JP4439745B2 - Method for producing polyketone fiber - Google Patents

Description

【００１０】
（請求項２）ポリケトンを紡糸し、乾燥して、延伸倍率３〜１２倍で延伸後、一旦巻き取ることを特徴とする請求項１記載のポリケトン繊維の製造方法、
（請求項３）繰り返し単位の９０モル％以上が下記式（１）で示されるポリケトンを紡糸し、延伸倍率３〜１２倍で延伸後、一旦巻き取り、次いで、（ａ）前記の延伸時よりも低い延伸速度で、延伸倍率１．０１〜１０の延伸を行った後に撚糸するか、（ｂ）前記の延伸時よりも低い延伸速度で、延伸倍率１．０１〜１０の延伸を行いつつ撚糸することを特徴とするポリケトン繊維の製造方法、
【００１１】
【化４】

【００１２】
（請求項４）ポリケトンを紡糸し、乾燥して、延伸倍率３〜１２倍で延伸後、一旦巻き取ることを特徴とする請求項３記載のポリケトン繊維の製造方法、
である。
本発明におけるポリケトンは、繰り返し単位の９０モル％以上が上記の式（１）で示されるポリケトンである。ポリマー中に、上記の式（１）以外の繰り返し単位、例えば、下記の式（２）に示したもの等を１０モル％未満、好ましくは３モル％未満、更に好ましくは１モル％未満の範囲で含有していてもよい。
【００１３】
【化５】

【００１４】
式中、Ｒはエチレン基以外の炭素数１〜３０の有機基であり、例えば、プロピレン基、ブチレン基、１−フェニルエチレン基等が例示される。これらの水素原子の一部又は全部が、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−フェニルエチレンと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、という観点から、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とが好ましく、最も好ましくは１００モル％である。
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。
【００１５】
本発明で使用するポリケトンの極限粘度［η］は、溶解性、紡糸性のかねあいから、好ましくは１〜２０、より好ましくは２〜１５である。
本発明のポリケトン繊維は、上記のポリケトンを紡糸し、必要に応じて乾燥後、延伸する方法において、前記の延伸における延伸倍率が３〜１２倍で延伸後、一旦巻き取り、その後、前記の延伸時よりも低い延伸速度で延伸倍率１．０１〜１０で延伸（後段の延伸）を行って製造できる。
【００１６】
後段の延伸後に撚糸するか、後段の延伸と同時に撚糸を行ってもよい。
紡糸方法としては、湿式紡糸法、乾式紡糸法、溶融紡糸法のいずれでもよいが、高強度、高弾性率が発現できる観点から、湿式紡糸法が最も好ましい。
湿式紡糸に用いる溶剤としては、特開平２−１２４１３号公報、特開平４−２２８６１３号公報、特表平４−５０５３４４号公報などに開示されている、例えばヘキサフルオロイソプロパノール、ｍ−クレゾール、レゾルシン、ハイドロキノンやこれらの混合物からなる有機溶剤を用いることができる。より好ましくは、本発明者らが提案している亜鉛塩、カルシウム塩、イソシアナート塩等の水溶液が、毒性が低く、不燃で、ポリケトンの溶解性が高いので好ましい（例えば、特願平１０−２３６５９５号に記載された方法）。この他に、沃化リチウム、臭化リチウム、塩化リチウム等のリチウム塩水溶液を用いることもできる。
【００１７】
より好ましくは、溶解性、紡糸安定性の観点から、少なくとも１種のハロゲン化亜鉛水溶液又は、少なくとも１種のハロゲン化亜鉛とハロゲン化亜鉛以外であって、５０℃の水に１質量％以上溶解する少なくとも１種の金属塩を含有する水溶液である。
ハロゲン化亜鉛としては、例えば、塩化亜鉛、臭化亜鉛、沃化亜鉛等が挙げられる。これらのハロゲン化亜鉛は純度が高ければ高いほどよく、好ましくは９０質量％以上であり、より好ましくは９５質量％以上である。回収使用する場合の回収のしやすさ、安定性、価格を考慮すると、特に、塩化亜鉛が好ましい。ハロゲン化亜鉛は、複数の種類のハロゲン化亜鉛を組み合わせて使用してもよい。これらのハロゲン化亜鉛は、結晶水を持った状態で使用しても何ら差し支えない。
【００１８】
５０℃の水に１質量％以上溶解する少なくとも１種の金属塩は、５０℃の水に１質量％以上溶解する金属塩であれば特に制限はなく、典型金属元素又は遷移金属元素のハロゲン化塩、硫酸塩、リン酸塩、硝酸塩等の無機塩、酢酸塩、ぎ酸塩、スルホン酸塩等の有機金属塩のいずれでもよい。ハロゲン化亜鉛と陰イオン元素を共通にすると回収しやすい、という利点を有するので、ハロゲンイオンが共通する金属塩が好ましい。
【００１９】
金属の種類としては、得られるポリマー溶液の溶液粘度低下の程度が大きい、という観点から、ハロゲン化アルカリ金属とハロゲン化アルカリ土類金属が好ましい。この場合、回収をしやすくする、という観点から、ハロゲン化亜鉛に用いたハロゲンと同じハロゲンを陰イオンに用いることが好ましく、特に、塩化物が好ましい。
好ましい具体例としては、塩化ナトリウム、塩化カルシウム、塩化リチウム、塩化バリウム、臭化ナトリウム、臭化カルシウム、臭化リチウム、臭化バリウム、沃化ナトリウム、沃化カルシウム、沃化リチウム、沃化バリウム等が挙げられ、ポリマー溶液の粘度低下の大きさ、紡糸の安定性、得られる繊維の着色の少なさ、回収のしやすさ、金属塩の安定性、コストの観点から、特に、塩化ナトリウム、塩化カルシウム、塩化バリウムが好ましい。このような金属塩は、複数の種類の金属塩を組み合わせて使用してもよい。
【００２０】
溶剤中に含まれる少なくとも１種のハロゲン化亜鉛の量としては、ハロゲン化亜鉛のみを用いる場合は、５０〜７５質量％が好ましい。少なくとも１種のハロゲン化亜鉛とハロゲン化亜鉛以外であって５０℃の水に１質量％以上溶解する少なくとも１種の金属塩を用いる場合、ハロゲン化亜鉛の濃度は、溶解性のよさから３０〜７５質量％が好ましく、より好ましくは４５〜７０質量％である。
