JPH0439423B2

JPH0439423B2 -

Info

Publication number: JPH0439423B2
Application number: JP12664984A
Authority: JP
Priority date: 1984-06-19
Filing date: 1984-06-19
Publication date: 1992-06-29
Also published as: JPS615942A

Description

[Detailed description of the invention]

Ａ本発明の技術分野本発明は、きわめてはげしい屈曲疲労にも、気
体遮断性の低下のないフレキシブル積層包装材に
関する。詳しくは酸素、炭酸ガスなどの気体遮断
性に優れるエチレン−酢酸ビニル共重合体けん化
物（以下EVOHと記す）の薄膜を中間層とし、
該中間層の両側に特定の、エチレン−不飽和カル
ボン酸またはその無水物変性のエチレン−酢酸ビ
ニル共重合体（以下EVA_Cと記す）または該特定
の変性EVA_Cと特定のEVA_Cとのブレンド物から
なる接着性樹脂を介して表面層を積層することに
よつて該包装材で包装された変質し易い物品の気
密包装体が輸送、取扱い時に該包装材が受けるき
わめてはげしい屈曲疲労に対しても、すぐれた気
体遮断性を保持することができる被包装物の変質
を防止するために有効な積層フレキシブル包装材
を提供するものである。Ｂ従来技術フレキシブル積層包装材の機能は基本的には、
被包装物の保存性、すなわち変質防止であり、そ
のために該包装材にあつては、特に輸送振動強
度、耐屈曲疲労性が要求され、就中所謂バツグイ
ンボツクス−折畳み可能なプラスチツクの薄肉内
容器と積み重ね性、持ち運び性、印刷適性を有す
る外装段ボール箱とを組合せた容器−の内容器と
して用いられる場合には、高度の該特性が要求さ
れる。該包装材は各種プラスチツクフイルムがそ
れぞれの素材を特性を活かして積層されて用いら
れるが、たとえば機械的強度を保持するための基
材フイルムと熱シール可能な素材との組合せが最
も一般的であり、被包装物の要謂に応じて素材が
選択される。就中、基材フイルムの酸素等の気体
遮断性では不満足な用途については、さらに高度
な気体遮断性を有するバリヤー層を基材層上に設
け、このバリヤー層を中間層としてヒートシール
可能な素材を少くとも一表面層となる如く熱可塑
性樹脂層を積層する方法が採用されている。たと
えば従来のバツグインボツクスの内容器の材質の
基本は、必ずヒートシール分があるのでヒートシ
ール可能なポリエチレン特に軟質ポリエチレンを
主体としているが、バツグインボツクスの特徴で
ある折り畳み可能であること、内容物が液体であ
ること等から物理的強度、前述の如く得に輸送振
動強度、耐屈曲疲労性が求められ、このために耐
ストレスクラツク性が良好であことと相俟つてエ
チレン−酢酸ビニル共重合樹脂がより好ましく用
いられている。最近要求性能の一層の高度化に伴
つて酸素等のガス遮断性が要求されるようにな
り、高度な該遮断性を付与するためにEVOH、
塩化ビニリデン、アルミ箔、金属などの蒸着フイ
ルムなどが用いられ始めている。しかしこれらは
該遮断性については優れているが、機械的強度は
一般に低く、得に屈曲疲労に耐え得るものではな
い。従つて機械的強度の優れた基材層とヒートシ
ール可能な素材の間に積層されて用いられるが、
なおたとえばバツグインボツクス内容器の構成材
として用いた場合、該構成材にピンホールを生じ
たり、該構成材にピンホールを生じない段階にお
いてさえ、中間層として用いた該バリヤー層に生
ずるクラツクやピンホール等に起因してパリヤー
性の低下を生ずるなどのため、はげしい屈曲疲労
に対してすぐれたガス遮断性を保持することがで
きず、実用的に満足なものは見出されていない。
すなわちポリ塩化ビニリデン樹脂を主体とする
層、アルミ箔、金属などの蒸着樹脂層などをバリ
ヤー層とする積層包装材の挙動はたとえば特開昭
55−7477号公報に示めされているが、実際に該包
装材を使用し包装された包装体の輸送、取扱い後
のガス遮断性が必ずしも満足できるものでなく、
最も必用性の高い一次流通後の実用保存性がしば
しば裏切られるのは中間層に位置する該バリヤー
層の損傷に起因している。ガス遮断性付与のため
に設ける中間層の素材としてはEVOH樹脂が最
も優れており、各種の多層フイルム、多層構造を
もつ容器のバリヤー材として好んで用いられる。
これはこの樹脂が抜群のバリヤー性を有するだけ
でなく、透明性、耐油性、印刷性、成形性などに
もすぐれていて、基材樹脂の特性を損うことがな
いというきわめて有利な性質をもつからである。
しかるに耐屈曲疲労性が特に要求される分野、就
中前述の如く輸送振動による屈曲疲労に耐えるこ
とが強く求められている酸素等のガス遮断性を有
するバツクインボツクスの内容器にEVOH樹脂
が用いられて該要求を満足するものは見出されて
おらず、EVOH層をバリヤー層とする優れたバ
リヤー性と輸送振動に耐える屈曲疲労強度をもつ
たフレキシブル積層包装材の開発は重要課題の一
つであつた。Ｃ本発明の目的、構成および作用効果本発明者らはEVOHフイルムは前記優れた諸
特性をもつている反面、ポリエチレン、ポリプロ
ピレン、ナイロン、熱可塑性ポリエステルなどの
熱可塑性フイルムに比べ、耐屈曲疲労性に著しく
劣るという大きな欠点を有するのみならず、前記
屈曲疲労に強い樹脂層と積層し、中間層として
EVOH樹脂層を用いた複層フレキシブル包装材
において予想外にもEVOHの剛性等の物理的特
性とも関連があるものとみられるが、該包装材の
耐屈曲疲労性は、前記屈曲疲労に強い熱可塑性樹
脂が単体で示す耐屈曲疲労性より顕著に低下し、
より少い屈曲疲労で積層包装材にピンホールを生
ずるようになること、該ピンホールの発生に至る
までは、該EVOH層が単独で耐え得る屈曲疲労
をこえてもなお屈曲疲労によるクラツク、ピンホ
ール等が該EVOH層に発生しないことに起因す
るとみられるが、バリヤー性の低下が殆んど認め
られない点で前記塩化ビニリデン樹脂等をバリヤ
ー層として中間層に用いた従来の積層包装材の挙
動と著しく異つていること、さらに従来全く見出
されていなかつた接着性樹脂の特性が耐屈曲疲労
性に極めて大きく関連している事実を見出し、該
観点からEVOH層をバリヤー層とする耐屈曲疲
労性に優れたフレキシブルな気体遮断性積層包装
材に関し鋭意検討を進めて本発明を完成するに至
つた。すなわち本発明はエチレン−酢酸ビニル共重合
体けん化物の薄膜を中間層とし、該中間層の両側
に表面層を有し該各層が接着性樹脂層を介して配
されてなるフレキシブル積層包装材において該接
着性樹脂が、酢酸ビニル含量が35重量％をこえて
55重量％以下のエチレン−酢酸ビニル共重合体
に、エチレン性不飽和カルボン酸またはその無水
物（Ｘ）を0.01〜15重量％以下化学的に結合させ
て得られる変性エチレン−酢酸ビニル共重合体で
ある高度な耐屈曲疲労性と気体遮断性を有するフ
レキシブル積層包装材、該接着性樹脂がエチレン
−酢酸ビニル共重合体にＸを0.01〜15重量％化学
的に結合させて得られる変性EVA_Cからなり、し
かも該エチレン−酢酸ビニル共重合体は(A)酢酸ビ
ニル含量20〜45重量％の変形エチレン−酢酸ビニ
ル共重合体と(B)酢酸ビニル含量35〜55重量％の変
性エチレン−酢酸ビニル共重合体のブレンド物で
あり、(A)と(B)の酢酸ビニル含量の差が少くとも10
重量％以上であり、さらにブレンド比（重量）
Ａ：Ｂが60：40〜５：95である該積層包装材、お
よび該接着性樹脂が(C)酢酸ビニル含量20〜55重量
％のEVA_CにＸを15重量％以下化学的に結合させ
て得られる変性EVA_Cと(D)酢酸ビニル含量20〜55
重量％の少くとも１種のEVA_Cとのブレンド物か
らなり、しかも該ブレンド物は酢酸ビニル含量35
重量％以上のＣおよび／またはＤを40重量％以上
含み、かつ化学的に結合したＸの含有量が0.01重
量％以上である該積層包装材を提供せんとするも
のである。耐屈曲疲労性は、所謂ゲルボフレツクステスタ
ーを用いて、評価することができる。すなわち該
テスターを用いて行う評価テストにおけるガスバ
リヤー性低下の屈曲回数依存性、ピンホール発生
に当るまでの屈曲回数等のデーターから種々の素
材、または種々の素材からなる積層包装材の耐屈
曲疲労性の優劣を判断することができる。本発明
者らは各種熱可塑性樹脂の単体フイルム、各種樹
脂からなる多層構成のラミネートフイルムについ
て、就中該各層間に用いられる接着性樹脂が異な
るラミネートフイルムについてゲルボフレツクス
テスターを用いて屈曲回数とピンホール発生数と
の関係、ピンホール発生に至る屈曲回数、さらに
多層構成のラミネート物についてはピンホール発
生に至るまでの過程における屈曲回数とバリヤー
性（たとえば酸素透過量）との関係を多岐に亘つ
て測定した結果いくつかの事実を見出した。すな
わち(1)EVOH樹脂フイルムはいづれも耐屈曲疲
労性は極めて不良であり、実用に耐える輸送振動
強度水準に遥かに及ばないこと、(2)従来一般的に
使用されている高圧法低密度ポリエチレン、低圧
法高密度ポリエチレン、ナイロン、ポリプロピレ
ン、熱可塑性ポリエステルなどの各樹脂のフイル
ムは該EVOH樹脂フイルムに比し、耐屈曲疲労
性は顕著に優れているけれども該樹脂フイルムを
EVOHを中間層として積層したラミネートフイ
ルムの耐屈曲疲労性は詳細は明らかでないが、
EVOH層が存在することに起因するとみられる
顕著な低下、つまり該樹脂単体フイルムの優れた
耐屈曲疲労性に比し著しい低下がみられること、
(3)EVOH層を中間層とした該積層物にピンホー
ルの発生を見るに至るまではガスバリヤー性の低
下の殆んどないこと、(4)就中EVOH層を中間層
に両表面層を接着性樹脂を介して設けるが、特定
のエチレン−酢酸ビニル共重合体系の接着性樹脂
を用いて積層された該積層物はEVOHを中間層
とするときに発現する耐屈曲疲労性の著しい悪化
を緩和し、該積層物の耐屈曲疲労性の改善が顕著
であることを認めた。従来からエチレン性不飽和カルボン酸またはそ
の無水物を化学的に結合させて得られる変性
EVA_Cは知られているとはいえ、それはかかる用
途を目指したものではなく、該現象は極めて特異
的であり、前記特定の接着性樹脂を用いて始めて
その顕著な改善効果が享受できるのであつて、該
変性EVA_Cの組成並びに該変性EVA_Cと未変性
EVA_Cの組成、ブレンド割合等を特定化すること
によつて、はじめて本発明の効果を発揮し得て、
該目的が達成されたものである。Ｄ本発明のより詳細な説明本発明の骨子の一つは接着性樹脂にある。本発
明に使用される接着性樹脂の一つは酢酸ビニル含
量が35重量％をこえて55重量％以下のエチレン−
酢酸ビニル共重合体に、エチレン性不飽和カルボ
ン酸またはその無水物（Ｘ）を0.01〜15重量％以
下化学的に結合させて得られる変性エチレン−酢
酸ビニル共重合体である。従来低酢酸ビニル含量
の該変性EVA_Cが接着性樹脂として用いられてい
るが、かかる該含量が35重量％以下のものでは、
該変性EVA_Cの柔軟性とも関連があるとみられる
ものの、詳細は明らかでないが、バツグインボツ
クスの内容器等に要求されるきわめてはげしい輸
送振動強度に耐え得る耐屈曲疲労性をもつたもの
とはなり得ず、本発明の効果は該含量が35重量％
を越えた領域において、はじめて享受することが
できる。酢酸ビニル含量が該領域にあれば、該変
性EVA_Cは１種の単独物であつても２種以上のブ
レンド物であつても好適に用いられて本発明の効
果を享受することができる。酢酸ビニル含量が55
重量％を越えると、その接着性は所謂粘着性の度
合を強め、物理的強度強靭さが低減することと関
連があるとみられるものの詳しくは明かでないが
本発明における如き薄層の接着性樹脂層が果す該
耐屈曲疲労性の改善効果は減殺されたものとなる
ので好ましくない。本発明にいうエチレン性不飽
和カルボン酸またはその無水物（Ｘ）としてはア
クリル酸、マレイン酸、イタコン酸等の酸または
その無水物が代表的なものである。就中無水マレ
イン酸が、特に好適である。該Ｘのエチレン−酢
酸ビニル共重合体に対し0.01〜15重量％、より好
ましくは0.05〜10重量％、さらに好ましくは0.05
〜５重量％である。該結合量が0.01重量％未満で
