JP4039011B2 - Heat resistant nonwoven fabric and binder resin - Google Patents
Heat resistant nonwoven fabric and binder resin Download PDFInfo
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- JP4039011B2 JP4039011B2 JP2001201268A JP2001201268A JP4039011B2 JP 4039011 B2 JP4039011 B2 JP 4039011B2 JP 2001201268 A JP2001201268 A JP 2001201268A JP 2001201268 A JP2001201268 A JP 2001201268A JP 4039011 B2 JP4039011 B2 JP 4039011B2
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Description
【０００１】
【発明の属する技術分野】
この発明は、耐熱性不織布およびバインダ−樹脂に関し、特に加熱工程において有機溶媒を実質的に使用することなく製造することができ、成形体が耐熱性および強度を保持している耐熱性不織布およびそれに使用されるバインダ−樹脂に関するものである。
【０００２】
【従来の技術】
近年、電気・電子産業分野や自動車・航空宇宙分野における小型化、軽量化の技術開発が進むなかで、長期耐熱性に優れた不織布が求められている。また、自動車等の塗装ラインの乾燥炉等には断熱材やフィルタ−として長期耐熱性のある耐熱不織布が必要になってきている。
【０００３】
従来、耐熱性不織布としてはアラミド繊維をフェノ−ル樹脂、エポキシ樹脂あるいは熱可塑性ポリエステルから成るバインダ−で固定した不織布等が開発されているが、バインダ−の耐熱性が不十分なために高温雰囲気下では長期に使用することはできなかった。また、水溶性のポリイミドワニス等がバインダ−として用いられた耐熱性不織布も開発されているが、これでもまだ２００℃以上の雰囲気下では強度が大幅に低下し実用的ではなかった。これらの耐熱性不織布は、不織布を構成する繊維の耐熱性は十分であるにもかかわらず、バインダ−の耐熱性が不十分であることが大きな問題であった。
【０００４】
このバインダ−の耐熱性を改良したものとして、不飽和結合を有するポリイミド系バインダ−が特開平６−１８４９０３号に記載されている。
しかし、上記公報に実施例として記載のバインダ−は、有機溶媒溶液として使用されており、作業環境の点において必ずしも有利とはいえず、用途が限定されている。
【０００５】
【発明が解決しようとする課題】
そこで、この発明者らは、２００℃以上の雰囲気下に置いてもその引張強度が大幅には低下せず、形態保持性の高い、耐熱性不織布に適用することができ、しかも耐熱性の繊維と混合する際に水溶液の状態で使用することができる新規なポリイミド樹脂バインダ−およびそれを用いた耐熱性不織布を提供することを目的に鋭意研究を重ねた結果、本発明を完成した。
【０００６】
【課題を解決するための手段】
すなわち、この発明は、１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルを含有する水溶性ポリイミド前駆体から得られたポリイミドを耐熱性樹脂製繊維のバインダ−樹脂とする耐熱性不織布に関する。
また、この発明は、耐熱性不織布に使用される１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルを含有する水溶性ポリイミド前駆体から得られたポリイミドからなるバインダ−樹脂に関する。
【０００７】
また、この発明は、耐熱性不織布に使用される水溶性ポリイミド前駆体から得られたポリイミドからなり、耐熱性不織布についての２００℃における引張り強度保持率が７０％以上であるバインダ−樹脂に関する。
さらに、この発明は、水溶性ポリイミド前駆体から得られたポリイミドをバインダ−樹脂としてなり、２００℃における引張り強度保持率が７０％以上である耐熱性不織布に関する。
【０００８】
【発明の実施の形態】
以下にこの発明の好ましい態様を列記する。
１）ポリイミドが、Ｘ線解析により非結晶性である上記の耐熱性不織布。
２）ポリイミドが、テトラカルボン酸成分として５０％以上を２，３，３’，４’−ビフェニルテトラカルボン酸成分として得られたものである上記の耐熱性不織布。
３）耐熱性樹脂製繊維が、アラミド繊維などの芳香族ポリアミド製繊維である上記の耐熱性不織布。
【０００９】
この発明においては、１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルを、好適にはポリイミド前駆体のカルボキシル基の０．２倍モル当量以上の１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルを含有させることが適当である。
前記の１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルをポリイミド前駆体とともに使用することによって、ポリイミド前駆体の水溶液が得られ、しかも得られるポリイミド成形体の熱的特性および機械的特性が良好である。
【００１０】
