JP3929342B2 - Method for producing dense meta-type wholly aromatic polyamide fiber - Google Patents

Description

【００２６】
かかるメタ型芳香族ジアミンの具体例としては、メタフェニレンジアミン、２，４−トリレンジアミン、２，６−トリレンジアミン、２，４−ジアミノクロルベンゼン、２，６−ジアミノクロルベンゼン等が挙げられる。その他のメタ型芳香族ジアミンとしては、３，４’−ジアミノジフェニルエーテル、３，４’−ジアミノジフェニルスルホン等が挙げられる。
【００２７】
本発明では、なかでも、メタフェニレンジアミンまたはこれを主体とする混合ジアミンが好ましい。メタフェニレンジアミンと併用する他の芳香族ジアミンとしては、上記のメタ型芳香族ジアミンのほかにパラフェニレンジアミン、２，５−ジアミノクロルベンゼン、２，５−ジアミノブロムベンゼン、アミノアニシジン等のようなベンゼン誘導体、１，５−ナフチレンジアミン、４，４’−ジアミノジフェニルエーテル、４，４’−ジアミノジフェニケトン、ビス（アミノフェニル）フェニルアミン、ビス（パラアミノフェニル）メタン等が用いられる。
【００２８】
溶解性の良い重合体が望まれる場合には、このような他の芳香族ジアミンは全体の２０モル％程度まで使用可能であるが、高結晶性の重合体が望まれる場合には、メタフェニレンジアミンが９０モル％以上、特に９５モル％以上含まれることが好ましい。
【００２９】
一方、本発明で使用する芳香族ジカルボン酸クロライドは、イソフタル酸クロライドまたはこれを主体とする芳香族ジカルボン酸クロライドである。イソフタル酸クロライドと併用し得る他の芳香族ジカルボン酸クロライドとしては、テレフタル酸クロライド、１，４−ナフタレンジカルボン酸クロライド、２，６−ナフタレンジカルボン酸クロライド、４，４’−ビフェニルジカルボン酸クロライド、５−クロルイソフタル酸クロライド、５−メトキシイソフタル酸クロライド、ビス（クロロカルボニルフェニル）エーテル等が挙げられる。
【００３０】
本発明の実施に当たって、溶解性の良好な重合体が望まれる場合は、これらの他の芳香族ジカルボン酸の高率（２０モル％程度まで）混合も可能であるが、高結晶性の重合体が望まれる場合は、イソフタル酸クロライドが９０モル％以上、特に９５モル％以上含まれることが好ましい。
【００３１】
上記のメタ型全芳香族ポリアミドの中でも、全ポリマー繰返し単位の９０〜１００モル％がメタフェニレンイソフタルアミド単位である重合体であって、塩類を実質的に含まないものが好適に使用される。
【００３２】
本発明においては、上記メタ型全芳香族ポリアミドがアミド系溶媒に溶解しており、かつ塩類（無機イオン性物質）を実質的に含まない重合体溶液を、後述する工程に供給する。かかる重合体溶液は、上記溶液重合等で得られたメタ型全芳香族ポリアミドを含むアミド系溶媒溶液から塩類を除去したものを用いてもよいし、上記溶液重合、界面重合等で得られたメタ型全芳香族ポリアミドを含む溶液から該メタ型全芳香族ポリアミドを単離し、これをアミド系溶媒に溶解したものを用いてもよい。ここで「塩類を実質的に含まない」とは、重合体溶液中の塩類の合計量が０．１重量％未満であることを意味し、ごく少量の塩類が含有することは許容されるが、その量は少なければ少ない方がよく０〜０．０１重量％であることが好ましい。
【００３３】
ここで用いられるアミド系溶媒としては、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン、ジメチルイミダゾリジノン等を例示することができるが、特に、溶液重合から湿式紡糸工程に至るまでの重合体溶液の安定性等から、Ｎ−メチル−２−ピロリドンが好ましい。
【００３４】
本発明において紡糸原液に用いる重合体溶液は、水を含んでいてもよい。このような水は必要に応じて添加することもあるが、溶液調製プロセスで必然的に生成するものであってもかまわない。その濃度としては、溶液が安定に存在する範囲であるならばいかなる濃度でもかまわないが、例えばポリマー重量に対して０〜６０重量％の範囲で添加、含有されるのが通常好ましく、特に１５重量％以下であることが好ましい。これを超える濃度では、ポリマー溶液の安定性が損なわれ、ポリマーの析出、ゲル化によって紡糸性が著しく損なわれることがある。
【００３５】
本発明において、重合体溶液を凝固浴中に吐出する場合、紡糸口金としては５００ホール以上の多ホールのものを用いる。実用上ホール数の上限は約５００００ホールであり、好ましくは１０００〜３００００ホール、特に３０００〜１００００ホールの紡糸口金が使用される。
【００３６】
本発明における凝固浴は、塩類を実質的に含まず、アミド系溶媒と水（Ｈ₂Ｏ）との２成分から実質的になる水溶液で構成される。この凝固浴組成において、アミド系溶媒としてはメタアラミドを溶解し、水と良好に混和するものであれば好適に用いることができるが、特に、Ｎ−メチル−２−ピロリドン、ジメチルアセトアミド、ジメチルホルムアミド、ジメチルイミダゾリジノン等を好適に用いることができる。溶媒の回収等を考慮すれば、紡糸原液中のアミド系溶媒と同じ種類のものを使用するのが好ましい。
【００３７】
アミド系溶媒と水との最適な混合比は、重合体溶液の条件によっても若干変化するが、凝固浴液中のアミド系溶媒の濃度が４０〜７０重量％、特に５０〜６５重量％、さらには５５〜６２重量％の範囲であることが好ましい。アミド系溶媒の濃度がこの範囲を下回る条件では、糸中に非常に大きなボイドが生じやすくなり、その後の糸切れの原因となりやすい。一方、この範囲を上回る条件では、凝固が進まず、糸条物同士の融着が起こりやすくなる。
【００３８】
凝固浴の温度は凝固液組成と密接な関係があるが、一般的には高温である方が、生成糸条物中にフィンガーとよばれる粗大な気泡上の空孔ができ難くなるので好ましい。しかし凝固液濃度が高い場合には、あまり高温にすると糸条物同士の融着が激しくなるので、凝固浴の好適な温度は４０〜７０℃であり、より好ましくは４５〜６５℃の範囲である。
【００３９】
凝固液は、実質的にアミド系溶媒と水だけで構成されることが好ましいが、これ以外に塩類が少量含まれていても差し支えない。特に、塩化カルシウム、水酸化カルシウム等の塩類は、微量残存しているポリマー溶液中から抽出されてくることがあるが、これは多孔凝固に対して何らこれを阻害することはなく、例えば凝固液に対し１０重量％以下、特に１重量％以下の低濃度であれば塩類が含まれていても問題はない。したがって、塩類の好適濃度は凝固液に対し０〜１０重量％の範囲である。凝固浴中での糸条物の浸漬時間は０．１〜３０秒が好ましい。浸漬時間が短かすぎると糸条物の形成が不十分となり断糸が発生するおそれがある。
【００４０】
本発明における可塑延伸浴としてはアミド系溶媒の水性溶液が用いられる。このアミド系溶媒としてはメタ型全芳香族ポリアミドを膨潤させ、水と良好に混和するものであれば好適に用いることができるが、特にＮ−メチル−２−ピロリドン、ジメチルアセトアミド、ジメチルホルムアミド、ジメチルイミダゾリジノン等は好適に用いることができる。またさらに好適には、凝固浴に用いたものと同じ溶媒を用いることが好ましい。凝固浴と同種の溶媒を用いれば、回収工程が簡略化され、経済的に有益である。
