JP2004018680A - Biodegradable resin, biodegradable resin composition, biodegradable molded article, and method for manufacturing biodegradable resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a resin molding technology which is capable of giving sufficient heat resistance, moldability, recyclability and biodegradability. <P>SOLUTION: The biodegradable resin is a thermally reversible crosslinking biodegradable resin which is characterized in that at least two functional groups of the biodegradable resin are electrostatically bonded forming a crosslink, the above crosslink being able to cleave by being heated over a definite temperature and the above crosslink being able to form again by being cooled. <P>COPYRIGHT: (C)2004,JPO

Description

【００６８】
（２）ニトロソ２量体型架橋
例えば、ニトロソベンゼンを架橋反応に用いる。ニトロソベンゼンとしては、例えば、ジニトロソプロパン、ジニトロソヘキサン、ジニトロソベンゼン、ジニトロソトルエン等を用いる。例えば、４−ニトロソ−３，５−ベンジル酸の２量体（米国特許第３，８７２，０５７号公報に、４−ニトロソ−３，５−ジクロロベンゾイルクロライドの２量体の合成方法が記載されている。）を用い、ヒドロキシル基を有する生分解性樹脂材料のヒドロキシル基、ヒドロキシル基で修飾された生分解性樹脂材料のヒドロキシル基などと反応する事により、ヒドロキシル基の存在している部位に容易に熱可逆的架橋部位を導入できる。また、酸塩化物を用いれば、アミノ基とも容易に反応するためアミノ酸類およびその誘導体のアミノ基側にも導入できる。
【００６９】
これらの官能基は、以下の一般式（ＩＩ）で示す様に、熱可逆性の架橋構造を形成する。
【００７０】
【化２】

【００７１】
一般式（ＩＩ）においては、冷却により２つのニトロソ基がニトロソ二量体を形成して架橋となる。この架橋は加熱により開裂する。
【００７２】
（３）酸無水物エステル型架橋
酸無水物およびヒドロキシル基を架橋反応に用いることができる。酸無水物としては、脂肪族無水カルボン酸および芳香族無水カルボン酸などを用いる。また、環状酸無水物基および非環状無水物基のいずれも用いることができるが、環状酸無水物基が好適に用いられる。環状酸無水物基は、例えば、無水マレイン酸基、無水フタル酸基、無水コハク酸基、無水グルタル酸基が挙げられ、非環状酸無水物基は、例えば、無水酢酸基、無水プロピオン酸基、無水安息香酸基が挙げられる。中でも、無水マレイン酸基、無水フタル酸基、無水コハク酸基、無水グルタル酸基、無水ピロメリット酸基、無水トリメリット酸基、ヘキサヒドロ無水フタル酸基、無水酢酸基、無水プロピオン酸基、無水安息香酸基およびこれらの置換体などが、ヒドロキシル基と反応して架橋構造を形成する酸無水物として好ましい。
【００７３】
ヒドロキシル基は、ヒドロキシル基を有する生分解性樹脂材料のヒドロキシル基、各種の反応によりヒドロキシル基が導入された生分解性樹脂材料などのヒドロキシル基を使用する。また、ジオール及びポリオール等のヒドロキシ化合物を架橋剤として用いても良い。更に、ジアミン及びポリアミンを架橋剤として用いることもできる。酸無水物として、例えば、無水ピロメリット酸のような酸無水物を２つ以上有するものを用いれば、ヒドロキシル基を有する生分解性樹脂材料、ヒドロキシル基で修飾された生分解性樹脂材料などに対し架橋剤として使用できる。
【００７４】
また、無水マレイン酸をビニル重合により不飽和化合物と共重合することにより２つ以上の無水マレイン酸を有する化合物が容易に得られる（特開平１１−１０６５７８号公報、特開２０００−３４３７６号公報）。これも、ヒドロキシル基を有する生分解性樹脂材料、ヒドロキシル基で修飾された生分解性樹脂材料などに対する架橋剤として使用できる。
【００７５】
以上の様な酸無水物とヒドロキシル基とは、以下の一般式（ＩＩＩ）で示す様に、熱可逆性の架橋構造を形成する。
【００７６】
【化３】

【００７７】
一般式（ＩＩＩ）においては、冷却により酸無水物基と水酸基とがエステルを形成して架橋となる。この架橋は加熱により開裂する。
【００７８】
（４）ハロゲン−アミン型架橋
ポリアミン及びテトラメチルヘキサンジアミン等とハロゲン化アルキルとから、熱可逆的架橋部位を形成できる。例えば、ヒドロキシル基を有する生分解性樹脂材料、ヒドロキシル基で修飾された生分解性樹脂材料などに、４−ブロモメチルベンゾイックアシッドのようなカルボキシル基を有するハロゲン化物をエステル結合する事によりハロゲン化物を得ることができる。これに、例えば、テトラメチルヘキサンジアミンを架橋剤として添加することにより、熱可逆的な架橋を形成する生分解性樹脂を得る。
【００７９】
ハロゲン化アルキル基は、例えば、アルキルブロミド、アルキルクロリド、フェニルブロミド、フェニルクロリド、ベンジルブロミド、ベンジルクロリドが挙げられる。
【００８０】
また、アミノ基としては第三級アミノ基が好ましく、例えば、ジメチルアミノ基、ジエチルアミノ基、ジフェニルアミノ基が挙げられる。中でも、ジメチルアミノ基が好ましい。ハロゲン化アルキル基と第三級アミノ基との組み合わせは、特に限定されないが、例えば、ベンジルブロミドとジメチルアミノ基との組み合わせを例示できる。
【００８１】
これらの官能基は、以下の一般式（ＩＶ）で示す様に、熱可逆性の架橋構造を形成する。
【００８２】
【化４】

【００８３】
一般式（ＩＶ）においては、冷却によりハロゲン化アルキル基と第三級アミンとが、第四級アンモニウム塩性の共有結合を形成して架橋となる。この架橋は加熱により開裂する。
【００８４】
（５）ウレタン型架橋
イソシアネートと活性水素とから熱可逆的な架橋部位を形成できる。例えば、多価イソシアネートを架橋剤として用い、生分解性樹脂材料およびその誘導体のヒドロキシル基、アミノ基、フェノール性水酸基と反応する。また、ヒドロキシル基、アミノ基およびフェノール性水酸基から選ばれた２つ以上の官能基を有する分子を架橋剤として加えることもできる。更に、開裂温度を所望の範囲とするために、触媒を添加することもできる。また、ジヒドロキシベンゼン、ジヒドロキシビフェニル、フェノール樹脂などを架橋剤として加えることもできる。
【００８５】
また、多価イソシアネートを架橋剤として用い、生分解性樹脂材料およびその誘導体のヒドロキシル基、アミノ基、フェノール性水酸基と反応させる。ジヒドロキシベンゼン、ジヒドロキシビフェニル、フェノール樹脂などを架橋剤として加えることもできる。多価イソシアネートとしては、トリレンジイソシアネート（ＴＤＩ）およびその重合体、４，４’−ジフェニルメタンシイソシアネート（ＭＤＩ）、ヘキサメチレンジイソシアネート（ＨＭＤＩ）、１，４−フェニレンジイソシアネート（ＤＰＤＩ）、１，３−フェニレンジイソシアネート、４，４’，４”−トリフェニルメタントリイソシアネート、キシリレンジイソシアネート等を用いることができる。
【００８６】
また、開裂温度を調整するために、１、３−ジアセトキシテトラブチルジスタノキサン等の有機化合物、アミン類、金属石鹸などを開裂触媒として用いても良い。
【００８７】
以上の官能基は、以下の一般式（Ｖ）で示す様に、熱可逆性の架橋構造を形成する。
【００８８】
【化５】

【００８９】
一般式（Ｖ）においては、冷却によりフェノール性水酸基とイソシアネート基とがウレタンを形成して架橋となる。この架橋は加熱により開裂する。
【００９０】
（６）アズラクトン−ヒドロキシアリール型架橋
アリール基としては、フェニル基、トリル基、キシリル基、ビフェニル基、ナフチル基、アントリル基、フェナントリル基およびこれらの基より誘導される基が挙げられ、これらの基に結合するフェノール性のヒドロキシル基が、架橋構造を形成する基に含まれるアズラクトン構造と反応する。フェノール性のヒドロキシル基を有するものとしては、フェノール性のヒドロキシル基を有する生分解性樹脂材料、ヒドロキシルフェノール類で修飾された生分解性樹脂材料などを使用する。
【００９１】
アズラクトン構造としては、１，４−（４，４’−ジメチルアズラクチル）ブタン、ポリ（２−ビニル−４，４’−ジメチルアザラクトン）、ビスアズラクトンベンゼン、ビスアズラクトンヘキサン等の多価アズラクトンが好ましい。
【００９２】
また、アズラクトン−フェノール反応架橋のビスアズラクチルブタン等も使用でき、これらは、例えば、Ｅｎｇｌｅら、Ｊ．Ｍａｃｒｏｍｏｌ．Ｓｃｉ．Ｒｅ．Ｍａｃｒｏｍｏｌ．Ｃｈｅｍ．Ｐｈｙｓ．、第Ｃ３３巻、第３号、第２３９〜２５７頁、１９９３年刊に記載されている。
【００９３】
これらの官能基は、以下の一般式（ＶＩ）で示す様に、熱可逆性の架橋構造を形成する。
【００９４】
【化６】

【００９５】
一般式（ＶＩ）においては、冷却によりアズラクトン基とフェノール性水酸基とが共有結合を形成して架橋となる。この架橋は加熱により開裂する。
【００９６】
（７）カルボキシル−アルケニルオキシ型架橋
カルボキシル基を有するものとしては、カルボキシル基を有する生分解性樹脂材料、カルボキシル基で修飾された生分解性樹脂材料などを使用する。また、アルケニルオキシ構造としては、ビニルエーテル、アリルエーテル及びこれらの構造より誘導される構造が挙げられ、２以上のアルケニルオキシ構造を有するものも使用できる。
【００９７】
また、ビス［４−（ビニロキシ）ブチル］アジペート及びビス［４−（ビニロキシ）ブチル］サクシネート等のアルケニルエーテル誘導体を架橋剤として用いることもできる。
【００９８】
これらの官能基は、以下の一般式（ＶＩＩ）で示す様に、熱可逆性の架橋構造を形成する。
【００９９】
【化７】

