JP2004058480A

JP2004058480A - Gas-permeable film

Info

Publication number: JP2004058480A
Application number: JP2002220722A
Authority: JP
Inventors: Hiroki Yamada; 山田　大機
Original assignee: NIDAIKI KK
Current assignee: NIDAIKI KK
Priority date: 2002-07-30
Filing date: 2002-07-30
Publication date: 2004-02-26

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas-permeable film applicable to the top film, peelable film, or the like of the lid material of a container for packaging an article producing gas such as food, medicine, plant, miscellaneous good, chemical, or the like. <P>SOLUTION: By boring a gas-permeable thermoplastic resin film 11 in the thickness direction excluding an extremely thin film part 14 close to the surface, innumerable micropores 15 with one end closed by the film part 14 are scattered at appropriate intervals. The gas-permeable film is coated with a perforated film, or the thermoplastic resin films are piled, and the peripheries of the micropores are joined. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、主として熱可塑性樹脂製フィルムを使って製造され、食品、薬品、植物、雑貨、その他の化学製品等でガスを発生する物品をパッケージングないし容器詰する容器の蓋材のトップフィルムやイージーピールフィルム等に利用可能なガス透過性フィルムに関する。
【０００２】
【従来の技術】
従来、前記パッケージング等の包装資材、副資材の分野では熱可塑性樹脂製のガス透過性フィルムが用いられるが、一般的にフィルムの厚みとガス透過度の関係は直線関係ではなく、指数関数で示されることが知られており、本発明の目的とするガス透過性を満足するためには、厚みを数１０μｍ以内に抑えなければならない。これ以上の厚いフィルムではガス透過性能が極端に低下して用を成さないからである。
【０００３】
一方、包装材や蓋材として使用するには内容物を保護するという包装資材本来の保護機能が要求され、所定の強度、引裂き強度、破裂強度があり、破れにくいことが必要である。しかし、これらの強度を保つためには一般的に、２０〜４００μｍ程度、場合によってはそれ以上の総厚が必要とされ、この厚みではガス透過性を満足することは困難である。
【０００４】
そこで、ガス透過性の薄膜を製造する方法として、　乾湿式法による表面に緻密なスキン層とそれを支えるポーラス構造からなる非対称膜の製法が公知であるが、この方法は特定のポリマーに限定される欠点を有する。また、本願発明者は先の出願（特開平８−２４４８４７号）、（特開平１１−３０１７４８号）（実登２５７４００６号）にて、微孔を透設した有孔フィルムの片面に透過性樹脂膜を被着した気体透過性フィルムを提供した。しかし、前記の透過性樹脂膜はガス透過性の点においては充分であるが、原料が製造上ポリエチレンに限定される点において問題点があった。
【０００５】
【発明が解決しようとする課題】
前記の問題点を解消するために、本発明は、フィルムに微細孔を穿孔する工程で部分的に極薄膜部を形成して、この極薄膜部を通してガス透過を効率よく行うことができ、しかも極薄膜部以外のフィルムベース部で包装資材としての強度を保持することができ、更にポリマーの種類に何ら限定されずに異なる種類の複合フィルムを使用することもできて、経済的に優れたガス透過性フィルムを提供することを目的とする。
【０００６】
【課題を解決するための手段】
前記の課題を解決するために、本発明は、ガス透過性を有する熱可塑性樹脂製フィルムに表面近傍の極薄膜部を除き厚み方向に穿孔することで、前記の極薄膜部によって一端が閉塞されてなる無数の微細孔が適宜間隔をおいて散在してなることを特徴とするガス透過性フィルムとする（請求項１）。また、「フィルム」なる用語は「シート」との対比において、形態や厚みによって区別して用いられることがあるが、本願明細書においては、一般的な「シート」の概念も含む膜状のものを広く含む概念で用いるものとする。
【０００７】
また、前記の課題を解決するために、本発明は、ガス透過性を有する熱可塑性樹脂製フィルムに表面近傍の極薄膜部を除き厚み方向に穿孔することで、前記の極薄膜部によって一端が閉塞されてなる無数の微細孔が適宜間隔をおいて散在してなることを特徴とするガス透過性フィルムからなる外フィルムと、フィルムを貫通する無数の微細孔を穿設した熱可塑性樹脂製の内フィルムを、外フィルムの微細孔が開口する面に内フィルムの何れかの面を対向させ、且つ前記の各フィルムに穿設された対向する微細孔の全部乃至一部が連通するようにして両フィルムを被着してなることを特徴とするガス透過性フィルムとする（請求項２）。
【０００８】
