JP4832687B2 - Water-soluble film for packaging acidic substances - Google Patents

Description

【００１４】
（式中、Ｒ ^１ は水素原子または炭素数１〜３のアルキル基を表し、Ｒ ^２ は水素原子または炭素数１〜５のアルキル基を表す）
【００１５】
上記式（Ｉ）において、Ｒ ^１ で表される炭素数１〜３のアルキル基としては、メチル基、エチル基、プロピル基、イソプロピル基などを挙げることができ、また、Ｒ ^２ で表される炭素数１〜５のアルキル基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｔ−ブチル基、ペンチル基、イソペンチル基などを挙げることができる。
【００１６】
上記式（Ｉ）で示される単量体として、具体的には、Ｎ−ビニルホルムアミド、Ｎ−メチル−Ｎ−ビニルホルムアミド、Ｎ−ビニルアセトアミド、Ｎ−メチル−Ｎ−ビニルアセトアミドなどを例示することができる。
【００１８】
Ｎ−ビニルアミド系単量体の中でも、耐酸性の観点から、上記式（Ｉ）で示される単量体またはＮ−ビニル−２−カプロラクタムが使用され、入手のし易さの点から好ましいのは、Ｎ−ビニルホルムアミド、Ｎ−ビニルアセトアミド、Ｎ−メチル−Ｎ−ビニルアセトアミドおよびＮ−ビニル−２−カプロラクタムであり、とりわけＮ−ビニル−２−カプロラクタムが形態安定性の点から好ましい。
【００１９】
本発明の水溶性フィルムにおいて、変性ＰＶＡに含まれるＮ−ビニルアミド系単量体単位の含有量（変性量）は、１〜１０モル％であることが必須であり、２〜８モル％であることが好ましい。Ｎ−ビニルアミド系単量体単位の含有量が１モル％未満の場合には、得られるフィルムの冷水溶解性が十分なものとはいえなくなる。一方、含有量が１０モル％を超える場合には、変性ＰＶＡの生分解性が低下するのみならず、吸湿性が大きくなるために、得られるフィルムに腰が無くなり、水溶性フィルムとしての実用物性に問題が生じることがある。なお、本発明において冷水とは０℃〜４０℃の水を意味する。
【００２０】
水溶性フィルムは厚みが１０〜２００μｍと薄くても高い強度と柔軟性が要求される場合があるため、フィルムの強度やタフネスの点から、本発明に用いられる変性ＰＶＡの重合度（粘度平均重合度）は３００〜３０００であることが好ましく、４００〜２５００であることがさらに好ましく、水溶性の点から５００〜２０００であることが特に好ましい。変性ＰＶＡの粘度平均重合度が３００未満の場合には、フィルムの強度が弱くなる傾向にあり、また、３０００より大きい場合には、フィルムを製膜するときに使用する製膜原料の溶液粘度または溶融粘度が高くなって作業性が低下したり、得られたフィルムの溶解性が低下する場合がある。粘度平均重合度はＪＩＳ記載の方法で測定される。
【００２１】
本発明において、変性ＰＶＡのけん化度は、得られるフィルムの強度、腰、製袋性の点から８２〜９９．５モル％であることが必須であり、耐薬品性の点から８６〜９９．４モル％であることが好ましく、９０〜９９．２モル％であることがより好ましく、９２〜９９．０モル％であることが特に好ましい。けん化度はＪＩＳ記載の方法により測定される。
変性ＰＶＡのけん化度が８２モル％より小さいと、フィルムが高湿下で吸湿して腰がなくなり形態安定性が低下したり、フィルムに酸性物質を包装して保管した場合に、フィルムの水溶性が低下したりする場合がある。一方、けん化度が９９．５モル％よりも大きい変性ＰＶＡは、工業的に安定に製造することができず、このような変性ＰＶＡからは製膜を安定に行うこともできない。
【００２２】
Ｎ−ビニルアミド系単量体単位を含有する変性ＰＶＡの製法としては、ビニルエステル系単量体とＮ−ビニルアミド系単量体を共重合して得られたビニルエステル系重合体を、アルコールまたはジメチルスルホキシドなどの溶液中でけん化する方法などが挙げられる。
【００２３】
上記のビニルエステル系単量体としては、ギ酸ビニル、酢酸ビニル、プロピオン酸ビニル、バレリン酸ビニル、カプリン酸ビニル、ラウリン酸ビニル、ステアリン酸ビニル、安息香酸ビニル、ピバリン酸ビニルおよびバーサティック酸ビニルなどが挙げられ、これらの中でも工業的に変性ＰＶＡを得る点からは酢酸ビニルが好ましい。
【００２４】
本発明において、変性ＰＶＡは、本発明の効果を損なわない範囲であれば、ビニルアルコール単位、ビニルエステル系単量体単位ならびにＮ−ビニルアミド系単量体単位を有する単量体単位以外に他の単量体単位を含有していてもよい。そのような単量体単位としては、エチレン、プロピレン、１−ヘキセンなどのα−オレフィン類；アクリルアミド、Ｎ−メチルアクリルアミドなどのアクリルアミド誘導体；メタクリルアミド、Ｎ−メチルメタクリルアミドなどのメタクリルアミド誘導体；メチルビニルエーテル、エチルビニルエーテル、ｎ−プロピルビニルエーテル、ｉ−プロピルビニルエーテル、ｎ−ブチルビニルエーテルなどのビニルエーテル類；エチレングリコールビニルエーテル、１，３−プロパンジオールビニルエーテル、１，４−ブタンジオールビニルエーテルなどのヒドロキシ基を含有するビニルエーテル類；アリルアセテート；プロピルアリルエーテルなどのアリルエーテル類；オキシアルキレン基を有する単量体；ビニルトリメトキシシランなどのビニルシラン類；酢酸イソプロペニル；３−ブテン−１−オール、４−ペンテン−１−オール、５−ヘキセン−１−オール、７−オクテン−１−オール、３−メチル−３−ブテン−１−オールなどのヒドロキシ基を含有するα−オレフィン類；エチレンスルホン酸、アリルスルホン酸、メタアリルスルホン酸、２−アクリルアミド−２−メチルプロパンスルホン酸などに由来するスルホン酸基を有する単量体；ビニロキシエチルトリメチルアンモニウムクロライド、ビニロキシブチルトリメチルアンモニウムクロライド、ビニロキシエチルジメチルアミン、ビニロキシメチルジエチルアミン、Ｎ−アクリルアミドメチルトリメチルアンモニウムクロライド、Ｎ−アクリルアミドエチルトリメチルアンモニウムクロライド、Ｎ−アクリルアミドジメチルアミン、アリルトリメチルアンモニウムクロライド、メタアリルトリメチルアンモニウムクロライド、ジメチルアリルアミン、アリルエチルアミンなどに由来するカチオン基を有する単量体などを共重合して得られる単量体単位が挙げられる。これらの単量体単位の含有量は、使用される目的や用途などによっても異なるが通常５モル％以下であり、好ましくは２モル％以下である。
【００２５】
前述のビニルエステル系単量体およびＮ−ビニルアミド系単量体を有する単量体の共重合の方法としては、塊状重合法、溶液重合法、懸濁重合法、乳化重合法などの公知の方法が挙げられる。その中でも、無溶媒で重合する塊状重合法またはアルコールなどの溶媒中で重合する溶液重合法が通常採用される。溶液重合時に溶媒として使用されるアルコールとしては、メタノール、エタノール、プロパノールなどの低級アルコールが挙げられる。共重合に使用される開始剤としては、２，２’−アゾビス（イソブチロニトリル）、２，２’−アゾビス（２，４−ジメチルバレロニトリル）などのアゾ系開始剤、または過酸化ベンゾイル、ｎ−プロピルパーオキシカーボネートなどの過酸化物系開始剤などの公知の開始剤が挙げられる。重合温度については特に制限はないが、０℃〜１５０℃の範囲が適当である。
【００２６】
本発明において変性ＰＶＡは、前述のビニルエステル系単量体およびＮ−ビニルアミド系単量体を共重合して得られたビニルエステル系重合体を、通常、メタノールなどのアルコール類、酢酸メチルなどのエステル類、ジメチルスルホキシドなどから選ばれる１種または２種以上の溶媒中、好ましくはメタノールなどの低級アルコール溶媒中で、水酸化カリウム、水酸化ナトリウムなどのアルカリ触媒や硫酸、塩酸、ｐ−トルエンスルホン酸などの酸触媒を用いてけん化することにより得ることができる。けん化反応の条件は、ビニルエステル系重合体の構造や目的とするビニルアルコール系重合体のけん化度によって適宜調整されるが、通常、触媒／ビニルエステル系単量体単位のモル比が０．００１〜５．０、反応温度が２０〜１８０℃、反応時間が０．１〜２０時間の範囲で実施される。けん化方法としてはバッチ法や連続法などの公知の方法が適用可能である。
