JP4790920B2 - Stretched molded product for packaging materials - Google Patents

Stretched molded product for packaging materials Download PDF

Info

Publication number
JP4790920B2
JP4790920B2 JP2001063616A JP2001063616A JP4790920B2 JP 4790920 B2 JP4790920 B2 JP 4790920B2 JP 2001063616 A JP2001063616 A JP 2001063616A JP 2001063616 A JP2001063616 A JP 2001063616A JP 4790920 B2 JP4790920 B2 JP 4790920B2
Authority
JP
Japan
Prior art keywords
heat
copolymer
glycolic acid
glycolide
stretched
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP2001063616A
Other languages
Japanese (ja)
Other versions
JP2002264206A (en
Inventor
和明 櫻井
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Asahi Kasei Chemicals Corp
Original Assignee
Asahi Kasei Chemicals Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Asahi Kasei Chemicals Corp filed Critical Asahi Kasei Chemicals Corp
Priority to JP2001063616A priority Critical patent/JP4790920B2/en
Publication of JP2002264206A publication Critical patent/JP2002264206A/en
Application granted granted Critical
Publication of JP4790920B2 publication Critical patent/JP4790920B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
    • Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Landscapes

  • Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
  • Biological Depolymerization Polymers (AREA)
  • Wrappers (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、包装材用途に好適なグリコール酸系共重合体を主体とする熱可塑性樹脂よりなる延伸成形体に関する。更に詳しくは、生分解性を有し、且つガスバリア性、耐熱性、透明性、機械的強度に優れ、容易に製造することが可能である、包装材用途に好適なグリコール酸系共重合体を主体とする熱可塑性樹脂よりなる延伸フィルムおよび延伸シートに関するものである。
【０００２】
【従来の技術】
食品や医薬品などの包装は、その内容物の輸送や分配の作業を容易にするものであると同時に、品質維持が特に重要な役割である。従って、包装材には、品質維持性能の高さが要求される。具体的には、長期保存時に内容物を保護する性能として、衝撃や突き刺しなどの外力に対する機械的強度や、外気酸素による内容物の酸化劣化や内容物の水分蒸発による劣化に対するガスバリア性、包装材自体が保存時や使用時に変性や変形しない耐油性や耐熱性などの安定性、包装材自体からの有害物質、異味、異臭の移行がない衛生性などが挙げられる。
【０００３】
従来から、これら包装材用途には、加工時や利用時の利便性からプラスチック製品が使用されていた。しかし、現在の消費社会では、その使用量は年々増加の一途をたどっており、同時にプラスチック廃棄物問題は年々深刻化している。プラスチック廃棄物は、多くは焼却や埋め立てにより処分されているが、近年は環境保全の観点から、回収して再びプラスチック製品の原料として用いるマテリアルリサイクルが提唱されている。
【０００４】
しかし、上述のとおり、プラスチック製品の包装材としての要求性能は多岐にわたり、単一種類のプラスチックのみではこれら全ての要求を満たすことが出来ず、例えば多層化してガスバリア性フィルムや成形容器にするなど、一般に数種類のプラスチックを組み合わせて用いられている。この様な包装材は、各種樹脂への分別が非常に困難であり、コスト面などを考慮するとマテリアルリサイクルは不可能である。
【０００５】
これに対し、例えば、特開平１０−６０１３６号公報には、融点Ｔｍが１５０℃以上、融解熱ΔＨｍが２０Ｊ／ｇ以上、無配向結晶化物の密度が１．５０ｇ／ｃｍ3以上である特定のポリグリコール酸を含有する熱可塑性樹脂よりなるポリグリコール酸配向フィルムが、土中崩壊性を示し、且つ強靭性やバリア性に優れる包材として使用することが出来ると開示されている。
しかしながら、上記特開平１０−６０１３６号公報に記載のポリグリコール酸配向フィルムは、融解熱ΔＨｍが２０Ｊ／ｇ以上、無配向結晶化物の密度が１．５０ｇ／ｃｍ3以上である非常に結晶性が高いポリグリコール酸を含有する熱可塑性樹脂材料から形成されることから、延伸前溶融成形シートの成形時に非晶状態となるよう急冷しなければ延伸配向させることが困難になり、該配向フィルムの製造工程が非常に煩雑になるという問題点があった。
【０００６】
また、包装材の要求特性としては、内容物の認識し易さや、購入者の購買意欲を促すディスプレイ効果により商品価値を高めるために、透明性も重要な因子である。ところが、該公報に記載のポリグリコール酸では、延伸前溶融成形シートの成形時に非常に煩雑な急冷操作を経て非晶状態としても、延伸時の加熱操作で白化し透明性が極度に劣る配向フィルムしか得られなかったり、透明性が優れる配向フィルムを得ようとする場合は延伸条件範囲が非常に狭く製造し難いという問題点があった。
【０００７】
更に、上記特開平１０−６０１３６号公報に記載のポリグリコール酸配向フィルムは、融点Ｔｍが１５０℃程度では依然として耐熱性が低く、電子レンジで使用する場合に発熱した内容物からの熱により大きく変形したり、溶融穿孔が起こったりする問題点があった。
なお、融解熱や密度と結晶性との関係は、詳しくは後述するが、例えば樹脂の結晶化度測定方法として熱分析法や密度法などがあり、一般に前者では融解熱、後者では密度と関連付けられている（日本分析化学会編、新版 高分子分析ハンドブック、ｐ．３４０、紀伊国屋書店（１９９５））。
【０００８】
【発明が解決しようとする課題】
本発明の課題は、生分解性を有し、且つガスバリア性、耐熱性、透明性、機械的強度に優れ、容易に製造することが可能であり、包装材用途に好適なグリコール酸系共重合体を主体とする熱可塑性樹脂組成物よりなる延伸成形体を提供することにある。
【０００９】
【課題を解決するための手段】
本発明者は、上記課題を達成する為に鋭意検討した結果、繰返し単位が主としてグリコール酸よりなる共重合体の融点、結晶化熱、融解熱、相対結晶化度、及び対数粘度数を特定すると共に、延伸成形体の１００℃１０分間における加熱収縮率を特定することにより、該共重合体を主体とする熱可塑性樹脂組成物よりなる延伸成形体が生分解性を有し、且つガスバリア性、耐熱性、透明性、機械的強度に優れ、包装材料用途に好適であることを見出し、本発明に到達した。
【００１０】
即ち、本発明は、
１． グリコール酸系共重合体の非晶シートを１５０℃で１００分間熱処理した試験片を用い、加熱速度および冷却速度が１０℃／分で測定した示差走査熱量測定（ＪＩＳ Ｋ７１２１、及びＫ７１２２準拠）において、１回目の昇温過程での融点Ｔｍ（℃）、１回目の冷却過程での結晶化熱ΔＨｃ（Ｊ／ｇ）、２回目の昇温過程での融解熱ΔＨｍ（Ｊ／ｇ）が下式（１）〜（３）を満たし、且つ下式（４）で表される相対結晶化度Ｘｒが３％以上５０％以下、対数粘度数［η］が１．５ｄｌ／ｇ以上であるグリコール酸系共重合体を主体とする熱可塑性樹脂組成物よりなり、１００℃１０分間における加熱収縮率ΔＬが０．５〜４５％であることを特徴とする包装材用延伸成形体、
式（１）１７５≦Ｔｍ≦２０５
式（２）ΔＨｃ＝０
式（３）０≦ΔＨｍ＜１８．０
式（４）Ｘｒ＝［（ρｂ−ρａ）／（ρｃ−ρａ）］×（ρｃ／ρｂ）×１００
但し、ρａ：非晶試験片の密度（ｇ／ｃｍ3）
ρｂ：１５０℃で５分間加熱した結晶化物の密度（ｇ／ｃｍ3）
ρｃ：１５０℃で１００分間加熱した結晶化物の密度（ｇ／ｃｍ3）
２． グリコール酸系共重合体が、グリコリドとグリコリド以外の単量体を用いて開環重合し得られる共重合体であって、グリコリドよりなる繰返し単位の成分割合が７８〜９０ｍｏｌ％と、グリコリド以外の単量体よりなる繰返し単位の成分割合が２２〜１０ｍｏｌ％であることを特徴とする１記載の包装材用延伸成形体、
３． グリコリド以外の単量体が脂肪族ヒドロキシカルボン酸類の環状二量体およびラクトン類から選ばれる少なくとも一種からなることを特徴とする１又は２記載の包装材用延伸成形体、である。
【００１１】
以下、本発明の包装材用延伸成形体について詳細に説明する。
本発明でいう延伸成形体とは、延伸フィルムおよび延伸シートを指す。但し、ブロー成形体は含まない。また、本発明において、フィルムとシートの区別は、単に厚みの違いによって異なる呼称を用いているものであり、以下、フィルムとシートを総称して成形体と称する。
本発明の包装材用延伸成形体は、本発明で規定する結晶化熱ΔＨｃ、融解熱ΔＨｍおよび相対結晶化度Ｘｒがそれぞれ特定範囲にあるような結晶性を有するグリコール酸系共重合体を用いることにより、延伸前溶融成形体の成形時に急冷するなどの煩雑な工程を必要としないため作業効率が大幅に向上し、更に延伸時の加熱操作で白化することなく、透明性の非常に優れた延伸成形体を容易に、且つ経済的に製造することが可能となる。
【００１２】
また、本発明においては、延伸成形体の加熱収縮率が、１００℃１０分間で０．５〜４５％であることから、本発明の延伸成形体は、該加熱収縮率が低い領域では、上記結晶化熱ΔＨｃ、融解熱ΔＨｍおよび相対結晶化度Ｘｒがそれぞれ特定範囲にあるような結晶性を有するグリコール酸系共重合体を用いた場合でも耐熱性を十分発揮することが可能になり包装材として使用することが可能となり、一方該加熱収縮率が高い領域では特に延伸成形体をシュリンク包装用途で使用する際にシワやタルミが発生せずフィット性を著しく高めることが可能になる。
【００１３】
重合体の結晶性とは、重合体の結晶化し易さを指しおり、一般には結晶化速度や結晶化度を指標として表される。
結晶化速度は、過冷却融体から結晶状態に非可逆的に転移するときの速度であり、その目安として熱分析における等速冷却過程での結晶化温度の測定が行われていて、結晶化速度が速い方が結晶化温度は高くなるとされている（日本分析化学会編、新版 高分子分析ハンドブック、ｐ．３３９、紀伊国屋書店（１９９５））。
【００１４】
本発明で用いるグリコール酸系共重合体は、冷却速度１０℃／分で測定した示差走査熱量測定（ ＪＩＳ Ｋ７１２１およびＫ７１２２に準拠 以下ＤＳＣという。）における１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇであることが必要である。即ちＤＳＣの測定条件（冷却速度１０℃／分）では結晶化が起こらない結晶化速度であることが必要である。ＤＳＣにおける等速冷却過程で結晶化ピークが現れない場合（結晶化熱ΔＨｃ＝０Ｊ／ｇ）、試験片の結晶性は、非晶質であり全く結晶化しないか、或いは結晶化速度が遅いためＤＳＣの測定条件（冷却速度１０℃／分）では結晶化が起こらないかの二通りが考えられる。ここで、本発明の重合体は、後述のとおりＤＳＣにおける１回目の昇温過程での融点Ｔｍが１７５〜２０５℃であるので、上述した非晶質であり全く結晶化しない場合とは異なるものである。
【００１５】
本発明で用いるグリコール酸系共重合体が、１回目の冷却過程において該結晶化熱ΔＨｃが０Ｊ／ｇとなる結晶化速度であれば、該共重合体を主体とする熱可塑性樹脂よりなる包装材用延伸成形体の製造は、延伸前溶融成形体の成形時に急冷操作などの特別な非晶化過程が不要で製造工程が簡便になり、更に延伸時の加熱操作で白化することもなく非常に透明性が優れた延伸成形体を製造することが可能である。
【００１６】
一方、結晶化度は、高分子固体における結晶領域の重量分率として定義され、例えば熱分析法や密度法などにより測定される。
熱分析法は、一般に理論融解熱ΔＨｆに対する試験片の実測融解熱ΔＨｍの比として、結晶化度Ｘｃ（％）＝ΔＨｍ／ΔＨｆ×１００より求められる（日本分析化学会編、新版 高分子分析ハンドブック、ｐ．３３９、紀伊国屋書店（１９９５））。該式において、ΔＨｍは示差走査熱量測定（ＪＩＳ Ｋ７１２２に準拠）により測定した値を用い、ΔＨｆはホモポリマーの場合は例えばＰＯＬＹＭＥＲ ＨＡＮＤＢＯＯＫ（ＪＯＨＮ ＷＩＬＥＹ ＆ ＳＯＮＳ）等に記載の値を用いる。
【００１７】
また、密度法は、一般に試験片の実測密度をｄ、完全非晶および完全結晶の密度をｄａおよびｄｃで表すと、結晶化度Ｘｃ（％）＝［（ｄ−ｄａ）／（ｄｃ−ｄａ）］×（ｄｃ／ｄ）×１００により求められる（日本分析化学会編、新版 高分子分析ハンドブック、ｐ．５８６、紀伊国屋書店（１９９５））。該式において、ｄやｄａは試験片や試験片を加熱融解した後急冷することで得られる非晶体を例えば浮沈法や密度勾配管法（ＪＩＳ Ｋ７１１２準拠）により測定した値を用い、ｄｃはホモポリマーの場合は例えばＰＯＬＹＭＥＲ ＨＡＮＤＢＯＯＫ（ＪＯＨＮ ＷＩＬＥＹ ＆ ＳＯＮＳ）等に記載の値を用いる。しかしながら、上記ΔＨｆやｄｃは、共重合体の場合は共重合成分やその成分割合が多岐に渡るために文献値が無い場合が多い。
【００１８】
熱分析法では、結晶化度Ｘｃを求める上記計算式は試験片の実測融解熱ΔＨｍが大きい方が結晶化度は高くなることを意味していることから、本発明においては、ΔＨｍの値によって結晶化度を判断する。本発明のグリコール酸系共重合体は、ＤＳＣ測定における２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ以上２０Ｊ／ｇ未満であることが必要である。
また、密度法では、本発明においては結晶化が十分進むと考えられる条件で加熱し結晶化させた場合の密度を用いて求めた相対結晶化度の値によって、共重合体の結晶化度を判断する。本発明のグリコール酸系共重合体は、下記式（４）で表される相対結晶化度Ｘｒが３％以上５０％以下の範囲内であることが必要である。
式（４）Ｘｒ＝［（ρｂ−ρａ）／（ρｃ−ρａ）］×（ρｃ／ρｂ）×１００
但し、ρａ：非晶試験片の密度（ｇ／ｃｍ3）
ρｂ：１５０℃で５分間加熱した結晶化物の密度（ｇ／ｃｍ3）
ρｃ：１５０℃で１００分間加熱した結晶化物の密度（ｇ／ｃｍ3）
【００１９】
本発明で用いるグリコール酸系共重合体の該ΔＨｍの値が０Ｊ／ｇということは、前述の結晶化熱ΔＨｃの場合と同様に、本発明の重合体が後述のとおりＤＳＣにおける１回目の昇温過程での融点Ｔｍが１７５〜２０５℃に規定しているので非晶質であり全く結晶化しない場合とは異なり、ＤＳＣの測定条件（昇温速度１０℃／分）では結晶化が起こらない結晶化速度であることを意味している。該ΔＨｍの値が２０Ｊ／ｇ以上の場合、該重合体は結晶性が非常に高いために、該重合体を主体とする熱可塑性樹脂よりなる包装材用延伸成形体の製造は、延伸前溶融成形シートの成形時に非晶状態となるよう急冷しなければ延伸配向させることが困難になり非常に煩雑になる。
【００２０】
また、延伸前溶融成形体の成形時に非常に煩雑な急冷操作を経て非晶状態としても、延伸時の加熱操作で白化し透明性が極度に劣る配向成形体しか得られなかったり、透明性が優れる配向成形体を得ようとする場合は延伸条件範囲が非常に狭く製造し難くなる。該ΔＨｍの値は、より容易に延伸成形体を製造することが可能で、より透明性が高い包装材用延伸成形体を得る為には、０Ｊ／ｇ以上１８．０Ｊ／ｇ以下の範囲が好ましい。
【００２１】
また、前記式（４）で表される相対結晶化度Ｘｒが３％より低い場合は、グリコール酸系共重合体の結晶性が低過ぎて、該重合体を主体とする熱可塑性樹脂よりなる包装材用延伸成形体は耐熱性が著しく劣るものとなる。一方、該Ｘｒの値が５０％より高い場合は、該重合体は結晶性が非常に高いために、該重合体を主体とする熱可塑性樹脂よりなる包装材用延伸成形体の製造は、延伸前溶融成形体の成形時に非晶状態となるよう急冷しなければ延伸配向させることが困難になり非常に煩雑になる。また、延伸前溶融成形体の成形時に非常に煩雑な急冷操作を経て非晶状態としても、延伸時の加熱操作で白化し透明性が極度に劣る配向成形体しか得られなかったり、透明性が優れる配向成形体を得ようとする場合は延伸条件範囲が非常に狭く製造し難くなる。該Ｘｒの値は、より高い耐熱性とより高い透明性を兼備する為には、１０％以上４０％以下の範囲であることが好ましい。
【００２２】
また、前記式（４）において、１５０℃で１００分間加熱した際の密度ρｃが、その加熱前の非晶試験片の密度ρａと等しい場合には、該式により相対結晶化度Ｘｒを算出することが出来ない。この場合には、測定に供したサンプルは、該加熱条件では結晶化せず結晶性が非常に低いか、或いは非晶性であることを意味しており、相対結晶化度Ｘｒは０％と見なし本発明の請求の範囲から外れるものである。
本発明では特定範囲の融点を有するグリコール酸系共重合体を用いることにある。かかる相違点により、本発明の包装材用延伸成形体は、電子レンジで使用する場合でも発熱した内容物からの熱で延伸成形体自体が溶融穿孔することなく、包装材の要求特性である高い耐熱性を満たすことが可能になる。
【００２３】
本発明で用いるグリコール酸系共重合体の融点は、グリコール酸系共重合体を２５０℃に設定した加熱プレス機で５分間加熱加圧し、その後２５℃に設定した冷却プレスで冷却し得られる厚み約２００μｍの非晶シートを、１５０℃に設定した熱風循環恒温槽中で１００分間加熱した結晶化物を試験片として、加熱及び冷却速度が１０℃／分の条件で測定した示差走査熱量測定（ＤＳＣ、ＪＩＳ Ｋ７１２１準拠）で一回目の昇温過程での融点Ｔｍが１７５℃以上２０５℃以下の範囲内である。該Ｔｍの値が１７５℃より低い場合は、グリコール酸系共重合体の融点が低過ぎて、該重合体を主体とする熱可塑性樹脂よりなる延伸成形体の耐熱性は著しく劣り、包装材として耐熱性を要求される用途では使用することが出来なくなる。
【００２４】
一方、該Ｔｍの値が２０５℃より高い場合は、グリコール酸系共重合体の結晶性が非常に高くなるために、該共重合体を主体とする熱可塑性樹脂組成物よりなる延伸成形体の製造は、延伸前溶融成形体の成形時に非晶状態となるよう急冷しなければ延伸配向させることが困難になり非常に煩雑になる。また、延伸前溶融成形シートの成形時に非常に煩雑な急冷操作を経て非晶状態としても、延伸時の加熱操作で白化し透明性が極度に劣る配向成形体しか得られなかったり、透明性が優れる配向成形体を得ようとする場合は延伸条件範囲が非常に狭く製造し難くなる。該Ｔｍの値は、より高い耐熱性とより高い透明性を兼備する為には、１８５℃以上２００℃以下の範囲から選ぶことが好ましい。なお、上記示差走査熱量測定において、結晶の融解に起因する吸熱ピークが複数存在する場合は、最も高温の吸熱ピーク温度を融点Ｔｍとする。
【００２５】
本発明の包装材用延伸成形体を構成する主たる素材であるグリコール酸系共重合体とは、主たる単量体にグリコール酸の環状二量体であるグリコリド（１，４−ジオキサ−２，５−ジオン）を用いての開環重合、又はグリコール酸を用いての直接脱水重縮合、例えばグリコール酸メチルなどのグリコール酸エステル類を用いて脱アルコールしながらの重縮合などにより得られる共重合体であって、これら主たる単量体と共重合し得るグリコリド以外の単量体を共重合させて得られるもののうち本発明の要件を満たすものである。
【００２６】
主たる単量体以外の共重合に用いられるグリコリド以外の単量体としては、例えば、Ｌ−乳酸、Ｄ−乳酸、２−ヒドロキシイソ酪酸を含む２−ヒドロキシ−２，２−ジアルキル酢酸、３−ヒドロキシ酪酸、３−ヒドロキシ吉草酸、３−ヒドロキシヘキサン酸、４−ヒドロキシブタン酸、その他公知の脂肪族ヒドロキシカルボン酸類、これら脂肪族ヒドロキシカルボン酸類のエステル誘導体、これら脂肪族ヒドロキシカルボン酸類の同種、又は異種の環状二量体など、およびβ−ブチロラクトン、β−プロピオラクトン、ピバロラクトン、γ−ブチロラクトン、δ−バレロラクトン、β−メチル−δ−バレロラクトン、ε−カプロラクトンなどのラクトン類から少なくとも一種が選ばれる。
【００２７】
