JP2004043705A - Electromagnetic wave absorbing composition and molding using the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、電磁波を吸収する樹脂組成物及びそれを用いて形成した成型品に関するものである。
【０００２】
【従来の技術】
交流電気鉄道、又は超高圧送電線（特に、直接接地方式送電線）の近くに架設されるケーブルにおいては、電磁波の発生が問題となるため、電磁しゃへい層を施す必要がある。
【０００３】
電磁しゃへい層としては、例えば、高分子材料中に電磁波吸収体（電磁波吸収特性を有する粒子）を混合・充填してなる電磁波吸収組成物を、導体の周りに射出成形したものが挙げられる。この電磁波吸収材料としては、次の３種類に大別される。
【０００４】
▲１▼ 磁性体粉末混合型
高分子材料中に磁性体粉末を混合・分散させ、磁性材料の複素比透磁率μｒの虚数部μ”ｒを利用し、透磁損失により電磁波を減衰させる磁性電波吸収材料であり、電磁波の磁界成分に作用して、そのエネルギーを熱に変換するもの。例えば、フェライトなどの磁性体の粉末を樹脂に混合・充填して一体化した製品などが挙げられる。
【０００５】
▲２▼ 導電性粉末混合型
絶縁体材料中に導電性粉末を混合・分散させ、抵抗率又は導電率と比誘電率を変化させると共に、特に複素比誘電率εｒの虚数部ε”ｒを大きくし、誘電損失により電磁波を減衰させる誘電性電波吸収材料であり、電磁波の電界成分に作用して、そのエネルギーを熱に変換するもの。例えば、導電性金属の粉末又はカーボン粉末などをゴム材料などに混合・充填したものなどが挙げられる。
【０００６】
▲３▼ λ／４型
金属膜などの電波反射膜の前面（電波入射面）側に、波長λの１／４の厚さの誘電体膜を形成し、その誘電体膜の表面に更に抵抗被膜（各種の導電体膜）を積層形成し、抵抗被膜表面で反射された表面反射波と電磁波吸収体内部の電波反射膜表面で反射された内部反射波とが逆位相で、かつ、同振幅となるようにインピーダンス整合を図ったもの。
【０００７】
また、▲１▼と▲２▼の複合型、例えば、▲２▼の誘電性電波吸収材料からなる膜の電波入射面と反対側の面に、▲１▼の磁性電波吸収材料からなる膜を積層したもの等もある。
【０００８】
【発明が解決しようとする課題】
従来の電磁波吸収材料において十分な電磁波吸収能を得るには、高分子材料中に配合・充填する電磁波吸収体の量を多くする必要があった。ところが、高分子材料中に配合・充填する電磁波吸収体の量を多くすると、射出成形性が悪化したり、高分子材料からなる母材の特性、例えば可撓性などを損なうといった問題があった。
【０００９】
以上の事情を考慮して創案された本発明の目的は、電磁波吸収体の混合・充填量が少なくても良好な電磁波吸収能を有する電磁波吸収組成物及びそれを用いて形成した成型品を提供することにある。
【００１０】
【課題を解決するための手段】
上記目的を達成すべく本発明に係る電磁波吸収組成物は、高分子材料中に電磁波吸収体を混合・充填してなる電磁波吸収組成物において、上記電磁波吸収体として、導電性又は磁性を有する多孔質粒子を混合・充填したものである。
【００１１】
より具体的には、請求項２に示すように、上記高分子材料１００重量部に対して、１５重量部以上〜７０重量部未満の上記多孔質粒子を混合・充填する。
【００１２】
また、請求項３に示すように、上記高分子材料が、クロロプレンゴム又はエチレンエチルアクリレート共重合樹脂であることが好ましい。
【００１３】
これによって、導電性又は磁性を有する多孔質粒子からなる電磁波吸収体を用いることで、従来の電磁波吸収体と比較して少ない配合量で、高分子材料及び電磁波吸収体の複合系の複素誘電率又は複素透磁率を大きくすることができ、その結果、電磁波吸収組成物の電磁波吸収能を高めることができる。
【００１４】
一方、本発明に係る電磁波吸収成型品は、上述した電磁波吸収組成物を用い、所定の形状に射出形成したものである。
【００１５】
これによって、電磁波吸収特性及び成形加工性が共に良好な電磁波吸収成型品を得ることができる。
【００１６】
【発明の実施の形態】
以下、本発明の好適一実施の形態を説明する。
【００１７】