【０１００】
一般式（ＶＩＩ）においては、冷却によりカルボキシル基とビニルエーテル基とがヘミアセタールエステルを形成して架橋となる。この架橋は加熱により開裂する（特開平１１−３５６７５号公報、特開昭６０−１７９４７９号公報）。
【０１０１】
（８）架橋剤
以上で説明した様に、熱可逆的な架橋部位を形成し得る官能基を２つ以上分子中に有する化合物は架橋剤となり得る。
【０１０２】
酸無水物基を有する架橋剤としては、例えば、ビス無水フタル酸化合物、ビス無水コハク酸化合物、ビス無水グルタル酸化合物、ビス無水マレイン酸化合物が挙げられる。
【０１０３】
水酸基を有する架橋剤としては、例えば、エチレングリコール、ジエチレングリコール、トリエチレングリコール等のグリコール類；１，４−ブタンジオール、１，６−ヘキサンジオール、１，８−オクタンジオール、１，１０−デカンジオール、トリメチロールエタン、トリメチロールプロパン、ペンタエリスリトール等のアルコール化合物が挙げられる。
【０１０４】
カルボキシル基を有する架橋剤としては、例えば、シュウ酸、マロン酸、コハク酸、グルタル酸、アジピン酸、フタル酸、マレイン酸、フマル酸が挙げられる。
【０１０５】
ビニルエーテル基を有する架橋剤としては、例えば、ビス［４−（ビニロキシ）ブチル］アジペート、ビス［４−（ビニロキシ）ブチル］サクシネート、エチレングリコールジビニルエーテル、ブタンジオールジビニルエーテル、２，２−ビス〔ｐ−（２−ビニロキシエトキシ）フェニル〕プロパンが挙げられる。
【０１０６】
ハロゲン化アルキル基を有する架橋剤としては、例えば、α，α’−ジブロモキシレン、α，α’−ジクロロキシレン、ビスブロモメチルビフェニル、ビスクロロメチルビフェニル、ビスブロモジフェニルメタン、ビスクロロジフェニルメタン、ビスブロモメチルベンゾフェノン、ビスクロロメチルベンゾフェノン、ビスブロモジフェニルプロパン、ビスクロロジフェニルプロパンが挙げられる。
【０１０７】
第三級アミノ基を有する架橋剤としては、例えば、テトラメチルエチレンジアミン、テトラメチルヘキサンジアミン、ビスジメチルアミノベンゼンが挙げられる。
【０１０８】
フェノール性水酸基を有する架橋剤としては、例えば、ジヒドロキシベンゼン、ジヒドロキシビフェニル、レゾール型フェノール樹脂、ノボラック型フェノール樹脂が挙げられる。
【０１０９】
イソシアネート基を有する架橋剤としては、例えば、２，４−トリレンジイソシアネート、２，６−トリレンジイソシアネート、４，４’−ジフェニルメタンジイソシアネート、２，４’−ジフェニルメタンジイソシアネート、ｐ−フェニレンジイソシアネート等の芳香族ジイソシアネート、ヘキサメチレンジイソシアネート等の脂肪族ジイソシアネート、イソホロンジイソシアネート等の脂環式ジイソシアネート、キシリレンジイソシアネート等のアリール脂肪族ジイソシアネート等が挙げられる。
【０１１０】
アズラクトン基を有する架橋剤としては、例えば、ビスアズラクトンブタン、ビスアズラクトンベンゼン、ビスアズラクトンヘキサンが挙げられる。
【０１１１】
ニトロソ基を有する架橋剤としては、例えば、ジニトロソプロパン、ジニトロソヘキサン、ジニトロソベンゼン、ジニトロソトルエンが挙げられる。
【０１１２】
ここで、共有結合性の官能基が２つ以上ある場合、一方の官能基（第１官能基）が存在している生分解性樹脂（第１生分解性樹脂）に他の官能基（第２官能基）が存在している場合もあれば、第２官能基は、第１官能基が存在している生分解性樹脂（第１生分解性樹脂）とは異なる生分解性樹脂（第２生分解性樹脂）に存在している場合もある。以下に、第１官能基および第２官能基の何れもが同一の第１生分解性樹脂に存在している例を挙げる。
【０１１３】
（１）アミロース及びセルロースのヒドロキシル基が無水マレイン酸とエステル結合を形成している多価カルボン酸樹脂を調製する。この樹脂のカルボン酸の一部に２−アミノエチルビニルエーテルをカルボジイミド類でエステル結合する。この場合、同一の生分解性樹脂（第１生分解性樹脂）にカルボン酸構造（第１官能基）とビニルエーテル基（第２官能基）とが存在しており、カルボキシルーアルケニルオキシ型の架橋を形成する。
【０１１４】
（２）ポリ乳酸のカルボキシル末端にペンタエリスリトールがエステル結合しているものの両末端にある４つのヒドロキシル基に対し、更にシクロペンタジエンカルボン酸とマレイミドのディールスアルダー反応物（３，５−ジオキソ−４−アザ−トリシクロ［５．２．１．０^２，６］デカ−８−エン−１０−カルボン酸）がエステル結合された第１生分解性樹脂の場合、第１官能基および第２官能基が同一のシクロペンタジエン誘導体で、第１官能基および第２官能基が同一の第１生分解性樹脂に存在しており、減圧下加熱によりマレイミドを除去することによりシクロペンタジエン同士のディールス−アルダー型の架橋を形成する。なお、架橋は第１生分解性樹脂の両末端で形成される。
【０１１５】
（３）両末端がヒドロキシル基のポリブチレンサクシネートの両末端にシクロペンタジエンカルボン酸がエステル結合された第１生分解性樹脂の場合、第１官能基および第２官能基が同一のシクロペンタ−２，４−ジエン−１−イル基で、第１官能基および第２官能基が同一の第１生分解性樹脂に存在しており、ディールス−アルダー型の架橋を形成する。なお、架橋は第１生分解性樹脂の分子鎖の両末端で形成される。
【０１１６】
（４）両末端がヒドロキシル基のポリブチレンサクシネートの両末端にニトロソ安息香酸がエステル結合された第１生分解性樹脂の場合、第１官能基および第２官能基が同一のニトロソベンゾイル基で、第１官能基および第２官能基が同一の第１生分解性樹脂に存在しており、ニトロソ２量体型の架橋を形成する。なお、架橋は第１生分解性樹脂の両末端で形成される。
【０１１７】
上記の（１）及び（２）の樹脂物は、第１生分解性樹脂材料に第１官能基および第２官能基を導入して得られる。例えば（２）の場合、ポリ乳酸のカルボキシル末端にペンタエリスリトールがエステル結合しているものの４つのヒドロキシル基に、塩化フル酸を反応させ、脱塩素反応を進行させる。
【０１１８】
また、上記の（３）及び（４）の樹脂物を製造する際には、架橋部位を形成する第１官能基と第２官能基とが予め共有結合しており、第１官能基および第２官能基以外に第１生分解性樹脂材料と反応する基を有している化合物（例えば、ジシクロペンタジエンジカルボン酸およびニトロソ安息香酸の２量体など）を架橋剤として用いることができる。この様な架橋剤と第１生分解性樹脂材料とを混合し反応させ、架橋剤を第１生分解性樹脂材料に結合すれば、架橋部位が架橋した状態の樹脂物を生産性良好に得ることができる。特に、上記の（３）及び（４）の様に、第１官能基および第２官能基が同一で、同一の官能基が対称的に結合して架橋部位を形成する場合、ジシクロペンタジエンジカルボン酸、ニトロソ安息香酸の２量体などの、官能基が対称的に結合した２量体を架橋剤として使用できる。
【０１１９】
なお、架橋剤が複数の官能基を含む場合、官能基が同種であれば、架橋剤の製造が容易であり、架橋反応を制御し易いため、好ましい。
【０１２０】
一方、第２官能基は、第１官能基の存在している第１生分解性樹脂と異なる第２生分解性樹脂に存在していても良い。この様な例としては、ポリ乳酸のカルボキシル基末端にペンタエリスリトールがエステル結合しているものの両末端の４つのヒドロキシル基に、更に３−マレイミドプロピオン酸がエステル結合された第１生分解性樹脂と、ポリ乳酸のカルボキシル基末端にペンタエリスリトールがエステル結合しているものの両末端の４つのヒドロキシル基に、更に３−フリルプロピオン酸がエステル結合された第２生分解性樹脂との組み合わせを挙げることができる。第１官能基はマレイミド構造であり、第２官能基はフリル基であり、これらの官能基はディールス−アルダー型で架橋する。なお、架橋は第１生分解性樹脂の分子鎖末端と、第２生分解性樹脂の分子鎖末端とで形成される。
【０１２１】
また、第１官能基および第２官能基の何れも有する第１生分解性樹脂、第１官能基および第２官能基の何れも有する第２生分解性樹脂、第１官能基および第２官能基の何れかのみを有する第１生分解性樹脂、第１官能基および第２官能基の何れかのみを有する第２生分解性樹脂などを含む混合物より樹脂物を構成することもできる。
【０１２２】
この様な樹脂物を製造する際にも、架橋部位を形成する第１官能基と第２官能基とが予め共有結合しており、第１官能基および第２官能基以外に第１生分解性樹脂材料と反応する基を有している化合物を架橋剤として用いることができる。この様な架橋剤と第１生分解性樹脂材料および第２生分解性樹脂材料とを混合し反応させ、架橋剤を第１生分解性樹脂材料および第２生分解性樹脂材料に結合すれば、架橋部位が架橋した状態の樹脂物を生産性良好に得ることができる。
【０１２３】
一方、第２官能基はリンカーに存在している場合もある。この場合、少なくとも、第１官能基を有する第１生分解性樹脂と、第２官能基を有するリンカーとから樹脂物は構成され、リンカーとしては、第１生分解性樹脂の生分解性を損なわないものが使用される。リンカーを使用することにより、より広範な樹脂物を実現できるため、樹脂物の生産性、樹脂物の成形性、成形体の性能（機械的特性および耐熱性など）などの自由度が広くなる。
【０１２４】
リンカーは１分子中に２つ以上の第２官能基を有しているモノマー、オリゴマー及びポリマー等で、リンカーの第２官能基は第１生分解性樹脂の第１官能基と架橋部位を形成する。この結果、成形体においては、２以上の第１生分解性樹脂がリンカーを介して架橋された状態となる。また、溶融時には架橋部位は開裂し、架橋部位の結合および開裂は熱可逆反応の関係にある。なお、１分子中に２つ以上の第２官能基を有しているリンカーを、架橋剤と呼ぶ場合もあり、この様なリンカーと第１生分解性樹脂とを混合し反応して、樹脂物を製造する。なお、必要に応じて、複数のリンカーを併用する場合もあれば、複数の第１生分解性樹脂を併用する場合もある。
【０１２５】
モノマー性のリンカーとしては、以下を例示できる。
【０１２６】
（１）トルエンジイソシアネートをリンカーとして使用する。この場合、第２官能基はイソシアネート基であり、第１生分解性樹脂としては、例えば、フェノール性水酸基を有する生分解性ポリエステルを使用する。第１官能基はフェノール性のヒドロキシル基であり、トルエンジイソシアネートのイソシアネート基は、生分解性ポリエステルのフェノール性のヒドロキシル基と、ウレタン結合により架橋を形成し、フェノール性水酸基を有する生分解性ポリエステルはトルエンジイソシアネートを介して架橋される。
【０１２７】
（２）Ｎ，Ｎ’−ビスマレイミド−４，４’−ジフェニルメタンをリンカーとして使用する。この場合、第２官能基はマレイミド構造であり、第１生分解性樹脂としては、例えば、フル酸がヒドロキシル基末端にエステル結合したポリ乳酸を使用する。第１官能基はフリル基であり、Ｎ，Ｎ’−ビスマレイミド−４，４’−ジフェニルメタンのマレイミド構造は、ポリ乳酸に結合しているフリル基と、ディールス−アルダー型の架橋を形成し、ポリ乳酸は、Ｎ，Ｎ’−ビスマレイミド−４，４’−ジフェニルメタンを介して、片末端で架橋される。
【０１２８】
（３）１，２，３，４−ブタンテトラカルボン酸二無水物（無水マレイン酸にビニル重合２量体）をリンカーとして使用する。この場合、第２官能基は無水マレイン酸構造であり、第１生分解性樹脂としては、例えば、両末端がヒドロキシル基の脂肪族ポリエステルを使用する。第１官能基はヒドロキシル基であり、１，２，３，４−ブタンテトラカルボン酸二無水物の無水マレイン酸構造は、脂肪族ポリエステルに結合しているヒドロキシル基と、酸無水物エステル型の架橋を形成し、両末端がヒドロキシル基の脂肪族ポリエステルは、１，２，３，４−ブタンテトラカルボン酸二無水物を介して、両末端で架橋される。
【０１２９】
また、無水ピロメリット酸なども同様に使用できる。
【０１３０】
一方、ポリマー性のリンカーとしては、例えば、無水マレイン酸とメチルビニルエーテルとの共重合体を挙げることができる。この場合、第２官能基は、無水マレイン酸由来の酸無水物構造であり、第１生分解性樹脂としては、例えば、両末端がヒドロキシル基のポリブチレンサクシネートを使用する。第１官能基はヒドロキシル基であり、無水マレイン酸由来の酸無水物構造は、両末端がヒドロキシル基のポリブチレンサクシネートのヒドロキシル基と、エステル結合により架橋を形成し、両末端がヒドロキシル基のポリブチレンサクシネートは、無水マレイン酸とメチルビニルエーテルとの共重合体を介して、両末端で架橋される。
【０１３１】
なお、リンカーが複数の官能基を含む場合、官能基が同種であれば、リンカーの製造が容易であり、架橋反応を制御し易いため、好ましい。
【０１３２】
（成形加工）
以上の様にして得られた熱可逆的な架橋を形成する生分解樹脂物を用いて成形体を作製する際には、無機フィラー、有機フィラー、補強材、着色剤、安定剤、抗菌剤、防かび材、難燃剤などを、必要に応じて併用できる。
【０１３３】
無機フィラーとしては、シリカ、アルミナ、タルク、砂、粘土、鉱滓などを使用できる。有機フィラーとしては、植物繊維などの有機繊維を使用できる。補強材としては、ガラス繊維、炭素繊維、針状無機物、繊維状テフロン樹脂などを使用できる。抗菌剤としては、銀イオン、銅イオン、これらを含有するゼオライトなどを使用できる。難燃剤としては、シリコーン系難燃剤、臭素系難燃剤、燐系難燃剤などを使用できる。
【０１３４】
なお、架橋部分の解離温度は、成形体の使用温度領域において十分な架橋が形成されるために、１００℃以上が好ましく、一方、生分解性樹脂物の熱劣化が問題とならない温度で溶融加工できるために、２８０℃以下が好ましく、２５０℃以下がより好ましい。また、架橋部分の解離温度は、成形体を作製する際の生分解性樹脂物の溶融加工温度に影響する。普通、溶融加工温度は解離温度の１０℃以上とされ、生分解性樹脂物の熱分解が問題となる温度以下とする。具体的には、良好な溶融状態を実現するために、１２０℃以上が好ましく、１５０℃以上がより好ましく、一方、溶融加工時に生分解性樹脂物が熱劣化することを抑制するため、３００℃以下が好ましく、２５０℃以下がより好ましい。そして、溶融後、生分解性樹脂物は冷却され賦形される。冷却温度は、十分な架橋が形成されるために、０℃以上が好ましく、１０℃以上がより好ましく、一方、１００℃以下が好ましく、８０℃以下がより好ましい。なお、冷却工程中および冷却工程後に、十分な架橋を形成し成形体の十分な特性を発現するために、必要に応じて、成形体を所定の温度で保持する場合もある。成形体を保温することにより、架橋の形成が更に進み、成形体の特性を向上することができる。
【０１３５】
また、同様の観点から、生分解性樹脂物の溶融温度（流動開始温度）も、１００℃以上が好ましく、一方、２８０℃以下が好ましく、２５０℃以下がより好ましい。
【０１３６】
以上の様な樹脂および樹脂組成物は、射出成形法、フィルム成形法、ブロー成形法、発泡成形法などの方法により、電化製品の筐体などの電気・電子機器用途、建材用途、自動車部品用途、日用品用途、医療用途、農業用途などの成形体に加工できる。
【０１３７】
【実施例】
以下に実施例によって本発明を更に詳細に説明するが、これらは、本発明を何ら限定するものではない。なお、以下特に明記しない限り、試薬等は市販の高純度品を用いた。なお、数平均分子量および重量平均分子量はゲルパーメーションクロマトグラム法により測定し、標準ポリスチレンを用いて換算した。
【０１３８】
（実施例１）
攪拌機、分流コンデンサー、温度計、窒素導入管を付した３Ｌのセパラブルフラスコに、コハク酸６００ｇ（５．１モル）、１，４−ブタンジオール４０６ｇ（４．５モル）を仕込み、窒素雰囲気下１８０〜２２０℃で７時間脱水縮合を行った。続いて、減圧下で水を留去して、数平均分子量２，０００の両末端カルボキシル基脂肪族ポリエステル（Ａ）を得た。
【０１３９】
この様にして得られた両末端カルボキシル基脂肪族ポリエステル（Ａ）１００ｇを窒素雰囲気下１３０℃で溶融し、これに酢酸ナトリウム水溶液（１規定）を３３ｍＬ加えて攪拌した。続いて溶媒を減圧留去することにより、カルボキシル基が３３％中和された組成物（Ａ−１）を得た。また、同様に、酢酸ナトリウム水溶液（１規定）を６６ｍＬ及び１００ｍＬ用い、それぞれカルボキシル基が６６％及び１００％中和された組成物（Ａ−２）及び（Ａ−３）を得た。
【０１４０】
更に、酢酸銅（ＩＩ）水溶液（０．１規定）を１６７ｍＬ、３３３ｍＬ及び５００ｍＬ用い、それぞれカルボキシル基が３３％、６６％及び１００％中和された組成物（Ａ−４）、（Ａ−５）及び（Ａ−６）を得た。
【０１４１】
（実施例２）
攪拌機、分流コンデンサー、温度計、窒素導入管を付した３Ｌのセパラブルフラスコに、コハク酸７１６ｇ（６．１モル）、１，４−ブタンジオール６１３ｇ（６．８モル）を仕込み、窒素雰囲気下１８０〜２２０℃で３時間脱水縮合を行った。続いて、触媒としてテトライソプロポキシチタネート０．１５ｇを加えて、１８０〜２２０℃で３時間脱グリコール反応を行い、数平均分子量１５，０００の両末端ヒドロキシル基脂肪族ポリエステル（Ｂ）を得た。
【０１４２】
一方、無水ピロメリット酸７３ｇを１Ｌのテトラヒドロフランに溶解し、窒素雰囲気下で還流した。これに、両末端ヒドロキシル基脂肪族ポリエステル（Ｂ）５００ｇを溶解した５０℃のクロロホルム溶液を１時間で滴下混合した。その後３時間還流を続け、溶媒を留去し、熱水にて過剰の無水ピロメリット酸を洗浄し、乾燥して、多価カルボン酸脂肪族ポリエステル（Ｃ）を得た。
【０１４３】
この様にして得られた多価カルボン酸脂肪族ポリエステル（Ｃ）１００ｇを窒素雰囲気下１３０℃で溶融し、これに酢酸ナトリウム水溶液（１規定）を１３ｍＬ加えて攪拌した。続いて溶媒を減圧留去することにより、カルボキシル基が３３％中和された組成物（Ｃ−１）を得た。また、同様に、酢酸ナトリウム水溶液（１規定）を２７ｍＬ及び４０ｍＬ用い、それぞれカルボキシル基が６６％及び１００％中和された組成物（Ｃ−２）及び（Ｃ−３）を得た。
【０１４４】
更に、酢酸銅（ＩＩ）水溶液（０．１規定）を１３３ｍＬ、２６７ｍＬ及び４００ｍＬ用い、それぞれカルボキシル基が３３％、６６％及び１００％中和された組成物（Ｃ−４）、（Ｃ−５）及び（Ｃ−６）を得た。
【０１４５】
（性能評価）
融点：セイコーインスツルメント社製ＤＳＣ測定装置ＤＳＣ６２００（商品名）を用いて測定した。
【０１４６】
耐熱性：島津製作所製ＴＧ−ＤＴＡ測定装置（商品名：ＴＭＡ−４０）を用いて針入れ度試験（ＪＩＳ　Ｋ　７１９６に準拠）を行い、１００℃以下において、変形の有ったものを×、変形の無かったものを○とした。また、特に耐熱性に優れるものを◎とした。
【０１４７】
生分解性：熱プレスにより成形体を作製し、土壌に埋設した後、６ヶ月後に分解性が認められたものを○、認められなかったものを×とした。
【０１４８】
リサイクル性：１８０℃まで加熱して溶融状態とし、これに続く常温までの冷却を５回繰り返した後、上記の耐熱性試験を行い、１００℃以下において、変形の有ったものを×、（１８０℃と常温とを５サイクル）変形の無かったものを○とした。また、特にリサイクル性に優れるものを◎とした。
【０１４９】
成形性：６．４ｍｍ×１２．５ｍｍ×１２５ｍｍの試験片を２００℃で射出成形し、成形できたものを○、できなかったものを×とした。
【０１５０】
以上の評価結果を表１に示した。
【０１５１】
【表１】