また、これらの他に、等モル量の多価アルコール類と多価カルボン酸を組み合わせて、上記主たる単量体と共重合させたものでもよい。多価アルコール類としては、例えば、エチレングリコール、プロピレングリコール、１，２−プロパンジオール、１，３−ブタンジオール、１，４−ブタンジオール、１，５−ペンタンジオール、２，２−ジメチル−１，３−プロパンジオール、１，６−ヘキサンジオール、１，３−シクロヘキサノール、１，４−シクロヘキサノール、１，３−シクロヘキサンジメタノール、１，４−シクロヘキサンジメタノールなどの脂肪族ジオール類、或いはこれら脂肪族ジオール類が複数結合した、例えばジエチレングリコール、トリエチレングリコール、テトラエチレングリコールなどが挙げられ、多価カルボン酸としては、マロン酸、コハク酸、グルタル酸、２，２−ジメチルグルタル酸、アジピン酸、ピメリン酸、スペリン酸、アゼライン酸、セバシン酸、１，３−シクロペンタンジカルボン酸、１，３−シクロヘキサンジカルボン酸、１，４−シクロヘキサンジカルボン酸、ジグリコール酸などの脂肪族ジカルボン酸類、テレフタル酸、イソフタル酸、１，４−ナフタリンジカルボン酸、２，６−ナフタリンジカルボン酸などの芳香族ジカルボン酸類、これら脂肪族ジカルボン酸類や芳香族ジカルボン酸類のエステル誘導体、これら脂肪族ジカルボン酸類の無水物などが挙げられ、これらを多成分に組み合わせてもよい。
【００２８】
上記に例示した本発明の包装材用延伸成形体を構成する主たる素材であるグリコール酸系共重合体のうち好ましい共重合体は、より分子量の高い共重合体を得易いという観点から、グリコリドとグリコリド以外の単量体を用いて開環重合し得られる共重合体であって、グリコリドよりなる繰返し単位の成分割合が７８〜９０ｍｏｌ％と、グリコリド以外の単量体よりなる繰返し単位の成分割合が２２〜１０ｍｏｌ％からなるものである。より好ましくはグリコリドよりなる繰返し単位の成分割合が８１〜８８ｍｏｌ％と、グリコリド以外の単量体よりなる繰返し単位の成分割合が１９〜１２ｍｏｌ％からなるものである。
【００２９】
該共重合体を構成する単量体のうちグリコリド以外の単量体としては、好ましくは脂肪族ヒドロキシカルボン酸類の環状二量体、およびラクトン類から少なくとも一種が選ばれ、乳酸の環状二量体であるラクチド（３，６−ジメチル−１，４−ジオキサ−２，５−ジオン）が特に好ましい。なお、ラクチドは光学活性物質でありＬ−体、Ｄ−体のいずれであってもよいし、Ｄ，Ｌ−体混合物やメソ体であってもよい。また、グリコリド−Ｌ−ラクチド共重合体とグリコリド−Ｄ−ラクチドの混合物であってもよい。
【００３０】
本発明で用いるグリコール酸系共重合体の製造方法は、特に限定されるものではなく従来公知の一般的な方法で行われる。例えば、主たる単量体にグリコリドを用いて開環重合しグリコール酸系共重合体を得るには、Ｇｉｌｄｉｎｇらの方法（Ｐｏｌｙｍｅｒ，ｖｏｌ．２０，Ｄｅｃｅｍｂｅｒ（１９７９））などが挙げられるが、これに限定されるものではない。
該共重合体の分子量は、該共重合体を主体とする熱可塑性樹脂よりなる延伸成形体が包装材として要求される外力に対する機械的強度を有する為には、対数粘度数で少なくとも１．５ｄｌ／ｇ以上が必要であり、１．８ｄｌ／ｇ以上であることが好ましい。対数粘度数［η］は、一般に下式（５）により求められる値であり、濃度０．２％以下の希薄溶液では高分子の分子量の指標として用いられる固有粘度に近似できる（化学大辞典 縮刷版、ｐ．７４６、共立出版（１９６３）、及び新版 高分子分析ハンドブック、ｐ．１２０、紀伊国屋書店（１９９５））。
式（５） ［η］＝｛ｌｎ（ｔ／ｔｏ）｝／ｃ
但し、ｔ：毛管粘度計で測定される高分子溶液の流下時間（秒）
ｔｏ：毛管粘度計で測定される溶媒の流下時間（秒）
ｃ：溶質高分子の濃度（ｇ／ｄｌ）
【００３１】
一方、該共重合体の分子量の上限は、延伸前溶融成形体をより容易に製造するためには対数粘度数で８．０ｄｌ／ｇ以下に留めることが望ましいが、可塑剤などの添加により溶融流動性を調節すれば良く特に限定されるものではない。
なお、本発明で用いるグリコール酸系共重合体の分子量は数平均分子量で表すと７．０×１０4以上、好ましくは１．０×１０5以上である。なお、該分子量の上限は、数平均分子量で表すと７．０×１０5以下、好ましくは６．０×１０5以下に留めることが望ましい。
本発明の包装材用延伸成形体は、上記特定のグリコール酸系共重合体を主体とする熱可塑性樹脂組成物よりなることを特徴としているが、以下に本発明でいう該熱可塑性樹脂組成物について説明する。
【００３２】
本発明において、上記特定のグリコール酸系共重合体を主体とする熱可塑性樹脂組成物とは、該グリコール酸系共重合体の単体、或いは該グリコール酸系共重合体と他の重合体との組成物、これらグリコール酸系共重合体の単体または共重合体と他の重合体との組成物と、可塑剤、酸化防止剤などの添加剤との組成物を指していう。該熱可塑性樹脂のうちグリコール酸系共重合体と他の重合体との組成物の場合には、その組成割合は、包装材として使用される時に要求される内容物の品質保持性能、例えばガスバリア性や耐熱性などによって異なるが、望ましくは該組成物の各重合体の繰返し単位全体のうち成分割合５０ｍｏｌ％以上がグリコリドからなる繰返し単位となるよう混合する場合であり、より高い内容物の品質保持性能が要求される包装材用途では、より望ましくは該成分割合が７０ｍｏｌ％以上の場合である。
【００３３】
具体的には、例えばグリコール酸系共重合体としてグリコリド８０ｍｏｌ％とラクチド２０ｍｏｌ％の繰返し単位からなる共重合体と、ラクチド１００ｍｏｌ％の繰返し単位からなるポリ乳酸とを混合する場合では、該混合組成物の全繰返し単位に占めるグリコリドの成分割合が５０ｍｏｌ％以上とする為には、該グリコール酸系共重合体の組成割合は６６．５重量％以上にしなければならない。又、グリコール酸系共重合体としてグリコリド９０ｍｏｌ％とラクチド１０ｍｏｌ％の繰返し単位からなる共重合体と、ラクチド１００ｍｏｌ％の繰返し単位からなるポリ乳酸とを混合する場合では、該混合組成物の全繰返し単位に占めるグリコリドの成分割合が５０ｍｏｌ％以上とする為には、該グリコール酸系共重合体の組成割合は６０．３重量％以上にしなければならない。
【００３４】
なお、延伸成形体を構成する熱可塑性樹脂組成物のグリコリドからなる繰返し単位の成分割合は、通常の分析手法により解析することができる。例えば、延伸成形体をヘキサフルオロイソプロパノール（以下、ＨＦＩＰと略記する。）に溶解し、ろ過して不溶分を取り除く。次いで、得られた熱可塑性樹脂のＨＦＩＰ溶液をメタノール中に注ぎ、樹脂成分を再沈殿させる。得られた再沈殿樹脂成分を真空乾燥機で十分乾燥した後、重水素化トリフルオロ酢酸または重水素化ＨＦＩＰを溶媒として１Ｈ−ＮＭＲや１３Ｃ−ＮＭＲを測定し、熱可塑性樹脂のグリコリドからなる繰返し単位の成分割合を解析することができる。
【００３５】
上記本発明の熱可塑性樹脂組成物において、本発明で特定するグリコール酸系共重合体に他の重合体を混合する場合には、混合しうる他の重合体としては、上記具体例として挙げたポリ乳酸や、下記に挙げる重合体より少なくとも一種が選ばれ、これらのうち生分解性を有するものが望ましい。例えば、グリコール酸系重合体では、本発明で特定するグリコール酸系共重合体よりもグリコリドの成分割合が高く結晶性が高いものであってもよいし、或いは該成分割合が低く結晶性が低いものでもよい。単量体が光学活性物質であるポリ乳酸では、Ｌ−体またはＤ−体の何れであってもよいし、Ｄ，Ｌ−体の混合割合が任意の混合組成物、Ｄ，Ｌ−体の共重合割合が任意の共重合体、或いはメソ体の何れであってもよい。
【００３６】
これらの他に、２−ヒドロキシイソ酪酸を含む２−ヒドロキシ−２，２−ジアルキル酢酸、３−ヒドロキシ酪酸、３−ヒドロキシ吉草酸、３−ヒドロキシヘキサン酸、４−ヒドロキシブタン酸、その他公知の脂肪族ヒドロキシカルボン酸類、これら脂肪族ヒドロキシカルボン酸類のエステル誘導体、これら脂肪族ヒドロキシカルボン酸類の同種、又は異種の環状二量体から得られる単独重合体、或いはこれらより任意に選択した二種以上から得られる共重合体であるポリヒドロキシカルボン酸類、β−ブチロラクトン、β−プロピオラクトン、ピバロラクトン、γ−ブチロラクトン、δ−バレロラクトン、β−メチル−δ−バレロラクトン、ε−カプロラクトンなどのラクトン類から得られる単独重合体、或いはこれらより任意に選択した二種以上から得られる共重合体であるポリラクトン類、等モル量の多価アルコールと多価カルボン酸を組み合わせであって、多価アルコールとして、例えば、エチレングリコール、プロピレングリコール、１，２−プロパンジオール、１，３−ブタンジオール、１，４−ブタンジオール、１，５−ペンタンジオール、２，２−ジメチル−１，３−プロパンジオール、１，６−ヘキサンジオール、１，３−シクロヘキサノール、１，４−シクロヘキサノール、１，３−シクロヘキサンジメタノール、１，４−シクロヘキサンジメタノールなどの脂肪族ジオール類、或いはこれら脂肪族ジオール類が複数結合した、例えばジエチレングリコール、トリエチレングリコール、テトラエチレングリコールなど、多価カルボン酸として、マロン酸、コハク酸、グルタル酸、２，２−ジメチルグルタル酸、アジピン酸、ピメリン酸、スペリン酸、アゼライン酸、セバシン酸、１，３−シクロペンタンジカルボン酸、１，３−シクロヘキサンジカルボン酸、１，４−シクロヘキサンジカルボン酸、ジグリコール酸などの脂肪族ジカルボン酸類、テレフタル酸、イソフタル酸、１，４−ナフタリンジカルボン酸、２，６−ナフタリンジカルボン酸などの芳香族ジカルボン酸類、これら脂肪族ジカルボン酸類や芳香族ジカルボン酸類のエステル誘導体、これら脂肪族ジカルボン酸類の無水物などから得られる多価アルコール類と多価カルボン酸が各々一種づつの単独重合体、或いは多価アルコール類と多価カルボン酸のうち何れか一方が一種で他方が任意に選択した二種以上から得られる共重合体、又は多価アルコール類と多価カルボン酸の各々が任意に選択した二種以上から得られる共重合体である脂肪族ポリエステル類、こられ以外の公知の生分解性プラスチックである、例えばポリアスパラギン酸などのポリアミノ酸類、酢酸セルロースなどのセルロースエステル類、脂肪族ポリエステルカーボネート類、ポリビニルアルコール類、ポリエチレンオキサイド、低分子量のポリエチレン等であってもよい。
【００３７】
尚、ここに挙げた種々の重合体を構成する単量体の二種以上を任意の割合で共重合させた共重合体であってもよく、該単量体が光学活性物質である場合には、Ｌ−体またはＤ−体の何れであってもよいし、Ｄ，Ｌ−体の混合割合が任意の混合組成物、Ｄ，Ｌ−体の共重合割合が任意の共重合体、或いはメソ体の何れであってもよい。
また、上記混合しうる他の重合体としては、生分解性を有しないものであっても、本発明の熱可塑性樹脂組成物の生分解性を阻害しない範囲で混合してもよい。例えば、ポリオレフィン類、芳香族ポリエステル類、ポリアミド類、エチレン−ビニルアルコール系共重合体類、石油樹脂類やテルペン系樹脂類、その水素添加物などが挙げられる。
【００３８】
本発明の熱可塑性樹脂組成物は、必要に応じて無機および／または有機化合物よりなる添加剤、例えば、可塑剤、滑剤、帯電防止剤、防曇剤、酸化防止剤、熱安定剤、光安定剤、紫外線吸収剤、着色剤、難燃剤、結晶核剤等が適宜混合されてもよい。使用される可塑剤の具体例としては、例えばジオクチルフタレートやジエチルフタレートなどのフタル酸エステル類、ラウリン酸エチルやオレイン酸ブチル、リノール酸オクチルなどの脂肪酸エステル類、ジオクチルアジペートやジブチルセバケートなどの脂肪族二塩基酸エステル類、アセチルくえん酸トリブチルなどの脂肪族三塩基酸エステル類、グリセリンジアセテートラウレートやグリセリントリアセテートなどのグリセリン脂肪酸エステル類、リン酸ジオクチルなどのリン酸エステル類、エポキシ化大豆油やエポキシ化アマニ油などの変性植物油類、ポリブチレンセバケートなどのポリエステル系可塑剤などが挙げられ、安全衛生性の観点からグリセリン脂肪酸エステル類が特に望ましい。
【００３９】
これらから一種、または二種以上を選び、添加量は熱可塑性樹脂１００重量部に対して１〜５０重量部程度である。また、使用される酸化防止剤の具体例としては、例えばフェノール系、フェニルアクリレート系、リン系、イオウ系等から一種、又は二種以上を選び、添加量は熱可塑性樹脂１００重量部に対して０．０１〜１０重量部程度である。
本発明における熱可塑性樹脂組成物の製造は、本発明の上記特定のグリコール酸系共重合体と、これと混合し得る他樹脂や添加剤などを、全部、或いは一部を単軸、又は二軸押出機、バンバリーミキサー、ミキシングロール、ニーダー等を使用して溶融混合させ用いるのが望ましい。
【００４０】
次に、本発明の延伸成形体について説明する。本発明でいう延伸成形体とは、前記したように延伸フィルムおよび延伸シートを指す。但し、ブロー成形体は含まない。
延伸成形体の製造方法は、特に限定されるものではなく従来公知の一般的な方法で行われる。例えば、延伸前溶融成形体の製造方法としては、溶融押出法、キャスティング法（溶液流延法）、カレンダー法、溶融プレス成形法などが挙げられる。具体的には、本発明のグリコール酸系共重合体を主体とする熱可塑性樹脂組成物を原料として用い、例えば溶融押出法では、該原料を押出機に供給して加熱溶融し、押出機の先端に接続したダイスより押出することにより製造することができる。また、溶融プレス成形法では、該原料を金型に供給し、常圧或いは減圧雰囲気下で加熱溶融させプレスすることにより製造することができる。この場合、原料の加熱融解は、通常は（融点−５℃）〜（融点＋６５℃）の温度範囲から適宜選ばれる温度が望ましい。
【００４１】
その後の延伸方法としては、一軸延伸の場合は、溶融押出法でＴダイより溶融押出し、キャストロールで冷却した延伸前溶融成形体を、ロール延伸機で樹脂の流れ方向に縦一軸延伸したり、該縦延伸倍率を極力抑えてテンターで横一軸延伸して製造する方法。或いは、二軸延伸の場合は、溶融押出法でＴダイより溶融押出し、キャストロールで冷却した延伸前溶融成形体を、ロール延伸機で縦延伸し、その後テンターで横延伸して製造したり、溶融押出法でサーキュラーダイより溶融押出し、水冷リング等で冷却した延伸前溶融成形環状体を、チューブラー延伸して製造する方法などである。この場合、延伸の操作は、通常はガラス転移温度〜（ガラス転移温度＋６０℃）の延伸温度で、少なくとも一軸方向に面積倍率２〜４０倍の延伸倍率で適宜選ばれる延伸条件で行われることが望ましく、さらに望ましい範囲を限定するとすれば、（ガラス転移温度＋５℃）〜（ガラス転移温度＋４０℃）の延伸温度で、少なくとも一軸方向に面積倍率４〜３５倍の延伸倍率で行うことである。
【００４２】
本発明者は、特定範囲の結晶性を有するグリコール酸系共重合体を包装材用途のフィルム、またはびシートとして使用するにあたり、延伸加工を施すことにより包装材の要求特性である機械的強度や透明性を高められることを見出した。これは、延伸することにより高分子鎖が配向して強度を発揮する効果を発現し、その後の熱処理を施す際に結晶サイズの成長を抑制する効果を発現するものである。従って、延伸加工を施さない場合は、高分子鎖の配向度合いが少なくて成形体は強度がより低いものとなり、或いは強度を高めようとして熱処理を施すと成長した結晶での光散乱により成形体が白化し透明性が損なわれたりする問題を生じる。
【００４３】
上記の延伸成形体の製造方法の他に、例えば、溶融押出法でインフレーションダイより溶融押出しした溶融チューブを内部の空気圧で膨張させ、空気冷却や水冷却により固定させるインフレーション法で製造する方法などでも良い。このインフレーション法は一般にフィルムの急冷が困難であることから、前記特開平１０−６０１３６号公報に記載のポリグリコール酸では、非常に結晶性が高いために透明性が優れる延伸フィルムを得ることは困難である。
【００４４】
本発明において延伸成形体とは延伸フィルムおよび延伸シートを言うが、その厚みは、その用途により適宜選ばれ、通常は延伸フィルムでは３〜１００μｍ、延伸シートでは０．１〜１ｍｍであるが特に限定されるものではない。これら延伸フィルム、及び延伸シートは、その厚みにおける製造し易さを勘案すると、通常は延伸フィルムはチューブラー延伸法で、延伸シートはテンター延伸法で製造することが望ましい。但し、フィルムとシートの区別は、単に厚みの違いによって異なる呼称を用いているものであって、本発明の課題であるところの透明性の高い延伸成形体を容易に製造できることに何ら差はない。従って、後述する実施例では、厚み約３０μｍの延伸フィルムをもって物性測定や評価を行って本発明を詳細に説明した。
【００４５】
得られた延伸成形体は、電子レンジなどで加熱して使用され耐熱性が要求される包装材や容器の用途で、発熱した内容物からの熱による変形や溶融穿孔を防ぐ目的で熱処理を施すことが好ましい。更に、経時寸法安定性や物性安定性を向上させる目的で、エージング処理などを施すことが望ましい。これらの目的を達成する為に、本発明の延伸成形体は、１００℃１０分間における加熱収縮率ΔＬが０．５〜４５％の範囲に留めることが必要であり、０．５〜３５％の範囲であることが好ましい。該値が４５％より大きい場合は、熱よる変形や溶融穿孔が起こり包装材としての機能が損なわれる。
【００４６】
一方、該値が０．５％より小さい場合は、延伸することで高分子鎖が配向して強度を発揮する効果が損なわれたり、配向度合いが少なくて熱処理を施すと成形体が白化し透明性が損なわれたりする問題を生じる。この場合、熱処理は通常は６０〜１６０℃の温度範囲から適宜選ばれる温度で１秒〜３時間行われることが好ましく、エージング処理は通常は２５〜６０℃の温度範囲から適宜選ばれる温度で３時間〜１０日間程度行われることが望ましい。
【００４７】
得られた延伸成形体は、そのまま家庭用ラップ等の包装材などとして使用しても良いが、必要に応じて帯電防止剤や防曇性を向上させる目的でコーティングやコロナ処理等の各種表面処理を施しても良いし、シール適性、防湿性、ガスバリア性、印刷適性などを向上させる目的でラミネート加工やコーティング加工、或いはアルミニウムなどの真空蒸着を施しても良い。更に、二次加工により、用途に応じた形状に成形して使用しても良い。二次加工品としては、例えば延伸フィルムの場合はピロー包装用途やウェルドタイプのケーシング包装用途などの包装材とするシール加工品があり、延伸シートの場合はプラグアシスト成形法やエアークッション成形法などの真空成形加工、圧空成形加工、雄雌型成形加工などを施してトレイやカップなどの容器、又はブリスターパッケージングシートなどがある。
【００４８】
得られた本発明の延伸成形体は、該延伸成形体を構成する主たる素材として特定範囲の結晶性を有するグリコール酸系共重合体を用い、且つ該延伸成形体の１００℃１０分間における加熱収縮率を規定することにより、生分解性を有し、且つガスバリア性、耐熱性、透明性、機械的強度に優れ、包装材用途に好適に利用できる。特に、可塑剤を比較的多量添加し引張弾性率が４．０ＧＰａ未満である軟質から中質の延伸フィルムは、ピロー包装、シュリンク包装、ストレッチ包装、ケーシング、家庭用ラップ等の包装材用途に好適である。
【００４９】
【発明の実施の形態】
以下、実施例を挙げて本発明を更に詳細に説明する。但し、これらの具体例は本発明の範囲を限定するものではない。また、物性測定方法、評価方法と尺度を下記に示すが、サンプルは特に断りのない限り測定サンプル作製後に温度（２３±２）℃、関係湿度（５０±５）％の雰囲気下に１〜３日間保管したものを物性測定や評価に供した。
［物性測定方法］
（１）示差走査熱量測定（ＤＳＣ）
融点Ｔｍ、結晶化熱ΔＨｃ、融解熱ΔＨｍは、測定装置にセイコー電子工業(株)製ＤＳＣ６２００を使用し、ＪＩＳ Ｋ７１２１、及びＫ７１２２に準拠して測定した。サンプルは、グリコール酸系共重合体を２５０℃に設定した加熱プレス機で５分間加熱加圧し、その後２５℃に設定した冷却プレスで冷却し得られた厚み約２００μｍの非晶シートを、１５０℃に設定した熱風循環恒温槽中で１００分間加熱した結晶化物を試験片として用いた。試験片重量は７．５ｍｇとして、先ず０℃で３分間保持した後、加熱速度１０℃／分で２５０℃まで加熱し１回目の昇温過程での融点Ｔｍを測定した。２５０℃で１分間保持した後、冷却速度１０℃／分で０℃まで冷却し１回目の冷却過程での結晶化熱ΔＨｃを測定した。次いで、０℃で１分間保持した後、再び加熱速度１０℃／分で２５０℃まで加熱し２回目の昇温過程での融解熱ΔＨｍを測定した。なお、温度と熱量の校正は、標準物質としてインジウムを用いて行った。なお、本発明でいう非晶シートとは、上記手順で作製したシートをサンプルとして、広角Ｘ線回折法により回折強度曲線を測定し、該回折強度曲線に結晶に起因する回折ピークが存在しないものを指す。また、上記示差走査熱量測定において、結晶の融解に起因する吸熱ピークが複数存在する場合は、最も高温の吸熱ピーク温度を融点Ｔｍとする。
【００５０】
（２）相対結晶化度
本発明では、式（４）で表される相対結晶化度の値を採用している。上記ＤＳＣ測定方法で示した手順によりグリコール酸系共重合体の非晶シートを得て、該非晶シートを１５０℃に設定した熱風循環恒温槽中で５分間、及び１００分間加熱結晶化させ結晶化物を得た。これら非晶シートの試験片、１５０℃で５分間加熱した結晶化物、１５０℃で１００分間加熱した結晶化物をサンプルとして、ＪＩＳ Ｋ７１１２Ｃ法に準拠して密度を測定した。密度測定は、２０℃でエタノール／塩化亜鉛水溶液系浮沈法により浮沈状態を観察して測定した。サンプルの密度測定結果から、式（４）により相対結晶化度Ｘｒを求めた。
式（４）Ｘｒ＝［（ρｂ−ρａ）／（ρｃ−ρａ）］×（ρｃ／ρｂ）×１００
但し、ρａ：非晶物の密度（ｇ／ｃｍ3）
ρｂ：１５０℃で５分間加熱した結晶化物の密度（ｇ／ｃｍ3）
ρｃ：１５０℃で１００分間加熱した結晶化物の密度（ｇ／ｃｍ3）
（３）対数粘度数
純溶媒ＨＦＩＰと、グリコール酸系共重合体の濃度が０．１ｇ／ｄｌとなるよう溶解したＨＦＩＰ溶液をサンプルとして、ウベローデ型毛管粘度計を使用し２０℃で毛管中を流下する時間を測定し、式（５）により対数粘度数［η］を求めた。
式（５） ［η］＝｛ｌｎ（ｔ／ｔｏ）｝／ｃ
但し、ｔ：毛管粘度計で測定される高分子溶液の流下時間（秒）
ｔｏ：毛管粘度計で測定される溶媒の流下時間（秒）
ｃ：溶質高分子の濃度（ｇ／ｄｌ）
【００５１】
（４）加熱収縮率
