JP3730805B2 - Aliphatic polyester resin pre-expanded particles having biodegradability, molded product thereof and method for producing the pre-expanded particles - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、生分解性を有する脂肪族ポリエステル樹脂予備発泡粒子、及びその成形体と該予備発泡粒子の製造方法に関する。
【０００２】
【従来の技術】
最近の環境問題の高まりから、生分解性を有するプラスチック発泡体の開発が広く行われるようになり、これまで脂肪族ポリエステル系樹脂やデンプンとプラスチックの混合樹脂等の押出発泡体が開発され一部実用化され始めている。また、いったん予備発泡粒子を製造し、次いで金型に充填して加熱し発泡成形体を得る、いわゆるビーズ発泡成形分野においても、次のような技術が開発されている。ウレタン結合を有し特定の溶融粘度を持った特殊な脂肪族ポリエステル樹脂粒子に揮発性発泡剤を含有させ発泡性粒子とした後、水蒸気加熱発泡により予備発泡粒子を得、次いでこれを金型に充填し加熱発泡し成形体を得る方法が特開平６−２４８１０６号公報に記載されているが、この技術では成形体を得るまでに、揮発性発泡剤を粒子に含浸させる工程、水蒸気の加熱によって発泡倍率５倍以上に発泡させる加熱発泡工程、該予備発泡粒子を乾燥熟成後、金型に充填して発泡成形体にする工程の煩雑な３工程を必要とし経済的な方法ではなかった。
また、特開平１０−３２４７６６号公報には架橋構造を有する脂肪族ポリエステル系樹脂発泡粒子とその成形体についての記載があり、特開平６−２４８１０６号公報記載の技術よりは成形性に優れた脂肪族ポリエステル系樹脂の生分解性発泡体が得られているが、予備発泡粒子を得るための製造工程として架橋工程と発泡工程の２工程、成形体を得るための工程の計３工程が必要で生産コストが高く、経済性に問題があった。
さらに、本発明と類似のポリ（３ＨＢ−ＣＯ−３ＨＨ）を基材樹脂とする脂肪族ポリエステル樹脂発泡体の例が米国特許５，５３６，５６４号に記載されている。しかしながら、従来公知の発泡体製法が羅列されている他は、実施例１２，１３に無架橋のポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂と熱分解型発泡剤を該発泡剤の分解温度以下で混練した後、該発泡剤の分解温度以上で加熱発泡させる技術が公開になっているだけで、本発明の示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有するポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂予備発泡粒子とその成形体の製造方法を示唆するものはない。
【０００３】
【発明が解決しようとする課題】
そこで、本発明の課題は、生分解性を有し、かつ成形性、物性が良好な脂肪族ポリエステル樹脂予備発泡粒子、及びその成形体と該予備発泡粒子の経済的な製造方法を提供することである。
【０００４】
【課題を解決するための手段】
本発明者らは、上記課題を解決するべく鋭意研究を重ねた結果、本発明を完成するに至った。本発明は脂肪族ポリエステル系樹脂の内、基材樹脂として特定の脂肪族ポリエステル樹脂を使用すれば、成形性、物性が良好な予備発泡粒子とその成形体が得られることが分かった。すなわち、本発明は、３−ヒドロキシブチレートと３−ヒドロキシヘキサノエートからなる脂肪族ポリエステル共重合体（以下、ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂という）を基材樹脂とし、示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有する生分解性の脂肪族ポリエステル樹脂予備発泡粒子（請求項１）、無架橋である請求項１記載の脂肪族ポリエステル樹脂予備発泡粒子（請求項２）、ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂を基材樹脂とし示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有する生分解性の脂肪族ポリエステル樹脂予備発泡粒子を金型に充填し、加熱成形してなる成形体（請求項３）、脂肪族ポリエステル樹脂予備発泡粒子が無架橋であることを特徴とする請求項３記載の成形体（請求項４）、ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂を基材樹脂とする脂肪族ポリエステル樹脂粒子を、分散剤とともに密閉容器内で水系分散媒に分散後、発泡剤を密閉容器内に導入し、該ポリエステル樹脂粒子の軟化温度以上に加熱した後、密閉容器の一端を解放し、該ポリエステル樹脂粒子と水系分散媒とを密閉容器の圧力よりも低圧の雰囲気下に放出して、該ポリエステル樹脂粒子を発泡させることを特徴とする請求項１記載の生分解性の脂肪族ポリエステル樹脂予備発泡粒子の製造方法（請求項５）及び、脂肪族ポリエステル樹脂予備発泡粒子が無架橋であることを特徴とする請求項５記載の製造方法（請求項６）に関する。
本発明の脂肪族ポリエステル樹脂予備発泡粒子は無架橋でしかも１工程で得ることもできるので、前期した公知技術の様な、揮発性発泡剤の含浸工程と水蒸気発泡工程（特開平６−２４８１０６号公報）、架橋工程と発泡工程がかならずしも不要であり（特開平１０−３２４７６６号公報）、生産コストが低く極めて経済的な方法とできる。
示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有するような予備発泡粒子は基材樹脂が結晶性のポリオレフィン系樹脂の場合に公知であり、このような発泡粒子はいわゆる放出発泡法（ドカン法ともいわれている）によって得られることが分かっている（特開昭５９−１７６３３６号公報、特開昭６０−４９０４０号公報など）。また、ＤＳＣ曲線において２つの融点を示す結晶構造を有するような予備発泡粒子は金型に充填して成形すると、成形性が幅広く、物性の良好な成形体が得られることも分かっている。そこで、本発明者らは、この原理が結晶性の脂肪族ポリエステル系樹脂にも適用できるのではないかと考え、前記放出発泡法、すなわち分散剤とともに密閉容器内で水系分散媒に分散後、発泡剤を密閉容器内に導入し、使用した樹脂粒子の軟化温度以上に加熱し、要すれば一定時間保持した後、密閉容器の一端を解放する方法において、各種脂肪族ポリエステル樹脂粒子と水系分散媒とを密閉容器の圧力よりも低圧の雰囲気下に放出する発泡実験を行った。
