JP3989406B2 - Polylactic acid-based resin composition, molded article and method for producing the same - Google Patents

Description

（式中、Ｒ ₁ 、Ｒ ₂ 、Ｒ ₃ およびＲ ₄ は各々独立に芳香族１価カルボン酸残基を、Ｒは脂肪族２価カルボン酸残基を表す。）

（式中、Ｒ ₅ およびＲ ₆ 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表す。）
【００２１】
また、本発明は、上記ヒドラジド化合物が融点３００℃以上の化合物である請求項１記載のポリ乳酸系樹脂組成物（請求項２）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、上記ヒドラジド化合物がドデカンジオイック酸ビス（２−（２−ヒドロキシベンゾイル）ヒドラジド）である請求項１記載のポリ乳酸系樹脂組成物（請求項３）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、上記ヒドラジド化合物がフタル酸ヒドラジドである請求項１記載のポリ乳酸系樹脂組成物（請求項４）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、含水珪酸マグネシウム（タルク）０．０１〜４０重量部を配合した請求項１〜４のいずれかに記載のポリ乳酸系樹脂組成物（請求項５）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】
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以下である請求項５記載のポリ乳酸系樹脂組成物（請求項６）を提供することにより、上記目的を達成したものである。
【００２７】
また、本発明は、請求項１〜６のいずれかに記載の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（請求項７）を提供することにより、上記目的を達成したものである。
【００２８】
また、本発明は、請求項１〜６のいずれかに記載の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（請求項１１）を提供することにより、上記目的を達成したものである。
【００２９】
【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。
【００３０】
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。
【００３１】
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。
【００３２】
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。
【００３３】
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。
【００３４】
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。
【００３５】
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。
【００３６】
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。
【００３７】
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。
【００３８】
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。
【００３９】
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。
【００４０】
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。
【００４１】
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。
【００４２】
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。
【００４３】
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。
【００４４】
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。
【００４５】
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。
【００４６】
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。
【００４７】
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。
【００４８】
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。
【００４９】
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、フェノール系酸化防止剤とアミド系化合物が配合される。
【００５０】
本発明に用いられるフェノール系酸化防止剤としては、特に限定されず、例えば、２，６−ジ第三ブチル−ｐ−クレゾール、２，６−ジフェニル−４−オクタデシロキシフェノール、ステアリル（３，５−ジ第三ブチル−４−ヒドロキシフェニル）プロピオネート、ジステアリル（３，５−ジ第三ブチル−４−ヒドロキシベンジル）ホスホネート、トリデシル・３，５−ジ第三ブチル−４−ヒドロキシベンジルチオアセテート、チオジエチレンビス［（３，５−ジ第三ブチル−４−ヒドロキシフェニル）プロピオネート］、４，４’−チオビス（６−第三ブチル−ｍ−クレゾール）、２−オクチルチオ−４，６−ジ（３，５−ジ第三ブチル−４−ヒドロキシフェノキシ）−ｓ−トリアジン、２，２’−メチレンビス（４−メチル−６−第三ブチルフェノール）、ビス[３，３−ビス（４−ヒドロキシ−３−第三ブチルフェニル）ブチリックアシッド]グリコールエステル、４，４’−ブチリデンビス（２，６−ジ第三ブチルフェノール）、４，４’−ブチリデンビス（６−第三ブチル−３−メチルフェノール）、２，２’−エチリデンビス（４，６−ジ第三ブチルフェノール）、１，１，３−トリス（２−メチル−４−ヒドロキシ−５−第三ブチルフェニル）ブタン、ビス[２−第三ブチル−４−メチル−６−（２−ヒドロキシ−３−第三ブチル−５−メチルベンジル）フェニル]テレフタレート、１，３，５−トリス（２，６−ジメチル−３−ヒドロキシ−４−第三ブチルベンジル）イソシアヌレート、１，３，５−トリス（３，５−ジ第三ブチル−４−ヒドロキシベンジル）イソシアヌレート、１，３，５−トリス（３，５−ジ第三ブチル−４−ヒドロキシベンジル）−２，４，６−トリメチルベンゼン、１，３，５−トリス[（３，５−ジ第三ブチル−４−ヒドロキシフェニル）プロピオニルオキシエチル]イソシアヌレート、テトラキス[メチレン−３−（３’，５’−ジ第三ブチル−４’−ヒドロキシフェニル）プロピオネート]メタン、２−第三ブチル−４−メチル−６−（２−アクロイルオキシ−３−第三ブチル−５−メチルベンジル）フェノール、３，９−ビス[２−（３−第三ブチル−４−ヒドロキシ−５−メチルヒドロシンナモイルオキシ）−１，１−ジメチルエチル]−２，４，８，１０−テトラオキサスピロ［５．５］ウンデカン、トリエチレングリコールビス［β−（３−第三ブチル−４−ヒドロキシ−５−メチルフェニル）プロピオネート］等が挙げられる。特に、１，３，５−トリス（２，６−ジメチル−３−ヒドロキシ−４−第三ブチルベンジル）イソシアヌレート、１，３，５−トリス（３，５−ジ第三ブチル−４−ヒドロキシベンジル）イソシアヌレート、１，３，５−トリス（３，５−ジ第三ブチル−４−ヒドロキシベンジル）−２，４，６−トリメチルベンゼン、１，３，５−トリス[（３，５−ジ第三ブチル−４−ヒドロキシフェニル）プロピオニルオキシエチル]イソシアヌレート、テトラキス[メチレン−３−（３’，５’−ジ第三ブチル−４’−ヒドロキシフェニル）プロピオネート]メタンなどが結晶化ピーク温度が高く、結晶化熱量が大きく、成形加工サイクルに優れたポリ乳酸系樹脂組成物が得られるので好ましい。
【００５１】
上記フェノール系酸化防止剤はポリ乳酸系樹脂１００重量部に対して０．０１〜１０重量部、好ましくは０．０３〜５重量部、より好ましくは０．０５〜３重量部配合する。０．０１未満では添加した効果が十分に得られず、１０重量部より多く配合すると得られる樹脂組成物の機械強度が不足したり、着色したりする。
【００５５】
（ｂ−３）鎖状ヒドラジドとしては、下記一般式（Ｉ）または（II）で表される化合物が挙げられる。
【００５６】
【化３】

