JP4342056B2 - Polyketone fiber and production method thereof - Google Patents

Description

【０００９】
【数２】
ピーク面積比率（％）＝［（Ａ１＋Ａ２＋・・）／Ａｍ］×１００ ・・（２）
ここで、Ａ１，Ａ２，・・はＴｍよりも低く１５０℃以上の温度に見られる吸熱ピークの面積であり、Ａｍは最大吸熱ピークの面積である。
本発明のポリケトン繊維は、繰り返し単位の９７モル％以上が上記の式（１）で示されるポリケトンである。３モル％未満の範囲で上記の式（１）以外の繰り返し単位、例えば下記の式（３）に示したもの等を含有していても良い。
【００１０】
【化３】

Ｒはエチレン以外の１〜３０の有機基であり、例えばプロピレン、ブチレン、１−フェニルエチレン等が例示される。これらの水素原子の一部または全部が、ハロゲン基、エステル基、アミド基、水酸基、エーテル基で置換されていてもよい。もちろん、Ｒは２種以上であってもよく、例えば、プロピレンと１−フェニルエチレンが混在していてもよい。高強度、高弾性率が達成可能で、高温での安定性が優れるという観点で繰り返し単位の９８モル％以上が上記の式（１）で示されるポリケトンであるこことが好ましく、最も好ましくは１００モル％である。
【００１１】
また、これらのポリケトンには必要に応じて、酸化防止剤、ラジカル抑制剤、他のポリマー、艶消し剤、紫外線吸収剤、難燃剤、金属石鹸等の添加剤を含んでいてもよい。
本発明のポリケトン繊維は、示差走査熱量計（ＤＳＣ）により観察されるＴｍが少なくとも２６５℃であり、上記の式（２）で定義されるピーク面積比率が１％以下である必要がある。実施例に示したような方法でＤＳＣ測定したときに、高度に熱延伸されたポリケトン繊維では、１５０℃以上Ｔｍ未満の間に吸熱ピークが１本以上見られる場合がある（図１）。同じＴｍをもったポリケトン繊維であっても、１５０℃以上Ｔｍ未満の温度範囲に見られる吸熱ピークの大きさにより、熱安定性が大きく異なる。Ｔｍが２６５℃以上であってもピーク面積比率が１％より大きい場合、熱安定性は不十分なものとなってしまう。また、Ｔｍが２６５℃より小さい場合、ピーク面積比率が１％以下であっても十分な熱安定性が得られない。熱安定性がさらに良いという点でＴｍは２７０℃以上が好ましく、さらに２７５℃以上が好ましい。また、ピーク面積比率も同様に０．５％以下が好ましく、０．３％以下がさらに好ましく、０％が最も好ましい。
【００１２】
本発明のポリケトン繊維の強度及び弾性率は高い方が好ましいが、特に弾性率は２００ｃＮ／ｄｔｅｘ以上であることが好ましく、さらに２５０ｃＮ／ｄｔｅｘであることが好ましい。
本発明のポリケトン繊維の極限粘度［η］は、３ｄｌ／ｇ以上が好ましい。３ｄｌ／ｇより小さいと、延伸による融点の向上効果が小さくなり、結果的に熱安定性の優れたものが得られにくい。ただし、［η］が２０ｄｌ／ｇより大きい場合、熱延伸性が悪くなる傾向が見られ、かえって熱安定性が低下する場合があるので、２０ｄｌ／ｇ以下であることが好ましい。好ましい［η］の範囲としては３〜１８ｄｌ／ｇが好ましく、さらに好ましくは、５〜１５ｄｌ／ｇである。
Ｔｍが２６５℃以上で、ピーク面積比率が１％以下の該ポリケトン繊維であれば、その製造方法は特に限定されるものではないが、以下に達成可能な製造法について説明する。
【００１３】
本発明に用いるポリケトンについては融点以上でポリマーの化学架橋反応によるゲル化の進行が早いため、湿式紡糸法または乾式紡糸を用いて行うことが好ましい。特開平２−１１２４１３号公報、特開平４−２２８６１３号公報、特表平４−５０５３４４号公報に記載の溶剤、例えば、ヘキサフルオロイソプロパノール、ｍ−クレゾール、クロロフェノール、レゾルシン／水、フェノール／アセトン、プロピレンカーボネート／ヒドロキノン、ピロール、レゾルシン／プロピレンカーボネート、ピリジン、ギ酸等の有機溶剤を用いて行うこともできるが、これらの溶剤は高価または毒性が高いものであったり、引火性の高い凝固剤を使用する必要がある等、工業的に使用するには問題がある。また、米国特許第５９２９１５０号明細書、国際特許出願第９９／１８１４３号では、例えば亜鉛塩溶液、リチウム塩の溶液が溶剤として使用できることが開示されている。しかしながら、リチウム塩の溶液は高価であるので、工業的に使用することができない。これに対して、亜鉛塩の溶液は安価であるが、ポリケトンを亜鉛塩の溶液に溶した場合、溶解から紡糸に至る間にポリマーの変成が起こり、長期にわたって安定に紡糸する事が困難であるという問題がある。本発明者らは、米国特許第５９２９１５０号明細書、国際特許出願第９９／１８１４３号とは独立にハロゲン化亜鉛とハロゲン化アルカリ金属及び／またはハロゲン化アルカリ土類金属の混合塩の水溶液を使用することで、上記の問題を解決している。したがって、ハロゲン化亜鉛とハロゲン化アルカリ金属及び／またはハロゲン化アルカリ土類金属の混合塩の水溶液を溶剤とした湿式紡糸法を一例として以下に説明する。
【００１４】
ハロゲン化亜鉛としては、例えば、塩化亜鉛、臭化亜鉛、よう化亜鉛等がある。ポリケトンの溶解性、溶媒のコスト、水溶液の安定性の点で塩化亜鉛が最も好ましい。ハロゲン化アルカリ金属、ハロゲン化アルカリ土類金属としては、例えば、塩化ナトリウム、塩化カリウム、塩化カルシウム、塩化マグネシウム、塩バリウム、臭化ナトリウム、臭化カルシウム、ヨウ化ナトリウム等がある。コスト、溶液の長期安定性、溶剤の回収のしやすさという点で塩化ナトリウム、塩化カルシウム、塩化マグネシウム、塩化バリウムが好ましく、さらに好ましくは、塩化ナトリウム、塩化カルシウムである。ハロゲン化亜鉛とハロゲン化アルカリ金属及び／またはハロゲン化アルカリ土類金属の混合塩水溶液の塩濃度としては、溶解性、コストやポリケトン溶液の安定性の観点から４０〜８０重量％が好ましく、さらに好ましくは５０〜７５％である。また、ハロゲン化亜鉛とハロゲン化アルカリ金属及び／またはハロゲン化アルカリ土類金属の混合重量比は、ポリケトンの溶解性、ポリケトン溶液の長期安定性の観点から、９５／５〜４０／６０が好ましく、さらに好ましくは９０／１０〜５５／４５である。
【００１５】
ポリケトン溶液中のポリマー濃度は０．００５〜７０重量％であることが好ましい。ポリマー濃度が０．００５重量％未満では濃度が低すぎて、凝固時に繊維になりにくい欠点を有する他、繊維の製造コストが高くなりすぎる欠点を有する。また、７０重量％を越えるともはやポリマーが溶剤に溶解しなくなる。溶解性、紡糸のしやすさ、繊維の製造コストの観点から、好ましくは０．５〜４０重量％、更に好ましくは１〜３０重量％である。