前記の１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルに代えて、他のジアミン化合物、例えばジエタノ−ルアミン、トリエタノ−ルアミン、Ｎ−メチルジエタノ−ルアミン、３−ジエチルアミノ−１−プロパノ−ルなどを使用すると、ポリイミド前駆体は水溶液となるが得られるポリイミド成形体の熱的特性および機械的特性が低下するので好ましくない。
【００１１】
前記の水溶性ポリイミド前駆体を与えるポリイミドは、テトラカルボン酸成分として、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，３，３’，４’−ビフェニルテトラカルボン酸二無水物、ピロメリット酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、２，２’−ビス（３，４−ジカルボキシフェニル）プロパンの二無水物、ビス（３，４−ジカルボキシフェニル）メタンの二無水物、ビス（３，４−ジカルボキシフェニル）エ−テルの二無水物やこれらのテトラカルボン酸やハ−フエステルなどを使用して得ることができる。前記芳香族テトラカルボン酸成分の一部あるいは全部を脂環式テトラカルボン酸成分で置き換えてもよい。特にテトラカルボン酸成分として、５０％以上が２，３，３’，４’−ビフェニルテトラカルボン酸成分であるものが好ましい。
【００１２】
また、前記の水溶性ポリイミド前駆体を与えるポリイミドは、芳香族ジアミン成分として、任意の芳香族ジアミン、例えばパラフェニレンジアミン（ｐ−フェニレンジアミン）、４，４’−ジアミノジフェニルエ−テル、１，３−ビス（４−アミノフェノキシ）ベンゼン、１，３−ビス（３−アミノフェノキシ）ベンゼン、４，４’−ジアミノジフェニルプロパン、４，４’−ジアミノジフェニルエタン、４，４’−ジアミノジフェニルメタン、２，２’−ビス〔４−（４−アミノフェノキシ）フェニル〕プロパン、２，２’−ビス〔４−（４−アミノフェノキシ）フェニル〕１，１，１，３，３，３−ヘキサフルオロプロパン、ビス〔４−（４−アミノフェノキシ）フェニル〕エ−テル、ビス［４−（３−アミノフェノキシ）フェニル］スルホンを使用して得ることができるが、好適には１，３−ビス（４−アミノフェノキシ）ベンゼン、１，３−ビス（３−アミノフェノキシ）ベンゼンを使用して得ることができる。前記芳香族ジアミンの一部を脂環式ジアミン、ジアミノポリシロキサンで置き換えてもよい。
【００１３】
この発明において、ポリイミドは好適にはＸ線解析により非結晶性である。
また、この発明におけるポリイミドは、好適には熱分解温度が５００℃以上で好適にはガラス転移温度（Ｔｇ）が２００より高く３５０℃以下、特に２５０〜３５０℃である。
また、この発明において、耐熱性繊維よりなる不織布に熱圧着するバインダ−としては、前記のポリイミド前駆体をイミド化したポリイミド樹脂が主成分であることが必要であるが、樹脂あるいは樹脂前駆体が水溶性であれば他の耐熱性樹脂（あるいは樹脂前駆体）をブレンドしても良い。
【００１４】
この発明において、ポリイミド前駆体の水溶液は、好適には水溶性ケトンおよび／又はアミド系溶媒中で、ポリイミド前駆体の濃度が０．１〜３０重量％程度となるなるように各成分を加えてテトラカルボン酸二無水物と芳香族ジアミンとを０〜４０℃で３０分〜２４時間程度反応させて得られるポリイミド前駆体を、ポリイミド前駆体のカルボキシル基の０．７倍モル当量以上の１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルと反応させた後、反応混合物から、析出物を濾集する方法や有機系貧溶媒、例えばアセトンなどにより析出させた析出物を濾集し、ポリイミド前駆体を粉末とし、１００℃以下の温度で乾燥し、水にこの粉末と更にポリイミド前駆体のカルボキシル基の０．２倍モル当量以上、特に０．７倍モル当量以上（合計量）、その中でも好ましくは０．９倍モル当量以上（合計量）の１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルとを添加し、均一に混合することによって得ることが好ましい。１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルは予め水に添加しておいてもよい。
前記のポリイミド前駆体水溶液は粘度（３０℃）が０．２〜８００ポイズ程度であることが好ましい。
【００１５】
前記のアミド系溶媒としては、Ｎ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ−メチルカプロラクタムが挙げられ、特にＮ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルアセトアミドが好適に使用される。
また、前記の水溶性ケトン類としては、アセトン、γ−ブチロラクトン、メチルエチルケトン、メチルイソブチルケトン、メチルｎ−ブチルケトン、シクロヘキサノンなどが挙げられる。
【００１６】
この発明において、前記のテトラカルボン酸二無水物と芳香族ジアミンとの反応時、好適には反応後にポリイミド前駆体（ポリアミック酸）と１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルとを共在させて反応させ、反応混合物からポリイミド前駆体の粉末状物を分離し、得られた粉末状物を水と混合してポリイミド前駆体水溶液を得る方法が好ましい。
【００１７】
前記の１，２−ジメチルイミダゾ−ル及び／又は１−メチル−２−エチルイミダゾ−ルの量は、反応混合液からポリイミド前駆体を粉末状物として分離する場合にはポリイミド前駆体のカルボキシル基の０．２倍モル当量以上の量であることが好ましい。前記の割合より少ない量では、ポリイミド前駆体がタ−ル化して反応混合物からポリイミド前駆体を粉末として分離することが容易でなくなる。
