JP3566114B2 - Retort food packaging film and method for producing the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明はレトルト食品包装用フィルムおよびその製造方法に関する。さらに詳しくは、低温での耐衝撃性と耐ブロッキング性、ヒートシール性に優れ、且つフィッシュアイの少ないレトルト食品包装用フィルムおよびその製造方法に関するものである。
【０００２】
【従来の技術】
ポリプロピレンは耐熱性、包装適性等に優れているため、食品包装、繊維包装などの包装分野で広く使用されている。
近年、食品包装分野などにおいて耐衝撃性、耐熱性、耐ブロッキング性、ヒートシール性を兼ね備えた材料が要望されている。しかし、プロピレン単独重合体、プロピレンとα−オレフィンのランダム共重合体は低温での耐衝撃性が不十分であり使用に制限があった。
耐衝撃性を付与させるための方法として、主にポリプロピレンブロック共重合体を用いて改良する試みがいくつかなされている。
プロピレン（以下、Ｐと記載する）とエチレン・プロピレン（以下、ＥＰと記載する）共重合体のブロック共重合体として、特開平６−９３０６１号公報にはチーグラー・ナッタ型触媒を用いて、実質的に不活性溶剤の不存在下に第一工程でプロピレンを主体とした重合体部分を重合し、次いで第二工程中で気相中にてエチレン・プロピレン共重合体を重合したＰ−ＥＰブロック共重合体が提案されている。
しかしながら、気相中での重合においては従来の溶剤法での重合体に比べ低温での耐衝撃性が良好である材料が得られるものの、ブロッキング性、ヒートシール性が低下する問題があった。
また、連続重合法においてはフィッシュアイの発生による外観不良を抑えるために、Ｐ部とＥＰ部の極限粘度比を限定する必要があり、フィルム性能にも限界があった。
【０００３】
【発明が解決しようとする課題】
本発明の課題は、従来公知のプロピレン系ブロック共重合体からなるレトルト食品包装用フィルムの欠点を改良し、耐熱性などポリプロピレンブロック共重合体が本来有する好ましい特性を損なうことなく、低温での耐衝撃性が良好であり、外観、耐ブロッキング性、ヒートシール性が良好なレトルト食品包装用フィルムを提供することにある。
【０００４】
【課題を解決するための手段】
本発明者らは種々の検討の結果、フィルムの２０℃キシレン可溶部（以下、ＣＸＳ部という）を制御することにより、良好な特性を発現するフィルムとなることを見出し、更に、フィルム製膜時の分解によるＣＸＳ部の極限粘度（以下、［η］という）の低下をある範囲に抑えるフィルムの製造方法により、より良好な特性を発現することを見出し本発明に至った。
【０００５】
即ち、本発明は、第一工程で実質的に不活性溶剤の不存在下にプロピレンを主体とした重合体部分（Ａ成分）を重合し、次いで第二工程を気相中でエチレン含有量が２０〜５０重量％のプロピレンとエチレンとの共重合体部分(Ｂ成分)を重合して得られるブロック共重合体とトコフェロール類を溶融混練してなり、２３０℃のメルトフローレートが２〜５ｇ／１０分であり、２０℃キシレン可溶部の極限粘度が２．４ｄｌ／ｇ以上である組成物を製膜してなるフィルムであって、以下の物性を満足するレトルト食品包装用フィルムに係るものである。
（１）フィルムの２０℃キシレン可溶部が８〜２５重量％
（２）フィルムの２０℃キシレン可溶部の極限粘度が２ｄｌ／ｇ以上
（３）フィルムの曇値（ＨＡＺＥ）が４５％以上
（４）直径２００μm以上のフィッシュアイが１ｍ2あたり１００個以下
【０００６】
また、本発明は、レトルト食品包装用フィルムの製造方法であって、第一工程で実質的に不活性溶剤の不存在下にプロピレンを主体とした重合体部分(Ａ成分)を重合し、次いで第二工程を気相中でエチレン含有量が２０〜５０重量％のプロピレンとエチレンとの共重合体部分(Ｂ成分)を重合して得られるブロック共重合体とトコフェロール類を溶融混練してなり、２３０℃のメルトフローレートが２〜５ｇ／１０分であり、２０℃キシレン可溶部の極限粘度が２．４ｄｌ／ｇ以上である組成物を製膜して、得られるフィルムの２０℃キシレン可溶部の極限粘度（[η]ｂ）と製膜される組成物の極限粘度（[η]ａ）との比[η]ｂ／[η]ａを０．７５以上にするレトルト食品包装用フィルムの製造方法に係るものである。
【０００７】
以下、本発明を具体的に記載する。
本発明のレトルト食品包装用フィルムに使用されるポリプロピレン系組成物は、第一工程で実質的に不活性溶剤の不存在下にプロピレンを主体とした重合体部分（Ａ成分）を重合し、次いで第二工程を気相中でエチレン含有量が２０〜５０重量％のプロピレンとエチレンとの共重合体部分（Ｂ成分）を重合して得られるブロック共重合体を溶融混練してなるものである。触媒としてはチーグラー・ナッタ型触媒を用いることができる。
