JP3600490B2 - Foamable composition for electroacoustic transducer and member for electroacoustic transducer using the same - Google Patents

Description

【００１０】
例えば、内部損失が小さいと機械抵抗が小さくなるため、下記の式（１）で示されるＱ（共振鋭度）が高くなり、スピーカーのピストンモーション領域から分割振動領域に移る周波数帯域（一般のフルレンジスピーカーでは中域付近となる）で発生する振動板とエッジの共振および逆共振が鋭くなり、結果としてこの帯域の周波数−音圧特性に大きな山や谷が発生してしまうこととなる。
【００１１】
また、内部損失が大きいと逆に機械抵抗が増大するため、下記の式（１）で示されるＱ（共振鋭度）が低くなり、共振および逆共振が鈍くなり、結果的にこの帯域における周波数−音圧特性の山や谷が小さくなり、より平坦な周波数−音圧特性が得られるようになる。
【００１２】
【数１】

【００１３】
ただし、内部損失には前述のように周波数依存性があるため、中域付近では高内部損失であるからといって、必ずしも他の周波数において高内部損失であるとは限らず、高域の改善度に対しては、高域の内部損失がどれくらい大きいかが問題となる。
【００１４】
本発明は、このような事情に鑑みなされたもので、充分な耐久性と高い内部損失を有することにより、周波数−音圧特性において、山や谷の少ない良好な特性を、自動車内部等の苛酷な環境下においても長期間にわたって提供することのできる電気音響変換器用発泡性組成物およびそれを用いた電気音響変換器用部材の提供をその目的とする。
【００１５】
【課題を解決するための手段】
上記の目的を達成するため、本発明は、下記の（Ａ）成分および（Ｂ）成分を必須成分とする電気音響変換器用発泡性組成物を第１の要旨とする。
（Ａ）下記の（ａ１）〜（ａ３）からなる共重合体。
（ａ１）エチレン。
（ａ２）α−オレフィン。
（ａ３）非共役二重結合を有する環状ポリエンまたは非共役二重結合を有する非環状ポリエン。
（Ｂ）ポリスチレンとポリイソプレンとからなるブロック共重合体を水素添加した熱可塑性エラストマー。
【００１６】
そして、上記電気音響変換器用発泡性組成物を用い、発泡加硫により所定の形状に成形してなる電気音響変換器用部材を第２の要旨とする。
【００１７】
すなわち、本発明者らは、上記目的を達成するために、発泡性組成物を構成する必須成分について研究を重ねた。その結果、前記特定の３成分からなる共重合体（Ａ成分）と、前記特定の熱可塑性エラストマー（Ｂ成分）を必須成分として用いると、前記Ａ成分に基づく耐久性の向上効果が得られるとともに、従来では得られなかった中域近傍の周波数帯域における良好な周波数−音圧特性が得られるようになり、所期の目的である高い内部損失と優れた耐久性の双方を有することを見出し本発明に到達した。
【００１８】
そして、上記必須成分において、Ｂ成分の配合量を、Ａ成分１００重量部（以下「部」と略す）に対して特定の割合となるよう設定することにより、より一層の高い内部損失と優れた耐久性が得られることを突き止めた。
【００１９】
【発明の実施の形態】
つぎに、本発明の実施の形態を詳しく説明する。
【００２０】
本発明の電気音響変換器用発泡性組成物（以下「発泡性組成物」という）は、特定の３成分からなる共重合体（Ａ成分）と、特定の熱可塑性エラストマー（Ｂ成分）とを用いて得られる。
【００２１】
上記特定の３成分からなる共重合体（Ａ成分）は、エチレン（ａ１）と、α−オレフィン（ａ２）と、非共役二重結合を有する環状ポリエンまたは非共役二重結合を有する非環状ポリエン（ａ３）の３成分からなるターポリマーである。
【００２２】
上記α−オレフィン（ａ２）としては、プロピレン、ブテン−１等があげられる。
【００２３】
上記非共役二重結合を有する環状ポリエンまたは非共役二重結合を有する非環状ポリエン（ａ３）としては、ジシクロペンタジエン、１，５−シクロオクタジエン、１，１−シクロオクタジエン、１，６−シクロドデカジエン、１，７−シクロドデカジエン、１，５，９−シクロドデカトリエン、１，４−シクロヘプタジエン、１，４−シクロヘキサジエン、ノルボルナジエン、エチレンノルボルネン、２−メチルペンタジエン−１，４、１，５−ヘキサジエン、１，６−ヘプタジエン、１，４−ヘキサジエン、メチル−テトラヒドロインデン等があげられる。