【００４１】
すなわち、重合体溶液、凝固浴および可塑延伸浴中のアミド系溶媒はすべて同種のものを使用するのが好ましく、かかる溶媒として、Ｎ−メチル−２−ピロリドン、ジメチルアセトアミド、ジメチルホルムアミドを単独で使用するかまたは２種以上を併用することが好都合である。
【００４２】
可塑延伸浴の組成と温度とはそれぞれ密接な関係にあるが、該水溶液中のアミド系溶媒の濃度２０〜７０重量％、温度２０〜９０℃の範囲が好適に用いられる。この範囲より低い領域では可塑化が十分に進まず、十分な延伸倍率をとることが困難であり、これを上回る範囲では糸の表面が溶解して融着しやすく良好な紡糸が困難になることが多い。
【００４３】
本発明の可塑延伸においては、通常１．５〜１０倍、好ましくは２〜１０倍の倍率で延伸するが、特に２．１〜６．０倍の倍率で延伸することがより好ましい。このように高倍率に延伸をかけることにより、メタアラミド繊維の強度、弾性率が向上し良好な物性を示すようになると同時に、多孔構造の孔が引きつぶされ、可塑延伸後に行われる熱処理による緻密化が良好に進行するようになる。但し、極端に高倍率に延伸した場合には、工程の調子が悪化して良好な製糸が困難になる。
【００４４】
上記可塑延伸浴の工程を経た浴上がりの糸条物は、次に、水あるいはアミド系溶媒を含んだ水にて、繊維中の含水率および含アミド系溶媒率が下記式（ａ）および（ｂ）を満足するように調整することが肝要である。
（ａ）０．３≦Ｎ／（Ｐ＋Ｎ）≦０．７、好ましくは０．３５≦Ｎ／（Ｐ＋Ｎ）≦０．６５
（ｂ）０．４≦Ｗ／（Ｐ＋Ｗ）≦０．７、好ましくは０．４５≦Ｗ／（Ｐ＋Ｗ）≦０．６５
但し、Ｐ、Ｎ、Ｗは、それぞれ繊維中の含ポリマー重量率、含アミド系溶媒重量率、含水重量率を表す。
【００４５】
含水率および含アミド系溶媒率を上記範囲に調整することにより、引続いて施される１００〜２５０℃の温度範囲での熱処理において、該熱処理時のポリマーの流動性が向上する。そして、引続きアミド系溶媒が蒸発して繊維から脱却する際に、配向および結晶化が促進されると考えられる。また、適量の水とアミド系溶媒とが共存することにより、これらが共沸してアミド系溶媒の蒸発を促進するものと考えられる。
【００４６】
なお、含水率および含アミド系溶媒率を上記範囲に調整する方法としては、可塑延伸後に１０〜７０℃の水浴あるいは１０〜４０℃のアミド系溶媒／水の混合浴等を通過させ、浸漬長を糸掛けターン数により調整するなどして容易に行なうことができる。
【００４７】
このようにして、繊維中の含水率および含アミド化合物溶媒率が調整された糸条は、加熱ローラ、加熱板、熱風等によって一旦１００〜２５０℃、好ましくは１００〜２００℃の温度範囲にて熱処理、好ましくは乾熱処理が施される。この１００〜２５０℃の温度範囲での熱処理工程は、多孔質の線状体のポリマーの配向および結晶化を促進せしめて、繊維の熱収縮安定性を発現させるために重要な工程である。熱処理温度が１００℃未満であると、水やアミド系溶媒の蒸発が著しく遅くなるため、生産性が低下するばかりでなく、結晶化の促進も妨げられるので好ましくない。一方２５０℃を超えると、アミド系溶媒の分解が一気に起こり結晶化促進の効果が十分に現れない懸念があり好ましくない。また、繊維の着色も起こり好ましくない。本熱処理においては、０．８〜３．０倍、好ましくは１．０〜２．０倍の延伸（１倍以下は収縮熱処理）下で、特に１．０〜１．５倍の延伸下で熱処理することが好ましい。
【００４８】
なお、先述のＮ／（Ｐ＋Ｎ）が０．３未満であると、この熱処理時のポリマー流動性向上への効果が発現しなく、良好な繊維物性が得られないので好ましくない。一方０．７を超えると、アミド化合物溶媒の蒸発に時間がかかり生産性およびエネルギー的に不利であり、また繊維の着色も起こり好ましくない。
【００４９】
また、Ｗ／（Ｐ＋Ｗ）が０．４未満であると、熱処理時に繊維同士が融着して繊維物性の低下を招く懸念があるので好ましくない。一方０．７を超えると、水の蒸発に時間がかかり生産性およびエネルギー的に不利であり好ましくない。
【００５０】
続いて施される温度２７０〜４００℃下の熱処理は、その処理温度と繊維密度とには密接な関係があり、好ましくは３００〜３７０℃の温度で処理する。４００℃を超える高温の処理では糸が激しく劣化し、着色し、場合によっては断糸する場合がある。一方２７０℃を下回る温度では十分に緻密化することができず、所望の繊維物性を発現することが困難となる。なお、ここでいう処理温度は熱板、加熱ローラ等の加熱手段の設定温度をいい、乾熱処理が特に好ましい。
【００５１】
このときの延伸倍率は、弾性率、強度の発現に密接な関係を有し、必要に応じて任意の倍率をとることができるが、通常、０．７〜４．０倍、特に１．０〜３．０倍の範囲に設定することで、良好な熱延伸性と、強度、弾性率の発現が得られる。なお、ここで延伸倍率０．７倍とは糸条が熱処理によって処理前の原長の３０％収縮することを意味し、本発明の熱処理は処理時に一定範囲内の制限収縮熱処理であっても差し支えないことを意味する。熱処理の延伸倍率は上述した可塑延伸の倍率を考慮して選定するのが好ましく、糸条物の緻密化と物性の発現、安定した製糸性の実現の観点から、可塑延伸および熱延伸を含めた全延伸倍率が３．０〜１２倍となるようにすること、さらには２．５〜６倍となるように設定すること、がより好ましい。本発明によるメタアラミド繊維は、延伸性がよく、可塑延伸や熱延伸時に断糸や毛羽の発生をともなうことなく円滑に高倍率まで延伸することができる。
【００５２】
さらに、このようにして製造された繊維は、必要に応じて捲縮加工が施され、適当な繊維長に切断され、紡績その他の次工程に提供される。
【００５３】
以上のごとき本発明によるメタ型全芳香族ポリアミド（メタアラミド）繊維は、通常のメタアラミド繊維と同様の緻密な構造を有し、３００℃乾熱収縮率が５％以下であり、かつ繊維の密度が１．２ｇ／ｃｍ³より大で、好ましくは１．３ｇ／ｃｍ³以上で、良好な繊維物性を備え、かつ繊維中の塩類の含有量が極めて小さく、繊維中の塩類の量が無機イオン性物質の全含有量にして５００ｐｐｍ以下、好ましくは３００ｐｐｍ以下である。そして、好ましい態様では、繊維物性や耐熱性、後加工性への悪影響が懸念される繊維中のカルシウム濃度が０〜１００ｐｐｍであり、また電気絶縁性等の電気特性に悪影響を及ぼす繊維中の塩化物の濃度が０〜１５０ｐｐｍであるという利点を有する。
【００５４】
以上のごとき本発明によるメタ型全芳香族ポリアミド（メタアラミド）繊維は、その耐熱性、耐炎性、力学特性を生かした各種の用途に応用することができ、特にイオン性物質の混入を嫌う用途には好適に用いることができる。例えば、単独あるいは他の繊維と組み合わせ、織編物にして消防服、防護服等の耐熱耐炎衣料、耐炎性の寝具、インテリア材料として有用であり、特に不織布としてフィルター等各種工業材料、あるいは合成紙、複合材料の原料として有効に使用することができるほか、イオン性物質の含有量がきわめて少ないため、織編物、不織布、合成紙等として電気絶縁材料、電子機器用部品、プリント配線基板等の分野で特に有効である。
【００５５】
【実施例】
以下、実施例により、本発明をさらに具体的に説明する。