また、前記の課題を解決するために、本発明は、熱可塑性樹脂製の内フィルムとガス透過性を有する熱可塑性樹脂製の外フィルムとを重ね合わせ、外フィルムの表面近傍の極薄膜部を除く外フィルムと内フィルムを厚み方向に貫通穿孔することで、前記の極薄膜部によって一端が閉塞されてなる無数の微細孔が適宜間隔をおいて散在し、前記微細孔の周縁部近傍において外フィルムと内フィルムが接合してなることを特徴とするガス透過性フィルムとする（請求項３）。
【０００９】
また、前記の課題を解決するために、本発明は、前記の熱可塑性樹脂製フィルムが二層乃至多層フィルムからなることを特徴とするガス透過性フィルムとすることが好ましい（請求項４）。
【００１０】
また、前記の課題を解決するために、本発明は、前記の極薄膜部は、厚さが１〜２０μｍの範囲内にあることを特徴とする前記のガス透過性フィルムとすることが好ましい（請求項５）。
【００１１】
また、前記の課題を解決するために、本発明は、前記のガス透過性フィルムを構成する内フィルムが透水可能に微細孔が設けられるとともに、内フィルムと外フィルムが手で容易に剥離できるように構成され、内フィルムと外フィルムが積層された複合フィルムとしては水密且つガス透過性フィルムとして機能し、外フィルムを剥離した残余の内フイルムが水透過性フィルムとして機能することを特徴とする前記のガス透過性フィルムとすることが好ましい（請求項６）。
【００１２】
【作用】
請求項１記載の発明に係るガス透過性フィルムは、極薄膜部によって閉塞された無数の微細孔によって塵や異物の侵入を有効に阻止するとともに、極薄膜に存在する分子構造による空隙や穿孔加工時に発生する小孔（ボイド）を通してガス透過性を示すものであり、パッケージングの内容物から発生するガスを抜き取り、或いは、炭酸ガス、窒素ガス、エチレンガス、酸素、水蒸気等を透過・置換する作用をなす。前記の極薄膜部は、有孔フィルムに極薄フィルムを貼り合わせるのではなく、熱溶融穿孔するときにフィルムの一部が極薄膜化したものであり、サーマルラミネートのように薄膜を加熱下テンションをかけて貼り合わせたフィルムに比較して内部歪が生じ難く、寸法安定性と汎用性に優れた特性を有する。
【００１３】
請求項２記載の発明に係るガス透過性フィルムは、請求項１記載の発明に係るガス透過性フィルムに有孔フィルムをサーマルラミネート乃至接着剤によって接着したものである。極薄フィルムをラミネートするのに比較すればラミネートは容易であり、内フィルムにヒートシール性フィルム乃至低融点ホットメルト系積層フィルムを使用すれば、袋の形成や容器用蓋材のシーリングにおけるヒートシール性を向上することができる。
【００１４】
請求項３記載の発明に係るガス透過性フィルムは、請求項１のガス透過性フィルムと同様の作用に加え、内フィルムと外フィルムとを重ね合わせておいて、内フィルム側から例えば熱針等で微細孔を穿設することによって、内フィルムと外フィルムは微細孔の周縁部近傍において熱融着により接合して両フィルムは密着する。また、内フィルムと外フィルムをサーマルラミネートした場合に比較して加工時のテンションによる内部歪の発生もなく、寸法安定性に優れた特性を有する。
【００１５】
請求項４記載の発明に係るガス透過性フィルムに使用する内フィルムに融点の異なる熱可塑性樹脂からなる二層乃至多層フィルム（共押し出しフィルム）を使用することによって、例えば、外フィルムと相溶性の良い高融点フィルムとヒートシール性乃至低融点ホットメルト系フィルムの二層ないし三層フィルム（共押出しフィルム）を使用すれば、前記のようにヒートシール性が向上する。また、外フィルムを透過させたいガスの種類に応じて、ガス透過性の異なる素材からなる積層フィルム（共押出しフィルム）等を用いることもできる。
【００１６】
請求項５記載の発明に係るガス透過性フィルムの極薄膜部は１〜２０μｍ、好ましくは３〜１０μｍ程度の極薄膜からなるので、前記の空隙や小孔（ボイド）を通してガスを透過することができる。極薄膜部の厚みは１μｍより薄くなると強度が弱く、且つ厚みのコントロールが困難であり、２０μｍより厚くなるとガス透過度が低下する。そしてフィルム全体に無数に穿設された微細孔の数ないし極薄膜部の面積を増減してフィルム全体のガス透過量を調整することができる。
【００１７】
請求項６記載の発明に係るガス透過性フィルム、特に請求項３記載のガス透過性フィルムは、微細孔の周縁部近傍における外フィルムと内フィルムが熱融着して水密可能に接合しているので、共押し出しフィルム等全面が接着している積層フィルムに比較して手で容易に剥離し易い。また、内フィルムの微細孔を透水可能な大きさに設定することによって、複合フィルムとしては水密且つガス透過性フィルムとして機能するが、外フィルムを剥離した残余の内フイルム単独では水透過性フィルムとして機能するように構成することが可能である。
【００１８】
【実施例】
以下に本発明の代表的な実施例について図に基づいて説明する。しかしながら、本願発明はかかる実施例によって限定されるものではなく、本願発明の趣旨に合致する限りにおいて、あらゆるガス透過性フィルムに適用可能であることは言うまでもない。
実施例１
図１に示す実施例１において、１１はガス透過性を備えた熱可塑性樹脂製フィルムであり、１４は極薄膜部であり、１５は微細孔である。熱可塑性樹脂製フィルム１１はガス透過性を有するものであれば特に限定されるものではないが、例えば、ポリプロピレン（ＰＰ）フィルム、ポリエチレン（ＰＥ）フィルム、一般用ポリスチレン（ＧＰ−ＰＳ）フィルム、耐衝撃性ポリエチレン（ＨＩ−ＰＳ）フィルム、二軸延伸ポリスチレン（ＯＰＳ）フィルム、ポリエステル（ＰＥＴ）フィルム、ポリカーボネート（ＰＣ）フィルム、ポリビニルアルコール（ＰＶＡ）フィルム、ポリ塩化ビニル（ＰＶＣ）フィルム、アイオノマーフィルム、セルロース系プラスチックフィルム、熱可塑性エラストマーフィルム等から使用目的に応じて選択することができる。更に、前記のような単一フィルムの他に共押出しフィルムや接着用樹脂層を介したドライラミネーション又はサンドラミネーションで貼り合わせた多層フィルムであってもよい。
【００１９】
【表１】