【００２４】
上記共重合体（Ａ成分）を構成する各モノマー（ａ１）〜（ａ３）において、適度な加硫速度が得られるという点から、エチレン（ａ１）とプロピレン（ａ２）とジシクロペンタジエンまたはエチレンノルボルネン（ａ３）との組み合わせが好ましい。
【００２５】
そして、上記各モノマーの共重合割合は、好ましくはエチレン（ａ１）が３０〜８０重量％、ポリエン（ａ３）が０．１〜２０重量％、残部がα−オレフィン（ａ２）の範囲となる設定である。特に好ましくは、エチレン（ａ１）が５０〜７０重量％、ポリエン（ａ３）が５〜１２重量％、残部がα−オレフィン（ａ２）の範囲となる設定である。
【００２６】
上記Ａ成分とともに必須成分として用いられる特定の熱可塑性エラストマー（Ｂ成分）は、ポリスチレンとポリイソプレンとからなるブロック共重合体を水素添加したものである。このような熱可塑性エラストマーにおいて、スチレン含有量が１０〜６５重量％の範囲のものが好ましい。特に好ましくはスチレン含有量が１３〜３５重量％である。また、ＤＳＣ法（示差熱法）による昇温速度１０℃／ｍｉｎでのガラス転移温度が−２５〜２０℃のものが好適に用いられる。具体的には、ポリイソプレン部が通常の１．４結合イソプレンからだけでなりたつのではなく、ビニルイソプレン（３．４結合）を含むものである。
【００２７】
上記Ｂ成分の配合量は、Ａ成分１００部に対してＢ成分が０．５〜１００部となるよう設定することが好ましい。より好ましくは１〜８０部、特に好ましくは５〜５５部である。すなわち、Ｂ成分の配合量が０．５部未満のように少な過ぎると、充分高い内部損失が得られ難く、逆にＢ成分が１００部を超え多過ぎると、加熱加圧成形時の作業性が悪化して成形型からの離型性が低下する傾向がみられるからである。
【００２８】
なお、本発明の発泡性組成物には、上記必須成分であるＡ成分およびＢ成分以外に、軟化剤、発泡剤、加硫剤、加硫促進剤、充填剤、ゴム補強剤、さらに紫外線吸収剤、老化防止剤、天然樹脂や合成樹脂、発泡助剤等の各種助剤を必要に応じて適宜配合することができる。
【００２９】
上記軟化剤としては、ジオクチルフタレート，ジブチルフタレート等の低分子可塑剤、ポリエステル可塑剤等のような高分子可塑剤、スピンドル油，マシン油，シリンダー油等の潤滑油類、パラフィン系プロセスオイル，ナフテン系プロセスオイル等のプロセスオイル類、流動パラフィン，ワセリン等のパラフィン類等の石油系軟化剤、コールタール，コールタールピッチ等のコールタール系軟化剤、ヒマシ油，綿実油等の脂肪族系軟化剤、蜜ロウ，ラノリン等のロウ類、常温で液状または固形の樹脂類、その他ポリブテン等の液状ゴム等があげられる。これらは単独でもしくは２種以上併せて用いられる。そして、上記軟化剤の配合量は、Ａ成分１００部に対して２００部以下、特に１〜１５０部の範囲に設定することが好ましい。
【００３０】
上記発泡剤としては、Ｎ，Ｎ′−ジニトロソペンタメチレンテトラミン、Ｎ，Ｎ′−ジメチル−Ｎ，Ｎ′−ジニトロソテレフタルアミド等のニトロソ化合物、アゾジカルボソアミド、アゾビスイソブチルニトリル、ジアゾアミノベンゼン等のアゾ化合物、ベンゼンスルホニルヒドラジド、トルエンスルホニルヒドラジド等のスルホニルヒドラジド化合物、ｐ−トルエンスルホニルアジド、４，４′−ジフェニルスルホニルアジド、４，４′−オキシビスベンゾソスルホニルヒドラジド等があげられる。これらは単独でもしくは２種以上併せて用いられる。そして、上記発泡剤の配合量は、Ａ成分１００部に対して０．１〜３０部の範囲に設定することが好ましく、より好ましくは１〜２０部である。
【００３１】
上記加硫剤としては、硫黄、塩化硫黄，二塩化硫黄等の硫黄化合物、ｐ−キノンジオキシム等のオキシム類、ヘキサジアミンカルバメート，エチレンジアミンカルバメート等のカルバメート類、その他、セレニウム、リサージ等があげられる。これらは単独でもしくは２種以上併せて用いられる。そして、上記加硫剤の配合量は、Ａ成分１００部に対して０．０１〜１０部の範囲に設定することが好ましく、特に好ましくは０．１〜５部である。
【００３２】