【０００８】
Ａ成分とＢ成分の割合は、必要な耐衝撃強度特性に応じて任意に選択することが可能であるが、フィルムのＣＸＳ部の量が８〜２５重量％となるように選択する必要がある。８重量％未満の場合は耐衝撃強度が低下するため好ましくなく、２５重量％を超える場合は耐ブロッキング性が悪化するため好ましくない。特に、９〜１６重量％の範囲が耐衝撃性と耐ブロッキング性のバランスからより好ましい。
また、Ｂ成分のエチレン含有量は２０〜５０重量％であることが必要である。好ましい範囲は、３０〜５０重量％である。
エチレン含有量が２０重量％未満の場合は、耐ブロッキング性が劣るため好ましくなく、５０重量％を超える場合は、耐衝撃性が劣るため好ましくない。
【０００９】
本発明のレトルト食品包装用に使用されるポリプロピレン系組成物はフィルム加工性を考慮すると２３０℃のメルトフローレートは２〜５ｇ／１０分である。
メルトフローレートが１．５ｇ／１０分未満の場合は押出特性が悪化するため好ましくなく、１０ｇ／１０分を超える場合は引き取り特性が悪化するため好ましくない。
【００１０】
本発明のレトルト食品包装用フィルムはフィルムのＣＸＳ部の［η］が２ｄｌ／ｇ以上であることが必要である。２ｄｌ／ｇ未満の場合は、耐ブロッキング性、ヒートシール性が低下するため好ましくない。好ましい範囲は、２．１ｄｌ／ｇ以上である。
また、フィルムの曇値（以下、ＨＡＺＥという）は４５％以上が必要である。好ましい範囲は、５０％以上である。
ＨＡＺＥの増加は表面の微少凹凸を促進することであり、耐ブロッキング性を改良することができる。ＨＡＺＥが４５％未満の場合は耐ブロッキング性が悪化するため好ましくない。
【００１１】
本発明のレトルト食品包装用フィルムは外観、特性の観点から直径２００μｍ以上のフィッシュアイが１ｍ２あたり１００個以下であることが必要である。
好ましい範囲は、５０個以下である。
【００１２】
本発明のレトルト食品包装用フィルムは、Ｔダイ法、チューブラー法などの公知のフィルム製膜法で製造することが可能であるが、特にＴダイ法による未延伸フィルムの製造法により好適に製造される。
フィルムの厚みは特に限定されないが、１０〜２５０μｍが好ましく、さらに好ましくは３０〜１５０μｍである。
【００１３】
本発明のレトルト食品包装用フィルムには、酸化防止剤として、ＣＸＳ部の [ η ] 低下抑制の観点から、トコフェロール類が添加される。
また、本発明のレトルト食品包装用フィルムには、中和剤、その他の酸化防止剤、紫外線吸収剤、帯電防止剤、滑剤、抗ブロッキング剤、造核剤などを必要に応じて添加することが可能である。
特に、中和剤としてはハイドロタルサイト類化合物、水酸化カルシウムなどが加工時の発煙低下には好ましい。
【００１４】
本発明のレトルト食品包装用フィルムは、その他のフィルム、例えばポリプロピレン二軸延伸フィルム、延伸ナイロンフィルム、延伸ポリテレフタル酸エチルフィルムやアルミニウム箔などのドライラミネート法、または押出ラミネート法などの方法で製造される複合フィルムの少なくとも一層としても好適に使用することが可能である。
【００１５】
本発明のレトルト食品包装用フィルムには、通常工業的に採用されている方法によって、コロナ放電処理、火炎処理、プラズマ処理、オゾン処理などの表面処理を施すこともできる。
【００１６】
本発明のレトルト食品包装用フィルムの製造方法は２０℃キシレン可溶部の極限粘度が２．４ｄｌ／ｇ以上である組成物をフィルムの２０℃キシレン可溶部の極限粘度（［η］ｂ）と組成物の極限粘度（［η］ａ）との比［η］ｂ／［η］ａが０．７５以上となる様にすることが必要である。
好ましい範囲は、０．８０以上である。
［η］ｂ／［η］ａが０．７５未満の場合は、ＣＸＳ部の分解が促進されるため耐ブロッキング性が悪化して好ましくない。
［η］ｂ／［η］ａは、組成物の安定剤処方、加工機の構造、加工温度等の加工条件によりコントロールすることが出来る。［η］ｂ／［η］ａを高くするためには、例えば、組成物の安定剤の強化、低せん断の加工機の選択、低温での加工などが効果的である。
【００１７】
特に、組成物の直径２００μｍ以上のフィッシュアイ個数がＮ１（個／ｍ２）であり、フィルムのフィッシュアイ個数をＮ２（個／ｍ２）としたとき、製造時にフィルター等を用いて、Ｎ１とＮ２の関係を、Ｎ２≦０．２×Ｎ１、Ｎ２≦１００を満足するようにすることがより好ましい。
フィルターとしては例えば、ろ過精度１０〜１５０μｍの金属製フィルターを１枚以上、数百枚まで重ねて使用することができ、特にろ過精度４０〜８０μｍの焼結繊維で構成されたフィルターを用いることが、加工性とフィッシュアイの削減効果から好ましい。
【００１８】
本発明のレトルト食品包装用フィルムは外観、耐熱性、低温での耐衝撃性、ヒートシール性、更には耐ブロッキング性に優れ、特に、低温下での重量物包装用途で好適に使用される。