【００１６】
このポリケトン溶液を紡糸口金から押し出し、続いて凝固浴中で繊維状に凝固させる。凝固浴の組成は、メタノール、アセトン等の有機溶剤、水、有機物水溶液、無機物水溶液等どのようなものであってもよいが、有機溶剤単独組成の凝固浴の場合には、凝固速度が著しく遅くなり工業的なスピードで、安価な設備で紡糸することが困難となってしまうため、少なくとも１重量％の水を含有する溶液であることが好ましい。回収効率の観点からは溶剤に使用された該混合塩の水溶液であることが好ましい。
【００１７】
紡糸速度や凝固温度によっては、凝固浴中で凝固糸中の該混合塩を十分に除去できない場合もあるので、必要に応じては凝固浴を出た凝固糸をさらに洗浄してもよい。洗浄には該混合塩を溶解する能力を有する液体であればどのようなものを用いてもよいが、安全性、溶液のコスト、回収のコスト等を考慮すると、水系の溶液が好ましく、ハロゲン化亜鉛の溶解性の観点からは水もしくは硫酸、塩酸、リン酸等の酸性水溶液が特に好ましい。
【００１８】
こうして洗浄された凝固糸は、水分の一部又は全部を除くために乾燥を行う。乾燥方法としては、定長であるいは収縮させながら乾燥してもよい。乾燥方法としては、バッチ乾燥法であっても、加熱したロールやプレート上あるいは加熱気体中を走行させて乾燥する連続乾燥法であってもよい。糸の均一性や製造コストの観点からは連続乾燥法が好ましい。乾燥温度は特に制約はないが、６０℃〜２６０℃の範囲が好ましい。
このようにして得られた乾燥糸を、以下に示すような特定の熱延伸温度及び延伸倍率で、２段以上の熱延伸を行うことで本発明のＴｍが２６５℃以上で、ピーク面積比率が１％以下のポリケトン繊維を得ることができる。
【００１９】
熱延伸温度は、ポリケトン繊維の緊張下融点に対して０〜３０℃低い温度である必要がある。ここで、緊張下融点とは、ポリケトン繊維に緊張がかかった状態でＤＳＣを用いて測定したときの最大吸熱ピーク温度（詳細は実施例に示した）のことであり、前述のＴｍと比較してより高い温度となる。熱延伸はポリケトン繊維に緊張がかかった状態で行われることを考えると、緊張下融点を基準に熱延伸温度を決定することは極めて重要である。延伸温度が緊張下融点から３０℃を越えて低いときは、Ｔｍが２６５℃以上でピーク面積比率が１％以下のポリケトン繊維が得られない。また、延伸温度が緊張下融点よりも高いときは、延伸不能となる。同様な観点から、好ましくは１０〜２０℃低い温度であり、さらに好ましくは１３〜１７℃低い温度である。
【００２０】
１段目の延伸は２〜８倍の範囲で行う必要がある。１段目の延伸倍率が８より高いときは、Ｔｍが２６５℃以上の繊維が得られなかったり、Ｔｍが２６５℃以上のポリケトン繊維は得られてもピーク面積比率が１％より大きくなる。１段目の延伸が２倍より低いときは、延伸の効率が悪くなるばかりか、到達物性が低くなる。好ましくは３〜７倍であり、さらに好ましくは４〜６倍である。２段目以降の延伸は、破断延伸倍率の３０〜８０％の延伸倍率で行う必要がある。ここで、破断延伸倍率とは、緊張下融点に対して０〜３０℃低い延伸温度で熱延伸したときに繊維の切断が起こる限界の延伸倍率のことである。延伸倍率が破断延伸倍率の８０％より大きいときは、延伸による強度の向上率が低くなるとともに、Ｔｍが２６５℃以上の繊維が得られなかったり、Ｔｍが２６５℃以上となってもピーク面積比率が１％よりも高くなる。延伸倍率が破断延伸倍率の３０％より小さい場合、たとえ多段で延伸を行っても高強度、高弾性率のポリケトン繊維を得ることが困難で、熱安定性も低いものとなる。同様な観点から４０〜７５％が好ましく、さらに好ましくは５０〜７０％である。
【００２１】
熱延伸の段数は２段以上であれば特に制限はないが、強度や弾性率の高いポリケトン繊維が得られやすいという点で３段以上が好ましい。ただし、７段より多くても強度や弾性率の向上率が小さくなるばかりか、設備が高価となったり、生産効率が悪くなるなど逆に不利益をもたらすため、７段以下が好ましい。さらに好ましくは４〜６段の範囲である。
熱延伸方法としては、加熱ロールまたはプレート上あるいは加熱気体中を走行させる方法や、走行糸にレーザーやマイクロ波、遠赤外線を照射する方法等の従来公知の装置、方法をそのままあるいは改良して採用することができる。
【００２２】
本発明のポリケトン繊維は、高温での弾性率保持性が高く、熱収縮率が小さいため、タイヤやベルト等の高温で使用される可能性がある繊維強化複合材料用途に適している。本発明のポリケトン繊維をタイヤコードとする場合は、公知の方法を用いることができる。タイヤコードとして用いる場合は、単糸繊度は１〜４ｄが好ましく、総繊度は５００〜３０００ｄが好ましい。必要に応じて他の繊維、例えば、レーヨン、ポリエステル繊維、アラミド繊維、ナイロン繊維、スチール繊維等と混合使用してもよいが、好ましくはタイヤ中に含まれる全タイヤコードの２０重量％、好ましくは５０重量％以上使用されていることが性能発揮の面から好ましい。得られたポリケトン繊維は、合撚して１００〜１０００Ｔ／ｍ、好ましくは、２００〜５００Ｔ／ｍの撚りを掛けた後、すだれ織りとした後、１０〜３０％のＲＦＬ（フェノール／ホルマリンラテックス）液を付着させ、少なくとも１００℃で固着させる。ＲＦＬ樹脂の付着量は、繊維重量に対して２〜７重量％が好ましい。こうして得られたタイヤコードは、特にラジアルタイヤ用カーカス材として有用である。
【００２３】
【実施例】
本発明を、下記の実施例などにより更に詳しく説明するがそれらは本発明の範囲を限定するものではない。
実施例の説明中に用いられる各測定値の測定方法は、次の通りである。
（１）極限粘度
極限粘度［η］は、次の定義式に基づいて求めた。
［η］＝ｌｉｍ（Ｔ−ｔ）／（ｔ・Ｃ）
Ｃ→０
定義式中のｔ及びＴは、純度９８％以上のヘキサフルオロイソプロパノール及び該ヘキサフルオロイソプロパノールに溶解したポリケトンの希釈溶液の２５℃での粘度管の流過時間である。また、Ｃは上記１００ｍｌ中のグラム単位による溶質重量値である。
（２）繊維の強度、弾性率
引張り物性測定器（オリエンテック社製、ＵＣＴ−１０Ｔ）を用いて、２５℃、試料長２０ｃｍ、クロスヘッドスピード２０ｃｍ／分で測定した。
【００２４】
（３）Ｔｍ及びピーク面積比率
長さ２ｍｍ程度に切断したポリケトン繊維２ｍｇを、窒素雰囲気下で、２０℃／分の昇温速度で、示差走査熱量計（ＰＥＲＫＩＮ ＥＬＭＥＲ社製 Ｐｙｒｉｓ １ ＤＳＣ）を用いて測定を行った。Ｔｍは、図１に示したように最も面積の大きい吸熱ピーク温度である。また、ピーク面積は図１のように点線のベースラインと吸熱ピークで囲まれた面積であり、ＰＥＲＫＩＮ ＥＬＭＥＲ社製 Ｐｙｒｉｓ １ ＤＳＣに付属した解析ソフト「Ｐｙｒｉｓ Ｄａｔａ Ａｎａｌｙｓｉｓ」を使用して計算した。
