JP3590498B2 - Saponified ethylene-vinyl ester copolymer composition and co-extruded multilayer molded article using the same - Google Patents
Saponified ethylene-vinyl ester copolymer composition and co-extruded multilayer molded article using the same Download PDFInfo
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- JP3590498B2 JP3590498B2 JP03494297A JP3494297A JP3590498B2 JP 3590498 B2 JP3590498 B2 JP 3590498B2 JP 03494297 A JP03494297 A JP 03494297A JP 3494297 A JP3494297 A JP 3494297A JP 3590498 B2 JP3590498 B2 JP 3590498B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、着色が少なく、かつ溶融成形時のブツの発生が少ない、しかも接着性に優れたエチレン−ビニルエステル共重合体ケン化物組成物およびそれを用いた共押出多層成形体に関する。
【０００２】
【従来の技術】
エチレン−ビニルエステル共重合体ケン化物は酸素遮蔽性、耐油性、非帯電性、機械強度等に優れた有用な高分子材料であり、フィルム、シート、容器など各種包装材料などとして広く用いられる。エチレン−ビニルエステル共重合体ケン化物を各種包装材として用いた場合、使用目的に対する性能はもとより、外観上のわずかな着色やフィッシュアイ、ブツ、肌荒れおよび透明性が問題視される。
【０００３】
しかしエチレン−ビニルエステル共重合体ケン化物は、溶融成形を行うに際し、着色やブツの発生といった問題を発生しやすいという問題を有している。そこで従来、その着色やブツの発生を抑制する方法として以下のような様々な手法が提案されている。
【０００４】
例えば、エチレン−ビニルエステル共重合体ケン化物に酢酸、リン酸等の酸および／またはそれらの塩を添加する方法については、特開昭４８−２５０４８、特開昭５１−２６９９３、特開昭５１−２８８９１、特開昭５１−４９２９４、特開昭５１−９１９８８、特開昭５２−９５４、特開昭５２−９５５、特開昭５２−９５６、特開昭５６−２００４４、特開昭５６−４１２０４、特開昭６１−９５０５３、特開昭６１−９５０５４、特開昭６２−１４３９５４等、多数出願されている。すなわち、着色やブツの発生の少ないエチレン−ビニルエステル共重合体ケン化物は、エチレン−ビニルエステル共重合体に苛性アルカリを加えてケン化し、水で洗浄後、酢酸、リン酸などの酸および／またはそれらの塩を添加し、さらに乾燥することにより得られる、とされている。
【０００５】
【発明が解決しようとする課題】
上記のごとく、エチレン−ビニルエステル共重合体ケン化物における着色やブツの発生などの問題に対してはさまざまな対策がとられている。しかし、エチレン−ビニルエステル共重合体ケン化物に酢酸、リン酸等の酸および／またはそれらの塩を添加する方法については、ケン化後の中和、洗浄が充分でなかったり、酢酸、リン酸等の酸および／またはそれらの塩の添加量が適当でないと、着色やブツの発生が増加しやすくなる。この欠点を改良するために、ケン化後の充分な洗浄や、酢酸、リン酸等の酸および／またはそれらの塩の添加量の最適化が行われているが、それでもなお、満足しえるレベルには到達していないのが現状である。
【０００６】
また、エチレン−ビニルエステル共重合体ケン化物と他の樹脂との接着性を良好にする手段として、エチレン−ビニルエステル共重合体ケン化物中にアルカリ金属塩を添加する方法があり、特に溶融状態で他の樹脂と接着させる共押出成形品の接着性の改善に有効である。しかしながら、エチレン−ビニルエステル共重合体ケン化物にアルカリ金属塩を添加した場合には、添加しない場合に比べてさらに着色しやすくブツが発生しやすくなるという問題を有している。
本発明の目的は、着色が少なく、成形時にブツの発生が少ない、しかも接着性に優れたエチレン−ビニルエステル共重合体ケン化物組成物およびそれを用いた共押出多層成形体を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的は、（１）ヒドロキシカルボン酸および／またはその塩をヒドロキシカルボン酸換算で１００〜５０００ｐｐｍ、（２）アルカリ金属塩を金属換算で５０〜５００ｐｐｍ、（３）アルカリ土類金属塩を金属換算で２０〜２００ｐｐｍ含むことを特徴とするエチレン−ビニルエステル共重合体ケン化物組成物を提供することによって達成される。さらに、（４）リン酸のアルカリまたはアルカリ土類金属塩をリン酸換算で５０〜５００ｐｐｍ含有すること、あるいは（５）ホウ素化合物をホウ素換算で２０〜２０００ｐｐｍ含有することでより効果的に達成される。また、かかる樹脂からなる層を少なくとも１層含む共押出多層成形体を提供することによっても効果的に達成される。
【０００８】
【発明の実施の形態】
本発明でいうヒドロキシカルボン酸とは、分子内に水酸基を有するカルボン酸のことをいう。分子中の水酸基、カルボキシル基の数は特に限定されるものではないが、カルボキシル基の数は１個であることが、ゲル化を防止する観点から好ましい。ヒドロキシカルボン酸の例としては、乳酸、グリコール酸などがあげられる。
【０００９】
分子内に水酸基を有しないモノカルボン酸のうちアルキル鎖の短いものとしては、酢酸、プロピオン酸等があげられる。これらのものは水溶性を有しているので水溶液としてエチレン−ビニルエステル共重合体ケン化物に添加する上で扱いやすいが、沸点が低いために乾燥工程でほとんど揮散し、着色、ゲル化防止の効果が小さい。一方、アルキル鎖の長いモノカルボン酸としては、ステアリン酸等があげられるが、これらのものは沸点は高いものの水溶性に乏しく扱いにくい。また、アジピン酸のようなジカルボン酸は、沸点が高く水溶性も良好であるものの、ゲル化しやすく、溶融不良となりやすい。これに対して、ヒドロキシカルボン酸を用いた場合には、乾燥工程で揮散しにくく品質変動を防止し、水溶性も良好で、効果的に着色、ゲル化を防止することができる。
【００１０】
本発明のエチレン−ビニルエステル共重合体ケン化物組成物中のヒドロキシカルボン酸および／またはその塩の含有量はヒドロキシカルボン酸換算で１００〜５０００ｐｐｍであり、好適範囲は５００〜３０００ｐｐｍである。１００ｐｐｍ未満の場合には着色が著しい。また５０００ｐｐｍを超える場合にはゲル化が激しく、溶融不良となる。ここでヒドロキシカルボン酸換算とは、ヒドロキシカルボン酸塩については等モル数のヒドロキシカルボン酸の重量として計算し、塩を形成していないヒドロキシカルボン酸の重量に加えたものをいう。なお、ヒドロキシカルボン酸の塩は特に限定されるものではなく、アルカリ金属塩、アルカリ土類金属塩、アンモニウム塩などがあげられる。
【００１１】
