JP3813020B2

JP3813020B2 - Sound absorbing plate having sandwich structure and manufacturing method thereof

Info

Publication number: JP3813020B2
Application number: JP13354798A
Authority: JP
Inventors: 敏之鈴木; 康典福島; 英雄竹中
Original assignee: 新日本熱学株式会社
Priority date: 1998-05-15
Filing date: 1998-05-15
Publication date: 2006-08-23
Anticipated expiration: 2018-05-15
Also published as: JPH11327564A

Description

【０００１】
【発明の属する技術分野】
本発明は、サンドイッチ構造を有する吸音板及びその製造方法に関し、さらに詳しくは住宅、音楽室、ホール、劇場、屋内プール、各種ビル、各種工場、機械廻り、鉄道、あるいは道路、トンネルなどに設置され、調音や騒音の低減を目的とする耐水性、耐候性に優れ、軽量かつ比強度の高い大判の吸音板及びその製造方法に関するものである。
【０００２】
【従来の技術】
従来から知られている吸音板としては、繊維系、セラミック焼結体系、金属焼結体系などがある。繊維系吸音板は、グラスウール、ロックウール等の無機繊維をフェノール樹脂等の熱硬化性樹脂バインダーで結合したものであるが、手で押すと簡単に凹んだり、耐水性、耐久性や耐気流性に劣る。また、セラミック焼結体系、金属焼結体系吸音板は、連続空隙を有するセラミック粒子や金属粒子を５００〜１０００℃以上の高温で焼結固着して板状に形成したものであり、静圧強度は高いが衝撃にはもろく、製造工程の制約から大判を製造しにくい。そして、原材料費及び製造費が高価であるうえに焼結時のエネルギー消費が大きく、環境負担の大きい製品である。
【０００３】
また、軽量吸音板については、一般的なものとして軽量骨材をバインダーで固めた軽量板や、高密度不定形粒子と軽量骨材を均一に混合してバインダーで結合した軽量吸音板（特公平９−３０６７４号公報）が提案されているが、いずれも強度が低く、実用的ではなかった。
【０００４】
さらに、従来のバインダーによる粒子系吸音板は、単一層のもので機械的強度を確保するためには板厚を厚くしたり、あるいは特開平５−２７３９８４号公報には後工程で補強層を接着したものが提案されている。しかしながら、板厚を厚くするとコストアップと重量増を招き、補強材の後接着は板の反り暴れや工程の煩雑化などの問題が生じる。
【０００５】
【発明が解決しようとする課題】
したがって、本発明の目的は、一つの吸音板において軽量化及び切削性向上のため、軽量骨材からなる内層の両面を重量骨材からなる高強度高硬度の外層でサンドイッチした構造を有し、高い吸音性能を有すると共に軽量大判で高強度の吸音板及びその製造方法を提供することにある。
【０００６】
【課題を解決するための手段】
すなわち、本発明は、かさ密度が０．１〜１ｇ／ｃｍ^３の無機質軽量骨材粒子の表面にバインダーを被覆し粒子同士を点状に結着してなる空隙率が５〜５０体積％の内層と、該内層の両面に位置し、かさ密度が１〜２ｇ／ｃｍ^３の無機質重量骨材粒子の表面にバインダーを被覆し粒子同士を点状に結着してなる空隙率が５〜５０体積％の外層を積層一体化してなるサンドイッチ構造を有する吸音板である。この吸音板において、内層の厚さ１００に対し外層の厚さが１０〜１００であることがよく、また軽量骨材の粒子径が０．３〜３ｍｍのものが８０重量％以上、重量骨材の粒子径が０．３〜３ｍｍのものが８０重量％以上であることがよい。
【０００７】
