JP7554425B2 - Sound absorbing materials and methods for using porous materials for sound absorbing materials - Google Patents
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Description
本発明は、吸音材に関する。本発明は、また、多孔質材料の吸音材への使用方法に関する。 The present invention relates to a sound absorbing material. The present invention also relates to a method for using a porous material as a sound absorbing material.
吸音材は、建築、モビリティー、音響などの様々な分野において用いられている。吸音材は、一般に、多孔質吸音材、孔あき吸音材、板状吸音材などが知られている。これらの吸音材の中でも、多孔質吸音材が多く開発されている（例えば、特許文献１）。例えば、ガラス等の短繊維をボード状に成形しグラスウールやロックウール製品、短繊維を粒状にした粒状綿などが実用化されている。 Sound-absorbing materials are used in various fields such as architecture, mobility, and acoustics. Generally, porous sound-absorbing materials, perforated sound-absorbing materials, and plate-shaped sound-absorbing materials are known as sound-absorbing materials. Among these sound-absorbing materials, many porous sound-absorbing materials have been developed (for example, Patent Document 1). For example, glass wool and rock wool products made by forming short fibers such as glass into a board shape, and granular cotton made by granulating short fibers have been put to practical use.
モビリティー分野、特に自動車における吸音材は、走行時の不快な騒音を低減し、車内の快適性を向上させるために用いられる。車内の騒音対策の対象となる周波数領域は５０００Ｈｚ未満であるが、１０００Ｈｚ以上の領域は、既存のフェルト、ウレタンなどの吸音材にて対策がなされている。 Sound-absorbing materials in the mobility sector, particularly in automobiles, are used to reduce unpleasant noise while driving and improve comfort inside the vehicle. The frequency range that is the target for noise control inside the vehicle is below 5000 Hz, but measures are taken for the range of 1000 Hz and above using existing sound-absorbing materials such as felt and urethane.
近年の自動車は、温室効果ガス削減のため、動力源の電動化が急速に進んでおり、将来にわたってこの傾向が続くことは明白である。動力源の電動化が進むと、エンジン音に埋もれていた、こもり音、透過音、ロードノイズなどに由来する１０００Ｈｚ未満の低周波数領域の騒音が顕在化するため、前記領域の騒音対策が新たな課題となっている。しかしながら、既存の吸音材では、１０００Ｈｚ未満の低周波数領域においては吸音効果が低いため、この周波数領域を対象とする吸音材が望まれている。吸音材は、使用量を増やすことで吸音性能を全体的に向上させられることが可能であるが、車体重量増加、燃費や電費などの効率低下、運動性能低下を招くため、高い吸音性能を維持しつつ、より軽量なものが望まれている。 In recent years, the power source of automobiles has been rapidly electrified in order to reduce greenhouse gas emissions, and it is clear that this trend will continue into the future. As the power source becomes more electrified, noise in the low frequency range below 1000 Hz, which is buried in the engine sound and originates from muffled sounds, transmitted sounds, road noise, etc., becomes apparent, and noise control in this range has become a new issue. However, existing sound-absorbing materials have a low sound-absorbing effect in the low frequency range below 1000 Hz, so sound-absorbing materials that target this frequency range are desired. Although it is possible to improve the overall sound-absorbing performance by increasing the amount of sound-absorbing material used, this leads to an increase in the vehicle body weight, a decrease in efficiency in fuel consumption and power consumption, and a decrease in driving performance, so there is a demand for lighter materials that maintain high sound-absorbing performance.
軽量かつ低周波数から高周波数までの幅広い周波数領域において、バランスの良い吸音性能を示す吸音材として、不織布が用いられる。例えば、３Ｍ社のシンサレートがよく知られている。 Nonwoven fabrics are used as sound-absorbing materials that are lightweight and have well-balanced sound-absorbing properties over a wide frequency range from low to high frequencies. For example, 3M's Thinsulate is well known.
多孔質吸音材料中に音が入射すると、音は、吸音材料内の小さな隙間に入るので、音の周波数に応じて空気が圧縮と膨張を繰り返す。繊維からなる細い管を想定すると、空気の粘性および管の断面寸法等によって決まるエネルギー損失によって音は消滅する。また、空気の圧縮と膨張過程で発生し、移動する熱の伝導によっても音は消滅する。さらに、繊維自体の振動によってもエネルギー損失が起こる。このように、音のエネルギーが熱エネルギーに変わって消滅して、吸音される。 When sound enters a porous sound-absorbing material, it enters small gaps within the sound-absorbing material, causing the air to repeatedly compress and expand depending on the frequency of the sound. If we imagine a thin tube made of fibers, the sound is extinguished due to energy loss determined by the viscosity of the air and the cross-sectional dimensions of the tube, among other things. Sound is also extinguished due to the conduction of heat that is generated and moved during the compression and expansion of the air. Furthermore, energy loss occurs due to the vibration of the fibers themselves. In this way, the sound energy is converted into thermal energy and is extinguished, resulting in sound absorption.
