JP4326188B2 - Gas barrier coating agent and film - Google Patents

Description

【００２２】
ここでＲは原子または原子団を表し、全て同じでも、全て異なっていてもよく、またいくつかは同じ原子または原子団であってもよい。Ｒとしてはたとえば水素や、塩素や臭素といったハロゲン原子のほか、水酸基、カルボキシル基、アミノ基、アミド基、エステル基、フェニル基等でもよく、メチル基やエチル基などのアルキル基でもよい。ただし、廃棄処理などを考慮すると、塩素などのハロゲン原子は含まれていないことがより好ましい。また、化合物（Ｂ）は環状になっていてもよく、芳香環であってもよい。そのような場合には構造式（１）におけるＲの数が少なくなることもある。
さらに、化合物（Ｂ）のカルボキシル基のうち、２つのカルボキシル基の間で作られる無水物構造を少なくとも１つ有する化合物も本発明においては構造式（1）で表される化合物と同様の効果を発現する。
この様な化合物としては高分子、オリゴマー、低分子化合物の何れでもよい。高分子やオリゴマーとしては、ポリマレイン酸やポリマレイン酸無水物、およびこれらの共重合体、例えば（無水）マレイン酸とアクリル酸の（交互）共重合体、などが挙げられるが、コート剤としては粘度が低い方が取り扱いやすいので、なかでも数平均分子量が１０，０００未満であるオリゴマーが好ましい。
低分子化合物を用いればさらに粘度が低く取り扱いやすいので、より好ましく用いられる。その様な化合物としては１，２，３−プロパントリカルボン酸、１，２，３，４−ブタンテトラカルボン酸、クエン酸、１，２，３−ベンゼントリカルボン酸、３−ブテン−１，２，３−トリカルボン酸、ブタン−１，２，３，４−テトラカルボン酸、１，２，３，４−シクロペンタンテトラカルボン酸、テトラヒドロフラン−２，３，４，５−テトラカルボン酸、ベンゼンペンタカルボン酸、ベンゼンヘキサカルボン酸、１，２，３，４，５，６−シクロヘキサンヘキサカルボン酸、ベンゼンヘキサカルボン酸、あるいはこれら化合物の無水物などが挙げられるが、特に１，２，３，４−ブタンテトラカルボン酸が反応性の点で好ましい。
【００２３】
本発明で好ましく用いられる１，２，３，４−ブタンテトラカルボン酸は部分的にエステル化もしくはアミド化されていてもよい。なお、１，２，３，４−ブタンテトラカルボン酸中のカルボキシル基は、乾燥状態では隣接カルボキシル基が脱水環化した酸無水物構造となりやすく、湿潤時や水溶液中では開環してカルボン酸構造となるが、本発明ではこれら閉環、開環を区別せず１，２，３，４−ブタンテトラカルボン酸として記述する。
【００２４】
本発明において、化合物（Ａ）と、化合物（Ｂ）の質量比は９５／５〜１０／９０の範囲であることが必要であり、高湿度雰囲気下での優れたバリア性を発現させるために８０／２０〜１０／９０であることが好ましく、７０／３０〜１５／８５であることがより好ましく、短時間の熱処理で優れた高湿度雰囲気下バリア性を発現させるために６５／３５〜１５／８５であることが特に好ましい。化合物（Ａ）が９５％を超えたり１０％未満では、特に高湿度雰囲気下におけるフィルムのガスバリア性を発現させるために有効な架橋密度が得られず、本発明の目的とするガスバリア性フィルムを得ることができない。
【００２５】
本発明において、ガスバリア層と基材フィルムとの接着性を向上させるためにポリスチレンスルホン酸および／またはその塩（Ｃ）を添加することが必要である。（Ｃ）の添加量は、固形分換算で（Ｃ）／[（Ａ）＋（Ｂ）]の値が０．０３〜１．０である必要があり、バリア性と接着性を共に発現させるために０．０３〜０．８であることが好ましく、０．０３〜０．５であることがより好ましく、０．０４〜０．４であることがさらに好ましく、０．０４〜０．３であることが特に好ましい。（Ｃ）の添加量が０．０３未満の場合は接着性の改善効果が認められず、１．０を超えた場合は、高湿度雰囲気下でのバリア性が低下したり、バリア性を発現するために高温で長時間の熱処理を必要としてしまう。
ポリスチレンスルホン酸および／またはその塩の分子量（重量平均）は特に限定されないが、１０００〜５００００００の範囲であれば良い。入手が容易である点からポリスチレンスルホン酸塩を用いることが好ましく、塩の種類としては、ナトリウム塩、カリウム塩、リチウム塩、アンモニウム塩などが挙げられ、中でもラミネート強度の点からポリスチレンスルホン酸ナトリウムまたはアンモニウムが好ましい。ポリスチレンスルホン酸（またはその塩）には、その他の化合物が共重合されていても良く、エチレンやプロピレンなどのオレフィン化合物、（メタ）アクリル酸、（メタ）アクリル酸エステル、（メタ）アクリル酸アミド、アルキルビニルエーテル、（無水）マレイン酸、酢酸ビニルまたはそのケン化物などが挙げられる。これらの共重合量は０〜５０ｍｏｌ％であればよい。
【００２６】
本発明のコート剤の溶媒としては、環境の面から水を使用することがガスバリア性フィルムを生産する上で好ましい。乾燥性を向上させる目的で少量の有機溶剤を添加しても良い。
【００２７】
コート剤の調製方法としては、撹拌機を備えた溶解釜等を用いて公知の方法で行えばよく、撹拌機としては、ホモジナイザー、ボールミル、高圧分散装置など公知の装置を用いることができる。この時次に述べるアルカリ化合物を、分子内に２個以上のカルボキシル基を有する化合物（Ｂ）の水溶液に加えておくことにより水溶液の安定性が向上する。
【００２８】
本発明のコート剤を調製する際には、アルカリ化合物を加えることが好ましい。特に化合物（Ｂ）のカルボキシル基に対して０．１〜３０当量％、好ましくは１〜３０当量％、より好ましくは２〜２８当量％のアルカリ化合物を加えることが好ましい。アルカリ化合物を適正量添加することにより、得られるフィルムのガスバリア性が格段に向上される。
アルカリ化合物としては、化合物（Ｂ）中のカルボキシル基を中和できるものであればよく、水酸化ナトリウム、水酸化カリウム、水酸化リチウム、水酸化カルシウムなどのアルカリ金属やアルカリ土類金属の水酸化物、水酸化アンモニウム、有機水酸化アンモニウム化合物等が挙げられ、特に水酸化ナトリウム、水酸化カリウムが好ましい。また、上記アルカリ化合物として、またはアルカリ化合物と併用して、アルカリ金属塩を加えることにより、アルカリ化合物と同様にガスバリア性が向上する。このようなアルカリ金属塩としては、リン酸塩、亜リン酸塩、次亜リン酸塩等が好ましく、特に、次亜リン酸ナトリウムが好ましい。
【００２９】
本発明のコート剤には、ガスバリア性や接着性といった特性を大きく損わない限りにおいて、熱安定剤、酸化防止剤、強化材、顔料、劣化防止剤、耐候剤、難燃剤、可塑剤、離型剤、滑剤などが添加されていてもよい。
【００３０】
熱安定剤、酸化防止剤及び劣化防止剤としては、例えばヒンダードフェノール類、リン化合物、ヒンダードアミン類、イオウ化合物、銅化合物、アルカリ金属のハロゲン化物あるいはこれらの混合物が挙げられる。
【００３１】
強化材としては、例えばクレー、タルク、炭酸カルシウム、炭酸亜鉛、ワラストナイト、シリカ、アルミナ、酸化マグネシウム、珪酸カルシウム、アルミン酸ナトリウム、アルミノ珪酸ナトリウム、珪酸マグネシウム、ガラスバルーン、カーボンブラック、酸化亜鉛、ゼオライト、モンモリロナイト、ハイドロタルサイト、フッ素雲母、金属繊維、金属ウィスカー、セラミックウィスカー、チタン酸カリウムウィスカー、窒化ホウ素、グラファイト、ガラス繊維、炭素繊維、フラーレン（Ｃ６０、Ｃ７０など）、カーボンナノチューブなどが挙げられる。
【００３２】
本発明において、コート剤に架橋剤成分を少量添加することによって、得られる成形体のガスバリア性をさらに向上させることができる。架橋剤としては、イソシアネート化合物、メラミン化合物、エポキシ化合物、カルボジイミド化合物、ジルコニウム塩化合物などが挙げられる。
【００３３】
本発明のコート剤を、各種基材フィルム上に塗布後、熱処理することにより、容易にガスバリア性の樹脂被膜層を得ることができる。この際に、コート剤中の化合物（Ａ）と（Ｂ）との間にエステル結合が形成され、硬化して水不溶性となる。この熱処理時間は比較的短くて済むため工業的に有利である。
【００３４】
本発明のガスバリア性フィルムに用いられる熱可塑性樹脂フィルム（基材フィルム）としては、ナイロン６、ナイロン６６、ナイロン４６等のポリアミド樹脂、ポリエチレンテレフタレート、ポリエチレンナフタレート、ポリトリメチレンテレフタレート、ポリトリメチレンナフタレート、ポリブチレンテレフタレート、ポリブチレンナフタレート等の芳香族ポリエステル樹脂、および液晶ポリエステル樹脂、ポリ乳酸などの脂肪族ポリエステル樹脂、ポリプロピレン、ポリエチレンなどのポリオレフィン樹脂、ポリアセタール、ポリカーボネート、ポリアリレート、ポリフェニレンサルファイド、ポリエーテルエーテルケトン、ポリサルホン、ポリエーテルサルホン、ポリアミドイミド、ポリエーテルイミド、直鎖状ポリイミドまたはそれらの混合物よりなるフィルムまたはそれらのフィルムの積層体が挙げられ、未延伸フィルムでも延伸フィルムでもよい。中でも、透明性の点からナイロン６フィルム、ポリエチレンテレフタレートフィルムが好ましい。
【００３５】
フィルムを製造する方法としては、熱可塑性樹脂を押出機で加熱・溶融してＴダイより押し出し、冷却ロールなどにより冷却固化させて未延伸フィルムを得るか、もしくは円形ダイより押し出して水冷あるいは空冷により固化させて未延伸フィルムを得る。
延伸フィルムを製造する場合は、未延伸フィルムを一旦巻き取った後、または連続して同時２軸延伸法または逐次２軸延伸法により延伸する方法が好ましい。フィルム機械的特性や厚み均一性能面からはＴダイによるフラット式製膜法とテンター延伸法を組み合わせる方法が好ましい。