また、本発明は、バインダーを表面に被覆したかさ密度が１〜２ｇ／ｃｍ³の無機質重量骨材粒子を散布し、次いでバインダーを表面に被覆したかさ密度が０．１〜１ｇ／ｃｍ³の無機質軽量骨材粒子を散布し、更に上記無機質重量骨材粒子を散布し、得られた積層物を同時に熱圧一体成形することを特徴とするサンドイッチ構造を有する吸音板の製造方法である。
【０００８】
【発明の実施の形態】
図１は、本発明の吸音板の一例を模式的に示す断面図である。図１において、サンドイッチ構造を有する吸音板Ａは、軽量のバインダー被覆無機質軽量骨材層（内層）１の両面に、高密度、高強度のバインダー被覆無機質重量骨材層（外層）２を積層一体化して構成したものである。
【０００９】
吸音板Ａの内層１にはかさ密度が０．１〜１ｇ／ｃｍ³、好ましくは０．１５〜０．８ｇ／ｃｍ³の無機質軽量骨材粒子（軽量骨材ともいう）を用いる。軽量骨材のかさ密度が０．１ｇ／ｃｍ³より小さいと成形する際に骨材が圧壊して強度が得られず、逆に１ｇ／ｃｍ³を超えると軽量性が損なわれる。また、この軽量骨材は、粒子径が０．３〜３ｍｍ、好ましくは０．５〜２ｍｍのものを８０重量％以上含むものであることがよい。粒子径０．３ｍｍ未満の細粒分が多くなると内層１が緻密化して吸音効果が低下する傾向があり、粒子径の粗粒分が多くなると空気流れ抵抗の減少により吸音性が低下すると共に成形板としての強度が低いものになる。このような軽量骨材としては、例えば黒曜石、真珠石、抗火石、シラス、頁岩、ガラス、セラミック等の各種発泡体などが挙げられる。これらの軽量骨材は単独で用いてもよいし、２種類以上を併用してもよい。
【００１０】
高密度の外層２には、かさ密度が１〜２ｇ／ｃｍ³、好ましくは１〜１．８ｇ／ｃｍ³の無機質重量骨材粒子（重量骨材ともいう）を用いる。重量骨材のかさ密度が１ｇ／ｃｍ³より小さいと所定の強度が得られず、逆に２ｇ／ｃｍ³を超えると吸音板としての軽量性が損なわれる。また、この重量骨材は、軽量骨材と同様に、粒子径が０．３〜３ｍｍのものを８０重量％以上含むものであることがよく、好ましくは０．５〜２ｍｍのものが８０重量％以上であることがよい。これは、軽量骨材と同様な理由によるものである。このような重量骨材としては、例えば天然石、けい砂、セラミック粒子、陶磁器の破砕物、ガラス粒子などが挙げられる。これらの重量骨材は単独で用いてもよいし、２種類以上を併用してもよい。
【００１１】
これらの軽量骨材及び重量骨材は、その粒子表面をバインダーで被覆したものを用いる。骨材粒子を被覆するのに用いるバインダーとしては、例えばフェノール樹脂、メラミン樹脂、エポキシ樹脂、不飽和ポリエステル樹脂、熱硬化型アクリル樹脂等の熱硬化性樹脂や、例えばケイ酸ソーダ、ポリリン酸等の無機系バインダーなどの１種又は２種以上が挙げられる。これらのバインダーの内、熱硬化性樹脂が好ましく、特にフェノール樹脂が好適である。このバインダーは未硬化であることが好ましく、最終的に積層物を熱圧一体成形する工程において、バインダーを加熱硬化させ各粒子間及び各層間を結着させることがよい。バインダー被覆骨材は、骨材粒子とバインダーをミキサー等の混合機で攪拌、混合することで製造することができる。このように、予めバインダーで骨材粒子を被覆することによって、バインダー量を減らして製造コストを低減できるのみならず、骨材の各粒子同士を点結着状態で強固に結合させて吸音板の強度が向上し、また空隙率を上げて吸音性能を向上させることができる。
【００１２】
骨材被覆用のバインダー使用量は、必要強度が得られかつ粒子間空隙をバインダーで埋めて吸音性能を阻害しないことを条件として決められるが、軽量骨材として例えばかさ密度０．５ｇ／ｃｍ³のガラス焼成発泡体を用いた場合は、ガラス焼成発泡体粒子１００重量部に対しバインダーを３〜７重量部とすることがよい。また、重量骨材として例えばかさ密度１．６ｇ／ｃｍ³の珪砂を用いた場合は、珪砂１００重量部に対しバインダーを１〜５重量部とすることがよい。