【００２７】
本発明の水溶性フィルムには、必要に応じて糖類を配合することができる。糖類としては、グルコースなどの単糖類、オリゴ糖、多糖類およびマンニットなどの鎖状糖アルコールが挙げられる。多糖類としては、澱粉、セルロース、キチン、キトサン、ヘミセルロース、ペクチン、プルラン、寒天、アルギン酸、カラギーナン、デキストリン、トレハロースなどが挙げられ、これらのうち１種または２種以上を用いることができる。鎖状糖アルコールとしては、トレイット、エリトリットなどの炭素数４のテトリット類、アラビット、キシリットなどの炭素数５のペンチット類、グリシット、マンニット、ソルビットなどの炭素数６のヘキシット類が挙げられる。糖類を添加することにより、フィルムの水溶性、生分解性および形態安定性をさらに高めたりすることができる。糖類添加時のフィルムの冷水溶解性が良好な点から、糖類のなかでも澱粉の配合が特に好ましい。澱粉としては、例えば、トウモロコシ、馬鈴薯などの生澱粉、これらに物理的または化学的処置を施した加工澱粉（デキストリン、酸化澱粉、エーテル化澱粉、カチオン化澱粉など）などを用いることができる。
【００２８】
糖類の配合量はフィルムの水溶性、生分解性、形態安定性の点から、変性ＰＶＡ１００重量部に対して１〜１００重量部であることが好ましく、２〜９０重量部であることがさらに好ましく、３〜８０重量部であることが特に好ましい。一般に、ＰＶＡと糖類とは相溶性が悪いため、糖類を多量にＰＶＡに配合した場合には配合フィルムの強度などの機械的物性は大幅に低下するが、本発明の水溶性フィルムに用いられる変性ＰＶＡは糖類、特に澱粉との相溶性に優れるという特徴を有するので、本発明の水溶性フィルムには糖類を多量に配合することができる。糖類の配合量が１重量部より小さいとフィルムの水溶性向上および生分解性向上の効果が発現しない場合がある。一方、糖類の配合量が１００重量部より多いと、フィルムの低温での耐衝撃性が低下し、破袋しやすくなる。
【００２９】
一般に、水溶性フィルムには、高温多湿の地域や寒冷地での使用にも耐え得るような強度やタフネスが要求され、特に低温での耐衝撃性が必要とされる。本発明の水溶性フィルムには、低温での耐衝撃性向上を目的として、フィルムのガラス転移点を下げるために種々の可塑剤を本発明の水溶性フィルムに配合することができる。さらに本発明の水溶性フィルムには、上記の目的に加えて、水に対する溶解性を向上させる目的で可塑剤を配合することができる。
【００３０】
本発明の水溶性フィルムに配合される可塑剤としては、ＰＶＡの可塑剤として一般に用いられているものなら特に制限はなく、例えば、グリセリン、ジグリセリン、ジエチレングリコール、トリエチレングリコール、プロピレングリコール、ジプロピレングリコール、トリメチロールプロパン、ペンタエリスリトール、１，３−ブタンジオールなどの多価アルコール類；ポリエチレングリコール、ポリプロピレングリコールなどのポリエーテル類；ポリビニルピロリドンなどのポリビニルアミド類；ビスフェノールＡ、ビスフェノールＳなどのフェノール誘導体；Ｎ−メチルピロリドン、ジメチルアセトアミドなどのアミド化合物；グリセリン、ペンタエリスリトール、ソルビトールなどの多価アルコールにエチレンオキサイドを付加した化合物や水などが挙げられ、これらは１種または２種以上を用いることができる。これらの可塑剤の中でも、水溶性を向上させる目的には、グリセリン、ジグリセリン、ジエチレングリコール、トリエチレングリコール、プロピレングリコール、ジプロピレングリコール、トリメチロールプロパン、ポリエチレングリコール、ポリビニルピロリドンを用いるのが好ましく、特に可塑剤のブリードアウトによるフィルムの水溶性低下を抑制する効果の点から、グリセリン、ジグリセリン、トリメチロールプロパン、ポリエチレングリコール、ポリビニルピロリドンを用いるのが特に好ましい。
【００３１】
可塑剤としてポリエチレングリコールを用いる場合のポリエチレングリコールの分子量について特に制限はないが、変性ＰＶＡとの相溶性およびブリードアウトによる水溶性の低下を抑制する効果の点から数平均分子量が１００〜１０００あることが好ましい。ポリビニルピロリドンの分子量についても特に制限はないが、ＰＶＡとの相溶性の点から重量平均分子量で１０００〜２００００であることが好ましい。
【００３２】
可塑剤の配合量は、変性ＰＶＡ１００重量部に対して１〜５０重量部であるのが好ましい。可塑剤の配合量が１重量部未満の場合には、可塑剤を配合することによる効果が発現しない場合がある。一方、可塑剤の配合量が５０重量部を超える場合には、可塑剤のブリードアウトが大きくなり、得られるフィルムの耐ブロッキング性が低下する場合がある。得られるフィルムの水に対する溶解速度の点からは、変性ＰＶＡ１００重量部に対して可塑剤を２０重量部以上の割合で配合するのが好ましい。一方、得られるフィルムの腰（製袋機などの工程通過性）の点からは、変性ＰＶＡ１００重量部に対して可塑剤を４０重量部以下の割合で配合するのが好ましい。得られるフィルムの水溶性を向上させる点からは、可塑剤の配合量は多いほど好ましく、さらに、可塑剤の配合量が多いほどヒートシール温度が低下し、フィルム製袋時の生産性が向上する傾向がある。特に、得られるフィルムのヒートシール温度が１７０℃以下となるような割合で可塑剤を配合することが好ましく、１６０℃以下となるような割合で可塑剤を配合することがさらに好ましい。また、可塑剤の配合量は得られるフィルムの強度やヤング率の大きさに影響を与えやすいが、得られるフィルムの実用性の点からは、フィルムの強度は１．０ｋｇ／ｃｍ²以上であることが好ましく、１．５ｋｇ／ｃｍ²以上であるのがさらに好ましい。得られるフィルムの形態安定性や製袋機などの工程通過性の点からは、フィルムのヤング率は１．５ｋｇ／ｍｍ²以上であるのが好ましく、２．０ｋｇ／ｍｍ²以上であるのがさらに好ましく、このような範囲のヤング率を有するフィルムが得られるように、可塑剤を配合することが好ましい。
【００３３】
本発明の水溶性フィルムには、さらに必要に応じて、無機フィラーを配合することができる。本発明の水溶性フィルムに用いられる無機フィラーとしては、例えば、シリカ、重質、軽質または表面処理された炭酸カルシウム、水酸化アルミニウム、酸化アルミニウム、酸化チタン、珪藻土、硫酸バリウム、硫酸カルシウム、ゼオライト、酸化亜鉛、珪酸、珪酸塩、マイカ、炭酸マグネシウム、カオリン、ハロサイト、パイロフェライト、セリサイトなどのクレー、タルクなどを挙げることができ、これらのうち１種または２種以上を用いることができる。これらのなかでも、特に変性ＰＶＡへの分散性の点から、シリカ、タルクを用いることが好ましい。無機フィラーの平均粒子径は、フィルムのブロッキング防止性の点から１μｍ以上が好ましく、一方で、変性ＰＶＡへの分散性の点から１０μｍ以下が好ましい。無機フィラーを配合することにより発現するフィルムのブロッキング防止性と、変性ＰＶＡへの無機フィラーの分散性の両方の要求性能を満足させるには、平均粒子径が１〜７μｍ程度の大きさの無機フィラーを用いるのがより好ましい。
【００３４】
無機フィラーの配合量は、フィルムのブロッキング防止性および変性ＰＶＡへの無機フィラーの分散性の点から、変性ＰＶＡ１００重量部に対して０．５〜２０重量部であることが好ましく、０．７〜１５重量部であることがより好ましく、１〜１０重量部であることが特に好ましい。なお、無機フィラーを２０重量部を超えて配合すると、変性ＰＶＡへの分散性が低下して無機フィラーが凝集してしまい、得られるフィルムの水溶性が低下する傾向がある。
【００３５】
本発明の水溶性フィルムには、さらに必要に応じて、着色剤、香料、増量剤、消泡剤、剥離剤、紫外線吸収剤、界面活性剤などの添加剤を適宜配合しても差し支えない。特に製膜装置のダイスやドラムなどの金属表面と、製膜したフィルムやフィルム原液との剥離性を向上させるために、変性ＰＶＡ１００重量部に対して界面活性剤を０．０１〜５重量部の割合で配合することが好ましい。また、本発明の水溶性フィルムには、必要に応じて、本発明の効果を損なわない範囲内で、本発明に用いられる変性ＰＶＡとは異なる種類のＰＶＡ、カルボキシメチルセルロース、ポリアクリルアミド、ポリアクリル酸またはその塩、メチルセルロース、ヒドロキシメチルセルロースなどの水溶性高分子を配合しても良い。特にフィルムの水溶性を向上させる観点から、低粘度タイプのカルボキシメチルセルロースを添加することが好ましい。