【００２０】
各種プラスチックフィルムのガス透過性については公知の資料によって明らかであって、例えば、前記の表１は各種プラスチックフィルムのガス非透過性を示したものである（高橋儀作著「プラスチックフィルム」より）。この表に示すように、ポリスチレンは水蒸気、酸素、香気の何れも透過性が大きいが、ポリエチレンとポリエステルはポリスチレンに比較して透過性が小さい。そこで、例えば、ガス透過性の比較的大きなポリスチレンを外側にして、ポリエチレンとポリエステルを内側にして多層フィルムを構成し、内側から溶融穿孔することによって、外側表面近傍にポリスチレンの極薄膜部１４と、ポリエチレンとポリエステル層を貫通し極薄膜部１４に連通する微細孔１５が形成されるので、内側のガスは微細孔１５を通過してポリスチレンの極薄膜部１４を透過することができるのである。このように熱可塑性樹脂製フィルム１１が多層フィルムの場合には、少なくとも最外側の層がガス透過性を備えていることが好ましい。
【００２１】
本実施例においては、熱可塑性樹脂製フィルム１１にガス透過性の比較的大きなポリスチレン層１１ａを外側にして、ポリエチレン層１１ｂ、ヒートシール性ポリエステル層１１ｃの順に接着用樹脂層１８ａ、１８ｂを介したドライラミネーション乃至ＰＥでのサンドラミネーションによる積層フィルム（各層１１ａ、１１ｂ、１１ｃの厚みが順に５０、２５、２５μｍ）を用いた。この積層フィルムを表面に熱針を植えた駆動ロールとバックアップロールの間（所定のギャップに設定されている）に、フィルムの内側（ポリエステル層）面を熱針に向けて挟持し、ライン速度で同調させつつフィルムの外側（ポリスチレン層）表面近傍に約５μｍの極薄膜部を残して無数の微細孔を溶融穿孔する。
【００２２】
熱針の温度はフィルムの融点（約２００℃）以上に設定されるが、ラインスピードとの関係で適宜温度にコントロールすることが好ましい。前記のいわゆる熱針ロールはロールの全面に針を植えてヒーターで熱したものであるが、この他にロールの表面に無数の突起を形成したいわゆる突起絞ロールを用いることもできる。このようにして、外側フィルム表面近傍の約５μｍの極薄膜部１４によって閉塞された直径約０．４ｍｍで約０．７ｍｍ間隔で穿孔された無数の微細孔１５が散在する透明なガス透過性フィルム１を得た。極薄膜部１４の膜厚はロール間のギャップ、フィルムの加工速度、フィルムの融点乃至加工温度の相関関係によって決まり、実際にはフィルムの加工速度を変えて微調整することができる。
【００２３】
実施例２
前記の実施例１において、ポリスチレン、ポリエチレン、ヒートシール性ポリエステルからなる熱可塑性樹脂製フィルム１１に代えて５０μｍ厚のポリスチレン（ＯＰＳ）フィルムを使用して、実施例１と同様にして得られたガス透過性フィルムを外フィルム１２として、この外フィルム１２の微細孔１５が開口する面に有孔フィルムからなる内フィルム１３をヒートシール等で被着して図２に示すような透明なガス透過性フィルム２を得た。内フィルム１３は単一フィルムでもよいが、ヒートシール性の良好な多層フィルムを使用することが好ましい。
【００２４】
本実施例においては内フィルムにポリエチレン（ＰＥ）層１１ｂ、接着用樹脂層１８ｂ、ヒートシール性ポリエステル（ＨＳＰＥＴ）層１１ｃの順に積層したフィルムのポリエチレン層１１ｂ側に低融点の接着用樹脂層１８ａを形成したフィルムを用い、接着用樹脂層１８ａ面を外フィルム１２側に向けて被着した。本実施例では内フィルムに前記構成のものを使用したが、ＨＳＰＥＴ層対Ａ−ＰＥＴ容器のシーラント層との融着性並びにＰＥ層対ＯＰＳフィルムとの融着性を考慮して汎用積層フィルム等から任意に選択することができる。外フィルム１２と内フィルム１３の各微細孔１５ａと１５ｂは連通するので、これらの微細孔１５ａ、１５ｂと極薄膜１４の空隙乃至ボイドを通してガスが透過できるのである。
【００２５】
実施例３
実施例２において、微細孔１５を形成した外フィルム１２と内フィルム１３に代えて微細孔１５を形成していない同様の外フィルム１２と内フィルム１３を重ね合わせ、実施例１と同様にして内フィルム１３側から熱針等によって表面近傍に約５μｍの極薄膜部１４を残して片面が閉塞する無数の微細孔１５を溶融穿孔して、図３に示すような透明なガス透過性フィルム３を得た。図３に示すようにガス透過性フィルム３は微細孔１５周縁部近傍の接合部１７において外フィルムと内フィルムが熱融着によって接合された複合フィルムを構成している。
【００２６】
前記の熱針ロール乃至熱突起絞ロールは表面全体が加熱されており、この熱で針ないし突起の周囲が熱融着されるばかりでなく、平面部においても外フィルムと内フィルムが密着し軽度に融着することによって両フィルム間の水密性が維持されると考えられる。また、実施例２乃至３においては外フィルム１２と内フィルム１３が１枚の単一乃至積層フィルムの場合を示したが、本発明はこれに限定されず、外フィルム１２と内フィルム１３の何れか乃至は何れもが複数枚の単一フィルム乃至積層フィルムであってもよい。
【００２７】
実施例４
実施例３における熱針の太さを変えて溶融穿孔することによって、ガス透過性フィルム３に穿孔された直径が約０．４ｍｍからなる微細孔１５に代えて、直径が約１〜２ｍｍからなる通水性孔１６が散在する透明なガス透過性フィルム４を得た。図４は前記の外フィルム１２の一部を剥離した状態のガス透過性フィルム４を示したものである。細い矢印はガスの透過状態を示し、太い矢印は水分の通過状態を示すものである。
【００２８】
使用例１
実施例１〜３のガス透過性フィルム１〜３を用いて１０ｃｍ×１４ｃｍの袋をそれぞれ作成した。各ガス透過性フィルムを微細孔１５の開口面が内側になるように折り曲げて周囲をヒートシールして一方向に開口する袋を作成し、この各袋にコーヒー粉をそれぞれ２０ｇずつ投入してヒートシールした。比較例として前記のガス透過性フィルム１〜３に代えて厚み５０μｍの無孔の２軸延伸ポリスチレン（ＯＰＳ）フィルムによって同様の袋を作成し比較した。前記のコーヒー粉を封入して２４時間後に観察した結果、ガス透過性フィルム１〜３を使用したものは何れもコーヒー粉を封入した直後と状態の変化がほとんどなく、コーヒーの香りが外部に漏れていることからガス透過性が確認された。これに対し、比較例は内部に充満したガスで袋が膨張し、手で圧縮しても元に戻らないことからガス透過性が殆どないことが確認された。
【００２９】
使用例２
実施例４のガス透過性フィルム４によって抽出用バック（ティーバック）を作成し、それぞれの抽出用バック中に緑茶と漢方薬を入れて封じ、外フィルムを剥離してそのまま湯に浸漬したところ市販のティーバックと同様にそれぞれのエキスを抽出した抽出液を得ることができた。また、微細孔の大きさや数を変えて抽出度を調整することもできる。次ぎに、同様の袋にナフタレン系防虫剤を封入し、外フィルムを剥離することによって、芳香や臭いのガス放出を高めることができ、好みに応じて何れかを選択して使用できる。
【００３０】
【発明の効果】
本発明に係るガス透過性フィルムは、前記のように構成したことによって、フィルムに微細孔を穿孔する工程で部分的に形成された極薄膜部を通して高度なガス透過性と強度を備え、包装資材として、食品、薬品、植物、雑貨、その他の化学製品等でガスを発生する物品をパッケージングしたときに、発生したガスを外部に透過乃至置換し、また、従来の納豆やキノコ類等の菌類の呼吸に必要な空気を導入して日保ちを良くし、新鮮さを維持し賞味期限の長期化を図る効果に加えて、お茶や漢方薬等の抽出用バック（ティーバック等）に利用すれば外部からの埃、異物、水分等の侵入を防ぐだけでなく、外フィルムを剥離してそのまま湯に浸漬させて内容物のエキスを抽出できて便利である。しかも、貼り合わせに溶剤系の接着剤を使用する必要がないので衛生的で安全であり、食品の包装資材として好適である。また、芳香剤や防虫剤の気化調整用の包装資材としても新規な用途であり将来性が大きい。更に、薬品劣化も一切なく、ヒートシール性の良い多層フィルムと複合してパッケージング作業性の向上に役立ち、経済的で汎用性に優れた効果を奏する。
【図面の簡単な説明】
【図１】実施例１に係るガス透過性フィルムの拡大縦断面図である。
【図２】実施例２に係るガス透過性フィルムの拡大縦断面図である。
【図３】実施例３に係るガス透過性フィルムの拡大縦断面図である。
【図４】実施例４に係るガス透過性フィルムの外フィルムの一部を剥離した状態を示す拡大縦断面図である。
【符号の説明】
１：実施例１に係るガス透過性フィルム、２：実施例２に係るガス透過性フィルム、３：実施例３に係るガス透過性フィルム、４：実施例４に係るガス透過性フィルム、