あると、接着性が悪くなり所望の効果が得られな
い。また15重量％を越えると樹脂が着色したり、
ゲル化が進み、異物発生の原因となるので好まし
くない。本発明に使用される接着性樹脂の他の一つは、
(A)酢酸ビニル含量が20〜45重量％のエチレン−酢
酸ビニル共重合体に前記Ｘを0.01〜15重量％化学
的に結合させて得られる砂くとも一種の変性
EVA_Cと、(B)酢酸ビニル含量が35〜55重量％の
EVA_CにＸを0.01〜15重量％化学的に結合させて
得られる少くとも一種の変性EVA_Cのブレンド物
であり、かつ隣接するＡの酢酸ビニル含量と、Ｂ
の該含量の差が少くとも10重量％以上であつて、
しかも重量ブレンド比Ａ：Ｂが60：40〜５：95で
ある変性EVA_Cブレンド樹脂である。前記の如く
酢酸ビニル含量35重量％未満のもの単独では本発
明の効果を享受し得るものとはならないが、該含
量が20重量％以上35重量％未満のものであつて
も、特定の該変性EVA_Cのブレンド物の一成分樹
脂として前記の特定の割合で存在するときには耐
屈曲性の改善効果は、予期に反し顕著なものとな
り、さらに溶融粘性、強靭さ等の物理的特性の異
なる該変性EVA_Cのブレンド物からなることに起
因して該接着性樹脂の溶融粘性をある程度任意に
選定できるようになること、該接着層の強靭さを
向上させ得ること等、より好ましい効果を併せも
たらす。該含量が20重量％未満の領域にある該変
性EVA_Cと前記Ｂとのブレンド物にあつては該効
果は減殺されものとなり好ましくない。該効果が
より顕著であるためには、(A)該含量が20〜45重量
％の領域にある該変性EVA_Cと、(B)該含量が35〜
55重量％の領域にある該変性EVA_Cのブレンド物
であつて隣接するＡの酢酸ビニル含量とＢの該含
量の差が少くとも10重量％以上であることを要
し、10重量％未満では顕著なものとはなり得な
い。さらにＡの該含量が20〜35重量％、Ｂの該含
量が35〜50重量％の領域にあることがより好まし
い、また該効果が顕著であるためにはＡとＢの重
量ブレンド比Ａ：Ｂが60：40〜５：95、より好ま
しくは50：50〜10：90であることが好適である。
ここでＡ及びＢはそれぞれ単独の変性EVA_Cであ
つても２種以上のブレンド物からなつていてもよ
い。本発明に用いられるさらに他の接着性樹脂は、
(C)酢酸ビニル含量が20〜55重量％のEVA_Cに前記
Ｘを15重量％以下化学的に結合させて得られる少
くとも１種の変性EVA_Cと、(D)酢酸ビニル含量20
〜55重量％の少くとも１種の未変性のEVA_Cとの
ブレンド物であり、しかも該ブレンド物は酢酸ビ
ニル含量35重量％以上のＣおよび／またはＤを40
重量％以上含み、かつ化学的に結合した前記Ｘの
含有量が0.01重量％以上であるEVA_C系ブレンド
樹脂である。この場合における変性EVA_C及び未
変性EVA_Cの酢酸ビニル含量は20〜55重量％の領
域内にあることを要し、前記の場合におけると同
じく、該含量が20重量％未満ではブレンド物にあ
つても本発明の耐屈曲疲労性の改善効果は減殺さ
れたものとなり好ましくなく、また該含量が55重
量％を越える領域では既述の理由から好ましくな
い。該変性EVA_Cはいづれもが前記Ｘを15重量％
以下化学的に結合させて有られる少くとも１種の
変成EVA_Cであり、該Ｘの結合量が15％を越える
ことは既述の理由からこの場合においても好まし
くない。該ブレンド物は化学的に結合したＸを
0.01重量％以上含むものでなければならず、0.05
重量％であることがより好ましい。0.01重量％未
満では接着性が悪くな、所望の効果が得られな
い。さらに該ブレンド物は、酢酸ビニル含量35重
量％以上のＣおよび／またはＤを40重量％以上含
むことは、本発明の効果を享受するための重要な
要件の一つであり、該含有量が40重量％未満で
は、耐屈曲疲労性の改善向上効果は減殺されたも
のとなる。該接着性樹脂は、Ｃの割合が小さすぎ
ると接着性に劣るものとなるのでＣの含量は、少
くとも５重量％以上あることが好ましい。10重量
％以上であることがより好ましく、15重量％以上
であることはさらに好適である。該変性EVA_Cは、酢酸ビニル含量または／およ
び前記Ｘの含有量に関して、１種である単独物で
あつても２種以上のブレンド物からなつていても
よく、また未変性EVA_Cは、酢酸ビニル含量に関
して、１種の単独物であつても、２種以上のブレ
ンド物からなつていてもよい。該変性EVA_Cを得るための手法としては前記Ｘ
をグラフト重合させる方法が好適に用いられる。
グラフト重合させる方法としては、グラフト用前
記Ｘおよび触媒を押出機中で溶融混練する方法、
キシレン等の適当な溶媒中に溶解しグラフト用前
記Ｘおよび触媒を添加し、加熱撹拌する方法、適
当な溶媒中に懸濁しているEVA_C粒子にグラフト
用前記Ｘおよび触媒を添加して加熱撹拌する方法
等、それ自体公知の方法が採用される。接着性樹脂層の厚さは、本発明の積層包装材の
耐屈曲疲労性と関連しており、しかも剛性の大き
いEVOHの影響の伝播を防止するためには柔軟
性のある接着性樹脂層の厚さが大きい方が有利で
あるとの予期に反し、該耐屈曲疲労性は、該層厚
さの増加とともに低下する。本発明の効果をより
顕著に発現させるためには該層厚さは15μ以下、
より好ましくは10μ以下が好適である。また接着
樹脂層が余りにも薄きに過ぎると該層を切れ目な
く均一な厚さで設ける技術上の困難さが増加する
ので、実用的には、該層厚さは1μ以上、より好
ましくは2μ以上が好適である。本発明の積層包装材は少くとも該ゲルボフレツ
クステスターによる耐屈曲疲労テスト時にデラミ
ネーシヨンを起すものであつてはならないが、本
発明の接着性樹脂はEVOHおよび各種ポリエチ
レン、ポリプロピレンなどのポリオレフイン樹
脂、エチレン−酢酸ビニル樹脂、各種ナイロンな
どのポリアミド樹脂、各種の熱可塑性ポリエステ
ル樹脂などの熱可塑性樹脂に対し優れた接着性を
示めし、極めてはげしい屈曲疲労に耐え得て全く
デラミネーシヨンを起さず、前記改善効果を顕著
に発揮する。本発明に用いられるEVOHは、エチレン含量、
25〜60モル％、酢酸ビニル成分のけん化度95モル
％以上のものがより好適に用いられる。エチレン
含量が25モル％以下では、成形性が低下するのみ
ならず、該EVOHの剛性が増加することと関連
があるとみられるが、該改善の効果の発現が減殺
され、またエチレン含量60モル％を越えると該剛
性は減少するものの、該樹脂の最も特徴とする酸
素等のガスバリヤー性が低下し、該特性が不満足
なものとなる。該EVOHは25〜60モル％の領域
内のエチレン含量をもつ２種またはそれ以上のエ
チレン含量の異なる該樹脂のブレンド物であつて
も相溶性に示めす範囲内のものであれば本発明の
効果を享受することができる。該樹脂のけん化度
は95％以上が好適であり、95％未満では該バリヤ
ー性が低下するので好ましくな。さらにホウ酸な
どのホウ素化合物で処理したEVOH、ケイ素含
有オレフイン性不飽和単量体など第３成分をエチ
レンおよび酢酸ビニルとともに共重合し、けん化
して得られる変性EVOHについても溶融成形可
能でバリヤー性を害しない範囲の変性度のもので
あれば本発明の効果を享受することができる。本
発明の積層包装材の構成における該改善の効果へ
のEVOHの層厚依存性は極めて顕著であり、
EVOH層の層の厚さが20μを越えると該改善の効
果は減殺されるので好ましくない。本発明の効果
を充分に享受するためには、EVOH層の厚さは
20μ以下が好適であり、15μ以下がより好ましい。
該改善の効果の観点からのみでは特に10μ以下が
最も好適である。しかし酸素等のガスバリヤー性
に関して、より高度な要求がある場合、20μ以下
の該中間層の厚さでは、該要求を満足できない場
合がしばしば生じる。耐屈曲疲労性及び該バリヤ
ー性に関し、より高度な要求を満足させる本発明
の最も好適な態様は、該EVOH層の厚さを20μ以
下好ましくは15μ以下、より好ましくは15μ以下、
より好ましくは10μ以下に選定して該バリヤー性
についての高度の要求の程度に応じて該EVOH
層を２またはそれ以上の複数設ける構成であり、
EVOH層をＸ、接着性樹脂をＹとするとき、
Ｘ／Ｙ／Ｘ、Ｘ／Ｙ／Ｘ／Ｙ／Ｘ等の複合豪勢で
あることを意味し、本構成をも本発明は抱含する
ものである。耐屈曲疲労性の観点からはEVOH
層の厚はできる限り小さい方が好ましいが成形加
工の技術の面からの困難性は、それだけ増加す
る。実用的には、2μ以上が好ましく、5μ以上が
該観点から比較的困難性も少くより好適である。
2μ以下ではしばしばピンホールの発生がEVOH
層に生じ、良品の歩留りが低下する。複数の該バ
リヤー層を設けるに当つては、該層のすべてにエ
チレン含量の同じEVOHを用いてもよく、また
容器等の内部の相対湿度が該容器の外部の相対湿
度より大きい場合、たとえば被包装物がワインな
どの水性混合物である場合などEVOHのバリヤ
ー性の湿度依存性とも関連して該複数のバリヤー
層の各層の位置関係はよりエチレン含量の小さい
EVOH層を外側に配し、よりエチレン含量の大
きいEVOH層を内側に配するのがより好適であ
り、該相対湿度の関係が逆の場合には、該
EVOH層の位置関係も逆に配するのが好ましい
など、それぞれの目的に応じて最適な構成を選定
することができる。この場合、該構成を採つたこ
とに基く効果を顕著に発現させるためには該バリ
ヤー層の少くとも２層が５モル％以上エチレン含
量を異にするEVOHで構成されることが好まし
い。本発明に係る積層包装材は、たとえばバツグイ
ンボツクスの内容器の構成材として用いる場合の
如く、熱シールして各種フレキシブル包装材とし
て用いることを目的の一つとするものであるり、
該熱可塑性樹脂の少くとも一つは熱シール可能な
熱可塑性樹脂である必要があるが、他の一つは、
熱シールにあまり適さない樹脂であつてもよい。
該熱可塑性樹脂としては、前出の各種熱可塑性樹
脂が用いられるが、これらの樹脂の中でも直鎖状
低密度ポリエチレン、エチレン−酢酸ビニル共重
合体がより好適に用いられる。直鎖状低密度ポリ
エチレンを前記Ｂの少くとも一つに用いた場合、
就中両方に用いたときには、本発明の接着性樹脂
を用いることによる該改善の効果がより顕著であ
る。ここで直鎖状低密度ポリエチレンとは、実質
的に長鎖分岐を持たない直鎖状の低密度ポリエチ
レンである。一般には長鎖分岐数の定量的な尺度
Ｇ＝〔η〕ｂ／〔η〕ｅ（〔η〕ｂは分岐ポリエチ
レンの極限粘度、〔η〕ｅは分岐ポリエチレンと
同じ分子量を持つ直鎖状ポリエチレンの極限粘
度）がほぼ１（一般的には0.9〜１の範囲にあり、
１に近い場合が多い）であり、密度が0.910〜
0.945のものである。（なお従来の通常の高圧法低
密度ポリエチレンのＧ値は、0.1〜0.6である。）
直鎖状低密度ポリエチレンの製造法は特に制限さ
れない。代表的な製造方法を例示すれば７〜45
Kg／cm²の圧力（高圧法低密度ポリエチレンの場合
は通常2000〜3000Kg／cm²）、75〜100℃の温度（高
圧法低密度ポリエチレンの場合は120〜250℃）で
クロム系触媒またはチーグラー触媒を用いて炭素
数３以上好ましくは５〜10のα−オレフインたと
えばプロピレン、ブテン−１、ヘキセン−１、オ
クテン−１等のα−オレフインを共重合成分とし
てエチレンの共重合を行う方法がある。重合方法
としては、溶液法液相法、スラリー法液相法、流
動床気相法、撹拌床気相法等が用いられる。詳細
は未だ有らかでないが、本発明に係る接着性樹脂
との協奏的効果の発現が特定の直鎖状低密度ポチ
レンとの関連においてより好適となるためであろ
うか、該改善の効果は直鎖状低密度ポリエチレン
の共重合成分であるα−オレフインの炭素数、示
差走査型熱量計（以下DSCと記す）の熱分析に
基づく融解熱20℃におけるヤング率等に深くかか
わつており、これらが選定された特定の領域にあ
る前述の直鎖状低密度ポリエチレンを採用したと
きに、より一層顕著である。より具体的に述べれ
ば次の通りである。すなわち該融解熱が25cal／
ｇ以下、好ましくは25〜5cal／ｇであるか、また
は20℃におけるヤング率が25Kg／mm²以下、好まし
くは22〜５Kg／mm²である該ポリエチレンについて
本発明の効果がより顕著であり、特に両者が前記
領域にある場合に最も顕著である。該融解熱、ヤ