その結果、ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂のみが、示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有するような予備発泡粒子が特に得られやすいことを見出し本発明をなすに至った。ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂以外の脂肪族ポリエステル樹脂、例えば、ポリカプロラクトン系樹脂（ダイセル化学工業（株）のセルグリーンＰ−Ｈ）、微生物生産法によるポリブチレンサクシネート系樹脂（日本モンサント（株）のバイオポールなど）、化学合成法によるポリブチレンサクシネート系樹脂（昭和高分子（株）のビオノーレなど）、ポリ乳酸系樹脂（三井化学工業（株）のレイシア）等も上記放出発泡の条件を変更しながら試みたが、いずれの樹脂も本発明の示差走査熱量測定法によるＤＳＣ曲線において２つの融点を明確に示す結晶構造を有するような予備発泡粒子は得られなかった。しかし、本発明のポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂を原料樹脂として放出発泡を行えば、従来の技術と異なり、示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有する予備発泡粒子が容易に得られ、しかも無架橋である場合でも、該予備粒子を金型に充填して成形を行う場合の成形性が優れ、こうして得られた成形体の特性も良好なものになることが分かった。本発明の予備発泡粒子の示差走査熱量測定法とは、たとえば、特開昭５９−１７６３３６号公報、特開昭６０−４９０４０号公報などに開示された方法と同様にして行い、示差走査熱量計によって１０℃／分の昇温速度で２００℃まで昇温することにより得られるＤＳＣ曲線から予備発泡粒子の結晶構造特性が判る。本発明の実施例１に示したポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂予備発泡粒子のＤＳＣ曲線を図１に示したが、結晶化に伴う２つの融点（低温と高温の２つの吸熱ピーク）が明確に現れていることがわかる。
【０００５】
【発明の実施の形態】
本発明のポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂のポリ（３ＨＢ−ＣＯ−３ＨＨ）とは３−ヒドロキシブチレートと３−ヒドロキシヘキサノエートのランダム共重合体で、化学合成又は微生物合成法によって得られるが、微生物合成法によるものが好ましい。尚、微生物合成法によるポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂は特開平５−９３０４９公報に記載の技術によって製造することが出来る。ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂の３−ヒドロキシヘキサノエートの含有量は通常３〜２０モル％である。ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂の３−ヒドロキシヘキサノエート含有量が３ｍｏｌ％未満では予備発泡粒子のＤＳＣ曲線における２つの融点の発現が明確でなくなってくる。一方、ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂の３−ヒドロキシヘキサノエート含有量が２０ｍｏｌ％を超えると樹脂の融点が低下し、機械的強度も低下してくるため、物性の劣った予備発泡粒子しか得られない。なお、３−ヒドロキシブチレートの含有量は、通常８０〜９７モル％である。
本発明のポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂に対しては、通常の配合剤、たとえば、酸化防止剤、紫外線吸収剤、染料、顔料などの着色剤、可塑剤、滑剤、結晶化核剤、タルク、炭カル等の無機充填剤等目的に応じて使用できる。また、予備発泡粒子の気泡径を調節する必要がある場合はポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂に気泡調整剤を添加することがある。気泡調整剤としては無機造核剤には、タルク、シリカ、ケイ酸カルシウム、炭酸カルシウム、酸化アルミニウム、酸化チタン、珪藻土、クレー、重曹、アルミナ、硫酸バリウム、酸化アルミニウム、ベントナイト等があり、その使用量は通常０．００５〜２重量部を添加する。
本発明のポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂予備発泡粒子は、まず基材樹脂であるポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂を押出機、ニーダ−、バンバリーミキサー、ロールなどを用いて加熱溶融混錬し、次いで円柱状、楕円柱状、球状、立方体状、直方体状などの本発明の発泡に利用しやすい粒子形状に成形することにより得られる。粒子１個当たりの粒重量は０．１〜２０ｍｇ、好ましくは０．５〜８ｍｇが好ましい。こうして得られたポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂粒子を分散剤とともに密閉容器内で水系分散媒に分散後、発泡剤を密閉容器内に導入し、該ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂粒子の軟化温度以上に加熱し、要すれば一定時間保持した後、密閉容器の一端を解放し、該ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂粒子と水系分散媒とを密閉容器の圧力よりも低圧の雰囲気下に放出して、示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有するポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂予備発泡粒子が製造される。
【０００６】
上記分散剤としては、第３リン酸カルシウム、ピロリン酸カルシウム、カオリン、塩基性炭酸マグネシウム、酸化アルミニウム、塩基性炭酸亜鉛等の無機物と、アニオン界面活性剤たとえば、ドデシルベンゼンスルホン酸ソーダ、α−オレフィンスルホン酸ソーダ、ノルマルパラフィンスルフォン酸ソーダ等を組み合わせて使用される。無機物の量は樹脂１００重量部に対して０、１〜３、０重量部、アニオン界面活性剤量は０、００１〜０、２重量部が通常である。また、水系分散媒としては水、エチレングリコール、メタノール、エタノール、ブタノールなどが使用できるが、経済性、取り扱い性の点から通常は水が好ましい。水系分散媒量は樹脂１００重量部に対して１００〜３００重量部が通常である。
前記の発泡剤としては、プロパン、ブタン、イソブタン、ペンタン、イソペンタン等脂肪族炭化水素、モノクロルメタン、ジクロロメタン、ジクロロジフルオロエタン等のハロゲン化炭化水素、二酸化炭素、窒素、空気などの無機ガス等が挙げられるが、これらの２種以上を併用してもよい。発泡剤の添加量は目的の予備発泡粒子の発泡倍率、発泡剤の種類、ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂の種類、樹脂粒子と水系分散媒の比率、含浸または発泡温度などによって異なるが樹脂粒子１００重量部に対し、通常５〜５０重量部の範囲である。
【０００７】
前記方法で得られたポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂予備発泡粒子は、要すれば加圧空気で加圧熟成し予備発泡粒子に発泡能を付与し閉鎖しうるが密閉できない金型に充填し、次いで、金型内に水蒸気を導入することにより予備発泡粒子同士を加熱融着させポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂粒子の発泡成形体が製造される。
【０００８】
以下、本発明を実施例に基づき更に詳細に説明する。
【０００９】
【実施例】
（実施例１）
