JP2004352872A - Polylactic acid resin composition, molded article and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid resin composition which gives with excellent moldability a molded article excellent in heat resistance and impact strength, a heat-resistant polylactic acid resin molded article comprised of the polylactic acid resin composition, and a manufacturing method of the heat-resistant polylactic acid resin molded article. <P>SOLUTION: The polylactic acid resin composition comprises 100 pts. wt. of polylactic acid and, incorporated therewith, 0.01-10 pts. wt. of a heterocyclic compound represented by any one of general formulae (I)-(IV). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

（式中、Ａ^１、Ａ^２、Ａ^３、Ａ^４、Ａ^５、Ａ^６、Ａ^７、Ａ^８、Ａ^９、Ｂ^１、Ｂ^２、Ｂ^３、Ｂ^４、Ｂ^５、Ｂ^６、Ｂ^７、Ｂ^８、Ｂ^９、Ｂ^１０、Ｂ^１１およびＢ^１２は各々独立に−ＣＨ_２−、−Ｃ（＝Ｏ）−、−Ｃ（＝Ｓ）−、−ＮＨ−、−ＮＲ_１３−、または−Ｓ（＝Ｏ）_２−を、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０、Ｒ_１１、およびＲ_１２は水素原子、ハロゲン原子、ヒドロキシ基、炭素原子数１〜１８のアルキル基、アルケニル基、アルキニル基、アルコキシ基、シクロアルキル基、またはアリール基を、Ｒ_１３は−ＮＨ_２、−ＮＨＲ_１４、−ＮＨＣ（＝Ｏ）−Ｒ_１５、炭素原子数１〜１８のアルキル基、シクロアルキル基、アルケニル基、またはアリール基を、Ｒ_１４およびＲ_１５は炭素原子数１〜１８のアルキル基、シクロアルキル基、アルケニル基、またはアリール基を表す。ただし、Ａ^１、Ａ^２、Ａ^３のいずれか１個以上は−Ｃ（＝Ｏ）−又は−Ｃ（＝Ｓ）−であり、いずれか１個以上は−ＮＨ−又は−ＮＲ_１３−であり、Ａ^４、Ａ^５、Ａ^６のいずれか１個以上は−Ｃ（＝Ｏ）−又は−Ｃ（＝Ｓ）−であり、いずれか１個以上は−ＮＨ−又は−ＮＲ_１３−であり、Ａ^７、Ａ^８、Ａ^９のいずれか１個以上は−Ｃ（＝Ｏ）−又は−Ｃ（＝Ｓ）−であり、いずれか１個以上は−ＮＨ−又は−ＮＲ_１３−であり、Ｂ^１、Ｂ^２、Ｂ^３、Ｂ^４のいずれか１個以上は−Ｃ（＝Ｏ）−又は−Ｃ（＝Ｓ）−であり、いずれか１個以上は−ＮＨ−又は−ＮＲ_１３−であり、Ｂ^５、Ｂ^６、Ｂ^７、Ｂ^８のいずれか１個以上は−Ｃ（＝Ｏ）−又は−Ｃ（＝Ｓ）−であり、いずれか１個以上は−ＮＨ−又は−ＮＲ_１３−であり、Ｂ^９、Ｂ^１０、Ｂ^１１、Ｂ^１２のいずれか１個以上は−Ｃ（＝Ｏ）−又は−Ｃ（＝Ｓ）−であり、いずれか１個以上は−ＮＨ−又は−ＮＲ_１３−である。）
【００１９】
また、本発明は、上記複素環化合物が上記一般式（Ｉ）又は（ＩＩ）で表される上記ポリ乳酸系樹脂組成物を提供することにより、上記目的を達成したものである。
【００２０】
また、本発明は、上記複素環化合物がフタル酸ヒドラジドである上記ポリ乳酸系樹脂組成物を提供することにより、上記目的を達成したものである。
【００２１】
また、本発明は、上記複素環化合物が融点３００℃以上の化合物である上記ポリ乳酸系樹脂組成物を提供することにより、上記目的を達成したものである。
【００２２】
また、本発明は、含水珪酸マグネシウム（タルク）０．０１〜４０重量部を配合した上記ポリ乳酸系樹脂組成物を提供することにより、上記目的を達成したものである。
【００２３】
また、本発明は、上記含水珪酸マグネシウム（タルク）の平均粒子径が、１０μｍ以下である上記ポリ乳酸系樹脂組成物を提供することにより、上記目的を達成したものである。
【００２４】
また、本発明は、上記ポリ乳酸系樹脂組成物を成形してなる耐熱性ポリ乳酸系樹脂成形品を提供することにより、上記目的を達成したものである。
【００２５】
また、本発明は、上記ポリ乳酸系樹脂組成物を溶融した後、溶融した該ポリ乳酸系樹脂組成物を、走査型示差熱量計（ＤＳＣ）における結晶化開始温度以下ガラス転移温度以上の範囲に設定された成形機の金型に充填し、結晶化させながら成形する耐熱性ポリ乳酸系樹脂成形品の製造方法を提供することにより、上記目的を達成したものである。
【００２６】
【発明の実施の形態】
本発明のポリ乳酸系樹脂組成物について、以下に詳述する。
本発明のポリ乳酸系樹脂組成物において用いられる上記ポリ乳酸（乳酸系ポリマー）としては、例えば、ポリ乳酸ホモポリマー、ポリ乳酸コポリマー、ポリ乳酸ホモポリマーとポリ乳酸コポリマーとのブレンドポリマーが挙げられる。また、本発明のポリ乳酸系樹脂組成物の特徴である結晶性を損なわない範囲であれば、ポリ乳酸を主体とするブレンドポリマーであっても良い。
【００２７】
上記ポリ乳酸の重量平均分子量（Ｍｗ）は、ゲルパーミエーションクロマトグラフ分析によるポリスチレン換算値で、通常５万〜５０万、好ましくは１０万〜２５万である。重量平均分子量が５万未満では、実用上必要な物性が得られにくく、一方、重量平均分子量が５０万を超えると、成形性が悪くなり易い。
【００２８】
上記ポリ乳酸におけるＬ−乳酸単位及びＤ−乳酸単位の構成モル比（Ｌ／Ｄ）は、特に制限されるものではなく、１００／０〜０／１００の範囲から選択することができるが、高い融点を有するポリ乳酸系樹脂組成物を得るには、Ｌ−乳酸単位及びＤ−乳酸単位のいずれかを７５モル％以上、更に高い融点を有するポリ乳酸系樹脂組成物を得るには、Ｌ−乳酸単位及びＤ−乳酸単位のいずれかを９０モル％以上含むことが好ましい。
【００２９】
また、上記ポリ乳酸コポリマーは、乳酸モノマー又はラクチドと、共重合可能な他の成分とが共重合されたものである。他の成分としては、エステル結合形成性の官能基を２個以上持つジカルボン酸、多価アルコール、ヒドロキシカルボン酸、ラクトン等、及びこれらを構成成分としてなる各種のポリエステル、ポリエーテル、ポリカーボネート等が挙げられる。
【００３０】
上記ジカルボン酸としては、コハク酸、アジピン酸、アゼライン酸、セバシン酸、テレフタル酸、イソフタル酸等が挙げられる。
【００３１】
上記多価アルコールとしては、ビスフェノールにエチレンオキサイドを付加反応させたもの等の芳香族多価アルコール、エチレングリコール、プロピレングリコール、ブタンジオール、ヘキサンジオール、オクタンジオール、グリセリン、ソルビタン、トリメチロールプロパン、ネオペンチルグリコール等の脂肪族多価アルコール、ジエチレングリコール、トリエチレングリコール、ポリエチレングリコール、ポリプロピレングリコール等のエーテルグリコール等が挙げられる。
【００３２】
上記ヒドロキシカルボン酸としては、グリコール酸、ヒドロキシブチルカルボン酸、特開平６−１８４４１７号公報に記載されているヒドロキシカルボン酸等が挙げられる。
【００３３】
上記ラクトンとしては、グリコリド、ε−カプロラクトングリコリド、ε−カプロラクトン、ε−プロピオラクトン、δ−ブチロラクトン、β−ブチロラクトン、γ−ブチロラクトン、ピバロラクトン、δ−バレロラクトン等が挙げられる。
【００３４】
本発明のポリ乳酸系樹脂組成物に用いられる上記ポリ乳酸は、合成方法に特に制限はなく、従来公知の方法で合成することができ、例えば、特開平７−３３８６１号公報、特開昭５９−９６１２３号公報、高分子討論会予稿集第４４巻、３１９８−３１９９頁等に記載されている乳酸モノマーからの直接脱水縮合、又は乳酸環状二量体ラクチドの開環重合によって合成することができる。
【００３５】