ハロゲン化亜鉛と、ハロゲン化亜鉛以外であって、５０℃の水に１質量％以上溶解する少なくとも１種の金属塩との比は、ポリケトンの溶液粘度の低下と着色の抑制の観点から９８／２〜２０／８０が好ましく、より好ましくは９０／１０〜４０／６０である。この溶液中の少なくとも１種のハロゲン化亜鉛と、ハロゲン化亜鉛以外であって、５０℃の水に１質量％以上溶解する少なくとも１種の金属塩は、溶液中で反応していてもよい。例えば、塩化亜鉛と塩化ナトリウムを用いた場合、溶解条件によっては四塩化亜鉛錯体を形成するが、このような状態になってもよい。
【００２１】
溶剤に用いる水は、工業的に用いることができるものであれば特に制限はなく、飲料水、硬水、軟水、イオン交換処理した水、川水等、任意のものが使用できる。更に、本発明の目的を阻害しない範囲、通常は溶剤中の５０質量％以内で、水以外の溶剤、例えば、メタノール、エタノール、エチレングリコール、アセトン、Ｎ−メチルピロリドン、ジメチルスルホキシド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジメチルホルムアミド等の有機溶剤や塩化水素、臭化水素、沃化水素、硫酸等の酸を含有してもよい。
【００２２】
本発明に用いるポリケトン溶液中のポリマー濃度は、０．００５〜７０質量％である。ポリマー濃度が０．００５質量％未満では、濃度が低すぎて繊維の製造コストが高くなる。ポリマー濃度が７０質量％を越えると、ポリマーの溶解が極めて困難になる。溶解性、繊維の製造コストの観点から、好ましくは０．２〜４０質量％、より好ましくは１〜３０質量％である。
ポリケトン溶液中には、本発明の目的を阻害しない範囲で任意の添加物を含有してもよい。そのような含有物としては、酸化防止剤、熱安定剤、艶消し剤、顔料、紫外線吸収剤、光安定剤等や、本発明に用いる溶液に溶解する他のポリマー、例えば、ポリアクリロニトリル、セルロース等が挙げられる。
【００２３】
ポリケトン溶液の調整方法としては、繰り返し単位の９０質量％以上が一酸化炭素とオレフィンの交互共重合体であるポリケトンを、上記で説明した水溶液に撹拌しながら一気に、又は数回に分けて添加し、その後、撹拌操作を続けて実質的に完全溶解させて製造することができる。
ポリケトン中に含まれるパラジウム、ニッケル、コバルト元素量は１００ｐｐｍ以下が好ましい。
【００２４】
ポリケトンの形態としては、粉、チップ等、特に制限はないが、溶解速度、重合過程で生成したゲル化物量が少ない、という観点から粉末が好ましい。
溶解する時の温度は、特に制限はないが、溶解速度、溶剤の安定性の観点から、通常は５〜１２０℃、好ましくは５０〜１００℃の範囲である。金属の種類、組み合わせによっては、添加した金属塩それ自体や、２種又はそれ以上の金属塩が互いに反応して生成する金属塩や錯体が、温度を下げると結晶化し析出する場合がある。そのような場合は、結晶が析出しない温度で溶解、紡糸を行うことが重要である。
【００２５】
溶解中にポリケトン溶液に気泡が入らないように、減圧下で溶解させることが好ましい。減圧の程度は特に制限はないが、０．０９５ＭＰａ以下が好ましく、より好ましくは０．０３ＭＰａ以下、最も好ましくは０．００５ＭＰａ以下である。溶解方法としては、例えば、撹拌羽根による撹拌、１軸又は２軸押出機を用いた撹拌、超音波を用いた撹拌等、公知の方法が適用できる。
こうして得られたポリケトン溶液は、ごみ、ゲル化物、少量の未溶解ポリマー、触媒残さ等を除去するために、必要に応じてフィルターを通した後、紡口口金から押し出し、凝固浴に通してポリケトンを繊維状物とする。
【００２６】
凝固浴は、ポリケトン溶液から金属塩の一部又は全部を除去し、凝固浴に満たされた溶剤にポリケトンが溶解しない状態に変えて繊維形状を保持させる役割を持つ。
凝固浴に用いる溶剤としては、特に制限はないが、５０質量％以上が水で構成された溶剤が脱塩速度が速い、という点で好ましく、例えば、水、ハロゲン化亜鉛及び／又はハロゲン化亜鉛以外であって５０℃の水に１質量％以上溶解する少なくとも１種の金属塩を５０質量％未満含む水溶液等である。５０質量％未満の範囲でメタノール、アセトン、アセトン、メチルエチルケトン等の有機溶剤、塩酸、臭化水素酸、硫酸、リン酸等を含有してもよい。
【００２７】
これらの溶剤は、必要に応じて２種以上混合してもよい。特に好ましくは、ハロゲン化亜鉛等の金属塩を繊維状物からできる限り除去できる、という点から、実質的に水１００％、ハロゲン化亜鉛を１〜４５質量％以下含む水溶液、又はハロゲン化亜鉛１〜３０質量％及びハロゲン化亜鉛以外であって、５０℃の水に１質量％以上溶解する少なくとも１種の金属塩１〜２０質量％を含有する水溶液が好ましい。
【００２８】
凝固浴の温度は、特に制限はないが、繊維状物からハロゲン化亜鉛等の金属塩の除去効率と、得られる凝固糸の緻密性の観点から、−１０〜５０℃が好ましい。凝固浴に用いる溶剤量は、１時間当たり紡口口金から吐出するポリケトン量の１倍以上が好ましく、より好ましくは３０倍以上である。
こうして固化した繊維状物は、必要に応じて水又はｐＨが４以下の水溶液で少なくとも１回洗浄してもよい。洗浄は、凝固浴で除去できなかった金属塩を溶解するために好ましい。特に、塩化亜鉛を用いる場合、塩化亜鉛を一度水に溶解させた後、水で希釈すると水に溶解しにくい亜鉛塩が生成する。この亜鉛塩を除くためには、大量の水で更に洗浄したり、好ましくはｐＨが４以下の水溶液、例えば、塩酸、臭化水素酸、硫酸、リン酸等の水溶液で洗浄することが極めて有効である。また、水に溶解しにくい亜鉛塩の溶解性を高めるためには、これらの洗浄水の温度を４０℃以上、好ましくは５０〜９５℃にする。
【００２９】
以上のような凝固、洗浄において、得られた繊維状物に含まれる亜鉛量を乾燥繊維量中３５００ｐｐｍ以下にすることが重要である。３５００ｐｐｍよりも亜鉛元素残量が多いと、延伸工程において、高い強度や弾性率を発現するための高倍率延伸ができなくなるのである。亜鉛残量を３５００ｐｐｍ以下にするには、凝固浴の長さ、洗浄時間を調節し、脱塩速度を上げるために凝固浴や洗浄水の温度を４０℃以上にすることで達成できる。
【００３０】
金属塩が除去された繊維状物は水を大量に含んでいるので、５０℃以上の温度で乾燥して水分の一部又は全部を除くことが好ましい。乾燥方法としては、延伸しながら、定長で又は収縮させながら乾燥してもよい。乾燥時の温度としては、目標とする乾燥程度により任意に設定できるが、通常５０〜３００℃、好ましくは１００〜２５０℃である。乾燥するための装置としては、トンネル型乾燥機、ロール加熱機等、公知の設備を用いることができる。
【００３１】
