JP3847515B2 - Method for producing dense meta-type aromatic polyamide fiber - Google Patents

Description

【００２４】
上記式において、Ｒは塩素原子、臭素原子等のハロゲン、又はメチル基、エチル基等の炭素数１〜３のアルキル基である。ｎは０又は１である。
【００２５】
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-トルエンジアミン、2,6-トルエンジアミン、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などが挙げられる。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などが挙げられる。
【００２６】
本発明では、なかでも、メタフェニレンジアミン又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、アミノアニシジンなどのようなベンゼン誘導体、1,5-パラ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）メタンなどが用いられる。
【００２７】
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、とくに９５モル％以上、含まれることが好ましい。
【００２８】
一方、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又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、3-クロルイソフタル酸クロライド、3-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）エーテルなどが挙げられる。
【００２９】
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。
【００３０】
溶液重合に用いる際は、重合溶媒としてアミド系溶媒を用いることができる。かか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などを用いることが出来るが、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などから、Ｎ−メチル−２−ピロリドン（本発明では「ＮＭＰ」と略す）を用いることがより好ましい。
【００３１】
溶液重合工程では、重合溶媒としてＮＭＰが好適に使用される。通常、ＮＭＰにメタ型芳香族ジアミンを溶解させた後、この溶液にイソフタル酸クロライドを主成分とする芳香族ジカルボン酸クロライドを粉末状態もしくは溶融状態で十分な撹拌下に加えて反応させる。反応温度としては、０〜８０℃、溶媒の使用量としては、原料合計に対して３〜３０重量％が好適である。
【００３２】
このようにして調製したメタ型芳香族ポリアミドの溶液は高濃度の塩化水素を含むので、これを水酸化カルシウムや水酸化ナトリウム、炭酸（水素）ナトリウムなどのアルカリによって中和することにより、反応が終結し好ましい重合度を持ち、化学的安定性の高いポリマー溶液をメタ型芳香族ポリアミド重合体溶液として得ることが出来る。
【００３３】
本発明において上記のごときメタ型芳香族ポリアミド溶液から力学的特性の良好な耐熱繊維を製造するには重合度の調節が重要である。とりわけ、ポリメタフェニレンイソフタラミド系重合体から性能が良好な繊維を得るには、３０℃の濃硫酸中、ポリマー濃度０．５ｇ／１００mlで測定した値から求めた固有粘度（Ｉ．Ｖ．）が０．８〜４．０、とくに１．０〜３．０、なかでも１．３〜２．４の重合体が好適である。重合体の重合度は、重合体又はその溶液が使用される目的や繊維の用途などによってその要求水準が設定されるので、必要に応じ、従来公知の方法によって重合度を制御して用いることができる。その代表的な方法の１つとして、末端停止剤（アニリン、トルイジン等のアルキルアニリン、安息香酸クロライド等）を用いて重合度を調節することができる。
【００３４】
本発明における重合体溶液中の重合体濃度は、重合体と溶媒（ＮＭＰ）との合計１００重量部に対する重量部（本発明では「ＰN濃度」と称する。なお、以下の説明ではＰN濃度の単位である重量部は省略する。）にして１０〜３０、好ましくは１６〜３０である。ＰN濃度が１０未満では、濃度が小さすぎて溶液の曳糸性が悪くなり、これに伴い繊維性能が低下するばかりでなく、低濃度のため、さらに溶媒（ＮＭＰ）の使用循環比が高くなり経済的にも好ましくない。また、ＰN濃度が高いほど成形物（繊維）の透明性は良好になる傾向があるが、ＰN濃度が３０を超えると粘度が高くなり過ぎて、重合反応及びとくに中和反応が順調に行えないなどの問題が生じる。したがって、重合反応で高濃度（例えばＰＮ濃度３０以上で）重合を行った場合、中和反応工程で中和剤である水酸化カルシウムをＮＭＰの適当量（例えば、最終的にＰＮ濃度が２５になる量）に分散させたスラリーを添加すると、中和反応が容易になると同時に重合体濃度（ＰＮ濃度）の調整を行うことがことができる。
【００３５】
本発明に用いる重合体溶液は、メタ型芳香族ポリアミドとアミド系溶媒とを含み、塩類を含むものであるが、さらに、水を含んでいてもよい。このような水や塩類は、上記溶液重合中に必然的に生成するが、さらに必要に応じて添加することできる。また、重合体溶液を他の溶液調製プロセスで製造する場合、塩類や水を外部より添加してもよい。このような塩類としてはこれに限定するものではないが、例えば塩化ナトリウム、よう化ナトリウム、塩化リチウムなどのアルカリ金属のハロゲン化物、塩化カルシウム、炭酸カルシウム、水酸化カルシウム、塩化マグネシウムなど、アルカリ土類金属のハロゲン化物や、炭酸塩、水酸化物などがあげられる。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以上６０％以下の範囲で添加、含有されるのが通常好ましく、特に５０％以下であることが好ましい。これを越える濃度では、溶液中の塩が析出するために溶液の安定性が損なわれるからである。
【００３６】
上記重合体溶液における水の含量は、全溶液重量に対して０から２０％の範囲で含んでいても良く、より好ましくは０から１５％の範囲である。これを越えると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。
【００３７】
特に上記溶液重合では、ポリマーの重合後溶液中に中和剤を添加し中和する。かかる中和剤としては、酸化カルシウム、水酸化カルシウム、炭酸カルシウムのうちの少なくとも１種を使用する。この中和反応により、重合反応で副生するＨＣｌを中和することで塩化カルシウム（ＣａＣｌ₂）が必然的に生成する。重合反応で副生するＨＣｌの量は、重合体の化学構造、最小単位の平均分子量によって異なるが、例えばポリメタフェニレンイソフタラミドの重合反応で副生するＨＣｌを上記化合物で１００％中和する場合、重合体１００（重量）部についてＣａＣｌ₂が４６．６４（重量）部生成する。ちなみに、この中和反応で生成したＣａＣｌ₂は重合体溶液中に溶存し、重合体溶液の安定性を高める働きをするが（特公昭35-16027号参照）、逆に、この多量に溶存するＣａＣｌ₂のため、従来はかかる重合体溶液からの湿式紡糸が困難であった。
【００３８】
一方、中和反応によって生成、含有される水の量は、中和剤の種類によって異なり、水酸化カルシウムによって中和すると重合体１００（重量）部に対して１５．１３（重量）部の水が生成する。一方、酸化カルシウム、炭酸カルシウムによって中和すると重合体１００部に対して７．５６部の水が生成する。また、これらの中和剤は水溶液や水、溶媒を含むスラリーとして添加されるため、ここで生成、添加した水も、重合体溶液に溶存しているが、上記の程度の量では溶液の安定性や中和後の組成物の特性をほとんど損なわない。むしろ、水の含有によって低粘度化などの好ましい特性を持たせることもあるが、余り多いと溶液の安定性を著しく低下させる（ゲル化する）ことになりこのましくない。従って、中和反応工程において添加する水の適量は、重合体濃度によって異なる。２．４２（重合体１００部に対して１５部）で、この水量の約６倍すなわち重合体１００部に対して約９０部まで溶解可能であるが、溶液の安定領域は重合体１００部に対して水が２．４２〜９．７部（水／重合体＝１５〜６０）の範囲である。また、例えばＰＮ濃度＝２０のときも上記ＰＮ濃度＝１６のときとほぼ同様で、重合体１００部に対し約１５〜６０部であり、ＰＮ濃度＝２５での安定領域は１５〜４５部となり、ＰＮ濃度＝３０では１５〜３０部である。上記に例示の範囲は重合体溶液を６０〜７０℃で静置した場合の概略値であり、重合体の重合度、静置保存温度などの条件によって幾分異なってくる。いずれにしても重合体溶液の水の溶存許容濃度は重合体濃度の増加に伴い限定されてくるが、本発明の実施に当っては好ましくは予め全重合体溶液中の水の濃度８％以下を目安に実験検討を実施することが、溶液のゲル化を防止し好ましい。
【００３９】
なお、本発明で用いる重合体溶液は前述の原料から合成し得る芳香族ポリアミドを含むものであればよく、例えば、前述の原料をTHF中で反応せしめ、アルカリ水溶液を加えてTHFと水溶液界面で、発生する塩化水素を中和して得た重合体をアミド系溶媒に溶解した溶液を用いても良いし、あるいは、界面重合法によって製造したポリマー溶液を用いてもかまわない。
【００４０】