直接脱水縮合を行う場合、Ｌ−乳酸、Ｄ−乳酸、ＤＬ−乳酸、及びこれらの混合物のいずれの乳酸を用いても良い。また、開環重合を行う場合は、Ｌ−ラクチド、Ｄ−ラクチド、ＤＬ−ラクチド、ｍｅｓｏ−ラクチド、及びこれらの混合物のいずれかのラクチドを用いても良い。
【００３６】
開環重合に用いるラクチドの合成、精製及び重合操作は、例えば、米国特許第４０５７５３７号明細書、欧州特許出願公開第２６１５７２号明細書、Ｐｏｌｙｍｅｒ Ｂｕｌｌｅｔｉｎ，１４，４９１−４９５（１９８５）、及びＭａｃｒｏｍｏｌ．Ｃｈｅｍ．、１８７、１６１１−１６２８（１９８６）等に記載されている。
【００３７】
上記ポリ乳酸を得る際の重合反応に用いる触媒は、特に限定されるものではないが、公知の乳酸重合用の触媒を用いることができる。該触媒としては、例えば、乳酸スズ、酒石酸スズ、ジカプリル酸スズ、ジラウリル酸スズ、ジパルミチン酸スズ、ジステアリン酸スズ、ジオレイン酸スズ、α−ナフトエ酸スズ、β−ナフトエ酸スズ、オクチル酸スズ等のスズ系化合物、粉末スズ、酸化スズ、亜鉛末、ハロゲン化亜鉛、酸化亜鉛、有機亜鉛系化合物、テトラプロピルチタネート等のチタン系化合物、ジルコニウムイソプロポキシド等のジルコニウム系化合物、三酸化アンチモン等のアンチモン系化合物、酸化ビスマス（ＩＩＩ）等のビスマス系化合物、酸化アルミニウム、アルミニウムイソプロポキシド等のアルミニウム系化合物等が挙げられる。
【００３８】
これらの中でも、スズ又はスズ化合物からなる触媒が活性の点から特に好ましい。上記触媒の使用量は、例えば、開環重合を行う場合、ラクチドに対して０．００１〜５重量％程度である。
【００３９】
重合反応は、上記触媒の存在下で、触媒の種類によって異なるが、通常１００〜２２０℃で行うことができる。また、例えば特開平７−２４７３４５号公報に記載されている２段階重合を行うことも好ましい。
【００４０】
また、上記のポリ乳酸を主体としたブレンドポリマーは、例えば、ポリ乳酸ホモポリマー及び／又はポリ乳酸コポリマーと、ポリ乳酸以外の脂肪族ポリエステル（以下、単に「脂肪族ポリエステル」という）とを混合、溶融して得られた混合物である。上記脂肪族ポリエステルをブレンドすると、成形品に柔軟性及び耐衝撃性を付与することができるため好ましい。上記ブレンドポリマーにおける混合割合は、通常、ポリ乳酸ホモポリマー及び／又はポリ乳酸コポリマー１００重量部に対して、上記脂肪族ポリエステル１０〜１００重量部程度である。
【００４１】
上記脂肪族ポリエステルは、１種のポリマーでも良く、又は２種以上のポリマーの複合でも良い。該ポリマーとしては、例えば、脂肪族カルボン酸と脂肪族アルコールとからなるポリマーや、ε−カプロラクトン等の環状無水物を開環重合して得られた脂肪族ヒドロキシカルボン酸ポリマー等が挙げられる。これらのポリマーを得る方法としては、直接重合して高分子量物を得る直接重合法、オリゴマー程度に重合した後、鎖延長剤等で高分子量物を得る間接重合法等が挙げられる。また、上記脂肪族ポリエステルは、上記脂肪族モノマー成分を主として構成されるポリマーであれば、共重合体であってもよく、あるいは他の樹脂との混合物であってもよい。
【００４２】
上記脂肪族ポリエステルは、脂肪族ジカルボン酸と脂肪族ジオールとからなるポリマーであることが好ましい。該脂肪族ジカルボン酸としては、例えば、コハク酸、アジピン酸、スベリン酸、セバシン酸、ドデカン酸、及びこれらの無水物や誘導体が挙げられ、該脂肪族ジオールとしては、例えば、エチレングリコール、ブタンジオール、ヘキサンジオール、オクタンジオール、シクロヘキサンジメタノール等のグリコール系化合物、及びこれらの誘導体が挙げられる。上記脂肪族ジカルボン酸及び上記脂肪族ジオールは、いずれも、好ましくは炭素数２〜１０のアルキレン基、シクロ環基又はシクロアルキレン基を持つモノマーである。これらの脂肪族ジカルボン酸及び脂肪族ジオールそれぞれの中から選択されたモノマー成分の重縮合により、上記脂肪族ポリエステルが製造されるのが好ましい。上記脂肪族ジカルボン酸及び上記脂肪族ジオールのいずれも、２種以上を用いても構わない。
【００４３】
また、溶融粘度の向上のために脂肪族ポリエステルとして用いる上記ポリマー中に分岐を設ける目的で、上記ポリマーを構成するモノマー成分として、３官能以上の多官能のカルボン酸、アルコールあるいはヒドロキシカルボン酸を用いても構わない。これらの多官能のモノマー成分は、多量に用いると得られるポリマーが架橋構造を持ち、熱可塑性ではなくなる場合や熱可塑性であっても部分的に高度に架橋構造をもったミクロゲルを生じる場合がある。従って、これらの多官能のモノマー成分は、ポリマー中に含まれる割合が極僅かで、ポリマーの化学的性質及び物理的性質を大きく左右しない程度で用いられる。多官能のモノマー成分としては、リンゴ酸、酒石酸、クエン酸、トリメリット酸、ピロメリット酸、あるいはペンタエリスリット、トリメチロールプロパン等を用いることができる。
【００４４】
上記脂肪族ポリエステルとして用いられるポリマーの製造方法のうち、上記直接重合法は、モノマー成分を選択し、該モノマー成分中に含まれる或いは重合中に発生する水分を除去しながら、高分子量物を得る方法である。また、上記間接重合法は、モノマー成分を選択し、オリゴマー程度に重合した後、分子量増大を目的として、少量の鎖延長剤、例えば、ヘキサメチレンジイソシアネート、イソホロンジイソシアネート、キシリレンジイソシアネート、ジフェニルメタンジイソシアネート等のジイソシアネート化合物を使用して高分子量化する方法である。これらの方法の他に、カーボネート化合物を用いて脂肪族ポリエステルカーボネートを得る方法等を用いてもよい。
【００４５】
また、本発明のポリ乳酸系樹脂組成物において、上記ポリ乳酸は、衝撃強度の改善等のために、必要に応じて、ポリ乳酸以外の汎用の樹脂とブレンドしてもよい。汎用の樹脂としては、エチレン−プロピレン共重合ゴム、エチレン−プロピレン−ジエン共重合体等の弾性を有する樹脂が好ましい。
【００４６】
本発明のポリ乳酸系樹脂組成物においては、上述したポリ乳酸に、結晶核剤として、上記一般式（Ｉ）で表される化合物が配合される。上記一般式（Ｉ）で表される化合物は、カルボキシル基とアミノ基を環構造中に有する複素環化合物である。
【００４７】
上記一般式（Ｉ）におけるＲ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０、Ｒ_１１、Ｒ_１２、Ｒ_１３、Ｒ_１４及びＲ_１５で表される炭素原子数１〜１８のアルキル基としては、例えば、メチル、エチル、プロピル、イソプロピル、ブチル、第二ブチル、第三ブチル、ペンチル、第三ペンチル、ヘキシル、ヘプチル、オクチル、イソオクチル、第三オクチル、２−エチルヘキシル、ノニル、イソノニル、デシル、イソデシル、ウンデシル、ドデシル、トリデシル、テトラデシル、ペンタデシル、ヘキサデシル、ヘプタデシル、オクタデシル等が挙げられる。アルケニル基としては、例えば、ビニル、プロペニル、ブテニル、オクテニル、オレイルなどが挙げられる。シクロアルキル基としては、例えば、シクロペンチル、シクロヘキシル、シクロヘプチルなどが挙げられる。
【００４８】
上記一般式（Ｉ）におけるＲ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０、Ｒ_１１及びＲ_１２で表される炭素原子数１〜１８のアルコキシ基としては、例えば、上記アルキル基に対応するアルコキシ基が挙げられる。
【００４９】
上記一般式（Ｉ）におけるＲ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０、Ｒ_１１及びＲ_１２で表されるハロゲン原子としては、フッ素、塩素、臭素などが挙げられる。
【００５０】
上記一般式（Ｉ）におけるＲ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、Ｒ_７、Ｒ_８、Ｒ_９、Ｒ_１０、Ｒ_１１、Ｒ_１２、Ｒ_１３、Ｒ_１４及びＲ_１５で表される炭素原子数６〜１８のアリール基としては、フェニル、ナフチル、ビフェニル等が挙げられる。
【００５１】
上記一般式（Ｉ）で表される化合物としては、より具体的には、以下の化合物Ｎｏ．１〜１０等が挙げられる。ただし、本発明は以下の化合物により何等制限されるものではない。
【００５２】
【化３】