【００１３】
このような吸音板Ａの構成において、内層１及び外層２の空隙率は、それぞれ５〜５０体積％であることが必要である。この空隙率が５体積％を下回ると吸音板が緻密化し、吸音効果が低下する傾向にある。また、５０体積％を超えると空気流れ抵抗の減少により吸音性が低下するとともに成形板としての強度が低下する。
【００１４】
本発明の吸音板Ａの層構成は、軽量骨材からなる内層１の厚さが１００に対して重量骨材からなる各外層２の合計厚さが１０〜１００であることがよい。また、各外層２は対称形に近いことが好ましく、例えばフェノール樹脂被覆ガラス焼成発泡体を用いた場合の内層１の厚さが７ｍｍに対して、フェノール樹脂被覆珪砂からなる各外層２がそれぞれ１．５ｍｍずつの対称形とし、その外層厚さの合計は３ｍｍであることがよい。各外層２の合計厚さが内層１の１００に対して１０を下回ると外層の形成が不十分となり、補強効果が得られない。また、１００を超えると吸音板全体の重量が重くなり、軽量性が損なわれるとともに外層の引っ張り力によって内層との層間での剥離を生じるおそれがある。さらに、各外層の厚さが極端にアンバランスであると厚い層の引っ張り力が優り、板に反りを生じるおそれがある。
【００１５】
図２は、本発明の吸音板の別例を模式的に示す断面図である。この吸音板Ｂが先の例の吸音板Ａと異なるところは、繊維補強材にバインダーを含浸し、半硬化させることによりプリプレグ化した補強層材料を吸音板の上面付近及び下面に配し、これらを熱圧一体成形して繊維補強層３、３’を設けた点である。
【００１６】
吸音板Ｂは、バインダー含浸補強繊維層３’の上にバインダー被覆重量骨材からなる高密度層２''を設け、この上にバインダー被覆軽量骨材からなる内層１を形成し、さらにバインダー含浸補強繊維層３を配し、最上部となる面にバインダー被覆重量骨材からなる高密度層２’を設けたものである。これらの層は、それぞれの層のバインダーにより接着され一体化されて吸音板Ｂを形成している。なお、補強層の数及び配置は、上記説明に限定されるものではなく、例えば内層１の中央部あるいは最下層の高密度層だけに単一補強層を設けてもよい。
【００１７】
また、繊維補強材としては、例えばガラス繊維、炭素繊維、セラミック繊維等の無機質繊維や、例えばポリエステル繊維、ポリアミド繊維、ポリアクリル繊維、ビニロン、ポリエチレン繊維、ポリプロピレン繊維等の合成繊維や、例えば木綿、麻、羊毛等の天然繊維などが挙げられるが、耐熱性と強度の観点から無機質繊維が好ましい。この繊維は、チョップドストランド、一方向配列繊維シート、織布、不織布など任意の形状のものを用いることができる。
【００１８】
繊維補強材に含浸するバインダーは、前記の骨材粒子を被覆するのに用いたバインダーと同じものを用いることがよい。バインダーの含浸量は、繊維同士を浸潤し、繊維表面にわずかに染み出す程度であればよく、ガラス繊維織物を用いた場合、バインダー量は繊維１００重量部に対し２０〜１００重量部がよい。
【００１９】
【実施例】
実施例１
原料として、粒子径０．５〜２ｍｍの範囲のものが８５重量％の珪砂（かさ密度１．６ｇ／ｃｍ³）、ガラス粉造粒発泡体（（株）サンライト製、商品名Ｇライト、かさ密度０．４５ｇ／ｃｍ³）をそれぞれ未硬化ノボラック型フェノール樹脂と攪拌混合し、樹脂量が２重量％のフェノール樹脂被覆珪砂及び樹脂量が５重量％のフェノール樹脂被覆ガラス粉造粒発泡体を用いた。まず、成形用金属板の表面に離型剤を塗布し、フェノール樹脂被覆珪砂を１０００ｍｍ×１０００ｍｍの面積に２．５Ｋｇを散布した。次に、この上にフェノール樹脂被覆ガラス粉体造粒発泡体を３．６Ｋｇを散布し積層した。さらに、この積層物にフェノール樹脂被覆珪砂を２．５Ｋｇを散布し三層構造の積層マットを得た。このマットに離型剤を塗布した成形用金属板を被せ、ホットプレスに入れて１６０℃、２ＭＰａ、１０分間の条件で熱圧成形した。このようにして作製した高密度外層−軽量内層−高密度外層のサンドイッチ構造の吸音板は、１０００ｍｍ×１０００ｍｍ、厚さ１０ｍｍであり、その空隙率は外層で２７．５体積％、内層で約３６体積％であり、吸音板全体の平均空隙率は約３３．５体積％であった。