【０１５２】
表１より、組成物（Ａ−１）〜（Ａ−６）及び組成物（Ｃ−１）〜（Ｃ−６）は、耐熱性、生分解性、リサイクル性および成形性の全の性能に優れていることが分かった。
【０１５３】
また、１価のナトリウムに比べ、２価の銅の方が中和物の耐熱性は良好であった。また、架橋密度の高いものの方が、耐熱性は高くなる傾向を示した。
【０１５４】
（ポリエステル樹脂Ｍ−１〜Ｍ−４）
（Ｍ−１）両末端カルボン酸ＰＢＳ：１，４−ブタンジオール及びコハク酸を、１，４−ブタンジオール／コハク酸（モル比）が１より小さく、より好ましくは０．９５以下、更に好ましくは０．９以下となるよう仕込み、脱水縮合反応を行うことにより数平均分子量１００〜１０００，０００の両末端がカルボキシル基のＰＢＳを得る。反応温度を１１０〜２５０℃として減圧することにより、脱水縮合反応が進行し分子量が増大する。また、テトライソプロポキシチタン等の触媒を、モノマー混合物１００質量部に対し０．１〜５質量部加えることによっても、脱水縮合反応が進行し分子量が増大する。
【０１５５】
（Ｍ−２）多価カルボン酸ＰＢＳ：１，４−ブタンジオール及びコハク酸を、１，４−ブタンジオール／コハク酸（モル比）が１より多く、より好ましくは１．０５以上、更に好ましくは１．１以上となるよう仕込み、脱水縮合反応を行うことにより数平均分子量１００〜１０００，０００の両末端がヒドロキシル基のＰＢＳを得る。反応温度を１１０〜２５０℃として減圧することにより、脱水縮合反応が進行し分子量が増大する。また、テトライソプロポキシチタン等の触媒を、モノマー混合物１００質量部に対し０．１〜５質量部加えることによっても、脱水縮合反応が進行し分子量が増大する。
【０１５６】
この様にして得られた両末端ヒドロキシＰＢＳと、ピロメリット酸とをエステル結合することにより、数平均分子量１００〜１０００，０００の多価カルボン酸ＰＢＳ（Ｍ−２）を得る。ヒドロキシル基に対して、ピロメリット酸を大過剰（１０〜１００モル倍）に用いることにより、両端末にピロメリット酸がエステル結合したＰＢＳを得る。クロロホルム及びＴＨＦの混合溶媒またはトルエン溶媒中で、両末端ヒドロキシＰＢＳとピロメリット酸とを還流することにより、エステル化反応を進行できる。なお、過剰に用いたピロメリット酸は、溶媒除去後に熱水洗浄することにより除去できる。
【０１５７】
（Ｍ−３）多価カルボン酸ＰＬＡ：ラクチド（乳酸の２量体）を開環重合することにより、数平均分子量１００〜１０００，０００のＰＬＡ（ポリ乳酸）を得る。反応温度を１２０〜２２０℃とすることにより、開環反応が進行する。また、モノマー１００質量部に対し０．０１〜１質量部のオクタン酸第一スズを触媒として使用することにより、更に脱水縮合反応を進行させ分子量を増大できる。
【０１５８】
この様にして得られたＰＬＡと、ピロメリット酸とをエステル結合することにより、数平均分子量１００〜１０００，０００の多価カルボン酸ＰＬＡ（Ｍ−３）を得る。ヒドロキシル基に対して、ピロメリット酸を大過剰（１０〜１００モル倍）に用いることにより、片端末にピロメリット酸がエステル結合したＰＬＡを得る。クロロホルム及びＴＨＦの混合溶媒またはトルエン溶媒中で、ＰＬＡとピロメリット酸とを還流することにより、エステル化反応を進行できる。なお、過剰に用いたピロメリット酸は、溶媒除去後に熱水洗浄することにより除去できる。
【０１５９】
（Ｍ−４）多価カルボン酸ＰＬＡ：ＰＬＡと、ペンタエリスリトールとをエステル結合することにより、数平均分子量１００〜１０００，０００の末端ヒドロキシＰＬＡを得る。クロロホルム溶媒中で、ピリジン及び１−エチル−３−（３’−ジメチルアミノプロピル）カルボジイミドヒドロクロライドを脱水触媒として等モル用いることにより、エステル化反応を進行できる。また、水洗により精製できる。
【０１６０】
この様にして得られた末端ヒドロキシＰＬＡと、大過剰（１０〜１００モル倍）のピロメリット酸とをエステル結合することにより、数平均分子量１００〜１０００，０００の多価カルボン酸ＰＬＡ（Ｍ−４）を得る。クロロホルム及びＴＨＦの混合溶媒またはトルエン溶媒中で、末端ヒドロキシＰＬＡとピロメリット酸とを還流することにより、エステル化反応を進行できる。なお、過剰に用いたピロメリット酸は、溶媒除去後に熱水洗浄することにより除去できる。
【０１６１】
（実施例３）
以上で得られたポリエステル樹脂（Ｍ−１）〜（Ｍ−４）を１００〜２００℃で溶融し、イオンを加える。イオン源（カチオン）としては、Ｃｕ、Ｎａ、Ｍｇ及びＣａ等を用いる。酢酸銅、酢酸ナトリウム、酢酸カルシウム及び酢酸マグネシウム等の水溶液を、中和度が好ましく１％以上、より好ましくは１０％以上、一方、１００％以下、より好ましくは９０％以下となるよう添加し、直ちに減圧下にて水を留去する。架橋部分の解離温度は１００〜２００℃であるが、成形可能な流動性が得られる温度は、用いるポリエステル樹脂の分子量、カルボキシル基密度、金属イオンによるカルボキシル基の中和度などにより調整できる。
【０１６２】
（実施例４）
ポリエステル樹脂（Ｍ−１）〜（Ｍ−４）をクロロホルム／エタノール／水の混合溶液に溶解し、ポリアミンを加える。中和度は１％以上が好ましく、１０％以上がより好ましく、一方、１００％以下であり、９０％以下が好ましく、ポリアミンを添加し、直ちに減圧下にて溶媒を留去する。架橋部分の解離温度は１００〜２００℃であるが、成形可能な流動性が得られる温度は、用いるポリエステル樹脂の分子量、カルボキシル基密度、ポリアミンによるカルボキシル基の中和度、ポリアミンの１分子当たりのアミノ基数およびアミノ基密度などを至適化することで実現する。
【０１６３】
（実施例５）共有結合性架橋構造の併用
以上で得られたポリエステル樹脂（Ｍ−１）〜（Ｍ−４）を１００〜２００℃で溶融し、イオンを加える。イオン源（カチオン）としては、Ｃｕ、Ｎａ、Ｍｇ及びＣａ等を用いる。酢酸銅、酢酸ナトリウム、酢酸カルシウム及び酢酸マグネシウム等の水溶液を、中和度が好ましく１％以上、より好ましくは１０％以上、一方、１００％以下、より好ましくは９５％以下となるよう添加し、直ちに減圧下にて水を留去する。架橋部分の解離温度は１００〜２００℃であるが、成形可能な流動性が得られる温度は、用いるポリエステル樹脂の分子量、カルボキシル基密度、金属イオンによるカルボキシル基の中和度などにより調整できる。
【０１６４】
この様にして得られた組成物を、例えば、ビス［４―（ビニルロキシ）ブチル］アジペート等を架橋剤として混合し、イオン性架橋構造と、カルボキシル−ビニルエーテル型の供給結合性架橋構造とを併用する。
【０１６５】
（実施例６）共有結合性架橋構造の併用
ポリエステル樹脂（Ｍ−１）〜（Ｍ−４）を１００〜２００℃で溶融し、イオンを加える。イオン源（カチオン）としては、Ｃｕ、Ｎａ、Ｍｇ及びＣａ等を用いる。酢酸銅、酢酸ナトリウム、酢酸カルシウム及び酢酸マグネシウム等の水溶液を、中和度が好ましく１％以上、より好ましくは１０％以上、一方、１００％以下、より好ましくは９０％以下となるよう添加し、直ちに減圧下にて水を留去する。
【０１６６】
一方、１，４−ブタンジオールジビニルエーテル等を架橋剤として用い、カルボキシル基を有するポリエステル樹脂（Ｍ−１）〜（Ｍ−４）と、それぞれ１５０〜２５０℃で溶融混合して、ヘミアセタールエステル結合を架橋部位とするカルボキシル−ビニルエーテル型架橋のポリエステル樹脂を得る。
【０１６７】
そして、これらの組成物を混合することにより、イオン性架橋構造と、カルボキシル−ビニルエーテル型の供給結合性架橋構造とを併用する。
【０１６８】
【発明の効果】
冷却により静電的に結合し、加熱により開裂する熱可逆的な架橋構造を形成する官能基を有する生分解性樹脂を用いることにより、十分な耐熱性、成形性、リサイクル性および生分解性を実現できる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a biodegradable resin and a resin composition that facilitates material recycling by using a thermoreversible cross-linking method, is excellent in heat resistance and moldability, and a method for producing these.
[0002]
[Prior art]
Plastics are widely used in a wide range of industrial fields because they have excellent properties such as easy shaping, light weight, low cost, and low corrosion resistance. However, due to the property of being hardly corroded, even if used plastic is disposed of in the natural world, it is not decomposed and may cause environmental problems. In addition, since it cannot be disposed of in the natural world, it is necessary to incinerate it after use.However, due to the large amount of heat generated during combustion, the incinerator may be damaged during incineration and dioxin may be generated during incineration. . From such a viewpoint, there is a demand for a biodegradable plastic that is recyclable and is degraded by microorganisms when disposed of after use. In particular, biodegradable plastics that are more material-recyclable than thermal-recyclable are desired from the viewpoint of reducing production energy and reducing carbon dioxide emissions.
[0003]
[Problems to be solved by the invention]
However, compared to general plastics, conventional biodegradable plastics may have insufficient properties such as heat resistance. Therefore, for the purpose of improving the properties such as heat resistance of the biodegradable plastic, for example, JP-A-6-192375, WO 97/03130, JP-A-2000-63511, JP-A-9-31176. And Japanese Patent Application Laid-Open No. 2001-40078 propose a technique for improving the heat resistance of a biodegradable plastic by introducing a covalently crosslinked structure.
[0004]
However, in the above-mentioned conventional technology, the heat resistance of the biodegradable plastic is improved by the crosslinked structure, but the fluidity during heating and melting is reduced, the moldability is insufficient, and the biodegradability is poor. May drop. Also, especially in the case of highly crosslinked biodegradable plastic, once molded, it behaves like a thermosetting resin, and if it is recovered and recycled, it must be sufficiently heated and melted during the second and subsequent molding. And recycling becomes difficult.
[0005]
For this purpose, it has been proposed to introduce a thermoreversible crosslinked structure by electrostatic bonding or covalent bonding into the biodegradable plastic for the purpose of improving the heat resistance of the biodegradable plastic and the recyclability. Examples of the introduction of a thermoreversible crosslinked structure by electrostatic bonding are described in JP-A-2000-281805 and Shinichi Yano, Physical Properties and Industrial Application of Ionomer; R. Tant et al., Ionomers (ISBN: 0-7514-0392-X). JP-A-2000-281805 discloses an ion-crosslinked film in which a carboxyl group of a polysaccharide such as carboxymethyl cellulose having a carboxyl group or a carboxyl group-containing starch is cross-linked with a polyvalent metal ion such as Mg ion.
[0006]
Examples of the introduction of a covalent thermoreversible crosslinked structure include JP 2001-81240 A, Engle et al. Macromol. Sci. Re. Macromol. Chem. Phys. C33, No. 3, pp. 239-257, 1993. JP-A-2001-81240 discloses a thermoreversible crosslinkable elastomer crosslinked by a reaction between an acid anhydride (such as a maleic anhydride group) and a hydroxyl group and a thermoreversible crosslinkable elastomer crosslinked by a reaction between an isocyanate group and a phenolic hydroxyl group. It has been disclosed.
[0007]
Not only biodegradable resins, but also many examples of thermoreversible crosslinked structures of various modes have been reported. For example, Yoshine Nakane and Masahiro Ishidoya et al., Color Materials, Vol. 67, No. 12, pp. 766-774, published in 1994; Yoshinori Nakane and Masahiro Ishidoya, Color Materials, Vol. 69, No. 11, 735- 742, 1996; JP-A-11-35675 describes a thermoreversible crosslinked structure utilizing a vinyl ether group. Also, E.I. Ruckenstein and X.M. Chen, J.M. Poly. Sci. , Part A: Polym. Chem. 38, 318-825, 2000; Chujo et al., Macromolecules, 23, 2636-2641, 1990, describe a thermoreversible crosslinked structure utilizing the Diels-Alder reaction. U.S. Pat. No. 3,872,057 describes a thermoreversible crosslinked structure utilizing a nitroso group.
[0008]
As described above, many proposals have been made to utilize various biodegradable polymers and to utilize various types of thermoreversible crosslinked structures. Not reached. In view of such circumstances, an object of the present invention is to provide a resin and a resin composition having sufficient heat resistance, moldability, recyclability, and biodegradability.
[0009]
[Means for Solving the Problems]
According to the present invention for achieving the above object, a biodegradable resin in which at least two functional groups are electrostatically bonded and cross-linked, the cross-link is cleaved by heating to a certain temperature or higher, and cooled. A thermoreversible crosslinkable biodegradable resin characterized in that the crosslink is formed again.
[0010]
Here, the electrostatic bond is an electrostatic bond, which means a bond formed by electrostatic attraction, and includes an ionic bond, a hydrogen bond, and the like. These bonds are formed directly between functional groups and functional groups, when formed between functional groups and functional groups via ions, when formed between functional groups and functional groups via polyions, and the like. There is.
[0011]
Examples of the electrostatic bond directly formed between the functional groups include a case where the electrostatic bond is formed between ion pairs between the ionic functional groups. Examples of the electrostatic bond formed between the functional group and the functional group via an ion include a case where two or more ionic functional groups are coordinated to one counter ion by electrostatic attraction. it can. Further, as an electrostatic bond formed between a functional group and a functional group via a polyion, a case where two or more ionic functional groups are coordinated to one ionic polymer by electrostatic attraction is cited. be able to.
[0012]
A first biodegradable resin having a first functional group that forms a thermoreversible cross-linking structure that forms an electrostatic bond by cooling and is cleaved by heating;
A second biodegradable resin having a second functional group that forms a thermoreversible crosslinked structure that forms an electrostatic bond with the first functional group by cooling and that is cleaved by heating;
A biodegradable resin composition comprising:
[0013]
Further, a biodegradable resin that forms a thermoreversible cross-linked structure in which a functional group is coordinated to a counter ion by electrostatic attraction by cooling and is cleaved by heating,
A biodegradable resin composition comprising the ion source of the counter ion is provided.
[0014]
The crosslinked structure of a biodegradable resin having a thermoreversible crosslinked structure is cleaved during melt molding. For this reason, even if the number of sites of the cross-linking structure necessary for sufficient properties such as heat resistance is introduced, it has an appropriate viscosity at the time of melting and can achieve good moldability. Also, once molded, the molded body does not behave like a thermosetting resin, and when it is collected and recycled, it is sufficiently heated and melted during the second and subsequent moldings, providing good recyclability. Can be realized. Further, when cooled, the molded body has sufficient heat resistance because it is solidified to form a crosslinked structure again.
[0015]
In particular, since the thermo-reversible cross-linked structure of electrostatic bonding has a moderate intermolecular force, by introducing this into a biodegradable material, the cross-linked structure is cleaved during high-temperature molding to ensure high fluidity. On the other hand, under the use environment, the heat resistance and strength, which are the drawbacks of the conventional biodegradable resin material, can be improved by the crosslinked structure. In addition, the electrostatically-bonded crosslinked structure is rapidly biodegraded in the presence of moisture, for example, when buried in soil.
[0016]
In the case of a thermoreversible crosslinked structure, after the crosslinked site is cleaved at a high temperature, the crosslinked site is formed again by a subsequent cooling operation. For this reason, the cleavage and re-formation of the crosslinked site can be repeated any number of times due to the temperature change. By introducing such a crosslinked structure into a biodegradable resin material, an excellent resin and resin composition can be obtained. That is, in a temperature range where a molded body is used, such as normal temperature, it is possible to form a high-order crosslinked structure to improve heat resistance and strength, and in a region above a melting temperature such as a molding temperature, the crosslinked structure is lost and the resin is lost. Is reduced in molecular weight, so that fluidity is improved, and moldability and material recyclability can be improved.
[0017]
Note that the molded body mainly contains a resin crosslinked by electrostatic bonding when it is solidified, but a crosslinked site is cleaved at the time of melting, so that it becomes a composition containing two or more resins. For this reason, when it is not necessary to particularly distinguish the resin and the resin composition, these are also referred to as a resin material.
[0018]
In addition, by introducing a covalent and thermoreversible crosslinked structure into the biodegradable resin in addition to the electrostatically and thermoreversibly crosslinked structure, it is possible to realize a wider range of physical properties with higher performance. As a specific example, a method of introducing a functional group forming an electrostatically-bonded cross-linking structure and a functional group forming a covalently-bonded cross-linking structure into the same biodegradable resin material; A method of mixing a biodegradable resin material into which a functional group to be formed is introduced and a biodegradable resin material into which a functional group to form a covalent cross-linking structure is introduced; both electrostatic bonding and covalent bonding And a method of introducing a functional group that forms a crosslinked structure having the following properties.
[0019]
As a result, a resin and a resin composition having sufficient heat resistance, moldability, recyclability and biodegradability can be realized.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0021]
(Biodegradable resin material)
The biodegradable resin material used as a raw material of the biodegradable resin includes mainly biodegradable monomers, oligomers and polymers that are artificially synthesized and available; mainly biodegradable monomers that are artificially synthesized and available. Derivatives, modified oligomers and modified polymers; mainly biodegradable monomers, oligomers and polymers which can be synthesized and obtained in nature; mainly biodegradable derivatives of monomers which can be synthesized and obtained in nature and modified oligomers And a modified polymer.
[0022]
Examples of artificially synthesized biodegradable oligomers and polymers include, for example, polylactic acid (manufactured by Shimadzu Corporation, trade name: Lacty, etc.), polyalphahydroxy acids such as polyglycolic acid, and polyomegahydroxyalkanoates such as polyepsilon caprolactone (Daicel Corporation). Polyesters such as polybutylene succinate, polybutylene succinate and / or polyalkylene alkanoate (trade name: Bionole, manufactured by Showa Polymer Co., Ltd.), and polybutylene succinate; Examples thereof include polyamino acids such as poly-γ-glutamate (manufactured by Ajinomoto Co., trade name: polyglutamic acid and the like), and polyols such as polyvinyl alcohol and polyethylene glycol.
[0023]
In addition, modified products of these artificially synthesized biodegradable oligomers and polymers can also be suitably used.
[0024]
Examples of natural synthetic biodegradable oligomers and polymers include starch, amylose, cellulose, cellulose ester, chitin, chitosan, gellan gum, carboxyl group-containing cellulose, carboxyl group-containing starch, pectic acid, alginic acid and other polysaccharides; Polybutahydroxyalkanoate, which is a polymer of hydroxybutyrate and / or hydroxyvalerate (manufactured by Zeneca Corporation, trade name: Biopol, etc.), among others, starch, amylose, cellulose, cellulose ester , Chitin, chitosan, polybutahydroxyalkanoate, which is a polymer of hydroxybutyrate and / or hydroxyvalerate synthesized by microorganisms, and the like.
[0025]
It should be noted that naturally-occurring biodegradable oligomers and modified polymers can also be suitably used.
[0026]
Furthermore, lignin or the like can be used as a modified product of a natural synthetic biodegradable oligomer or polymer. Lignin is a dehydrogenated polymer of coniferyl alcohol and sinapyr alcohol, which is contained in wood at 20-30%, and is biodegraded.
[0027]
Among the biodegradable resin materials as described above, artificially synthesized biodegradable oligomers and polymers, modified products of artificially synthesized biodegradable oligomers and polymers, and modified products of naturally synthesized biodegradable oligomers and polymers are used for bonding between molecules. Since the force is appropriate, the thermoplastic resin is excellent in thermoplasticity, the viscosity at the time of melting is not significantly increased, and the moldability is good.
[0028]
Among them, polyesters and modified polyesters are preferred, and aliphatic polyesters and modified polyesters are more preferred. Further, polyamino acids and modified products of polyamino acids are preferable, and aliphatic polyamino acids and modified products of aliphatic polyamino acids are more preferable. Further, polyols and modified products of polyols are preferable, and aliphatic polyols and modified products of aliphatic polyols are more preferable.
[0029]
The weight-average molecular weight of the biodegradable resin material as a raw material is preferably 100 or more from the viewpoint of the performance (processability, heat resistance of a molded article, mechanical properties of a molded article, etc.) of the obtained biodegradable resin. On the other hand, it is preferably 1,000,000 or less, more preferably 500,000 or less, further preferably 100,000 or less, and most preferably 10,000 or less.
[0030]
A thermoreversible crosslinkable biodegradable resin can be produced by introducing a functional group that forms a thermoreversible crosslinked structure into the above-described biodegradable resin material, a derivative thereof, or a modified product thereof.
[0031]
