JP2004332166A - Polylactic acid fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid fiber improved in heat resistance and hydrolytic resistance and having good color tone and a fiber product composed of the polylactic acid fibers. <P>SOLUTION: The polylactic acid fiber is obtained by mixing a polylactic acid with a specific polycarbodiimide compound having two or more carbodiimide groups in the molecule and sealing the terminals of these carbodiimide groups with a carboxylic acid. In the polylactic acid fiber, the terminals of carboxy groups are blocked by the polycarbodiimide compound and total carboxy group terminal concentration is ≤10 equivalent/ton. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１７】
で表される４，４’−ジシクロヘキシルメタンジイソシアネート、および、式２
【００１８】
【化５】

【００１９】
で表されるイソホロンジイソシアネート、および、式３
【００２０】
【化６】

【００２１】
で表されるテトラメチルキシリレンジイソシアネートの少なくとも１種に由来し、分子中に２以上のカルボジイミド基を有し、かつそのイソシアネート末端がカルボン酸で封止されてなるポリカルボジイミド化合物であって、トータルカルボキシル末端濃度が１０当量／ｔｏｎ以下であることを特徴とするポリ乳酸繊維により達成される。
【００２２】
【発明の実施の形態】
本発明でいうポリ乳酸とは、−（Ｏ−ＣＨＣＨ_３−ＣＯ）ｎ−を繰り返し単位とするポリマーであり、乳酸やラクチド等の乳酸のオリゴマーを重合したものをいう。乳酸にはＤ−乳酸とＬ−乳酸の２種類の光学異性体が存在するため、その重合体もＤ体のみからなるポリ（Ｄ−乳酸）とＬ体のみからなるポリ（Ｌ−乳酸）および両者からなるポリ乳酸がある。ポリ乳酸中のＤ−乳酸、あるいはＬ−乳酸の光学純度は、それらが低くなるとともに結晶性が低下し、融点降下が大きくなる。そのため、耐熱性を高めるために光学純度は９０％以上であることが好ましい。
【００２３】
ただし、上記のように２種類の光学異性体が単純に混合している系とは別に、前記２種類の光学異性体をブレンドして繊維に成形した後、１４０℃以上の高温熱処理を施してラセミ結晶を形成させたステレオコンプレックスにすると、融点を飛躍的に高めることができるためより好ましい。
【００２４】
また、ポリ乳酸中には低分子量残留物として残存ラクチドが存在するが、これら低分子量残留物は、延伸や仮撚加工工程での加熱ヒーター汚れや染色加工工程での染め斑等の染色異常を誘発する原因となる。また、繊維や繊維成型品の加水分解を促進し、耐久性を低下させる。そのため、残存ラクチド量は好ましくは３０００ｐｐｍ以下、より好ましくは１０００ｐｐｍ以下、さらに好ましくは３００ｐｐｍ以下である。
【００２５】
また、ポリ乳酸の性質を損なわない範囲で、乳酸以外の成分を共重合していてもよい。共重合する成分としては、ポリエチレングリコールなどのポリエーテル、ポリブチレンサクシネートやポリグリコール酸などの脂肪族ポリエステル、ポリエチレンイソフタレートなどの芳香族ポリエステル、及びヒドロキシカルボン酸、ラクトン、ジカルボン酸、ジオールなどのエステル結合形成性の単量体が挙げられる。ただし、バイオマス利用、生分解性の観点から、ポリ乳酸繊維を構成する重合体中の乳酸モノマー比率は５０重量％以上とすることが必要である。重合体を構成する乳酸モノマー比率は好ましくは７５重量％以上、より好ましくは９６重量％以上である。また、ポリ乳酸以外の熱可塑性重合体をブレンドしたり、両成分を複合（芯鞘型、バイメタル型、海島型）してもよい。さらに改質剤として粒子、難燃剤、可塑剤、帯電防止剤、抗酸化剤や紫外線吸収剤等の添加物を含有していてもよい。また、ポリ乳酸重合体の分子量は、重量平均分子量で５万〜３５万であると、繊維の力学特性と成形性のバランスがよく好ましく、１０万〜２５万であると、より好ましい。
【００２６】
本発明のポリ乳酸の製造方法は、特に限定されない。具体的には、特開平６−６５３６０号公報に開示されている方法が挙げられる。すなわち、乳酸を有機溶媒及び触媒の存在下、そのまま脱水縮合する直接脱水縮合法である。また、特開平７−１７３２６６号公報に開示されている少なくとも２種類のホモポリマーを重合触媒の存在下、共重合並びにエステル交換反応させる方法である。さらには、米国特許第２，７０３，３１６号明細書に開示されている方法がある。すなわち、乳酸を一旦脱水し、環状二量体とした後に、開環重合する間接重合法である。
【００２７】
本発明では、耐加水分解安定剤として特定のポリカルボジイミド化合物をポリ乳酸に添加混合し、ポリ乳酸に含まれるカルボキシル基末端を封鎖することが重要である。
【００２８】
本発明者らは、ポリ乳酸中でのポリカルボジイミド化合物の挙動を詳細に検討した結果、反応活性末端と反応していない、いわゆる未反応のポリカルボジイミド化合物が、ポリ乳酸の溶融紡糸温度やバインダーとして用いるときの成形温度である２００〜２５０℃で急激に熱分解するため、それが製糸性や色調に悪影響を与え、さらには発生する不快な刺激臭によって、作業環境の悪化を招くことを突き止めた。これらの問題を解決するためは、後述する特定のポリカルボジイミド化合物を用い、さらにその化合物の添加量、および混練や紡糸時の溶融温度と滞留時間の制御が重要であることを見出した。
【００２９】
ポリ乳酸繊維に混合されるポリカルボジイミド化合物は、上記式１で表される４，４’−ジシクロヘキシルメタンジイソシアネート（以下、ＨＭＤＩと略記）、又は、上記式２で表されるイソホロンジイソシアネート（以下、ＩＰＤＩと略記）、又は、上記式３で表されるテトラメチルキシリレンジイソシアネート（以下、ＴＭＸＤＩと略記）のいずれか１種に由来するカルボジイミド、もしくは上記化合物の２種混合物、又は３種混合物のいずれかの混合物に由来するカルボジイミドで、分子中に２以上のカルボジイミド基、好ましくは５以上のカルボジイミド基を有するものを主成分とする。なお、ポリカルボジイミド中のカルボジイミド基の上限は２０である。このようなカルボジイミドは、ＨＭＤＩ、又はＩＰＤＩ、又はＴＭＸＤＩ又は上記化合物の２種混合物、又は３種混合物を原料とする脱二酸化炭素反応を伴うカルボジイミド化反応により製造することができる。なお、この中でも、得られた繊維の力学的特性が優れているという点で、ＨＭＤＩを５０重量％以上用いたカルボジイミドが好ましく、ＨＭＤＩを８０重量％以上用いたカルボジイミドがより好ましい。
【００３０】
上記カルボジイミド化反応は適当なカルボジイミド化触媒の存在下で行うもので、使用し得るカルボジイミド化触媒としては、有機リン系化合物が好適であり、特に活性の面でフォスフォレンオキシド類が好ましい。具体的には、３−メチル−１−フェニル−２−フォスフォレン−１−オキシド、３−メチル−１−エチル−２−フォスフォレン−１−オキシド、１，３−ジメチル−２−フォスフォレン−１−オキシド、１−フェニル−２−フォスフォレン−１−オキシド、１−メチル−２−フォスフォレン−１−オキシドおよびこれらの二重結合異性体を例示することができ、中でも工業的に入手が容易な３−メチル−１−フェニル−２−フォスフォレン−１−オキシドが特に好ましい。
【００３１】
前記カルボジイミド化反応は、従来より知られている方法により行うことができ、例えばＨＭＤＩ、又はＩＰＤＩ、又はＴＭＸＤＩ又は上記化合物の２種混合物、又は３種混合物を、それに対し不活性な溶媒に溶解し又は無溶媒で、窒素等の不活性気体の気流下又はバブリング下、上記触媒を全イソシアネートに対し０．１〜１０重量％、好ましくは０．５〜５重量％加え、１５０〜２００℃反応温度範囲内で加熱及び攪拌することにより脱二酸化炭素反応を伴うカルボジイミド化反応を進めればよい。
【００３２】
上記反応の反応時間は、反応温度、触媒種や量等により変化するが、通常は、例えばＨＭＤＩを原料とし、３−メチル−１−フェニル−２−フォスフォレン−１−オキシドを全イソシアネートに対し１重量％加え、反応温度を１８０℃として反応させると、約２０時間程度でＨＭＤＩ由来のカルボジイミド化合物を得ることができ、ＩＰＤＩやＴＭＸＤＩを原料とした場合も同様である。
【００３３】
なお、反応の進行は、赤外線吸収スペクトルにおいて２２５８ｃｍ^−１に観察されるイソシアネート基の吸収をみても、滴定法により確認してもよい。
【００３４】
上記反応において、ＨＭＤＩ、又はＩＰＤＩ、又はＴＭＸＤＩ又は上記化合物のいずれか２種の混合物を用いると、次の式で表されるカルボジイミドを得ることができる。
【００３５】
ＯＣＮ−（Ｒ_１−ＮＣＮ）ｎ−Ｒ_２−ＮＣＯ
なお、上記の式において、Ｒ_１およびＲ_２は反応に使用したＨＭＤＩ、又はＩＰＤＩ、又はＴＭＸＤＩのＮＣＯ基を除く残基で、その重合の態様はランダムでもブロックでもよく、またＲ_１とＲ_２が同一物質でもよい。ｎは２以上の整数を示す。
【００３６】
また、本発明のポリ乳酸に混合するポリカルボジイミド化合物としては、上記の方法で得られた末端イソシアネートのカルボジイミドを、カルボン酸を用いて末端を封止したものであることが必要である。好ましく用いられるカルボン酸はモノカルボン酸であり、例えばシクロヘキサンカルボン酸、安息香酸、無水トリメリット酸、２−ナフトエ酸、ニコチン酸、イソニコチン酸、２−フル酸、プロピオン酸、酪酸、イソ酪酸、メタクリル酸、パルミチン酸、ステアリン酸、オレイン酸、ケイ皮酸、グリセリン酸、アセト酢酸、ベンジル酸、アントラニル酸等が挙げられ、この中で最も好ましいのはシクロヘキサンカルボン酸である。
【００３７】
カルボジイミドの末端のイソシアネートを、これらカルボン酸により封止することで、ポリ乳酸中に未反応のポリカルボジイミド化合物が存在しても、熱安定性に優れるために上記の製糸性の悪化や色調不良、さらには刺激性ガスの発生を抑えることができるのである。末端イソシアネートのカルボジイミドを、カルボン酸を用いて末端を封止した場合、脱二酸化炭素反応により、次の式で表されるカルボジイミドを得ることができる。
【００３８】
Ｒ_３−ＣＯＮＨ−（Ｒ_１−ＮＣＮ）ｎ−Ｒ_２−ＣＯＮＨ−Ｒ_４
なお、上記の式において、Ｒ_３及びＲ_４はイソシアネート基と反応したカルボン酸の残基、ｎは２以上の整数であり、Ｒ_３及びＲ_４は同一であっても異なっていてもよい。
【００３９】
上記のように、カルボジイミドの末端をカルボン酸で封止する場合、イソシアネートとこれらカルボン酸との反応は、カルボジイミド化の前に行っても、或いは適当な重合度までカルボジイミド化させた後に残存イソシアネートに対し当量の封止剤を加えることにより行ってもよい。
【００４０】
本発明は、ポリ乳酸ポリマーおよびそれに含まれるオリゴマーの反応活性末端を、上記のポリカルボジイミド化合物で封鎖することにより、ポリマー中の反応活性末端を不活性化し、ポリ乳酸の加水分解を抑制するものである。この反応活性末端は水酸基、カルボキシル基があるが、カルボジイミド化合物はカルボキシル基の封鎖性に優れている。
【００４１】
また、上記ポリカルボジイミド化合物の添加量は、ポリ乳酸の重量に対して決めるよりも、カルボキシル基末端に対して決めることが重要である。さらに、残存モノマー及び残存オリゴマーも加水分解によりカルボキシル基末端を生じることから、ポリマーのカルボキシル基末端だけでなく、残存オリゴマーやモノマー由来のものも併せたトータルカルボキシル基末端量が重要である。ポリカルボジイミド化合物を添加し、ポリ乳酸繊維のトータルカルボキシル基末端濃度がポリ乳酸繊維全体に対し１０当量／ｔｏｎ以下になることで、目的とする耐熱性と耐加水分解性が得られるのである。ポリカルボジイミド化合物により末端を封止した後のトータルカルボキシル基末端濃度は、好ましくは８当量／ｔｏｎ以下であり、より好ましくは５当量／ｔｏｎ以下である。
【００４２】
なお、未反応のポリカルボジイミド化合物の熱劣化によって生じる熱分解ガスの発生量を減じるため、ポリカルボジイミド化合物の添加量を、カルボジイミド基当量としてポリ乳酸のトータルカルボキシル基末端量の２倍当量以下にすることが好ましい。ポリカルボジイミド化合物の添加量は、より好ましくはトータルカルボキシル基末端量の１．５倍当量以下であり、さらに好ましくは１．２倍当量以下である。
【００４３】
本発明のポリ乳酸繊維は、黄味の色調の指標であるｂ^＊値が７以下であることが好ましい。これにより、衣料用途等の色調が重要な用途にも使用可能となる。ｂ^＊値は好ましくは５以下、さらに好ましくは３．５以下である。
【００４４】
ポリ乳酸繊維のｂ^＊値の改善については、汎用ポリエステルで用いられているような酢酸コバルト等の青味付け化合物や、着色剤を併用したりすることも可能であるが、あまり多量に用いると耐熱性が低下するために製糸性が損なわれるばかりか、染色時に色が濁り、ポリ乳酸繊維の特徴である鮮明な発色性が損なわれる。そのため、併用するにしても添加量はポリ乳酸重量に対し５００ｐｐｍ以下にすることが好ましい。
【００４５】
本発明における耐加水分解性は、繊維の粘度保持率や強度保持率で評価することが可能である。本発明においては繊維試料３０ｇと水３００ｇを圧力容器に入れ、１２０℃で６０分間熱水処理を行い、熱処理前の粘度に対する粘度保持率が７５％以上であることが好ましい。粘度保持率は、より好ましくは８５％以上である。また、上記した熱水処理前後の繊維の強度保持率は７０％以上が好ましい。強度保持率は、より好ましくは８５％以上である。