こうして得られた未延伸糸は、延伸倍率３〜１２倍で延伸後、一旦巻き取り、その後、前記の延伸時よりも低い延伸速度で延伸倍率１．０１〜１０の延伸（後段の延伸）を行うことが必要である。
まず、未延伸糸は、延伸倍率３〜１２倍に延伸することが必要である。延伸倍率が３倍未満では、後段の延伸で高強度が達成しにくくなる他、結晶化度や非晶部分の配向が不十分なので繊維の構造変化が起きやすく、保存安定性及び取り扱い性の点で問題になりやすい。また、その後の延伸倍率が高くなって、長大な設備が必要となる。延伸倍率が１２倍を越えると、繊維にボイドや欠陥が生じ、後段の延伸を行っても強度や弾性率の発現の程度が低くなる。
【００３２】
未延伸糸は適度に分子が配向し、物性に経時変化がなく、保存安定性が増すと同時に取り扱いが容易になり、かつ、高強度や高弾性率が発現できる、という観点から、延伸倍率は、好ましくは５〜１０倍、より好ましくは６〜９倍である。
延伸は加熱下で行うことが好ましく、好ましくは１５０〜３００℃、より好ましくは２００〜２７０℃である。必要に応じて２段階以上に延伸倍率を変えて延伸することが糸切れや毛羽を減らせる点で好ましい。この場合、延伸の回数が増加すると共に、分子配向や結晶化が進行するので、より配向した構造を解きほぐすために、前の延伸と同じ温度か、それよりも高い温度を適用することが好ましい。例えば、１０倍の延伸を行うには、２６５℃で１回で熱延伸するよりも、まず、２６０℃で７倍の延伸を行い、その後、２６８℃で１．４３倍の延伸を行うことが好ましい。
【００３３】
延伸速度は、特に制限はないが、通常は３０〜２０００ｍ／ｍｉｎ、好ましくは１００〜１５００ｍ／ｍｉｎである。こうして延伸されたポリケトン繊維は、通常、強度１．８〜１３．５ｃＮ／ｄｔｅｘ、伸度３〜２０％の値を示す。
以上のようにして、３〜１２倍に延伸されたポリケトン繊維は、一旦巻き取る必要がある。一旦巻き取ることにより、後段の延伸を低速で行うことが可能となる。巻き取りは公知の巻き取り設備を使用してよく、巻き取り速度は延伸速度と同じか、それよりも低い速度で巻き取ることが、巻き取り時の巻き締まりが起こらないでの好ましい。巻き締まりとは、巻き取った糸によって紙管が締め付けられ、巻きフォームが悪くなったり、巻き糸が巻き取り機から取り外せなくなることを指す。
【００３４】
巻き取る量には特に制限はないが、切り替えの効率と取り扱い性の点から０．５〜２０ｋｇ、好ましくは２〜１５ｋｇである。
こうして巻き取られたポリケトン繊維は、後段の延伸として、前記の延伸時よりも低い延伸速度で延伸倍率１．０１〜１０の延伸を行うことが必要である。延伸を連続して行うと、後段の延伸は高速延伸となり長大な加熱ヒーターが必要となるが、このように延伸を２段に分けて行うことで、後段の延伸は低速で行うことが可能となる。その結果、短いヒーターであっても糸切れや毛羽が少なく、安定に高強度、高弾性率繊維を得ることが可能となる。
【００３５】
特に、ポリケトン繊維の用途はタイヤコードや各種補強材が主となるが、これらの用途において、ポリケトン繊維は加撚工程を経て撚糸として使用される。加撚は、通常、数１０〜１５０ｍ／ｍｉｎで行われるので、その前に延伸を行えば、予め、高価な長大なヒーターを用いて高強度、高弾性率繊維を製造しなくても、撚糸機を改造するだけで安定に効率よくポリケトン繊維の撚糸を生産することができる。これが本発明の最大の特徴である。
【００３６】
一旦巻き取った後の延伸（後段の延伸）の延伸倍率が１．０１倍未満では、高強度、高弾性率は達成できない。延伸倍率が１０倍を超えると、糸切れや毛羽の発生比率が高くなる。好ましくは、１．０５〜５倍、より好ましくは、１．１〜２倍である。延伸は加熱下で行うことが好ましく、好ましくは２００〜２８０℃、より好ましくは２５０〜２７０℃である。また、必要に応じて２段階以上に延伸倍率を変えて延伸することが糸切れや毛羽を減らせる点で好ましい。
【００３７】
こうして延伸を受けた繊維はそのまま巻き取ることもできるし、巻き取ることなくそのまま撚糸してもよい。撚糸の方法は公知の方法をそのまま使用することができる。
例えば、原糸に下撚りをかけ、次いで、これを２〜３本合わせて逆方向に上撚りを施してもよい。１本だけに撚りをかけてもよい。撚り数としては、好ましくは耐疲労性と強度の観点から１０〜５００Ｔ／ｍ、より好ましくは１００〜４５０Ｔ／ｍである。
また、後段の延伸を行いつつ、上記の撚糸を同時に行ってもよい。
【００３８】
【発明の実施の形態】
本発明を実施例により具体的に説明するが、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られる値である。
［η］＝ｌｉｍ（Ｔ−ｔ）／（ｔ・Ｃ）
Ｃ→０
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と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。Ｃは、上記溶液１００ｍＬ中のグラム単位による溶質質量値である。
（２）強伸度
繊維の強伸度は、ＪＩＳ−Ｌ−１０１３に準じて測定した。
【００３９】
【実施例１】
極限粘度５．６のエチレン／一酸化炭素完全交互コポリマーを塩化亜鉛／塩化カルシウム／水（質量比２２／４０／３８）からなる溶剤に、ポリマー濃度が７．５質量％になるように溶解して紡糸原液を製造し、８０℃で紡孔径０．１６ｍｍ、孔数２０の紡口口金から吐出し、１０ｍｍのエアギャップを通して、５℃の水を満たした浴長１．２ｍの凝固浴、２％の硫酸を含む浴長２ｍの洗浄浴、水を連続的に吹きかけるネルソンロールを順次通し、定長で２２０℃の乾燥ラインを通した後、連続する２つのホットプレートを通して延伸を行い、巻き取った。延伸倍率は、２２５℃の第一ホットプレートで７倍、２４０℃の第２ホットプレートで１．３倍（総延伸倍率は、９．１倍）、延伸速度は7０ｍ／ｍｉｎとした。
【００４０】
こうして巻き取った繊維を、２つの連続するホットプレート(各加熱長２ｍ）を介して、順に１．４倍、１．３倍で延伸後、３０ｍ／ｍｉｎで巻き取った。この時の２つのホットプレート温度をそれぞれ、２５０℃と２７０℃に設定した。
延伸による毛羽や糸切れの発生はなく、安定的に延伸を行うことができた。得られた延伸糸の強度は１７．２ｃＮ／ｄｔｅｘ、伸度は４．２％、弾性率は４２３ｃＮ／ｄｔｅｘと良好な結果を示した。
【００４１】