ング率が前記領域にあるものは、重合法、重合条
件によつて多少異なるが、概していえば、共重合
成分である該α−オレフインの含有量が約２モル
％以上、好ましくは約２〜７モル％の領域で得ら
れる場合が多い。共重合成分がブテン−１である
直鎖状低密度ポリエチレンについては、該融解熱
が15cal／ｇ如何であるか、または20℃における
ヤング率が15Kg／mm²以下である場合に該改善の効
果はより顕著であり、特に該両者が前記領域にあ
る場合に最も顕著に該効果を享受することができ
る。該融解熱ヤング率が前記領域にある該低密度
ポリエチレンは、概していえばブテン−１の含有
量が約４モル％以上の領域で得られる場合が多
い。概含有量が多くなり過ぎると該ポリエチレン
のもつ他の物理的物性が不満足なものとなり好ま
しくなく、該含有量は高々数モル％、たとえば７
モル％であることが望ましい。また該改善の効果
は前述の如く該融解熱または／およびヤング率が
前記特定の量域にある直鎖状低密度ポリエチレン
について享受し得るが、特に炭素数５以上たとえ
ば５〜10のα−オレフインを共重合成分とする該
ポリエチレンについて該接着性樹脂との協奏的効
果を一層発現し得て、該改善の効果をより一層顕
著に享受することができる。この場合、前述と同
様の理由から該α−オレフインの含有量は２〜７
モル％が好ましく、２〜６モル％であることがよ
り好適であり、また該融解熱は前記の如く、該α
−オレフイン含有量等と関連しているが、就中該
融解熱は25〜5cal／ｇであることが好ましく、ま
たヤング率は22Kg／mm²以下、好ましくは22〜３
Kg／mm²である。さらに好ましくは22〜５Kg／mm²で
ある。該オレフインの中でも本発明の改善効果が
より顕著であり、工業的にも容易に得られる４−
メチル−１−ペンテンを共重合成分とする直鎖状
低密度ポリエチレンは最も好適なものの一つであ
る。本発明の表面層に用いられる他の熱可塑性樹脂
としては、エチレン−酢酸ビニル共重合体があ
る。就中酢酸ビニル含量が少くとも７重量％であ
る該共重合体はより顕著に本発明の効果を享受す
ることができる。該含量があまりに多きに過ぎると該樹脂表面が
粘着性を示すようになり好ましくなく、12重量％
以下であることが好ましい。本発明の積層包装材
からなる包装容器などへの充填物が水性混合物ま
たは含水食品などの場合には、内外両表面層の透
湿速度とも関連して該共重合体を外表面層に、前
記直鎖状低密度ポリエチレンを内表面層に用いる
態様は、中間層として配されたEVOH層の定常
湿分をより低く保持し得て、該積層包装材の好ま
しい構成の一つである。さらに該包装充填物の場
合に、さらに優れた耐屈曲疲労性が要求されると
きには、該バリヤー性の要求を満たす限度内にお
いて内外両表面層に前記ポリエチレンより透湿度
の大きい該共重合体を用い、内表面層の厚さを前
記透湿速度についての条件を満すように選定して
EVOH層の定常湿分を好適な領域に保持するよ
うに構成して好適に用いることができる。本発明では、EVOH単体フイルムの耐ピンホ
ール性が極めて不良であるにも抱らず、本発明の
構成をもつ積層フイルムの耐ピンホール性が顕著
に向上した時点において、つまりEVOH単体フ
イルムの特性に鑑みて判断すれば、当然に中間層
であるEVOH層にクラツクないしはピンホール
が発生し、該積層包装材のバリヤー性が低下する
ことが予想される段階において、該積層包装材の
バリヤー性の低下が認められない点は前記塩化ビ
ニリデン等のバリヤー材を用いた前記従来の積層
包装材と異なり、極めて特異的である。本発明の積層包装材にあつては該表面層の各層
があまりにも薄すぎると、たとえば10μ以下に至
ると、強度などの他の物理的特性が低下するので
10μ以上であることが好ましく、20μ以上である
ことがより好適である。またあまりに厚さが増加
しすぎると、本発明の効果が減殺されるので、該
表面層の各層は60μ以下で用いることがより好ま
しい。特にバツグインボツクスの内容器の構成材
には通常25〜60μの厚さ領域から内容量に応じて
選定して好適に用いることができる。本発明に係る積層包装材は、それ自体公知の方
法就中多層用ダイを用いた共押出法で好適に得ら
れる。また、たとえば該積層材を用いたバツグイ
ンボツクス内容器は、該積層構成のフイルムを公
知の方法で得た後口金を装着するフイルム・シー
ル方式、製品形状に合せてあらかじめ成膜して得
た該積層構成のシートより成形した後、口金を物
理的に固定する真空成形方式、多層溶融押出成形
方式で本発明の素材の組合せからなる多層パリソ
ンを口金を挿入した金型ではさみ、圧縮空気で成
形し、この時のパリソンの熱と空気圧力で本体と
口金を熱接着するブロー成形方式など公知の方法
で得ることができる。以下実施例により本発明をさらに詳細に説明す
るが、本発明はこれに限定させるものではない。実施例１エチレン含量31.5モル％、けん化度99.5％の
EVOH樹脂からなる厚さ12μの中間層と、該中間
層の両側に厚さ35μの４−メチル−１−ペンテン
を共重合成分とし、該共重合成分を3.2モル％含
み、190℃2160ｇ荷重の条件下にASTM Ｄ−
1238−65Tに準じて測定したメルトインデツクス
（以下MI値と記す）2.1ｇ／10分、DSCによる融
解熱が19cal／ｇの直鎖状低密度ポリエチレン
（以下LLDPEと記す）からなる表面層を有し、各
層間に厚さ5μの酢酸ビニル38重量％、無水マレ
ンイン酸変性度1.6重量％の変性EVA_Cからなる接
着性樹脂層を介して配された積層フイルムを３基
の押出機、３種５層用多層ダイヘツドを用いて共
押出法により得た。得られた積層フイルムについ
て屈曲疲労テストを該積層フイルムにピンホール
の発生を認めるまで行うとともに、該ピンホール
発生に至るまでの各段階での酸素ガス透過量を測
定した。該屈曲疲労テストはゲルボフレツクステ
スター（理学工業(株)製）を用い、12in×8inの試
料片を直径３１／２inの円筒状となし、両端を把持し、初期把持間隔7in、最大屈曲時の把持間隔
1in、ストロークの最初の３１／２inで、440°の角度のひねりを加え、その後の２１／２inは直線水平動である動作のくり返し往復動を40回／分の速さで
20℃、相対湿度65％の条件下に行うものである。
酸素ガス透過量の測定は、Modern Control社製
OX−TRAN100を使用し、20℃、相対湿度（RH
と以下記す）65％および20℃、80％RHで測定し
た。各段階の屈曲疲労テスト後の試料については
12in×8inの平面となし、その中央部で測定した。
またヤング率は、ASTM Ｄ−882−67に準じて
20℃相対湿度65％で測定した。測定結果を第１表
に示す。ピンホール発生に至るまでの屈曲疲労テ
スト過程においては酸素透過量の変化は殆んどな
かつた。またピンホール発生は該屈曲疲労テスト
5000往復を経過するまで認められず、5100往復経
過後、ピンホールの有無を検査に付した時点でピ
ンホール１ケが既に発生しているのを認めた。ま
た各層間のデラミネーシヨンは、全くみられなか
つた。なお該LLDPEのフイルムを別に得て20℃
においてヤング率を測定した結果13Kg／mm²であつ
た。 A: Technical Field of the Invention The present invention relates to a flexible laminated packaging material whose gas barrier properties do not deteriorate even under extremely severe bending fatigue. Specifically, the intermediate layer is a thin film of saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH), which has excellent barrier properties against gases such as oxygen and carbon dioxide.
A specific ethylene-vinyl acetate copolymer modified with an ethylene-unsaturated carboxylic acid or its anhydride (hereinafter referred to as EVA _C ) or a blend of the specific modified EVA _C and the specific EVA _C on both sides of the intermediate layer. By laminating a surface layer through an adhesive resin consisting of a material, airtight packaging for easily deteriorating products wrapped in the packaging material can be protected against the extremely severe bending fatigue that the packaging material undergoes during transportation and handling. The present invention also provides a laminated flexible packaging material that can maintain excellent gas barrier properties and is effective in preventing deterioration of packaged items. B. Prior art The functions of flexible laminated packaging materials are basically:
It is the preservation of the packaged product, that is, the prevention of deterioration, and for this purpose, the packaging material is particularly required to have transport vibration strength and bending fatigue resistance, especially for so-called bag-in boxes - thin contents of foldable plastic. When used as the inner container of a container that combines a container with an outer cardboard box that is stackable, portable, and printable, a high degree of these characteristics is required. This packaging material is used by laminating various plastic films by taking advantage of the characteristics of each material, but the most common combination is, for example, a base film to maintain mechanical strength and a heat-sealable material. The material is selected depending on the requirements of the packaged item. In particular, for applications where the base film's barrier properties against oxygen and other gases are unsatisfactory, a barrier layer with even higher gas barrier properties is provided on the base layer, and this barrier layer serves as an intermediate layer for heat-sealable materials. A method has been adopted in which thermoplastic resin layers are laminated so as to form at least one surface layer. For example, the basic material for the inner container of conventional bag-in boxes is polyethylene, especially soft polyethylene, which can be heat-sealed because it always has a heat-sealable component. Since the material is a liquid, physical strength, especially transportation vibration strength and bending fatigue resistance as mentioned above, are required. Copolymer resins are more preferably used. Recently, as the required performance has become more advanced, gas barrier properties such as oxygen have been required, and in order to provide a high degree of barrier properties, EVOH,