【００４６】
本発明のポリ乳酸繊維は、工程通過性や製品の力学的強度を実用性のあるものにするために、強度２ｃＮ／ｄｔｅｘ以上とすることが好ましい。より好ましくは３ｃＮ／ｄｔｅｘ以上である。また、本発明の繊維の伸度は１５〜７０％であると、工程通過性が向上するため好ましい。伸度は、より好ましくは２５〜５０％である。
【００４７】
本発明のポリ乳酸繊維は、沸騰水収縮率が０〜２０％であれば繊維および繊維製品の寸法安定性がよく好ましい。より好ましくは２〜１０％である。
【００４８】
本発明のポリ乳酸繊維の断面形状は、丸断面、三角断面、マルチローバル断面、中空断面、偏平断面、Ｗ断面およびＸ型断面その他の異形断面のいずれであってもよい。また、繊維の形態は、長繊維、短繊維等特に制限はなく、長繊維の場合はマルチフィラメントであっても、モノフィラメントでもよい。
【００４９】
本発明のポリ乳酸繊維の製造方法は、特に限定されるものではないが、例えば以下のような方法を採用することができる。
【００５０】
まず、上記の方法によりポリカルボジイミド化合物およびポリ乳酸を製造する。なお、残存ラクチド量を減ずる具体的方法としては、例えば特表平７−５０４９３９号公報記載のように、金属不活性化剤や酸化防止剤等を使用したり、重合温度の低温化、触媒添加率の抑制を行うことが好ましい。また、ポリマーを減圧処理したり、クロロホルム等で抽出することによっても、残存ラクチド量を大幅に低減することができる。
【００５１】
次に、得られたポリ乳酸のトータルカルボキシル基末端濃度を、特開２００１−２６１７９７号公報記載の方法を参考にして求める。すなわち、秤量した試料をｏ−クレゾールに溶解し、ジクロロメタンを適量添加した後、０．０２規定のＫＯＨメタノール溶液で滴定する。この時、乳酸の環状２量体であるラクチド等のオリゴマーは加水分解し、カルボキシル基末端を生じるため、ポリマーのカルボキシル基末端およびモノマー由来のカルボキシル基末端、オリゴマー由来のカルボキシル基末端の全てを合計したトータルカルボキシル基末端濃度が求められる。
【００５２】
次に、ポリ乳酸とポリカルボジイミド化合物を溶融混練し、溶融紡糸によって繊維に成型する。混練および溶融紡糸の際、ポリカルボジイミド化合物とポリ乳酸との末端封止反応を促進させ、かつ未反応のポリカルボジイミド化合物の熱分解を抑制することが重要となる。そのため、混練時および溶融紡糸時の温度Ｔ及び溶融滞留時間ｐｔから求められる溶融滞留指数Ｔ^＊は下式の範囲で制御することが好ましい。ここで、溶融滞留時間ｐｔとは、実質的に１９０〜２５０℃に加熱された部分を通過する時間であるが、これは混練機や溶融部の温度設定および配管サイズ、紡糸パック内の寸法と、ポリ乳酸の溶融状態における密度から見積もることができる。また、ポリカルボジライト化合物とポリ乳酸とを混練する工程と、溶融紡糸する工程とが分かれている場合は、別々に溶融滞留指数を計算し、合算した値を溶融滞留指数Ｔ^＊とする。
【００５３】
溶融滞留指数Ｔ^＊＝ｐｔ×（Ｔ−１００）^１．５
１９０≦Ｔ≦２５０
（単位 Ｔ：℃、ｐｔ：分）
１０，０００≦Ｔ^＊≦４０，０００
溶融滞留指数Ｔ^＊を１０，０００以上にすることで、ポリカルボジイミド化合物とポリ乳酸との末端封止反応を促進させることができ、好ましい。一方、溶融滞留指数Ｔ^＊を４０，０００以下にすることで、未反応のポリカルボジイミド化合物の熱分解を抑制することができ、好ましい。なお、未反応のポリカルボジイミド化合物の分解を抑制するため、溶融混練温度Ｔの上限は好ましくは２４０℃であり、より好ましくは２３０℃である。
【００５４】
ポリカルボジイミド化合物の混合方法は、前記した様にポリ乳酸とポリカルボジイミド化合物をそれぞれ別々に乾燥した後、混練機により一旦マスターチップを作成しておき、マスターチップとポリ乳酸とをチップブレンドして乾燥を行い、溶融紡糸してもよいし、溶融紡糸時に乾燥したポリカルボジイミド化合物を直接添加してもよい。直接添加する場合は、ポリ乳酸の溶融部でポリカルボジイミド化合物を添加したり、別々に溶融したポリカルボジイミド化合物とポリ乳酸とを紡糸パック内で静止混練器やサンド濾層等により混練する方法がある。また、混練および溶融紡糸の際にはポリ乳酸の酸化分解を抑制するため、チップ配管および溶融部に供給する部分を窒素でシールすることが好ましい。
【００５５】
この時、ポリカルボジイミド化合物の添加量は前記したように、トータルカルボキシル基末端量の２倍当量以下とすると、ポリカルボジイミド化合物とポリ乳酸との末端封止反応を促進させつつ、未反応のポリカルボジイミド化合物の熱分解を抑制することができる。ここで、ポリ乳酸のトータルカルボキシル基末端量に対して添加量を決めることが重要であり、例えばポリ乳酸の全重量に対しては少量添加であっても、ポリカルボジイミド化合物を添加する前のポリ乳酸のトータルカルボキシル基末端量が少なければ未反応のポリカルボジイミド化合物が増加してしまい、熱劣化によって生じる熱分解ガスの発生量が増加してしまう。一方、ポリカルボジイミド化合物を添加する前のポリ乳酸のトータルカルボキシル基末端量が多ければ、末端封止が不充分となり、耐加水分解性の向上効果が小さいものとなってしまう。また、紡糸機内でのポリカルボジイミド化合物の溶融滞留時間は、前記したように混練工程と合わせて設定することが好ましい。
【００５６】
紡糸口金から紡出された糸条は、チムニーにより冷却固化させた後、給油装置により紡糸油剤が付与され、ゴデットロール等を用いて引き取られる。
【００５７】
長繊維の場合は、引き取った糸条を一旦チーズ状パッケージに巻き取った後、延伸及び／または仮撚を行ってもよいし、直接紡糸延伸装置を用いて１工程で延伸糸としてもよい。この時、第１ゴデットロール（直接紡糸延伸の場合は第１ホットロール）の周速度（以下、紡糸速度という）は２５００〜７０００ｍ／分とすると、繊維の配向結晶化により延伸性や仮撚加工性が向上し、好ましい。また、延伸する際の延伸温度は８０〜１５０℃とすると糸の均一性が向上し、好ましい。特に高強度のために残留伸度を１５〜２５％程度まで延伸する場合には、失透現象と呼ばれる不連続構造を抑制するために、１１０〜１５０℃で延伸することが好ましい。また、熱処理温度はポリ乳酸繊維の沸騰水収縮率に合わせて変えればよいが、製品の寸法安定性を高くするためには熱処理温度は１１０〜１５０℃、より好ましくは１３０〜１５０℃である。なお、延伸は１段で行ってもよいし、多段で行ってもよい。また、必要に応じ仮撚加工や押し込み加工、機械捲縮を行うこともできる。
【００５８】
短繊維の場合は、引き取った糸条を合糸し、一旦バンカーに受けた後、さらにこれらを合糸してトウとした後、延伸、機械捲縮を施し、次工程に適した油剤を付与した後に所望の長さに切断する。延伸の際は、トウが太く熱伝達が悪いことを考慮し、スチーム延伸や液浴延伸を採用することが好ましく、この時の液浴温度は７５〜１００℃とすることが好ましい。
【００５９】
また、不織布の場合は、上記した短繊維を用いてもよいし、いわゆるスパンボンドやメルトブロー等の紡糸と不織布形成工程が連続した方法を採用してもよい。
【００６０】
本発明のポリ乳酸繊維は、織物、編物、不織布の他、繊維ボード等の成形体のように様々な繊維製品の形態を採ることができる。
【００６１】
また、本発明のポリ乳酸繊維は、植物由来原料からなる素材と混用されていてもよい。例えば絹、綿、麻等の天然繊維やレーヨンやアセテート等の再生繊維と混繊したり、交織や交編したものが挙げられる。
【００６２】
また、本発明のポリ乳酸は溶融時の耐熱性に優れ、従来問題となっていた刺激性のガスの発生がほとんどないことから、バインダー繊維として好ましく用いることができる。特にポリ乳酸の生分解性を活かしてパルプや天然繊維等の生分解性を有する素材と混用し、不織布や成形体に用いることが好ましい。
【００６３】
本発明のポリ乳酸繊維は、シャツやブルゾン、パンツといった衣料用途のみならず、カップやパッド等の衣料資材用途、カーテンやカーペット、マット、壁紙、家具等のインテリア用途や車両部材用途、ベルト、ネット、ロープ、重布、袋類、縫い糸の産業資材用途、フェルト、不織布、フィルター、人工芝等に好適に用いることができる。
【００６４】
【実施例】
以下、本発明のポリ乳酸繊維について実施例を用いて詳細に説明する。なお、実施例における物性等の測定と評価方法には、以下の方法を用いた。
Ａ．ポリ乳酸の溶液比粘度（ηｒ）
ｏ−クロロフェノール１００ｍｌに対し、秤量した試料３ｇを溶解し、溶液を調整した。次に、２５℃でオストワルド式粘度計を用いて、これの比粘度を測定した。
Ｂ．トータルカルボキシル基末端濃度
精秤した試料をｏ−クレゾール（水分５％）に溶解し、この溶液にジクロロメタンを適量添加した後、０．０２規定のＫＯＨメタノール溶液にて滴定することにより求めた。この時、乳酸の環状２量体であるラクチド等のオリゴマーが加水分解し、カルボキシル基末端を生じるため、ポリマーのカルボキシル基末端およびモノマー由来のカルボキシル基末端、オリゴマー由来のカルボキシル基末端の全てを合計したカルボキシル基末端濃度が求まる。
Ｃ．残存ラクチド量
試料１ｇをジクロロメタン２０ｍｌに溶解し、この溶液にアセトン５ｍｌを添加する。さらにシクロヘキサンで定容して析出させ、島津社製ＧＣ１７Ａを用いて液体クロマトグラフにより分析し、絶対検量線にてラクチド量を求めた。
Ｄ．ポリカルボジイミド化合物の重量減少率
マックサイエンス（ＭＡＣ ＳＣＩＥＮＣＥ）社製“ＴＧ−ＤＴＡ２０００Ｓ”ＴＧ−ＤＴＡ測定器により、試料重量約１０ｍｇ、窒素雰囲気下にて昇温速度２０℃で昇温し、２４０℃に到達後、６０分間保持したときの重量減少率を求めた。
Ｅ．熱水処理後のηｒ保持率（Ｒηｒ）
試料３０ｇと水３００ｇを圧力容器に入れ、１２０℃、６０分間熱水処理を行った。そして、これのηｒを測定し、以下の式によりＲηｒを求めた。なお、試料が繊維の場合は糸カセを作製し、これの熱水処理を行った。
【００６５】
Ｒηｒ（％）＝（熱水処理後サンプルのηｒ／熱水処理前のηｒ）×１００
Ｆ．熱水処理後の強度保持率（ＲＴ）
Ｄと同様に試料の熱水処理を行い、以下の式によりＲＴを求めた。なお、熱水処理前のポリ乳酸繊維の強度および熱水処理後のポリ乳酸繊維の強度はＨ項に示す測定方法で測定を行った。
【００６６】
ＲＴ（％）＝（熱水処理後サンプルの強度／熱水処理前の強度）×１００
Ｇ．色調（ｂ＊値）
精練上がりの織編物を、下地の白色板が無視できる程度まで積層し、ミノルタ社製「スペクトロフォトメーターＣＭ−３７００ｄ」を用いてｂ＊値を測定した。このとき、光源としてはＤ６５（色温度６５０４Ｋ）を用い、１０°視野で測定を
Ｈ．強度および伸度
試料をオリエンテック（株）社製テンシロン（ＴＥＮＳＩＬＯＮ）ＵＣＴ−１００でＪＩＳ Ｌ１０１３（化学繊維フィラメント糸試験方法）に示される定速伸長条件で測定した。なお、破断伸度はＳ−Ｓ曲線における最大強力を示した点の伸びから求めた。
Ｉ．沸騰水収縮率
ＪＩＳ Ｌ １０１３（化学繊維フィラメント糸試験方法）に準じて測定した。 未延伸糸パッケージから検尺機でカセを採取し、９０×１０^−３ｃＮ／ｄｔｅｘの実長測定荷重を架けてカセ長Ｌ１を測定し、引き続いて実長測定荷重をはずし、沸騰水中に１５分間投入した後取り出し、風乾し、再び実長測定荷重を架けてカセ長Ｌ２を測定し、次式により沸騰水収縮率を算出した。
【００６７】
沸騰水収縮率（％）＝［（Ｌ１−Ｌ２）／Ｌ１］×１００
ポリ乳酸の製造
光学純度９９．５％のＬ乳酸から製造したラクチドを、ビス（２−エチルヘキサノエート）スズ触媒（ラクチド対触媒モル比＝１００００：１）を存在させて窒素雰囲気下１８０℃で２２０分間重合を行った。引き続いて１８０℃減圧下で脱ラクチド処理した。なお、重合時に安定剤としてＧＥ社製“Ｕｌｔｒａｎｏｘ ６２６”をラクチド対比０．２重量％加えた。得られたポリ乳酸のηｒは１１．４、トータルカルボキシル基末端濃度は２５当量／ｔｏｎ、残存ラクチド量は２４０ｐｐｍであった。
【００６８】
カルボジイミドの合成例１〜３
ＨＭＤＩを２ｋｇに、末端封止剤としてシクロヘキサンカルボン酸１８０ｇを加え、カルボジイミド化触媒として３−メチル−１−フェニル−２−フォスフォレン−１−オキシドを１０ｇを加えて窒素をバブリングしながら１９０℃で１２時間反応させ、重合度８のカルボジイミド化合物（合成例１）を得た。また、末端封止剤を安息香酸に変えた以外は合成例１と同様にして重合度８のカルボジイミド化合物（合成例２）を得た。また、末端封止剤を無水トリメリット酸に変えた以外は合成例１と同様にして重合度８のカルボジイミド化合物（合成例３）を得た。合成例１〜３の耐熱性（重量減少率）を表１に示す。
【００６９】
カルボジイミドの合成例４〜６
末端封止剤をシクロヘキシルアミンに変えた以外は合成例１と同様にして重合度８のカルボジイミド化合物（合成例４）を得た。また、末端封止剤をジブチルアミンに変えた以外は合成例１と同様にして重合度８のカルボジイミド化合物（合成例５）を得た。また、末端封止剤を無水フタル酸に変えた以外は合成例１と同様にして重合度８のカルボジイミド化合物（合成例６）を得た。合成例４〜６の耐熱性（重量減少率）を表１に示す。
【００７０】
カルボジイミドの合成例７及び８
ＩＰＤＩを２ｋｇに、末端封止剤としてシクロヘキサンカルボン酸１８０ｇを加え、カルボジイミド化触媒として３−メチル−１−フェニル−２−フォスフォレン−１−オキシドを１８ｇを加え、窒素をバブリングしながら１９０℃で１６時間反応させ、ＩＰＤＩ由来のカルボジイミド化合物（重合度８）を得た。
【００７１】
また、ＴＭＸＤＩを２ｋｇに、末端封止剤としてシクロヘキサンカルボン酸１８０ｇを加え、カルボジイミド化触媒として３−メチル−１−フェニル−２−フォスフォレン−１−オキシドを２１ｇを加え、窒素をバブリングしながら１９０℃で２１時間反応させ、ＴＭＸＤＩ由来のカルボジイミド（重合度８）を得た。
【００７２】
合成例７及び８の耐熱性（重量減少率）を表１に示す。
【００７３】
【表１】