本実施の形態に係る電磁波吸収組成物は、高分子材料中に、導電性又は磁性を有する多孔質粒子からなる電磁波吸収体を混合・充填してなるものであり、高分子材料１００重量部に対して、多孔質粒子の充填量（配合量）を１５重量部以上〜７０重量部未満、好ましくは１５重量部以上〜６０重量部以下、より好ましくは３０重量部以上〜６０重量部未満としたものである。
【００１８】
得られた電磁波吸収組成物は射出成型機などの成形加工機に供給される。ケーブルなどの電磁しゃへい層であれば導体の周囲に層状に被覆形成することで、また、携帯電話などの筐体であれば所望の形状に射出成形することで、電磁波吸収成型品が得られる。
【００１９】
ここで、導電性又は磁性を有する多孔質粒子の比表面積（１グラム当たりの表面積）は、３００（ｍ２／ｇ）以上、好ましくは７００〜２，０００（ｍ２／ｇ）である。
【００２０】
多孔質粒子の孔サイズは特に限定するものではないが、平均細孔直径として１０ｎｍ以下、好ましくは１〜５ｎｍである。また、多孔質粒子の粒径は特に限定するものではないが、平均粒子直径として５０μｍ以下、好ましくは５〜３０μｍである。このことから、好ましい多孔質粒子の粒径と孔サイズとの比（粒径／孔サイズ）は、１，０００〜３０，０００である。
【００２１】
高分子材料としては、電磁波吸収材料の母材として慣用的に用いられているものであれば特に限定するものではないが、例えば、クロロプレンゴムなどのゴム材料、エチレンエチルアクリレート共重合樹脂（ＥＥ）などのポリオレフィン系樹脂材料などが挙げられる。
【００２２】
本実施の形態においては、電磁波吸収特性を有する電磁波吸収体の、体積当たりの電磁波吸収能を高めるべく、導電性又は磁性を有する多孔質粒子からなる電磁波吸収体を用いている。多孔質粒子は、同体積の非多孔質粒子と比べて表面積が大きい（比表面積が大きい）ため、電磁波吸収体として導電性（又は磁性）を有する多孔質粒子を用いた場合、従来の電磁波吸収体と比較して少ない配合量で、母材（高分子材料）及び電磁波吸収体の、複合系の複素誘電率（又は複素透磁率）を大きくすることができ、その結果、電磁波吸収組成物の電磁波吸収能を高めることができる。
【００２３】
よって、本実施の形態に係る電磁波吸収組成物において、従来の電磁波吸収組成物と同等の電磁波吸収能を得たい場合、従来と比較して電磁波吸収体の配合量（充填量）を少なくすることができるため、射出成形などの成形加工性をより高めることができる。また、従来と比較して、電磁波吸収体の配合量（充填量）を少なくすることができるため、母材が有する可撓性などの特性を損なうことなく、電磁波吸収成型品を作製することができ、この電磁波吸収成型品においても良好な可撓性などが得られる。
【００２４】
また、本実施の形態に係る電磁波吸収組成物において、電磁波吸収体の配合量（充填量）を従来の電磁波吸収組成物と同等とした場合、従来と比較して、より高い電磁波吸収能を得ることができる。
【００２５】
また、本実施の形態に係る電磁波吸収成型品において、電磁波吸収体の配合量（充填量）を、従来の電磁波吸収成型品と同等としたまま、従来の電磁波吸収成型品と同等の電磁波吸収能を得たい場合、従来と比較して、電磁波吸収成型品の層厚又は肉厚を薄くすることができ、延いては電磁波吸収成型品の軽量化を図ることができる。
【００２６】
一方、本実施の形態に係る電磁波吸収組成物は、交流電気鉄道、又は超高圧送電線の近くに架設されるケーブルの電磁しゃへい層に適用することができる。この時、電磁しゃへい層は射出成形により形成されるが、射出成形性は良好であると共に、従来と同等又はそれ以上の十分な電磁しゃへい効果が得られる。
【００２７】
また、本実施の形態に係る電磁波吸収組成物又は電磁波吸収成型品は、橋などの大型建造物の電波吸収材として適用することができる。橋などの大型建造物に塗布したり、貼り付けたりすることで、レーダ、特に船舶・航空用レーダの偽像防止を図ることができる。ここで、前述したように、従来と比較して、電磁波吸収組成物又は電磁波吸収成型品の層厚又は肉厚を薄くすることができることから、大型建造物に対する塗布・貼付量を低減することができ、その結果、材料コストの低減を図ることができる。
【００２８】