なお、実施例及び比較例中、還元粘度（Ｉ．Ｖ．）は、重合体溶液から芳香族ポリアミドポリマーを単離して乾燥した後、濃硫酸中、ポリマー濃度１００ｍｇ／１００ｍｌ硫酸で３０℃において測定した値である。また、「部」及び「％」は特に断らない限りすべて重量に基づくものであり、量比は特に断らない限り重量比を示す。さらに、紡糸に用いる重合体溶液（紡糸原液）における重合体濃度（ＰＮ濃度）は、全重量部に対する重合体の重量％、すなわち｛重合体／（重合体＋溶媒＋その他）｝１００（％）である。
【００５６】
また、凝固により得られた多孔質の線状体の密度は、ＡＳＴＭ Ｄ２１３０にしたがって測定した繊維径と繊度から算出した。
【００５７】
得られた繊維中の金属濃度は、アルカリ金属については原子吸光法を用いて、その他の金属イオン濃度はＩＣＰを用いて定量を行なった。また、塩化物の濃度はドーマン微量電量滴定法により定量した。
得られた繊維の３００℃乾熱収縮率は、以下の方法により測定した。すなわち、３３００ｄｔｅｘ（３０００デニール）のトウに９８ｃＮ（１００ｇ）の荷重を吊るし、３０ｃｍ離れた箇所に印をつける。荷重を除去後、トウを３００℃雰囲気下に１５分間置いた後の印間長Ｌを測定する。（３０−Ｌ）／×１００の値を３００℃乾熱収縮率（％）とした。
【００５８】
１００〜２５０℃熱処理前の繊維中のポリマー重量率Ｐ、アミド系溶媒重量率Ｎ、水分重量率Ｗは、以下の方法により測定した。
１００〜２５０℃熱処理前の繊維を遠心分離機（回転数５０００ｒｐｍ）に１０分かけ、このときの繊維重量Ｍ１を測定する。この繊維を重量Ｍ２ｇのメタノール中で４時間煮沸し、繊維中のアミド化合物溶媒および水を抽出する。抽出後繊維を１０５℃雰囲気下で乾燥させ、乾燥後の繊維重量を測定し、これをＰ１とする。抽出液中のアミド化合物溶媒重量濃度Ｃ（％）を、ガスクロマトグラフにより求める。これらより、Ｎ１＝Ｃ／１００×（Ｍ１＋Ｍ２−Ｐ１）、Ｗ１＝Ｍ１−Ｐ１−Ｎ１を算出し、ついで、次式よりＰ、Ｎ、Ｗを算出する。
Ｐ＝Ｐ１／（Ｐ１＋Ｎ１＋Ｗ１）×１００
Ｎ＝Ｎ１／（Ｐ１＋Ｎ１＋Ｗ１）×１００
Ｗ＝Ｗ１／（Ｐ１＋Ｎ１＋Ｗ１）×１００
【００５９】
［実施例１］
特公昭４７−１０８６３号公報記載の方法に準じた界面重合法により製造したＩ．Ｖ．＝１．９のポリメタフェニレンイソフタルアミド粉末２１．５重量部を、−１０℃に冷却したＮ−メチル−２−ピロリドン７８．５重量部中に懸濁させ、スラリー状にした後、６０℃まで昇温して溶解させ、透明なポリマー溶液Ａを得た。なお、上記ポリマー粉末の無機イオン濃度は、Ｎａ：７３０ｐｐｍ、Ｋ：８．８ｐｐｍ、Ｃａ：５ｐｐｍ、Ｆｅ：２．３ｐｐｍであった。また、上記ポリマー溶液のポリマー濃度は２１．５％であった。
【００６０】
ポリマー溶液Ａを紡糸原液として、孔径０．０７ｍｍ、孔数５０００の紡糸口金より浴温度５０℃の凝固浴中に吐出して紡糸した。この凝固浴は、水／ＮＭＰ＝４０／６０の組成の浴を用い、浸漬長（有効凝固浴長）４０ｃｍにて糸速７ｍ／分で通過させた後、いったん空気中に引き出した。
【００６１】
引続き、可塑延伸浴中にて３．６倍の延伸倍率で延伸を行った。この時の可塑延伸浴は、水／ＮＭＰ＝４０／６０の組成の浴を用い、温度２０℃であった。延伸後、２０℃の水／ＮＭＰ＝７０／３０浴に通し（浸漬長１．８ｍ）、さらに２０℃の水浴に通した（浸漬長１．８ｍ）。このときＮ／（Ｐ＋Ｎ）＝０．３８、Ｗ／（Ｐ＋Ｗ）＝０．５９であった。その後、表面温度１２０℃ローラーに巻き回して乾熱処理（定長）し、引続き表面温度１６０℃ローラーに巻き回して乾熱処理（定長）した。さらに表面温度３３０℃の熱板にて定長で乾熱処理を施し、ポリメタフェニレンイソフタルアミド繊維を得た。
【００６２】
得られた繊維の力学的特性は、繊度２．１１ｄｔｅｘ（１．９ｄｅ）、密度１．３５ｇ／ｃｍ³、引張強度３．６５ｃＮ／ｄｔｅｘ（４．１２ｇ／ｄｅ）、伸度３１．５％、ヤング率７４．９ｃＮ／ｄｔｅｘ（８４．６ｇ／ｄｅ）であり、良好な数値を示した。また、３００℃乾熱収縮率は４．１％であり、優れた熱収縮安定性を示した。さらに繊維中のイオン濃度は、表１に示すとおりであり、きわめて低い含量を示した。
【００６３】
【表１】

【００６４】
［比較例１］
ポリマー溶液Ａを紡糸原液として、孔径０．０７ｍｍ、孔数５０００の紡糸口金より浴温度５０℃の凝固浴中に吐出して紡糸した。この凝固浴は、水／ＮＭＰ＝４０／６０の組成の浴を用い、浸漬長（有効凝固浴長）４０ｃｍにて糸速７ｍ／分で通過させた後、いったん空気中に引き出した。
【００６５】
引続き、可塑延伸浴中にて３．６倍の延伸倍率で延伸を行った。この時の可塑延伸浴は、水／ＮＭＰ＝４０／６０の組成の浴を用い、温度２０℃であった。延伸に続いて、水洗長を７．２ｍとして２０℃水浴にて水洗した。このときのＮ／（Ｐ＋Ｎ）＝０．２５、Ｗ／（Ｐ＋Ｗ）＝０．６０であった。その後、表面温度１２０℃ローラーに巻き回して乾熱処理（定長）し、引続き表面温度１６０℃ローラーに巻き回して乾熱処理（定長）した。さらに表面温度３３０℃の熱板にて定長で乾熱処理を施し、ポリメタフェニレンイソフタルアミド繊維を得た。
【００６６】
得られた繊維の力学的特性は、繊度２．２８ｄｔｅｘ（２．０５ｄｅ）、密度１．３２ｇ／ｃｍ³、引張強度３．３８ｃＮ／ｄｔｅｘ（３．８２ｇ／ｄｅ）、伸度３３．２％、ヤング率５７．３ｃＮ／ｄｔｅｘ（６４．８ｇ／ｄｅ）であった。しかし、３００℃乾熱収縮率は１６．２％であり、熱収縮安定性に劣るものであった。
【００６７】
【発明の効果】
本発明方法によれば、力学特性、耐熱性等の良好で実質的に塩類を含まない緻密なメタ型全芳香族ポリアミド繊維（特にポリメタフェニレンイソフタルアミド系繊維）を実質工業的な生産性で製造することができる。このような塩類を実質的に含まないすなわち無機イオン性物質の濃度が極限的に低いメタ型全芳香族ポリアミド繊維は、耐熱性、難燃性、電気絶縁性等のメタ型全芳香族ポリアミド繊維が本来もつ性質に加えて、電気特性等に影響する実質的な量の無機イオンを含まないため、電子用材料として用いる際に電気特性を損なわない等の特性を有するので有効に使用することができる。
【００６８】
このように、本発明によるメタ型全芳香族ポリアミド繊維は、その耐熱性、耐炎性、力学特性を生かした各種の用途に応用することができ、特に無機イオン性物質の混入を嫌う用途には特に好適に用いることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing meta-type wholly aromatic polyamide fibers having a main component of a metaphenylene isophthalamide skeleton having good mechanical properties, heat resistance, etc. by wet spinning with high productivity, and substantially obtained by the method. Relates to a wholly aromatic polyamide fiber which does not contain salts.
