as follows.
Long axis length L: preferably 10 to 500 μm, more preferably 25 to 400 μm, still more preferably 40 to 300 μm
Short axis length D: preferably 1 to 12 μm, more preferably 2 to 10 μm
It is preferable that the major axis length L of the (B) loss material be 10 μm or more, in order to express high electromagnetic wave absorption performance with a small amount of addition, and (A) the dispersibility in the polymer component and the electromagnetic wave absorber From the viewpoint of processability, the thickness is preferably 500 μm or less.

The dielectric loss material as the (B) loss material in the present invention is a material that converts electromagnetic wave energy to heat by the dielectric loss ability. Such dielectric loss material, carbon material charges used.
Examples of the carbon material include graphite, carbon fiber, carbon micro coil, carbon nanotube, graphene and the like.
The above-mentioned graphite can be obtained, for example, by finely grinding coal coke and classifying it. As the shape of the graphite, scaly black smoke is preferable from the viewpoint of orientation when used as an electromagnetic wave absorber.
Examples of the carbon fiber include carbon fibers obtained by carbonizing organic fibers (for example, polyacrylonitrile) at high temperature; petroleum pitch, coal pitch or coal tar pitch at high temperature, etc. It may be. This carbon nanofiber can be obtained by a known substrate growth method or vapor phase growth method.
The carbon micro coil is a kind of vapor grown carbon fiber obtained mainly by catalytic activation thermal decomposition of acetylene, and is a material having a 3D-helical / helical structure with a coil diameter of micron order. The diameter of the coil is preferably 1 to 10 μm, the diameter of the carbon fiber forming the coil is preferably 0.1 to 1 μm, and the length of the coil is preferably 1 to 10 mm.
Specifically, the carbon nanotubes can be obtained by, for example, a vapor phase growth method such as an arc discharge method, a laser evaporation method, or a thermal decomposition method. The carbon nanotube in the present invention may be either single-walled or multi-walled.
The graphene can be obtained, for example, by a peeling transfer method, a SiC thermal decomposition method, a chemical vapor deposition method, a method of cutting a carbon nanotube, or the like. As the graphene in the present invention, it is preferable to use a flake-shaped powdery graphene from the viewpoint of easily obtaining the aspect ratio specified in the present invention and the orientation in the electromagnetic wave absorber.

Dielectric loss material such as the above SL may be provided for use after treatment in terms of a suitable surface treating agent to improve the dispersibility of the polymer (A) component. As surface treatment agents used here, for example, in addition to coupling agents such as silane coupling agents, titanate coupling agents, and aluminum coupling agents;
Examples include block copolymers or graphs and copolymers having nonpolar segments and polar segments.

The preferred content of (B) loss material in the electromagnetic absorbing composition of the present invention, (A) with respect to the polymer component 100 parts by weight, good Mashiku 5-100 parts by weight, more preferably 10 to 80 wt Part, more preferably 20 to 70 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 in addition to these. Other components that can be used here include, for example, flame retardants, crosslinking agents, crosslinking aids, inorganic fillers, solid lubricants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, neutralization Agents, lubricants, compatibilizers, antifogging agents, antiblocking agents, slip agents, dispersants, colorants, antifungal agents, fluorescent whitening agents, softeners, resins, rubbers other than (A) polymer components, etc. It can be mentioned.