微生物合成法で製造された３−ヒドロキシヘキサノエートの含有量が１０モル％、３−ヒドロキシブチレートの含有量が９０モル％、ＭＩ３．８（１９０℃、２．１６ｋｇ）であるポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂を押出機で溶融混錬し、押出機先端に取り付けられた小孔ダイより粒重量２．５ｍｇの粒子を作成した。該脂肪族ポリエステル粒子１００重量部、水３００重量部、分散剤として第３リン酸カルシウム１．５重量部およびノルマルパラフィンスルフォン酸ソーダ０．０５重量部を１０Ｌ耐圧容器に仕込んだ後，発泡剤としてイソブタン１５重量部を添加し、攪拌下、１４０℃にまで昇温し、容器内圧をイソブタン追加調整し３０分保持後、耐圧容器下部に設けた小孔ノズルを通して水分散物を大気圧下に放出発泡し、見かけ発泡倍率が約４０倍で、図１に示すように示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有する無架橋ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂の予備発泡粒子を得た。示差走査熱量測定は予備発泡粒子約５ｍｇを精秤し、示差走査熱量計（セイコー電子工業（株）製、ＳＳＣ５２００）にての昇温速度で室温から２００℃まで昇温してＤＳＣ曲線を得た。
【００１０】
得られた予備発泡粒子は加圧空気で処理し発泡能を付与後、３００×３００×６０ｍｍの金型に充填し、２〜３ｋｇ／ｃｍ２（ゲージ）の水蒸気を金型に導入し予備発泡粒子同士を加熱、融着させ型内発泡成形体を得た。成形時の加熱幅は下記基準で評価したが成形性は良好であった。成形体は７５℃の乾燥室で２４時間乾燥，養生した後、成形体の特性（発泡倍率、表面性、寸法性）、及び生分解性を下記方法により測定し、予備発泡粒子特性、成形加熱幅などとともに結果を表１に示した。
（成形加熱幅）
○：成形可能な水蒸気圧力範囲が０．３ｋｇ／ｃｍ２（ゲージ）以上
△：成形可能な水蒸気圧力範囲が０．１ｋｇ／ｃｍ2（ゲージ）以上０．３ｋｇ／ｃｍ２（ゲージ）未満
×：成形可能な水蒸気圧力範囲が０．１ｋｇ／ｃｍ２（ゲージ）未満
（成形体発泡倍率）
成形体の重量と成形体の体積を求め下式より求めた。
成形体発泡倍率＝樹脂密度（ｇ／ｃｃ）×成形体の体積(ｃｃ)／成形体の重量（ｇ）
（成形体物性）
１）表面性
成形体表面を目視で観察し下記基準によって評価した。
【００１１】
○：表面粒子間の凸凹が少なく、表面が平滑である
△：表面粒子間の凸凹がやや多く、表面平滑性にやや欠ける
×：表面粒子間の凸凹が多く、表面平滑性に欠ける
２）寸法性
成形体寸法の対金型寸法に対する収縮率を下記基準によって評価した。
【００１２】
○：収縮率が１〜４％
△：収縮率が４〜８％
×：収縮率が８％以上
３）生分解性評価
発泡成形体を１０ｃｍ×１０ｃｍ×１ｃｍの形状に加工し深さ１５ｃｍの土中に埋めて６ヶ月後、形状変化を観察し分解性を以下の基準で評価した。
【００１３】
○：形状が確認できないほど分解。
【００１４】
△：かなりの部分分解されているが形状は何とか確認できる
×：ほとんど形状に変化なく分解していない
（実施例２）
微生物合成法で得られた、３−ヒドロキシヘキサノエートの含有量が５モル％、３−ヒドロキシブチレートの含有量９５モル％、ＭＩ５．８（１９０℃、２．１６ｋｇ）であるポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂に変更した他は、実施例１と同様に実施し、見かけ発泡倍率が約４５倍で、示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有する無架橋ポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂の予備発泡粒子と型内発泡成形体を得た。成形体の特性を表１に示す。
【００１５】
（比較例１）
実施例１で使用したポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂粒子１００重量部、水３００重量部、分散剤として第３リン酸カルシウム１．５重量部およびノルマルパラフィンスルフォン酸ソーダ０．０５重量部を１０Ｌ耐圧容器に仕込んだ後，発泡剤としてイソブタン２０重量部を添加し、攪拌下、１００℃にまで昇温し２時間発泡剤含浸処理を行った後、２５℃まで冷却しブタンが含浸された発泡性粒子を作成した。次いでこの発泡性粒子を水蒸気加熱し見かけ発泡倍率３０倍の予備発泡粒子を得た。該予備発泡粒子は示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有していなかった。次いで、該予備発泡粒子を乾燥熟成し、加圧空気で処理し発泡能を付与後、３００×３００×６０ｍｍの金型に充填し、２〜３ｋｇ／ｃｍ２（ゲージ）の水蒸気を金型に導入し予備発泡粒子同士を加熱、融着させ型内発泡成形体を得た。成形体は７５℃の乾燥室で２４時間乾燥，養生した後、成形体の物性（発泡倍率、表面性、寸法性）を下記方法により測定し、結果を表１に示した。本比較例の予備発泡粒子の成形加熱幅は極めて狭く、得られた成形体の生分解性は良好であったが、表面性、寸法性が劣るもので商品的価値の乏しいものであった。
【００１６】
（比較例２）
脂肪族ポリエステル樹脂として１，４−ブタンジオールとコハク酸を主成分とするビオノーレ＃１９０１（昭和高分子（株）製）の樹脂粒子１００重量部、水３００重量部、分散剤として第３リン酸カルシウム１．５重量部およびノルマルパラフィンスルフォン酸ソーダ０．０５重量部を１０Ｌ耐圧容器に仕込んだ後，発泡剤としてイソブタン２０重量部を添加し、攪拌下、１００℃にまで昇温し２時間発泡剤含浸処理を行った後、２５℃まで冷却しブタンが含浸された発泡性粒子を作成した。次いでこの発泡性粒子を水蒸気加熱し見かけ発泡倍率２０倍の予備発泡粒子を得た。該予備発泡粒子は示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有していなかった。次いで、該予備発泡粒子を乾燥熟成し、加圧空気で処理し発泡能を付与後、３００×３００×６０ｍｍの金型に充填し、０．１〜０．３ｋｇ／ｃｍ２（ゲージ）の水蒸気を金型に導入し予備発泡粒子同士を加熱、融着させ型内発泡成形体を得た。成形体は６０℃の乾燥室で２４時間乾燥，養生した後、成形体の物性（発泡倍率、表面性、寸法性）を下記方法により測定し、結果を表１に示した。本比較例の予備発泡粒子の成形加熱幅は極めて狭く、得られた成形体の生分解性は良好であったが表面性、寸法性が劣るもので商品的価値の乏しいものであった。
【００１７】
（比較例３）
脂肪族ポリエステル樹脂を１，４−ブタンジオールとコハク酸を主成分とするポリブチレンサクシネート系樹脂のビオノーレ＃１９０１（昭和高分子（株）製）に変更し、発泡温度を１０３℃に変更した他は、実施例１と同様にして見かけ発泡倍率２５倍の予備発泡粒子を得た。該予備発泡粒子は示差走査熱量測定法によるＤＳＣ曲線を図２に示すが、９０℃付近にショルダー様の疑似ピークがあるものの明確に２つの融点を示す結晶構造を有していない。
次いで、該予備発泡粒子を乾燥熟成し、加圧空気で処理し発泡能を付与後、３００×３００×６０ｍｍの金型に充填し、０．１〜０．３ｋｇ／ｃｍ２（ゲージ）の水蒸気を金型に導入し予備発泡粒子同士を加熱、融着させ型内発泡成形体を得た。成形体は６０℃の乾燥室で２４時間乾燥，養生した後、成形体の物性（発泡倍率、表面性、寸法性）を下記方法により測定し、結果を表１に示した。本比較例で得られた予備発泡粒子の成形加熱幅は狭く、成形体の表面性、寸法性が劣るもので商品的価値の乏しいものであった。
【００１８】
【表１】
【発明の効果】