[0002]
[Prior art]
It has been well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dichlorides are excellent in heat resistance and flame retardancy, and these wholly aromatic polyamides can be used as amide solvents. It is also well known that these polymers can be made into fibers from these polymer solutions by methods such as dry spinning, wet spinning, and semi-dry semi-wet spinning.
[0003]
Among such wholly aromatic polyamides, fibers of meta-type wholly aromatic polyamides represented by polymetaphenylene isophthalamide (hereinafter sometimes referred to as “meta-aramid”) are particularly useful as heat-resistant and flame-retardant fibers. It is said that such meta-aramid fibers are currently industrially produced mainly by the following two methods (a) and (b), and in addition to these, production of meta-aramid fibers As methods, the following methods (c) to (f) have been proposed.
[0004]
(A) A polymetaphenylene isophthalamide solution is prepared by subjecting metaphenylenediamine and isophthalic acid chloride to low-temperature solution polymerization in N, N-dimethylacetamide, and then, by-product hydrochloric acid is hydroxylated. A method for producing polymetaphenylene isophthalamide fiber by dry spinning a polymer solution containing calcium chloride obtained by neutralization with calcium (see Japanese Patent Publication No. 35-14399, US Pat. No. 3,360,595) .
[0005]
(B) Contacting an organic solvent system (for example, tetrahydrofuran) that is not a good solvent for the resulting polyamide containing metaphenylenediamine salt and isophthalic acid chloride and an aqueous system containing an inorganic acid acceptor and a soluble neutral salt. A method of isolating a powder of a metaphenylene isophthalalamide polymer (see Japanese Patent Publication No. 47-10863), re-dissolving the polymer powder in an amide solvent, and then performing wet spinning in an inorganic salt-containing aqueous coagulation bath ( (See Japanese Patent Publication No. 48-17551).
[0006]
(C) From a meta-aramid solution prepared by dissolving and isolating a meta-aramid synthesized by a solution polymerization method in an amide solvent and containing no inorganic salt or a small amount (2 to 3%) of lithium chloride by a wet molding method. A method for producing a molded product such as a fiber (see JP-A-50-52167).
[0007]
(D) A meta-aramid polymer solution containing calcium chloride and water produced by solution polymerization in an amide solvent and neutralized with calcium hydroxide, calcium oxide or the like is extruded into the gas from the orifice, After passing, it introduce | transduces into an aqueous coagulation bath, Then, it passes in inorganic salt aqueous solution, such as calcium chloride, and shape | molds into a thread (refer Unexamined-Japanese-Patent No. 56-31209).
[0008]
(E) A meta-aramid polymer solution containing calcium chloride and water produced by solution polymerization in an amide solvent and neutralized with calcium hydroxide, calcium oxide, etc. A method of spinning in a coagulation bath to form a yarn (see JP-A-8-074121, JP-A-10-88421, etc.).
[0009]
(F) An amide solvent solution containing an inorganic salt of meta-aramid is discharged to a high temperature spinning cylinder, and immediately after leaving the spinning cylinder, it is cooled and swollen with a low temperature aqueous solution, and this is an aqueous solution containing a plasticized salt. By stretching in a stretching bath, a density of 1.3 g / cm having many very fine pores ^Three A method for producing less than easily dyeable porous fibers (see Japanese Patent Publication No. 52-43930).
[0010]
The above method (a) has the advantage that a polymer solution for spinning (spinning stock solution) can be prepared without isolating the polymer, but it is energy for production because of dry spinning using an amide solvent having a high boiling point. If the cost is high and the number of holes per spinneret is increased, the spinning stability rapidly decreases. In addition, since it is often the case that only a weak fiber with high devitrification is obtained when trying to wet-spin this polymer solution in an aqueous coagulation bath, a meta-aramid polymer solution obtained by solution polymerization is still wet-spun using an aqueous coagulation bath. The method is believed to have many difficulties and has not been implemented industrially. On the other hand, the method (b) (c) avoids the above-mentioned problem of dry spinning, but the solvent is different between the polymerization system and the spinning system, and the process for re-dissolving the polymer once isolated In order to obtain a stable solution by re-dissolution, special consideration and meticulous process control are required (see Japanese Patent Publication No. 48-4661). In the method (d), when spinning from the spinneret into the air, increasing the number of holes per spine significantly reduces the spinning stability, resulting in low productivity and inefficiency. Furthermore, although the method (e) gives fibers with good physical properties, there is a problem in productivity because it is difficult to increase the spinning speed. The method (f) has a density of 1.3 g / cm. ^Three Although it is a method of producing a considerably smaller porous fiber, this is an applied technique of the dry spinning method and has the same problems as the dry spinning method.
[0011]
In addition, meta-aramid fibers are used as electronic materials because of their heat resistance and insulation properties, but in order to use them as electronic materials, it is required to reduce the contamination of ionic substances as much as possible, and if possible inorganic ionic substances Is preferably not contained at all. However, in the production methods known so far, in the spinning process, the salt solution and the coagulation bath have a very high affinity for polymer dopes such as calcium chloride and lithium chloride, and the salts that are easily dissolved are considerably high. It is essential to include it in a concentration, and therefore it is inevitable that a large amount of salt is included in the produced fiber. In order to remove the salt remaining in the fiber, it is necessary to provide a large-scale water washing process, but it is impossible to completely remove the salt of the fiber.
[0012]
As a means for improving such a problem, Japanese Patent Application Laid-Open No. 2000-303365 discloses that a meta type wholly aromatic polyamide mainly composed of metaphenylene isophthalamide obtained by the same method as (b) is dissolved in an amide solvent. The polymer solution substantially free of salts is discharged into a coagulation bath consisting of an amide solvent and water and substantially free of salts to solidify as a porous linear body, Subsequently, this is stretched in a plastic stretching bath made of an aqueous solution of an amide solvent, washed with water, and heat-treated to form a dense meta-type wholly aromatic substantially free of salts (inorganic ionic substances). A method for producing a polyamide fiber has been proposed.
[0013]
Certainly, this method is excellent as a method for obtaining a meta-aramid fiber substantially free of salts, but if the spinneret hole exceeds 500 holes, sufficient fiber physical properties cannot be obtained, and in particular, heat shrink stability is inferior. It is not useful as an industrial production method. The reason why sufficient fiber properties cannot be obtained when the number of spinneret holes is increased is considered to be that when the number of spinneret holes is increased, the concentration in the vicinity of the discharge portion of the amide solvent, which is a dope solvent, is increased. Industrial production is also difficult because yarn breakage tends to occur without solidifying.