【００３６】
また、フィルムとガスバリア層の接着性を向上するためにフィルム表面にコロナ放電処理をしてもよく、アンカーコートをしてもよい。
【００３７】
上記ガスバリア性フィルムにおいて、化合物（Ａ）がポリビニルアルコールであり、化合物（Ｂ）が１，２，３，４−ブタンテトラカルボン酸であり、１，２，３，４−ブタンテトラカルボン酸中のカルボキシル基に対して０．１〜３０当量％のアルカリ化合物を層に含有することが特に好ましい。
【００３８】
本発明におけるガスバリア性フィルムのガスバリア層の厚みは、フィルムのガスバリア性を十分高めるためには少なくとも０．０３μｍより厚くすることが望ましい。上限としては特にないが、あまり厚すぎるとベースフィルムの特性が活かせなくなるので、通常１００μｍ以下、好ましくは５０μｍ以下、より好ましくは１０μｍ以下、さらに好ましくは５μｍ以下であることが望まい。
【００３９】
また、化合物（Ａ）、化合物（Ｂ）、及びポリスチレンスルホン酸および／またはその塩（Ｃ）からなる混合溶液をフィルムにコートする際の溶液濃度は、液の粘度や反応性、用いる装置の仕様によって適宜変更されるものであるが、あまりに希薄な溶液ではガスバリア性を発現するのに充分な厚みの層をコートすることが困難となり、また、その後の乾燥工程において長時間を要するという問題を生じやすい。一方、溶液の濃度が高すぎると、混合操作や保存性などに問題を生じることがある。この様な観点から、本発明のコート剤における固形分濃度は５〜６０質量％の範囲であることが好ましく、１０〜５０質量％の範囲であることがより好ましい。
【００４０】
混合溶液をフィルムにコーティングする方法は特に限定されないが、グラビアロールコーティング、リバースロールコーティング、ワイヤーバーコーティング等の通常の方法を用いることができる。また、延伸に先だってコーティングを行うには、まず未延伸フィルムにコーティングして乾燥した後、テンター式延伸機に供給してフィルムを走行方向と幅方向に同時に延伸（同時２軸延伸）、熱処理するか、あるいは、多段熱ロール等を用いてフィルムの走行方向に延伸を行った後にコーティングし、乾燥後、テンター式延伸機によって幅方向に延伸（逐次２軸延伸）してもよい。また、走行方向の延伸とテンターでの同時２軸延伸を組み合わせることも可能である。
【００４１】
本発明においては、ガスバリア層を形成するために、コーティング後にフィルムを１３０℃以上で熱処理する必要であり、熱処理時間を短くするために１５０℃以上で熱処理することが好ましい。熱処理温度が低いとガスバリア層におけるエステル架橋反応を充分に進行させることができず、充分なガスバリア性を有するフィルムを得ることが困難になる。
熱処理時間があまり短すぎると上記架橋反応を充分に進行させることができず、充分なガスバリア性を有するフィルムを得ることが困難になる。熱処理時間は通常１秒以上、好ましくは３秒以上がよい。
ガスバリア性を高めるためには高温で長時間熱処理する必要がある。たとえば２００℃で３分以上、あるいは２２０℃で１５秒以上熱処理すれば非常に高いガスバリア性を示すフィルムが得られる。
【００４２】
熱処理などにより化合物（Ａ）と化合物（Ｂ）がエステル結合で架橋されていることがバリア性の発現に必要である。エステル結合の分析は、ＡＴＲ法によってガスバリア層の赤外スペクトルを測定することで分析することができる。化合物（Ａ）と化合物（Ｂ）がエステル結合で架橋された場合、化合物（Ｂ）中のカルボニル基の吸収ピークが高波数側にシフトする。従って、本発明のガスバリア層から化合物（Ｂ）の差スペクトルをとって残る吸収ピークをエステル結合に由来するピークとする。ここでは、１６００〜１８５０ｃｍ^-1の領域に限定してベースラインをとり、ガスバリア層と化合物（Ｂ）のカルボニル基のピークの吸光度を規格化し、ベースラインを下回らないように両者ピークの差スペクトルをとり、１６９５〜１８００ｃｍ^-1に残る吸収ピークをエステル結合由来のピークと判断した。例えば、化合物（Ａ）と化合物（Ｂ）がそれぞれポリビニルアルコールと１，２，３，４−ブタンテトラカルボン酸の場合、上記の方法で差スペクトルをとり、残った１７２０ｃｍ^-1付近のピークをエステル結合のカルボニルに由来するピークと判断した。
【００４３】
本発明によって得られるガスバリア性フィルムは、ガスバリア性の観点から２０℃、９０％ＲＨにおけるガスバリア層の酸素透過係数が１０００ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａ以下であることが好ましく、より好ましくは５００ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａ以下であり、さらに好ましくは３００ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａ以下であり、特に好ましくは１００ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａ以下である。なお、ガスバリア層の酸素透過係数は後述する方法で求めた。
【００４４】
本発明においては、フィルムのガスバリア性は基材フィルムの種類や厚み、およびガスバリア層の厚みにより変化するため、ガスバリア層自体の酸素透過係数も評価した。
酸素透過係数は、下記式より求めた。
１／Ｑ_F＝１／Ｑ_B＋Ｌ／Ｐ_C
ただし、Ｑ_F：ガスバリア性フィルムの酸素透過度（ｍｌ／ｍ²・ｄａｙ・ＭＰａ）
Ｑ_B：熱可塑性樹脂フィルムの酸素透過度（ｍｌ／ｍ²・ｄａｙ・ＭＰａ）
Ｐ_C：ガスバリア層の酸素透過係数（ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａ）
Ｌ：ガスバリア層厚み（μｍ）
したがって、ガスバリア層の酸素透過係数Ｐ_Cは、Ｑ_F、Ｑ_B、およびＬが分かれば上式より見積もることができる。
【００４５】
さらに、該ガスバリア性フィルムのガスバリア層上に接着層を設け、さらにその上にポリオレフィン樹脂フィルムを積層（ラミネート）してもよい。接着層は、良好な接着性を有している化合物であれば良い。ポリオレフィン樹脂フィルムとしては、ポリエチレンおよび／またはポリプロピレンを主成分とする樹脂から成るフィルムが好ましい。ポリエチレンには、酢酸ビニル、（メタ）アクリル酸、（メタ）アクリル酸エステルなどが共重合されていても良い。ポリプロピレンの立体構造は特に限定されず、シンジオタクチック、イソタクチック、アタクチックいずれでも良く、エチレンやα−オレフィンが共重合されていても良い。
この際、フィルムに印刷が成されていても良い。印刷の位置、印刷に用いるインキの種類は特に限定されないが、食品包装用フィルムの場合、ガスバリア層と接着剤層との間に印刷されることが多い。
【００４６】
ガスバリアガスバリア性フィルムとポリオレフィン樹脂から成るラミネートフィルムに関して、基材フィルムとガスバリア層との接着強度は０．７Ｎ／ｃｍ以上が好ましく、１Ｎ／ｃｍ以上がより好ましく、１．５Ｎ／ｃｍ以上がより好ましい。接着強度が０．７Ｎ／ｃｍ以上でないと、簡単に剥離してしまうために使用上、問題を生じる場合がある。
【００４７】
【実施例】
次に、本発明を実施例及び比較例により具体的に説明するが、本発明は、これらの実施例のみに限定されるものではない。
【００４８】
酸素バリア性は、モコン社製酸素バリア測定器（ＯＸ−ＴＲＡＮ ２／２０）により２０℃、相対湿度９０％の雰囲気における酸素透過度を測定した。
また、ガスバリア層の酸素透過係数は、モコン社製酸素バリア測定器によりガスバリア性フィルムの２０℃、相対湿度９０％の雰囲気における酸素透過度を測定し、Ｑ_Fとした。一方、コートしていないフィルムの酸素透過度を測定し、Ｑ_Bとした。次に、未コートフィルムとガスバリア性フィルムの平均厚みの差からコート厚みを求め、Ｌとした。以上の数値から前記式を用いてガスバリア層の酸素透過係数Ｐ_Cを算出した。
なお、厚み１２μｍのＰＥＴフィルムの酸素透過度は９００ｍｌ／ｍ²・ｄａｙ・ＭＰａ、また、厚み１５μｍのナイロン６フィルムの酸素透過度は５００ｍｌ／ｍ²・ｄａｙ・ＭＰａとした。
【００４９】
基材フィルムとガスバリア層との接着強度の測定方法を以下に示す。各種熱可塑性樹脂フィルム（基材フィルム）のコロナ処理面または非コロナ処理面に本発明のコート剤を所定のコート条件（実施例中に記載）でコートしてガスバリア性フィルムを得た。グラビアコート法によりコート面に接着剤（（ａ）主剤ディックドライＬＸ６３Ｆ（大日本インキ化学工業製）、（ｂ）硬化剤ＫＰ−９０（大日本インキ化学工業製）、（ｃ）酢酸エチル：（ａ）／（ｂ）／（ｃ）＝１／１２／１０（質量比））を厚み約１μｍとなるように塗布した後、８０℃熱風で２０秒間熱風乾燥した。続いて接着面にポリエチレンシーラント（東セロ社製、ＴＵＸＦＣＳ＃５０：厚み５０μｍ）を、８０℃の熱ロールを用いてプレス圧０．２ＭＰａでドライラミネートした後、４０℃で４８時間エージング処理した。このようにして得られたラミネートフィルムについて、幅１５ｍｍ、長さ１５０ｍｍの試験片を切り出し、Ｔ型剥離強度を測定し、これを接着強度とした。測定には島津製作所製Ａｕｔｏｇｒａｐｈ／ＡＧＳ−１００Ｇを用い、引張速度３００ｍｍ／分の条件で測定した。なお、このとき、実施例４を除いて、すべて基材フィルムとガスバリア層との間で剥離が起こった。
【００５０】
実施例１
