JP2004352334A

JP2004352334A - Stretched polylactic acid packaging film and bag

Info

Publication number: JP2004352334A
Application number: JP2003154494A
Authority: JP
Inventors: Hiroyuki Tanaka; 裕之田中; Hiroshi Niinumadate; 浩新沼舘; Kenichi Yakushido; 健一藥師堂
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2003-05-30
Filing date: 2003-05-30
Publication date: 2004-12-16
Anticipated expiration: 2023-05-30
Also published as: JP4329411B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stretched polylactic acid packaging film that is flexible and stretchable and is suitable as a packaging bag that is excellent in openability. <P>SOLUTION: In the polylactic acid packaging film comprising (A) 5 to 60 parts by weight of polylactic acid, (B) a polyester resin comprising 40 to 95 parts by weight of a copolymer of polyester resin that has a fusing point of 90 to 210°C, and (C) inorganic particles as its main constituent, the content of the inorganic particles is 0.01 to 20 wt. % of the film. In addition, the elongation at rupture and elastic modulus of the film in the directions of its length and width satisfy the following relational expressions (1) and (2) at the same time: (1) 450≤La+Lb≤900 and (2) 600≤Ea+Eb≤1,200. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は包装用二軸延伸ポリ乳酸系フィルムおよび袋に関する。特に詳しくは、柔軟で、優れたストレッチ性を有し、かつ開封性に優れた包装用二軸延伸ポリ乳酸系フィルムおよびそれを用いた包装用袋に関する。
【０００２】
【従来の技術】
従来、ポリ乳酸を始めとする脂肪族ポリエステルフィルムは、自然環境に廃棄された際に分解すること、例えば土壌中で自然に加水分解した後に微生物によって無害な分解物となることを特徴として開発され、環境対応の面から注目されている。しかしながら、ポリ乳酸は脆く、伸びないという欠点から、使用時に張力によってある程度伸び、内容物を保持するストレッチ性が要求される様な形態の包装袋には用いることができなかった。かかる欠点を克服するため、ポリ乳酸への可塑剤の添加が数多く検討されてきた。例えば、ポリ乳酸と融点が８０〜２５０℃の生分解性脂肪族ポリエステル系高分子成分、生分解性可塑剤および多糖類などの生分解性天然物からなるフィルムなどが知られている（特許文献１参照）。
【０００３】
しかしながら、このような可塑剤を配合したフィルムでは、可塑剤のブリードアウトを低減する工夫がされているものの、可塑剤を添加することが前提となるため、可塑剤の経時的なブリードアウトによる問題を避けることができなかった。
【０００４】
【特許文献１】特開平１１−２４１００８号公報（請求項１０等）
【０００５】
【発明が解決しようとする課題】
本発明は、かかる課題を解決するために、柔軟で破断伸度が大きくストレッチ性を有し、さらには開封性に優れた包装用袋用として好適な包装用延伸ポリ乳酸系フィルムに関する。
【０００６】
【課題を解決するための手段】
上記課題を達成するするため、本発明の成形用二軸延伸フィルムは次の構成を有する。
【０００７】
すなわち、（Ａ）ポリ乳酸樹脂５〜６０重量部と、（Ｂ）融点が９０〜２１０℃である共重合ポリエステル樹脂４０〜９５重量部からなるポリエステル樹脂と、（Ｃ）無機粒子を主成分とする包装用二軸延伸ポリ乳酸系フィルムであって、無機粒子の含有量がフィルムの０．０１〜２０重量％であり、かつフィルムの長手方向と幅方向の破断伸度および弾性率が下記関係式（１）、（２）を同時に満足する包装用延伸ポリ乳酸系フィルムである。
４５０≦Ｌａ＋Ｌｂ≦９００…（１）
６００ ≦ Ｅａ＋Ｅｂ ≦ １２００ …（２）
ここで、Ｌａはフィルム長手方向および幅方向の破断伸度のうち、大きい方の値（％）、Ｌｂはフィルム長手方向および幅方向の破断伸度のうち、小さい方の値（％）、Ｅａ（ＭＰａ），Ｅｂ（ＭＰａ）はＬａ，Ｌｂに対応する方向の弾性率を示す。
【０００８】
【発明の実施の形態】
本発明で用いられるポリ乳酸樹脂とは、Ｌ−乳酸および／またはＤ−乳酸を主たる構成成分とするポリマーをいうが、乳酸以外の他の共重合成分を０〜１０モル％含んでいてもよい。乳酸以外の共重合成分としてはグリコール酸、３−ヒドロキシ酪酸、４−ヒドロキシ酪酸、３−ヒドロキシ吉草酸、４−ヒドロキシ吉草酸、６−ヒドロキシカプロン酸などのヒドロキシカルボン酸、ポリエチレングリコールやポリメチレングリコールなどのポリオキシアルキレングリコールなどが好ましく用いられる。
【０００９】