本発明のエチレン−ビニルエステル共重合体ケン化物組成物中のアルカリ金属塩の含量は、金属換算で５０〜５００ｐｐｍであり、好ましくは５０〜４００ｐｐｍである。５０ｐｐｍ未満の場合には他樹脂との接着性に劣り、特に共押出成形の際の層間接着性に問題を有する。また、５００ｐｐｍを超える場合には着色が著しい。アルカリ金属塩は特に限定されるものではないが、ナトリウム塩、カリウム塩等があげられる。またアルカリ金属塩のアニオン種も特に限定されるものではないが、ヒドロキシカルボン酸、酢酸等の各種カルボン酸アニオンやリン酸アニオン等があげられる。
【００１２】
また、本発明のエチレン−ビニルエステル共重合体ケン化物組成物中のアルカリ土類金属塩の含量は、金属換算で２０〜２００ｐｐｍであり、好ましくは２０〜１００ｐｐｍである。かかる範囲にあることで、エチレン−ビニルエステル共重合体ケン化物組成物の経時的粘性のコントロールが可能である。２０ｐｐｍ未満の場合にはゲル化抑制の効果が小さく、２００ｐｐｍを超えると着色が激しい。アルカリ土類金属塩は特に限定されるものではないが、マグネシウム塩、カルシウム塩、バリウム塩、ベリリウム塩等があげられる。またアルカリ土類金属塩のアニオン種も特に限定されるものではないが、ヒドロキシカルボン酸、酢酸等の各種カルボン酸アニオンやリン酸アニオン等があげられる。
【００１３】
本発明のエチレン−ビニルエステル共重合体ケン化物組成物中のリン化合物は特に限定されない。リン酸、亜リン酸等の各種の酸やその塩等を用いることができる。リン酸塩としては第１リン酸塩、第２リン酸塩、第３リン酸塩のいずれの形で含まれていても良く、そのカチオン種も特に限定されるものではないが、上述のようなアルカリ金属塩、アルカリ土類金属塩であることが好ましい。リン化合物の含有量はリン換算で５０〜５００ｐｐｍが好ましく、５０〜２００ｐｐｍがより好ましい。かかる範囲のリン化合物を含有することで、より着色が少なく、ゲル化しにくいエチレン−ビニルエステル共重合体ケン化物組成物を得ることができる。５０ｐｐｍ未満ではそのような改善効果が小さく、５００ｐｐｍを超えるとゲル化しやすくなる。中でも、リン酸２水素ナトリウム、リン酸２水素カリウム、リン酸水素２ナトリウム、リン酸水素２カリウムの形でリン化合物を添加することが好ましい。
【００１４】
本発明のエチレン−ビニルエステル共重合体ケン化物組成物中のホウ素化合物も特に限定されない。ホウ素化合物としては、ホウ酸類、ホウ酸エステル、ホウ酸塩、水素化ホウ素類等が挙げられる。具体的には、ホウ酸類としては、オルトホウ酸、メタホウ酸、四ホウ酸などが挙げられ、ホウ酸エステルとしてはホウ酸トリエチル、ホウ酸トリメチルなどが挙げられ、ホウ酸塩としては上記の各種ホウ酸類のアルカリ金属塩、アルカリ土類金属塩、ホウ砂などが挙げられる。これらの化合物うちでもオルトホウ酸（単にホウ酸と表示）、ＮａＢＨ４が好ましい。
ホウ素化合物の含有量はホウ素換算で２０〜２０００ｐｐｍ、望ましくは５０〜１０００ｐｐｍである。この範囲にあることで加熱溶融時のトルク変動が抑制されたエチレン−ビニルエステル共重合体ケン化物組成物を得ることができる。２０ｐｐｍ未満ではそのような効果が小さく、２０００ｐｐｍを超えるとゲル化しやすく、成形性不良となる場合がある。
【００１５】
本発明に用いるエチレン−ビニルエステル共重合体は、エチレンとビニルエステルを共重合して得られるが、ビニルエステルの種類は特に限定されるものではない。例えば、酢酸ビニル、プロピオン酸ビニル、バーサチック酸ビニル、ピバリン酸ビニルなどの脂肪族ビニルエステルがあげられ、芳香族カルボン酸のビニルエステルであっても構わない。これらのビニルエステルの中で、価格の面から酢酸ビニルが好ましい。
【００１６】
本発明のエチレン−ビニルエステル共重合体ケン化物は、エチレン含有量が１０〜６０モル％、好ましくは２０〜５５モル％、ビニルエステル成分のケン化度９０モル％以上、好ましくは９５モル％以上のものである。エチレン含量が２０モル％以下では高湿時の酸素遮断性が低下し、一方６０モル％以上では充分な酸素遮断性や印刷適性等の物性が低下する。また、ケン化度が９０モル％以下では、酸素遮断性や耐湿性が低下する。
【００１７】
以下に製造方法を具体的に説明する。エチレンとビニルエステルの重合は溶液重合に限るものではなく、連続式、回分式のいずれであってもよいが、例えば、回分式の溶液重合の場合の重合条件は次の通りである。
【００１８】
溶媒；アルコール類が好ましいが、その他エチレン、ビニルエステルおよびエチレン−ビニルエステル共重合体を溶解し得る有機溶剤（ジメチルスルホキシドなど）を用いることができる。アルコール類としてはメチルアルコール、エチルアルコール、プロピルアルコール、ｎ−ブチルアルコール、ｔ−ブチルアルコール等を用いることができ、特にメチルアルコールが好ましい。
触媒；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）、２，２’−アゾビス−（４−メチル−２，４−ジメチルバレロニトリル）、２，２’−アゾビス−（２−シクロプロピルプロピオニトリル）等のアゾニトリル系開始剤およびイソブチリルパーオキサイド、クミルパーオキシネオデカノエイト、ジイソプロピルパーオキシカーボネート、ジ−ｎ−プロピルパーオキシジカーボネート、ｔ−ブチルパーオキシネオデカノエイト、ラウロイルパーオキサイド、ベンゾイルパーオキサイド、ｔ−ブチルハイドロパーオキサイド等の有機過酸化物系開始剤等を用いることができる。
温度；２０〜９０℃、好ましくは４０℃〜７０℃。
時間；２〜１５時間、好ましくは３〜１１時間。
重合率；仕込みビニルエステルに対して１０〜９０％、好ましくは３０〜８０％。
重合後の溶液中の樹脂分；５〜８５％、好ましくは２０〜７０％。
共重合体中のエチレン含有率；２０〜６０モル％、好ましくは２５〜５５モル％。
【００１９】
なお、エチレンとビニルエステル以外にこれらと共重合し得る単量体、例えば、プロピレン、イソブチレン、α−オクテン、α−ドデセン等のα−オレフィン；アクリル酸、メタクリル酸、クロトン酸、マレイン酸、イタコン酸等の不飽和酸またはその無水物、塩、あるいはモノまたはジアルキルエステル等；アクリロニトリル、メタクリロニトリル等のニトリル類；アクリルアミド、メタクリルアミド等のアミド類；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等のオレフィンスルホン酸またはその塩；アルキルビニルエーテル類、ビニルケトン、Ｎ−ビニルピロリドン、塩化ビニル、塩化ビニリデン等を少量共存させることも可能である。
【００２０】
所定時間の重合後、所定の重合率に達した後、必要に応じて重合禁止剤を添加し、未反応のエチレンガスを蒸発除去した後、未反応ビニルエステルを追い出す。エチレンを蒸発除去したエチレン−ビニルエステル共重合体から未反応のビニルエステルを追い出す方法としては、例えば、ラシヒリングを充填した塔の上部から該共重合体溶液を一定速度で連続的に供給し、塔下部よりメタノール等の有機溶剤蒸気を吹き込み塔頂部よりメタノール等の有機溶剤と未反応ビニルエステルの混合蒸気を流出させ、塔底部より未反応ビニルエステルを除去した該共重合体溶液を取り出す方法などが採用される。
【００２１】
未反応ビニルエステルを除去した該共重合体溶液にアルカリ触媒を添加し、該共重合体中のビニルエステル成分をケン化する。ケン化方法は連続式、回分式いずれも可能である。アルカリ触媒としては水酸化ナトリウム、水酸化カリウム、アルカリ金属アルコラートなどが用いられる。例えば、回分式の場合のケン化条件は次の通りである。
該共重合体溶液濃度；１０〜５０％。
反応温度；３０〜６０℃。