[0014]
Such a thread breakage problem can be substantially industrially produced by adjusting the concentration of the amide solvent in the coagulation bath (amide compound solvent weight ratio in the coagulation liquid). However, since the amide solvent concentration of the coagulation bath specified in this method is still low, the properties of the fiber that has left the coagulation bath are different from the properties originally intended by this method, and plastic stretching and drying heat treatment are similarly performed. Even when applied, the final fiber obtained does not have sufficient physical properties. In particular, it does not have sufficient heat shrink stability. This is considered because sufficient orientation and crystallization are not performed.
[0015]
As described above, a method that can produce a meta-aramid fiber satisfying fiber properties and containing no salt at a substantially industrial production level has not been proposed yet.
[0016]
[Problems to be solved by the invention]
The main object of the present invention is to provide a novel method capable of advantageously producing meta-aramid fibers free from salts having good mechanical properties and thermal properties at a practical industrial production level. Another object of the present invention is to provide a meta-aramid fiber that is substantially free of salts and is dense and excellent in heat shrink stability.
[0017]
[Means for Solving the Problems]
The main object of the present invention is to perform wet spinning of a meta-type wholly aromatic polyamide polymer solution in which a meta-type wholly aromatic polyamide mainly composed of a metaphenylene isophthalamide skeleton is dissolved in an amide solvent. In the method for producing a wholly wholly aromatic polyamide fiber, (1) a polymer solution substantially free of salts is used as a spinning dope, which comprises a spinneret having 500 or more holes, an amide solvent and water; It is discharged into a coagulation bath substantially free of salts and coagulated as a porous linear body, (2) stretched in a plastic stretching bath comprising an aqueous solution of an amide solvent, and (3) subsequently The water content in the fiber and the water content of the amide-based solvent are adjusted so as to satisfy the following formulas (a) and (b) with water containing water or amide-based solvent, and (4) the temperature is 100 to 250. It has been found that can be achieved by the method for producing a dense meta-type wholly aromatic polyamide fiber characterized by heat treatment in an additional temperature 270 to 400 ° C. After heat treatment.
(A) 3 ≦ N / (P + N) ≦ 0.7
(B) 0.4 ≦ W / (P + W) ≦ 0.7
However, P, N, and W represent the polymer-containing weight ratio, the amide-containing solvent weight ratio, and the water-containing weight ratio in the fiber, respectively.
[0018]
Further, it has been found that another object of the present invention can be achieved by a meta-type wholly aromatic polyamide fiber produced by the above method and having a 300 ° C. dry heat shrinkage of 5% or less.
[0019]
That is, according to the present invention, a meta-type wholly aromatic polyamide fiber is obtained by wet spinning a polymer solution in which a meta-type wholly aromatic polyamide having a metaphenylene isophthalamide skeleton as a main component is dissolved in an amide solvent. In the production method, (1) in the spinning step, a polymer solution substantially free of salts is used, and this is coagulated from a spinneret having 500 or more holes, consisting of an amide solvent and water, and substantially free of salts. Wet spinning in a bath to solidify as a porous linear body, (2) Subsequently, this is stretched in a plastic stretching bath made of an aqueous solution of an amide solvent in a stretching step, (3) Subsequently, the water content in the fiber and the amide solvent content are adjusted with water or water containing an amide solvent, and at that time, adjustment may be made so as to satisfy the following formulas (a) and (b). It ’s important, 4) subsequently, heat treating the fiber content was adjusted for this water and an amide solvent at a temperature further 270 to 400 ° C. After heat treatment at 100 to 250 ° C..
(A) 0.3 ≦ N / (P + N) ≦ 0.7
(B) 0.4 ≦ W / (P + W) ≦ 0.7
However, P, N, and W represent the polymer-containing weight ratio, the amide-containing solvent weight ratio, and the water-containing weight ratio in the fiber, respectively.
[0020]
At this time, in the spinning step (1), the coagulation bath is made into an aqueous coagulation bath in which the composition of the amide solvent and water is 50/50 to 65/35 by weight and the temperature is 40 to 70 ° C., In the plastic stretching step (2), a stretching bath in which the composition of the amide solvent and water is 20/80 to 70/30 by weight and the temperature is 20 to 90 ° C. is used. The film is stretched in the range of 10 times, and further, in the heat treatment step (4), the heat treatment is once performed at a stretch ratio of 0.8 to 3.0 times in the temperature range of 100 to 250 ° C. To produce a meta-aramid fiber that has particularly good physical properties and is substantially free of salts and excellent thermal shrinkage stability with good productivity by heat treatment at a draw ratio of 0.7 to 4 times. can do.
[0021]
And by such a method, 300 degreeC dry-heat shrinkage rate is 5% or less, and the density of a fiber is 1.2 g / cm. ^Three Larger (preferably 1.3 g / cm ^Three And a meta-type wholly aromatic polyamide fiber having a total inorganic ionic substance content of 500 ppm or less, a calcium concentration of 100 ppm or less, and a chloride concentration of 150 ppm or less. it can.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, a dense meta-type polymer substantially free of salts can be obtained by wet spinning a polymer solution comprising an amide solvent containing a meta-type wholly aromatic polyamide having a metaphenylene isophthalamide skeleton as a main component. A method for producing an aromatic polyamide fiber, which is substantially dense and substantially free of salts by sequentially performing the specific steps (1), (2), (3) and (4) described in detail below. Meta-type wholly aromatic polyamide fibers having excellent thermal stability are produced.
[0023]
Hereinafter, the details will be described in order.
The meta-type wholly aromatic polyamide used in the present invention has metaphenylene isophthalamide as the main skeleton, and its production method is not particularly limited. For example, meta-type aromatic diamine and aromatic dicarboxylic acid chloride Can be produced by solution polymerization, interfacial polymerization or the like.
[0024]
As the meta-type aromatic diamine which is one of such raw materials, diamines represented by the following formula are mainly used.
[0025]
[Chemical 1]

[0026]
Specific examples of such meta-type aromatic diamines include metaphenylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene, and the like. It is done. Examples of other meta-type aromatic diamines include 3,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl sulfone.
[0027]
In the present invention, among them, metaphenylenediamine or mixed diamine mainly composed of this is preferable. Other aromatic diamines used in combination with metaphenylenediamine include paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene, aminoanisidine, etc. in addition to the above-mentioned meta-type aromatic diamine. Benzene derivatives, 1,5-naphthylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodipheniketone, bis (aminophenyl) phenylamine, bis (paraaminophenyl) methane and the like are used.
[0028]
When a polymer with good solubility is desired, such other aromatic diamines can be used up to about 20 mol% of the whole. However, when a highly crystalline polymer is desired, metaphenylene can be used. It is preferable that diamine is contained at 90 mol% or more, particularly 95 mol% or more.
[0029]
On the other hand, the aromatic dicarboxylic acid chloride used in the present invention is isophthalic acid chloride or an aromatic dicarboxylic acid chloride mainly composed thereof. Other aromatic dicarboxylic acid chlorides that can be used in combination with isophthalic acid chloride include terephthalic acid chloride, 1,4-naphthalenedicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, 4,4′-biphenyldicarboxylic acid chloride, 5 -Chlorisophthalic acid chloride, 5-methoxyisophthalic acid chloride, bis (chlorocarbonylphenyl) ether and the like.