本発明に用いられるポリ乳酸樹脂は、適度な製膜、延伸適性および実用的な機械特性を満足させるため、重量平均分子量が５万以上、さらに好ましくは８万以上である事が好ましい。ここでいう重量平均分子量とは、ゲルパーミテーションクロマトグラフィーで測定したポリメチルメタクリレート（ＰＭＭＡ）換算の分子量をいう。
【００１０】
一方、本発明で用いる融点が９０〜２１０℃である共重合ポリエステル樹脂としては、芳香族ポリエステル単位と柔軟成分の共重合体であることが好ましく、芳香族ポリエステル単位としては、エチレンテレフタレート、ブチレンテレフタレート、ヘキサメチレンテレフタレート、エチレン−２，６−ナフタレート、ブチレン−２，６−ナフタレートから選ばれる少なくとも１種の芳香族ポリエステル単位であることが、柔軟成分としては、脂肪族カルボン酸および／またはポリオキシアルキレングリコールを主たる構成単位とすることが好ましい。中でも、得られるフィルムの柔軟性を高めるために、ブチレンテレフタレートと脂肪族カルボン酸を主たる構成単位とする、融点が９０〜１４０℃の共重合ポリエステルが好ましい。
【００１１】
本発明の包装用延伸ポリ乳酸系フィルムとしては、上記ポリ乳酸樹脂を５〜６０重量部、好ましくは１０〜４０重量部と、共重合ポリエステル４０〜９５重量部、好ましくは６０〜９０重量部と無機粒子を主成分とする事が必要である。
【００１２】
ポリ乳酸樹脂が５重量％より少ないか、共重合ポリエステルが９５重量部より多い場合は、開封性に優れたフィルムを得ることが困難であり、ポリ乳酸樹脂が６０重量％より多いか、共重合ポリエステルが４０重量部より少ない場合は柔軟性に優れたフィルムを得ることが困難である。
【００１３】
フィルムに添加する無機粒子としては、凝集シリカ、コロイダルシリカ、酸化チタン、炭酸カルシウム、タルク、珪酸アルミなどから選ぶことができる。
【００１４】
本発明の包装用延伸ポリ乳酸系フィルムには、上記無機粒子をフィルムの滑り性付与のために、フィルムに対し、０．０１〜２０重量％添加する必要がある。特に、印刷を行い、パッケージとしての清潔感、印刷時の高コントラストが求められる用途では酸化チタンおよび／または炭酸カルシウム粒子をフィルムに対して５〜２０重量％添加することが好ましい。一方で、内容物の確認のため、透明性が好まれる用途では、凝集シリカ、コロイダルシリカ、珪酸アルミなどの粒子をフィルムに対して０．０１〜０．５重量％添加することが好ましい。
【００１５】
また、本発明の目的を阻害しない範囲であれば、取扱性、加工性、物性を調整する目的で、可塑剤、滑剤、有機粒子、熱安定剤、着色防止剤、紫外線吸収剤、光安定剤、酸化防止剤等の添加剤を１〜１０重量％含有させてもよい。
【００１６】
本発明の包装用延伸ポリ乳酸系フィルムは、柔軟性と使用時のストレッチ性、および良好な開封性を達成するために、下式（１）および（２）を満足する必要がある。
４５０≦Ｌａ＋Ｌｂ≦９００…（１）
６００ ≦ Ｅａ＋Ｅｂ ≦ １２００ …（２）
ここで、Ｌａはフィルム長手方向および幅方向の破断伸度のうち、大きい方の値（％）、Ｌｂはフィルム長手方向および幅方向の破断伸度のうち、小さい方の値（％）、Ｅａ（ＭＰａ），Ｅｂ（ＭＰａ）はＬａ，Ｌｂと同方向の弾性率を示す。
【００１７】
より好ましくは、式（１）のＬａ＋Ｌｂが５００以上７００以下であること、および式（２）のＥａ＋Ｅｂが８００以上１１００以下であることの少なくとも１つを満たすことである。式（１）のＬａ＋Ｌｂが上記下限値より小さいか、式（２）のＥａ＋Ｅｂが上記上限値より大きい場合は、脆く、包装用袋としては不適なフィルムとなってしまうか、伸びに必要な張力が大ききなりすぎて袋として使用した場合に適度な伸びを示さない、ストレッチ性の無いフィルムとなってしまう。また、式（１）のＬａ＋Ｌｂが上記上限値より大きいか、式（２）のＥａ＋Ｅｂが上記下限値より小さい場合は、あらかじめ袋に切り込みや破線を入れておいた場合でも手で開封することが困難であったり、開封できた場合でも端面が大きくうねる開封性に劣ったフィルムになってしまうためである。
【００１８】
ここで、上記式（２）のＥａ＋Ｅｂを６００以上１２００以下とする手段としては、例えば、本発明のフィルムを構成するポリエステル樹脂中の共重合ポリエステル樹脂の構成比率を６０重量％以上９０重量％以下とし、フィルム長手方向および幅方向の延伸倍率の積を３．０倍以上６倍以下とすることが好ましく、さらに式（２）のＥａ＋Ｅｂを好ましい範囲である８００以上１１００以下とするためには、本発明のフィルムを構成するポリエステル樹脂中の共重合ポリエステル樹脂の構成比率を７０重量％以上９０重量％以下とし、フィルム長手方向および幅方向の延伸倍率の積を３．０倍以上５．０倍以下とすることが好ましい。また、上記式（１）のＬａ＋Ｌｂを４５０以上９００以下とするためには上記延伸条件に加えて延伸後の熱処理を７０℃から１１０℃で２〜１０秒間行うことが好ましい。また、上記式式（１）のＬａ＋Ｌｂを５００以上７００以下とするためには、上記延伸条件に加えて延伸後の熱処理を７０℃から１００℃で４〜１０秒間行うことが好ましい。
【００１９】
本発明の包装用延伸ポリ乳酸系フィルムは、手切れでの開封性を高めるために切り込みや破線を入れた時の、特定方向への開封性、手切れ性を達成するためには、フィルム長手方向と幅方向の破断伸度が下記関係式（３）を満足することが好ましい。
【００２０】
１．４ ≦ Ｌａ／Ｌｂ ≦ ４．０ …（３）
式（３）をＬａ／Ｌｂを好ましくは１．４以上４．０以下、さらに好ましくは１．８以上３．０倍以下とすることにより、特定方向への手切れ性が良好なフィルムを得ることができる。Ｌａ／Ｌｂが上記下限値より小さい場合は特定方向へ手で切ろうとしたときに端面が安定しないといった問題が発生しやすくなり、上記上限値より大きい場合は、二軸方向に張力を受けたときに、破断伸度の小さな方向に破断しやすくなると言ったハンドリング上の問題が発生しやすいため、好ましくない。
【００２１】
さらに、本発明の包装用延伸ポリ乳酸系フィルムにおいて、安定した特定方向への開封性、手切れ性を実現するためには、下記関係式（４）および（５）を同時に満足することが好ましい。
【００２２】
５０ ≦ Ｐｂ ≦ ２５０ …（４）