上記加硫促進剤としては、ジフェニルグアニジン，トリフェニルグアニジン等のグアニジン系化合物、２−メルカプトベンゾチアゾール，ジベンゾチアゾルジスルフィド等のチアゾール化合物、チオカルバニリド，ジエチルチオユリア等のチオユリア系化合物、テトラメチルチウラムモノスルフィド，テトラメチルチウラムジスルフィド等のチウラム系化合物、ジメチルジチオカルバミン酸亜鉛，ジメチルジチオカルバミン酸ナトリウム等のジチオカルバメート系化合物等があげられる。これらは単独でもしくは２種以上併せて用いられる。そして、上記加硫促進剤の配合量は、Ａ成分１００部に対して０．１〜２０部の範囲に設定することが好ましい。
【００３３】
上記充填剤としては、炭酸カルシウム，タルク，クレー，アスベスト，軽石粉，ガラス繊維，マイカ，シリカ，中空ビーズ等の無機充填剤、再生ゴム，セラック，木粉，コルク粉末等の有機充填剤の他、ポリエステル，アクリル，ナイロン，アラミド，セルロース等の繊維があげられる。これらは単独でもしくは２種以上併せて用いられる。そして、上記充填剤の配合量は、Ａ成分１００部に対して１０〜２００部の範囲に設定することが好ましい。
【００３４】
上記ゴム補強剤としては、チャネルブラック，ファーネスブラック等のカーボンブラック、シリカ類等があげられる。これらは単独でもしくは２種以上併せて用いられる。そして、上記ゴム補強剤の配合量は、Ａ成分１００部に対して１０〜１００部の範囲に設定することが好ましい。
【００３５】
さらに、上記各種助剤のうち、紫外線吸収剤としては、ベンゾフェノン系化合物，ベンゾトリアゾール系化合物等があげられる。また、上記老化防止剤としては、フェノール系化合物，アミンケトン系化合物，芳香族アミン系化合物等があげられる。そして、上記発泡助剤としては、サルチル酸，尿素等があげられる。上記各種助剤の配合量は、Ａ成分１００部に対して、助剤の合計量が０．１〜１００部に設定することが好ましい。
【００３６】
上記天然樹脂や合成樹脂としては、従来公知のもの、例えば、クマロン樹脂、フェノール樹脂、テルペン樹脂、水添石油系樹脂があげられる。これらは単独でもしくは２種以上併せて用いられる。好ましいのは、相溶性および耐久性の点から、水添石油系樹脂があげられる。上記樹脂の配合量は、Ａ成分１００部に対して１００部以下、特に１〜６０部となるよう設定することが好ましい。
【００３７】
上記発泡性組成物の配合成分において、特に好ましい配合の組み合わせは、適度な加硫速度が得られるという観点から、Ａ成分としてエチレン−プロピレン−エチレンノルボルネンの三元共重合体、Ｂ成分としてガラス転移温度（Ｔｇ）が−２０〜１０℃（ＤＳＣ法による）のポリスチレンとポリイソプレン共重合体の水添物、軟化剤としてパラフィン系軟化剤、発泡剤としてアゾジカルボソアミド、加硫剤として硫黄、加硫助剤として酸化亜鉛、加硫促進剤としてテトラメチルチウラムジスルフィド、充填剤としてタルク、ゴム補強剤としてカーボンブラック、発泡助剤として尿素、さらに水添石油系樹脂を用いる組み合わせである。
【００３８】
本発明の発泡性組成物は、例えばつぎのようにして作製される。すなわち、上記必須成分であるＡ成分およびＢ成分、および必要に応じて上記各種添加剤を適宜に配合し混練し、さらに適宜の手段を用いてシート状（厚み１〜３ｍｍ程度）、あるいはフィルム状（厚み０．１〜１ｍｍ未満）に成形することにより作製される。
【００３９】
このようにして得られる発泡性組成物を用いてなる電気音響変換器用部材は、例えば、上記発泡性組成物を所定の形状の成形用金型内に投入し、加熱加圧して発泡させるとともに加硫することにより製造することができる。なお、上記シート状あるいはフィルム状に成形した発泡性組成物を所定形状に打ち抜いた後、この打ち抜き品を成形用金型内で加熱加圧してもよい。
【００４０】
上記成形用金型による加熱加圧成形条件は、上記発泡性組成物の配合成分の組成やシート状あるいはフィルム状の成形物の厚み等によって適宜に設定されるが、一般的に、温度８０〜２５０℃、圧力１〜１０ｋｇ／ｃｍ^２ 、時間０．０２〜３０分に設定される。
【００４１】
上記加熱加圧成形により得られる電気音響変換器用部材の発泡倍率は、１．０５〜３０倍、特に好ましくは１．１〜１５倍となるよう設計することが望ましい。
【００４２】
さらに、得られる電気音響変換器用部材の内部損失（ｔａｎδ）は、前記発泡性組成物の配合成分の組成によって適宜に変化させることができる。
【００４３】
なお、上記内部損失（ｔａｎδ）は、下記のように定義される。
【００４４】
【数２】