The functional group necessary for thermoreversible cross-linking may be introduced into the molecular chain terminal of the biodegradable resin material, or may be introduced into the molecular chain. In addition, as a method of introduction, an addition reaction, a condensation reaction, a copolymerization reaction, or the like can be used. Many biodegradable resin materials have an ionic functional group such as a hydroxyl group, a carboxyl group, and an amino group. Therefore, these ionic functional groups can be directly used as thermoreversible crosslinking sites, or these ionic functional groups can be derived into functional groups that form thermoreversible crosslinking.
[0032]
For example, when a hydroxyl group is required, the following method is possible.
(A) Polysaccharides and polyols already have a hydroxyl group.
(A) Polyesters have a hydroxyl group and / or a carboxyl group at the molecular chain terminal. Examples of polyesters having hydroxyl groups at both ends of the molecular chain include hydroxy PBS at both ends (polybutylene succinate). The hydroxy PBS at both ends is, for example, a mixture of 1,4-butanediol and succinic acid in which 1,4-butanediol / succinic acid (molar ratio) is more than 1, more preferably 1.05 or more, and further preferably 1. It is obtained by charging so as to be 1 or more and performing a dehydration condensation reaction.
(C) On the other hand, with respect to polyesters having a carboxyl group at the terminal of the molecular chain, polyesters having hydroxyl groups at both ends can be obtained by sealing the carboxyl group with a hydroxyl group. As a compound used for sealing, a compound having two or more hydroxyl groups such as a diol and a polyol is preferable, and a compound having three or more hydroxyl groups can form a cross-linking point of a three-dimensional cross-linked structure. desirable. For example, a polyester having a hydroxyl group at both ends of a molecular chain can be obtained by esterifying a carboxyl group of polylactic acid obtained by ring-opening polymerization of lactide with pentaerythritol and sealing it. Here, “sealing with a hydroxyl group” means, for example, that the terminal is induced to a hydroxyl group.
[0033]
In the esterification reaction, reagents such as carbodiimides can be used in addition to acids and alkalis. It is also possible to convert the carboxyl group into an acid chloride using thionyl chloride, allyl chloride or the like, followed by esterification by reacting with a hydroxyl group. For those synthesized using dicarboxylic acids and diols as raw materials, such as polybutylene succinate, polyethylene succinate and polybutylene succinate adipate, the molar ratio of diol / dicarboxylic acid of the raw materials used is set to be more than 1. This makes it possible to make all the terminal groups of the molecular chain hydroxyl groups.
[0034]
If the biodegradable resin material and the biodegradable resin material modified with a hydroxyl group are subjected to an ester reaction with hydroxybenzoic acid, the hydroxyl group can be modified into a phenolic hydroxyl group.
[0035]
When a carboxyl group is required, it can be modified into a carboxyl group by bonding a compound having a bifunctional or more carboxylic acid to the hydroxyl group of the biodegradable resin material by the above-described esterification reaction. . In particular, when an acid anhydride is used, a biodegradable resin material having a carboxyl group can be easily prepared. As the acid anhydride, pyromellitic anhydride, trimellitic anhydride, phthalic anhydride, hexahydrophthalic anhydride, maleic anhydride and derivatives thereof can be used.
[0036]
(Electrostatic coupling)
The biodegradable resin obtained from the biodegradable resin material as described above has a functional group. As a mode of electrostatic bonding, when the functional group forms an ion pair, the functional group is a counter ion. In some cases, the functional group is coordinated to the polyion by electrostatic attraction.
[0037]
The form in which the functional group forms an ion pair is an example in which an electrostatic bond is directly formed between the functional group and the functional group.For example, a carboxyl group in a biodegradable resin becomes a carboxylate anion. And the case where the amino group in the biodegradable resin becomes an ammonium cation, and these form an ion pair to form an organic salt.
[0038]
The form in which a functional group is coordinated to a counter ion by electrostatic attraction is an example in which an electrostatic bond is formed between a functional group and a functional group via an ion. For example, a biodegradable resin This is the case, for example, when two or more carboxyl groups therein are ionically bonded to one metal cation.
[0039]
Furthermore, the form in which a functional group is coordinated to a polyion by electrostatic attraction is an example in which an electrostatic bond is formed between a functional group and a functional group via a polyion. When two or more carboxyl groups are ionic bonded to one polycation such as pentaethylenehexamine or polyamine, two or more amino groups in the biodegradable resin are similar to benzenetricarboxylic acid or polyacrylic acid. For example, a case where the polyanion is ionically bonded. As the polyion, a monomer having one or more, preferably two or more ionic functional groups; an oligomer having one or more ionic functional groups, preferably two or more; one or more ionic functional groups , Preferably a polymer having two or more.
[0040]
An ionic functional group is a functional group that dissociates with an ion or binds to an ion to become itself an ion. The electrostatically-bonded cross-linking structure formed from the ionic functional group can be formed from the cationic functional group and the anionic functional group using electrostatic bonding. As the cationic functional group, an amino group, an imino group, and the like are used. As the anionic functional group, a carboxyl group, a sulfonyl group, a phosphate group, a group containing a halide ion, a hydroxyl group, a phenolic hydroxyl group, a thiocarboxyl group and the like are used. In addition, a molecule having one or more ionic functional groups such as an alkali metal ion, an alkaline earth metal ion, a transition metal ion, an anion, a polycation, and a polyanion is used in place of the cationic functional group or the anionic functional group. Thereby, a crosslinkable structure having an electrostatic bond can be formed.
[0041]
Hereinafter, a specific example of the form of the electrostatic coupling will be described.
[0042]
(1) Bonding through ions
A crosslinked structure by electrostatic bonding via ions is called ionic crosslinking. In the case of ionic crosslinking, for example, a biodegradable resin material having an anionic functional group such as a carboxyl group is used, or a carboxyl group or the like is used as the biodegradable resin material. The one into which an anionic functional group is introduced is used. And, as the cationic functional group, using a halide, an inorganic acid salt, a sulfate, a nitrate, a phosphate, an organic acid salt, a carboxylate, etc., the biodegradable resin material having a carboxyl group as described above. By neutralizing, a cationic functional group can be introduced as a counter ion of the anionic functional group. In the neutralization treatment, one or more salts selected from the above salts may be directly added to the biodegradable resin material in a molten state, or may be added as an aqueous solution. In addition, after dissolving the biodegradable resin material in water and / or an organic solvent, one or more salts selected from the above salts may be added.
[0043]
The form of the biodegradable resin thus obtained has a structure in which two or more cations are electrostatically bonded via one anion, and two or more anions are electrostatically bonded via one cation. There is a structure that is dynamically connected.
[0044]
The ions used for ionic crosslinking include alkali metal ions, alkaline earth metal ions, transition metal ions, organic ammonium, halide ions, carboxylate anions, alcoholate anions, phenolate anions, thiocarboxylate anions, and sulfonate anions. And the like, and if necessary, two or more kinds can be used in combination.
[0045]
Among these ions, divalent or higher ions are preferable from the viewpoint of heat resistance.
[0046]
Further, from the viewpoint of the performance (mechanical properties and heat resistance, etc.) of the obtained resin product and molded article, a combination of a biodegradable resin having a carboxyl group and a metal ion is preferable. As the metal ion, sodium ion, Calcium ion, zinc ion, magnesium ion, copper ion and the like are preferable. If necessary, two or more metal ions can be used in combination.
[0047]
The neutralization ratio of the carboxyl group is preferably 1% or more, more preferably 5% or more, further preferably 10% or more, and most preferably 15% or more. The neutralization ratio of the carboxyl group is 100% or less, and preferably 95% or less.
[0048]
The biodegradable resin thus obtained has a structure in which two or more carboxyl groups are electrostatically bonded via a metal ion.
[0049]
(2) Bonding via polyion
A crosslinked structure by electrostatic bonding via a polyion is referred to as a polyion crosslinked. Among polyions used in the polyion crosslinked, a polycation monomer having one or more, preferably two or more ionic functional groups is pentaethylene. In addition to hexamine, tetraethylenepentamine, hexanediamine, 2,4,6-triaminotoluene and the like can be used.
[0050]
Further, as the polyanionic monomer having one or more, preferably two or more ionic functional groups, besides benzenetricarboxylic acid, 2,3-dimethylbutane-1,2,3-tricarboxylic acid or the like can be used. .
[0051]
Further, as the polycation oligomer and polymer having one or more, preferably two or more ionic functional groups, besides polyamine, polyamines such as polyvinylamine and polyethyleneimine can be used.
[0052]
As the polyanion oligomer and polymer having one or more, preferably two or more ionic functional groups, besides polyacrylic acid, polystyrene sulfonic acid, polyphosphoric acid and the like can be used.
[0053]
(3) Bonding by formation of organic salt
For example, a crosslinking site can be formed by utilizing a bond formed electrostatically between a cationic functional group such as an amino group and an anionic functional group such as a carboxyl group.
[0054]
(Structure of crosslinked product)
The cross-linking site described above is composed of two first functional groups and second functional groups that are cleaved by heating and electrostatically bonded by cooling. When solidifying at a lower temperature than the melt processing temperature, the first functional group and the second functional group form a cross-link by electrostatic bonding. And the second functional group. The binding reaction and the cleavage reaction at the cross-linking site proceed reversibly by a change in temperature. Note that the first functional group and the second functional group may be different functional groups or the same functional group. When two identical functional groups are symmetrically combined to form a crosslink, the same functional group can be used as the first functional group and the second functional group.
[0055]
At least one of these functional groups is contained in the first biodegradable resin, and two or more first functional groups and two or more second functional groups are contained in the first biodegradable resin. In some cases.
[0056]
The first functional group may be present at the molecular chain terminal of the first biodegradable resin, or may be present at a terminal other than the terminal such as a side chain. For example, when the first functional group is a carboxyl group, polybutylene succinate having carboxyl groups at both terminals is an example of the first biodegradable resin having the first functional group at the terminal. In this case, the first functional group is present at both ends of the first biodegradable resin, but may be present only at one end.
[0057]
In the case where the first functional group is a hydroxyl group, amylose and cellulose having both terminals methylated are examples of the first biodegradable resin in which the first functional group is present at a position other than the terminal.
[0058]
The main chain of the first biodegradable resin may be either linear or branched. For example, an ester in which 4 mol parts of polylactic acid is bound radially around 1 mol part of pentaerythritol is a branched one. It is an example of a first biodegradable resin in a shape. In addition, when the first functional group is present at the terminal, there are cases where the first functional group is present at all terminals, and when the first functional group is present only at some terminals. is there.
[0059]
Furthermore, a plurality of first functional groups may be bonded to the same site in the molecular chain of the first biodegradable resin. For example, when pentaerythritol is ester-bonded to a carboxyl group terminal of polylactic acid, This is an example in which three hydroxyl groups are bonded to the carboxyl group terminal of polylactic acid. In this case, the carbon derived from methane at the center of pentaerythritol is the same site, and a hydroxyl group as the first functional group is bonded to this carbon via methylene. Note that the phrase “a plurality of first functional groups are bonded to the same site” means that a plurality of first functional groups are bonded via 0 to 5 atoms counted from one atom. From the viewpoint of the performance of the thermoreversible crosslinkable biodegradable resin to be obtained, it is preferable that a plurality of first functional groups are bonded via 0 to 3 atoms.
[0060]
In addition, from the viewpoints of productivity of the resin material, moldability of the resin material, and the like, a first biodegradable resin having a first functional group at a terminal of a molecular chain is preferable. In this case, during the melt processing, the interaction between the first functional groups of different molecular chains is moderate, so that good fluidity and workability can be realized. Further, from the viewpoint of the performance (mechanical properties and heat resistance, etc.) of the molded article, the first biodegradable resin having a branched shape or the first biodegradable resin having a plurality of first functional groups bonded to the same site is preferred. Is preferred. In this case, since a three-dimensional crosslink is formed in the molded article, a molded article having good mechanical properties and heat resistance can be obtained.
[0061]
In addition, the number of functional groups of the biodegradable resin, the mixing ratio of each member, and the like are determined so that the crosslink density becomes a desired value. The crosslinking density is represented by the number of moles of the crosslinking site contained per 100 g of the resin material, and is preferably 0.0001 or more, more preferably 0.001 or more, still more preferably 0.002 or more to realize sufficient heat resistance. On the other hand, in order to realize sufficient moldability, recyclability and biodegradability, it is preferably 10 or less, more preferably 5 or less, and still more preferably 3 or less.
[0062]
(Combined use of covalent cross-linking structure)
The chemical structure of the covalent cross-linking site used in combination with the electrostatic bond is not limited as long as it is a structure that realizes a reversible reaction of forming a cross-linking site by heating to form a cross-linking site and cleaving by cooling. From the viewpoints of productivity of the resin material, moldability of the resin material, performance of the molded body (mechanical properties, heat resistance, and the like), it is desirable to select from the following.
[0063]
(1) Diels-Alder cross-linking
Utilizes a Diels-Alder [4 + 2] cyclization reaction. By introducing conjugated dienes and dienophiles as functional groups, a biodegradable resin that forms thermoreversible crosslinks is obtained. Examples of the conjugated diene include a furan ring, a thiophene ring, a pyrrole ring, a cyclopentadiene ring, 1,3-butadiene, a thiophene-1-oxide ring, a thiophene-1,1-dioxide ring, and a cyclopenta-2,4-dienone. Ring, 2H pyran ring, cyclohexa-1,3-diene ring, 2H pyran 1-oxide ring, 1,2-dihydropyridine ring, 2H thiopyran-1,1-dioxide ring, cyclohexa-2,4-dienone ring, pyran A -2-one ring and a substituent thereof are used as a functional group. As dienophile, use is made of unsaturated compounds which additionally react with conjugated dienes to give cyclic compounds. For example, a vinyl group, an acetylene group, an allyl group, a diazo group, a nitro group, a substituted product thereof, or the like is used as a functional group. The conjugated diene may also act as a dienophile.
[0064]
Among these, for example, cyclopentadiene can be used for the crosslinking reaction. Dicyclopentadiene has both conjugated diene and dienophile effects. Dicyclopentadiene dicarboxylic acid, a dimer of cyclopentadiene carboxylic acid, can be easily obtained from commercially available sodium cyclopentadienyl (E. Rukcenstein et al., J. Polym. Sci. Part A: Polym. Chem. 38, 818-825, 2000). This dicyclopentadiene dicarboxylic acid is introduced as a cross-linking site into a site where a hydroxyl group is present by an esterification reaction into a biodegradable resin material having a hydroxyl group, a biodegradable resin material modified with a hydroxyl group, and the like. You.
[0065]
In addition, for example, when 3-maleimidopropionic acid and 3-furylpropionic acid are used, a biodegradable resin material having a hydroxyl group, a biodegradable resin material modified with a hydroxyl group, and the like can be converted into a hydroxyl group by an esterification reaction. Crosslinking sites can be easily introduced into existing sites (Chujo et al., Macromolecules, Vol. 23, pp. 2636-2641, 1990). For these esterification reactions, catalysts such as carbodiimides can be used in addition to acids and alkalis. Further, it is also possible to convert the carboxyl group into an acid chloride using thionyl chloride or allyl chloride and then esterify it by reacting with a hydroxyl group. When an acid chloride is used, it easily reacts with an amino group, so that it can be introduced into the amino group of amino acids and derivatives thereof.
[0066]
These functional groups form a thermoreversible crosslinked structure as shown in the following general formula (I).
[0067]
Embedded image