【００７４】
実施例１
ポリ乳酸の製造で得られたηｒ１１．４のポリ乳酸と、合成例１で得たＨＭＤＩ由来のポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２７２ｇ）を重量比で９９．３：０．７（トータルカルボキシル基末端量に対し１．０倍当量）で混合してホッパー１に仕込み、２軸押出混練機２に導き、溶融温度Ｔ１：２２０℃で溶融混練し、引き続き紡糸温度Ｔ２：２２０℃に加温されたスピンブロック３に内蔵された紡糸パック４に溶融ポリマーを導き、吐出孔径０．３ｍｍ、孔深度０．６ｍｍ、孔数３６孔の口金５から紡出した（図１参照）。なお、このときの溶融滞留時間ｐｔは、混練工程５分、溶融紡糸工程７分であり、合計１２分であった。このとき、口金下１０ｃｍの位置に吸引装置７を設置し、吸引速度２５ｍ／分にて昇華するモノマー及びオリゴマーを取り除いた。紡出した糸条は冷却チムニー６により風速２５ｍ／分で冷却固化させた後、口金下２ｍに設置された給油装置８により給油した。紡糸油剤には、平滑剤として脂肪酸エステルを７０重量％、その他の添加剤（乳化剤、制電剤、抗酸化剤、防錆剤）を３０重量％の比率で調整し、さらにこの油剤を濃度１５重量％になるように水エマルジョンとして調整し、繊維に対して６重量％付着した（純油分として０．９重量％付着）。
【００７５】
次に、０．１ＭＰａにて交絡ノズル９により交絡を付与し、周速度３０００ｍ／分の第１ゴデットロール１０にて引き取り、続いて第２ゴデットロール１１を介して巻取装置１２で巻き取り、１７０ｄｔｅｘ、３６フィラメントの未延伸糸（チーズ状パッケージ１３）を得た。口金直下での紡出糸条からの刺激臭は全く感じられず、紡糸時の糸切れ、毛羽の発生もなく、紡糸性は良好であった。
【００７６】
さらにこの糸を第１ホットロール温度９５℃で予熱した後、１．３倍に延伸し、第２ホットロール温度１３０℃で熱セットを行い、非加熱の冷ロールを介して巻き取り、１３０ｄｔｅｘ、３６フィラメントの延伸糸を得た。ここでの延伸性にも全く問題がなく、１ｋｇ巻を５本サンプリングしたが、糸切れはゼロであった。
【００７７】
得られた延伸糸のｂ^＊値は３．２であり、衣料用として制限無く使用できる優れた色調を示した。また、トータルカルボキシル基末端濃度は４．５当量／ｔｏｎであり、優れた耐加水分解性を示した。
【００７８】
実施例２
ポリカルボジイミド化合物として合成例２で得たポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２７１ｇ）を用いた以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。実施例２の紡糸では若干の発煙があったが、刺激臭はほとんど感じられなかった。また、紡糸性、延伸性ともに良好であり、実施例１と同様に糸切れはゼロであった。
【００７９】
得られた延伸糸のｂ^＊値は３．８であり、衣料用として制限無く使用できる優れた色調を示した。また、トータルカルボキシル基末端濃度は４．８当量／ｔｏｎであり、優れた耐加水分解性を示した。
【００８０】
実施例３
ポリカルボジイミド化合物として合成例３で得たポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２８９ｇ）を用いた以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。実施例３は実施例１と同様、刺激臭はほとんど感じられなかった。また、紡糸性、延伸性ともに良好であった。 得られた延伸糸のｂ^＊値は３．５であり、衣料用として制限無く使用できる優れた色調を示した。また、トータルカルボキシル基末端濃度は７．２当量／ｔｏｎであり、優れた耐加水分解性を示した。
【００８１】
比較例１
ポリカルボジイミド化合物を添加することなく、実施例１と同様に紡糸、延伸を行い１３０ｄｔｅｘ、３６フィラメントの延伸糸を得た。
【００８２】
得られた延伸糸のｂ^＊値は１．７であり、優れた色調を示した。しかしながら、カルボキシル基末端濃度は３５当量／ｔｏｎであり、耐加水分解性が著しく劣っていた。
【００８３】
比較例２
ポリカルボジイミド化合物として合成例４で得たポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２７６ｇ）を用いた以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。比較例２は溶融紡糸工程で刺激性ガスの発生が酷く、作業環境が極めて悪いものであった。また、得られた延伸糸のｂ^＊値は５．２であり、衣料用として用途限定すれば使用できる色調を示した。
【００８４】
比較例３
ポリカルボジイミド化合物として合成例５で得たポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２８４ｇ）を用いた以外は実施例１と同様に紡糸、延伸を行い、延伸糸を得た。比較例３は、比較例２と同様、溶融紡糸工程で刺激性ガスの発生が酷く、作業環境が極めて悪いものであった。
【００８５】
比較例４
ポリカルボジイミド化合物として合成例６で得たポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２７７ｇ）を用いた以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。比較例４は、比較例１よりは刺激性ガスの発生は少ないものの、得られた繊維は耐熱性が悪いためにｂ^＊値が８．１であり、衣料用としては用途がかなり限定されてしまうものであった。
【００８６】
実施例４
ポリ乳酸とポリカルボジイミド化合物との混合比率を９８．８：１．２（トータルカルボキシル基末端量に対し１．８倍当量）で混合した以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。
【００８７】
得られた延伸糸のｂ^＊値は５．５であり、衣料用として用途限定すれば使用できる色調を示した。また、カルボキシル基末端濃度は３．８当量／ｔｏｎであり、優れた耐加水分解性を示した。
【００８８】
実施例５
ポリ乳酸とポリカルボジイミド化合物との混合比率を９９．５：０．５（トータルカルボキシル基末端量に対し０．７倍当量）で混合した以外は実施例１と同様に紡糸、延伸を行い、延伸糸を得た。
【００８９】
得られた延伸糸のｂ^＊値は２．６であり、衣料用として制限無く使用できる優れた色調であった。また、カルボキシル基末端濃度は８当量／ｔｏｎであり、優れた耐加水分解性を示した。
【００９０】
実施例６
ポリ乳酸とポリカルボジイミド化合物との混合比率を９８：２（トータルカルボキシル基末端量に対し３．０倍当量）で混合した以外は実施例１と同様に紡糸、延伸を行い、延伸糸を得た。
【００９１】
比較例５の溶融紡糸では、未反応のポリカルボジイミド化合物の熱分解により、紡糸・延伸とも糸切れが発生した。また、得られた延伸糸のｂ^＊値は８．８であり、衣料用としては用途がかなり限定されてしまうものであった。
【００９２】
【表２】

