JP4731699B2

JP4731699B2 - Thermal fusion film and package comprising the same

Info

Publication number: JP4731699B2
Application number: JP2001040808A
Authority: JP
Inventors: 栄一田口
Original assignee: Mitsui Chemicals Tohcello Inc
Current assignee: Mitsui Chemicals Tohcello Inc
Priority date: 2001-02-16
Filing date: 2001-02-16
Publication date: 2011-07-27
Anticipated expiration: 2021-02-16
Also published as: JP2002241716A

Description

【０００１】
【発明の技術分野】
本発明は、低密度ポリエチレン組成物からなる易剥離性、開封時のソフト感、耐ブロッキング性、衛生性、製膜加工性、ラミネート加工性に優れた熱融着層を備えた熱融着フィルム、かかる熱融着フィルムからなる蓋材及びそれを用いた包装体に関する。
【０００２】
【発明の技術的背景】
せんべい、ポテトチップス等のスナック菓子包装、あるいはゼリー、ミルク、ヨーグルト、プリン、とうふ、乳酸飲料等の食品包装や、ブリスター包装、その他日用品や雑貨等の包装として、ボトル、カップ、ないしトレー状のプラスチック容器をプラスチックラミネートフィルムないしアルミ箔ラミネートフィルムからなる蓋材でシールした包装が広く採用されている。このような包装に要求されることは、流通経路に耐える機械的な強度、衛生性の保持ができるシール強度および使用時における開封性の良さである。
【０００３】
そのような包装に使われる資材の一つとして、一方を易開封性（イージーピール性）フィルムと呼ばれる範疇のフィルムを、最内層である熱融着層とした袋に、あるいは蓋材に用いた包装体が広く利用されている。しかし、これまで提案されている各種の熱融着層は、密封するためのヒートシール強度は高いが、開封時のイージーピール性は必ずしも十分ではなく、両者の間に適度なバランスをとることが求められている。ここでイージーピール性に求められている特性は、単に開封性の容易さのみならず、開封後に開封部に糸引き現象等による樹脂断片の付着残留物がなく、開封部の外観の良さをも含めた総合評価であり、それによってその良否が判定されている。
【０００４】
かかる欠点を解決する手段として、エチレン−ビニルエステル共重合体、低結晶性または非晶性のエチレン共重合体と粘着付与剤とからなるヒートシール性樹脂組成物（特公昭６３−２９８９４号公報）、低密度ポリエチレンとポリブテン−１からなる層を用いる易開封性複合フィルム（特開平１０−３３７８２９号公報）、エチレン−αオレフィン共重合体、プロピレン−エチレン共重合体及び低密度ポリエチレンからなる易開封性ヒートシール用樹脂組成物（特開平２−１８５５４７号公報）等種々提案されている。
【０００５】
しかしながら、低密度ポリエチレンをラミネートした紙容器の蓋材に、かかる構成のシール材を用いても見かけ上の密封シールをすることは可能であるが、容器表面にラミネートした低密度ポリエチレンと完全シ−ルとなり、開封した場合に紙容器の低密度ポリエチレンが剥離して紙剥けした状態で、強い強度で剥離してしまう傾向が強く、開封強度、見栄えで良くない虞がある。特に、紙くず等が内容物に落下したりして、内容物と一緒に食べてしまう可能性があったり、容器が変形して内容物がこぼれてしまう可能性がある。
【０００６】
【発明が解決しようとする課題】
本発明は、耐ブロッキング性、ソフトな開封性、衛生性、加工性に優れ、低密度ポリエチレン層からなる熱シール層と熱融着した際の熱融着強度の温度依存性が小さく、輸送時等には被包装物が漏れ出る虞がない熱融着強度を有しながら被包装物を取出す際には、容易に剥離し、剥離時にソフトで紙容器表面にコ−ト・押出しされた低密度ポリエチレンとの間で糸引き等が無く、綺麗な凝集剥離・界面剥離・層間剥離等で剥離するフィルム及び包装体を得るべく、又、夏場の気候のような場合に気温が３０℃以上の時、あるいは流通時・倉庫保管時で５０〜６０℃程度の高温時における保管時においてもシ−ル部、特に容器の段差と蓋材シ−ルの部分でのエアリ−ク・パンクしない耐熱性があり、つまり容器としての封緘性に優れている易開封性可能な熱融着フィルム及び包装体を得るべく、種々検討した。
【０００７】
【課題を解決するための手段】
【発明の概要】
本発明は、低密度ポリエチレン（A）９９〜５５重量％とプロピレン重合体（B）１〜４５重量％の低密度ポリエチレン組成物（C）からなる熱融着層を有することを特徴とする熱融着フィルム、それを用いた易開封性包装材料、容器蓋材及び相対する面が、低密度ポリエチレン（A）９９〜５５重量％とプロピレン重合体（B）１〜４５重量％の低密度ポリエチレン組成物（C）からなる熱融着層と低密度ポリエチレン層からなる熱シール層を備えたことを特徴とする包装体に関する。
【０００８】
【発明の具体的説明】
低密度ポリエチレン（Ａ）
本発明に係わる低密度ポリエチレン（A）は、通常、密度が０．９０５〜０．９３５ｇ／ｃｍ^３、好ましくは０．９１０〜０．９３５ｇ／ｃｍ^３、ＭＦＲ（ＡＳＴＭＤ１２３８荷重２１６０ｇ、温度１９０℃）が０．５〜３０ｇ／１０分、好ましくは１〜１０ｇ／１０分の高圧下で重合されるエチレンの単独重合体、若しくは５重量％以下の、他のα−オレフィンあるいは酢酸ビニル等のビニル化合物との共重合体で、通常高圧法低密度ポリエチレンと呼ばれている低密度ポリエチレン、及びエチレンと炭素数が３〜１０のα−オレフィン、例えばプロピレン、ブテン−１、ヘプテン−１、ヘキセン−１、オクテン−１、４−メチル−ペンテン−１とのランダム共重合体で、分子量分布（重量平均分子量：Ｍｗ、と数平均分子量：Ｍｎ、との比：Ｍｗ／Ｍｎで表示）が通常１．５〜４．０、好ましくは１．８〜３．５の範囲にある、通常、直鎖状低密度ポリエチレン（ＬＬＤＰＥ）と呼ばれているエチレン・α―オレフィンランダム共重合体等である。これらの中でも高圧法低密度ポリエチレンが熱融着層に用いた場合に、低温シ−ル性に優れ、しかも熱融着面を剥離した際に、凝集剥離を起こし、且つ剥離面での糸引きが生ぜず綺麗な剥離面が得られるので好ましい。
【０００９】
プロピレン重合体（ B ）
本発明に係わるプロピレン重合体（B）は、一般にポリプロピレンの名称で製造・販売されている樹脂で、通常、密度が０．８９０〜０．９３０ｇ／ｃｍ^３、ＭＦＲ（ＡＳＴＭＤ１２３８荷重２１６０ｇ、温度２３０℃）が０．５〜６０ｇ／１０分、好ましくは０．５〜１０ｇ／１０分のプロピレンの単独重合体若しくはプロピレンと他の少量のα−オレフィン、例えばエチレン、ブテン、ヘキセン−１等とのランダムあるいはブロック共重合体である。
【００１０】
低密度ポリエチレン組成物（ C ）
本発明に係わる低密度ポリエチレン組成物（C）は、前記、低密度ポリエチレン（A）が９９〜５５重量％、好ましくは９８〜６０重量％とプロピレン重合体（B）が１〜４５重量％、好ましくは２〜４０重量％とからなり、通常、ＭＦＲ（ＡＳＴＭＤ１２３８荷重２１６０ｇ、温度１９０℃）が０．１〜２０ｇ／１０分、好ましくは０．５〜１０ｇ／１０分の範囲にある。プロピレン重合体（B）の量が１重量％未満では低密度ポリエチレン層と熱融着した際に、ヒートシール強度が強くなり過ぎて易剥離性に劣る傾向にあり、一方４５重量％を越えると低温ヒートシール性、開封強度・実用上での封緘性・密封性（耐熱性）に劣る傾向にある。
【００１１】
又、本発明に係わる低密度ポリエチレン（A）、プロピレン重合体（B）あるいはその低密度ポリエチレン組成物（Ｃ）には、本発明の目的を損なわない範囲で、通常用いられる酸化防止剤、耐候安定剤、帯電防止剤、防曇剤等の添加剤を必要に応じて配合することができる。特に、アンチブロッキング剤、スリップ剤を配合することによって、フィルム成形時、ラミネート加工時、包装作業時等における加工性や作業性を向上させることができる。