本発明によれば、湿式紡糸において、多孔凝固と後緻密化というメタ系アラミドでは従来不可能と考えられてきた新規な紡糸、製糸プロセスをとることにより、優れた力学特性、耐熱性を有するメタ型アラミド繊維を効率的に良好な生産性で製造することができる。
【００４１】
従来、等モル含ＣａＣｌ₂（溶液重合で合成した際、アミド残基に対して当モルに生じる塩化カルシウムという）メタ型アラミド重合体溶液は湿式紡糸によって繊維化することが困難なため、従来はこれを紡糸する方法として乾式紡糸や半乾半湿式紡糸が採用されてきた。また、これを湿式紡糸するには、溶液重合、界面重合のいずれの場合も副生するＨＣｌの中和によって生成した塩化物塩類（ＣａＣｌ₂、ＮａＣｌ、ＮＨ₄Ｃｌ等）を何等かの手段で少なくとも７０％以下まで、好ましくは２０％以下まで、減少させた減塩重合体溶液を調製する必要があった。しかしながら、これらの手段による塩化物の除去は工業的に困難なことが多く、例えば、界面重合で重合体を合成した場合、重合溶媒と紡糸用溶媒とが異なるため、それらの回収に別々の回収装置を要するとか、あるいは溶液重合で合成した重合体溶液を同一溶媒を用いて紡糸する場合でも中和によって副生する無機塩化物を加圧濾過によって除去する（高粘度のため工業的に極めて困難）とか、重合体溶液に水を加えて無機塩化物を水洗除去した後、重合体を乾燥して再溶解するなど、困難な工程を必要とするため、エネルギーコスト的にも、環境汚染的にも難点が多く、いずれも好ましい方法とは言い難い。
【００４２】
本発明によれば、従来実施困難とされていた、この等モル含ＣａＣｌ₂重合体溶液を用いても、紡糸口金を通じて、塩類を実質的に含まない特定組成からなる凝固浴中に直接紡出する湿式紡糸法によって、光沢や力学特性、耐熱性などに優れたメタ型アラミド繊維を製造することを、可能にするものである。
【００４３】
本発明では、アミド系溶媒の水溶液という非常に簡単な組成の凝固浴を用い、これにより均質な多孔質の線状体として重合体溶液を凝固する。すなわち、本発明では、先に述べた重合体溶液を、好ましくは２０〜９０℃の範囲内で凝固浴温度に対応する温度に調整した後、紡糸口金から後述する組成、温度の凝固浴中に直接紡出（出糸）し、糸条物を多孔質体として形成せしめた後、この糸条物を凝固浴から引き出し、引き続きアミド系溶媒の水溶液中で（好ましくは2倍以上10倍以下の延伸倍率で）延伸し、さらに水洗、乾燥し好ましくはさらに250℃から400℃の範囲の温度で熱処理して繊維化する。
【００４４】
以下に上記重合体溶液を用いて行う工程（１）、（２）及び（３）について説明する。
【００４５】
［工程(１）］
本発明において、後工程で十分に物性を出し得る程度の緻密化をするためには、凝固段階で出来る多孔体の構造を出来る限り均質なものとすることが極めて重要である。多孔構造と浴の条件は緊密な関係にあり、凝固浴の組成と温度条件の選定は極めて重要である。
【００４６】
本発明における凝固浴は、実質的にアミド系溶媒と水（Ｈ₂Ｏ）との２成分からなる水溶液で構成さるが、この凝固浴組成において、アミド系溶媒としてはメタ型芳香族ポリアミドを溶解し、水と良好に混和するものであれば好適に用いることが出来るが、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などを好適に用いることが出来る。
【００４７】
アミド系溶媒と水の最適な混合比は、重合体溶液の条件によっても若干変化するが、アミド系溶媒の重量比が４０％から７０％の範囲であることが好ましい。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く、この範囲を上回る条件では凝固が進まず、糸の融着が起こるためである。
【００４８】
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とフィンガーとよばれる粗大な気泡上の空孔が出来にくく好ましい。しかし凝固液濃度が高い場合には高温にすると融着が激しくなるので、その好適な範囲は２０〜９０℃であり、より好ましくは３０〜８０℃の範囲である。
【００４９】
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良い。特に、塩化カルシウム、水酸化カルシウムなどの塩類はポリマー溶液中から抽出されてくるが、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、低濃度であれば含まれていてもまったく問題はない。したがって、これに限定するものではないが、この好適濃度は凝固液に対し重量比０から１０％の範囲である。
【００５０】
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。
【００５１】
このように糸条物として得られる多孔質の線状体は、でき得る限り密度の高い方が後の緻密化をスムーズに行うために好ましいが、好ましくは０．３ｇ／ｃｍ ^３ 以上、より好ましくは０．５ｇ／ｃｍ ^３ 以上の密度である。０．３ｇ／ｃｍ ^３ を下回る密度では多孔度が高く線状体を後の延伸工程で緻密化することが困難になる。この密度は、ASTM D2130にしたがって測定した糸太さ及び繊度をもとに算出した値である。
【００５２】
この多孔構造は非常に均質な微細孔で形成されていることを特徴とする。その孔サイズは走査型顕微鏡で測定すると０．２から１μ程度のサブミクロンオーダーの大きさを持ち、ボイドまたはフィンガーと呼ばれるような数μの大きさの孔は基本的には存在しない。このような非常に緊密で均質な微細孔構造を持つことによって、延伸時の断糸を防止し、最終熱セット時の緻密化と糸物性の発現が可能になる。このような均質な多孔構造は、たとえば凝固に伴うスピノーダル分解によって形成されることが知られている。
【００５３】
重合体溶液を凝固浴中に吐出する場合、紡糸口金は多ホールのものを用いることができる。ホール数としては５００００個以下、好ましくは３００〜３００００個である。
【００５４】
［工程（２）］
凝固により得られた多孔線状体は引き続きアミド系溶媒の水性溶液からなる可塑延伸浴中に浸漬し、この浴中で延伸する。
【００５５】
本発明における可塑延伸浴はアミド系溶媒の水溶液からなり、塩類は実質的に含まれない。このアミド系溶媒としてはメタ系アラミドを膨潤させ、水と良好に混和するものであれば好適に用いることが出来る。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などは好適に用いることが出来る。また更に好適には上記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。かかる凝固浴と同じ溶媒を用いれば、回収工程が簡略化され、経済的に有益である。
【００５６】
すなわち、重合体溶液、凝固浴及び可塑延伸浴に用いるアミド系溶媒は同一であることが好ましく、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のうち１種または２種以上の混合液を用いることが好都合である。
【００５７】
可塑延伸浴の温度と組成はそれぞれ密接な関係にあるが、アミド系溶媒の重量濃度が２０％から７０％、温度が２０℃から９０℃の範囲であれば好適に用いることが出来る。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するため良好な紡糸が困難になる。
【００５８】
本発明においては、通常１．５倍以上１０倍以下、好ましくは２倍以上１０倍以下、より好ましくは２．１倍以上６倍以下の倍率で延伸する。高倍率に延伸をかけることにより糸の強度、弾性率が向上し良好な物性を示すようになると同時に、孔が引きつぶされ、熱セットによる緻密化が良好に進行するようになる。また、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。
【００５９】
［工程（３）］
上記可塑延伸浴の工程を経た糸条物は、次に、通常３０℃以下の冷水で洗浄し、つづいて通常５０〜９０℃の温水で洗浄した後、加熱ローラー、熱風などによって通常１００℃以上の温度で乾燥する。その後以下に述べるように、熱板、熱ローラなどを用いて好ましくは２５０〜４００℃、より好ましくは２７０〜４００℃の温度で乾熱延伸等の熱処理に付される。
【００６０】
この乾熱延伸工程は、多孔質の線状体を緻密化せしめ強度、伸度を発現させるために重要な工程である。特に乾熱延伸の温度は密度と密接な関係にあり、２７０℃以上４００℃以下の温度範囲で処理することが好ましい。さらに好ましくは３００℃以上３７０℃以下の温度である。４００℃を超える高温では糸が激しく劣化し、着色し、さらには断糸することがある。また２７０℃を下回る温度では十分に緻密化することが出来ず、糸物性を発現することが困難である。
【００６１】
この時の延伸倍率は、弾性率、強度の発現に密接な関係を持っており、必要に応じて任意の倍率をとることが出来るが、通常、０．７倍から４倍、好ましくは１〜３倍の範囲で設定することで、良好な紡糸性と、強度、弾性率の発現が得られる。従って、緻密化と糸物性の発現、安定した紡糸性の発現には、可塑延伸、熱板延伸を含めて全延伸倍率が２．５〜１２であることが好ましく、さらには２．５から５倍となるように設定することがより好ましい。
【００６２】
本発明により得られるメタ型アラミド繊維は、延伸性がよく、温水浴延伸、乾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。
【００６３】