１００℃１０分間における加熱収縮率ΔＬは、延伸成形体をサンプルとして、ＪＩＳ Ｋ７１３３に準拠して測定した。サンプルを、一辺１２０ｍｍの正方形に切り出し、これに辺に沿った標線間の距離が１００ｍｍとなるように４点の印を付け、試験片とした。この試験片を、カオリンやタルクなどの粉末を振りかけてカオリン床に平らに置き、１００℃に設定した熱風循環恒温槽中で１０分間加熱した。その後、試験片を取り出して直交する２方向の標線間距離を測り、式（６）により加熱前の標線間距離に対する加熱後の標線間距離の収縮量の比の百分率ΔＬ（％）を算出した。加熱収縮率ΔＬの測定結果は、試験片数３個について各々直交２方向の測定を行い、それらの平均値で示した。なお、本発明では、収縮率が正の値となるように式（６）を採用している。但し、延伸前溶融成形シートがヘーズ２０％以上となる場合、原料として用いたグリコール酸系共重合体は、結晶性が高く本発明の特定の結晶性から外れるものである。この場合は延伸操作を行わず、加熱収縮率ΔＬの測定も行わなかった。
式（６） ΔＬ＝［（Ｌｏ−Ｌ）／Ｌｏ］×１００
但し、Ｌｏ：加熱前の標線間距離１００ｍｍ
Ｌ：加熱後の標線間距離（ｍｍ）
【００５２】
［評価方法と尺度］
（１）透明性
透明性は、延伸フィルムをサンプルとして、ヘーズを測定し評価した。ヘーズの測定は、測定装置に村上色彩技術研究所社製ヘーズ計ＨＲ−１００を使用し、ＪＩＳ Ｋ７１０５に準拠して測定した。厚み約３０μｍの延伸フィルムサンプルを、一辺５０ｍｍの正方形に切り出し、これをホルダーにセットしサンプルのヘーズを測定した。ヘーズの測定結果は、サンプル数５個づつ測定し、その平均値で示した。このヘーズを透明性の指標とした。但し、後述の延伸前溶融成形シートの作製手順で得られたシートがヘーズ２０％以上となる場合は、延伸加工が容易ではないことから、評価から除外し判定は「×」とした。
＜評価尺度＞
ヘーズ 判 定 備 考
２％未満 ◎ 透明で視認性は非常に優れる
２％以上５％未満 ○ 若干白化する程度で視認性は優れる
５％以上１０％未満 △ 白化し視認性が劣る
１０％以上 × 著しく白化し視認性が非常に劣る
【００５３】
（２）機械的強度
機械的強度は、延伸フィルムをサンプルとして、引張破断強さを測定し評価した。引張破断強さの測定は、測定装置に島津製作所社製オートグラフＡＧＳ−１ｋＮＧを使用し、ＪＩＳ Ｋ７１２７に準拠して測定した。厚み約３０μｍの延伸フィルムサンプルを、長さ２００ｍｍ、幅１０ｍｍの短冊形に切り出し、これをチャック間１００ｍｍに設定したチャックに装着し、引張速度１００ｍｍ／分で試験を行った。引張破断強さの測定結果は、サンプル数１０個づつ測定し、その平均値で示した。この引張破断強さを機械的強度の指標とした。但し、後述の延伸前溶融成形シートの作製手順で得られたシートがヘーズ２０％以上となる場合は、延伸加工が容易ではないことから、評価から除外し判定は「×」とした。
＜評価尺度＞
引張破断強さ 判 定 備 考
１５０ＭＰａ以上 ◎ 非常に強く実用上問題はない
５０ＭＰａ以上１５０ＭＰａ未満 ○ 強く高強度用途以外で使用可
１５ＭＰａ以上５０ＭＰａ未満 △ 弱く実用上問題がある
１５ＭＰａ未満 × 非常に弱く実用に耐えない
【００５４】
（３）ガスバリア性
ガスバリア性は、延伸フィルムをサンプルとして、酸素透過度を測定し評価した。酸素透過度の測定は、測定装置にｍｏｃｏｎ社製酸素透過率測定装置ＯＸ−ＴＲＡＮ２００Ｈ型を使用し、ＪＩＳ Ｋ７１２６Ｂ法に準拠して測定した。厚み約３０μｍの延伸サンプルを、一辺１２０ｍｍの正方形状に切り出し、温度２３℃、関係湿度６５％の条件で試験を行った。酸素透過度の測定結果は、サンプル数３個づつ測定し、厚み１０μｍに換算した値の平均値で示した。この酸素透過度をガスバリア性の指標とした。但し、後述の延伸前溶融成形シートの作製手順で得られたシートがヘーズ２０％以上となる場合は、延伸加工が容易ではないことから、評価から除外し判定は「×」とした。
＜評価尺度＞
酸素透過度 判 定 備 考
１００未満 ◎ ガスバリア性が非常に高い
１００以上５００未満 ○ ガスバリア性が高い
５００以上１０００未満 △ ガスバリア性が低く用途により使用不可
１０００以上 × ガスバリア性が非常に低く用途により使用不可酸素透過度の単位：ｃｃ・１０μｍ／ｍ2・ｄａｙ・ａｔｍ
【００５５】
（４）耐熱性
耐熱性は、耐荷重切断試験と耐溶融穿孔試験の評価結果を指標とし、この両者の判定結果のうち低い方の判定結果をそのまま耐熱性の判定結果とした。耐荷重切断試験は、短冊状試験片に荷重３０ｇをかけた状態で、一定温度に設定した熱風循環恒温槽中で１時間加熱し試験片の切断の有無を調べ、試験片が切断しない最高温度を測定した。厚み約３０μｍの延伸フィルムを、縦１４０ｍｍ、横３０ｍｍの短冊状に切り出した。短冊状試験片の上下端２５ｍｍづつの部分に固定治具と荷重治具を各々取り付け、一定温度に設定した熱風循環恒温槽中で１時間加熱し試験片の切断の有無を調べた。短冊状試験片が切断しない場合は、新しい試験片で設定温度を５℃上げて前記手順を繰返し試験した。短冊状試験片が切断しない最高温度の測定結果は、この試験を各延伸フィルムにつき５回づつ行い最頻値で示した。
【００５６】
耐溶融穿孔試験は、金枠に緊張状態で張った試験片の中央部に、一定温度に設定した熱風を吹き付けて試験片の穿孔の有無を調べ、試験片が穿孔しない最高温度を測定した。厚み約３０μｍの延伸フィルムを、一辺１８０ｍｍの正方形に切り出し試験片とした。外寸法一辺１８０ｍｍ、内寸法一辺１５０ｍｍの正方形の金枠に、この試験片の外縁が金枠の外縁と重なるようにして周辺を固定した。試験片を固定した金枠を水平に設置し、熱風発生機に接続した直径５０ｍｍの円形ノズルから、ノズル先端部での風速が２ｍ／秒、ノズル先端部から試験片までの距離が５０ｍｍとなるように、試験片中央部に下から垂直に一定温度に設定した熱風を１０分間吹き付け、試験片の穿孔の有無を調べた。
【００５７】
試験片に穿孔が発生しない場合は、新しい試験片で設定温度を５℃上げて前記手順を繰返し試験した。試験片が穿孔しない最高温度の測定結果は、この試験を各延伸フィルムにつき５回づつ行い最頻値で示した。但し、後述の延伸前溶融成形シートの作製手順で得られたシートがヘーズ２０％以上となる場合は、延伸加工が容易ではないことから、評価から除外し判定は「×」とした。
＜評価尺度＞
耐荷重切断試験 判 定 備 考
１８０℃以上 ◎ 耐熱性が非常に高く実用上問題はない
１６０〜１７５℃ ○ 耐熱性が高く用途により使用可
１４０〜１５５℃ △ 耐熱性が劣り用途が制限される
１３５℃以下 × 耐熱性は著しく低く実用に耐えない
＜評価尺度＞
耐溶融穿孔試験 判 定 備 考
１８０℃以上 ◎ 耐熱性が非常に高く実用上問題はない
１６０〜１７５℃ ○ 耐熱性が高く用途により使用可
１４０〜１５５℃ △ 耐熱性が劣り用途が制限される
１３５℃以下 × 耐熱性は著しく低く実用に耐えない
【００５８】
【実施例１】
［単量体の精製］
グリコリド２５０ｇを、脱水酢酸エチル５００ｇに７５℃で溶解させた後、室温にて１０時間放置し析出させた。濾取した析出物を、室温で約５００ｇの脱水酢酸エチルを用いて洗浄を行った。再度この洗浄操作を繰返した後、洗浄物をナス型フラスコ内に入れ、６０℃に設定したオイルバスに浸漬し２４時間真空乾燥を行った。この乾燥物を、１７０℃に設定したオイルバスに浸漬し、乾燥窒素雰囲気下で６〜７ｍｍＨｇに減圧し単蒸留にて１３３〜１３４℃の留出物として蒸留精製グリコリド８０ｇを得た。
【００５９】
Ｌ−ラクチド２５０ｇを、脱水トルエン５００ｇに８０℃で溶解させた後、室温にて１０時間放置して析出させた。濾取した析出物を、室温で約５００ｇの脱水トルエンを用いて洗浄を行った。再度この洗浄操作を繰返した後、洗浄物をナス型フラスコ内に入れ６０℃に設定したオイルバスに浸漬して２４時間真空乾燥を行い、精製Ｌ−ラクチド１２０ｇを得た。
［重合体の調製］
上記単量体の精製で得られたグリコリド７０ｇとラクチド３２ｇ、及び触媒として２−エチルヘキサン酸すず０．０３ｇと脱水ラウリルアルコール０．０１ｇを耐圧管に仕込み、乾燥窒素を吹き込みながら約３０分間室温で乾燥した。次いで、乾燥窒素を吹き込みながら１３０℃に設定したオイルバスに浸漬し、２０時間撹拌して重合を行った。重合操作の終了後、室温まで冷却し、耐圧管から取り出した塊状ポリマーを約３ｍｍ以下の細粒に粉砕した。この粉砕物を、脱水酢酸エチルを用いて１０時間ソックスレー抽出した後、ＨＦＩＰ２００ｇに５０℃で溶解し、次いで２０００ｇの精製メタノールで再沈殿させた。この再沈殿物を、１１０℃に設定した真空乾燥機内で２４時間真空乾燥を行い、グリコール酸系共重合体８５ｇを得た。得られた該共重合体をＰ１とする。
【００６０】
該共重合体Ｐ１は、グリコリドからなる繰返し単位の成分割合が８６ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が１４ｍｏｌ％であった。該共重合体Ｐ１をＨＦＩＰに溶解しガスクロマトグラフィーにて残存する単量体を定量したところ、単量体であるグリコリドとラクチドの残量は両者の合計で４９０ｐｐｍであった。該共重合体Ｐ１をサンプルとして、前述のＤＳＣ、相対結晶化度、対数粘度数の測定を行ったところ、ＤＳＣにおける１回目の昇温過程での融点Ｔｍは１９４℃、１回目の冷却過程での結晶化熱ΔＨｃは０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍは０Ｊ／ｇ、相対結晶化度Ｘｒは３３％、対数粘度数［η］は２．５ｄｌ／ｇであった。
【００６１】
［延伸前溶融成形シートの作製］
上記重合体の調製で得られたグリコール酸系共重合体Ｐ１を、１３０℃に設定した熱風循環恒温槽中で含有水分量が２００ｐｐｍ以下になるまで約２時間放置して乾燥操作を行った後、２５０℃に設定した加熱プレス機で５分間加熱加圧し、その後２５℃に設定した冷却プレスで冷却し厚み３５０μｍの非晶シートを得た。
［延伸フィルムの作製、及び評価］
上記延伸前溶融成形シートの延伸は、東洋精機社製二軸延伸試験装置を使用して行った。上記延伸前溶融成形シートの作製で得られた非晶シートを、一辺９０ｍｍの正方形に切り出して、延伸温度６５℃に設定したチャンバー内にクランプ間８０ｍｍのクランプに装着し、延伸速度５０％／分で縦３．５倍、横３．５倍まで同時二軸延伸を行った。延伸操作の終了後、直ちに冷風を吹き付けて冷却し延伸フィルムを得た。得られた延伸フィルムを、金枠に固定して、１２０℃に設定した熱風循環恒温槽中で１分間熱処理を行い厚み３０μｍの延伸フィルムを得た。該熱処理した延伸フィルムをサンプルとして、前述の加熱収縮率の測定を行ったところ、１００℃１０分間における加熱収縮率ΔＬは２％であった。
【００６２】
該熱処理した延伸フィルムをサンプルとして、前述の透明性、機械的強度、ガスバリア性、耐熱性の評価を行ったところ、ヘーズは１．５％、引張破断強さは１９８ＭＰａ、酸素透過度は２１．２ｃｃ・１０μｍ／ｍ2・ｄａｙ・ａｔｍ、切断しない最高温度は１８５℃であり、判定は透明性が◎、機械的強度が◎、ガスバリア性が◎、耐熱性が◎、総合判定が◎であった。
以上の評価結果から、グリコール酸系共重合体Ｐ１を主体とする熱可塑性樹脂よりなる延伸フィルムは、生分解性樹脂よりなり、且つガスバリア性、耐熱性、透明性、機械的強度に優れ、包装材用途に好適であることが判る。
【００６３】
【実施例２〜４、実施例６〜７、参考例１、及び比較例１〜４】
次いで、グリコリドを６５ｇ、ラクチドを３６ｇ、重合時間を３０時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ２とする。該共重合体Ｐ２は、グリコリドからなる繰返し単位の成分割合が８３ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が１７ｍｏｌ％であった。該共重合体Ｐ２は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが１８８℃、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ、相対結晶化度Ｘｒが３４％、対数粘度数［η］が３．６ｄｌ／ｇであった。該共重合体Ｐ２を用いることの他は上記実施例１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが２％であった（実施例２）。
【００６４】
ラクチドを２９ｇ、重合時間を２５時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ３とする。該共重合体Ｐ３は、グリコリドからなる繰返し単位の成分割合が８８ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が１２ｍｏｌ％であった。該共重合体Ｐ３は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが１９９℃、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが５．８Ｊ／ｇ、相対結晶化度Ｘｒが３３％、対数粘度数［η］が２．９ｄｌ／ｇであった。該共重合体Ｐ３を用いることの他は上記実施例１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが３％であった（実施例３）。
【００６５】
グリコリドを６０ｇ、ラクチドを３８ｇ、重合時間を４０時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ４とする。該共重合体Ｐ４は、グリコリドからなる繰返し単位の成分割合が８０ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が２０ｍｏｌ％であった。該共重合体Ｐ４は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが１８２℃、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ、相対結晶化度Ｘｒが１９％、対数粘度数［η］が４．０ｄｌ／ｇであった。該共重合体Ｐ４を用いることの他は上記実施例１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが３％であった（実施例４）。
【００６６】
グリコリドを７５ｇ、ラクチドを２６ｇ、重合時間を１５時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ５とする。該共重合体Ｐ５は、グリコリドからなる繰返し単位の成分割合が９０ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が１０ｍｏｌ％であった。該共重合体Ｐ５は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが２０３℃、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが１８．２Ｊ／ｇ、相対結晶化度Ｘｒが３０％、対数粘度数［η］が１．９ｄｌ／ｇであった。該共重合体Ｐ５を用いることの他は上記実施例１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが２％であった（参考例１）。
【００６７】
グリコリドを６０ｇ、ラクチドを４６ｇとすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ６とする。該共重合体Ｐ６は、グリコリドからなる繰返し単位の成分割合が７８ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が２２ｍｏｌ％であった。該共重合体Ｐ６は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが１７５℃、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ、相対結晶化度Ｘｒが１４％、対数粘度数［η］が２．４ｄｌ／ｇであった。該共重合体Ｐ６を用いることの他は上記実施例１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが３％であった（実施例６）。
【００６８】
グリコリドを５５ｇ、ラクチドを２４ｇ、無水炭酸カリウムで脱水乾燥後に蒸留して精製したε−カプロラクトン（６−ヘキサノラクトン）を２ｇ、触媒をジブチルすずジメトキシド０．２ｇ、重合時間を３０時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ７とする。該共重合体Ｐ７は、グリコリドからなる繰返し単位の成分割合が８６ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が１０ｍｏｌ％、ε−カプロラクトンからなる繰返し単位の成分割合が４ｍｏｌ％であった。該共重合体Ｐ７は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが１８５℃、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ、相対結晶化度Ｘｒが２５％、対数粘度数［η］が２．２ｄｌ／ｇであった。該共重合体Ｐ７を用いることの他は上記実験Ｎｏ．１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが４％であった（実施例７）。
【００６９】
グリコリドを８０ｇ、ラクチドを２２ｇ、重合時間を１０時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ８とする。該共重合体Ｐ８は、グリコリドからなる繰返し単位の成分割合が９３ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が７ｍｏｌ％であった。該共重合体Ｐ８は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが２０６℃、１回目の冷却過程での結晶化熱ΔＨｃが−３６．５Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが５１．６Ｊ／ｇ、相対結晶化度Ｘｒが７８％、対数粘度数［η］が１．０ｄｌ／ｇであった。該共重合体Ｐ８を用いることの他は上記実施例１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが２％であった（比較例１）。
【００７０】
グリコリドを９０ｇ、ラクチドを１０ｇ、重合時間を１５時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ９とする。該共重合体Ｐ９は、グリコリドからなる繰返し単位の成分割合が９７ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が３ｍｏｌ％であった。該共重合体Ｐ９は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが２１８℃、１回目の冷却過程での結晶化熱ΔＨｃが−５８．２Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが５５．５Ｊ／ｇ、相対結晶化度Ｘｒが１００％、対数粘度数［η］が１．９ｄｌ／ｇであった。該共重合体Ｐ９を用いることの他は上記実施例１と同じ実験を試みたが、延伸前溶融成形シートのヘーズが２３．８％であったため延伸操作を行わず、加熱収縮率ΔＬの測定も行わなかった（比較例２）。
【００７１】
グリコリドを１００ｇ、ラクチドを使用せず、重合時間を５時間とすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸単独重合体をＰ１０とする。該共重合体Ｐ１０は、グリコリドからなる繰返し単位の成分割合が１００ｍｏｌ％であった。該重合体Ｐ１０は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが２２２℃、１回目の冷却過程での結晶化熱ΔＨｃが−６９．６Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが７２．６Ｊ／ｇ、相対結晶化度Ｘｒが１００％、対数粘度数［η］が０．８ｄｌ／ｇであった。該重合体Ｐ１０を用いることの他は上記実施例１と同じ実験を試みたが、非晶の延伸前溶融成形シートを得ることが困難であった。該重合体Ｐ１０を使用して前述の延伸前溶融成形シートの作製方法と同様にし得られた結晶化しているシートは、脆弱で割れ易く延伸は困難であった。従って、加熱収縮率ΔＬの測定も行えなかった（比較例３）。
【００７２】
グリコリドを５５ｇ、ラクチドを４６ｇとすることの他は上記実施例１と同じ実験を繰返し、得られたグリコール酸系共重合体をＰ１１とする。該共重合体Ｐ１１は、グリコリドからなる繰返し単位の成分割合が７５ｍｏｌ％、ラクチドからなる繰返し単位の成分割合が２５ｍｏｌ％であった。該共重合体Ｐ１１は、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが現れず、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ、相対結晶化度Ｘｒが０％、対数粘度数［η］が２．５ｄｌ／ｇであった。該共重合体Ｐ１１を用いることの他は上記実施例１と同じ実験を繰返し、得られた熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが５％であった（比較例４）。
これらグリコール酸系共重合体、及びグリコール酸単独重合体のＰ１〜１１について、前述のＤＳＣ、相対結晶化度、対数粘度数、加熱収縮率の測定結果を表１、及び表２にまとめる。
【００７３】
【表１】