触媒使用量；０．０２〜０．６当量（ビニルエステル成分当り）。
時間；１〜６時間。
ケン化反応後のケン化度は目的により異なるが通常ビニルエステル成分の９０％以上であり、好ましくは９５％以上である。ケン化度は条件によって任意に調整できる。
【００２２】
反応後のエチレン−ビニルエステル共重合体ケン化物はアルカリ触媒、副生塩類、その他不純物等を含有するため、これらを必要に応じて中和、洗浄することにより除去する。
【００２３】
得られたエチレン−ビニルエステル共重合体ケン化物にヒドロキシカルボン酸および／またはその塩、アルカリ金属塩、アルカリ土類金属塩、リン化合物、ホウ素化合物を含有させる方法は特に限定されない。例えば、上記化合物が溶解している溶液に該ケン化物を浸漬させる方法、該ケン化物を溶融させて上記化合物を混合する方法、該ケン化物を適当な溶媒に溶解させて上記化合物を混合させる方法等がある。
【００２４】
なかでも、本発明の効果をより顕著に発揮させるためには、エチレン−ビニルエステル共重合体ケン化物を上記化合物の溶液に浸漬させる方法が望ましい。この処理は、バッチ方式、連続方式のいずれによる操作でも実施可能である。また、その際該ケン化物の形状は、粉末、粒状、球状、円柱形チップ状等の任意の形状であってよい。
【００２５】
エチレン−ビニルエステル共重合体ケン化物をヒドロキシカルボン酸および／またはその塩、アルカリ金属塩、アルカリ土類金属塩、リン化合物、ホウ素化合物を含む溶液に浸漬する場合、上記溶液中のヒドロキシカルボン酸および／またはその塩、アルカリ金属塩、アルカリ土類金属塩、リン化合物、ホウ素化合物の濃度は、特に限定されるものではない。また溶液の溶媒は特に限定されないが、取扱い上の理由等から水溶液であることが好ましい。該ケン化物を浸漬する際の溶液の重量が、乾燥時の該ケン化物重量に対して３倍以上、好ましくは２０倍以上であることが望ましい。浸漬時間はエチレン−ビニルエステル共重合体ケン化物の形態によってその好適範囲は異なるが、１〜１０ｍｍ程度のチップの場合には１時間以上、好ましくは２時間以上が望ましい。
【００２６】
上記各種化合物の溶液への浸漬処理は、複数の溶液に分けて浸漬してもよく、一度に処理しても構わない。なかでも、ヒドロキシカルボン酸および／またはその塩、アルカリ金属塩、アルカリ土類金属塩（さらに必要に応じてリン酸塩、ホウ素化合物）の全てを含む溶液で処理することが、工程の簡素化の点から好ましい。上記のように溶液に浸漬して処理した場合、最後に乾燥し目的とするエチレン−ビニルエステル共重合体ケン化物組成物が得られる。
【００２７】
本発明で得られたエチレン−ビニルエステル共重合体ケン化物の好適なメルトインデックス（ＭＩ）（１９０℃、２１６０ｇ荷重下で測定；ただし、融点が１９０℃付近あるいは１９０℃を越えるものは２１６０ｇ荷重下、融点以上の複数の温度で測定し、片対数グラフで絶対温度の逆数を横軸、メルトインデックスを縦軸（対数）としてプロットし、１９０℃に外挿した値）は０．１〜２００ｇ／１０ｍｉｎ．、最適には０．２〜１００ｇ／１０ｍｉｎ．である。
【００２８】
得られたエチレン−ビニルエステル共重合体ケン化物組成物は溶融成形によりフィルム、シート、容器、パイプ、繊維等、各種の成形体に成形される。これらの成形物は再使用の目的で粉砕し再度成形することも可能である。また、フィルム、シート、繊維等を一軸または二軸延伸することも可能である。溶融成形法としては押出成形、インフレーション押出、ブロー成形、溶融紡糸、射出成形等が可能である。溶融温度は該共重合体の融点等により異なるが１５０〜２７０℃程度が好ましい。
【００２９】
なかでも、共押出多層成形を行うときには層間接着性が良好であり好ましい。共押出成形によって得られる形状は特に限定されず、シート、フィルム、パイプなどの形状が挙げられる。さらにこうして得られたシート等を用いて、さらに成形を施しても良い。また、該ケン化物組成物を紙、プラスチックフィルムおよび金属箔等の基材フィルムに共押出しコートすることも可能である。エチレン−ビニルエステル共重合体ケン化物組成物と共押出する樹脂は特に限定されず、ポリオレフィン、ポリアミド、ポリエステルなどを用いることができる。該ケン化物と隣接する樹脂層としては、接着性に優れるカルボン酸変性ポリオレフィンが好ましい。
【００３０】
該ケン化物組成物に、重合度、エチレン含有率およびケン化度の異なるエチレン−ビニルエステル共重合体ケン化物をブレンドし溶融成形することも可能である。また、該ケン化物組成物に他の各種可塑剤、安定剤、界面活性剤、色剤、紫外線吸収剤、スリップ剤、帯電防止剤、乾燥剤、架橋剤、金属塩、充填剤、各種繊維等の補強剤等を適量添加することも可能である。
【００３１】
また、該ケン化物組成物以外の熱可塑性樹脂を適量配合することも可能である。熱可塑性樹脂としては各種ポリオレフィン（ポリエチレン、ポリプロピレン、ポリ１−ブテン、ポリ４−メチル−１−ペンテン、エチレン−プロピレン共重合体、エチレンと炭素数４以上のα−オレフィンとの共重合体、ポリオレフィンと無水マレイン酸との共重合体、エチレン−ビニルエステル共重合体、エチレン−アクリル酸エステル共重合体、またはこれらを不飽和カルボン酸またはその誘導体でグラフト変性した変性ポリオレフィンなど）、各種ナイロン（ナイロン６、ナイロン６６、ナイロン６／６６共重合体など）、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリエステル、ポリスチレン、ポリアクリロニトリル、ポリウレタン、ポリアセタールおよび変性ポリビニルアルコール樹脂などが用いられる。
【００３２】
次に実例をあげて本発明の組成物をさらに具体的に説明する。以下「％」、「部」とあるのは特に断わりのない限り重量基準である。尚、水はすべてイオン交換水を使用した。
【００３３】
（１）酢酸イオン、乳酸イオン、グリコール酸イオン、アジピン酸イオンおよびリン酸イオンの定量
試料とする乾燥チップ１０ｇを０．０１規定の塩酸水溶液５０ｍｌに投入し、９５℃で６時間攪拌した。攪拌後の水溶液をイオンクロマトグラフィーを用いて定量分析し、酢酸イオン、乳酸イオン、グリコール酸イオン、アジピン酸イオンおよびリン酸イオンの量を定量した。カラムは、（株）横河電機製のＩＣＳ−Ａ２３を使用し、溶離液は２．５ｍＭの炭酸ナトリウムと１．０ｍＭの炭酸水素ナトリウムを含む水溶液とした。なお、定量に際してはそれぞれ酢酸、乳酸、グリコール酸、アジピン酸、リン酸水溶液で作成した検量線を用いた。こうして得られた酢酸イオン、乳酸イオン、グリコール酸イオン、アジピン酸イオンの量から、それぞれの酸および／またはその塩の含有量をそれぞれの酸換算の量で得た。また、得られたリン酸イオンの量から、リン化合物の含有量をリン換算で得た。
【００３４】
（２）Ｎａ、Ｋ、Ｍｇイオンの定量
試料とする乾燥チップ１０ｇを０．０１規定の塩酸水溶液５０ｍｌに投入し、９５℃で６時間攪拌した。攪拌後の水溶液をイオンクロマトグラフィーを用いて定量分析し、Ｎａイオン、ＫイオンおよびＭｇイオンの量を定量した。カラムは、（株）横河電機製のＩＣＳ−Ｃ２５を使用し、溶離液は５．０ｍＭの酒石酸と１．０ｍＭの２，６−ピリジンジカルボン酸を含む水溶液とした。なお、定量に際してはそれぞれ塩化ナトリウム、塩化カリウムおよび塩化マグネシウム水溶液で作成した検量線を用いた。こうして得られたＮａイオン、ＫイオンおよびＭｇイオンの量から、乾燥チップ中のアルカリ金属塩およびアルカリ土類金属塩の量を金属換算の量で得た。