本発明では上述した溶液重合−中和反応−湿式紡糸−洗浄・乾燥・延伸をすべて連続した一貫工程で実施することができ、これが本発明方法の利点の一つでもあるが、場合よっては、幾つかの工程に分割して実施してもよい。
【００６４】
優れた耐熱性、力学特性を有するメタ型アラミド繊維が、塩類を含む重合体溶液から、単純な凝固浴を用いることにより、湿式紡糸によって生産性よく製造される。例えば、本発明方法では、従来の溶液重合によるメタ型アラミド溶液からの湿式紡糸により引張強度が４．０ｇ／ｄｅ（３．５３ｃＮ／ｄｔｅｘ）を越えるメタ型アラミド繊維を容易に製造することが可能となる。
【００６５】
このようにして製造されたメタ型アラミド繊維は、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、次工程に提供される。
【００６６】
以上のごとき本発明によるメタ型芳香族ポリアミド（メタ型アラミド）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、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、防護服などの耐熱耐炎衣料、耐炎性の寝具、インテリア材料として有用であり、不織布としてフィルターなど各種工業材料、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。
【００６７】
【実施例】
以下、実施例及び比較例により本発明を更に詳しく具体的に説明する。ただし、これらの実施例及び比較例は本発明の理解を助けるためのものであって、これらの記載によって本発明の範囲が限定されるのものではない。
【００６８】
なお、実施例及び比較例中、固有粘度（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０．５ｇ／１００ml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部［＝重合体／（重合体＋溶媒＋その他）］であり、塩化カルシウム及び水の濃度はそれぞれ重合体１００重量部に対する重量部である。
【００６９】
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見かけ密度ｄ１であり、緻密糸の密度はテトラクロロエタンとシクロヘキサンを溶媒に用いる浮沈法によって測定した値である。
【００７０】
［実施例１］
（ａ）溶液重合紡糸原液の調製温度計、攪拌装置及び原料投入口を備えた反応容器に、モレキュラーシーブスで脱水したＮＭＰ８１５部を入れ、このＮＭＰ中にメタフェニレンジアミン（以下、ｍＰＤＡと略す）１０８部を溶解した後、０℃に冷却した。この冷却したジアミン溶液に、蒸留精製し窒素雰囲気中で粉砕したイソフタル酸クロライド（以下、ＩＰＣと略す）２０３部を攪拌下に添加して反応せしめた。反応温度は約５０℃に上昇し、この温度で６０分間攪拌を継続し、さらに６０℃に加温して６０分間反応させた。反応終了後、水酸化カルシウム７０部を微粉末状で添加して６０分かけ中和溶解した（１次中和）。残りの水酸化カルシウム４部をＮＭＰ８３部に分散したスラリー液を調製し、この水酸化カルシウム含有スラリー（中和剤）を重合溶液に攪拌しながら添加した（２次中和）。この２次中和は４０〜６０℃で約６０分間攪拌して実施し、水酸化カルシウムを完全に溶解させた紡糸原液となる重合体溶液を調製した。
【００７１】
この溶液（紡糸原液）の重合体濃度（ＰＮ濃度、すなわち重合体とＮＭＰの合計１００重量部に対する重合体の重量部）は１４であり、生成したポリメタフェニレンイソフタラミド重合体のＩ．Ｖ．は２．４であった。また、この重合体溶液の塩化カルシウム濃度及び水の濃度は、重合体１００部に対し塩化カルシウム４６．６部、水１５．１部であった。
【００７２】
（ｂ）湿式紡糸・可塑延伸・乾燥熱延伸
上記（ａ）で調製した紡糸原液を孔径０．０９ｍｍ、孔数５０の口金より浴温度８０℃の凝固浴中に吐出して紡糸した。この凝固浴は、水／ＮＭＰ＝５０／５０（重量比）の組成の浴を用い、浸漬長（有効凝固浴長）６０ｃｍにて糸速８ｍ／分で通過させた後、いったん空気中に引き出し、引き続き、可塑延伸浴中にて３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＝４５／５５（重量比）の組成の浴を用い、温度４０℃であった。更に、冷水による水洗を十分に行った後、さらに８０℃の温水で洗浄した。引き続き、この温水延伸糸を表面温度１２０℃の乾燥ローラーで乾燥し、３４０〜３６０℃の熱板上で１．２倍に乾熱延伸して、巻き取った。本実施例における全延伸倍率は３．６倍で、延伸繊維の最終巻き取り速度は２８．８ｍ／分であった。
【００７３】
途中凝固浴より得られた多孔質の線状体の密度は０．７４ｇ／ｃｍ ^３ であった。
【００７４】
得られたポリメタフェニレンイソフタルアミド延伸繊維の力学的特性は、繊度１．７ｄｅ（１．８９ｄｔｅｘ）、密度１．３３ｇ／ｃｍ^３、引張強度４．１ｇ／ｄｅ（３．６２ｃＮ／ｄｔｅｘ）、伸度３８％、ヤング率９８ｇ／ｄｅ（８６．５ｃＮ／ｄｔｅｘ）であり、良好な力学特性を示した。
【００７５】
［実施例２］
実施例１と同じ重合体溶液を用いて紡糸を行った。同紡糸原液を、孔径０．０９ｍｍ、孔数５００の紡糸口金より、浴温度８０℃の凝固浴中に吐出して糸条物を形成させた。この際、凝固浴として水／ＮＭＰ＝４５／５５の組成の浴、及び可塑延伸浴として水／ＮＭＰ＝４５／５５の組成の浴を用い、上記糸条物を浸漬長５０ｃｍで糸速８ｍ／分で通過させた後、実施例１と同様な操作で可塑延伸、水洗、乾燥、乾熱延伸して、ポリメタフェニレンイソフタルアミド繊維を得た。途中、凝固浴より得られた多孔線状体の密度は０．８２ｇ／ｃｍ^３であった。この糸の物性は繊度１．９ｄｅ（２．１１ｄｔｅｘ）、密度１．３２ｇ／ｃｍ^３、引張強度４．２ｇ／ｄｅ（３．７１ｃＮ／ｄｔｅｘ）、伸度２１％、ヤング率９６ｇ／ｄｅ（８４．７ｃＮ／ｄｔｅｘ）であり、良好な力学特性を示した。
【００７６】
【発明の効果】
本発明によれば、溶液重合法により製造した、中和塩を含むメタ型ポリアミド重合体溶液を塩を分離すること無く、直接アミド系溶媒と水とからなる凝固浴中に吐出し多孔質の線状体として凝固せしめる工程を経ることにより、優れた力学的特性を有し且つ、耐熱性、難燃性も良好なメタ型アラミド繊維を良好な生産性により製造することが出来た。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a meta-type aromatic polyamide fiber having, as a main component, a good metaphenylenediamine skeleton such as mechanical properties and heat resistance by wet spinning with high productivity. More specifically, a novel wet spinning method using special coagulation and spinning conditions from a meta-aromatic polyamide polymer solution containing salts has excellent mechanical properties, heat resistance and flame resistance. The present invention relates to a method for producing a good meta-type aromatic polyamide fiber with good productivity.
[0002]
[Prior art]
It has been well known that aromatic polyamides (hereinafter sometimes referred to as aramids) produced from aromatic diamines and aromatic dicarboxylic acid dichlorides are excellent in heat resistance and flame retardancy. It is also well known that these aramid solutions are soluble in amide solvents and can be made into fibers by methods such as dry spinning, wet spinning, and semi-dry semi-wet spinning.
[0003]
Among such aramids, fibers of meta-type aromatic polyamides represented by polymetaphenyleniisophthalamide (hereinafter sometimes referred to as meta-type aramids) are particularly useful as heat-resistant and flame-retardant fibers, At present, it is said that industrial production is carried out mainly by the following two methods (a) and (b). In addition, the following methods (c) to (f) have been proposed as methods for producing meta-aramid fibers.