[0068]
(2) Nitroso dimer crosslinking
For example, nitrosobenzene is used for the crosslinking reaction. As nitrosobenzene, for example, dinitrosopropane, dinitrosohexane, dinitrosobenzene, dinitrosotoluene and the like are used. For example, a dimer of 4-nitroso-3,5-benzylic acid (US Pat. No. 3,872,057) describes a method for synthesizing a dimer of 4-nitroso-3,5-dichlorobenzoyl chloride. By reacting with the hydroxyl group of a biodegradable resin material having a hydroxyl group, the hydroxyl group of a biodegradable resin material modified with a hydroxyl group, etc. A thermoreversible crosslinking site can be easily introduced. In addition, when an acid chloride is used, it can easily react with an amino group and can be introduced into the amino group of amino acids and derivatives thereof.
[0069]
These functional groups form a thermoreversible crosslinked structure as shown by the following general formula (II).
[0070]
Embedded image

[0071]
In the general formula (II), two nitroso groups form a nitroso dimer and are crosslinked by cooling. This crosslink is cleaved by heating.
[0072]
(3) Acid anhydride ester type crosslinking
Acid anhydrides and hydroxyl groups can be used in the crosslinking reaction. As the acid anhydride, an aliphatic carboxylic anhydride, an aromatic carboxylic anhydride, or the like is used. Further, any of a cyclic acid anhydride group and a non-cyclic anhydride group can be used, but a cyclic acid anhydride group is preferably used. Examples of the cyclic acid anhydride group include a maleic anhydride group, a phthalic anhydride group, a succinic anhydride group, and a glutaric anhydride group.Examples of the non-cyclic acid anhydride group include an acetic anhydride group and a propionic anhydride group. And a benzoic anhydride group. Among them, maleic anhydride group, phthalic anhydride group, succinic anhydride group, glutaric anhydride group, pyromellitic anhydride group, trimellitic anhydride group, hexahydrophthalic anhydride group, acetic anhydride group, propionic anhydride group, anhydride Benzoic acid groups and their substituted products are preferred as acid anhydrides that react with hydroxyl groups to form a crosslinked structure.
[0073]
As the hydroxyl group, a hydroxyl group of a biodegradable resin material having a hydroxyl group or a hydroxyl group of a biodegradable resin material into which a hydroxyl group is introduced by various reactions is used. Further, hydroxy compounds such as diols and polyols may be used as the crosslinking agent. Furthermore, diamines and polyamines can be used as crosslinking agents. As the acid anhydride, for example, when using two or more acid anhydrides such as pyromellitic anhydride, a biodegradable resin material having a hydroxyl group, a biodegradable resin material modified with a hydroxyl group, and the like On the other hand, it can be used as a crosslinking agent.
[0074]
Further, a compound having two or more maleic anhydrides can be easily obtained by copolymerizing maleic anhydride with an unsaturated compound by vinyl polymerization (JP-A-11-106578, JP-A-2000-34376). . This can also be used as a crosslinking agent for a biodegradable resin material having a hydroxyl group, a biodegradable resin material modified with a hydroxyl group, and the like.
[0075]
The acid anhydride and the hydroxyl group as described above form a thermoreversible crosslinked structure as shown by the following general formula (III).
[0076]
Embedded image