【００２０】
実施例２
実施例１と同様な原料と条件で成形するにあたり、吸音板の上下層にガラスクロスプリプレグを一体成形し、板材の強度及び剛性を高めた。このガラスクロスプリプレグは、開口率２３面積％のガラスクロス（安全基材（株）製、商品名ＥＭ−９０、１４０ｇ／ｍ²）に半硬化のフェノール樹脂を含浸したものである。まず、離型剤を塗布した成形用金属板に、１０００×１０００ｍｍに予めカットしたガラスクロスプリプレグを敷き、この上にフェノール樹脂被覆珪砂を２．５Ｋｇ散布した。次に、この上にフェノール樹脂被覆ガラス粉体造粒発泡体を３．６Ｋｇを散布積層した。さらに、この積層物にガラスクロスプリプレグを載せ、最後にフェノール樹脂で被覆された珪砂を２．５Ｋｇを散布して三層構造の積層マットを得た。このマットに離型剤を塗布した成形用金属板を被せ、ホットプレスに入れて１６０℃、２ＭＰａ、１０分間の条件で熱圧成形した。このようにして作製した補強層−高密度層−軽量内層−補強層−高密度外層の複層サンドイッチ構造の吸音板は厚さ１０ｍｍであり、その全体の平均空隙率は３３．５体積％であった。
【００２１】
比較例１
実施例１で用いたフェノール樹脂被覆珪砂５Ｋｇとフェノール樹脂被覆ガラス粉体造粒発泡体を３．６Ｋｇをドラムブレンダーで１０分間混ぜ、この混合物を離型剤を塗布した成形用金属板上に１０００ｍｍ×１０００ｍｍの面積に散布した。得られた混合マットに離型剤を塗布した成形用金属板を被せ、ホットプレスに入れて１６０℃、２ＭＰａ、１０分間の条件で熱圧成形した。このようにして作製した吸音板は厚さ９ｍｍであり、その全体の平均空隙率は３０体積％であった。ただし、原料の比重差により不均一で吸音板内では比重の高い珪砂が下部に偏析し、下側凹の反りを生じた。
【００２２】
比較例２
実施例１で用いたフェノール樹脂被覆珪砂１７Ｋｇを離型剤を塗布した成形用金属板上に１０００ｍｍ×１０００ｍｍの面積に散布した。得られたマットに成形用金属板を被せ、ホットプレスに入れて１６０℃、２ＭＰａ、１０分間の条件で熱圧成形した。このようにして作製した吸音板は厚さ１０ｍｍであり、その全体の平均空隙率は２６体積％であった。
【００２３】
比較例３
実施例１で用いたフェノール樹脂被覆ガラス粉造粒発泡体を５．４Ｋｇを離型剤を塗布した成形用金属板上に１０００ｍｍ×１０００ｍｍの面積に散布した。得られたマットに成形用金属板を被せ、ホットプレスに入れて１６０℃、２ＭＰａ、１０分間の条件で熱圧成形した。このようにして作製した吸音板は厚さ１０ｍｍであり、その全体の平均空隙率は３３体積％であった。
【００２４】
実施例１、２及び比較例１〜３によって得られたそれぞれ吸音板１〜５について、それぞれ厚さ、かさ比重、平面度、３点曲げ強度、弾性率、耐衝撃性及び垂直入射吸音率を測定した。なお、かさ比重はＪＩＳＡ５９０８に準拠して行い、平面度は１０００×１０００ｍｍの吸音板の下側中央凹部の深さを測定し、３点曲げ試験及び弾性率はＪＩＳＡ１４０８に準拠して行った。試験体寸法は３０×２００ｍｍとし、試験体の金型面すなわち積層順の下面側を下にしてスパン１８０ｍｍの条件で行った。耐衝撃性はＪＩＳＡ１４０８に準拠して行った。試験体寸法は５００×５００ｍｍとし、試験体を砂の上に支持し、中央部に５００ｇのなす型錘を所定の高さから自由落下させ衝撃を加えて、状態を観察した。吸音率はＪＩＳＡ１４０５に準拠して管内法による垂直入射吸音率（背後空気層５０ｍｍ）を測定した。試験結果を表１に、垂直入射吸音率を図２に示す。
【００２５】
【表１】