[0004]
(a) A polymetaphenylene isophthalamide solution is prepared by low-temperature solution polymerization of metaphenylenediamine and isophthalic acid chloride in N, N-dimethylacetamide, and then the by-product hydrochloric acid is hydroxylated. A method of producing a fiber by dry spinning a polymer solution containing calcium chloride obtained by neutralization with calcium (Japanese Patent Publication No. 35-14399, US Pat. No. 3,360,595).
[0005]
(b) A polyacrylamide is obtained by contacting an organic solvent system (for example, tetrahydrofuran), which is not a good solvent, of the resulting polyamide containing metaphenylenediamine salt and isophthalic acid chloride with an aqueous solution system containing an inorganic acid acceptor and a soluble neutral salt. Method of isolating metaphenylene isophthalamide polymer powder (see Japanese Examined Patent Publication No. 4-7-10863), re-dissolving the polymer powder in an amide solvent, and then wet spinning in an aqueous coagulation bath containing inorganic salt (Japanese Patent Publication No. 48-17551).
[0006]
(c) A meta-aramid synthesized by a solution polymerization method is dissolved in an amide solvent, from a meta-aramid solution containing no inorganic salt or containing a small amount (2 to 3%) of lithium chloride. A method for producing a molded article such as a fiber by 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 from the orifice into the gas, and the gas After passing through the inside, it is introduced into an aqueous coagulation bath and then passed through an aqueous inorganic salt solution such as calcium chloride to form a yarn (Japanese Patent Laid-Open No. 56-31009).
[0008]
(e) A meta-aramid polymer solution containing calcium chloride and water produced by solution polymerization in an amide-based solvent and neutralized with calcium hydroxide, calcium oxide, etc. A method of forming into a yarn by spinning in an aqueous coagulation bath containing (JP-A-8-074121, JP-A-10-88421).
[0009]
(f) The polymer solution of the amide solvent is discharged to a high-temperature spinning tower, cooled with a low-temperature aqueous solution when it exits from the spinning tower, and stretched in a plastic bath, so that it has a very dense porous structure. A method of forming a fiber having a density of 1.3 or less. (Japanese Patent Laid-Open No. 52-43930)
[0010]
The method (a) has an advantage that a solution for spinning can be prepared without isolating the polymer, but because of dry spinning using an amide solvent having a high boiling point, the production energy cost is high and the amount per spinneret is high. As the number of holes increases, the spinning stability decreases rapidly. In addition, since it is often possible to obtain only weak fibers with a large amount of devitrification when trying to wet-spin this polymer solution in an aqueous coagulation bath, the meta-aramid solution by solution polymerization is still wet-spun using an aqueous coagulation bath. The method is believed to have many difficulties and has not yet been implemented industrially.
[0011]
On the other hand, the methods (b) and (c) avoid the above-mentioned problem of dry spinning, but the solvent is different between the polymerization system and the spinning system, and the step for redissolving the polymer once isolated In order to obtain a stable solution by re-dissolution, special consideration and meticulous process control are required (Japanese Patent Publication No. 48-4661).
[0012]
In the method (d), when the yarn is discharged from the spinneret into the air, if the number of holes per die is increased, the spinning stability is remarkably lowered, so that the productivity is low and not efficient.
[0013]
Further, although the method (e) gives a yarn having good physical properties, it is difficult to increase the spinning speed.
[0014]
Furthermore, the method (f) is a method for producing a porous yarn having a density of 1.3 or less, which is an applied technique of the dry spinning method and has the same problems as the dry method.