本発明の課題は、多孔質材料からなる吸音材であって、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音性能を示す不織布よりも、低周波数領域においてさらに高い吸音率を発現できる、吸音材を提供することにある。また、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音性能を示す不織布よりも、低周波数領域において、さらに高い吸音率を発現できる吸音材を提供することを目的とする、多孔質材料の吸音材への使用方法を提供することにある。 The object of the present invention is to provide a sound-absorbing material made of a porous material, which is capable of exhibiting a higher sound absorption rate in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit well-balanced sound-absorbing performance in a wide range from low to high frequencies. It is also an object of the present invention to provide a method for using a porous material in a sound-absorbing material, with the aim of providing a sound-absorbing material that is capable of exhibiting a higher sound absorption rate in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit well-balanced sound-absorbing performance in a wide range from low to high frequencies.
本発明の実施形態による吸音材は、
繊維を含み、密度が０．５ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３である、多孔質材料からなる。
The sound absorbing material according to an embodiment of the present invention comprises:
It is made of a porous material containing fibers and having a density of 0.5 mg/cm 3 to 20 mg/cm 3 .
一つの実施形態においては、上記多孔質材料がエアロゲルである。 In one embodiment, the porous material is an aerogel.
一つの実施形態においては、上記繊維の直径が１ｎｍ～１０００ｎｍである。 In one embodiment, the diameter of the fibers is 1 nm to 1000 nm.
一つの実施形態においては、上記多孔質材料が２つ以上の層の積層体であり、該２つ以上の層の中の少なくとも２つの層の密度が互いに異なる。 In one embodiment, the porous material is a laminate of two or more layers, and at least two of the two or more layers have different densities.
一つの実施形態においては、上記吸音材は、ＪＩＳ－Ａ－１４０５－２による吸音率測定において、周波数６００Ｈｚにおける吸音率が０．１０以上である。 In one embodiment, the sound absorbing material has a sound absorption coefficient of 0.10 or more at a frequency of 600 Hz when measured according to JIS-A-1405-2.
本発明の実施形態による多孔質材料の使用方法は、
繊維を含み、密度が０．５ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３である多孔質材料を、吸音材として使用する。
A method of using a porous material according to an embodiment of the present invention comprises:
A porous material containing fibers and having a density of 0.5 mg/cm 3 to 20 mg/cm 3 is used as the sound absorbing material.
一つの実施形態においては、上記多孔質材料がエアロゲルである。 In one embodiment, the porous material is an aerogel.
一つの実施形態においては、上記繊維の直径が１ｎｍ～１０００ｎｍである。 In one embodiment, the diameter of the fibers is 1 nm to 1000 nm.
一つの実施形態においては、上記多孔質材料が２つ以上の層の積層体であり、該２つ以上の層の中の少なくとも２つの層の密度が互いに異なる。 In one embodiment, the porous material is a laminate of two or more layers, and at least two of the two or more layers have different densities.
一つの実施形態においては、上記吸音材は、ＪＩＳ－Ａ－１４０５－２による吸音率測定において、周波数６００Ｈｚにおける吸音率が０．１０以上である。 In one embodiment, the sound absorbing material has a sound absorption coefficient of 0.10 or more at a frequency of 600 Hz when measured according to JIS-A-1405-2.
本発明によれば、多孔質材料からなる吸音材であって、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率を発現できる、吸音材を提供することができる。また、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域において、さらに高い吸音率を発現できる吸音材を提供することを目的とする、多孔質材料の吸音材への使用方法を提供することができる。 According to the present invention, it is possible to provide a sound-absorbing material made of a porous material, which is capable of exhibiting a higher sound absorption rate in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption rate in a wide range from low to high frequencies. It is also possible to provide a method for using a porous material in a sound-absorbing material, with the aim of providing a sound-absorbing material that is capable of exhibiting a higher sound absorption rate in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption rate in a wide range from low to high frequencies.
≪吸音材≫
本発明の実施形態による吸音材は、繊維を含み、密度が０．５ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３である、多孔質材料からなる。本発明の実施形態による吸音材が上記のような多孔質材料からなれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率を発現できる、吸音材を提供し得る。
<Sound absorbing material>
The sound-absorbing material according to the embodiment of the present invention is made of a porous material that contains fibers and has a density of 0.5 mg/cm 3 to 20 mg/cm 3. If the sound-absorbing material according to the embodiment of the present invention is made of such a porous material, it is possible to provide a sound-absorbing material that can exhibit a higher sound absorption coefficient in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption coefficient in a wide range from low to high frequencies.