【００４５】
このようにして得られる電気音響変換器用部材の具体的な例としては、例えば、電気音響変換器用エッジ材、電気音響変換器用防塵キャップ等があげられる。
【００４６】
つぎに、実施例について比較例と併せて説明する。
【００４７】
【実施例１〜７、比較例１〜２】
下記の表２〜表３に示す各成分を同表に示す割合で配合することにより発泡性組成物を作製した。ついで、上記発泡性組成物を、厚み１．５ｍｍのシート状に成形し、このシート状成形物を所定の寸法に切断して、所定のスピーカーエッジ成形用金型のキャビティーに入れ４ｋｇ／ｃｍ^２ の圧力で型締めを行い、２００℃×１分の加熱条件にて発泡加硫することにより所定形状の発泡ゴムエッジを得た。
【００４８】
ついで、得られた発泡ゴムエッジを所定の寸法に打ち抜き、さらに予め所定の形状に成形し打ち抜きされているコーン形の紙製振動板本体（重量２．７ｇ）と貼り合わせ、およそ直径１６ｃｍの振動板を作製した。
【００４９】
【表２】

【００５０】
【表３】

【００５１】
上記得られた発泡ゴムエッジの発泡倍率をつぎのように従い測定・算出した。すなわち、ＪＩＳ Ｋ ６７６７に準じて比重を測定し、この比重からの逆算法により算出した。この結果を後記の表４〜表５に示す。
【００５２】
また、このようにして得られた実施例２，５，６品および比較例１品の振動板をスピーカーに組み込み、下記の方法に従って周波数−音圧特性の関係を測定した。その結果を図１（実施例２品）、図２（実施例５品）、図３（実施例６品）および図４（比較例１品）に示す。上記図１〜４の結果から、内部損失の高い実施例品は内部損失の低い比較例品に比べて、周波数−音圧特性の、特に中域（横軸の周波数帯域８００〜１５００Ｈｚ）がよりフラットになっていることがわかる。つぎに、上記測定に供した実施例品以外の実施例品についても測定したが、同様の結果が得られた。
【００５３】
また、上記振動板を組み込んだスピーカーを１１０℃×９６時間の耐熱試験に供してｆ_０ （最低共振周波数）の変化率を測定した。さらに、特定周波数における内部損失（ｔａｎδ）を下記の方法に従って測定した。これらの結果を後記の表４〜表５に示す。
【００５４】
〔内部損失〕
厚み１．５ｍｍのシート状に形成された発泡性組成物を、２００℃×１分の加熱条件で発泡加硫し、厚み約１ｍｍのシートを作製した。ついで、このシートを所定の形状に打ち抜き、動的粘弾性測定装置（測定周波数を下記の表４〜表５に記載）を用いて測定した。
【００５５】
〔プレス成形性〕
上記実施例および比較例の、スピーカーエッジ成形用金型での成形時における金型から離型性および取り出し後の変形の度合いを調べ、プレス成形性として評価した。すなわち、離型性については、人の手による剥離抵抗を調べ、量産性に対する合否で判定した。また、変形度合いについては、寸法を測定し図面寸法規格（公差）に対する合否で判定した。
【００５６】
【表４】

【００５７】
【表５】

【００５８】
上記表４〜表５から、実施例品は、高い内部損失を有し、しかもｆ_０ 変化率も小さいことから優れた音響特性と耐久性を備えていることがわかる。これに対して、比較例品に関して、比較例１品（ＥＰＤＭ１００％）は耐久性に優れているが、１０００Ｈｚ付近の内部損失が小さいため、本発明が問題としている周波数−音圧特性の中域（５００〜２ｋＨｚ）付近に山−谷を生じてしまう。また、比較例２品（ＳＢＲ１００％）は１０００Ｈｚ付近で高い内部損失を有しているため、本発明が問題としている中域（５００〜２ｋＨｚ）付近の周波数−音圧特性は山−谷の少ない優れたものであるが、耐久性に問題がある。
【００５９】
【発明の効果】
以上のように、本発明は、前記特定の３成分からなる共重合体（Ａ成分）と前記特定の熱可塑性エラストマー（Ｂ成分）を必須成分とする発泡性組成物である。このため、この発泡性組成物を用いて得られる電気音響変換器用部材は、耐久性に優れるとともに高い内部損失を有することにより、特に本発明が問題とする中域帯域での周波数−音圧特性において、山や谷の少ない良好な特性を苛酷な環境下においても長期間にわたり備えることができるようになる。
【００６０】
そして、上記必須成分において、Ｂ成分の配合量をＡ成分１００部に対して特定の範囲となるよう設定することにより、より一層高い内部損失と優れた耐久性が得られる。
【００６１】
したがって、本発明の発泡性組成物は、電気音響変換器用エッジ材や、電気音響変換器用防塵キャップである電気音響変換器用部材の成形材料として最適である。
【図面の簡単な説明】
【図１】実施例２品の周波数−音圧特性を示す図である。
【図２】実施例５品の周波数−音圧特性を示す図である。
【図３】実施例６品の周波数−音圧特性を示す図である。
【図４】比較例１品の周波数−音圧特性を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a foamable composition for an electroacoustic transducer used for an edge portion or the like which is a support system member of an acoustic transducer such as a speaker, and an electroacoustic transducer member using the same.
[0002]
[Prior art]
The conditions required for the edge, which is one of the supporting components of the electroacoustic transducer such as speakers, are that the linearity is good, that it is lightweight, that it has high internal loss, and that it has a unique sound. That they are not reliable, have sufficient reliability, and are easy and inexpensive to manufacture.
[0003]
Under such circumstances, the fixed edge, in which the diaphragm and the edge are integrated, has an advantage that the manufacturing process can be simplified and the material yield of the edge portion is good, so that an inexpensive diaphragm can be provided. have. However, due to its structure, the same material as the diaphragm, that is, a material having a relatively high elastic modulus is also used for the edge, so that it was difficult to obtain the above-described ideal function as the edge.