【００５３】
【化４】

【００５４】
【化５】

【００５５】
【化６】

【００５６】
【化７】

【００５７】
【化８】

【００５８】
【化９】

【００５９】
【化１０】

【００６０】
【化１１】

【００６１】
【化１２】

【００６２】
【化１３】

【００６３】
【化１４】

【００６４】
【化１５】

【００６５】
【化１６】

【００６６】
【化１７】

【００６７】
本発明のポリ乳酸系樹脂組成物において、上記一般式（Ｉ）で表される化合物は、上記ポリ乳酸１００重量部に対して、０．０１〜１０重量部、好ましくは０．０５〜５重量部、より好ましくは０．１〜３重量部配合される。０．０１重量部より少ないと添加効果が不十分であり、１０重量部より多いとポリ乳酸系樹脂組成物の表面に噴出する等の現象が発生するようになる。
【００６８】
また、本発明のポリ乳酸系樹脂組成物には、さらに含水珪酸マグネシウム（タルク）を配合することが好ましい。該含水珪酸マグネシウム（タルク）の平均粒子径は、１０μｍ以下であることが好ましく、１〜５μｍであることがより好ましい。平均粒子径が１０μｍを超える含水珪酸マグネシウム（タルク）を用いても効果はあるが、１０μｍ以下の場合は、結晶核の形成促進効果がより高く、成形品の耐熱性をより向上させることができる。
【００６９】
上記含水珪酸マグネシウム（タルク）の配合量は、上記ポリ乳酸１００重量部に対して。０．０１〜４０重量部とすることが好ましく、０．０１〜３０重量部とすることがより好ましい。０．０１重量部未満の配合量では、添加の効果があまり得られず、４０重量部を超えて配合するとポリ乳酸系樹脂組成物の比重が重くなるだけでなく、耐衝撃性も低下する惧れがある。
【００７０】
さらに、本発明のポリ乳酸系樹脂組成物には、必要に応じて、従来公知の可塑剤、酸化防止剤、熱安定剤、光安定剤、紫外線吸収剤、顔料、着色剤、各種フィラー、帯電防止剤、金属石鹸、ワックス、離型剤、香料、滑剤、難燃剤、発泡剤、充填剤、抗菌剤・抗カビ剤、上記一般式（Ｉ）で表される化合物以外の結晶核剤等の各種添加剤を配合してもよい。
【００７１】
本発明のポリ乳酸系樹脂組成物において、上記ポリ乳酸に、上記一般式（Ｉ）で表される化合物、上記含水珪酸マグネシウム（タルク）等の添加剤を配合する方法は、特に制限されるものではなく、従来公知の方法によって行うことができる。例えば、ポリ乳酸粉末あるいはペレットと添加剤とをドライブレンドで混合してもよく、添加剤の一部をプリブレンドした後、残りの成分とドライブレンドしてもよい。ドライブレンドの後に、例えば、ミルロール、バンバリーミキサー、スーパーミキサー等を用いて混合し、単軸あるいは二軸押出機等を用いて混練してもよい。この混合混練は、通常１５０〜３００℃程度の温度で行われる。また、ポリ乳酸の重合段階で、添加剤を添加する方法、添加剤を高濃度で含有するマスターバッチを作成し、該マスターバッチをポリ乳酸に添加する方法等を用いることもできる。
【００７２】
本発明のポリ乳酸系樹脂組成物は、主として、一般のプラスチックと同様に、各種成形品の成形材料として用いられる。
【００７３】
本発明のポリ乳酸系樹脂組成物を成形してなる本発明の耐熱性ポリ乳酸系樹脂成形品、及びその好ましい製造方法である本発明の製造方法について、以下に説明する。
【００７４】
ポリ乳酸系樹脂組成物を結晶化させる方法としては、例えば、ポリ乳酸系樹脂組成物で成形品を形成した後、ポリ乳酸系樹脂組成物が結晶化可能な温度で該成形品をアニール処理する方法が挙げられるが、この方法においては、アニール処理における結晶化過程で成形品が変形しやすいという欠点がある。この欠点を解消するため、本発明の製造方法においては、本発明のポリ乳酸系樹脂組成物を成形するときに、成形機の金型を、本発明のポリ乳酸系樹脂組成物が結晶化可能な温度に設定し、一定時間保持する。
【００７５】
本発明の製造方法においては、本発明のポリ乳酸系樹脂組成物を溶融した後、該ポリ乳酸系樹脂組成物が結晶化可能な温度、即ちＤＳＣにおける結晶化開始温度以下ガラス転移温度以上の温度範囲、好ましくは結晶化開始温度以下結晶化終了温度以上の温度範囲に設定された成形機の金型に、溶融した上記ポリ乳酸系樹脂組成物を充填し、一定時間保持することにより、結晶化させながら成形する。本発明のポリ乳酸系樹脂組成物は、上述したように、結晶核剤として上記一般式（Ｉ）で表される化合物を含んでいるので、本発明の製造方法によれば、金型内にて結晶化が完了し、耐熱性及び耐衝撃性に優れたポリ乳酸系樹脂組成物を得ることができる。
【００７６】
適切な金型温度は、成形に用いられる本発明のポリ乳酸系樹脂組成物に含まれるポリ乳酸や添加剤の種類等により異なるので、予めＤＳＣ法によりポリ乳酸系樹脂組成物の結晶化温度（結晶化ピーク温度、結晶化開始温度、ガラス転移温度、結晶化終了温度）を測定し、結晶化開始温度以下ガラス転移温度以上の温度範囲、好ましくは結晶化開始温度以下結晶化終了温度以上の温度範囲から選択する。この温度範囲であれば、本発明のポリ乳酸系樹脂組成物は容易に結晶化し、さらには寸法精度のよい成形品を得ることができる。蒸気温度範囲を外れると、結晶化が遅くなり、成形時の固化時間も長くなるため、実用上適さない。尚、上記結晶化温度は、例えば、ＤＳＣにより、ペレットサンプル５ｍｇを５０℃／分で室温から２００℃まで昇温し、５分間保持した後、５℃／分の降温速度で測定することができる。
【００７７】
本発明のポリ乳酸系樹脂組成物を成形するに際しては、一般のプラスチックと同様の押出成形、射出成形、ブロー成形、真空成形、圧縮成形等の成形を行うことができ、シート、棒、ビン、容器等の各種成形品を容易に得ることができる。
【００７８】
本発明の耐熱性ポリ乳酸系樹脂成形品は、優れた耐熱性を有する。耐熱性の指標としては、例えば、ＪＩＳ Ｋ ７２０７Ａ法における低荷重たわみ温度を用いることができる。低荷重たわみ温度とは、加熱浴槽中の試験片に０．４５ＭＰａの曲げ応力を加えながら、一定速度で伝熱媒体を昇温させ、試験片が規定のたわみ量に達した時の伝熱媒体の温度をいう。本発明の耐熱性ポリ乳酸系樹脂成形品の低荷重たわみ温度は、該成形品の用途に応じて結晶核剤の添加量等によって適宜調整することができ、例えば、家電用品の比較的高温に晒されないような部品として用いる場合においても、実用上８０℃以上とすることが好ましく、９０℃以上とすることがさらに好ましく、１００℃以上とすることが最も好ましい。
【００７９】
【実施例】
以下に、実施例及び比較例を挙げて、本発明をさらに具体的に説明するが、本発明はこれらの実施例等によって制限されるものではない。
【００８０】
［実施例１〜３及び比較例１］
表１に示す配合成分をドライブレンドし、２００℃の二軸混練押出機にて平均４分間溶融混合し、口金よりストランド状に押出し、水冷後、切断し、結晶核剤を含むポリ乳酸系樹脂組成物のペレットを得た。
【００８１】
得られたペレットについて、結晶化ピーク温度及び結晶化熱量を測定した。これらの測定は、ＤＳＣ（パーキンエルマー社製、Ｄｉａｍｏｎｄ ＤＳＣ）により、ペレットサンプル５ｍｇを５０℃／分で室温から２００℃まで昇温し、５分間保持した後、５℃／分の降温速度で測定した。これらの測定結果を表１に示す。
【００８２】
次いで、得られたペレットを８０℃で真空乾燥して、絶乾状態にした後、金型温度を１１０℃、冷却時間を１２０秒に保ち、射出成形により、ＪＩＳ Ｋ ７１１０（１号Ａ試験片）の作成における離型時に、離型性及び変形の評価を行った。評価においては、試験片作成の離型時における金型への付着の有無及び程度並びに変形の有無及び程度を目視により確認した。評価基準は、金型付着がなく、変形のないものを◎、金型へやや貼りつき気味で、変形のないものを○、金型へ貼りつき気味で、明らかに変形しているものを△、金型へ貼りつき離型が困難で大きく、変形しているものを×とした。これらの評価結果を表１に示す。
【００８３】
尚、表１における配合成分は、それぞれ以下の通りである。
ポリ乳酸：トヨタ自動車（株）製、商品名「＃５４００」、重量平均分子量１６０，０００（ゲルパーミエーションクロマトグラフ分析によるポリスチレン換算値）
タルク：日本タルク（株）製、微粉末タルク、商品名「ミクロエースＰ−６」
化合物Ｎｏ．１：フタル酸ヒドラジド（融点＞３００℃）
化合物Ｎｏ．２：マレイン酸ヒドラジド（融点＞２６０℃（分解））
化合物Ｎｏ．３：サッカリン（融点＝２３０℃）
比較化合物１：ビス〔３−（３，５−ジ第三ブチル−４−ヒドロキシフェニル）プロピオン酸〕ヒドラジド（融点＝２２８℃）
【００８４】
【表１】