（式中、Ｒ ₁ 、Ｒ ₂ 、Ｒ ₃ およびＲ ₄ は各々独立に芳香族１価カルボン酸残基を、Ｒは脂肪族２価カルボン酸残基を表す。）
【００５７】
Ｒ ₁ 、Ｒ ₂ 、Ｒ ₃ およびＲ ₄ で表される芳香族１価カルボン酸としては、安息香酸、４−ブチル安息香酸、サリチル酸、ナフチル酸などの芳香族酸が挙げられ、Ｒで表される脂肪族２価カルボン酸としては、コハク酸、アジピン酸、アゼライン酸、セバシン酸等が挙げられる。
【００５８】
（ｂ−４）環状ヒドラジドは、下記一般式（ III ）で表される化合物であり、具体的には、フタル酸ヒドラジドなどが挙げられる。
【化４】

（式中、Ｒ ₅ およびＲ ₆ 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表す。）
【００５９】
一般式（Ｉ）〜（III）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及び２が挙げられる。ただし、以下の化合物により本発明はなんら制限されるものではない。
【００６０】
【化５】

【００７６】
【化６】

【００７７】
本発明のポリ乳酸系樹脂組成物において、（Ｂ）成分は、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。
【００７８】
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。
【００７９】
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。
【００８０】
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。
【００８１】
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。
【００８２】
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。
【００８３】
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。
【００８４】
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成形した後、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。
【００８５】
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。
【００８６】
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。上記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２３０℃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。
【００８７】
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。
【００８８】
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。
【００８９】
【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。
【００９０】
［実施例１〜５及び比較例１〜２］
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。
【００９１】
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２３０℃まで昇温し、１０分間保持した後、５℃／分の降温速度で測定した。結晶化ピーク温度が高いほど成形サイクルに優れ、結晶化熱量が大きいほど結晶化が促進されて透明性に優れる樹脂組成物が得られることを示す。これらの測定結果を表１に示す。
【００９２】
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。
【００９３】
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」フェノール系酸化防止剤として
化合物Ｎｏ．１：１，３，５−トリス（３，５−ジ第三ブチル−４−ヒドロキシベンジル）イソシアヌレート
化合物Ｎｏ．２：テトラキス［メチレン−３−（３'，５'−ジ第三ブチル−４'−ヒドロキシフェニル）プロピオネート］メタン
化合物Ｎｏ．３：１，３，５−トリス（３，５−ジ第三ブチル−４−ヒドロキシベンジル）−２，４，６−トリメチルベンゼン
アミド系化合物として
化合物Ｎｏ．４：旭電化工業株式会社製：アデカスタブＣＤＡ−６（下記〔化７〕で表される化合物）、融点＝２１２℃
【００９４】
【化７】

【００９５】
化合物Ｎｏ．５：フタル酸ヒドラジド、融点＞３００℃
化合物Ｎｏ．６：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℃
【００９６】
【表１】