５ ≦ Ｐａ／Ｐｂ ≦ ２０ …（５）
ここで、Ｐａはフィルム長手方向および幅方向の引き裂き強度のうち、大きい方の値（ｍＮ）、Ｐｂはフィルム長手方向および幅方向の引き裂き強度のうち、小さい方の値（ｍＮ）を示す。
【００２３】
ここで、Ｐｂは好ましくは５０ｍＮ以上２５０ｍＮ以下、さらに好ましくは１００ｍＮ以上であり、Ｐａ／Ｐｂは好ましくは５以上２０以下、さらに好ましくは１０以上２０以下である。Ｐｂが上記下限値より小さい場合やＰａ／Ｐｂが上記上限値より大きい場合は特定の方向に破断しやすくなりすぎるためハンドリング上の問題が発生しやすくなり、Ｐａ／Ｐｂが５より小さい場合は切断面が安定しないという問題が発生しやすくなるため好ましくない。また、Ｐｂが２５０より大きい場合は、引き裂き強度が大きすぎるため手での開封が困難になる。
【００２４】
本発明の包装用延伸ポリ乳酸系フィルムの厚さは、加工工程でのハンドリング性や手切れによる開封性のため、１０μｍ以上１００μｍ以下、好ましくは２５μｍ以上６０μｍ以下である。
【００２５】
ここで、上記式（３）と（５）を満たすフィルムを得る手段としては、例えば、上記の延伸条件および熱処理条件に加え、フィルム長手方向と幅方向のうちの一方の延伸倍率を他方の２倍以上４倍以下、より好ましくは２．５倍以上３倍以下とすることが好ましい。また、式（４）を満足するフィルムを得るためには、例えば、上記に加え本発明のフィルムを構成するポリエステル樹脂中の共重合ポリエステル樹脂の構成比率を７０重量％以上８５重量％以下とし、かつフィルム長手方向または幅方向の延伸倍率のうちの小さい方を１．５倍以上２．０倍以下とすることが好ましい。ただし、以上で述べた好ましい製膜条件は製膜条件相互の関連が大きいため、これに限定するものではない。例えば、好ましい延伸倍率については、例えば用いる共重合ポリエステルのガラス転移温度が低いか、ポリエステル樹脂中の共重合ポリエステル樹脂の構成比率が上記好ましい範囲内であっても比較的高い場合、延伸温度が高い場合は上記好ましい範囲より大きくても上記式（１）〜（５）を満足するフィルムを得ることができる。
【００２６】
本発明の包装用延伸ポリ乳酸系フィルムは必要に応じて印刷を施し、フィルム単体またはヒートシール層を設けた形でヒートシールすることによって包装用袋として用いる事ができる。特に溶断シールなどによって筒状に加工した袋を用い、紙おむつや衛生用品、トイレットペーパーといった様な柔軟性のある内容物を、本フィルムの有するストレッチ性を利用して荷崩れしない様に保持する様な包装用袋として特に好ましく用いることができる。
【００２７】
本発明の包装用延伸ポリ乳酸系フィルムは、単層フィルムでも良いが、少なくとも２層以上からなる積層フィルムとして、片面に低融点のヒートシール層を設けたり、両面に耐摩耗性を付与するために有機粒子および／または無機粒子を特定量添加した層を設けることができる。また、ブロッキング防止、帯電防止、離型性付与、耐傷付き性改良などの目的で、表面にコーティング機能層を設けることが有効であり、この機能層の形成には、包装用延伸ポリ乳酸系フィルムの製造工程内で行うインラインコーティング法、包装用延伸ポリ乳酸系フィルムの巻き取り後に行うオフラインコーティング法を用いることができる。
【００２８】
次に本発明の包装用延伸ポリ乳酸系フィルムの製造方法について説明する。本発明の包装用延伸ポリ乳酸系フィルムを製造する際には、インフレーション法またはインフレーション法により得られたフィルムをさらにフィルム長手方向もしくは幅方向に延伸を行い、その後熱処理を行う方法、Ｔダイ法により押し出したフィルムをロール間の周速差を利用してフィルム長手方向に延伸し、その後熱処理を行う長手方向一軸延伸法、Ｔダイ法により押し出したフィルムの両端をクリップで把持し、テンターを用いてフィルム幅方向に延伸を行い、その後熱処理を行う幅方向一軸延伸法、Ｔダイ、長手方向延伸ロール群、テンターを用いる逐次二軸延伸法のいずれかでも製膜することができるが、逐次二軸延伸法でフィルム長手方向もしくは幅方向の延伸倍率を小さく、他方を大きくすることによってフィルムの各方向の破断伸度や引き裂き強度を調節する方法が最も好ましい。
【００２９】
ポリ乳酸樹脂、共重合ポリエステル樹脂、無機粒子からなる樹脂組成物を押し出す場合、あらかじめこれらの成分を溶融混練した単一原料ペレットを用いたり、各成分を計量しながら供給し、二軸押出機を用いるなどして強剪断力下で混練し押し出す方法でも良いが、重合時添加や重合後の溶融混練によってポリ乳酸樹脂もしくは共重合ポリエステル樹脂のいずれかに高濃度に無機粒子を添加した粒子マスターペレットをあらかじめ準備しておき、上記粒子マスターペレットとポリ乳酸樹脂ペレット、および共重合ポリエステル樹脂ペレットの３種のペレットと、必要に応じて他の添加物を含有するペレットを混合して押出機に供給する方法が、生産性の面から好ましい。
【００３０】
以下に、厚みむらなどのフィルム品質と生産性、手切れによる開封の方向性の制御の面で最も好ましい逐次二軸延伸法を用いて本発明の包装用延伸ポリ乳酸系フィルムを製造する場合の製造方法例を述べる。
【００３１】
あらかじめ無機粒子をポリ乳酸に高濃度に混練したマスターペレット、ポリ乳酸樹脂ペレット、共重合樹脂ペレットの３種類のペレットを準備し、必要量混合した後、減圧下で１００℃６時間の乾燥処理を行い、単軸押出機に供給した。Ｔダイよりシート状に押し出し、表面温度５〜４０℃、好ましくは５〜２０℃の金属冷却ロール上に静電気によって密着させ、無配向シートを得る。この無配向シートを３０〜９０℃、好ましくは４０〜８０℃の加熱ロール状で加熱し、ロール間の周速差を用いてフィルム長手方向に１．５〜５．０倍延伸を行う。この一軸延伸フィルムの両端をクリップで把持してテンターを用いて３０〜９０℃でフィルム幅方向に１．２〜４．０倍延伸を行う。特に、手切れによるフィルム長手方向もしくは幅方向への開封性を特に高めたい場合は、手切れ性を高めたい方向と直交する方向の延伸倍率を他方の延伸倍率の２倍以上、好ましくは３．０倍以上とすることが好ましい。幅方向の延伸を行った後、両端をクリップに把持したまま、一定幅もしくは１〜５％幅を漸減させながら７０〜１４０℃、好ましくは７０〜１１０℃で２〜３０秒、好ましくは２〜１０秒熱処理を行い、巻き取ることによって、本発明の包装用延伸ポリ乳酸系フィルムを得ることができる。
