JP2004003049A - Method for producing compact meta type wholly aromatic polyamide fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing compact meta type wholly aromatic polyamide fibers, by which the meta-aramid fibers not containing a salt and having good mechanical characteristics and thermal properties can be produced in good productivity. <P>SOLUTION: This method for producing compact meta type wholly aromatic polyamide fibers comprises extruding a salt-free polymer solution prepared by dissolving a meta type wholly aromatic polyamide having a meta-phenylene isophthalamide skeleton as a main component in an amide-based solvent into a salt-free coagulation bath comprising the amide-based solvent and water to coagulate the polymer as the porous linear product, immersing the porous linear product in a plasticizing bath comprising the aqueous solution of the amide-based solvent to control the contents of the water and the amide-based solvent in the fibers, drawing the fibers in a plasticizing drawing bath comprising the aqueous solution of the amide-based solvent, washing the fibers with water or the aqueous solution of the amide-based solvent, thermally treating the washed fibers at 100 to 250°C, and then further thermally treating the fibers at 270 to 400°C. The compact meta type wholly aromatic polyamide fibers substantially not containing a salt (inorganic ionic substance) and having excellent thermal shrinkage stability are profitably produced in substantially industrial productivity. The meta type wholly aromatic polyamide fibers having low inorganic ion concentration have characteristics such as the maintenance of electric characteristics, when used as an electronic material. <P>COPYRIGHT: (C)2004,JPO

Description

【００２４】
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。
【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
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。
【００２９】
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。
【００３０】
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。
【００３１】
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。
【００３２】
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。
【００３３】
本発明において、重合体溶液を凝固浴中に吐出する場合、紡糸口金としては多ホールのものを用いることができる。実用上ホール数の上限は約５００００ホールであり、好ましくは３００〜３００００ホール、特に３０００〜１００００ホールの紡糸口金が使用される。
【００３４】
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（Ｈ_２Ｏ）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。
【００３５】
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％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。
【００３６】
凝固浴の温度（Ｔ１）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２０〜７０℃であり、より好ましくは４０〜６５℃の範囲である。
【００３７】
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。
【００３８】
次に、本発明における可塑浴は、前記凝固浴と同じく塩類を実質的に含まず、アミド系溶媒と水（Ｈ_２Ｏ）との２成分から実質的になる水溶液で構成される。アミド系溶媒と水との最適な混合比は、多孔質線状体の条件によっても若干変化するが、可塑浴中のアミド系溶媒の濃度が４０〜７０重量％、特に５０〜６５重量％の範囲であることが好ましい。一方可塑浴の温度（Ｔ２）は、（Ｔ１＋５）℃〜９０℃の範囲とする必要があり、この温度範囲とすることにより、多孔質線状体中のアミド化合物溶媒重量と水分重量を増加せしめて、より均質な多孔質の繊維を形成することができる。この温度がＴ１＋５℃未満である場合には、可塑浴に浸漬してもアミド化合物溶媒重量と水分重量を十分増加させることができず、多孔内に凝固液を含んだ凝固糸と差がなくなる。一方Ｔ２が９０℃を超える場合には、糸条物同士の融着が激しくなったり、部分的に再溶解して単糸切れを生じるので好ましくない。
【００３９】
可塑液も凝固液と同じく、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。例えば可塑液に対し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、塩類の好適濃度は可塑液に対し０〜１０重量％の範囲である。可塑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アミド系溶媒重量と水分重量とを十分増加させることができず、多孔内に凝固液を含んだ凝固糸と差がなくなる。
【００４０】
本発明においては、上記可塑浴中への浸漬の工程を経た繊維は、そ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必要があり、かくすることにより、より均質な多孔質の繊維を形成することができる。
（ａ）０．３≦Ｎ／（Ｐ＋Ｎ）≦０．７、好ましくは０．４５≦Ｎ／（Ｐ＋Ｎ）≦０．６５
（ｂ）０．１≦Ｗ／（Ｐ＋Ｗ）≦０．３、好ましくは０．１５≦Ｗ／（Ｐ＋Ｗ）≦０．２５
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。
【００４１】
このようにして、繊維中のアミド系溶媒率および含水率が調整された多孔質の線状体は、アミド系溶媒の水性溶液中で可塑延伸する必要がある。ここで用いられる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よいが、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。
【００４２】
すなわち、重合体溶液、凝固浴、可塑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。
【００４３】
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、まず第１段目の可塑延伸では、該可塑延伸浴中のアミド系溶媒の濃度は２０〜７０重量％、温度は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。
【００４４】
可塑延伸は、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、後述する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。
【００４５】
上記可塑延伸浴の工程を経た浴上がりの繊維は、水あるいはアミド系溶媒の水性溶液にて洗浄するが、洗浄後そのまま後述する熱処理に供する場合には、その繊維中の含水率および含アミド系溶媒率を、下記式（ｃ）および（ｄ）を満足するように調整することが好ましい。
（ｃ）０．３≦Ｎ／（Ｐ＋Ｎ）≦０．７、好ましくは０．３５≦Ｎ／（Ｐ＋Ｎ）≦０．６５
（ｄ）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。
【００４６】
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。
【００４７】
ここで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効果が小さく、良好な繊維物性は得難くなる。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やすくなる。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り、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る。
【００４８】
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。
【００４９】
本発明においては、可塑延伸・洗浄された繊維は、（５）の熱処理工程の後に第２段の可塑延伸を施しても構わない。その際には、水あるいはアミド系溶媒の水性溶液にて洗浄後の繊維中の含水率および含アミド系溶媒率は、下記式（ｅ）および（ｆ）を満足するように調整することが好ましい。
（ｅ）０．１≦Ｎ／（Ｐ＋Ｎ）≦０．３、好ましくは０．１５≦Ｎ／（Ｐ＋Ｎ）≦０．２５
（ｆ）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。
【００５０】
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℃での熱処理において、該熱処理時のポリマーの流動性が適度に向上し、配向は進むが結晶化は抑制されて、繊維の緻密化が促進されるものと考えられる。
【００５１】