【００３５】
（３）ホウ素化合物の定量
試料とする乾燥チップ１００ｇを磁性ルツボに入れ、電気炉内で灰化させた。得られた灰分を０．０１規定の硝酸水溶液２００ｍＬに溶解し、原子吸光分析によって定量し、ホウ素換算の量でホウ素化合物の含有量を得た。
【００３６】
（４）酸成分残存率
エチレン−ビニルエステル共重合体ケン化物ペレットをヒドロキシカルボン酸等を含む水溶液で処理し脱液した段階の含水チップを乾燥前試料とし、熱風乾燥機で乾燥した後の乾燥チップを乾燥後試料とし、その両試料の酸成分（塩を除く）の含量から酸成分残存率を求めた。ここで、それぞれの試料の酸成分の含有量は以下のようにして求めた。試料ペレット５ｇを５０ｇのイオン交換水に投入し、９５℃で６時間抽出し、抽出液を０．０１規定の水酸化ナトリウムで中和滴定し、それぞれの試料に含まれる酸成分として定量した。乾燥工程における酸成分の揮散度を乾燥前の酸成分の量に対する乾燥後の酸成分の量として酸成分残存率（％）を得て、その値により以下のように判定した。
Ａ；９０〜１００％ Ｂ；６０〜９０％ Ｃ；６０％未満
【００３７】
（５）加熱溶融着色試験
試料とする乾燥チップ８ｇを２３０℃に加熱した熱板（シンドー式卓上テストプレスＹＳ−５）の間にはさみ、熱板間の間隙を５ｍｍに保って１０分間加熱し、着色度を肉眼で判定し以下のように判定した。
Ａ；着色なし Ｂ；やや黄変 Ｃ；黄変 Ｄ；激しい着色
【００３８】
（６）モーター負荷電流変動幅測定試験
試料とする乾燥チップを２５０℃で押出成形し、成形開始１５分後から５分間の押出機のモーター負荷電流の変動幅を測定した。押出機の仕様は以下の通り。
形式 単軸押出機（ノンベントタイプ）
Ｌ／Ｄ ２６
口径 ４０ｍｍφ
スクリュー 一条フルフライトタイプ、表面窒化鋼
回転数 ４０ｒｐｍ
モーター容量 ＤＣ７．５ＫＷ（定格４５Ａ）
ヒーター ４分割タイプ
先端樹脂温度 ２５０℃
負荷電流の変動幅の値によって以下のように判定した。
Ａ；５Ａ未満 Ｂ；５〜１０Ａ Ｃ；１０〜１５Ａ Ｄ；１５Ａ以上
【００３９】
（７）成形物中のブツの個数
共押出成形によって得られた３種５層フィルムのゲル状ブツ（肉眼で確認できる約１００μｍ以上のもの）を数え、１．０ｍ２あたりに換算した。物の個数によって以下のように判定した。
Ａ；２０個未満 Ｂ；２０〜４０個 Ｃ；４０〜６０個 Ｄ；６０個以上
【００４０】
（８）層間接着力
共押出成形によって得られた３種５層フィルムの製膜直後のエチレン−ビニルエステル共重合体ケン化物／接着性樹脂間のＴ型剥離強度をオートグラフ（引張速度３５０ｍｍ／ｍｉｎ）を用いて測定した。剥離強度の値によって以下のように判定した。
Ａ；６００ｇ／ｃｍ以上 Ｂ；６００〜４００ Ｃ；４００〜２００ Ｄ；２００未満
【００４１】
【実施例】
以下、実施例により具体的に説明する。なお、（部）、（％）は特に断わりのない限り重量基準で表したものである。
【００４２】
実施例１
耐圧１００ｋｇ／ｃｍ２の重合槽に酢酸ビニル１９６００部、メタノール２１８０部、ＡＩＢＮ（アゾビスイソブチロニトリル）７．５部を仕込み、攪拌しながら窒素置換後、昇温、昇圧し内温６０℃、エチレン圧力３５．５ｋｇ／ｃｍ２に調整した。３．５時間その温度、圧力を保持し重合させた後、ハイドロキノン５部を添加し、重合槽を常圧に戻し、エチレンを蒸発除去した。引き続き、このメタノール溶液をラシヒリングを充填した追い出し塔の塔上部より連続的に流下させ、一方、塔底部よりメタノール蒸気を吹き込んで未反応酢酸ビニル単量体をメタノール蒸気とともに塔頂部より放出させコンデンサーを通して除去することにより、未反応酢酸ビニル０．０１％以下のエチレン−酢酸ビニル共重合体の４５％メタノール溶液を得た。この時の重合率は仕込み酢酸ビニルに対して４７％、エチレン含有率は３３モル％であった。
【００４３】
次に、エチレン−酢酸ビニル共重合体のメタノール溶液をケン化反応器に仕込み、苛性ソーダ／メタノール溶液（８０ｇ／Ｌ）を共重合体中の酢酸ビニル成分に対し、０．４当量となるように添加し、メタノールを添加して共重合体濃度が２０％になるように調整した。６０℃に昇温し反応器内に窒素ガスを吹き込みながら約４時間反応させた。４時間後、酢酸で中和し反応を停止させ、円形の開口部を有する金板から水中に押し出して析出させ、切断することで直径約３ｍｍ、長さ約５ｍｍのチップを得た。得られたチップは遠心分離機で脱液しさらに大量の水を加え脱液する操作を繰り返した。
【００４４】
こうして得られたエチレン−ビニルエステル共重合体ケン化物の含水チップ３ｋｇを、乳酸０．２０ｇ／Ｌ、乳酸ナトリウム１．２２ｇ／Ｌ、乳酸マグネシウム０．３０ｇ／Ｌ、リン酸二水素カリウム０．１４ｇ／Ｌ、ホウ酸０．３５ｇ／Ｌを含有する水溶液４０Ｌに２５℃で４時間浸漬した。浸漬後脱液し、８０℃で３時間、引き続いて１０５℃で１５時間熱風乾燥機を用いて乾燥を行い、乾燥チップを得た。
【００４５】
得られた乾燥チップ中の乳酸および／または乳酸塩の含有量は乳酸換算で２０００ｐｐｍ、アルカリ金属塩の含有量は金属換算で３５０ｐｐｍ、アルカリ土類金属塩の含有量は金属換算で５０ｐｐｍ、リン化合物の含有量はリン換算で３０ｐｐｍ、ホウ素化合物の含有量はホウ素換算で４０ｐｐｍであった。また、ＭＩは１．５ｇ／１０ｍｉｎであった。この乾燥チップの酸成分残存率、加熱溶融着色試験、モーター負荷電流幅はいずれもＡ判定であった。
【００４６】
得られた乾燥チップを用い、ＬＬＤＰＥ／接着性樹脂／エチレン−ビニルエステル共重合体ケン化物組成物／接着性樹脂／ＬＬＤＰＥの３種５層共押出フィルム（厚み５０／１０／７．５／１０／５０：単位はμｍ）を成形した。
ここでＬＬＤＰＥとして、三井石油化学製「ウルトゼックス２０２２Ｌ」｛ＭＩ＝２．１ｇ／１０分（２１０℃、２１６０ｇ荷重）｝を、接着性樹脂として無水マレイン酸変性ポリエチレンである三井石油化学製「アドマーＧＴ４」｛ＭＩ＝０．２ｇ／１０分（１９０℃、２１６０ｇ荷重）｝を用いた。エチレン−ビニルエステル共重合体ケン化物組成物、ＬＬＤＰＥ、接着性樹脂の押出温度はそれぞれ２３０℃、２２０℃、２３０℃で、ダイ温度は２２０℃に設定した。
【００４７】
製膜直後のエチレン−ビニルエステル共重合体ケン化物組成物／接着性樹脂間のＴ型剥離強度はＡ判定であり、フィルムのブツ個数もＡ判定であった。
【００４８】
実施例２〜７、比較例１〜１０
ケン化、洗浄、脱液後のエチレン−ビニルエステル共重合体ケン化物を浸漬する液の組成を表１にまとめて示すように変更することを除いて実施例１と同様にして乾燥チップを作成し、共押出成形フィルムを作成した。評価結果を表２にまとめて示す。
【００４９】
【表１】
【表２】
【発明の効果】
着色が少なく、成形時にブツの発生が少ない、しかも接着性に優れたエチレン−ビニルエステル共重合体ケン化物組成物およびそれを用いた共押出多層成形体を提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a saponified ethylene-vinyl ester copolymer composition having little coloring and little occurrence of bumps during melt molding and excellent in adhesiveness, and a co-extruded multilayer molded article using the same.