以上説明した通り、本発明のポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂からなる予備発泡粒子は、示差走査熱量測定法によるＤＳＣ曲線において２つの融点を示す結晶構造を有し、無架橋であるので、従来の発泡剤含浸工程や架橋工程が不要で生産工程が少なく生産コストが低く経済的利益な方法で、成形性、物性に優れた生分解性の発泡成形体が得られ、本発明の予備発泡粒子とその成形体はワンウエイの緩衝包装材等に好適に使用することが出来る。
【図面の簡単な説明】
【図１】 本発明の実施例１で得られたポリ（３ＨＢ−ＣＯ−３ＨＨ）系脂肪族ポリエステル樹脂予備発泡粒子の示差走査熱量測定におけるＤＳＣ曲線で、２つの融点が明確に示されている。
【図２】 比較例３で得られたポリブチレンサクシネート系脂肪族ポリエステル樹脂の予備発泡粒子の示差走査熱量測定におけるＤＳＣ曲線で明確な２つの融点がない。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to biodegradable aliphatic polyester resin pre-expanded particles, a molded product thereof, and a method for producing the pre-expanded particles.
[0002]
[Prior art]
Due to the recent increase in environmental problems, biodegradable plastic foams have been widely developed. Extruded foams such as aliphatic polyester resins and starch / plastic mixed resins have been developed. It is starting to be put into practical use. The following techniques have also been developed in the so-called bead foam molding field in which pre-expanded particles are once manufactured, then filled in a mold and heated to obtain a foam molded article. A special aliphatic polyester resin particle having a urethane bond and containing a volatile foaming agent in a special aliphatic polyester resin particle having a specific melt viscosity is made into a foamable particle. Then, pre-foamed particles are obtained by steam heating foaming, and this is then used as a mold. A method of filling and heating and foaming to obtain a molded body is described in JP-A-6-248106, but in this technique, before obtaining a molded body, a step of impregnating particles with a volatile foaming agent, heating water vapor This is not an economical method because it requires three complicated steps, a heating and foaming step of foaming to a foaming ratio of 5 times or more, and a step of drying and aging the pre-foamed particles and then filling the mold into a foamed molded product.
Japanese Patent Laid-Open No. 10-324766 describes aliphatic polyester resin expanded particles having a cross-linked structure and a molded product thereof, and is more excellent in moldability than the technique described in Japanese Patent Laid-Open No. 6-248106. Although a biodegradable foam of an aliphatic polyester-based resin has been obtained, a total of three steps, a cross-linking step and a foaming step, and a step for obtaining a molded body are required as manufacturing steps for obtaining pre-foamed particles. Production cost was high and there was a problem with economy.
Furthermore, an example of an aliphatic polyester resin foam using poly (3HB-CO-3HH) similar to the present invention as a base resin is described in US Pat. No. 5,536,564. However, except that the conventionally known methods for producing foams are listed, Examples 12 and 13 show that the non-crosslinked poly (3HB-CO-3HH) aliphatic polyester resin and the thermally decomposable foaming agent are decomposed. A technology having a crystal structure showing two melting points in a DSC curve according to the differential scanning calorimetry method of the present invention is disclosed only by the technology of kneading below the temperature and then heating and foaming above the decomposition temperature of the blowing agent. There is no suggestion of a method for producing (3HB-CO-3HH) -based aliphatic polyester resin pre-expanded particles and molded articles thereof.