１１：熱可塑性樹脂製フィルム、１１ａ：ポリスチレン層、１１ｂ：ポリエチレン層、１１ｃ：ヒートシール性ポリエステル層、１２：外フィルム、１３：内フィルム、１４：極薄膜部、１５：微細孔、１５ａ：外フィルム微細孔、１５ｂ：内フィルム微細孔、１６：通水性孔、１７：接合部、１８ａ，１８ｂ：接着用樹脂層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is mainly manufactured using a thermoplastic resin film, food, medicine, plants, miscellaneous goods, other chemical products and the like, such as a top film of a lid material of a container for packaging or packing a product that generates gas or the like. The present invention relates to a gas permeable film that can be used for an easy peel film or the like.
[0002]
[Prior art]
Conventionally, in the field of packaging materials such as the packaging and auxiliary materials, a gas permeable film made of a thermoplastic resin is used.In general, the relationship between the film thickness and gas permeability is not a linear relationship but an exponential function. It is known that the thickness must be kept within several tens of μm in order to satisfy the target gas permeability of the present invention. This is because the gas permeation performance is extremely reduced with a thicker film than this, and it is not useful.
[0003]
On the other hand, when used as a packaging material or a lid material, the original protective function of the packaging material for protecting the contents is required, and it is necessary that the material has predetermined strength, tear strength, burst strength, and is hardly torn. However, in order to maintain these strengths, generally, a total thickness of about 20 to 400 μm, or more in some cases, is required, and it is difficult to satisfy gas permeability with this thickness.
[0004]
Therefore, as a method of producing a gas-permeable thin film, a method of producing an asymmetric membrane having a dense skin layer on the surface and a porous structure supporting the same by a dry-wet method is known, but this method is limited to a specific polymer. Disadvantages. In addition, the inventor of the present application, in the earlier application (Japanese Patent Application Laid-Open No. H8-244847) and Japanese Patent Application Laid-Open No. H11-301748 (Japanese Utility Model No. 2574006), disclosed a transparent resin on one side of a perforated film having micropores. A gas permeable film having a membrane applied was provided. However, the above-mentioned permeable resin membrane is sufficient in terms of gas permeability, but has a problem in that the raw material is limited to polyethylene in production.
[0005]
[Problems to be solved by the invention]
In order to solve the above problems, the present invention can partially form an ultra-thin film in a process of perforating micro holes in a film, and can efficiently perform gas permeation through this ultra-thin film, and It is possible to maintain the strength as a packaging material in the film base portion other than the ultra-thin film portion. Furthermore, it is possible to use different types of composite films without being limited to the type of polymer, and it is economically superior gas. It is intended to provide a permeable film.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention provides a gas-permeable thermoplastic resin film by piercing in the thickness direction except for an ultra-thin film portion near the surface, whereby one end is closed by the ultra-thin film portion. The gas permeable film is characterized in that a myriad of micropores are scattered at appropriate intervals (claim 1). In addition, the term “film” is sometimes used in distinction depending on the form and thickness in comparison with “sheet”, but in the specification of the present application, the term “film” includes the general concept of “sheet”. It shall be used in the concept including widely.
[0007]