Figure 0004790920
【００７４】
【表２】
Figure 0004790920
【００７５】
上記グリコール酸系共重合体、及びグリコール酸単独重合体のＰ２〜１１について、上記実施例１と同様に得られた延伸フィルムをサンプルとして評価を行った。これらの評価結果を表３、及び表４にまとめる。
【００７６】
【表３】
Figure 0004790920
【００７７】
【表４】
Figure 0004790920
【００７８】
表３によると、ＤＳＣにおける１回目の昇温過程での融点Ｔｍが１７５℃以上２０５℃以下、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇ、２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ以上２０Ｊ／ｇ未満、相対結晶化度Ｘｒが３％以上５０％以下、対数粘度数［η］が１．５ｄｌ／ｇであるグリコール酸系共重合体を主体とする熱可塑性樹脂よりなる延伸フィルムは、生分解性樹脂よりなり、且つガスバリア性、耐熱性、透明性、機械的強度に優れた包装材用途に好適な延伸フィルムであることが判る（実施例１〜７）。なかでも、グリコール酸系共重合体のＤＳＣにおける１回目の昇温過程での融点Ｔｍが１８５℃以上２００℃以下、２回目の昇温過程での融解熱ΔＨｍが０Ｊ／ｇ以上１８Ｊ／ｇ以下である場合には、該共重合体を主体とする熱可塑性樹脂よりなる延伸フィルムは耐熱性と透明性の両特性が著しく優れ、包装材用途に特に好適であることが判る（実施例１〜３）。
【００７９】
これらに対し、表４によると、グリコール酸系共重合体、或いはグリコール酸単独重合体のＤＳＣにおける１回目の昇温過程での融点Ｔｍが２０５℃より高く、１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇではなく、２回目の昇温過程での融解熱ΔＨｍが２０Ｊ／ｇ以上であり、相対結晶化度Ｘｒが５０％より高い場合には、該重合体を主体とする熱可塑性樹脂よりなる延伸フィルムは、耐熱性やガスバリア性は優れているものの、透明性や機械的強度が著しく劣ったり、延伸加工が困難であったりして包装材用途には適さないことが判る（比較例１〜３）。特に、前述した１回目の冷却過程での結晶化熱ΔＨｃが０Ｊ／ｇではない場合には、例え対数粘度数［η］が１．５ｄｌ／ｇ以上であっても、結晶性が高い為に延伸前溶融成形シートの作製時に結晶化し、該シートのヘーズが２３．８％となり延伸加工することが出来なかった（比較例２）。
【００８０】
また、対数粘度数［η］が０．８０ｄｌ／ｇと低く、且つ結晶性が非常に高いグリコール酸単独重合体Ｐ１０では、非晶の延伸前溶融成形シートを得ることが困難であった。該単独重合体Ｐ１０を使用して上記方法と同様にし得られた結晶化しているシートは、脆弱で割れ易く延伸加工することが出来ず、延伸フィルムの透明性、ガスバリア性、耐熱性の評価は行えなかった（比較例３）。
一方、グリコール酸系共重合体のＤＳＣにおける１回目の昇温過程での融点Ｔｍが１７５℃より低い場合、詳しくは該融点Ｔｍを１７５℃より低くなるであろう共重合成分割合のグリコール酸系共重合体の場合には、著しく結晶性が低い為に１５０℃で加熱しても結晶化せず、該共重合体を主体とする熱可塑性樹脂よりなる延伸フィルムは、透明性は優れているものの、耐熱性が著しく劣り、包装材用途には適さないことが判る（比較例４）。
【００８１】
【実施例８〜９、及び比較例５〜６】
次ぎに挙げる実験は、延伸フィルムの１００℃１０分間における加熱収縮率について着目した実験である。従って、原料とするグリコール酸系共重合体は上記実施例１と同じ樹脂記号Ｐ１の共重合体を使用し、延伸前溶融成形シートの作製、及び延伸フィルムの作製における延伸操作も上記実施例１と同じ方法で行っている。
【００８２】
熱処理の条件を１５０℃３０秒間とすることの他は上記実施例１と同じ実験を繰返し、熱処理した延伸フィルムを得た。該熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが１％であった（実施例８）。
熱処理の条件を９０℃３分間とすることの他は上記実施例１と同じ実験を繰返し、熱処理した延伸フィルムを得た。該熱処理した延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが４％であった（実施例９）。
【００８３】
熱処理の操作を行わないことの他は上記実施例１と同じ実験を繰返し、熱処理していない延伸フィルムを得た。該熱処理していない延伸フィルムは、１００℃１０分間における加熱収縮率ΔＬが６４％であった（比較例５）。
原料とするグリコール酸系共重合体は上記実施例１と同じ樹脂記号Ｐ１の共重合体を使用し、非晶シートの厚みが約３０μｍとなるように金型を使用することの他は前述した延伸前溶融成形シートの作製と同じ操作を行い溶融成形フィルムを得た。該溶融成形フィルムを用いて、前述した延伸フィルムの作製における熱処理と同じ操作、即ち金枠に固定して１２０℃に設定した熱風循環恒温槽中で１分間熱処理を行って厚み３０μｍの熱処理した延伸していないフィルムを得た。該熱処理した延伸していないフィルムは、１００℃１０分間における加熱収縮率ΔＬが０％であった（比較例６）。
【００８４】
これらの熱処理した延伸フィルム（実施例８〜９）、熱処理していない延伸フィルム（比較例５）、及び熱処理した延伸していないフィルム（比較例６）について、前述の透明性、機械的強度、ガスバリア性、耐熱性の評価を行った。これら、及び実施例１のフィルムの１００℃１０分間における加熱収縮率と透明性、機械的強度、ガスバリア性、耐熱性の評価結果を表５にまとめる。
【００８５】
【表５】
Figure 0004790920
【００８６】
表５によると、１００℃１０分間における加熱収縮率ΔＬが０．５〜４５％である延伸フィルムは、生分解性樹脂よりなり、且つガスバリア性、耐熱性、透明性、機械的強度に優れた包装材用途に好適な延伸フィルムであることが判る（実施例１、及び８〜９）。
これらに対し、延伸後に熱処理を行わず１００℃１０分間における加熱収縮率ΔＬが４５％より高い延伸フィルムは、透明性は優れているが、耐熱性が劣るものとなった（比較例５）。一方、延伸を行わずに熱処理を施した１００℃１０分における加熱収縮率ΔＬが０．５％より低いフィルムは、耐熱性は優れているが、透明性が著しく劣り、更に機械的強度も若干低いものとなった（比較例６）。
【００８７】
【発明の効果】
本発明によれば、特定範囲の結晶性を有するグリコール酸系共重合体を用い、且つ１００℃１０分間における加熱収縮率を規定することにより、生分解性を有し、且つガスバリア性、耐熱性、透明性、機械的強度に優れ、容易に製造することが可能である、包装材用途に好適な延伸フィルム、及び延伸シートを提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stretch-molded body made of a thermoplastic resin mainly composed of a glycolic acid copolymer suitable for packaging materials. More specifically, a glycolic acid copolymer that is biodegradable and excellent in gas barrier properties, heat resistance, transparency, mechanical strength, and can be easily produced is suitable for packaging materials. The present invention relates to a stretched film and a stretched sheet made of a thermoplastic resin as a main component.
[0002]
[Prior art]
The packaging of food and pharmaceutical products facilitates the work of transporting and distributing the contents, and at the same time maintaining the quality is an especially important role. Therefore, the packaging material is required to have high quality maintenance performance. Specifically, as a performance to protect the contents during long-term storage, mechanical strength against external forces such as impact and stab, gas barrier properties against oxidative deterioration of contents due to outside oxygen and moisture evaporation of contents, packaging materials These include stability such as oil resistance and heat resistance that does not denature or deform itself during storage or use, and hygiene that does not transfer harmful substances, off-flavors, or off-flavors from the packaging material itself.
[0003]
Conventionally, plastic products have been used for these packaging materials for convenience during processing and use. However, in the current consumer society, the amount of use has been increasing year by year, and at the same time, the plastic waste problem has become more serious every year. Most plastic waste is disposed of by incineration or landfill, but in recent years, from the viewpoint of environmental conservation, material recycling has been proposed for use as a raw material for plastic products.
[0004]
However, as described above, the required performance of plastic products as a packaging material is diverse, and it is not possible to satisfy all these requirements with only a single type of plastic. For example, it is possible to make a gas barrier film or a molded container by multilayering. In general, several types of plastics are used in combination. Such a packaging material is very difficult to be separated into various resins, and material recycling is impossible in consideration of cost and the like.
[0005]
On the other hand, for example, in JP-A-10-60136, the melting point Tm is 150 ° C. or more, the heat of fusion ΔHm is 20 J / g or more, and the density of the non-oriented crystallized product is 1.50 g / cm.ThreeIt is disclosed that a polyglycolic acid oriented film made of a thermoplastic resin containing a specific polyglycolic acid as described above can be used as a packaging material exhibiting disintegration in soil and excellent in toughness and barrier properties. Yes.
However, the polyglycolic acid oriented film described in JP-A-10-60136 has a heat of fusion ΔHm of 20 J / g or more and a density of non-oriented crystallized material of 1.50 g / cm.ThreeSince it is formed from a thermoplastic resin material containing polyglycolic acid having a very high crystallinity as described above, it is difficult to stretch and align unless it is rapidly cooled so as to be in an amorphous state during molding of the melt-formed sheet before stretching. Therefore, there is a problem that the manufacturing process of the oriented film becomes very complicated.
[0006]
In addition, as a required characteristic of the packaging material, transparency is an important factor in order to increase the value of the product by the display effect that facilitates the recognition of the contents and the purchase intention of the purchaser. However, in the polyglycolic acid described in the publication, even if it is in an amorphous state through a very complicated quenching operation at the time of forming a melt-formed sheet before stretching, it is whitened by a heating operation at the time of stretching and the orientation film is extremely inferior in transparency. However, in the case of obtaining an oriented film having excellent transparency, the stretching condition range is very narrow and it is difficult to produce.
[0007]
Furthermore, the polyglycolic acid oriented film described in JP-A-10-60136 is still low in heat resistance when the melting point Tm is about 150 ° C., and greatly deformed by heat from the contents generated when used in a microwave oven. Or melt-drilling occurs.
The relationship between heat of fusion, density, and crystallinity will be described in detail later. For example, there are thermal analysis and density methods as methods for measuring the crystallinity of a resin. Generally, the former is related to heat of fusion, and the latter is related to density. (Analytical Society of Japan, New Edition Polymer Analysis Handbook, p.340, Kinokuniya (1995)).
[0008]
[Problems to be solved by the invention]
An object of the present invention is a glycolic acid copolymer having biodegradability, excellent gas barrier properties, heat resistance, transparency, mechanical strength, and capable of being easily manufactured, and suitable for packaging materials. An object of the present invention is to provide a stretch-molded body comprising a thermoplastic resin composition mainly composed of a coalescence.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned problems, the present inventors specify the melting point, heat of crystallization, heat of fusion, relative crystallinity, and logarithmic viscosity number of a copolymer whose repeating unit is mainly glycolic acid. In addition, by specifying the heat shrinkage rate of the stretched molded product at 100 ° C. for 10 minutes, the stretched molded product made of the thermoplastic resin composition mainly composed of the copolymer has biodegradability and gas barrier properties, The present inventors have found that it is excellent in heat resistance, transparency, and mechanical strength and is suitable for packaging materials, and has reached the present invention.
[0010]
  That is, the present invention
  1. In a differential scanning calorimetry (based on JIS K7121 and K7122) using a test piece obtained by heat-treating an amorphous sheet of a glycolic acid copolymer at 150 ° C. for 100 minutes, the heating rate and the cooling rate were 10 ° C./min. Melting point Tm (° C.) in the first temperature raising process, heat of crystallization ΔHc (J / g) in the first cooling process, heat of fusion ΔHm (J / g) in the second temperature raising process Glycolic acid satisfying (1) to (3), having a relative crystallinity Xr represented by the following formula (4) of 3% to 50% and a logarithmic viscosity number [η] of 1.5 dl / g or more A stretch molded article for a packaging material, characterized by comprising a thermoplastic resin composition mainly composed of a copolymer and having a heat shrinkage ratio ΔL at 100 ° C. for 10 minutes of 0.5 to 45%,
Formula (1) 175 ≦ Tm ≦ 205
Expression (2) ΔHc = 0
Formula (3) 0 ≦ ΔHm <18.0
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of the amorphous specimen (g / cmThree)
      ρb: Density of crystallized product heated at 150 ° C. for 5 minutes (g / cmThree)
      ρc: Density of crystallized product heated at 150 ° C. for 100 minutes (g / cmThree)
  2. The glycolic acid copolymer is a copolymer obtained by ring-opening polymerization using glycolide and a monomer other than glycolide, and the proportion of the repeating unit composed of glycolide is 78 to 90 mol%, and other than glycolide 2. The stretched molded product for packaging material according to 1, wherein the proportion of the repeating unit composed of the monomer is 22 to 10 mol%,
  3. The monomer other than glycolide is composed of at least one selected from cyclic dimers of aliphatic hydroxycarboxylic acids and lactones1 or2. The stretched molded product for packaging material according to 2.
[0011]
Hereinafter, the stretched molded product for packaging material of the present invention will be described in detail.
The stretched molded product as used in the present invention refers to a stretched film and a stretched sheet. However, the blow molded product is not included. Further, in the present invention, the distinction between a film and a sheet simply uses a different name depending on the difference in thickness. Hereinafter, the film and the sheet are collectively referred to as a molded body.
The stretched molded article for packaging material of the present invention uses a glycolic acid copolymer having crystallinity such that the heat of crystallization ΔHc, heat of fusion ΔHm and relative crystallinity Xr specified in the present invention are in specific ranges, respectively. This eliminates the need for cumbersome processes such as rapid cooling during the molding of the melt-formed product before stretching, greatly improving the work efficiency, and is extremely excellent in transparency without whitening during heating during stretching. It becomes possible to easily and economically produce the stretched molded body.
[0012]
Further, in the present invention, since the heat shrinkage rate of the stretched molded product is 0.5 to 45% at 100 ° C. for 10 minutes, the stretched molded product of the present invention is the above in the region where the heat shrinkage rate is low. Even when a glycolic acid copolymer having a crystallinity such that the crystallization heat ΔHc, the heat of fusion ΔHm, and the relative crystallinity Xr are in specific ranges is used, the heat resistance can be sufficiently exerted and the packaging material On the other hand, in the region where the heat shrinkage rate is high, especially when the stretched molded product is used for shrink wrapping, wrinkles and tarmi are not generated, and the fitting property can be remarkably enhanced.
[0013]
The crystallinity of the polymer refers to the ease of crystallization of the polymer, and is generally expressed by using the crystallization speed and the crystallinity as an index.
The crystallization speed is the speed when irreversibly transitioning from the supercooled melt to the crystalline state. As a guideline, the crystallization temperature is measured during the constant cooling process in thermal analysis. It is said that the higher the speed, the higher the crystallization temperature (edited by Japan Society for Analytical Chemistry, New Edition Polymer Analysis Handbook, p.339, Kinokuniya (1995)).
[0014]
The glycolic acid copolymer used in the present invention has a crystallization heat ΔHc in the first cooling process in differential scanning calorimetry (according to JIS K7121 and K7122 and hereinafter referred to as DSC) measured at a cooling rate of 10 ° C./min. It must be 0 J / g. That is, it is necessary that the crystallization rate be such that crystallization does not occur under the DSC measurement conditions (cooling rate 10 ° C./min). When no crystallization peak appears in the constant speed cooling process in DSC (crystallization heat ΔHc = 0 J / g), the crystallinity of the test piece is amorphous and does not crystallize at all, or the crystallization speed is slow. There are two possible cases where crystallization does not occur under the DSC measurement conditions (cooling rate 10 ° C./min). Here, since the polymer of the present invention has a melting point Tm of 175 to 205 ° C. in the first temperature raising process in DSC as described later, it is different from the case where it is amorphous and does not crystallize at all. It is.
[0015]
If the glycolic acid copolymer used in the present invention has a crystallization rate at which the crystallization heat ΔHc is 0 J / g in the first cooling process, the packaging is made of a thermoplastic resin mainly composed of the copolymer. The production of stretch moldings for materials is not necessary for special non-amorphization processes such as a rapid cooling operation during the molding of melt-molded bodies before stretching, and the manufacturing process is simplified, and further, there is no whitening due to heating operations during stretching. It is possible to produce a stretch-molded body having excellent transparency.
[0016]
On the other hand, the crystallinity is defined as the weight fraction of the crystal region in the polymer solid, and is measured by, for example, a thermal analysis method or a density method.
The thermal analysis method is generally obtained from the crystallinity Xc (%) = ΔHm / ΔHf × 100 as the ratio of the measured melting heat ΔHm of the test piece to the theoretical heat of fusion ΔHf (edited by the Japan Society for Analytical Chemistry, New Edition Polymer Analysis Handbook) , P.339, Kinokuniya (1995)). In this equation, ΔHm uses a value measured by differential scanning calorimetry (based on JIS K7122), and ΔHf uses a value described in, for example, POLYMER HANDBOOK (John Wiley & Sons) in the case of a homopolymer.
[0017]
Further, in the density method, in general, when the measured density of a test piece is represented by d and the densities of completely amorphous and completely crystallized by da and dc, the crystallinity Xc (%) = [(d-da) / (dc-da )] × (dc / d) × 100 (Edited by Japan Society for Analytical Chemistry, New Edition Polymer Analysis Handbook, p. 586, Kinokuniya (1995)). In this equation, d and da are values obtained by measuring a test piece or an amorphous material obtained by rapidly cooling the test piece and then rapidly cooling it, for example, by a floatation method or a density gradient tube method (based on JIS K7112). In the case of a polymer, for example, values described in POLYMER HANDBOOK (JOHN WILEY & SONS) are used. However, in the case of a copolymer, the above ΔHf and dc often have no literature values because the copolymer components and their component ratios are diverse.
[0018]
In the thermal analysis method, the above formula for obtaining the degree of crystallinity Xc means that the higher the measured melting heat ΔHm of the test piece, the higher the degree of crystallinity. Therefore, in the present invention, the value of ΔHm Determine crystallinity. The glycolic acid copolymer of the present invention is required to have a heat of fusion ΔHm of 0 J / g or more and less than 20 J / g in the second temperature rising process in DSC measurement.
In the density method, in the present invention, the crystallinity of the copolymer is determined based on the relative crystallinity obtained by using the density when heated and crystallized under conditions where crystallization is considered to proceed sufficiently. to decide. The glycolic acid copolymer of the present invention needs to have a relative crystallinity Xr represented by the following formula (4) in the range of 3% to 50%.
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of the amorphous specimen (g / cmThree)
ρb: Density of crystallized product heated at 150 ° C. for 5 minutes (g / cmThree)
ρc: Density of crystallized product heated at 150 ° C. for 100 minutes (g / cmThree)
[0019]
The value of ΔHm of the glycolic acid copolymer used in the present invention is 0 J / g, as in the case of the above-described crystallization heat ΔHc. Unlike the case where it is amorphous and does not crystallize at all because the melting point Tm in the temperature process is 175 to 205 ° C., crystallization does not occur under the DSC measurement conditions (temperature increase rate 10 ° C./min). It means crystallization speed. When the value of ΔHm is 20 J / g or more, since the polymer has very high crystallinity, the production of a stretched molded product for a packaging material made of a thermoplastic resin mainly composed of the polymer is melted before stretching. If the molded sheet is not rapidly cooled so as to be in an amorphous state, it is difficult to stretch and align, and it becomes very complicated.
[0020]
In addition, even if it is in an amorphous state through a very complicated quenching operation during molding of the melt-molded product before stretching, only an oriented molded product that is whitened by heating operation during stretching and extremely poor in transparency can be obtained. When trying to obtain an excellent oriented molded article, the range of stretching conditions is very narrow, making it difficult to produce. The value of ΔHm is such that a stretched molded body can be produced more easily, and a range of 0 J / g or more and 18.0 J / g or less is required in order to obtain a highly transparent stretched molded body for a packaging material. preferable.
[0021]
When the relative crystallinity Xr represented by the formula (4) is lower than 3%, the glycolic acid copolymer is too low in crystallinity and is made of a thermoplastic resin mainly composed of the polymer. The stretched molded product for packaging material is extremely inferior in heat resistance. On the other hand, when the value of Xr is higher than 50%, since the polymer has very high crystallinity, the production of the stretch-molded body for a packaging material made of a thermoplastic resin mainly composed of the polymer is performed by stretching. If the pre-melt molded body is not cooled rapidly so as to be in an amorphous state, it is difficult to stretch and align, and it becomes very complicated. In addition, even if it is in an amorphous state through a very complicated quenching operation during molding of the melt-molded product before stretching, only an oriented molded product that is whitened by heating operation during stretching and extremely poor in transparency can be obtained. When trying to obtain an excellent oriented molded article, the range of stretching conditions is very narrow, making it difficult to produce. The value of Xr is preferably in the range of 10% to 40% in order to combine higher heat resistance and higher transparency.
[0022]
Moreover, in the said Formula (4), when the density (rho) c at the time of heating for 100 minutes at 150 degreeC is equal to the density (rho) of the amorphous test piece before the heating, relative crystallinity degree Xr is calculated by this formula. I can't. In this case, the sample used for the measurement does not crystallize under the heating condition, which means that the crystallinity is very low or amorphous, and the relative crystallinity Xr is 0%. It is beyond the scope of the claimed invention.
In the present invention, a glycolic acid copolymer having a specific melting point is used. Due to such differences, the stretch molded body for packaging material of the present invention has high characteristics required for the packaging material without melting and perforating the stretch molded body itself due to the heat from the heated contents even when used in a microwave oven. It becomes possible to satisfy heat resistance.
[0023]
The melting point of the glycolic acid copolymer used in the present invention is such that the glycolic acid copolymer is heated and pressurized for 5 minutes with a heating press set at 250 ° C., and then cooled with a cooling press set at 25 ° C. Differential scanning calorimetry (DSC) using a crystallized product obtained by heating an amorphous sheet of about 200 μm for 100 minutes in a hot air circulating thermostat set at 150 ° C. under a heating and cooling rate of 10 ° C./min. , In accordance with JIS K7121), the melting point Tm in the first temperature raising process is in the range of 175 ° C. or higher and 205 ° C. or lower. When the Tm value is lower than 175 ° C., the melting point of the glycolic acid copolymer is too low, and the heat resistance of the stretched molded body made of a thermoplastic resin mainly composed of the polymer is extremely inferior. It cannot be used in applications that require heat resistance.
[0024]
On the other hand, when the value of Tm is higher than 205 ° C., the crystallinity of the glycolic acid copolymer becomes very high, so that the stretch molded body made of a thermoplastic resin composition mainly composed of the copolymer is used. The production becomes very complicated because it becomes difficult to achieve orientation without rapid cooling so as to be in an amorphous state during molding of the pre-stretched melt-formed product. In addition, even when the melt-formed sheet before stretching is formed into an amorphous state through a very complicated quenching operation, only an oriented molded body that is whitened by heating operation during stretching and extremely poor in transparency can be obtained. When trying to obtain an excellent oriented molded article, the range of stretching conditions is very narrow, making it difficult to produce. The Tm value is preferably selected from the range of 185 ° C. or higher and 200 ° C. or lower in order to combine higher heat resistance and higher transparency. In the differential scanning calorimetry, when there are a plurality of endothermic peaks due to crystal melting, the highest endothermic peak temperature is defined as the melting point Tm.
[0025]
The glycolic acid copolymer, which is the main material constituting the stretched molded article for packaging materials of the present invention, is glycolide (1,4-dioxa-2,5), which is a cyclic dimer of glycolic acid as the main monomer. -Dione), or a copolymer obtained by direct dehydration polycondensation using glycolic acid, for example, polycondensation while dealcoholizing with glycolic acid esters such as methyl glycolate However, among those obtained by copolymerizing monomers other than glycolide that can be copolymerized with these main monomers, the requirements of the present invention are satisfied.
[0026]
Examples of monomers other than glycolide used for copolymerization other than the main monomer include L-lactic acid, D-lactic acid, 2-hydroxy-2,2-dialkylacetic acid including 2-hydroxyisobutyric acid, 3- Hydroxybutyric acid, 3-hydroxyvaleric acid, 3-hydroxyhexanoic acid, 4-hydroxybutanoic acid, other known aliphatic hydroxycarboxylic acids, ester derivatives of these aliphatic hydroxycarboxylic acids, the same kind of these aliphatic hydroxycarboxylic acids, or And at least one kind of lactones such as different kinds of cyclic dimers, and β-butyrolactone, β-propiolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, ε-caprolactone, etc. To be elected.
[0027]
In addition to these, an equimolar amount of a polyhydric alcohol and a polyvalent carboxylic acid may be combined and copolymerized with the main monomer. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 2,2-dimethyl-1. Aliphatic diols such as 1,3-propanediol, 1,6-hexanediol, 1,3-cyclohexanol, 1,4-cyclohexanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, or For example, diethylene glycol, triethylene glycol, tetraethylene glycol and the like in which a plurality of these aliphatic diols are bonded. Examples of the polyvalent carboxylic acid include malonic acid, succinic acid, glutaric acid, 2,2-dimethylglutaric acid, and adipine. Acid, pimelic acid, speric acid, azelaic acid, Aliphatic dicarboxylic acids such as vasic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, diglycolic acid, terephthalic acid, isophthalic acid, 1,4-naphthalene dicarboxylic acid Acid, aromatic dicarboxylic acids such as 2,6-naphthalene dicarboxylic acid, ester derivatives of these aliphatic dicarboxylic acids and aromatic dicarboxylic acids, anhydrides of these aliphatic dicarboxylic acids, and the like. Also good.
[0028]
Among the glycolic acid copolymers that are the main materials constituting the stretched molded article for packaging materials of the present invention exemplified above, a preferred copolymer is glycolide from the viewpoint of easily obtaining a copolymer having a higher molecular weight. A copolymer obtained by ring-opening polymerization using a monomer other than glycolide, wherein the proportion of the repeating unit composed of glycolide is 78 to 90 mol%, and the proportion of the repeating unit composed of a monomer other than glycolide Is composed of 22 to 10 mol%. More preferably, the component ratio of the repeating unit made of glycolide is 81 to 88 mol%, and the component ratio of the repeating unit made of a monomer other than glycolide is 19 to 12 mol%.
[0029]
Among the monomers constituting the copolymer, the monomer other than glycolide is preferably at least one selected from cyclic dimers of aliphatic hydroxycarboxylic acids and lactones, and a cyclic dimer of lactic acid. Lactide (3,6-dimethyl-1,4-dioxa-2,5-dione) is particularly preferred. Lactide is an optically active substance and may be either L-form or D-form, or a D, L-form mixture or meso form. Further, it may be a mixture of glycolide-L-lactide copolymer and glycolide-D-lactide.
[0030]
