JP4146169B2 - Gas barrier composition, coating agent and film - Google Patents

Description

【００２１】
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（Ｃ）は環状になっていてもよく、その場合には構造式（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（Ｃ）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ので本発明において用いることができる。
【００２２】
このよう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が、コート剤の粘度を考えた時、低分子化合物の方が粘度が低く取り扱いやすいので、オリゴマーや低分子化合物が好ましく、低分子化合物がより好ましい。
そのような化合物としては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、１，２，３，４−シクロブタンテトラカルボン酸、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】
本発明のガスバリア組成物において、化合物（Ａ）と化合物（Ｂ）の質量比（Ａ）／（Ｂ）は９５／５〜５／９５、好ましくは、９０／１０〜１０／９０、より好ましくは、８０／２０〜２０／８０の範囲であることが必要である。（Ａ）が９５％を超えたり５％未満のときは、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ことができない。さらに、化合物（Ｂ）と化合物（Ｃ）の質量比（Ｂ）／（Ｃ）は５０／５０〜９５／５、好ましくは、５５／４５〜９０／１０、より好ましくは、５５／４５〜８５／１５の範囲であることが必要である。（Ｂ）が９５％を超えたり５０％未満のときは、、反応性の高い化合物（Ｃ）が少ないために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を短時間で得ることができないか、または、比較的安価なポリ（メタ）アクリル酸が少なくなるためにコスト的に不利となるため、本発明の目的とする生産性に優れたガスバリア性フィルムを得ることができない。
【００２５】
本発明のガスバリア性組成物においては、熱処理などにより化合物（Ｂ）と化合物（Ｃ）の少なくとも一方と化合物（Ａ）と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のためには好ましい。エステル結合の分析は、ＡＴＲ法によってコート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（Ｂ）と化合物（Ｃ）の少なくとも一方と化合物（Ａ）とがエステル結合で架橋された場合、化合物（Ｂ）または化合物（Ｃ）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性組成物から化合物（Ｂ）または化合物（Ｃ）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、ガスバリア性組成物と化合物（Ｃ）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した。例えば、化合物（Ａ）と化合物（Ｃ）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した。
【００２６】
本発明のガスバリア性組成物には、エステル化反応を促進する目的で公知の触媒を加えることができる。例えば、マンガン、カルシウム、コバルト、マグネシウム、亜鉛、鉛、アンチモンなどの酸化物や酢酸塩や炭酸塩、チタン、スズ、鉛などの有機金属化合物、塩化ハフニウム(IV)・テトラヒドロフランやハフニウムtert-ブトキシドなどのハフニウム塩、ジフェニルアンモニウムトリフラートなどが挙げられる。
【００２７】
また、本発明のガスバリア性組成物には、さらにガスバリア性を高める目的で層状化合物を添加することもできる。例えば、モンモリロナイト、バイデライト、サポナイト、ヘクトライト、ソーコナイト、バーミキュライト、フッ素雲母、白雲母、パラゴナイト、金雲母、黒雲母、レピドライト、マーガライト、クリントナイト、アナンダイト、緑泥石、ドンバサイト、スドーアイト、クッケアイト、クリノクロア、シャモサイト、ニマイト、テトラシリリックマイカ、タルク、パイロフィライト、ナクライト、カオリナイト、ハロイサイト、クリソタイル、ナトリウムテニオライト、ザンソフィライト、アンチゴライト、ディッカイト、ハイドロタルサイトなどが挙げられ、膨潤性フッ素雲母やモンモリロナイトが特に好ましい。添加量としては、化合物（Ａ）〜（Ｃ）の総量１００質量部に対して、０．１〜１００質量部が好ましく、さらに好ましくは１〜２０質量部である。
【００２８】
これらの無機層状化合物は、天然に産するものであっても、人工的に合成あるいは変性されたものでもよく、またそれらをオニウム塩などの有機物で処理したものであってもよい。
【００２９】
本発明のガスバリア性組成物に架橋剤成分を少量添加することによって、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、オキサゾリン化合物などが挙げられる。好ましい添加量は、化合物（Ａ）〜（Ｃ）の総量１００質量部に対して、１〜２０質量部である。
【００３０】
本発明のガスバリア性組成物には、その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、顔料、劣化防止剤、耐候剤、難燃剤、可塑剤、離型剤、滑剤、粘着付与剤などが添加されていてもよい。
【００３１】
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。