Vapor-deposited films such as vinylidene chloride, aluminum foil, and metals are beginning to be used. However, although these have excellent barrier properties, their mechanical strength is generally low, and in particular they cannot withstand bending fatigue. Therefore, it is used by being laminated between a base material layer with excellent mechanical strength and a heat-sealable material.
For example, when used as a component of a bag-in-box inner container, pinholes may occur in the component, and even at the stage where no pinholes occur in the component, cracks or cracks may occur in the barrier layer used as an intermediate layer. Due to the deterioration of barrier properties due to pinholes, etc., excellent gas barrier properties cannot be maintained against severe bending fatigue, and no material that is practically satisfactory has been found.
In other words, the behavior of a laminated packaging material whose barrier layer is a layer mainly made of polyvinylidene chloride resin, a vapor-deposited resin layer made of aluminum foil, metal, etc.
Although it is shown in Publication No. 55-7477, the gas barrier properties after transportation and handling of packages actually packaged using this packaging material are not necessarily satisfactory;
Practical shelf life after primary distribution, which is most essential, is often compromised due to damage to the barrier layer located in the intermediate layer. EVOH resin is the best material for the intermediate layer provided to provide gas barrier properties, and is preferably used as a barrier material for various multilayer films and containers with multilayer structures.
This is because this resin not only has outstanding barrier properties, but also has excellent transparency, oil resistance, printability, moldability, etc., and has extremely advantageous properties that do not impair the properties of the base resin. It's because it's motsu.
However, EVOH resin is used in fields where bending fatigue resistance is particularly required, and in particular, in the inner container of back-in-boxes that have gas barrier properties such as oxygen, which are strongly required to withstand bending fatigue caused by transportation vibration as mentioned above. However, no material has been found that satisfies these requirements, and one of the important issues is the development of a flexible laminated packaging material that uses an EVOH layer as a barrier layer and has excellent barrier properties and bending fatigue strength that can withstand transportation vibrations. It was hot. C. Objectives, Structure, and Effects of the Present Invention The present inventors found that EVOH film has the above-mentioned excellent properties, but has better bending fatigue resistance than thermoplastic films such as polyethylene, polypropylene, nylon, and thermoplastic polyester. Not only does it have the major drawback of being significantly inferior to
In multilayer flexible packaging materials using EVOH resin layers, it seems that there is an unexpected relationship with physical properties such as EVOH stiffness, but the bending fatigue resistance of the packaging materials is higher than that of thermoplastics that are resistant to bending fatigue. The bending fatigue resistance is significantly lower than that of the resin alone,
Pinholes will occur in the laminated packaging material with less bending fatigue, and until the pinholes occur, cracks and pins due to bending fatigue will occur even if the EVOH layer exceeds the bending fatigue that it can withstand alone. This seems to be due to the fact that holes etc. do not occur in the EVOH layer, but there is almost no deterioration in barrier properties compared to conventional laminated packaging materials that use vinylidene chloride resin as a barrier layer and as an intermediate layer. In addition, we discovered that the characteristics of adhesive resin, which had not been discovered previously, were extremely closely related to bending fatigue resistance. The present invention has been completed through extensive research into a flexible gas-barrier laminated packaging material with excellent fatigue resistance. That is, the present invention provides a flexible laminated packaging material in which a thin film of saponified ethylene-vinyl acetate copolymer is used as an intermediate layer, surface layers are provided on both sides of the intermediate layer, and each layer is arranged with an adhesive resin layer interposed therebetween. The adhesive resin has a vinyl acetate content of more than 35% by weight.