【００８５】
表１から明らかなように、特定の複素環化合物が配合された本発明のポリ乳酸系樹脂組成物を用いて射出成形品を得た場合、成形性に優れ、離型時の変形もなかった（実施例１〜３）。これに対し、従来の触媒脱活剤であるヒドラジド化合物が配合されたポリ乳酸系樹脂組成物は、結晶化熱量が４０Ｊ／ｇ未満で、成形性が悪かった（比較例１）。
【００８６】
【発明の効果】
本発明によれば、ポリ乳酸に、結晶核剤として特定の複素環化合物を配合することにより、結晶化速度が速いポリ乳酸系樹脂組成物を提供することができ、該ポリ乳酸系樹脂組成物からは、優れた曲げ強度及び衝撃強度を有する耐熱性ポリ乳酸系樹脂成形品を成形性良く得ることができる。また、本発明によれば、上記ポリ乳酸系樹脂組成物を金型内にて結晶化させる。耐熱性ポリ乳酸系樹脂成形品の簡便で生産効率の高い製造方法を提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a molded article having excellent impact strength and heat resistance, a polylactic acid-based resin composition obtained with good moldability, a heat-resistant polylactic acid-based resin molded article obtained from the polylactic acid-based resin composition, and The present invention relates to a method for producing a heat-resistant polylactic acid-based resin molded product.
[0002]
[Prior art]
In recent years, from the viewpoint of protection of the natural environment, biodegradable polymers that degrade in the natural environment and molded articles formed from the biodegradable polymers have been demanded, and research on biodegradable polymers such as aliphatic polyesters has been actively conducted. Is being done. In particular, a lactic acid-based polymer has a sufficiently high melting point of 140 to 180 ° C. and is excellent in transparency, and thus is greatly expected as a packaging material or a molded product utilizing transparency.
[0003]
However, a container obtained by injection molding of a lactic acid-based polymer or the like has excellent rigidity, but has low heat resistance, or may have both low heat resistance and low impact resistance. Cannot use hot water or a microwave oven, and its use is limited.
[0004]
In order to obtain a heat-resistant molded product, it is necessary to cool the mold during molding for a long time, or to anneal the molded product after molding to highly crystallize the resin. However, a long cooling step during molding is not practical and crystallization tends to be insufficient, and crystallization by annealing after molding tends to be deformed in the process of crystallization of the molded article. There is a disadvantage that.
[0005]
As a method for increasing the crystallization rate of a resin, for example, Patent Document 1 listed below discloses that terephthalic acid and resorcinol are main constituent units as crystal nucleating agents in order to promote crystallization of polyethylene terephthalate (PET). It is described that a wholly aromatic polyester fine powder is added. As described above, a method of adding a crystal nucleating agent to promote crystallization of a resin is generally known.
[0006]
On the other hand, Patent Documents 2 to 10 below describe that an additive such as a crystal nucleating agent is added to a polymer having biodegradability.
[0007]
Patent Document 2 below discloses that a biodegradable plastic such as a poly-3-hydroxybutyrate / poly-3-hydroxyvalerate copolymer, polycaprolactone or polylactic acid is coated with calcium carbonate or talc having an average particle size of 20 μm or less. A material for a plastic container which is mixed by 10 to 40% by weight is disclosed. However, this technique promotes the decomposition of biodegradable plastic after disposal by adding a large amount of inorganic filler, and does not improve the heat resistance of molded products by crystallizing the biodegradable polymer. Absent.
[0008]
Patent Document 3 below describes that by adding an inorganic compound such as silica or kaolinite as a filler to a lactide thermoplastic, the properties of hardness, strength, and temperature resistance can be changed. Further, in the example, 5% by weight of calcium lactate was added as a nucleating agent to the L, DL-lactide copolymer and blended for 5 minutes with a heating roll at 170 ° C. to obtain a sheet. It has excellent rigidity and strength, is cloudy, and has an increased crystallinity.
[0009]
Patent Literature 4 below describes that lactic acid or a lactic acid oligomer is useful as a plasticizer for polylactic acid and can lower the glass transition temperature and impart flexibility.
[0010]
Patent Document 5 listed below discloses lactate and benzoate as nucleating agents to be incorporated in a biodegradable composition containing polylactic acid. In Examples, 1% lactic acid is added to a polylactide copolymer. Injection molding was performed in a mold containing calcium and holding at about 85 ° C. for a residence time of 2 minutes. However, due to insufficient crystallinity, it was further described that annealing was performed at about 110 to 135 ° C. in the mold. ing.
[0011]
However, Patent Literature 6 below discloses that, when talc, silica, calcium lactate, or the like is usually added as a nucleating agent to a lactic acid-based polymer and injection molding is attempted, the crystallization speed is low, Since the molded product is brittle, it is not possible to obtain a molded product that can withstand practical use. Therefore, the lactic acid-based polymer is added with ordinary talc, silica, calcium lactate, etc., and is commonly used for injection molding, blow molding, compression molding, etc. It is described that the crystallization rate is low, the practical heat resistance of the obtained molded product is as low as 100 ° C. or less, and the impact resistance is not strong.
[0012]
Patent Document 7 below discloses that polyglycolic acid and / or a derivative thereof are added as a crystal nucleating agent to poly-L-lactide or the like to increase the crystallization rate, thereby shortening the injection molding cycle time. It is described that a molded article having excellent mechanical properties can be obtained.In addition, when injection molding was performed, the crystallinity at a cooling time of 60 seconds was determined when no crystal nucleating agent was added. Is 22.6%, and 45.5% when a nucleating agent is added. However, in Patent Document 6 below, when injection molding was attempted without actually adding a crystal nucleating agent to a lactic acid-based polymer, the condition that the mold temperature was equal to or higher than the glass transition temperature as described in Patent Document 7 was used. States that it could not be molded.
[0013]
Patent Document 8 below proposes to add an effective amount of a stabilizer to a polylactide mixture to reduce the rate of depolymerization at a temperature equal to or higher than the glass transition temperature. Examples of the stabilizer include an antioxidant and a dehydrating agent. Agents, desiccants, and catalyst deactivators are described. Examples of the catalyst deactivator include alkylhydrazine, arylhydrazine, amide, cyclic amide, hydrazone, carboxylic acid hydrazide, bisacylated hydrazine derivative, heterocycle, and bis [3 -(3,5-Ditert-butyl-4-hydroxyphenyl) propionic acid] hydrazide is described as a preferable catalyst deactivator, and although depolymerization in a molten state is suppressed, bis [3- (3,3 5-di-tert-butyl-4-hydroxyphenyl) propionic acid] is excellent in crystallinity and transparency even when hydrazide is added. Engineering can resin composition could not be obtained. That is, even if the catalyst was deactivated, it did not contribute to the improvement of the molding cycle.
[0014]
Further, in Patent Documents 9 to 11 below, a molded product excellent in crystallinity, transparency and heat resistance can be obtained by mixing an aromatic or aliphatic carboxylic acid amide compound with polylactic acid or aliphatic polyester. However, if injection molding or the like is actually performed, molding cannot be performed in a molding cycle comparable to that of a general-purpose resin, and practical application is difficult.
[0015]
[Patent Document 1]
JP-A-60-86156 [Patent Document 2]
JP-A-5-70696 [Patent Document 3]
JP-T-5-504731 (International Publication No. 90/001521 pamphlet)
[Patent Document 4]
US Pat. No. 5,180,765 [Patent Document 5]
Japanese Patent Publication No. 6-504799 [Patent Document 6]
JP-A-8-193165 [Patent Document 7]
JP-A-4-220456 [Patent Document 8]
Japanese Patent Publication No. 7-504939 [Patent Document 9]
Japanese Patent Application Laid-Open No. 9-278991 [Patent Document 10]
Japanese Patent Application Laid-Open No. Hei 10-87975 [Patent Document 11]
JP-A-11-5849
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to obtain a polylactic acid-based resin composition from which a molded article excellent in heat resistance and impact strength can be obtained with good moldability, and the polylactic acid-based resin composition. An object of the present invention is to provide a heat-resistant polylactic acid-based resin molded article and a method for producing the heat-resistant polylactic acid-based resin molded article.
[0017]
[Means for Solving the Problems]
The present invention provides a polylactic acid-based resin composition comprising 100 parts by weight of polylactic acid and 0.01 to 10 parts by weight of a heterocyclic compound represented by any of the following formulas (I) to (VI). Thereby, the above object has been achieved.
[0018]
Embedded image