【００３２】
その他の添加剤としては、例えば炭酸カルシウム、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、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。
【００３３】
粘着付与剤としては、Ｃ₅、Ｃ₉系石油樹脂、キシレン樹脂、クマロンインデン樹脂、アルキルフェノール樹脂などの合成樹脂系のものやロジン、テルペンなどの天然樹脂系のものなどが挙げられる。これらは、水素化、不均化、二量化、エステル化などの変性物でもよく、混合性の点から水系で用いる際にはエマルションの形態で使用することが好ましい。
【００３４】
本発明のガスバリア性組成物は、前記した化合物（Ａ）〜（Ｃ）及び溶媒（Ｄ）を主な成分とするコート剤として使用することができる。溶媒（Ｄ）としては、フィルム生産時の環境の点から水を使用することが好ましい。溶解性の向上や乾燥工程の短縮、溶液の安定性の改善といった目的により、アルコールなどの有機溶媒を少量添加することもできる。
【００３５】
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、化合物（Ｂ）と化合物（Ｃ）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。
【００３６】
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）と化合物（Ｃ）に含まれるカルボキシル基に対して０．１〜３０モル％のアルカリ化合物を加えることが好ましい。なお、ポリ（メタ）アクリル酸および１，２，３，４−ブタンテトラカルボン酸は、アルカリ化合物を添加しなくても水溶液にすることができるが、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）と化合物（Ｃ）に含まれるカルボキシル基を中和できるものであれば特に限定されず、水酸化ナトリウム、水酸化カリウム、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る。また、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。
【００３７】
本発明のガスバリア性フィルムは、熱可塑性樹脂フィルムの少なくとも片面に、化合物（Ａ）と化合物（Ｂ）と化合物（Ｃ）を前述のように規定された配合比で含有してなるガスバリア性組成物の層が形成されたものであり、本発明のガスバリア性コート剤をフィルムの表面にコートした後、加熱乾燥することによって得られる。
【００３８】
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。
【００３９】
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。
【００４０】
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。
【００４１】
本発明のガスバリア性フィルムにおいては、ガスバリア層として、化合物（Ａ）がポリビニルアルコールであり、化合物（Ｂ）がポリ（メタ）アクリル酸であり、化合物（Ｃ）が１，２，３，４−ブタンテトラカルボン酸であり、ポリ（メタ）アクリル酸と１，２，３，４−ブタンテトラカルボン酸に含まれるカルボキシル基に対して０．１〜３０モル％のアルカリ化合物を含有することが最も好ましい。
【００４２】
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しい。
【００４３】
また、コート剤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。
【００４４】
コート剤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。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。
【００４５】
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℃以上で熱処理することが好ましく、さらに好ましくは１５０℃以上である。また、熱処理時間は通常１秒以上、好ましくは３秒以上がよい。熱処理温度が低い場合、熱処理時間が短かすぎる場合にには、ガスバリア性が不十分となる場合がある。
【００４６】
本発明のガスバリア性組成物は、２０℃、８５％ＲＨにおける酸素透過係数が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３００ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａ以下が好ましい。
【００４７】
さらに、該コート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。
【００４８】
【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。
【００４９】
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８５％の雰囲気における値を測定した。
また、ガスバリア層の酸素透過係数Ｐｃは、下記式から算出した。
１／Ｑ_F＝１／Ｑ_B＋Ｌ／Ｐ_C
ただし、Ｑ_F：ガスバリア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）
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４００ｍｌ／ｍ²・ｄａｙ・ＭＰａ、厚み１００μｍのポリカーボネートフィルムの酸素透過度は９５００ｍｌ／ｍ²・ｄａｙ・ＭＰａ、とした。
