JP4993238B2 - Molded body for packaging materials - Google Patents
Molded body for packaging materials Download PDFInfo
- Publication number
- JP4993238B2 JP4993238B2 JP2001052016A JP2001052016A JP4993238B2 JP 4993238 B2 JP4993238 B2 JP 4993238B2 JP 2001052016 A JP2001052016 A JP 2001052016A JP 2001052016 A JP2001052016 A JP 2001052016A JP 4993238 B2 JP4993238 B2 JP 4993238B2
- Authority
- JP
- Japan
- Prior art keywords
- copolymer
- glycolide
- glycolic acid
- heat
- mol
- 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
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
- Polyesters Or Polycarbonates (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組成物よりなる成形体に関する。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組成物よりなる成形体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、特開平10−60137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シートが開示され、該ポリグリコール酸シートが土中崩壊性を示し、且つ強靭性やバリア性に優れる容器や包材として使用することが出来る旨の記載もある。
【0006】
しかしながら、上記特開平10−60137号公報に記載のポリグリコール酸シートは、融点Tmが150℃程度では依然として耐熱性が不充分であり、電子レンジ容器として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。
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、上記特開平10−60137号公報に記載のポリグリコール酸シートは、融解熱ΔHmが20J/g以上、無配向結晶化物の密度が1.50g/cm3以上であることから、非常に結晶性が高いために透明なシートが得られ難かったり、透明性を向上させるためには成形時に急冷しなければならずシート製造工程が非常に煩雑になるという問題点があった。
【0007】
尚、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組成物よりなる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ことにより、該重合体を主体とする熱可塑性樹脂組成物よりなる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及び冷却速度が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0.15m3/kg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、前記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%であり、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包装材用成形体、
式(1)175≦Tm≦205
式(2)ΔHc=0
式(3)0≦ΔHm<20
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)
2. 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上記1に記載の包装材用成形体、である。
【0011】
以下、本発明の包装材用成形体について詳細に説明する。
本発明の包装材用成形体は、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、成形体製造時に急冷するなどの煩雑な工程を経なくとも透明性が得られ、更に成形体を長期間保管した場合でも透明性は高いレベルに維持することが可能になることを見出したことに基くものである。
【0012】
重合体の結晶性とは、重合体の結晶化し易さを指しおり、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))。
【0013】
本発明で用いるグリコール酸系共重合体は、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 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を有す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、本発明のグリコール酸系重合体は、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℃以上205℃以下であるので、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。
【0014】
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以外では、該重合体を主体とする熱可塑性樹脂組成物よりなる包装材用成形体は、その製造時に急冷操作など特別な非晶化過程が必要となり、また該成形体の透明性を高いレベルに維持することができない。
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。
【0015】
熱分析法では、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(DSC;JIS K7122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)等に記載の値が用いられている。
【0016】
また、密度法では、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それぞれ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物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)等に記載の値が用いられている。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亘るために文献値が無い場合が多い。
【0017】
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。 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、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、重合体の結晶化度を判断する。本発明においては、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)
【0018】
本発明において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℃以上205℃以下であ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おり、該重合体を主体とする熱可塑性樹脂組成物よりなる包装材用成形体は、その製造時に急冷操作など特別な非晶化過程が不用で製造工程が簡便になり、更に該成形体は透明性が優れ、長期間保管した場合でも透明性は高いレベルに維持することが可能になる。
【0019】
一方、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組成物よりなる包装材用成形体は、透明性が著しく悪化したり、透明性を向上させるためには成形時に急冷操作など特別な非晶化工程が必用になり製造工程が煩雑になる。該ΔHmの値は、より透明性が高い包装材用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。
【0020】
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組成物よりなる包装材用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組成物よりなる包装材用成形体は、透明性が著しく悪化したり、透明性を向上させるためには成形時に急冷操作など特別な非晶化工程が必要になり製造工程が煩雑になる。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%以下の範囲が好ましい。
【0021】
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、その加熱前の非晶物の密度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。
【0022】
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分間加熱加圧したのち冷却プレスで急冷し得られた非晶シートを、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組成物よりなる成形体の耐熱性は著しく劣り、包装材や容器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。
【0023】
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、該重合体を主体とする熱可塑性樹脂組成物よりなる成形体は、透明性が著しく悪化し包装材として透明性を要求される用途では使用することが出来なくなったり、透明性を向上させるために成形時に急冷操作など特別な非晶化工程が必要になり製造工程が煩雑になる。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。
【0024】
本発明の包装材用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。
【0025】
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。
【0026】
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。
【0027】
上記に例示した本発明の包装材用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。
【0028】
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。
【0029】
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。
【0030】
該重合体の分子量は、該重合体を主体とする熱可塑性樹脂組成物よりなる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0.15m3/kg以上が必要であり、0.18m3/kg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(kg/m3)
【0031】
一方、該重合体の分子量の上限は、より容易に成形体に成形加工するためには対数粘度数で0.80m3/kg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、これら共重合体単体や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。
該熱可塑性樹脂組成物の組成割合は、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、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、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組成物のHFIP溶液をメタノール中に注ぎ、樹脂組成物成分を再沈殿させる。得られた再沈殿樹脂組成物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、熱可塑性樹脂組成物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から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】
なお、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やアセチルくえん酸トリエ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。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組成物100重量部に対して1〜30重量部程度である。
【0039】
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組成物100重量部に対して0.01〜10重量部程度である。
本発明において用い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必要に応じて用いる添加剤などを、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のが望ましい。
【0040】