In addition, in order to solve the above-described problem, the present invention provides a gas-permeable thermoplastic resin film by piercing in the thickness direction except for an ultra-thin film portion near the surface, so that one end is formed by the ultra-thin film portion. An outer film made of a gas-permeable film, characterized by being formed with a myriad of micropores that are closed and scattered at appropriate intervals, and made of a thermoplastic resin having a myriad of micropores penetrating the film. The inner film, with any surface of the inner film facing the surface of the outer film where the micropores are opened, and all or a part of the opposing micropores formed in each of the films communicate with each other. A gas permeable film is obtained by applying both films (claim 2).
[0008]
Further, in order to solve the above-mentioned problem, the present invention superimposes an inner film made of a thermoplastic resin and an outer film made of a thermoplastic resin having gas permeability, and forms an ultra-thin portion near the surface of the outer film. By piercing the outer film and the inner film excluding in the thickness direction, innumerable fine holes having one end closed by the ultrathin film portion are scattered at appropriate intervals, and the outer film is formed in the vicinity of the peripheral portion of the fine hole. A gas permeable film is formed by joining a film and an inner film (claim 3).
[0009]
In order to solve the above-mentioned problems, the present invention preferably provides a gas-permeable film, wherein the thermoplastic resin film is formed of a two-layer or multilayer film (claim 4).
[0010]
Further, in order to solve the above-mentioned problem, in the present invention, it is preferable that the ultra-thin film portion is the gas-permeable film, wherein the thickness is in a range of 1 to 20 μm ( Claim 5).
[0011]
Further, in order to solve the above-mentioned problems, the present invention provides an inner film constituting the gas permeable film, in which fine holes are provided so as to allow water permeation, and the inner film and the outer film can be easily separated by hand. The composite film in which the inner film and the outer film are laminated functions as a water-tight and gas-permeable film, and the remaining inner film from which the outer film has been peeled functions as a water-permeable film. It is preferable to use a gas permeable film (claim 6).
[0012]
[Action]
In the gas permeable film according to the first aspect of the present invention, the intrusion of dust and foreign matters is effectively prevented by the myriad of fine pores closed by the ultrathin film portion, and voids and perforations due to the molecular structure present in the ultrathin film are formed. It shows gas permeability through small holes (voids) generated at the time, and extracts gas generated from the contents of the packaging, or permeates and replaces carbon dioxide, nitrogen gas, ethylene gas, oxygen, water vapor, etc. Works. The ultra-thin film portion is a film in which a part of the film is ultra-thin when hot-melt perforation is performed, instead of laminating the ultra-thin film to the perforated film, and the thin film is heated under tension as in the case of thermal lamination. Internal distortion is less likely to occur compared to a film laminated by applying the heat treatment, and it has excellent dimensional stability and versatility.
[0013]
The gas permeable film according to the second aspect of the present invention is obtained by bonding a perforated film to the gas permeable film according to the first aspect of the present invention with a thermal laminate or an adhesive. Laminating is easier than laminating an ultra-thin film. If a heat-sealable film or a low-melting hot-melt laminated film is used for the inner film, heat-sealing in forming a bag or sealing a lid for a container can be performed. Performance can be improved.
[0014]