【００１２】
熱融着フィルム
本発明に係わる熱融着フィルムは種々公知の方法で製造できる。例えば、低密度ポリエチレン（A）とプロピレン重合体（B）とを所定の量で混合した後、直接フィルム成形機に投入してＴ−ダイ、環状ダイ等を用いてフィルムにする方法、予め低密度ポリエチレン（A）、プロピレン重合体（B）とを所定の量で混合して押出機等で溶融混練して低密度ポリエチレン組成物（C）を得た後、Ｔ−ダイ、環状ダイ等を用いてフィルム成形する方法が例示できる。熱融着フィルムは単層でも用いられるが、補強層として上記低密度ポリエチレンを始め、中密度ポリエチレン、高密度ポリエチレン、ポリブテン、エチレン・酢酸ビニル共重合体等のオレフィン系重合体あるいは後述の熱可塑性樹脂からなる補強材との積層フィルムを得る場合には、熱融着層となる低密度ポリエチレン組成物（C）と補強層に用いる樹脂とを多層ダイを用いて共押出し熱融着フィルムとしても良い。又、予め得られた補強材に低密度ポリエチレン組成物（C）を押出しラミネートあるいは押出しコーティングして熱融着層を有する積層体としても良いし、あるいは夫々別個に得たフィルムを貼り合せて熱融着層を有する積層体としても良い。又、蓋材として用いる場合は、前記製法で得た熱融着層を備えた単層あるいは積層フィルム若しくはシート状の積層体をそのまま蓋材として用いても良いし、印刷して用いても良い。更に印刷されたあるいはされていない紙、アルミ箔等と貼り合せて蓋材にしても良い。又、用途によっては予め容器形状に合わせてカットして蓋材にしても良い。
【００１３】
熱融着フィルムの厚さは、用途に応じて適宜決め得るが、通常、通常１〜１０００μｍ、好ましくは２〜１００μｍの範囲にある。熱融着フィルムを単層フィルムとして用いる場合は、成形加工上、５μｍ以上の厚さが必要であるが、熱融着フィルムを補強層との積層体として用い得る場合は、熱融着層を１μｍと薄くしても優れたシール特性を発揮できる。
【００１４】
基材層
本発明に係わる熱融着層に積層される基材層としては、たとえば、ポリエチレンテレフタレートに代表されるポリエステルフィルム、ポリアミドフィルム、ポリプロピレンフィルム等の熱可塑性樹脂製フィルム、アルミニューム箔、紙等が挙げられる。かかる熱可塑性樹脂製フィルムからなる補強材は無延伸であっても一軸あるいは二軸延伸フィルムあるいはシ−ト等のあらゆる基材であっても良い。勿論、基材層は１層でも２層以上としても良い。
【００１５】
熱シール層
本発明に係わる熱シール層は、被包装材料に合わせて低密度ポリエチレンを公知の方法でフィルム、シート、トレー、カップ、ボトル等の種々の形状とすることができる。フィルム若しくはシートの場合は、上記熱融着フィルムと同様な方法で製造し得る。トレー若しくはカップの場合は、一旦上記方法でシートを製造した後、真空成形、圧空成形等の熱成形によりトレー、カップ等の容器とすることにより製造し得る。又、カップあるいはボトルの場合は射出成形、射出中空成形（インジェクションブロー）、中空成形等により容器として成形し得る。更に用途によっては紙等の上記補強材に低密度ポリエチレンを押出しラミネートあるいは押出しコーティング等により積層してもよい。かかる低密度ポリエチレンは、熱融着フィルムに用いる低密度ポリエチレン（A）と同一の範疇のものであるが、個々の物性は同一であっても異なっていてもよい。
【００１６】
容器蓋材
本発明の易開封性包装体に係わる容器蓋材は、前記熱融着フィルムを最内層としてなる。容器蓋材とする場合には、通常前記熱融着フィルムに基材層として例示される種々材料が積層される。
【００１７】
容器
本発明の易開封性包装体に係わる容器は、前記低密度ポリエチレンからなる熱シール層を最内層としてなる。容器とする場合は、通常低密度ポリエチレンからなる熱シール層に例えば紙等の基材層として積層される材料が積層される。容器はシート、トレー、カップ、ボトル等の形状が例示できるがそれらに限定はされない。
【００１８】
【実施例】
次に実施例を挙げて本発明を更に具体的に説明するが、本発明はその要旨を越えない限りこれらの実施例に制約されるものではない。
【００１９】
実施例及び比較例で使用した原料は次の通りである。
（１）低密度ポリエチレン：ＬＤＰＥ（高圧法低密度ポリエチレン）：
三井化学社製（商品名；ミラソン、銘柄名；Ｍ１２Ｐ）
密度０．９２７ｇ／ｃｍ³、ＭＦＲ３．０ｇ／１０分、融点１１４℃
（２）プロピレン重合体−１（ＰＰ−１）
エチレン含量３モル％・ブテン含量１．６モル％のプロピレンランダム共重合体：
密度０．９０ｇ／ｃｍ³、ＭＦＲ７．０ｇ／１０分、融点１３８℃
（３）プロピレン重合体−２（ＰＰ−２）
プロピレン単独重合体：
密度０．９１ｇ／ｃｍ³、ＭＦＲ７．０ｇ／１０分、融点１６１℃
（４）プロピレン重合体−３（ＰＰ−３）
プロピレン単独重合体：
密度０．９１ｇ／ｃｍ³、ＭＦＲ２．０ｇ／１０分、融点１６０℃
（５）エチレン重合体−１（シングルサイト触媒重合直鎖状低密度ポリエチレン）：
三井化学社製（商品名；エボリュー、銘柄名；ＳＰ２５４０）
密度０．９２５ｇ／ｃｍ³、ＭＦＲ４ｇ／１０分、融点１２０℃
（６）エチレン重合体−２（直鎖状低密度ポリエチレン）
三井化学社製（商品名；ウルトゼックス、銘柄名；ＵＺ３５２３Ｌ）
密度０．９３５ｇ／ｃｍ³、ＭＦＲ２．１ｇ／１０分、融点１２３℃
【００２０】
実施例１
熱融着層となるＬＤＰＥ：９７重量％とＰＰ―１：３重量％をドライブレンドした低密度ポリエチレン組成物と、基材層となるエチレン重合体（エチレン重合体−１：エチレン重合体−２＝３０重量％：７０重量％を混合したもの）を別々の押出機に供給し、Ｔダイ法によって熱融着層／基材層なる構成の２層共押出フイルムからなる熱融着フィルムを得た。フィルムの総厚は３０μｍで、各層の厚みは熱融着層：補強層＝４：２６μｍであった。
【００２１】
実施例２
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９５重量％とＰＰ―１：５重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２２】
実施例３
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９０重量％とＰＰ―１：１０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２３】
実施例４
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：８０重量％とＰＰ―１：２０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２４】
実施例５
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：７０重量％とＰＰ―１：３０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２５】
実施例６
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：６０重量％とＰＰ―１：４０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２６】
実施例７
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９７重量％とＰＰ―２：３重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２７】
実施例８
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９５重量％とＰＰ―２：５重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２８】