【００２６】
表１の結果から、サンドイッチ構造とした吸音板１及び２は、かさ比重に対する強度（比強度）が単独層吸音板３〜５に比べて高いことが認められた。すなわち、軽量性と強度のバランスがとれた板状吸音体が得られた。特に、無機質繊維で補強した吸音板２は耐衝撃性を含め優れた吸音特性を示した。また、板の形状も吸音板１及び２はほぼフラットな面であるのに対して珪砂とガラス粉造粒発泡体の混合単独層吸音板３は均一層が形成できずに高比重の珪砂が下側に偏析して下に大きな反りが生じ、実用不向きな板であった。また、吸音板４は重量平方メートルあたり１７Ｋｇとサンドイッチ型の約２倍と重く、吸音板５は軽量ではあるものの強度が低く、実用的ではなかった。
【００２７】
【発明の効果】
本発明のサンドイッチ構造を有する吸音板は、軽量で高い吸音性能を有し、形状の安性に優れ、曲げ強度が高く、しかもその製造コストが低廉でかつ大判の吸音板を効率的に製造することが可能となった。
【図面の簡単な説明】
【図１】本発明のサンドイッチ構造を有する吸音板の構成の一例を模式的に示す断面図である。
【図２】本発明のサンドイッチ構造を有する吸音板の構成の別例を模式的に示す断面図である。
【図３】実施例及び比較例の吸音板の垂直入射吸音率を示すグラフである。
【符号の説明】
Ａ、Ｂ：吸音板
１：バインダー被覆軽量骨材層（内層）
２：バインダー被覆重量骨材層（外層）
２’、２''：バインダー被覆重量骨材層（表面層）
３、３’：バインダー含浸補強繊維層（補強層）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sound-absorbing plate having a sandwich structure and a method for manufacturing the same, and more specifically, installed in a house, a music room, a hall, a theater, an indoor pool, various buildings, various factories, machines, a railway, a road, a tunnel, or the like. The present invention relates to a large-sized sound-absorbing plate that is excellent in water resistance and weather resistance for the purpose of noise reduction and noise reduction, and is lightweight and has high specific strength, and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally known sound absorbing plates include fiber systems, ceramic sintered systems, and metal sintered systems. A fiber-based sound absorbing board is made by bonding inorganic fibers such as glass wool and rock wool with a thermosetting resin binder such as phenol resin, but it can be easily recessed when pressed by hand, and has water resistance, durability, and air resistance. Inferior to Moreover, the ceramic sintered system and the metal sintered system sound-absorbing plate are formed by sintering and fixing ceramic particles and metal particles having continuous voids at a high temperature of 500 to 1000 ° C. or more in a plate shape. Although it is expensive, it is fragile and it is difficult to manufacture a large format due to restrictions on the manufacturing process. In addition, the raw material cost and the manufacturing cost are high, and the energy consumption during sintering is large, resulting in a large environmental burden.
[0003]
In addition, as for light-weight sound-absorbing plates, generally, light-weight sound-absorbing plates in which light-weight aggregates are hardened with a binder, or light-weight sound-absorbing plates in which high-density irregularly shaped particles and light-weight aggregates are uniformly mixed and bonded with a binder. No. 9-30664) has been proposed, but all of them were low in strength and not practical.
[0004]
Further, the conventional particle-based sound absorbing plate made of a binder is a single layer, and the plate thickness is increased in order to ensure mechanical strength, or a reinforcing layer is bonded in a later step in JP-A-5-273984. What has been proposed. However, increasing the plate thickness causes an increase in cost and weight, and post-adhesion of the reinforcing material causes problems such as the warpage of the plate and the complexity of the process.
[0005]
[Problems to be solved by the invention]
Therefore, the object of the present invention has a structure in which both sides of the inner layer made of lightweight aggregate are sandwiched with the outer layer of high strength and high hardness made of heavy aggregate in order to reduce the weight and improve the cutting performance in one sound absorbing plate, An object of the present invention is to provide a sound absorbing plate having a high sound absorbing performance and having a light weight and a large size, and a manufacturing method thereof.
[0006]
[Means for Solving the Problems]
That is, the present invention has a porosity of 5 to 50% by volume formed by covering the surface of inorganic lightweight aggregate particles having a bulk density of 0.1 to 1 g / cm ³ and binding the particles in a dot-like manner. The porosity formed by coating the binder on the surface of inorganic heavy weight aggregate particles having a bulk density of 1 to 2 g / cm ³ and binding the particles in a dot-like manner is located on both sides of the inner layer and the inner layer. A sound absorbing plate having a sandwich structure in which 50% by volume of outer layers are laminated and integrated. In this sound-absorbing plate, the thickness of the outer layer is preferably 10 to 100 with respect to the thickness 100 of the inner layer, and the lightweight aggregate having a particle diameter of 0.3 to 3 mm is 80% by weight or more. The particle diameter of 0.3 to 3 mm is preferably 80% by weight or more.
[0007]
In the present invention, inorganic heavy aggregate particles having a bulk density of 1-2 g / cm ³ with a binder coated on the surface are sprayed, and then the bulk density of the binder coated on the surface is 0.1-1 g / cm ³ . A method for producing a sound-absorbing plate having a sandwich structure, characterized in that inorganic light-weight aggregate particles are dispersed, the inorganic heavy-weight aggregate particles are further dispersed, and the resulting laminate is simultaneously integrally formed by hot-pressing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view schematically showing an example of a sound absorbing plate of the present invention. In FIG. 1, a sound-absorbing plate A having a sandwich structure has a high-density, high-strength binder-coated inorganic heavy-weight aggregate layer (outer layer) 2 laminated on both sides of a lightweight binder-coated inorganic light-weight aggregate layer (inner layer) 1. It is made up of.
[0009]