（４）緊張下融点
長さ５ｍｍ、幅２ｍｍ、厚さ０．２ｍｍのアルミ製の板に、ポリケトン繊維を１．０ｃＮ／ｄｔｅｘの荷重をかけて２ｍｇ巻き付け固定し、これを２０℃／分の昇温速度で、窒素雰囲気下で、示差走査熱量計（ＰＥＲＫＩＮ ＥＬＭＥＲ社製 Ｐｙｒｉｓ １ ＤＳＣ）を用いて測定を行った。緊張下融点は、最も面積の大きい吸熱ピーク温度である。
【００２５】
（５）破断延伸倍率
図２に示した装置を用いて、所定のホットプレート温度で、送りロール速度を２ｍ／分とし、巻き取りロールを２ｍ／分から１０ｍ／分／分の加速度で速度を徐々に上げ、糸が切断したときの巻き取りロールの速度（ｍ／分）を測定した。破断延伸倍率は以下の式より計算した。
破断延伸倍率＝糸が切断したときの巻き取りロールの速度／２
（６）延伸倍率比
延伸倍率比は破断延伸倍率に対する実際に延伸した延伸倍率の比であり、以下の式より計算した。
延伸倍率比（％）＝延伸倍率／破断延伸倍率×１００
【００２６】
（７）弾性率の保持率
サンプル設置部をヒーターボックスで囲み、試料温度が２００℃となるようにして、それ以外は（２）と同様な条件で弾性率を測定した。保持率は以下の式に示す式より計算した。
保持率（％）＝［弾性率（２００℃）／弾性率（２５℃）］×１００
（８）熱収縮率
ポリケトン繊維を２００℃、３０分の無緊張状態で熱処理したときの繊維長の変化を測定し、以下に示した式より熱収縮率を計算した。
熱収縮率（％）＝
［（熱処理前の繊維長−熱処理後の繊維長）／熱処理前の繊維長］×１００
【００２７】
【実施例１〜２、比較例１〜３】
７５重量％の塩化亜鉛と塩化ナトリウムの混合塩（塩化亜鉛と塩化ナトリウムの重量比は６５／１０）水溶液に、極限粘度が６．０ｄｌ／ｇで、実質的に繰り返し単位の１００モル％が式（１）で示されるポリケトンを７重量％となるように混合し、これを８０℃で３時間攪拌することにより均一で透明なポリケトン溶液を得た。
【００２８】
このポリケトン溶液を２０μｍのフィルターを通過させた後、直径０．１ｍｍの穴が５０個ある紡糸口金からプランジャー型押出機を用いて、８０℃、６ｍ／分の速度で押し出し、エアギャップ長１０ｍｍを通過させ、そのまま１０℃の水である浴中を通した後、６ｍ／分の速度でネルソンロールを用いて引き上げた。次いでそのネルソンロール上で水を吹きかけて洗浄し、さらに２％の硫酸浴を通してネルソンロールで引き上げた後ネルソンロール上で水を吹きかけて洗浄し、水を含んだ状態で管上に巻き取った。この糸を２４０℃のホットプレート上を２ｍ／分の速度で通して乾燥した。このポリケトン繊維の緊張下融点は、２５３℃であった。
【００２９】
このポリケトン繊維を、図２に示した装置を用い、表１の条件で熱延伸した。尚、送りロール速度は２ｍ／分である。表１には、それぞれの延伸段階での緊張下融点及び延伸温度、延伸温度での破断延伸倍率、延伸倍率及び延伸倍率比を示した。表２には、３段延伸後のポリケトン繊維のＴｍ、ピーク面積比率、［η］、２５℃での強度及び弾性率、２００℃での弾性率の保持率、２００℃での熱収縮率を示した。
表２に示すように、実施例１〜２のポリケトン繊維は、弾性率の保持率が高く、熱収縮率が小さくなっており、高い熱安定性を示す。一方、比較例１では１段延伸の延伸温度が低すぎ、比較例２では１段延伸の延伸倍率が高すぎ、比較例３では３段延伸の延伸倍率が高すぎるために、弾性率は本発明と同程度であるが熱安定性が低いものとなっている。
【００３０】
【実施例３〜４、比較例４】
６３重量％の塩化亜鉛と塩化カルシウムの混合塩（塩化亜鉛と塩化カルシウムの重量比は５１／４９）水溶液に、極限粘度が７．６ｄｌ／ｇで、実質的に繰り返し単位の１００モル％が式（１）であるポリケトンを８重量％となるように３０℃で混合し、１０ｔｏｒｒまで減圧した。泡の発生が無くなった後減圧のまま密閉し、これを１２０℃で５時間攪拌することにより均一で透明なポリケトン溶液を得た。
【００３１】
このポリケトン溶液を２０μｍのフィルターを通過させた後、直径０．１ｍｍの穴が５０個ある紡糸口金からプランジャー型押出機を用いて、１００℃、６ｍ／分の速度で押し出し、エアギャップ長１０ｍｍを通過させ、そのまま−２０℃の３０重量％メタノール水溶液である浴中を通した後、６ｍ／分の速度でネルソンロールを用いて引き上げた。次いでそのネルソンロール上で水を吹きかけて洗浄し、さらに２％の硫酸浴を通してネルソンロールで引き上げた後ネルソンロール上で水を吹きかけて洗浄し、水を含んだ状態で管上に巻き取った。この糸を２４０℃のホットプレート上を２ｍ／分の速度で通して乾燥した。このポリケトン繊維の緊張下融点は、２５５℃であった。
【００３２】
このポリケトン繊維を、図２に示した装置を用いて、表３に示す条件で熱延伸を行った。尚、送りロール速度は２ｍ／分である。表３には、それぞれの延伸段階での緊張下融点及び延伸温度、延伸温度での破断延伸倍率、延伸倍率比を示した。表４には、４段延伸後のポリケトン繊維のＴｍ、ピーク面積比率、［η］、２５℃での強度及び弾性率、２００℃での弾性率の保持率、２００℃での熱収縮率を示した。
表４に示すように、実施例３〜４のポリケトン繊維は、弾性率の保持率が高く、熱収縮率が小さくなっており、高い熱安定性を示す。一方、比較例４では４段延伸の延伸倍率が高すぎるために、弾性率は本発明と同程度であるが熱安定性が低いものとなっている。
【００３３】
【実施例５、比較例５】
極限粘度が６．２ｄｌ／ｇで、実質的に繰り返し単位の１００モル％が式（１）であるポリケトンを用いて、特開平４−２２８６１３号公報の実施例３に従って湿式紡糸を行った。乾燥後の緊張下融点は、２５５℃であった。
これを図２に示した装置を用い、表５の条件で熱延伸した。尚、送りロール速度は２ｍ／分である。表５には、それぞれの延伸段階での緊張下融点及び延伸温度、延伸温度での破断延伸倍率、延伸倍率及び延伸倍率比を示した。表６には、３段延伸後のポリケトン繊維のＴｍ、ピーク面積比率、［η］、２５℃での強度及び弾性率、２００℃での弾性率の保持率、２００℃での熱収縮率を示した。
【００３４】
表６に示すように、実施例５のポリケトン繊維は、弾性率の保持率が高く、熱収縮率が小さくなっており、高い熱安定性を示す。一方、比較例５（特開平４−２２８６１３号公報の実施例３の熱延伸方法）では１段延伸の延伸温度が低すぎる上に２段延伸の延伸倍率が高すぎるために、弾性率は本発明と同程度であるが熱安定性が低いものとなっている。
【００３５】
【表１】