【００３２】
【実施例】
以下、実施例により本発明をさらに説明する。
［特性の測定方法］
（１）フィルム長手方向および幅方向の破断伸度（Ｌａ、Ｌｂ）、弾性率（Ｅａ，Ｅｂ）
オリエンテック社製ＴＥＮＳＩＬＯＮＵＣＴ−１００を用いて測定した。サンプルは、フィルム長手方向および幅方向に、測定方向に長さ２００ｍｍ、幅１０ｍｍの短冊状に切り出し、ＪＩＳＫ−７１２７に規定された方法にしたがって測定を行い、フィルム長手方向および幅方向についてそれぞれ破断伸度、弾性率を求め、破断伸度の大きな方向をａ、他方をｂとし、それぞれの方向の破断伸度、弾性率をＬａ，Ｌｂ，Ｅａ，Ｅｂとした。
（２）白色度（％）
分光式色差計ＳＥ−２０００（日本電色工業（株）製）を用いてＬ，ａ，ｂ値を求め、ＪＩＳＬ１０１５Ｃ法に従い下式を用いて白色度を求めた。
【００３３】
白色度（％）＝１００−｛（１００−Ｌ）^２＋ａ^２＋ｂ^２｝^１／２
（３）全光線透過率
ＪＩＳＫ６７１４−５８に準じて、ＳＥＰ−Ｈ−２系濁度計（日本精密光学社製）を用いて全光線透過率を測定した。
（４）引き裂き強度
オリエンテック社製ＴＥＮＳＩＬＯＮＵＣＴ−１００を用い、ＪＩＳ７１２８−１に従ってトラウザー引裂法による引裂強さを求めた。
（５）ストレッチ性
フィルムをフィルム幅方向に長さ２００ｍｍ、幅１０ｍｍにサンプリングし、オリエンテック社製ＴＥＮＳＩＬＯＮＵＣＴ−１００にチャック間距離１００ｍｍでセットし、２００ｍｍ／分で１０％引張変形させた後直ちに２００ｍｍ／分でチャック間距離を元に戻し、張力が０を示す変位（Ｌ）から、（６）式を用いて弾性回復率Ａを求めた。
Ａ＝（１０−Ｌ）／１０×１００ …（６）
ストレッチ性の評価として、弾性回復率を下記基準で判定した。
◎：弾性回復率８０％以上
○：弾性回復率７０％以上〜８０％未満
△：弾性回復率６０％以上〜７０％未満
×：弾性回復率５０％未満
（６）開封性
一辺１５０ｍｍの正方形に切り出したサンプルの中央部分に、フィルム長手方向と幅方向のうち破断伸度の大きい方向ａと並行に、カッターを用いて１５ｍｍおきに５ｍｍ長さの穴（ミシン目）を入れ、手で切り裂き、破断面の様子を下記基準で判定した。
３点：ミシン目に沿ってきれいに切れ、破断面も直線である。
２点：ミシン目に沿って切れるが、ミシン目間の破断面が曲がっている。
１点：切断面がミシン目からそれるか、フィルムが伸びて破断しない。
５つのサンプルについて評価を行い、平均点から手切れ性を下記基準で判定した。
○：平均点２．５以上
△：平均点２．０以上２．５未満
×：平均点２．０未満
（７）隠蔽性
上級紙に黒色トナーで２０ポイント、ゴシック体で打ち出した文字の上にフィルムを１枚重ね、以下の判定を行った。
○：文字の位置が判別できない。
△：文字は判別できないが、文字の位置は判別できる。
×：文字が判別できる。
【００３４】
（ポリ乳酸樹脂の準備）
ポリ乳酸樹脂：重量平均分子量約２０万のＬ−ポリ乳酸（融点１７０℃；Ｄ−ポリ乳酸の含有量１．５重量％）を用いた。
【００３５】
（ポリ乳酸樹脂粒子マスターペレットの準備）
ポリ乳酸樹脂粒子マスターペレットＡ：ポリ乳酸樹脂に対し、二軸押出機を用いて２００℃でシリカ粒子（富士シリシア化学（株）製サイリシア）を添加量が３．０重量％となるように混練し、マスターペレットとした。
【００３６】
ポリ乳酸樹脂粒子マスターペレットＢ：ポリ乳酸樹脂Ａに対し、二軸押出機を用いて２００℃で酸化チタン（石原産業（株）製タイペークＣＲ６０−１）を混練し、酸化チタン濃度４０重量％のマスターペレットとした。
【００３７】
（共重合ポリエステルの準備）
共重合ポリエステルＡ：ジメチルテレフタレート３４１ｇ、１，４−ブタンジオール６４５ｇ、ピロメリット酸ジアンヒドリド０．６５ｇ、テトラブチルオルトチタネートを窒素雰囲気下でゆっくり撹拌しながら１８０℃で処理し、反応で生成したメタノールを除去した。これにアジピン酸３１２ｇを添加した後、混合物を撹拌しながら２時間にわたり２３０℃まで加熱し、反応で生成した水を除去した。さらに１時間後に５０重量％亜リン酸水溶液０．４ｇを添加し、１時間かけて圧力を２ミリバール以下とし、２４０℃で１時間加熱した。その間過剰の１，４ブタンジオールを除去した。融点は１１０℃であった。
共重合ポリエステルＢ：テレフタル酸１００重量部、１，４−ブタンジオール１００重量部および数平均分子量約１５００のポリテトラメチレングリコール６０重量部の混合物に、テレフタル酸に対してチタンテトラブトキシド０．０４７重量％を添加し、１９０〜２２５℃でエステル化反応を行なった。次いで酸化防止剤を０．２重量％添加し、減圧下で常法により重縮合反応を行い共重合ポリエステルＢを得た。融点は１７０℃であった。
上記原料チップは全て真空下、６０℃で１５時間乾燥した後に用いた。
【００３８】
実施例１
ポリ乳酸樹脂粒子マスターペレットＢを３０重量％、共重合ポリエステルＡを７０重量％混合して用いた。混合した原料チップを押出機に供給し、Ｔダイ口金温度２００℃でフィルム状に押し出し、３０℃に冷却したドラム上にキャストして未延伸フィルムを作製した。連続して加熱ロール間でフィルム長手方向に７０℃で３．５倍の延伸を行い、この一軸延伸フィルムを一旦冷却ロール上で冷却した後、両端をクリップで把持してテンター内に導き、８０℃の温度で加熱しつつ横方向に１．２倍延伸し、幅方向に固定した状態で９０℃、１０秒間の熱処理を行い、厚さ５０μｍのフィルムを得た。得られたフィルムのフィルム特性は表２に示した通りであり、ストレッチ性、開封性、隠蔽性に優れたものであった。
【００３９】
実施例２〜４および比較例１〜４
原料組成、延伸倍率を表１の様に変更した以外は実施例１と同様にして延伸ポリ乳酸系フィルムを得た。得られたフィルムの特性を表２に示す。実施例のフィルムは良好なストレッチ性、開封性を有するが、比較例のフィルムは少なくともストレッチ性、開封性のいずれかが劣るものであった。
【００４０】
【表１】