また、本実施の形態に係る電磁波吸収成型品は、携帯電話、電子レンジなどの筐体として適用することができる。本実施の形態に係る電磁波吸収組成物を用いて射出成形などを行うことで、漏れ電波などの電磁波吸収能は同じまま、従来と比較して、射出成形などの成形性を高めること、又は射出成形などの成形性は同じまま、従来と比較して、電磁波吸収能を高めることができる。ここで、前述したように、従来と比較して、電磁波吸収組成物又は電磁波吸収成型品の層厚又は肉厚を薄くすることができることから、筐体重量及び筐体肉厚の低減を図ることができ、その結果、携帯電話、電子レンジなどの軽量化・小型化を図ることができる。
【００２９】
以上、本発明の実施の形態は、上述した実施の形態に限定されるものではなく、他にも種々のものが想定されることは言うまでもない。
【００３０】
【実施例】
次に、本発明について、実施例に基づいて説明するが、本発明はこれらの実施例に限定されるものではない。
【００３１】
（実施例１）
クロロプレンゴムの溶融樹脂１００重量部に対して、粒径が５〜３０μｍで、導電性を有する多孔質粒子を３０重量部充填・配合して電磁波吸収組成物を形成した。この多孔質粒子は、比表面積が１，３００ｍ２／ｇで、サイズが１ｎｍ（小）の特殊炭粒子（以下、炭粒子Ａと表す）からなるものである。
【００３２】
この電磁波吸収組成物を用い、射出成形により肉厚１．５ｍｍのシート材を作製する（試料１）。
【００３３】
（実施例２）
多孔質粒子として、比表面積が７００ｍ２／ｇで、サイズが５ｎｍ（中）の特殊炭粒子（以下、炭粒子Ｂと表す）を用いる以外は実施例１と同様にして、肉厚１．５ｍｍのシート材を作製する（試料２）。
【００３４】
（実施例３）
多孔質粒子として、比表面積が３００ｍ２／ｇで、サイズが１０ｎｍ（大）の特殊炭粒子（以下、炭粒子Ｃと表す）を用いる以外は実施例１と同様にして、肉厚１．５ｍｍのシート材を作製する（試料３）。
【００３５】
（実施例４）
炭粒子Ｃの充填・配合量が４０重量部である以外は実施例３と同様にして、肉厚１．５ｍｍのシート材を作製する（試料４）。
【００３６】
（実施例５）
炭粒子Ｃの充填・配合量が５０重量部である以外は実施例３と同様にして、肉厚１．５ｍｍのシート材を作製する（試料５）。
【００３７】
（実施例６）
炭粒子Ｃの充填・配合量が６０重量部である以外は実施例３と同様にして、肉厚１．５ｍｍのシート材を作製する（試料６）。
【００３８】
（比較例１）
炭粒子Ｃの充填・配合量が７０重量部である以外は実施例３と同様にして、肉厚１．５ｍｍのシート材を作製する（試料７）。
【００３９】
（従来例１）
クロロプレンゴムの溶融樹脂１００重量部に対して、粒径が５〜３０μｍで、非多孔質のカーボン粒子を３０重量部充填・配合して電磁波吸収組成物を形成した。
【００４０】
この電磁波吸収組成物を用い、射出成形により肉厚１．５ｍｍのシート材を作製する（試料８）。
【００４１】
実施例１〜６、比較例、及び従来例の各試料（試料１〜８）の諸元を表１に示す。
【００４２】
【表１】
次に、試料１〜８について、自由空間法による斜め入射電波の吸収特性評価を行った。吸収特性の評価は、２つの周波数領域（０．５〜２．５ＧＨｚ、５〜１５ＧＨｚ）における電磁波吸収量（ｄＢ）のピーク値によって行った。また、各試料の射出成形時における成形性の評価も行った。この時、射出成形性が良好なものを○、やや良好なものを△、射出成形できなかったものを×と評価した。各評価結果を表２に示す。
【００４４】
【表２】
表２に示すように、従来例の試料８と比較して、実施例１〜６の各試料（試料１〜６）は、０．５〜２．５ＧＨｚの周波数領域では２．３〜４倍、５〜１５ＧＨｚの周波数領域では約１．９〜４．３倍の電磁波吸収能を有することが確認できた。また、電磁波吸収能は、電磁波吸収体の配合・充填量が同じ場合、炭粒子Ａを用いた試料＜炭粒子Ｂを用いた試料＜炭粒子Ｃを用いた試料の順、すなわち試料１＜試料２＜試料３の順に大きくなっていた。さらに、電磁波吸収能は、同じ電磁波吸収体（炭粒子Ｃ）を用いた場合、電磁波吸収体の配合・充填量が多い試料ほど、すなわち試料３＜試料４＜試料５＜試料６の順に大きくなっていた。
【００４６】
ここで、比較例１の試料７は、電磁波吸収体の配合・充填量が７０重量部と多いため、射出成形が不可能であり、シート材を作製することができなかった。これによって、電磁波吸収体の配合・充填量の上限を７０重量部未満と規定している。