【００９３】
実施例７、実施例８
ポリカルボジイミド化合物として、合成例７で得たポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２２７ｇ）を用いた以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た（実施例７）。また、ポリカルボジイミド化合物として合成例８で得たポリカルボジイミド化合物（カルボジイミド１当量／カルボジイミド化合物２５２ｇ）を用いた以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た（実施例８）。実施例７及び実施例８で得られた延伸糸は、いずれも実施例１よりも低強度であるが、色調および耐加水分解性は実施例１と同様、優れたものであった。
【００９４】
実施例９
溶融温度Ｔ１及び紡糸温度Ｔ２を２４５℃にした以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。実施例９の溶融紡糸では、未反応のポリカルボジイミド化合物の熱分解により若干の刺激性ガスが発生した。また、紡糸性は良好であったが、延伸でホットロール上に単糸巻きが発生した。
【００９５】
得られた延伸糸のｂ^＊値は６．１であり、用途は限定されるものの、衣料用として十分使用できるものであった。
【００９６】
実施例１０
溶融温度Ｔ１及び紡糸温度Ｔ２を２００℃にした以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。実施例１０は溶融紡糸での刺激臭の発生はなく、紡糸性、延伸性ともに良好であった。また、得られた延伸糸のｂ^＊値は２．５であり、実施例１よりも優れていた。また、耐加水分解性も十分実用に耐えうるレベルであった。
【００９７】
実施例１１
紡糸温度Ｔ２を２５５℃にした以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。未反応のポリカルボジイミド化合物の熱分解により刺激性ガスが多量に発生した。また、紡糸、延伸で頻繁に糸切れが発生した。
【００９８】
得られた延伸糸は耐加水分解性には優れるもののｂ^＊値は１０．２であり、衣料等としてはかなり用途限定を受けるものであった。
【００９９】
実施例１２
紡糸パック４の濾層を縮小したものに変更し、溶融紡糸工程の溶融滞留時間を４．５分（合計の溶融滞留時間ｐｔ：９．５分）にした以外は実施例１０と同様に紡糸・延伸を行い、延伸糸を得た。実施例１２は溶融紡糸での刺激臭の発生はなく、紡糸性、延伸性ともに良好であった。また、得られた延伸糸のｂ^＊値は２．３であり、実施例１０よりも優れていた。
【０１００】
実施例１３
紡糸パック４の濾層を拡大したものに変更し、合計の溶融滞留時間ｐｔを３２分にした以外は実施例１と同様に紡糸・延伸を行い、延伸糸を得た。実施例１３は耐加水分解性には優れるものの、ｂ^＊値は７．３であり、衣料用としては用途がかなり限定されてしまうものであった。
【０１０１】
実施例１４
ポリ乳酸の製造で得られたηｒ１１．４のポリ乳酸を固相重合し、ηｒを１４とした。さらに紡糸速度を５０００ｍ／分として実施例１と同様に紡糸を行い、未延伸糸を得た。さらにこの未延伸糸を３本合糸し、第１ホットロール温度９０℃、第２ホットロール温度１２０℃、第３ホットロール温度１５０℃とし、第１ホットロールと第２ホットロールの間で１．３倍に延伸し、さらに第２ホットロールと第３ホットロールの間で１．２倍で延伸し、第３ホットロールと非加熱の冷ロールの間を３％の弛緩処理とし、延伸速度は８００ｍ／分で巻き取った。得られた２０５ｄｔｅｘ、１０８フィラメントの延伸糸のｂ^＊値は３．５であった。また、カルボキシル基末端濃度は４．６当量／ｔｏｎであり、優れた耐加水分解性を示した。実施例１４は強度が５．８ｃＮ／ｄｔｅｘと極めて高く、寸法安定性に優れるため、高強力が要求される衣料用途に最適であった。
【０１０２】
実施例１５
ポリ乳酸の製造で得られたηｒ１１．４のポリ乳酸と、合成例１で得たポリカルボジイミド化合物とを重量比で８０：２０で混合して溶融温度２１０℃で２軸押出機に導き、ポリカルボジイミド化合物のマスターチップを作製した。なお、このときの溶融滞留時間は５分であった。さらにポリ乳酸とこのマスターチップを１９：１で混合して１軸押出機に導き、溶融温度Ｔ１：２２５℃で溶融混練し、引き続き紡糸温度Ｔ２：２２５℃で紡糸を行った。なお、このときの溶融滞留時間は１０分であった。この糸条を周速度１５００ｍ／分の第１引取ロールにて未延伸糸を引き取り、合糸した後、バンカーに受けた。そして、バンカーに受けた糸条をさらに合糸し、１２０，０００ｄｔｅｘのトウとした。これを９０℃熱水中で２．６倍に延伸した。そして、クリンパーを通した後、給油し、繊維長５２ｍｍにカットした。
【０１０３】
得られた短繊維は、単繊維繊度５ｄｔｅｘ、捲縮数２２個／ｍであった。また、ｂ^＊値は４．０であり、衣料用として使用できる優れた色調であるとともに、カルボキシル基末端濃度は５当量／ｔｏｎであり、優れた耐加水分解性を示した。
【０１０４】
なお、ｂ^＊値、耐加水分解性等の繊維物性評価は、クリンパー／給油間の糸を一部サンプリングして行った。
【０１０５】
【表３】

【０１０６】
実施例１６
実施例１で得られた糸を経糸および緯糸に用い、平織りを作製した。得られた平織りを常法に従い７０℃で精練した後、１４０℃で中間セットを施した。さらに常法に従い１２０℃で染色した。得られた布帛は、きしみ感、ソフト感があり、衣料用として優れた風合いを有するとともに、鮮やかな発色を示した。
【０１０７】
比較例６
比較例１で得られた糸を経糸および緯糸に用い、実施例１５と同様に平織りを作製し、１２０℃で染色を行った。得られた布帛は引裂強力が極めて低いものであり、実用に耐えないものであった。。
【０１０８】
実施例１６
実施例１５で得られた短繊維と、繊維長５８ｍｍにカットしたラミーとを重量比で５０：５０で混綿、開繊してシート状にしたものを積層、圧縮して積層体を得た。さらにこの積層体を２３５℃、３ＭＰａで加熱・加圧してポリ乳酸とラミーからなる厚さ６ｍｍの繊維成形体を得た。
【０１０９】
この成形体は、適度な堅さと吸音性、衝撃吸収性を備えており、住宅用壁材や床材等に最適なものであった。
【０１１０】
【発明の効果】
本発明の耐熱性、耐加水分解性および色調に優れたポリ乳酸繊維により、ポリ乳酸繊維を衣料用途に拡大展開することができる。
【図面の簡単な説明】
【図１】本発明で好ましく用いられる紡糸装置を示す概略図である。
【符号の説明】
１：ホッパー
２：エクストルーダー
３：紡糸ブロック
４：紡糸パック
５：紡糸口金
６：吸引装置
７：冷却チムニー
８：給油装置
９：交絡ノズル
１０：第１ゴデットロール
１１：第２ゴデットロール
１２：巻取装置
１３：チーズ状パッケージ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polylactic acid fiber having improved hydrolysis resistance and a good color tone, and, when processed into a fiber product, a pungent unpleasant odor due to a thermal decomposition product derived from a carbodiimide compound. The present invention relates to a polylactic acid fiber which does not generate and is excellent in handleability.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with an increase in environmental awareness on a global scale, development of a fiber material that decomposes in a natural environment has been desired. For example, since conventional general-purpose plastics mainly use petroleum resources, depletion of petroleum resources in the future and global warming caused by mass consumption of petroleum resources have been taken up as major problems.
[0003]
Therefore, in recent years, research and development of various plastics and fibers such as aliphatic polyesters have been activated. Among them, attention has been focused on fibers made of plastics that are degraded by microorganisms, that is, biodegradable plastics.
[0004]
In addition, by using carbon dioxide as a raw material from plant resources that grow by taking in carbon dioxide from the atmosphere, it is expected that global warming can be suppressed by the circulation of carbon dioxide, and the problem of resource depletion may be solved. Therefore, plastics starting from plant resources, that is, plastics using biomass, are attracting attention.
[0005]
Heretofore, biodegradable plastics using biomass have problems such as low mechanical properties and heat resistance and high production costs, and have not been used as general-purpose plastics. On the other hand, in recent years, as a biodegradable plastic having relatively high mechanical properties and heat resistance and low production cost, polylactic acid made from lactic acid obtained by fermenting starch has been in the spotlight.
[0006]
Polylactic acid has long been used in the medical field, for example, as a surgical suture, but has recently been able to compete with other general-purpose plastics in price due to improvements in mass production technology. Therefore, the development of products as fibers has been activated.
[0007]
Agricultural materials and civil engineering materials that utilize biodegradability are ahead of the development of polylactic acid fibers. It is also expected to be applied to However, when it is applied to clothing and industrial materials, the high hydrolyzability of polylactic acid poses a major problem. In the clothing use of polylactic acid fiber, it is dyed in most cases, but it is difficult to dye it in a dark color. Therefore, a dyeing temperature of 110 ° C. or more is essential to increase the exhaustion rate. However, when dyeing at a temperature of 110 ° C. or higher, the hydrolysis of polylactic acid proceeds rapidly and the molecular weight decreases, and thus there is a problem that the tear strength of the fabric does not satisfy a practical level.
[0008]
In addition, since the hydrolysis proceeds even in the use environment, there is a problem that the product life is short especially in industrial material applications that require a high strength retention.
[0009]
In order to solve this problem, a polylactic acid fiber having improved hydrolysis resistance by adding a monocarbodiimide compound has been disclosed (see Patent Document 1). However, monocarbodiimide compounds are expensive and have a problem that bleed-out makes it difficult to obtain a high-concentration master. On the other hand, as relatively inexpensive carbodiimide compounds, resins and films in which polycarbodiimide is added to improve hydrolysis resistance have been disclosed (see Patent Documents 2 and 3). However, the polycarbodiimide compound has low dispersibility in polylactic acid, and is liable to gel, and the hydrolysis resistance is not sufficiently improved. It was hard. Furthermore, according to the study of the present inventors, due to poor heat resistance, when a polymer to which a polycarbodiimide compound is added is melt-spun, an irritating decomposition gas derived from the carbodiimide compound is generated, so that the working environment is reduced. It has been found that the same problem occurs when melt molding is carried out using the obtained polylactic acid fiber as a binder. Further, the polylactic acid fiber has a poor color tone, and is an index of the color tone.^*Only those having a strong yellowish color with a value exceeding 10 were obtained.
[0010]
Due to the problems described above, polylactic acid fibers having excellent hydrolysis resistance have not been able to be stably produced, and there has been a great limitation on the development of applications. Therefore, a polylactic acid fiber having improved heat resistance and hydrolysis resistance and good color tone has been desired.
[0011]
[Patent Document 1]
JP 2001-261797 A (pages 2 to 4)
[0012]
[Patent Document 2]
JP-A-9-296097 (pages 5 to 6)
[0013]
[Patent Document 3]
JP-A-11-80522 (pages 2 to 4)
[0014]
[Problems to be solved by the invention]
An object of the present invention is to provide a polylactic acid fiber which is improved in heat resistance at the time of melt molding, does not generate an unpleasant pungent odor, has good hydrolysis resistance and color tone, and a fiber product comprising the same.
[0015]
[Means for Solving the Problems]
An object of the present invention is to provide a polylactic acid fiber in which at least a part of a carboxyl group terminal is blocked by a carbodiimide compound, wherein the carbodiimide compound has the formula 1
[0016]
Embedded image