【００３６】
本発明の水溶性フィルムの製造するにあたり、その製造原料は、前記の変性ＰＶＡに、必要に応じて、可塑剤、糖類、無機フィラーやその他の成分を配合し、撹拌槽中にて溶媒に溶解または分散させる方法や押出機中にて溶融混練する方法など、公知の方法で混合することにより調製することができる。
【００３７】
本発明の水溶性フィルムは、一般にフィルムを製膜する際に用いられている製膜方法、例えば、流延製膜法、湿式製膜法、乾式製膜法、押出製膜法、溶融製膜法、コート法、インフレーション製膜法などの製膜方法で製造することができる。例えば、本発明の水溶性フィルムの製膜に必要な成分を、水、ジメチルスルホキシド、ジメチルホルムアミド、ジメチルアセトアミド、メタノール、ｎ−プロパノール、ｉ−プロパノール、フェノールなどに例示される溶媒の１種または２種以上の混合液に溶解し、均一な製膜原液を調製した後、流延製膜法などの製膜方法で製造することができる。この製膜原液の濃度は、粘度の点から５０重量％以下（溶媒の含有量が５０重量％以上）であることが好ましく、製膜したフィルムの表面におけるマット状態の形成されやすさの点から３０重量％以下（溶媒の含有量が７０重量％以上）であることがさらに好ましい。
【００３８】
本発明の水溶性フィルムの厚みは１０〜２００μｍであるのが好ましく、フィルムの強度と水溶性のバランスの点から２０〜１５０μｍであるのがより好ましく、３０〜１２０μｍであるのが特に好ましい。
【００３９】
本発明の水溶性フィルムのブロッキング防止性を向上させるために、必要に応じて、該水溶性フィルム表面をロールマット化したり、シリカや澱粉などのブロッキング防止用の粉体を水溶性フィルムに塗布したり、エンボス処理を行うことができる。フィルム表面のロールマット化は、製膜時に乾燥前のフィルムが接するロールに微細な凹凸を形成しておくことにより施すことができる。エンボス処理は一般にフィルムが形成された後で、熱や圧力を加えながらエンボスロールとゴムロールでニップすることで行うことができる。粉体の塗布はブロッキング防止の効果が大きいが、用途によっては使用できないことがあるため、ブロッキング防止のためにはロールマット化やエンボス処理を施すことでブロッキング防止をはかるのが好ましく、ブロッキング防止効果の大きさの点からロールマット化することが特に好ましい。
【００４０】
本発明の水溶性フィルムは、冷水への溶解速度が優れており、１０℃水中での完全溶解時間（フィルムの厚さ５０μｍ）は好ましくは２００秒以下であり、より好ましくは１５０秒以下であり、特に好ましくは１００秒以下である。本明細書でいう１０℃水中での完全溶解時間とは、厚さ５０μｍのフィルムを４０×４０ｍｍの正方形に切り、これをスライドマウントにはさみ、１０℃の撹拌している水中に浸漬してフィルムが完全に溶解するまでの時間を測定した値であり、フィルムの厚さが５０μｍとは異なるものを使用する場合には、下記の式（１）によりフィルムの厚さ５０μｍの場合に換算した値である。
溶解時間（秒）＝（５０／フィルムの厚み（μｍ））²×溶解時間（秒）（１）
【００４１】
本発明の水溶性フィルムの生分解性は好ましくは６０％以上であり、より好ましくは６５％以上であり、さらに好ましくは７０％以上であり、特に好ましくは７５％以上である。ＰＶＡの生分解性は、ＩＳＯ１４８５１に準じた方法に従って活性汚泥を用いて測定される。本発明の水溶性フィルムは、未変性の部分けん化ＰＶＡやイオン変性ＰＶＡを用いた従来の水溶性フィルムと比較して生分解性に優れている。
【００４２】
本発明の水溶性フィルムは、冷水への溶解性が優れているのみならず、生分解性、耐薬品性および強度や腰などの実用物性にも優れているので、公知の農薬や洗剤など水に溶解して使用される物質の包装材料として極めて有用である。本発明の水溶性フィルムから製造された包装袋は、そのまま水中に投入するだけで速やかに溶解し、その内容物は速やかに水中に放出される。
【００４３】
本発明の水溶性フィルムは、液体、固体、粉体、顆粒状などの酸性物質の包装に用いることができ、包装される酸性物質の形態について特に制限はないが、なかでも、従来水溶性フィルムによる包装が困難であった液体状の酸性物質の包装に特に好適に用いられる。酸性物質が液体状の場合には、フィルムで包装したときに高い形態安定性が必要であり、また、固体状の酸性物質を包装した場合には酸性物質が接触するフィルム表面の物性の低下が問題になるのみであるが、液体状の場合にはフィルムの内部全体に酸性物質が浸透するため、物性の低下が著しいという問題があった。本発明の水溶性フィルムは、優れた形態安定性、耐酸性を有するために、液体状の酸性物質でも包装することができる。
本発明の水溶性フィルムが適用される酸性物質としては、１重量％の水溶液または水分散液にしたときのｐＨが６以下であればよく、農薬、消臭剤、洗剤など種々のものが含まれる。
【００４４】
以下に実施例を挙げて本発明をさらに詳しく説明するが、本発明はこれによって何ら限定されるものではない。なお、実施例中「部」および「％」は、特に断らない限り「重量部」および「重量％」をそれぞれ意味する。なお実施例中、フィルムの各種特性の測定および評価は以下の方法により行った。
【００４５】
［フィルムの水溶性の測定方法］
１０℃の恒温バスにマグネティックスターラーを設置する。１リットルの蒸留水を入れた１リットルのガラスビーカーを上記の恒温バスに入れ、５ｃｍの回転子を用いて２５０ｒｐｍで撹拌を行う。ビーカー内の蒸留水が１０℃になった後、水溶性の測定を開始する。
フィルムを４０×４０ｍｍの正方形に切り、これをスライドマウントにはさみ、１０℃の撹拌している水中に浸漬してフィルムの溶解状態を観察し、フィルムが完全に溶解するまでの時間（秒数）を測定した。なお、フィルムの厚さが５０μｍとは異なるフィルムを用いる場合には、下記の式（１）に従ってフィルムの厚さ５０μｍの値に換算する。
【００４６】
溶解時間（秒）＝（５０／フィルムの厚み（μｍ））²×溶解時間（秒）（１）
【００４７】
［ヤング率、強度の測定方法］
幅１０ｍｍのフィルムを、２０℃６５％ＲＨの雰囲気のもとで１週間調湿した後、オートグラフで引張り試験を行った。チャック間隔は５０ｍｍ、引張り速度は５００ｍｍ／ｍｉｎであった。
【００４８】
［耐薬品性の評価方法］
フィルムから１０ｃｍ×１５ｃｍの袋を作り、内部に薬品としてコハク酸の微粉末（１重量％水溶液のｐＨ２．４）３５ｇを入れ、熱シールして密封した。この包装袋をさらにアルミニウムにポリエチレンをラミネートしたフィルムで包み、熱シールすることにより２重に密封包装し、薬品を密封した包装袋から水や可塑剤が飛散しないようにした。この袋を長期保存の促進試験として、４０℃の恒温器に入れて放置し、４週間後に取り出して、包装していたフィルムの水溶性を前述の測定方法にて測定し、薬品包装前との経時変化を調べた。
【００４９】
合成例１（変性ＰＶＡの合成例）
撹拌機、還流冷却管、窒素導入管および温度計を取り付けた５Ｌの反応器に、酢酸ビニル単量体２３４０ｇ、メタノール５６９．４ｇ、Ｎ−ビニル−２−カプロラクタムの５０％メタノール溶液１８１．１ｇを仕込み、窒素ガスを３０分バブリングして脱気した。反応器の昇温を開始し、内温が６０℃となったところで、２，２’−アゾビス（イソブチロニトリル）１．５ｇを添加し重合を開始した。Ｎ−ビニル−２−カプロラクタムの５０％メタノール溶液を酢酸ビニル単量体とのモル比率が一定になるように逐次添加しながら重合を行い、４時間後に冷却して重合を停止した。このときの固形分濃度は３９％であった。次いで３０℃減圧下でメタノールを時々添加しながら未反応の酢酸ビニル単量体の除去を行い、ポリ酢酸ビニル共重合体のメタノール溶液（濃度３３％）を得た。次に、メタノールを加えて濃度を２５％に調整したポリ酢酸ビニル共重合体のメタノール溶液にアルカリモル比（ＮａＯＨのモル数／酢酸ビニル単量体単位のモル数）０．０３のＮａＯＨメタノール溶液（１０％濃度）を添加してけん化した。得られた変性ＰＶＡ（ＰＶＡ−１）のけん化度は９８．４モル％であった。