[0004]
On the other hand, in order to improve the functional defect of the fixed edge, various free edges in which the edge portion of the diaphragm main body and the edge portion are formed of different materials have been conventionally proposed and put to practical use. For example,
(1) A sheet in which a woven fabric of natural fibers or synthetic fibers is coated with a relatively soft material having a large internal loss, such as rubber or acrylic, and further impregnated with a thermosetting resin for hardness control as required. A coated cloth edge obtained by heating and molding a material into a predetermined edge shape. [2] A urethane foam edge obtained by heating and molding a urethane foam sheet into a predetermined edge shape. [3] A rubber mixture mainly composed of a raw rubber and a vulcanizing agent. Vulcanized rubber edge formed by heating (vulcanizing) to the edge shape of (4) TPE sheet edge formed by heating and molding a thermoplastic elastomer (TPE) sheet into a predetermined edge shape (5) Injecting pelletized thermoplastic elastomer (TPE) Injection TPE edges and the like formed into a predetermined edge shape by a molding method can be cited. Has various drawbacks, more recently, improved these drawbacks vulcanized foam rubber edge is used is proposed.
[0005]
[Problems to be solved by the invention]
However, the vulcanized foamed rubber edge also has the following disadvantages. That is,
{Circle around (1)} A material using styrene-butadiene rubber (SBR) has excellent moldability and a large internal loss, so it can be said that it is an excellent material in these respects. However, weather resistance (particularly heat resistance and cold resistance) Poor) and has a problem in durability.
(2) Those containing ethylene-propylene-terpolymer rubber (EPT) as a main component are excellent in weather resistance, but have a problem that internal loss is small.
[0006]
For example, in the embodiment described in Japanese Patent Application Laid-Open No. 7-240994, there is almost no difference in the internal loss between the above-described one having EPT as the main component and the one having SBR as the main component, but this measurement was performed at a frequency of 1 Hz. This is a condition largely different from the frequency band of the present invention.
[0007]
In general, the internal loss has a frequency dependency, and the fact that the internal loss has a high internal loss at an extremely low frequency of 1 Hz as described above means that the internal loss has the same high value at other frequencies. Not necessarily.
[0008]
Normally, the reproduction frequency band of the speaker system is about 50 Hz to 30 kHz, and particularly in the vicinity of the midrange which is a problem of the present invention, the range of about 500 Hz to 2 kHz is a problem. Therefore, in the present invention, the internal loss was measured and compared with those having EPT as the main component and those having SBR as the main component at a frequency as close as possible to the frequency in question. The results are shown in Table 1 below.
[0009]
[Table 1]