【００９７】
表１から明らかなように、フェノール系酸化防止剤と特定のヒドラジド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、結晶化ピーク温度が高く、結晶化熱量が大きく、成形性に優れ、離型時の変形もなかった（実施例１〜４）。これに対し、フェノール系酸化防止剤単独や従来の触媒脱活剤であるヒドラジド化合物単独では得られるポリ乳酸系樹脂組成物は、結晶化ピーク温度が１２０℃未満で、結晶化熱量が４０Ｊ／ｇ未満で、成形性が悪かった（比較例１および２）。なお、実施例５は参考例である。
【００９８】
【発明の効果】
本発明によれば、ポリ乳酸に、フェノール系酸化防止剤と特定のヒドラジド化合物を配合することにより、結晶化速度が速い成形性に優れた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は、成形サイクルに優れることが期待できる。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]
BACKGROUND OF THE INVENTION
The present invention provides a polylactic acid resin composition in which a molded article having excellent impact strength and heat resistance is obtained with good moldability, a heat resistant polylactic acid resin molded article obtained from the polylactic acid resin composition, and the The present invention relates to a method for producing a heat-resistant polylactic acid resin molded product.
[0002]
[Prior art]
In recent years, from the viewpoint of protecting the natural environment, biodegradable polymers that decompose in the natural environment and molded articles molded from biodegradable polymers have been demanded, and research on biodegradable polymers such as aliphatic polyesters has been actively conducted. Has been done. In particular, a lactic acid polymer has a sufficiently high melting point of 140 to 180 ° C. and is excellent in transparency, and therefore is highly expected as a packaging material or a molded product utilizing transparency.
[0003]
However, a container obtained by injection molding of a lactic acid polymer is excellent in rigidity, but has low heat resistance, or may have both low heat resistance and impact resistance. For example, when a packaging container is used. Cannot use hot water or a microwave oven, and its application is limited.
[0004]
In order to obtain a molded product having heat resistance, it was necessary to cool the mold for a long time during molding or to anneal the molded product after molding to highly crystallize the resin. However, a long cooling process at the time of molding is not practical and crystallization tends to be insufficient, and crystallization by annealing after molding tends to be deformed in the process of crystallizing the molded product. There is a drawback.
[0005]
Further, as a method for increasing the crystallization speed of a resin, for example, in Patent Document 1 below, terephthalic acid and resorcin are used as main structural units as a crystal nucleating agent in order to promote crystallization of polyethylene terephthalate (PET). The addition of a wholly aromatic polyester fine powder is described. As described above, a method of adding a crystal nucleating agent in order to promote crystallization of a resin is generally known.
[0006]
On the other hand, the following Patent Documents 2 to 11 describe adding an additive such as a crystal nucleating agent to a biodegradable polymer.
[0007]
In Patent Document 2 below, calcium carbonate or talc having an average particle size of 20 μm or less is added to a biodegradable plastic such as a poly-3-hydroxybutyrate / poly-3-hydroxyvalerate copolymer, polycaprolactone, or polylactic acid. The material of the plastic container formed by mixing 10 to 40% by weight is disclosed. However, this technology promotes the decomposition of the biodegradable plastic after disposal by adding a large amount of inorganic filler, and does not improve the heat resistance of the molded product by crystallizing the biodegradable polymer. Absent.
[0008]
Patent Document 3 below describes that the properties of hardness, strength, and temperature resistance can be changed by adding an inorganic compound such as silica or kaolinite as a filler to lactide thermoplastics, Moreover, in the Example, when 5 weight% of calcium lactate was added to L, DL-lactide copolymer as a crystal nucleating agent, and it blended for 5 minutes with a 170 degreeC heating roll, the sheet | seat was obtained. It is described that it has excellent rigidity and strength, is cloudy, and has an increased crystallinity.
[0009]
Patent Document 4 listed 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 describes lactate and benzoate as crystal nucleating agents blended in a biodegradable composition containing polylactic acid. In the examples, 1% lactic acid is added to polylactide copolymer. It was described that injection molding was performed with a mold containing calcium and held at about 85 ° C. with a residence time of 2 minutes, but because of insufficient crystallinity, it was further annealed at about 110-135 ° C. in the mold. ing.
[0011]
However, in Patent Document 6 below, when talc, silica, calcium lactate, or the like is added to a lactic acid polymer as a crystal nucleating agent and injection molding is attempted, the crystallization rate is low, Since the molded product is brittle, it is impossible to obtain a molded product that can withstand practical use. Therefore, lactic acid-based polymers can be added to ordinary talc, silica, calcium lactate, etc., and general injection molding, blow molding, compression molding, etc. Even if it is used, the crystallization speed is slow, the practical heat resistance of the resulting molded article is as low as 100 ° C. or less, and the impact resistance is not strong.
[0012]
Further, in Patent Document 7 below, polyglycolic acid and / or a derivative thereof is added to poly L-lactide or the like as a crystal nucleating agent to increase the crystallization speed, thereby shortening the injection molding cycle time. In addition, it is described that a molded product having excellent mechanical properties can be obtained, and when it is injection molded, the crystallinity at a cooling time of 60 seconds is obtained when no crystal nucleating agent is added. Is 22.6%, and 45.5% when a crystal 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 is equal to or higher than the glass transition temperature as described in Patent Document 7 is used. Describes that it could not be molded.
[0013]
Patent Document 8 below proposes adding an effective amount of a stabilizer to the polylactide mixture in order to reduce the depolymerization reaction rate above the glass transition temperature. Agents, desiccants and catalyst deactivators are described. Examples of the catalyst deactivators include alkyl hydrazines, aryl hydrazines, amides, cyclic amides, hydrazones, carboxylic acid hydrazides, bisacylated hydrazine derivatives, and heterocyclic rings. -(3,5-ditert-butyl-4-hydroxyphenyl) propionic acid] hydrazide is described as a preferred catalyst deactivator and depolymerization in the molten state is suppressed, but bis [3- (3 5-di-tert-butyl-4-hydroxyphenyl) propionic acid] hydrazide is excellent in crystallinity and transparency even with the addition of a general-purpose resin molding cycle 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]
Furthermore, in the following Patent Documents 9 to 11, a molded article having excellent crystallinity, transparency and heat resistance is obtained by mixing an aromatic or aliphatic carboxylic acid amide compound with polylactic acid or aliphatic polyester. However, when injection molding or the like is actually performed, it cannot be molded in a molding cycle similar to that of general-purpose resins, and practical application is difficult.
[0015]
Patent Document 12 discloses that phenolic antioxidants such as 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) isocyanurate are effective for stabilizing polylactic acid. Is described.
[0016]
[Patent Document 1]
JP-A-60-86156 [Patent Document 2]
JP-A-5-70696 [Patent Document 3]
No. 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]
JP 7-504939 A [Patent Document 9]
JP-A-9-278991 [Patent Document 10]
Japanese Patent Laid-Open No. 10-87975 [Patent Document 11]
Japanese Patent Laid-Open No. 11-5849 [Patent Document 12]
Japanese Patent Laid-Open No. 10-158370
[Problems to be solved by the invention]
Accordingly, the object of the present invention is to solve the above-mentioned problems of the prior art and to obtain a molded product excellent in heat resistance and impact strength with good moldability, and the polylactic acid-based resin composition. The object is to provide a heat-resistant polylactic acid-based resin molded product and a method for producing the heat-resistant polylactic acid-based resin molded product.
[0018]
[Means for Solving the Problems]
In the present invention, 100 parts by weight of polylactic acid is selected from (A) 0.01 to 10 parts by weight of a phenolic antioxidant, and (B) (b-3) a chain hydrazide and (b-4) a cyclic hydrazide. A polylactic acid resin composition containing 0.01 to 10 parts by weight of one or more hydrazide compounds, wherein the (b-3) chain hydrazide is represented by the following general formula (I) or ( II ): the (b-4) cyclic hydrazide, by providing the following general formula (III) polylactic acid resin composition you express at (claim 1), in which to achieve the above objects.
[Chemical formula 2]

( Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents an aromatic monovalent carboxylic acid residue, and R represents an aliphatic divalent carboxylic acid residue. )

( Wherein R ₅ and R ₆ represent 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. )
[0021]
Further, the present invention is to provide the hydrazide compound is provided polylactic acid resin composition of claim 1 wherein the compound of above the melting point 300 ° C. (the second aspect), in which to achieve the above objects.
[0022]
Moreover, this invention provides the polylactic acid-type resin composition (Claim 3 ) of Claim 1 whose said hydrazide compound is dodecandioic acid bis (2- (2-hydroxybenzoyl) hydrazide), The above objective has been achieved.
[0023]
Moreover, this invention achieves the said objective by providing the polylactic acid-type resin composition (Claim 4 ) of Claim 1 whose said hydrazide compound is a phthalic hydrazide.
[0025]
Further, the present invention is to provide a hydrated magnesium silicate (talc) 0.01 to 40 parts by weight of polylactic acid based resin composition according to any one of claims 1-4 formulated with (Claim 5), The above objective has been achieved.
[0026]
Moreover, this invention achieved the said objective by providing the polylactic acid-type resin composition (Claim 6 ) of Claim 5 whose average particle diameter of the said hydrous magnesium silicate (talc) is 10 micrometers or less. Is.
[0027]
In addition, the present invention provides the above-mentioned object by providing a heat-resistant polylactic acid resin molded product (invention 7 ) formed by molding the polylactic acid resin composition according to any one of claims 1 to 6. Achieved.
[0028]
Moreover, this invention melts the polylactic acid-type resin composition in any one of Claims 1-6 , and crystallizes this molten polylactic acid-type resin composition in a scanning differential calorimeter (DSC). was filled in a mold of the set in a range of more than starting temperature below the glass transition temperature of the molding machine, by providing a heat-resistant polylactic acid production method of the resin molded article for molding while crystallization (claim 11), The above objective has been achieved.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
The polylactic acid 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 polylactic acid homopolymers, polylactic acid copolymers, and blend polymers of polylactic acid homopolymers and polylactic acid copolymers. In addition, a blend polymer containing polylactic acid as a main component may be used as long as the crystallinity characteristic of the polylactic acid resin composition of the present invention is not impaired.
[0030]
The weight average molecular weight (Mw) of the polylactic acid is a polystyrene equivalent value determined by gel permeation chromatography analysis, and is usually 50,000 to 500,000, preferably 100,000 to 250,000. If the weight average molecular weight is less than 50,000, it is difficult to obtain practically required physical properties. On the other hand, if the weight average molecular weight exceeds 500,000, the moldability tends to deteriorate.
[0031]
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 resin composition having a melting point, either L-lactic acid unit or D-lactic acid unit is 75 mol% or more, and in order to obtain a polylactic acid resin composition having a higher melting point, L- It is preferable to contain 90 mol% or more of either lactic acid units or D-lactic acid units.
[0032]
The polylactic acid copolymer is obtained by copolymerizing a lactic acid monomer or lactide and another copolymerizable component. Examples of other components include dicarboxylic acids having two or more functional groups capable of forming an ester bond, polyhydric alcohols, hydroxycarboxylic acids, lactones, and the like, and various polyesters, polyethers, polycarbonates, and the like comprising these as constituent components. It is done.
[0033]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0034]
Examples of the polyhydric alcohol include aromatic polyhydric alcohols such as those obtained by addition reaction of bisphenol with ethylene oxide, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, neopentyl. Examples include aliphatic polyhydric alcohols such as glycol, ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol.
[0035]
Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutylcarboxylic acid, and hydroxycarboxylic acid described in JP-A-6-184417.
[0036]
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.
[0037]
The polylactic acid used in the polylactic acid 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. It 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 JP-96123A, Polymer Proceedings Vol. 44, 3198-3199, etc. .
[0038]
When direct dehydration condensation is performed, 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.
[0039]
Synthesis, purification and polymerization operations of lactide used in ring-opening polymerization are described in, for example, US Pat. No. 4,057,537, European Patent Application No. 261572, Polymer Bulletin, 14, 491-495 (1985), and Macromol. Chem. 187, 1611-1628 (1986).
[0040]
The catalyst used in 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, dicaprylate, dilaurate, dipalmitate, distearate, dioleate, alpha-naphthoate, beta-naphthoate, and octylate. Tin compounds, powder 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, etc. Examples thereof include antimony compounds, bismuth compounds such as bismuth (III) oxide, and aluminum compounds such as aluminum oxide and aluminum isopropoxide.
[0041]
Among these, a catalyst made of tin or a tin compound is particularly preferable from the viewpoint of activity. The amount of the catalyst used is, for example, about 0.001 to 5% by weight with respect to lactide when ring-opening polymerization is performed.
[0042]