As said flame retardant material, magnesium hydroxide, aluminum hydroxide etc. can be mentioned, for example. 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, peroxide, sulfur etc. can be mentioned, for example. The content ratio 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 assistant 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 fluorocarbon resin 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 each component as described above, and the electromagnetic wave absorber of the present invention is a molded article of the above electromagnetic wave absorbing composition.
The above components may be collectively prepared from the above components through the electromagnetic wave absorbing composition to the electromagnetic wave absorber; or first, the electromagnetic wave absorbing composition may be produced from the above respective components, and the electromagnetic wave is absorbed from the above composition in a separate process. The body may be manufactured.
In the former case, the electromagnetic wave absorber can be obtained by collectively or sequentially feeding all or each of the above components into a suitable kneading / forming apparatus and performing kneading / forming. Here, in kneading or molding, it is preferable to use a device in which a shear in a certain direction is applied to the raw material mixture, thereby forming a molded article in which the (B) loss material is oriented. As such a kneading and forming method, for example, roll forming, calendar roll forming, kneading extrusion forming (uniaxial or biaxial) and the like can be mentioned;
For example, injection molding, blow molding, vacuum molding and the like can be exemplified by performing an appropriate mold at the outlet of the kneading extruder.
In the latter case, at least one of the step of producing the composition and the step of producing the electromagnetic wave absorber adopts a device in which the raw material mixture or the composition has a shear in a certain direction, It is preferable to use a molded article in which the loss material is oriented.
As a kneader in which a share in a certain direction is given to the raw material mixture, for example, a roll, a calender roll, a kneader extruder (single screw or twin screw), etc .;
As a kneading apparatus in which the share in the fixed direction is not applied to the raw material mixture, for example, a Banbury mixer, a Brabender, a kneader, etc. can be mentioned, respectively. The shape of the electromagnetic wave absorbing composition obtained after kneading may be, for example, a block (indeterminate shape), a sheet, a pellet, a powder, a granule, or the like according to the properties of the kneading apparatus.

Then, the composition of the present invention is supplied to a suitable molding apparatus and molded to obtain the electromagnetic wave absorber of the present invention.
As a forming apparatus which causes a shear in a certain direction in the composition, for example, a roll, a calender roll, a kneading extruder (single or twin screw), an injection molding machine, a blow molding machine, a vacuum molding machine, a slit die coating machine Etc;
As a forming apparatus in which the share in a certain direction is not applied to the composition, for example, a pressing apparatus and the like can be mentioned.
Kneading and molding can be carried out at any temperature, but from the viewpoint that each component is well dispersed and (B) the loss material rapidly obtains a composition or a molded body oriented within the predetermined range of the present invention. Therefore, it is preferable to carry out in the range of 30-200 degreeC. More preferably, the temperature is 0 to 100 ° C. higher, more preferably 20 to 80 ° C. higher, more preferably 20 to 80 ° C. higher than the flow start temperature Ts (° C.) of the polymer component (A) used. It is between 30 and 60 ° C. high temperature. The processing temperature at the stage of applying shear in a certain direction to the raw material mixture or composition in the kneading and forming steps may be between 20 and 60 ° C. higher than Ts (° C.) (B B) preferred in view of the orientation of the loss material.
The shape of the electromagnetic wave absorber obtained as described above is, for example, sheet, plate, film, rod, cuboid, column, polygonal column (especially triangular prism, square prism or hexagonal prism), polygonal pyramid ( It is preferable to set it as the shape which can utilize the orientation of the (B) loss material in the use application assumed especially, such as a triangular pyramid or a quadrangular pyramid.
The size of the electromagnetic wave absorber is arbitrary. When the electromagnetic wave absorber is formed into a sheet, for example, the thickness d is, for example, 0.1 to 10 mm, and the parameter d / λ when the wavelength of the electromagnetic wave to be a target is λ is as shown in FIG. It is preferable to set as close as possible to the reflection curve.

  In the electromagnetic wave absorber of the present invention, the (B) loss material is aligned such that the alignment strength in the long axis direction is 1.2 or more. The long-axis alignment strength means the degree of alignment of the (B) alignment agent in the electromagnetic wave absorber, and the larger the value, the higher the electromagnetic wave absorption effect. More specifically, the electromagnetic wave absorber sample cut out in sheet form is photographed with an electron microscope, the angular distribution of the (B) loss material in the field of view is examined, and the ratio of the major axis to the minor axis in the elliptical approximation It is evaluated as axial orientation strength. A specific approximation method and calculation procedure are described in Non-Patent Document 1 (Enomae et al., Nordic Pulp and Paper Research Journal, 21 (2), pp 253-259 (2006)). The maximum value of the long-axis alignment strength is theoretically 2.5, but in the context of the present invention, 1.6 or less is sufficient. The alignment strength in the major axis direction of the (B) loss material in the electromagnetic wave absorber of the present invention is preferably 1.3 to 1.6.