(Where A ¹ , A ² , A ³ , A ⁴ , A ⁵ , A ⁶ , A ⁷ , A ⁸ , A ⁹ , B ¹ , B ² , B ³ , B ⁴ , B ⁵ , B ⁶ , B ^{6 7} , B ⁸ , B ⁹ , B ¹⁰ , B ¹¹ and B ¹² each independently represent —CH ₂ —, —C (＝ O) —, —C (＝ S) —, —NH—, —NR ₁₃ —, Or -S (= O) _2- , wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , and R ₁₂ are a hydrogen atom A halogen atom, a hydroxy group, an alkyl group having 1 to 18 carbon atoms, an alkenyl group, an alkynyl group, an alkoxy group, a cycloalkyl group, or an aryl group, R ₁₃ represents —NH ₂ , —NHR ₁₄ , —NHC (= O) —R ₁₅ , an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group, or an aryl R ₁₄ and R ₁₅ represent an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group or an aryl group, provided that at ^{least one} of A ¹ , A ² and A ³ is —C (＝ O) — or —C (＝ S) —, wherein at least one is —NH— or —NR ₁₃ —, and at least one of A ⁴ , A ⁵ , and A ⁶ is —C (＝ O) — or —C (＝ S) —, at least one of which is —NH— or —NR ₁₃ —, and at least one of A ⁷ , A ⁸ , and A ⁹ is —C (＝ O) — or —C (＝ S) —, at least one of which is —NH— or —NR ₁₃ —, and any one of B ¹ , B ² , B ³ , and B ⁴ FOB is -C (= O) - or -C (= S) - and is, any one or more -NH- or _{-NR 13} - and ^{is, B} 5, B , Any one or more -C of ^{B 7, B 8 (= O} ) - or -C (= S) -, wherein 1 or more either is -NH- or _{-NR 13} - and is, ^{B 9} , B ¹⁰ , B ¹¹ , and B ¹² are at least one of —C (＝ O) — or —C (＝ S) —, and at least one of them is —NH— or —NR ₁₃ —. .)
[0019]
Further, the present invention has achieved the above-mentioned object by providing the above-mentioned polylactic acid-based resin composition wherein the above-mentioned heterocyclic compound is represented by the above-mentioned general formula (I) or (II).
[0020]
Further, the present invention has achieved the above-mentioned object by providing the above-mentioned polylactic acid-based resin composition wherein the above-mentioned heterocyclic compound is phthalic hydrazide.
[0021]
Further, the present invention has achieved the above-mentioned object by providing the above-mentioned polylactic acid-based resin composition wherein the above-mentioned heterocyclic compound is a compound having a melting point of 300 ° C. or more.
[0022]
Further, the present invention has achieved the above-mentioned object by providing the above-mentioned polylactic acid-based resin composition containing 0.01 to 40 parts by weight of hydrous magnesium silicate (talc).
[0023]
Further, the present invention has achieved the above-mentioned object by providing the above-mentioned polylactic acid-based resin composition wherein the average particle diameter of the above-mentioned hydrous magnesium silicate (talc) is 10 µm or less.
[0024]
Further, the present invention has achieved the above-mentioned object by providing a heat-resistant polylactic acid-based resin molded product obtained by molding the above-mentioned polylactic acid-based resin composition.
[0025]
In addition, the present invention provides a method in which after melting the above-mentioned polylactic acid-based resin composition, the melted polylactic acid-based resin composition is brought into a range of a crystallization start temperature or lower and a glass transition temperature or higher in a scanning differential calorimeter (DSC). The object has been achieved by providing a method for producing a heat-resistant polylactic acid-based resin molded product which is filled in a set mold of a molding machine and molded while being crystallized.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
The polylactic acid-based resin composition of the present invention will be described in detail below.
Examples of the polylactic acid (lactic acid-based polymer) used in the polylactic acid-based resin composition of the present invention include a polylactic acid homopolymer, a polylactic acid copolymer, and a blend polymer of a polylactic acid homopolymer and a polylactic acid copolymer. Further, as long as the crystallinity characteristic of the polylactic acid-based resin composition of the present invention is not impaired, a blend polymer mainly composed of polylactic acid may be used.
[0027]
The weight average molecular weight (Mw) of the polylactic acid is usually 50,000 to 500,000, and preferably 100,000 to 250,000, in terms of polystyrene by gel permeation chromatography. When the weight average molecular weight is less than 50,000, it is difficult to obtain physical properties necessary for practical use. On the other hand, when the weight average molecular weight exceeds 500,000, moldability tends to deteriorate.
[0028]
The constituent molar ratio (L / D) of the L-lactic acid unit and the D-lactic acid unit in the polylactic acid is not particularly limited and can be selected from the range of 100/0 to 0/100, but is high. In order to obtain a polylactic acid-based resin composition having a melting point, at least 75 mol% of either the L-lactic acid unit or the D-lactic acid unit is required. It is preferable to contain 90 mol% or more of either the lactic acid unit or the D-lactic acid unit.
[0029]
The polylactic acid copolymer is obtained by copolymerizing a lactic acid monomer or lactide with another copolymerizable component. Other components include dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones, and the like having two or more ester bond-forming functional groups, and various polyesters, polyethers, polycarbonates, and the like containing these as components. Can be
[0030]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0031]
Examples of the polyhydric alcohol include aromatic polyhydric alcohols such as those obtained by adding ethylene oxide to bisphenol, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, neopentyl. And aliphatic polyhydric alcohols such as glycol, ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol.
[0032]
Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutylcarboxylic acid, and hydroxycarboxylic acids described in JP-A-6-184417.
[0033]
Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, ε-propiolactone, δ-butyrolactone, β-butyrolactone, γ-butyrolactone, pivalolactone, δ-valerolactone, and the like.
[0034]
The polylactic acid used in the polylactic acid-based resin composition of the present invention is not particularly limited in the synthesis method, and can be synthesized by a conventionally known method. For example, JP-A-7-33861 and JP-A-59-33861 can be used. No.-96123, can be synthesized by direct dehydration condensation from a lactic acid monomer or ring-opening polymerization of a lactic acid cyclic dimer lactide described in Polymer Symposium Proceedings, Vol. 44, pp. 3198-3199. .
[0035]
When performing direct dehydration condensation, any lactic acid of L-lactic acid, D-lactic acid, DL-lactic acid, and a mixture thereof may be used. When ring-opening polymerization is performed, any one of L-lactide, D-lactide, DL-lactide, meso-lactide, and a mixture thereof may be used.
[0036]
The synthesis, purification and polymerization procedures of lactide used for ring-opening polymerization are described, for example, in US Pat. No. 4,057,537, EP-A-261572, Polymer Bulletin, 14, 491-495 (1985), and Macromol. Chem. , 187, 1611-1628 (1986).
[0037]
The catalyst used for the polymerization reaction for obtaining the polylactic acid is not particularly limited, but a known catalyst for lactic acid polymerization can be used. Examples of the catalyst include tin lactate, tin tartrate, tin dicaprylate, tin dilaurate, tin dipalmitate, tin distearate, tin dioleate, tin α-naphthoate, β-tin naphthoate, tin octylate, and the like. Tin compounds, powdered tin, tin oxide, zinc powder, zinc halide, zinc oxide, organic zinc compounds, titanium compounds such as tetrapropyl titanate, zirconium compounds such as zirconium isopropoxide, antimony trioxide and the like Examples include antimony compounds, bismuth compounds such as bismuth (III) oxide, aluminum compounds such as aluminum oxide and aluminum isopropoxide.
[0038]
Among these, a catalyst composed of tin or a tin compound is particularly preferred from the viewpoint of activity. The amount of the catalyst used is, for example, about 0.001 to 5% by weight based on lactide when performing ring-opening polymerization.
[0039]
The polymerization reaction can be usually performed at 100 to 220 ° C. in the presence of the above-mentioned catalyst, depending on the type of the catalyst. It is also preferable to perform two-stage polymerization described in, for example, JP-A-7-247345.
[0040]