[0017]
4,4'-dicyclohexylmethane diisocyanate represented by the formula:
[0018]
Embedded image

[0019]
An isophorone diisocyanate represented by the formula:
[0020]
Embedded image

[0021]
Is a polycarbodiimide compound derived from at least one kind of tetramethylxylylene diisocyanate represented by and having two or more carbodiimide groups in the molecule, and the isocyanate terminal of which is sealed with a carboxylic acid, This is achieved by a polylactic acid fiber characterized by having a carboxyl terminal concentration of 10 equivalents / ton or less.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
The polylactic acid referred to in the present invention is-(O-CHCH₃-CO) A polymer having a repeating unit of n-, which is obtained by polymerizing an oligomer of lactic acid such as lactic acid or lactide. Since two kinds of optical isomers of D-lactic acid and L-lactic acid exist in lactic acid, their polymers are also poly (D-lactic acid) composed of only D-form and poly (L-lactic acid) composed only of L-form and There is a polylactic acid consisting of both. As for the optical purity of D-lactic acid or L-lactic acid in polylactic acid, as they become lower, the crystallinity becomes lower and the melting point drop becomes larger. Therefore, in order to enhance heat resistance, the optical purity is preferably 90% or more.
[0023]
However, apart from a system in which two types of optical isomers are simply mixed as described above, after blending the two types of optical isomers to form a fiber, a high-temperature heat treatment of 140 ° C. or more is performed. It is more preferable to use a stereocomplex in which a racemic crystal is formed because the melting point can be dramatically increased.
[0024]
In addition, residual lactide exists as low-molecular-weight residues in polylactic acid, and these low-molecular-weight residues cause staining abnormalities such as heating heater stains in the stretching and false twisting steps and spotting in the dyeing step. It can be a trigger. In addition, it promotes hydrolysis of fibers and fiber molded products, and reduces durability. Therefore, the amount of residual lactide is preferably 3000 ppm or less, more preferably 1000 ppm or less, and still more preferably 300 ppm or less.
[0025]
Further, components other than lactic acid may be copolymerized as long as the properties of polylactic acid are not impaired. Components to be copolymerized include polyethers such as polyethylene glycol, aliphatic polyesters such as polybutylene succinate and polyglycolic acid, aromatic polyesters such as polyethylene isophthalate, and hydroxycarboxylic acids, lactones, dicarboxylic acids, and diols. Ester bond-forming monomers are exemplified. However, from the viewpoint of biomass utilization and biodegradability, the lactic acid monomer ratio in the polymer constituting the polylactic acid fiber must be 50% by weight or more. The ratio of the lactic acid monomer constituting the polymer is preferably at least 75% by weight, more preferably at least 96% by weight. Further, a thermoplastic polymer other than polylactic acid may be blended, or both components may be combined (core-sheath type, bimetal type, sea-island type). Further, additives such as particles, flame retardants, plasticizers, antistatic agents, antioxidants and ultraviolet absorbers may be contained as modifiers. When the molecular weight of the polylactic acid polymer is 50,000 to 350,000 in terms of weight average molecular weight, the balance between the mechanical properties of the fiber and the moldability is good, and the molecular weight is more preferably 100,000 to 250,000.
[0026]
The method for producing the polylactic acid of the present invention is not particularly limited. Specifically, a method disclosed in JP-A-6-65360 can be mentioned. That is, it is a direct dehydration condensation method in which lactic acid is directly dehydrated and condensed in the presence of an organic solvent and a catalyst. Also, this is a method disclosed in JP-A-7-173266, in which at least two kinds of homopolymers are copolymerized and transesterified in the presence of a polymerization catalyst. Further, there is a method disclosed in U.S. Pat. No. 2,703,316. That is, it is an indirect polymerization method in which lactic acid is once dehydrated to form a cyclic dimer, and then subjected to ring-opening polymerization.
[0027]
In the present invention, it is important to add and mix a specific polycarbodiimide compound as a hydrolysis-resistant stabilizer to polylactic acid to block the carboxyl group terminal contained in the polylactic acid.
[0028]
The present inventors have studied the behavior of the polycarbodiimide compound in polylactic acid in detail, and found that a so-called unreacted polycarbodiimide compound that has not reacted with a reactive active terminal is used as a melt spinning temperature or a binder of polylactic acid. It rapidly decomposed at a molding temperature of 200 to 250 ° C. at the time of use, which adversely affected the spinnability and color tone, and furthermore, caused the unpleasant irritating odor to occur, thereby deteriorating the working environment. . In order to solve these problems, it has been found that it is important to use a specific polycarbodiimide compound described later, and to control the addition amount of the compound and the melting temperature and residence time during kneading and spinning.
[0029]
The polycarbodiimide compound to be mixed with the polylactic acid fiber is 4,4′-dicyclohexylmethane diisocyanate (hereinafter abbreviated as HMDI) represented by the above formula 1, or isophorone diisocyanate (hereinafter, IPDI) represented by the above formula 2 Carbodiimide derived from any one of tetramethylxylylene diisocyanate (hereinafter abbreviated as TMXDI) represented by the above formula 3, or a mixture of two or three of the above compounds Of carbodiimides derived from the above-mentioned mixture and having two or more carbodiimide groups, preferably 5 or more carbodiimide groups in the molecule. In addition, the upper limit of the carbodiimide group in polycarbodiimide is 20. Such a carbodiimide can be produced by a carbodiimidization reaction involving HMDI, IPDI, or TMXDI or a mixture of two or a mixture of the above compounds, which is accompanied by a decarbonation reaction. Among these, carbodiimide using HMDI of 50% by weight or more is preferable, and carbodiimide using HMDI of 80% by weight or more is more preferable in that the obtained fibers have excellent mechanical properties.
[0030]
The carbodiimidization reaction is carried out in the presence of a suitable carbodiimidization catalyst. As a carbodiimidization catalyst that can be used, an organic phosphorus compound is preferable, and phosphorene oxides are particularly preferable in terms of activity. Specifically, 3-methyl-1-phenyl-2-phospholene-1-oxide, 3-methyl-1-ethyl-2-phospholene-1-oxide, 1,3-dimethyl-2-phospholene-1-oxide , 1-phenyl-2-phospholene-1-oxide, 1-methyl-2-phospholene-1-oxide and their double bond isomers, and among them, 3-methyl which is industrially easily available -1-Phenyl-2-phospholene-1-oxide is particularly preferred.
[0031]
The carbodiimidization reaction can be performed by a conventionally known method. For example, HMDI, or IPDI, or TMXDI or a mixture of two or three of the above compounds is dissolved in a solvent inert thereto. Alternatively, in the absence of a solvent, under a stream of an inert gas such as nitrogen or under bubbling, the above catalyst is added in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight based on all isocyanates, and the reaction temperature is 150 to 200 ° C. The carbodiimidization reaction accompanying the decarbonation reaction may be advanced by heating and stirring within the range.
[0032]
The reaction time of the above reaction varies depending on the reaction temperature, the type and amount of the catalyst, and the like. Usually, for example, HMDI is used as a raw material, and 3-methyl-1-phenyl-2-phospholene-1-oxide is added to the total isocyanate at a ratio of 1 to 1%. When the reaction temperature is set to 180 ° C. and the reaction temperature is set to 180 ° C., a carbodiimide compound derived from HMDI can be obtained in about 20 hours, and the same applies when IPDI or TMXDI is used as a raw material.
[0033]
The progress of the reaction was 2258 cm in the infrared absorption spectrum.^-1The absorption of the isocyanate group observed in the above may be confirmed by a titration method.
[0034]
When HMDI, IPDI, TMXDI, or a mixture of any two of the above compounds is used in the above reaction, a carbodiimide represented by the following formula can be obtained.
[0035]
OCN- (R₁-NCN) n-R₂-NCO
In the above equation, R₁And R₂Is a residue other than the NCO group of HMDI, IPDI, or TMXDI used in the reaction. The mode of polymerization may be random or block.₁And R₂May be the same substance. n represents an integer of 2 or more.
[0036]
Further, as the polycarbodiimide compound to be mixed with the polylactic acid of the present invention, it is necessary that the carbodiimide of the terminal isocyanate obtained by the above-mentioned method is a compound whose terminal is blocked with a carboxylic acid. The carboxylic acids preferably used are monocarboxylic acids, for example, cyclohexanecarboxylic acid, benzoic acid, trimellitic anhydride, 2-naphthoic acid, nicotinic acid, isonicotinic acid, 2-furic acid, propionic acid, butyric acid, isobutyric acid, Examples include methacrylic acid, palmitic acid, stearic acid, oleic acid, cinnamic acid, glyceric acid, acetoacetic acid, benzylic acid, and anthranilic acid, among which cyclohexanecarboxylic acid is most preferred.
[0037]
By closing the isocyanate at the terminal of carbodiimide with these carboxylic acids, even if an unreacted polycarbodiimide compound is present in polylactic acid, the above-mentioned deterioration in thread formability and poor color tone due to excellent thermal stability, Furthermore, generation of irritating gas can be suppressed. When the carbodiimide having a terminal isocyanate is blocked with a carboxylic acid at the terminal, a carbodiimide represented by the following formula can be obtained by a decarbonation reaction.
[0038]
R₃-CONH- (R₁-NCN) n-R₂-CONH-R₄
In the above equation, R₃And R₄Is a residue of a carboxylic acid reacted with an isocyanate group, n is an integer of 2 or more,₃And R₄May be the same or different.
[0039]
As described above, when the terminal of the carbodiimide is capped with a carboxylic acid, the reaction between the isocyanate and these carboxylic acids may be performed before the carbodiimidation, or after the carbodiimidation to an appropriate degree of polymerization, to the remaining isocyanate. Alternatively, it may be performed by adding an equivalent amount of a sealing agent.
[0040]
The present invention is intended to deactivate the reactive terminal in the polymer by blocking the reactive terminal of the polylactic acid polymer and the oligomer contained therein with the above-mentioned polycarbodiimide compound, thereby suppressing the hydrolysis of polylactic acid. is there. The reactive end has a hydroxyl group and a carboxyl group, but the carbodiimide compound has an excellent carboxyl group-blocking property.
[0041]
It is more important to determine the amount of the polycarbodiimide compound to be added to the carboxyl group terminal than to the weight of polylactic acid. Furthermore, since the residual monomer and the residual oligomer also generate a carboxyl group terminal by hydrolysis, not only the carboxyl group terminal of the polymer but also the total amount of the terminal carboxyl group including those derived from the residual oligomer and the monomer is important. By adding a polycarbodiimide compound and making the total carboxyl group terminal concentration of the polylactic acid fiber 10 equivalents / ton or less based on the entire polylactic acid fiber, the desired heat resistance and hydrolysis resistance can be obtained. The total carboxyl group terminal concentration after the terminal is blocked with the polycarbodiimide compound is preferably 8 equivalents / ton or less, more preferably 5 equivalents / ton or less.
[0042]
In order to reduce the amount of pyrolysis gas generated due to thermal degradation of the unreacted polycarbodiimide compound, the amount of the polycarbodiimide compound to be added is not more than twice as much as the total carboxyl group terminal amount of polylactic acid as the carbodiimide group equivalent. Is preferred. The addition amount of the polycarbodiimide compound is more preferably 1.5 times equivalent or less, more preferably 1.2 times equivalent or less, of the total amount of carboxyl groups.
[0043]
The polylactic acid fiber of the present invention has an index of yellow tint b^*Preferably the value is 7 or less. As a result, it can be used for applications where the color tone is important, such as clothing. b^*The value is preferably 5 or less, more preferably 3.5 or less.
[0044]
Polylactic acid fiber b^*For the improvement of the value, it is possible to use a bluing compound such as cobalt acetate or the like used in general-purpose polyesters, or a colorant, but if too much is used, the heat resistance decreases. In addition to impairing the yarn formability, the color becomes turbid at the time of dyeing, and the vivid color development characteristic of polylactic acid fibers is impaired. Therefore, even when used in combination, it is preferable that the amount added be 500 ppm or less based on the weight of polylactic acid.
[0045]
The hydrolysis resistance in the present invention can be evaluated by the fiber viscosity retention or strength retention. In the present invention, it is preferable that 30 g of a fiber sample and 300 g of water are placed in a pressure vessel and subjected to a hot water treatment at 120 ° C. for 60 minutes, and the viscosity retention ratio with respect to the viscosity before the heat treatment is 75% or more. The viscosity retention is more preferably at least 85%. The strength retention of the fibers before and after the above-mentioned hot water treatment is preferably 70% or more. The strength retention is more preferably at least 85%.
[0046]
The polylactic acid fiber of the present invention preferably has a strength of 2 cN / dtex or more in order to make the process passability and the mechanical strength of the product practical. More preferably, it is 3 cN / dtex or more. Further, it is preferable that the elongation of the fiber of the present invention is 15 to 70%, because the processability is improved. The elongation is more preferably 25 to 50%.
[0047]
The polylactic acid fiber of the present invention preferably has good dimensional stability of the fiber and the fiber product if the boiling water shrinkage is 0 to 20%. More preferably, it is 2 to 10%.
[0048]
The cross-sectional shape of the polylactic acid fiber of the present invention may be any of a round cross section, a triangular cross section, a multi-lobal cross section, a hollow cross section, a flat cross section, a W cross section, an X cross section, and other irregular cross sections. The form of the fibers is not particularly limited, such as long fibers and short fibers. In the case of long fibers, multifilaments or monofilaments may be used.
[0049]
The method for producing the polylactic acid fiber of the present invention is not particularly limited. For example, the following method can be employed.
[0050]