また、ポリイミド前駆体の水溶液とする際に、ポリイミド前駆体のカルボキシル基の０．７倍モル当量以上（合計）の量であることが好ましい。前記の割合より少ない量では、ポリイミド前駆体の均一な水溶液を得ることが困難である。
【００１８】
この発明において、ポリイミド前駆体水溶液からバインダ−としてのポリイミド樹脂を得る方法としては、例えば、ポリイミド前駆体水溶液を、例えば、耐熱性繊維のＥＧカット（紡糸した後３ｍｍあるいは６ｍｍ程度の長さにカットしたもの、電気絶縁性を改良したものをＥＧという）、チョップドファイバ−、ステ−プル、ドライパルプに含ませて、加熱してイミド化する方法が挙げられる。
【００１９】
この発明における耐熱性繊維としては、全芳香族ポリアミド繊維、ガラス繊維、カ−ボン繊維、全芳香族ポリエステル繊維、ＰＰＳ繊維、ポリパラフェニレンスルホン繊維、ポリイミド繊維等が挙げられる。中でも、全芳香族ポリアミド繊維、全芳香族ポリエステル繊維、ポリイミド繊維等が好ましく、特に入手の容易性と性能とからケブラ−（デュポン社、東レ・デュポン社）等の芳香族ポリアミド繊維が好ましい。
また、耐熱性繊維とともに、人造ダイヤモンド、シリカ、マイカ、カオリン、窒化ほう素、酸化アルミニウム、酸化鉄、グラファイト、硫化モリブデン、硫化鉄などの無機粒子状充填剤や有機あるいは無機顔料・着色剤を併用してもよい。これらの添加法としては特に制限はなく、例えばポリイミド前駆体水溶液に加えてもよい。
【００２０】
この発明の耐熱性不織布は、ポリイミド前駆体水溶液と耐熱性繊維、好適にはこれらの積層物とを混合し、１００〜４５０℃程度の温度、好適にはポリイミドのガラス転移温度以上の温度、特にポリイミドのガラス転移温度より約２０℃以上で４５０℃以下の温度で５〜１２０分間加熱し、加熱圧縮成形して、耐熱性不織布を形成することができる。
【００２１】
この発明における耐熱性不織布の製造法としては、先ず、耐熱性繊維の短繊維（チョップドファイバ−、ドライパルプ）を大量の水中に分散させて、網上に抄紙して湿潤ウエッブを作成する抄紙法、あるいは耐熱性繊維のステ−プルをロ−ラカ−ド機に通してウエッブを作成するカ−ド法によって湿潤ウエッブを得る。
【００２２】
次いで、この湿潤ウエッブをテトラン布のような厚手の合成樹脂製布で挟み、さらに両側から吸水性基材（例えばで濾紙）で挟み、過剰な水分を除去して後、加熱炉中で１２０℃程度に加熱して水分を除き乾燥ウエッブを得る。そして、ウエッブのみを金網（例えば、５０メッシュ程度のＳＵＳ製金網）で挟み、前記のポリイミド前駆体水溶液であるド−プに所定時間（０．１〜５分程度）漬け、過剰なド−プ液を吸水性基材（例えばで濾紙）に挟んで除いて、ド−プ含浸ウエッブを得る。
【００２３】
次いで、このド−プ含浸ウエッブを１００℃程度に調節した加熱炉中で１０〜３０分間程度乾燥した後、熱可塑性性ポリイミド樹脂のガラス転移温度以上の温度、好適には２１０〜４００℃、特に２５０〜４００℃程度で１０〜６０分間程度加熱してイミド化して、イミド化不織布を得る。
この際、バインダ−である熱可塑性性ポリイミド樹脂の量は、前記の乾燥ウエッブ重量とイミド化後の不織布重量との差から求めることができる。
【００２４】
次いで、予め３００〜４００℃程度にぷプレス温度設定しておき、前記のイミド化不織布を耐熱性フィルム（例えば、ポリイミドフィルム）に挟み、プレス圧１〜３００Ｋｇｆ／ｃｍ２程度で加熱圧着して、耐熱性不織布を得ることができる。
【００２５】
この発明によって得られる耐熱性不織布は、バインダ−樹脂を使用するため毛羽抜けの問題が生じず、しかもバインダ−樹脂である熱可塑性ポリイミドを加熱成形して得られるものであり、良好な熱特性および機械特性を示し、特に耐熱性不織布についての２００℃における引張り強度保持率が７０％以上である。
【００２６】
【実施例】
以下の記載において、各略号は次の化合物を意味する。
ａ−ＢＰＤＡ：２，３，３’，４’−ビフェニルテトラカルボン酸二無水物
ＴＰＥ−Ｒ：１，３−ビス（４−アミノフェノキシ）ベンゼン
ＤＭＺ：１，２−ジメチルイミダゾ−ル
ＤＭＡｃ：Ｎ，Ｎ−ジメチルアセトアミド
【００２７】
以下の各例において、ポリイミドの物性は以下の方法によって求めた。
▲１▼ポリイミドフィルムの熱分解温度
ポリイミドフィルムをセイコ−インスツルメンツ社製ＳＳＣ５２００ ＴＧＡ ３２０において、窒素中１０℃／分で昇温し重量減少を測定した。そして、重量減が３％に達したときの温度を熱分解温度とした。
▲２▼ポリイミドフィルムのガラス点移転温度
ポリイミドフィルムをセイコ−インスツルメンツ社製ＳＳＣ５２００ ＤＳＣ ３２０Ｃにおいて、窒素中２０℃／分で昇温し示差熱を測定した。
【００２８】
以下の各例において、耐熱性不織布の物性は以下の方法によって求めた。
▲３▼目付
不織布の重量を面積で除して目付（ｇ／ｍ２）を求めた。
▲４▼厚み
ＤＩＡＬ ＴＨＩＣＫＮＥＳＳ ＧＡＵＧＥ（心棒の直径：１０ｍｍ、最小メモリ：０．０１ｍｍ）を使用して測定した。
▲５▼強度
ＪＩＳ Ｐ８１１３に準じて、幅２５ｍｍ、つかみ間隔１００ｍｍ、引張り速度：５０ｍｍ／ｍｉｎ．でＮＭＢミネベア社製インストロン型万能試験機：型番ＴＣＭ５００００Ｄを使用し引張り強度を測定した。
【００２９】
▲６▼伸度
強度と同様の方法で引張り破断時の伸度を測定した。
▲７▼加熱雰囲気下での引張り試験
板橋理化工業社製ＩＲＫ式低温度ブライン高温槽：型番ＬＴＢ型を引張り試験機にセットし、所定の温度に昇温完了後引張り試験を行った。