【００１９】
【実施例】
以下、実施例によって本発明をより具体的に説明するが、本発明の範囲は何ら実施例のみに限定されるものではない。なお、発明の詳細な説明および実施例中の各項目の測定値は、下記の方法で測定した。
【００２０】
（１）プロピレン−エチレン共重合体部分（Ｂ成分）中のエチレン濃度
高分子ハンドブック（１９９５年、紀伊国屋書店発行）の６１６ページに記載されている１３Ｃ−ＮＭＲの測定を行い、組成物のエチレン含量を求めた。Ｂ成分中のエチレン濃度は物質収支から求めたＢ成分含有量を用いて次式により計算した。
（組成物のエチレン濃度）×１００／（Ｂ成分含有量 （重量％））
（２）極限粘度（［η］）
ウベローデ型粘度計を用いて１３５℃テトラリン中で測定を行った。
（３）２０℃キシレン可溶部（ＣＸＳ）
ポリプロピレン５ｇを沸騰キシレン５００ｍｌに完全に溶解させた後、２０℃に降温し、４時間以上放置する。その後、これを析出物と溶液とにろ別し可溶部と不溶部に分離した。可溶部はろ液を乾固して減圧下７０℃で乾燥し、その重量を測定して含有量（重量％）を求めた。
【００２１】
（４）メルトフローレイト
ＪＩＳ Ｋ７２１０に従い、条件−１４の方法で測定した。
（５）耐衝撃性
試料を０℃に保持しておき、２ｍの高さから５３５．１ｇの鉄球を落とし、試料を破壊貫通した時の落下速度と、試料のない場合の鉄球のみの落下速度との、速度差から耐衝撃エネルギーを求めた。
その計算は次式による。
Ｅ＝（１／２）・Ｍ・Ｌ２（１／ｔ０ ２−１／ｔ１ ２）
Ｅ：耐衝撃エネルギー［Ｊ］
Ｍ：ボールの重量［０．５３５１ｋｇ］
Ｌ：二つの光電管管の距離［０．１ｍ］
ｔ０：フィルムのない場合の鉄球通過時間［Ｓ］
ｔ１：フィルムを破壊貫通時の鉄球通過時間［Ｓ］
【００２２】
（６）透明性（ヘイズ）
ＪＩＳ Ｋ７１０５に従い測定した。
（７）フィッシュアイ（ＦＥ）
組成物のＦＥ個数（Ｎ１）は、φ５０押出機で＃８０／＃１００／＃１２０のスクリーンメッシュを使用して製膜した厚み５０μｍのフィルムを目視により、直径が２００μｍ以上のＦＥ個数を観測した。
本発明フィルムのＦＥの個数（Ｎ２）は本特許記載のフィルターを使用して製膜したフィルムを目視により、直径が２００μｍ以上のＦＥ個数を観測した。
（８）耐ブロッキング性
２２５ｍｍ×５０ｍｍのフィルムを用いて、フィルム同志を重ねあわせ、１００ｍｍ×５０ｍｍの範囲を４０ｇ／ｃｍ２の荷重下で６０℃、８０℃で３時間状態調整を行った。その後、２３℃、湿度５０％の雰囲気下に３０分以上放置し、島津製作所製ブロッキングテスターを用いて２０ｇ／分の剥離荷重速度で試料の剥離に要する強度を測定した。
（９）ヒートシール強度
東洋テスター工業（株）性ヒートシーラーを使用し次の条件でシールし、次いでシール片を１５ｍｍ幅に切り、剥離角９０°で（株）オリエンテック製テンシロンを用いて測定した。
［シール条件］
シールバー：平面両面加熱、シール温度：２００℃
シール圧力：１．０ｋｇ／ｃｍ２、シール時間：１．０秒
裏打ち補強剤：ＰＥＴ＃１２／ＡＬ＃９／ＣＰＰ＃７０構成のドライラミネートフィルム
【００２３】
実施例１
チーグラーナッタ型触媒を用いて第一工程で気相中でプロピレン単独重合体部分を重合し、次いで第二工程を気相中でエチレン含有量が３４重量％のプロピレンとエチレンとの共重合体部分を重合した。得られた共重合体１００部に水酸化カルシウム０．０３部、ビタミンＥ０．０５部を加えて溶融混練し組成物とした。組成物に含まれるＣＸＳ量は１３．７重量％、ＣＸＳ部の［η］は３．２９ｄｌ／ｇ、フィッシュアイ個数は２１５０個／ｍ２であった。
本組成物をろ過精度６０μｍの金属フィルターを使用して濾過し、次いでＴダイ加工法により、２７０℃の温度で製膜して厚み７０μｍのレトルト食品包装用フィルムを得た。
得られたフィルムのＣＸＳ量は１２．８重量％、ＣＸＳ部の［η］は２．５７ｄｌ／ｇ、フィッシュアイ個数は９８個／ｍ２であった。
フィルムの物性は表１、表２に示す様に、フィッシュアイは多めであるが、耐ブロッキング性、耐衝撃性、ヒートシール強度の良好なフィルムであった。
【００２４】
実施例２
チーグラーナッタ型触媒を用いて第一工程で気相中でプロピレン単独重合体部分を重合し、次いで第二工程を気相中でエチレン含有量が３６重量％のプロピレンとエチレンとの共重合体部分を重合した。得られた共重合体１００部に水酸化カルシウムを０．０１部、ビタミンＥを０．０５部を加えて溶融混練して組成物とした。組成物に含まれるＣＸＳ量は１３．５重量％、ＣＸＳ部の ［ η ］ は２．６２ｄｌ／ｇ、フィッシュアイ個数は６８０個／ｍ ２ であった。実施例１と同様にレトルト食品包装用フィルムを得た。
得られたフィルムのＣＸＳ量は１３．３重量％、ＣＸＳ部の［η］は２．１７ｄｌ／ｇ、フィッシュアイ個数は２０個／ｍ２であった。