The manufacturing method of the glycolic acid type copolymer used by this invention is not specifically limited, It is performed by a conventionally well-known general method. For example, ring-opening polymerization using glycolide as a main monomer to obtain a glycolic acid copolymer includes the method of Gilding et al. (Polymer, vol. 20, December (1979)). It is not limited.
The molecular weight of the copolymer is at least 1.5 dl in terms of logarithmic viscosity so that the stretched molded body made of a thermoplastic resin mainly composed of the copolymer has mechanical strength against external force required as a packaging material. / G or more is required, and it is preferably 1.8 dl / g or more. The logarithmic viscosity number [η] is generally a value obtained by the following formula (5), and can be approximated to the intrinsic viscosity used as an index of the molecular weight of a polymer in a dilute solution having a concentration of 0.2% or less (Chemical Dictionary Dictionary Reprint) Edition, p.746, Kyoritsu Shuppan (1963), and the new edition Polymer Analysis Handbook, p.120, Kinokuniya (1995)).
Formula (5) [η] = {ln (t / to)} / c
Where t: flow time of the polymer solution measured with a capillary viscometer (seconds)
to: Flow time of the solvent (seconds) measured with a capillary viscometer
c: Concentration of solute polymer (g / dl)
[0031]
On the other hand, the upper limit of the molecular weight of the copolymer is preferably not more than 8.0 dl / g in terms of logarithmic viscosity in order to more easily produce a melt-formed body before stretching. There is no particular limitation as long as the fluidity is adjusted.
The molecular weight of the glycolic acid copolymer used in the present invention is 7.0 × 10 in terms of number average molecular weight.FourOr more, preferably 1.0 × 10FiveThat's it. The upper limit of the molecular weight is 7.0 × 10 in terms of number average molecular weight.FiveOr less, preferably 6.0 × 10FiveIt is desirable to keep it below.
The stretched molded product for packaging material according to the present invention is characterized by comprising a thermoplastic resin composition mainly composed of the above-mentioned specific glycolic acid copolymer. The thermoplastic resin composition referred to in the present invention is described below. Will be described.
[0032]
In the present invention, the thermoplastic resin composition mainly composed of the specific glycolic acid copolymer is a simple substance of the glycolic acid copolymer, or the glycolic acid copolymer and another polymer. It refers to a composition, a composition of a glycolic acid copolymer alone or a copolymer and another polymer, and a composition such as a plasticizer and an antioxidant. In the case of a composition of a glycolic acid copolymer and another polymer among the thermoplastic resins, the composition ratio is the quality maintaining performance of the content required when used as a packaging material, such as a gas barrier. It is a case where it mixes so that the component ratio 50 mol% or more may become the repeating unit which consists of glycolide among all the repeating units of each polymer of this composition, although it changes with property, heat resistance, etc., and the quality of higher content For packaging materials that require retention performance, the component ratio is more preferably 70 mol% or more.
[0033]
Specifically, for example, in the case of mixing a glycolic acid copolymer comprising a glycolide 80 mol% and lactide 20 mol% repeating unit and a lactide 100 mol% repeating unit, the mixed composition In order to make the glycolide component ratio in all the repeating units of the product 50 mol% or more, the composition ratio of the glycolic acid copolymer must be 66.5 wt% or more. In the case of mixing a glycolic acid-based copolymer consisting of 90 mol% glycolide and 10 mol% lactide repeating units with polylactic acid consisting of 100 mol% lactide repeating units, all the repetitions of the mixture composition are repeated. In order to make the glycolide component ratio in the unit 50 mol% or more, the composition ratio of the glycolic acid copolymer must be 60.3% by weight or more.
[0034]
In addition, the component ratio of the repeating unit which consists of glycolide of the thermoplastic resin composition which comprises an extending | stretching molded object can be analyzed with a normal analysis method. For example, the stretched molded product is dissolved in hexafluoroisopropanol (hereinafter abbreviated as HFIP) and filtered to remove insoluble components. Next, the obtained HFIP solution of the thermoplastic resin is poured into methanol to reprecipitate the resin component. The obtained reprecipitation resin component is sufficiently dried with a vacuum dryer, and then 1H-NMR and 13C-NMR are measured using deuterated trifluoroacetic acid or deuterated HFIP as a solvent, and repeatedly composed of glycolide of a thermoplastic resin. The component ratio of the unit can be analyzed.
[0035]
In the thermoplastic resin composition of the present invention, when another polymer is mixed with the glycolic acid copolymer specified in the present invention, other polymers that can be mixed are listed as specific examples. At least one selected from polylactic acid and the following polymers is preferable, and those having biodegradability are preferable. For example, the glycolic acid polymer may have a higher glycolide component ratio and higher crystallinity than the glycolic acid copolymer specified in the present invention, or may have a lower component ratio and lower crystallinity. It may be a thing. In the polylactic acid whose monomer is an optically active substance, either L-form or D-form may be used, and the mixing ratio of D, L-form may be any mixture composition, D, L-form The copolymer may be an arbitrary copolymer or meso form.
[0036]
Besides these, 2-hydroxy-2,2-dialkylacetic acid containing 2-hydroxyisobutyric acid, 3-hydroxybutyric acid, 3-hydroxyvaleric acid, 3-hydroxyhexanoic acid, 4-hydroxybutanoic acid, and other known fats Obtained from aromatic hydroxycarboxylic acids, ester derivatives of these aliphatic hydroxycarboxylic acids, homopolymers obtained from the same or different cyclic dimers of these aliphatic hydroxycarboxylic acids, or two or more arbitrarily selected from these Obtained from lactones such as polyhydroxycarboxylic acids, β-butyrolactone, β-propiolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, and ε-caprolactone. Homopolymers, or two or more arbitrarily selected from these Polylactones, which are copolymers obtained from a combination of an equimolar amount of a polyhydric alcohol and a polycarboxylic acid, and examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,2-propanediol, , 3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 1,3-cyclohexanol, 1,4 -Aliphatic diols such as cyclohexanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, or a combination of a plurality of these aliphatic diols such as diethylene glycol, triethylene glycol, tetraethylene glycol, etc. Carboxylic acids such as malonic acid, succinic acid, Rutaric acid, 2,2-dimethylglutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid , Aliphatic dicarboxylic acids such as diglycolic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 1,4-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, aliphatic dicarboxylic acids and aromatic dicarboxylic acids Polyesters and polycarboxylic acids obtained from ester derivatives, anhydrides of these aliphatic dicarboxylic acids, etc., each of which is a homopolymer, or any one of polyhydric alcohols and polycarboxylic acids And the other is a copolymer obtained from two or more types selected arbitrarily, or a polyvalent polymer. Aliphatic polyesters, which are copolymers obtained from two or more of each selected from coles and polycarboxylic acids, and other known biodegradable plastics such as polyaspartic acid They may be amino acids, cellulose esters such as cellulose acetate, aliphatic polyester carbonates, polyvinyl alcohols, polyethylene oxide, low molecular weight polyethylene and the like.
[0037]
Incidentally, it may be a copolymer obtained by copolymerizing two or more of the monomers constituting the various polymers listed here at an arbitrary ratio, and when the monomer is an optically active substance. May be any of L-form or D-form, a mixed composition having an arbitrary mixing ratio of D, L-form, a copolymer having an arbitrary copolymerization ratio of D, L-form, or Any meso form may be used.
Moreover, as said other polymer which can be mixed, even if it does not have biodegradability, you may mix in the range which does not inhibit the biodegradability of the thermoplastic resin composition of this invention. Examples thereof include polyolefins, aromatic polyesters, polyamides, ethylene-vinyl alcohol copolymers, petroleum resins and terpene resins, and hydrogenated products thereof.
[0038]
The thermoplastic resin composition of the present invention is optionally made of an additive comprising an inorganic and / or organic compound, such as a plasticizer, a lubricant, an antistatic agent, an antifogging agent, an antioxidant, a thermal stabilizer, and a light stabilizer. An agent, an ultraviolet absorber, a colorant, a flame retardant, a crystal nucleating agent, and the like may be appropriately mixed. Specific examples of the plasticizer used include, for example, phthalates such as dioctyl phthalate and diethyl phthalate, fatty acid esters such as ethyl laurate, butyl oleate and octyl linoleate, and fats such as dioctyl adipate and dibutyl sebacate. Aliphatic dibasic acid esters, aliphatic tribasic acid esters such as tributyl acetylcitrate, glycerin fatty acid esters such as glycerol diacetate laurate and glycerol triacetate, phosphate esters such as dioctyl phosphate, epoxidized soybean oil And modified vegetable oils such as epoxidized linseed oil, and polyester plasticizers such as polybutylene sebacate. Glycerin fatty acid esters are particularly desirable from the viewpoint of safety and health.
[0039]
One or two or more are selected from these, and the addition amount is about 1 to 50 parts by weight with respect to 100 parts by weight of the thermoplastic resin. Moreover, as a specific example of the antioxidant used, for example, one type or two or more types are selected from phenol, phenyl acrylate, phosphorus, sulfur and the like, and the addition amount is 100 parts by weight of the thermoplastic resin. About 0.01 to 10 parts by weight.
The production of the thermoplastic resin composition in the present invention is carried out by using the specific glycolic acid copolymer of the present invention and other resins and additives that can be mixed therewith, in whole or in part, uniaxially or biaxially. It is desirable to melt and mix using a screw extruder, Banbury mixer, mixing roll, kneader or the like.
[0040]
Next, the stretched molded product of the present invention will be described. The stretched molded product referred to in the present invention refers to a stretched film and a stretched sheet as described above. However, the blow molded product is not included.
The manufacturing method of an extending | stretching molded object is not specifically limited, A conventionally well-known general method is performed. For example, examples of the method for producing a melt-formed body before stretching include a melt extrusion method, a casting method (solution casting method), a calendar method, and a melt press molding method. Specifically, the thermoplastic resin composition mainly comprising the glycolic acid copolymer of the present invention is used as a raw material. For example, in the melt extrusion method, the raw material is supplied to an extruder and heated and melted. It can be manufactured by extruding from a die connected to the tip. In the melt press molding method, the raw material is supplied to a mold, heated and melted under normal pressure or reduced pressure, and then pressed. In this case, the heating and melting of the raw material is usually preferably performed at a temperature appropriately selected from a temperature range of (melting point−5 ° C.) to (melting point + 65 ° C.).
[0041]
As a subsequent stretching method, in the case of uniaxial stretching, melt-extruded from a T-die by a melt extrusion method, and a melt-formed body before stretching cooled by a cast roll is longitudinally uniaxially stretched in a resin flow direction by a roll stretching machine, A method of producing by transversely uniaxially stretching with a tenter while suppressing the longitudinal stretching ratio as much as possible. Alternatively, in the case of biaxial stretching, melt-extruded from a T-die by a melt extrusion method, and a melt-formed body before stretching cooled by a cast roll is longitudinally stretched by a roll stretching machine, and then laterally stretched by a tenter, and manufactured. For example, a melt-formed annular body before stretching that has been melt-extruded from a circular die by a melt extrusion method and cooled by a water-cooling ring or the like is manufactured by tubular stretching. In this case, the stretching operation is usually performed at a stretching temperature of a glass transition temperature to (glass transition temperature + 60 ° C.) and at a stretching condition appropriately selected at a stretching ratio of 2 to 40 times the area ratio in at least a uniaxial direction. Desirably, the more desirable range is limited to the stretching temperature of (glass transition temperature + 5 ° C.) to (glass transition temperature + 40 ° C.) at least at a stretching ratio of 4 to 35 times in the uniaxial direction.
[0042]
The present inventor, when using a glycolic acid-based copolymer having a specific range of crystallinity as a film or a sheet for packaging materials, by applying a stretching process, mechanical strength and the required characteristics of the packaging material We found that transparency can be improved. This expresses the effect that the polymer chains are oriented by stretching to exhibit strength, and the effect of suppressing the growth of crystal size when the subsequent heat treatment is performed. Therefore, when the stretching process is not performed, the degree of orientation of the polymer chains is small and the molded body has a lower strength, or when the heat treatment is performed to increase the strength, the molded body is scattered by light scattering in the grown crystal. This causes a problem of whitening and loss of transparency.
[0043]
In addition to the production method of the stretched molded article described above, for example, a method of producing by an inflation method in which a melt tube melt-extruded from an inflation die by a melt extrusion method is expanded by an internal air pressure and fixed by air cooling or water cooling, etc. good. Since this inflation method generally makes it difficult to rapidly cool the film, it is difficult to obtain a stretched film having excellent transparency because the polyglycolic acid described in JP-A-10-60136 has very high crystallinity. It is.
[0044]
In the present invention, the stretched molded product refers to a stretched film and a stretched sheet, and the thickness thereof is appropriately selected depending on the application, and is usually 3 to 100 μm for a stretched film and 0.1 to 1 mm for a stretched sheet, but is particularly limited. Is not to be done. Considering the ease of production of these stretched films and stretched sheets, it is usually desirable to produce stretched films by the tubular stretching method and stretched sheets by the tenter stretching method. However, the distinction between a film and a sheet simply uses different names depending on the difference in thickness, and there is no difference in that a stretched molded article with high transparency, which is the subject of the present invention, can be easily produced. . Therefore, in the examples described later, the present invention was described in detail by measuring and evaluating physical properties of a stretched film having a thickness of about 30 μm.
[0045]
The obtained stretched molded body is used for packaging materials and containers that are heated by a microwave oven or the like and require heat resistance. It is preferable. Furthermore, it is desirable to perform an aging treatment or the like for the purpose of improving dimensional stability over time and physical property stability. In order to achieve these objects, the stretched molded product of the present invention needs to have a heat shrinkage ratio ΔL at 100 ° C. for 10 minutes of 0.5 to 45%, and 0.5 to 35%. A range is preferable. When the value is larger than 45%, deformation due to heat and melt perforation occur, and the function as a packaging material is impaired.
[0046]
On the other hand, when the value is smaller than 0.5%, the effect of exerting strength by aligning the polymer chain is impaired by stretching, or the molded body becomes whitened and transparent when heat treatment is performed with a small degree of orientation. This causes problems such as loss of sex. In this case, the heat treatment is preferably performed at a temperature appropriately selected from a temperature range of 60 to 160 ° C. for 1 second to 3 hours, and the aging treatment is usually performed at a temperature appropriately selected from a temperature range of 25 to 60 ° C. It is desirable to be performed for about 10 days.
[0047]
The obtained stretched molded product may be used as it is as a packaging material for household wraps, but various surface treatments such as coating and corona treatment for the purpose of improving antistatic agents and antifogging properties as necessary. In order to improve sealability, moisture resistance, gas barrier properties, printability and the like, lamination processing, coating processing, or vacuum deposition of aluminum or the like may be performed. Furthermore, you may shape | mold and use it according to a use by the secondary process. Examples of secondary processed products include seal processed products that are used for packaging materials such as pillow packaging and weld-type casing packaging in the case of stretched films, and plug assist molding methods and air cushion molding methods in the case of stretched sheets. There are containers such as trays and cups, blister packaging sheets, etc. by performing vacuum forming processing, pressure forming processing, male / female molding processing, and the like.
[0048]
The obtained stretched molded product of the present invention uses a glycolic acid copolymer having a crystallinity in a specific range as a main material constituting the stretched molded product, and the heat-shrinkage of the stretched molded product at 100 ° C. for 10 minutes. By defining the rate, it has biodegradability and is excellent in gas barrier properties, heat resistance, transparency and mechanical strength, and can be suitably used for packaging materials. In particular, a soft to medium stretched film with a relatively large amount of plasticizer and a tensile modulus of less than 4.0 GPa is suitable for packaging materials such as pillow packaging, shrink packaging, stretch packaging, casing, and household wrap. It is.
[0049]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to examples. However, these specific examples do not limit the scope of the present invention. In addition, physical property measurement methods, evaluation methods and scales are shown below. Samples are prepared in an atmosphere of temperature (23 ± 2) ° C. and relative humidity (50 ± 5)% after preparation of measurement samples unless otherwise specified. What was stored for a day was subjected to physical property measurement and evaluation.
[Physical property measurement method]
(1) Differential scanning calorimetry (DSC)
The melting point Tm, the heat of crystallization ΔHc, and the heat of fusion ΔHm were measured according to JIS K7121 and K7122 using a DSC6200 manufactured by Seiko Denshi Kogyo Co., Ltd. as a measuring device. The sample was heated and pressed for 5 minutes with a heating press set with a glycolic acid copolymer at 250 ° C., and then cooled with a cooling press set at 25 ° C., and an amorphous sheet having a thickness of about 200 μm was obtained at 150 ° C. A crystallized product heated for 100 minutes in a hot-air circulating thermostat set to 1 was used as a test piece. The weight of the test piece was 7.5 mg, and the sample was first held at 0 ° C. for 3 minutes, and then heated to 250 ° C. at a heating rate of 10 ° C./min, and the melting point Tm in the first temperature rising process was measured. After maintaining at 250 ° C. for 1 minute, it was cooled to 0 ° C. at a cooling rate of 10 ° C./min, and the crystallization heat ΔHc in the first cooling process was measured. Subsequently, after maintaining at 0 ° C. for 1 minute, the mixture was heated again to 250 ° C. at a heating rate of 10 ° C./min, and the heat of fusion ΔHm in the second temperature raising process was measured. The calibration of temperature and heat quantity was performed using indium as a standard substance. The amorphous sheet referred to in the present invention is a sheet prepared by the above procedure as a sample, a diffraction intensity curve is measured by a wide-angle X-ray diffraction method, and a diffraction peak due to the crystal does not exist in the diffraction intensity curve. Point to. In the differential scanning calorimetry, when there are a plurality of endothermic peaks due to crystal melting, the highest endothermic peak temperature is defined as the melting point Tm.
[0050]
(2) Relative crystallinity
In the present invention, the relative crystallinity value represented by the formula (4) is adopted. An amorphous sheet of glycolic acid copolymer was obtained by the procedure shown in the DSC measurement method, and the amorphous sheet was crystallized by heating and crystallization in a hot air circulating thermostat set at 150 ° C. for 5 minutes and 100 minutes. Got. The density was measured in accordance with the JIS K7112C method using these amorphous sheet test pieces, a crystallized product heated at 150 ° C. for 5 minutes, and a crystallized product heated at 150 ° C. for 100 minutes as samples. The density was measured by observing the floatation state by an ethanol / zinc chloride aqueous solution floatation method at 20 ° C. From the density measurement result of the sample, the relative crystallinity Xr was determined by the equation (4).
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of amorphous material (g / cmThree)
ρb: Density of crystallized product heated at 150 ° C. for 5 minutes (g / cmThree)
ρc: Density of crystallized product heated at 150 ° C. for 100 minutes (g / cmThree)
(3) Logarithmic viscosity number
Using an Ubbelohde capillary viscometer as a sample, measure the time to flow down in the capillary at 20 ° C. using a pure solvent HFIP and a HFIP solution dissolved so that the concentration of glycolic acid copolymer is 0.1 g / dl. The logarithmic viscosity number [η] was determined from the equation (5).
Formula (5) [η] = {ln (t / to)} / c
Where t: flow time of the polymer solution measured with a capillary viscometer (seconds)
to: Flow time of the solvent (seconds) measured with a capillary viscometer
c: Concentration of solute polymer (g / dl)
[0051]
(4) Heat shrinkage rate
The heat shrinkage rate ΔL at 100 ° C. for 10 minutes was measured according to JIS K7133 using a stretched molded product as a sample. The sample was cut into a square with a side of 120 mm and marked with 4 points so that the distance between the marked lines along the side was 100 mm to obtain a test piece. The test piece was sprinkled with powder of kaolin, talc or the like, placed flat on the kaolin floor, and heated in a hot air circulating thermostat set at 100 ° C. for 10 minutes. Thereafter, the test piece is taken out, the distance between the marked lines in two directions orthogonal to each other is measured, and the percentage ΔL (%) of the ratio of the contraction amount of the distance between the marked lines after heating to the distance between the marked lines before heating by the equation (6). Was calculated. The measurement result of the heat shrinkage ratio ΔL was measured by measuring two test pieces in two orthogonal directions, and the average value thereof was shown. In the present invention, equation (6) is adopted so that the shrinkage rate becomes a positive value. However, when the melt-formed sheet before stretching has a haze of 20% or more, the glycolic acid copolymer used as a raw material has high crystallinity and deviates from the specific crystallinity of the present invention. In this case, the stretching operation was not performed, and the heat shrinkage rate ΔL was not measured.
Expression (6) ΔL = [(Lo−L) / Lo] × 100
However, Lo: Distance between marked lines before heating 100 mm
L: Distance between marked lines after heating (mm)
[0052]
[Evaluation method and scale]
(1) Transparency
Transparency was evaluated by measuring haze using a stretched film as a sample. The haze was measured according to JIS K7105 using a haze meter HR-100 manufactured by Murakami Color Research Laboratory Co., Ltd. as a measuring device. A stretched film sample having a thickness of about 30 μm was cut into a square with a side of 50 mm, and this was set in a holder, and the haze of the sample was measured. The measurement result of haze was measured by 5 samples and expressed as an average value. This haze was used as an index of transparency. However, when the sheet obtained by the preparation procedure of the melt-formed sheet before stretching described later has a haze of 20% or more, the stretching process is not easy, so it was excluded from the evaluation, and the determination was “x”.
<Evaluation scale>
Haze judgment Remarks
Less than 2% ◎ Transparent and very good visibility
2% or more and less than 5% ○ Visibility is excellent with slight whitening
5% or more and less than 10% △ Whitening and poor visibility
10% or more × Remarkably whitened and very poor in visibility
[0053]
(2) Mechanical strength
The mechanical strength was evaluated by measuring the tensile strength at break using a stretched film as a sample. The tensile strength at break was measured using an autograph AGS-1kNG manufactured by Shimadzu Corporation as a measuring device, in accordance with JIS K7127. A stretched film sample having a thickness of about 30 μm was cut into a strip shape having a length of 200 mm and a width of 10 mm, and this was mounted on a chuck set to 100 mm between chucks, and the test was performed at a tensile speed of 100 mm / min. The measurement result of the tensile strength at break was measured for every 10 samples and indicated by the average value. This tensile breaking strength was used as an index of mechanical strength. However, when the sheet obtained by the preparation procedure of the melt-formed sheet before stretching described later has a haze of 20% or more, the stretching process is not easy, so it was excluded from the evaluation, and the determination was “x”.
<Evaluation scale>
Judgment of tensile strength at break Remarks
150MPa or more ◎ Very strong and practically no problem
50 MPa or more and less than 150 MPa ○ Can be used for applications other than strong and high strength applications
15 MPa or more and less than 50 MPa △ Weak and practically problematic
Less than 15 MPa × Very weak and unbearable for practical use
[0054]
(3) Gas barrier properties