【００５０】
コートフィルムの外観は目視で判断した。無色透明であれば○、半透明であれば△、白濁していれば×とし、下記の実施例に合わせて表１に示した。
【００５１】
参考例（各溶液の調製）
（ア）中和度１０％のポリアクリル酸水溶液（Ｉ）の調製
水５０．６７ｇに水酸化ナトリウム０．６７ｇとポリアクリル酸２５０００（和光純薬工業社製、試薬一級）１２．００ｇを添加、溶解し２０質量％水溶液（Ｉ）とした。
（イ）中和度１０％の１，２，３，４−ブタンテトラカルボン酸水溶液（ＩＩ）の調製
水４２．７３ｇに水酸化ナトリウム０．６８ｇと１，２，３，４−ブタンテトラカルボン酸（和光純薬工業社製、試薬一級）１０．００ｇを添加、溶解し２０質量％水溶液（ＩＩ）とした。
（ウ）ポリビニルアルコール水溶液の調製
水２０．００ｇにポリビニルアルコール（ユニチカケミカル社製 ＵＭＲ−１０ＨＨ、重合度２４０、ケン化度９８．９）５．００ｇを添加・溶解し２０質量％水溶液（ＩＩＩ）とした。
【００５２】
実施例１
上記の溶液（Ｉ）５１．７２ｇと溶液（ＩＩ）２２．４４ｇと溶液（ＩＩＩ）２１．００ｇとを混合、攪拌して、ポリビニルアルコールとポリアクリル酸の質量比が３０／７０、ポリアクリル酸と１，２，３，４−ブタンテトラカルボン酸の質量比が７０／３０、固形分濃度２０質量％の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）上に乾燥後の塗膜厚みが約２μｍ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１５秒間熱処理した。
得られたコートフィルムは透明であり、このフィルムの２０℃、８５％ＲＨにおける酸素透過度は１４ｍｌ／ｍ²・ｄａｙ・ＭＰａ、コート層の酸素透過係数は２８ｍｌ・μｍ／ｍ²・ｄａｙ・ＭＰａと優れたガスバリア性を示した。詳細は表１に示した。
【００５３】
実施例２〜５
溶液（Ｉ）〜（ＩＩＩ）を用いて、ポリビニルアルコールとポリアクリル酸と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と同様の手順でコート剤、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、ガスバリア性に優れていた。表１にこれらのフィルムの物性をまとめた。
【００５４】
実施例６〜８
参考例において、水酸化ナトリウムの添加量を変えて、化合物（Ａ）と化合物（Ｂ）の中和度の異なる溶液を得、これを用いて、各成分が表１に示す質量比率なるように実施例１と同様の手順でコート剤、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、ガスバリア性に優れていた。表１にこのフィルムの物性をまとめた。
【００５５】
実施例９
実施例１のコート剤に、さらにクニピアＦ（クニミネ工業製モンモリロナイト）を０．９１ｇ（化合物（Ａ）〜（Ｃ）の総量１００質量部あたり５質量部に相当。）を添加、撹拌してコート剤を得た。このコート剤を用いた以外は実施例１と同様の手順でコートフィルムを作製した。得られたフィルムは透明であり、ガスバリア性に優れていた。表１にこのフィルムの物性をまとめた。
【００５６】
実施例１０
基材フィルムをポリカーボネートフィルム（日本ジーイープラスチック社製レキサン、厚み１００μｍ）に変えた以外は実施例１と同様の手順でコート剤、およびコートフィルムを得た。得られたフィルムは透明であり、ガスバリア性に優れていた。表１にこのフィルムの物性をまとめた。
【００５７】
実施例１１
まず、実施例１と同様にしてコート剤を調製した。
次に、ナイロン６樹脂をＴダイを備えた押出機（７５ｍｍ径、Ｌ／Ｄが４５の緩圧縮タイプ単軸スクリュー）を用いて、シンリンダー温度２６０℃、Ｔダイ温度２７０℃でシート状に押出し、表面温度１０℃に調節された冷却ロール上に密着させて急冷し、厚み１５０μｍの未延伸フィルムとした。続いて、未延伸フィルムをグラビアロール式コーターに導き、乾燥後のコート厚みが２０μｍになるようにコーティングし、８０℃の熱風ドライヤー中で３０秒間乾燥した。次に、フィルムをテンター式同時２軸延伸機に供給し、温度１００℃で２秒間予熱した後、１７０℃で縦方向に３倍、横方向に３．５倍の倍率で延伸した。次に、横方向弛緩率５％で、２００℃で３０秒間の熱処理を行い、室温まで冷却後延伸フィルムを巻き取った。こうして得られたコートフィルムは厚みが１６．９μｍ、コート層の厚みが１．９μｍであった。得られたフィルムは透明であり、ガスバリア性に優れたものであった。表１にこのフィルムの物性を示した。
【００５８】
比較例１〜４
ポリビニルアルコールとポリアクリル酸と１，２，３，４−ブタンテトラカルボン酸の組成を表１に示すとおりにし、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。得られたコートフィルムの物性を表１に示したが、いずれもガスバリア性に劣るものであった。
【００５９】
比較例５
化合物（Ｃ）として、コハク酸を用いた以外は実施例１と同様の手順でコート剤、およびコートフィルムを得た。コハク酸は分子内の連続する３個以上の炭素原子のそれぞれにカルボキシル基が少なくとも１個ずつ結合されている化合物ではなく、得られたフィルムはバリア性が著しく悪化した。表１にこのフィルムの物性をまとめた。
【００６０】
【表１】

【００６１】
【発明の効果】
本発明によれば、優れたガスバリア性能を有するフィルムを生産性良く製造することができ、また、高湿度下でも優れたガスバリア性を保持することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas barrier composition, a coating agent and a film having excellent gas barrier properties even under high humidity.