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、第１段目の可塑延伸後に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。
【００５２】
このように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繊維は、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された後に第２段の可塑延伸される。
【００５３】
なお、先述のＮ／（Ｐ＋Ｎ）が０．１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不十分となり、繊維の緻密化が不十分となって良好な繊維物性が得ることが困難になる。一方０．３を超えると、熱処理時の結晶化が進みやすくなると同時に繊維の密着も発生しやすくなるため、同じく良好な繊維物性を得ることが困難になる。また、Ｗ／（Ｐ＋Ｗ）が０．４未満であると、熱処理時にポリマーの流動性が低下して繊維の緻密化が不十分となり、繊維物性の低下を招く懸念がある。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る。
【００５４】
この第２段の可塑延伸浴の組成と温度も、第１段の可塑延伸と同じく密接な関係にあるが、アミド系溶媒の濃度は低めの０〜４０重量％、温度は２０〜１００℃の範囲が好適に用いられる。アミド系溶媒の濃度や温度が高くなりすぎると、繊維の配向が不十分となって繊維物性が低下しやすい。延伸倍率は、１倍〜３倍、好ましくは１〜２倍の範囲が適当であるが、特に１．０〜１．５倍が好ましい。第２段目以後の延伸工程を加える多段延伸とすることにより、メタアラミド繊維の強度、弾性率がさらに向上し良好な物性を示すようになる。
【００５５】
このように１段または２段以上に多段の可塑延伸された繊維は、工程（４）の水またはアミド系溶媒の水性溶液で洗浄した後に、工程（５）の加熱ローラ、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。
【００５６】
続いて施される工程（６）の温度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。
【００５７】
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、０．７〜３．０倍、特に１．０〜２．７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。
【００５８】
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。
【００５９】
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％以下といった熱安定性に優れた特性を有する。また、繊維の密度が１．２ｇ／ｃｍ^３より大で、好ましくは１．３ｇ／ｃｍ^３以上で、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以下のものを容易に得ることができる。さらに、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。
【００６０】
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。
【００６１】
【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。
【００６２】
また、凝固により得られた多孔質の線状体の密度は、ＡＳＴＭＤ２１３０にしたがって測定した繊維径と繊度から算出した。
【００６３】
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）／３０×１００の値を３００℃乾熱収縮率（％）とした。
【００６４】
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。抽出後の繊維と抽出液の全重量Ｍ２を測定する。また抽出後の繊維を取出して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＝（Ｍ２−Ｐ１）×Ｃ／１００、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
【００６５】
［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。
【００６６】
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）３０ｃｍ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て、ポリマー重量率Ｐ、アミド系溶媒重量率Ｎ、水分重量率ＷがＮ／（Ｐ＋Ｎ）＝０．４４、Ｗ／（Ｐ＋Ｗ）＝０．０９を満たす凝固糸を得た。
【００６７】
次いで、水／ＮＭＰ＝４０／６０の組成で温度６０℃の可塑浴により、浸漬長８０ｃｍにて可塑液を含ませた後、ポリマー重量率Ｐ、アミド系溶媒重量率Ｎ、水分重量率Ｗの関係Ｎ／（Ｐ＋Ｎ）＝０．５５、Ｗ／（Ｐ＋Ｗ）＝０．１７である多孔質の繊維を得た。
【００６８】
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の組成で、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）＝０．４１、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し、引続き表面温度１６０℃ローラーに巻き回して乾熱処理した。さらに表面温度３３０℃の熱板で定長にて乾熱処理を施し、ポリメタフェニレンイソフタルアミド繊維を得た。
【００６９】
この繊維の力学的特性は、繊度２．２ｄｔｅｘ（２．０ｄｅ）、密度１．３６ｇ／ｃｍ^３、引張強度３．９５ｃＮ／ｄｔｅｘ（４．５０ｇ／ｄｅ）、伸度３６．０％、であり、良好な数値を示した。また、３００℃乾熱収縮率は３．５％であり、優れた熱収縮安定性を示した。
【００７０】
得られた繊維のイオン濃度は、Ｎａ７５ｐｐｍ、Ｋ５ｐｐｍ、Ｃａ５ｐｐｍ、Ｆｅ７ｐｐｍ、Ｃｌ９０ｐｐｍ、全イオン性物質１９２ｐｐｍであり、きわめて低い含量を示した。
【００７１】
［実施例２および比較例１〜４］
実施例１で用いたポリマー溶液Ａを紡糸原液とし、孔径０．０７ｍｍ、孔数５０００の紡糸口金より浴温度５５℃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）２０ｃｍ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、ポリマー重量率Ｐ、アミド系溶媒重量率Ｎ、水分重量率ＷがＮ／（Ｐ＋Ｎ）＝０．４４、Ｗ／（Ｐ＋Ｗ）＝０．０９の関係を満たす凝固糸を得た。次いで、表１記載のとおりの条件で、可塑浴処理なしまたは可塑浴の温度と浸漬長を変更する以外は実施例１と同条件で処理した。可塑浴処理後の多孔質の繊維のＮ／（Ｐ＋Ｎ）、Ｗ／（Ｐ＋Ｗ）を、実施例１と併せて表１に示す。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。延伸後の水浴の温度と浸漬長を表１記載のとおり変更して、水洗後のＮ／（Ｐ＋Ｎ）とＷ／（Ｐ＋Ｗ）を変更する以外は実施例１と同条件で熱処理して得たポリメタフェニレンイソフタルアミド繊維の密度、引張強度、伸度、３００℃乾熱収縮率の値を、実施例１と併せて表１に示す。
【００７２】
【表１】

【００７３】
［実施例３］
実施例１で用いたポリマー溶液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、ポリマー重量率Ｐ、アミド系溶媒重量率Ｎ、水分重量率ＷがＮ／（Ｐ＋Ｎ）＝０．４４、Ｗ／（Ｐ＋Ｗ）＝０．０９を満たす凝固糸を得た。次いで、水／ＮＭＰ＝４０／６０、温度６０℃の可塑浴を用い、浸漬長８０ｃｍにて可塑液を含ませてポリマー重量率Ｐ、アミド系溶媒重量率Ｎ、水分重量率Ｗの関係がＮ／（Ｐ＋Ｎ）＝０．５５、Ｗ／（Ｐ＋Ｗ）＝０．１７である多孔質の繊維を得た。
【００７４】
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℃の水浴に通した（浸漬長９．０ｍ）。このときＮ／（Ｐ＋Ｎ）＝０．２１、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した。
【００７５】
続いて、第２段目の可塑延伸浴中にて１．４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＝９９／１の組成の浴を用い、温度９０℃であった。延伸後、９０℃の水浴に通した（浸漬長３．６ｍ）。その後、表面温度１２０℃ローラーに巻き回して乾熱処理し、引続き表面温度１６０℃ローラーに巻き回して乾熱処理した。さらに表面温度３３０℃の熱板で定長にて乾熱処理を施し、ポリメタフェニレンイソフタルアミド繊維を得た。
【００７６】
得られた繊維の力学的特性は、繊度２．２２ｄｔｅｘ（２．０ｄｅ）、密度１．３６ｇ／ｃｍ^３、引張強度４．０６ｃＮ／ｄｔｅｘ（４．６０ｇ／ｄｅ）、伸度３４．０％であり、良好な数値を示した。また、３００℃乾熱収縮率は４．３％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、Ｎａ７５ｐｐｍ、Ｋ７ｐｐｍ、Ｃａ５ｐｐｍ、Ｆｅ６ｐｐｍ、Ｃｌ１００ｐｐｍ、全イオン性物質２０５ｐｐｍであり、きわめて低い含量を示した。
【００７７】
［実施例４および比較例５〜８］
実施例１で用いたポリマー溶液Ａを紡糸原液とし、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、ポリマー重量率Ｐ、アミド系溶媒重量率Ｎ、水分重量率ＷがＮ／（Ｐ＋Ｎ）＝０．４４、Ｗ／（Ｐ＋Ｗ）＝０．０９を満たす凝固糸を得た。次いで、可塑浴処理なしまたは可塑浴の温度と浸漬長を変更する以外は実施例１と同条件で処理した。可塑浴の温度、浸漬長、可塑浴処理後の多孔質の繊維のＮ／（Ｐ＋Ｎ）、Ｗ／（Ｐ＋Ｗ）を、実施例３と併せて表２に示す。
【００７８】
引続き、第１段目の可塑延伸浴中にて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。延伸後の水浴の温度と浸漬長を変更して、水洗後のＮ／（Ｐ＋Ｎ）とＷ／（Ｐ＋Ｗ）を変更する以外は実施例３と同条件で延伸して得たポリメタフェニレンイソフタルアミド繊維の密度、引張強度、伸度、３００℃乾熱収縮率の値を、実施例３と併せて表２に示す。
【００７９】
【表２】

【００８０】
【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。
【００８１】
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]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a method for producing, with high productivity, a meta-type wholly aromatic polyamide fiber having a metaphenylene isophthalamide skeleton as a main component having good mechanical properties and heat resistance by wet spinning with high productivity, and a substantial method obtained by the method. And meta-type wholly aromatic polyamide fibers containing no salts.