[0002]
[Prior art]
Saponified ethylene-vinyl ester copolymer is a useful polymer material excellent in oxygen shielding property, oil resistance, non-charging property, mechanical strength and the like, and is widely used as various packaging materials such as films, sheets and containers. When the saponified ethylene-vinyl ester copolymer is used as various packaging materials, not only performance for the intended use but also slight coloring in appearance, fish eyes, spots, rough skin, and transparency are regarded as problems.
[0003]
However, the saponified ethylene-vinyl ester copolymer has a problem in that it tends to cause problems such as coloring and blemishes during melt molding. Therefore, conventionally, the following various methods have been proposed as methods for suppressing the occurrence of coloring and blemishes.
[0004]
For example, methods for adding an acid such as acetic acid or phosphoric acid and / or a salt thereof to a saponified ethylene-vinyl ester copolymer are described in JP-A-48-25048, JP-A-51-26993, and JP-A-51-26993. -28891, JP-A-51-49294, JP-A-51-91988, JP-A-52-954, JP-A-52-955, JP-A-52-956, JP-A-56-20044, JP-A-56-20044. Many applications have been filed, such as 41204, JP-A-61-95053, JP-A-61-95054, and JP-A-62-143954. That is, the saponified ethylene-vinyl ester copolymer having little coloring or lumps is saponified by adding a caustic alkali to the ethylene-vinyl ester copolymer, washed with water, and then added with an acid such as acetic acid or phosphoric acid. Alternatively, they are obtained by adding a salt thereof and further drying.
[0005]
[Problems to be solved by the invention]
As described above, various countermeasures have been taken against problems such as coloring and occurrence of bumps in the saponified ethylene-vinyl ester copolymer. However, regarding the method of adding an acid such as acetic acid and phosphoric acid and / or a salt thereof to the saponified ethylene-vinyl ester copolymer, neutralization and washing after saponification are not sufficient, If the acid and / or salt thereof are not added in an appropriate amount, coloring and blemishes tend to increase. In order to remedy this drawback, sufficient washing after saponification and optimization of the amount of an acid such as acetic acid and phosphoric acid and / or a salt thereof have been carried out. Is not yet reached.
[0006]
Further, as a means for improving the adhesiveness between the saponified ethylene-vinyl ester copolymer and another resin, there is a method of adding an alkali metal salt to the saponified ethylene-vinyl ester copolymer, particularly in a molten state. This is effective in improving the adhesiveness of a co-extruded product to be bonded to another resin. However, when an alkali metal salt is added to a saponified ethylene-vinyl ester copolymer, there is a problem that coloring is more likely to occur and spots are more likely to occur than when no alkali metal salt is added.
An object of the present invention is to provide a saponified ethylene-vinyl ester copolymer composition having less coloring, less occurrence of bumps during molding, and excellent adhesiveness, and a co-extruded multilayer molded article using the same. is there.
[0007]
[Means for Solving the Problems]
The objectives are (1) hydroxycarboxylic acid and / or its salt in 100 to 5000 ppm in terms of hydroxycarboxylic acid, (2) alkali metal salt in 50 to 500 ppm in terms of metal, and (3) alkaline earth metal salt in terms of metal. By providing a saponified ethylene-vinyl ester copolymer composition characterized by containing 20 to 200 ppm by weight. Furthermore, it is more effectively achieved by containing (4) an alkali or alkaline earth metal salt of phosphoric acid in an amount of 50 to 500 ppm in terms of phosphoric acid, or (5) containing a boron compound in an amount of 20 to 2000 ppm in terms of boron. You. It is also effectively achieved by providing a co-extruded multilayer molded article containing at least one layer made of such a resin.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The hydroxycarboxylic acid as used in the present invention refers to a carboxylic acid having a hydroxyl group in a molecule. The number of hydroxyl groups and carboxyl groups in the molecule is not particularly limited, but the number of carboxyl groups is preferably one from the viewpoint of preventing gelation. Examples of hydroxycarboxylic acids include lactic acid, glycolic acid and the like.
[0009]
Among monocarboxylic acids having no hydroxyl group in the molecule, those having a short alkyl chain include acetic acid and propionic acid. Since these are water-soluble, they are easy to handle when added to the saponified ethylene-vinyl ester copolymer as an aqueous solution, but because of their low boiling point, they are almost volatilized in the drying step, and they prevent coloring and gelation. The effect is small. On the other hand, examples of monocarboxylic acids having a long alkyl chain include stearic acid and the like, but these have high boiling points but are poor in water solubility and are difficult to handle. In addition, dicarboxylic acids such as adipic acid have a high boiling point and good water solubility, but are liable to gel and easily melt. On the other hand, when hydroxycarboxylic acid is used, it is difficult to volatilize in the drying step, prevents quality fluctuation, has good water solubility, and can effectively prevent coloring and gelling.
[0010]
The content of hydroxycarboxylic acid and / or a salt thereof in the saponified ethylene-vinyl ester copolymer composition of the present invention is 100 to 5000 ppm in terms of hydroxycarboxylic acid, and a preferable range is 500 to 3000 ppm. When the amount is less than 100 ppm, coloring is remarkable. If it exceeds 5,000 ppm, gelation will be severe and poor melting will occur. Here, the term "hydroxycarboxylic acid conversion" refers to a hydroxycarboxylic acid salt calculated as the weight of an equimolar number of hydroxycarboxylic acids and added to the weight of the hydroxycarboxylic acid not forming a salt. The salt of the hydroxycarboxylic acid is not particularly limited, and examples thereof include an alkali metal salt, an alkaline earth metal salt, and an ammonium salt.
[0011]
The content of the alkali metal salt in the saponified ethylene-vinyl ester copolymer composition of the present invention is 50 to 500 ppm, preferably 50 to 400 ppm in terms of metal. When the amount is less than 50 ppm, the adhesion to other resins is poor, and there is a problem particularly in the interlayer adhesion during coextrusion molding. If it exceeds 500 ppm, coloring is remarkable. The alkali metal salt is not particularly limited, and examples thereof include a sodium salt and a potassium salt. The anion species of the alkali metal salt is not particularly limited, but examples thereof include various carboxylate anions such as hydroxycarboxylic acid and acetic acid, and phosphate anions.
[0012]
The content of the alkaline earth metal salt in the saponified ethylene-vinyl ester copolymer composition of the present invention is 20 to 200 ppm, preferably 20 to 100 ppm in terms of metal. When the content is within such a range, the viscosity over time of the saponified ethylene-vinyl ester copolymer composition can be controlled. If it is less than 20 ppm, the effect of suppressing gelation is small, and if it exceeds 200 ppm, coloring is severe. Alkaline earth metal salts are not particularly limited, but include magnesium salts, calcium salts, barium salts, beryllium salts and the like. The anion species of the alkaline earth metal salt is not particularly limited, but examples thereof include various carboxylate anions such as hydroxycarboxylic acid and acetic acid, and phosphate anions.
[0013]
The phosphorus compound in the saponified ethylene-vinyl ester copolymer composition of the present invention is not particularly limited. Various acids such as phosphoric acid and phosphorous acid and salts thereof can be used. The phosphate may be contained in any form of a first phosphate, a second phosphate, and a third phosphate, and the cation species is not particularly limited. Preferred are alkali metal salts and alkaline earth metal salts. The content of the phosphorus compound is preferably 50 to 500 ppm in terms of phosphorus, more preferably 50 to 200 ppm. By containing the phosphorus compound in such a range, it is possible to obtain a saponified ethylene-vinyl ester copolymer composition that is less colored and hardly gels. If it is less than 50 ppm, such an improvement effect is small, and if it exceeds 500 ppm, gelation tends to occur. Especially, it is preferable to add a phosphorus compound in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate.