【実施例２】
極限粘度５．６のエチレン／一酸化炭素完全交互コポリマーを塩化亜鉛／塩化カルシウム／水（質量比２２／４０／３８）からなる溶剤に、ポリマー濃度が７．５質量％になるように溶解して紡糸原液を製造し、８０℃で紡孔径０．１６ｍｍ、孔数５０の紡口口金から吐出した。次いで、１０ｍｍのエアギャップ、５℃の水を満たした浴長１．２ｍの凝固浴、２％の硫酸を含む浴長２ｍの洗浄浴を順次通した。洗浄された繊維を、水を連続的に吹きかけるネルソンロールに通し、定長で２２０℃の乾燥機で乾燥した。次いで、連続する２つのホットプレートを通して延伸を行った。
【００４２】
延伸倍率は、２２５℃の第一ホットプレートで７倍、２４０℃の第２ホットプレートで１．３倍（総延伸倍率は、９．１倍）、延伸速度は６０ｍ／ｍｉｎとした。延伸したポリケトン繊維を２０本合わせて巻き取った。
巻き取った繊維を、２つの連続するホットプレート（各加熱長２ｍ）を介し、順に、１．３５、１．２５倍で延伸後、連続して撚糸機に導いた。この時の２つのホットプレート温度は、それぞれ２５０℃と２６０℃に設定し、３９０Ｔ／ｍの撚りを掛けながら、３０ｍ／ｍｉｎで巻き取った。
撚糸の際に毛羽やループの発生はなく、安定的に撚糸を行うことができた。得られた撚糸の強度は１３．７ｃＮ／ｄｔｅｘと良好であった。
【００４３】
【比較例１】
実施例１において、一旦巻き取ることなく、連続的に延伸を行ったが、３段目、４段目の延伸に、実施例１で用いた加熱長２ｍのホットプレートを使用すると糸切れが発生し、延伸糸を巻き取ることができなかった。
そこで、３段目、４段目の延伸の際に、加熱長が６ｍの筒型加熱炉を用いたところ、延伸を行うことができた。この結果からもわかるように、３段、４段を連続延伸するには、長大な加熱長が必要となる。
【００４４】
【発明の効果】
高強度、高弾性率を有するポリケトン繊維の生産性を高めるには、多段延伸を行うと共に、延伸速度を増加させる必要があり、そのためには長大な延伸機を必要とする。しかしながら、本発明の方法によると、比較的コンパクトな延伸機を用いて、糸切れや毛羽の発生もなく、安定してポリケトン繊維を製造することができる。
特に、ポリケトン繊維はタイヤコード、各種補強材等、撚糸形態で使用することが多いので、撚糸は数１０ｍ／ｍｉｎ〜１５０ｍ／ｍｉｎの低速で行うのが常である。本発明のように、撚糸の前に後段の延伸を行えば、高延伸倍率を施したポリケトン繊維をわざわざ製造しなくても、効率よくポリケトン撚糸を製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing polyketone fibers. More specifically, a method for producing polyketone drawn yarns and twisted yarns having high strength and high elastic modulus with a relatively compact drawing equipment without using a long drawing machine, with less yarn breakage and fluff and high productivity. About.
[0002]
[Prior art]
By polymerizing carbon monoxide and olefins such as ethylene and propylene using a transition metal complex such as palladium or nickel as a catalyst, it is possible to obtain a polyketone in which carbon monoxide and olefin are substantially completely alternately copolymerized. Is known (Industrial Materials, December issue, page 5, 1997).
Many researchers have studied the application of polyketone as a fiber for industrial materials, making use of high-strength, high-elastic modulus, dimensional stability at high temperatures, adhesiveness, and creep resistance, and forming a twisted cord into a tire. Application to composite materials such as cords, belts and other reinforcing fibers is expected.
[0003]
When producing a polyketone fiber having a high strength and a high elastic modulus, it is necessary to stretch the unstretched yarn of the polyketone fiber at least 10 times, preferably 15 times or more. In the stretching step, the degree of crystallinity and molecular orientation increase as the stretching ratio increases, so that it becomes necessary to stretch at a higher temperature as the stretching ratio increases. Therefore, it is necessary to design the polyketone fiber drawing equipment so that the draw ratio can be increased while gradually increasing the temperature of the drawing zone.