The gas barrier property was evaluated by measuring oxygen permeability using a stretched film as a sample. The oxygen permeability was measured according to the JIS K7126B method using an oxygen permeability measuring device OX-TRAN200H manufactured by mocon as a measuring device. A stretched sample having a thickness of about 30 μm was cut into a square shape with a side of 120 mm, and the test was performed under the conditions of a temperature of 23 ° C. and a relative humidity of 65%. The measurement result of the oxygen permeability was measured as an average value of values obtained by measuring three samples and converting to a thickness of 10 μm. This oxygen permeability was used as an index of gas barrier properties. However, when the sheet obtained by the preparation procedure of the melt-formed sheet before stretching described later has a haze of 20% or more, the stretching process is not easy, so it was excluded from the evaluation, and the determination was “x”.
<Evaluation scale>
Oxygen permeability determination Remarks
Less than 100 ◎ Very high gas barrier property
100 to less than 500 ○ High gas barrier property
500 or more but less than 1000
1000 or more × Gas barrier property is very low, depending on usage, oxygen permeability cannot be used Unit: cc · 10 μm / m2・ Day ・ atm
[0055]
(4) Heat resistance
For the heat resistance, the evaluation results of the load-breaking cutting test and the melt drilling test were used as indices, and the lower determination result of these both determination results was used as the heat resistance determination result. In the load-resistant cutting test, with a load of 30 g applied to a strip-shaped test piece, the test piece is heated for 1 hour in a hot air circulating thermostat set at a constant temperature to check whether the test piece is cut or not. Was measured. A stretched film having a thickness of about 30 μm was cut into a strip shape having a length of 140 mm and a width of 30 mm. A fixing jig and a load jig were attached to each of the upper and lower ends of the strip-shaped test piece 25 mm, respectively, and heated for 1 hour in a hot air circulating thermostat set at a constant temperature to examine whether or not the test piece was cut. In the case where the strip-shaped test piece did not cut, the above procedure was repeated by increasing the set temperature by 5 ° C. with a new test piece. The measurement result of the maximum temperature at which the strip-shaped test piece was not cut was shown as a mode value by performing this test five times for each stretched film.
[0056]
In the melt-resistant perforation test, hot air set at a constant temperature was blown to the center of a test piece stretched in a tension state on a metal frame to examine whether or not the test piece was perforated, and the maximum temperature at which the test piece did not perforate was measured. A stretched film having a thickness of about 30 μm was cut into a square having a side of 180 mm and used as a test piece. The periphery was fixed to a square metal frame having an outer dimension of 180 mm and an inner dimension of 150 mm so that the outer edge of the test piece overlapped with the outer edge of the metal frame. From a circular nozzle with a diameter of 50 mm connected to a hot air generator, a metal frame with a fixed test piece is installed horizontally, the wind speed at the nozzle tip is 2 m / sec, and the distance from the nozzle tip to the test piece is 50 mm. As described above, hot air set at a constant temperature was blown vertically from the bottom to the center of the test piece for 10 minutes to examine whether the test piece was perforated.
[0057]
When no perforation occurred in the test piece, the above procedure was repeated by increasing the set temperature by 5 ° C. with a new test piece. The measurement result of the maximum temperature at which the test piece did not perforate was shown as a mode value by performing this test five times for each stretched film. However, when the sheet obtained by the preparation procedure of the melt-formed sheet before stretching described later has a haze of 20% or more, the stretching process is not easy, so it was excluded from the evaluation, and the determination was “x”.
<Evaluation scale>
Load-resistant cutting test Judgment Remarks
180 ° C or higher ◎ Very high heat resistance, no problem in practical use
160-175 ° C ○ High heat resistance, can be used depending on the application
140-155 ° C △ heat resistance is poor and uses are limited
135 ° C or less × Heat resistance is extremely low and cannot withstand practical use
<Evaluation scale>
Melt drilling test Judgment Remarks
180 ° C or higher ◎ Very high heat resistance, no problem in practical use
160-175 ° C ○ High heat resistance, can be used depending on the application
140-155 ° C △ heat resistance is poor and uses are limited
135 ° C or less × Heat resistance is extremely low and cannot withstand practical use
[0058]
[Example 1]
[Purification of monomer]
After 250 g of glycolide was dissolved in dehydrated ethyl acetate 500 g at 75 ° C., it was allowed to stand at room temperature for 10 hours to precipitate. The precipitate collected by filtration was washed with about 500 g of dehydrated ethyl acetate at room temperature. After repeating this washing operation again, the washed product was put in an eggplant type flask, immersed in an oil bath set at 60 ° C., and vacuum-dried for 24 hours. This dried product was immersed in an oil bath set at 170 ° C., and the pressure was reduced to 6 to 7 mmHg under a dry nitrogen atmosphere, and 80 g of distilled and purified glycolide was obtained as a distillate at 133 to 134 ° C. by simple distillation.
[0059]
L-lactide (250 g) was dissolved in dehydrated toluene (500 g) at 80 ° C., and allowed to stand at room temperature for 10 hours for precipitation. The precipitate collected by filtration was washed with about 500 g of dehydrated toluene at room temperature. After repeating this washing operation again, the washed product was put in an eggplant-shaped flask and immersed in an oil bath set at 60 ° C. and vacuum-dried for 24 hours to obtain 120 g of purified L-lactide.
[Preparation of polymer]
70 g of glycolide and 32 g of lactide obtained by purification of the above monomer and 0.03 g of 2-ethylhexanoic acid and 0.01 g of dehydrated lauryl alcohol as a catalyst were charged into a pressure tube, and room temperature was kept for about 30 minutes while blowing dry nitrogen. And dried. Next, it was immersed in an oil bath set at 130 ° C. while blowing dry nitrogen and stirred for 20 hours for polymerization. After completion of the polymerization operation, the polymer was cooled to room temperature, and the bulk polymer taken out from the pressure tube was pulverized into fine particles of about 3 mm or less. This pulverized product was Soxhlet extracted with dehydrated ethyl acetate for 10 hours, dissolved in 200 g of HFIP at 50 ° C., and then reprecipitated with 2000 g of purified methanol. This re-precipitate was vacuum-dried for 24 hours in a vacuum dryer set at 110 ° C. to obtain 85 g of a glycolic acid copolymer. The obtained copolymer is designated as P1.
[0060]
In the copolymer P1, the proportion of repeating units composed of glycolide was 86 mol%, and the proportion of repeating units composed of lactide was 14 mol%. When the copolymer P1 was dissolved in HFIP and the remaining monomer was quantified by gas chromatography, the residual amounts of glycolide and lactide as monomers were 490 ppm in total. When the DSC, the relative crystallinity, and the logarithmic viscosity number were measured using the copolymer P1 as a sample, the melting point Tm in the first heating process in the DSC was 194 ° C. in the first cooling process. The heat of crystallization ΔHc was 0 J / g, the heat of fusion ΔHm in the second temperature raising process was 0 J / g, the relative crystallinity Xr was 33%, and the logarithmic viscosity number [η] was 2.5 dl / g. .
[0061]
[Preparation of melt-formed sheet before stretching]
After the glycolic acid copolymer P1 obtained by the preparation of the above polymer is left to stand for about 2 hours in a hot air circulating thermostatic bath set at 130 ° C. until the water content becomes 200 ppm or less, and a drying operation is performed. The film was heated and pressed for 5 minutes with a heating press set at 250 ° C., and then cooled with a cooling press set at 25 ° C. to obtain an amorphous sheet having a thickness of 350 μm.
[Production and evaluation of stretched film]
The melt-formed sheet before stretching was stretched using a biaxial stretching test apparatus manufactured by Toyo Seiki Co., Ltd. The amorphous sheet obtained by the preparation of the melt-formed sheet before stretching is cut into a square having a side of 90 mm, and is attached to a clamp having a clamp distance of 80 mm in a chamber set at a stretching temperature of 65 ° C., and a stretching speed of 50% / min. Were simultaneously biaxially stretched up to 3.5 times in length and 3.5 times in width. Immediately after the stretching operation was completed, cold air was blown and cooled to obtain a stretched film. The obtained stretched film was fixed to a metal frame and heat-treated for 1 minute in a hot air circulating thermostat set at 120 ° C. to obtain a stretched film having a thickness of 30 μm. When the heat shrinkage rate was measured using the stretched film subjected to the heat treatment as a sample, the heat shrinkage rate ΔL at 100 ° C. for 10 minutes was 2%.
[0062]
Using the heat-treated stretched film as a sample, the above-described evaluation of transparency, mechanical strength, gas barrier property, and heat resistance was carried out. As a result, haze was 1.5%, tensile break strength was 198 MPa, and oxygen permeability was 21. 2cc ・ 10μm / m2Day / atm, the maximum temperature at which cutting is not performed is 185 ° C., and the judgment is transparency 透明, mechanical strength ◎, gas barrier property ◎, heat resistance ◎, and overall judgment ◎.
From the above evaluation results, the stretched film made of a thermoplastic resin mainly composed of glycolic acid copolymer P1 is made of a biodegradable resin and has excellent gas barrier properties, heat resistance, transparency, and mechanical strength, and packaging. It turns out that it is suitable for a material use.
[0063]
[Examples 2 to 4, Examples 6 to 7, Reference Example 1,And Comparative Examples 1 to 4]
  Next, the same experiment as in Example 1 was repeated except that 65 g of glycolide, 36 g of lactide, and 30 hours of polymerization were performed, and the resulting glycolic acid copolymer was designated as P2. In the copolymer P2, the proportion of repeating units composed of glycolide was 83 mol%, and the proportion of repeating units composed of lactide was 17 mol%. The copolymer P2 has a melting point Tm of 188 ° C. in the first heating process in DSC, a crystallization heat ΔHc in the first cooling process of 0 J / g, and a heat of fusion ΔHm in the second heating process. Was 0 J / g, the relative crystallinity Xr was 34%, and the logarithmic viscosity number [η] was 3.6 dl / g. The same experiment as Example 1 was repeated except that the copolymer P2 was used. The heat-treated stretched film obtained had a heat shrinkage ΔL at 100 ° C. for 10 minutes of 2% (Example 2). .
[0064]
The same experiment as in Example 1 was repeated except that 29 g of lactide and 25 hours of polymerization time were used, and the resulting glycolic acid copolymer was designated as P3. In the copolymer P3, the proportion of repeating units composed of glycolide was 88 mol%, and the proportion of repeating units composed of lactide was 12 mol%. The copolymer P3 has a melting point Tm of 199 ° C. in the first temperature raising process in DSC, a crystallization heat ΔHc in the first cooling process of 0 J / g, and a heat of fusion ΔHm in the second temperature raising process. Was 5.8 J / g, the relative crystallinity Xr was 33%, and the logarithmic viscosity number [η] was 2.9 dl / g. The same experiment as in Example 1 was repeated except that the copolymer P3 was used. The heat-treated stretched film obtained had a heat shrinkage ΔL of 3% at 100 ° C. for 10 minutes (Example 3). .
[0065]
The same experiment as in Example 1 was repeated except that 60 g of glycolide, 38 g of lactide, and 40 hours of polymerization time were used, and the resulting glycolic acid copolymer was designated as P4. In the copolymer P4, the proportion of repeating units composed of glycolide was 80 mol%, and the proportion of repeating units composed of lactide was 20 mol%. The copolymer P4 has a melting point Tm of 182 ° C. in the first heating process in DSC, a crystallization heat ΔHc of 0 J / g in the first cooling process, and a heat of fusion ΔHm in the second heating process. Was 0 J / g, the relative crystallinity Xr was 19%, and the logarithmic viscosity number [η] was 4.0 dl / g. The same experiment as in Example 1 was repeated except that the copolymer P4 was used. The heat-treated stretched film obtained had a heat shrinkage ΔL of 3% at 100 ° C. for 10 minutes (Example 4). .
[0066]
  The same experiment as in Example 1 was repeated except that 75 g of glycolide, 26 g of lactide, and 15 hours of polymerization time, and the resulting glycolic acid copolymer was designated P5. In the copolymer P5, the proportion of repeating units composed of glycolide was 90 mol%, and the proportion of repeating units composed of lactide was 10 mol%. The copolymer P5 has a melting point Tm of 203 ° C. in the first heating process in DSC and a crystallization heat ΔHc of 0 J / g in the first cooling process and a heat of fusion ΔHm in the second heating process. Was 18.2 J / g, the relative crystallinity Xr was 30%, and the logarithmic viscosity number [η] was 1.9 dl / g. The same experiment as in Example 1 was repeated except that the copolymer P5 was used. The obtained heat-treated stretched film had a heat shrinkage ΔL at 100 ° C. for 10 minutes of 2% (Reference example 1).
[0067]
The same experiment as in Example 1 was repeated except that 60 g of glycolide and 46 g of lactide were used, and the resulting glycolic acid copolymer was designated P6. In copolymer P6, the proportion of repeating units composed of glycolide was 78 mol%, and the proportion of repeating units composed of lactide was 22 mol%. The copolymer P6 has a melting point Tm of 175 ° C. in the first heating process in DSC, a crystallization heat ΔHc of 0 J / g in the first cooling process, and a heat of fusion ΔHm in the second heating process. Was 0 J / g, the relative crystallinity Xr was 14%, and the logarithmic viscosity number [η] was 2.4 dl / g. The same experiment as in Example 1 was repeated except that the copolymer P6 was used, and the obtained heat-treated stretched film had a heat shrinkage ΔL of 3% at 100 ° C. for 10 minutes (Example 6). .
[0068]
55 g of glycolide, 24 g of lactide, 2 g of ε-caprolactone (6-hexanolactone) purified by dehydration after drying with anhydrous potassium carbonate, 2 g of catalyst, 0.2 g of dibutyltin dimethoxide, and polymerization time of 30 hours Otherwise, the same experiment as in Example 1 was repeated, and the resulting glycolic acid copolymer was designated as P7. In the copolymer P7, the proportion of repeating units composed of glycolide was 86 mol%, the proportion of repeating units composed of lactide was 10 mol%, and the proportion of repeating units composed of ε-caprolactone was 4 mol%. The copolymer P7 has a melting point Tm of 185 ° C. in the first heating process in DSC, a crystallization heat ΔHc of 0 J / g in the first cooling process, and a melting heat ΔHm in the second heating process. Was 0 J / g, the relative crystallinity Xr was 25%, and the logarithmic viscosity number [η] was 2.2 dl / g. Other than using the copolymer P7, the above experiment No. The same experiment as 1 was repeated, and the heat-treated stretched film obtained had a heat shrinkage ΔL at 100 ° C. for 10 minutes of 4% (Example 7).
[0069]
The same experiment as in Example 1 was repeated except that 80 g of glycolide, 22 g of lactide, and 10 hours of polymerization time, and the resulting glycolic acid copolymer was designated as P8. In the copolymer P8, the proportion of repeating units composed of glycolide was 93 mol%, and the proportion of repeating units composed of lactide was 7 mol%. The copolymer P8 has a melting point Tm of 206 ° C. in the first heating process in DSC, a crystallization heat ΔHc in the first cooling process of −36.5 J / g, and a second heating process. The heat of fusion ΔHm was 51.6 J / g, the relative crystallinity Xr was 78%, and the logarithmic viscosity number [η] was 1.0 dl / g. The same experiment as in Example 1 was repeated except that the copolymer P8 was used, and the obtained heat-treated stretched film had a heat shrinkage ΔL of 2% at 100 ° C. for 10 minutes (Comparative Example 1). .
[0070]
The same experiment as in Example 1 was repeated except that 90 g of glycolide, 10 g of lactide, and 15 hours of polymerization time were used, and the resulting glycolic acid copolymer was designated as P9. In the copolymer P9, the proportion of the repeating unit composed of glycolide was 97 mol%, and the proportion of the repeating unit composed of lactide was 3 mol%. The copolymer P9 has a melting point Tm of 218 ° C. in the first heating process in DSC, a crystallization heat ΔHc in the first cooling process of −58.2 J / g, and a second heating process. The heat of fusion ΔHm was 55.5 J / g, the relative crystallinity Xr was 100%, and the logarithmic viscosity number [η] was 1.9 dl / g. The same experiment as in Example 1 was attempted except that the copolymer P9 was used. However, since the haze of the melt-formed sheet before stretching was 23.8%, the stretching operation was not performed and the measurement of the heat shrinkage ratio ΔL was performed. (Comparative Example 2).
[0071]
The same experiment as in Example 1 was repeated except that 100 g of glycolide, lactide was not used, and the polymerization time was 5 hours, and the resulting glycolic acid homopolymer was designated as P10. In the copolymer P10, the component ratio of the repeating unit composed of glycolide was 100 mol%. The polymer P10 has a melting point Tm of 222 ° C. in the first heating process in DSC and a crystallization heat ΔHc in the first cooling process of −69.6 J / g, and melting in the second heating process. The thermal ΔHm was 72.6 J / g, the relative crystallinity Xr was 100%, and the logarithmic viscosity number [η] was 0.8 dl / g. The same experiment as in Example 1 was tried except that the polymer P10 was used, but it was difficult to obtain an amorphous pre-stretched melt-formed sheet. A crystallized sheet obtained by using the polymer P10 in the same manner as the above-described method for producing a pre-stretched melt-formed sheet was brittle and easily cracked, and was difficult to stretch. Therefore, the measurement of the heat shrinkage rate ΔL could not be performed (Comparative Example 3).
[0072]
The same experiment as in Example 1 was repeated except that 55 g of glycolide and 46 g of lactide were used, and the resulting glycolic acid copolymer was designated as P11. In the copolymer P11, the proportion of repeating units composed of glycolide was 75 mol%, and the proportion of repeating units composed of lactide was 25 mol%. In the copolymer P11, the melting point Tm in the first heating process in DSC does not appear, and the crystallization heat ΔHc in the first cooling process is 0 J / g, and the melting heat ΔHm in the second heating process. Was 0 J / g, the relative crystallinity Xr was 0%, and the logarithmic viscosity number [η] was 2.5 dl / g. The same experiment as in Example 1 was repeated except that the copolymer P11 was used, and the heat-treated stretched film obtained had a heat shrinkage ΔL at 100 ° C. for 10 minutes of 5% (Comparative Example 4). .
Tables 1 and 2 summarize the measurement results of the aforementioned DSC, relative crystallinity, logarithmic viscosity, and heat shrinkage ratio for these glycolic acid copolymers and P1 to 11 of the glycolic acid homopolymer.
[0073]
[Table 1]
Figure 0004790920
[0074]
[Table 2]
Figure 0004790920
[0075]
About the said glycolic acid type copolymer and P2-11 of glycolic acid homopolymer, the stretched film obtained similarly to the said Example 1 was evaluated as a sample. These evaluation results are summarized in Table 3 and Table 4.
[0076]
[Table 3]
Figure 0004790920
[0077]
[Table 4]
Figure 0004790920
[0078]
According to Table 3, the melting point Tm in the first heating process in DSC is 175 ° C. or more and 205 ° C. or less, the crystallization heat ΔHc in the first cooling process is 0 J / g, and the melting in the second heating process. Heat mainly composed of a glycolic acid copolymer having a heat ΔHm of 0 J / g or more and less than 20 J / g, a relative crystallinity Xr of 3% or more and 50% or less, and a logarithmic viscosity number [η] of 1.5 dl / g. It can be seen that the stretched film made of a plastic resin is made of a biodegradable resin and is a stretched film suitable for packaging material applications having excellent gas barrier properties, heat resistance, transparency, and mechanical strength (Examples 1 to 7). ). Among them, the melting point Tm of the glycolic acid copolymer in the first temperature raising process in DSC is 185 ° C. or more and 200 ° C. or less, and the heat of fusion ΔHm in the second temperature raising process is 0 J / g or more and 18 J / g or less. In this case, the stretched film made of the thermoplastic resin mainly composed of the copolymer is remarkably excellent in both heat resistance and transparency, and is particularly suitable for packaging materials (Example 1 to Example 1). 3).
[0079]
On the other hand, according to Table 4, the melting point Tm of the glycolic acid copolymer or glycolic acid homopolymer in the first heating process in DSC is higher than 205 ° C., and the crystallization is performed in the first cooling process. When the heat ΔHc is not 0 J / g but the heat of fusion ΔHm in the second temperature raising process is 20 J / g or more and the relative crystallinity Xr is higher than 50%, the heat mainly composed of the polymer A stretched film made of a plastic resin has excellent heat resistance and gas barrier properties, but is not suitable for packaging materials due to its extremely poor transparency and mechanical strength or difficulty in stretching. Comparative Examples 1-3). Particularly, when the heat of crystallization ΔHc in the first cooling process is not 0 J / g, the crystallinity is high even if the logarithmic viscosity number [η] is 1.5 dl / g or more. Crystallization occurred during the production of the pre-stretched melt-formed sheet, and the haze of the sheet was 23.8% and could not be stretched (Comparative Example 2).
[0080]
Further, with the glycolic acid homopolymer P10 having a low logarithmic viscosity number [η] of 0.80 dl / g and very high crystallinity, it was difficult to obtain an amorphous pre-stretched melt-formed sheet. The crystallized sheet obtained using the homopolymer P10 in the same manner as described above is fragile and easily cracked and cannot be stretched. Evaluation of the transparency, gas barrier property, and heat resistance of the stretched film is as follows. It was not possible (Comparative Example 3).
On the other hand, when the melting point Tm of the glycolic acid copolymer in the first heating process in DSC is lower than 175 ° C., the glycolic acid type of the copolymer component ratio that will be lower than 175 ° C. in detail. In the case of a copolymer, since the crystallinity is extremely low, it does not crystallize even when heated at 150 ° C., and the stretched film made of a thermoplastic resin mainly composed of the copolymer has excellent transparency. However, heat resistance is remarkably inferior and it turns out that it is not suitable for a packaging material use (comparative example 4).
[0081]
Examples 8-9 and Comparative Examples 5-6
The following experiment is an experiment focusing on the heat shrinkage rate of the stretched film at 100 ° C. for 10 minutes. Therefore, the glycolic acid copolymer used as the raw material is the same copolymer of P1 as in Example 1, and the stretching operation in the production of the pre-stretched melt-formed sheet and the stretched film is also in the above Example 1. Is done in the same way.
[0082]
The same experiment as in Example 1 was repeated except that the heat treatment condition was 150 ° C. for 30 seconds to obtain a heat-treated stretched film. The heat-treated stretched film had a heat shrinkage ΔL at 100 ° C. for 10 minutes of 1% (Example 8).
The same experiment as in Example 1 was repeated except that the heat treatment condition was 90 ° C. for 3 minutes to obtain a heat-treated stretched film. The heat-treated stretched film had a heat shrinkage ΔL of 4% at 100 ° C. for 10 minutes (Example 9).
[0083]
Except not performing the heat treatment operation, the same experiment as in Example 1 was repeated to obtain a stretched film that was not heat-treated. The stretched film that was not heat-treated had a heat shrinkage ΔL at 100 ° C. for 10 minutes of 64% (Comparative Example 5).
The glycolic acid copolymer used as a raw material was the same as that of Example 1 described above except that a copolymer was used so that the amorphous sheet had a thickness of about 30 μm. The same operation as the preparation of the melt-formed sheet before stretching was performed to obtain a melt-formed film. Using the melt-formed film, the same heat treatment as in the production of the stretched film described above, that is, stretched by heat treatment for 30 minutes in a hot air circulating thermostat fixed to a metal frame and set at 120 ° C. for 1 minute. An unfinished film was obtained. The unstretched film that had been heat-treated had a heat shrinkage ΔL at 100 ° C. for 10 minutes of 0% (Comparative Example 6).
[0084]
About these heat-treated stretched films (Examples 8 to 9), unheated stretched film (Comparative Example 5), and heat-treated stretched film (Comparative Example 6), the above-described transparency, mechanical strength, Gas barrier properties and heat resistance were evaluated. Table 5 summarizes the heat shrinkage ratio and transparency, mechanical strength, gas barrier properties, and heat resistance evaluation results of these and the film of Example 1 at 100 ° C. for 10 minutes.
[0085]
[Table 5]
Figure 0004790920
[0086]
According to Table 5, the stretched film having a heat shrinkage ΔL at 100 ° C. for 10 minutes of 0.5 to 45% is made of a biodegradable resin and excellent in gas barrier properties, heat resistance, transparency, and mechanical strength. It turns out that it is a stretched film suitable for a packaging material use (Example 1, and 8-9).
In contrast, a stretched film having a heat shrinkage ratio ΔL higher than 45% at 100 ° C. for 10 minutes without heat treatment after stretching was excellent in transparency but inferior in heat resistance (Comparative Example 5). On the other hand, a film having a heat shrinkage ΔL lower than 0.5% at 100 ° C. for 10 minutes that has been heat-treated without stretching is excellent in heat resistance, but has extremely poor transparency and a little mechanical strength. It became low (Comparative Example 6).
[0087]
【The invention's effect】
According to the present invention, by using a glycolic acid-based copolymer having crystallinity in a specific range and defining a heat shrinkage rate at 100 ° C. for 10 minutes, it has biodegradability, gas barrier properties, and heat resistance. Further, it is possible to provide a stretched film and a stretched sheet suitable for packaging materials, which are excellent in transparency and mechanical strength and can be easily produced.