多孔質材料に含まれる繊維としては、本発明の効果を損なわない範囲で任意の適切な繊維を採用し得る。このような繊維としては、例えば、炭素繊維、無機繊維、金属繊維、有機繊維などが挙げられる。このような繊維は、１種のみであってもよいし、２種以上であってもよい。 As the fibers contained in the porous material, any appropriate fibers may be used as long as they do not impair the effects of the present invention. Examples of such fibers include carbon fibers, inorganic fibers, metal fibers, and organic fibers. There may be only one type of such fibers, or two or more types.
炭素繊維としては、例えば、カーボンナノチューブ繊維、ピッチ系炭素繊維、ＰＡＮ系炭素繊維、気相成長炭素繊維（ＶＦＣＧ）、セルロースナノファイバーや発酵ナノセルロース等のセルロース系炭素繊維、キチンナノファイバー、キトサンナノファイバー、黒鉛繊炭素繊維などが挙げられる。好ましくは、カーボンナノチューブ繊維およびセルロースナノファイバーであり、より好ましくはカーボンナノチューブ繊維である。 Examples of carbon fibers include carbon nanotube fibers, pitch-based carbon fibers, PAN-based carbon fibers, vapor-grown carbon fibers (VFCG), cellulose-based carbon fibers such as cellulose nanofibers and fermented nanocellulose, chitin nanofibers, chitosan nanofibers, and graphite carbon fibers. Carbon nanotube fibers and cellulose nanofibers are preferred, and carbon nanotube fibers are more preferred.
無機繊維としては、例えば、グラスファイバー、ガラス繊維、セラミックス繊維、ボロン繊維、ロックウール等の人造鉱物繊維、天然鉱物繊維、シリカ繊維、アルミナナノファイバー、酸化チタンナノチューブなどが挙げられる。 Examples of inorganic fibers include glass fiber, glass fibers, ceramic fibers, boron fibers, artificial mineral fibers such as rock wool, natural mineral fibers, silica fibers, alumina nanofibers, and titanium oxide nanotubes.
金属繊維としては、例えば、アルミニウム、黄銅、ステンレス、チタン、スチールなどの金属からなる繊維が挙げられる。 Metal fibers include, for example, fibers made of metals such as aluminum, brass, stainless steel, titanium, and steel.
有機繊維としては、例えば、ポリエステル繊維、ポリアミド繊維、アラミド繊維、ポリアセタール繊維、ＰＢＯ繊維、ポリフェニレンスルフィド繊維、ポリアクリル繊維、ポリエチレン繊維、ポリアクリル繊維、ナイロン繊維、これらの混合繊維などが挙げられる。 Examples of organic fibers include polyester fibers, polyamide fibers, aramid fibers, polyacetal fibers, PBO fibers, polyphenylene sulfide fibers, polyacrylic fibers, polyethylene fibers, polyacrylic fibers, nylon fibers, and mixed fibers thereof.
多孔質材料に含まれる繊維の直径は、好ましくは１ｎｍ～１０００ｎｍであり、より好ましくは１ｎｍ～５００ｎｍであり、さらに好ましくは１ｎｍ～１００ｎｍであり、特に好ましくは２ｎｍ～２０ｎｍである。ここで直径とは、走査型電子顕微鏡や透過型電子顕微鏡で繊維を観察し、その幅を多数測定したものの平均値を指す。なお、上記繊維の断面は、丸状である必要はない。上記繊維の断面は、楕円形、多角形、Ｙ字型等でも構わない。上記繊維の断面が丸状以外の場合（例えば、上記の楕円形、多角形、Ｙ字型等）においても、その直径は上記測定方法で直径を算出することは可能であるが、算出が困難な場合には、断面の外接円の直径を繊維の直径としてもよい。上記繊維の長さについては、特に限定されないが、直径の１００倍～２０００００倍であることが好ましい。繊維の長さが直径に対して上記の範囲である場合、後述するエアロゲル粒子が結合したクラスター構造の形成が促進され、吸音性能が向上する傾向にある。 The diameter of the fibers contained in the porous material is preferably 1 nm to 1000 nm, more preferably 1 nm to 500 nm, even more preferably 1 nm to 100 nm, and particularly preferably 2 nm to 20 nm. Here, the diameter refers to the average value of the widths of the fibers observed with a scanning electron microscope or a transmission electron microscope. The cross section of the fiber does not have to be round. The cross section of the fiber may be elliptical, polygonal, Y-shaped, etc. Even if the cross section of the fiber is other than round (for example, the above-mentioned elliptical, polygonal, Y-shaped, etc.), the diameter can be calculated by the above-mentioned measurement method, but if calculation is difficult, the diameter of the circumscribed circle of the cross section may be used as the diameter of the fiber. The length of the fiber is not particularly limited, but is preferably 100 to 200,000 times the diameter. When the length of the fiber is within the above range relative to the diameter, the formation of a cluster structure in which the aerogel particles are bonded, which will be described later, is promoted, and the sound absorption performance tends to be improved.