<Use mode of the electromagnetic wave absorber>
The electromagnetic wave absorber of the present invention may be used alone or in combination of 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 respectively formed into a sheet, and a laminated absorber formed by laminating these sheets;
A laminated absorber etc. formed by laminating | stacking several sheets which have the same or different complex specific dielectric constant so that the orientation direction of the (B) loss material may differ between layers can be illustrated preferably. Examples of the method for producing the laminated absorbent body include multilayer laminate extrusion molding, insert injection molding, multicolor injection molding (core back molding, rotation molding and the like), and the like.
The electromagnetic wave absorbers of the present invention may be used, for example, with metal layers or metal oxide layers. In this case, the metal layer is preferably provided on at least one of the surfaces of the electromagnetic wave absorber. Examples of metal species include copper, nickel, iron, zinc, titanium, silver and the like. Examples of metal oxides include oxides of these metals. The thickness of the metal layer or the metal oxide layer is preferably 0.1 to 20 mm, more preferably 0.5 to 10 mm. The most preferred embodiment when used with a metal layer is
The metal layer can be formed by, for example, a method of attaching a separately manufactured metal plate, lamination, metal film in-mold molding, plating method, vacuum evaporation method, sputtering method 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 the polymer component The flow start temperature Ts of the polymer component is manufactured by Shimadzu Corporation in accordance with the “flow test method for thermoplastics” described in JIS-K 7210 (1999). It calculated | required by the iso-velocity temperature rising test using heat flow evaluation apparatus "CFT-500D."
The measurement conditions were as follows.
Heating rate: 5 ° C / min Load: 100 kgf
Capillary die size: internal diameter 1.00 mm and length 1.00 mm
(2) Stress relaxation rate of polymer component The stress relaxation rate of the polymer component is processed into a cylindrical shape having a height of 2 mm and a diameter of 20 mm using a visco-elasticity measuring device "MR-500" manufactured by UFM 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, which is 40 ° C. higher than the flow start temperature Ts, using the above parallel plate, adjust the rotation angle so that the shear strain becomes 30% with the vertical load at the start of measurement being 4.9 N. The shear stress over time was measured. Then, the shear stress τ (0), τ (1) and τ (1,000) after 0 sec, 1 sec and 1,000 sec after the shear strain reaches 30% are examined, and these values are obtained. The stress relaxation rate R1 after 1 second and the stress relaxation rate R2 after 1,000 seconds were determined by substituting the above expressions (R1) and (R2).
(3) Glass transition temperature of polymer component The glass transition temperature of the polymer component is measured according to JIS K 7121 (1987) using a differential scanning calorimeter (manufactured by NETZSCH, type "DSC 204 F1"). It was measured by differential scanning calorimetry (DSC).

(4) Orientation of loss material in electromagnetic wave absorber The orientation of loss material in electromagnetic wave absorber is described in Non-Patent Document 1 (Enomae et al., Nordic Pulp and Paper Research Journal, 21 (2), pp 253-259 (2006). It evaluated based on the analysis method as described in 2.).
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 plane was parallel to the orientation axis. Using a field emission scanning electron microscope (product name: S-4300) manufactured by Hitachi High-Technologies Corp., place the sample for photography so that the orientation axis of the loss material in the cross section is in the horizontal direction, and shoot did.
About the obtained image, a 1024 × 1024 pixcel portion is trimmed, and 8-bit grayscale processing is performed, and the orientation intensity calculated using the analysis software “Fiber-Orientation-Analysis-8.13” is taken as the longitudinal direction orientation mirror intensity and did.

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

<Production Example of (A) Polymer Component>
Production Example 1
85 parts by weight of ethyl acrylate, 12 parts by weight of acrylonitrile and 3 parts by weight of trimethylolpropane triacrylate were added to an aqueous solution of 5 parts by weight of sodium dodecylbenzenesulfonate as an emulsifier in 200 parts by weight of distilled water, and cooled to 10 ° C. Thereafter, 0.02 parts by weight of paramenthane hydroperoxide was added, and a polymerization reaction was carried out at 10 ° C. After the polymerization conversion reached about 90% by weight, 0.5 parts by weight of N, N-diethylhydroxylamine was added to the reaction system to terminate the copolymerization reaction to obtain a copolymer latex (reaction time) 6 hours). The resulting 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, thoroughly washed with water, and dried at about 90 ° C. for 3 hours to obtain a copolymer 1.
In addition, a portion of the obtained latex is diluted 10 times by volume ratio with a chloroform / toluene mixed solvent (volume ratio 4: 1) to obtain a dynamic light scattering nanotrack particle size analyzer (type “UPA-EX150”, It was 189 nm when the volume average particle diameter was computed using Nikkiso Co., Ltd. product). Moreover, the glass transition temperature of the copolymer 1 was 0 degreeC.