実施例９
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９０重量％とＰＰ―２：１０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００２９】
実施例１０
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９７重量％とＰＰ―３：３重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００３０】
実施例１１
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９５重量％とＰＰ―３：５重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００３１】
実施例１２
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：９０重量％とＰＰ―３：１０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００３２】
比較例１
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥを用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００３３】
比較例２
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：５０重量％とＰＰ―１：５０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００３４】
比較例３
実施例１で用いた低密度ポリエチレン組成物に代えて、ＬＤＰＥ：３０重量％とＰＰ―１：７０重量％をドライブレンドした低密度ポリエチレン組成物を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
【００３５】
比較例４
実施例１で用いた低密度ポリエチレン組成物に代えて、ＰＰ―１を用いる以外は実施例１と同様に行い、熱融着層：基材層＝４：２６μｍの熱融着フィルムを得た。
各実施例、比較例及び参考例で得られたフィルムの特性値は以下の方法で測定した。
【００３６】
実施例１３
実施例１で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００３７】
実施例１４
実施例２で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００３８】
実施例１５
実施例３で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００３９】
実施例１６
実施例７で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００４０】
実施例１７
実施例８で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００４１】
実施例１８
実施例９で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００４２】
実施例１９
実施例１０で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００４３】
実施例２０
実施例１１で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００４４】
実施例１３
実施例１２で用いたのと同じ構成で、熱融着フィルム層の厚さのみを代えて、熱融着層：基材層＝６．６：４３．４μｍの熱融着フィルムを得た。
【００４５】
（１）ヒ−トシ−ル性の評価：
▲１▼積層フィルム：
厚さ１２μｍの二軸延伸ポリエチレンテレフタレ−トフィルム（ＰＥＴ）に、上記各実施例および比較例で得られた熱融着フィルムの基材層とをウレタン系接着剤を用いてドライラミネ−ションにより積層して、積層フィルムとした。
▲２▼被着体：
前記積層フィルムと熱融着（ヒートシール）する被着体は、以下の種類の被着体を用いた。
ａ．厚さ１２μｍの二軸延伸ポリエチレンテレフタレ−トフィルム（ＰＥＴ）に被着層として、厚さ２０μｍの高圧法低密度ポリエチレン（密度：０．９２３ｇ／ｃｍ³）を押出ラミネ−トした積層フィルム。
ｂ．厚さ１５μｍの二軸延伸ポリアミドフィルム（Ｏ−ＮＹ）に被着層として、厚さ５０μｍの直鎖状低密度ポリエチレン（密度：０．９１５ｇ／ｃｍ³）を押出ラミネ−トした積層フィルム。
ｃ．厚さ３００μｍのポリプロピレンシ−ト。
ｄ．積層フィルム。
▲３▼ヒートシール試験：
１）上記積層フィルムの熱融着層面と上記各被着体の被着層面を重ね合せ、所定の温度で、幅５ｍｍのシールバーを用い、０．２ＭＰａの圧力で１秒間シールした後放冷した。これから１５ｍｍ幅の試験片を切り取りクロスヘッド速度５００ｍｍ／ｍｉｎでヒートシール部を剥離し、その強度をヒートシール強度とした。
耐熱水処理後の適正は上記方法でヒートシールした試験片を９０℃の熱水中で１日間放置した冷却したのち自然乾燥し、上記方法でヒートシール強度を測定した。
２）被着体ａ．との評価は、凝集剥離を○、界面剥離を△、完全ヒ−トシ−ルされているものを×、糸引きがあり層間剥離傾向のあるものを□とした。強度的には、１〜１０N／１５ｍｍの範囲にあり、凝集剥離するものが適している。
３）被着体ｂ．との評価は、凝集剥離を○、界面剥離を△、完全ヒ−トシ−ルされているものを×とした。
４）被着体ｃ．との評価は、凝集剥離を○、界面剥離を△とした。
５）被着体ｄ．との評価は、凝集剥離を○、界面剥離を△、完全ヒ−トシ−ルされているものを×とした。
【００４６】
（２）容器との封緘性及び開封性の評価
▲１▼包装体の調整：
内面に高圧法低密度ポリエチレンがラミネートされた紙基材製容器〔東罐興業株式会社製：タイプＡＣ−４３０ＥＰ（無地）〕と上記各実施例及び比較例で得た熱融着フィルムとを、エ−シンパック工業株式会社製のエ−シンパックシ−ラ半自動Ｏ型タイプを用いて、温度１８０℃、１容器に対してのヒ−トシ−ル実圧力９００Ｎ、シ−ル時間１秒で口部を熱融着（カップシ−ル）した。
▲２▼封緘性の評価：
株式会社サン科学製のシ−ルテスタ−ＦＫＴタイプを用い、上記調整法で得た包装体の破裂強度を測定した。尚、破裂強度試験は熱処理しない容器及び６０℃のオ−ブンで２４時間熱処理した後、２３℃・相対湿度６５％の雰囲気下で２４時間放置後の熱処理した容器で行った。
封緘性の評価は、熱処理しない容器と熱処理した容器との破裂強度の低下が３ＭＰａ以下で且つ熱処理後の破裂強度が１２ＭＰａ以上のものを◎、熱処理後の破裂強度が１０ＭＰａを越えるものを○、熱処理後の破裂強度が１０ＭＰａ前後のものを△、熱処理後の破裂強度が１０ＭＰａ未満のものを×とした。
▲３▼開封性の評価：
破裂強度を測定したサンプルを用いて、手で熱融着フィルムを剥離し、以下の基準で開封性を評価した。
ａ．開封強度：
ホットメルト材でシールされたスナック容器（市販品）の開封強度と比較して、同程度のもの：◎、少し弱めのもの：○、弱めなもの：△、弱いもの：×、強いもの：××とした。
ｂ．開封時の糸引き：
糸引きなし：◎、微量あり：○、少しあり：△、多数あり：×
ｃ．紙剥け：
熱融着フィルムを紙基材製容器から剥離した際に、紙の内面にラミネートされた高圧法低密度ポリエチレンと紙とが剥離する現象を紙剥けと称し、それぞれ、紙剥けなし：◎、微量あり：○、容器開封部の１／４未満に紙剥けあり：△、容器開封部の１／４以上の紙剥けあり：×として評価した。
【００４７】
各実施例、比較例及び参考例で得られたフィルムの特性値を表１及び表２に示す。
【００４８】
【表１】