[0077]
In the general formula (III), the acid anhydride group and the hydroxyl group form an ester and are crosslinked by cooling. This crosslink is cleaved by heating.
[0078]
(4) Halogen-amine type crosslinking
A thermoreversible crosslinking site can be formed from a polyamine, tetramethylhexanediamine, or the like and an alkyl halide. For example, a halide having a carboxyl group such as 4-bromomethylbenzoic acid is ester-bonded to a biodegradable resin material having a hydroxyl group, a biodegradable resin material modified with a hydroxyl group, or the like. Can be obtained. To this, for example, by adding tetramethylhexanediamine as a crosslinking agent, a biodegradable resin that forms thermoreversible crosslinking is obtained.
[0079]
Examples of the halogenated alkyl group include alkyl bromide, alkyl chloride, phenyl bromide, phenyl chloride, benzyl bromide, and benzyl chloride.
[0080]
Moreover, as the amino group, a tertiary amino group is preferable, and examples thereof include a dimethylamino group, a diethylamino group, and a diphenylamino group. Among them, a dimethylamino group is preferable. The combination of the halogenated alkyl group and the tertiary amino group is not particularly limited, and examples thereof include a combination of benzyl bromide and a dimethylamino group.
[0081]
These functional groups form a thermoreversible crosslinked structure as shown by the following general formula (IV).
[0082]
Embedded image

[0083]
In the general formula (IV), the alkyl halide group and the tertiary amine form a quaternary ammonium salt covalent bond upon cooling to form a crosslink. This crosslink is cleaved by heating.
[0084]
(5) Urethane type crosslinking
A thermoreversible crosslinking site can be formed from isocyanate and active hydrogen. For example, a polyvalent isocyanate is used as a crosslinking agent to react with a hydroxyl group, an amino group, and a phenolic hydroxyl group of a biodegradable resin material and a derivative thereof. Further, a molecule having two or more functional groups selected from a hydroxyl group, an amino group and a phenolic hydroxyl group can be added as a crosslinking agent. Further, a catalyst can be added to keep the cleavage temperature in a desired range. Further, dihydroxybenzene, dihydroxybiphenyl, a phenol resin or the like can be added as a crosslinking agent.
[0085]
In addition, a polyvalent isocyanate is used as a cross-linking agent to react with a hydroxyl group, an amino group, and a phenolic hydroxyl group of a biodegradable resin material and a derivative thereof. Dihydroxybenzene, dihydroxybiphenyl, phenolic resin and the like can be added as a crosslinking agent. Examples of the polyvalent isocyanate include tolylene diisocyanate (TDI) and a polymer thereof, 4,4′-diphenylmethanesiocyanate (MDI), hexamethylene diisocyanate (HMDI), 1,4-phenylene diisocyanate (DPDI), 1,3- Phenylene diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, xylylene diisocyanate and the like can be used.
[0086]
Further, in order to adjust the cleavage temperature, an organic compound such as 1,3-diacetoxytetrabutyldistannoxane, amines, metal soap, or the like may be used as a cleavage catalyst.
[0087]
The above functional groups form a thermoreversible crosslinked structure as shown by the following general formula (V).
[0088]
Embedded image

[0089]
In the general formula (V), the phenolic hydroxyl group and the isocyanate group form urethane and become crosslinked by cooling. This crosslink is cleaved by heating.
[0090]
(6) Azlactone-hydroxyaryl type crosslink
Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, a naphthyl group, an anthryl group, a phenanthryl group and a group derived from these groups, and a phenolic hydroxyl group bonded to these groups. Reacts with the azlactone structure contained in the group forming the crosslinked structure. As a material having a phenolic hydroxyl group, a biodegradable resin material having a phenolic hydroxyl group, a biodegradable resin material modified with hydroxylphenols, or the like is used.
[0091]
Examples of the azlactone structure include polyvalent compounds such as 1,4- (4,4′-dimethylazlactyl) butane, poly (2-vinyl-4,4′-dimethylazalactone), bisazlactonebenzene, and bisazlactonehexane. Azlactone is preferred.
[0092]
Also, azlactone-phenol reaction-crosslinked bisazlactylbutane and the like can be used, and these are described, for example, in Engle et al. Macromol. Sci. Re. Macromol. Chem. Phys. C33, No. 3, pp. 239-257, 1993.
[0093]
These functional groups form a thermoreversible crosslinked structure as shown by the following general formula (VI).
[0094]
Embedded image

[0095]
In the general formula (VI), the azlactone group and the phenolic hydroxyl group form a covalent bond upon cooling to form a crosslink. This crosslink is cleaved by heating.
[0096]
(7) Carboxyl-alkenyloxy type crosslinking
As a material having a carboxyl group, a biodegradable resin material having a carboxyl group, a biodegradable resin material modified with a carboxyl group, or the like is used. Examples of the alkenyloxy structure include vinyl ether, allyl ether and structures derived from these structures, and those having two or more alkenyloxy structures can also be used.
[0097]
Also, alkenyl ether derivatives such as bis [4- (vinyloxy) butyl] adipate and bis [4- (vinyloxy) butyl] succinate can be used as a crosslinking agent.
[0098]
These functional groups form a thermoreversible crosslinked structure as shown in the following general formula (VII).
[0099]
Embedded image