[0002]
[Prior art]
It is well known that a wholly aromatic polyamide produced from an aromatic diamine and an aromatic dicarboxylic acid dichloride has excellent heat resistance and flame retardancy, and these wholly aromatic polyamides can be used in amide solvents. It is also well-known that the polymer solution can be formed into a fiber from these polymer solutions by a method such as dry spinning, wet spinning, and semi-dry semi-wet spinning.
[0003]
Among such wholly aromatic polyamides, fibers of a meta-type wholly aromatic polyamide (hereinafter sometimes abbreviated as “meta-aramid”) represented by polymetaphenylene isophthalamide are particularly useful as heat-resistant and flame-retardant fibers. It is said that such a meta-aramid fiber is currently produced industrially mainly by the following two methods (a) and (b). As methods, the following methods (c) to (f) have been proposed.
[0004]
(A) A low-temperature solution polymerization of metaphenylenediamine and isophthalic acid chloride in N, N-dimethylacetamide to prepare a polymetaphenylene isophthalamide solution. A method for producing a 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) The contact between an organic solvent system (eg, tetrahydrofuran) which is not a good solvent for the formed 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-based solvent, and wet-spinning in an inorganic salt-containing aqueous coagulation bath ( See JP-B-48-17551).
[0006]
(C) A meta-aramid solution synthesized and isolated by a solution polymerization method dissolved in an amide-based solvent and containing no inorganic salt or containing a small amount (2 to 3%) of lithium chloride by a wet molding method. A method for producing a molded article such as a fiber (see Japanese Patent Application Laid-Open No. 50-52167).
[0007]
(D) A solution of the meta-aramid polymer containing calcium chloride and water produced by solution polymerization in an amide solvent and neutralization with calcium hydroxide, calcium oxide, etc. is extruded from the orifice into a gas, and the gas is extruded. After passing through, it is introduced into an aqueous coagulation bath and then passed through an aqueous solution of an inorganic salt such as calcium chloride to form a yarn (see JP-A-56-31009).
[0008]
(E) A solution of a meta-aramid polymer containing calcium chloride and water produced by solution polymerization in an amide-based solvent and neutralization with calcium hydroxide, calcium oxide, etc., is passed through an orifice to an aqueous solution containing calcium chloride at a high concentration. A method of spinning in a coagulation bath to form a yarn (see JP-A-8-07421, JP-A-10-88421, etc.).
[0009]
(F) An amide-based solvent solution containing an inorganic salt of meta-aramid is discharged to a high-temperature spinning tube, and immediately after exiting the spinning tube, cooled with a low-temperature aqueous solution to swell, and the aqueous solution containing a plasticizing salt is discharged. By stretching in a stretching bath, a density of 1.3 g / cm having many very fine pores ³ A method for producing an easily dyeable porous fiber of less than (see Japanese Patent Publication No. 52-43930).
[0010]
The above method (a) has an advantage that a polymer solution for spinning (stock solution for spinning) can be prepared without isolating the polymer. However, since dry spinning using an amide-based solvent having a high boiling point is used, the production energy is low. The cost is high, and the spinning stability decreases rapidly as the number of holes per spinneret increases. In addition, even if the polymer solution is wet-spun into an aqueous coagulation bath, only weak fibers with much devitrification are often obtained. Therefore, the meta-aramid polymer solution obtained by solution polymerization is still wet-spun using the aqueous coagulation bath. The method is believed to have many difficulties and has not been implemented industrially. On the other hand, the methods (b) and (c) avoid the above-mentioned problem of dry spinning, but use different solvents in the polymerization system and the spinning system, and a process for re-dissolving the polymer once isolated. In addition, there is a problem that special consideration and meticulous process control are required to obtain a stable solution by re-dissolving (see Japanese Patent Publication No. 48-4661). In the method (d), when spinning from a spinneret into the air, increasing the number of holes per spinner significantly lowers spinning stability, resulting in low productivity and low efficiency. Furthermore, although the method (e) gives fibers having good physical properties, it is difficult to increase the spinning speed, and thus there is a problem in productivity. The method (f) has a density of 1.3 g / cm. ³ Although this is a method of producing much smaller porous fibers, 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.To use them as electronic materials, it is required to minimize the contamination of ionic substances and the like. Is preferably not contained at all. However, in the production method known so far, in the spinning process, the affinity for the polymer dope such as calcium chloride and lithium chloride is very high in the spinning solution or the coagulation bath, and the salts which are easily dissolved are considerably high. It is essential to include them in a concentration, so that it is unavoidable to include a large amount of salts in the fiber produced. In order to remove salts remaining in the fiber, a large-scale washing step had to be provided, and it was not possible to completely remove the salts of the fiber.
[0012]
As a means for solving such a problem, Japanese Patent Application Laid-Open No. 2001-303365 discloses that a meta-type wholly aromatic polyamide containing metaphenylene isophthalamide as a main component obtained by the same method as in (b) is dissolved in an amide solvent. The polymer solution substantially free of salts, comprising an amide-based solvent and water, and discharged into a coagulation bath substantially free of salts to coagulate as a porous linear body, Subsequently, this is stretched in a plastic stretching bath composed of an aqueous solution of an amide solvent, washed with water, and then heat-treated to form a dense meta-type wholly aromatic material substantially free of salts (inorganic ionic substances). Japanese Patent Application Laid-Open No. 2001-348726 discloses a method for producing a polyamide fiber. In the same manner, a method of coagulating as a porous linear body, followed by heating in air as it is or after impregnating with a plastic liquid. Enlargement, a method of heat treatment after once heated at a low temperature of 100 to 200 ° C. without drying at a higher temperature of 250 to 400 ° C. and then is proposed.
[0013]
Certainly, although these methods are excellent as methods for obtaining meta-aramid fibers substantially free of salts, it is considered that sufficient orientation and crystallization are not performed, and sufficient fiber physical properties cannot be obtained. In particular, only those having poor heat shrinkage stability are obtained, which is not useful as an industrial production method.
[0014]
As described above, a method for producing a meta-aramid fiber satisfying fiber properties and containing no salts at a practical industrial production level has not yet been proposed.
[0015]
[Problems to be solved by the invention]
A main object of the present invention is to provide a novel method capable of advantageously producing salt-free meta-aramid fibers having good mechanical properties and thermal properties at a substantially industrial production level. Another object of the present invention is to provide a meta-aramid fiber which does not substantially contain salts and is dense and excellent in heat shrink stability.