【００４１】
【表２】

【００４２】
【発明の効果】
柔軟でストレッチ性を有し、さらには開封性に優れた包装用袋用として好適な包装用延伸ポリ乳酸系フィルムを得ることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a biaxially stretched polylactic acid-based film and a bag for packaging. More particularly, the present invention relates to a biaxially stretched polylactic acid-based film for packaging, which is flexible, has excellent stretchability, and is excellent in opening property, and a packaging bag using the same.
[0002]
[Prior art]
Conventionally, aliphatic polyester films such as polylactic acid have been developed to be degraded when disposed of in the natural environment, for example, after being naturally hydrolyzed in soil, become harmless degradation products by microorganisms. , Attention has been paid to environmental protection. However, polylactic acid is fragile and cannot be stretched. Therefore, it cannot be used for a packaging bag in a form that requires some stretchability by use of tension during use and requires stretchability to hold contents. In order to overcome such disadvantages, many studies have been made on the addition of a plasticizer to polylactic acid. For example, a film composed of polylactic acid, a biodegradable aliphatic polyester-based polymer component having a melting point of 80 to 250 ° C., a biodegradable plasticizer, and a biodegradable natural product such as a polysaccharide is known (Patent Document 1). 1).
[0003]
However, in the film containing such a plasticizer, although a measure is taken to reduce the bleed-out of the plasticizer, it is premised that the plasticizer is added. Could not be avoided.
[0004]
[Patent Document 1] JP-A-11-241008 (Claim 10 etc.)
[0005]
[Problems to be solved by the invention]
The present invention relates to a stretched polylactic acid-based film for packaging, which is suitable for use as a packaging bag, which is flexible, has a large elongation at break and stretchability, and is excellent in openability.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a biaxially stretched film for molding of the present invention has the following constitution.
[0007]
That is, (A) 5 to 60 parts by weight of a polylactic acid resin, (B) a polyester resin comprising 40 to 95 parts by weight of a copolymerized polyester resin having a melting point of 90 to 210 ° C., and (C) inorganic particles as main components. A biaxially oriented polylactic acid-based film for packaging, wherein the content of inorganic particles is 0.01 to 20% by weight of the film, and the elongation at break and elastic modulus in the longitudinal and width directions of the film have the following relationship: This is a stretched polylactic acid-based film for packaging that simultaneously satisfies the formulas (1) and (2).
450 ≦ La + Lb ≦ 900 (1)
600 ≦ Ea + Eb ≦ 1200 (2)
Here, La is the larger value (%) of the breaking elongations in the film longitudinal direction and the width direction, and Lb is the smaller value (%) of the breaking elongations in the film longitudinal direction and the width direction. (MPa) and Eb (MPa) indicate elastic moduli in directions corresponding to La and Lb.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The polylactic acid resin used in the present invention refers to a polymer having L-lactic acid and / or D-lactic acid as a main component, but may contain 0 to 10 mol% of a copolymer component other than lactic acid. . Other copolymerizable components other than lactic acid include hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid and 6-hydroxycaproic acid, polyethylene glycol and polymethylene glycol. And the like are preferably used.
[0009]
The polylactic acid resin used in the present invention preferably has a weight average molecular weight of 50,000 or more, more preferably 80,000 or more, in order to satisfy appropriate film formation, stretchability and practical mechanical properties. The term “weight average molecular weight” as used herein means a molecular weight in terms of polymethyl methacrylate (PMMA) measured by gel permeation chromatography.
[0010]
On the other hand, the copolymerized polyester resin having a melting point of 90 to 210 ° C. used in the present invention is preferably a copolymer of an aromatic polyester unit and a flexible component, and the aromatic polyester unit includes ethylene terephthalate and butylene terephthalate. And at least one aromatic polyester unit selected from hexamethylene terephthalate, ethylene-2,6-naphthalate and butylene-2,6-naphthalate. It is preferable that alkylene glycol be the main structural unit. Above all, in order to increase the flexibility of the obtained film, a copolymerized polyester having butylene terephthalate and an aliphatic carboxylic acid as main constituent units and a melting point of 90 to 140 ° C. is preferable.
[0011]
As the stretched polylactic acid-based film for packaging of the present invention, 5 to 60 parts by weight of the polylactic acid resin, preferably 10 to 40 parts by weight, and 40 to 95 parts by weight of the copolymerized polyester, preferably 60 to 90 parts by weight. It is necessary to use inorganic particles as a main component.
[0012]
When the polylactic acid resin is less than 5% by weight or the copolymerized polyester is more than 95 parts by weight, it is difficult to obtain a film having excellent opening properties. When the amount of the polyester is less than 40 parts by weight, it is difficult to obtain a film having excellent flexibility.
[0013]
The inorganic particles added to the film can be selected from aggregated silica, colloidal silica, titanium oxide, calcium carbonate, talc, aluminum silicate and the like.
[0014]
In the stretched polylactic acid-based film for packaging of the present invention, the inorganic particles need to be added in an amount of 0.01 to 20% by weight based on the film in order to impart slipperiness of the film. In particular, in applications where printing is required, and a clean feeling as a package and high contrast at the time of printing are required, it is preferable to add 5 to 20% by weight of titanium oxide and / or calcium carbonate particles to the film. On the other hand, in applications where transparency is preferred for checking the contents, it is preferable to add 0.01 to 0.5% by weight of particles such as aggregated silica, colloidal silica, and aluminum silicate to the film.
[0015]
In addition, as long as the object of the present invention is not impaired, in order to adjust handleability, processability, and physical properties, a plasticizer, a lubricant, an organic particle, a heat stabilizer, a coloring inhibitor, an ultraviolet absorber, and a light stabilizer. And an additive such as an antioxidant may be contained in an amount of 1 to 10% by weight.
[0016]
The stretched polylactic acid-based film for packaging of the present invention needs to satisfy the following expressions (1) and (2) in order to achieve flexibility, stretchability during use, and good openability.
450 ≦ La + Lb ≦ 900 (1)
600 ≦ Ea + Eb ≦ 1200 (2)
Here, La is the larger value (%) of the breaking elongations in the film longitudinal direction and the width direction, and Lb is the smaller value (%) of the breaking elongations in the film longitudinal direction and the width direction. (MPa) and Eb (MPa) indicate the elastic modulus in the same direction as La and Lb.
[0017]
More preferably, it satisfies at least one of La + Lb in the formula (1) being 500 or more and 700 or less and Ea + Eb in the formula (2) being 800 or more and 1100 or less. When La + Lb in the formula (1) is smaller than the above lower limit value or Ea + Eb in the formula (2) is larger than the above upper limit value, the film becomes brittle and becomes an unsuitable film as a packaging bag, or the tension required for elongation. Is too large and does not show proper elongation when used as a bag, resulting in a film without stretchability. When La + Lb in the formula (1) is larger than the upper limit or Ea + Eb in the formula (2) is smaller than the lower limit, the bag can be opened by hand even if a cut or a broken line has been made in the bag in advance. This is because it is difficult, or even if the film can be opened, the end face becomes large and the film becomes poor in openability.
[0018]