[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 resin has a low environmental impact and high gas barrier properties in a low-humidity atmosphere, but as the humidity increases, the gas barrier properties deteriorate rapidly and may not be used for packaging foods that contain moisture. Many.
[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]
On the other hand, a technique for reacting with a polymer containing a maleic acid unit as a modification of polyvinyl alcohol is widely known. For example, JP-A-8-66991 discloses a layer comprising 25-50% partially neutralized isobutylene-maleic anhydride copolymer and polyvinyl alcohol, and JP-A-49-1649 discloses. Discloses mixing an alkyl vinyl ether-maleic acid copolymer with polyvinyl alcohol. However, all of these techniques are intended to make polyvinyl alcohol water resistant (that is, water-insoluble) and have not improved gas barrier properties.
[0008]
[Problems to be solved by the invention]
In order to solve the above-described problems, the present inventors intend to provide a gas barrier composition that exhibits high gas barrier properties and transparency even under high humidity and is excellent in productivity.
[0009]
[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.
At least one carboxyl group is bonded to each of the compound (A) having two or more hydroxyl groups in the molecule, poly (meth) acrylic acid (B), and three or more consecutive carbon atoms in the molecule. A compound (C) comprising:Compound (C) is 1,2,3,4-butanetetracarboxylic acid,Each gas ratio of (A), (B), (C) satisfies following formula (1), (2), The gas barrier composition characterized by the above-mentioned.
(A) / (B) = 95 / 5-5 / 95 (1)
(B) / (C) = 50/50 to 95/5 (2)
Further, a gas barrier film comprising a solvent (D) in addition to the compounds (A) to (C) and a layer of the gas barrier composition provided on the surface of the thermoplastic resin film. This is the gist.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0011]
First, components (A) to (C) common to the gas barrier composition and the coating agent will be described.
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.
[0012]
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.
[0013]
It is also possible to copolymerize other vinyl compounds 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.
[0014]
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.
[0015]
Moreover, when the ratio of the hydroxyl group in the polyvinyl alcohol laminated | stacked on a film is too low, at least 1 carboxyl group will exist in each of poly (meth) acrylic acid (B) and three or more continuous carbon atoms in a molecule | numerator. The esterification reaction rate with the compound (C) which is couple | bonded falls, and the gas-barrier film made into the objective of this invention cannot be obtained. Further, when a large amount of a hydrophobic copolymer component is contained, water solubility is impaired when a coating agent is formed. Therefore, the molar ratio of the vinyl alcohol unit to other vinyl compound units in the polyvinyl alcohol is preferably 10/90 to 100/0.
[0016]
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. .
[0017]
The polyacrylic acid or polymethacrylic acid (B) in the present invention (hereinafter sometimes referred to as “poly (meth) acrylic acid”) is a known method such as solution radical polymerization of an acrylic acid monomer or a methacrylic acid monomer. It can be obtained by polymerizing with. The number average molecular weight of poly (meth) acrylic acid is not particularly limited, but is preferably in the range of 2000 to 200000.
[0018]
In addition, poly (meth) acrylic acid (B) may contain other vinyl as long as the effects of the present invention are not impaired.
A small amount of the compound can be copolymerized. Other vinyl compounds include, for example, methacrylate.
Luric acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, etc.
Acrylic esters, vinyl esters such as vinyl formate and vinyl acetate, styrene,
2-30 carbon atoms such as p-styrene sulfonic acid, ethylene, propylene, isobutylene
Examples thereof include olefins and compounds having a reactive group that reacts with a hydroxyl group or a crosslinking agent of polyvinyl alcohol. A copolymer of polyacrylic acid and polymethacrylic acid can also be used.
[0019]
The compound (C) 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.
[0020]
[Chemical 1]

[0021]
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. Further, the compound (C) may be cyclic, in which case the number of R in the structural formula (1) may be reduced.
Furthermore, among the carboxyl groups of compound (C), a compound having at least one anhydride structure formed between two carboxyl groups also has the same effect as the compound represented by structural formula (1) in the present invention. Since it is expressed, it can be used in the present invention.
[0022]
Such a compound may be a polymer, an oligomer, or a low molecular weight compound, but when considering the viscosity of the coating agent, the low molecular weight compound has a lower viscosity and is easier to handle. Low molecular weight compounds are more preferred.