多孔質材料に含まれる繊維の直径が上記範囲内にあれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率を発現できる、吸音材を提供し得る。 If the diameter of the fibers contained in the porous material is within the above range, it is possible to provide a sound-absorbing material that can exhibit a higher sound absorption rate in the low frequency range than nonwoven fabrics, which are currently lightweight and exhibit a well-balanced sound absorption rate in a wide range from low to high frequencies.
多孔質材料中の繊維の含有割合は、好ましくは１質量％～７０質量％であり、より好ましくは５質量％～６０質量％であり、さらに好ましくは１０質量％～５０質量％であり、特に好ましくは１５質量％～４５質量％である。多孔質材料中の繊維の含有割合が上記範囲内にあれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率をより発現できる、吸音材を提供し得る。 The fiber content in the porous material is preferably 1% by mass to 70% by mass, more preferably 5% by mass to 60% by mass, even more preferably 10% by mass to 50% by mass, and particularly preferably 15% by mass to 45% by mass. If the fiber content in the porous material is within the above range, it is possible to provide a sound-absorbing material that can exhibit a higher sound absorption coefficient in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption coefficient in a wide range from low to high frequencies.
多孔質材料の密度は、０．５ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３であり、好ましくは１．０ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３であり、より好ましくは１．０ｍｇ／ｃｍ３～１８ｍｇ／ｃｍ３であり、さらに好ましくは１．５ｍｇ／ｃｍ３～１８ｍｇ／ｃｍ３であり、特に好ましくは２．０ｍｇ／ｃｍ３～１５ｍｇ／ｃｍ３である。多孔質材料の密度が上記範囲内にあれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率を発現できる、吸音材を提供し得る。 The density of the porous material is 0.5 mg/cm 3 to 20 mg/cm 3 , preferably 1.0 mg/cm 3 to 20 mg/cm 3 , more preferably 1.0 mg/cm 3 to 18 mg/cm 3 , even more preferably 1.5 mg/cm 3 to 18 mg/cm 3 , and particularly preferably 2.0 mg/cm 3 to 15 mg/cm 3. If the density of the porous material is within the above range, it is possible to provide a sound-absorbing material that can exhibit a higher sound absorption coefficient in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption coefficient in a wide range from low to high frequencies.
多孔質材料は、バインダーを含むことが好ましい。バインダーは、繊維を分散できるものであれば、本発明の効果を損なわない範囲で任意の適切なバインダーを採用し得る。このようなバインダーとしては、例えば、アクリル酸、メタクリル酸、マレイン酸等のカルボキシ基含有単量体の（共）重合体；カルボキシメチルセルロース（ＣＭＣ）等のカルボキシ基含有（共）重合体；スチレンスルホン酸、２－アクリルアミド－２－メチルプロパンスルホン酸等のスルホン酸基含有単量体の（共）重合体；リグニンスルホン酸、ナフタレンスルホン酸等のスルホン酸基含有（共）重合体；リン酸基含有（共）重合体；等が挙げられる。上記（共）重合体は、含まれる酸基が中和されていなくても、一部または全部が中和されていてもかまわない。上記共重合体における共重合体成分としては、本発明の効果を損なわない範囲で任意の適切な共重合体成分を採用し得る。このような共重合体成分としては、例えば、アクリル酸エステル、メタクリル酸エステル、アミド基含単量体等のノニオン性単量体などが挙げられる。例えば、ＣＭＣは水溶媒に速やかに溶けて分散し、水溶媒中で繊維の凝集を抑えることができる。これにより、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率をより発現できる、吸音材を提供し得る。 The porous material preferably contains a binder. As long as the binder can disperse the fibers, any suitable binder can be used within a range that does not impair the effects of the present invention. Examples of such binders include (co)polymers of carboxyl group-containing monomers such as acrylic acid, methacrylic acid, and maleic acid; carboxyl group-containing (co)polymers such as carboxymethyl cellulose (CMC); (co)polymers of sulfonic acid group-containing monomers such as styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid; sulfonic acid group-containing (co)polymers such as lignin sulfonic acid and naphthalene sulfonic acid; phosphoric acid group-containing (co)polymers; and the like. The acid groups contained in the (co)polymer may not be neutralized, or may be partially or completely neutralized. As the copolymer component in the copolymer, any suitable copolymer component can be used within a range that does not impair the effects of the present invention. Examples of such copolymer components include nonionic monomers such as acrylic acid esters, methacrylic acid esters, and amide group-containing monomers. For example, CMC quickly dissolves and disperses in an aqueous solvent, and can suppress the aggregation of fibers in the aqueous solvent. This makes it possible to provide a sound-absorbing material that can achieve a higher sound absorption rate in the low frequency range than nonwoven fabrics that are currently lightweight and have a well-balanced sound absorption rate in a wide range from low to high frequencies.