【００４９】
【表２】

【００５０】
【表３】

【００５１】
【発明の効果】
本発明の熱融着フィルムは、低密度ポリエチレンとプロピレン重合体との組成物とが特定の割合で混合された熱融着層を有する熱融着フィルムである。かかる熱融着フィルムを用いて当該フィルムを熱融着層とした包装袋等の包装材、あるいは被着材である各種ポリエチレン、ポリプロピレンを用いた包装材は、被包装物を包装する際に、低温ヒ−トシ−ル性（低温熱融着性）があり、ヒ−トシ−ル温度幅も広く、又、得られた包装体を、ボイル処理した際にもヒートシール（熱融着）部の強度の変化も少なく、且つ適度なヒートシール強度を有しているので、開封時にはソフトに容易に開封できるという特性を有している。又、本発明の熱融着フィルムはブロキング性にも優れているので加工時の粉振り加工が不要で、ラミネート品のエ−ジング温度を一般のフィルム並以下に低くすることも必要なく、そのまま包装材料に加工することができる。
【００５２】
本発明の蓋材を用いた紙容器は、熱融着強度の温度依存性が小さく、輸送時等には被包装物が漏れ出る虞がない熱融着強度を有しながら、被包装物を取出す際には容易に剥離し、剥離時にソフトで紙容器表面の低密度ポリエチレン層との間で糸引き等が無く、且つ紙剥けの発生がなく、綺麗な凝集剥離で剥離する。又、夏場の気候のような場合に気温が３０℃以上、あるいは流通時・倉庫保管時での５０〜６０℃程度の高温下における保管時にもシ−ル部、特に容器の段差と蓋材シ−ルの部分での空気漏れ、あるいはパンクしない耐熱性、つまり容器としての封緘性に優れているという特徴を有している。
【００５３】
かかる特徴を活かして、本発明の熱融着フィルム、易開封性包装材料、容器蓋材あるいはこれら材料を用いた容器等の包装体は、広く各種のヨ−グルト、プリン、ゼリ−、スナック、麺などの紙ポリ容器の食品包装やブリスタ−包装、その他日用品や雑貨等の袋物包装、ボトル、カップ、ないしトレ−のプラスチックス容器などのシ−ル材等の包装体として好適に利用することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a heat-sealing film comprising a heat-sealing layer comprising a low-density polyethylene composition, easy peelability, soft feeling at the time of opening, blocking resistance, hygiene, film forming workability, and laminate workability. The present invention also relates to a lid made of such a heat-sealing film and a package using the same.
[0002]
TECHNICAL BACKGROUND OF THE INVENTION
Packaging for snacks such as rice crackers, potato chips, etc., food packaging such as jelly, milk, yogurt, pudding, tofu, lactic acid beverages, blister packaging, and other daily necessities and miscellaneous goods packaging, bottles, cups or tray-like plastic containers Wrapped in a lid made of a plastic laminate film or aluminum foil laminate film is widely used. What is required for such packaging is mechanical strength that can withstand distribution channels, sealing strength that can maintain hygiene, and good openability during use.
[0003]
As one of the materials used for such packaging, one of them was used for a bag having a category called an easy-opening (easy peel) film as a heat-sealing layer as the innermost layer, or as a cover material. Packaging is widely used. However, various heat-sealing layers proposed so far have high heat-sealing strength for sealing, but easy peelability at the time of opening is not always sufficient, and an appropriate balance between them can be obtained. It has been demanded. Here, the characteristics required for easy peelability are not only ease of opening, but also there is no residue of resin fragments adhering to the opening after opening due to stringing, etc., and the appearance of the opening is good. It is comprehensive evaluation including, and the quality is judged by it.
[0004]
As a means for solving this drawback, a heat-sealable resin composition comprising an ethylene-vinyl ester copolymer, a low crystalline or amorphous ethylene copolymer and a tackifier (Japanese Patent Publication No. 63-29894) , An easy-open composite film using a layer composed of low-density polyethylene and polybutene-1 (Japanese Patent Laid-Open No. 10-337829), an easy-open film composed of an ethylene-α olefin copolymer, a propylene-ethylene copolymer and low-density polyethylene Various heat-sealable resin compositions (JP-A-2-185547) have been proposed.
[0005]
However, it is possible to provide an apparent hermetic seal to the lid of a paper container laminated with low-density polyethylene even if such a sealing material is used. When opened, the low-density polyethylene in the paper container is peeled off and the paper is peeled off, and there is a strong tendency to peel off with strong strength, and there is a possibility that the opening strength and appearance are not good. In particular, there is a possibility that waste paper or the like may fall on the contents and eat with the contents, or the container may be deformed and the contents may be spilled.
[0006]
[Problems to be solved by the invention]
The present invention is excellent in blocking resistance, soft openability, hygiene, and processability, and the temperature dependence of the heat-sealing strength when heat-sealing with a heat-seal layer made of a low-density polyethylene layer is small. For example, when taking out the package while having the heat-sealing strength that prevents the package from leaking out, it is easy to peel off and softly coated and extruded on the surface of the paper container at the time of peeling. In order to obtain a film and package that can be peeled off by density cohesive peeling, interfacial peeling, delamination, etc., without stringing, etc. with high density polyethylene. Heat resistance that does not cause air leak or puncture at the seal part, especially at the step of the container and the seal part of the lid, even during storage or storage at high temperatures of about 50-60 ° C. In other words, easy opening that has excellent sealing performance as a container To obtain a sexual possible heat-sealing film and package, were studied.
[0007]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION
The present invention comprises a heat-sealing layer comprising a low-density polyethylene (A) 99 to 55% by weight and a propylene polymer (B) 1 to 45% by weight of a low-density polyethylene composition (C). Fusing film, easy-open packaging material using the same, container lid and low-density polyethylene (A) 99-55 wt% and propylene polymer (B) 1-45 wt% The present invention relates to a package comprising a heat sealing layer comprising a composition (C) and a heat sealing layer comprising a low density polyethylene layer.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Low density polyethylene (A)
The low density polyethylene (A) according to the present invention usually has a density of 0.905 to 0.935 g / cm ³ , preferably 0.910 to 0.935 g / cm ³ , MFR (ASTM D1238 load 2160 g, temperature 190 ° C. ) Is a homopolymer of ethylene that is polymerized under a high pressure of 0.5 to 30 g / 10 minutes, preferably 1 to 10 g / 10 minutes, or other α-olefin or vinyl acetate such as vinyl acetate having a content of 5% by weight or less. A low-density polyethylene which is a copolymer with a compound and is usually called a high-pressure low-density polyethylene, and ethylene and an α-olefin having 3 to 10 carbon atoms, such as propylene, butene-1, heptene-1, hexene 1, random copolymer with octene-1,4-methyl-pentene-1, molecular weight distribution (weight average molecular weight: Mw, number average molecular weight: Mn, and Ratio (expressed in Mw / Mn) is usually in the range of 1.5 to 4.0, preferably 1.8 to 3.5, and is usually referred to as linear low density polyethylene (LLDPE). α-olefin random copolymer. Among these, when high-pressure low-density polyethylene is used for the heat-sealing layer, it has excellent low-temperature sealing properties, and when the heat-sealing surface is peeled off, it causes cohesive peeling and stringing on the peeling surface. This is preferable because a beautiful peeled surface can be obtained.