Modified ethylene-vinyl acetate copolymer obtained by chemically bonding 0.01 to 15% by weight or less of ethylenically unsaturated carboxylic acid or its anhydride (X) to 55% by weight or less of ethylene-vinyl acetate copolymer A flexible laminated packaging material having high bending fatigue resistance and gas barrier properties, the adhesive resin being a modified EVA _C obtained by chemically bonding 0.01 to 15% by weight of X to an ethylene-vinyl acetate copolymer. Moreover, the ethylene-vinyl acetate copolymer is composed of (A) a modified ethylene-vinyl acetate copolymer having a vinyl acetate content of 20 to 45% by weight, and (B) a modified ethylene-vinyl acetate copolymer having a vinyl acetate content of 35 to 55% by weight. A blend of vinyl copolymers in which the difference in vinyl acetate content between (A) and (B) is at least 10
weight% or more, and also the blend ratio (weight)
The laminated packaging material has a ratio of A:B of 60:40 to 5:95, and the adhesive resin is (C) EVA _C having a vinyl acetate content of 20 to 55% by weight, in which X is chemically bonded to 15% by weight or less. Modified EVA _C and (D) vinyl acetate content 20-55
% by weight of at least one EVA _C , the blend having a vinyl acetate content of 35
It is an object of the present invention to provide a laminated packaging material containing at least 40% by weight of C and/or D and at least 0.01% by weight of chemically bonded X. The bending fatigue resistance can be evaluated using a so-called Gelbo Flex Tester. In other words, the bending fatigue resistance of various materials or laminated packaging materials made of various materials can be determined from data such as the dependence of gas barrier property deterioration on the number of bends and the number of times of bending until a pinhole occurs in an evaluation test conducted using the tester. Can judge the superiority or inferiority of sex. The present inventors tested single films made of various thermoplastic resins and laminate films with a multilayer structure made of various resins, particularly laminate films with different adhesive resins used between the layers, using a Gelbo Flex Tester to determine the number of bends. The relationship between the number of bends and the number of pinholes, the number of bends that lead to the formation of pinholes, and the relationship between the number of bends and barrier properties (for example, oxygen permeation rate) in the process of forming pinholes for multilayer laminates. As a result of our measurements, we discovered several facts. In other words, (1) all EVOH resin films have extremely poor bending fatigue resistance, far below the transportation vibration strength level that can withstand practical use, and (2) the conventionally commonly used high-pressure process low-density polyethylene Films made of various resins such as low-pressure high-density polyethylene, nylon, polypropylene, and thermoplastic polyester have significantly superior bending fatigue resistance compared to the EVOH resin film.
Although the details of the bending fatigue resistance of a laminated film laminated with EVOH as an intermediate layer are not clear,
There is a significant decrease in bending fatigue resistance that is considered to be due to the presence of the EVOH layer, that is, a significant decrease in bending fatigue resistance compared to the excellent bending fatigue resistance of the single resin film,
(3) There is almost no deterioration in gas barrier properties until pinholes appear in the laminate with the EVOH layer as the intermediate layer; is provided through an adhesive resin, but the laminates laminated using a specific ethylene-vinyl acetate copolymer adhesive resin have a significant deterioration in bending fatigue resistance that occurs when EVOH is used as an intermediate layer. It was observed that the bending fatigue resistance of the laminate was significantly improved. Conventionally, modifications obtained by chemically bonding ethylenically unsaturated carboxylic acids or their anhydrides
Although EVA _C is known, it is not intended for such uses; the phenomenon is extremely specific, and its remarkable improvement effect can only be enjoyed by using the specific adhesive resin mentioned above. The composition of the modified EVA _C and the composition of the modified EVA C and unmodified EVA _C.
The effects of the present invention can only be achieved by specifying the composition, blending ratio, etc. of EVA _C.
This objective has been achieved. D More detailed description of the present invention One of the main points of the present invention is the adhesive resin. One of the adhesive resins used in the present invention is ethylene containing vinyl acetate of more than 35% by weight and less than 55% by weight.
This is a modified ethylene-vinyl acetate copolymer obtained by chemically bonding 0.01 to 15% by weight of an ethylenically unsaturated carboxylic acid or its anhydride (X) to a vinyl acetate copolymer. Conventionally, the modified EVA _C with a low vinyl acetate content has been used as an adhesive resin, but when the content is 35% by weight or less,
Although it seems to be related to the flexibility of the modified EVA _C , the details are not clear, but it is said that it has bending fatigue resistance that can withstand the extremely severe transport vibration strength required for bag-in-box inner containers. The effect of the present invention is that the content is 35% by weight.
It can be enjoyed for the first time in a realm that goes beyond. If the vinyl acetate content is within this range, the modified EVA _C can be suitably used to enjoy the effects of the present invention, whether it is one type alone or a blend of two or more types. Vinyl acetate content is 55
% by weight, the adhesiveness increases so-called tackiness, and although it seems to be related to a decrease in physical strength and toughness, the details are not clear, but the thin adhesive resin layer as in the present invention This is not preferable because the effect of improving the bending fatigue resistance is diminished. Typical examples of the ethylenically unsaturated carboxylic acid or its anhydride (X) referred to in the present invention include acrylic acid, maleic acid, itaconic acid, and other acids or their anhydrides. Among these, maleic anhydride is particularly preferred. 0.01 to 15% by weight, more preferably 0.05 to 10% by weight, even more preferably 0.05% by weight based on the ethylene-vinyl acetate copolymer of X
~5% by weight. If the amount of bonding is less than 0.01% by weight, the adhesiveness will be poor and the desired effect will not be obtained. Also, if it exceeds 15% by weight, the resin may become colored or
This is not preferable because gelation progresses and causes the generation of foreign substances. Another adhesive resin used in the present invention is
(A) A type of modified sand obtained by chemically bonding 0.01 to 15% by weight of the above X to an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20 to 45% by weight.
EVA _C and (B) vinyl acetate content of 35-55% by weight.
It is a blend of at least one type of modified EVA _C obtained by chemically bonding 0.01 to 15% by weight of X to EVA _C , and the vinyl acetate content of adjacent A and B
The difference in content is at least 10% by weight or more,
Moreover, it is a modified EVA _C blend resin in which the weight blend ratio A:B is 60:40 to 5:95. As mentioned above, if the vinyl acetate content is less than 35% by weight, it will not be possible to enjoy the effects of the present invention, but even if the vinyl acetate content is 20% by weight or more and less than 35% by weight, the specific modified When present as a component resin in a blend of EVA _C in the above-mentioned specific proportions, the effect of improving flex resistance is unexpectedly significant, and furthermore, the modified resin has different physical properties such as melt viscosity and toughness. Since it is made of a blend of EVA _C , it brings about more desirable effects such as being able to arbitrarily select the melt viscosity of the adhesive resin and improving the toughness of the adhesive layer. In the case of a blend of the modified EVA _C and the above-mentioned B in which the content is less than 20% by weight, the effect is diminished, which is not preferable. In order for this effect to be more pronounced, (A) the modified EVA _C has a content in the range of 20 to 45% by weight, and (B) the content is in the range of 35 to 45% by weight.
It is a blend of the modified EVA _C in the range of 55% by weight, and the difference between the vinyl acetate content of adjacent A and the content of B is at least 10% by weight, and if it is less than 10% by weight, It can't be anything significant. Furthermore, it is more preferable that the content of A is in the range of 20 to 35% by weight, and the content of B is in the range of 35 to 50% by weight, and in order for the effect to be significant, the weight blend ratio of A and B is A: It is suitable that B is 60:40 to 5:95, more preferably 50:50 to 10:90.
Here, A and B may each be a single modified EVA _C or a blend of two or more thereof. Still other adhesive resins used in the present invention are:
(C) at least one type of modified EVA _C obtained by chemically bonding the above-mentioned X to EVA _C having a vinyl acetate content of 20 to 55% by weight;
~55% by weight of at least one unmodified EVA _C , and the blend contains 40% by weight of C and/or D with a vinyl acetate content of 35% by weight or more.
The EVA _C -based blend resin contains at least 0.01% by weight of the chemically bonded X. In this case, the vinyl acetate content of the modified EVA _C and the unmodified EVA _C must be in the range of 20 to 55% by weight, and as in the previous case, if the content is less than 20% by weight, it will not be suitable for blends. However, the effect of improving the bending fatigue resistance of the present invention is undesirably diminished, and a content exceeding 55% by weight is undesirable for the reasons mentioned above. Each of the modified EVA _C contains 15% by weight of the above X.
Hereinafter, at least one type of modified EVA _C is chemically bonded, and it is not preferable in this case that the bonding amount of X exceeds 15% for the reasons mentioned above. The blend contains chemically bonded X
Must contain 0.01% by weight or more, and 0.05
More preferably it is % by weight. If the amount is less than 0.01% by weight, the adhesion will be poor and the desired effect will not be obtained. Furthermore, it is one of the important requirements for enjoying the effects of the present invention that the blend contains 40% by weight or more of C and/or D with a vinyl acetate content of 35% by weight or more; If it is less than 40% by weight, the effect of improving bending fatigue resistance will be diminished. If the proportion of C in the adhesive resin is too small, the adhesive properties will be poor, so the content of C is preferably at least 5% by weight or more. The content is more preferably 10% by weight or more, and even more preferably 15% by weight or more. The modified EVA _C may be a single substance or a blend of two or more types in terms of vinyl acetate content and _/ or the content of the above-mentioned Regarding the vinyl content, it may be one type alone or a blend of two or more types. The method for obtaining the modified EVA _C is as follows:
A method of graft polymerizing is preferably used.
The graft polymerization method includes a method of melt-kneading the above-mentioned X for grafting and a catalyst in an extruder;
A method of adding the above X for grafting and a catalyst dissolved in an appropriate solvent such as xylene, and heating and stirring; Adding the above X for grafting and a catalyst to EVA _C particles suspended in an appropriate solvent and heating and stirring. A method known per se, such as a method to do this, may be employed. The thickness of the adhesive resin layer is related to the bending fatigue resistance of the laminated packaging material of the present invention, and the thickness of the flexible adhesive resin layer is related to the bending fatigue resistance of the laminated packaging material of the present invention. Contrary to the expectation that greater thickness would be advantageous, the flex fatigue resistance decreases with increasing layer thickness. In order to more clearly exhibit the effects of the present invention, the layer thickness should be 15μ or less.