次に、本発明の成形体について説明する。成形体の種類としては、射出成形、ブロー成形、シート成形により得られる容器包装材用の成形体が挙げられる。成形体の製法としては、例えばシート状成形体の場合は、キャスティング法、溶融押出法、カレンダー法、溶融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。又、ここに例示した成形方法により得られるシート状成形体の厚みは、その用途により適宜選ばれ、通常は5μm〜1mmであるが特に限定されるものではない。
【0041】
得られた成形体は、そのまま包装材として使用しても良いが、必要に応じてシール適性、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たり、その後の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具体的には、例えばシート状成形体の場合は、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により得られる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挙げられる。これら具体例の二次加工品を得る為には、シート状成形体は溶融押出法でTダイより溶融押出して製造する方法が望ましい。
【0042】
得られた成形体は、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、或いは物性安定性を向上させる目的で、熱処理やエージング処理等を施すことが望ましい。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望ましい。又、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。
【0043】
得られた本発明の成形体は、該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ることにより、生分解性を有し、且つガスバリア性、耐熱性に優れ、成形体製造時に急冷するなどの煩雑な工程を必要とせずに透明性を高めることが可能であり、該成形体を長期間保管した場合でも透明性は高いレベルに維持することが可能であり、更に脆化せずに優れた機械的強度を保持しており、包装材用途に好適に利用できる。
【0044】
【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、250℃に設定した加熱プレス機(テスター産業(株)製圧縮成形機SA−301)でグリコール酸系共重合体を5分間約12Pa加圧した後、冷却プレスで急冷し厚み約200μm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100分間加熱結晶化させて作製した。サンプル量は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。
【0045】
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。尚、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。
【0046】
(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)
【0047】
(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1.0kg/m3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(kg/m3)
【0048】
[評価方法と尺度]
(1)透明性
上記DSC測定方法で示した手順により得られたグリコール酸系共重合体の非晶シート、該非晶シートを150℃に設定した熱風循環恒温槽中で5分間加熱結晶化させた結晶化物、該非晶シートを(23±2)℃、関係湿度(50±5)%に設定した恒温恒湿槽中で50日保存した長期保存シートのヘーズを測定した。熱処理による透明性の変化として結晶化物のヘーズHcと非晶シートのヘーズHaとの比Hc/Haを、長期保存による透明性の変化として長期保存ヘーズHkと非晶シートのヘーズHaとの比Hk/Haを、各々算出して両者の判定結果から透明性を評価した。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。得られた厚み約200μmの上記非晶シート、及び上記150℃で5分間加熱結晶化させた結晶化物、上記恒温恒湿槽中で50日保存した長期保存シートの各シート状サンプルを、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毎のヘーズを測定した。
【0049】
測定結果は、サンプル数各々5個づつ測定して平均値を求め、上記ヘーズ比Hc/Ha、及びHk/Haを算出した。得られたヘーズ比Hc/Ha、及びHk/Haの値を指標として判定し、この両者のうち低い方の判定結果をそのまま透明性の判定結果とした。但し、上記非晶シートの作製手順で得られたシートのヘーズが2.0%以上となる場合は、透明性の優れた成形体を製造すること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>
ヘーズ比Hc/Ha 判 定 備 考
50未満 ◎ 若干白化する程度で視認性は優れる
50以上70未満 ○ 白化するが視認性には問題ない
70以上80未満 △ 白化し視認性が劣る
80以上 × 著しく白化し視認性が非常に劣る
<評価尺度>
ヘーズ比Hk/Ha 判 定 備 考
2未満 ◎ 透明性を維持し視認性は優れる
2以上5未満 ○ 視認性に変化は認められない
5以上10未満 △ 僅かに白化する
10以上 × 白化する
【0050】
(2)機械的強度
機械的強度は、測定装置に(株)東洋精機製作所製MIT耐揉疲労試験機を使用して、JIS P8115を参考にシート状成形体の耐折強さを測定し評価した。上記DSC測定方法で示した手順により得られたグリコール酸系共重合体の非晶シートをサンプルとして、縦150mm、幅15mmの短冊状に切り出した。折り曲げ角度135°、折り曲げ速度175cpm、荷重0.5kgの条件で試験を行い、破断するまでの折り曲げ回数を測定した。折り曲げ回数の測定結果は、上記手順によりサンプル数5個づつ測定し平均値で示した。この折り曲げ回数を機械的強度の指標とた。
<評価尺度>
折り曲げ回数 判 定 備 考
100回以上 ◎ 耐折強さが非常に高く実用上問題はない
50〜99回 ○ 耐折強さが高く用途により使用可
1〜49回 △ 耐折強さが低く実用に耐えない
0回 × 非常に脆く折り曲げ出来ない
【0051】
(3)ガスバリア性
ガスバリア性は、測定装置にmocon社製酸素透過率測定装置OX−TRAN200H型を使用して、JIS K7126B法に準拠し酸素透過度を測定し評価した。上記DSC測定方法で示した手順により得られたグリコール酸系共重合体の非晶シートをサンプルとし、一辺120mmの正方形状に切り出した。温度23℃、関係湿度65%の条件で試験を行い、酸素透過度を測定した。酸素透過度の測定結果は、上記手順によりサンプル数3個づつ測定して平均し、厚み10μmに換算して示した。この酸素透過度をガスバリア性の指標とした。
<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
【0052】
(4)耐熱性
耐熱性は、短冊状サンプルに荷重50g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時間加熱しサンプルの切断の有無を調べ、サンプルが切断しない最高温度として評価した。上記DSC測定方法で示した手順により得られたグリコール酸系共重合体の非晶シートを、150℃に設定した熱風循環恒温槽中で5分間加熱結晶化させた結晶化物をサンプルとし、縦140mm、横10mmの短冊状に切り出した。短冊状サンプルの上下端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時間加熱しサンプルの切断の有無を調べた。短冊状サンプルが切断しない場合は、新しいサンプルで設定温度を5℃上げて前記手順を繰返し試験した。短冊状サンプルが切断しない最高温度の測定結果は、この試験を各シートサンプルにつき5回づつ行い最頻値で示した。この短冊状サンプルが切断しない最高温度を耐熱性の指標とした。
<評価尺度>
切断しない最高温度 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
【0053】
【実施例1】
[単量体の精製]
グリコリド(MAYBRIDGE社製1,4−ジオキサン−2,5−ジオン、融点81〜83℃)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。
【0054】
L−ラクチド(和光純薬社製一級試薬)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(和光純薬社製)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。
【0055】
得られた該共重合体をP1とする。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0.25m3/kgであった。
【0056】
[シート状成形体の作製、及び評価]
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、その後冷却プレスで急冷し厚み約200μmの非晶シートを得た。該非晶シートをサンプルとして、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、ヘーズ比Hc/Haは45、ヘーズ比Hk/Haは1、折り曲げ回数は140回、酸素透過度は10.7cc・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組成物よりなるシート状成形体は、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成形体であることが判る。
【0057】
【実施例2〜7、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0.36m3/kgであった(実施例2)。
【0058】
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0.29m3/kgであった(実施例3)。
【0059】
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0.40m3/kgであった(実施例4)。
【0060】
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0.19m3/kgであった(実施例5)。
【0061】
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0.24m3/kgであった(実施例6)。
【0062】
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−カプロラクトンより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0.22m3/kgであった(実施例7)。
【0063】
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0.10m3/kgであった(比較例1)。
【0064】
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0.19m3/kgであった(比較例2)。
【0065】
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0.08m3/kgであった(比較例3)。
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0.25m3/kg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、対数粘度数の測定結果を表1、及び表2にまとめる。
【0066】
【表1】
【0067】
【表2】
【0068】
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、前述のシート状成形体の作製、及び評価と同様に非晶シートを作製し、該非晶シートをサンプルとして評価を行った。これら重合体P1〜11の評価結果を表3、及び表4にまとめる。
【0069】
【表3】
【0070】
【表4】
【0071】
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0.15m3/kg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るシート状成形体は、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成形体であることが判る(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組成物よりなるシート状成形体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)。
【0072】
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組成物よりなるシート状成形体は、ガスバリア性や耐熱性は優れているものの、透明性や機械的強度が著しく劣り、包装材用途には適さないことが判る(比較例1〜3)。更に詳しくは、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0.15m3/kg以上であっても、結晶性が高い為に包装材用途として使用する厚み5〜500μm程度のシート状成形体、或いはフィルム状成形体が非常に脆弱なものになることが判る(比較例2)。
【0073】