[0014]
The boron compound in the saponified ethylene-vinyl ester copolymer composition of the present invention is not particularly limited. Examples of the boron compound include boric acids, borate esters, borates, and borohydrides. Specifically, examples of boric acids include orthoboric acid, metaboric acid, tetraboric acid, and the like.Examples of borate esters include triethyl borate, trimethyl borate, and the like. Examples include alkali metal salts, alkaline earth metal salts of acids, borax, and the like. Of these compounds, orthoboric acid (hereinafter simply referred to as boric acid) and NaBH4 are preferred.
The content of the boron compound is 20 to 2000 ppm, preferably 50 to 1000 ppm in terms of boron. When the content is within this range, a saponified ethylene-vinyl ester copolymer composition in which torque fluctuation during heating and melting is suppressed can be obtained. If it is less than 20 ppm, such an effect is small, and if it exceeds 2,000 ppm, gelation is likely to occur, resulting in poor moldability.
[0015]
The ethylene-vinyl ester copolymer used in the present invention is obtained by copolymerizing ethylene and vinyl ester, but the type of vinyl ester is not particularly limited. Examples thereof include aliphatic vinyl esters such as vinyl acetate, vinyl propionate, vinyl versatate, and vinyl pivalate, and may be vinyl esters of aromatic carboxylic acids. Among these vinyl esters, vinyl acetate is preferred from the viewpoint of cost.
[0016]
The saponified ethylene-vinyl ester copolymer of the present invention has an ethylene content of 10 to 60 mol%, preferably 20 to 55 mol%, and a saponification degree of the vinyl ester component of 90 mol% or more, preferably 95 mol% or more. belongs to. When the ethylene content is 20 mol% or less, the oxygen barrier property at high humidity decreases, while when the ethylene content is 60 mol% or more, physical properties such as sufficient oxygen barrier property and printability deteriorate. On the other hand, when the saponification degree is 90 mol% or less, oxygen barrier properties and moisture resistance are reduced.
[0017]
Hereinafter, the manufacturing method will be specifically described. The polymerization of ethylene and vinyl ester is not limited to solution polymerization, and may be a continuous type or a batch type. For example, the polymerization conditions in the case of batch type solution polymerization are as follows.
[0018]
Solvent: Alcohols are preferable, but other organic solvents (such as dimethyl sulfoxide) that can dissolve ethylene, vinyl ester and ethylene-vinyl ester copolymer can be used. As the alcohols, methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, t-butyl alcohol and the like can be used, and methyl alcohol is particularly preferable.
Catalyst: 2,2'-azobisisobutyronitrile, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis- (4-methyl-2,4-dimethylvaleronitrile) ), Azonitrile initiators such as 2,2'-azobis- (2-cyclopropylpropionitrile) and isobutyryl peroxide, cumyl peroxy neodecanoate, diisopropyl peroxy carbonate, di-n-propyl peroxy Organic peroxide initiators such as dicarbonate, t-butylperoxy neodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide can be used.
Temperature: 20-90C, preferably 40-70C.
Time; 2 to 15 hours, preferably 3 to 11 hours.
Polymerization rate: 10 to 90%, preferably 30 to 80%, based on the charged vinyl ester.
Resin content in solution after polymerization; 5 to 85%, preferably 20 to 70%.
Ethylene content in the copolymer: 20 to 60 mol%, preferably 25 to 55 mol%.
[0019]
In addition, other than ethylene and vinyl ester, monomers copolymerizable therewith, for example, α-olefins such as propylene, isobutylene, α-octene, α-dodecene; acrylic acid, methacrylic acid, crotonic acid, maleic acid, itacone Unsaturated acids such as acids or anhydrides, salts or mono- or dialkyl esters thereof; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfone An olefin sulfonic acid such as an acid or a salt thereof; alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride and the like can be coexisted in a small amount.
[0020]
After the polymerization for a predetermined time, after reaching a predetermined polymerization rate, if necessary, a polymerization inhibitor is added, unreacted ethylene gas is removed by evaporation, and then unreacted vinyl ester is expelled. As a method of driving out unreacted vinyl ester from the ethylene-vinyl ester copolymer from which ethylene has been removed by evaporation, for example, the copolymer solution is continuously supplied at a constant rate from the top of a column filled with Raschig rings, An organic solvent vapor such as methanol is blown from the bottom, a mixed vapor of an organic solvent such as methanol and unreacted vinyl ester is discharged from the top of the tower, and the copolymer solution from which the unreacted vinyl ester is removed from the bottom of the tower is taken out. Adopted.
[0021]
An alkali catalyst is added to the copolymer solution from which unreacted vinyl ester has been removed to saponify the vinyl ester component in the copolymer. The saponification method can be either a continuous type or a batch type. As the alkali catalyst, sodium hydroxide, potassium hydroxide, alkali metal alcoholate and the like are used. For example, the saponification conditions in the case of the batch system are as follows.
Concentration of the copolymer solution; 10 to 50%.
Reaction temperature;
Amount of catalyst used: 0.02 to 0.6 equivalent (per vinyl ester component).
Time; 1-6 hours.
Although the degree of saponification after the saponification reaction varies depending on the purpose, it is usually at least 90%, preferably at least 95% of the vinyl ester component. The saponification degree can be arbitrarily adjusted depending on the conditions.
[0022]
Since the saponified ethylene-vinyl ester copolymer after the reaction contains an alkali catalyst, by-product salts, and other impurities, they are removed by neutralization and washing as necessary.
[0023]
The method for causing the obtained saponified ethylene-vinyl ester copolymer to contain a hydroxycarboxylic acid and / or a salt thereof, an alkali metal salt, an alkaline earth metal salt, a phosphorus compound, or a boron compound is not particularly limited. For example, a method of immersing the saponified product in a solution in which the compound is dissolved, a method of melting the saponified product and mixing the compound, and a method of dissolving the saponified product in an appropriate solvent and mixing the compound Etc.
[0024]
Among them, a method of dipping a saponified ethylene-vinyl ester copolymer in a solution of the above compound is desirable in order to exert the effects of the present invention more remarkably. This processing can be performed by either a batch method or a continuous method. In this case, the shape of the saponified product may be any shape such as powder, granule, sphere, and columnar chip.
[0025]
When the saponified ethylene-vinyl ester copolymer is immersed in a solution containing hydroxycarboxylic acid and / or a salt thereof, an alkali metal salt, an alkaline earth metal salt, a phosphorus compound, and a boron compound, the hydroxycarboxylic acid and The concentration of the salt, the alkali metal salt, the alkaline earth metal salt, the phosphorus compound, and the boron compound is not particularly limited. The solvent of the solution is not particularly limited, but is preferably an aqueous solution for reasons such as handling. It is desirable that the weight of the solution when the saponified product is immersed is at least 3 times, preferably at least 20 times the weight of the saponified product when dried. The suitable range of the immersion time varies depending on the form of the saponified ethylene-vinyl ester copolymer, but is preferably 1 hour or more, preferably 2 hours or more in the case of a chip of about 1 to 10 mm.
[0026]
The immersion treatment of the above various compounds in a solution may be performed by dividing into a plurality of solutions and immersion at once. In particular, treatment with a solution containing all of a hydroxycarboxylic acid and / or a salt thereof, an alkali metal salt, and an alkaline earth metal salt (and a phosphate or a boron compound, if necessary) can simplify the process. Preferred from the point. When immersed in a solution and treated as described above, it is finally dried to obtain the desired saponified ethylene-vinyl ester copolymer composition.