【００４７】
また、５〜１５ＧＨｚの周波数領域において、実施例１の試料１の電磁波吸収量は１３ｄＢであり、従来例１の試料８の電磁波吸収量（７ｄＢ）の約２倍である。このことから、電磁波吸収体の配合・充填量が実施例１の試料１の半分（１５重量部）であっても、従来例１の試料８と同等の電磁波吸収能が得られると推定される。これによって、電磁波吸収体の配合・充填量の下限を１５重量部以上と規定している。
【００４８】
【発明の効果】
以上要するに本発明によれば、次のような優れた効果を発揮する。
【００４９】
（１） 高分子材料中に、導電性又は磁性を有する多孔質粒子からなる電磁波吸収体を混合・充填することで、従来の電磁波吸収体と比較して少ない配合量で、高分子材料及び電磁波吸収体の複合系の複素誘電率又は複素透磁率を大きくすることができ、その結果、電磁波吸収組成物の電磁波吸収能を高めることができる。
【００５０】
（２） （１）の電磁波吸収組成物を用いることで、電磁波吸収特性及び成形加工性が共に良好な電磁波吸収成型品を得ることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a resin composition that absorbs electromagnetic waves and a molded product formed using the same.
[0002]
[Prior art]
In a cable installed near an AC electric railway or an ultra-high-voltage transmission line (in particular, a direct grounding type transmission line), generation of electromagnetic waves becomes a problem, and therefore, it is necessary to apply an electromagnetic shielding layer.
[0003]
Examples of the electromagnetic shielding layer include those obtained by injection molding an electromagnetic wave absorbing composition obtained by mixing and filling an electromagnetic wave absorber (particles having electromagnetic wave absorbing properties) in a polymer material around a conductor. This electromagnetic wave absorbing material is roughly classified into the following three types.
[0004]
{Circle around (1)} Magnetic powder that mixes and disperses magnetic powder in a magnetic powder-mixed polymer material and uses the imaginary part μ ″ r of the complex relative magnetic permeability μr of the magnetic material to attenuate electromagnetic waves by magnetic permeability loss. An absorbing material that acts on a magnetic field component of an electromagnetic wave to convert its energy into heat, such as a product obtained by mixing and filling a resin with a powder of a magnetic substance such as ferrite.