また、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、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組成物よりなるシート状成形体は、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)。
【0074】
【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、機械的強度に優れた包装材用途に好適な成形体を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molded article made of a thermoplastic resin composition mainly composed of a glycolic acid copolymer suitable for packaging materials. More specifically, it is composed of a thermoplastic resin composition mainly composed of a glycolic acid copolymer having biodegradability and excellent gas barrier properties, heat resistance, transparency, and mechanical strength and suitable for packaging materials. The present invention relates to a molded body.
[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]
In contrast, JP-A-10-60137 discloses that the melting point Tm is 150 ° C. or higher, the heat of fusion ΔHm is 20 J / g or higher, and the density of the non-oriented crystallized material is 1.50 g / cm. Three A polyglycolic acid sheet comprising a thermoplastic resin containing the specific polyglycolic acid as described above is disclosed, and the polyglycolic acid sheet exhibits disintegration in the soil and is excellent in toughness and barrier properties as a container or packaging material. There is also a statement that it can be used.
[0006]
However, the polyglycolic acid sheet described in JP-A-10-60137 still has insufficient heat resistance when the melting point Tm is about 150 ° C., and heat from the contents generated when it is used as a microwave oven container. However, there was a problem that it deformed greatly and melt drilling occurred.
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, the polyglycolic acid sheet described in JP-A-10-60137 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. Three Because of the above, it is difficult to obtain a transparent sheet due to its very high crystallinity, or in order to improve the transparency, the sheet manufacturing process has to be very complicated because it must be rapidly cooled during molding There was a point.
[0007]
The relationship between the 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. In general, 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 thermoplastic resin composition mainly composed of a glycolic acid copolymer having biodegradability and excellent gas barrier properties, heat resistance, transparency, and mechanical strength and suitable for packaging materials. It is providing the molded object which consists of.
[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. Accordingly, a molded body made of a thermoplastic resin composition mainly composed of the polymer has biodegradability and is excellent in gas barrier properties, heat resistance, transparency, and mechanical strength, and is suitable for packaging material applications. The present invention has been found.
[0010]
That is, the present invention
1. First in differential scanning calorimetry (based on JIS K7121 and K7122) using a test piece obtained by heat-treating an amorphous sheet of glycolic acid copolymer at 150 ° C. for 100 minutes at a heating and cooling rate of 10 ° C./min. Melting point Tm (° C.) in the temperature raising process, heat of crystallization ΔHc (J / g) in the first cooling process, and heat of fusion ΔHm (J / g) in the second temperature raising process are expressed by the following formula (1) To (3), the relative crystallinity Xr represented by the following formula (4) is 3% to 50%, and the logarithmic viscosity number [η] is 0.15 m. Three / Kg or more thermoplastic resin composition mainly composed of glycolic acid copolymer 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%. The proportion of the repeating unit composed of monomers other than glycolide is 22 to 10 mol%. Molded body for packaging material, characterized by
Formula (1) 175 ≦ Tm ≦ 205
Expression (2) ΔHc = 0
Formula (3) 0 ≦ ΔHm <20
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of amorphous material (g / cm Three )
ρb: Density of crystallized product heated at 150 ° C. for 5 minutes (g / cm Three )
ρc: Density of crystallized product heated at 150 ° C. for 100 minutes (g / cm Three )
2 . The monomer other than glycolide comprises at least one selected from cyclic dimers of aliphatic hydroxycarboxylic acids and lactones 1 It is a molded object for packaging materials as described in above.
[0011]
Hereinafter, the molded body for packaging material of the present invention will be described in detail.
The 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. Thus, it has been found that transparency can be obtained without going through complicated steps such as rapid cooling during the production of a molded product, and even when the molded product is stored for a long period of time, the transparency can be maintained at a high level. It is based on that.
[0012]
The crystallinity of the polymer refers to the ease of crystallization of the polymer, and is expressed 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)).
[0013]
The glycolic acid copolymer used in the present invention has a crystallization heat ΔHc in the first cooling process in differential scanning calorimetry (based on JIS K7121 and K7122 and hereinafter referred to as DSC) measured at a cooling rate of 10 ° C./min. Must be 0 J / g. That is, it is necessary to have a crystallization rate at which crystallization does not occur under 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 rate 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 glycolic acid polymer of the present invention has a melting point Tm of 175 ° C. or more and 205 ° C. or less in the first temperature raising process in DSC as described later, it is amorphous and does not crystallize at all. It is different from the case.
[0014]
When the glycolic acid copolymer used in the present invention has a crystallization heat ΔHc other than 0 J / g in the first cooling process, a molded article for packaging material comprising a thermoplastic resin composition mainly composed of the polymer is Further, a special amorphous process such as a rapid cooling operation is required at the time of production, and the transparency of the molded product cannot be maintained at a high level.
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.