[0027]
Suitable melt index (MI) of the saponified ethylene-vinyl ester copolymer obtained in the present invention (measured at 190 ° C. under a load of 2160 g; if the melting point is around 190 ° C. or exceeds 190 ° C., a load of 2160 g is applied) , Measured at a plurality of temperatures equal to or higher than the melting point, and plotted on the semi-logarithmic graph with the reciprocal of the absolute temperature as the horizontal axis and the melt index as the vertical axis (logarithm), and extrapolated to 190 ° C.). 10 min. , Optimally 0.2 to 100 g / 10 min. It is.
[0028]
The obtained saponified ethylene-vinyl ester copolymer composition is formed into various molded products such as films, sheets, containers, pipes, and fibers by melt molding. These molded products can be crushed and molded again for the purpose of reuse. It is also possible to uniaxially or biaxially stretch films, sheets, fibers and the like. Examples of the melt molding method include extrusion molding, inflation extrusion, blow molding, melt spinning, and injection molding. The melting temperature varies depending on the melting point of the copolymer and the like, but is preferably about 150 to 270 ° C.
[0029]
Above all, when co-extrusion multilayer molding is performed, good interlayer adhesion is preferable. The shape obtained by co-extrusion molding is not particularly limited, and examples include shapes of sheets, films, pipes and the like. Further, the sheet or the like thus obtained may be further molded. Further, the saponified composition can be co-extruded and coated on a base film such as paper, a plastic film and a metal foil. The resin coextruded with the saponified ethylene-vinyl ester copolymer composition is not particularly limited, and polyolefin, polyamide, polyester, and the like can be used. As the resin layer adjacent to the saponified product, a carboxylic acid-modified polyolefin having excellent adhesiveness is preferable.
[0030]
It is also possible to blend the saponified composition with saponified ethylene-vinyl ester copolymers having different degrees of polymerization, ethylene content and saponification degree, and melt-mold the mixture. In addition, other various plasticizers, stabilizers, surfactants, coloring agents, ultraviolet absorbers, slip agents, antistatic agents, drying agents, crosslinking agents, metal salts, fillers, various fibers, etc. It is also possible to add an appropriate amount of a reinforcing agent or the like.
[0031]
It is also possible to mix an appropriate amount of a thermoplastic resin other than the saponified composition. Examples of the thermoplastic resin include various polyolefins (polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, ethylene-propylene copolymer, copolymer of ethylene and α-olefin having 4 or more carbon atoms, polyolefin Copolymer of ethylene and maleic anhydride, ethylene-vinyl ester copolymer, ethylene-acrylate ester copolymer, or modified polyolefin obtained by graft-modifying these with unsaturated carboxylic acid or a derivative thereof), various nylons (nylons) 6, nylon 66, nylon 6/66 copolymer), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, and modified polyvinyl alcohol resin.
[0032]
Next, the composition of the present invention will be described more specifically by way of examples. Hereinafter, “%” and “parts” are based on weight unless otherwise specified. In addition, all the water used ion-exchange water.
[0033]
(1) Determination of acetate, lactate, glycolate, adipate and phosphate ions
10 g of a dry chip as a sample was put into 50 ml of a 0.01 N hydrochloric acid aqueous solution and stirred at 95 ° C. for 6 hours. The aqueous solution after stirring was quantitatively analyzed using ion chromatography, and the amounts of acetate ion, lactate ion, glycolate ion, adipate ion and phosphate ion were quantified. The column used was ICS-A23 manufactured by Yokogawa Electric Corporation, and the eluent was an aqueous solution containing 2.5 mM sodium carbonate and 1.0 mM sodium hydrogen carbonate. In the determination, a calibration curve prepared with an aqueous solution of acetic acid, lactic acid, glycolic acid, adipic acid, and phosphoric acid was used. From the amounts of acetate ion, lactate ion, glycolate ion and adipate ion thus obtained, the content of each acid and / or salt thereof was obtained in the amount of each acid. From the amount of the obtained phosphate ions, the content of the phosphorus compound was obtained in terms of phosphorus.
[0034]
(2) Determination of Na, K, Mg ions
10 g of a dry chip as a sample was put into 50 ml of a 0.01 N hydrochloric acid aqueous solution and stirred at 95 ° C. for 6 hours. The aqueous solution after stirring was quantitatively analyzed using ion chromatography, and the amounts of Na ions, K ions and Mg ions were quantified. The column used was ICS-C25 manufactured by Yokogawa Electric Corporation, and the eluent was an aqueous solution containing 5.0 mM tartaric acid and 1.0 mM 2,6-pyridinedicarboxylic acid. In the determination, a calibration curve prepared with an aqueous solution of sodium chloride, potassium chloride and magnesium chloride was used. From the amounts of Na ion, K ion and Mg ion thus obtained, the amounts of alkali metal salt and alkaline earth metal salt in the dried chip were obtained in terms of metal.
[0035]
(3) Determination of boron compound
100 g of a dry chip as a sample was placed in a magnetic crucible and ashed in an electric furnace. The obtained ash was dissolved in 200 mL of a 0.01 N aqueous nitric acid solution and quantified by atomic absorption spectrometry, and the content of the boron compound was obtained in terms of boron.
[0036]
(4) Residual rate of acid component
The saponified ethylene-vinyl ester copolymer pellets were treated with an aqueous solution containing hydroxycarboxylic acid and the like, and the wet chips at the stage of dehydration were used as a sample before drying, and the dried chips after drying with a hot air dryer were used as a sample after drying. The residual ratio of the acid component was determined from the content of the acid component (excluding the salt) in both samples. Here, the content of the acid component of each sample was determined as follows. 5 g of the sample pellet was put into 50 g of ion-exchanged water, extracted at 95 ° C. for 6 hours, and the extract was subjected to neutralization titration with 0.01 N sodium hydroxide to quantify as an acid component contained in each sample. The volatility of the acid component in the drying step was determined as the acid component residual ratio (%) as the amount of the acid component after drying with respect to the amount of the acid component before drying, and the value was evaluated as follows.
A; 90 to 100% B; 60 to 90% C; less than 60%
[0037]
(5) Heat melting color test
8 g of the dried chips to be used as samples are sandwiched between hot plates heated at 230 ° C. (Sindoh tabletop test press YS-5), heated for 10 minutes while keeping the gap between the hot plates at 5 mm, and the degree of coloring is visually determined. It was determined as follows.
A: No coloring B: Slightly yellowing C: Yellowing D: Intense coloring
[0038]
(6) Motor load current fluctuation range measurement test
A dry chip as a sample was extruded at 250 ° C., and the fluctuation width of the motor load current of the extruder for 5 minutes from 15 minutes after the start of molding was measured. The specifications of the extruder are as follows.
Model Single screw extruder (non-vent type)
L / D 26
Diameter 40mmφ
Screw Single-row full flight type, surface nitrided steel
Rotation speed 40 rpm
Motor capacity DC 7.5KW (Rating 45A)
Heater 4-split type
Tip resin temperature 250 ° C
The following judgment was made based on the value of the variation width of the load current.
A: less than 5A B: 5 to 10A C; 10 to 15AD: 15A or more
[0039]
(7) Number of bumps in the molded product
The gel-like bumps (those having a size of about 100 μm or more that can be confirmed with the naked eye) of the three-layer five-layer film obtained by coextrusion molding were counted, and 1.0 m 2 It was converted to per. The following judgment was made based on the number of objects.
A: less than 20 B: 20 to 40 C: 40 to 60 D: 60 or more
[0040]
(8) Interlayer adhesion
The T-peel strength between the saponified ethylene-vinyl ester copolymer / adhesive resin immediately after the formation of the three-layer five-layer film obtained by coextrusion molding was measured using an autograph (tensile speed: 350 mm / min). did. The value was determined as follows based on the peel strength.
A: 600 g / cm or more B: 600 to 400 C; 400 to 200 D; less than 200
[0041]
【Example】
Hereinafter, specific examples will be described. In addition, (part) and (%) are expressed on a weight basis unless otherwise specified.