[0016]
[Means for Solving the Problems]
The main object of the present invention is to form a meta-type wholly aromatic polyamide 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 by wet spinning. In the method for producing a wholly aromatic polyamide fiber, (1) a polymer solution substantially free of salts is used as a stock solution for spinning, and the solution is composed of an amide-based solvent and water from a spinneret and substantially converts salts. The mixture is discharged into a coagulation bath having a temperature (T1) of 20 to 70 ° C. and solidified as a porous linear body. (2) An aqueous solution of an amide-based solvent having a temperature (T2) of (T1 + 5 ° C.) After immersion in a plastic bath at ~ 90 ° C to adjust the water content and the amide-containing solvent ratio in the fiber so as to satisfy the following formulas (a) and (b), (3) the amide-based solvent From aqueous solutions (4) Then, it is washed with water or water containing an amide-based solvent, and (5) heat-treated at a temperature of 100 to 250 ° C. It has been found that this can be achieved by a method for producing a dense meta-type wholly aromatic polyamide fiber, which is characterized by performing a heat treatment at -400 ° C.
(A) 0.3 ≦ N / (P + N) ≦ 0.7
(B) 0 ≦ W / (P + W) ≦ 0.3
Here, 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.
[0017]
It has also 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 dry heat shrinkage of 300 ° C. of 5% or less.
[0018]
At this time, in the spinning step (1), the composition of the coagulation bath was adjusted to a weight ratio of 40/60 to 70/30 of the amide solvent and water, and in the step (2), the plastic bath was changed to the amide solvent and water. In the plastic stretching step (3), the composition of the amide solvent and water is 20 / 80-70 / 30 in weight ratio, and the temperature is 20-80. The film is stretched in a range of 1.5 to 10 times using a stretching bath at 90 ° C., and in the washing step (4), the water content and the amide-containing solvent ratio in the fiber satisfy the following (c) and (d). Adjust to your satisfaction,
(C) 0.3 ≦ N / (P + N) ≦ 0.7
(D) 0.4 ≦ W / (P + W) ≦ 0.7
Alternatively, in the above plastic stretching step (3), the composition of the amide solvent and water is 20/80 to 70/30 by weight and is 1.5 to 10 times using a stretching bath having a temperature of 20 to 90 ° C. And in the washing step (4), the water content and the amide-containing solvent content in the fiber are adjusted so as to satisfy the following (e) and (f):
(E) 0.1 ≦ N / (P + N) ≦ 0.3
(F) 0.4 ≦ W / (P + W) ≦ 0.7
Again, a step of re-stretching 1.0 to 3 times in a plastic stretching bath in which the composition of water or the amide solvent is 0/100 to 40/60 by weight and the temperature is 20 to 100 ° C., Or a step of washing again with an aqueous solution of an amide-based solvent and then a heat treatment at a temperature of 100 to 250 ° C., followed by a heat treatment in the above step (6), whereby salts having particularly good physical properties and substantially eliminating salts are obtained. It is possible to produce a meta-aramid fiber which does not contain the polymer and is excellent in heat shrink stability with good productivity.
[0019]
According to such a method, the dry heat shrinkage at 300 ° C. is 5% or less, and more preferably the fiber density is 1.2 g / cm. ³ Larger (preferably 1.3 g / cm ³ Above), it is possible to easily produce 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.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the present invention, the dense meta-form substantially free of salts by wet spinning a polymer solution comprising an amide-based solvent containing a meta-type wholly aromatic polyamide having a metaphenylene isophthalamide skeleton as a main component This is a method for producing an aromatic polyamide fiber, wherein a specific step (1) to (6), which will be described in detail below, is carried out sequentially to obtain a metal which is substantially free of salts and has excellent heat stability. Molded wholly aromatic polyamide fibers are produced.
[0021]
The details will be described below step by step.
The meta-type wholly aromatic polyamide used in the present invention has meta-phenylene isophthalamide as a main skeleton, and its production method is not particularly limited.For example, meta-type aromatic diamine and aromatic dicarboxylic acid chloride may be used. Can be produced by solution polymerization, interfacial polymerization, or the like using as a raw material.
[0022]
As a meta-type aromatic diamine which is one of such raw materials, a diamine represented by the following formula is mainly used.
[0023]
Embedded image

[0024]
Specific examples of such meta-type aromatic diamines include metaphenylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, 2,4-diaminochlorobenzene, and 2,6-diaminochlorobenzene. Can be Other meta-type aromatic diamines include 3,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl sulfone, and the like.
[0025]
In the present invention, particularly, metaphenylenediamine or a mixed diamine containing the same as the main component is preferred. Other aromatic diamines used in combination with metaphenylenediamine include, in addition to the above meta-type aromatic diamines, paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene, aminoanisidine and the like. Benzene derivatives, 1,5-naphthylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylketone, bis (aminophenyl) phenylamine, bis (paraaminophenyl) methane, and the like.
[0026]
When a polymer having good solubility is desired, such other aromatic diamine can be used up to about 20 mol% of the whole, but when a polymer having high crystallinity is desired, metaphenylene is used. It is preferable that the diamine is contained in an amount of 90 mol% or more, particularly 95 mol% or more.
[0027]
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 containing the same. 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, and -Chloroisophthalic acid chloride, 5-methoxyisophthalic acid chloride, bis (chlorocarbonylphenyl) ether and the like.
[0028]
In the practice of the present invention, if a polymer having good solubility is desired, a high ratio (up to about 20 mol%) of these other aromatic dicarboxylic acids can be mixed, but a polymer having a high crystallinity can be used. Is desirable, it is preferable that isophthalic acid chloride is contained in an amount of 90 mol% or more, particularly 95 mol% or more.
[0029]
Among the meta-type wholly aromatic polyamides described above, a polymer in which 90 to 100 mol% of the total polymer repeating units are metaphenylene isophthalamide units and substantially free of salts is preferably used.
[0030]
In the present invention, a polymer solution in which the meta-type wholly aromatic polyamide is dissolved in an amide-based solvent and substantially does not contain salts (inorganic ionic substances) is supplied to the process described below. Such a polymer solution may be one obtained by removing salts from an amide-based solvent solution containing a meta-type wholly aromatic polyamide obtained by the above solution polymerization or the like, or may be obtained by the above solution polymerization, interfacial polymerization or the like. The meta-type wholly aromatic polyamide may be isolated from a solution containing the meta-type wholly aromatic polyamide and dissolved in an amide-based solvent. Here, “substantially free of salts” means that the total amount of salts in the polymer solution is less than 0.1% by weight, and it is acceptable that a very small amount of salts is contained. The smaller the amount, the better, and preferably 0 to 0.01% by weight.
[0031]
Examples of the amide solvent used herein include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone, and the like. N-methyl-2-pyrrolidone is preferred from the viewpoint of the stability of the polymer solution up to the wet spinning step.
[0032]
In the present invention, the polymer solution used for the spinning dope may contain water. Such water may be added as needed, but may be formed inevitably in the solution preparation process. The concentration may be any concentration as long as the solution is in a stable range. For example, it is usually preferably added and contained in the range of 0 to 60% by weight based on the weight of the polymer, and particularly preferably 15% by weight. % Is preferable. If the concentration exceeds this, the stability of the polymer solution is impaired, and the spinnability may be significantly impaired due to precipitation and gelation of the polymer.
[0033]
In the present invention, when the polymer solution is discharged into a coagulation bath, a multi-hole spinneret can be used. In practice, the upper limit of the number of holes is about 50,000 holes, and preferably a spinneret having 300 to 30,000 holes, particularly 3000 to 10,000 holes is used.