The polymerization reaction can be usually performed at 100 to 220 ° C. in the presence of the catalyst, although it varies depending on the type of the catalyst. It is also preferable to carry out the two-stage polymerization described in, for example, JP-A-7-247345.
[0043]
The blend polymer mainly composed of polylactic acid is, for example, a mixture of a polylactic acid homopolymer and / or a polylactic acid copolymer and an aliphatic polyester other than polylactic acid (hereinafter simply referred to as “aliphatic polyester”). It is a mixture obtained by melting. Blending the aliphatic polyester is preferable 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 with respect to 100 parts by weight of the polylactic acid homopolymer and / or polylactic acid copolymer.
[0044]
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 for directly polymerizing to obtain a high molecular weight product, and an indirect polymerization method for obtaining a high molecular weight product with a chain extender after polymerization to the extent of an oligomer. The aliphatic polyester may be a copolymer or a mixture with other resins as long as it is a polymer mainly composed of the aliphatic monomer component.
[0045]
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. Examples of the aliphatic diol include ethylene glycol and butanediol. , Glycol 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 monomer components selected from these aliphatic dicarboxylic acids and aliphatic diols. Two or more kinds of the aliphatic dicarboxylic acid and the aliphatic diol may be used.
[0046]
In addition, 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 doesn't matter. When these polyfunctional monomer components are used in a large amount, the resulting polymer has a cross-linked structure and may not be thermoplastic, or even a thermoplastic may produce a microgel partially having a highly cross-linked structure. . Therefore, these polyfunctional monomer components are used in such an extent that the proportion contained in the polymer is very small and does not greatly influence the chemical properties and physical properties of the polymer. As the polyfunctional monomer component, malic acid, tartaric acid, citric acid, trimellitic acid, pyromellitic acid, pentaerythritol, trimethylolpropane, or the like can be used.
[0047]
Among the methods for producing the polymer used as the aliphatic polyester, the direct polymerization method selects a monomer component and obtains a high molecular weight product while removing water contained in the monomer component or generated during the polymerization. Is the method. In the indirect polymerization method, a monomer component is selected, polymerized to an oligomer level, and then a small amount of chain extender such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, etc. for the purpose of increasing 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 may be used.
[0048]
In the polylactic acid 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 the general-purpose resin, an elastic resin such as an ethylene-propylene copolymer rubber or an ethylene-propylene-diene copolymer is preferable.
[0049]
In the polylactic acid resin composition of the present invention, a phenolic antioxidant and an amide compound are blended with the polylactic acid described above.
[0050]
The phenolic antioxidant used in the present invention is not particularly limited, and examples thereof include 2,6-ditert-butyl-p-cresol, 2,6-diphenyl-4-octadecyloxyphenol, stearyl (3, 5-ditert-butyl-4-hydroxyphenyl) propionate, distearyl (3,5-ditert-butyl-4-hydroxybenzyl) phosphonate, tridecyl 3,5-ditert-butyl-4-hydroxybenzylthioacetate Thiodiethylenebis [(3,5-ditert-butyl-4-hydroxyphenyl) propionate], 4,4′-thiobis (6-tert-butyl-m-cresol), 2-octylthio-4,6-di (3,5-ditert-butyl-4-hydroxyphenoxy) -s-triazine, 2,2'-methylenebis (4-methyl-6-tert-butyl) Phenol), bis [3,3-bis (4-hydroxy-3-tert-butylphenyl) butyric acid] glycol ester, 4,4′-butylidenebis (2,6-ditert-butylphenol), 4,4 ′ -Butylidenebis (6-tert-butyl-3-methylphenol), 2,2'-ethylidenebis (4,6-ditert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5) -Tert-butylphenyl) butane, bis [2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-5-methylbenzyl) phenyl] terephthalate, 1,3,5-tris ( 2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) isocyanurate 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 1,3,5-tris [(3,5-ditert-butyl -4-hydroxyphenyl) propionyloxyethyl] isocyanurate, tetrakis [methylene-3- (3 ', 5'-ditert-butyl-4'-hydroxyphenyl) propionate] methane, 2-tert-butyl-4-methyl -6- (2-Acroyloxy-3-tert-butyl-5-methylbenzyl) phenol, 3,9-bis [2- (3-tert-butyl-4-hydroxy-5-methylhydrocinnamoyloxy) -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, triethylene glycol bis [β- (3-tert-butyl-4-hydroxy-5-methylpheny ) Propionate], and the like. In particular, 1,3,5-tris (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, 1,3,5-tris (3,5-ditert-butyl-4-hydroxy Benzyl) isocyanurate, 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 1,3,5-tris [(3,5- Ditertiary butyl-4-hydroxyphenyl) propionyloxyethyl] isocyanurate, tetrakis [methylene-3- (3 ′, 5′-ditertiarybutyl-4′-hydroxyphenyl) propionate] methane, etc. Is preferable because a polylactic acid resin composition having a high crystallization heat amount and an excellent molding process cycle can be obtained.
[0051]
The phenolic antioxidant is blended in an amount of 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, and more preferably 0.05 to 3 parts by weight with respect to 100 parts by weight of the polylactic acid resin. If it is less than 0.01, the added effect cannot be sufficiently obtained, and if it is added in an amount of more than 10 parts by weight, the resulting resin composition lacks the mechanical strength or is colored.
[0055]
(B-3) As chain hydrazide, the compound represented by the following general formula ( I ) or ( II ) is mentioned.
[0056]
[Chemical 3]

( Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents an aromatic monovalent carboxylic acid residue, and R represents an aliphatic divalent carboxylic acid residue. )
[0057]
The R _1, R _2, aromatic monocarboxylic acid represented by R ₃ and R _4, Ahn Ikikosan, 4-butyl benzoic acid, salicylic acid, aromatic acids such as naphthyl acid and the like, with R Examples of the aliphatic divalent carboxylic acid represented include succinic acid, adipic acid, azelaic acid, and sebacic acid .
[0058]
(B-4) cyclic hydrazide de is a compound represented by the following formula (III), and specific examples thereof include phthalic acid hydrazide.
[Formula 4]

( Wherein R ₅ and R ₆ represent 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. )
[0059]
As the compounds represented by the general formulas (I) to ( III ), more specifically, the following compound Nos. 1 and 2 are mentioned. However, this invention is not restrict | limited at all by the following compounds.
[0060]
[Chemical formula 5]

[0076]
[Chemical 6]

[0077]
In the polylactic acid-based resin composition of the present invention, the component (B) is 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, more preferably 0.00 parts, per 100 parts by weight of the polylactic acid. 1 to 3 parts by weight is blended. When the amount is less than 0.01 parts by weight, the effect of addition is insufficient, and when the amount is more than 10 parts by weight, a phenomenon such as ejection on the surface of the polylactic acid resin composition occurs.
[0078]
Moreover, it is preferable to mix | blend hydrous magnesium silicate (talc) with the polylactic acid-type resin composition of this invention. The average particle diameter of the hydrous magnesium silicate (talc) is preferably 10 μm or less, and more preferably 1 to 5 μm. The use of hydrous magnesium silicate (talc) having an average particle diameter exceeding 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 product can be further improved. .
[0079]
The amount of the hydrated magnesium silicate (talc) is preferably 0.01 to 40 parts by weight, more preferably 0.01 to 30 parts by weight with respect to 100 parts by weight of the polylactic acid. If the blending amount is less than 0.01 parts by weight, the effect of addition is not obtained so much that if it exceeds 40 parts by weight, not only the specific gravity of the polylactic acid resin composition becomes heavy, but also the impact resistance may be lowered. There is.
[0080]
Furthermore, the polylactic acid-based resin composition of the present invention includes, as necessary, conventionally known plasticizers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, pigments, colorants, various fillers, charging agents. Inhibitors, metal soaps, waxes, mold release agents, fragrances, lubricants, flame retardants, foaming agents, fillers, antibacterial / antifungal agents, crystal nucleating agents other than the compounds represented by the above general formula (I), etc. Various additives may be blended.
[0081]
In the polylactic acid-based resin composition of the present invention, the method of blending the polylactic acid with an additive such as the compound represented by the general formula (I) and the hydrous magnesium silicate (talc) is particularly limited. Instead, it can be performed by a conventionally known method. For example, polylactic acid powder or pellets and an additive may be mixed by dry blending, or after a part of the additive is preblended, the remaining components may be dry blended. After dry blending, for example, mixing may be performed using a mill roll, a Banbury mixer, a super mixer, or the like, and kneading may be performed using a single screw or twin screw extruder. This mixing and kneading is usually performed at a temperature of about 150 to 300 ° C. In addition, a method of adding an additive in a polymerization step of polylactic acid, a method of preparing a master batch containing the additive at a high concentration, and adding the master batch to polylactic acid can be used.
[0082]
The polylactic acid-based resin composition of the present invention is mainly used as a molding material for various molded products in the same manner as general plastics.
[0083]
The heat-resistant polylactic acid resin molded product of the present invention formed by molding the polylactic acid resin composition of the present invention and the production method of the present invention which is a preferred production method thereof will be described below.
[0084]
As a method for crystallizing the polylactic acid-based resin composition, for example, after molding a molded product with the polylactic acid-based resin composition, the molded product is annealed at a temperature at which the polylactic acid-based resin composition can be crystallized. Although there is a method, this method has a drawback that the molded product is easily deformed during the crystallization process in the annealing treatment. In order to eliminate this drawback, in the production method of the present invention, when the polylactic acid resin composition of the present invention is molded, the mold of the molding machine can be crystallized with the polylactic acid resin composition of the present invention. Set to a suitable temperature and hold for a certain time.
[0085]