In addition, the blend polymer mainly composed of polylactic acid is, for example, a polylactic acid homopolymer and / or a polylactic acid copolymer mixed with an aliphatic polyester other than polylactic acid (hereinafter, simply referred to as “aliphatic polyester”). It is a mixture obtained by melting. It is preferable to blend the above aliphatic polyester because flexibility and impact resistance can be imparted to the molded product. The mixing ratio in the blend polymer is usually about 10 to 100 parts by weight of the aliphatic polyester per 100 parts by weight of the polylactic acid homopolymer and / or polylactic acid copolymer.
[0041]
The aliphatic polyester may be a single polymer or a composite of two or more polymers. Examples of the polymer include a polymer composed of an aliphatic carboxylic acid and an aliphatic alcohol, and an aliphatic hydroxycarboxylic acid polymer obtained by ring-opening polymerization of a cyclic anhydride such as ε-caprolactone. Examples of a method for obtaining these polymers include a direct polymerization method of directly polymerizing to obtain a high molecular weight product, and an indirect polymerization method of polymerizing to about an oligomer and then obtaining a high molecular weight product with a chain extender or the like. The aliphatic polyester may be a copolymer or a mixture with another resin as long as the polymer is mainly composed of the aliphatic monomer component.
[0042]
The aliphatic polyester is preferably a polymer composed of an aliphatic dicarboxylic acid and an aliphatic diol. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanoic acid, and anhydrides and derivatives thereof, and examples of the aliphatic diol include ethylene glycol and butanediol. And glycol-based compounds such as hexanediol, octanediol, and cyclohexanedimethanol, and derivatives thereof. Each of the aliphatic dicarboxylic acid and the aliphatic diol is preferably a monomer having an alkylene group, a cyclocyclic group or a cycloalkylene group having 2 to 10 carbon atoms. The aliphatic polyester is preferably produced by polycondensation of a monomer component selected from each of these aliphatic dicarboxylic acids and aliphatic diols. Any of the above aliphatic dicarboxylic acids and the above aliphatic diols may be used in combination of two or more.
[0043]
Further, for the purpose of providing a branch in the polymer used as the aliphatic polyester for improving the melt viscosity, a trifunctional or higher polyfunctional carboxylic acid, alcohol or hydroxycarboxylic acid is used as a monomer component constituting the polymer. It does not matter. When these polyfunctional monomer components are used in a large amount, the resulting polymer has a crosslinked structure and may not be thermoplastic, or a microgel having a partially highly crosslinked structure may be produced even if it is thermoplastic. . Therefore, these polyfunctional monomer components are used in such an amount that the content of the polyfunctional monomer component in the polymer is extremely small and does not greatly affect the chemical and physical properties of the polymer. As the polyfunctional monomer component, malic acid, tartaric acid, citric acid, trimellitic acid, pyromellitic acid, pentaerythritol, trimethylolpropane, and the like can be used.
[0044]
Among the methods for producing the polymer used as the aliphatic polyester, in the direct polymerization method, a monomer component is selected, and a high molecular weight product is obtained while removing water contained in the monomer component or generated during polymerization. Is the way. In the indirect polymerization method, a monomer component is selected, and after polymerization into an oligomer, a small amount of a chain extender, for example, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, etc., for the purpose of increasing the molecular weight. This is a method of increasing the molecular weight using a diisocyanate compound. In addition to these methods, a method of obtaining an aliphatic polyester carbonate using a carbonate compound or the like may be used.
[0045]
Further, in the polylactic acid-based resin composition of the present invention, the polylactic acid may be blended with a general-purpose resin other than polylactic acid, if necessary, for improving impact strength and the like. As general-purpose resins, resins having elasticity such as ethylene-propylene copolymer rubber and ethylene-propylene-diene copolymer are preferable.
[0046]
In the polylactic acid-based resin composition of the present invention, the compound represented by the general formula (I) is blended with the above-described polylactic acid as a crystal nucleating agent. The compound represented by the general formula (I) is a heterocyclic compound having a carboxyl group and an amino group in a ring structure.
[0047]
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R _14, and R in the general formula (I) Examples of the alkyl group having 1 to 18 carbon atoms represented by ₁₅ include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, tert-pentyl, hexyl, heptyl, octyl, and isooctyl. Tert-octyl, 2-ethylhexyl, nonyl, isononyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl and the like. Alkenyl groups include, for example, vinyl, propenyl, butenyl, octenyl, oleyl and the like. Examples of the cycloalkyl group include cyclopentyl, cyclohexyl, cycloheptyl and the like.
[0048]
1 carbon atom represented by R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ and R ₁₂ in the general formula (I). Examples of the alkoxy group of Nos. 1 to 18 include an alkoxy group corresponding to the above-mentioned alkyl group.
[0049]
As the halogen atom represented by R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ and R ₁₂ in the general formula (I), , Fluorine, chlorine, bromine and the like.
[0050]
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R _14, and R in the general formula (I) Examples of the aryl group having 6 to 18 carbon atoms represented by ₁₅ include phenyl, naphthyl, biphenyl and the like.
[0051]
More specifically, as the compound represented by the above general formula (I), the following compound No. 1 to 10 and the like. However, the present invention is not limited at all by the following compounds.
[0052]
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[0053]
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[0054]
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[0055]
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[0056]
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[0057]
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[0058]
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[0059]
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[0060]
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[0061]
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[0062]
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[0063]
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[0064]
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[0065]
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[0066]
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[0067]
In the polylactic acid-based resin composition of the present invention, the compound represented by the general formula (I) is used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the polylactic acid. Parts, more preferably 0.1 to 3 parts by weight. If the amount is less than 0.01 part by weight, the effect of addition is insufficient. If the amount is more than 10 parts by weight, phenomena such as ejection to the surface of the polylactic acid-based resin composition may occur.
[0068]
It is preferable that the polylactic acid-based resin composition of the present invention further contains hydrous magnesium silicate (talc). The average particle size of the hydrous magnesium silicate (talc) is preferably 10 μm or less, more preferably 1 to 5 μm. Use of hydrous magnesium silicate (talc) having an average particle diameter of more than 10 μm is effective, but when it is 10 μm or less, the effect of promoting the formation of crystal nuclei is higher, and the heat resistance of the molded article can be further improved. .
[0069]
The amount of the hydrous magnesium silicate (talc) is based on 100 parts by weight of the polylactic acid. The content is preferably 0.01 to 40 parts by weight, more preferably 0.01 to 30 parts by weight. If the amount is less than 0.01 part by weight, the effect of the addition is not so obtained. If the amount exceeds 40 parts by weight, not only the specific gravity of the polylactic acid-based resin composition becomes heavy, but also the impact resistance may decrease. There is.
[0070]