フィルムの物性は表１、表２に示す様に、フィッシュアイが少なく、耐ブロッキング性、耐衝撃性、ヒートシール強度の良好なフィルムであった。
【００２５】
実施例３
実施例２の共重合体１００部に水酸化カルシウムを０．０１部、ビタミンＥを０．０３部、イルガノックス１０１０（商品名：チバスペシャリティーケミカルズ社製）０．１部を用いたこと以外は実施例２と同様にレトルト食品包装用フィルムを得た。
得られたフィルムのＣＸＳ量は１３．７重量％、ＣＸＳ部の［η］は２．１７ｄｌ／ｇ、フィッシュアイ個数は１０個／ｍ２であった。
フィルムの物性は表１、表２に示す様に、フィッシュアイが更に少なく、耐ブロッキング性、耐衝撃性、ヒートシール強度の良好なフィルムであった。
【００２６】
比較例１
チーグラーナッタ型触媒を用いて第一工程で気相中でプロピレン単独重合体部分を重合し、次いで第二工程を気相中でエチレン含有量が４１重量％のプロピレンとエチレンとの共重合体部分を重合した。共重合体１００部に水酸化カルシウム０．０３部、イルガノックス１０１０を０．２部、イルガノックス３１１４（商品名：チバスペシャリティーケミカルズ社製）を０．０７５部、イルガフォス１６８（商品名：チバスペシャリティーケミカルズ社製）を０．０５部を加えて組成物とした。組成物に含まれるＣＸＳ量は１４．８重量％、ＣＸＳ部の［η］は１．６４ｄｌ／ｇ、フィッシュアイ個数は１７０個／ｍ２であった。
本組成物を実施例１と同様の方法にてレトルト食品包装用フィルムを得た。得られたフィルムのＣＸＳ量は１２．２重量％、ＣＸＳ部の［η］は１．５６ｄｌ／ｇ、フィッシュアイ個数は７個／ｍ２であった。
フィルムの物性は表１、表２に示す様に、フィッシュアイは少ないが、耐ブロッキング性、耐衝撃性が劣るフィルムであった。
【００２７】
比較例２
実施例２で得られた共重合体１００重量部、水酸化カルシウム０．０３部、イルガノックス１０１０を０．２部を用いた以外は実施例２と同様にレトルト食品包装用フィルムを得た。
得られたフィルムのＣＸＳ量は１３．４重量％、ＣＸＳ部の［η］は１．９５ｄｌ／ｇとＣＸＳ部の分解が進んでいた。
フィルムの物性は表１、表２に示す様に、耐ブロッキング性、耐衝撃性が劣るフィルムであった。
【００２８】
【表１】
【表２】
【発明の効果】
本発明により、低温での耐衝撃性が良好であり、外観、耐ブロッキング性、ヒートシール性が良好なレトルト食品包装用フィルムおよびその製造法が提供される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a retort food packaging film and a method for producing the same. More specifically, the present invention relates to a retort food packaging film having excellent low-temperature impact resistance, anti-blocking properties, and heat-sealing properties and having little fish eyes, and a method for producing the same.
[0002]
[Prior art]
Polypropylene is widely used in packaging fields such as food packaging and fiber packaging because of its excellent heat resistance and packaging suitability.
In recent years, materials having both impact resistance, heat resistance, blocking resistance, and heat sealability have been demanded in the field of food packaging and the like. However, propylene homopolymers and random copolymers of propylene and α-olefins have insufficient impact resistance at low temperatures, and their use has been limited.
As a method for imparting impact resistance, some attempts have been made mainly to improve the impact resistance by using a polypropylene block copolymer.