▲８▼裂断長計算方法
裂断長＝［引張り強度］×１０００／［Ｂ（ｍｍ）×Ｗ（ｇ／ｍ２）］
Ｗ：目付、Ｂ：試料幅
▲９▼耐熱性不織布の引張り強度高温保持率（％）
引張り強度高温保持率＝２００での引張り強度／常温での引張り強度
【００３０】
実施例１
［ポリイミド前駆体水溶液の製造］
ＴＰＥ−Ｒ２９．２３ｇ（０．１ｍｏｌ）とＤＭＡｃ２３４．６０ｇを、攪拌機、還流冷却器（水分離器付き）、温度計、窒素導入管を備えた容量１０００ｍｌの四つ口セパラブルフラスコに、室温において添加し、その混合液に窒素ガス流通と攪拌しながら、ａ−ＢＰＤＡ２９．４２ｇ（０．１ｍｏｌ）を添加し、２時間反応しポリイミド前駆体溶液を得た。
【００３１】
そして、この溶液をＤＭＡｃ２９３．２５ｇで希釈し３０℃において１．５ポイズとし、またこの溶液にＤＭＺを５．８７ｇ（０．０６ｍｏｌ）を添加し、この溶液をホモジナイザー（ヤマト科学株式会社製オムニミキサ−ＬＴ）を備えたアセトン浴（６．５Ｌ）に徐々に加えポリイミド前駆体化合物粉末を析出させた。この懸濁液は、濾過およびアセトン洗浄し、４０℃で１０時間真空乾燥して、６３．４２ｇのポリイミド前駆体の粉末を得た。
このポリイミド前駆体粉末３ｇに対して、水２６．１０ｇおよびＤＭＺ０．９ｇ（０．００９４ｍｏｌ）を加え６０℃で攪拌しながら２時間で溶解し均一液とした後、加圧下７μｍのフィルタ−で濾過し、ポリイミド前駆体水溶液を得た。
このポリイミド前駆体水溶液に水を添加し２．５重量％及び１．５重量％の濃度のポリイミド前駆体水溶液（ド−プ）とした。
【００３２】
［ポリイミドの製造、物性測定］
この溶液をガラス基板上に塗布し、空気中において６０℃で１０分間、１００℃で１０分間、１５０℃で１０分間、１８０℃で１０分間、２１０℃で１０分間、３００℃で１０分間の加熱処理しポリイミド膜を得た。
このポリイミド膜は、熱分解温度が５２５℃であり、ガラス転移温度が２５７℃であり、引張破断強度が９６９Ｋｇｆ／ｃｍ２で、引張り破断伸びが７０％で、Ｘ線解析により非結晶性であることが確認された。
【００３３】
以下の手順に従って耐熱性不織布を得た。
［耐熱性不織布の製造］
１．不織布化方法
抄紙法：ＫＥＶＬＡＲ：ケブラ−短繊維（ドライパルプ、チョップドファイバ−、ＥＧカット）を、水１０リットル中に均一に分散させ、寸法２５０ｍｍ×２００ｍｍのメッシュ上に抄紙して湿潤ウエッブを作成した。
カ−ド法：ＫＥＶＬＡＲ：ケブラ−ステプ−ルをロ−ラ−カ−ド機に通し、ウエッブを作成した。
なお、使用したＫＥＶＬＡＲ短繊維の品種は以下の通りである。
ＫＥＶＬＡＲステプ−ル：９７０−１．７Ｔ３８−７
ＫＥＶＬＡＲドライパルプ：９７９−Ｓ−ＰＬ−Ｆ５３８−Ａ１１−１
ＫＥＶＬＡＲチョップドファイバ−：９７０−１．７Ｔ６−７
ＫＥＶＬＡＲＥＧカット：９６５−１．７Ｔ３−０１
【００３４】
２．ド−プ含浸条件
条件：抄紙法またはカ−ド法で得られた湿潤ウエッブをテトラン布（東レ社、品番９９００）で挟み、更に両側から濾紙で挟み、過剰な水分を除去し、１２０℃程度に加熱したオ−ブン中で完全に水分を除く。その後、ウエッブのみを５０メッシュのＳＵＳ製金網で挟み、２．５重量％または１．０重量％のポリイミド前駆体ド−プに１分間漬け込む。過剰なド−プ液を濾紙に挟んで除去する。
３．熱可塑性ポリイミド量
熱可塑性ポリイミド量：抄紙後の乾燥ウエッブ重量とイミド化後の不織布重量との差から求めた。
【００３５】
４．イミド化
条件：予め１００℃に調節したファインオ−ブン中でド−プ含浸ウエッブを３０分間乾燥した後、２８５℃に設定程度を上げイミド化を行った。
この際の加熱条件は、１００〜２３０℃：約３０分、２３０〜２５０℃：約１０分、２５０〜２８５℃：約２０分であった。
【００３６】
５．熱圧着
条件：予め３００〜４００℃程度にぷプレス温度設定しておき、前記のイミド化不織布を耐熱性フィルム（例えば、ポリイミドフィルム）に挟み、プレス圧３００Ｋｇｆ／ｃｍ２（最高使用圧力、面圧：３００Ｋｇｆ／ｃｍ２）で加熱圧着し、直ぐに圧力を下げ取り出して、耐熱性不織布を得た。
結果をまとめて表１に示す。
【００３７】
実施例２〜７
ＫＥＶＬＡＲの種類、不織布化方法、含浸ド−プ濃度および熱可塑性ポリイミド（ＰＩ）の量を表１に示すように変えた他は実施例１と同様にして、耐熱性不織布を得た。
結果をまとめて表１に示す。
【００３８】
【表１】
【表２】
【表３】
比較例１
実施例２で合成したポリイミド前駆体粉末３ｇに、水１６．２ｇおよび２ＭＺ０．７７ｇ（０．００９４ｍｏｌ）を加えたが、ポリイミド前駆体粉末は溶解しなかった。
【００４２】
【発明の効果】
この発明は以上詳述したような構成を有しているため、下記のような効果を奏する。
この発明によれば、加熱工程において有機溶媒を実質的に使用することなく耐熱性不織布を製造することができる。
また、この発明によれば、耐熱性および強度を保持している耐熱性不織布を得ることができる。[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a heat-resistant nonwoven fabric and a binder resin, and in particular, can be produced without substantially using an organic solvent in a heating process, and a molded body having heat resistance and strength, and It relates to the binder resin used.