化合物（Ｂ）として１，２，３，４−ブタンテトラカルボン酸（新日本理化株式会社製、リカシッドＢＴＷ）を、カルボキシル基に対して１５モル％の水酸化ナトリウムを含む水溶液に溶解し１０質量％溶液とした。この溶液と、化合物（Ａ）としてポリビニルアルコール（ユニチカケミカル株式会社製、ＵＦ−１００、重合度１０００、ケン化度９９．４）の１０質量％水溶液とをポリビニルアルコールと１，２，３，４−ブタンテトラカルボン酸の固形分質量比が３０／７０となるように混合、攪拌した。さらに、この混合溶液に（Ｃ）ポリスチレンスルホン酸ナトリウム水溶液（東ソー社製、ＰＳ−５、固形分約２０質量％、分子量５〜１０万）をポリビニルアルコールと１，２，３，４−ブタンテトラカルボン酸との総固形分１に対して０．１添加した後、攪拌してコート剤を調製した。
このコート剤を２軸延伸ポリエステルフィルム（ユニチカ社製エンブレットＰＥＴ１２、厚み１２μｍ）のコロナ処理面上に乾燥後の塗膜厚みが約１μｍになるようにメイヤーバーでコートし、１００℃で２分間乾燥した後、２２０℃で３０秒間熱処理した。
得られたガスバリア性フィルムは透明であり、ガスバリア層は水に不溶であった。このフィルムの２０℃、９０％ＲＨにおける酸素透過度は８ｍｌ／ｍ²・ｄａｙ・ＭＰａ、ガスバリア層の酸素透過係数は８．１ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａと優れたガスバリア性を示した。また、接着強度は４．４Ｎ／ｃｍと優れた接着性を示した。表１にフィルムの物性をまとめた。
【００５１】
実施例２、３
ポリビニルアルコールと１，２，３，４−ブタンテトラカルボン酸の組成を変えて実施例１と同様の操作でコート剤、およびガスバリア性フィルムを得た。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００５２】
実施例４
（Ｃ）ポリスチレンスルホン酸ナトリウム水溶液の添加量をポリビニルアルコールと１，２，３，４−ブタンテトラカルボン酸との総固形分１に対して０．３とした以外は実施例１と同様の操作でコート剤、およびガスバリア性フィルムを得た。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性は若干低下した。接着強度の測定の結果、剥離面は接着剤層とガスバリア層との間であり、この時の値は４．１Ｎ／ｃｍであった。基材フィルムとガスバリア層と界面に剥離は生じておらず、接着強度はさらに高いと推定される。
【００５３】
実施例５
（Ｃ）の種類をポリスチレンスルホン酸ナトリウム水溶液（東ソー社製、ＰＳ−１、固形分約２０質量％、分子量１〜３万）とした以外は実施例１と同様の操作でコート剤、およびガスバリア性フィルムを得た。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００５４】
実施例６、７
（Ｃ）の種類をポリスチレンスルホン酸ナトリウム水溶液（東ソー社製、ＰＳ−１００、固形分約２０質量％、分子量８０〜１２０万）とし、その添加量をポリビニルアルコールと１，２，３，４−ブタンテトラカルボン酸との総固形分１に対して０．０５（実施例６）、０．１（実施例７）とした以外は実施例１と同様の操作でコート剤、およびガスバリア性フィルムを得た。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。分子量の高いポリスチレンスルホン酸を用いた方が、接着性がより向上した。
【００５５】
実施例８
（Ｃ）の種類をスチレンスルホン酸ナトリウム−メタクリル酸共重合体水溶液（東ソー社製、固形分約２１．５質量％、分子量２７００、スチレンスルホン酸ナトリウム−メタクリル酸共重比３／１）とした以外は実施例１と同様の操作でコート剤、およびガスバリア性フィルムを得た。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００５６】
実施例９
（Ｃ）の種類をポリスチレンスルホン酸アンモニウム水溶液（東ソー社製、固形分約２２質量％、分子量３２００００、ＰＳ-Ｎと呼ぶ）とした以外は実施例１と同様の操作でコート剤、およびコートフィルムを得た。得られたフィルムはいずれも透明であり、コート層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００５７】
実施例１０
化合物（Ｂ）としてポリアクリル酸（和光純薬工業社製、ポリアクリル酸２５重量％水溶液、数平均分子量１５００００）を用い、カルボキシル基に対して１０モル％の水酸化ナトリウムを含む水溶液に溶解し１０質量％溶液とした。この液を用い、実施例１と同様の操作でコート剤を得た。このコート剤を２軸延伸ポリエステルフィルム（ユニチカ社製エンブレットＰＥＴ１２、厚み１２μｍ）のコロナ処理面上に乾燥後の塗膜厚みが約１μｍになるようにメイヤーバーでコートし、１００℃で２分間乾燥した後、２００℃で５分間熱処理した。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００５８】
実施例１１
化合物（Ｂ）としてエチレン−マレイン酸交互共重合体（ＡＬＤＲＩＣＨ社製、重量均分子量１００,０００〜５００,０００）を用いた以外は実施例１と同様の操作でコート剤、およびガスバリア性フィルムを得た。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００５９】
実施例１２
実施例１と同様の操作で得たコート剤を２軸延伸ポリエステルフィルム（ユニチカ社製エンブレットＰＥＴ１２、厚み１２μｍ）の非コロナ処理面上に実施例１と同様の操作でガスバリア性フィルムを得た。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００６０】
実施例１３
実施例１と同様の操作でコート剤を得た。このコート液を２軸延伸ナイロンフィルム（ユニチカ社製エンブレム、厚み１５μｍ）のコロナ処理面に乾燥後の塗膜厚みが約１μｍになるようにメイヤーバーでコートし、１００℃で２分間乾燥した後、２００℃で５分間熱処理した。得られたフィルムはいずれも透明であり、ガスバリア層は水に不溶であった。表１にフィルムの物性をまとめた。フィルムのガスバリア性、接着性は共に優れていた。
【００６１】
比較例１
（Ｃ）ポリスチレンスルホン酸ナトリウム水溶液を加えなかった以外は実施例１と同様の手順でコート剤を調製した。このコート剤を実施例１と同様にしてポリエステルフィルムにコート、乾燥、熱処理した。得られたガスバリア性フィルムの物性を表１に示したが、ラミネート強度は低く、接着性は悪かった。
【００６２】
比較例２
（Ｃ）ポリスチレンスルホン酸ナトリウム水溶液を加えなかった以外は実施例９と同様の手順でコート剤を調製した。このコート剤を実施例１と同様にしてポリエステルフィルムにコート、乾燥、熱処理した。得られたガスバリア性フィルムの物性を表１に示したが、ラミネート強度は低く、接着性は悪かった。
【００６３】
比較例３
（Ｃ）ポリスチレンスルホン酸ナトリウム水溶液を加えなかった以外は実施例１０と同様の手順でコート剤を調製した。このコート剤を実施例１と同様にしてポリエステルフィルムにコート、乾燥、熱処理した。得られたガスバリア性フィルムの物性を表１に示したが、ラミネート強度は低く、接着性は悪かった。
【００６４】
比較例４、５
（Ｃ）ポリスチレンスルホン酸ナトリウム水溶液（東ソー社製、ＰＳ−５、固形分約２０質量％、分子量５〜１０万）の添加量を表１のように変更した以外は実施例１と同様の手順でコート剤、およびガスバリア性フィルムを得た。得られたフィルムはいずれも透明であった。表１にフィルムの物性をまとめた。（Ｃ）の添加量が本発明の範囲を外れると、フィルムのガスバリア性、接着性を両立させることはできなかった。具体的には、添加量が少なければ接着性の改善効果が認められず、添加量が多ければ、著しくバリア性が低下した。
【００６５】
比較例６
（Ｃ）ポリスチレンスルホン酸ナトリウム水溶液（東ソー社製、ＰＳ−５、固形分約２０質量％、分子量５〜１０万）のみを用いた以外は実施例１と同様の手順でコート剤、およびガスバリア性フィルムを得た。表１にフィルムの物性をまとめた。ポリスチレンスルホン酸ナトリウムのみでは、高湿度下でのバリア性は無く、基材フィルムとの接着性も低かった。
【００６６】
【表１】

【００６７】
【発明の効果】
本発明のコート剤を熱可塑性樹脂フィルムの表面に形成させることにより、高湿度下でも優れたガスバリア性を有しており、さらに熱可塑性樹脂フィルムとガスバリア層との接着性に優れたガスバリア性フィルムを得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas barrier film having excellent gas barrier properties even under high humidity, and further having excellent adhesion between a base film and a gas barrier layer.
[0002]
[Prior art]
Thermoplastic resin films such as polyamide and polyester are excellent in strength, transparency, moldability, and gas barrier properties, and thus are used in a wide range of applications as packaging materials. However, when used for applications that require long-term storage, such as retort-treated foods, higher gas barrier properties are required.