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, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, tetrahydrofuran-2,3,4,5-tetracarboxylic acid, benzenepentacarboxylic acid , Benzenehexacarboxylic acid, 1,2,3,4,5,6-cyclohexanehexacarboxylic acid, benzenehexacarboxylic acid or anhydrides of these compounds, particularly 1,2,3,4-butanetetra Carboxylic 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 gas barrier composition of the present invention, the mass ratio (A) / (B) of the compound (A) to the compound (B) is 95/5 to 5/95, preferably 90/10 to 10/90, more preferably , 80/20 to 20/80. When (A) exceeds 95% or less than 5%, the gas barrier property of the film particularly in a high humidity atmosphere cannot be exhibited. Further, the mass ratio (B) / (C) of the compound (B) to the compound (C) is 50/50 to 95/5, preferably 55/45 to 90/10, more preferably 55/45 to 85. It is necessary to be in the range of / 15. When (B) exceeds 95% or less than 50%, the amount of the highly reactive compound (C) is small, so that the crosslinking density effective for expressing the gas barrier property of the film particularly in a high humidity atmosphere is shortened. Obtaining a gas barrier film excellent in productivity, which is the object of the present invention, because it cannot be obtained in time or is disadvantageous in terms of cost due to a decrease in relatively inexpensive poly (meth) acrylic acid I can't.
[0025]
In the gas barrier composition of the present invention, it is preferable that at least one of the compound (B) and the compound (C) and the compound (A) are cross-linked by an ester bond by heat treatment or the like for the expression of the barrier property. . The analysis of the ester bond can be analyzed by measuring the infrared spectrum of the coat layer by the ATR method. When at least one of the compound (B) and the compound (C) and the compound (A) are crosslinked by an ester bond, the absorption peak of the carbonyl group in the compound (B) or the compound (C) is shifted to the high wave number side. . Therefore, the absorption peak remaining after taking the difference spectrum of the compound (B) or the compound (C) from the gas barrier composition of the present invention is defined as a peak derived from an ester bond. Here, 1600-1850 cm^-1The base line is limited to the region of, the absorbance of the peak of the carbonyl group of the gas barrier composition and the compound (C) is normalized, the difference spectrum between the two peaks is taken so that it does not fall below the baseline, and 1695-1800 cm^-1The absorption peak remaining in was used as an ester bond-derived peak. For example, when the compound (A) and the compound (C) are polyvinyl alcohol and 1,2,3,4-butanetetracarboxylic acid, respectively, a difference spectrum is taken by the above method, and the remaining 1720 cm^-1A nearby peak was defined as a peak derived from ester bond carbonyl.
[0026]
A known catalyst can be added to the gas barrier composition of the present invention for the purpose of promoting the esterification reaction. For example, oxides such as manganese, calcium, cobalt, magnesium, zinc, lead and antimony, acetates and carbonates, organometallic compounds such as titanium, tin and lead, hafnium chloride (IV), tetrahydrofuran and hafnium tert-butoxide Hafnium salt, diphenylammonium triflate, and the like.
[0027]
In addition, a layered compound can be added to the gas barrier composition of the present invention for the purpose of further improving the gas barrier property. For example, montmorillonite, beidellite, saponite, hectorite, soconite, vermiculite, fluorite mica, muscovite, paragonite, phlogopite, biotite, lepidrite, margarite, clintonite, anandite, chlorite, donbacite, sudite, kukeite, clinochlore , Chamosite, nimite, tetrasilic mica, talc, pyrophyllite, nacrite, kaolinite, halloysite, chrysotile, sodium teniolite, xanthophyllite, antigolite, dickite, hydrotalcite, etc. Fluorine mica and montmorillonite are particularly preferred. As addition amount, 0.1-100 mass parts is preferable with respect to 100 mass parts of total amounts of compound (A)-(C), More preferably, it is 1-20 mass parts.
[0028]
These inorganic layered compounds may be naturally occurring, artificially synthesized or modified, or those treated with an organic material such as an onium salt.
[0029]
The gas barrier property can be further improved by adding a small amount of a crosslinking agent component to the gas barrier composition of the present invention. Examples of the crosslinking agent include isocyanate compounds, melamine compounds, epoxy compounds, carbodiimide compounds, zirconium salt compounds, oxazoline compounds, and the like. A preferable addition amount is 1 to 20 parts by mass with respect to 100 parts by mass of the total amount of the compounds (A) to (C).
[0030]
In the gas barrier composition of the present invention, a heat stabilizer, an antioxidant, a pigment, a deterioration inhibitor, a weathering agent, a flame retardant, a plasticizer, a mold release agent, a lubricant, and an adhesive are used as long as the characteristics are not greatly impaired. An imparting agent or the like may be added.
[0031]
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.
[0032]
Other additives include, for example, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon black, zinc oxide, zeolite, Metal fiber, metal whisker, ceramic whisker, potassium titanate whisker, boron nitride, graphite, glass fiber, carbon fiber, fullerene (C₆₀, C₇₀And carbon nanotubes.