[0005]
{Circle around (2)} The conductive powder is mixed and dispersed in the conductive powder mixed type insulator material to change the resistivity or the conductivity and the relative permittivity, and particularly, to increase the imaginary part ε ″ r of the complex relative permittivity εr. A dielectric wave absorbing material that attenuates electromagnetic waves due to dielectric loss and acts on the electric field component of electromagnetic waves to convert the energy into heat, such as converting conductive metal powder or carbon powder into rubber material. And the like mixed and filled.
[0006]
{Circle around (3)} A dielectric film having a thickness of １ ／ of the wavelength λ is formed on the front side (radio wave incident surface) of a radio wave reflection film such as a λ / 4 type metal film, and a resistance is further added to the surface of the dielectric film. Coatings (various conductor films) are formed in layers, and the surface reflected wave reflected on the surface of the resistive film and the internal reflected wave reflected on the surface of the radio wave reflecting film inside the electromagnetic wave absorber have opposite phases and the same amplitude. Impedance matching so that
[0007]
In addition, a film made of a magnetic wave absorbing material of (1) is provided on the surface of the film made of the dielectric wave absorbing material of (2) opposite to the wave incident surface of the film of the compound of (1) and (2). There are also laminated ones.
[0008]
[Problems to be solved by the invention]
In order to obtain a sufficient electromagnetic wave absorbing ability in a conventional electromagnetic wave absorbing material, it was necessary to increase the amount of the electromagnetic wave absorber to be blended and filled in the polymer material. However, when the amount of the electromagnetic wave absorber mixed and filled in the polymer material is increased, there is a problem that the injection moldability is deteriorated and the properties of the base material made of the polymer material, such as flexibility, are impaired. .
[0009]
SUMMARY OF THE INVENTION The object of the present invention, which has been made in consideration of the above circumstances, is to provide an electromagnetic wave absorbing composition having good electromagnetic wave absorbing ability even with a small mixing / filling amount of an electromagnetic wave absorber, and a molded article formed using the same. Is to do.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the electromagnetic wave absorbing composition according to the present invention is an electromagnetic wave absorbing composition obtained by mixing and filling an electromagnetic wave absorber in a polymer material. The particles are mixed and filled with porous particles.
[0011]
More specifically, as described in claim 2, 15 to 70 parts by weight of the porous particles are mixed and filled with 100 parts by weight of the polymer material.
[0012]
Further, as described in claim 3, the polymer material is preferably chloroprene rubber or ethylene ethyl acrylate copolymer resin.
[0013]
Thus, by using the electromagnetic wave absorber made of conductive or magnetic porous particles, the complex dielectric constant of the composite system of the polymer material and the electromagnetic wave absorber can be reduced with a smaller amount than the conventional electromagnetic wave absorber. Alternatively, the complex magnetic permeability can be increased, and as a result, the electromagnetic wave absorbing ability of the electromagnetic wave absorbing composition can be increased.
[0014]
On the other hand, an electromagnetic wave absorbing molded product according to the present invention is formed by injection molding into a predetermined shape using the above-described electromagnetic wave absorbing composition.
[0015]
As a result, it is possible to obtain an electromagnetic wave absorption molded product having both good electromagnetic wave absorption characteristics and good moldability.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described.
[0017]
The electromagnetic wave absorbing composition according to the present embodiment is obtained by mixing and filling an electromagnetic wave absorber made of conductive or magnetic porous particles in a polymer material, and 100 parts by weight of the polymer material. On the other hand, the filling amount (blending amount) of the porous particles is 15 parts by weight or more and less than 70 parts by weight, preferably 15 parts by weight or more and 60 parts by weight or less, more preferably 30 parts by weight or more and less than 60 parts by weight. Things.
[0018]
The obtained electromagnetic wave absorbing composition is supplied to a molding machine such as an injection molding machine. In the case of an electromagnetic shielding layer such as a cable, an electromagnetic wave absorption molded product can be obtained by forming a layer around the conductor, or in the case of a housing of a mobile phone or the like by injection molding into a desired shape.