[0002]
[Prior art]
In recent years, nonwoven fabrics with excellent long-term heat resistance have been demanded as technological developments for downsizing and weight reduction have progressed in the fields of electric and electronic industries and automobiles and aerospace. Further, a heat-resistant nonwoven fabric having long-term heat resistance as a heat insulating material or a filter is required for a drying furnace or the like of a painting line of an automobile or the like.
[0003]
Conventionally, as a heat-resistant nonwoven fabric, a nonwoven fabric in which aramid fibers are fixed with a binder made of phenol resin, epoxy resin or thermoplastic polyester has been developed. Below it could not be used for a long time. In addition, a heat-resistant nonwoven fabric in which a water-soluble polyimide varnish or the like is used as a binder has been developed. However, even in an atmosphere of 200 ° C. or higher, the strength is greatly lowered and is not practical. These heat-resistant non-woven fabrics have a big problem that the heat resistance of the binder is insufficient, although the heat resistance of the fibers constituting the non-woven fabric is sufficient.
[0004]
As an improvement of the heat resistance of this binder, a polyimide binder having an unsaturated bond is described in JP-A-6-184903.
However, the binder described as an example in the above publication is used as an organic solvent solution, which is not necessarily advantageous in terms of the working environment, and uses are limited.
[0005]
[Problems to be solved by the invention]
Therefore, the present inventors can apply to a heat-resistant non-woven fabric having a high form-retaining property, even when placed in an atmosphere of 200 ° C. or higher, and can be applied to a heat-resistant nonwoven fabric. As a result of earnest research for the purpose of providing a novel polyimide resin binder that can be used in the state of an aqueous solution when mixed with and a heat-resistant nonwoven fabric using the same, the present invention has been completed.
[0006]
[Means for Solving the Problems]
That is, the present invention relates to a polyimide resin obtained from a water-soluble polyimide precursor containing 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole and a binder resin of a fiber made of heat-resistant resin. It relates to a heat-resistant nonwoven fabric.
The present invention also relates to a binder comprising a polyimide obtained from a water-soluble polyimide precursor containing 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole used for a heat-resistant nonwoven fabric. -Relating to resins;
[0007]
Moreover, this invention relates to the binder resin which consists of a polyimide obtained from the water-soluble polyimide precursor used for a heat resistant nonwoven fabric, and the tensile strength retention in 200 degreeC about a heat resistant nonwoven fabric is 70% or more.
Furthermore, the present invention relates to a heat-resistant nonwoven fabric in which a polyimide obtained from a water-soluble polyimide precursor is used as a binder resin and the tensile strength retention at 200 ° C. is 70% or more.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the present invention are listed below.
1) Said heat resistant nonwoven fabric whose polyimide is non-crystalline by X-ray analysis.
2) The above heat-resistant nonwoven fabric, wherein the polyimide is obtained by using 50% or more of the tetracarboxylic acid component as the 2,3,3 ′, 4′-biphenyltetracarboxylic acid component.
3) The above heat-resistant nonwoven fabric, wherein the heat-resistant resin fibers are aromatic polyamide fibers such as aramid fibers.
[0009]
In this invention, 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole is preferably used in an amount of 0.2-fold molar equivalent or more of 1,2-dimethylimidazole. It is suitable to contain dimethylimidazole and / or 1-methyl-2-ethylimidazole.
By using the 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole together with the polyimide precursor, an aqueous solution of the polyimide precursor is obtained, and the heat of the polyimide molded body obtained is obtained. Good mechanical and mechanical properties.
[0010]
In place of the 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole, other diamine compounds such as diethylamine, triethanolamine, N-methyldiethanolamine, 3-diethylamino When -1-propanol or the like is used, the polyimide precursor becomes an aqueous solution, but the thermal characteristics and mechanical characteristics of the resulting polyimide molded body are deteriorated, which is not preferable.
[0011]
The polyimide that gives the water-soluble polyimide precursor has 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic acid as a tetracarboxylic acid component. Dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, dianhydride of 2,2′-bis (3,4-dicarboxyphenyl) propane, Obtained by using bis (3,4-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, tetracarboxylic acids or half esters of these Can do. A part or all of the aromatic tetracarboxylic acid component may be replaced with an alicyclic tetracarboxylic acid component. In particular, the tetracarboxylic acid component is preferably one in which 50% or more is a 2,3,3 ′, 4′-biphenyltetracarboxylic acid component.