【００５０】
得られた変性ＰＶＡ１ｇにメタノール１０ｇを加え、６０℃に加温して変性ＰＶＡを膨潤させた後、ＮａＯＨのメタノール溶液（１０％濃度）５ｇを加えて６０℃で３時間撹拌したものについて、メタノールソックスレー抽出を３日間実施し、次いで乾燥して変性ＰＶＡの精製物を得た。該変性ＰＶＡ精製物のプロトンＮＭＲ測定から求めたＮ−ビニル−２−カプロラクタム単量体単位の変性量は６．０モル％であった。また、該ＰＶＡの平均重合度を常法のＪＩＳ Ｋ６７２６に準じて測定したところ１５００であった。
【００５１】
Ｎ−ビニルアミド系単量体の種類と変性量、重合度、けん化度が下記の表１になるように重合条件を変更したこと以外はＰＶＡ−１と同様の方法で変性ＰＶＡ（ＰＶＡ−２〜７およびＰＶＡ１０、１１）を合成した。合成した結果を下記の表１に示す。
【００５２】
合成例２（ＰＶＡの合成例）
攪拌機、還流冷却管、窒素導入管および温度計を取り付けた５Ｌ反応器に酢酸ビニル単量体２１００ｇ、メタノール９００ｇを仕込み、窒素ガスを３０分バブリングして脱気した。反応器の昇温を開始し、内温が６０℃となったところで、２，２’−アゾビス（イソブチロニトリル）０．４ｇを添加し重合を開始した。５時間後に冷却して重合を停止した。このときの固形分濃度は２７％であった。次いで、３０℃減圧下にメタノールを時々添加しながら未反応酢酸ビニルモノマーの除去を行い、ポリ酢酸ビニルのメタノール溶液（濃度３３％）を得た。次に、メタノールを加えて濃度を２５％に調整したポリ酢酸ビニルのメタノール溶液にアルカリモル比（ＮａＯＨのモル数／酢酸ビニル単量体単位のモル数）０．０２５のＮａＯＨメタノール溶液（１０％濃度）を添加してけん化した。得られたＰＶＡ（ＰＶＡ−８）のけん化度は９８．５モル％であった。
【００５３】
得られたＰＶＡ１ｇにメタノール１０ｇを加え、６０℃に加温してＰＶＡを膨潤させた後、ＮａＯＨのメタノール溶液（１０％濃度）５ｇを加えて６０℃で３時間撹拌したものについて、メタノールソックスレー抽出を３日間実施し、次いで乾燥してＰＶＡの精製物を得た。該ＰＶＡの平均重合度を常法のＪＩＳ Ｋ６７２６に準じて測定したところ１５００であった。
けん化度が下記の表１になるようにけん化条件を変更したこと以外はＰＶＡ−８と同様の方法でＰＶＡ−９を合成した。合成した結果を下記の表１に示す。
【００５４】
実施例１
表１に示される変性ＰＶＡ（ＰＶＡ−１）１００重量部に対し、可塑剤としてグリセリン１５重量部、エーテル化澱粉２０重量部、タルク５重量部、および水を添加して均一な５％水溶液（含水率９５％）を作成し、ポリエステルフィルム上に流延して室温で乾燥した後、ポリエステルフィルムから剥離することにより、厚さ５０μｍのフィルムを得た。得られたフィルムに１００℃で１０分間熱処理を行った。このフィルムの水溶性を測定したところ、１０℃水中での完全溶解時間は６７秒であった。また、フィルムの腰に代表される工程通過性などの取扱性の指標として、２０℃、６５％ＲＨに調湿してヤング率の測定を行ったところ２．９ｋｇ／ｍｍ²、強度は２．４ｋｇ／ｃｍ²であった。また、ＩＳＯ１４８５１に準じた方法で生分解性を評価したところ、生分解率は８０％であった。
続いて、耐薬品性を評価したところ、薬品包装後のフィルムの１０℃水中での完全時間は６９秒であり、水溶性の低下は見られなかった。
【００５５】
実施例２〜６および比較例１
変性ＰＶＡの内容、ならびに可塑剤、糖類および無機フィラーの種類と配合量を下記の表１および表２のように変更したこと以外は、実施例１と同様にしてフィルムを作製し、各種評価を行った。評価結果を下記の表３に示した。
【００５６】
実施例７
薬品としてグリセリンと乳酸の混合物（１重量％水溶液のｐＨ４）を用いて耐薬品性を評価したこと以外は、実施例１と同様にしてフィルムを製造し、各種評価を行った。評価結果を下記の表３に示した。
【００５７】
比較例２、４および５
ＰＶＡの内容を下記の表１のように変更したこと以外は、実施例１と同様にしてフィルムを製造し、各種評価を行った。評価結果を下記の表３に示した。けん化度が９８．５モル％の無変性ＰＶＡからなるフィルムは水溶性が劣る（比較例２）。変性ＰＶＡのＮ−ビニルアミド基の変性量が大きい場合には生分解性が劣る（比較例４）。けん化度が８０モル％と低い場合にはフィルムのヤング率が低いのみならず、薬品包装後の水溶性が低下し、耐薬品性が劣る（比較例５）。
【００５８】
比較例３
ＰＶＡの内容を下記の表１のように変更し、薬品としてグリセリンと乳酸の混合物（１重量％水溶液のｐＨ４）を用いて耐薬品性を評価したこと以外は、実施例１と同様にしてフィルムを製造し、各種評価を行った。評価結果を下記の表３に示した。けん化度が８８．０モル％の無変性ＰＶＡからなるフィルムは薬品包装後の水溶性が低下しており、耐薬品性が劣る（比較例３）。
【００５９】
【表１】

【００６０】
【表２】

【００６１】
【表３】

【００６２】
【発明の効果】
本発明の水溶性フィルムは、冷水に対する溶解性が優れているのみならず、酸性物質包装後においても水に対する溶解性は低下せず、生分解性、および強度や腰などの実用物性なども同時に優れており、特に農薬や洗剤などの包装用途に好ましく用いられる。[0001]
BACKGROUND OF THE INVENTION
  The present invention is an acidsexThe present invention relates to a water-soluble film for packaging materials. More specifically, the present invention comprises an N-vinylamide monomer unit and a modified polyvinyl alcohol having a specified degree of saponification (hereinafter, polyvinyl alcohol may be abbreviated as “PVA”). The present invention relates to a water-soluble film for packaging acidic substances, which is excellent in biodegradability, chemical resistance and practical physical properties such as strength and waist.
[0002]
[Prior art]
In recent years, as a method of using various chemicals including agricultural chemicals, laundry detergents, bleaching agents, toiletry products, industrial chemicals, etc., these chemicals are sealed and packaged in units of water-soluble films (unit packaging). At times, the packaging form is put into water, and the contents are used together with the packaging film dissolved or dispersed in water. The advantages of this unit packaging are that it can be used without direct contact with hazardous chemicals during use, that a certain amount of contents are packed, so there is no need to weigh during use, For example, the processing after use is unnecessary.