[0015]
In the thermal analysis method, the ratio of the measured melting heat ΔHm of the test piece to the theoretical melting heat ΔHf is generally obtained from the crystallinity Xc (%) = ΔHm / ΔHf × 100 (Edited by Japan Analytical Society, New Edition Polymer Analysis Handbook) , P.339, Kinokuniya (1995)). In this equation, ΔHm is a value measured by differential scanning calorimetry (DSC; conforming to JIS K7122), and ΔHf is a value described in, for example, POLYMER HANDBOOK (JOHN WILEY & SONS) in the case of a homopolymer. .
[0016]
In the density method, generally, when the measured density of a test piece is represented by d and the densities of completely amorphous and completely crystal are represented by da and dc, respectively, the degree of crystallinity Xc (%) = [(d−da) / (dc− da)] × (dc / d) × 100 (Edited by Japan Analytical Society, New Edition Polymer Analysis Handbook, p.586, Kinokuniya (1995)). In this formula, d and da are values obtained by measuring the amorphous material obtained by heating and melting the test piece or the test piece and then rapidly cooling it, for example, by the floatation method or density gradient tube method (conforming to JIS K7112). In the case of a homopolymer, 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 of a wide variety of copolymer components and their component ratios.
[0017]
In the thermal analysis method, the above formula for obtaining the degree of crystallinity Xc means that the crystallinity becomes higher when the measured heat of fusion ΔHm of the test piece is larger. Therefore, in the present invention, the value of ΔHm To determine the crystallinity. It is necessary that the heat of fusion ΔHm in the second temperature raising process in the DSC measurement be 0 J / g or more and less than 20 J / g.
In the density method, the crystallinity of the polymer is determined based on the value of the relative crystallinity obtained using the density when heated and crystallized under conditions where crystallization is considered to proceed sufficiently. In the present invention, the relative crystallinity Xr represented by the following formula (4) needs to be in the range of 3% to 50%.
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of amorphous material (g / cm Three )
ρb: Density of crystallized product heated at 150 ° C. for 5 minutes (g / cm Three )
ρc: Density of crystallized product heated at 150 ° C. for 100 minutes (g / cm Three )
[0018]
The value of ΔHm of the glycolic acid copolymer used in the present invention is 0 J / g, as in the case of the heat of crystallization ΔHc described above, the polymer of the present invention is the first rise in DSC as described later. Unlike the case where the melting point Tm in the temperature process is 175 ° C. or higher and 205 ° C. or lower and is amorphous and does not crystallize at all, a crystal that does not crystallize under DSC measurement conditions (temperature rising rate 10 ° C./min). The molding material for the packaging material comprising the thermoplastic resin composition mainly composed of the polymer does not require a special amorphous process such as a rapid cooling operation during its production, and the production process is not required. Further, the molded body is excellent in transparency, and even when stored for a long time, the transparency can be maintained at a high level.
[0019]
On the other hand, when the value of ΔHm is 20 J / g or more, since the polymer has very high crystallinity, the molded article for packaging material made of the thermoplastic resin composition mainly composed of the polymer is transparent. However, in order to improve the transparency, a special amorphous process such as a rapid cooling operation is required at the time of molding, and the manufacturing process becomes complicated. The value of ΔHm is preferably in the range of 0 J / g or more and 18.0 J / g or less in order to obtain a molded article for packaging material having higher transparency.
[0020]
Further, when the relative crystallinity Xr represented by the formula (4) is lower than 3%, the crystallinity of the glycolic acid copolymer is too low, and the thermoplastic resin composition mainly composed of the polymer. The molded article 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 molded article for packaging material made of the thermoplastic resin composition mainly composed of the polymer is transparent. However, in order to improve the transparency, a special amorphous process such as a rapid cooling operation is required at the time of molding, and the manufacturing process becomes complicated. The value of Xr is preferably in the range of 10% to 40% in order to combine higher heat resistance and higher transparency.
[0021]
In the above formula (4), when the density ρc when heated at 150 ° C. for 100 minutes is equal to the density ρa of the amorphous material before the heating, the relative crystallinity Xr is calculated by the 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.
[0022]
The melting point of the glycolic acid copolymer used in the present invention is an amorphous sheet obtained by heating and pressurizing the glycolic acid copolymer for 5 minutes with a heating press set at 250 ° C. and then rapidly cooling with a cooling press. First time in differential scanning calorimetry (DSC, conforming to JIS K7121) using a crystallized product heated for 100 minutes in a hot air circulating thermostat set at 150 ° C. under the condition of heating and cooling rate of 10 ° C./min. The melting point Tm in the temperature rising process is in the range of 175 ° C. or higher and 205 ° C. or lower. When the value of Tm is lower than 175 ° C., the melting point of the glycolic acid copolymer is too low, and the heat resistance of the molded body made of the thermoplastic resin composition mainly composed of the polymer is remarkably inferior. And cannot be used in applications that require heat resistance as a container.
[0023]
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 a molded body made of a thermoplastic resin composition mainly composed of the polymer is transparent. It is not possible to use it in applications where transparency is significantly deteriorated and transparency is required as a packaging material, or a special amorphous process such as a rapid cooling operation is required at the time of molding in order to improve transparency, making the manufacturing process complicated. become. 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.
[0024]
The glycolic acid copolymer which is the main material constituting the molded article for packaging material of the present invention is glycolide (1,4-dioxa-2,5-5-glycolic acid cyclic dimer as a main monomer. A copolymer obtained by ring-opening polymerization using dione) or direct dehydration polycondensation using glycolic acid, such as polycondensation while dealcoholizing with glycolic acid esters such as methyl glycolate. Thus, 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.
[0025]
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.
[0026]
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.
[0027]
Among the glycolic acid copolymers that are the main materials constituting the molded article for packaging material of the present invention exemplified above, preferred copolymers are glycolide and glycolide from the viewpoint of easily obtaining a copolymer having a higher molecular weight. Is a copolymer obtained by ring-opening polymerization using a monomer other than the above, wherein the proportion of the repeating unit composed of glycolide is 78 to 90 mol%, and the proportion of the repeating unit composed of the monomer other than glycolide is It consists of 22-10 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%.
[0028]
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.
[0029]
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.