[0030]
In the practice of the present invention, when a polymer having good solubility is desired, a high ratio (up to about 20 mol%) of these other aromatic dicarboxylic acids can be mixed. Is desired, isophthalic acid chloride is preferably contained in an amount of 90 mol% or more, particularly 95 mol% or more.
[0031]
Among the above-mentioned meta-type wholly aromatic polyamides, a polymer in which 90 to 100 mol% of all polymer repeating units are metaphenylene isophthalamide units, and substantially free of salts is preferably used.
[0032]
In the present invention, a polymer solution in which the meta-type wholly aromatic polyamide is dissolved in an amide-based solvent and substantially free of salts (inorganic ionic substances) is supplied to the process described later. Such a polymer solution may be obtained by removing salts from an amide solvent solution containing a meta-type wholly aromatic polyamide obtained by the above solution polymerization or the like, or obtained by the above solution polymerization, interfacial polymerization or the like. A solution obtained by isolating the meta type wholly aromatic polyamide from a solution containing the meta type wholly aromatic polyamide and dissolving it in an amide solvent may be used. Here, “substantially free of salts” means that the total amount of salts in the polymer solution is less than 0.1% by weight, and a very small amount of salts is allowed to be contained. The amount is preferably as small as possible, and is preferably 0 to 0.01% by weight.
[0033]
Examples of the amide solvent used here include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone and the like. N-methyl-2-pyrrolidone is preferable from the viewpoint of the stability of the polymer solution up to the wet spinning process.
[0034]
In the present invention, the polymer solution used for the spinning dope may contain water. Such water may be added as necessary, but it may be inevitably produced in the solution preparation process. The concentration may be any concentration as long as the solution is stably present, but it is usually preferably added and contained, for example, in the range of 0 to 60% by weight with respect to the polymer weight, particularly 15% by weight. % Or less is preferable. If the concentration exceeds this, the stability of the polymer solution is impaired, and the spinnability may be significantly impaired by the precipitation and gelation of the polymer.
[0035]
In the present invention, when the polymer solution is discharged into a coagulation bath, a spinneret having a number of holes of 500 holes or more is used. Practically, the upper limit of the number of holes is about 50,000 holes, preferably 1000 to 30,000 holes, particularly 3000 to 10000 holes.
[0036]
The coagulation bath in the present invention is substantially free of salts and contains an amide solvent and water (H ₂ O) and an aqueous solution substantially consisting of two components. In this coagulation bath composition, the amide solvent can be suitably used as long as it dissolves meta-aramid and is miscible with water. Particularly, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, Dimethylimidazolidinone and the like can be suitably used. In consideration of recovery of the solvent and the like, it is preferable to use the same type of amide solvent in the spinning dope.
[0037]
The optimum mixing ratio of the amide solvent and water varies slightly depending on the conditions of the polymer solution, but the concentration of the amide solvent in the coagulation bath liquid is 40 to 70% by weight, particularly 50 to 65% by weight, Is preferably in the range of 55 to 62% by weight. Under conditions where the concentration of the amide solvent is below this range, very large voids are likely to be formed in the yarn, which is likely to cause subsequent yarn breakage. On the other hand, under conditions exceeding this range, solidification does not proceed and the yarns are easily fused.
[0038]
The temperature of the coagulation bath is closely related to the composition of the coagulation solution, but generally a higher temperature is preferable because pores on coarse bubbles called fingers are hardly formed in the formed yarn. However, when the concentration of the coagulation liquid is high, the fusion between the yarns becomes intense if the temperature is too high, so the suitable temperature of the coagulation bath is 40 to 70 ° C, more preferably in the range of 45 to 65 ° C. is there.
[0039]
The coagulation liquid is preferably substantially composed of only an amide solvent and water, but may contain a small amount of salts other than this. In particular, salts such as calcium chloride and calcium hydroxide may be extracted from the polymer solution remaining in a trace amount, but this does not inhibit the porous coagulation at all. However, there is no problem even if salts are contained at a low concentration of 10% by weight or less, particularly 1% by weight or less. Therefore, the preferred concentration of the salt is in the range of 0 to 10% by weight with respect to the coagulating liquid. The immersion time of the yarn in the coagulation bath is preferably 0.1 to 30 seconds. If the dipping time is too short, the formation of the yarn is insufficient and there is a possibility that the yarn breaks.
[0040]
As the plastic stretching bath in the present invention, an aqueous solution of an amide solvent is used. As the amide-based solvent, any swellable meta-type wholly aromatic polyamide can be suitably used as long as it is well mixed with water. Particularly, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethyl Imidazolidinone and the like can be preferably used. More preferably, the same solvent as that used in the coagulation bath is preferably used. If the same type of solvent as the coagulation bath is used, the recovery process is simplified, which is economically beneficial.
[0041]
That is, it is preferable to use the same type of amide solvents in the polymer solution, the coagulation bath, and the plastic drawing bath. As such solvents, N-methyl-2-pyrrolidone, dimethylacetamide, and dimethylformamide are used alone. It is convenient to use two or more in combination.
[0042]
The composition and temperature of the plastic drawing bath are closely related to each other, but a concentration of amide solvent in the aqueous solution of 20 to 70% by weight and a temperature of 20 to 90 ° C. is preferably used. In regions below this range, plasticization does not proceed sufficiently, and it is difficult to obtain a sufficient draw ratio. Above this range, the surface of the yarn is melted and easily melted, making it difficult to perform good spinning. There are many.
[0043]
In the plastic stretching of the present invention, the film is usually stretched at a magnification of 1.5 to 10 times, preferably 2 to 10 times, and more preferably at a magnification of 2.1 to 6.0 times. By stretching at a high magnification in this way, the strength and elastic modulus of the meta-aramid fiber are improved, and good physical properties are exhibited. At the same time, the pores of the porous structure are crushed and densified by a heat treatment performed after plastic stretching. Will progress well. However, when the film is stretched at an extremely high magnification, the process tone is deteriorated and it becomes difficult to produce a good yarn.
[0044]
The yarn after the plastic drawing bath has been subjected to the following steps (a) and (a) in which the water content and the amide solvent content in the fiber are water or water containing an amide solvent. It is important to adjust so as to satisfy b).
(A) 0.3 ≦ N / (P + N) ≦ 0.7, preferably 0.35 ≦ N / (P + N) ≦ 0.65
(B) 0.4 ≦ W / (P + W) ≦ 0.7, preferably 0.45 ≦ W / (P + W) ≦ 0.65
However, P, N, and W represent the polymer-containing weight ratio, the amide-containing solvent weight ratio, and the water-containing weight ratio in the fiber, respectively.
[0045]
By adjusting the water content and the amide solvent content to the above ranges, the fluidity of the polymer during the heat treatment is improved in the subsequent heat treatment at a temperature range of 100 to 250 ° C. Then, it is considered that orientation and crystallization are promoted when the amide solvent subsequently evaporates and escapes from the fiber. Moreover, it is considered that when an appropriate amount of water and an amide solvent coexist, they azeotrope to promote evaporation of the amide solvent.
[0046]
In addition, as a method of adjusting the water content and the amide-based solvent ratio to the above ranges, after the plastic stretching, the immersion length is passed through a 10-70 ° C. water bath or a 10-40 ° C. amide solvent / water mixed bath, Can be easily carried out by adjusting the number of yarns depending on the number of threading turns.