Further, the polylactic acid-based resin composition of the present invention may contain, if necessary, conventionally known plasticizers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, pigments, colorants, various fillers, Inhibitors, metal soaps, waxes, mold release agents, fragrances, lubricants, flame retardants, foaming agents, fillers, antibacterial and antifungal agents, crystal nucleating agents other than the compounds represented by the above general formula (I), etc. Various additives may be blended.
[0071]
In the polylactic acid-based resin composition of the present invention, the method of blending the polylactic acid with the compound represented by the general formula (I) and the additive such as the hydrous magnesium silicate (talc) is particularly limited. Instead, it can be performed by a conventionally known method. For example, the polylactic acid powder or pellets and the additive may be mixed by dry blending, or a part of the additive may be preblended and then dry blended with the remaining components. After the dry blending, for example, the mixture may be mixed using a mill roll, a Banbury mixer, a super mixer, or the like, and may be kneaded using a single-screw or twin-screw extruder. The mixing and kneading are usually performed at a temperature of about 150 to 300 ° C. It is also possible to use a method in which an additive is added at the polymerization stage of polylactic acid, a method in which a masterbatch containing the additive at a high concentration is prepared, and the masterbatch is added to polylactic acid.
[0072]
The polylactic acid-based resin composition of the present invention is mainly used as a molding material for various molded articles, like general plastics.
[0073]
The heat-resistant polylactic acid-based resin molded article of the present invention obtained by molding the polylactic acid-based resin composition of the present invention, and the production method of the present invention, which is a preferable production method thereof, will be described below.
[0074]
As a method of crystallizing the polylactic acid-based resin composition, for example, after forming a molded article with the polylactic acid-based resin composition, annealing the molded article at a temperature at which the polylactic acid-based resin composition can be crystallized. Although a method can be mentioned, this method has a drawback that a molded article is easily deformed in a crystallization process in an annealing treatment. In order to solve this drawback, in the production method of the present invention, when molding the polylactic acid-based resin composition of the present invention, the mold of the molding machine can be crystallized with the polylactic acid-based resin composition of the present invention. Temperature and hold it for a certain time.
[0075]
In the production method of the present invention, after melting the polylactic acid-based resin composition of the present invention, the temperature at which the polylactic acid-based resin composition can be crystallized, that is, the temperature at which the crystallization start temperature in DSC is lower than the glass transition temperature or higher. The range is preferably filled with the molten polylactic acid-based resin composition in a mold of a molding machine set to a temperature range equal to or lower than the crystallization start temperature and equal to or higher than the crystallization end temperature, and the crystallization is performed by holding for a predetermined time. And molding. As described above, the polylactic acid-based resin composition of the present invention contains the compound represented by the general formula (I) as a crystal nucleating agent. Thus, crystallization is completed, and a polylactic acid-based resin composition having excellent heat resistance and impact resistance can be obtained.
[0076]
Since the appropriate mold temperature varies depending on the type of polylactic acid and additives contained in the polylactic acid resin composition of the present invention used for molding, the crystallization temperature of the polylactic acid resin composition in advance by the DSC method ( The crystallization peak temperature, the crystallization start temperature, the glass transition temperature, and the crystallization end temperature) are measured, and the temperature range is from the crystallization start temperature to the glass transition temperature or higher, preferably the crystallization start temperature or lower and the crystallization end temperature or higher. Select from a range. Within this temperature range, the polylactic acid-based resin composition of the present invention can be easily crystallized, and a molded article having high dimensional accuracy can be obtained. Outside the steam temperature range, crystallization is slowed down and the solidification time during molding is prolonged, which is not suitable for practical use. The crystallization temperature can be measured, for example, by DSC, by heating 5 mg of a pellet sample from room temperature to 200 ° C. at 50 ° C./min, holding for 5 minutes, and then decreasing the temperature at a rate of 5 ° C./min. .
[0077]
When molding the polylactic acid-based resin composition of the present invention, extrusion molding, injection molding, blow molding, vacuum molding, compression molding and the like can be performed in the same manner as general plastics, and sheets, rods, bottles, Various molded articles such as containers can be easily obtained.
[0078]
The heat-resistant polylactic acid-based resin molded article of the present invention has excellent heat resistance. As the heat resistance index, for example, a low load deflection temperature according to JIS K 7207A method can be used. The low load deflection temperature is the temperature at which the heat transfer medium is heated at a constant rate while applying a bending stress of 0.45 MPa to the test piece in the heating bath, and the test piece reaches a prescribed deflection amount. Temperature. The low-load deflection temperature of the heat-resistant polylactic acid-based resin molded article of the present invention can be appropriately adjusted by the amount of the crystal nucleating agent added depending on the use of the molded article. Even when used as a part that is not exposed, the temperature is preferably 80 ° C. or higher for practical use, more preferably 90 ° C. or higher, and most preferably 100 ° C. or higher.
[0079]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and the like.
[0080]
[Examples 1 to 3 and Comparative Example 1]
The blending components shown in Table 1 were dry-blended, melt-mixed on a biaxial kneading extruder at 200 ° C. for an average of 4 minutes, extruded into a strand from a die, cooled with water, cut, and a polylactic acid resin containing a crystal nucleating agent A pellet of the composition was obtained.
[0081]
With respect to the obtained pellets, the crystallization peak temperature and the heat of crystallization were measured. In these measurements, 5 mg of the pellet sample was heated from room temperature to 200 ° C. at 50 ° C./min by DSC (Diamond DSC, manufactured by Perkin Elmer), held for 5 minutes, and then measured at a cooling rate of 5 ° C./min. did. Table 1 shows the measurement results.
[0082]
Next, the obtained pellets were vacuum-dried at 80 ° C. to make them absolutely dry, then the mold temperature was kept at 110 ° C., the cooling time was kept at 120 seconds, and JIS K 7110 (No. 1A test piece) was injected. ) Was evaluated at the time of mold release. In the evaluation, the presence / absence and degree of adhesion to the mold and the presence / absence and degree of deformation at the time of releasing the test piece were visually confirmed. The evaluation criteria were as follows: ◎: no adhesion of the mold and no deformation, ○: slightly sticking to the mold, ○: no deformation, ○: sticking to the mold, clearly deformed Those that were large and deformed because they were difficult to release and stuck to the mold were marked as x. Table 1 shows the evaluation results.
[0083]
The components in Table 1 are as follows.
Polylactic acid: manufactured by Toyota Motor Corporation, trade name "# 5400", weight average molecular weight 160,000 (polystyrene equivalent by gel permeation chromatography analysis)
Talc: Nippon Talc Co., Ltd., fine powder talc, trade name "Micro Ace P-6"
Compound No. 1: phthalic hydrazide (melting point> 300 ° C)
Compound No. 2: Maleic hydrazide (melting point> 260 ° C (decomposition))
Compound No. 3: Saccharin (melting point = 230 ° C)
Comparative compound 1: bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] hydrazide (melting point = 228 ° C.)
[0084]
[Table 1]