For the inner layer 1 of the sound absorbing plate A, inorganic lightweight aggregate particles (also referred to as lightweight aggregate) having a bulk density of 0.1 to 1 g / cm ³ , preferably 0.15 to 0.8 g / cm ³ are used. If the bulk density of the lightweight aggregate is less than 0.1 g / cm ³ , the aggregate will be crushed during molding and strength will not be obtained. Conversely, if it exceeds 1 g / cm ³ , the lightness will be impaired. The lightweight aggregate should contain 80% by weight or more of particles having a particle diameter of 0.3 to 3 mm, preferably 0.5 to 2 mm. When the fine particle content with a particle diameter of less than 0.3 mm increases, the inner layer 1 tends to be densified and the sound absorption effect tends to decrease. When the coarse particle content with a particle diameter increases, the sound absorption decreases due to a decrease in air flow resistance and molding The strength as a plate is low. Examples of such lightweight aggregates include various foams such as obsidian, pearlite, anti-fluorite, shirasu, shale, glass, and ceramic. These lightweight aggregates may be used alone or in combination of two or more.
[0010]
For the high-density outer layer 2, inorganic heavy aggregate particles (also referred to as heavy aggregate) having a bulk density of 1 to 2 g / cm ³ , preferably 1 to 1.8 g / cm ³ are used. If the bulk density of the heavy aggregate is less than 1 g / cm ³ , a predetermined strength cannot be obtained, and conversely if it exceeds 2 g / cm ³ , the lightness as a sound absorbing plate is impaired. Further, this heavy aggregate, like the lightweight aggregate, may contain 80% by weight or more of particles having a particle diameter of 0.3 to 3 mm, and preferably 80% by weight or more of 0.5 to 2 mm. It is good that it is. This is for the same reason as the lightweight aggregate. Examples of such heavy aggregate include natural stone, silica sand, ceramic particles, crushed ceramics, and glass particles. These heavy aggregates may be used alone or in combination of two or more.
[0011]
As these lightweight aggregate and heavy aggregate, those whose particle surfaces are coated with a binder are used. Examples of the binder used to coat the aggregate particles include thermosetting resins such as phenol resin, melamine resin, epoxy resin, unsaturated polyester resin, thermosetting acrylic resin, and so on such as sodium silicate and polyphosphoric acid. 1 type, or 2 or more types, such as an inorganic binder, are mentioned. Of these binders, thermosetting resins are preferable, and phenol resins are particularly preferable. This binder is preferably uncured, and in the final step of hot-pressing and integrally forming the laminate, the binder is preferably heat-cured to bond the particles and the layers. The binder-coated aggregate can be produced by stirring and mixing the aggregate particles and the binder with a mixer such as a mixer. Thus, by covering the aggregate particles with the binder in advance, not only can the amount of the binder be reduced to reduce the manufacturing cost, but also the particles of the aggregate can be firmly bonded in a point-bonded state to form the sound absorbing plate. The strength can be improved, and the sound absorption performance can be improved by increasing the porosity.
[0012]
The amount of binder used for coating the aggregate is determined on condition that the required strength is obtained and that the interparticle voids are filled with the binder so as not to impair the sound absorption performance. For example, a bulk density of 0.5 g / cm ^{3 is} used as a lightweight aggregate. When the glass fired foam is used, the binder is preferably 3 to 7 parts by weight with respect to 100 parts by weight of the glass fired foam particles. Moreover, when silica sand with a bulk density of 1.6 g / cm ³ is used as the heavy aggregate, for example, the binder is preferably 1 to 5 parts by weight with respect to 100 parts by weight of silica sand.
[0013]
In such a structure of the sound absorbing plate A, the porosity of the inner layer 1 and the outer layer 2 needs to be 5 to 50% by volume, respectively. If this porosity is less than 5% by volume, the sound absorbing plate becomes dense and the sound absorbing effect tends to be reduced. On the other hand, if it exceeds 50% by volume, the sound absorption is lowered due to the decrease in air flow resistance and the strength as a molded plate is lowered.
[0014]
In the layer structure of the sound absorbing plate A of the present invention, the total thickness of the outer layers 2 made of heavy aggregate is preferably 10 to 100 with respect to the thickness of the inner layer 1 made of lightweight aggregate. Moreover, it is preferable that each outer layer 2 is close to a symmetrical shape. For example, when the thickness of the inner layer 1 is 7 mm when a phenol resin-coated glass fired foam is used, each outer layer 2 made of phenol resin-coated quartz sand is 1 each. It is preferable that the thickness is symmetrical by 5 mm, and the total thickness of the outer layers is 3 mm. If the total thickness of each outer layer 2 is less than 10 with respect to 100 of the inner layer 1, the formation of the outer layer becomes insufficient and a reinforcing effect cannot be obtained. On the other hand, if it exceeds 100, the weight of the entire sound-absorbing plate becomes heavy, and the lightness may be impaired. Furthermore, if the thickness of each outer layer is extremely unbalanced, the pulling force of the thick layer is excellent, and the board may be warped.
[0015]
FIG. 2 is a cross-sectional view schematically showing another example of the sound absorbing plate of the present invention. The sound absorbing plate B is different from the sound absorbing plate A of the previous example in that the reinforcing layer material prepreg-impregnated by impregnating the fiber reinforcing material with a binder and semi-curing is disposed near the upper surface and the lower surface of the sound absorbing plate. This is a point in which the