[0015]
Therefore, there is a demand for a method for producing a meta-aramid fiber that satisfies the physical properties of the yarn and has high productivity. Particularly, a method of spinning a polymer solution containing salts at a high speed by a wet spinning method using a die having a large number of holes. Has been sought as a productive method, but no one has been successful so far.
[0016]
[Problems to be solved by the invention]
The present invention eliminates the problems in the conventional method for producing meta-aramid fibers as described above, and is industrially advantageous for meta-aramid fibers that are homogeneous and have good mechanical and thermal properties with good productivity. It is intended to provide a new way to produce.
[0017]
A further object of the present invention is to produce calcium chloride by reacting a meta-type aromatic diamine with an aromatic dicarboxylic acid mainly composed of isophthalic acid chloride in an amide solvent, and then neutralizing by-product hydrochloric acid. Another object of the present invention is to provide a novel method capable of industrially producing meta-aramid fibers having good mechanical properties by wet spinning a polymer solution containing water and water directly.
[0018]
[Means for Solving the Problems]
  The object of the present invention is to form a meta type by wet spinning a meta type aromatic polyamide polymer solution comprising a meta type aromatic polyamide having a metaphenylenediamine isophthalamide skeleton as a main component and an amide solvent containing salts. In the method for producing an aromatic polyamide fiber, (1) the polymer solution is composed of an amide solvent and water and is substantially free of salts, and the composition of the amide solvent and water is in a weight ratio.50/50To 70/30, the temperature is80To a coagulation bath in the range of 90 ° C to a density of 0.3 g / cm³(2) Subsequently, the composition of the amide solvent 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. It is achieved by a method for producing a dense meta-type aromatic polyamide fiber, which is characterized by stretching in a plastic stretching bath made of an aqueous solution, and (3) washing with water and then heat-treating.
[0019]
Furthermore, after reacting an aromatic diamine with an aromatic dicarboxylic acid chloride in the presence of an amide-based solvent, a meta-type polyamide solution containing calcium chloride and water produced by neutralizing by-product hydrogen chloride and water Even in the case of using, it is possible to provide a method for producing meta-aramid fibers having good physical properties and high productivity.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a meta-type aromatic polyamide is obtained by wet spinning a meta-type aromatic polyamide polymer solution comprising a meta-type aromatic polyamide having a metaphenylenediamine isophthalamide skeleton as a main component and an amide solvent containing salts. This is a method for producing a fiber, and a specific meta-type aromatic polyamide fiber is provided by sequentially performing the specific steps (1), (2) and (3).
[0021]
The meta-type aromatic polyamide used in the present invention is mainly composed of metaphenylenediamine isophthalamide, 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 using these as raw materials.
[0022]
As the meta-type aromatic diamine which is one of such raw materials, diamines represented by the following formula are mainly used.
[0023]
[Chemical 1]

[0024]
In the above formula, R is a halogen such as a chlorine atom or a bromine atom, or an alkyl group having 1 to 3 carbon atoms such as a methyl group or an ethyl group. n is 0 or 1.
[0025]
Specific examples of such meta-type aromatic diamines include metaphenylene diamine, 2,4-toluenediamine, 2,6-toluenediamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene and the like. Examples of other meta-type aromatic diamines include 3,4′-diaminodiphenyl ether and 3,4′-diaminodiphenyl sulfone.
[0026]
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 meta-type aromatic diamine. Benzene derivatives, 1,5-paranaphthylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylketone, bis (aminophenyl) phenylamine, bis (paraaminophenyl) methane and the like are used.
[0027]
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 90 mol% or more, especially 95 mol% or more of diamine is contained.
[0028]
On the other hand, the aromatic dicarboxylic acid chloride 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, 3 -Chlorisophthalic acid chloride, 3-methoxyisophthalic acid chloride, bis (chlorocarbonylphenyl) ether and the like.
[0029]
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.
[0030]
When used for solution polymerization, an amide solvent can be used as a polymerization solvent. As such an amide solvent, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone and the like can be used, and in particular, from solution polymerization to wet spinning process. From the viewpoint of the stability of the polymer solution up to now, it is more preferable to use N-methyl-2-pyrrolidone (abbreviated as “NMP” in the present invention).
[0031]
In the solution polymerization step, NMP is preferably used as a polymerization solvent. Usually, after a meta-type aromatic diamine is dissolved in NMP, an aromatic dicarboxylic acid chloride containing isophthalic acid chloride as a main component is added to this solution in a powdered or molten state with sufficient stirring and reacted. The reaction temperature is preferably 0 to 80 ° C., and the amount of solvent used is preferably 3 to 30% by weight with respect to the total raw materials.
[0032]
Since the solution of the meta-type aromatic polyamide thus prepared contains a high concentration of hydrogen chloride, the reaction can be carried out by neutralizing it with an alkali such as calcium hydroxide, sodium hydroxide or sodium hydrogen carbonate. A polymer solution which is terminated and has a preferable degree of polymerization and high chemical stability can be obtained as a meta-type aromatic polyamide polymer solution.
[0033]
In the present invention, it is important to adjust the degree of polymerization in order to produce heat-resistant fibers having good mechanical properties from a meta-type aromatic polyamide solution as described above. In particular, in order to obtain a fiber having good performance from a polymetaphenylene isophthalamide polymer, an intrinsic viscosity (IV) determined from a value measured at a polymer concentration of 0.5 g / 100 ml in concentrated sulfuric acid at 30 ° C. ) Is 0.8 to 4.0, particularly 1.0 to 3.0, and particularly 1.3 to 2.4. The required degree of polymerization of the polymer is set according to the purpose for which the polymer or its solution is used, the use of the fiber, and the like. it can. As one of the typical methods, the degree of polymerization can be adjusted by using a terminal terminator (an alkylaniline such as aniline or toluidine, benzoic acid chloride or the like).
[0034]
The polymer concentration in the polymer solution in the present invention is the weight part (referred to as “PN concentration” in the present invention) relative to 100 parts by weight of the polymer and the solvent (NMP). The weight part is omitted.) Is 10 to 30, preferably 16 to 30. If the PN concentration is less than 10, the concentration is too low and the spinnability of the solution deteriorates. As a result, not only does the fiber performance deteriorate, but the concentration ratio of the solvent (NMP) increases further due to the low concentration. It is not economically preferable. Also, the higher the PN concentration, the better the transparency of the molded product (fiber). However, when the PN concentration exceeds 30, the viscosity becomes too high, and the polymerization reaction and particularly the neutralization reaction cannot be performed smoothly. Problems arise. Therefore, when polymerization is carried out at a high concentration (for example, at a PN concentration of 30 or more) in the polymerization reaction, an appropriate amount of NMP (for example, the PN concentration is finally reduced to 25) is added as a neutralizing agent in the neutralization reaction step. When the slurry dispersed in the amount is added, the neutralization reaction is facilitated, and at the same time, the polymer concentration (PN concentration) can be adjusted.