[0009]
Propylene polymer ( B )
The propylene polymer (B) according to the present invention is a resin that is generally produced and sold under the name of polypropylene, and usually has a density of 0.890 to 0.930 g / cm ³ , MFR (ASTM D1238 load 2160 g, temperature 230). ° C) of 0.5 to 60 g / 10 min, preferably 0.5 to 10 g / 10 min of a propylene homopolymer or propylene and a small amount of other α-olefin such as ethylene, butene, hexene-1, etc. Random or block copolymer.
[0010]
Low density polyethylene composition ( C )
In the low density polyethylene composition (C) according to the present invention, the low density polyethylene (A) is 99 to 55% by weight, preferably 98 to 60% by weight and the propylene polymer (B) is 1 to 45% by weight, Preferably it consists of 2 to 40% by weight, and usually the MFR (ASTM D1238 load 2160 g, temperature 190 ° C.) is in the range of 0.1 to 20 g / 10 minutes, preferably 0.5 to 10 g / 10 minutes. When the amount of the propylene polymer (B) is less than 1% by weight, when heat-sealing with the low density polyethylene layer, the heat seal strength tends to be too strong and tends to be inferior in peelability, while when it exceeds 45% by weight. It tends to be inferior in low-temperature heat sealability, opening strength, practical sealing properties, and sealing properties (heat resistance).
[0011]
Further, the low density polyethylene (A), the propylene polymer (B) or the low density polyethylene composition (C) according to the present invention is not limited to the antioxidants and weather resistance that are usually used within the range not impairing the object of the present invention. Additives such as stabilizers, antistatic agents and antifogging agents can be blended as necessary. In particular, by blending an anti-blocking agent and a slip agent, workability and workability during film forming, laminating, packaging, etc. can be improved.
[0012]
Heat-sealing film The heat-sealing film according to the present invention can be produced by various known methods. For example, a method in which a low density polyethylene (A) and a propylene polymer (B) are mixed in a predetermined amount and then directly put into a film forming machine to form a film using a T-die, an annular die, etc. After the density polyethylene (A) and the propylene polymer (B) are mixed in a predetermined amount and melt kneaded with an extruder or the like to obtain a low density polyethylene composition (C), a T-die, a cyclic die, etc. A method for forming a film using the film can be exemplified. The heat-sealing film can be used as a single layer, but the olefinic polymer such as the above-mentioned low-density polyethylene, medium-density polyethylene, high-density polyethylene, polybutene, ethylene / vinyl acetate copolymer, etc. When a laminated film with a reinforcing material made of resin is obtained, a low-density polyethylene composition (C) that becomes a heat-sealing layer and a resin that is used for the reinforcing layer can be co-extruded using a multilayer die as a heat-sealing film good. Alternatively, the low-density polyethylene composition (C) may be extrusion laminated or extrusion coated on a previously obtained reinforcing material to form a laminate having a heat-sealing layer, or a film obtained separately may be bonded to heat. It is good also as a laminated body which has a melt | fusion layer. When used as a lid, a single layer or a laminated film or a sheet-like laminate provided with the heat-sealing layer obtained by the above production method may be used as a lid, or may be printed and used. . Further, it may be bonded to paper that is printed or not, aluminum foil, or the like to form a lid. Further, depending on the application, it may be cut in advance according to the shape of the container to form a lid.
[0013]
Although the thickness of a heat-fusion film can be suitably determined according to a use, it is usually 1-1000 micrometers normally, Preferably it exists in the range of 2-100 micrometers. When the heat-sealing film is used as a single-layer film, a thickness of 5 μm or more is necessary for molding. However, when the heat-sealing film can be used as a laminate with a reinforcing layer, the heat-sealing layer is used. Excellent sealing properties can be exhibited even when made as thin as 1 μm.
[0014]
Base material layer The base material layer laminated on the heat- sealing layer according to the present invention includes, for example, a film made of a thermoplastic resin such as a polyester film represented by polyethylene terephthalate, a polyamide film, a polypropylene film, and aluminum. Pneumatic foil, paper, etc. are mentioned. The reinforcing material made of such a thermoplastic resin film may be non-stretched or any substrate such as a uniaxial or biaxially stretched film or a sheet. Of course, the base material layer may be one layer or two or more layers.
[0015]
Heat-seal layer The heat-seal layer according to the present invention can be formed into various shapes such as a film, a sheet, a tray, a cup, and a bottle by a known method using low-density polyethylene in accordance with the material to be packaged. In the case of a film or a sheet, it can be produced by the same method as that for the heat fusion film. In the case of a tray or a cup, it can be produced by once producing a sheet by the above method and then forming a container such as a tray or a cup by thermoforming such as vacuum forming or pressure forming. In the case of a cup or bottle, it can be molded as a container by injection molding, injection hollow molding (injection blow), hollow molding or the like. Further, depending on the application, low density polyethylene may be laminated on the reinforcing material such as paper by extrusion lamination or extrusion coating. Such low-density polyethylene is in the same category as the low-density polyethylene (A) used for the heat-sealing film, but the individual physical properties may be the same or different.
[0016]