[0012]
Moreover, the polyimide which gives the said water-soluble polyimide precursor is arbitrary aromatic diamine, for example, paraphenylenediamine (p-phenylenediamine), 4,4'- diaminodiphenyl ether, 1, as an aromatic diamine component. 3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylethane, 4,4′-diaminodiphenylmethane, 2,2′-bis [4- (4-aminophenoxy) phenyl] propane, 2,2′-bis [4- (4-aminophenoxy) phenyl] 1,1,1,3,3,3-hexafluoro Propane, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] sulfone It can be obtained by use, but can be suitably obtained using 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene. A part of the aromatic diamine may be replaced with an alicyclic diamine or diaminopolysiloxane.
[0013]
In the present invention, the polyimide is preferably amorphous by X-ray analysis.
Further, the polyimide in the present invention preferably has a thermal decomposition temperature of 500 ° C. or higher, preferably a glass transition temperature (Tg) higher than 200 and 350 ° C. or lower, particularly 250 to 350 ° C.
In this invention, the binder to be thermocompression bonded to the nonwoven fabric made of heat-resistant fibers is required to have a polyimide resin obtained by imidizing the polyimide precursor as a main component. Other water-resistant resins (or resin precursors) may be blended as long as they are water-soluble.
[0014]
In the present invention, the polyimide precursor aqueous solution is preferably prepared by adding each component in a water-soluble ketone and / or amide solvent so that the concentration of the polyimide precursor is about 0.1 to 30% by weight. A polyimide precursor obtained by reacting a tetracarboxylic dianhydride and an aromatic diamine at 0 to 40 ° C. for about 30 minutes to 24 hours, After reacting with 2-dimethylimidazole and / or 1-methyl-2-ethylimidazole, precipitation from the reaction mixture or precipitation with an organic poor solvent such as acetone The product is collected by filtration, the polyimide precursor is powdered, dried at a temperature of 100 ° C. or less, and this powder and further 0.2 times the molar equivalent of the carboxyl group of the polyimide precursor in water, 0.7-fold molar equivalent or more (total amount), preferably 0.9-fold molar equivalent or more (total amount) of 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole. It is preferable to obtain by adding and mixing uniformly. 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole may be added in advance to water.
The polyimide precursor aqueous solution preferably has a viscosity (30 ° C.) of about 0.2 to 800 poise.
[0015]
Examples of the amide solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, and N-methylcaprolactam, and particularly N-methyl-2-pyrrolidone, N, N -Dimethylacetamide is preferably used.
Examples of the water-soluble ketones include acetone, γ-butyrolactone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-butyl ketone, and cyclohexanone.
[0016]
In the present invention, during the reaction of the tetracarboxylic dianhydride and the aromatic diamine, preferably after the reaction, a polyimide precursor (polyamic acid), 1,2-dimethylimidazole and / or 1-methyl-2 -A method is preferred in which ethyl imidazole is allowed to coexist and react to separate the polyimide precursor powder from the reaction mixture, and the resulting powder is mixed with water to obtain a polyimide precursor aqueous solution.
[0017]
When the amount of 1,2-dimethylimidazole and / or 1-methyl-2-ethylimidazole is separated from the reaction mixture as a powder, the carboxyl group of the polyimide precursor The amount is preferably 0.2 times the molar equivalent or more. If the amount is less than the above ratio, the polyimide precursor is tarred and it is not easy to separate the polyimide precursor from the reaction mixture as a powder.
Moreover, when setting it as the aqueous solution of a polyimide precursor, it is preferable that it is the quantity of 0.7 times molar equivalent or more (total) of the carboxyl group of a polyimide precursor. If the amount is less than the above ratio, it is difficult to obtain a uniform aqueous solution of the polyimide precursor.
[0018]
In this invention, as a method of obtaining a polyimide resin as a binder from an aqueous polyimide precursor solution, for example, an aqueous polyimide precursor solution is cut into, for example, an EG cut of a heat-resistant fiber (after spinning to a length of about 3 mm or 6 mm) And those having improved electrical insulation are referred to as EG), chopped fiber, staple, dry pulp, and heating to imidize.
[0019]
Examples of the heat resistant fiber in this invention include wholly aromatic polyamide fiber, glass fiber, carbon fiber, wholly aromatic polyester fiber, PPS fiber, polyparaphenylene sulfone fiber, polyimide fiber and the like. Among them, wholly aromatic polyamide fibers, wholly aromatic polyester fibers, polyimide fibers and the like are preferable, and aromatic polyamide fibers such as Kevlar (DuPont, Toray DuPont) are particularly preferable because of their availability and performance.
In addition to heat-resistant fibers, inorganic particulate fillers such as artificial diamond, silica, mica, kaolin, boron nitride, aluminum oxide, iron oxide, graphite, molybdenum sulfide and iron sulfide, and organic or inorganic pigments and colorants are used in combination. May be. There is no restriction | limiting in particular as these addition methods, For example, you may add to a polyimide precursor aqueous solution.
[0020]
The heat-resistant nonwoven fabric of this invention is a mixture of polyimide precursor aqueous solution and heat-resistant fiber, preferably a laminate of these, and a temperature of about 100-450 ° C., preferably a temperature above the glass transition temperature of polyimide, especially A heat-resistant nonwoven fabric can be formed by heating at a temperature of about 20 ° C. to 450 ° C. for 5 to 120 minutes from the glass transition temperature of polyimide, followed by heat compression molding.