The gas permeable film according to the third aspect of the present invention has the same effect as the gas permeable film of the first aspect, and further has an inner film and an outer film which are overlapped, and a heat needle or the like is provided from the inner film side. The inner film and the outer film are joined by heat fusion in the vicinity of the periphery of the fine holes, so that the two films adhere to each other. Further, as compared with the case where the inner film and the outer film are thermally laminated, there is no occurrence of internal strain due to tension during processing, and the characteristics are excellent in dimensional stability.
[0015]
By using a two-layer or multi-layer film (co-extruded film) made of a thermoplastic resin having a different melting point as the inner film used for the gas-permeable film according to the fourth aspect of the present invention, for example, the inner film is compatible with the outer film. If a two-layer or three-layer film (co-extruded film) of a good high-melting film and a heat-sealing or low-melting hot-melt film is used, the heat-sealing property is improved as described above. Also, a laminated film (co-extruded film) or the like made of a material having different gas permeability may be used according to the type of gas to be transmitted through the outer film.
[0016]
Since the ultra-thin film portion of the gas-permeable film according to the invention of claim 5 is formed of an ultra-thin film having a thickness of about 1 to 20 μm, preferably about 3 to 10 μm, gas can be transmitted through the voids and small holes (voids). it can. When the thickness of the ultra-thin film portion is less than 1 μm, the strength is weak, and it is difficult to control the thickness. When the thickness is more than 20 μm, the gas permeability decreases. The gas permeation amount of the entire film can be adjusted by increasing or decreasing the number of micropores or the area of the ultra-thin film portion innumerably formed throughout the film.
[0017]
In the gas permeable film according to the invention of claim 6, particularly the gas permeable film of claim 3, the outer film and the inner film in the vicinity of the peripheral edge of the fine hole are heat-sealed and joined in a watertight manner. Therefore, it can be easily peeled off by hand as compared with a laminated film such as a co-extruded film which is adhered on the whole surface. Also, by setting the micropores of the inner film to a size that allows water permeation, the composite film functions as a water-tight and gas-permeable film, but the remaining inner film alone from which the outer film has been peeled off serves as a water-permeable film. It can be configured to work.
[0018]
【Example】
Hereinafter, a typical embodiment of the present invention will be described with reference to the drawings. However, it is needless to say that the invention of the present application is not limited by such examples, and can be applied to any gas permeable film as long as it meets the gist of the present invention.
Example 1
In Example 1 shown in FIG. 1, 11 is a thermoplastic resin film having gas permeability, 14 is an extremely thin film portion, and 15 is a fine hole. The thermoplastic resin film 11 is not particularly limited as long as it has gas permeability. For example, a polypropylene (PP) film, a polyethylene (PE) film, a general-purpose polystyrene (GP-PS) film, Impact polyethylene (HI-PS) film, biaxially oriented polystyrene (OPS) film, polyester (PET) film, polycarbonate (PC) film, polyvinyl alcohol (PVA) film, polyvinyl chloride (PVC) film, ionomer film, cellulose It can be selected from a system plastic film, a thermoplastic elastomer film and the like according to the purpose of use. Further, in addition to the single film as described above, a co-extruded film or a multilayer film bonded by dry lamination or sand lamination via an adhesive resin layer may be used.
[0019]
[Table 1]