[0035]
The polymer solution used in the present invention contains a meta-type aromatic polyamide and an amide solvent and contains salts, but may further contain water. Such water and salts are inevitably produced during the solution polymerization, but can be further added as necessary. Moreover, when manufacturing a polymer solution with another solution preparation process, you may add salts and water from the outside. Examples of such salts include, but are not limited to, alkali metal halides such as sodium chloride, sodium iodide, and lithium chloride, alkaline earths such as calcium chloride, calcium carbonate, calcium hydroxide, and magnesium chloride. Examples thereof include metal halides, carbonates and hydroxides. The concentration may be any concentration as long as the solution is stably present. For example, it is preferably added and contained in a range of 0 to 60%, particularly 50%, based on the polymer weight. The following is preferable. This is because at a concentration exceeding this, the salt in the solution precipitates and the stability of the solution is impaired.
[0036]
The content of water in the polymer solution may be included in the range of 0 to 20% with respect to the total solution weight, and more preferably in the range of 0 to 15%. Beyond this, the stability of the polymer solution is impaired, and the spinnability may be significantly impaired by polymer precipitation and gelation.
[0037]
Particularly in the above solution polymerization, a neutralizing agent is added to the solution after the polymerization of the polymer to neutralize it. As such a neutralizing agent, at least one of calcium oxide, calcium hydroxide, and calcium carbonate is used. By this neutralization reaction, HCl by-produced in the polymerization reaction is neutralized to obtain calcium chloride (CaCl₂) Will inevitably be generated. The amount of HCl produced as a by-product in the polymerization reaction varies depending on the chemical structure of the polymer and the average molecular weight of the smallest unit. For example, HCl produced as a by-product in the polymerization reaction of polymetaphenylene isophthalamide is neutralized 100% with the above compound. In this case, about 100 parts by weight of the polymer (CaCl)₂Produces 46.64 (weight) parts. Incidentally, the CaCl produced by this neutralization reaction₂Dissolves in the polymer solution and works to increase the stability of the polymer solution (see Japanese Patent Publication No. 35-16027).₂Therefore, conventionally, wet spinning from such a polymer solution has been difficult.
[0038]
On the other hand, the amount of water produced and contained by the neutralization reaction varies depending on the type of neutralizing agent, and when neutralized with calcium hydroxide, 15.13 (weight) parts of water with respect to 100 parts (weight) of polymer. Produces. On the other hand, when neutralized with calcium oxide or calcium carbonate, 7.56 parts of water is produced with respect to 100 parts of the polymer. In addition, since these neutralizing agents are added as a slurry containing an aqueous solution, water, and solvent, the water generated and added here is also dissolved in the polymer solution. And properties of the composition after neutralization are hardly impaired. Rather, the inclusion of water may give favorable properties such as lowering the viscosity, but if it is too much, the stability of the solution will be significantly reduced (gelled), which is not good. Accordingly, the appropriate amount of water added in the neutralization reaction step varies depending on the polymer concentration. 2.42 (15 parts with respect to 100 parts of polymer) can dissolve up to about 6 times this amount of water, ie, about 90 parts with respect to 100 parts of polymer, but the stable region of the solution is 100 parts of polymer. On the other hand, water is in the range of 2.42 to 9.7 parts (water / polymer = 15 to 60). Further, for example, when PN concentration = 20, it is almost the same as when PN concentration = 16, and is about 15-60 parts with respect to 100 parts of polymer, and the stable region at PN concentration = 25 is 15-45 parts. PN concentration = 30 is 15 to 30 parts. The ranges exemplified above are approximate values when the polymer solution is allowed to stand at 60 to 70 ° C., and vary somewhat depending on conditions such as the degree of polymerization of the polymer and the storage temperature at standing. In any case, the permissible concentration of water in the polymer solution is limited as the polymer concentration increases. However, in the practice of the present invention, the concentration of water in the total polymer solution is preferably 8% or less in advance. It is preferable to conduct an experimental study with reference to the above to prevent gelation of the solution.
[0039]
The polymer solution used in the present invention only needs to contain an aromatic polyamide that can be synthesized from the above raw materials. For example, the above raw materials are reacted in THF, and an alkaline aqueous solution is added to the interface between the THF and the aqueous solution. Alternatively, a solution obtained by dissolving a polymer obtained by neutralizing generated hydrogen chloride in an amide solvent may be used, or a polymer solution produced by an interfacial polymerization method may be used.
[0040]
According to the present invention, in wet spinning, a new spinning and spinning process, which has been considered impossible with meta-aramids such as porous coagulation and post-densification, can be used to achieve excellent mechanical properties and heat resistance. Type aramid fibers can be efficiently produced with good productivity.
[0041]
Conventionally, equimolar CaCl₂The meta-aramid polymer solution (called calcium chloride generated in an equimolar amount with respect to the amide residue when synthesized by solution polymerization) is difficult to fiberize by wet spinning. Spinning and semi-dry and semi-wet spinning have been employed. In addition, in order to wet-spin this, chloride salts (CaCl generated by neutralization of HCl produced as a by-product in both solution polymerization and interfacial polymerization).₂, NaCl, NH_FourIt has been necessary to prepare a salt-reduced polymer solution that has been reduced to at least 70% or less, preferably 20% or less by any means. However, removal of chlorides by these means is often difficult industrially. For example, when a polymer is synthesized by interfacial polymerization, the polymerization solvent and the spinning solvent are different, so that the recovery is performed separately. Even if a device is required or a polymer solution synthesized by solution polymerization is spun using the same solvent, inorganic chloride produced as a by-product due to neutralization is removed by pressure filtration. ) Or after adding water to the polymer solution to remove inorganic chlorides by washing, and then drying the polymer and re-dissolving it, it requires a difficult process. However, it is difficult to say that these are preferable methods.
[0042]
According to the present invention, this equimolar CaCl, which has been difficult to implement in the past.₂A meta-aramid that excels in gloss, mechanical properties, heat resistance, etc. by a wet spinning method in which a polymer solution is spun directly into a coagulation bath having a specific composition substantially free of salts through a spinneret. It makes it possible to produce fibers.
[0043]
In the present invention, a coagulation bath having a very simple composition, ie, an aqueous solution of an amide solvent, is used to coagulate the polymer solution as a homogeneous porous linear body. That is, in the present invention, the polymer solution described above is preferably adjusted to a temperature corresponding to the coagulation bath temperature within a range of 20 to 90 ° C., and then, from the spinneret into a coagulation bath having the composition and temperature described later. After spinning directly (threading) and forming the yarn as a porous body, the yarn is pulled out from the coagulation bath, and subsequently in an aqueous solution of an amide solvent (preferably 2 to 10 times) It is stretched (at a draw ratio), further washed with water and dried, and is further heat treated at a temperature in the range of 250 ° C. to 400 ° C. to be fiberized.
[0044]
The steps (1), (2) and (3) performed using the polymer solution will be described below.
[0045]
[Step (1)]
In the present invention, it is extremely important to make the structure of the porous body formed in the solidification stage as homogeneous as possible in order to make it dense enough to give sufficient physical properties in the subsequent process. The porous structure and bath conditions are closely related, and the selection of the composition and temperature conditions of the coagulation bath is extremely important.