【００３６】
【表２】

【００３７】
【表３】

【００３８】
【表４】

【００３９】
【表５】

【００４０】
【表６】

【００４１】
【発明の効果】
高温での弾性率の保持率が高く、熱収縮率が低いなど、熱安定性に優れたポリケトン繊維を提供することが可能となった。本発明のポリケトン繊維は、高温での弾性率保持性が高く、熱収縮率が小さいため、タイヤやベルト等の高温で使用される可能性がある繊維強化複合材料用途に適している。
【図面の簡単な説明】
【図１】Ｔｍとピーク面積比率を説明するためのＤＳＣ曲線図である。
【図２】本発明に用いた熱延伸機の概要を示す図である。
【符号の説明】
１ 延伸前の糸
２ 送りロール
３ ホットプレート
４ 巻き取りロール
５ ワインダー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyketone fiber having a high strength and a high elastic modulus, a high elastic modulus retention rate at a high temperature, and a low thermal shrinkage rate, and a method for producing the same.
[0002]
[Prior art]
By polymerizing carbon monoxide and an olefin such as ethylene or propylene using a transition metal complex such as palladium or nickel as a catalyst, a polyketone in which carbon monoxide and the olefin are substantially completely alternately copolymerized can be obtained. Is known (Industrial Materials, December issue, page 5, 1997). Many researchers have studied the application of polyketone as a fiber for industrial materials, taking advantage of its high strength, high elastic modulus, heat resistance, dimensional stability at high temperatures, adhesion, and creep resistance properties such as tire cords and belts. Application to composite materials such as reinforcing fibers and concrete reinforcing fibers is expected.
[0003]
In particular, polyketone composed of ethylene and carbon monoxide (hereinafter abbreviated as ECO) has high crystallinity, so it is most easy to obtain fibers with high strength and high elastic modulus, and changes in physical properties and shrinkage are small at high temperatures. The thermal stability is also the best. When the fiber is used as a tire cord, it is required to have an elastic modulus of 200 cN / dtex or more and excellent thermal stability, and ECO fiber is most appropriate. As methods for producing this ECO fiber, JP-A-2-112413, JP-A-4-505344, JP-A-4-228613, JP-A-5-504371, JP-A-7-508317 This is disclosed in Japanese Patent Publication No. 8-507328 and International Patent Application No. 99/18143. Since ECO is difficult to be melt-spun, ECO is dissolved in a solvent and fiberized by a dry or wet spinning method. In order to obtain a high-performance ECO fiber having an elastic modulus of 200 cN / dtex or more, a high degree of thermal stretching is required, and single-stage or multi-stage thermal stretching is performed at a high magnification of 9 to 26 times. It is also known that ECO fibers having a high elastic modulus can be obtained by heat drawing in multiple stages rather than heat drawing in one stage.
[0004]
[Problems to be solved by the present invention]
Although it is known to increase the elastic modulus by performing such a high degree of heat drawing, according to the study by the present inventors, if the heat drawing method is different, a polyketone fiber having the same elastic modulus can be obtained. However, it was found that the elastic modulus retention at high temperature and dimensional stability (hereinafter abbreviated as thermal stability) are different. When using a polyketone fiber as a tire cord application, there is a possibility of being heated at 170 to 200 ° C. in the vulcanization process when processed into a tire, or being heated at 150 ° C. or more due to heat generation of the tire due to high speed running, Thermal stability is extremely important as a required performance. In order to simultaneously satisfy a high elastic modulus of 200 cN / dtex or more and excellent thermal stability, the present inventors set very limited specific heat drawing conditions and the resulting fibers exhibit specific thermal properties. I found that it was necessary. In Example 3 of JP-A-4-228613, an ECO fiber having an elastic modulus of 200 cN / dtex or more is certainly shown. However, since the first stage stretching temperature is 175 ° C. and the melting point under tension of the ECO fiber according to the present invention is 250 ° C. or more, the stretching is performed at a temperature lower by 75 ° C. or more than the melting point under tension. . For this reason, it becomes a fiber with low thermal stability that stretch tension is high and molecular breakage or strain tends to remain, for example, the elastic modulus retention at 200 ° C. is 70% or less. Also, polyketone fibers having an elastic modulus of 200 cN / dtex or more are shown in Examples of JP-A-2-111413 and Example 10 of JP-T-5-504371. Stretching is performed at a high draw ratio of 9 times or more, and molecular cutting or non-uniform stretching due to high tension is likely to occur, resulting in a fiber having low thermal stability. Also in the examples of JP-A-4-505344, JP-A-4-228613, JP-A-5-504371, JP-A-7-508317, and JP-A-8-507328. It is shown that an elastic modulus of 200 cN / dtex or more can be obtained by multi-stage stretching. However, there is no description of the combination of the stretching temperature and the stretching ratio of each stage in the multi-stage stretching, and no suggestion about a method for maximizing the thermal stability is made.
[0005]
An object of the present invention is to provide a polyketone fiber having a high elastic modulus, a high elastic modulus retention rate at a high temperature, and a low thermal shrinkage rate. Specifically, the present invention provides a polyketone fiber having a Tm of at least 265 ° C. observed by DSC and a ratio of the endothermic peak area seen in the temperature range of 150 ° C. to Tm to the Tm peak area of 1% or less. It is.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors perform spinning and drawing of polyketone fibers by various methods, and maintain elastic modulus retention and dimensional stability (hereinafter referred to as thermal stability) at high temperatures and structural parameters. As a result of examining the relationship in detail, the maximum endothermic peak temperature (hereinafter referred to as Tm) observed by a differential scanning calorimeter (DSC) and the endothermic peak area seen in the temperature range of 150 ° C. to Tm with respect to the maximum endothermic peak area It has been found that if the ratio is in a specific range, it is possible to provide a polyketone fiber having excellent thermal stability, and the present invention has been achieved.
[0007]
That is, in the present invention, the maximum endothermic peak temperature (hereinafter referred to as Tm) observed by a differential scanning calorimeter (DSC) in a polyketone fiber in which 97 mol% or more of the repeating units are composed of a polyketone represented by the following formula (1): ) Is at least 265 ° C., the peak area ratio defined by the following formula (2) is 1% or less , the heat shrinkage rate at 200 ° C. is 3.2% or less, and the elastic modulus retention at 200 ° C. Is to provide a polyketone fiber characterized by being 75% or more .
[0008]
[Chemical formula 2]

[0009]
[Expression 2]
Peak area ratio (%) = [(A1 + A2 + ..) / Am] × 100 (2)
Here, A1, A2,... Are areas of endothermic peaks observed at temperatures lower than Tm and 150 ° C. or higher, and Am is the area of the maximum endothermic peak.
The polyketone fiber of the present invention is a polyketone in which 97 mol% or more of repeating units are represented by the above formula (1). A repeating unit other than the above formula (1), for example, one shown in the following formula (3) may be contained within a range of less than 3 mol%.
[0010]
[Chemical 3]