[0021]
As a method for producing a heat-resistant nonwoven fabric in the present invention, first, a paper-making method in which short fibers of heat-resistant fibers (chopped fiber, dry pulp) are dispersed in a large amount of water and paper is made on a net to create a wet web. Alternatively, a wet web is obtained by a card method in which staples of heat-resistant fibers are passed through a roller card machine to create a web.
[0022]
Next, the wet web is sandwiched between thick synthetic resin cloths such as tetran cloth, and further sandwiched between water-absorbent substrates (for example, filter paper) from both sides to remove excess moisture, and then 120 ° C. in a heating furnace. Heat to an extent to remove moisture and obtain a dry web. Then, only the web is sandwiched between wire meshes (for example, a SUS wire mesh of about 50 mesh), and immersed in a dope that is the polyimide precursor aqueous solution for a predetermined time (about 0.1 to 5 minutes). The liquid is sandwiched between water-absorbing substrates (for example, filter paper) to obtain a dope-impregnated web.
[0023]
Next, after the dope-impregnated web is dried in a heating furnace adjusted to about 100 ° C. for about 10 to 30 minutes, the temperature is equal to or higher than the glass transition temperature of the thermoplastic polyimide resin, preferably 210 to 400 ° C. It is imidized by heating at about 250 to 400 ° C. for about 10 to 60 minutes to obtain an imidized nonwoven fabric.
Under the present circumstances, the quantity of the thermoplastic polyimide resin which is a binder can be calculated | required from the difference of the said dry web weight and the nonwoven fabric weight after imidation.
[0024]
Subsequently, the press temperature is set to about 300 to 400 ° C. in advance, the imidized nonwoven fabric is sandwiched between heat resistant films (for example, polyimide film), and heat-pressed with a press pressure of about 1 to 300 kgf / cm 2 , A heat resistant nonwoven fabric can be obtained.
[0025]
The heat-resistant nonwoven fabric obtained by the present invention does not cause the problem of fluff removal because it uses a binder resin, and is obtained by thermoforming a thermoplastic polyimide that is a binder resin, and has good thermal properties and It exhibits mechanical properties, in particular, the tensile strength retention at 200 ° C. for the heat-resistant nonwoven fabric is 70% or more.
[0026]
【Example】
In the following description, each abbreviation means the following compound.
a-BPDA: 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride TPE-R: 1,3-bis (4-aminophenoxy) benzene DMZ: 1,2-dimethylimidazole DMAc: N , N-dimethylacetamide [0027]
In each of the following examples, the physical properties of polyimide were determined by the following method.
(1) Thermal Decomposition Temperature of Polyimide Film A polyimide film was heated at 10 ° C./min in nitrogen using SSC5200 TGA 320 manufactured by Seiko Instruments Inc., and the weight loss was measured. And the temperature when weight loss reached 3% was made into thermal decomposition temperature.
(2) Glass point transition temperature of polyimide film The polyimide film was heated at 20 ° C./min in nitrogen using SSC5200 DSC 320C manufactured by Seiko Instruments Inc., and the differential heat was measured.
[0028]
In each of the following examples, the physical properties of the heat resistant nonwoven fabric were determined by the following methods.
( 3 ) The basis weight (g / m 2 ) was determined by dividing the weight of the nonwoven fabric per unit area by the area.
(4) Thickness DIAL THICKNESS GAUGE (diameter of mandrel: 10 mm, minimum memory: 0.01 mm) was measured.
(5) Strength In accordance with JIS P8113, width 25 mm, gripping interval 100 mm, pulling speed: 50 mm / min. Instron type universal testing machine manufactured by NMB Minebea Co., Ltd .: Tensile strength was measured using model number TCM50000D.
[0029]
(6) The elongation at the time of tensile fracture was measured by the same method as the elongation strength.
(7) Tensile test in heated atmosphere IRK type low temperature brine high temperature bath manufactured by Itabashi Rika Kogyo Co., Ltd .: Model LTB type was set in a tensile tester, and a tensile test was performed after completion of temperature rise to a predetermined temperature.
(8) Breaking length calculation method Breaking length = [Tensile strength] × 1000 / [B (mm) × W (g / m 2 )]
W: Weight per unit area, B: Sample width (9) Tensile strength of heat-resistant nonwoven fabric at high temperature (%)
Tensile strength retention at high temperature = tensile strength at 200 / tensile strength at room temperature
Example 1
[Production of polyimide precursor aqueous solution]
29.23 g (0.1 mol) of TPE-R and 234.60 g of DMAc were placed in a four-necked separable flask having a capacity of 1000 ml equipped with a stirrer, a reflux condenser (with a water separator), a thermometer, and a nitrogen introduction tube at room temperature. Then, 29.42 g (0.1 mol) of a-BPDA was added to the mixed solution with nitrogen gas flow and stirring, and reacted for 2 hours to obtain a polyimide precursor solution.
[0031]
The solution was diluted with 293.25 g of DMAc to 1.5 poise at 30 ° C., and 5.87 g (0.06 mol) of DMZ was added to this solution, and this solution was added to a homogenizer (Omnimixer manufactured by Yamato Scientific Co., Ltd.). It was gradually added to an acetone bath (6.5 L) equipped with (LT) to precipitate a polyimide precursor compound powder. This suspension was filtered, washed with acetone, and vacuum-dried at 40 ° C. for 10 hours to obtain 63.42 g of polyimide precursor powder.