Here, as means for setting Ea + Eb in the above formula (2) to 600 or more and 1200 or less, for example, the constituent ratio of the copolymerized polyester resin in the polyester resin constituting the film of the present invention is 60% by weight or more and 90% by weight or less. It is preferable that the product of the stretching ratio in the longitudinal direction and the width direction of the film is 3.0 times or more and 6 times or less. Further, in order to make Ea + Eb in the formula (2) a preferable range of 800 or more and 1100 or less, The composition ratio of the copolymerized polyester resin in the polyester resin constituting the film of the present invention is 70% by weight or more and 90% by weight or less, and the product of the stretching ratio in the longitudinal direction and the width direction of the film is 3.0 times or more and 5.0 times. It is preferable to set the following. Further, in order to make La + Lb in the above formula (1) 450 to 900 or less, it is preferable to perform heat treatment after stretching at 70 to 110 ° C. for 2 to 10 seconds in addition to the above stretching conditions. Further, in order to make La + Lb of the above formula (1) 500 to 700 or less, it is preferable to perform heat treatment after stretching at 70 ° C. to 100 ° C. for 4 to 10 seconds in addition to the above stretching conditions.
[0019]
The stretched polylactic acid-based film for packaging of the present invention, when a cut or a broken line is made to enhance the openability by hand cutting, the opening in a specific direction, in order to achieve the hand It is preferable that the breaking elongation in the direction and the width direction satisfy the following relational expression (3).
[0020]
1.4 ≦ La / Lb ≦ 4.0 (3)
By setting the ratio of La / Lb in the formula (3) to preferably 1.4 or more and 4.0 or less, more preferably 1.8 or more and 3.0 or less, a film having good hand-cutting properties in a specific direction can be obtained. be able to. When La / Lb is smaller than the above lower limit, a problem that the end face is not stable when trying to cut in a specific direction by hand tends to occur, and when La / Lb is larger than the above upper limit, when tension is applied in biaxial directions. In addition, handling problems such as easy breaking in the direction of small breaking elongation tend to occur, which is not preferable.
[0021]
Furthermore, in the stretched polylactic acid-based film for packaging of the present invention, it is preferable to satisfy the following relational expressions (4) and (5) at the same time in order to realize stable opening property and hand-cutting property in a specific direction. .
[0022]
50 ≦ Pb ≦ 250 (4)
5 ≦ Pa / Pb ≦ 20 (5)
Here, Pa indicates the larger value (mN) of the tear strength in the film longitudinal direction and the width direction, and Pb indicates the smaller value (mN) of the tear strength in the film longitudinal direction and the width direction.
[0023]
Here, Pb is preferably 50 mN or more and 250 mN or less, more preferably 100 mN or more, and Pa / Pb is preferably 5 or more and 20 or less, more preferably 10 or more and 20 or less. When Pb is smaller than the above lower limit or when Pa / Pb is larger than the above upper limit, it is easy to break in a specific direction and a handling problem is apt to occur, and when Pa / Pb is smaller than 5, cutting is performed. This is not preferable because the problem that the surface is unstable tends to occur. On the other hand, when Pb is larger than 250, the tear strength is too large, so that it is difficult to open by hand.
[0024]
The thickness of the stretched polylactic acid-based film for packaging of the present invention is 10 μm or more and 100 μm or less, preferably 25 μm or more and 60 μm or less because of the handling property in the processing step and the opening property by hand cutting.
[0025]
Here, as means for obtaining a film satisfying the above formulas (3) and (5), for example, in addition to the above stretching conditions and heat treatment conditions, one of the stretching ratios in the longitudinal direction and the width direction of the film is set to 2 It is preferably at least 2 times and at most 4 times, more preferably at least 2.5 times and at most 3 times. In order to obtain a film satisfying the formula (4), for example, in addition to the above, the constituent ratio of the copolymerized polyester resin in the polyester resin constituting the film of the present invention is set to 70% by weight or more and 85% by weight or less, In addition, it is preferable that the smaller one of the stretching ratios in the longitudinal direction or the width direction of the film is 1.5 times or more and 2.0 times or less. However, the preferable film forming conditions described above are not limited to the above because the film forming conditions are closely related to each other. For example, for a preferred stretching ratio, for example, if the glass transition temperature of the copolymerized polyester used is low, or if the composition ratio of the copolymerized polyester resin in the polyester resin is relatively high even within the above preferred range, the stretching temperature is high. In such a case, a film satisfying the above formulas (1) to (5) can be obtained even if it is larger than the above preferable range.
[0026]
The stretched polylactic acid-based film for packaging of the present invention can be used as a packaging bag by printing as needed and heat-sealing the film alone or in a form provided with a heat-sealing layer. In particular, using a bag processed into a tubular shape with a fusing seal, etc., the flexible contents such as disposable diapers, sanitary goods, and toilet paper are held by using the stretch property of this film so as not to collapse. It can be particularly preferably used as a simple packaging bag.
[0027]
The stretched polylactic acid-based film for packaging of the present invention may be a single-layer film, but as a laminated film composed of at least two or more layers, for providing a low-melting heat seal layer on one side or imparting abrasion resistance to both sides. To which a specific amount of organic particles and / or inorganic particles is added. It is also effective to provide a coating functional layer on the surface for the purpose of preventing blocking, preventing static charge, imparting releasability, improving scratch resistance, and the like. And an off-line coating method performed after winding the stretched polylactic acid-based film for packaging.
[0028]
Next, a method for producing a stretched polylactic acid-based film for packaging according to the present invention will be described. In producing the stretched polylactic acid-based film for packaging of the present invention, a film obtained by the inflation method or the inflation method is further stretched in the film longitudinal direction or the width direction, and then subjected to a heat treatment method, by a T-die method. The extruded film is stretched in the longitudinal direction of the film by using a peripheral speed difference between rolls, and thereafter, both ends of the extruded film are gripped with clips by a longitudinal uniaxial stretching method in which heat treatment is performed, and a T-die method, and a tenter is used. The film can be formed by any of a width direction uniaxial stretching method in which the film is stretched in the film width direction and then heat treatment, a T-die, a longitudinal direction stretching roll group, and a sequential biaxial stretching method using a tenter. In the stretching method, the stretching ratio in the longitudinal direction or width direction of the film is reduced, and the other is increased. Methods of modulating DanShindo and tear strength are most preferred.
[0029]
When extruding a resin composition comprising a polylactic acid resin, a copolyester resin, and inorganic particles, use a single raw material pellet in which these components are melt-kneaded in advance, or supply each component while measuring each component. A method of kneading and extruding under strong shearing force, such as by using, may be used, but a particle master pellet in which inorganic particles are added at a high concentration to either a polylactic acid resin or a copolymerized polyester resin by addition during polymerization or melt kneading after polymerization. Are prepared in advance, and the three types of pellets, the above-mentioned particle master pellets, polylactic acid resin pellets, and copolymerized polyester resin pellets, and if necessary, pellets containing other additives are mixed and supplied to an extruder. Is preferred in terms of productivity.
[0030]
Below, in the case of producing the stretched polylactic acid-based film for packaging of the present invention using the most preferred sequential biaxial stretching method in terms of film quality and productivity such as thickness unevenness and control of the direction of opening by hand cutting. An example of a manufacturing method will be described.
[0031]