[0004]
The inventors usually divide the stretching zone into two or more stages, preferably three or more stages, and while stretching in each stretching zone, as the stretching zone progresses, the temperature is higher by several degrees C. to 20 degrees C. than the previous stretching zone. It has been found that a polyketone fiber having the highest strength and high elastic modulus can be produced by stretching at a high temperature.
For example, in the case of an ethylene / carbon monoxide copolymer, 5 to 8 times at 210 to 230 ° C. in the first stretching zone and 1.1 to 0.1 at 230 to 250 ° C. in the second stretching zone. In the third stretching zone, stretching is performed at 255 to 265 ° C. at 1.05 to 1.5 times, and in the fourth stretching zone, stretching is performed at 255 to 265 ° C. at 1.05 to 1.3 times.
[0005]
[Problems to be solved by the invention]
In order to industrially perform the above-described multi-stage stretching, in order to increase productivity, heating devices such as stretching rolls and hot plates are continuously arranged in each stretching zone, and stretching is performed sequentially at a higher stretching speed. Is preferred.
However, in the above-described multi-stage stretching, the first stretching zone and the second stretching zone can be stretched at high speed even with a heater having a relatively short heating length, but the third and subsequent stretching zones have greatly advanced fiber crystallization and orientation. It was found that the fiber was difficult to stretch, and a long heating zone was required to stretch at high speed.
[0006]
Although the length of this heater depends on the stretching speed, it usually ranges from several tens of meters to several hundreds of meters in order to achieve an industrial stretching speed. Such a long drawing zone has a high equipment cost, and it is difficult to thread, or when thread breakage occurs during drawing, it is practically impossible to thread again.
The problem to be solved by the present invention is based on the background described above, and the polyketone fiber having high strength and high elastic modulus is used with relatively inexpensive equipment without using a long stretch zone, and there is little thread breakage or the like. It is to provide a method of manufacturing with good productivity.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have studied various stretching techniques for polyketone fibers, and as a result, without stretching at once to the target high-strength and high-modulus fibers, stretching is performed at an intermediate stage. By completing the second half of the drawing, it was found that a high-strength, high-modulus polyketone fiber could be obtained with a relatively inexpensive drawing facility without using a long heater. In particular, it was found that performing the latter half of the drawing process before the twisting process, which is the largest use of polyketone fibers, was the most efficient drawing method, and as a result of further studies, the present invention was achieved.
[0008]
That is, the present invention
(Claim 1) 90 mol% or more of repeating units are spun with a polyketone represented by the following formula (1), stretched at a stretch ratio of 3 to 12 times, and then wound up, and then stretched at a lower rate than in the above stretching A method for producing a polyketone fiber, characterized by performing stretching at a stretching ratio of 1.01 to 10 at a speed,
[0009]
[Chemical 3]

[0010]
(Claim 2) The method for producing a polyketone fiber according to claim 1, wherein the polyketone fiber is spun, dried, drawn at a draw ratio of 3 to 12 and then wound up.
(Claim 3) 90 mol% or more of repeating units are spun a polyketone represented by the following formula (1), stretched at a stretching ratio of 3 to 12 times, and then wound up, and then (a) from the above stretching The yarn is twisted after being drawn at a draw rate of 1.01 to 10 at a low draw rate, or (b) while being drawn at a draw rate of 1.01 to 10 at a draw rate lower than that at the time of drawing. A method for producing polyketone fibers, characterized by:
[0011]
[Formula 4]

[0012]
(Claim 4) The method for producing a polyketone fiber according to claim 3, wherein the polyketone is spun, dried, drawn at a draw ratio of 3 to 12 and then wound up.
It is.
The polyketone in the present invention is a polyketone in which 90 mol% or more of the repeating units is represented by the above formula (1). In the polymer, a repeating unit other than the above formula (1), for example, one represented by the following formula (2) is less than 10 mol%, preferably less than 3 mol%, more preferably less than 1 mol%. It may contain.
[0013]
[Chemical formula 5]

[0014]
In the formula, R is an organic group having 1 to 30 carbon atoms other than an ethylene group, and examples thereof include a propylene group, a butylene group, and a 1-phenylethylene group. 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.
From the viewpoint that high strength and high elastic modulus can be achieved, and stability at high temperature is excellent, it is preferable that 98 mol% or more of the repeating units be the polyketone represented by the above formula (1), and most preferably 100 mol%.
These polyketones may contain additives such as antioxidants, radical inhibitors, other polymers, matting agents, ultraviolet absorbers, flame retardants, and metal soaps as necessary.
[0015]
The intrinsic viscosity [η] of the polyketone used in the present invention is preferably 1 to 20 and more preferably 2 to 15 because of the balance between solubility and spinnability.
In the polyketone fiber of the present invention, the above polyketone is spun, dried if necessary, and then stretched. After stretching at a stretching ratio of 3 to 12 times in the above stretching, the polyketone fiber is wound up once, and then stretched as described above. It can be produced by stretching at a draw rate of 1.01 to 10 at a drawing speed lower than the time (drawing in the latter stage).
[0016]
Twisting may be performed after the subsequent stretching, or may be performed simultaneously with the subsequent stretching.
The spinning method may be any of a wet spinning method, a dry spinning method, and a melt spinning method, but the wet spinning method is most preferable from the viewpoint of achieving high strength and high elastic modulus.
Solvents used for wet spinning are disclosed in JP-A-2-12413, JP-A-4-228613, JP-A-4-505344, etc., for example, hexafluoroisopropanol, m-cresol, resorcin, An organic solvent composed of hydroquinone or a mixture thereof can be used. More preferably, an aqueous solution of zinc salt, calcium salt, isocyanate salt or the like proposed by the present inventors is preferable because it has low toxicity, is nonflammable, and has high solubility of polyketone (for example, Japanese Patent Application No. 10-101). 236595). In addition, an aqueous lithium salt solution such as lithium iodide, lithium bromide, or lithium chloride can also be used.
[0017]
More preferably, from the viewpoint of solubility and spinning stability, at least one kind of zinc halide aqueous solution or at least one kind of zinc halide and zinc halide other than at least 1% by weight dissolved in water at 50 ° C. An aqueous solution containing at least one metal salt.