[0046]
The coagulation bath in the present invention is substantially composed of an amide solvent and water (H₂O) In this coagulation bath composition, the amide solvent can be suitably used as long as it dissolves meta-type aromatic polyamide and mixes well with water. However, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylimidazolidinone and the like can be preferably used.
[0047]
The optimum mixing ratio of the amide solvent and water varies slightly depending on the conditions of the polymer solution, but the weight ratio of the amide solvent is preferably in the range of 40% to 70%. This is because very large voids are likely to be generated in the yarn under conditions below this range, and this is likely to cause subsequent thread breakage. Under conditions above this range, solidification does not proceed and the yarns are fused.
[0048]
The temperature of the coagulation bath is closely related to the composition of the coagulation solution, but generally a high temperature is preferable because it is difficult to form pores on coarse bubbles called fingers. However, when the concentration of the coagulating liquid is high, the fusion becomes intense at a high temperature. Therefore, the preferable range is 20 to 90 ° C, and more preferably 30 to 80 ° C.
[0049]
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 are extracted from the polymer solution, but this does not impede the porous coagulation at all, and even if it is contained at a low concentration, there is no problem. There is no. Therefore, although not limited to this, this preferred concentration is in the range of 0 to 10% by weight with respect to the coagulation liquid.
[0050]
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 breaks.
[0051]
  In this way, the porous linear body obtained as a yarn is preferably as dense as possible for smooth subsequent densification, but preferably 0.3%.g / cm ³ Or more, more preferably 0.5g / cm ³ It is the above density. 0.3g / cm ³ If the density is less than 1, the porosity is high and it becomes difficult to densify the linear body in a subsequent stretching step. This density is a value calculated based on the yarn thickness and fineness measured according to ASTM D2130.
[0052]
This porous structure is characterized by being formed with very uniform fine pores. The pore size measured by a scanning microscope has a size on the order of 0.2 to 1 μm, and there are basically no holes of several μm size called voids or fingers. By having such a very close and homogeneous microporous structure, yarn breakage during stretching can be prevented, and densification during final heat setting and expression of yarn physical properties can be achieved. It is known that such a homogeneous porous structure is formed by spinodal decomposition accompanying solidification, for example.
[0053]
When the polymer solution is discharged into the coagulation bath, a multi-hole spinneret can be used. The number of holes is 50000 or less, preferably 300 to 30000.
[0054]
[Step (2)]
The porous linear body obtained by coagulation is subsequently immersed in a plastic stretching bath made of an aqueous solution of an amide solvent, and stretched in this bath.
[0055]
The plastic stretching bath in the present invention is composed of an aqueous solution of an amide solvent and is substantially free of salts. Any amide-based solvent can be used as long as it swells meta-aramid and mixes well with water. In particular, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylimidazolidinone and the like can be preferably used. More preferably, the same solvent as that used in the coagulation bath is used. Using the same solvent as the coagulation bath simplifies the recovery process and is economically beneficial.
[0056]
That is, the amide solvents used for the polymer solution, the coagulation bath, and the plastic drawing bath are preferably the same, and as such a solvent, one or more of N-methyl-2-pyrrolidone, dimethylacetamide, and dimethylformamide are used. It is convenient to use a mixture of
[0057]
The temperature and composition of the plastic stretching bath are closely related to each other, but can be suitably used if the weight concentration of the amide solvent is 20% to 70% and the temperature is in the range of 20 ° C to 90 ° C. In the region lower than this range, plasticization does not proceed sufficiently and it is difficult to obtain a sufficient draw ratio, and in the range exceeding this range, the surface of the yarn is melted and fused, making it difficult to perform good spinning.
[0058]
In the present invention, the film is usually stretched at a magnification of 1.5 to 10 times, preferably 2 to 10 times, more preferably 2.1 to 6 times. By stretching at a high magnification, the strength and elastic modulus of the yarn are improved to exhibit good physical properties, and at the same time, the holes are crushed and the densification by heat setting proceeds well. In addition, when the film is stretched at an extremely high magnification, the process condition is deteriorated and it is difficult to produce a good yarn.
[0059]
[Step (3)]
The yarn product that has undergone the plastic stretching bath step is then usually washed with cold water of 30 ° C. or lower, followed by washing with hot water of usually 50 to 90 ° C., and then usually 100 ° C. or higher with a heating roller, hot air, etc. Dry at the temperature of Thereafter, as described below, it is subjected to a heat treatment such as dry heat stretching at a temperature of preferably 250 to 400 ° C., more preferably 270 to 400 ° C., using a hot plate, a heat roller or the like.
[0060]
This dry heat drawing step is an important step for densifying the porous linear body to develop strength and elongation. In particular, the temperature of the dry heat stretching is closely related to the density, and it is preferable to perform the treatment in a temperature range of 270 ° C. to 400 ° C. More preferably, the temperature is 300 ° C. or higher and 370 ° C. or lower. If the temperature exceeds 400 ° C., the yarn may be severely deteriorated, colored, and further broken. Further, at a temperature lower than 270 ° C., it cannot be sufficiently densified, and it is difficult to develop yarn physical properties.
[0061]
The draw ratio at this time is closely related to the expression of elastic modulus and strength, and can take any ratio as necessary, but is usually 0.7 to 4 times, preferably 1 to By setting in the range of 3 times, good spinnability, strength and elastic modulus can be obtained. Therefore, in order to achieve densification, manifestation of yarn properties, and stable spinnability, the total draw ratio including plastic drawing and hot plate drawing is preferably 2.5 to 12, more preferably 2.5 to 5. It is more preferable to set so as to be doubled.
[0062]
The meta-aramid fiber obtained by the present invention has good drawability and can be drawn smoothly to a high magnification without causing yarn breakage or fluffing during hot water bath drawing or dry heat drawing.
[0063]
In the present invention, the above-described solution polymerization-neutralization reaction-wet spinning-washing / drying / drawing can be carried out in a continuous continuous process, which is one of the advantages of the method of the present invention. The process may be divided into several steps.
[0064]
A meta-aramid fiber having excellent heat resistance and mechanical properties is produced with high productivity by wet spinning from a polymer solution containing salts by using a simple coagulation bath. For example, in the method of the present invention, it is possible to easily produce meta-aramid fibers having a tensile strength exceeding 4.0 g / de (3.53 cN / dtex) by wet spinning from a meta-aramid solution by conventional solution polymerization. It becomes.
[0065]
The meta-type aramid fiber produced in this way is crimped as necessary, cut into an appropriate fiber length, and provided to the next step.
[0066]
As described above, the meta-type aromatic polyamide (meta-type aramid) fiber according to the present invention can be applied to various uses utilizing its heat resistance, flame resistance and mechanical properties, for example, alone or in combination with other fibers. It is useful as heat-resistant and flame-resistant clothing such as fire-fighting clothes and protective clothing, flame-resistant bedding, interior materials, and as a raw material for various industrial materials such as filters, synthetic paper, and composite materials. Can do.
[0067]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, these Examples and Comparative Examples are for helping understanding of the present invention, and the scope of the present invention is not limited by these descriptions.