In the production method of the present invention, after melting the polylactic acid resin composition of the present invention, the temperature at which the polylactic acid resin composition can be crystallized, that is, the temperature not higher than the crystallization start temperature in DSC and not lower than the glass transition temperature. Crystallization is performed by filling the molten polylactic acid-based resin composition in a mold of a molding machine set in a range, preferably a temperature range of a crystallization start temperature or less and a crystallization end temperature or more, and holding the molten polylactic acid resin composition for a certain period of time. Mold while letting. As described above, the polylactic acid-based resin composition of the present invention contains a compound represented by the above general formula (I) as a crystal nucleating agent. Therefore, according to the production method of the present invention, Thus, crystallization is completed, and a polylactic acid resin composition excellent in heat resistance and impact resistance can be obtained.
[0086]
The appropriate mold temperature varies depending on the type of polylactic acid and additives contained in the polylactic acid-based resin composition of the present invention used for molding, so the crystallization temperature of the polylactic acid-based resin composition (by the DSC method in advance) A crystallization peak temperature, a crystallization start temperature, a glass transition temperature, a crystallization end temperature), and a temperature range not higher than the crystallization start temperature and not lower than the glass transition temperature, preferably not higher than the crystallization start temperature and not lower than the crystallization end temperature. Select from a range. If it is this temperature range, the polylactic acid-type resin composition of this invention will crystallize easily, and also a molded article with a sufficient dimensional accuracy can be obtained. If the temperature is out of the above temperature range, crystallization is slowed and the solidification time at the time of molding becomes long, which is not suitable for practical use. The crystallization temperature can be measured, for example, by DSC, by heating a 5 mg pellet sample at 50 ° C./min from room temperature to 230 ° C. and holding it for 5 minutes, followed by a temperature drop rate of 5 ° C./min. .
[0087]
When molding the polylactic acid-based resin composition of the present invention, it is possible to perform extrusion molding, injection molding, blow molding, vacuum molding, compression molding, and the like similar to general plastics, sheets, bars, bottles, Various molded products such as containers can be easily obtained.
[0088]
The heat-resistant polylactic acid-based resin molded product of the present invention has excellent heat resistance. As an index of heat resistance, for example, a low load deflection temperature in JIS K 7207A method can be used. The low load deflection temperature means that the heat transfer medium is heated when the heat transfer medium is heated at a constant speed while applying a bending stress of 0.45 MPa to the test piece in the heating bath, and the test piece reaches the specified deflection amount. Temperature. The low load deflection temperature of the heat-resistant polylactic acid-based resin molded product of the present invention can be adjusted as appropriate depending on the amount of the crystal nucleating agent depending on the use of the molded product, for example, at a relatively high temperature of household appliances. Even when used as a component that is not exposed, it is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, and most preferably 100 ° C. or higher.
[0089]
【Example】
EXAMPLES 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.
[0090]
[Examples 1-5 and Comparative Examples 1-2]
The blended ingredients shown in Table 1 are dry blended, melted and mixed for an average of 4 minutes in a twin-screw kneading extruder at 200 ° C., extruded into a strand shape from a die, cooled with water, cut, and a polylactic acid resin containing a crystal nucleating agent A pellet of the composition was obtained.
[0091]
About the obtained pellet, the crystallization peak temperature and the crystallization calorie | heat amount were measured. These measurements were carried out by DSC (Perkin Elmer, Diamond DSC), 5 mg of pellet sample was heated from room temperature to 230 ° C. at 50 ° C./min, held for 10 minutes, and then measured at a rate of 5 ° C./min. did. The higher the crystallization peak temperature, the better the molding cycle, and the higher the amount of crystallization heat, the more the crystallization is promoted, indicating that a resin composition having excellent transparency can be obtained. These measurement results are shown in Table 1.
[0092]
Next, the obtained pellets were vacuum-dried at 80 ° C. to make it completely dry, and then the mold temperature was kept at 110 ° C. and the cooling time was kept at 120 seconds, and by injection molding, JIS K 7110 (No. 1A test piece) The mold release property and deformation were 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 are: ◎ non-deformed and non-deformable, slightly sticking to the mold, ○ undeformed, sticking to the mold, and △ clearly deformed The case where it was stuck to the mold and was difficult to release and was large and deformed was designated as x. These evaluation results are shown in Table 1.
[0093]
In addition, the compounding component in Table 1 is as follows, respectively.
Polylactic acid: manufactured by Toyota Motor Corporation, trade name “# 5400”, weight average molecular weight 160,000 (polystyrene conversion value by gel permeation chromatographic analysis)
Talc: Nippon Talc Co., Ltd., fine powder talc, trade name “Microace P-6” as a phenolic antioxidant 1: 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) isocyanurate Compound No. 1 2: Tetrakis [methylene-3- (3 ′, 5′-ditert-butyl-4′-hydroxyphenyl) propionate] methane Compound no. 3: 1,3,5-tris (3,5-ditert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzeneamide compound No. 4: Asahi Denka Kogyo Co., Ltd .: ADK STAB CDA-6 (compound represented by [Chemical Formula 7 ] below), melting point = 212 ° C.
[0094]
[Chemical 7]