[0020]
The gas permeability of various plastic films is apparent from known materials. For example, Table 1 shows the gas non-permeability of various plastic films (from "Plastic Film" by Yoshisaku Takahashi). . As shown in this table, polystyrene has high permeability to water vapor, oxygen, and aroma, but polyethylene and polyester have low permeability as compared to polystyrene. Therefore, for example, with a relatively large gas permeable polystyrene outside, polyethylene and polyester inside to form a multilayer film, and by melt perforation from the inside, the polystyrene ultra-thin film portion 14 near the outer surface, Since the fine holes 15 penetrating the polyethylene and polyester layers and communicating with the ultra-thin film portion 14 are formed, the gas inside can pass through the fine holes 15 and pass through the ultra-thin film portion 14 of polystyrene. As described above, when the thermoplastic resin film 11 is a multilayer film, it is preferable that at least the outermost layer has gas permeability.
[0021]
In the present embodiment, the polyethylene resin layer 11b and the heat-sealing polyester layer 11c are interposed in this order via the bonding resin layers 18a and 18b with the relatively large gas-permeable polystyrene layer 11a on the thermoplastic resin film 11 outside. Laminated films obtained by dry lamination or sand lamination with PE (the thickness of each of the

layers

11a, 11b, and 11c was 50, 25, and 25 μm in this order) were used. The laminated film is sandwiched between the drive roll and the backup roll (on which a predetermined gap is set) having the thermal needles planted on the surface thereof, with the inner side (polyester layer) of the film facing the thermal needles, and at a line speed. While synchronizing, innumerable micropores are melt-punched except for an extremely thin portion of about 5 μm near the outer surface (polystyrene layer) of the film.
[0022]
The temperature of the heating needle is set to be equal to or higher than the melting point of the film (about 200 ° C.), but it is preferable to control the temperature appropriately in relation to the line speed. The above-mentioned so-called hot needle roll is a roll in which needles are planted on the entire surface of the roll and heated by a heater. In addition, a so-called projection squeezing roll in which countless projections are formed on the surface of the roll can also be used. In this manner, a transparent gas-permeable film in which a myriad of fine holes 15 pierced at intervals of about 0.7 mm and having a diameter of about 0.4 mm closed by an ultrathin film section 14 of about 5 μm near the outer film surface is scattered. 1 was obtained. The thickness of the ultra-thin film portion 14 is determined by the gap between the rolls, the processing speed of the film, and the correlation between the melting point and the processing temperature of the film, and can be finely adjusted by actually changing the processing speed of the film.
[0023]
Example 2
A gas obtained in the same manner as in Example 1 except that a polystyrene (OPS) film having a thickness of 50 μm was used instead of the thermoplastic resin film 11 made of polystyrene, polyethylene, and heat-sealable polyester. The permeable film is used as the outer film 12, and the inner film 13 made of a perforated film is applied to the surface of the outer film 12 where the fine holes 15 are opened by heat sealing or the like, and a transparent gas permeable film as shown in FIG. Film 2 was obtained. The inner film 13 may be a single film, but it is preferable to use a multilayer film having good heat sealability.
[0024]
In this embodiment, a polyethylene (PE) layer 11b, an adhesive resin layer 18b, and a heat-sealing polyester (HSPET) layer 11c are laminated on the inner film in this order. Using the formed film, the adhesive resin layer 18a was applied to the outer film 12 side. In this example, the inner film having the above-mentioned structure was used. However, a general-purpose laminated film or the like is used in consideration of the fusion property between the HSPET layer and the sealant layer of the A-PET container and the fusion property between the PE layer and the OPS film. Can be selected arbitrarily. Since the

fine holes

15a and 15b of the outer film 12 and the inner film 13 communicate with each other, gas can permeate through these