Production Example 2
In an aqueous solution prepared by dissolving 5 parts by weight of sodium dodecylbenzene sulfonate as an emulsifier 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 terminate the copolymerization reaction, to obtain a copolymer latex (reaction time 4) time). The resulting 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, thoroughly washed with water, and dried at about 90 ° C. for 3 hours to obtain a copolymer 2.
The volume average particle diameter of the copolymer 2 was calculated in the same manner as in Production Example 1 using the obtained latex, and it was 178 nm. Moreover, the glass transition temperature of the copolymer 2 was -11 degreeC.

Production Example 3
The copolymer 3 is prepared in the same manner as in Production Example 1 except that the preparation amount is 77 parts by weight of ethyl acrylate, 6 parts by weight of acrylonitrile and 17 parts by weight of trimethylolpropane triacrylate in the above Production Example 1. 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 as a raw material monomer, 28 parts by weight of acrylonitrile and 6 parts by weight of divinylbenzene, and a redox catalyst are charged in an autoclave at 10 ° C. After the temperature was adjusted, 0.01 part of paramenthane hydroxide was added as a polymerization initiator, and emulsion polymerization was performed to a polymerization conversion rate of 95%. Then, the reaction terminator N, N-diethylhydroxylamine was added to synthesize a copolymer emulsion. Thereafter, steam is blown into the solution to remove unreacted raw material monomers, and then the solution is added to a 5% aqueous solution of calcium chloride, and the precipitated copolymer is dried by an air blower set at 80 ° C. Thus, copolymer 4 was obtained.
The volume average particle diameter 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
A mixing roll manufactured by Kansai Roll Co., Ltd., in which a mixture of 100 parts by weight of vinyl chloride (product name: TH-1400) manufactured by Taiyokai PVC Co., Ltd. and 400 parts by weight of dioctyl phthalate as a plasticizer is adjusted to 100 ° C. The soft polyvinyl chloride composition was obtained by kneading for 1 minute with a roll rotation speed of 20 rpm before and 22 rpm after.

<Manufacturing 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 ) with a thickness of 10 nm is plastically deformed by processing it for 2 minutes using an attritor to form 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 adopts the optimum composition determined by the following preliminary experiments.
Several types of preliminary samples were prepared in which the loss material was varied with respect to 100 parts by weight of the polymer component. For each sample
Loss material is determined Me a real component epsilon _{r 'and} imaginary components epsilon _r "of the complex relative permittivity in the case of a dielectric loss material, the relationship of these real and imaginary components are taken from the composition close to non-reflection curve As the d / λ value in the example and the comparative example, in the plot of imaginary component (vertical axis) versus real component (horizontal axis), a line parallel to the vertical axis originating from the plotted point intersects the non-reflection curve The d / λ value of the point was used.
Preparation of a preliminary sample was according to the following method.
Using a mixing roll manufactured by Kansai Roll Co., Ltd., adjusted to a predetermined temperature, the mass of 100 parts by weight of the polymer component is kneaded for 1 minute at a roll rotation number of 20 rpm and 22 rpm, and then a predetermined amount of loss material Was added and mixed for another 3 minutes. A preliminary sample was obtained by forming and processing the material after kneading 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 carried out to determine the compositions of Example E1 and Comparative Example e1. As the composition of Example E1, the composition of the preliminary experimental example 2 in which the relationship between the real component ε _r ′ of the complex relative dielectric constant and the imaginary component ε _r ′ ′ is closest to the non-reflection curve among the preliminary experimental examples 1 to 3 is
As the composition of the comparative example e1, of 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 ′ of the complex relative permittivity and the imaginary component ε _r ′ ′ is closest to the non-reflection curve,
Each adopted.