[0047]
Thus, the yarn in which the water content and the amide-containing compound solvent rate in the fiber are adjusted is once within a temperature range of 100 to 250 ° C., preferably 100 to 200 ° C., by a heating roller, a heating plate, hot air, or the like. Heat treatment, preferably dry heat treatment is performed. This heat treatment step in the temperature range of 100 to 250 ° C. is an important step for promoting the orientation and crystallization of the polymer of the porous linear body and expressing the heat shrink stability of the fiber. If the heat treatment temperature is less than 100 ° C., the evaporation of water and amide solvents is remarkably slow, which not only reduces productivity but also hinders the promotion of crystallization. On the other hand, when the temperature exceeds 250 ° C., the amide solvent is decomposed at once and there is a concern that the effect of promoting crystallization does not sufficiently appear, which is not preferable. Further, the coloring of the fiber occurs, which is not preferable. In this heat treatment, under stretching of 0.8 to 3.0 times, preferably 1.0 to 2.0 times (less than 1 time is shrink heat treatment), particularly under stretching of 1.0 to 1.5 times. It is preferable to heat-treat.
[0048]
If N / (P + N) is less than 0.3, the effect of improving the polymer fluidity during the heat treatment is not exhibited, and good fiber properties cannot be obtained. On the other hand, if it exceeds 0.7, it takes time for the amide compound solvent to evaporate, which is disadvantageous in terms of productivity and energy.
[0049]
Moreover, it is not preferable that W / (P + W) is less than 0.4 because fibers may be fused to each other during heat treatment to cause deterioration of fiber properties. On the other hand, if it exceeds 0.7, it takes a long time to evaporate water, which is disadvantageous in terms of productivity and energy.
[0050]
The subsequent heat treatment at a temperature of 270 to 400 ° C. has a close relationship between the treatment temperature and the fiber density, and is preferably treated at a temperature of 300 to 370 ° C. When the treatment is performed at a high temperature exceeding 400 ° C., the yarn is severely deteriorated and colored, and in some cases, the yarn may be broken. On the other hand, when the temperature is lower than 270 ° C., it cannot be sufficiently densified, and it becomes difficult to express desired fiber properties. The treatment temperature here refers to the set temperature of a heating means such as a hot plate or a heating roller, and dry heat treatment is particularly preferred.
[0051]
The draw ratio at this time is closely related to the development of the elastic modulus and strength, and can take any ratio as necessary, but is usually 0.7 to 4.0 times, particularly 1.0. By setting it in a range of ˜3.0 times, good thermal stretchability, strength and elasticity can be obtained. Here, the draw ratio of 0.7 times means that the yarn shrinks by 30% of the original length before the treatment by heat treatment, and the heat treatment of the present invention is a limited shrink heat treatment within a certain range during the treatment. It means that there is no problem. It is preferable to select the draw ratio of the heat treatment in consideration of the above-described plastic draw ratio. From the viewpoint of densification of the yarn and the manifestation of physical properties, and the realization of stable yarn forming properties, the plastic draw and the hot draw are included. It is more preferable to set the total draw ratio to 3.0 to 12 times, and further to set to 2.5 to 6 times. The meta-aramid fiber according to the present invention has good stretchability and can be smoothly stretched to a high magnification without causing yarn breakage or fluff during plastic stretching or heat stretching.
[0052]
Furthermore, the fibers produced in this manner are crimped as necessary, cut into an appropriate fiber length, and provided to spinning and other subsequent processes.
[0053]
As described above, the meta-type wholly aromatic polyamide (meta-aramid) fiber according to the present invention has a dense structure similar to that of a normal meta-aramid fiber, has a dry heat shrinkage of 300 ° C. of 5% or less, and the density of the fiber. 1.2g / cm ^Three Larger, preferably 1.3 g / cm ^Three As described above, the fiber has good physical properties, the content of salts in the fiber is extremely small, and the amount of salts in the fiber is 500 ppm or less, preferably 300 ppm or less in terms of the total content of inorganic ionic substances. In a preferred embodiment, the calcium concentration in the fiber, which has a concern about adverse effects on fiber properties, heat resistance, and post-processability, is 0 to 100 ppm, and the chlorination in the fiber adversely affects electrical properties such as electrical insulation. It has the advantage that the concentration of the product is 0 to 150 ppm.
[0054]
As described above, the meta-type wholly aromatic polyamide (meta-aramid) fiber according to the present invention can be applied to various uses utilizing its heat resistance, flame resistance, and mechanical properties, and particularly for uses in which an ionic substance is not mixed. Can be preferably used. For example, it is useful as a heat-resistant flame-resistant garment such as fire fighting clothes and protective clothing, flame-resistant bedding, interior materials, woven and knitted alone or in combination with other fibers, especially various industrial materials such as filters as non-woven fabrics, or synthetic paper, In addition to being able to be used effectively as a raw material for composite materials, the content of ionic substances is extremely low, so in the fields of electrical insulation materials, parts for electronic equipment, printed wiring boards, etc. It is particularly effective.
[0055]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
In Examples and Comparative Examples, the reduced viscosity (IV) was measured at 30 ° C. with a polymer concentration of 100 mg / 100 ml sulfuric acid in concentrated sulfuric acid after the aromatic polyamide polymer was isolated and dried from the polymer solution. It is the value. Further, “parts” and “%” are all based on weight unless otherwise specified, and the quantity ratio indicates a weight ratio unless otherwise specified. Further, the polymer concentration (PN concentration) in the polymer solution (spinning stock solution) used for spinning is the polymer weight% with respect to the total weight part, that is, {polymer / (polymer + solvent + other)} 100 (%) It is.
[0056]
Moreover, the density of the porous linear body obtained by coagulation was calculated from the fiber diameter and fineness measured according to ASTM D2130.
[0057]
The metal concentration in the obtained fiber was quantified using an atomic absorption method for alkali metals and the other metal ion concentrations using ICP. The chloride concentration was determined by the Dorman microcoulometric titration method.
The 300 degreeC dry heat shrinkage rate of the obtained fiber was measured with the following method. That is, a load of 98 cN (100 g) is hung on a 3300 dtex (3000 denier) tow, and a mark is made at a location 30 cm away. After removing the load, the mark length L after the tow is placed in an atmosphere of 300 ° C. for 15 minutes is measured. The value of (30−L) / × 100 was defined as 300 ° C. dry heat shrinkage (%).
[0058]
The polymer weight ratio P, the amide solvent weight ratio N, and the moisture weight ratio W in the fiber before heat treatment at 100 to 250 ° C. were measured by the following methods.
The fiber before heat treatment at 100 to 250 ° C. is subjected to a centrifuge (rotation speed: 5000 rpm) for 10 minutes, and the fiber weight M1 at this time is measured. The fiber is boiled in methanol having a weight of 2 g for 4 hours to extract the amide compound solvent and water in the fiber. The fiber after extraction is dried in an atmosphere of 105 ° C., and the weight of the fiber after drying is measured. This is defined as P1. The amide compound solvent weight concentration C (%) in the extract is determined by gas chromatography. From these, N1 = C / 100 × (M1 + M2−P1) and W1 = M1−P1−N1 are calculated, and then P, N, and W are calculated from the following equations.
P = P1 / (P1 + N1 + W1) × 100
N = N1 / (P1 + N1 + W1) × 100
W = W1 / (P1 + N1 + W1) × 100
[0059]
[Example 1]
Produced by an interfacial polymerization method according to the method described in JP-B 47-10863. V. = 21.5 parts by weight of polymetaphenylene isophthalamide powder of 1.9 was suspended in 78.5 parts by weight of N-methyl-2-pyrrolidone cooled to −10 ° C. The solution was heated up to be dissolved to obtain a transparent polymer solution A. The inorganic ion concentration of the polymer powder was Na: 730 ppm, K: 8.8 ppm, Ca: 5 ppm, Fe: 2.3 ppm. The polymer concentration of the polymer solution was 21.5%.