[0030]
The molecular weight of the polymer is at least 0.15 m in terms of logarithmic viscosity in order that the molded body comprising the thermoplastic resin composition mainly composed of the polymer has mechanical strength against external force required as a packaging material. Three / Kg or more is required, 0.18m Three / Kg or more is preferable. 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 (kg / m Three )
[0031]
On the other hand, the upper limit of the molecular weight of the polymer is 0.80 m in terms of logarithmic viscosity for easier molding into a molded product. Three / Kg or less, but it is not particularly limited as long as the melt flowability is adjusted by adding a plasticizer or the like.
The molecular weight of the glycolic acid copolymer used in the present invention is 7.0 × 10 in terms of number average molecular weight. Four Or more, preferably 1.0 × 10 Five That's it. The upper limit of the molecular weight is 7.0 × 10 in terms of number average molecular weight. Five Or less, preferably 6.0 × 10 Five It is desirable to keep it below.
The molded article for packaging material of the present invention is characterized by comprising a thermoplastic resin composition mainly composed of the specific glycolic acid-based copolymer. The thermoplastic resin composition referred to in the present invention is described below. explain.
[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 copolymer alone or a composition of a copolymer and another polymer, and a composition of additives such as a plasticizer and an antioxidant.
The composition ratio of the thermoplastic resin composition varies depending on the quality maintaining performance of the content required when used as a packaging material, such as gas barrier properties and heat resistance, but it is desirable to repeat each polymer of the composition. This is a case where mixing is performed so that a component ratio of 50 mol% or more of the entire unit is a repeating unit composed of glycolide. For packaging materials that require higher content quality retention performance, the component ratio is more preferably 70 mol%. This is the case.
[0033]
Specifically, for example, when a glycolic acid copolymer comprising a copolymer composed of 80 mol% glycolide and 20 mol% lactide repeating units and a polylactic acid composed of 100 mol% lactide repeating units are mixed, the composition In order that the proportion of the glycolide component in all the repeating units is 50 mol% or more, the composition ratio of the glycolic acid copolymer must be 66.5 wt% or more. Further, when a glycolic acid copolymer comprising a copolymer composed of 90 mol% glycolide and 10 mol% lactide repeating units and a polylactic acid composed of 100 mol% lactide repeating units are mixed, all repeating units of the composition are used. In order for the glycolide component ratio to be 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 a molded object can be analyzed with a normal analysis method. For example, the molded body is dissolved in hexafluoroisopropanol (hereinafter abbreviated as HFIP) and filtered to remove insolubles. Next, the obtained HFIP solution of the thermoplastic resin composition is poured into methanol to reprecipitate the resin composition components. After sufficiently drying the obtained reprecipitation resin composition component with a vacuum dryer, 1H-NMR or 13C-NMR was measured using deuterated trifluoroacetic acid or deuterated HFIP as a solvent, and the thermoplastic resin composition The component ratio of the repeating unit consisting of glycolide 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 polymers listed below 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]
In addition, it may be a copolymer obtained by copolymerizing two or more 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. Dibasic acid esters, aliphatic tribasic acid esters such as tributyl acetylcitrate and triethyl acetylcitrate, glycerin fatty acid esters such as glycerol diacetate laurate and glycerol triacetate, and phosphate esters such as dioctyl phosphate , Modified vegetable oils such as epoxidized soybean oil and epoxidized linseed oil, and polyester plasticizers such as polybutylene sebacate. Glycerin fatty acid esters are particularly desirable from the viewpoint of safety and health. One or two or more are selected from these, and the addition amount is about 1 to 30 parts by weight with respect to 100 parts by weight of the thermoplastic resin composition.
[0039]
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, etc., and the addition amount is 100 parts by weight of the thermoplastic resin composition. On the other hand, it is about 0.01 to 10 parts by weight.
The production of the thermoplastic resin composition used in the present invention includes all or part of the specific glycolic acid copolymer of the present invention, other resins that can be mixed with the copolymer, and additives used as necessary. Is preferably melt-mixed using a single-screw or twin-screw extruder, a Banbury mixer, a mixing roll, a kneader or the like.
[0040]
Next, the molded product of the present invention will be described. As a kind of molded object, the molded object for container packaging materials obtained by injection molding, blow molding, and sheet molding is mentioned. Examples of the method for producing the molded body include a casting method, a melt extrusion method, a calendar method, and a melt molding method in the case of a sheet-shaped molded body. 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 molding method, the raw material can be produced by supplying the raw material to a mold, heating and melting it under a normal pressure or reduced pressure atmosphere, and pressing it. 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.). Moreover, the thickness of the sheet-like molded body obtained by the molding method exemplified here is appropriately selected depending on the application, and is usually 5 μm to 1 mm, but is not particularly limited.
[0041]
The obtained molded body may be used as it is as a packaging material, but for the purpose of improving sealing suitability, moisture proofing, gas barrier properties, printing suitability, etc., as needed, it is laminated or coated, or vacuum such as aluminum. You may use it by shape | molding in the shape according to a use by performing vapor deposition or subsequent secondary processing. Specifically, as the secondary processed product, for example, in the case of a sheet-like molded body, a tray obtained by vacuum forming processing such as plug assist molding method and air cushion molding method, pressure forming processing, male and female mold processing, etc. A container such as a cup, or a blister packaging sheet may be mentioned. In order to obtain the secondary processed products of these specific examples, it is desirable that the sheet-like molded body is produced by melt extrusion from a T die by a melt extrusion method.
[0042]
The resulting molded body is used for packaging materials and containers that are heated by a microwave oven and require heat resistance, for the purpose of preventing deformation and melt-drilling due to heat from the heated contents, or stable physical properties In order to improve the properties, it is desirable to perform heat treatment or aging treatment. In this case, it is desirable that the heat treatment is usually performed at a temperature appropriately selected from a temperature range of 60 to 160 ° C. for 1 second to 3 hours. Moreover, you may perform various surface treatments, such as coating and a corona treatment, in order to improve an antistatic agent and anti-fogging property as needed.
[0043]
The obtained molded article of the present invention is biodegradable by using a glycolic acid copolymer having a specific range of crystallinity as a main material constituting the molded article, and has gas barrier properties and heat resistance. It is possible to improve transparency without the need for complicated processes such as rapid cooling during the production of molded products, and the transparency can be maintained at a high level even when the molded products are stored for a long period of time. Furthermore, it retains excellent mechanical strength without causing embrittlement and can be suitably used for packaging materials.