[0034]
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 consisting essentially of two components. In this coagulation bath composition, as the amide-based solvent, meta-aramid can be suitably used as long as it dissolves and mixes well with water. In particular, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, Dimethylimidazolidinone or the like can be suitably used. Considering the recovery of the solvent and the like, it is preferable to use the same type as the amide solvent in the spinning stock solution.
[0035]
Although the optimum mixing ratio of the amide solvent and water slightly varies depending on the conditions of the polymer solution, the concentration of the amide solvent in the coagulation bath is in the range of 40 to 70% by weight, particularly 50 to 65% by weight. It is preferable that If the concentration of the amide solvent is below this range, very large voids are likely to occur 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 fusion of the yarns easily occurs.
[0036]
The temperature (T1) of the coagulation bath is closely related to the composition of the coagulation solution, but generally, a higher temperature is preferable because it is difficult to form pores on the generated bubbles called coarse fingers in the produced yarn. . However, when the concentration of the coagulating solution is high, if the temperature is too high, the fusion between the yarns becomes intense. Therefore, the preferable temperature of the coagulating bath is 20 to 70 ° C, more preferably 40 to 65 ° C. is there.
[0037]
The coagulation liquid is preferably substantially composed of only the amide solvent and water, but may contain a small amount of salts. In particular, salts such as calcium chloride and calcium hydroxide may be extracted from the remaining polymer solution in a trace amount, but this does not inhibit porous coagulation at all, for example, coagulation liquid If the concentration is as low as 10% by weight or less, particularly 1% by weight or less, there is no problem even if salts are contained. Therefore, the preferred concentration of salts is in the range of 0 to 10% by weight based on the coagulation liquid. The immersion time of the yarn in the coagulation bath is preferably 0.1 to 30 seconds. If the immersion time is too short, the formation of the yarn is insufficient, and the yarn may be broken.
[0038]
Next, the plastic bath in the present invention is substantially free of salts like the coagulation bath, and contains an amide solvent and water (H ₂ O) and an aqueous solution consisting essentially of two components. The optimum mixing ratio of the amide solvent and water slightly varies depending on the conditions of the porous linear material, but the concentration of the amide solvent in the plastic bath is 40 to 70% by weight, particularly 50 to 65% by weight. It is preferably within the range. On the other hand, the temperature (T2) of the plastic bath must be in the range of (T1 + 5) ° C. to 90 ° C. By setting the temperature range, the weight of the amide compound solvent and the weight of water in the porous linear body are increased. Thus, a more uniform porous fiber can be formed. If this temperature is less than T1 + 5 ° C., the weight of the amide compound solvent and the weight of water cannot be sufficiently increased even when immersed in a plastic bath, and there is no difference from a coagulated yarn containing a coagulating liquid in the pores. On the other hand, if T2 is higher than 90 ° C., it is not preferable because the fusion of the yarns becomes severe or a single yarn breaks due to partial re-melting.
[0039]
Like the coagulating liquid, the plasticizing liquid is preferably substantially composed of only the amide solvent and water, but may contain a small amount of salts. For example, if the concentration is as low as 10% by weight or less, particularly 1% by weight or less with respect to the plastic liquid, there is no problem even if salts are contained. Therefore, the preferred concentration of salts is in the range of 0 to 10% by weight based on the plastic liquid. The immersion time of the yarn in the plastic bath is preferably 0.1 to 30 seconds. If the immersion time is too short, the weight of the amide-based solvent and the weight of the water cannot be sufficiently increased, and there is no difference between the immersion time and the coagulated yarn containing the coagulation liquid in the pores.
[0040]
In the present invention, the fiber that has been subjected to the step of immersion in the plastic bath needs to be adjusted so that the water content and the amide-containing solvent content satisfy the following formulas (a) and (b). By doing so, a more uniform porous fiber can be formed.
(A) 0.3 ≦ N / (P + N) ≦ 0.7, preferably 0.45 ≦ N / (P + N) ≦ 0.65
(B) 0.1 ≦ W / (P + W) ≦ 0.3, preferably 0.15 ≦ W / (P + W) ≦ 0.25
Here, 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.
[0041]
In this way, the porous linear body in which the amide solvent content and the water content in the fiber are adjusted needs to be plastically stretched in an aqueous solution of the amide solvent. As the amide solvent used here, any solvent may be used as long as it swells the meta-type wholly aromatic polyamide and mixes well with water. In particular, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylimidazo Lidinone and the like can be suitably used. More preferably, the same solvent as that used in the coagulation bath is preferably used. The use of the same type of solvent as the coagulation bath simplifies the recovery step and is economically advantageous.
[0042]
That is, the amide solvents in the polymer solution, coagulation bath, plastic bath and plastic stretching bath are all preferably the same, and as such a solvent, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide is used. It is convenient to use them alone or in combination of two or more.
[0043]
Although the composition and the temperature of the plastic stretching bath are closely related to each other, first, in the first-stage plastic stretching, the concentration of the amide-based solvent in the plastic stretching bath is 20 to 70% by weight, and the temperature is 20 to 90%. The range of ° C. is preferably used. In a region lower than this range, plasticization does not proceed sufficiently, and it is difficult to obtain a sufficient draw ratio, and in a range exceeding this range, the surface of the yarn is melted and easily fused, and good spinning becomes difficult. There are many.
[0044]
The plastic stretching is usually performed 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 manner, 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 the heat treatment is performed after plastic stretching described below. Densification proceeds well. However, when the film is stretched at an extremely high magnification, the condition of the process deteriorates, and it becomes difficult to produce a good yarn.
[0045]
After the plastic stretching bath, the fiber after the bath is washed with water or an aqueous solution of an amide-based solvent. It is preferable to adjust the solvent ratio so as to satisfy the following formulas (c) and (d).
(C) 0.3 ≦ N / (P + N) ≦ 0.7, preferably 0.35 ≦ N / (P + N) ≦ 0.65
(D) 0.4 ≦ W / (P + W) ≦ 0.7, preferably 0.45 ≦ W / (P + W) ≦ 0.65
Here, 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.
[0046]
By adjusting the water content and the amide-containing solvent content within the above ranges, the fluidity of the polymer during the heat treatment is improved in the subsequent heat treatment in a temperature range of 100 to 250 ° C. Then, it is considered that the orientation and crystallization are promoted when the amide solvent subsequently evaporates and escapes from the fiber. Further, it is considered that when an appropriate amount of water and the amide solvent coexist, they azeotropically promote the evaporation of the amide solvent.
[0047]
If N / (P + N) is less than 0.3, the effect of improving the polymer fluidity during this heat treatment is small, and it is difficult to obtain good fiber properties. On the other hand, when it exceeds 0.7, it takes time to evaporate the amide compound solvent, which is disadvantageous in terms of productivity and energy, and the fiber is liable to be colored. Further, if W / (P + W) is less than 0.4, the fibers may be fused together during the heat treatment, resulting in a decrease in fiber physical properties. Disadvantageous in productivity and energy.
[0048]
In addition, as a method of adjusting the water content and the amide-containing solvent ratio to the above ranges, after the plastic stretching, the immersion length is passed through a water bath at 10 to 70 ° C. or a mixed bath of amide solvent / water at 10 to 40 ° C. Can be easily adjusted by adjusting the number of threading turns.
[0049]
In the present invention, the fiber subjected to plastic stretching and washing may be subjected to the second stage plastic stretching after the heat treatment step (5). At that time, the water content and the amide-containing solvent ratio in the fiber after washing with water or an aqueous solution of an amide-based solvent are preferably adjusted so as to satisfy the following formulas (e) and (f). .