[0003]
In order to improve gas barrier properties, a film in which polyvinylidene chloride (PVDC) is laminated on the surface of these thermoplastic resin films has been widely used for food packaging, etc. PVDC uses organic substances such as acid gas during incineration. In recent years, there has been a growing interest in the environment, and there is a strong demand for a shift to other materials.
[0004]
An example of a material that can replace PVDC is polyvinyl alcohol. This does not generate toxic gases and has a high gas barrier property in a low-humidity atmosphere, but as the humidity increases, the gas barrier property decreases rapidly, and in many cases, it cannot be used for packaging foods containing moisture. .
[0005]
A film made of a copolymer (EVOH) of vinyl alcohol and ethylene is known as a film that has improved the deterioration of the gas barrier property under high humidity of polyvinyl alcohol. However, the gas barrier property under high humidity is at a practical level. In order to maintain it, it is necessary to increase the ethylene content to some extent. When EVOH is used as a coating material, it must be dissolved using an organic solvent or a mixed solvent of water and an organic solvent, which is not desirable from the viewpoint of environmental problems, and requires a recovery step of the organic solvent. Therefore, there is a problem that the cost becomes high.
[0006]
In addition, a method of coating a film with an aqueous solution consisting of a partially neutralized polyacrylic acid or polymethacrylic acid and polyvinyl alcohol and heat-treating the film has been proposed (Japanese Patent Laid-Open No. 10-237180). In order to improve the gas barrier property, heating at a high temperature for a long time is required, and there is a problem in productivity. Furthermore, since the film is colored by reacting at a high temperature for a long time and the appearance is impaired, improvement for food packaging is necessary.
[0007]
Various techniques for making water resistant by adding a cross-linking agent to polyvinyl alcohol and making it cross-linked have been conventionally known. For example, a polymer containing a maleic acid unit reacts with a hydroxyl group such as polyvinyl alcohol or polysaccharide to make it water resistant. That is widely known. For example, JP-A-8-66991 discloses that a layer composed of 25-50% partially neutralized isobutylene-maleic anhydride copolymer and polyvinyl alcohol has excellent water resistance. Japanese Patent Application Laid-Open No. 49-1649 describes a method for making a polyvinyl alcohol film water resistant by mixing an alkyl vinyl ether-maleic acid copolymer with polyvinyl alcohol.
[0008]
However, water resistance (that is, water-insolubilization) and gas barrier properties are different, and water resistance is generally achieved by crosslinking polymer molecules, but gas barrier properties prevent the penetration and diffusion of relatively small molecules such as oxygen. For example, a three-dimensional crosslinkable polymer such as an epoxy resin or a phenol resin does not have a gas barrier property.
[0009]
In addition, the gas barrier layer obtained by heat-treating a partially neutralized product of polyvinyl alcohol and polycarboxylic acid (polyacrylic acid, polymethacrylic acid, polymer containing maleic acid unit, etc.) has very good adhesion to the substrate film. There was a problem of being low.
[0010]
[Problems to be solved by the invention]
The present inventors have a high gas barrier property even under high humidity and can form a highly transparent barrier layer with respect to the above-mentioned problems, and also have good adhesion to a base film. An object of the present invention is to provide an excellent barrier coating agent.
[0011]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that the above problem can be solved by applying a coating agent containing a specific resin composition to the surface of the film to form a layer comprising the resin composition. The present invention has been reached.
That is, the gist of the present invention is as follows.