Container lid material The container lid material according to the easy-open packaging body of the present invention has the heat-sealing film as the innermost layer. When the container lid is used, various materials exemplified as a base material layer are usually laminated on the heat-sealing film.
[0017]
Container The container according to the easy-open packaging body of the present invention has the heat seal layer made of low-density polyethylene as the innermost layer. In the case of a container, a material to be laminated as a base material layer such as paper is laminated on a heat seal layer usually made of low density polyethylene. Examples of the container include, but are not limited to, a sheet, a tray, a cup, and a bottle.
[0018]
【Example】
EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist.
[0019]
The raw materials used in Examples and Comparative Examples are as follows.
(1) Low density polyethylene: LDPE (high pressure method low density polyethylene):
Made by Mitsui Chemicals (trade name; Mirason, brand name; M12P)
Density 0.927g / cm ³ , MFR 3.0g / 10min, melting point 114 ° C
(2) Propylene polymer-1 (PP-1)
Propylene random copolymer having an ethylene content of 3 mol% and a butene content of 1.6 mol%:
Density 0.90 g / cm ³ , MFR 7.0 g / 10 min, melting point 138 ° C.
(3) Propylene polymer-2 (PP-2)
Propylene homopolymer:
Density 0.91 g / cm ³ , MFR 7.0 g / 10 min, melting point 161 ° C.
(4) Propylene polymer-3 (PP-3)
Propylene homopolymer:
Density 0.91 g / cm ³ , MFR 2.0 g / 10 min, melting point 160 ° C.
(5) Ethylene polymer-1 (single site catalyst polymerization linear low density polyethylene):
Made by Mitsui Chemicals (trade name: Evolue, brand name: SP2540)
Density 0.925g / cm ³ , MFR 4g / 10min, melting point 120 ° C
(6) Ethylene polymer-2 (linear low density polyethylene)
Made by Mitsui Chemicals, Inc. (trade name; Ultzex, brand name; UZ3523L)
Density 0.935 g / cm ³ , MFR 2.1 g / 10 min, melting point 123 ° C.
[0020]
Example 1
LDPE as a heat-sealing layer: low-density polyethylene composition obtained by dry blending 97% by weight and PP-1: 3% by weight, and an ethylene polymer as a base layer (ethylene polymer-1: ethylene polymer-2) = 30 wt%: 70 wt% mixed) is supplied to separate extruders to obtain a heat-sealing film comprising a two-layer coextrusion film having a constitution of heat-sealing layer / base material layer by the T-die method. It was. The total thickness of the film was 30 μm, and the thickness of each layer was heat fusion layer: reinforcing layer = 4: 26 μm.
[0021]
Example 2
In place of the low density polyethylene composition used in Example 1, the same procedure as in Example 1 was used except that a low density polyethylene composition obtained by dry blending LDPE: 95% by weight and PP-1: 5% by weight was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0022]
Example 3
In place of the low density polyethylene composition used in Example 1, LDPE: 90% by weight and PP-1: 10% by weight were used in the same manner as in Example 1 except that a low density polyethylene composition dry-blended was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0023]
Example 4
In place of the low density polyethylene composition used in Example 1, LDPE: 80% by weight and PP-1: 20% by weight were used in the same manner as in Example 1 except that a low density polyethylene composition dry-blended was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0024]
Example 5
In place of the low density polyethylene composition used in Example 1, LDPE: 70% by weight and PP-1: 30% by weight were used in the same manner as in Example 1 except that a low density polyethylene composition dry-blended was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0025]
Example 6
In place of the low density polyethylene composition used in Example 1, the same procedure as in Example 1 was used except that a low density polyethylene composition obtained by dry blending LDPE: 60 wt% and PP-1: 40 wt% was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0026]
Example 7
In place of the low density polyethylene composition used in Example 1, a low density polyethylene composition obtained by dry blending 97% by weight of LDPE and 3% by weight of PP-2 was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0027]
Example 8
In place of the low density polyethylene composition used in Example 1, a low density polyethylene composition obtained by dry blending 95% by weight of LDPE and 5% by weight of PP-2 was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0028]
Example 9
In place of the low density polyethylene composition used in Example 1, a low density polyethylene composition obtained by dry blending 90% by weight of LDPE and 10% by weight of PP-2 was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0029]
Example 10
In place of the low density polyethylene composition used in Example 1, a low density polyethylene composition obtained by dry blending 97% by weight of LDPE and 3% by weight of PP-3 was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0030]
Example 11
In place of the low density polyethylene composition used in Example 1, a low density polyethylene composition obtained by dry blending LDPE: 95% by weight and PP-3: 5% by weight was used in the same manner as in Example 1, Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0031]
Example 12
In place of the low density polyethylene composition used in Example 1, a low density polyethylene composition obtained by dry blending 90% by weight of LDPE and 10% by weight of PP-3 was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0032]
Comparative Example 1
It replaced with the low density polyethylene composition used in Example 1, and carried out similarly to Example 1 except using LDPE, and obtained the heat sealing | fusion film of heat sealing | fusion layer: base material layer = 4:26 micrometers.
[0033]
Comparative Example 2
In place of the low density polyethylene composition used in Example 1, the same procedure as in Example 1 was used except that a low density polyethylene composition obtained by dry blending LDPE: 50% by weight and PP-1: 50% by weight was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0034]
Comparative Example 3
In place of the low density polyethylene composition used in Example 1, the same procedure as in Example 1 was used except that a low density polyethylene composition obtained by dry blending LDPE: 30% by weight and PP-1: 70% by weight was used. Fusing layer: base material layer = 4: A heat-sealing film having a thickness of 26 μm was obtained.
[0035]
Comparative Example 4