[0033]
As a tackifier, C_Five, C₉Synthetic resin type such as petroleum petroleum resin, xylene resin, coumarone indene resin and alkylphenol resin, and natural resin type such as rosin and terpene. These may be modified products such as hydrogenation, disproportionation, dimerization, and esterification, and are preferably used in the form of an emulsion when used in an aqueous system from the viewpoint of mixing properties.
[0034]
The gas barrier composition of the present invention can be used as a coating agent containing the aforementioned compounds (A) to (C) and a solvent (D) as main components. As the solvent (D), it is preferable to use water from the viewpoint of the environment during film production. A small amount of an organic solvent such as alcohol can be added for the purpose of improving the solubility, shortening the drying process, and improving the stability of the solution.
[0035]
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) and the compound (C).
[0036]
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 mol% of an alkali compound with respect to the carboxyl group contained in the compound (B) and the compound (C). Poly (meth) acrylic acid and 1,2,3,4-butanetetracarboxylic acid can be made into an aqueous solution without adding an alkali compound, but can be obtained by adding an appropriate amount of an alkali compound. The gas barrier property of the obtained film is remarkably improved.
The alkali compound is not particularly limited as long as it can neutralize the carboxyl groups contained in the compound (B) and the compound (C). Alkali metals such as sodium hydroxide, potassium hydroxide, calcium hydroxide and alkaline earth Metal hydroxide, ammonium hydroxide, organic ammonium hydroxide compound and the like. Moreover, gas barrier property improves by using together with an alkali compound and adding an alkali metal salt. As such an alkali metal salt, phosphate, phosphite, hypophosphite and the like are preferable, and sodium hypophosphite is particularly preferable.
[0037]
The gas barrier film according to the present invention comprises a compound (A), a compound (B), and a compound (C) in a compounding ratio specified as described above on at least one surface of a thermoplastic resin film. This layer is formed by coating the surface of the film with the gas barrier coating agent of the present invention and then drying by heating.
[0038]
Examples of the thermoplastic resin film used for 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 naphthalate, polybutylene terephthalate. , Aromatic polyester resins such as 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, polyether ether ketone, polysulfone , Polyethersulfone, polyamideimide, polyetherimide, linear polyimide or a mixture thereof. Film or laminate of the 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.
[0039]
As a method for producing a film, a thermoplastic resin is heated and melted by an extruder and extruded from a T die, and cooled and solidified by a cooling roll or the like to obtain an unstretched film, or is 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.
[0040]
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.
[0041]
In the gas barrier film of the present invention, as the gas barrier layer, the compound (A) is polyvinyl alcohol, the compound (B) is poly (meth) acrylic acid, and the compound (C) is 1,2,3,4- It is butanetetracarboxylic acid and most preferably contains 0.1 to 30 mol% of an alkali compound with respect to the carboxyl group contained in poly (meth) acrylic acid and 1,2,3,4-butanetetracarboxylic acid. preferable.
[0042]
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. There is no particular upper limit, but if it is too thick, the characteristics of the base film cannot be utilized. 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.
[0043]
In addition, the solution concentration when coating the film with the coating agent is appropriately changed according to the viscosity and reactivity of the solution, and the specifications of the apparatus to be used. However, a too dilute solution is sufficient to exhibit gas barrier properties. It becomes difficult to coat a layer having a thickness, and a problem that a long time is required in the subsequent drying process tends to occur. 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.
[0044]
The method of coating the coating agent 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, the film is first coated on an unstretched film and dried, and then supplied to a tenter-type stretching machine to simultaneously stretch the film in the running direction and the width direction (simultaneous biaxial stretching), or heat treatment, Alternatively, the film may be stretched in the running direction of the film using a multistage hot 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.
[0045]
In the present invention, in order to form a gas barrier layer, the film is preferably heat-treated at 130 ° C. or higher after coating, more preferably 150 ° C. or higher. The heat treatment time is usually 1 second or longer, preferably 3 seconds or longer. When the heat treatment temperature is low, when the heat treatment time is too short, the gas barrier property may be insufficient.
[0046]
The gas barrier composition of the present invention has an oxygen permeability coefficient of 1000 ml · μm / m at 20 ° C. and 85% RH.²· Day · MPa or less is preferable, more preferably 500 ml · μm / m²・ Day ・ MPa or less, and 300ml ・ μm / m²· Day · MPa or less is preferable.
[0047]
Furthermore, an adhesive layer may be provided on the gas barrier layer of the coat 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.
[0048]
【Example】
EXAMPLES Next, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited only to these Examples.
[0049]
For the oxygen barrier property, a value in an atmosphere of 20 ° C. and a relative humidity of 85% was measured by an oxygen barrier measuring device (OX-TRAN 2/20) manufactured by Mocon.