fine holes

15a and 15b and the voids or voids of the ultrathin film 14.
[0025]
Example 3
In Example 2, instead of the outer film 12 and the inner film 13 in which the fine holes 15 are formed, a similar outer film 12 and the inner film 13 in which the fine holes 15 are not formed are overlapped. Melt perforation from the film 13 side with a hot needle or the like to form an infinite number of micropores 15 whose one surface is closed while leaving an extremely thin film portion 14 of about 5 μm in the vicinity of the surface to form a transparent gas permeable film 3 as shown in FIG. Obtained. As shown in FIG. 3, the gas permeable film 3 forms a composite film in which an outer film and an inner film are joined by heat fusion at a joint 17 near the peripheral edge of the fine holes 15.
[0026]
The entire surface of the above-mentioned hot needle roll or hot protrusion squeezing roll is heated, and this heat not only causes the periphery of the needle or protrusion to be heat-sealed, but also causes the outer film and the inner film to adhere to each other even in a flat portion, so that mild It is thought that the watertightness between the two films is maintained by fusing to the films. Further, in Examples 2 and 3, the case where the outer film 12 and the inner film 13 are one single or laminated film is shown, but the present invention is not limited to this, and any one of the outer film 12 and the inner film 13 is used. Any one of them may be a single film or a plurality of laminated films.
[0027]
Example 4
The diameter of the gas permeable film 3 is about 1 to 2 mm instead of the fine hole 15 having a diameter of about 0.4 mm by performing melt perforation while changing the thickness of the thermal needle in Example 3. The transparent gas permeable film 4 in which the water-permeable holes 16 are scattered was obtained. FIG. 4 shows the gas permeable film 4 in a state where a part of the outer film 12 is peeled off. A thin arrow indicates a gas permeation state, and a thick arrow indicates a moisture permeation state.
[0028]
Usage example 1
Using the gas permeable films 1 to 3 of Examples 1 to 3, bags of 10 cm × 14 cm were prepared. Each gas permeable film is bent so that the opening surface of the fine holes 15 is on the inside, and the periphery thereof is heat-sealed to form bags which are opened in one direction. Sealed. As a comparative example, a similar bag was prepared using a non-porous biaxially stretched polystyrene (OPS) film having a thickness of 50 μm instead of the gas permeable films 1 to 3 described above. As a result of observing 24 hours after enclosing the coffee powder, any one using gas permeable films 1 to 3 hardly changed in state immediately after enclosing the coffee powder, and the scent of coffee leaked to the outside As a result, gas permeability was confirmed. On the other hand, in the comparative example, the bag was inflated by the gas filled inside, and did not return to the original state even when compressed by hand, so that it was confirmed that there was almost no gas permeability.
[0029]
Usage example 2
Extraction bags (tea bags) were prepared with the gas permeable film 4 of Example 4, green tea and Chinese herbal medicine were put in each extraction bag, sealed, and the outer film was peeled off and immersed in hot water. Extracts obtained by extracting the respective extracts were obtained in the same manner as in the tea bag. Further, the extraction degree can be adjusted by changing the size and the number of the fine holes. Next, the naphthalene-based insect repellent is sealed in the same bag, and the outer film is peeled off, so that the emission of fragrance and odor can be increased, and any one can be selected and used according to preference.
[0030]
【The invention's effect】
The gas permeable film according to the present invention has a high gas permeability and strength through an ultrathin film portion formed partially in a step of perforating micropores in the film by being configured as described above. When packaging products that generate gas such as food, medicine, plants, miscellaneous goods, and other chemical products, the generated gas is permeated or replaced to the outside, and conventional fungi such as natto and mushrooms In addition to the effect of introducing the air required for breathing to improve the keeping of the sun, maintain the freshness and prolong the expiration date, if it is used for tea or herbal medicine extraction bags (tea bags etc.), In addition to preventing the intrusion of dust, foreign matter, moisture and the like from the outside, the outer film is peeled off and immersed in hot water to extract the contents, which is convenient. In addition, since it is not necessary to use a solvent-based adhesive for bonding, it is hygienic and safe, and is suitable as a food packaging material. It is also a novel use as a packaging material for adjusting the vaporization of fragrances and insect repellents, and has great potential. Furthermore, it does not undergo any chemical deterioration, and is combined with a multi-layer film having good heat sealing properties to help improve packaging workability, and is economical and excellent in versatility.
[Brief description of the drawings]
FIG. 1 is an enlarged longitudinal sectional view of a gas permeable film according to Example 1.
FIG. 2 is an enlarged longitudinal sectional view of a gas permeable film according to Example 2.
FIG. 3 is an enlarged longitudinal sectional view of a gas permeable film according to Example 3.
FIG. 4 is an enlarged longitudinal sectional view showing a state in which a part of an outer film of a gas permeable film according to Example 4 is peeled off.
[Explanation of symbols]
1: gas permeable film according to Example 1, 2: gas permeable film according to Example 2, 3: gas permeable film according to Example 3, 4: gas permeable film according to Example 4,
11: thermoplastic resin film, 11a: polystyrene layer, 11b: polyethylene layer, 11c: heat-sealable polyester layer, 12: outer film, 13: inner film, 14: extremely thin film part, 15: micropore, 15a: outer Film fine hole, 15b: Inner film fine hole, 16: Water-permeable hole, 17: Joint, 18a, 18b: Adhesive resin layer

Claims

By perforating the thermoplastic resin film having gas permeability in the thickness direction except for the ultra-thin film portion near the surface, innumerable micropores whose one end is closed by the ultra-thin film portion are scattered at appropriate intervals. A gas permeable film, characterized by being formed by:

By perforating the thermoplastic resin film having gas permeability in the thickness direction except for the ultra-thin film portion near the surface, innumerable micropores whose one end is closed by the ultra-thin film portion are scattered at appropriate intervals. An outer film made of a gas permeable film, characterized by being formed, and an inner film made of a thermoplastic resin having a myriad of fine holes penetrating the film, and an inner film formed on the surface where the fine holes of the outer film are opened. Gas permeation characterized in that both surfaces of the film are opposed to each other, and both films are attached so that all or a part of opposed fine holes formed in each of the films communicate with each other. Film.

By laminating an inner film made of a thermoplastic resin and an outer film made of a thermoplastic resin having gas permeability, through-piercing the outer film and the inner film in the thickness direction except for an extremely thin portion near the surface of the outer film. A gas characterized in that innumerable micropores, one end of which is closed by the ultra-thin film portion, are scattered at appropriate intervals, and an outer film and an inner film are joined in the vicinity of a peripheral portion of the micropores. Permeable film.

4. A gas-permeable film, wherein the thermoplastic resin film according to claim 1 comprises a two-layer or multilayer film.

The gas permeable film according to any one of claims 1 to 3, wherein the ultra-thin film portion has a thickness in a range of 1 to 20 µm.

A composite film in which the inner film constituting the gas permeable film is provided with fine holes so that water can pass therethrough, and the inner film and the outer film can be easily separated by hand, and the inner film and the outer film are laminated. 4. The gas-permeable film according to claim 2, wherein the film functions as a water-tight and gas-permeable film, and the remaining inner film from which the outer film has been peeled functions as a water-permeable film.