(E) 0.1 ≦ N / (P + N) ≦ 0.3, preferably 0.15 ≦ N / (P + N) ≦ 0.25
(F) 0.4 ≦ W / (P + W) ≦ 0.7, preferably 0.45 ≦ W / (P + W) ≦ 0.65
Here, 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.
[0050]
By adjusting the water content and the amide-containing solvent ratio to the above ranges, in the subsequent heat treatment at 100 to 250 ° C., the fluidity of the polymer during the heat treatment is appropriately improved, and the orientation proceeds. It is considered that the crystallization is suppressed and the densification of the fiber is promoted.
[0051]
In addition, as a method of adjusting the water content and the amide-containing solvent ratio to the above ranges, a water bath at 10 to 70 ° C. or a mixed bath of amide-based solvent / water at 10 to 40 ° C. after the first-stage plastic stretching is used. It can be easily carried out by passing through and adjusting the immersion length by the number of threading turns.
[0052]
The fiber in which the water content and the amide-containing compound solvent ratio in the fiber were adjusted as described above was once heat-treated in 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. Later, the second stage is plastically stretched.
[0053]
If the above-mentioned N / (P + N) is less than 0.1, the effect of improving the fluidity of the polymer during the heat treatment becomes insufficient, and the densification of the fiber becomes insufficient, so that good fiber properties are obtained. It becomes difficult. On the other hand, if it exceeds 0.3, the crystallization during the heat treatment is apt to proceed, and at the same time, the adhesion of the fibers is liable to occur, so it is difficult to obtain the same good fiber properties. Further, if W / (P + W) is less than 0.4, the fluidity of the polymer during the heat treatment is reduced, the densification of the fiber becomes insufficient, and there is a concern that the physical properties of the fiber may be reduced. On the other hand, if it exceeds 0.7, it takes time to evaporate water, which is disadvantageous in productivity and energy.
[0054]
The composition and temperature of the second-stage plastic stretching bath are also in the same close relationship as in the first-stage plastic stretching, but the concentration of the amide-based solvent is slightly lower at 0 to 40% by weight and the temperature is 20 to 100 ° C. Ranges are preferably used. If the concentration or the temperature of the amide-based solvent is too high, the orientation of the fibers becomes insufficient, and the physical properties of the fibers tend to deteriorate. The stretching ratio is suitably in the range of 1 to 3 times, preferably 1 to 2 times, and particularly preferably 1.0 to 1.5 times. By performing multi-stage drawing by adding a drawing step after the second stage, the strength and elastic modulus of the meta-aramid fiber are further improved, and good physical properties are exhibited.
[0055]
The fibers plastically stretched in one or two or more stages are washed with water or an aqueous solution of an amide solvent in step (4), and then heated with a heating roller, a heating plate, hot air, etc. in step (5). Heat treatment, preferably dry heat treatment, in a temperature range of 100 to 250 ° C, preferably 100 to 200 ° C.
[0056]
The subsequent heat treatment at a temperature of 270 to 400 ° C. in step (6) has a close relationship between the processing temperature and the fiber density, and is preferably performed at a temperature of 300 to 370 ° C. At a high temperature exceeding 400 ° C., the yarn may be severely deteriorated, colored, and in some cases, broken. On the other hand, if the temperature is lower than 270 ° C., the fiber cannot be sufficiently densified, and it becomes difficult to express desired fiber properties. Here, the treatment temperature refers to a set temperature of a heating means such as a hot plate or a heating roller, and a dry heat treatment is particularly preferable.
[0057]
The stretching ratio at this time has a close relationship with the expression of the elastic modulus and the strength, and can be set to an arbitrary ratio as needed, but is usually 0.7 to 3.0 times, particularly 1.0 times. By setting the value in the range of ~ 2.7 times, good thermal stretchability, and the development of strength and elastic modulus 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 the heat treatment, and the heat treatment of the present invention is limited heat treatment within a certain range during the treatment. Means no problem. The draw ratio of the heat treatment is preferably selected in consideration of the draw ratio of the plastic draw described above, and from the viewpoint of the densification of the yarn and the development of the physical properties, the realization of a stable yarn forming property, the draw ratio includes the plastic draw and the hot draw. More preferably, the total stretching ratio is set to be 3.0 to 12 times, and more preferably, set to be 2.5 to 6 times. The meta-aramid fiber according to the present invention has good stretchability and can be smoothly drawn to a high magnification without causing breakage or fluff during plastic stretching or hot stretching.
[0058]
Further, the fiber thus produced is subjected to a crimping process as required, cut into an appropriate fiber length, and provided to spinning and other subsequent steps.
[0059]
As described above, the meta-type wholly aromatic polyamide (meta-aramid) fiber according to the present invention has the same dense structure as ordinary meta-aramid fiber, and has excellent heat stability such that the dry heat shrinkage at 300 ° C. is 5% or less. Having. The fiber density is 1.2 g / cm ³ Larger, preferably 1.3 g / cm ³ As described above, 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. Further, in a preferred embodiment, the calcium concentration in the fiber, which has a concern about adverse effects on fiber physical properties, heat resistance, and post-processability, is 0 to 100 ppm, and chloride in the fiber, which adversely affects electrical properties such as electrical insulation. It has the advantage that the concentration of the substance is 0 to 150 ppm.
[0060]
As described above, the meta-type wholly aromatic polyamide (metaramid) fiber according to the present invention can be applied to various uses taking advantage of its heat resistance, flame resistance, and mechanical properties, and particularly to applications that dislike the incorporation of ionic substances. Can be suitably used. For example, alone or in combination with other fibers, heat-resistant and flame-resistant clothing such as fire-fighting clothing, protective clothing, flaming-resistant bedding, interior clothing, and other industrial materials such as filters as non-woven fabric, or synthetic paper, It can be used effectively as a raw material for composite materials, and because of its extremely low content of ionic substances, it can be used in the fields of electrical insulation materials, electronic equipment parts, printed wiring boards, etc. Especially effective.
[0061]
【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. in concentrated sulfuric acid at a polymer concentration of 100 mg / 100 ml sulfuric acid after isolating and drying an aromatic polyamide polymer from a polymer solution. Value. Further, “parts” and “%” are all based on weight unless otherwise specified, and quantitative ratios indicate weight ratios unless otherwise specified. Further, the polymer concentration (PN concentration) in the polymer solution (spun stock solution) used for spinning is the weight% of the polymer based on the total weight parts, that is, {polymer / (polymer + solvent + other)} 100 (%) It is.
[0062]
The density of the porous linear body obtained by coagulation was calculated from the fiber diameter and fineness measured according to ASTM D2130.
[0063]
The metal concentration in the obtained fiber was quantified using an atomic absorption method for alkali metals, and the other metal ion concentrations were quantified using ICP. The chloride concentration was determined by Dorman microcoulometric titration.
The dry heat shrinkage at 300 ° C. of the obtained fiber was measured by the following method. That is, a load of 98 cN (100 g) is hung on a 3300 dtex (3000 denier) tow, and a mark 30 cm apart is marked. After removing the load, the toe length L is measured after placing the tow in an atmosphere of 300 ° C. for 15 minutes. The value of (30-L) / 30 × 100 was defined as the dry heat shrinkage (%) at 300 ° C.