It replaced with the low density polyethylene composition used in Example 1, and carried out similarly to Example 1 except using PP-1, and obtained the heat sealing | fusion film of heat sealing | fusion layer: base material layer = 4:26 micrometers. .
The characteristic value of the film obtained by each Example, the comparative example, and the reference example was measured with the following method.
[0036]
Example 13
With the same configuration as used in Example 1, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0037]
Example 14
With the same configuration as that used in Example 2, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0038]
Example 15
With the same configuration as used in Example 3, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0039]
Example 16
With the same configuration as that used in Example 7, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0040]
Example 17
With the same configuration as that used in Example 8, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0041]
Example 18
With the same configuration as used in Example 9, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0042]
Example 19
With the same configuration as used in Example 10, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0043]
Example 20
With the same configuration as used in Example 11, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0044]
Example 13
With the same configuration as used in Example 12, only the thickness of the heat-sealing film layer was changed, and a heat-sealing film of heat-sealing layer: base material layer = 6.6: 43.4 μm was obtained.
[0045]
(1) Evaluation of heat sealability:
(1) Laminated film:
A 12 μm-thick biaxially stretched polyethylene terephthalate film (PET) is laminated by dry lamination using a urethane adhesive with the base material layer of the heat-sealed film obtained in each of the above Examples and Comparative Examples. Thus, a laminated film was obtained.
(2) Substrate:
The following types of adherends were used as adherends to be heat-sealed (heat sealed) with the laminated film.
a. A laminated film obtained by extrusion laminating high-pressure low-density polyethylene (density: 0.923 g / cm ³ ) having a thickness of 20 μm as a coating layer on a biaxially stretched polyethylene terephthalate film (PET) having a thickness of 12 μm.
b. A laminated film obtained by extrusion laminating a linear low density polyethylene (density: 0.915 g / cm ³ ) having a thickness of 50 μm as an adherent layer to a biaxially stretched polyamide film (O—NY) having a thickness of 15 μm.
c. A polypropylene sheet having a thickness of 300 μm.
d. Laminated film.
(3) Heat seal test:
1) The heat-sealable layer surface of the laminated film and the adherend layer surface of each adherend are overlaid, sealed at a predetermined temperature using a seal bar having a width of 5 mm and a pressure of 0.2 MPa for 1 second, and then allowed to cool. did. From this, a test piece having a width of 15 mm was cut, and the heat seal part was peeled off at a crosshead speed of 500 mm / min, and the strength was defined as the heat seal strength.
Appropriate after the heat-resistant water treatment, the test piece heat-sealed by the above method was left to stand in 90 ° C. hot water for 1 day, then naturally dried, and the heat seal strength was measured by the above method.
2) Substrate a. In the evaluation, the cohesive peeling was evaluated as “◯”, the interface peeling as “Δ”, the completely heat-sealed as “X”, and the thread peeling and the delamination tendency as “□”. In terms of strength, those that are in the range of 1 to 10 N / 15 mm and that peel off are suitable.
3) adherend b. In the evaluation, agglomerated exfoliation was evaluated as ◯, interfacial exfoliation as Δ, and complete heat sealed as x.
4) Adherent c. In the evaluation, agglomerated peeling was indicated by ◯, and interface peeling was indicated by △.
5) Substrate d. In the evaluation, agglomerated exfoliation was evaluated as ◯, interfacial exfoliation as Δ, and complete heat sealed as x.
[0046]
(2) Evaluation of sealability and openability with containers (1) Adjustment of package:
A paper base container (made by Toago Kogyo Co., Ltd .: type AC-430EP (plain fabric)) laminated with high-pressure low-density polyethylene on the inner surface and the heat-sealing film obtained in each of the above Examples and Comparative Examples, Using Ashin Pack Sealer semi-automatic O type manufactured by A Shin Pack Industry Co., Ltd., temperature 180 ° C, heat seal actual pressure 900N for 1 container, seal time 1 second. Was heat-sealed (cup seal).
(2) Evaluation of sealing property:
Using a seal tester-FKT type manufactured by San Kagaku Co., Ltd., the burst strength of the package obtained by the above adjustment method was measured. The burst strength test was carried out in a container that was not heat-treated and a heat-treated container that was heat-treated for 24 hours in an oven at 60 ° C. and then left for 24 hours in an atmosphere of 23 ° C. and 65% relative humidity.
The evaluation of sealing performance is ◎ when the burst strength decrease between the unheated container and the heat-treated container is 3 MPa or less and the burst strength after the heat treatment is 12 MPa or more, and the burst strength after the heat treatment exceeds 10 MPa. The case where the burst strength after heat treatment was around 10 MPa was indicated by Δ, and the case where the burst strength after heat treatment was less than 10 MPa was indicated by ×.
(3) Evaluation of openability:
Using the sample whose burst strength was measured, the heat-sealing film was peeled off by hand, and the openability was evaluated according to the following criteria.
a. Opening strength:
Compared to the opening strength of a snack container sealed with a hot-melt material (commercially available): ◎, slightly weak: ○, weak: △, weak: ×, strong: × X.
b. Threading when opened:
No stringing: ◎, trace amount: ○, slightly: △, many: ×
c. Paper peeling:
When the heat-sealing film is peeled from the paper base container, the phenomenon that the paper is peeled off from the high-pressure low-density polyethylene laminated on the inner surface of the paper is called paper peeling. Existence: ○, less than 1/4 of the container opening part was peeled off: Δ, more than 1/4 of the container opening part was peeled off: evaluated as x.
[0047]
Tables 1 and 2 show the characteristic values of the films obtained in the examples, comparative examples, and reference examples.
[0048]
[Table 1]