More preferably, the thickness is 10μ or less. Furthermore, if the adhesive resin layer is too thin, the technical difficulty of providing the layer with a uniform thickness without any breaks increases, so in practical terms, the layer thickness should be 1μ or more, more preferably 2μ or more. is suitable. The laminated packaging material of the present invention must not cause delamination at least during the bending fatigue test using the Gelbo Flex Tester. It exhibits excellent adhesion to thermoplastic resins such as resins, ethylene-vinyl acetate resins, various polyamide resins such as nylon, and various thermoplastic polyester resins, and can withstand extremely severe bending fatigue without causing any delamination. However, the above-mentioned improvement effect is significantly exhibited. The EVOH used in the present invention has an ethylene content,
A saponification degree of 25 to 60 mol % and a saponification degree of vinyl acetate component of 95 mol % or more are more preferably used. When the ethylene content is 25 mol% or less, not only the moldability decreases but also the stiffness of the EVOH seems to increase. If it exceeds this, although the rigidity decreases, the gas barrier property against oxygen and the like, which is the most characteristic feature of the resin, decreases, and the properties become unsatisfactory. Even if the EVOH is a blend of two or more resins having different ethylene contents with an ethylene content in the range of 25 to 60 mol%, it can be used in the present invention as long as it is compatible with the resin. You can enjoy the effects. The degree of saponification of the resin is preferably 95% or more, and a degree of saponification of less than 95% is undesirable because the barrier properties deteriorate. Furthermore, EVOH treated with boron compounds such as boric acid, and modified EVOH obtained by copolymerizing a third component such as a silicon-containing olefinic unsaturated monomer with ethylene and vinyl acetate and saponifying it, can also be melt molded and have barrier properties. The effects of the present invention can be enjoyed as long as the degree of modification is within a range that does not impair the effects of the present invention. The effect of this improvement in the structure of the laminated packaging material of the present invention is extremely dependent on the layer thickness of EVOH,
If the thickness of the EVOH layer exceeds 20 μm, the improvement effect will be diminished, which is not preferable. In order to fully enjoy the effects of the present invention, the thickness of the EVOH layer must be
The thickness is preferably 20μ or less, more preferably 15μ or less.
In terms of the improvement effect alone, a thickness of 10 μm or less is most preferable. However, when there are more advanced requirements regarding gas barrier properties such as oxygen, it is often impossible to satisfy the requirements with a thickness of the intermediate layer of 20 μm or less. The most preferred embodiment of the present invention that satisfies higher requirements regarding bending fatigue resistance and barrier properties is that the thickness of the EVOH layer is 20μ or less, preferably 15μ or less, more preferably 15μ or less.
More preferably, the EVOH is selected to be 10μ or less depending on the degree of high requirement for the barrier property.
It is a configuration in which two or more layers are provided,
When the EVOH layer is X and the adhesive resin is Y,
This means a composite structure such as X/Y/X, X/Y/X/Y/X, and the present invention also includes this configuration. EVOH from the viewpoint of bending fatigue resistance
Although it is preferable that the layer thickness be as small as possible, the difficulty from the viewpoint of molding technology increases accordingly. Practically speaking, 2 μ or more is preferable, and 5 μ or more is more suitable from this point of view since it is relatively less difficult.
Below 2μ, pinholes often occur due to EVOH.
This occurs in layers, reducing the yield of non-defective products. When providing a plurality of barrier layers, EVOH with the same ethylene content may be used in all of the layers, and if the relative humidity inside the container is greater than the relative humidity outside the container, e.g. When the packaged product is an aqueous mixture such as wine, etc., the positional relationship of each layer of the plurality of barrier layers is such that the ethylene content is lower, in relation to the humidity dependence of the barrier properties of EVOH.
It is more preferable to arrange the EVOH layer on the outside and the EVOH layer with higher ethylene content on the inside.
For example, it is preferable to reverse the positional relationship of the EVOH layers, so that the optimal configuration can be selected according to each purpose. In this case, in order to achieve remarkable effects based on this configuration, it is preferable that at least two layers of the barrier layer are composed of EVOH having different ethylene contents of 5 mol% or more. One of the purposes of the laminated packaging material according to the present invention is to heat seal it and use it as various flexible packaging materials, such as when used as a component of the inner container of a bag-in box.
At least one of the thermoplastic resins must be a heat-sealable thermoplastic resin;
It may also be a resin that is not well suited for heat sealing.
As the thermoplastic resin, the various thermoplastic resins mentioned above are used, and among these resins, linear low-density polyethylene and ethylene-vinyl acetate copolymer are more preferably used. When linear low density polyethylene is used for at least one of the above B,
In particular, when the adhesive resin of the present invention is used for both, the improvement effect obtained by using the adhesive resin of the present invention is more remarkable. Here, the linear low-density polyethylene is linear low-density polyethylene that does not substantially have long chain branches. In general, the quantitative measure of the number of long chain branches is G = [η]b/[η]e ([η]b is the intrinsic viscosity of branched polyethylene, and [η]e is linear polyethylene with the same molecular weight as branched polyethylene. (intrinsic viscosity) is approximately 1 (generally in the range of 0.9 to 1,
(often close to 1), and the density is 0.910~
It is of 0.945. (The G value of conventional high-pressure low-density polyethylene is 0.1 to 0.6.)
The method for producing linear low density polyethylene is not particularly limited. Examples of typical manufacturing methods are 7 to 45.
Chromium-based catalyst or Ziegler at a pressure of Kg/ ^cm2 (usually 2000-3000Kg/ ^cm2 for high-pressure low-density polyethylene) and a temperature of 75-100℃ (120-250℃ for high-pressure low-density polyethylene). There is a method of copolymerizing ethylene using a catalyst as a copolymerization component of an α-olefin having 3 or more carbon atoms, preferably 5 to 10 carbon atoms, such as propylene, 1-butene, 1-hexene, and 1-octene. . As the polymerization method, a solution method, liquid phase method, slurry method, liquid phase method, fluidized bed gas phase method, stirred bed gas phase method, etc. are used. Although the details are not yet clear, this improvement may be due to the fact that the cooperative effect with the adhesive resin of the present invention becomes more suitable in relation to a specific linear low-density polyethylene. It is closely related to the carbon number of α-olefin, which is a copolymerization component of linear low-density polyethylene, and the Young's modulus at a heat of fusion of 20°C based on thermal analysis using a differential scanning calorimeter (hereinafter referred to as DSC). This is even more noticeable when the above-mentioned linear low-density polyethylene is used in a selected specific region. More specifically, it is as follows. In other words, the heat of fusion is 25 cal/
The effect of the present invention is more remarkable for polyethylene having a Young's modulus of 25 kg/mm ² or less, preferably 22 to 5 kg/mm ² at 20° C. This is particularly noticeable when both are in the above range. The heat of fusion and Young's modulus in the above range vary somewhat depending on the polymerization method and polymerization conditions, but generally speaking, the content of the α-olefin, which is a copolymerization component, is about 2 mol% or more, preferably is often obtained in the range of about 2 to 7 mol%. For linear low-density polyethylene whose copolymerization component is butene-1, the improvement effect is determined when the heat of fusion is 15 cal/g or the Young's modulus at 20°C is 15 kg/mm ² or less. is more noticeable, and especially when both are in the above range, the effect can be most noticeably enjoyed. The low-density polyethylene having the Young's modulus of heat of fusion in the above range is generally obtained in many cases where the content of butene-1 is about 4 mol % or more. If the approximate content is too large, the other physical properties of the polyethylene will become unsatisfactory, which is undesirable.
It is desirable that it is mol%. Further, as described above, the improvement effect can be enjoyed with linear low-density polyethylene whose heat of fusion and/or Young's modulus is in the above-mentioned specific range, but especially with α-olefins having 5 or more carbon atoms, for example, 5 to 10 carbon atoms. The polyethylene containing as a copolymerization component can further exhibit a cooperative effect with the adhesive resin, and the improved effect can be enjoyed even more markedly. In this case, for the same reason as mentioned above, the content of the α-olefin is 2 to 7.
mol % is preferable, and 2 to 6 mol % is more preferable, and the heat of fusion is as described above.
- It is related to the olefin content, etc., but the heat of fusion is preferably 25 to 5 cal/g, and the Young's modulus is 22 kg/mm ² or less, preferably 22 to 3
Kg/ ^mm2 . More preferably, it is 22 to 5 Kg/mm ² . Among these olefins, the improvement effect of the present invention is more remarkable, and 4-
Linear low density polyethylene containing methyl-1-pentene as a copolymerization component is one of the most preferred. Other thermoplastic resins used in the surface layer of the present invention include ethylene-vinyl acetate copolymers. In particular, copolymers having a vinyl acetate content of at least 7% by weight can enjoy the effects of the present invention more markedly. If the content is too large, the resin surface will become sticky, which is undesirable;
It is preferable that it is below. When the filling in a packaging container made of the laminated packaging material of the present invention is an aqueous mixture or a water-containing food, the copolymer is added to the outer surface layer in relation to the moisture permeation rate of both the inner and outer surface layers. The embodiment in which linear low-density polyethylene is used for the inner surface layer is one of the preferable configurations of the laminated packaging material, since it is possible to maintain a lower constant humidity of the EVOH layer disposed as the intermediate layer. Furthermore, in the case of the packaging filling, when even better bending fatigue resistance is required, the copolymer having a higher water vapor permeability than the polyethylene is used for both the inner and outer surface layers within the limit that satisfies the barrier property requirements. , the thickness of the inner surface layer is selected so as to satisfy the above-mentioned conditions regarding the moisture permeation rate.
It can be suitably used by configuring the EVOH layer to maintain its constant humidity within a suitable range. In the present invention, even though the pinhole resistance of the EVOH single film is extremely poor, the pinhole resistance of the laminated film having the structure of the present invention has been significantly improved, that is, the characteristics of the EVOH single film. Judging from the above, it is obvious that cracks or pinholes will occur in the EVOH layer, which is the intermediate layer, and the barrier properties of the laminated packaging material will deteriorate at a stage when the barrier properties of the laminated packaging material are expected to deteriorate. The fact that no deterioration is observed is different from the conventional laminated packaging material using a barrier material such as vinylidene chloride, and is extremely specific. In the case of the laminated packaging material of the present invention, if each layer of the surface layer is too thin, for example, 10μ or less, other physical properties such as strength will deteriorate.