First, a compound (A) having two or more hydroxyl groups in the molecule, a compound (B) having two or more carboxyl groups in the molecule, polystyrene sulfonic acid and / or a salt thereof (C), and a solvent. It is a coating agent as the main ingredient,The compound (A) is polyvinyl alcohol, and the compound (B) is at least selected from poly (meth) acrylic acid, a polymer having a maleic anhydride structure, and 1,2,3,4-butanetetracarboxylic acid. 1 type, the previous solvent is water,(A), (B), (C) solid content mass ratio is a gas barrier coating agent characterized by satisfying the following formulas (1), (2),
(A) / (B) = 95 / 5-10 / 90 (1)
(C) / [(A) + (B)] ≦ 0.03-1.0 (2)
Second, a gas barrier film in which a gas barrier layer formed by removing a solvent from the gas barrier coating agent is formed on at least one surface of a thermoplastic resin film,
Third, in the second invention, the oxygen barrier coefficient of the gas barrier layer at 20 ° C. and 90% RH is 1000 ml · μm / m.²-It is a gas barrier film that is not more than day-MPa,
Fourth, on at least one side of the thermoplastic film,AboveA method for producing a gas barrier film, which is characterized by applying a gas barrier coating agent and then performing a heat treatment at 130 ° C. or higher,
Fifth, a gas barrier laminate film in which an adhesive layer is provided on the gas barrier layer of the gas barrier film of the fourth invention and a polyolefin resin film is further laminated thereon.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0013]
In the present invention, the compound (A) having two or more hydroxyl groups in the molecule may be any of a polymer, an oligomer and a low molecular compound. Examples of the polymer compound include polyvinyl alcohol, polyhydroxyethyl methacrylate, copolymers thereof, saccharides, various polymer compounds modified with hydroxyl groups, and polymer compounds having hydroxyl groups at both ends, such as polyethylene glycol. Is mentioned. Examples of the oligomer include oligosaccharides and those having a short molecular chain in the above polymer compound. Examples of low molecular weight compounds include ethylene glycol, diethylene glycol, glycerin, monosaccharides, sugar alcohols, and further aromatic compounds such as catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), hydroquinone (1, 4-dihydroxybenzene) and the like. Among these compounds, polyvinyl alcohol is most preferable from the viewpoint of gas barrier properties.
[0014]
The polyvinyl alcohol preferably used in the present invention can be obtained by a known method such as complete or partial saponification of a vinyl ester polymer. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, vinyl versatate, etc. Among them, vinyl acetate is industrially most preferable.
[0015]
Other vinyl compounds may be copolymerized with the vinyl ester as long as the effects of the present invention are not impaired. Other vinyl monomers include unsaturated monocarboxylic acids such as crotonic acid, acrylic acid, and methacrylic acid and their esters, salts, anhydrides, amides, nitriles, and unsaturated acids such as maleic acid, itaconic acid, and fumaric acid. Examples thereof include dicarboxylic acids and salts thereof, α-olefins having 2 to 30 carbon atoms, alkyl vinyl ethers, vinyl pyrrolidones and the like.
[0016]
As the saponification method, a known alkali saponification method or acid saponification method can be used, and among them, a method of alcoholysis using an alkali hydroxide in methanol is preferable.
The degree of saponification is preferably closer to 100% from the viewpoint of gas barrier properties. If the degree of saponification is too low, the barrier performance will decrease. The saponification degree is usually about 90% or more, preferably 95% or more, and the average degree of polymerization is 50 to 3000, preferably 80 to 2500, more preferably 100 to 2000.
[0017]
Moreover, when the ratio of the hydroxyl group in the polyvinyl alcohol laminated | stacked on a film is too low, the esterification reaction rate with the compound (B) which has a 2 or more carboxyl group in a molecule | numerator will fall, and it is the objective of this invention A gas barrier film cannot be obtained. For this purpose, the molar ratio of the vinyl alcohol unit to other vinyl compound units in the polyvinyl alcohol is preferably 10/90 to 100/0.
[0018]
In the present invention, it is preferable from the viewpoint of production that the coating agent laminated for imparting gas barrier properties to the film surface is water-soluble, and if a large amount of a hydrophobic copolymer component is contained, the water-solubility is impaired, which is not preferable. .
[0019]
The compound (B) having two or more carboxyl groups in the molecule may be any of a polymer, an oligomer and a low molecular compound. For example, polymers having (maleic) anhydride structures such as poly (meth) acrylic acid, ethylene-maleic anhydride alternating copolymer, methyl vinyl ether-maleic anhydride alternating copolymer, isobutylene-maleic anhydride alternating copolymer, etc. , A compound in which at least one carboxyl group is bonded to each of three or more consecutive carbon atoms in the molecule, maleic acid, phthalic acid, fumaric acid, succinic acid, pyromellitic acid, trimellitic acid, phthalic acid And low molecular carboxylic acids such as, or their anhydrides. Among these, from the viewpoint of good barrier properties, poly (meth) acrylic acid, a polymer having a (anhydrous) maleic acid structure, and at least one carboxyl group for each of three or more consecutive carbon atoms in the molecule. Bound compounds are preferred.
[0020]
The compound (B) in which at least one carboxyl group is bonded to each of three or more consecutive carbon atoms in the molecule refers to a compound having a structure represented by the following structural formula (1) in the molecule. That is.
[0021]
[Chemical 1]

[0022]
Here, R represents an atom or an atomic group, and may be all the same or different, and some may be the same atom or atomic group. R may be, for example, hydrogen, a halogen atom such as chlorine or bromine, a hydroxyl group, a carboxyl group, an amino group, an amide group, an ester group, a phenyl group, or an alkyl group such as a methyl group or an ethyl group. However, in consideration of disposal treatment, it is more preferable that halogen atoms such as chlorine are not included. In addition, the compound (B) may be cyclic or aromatic. In such a case, the number of R in the structural formula (1) may be reduced.
Furthermore, among the carboxyl groups of compound (B), a compound having at least one anhydride structure formed between two carboxyl groups has the same effect as the compound represented by structural formula (1) in the present invention. To express.
Such a compound may be a polymer, an oligomer, or a low molecular compound. Examples of the polymer and oligomer include polymaleic acid and polymaleic anhydride, and copolymers thereof (for example, (alternating) copolymers of (anhydrous) maleic acid and acrylic acid. Is lower, the number average molecular weight is less than 10,000.
Use of a low molecular weight compound is more preferred because it has a lower viscosity and is easy to handle. Such compounds include 1,2,3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, citric acid, 1,2,3-benzenetricarboxylic acid, 3-butene-1,2, 3-tricarboxylic acid, butane-1,2,3,4-tetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, tetrahydrofuran-2,3,4,5-tetracarboxylic acid, benzenepentacarboxylic Examples include acids, benzenehexacarboxylic acid, 1,2,3,4,5,6-cyclohexanehexacarboxylic acid, benzenehexacarboxylic acid, and anhydrides of these compounds. Butanetetracarboxylic acid is preferred in terms of reactivity.
[0023]
The 1,2,3,4-butanetetracarboxylic acid preferably used in the present invention may be partially esterified or amidated. In addition, the carboxyl group in 1,2,3,4-butanetetracarboxylic acid is likely to have an acid anhydride structure in which the adjacent carboxyl group is dehydrated and cyclized in a dry state. Although it becomes a structure, in the present invention, it is described as 1,2,3,4-butanetetracarboxylic acid without distinguishing between ring closure and ring opening.
[0024]
In the present invention, the mass ratio of the compound (A) and the compound (B) needs to be in the range of 95/5 to 10/90, in order to exhibit excellent barrier properties in a high humidity atmosphere. 80/20 to 10/90 is preferable, 70/30 to 15/85 is more preferable, and 65/35 to 15 for exhibiting excellent barrier properties in a high-humidity atmosphere by a short heat treatment. Particularly preferred is / 85. When the compound (A) exceeds 95% or less than 10%, a crosslinking density effective for expressing the gas barrier property of the film particularly in a high humidity atmosphere cannot be obtained, and the gas barrier film targeted by the present invention is obtained. I can't.
[0025]
In the present invention, it is necessary to add polystyrene sulfonic acid and / or a salt thereof (C) in order to improve the adhesion between the gas barrier layer and the base film. The amount of (C) added needs to have a value of (C) / [(A) + (B)] of 0.03 to 1.0 in terms of solid content, and exhibits both barrier properties and adhesiveness. Therefore, it is preferably 0.03 to 0.8, more preferably 0.03 to 0.5, still more preferably 0.04 to 0.4, and 0.04 to 0.3. It is particularly preferred that When the addition amount of (C) is less than 0.03, the effect of improving adhesiveness is not recognized, and when it exceeds 1.0, the barrier property under a high humidity atmosphere is lowered or the barrier property is expressed. In order to do so, a long-time heat treatment is required at a high temperature.