Examples of the zinc halide include zinc chloride, zinc bromide, and zinc iodide. These zinc halides should have a higher purity, preferably 90% by mass or more, and more preferably 95% by mass or more. In view of ease of recovery, stability, and price in the case of recovery and use, zinc chloride is particularly preferable. As the zinc halide, a plurality of types of zinc halides may be used in combination. These zinc halides can be used in the state of having crystal water.
[0018]
There is no particular limitation on the at least one metal salt that dissolves in 1% by mass or more in 50 ° C. water as long as it is a metal salt that dissolves in 1% by mass or more in 50 ° C. water. Any of inorganic salts such as salts, sulfates, phosphates and nitrates, and organic metal salts such as acetates, formates and sulfonates may be used. A metal salt having a common halogen ion is preferred because it has the advantage of being easy to recover when the zinc halide and the anionic element are used in common.
[0019]
As the type of metal, an alkali metal halide and an alkaline earth metal halide are preferable from the viewpoint that the degree of decrease in the solution viscosity of the resulting polymer solution is large. In this case, from the viewpoint of facilitating recovery, the same halogen as that used for zinc halide is preferably used for the anion, and chloride is particularly preferable.
Preferred examples include sodium chloride, calcium chloride, lithium chloride, barium chloride, sodium bromide, calcium bromide, lithium bromide, barium bromide, sodium iodide, calcium iodide, lithium iodide, barium iodide and the like. In view of the magnitude of viscosity reduction of the polymer solution, spinning stability, low coloration of the resulting fiber, ease of recovery, metal salt stability, cost, especially sodium chloride, chloride Calcium and barium chloride are preferred. Such metal salts may be used in combination of a plurality of types of metal salts.
[0020]
The amount of at least one zinc halide contained in the solvent is preferably 50 to 75% by mass when only zinc halide is used. In the case of using at least one kind of metal salt other than at least one kind of zinc halide and zinc halide and dissolved in 1% by mass or more in water at 50 ° C., the concentration of zinc halide is from 30 to 30 because of good solubility. 75 mass% is preferable, More preferably, it is 45-70 mass%.
The ratio of zinc halide to at least one metal salt other than zinc halide and dissolved in water of 50 ° C. in an amount of 1 mass% or more is 98/98 from the viewpoint of lowering the solution viscosity of the polyketone and suppressing coloration. 2-20 / 80 is preferable, More preferably, it is 90 / 10-40 / 60. At least one kind of zinc halide in this solution and at least one kind of metal salt other than zinc halide and dissolved in water at 50 ° C. in an amount of 1% by mass or more may react in the solution. For example, when zinc chloride and sodium chloride are used, a zinc tetrachloride complex is formed depending on dissolution conditions, but such a state may be obtained.
[0021]
The water used for the solvent is not particularly limited as long as it can be used industrially, and any water such as drinking water, hard water, soft water, ion-exchanged water, and river water can be used. Furthermore, in a range not impairing the object of the present invention, usually within 50% by mass in the solvent, a solvent other than water, for example, methanol, ethanol, ethylene glycol, acetone, N-methylpyrrolidone, dimethyl sulfoxide, N, N- You may contain organic solvents, such as a dimethylacetamide and N, N- dimethylformamide, and acids, such as hydrogen chloride, hydrogen bromide, hydrogen iodide, and a sulfuric acid.
[0022]
The polymer concentration in the polyketone solution used in the present invention is 0.005 to 70% by mass. When the polymer concentration is less than 0.005% by mass, the concentration is too low and the production cost of the fiber is increased. When the polymer concentration exceeds 70% by mass, it is very difficult to dissolve the polymer. From the viewpoint of solubility and fiber production cost, it is preferably 0.2 to 40% by mass, more preferably 1 to 30% by mass.
The polyketone solution may contain any additive as long as the object of the present invention is not impaired. Such inclusions include antioxidants, heat stabilizers, matting agents, pigments, UV absorbers, light stabilizers, and other polymers that are soluble in the solution used in the present invention, such as polyacrylonitrile, cellulose. Etc.
[0023]
As a method for preparing the polyketone solution, a polyketone in which 90% by mass or more of the repeating units is an alternating copolymer of carbon monoxide and olefin is added to the above-described aqueous solution at once or in several portions while stirring. Thereafter, the stirring operation is continued and it can be produced by substantially complete dissolution.
The amount of palladium, nickel and cobalt elements contained in the polyketone is preferably 100 ppm or less.
[0024]
The form of the polyketone is not particularly limited, such as powder and chips, but powder is preferred from the viewpoint of dissolution rate and a small amount of gelated product generated in the polymerization process.
Although the temperature at the time of melt | dissolution does not have a restriction | limiting in particular, From a melt | dissolution rate and a viewpoint of solvent stability, it is 5-120 degreeC normally, Preferably it is the range of 50-100 degreeC. Depending on the type and combination of metals, the added metal salt itself, or a metal salt or complex formed by reacting two or more metal salts with each other, may crystallize and precipitate when the temperature is lowered. In such a case, it is important to perform melting and spinning at a temperature at which crystals do not precipitate.
[0025]
It is preferable to dissolve under reduced pressure so that bubbles do not enter the polyketone solution during dissolution. The degree of decompression is not particularly limited, but is preferably 0.095 MPa or less, more preferably 0.03 MPa or less, and most preferably 0.005 MPa or less. As the dissolution method, for example, a known method such as stirring with a stirring blade, stirring using a single or twin screw extruder, stirring using ultrasonic waves, and the like can be applied.
The polyketone solution thus obtained is passed through a filter as necessary to remove dust, gelled material, a small amount of undissolved polymer, catalyst residue, etc., and then extruded from a spinneret and passed through a coagulation bath to polyketone. Is a fibrous material.
[0026]
The coagulation bath has a role of removing a part or all of the metal salt from the polyketone solution and changing the state so that the polyketone is not dissolved in the solvent filled in the coagulation bath to maintain the fiber shape.
The solvent used in the coagulation bath is not particularly limited, but a solvent comprising 50% by mass or more of water is preferable in that the desalting rate is high. For example, water, zinc halide and / or zinc halide And an aqueous solution containing less than 50% by mass of at least one metal salt that dissolves in 1% by mass or more in water at 50 ° C. You may contain organic solvents, such as methanol, acetone, acetone, and methyl ethyl ketone, hydrochloric acid, hydrobromic acid, a sulfuric acid, phosphoric acid, etc. in the range below 50 mass%.