[0019]
Here, the specific surface area (surface area per gram) of the conductive or magnetic porous particles is 300 (m 2 / g) or more, preferably 700 to 2,000 (m 2 / g).
[0020]
Although the pore size of the porous particles is not particularly limited, the average pore diameter is 10 nm or less, preferably 1 to 5 nm. The particle size of the porous particles is not particularly limited, but is 50 μm or less, preferably 5 to 30 μm as an average particle diameter. For this reason, a preferable ratio of the particle size of the porous particles to the pore size (particle size / pore size) is 1,000 to 30,000.
[0021]
The polymer material is not particularly limited as long as it is a material commonly used as a base material of an electromagnetic wave absorbing material. For example, a rubber material such as chloroprene rubber, ethylene ethyl acrylate copolymer resin (EE) And the like.
[0022]
In the present embodiment, an electromagnetic wave absorber made of conductive or magnetic porous particles is used in order to enhance the electromagnetic wave absorbing ability per volume of the electromagnetic wave absorber having the electromagnetic wave absorbing characteristics. Porous particles have a larger surface area (larger specific surface area) than non-porous particles of the same volume. Therefore, when conductive (or magnetic) porous particles are used as the electromagnetic wave absorber, the conventional electromagnetic wave absorption The complex dielectric constant (or complex permeability) of the composite material of the base material (polymer material) and the electromagnetic wave absorber can be increased with a smaller blending amount than the body, and as a result, the electromagnetic wave absorbing composition of the electromagnetic wave absorbing composition can be increased. The ability to absorb electromagnetic waves can be increased.
[0023]
Therefore, in the electromagnetic wave absorbing composition according to the present embodiment, when it is desired to obtain an electromagnetic wave absorbing ability equivalent to that of the conventional electromagnetic wave absorbing composition, the blending amount (filling amount) of the electromagnetic wave absorber should be reduced as compared with the conventional case. Therefore, molding processability such as injection molding can be further improved. Further, since the compounding amount (filling amount) of the electromagnetic wave absorber can be reduced as compared with the conventional case, it is possible to produce an electromagnetic wave absorbing molded product without impairing the properties such as flexibility of the base material. Good flexibility and the like can be obtained with this electromagnetic wave absorbing molded product.
[0024]
Further, in the electromagnetic wave absorbing composition according to the present embodiment, when the blending amount (filling amount) of the electromagnetic wave absorber is equal to that of the conventional electromagnetic wave absorbing composition, a higher electromagnetic wave absorbing ability is obtained as compared with the related art. be able to.
[0025]
In addition, in the electromagnetic wave absorbing molded product according to the present embodiment, while the compounding amount (filling amount) of the electromagnetic wave absorber is equal to that of the conventional electromagnetic wave absorbing molded product, the electromagnetic wave absorbing ability is the same as that of the conventional electromagnetic wave absorbing molded product. When it is desired to obtain, the thickness or thickness of the electromagnetic wave absorption molded product can be reduced as compared with the related art, and the weight of the electromagnetic wave absorption molded product can be reduced.
[0026]
On the other hand, the electromagnetic wave absorbing composition according to the present embodiment can be applied to an AC electric railway or an electromagnetic shielding layer of a cable installed near an ultra-high-voltage transmission line. At this time, although the electromagnetic shielding layer is formed by injection molding, the injection molding properties are good and a sufficient electromagnetic shielding effect equal to or higher than that of the related art can be obtained.
[0027]
Further, the electromagnetic wave absorbing composition or the electromagnetic wave absorbing molded product according to the present embodiment can be applied as a radio wave absorbing material of a large building such as a bridge. By applying or sticking it to a large building such as a bridge, it is possible to prevent a false image of a radar, especially a ship / aviation radar. Here, as described above, since the layer thickness or wall thickness of the electromagnetic wave absorbing composition or the electromagnetic wave absorbing molded product can be reduced as compared with the related art, it is possible to reduce the amount of application / sticking to a large building. As a result, material costs can be reduced.