[0044]
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 pressurized with about 12 Pa of glycolic acid-based copolymer for 5 minutes with a heating press set at 250 ° C. (compression molding machine SA-301 manufactured by Tester Sangyo Co., Ltd.), then rapidly cooled with a cooling press to a thickness of about 200 μm. This amorphous sheet was obtained, and the amorphous sheet was heated and crystallized for 100 minutes in a hot air circulating thermostat set at 150 ° C. The sample amount was 7.5 mg. First, the sample was held at 0 ° C. for 3 minutes, then heated to 250 ° C. at a heating rate of 10 ° C./min, and the melting point Tm in the first temperature raising process was measured. After being held 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.
[0045]
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. In addition, 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.
[0046]
(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 degree of crystallinity Xr was determined by equation (4).
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of amorphous material (g / cm Three )
ρb: Density of crystallized product heated at 150 ° C. for 5 minutes (g / cm Three )
ρc: of crystallized product heated at 150 ° C. for 100 minutes
Density (g / cm Three )
[0047]
(3) Logarithmic viscosity number
The concentration of pure solvent HFIP and glycolic acid copolymer is 1.0 kg / m Three The HFIP solution dissolved so as to be a sample was used to measure the time for flowing through the capillary at 20 ° C. using an Ubbelohde capillary viscometer, and the logarithmic viscosity number [η] was determined by 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 (kg / m Three )
[0048]
[Evaluation method and scale]
(1) Transparency
Amorphous sheet of glycolic acid copolymer obtained by the procedure shown in the DSC measurement method, a crystallized product obtained by heating and crystallizing the amorphous sheet in a hot air circulating thermostat set at 150 ° C., the amorphous The haze of a long-term storage sheet stored for 50 days in a constant temperature and humidity chamber set at (23 ± 2) ° C. and a relative humidity (50 ± 5)% was measured. The ratio Hc / Ha of the crystallized haze Hc and the amorphous sheet haze Ha as a change in transparency due to heat treatment, and the ratio Hk between the long-term storage haze Hk and the amorphous sheet haze Ha as a change in transparency due to long-term storage. / Ha was calculated, and transparency was evaluated from the determination results of both. 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. Each sheet-like sample of the obtained amorphous sheet having a thickness of about 200 μm, the crystallized product heated and crystallized at 150 ° C. for 5 minutes, and the long-term storage sheet stored for 50 days in the constant temperature and humidity chamber is 50 mm on a side. Were cut into squares, set in a holder, and the haze for each sample was measured.
[0049]
The measurement results were obtained by measuring 5 samples each and calculating the average value, and calculating the haze ratios Hc / Ha and Hk / Ha. The values of the obtained haze ratios Hc / Ha and Hk / Ha were determined as indexes, and the lower determination result of these values was used as the transparency determination result. However, if the haze of the sheet obtained by the above-described amorphous sheet production procedure is 2.0% or more, it is not easy to produce a molded article having excellent transparency, and therefore it is excluded from the evaluation. Is “×”.
<Evaluation scale>
Haze ratio Hc / Ha judgment Remarks
Less than 50 ◎ Visibility is excellent with slight whitening
50 or more and less than 70 ○ Whitening but no problem with visibility
70 to less than 80 △ Whitening and poor visibility
80 or more × Remarkably whitened and very poor in visibility
<Evaluation scale>
Haze ratio Hk / Ha judgment Remarks
Less than 2 ◎ Maintains transparency and excellent visibility
2 to less than 5 ○ No change in visibility
5 or more and less than 10 △ Slightly whitening
10 or more x Whitening
[0050]
(2) Mechanical strength
The mechanical strength was evaluated by measuring the bending strength of the sheet-like molded body with reference to JIS P8115 using an MIT fatigue resistance tester manufactured by Toyo Seiki Seisakusho Co., Ltd. as a measuring device. A non-crystalline sheet of glycolic acid copolymer obtained by the procedure shown in the DSC measurement method was cut into a strip having a length of 150 mm and a width of 15 mm. A test was performed under the conditions of a bending angle of 135 °, a bending speed of 175 cpm, and a load of 0.5 kg, and the number of times of bending until breakage was measured. The measurement results of the number of bendings were measured by 5 samples per the above procedure and indicated as an average value. This number of bendings was used as an index of mechanical strength.
<Evaluation scale>
Judgment of bending times Remarks
100 times or more ◎ Fracture resistance is very high and there is no practical problem
50 to 99 times ○ High folding resistance, can be used depending on the application
1 to 49 times △ Fracture strength is low and cannot be used practically
0 times × Very brittle and cannot be folded
[0051]
(3) Gas barrier properties
The gas barrier property was evaluated by measuring oxygen permeability according to the JIS K7126B method using an oxygen permeability measuring device OX-TRAN200H type manufactured by mocon as a measuring device. An amorphous sheet of glycolic acid copolymer obtained by the procedure shown in the DSC measurement method was used as a sample, and cut into a square shape having a side of 120 mm. The test was conducted at a temperature of 23 ° C. and a relative humidity of 65%, and the oxygen transmission rate was measured. The measurement result of oxygen permeability was measured by averaging three samples every three times according to the above procedure, and converted to a thickness of 10 μm. This oxygen permeability was used as an index of gas barrier properties.
<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 and cannot be used depending on the application
Unit of oxygen permeability: cc · 10 μm / m 2 ・ Day ・ atm
[0052]
(4) Heat resistance
The heat resistance was evaluated as the maximum temperature at which the sample was not cut by heating for 1 hour in a hot-air circulating thermostat set at a constant temperature with a load of 50 g applied to the strip-shaped sample, and examining whether or not the sample was cut. A non-crystalline sheet of glycolic acid copolymer obtained by the procedure shown in the DSC measurement method was crystallized by heating and crystallizing in a hot air circulating thermostat set at 150 ° C. for 5 minutes, and the length was 140 mm. And cut into a strip shape of 10 mm in width. A fixing jig and a load jig were respectively attached to portions of the upper and lower ends of the strip-shaped sample 25 mm, and heated for 1 hour in a hot air circulating thermostat set at a constant temperature to examine whether or not the sample was cut. When the strip-shaped sample did not cut, the above procedure was repeatedly tested by raising the set temperature by 5 ° C. with a new sample. The measurement result of the maximum temperature at which the strip-shaped sample was not cut was shown as a mode value by performing this test five times for each sheet sample. The maximum temperature at which this strip sample was not cut was used as an index of heat resistance.