[0003]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide an aliphatic polyester resin pre-foamed particle having biodegradability and good moldability and physical properties, and a molded body thereof and an economical method for producing the pre-foamed particle. It is.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. In the present invention, it has been found that when a specific aliphatic polyester resin is used as the base resin among the aliphatic polyester resins, pre-expanded particles having excellent moldability and physical properties and molded articles thereof can be obtained. That is, the present invention uses, as a base resin, an aliphatic polyester copolymer composed of 3-hydroxybutyrate and 3-hydroxyhexanoate (hereinafter referred to as poly (3HB-CO-3HH) -based aliphatic polyester resin). The predefoamed aliphatic polyester resin pre-foamed particles according to claim 1, which are non-crosslinked, biodegradable aliphatic polyester resin pre-foamed particles having a crystal structure having two melting points in the DSC curve obtained by differential scanning calorimetry. Particles (Claim 2), biodegradable aliphatic polyester having a crystal structure having two melting points in a DSC curve by differential scanning calorimetry using a poly (3HB-CO-3HH) aliphatic polyester resin as a base resin Molded body obtained by filling resin pre-expanded particles into a mold and thermoforming (Claim 3), aliphatic polyester resin pre-expanded particles The molded product according to claim 3 (claim 4), wherein aliphatic polyester resin particles containing a poly (3HB-CO-3HH) aliphatic polyester resin as a base resin are dispersed. After being dispersed in an aqueous dispersion medium in an airtight container together with an agent, a foaming agent is introduced into the airtight container, heated to a temperature equal to or higher than the softening temperature of the polyester resin particles, one end of the airtight container is released, and the polyester resin particles and the aqueous 2. The method for producing biodegradable aliphatic polyester resin pre-expanded particles according to claim 1, wherein the polyester resin particles are foamed by releasing the dispersion medium in an atmosphere lower than the pressure in the sealed container. (Claim 5) The aliphatic polyester resin pre-expanded particles are non-crosslinked, and the production method according to claim 5 (Claim 6).
Since the aliphatic polyester resin pre-expanded particles of the present invention can be obtained in one step without crosslinking, a volatile foaming agent impregnation step and a steam foaming step (Japanese Patent Laid-Open No. 6-248106) as in the prior art. Publication), the crosslinking step and the foaming step are not necessarily required (Japanese Patent Laid-Open No. 10-324766), and the production cost is low and the method can be made extremely economical.
Pre-expanded particles having a crystal structure having two melting points in a DSC curve obtained by differential scanning calorimetry are known when the base resin is a crystalline polyolefin-based resin. It is known that it can be obtained by a method (also referred to as a docan method) (JP 59-176336, JP 60-49040, etc.). It has also been found that when pre-expanded particles having a crystal structure having two melting points in the DSC curve are filled in a mold and molded, a molded product having a wide range of moldability and good physical properties can be obtained. Therefore, the present inventors consider that this principle can be applied to a crystalline aliphatic polyester resin, and the foaming method after the dispersion in the aqueous dispersion medium in a closed container together with the release foaming method, that is, the dispersant. In the method in which the agent is introduced into the sealed container, heated above the softening temperature of the resin particles used, and held for a certain period of time if necessary, then one end of the sealed container is released, and various aliphatic polyester resin particles and an aqueous dispersion medium are used. Foaming experiment was carried out in an atmosphere at a pressure lower than the pressure in the sealed container.
As a result, it has been found that only the poly (3HB-CO-3HH) -based aliphatic polyester resin is particularly easy to obtain pre-expanded particles having a crystal structure having two melting points in the DSC curve by differential scanning calorimetry. It came to make this invention. Aliphatic polyester resins other than poly (3HB-CO-3HH) aliphatic polyester resins, for example, polycaprolactone resins (Cell Green PH of Daicel Chemical Industries, Ltd.), polybutylene succinates based on microbial production methods Resin (Nippon Monsanto Co., Ltd. Biopol), chemical synthesis polybutylene succinate resin (Showa High Polymer Co., Ltd. Bionore), polylactic acid resin (Mitsui Chemicals Co., Ltd. Lacia) Although no attempt was made to change the above-mentioned foaming conditions for release, no prefoamed particles having a crystal structure clearly showing two melting points in the DSC curve according to the differential scanning calorimetry of the present invention were obtained. It was. However, if release foaming is performed using the poly (3HB-CO-3HH) aliphatic polyester resin of the present invention as a raw material resin, the crystal structure showing two melting points in the DSC curve by differential scanning calorimetry, unlike the conventional technique Even when the pre-expanded particles having the above are easily obtained and non-crosslinked, the moldability when the pre-particles are filled in a mold and molding is excellent, and the properties of the molded body thus obtained are also good. I knew it would be something. The differential scanning calorimetry of the pre-expanded particles of the present invention is carried out in the same manner as disclosed in, for example, JP-A-59-176336 and JP-A-60-49040, and a differential scanning calorimeter. From the DSC curve obtained by raising the temperature to 200 ° C. at a rate of 10 ° C./min, the crystal structure characteristics of the pre-expanded particles can be understood. The DSC curve of the poly (3HB-CO-3HH) -based aliphatic polyester resin pre-expanded particles shown in Example 1 of the present invention is shown in FIG. It can be seen that an endothermic peak) clearly appears.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The poly (3HB-CO-3HH) aliphatic polyester resin poly (3HB-CO-3HH) of the present invention is a random copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, which is chemically synthesized or microorganisms. Although obtained by a synthesis method, those obtained by a microorganism synthesis method are preferred. A poly (3HB-CO-3HH) aliphatic polyester resin obtained by a microbial synthesis method can be produced by the technique described in JP-A-5-93049. The content of 3-hydroxyhexanoate in the poly (3HB-CO-3HH) aliphatic polyester resin is usually 3 to 20 mol%. When the poly (3HB-CO-3HH) aliphatic polyester resin has a 3-hydroxyhexanoate content of less than 3 mol%, the two melting points on the DSC curve of the pre-expanded particles are not clearly expressed. On the other hand, if the content of 3-hydroxyhexanoate in the poly (3HB-CO-3HH) -based aliphatic polyester resin exceeds 20 mol%, the melting point of the resin is lowered and the mechanical strength is also lowered, resulting in poor physical properties. Only pre-expanded particles are obtained. The content of 3-hydroxybutyrate is usually 80 to 97 mol%.