[0049]
[Table 2]

[0050]
[Table 3]

[0051]
【The invention's effect】
The heat-sealing film of the present invention is a heat-sealing film having a heat-sealing layer in which a composition of low-density polyethylene and a propylene polymer is mixed at a specific ratio. A packaging material such as a packaging bag having the film as a heat-sealing layer using such a heat-sealing film, or a packaging material using various polyethylene and polypropylene as adherends, It has a low temperature heat seal property (low temperature heat fusion property), a wide heat seal temperature range, and a heat seal (heat fusion) part even when the resulting package is boiled. There is little change in strength, and since it has an appropriate heat seal strength, it has a characteristic that it can be easily opened softly when opened. In addition, since the heat-sealing film of the present invention is also excellent in blocking properties, it is not necessary to shake the powder during processing, and it is not necessary to lower the aging temperature of the laminated product to the level of a general film or less. Can be processed into packaging materials.
[0052]
The paper container using the lid material of the present invention is less dependent on the temperature of the heat-sealing strength, and has a heat-sealing strength that prevents the material to be packaged from leaking during transportation, etc. It peels off easily when taken out, and is soft and free of stringing between the low-density polyethylene layer on the surface of the paper container at the time of peeling. In addition, when the temperature is 30 ° C or higher, such as in summer, or when storing at a high temperature of about 50-60 ° C during distribution or storage in a warehouse, the seal part, especially the step of the container and the cover material -It has the characteristic that it is excellent in heat leakage that does not puncture, or in other words, sealing performance as a container.
[0053]
Taking advantage of such characteristics, the heat-sealing film of the present invention, easy-open packaging materials, container lid materials or containers such as containers using these materials are widely used in various yogurts, puddings, jellies, snacks, It should be suitably used as packaging for food packaging such as paper plastic containers such as noodles, blister packaging, bag packaging such as daily necessities and miscellaneous goods, and seal materials such as bottles, cups, and plastic containers for trays. Can do.

Claims

Opposite surfaces are composed of a low-density polyethylene (A) 98 to 60 % by weight and a propylene polymer (B) 2 to 40 % by weight of a low-density polyethylene composition (C) and a heat-fused layer and a low-density polyethylene layer. A package comprising a heat seal layer.

Package of claim 1, wherein the low density polyethylene (A) is a high-pressure low-density polyethylene.

The package according to claim 1 or 2, comprising a container in which a lid provided with a heat-sealing layer comprising a low-density polyethylene composition (C) and a heat-sealing layer comprising a low-density polyethylene layer are laminated on a paper substrate. .