fiber reinforcement layers

3 and 3 ′ are provided by hot-pressure integrated molding.
[0016]
The sound-absorbing plate B is provided with a high-density layer 2 ″ made of a binder-coated heavy aggregate on a binder-impregnated reinforcing fiber layer 3 ′, on which an inner layer 1 made of a binder-coated lightweight aggregate is formed, and further impregnated with the binder A reinforcing fiber layer 3 is arranged, and a high-density layer 2 ′ made of a binder-coated heavy aggregate is provided on the uppermost surface. These layers are bonded and integrated with the binder of each layer to form the sound absorbing plate B. The number and arrangement of the reinforcing layers are not limited to the above description, and for example, a single reinforcing layer may be provided only in the central portion of the inner layer 1 or the lowermost high-density layer.
[0017]
Examples of the fiber reinforcing material include inorganic fibers such as glass fiber, carbon fiber, and ceramic fiber, synthetic fibers such as polyester fiber, polyamide fiber, polyacrylic fiber, vinylon, polyethylene fiber, and polypropylene fiber, and cotton, Examples thereof include natural fibers such as hemp and wool, but inorganic fibers are preferable from the viewpoint of heat resistance and strength. As this fiber, chopped strands, unidirectionally arranged fiber sheets, woven fabrics, non-woven fabrics and the like can be used.
[0018]
The binder used for impregnating the fiber reinforcing material is preferably the same as the binder used to coat the aggregate particles. The amount of the binder impregnated is only required to infiltrate the fibers and slightly exude on the fiber surface. When a glass fiber fabric is used, the amount of the binder is preferably 20 to 100 parts by weight with respect to 100 parts by weight of the fibers.
[0019]
【Example】
Example 1
As raw materials, silica sand (bulk density 1.6 g / cm ³ ) having a particle size of 0.5 to 2 mm, glass powder granulated foam (manufactured by Sunlite Co., Ltd., trade name G Light, Bulk density 0.45 g / cm ³ ) was mixed with an uncured novolac-type phenol resin by stirring, respectively, and a phenol resin-coated silica sand having a resin amount of 2% by weight and a phenol resin-coated glass powder granulated foam having a resin amount of 5% by weight. Was used. First, a release agent was applied to the surface of the forming metal plate, and 2.5 kg of a phenol resin-coated silica sand was sprayed over an area of 1000 mm × 1000 mm. Next, 3.6 kg of phenol resin-coated glass powder granulated foam was sprayed thereon and laminated. Further, 2.5 kg of phenol resin-coated silica sand was sprayed on the laminate to obtain a laminated mat having a three-layer structure. The mat was covered with a forming metal plate coated with a release agent, and placed in a hot press to perform hot-pressure forming under conditions of 160 ° C., 2 MPa, and 10 minutes. The sound absorbing plate having a sandwich structure of high density outer layer-light weight inner layer-high density outer layer produced in this manner has a size of 1000 mm × 1000 mm and a thickness of 10 mm, and its porosity is 27.5% by volume in the outer layer and about 36 in the inner layer. The average porosity of the entire sound absorbing plate was about 33.5% by volume.
[0020]
Example 2
In forming with the same raw materials and conditions as in Example 1, glass cloth prepregs were integrally formed on the upper and lower layers of the sound absorbing plate to increase the strength and rigidity of the plate material. This glass cloth prepreg is obtained by impregnating a semi-cured phenolic resin into a glass cloth having an aperture ratio of 23 area% (trade name EM-90, 140 g / m ² manufactured by Safety Base Co., Ltd.). First, a glass cloth prepreg cut in advance to 1000 × 1000 mm was laid on a forming metal plate coated with a release agent, and 2.5 kg of phenol resin-coated silica sand was sprayed thereon. Next, 3.6 kg of phenol resin-coated glass powder granulated foam was sprayed and laminated thereon. Further, a glass cloth prepreg was placed on the laminate, and finally 2.5 kg of silica sand coated with phenol resin was sprayed to obtain a three-layer laminated mat. The mat was covered with a forming metal plate coated with a release agent, and placed in a hot press to perform hot-pressure forming under conditions of 160 ° C., 2 MPa, and 10 minutes. The sound absorbing plate having a multilayer sandwich structure of reinforcing layer-high density layer-light weight inner layer-reinforcing layer-high density outer layer thus produced has a thickness of 10 mm, and the overall average porosity is 33.5% by volume. there were.
[0021]
Comparative Example 1
5 kg of phenolic resin-coated silica sand used in Example 1 and 3.6 kg of phenolic resin-coated glass powder granulated foam were mixed with a drum blender for 10 minutes, and this mixture was 1000 mm on a metal plate for forming coated with a release agent. It sprayed on the area of * 1000mm. The obtained mixed mat was covered with a molding metal plate coated with a release agent, placed in a hot press, and hot pressed under conditions of 160 ° C., 2 MPa, and 10 minutes. The sound absorbing plate thus produced was 9 mm in thickness, and the overall average porosity was 30% by volume. However, due to the difference in specific gravity of the raw materials, the silica sand which is non-uniform and has a high specific gravity within the sound absorbing plate segregates in the lower part, resulting in warping of the lower concave.
[0022]
Comparative Example 2
17 kg of the phenol resin-coated silica sand used in Example 1 was sprayed over an area of 1000 mm × 1000 mm on a forming metal plate coated with a release agent. The obtained mat was covered with a molding metal plate, placed in a hot press, and hot-press molded at 160 ° C., 2 MPa for 10 minutes. The sound absorbing plate thus produced was 10 mm in thickness, and the overall average porosity was 26% by volume.
[0023]
Comparative Example 3
5.4 Kg of the phenol resin-coated glass powder granulated foam used in Example 1 was sprayed over an area of 1000 mm × 1000 mm on a forming metal plate coated with a release agent. The obtained mat was covered with a molding metal plate, placed in a hot press, and hot-press molded at 160 ° C., 2 MPa for 10 minutes. The sound absorbing plate thus produced was 10 mm in thickness, and the overall average porosity was 33% by volume.
[0024]
For each of the sound absorbing plates 1 to 5 obtained in Examples 1 and 2 and Comparative Examples 1 to 3, the thickness, bulk specific gravity, flatness, three-point bending strength, elastic modulus, impact resistance, and normal incidence sound absorbing coefficient are set respectively. It was measured. The bulk specific gravity was measured according to JIS A5908, the flatness was measured by measuring the depth of the lower central recess of the sound absorbing plate of 1000 × 1000 mm, and the three-point bending test and the elastic modulus were performed according to JIS A 1408. . The test body size was 30 × 200 mm, and the test was performed under the condition of a span of 180 mm with the mold surface of the test body, that is, the lower surface side in the stacking order down. Impact resistance was performed in accordance with JISA 1408. The size of the test body was 500 × 500 mm, the test body was supported on sand, a mold weight of 500 g was freely dropped from a predetermined height at the center, an impact was applied, and the state was observed. As for the sound absorption coefficient, the normal incident sound absorption coefficient (back air layer: 50 mm) was measured by a pipe method according to JIS A1405. The test results are shown in Table 1, and the normal incident sound absorption coefficient is shown in FIG.
[0025]
[Table 1]