Preparing three types of pellets, a master pellet, a polylactic acid resin pellet, and a copolymer resin pellet in which inorganic particles are kneaded with polylactic acid at a high concentration in advance, mixing necessary amounts, and then performing a drying process at 100 ° C. for 6 hours under reduced pressure. And fed to a single screw extruder. It is extruded into a sheet shape from a T-die, and is adhered to a metal cooling roll having a surface temperature of 5 to 40 ° C., preferably 5 to 20 ° C. by static electricity to obtain a non-oriented sheet. This non-oriented sheet is heated in the form of a heated roll at 30 to 90 ° C., preferably 40 to 80 ° C., and is stretched 1.5 to 5.0 times in the longitudinal direction of the film using a peripheral speed difference between the rolls. Both ends of the uniaxially stretched film are gripped with clips and stretched 1.2 to 4.0 times in the film width direction at 30 to 90 ° C. using a tenter. In particular, when it is desired to particularly enhance the opening property in the longitudinal direction or the width direction of the film due to hand cutting, the stretching ratio in the direction orthogonal to the direction in which the hand cutting property is desired to be increased is at least two times, preferably 3. It is preferable that it be 0 times or more. After stretching in the width direction, while holding both ends to the clip, while gradually reducing the fixed width or the width by 1 to 5% at 70 to 140 ° C, preferably 70 to 110 ° C for 2 to 30 seconds, preferably 2 to 30 ° C. By performing a heat treatment for 10 seconds and winding the film, the stretched polylactic acid-based film for packaging of the present invention can be obtained.
[0032]
【Example】
Hereinafter, the present invention will be further described with reference to examples.
[Method of measuring characteristics]
(1) Elongation at break (La, Lb) and modulus of elasticity (Ea, Eb) in the longitudinal and width directions of the film
The measurement was performed using TENSILON UCT-100 manufactured by Orientec. The sample was cut into a strip having a length of 200 mm and a width of 10 mm in the measurement direction in the longitudinal direction and the width direction of the film, and measured in accordance with the method specified in JIS K-7127. The elongation and the elastic modulus were determined, and the direction of the large elongation at break was a, and the other was b, and the elongation at break and the elastic modulus in each direction were La, Lb, Ea, and Eb.
(2) Whiteness (%)
The L, a, and b values were determined using a spectroscopic color difference meter SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and the whiteness was determined using the following equation according to JIS L1015C method.
[0033]
Whiteness (%) = 100 − {(100−L) ² + a ² + b ² } ^1/2
(3) Total light transmittance According to JIS K 6714-58, the total light transmittance was measured using a SEP-H-2 turbidimeter (manufactured by Nippon Seimitsu Optical Co., Ltd.).
(4) Tear strength The tear strength by the trouser tear method was determined according to JIS 7128-1 using TENSILON UCT-100 manufactured by Orientec.
(5) The stretchable film was sampled in the film width direction to a length of 200 mm and a width of 10 mm, and was set on a TENSILON UCT-100 manufactured by Orientec Co. at a distance of 100 mm between the chucks, and immediately after being subjected to 10% tensile deformation at 200 mm / min. The distance between the chucks was returned to the original at 200 mm / min, and the elastic recovery rate A was obtained from the displacement (L) at which the tension was 0 using the equation (6).
A = (10−L) / 10 × 100 (6)
As the evaluation of the stretchability, the elastic recovery rate was determined based on the following criteria.
◎: Elastic recovery rate of 80% or more ：: Elastic recovery rate of 70% or more to less than 80% △: Elastic recovery rate of 60% or more to less than 70% ×: Elastic recovery rate of less than 50% A hole (perforation) having a length of 5 mm was inserted into the central portion of the cut sample at intervals of 15 mm using a cutter in parallel with the direction a having a large elongation at break in the film longitudinal direction and the width direction. The state of the fracture surface was determined based on the following criteria.
3 points: Cuts cleanly along the perforation, and the fracture surface is also straight.
2 points: Cut along perforations, but the fractured surface between perforations is bent.
1 point: The cut surface deviates from the perforation, or the film extends and does not break.
Five samples were evaluated, and the hand-cutting property was determined from the average score according to the following criteria.
：: Average score of 2.5 or more Δ: Average score of 2.0 or more and less than 2.5 X: Average score of less than 2.0 (7) Concealment 20 points with black toner on high-grade paper, on characters embossed in Gothic , And the following judgment was made.
：: The position of the character cannot be determined.
Δ: Characters cannot be identified, but character positions can be identified.
×: Characters can be identified.
[0034]
(Preparation of polylactic acid resin)
Polylactic acid resin: L-polylactic acid having a weight average molecular weight of about 200,000 (melting point: 170 ° C .; D-polylactic acid content: 1.5% by weight) was used.
[0035]
(Preparation of polylactic acid resin particle master pellet)
Polylactic acid resin particle master pellet A: Knead the polylactic acid resin with a twin screw extruder at 200 ° C. at 200 ° C. so that the added amount becomes 3.0% by weight. To obtain a master pellet.
[0036]
Polylactic acid resin particle master pellet B: Polylactic acid resin A is kneaded with titanium oxide (Taipeku CR60-1 manufactured by Ishihara Sangyo Co., Ltd.) at 200 ° C. using a twin screw extruder to obtain a titanium oxide concentration of 40% by weight. Master pellets were used.
[0037]
(Preparation of copolymerized polyester)
Copolymerized polyester A: 341 g of dimethyl terephthalate, 645 g of 1,4-butanediol, 0.65 g of pyromellitic dianhydride, and tetrabutyl orthotitanate treated at 180 ° C. while slowly stirring under a nitrogen atmosphere, and methanol formed by the reaction. Was removed. After adding 312 g of adipic acid thereto, the mixture was heated to 230 ° C. for 2 hours while stirring to remove water generated by the reaction. One hour later, 0.4 g of a 50% by weight aqueous phosphorous acid solution was added, the pressure was reduced to 2 mbar or less over 1 hour, and the mixture was heated at 240 ° C. for 1 hour. During that time, excess 1,4 butanediol was removed. The melting point was 110 ° C.
Copolyester B: A mixture of 100 parts by weight of terephthalic acid, 100 parts by weight of 1,4-butanediol and 60 parts by weight of polytetramethylene glycol having a number average molecular weight of about 1500, and 0.047 parts by weight of titanium tetrabutoxide based on terephthalic acid %, And an esterification reaction was carried out at 190 to 225 ° C. Next, 0.2% by weight of an antioxidant was added, and a polycondensation reaction was carried out under reduced pressure by a conventional method to obtain a copolymerized polyester B. The melting point was 170 ° C.
All the raw material chips were used after drying at 60 ° C. for 15 hours under vacuum.
[0038]
Example 1
The polylactic acid resin particle master pellet B was mixed with 30% by weight and the copolyester A was mixed with 70% by weight. The mixed raw material chips were supplied to an extruder, extruded into a film at a T die die temperature of 200 ° C., and cast on a drum cooled to 30 ° C. to produce an unstretched film. The film is continuously stretched 3.5 times at 70 ° C. in the longitudinal direction of the film between the heating rolls. After the uniaxially stretched film is once cooled on a cooling roll, both ends are gripped with clips and guided into a tenter. The film was stretched 1.2 times in the horizontal direction while being heated at a temperature of 90 ° C., and heat-treated at 90 ° C. for 10 seconds while being fixed in the width direction to obtain a film having a thickness of 50 μm. The film properties of the obtained film were as shown in Table 2, and were excellent in stretchability, openability, and concealment.
[0039]
Examples 2 to 4 and Comparative Examples 1 to 4
A stretched polylactic acid-based film was obtained in the same manner as in Example 1 except that the raw material composition and the stretching ratio were changed as shown in Table 1. Table 2 shows the properties of the obtained film. The films of Examples had good stretchability and openability, whereas the films of Comparative Examples were at least inferior in either stretchability or openability.
[0040]
[Table 1]