[0068]
In Examples and Comparative Examples, the intrinsic viscosity (IV) was measured at 30 ° C. at a polymer concentration of 0.5 g / 100 ml in concentrated sulfuric acid after the aromatic polyamide polymer was isolated from the polymer solution and dried. 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 used for spinning is the weight part of the polymer [= polymer / (polymer + solvent + others)] with respect to the total weight part, and the concentration of calcium chloride and water. Are parts by weight per 100 parts by weight of the polymer.
[0069]
The density of the porous linear body obtained by coagulation is the apparent density d1 calculated from the fiber diameter and fineness measured according to ASTM D2130, and the density of the dense yarn is floated and settled using tetrachloroethane and cyclohexane as the solvent. It is a value measured by the method.
[0070]
[Example 1]
(A) Preparation of Solution Polymerization Spinning Stock Solution Into a reaction vessel equipped with a thermometer, a stirrer, and a raw material inlet, 815 parts of NMP dehydrated with molecular sieves is placed, and metaphenylenediamine (hereinafter abbreviated as mPDA) 108 in this NMP. After dissolving the part, it was cooled to 0 ° C. To this cooled diamine solution, 203 parts of isophthalic acid chloride (hereinafter abbreviated as IPC) purified by distillation and ground in a nitrogen atmosphere was added and reacted. The reaction temperature rose to about 50 ° C., stirring was continued for 60 minutes at this temperature, and the mixture was further heated to 60 ° C. for reaction for 60 minutes. After completion of the reaction, 70 parts of calcium hydroxide was added in the form of fine powder and neutralized and dissolved over 60 minutes (primary neutralization). A slurry liquid in which 4 parts of the remaining calcium hydroxide was dispersed in 83 parts of NMP was prepared, and this calcium hydroxide-containing slurry (neutralizing agent) was added to the polymerization solution while stirring (secondary neutralization). This secondary neutralization was carried out with stirring at 40 to 60 ° C. for about 60 minutes to prepare a polymer solution as a spinning dope in which calcium hydroxide was completely dissolved.
[0071]
The polymer concentration of this solution (spinning stock solution) (PN concentration, that is, parts by weight of the polymer with respect to 100 parts by weight of the total of the polymer and NMP) is 14, and the resulting polymetaphenylene isophthalamide polymer has an I.V. V. Was 2.4. Further, the calcium chloride concentration and the water concentration of this polymer solution were 46.6 parts of calcium chloride and 15.1 parts of water with respect to 100 parts of the polymer.
[0072]
(B) Wet spinning, plastic drawing, dry heat drawing
The spinning solution prepared in the above (a) was spun by discharging it from a die having a pore diameter of 0.09 mm and a hole number of 50 into a coagulation bath having a bath temperature of 80 ° C. As this coagulation bath, a bath having a composition of water / NMP = 50/50 (weight ratio) was used. After passing through an immersion length (effective coagulation bath length) of 60 cm at a yarn speed of 8 m / min, it was once drawn into the air. Subsequently, the film was stretched at a stretch ratio of 3 in a plastic stretching bath. The plastic stretching bath at this time was a bath having a composition of water / NMP = 45/55 (weight ratio), and the temperature was 40 ° C. Furthermore, after sufficiently washing with cold water, it was further washed with warm water at 80 ° C. Subsequently, the hot-water drawn yarn was dried with a drying roller having a surface temperature of 120 ° C., stretched 1.2 times on a hot plate at 340 to 360 ° C., and wound up. In this example, the total draw ratio was 3.6 times, and the final winding speed of the drawn fibers was 28.8 m / min.
[0073]
  The density of the porous linear body obtained from the coagulation bath on the way is 0.74g / cm ³ Met.
[0074]
  The mechanical properties of the obtained polymetaphenylene isophthalamide drawn fiber have a fineness of 1.7 de (1.89dtex), density 1.33 g / cm³The tensile strength was 4.1 g / de (3.62 cN / dtex), the elongation was 38%, the Young's modulus was 98 g / de (86.5 cN / dtex), and good mechanical properties were exhibited.
[0075]
    [Example 2]
  Spinning was carried out using the same polymer solution as in Example 1. The spinning dope was discharged from a spinning nozzle having a hole diameter of 0.09 mm and a hole number of 500 into a coagulation bath having a bath temperature of 80 ° C. to form a yarn. At this time, a water / NMP = 45/55 composition bath was used as the coagulation bath, and a water / NMP = 45/55 composition bath was used as the plastic drawing bath. After passing in minutes, plastic stretching, washing with water, drying and dry heat stretching were performed in the same manner as in Example 1 to obtain polymetaphenylene isophthalamide fibers. On the way, the density of the porous linear body obtained from the coagulation bath is 0.82 g / cm.³Met. The physical properties of this yarn are 1.9 de (2.11dtex), density 1.32 g / cm³The tensile strength was 4.2 g / de (3.71 cN / dtex), the elongation was 21%, the Young's modulus was 96 g / de (84.7 cN / dtex), and good mechanical properties were exhibited.
[0076]
【The invention's effect】
According to the present invention, a meta-type polyamide polymer solution containing a neutralized salt produced by a solution polymerization method is directly discharged into a coagulation bath composed of an amide solvent and water without separating the salt. Through the process of solidifying as a linear body, a meta-aramid fiber having excellent mechanical properties and good heat resistance and flame retardancy could be produced with good productivity.

Claims (5)

Method for producing meta-type aromatic polyamide fiber by wet-spinning a meta-type aromatic polyamide polymer solution comprising a meta-type aromatic polyamide mainly comprising a metaphenylenediamine isophthalamide skeleton and an amide solvent containing salts (1) The polymer solution is composed of an amide solvent and water and is substantially free of salts. The composition of the amide solvent and water is 50/50 to 70/30 by weight, and the temperature is 80 to 90. It is discharged into a coagulation bath having a temperature range of 0 ° C. and solidified as a porous linear body having a density of 0.3 g / cm ³ or more. (2) Subsequently, the composition of the amide solvent and water is in a weight ratio. Stretching in a plastic stretching bath composed of an aqueous solution of an amide solvent having a temperature of 20/80 to 70/30 and a temperature of 20 to 90 ° C., (3) Dense, characterized by being washed with water and then heat-treated Na Method for producing meta-type aromatic polyamide fiber. The method for producing a dense meta-type aromatic polyamide fiber according to claim 1 , wherein in the step (2), stretching is performed in a range of 1.5 to 10 times. The method for producing a dense meta-type aromatic polyamide fiber according to claim 1 or 2 , wherein in the step (3), heat treatment is performed at a draw ratio of 0.7 to 4 times under a condition of 250 ° C or more and 400 ° C or less. As a polymer solution, after reacting an aromatic diamine with an aromatic dicarboxylic acid chloride in the presence of an amide solvent, a meta-type aromatic containing calcium chloride and water produced by neutralizing by-product hydrogen chloride. A method for producing a dense meta-type aromatic polyamide fiber according to any one of claims 1 to 3, wherein an aromatic polyamide solution is used. As the amide solvent contained in the polymer solution, the coagulation bath, and the plastic drawing bath, one or a mixture of two or more selected from the group consisting of N-methyl-2-pyrrolidone, dimethylacetamide and dimethylformamide is used. The method for producing a dense meta-type aromatic polyamide fiber according to any one of claims 1 to 4 .