The molecular weight (weight average) of polystyrene sulfonic acid and / or its salt is not particularly limited, but may be in the range of 1000 to 5000000. Polystyrene sulfonate is preferably used from the viewpoint of easy availability, and examples of the salt include sodium salt, potassium salt, lithium salt, ammonium salt, etc. Among them, sodium polystyrene sulfonate or Ammonium is preferred. Other compounds may be copolymerized with polystyrene sulfonic acid (or its salt), such as olefin compounds such as ethylene and propylene, (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylic acid amide. , Alkyl vinyl ether, (anhydrous) maleic acid, vinyl acetate or a saponified product thereof. These copolymerization amounts should just be 0-50 mol%.
[0026]
As a solvent for the coating agent of the present invention, it is preferable to use water from the viewpoint of the environment when producing a gas barrier film. A small amount of an organic solvent may be added for the purpose of improving the drying property.
[0027]
The coating agent may be prepared by a known method using a dissolution vessel equipped with a stirrer, and a known device such as a homogenizer, a ball mill, or a high-pressure dispersion device can be used as the stirrer. At this time, the stability of the aqueous solution is improved by adding the alkali compound described below to the aqueous solution of the compound (B) having two or more carboxyl groups in the molecule.
[0028]
In preparing the coating agent of the present invention, it is preferable to add an alkali compound. In particular, it is preferable to add 0.1 to 30 equivalent%, preferably 1 to 30 equivalent%, more preferably 2 to 28 equivalent% of an alkali compound with respect to the carboxyl group of the compound (B). By adding an appropriate amount of an alkali compound, the gas barrier properties of the resulting film are significantly improved.
Any alkali compound may be used as long as it can neutralize the carboxyl group in the compound (B). Hydroxylation of an alkali metal such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, or an alkaline earth metal. Products, ammonium hydroxide, organic ammonium hydroxide compounds and the like, and sodium hydroxide and potassium hydroxide are particularly preferable. Further, by adding an alkali metal salt as the alkali compound or in combination with the alkali compound, the gas barrier property is improved as in the case of the alkali compound. As such an alkali metal salt, phosphate, phosphite, hypophosphite and the like are preferable, and sodium hypophosphite is particularly preferable.
[0029]
The coating agent of the present invention includes a heat stabilizer, an antioxidant, a reinforcing material, a pigment, a deterioration inhibitor, a weathering agent, a flame retardant, a plasticizer, a release agent, as long as the properties such as gas barrier properties and adhesiveness are not significantly impaired. Molding agents, lubricants and the like may be added.
[0030]
Examples of the heat stabilizer, antioxidant, and deterioration inhibitor include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and mixtures thereof.
[0031]
Examples of the reinforcing material include clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon black, zinc oxide, Zeolite, montmorillonite, hydrotalcite, fluorine mica, metal fiber, metal whisker, ceramic whisker, potassium titanate whisker, boron nitride, graphite, glass fiber, carbon fiber, fullerene (C60, C70, etc.), carbon nanotube, etc. .
[0032]
In the present invention, the gas barrier property of the obtained molded product can be further improved by adding a small amount of a crosslinking agent component to the coating agent. Examples of the crosslinking agent include isocyanate compounds, melamine compounds, epoxy compounds, carbodiimide compounds, zirconium salt compounds and the like.
[0033]
A gas barrier resin coating layer can be easily obtained by applying a heat treatment after applying the coating agent of the present invention on various substrate films. At this time, an ester bond is formed between the compounds (A) and (B) in the coating agent and is cured to become water-insoluble. This heat treatment time is industrially advantageous because it requires a relatively short time.
[0034]
Examples of the thermoplastic resin film (base film) used in the gas barrier film of the present invention include polyamide resins such as nylon 6, nylon 66, nylon 46, polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene na Aromatic polyester resins such as phthalate, polybutylene terephthalate and polybutylene naphthalate, and liquid crystalline polyester resins, aliphatic polyester resins such as polylactic acid, polyolefin resins such as polypropylene and polyethylene, polyacetal, polycarbonate, polyarylate, polyphenylene sulfide, poly Ether ether ketone, polysulfone, polyethersulfone, polyamideimide, polyetherimide, linear polyimide or it Mixture consisting of compound films or laminates of these films, and the like, may be oriented film in unstretched film. Among these, nylon 6 film and polyethylene terephthalate film are preferable from the viewpoint of transparency.
[0035]
As a method for producing a film, a thermoplastic resin is heated and melted by an extruder and extruded from a T die, and is cooled and solidified by a cooling roll or the like to obtain an unstretched film, or extruded from a circular die by water cooling or air cooling. Solidify to obtain an unstretched film.
In the case of producing a stretched film, a method in which an unstretched film is once wound or continuously stretched by a simultaneous biaxial stretching method or a sequential biaxial stretching method is preferable. From the viewpoint of film mechanical properties and uniform thickness performance, a method of combining a flat-type film forming method using a T die and a tenter stretching method is preferable.
[0036]
Moreover, in order to improve the adhesiveness between the film and the gas barrier layer, the film surface may be subjected to a corona discharge treatment or an anchor coat.
[0037]
In the gas barrier film, the compound (A) is polyvinyl alcohol, the compound (B) is 1,2,3,4-butanetetracarboxylic acid, and 1,2,3,4-butanetetracarboxylic acid in It is particularly preferable that the layer contains an alkali compound in an amount of 0.1 to 30 equivalent% with respect to the carboxyl group.
[0038]
The thickness of the gas barrier layer of the gas barrier film in the present invention is desirably at least 0.03 μm in order to sufficiently enhance the gas barrier property of the film. Although there is no particular upper limit, if the film is too thick, the properties of the base film cannot be used. Therefore, it is usually 100 μm or less, preferably 50 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less.
[0039]
In addition, the solution concentration when the film is coated with a mixed solution composed of the compound (A), the compound (B), and the polystyrene sulfonic acid and / or its salt (C) depends on the viscosity and reactivity of the solution, and the specifications of the apparatus used. However, if the solution is too dilute, it becomes difficult to coat a layer having a sufficient thickness to exhibit gas barrier properties, and the subsequent drying process takes a long time. Cheap. On the other hand, if the concentration of the solution is too high, problems may arise in the mixing operation, storage stability, and the like. From such a viewpoint, the solid content concentration in the coating agent of the present invention is preferably in the range of 5 to 60% by mass, and more preferably in the range of 10 to 50% by mass.
[0040]
The method for coating the mixed solution on the film is not particularly limited, and usual methods such as gravure roll coating, reverse roll coating, and wire bar coating can be used. In order to perform coating prior to stretching, first, an unstretched film is coated and dried, then supplied to a tenter-type stretching machine, and the film is stretched simultaneously in the running direction and the width direction (simultaneous biaxial stretching) and heat-treated. Alternatively, the film may be stretched in the running direction of the film using a multistage heat roll or the like, coated, dried, and then stretched in the width direction (sequential biaxial stretching) by a tenter type stretching machine. It is also possible to combine running direction stretching and simultaneous biaxial stretching with a tenter.
[0041]
In the present invention, in order to form a gas barrier layer, the film needs to be heat-treated at 130 ° C. or higher after coating, and is preferably heat-treated at 150 ° C. or higher in order to shorten the heat treatment time. When the heat treatment temperature is low, the ester cross-linking reaction in the gas barrier layer cannot sufficiently proceed, and it becomes difficult to obtain a film having sufficient gas barrier properties.
If the heat treatment time is too short, the crosslinking reaction cannot sufficiently proceed, and it becomes difficult to obtain a film having sufficient gas barrier properties. The heat treatment time is usually 1 second or longer, preferably 3 seconds or longer.
In order to improve the gas barrier property, it is necessary to perform heat treatment at a high temperature for a long time. For example, if a heat treatment is performed at 200 ° C. for 3 minutes or more, or 220 ° C. for 15 seconds or more, a film having very high gas barrier properties can be obtained.