多孔質材料中のバインダーの含有割合は、好ましくは１０質量％～９５質量％であり、より好ましくは２０質量％～９０質量％であり、さらに好ましくは３０質量％～９０質量％であり、特に好ましくは４０質量％～８５質量％である。多孔質材料中のバインダーの含有割合が上記範囲内にあれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率をより発現できる、吸音材を提供し得る。 The binder content in the porous material is preferably 10% by mass to 95% by mass, more preferably 20% by mass to 90% by mass, even more preferably 30% by mass to 90% by mass, and particularly preferably 40% by mass to 85% by mass. If the binder content in the porous material is within the above range, it is possible to provide a sound-absorbing material that can exhibit a higher sound absorption rate in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption rate in a wide range from low to high frequencies.
多孔質材料は、必要に応じて、粒子状物質を含んでいてもよい。多孔質材料に粒子状物質を適切に含ませることにより、多孔質材料の細孔を微小化することができ、多孔質材料の密度を調整することができる。粒子状物質としては、本発明の効果を損なわない範囲で任意の適切な粒子状物質を採用し得る。このような粒子状物質としては、例えば、有機材料、無機材料、有機無機複合材料などが挙げられる。このような粒子状物質としては、好ましくは、金属、金属酸化物などの無機材料から選択され、特に好ましくは、空隙を持つ無機多孔質材料が選択される。このような無機多孔質材料としては、例えば、シリカ、アルミナ、チタニア、ジルコニアからなる群から選ばれる少なくとも１種からなる粉末、或いはゾルを用いることができる。 The porous material may contain a particulate material as necessary. By appropriately incorporating a particulate material into the porous material, the pores of the porous material can be made smaller, and the density of the porous material can be adjusted. As the particulate material, any appropriate particulate material can be adopted as long as it does not impair the effects of the present invention. Examples of such particulate materials include organic materials, inorganic materials, and organic-inorganic composite materials. As such particulate materials, inorganic materials such as metals and metal oxides are preferably selected, and inorganic porous materials having voids are particularly preferably selected. As such inorganic porous materials, for example, powders or sols consisting of at least one material selected from the group consisting of silica, alumina, titania, and zirconia can be used.
多孔質材料中の粒子状物質の含有割合は、好ましくは２０質量％以下である。多孔質材料中の粒子状物質の含有割合が上記範囲内にあれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率をより発現できる、吸音材を提供し得る。 The content of particulate matter in the porous material is preferably 20% by mass or less. If the content of particulate matter in the porous material is within the above range, it is possible to provide a sound-absorbing material that can exhibit a higher sound absorption coefficient in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption coefficient in a wide range from low to high frequencies.
多孔質材料は、好ましくは、スポンジ状のエアロゲルである。エアロゲルとは、湿潤ゲルを超臨界乾燥させて得られた低密度の乾燥ゲルを指す。一般的にエアロゲルの内部は網目状の微細構造となっており、２～２０ｎｍ程度のエアロゲル粒子（エアロゲルを構成する粒子）が結合したクラスター構造を有している。このクラスターにより形成される骨格間には、２００ｎｍに満たない微細な細孔が存在し、三次元的に微細な多孔性の構造をしている。 The porous material is preferably a sponge-like aerogel. Aerogel refers to a low-density dry gel obtained by supercritical drying of a wet gel. Generally, the inside of aerogel has a mesh-like microstructure, and has a cluster structure in which aerogel particles (particles that make up aerogel) of about 2 to 20 nm are bonded together. Between the skeletons formed by these clusters, there are microscopic pores of less than 200 nm, giving it a three-dimensional microscopic porous structure.
本発明の実施形態における吸音材を構成する多孔質材料は、繊維を主成分とし、好ましくは繊維とバインダーを含むスポンジ状のエアロゲルである。 The porous material constituting the sound-absorbing material in this embodiment of the present invention is a sponge-like aerogel that is primarily composed of fibers and preferably contains fibers and a binder.
本発明の実施形態における吸音材は、ＪＩＳ－Ａ－１４０５－２による吸音率測定において、周波数６００Ｈｚにおける吸音率が、好ましくは０．１０以上である。上記吸音率が上記範囲内にあれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率をより発現できる、吸音材を提供し得る。 The sound absorbing material in the embodiment of the present invention preferably has a sound absorption coefficient of 0.10 or more at a frequency of 600 Hz, as measured by JIS-A-1405-2. If the sound absorption coefficient is within the above range, it is possible to provide a sound absorbing material that can exhibit a higher sound absorption coefficient in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit well-balanced sound absorption coefficients in a wide range from low to high frequencies.
本発明の吸音材の一つの実施形態（吸音材実施形態１）は、多孔質材料が１つの層からなる。ここにいう層は、層状であればよく、厚みが一定である必要はない。また、層の厚みは、吸音材として配置する場所や環境などに応じて、任意の適切な厚みを採用し得る。 One embodiment of the sound-absorbing material of the present invention (sound-absorbing material embodiment 1) is made of one layer of porous material. The layer referred to here only needs to be layered, and does not need to have a constant thickness. Furthermore, the layer thickness can be any appropriate thickness depending on the location and environment in which the sound-absorbing material is placed.