<Evaluation scale>
Maximum temperature at which cutting does not occur 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
[0053]
[Example 1]
[Purification of monomer]
250 g of glycolide (manufactured by MAYBRIDGE, 1,4-dioxane-2,5-dione, melting point 81-83 ° C.) was dissolved in dehydrated ethyl acetate 500 g at 75 ° 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 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.
[0054]
250 g of L-lactide (a first grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 500 g of dehydrated toluene at 80 ° C., and then 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, 0.03 g of 2-ethylhexanoic acid tin (manufactured by Wako Pure Chemical Industries, Ltd.) and 0.01 g of dehydrated lauryl alcohol as a catalyst were placed in a pressure tube, and dried nitrogen For about 30 minutes at room temperature. 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.
[0055]
The obtained copolymer is designated as P1. 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, relative crystallinity, and logarithmic viscosity number were measured using the copolymer P1 as a sample, the melting point Tm in the first heating process in DSC was 194 ° C. The heat of crystallization ΔHc is 0 J / g, the heat of fusion ΔHm in the second temperature raising process is 0 J / g, the relative crystallinity Xr is 33%, and the logarithmic viscosity number [η] is 0.25 m. Three / Kg.
[0056]
[Production and evaluation of sheet-like molded product]
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 rapidly cooled with a cooling press to obtain an amorphous sheet having a thickness of about 200 μm. Using the amorphous sheet as a sample, the transparency, mechanical strength, gas barrier property, and heat resistance were evaluated. As a result, the haze ratio Hc / Ha was 45, the haze ratio Hk / Ha was 1, and the number of bendings was 140 times. Oxygen permeability is 10.7cc · 10μm / m 2 Day / 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 sheet-like molded body made of a thermoplastic resin composition mainly composed of glycolic acid copolymer P1 is made of a biodegradable resin and has gas barrier properties, heat resistance, transparency, mechanical strength. It can be seen that it is a molded article suitable for packaging materials excellent in use.
[0057]
Examples 2 to 7 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. Is 0 J / g, relative crystallinity Xr is 34%, logarithmic viscosity number [η] is 0.36 m Three / Kg (Example 2).
[0058]
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. Is 5.8 J / g, the relative crystallinity Xr is 33%, and the logarithmic viscosity number [η] is 0.29 m. Three / Kg (Example 3).
[0059]
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. Is 0 J / g, the relative crystallinity Xr is 19%, and the logarithmic viscosity number [η] is 0.40 m. Three / Kg (Example 4).
[0060]
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. Is 18.2 J / g, relative crystallinity Xr is 30%, and logarithmic viscosity number [η] is 0.19 m. Three / Kg (Example 5).
[0061]
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. Is 0 J / g, the relative crystallinity Xr is 14%, and the logarithmic viscosity number [η] is 0.24 m. Three / Kg (Example 6).
[0062]
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. Is 0 J / g, relative crystallinity Xr is 25%, and logarithmic viscosity number [η] is 0.22 m. Three / Kg (Example 7).
[0063]
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. Heat of fusion ΔHm is 51.6 J / g, relative crystallinity Xr is 78%, logarithmic viscosity number [η] is 0.10 m Three / Kg (Comparative Example 1).
[0064]
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. Heat of fusion ΔHm is 55.5 J / g, relative crystallinity Xr is 100%, logarithmic viscosity number [η] is 0.19 m Three / Kg (Comparative Example 2).
[0065]
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. Thermal ΔHm is 72.6 J / g, relative crystallinity Xr is 100%, logarithmic viscosity number [η] is 0.08 m Three / Kg (Comparative Example 3).
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. Is 0 J / g, relative crystallinity Xr is 0%, and logarithmic viscosity number [η] is 0.25 m. Three / Kg (Comparative Example 4).
Tables 1 and 2 summarize the measurement results of the aforementioned DSC, relative crystallinity, and logarithmic viscosity number of P1 to 11 of the glycolic acid copolymer and glycolic acid homopolymer.
[0066]
[Table 1]
[0067]
[Table 2]
[0068]
About P2-11 of the above-mentioned glycolic acid copolymer and glycolic acid homopolymer, an amorphous sheet was prepared in the same manner as the preparation and evaluation of the above-mentioned sheet-like molded product, and the amorphous sheet was evaluated as a sample. It was. The evaluation results of these polymers P1 to P11 are summarized in Table 3 and Table 4.
[0069]
[Table 3]
[0070]
[Table 4]
[0071]
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. Thermal ΔHm is 0 J / g or more and less than 20 J / g, relative crystallinity Xr is 3% or more and 50% or less, and logarithmic viscosity number [η] is 0.15 m. Three A sheet-like molded body made of a thermoplastic resin composition mainly composed of a glycolic acid copolymer of / kg is made of a biodegradable resin and has excellent gas barrier properties, heat resistance, transparency, and mechanical strength. It turns out that it is a molded object suitable for a packaging material use (Examples 1-7). 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, it can be seen that the sheet-like molded article comprising the thermoplastic resin composition mainly composed of the copolymer is remarkably excellent in both heat resistance and transparency, and is particularly suitable for packaging material use ( Examples 1 to 3).
[0072]
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 It can be seen that the sheet-like molded body made of the plastic resin composition is excellent in gas barrier properties and heat resistance, but is inferior in transparency and mechanical strength and is not suitable for packaging materials (Comparative Examples 1 to 3). . More specifically, when the heat of crystallization ΔHc in the first cooling process described above is not 0 J / g, the logarithmic viscosity number [η] is 0.15 m, for example. Three / Kg or more, it can be seen that a sheet-like molded article or a film-like molded article having a thickness of about 5 to 500 μm, which is used as a packaging material because of its high crystallinity, becomes very brittle (Comparative Example). 2).