First, a polycarbodiimide compound and polylactic acid are produced by the above method. Specific methods for reducing the amount of residual lactide include, for example, using a metal deactivator, an antioxidant, or the like, lowering the polymerization temperature, and adding a catalyst, as described in Japanese Patent Application Publication No. 7-504939. It is preferable to control the rate. Also, the amount of residual lactide can be significantly reduced by subjecting the polymer to a vacuum treatment or extraction with chloroform or the like.
[0051]
Next, the total carboxyl group terminal concentration of the obtained polylactic acid is determined with reference to the method described in JP-A-2001-261797. That is, the weighed sample is dissolved in o-cresol, an appropriate amount of dichloromethane is added, and the sample is titrated with a 0.02 N KOH methanol solution. At this time, oligomers such as lactide, which is a cyclic dimer of lactic acid, are hydrolyzed to form carboxyl group terminals. Therefore, all of the polymer carboxyl group terminals, monomer-derived carboxyl group terminals, and oligomer-derived carboxyl group terminals are summed up. The calculated total carboxyl group terminal concentration is determined.
[0052]
Next, the polylactic acid and the polycarbodiimide compound are melt-kneaded and formed into fibers by melt spinning. At the time of kneading and melt spinning, it is important to promote a terminal blocking reaction between the polycarbodiimide compound and polylactic acid and to suppress the thermal decomposition of the unreacted polycarbodiimide compound. Therefore, the melt retention index T determined from the temperature T during kneading and melt spinning and the melt retention time pt^*Is preferably controlled within the range of the following expression. Here, the melt residence time pt is a time that substantially passes through a portion heated to 190 to 250 ° C., which is a temperature setting of a kneader or a melting part, a pipe size, a dimension in a spinning pack, and the like. Can be estimated from the density of the polylactic acid in the molten state. When the step of kneading the polycarbodilite compound and the polylactic acid and the step of melt-spinning are separated, the melt retention index is calculated separately, and the sum is used as the melt retention index T^*And
[0053]
Melt retention index T^*= Pt x (T-100)^1.5
190 ≦ T ≦ 250
(Unit T: ° C, pt: minute)
10,000 ≦ T^*≤40,000
Melt retention index T^*Is 10,000 or more, since the end-capping reaction between the polycarbodiimide compound and polylactic acid can be promoted, which is preferable. On the other hand, the melt retention index T^*Is not more than 40,000, thermal decomposition of unreacted polycarbodiimide compound can be suppressed, which is preferable. In order to suppress the decomposition of the unreacted polycarbodiimide compound, the upper limit of the melt kneading temperature T is preferably 240 ° C., and more preferably 230 ° C.
[0054]
As described above, the mixing method of the polycarbodiimide compound is as described above. After separately drying the polylactic acid and the polycarbodiimide compound, a master chip is once prepared by a kneading machine, and the master chip and the polylactic acid are chip-blended and dried. And spinning may be performed, or a dried polycarbodiimide compound may be directly added during melt spinning. In the case of direct addition, there is a method in which a polycarbodiimide compound is added in a molten portion of polylactic acid, or a separately melted polycarbodiimide compound and polylactic acid are kneaded in a spinning pack using a static kneader or a sand filter layer. . In addition, at the time of kneading and melt spinning, in order to suppress the oxidative decomposition of polylactic acid, it is preferable to seal the part to be supplied to the chip pipe and the melting part with nitrogen.
[0055]
At this time, if the addition amount of the polycarbodiimide compound is not more than twice equivalent to the total terminal amount of the carboxyl group as described above, the unreacted polycarbodiimide is promoted while promoting the end-capping reaction between the polycarbodiimide compound and polylactic acid. Thermal decomposition of the compound can be suppressed. Here, it is important to determine the amount of polylactic acid to be added to the total amount of terminal carboxyl groups. For example, even if a small amount is added to the total weight of polylactic acid, the amount of polylactic acid before adding the polycarbodiimide compound is important. If the total carboxyl group terminal amount of lactic acid is small, the amount of unreacted polycarbodiimide compound increases, and the amount of pyrolysis gas generated by thermal deterioration increases. On the other hand, if the total carboxyl group terminal amount of the polylactic acid before the addition of the polycarbodiimide compound is large, the terminal capping will be insufficient and the effect of improving the hydrolysis resistance will be small. Further, it is preferable to set the melting residence time of the polycarbodiimide compound in the spinning machine in accordance with the kneading step as described above.
[0056]
After the yarn spun from the spinneret is cooled and solidified by chimney, a spinning oil agent is applied by an oil supply device, and is taken up using a godet roll or the like.
[0057]
In the case of long fibers, the drawn yarn may be once wound into a cheese-like package and then drawn and / or false-twisted, or drawn directly in one step using a spinning drawing apparatus. At this time, if the peripheral speed (hereinafter referred to as spinning speed) of the first godet roll (first hot roll in the case of direct spinning drawing) is 2500 to 7000 m / min, the drawability and false twisting workability due to the oriented crystallization of the fiber. Is preferred. Further, it is preferable that the stretching temperature at the time of stretching is 80 to 150 ° C., because the uniformity of the yarn is improved. Particularly when the film is stretched to a residual elongation of about 15 to 25% for high strength, the film is preferably stretched at 110 to 150 ° C. in order to suppress a discontinuous structure called a devitrification phenomenon. The heat treatment temperature may be changed according to the boiling water shrinkage of the polylactic acid fiber, but the heat treatment temperature is 110 to 150 ° C, more preferably 130 to 150 ° C, in order to increase the dimensional stability of the product. The stretching may be performed in one step or may be performed in multiple steps. Further, if necessary, false twisting, indentation, and mechanical crimping can be performed.
[0058]
In the case of short fibers, the drawn yarns are combined, temporarily received in a bunker, further combined into a tow, stretched and mechanically crimped, and an oil agent suitable for the next step is applied. And then cut to the desired length. At the time of stretching, it is preferable to adopt steam stretching or liquid bath stretching in consideration of the fact that the tow is thick and poor heat transfer, and the liquid bath temperature at this time is preferably 75 to 100 ° C.
[0059]
In the case of a non-woven fabric, the above-mentioned short fibers may be used, or a method in which spinning such as so-called spun bonding or melt blowing and a non-woven fabric forming step are continuous may be employed.
[0060]
The polylactic acid fiber of the present invention can take various fiber product forms, such as a woven fabric, a knitted fabric, a nonwoven fabric, and a molded product such as a fiber board.
[0061]
Further, the polylactic acid fiber of the present invention may be mixed with a raw material derived from a plant-derived material. For example, a fiber mixed with natural fibers such as silk, cotton, and hemp, and regenerated fibers such as rayon and acetate, or mixed and woven or knitted may be used.
[0062]
Further, the polylactic acid of the present invention is excellent in heat resistance at the time of melting and hardly generates irritating gas, which has been a problem in the past, and thus can be preferably used as a binder fiber. In particular, it is preferable to use the mixture with a biodegradable material such as pulp or natural fiber by utilizing the biodegradability of polylactic acid and use it for a nonwoven fabric or a molded article.
[0063]
The polylactic acid fiber of the present invention can be used not only for clothing such as shirts, blousons, and pants, but also for clothing materials such as cups and pads, curtains, carpets, mats, wallpapers, furniture and other interior uses, vehicle member uses, belts, and nets. , Ropes, heavy cloths, bags, sewing thread, industrial materials, felts, nonwoven fabrics, filters, artificial turf and the like.
[0064]
【Example】
Hereinafter, the polylactic acid fiber of the present invention will be described in detail using examples. The following methods were used for measuring and evaluating physical properties and the like in the examples.
A. Solution specific viscosity of polylactic acid (ηr)
3 g of the weighed sample was dissolved in 100 ml of o-chlorophenol to prepare a solution. Next, the specific viscosity was measured at 25 ° C. using an Ostwald viscometer.
B. Total carboxyl group terminal concentration
A precisely weighed sample was dissolved in o-cresol (5% water), an appropriate amount of dichloromethane was added to this solution, and the solution was titrated with a 0.02 N KOH methanol solution. At this time, an oligomer such as lactide, which is a cyclic dimer of lactic acid, is hydrolyzed to generate a carboxyl group terminal. Therefore, all of the polymer carboxyl group terminal, monomer-derived carboxyl group terminal, and oligomer-derived carboxyl group terminal are summed up. The obtained carboxyl group terminal concentration is determined.
C. Remaining lactide amount
1 g of a sample is dissolved in 20 ml of dichloromethane, and 5 ml of acetone is added to this solution. Further, the solution was precipitated with a fixed volume of cyclohexane, analyzed by liquid chromatography using GC17A manufactured by Shimadzu Corporation, and the amount of lactide was determined by an absolute calibration curve.
D. Weight loss rate of polycarbodiimide compound
TG-DTA2000S manufactured by Mac Science (MAC SCIENCE) Co., Ltd. Using a TG-DTA measuring device, the sample was heated at a rate of 20 ° C. under a nitrogen atmosphere with a sample weight of about 10 mg, and was kept at 240 ° C. for 60 minutes. The weight loss rate at that time was determined.
E. FIG. Ηr retention after hot water treatment (Rηr)
30 g of a sample and 300 g of water were placed in a pressure vessel and subjected to a hot water treatment at 120 ° C. for 60 minutes. Then, ηr was measured, and Rηr was obtained by the following equation. In addition, when the sample was a fiber, a thread flute was prepared and subjected to hot water treatment.
[0065]
Rηr (%) = (ηr of sample after hot water treatment / ηr before hot water treatment) × 100
F. Strength retention after hot water treatment (RT)
The sample was subjected to hot water treatment in the same manner as in D, and the RT was determined by the following equation. In addition, the strength of the polylactic acid fiber before the hot water treatment and the strength of the polylactic acid fiber after the hot water treatment were measured by the measuring method described in the section H.
[0066]
RT (%) = (strength of sample after hot water treatment / strength before hot water treatment) × 100
G. FIG. Color tone (b * value)
The scoured and knitted fabrics were laminated so that the underlying white plate was negligible, and the b * value was measured using Minolta “Spectrophotometer CM-3700d”. At this time, D65 (color temperature 6504K) was used as a light source, and measurement was performed in a 10 ° visual field.
H. Strength and elongation
The sample was measured with TENSILON UCT-100 manufactured by Orientec Co., Ltd. under constant-speed elongation conditions specified in JIS L1013 (Testing method for chemical fiber filament yarn). The elongation at break was determined from the elongation at the point showing the maximum strength in the SS curve.
I. Boiling water shrinkage
It was measured according to JIS L 1013 (test method for chemical fiber filament yarn). The scalpel was collected from the undrawn yarn package using a measuring machine, and 90 × 10^-3The actual length measurement load of cN / dtex was applied to measure the length L1. Subsequently, the actual length measurement load was removed, put in boiling water for 15 minutes, taken out, air-dried, and again applied the actual length measurement load. L2 was measured, and the boiling water shrinkage was calculated by the following equation.
[0067]
Boiling water shrinkage (%) = [(L1−L2) / L1] × 100
Production of polylactic acid
Lactide prepared from L-lactic acid having an optical purity of 99.5% is polymerized in the presence of a bis (2-ethylhexanoate) tin catalyst (lactide to catalyst molar ratio = 10000: 1) at 180 ° C. for 220 minutes in a nitrogen atmosphere. Was done. Subsequently, delactide treatment was performed at 180 ° C. under reduced pressure. At the time of polymerization, "Ultranox 626" manufactured by GE was added as a stabilizer in an amount of 0.2% by weight relative to lactide. The obtained polylactic acid had ηr of 11.4, a total carboxyl group terminal concentration of 25 equivalents / ton, and a residual lactide amount of 240 ppm.
[0068]
Synthesis examples 1 to 3 of carbodiimide
To 2 kg of HMDI, 180 g of cyclohexanecarboxylic acid was added as a terminal blocking agent, and 10 g of 3-methyl-1-phenyl-2-phospholene-1-oxide was added as a carbodiimidation catalyst. The reaction was carried out for an hour to obtain a carbodiimide compound having a degree of polymerization of 8 (Synthesis Example 1). Further, a carbodiimide compound having a polymerization degree of 8 (Synthesis Example 2) was obtained in the same manner as in Synthesis Example 1 except that the terminal blocking agent was changed to benzoic acid. Further, a carbodiimide compound having a polymerization degree of 8 (Synthesis Example 3) was obtained in the same manner as in Synthesis Example 1 except that the terminal blocking agent was changed to trimellitic anhydride. Table 1 shows the heat resistance (weight loss rate) of Synthesis Examples 1 to 3.
[0069]
Synthesis Examples 4 to 6 of Carbodiimide
A carbodiimide compound having a polymerization degree of 8 (Synthesis Example 4) was obtained in the same manner as in Synthesis Example 1 except that the terminal blocking agent was changed to cyclohexylamine. Also, a carbodiimide compound having a polymerization degree of 8 (Synthesis Example 5) was obtained in the same manner as in Synthesis Example 1 except that the terminal blocking agent was changed to dibutylamine. Further, a carbodiimide compound having a polymerization degree of 8 (Synthesis Example 6) was obtained in the same manner as in Synthesis Example 1 except that the terminal blocking agent was changed to phthalic anhydride. Table 1 shows the heat resistance (weight loss rate) of Synthesis Examples 4 to 6.
[0070]
Synthesis Examples 7 and 8 of Carbodiimide
To 2 kg of IPDI, 180 g of cyclohexanecarboxylic acid as a terminal blocking agent, 18 g of 3-methyl-1-phenyl-2-phospholene-1-oxide as a carbodiimidation catalyst, and 16 g at 190 ° C. while bubbling nitrogen through. The reaction was carried out for an hour to obtain a carbodiimide compound derived from IPDI (polymerization degree 8).
[0071]
To 2 kg of TMXDI, 180 g of cyclohexanecarboxylic acid as a terminal blocking agent was added, 21 g of 3-methyl-1-phenyl-2-phospholene-1-oxide was added as a carbodiimidation catalyst, and the mixture was heated at 190 ° C. while bubbling nitrogen. For 21 hours to obtain carbodiimide derived from TMXDI (polymerization degree 8).
[0072]
Table 1 shows the heat resistance (weight loss rate) of Synthesis Examples 7 and 8.
[0073]
[Table 1]