[0060]
The polymer solution A was spun as a spinning dope from a spinneret having a hole diameter of 0.07 mm and a hole number of 5000 into a coagulation bath having a bath temperature of 50 ° C. As this coagulation bath, a bath having a composition of water / NMP = 40/60 was used. The bath was passed at an immersion length (effective coagulation bath length) of 40 cm at a yarn speed of 7 m / min, and then drawn out into the air.
[0061]
Subsequently, the film was stretched at a stretching ratio of 3.6 times in a plastic stretching bath. The plastic stretching bath at this time was a bath having a composition of water / NMP = 40/60, and the temperature was 20 ° C. After stretching, it was passed through a 20 ° C. water / NMP = 70/30 bath (immersion length 1.8 m) and further passed through a 20 ° C. water bath (immersion length 1.8 m). At this time, N / (P + N) = 0.38 and W / (P + W) = 0.59. Thereafter, the film was wound around a roller having a surface temperature of 120 ° C. and subjected to a dry heat treatment (constant length), and subsequently wound around a roller having a surface temperature of 160 ° C. to perform a heat treatment (constant length). Furthermore, dry heat treatment was performed at a constant length on a hot plate having a surface temperature of 330 ° C. to obtain polymetaphenylene isophthalamide fibers.
[0062]
The mechanical properties of the obtained fiber are fineness of 2.11 dtex (1.9 de), density of 1.35 g / cm. ^Three The tensile strength was 3.65 cN / dtex (4.12 g / de), the elongation was 31.5%, and the Young's modulus was 74.9 cN / dtex (84.6 g / de). The 300 ° C. dry heat shrinkage ratio was 4.1%, which showed excellent heat shrinkage stability. Furthermore, the ion concentration in the fiber is as shown in Table 1, indicating a very low content.
[0063]
[Table 1]

[0064]
[Comparative Example 1]
The polymer solution A was spun as a spinning dope from a spinneret having a hole diameter of 0.07 mm and a hole number of 5000 into a coagulation bath having a bath temperature of 50 ° C. As this coagulation bath, a bath having a composition of water / NMP = 40/60 was used. The bath was passed at an immersion length (effective coagulation bath length) of 40 cm at a yarn speed of 7 m / min, and then drawn out into the air.
[0065]
Subsequently, the film was stretched at a stretching ratio of 3.6 times in a plastic stretching bath. The plastic stretching bath at this time was a bath having a composition of water / NMP = 40/60, and the temperature was 20 ° C. Subsequent to stretching, the length of water washing was 7.2 m and water washing was performed in a 20 ° C water bath. At this time, N / (P + N) = 0.25 and W / (P + W) = 0.60. Thereafter, the film was wound around a roller having a surface temperature of 120 ° C. and subjected to a dry heat treatment (constant length), and subsequently wound around a roller having a surface temperature of 160 ° C. to perform a heat treatment (constant length). Furthermore, dry heat treatment was performed at a constant length on a hot plate having a surface temperature of 330 ° C. to obtain polymetaphenylene isophthalamide fibers.
[0066]
The mechanical properties of the obtained fiber are: fineness 2.28 dtex (2.05 de), density 1.32 g / cm. ^Three The tensile strength was 3.38 cN / dtex (3.82 g / de), the elongation was 33.2%, and the Young's modulus was 57.3 cN / dtex (64.8 g / de). However, the 300 ° C. dry heat shrinkage ratio was 16.2%, which was inferior in heat shrink stability.
[0067]
【The invention's effect】
According to the method of the present invention, a dense meta-type wholly aromatic polyamide fiber (especially polymetaphenylene isophthalamide fiber) having good mechanical properties, heat resistance and the like and substantially free of salts can be produced with substantially industrial productivity. Can be manufactured. Meta-type wholly aromatic polyamide fibers that do not substantially contain such salts, that is, the concentration of inorganic ionic substances is extremely low, are meta-type wholly aromatic polyamide fibers that have heat resistance, flame resistance, electrical insulation, etc. In addition to the properties inherent in the product, it does not contain a substantial amount of inorganic ions that affect the electrical properties, etc., so it has properties such as not damaging electrical properties when used as an electronic material, so it can be used effectively. it can.
[0068]
As described above, the meta-type wholly aromatic polyamide fiber according to the present invention can be applied to various applications utilizing its heat resistance, flame resistance, and mechanical properties, and particularly for applications that do not want to contain inorganic ionic substances. It can be particularly preferably used.

Claims (10)

Meta-type wholly aromatic polyamide fiber is produced by wet spinning a meta-type wholly aromatic polyamide polymer solution in which a meta-type wholly aromatic polyamide mainly composed of metaphenylene isophthalamide skeleton is dissolved in an amide solvent. In the method, (1) a polymer solution substantially free of salts is used as a spinning dope, and this is composed of a spinneret having a hole number of 500 or more, an amide solvent and water, and is substantially free of salts. (2) stretched in a plastic stretching bath made of an aqueous solution of an amide solvent, and (3) subsequently contained water or an amide solvent. The water content and the amide solvent content in the fiber were adjusted so as to satisfy the following formulas (a) and (b) with water. (4) After heat-treating this at a temperature of 100 to 250 ° C., the temperature 2 Dense meta-type method for producing a wholly aromatic polyamide fiber characterized by a heat treatment at 0 to 400 ° C..
(A) 0.3 ≦ N / (P + N) ≦ 0.7
(B) 0.4 ≦ W / (P + W) ≦ 0.7
However, P, N, and W represent the polymer-containing weight ratio, the amide-containing solvent weight ratio, and the water-containing weight ratio in the fiber, respectively. The meta-type total fragrance according to claim 1, wherein in the step (1), the composition of the amide solvent and water in the coagulation bath is 50/50 to 65/35 by weight and the coagulation bath temperature is 40 to 70 ° C. For producing an aromatic polyamide fiber. In the step (2), the stretch ratio of 1.5 times to 10 times in a plastic stretching bath in which the composition of the amide solvent and water is 20/80 to 70/30 by weight and the temperature is 20 to 90 ° C. The method for producing a meta-type wholly aromatic polyamide fiber according to claim 1 or 2, wherein the meta-type wholly aromatic polyamide fiber is stretched by. In the step (4), the film is stretched 0.8 to 3.0 times under a heat treatment at a temperature of 100 to 250 ° C, and further stretched 0.7 to 4 times under a heat treatment at a temperature of 270 to 400 ° C. A process for producing a meta-type wholly aromatic polyamide fiber according to any one of claims 3 to 4. The amide solvent contained in the polymer solution, the coagulation bath and the plastic drawing bath is composed of at least one selected from the group consisting of N-methyl-2-pyrrolidone, dimethylacetamide and dimethylformamide. The method for producing a meta-type wholly aromatic polyamide fiber according to any one of the above. A meta-type wholly aromatic polyamide fiber manufactured by the method according to any one of claims 1 to 5, wherein a dry heat shrinkage at 300 ° C is 5% or less. Group polyamide fiber. The meta-type wholly aromatic polyamide fiber according to claim 6, wherein the density of the fiber is larger than 1.2 g / cm ³ and the content of the total inorganic ionic substance in the fiber is 500 ppm or less. The meta-type wholly aromatic polyamide fiber according to claim 6 or 7, wherein the calcium concentration in the fiber is 100 ppm or less. The meta-type wholly aromatic polyamide fiber according to any one of claims 6 to 8, wherein a concentration of chloride in the fiber is 150 ppm or less. The density of the fiber is 1.3 g / cm ³ or more, and the content of all inorganic ionic substances in the fiber is 500 ppm or less, the calcium concentration is 100 ppm or less, and the chloride concentration is 150 ppm or less. Meta-type wholly aromatic polyamide fiber.