[0100]
In the general formula (VII), the carboxyl group and the vinyl ether group form a hemiacetal ester by cooling to form a crosslink. This cross-link is cleaved by heating (JP-A-11-35675, JP-A-60-179479).
[0101]
(8) Crosslinking agent
As described above, a compound having two or more functional groups capable of forming a thermoreversible crosslinking site in a molecule can be a crosslinking agent.
[0102]
Examples of the crosslinking agent having an acid anhydride group include a bisphthalic anhydride compound, a bissuccinic anhydride compound, a bisglutaric anhydride compound, and a bismaleic anhydride compound.
[0103]
Examples of the crosslinking agent having a hydroxyl group include glycols such as ethylene glycol, diethylene glycol, and triethylene glycol; 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol. And alcohol compounds such as trimethylolethane, trimethylolpropane and pentaerythritol.
[0104]
Examples of the crosslinking agent having a carboxyl group include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, maleic acid, and fumaric acid.
[0105]
Examples of the crosslinking agent having a vinyl ether group include bis [4- (vinyloxy) butyl] adipate, bis [4- (vinyloxy) butyl] succinate, ethylene glycol divinyl ether, butanediol divinyl ether, and 2,2-bis [p -(2-vinyloxyethoxy) phenyl] propane.
[0106]
Examples of the crosslinking agent having a halogenated alkyl group include α, α′-dibromoxylene, α, α′-dichloroxylene, bisbromomethylbiphenyl, bischloromethylbiphenyl, bisbromodiphenylmethane, bischlorodiphenylmethane, and bisbromomethyl. Benzophenone, bischloromethylbenzophenone, bisbromodiphenylpropane, bischlorodiphenylpropane.
[0107]
Examples of the crosslinking agent having a tertiary amino group include tetramethylethylenediamine, tetramethylhexanediamine, and bisdimethylaminobenzene.
[0108]
Examples of the crosslinking agent having a phenolic hydroxyl group include dihydroxybenzene, dihydroxybiphenyl, a resol type phenol resin, and a novolak type phenol resin.
[0109]
Examples of the crosslinking agent having an isocyanate group include aromatic compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, and p-phenylene diisocyanate. Aliphatic diisocyanates such as aliphatic diisocyanate and hexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate; and aryl aliphatic diisocyanates such as xylylene diisocyanate.
[0110]
Examples of the crosslinking agent having an azlactone group include bisazlactone butane, bisazlactonebenzene, and bisazlactonehexane.
[0111]
Examples of the crosslinking agent having a nitroso group include dinitrosopropane, dinitrosohexane, dinitrosobenzene, and dinitrosotoluene.
[0112]
Here, when there are two or more covalently bonding functional groups, one functional group (first functional group) is present in the biodegradable resin (first biodegradable resin) and the other functional group (first functional group). In some cases, the second functional group is present in a biodegradable resin (first biodegradable resin) different from the biodegradable resin (first biodegradable resin) in which the first functional group is present. (2 biodegradable resins). Hereinafter, an example in which both the first functional group and the second functional group are present in the same first biodegradable resin will be described.
[0113]
(1) A polycarboxylic acid resin in which the hydroxyl group of amylose and cellulose forms an ester bond with maleic anhydride is prepared. 2-aminoethyl vinyl ether is ester-bonded to a part of the carboxylic acid of the resin with carbodiimides. In this case, a carboxylic acid structure (first functional group) and a vinyl ether group (second functional group) are present in the same biodegradable resin (first biodegradable resin), and a carboxyl-alkenyloxy-type cross-linking occurs. To form
[0114]
(2) Although pentaerythritol is ester-bonded to the carboxyl terminal of polylactic acid, a Diels-Alder reaction product of cyclopentadienecarboxylic acid and maleimide (3,5-dioxo-4-) is added to the four hydroxyl groups at both terminals. Aza-tricyclo [5.2.1.0 ^2,6 In the case of the first biodegradable resin to which deca-8-ene-10-carboxylic acid is ester-bonded, the first functional group and the second functional group are the same cyclopentadiene derivative, and the first functional group and the second functional group are the same. The functional group is present in the same first biodegradable resin, and forms a Diels-Alder crosslink between cyclopentadienes by removing maleimide by heating under reduced pressure. The crosslink is formed at both ends of the first biodegradable resin.
[0115]
(3) In the case of the first biodegradable resin in which cyclopentadiene carboxylic acid is ester-bonded to both ends of polybutylene succinate having hydroxyl groups at both ends, the first functional group and the second functional group have the same cyclopenta-2 , 4-dien-1-yl group in which the first and second functional groups are present in the same first biodegradable resin, forming a Diels-Alder type crosslink. The cross-links are formed at both ends of the molecular chain of the first biodegradable resin.
[0116]
(4) In the case of the first biodegradable resin in which nitrosobenzoic acid is ester-bonded to both ends of polybutylene succinate having hydroxyl groups at both ends, the first functional group and the second functional group are the same nitrosobenzoyl group. , The first functional group and the second functional group are present in the same first biodegradable resin, forming a nitroso dimer type crosslink. The crosslink is formed at both ends of the first biodegradable resin.
[0117]
The resin products (1) and (2) are obtained by introducing a first functional group and a second functional group into a first biodegradable resin material. For example, in the case of (2), pentaerythritol is ester-bonded to the carboxyl terminal of polylactic acid, but the four hydroxyl groups are reacted with fluoric acid to progress the dechlorination reaction.
[0118]
Further, when producing the resin products of the above (3) and (4), the first functional group and the second functional group that form the cross-linking site are covalently bonded in advance, and the first functional group and the second functional group are formed. A compound having a group that reacts with the first biodegradable resin material in addition to the bifunctional group (for example, a dimer of dicyclopentadiene dicarboxylic acid and nitrosobenzoic acid) can be used as a crosslinking agent. If such a cross-linking agent and the first biodegradable resin material are mixed and reacted, and the cross-linking agent is bonded to the first biodegradable resin material, a resin product having a cross-linked site cross-linked can be obtained with good productivity. be able to. In particular, as in the above (3) and (4), when the first functional group and the second functional group are the same and the same functional groups are symmetrically bonded to form a crosslinked site, dicyclopentadienedicarboxylic acid is used. Dimers with symmetrically linked functional groups, such as dimers of acids and nitrosobenzoic acids, can be used as crosslinking agents.
[0119]
In addition, when the crosslinking agent contains a plurality of functional groups, it is preferable that the functional groups are of the same kind, because the production of the crosslinking agent is easy and the crosslinking reaction is easily controlled.
[0120]
On the other hand, the second functional group may be present in a second biodegradable resin different from the first biodegradable resin in which the first functional group is present. An example of such a case is a first biodegradable resin in which pentaerythritol is ester-bonded to the carboxyl group terminal of polylactic acid but 3-maleimidopropionic acid is further ester-bonded to the four hydroxyl groups at both terminals. A combination of a pentaerythritol ester-bonded to the carboxyl group terminal of polylactic acid but a 4-biodegradable resin in which 3-furylpropionic acid is further ester-bonded to the four hydroxyl groups at both ends. it can. The first functional group is a maleimide structure, the second functional group is a furyl group, and these functional groups crosslink in a Diels-Alder type. The cross-link is formed between the molecular chain terminal of the first biodegradable resin and the molecular chain terminal of the second biodegradable resin.
[0121]
Also, a first biodegradable resin having both the first functional group and the second functional group, a second biodegradable resin having both the first functional group and the second functional group, the first functional group and the second functional group The resin material may be composed of a mixture containing a first biodegradable resin having only one of the groups, a second biodegradable resin having only one of the first functional group and the second functional group, and the like.
[0122]
Even when such a resin product is manufactured, the first functional group and the second functional group that form the cross-linking site are covalently bonded in advance, and the first biodegradation other than the first functional group and the second functional group is performed. A compound having a group that reacts with the conductive resin material can be used as a crosslinking agent. By mixing and reacting such a crosslinking agent with the first biodegradable resin material and the second biodegradable resin material, and bonding the crosslinking agent to the first biodegradable resin material and the second biodegradable resin material, In addition, it is possible to obtain a resin product having a crosslinked site crosslinked with good productivity.
[0123]
On the other hand, the second functional group may be present in the linker. In this case, the resin material is composed of at least a first biodegradable resin having a first functional group and a linker having a second functional group, and the linker impairs the biodegradability of the first biodegradable resin. None are used. By using a linker, a wider range of resin products can be realized, so that the degree of freedom such as the productivity of the resin product, the moldability of the resin product, and the performance (such as mechanical properties and heat resistance) of the molded product is widened.
[0124]
The linker is a monomer, oligomer, polymer, or the like having two or more second functional groups in one molecule, and the second functional group of the linker forms a crosslinking site with the first functional group of the first biodegradable resin. I do. As a result, in the molded article, two or more first biodegradable resins are crosslinked via the linker. Further, at the time of melting, the crosslinked site is cleaved, and the bonding and cleavage of the crosslinked site are in a thermoreversible reaction. A linker having two or more second functional groups in one molecule may be called a cross-linking agent. Such a linker and the first biodegradable resin are mixed and reacted to form a resin. Manufacturing things. If necessary, a plurality of linkers may be used in combination, or a plurality of first biodegradable resins may be used in combination.
[0125]
Examples of the monomeric linker include the following.
[0126]
(1) Toluene diisocyanate is used as a linker. In this case, the second functional group is an isocyanate group, and as the first biodegradable resin, for example, a biodegradable polyester having a phenolic hydroxyl group is used. The first functional group is a phenolic hydroxyl group, and the isocyanate group of the toluene diisocyanate forms a crosslink with the phenolic hydroxyl group of the biodegradable polyester by a urethane bond, and the biodegradable polyester having a phenolic hydroxyl group is Crosslinked via toluene diisocyanate.
[0127]
(2) N, N'-bismaleimide-4,4'-diphenylmethane is used as a linker. In this case, the second functional group has a maleimide structure, and as the first biodegradable resin, for example, polylactic acid in which furic acid is ester-bonded to a hydroxyl group terminal is used. The first functional group is a furyl group, and the maleimide structure of N, N′-bismaleimide-4,4′-diphenylmethane forms a Diels-Alder type crosslink with a furyl group bonded to polylactic acid, Polylactic acid is cross-linked at one end via N, N'-bismaleimide-4,4'-diphenylmethane.
[0128]
(3) 1,2,3,4-butanetetracarboxylic dianhydride (maleic anhydride and vinyl polymer dimer) is used as a linker. In this case, the second functional group has a maleic anhydride structure, and as the first biodegradable resin, for example, an aliphatic polyester having hydroxyl groups at both ends is used. The first functional group is a hydroxyl group, and the maleic anhydride structure of 1,2,3,4-butanetetracarboxylic dianhydride has a hydroxyl group bonded to an aliphatic polyester and an acid anhydride ester type. Aliphatic polyesters which form crosslinks and have hydroxyl groups at both ends are crosslinked at both ends via 1,2,3,4-butanetetracarboxylic dianhydride.
[0129]
Further, pyromellitic anhydride and the like can be used in the same manner.
[0130]
On the other hand, examples of the polymeric linker include a copolymer of maleic anhydride and methyl vinyl ether. In this case, the second functional group has an acid anhydride structure derived from maleic anhydride, and as the first biodegradable resin, for example, polybutylene succinate having hydroxyl groups at both ends is used. The first functional group is a hydroxyl group, and the acid anhydride structure derived from maleic anhydride forms a cross-link with the hydroxyl group of polybutylene succinate having hydroxyl groups at both ends by an ester bond. Polybutylene succinate is cross-linked at both ends via a copolymer of maleic anhydride and methyl vinyl ether.
[0131]
When the linker contains a plurality of functional groups, it is preferable that the functional groups are of the same kind, since the linker can be easily produced and the crosslinking reaction can be easily controlled.
[0132]
(Molding)
When producing a molded body using the biodegradable resin material that forms a thermoreversible crosslink obtained as described above, an inorganic filler, an organic filler, a reinforcing material, a coloring agent, a stabilizer, an antibacterial agent, A fungicide, a flame retardant, and the like can be used in combination as needed.
[0133]
As the inorganic filler, silica, alumina, talc, sand, clay, slag, and the like can be used. Organic fibers such as vegetable fibers can be used as the organic filler. As the reinforcing material, glass fiber, carbon fiber, acicular inorganic substance, fibrous Teflon resin, or the like can be used. As the antibacterial agent, silver ions, copper ions, zeolites containing these, and the like can be used. As the flame retardant, a silicone flame retardant, a bromine flame retardant, a phosphorus flame retardant, or the like can be used.
[0134]
In addition, the dissociation temperature of the crosslinked portion is preferably 100 ° C. or higher in order to form a sufficient crosslink in the operating temperature range of the molded body. On the other hand, melt processing is performed at a temperature at which thermal degradation of the biodegradable resin material is not a problem. For this reason, the temperature is preferably 280 ° C or lower, more preferably 250 ° C or lower. Further, the dissociation temperature of the crosslinked portion affects the melt processing temperature of the biodegradable resin when producing a molded article. Usually, the melt processing temperature is set to 10 ° C. or more of the dissociation temperature, and is set to a temperature or less at which thermal decomposition of the biodegradable resin material becomes a problem. Specifically, in order to realize a favorable molten state, the temperature is preferably 120 ° C. or higher, more preferably 150 ° C. or higher. On the other hand, 300 ° C. Or less, and more preferably 250 ° C. or less. Then, after melting, the biodegradable resin material is cooled and shaped. The cooling temperature is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, and is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, in order to form a sufficient crosslink. In addition, during the cooling step and after the cooling step, the molded body may be held at a predetermined temperature as necessary in order to form a sufficient cross-link and to exhibit sufficient characteristics of the molded body. By maintaining the temperature of the molded body, the formation of the crosslinks further proceeds, and the characteristics of the molded body can be improved.
[0135]
In addition, from the same viewpoint, the melting temperature (flow starting temperature) of the biodegradable resin material is preferably 100 ° C. or higher, while 280 ° C. or lower is preferable, and 250 ° C. or lower is more preferable.
[0136]
The resins and resin compositions as described above are used for injection molding, film molding, blow molding, foam molding, etc., for electrical and electronic equipment such as housing for electric appliances, building materials, and automotive parts. It can be processed into molded products for daily necessities, medical uses, agricultural uses, etc.
[0137]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but these do not limit the present invention in any way. Unless otherwise specified below, commercially available high-purity reagents were used. In addition, the number average molecular weight and the weight average molecular weight were measured by a gel permeation chromatogram method, and were converted using standard polystyrene.
[0138]
(Example 1)
600 g (5.1 mol) of succinic acid and 406 g (4.5 mol) of 1,4-butanediol were charged into a 3 L separable flask equipped with a stirrer, a flow condenser, a thermometer, and a nitrogen inlet tube. Dehydration condensation was performed at 180 to 220 ° C. for 7 hours. Subsequently, water was distilled off under reduced pressure to obtain an aliphatic polyester (A) having a carboxyl group at both ends having a number average molecular weight of 2,000.
[0139]
100 g of the aliphatic polyester (A) having carboxyl groups at both ends thus obtained was melted at 130 ° C. in a nitrogen atmosphere, and 33 mL of an aqueous sodium acetate solution (1 N) was added thereto, followed by stirring. Subsequently, the solvent was distilled off under reduced pressure to obtain a composition (A-1) in which the carboxyl group was neutralized by 33%. Similarly, using 66 mL and 100 mL of an aqueous sodium acetate solution (1 N), compositions (A-2) and (A-3) having carboxyl groups neutralized at 66% and 100%, respectively, were obtained.
[0140]
Further, using 167 mL, 333 mL, and 500 mL of an aqueous copper (II) acetate solution (0.1 N), the compositions (A-4) and (A-5) in which carboxyl groups were neutralized by 33%, 66%, and 100%, respectively. ) And (A-6).
[0141]
(Example 2)
A 3 L separable flask equipped with a stirrer, a flow condenser, a thermometer, and a nitrogen inlet tube was charged with 716 g (6.1 mol) of succinic acid and 613 g (6.8 mol) of 1,4-butanediol, and placed under a nitrogen atmosphere. Dehydration condensation was performed at 180 to 220 ° C. for 3 hours. Subsequently, 0.15 g of tetraisopropoxytitanate was added as a catalyst, and a deglycol-reaction was performed at 180 to 220 ° C. for 3 hours to obtain a hydroxyl group-terminated aliphatic polyester (B) having a number average molecular weight of 15,000.
[0142]
On the other hand, 73 g of pyromellitic anhydride was dissolved in 1 L of tetrahydrofuran and refluxed under a nitrogen atmosphere. To this, a chloroform solution at 50 ° C. in which 500 g of both-end hydroxyl group aliphatic polyester (B) was dissolved was dropped and mixed for 1 hour. Thereafter, reflux was continued for 3 hours, the solvent was distilled off, excess pyromellitic anhydride was washed with hot water, and dried to obtain a polycarboxylic aliphatic polyester (C).
[0143]
100 g of the polycarboxylic acid aliphatic polyester (C) thus obtained was melted at 130 ° C. in a nitrogen atmosphere, and 13 mL of an aqueous sodium acetate solution (1 N) was added thereto, followed by stirring. Subsequently, the solvent was distilled off under reduced pressure to obtain a composition (C-1) in which the carboxyl group was neutralized by 33%. Similarly, 27 mL and 40 mL of an aqueous sodium acetate solution (1 N) were used to obtain compositions (C-2) and (C-3) in which carboxyl groups were neutralized at 66% and 100%, respectively.
[0144]
Further, 133 mL, 267 mL and 400 mL of an aqueous copper (II) acetate solution (0.1 N) were used, and the compositions (C-4) and (C-5) in which the carboxyl groups were neutralized by 33%, 66% and 100%, respectively. ) And (C-6).
[0145]
(Performance evaluation)
Melting point: Measured using a DSC measuring device DSC6200 (trade name) manufactured by Seiko Instruments Inc.
[0146]
Heat resistance: A penetration test (based on JIS K 7196) was performed using a TG-DTA measuring device (trade name: TMA-40) manufactured by Shimadzu Corporation. The sample without any deformation was marked with “○”. In addition, those having particularly excellent heat resistance were rated as ◎.
[0147]
Biodegradability: A molded article was prepared by hot pressing and buried in the soil. After 6 months, a substance having degradability was recognized as ○, and a specimen not degradable was rated as ×.
[0148]
Recyclability: After heating to 180 ° C. to form a molten state, and subsequently cooling to room temperature five times, the above heat resistance test was performed. 180 ° C. and normal temperature for 5 cycles) No deformation was evaluated as ○. In addition, those having particularly excellent recyclability were rated as ◎.
[0149]
Moldability: A test piece of 6.4 mm × 12.5 mm × 125 mm was injection-molded at 200 ° C .;
[0150]
Table 1 shows the evaluation results.
[0151]
[Table 1]