As a block copolymer of propylene (hereinafter, referred to as P) and ethylene / propylene (hereinafter, referred to as EP) copolymer, a Ziegler-Natta type catalyst is disclosed in JP-A-6-93061. P-EP block obtained by polymerizing a polymer portion mainly composed of propylene in the first step in the absence of an inert solvent and then polymerizing an ethylene-propylene copolymer in the gas phase in the second step Copolymers have been proposed.
However, in the polymerization in the gas phase, although a material having better impact resistance at a lower temperature than that of a polymer obtained by a conventional solvent method can be obtained, there is a problem that the blocking property and the heat sealing property are deteriorated.
In addition, in the continuous polymerization method, it is necessary to limit the limiting viscosity ratio between the P part and the EP part in order to suppress appearance defects due to generation of fish eyes, and there is a limit in film performance.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to improve the drawbacks of a conventionally known retort food packaging film made of a propylene-based block copolymer, and to withstand the low-temperature resistance without impairing the inherent characteristics of the polypropylene block copolymer, such as heat resistance. An object of the present invention is to provide a retort food packaging film having good impact properties and good appearance, blocking resistance and heat sealability.
[0004]
[Means for Solving the Problems]
As a result of various studies, the present inventors have found that controlling the xylene-soluble portion (hereinafter referred to as CXS portion) at 20 ° C. of a film results in a film exhibiting good characteristics. The present inventors have found out that better properties are exhibited by a method for producing a film in which a decrease in the intrinsic viscosity (hereinafter referred to as [η]) of the CXS portion due to decomposition during a certain period is exhibited, and the present invention has been accomplished.
[0005]
That is, in the present invention, in the first step, a polymer portion mainly composed of propylene (component (A)) is polymerized in the substantially absence of an inert solvent, and then the ethylene content in the gas phase in the second step is reduced. A block copolymer obtained by polymerizing 20 to 50% by weight of a copolymer portion (component B) of propylene and ethylene and a tocopherol are melt-kneaded, and the melt flow rate at 230 ° C is 2 to 5 g / 10 min, a film with an intrinsic viscosity of 20 ° C. xylene-soluble portion formed by film formation of the composition is 2.4 dl / g or more, relates to a retort food packaging film which satisfies the following physical properties It is.
(1) The xylene-soluble portion at 20 ° C. of the film is 8 to 25% by weight.
(2) The limiting viscosity of the xylene-soluble portion of the film at 20 ° C. is 2 dl / g or more. (3) The haze value (HAZE) of the film is 45% or more. (4) 100 or less fish eyes with a diameter of 200 μm or more per 1 m 2 [ [0006]
Further, the present invention is a method for producing a film for retort food packaging, wherein in the first step, a polymer portion mainly composed of propylene (A component) is polymerized substantially in the absence of an inert solvent, In the second step, a block copolymer obtained by polymerizing a copolymer part (component B) of propylene and ethylene having an ethylene content of 20 to 50% by weight in a gas phase and a tocopherol are melt-kneaded. , a melt flow rate of 230 ° C. is 2-5 g / 10 min, 20 ° C. the intrinsic viscosity of the xylene-soluble portion is to form a film of the composition is 2.4 dl / g or more, 20 ° C. xylene resulting film the intrinsic viscosity of the soluble portion ([η] b) the intrinsic viscosity of film-forming composition being ([eta] a) the ratio [η] b / [η] retort food packaging to 0.75 or more a The present invention relates to a method for producing a film for use.
[0007]
Hereinafter, the present invention will be specifically described.
The polypropylene composition used in the retort food packaging film of the present invention is obtained by polymerizing a propylene-based polymer portion (A component) in the first step in the absence of an inert solvent, In the second step, a block copolymer obtained by polymerizing a copolymer portion (component B) of propylene and ethylene having an ethylene content of 20 to 50% by weight in a gas phase is melt-kneaded. . As the catalyst, a Ziegler-Natta type catalyst can be used.
[0008]
The ratio between the component A and the component B can be arbitrarily selected according to the required impact resistance characteristics, but it is necessary to select the ratio so that the amount of the CXS portion of the film is 8 to 25% by weight. . If the amount is less than 8% by weight, the impact resistance is lowered, which is not preferable. In particular, the range of 9 to 16% by weight is more preferable from the balance of impact resistance and blocking resistance.
Further, the ethylene content of the component B needs to be 20 to 50% by weight. A preferred range is 30 to 50% by weight.
If the ethylene content is less than 20% by weight, the blocking resistance is poor, which is not preferable. If it exceeds 50% by weight, the impact resistance is poor, which is not preferable.
[0009]
The polypropylene-based composition used for retort food packaging of the present invention has a melt flow rate at 230 ° C. of 2 to 5 g / 10 minutes in consideration of film processability.
If the melt flow rate is less than 1.5 g / 10 minutes, the extrusion characteristics deteriorate, and if it exceeds 10 g / 10 minutes, the take-off characteristics deteriorate, which is not preferable.
[0010]
In the retort food packaging film of the present invention, it is necessary that the [η] of the CXS portion of the film is 2 dl / g or more. If it is less than 2 dl / g, the blocking resistance and the heat sealing property are undesirably reduced. A preferred range is 2.1 dl / g or more.