R is 1-30 organic groups other than ethylene, for example, propylene, butylene, 1-phenylethylene and the like. Some or all of these hydrogen atoms may be substituted with a halogen group, an ester group, an amide group, a hydroxyl group, or an ether group. Of course, R may be two or more, for example, propylene and 1-phenylethylene may be mixed. It is preferable that 98 mol% or more of the repeating unit is a polyketone represented by the above formula (1) in view of achieving high strength and high elastic modulus and excellent stability at high temperature, and most preferably 100 Mol%.
[0011]
These polyketones may contain additives such as antioxidants, radical inhibitors, other polymers, matting agents, ultraviolet absorbers, flame retardants, and metal soaps as necessary.
In the polyketone fiber of the present invention, Tm observed by a differential scanning calorimeter (DSC) is at least 265 ° C., and the peak area ratio defined by the above formula (2) needs to be 1% or less. When the DSC measurement is performed by the method as shown in the Examples, in the polyketone fiber that is highly heat-stretched, one or more endothermic peaks may be observed between 150 ° C. and less than Tm (FIG. 1). Even in the case of polyketone fibers having the same Tm, the thermal stability varies greatly depending on the size of the endothermic peak observed in the temperature range of 150 ° C. or higher and lower than Tm. Even if Tm is 265 ° C. or higher, if the peak area ratio is larger than 1%, the thermal stability becomes insufficient. Moreover, when Tm is smaller than 265 ° C., sufficient thermal stability cannot be obtained even if the peak area ratio is 1% or less. Tm is preferably 270 ° C. or higher, and more preferably 275 ° C. or higher in terms of better thermal stability. Similarly, the peak area ratio is preferably 0.5% or less, more preferably 0.3% or less, and most preferably 0%.
[0012]
The strength and elastic modulus of the polyketone fiber of the present invention are preferably high, but the elastic modulus is particularly preferably 200 cN / dtex or more, and more preferably 250 cN / dtex.
The intrinsic viscosity [η] of the polyketone fiber of the present invention is preferably 3 dl / g or more. If it is less than 3 dl / g, the effect of improving the melting point by stretching becomes small, and as a result, it is difficult to obtain a product having excellent thermal stability. However, when [η] is larger than 20 dl / g, the heat stretchability tends to be deteriorated, and the thermal stability may be lowered. Therefore, it is preferably 20 dl / g or less. The range of [η] is preferably 3 to 18 dl / g, more preferably 5 to 15 dl / g.
The production method is not particularly limited as long as the polyketone fiber has a Tm of 265 ° C. or more and a peak area ratio of 1% or less, but a production method that can be achieved will be described below.
[0013]
The polyketone used in the present invention is preferably carried out using a wet spinning method or a dry spinning method since the gelation proceeds rapidly due to the chemical crosslinking reaction of the polymer at a melting point or higher. Solvents described in JP-A-2-112413, JP-A-4-228613, JP-A-4-505344, for example, hexafluoroisopropanol, m-cresol, chlorophenol, resorcin / water, phenol / acetone, It can also be carried out using organic solvents such as propylene carbonate / hydroquinone, pyrrole, resorcin / propylene carbonate, pyridine, formic acid, etc., but these solvents are expensive or highly toxic or use a highly flammable coagulant. There is a problem in industrial use, such as the need to do so. In addition, US Pat. No. 5,929,150 and International Patent Application No. 99/18143 disclose that, for example, a zinc salt solution or a lithium salt solution can be used as a solvent. However, lithium salt solutions are expensive and cannot be used industrially. In contrast, a zinc salt solution is inexpensive, but when a polyketone is dissolved in a zinc salt solution, polymer transformation occurs during dissolution and spinning, making it difficult to spin stably over a long period of time. There is a problem. The inventors use an aqueous solution of a mixed salt of zinc halide and alkali metal halide and / or alkaline earth metal halide independently of US Pat. No. 5,929,150 and International Patent Application No. 99/18143. By doing so, the above problem is solved. Therefore, a wet spinning method using an aqueous solution of a mixed salt of zinc halide and alkali metal halide and / or alkaline earth metal halide as a solvent will be described below as an example.
[0014]
Examples of the zinc halide include zinc chloride, zinc bromide, and zinc iodide. Zinc chloride is most preferred from the viewpoint of the solubility of the polyketone, the cost of the solvent, and the stability of the aqueous solution. Examples of the alkali metal halide and alkaline earth metal halide include sodium chloride, potassium chloride, calcium chloride, magnesium chloride, barium salt, sodium bromide, calcium bromide, and sodium iodide. Sodium chloride, calcium chloride, magnesium chloride, and barium chloride are preferable in terms of cost, long-term stability of the solution, and ease of solvent recovery, and sodium chloride and calcium chloride are more preferable. The salt concentration of the mixed salt aqueous solution of zinc halide and alkali metal halide and / or alkaline earth metal halide is preferably 40 to 80% by weight, more preferably from the viewpoint of solubility, cost and stability of the polyketone solution. Is 50-75%. The mixing weight ratio of zinc halide and alkali metal halide and / or alkaline earth metal halide is preferably 95/5 to 40/60 from the viewpoint of the solubility of the polyketone and the long-term stability of the polyketone solution. More preferably, it is 90 / 10-55 / 45.
[0015]
The polymer concentration in the polyketone solution is preferably 0.005 to 70% by weight. If the polymer concentration is less than 0.005% by weight, the concentration is too low, and it has the disadvantage that it is difficult to become a fiber at the time of coagulation, and the production cost of the fiber is too high. On the other hand, when it exceeds 70% by weight, the polymer is no longer dissolved in the solvent. From the viewpoints of solubility, ease of spinning, and fiber production cost, it is preferably 0.5 to 40% by weight, more preferably 1 to 30% by weight.
[0016]
This polyketone solution is extruded from a spinneret and subsequently coagulated into fibers in a coagulation bath. The composition of the coagulation bath may be any organic solvent such as methanol, acetone, water, organic aqueous solution, inorganic aqueous solution, etc., but in the case of the coagulation bath of the organic solvent single composition, the coagulation rate is extremely slow. Therefore, it is difficult to spin with inexpensive equipment at an industrial speed, and therefore, a solution containing at least 1% by weight of water is preferable. From the viewpoint of recovery efficiency, an aqueous solution of the mixed salt used as a solvent is preferable.
[0017]