For the poly (3HB-CO-3HH) aliphatic polyester resin of the present invention, usual compounding agents, for example, colorants such as antioxidants, ultraviolet absorbers, dyes, pigments, plasticizers, lubricants, crystals Inorganic fillers such as nucleating agents, talc, and charcoal can be used according to the purpose. Moreover, when it is necessary to adjust the bubble diameter of pre-expanded particle, a bubble regulator may be added to poly (3HB-CO-3HH) type aliphatic polyester resin. Inorganic nucleating agents include talc, silica, calcium silicate, calcium carbonate, aluminum oxide, titanium oxide, diatomaceous earth, clay, baking soda, alumina, barium sulfate, aluminum oxide, bentonite, etc. The amount is usually 0.005 to 2 parts by weight.
The poly (3HB-CO-3HH) aliphatic polyester resin pre-expanded particles of the present invention are obtained by first extruding a poly (3HB-CO-3HH) aliphatic polyester resin as a base resin, an extruder, a kneader, a Banbury mixer, It is obtained by heat-melt kneading using a roll or the like, and then forming into a particle shape that can be easily used for foaming of the present invention, such as a cylindrical shape, an elliptical column shape, a spherical shape, a cubic shape, or a rectangular parallelepiped shape. The particle weight per particle is 0.1 to 20 mg, preferably 0.5 to 8 mg. The poly (3HB-CO-3HH) aliphatic polyester resin particles thus obtained are dispersed in an aqueous dispersion medium in a closed container together with a dispersing agent, and then a foaming agent is introduced into the sealed container, and the poly (3HB-CO- 3HH) Heating above the softening temperature of the aliphatic polyester resin particles, if necessary, holding for a certain period of time, then releasing one end of the sealed container, the poly (3HB-CO-3HH) aliphatic polyester resin particles and aqueous A poly (3HB-CO-3HH) -based aliphatic polyester resin having a crystal structure having two melting points in a DSC curve obtained by differential scanning calorimetry by discharging the dispersion medium into an atmosphere lower than the pressure in the sealed container Pre-expanded particles are produced.
[0006]
Examples of the dispersant include inorganic substances such as tricalcium phosphate, calcium pyrophosphate, kaolin, basic magnesium carbonate, aluminum oxide, basic zinc carbonate, and anionic surfactants such as sodium dodecylbenzene sulfonate and sodium α-olefin sulfonate. In addition, normal paraffin sulfonic acid soda is used in combination. The amount of the inorganic substance is usually 0, 1-3, 0 parts by weight with respect to 100 parts by weight of the resin, and the amount of the anionic surfactant is usually 0, 001-0, 2 parts by weight. In addition, water, ethylene glycol, methanol, ethanol, butanol and the like can be used as the aqueous dispersion medium, but water is usually preferable from the viewpoint of economy and handleability. The amount of the aqueous dispersion medium is usually 100 to 300 parts by weight with respect to 100 parts by weight of the resin.
Examples of the blowing agent include aliphatic hydrocarbons such as propane, butane, isobutane, pentane and isopentane, halogenated hydrocarbons such as monochloromethane, dichloromethane and dichlorodifluoroethane, and inorganic gases such as carbon dioxide, nitrogen and air. However, two or more of these may be used in combination. The amount of foaming agent added is the expansion ratio of the desired pre-expanded particles, the type of foaming agent, the type of poly (3HB-CO-3HH) aliphatic polyester resin, the ratio of resin particles to aqueous dispersion medium, the impregnation or foaming temperature, etc. Depending on the resin particle, it is usually in the range of 5 to 50 parts by weight per 100 parts by weight of the resin particles.
[0007]
The poly (3HB-CO-3HH) -based aliphatic polyester resin pre-expanded particles obtained by the above method can be closed by pressurizing and aging with pressurized air to give the pre-expanded particles foaming ability, if necessary. Filling the mold and then introducing water vapor into the mold to heat-fuse the pre-expanded particles together to produce a foamed molded article of poly (3HB-CO-3HH) -based aliphatic polyester resin particles.
[0008]
Hereinafter, the present invention will be described in more detail based on examples.
[0009]
【Example】
Example 1
Poly (3HB) produced by a microbial synthesis method having a 3-hydroxyhexanoate content of 10 mol%, a 3-hydroxybutyrate content of 90 mol%, and MI 3.8 (190 ° C., 2.16 kg) -CO-3HH) type aliphatic polyester resin was melted and kneaded with an extruder, and particles having a particle weight of 2.5 mg were prepared from a small hole die attached to the tip of the extruder. 100 parts by weight of the aliphatic polyester particles, 300 parts by weight of water, 1.5 parts by weight of tricalcium phosphate as a dispersant and 0.05 parts by weight of normal paraffin sulfonate sodium were charged in a 10 L pressure vessel, and then isobutane 15 as a blowing agent. Add parts by weight, raise the temperature to 140 ° C with stirring, adjust the internal pressure of the vessel to additional isobutane, hold it for 30 minutes, then discharge the aqueous dispersion under atmospheric pressure through a small nozzle provided at the bottom of the pressure vessel, and foam. The non-crosslinked poly (3HB-CO-3HH) type aliphatic polyester resin having a crystal structure having an apparent expansion ratio of about 40 times and a crystal structure showing two melting points in a DSC curve by differential scanning calorimetry as shown in FIG. Pre-expanded particles were obtained. In differential scanning calorimetry, about 5 mg of pre-expanded particles are precisely weighed, and the DSC curve is obtained by raising the temperature from room temperature to 200 ° C. at a rate of temperature rise with a differential scanning calorimeter (Seiko Electronics Co., Ltd., SSC5200). It was.