[0003]
Conventionally, a PVA film has been often used as such a water-soluble film for unit packaging. PVA film generally has the characteristics that the film is tough, excellent in transparency, and has good printability. However, PVA has higher crystallinity as the degree of saponification increases, and the proportion of crystal parts that do not dissolve in cold water. Therefore, non-denatured partially saponified PVA has been used for cold water-soluble film applications such as for unit packaging, instead of PVA having a high degree of saponification, which is called a complete saponification type. The water-soluble film using this unmodified partially-saponified PVA has characteristics such as being easily soluble in cold water and warm water and having excellent mechanical strength. However, in recent years, from the viewpoints of workability, chemical resistance, environmental protection, etc., the dissolution rate in water is faster, the bag breakage due to impact is less likely to occur, the shape stability is good, and the water solubility changes over time during storage. There is a need for a water-soluble film that simultaneously satisfies many required performances, such as low biodegradability and good biodegradability. The conventional unmodified partially saponified PVA film has sufficient cold water solubility at the beginning of the production of the film. However, when an acidic substance is packaged and stored for a long period of time, The saponification of the acetic acid group remaining in the film occurs, and the crystallization proceeds to insolubilize the film. Therefore, the required performance is not satisfied.
[0004]
In order to solve such problems, various water-soluble films made of modified PVA have been proposed. Examples of the modified PVA include carboxyl group-modified PVA (“Application and Market of Water-Soluble Polymers”, No. 266- 277, CMC, issued in 1984), saponified copolymer of allyl ester and vinyl ester (Japanese Patent Laid-Open No. Sho 62-179550), at least one of oxyalkylene group, sulfonic acid group and cationic group PVA contained (JP-A 63-168437), 2-pyrrolidone ring-containing PVA (JP 2-124945), saponified copolymer of N-vinylacetamide and vinyl ester (Patent No. 3066130) Saponified copolymer of diacetone acrylamide and vinyl ester (Patent No. 309207) JP), etc. saponified copolymers of oxyalkylene group-containing vinyl ether and vinyl ester (JP-A-11-236419) is known.
[0005]
However, a water-soluble film made of carboxyl group-modified PVA has a disadvantage that the cold water solubility is impaired when it comes into contact with an acidic substance. Furthermore, the carboxyl group-modified PVA may be gelled by heat. In addition, the carboxyl group-modified PVA can increase the cold water solubility by increasing the carboxyl group content (modification amount), but on the other hand, the biodegradability of the modified PVA is reduced. The use of a water-soluble film composed of carboxyl group-modified PVA having reduced biodegradability is not preferred because it is dissolved in water and discharged into the environment.
[0006]
From saponified products of copolymers of allyl esters and vinyl esters, saponified products of copolymers of oxyalkylene group-containing allyl ethers and vinyl esters, saponified products of copolymers of oxyalkylene group-containing vinyl ethers and vinyl esters, etc. The resulting film has problems that allyl ester, oxyalkylene group-containing allyl ether and oxyalkylene group-containing vinyl ether and vinyl ester have low copolymerization properties, so that the amount of PVA modification remains low and water solubility is not sufficient. ing. In addition, when the amount of modification of the modified PVA is increased by increasing the amount of allyl ester, oxyalkylene group-containing allyl ether and oxyalkylene group-containing vinyl ether relative to the vinyl ester during copolymerization, a film produced from the resulting modified PVA is Not only the biodegradability is impaired, but also the degree of polymerization of the modified PVA is lowered, so that the film produced from the modified PVA cannot be said to have sufficient strength and impact resistance to be used for packaging applications. The bag breakage increases, which is not preferable.
[0007]
Films made of modified PVA into which ionic groups such as sulfonic acid groups and cationic groups are introduced, and films made of a saponified copolymer of diacetone acrylamide and vinyl ester are biodegradable as the amount of modification increases. However, a water-soluble film that satisfies practical physical properties such as water solubility, biodegradability and strength has not been obtained.
[0008]
A film composed of 2-pyrrolidone ring-containing PVA and a film composed of a saponified product of a copolymer of N-vinylacetamides and vinyl esters are composed of a nonionic monomer having a 2-pyrrolidone ring-containing monomer and N-vinylacetamides. Since it is a body, it has the problem that cold water solubility is not enough. In order to solve this cold water solubility problem, methods such as increasing the amount of modification and lowering the degree of saponification have been tried, but in such a case, the Young's modulus of the film decreases and the form stability becomes low. Since it has the problem of becoming low, it was not satisfactory as a film used for packaging applications.
[0009]
[Problems to be solved by the invention]
The object of the present invention is to eliminate the above-mentioned drawbacks, to have good cold water solubility and biodegradability, to be excellent in practical physical properties such as strength and waist, and to reduce various physical properties over time even when an acidic substance is packaged. An object of the present invention is to provide a water-soluble PVA-based film.
[0010]
[Means for Solving the Problems]
As a result of intensive studies in view of the present situation, the present inventors have found that N-vinylamide monomer units and modified PVA with a specified saponification degree are extremely useful as a raw material for producing a target water-soluble film. The present invention has been completed.
[0011]
  That is, the present invention providesspecificThe pH when it is made into a 1% by weight aqueous solution or aqueous dispersion composed of a modified polyvinyl alcohol containing 1 to 10 mol% of N-vinylamide monomer units and a saponification degree of 82 to 99.5 mol% is 6 The following water-soluble film for packaging acidic substances.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  The present invention is described in detail below.
  It is essential that the modified PVA used in the present invention has an N-vinylamide monomer unit.hereN-vinylamide single monomerBody is belowMonomer represented by the formula (I)OrN-vinyl-2-caprolactamInThe
[0013]
[Chemical 2]

[0014]
(Wherein R ¹ Represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ² Represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms)
[0015]
  In the above formula (I), R ¹ Examples of the alkyl group having 1 to 3 carbon atoms represented by the formula include a methyl group, an ethyl group, a propyl group, and an isopropyl group. ² Examples of the alkyl group having 1 to 5 carbon atoms represented by the formula include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, and isopentyl group.
[0016]
Specific examples of the monomer represented by the above formula (I) include N-vinylformamide, N-methyl-N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylacetamide and the like. Can do.
[0018]
  Among the N-vinylamide monomers, from the viewpoint of acid resistance, the monomer represented by the above formula (I)OrN-vinyl-2-caprolactamUsedIs it easy to obtain?GoodPreferred are N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylacetamide and N-vinyl-2-caprolactam, with N-vinyl-2-caprolactam being particularly preferred from the viewpoint of form stability. .
[0019]
In the water-soluble film of the present invention, the content (modified amount) of the N-vinylamide monomer unit contained in the modified PVA is essential to be 1 to 10 mol%, and is 2 to 8 mol%. It is preferable. If the content of the N-vinylamide monomer unit is less than 1 mol%, the resulting film cannot be said to have sufficient cold water solubility. On the other hand, when the content exceeds 10 mol%, not only the biodegradability of the modified PVA is lowered, but also the hygroscopicity is increased, so that the obtained film loses its elasticity and is practically used as a water-soluble film. May cause problems. In the present invention, cold water means water at 0 ° C. to 40 ° C.
[0020]
Even if the water-soluble film is as thin as 10 to 200 μm, high strength and flexibility may be required. Therefore, from the viewpoint of film strength and toughness, the degree of polymerization of the modified PVA used in the present invention (viscosity average polymerization) The degree) is preferably 300 to 3000, more preferably 400 to 2500, and particularly preferably 500 to 2000 from the viewpoint of water solubility. When the viscosity average polymerization degree of the modified PVA is less than 300, the strength of the film tends to be weak, and when it is more than 3000, the solution viscosity of the film forming raw material used when forming the film or In some cases, the melt viscosity becomes high and the workability is lowered, or the solubility of the obtained film is lowered. The viscosity average degree of polymerization is measured by the method described in JIS.
[0021]
In the present invention, the degree of saponification of the modified PVA is essential to be 82 to 99.5 mol% from the viewpoint of the strength, waist and bag-making property of the obtained film, and from 86 to 99. It is preferably 4 mol%, more preferably 90 to 99.2 mol%, and particularly preferably 92 to 99.0 mol%. The degree of saponification is measured by the method described in JIS.
If the degree of saponification of the modified PVA is less than 82 mol%, the film absorbs moisture under high humidity and loses its elasticity, and the stability of the shape is reduced. May decrease. On the other hand, modified PVA having a saponification degree larger than 99.5 mol% cannot be produced industrially stably, and film formation cannot be performed stably from such modified PVA.
[0022]
As a method for producing a modified PVA containing an N-vinylamide monomer unit, a vinyl ester polymer obtained by copolymerizing a vinyl ester monomer and an N-vinylamide monomer is used as an alcohol or dimethyl ester. Examples thereof include a method of saponification in a solution of sulfoxide or the like.
[0023]
Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate. Among these, vinyl acetate is preferable from the viewpoint of industrially obtaining modified PVA.