[0010]
For example, when the internal loss is small, the mechanical resistance becomes small, so that Q (resonance sharpness) expressed by the following equation (1) increases, and a frequency band (general full range) that shifts from the piston motion region of the speaker to the divided vibration region is used. The resonance and the inverse resonance of the diaphragm and the edge generated near the mid-range in the speaker become sharp, and as a result, large peaks and valleys occur in the frequency-sound pressure characteristics of this band.
[0011]
On the other hand, if the internal loss is large, the mechanical resistance increases, and consequently, the Q (resonance sharpness) shown by the following equation (1) decreases, and the resonance and the inverse resonance become dull. As a result, the frequency in this band is reduced. The peaks and valleys of the sound pressure characteristic are reduced, and a flatter frequency-sound pressure characteristic can be obtained.
[0012]
(Equation 1)

[0013]
However, since the internal loss has frequency dependence as described above, the high internal loss near the middle frequency does not necessarily mean that the internal loss is high at other frequencies. The degree is a matter of how large the internal loss in the high frequency range is.
[0014]
The present invention has been made in view of such circumstances, and by having sufficient durability and high internal loss, in the frequency-sound pressure characteristics, good characteristics with few peaks and valleys can be obtained under severe conditions such as in an automobile. It is an object of the present invention to provide a foamable composition for an electro-acoustic transducer that can be provided for a long period of time even in a natural environment, and a member for an electro-acoustic transducer using the same.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is a foamable composition for an electroacoustic transducer containing the following components (A) and (B) as essential components.
(A) A copolymer comprising the following (a1) to (a3).
(A1) ethylene.
(A2) α-olefin.
(A3) A cyclic polyene having a non-conjugated double bond or a non-cyclic polyene having a non-conjugated double bond.
(B) A thermoplastic elastomer obtained by hydrogenating a block copolymer composed of polystyrene and polyisoprene.
[0016]
A second aspect of the present invention is to provide a member for an electroacoustic transducer formed into a predetermined shape by foaming and vulcanization using the foamable composition for an electroacoustic transducer.
[0017]
That is, the present inventors have repeatedly studied essential components constituting the foamable composition in order to achieve the above object. As a result, the use of the specific three-component copolymer (component A) and the specific thermoplastic elastomer (component B) as essential components provides an effect of improving durability based on the component A, and It has been found that good frequency-sound pressure characteristics can be obtained in a frequency band near the mid range, which has not been obtained in the past, and that it has both the intended high internal loss and excellent durability. The invention has been reached.
[0018]
Further, by setting the blending amount of the component B in the essential component to a specific ratio with respect to 100 parts by weight of the component A (hereinafter abbreviated as “parts”), a higher internal loss and more excellent. They found that durability was obtained.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail.
[0020]
The foamable composition for an electroacoustic transducer of the present invention (hereinafter referred to as “foamable composition”) uses a copolymer composed of specific three components (component A) and a specific thermoplastic elastomer (component B). Obtained.
[0021]
The copolymer (component A) comprising the above three specific components is ethylene (a1), α-olefin (a2), and a cyclic polyene having a non-conjugated double bond or a non-cyclic polyene having a non-conjugated double bond. It is a terpolymer composed of the three components (a3).
[0022]
Examples of the α-olefin (a2) include propylene and butene-1.
[0023]
Examples of the cyclic polyene having a non-conjugated double bond or the non-cyclic polyene having a non-conjugated double bond (a3) include dicyclopentadiene, 1,5-cyclooctadiene, 1,1-cyclooctadiene, 1,6 -Cyclododecadiene, 1,7-cyclododecadiene, 1,5,9-cyclododecatriene, 1,4-cycloheptadiene, 1,4-cyclohexadiene, norbornadiene, ethylene norbornene, 2-methylpentadiene-1, Examples thereof include 4,1,5-hexadiene, 1,6-heptadiene, 1,4-hexadiene, and methyl-tetrahydroindene.
[0024]
Ethylene (a1), propylene (a2), dicyclopentadiene or ethylene norbornene, from the viewpoint that an appropriate vulcanization rate can be obtained in each of the monomers (a1) to (a3) constituting the copolymer (A component). The combination with (a3) is preferred.
[0025]
The copolymerization ratio of each of the above monomers is preferably such that ethylene (a1) is in the range of 30 to 80% by weight, polyene (a3) is in the range of 0.1 to 20% by weight, and the balance is α-olefin (a2). It is. Particularly preferably, the setting is such that ethylene (a1) is in the range of 50 to 70% by weight, polyene (a3) is in the range of 5 to 12% by weight, and the balance is α-olefin (a2).
[0026]
The specific thermoplastic elastomer (component B) used as an essential component together with the component A is obtained by hydrogenating a block copolymer composed of polystyrene and polyisoprene. In such a thermoplastic elastomer, those having a styrene content in the range of 10 to 65% by weight are preferable. Particularly preferably, the styrene content is 13 to 35% by weight. Further, those having a glass transition temperature of −25 to 20 ° C. at a heating rate of 10 ° C./min by the DSC method (differential heat method) are preferably used. More specifically, the polyisoprene portion does not consist solely of ordinary 1.4-bonded isoprene, but contains vinyl isoprene (3.4 bonds).
[0027]
The amount of the component B is preferably set so that the component B is 0.5 to 100 parts with respect to 100 parts of the component A. It is more preferably from 1 to 80 parts, particularly preferably from 5 to 55 parts. That is, if the blending amount of the component B is too small, such as less than 0.5 part, it is difficult to obtain a sufficiently high internal loss. This is because there is a tendency that the moldability deteriorates and the releasability from the mold decreases.
[0028]
The foamable composition of the present invention contains, in addition to the essential components A and B, a softener, a foaming agent, a vulcanizing agent, a vulcanization accelerator, a filler, a rubber reinforcing agent, and an ultraviolet absorbing agent. Various auxiliaries such as agents, antioxidants, natural resins and synthetic resins, and foaming auxiliaries can be appropriately compounded as required.