[0026]
From the results of Table 1, it was recognized that the

sound absorbing plates

1 and 2 having the sandwich structure had higher strength (specific strength) with respect to the bulk specific gravity than the single layer sound absorbing plates 3 to 5. That is, a plate-like sound absorber having a balance between lightness and strength was obtained. In particular, the sound absorbing plate 2 reinforced with inorganic fibers showed excellent sound absorbing characteristics including impact resistance. In addition, the

sound absorbing plates

1 and 2 are substantially flat surfaces, whereas the mixed single layer sound absorbing plate 3 of silica sand and glass powder granulated foam cannot form a uniform layer and has high specific gravity silica sand. The plate was segregated to the lower side and a large warp was generated underneath, which was not suitable for practical use. Further, the sound absorbing plate 4 is 17 kg per square meter, which is about twice as heavy as the sandwich type, and the sound absorbing plate 5 is light but has low strength and is not practical.
[0027]
【The invention's effect】
The sound-absorbing plate having the sandwich structure of the present invention is lightweight and has high sound-absorbing performance, excellent shape safety, high bending strength, and low production cost, and efficiently manufactures a large-sized sound-absorbing plate. It became possible.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a sound absorbing plate having a sandwich structure of the present invention.
FIG. 2 is a cross-sectional view schematically showing another example of the configuration of the sound absorbing plate having the sandwich structure of the present invention.
FIG. 3 is a graph showing the normal incident sound absorption coefficient of the sound absorbing plates of Examples and Comparative Examples.
[Explanation of symbols]
A, B: Sound absorption plate 1: Binder-coated lightweight aggregate layer (inner layer)
2: Binder coating weight aggregate layer (outer layer)
2 ', 2'': Binder coating weight aggregate layer (surface layer)
3, 3 ': Binder-impregnated reinforcing fiber layer (reinforcing layer)

Claims

An inner layer having a porosity of 5 to 50% by volume formed by coating a binder on the surface of inorganic lightweight aggregate particles having a bulk density of 0.1 to 1 g / cm ³ and binding the particles to each other in the form of dots, and the inner layer An outer layer having a porosity of 5 to 50% by volume formed by coating a binder on the surface of inorganic heavy aggregate particles having a bulk density of 1 to 2 g / cm ³ and binding the particles in a dot-like manner. A sound-absorbing plate having a sandwich structure obtained by laminating and integrating.

The sound absorbing plate having a sandwich structure according to claim 1, wherein the total thickness of the outer layer is 10 to 100 with respect to the thickness 100 of the inner layer.

The inorganic light-weight aggregate particles having a particle diameter of 0.3 to 3 mm are 80% by weight or more, and the inorganic light-weight aggregate particles having a particle diameter of 0.3 to 3 mm are 80% by weight or more. A sound-absorbing plate having the sandwich structure according to 1 or 2.

Bulk density was coated with a binder on the surface sprayed with inorganic weight aggregate particles of 1 to 2 g / cm ^3, then bulk density was coated on the surface of the binder to inorganic lightweight aggregate particles of 0.1 to 1 g / cm ³ A method for producing a sound-absorbing plate having a sandwich structure, characterized by spraying, further spraying the above-mentioned inorganic weight aggregate particles, and simultaneously forming the obtained laminate by hot-pressure integrated molding.