Depending on the spinning speed and coagulation temperature, the mixed salt in the coagulated yarn may not be sufficiently removed in the coagulation bath. Therefore, if necessary, the coagulated yarn that has exited the coagulation bath may be further washed. Any liquid may be used for washing as long as it is capable of dissolving the mixed salt. However, in view of safety, solution cost, recovery cost, etc., an aqueous solution is preferable, and halogenated From the viewpoint of zinc solubility, water or an acidic aqueous solution such as sulfuric acid, hydrochloric acid or phosphoric acid is particularly preferred.
[0018]
The coagulated yarn thus washed is dried to remove some or all of the moisture. As a drying method, drying may be performed at a constant length or while shrinking. The drying method may be a batch drying method or a continuous drying method in which drying is performed by running on a heated roll or plate or in a heated gas. From the viewpoint of yarn uniformity and production cost, the continuous drying method is preferred. Although there is no restriction | limiting in particular in drying temperature, The range of 60 to 260 degreeC is preferable.
The dry yarn thus obtained is subjected to two or more stages of thermal stretching at a specific thermal stretching temperature and stretching ratio as shown below, so that the Tm of the present invention is 265 ° C. or higher and the peak area ratio is A polyketone fiber of 1% or less can be obtained.
[0019]
The heat drawing temperature needs to be 0 to 30 ° C. lower than the melting point under tension of the polyketone fiber. Here, the melting point under tension is the maximum endothermic peak temperature (details are shown in the examples) when measured using DSC in a state where the polyketone fiber is in tension, and compared with the above-mentioned Tm. Higher temperature. Considering that the heat stretching is performed in a state in which the polyketone fiber is under tension, it is extremely important to determine the heat stretching temperature based on the melting point under tension. When the stretching temperature is lower than 30 ° C. from the melting point under tension, a polyketone fiber having a Tm of 265 ° C. or more and a peak area ratio of 1% or less cannot be obtained. Further, when the stretching temperature is higher than the melting point under tension, the stretching becomes impossible. From the same viewpoint, the temperature is preferably 10 to 20 ° C lower, and more preferably 13 to 17 ° C lower.
[0020]
The first-stage stretching needs to be performed in a range of 2 to 8 times. When the first stage draw ratio is higher than 8, even if a fiber having a Tm of 265 ° C. or higher is not obtained or a polyketone fiber having a Tm of 265 ° C. or higher is obtained, the peak area ratio is larger than 1%. When the first-stage stretching is lower than twice, not only the stretching efficiency is deteriorated but also the ultimate physical properties are lowered. Preferably it is 3-7 times, More preferably, it is 4-6 times. The second and subsequent stretches need to be performed at a stretch ratio of 30 to 80% of the breaking stretch ratio. Here, the breaking draw ratio is the limit draw ratio at which fiber cutting occurs when heat drawing is performed at a drawing temperature lower by 0 to 30 ° C. than the melting point under tension. When the draw ratio is larger than 80% of the breaking draw ratio, the strength improvement rate by drawing becomes low, and a fiber having a Tm of 265 ° C. or higher cannot be obtained, or even if the Tm is 265 ° C. or higher, the peak area ratio Is higher than 1%. When the draw ratio is less than 30% of the break draw ratio, it is difficult to obtain a polyketone fiber having high strength and high elastic modulus even if the drawing is performed in multiple stages, and the thermal stability is low. From the same viewpoint, 40 to 75% is preferable, and 50 to 70% is more preferable.
[0021]
The number of stages of hot drawing is not particularly limited as long as it is 2 or more, but 3 or more is preferable in that a polyketone fiber having high strength and elastic modulus can be easily obtained. However, if it exceeds 7 steps, not only the improvement rate of strength and elastic modulus becomes small, but also the equipment becomes expensive and the production efficiency deteriorates. More preferably, it is the range of 4-6 steps.
As the heat stretching method, a conventionally known apparatus and method such as a method of traveling on a heated roll or plate or in a heated gas, a method of irradiating a traveling yarn with laser, microwave, or far-infrared ray, etc. are employed as they are or as they are improved. can do.
[0022]
Since the polyketone fiber of the present invention has high elastic modulus retention at high temperatures and a small heat shrinkage rate, it is suitable for fiber-reinforced composite materials that may be used at high temperatures such as tires and belts. When the polyketone fiber of the present invention is used as a tire cord, a known method can be used. When used as a tire cord, the single yarn fineness is preferably 1 to 4d, and the total fineness is preferably 500 to 3000d. If necessary, it may be mixed with other fibers such as rayon, polyester fiber, aramid fiber, nylon fiber, steel fiber, etc., but preferably 20% by weight of the total tire cord contained in the tire, preferably 50% by weight or more is preferably used from the viewpoint of performance. The obtained polyketone fiber is twisted and twisted at 100 to 1000 T / m, preferably 200 to 500 T / m, and then made into a weave and then 10-30% RFL (phenol / formalin latex) Allow the liquid to adhere and fix at least 100 ° C. The adhesion amount of the RFL resin is preferably 2 to 7% by weight with respect to the fiber weight. The tire cord thus obtained is particularly useful as a carcass material for radial tires.
[0023]
【Example】
The present invention will be described in more detail with reference to the following examples, but they are not intended to limit the scope of the present invention.
The measurement method of each measurement value used in the description of the examples is as follows.
(1) Intrinsic viscosity Intrinsic viscosity [η] was determined based on the following defining formula.
[Η] = lim (T−t) / (t · C)
C → 0
In the definition formula, t and T are the flow times of a viscosity tube at 25 ° C. of a diluted solution of hexafluoroisopropanol having a purity of 98% or more and a polyketone dissolved in the hexafluoroisopropanol. C is the solute weight value in grams in 100 ml.
(2) Using a fiber strength / elastic modulus tensile property measuring instrument (UCT-10T, manufactured by Orientec Co., Ltd.), measurement was performed at 25 ° C., a sample length of 20 cm, and a crosshead speed of 20 cm / min.
[0024]
(3) Using a differential scanning calorimeter (Pyris 1 DSC, manufactured by PERKIN ELMER) at a rate of temperature increase of 20 ° C./min under a nitrogen atmosphere, 2 mg of polyketone fiber cut to about 2 mm in Tm and peak area ratio length And measured. Tm is the endothermic peak temperature having the largest area as shown in FIG. Further, the peak area is an area surrounded by a dotted base line and an endothermic peak as shown in FIG. 1, and was calculated using analysis software “Pyris Data Analysis” attached to Pyris 1 DSC manufactured by PERKIN ELMER.
(4) Under tension, 2 mg of polyketone fiber is wound around an aluminum plate having a length of 5 mm, a width of 2 mm, and a thickness of 0.2 mm under a tension of 1.0 cN / dtex, and this is fixed at 20 ° C./min. The measurement was performed using a differential scanning calorimeter (Pyris 1 DSC manufactured by PERKIN ELMER) at a temperature rising rate under a nitrogen atmosphere. The melting point under tension is the endothermic peak temperature with the largest area.