[0029]
Examples of the softener include low molecular weight plasticizers such as dioctyl phthalate and dibutyl phthalate; high molecular weight plasticizers such as polyester plasticizers; lubricating oils such as spindle oil, machine oil and cylinder oil; paraffinic process oils; Oils such as process oils such as system process oils, paraffins such as liquid paraffin and petrolatum, coal tar softeners such as coal tar and coal tar pitch, and aliphatic softeners such as castor oil and cottonseed oil; Examples include waxes such as beeswax and lanolin, resins that are liquid or solid at ordinary temperature, and liquid rubbers such as polybutene. These may be used alone or in combination of two or more. The amount of the softening agent is preferably set to 200 parts or less, especially 1 to 150 parts, per 100 parts of the component A.
[0030]
Examples of the foaming agent include nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, N, N'-dimethyl-N, N'-dinitrosoterephthalamide, azodicarbosoamide, azobisisobutylnitrile, and diazoamino. Examples thereof include azo compounds such as benzene, sulfonyl hydrazide compounds such as benzenesulfonyl hydrazide and toluenesulfonyl hydrazide, p-toluenesulfonyl azide, 4,4'-diphenylsulfonyl azide, and 4,4'-oxybisbenzososulfonyl hydrazide. These may be used alone or in combination of two or more. The amount of the foaming agent is preferably set in the range of 0.1 to 30 parts, more preferably 1 to 20 parts, per 100 parts of the component A.
[0031]
Examples of the vulcanizing agent include sulfur, sulfur compounds such as sulfur chloride and sulfur dichloride, oximes such as p-quinone dioxime, carbamates such as hexadiamine carbamate and ethylenediamine carbamate, and selenium and litharge. . These may be used alone or in combination of two or more. The amount of the vulcanizing agent is preferably set in the range of 0.01 to 10 parts, more preferably 0.1 to 5 parts, per 100 parts of the component A.
[0032]
Examples of the vulcanization accelerator include guanidine compounds such as diphenylguanidine and triphenylguanidine; thiazole compounds such as 2-mercaptobenzothiazole and dibenzothiazol disulfide; thiourea compounds such as thiocarbanilide and diethylthiourea; and tetramethylthiurammono. Thiuram-based compounds such as sulfide and tetramethylthiuram disulfide; and dithiocarbamate-based compounds such as zinc dimethyldithiocarbamate and sodium dimethyldithiocarbamate. These may be used alone or in combination of two or more. The amount of the vulcanization accelerator is preferably set in the range of 0.1 to 20 parts with respect to 100 parts of the component A.
[0033]
Examples of the filler include inorganic fillers such as calcium carbonate, talc, clay, asbestos, pumice powder, glass fiber, mica, silica, and hollow beads, and organic fillers such as recycled rubber, shellac, wood powder, and cork powder. And fibers of polyester, acrylic, nylon, aramid, cellulose and the like. These may be used alone or in combination of two or more. The amount of the filler is preferably set in the range of 10 to 200 parts with respect to 100 parts of the component A.
[0034]
Examples of the rubber reinforcing agent include carbon black such as channel black and furnace black, and silicas. These may be used alone or in combination of two or more. The amount of the rubber reinforcing agent is preferably set in the range of 10 to 100 parts based on 100 parts of the component A.
[0035]
Further, among the various assistants, examples of the ultraviolet absorber include benzophenone-based compounds and benzotriazole-based compounds. Examples of the antioxidants include phenol compounds, amine ketone compounds, and aromatic amine compounds. Examples of the foaming aid include salicylic acid and urea. It is preferable that the compounding amount of the various assistants is set such that the total amount of the assistants is 0.1 to 100 parts with respect to 100 parts of the component A.
[0036]
Examples of the natural resin and the synthetic resin include conventionally known ones, for example, a coumarone resin, a phenol resin, a terpene resin, and a hydrogenated petroleum resin. These may be used alone or in combination of two or more. Preferred are hydrogenated petroleum resins from the viewpoint of compatibility and durability. The amount of the resin is preferably set to 100 parts or less, particularly 1 to 60 parts, per 100 parts of the component A.
[0037]
Among the components of the foamable composition, a particularly preferable combination is a ternary copolymer of ethylene-propylene-ethylenenorbornene as the component A and a glass transition as the component B from the viewpoint that an appropriate vulcanization rate is obtained. A hydrogenated product of polystyrene and polyisoprene copolymer having a temperature (Tg) of -20 to 10 ° C (by the DSC method), a paraffin-based softening agent as a softening agent, azodicarbosamide as a foaming agent, sulfur as a vulcanizing agent, A combination using zinc oxide as a vulcanization aid, tetramethylthiuram disulfide as a vulcanization accelerator, talc as a filler, carbon black as a rubber reinforcing agent, urea as a foaming aid, and a hydrogenated petroleum resin.
[0038]
The foamable composition of the present invention is produced, for example, as follows. That is, the components A and B, which are the essential components, and the above-mentioned various additives, if necessary, are appropriately mixed and kneaded, and further, by appropriate means, in a sheet form (thickness of about 1 to 3 mm) or a film form. (Thickness of less than 0.1 to 1 mm).
[0039]
The member for an electroacoustic transducer using the foamable composition obtained in this manner is, for example, charged into a molding die having a predetermined shape, heated and pressurized to foam and add. It can be produced by sulfurizing. After the foamable composition formed into a sheet or film is punched into a predetermined shape, the punched product may be heated and pressed in a molding die.
[0040]
The heating and pressure molding conditions using the molding die are appropriately set depending on the composition of the components of the foamable composition, the thickness of the sheet-like or film-like molded product, and the like. The temperature is set to 250 ° C., the pressure is set to 1 to 10 kg / cm ² , and the time is set to 0.02 to 30 minutes.
[0041]
It is desirable that the expansion ratio of the member for the electroacoustic transducer obtained by the above-mentioned heating and pressing is designed to be 1.05 to 30 times, particularly preferably 1.1 to 15 times.
[0042]
Furthermore, the internal loss (tan δ) of the obtained member for an electroacoustic transducer can be appropriately changed depending on the composition of the components of the foamable composition.
[0043]
The internal loss (tan δ) is defined as follows.
[0044]
(Equation 2)