Further, the haze value of the film (hereinafter, referred to as HAZE) needs to be 45% or more. A preferred range is 50% or more.
An increase in HAZE is to promote fine irregularities on the surface, and the blocking resistance can be improved. If the HAZE is less than 45%, the blocking resistance is undesirably deteriorated.
[0011]
The retort food packaging film of the present invention is required to have not more than 100 fish eyes having a diameter of 200 μm or more per 1 m 2 from the viewpoint of appearance and properties.
A preferred range is 50 or less.
[0012]
The retort food packaging film of the present invention can be produced by a known film forming method such as a T-die method or a tubular method, but is particularly suitably produced by a method of producing an unstretched film by the T-die method. Is done.
The thickness of the film is not particularly limited, but is preferably from 10 to 250 µm, and more preferably from 30 to 150 µm.
[0013]
Tocopherols are added to the retort food packaging film of the present invention as an antioxidant from the viewpoint of suppressing the decrease of [ η ] in the CXS part .
In addition, the retort food packaging film of the present invention may contain a neutralizing agent, another antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, an anti-blocking agent, a nucleating agent, and the like, if necessary. It is possible.
In particular, as the neutralizing agent, hydrotalcite compounds, calcium hydroxide, and the like are preferable for reducing smoke generation during processing.
[0014]
The retort food packaging film of the present invention is manufactured by a method such as a dry lamination method such as a biaxially stretched polypropylene film, a stretched nylon film, a stretched polyethyl terephthalate film or an aluminum foil, or an extrusion lamination method. The composite film can be suitably used as at least one layer.
[0015]
The retort food packaging film of the present invention can be subjected to a surface treatment such as a corona discharge treatment, a flame treatment, a plasma treatment, and an ozone treatment by a method generally employed in industry.
[0016]
In the method for producing a film for packaging a retort food according to the present invention, the composition having an intrinsic viscosity of a 20 ° C. xylene-soluble part of 2.4 dl / g or more is used as an intrinsic viscosity ([η] b) of a 20 ° C. xylene-soluble part of the film. It is necessary that the ratio [η] b / [η] a of the composition and the intrinsic viscosity ([η] a) of the composition be 0.75 or more.
A preferred range is 0.80 or more.
When [η] b / [η] a is less than 0.75, the decomposition of the CXS portion is promoted, so that the blocking resistance deteriorates, which is not preferable.
[Η] b / [η] a can be controlled by processing conditions such as the formulation of the stabilizer for the composition, the structure of the processing machine, and the processing temperature. In order to increase [η] b / [η] a, for example, it is effective to strengthen the stabilizer of the composition, select a low-shear processing machine, and process at low temperature.
[0017]
In particular, when the number of fish eyes having a diameter of 200 μm or more of the composition is N 1 (pieces / m 2 ) and the number of fish eyes of the film is N 2 (pieces / m 2 ), a filter or the like is used during production, More preferably, the relationship between N 1 and N 2 satisfies N 2 ≦ 0.2 × N 1 and N 2 ≦ 100.
As the filter, for example, one or more metal filters with a filtration accuracy of 10 to 150 μm can be used by stacking up to several hundreds, and in particular, a filter made of sintered fibers with a filtration accuracy of 40 to 80 μm can be used. It is preferable from the viewpoint of workability and the effect of reducing fish eyes.
[0018]
The retort food packaging film of the present invention is excellent in appearance, heat resistance, low-temperature impact resistance, heat-sealing property, and blocking resistance, and is particularly suitably used in heavy-duty packaging at low temperatures.
[0019]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the scope of the present invention is not limited to the examples. In addition, the measured value of each item in the detailed description of the invention and the examples was measured by the following method.
[0020]
(1) Ethylene Concentration in Propylene-Ethylene Copolymer Part (Component B) 13C-NMR measurement described on page 616 of Handbook of Polymers (1995, published by Kinokuniya Bookstore) was carried out, and ethylene in the composition was measured. The content was determined. The ethylene concentration in the B component was calculated by the following equation using the B component content obtained from the material balance.
(Ethylene concentration of composition) × 100 / (B component content (% by weight))
(2) Intrinsic viscosity ([η])
The measurement was performed at 135 ° C. in tetralin using an Ubbelohde viscometer.
(3) Xylene soluble part at 20 ° C (CXS)
After completely dissolving 5 g of polypropylene in 500 ml of boiling xylene, the temperature is lowered to 20 ° C. and left for 4 hours or more. Thereafter, this was separated by filtration into a precipitate and a solution, and separated into a soluble part and an insoluble part. The soluble part of the filtrate was dried and dried at 70 ° C. under reduced pressure, and its weight was measured to determine its content (% by weight).
[0021]
(4) Melt flow rate Measured according to JIS K7210 under the condition -14.
(5) Impact resistance The sample was kept at 0 ° C., 535.1 g of iron balls were dropped from a height of 2 m, and the drop speed when breaking through the sample and the iron ball only when there was no sample were measured. The impact energy was determined from the speed difference from the falling speed.