To 3 g of this polyimide precursor powder, 26.10 g of water and 0.9 g (0.0094 mol) of DMZ were added, dissolved in 2 hours with stirring at 60 ° C. to obtain a uniform solution, and then filtered through a 7 μm filter under pressure. Thus, an aqueous polyimide precursor solution was obtained.
Water was added to the polyimide precursor aqueous solution to obtain polyimide precursor aqueous solutions (dope) having concentrations of 2.5 wt% and 1.5 wt%.
[0032]
[Production of polyimide, measurement of physical properties]
This solution is applied on a glass substrate and heated in air at 60 ° C. for 10 minutes, 100 ° C. for 10 minutes, 150 ° C. for 10 minutes, 180 ° C. for 10 minutes, 210 ° C. for 10 minutes, and 300 ° C. for 10 minutes. It processed and obtained the polyimide film.
This polyimide film has a thermal decomposition temperature of 525 ° C., a glass transition temperature of 257 ° C., a tensile breaking strength of 969 Kgf / cm 2 , a tensile breaking elongation of 70%, and is amorphous by X-ray analysis. It was confirmed.
[0033]
A heat-resistant nonwoven fabric was obtained according to the following procedure.
[Manufacture of heat-resistant nonwoven fabric]
1. Nonwoven manufacturing method Papermaking method: KEVLAR: Kevlar-short fibers (dry pulp, chopped fiber, EG cut) are uniformly dispersed in 10 liters of water, and paper is made on a mesh with dimensions of 250 mm x 200 mm to create a wet web. did.
Card method: KEVLAR: A Kevlar staple was passed through a roller card machine to prepare a web.
The varieties of KEVLAR short fibers used are as follows.
KEVLAR step: 970-1.7T38-7
KEVLAR dry pulp: 979-S-PL-F538-A11-1
KEVLAR chopped fiber-970-1.7T6-7
KEVLAREG cut: 965-1.7T3-01
[0034]
2. Doping impregnation condition: A wet web obtained by a paper making method or a card method is sandwiched between tetrane cloths (Toray Industries Inc., product number 9900) and further sandwiched with filter paper from both sides to remove excess moisture, and about 120 ° C. Remove moisture completely in the oven heated to 1. Thereafter, only the web is sandwiched between 50 mesh SUS metal nets and immersed in a 2.5% by weight or 1.0% by weight polyimide precursor dope for 1 minute. Excess dope is removed with filter paper.
3. Thermoplastic polyimide amount Thermoplastic polyimide amount: It was determined from the difference between the dry web weight after papermaking and the non-woven fabric weight after imidization.
[0035]
4). Imidization conditions: After the dope-impregnated web was dried for 30 minutes in a fine oven adjusted to 100 ° C. in advance, the setting was raised to 285 ° C. and imidization was performed.
The heating conditions at this time were 100 to 230 ° C .: about 30 minutes, 230 to 250 ° C .: about 10 minutes, and 250 to 285 ° C .: about 20 minutes.
[0036]
5. Thermocompression bonding conditions: The press temperature is set to about 300 to 400 ° C. in advance, and the imidized non-woven fabric is sandwiched between heat resistant films (for example, polyimide film), and the press pressure is 300 kgf / cm 2 (maximum use pressure, surface pressure). : 300 kgf / cm 2 ), and pressure-removed immediately to obtain a heat-resistant nonwoven fabric.
The results are summarized in Table 1.
[0037]
Examples 2-7
A heat-resistant nonwoven fabric was obtained in the same manner as in Example 1 except that the type of KEVLAR, the nonwoven fabric forming method, the impregnation dopant concentration and the amount of thermoplastic polyimide (PI) were changed as shown in Table 1.
The results are summarized in Table 1.
[0038]
[Table 1]
[Table 2]
[Table 3]
Comparative Example 1
Although 16.2 g of water and 0.77 g (0.0094 mol) of 2MZ were added to 3 g of the polyimide precursor powder synthesized in Example 2, the polyimide precursor powder did not dissolve.
[0042]
【The invention's effect】
Since the present invention has the configuration as described in detail above, the following effects can be obtained.
According to this invention, a heat resistant nonwoven fabric can be manufactured without substantially using an organic solvent in a heating process.
Moreover, according to this invention, the heat resistant nonwoven fabric holding heat resistance and intensity | strength can be obtained.
Claims (5)
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| Application Number | Priority Date | Filing Date | Title |
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| JP2001201268A JP4039011B2 (en) | 2001-07-02 | 2001-07-02 | Heat resistant nonwoven fabric and binder resin |
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| JP2001201268A JP4039011B2 (en) | 2001-07-02 | 2001-07-02 | Heat resistant nonwoven fabric and binder resin |
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| JP2007247090A Division JP5186855B2 (en) | 2007-09-25 | 2007-09-25 | Binder resin |
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| JP4039011B2 true JP4039011B2 (en) | 2008-01-30 |
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Cited By (2)
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| JP2008050611A (en) * | 2007-09-25 | 2008-03-06 | Ube Ind Ltd | Binder resin |
| KR101595729B1 (en) | 2013-12-30 | 2016-02-19 | 코오롱인더스트리 주식회사 | Bullet-proof material and method for manufacturing the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008050611A (en) * | 2007-09-25 | 2008-03-06 | Ube Ind Ltd | Binder resin |
| KR101595729B1 (en) | 2013-12-30 | 2016-02-19 | 코오롱인더스트리 주식회사 | Bullet-proof material and method for manufacturing the same |
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