[0074]
Example 1
The polylactic acid of ηr11.4 obtained in the production of polylactic acid and the polycarbodiimide compound derived from HMDI obtained in Synthesis Example 1 (1 equivalent of carbodiimide / 272 g of carbodiimide compound) in a weight ratio of 99.3: 0.7 (total). (Equivalent to 1.0 times the amount of the carboxyl group end), charged into a hopper 1, introduced into a twin screw extruder 2 and melt-kneaded at a melting temperature T1: 220 ° C., and subsequently heated to a spinning temperature T2: 220 ° C. The molten polymer was guided to the spinning pack 4 incorporated in the heated spin block 3 and spun out from a die 5 having a discharge hole diameter of 0.3 mm, a hole depth of 0.6 mm, and 36 holes (see FIG. 1). The melt residence time pt at this time was 5 minutes for the kneading step and 7 minutes for the melt spinning step, for a total of 12 minutes. At this time, the suction device 7 was installed at a position 10 cm below the base, and the subliming monomers and oligomers were removed at a suction speed of 25 m / min. The spun yarn was cooled and solidified at a wind speed of 25 m / min by a cooling chimney 6, and then refueled by an oiling device 8 installed 2 m below the base. In the spinning oil, a fatty acid ester is adjusted as a leveling agent at 70% by weight, and other additives (emulsifier, antistatic agent, antioxidant, rust inhibitor) are adjusted at a ratio of 30% by weight. The water emulsion was adjusted so as to have a weight percentage of 6% by weight and adhered to the fiber (0.9% by weight as pure oil).
[0075]
Next, entanglement is imparted by the entanglement nozzle 9 at 0.1 MPa, taken up by the first godet roll 10 at a peripheral speed of 3000 m / min, and subsequently taken up by the winding device 12 via the second godet roll 11, and 170 dtex, An undrawn yarn (cheese package 13) of 36 filaments was obtained. No irritating odor from the spun yarn immediately below the spinneret was felt at all, there was no yarn breakage or fluff during spinning, and the spinnability was good.
[0076]
The yarn is further preheated at a first hot roll temperature of 95 ° C., stretched 1.3 times, heat-set at a second hot roll temperature of 130 ° C., wound up through a non-heated cold roll, and extruded at 130 dtex, A 36 filament drawn yarn was obtained. There was no problem in the stretchability at this point, and five 1 kg windings were sampled, but the yarn breakage was zero.
[0077]
B of the obtained drawn yarn^*The value was 3.2, indicating an excellent color tone that could be used without limitation for clothing. The total carboxyl group terminal concentration was 4.5 equivalents / ton, indicating excellent hydrolysis resistance.
[0078]
Example 2
Spinning and stretching were carried out in the same manner as in Example 1 except that the polycarbodiimide compound obtained in Synthesis Example 2 (1 equivalent of carbodiimide / 271 g of carbodiimide compound) was used as the polycarbodiimide compound to obtain a drawn yarn. The spinning of Example 2 produced some smoke, but hardly any pungent odor. In addition, both spinnability and stretchability were good, and the thread breakage was zero as in Example 1.
[0079]
B of the obtained drawn yarn^*The value was 3.8, indicating an excellent color tone that could be used without limitation for clothing. The total carboxyl group terminal concentration was 4.8 eq / ton, indicating excellent hydrolysis resistance.
[0080]
Example 3
Spinning and stretching were carried out in the same manner as in Example 1 except that the polycarbodiimide compound (1 equivalent of carbodiimide / 289 g of carbodiimide compound) obtained in Synthesis Example 3 was used as the polycarbodiimide compound, to obtain a drawn yarn. In Example 3, as in Example 1, almost no pungent odor was felt. Further, both spinnability and stretchability were good. B of the obtained drawn yarn^*The value was 3.5, indicating an excellent color tone that could be used without limitation for clothing. The total carboxyl group terminal concentration was 7.2 equivalents / ton, indicating excellent hydrolysis resistance.
[0081]
Comparative Example 1
Spinning and stretching were performed in the same manner as in Example 1 without adding the polycarbodiimide compound, to obtain a 130 dtex, 36 filament drawn yarn.
[0082]
B of the obtained drawn yarn^*The value was 1.7, indicating an excellent color tone. However, the carboxyl group terminal concentration was 35 equivalents / ton, and the hydrolysis resistance was extremely poor.
[0083]
Comparative Example 2
Spinning and stretching were carried out in the same manner as in Example 1 except that the polycarbodiimide compound (1 equivalent of carbodiimide / 276 g of carbodiimide compound) obtained in Synthesis Example 4 was used as the polycarbodiimide compound, to obtain a drawn yarn. In Comparative Example 2, the generation of irritating gas in the melt spinning process was severe, and the working environment was extremely poor. In addition, b of the obtained drawn yarn^*The value was 5.2, indicating a usable color tone if the application was limited for clothing.
[0084]
Comparative Example 3
Spinning and stretching were performed in the same manner as in Example 1 except that the polycarbodiimide compound (1 equivalent of carbodiimide / 284 g of carbodiimide compound) obtained in Synthesis Example 5 was used as the polycarbodiimide compound, to obtain a drawn yarn. In Comparative Example 3, as in Comparative Example 2, the generation of irritating gas in the melt spinning step was severe, and the working environment was extremely poor.
[0085]
Comparative Example 4
Spinning and stretching were carried out in the same manner as in Example 1 except that the polycarbodiimide compound (1 equivalent of carbodiimide / 277 g of carbodiimide compound) obtained in Synthesis Example 6 was used as the polycarbodiimide compound, to obtain a drawn yarn. In Comparative Example 4, although the generation of the irritating gas was smaller than that of Comparative Example 1, the obtained fiber had poor heat resistance, and^*The value was 8.1, and the use for clothing was considerably limited.
[0086]
Example 4
Spinning and stretching were carried out in the same manner as in Example 1 except that the mixing ratio of the polylactic acid and the polycarbodiimide compound was 98.8: 1.2 (1.8 equivalents to the total amount of carboxyl groups), and the stretching was carried out. Yarn was obtained.
[0087]
B of the obtained drawn yarn^*The value was 5.5, indicating a usable color tone if the application was limited for clothing. The carboxyl group terminal concentration was 3.8 equivalents / ton, indicating excellent hydrolysis resistance.
[0088]
Example 5
Spinning and stretching were performed in the same manner as in Example 1 except that the mixing ratio of the polylactic acid and the polycarbodiimide compound was 99.5: 0.5 (equivalent to 0.7 times the total amount of carboxyl groups), and the stretching was performed. Yarn was obtained.
[0089]
B of the obtained drawn yarn^*The value was 2.6, which was an excellent color tone that could be used without limitation for clothing. Further, the carboxyl group terminal concentration was 8 equivalents / ton, indicating excellent hydrolysis resistance.
[0090]
Example 6
Spinning and stretching were performed in the same manner as in Example 1 except that the mixing ratio of the polylactic acid and the polycarbodiimide compound was 98: 2 (3.0 equivalents to the total amount of carboxyl group terminals), and a drawn yarn was obtained. .
[0091]
In the melt spinning of Comparative Example 5, yarn breakage occurred in both spinning and drawing due to thermal decomposition of the unreacted polycarbodiimide compound. In addition, b of the obtained drawn yarn^*The value was 8.8, which meant that the use for clothing was considerably limited.
[0092]
[Table 2]