[0027]
Two or more of these solvents may be mixed as necessary. Particularly preferably, from the viewpoint that metal salts such as zinc halide can be removed from the fibrous material as much as possible, an aqueous solution substantially containing 100% water and 1 to 45% by mass or less of zinc halide, or zinc halide 1 An aqueous solution containing 1 to 20% by mass of at least one metal salt that dissolves in an amount of 1% by mass or more in 50 ° C. water other than 30% by mass and zinc halide is preferable.
[0028]
Although there is no restriction | limiting in particular in the temperature of a coagulation bath, -10-50 degreeC is preferable from a viewpoint of the removal efficiency of metal salts, such as a zinc halide from a fibrous material, and the compactness of the coagulated yarn obtained. The amount of solvent used in the coagulation bath is preferably at least 1 time, more preferably at least 30 times the amount of polyketone discharged from the spinneret per hour.
The fibrous material thus solidified may be washed at least once with water or an aqueous solution having a pH of 4 or less as necessary. Washing is preferred to dissolve metal salts that could not be removed in the coagulation bath. In particular, when zinc chloride is used, a zinc salt that hardly dissolves in water is produced when zinc chloride is once dissolved in water and then diluted with water. In order to remove this zinc salt, it is very effective to further wash with a large amount of water, or preferably with an aqueous solution having a pH of 4 or less, such as an aqueous solution of hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid or the like. It is. Moreover, in order to improve the solubility of the zinc salt which is difficult to dissolve in water, the temperature of these washing waters is set to 40 ° C. or higher, preferably 50 to 95 ° C.
[0029]
In the solidification and washing as described above, it is important that the amount of zinc contained in the obtained fibrous material is 3500 ppm or less in the amount of dry fiber. When the amount of zinc element remaining is more than 3500 ppm, high-stretching for expressing high strength and elastic modulus cannot be performed in the stretching process. The amount of zinc remaining can be reduced to 3500 ppm or less by adjusting the length of the coagulation bath and the washing time, and setting the temperature of the coagulation bath and washing water to 40 ° C. or higher in order to increase the desalting rate.
[0030]
Since the fibrous material from which the metal salt has been removed contains a large amount of water, it is preferable to remove some or all of the water by drying at a temperature of 50 ° C. or higher. As a drying method, drying may be performed while stretching, at a constant length, or while shrinking. Although it can set arbitrarily as temperature at the time of drying by the target drying degree, it is 50-300 degreeC normally, Preferably it is 100-250 degreeC. As an apparatus for drying, known equipment such as a tunnel dryer and a roll heater can be used.
[0031]
The undrawn yarn obtained in this manner was once wound after being drawn at a draw ratio of 3 to 12, and then drawn at a draw ratio of 1.01 to 10 (lower stretch) at a lower drawing speed than that at the time of drawing. It is necessary to do.
First, the undrawn yarn needs to be drawn at a draw ratio of 3 to 12 times. If the draw ratio is less than 3 times, it will be difficult to achieve high strength by subsequent drawing, and the crystallinity and the orientation of the amorphous part will be insufficient, so that the structure of the fiber is likely to change. It tends to be a problem. Moreover, the draw ratio after that becomes high and a long installation is needed. When the draw ratio exceeds 12 times, voids and defects are generated in the fiber, and the degree of expression of strength and elastic modulus is lowered even if the subsequent drawing is performed.
[0032]
The unstretched yarn has a moderately oriented molecular orientation, no change in physical properties over time, storage stability increases, and handling becomes easy and high strength and high elastic modulus can be expressed. , Preferably 5 to 10 times, more preferably 6 to 9 times.
The stretching is preferably performed under heating, preferably 150 to 300 ° C, more preferably 200 to 270 ° C. If necessary, it is preferable to stretch the film by changing the stretching ratio in two or more stages from the viewpoint of reducing yarn breakage and fluff. In this case, since the number of stretching increases and molecular orientation and crystallization progress, it is preferable to apply the same temperature as the previous stretching or a higher temperature in order to unravel the more oriented structure. For example, to stretch 10 times, it is necessary to first stretch 7 times at 260 ° C. and then stretch 1.43 times at 268 ° C., rather than heat stretching at 265 ° C. once. preferable.
[0033]
The stretching speed is not particularly limited, but is usually 30 to 2000 m / min, preferably 100 to 1500 m / min. The polyketone fiber thus stretched usually exhibits a strength of 1.8 to 13.5 cN / dtex and an elongation of 3 to 20%.
As described above, the polyketone fiber drawn 3 to 12 times needs to be wound once. By winding it once, it is possible to perform subsequent stretching at a low speed. The winding may be performed by using a known winding equipment, and it is preferable that the winding speed is the same as or lower than the stretching speed so that winding does not occur during winding. “Tightening” means that the paper tube is tightened by the wound yarn and the wound form is deteriorated or the wound yarn cannot be removed from the winder.
[0034]
Although there is no restriction | limiting in particular in the amount wound up, it is 0.5-20 kg from the point of the efficiency of switching, and a handleability, Preferably it is 2-15 kg.
The polyketone fiber wound up in this way needs to be drawn at a draw ratio of 1.01 to 10 at a lower drawing speed than the above drawing as the subsequent drawing. If stretching is performed continuously, the subsequent stretching will be a high-speed stretching and a long heater will be required, but if the stretching is performed in two stages in this way, the subsequent stretching can be performed at a low speed. Become. As a result, even with a short heater, yarn breakage and fluff are few, and it is possible to stably obtain high strength and high elastic modulus fibers.
[0035]
In particular, tire cords and various reinforcing materials are mainly used for polyketone fibers. In these applications, polyketone fibers are used as twisted yarns through a twisting step. Twisting is usually carried out at several 10 to 150 m / min, so if it is stretched before that, it is possible to twist the yarn without producing a high-strength, high-modulus fiber in advance using an expensive and long heater. Polyketone fiber twisted yarn can be produced stably and efficiently simply by remodeling the machine. This is the greatest feature of the present invention.
[0036]
If the draw ratio of the stretch after winding (stretching at the latter stage) is less than 1.01, high strength and high elastic modulus cannot be achieved. When the draw ratio exceeds 10 times, the generation ratio of yarn breakage and fluff increases. Preferably, it is 1.05 to 5 times, more preferably 1.1 to 2 times. The stretching is preferably performed under heating, preferably 200 to 280 ° C, more preferably 250 to 270 ° C. In addition, it is preferable that stretching is performed by changing the stretching ratio to two or more stages as necessary in terms of reducing yarn breakage and fluff.