[0095]
Compound No. 5: Phthalic acid hydrazide, melting point> 300 ° C.
Compound No. 6: Bis [3- (3,5-ditert-butyl-4-hydroxyphenyl) propionic acid] hydrazide, melting point = 228 ° C.
[0096]
[Table 1]

[0097]
As apparent from Table 1, if a particular hydrazide compound with a phenolic antioxidant to obtain an injection molded article using the polylactic acid resin composition of the present invention formulated, high crystallization peak temperature, crystal The amount of heat of conversion was large, the moldability was excellent, and there was no deformation at the time of release (Examples 1 to 4 ). In contrast, a polylactic acid resin composition obtained by using only a phenolic antioxidant alone or a hydrazide compound that is a conventional catalyst deactivator alone has a crystallization peak temperature of less than 120 ° C and a crystallization heat of 40 J / g. The moldability was poor at less than (Comparative Examples 1 and 2). Note that Example 5 is a reference example.
[0098]
【The invention's effect】
According to the present invention, by blending polylactic acid with a phenolic antioxidant and a specific hydrazide compound, it is possible to provide a polylactic acid-based resin composition having a high crystallization speed and excellent moldability. The polylactic acid-based resin composition can be expected to be excellent in the molding cycle. Moreover, according to this invention, the said polylactic acid-type resin composition is crystallized within a metal mold | die. It is possible to provide a simple and highly efficient production method for heat-resistant polylactic acid resin molded products.

Claims (8)

A hydrazide compound 1 selected from (A) 0.01 to 10 parts by weight of a phenolic antioxidant and (B) (b-3) a chain hydrazide and (b-4) a cyclic hydrazide in 100 parts by weight of polylactic acid A polylactic acid resin composition containing 0.01 to 10 parts by weight of seeds or more,
The (b-3) a chain hydrazide is represented by the following general formula (I) or (II), the (b-4) cyclic hydrazide, polylactic acid resin composition you express the following general formula (III) object.

( Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents an aromatic monovalent carboxylic acid residue, and R represents an aliphatic divalent carboxylic acid residue. )

(Wherein, R ₅ and R ₆ are a hydrogen atom, a halogen atom, a hydroxyl 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.)   The polylactic acid resin composition according to claim 1, wherein the hydrazide compound is a compound having a melting point of 300 ° C or higher.   The polylactic acid resin composition according to claim 1, wherein the hydrazide compound is bis (2- (2-hydroxybenzoyl) hydrazide) dodecandioic acid.   2. The polylactic acid resin composition according to claim 1, wherein the hydrazide compound is phthalic hydrazide.   The polylactic acid-type resin composition in any one of Claims 1-4 which mix | blended 0.01-40 weight part of hydrous magnesium silicate (talc).   The polylactic acid resin composition according to claim 5, wherein the hydrous magnesium silicate (talc) has an average particle size of 10 μm or less.   A heat-resistant polylactic acid resin molded product obtained by molding the polylactic acid resin composition according to any one of claims 1 to 6.   After melting the polylactic acid-based resin composition according to any one of claims 1 to 6, the molten polylactic acid-based resin composition has a glass transition temperature not higher than a crystallization start temperature in a scanning differential calorimeter (DSC). A method for producing a heat-resistant polylactic acid resin molded product, which is filled in a mold of a molding machine set in the above range and molded while crystallizing.