[0073]
In addition, it is difficult to obtain an amorphous sheet with the glycolic acid homopolymer P10 having very high crystallinity. The crystallized sheet obtained by using the homopolymer P10 in the same manner as described above was fragile and easily broken, and the evaluation of transparency, gas barrier properties and heat resistance could not be performed (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 remarkably low, it does not crystallize even when heated at 150 ° C., and a sheet-like molded body made of a thermoplastic resin composition mainly composed of the copolymer is transparent. Although it is excellent, heat resistance is remarkably inferior and it turns out that it is not suitable for a packaging material use (comparative example 4).
[0074]
【Effect of the invention】
According to the present invention, by using a glycolic acid copolymer having a specific range of crystallinity, it is biodegradable and has excellent gas barrier properties, heat resistance, transparency, and mechanical strength. It is possible to provide a molded article suitable for the above.
Claims (2)
式(1)175≦Tm≦205
式(2)ΔHc=0
式(3)0≦ΔHm<20
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)1 in differential scanning calorimetry (conforming to 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 and a heating rate and a cooling rate of 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 0.15 m 3 / kg or more Ri Na from thermoplastic resin composition mainly comprising a system copolymer, the glycolic acid copolymer is a copolymer which is obtained by ring-opening polymerization using a monomer other than glycolide and glycolide, The ratio of the repeating unit composed of glycolide is 78-9. A molded article for a packaging material, characterized in that the proportion of a repeating unit composed of a monomer other than glycolide is 0 to 10 mol%, and is 22 to 10 mol% .
Formula (1) 175 ≦ Tm ≦ 205
Expression (2) ΔHc = 0
Formula (3) 0 ≦ ΔHm <20
Formula (4) Xr = [(ρb−ρa) / (ρc−ρa)] × (ρc / ρb) × 100
Where ρa: density of amorphous material (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 )
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2001052016A JP4993238B2 (en) | 2001-02-27 | 2001-02-27 | Molded body for packaging materials |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2001052016A JP4993238B2 (en) | 2001-02-27 | 2001-02-27 | Molded body for packaging materials |
Publications (2)
Publication Number | Publication Date |
---|---|
JP2002249556A JP2002249556A (en) | 2002-09-06 |
JP4993238B2 true JP4993238B2 (en) | 2012-08-08 |
Family
ID=18912707
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2001052016A Expired - Fee Related JP4993238B2 (en) | 2001-02-27 | 2001-02-27 | Molded body for packaging materials |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP4993238B2 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4790920B2 (en) * | 2001-03-07 | 2011-10-12 | 旭化成ケミカルズ株式会社 | Stretched molded product for packaging materials |
JP4693346B2 (en) * | 2003-10-21 | 2011-06-01 | 旭化成ケミカルズ株式会社 | Process for producing aliphatic polyhydroxycarboxylic acid granular crystallized product |
JP2010229243A (en) * | 2009-03-26 | 2010-10-14 | Kureha Corp | Ultraviolet-screening material, and method for manufacturing the same |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4048256A (en) * | 1976-06-01 | 1977-09-13 | American Cyanamid Company | Normally-solid, bioabsorbable, hydrolyzable, polymeric reaction product |
JPH0616790A (en) * | 1991-08-13 | 1994-01-25 | Toyobo Co Ltd | Aliphatic polyester and its production |
JPH0543665A (en) * | 1991-08-13 | 1993-02-23 | Toyobo Co Ltd | Production of aliphatic polyester |
JPH06256480A (en) * | 1993-03-04 | 1994-09-13 | Toyobo Co Ltd | Biodegradable packaging film |
JPH06278785A (en) * | 1993-03-24 | 1994-10-04 | Chuo Kagaku Kk | Biodegradable sauce bottle |
JP4073052B2 (en) * | 1996-04-30 | 2008-04-09 | 株式会社クレハ | Polyglycolic acid sheet and method for producing the same |
JP3809850B2 (en) * | 1996-05-09 | 2006-08-16 | 株式会社クレハ | Stretch blow container and manufacturing method thereof |
-
2001
- 2001-02-27 JP JP2001052016A patent/JP4993238B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JP2002249556A (en) | 2002-09-06 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5157035B2 (en) | POLYLACTIC ACID RESIN COMPOSITION, PROCESS FOR PRODUCING THE SAME, AND MOLDED ARTICLE | |
JP5239336B2 (en) | Polyether-polylactic acid composition and polylactic acid film containing the same | |
JP4363325B2 (en) | Polylactic acid polymer composition, molded article thereof, and film | |
EP1577346B1 (en) | Polylactic acid polymer composition for thermoforming, polylactic acid polymer sheet for thermoforming, and thermoformed object obtained therefrom | |
JP5400271B2 (en) | Aromatic polyester resin molded body and method for producing the same | |
WO2003037956A9 (en) | Crystalline polyglycolic acid, polyglycolic acid composition and processes for production of both | |
JPH09111107A (en) | Biodegradable film or sheet and biodegradable plastic molding | |
KR20130010080A (en) | Process for producing cling films | |
US6027677A (en) | Films containing poly(hydroxy acid)s | |
DK2628761T3 (en) | Biodegradable polyesteretheramid | |
JP4180606B2 (en) | Biodegradable sheet, molded body using this sheet, and molding method thereof | |
JP2002292665A (en) | Method for manufacturing lactic acid polymer sheet | |
JP4993238B2 (en) | Molded body for packaging materials | |
JP4245306B2 (en) | Biodegradable polyester stretch molding | |
JP4245300B2 (en) | Method for producing biodegradable polyester stretch molded article | |
JP4790920B2 (en) | Stretched molded product for packaging materials | |
JP4693254B2 (en) | Glycolic acid resin composition | |
JP2003231798A (en) | Lactic acid resin composition and sheet product of the same, and bag product | |
JP4260521B2 (en) | Glycolic acid polymer composition | |
JP4326828B2 (en) | Composition of glycolic acid copolymer | |
JP4270857B2 (en) | Lactic acid polymer composition and processed product thereof | |
JP4260526B2 (en) | Composition of glycolic acid polymer | |
KR20120126936A (en) | Method of manufacturing biodegradable polyester resin | |
KR102410624B1 (en) | Biodegradable polyester resin composition, biodegradable polyester film and preperation method thereof | |
JP3783008B2 (en) | Aliphatic polyester copolymer, molded product, and agricultural multi-film |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20080225 |
|
A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20101207 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20110118 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20111216 |
|
A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20120111 |
|
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: 20120425 |
|
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: 20120426 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20150518 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 |