[0064]
The polymer weight ratio P, the amide solvent weight ratio N, and the water weight ratio W in the fiber before the heat treatment at 100 to 250 ° C were measured by the following methods.
The fiber before heat treatment at 100 to 250 ° C. is centrifuged for 10 minutes in a centrifuge (5,000 rpm), and the fiber weight M1 at this time is measured. The fiber is boiled in methanol for 4 hours to extract the amide compound solvent and water in the fiber. The total weight M2 of the fiber after extraction and the extract is measured. Further, the fiber after extraction is taken out and dried under an atmosphere of 105 ° C., and the weight of the fiber after drying is measured, which is designated as P1. The amide compound solvent weight concentration C (%) in the extract is determined by gas chromatography. From these, N1 = (M2−P1) × C / 100, and W1 = M1−P1−N1, 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
[0065]
[Example 1]
I.I. produced by an interfacial polymerization method according to the method described in JP-B-47-10863. V. = 1.9 parts by weight of N-methyl-2-pyrrolidone cooled to −10 ° C. were suspended in 78.5 parts by weight of N-methyl-2-pyrrolidone cooled to −10 ° C. The mixture was dissolved by heating to obtain a transparent polymer solution A. In addition, the inorganic ion concentration of the said polymer powder was 730 ppm of Na, 8.8 ppm of K, 5 ppm of Ca, and 2.3 ppm of Fe. The polymer concentration of the polymer solution was 21.5%.
[0066]
The polymer solution A was used as a spinning dope and discharged from a spinneret having a hole diameter of 0.07 mm and a number of holes of 5,000 into a coagulation bath at a bath temperature of 50 ° C. and spun. The coagulation bath used was a bath having a composition of water / NMP = 40/60. After passing through an immersion length (effective coagulation bath length) of 30 cm at a yarn speed of 7 m / min, the coagulation bath was once drawn out into the air to obtain a polymer weight. A coagulated yarn having a ratio P, an amide solvent weight ratio N, and a water weight ratio W satisfying N / (P + N) = 0.44 and W / (P + W) = 0.09 was obtained.
[0067]
Then, after a plastic solution was contained at a immersion length of 80 cm in a plastic bath at a temperature of 60 ° C. with a composition of water / NMP = 40/60, a polymer weight ratio P, an amide solvent weight ratio N, and a water weight ratio W were determined. A porous fiber having the relationship N / (P + N) = 0.55 and W / (P + W) = 0.17 was obtained.
[0068]
Subsequently, stretching was performed in a plastic stretching bath at a stretch ratio of 3.6 times. At this time, the plastic stretching bath had a composition of water / NMP = 40/60 and a temperature of 20 ° C. After stretching, the film was passed through a water / NMP = 70/30 bath at 20 ° C. (immersion length 1.8 m), and further passed through a water bath at 20 ° C. (immersion length 1.8 m). At this time, N / (P + N) = 0.41 and W / (P + W) = 0.60. Thereafter, it was wound around a roller having a surface temperature of 120 ° C. to perform a dry heat treatment, and subsequently was wound around a roller having a surface temperature of 160 ° C. to perform a dry heat treatment. Further, a dry heat treatment was performed at a fixed length on a hot plate having a surface temperature of 330 ° C. to obtain a polymetaphenylene isophthalamide fiber.
[0069]
The mechanical properties of this fiber were as follows: fineness 2.2 dtex (2.0 de), density 1.36 g / cm ³ , Tensile strength of 3.95 cN / dtex (4.50 g / de) and elongation of 36.0%, showing good numerical values. Further, the dry heat shrinkage at 300 ° C. was 3.5%, indicating excellent heat shrinkage stability.
[0070]
The ionic concentration of the obtained fiber was 75 ppm of Na, 5 ppm of K, 5 ppm of Ca, 7 ppm of Fe, 90 ppm of Cl, and 192 ppm of all ionic substances, indicating a very low content.
[0071]
[Example 2 and Comparative Examples 1-4]
The polymer solution A used in Example 1 was used as a spinning dope and discharged from a spinneret having a hole diameter of 0.07 mm and a number of holes of 5,000 into a coagulation bath at a bath temperature of 55 ° C. and spun. The coagulation bath used was a bath having a composition of water / NMP = 40/60. After passing through an immersion length (effective coagulation bath length) of 20 cm at a yarn speed of 7 m / min, the coagulation bath was once drawn out into the air, and the polymer weight ratio was changed. A coagulated yarn was obtained in which P, the amide solvent weight ratio N, and the water weight ratio W satisfied the relationships of N / (P + N) = 0.44 and W / (P + W) = 0.09. Next, the treatment was carried out under the same conditions as in Example 1 under the conditions shown in Table 1, except that no plastic bath treatment was performed or the temperature and the immersion length of the plastic bath were changed. Table 1 shows N / (P + N) and W / (P + W) of the porous fibers after the plastic bath treatment together with Example 1. Subsequently, the film was stretched in a plastic stretching bath at a stretch ratio of 3.6 times. The plastic stretching bath at this time was a bath having a composition of water / NMP = 40/60, and was at a temperature of 20 ° C. The temperature and the immersion length of the water bath after stretching were changed as shown in Table 1, and N / (P + N) and W / (P + W) after water washing were changed, and heat treatment was performed under the same conditions as in Example 1 to obtain. The density, tensile strength, elongation, and dry heat shrinkage at 300 ° C. of the polymetaphenylene isophthalamide fiber are shown in Table 1 together with Example 1.
[0072]
[Table 1]

[0073]
[Example 3]
The polymer solution A used in Example 1 was discharged as a stock spinning solution from a spinneret having a hole diameter of 0.07 mm and a number of holes of 5,000 into a coagulation bath at a bath temperature of 50 ° C and spun. The coagulation bath used was a bath having a composition of water / NMP = 40/60. After passing through a dipping length (effective coagulation bath length) of 40 cm at a yarn speed of 7 m / min, the coagulation bath was once drawn out into the air, and the polymer weight ratio was changed. A coagulated yarn was obtained in which P, the amide solvent weight ratio N, and the water weight ratio W satisfied N / (P + N) = 0.44 and W / (P + W) = 0.09. Then, using a plastic bath having a water / NMP ratio of 40/60 and a temperature of 60 ° C., and containing a plastic liquid at an immersion length of 80 cm, the relationship between the polymer weight ratio P, the amide solvent weight ratio N, and the water weight ratio W is N. /(P+N)=0.55 and W / (P + W) = 0.17 to obtain a porous fiber.
[0074]
Subsequently, the film was stretched in a plastic stretching bath at a stretch ratio of 3.6 times. The plastic stretching bath at this time was a bath having a composition of water / NMP = 40/60, and was at a temperature of 20 ° C. After stretching, it was passed through a water bath at 20 ° C. (immersion length 9.0 m). At this time, N / (P + N) = 0.21 and W / (P + W) = 0.60. Thereafter, the film was wound around a roller having a surface temperature of 120 ° C. and subjected to dry heat treatment.
[0075]
Subsequently, stretching was performed in a second-stage plastic stretching bath at a stretching ratio of 1.4 times. The plastic stretching bath at this time was a bath having a composition of water / NMP = 99/1, and was at a temperature of 90 ° C. After stretching, it was passed through a water bath at 90 ° C. (immersion length 3.6 m). Thereafter, it was wound around a roller having a surface temperature of 120 ° C. to perform a dry heat treatment, and subsequently was wound around a roller having a surface temperature of 160 ° C. to perform a dry heat treatment. Further, a dry heat treatment was performed at a fixed length on a hot plate having a surface temperature of 330 ° C. to obtain a polymetaphenylene isophthalamide fiber.