[0010]
The pre-expanded particles obtained were treated with pressurized air to give foaming ability, filled into a 300 × 300 × 60 mm mold, and steam of 2-3 kg / cm 2 (gauge) was introduced into the mold to prepare the pre-expanded particles They were heated and fused together to obtain an in-mold foam molded product. The heating width at the time of molding was evaluated according to the following criteria, but the moldability was good. The molded body is dried and cured in a drying room at 75 ° C. for 24 hours, and then the characteristics (foaming ratio, surface property, dimensionality) and biodegradability of the molded body are measured by the following methods, pre-expanded particle characteristics, molding heating The results are shown in Table 1 along with the width.
(Molding heating width)
○: Moldable water vapor pressure range is 0.3 kg / cm 2 (gauge) or more Δ: Moldable water vapor pressure range is 0.1 kg / cm 2 (gauge) or more and less than 0.3 kg / cm 2 (gauge) ×: Moldable Water vapor pressure range of less than 0.1 kg / cm2 (gauge) (foaming ratio of molded product)
The weight of the molded body and the volume of the molded body were determined from the following formula.
Foaming ratio of molded article = resin density (g / cc) × volume of molded article (cc) / weight of molded article (g)
(Molded body properties)
1) The surface molding surface was visually observed and evaluated according to the following criteria.
[0011]
○: There are few unevenness between surface particles, and the surface is smooth. Δ: There are a little more unevenness between surface particles, and the surface smoothness is slightly lacking. X: There are many unevennesses between surface particles, and the surface smoothness is not good. 2) Dimensions The shrinkage ratio of the size of the molded product to the size of the mold was evaluated according to the following criteria.
[0012]
○: Shrinkage is 1 to 4%
Δ: Shrinkage is 4-8%
×: Shrinkage rate of 8% or more 3) Evaluation of biodegradability The foamed molded product was processed into a shape of 10 cm × 10 cm × 1 cm, embedded in soil with a depth of 15 cm, and after 6 months, the shape change was observed and the degradability was as follows: Evaluation based on the criteria.
[0013]
○: Decomposition so that the shape cannot be confirmed.
[0014]
Δ: Although it is partly decomposed, the shape can be confirmed somehow ×: Almost no change in shape (Example 2)
Poly (3HB) obtained by a microbial synthesis method having a 3-hydroxyhexanoate content of 5 mol%, a 3-hydroxybutyrate content of 95 mol%, and MI 5.8 (190 ° C., 2.16 kg) -CO-3HH) A crystal structure which is the same as that of Example 1 except that the aliphatic polyester resin is changed, has an apparent foaming ratio of about 45 times, and shows two melting points in a DSC curve by differential scanning calorimetry. Pre-expanded particles of an uncrosslinked poly (3HB-CO-3HH) -based aliphatic polyester resin having an in-mold foam molded product were obtained. Table 1 shows the characteristics of the molded body.
[0015]
(Comparative Example 1)
100 parts by weight of poly (3HB-CO-3HH) -based aliphatic polyester resin particles used in Example 1, 300 parts by weight of water, 1.5 parts by weight of tribasic calcium phosphate as a dispersant, and 0.05 parts by weight of normal paraffin sulfonate sodium After adding 10 parts into a 10 L pressure vessel, 20 parts by weight of isobutane was added as a foaming agent, and the temperature was raised to 100 ° C. with stirring and subjected to a foaming agent impregnation treatment for 2 hours, followed by cooling to 25 ° C. and impregnation with butane. Expanded foam particles were prepared. Next, the expandable particles were heated with steam to obtain pre-expanded particles having an apparent expansion ratio of 30 times. The pre-expanded particles did not have a crystal structure showing two melting points in the DSC curve by differential scanning calorimetry. Next, the pre-expanded particles are dried and aged, treated with pressurized air to give foaming ability, then filled into a 300 × 300 × 60 mm mold, and 2 to 3 kg / cm 2 (gauge) water vapor is introduced into the mold Then, the pre-expanded particles were heated and fused together to obtain an in-mold expanded molded body. The molded body was dried and cured in a drying room at 75 ° C. for 24 hours, and the physical properties (foaming ratio, surface property, dimensionality) of the molded body were measured by the following methods. The results are shown in Table 1. The pre-expanded particles in this comparative example had a very narrow molding heating width, and the resulting molded article had good biodegradability, but had poor surface properties and dimensional properties and poor commercial value.
[0016]
(Comparative Example 2)
100 parts by weight of resin particles of Bionore # 1901 (manufactured by Showa High Polymer Co., Ltd.) mainly composed of 1,4-butanediol and succinic acid as an aliphatic polyester resin, 300 parts by weight of water, and tricalcium phosphate 1 as a dispersant .5 parts by weight and normal paraffin sulfonate 0.05 parts by weight were charged into a 10 L pressure vessel, and then 20 parts by weight of isobutane was added as a foaming agent. The temperature was raised to 100 ° C. with stirring and impregnated with the foaming agent for 2 hours. After the treatment, it was cooled to 25 ° C. to produce expandable particles impregnated with butane. Next, the expandable particles were heated with steam to obtain pre-expanded particles having an apparent expansion ratio of 20 times. The pre-expanded particles did not have a crystal structure showing two melting points in the DSC curve by differential scanning calorimetry. Next, the pre-expanded particles are dried and aged, treated with pressurized air to give foaming ability, and then filled in a 300 × 300 × 60 mm mold, and 0.1 to 0.3 kg / cm 2 (gauge) of water vapor is added. It was introduced into a mold and the pre-expanded particles were heated and fused together to obtain an in-mold foam molded product. The molded body was dried and cured in a drying room at 60 ° C. for 24 hours, and then the physical properties (foaming ratio, surface property, dimensionality) of the molded body were measured by the following methods, and the results are shown in Table 1. The pre-expanded particles of this comparative example had a very narrow molding heating width, and the resulting molded article had good biodegradability, but had poor surface properties and dimensional properties and poor commercial value.