[0045]
Specific examples of the electroacoustic transducer member thus obtained include, for example, an electroacoustic transducer edge material and an electroacoustic transducer dustproof cap.
[0046]
Next, examples will be described together with comparative examples.
[0047]
Examples 1 to 7, Comparative Examples 1 and 2
An expandable composition was prepared by blending the components shown in Tables 2 and 3 below in the proportions shown in the table. Next, the foamable composition is formed into a sheet having a thickness of 1.5 mm, and the sheet is cut into a predetermined size, put into a cavity of a predetermined speaker edge molding die, and placed in a cavity of 4 kg / cm. ^The mold was clamped at a pressure of ² and foamed and vulcanized under heating conditions of 200 ° C. × 1 minute to obtain a foamed rubber edge having a predetermined shape.
[0048]
Then, the obtained foamed rubber edge is punched into a predetermined size, and is further formed into a predetermined shape in advance and bonded to a cone-shaped paper-made diaphragm main body (2.7 g in weight). Was prepared.
[0049]
[Table 2]

[0050]
[Table 3]

[0051]
The expansion ratio of the obtained foamed rubber edge was measured and calculated as follows. That is, the specific gravity was measured according to JIS K 6767, and the specific gravity was calculated from the specific gravity. The results are shown in Tables 4 and 5 below.
[0052]
The thus obtained diaphragms of Examples 2, 5, and 6 and Comparative Example 1 were assembled in a speaker, and the relationship between frequency and sound pressure characteristics was measured according to the following method. The results are shown in FIG. 1 (Example 2 product), FIG. 2 (Example 5 product), FIG. 3 (Example 6 product) and FIG. 4 (Comparative example 1 product). From the results of FIGS. 1 to 4 above, the product having a high internal loss has a higher frequency-sound pressure characteristic, especially in the middle range (frequency band of 800 to 1500 Hz on the horizontal axis) than the comparative product having a low internal loss. You can see that it is flat. Next, measurement was also performed on example products other than the example product subjected to the above measurement, and similar results were obtained.
[0053]
Further, the speaker incorporating the diaphragm was subjected to a heat resistance test at 110 ° C. for 96 hours, and the rate of change of f ₀ (minimum resonance frequency) was measured. Further, the internal loss (tan δ) at a specific frequency was measured according to the following method. The results are shown in Tables 4 and 5 below.
[0054]
(Internal loss)
The foamable composition formed into a sheet having a thickness of 1.5 mm was foamed and vulcanized under heating conditions of 200 ° C. × 1 minute to prepare a sheet having a thickness of about 1 mm. Next, the sheet was punched into a predetermined shape, and measured using a dynamic viscoelasticity measuring device (measurement frequencies are described in Tables 4 and 5 below).
[0055]
[Press formability]
In the above Examples and Comparative Examples, the mold releasability and the degree of deformation after removal from the mold at the time of molding with the speaker edge molding mold were examined and evaluated as press moldability. That is, regarding the releasability, the peeling resistance by a human hand was examined, and the pass / fail with respect to mass productivity was determined. Regarding the degree of deformation, the dimensions were measured and judged based on the pass / fail of the drawing dimensional standard (tolerance).
[0056]
[Table 4]

[0057]
[Table 5]

[0058]
From the above Tables 4 to 5, embodiments product has a high internal loss, yet it can be seen that with excellent acoustic characteristics and durability since f ₀ change rate is small. On the other hand, as for the comparative example, the comparative example 1 (EPDM 100%) is excellent in durability, but the internal loss around 1000 Hz is small, so that the frequency-sound pressure characteristic in the middle of the present invention is a problem. Peaks and valleys occur near (500 to 2 kHz). In addition, since the product of Comparative Example 2 (SBR 100%) has a high internal loss near 1000 Hz, the frequency-sound pressure characteristic near the middle range (500 to 2 kHz) which is a problem of the present invention has few peaks and troughs. Although excellent, there is a problem in durability.
[0059]
【The invention's effect】
As described above, the present invention is a foamable composition containing the above-mentioned specific three-component copolymer (component A) and the specific thermoplastic elastomer (component B) as essential components. For this reason, the member for an electroacoustic transducer obtained by using this foamable composition has excellent durability and high internal loss, so that the frequency-sound pressure characteristics particularly in the mid-range band where the present invention is problematic. In this case, good characteristics with few peaks and valleys can be provided for a long period of time even in a severe environment.
[0060]
By setting the blending amount of the component B in the above-mentioned essential component so as to be in a specific range with respect to 100 parts of the component A, higher internal loss and excellent durability can be obtained.
[0061]
Therefore, the foamable composition of the present invention is most suitable as a molding material for an electroacoustic transducer edge material and an electroacoustic transducer member that is a dustproof cap for an electroacoustic transducer.
[Brief description of the drawings]
FIG. 1 is a diagram showing frequency-sound pressure characteristics of a product of Example 2.
FIG. 2 is a diagram showing frequency-sound pressure characteristics of a product of Example 5.
FIG. 3 is a view showing frequency-sound pressure characteristics of a product of Example 6.
FIG. 4 is a diagram showing frequency-sound pressure characteristics of a first comparative example.

Claims (5)

A foamable composition for an electroacoustic transducer, comprising the following components (A) and (B) as essential components.
(A) A copolymer comprising the following (a1) to (a3).
(A1) ethylene.
(A2) α-olefin.
(A3) A cyclic polyene having a non-conjugated double bond or a non-cyclic polyene having a non-conjugated double bond.
(B) A thermoplastic elastomer obtained by hydrogenating a block copolymer composed of polystyrene and polyisoprene. The foamable composition for an electroacoustic transducer according to claim 1, wherein the amount of the component (B) is set to 0.5 to 100 parts by weight based on 100 parts by weight of the component (A). A member for an electroacoustic transducer, wherein the foamable composition for an electroacoustic transducer according to claim 1 or 2 is molded into a predetermined shape by foaming vulcanization. 4. The electroacoustic transducer member according to claim 3, wherein the electroacoustic transducer member is an electroacoustic transducer edge material. The electroacoustic transducer member according to claim 3, wherein the electroacoustic transducer member is a dustproof cap for an electroacoustic transducer.

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