[0037]
The fiber thus stretched can be wound as it is, or it can be twisted as it is without being wound. As the twisting method, a known method can be used as it is.
For example, the raw yarn may be subjected to a lower twist, and then two or three of these may be combined and subjected to an upper twist in the opposite direction. Only one may be twisted. The number of twists is preferably 10 to 500 T / m, more preferably 100 to 450 T / m from the viewpoint of fatigue resistance and strength.
Further, the above-described twisted yarn may be simultaneously performed while performing subsequent drawing.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described by way of 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
The intrinsic viscosity [η] is a value obtained based on the following definition formula.
[Η] = lim (T−t) / (t · C)
C → 0
In the formula, t and T are the flow time of the viscosity tube at 25 ° C. of hexafluoroisopropanol having a purity of 98% or more and a polyketone diluted solution dissolved in hexafluoroisopropanol. C is the solute mass value in grams in 100 mL of the solution.
(2) Strong elongation
The high elongation of the fiber was measured according to JIS-L-1013.
[0039]
[Example 1]
An ethylene / carbon monoxide complete alternating copolymer having an intrinsic viscosity of 5.6 was dissolved in a solvent consisting of zinc chloride / calcium chloride / water (mass ratio 22/40/38) so that the polymer concentration was 7.5% by mass. A spinning stock solution is produced at 80 ° C., discharged from a spinneret with a hole diameter of 0.16 mm and a hole number of 20, and a coagulation bath having a bath length of 1.2 m, filled with water at 5 ° C. through a 10 mm air gap, A 2m long washing bath containing 1% sulfuric acid, a Nelson roll that is continuously sprayed with water, passed through a drying line at a constant length of 220 ° C, and then stretched through two continuous hot plates. It was. The draw ratio was 7 times for the first hot plate at 225 ° C., 1.3 times for the second hot plate at 240 ° C. (total draw ratio was 9.1 times), and the draw speed was 70 m / min.
[0040]
The fibers wound up in this way were stretched by 1.4 times and 1.3 times in order through two continuous hot plates (each heating length 2 m), and then wound at 30 m / min. The two hot plate temperatures at this time were set to 250 ° C. and 270 ° C., respectively.
There was no fluff or yarn breakage due to stretching, and the stretching could be performed stably. The obtained drawn yarn had good strength of 17.2 cN / dtex, elongation of 4.2%, and elastic modulus of 423 cN / dtex.
[0041]
[Example 2]
An ethylene / carbon monoxide complete alternating copolymer having an intrinsic viscosity of 5.6 was dissolved in a solvent consisting of zinc chloride / calcium chloride / water (mass ratio 22/40/38) so that the polymer concentration was 7.5% by mass. A spinning stock solution was prepared and discharged from a spinneret having a hole diameter of 0.16 mm and a hole number of 50 at 80 ° C. Subsequently, a coagulation bath having a length of 1.2 m filled with a 10 mm air gap and water at 5 ° C. was sequentially passed through a washing bath having a length of 2 m containing 2% sulfuric acid. The washed fiber was passed through a Nelson roll that was continuously sprayed with water and dried in a dryer at a constant length of 220 ° C. Next, stretching was performed through two consecutive hot plates.
[0042]
The draw ratio was 7 times for the first hot plate at 225 ° C., 1.3 times for the second hot plate at 240 ° C. (total draw ratio was 9.1 times), and the draw speed was 60 m / min. 20 stretched polyketone fibers were combined and wound up.
The wound fiber was sequentially drawn through a continuous hot plate (each heating length: 2 m) at 1.35 and 1.25 times, and then led to a twisting machine. Two hot plate temperatures at this time were set to 250 ° C. and 260 ° C., respectively, and wound at 30 m / min while applying a twist of 390 T / m.
There was no occurrence of fluff or loops during twisting, and the twisting could be performed stably. The strength of the obtained twisted yarn was as good as 13.7 cN / dtex.
[0043]
[Comparative Example 1]
In Example 1, the film was continuously stretched without being wound once. However, when the hot plate having a heating length of 2 m used in Example 1 was used for the third and fourth stages, yarn breakage occurred. However, the drawn yarn could not be wound.
Therefore, when the third-stage and fourth-stage stretching was performed using a cylindrical heating furnace having a heating length of 6 m, the stretching could be performed. As can be seen from this result, a long heating length is required to continuously stretch the third and fourth stages.
[0044]
【The invention's effect】
In order to increase the productivity of polyketone fibers having high strength and high elastic modulus, it is necessary to perform multi-stage stretching and increase the stretching speed, which requires a long stretcher. However, according to the method of the present invention, a polyketone fiber can be produced stably using a relatively compact drawing machine without the occurrence of yarn breakage or fluff.
In particular, since polyketone fibers are often used in the form of twisted yarns such as tire cords and various reinforcing materials, twisting yarns are usually performed at a low speed of several tens m / min to 150 m / min. If the subsequent drawing is performed before the twisted yarn as in the present invention, the polyketone twisted yarn can be efficiently produced without needing to produce a polyketone fiber having a high draw ratio.

Claims (4)

90 mol% or more of the repeating unit is spun a polyketone represented by the following formula (1), stretched at a stretching ratio of 3 to 12 times, and then wound up, and then stretched at a lower stretching speed than that at the time of stretching. A method for producing a polyketone fiber, which comprises stretching 1.01 to 10.

The method for producing a polyketone fiber according to claim 1, wherein the polyketone is spun, dried, drawn at a draw ratio of 3 to 12 and then wound up. 90 mol% or more of the repeating units are spun with a polyketone represented by the following formula (1), drawn at a draw ratio of 3 to 12 times, and then wound up, and then (a) at a lower drawing speed than that at the time of drawing. The yarn is twisted after being drawn at a draw ratio of 1.01 to 10, or (b) twisted while being drawn at a draw ratio of 1.01 to 10 at a drawing speed lower than that at the time of drawing. A method for producing polyketone fibers.

The method for producing a polyketone fiber according to claim 3, wherein the polyketone is spun, dried, drawn at a draw ratio of 3 to 12 and then wound up.