[0028]
In addition, the molded product for absorbing electromagnetic waves according to the present embodiment can be applied to a housing of a mobile phone, a microwave oven, or the like. By performing injection molding or the like using the electromagnetic wave absorbing composition according to the present embodiment, it is possible to improve the moldability of injection molding or the like, or to improve the moldability of injection molding or the like, as compared with the related art, while maintaining the same electromagnetic wave absorbing ability as leak radio waves. The electromagnetic wave absorbing ability can be increased as compared with the related art while maintaining the same moldability such as molding. Here, as described above, since the layer thickness or the thickness of the electromagnetic wave absorbing composition or the electromagnetic wave absorbing molded product can be reduced as compared with the related art, the housing weight and the housing thickness can be reduced. As a result, the weight and size of a mobile phone, a microwave oven, and the like can be reduced.
[0029]
As described above, the embodiments of the present invention are not limited to the above-described embodiments, and it is needless to say that various other embodiments are also conceivable.
[0030]
【Example】
Next, the present invention will be described based on examples, but the present invention is not limited to these examples.
[0031]
(Example 1)
30 parts by weight of electrically conductive porous particles having a particle size of 5 to 30 μm were filled and blended with 100 parts by weight of the molten resin of chloroprene rubber to form an electromagnetic wave absorbing composition. The porous particles are made of special charcoal particles having a specific surface area of 1,300 m 2 / g and a size of 1 nm (small) (hereinafter, referred to as charcoal particles A).
[0032]
Using this electromagnetic wave absorbing composition, a sheet material having a thickness of 1.5 mm is prepared by injection molding (sample 1).
[0033]
(Example 2)
The same procedure as in Example 1 was carried out except that special carbon particles having a specific surface area of 700 m 2 / g and a size of 5 nm (medium) (hereinafter, referred to as carbon particles B) were used as the porous particles, and the wall thickness was 1.5 mm. (Sample 2).
[0034]
(Example 3)
The same procedure as in Example 1 was carried out except that special carbon particles having a specific surface area of 300 m 2 / g and a size of 10 nm (large) (hereinafter referred to as carbon particles C) were used as the porous particles, and the wall thickness was 1.5 mm. (Sample 3).
[0035]
(Example 4)
A sheet material having a thickness of 1.5 mm is prepared in the same manner as in Example 3 except that the filling and blending amount of the carbon particles C is 40 parts by weight (sample 4).
[0036]
(Example 5)
A sheet material having a thickness of 1.5 mm is prepared in the same manner as in Example 3 except that the filling and blending amount of the carbon particles C is 50 parts by weight (Sample 5).
[0037]
(Example 6)
A sheet material having a thickness of 1.5 mm is prepared in the same manner as in Example 3 except that the filling and blending amount of the carbon particles C is 60 parts by weight (Sample 6).
[0038]
(Comparative Example 1)
A sheet material having a thickness of 1.5 mm is prepared in the same manner as in Example 3 except that the filling and blending amount of the carbon particles C is 70 parts by weight (Sample 7).
[0039]
(Conventional example 1)
30 parts by weight of non-porous carbon particles having a particle size of 5 to 30 μm were filled and blended with 100 parts by weight of the molten resin of chloroprene rubber to form an electromagnetic wave absorbing composition.
[0040]
Using this electromagnetic wave absorbing composition, a sheet material having a thickness of 1.5 mm is prepared by injection molding (sample 8).
[0041]
Table 1 shows the specifications of the samples (samples 1 to 8) of Examples 1 to 6, the comparative example, and the conventional example.
[0042]
[Table 1]
Next, the absorption characteristics of obliquely incident radio waves were evaluated for the samples 1 to 8 by the free space method. The evaluation of the absorption characteristics was performed based on the peak values of the electromagnetic wave absorption (dB) in two frequency ranges (0.5 to 2.5 GHz and 5 to 15 GHz). The moldability of each sample during injection molding was also evaluated. At this time, a sample having good injection moldability was evaluated as ○, a slightly good one was evaluated as △, and a sample that could not be injection molded was evaluated as ×. Table 2 shows the evaluation results.