[0093]
Example 7 and Example 8
Spinning and stretching were performed in the same manner as in Example 1 except that the polycarbodiimide compound (1 equivalent of carbodiimide / 227 g of carbodiimide compound) obtained in Synthesis Example 7 was used as the polycarbodiimide compound, to obtain a drawn yarn (Example 7). . Further, spinning and stretching were performed in the same manner as in Example 1 except that the polycarbodiimide compound (1 equivalent of carbodiimide / 252 g of carbodiimide compound) obtained in Synthesis Example 8 was used as the polycarbodiimide compound, to obtain a drawn yarn (Example 8). ). The drawn yarns obtained in Example 7 and Example 8 each had lower strength than Example 1, but were excellent in color tone and hydrolysis resistance as in Example 1.
[0094]
Example 9
Spinning and drawing were performed in the same manner as in Example 1 except that the melting temperature T1 and the spinning temperature T2 were set to 245 ° C., to obtain a drawn yarn. In the melt spinning of Example 9, a slight irritating gas was generated due to the thermal decomposition of the unreacted polycarbodiimide compound. In addition, although the spinnability was good, a single yarn was wound on a hot roll by stretching.
[0095]
B of the obtained drawn yarn^*The value was 6.1, and although the use was limited, it could be sufficiently used for clothing.
[0096]
Example 10
Spinning and drawing were performed in the same manner as in Example 1 except that the melting temperature T1 and the spinning temperature T2 were set to 200 ° C., to obtain a drawn yarn. In Example 10, no pungent odor was generated during melt spinning, and both spinnability and stretchability were good. In addition, b of the obtained drawn yarn^*The value was 2.5, which was better than Example 1. Further, the hydrolysis resistance was also at a level that could sufficiently withstand practical use.
[0097]
Example 11
Spinning and stretching were performed in the same manner as in Example 1 except that the spinning temperature T2 was set to 255 ° C., to obtain a drawn yarn. A large amount of irritating gas was generated by thermal decomposition of unreacted polycarbodiimide compound. In addition, yarn breakage frequently occurred during spinning and drawing.
[0098]
Although the obtained drawn yarn is excellent in hydrolysis resistance, b^*The value was 10.2, and the application was considerably limited as clothing.
[0099]
Example 12
Spinning was performed in the same manner as in Example 10 except that the filter layer of the spinning pack 4 was changed to a reduced one and the melt residence time in the melt spinning step was set to 4.5 minutes (total melt residence time pt: 9.5 minutes).・ Drawing was performed to obtain a drawn yarn. In Example 12, no pungent odor was generated in melt spinning, and both spinnability and stretchability were good. In addition, b of the obtained drawn yarn^*The value was 2.3, which was better than that of Example 10.
[0100]
Example 13
Spinning and stretching were performed in the same manner as in Example 1 except that the filter layer of the spinning pack 4 was changed to an enlarged one and the total melt residence time pt was set to 32 minutes, to obtain a drawn yarn. Example 13 has excellent hydrolysis resistance, but b^*The value was 7.3, and the use was considerably limited for clothing.
[0101]
Example 14
The polylactic acid having ηr11.4 obtained in the production of polylactic acid was subjected to solid-state polymerization, and ηr was set to 14. Furthermore, spinning was performed in the same manner as in Example 1 except that the spinning speed was 5000 m / min, and an undrawn yarn was obtained. Further, three unstretched yarns are combined, and the first hot roll temperature is 90 ° C., the second hot roll temperature is 120 ° C., and the third hot roll temperature is 150 ° C., and the temperature between the first hot roll and the second hot roll is 1. Stretched 3 times, further stretched 1.2 times between the second hot roll and the third hot roll, and performed a 3% relaxation treatment between the third hot roll and the unheated cold roll. Was wound at 800 m / min. B of the obtained 205 dtex, 108 filament drawn yarn^*The value was 3.5. The carboxyl group terminal concentration was 4.6 equivalents / ton, indicating excellent hydrolysis resistance. Example 14 had an extremely high strength of 5.8 cN / dtex and was excellent in dimensional stability, and was therefore most suitable for clothing applications requiring high strength.
[0102]
Example 15
The polylactic acid having ηr11.4 obtained in the production of polylactic acid and the polycarbodiimide compound obtained in Synthesis Example 1 were mixed at a weight ratio of 80:20, and the mixture was led to a twin-screw extruder at a melting temperature of 210 ° C. A master chip of a carbodiimide compound was prepared. In addition, the melting residence time at this time was 5 minutes. Further, polylactic acid and this master chip were mixed at a ratio of 19: 1, guided to a single screw extruder, melt-kneaded at a melting temperature T1: 225 ° C., and subsequently spun at a spinning temperature T2: 225 ° C. The melting residence time at this time was 10 minutes. The undrawn yarn was taken up by a first take-up roll having a peripheral speed of 1500 m / min and the yarn was combined, and then received in a bunker. Then, the yarn received by the bunker was further combined into a 120,000 dtex tow. This was stretched 2.6 times in hot water at 90 ° C. And after passing through a crimper, it was refueled and cut into a fiber length of 52 mm.
[0103]
The obtained short fibers had a single fiber fineness of 5 dtex and a number of crimps of 22 / m. Also, b^*The value was 4.0, which was an excellent color tone that could be used for clothing, and the carboxyl group terminal concentration was 5 equivalents / ton, showing excellent hydrolysis resistance.
[0104]
Note that b^*Evaluation of fiber properties such as value and hydrolysis resistance was performed by partially sampling the yarn between the crimper and the oil supply.
[0105]
[Table 3]

[0106]
Example 16
Plain weave was produced using the yarn obtained in Example 1 for warp and weft. The resulting plain weave was scoured at 70 ° C according to a conventional method, and then subjected to an intermediate setting at 140 ° C. Further, staining was performed at 120 ° C. according to a conventional method. The obtained fabric had a squeaky feeling and a soft feeling, had an excellent texture for clothing, and exhibited a vivid coloration.
[0107]
Comparative Example 6
Using the yarn obtained in Comparative Example 1 as a warp and a weft, a plain weave was produced in the same manner as in Example 15, and dyed at 120 ° C. The resulting fabric had extremely low tear strength and was not practical. .
[0108]
Example 16
The short fiber obtained in Example 15 and a ramie cut to a fiber length of 58 mm were cotton-mixed at a weight ratio of 50:50, opened and sheeted, and laminated and compressed to obtain a laminate. Further, this laminate was heated and pressed at 235 ° C. and 3 MPa to obtain a 6 mm-thick fiber molded body composed of polylactic acid and ramie.
[0109]
This molded article had appropriate hardness, sound absorbing properties, and shock absorbing properties, and was optimal for a wall material or a floor material for a house.
[0110]
【The invention's effect】
The polylactic acid fiber of the present invention having excellent heat resistance, hydrolysis resistance and color tone allows the polylactic acid fiber to be expanded and developed for use in clothing.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a spinning apparatus preferably used in the present invention.
[Explanation of symbols]
1: Hopper
2: Extruder
3: Spinning block
4: Spinning pack
5: Spinneret
6: suction device
7: Cooling chimney
8: Refueling device
9: Confounding nozzle
10: 1st godet roll
11: Second godet roll
12: Winding device
13: Cheese-like package

Claims (3)

A polylactic acid fiber in which at least a part of a carboxyl group terminal is blocked by a carbodiimide compound, wherein the carbodiimide compound has the formula 1

4,4′-dicyclohexylmethane diisocyanate represented by the formula:

An isophorone diisocyanate represented by the formula:

A polycarbodiimide compound derived from at least one of tetramethylxylylene diisocyanate represented by and having two or more carbodiimide groups in the molecule, and the isocyanate terminal of which is sealed with a carboxylic acid, A polylactic acid fiber having a carboxyl terminal concentration of 10 equivalents / ton or less. 2. The polylactic acid fiber according to claim 1, wherein the b ^* value as an index of color tone is 7 or less. A biodegradable fiber product using the polylactic acid fiber according to claim 1 or 2 at least in part.

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