[0152]
As shown in Table 1, the compositions (A-1) to (A-6) and the compositions (C-1) to (C-6) have all the properties of heat resistance, biodegradability, recyclability and moldability. It turned out to be excellent.
[0153]
The heat resistance of the neutralized product was better with divalent copper than with monovalent sodium. In addition, those having a higher cross-link density tended to have higher heat resistance.
[0154]
(Polyester resin M-1 to M-4)
(M-1) Carboxylic acid at both ends PBS: 1,4-butanediol and succinic acid, 1,4-butanediol / succinic acid (molar ratio) is smaller than 1, more preferably 0.95 or less, and still more preferably. Is adjusted to 0.9 or less, and a dehydration condensation reaction is performed to obtain PBS having a number average molecular weight of 100 to 1,000,000 and carboxyl groups at both ends. By reducing the pressure at a reaction temperature of 110 to 250 ° C., the dehydration condensation reaction proceeds and the molecular weight increases. Also, by adding 0.1 to 5 parts by mass of a catalyst such as tetraisopropoxy titanium to 100 parts by mass of the monomer mixture, the dehydration condensation reaction proceeds and the molecular weight increases.
[0155]
(M-2) Polyvalent carboxylic acid PBS: 1,4-butanediol and succinic acid, wherein 1,4-butanediol / succinic acid (molar ratio) is more than 1, more preferably 1.05 or more, and still more preferably Is adjusted to 1.1 or more, and a dehydration-condensation reaction is performed to obtain PBS having hydroxyl groups at both ends with a number average molecular weight of 100 to 1,000,000. By reducing the pressure at a reaction temperature of 110 to 250 ° C., the dehydration condensation reaction proceeds and the molecular weight increases. Also, by adding 0.1 to 5 parts by mass of a catalyst such as tetraisopropoxy titanium to 100 parts by mass of the monomer mixture, the dehydration condensation reaction proceeds and the molecular weight increases.
[0156]
An ester bond is formed between the thus-obtained hydroxy-terminated hydroxy PBS and pyromellitic acid to obtain a polycarboxylic acid PBS (M-2) having a number average molecular weight of 100 to 1,000,000. By using pyromellitic acid in a large excess (10 to 100 times by mole) with respect to the hydroxyl group, a PBS in which pyromellitic acid is ester-bonded to both terminals is obtained. The esterification reaction can proceed by refluxing the hydroxy-terminated hydroxyPBS and pyromellitic acid in a mixed solvent of chloroform and THF or a toluene solvent. In addition, the pyromellitic acid used in excess can be removed by washing with hot water after removing the solvent.
[0157]
(M-3) Polycarboxylic acid PLA: PLA (polylactic acid) having a number average molecular weight of 100 to 1,000,000 is obtained by ring-opening polymerization of lactide (dimer of lactic acid). The ring opening reaction proceeds by setting the reaction temperature to 120 to 220 ° C. Further, by using 0.01 to 1 part by mass of stannous octoate as a catalyst with respect to 100 parts by mass of the monomer, the dehydration condensation reaction can be further advanced to increase the molecular weight.
[0158]
An ester bond is formed between the PLA thus obtained and pyromellitic acid to obtain a polycarboxylic acid PLA (M-3) having a number average molecular weight of 100 to 1,000,000. By using pyromellitic acid in a large excess (10 to 100 times by mole) with respect to the hydroxyl group, a PLA in which pyromellitic acid is ester-bonded to one terminal is obtained. By refluxing PLA and pyromellitic acid in a mixed solvent of chloroform and THF or a toluene solvent, the esterification reaction can proceed. In addition, the pyromellitic acid used in excess can be removed by washing with hot water after removing the solvent.
[0159]
(M-4) Polyvalent carboxylic acid PLA: An ester bond is formed between PLA and pentaerythritol to obtain a terminal hydroxy PLA having a number average molecular weight of 100 to 1,000,000. The esterification reaction can proceed by using equimolar amounts of pyridine and 1-ethyl-3- (3′-dimethylaminopropyl) carbodiimide hydrochloride as a dehydration catalyst in a chloroform solvent. Further, it can be purified by washing with water.
[0160]
An ester bond is formed between the terminal hydroxy PLA thus obtained and a large excess (10 to 100 times by mole) of pyromellitic acid, whereby a polyvalent carboxylic acid PLA having a number average molecular weight of 100 to 1,000,000 (M- Obtain 4). By refluxing the terminal hydroxy PLA and pyromellitic acid in a mixed solvent of chloroform and THF or a toluene solvent, the esterification reaction can proceed. In addition, the pyromellitic acid used in excess can be removed by washing with hot water after removing the solvent.
[0161]
(Example 3)
The polyester resins (M-1) to (M-4) obtained above are melted at 100 to 200 ° C., and ions are added. Cu, Na, Mg, Ca, or the like is used as an ion source (cation). An aqueous solution of copper acetate, sodium acetate, calcium acetate, magnesium acetate or the like is added so that the degree of neutralization is preferably 1% or more, more preferably 10% or more, while 100% or less, more preferably 90% or less; Water is immediately distilled off under reduced pressure. The dissociation temperature of the crosslinked portion is 100 to 200 ° C., but the temperature at which moldable fluidity is obtained can be adjusted by the molecular weight of the polyester resin used, the carboxyl group density, the degree of neutralization of the carboxyl group by metal ions, and the like.
[0162]
(Example 4)
Polyester resins (M-1) to (M-4) are dissolved in a mixed solution of chloroform / ethanol / water, and a polyamine is added. The degree of neutralization is preferably 1% or more, more preferably 10% or more, while it is 100% or less, preferably 90% or less. The polyamine is added, and the solvent is immediately distilled off under reduced pressure. The dissociation temperature of the crosslinked portion is 100 to 200 ° C., but the temperature at which moldable fluidity is obtained depends on the molecular weight of the polyester resin used, the carboxyl group density, the degree of neutralization of the carboxyl group by the polyamine, and the per molecule of the polyamine. It is realized by optimizing the number of amino groups and the density of amino groups.
[0163]
(Example 5) Combined use of covalently crosslinked structure
The polyester resins (M-1) to (M-4) obtained above are melted at 100 to 200 ° C., and ions are added. Cu, Na, Mg, Ca, or the like is used as an ion source (cation). Aqueous solutions such as copper acetate, sodium acetate, calcium acetate and magnesium acetate are added so that the degree of neutralization is preferably 1% or more, more preferably 10% or more, while 100% or less, more preferably 95% or less; Water is immediately distilled off under reduced pressure. The dissociation temperature of the crosslinked portion is 100 to 200 ° C., but the temperature at which moldable fluidity can be obtained can be adjusted by the molecular weight of the polyester resin used, the carboxyl group density, the degree of neutralization of the carboxyl group by metal ions, and the like.
[0164]
The composition thus obtained is mixed with, for example, bis [4- (vinyloxy) butyl] adipate as a crosslinking agent, and an ionic cross-linking structure and a carboxyl-vinyl ether-type supply-bonding cross-linking structure are used in combination. I do.
[0165]
(Example 6) Combined use of covalent cross-linking structure
The polyester resins (M-1) to (M-4) are melted at 100 to 200 ° C., and ions are added. Cu, Na, Mg, Ca, or the like is used as an ion source (cation). An aqueous solution of copper acetate, sodium acetate, calcium acetate, magnesium acetate or the like is added so that the degree of neutralization is preferably 1% or more, more preferably 10% or more, while 100% or less, more preferably 90% or less; Water is immediately distilled off under reduced pressure.
[0166]
On the other hand, hemiacetal ester was melt-mixed with polyester resins (M-1) to (M-4) having a carboxyl group at 150 to 250 ° C. using 1,4-butanediol divinyl ether or the like as a crosslinking agent. A carboxyl-vinyl ether type cross-linked polyester resin having a bond as a cross-linking site is obtained.
[0167]
Then, by mixing these compositions, an ionic cross-linking structure and a carboxyl-vinyl ether type supply-bonding cross-linking structure are used in combination.
[0168]
【The invention's effect】
Sufficient heat resistance, moldability, recyclability and biodegradability are achieved by using a biodegradable resin that has a functional group that forms a thermoreversible cross-linked structure that is electrostatically bonded by cooling and that is cleaved by heating. realizable.

Claims (15)

A biodegradable resin in which at least two functional groups are electrostatically bonded and cross-linked, wherein the cross-link is cleaved by heating to a certain temperature or higher, and the cross-link is formed again by cooling. Reversible crosslinkable biodegradable resin. The electrostatic bonding is performed when the functional group forms an ion pair, the functional group is coordinated to a counter ion by electrostatic attraction, or the functional group is coordinated to a polyion by electrostatic attraction. 2. The biodegradable resin according to claim 1, wherein the resin is at least one of modes. The functional group is one or more ionic functional groups selected from the group consisting of a hydroxyl group, a phenolic hydroxyl group, a carboxyl group, a sulfonyl group, a phosphoric acid group, a thiocarboxyl group, a group containing halogen, an amino group and an imino group. The biodegradable resin according to claim 1 or 2, wherein The biodegradable resin according to any one of claims 1 to 3, wherein the biodegradable resin has one or more structures selected from the group consisting of polyesters, polyamino acids, and polyols. The biodegradable resin according to any one of claims 1 to 4, wherein the main chain of the biodegradable resin has at least one of a linear structure and a branched structure. The functional group according to any one of claims 1 to 5, wherein one or two or more of the functional groups are present at the same site in at least one of a terminal and a side chain of the biodegradable resin. Biodegradable resin. The biodegradable resin according to any one of claims 1 to 6, wherein a covalent and thermoreversible crosslinked structure is used in combination. A first biodegradable resin having a first functional group that forms a thermoreversible cross-linked structure that forms an electrostatic bond by cooling and that is cleaved by heating;
A biodegradable resin composition comprising: a second biodegradable resin having a second functional group that forms an electrostatic bond with the first functional group upon cooling and forms a thermoreversible crosslinked structure that is cleaved by heating. A biodegradable resin that forms a thermoreversible cross-linked structure in which a functional group is coordinated to a counter ion by cooling by cooling and is cleaved by heating;
A biodegradable resin composition comprising the ion source of the counter ion. The counter ion is an alkali metal ion, an alkaline earth metal ion, a transition metal ion, an organic ammonium, a halide ion, a carboxylate anion, an alcoholate anion, a phenolate anion, a thiocarboxylate anion and a sulfonate anion. The biodegradable resin composition according to claim 9, wherein the composition is at least one selected from the group consisting of: The biodegradable resin composition according to claim 9, wherein the counter ion is divalent or higher. A biodegradable resin having a carboxyl group,
A biodegradable resin composition containing one or more metal ions selected from the group consisting of sodium ions, calcium ions, zinc ions, magnesium ions and copper ions. The biodegradable resin composition according to claim 12, wherein a neutralization ratio of the carboxyl group is 10% or more. A biodegradable resin comprising the biodegradable resin according to any one of claims 1 to 7, or the biodegradable resin composition according to any one of claims 8 to 13. The method includes a step of heating and melting a biodegradable resin which forms a thermoreversible cross-linked structure in which a functional group is coordinated to a counter ion by cooling and which is cleaved by heating when cooled, and mixing an ion source of the counter ion. A method for producing a biodegradable resin composition.