本発明の吸音材の別の一つの実施形態（吸音材実施形態２）は、多孔質材料が２つ以上の層の積層体であり、該２つ以上の層の中の少なくとも２つの層の密度が互いに異なる。ここにいう層は、層状であればよく、厚みが一定である必要はない。また、層の厚みは、吸音材として配置する場所や環境などに応じて、任意の適切な厚みを採用し得る。 In another embodiment of the sound-absorbing material of the present invention (sound-absorbing material embodiment 2), the porous material is a laminate of two or more layers, and at least two of the two or more layers have different densities. The layers referred to here need only be layered, and do not need to have a constant thickness. In addition, the layer thickness may be any appropriate thickness depending on the location and environment in which the sound-absorbing material is placed.
吸音材実施形態２において、３つ以上の密度の異なる層が積層される場合、密度が小さいものから大きいものに、もしくは密度が大きいものから小さいものに順に積層されていてもよく、密度が大きいものと小さいものとが交互に積層されていてもよい。 In the second embodiment of the sound-absorbing material, when three or more layers of different densities are stacked, they may be stacked from lowest density to highest density, or from highest density to lowest density, or may be stacked alternately with higher and lower densities.
本発明の吸音材は、例えば、含まれる繊維もしくはバインダー等の材質や組成が異なる多孔質体が積層されている形態であっても良い。 The sound-absorbing material of the present invention may be in the form of a laminate of porous bodies containing different materials or compositions, such as fibers or binders.
吸音材実施形態２が、低周波数領域において高い吸音率を発現できることは、例えば、シミュレーションによって実証できている。具体的には、伝達関数法による吸音率測定を模擬した数値計算において、吸音材を粘弾性試料と見なし、２つのマイクの設置位置における音圧の複素振幅を境界要素法により計算することで実証した。その際、前記試料の材料パラメーターとして、密度、ヤング率、ポアソン比、粘性係数などの物性を反映させた。これにより、密度および厚みの異なる２つの試料を積層すると、５００Ｈｚ～１０００Ｈｚにおいて０．４～１．０の吸音率を与えることが示唆された。 The fact that the sound-absorbing material embodiment 2 can exhibit a high sound absorption coefficient in the low frequency range has been demonstrated, for example, by simulation. Specifically, in a numerical calculation simulating sound absorption coefficient measurement using the transfer function method, the sound-absorbing material was considered as a viscoelastic sample, and the complex amplitude of the sound pressure at the installation positions of the two microphones was calculated using the boundary element method to demonstrate this. In this case, physical properties such as density, Young's modulus, Poisson's ratio, and viscosity coefficient were reflected as material parameters of the sample. This suggests that stacking two samples with different densities and thicknesses will give a sound absorption coefficient of 0.4 to 1.0 at 500 Hz to 1000 Hz.
本発明の実施形態における吸音材を構成する多孔質材料は、炭素原子（Ｃ）の含有割合が、好ましくは１０質量％～９５質量％であり、より好ましくは２０質量％～９０質量％であり、さらに好ましくは２５質量％～８５質量％であり、特に好ましくは３０質量％～８０質量％である。本発明の実施形態における吸音材を構成する多孔質材料中の炭素原子（Ｃ）の含有割合が上記範囲内にあれば、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率をより発現できる、吸音材を提供し得る。 The porous material constituting the sound-absorbing material in the embodiment of the present invention preferably has a carbon atom (C) content of 10% by mass to 95% by mass, more preferably 20% by mass to 90% by mass, even more preferably 25% by mass to 85% by mass, and particularly preferably 30% by mass to 80% by mass. If the carbon atom (C) content in the porous material constituting the sound-absorbing material in the embodiment of the present invention is within the above range, it is possible to provide a sound-absorbing material that can exhibit a higher sound absorption coefficient in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption coefficient in a wide range from low to high frequencies.
≪吸音材の製造≫
本発明の実施形態における吸音材の製造方法としては、本発明の効果を損なわない範囲で、任意の適切な方法によって製造し得る。このような製造方法としては、代表的には、繊維と、好ましくはバインダーと、必要に応じて粒子状物質を、水中で分散させ、これを低温下で凍結乾燥することにより得ることができる。密度の異なる多孔質材料を積層する場合は、繊維とバインダーなどからなる濃度の異なる複数の分散溶液を逐次凍結乾燥すればよい。
<Production of sound-absorbing materials>
The sound-absorbing material according to the embodiment of the present invention may be manufactured by any suitable method as long as the effect of the present invention is not impaired. A representative example of such a manufacturing method is to disperse fibers, preferably a binder, and, if necessary, a particulate substance in water, and freeze-dry the dispersion at a low temperature. When laminating porous materials with different densities, multiple dispersion solutions with different concentrations of fibers, binders, etc. may be freeze-dried in sequence.