[0085]
As is clear from Table 1, when the injection molded article was obtained using the polylactic acid-based resin composition of the present invention in which the specific heterocyclic compound was blended, the moldability was excellent and there was no deformation at the time of mold release. (Examples 1 to 3). On the other hand, the polylactic acid-based resin composition containing the hydrazide compound as the conventional catalyst deactivator had a heat of crystallization of less than 40 J / g and was poor in moldability (Comparative Example 1).
[0086]
【The invention's effect】
According to the present invention, a polylactic acid-based resin composition having a high crystallization rate can be provided by blending a specific heterocyclic compound as a crystal nucleating agent with polylactic acid, and the polylactic acid-based resin composition can be provided. From this, a heat-resistant polylactic acid-based resin molded product having excellent bending strength and impact strength can be obtained with good moldability. According to the present invention, the polylactic acid-based resin composition is crystallized in a mold. It is possible to provide a simple and highly efficient production method of a heat-resistant polylactic acid-based resin molded product.

Claims (8)

A polylactic acid resin composition comprising 100 parts by weight of polylactic acid and 0.01 to 10 parts by weight of a heterocyclic compound represented by any of the following formulas (I) to (VI).

(Where A ¹ , A ² , A ³ , A ⁴ , A ⁵ , A ⁶ , A ⁷ , A ⁸ , A ⁹ , B ¹ , B ² , B ³ , B ⁴ , B ⁵ , B ⁶ , B ^{6 7} , B ⁸ , B ⁹ , B ¹⁰ , B ¹¹ and B ¹² each independently represent —CH ₂ —, —C (＝ O) —, —C (＝ S) —, —NH—, —NR ₁₃ —, Or -S (= O) _2- , wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , and R ₁₂ are a hydrogen atom A halogen atom, a hydroxy group, an alkyl group having 1 to 18 carbon atoms, an alkenyl group, an alkynyl group, an alkoxy group, a cycloalkyl group, or an aryl group, R ₁₃ represents —NH ₂ , —NHR ₁₄ , —NHC (= O) —R ₁₅ , an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group, or an aryl R ₁₄ and R ₁₅ represent an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group or an aryl group, provided that at ^{least one} of A ¹ , A ² and A ³ is —C (＝ O) — or —C (＝ S) —, wherein at least one is —NH— or —NR ₁₃ —, and at least one of A ⁴ , A ⁵ , and A ⁶ is —C (＝ O) — or —C (＝ S) —, at least one of which is —NH— or —NR ₁₃ —, and at least one of A ⁷ , A ⁸ , and A ⁹ is —C (＝ O) — or —C (＝ S) —, at least one of which is —NH— or —NR ₁₃ —, and any one of B ¹ , B ² , B ³ , and B ⁴ FOB is -C (= O) - or -C (= S) - and is, any one or more -NH- or _{-NR 13} - and ^{is, B} 5, B , Any one or more -C of ^{B 7, B 8 (= O} ) - or -C (= S) -, wherein 1 or more either is -NH- or _{-NR 13} - and is, ^{B 9} , B ¹⁰ , B ¹¹ , and B ¹² are at least one of —C (＝ O) — or —C (＝ S) —, and at least one of them is —NH— or —NR ₁₃ —. .) The polylactic acid-based resin composition according to claim 1, wherein the heterocyclic compound is represented by the general formula (I) or (II). The polylactic acid-based resin composition according to claim 1, wherein the heterocyclic compound is phthalic hydrazide. The polylactic acid-based resin composition according to claim 1, wherein the heterocyclic compound is a compound having a melting point of 300 ° C or higher. The polylactic acid-based resin composition according to claim 1, further comprising 0.01 to 40 parts by weight of hydrous magnesium silicate (talc). The polylactic acid-based resin composition according to claim 5, wherein the average particle diameter of the hydrous magnesium silicate (talc) is 10 µm or less. A heat-resistant polylactic acid resin molded article obtained by molding the polylactic acid resin composition according to claim 1. After melting the polylactic acid-based resin composition according to any one of claims 1 to 6, the melted polylactic acid-based resin composition is heated to a glass transition temperature equal to or lower than a crystallization start temperature in a scanning differential calorimeter (DSC). A method for producing a heat-resistant polylactic acid-based resin molded product, which is charged into a mold of a molding machine set in the above range and molded while being crystallized.