The calculation is based on the following equation.
E = (1/2) · M · L 2 (1 / t 0 2 -1 / t 1 2)
E: Impact resistance [J]
M: Weight of ball [0.5351 kg]
L: distance between two phototubes [0.1 m]
t 0: iron ball passing time in the absence of film [S]
t 1 : Iron ball passage time when breaking through the film [S]
[0022]
(6) Transparency (haze)
It was measured according to JIS K7105.
(7) Fisheye (FE)
The number of FEs having a diameter of 200 μm or more was observed by visually observing a 50 μm thick film formed using a # 80 / # 100 / # 120 screen mesh with a φ50 extruder using the FE number (N 1 ) of the composition. did.
Regarding the number of FEs (N 2 ) of the film of the present invention, the number of FEs having a diameter of 200 μm or more was visually observed for a film formed using the filter described in the present patent.
(8) Blocking resistance Using a film of 225 mm × 50 mm, the films were superposed on each other, and the condition of 100 mm × 50 mm was adjusted at 60 ° C. and 80 ° C. for 3 hours under a load of 40 g / cm 2 . Thereafter, the sample was allowed to stand in an atmosphere of 23 ° C. and a humidity of 50% for 30 minutes or more, and the strength required for peeling the sample was measured at a peeling load speed of 20 g / min using a blocking tester manufactured by Shimadzu Corporation.
(9) Heat seal strength Sealing was performed using a heat sealer manufactured by Toyo Tester Co., Ltd. under the following conditions. Then, a seal piece was cut to a width of 15 mm, and measured at a peel angle of 90 ° using Tensilon manufactured by Orientec. did.
[Seal conditions]
Seal bar: heating both sides of the plane, sealing temperature: 200 ° C
Sealing pressure: 1.0 kg / cm 2 , Sealing time: 1.0 second Backing reinforcing agent: Dry laminated film composed of PET # 12 / AL # 9 / CPP # 70
Example 1
In a first step, a propylene homopolymer portion is polymerized in a gas phase using a Ziegler-Natta type catalyst, and then in a second step, a copolymer portion of propylene and ethylene having an ethylene content of 34% by weight in a gas phase. Was polymerized. To 100 parts of the obtained copolymer, 0.03 part of calcium hydroxide and 0.05 part of vitamin E were added and melt-kneaded to obtain a composition. The CXS amount contained in the composition was 13.7% by weight, [η] of the CXS part was 3.29 dl / g, and the number of fish eyes was 2150 / m 2 .
This composition was filtered using a metal filter having a filtration accuracy of 60 µm, and then formed into a film at a temperature of 270 ° C by a T-die processing method to obtain a 70 µm-thick retort food packaging film.
The CXS amount of the obtained film was 12.8% by weight, [η] in the CXS portion was 2.57 dl / g, and the number of fish eyes was 98 / m 2 .
As shown in Tables 1 and 2, the physical properties of the film were such that the fish eyes were large, but the film had good blocking resistance, impact resistance and heat seal strength.
[0024]
Example 2
In a first step, a propylene homopolymer portion is polymerized in the gas phase using a Ziegler-Natta type catalyst, and then in a second step, a copolymer portion of propylene and ethylene having an ethylene content of 36% by weight in the gas phase. Was polymerized. To 100 parts of the obtained copolymer, 0.01 part of calcium hydroxide and 0.05 part of vitamin E were added and melt-kneaded to obtain a composition. CXS content in the composition 13.5 wt%, the CXS portion [eta] is 2.62dl / g, the fisheye number was 680 pieces / m 2. A retort food packaging film was obtained in the same manner as in Example 1.
The CXS amount of the obtained film was 13.3% by weight, [η] in the CXS portion was 2.17 dl / g, and the number of fish eyes was 20 / m 2 .
As shown in Tables 1 and 2, the physical properties of the film were such that there were few fish eyes, and the film had good blocking resistance, impact resistance and heat seal strength.
[0025]
Example 3
Except that 0.01 part of calcium hydroxide, 0.03 part of vitamin E and 0.1 part of Irganox 1010 (trade name: manufactured by Ciba Specialty Chemicals) were used for 100 parts of the copolymer of Example 2. In the same manner as in Example 2, a retort food packaging film was obtained.
The CXS amount of the obtained film was 13.7% by weight, [η] in the CXS portion was 2.17 dl / g, and the number of fish eyes was 10 / m 2 .
As shown in Tables 1 and 2, the physical properties of the film were such that the film had less fish eyes and had good blocking resistance, impact resistance and heat seal strength.
[0026]
Comparative Example 1
In a first step, a propylene homopolymer portion is polymerized in a gas phase using a Ziegler-Natta type catalyst, and then in a second step, a copolymer portion of propylene and ethylene having an ethylene content of 41% by weight in a gas phase. Was polymerized. To 100 parts of the copolymer, 0.03 part of calcium hydroxide, 0.2 part of Irganox 1010, 0.075 part of Irganox 3114 (trade name, manufactured by Ciba Specialty Chemicals), and Irgafos 168 (trade name: Ciba) Specialty Chemicals) (0.05 parts) was added to give a composition. The amount of CXS contained in the composition was 14.8% by weight, [η] of the CXS part was 1.64 dl / g, and the number of fish eyes was 170 / m 2 .