[0042]
Example 1
Withstand pressure 100kg / cm 2 19,600 parts of vinyl acetate, 2180 parts of methanol, and 7.5 parts of AIBN (azobisisobutyronitrile) were charged into a polymerization tank, and the mixture was purged with nitrogen while stirring. 5kg / cm 2 Was adjusted to After maintaining the temperature and pressure for 3.5 hours for polymerization, 5 parts of hydroquinone was added, the polymerization tank was returned to normal pressure, and ethylene was removed by evaporation. Subsequently, this methanol solution was continuously allowed to flow down from the top of the effluent tower filled with Raschig rings, while methanol vapor was blown from the bottom of the tower to release unreacted vinyl acetate monomer together with methanol vapor from the top of the tower and passed through a condenser. By removing, a 45% methanol solution of ethylene-vinyl acetate copolymer having 0.01% or less of unreacted vinyl acetate was obtained. At this time, the polymerization rate was 47% based on the charged vinyl acetate, and the ethylene content was 33% by mole.
[0043]
Next, a methanol solution of the ethylene-vinyl acetate copolymer was charged into a saponification reactor, and a sodium hydroxide / methanol solution (80 g / L) was adjusted to 0.4 equivalent to the vinyl acetate component in the copolymer. Then, methanol was added to adjust the copolymer concentration to 20%. The temperature was raised to 60 ° C., and the reaction was performed for about 4 hours while blowing nitrogen gas into the reactor. After 4 hours, the reaction was stopped by neutralization with acetic acid, and the mixture was extruded into water from a metal plate having a circular opening to be precipitated, and cut to obtain a chip having a diameter of about 3 mm and a length of about 5 mm. The operation of removing the obtained chips by a centrifuge and further adding a large amount of water to remove the chips was repeated.
[0044]
3 kg of a water-containing chip of the saponified ethylene-vinyl ester copolymer obtained in this manner was used to prepare 0.20 g / L of lactic acid, 1.22 g / L of sodium lactate, 0.30 g / L of magnesium lactate, and 0.14 g of potassium dihydrogen phosphate. / L, 40 L of an aqueous solution containing 0.35 g / L of boric acid at 25 ° C. for 4 hours. After immersion, the solution was drained and dried at 80 ° C. for 3 hours and subsequently at 105 ° C. for 15 hours using a hot-air drier to obtain dried chips.
[0045]
The content of lactic acid and / or lactate in the obtained dried chips was 2000 ppm in terms of lactic acid, the content of alkali metal salts was 350 ppm in terms of metals, the content of alkaline earth metal salts was 50 ppm in terms of metals, and phosphorus compounds. Was 30 ppm in terms of phosphorus, and the content of boron compound was 40 ppm in terms of boron. MI was 1.5 g / 10 min. The residue of the acid component, the heat fusion coloring test, and the motor load current width of the dried chips were all A.
[0046]
Using the obtained dried chips, a three-layer, five-layer coextruded film of LLDPE / adhesive resin / saponified ethylene-vinyl ester copolymer composition / adhesive resin / LLDPE (thickness 50/10 / 7.5 / 10) / 50: unit is μm).
Here, "Ultzex 2022L" manufactured by Mitsui Petrochemical Co., Ltd. (MI = 2.1 g / 10 min (210 ° C., 2160 g load)) is used as LLDPE, and "Admer" manufactured by Mitsui Petrochemical Co., Ltd., which is a maleic anhydride-modified polyethylene, is used as the adhesive resin. GT4 "(MI = 0.2 g / 10 min (190 ° C, 2160 g load)" was used. The extrusion temperatures of the saponified ethylene-vinyl ester copolymer composition, LLDPE, and the adhesive resin were set at 230 ° C, 220 ° C, and 230 ° C, respectively, and the die temperature was set at 220 ° C.
[0047]
The T-type peel strength between the saponified ethylene-vinyl ester copolymer composition / adhesive resin immediately after film formation was determined as A, and the number of pieces of the film was also determined as A.
[0048]
Examples 2 to 7, Comparative Examples 1 to 10
A dried chip was prepared in the same manner as in Example 1 except that the composition of the liquid in which the saponified ethylene-vinyl ester copolymer after saponification, washing, and dewatering was immersed was changed as shown in Table 1. Then, a co-extruded film was prepared. Table 2 shows the evaluation results.
[0049]
[Table 1]
[Table 2]
【The invention's effect】
It is possible to provide a saponified ethylene-vinyl ester copolymer composition which is less colored, has less occurrence of bumps during molding, and is excellent in adhesiveness, and a co-extruded multilayer molded article using the same.
Claims (4)
Priority Applications (1)
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| JP03494297A JP3590498B2 (en) | 1996-06-19 | 1997-02-19 | Saponified ethylene-vinyl ester copolymer composition and co-extruded multilayer molded article using the same |
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| JP15841096 | 1996-06-19 | ||
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| JP03494297A JP3590498B2 (en) | 1996-06-19 | 1997-02-19 | Saponified ethylene-vinyl ester copolymer composition and co-extruded multilayer molded article using the same |
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| JP4125417B2 (en) * | 1998-04-08 | 2008-07-30 | 日本合成化学工業株式会社 | Manufacturing method of resin composition |
| JP3841943B2 (en) * | 1997-10-09 | 2006-11-08 | 日本合成化学工業株式会社 | Production method of resin composition |
| JP4082780B2 (en) * | 1998-04-08 | 2008-04-30 | 日本合成化学工業株式会社 | Manufacturing method of resin composition |
| JP4164151B2 (en) * | 1998-04-08 | 2008-10-08 | 日本合成化学工業株式会社 | Manufacturing method of resin composition |
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| JP2000177067A (en) * | 1998-10-07 | 2000-06-27 | Kuraray Co Ltd | Multilayered structure obtained by co-extrusion coating and production thereof |
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| JP2000177068A (en) * | 1998-10-07 | 2000-06-27 | Kuraray Co Ltd | Multilayered structure and production thereof |
| JP4712140B2 (en) * | 1998-11-24 | 2011-06-29 | 日本合成化学工業株式会社 | Molded articles and laminates |
| JP2000178396A (en) * | 1998-12-18 | 2000-06-27 | Kuraray Co Ltd | Melt-moldable polyvinyl alcohol resin composition |
| JP4115620B2 (en) * | 1999-01-06 | 2008-07-09 | 株式会社クラレ | Hydraulic material reinforcing fiber and cured body |
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| JP4647065B2 (en) * | 1999-07-07 | 2011-03-09 | 株式会社クラレ | Resin composition comprising ethylene-vinyl alcohol copolymer and multilayer structure using the same |
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| JP2001293816A (en) * | 2000-04-14 | 2001-10-23 | Jsr Corp | Molded article |
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| CA2473520C (en) * | 2003-08-11 | 2012-03-27 | Kuraray Co., Ltd. | Blow molded container and method for producing the same |
| WO2007129371A1 (en) | 2006-04-25 | 2007-11-15 | The Nippon Synthetic Chemical Industry Co., Ltd. | Multilayer film |
| JP5619874B2 (en) | 2010-03-25 | 2014-11-05 | 株式会社クラレ | Resin composition, method for producing the same, and multilayer structure |
| WO2013005807A1 (en) | 2011-07-07 | 2013-01-10 | 株式会社クラレ | Ethylene-vinyl alcohol copolymer resin composition and method for producing same |
| JP6848856B2 (en) * | 2015-12-25 | 2021-03-24 | 三菱ケミカル株式会社 | Ethylene-vinyl ester copolymer saponified composition and method for producing the same |
| JP7167423B2 (en) * | 2017-09-27 | 2022-11-09 | 三菱ケミカル株式会社 | Resin composition and multilayer structure using the same |
| WO2019130799A1 (en) * | 2017-12-27 | 2019-07-04 | 株式会社クラレ | Resin composition including ethylene/vinyl alcohol copolymer, molded object, and packaging material |
-
1997
- 1997-02-19 JP JP03494297A patent/JP3590498B2/en not_active Expired - Lifetime
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