Claims (3)

グリコール酸系共重合体の非晶シートを１５０℃で１００分間熱処理した試験片を用い、加熱速度または冷却速度を１０℃／分で測定した示差走査熱量測定（ＪＩＳ Ｋ７１２１およびＫ７１２２準拠）において、１回目の昇温過程での融点Ｔｍ（℃）、１回目の冷却過程での結晶化熱ΔＨｃ（Ｊ／ｇ）、２回目の昇温過程での融解熱ΔＨｍ（Ｊ／ｇ）が下式（１）〜（３）を満たし、且つ下式（４）で表される相対結晶化度Ｘｒが３％以上５０％以下、対数粘度数［η］が１．５ｄｌ／ｇ以上であるグリコール酸系共重合体を主体とする熱可塑性樹脂組成物よりなり、１００℃１０分間における加熱収縮率ΔＬが０．５〜４５％であることを特徴とする包装材用延伸成形体。
式（１）１７５≦Ｔｍ≦２０５
式（２）ΔＨｃ＝０
式（３）０≦ΔＨｍ＜１８．０
式（４）Ｘｒ＝［（ρｂ−ρａ）／（ρｃ−ρａ）］×（ρｃ／ρｂ）×１００
但し、ρａ：非晶試験片の密度（ｇ／ｃｍ3）
ρｂ：１５０℃で５分間加熱した結晶化物の密度（ｇ／ｃｍ3）
ρｃ：１５０℃で１００分間加熱した結晶化物の密度（ｇ／ｃｍ3）In differential scanning calorimetry (based on JIS K7121 and K7122) using a test piece obtained by heat-treating an amorphous sheet of a glycolic acid copolymer at 150 ° C. for 100 minutes, the heating rate or cooling rate was measured at 10 ° C./min. Melting point Tm (° C.) in the first temperature raising process, heat of crystallization ΔHc (J / g) in the first cooling process, heat of fusion ΔHm (J / g) in the second temperature raising process A glycolic acid system satisfying 1) to (3), having a relative crystallinity Xr represented by the following formula (4) of 3% to 50% and a logarithmic viscosity number [η] of 1.5 dl / g or more A stretch molded article for a packaging material, comprising a thermoplastic resin composition mainly comprising a copolymer and having a heat shrinkage ΔL at 100 ° C. for 10 minutes of 0.5 to 45%.
Formula (1) 175 ≦ Tm ≦ 205
Expression (2) ΔHc = 0
Formula (3) 0 ≦ ΔHm < 18.0
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of the amorphous specimen (g / cm 3 )
ρb: Density of crystallized product heated at 150 ° C. for 5 minutes (g / cm 3 )
ρc: density of crystallized product heated at 150 ° C. for 100 minutes (g / cm 3 ) グリコール酸系共重合体が、グリコリドとグリコリド以外の単量体を用いて開環重合し得られる共重合体であって、グリコリドよりなる繰返し単位の成分割合が７８〜９０ｍｏｌ％と、グリコリド以外の単量体よりなる繰返し単位の成分割合が２２〜１０ｍｏｌ％であることを特徴とする請求項１記載の包装材用延伸成形体。  The glycolic acid copolymer is a copolymer obtained by ring-opening polymerization using glycolide and a monomer other than glycolide, and the proportion of the repeating unit composed of glycolide is 78 to 90 mol%, and other than glycolide The stretch molded body for a packaging material according to claim 1, wherein the proportion of the repeating unit composed of the monomer is 22 to 10 mol%. 開環重合し得られるグリコール酸系共重合体が、該共重合体を構成する単量体のうちグリコリドの他の単量体が脂肪族ヒドロキシカルボン酸類の環状二量体、又はラクトン類から選ばれる少なくとも一種からなることを特徴とする請求項１又は請求項２記載の包装材用延伸成形体。The glycolic acid copolymer obtained by ring-opening polymerization is selected from cyclic dimers of aliphatic hydroxycarboxylic acids or lactones as other monomers of glycolide among monomers constituting the copolymer. The stretch molded body for a packaging material according to claim 1 or 2, wherein the stretch molded body is composed of at least one kind.
JP2001063616A 2001-03-07 2001-03-07 Stretched molded product for packaging materials Expired - Fee Related JP4790920B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2001063616A JP4790920B2 (en) 2001-03-07 2001-03-07 Stretched molded product for packaging materials