≪多孔質材料の使用方法≫
本発明の実施形態における多孔質材料の使用方法は、繊維を含み、密度が０．５ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３である多孔質材料を、吸音材として使用する。
<How to use porous materials>
In a method for using a porous material according to an embodiment of the present invention, the porous material contains fibers and has a density of 0.5 mg/cm 3 to 20 mg/cm 3 , and is used as a sound absorbing material.
本発明の実施形態における多孔質材料の使用方法において使用する多孔質材料は、前述の≪吸音材≫の項における多孔質材料の説明を援用し得る。 The porous material used in the method of using the porous material in the embodiment of the present invention may refer to the description of the porous material in the above section on "sound absorbing material."
以下、実施例を挙げて本発明を具体的に説明するが、本発明はこれらの実施例に限定されるものではない。なお、特に断りのない限り、「部」は「質量部」を、「％」は「質量％」を意味する。 The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."
＜吸音率の測定方法＞
吸音率は、ＪＩＳ－Ａ－１４０５－２に従い、日本音響エンジニアリング製のＷｉｎＺａｃＭＴＸを用いて、背後空気層のない剛壁密着条件における垂直入射吸音率を測定した。
<Method of measuring sound absorption coefficient>
The sound absorption coefficient was measured in accordance with JIS-A-1405-2 using a WinZac MTX made by Nihon Onkyo Engineering Co., Ltd., where the normal incident sound absorption coefficient was measured in a state where the material was in close contact with a solid wall with no air gap behind.
［実施例１］
直径が２．０ｎｍ±０．５ｎｍであるシングルウォールカーボンナノチューブ（株式会社名城ナノカーボン製、Ｍｅｉｊｏ ｅＤＩＰＳ ＥＣ２．０）０．２００ｇとカルボキシメチルセルロースナトリウム（富士フィルム和光純薬株式会社製、分子量：１００，０００～１１０，０００、Ｎａ含有率：６．５質量％～８．５質量％）０．３００ｇを混合し、純水に分散させ２００ｍＬとした。これを直径約１００ｍｍ×深さ１３ｍｍのシャーレに入れ、５℃で予備冷却の後、－８０℃で凍結した。これをさらに－４５℃～－５０℃、圧力１０Ｐａ～２０Ｐａで凍結乾燥した。その後、常圧室温下でシャーレからエアロゲルを取り出して、密度３．４ｍｇ／ｃｍ３の吸音材（１）を得た。結果を図１に示す。
図１に示すように、吸音材（１）は、周波数６００Ｈｚにおける吸音率が０．１１であった。
[Example 1]
0.200 g of single-walled carbon nanotubes (Meijo Nanocarbon Co., Ltd., Meijio eDIPS EC2.0) with a diameter of 2.0 nm ± 0.5 nm and 0.300 g of sodium carboxymethylcellulose (Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight: 100,000 to 110,000, Na content: 6.5% by mass to 8.5% by mass) were mixed and dispersed in pure water to make 200 mL. This was placed in a petri dish with a diameter of about 100 mm x depth of 13 mm, pre-cooled at 5 ° C., and then frozen at -80 ° C. This was further freeze-dried at -45 ° C. to -50 ° C. and a pressure of 10 Pa to 20 Pa. Thereafter, the aerogel was removed from the petri dish under normal pressure and room temperature to obtain a sound-absorbing material (1) with a density of 3.4 mg / cm 3. The results are shown in FIG. 1.
As shown in FIG. 1, the sound absorbing material (1) had a sound absorption coefficient of 0.11 at a frequency of 600 Hz.
［実施例２］
直径が２．０ｎｍ±０．５ｎｍであるシングルウォールカーボンナノチューブ（株式会社名城ナノカーボン製、Ｍｅｉｊｏ ｅＤＩＰＳ ＥＣ２．０）０．４００ｇとカルボキシメチルセルロースナトリウム（富士フィルム和光純薬株式会社製、分子量：１００，０００～１１０，０００、Ｎａ含有率：６．５質量％～８．５質量％）０．６００ｇを用いたこと以外は、実施例１と同様にして、密度６．１ｍｇ／ｃｍ３の吸音材（２）を得た。当該吸音材の密度は６．１ｍｇ／ｃｍ３であった。結果を図１に示す。
図１に示すように、吸音材（２）は、周波数６００Ｈｚにおける吸音率が０．１６であった。
[Example 2]
A sound-absorbing material (2) having a density of 6.1 mg/cm 3 was obtained in the same manner as in Example 1, except that 0.400 g of single-walled carbon nanotubes (Meijo eDIPS EC2.0, manufactured by Meijo Nano Carbon Co., Ltd.) having a diameter of 2.0 nm±0.5 nm and 0.600 g of sodium carboxymethylcellulose (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight: 100,000 to 110,000 , Na content: 6.5% by mass to 8.5% by mass) were used. The density of the sound-absorbing material was 6.1 mg/cm 3. The results are shown in FIG. 1.