The oxygen permeability coefficient Pc of the gas barrier layer was calculated 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)
The oxygen permeability of a PET film having a thickness of 12 μm is 900 ml / m.²-Day-MPa, and the oxygen permeability of nylon 6 film with a thickness of 15 μm is 400 ml / m²-The oxygen permeability of a polycarbonate film with a day-MPa and a thickness of 100 μm is 9500 ml / m²· Day · MPa.
[0050]
The appearance of the coated film was judged visually. The results are shown in Table 1 in conformity with the following examples, where ◯ is colorless and transparent, Δ is semi-transparent, and x is cloudy.
[0051]
Reference example (preparation of each solution)
(A) Preparation of aqueous polyacrylic acid solution (I) having a neutralization degree of 10%
To 50.67 g of water, 0.67 g of sodium hydroxide and 12.00 g of polyacrylic acid 25000 (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade 1) were added and dissolved to obtain a 20 mass% aqueous solution (I).
(A) Preparation of 1,2,3,4-butanetetracarboxylic acid aqueous solution (II) having a neutralization degree of 10%
To 42.73 g of water, 0.68 g of sodium hydroxide and 10.00 g of 1,2,3,4-butanetetracarboxylic acid (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade 1) are added and dissolved to obtain a 20% by mass aqueous solution (II). It was.
(C) Preparation of aqueous polyvinyl alcohol solution
To 20.00 g of water, 5.00 g of polyvinyl alcohol (UMR-10HH, polymerization degree 240, saponification degree 98.9, manufactured by Unitika Chemical Co., Ltd.) was added and dissolved to obtain a 20% by mass aqueous solution (III).
[0052]
Example 1
The above solution (I) 51.72 g, solution (II) 22.44 g and solution (III) 21.00 g were mixed and stirred, and the mass ratio of polyvinyl alcohol to polyacrylic acid was 30/70, polyacrylic acid. And a coating agent having a mass ratio of 1,2,3,4-butanetetracarboxylic acid of 70/30 and a solid content concentration of 20% by mass was prepared.
After coating this coating agent on a biaxially stretched polyester film (Embret PET12 manufactured by Unitika, thickness 12 μm) with a Mayer bar so that the coating thickness after drying was about 2 μm, and drying at 100 ° C. for 2 minutes, Heat treatment was performed at 200 ° C. for 15 seconds.
The obtained coated film was transparent, and the oxygen permeability of this film at 20 ° C. and 85% RH was 14 ml / m.²-Day-MPa, oxygen permeability coefficient of coat layer is 28ml / μm / m²-Excellent gas barrier properties such as day-MPa. Details are shown in Table 1.
[0053]
Examples 2-5
Using the solutions (I) to (III), the composition of polyvinyl alcohol, polyacrylic acid, and 1,2,3,4-butanetetracarboxylic acid was changed and the coating agent and the coating film were processed in the same procedure as in Example 1. Got. All of the obtained films were transparent and excellent in gas barrier properties. Table 1 summarizes the physical properties of these films.
[0054]
Examples 6-8
In the reference example, the amount of sodium hydroxide added was changed to obtain solutions having different degrees of neutralization of the compound (A) and the compound (B), and using this, each component had a mass ratio shown in Table 1. A coating agent and a coated film were obtained in the same procedure as in Example 1. All of the obtained films were transparent and excellent in gas barrier properties. Table 1 summarizes the physical properties of this film.
[0055]
Example 9
To the coating agent of Example 1, 0.91 g (corresponding to 5 parts by mass per 100 parts by mass of the total amount of compounds (A) to (C)) of Kunipia F (Kunimine Kogyo's montmorillonite) was added and stirred to coat. An agent was obtained. A coated film was produced in the same procedure as in Example 1 except that this coating agent was used. The obtained film was transparent and excellent in gas barrier properties. Table 1 summarizes the physical properties of this film.
[0056]
Example 10
A coating agent and a coated film were obtained in the same procedure as in Example 1 except that the base film was changed to a polycarbonate film (Lexan manufactured by GE Plastics, Inc., thickness: 100 μm). The obtained film was transparent and excellent in gas barrier properties. Table 1 summarizes the physical properties of this film.
[0057]
Example 11
First, a coating agent was prepared in the same manner as in Example 1.