It is preferably 10μ or more, more preferably 20μ or more. Moreover, if the thickness increases too much, the effects of the present invention will be diminished, so it is more preferable that each layer of the surface layer is used with a thickness of 60 μm or less. In particular, for the constituent material of the inner container of a bag-in box, it can be suitably selected from a thickness range of 25 to 60 μm depending on the content. The laminated packaging material according to the present invention can be suitably obtained by a method known per se, particularly a coextrusion method using a multilayer die. For example, a bag-in-box inner container using the laminated material can be obtained by a film seal method in which a film with the laminated structure is obtained by a known method and then a cap is attached, or by a film formed in advance according to the shape of the product. After molding the sheet with the laminated structure, a multilayer parison made of the combination of materials of the present invention is sandwiched between molds into which the caps are inserted, using a vacuum forming method in which the caps are physically fixed, or a multilayer melt extrusion molding method, and then molded with compressed air. It can be obtained by a known method such as a blow molding method in which the main body and the cap are thermally bonded by molding and using the heat of the parison and air pressure at this time. EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. Example 1 Ethylene content 31.5 mol%, saponification degree 99.5%
An intermediate layer with a thickness of 12μ made of EVOH resin and 4-methyl-1-pentene with a thickness of 35μ on both sides of the intermediate layer are copolymerized, containing 3.2 mol% of the copolymerization component, and a load of 2160g at 190℃. ASTM D- under conditions
A surface layer made of linear low-density polyethylene (hereinafter referred to as LLDPE) with a melt index (hereinafter referred to as MI value) of 2.1 g/10 minutes measured according to 1238-65T and a heat of fusion of 19 cal/g by DSC. Three extruders, _three extruders, It was obtained by a coextrusion method using a multilayer die head for five layers. The obtained laminated film was subjected to a bending fatigue test until the generation of pinholes was observed in the laminated film, and the amount of oxygen gas permeation was measured at each stage up to the generation of pinholes. The bending fatigue test was performed using a Gerbo Flex Tester (manufactured by Rigaku Kogyo Co., Ltd.). A 12 inch x 8 inch sample piece was shaped into a cylinder with a diameter of 31/2 inches, gripped at both ends, and the initial grip interval was 7 inches, and the maximum bending was performed. Gripping interval at time
1in, the first 31/2in of the stroke is a twist at an angle of 440°, and the subsequent 21/2in is a linear horizontal motion, repeating the same reciprocating motion at a speed of 40 times/min.
It is conducted under conditions of 20°C and 65% relative humidity.
The measurement of oxygen gas permeation is made by Modern Control.
Using OX-TRAN100, 20℃, relative humidity (RH
(described below) at 65% and 20°C and 80% RH. For samples after each stage of bending fatigue test
A flat surface of 12 inches x 8 inches was prepared, and the measurement was taken at the center of the plane.
Young's modulus is determined according to ASTM D-882-67.
Measured at 20°C and 65% relative humidity. The measurement results are shown in Table 1. During the bending fatigue test up to the occurrence of pinholes, there was almost no change in the amount of oxygen permeation. In addition, the occurrence of pinholes is confirmed by the bending fatigue test.
It was not noticed until after 5,000 round trips, and when the pinhole was inspected after 5,100 round trips, it was found that one pinhole had already occurred. Moreover, no delamination between the layers was observed. The LLDPE film was obtained separately and heated to 20°C.
The Young's modulus was measured at 13 kg/mm ² .

【表】実施例２エチレン含量45モル％、けん化度92.2％、
EVOH樹脂を中間層とし、また該中間層の両側
に配される表面層（LLDPE）の厚さを一方を
40μ、他方を30μとし、さらに接着性樹脂として、
酢酸ビニル25重量％で無水マレイン酸変性度2.1
重量％の変性EVA_C40重量部と酢酸ビニル含量41
重量％のEVA_C60重量部のブレンド物を用いた以
外は、実施例１と同様に行つた。該屈曲疲労テス
ト5000往復を経過するまでピンホールは認められ
ず5700往復過程後ピンホールの１ケ発生している
のを認めた。酸素透過量の測定値は第２表に示
す。各層間のデラミネーシヨンは、全く認められ
なかつた。[Table] Example 2 Ethylene content 45 mol%, saponification degree 92.2%,
EVOH resin is used as an intermediate layer, and the thickness of the surface layer (LLDPE) arranged on both sides of the intermediate layer is
40μ and the other 30μ, and further as adhesive resin,
Maleic anhydride modification degree 2.1 with vinyl acetate 25% by weight
Modified EVA _C 40 parts by weight and vinyl acetate content 41% by weight
Example 1 was carried out as in Example 1, except that a blend of 60 parts by weight of EVA _C was used. No pinholes were observed until 5,000 cycles of the bending fatigue test had been completed, and one pinhole was observed after 5,700 cycles. The measured values of oxygen permeation are shown in Table 2. No delamination between the layers was observed.

【表】実施例３Ｄ／Ad／Ｅ／Ad／Ｆ／Ad／Ｇなる構成の積
層フイルムを３種７層用多層ダイヘツドを有する
共押出設備を用いて得た。各層はそれぞれ次に示
す各樹脂及び層厚さからなる。 Ad；酢酸ビニル含量26重量％、無水マレイン酸
変性度0.75重量％の変性EVA_C48重量部と酢酸
ビニル含量４重量％、無水マレイン酸変性度
1.1重量％の変性EVA_C52重量部の、層厚さ5μ
のブレンド樹脂層Ｄ、Ｇ；４−メチル−１−ペンテン4.1モル％を
共重合成分として含有するメルトインデツクス
2.3ｇ／10分、DSCによる融解熱15cal／ｇの厚
さ38μのLLDPE層Ｅ、Ｆ；エチレン含有量38モル％、けん化度99.4
％、厚さ6μのEVOH樹脂層実施例１に準じて屈曲疲労テストを行つた。該
屈曲疲労テスト6000往復経過後もピンホールの発
生を認めなかつた。該6000往復に至る各段階にお
ける酸素透過量の測定値を第３表に示めす。各層
間のデラミネーシヨンは認められなかつた。なお
該LLDPEのフイルムを別に得て20℃で測定した
ヤング率は、7.5Kg／mm²であつた。[Table] Example 3 A laminated film having the structure D/Ad/E/Ad/F/Ad/G was obtained using coextrusion equipment having a multilayer die head for three types and seven layers. Each layer consists of each resin and layer thickness shown below. Ad; 48 parts by weight of modified EVA _C with a vinyl acetate content of 26% by weight and a maleic anhydride modification degree of 0.75% by weight and a vinyl acetate content of 4% by weight and a maleic anhydride modification degree of
1.1% by weight of modified EVA _C 52 parts by weight, layer thickness 5μ
Blend resin layers D and G: Melt index containing 4.1 mol% of 4-methyl-1-pentene as a copolymerization component
2.3 g/10 min, 38 μ thick LLDPE layer E, F with heat of fusion 15 cal/g by DSC; ethylene content 38 mol%, saponification degree 99.4
%, EVOH resin layer with a thickness of 6 μm. A bending fatigue test was conducted according to Example 1. No pinholes were observed even after 6000 cycles of the bending fatigue test. Table 3 shows the measured values of the amount of oxygen permeation at each stage up to the 6000 round trip. No delamination between layers was observed. Note that the Young's modulus of the LLDPE film obtained separately and measured at 20° C. was 7.5 Kg/mm ² .

【表】実施例４Ｅを実施例１と同じEVOH樹脂からなる厚さ
8μの層Ｆを実施例２と同じEVOH樹脂からなる
厚さ6μの層、接着性樹脂層Adを酢酸ビニル含量
25重量％のEVA_C40重量部と酢酸ビニル含量40重
量％、無水マレイン酸変性度1.3重量％の変性
EVA_C60重量部のブレンド樹脂層とした以外は、
実施例３と同様に行つた。該屈曲疲労テスト6000
往復経過後もピンホールの発生を認めなかつた。
該6000往復経過後の酸素透過量の値は20℃、65％
RHで0.8c.c.／m²・24hr、20℃、80％RHで1.7c.c.／
m²・24hrであり該テスト開始前の値と殆んど同じ
であつた。なお、各層間のデラミネーシヨンは認
められなかつた。実施例５実施例１において両表面層に共重合成分を１−
ヘプテンとし、該含有量が2.9モル％、DSCによ
る融解熱が21cal／ｇの別に得て20℃で測定した
ヤング率が15Kg／mm²のLLDPEを、接着性樹脂と
して実施例２に用いたブレンドEVA_C系樹脂を使
用した以外は実施例１と同様に行つた。該屈曲テ
スト5500往復経過するもピンホールの発生は認め
られず、酸素透過量の値も殆んど変化なく、ほぼ
1.4c.c.／m²、24hr（20℃、80％RH）であつた。実施例６実施例１においてブテン−１を共重合成分とし
該成分含有量5.1モル％、DSCによる融解熱が
12cal／ｇのフイルムを別に得て、20℃で測定し
たヤング率が８Kg／mm²のLLDPEで両表面層を構
成した以外は実施例１と同様に行つた。該疲労テ
スト5000往復を経過するもピンホールの発生は認
められず、また酸素透過量の値も殆んど変化がな
く1.5c.c.／m²・24hr（20℃、80％RH）であつた。実施例７エチレン含量31モル％、けん化度99.3％の
EVOH樹脂からなる厚さ12μの中間層、該中間層
の両側に位置する表面層の片方に厚さ35μの実施
例１で用いたLLDPEかなる表面層及び他の片方
に、酢酸ビニル含量、８重量％のEVA_Cからなる
厚さ35μの表面層を有し各層間に6μの実施例２で
用いた接着性樹脂層を介して配された積層フイル
ムを４基の押出機、４種５層用多層ダイヘツドを
用いて、共押出法により得て屈曲疲労テストに付
した。結果を第４表に示す。ピンホールの発生に
至るまでの屈曲疲労テスト過程においては、酸素
透過量の変化は殆んどなかつた。またピンホール
の発生は該屈曲疲労テスト4600往復を経過するま
で認められず、4700往復経過後ピンホールの発生
の有無を検査に付したところ、ピンホール１ケが
既に発生しているのを認めた。また各層間のデラ
ミネーシヨンは全くみられなかつた。[Table] Example 4 E is made of the same EVOH resin as Example 1 and has a thickness
The 8μ layer F is a 6μ thick layer made of the same EVOH resin as in Example 2, and the adhesive resin layer Ad is a layer with a vinyl acetate content.