[0042]
It is necessary for the expression of the barrier property that the compound (A) and the compound (B) are cross-linked by an ester bond by heat treatment or the like. The ester bond can be analyzed by measuring the infrared spectrum of the gas barrier layer by the ATR method. When the compound (A) and the compound (B) are cross-linked by an ester bond, the absorption peak of the carbonyl group in the compound (B) is shifted to the high wave number side. Therefore, the absorption peak remaining by taking the difference spectrum of the compound (B) from the gas barrier layer of the present invention is defined as a peak derived from an ester bond. Here, 1600-1850 cm^-1Baseline is limited to the region of, the absorbance of the peak of the carbonyl group of the gas barrier layer and the compound (B) is normalized, the difference spectrum of both peaks is taken so that it does not fall below the baseline, and 1695-1800 cm^-1The remaining absorption peak was determined as an ester bond-derived peak. For example, when the compound (A) and the compound (B) are polyvinyl alcohol and 1,2,3,4-butanetetracarboxylic acid, respectively, a difference spectrum is obtained by the above method, and the remaining 1720 cm^-1The nearby peak was judged to be a peak derived from the carbonyl of the ester bond.
[0043]
The gas barrier film obtained by the present invention has a gas barrier layer oxygen permeability coefficient of 1000 ml · μm / m at 20 ° C. and 90% RH from the viewpoint of gas barrier properties.²· Day · MPa or less is preferable, more preferably 500 ml · μm / m²· Day · MPa or less, more preferably 300ml · μm / m²Day / MPa or less, particularly preferably 100 ml / μm / m²-It is below day * MPa. The oxygen permeability coefficient of the gas barrier layer was determined by the method described later.
[0044]
In the present invention, since the gas barrier property of the film varies depending on the type and thickness of the base film and the thickness of the gas barrier layer, the oxygen permeability coefficient of the gas barrier layer itself was also evaluated.
The oxygen transmission coefficient was obtained from the following formula.
1 / Q_F= 1 / Q_B+ L / P_C
However, Q_F: Oxygen permeability of gas barrier film (ml / m²・ Day ・ MPa)
Q_B: Oxygen permeability of thermoplastic resin film (ml / m²・ Day ・ MPa)
P_C: Oxygen permeability coefficient of gas barrier layer (ml · μm / m²・ Day ・ MPa)
L: Gas barrier layer thickness (μm)
Therefore, the oxygen permeability coefficient P of the gas barrier layer_CQ_F, Q_B, And L can be estimated from the above equation.
[0045]
Furthermore, an adhesive layer may be provided on the gas barrier layer of the gas barrier film, and a polyolefin resin film may be further laminated (laminated) thereon. The adhesive layer may be a compound having good adhesiveness. The polyolefin resin film is preferably a film made of a resin mainly composed of polyethylene and / or polypropylene. Polyethylene may be copolymerized with vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester and the like. The three-dimensional structure of polypropylene is not particularly limited, and any of syndiotactic, isotactic, and atactic may be used, and ethylene or α-olefin may be copolymerized.
At this time, printing may be performed on the film. The position of printing and the type of ink used for printing are not particularly limited, but in the case of a food packaging film, printing is often performed between the gas barrier layer and the adhesive layer.
[0046]
Regarding the laminate film composed of the gas barrier gas barrier film and the polyolefin resin, the adhesive strength between the base film and the gas barrier layer is preferably 0.7 N / cm or more, more preferably 1 N / cm or more, and more preferably 1.5 N / cm or more. . If the adhesive strength is not 0.7 N / cm or more, it peels off easily, which may cause problems in use.
[0047]
【Example】
EXAMPLES Next, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited only to these Examples.
[0048]
The oxygen barrier property was measured by measuring oxygen permeability in an atmosphere of 20 ° C. and a relative humidity of 90% using an oxygen barrier measuring device (OX-TRAN 2/20) manufactured by Mocon.
The oxygen permeability coefficient of the gas barrier layer was determined by measuring the oxygen permeability of the gas barrier film in an atmosphere of 20 ° C. and 90% relative humidity with an oxygen barrier measuring device manufactured by Mocon._FIt was. On the other hand, the oxygen permeability of the uncoated film was measured and Q_BIt was. Next, the coat thickness was determined from the difference in average thickness between the uncoated film and the gas barrier film, and was designated as L. From the above numerical values, the oxygen permeability coefficient P of the gas barrier layer is calculated using the above formula._CWas calculated.
The oxygen permeability of a PET film having a thickness of 12 μm is 900 ml / m.²-Day-MPa, and the nylon 6 film with a thickness of 15 μm has an oxygen permeability of 500 ml / m²-It was set to day * MPa.
[0049]
A method for measuring the adhesive strength between the base film and the gas barrier layer is shown below. The coating agent of the present invention was coated on the corona-treated surface or non-corona-treated surface of various thermoplastic resin films (base film) under predetermined coating conditions (described in Examples) to obtain gas barrier films. By the gravure coating method, an adhesive ((a) main agent Dick Dry LX63F (manufactured by Dainippon Ink and Chemicals), (b) curing agent KP-90 (manufactured by Dainippon Ink and Chemicals), (c) ethyl acetate: ( a) / (b) / (c) = 1/12/10 (mass ratio)) was applied so as to have a thickness of about 1 μm, and then dried with hot air at 80 ° C. for 20 seconds. Subsequently, a polyethylene sealant (TUXFCS # 50: thickness 50 μm, manufactured by Tosero Co., Ltd.) was dry-laminated at a press pressure of 0.2 MPa using a hot roll at 80 ° C., and then subjected to an aging treatment at 40 ° C. for 48 hours. A test piece having a width of 15 mm and a length of 150 mm was cut out from the laminate film thus obtained, and T-type peel strength was measured, which was defined as adhesive strength. For the measurement, Autograph / AGS-100G manufactured by Shimadzu Corporation was used, and measurement was performed under the condition of a tensile speed of 300 mm / min. At this time, except for Example 4, peeling occurred between the base film and the gas barrier layer.
[0050]
Example 1
As a compound (B), 1,2,3,4-butanetetracarboxylic acid (manufactured by Shin Nippon Chemical Co., Ltd., Ricacid BTW) is dissolved in an aqueous solution containing 15 mol% sodium hydroxide with respect to the carboxyl group, and 10 mass. % Solution. This solution and a 10 mass% aqueous solution of polyvinyl alcohol (manufactured by Unitika Chemical Co., Ltd., UF-100, polymerization degree 1000, saponification degree 99.4) as a compound (A) were combined with polyvinyl alcohol and 1,2,3,4. -It mixed and stirred so that the solid content mass ratio of butanetetracarboxylic acid might be set to 30/70. Further, to this mixed solution, (C) aqueous polystyrene sulfonate solution (manufactured by Tosoh Corporation, PS-5, solid content of about 20% by mass, molecular weight of 50,000 to 100,000) was added with polyvinyl alcohol and 1,2,3,4-butanetetra. After adding 0.1 to the total solid content 1 with carboxylic acid, the mixture was stirred to prepare a coating agent.
This coating agent is coated on a corona-treated surface of a biaxially stretched polyester film (Embret PET12 manufactured by Unitika Ltd., thickness 12 μm) with a Mayer bar so that the coating thickness after drying is about 1 μm, and at 100 ° C. for 2 minutes. After drying, heat treatment was performed at 220 ° C. for 30 seconds.
The obtained gas barrier film was transparent, and the gas barrier layer was insoluble in water. The oxygen permeability of this film at 20 ° C. and 90% RH is 8 ml / m.²-Day-MPa, oxygen permeability coefficient of gas barrier layer is 8.1 ml-μm / m²-Excellent gas barrier properties such as day-MPa. Further, the adhesive strength was 4.4 N / cm, indicating excellent adhesiveness. Table 1 summarizes the physical properties of the film.
[0051]
Examples 2 and 3
A coating agent and a gas barrier film were obtained in the same manner as in Example 1 except that the compositions of polyvinyl alcohol and 1,2,3,4-butanetetracarboxylic acid were changed. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0052]
Example 4
(C) The same operation as in Example 1 except that the amount of sodium polystyrenesulfonate aqueous solution added was 0.3 with respect to the total solid content 1 of polyvinyl alcohol and 1,2,3,4-butanetetracarboxylic acid. Thus, a coating agent and a gas barrier film were obtained. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property of the film slightly decreased. As a result of measuring the adhesive strength, the peeled surface was between the adhesive layer and the gas barrier layer, and the value at this time was 4.1 N / cm. Peeling does not occur at the interface between the base film and the gas barrier layer, and the adhesive strength is estimated to be even higher.