[0024]
In the present invention, as long as the modified PVA is within the range not impairing the effects of the present invention, other than the monomer unit having a vinyl alcohol unit, a vinyl ester monomer unit and an N-vinylamide monomer unit, It may contain monomer units. Examples of such monomer units include α-olefins such as ethylene, propylene, and 1-hexene; acrylamide derivatives such as acrylamide and N-methylacrylamide; methacrylamide derivatives such as methacrylamide and N-methylmethacrylamide; Vinyl ethers such as vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether and n-butyl vinyl ether; containing hydroxy groups such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether and 1,4-butanediol vinyl ether Vinyl ethers; allyl acetates; allyl ethers such as propyl allyl ether; monomers having an oxyalkylene group; vinyl trimethoxysilane and other vinyl Silanes; isopropenyl acetate; 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 3-methyl-3-buten-1-ol Α-olefins containing a hydroxy group such as: monomers having a sulfonic acid group derived from ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc .; vinyloxy Ethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamide dimethyl Amines, allyl trimethyl ammonium chloride, methallyl trimethylammonium chloride, dimethyl allyl amine, include monomeric units obtained by copolymerization of such a monomer having a cationic group such as from allyl ethylamine. The content of these monomer units is usually 5 mol% or less, preferably 2 mol% or less, although it varies depending on the purpose and application used.
[0025]
As a method for copolymerization of the above-mentioned monomer having a vinyl ester monomer and an N-vinylamide monomer, known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method are used. Is mentioned. Among them, a bulk polymerization method that polymerizes without solvent or a solution polymerization method that polymerizes in a solvent such as alcohol is usually employed. Examples of the alcohol used as a solvent during solution polymerization include lower alcohols such as methanol, ethanol, and propanol. Examples of the initiator used for copolymerization include azo initiators such as 2,2′-azobis (isobutyronitrile) and 2,2′-azobis (2,4-dimethylvaleronitrile), or benzoyl peroxide. And known initiators such as peroxide initiators such as n-propyl peroxycarbonate. Although there is no restriction | limiting in particular about superposition | polymerization temperature, The range of 0 to 150 degreeC is suitable.
[0026]
In the present invention, the modified PVA is a vinyl ester polymer obtained by copolymerizing the above vinyl ester monomer and N-vinyl amide monomer, usually with alcohols such as methanol, methyl acetate or the like. Alkali catalysts such as potassium hydroxide and sodium hydroxide, sulfuric acid, hydrochloric acid, p-toluenesulfone in one or more solvents selected from esters, dimethyl sulfoxide, etc., preferably in a lower alcohol solvent such as methanol. It can be obtained by saponification using an acid catalyst such as an acid. The conditions for the saponification reaction are appropriately adjusted depending on the structure of the vinyl ester polymer and the saponification degree of the target vinyl alcohol polymer, but the molar ratio of the catalyst / vinyl ester monomer unit is usually 0.001. To 5.0, the reaction temperature is 20 to 180 ° C., and the reaction time is 0.1 to 20 hours. As the saponification method, a known method such as a batch method or a continuous method can be applied.
[0027]
In the water-soluble film of the present invention, saccharides can be blended as necessary. Examples of the saccharide include monosaccharides such as glucose, chain sugar alcohols such as oligosaccharides, polysaccharides, and mannitol. Examples of the polysaccharide include starch, cellulose, chitin, chitosan, hemicellulose, pectin, pullulan, agar, alginic acid, carrageenan, dextrin, and trehalose, and one or more of these can be used. Examples of the chain sugar alcohol include tetrites having 4 carbon atoms such as trait and erythrite, pentites having 5 carbon atoms such as arabit and xylit, and hexits having 6 carbon atoms such as glycit, mannitol and sorbit. By adding saccharides, the water solubility, biodegradability, and form stability of the film can be further enhanced. From the viewpoint of good cold water solubility of the film when saccharides are added, starch is particularly preferred among saccharides. As the starch, for example, raw starch such as corn and potato, and processed starch obtained by subjecting these to physical or chemical treatment (dextrin, oxidized starch, etherified starch, cationized starch, etc.) can be used.
[0028]
The blending amount of the saccharide is preferably 1 to 100 parts by weight, more preferably 2 to 90 parts by weight with respect to 100 parts by weight of the modified PVA, from the viewpoint of water solubility, biodegradability, and form stability of the film. 3 to 80 parts by weight is particularly preferable. In general, PVA and saccharides have poor compatibility. Therefore, when a large amount of saccharide is blended with PVA, mechanical properties such as strength of the blended film are greatly reduced, but the modification used in the water-soluble film of the present invention. Since PVA has the characteristic that it is excellent in compatibility with saccharides, especially starch, a large amount of saccharides can be added to the water-soluble film of the present invention. If the amount of the saccharide is less than 1 part by weight, the effect of improving the water solubility and biodegradability of the film may not be exhibited. On the other hand, when the compounding amount of the saccharide is more than 100 parts by weight, the impact resistance of the film at a low temperature is lowered and the bag is easily broken.
[0029]
In general, a water-soluble film is required to have strength and toughness that can withstand use in a hot and humid region or a cold region, and particularly needs impact resistance at a low temperature. In the water-soluble film of the present invention, various plasticizers can be added to the water-soluble film of the present invention in order to lower the glass transition point of the film for the purpose of improving impact resistance at low temperatures. Furthermore, in addition to the above purpose, the water-soluble film of the present invention can be blended with a plasticizer for the purpose of improving the solubility in water.
[0030]
The plasticizer blended in the water-soluble film of the present invention is not particularly limited as long as it is generally used as a plasticizer for PVA. For example, glycerin, diglycerin, diethylene glycol, triethylene glycol, propylene glycol, dipropylene Polyhydric alcohols such as glycol, trimethylolpropane, pentaerythritol, and 1,3-butanediol; Polyethers such as polyethylene glycol and polypropylene glycol; Polyvinylamides such as polyvinylpyrrolidone; Phenol derivatives such as bisphenol A and bisphenol S An amide compound such as N-methylpyrrolidone or dimethylacetamide; a compound obtained by adding ethylene oxide to a polyhydric alcohol such as glycerin, pentaerythritol or sorbitol Such goods and water and the like, which can be used either alone or in combination. Among these plasticizers, for the purpose of improving water solubility, it is preferable to use glycerin, diglycerin, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, polyethylene glycol, and polyvinyl pyrrolidone. From the viewpoint of the effect of suppressing the decrease in water solubility of the film due to plasticizer bleed-out, it is particularly preferable to use glycerin, diglycerin, trimethylolpropane, polyethylene glycol, or polyvinylpyrrolidone.
[0031]
There is no particular restriction on the molecular weight of polyethylene glycol when polyethylene glycol is used as a plasticizer, but the number average molecular weight should be 100 to 1000 in terms of compatibility with modified PVA and the effect of suppressing water-soluble deterioration due to bleed-out. Is preferred. Although there is no restriction | limiting in particular also about the molecular weight of polyvinylpyrrolidone, It is preferable that it is 1000-20000 in a weight average molecular weight from a compatible point with PVA.
[0032]
The compounding amount of the plasticizer is preferably 1 to 50 parts by weight with respect to 100 parts by weight of the modified PVA. When the blending amount of the plasticizer is less than 1 part by weight, the effect of blending the plasticizer may not be manifested. On the other hand, when the compounding amount of the plasticizer exceeds 50 parts by weight, the bleed-out of the plasticizer increases, and the blocking resistance of the resulting film may be lowered. From the viewpoint of the dissolution rate of the resulting film in water, it is preferable to blend the plasticizer at a ratio of 20 parts by weight or more with respect to 100 parts by weight of the modified PVA. On the other hand, it is preferable to blend the plasticizer in a proportion of 40 parts by weight or less with respect to 100 parts by weight of the modified PVA from the viewpoint of the waist of the film obtained (process passability such as a bag making machine). From the viewpoint of improving the water solubility of the obtained film, the larger the amount of the plasticizer, the better. Further, the larger the amount of the plasticizer, the lower the heat seal temperature and the productivity at the time of making the film is improved. Tend. In particular, the plasticizer is preferably blended at a rate such that the heat seal temperature of the resulting film is 170 ° C. or lower, and more preferably blended at a rate such that the heat seal temperature is 160 ° C. or lower. Further, the compounding amount of the plasticizer tends to affect the strength of the resulting film and the Young's modulus, but from the practical point of the obtained film, the strength of the film is 1.0 kg / cm.²Or more, preferably 1.5 kg / cm²The above is more preferable. The Young's modulus of the film is 1.5 kg / mm from the viewpoint of the form stability of the resulting film and the processability of the bag making machine.²Preferably, it is 2.0 kg / mm²The above is more preferable, and it is preferable to add a plasticizer so that a film having a Young's modulus in such a range can be obtained.