Next, nylon 6 resin was extruded into a sheet form at a cylinder temperature of 260 ° C. and a T die temperature of 270 ° C. using an extruder equipped with a T die (75 mm diameter, L / D 45 slow compression type single screw). The film was brought into close contact with a cooling roll adjusted to a surface temperature of 10 ° C. and rapidly cooled to obtain an unstretched film having a thickness of 150 μm. Subsequently, the unstretched film was guided to a gravure roll coater, coated so that the coating thickness after drying was 20 μm, and dried in a hot air dryer at 80 ° C. for 30 seconds. Next, the film was supplied to a tenter simultaneous biaxial stretching machine, preheated at a temperature of 100 ° C. for 2 seconds, and then stretched at 170 ° C. at a magnification of 3 times in the machine direction and 3.5 times in the transverse direction. Next, heat treatment was performed at 200 ° C. for 30 seconds with a transverse relaxation rate of 5%, and after cooling to room temperature, the stretched film was wound up. The coated film thus obtained had a thickness of 16.9 μm and a coating layer thickness of 1.9 μm. The obtained film was transparent and excellent in gas barrier properties. Table 1 shows the physical properties of this film.
[0058]
Comparative Examples 1-4
The composition of polyvinyl alcohol, polyacrylic acid and 1,2,3,4-butanetetracarboxylic acid was as shown in Table 1, and a coating agent was prepared in the same procedure as in Example 1. 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 resulting coated film are shown in Table 1, and all were inferior in gas barrier properties.
[0059]
Comparative Example 5
A coating agent and a coating film were obtained in the same procedure as in Example 1 except that succinic acid was used as the compound (C). Succinic acid is not a compound in which at least one carboxyl group is bonded to each of three or more consecutive carbon atoms in the molecule, and the obtained film has a markedly deteriorated barrier property. Table 1 summarizes the physical properties of this film.
[0060]
[Table 1]

[0061]
【The invention's effect】
According to the present invention, a film having excellent gas barrier performance can be produced with good productivity, and excellent gas barrier properties can be maintained even under high humidity.

Claims (15)

At least one carboxyl group is bonded to each of the compound (A) having two or more hydroxyl groups in the molecule, polyacrylic acid or polymethacrylic acid (B), and three or more consecutive carbon atoms in the molecule. The compound (C) is 1,2,3,4-butanetetracarboxylic acid, and the mass ratio of (A), (B), (C) is represented by the following formula: A gas barrier composition characterized by satisfying (1) and (2).
(A) / (B) = 95 / 5-5 / 95 (1)
(B) / (C) = 50/50 to 95/5 (2) The gas barrier composition according to claim 1, wherein the compound (A) is polyvinyl alcohol. 3. The gas barrier composition according to claim 1 , comprising 0.1 to 30 mol% of an alkali compound with respect to the carboxyl group contained in the compound (B) and the compound (C). The gas barrier composition according to any one of claims 1 to 3, wherein at least one of the compound (B) and the compound (C) and the compound (A) are connected by an ester bond. object. 5. The gas barrier composition according to claim 1, wherein the oxygen permeability coefficient at 20 ° C. and 85% RH is 1000 ml · μm / m ² · day · MPa or less. At least one carboxyl group is bonded to each of the compound (A) having two or more hydroxyl groups in the molecule, polyacrylic acid or polymethacrylic acid (B), and three or more consecutive carbon atoms in the molecule. The compound (C) and the solvent (D), the compound (C) is 1,2,3,4-butanetetracarboxylic acid, and the masses of (A), (B) and (C) A gas barrier coating agent characterized in that the ratio satisfies the following formulas (1) and (2).
(A) / (B) = 95 / 5-5 / 95 (1)
(B) / (C) = 50/50 to 95/5 (2) The gas barrier coating agent according to claim 6, wherein the compound (A) is polyvinyl alcohol. The gas barrier coating agent according to claim 6 or 7 , comprising 0.1 to 30 mol% of an alkali compound based on the carboxyl group contained in the compound (B) and the compound (C). The gas barrier coating agent according to any one of claims 6 to 8, wherein the solvent (D) is water. A gas barrier film comprising a gas barrier layer comprising the gas barrier composition according to any one of claims 1 to 5 on at least one surface of a thermoplastic resin film. The gas barrier film according to claim 10, wherein the thermoplastic resin film is a nylon 6 film or a polyethylene terephthalate film. The gas barrier film according to claim 10, wherein the thermoplastic resin film is a film made of one kind selected from polyarylate, polycarbonate and polyethersulfone, or a mixture of two or more kinds thereof. A method for producing a gas barrier film, comprising applying the gas barrier coating agent according to any one of claims 6 to 9 to at least one surface of a thermoplastic resin film, and then performing 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 any one of claims 10 to 12, and a polyolefin resin film is further laminated thereon. The gas barrier laminate film according to claim 14, wherein the polyolefin resin film comprises a resin mainly composed of polyethylene and / or polypropylene.