A retort food packaging film was obtained from this composition in the same manner as in Example 1. The CXS amount of the obtained film was 12.2% by weight, [η] in the CXS portion was 1.56 dl / g, and the number of fish eyes was 7 / m 2 .
As shown in Tables 1 and 2, the physical properties of the film were low in fish eyes, but were poor in blocking resistance and impact resistance.
[0027]
Comparative Example 2
A retort food packaging film was obtained in the same manner as in Example 2, except that 100 parts by weight of the copolymer obtained in Example 2, 0.03 part of calcium hydroxide, and 0.2 part of Irganox 1010 were used.
The CXS amount of the obtained film was 13.4% by weight, and [η] of the CXS portion was 1.95 dl / g, indicating that decomposition of the CXS portion was in progress.
As shown in Tables 1 and 2, the physical properties of the film were poor in blocking resistance and impact resistance.
[0028]
[Table 1]
[Table 2]
【The invention's effect】
According to the present invention, there is provided a retort food packaging film having good impact resistance at low temperatures, good appearance, blocking resistance, and good heat sealability, and a method for producing the same.
Claims (4)
（１）フィルムの２０℃キシレン可溶部が８〜２５重量％
（２）フィルムの２０℃キシレン可溶部の極限粘度が２ｄｌ／ｇ以上
（３）フィルムの曇値（ＨＡＺＥ）が４５％以上
（４）直径２００μm以上のフィッシュアイが１ｍ2あたり１００個以下In the first step, a polymer portion mainly composed of propylene (component (A)) is polymerized substantially in the absence of an inert solvent, and then the second step is carried out in a gas phase with an ethylene content of 20 to 50% by weight. A block copolymer obtained by polymerizing a copolymer portion (component (B)) of propylene and ethylene and a tocopherol are melt-kneaded. The melt flow rate at 230 ° C is 2 to 5 g / 10 minutes, and 20 ℃ intrinsic viscosity of the xylene-soluble portion is a film obtained by film formation of the composition is 2.4 dl / g or more, retort food packaging film which satisfies the following physical properties.
(1) The xylene-soluble portion at 20 ° C. of the film is 8 to 25% by weight.
(2) The limiting viscosity of the xylene-soluble portion of the film at 20 ° C. is 2 dl / g or more. (3) The haze value (HAZE) of the film is 45% or more. (4) 100 or less fish eyes with a diameter of 200 μm or more per m 2.
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|---|---|---|---|
| JP36458298A JP3566114B2 (en) | 1998-12-22 | 1998-12-22 | Retort food packaging film and method for producing the same |
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|---|---|---|---|
| JP36458298A JP3566114B2 (en) | 1998-12-22 | 1998-12-22 | Retort food packaging film and method for producing the same |
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| JP3566114B2 true JP3566114B2 (en) | 2004-09-15 |
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| JP4507807B2 (en) * | 2004-10-04 | 2010-07-21 | 住友化学株式会社 | Polypropylene resin composition and film comprising the same |
| KR101234130B1 (en) | 2004-11-29 | 2013-02-19 | 스미또모 가가꾸 가부시끼가이샤 | Polypropylene film and layered product thereof |
| JP5023493B2 (en) * | 2005-01-07 | 2012-09-12 | 住友化学株式会社 | Method for producing polypropylene resin composition |
| JP5114724B2 (en) * | 2006-07-21 | 2013-01-09 | 東洋紡株式会社 | Polypropylene resin film |
| JP5024757B2 (en) * | 2007-04-09 | 2012-09-12 | 東レフィルム加工株式会社 | Polypropylene film and laminate thereof |
| JP2012224817A (en) * | 2011-04-22 | 2012-11-15 | Sumitomo Chemical Co Ltd | Polypropylene resin composition for film, and film including the same |
| KR101496028B1 (en) * | 2013-08-28 | 2015-02-25 | 삼성토탈 주식회사 | Polypropylene for protective film and protective film |
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| JP7404739B2 (en) * | 2019-09-26 | 2023-12-26 | 東洋製罐グループホールディングス株式会社 | Heat sealing film |
| WO2021200592A1 (en) | 2020-03-30 | 2021-10-07 | 東洋紡株式会社 | Polyolefin resin film |
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| US20240076487A1 (en) | 2021-01-15 | 2024-03-07 | Toyobo Co., Ltd. | Polyolefin-based resin film and laminated body |
| WO2023233685A1 (en) * | 2022-05-31 | 2023-12-07 | 東レフィルム加工株式会社 | Polypropylene-based film for retort packaging, and laminate |
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1998
- 1998-12-22 JP JP36458298A patent/JP3566114B2/en not_active Expired - Fee Related
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| JP2000186159A (en) | 2000-07-04 |
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