[0033]
If necessary, the water-soluble film of the present invention can further contain an inorganic filler. Examples of the inorganic filler used in the water-soluble film of the present invention include silica, heavy, light or surface-treated calcium carbonate, aluminum hydroxide, aluminum oxide, titanium oxide, diatomaceous earth, barium sulfate, calcium sulfate, zeolite, Examples include zinc oxide, silicic acid, silicate, mica, magnesium carbonate, kaolin, halosite, pyroferrite, sericite and other clays, talc, and the like, and one or more of these can be used. Among these, silica and talc are preferably used from the viewpoint of dispersibility in modified PVA. The average particle diameter of the inorganic filler is preferably 1 μm or more from the viewpoint of the anti-blocking property of the film, and is preferably 10 μm or less from the viewpoint of dispersibility in the modified PVA. An inorganic filler having an average particle size of about 1 to 7 μm in order to satisfy the required performance of both the anti-blocking property of the film expressed by blending the inorganic filler and the dispersibility of the inorganic filler in the modified PVA. Is more preferable.
[0034]
The blending amount of the inorganic filler is preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the modified PVA, from the viewpoint of blocking prevention of the film and dispersibility of the inorganic filler in the modified PVA. The amount is more preferably 15 parts by weight, and particularly preferably 1 to 10 parts by weight. If the inorganic filler is added in an amount exceeding 20 parts by weight, the dispersibility in the modified PVA is lowered and the inorganic filler is aggregated, so that the water solubility of the resulting film tends to be lowered.
[0035]
In the water-soluble film of the present invention, additives such as a colorant, a fragrance, an extender, an antifoaming agent, a release agent, an ultraviolet absorber, and a surfactant may be appropriately blended as necessary. In particular, in order to improve the releasability between the metal surface such as the die or drum of the film forming apparatus and the formed film or film stock solution, 0.01 to 5 parts by weight of the surfactant is added to 100 parts by weight of the modified PVA. It is preferable to mix | blend in a ratio. In addition, the water-soluble film of the present invention, if necessary, is a different type of PVA, carboxymethylcellulose, polyacrylamide, polyacrylic acid from the modified PVA used in the present invention, as long as the effects of the present invention are not impaired. Alternatively, a water-soluble polymer such as a salt thereof, methylcellulose, or hydroxymethylcellulose may be blended. In particular, from the viewpoint of improving the water solubility of the film, it is preferable to add a low viscosity type carboxymethylcellulose.
[0036]
In the production of the water-soluble film of the present invention, the production raw material is blended with the modified PVA, if necessary, with a plasticizer, saccharide, inorganic filler and other components, and dissolved in a solvent in a stirring tank. Or it can prepare by mixing by well-known methods, such as the method of disperse | distributing and the method of melt-kneading in an extruder.
[0037]
The water-soluble film of the present invention is a film-forming method generally used when forming a film, for example, a casting film-forming method, a wet film-forming method, a dry film-forming method, an extrusion film-forming method, a melt film-forming method. It can be manufactured by a film forming method such as a method, a coating method or an inflation film forming method. For example, the components necessary for the production of the water-soluble film of the present invention are one or two of the solvents exemplified by water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, methanol, n-propanol, i-propanol, phenol and the like. After being dissolved in a mixed solution of at least seeds to prepare a uniform film-forming stock solution, it can be produced by a film-forming method such as a casting film-forming method. The concentration of the film forming stock solution is preferably 50% by weight or less (the solvent content is 50% by weight or more) from the viewpoint of viscosity, and from the viewpoint of easy formation of a matte state on the surface of the film formed. More preferably, it is 30% by weight or less (the solvent content is 70% by weight or more).
[0038]
The thickness of the water-soluble film of the present invention is preferably 10 to 200 μm, more preferably 20 to 150 μm, and particularly preferably 30 to 120 μm from the viewpoint of the balance between the strength of the film and the water solubility.
[0039]
In order to improve the anti-blocking property of the water-soluble film of the present invention, the surface of the water-soluble film is roll-mated as necessary, or a powder for preventing blocking such as silica or starch is applied to the water-soluble film. Or embossing. Roll matting of the film surface can be performed by forming fine irregularities on the roll that comes into contact with the film before drying during film formation. The embossing treatment can be generally performed by nipping between an embossing roll and a rubber roll while applying heat and pressure after the film is formed. Application of powder has a large anti-blocking effect, but it may not be used depending on the application, so it is preferable to prevent blocking by applying roll matting or embossing to prevent blocking. From the viewpoint of the size, roll matting is particularly preferable.
[0040]
The water-soluble film of the present invention has an excellent dissolution rate in cold water, and the complete dissolution time in 10 ° C. water (film thickness 50 μm) is preferably 200 seconds or less, more preferably 150 seconds or less. Especially preferably, it is 100 seconds or less. In this specification, the complete dissolution time in 10 ° C. water means that a film having a thickness of 50 μm is cut into a 40 × 40 mm square, which is sandwiched between slide mounts and immersed in 10 ° C. stirring water. Is a value obtained by measuring the time until the film completely dissolves, and when using a film having a thickness different from 50 μm, a value converted into a film thickness of 50 μm by the following formula (1) It is.
Dissolution time (seconds) = (50 / film thickness (μm))²× Dissolution time (seconds) (1)
[0041]
The biodegradability of the water-soluble film of the present invention is preferably 60% or more, more preferably 65% or more, still more preferably 70% or more, and particularly preferably 75% or more. The biodegradability of PVA is measured using activated sludge according to a method according to ISO148851. The water-soluble film of the present invention is superior in biodegradability compared to conventional water-soluble films using unmodified partially saponified PVA or ion-modified PVA.
[0042]
The water-soluble film of the present invention not only has excellent solubility in cold water, but also has excellent biodegradability, chemical resistance, and practical physical properties such as strength and waist. It is extremely useful as a packaging material for substances that are used by dissolving in water. The packaging bag manufactured from the water-soluble film of the present invention dissolves quickly just by being put into water as it is, and its contents are quickly released into water.
[0043]
The water-soluble film of the present invention can be used for packaging acidic substances such as liquids, solids, powders, and granules, and there are no particular restrictions on the form of the acidic substance to be packaged. It is particularly preferably used for packaging of a liquid acidic substance that has been difficult to be packaged. When the acidic substance is in a liquid form, high form stability is required when packaged with a film, and when a solid acidic substance is packaged, the physical properties of the film surface in contact with the acidic substance are reduced. Although only a problem, in the case of a liquid, there is a problem that an acidic substance permeates the entire inside of the film, so that the physical properties are significantly deteriorated. Since the water-soluble film of the present invention has excellent shape stability and acid resistance, it can be packaged even with a liquid acidic substance.
The acidic substance to which the water-soluble film of the present invention is applied only needs to have a pH of 6 or less when made into a 1% by weight aqueous solution or aqueous dispersion, and includes various substances such as agricultural chemicals, deodorants and detergents. It is.
[0044]
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the examples, “parts” and “%” mean “parts by weight” and “% by weight” unless otherwise specified. In the examples, various properties of the film were measured and evaluated by the following methods.
[0045]
[Method of measuring water solubility of film]
Install a magnetic stirrer in a constant temperature bath at 10 ° C. A 1 liter glass beaker containing 1 liter of distilled water is placed in the above-mentioned constant temperature bath and agitated at 250 rpm using a 5 cm rotor. After the distilled water in the beaker reaches 10 ° C., the water solubility measurement is started.
Cut the film into 40 x 40 mm squares, put them in a slide mount, immerse them in 10 ° C agitated water, observe the dissolution state of the film, and time (seconds) until the film is completely dissolved Was measured. When a film having a film thickness different from 50 μm is used, the film thickness is converted to a value of 50 μm according to the following formula (1).
[0046]
Dissolution time (seconds) = (50 / film thickness (μm))²× Dissolution time (seconds) (1)
[0047]
[Measurement method of Young's modulus and strength]
A film with a width of 10 mm was conditioned for 1 week under an atmosphere of 20 ° C. and 65% RH, and then a tensile test was performed with an autograph. The chuck interval was 50 mm and the pulling speed was 500 mm / min.