[0044]
[Table 2]
As shown in Table 2, each of the samples of Examples 1 to 6 (Samples 1 to 6) was 2.3 to 4 times in the frequency range of 0.5 to 2.5 GHz as compared with Sample 8 of the conventional example. , In the frequency range of 5 to 15 GHz. In addition, when the mixing and filling amounts of the electromagnetic wave absorbers are the same, the electromagnetic wave absorbing ability is in the order of the sample using the coal particles A <the sample using the carbon particles B <the sample using the carbon particles C, ie, sample 1 <sample 2 <sample 3 increased in order. Further, when the same electromagnetic wave absorber (charcoal particles C) is used, the electromagnetic wave absorbing ability of the sample having a larger blending / filling amount of the electromagnetic wave absorber, that is, the order of sample 3 <sample 4 <sample 5 <sample 6 increases. I was
[0046]
Here, since Sample 7 of Comparative Example 1 had a large mixing and filling amount of the electromagnetic wave absorber of 70 parts by weight, injection molding was impossible, and a sheet material could not be produced. Thereby, the upper limit of the blending / filling amount of the electromagnetic wave absorber is specified to be less than 70 parts by weight.
[0047]
In the frequency range of 5 to 15 GHz, the electromagnetic wave absorption of the sample 1 of the first embodiment is 13 dB, which is about twice the electromagnetic wave absorption (7 dB) of the sample 8 of the first conventional example. From this, it is presumed that even if the blending / filling amount of the electromagnetic wave absorber is half (15 parts by weight) of Sample 1 of Example 1, the same electromagnetic wave absorbing ability as that of Sample 8 of Conventional Example 1 can be obtained. . Thereby, the lower limit of the blending / filling amount of the electromagnetic wave absorber is specified as 15 parts by weight or more.
[0048]
【The invention's effect】
In short, according to the present invention, the following excellent effects are exhibited.
[0049]
(1) By mixing and filling an electromagnetic wave absorber made of porous particles having conductivity or magnetism into a polymer material, the polymer material and the electromagnetic wave can be mixed in a smaller amount than a conventional electromagnetic wave absorber. The complex permittivity or complex permeability of the composite system of the absorber can be increased, and as a result, the electromagnetic wave absorbing ability of the electromagnetic wave absorbing composition can be increased.
[0050]
(2) By using the electromagnetic wave absorbing composition of (1), it is possible to obtain an electromagnetic wave absorbing molded product having good electromagnetic wave absorbing properties and good moldability.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| JP2002205333A JP2004043705A (en) | 2002-07-15 | 2002-07-15 | Electromagnetic wave absorbing composition and molding using the same |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005332919A (en) * | 2004-05-19 | 2005-12-02 | Hattori Sangyo Kk | Digital apparatus casing and its manufacturing method |
| JP2010161337A (en) * | 2008-09-29 | 2010-07-22 | Sanwa Yushi Kk | Plant baked body and electromagnetic wave shielding body |
| JP2010161338A (en) * | 2008-09-29 | 2010-07-22 | Sanwa Yushi Kk | Plant baked body, electromagnetic wave shielding body provided with the same, electronic device, inspection device of electronic device, and building material |
| WO2023100923A1 (en) * | 2021-12-01 | 2023-06-08 | 京セラ株式会社 | Electromagnetic interference suppressing material |
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2002
- 2002-07-15 JP JP2002205333A patent/JP2004043705A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005332919A (en) * | 2004-05-19 | 2005-12-02 | Hattori Sangyo Kk | Digital apparatus casing and its manufacturing method |
| JP2010161337A (en) * | 2008-09-29 | 2010-07-22 | Sanwa Yushi Kk | Plant baked body and electromagnetic wave shielding body |
| JP2010161338A (en) * | 2008-09-29 | 2010-07-22 | Sanwa Yushi Kk | Plant baked body, electromagnetic wave shielding body provided with the same, electronic device, inspection device of electronic device, and building material |
| WO2023100923A1 (en) * | 2021-12-01 | 2023-06-08 | 京セラ株式会社 | Electromagnetic interference suppressing material |
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