As shown in FIG. 1, the sound absorbing material (2) had a sound absorption coefficient of 0.16 at a frequency of 600 Hz.
［実施例３］
直径が３ｎｍ～５ｎｍ、配向集合体長さ１００μｍ～６００μｍであるシングルウォールカーボンナノチューブ（ゼオンナノテクノロジー株式会社製、ＺＥＯＮＡＮＯ ＳＧ１０１）０．８００ｇとカルボキシメチルセルロースナトリウム（富士フィルム和光純薬株式会社製、分子量：１００，０００～１１０，０００、Ｎａ含有率：６．５質量％～８．５質量％）１．２００ｇを用いたこと以外は実施例１と同様にして、密度１２．２ｍｇ／ｃｍ３の吸音材（３）を得た。結果を図１に示す。
図１に示すように、吸音材（３）は、周波数６００Ｈｚにおける吸音率が０．２６であった。
[Example 3]
A sound absorbing material (3) having a density of 12.2 mg/cm 3 was obtained in the same manner as in Example 1, except that 0.800 g of single-walled carbon nanotubes (ZEON NANO SG101, manufactured by Zeon Nano Technology Co., Ltd.) having a diameter of 3 nm to 5 nm and an oriented aggregate length of 100 μm to 600 μm and 1.200 g of sodium carboxymethylcellulose (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight: 100,000 to 110,000, Na content: 6.5% by mass to 8.5% by mass) were used. The results are shown in FIG. 1.
As shown in FIG. 1, the sound absorbing material (3) had a sound absorption coefficient of 0.26 at a frequency of 600 Hz.
［比較例１］
１μｍ～４μｍおよび２０μｍ～３０μｍの直径を有する繊維からなり、組成の６５％がポリプロピレンであり、厚さが約１３ｍｍ、密度が１８.０ｍｇ／ｃｍ３の不織布吸音材（Ｃ１）を入手した。この不織布吸音材（Ｃ１）を直径約１００ｍｍの円形に切り抜いた。結果を図１に示す。
図１に示すように、吸音材（Ｃ１）は、周波数６００Ｈｚにおける吸音率が０．０８であった。
[Comparative Example 1]
A nonwoven sound-absorbing material (C1) was obtained, which was made of fibers having diameters of 1 μm to 4 μm and 20 μm to 30 μm, had a composition of 65% polypropylene, had a thickness of about 13 mm, and had a density of 18.0 mg/ cm3 . This nonwoven sound-absorbing material (C1) was cut into a circle having a diameter of about 100 mm. The results are shown in FIG.
As shown in FIG. 1, the sound-absorbing material (C1) had a sound absorption coefficient of 0.08 at a frequency of 600 Hz.
本発明の実施形態による吸音材は、現時点で軽量かつ低周波数から高周波数までの幅広い領域においてバランスの良い吸音率を示す不織布よりも、低周波数領域においてさらに高い吸音率を発現できるので、低周波数領域の吸音が求められる各種分野の製品の吸音対策として利用可能である。
The sound-absorbing material according to an embodiment of the present invention can exhibit a higher sound absorption coefficient in the low frequency range than nonwoven fabrics that are currently lightweight and exhibit a well-balanced sound absorption coefficient over a wide range from low to high frequencies, and can therefore be used as a sound absorption measure for products in various fields where sound absorption in the low frequency range is required.
Claims (8)
前記多孔質材料が、繊維と、前記繊維を分散可能なバインダーと、を含み、
前記多孔質材料の密度が０．５ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３であり、
前記繊維がカーボンナノチューブ繊維であり、
前記多孔質材料がエアロゲルである、吸音材。 A sound absorbing material made of a porous material,
The porous material includes fibers and a binder capable of dispersing the fibers;
The density of the porous material is 0.5 mg/cm 3 to 20 mg/cm 3 ;
the fibers are carbon nanotube fibers,
The sound-absorbing material , wherein the porous material is an aerogel .
前記多孔質材料が、繊維と、前記繊維を分散可能なバインダーと、を含み、
前記多孔質材料の密度が０．５ｍｇ／ｃｍ３～２０ｍｇ／ｃｍ３であり、
前記繊維がカーボンナノチューブ繊維であり、
前記多孔質材料がエアロゲルである、多孔質材料の使用方法。 A method of using a porous material as a sound absorbing material, comprising the steps of:
The porous material includes fibers and a binder capable of dispersing the fibers;
The density of the porous material is 0.5 mg/cm 3 to 20 mg/cm 3 ;
the fibers are carbon nanotube fibers,
A method of using a porous material , wherein the porous material is an aerogel .
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