[0041]
[Table 2]

[0042]
【The invention's effect】
It is possible to obtain a stretched polylactic acid-based film for packaging, which is suitable for use as a packaging bag which is flexible and stretchable and has excellent opening properties.

Claims

(A) 5 to 60 parts by weight of a polylactic acid resin, (B) a polyester resin consisting of 40 to 95 parts by weight of a copolymerized polyester resin having a melting point of 90 to 210 ° C., and (C) a packaging mainly composed of inorganic particles. Biaxially stretched polylactic acid-based film, wherein the content of inorganic particles is 0.01 to 20% by weight of the film, and the elongation at break and elastic modulus in the longitudinal and width directions of the film are represented by the following relational expression ( A stretched polylactic acid-based film for packaging that simultaneously satisfies 1) and 2).
450 ≦ La + Lb ≦ 900 (1)
600 ≦ Ea + Eb ≦ 1200 (2)
Here, La is the larger value (%) of the breaking elongations in the film longitudinal direction and the width direction, and Lb is the smaller value (%) of the breaking elongations in the film longitudinal direction and the width direction. (MPa) and Eb (MPa) indicate elastic moduli in directions corresponding to La and Lb.

The stretched polyester film for packaging according to claim 1, wherein the copolymerized polyester is a copolymerized polyester having butylene terephthalate and / or ethylene terephthalate and aliphatic carboxylic acid and / or polyoxyalkylene glycol as main constituent units.

The stretched polyester film for packaging according to claim 1 or 2, wherein the copolymerized polyester is a copolymerized polyester having butylene terephthalate and an aliphatic carboxylic acid as main constituent units and having a melting point of 90 to 140 ° C.

The stretched polylactic acid-based film for packaging according to any one of claims 1 to 3, wherein the elongation at break in the longitudinal direction and the width direction of the film satisfies the following relational expression (3).
1.4 ≦ La / Lb ≦ 4.0 (3)

The stretched polylactic acid-based film for packaging according to any one of claims 1 to 4, wherein the tear strength in the longitudinal direction of the film and the tear strength in the width direction of the film satisfy the following relational expressions (4) and (5).
50 ≦ Pb ≦ 250 (4)
5 ≦ Pa / Pb ≦ 20 (5)
Here, Pa indicates the larger value (mN) of the tear strength in the film longitudinal direction and the width direction, and Pb indicates the smaller value (mN) of the tear strength in the film longitudinal direction and the width direction.

The stretched polylactic acid-based film for packaging according to any one of claims 1 to 5, wherein the copolymerized polyester contains an aromatic polyester.

A bag using the stretched polylactic acid-based film according to any one of claims 1 to 6.