The abbreviation of each component in the above-mentioned Table 1 has the following meanings, respectively.
[Polymer component]
Copolymer 1: "Copolymer 1" produced in the above-mentioned Production Example 1
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 Resins Co., Ltd., trade name "Dyaleed K223HM"

<Example and Comparative Example Using Dielectric Loss Material>
Examples E1 to E7 and Comparative Examples e1 to e4
Each experiment was conducted using the types and amounts (parts by weight) of polymer components and loss materials listed in Table 2. The compositional ratio of the polymer component and the loss material and the d / λ ratio were determined by preliminary experiments conducted by the same method as described above.
Using a mixing roll manufactured by Kansai Roll Co., Ltd., which has been temperature-controlled to the temperature described in Table 2, a predetermined amount of polymer component is masticated for 1 minute, with the roll rotation number being 20 rpm before and 22 rpm after A fixed quantity of loss material was added and kneaded for another 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 material after the above-mentioned kneading was pressure-formed using a 300ton press machine manufactured by Kansai Roll Co., Ltd. to obtain two sheets of different thickness for each frequency band. The thicknesses of these sheets are determined by substituting the frequencies 5.8 GHz and 22 GHz for the d / λ ratio obtained in the preliminary experiment. Then, each sheet was cut into a size for each frequency band, and the electromagnetic wave absorption performance was evaluated.
The evaluation results are shown in Table 2.

The abbreviation of each component in the above-mentioned Table 2 has the following meanings, respectively.
[Polymer component]
Copolymer 1: "Copolymer 1" produced in the above-mentioned Production Example 1
Copolymer 2: "Copolymer 2" produced in the above-mentioned Production Example 2
Soft polyvinyl chloride: "Soft polyvinyl chloride composition" manufactured in the above Comparative Production Example 1
Copolymer 3: "Copolymer 3" produced in the above-mentioned Production Example 3
Copolymer 4: "Copolymer 4" manufactured in the above-mentioned Preparation Example 4
CEBC: olefin crystal / ethylene / butylene / olefin crystal block copolymer, manufactured by JSR Co., Ltd., product name “DR6100”
EPDM: ethylene / propylene / diene rubber, manufactured by JSR Corporation, product name "EP 51"
[Loss material]
Carbon fiber: Mitsubishi Resins Co., Ltd. product name "Dyaleed K223HM", aspect ratio 20
Graphite: manufactured by Chuetsu Graphite Co., Ltd., product name "SB # 1", aspect ratio 3
Spheroidal graphite: manufactured by Chuetsu Graphite Co., Ltd., product name "WF-15C", aspect ratio 1

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

The abbreviation of each component in the above-mentioned Table 3 means the following, respectively.
[Polymer component]
Copolymer 1: "Copolymer 1" produced in the above-mentioned Production Example 1
EPDM: ethylene / propylene / diene rubber, manufactured by JSR Corporation, product name "EP 51"
[Loss material]
Soft magnetic iron powder 1: aspect ratio 1
Soft magnetic iron powder 2: "Soft magnetic iron powder 2" manufactured in the above-mentioned Production Example 5, aspect ratio 20

Claims (5)

(A) A polymer component obtained by copolymerizing a polyfunctional monomer and having a glass transition temperature of + 5 ° C. or less measured by a differential scanning calorimeter, and (B) major axis length L and minor axis An electromagnetic wave absorbing composition comprising a dielectric loss material of a carbon material having a ratio L / D to the length D of 2 to 100.   The polymer component (A) is selected from acrylic rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber, fluororubber and styrene butadiene rubber, provided that the polyfunctional monomer is copolymerized. The electromagnetic wave absorbing composition of claim 1.   The electromagnetic wave absorptive composition of Claim 2 whose copolymerization ratio of the polyfunctional monomer in said (A) polymer component is 0.5-7 mol%. It consists of a molded object of the electromagnetic wave absorptive composition as described in any one of Claims 1-3 , and (B) loss material in this molded object is set to 1.2 or more orientation strength of a major axis direction. An electromagnetic wave absorber characterized in that it is oriented. An electronic device comprising the electromagnetic wave absorber according to claim 4 .

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