Modified with 40 parts by weight of 25% EVA _C , vinyl acetate content 40% by weight, degree of maleic anhydride modification 1.3% by weight
Except for the blended resin layer containing 60 parts by weight of EVA _C.
The same procedure as in Example 3 was carried out. The bending fatigue test 6000
No pinholes were observed even after reciprocation.
The value of oxygen permeation after 6000 cycles is 20℃, 65%
0.8cc/ ^m2・24hr at RH, 1.7cc/m at 20℃, 80%RH
^m2.24hr , which was almost the same as the value before the start of the test. Note that no delamination between the layers was observed. Example 5 In Example 1, a 1-copolymer component was added to both surface layers.
Blend used in Example 2 as adhesive resin, LLDPE with heptene content of 2.9 mol%, heat of fusion by DSC of 21 cal/g, and Young's modulus of 15 Kg/mm ² measured at 20°C The same procedure as in Example 1 was carried out except that EVA _C- based resin was used. Even after 5,500 cycles of the bending test, no pinholes were observed, and the oxygen permeation value remained almost unchanged.
It was 1.4 cc/m ² , 24 hr (20°C, 80% RH). Example 6 In Example 1, butene-1 was used as a copolymerization component, the content of the component was 5.1 mol%, and the heat of fusion by DSC was
The same procedure as in Example 1 was conducted except that a 12 cal/g film was separately obtained and both surface layers were made of LLDPE having a Young's modulus of 8 Kg/mm ² measured at 20°C. Even after 5,000 cycles of the fatigue test, no pinholes were observed, and the oxygen permeation rate remained almost unchanged at 1.5 cc/m ² ·24 hr (20°C, 80% RH). Example 7 Ethylene content 31 mol%, saponification degree 99.3%
An intermediate layer with a thickness of 12μ made of EVOH resin, one of the surface layers located on both sides of the intermediate layer is made of LLDPE used in Example 1 with a thickness of 35μ, and the other side has a vinyl acetate content of 8. A laminated film with a surface layer of 35 μm thick made of EVA _C (wt%) and 6 μm adhesive resin layer between each layer, which was used in Example 2, was fabricated using 4 extruders and 5 layers of 4 types. A multilayer die head was obtained by a coextrusion method and subjected to a bending fatigue test. The results are shown in Table 4. During the bending fatigue test process up to the occurrence of pinholes, there was almost no change in the amount of oxygen permeation. In addition, the occurrence of pinholes was not observed until 4,600 cycles had passed in the bending fatigue test, and after 4,700 cycles, an inspection was conducted to see if pinholes had occurred, and one pinhole had already occurred. Ta. Furthermore, no delamination between the layers was observed.

【表】実施例８実施例７においてEVOH層をエチレン含量46
モル％、けん化度99.3％のEVOH樹脂からなる厚
さ14μの層とし該中間層の片方に用いるエチレン
−酢酸ビニル共重合体の層を、酢酸ビニル含量が
９重量％の該共重合体からなる、厚さ40μとし、
接着性樹脂として酢酸ビニル含量45重量％の
EVA_C75重量部と、酢酸ビニル含量24重量％、無
水マレイン酸変性度3.2重量％の変性EVA_C25重量
部のブレンド樹脂を用いた以外は実施例７に準じ
て行つた。該屈曲疲労テスト5500往復経過するま
でピンホールの発生は認められず、6000往復経過
後ピンホール１ケが発生しているのがみられた。
5500往復経過後までの各段階で酸素透過量を測定
したが、いずれも20℃、65％RH、及び80％RH
の条件下でそれぞれ2.0c.c.／m²・24hr、3.5c.c.／
m²・24hrで殆んど変化が認められなかつた。また
各層間のデラミネーシヨンは全く認められなかつ
た。実施例９実施例１において、接着性樹脂として、酢酸ビ
ニル含量27重量％、無水マレイン酸変性度0.9重
量％の変性EVA_C35重量部と、酢酸ビニル含量39
重量％、無水マレイン酸変性度0.9重量％の変性
EVA_C65重量部からなるブレンド物を用いた以外
は、実施例１に準じて行つた。該屈曲疲労テスト
5000往復を経過するも、該積層フイルムにはピン
ホールの発生を認めず、また各層間のデラミネー
シヨンは、全く認められなかつた。[Table] Example 8 In Example 7, the EVOH layer had an ethylene content of 46
A 14μ thick layer made of EVOH resin with a mole% saponification degree of 99.3%, and a layer of ethylene-vinyl acetate copolymer used as one of the intermediate layers is made of the copolymer with a vinyl acetate content of 9% by weight. , the thickness is 40μ,
Vinyl acetate content 45% by weight as adhesive resin
The procedure of Example 7 was repeated except that a blend resin of 75 parts by weight of EVA _C and 25 parts by weight of modified EVA _C having a vinyl acetate content of 24% by weight and a degree of maleic anhydride modification of 3.2% by weight was used. No pinholes were observed until 5,500 cycles of the bending fatigue test had passed, and one pinhole was observed after 6,000 cycles.
The amount of oxygen permeation was measured at each stage until after 5500 cycles had passed, all at 20℃, 65%RH, and 80%RH.
2.0cc/ ^m2・24hr and 3.5cc/m2 under the conditions of
Almost no change was observed at ^m2・24 hours. Furthermore, no delamination between the layers was observed. Example 9 In Example 1, the adhesive resin was 35 parts by weight of modified EVA _C with a vinyl acetate content of 27% by weight and a degree of maleic anhydride modification of 0.9% by weight, and a vinyl acetate content of 39% by weight.
Modification by weight%, degree of maleic anhydride modification 0.9% by weight
The procedure of Example 1 was followed except that a blend consisting of 65 parts by weight of EVA _C was used. The bending fatigue test
Even after 5,000 reciprocations, no pinholes were observed in the laminated film, and no delamination between layers was observed at all.

Claims

[Claims] 1. A thin film of saponified ethylene-vinyl acetate copolymer as an intermediate layer, surface layers on both sides of the intermediate layer, and each layer is arranged with an adhesive resin layer interposed therebetween. In the flexible laminated packaging material, the adhesive resin is an ethylene-vinyl acetate copolymer with a vinyl acetate content of more than 35% by weight and less than 55% by weight, and 0.01% of an ethylenically unsaturated carboxylic acid or its anhydride.
A flexible laminated packaging material having bending fatigue resistance and gas barrier properties, which is a modified ethylene-vinyl acetate copolymer obtained by chemically bonding ~15% by weight. 2. The laminated packaging material according to claim 1, wherein the adhesive resin layer has a thickness of 2 to 10 μm. 3. The laminated packaging material according to claim 1 or 2, wherein the laminated packaging material is a constituent material of a packaging container in which the packaging filler is an aqueous mixture or a water-containing substance. 4. The laminated packaging material according to claim 1, 2, or 3, wherein the packaging material is a component of a bag-in-box inner container. 5. A flexible laminated packaging material comprising a thin film of saponified ethylene-vinyl acetate copolymer as an intermediate layer, surface layers on both sides of the intermediate layer, and each layer being arranged with an adhesive resin layer interposed therebetween, The adhesive resin is an ethylene-vinyl acetate copolymer containing 0.01 to 15% of an ethylenically unsaturated carboxylic acid or its anhydride.
It consists of a modified ethylene-vinyl acetate copolymer obtained by chemically bonding the modified ethylene-vinyl acetate copolymer with (A) a vinyl acetate content of 20 to 20% by weight;
45% by weight of modified ethylene-vinyl acetate copolymer and
(B) Modified ethylene with vinyl acetate content of 35 to 55% by weight
It is a blend of vinyl acetate copolymers, (A) and (B)
The difference in vinyl acetate content is at least 10% by weight or more, and the blend ratio (weight) A:B is 60:40.
A flexible laminated packaging material having bending fatigue resistance and gas barrier properties of ~5:95. 6. The laminated packaging material according to claim 5, wherein the adhesive resin layer has a thickness of 2 to 10 μm. 7. The laminated packaging material according to claim 5 or 6, wherein the packaging material is a constituent material of a packaging container in which the packaging filler is an aqueous mixture or a water-containing material. 8. The laminated packaging material according to claim 5, 6, or 7, wherein the packaging material is a component of a bag-in-box inner container. 9. A flexible laminated packaging material comprising a thin film of saponified ethylene-vinyl acetate copolymer as an intermediate layer, surface layers on both sides of the intermediate layer, and each layer being arranged with an adhesive resin layer interposed therebetween, The adhesive resin is made by chemically bonding (C) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20 to 55% by weight with 15% by weight or less of an ethylenically unsaturated carboxylic acid or its anhydride (X). It consists of a blend of the obtained modified ethylene-vinyl acetate copolymer and (D) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20 to 55% by weight, and the blend has a vinyl acetate content of 35% by weight or more. Flexible material containing 40% by weight or more of (C) and/or (D) and having flexural fatigue resistance and gas barrier properties, containing 0.01% by weight or more of chemically bonded X based on the blend. Laminated packaging material. 10. The laminated packaging material according to claim 9, wherein the adhesive resin layer has a thickness of 2 to 10 μm. 11. The laminated packaging material according to claim 9 or 10, wherein the laminated packaging material is a constituent material of a packaging container in which the packaging filler is an aqueous mixture or a water-containing substance. 12. The laminated packaging material according to claim 9, 10, or 11, wherein the packaging material is a component of a bag-in-box inner container.