[0025]
(5) Breaking stretch ratio Using the apparatus shown in FIG. 2, at a predetermined hot plate temperature, the feed roll speed is 2 m / min, and the winding roll is gradually increased from 2 m / min to 10 m / min / min. The speed (m / min) of the take-up roll when the yarn was cut was measured. The breaking stretch ratio was calculated from the following formula.
Breaking draw ratio = Speed of winding roll when yarn is cut / 2
(6) Stretch ratio ratio The stretch ratio is the ratio of the stretch ratio actually stretched to the break stretch ratio, and was calculated from the following equation.
Stretch ratio (%) = stretch ratio / break stretch ratio × 100
[0026]
(7) Retention rate of elastic modulus The sample installation part was surrounded by a heater box, and the elastic modulus was measured under the same conditions as in (2) except that the sample temperature was 200 ° C. The retention rate was calculated from the formula shown below.
Retention rate (%) = [elastic modulus (200 ° C.) / Elastic modulus (25 ° C.)] × 100
(8) Heat shrinkage rate The change in fiber length was measured when the polyketone fiber was heat-treated at 200 ° C. for 30 minutes in an unstrained state, and the heat shrinkage rate was calculated from the following formula.
Thermal shrinkage (%) =
[(Fiber length before heat treatment−Fiber length after heat treatment) / Fiber length before heat treatment] × 100
[0027]
Examples 1-2 and Comparative Examples 1-3
In an aqueous solution of 75 wt% zinc chloride and sodium chloride (weight ratio of zinc chloride to sodium chloride is 65/10), the intrinsic viscosity is 6.0 dl / g. The polyketone represented by (1) was mixed so that it might become 7 weight%, and this was stirred at 80 degreeC for 3 hours, and the uniform and transparent polyketone solution was obtained.
[0028]
After passing this polyketone solution through a 20 μm filter, it was extruded from a spinneret having 50 holes with a diameter of 0.1 mm at a speed of 6 m / min at 80 ° C. using a plunger extruder, and an air gap length of 10 mm. And passed through a bath of 10 ° C. water as it was, and then pulled up using a Nelson roll at a speed of 6 m / min. Next, water was sprayed on the Nelson roll for cleaning, and then the Nelson roll was pulled up through a 2% sulfuric acid bath, and then water was sprayed on the Nelson roll for cleaning, and wound on a tube while containing water. The yarn was dried by passing through a hot plate at 240 ° C. at a speed of 2 m / min. The melting point of this polyketone fiber under tension was 253 ° C.
[0029]
This polyketone fiber was hot-drawn under the conditions shown in Table 1 using the apparatus shown in FIG. The feed roll speed is 2 m / min. Table 1 shows the melting point under tension and stretching temperature at each stretching stage, the breaking stretch ratio at the stretching temperature, the stretch ratio, and the stretch ratio. Table 2 shows the Tm, peak area ratio, [η], strength and elastic modulus at 25 ° C., retention rate of elastic modulus at 200 ° C., and heat shrinkage at 200 ° C. after three-stage drawing. Indicated.
As shown in Table 2, the polyketone fibers of Examples 1 and 2 have a high elastic modulus retention rate and a low thermal shrinkage rate, and exhibit high thermal stability. On the other hand, in Comparative Example 1, the stretching temperature for one-stage stretching is too low, in Comparative Example 2, the stretching ratio for one-stage stretching is too high, and in Comparative Example 3, the stretching ratio for three-stage stretching is too high. Although it is comparable to the invention, the thermal stability is low.
[0030]
Examples 3 to 4 and Comparative Example 4
In an aqueous solution of 63% by weight of zinc chloride and calcium chloride (weight ratio of zinc chloride to calcium chloride is 51/49), the intrinsic viscosity is 7.6 dl / g and substantially 100 mol% of the repeating unit is represented by the formula The polyketone (1) was mixed at 30 ° C. to 8 wt%, and the pressure was reduced to 10 torr. After generation | occurrence | production of foam disappeared, it sealed under pressure reduction, and stirred this at 120 degreeC for 5 hours, and the uniform and transparent polyketone solution was obtained.
[0031]
After passing this polyketone solution through a 20 μm filter, it was extruded from a spinneret having 50 holes with a diameter of 0.1 mm at a rate of 6 m / min using a plunger-type extruder at an air gap length of 10 mm. And passed through a bath of 30% by weight aqueous methanol at −20 ° C. as it was, and then pulled up using a Nelson roll at a speed of 6 m / min. Next, water was sprayed on the Nelson roll for cleaning, and then the Nelson roll was pulled up through a 2% sulfuric acid bath, and then water was sprayed on the Nelson roll for cleaning, and wound on a tube while containing water. The yarn was dried by passing through a hot plate at 240 ° C. at a speed of 2 m / min. The melting point of this polyketone fiber under tension was 255 ° C.
[0032]
This polyketone fiber was hot-drawn under the conditions shown in Table 3 using the apparatus shown in FIG. The feed roll speed is 2 m / min. Table 3 shows the melting point under tension and the stretching temperature at each stretching stage, the breaking stretch ratio at the stretching temperature, and the stretch ratio. Table 4 shows Tm, peak area ratio, [η], strength and elastic modulus at 25 ° C., retention of elastic modulus at 200 ° C., and heat shrinkage at 200 ° C. Indicated.
As shown in Table 4, the polyketone fibers of Examples 3 to 4 have a high elastic modulus retention rate, a small thermal shrinkage rate, and high thermal stability. On the other hand, in Comparative Example 4, since the stretch ratio of the four-stage stretching is too high, the elastic modulus is the same as that of the present invention, but the thermal stability is low.
[0033]
Example 5 and Comparative Example 5
Using a polyketone having an intrinsic viscosity of 6.2 dl / g and substantially 100 mol% of the repeating unit of the formula (1), wet spinning was performed according to Example 3 of JP-A-4-228613. The melting point under tension after drying was 255 ° C.
This was hot stretched under the conditions shown in Table 5 using the apparatus shown in FIG. The feed roll speed is 2 m / min. Table 5 shows the melting point under tension and the stretching temperature at each stretching stage, the breaking stretch ratio at the stretching temperature, the stretch ratio, and the stretch ratio. Table 6 shows the Tm, peak area ratio, [η], strength and elastic modulus at 25 ° C., retention rate of elastic modulus at 200 ° C., and heat shrinkage at 200 ° C. of the polyketone fiber after three-stage drawing. Indicated.
[0034]
As shown in Table 6, the polyketone fiber of Example 5 has a high elastic modulus retention rate and a low thermal shrinkage rate, and exhibits high thermal stability. On the other hand, in Comparative Example 5 (the method of thermal stretching in Example 3 of JP-A-4-228613), the stretching temperature of the first-stage stretching is too low and the stretching ratio of the two-stage stretching is too high. Although it is comparable to the invention, the thermal stability is low.
[0035]
[Table 1]