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2001063616A JP4790920B2 (en) 2001-03-07 2001-03-07 Stretched molded product for packaging materials

Publications (2)

Publication Number Publication Date
JP2002264206A JP2002264206A (en) 2002-09-18
JP4790920B2 true JP4790920B2 (en) 2011-10-12

Family

ID=18922577

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2001063616A Expired - Fee Related JP4790920B2 (en) 2001-03-07 2001-03-07 Stretched molded product for packaging materials

Country Status (1)

Country Link
JP (1) JP4790920B2 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5100946B2 (en) * 2002-09-25 2012-12-19 株式会社クレハ Strongly stretched aliphatic polyester polymer molding
TWI247782B (en) * 2003-01-10 2006-01-21 Mitsui Chemicals Inc Polyester resins composition

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000026624A (en) * 1998-07-13 2000-01-25 Asahi Chem Ind Co Ltd Adhering heat-resistant wrapping film
JP2001106805A (en) * 1999-10-04 2001-04-17 Asahi Kasei Corp Adhesive heat resistant wrap film
JP5213294B2 (en) * 2001-01-31 2013-06-19 旭化成ケミカルズ株式会社 Polyglycolic acid resin composition
JP4693254B2 (en) * 2001-01-31 2011-06-01 旭化成ケミカルズ株式会社 Glycolic acid resin composition
JP4993238B2 (en) * 2001-02-27 2012-08-08 旭化成ケミカルズ株式会社 Molded body for packaging materials

Also Published As

Publication number Publication date
JP2002264206A (en) 2002-09-18

Similar Documents

Publication Publication Date Title
JP4363325B2 (en) Polylactic acid polymer composition, molded article thereof, and film
JP4704456B2 (en) Crystalline polyglycolic acid, polyglycolic acid composition, and methods for producing them
JP5239336B2 (en) Polyether-polylactic acid composition and polylactic acid film containing the same
JP5291461B2 (en) Aliphatic polyester composition and method for producing the same
JP4804179B2 (en) Polylactic acid composition and molded product comprising the composition
JPH09111107A (en) Biodegradable film or sheet and biodegradable plastic molding
JP5145695B2 (en) Method for producing polylactic acid resin film
JP3182077B2 (en) Biodegradable film
JP2002292665A (en) Method for manufacturing lactic acid polymer sheet
KR20120060571A (en) Polyester film and preparation method thereof
JP4245306B2 (en) Biodegradable polyester stretch molding
JP5376749B2 (en) Polylactic acid film
JP4790920B2 (en) Stretched molded product for packaging materials
JP4511099B2 (en) Lactic acid-based resin composition, sheet-like product thereof, and bag-like product
JP3670912B2 (en) Polylactic acid-based shrink film or sheet
JP4245300B2 (en) Method for producing biodegradable polyester stretch molded article
JP4993238B2 (en) Molded body for packaging materials
JP4326828B2 (en) Composition of glycolic acid copolymer
JP3674594B2 (en) Packaging material made of lactic acid copolymer polyester
JP4260521B2 (en) Glycolic acid polymer composition
JP4260526B2 (en) Composition of glycolic acid polymer
JP3421620B2 (en) Document holder
JP2008200860A (en) Method for producing polylactic acid resin film
JP2006335904A (en) Polylactic acid-based oriented film
TW201439159A (en) Molded body and production method therefor

Legal Events

Date Code Title Description
A711 Notification of change in applicant

Free format text: JAPANESE INTERMEDIATE CODE: A711

Effective date: 20031211

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A821

Effective date: 20031212

A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20080228

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20101130

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20101207

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20110207

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20110719

A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20110721

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20140729

Year of fee payment: 3

R150 Certificate of patent or registration of utility model

Free format text: JAPANESE INTERMEDIATE CODE: R150

S111 Request for change of ownership or part of ownership

Free format text: JAPANESE INTERMEDIATE CODE: R313111

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350

LAPS Cancellation because of no payment of annual fees