[0053]
Example 5
The coating agent and gas barrier were the same as in Example 1 except that the type of (C) was an aqueous polystyrene sodium sulfonate solution (manufactured by Tosoh Corporation, PS-1, solid content of about 20% by mass, molecular weight of 1 to 30,000). A characteristic film was obtained. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0054]
Examples 6 and 7
The type of (C) is polystyrene sodium sulfonate aqueous solution (manufactured by Tosoh Corporation, PS-100, solid content of about 20% by mass, molecular weight of 80 to 1,200,000), and the amount added is polyvinyl alcohol and 1,2,3,4- A coating agent and a gas barrier film were prepared in the same manner as in Example 1 except that 0.05 (Example 6) and 0.1 (Example 7) were used for the total solid content of 1 with butanetetracarboxylic acid. Obtained. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent. Adhesion was further improved when polystyrene sulfonic acid having a high molecular weight was used.
[0055]
Example 8
The type of (C) was a sodium styrenesulfonate-methacrylic acid copolymer aqueous solution (manufactured by Tosoh Corporation, solid content of about 21.5 mass%, molecular weight 2700, sodium styrenesulfonate-methacrylic acid copolymer ratio 3/1). Except for the above, a coating agent and a gas barrier film were obtained in the same manner as in Example 1. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0056]
Example 9
A coating agent and a coating film were prepared in the same manner as in Example 1 except that the type of (C) was an aqueous polystyrene sulfonate ammonium solution (manufactured by Tosoh Corporation, solid content of about 22% by mass, molecular weight 320,000, referred to as PS-N). Got. All of the obtained films were transparent, and the coat layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0057]
Example 10
As a compound (B), polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., polyacrylic acid 25 wt% aqueous solution, number average molecular weight 150,000) was dissolved in an aqueous solution containing 10 mol% sodium hydroxide with respect to the carboxyl group. A 10% by mass solution was obtained. Using this liquid, a coating agent was obtained in the same manner as in Example 1. This coating agent is coated on a corona-treated surface of a biaxially stretched polyester film (Embret PET12 manufactured by Unitika Ltd., thickness 12 μm) with a Mayer bar so that the coating thickness after drying is about 1 μm, and at 100 ° C. for 2 minutes. After drying, heat treatment was performed at 200 ° C. for 5 minutes. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0058]
Example 11
A coating agent and a gas barrier film were prepared in the same manner as in Example 1 except that an ethylene-maleic acid alternating copolymer (ALDRICH, weight average molecular weight 100,000 to 500,000) was used as the compound (B). Obtained. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0059]
Example 12
A gas barrier film was obtained in the same manner as in Example 1 on the non-corona-treated surface of the biaxially stretched polyester film (Embret PET12 manufactured by Unitika Ltd., thickness 12 μm) obtained by the same operation as in Example 1. . All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0060]
Example 13
A coating agent was obtained in the same manner as in Example 1. After this coating solution is coated on a corona-treated surface of a biaxially stretched nylon film (emblem manufactured by Unitika, thickness 15 μm) with a Mayer bar so that the coating thickness after drying is about 1 μm, it is dried at 100 ° C. for 2 minutes. And heat treatment at 200 ° C. for 5 minutes. All of the obtained films were transparent, and the gas barrier layer was insoluble in water. Table 1 summarizes the physical properties of the film. The gas barrier property and adhesiveness of the film were both excellent.
[0061]
Comparative Example 1
(C) A coating agent was prepared in the same procedure as in Example 1 except that the aqueous sodium polystyrenesulfonate solution was not added. This coating agent was coated, dried and heat treated on the polyester film in the same manner as in Example 1. The physical properties of the obtained gas barrier film are shown in Table 1, but the laminate strength was low and the adhesiveness was poor.
[0062]
Comparative Example 2
(C) A coating agent was prepared in the same procedure as in Example 9 except that the aqueous sodium polystyrenesulfonate solution was not added. This coating agent was coated, dried and heat treated on the polyester film in the same manner as in Example 1. The physical properties of the obtained gas barrier film are shown in Table 1, but the laminate strength was low and the adhesiveness was poor.
[0063]
Comparative Example 3
(C) A coating agent was prepared in the same manner as in Example 10 except that the aqueous sodium polystyrenesulfonate solution was not added. This coating agent was coated, dried and heat treated on the polyester film in the same manner as in Example 1. The physical properties of the obtained gas barrier film are shown in Table 1, but the laminate strength was low and the adhesiveness was poor.
[0064]
Comparative Examples 4 and 5
(C) The same procedure as in Example 1 except that the amount of sodium polystyrene sulfonate aqueous solution (PS-5, solid content of about 20% by mass, molecular weight of 50,000 to 100,000) was changed as shown in Table 1. Thus, a coating agent and a gas barrier film were obtained. All of the obtained films were transparent. Table 1 summarizes the physical properties of the film. If the amount of (C) added is outside the scope of the present invention, the gas barrier properties and adhesiveness of the film cannot be made compatible. Specifically, when the addition amount is small, the effect of improving the adhesiveness is not recognized, and when the addition amount is large, the barrier property is remarkably lowered.
[0065]
Comparative Example 6
(C) Coating agent and gas barrier properties in the same procedure as in Example 1 except that only sodium polystyrene sulfonate aqueous solution (PS-5, solid content of about 20% by mass, molecular weight of 50,000 to 100,000, manufactured by Tosoh Corporation) was used. A film was obtained. Table 1 summarizes the physical properties of the film. With only sodium polystyrene sulfonate, there was no barrier property under high humidity, and adhesion to the substrate film was low.
[0066]
[Table 1]

[0067]
【The invention's effect】
By forming the coating agent of the present invention on the surface of a thermoplastic resin film, the gas barrier film has excellent gas barrier properties even under high humidity, and has excellent adhesion between the thermoplastic resin film and the gas barrier layer. Can be obtained.

Claims (11)

A compound (A) having two or more hydroxyl groups in the molecule, a compound (B) having two or more carboxyl groups in the molecule, polystyrene sulfonic acid and / or a salt thereof (C), and a solvent as main components The compound (A) is polyvinyl alcohol, the compound (B) is poly (meth) acrylic acid, a polymer having a maleic anhydride structure, 1,2,3,4-butanetetra It is at least one selected from carboxylic acids, the previous solvent is water, and the solid content mass ratio of (A), (B), (C) satisfies the following formulas (1), (2) Gas barrier coating agent.
(A) / (B) = 95 / 5-10 / 90 (1)
(C) / [(A) + (B)] = 0.03 to 1.0 (2) The gas barrier coating agent according to claim 1 , comprising 0.1 to 30 mol% of an alkali compound with respect to the carboxyl group in the compound (B). A gas barrier film comprising a gas barrier layer made of a composition obtained by removing a solvent from the gas barrier coating agent according to claim 1 or 2 on at least one surface of a thermoplastic resin film. A gas barrier film in which the compound (A) and the compound (B) in the gas barrier layer according to claim 3 are connected by an ester bond. 5. The gas barrier film according to claim 3 , wherein an oxygen permeability coefficient of the gas barrier layer at 20 ° C. and 90% RH is 1000 ml · μm / m ² · day · MPa or less. The gas barrier film according to any one of claims 3 to 5, wherein the thermoplastic resin film is a nylon 6 film. The gas barrier film according to any one of claims 3 to 5, wherein the thermoplastic resin film is a polyethylene terephthalate film. A method for producing a gas barrier film, comprising: applying a gas barrier coating agent according to claim 1 or 2 to at least one surface of a thermoplastic resin film, and then performing a heat treatment at 130 ° C or higher. A gas barrier laminate film in which an adhesive layer is provided on the gas barrier layer of the gas barrier film according to claim 3 and a polyolefin resin film is further laminated thereon. The gas barrier laminate film according to claim 9, wherein the polyolefin resin film comprises a resin mainly composed of polyethylene and / or polypropylene. The gas barrier laminate film according to claim 9 or 10, wherein the adhesive strength between the thermoplastic resin film and the gas barrier layer is 0.7 N / cm or more.