[0048]
[Chemical resistance evaluation method]
A 10 cm × 15 cm bag was made from the film, and 35 g of a fine powder of succinic acid (pH of 1 wt% aqueous solution of 2.4) was placed inside as a medicine, which was then heat-sealed and sealed. This packaging bag was further wrapped in a film of aluminum laminated with polyethylene and heat sealed, and double sealed and sealed, so that water and plasticizer were not scattered from the packaging bag sealed with chemicals. As an accelerated test for long-term storage, this bag is left in a thermostat at 40 ° C., taken out after 4 weeks, and the water solubility of the packaged film is measured by the above-described measurement method. The change with time was examined.
[0049]
Synthesis example 1 (Synthesis example of modified PVA)
A 5 L reactor equipped with a stirrer, reflux condenser, nitrogen inlet tube and thermometer was charged with 2340 g of vinyl acetate monomer, 569.4 g of methanol, and 181.1 g of a 50% methanol solution of N-vinyl-2-caprolactam. Charged and degassed by bubbling nitrogen gas for 30 minutes. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 1.5 g of 2,2′-azobis (isobutyronitrile) was added to initiate polymerization. Polymerization was carried out while sequentially adding a 50% methanol solution of N-vinyl-2-caprolactam so that the molar ratio with the vinyl acetate monomer was constant, and the polymerization was stopped after 4 hours by cooling. The solid concentration at this time was 39%. Subsequently, unreacted vinyl acetate monomer was removed while sometimes adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution (concentration 33%) of a polyvinyl acetate copolymer. Next, a methanol solution of a polyvinyl acetate copolymer adjusted to a concentration of 25% by adding methanol to a methanol solution with an alkali molar ratio (number of moles of NaOH / number of moles of vinyl acetate monomer units) of 0.03 (10% concentration) was added to saponify. The degree of saponification of the obtained modified PVA (PVA-1) was 98.4 mol%.
[0050]
10 g of methanol was added to 1 g of the obtained modified PVA, heated to 60 ° C. to swell the modified PVA, 5 g of NaOH methanol solution (10% concentration) was added, and the mixture was stirred at 60 ° C. for 3 hours. Soxhlet extraction was carried out for 3 days, followed by drying to obtain a purified modified PVA. The amount of modification of the N-vinyl-2-caprolactam monomer unit determined from proton NMR measurement of the modified PVA product was 6.0 mol%. The average degree of polymerization of the PVA was 1500 when measured according to JIS K6726 of a conventional method.
[0051]
  N-vinylamidesystemModified PVA (PVA-2 to 7 and PVA10, PVA-1 and PVA10) in the same manner as PVA-1, except that the polymerization conditions were changed so that the type and modification amount of the monomer, the degree of polymerization, and the degree of saponification were as shown in Table 1 below. 11) was synthesized. The synthesized results are shown in Table 1 below.
[0052]
Synthesis example 2 (PVA synthesis example)
  A 5 L reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet tube and a thermometer was charged with 2100 g of vinyl acetate monomer and 900 g of methanol, and degassed by bubbling nitrogen gas for 30 minutes. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.4 g of 2,2′-azobis (isobutyronitrile) was added to initiate polymerization. After 5 hours, the polymerization was stopped by cooling. The solid concentration at this time was 27%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration 33%). Next, polyvinyl acetate adjusted to a concentration of 25% by adding methanol.LeThe methanol solution was saponified by adding an NaOH methanol solution (10% concentration) having an alkali molar ratio (number of moles of NaOH / number of moles of vinyl acetate monomer unit) of 0.025. ObtainedPThe degree of saponification of VA (PVA-8) was 98.5 mol%.
[0053]
  ObtainedPAdd 10g of methanol to 1g of VA and warm to 60 ° C.PAfter swelling VA, 5 g of NaOH methanol solution (10% concentration) was added and stirred at 60 ° C. for 3 hours. Then, methanol Soxhlet extraction was performed for 3 days, followed by drying to obtain a purified product of PVA. . When the average degree of polymerization of the PVA was measured according to JIS K6726 of a conventional method, it was 1500.
  PVA-9 was synthesized by the same method as PVA-8 except that the saponification conditions were changed so that the saponification degree was as shown in Table 1 below. The synthesized results are shown in Table 1 below.
[0054]
Example 1
To 100 parts by weight of the modified PVA (PVA-1) shown in Table 1, 15 parts by weight of glycerin, 20 parts by weight of etherified starch, 5 parts by weight of talc, and water as a plasticizer are added to form a uniform 5% aqueous solution ( (Water content 95%) was prepared, cast on a polyester film, dried at room temperature, and then peeled off from the polyester film to obtain a film having a thickness of 50 μm. The obtained film was heat-treated at 100 ° C. for 10 minutes. When the water solubility of this film was measured, the complete dissolution time in water at 10 ° C. was 67 seconds. In addition, the Young's modulus was measured by adjusting the humidity to 20 ° C. and 65% RH as an index of handleability such as process passability typified by the waist of the film, and 2.9 kg / mm.²The strength is 2.4kg / cm²Met. Moreover, when biodegradability was evaluated by a method according to ISO 14851, the biodegradation rate was 80%.
Subsequently, when the chemical resistance was evaluated, the complete time of the film after chemical packaging in 10 ° C. water was 69 seconds, and no decrease in water solubility was observed.
[0055]
Example 26 and Comparative Example 1
  A film was prepared in the same manner as in Example 1 except that the contents of the modified PVA and the types and blending amounts of the plasticizer, saccharide and inorganic filler were changed as shown in Table 1 and Table 2 below. went. The evaluation results are shown in Table 3 below.
[0056]
Example7
  A film was produced in the same manner as in Example 1 except that a chemical resistance was evaluated using a mixture of glycerin and lactic acid (pH 4 of a 1 wt% aqueous solution) as a chemical, and various evaluations were performed. The evaluation results are shown in Table 3 below.
[0057]
Comparative example2,4and5
  A film was produced in the same manner as in Example 1 except that the content of PVA was changed as shown in Table 1 below, and various evaluations were performed. The evaluation results are shown in Table 3 below. A film made of unmodified PVA having a saponification degree of 98.5 mol% is poor in water solubility (Comparative Example).2). Biodegradability is poor when the amount of modification of the N-vinylamide group of the modified PVA is large (Comparative Example)4). When the saponification degree is as low as 80 mol%, not only the Young's modulus of the film is low, but also the water solubility after chemical packaging is lowered and the chemical resistance is poor (Comparative Example).5).
[0058]
  Comparative example3
  The film was changed in the same manner as in Example 1 except that the content of PVA was changed as shown in Table 1 below, and the chemical resistance was evaluated using a mixture of glycerin and lactic acid (pH 4 of 1% by weight aqueous solution) as a chemical. Were manufactured and evaluated in various ways. The evaluation results are shown in Table 3 below. A film made of unmodified PVA having a saponification degree of 88.0 mol% has poor water resistance after chemical packaging and poor chemical resistance (Comparative Example).3).
[0059]
[Table 1]

[0060]
[Table 2]

[0061]
[Table 3]

[0062]
【The invention's effect】
The water-soluble film of the present invention not only has excellent solubility in cold water, but also does not decrease water solubility even after packaging with an acidic substance, and simultaneously has biodegradability and practical physical properties such as strength and waist. It is excellent and is particularly preferably used for packaging applications such as agricultural chemicals and detergents.

Claims (5)

When a 1% by weight aqueous solution or aqueous dispersion comprising a modified polyvinyl alcohol containing 1 to 10 mol% of N-vinyl- 2-caprolactam units in the molecule and having a saponification degree of 82 to 99.5 mol% A water-soluble film for packaging acidic substances having a pH of 6 or less . 1% by weight aqueous solution or water dispersion comprising a modified polyvinyl alcohol containing 1 to 10 mol% of a monomer unit represented by the following formula (I) in the molecule and having a saponification degree of 82 to 99.5 mol% A water-soluble film for packaging acidic substances having a pH of 6 or less when made into a liquid .

(Wherein R ¹ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ² represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms) The water-soluble film for acidic substance packaging according to claim 1 or 2 , further comprising 1 to 100 parts by weight of a saccharide based on 100 parts by weight of the modified polyvinyl alcohol. Modified polyvinyl against alcohol 100 parts by weight, more acidic substance packaging water-soluble film according to any one of claims 1 to 3 in which the inorganic filler by blending 0.5 to 20 parts by weight. A package comprising an acidic substance having a pH of 6 or less when packaged with a 1% by weight aqueous solution or aqueous dispersion, using the water-soluble film for packaging acidic substances according to any one of claims 1 to 4.