[0017]
(Comparative Example 3)
The aliphatic polyester resin was changed to Bionole # 1901 (produced by Showa Polymer Co., Ltd.), a polybutylene succinate resin mainly composed of 1,4-butanediol and succinic acid, and the foaming temperature was changed to 103 ° C. Others were obtained in the same manner as in Example 1 to obtain pre-expanded particles having an apparent expansion ratio of 25 times. FIG. 2 shows a DSC curve obtained by differential scanning calorimetry. The pre-expanded particles have a shoulder-like pseudo peak near 90 ° C., but do not have a crystal structure clearly showing two melting points.
Next, the pre-expanded particles are dried and aged, treated with pressurized air to give foaming ability, and then filled in a 300 × 300 × 60 mm mold, and 0.1 to 0.3 kg / cm 2 (gauge) of water vapor is added. It was introduced into a mold and the pre-expanded particles were heated and fused together to obtain an in-mold foam molded product. The molded body was dried and cured in a drying room at 60 ° C. for 24 hours, and then the physical properties (foaming ratio, surface property, dimensionality) of the molded body were measured by the following methods, and the results are shown in Table 1. The pre-expanded particles obtained in this comparative example had a narrow molding heating width, and the molded article was poor in surface properties and dimensional properties, and was poor in commercial value.
[0018]
[Table 1]
【The invention's effect】
As described above, the pre-expanded particles made of the poly (3HB-CO-3HH) aliphatic polyester resin of the present invention have a crystal structure showing two melting points in a DSC curve obtained by differential scanning calorimetry, and are non-crosslinked. Therefore, the conventional foaming agent impregnation step and the crosslinking step are not required, the production process is low, the production cost is low, and the economically profitable method can be used to obtain a biodegradable foam molded article having excellent moldability and physical properties. The pre-expanded particles of the invention and the molded product thereof can be suitably used for a one-way buffer packaging material or the like.
[Brief description of the drawings]
FIG. 1 is a DSC curve in differential scanning calorimetry of poly (3HB-CO-3HH) -based aliphatic polyester resin pre-expanded particles obtained in Example 1 of the present invention, which clearly shows two melting points. .
FIG. 2 does not have two melting points which are clear in the DSC curve in differential scanning calorimetry of pre-expanded particles of polybutylene succinate aliphatic polyester resin obtained in Comparative Example 3.
Claims (6)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12997099A JP3730805B2 (en) | 1999-05-11 | 1999-05-11 | Aliphatic polyester resin pre-expanded particles having biodegradability, molded product thereof and method for producing the pre-expanded particles |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12997099A JP3730805B2 (en) | 1999-05-11 | 1999-05-11 | Aliphatic polyester resin pre-expanded particles having biodegradability, molded product thereof and method for producing the pre-expanded particles |
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| JP2000319438A JP2000319438A (en) | 2000-11-21 |
| JP3730805B2 true JP3730805B2 (en) | 2006-01-05 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP4582871B2 (en) * | 2000-07-07 | 2010-11-17 | 旭化成ケミカルズ株式会社 | Non-crosslinked resin foamable particles |
| JP4816853B2 (en) * | 2001-09-13 | 2011-11-16 | アキレス株式会社 | Polylactic acid-based expandable resin particles |
| CN100344680C (en) * | 2002-07-01 | 2007-10-24 | 株式会社Jsp | Polylactic acid resin foam particle and polymactic acid resin foam particle porming body |
| CN1308395C (en) * | 2002-11-08 | 2007-04-04 | 株式会社钟化 | Aqueous dispersion of biodegradable polyester and method for production thereof |
| EP1867677A4 (en) * | 2005-03-25 | 2009-08-12 | Kaneka Corp | Foamed polyhydroxyalkanoate resin particles |
| EP1870431B1 (en) * | 2005-03-25 | 2011-06-01 | Kaneka Corporation | Method of producing polyhydroxyalkanoate resin foamed particles |
| WO2006103971A1 (en) * | 2005-03-25 | 2006-10-05 | Kaneka Corporation | Foamed thermoplastic resin particles and method of producing the foamed particles |
| EP1873195B1 (en) | 2005-04-14 | 2013-09-11 | Kaneka Corporation | Method of producing a molded product |
| WO2007049694A1 (en) | 2005-10-26 | 2007-05-03 | Kaneka Corporation | Expanded polyhydroxyalkanoate resin bead, molded object thereof, and process for producing the expanded resin bead |
| JP4989099B2 (en) * | 2006-04-21 | 2012-08-01 | 株式会社カネカ | POLY (3-HYDROXYALKANOATE) RESIN FOAM MOLDED BODY AND PROCESS FOR PRODUCING THE SAME |
| JP2007314670A (en) * | 2006-05-26 | 2007-12-06 | Kaneka Corp | Foamed polylactic acid-resin particle molding and method for producing the same |
| JP2009263483A (en) * | 2008-04-24 | 2009-11-12 | Kaneka Corp | New biodegradable aliphatic polyester-based resin foamed particle molded article |
| EP2978801B1 (en) * | 2013-03-28 | 2018-03-07 | Synbra Technology B.V. | A method for the preparation of pla bead foams |
| EP3744771A4 (en) | 2018-01-26 | 2021-10-20 | Kaneka Corporation | Poly(3-hydroxyalkanoate) foam particles and poly(3-hydroxyalkanoate) foam molded body |
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