[0036]
[Table 2]

[0037]
[Table 3]

[0038]
[Table 4]

[0039]
[Table 5]

[0040]
[Table 6]

[0041]
【The invention's effect】
It has become possible to provide a polyketone fiber having excellent thermal stability, such as high elastic modulus retention at high temperatures and low thermal shrinkage. Since the polyketone fiber of the present invention has high elastic modulus retention at high temperatures and a small heat shrinkage rate, it is suitable for fiber-reinforced composite materials that may be used at high temperatures such as tires and belts.
[Brief description of the drawings]
FIG. 1 is a DSC curve diagram for explaining Tm and a peak area ratio.
FIG. 2 is a diagram showing an outline of a heat stretching machine used in the present invention.
[Explanation of symbols]
1 Thread before stretching 2 Feed roll 3 Hot plate 4 Winding roll 5 Winder

Claims (3)

In a polyketone fiber in which 97 mol% or more of the repeating units are composed of a polyketone represented by the following formula (1), the maximum endothermic peak temperature (hereinafter referred to as Tm) observed by a differential scanning calorimeter (DSC) is at least 265 ° C. Yes, the peak area ratio defined by the following formula (2) is 1% or less , the thermal shrinkage at 200 ° C. is 3.2% or less, and the elastic modulus retention at 200 ° C. is 75% or more . Polyketone fiber characterized by that.

[ Equation 1 ]
Peak area ratio (%) = [(A1 + A2 + ..) / Am] × 100 (2)
Here, A1, A2,... Are areas of endothermic peaks observed at temperatures lower than Tm and 150 ° C. or higher, and Am is the area of the maximum endothermic peak. Polyketone fiber according to claim 1, wherein Tm is equal to or is at least 270 ° C.. A tire cord comprising 50% by weight or more of the polyketone fiber according to any one of claims 1 and 2 .

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