[0076]
The mechanical properties of the obtained fiber were as follows: fineness 2.22 dtex (2.0 de), density 1.36 g / cm. ³ , A tensile strength of 4.06 cN / dtex (4.60 g / de) and an elongation of 34.0%, showing good numerical values. The dry heat shrinkage at 300 ° C. was 4.3%, showing excellent heat shrinkage stability. Further, the ion concentration in the fiber was 75 ppm of Na, 7 ppm of K, 5 ppm of Ca, 6 ppm of Fe, 100 ppm of Cl, and 205 ppm of all ionic substances, indicating extremely low contents.
[0077]
[Example 4 and Comparative Examples 5 to 8]
The polymer solution A used in Example 1 was used as a spinning stock solution, and was discharged from a spinneret having a hole diameter of 0.07 mm and a number of holes of 5,000 into a coagulation bath at a bath temperature of 50 ° C and spun. The coagulation bath used was a bath having a composition of water / NMP = 40/60. After passing through a dipping length (effective coagulation bath length) of 40 cm at a yarn speed of 7 m / min, the coagulation bath was once drawn out into the air, and the polymer weight ratio was changed. A coagulated yarn was obtained in which P, the amide solvent weight ratio N, and the water weight ratio W satisfied N / (P + N) = 0.44 and W / (P + W) = 0.09. Next, processing was performed under the same conditions as in Example 1 except that no plastic bath treatment was performed or the temperature and the immersion length of the plastic bath were changed. Table 2 shows the temperature of the plastic bath, the immersion length, and N / (P + N) and W / (P + W) of the porous fibers after the plastic bath treatment together with Example 3.
[0078]
Subsequently, the film was stretched in the first stage plastic stretching bath at a stretch ratio of 3.6 times. The plastic stretching bath at this time was a bath having a composition of water / NMP = 40/60, and was at a temperature of 20 ° C. Polymetaphenylene isophthalamide obtained by stretching under the same conditions as in Example 3 except that the temperature of the water bath after stretching and the immersion length are changed, and N / (P + N) and W / (P + W) after washing are changed. The values of the fiber density, tensile strength, elongation, and dry heat shrinkage at 300 ° C. are shown in Table 2 together with Example 3.
[0079]
[Table 2]

[0080]
【The invention's effect】
According to the method of the present invention, a dense meta-type wholly aromatic polyamide fiber (particularly, polymetaphenylene isophthalamide-based fiber) having good mechanical properties, heat resistance and the like and containing substantially no salts is produced with substantially industrial productivity. Can be manufactured. Meta-type wholly aromatic polyamide fibers which are substantially free of such salts, that is, whose concentration of inorganic ionic substances is extremely low, are meta-type wholly aromatic polyamide fibers having heat resistance, flame retardancy, electrical insulation and the like. In addition to its inherent properties, it does not contain a substantial amount of inorganic ions that affect electrical properties, etc., and has properties such as not impairing electrical properties when used as an electronic material, so it can be used effectively it can.
[0081]
As described above, the meta-type wholly aromatic polyamide fiber according to the present invention can be applied to various uses utilizing its heat resistance, flame resistance, and mechanical properties. It can be used particularly preferably.

Claims (11)

Production of meta-type wholly aromatic polyamide fibers by wet spinning a meta-type wholly aromatic polyamide 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 method, (1) a polymer solution substantially free of salts is used as a spinning solution, and the solution (T1) consisting of an amide-based solvent and water from a spinneret and substantially free of salts has a temperature of 20 to It is discharged into a coagulation bath at 70 ° C. and coagulated as a porous linear body. (2) An aqueous solution of an amide-based solvent in a plastic bath having a temperature (T2) of (T1 + 5 ° C.) to 90 ° C. After being immersed and adjusted so that the water content and the amide-containing solvent ratio in the fiber satisfy the following formulas (a) and (b), (3) a plastic stretching bath composed of an aqueous solution of an amide solvent is used. Stretching 4) Next, the substrate is washed with water or water containing an amide solvent, (5) heat-treated at a temperature of 100 to 250 ° C., and (6) further heat-treated at a temperature of 270 to 400 ° C. A method for producing dense meta-type wholly aromatic polyamide fibers.
(A) 0.3 ≦ N / (P + N) ≦ 0.7
(B) 0 ≦ W / (P + W) ≦ 0.3
Here, 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 wholly aromatic polyamide according to claim 1, wherein the composition of the amide solvent and the water in the coagulation bath in the step (1) and the plastic bath in the step (2) are 40/60 to 70/30 by weight, respectively. Fiber manufacturing method. In the above step (3), the draw ratio is 1.5 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. Then, in the above step (4), the fiber is washed with water or water containing an amide-based solvent, and the water content and the amide-containing solvent ratio in the fiber satisfy the following formulas (c) and (d). The method for producing a meta-type wholly aromatic polyamide fiber according to claim 1 or 2, wherein the adjustment is performed in the following manner.
(C) 0.3 ≦ N / (P + N) ≦ 0.7
(D) 0.4 ≦ W / (P + W) ≦ 0.7
Here, 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. In the above step (3), the draw ratio is 1.5 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. Then, in the above step (4), the fiber is washed with water or water containing an amide-based solvent, and the water content and the amide-containing solvent ratio in the fiber satisfy the following formulas (e) and (f). The meta-type wholly aromatic polyamide according to claim 1 or 2, wherein the following series of steps (7) to (8) are performed at least once between the steps (5) and (6). Fiber manufacturing method.
(E) 0.1 ≦ N / (P + N) ≦ 0.3
(F) 0.4 ≦ W / (P + W) ≦ 0.7
Here, 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.
(7) A step of re-stretching 1.0 to 3 times in a plastic stretching bath in which the composition of water or an amide solvent is 0/100 to 40/60 by weight and the temperature is 20 to 100 ° C (8) ) A step of washing with water or an aqueous solution of an amide solvent and then re-heat-treating at a temperature of 100 to 250 ° C. The method for producing a meta-type wholly aromatic polyamide fiber according to any one of claims 1 to 4, wherein in the step (6), heat treatment is performed in a temperature range of 270 to 400 ° C under stretching 0.7 to 4 times. . The amide-based solvent contained in the polymer solution, the coagulation bath and the plastic stretching 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 produced by the method according to any one of claims 1 to 6, wherein the dry heat shrinkage at 300 ° C is 5% or less. Group polyamide fiber. It is greater than the density of the fibers 1.2 g / cm ^3, and meta-type wholly aromatic polyamide fiber according to claim 7, wherein the content of total inorganic ionic substances is 500ppm or less in the fiber. The meta-type wholly aromatic polyamide fiber according to claim 7 or 8, 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 7 to 9, wherein the concentration of chloride in the fiber is 150 ppm or less. Is the density of the fiber is 1.3 g / cm ³ or more and is 500ppm or less content of total inorganic ionic substances in the fiber, calcium concentration 100ppm or less, according to claim 7 wherein the concentration of chloride is not more than 150ppm Meta-type wholly aromatic polyamide fiber.