JP4228197B2 - Biaxially stretched film and method for producing the same - Google Patents

Description

尚、式（１）〜（６）において
Ｔｇ：ポリアミド樹脂（Ａ）のガラス転移温度
Ｔ：延伸温度
ｔ１：ｘ軸延伸に要する時間
ｔ２：ｘ軸延伸を始めてからｙ軸延伸を始めるまでの経過時間
ｔ３：ｘ軸延伸を始めてからｙ軸延伸が終了するまでの経過時間
ｘ０：延伸前のフィルムのｘ軸方向長さ
ｘ：延伸後のフィルムのｘ軸方向長さ
ｙ０：延伸前のフィルムのｙ軸方向長さ
ｙ：延伸後のフィルムのｙ軸方向長さ
ここで、ｘ軸とｙ軸は直交する。ｘ軸方向がＭＤ方向（シート押出方向）の時は、ｙ軸方向はＴＤ方向（シートの幅方向）を意味し、ｘ軸方向がＴＤ方向の時は、ｙ軸方向はＭＤ方向を意味する。
【０００８】
【発明の実施の態様】
以下に本発明を詳しく説明する。本発明で使用するポリアミド（Ａ）は、メタキシリレンジアミンを主成分とするジアミン成分と炭素数４〜２０のα，ω−直鎖脂肪族ジカルボン酸を主成分とするジカルボン酸成分とを重合することにより得られるポリアミドである。
【０００９】
本発明で使用するジアミン成分は、メタキシリレンジアミンを７０モル％以上、好ましくは７５モル％以上、さらに好ましくは８０モル％以上含むものである。ジアミン成分中のメタキシリレンジアミン量が７０モル％より少ないと、ポリアミド（Ａ）のガスバリア性が低下するため好ましくない。本発明においてメタキシリレンジアミン以外に使用できるジアミン成分としては、テトラメチレンジアミン、ペンタメチレンジアミン、２−メチルペンタンジアミン、ヘキサメチレンジアミン、ヘプタメチレンジアミン、オクタメチレンジアミン、ノナメチレンジアミン、デカメチレンジアミン、ドデカメチレンジアミン、２，２，４−トリメチル−ヘキサメチレンジアミン、２，４，４−トリメチルヘキサメチレンジアミン、等の脂肪族ジアミン、１，３−ビス（アミノメチル）シクロヘキサン、１，４−ビス（アミノメチル）シクロヘキサン、１，３−ジアミノシクロヘキサン、１，４−ジアミノシクロヘキサン、ビス（４−アミノシクロヘキシル）メタン、２，２−ビス（４−アミノシクロヘキシル）プロパン、ビス（アミノメチル）デカリン、ビス（アミノメチル）トリシクロデカン等の脂環族ジアミン、ビス（４−アミノフェニル）エーテル、パラフェニレンジアミン、パラキシリレンジアミン、ビス（アミノメチル）ナフタレン等の芳香環を有するジアミン類等を例示することができるが、これらに限定されるものではない。
【００１０】
本発明で使用するジカルボン酸成分は、炭素数４〜２０のα，ω−直鎖脂肪族ジカルボン酸を７０モル％以上、好ましくは７５モル％以上、さらに好ましくは８０モル％以上含むものである。ジカルボン酸成分中の炭素数４〜２０のα，ω−直鎖脂肪族ジカルボン酸が７０モル％より少ないとポリアミド（Ａ）の結晶性が低下してポリアミド（Ａ）のガスバリア性が低下するため好ましくない。本発明で使用する炭素数４〜２０のα，ω−直鎖脂肪族ジカルボン酸としては、例えばコハク酸、グルタル酸、ピメリン酸、スベリン酸、アゼライン酸、アジピン酸、セバシン酸、ウンデカン二酸、ドデカン二酸等の脂肪族ジカルボン酸が例示できるが、これら中でもアジピン酸が好ましい。また本発明では上記α，ω−直鎖脂肪族ジカルボン酸以外のジカルボン酸として、テレフタル酸、イソフタル酸、２，６−ナフタレンジカルボン酸等に例示される芳香族ジカルボン酸類を添加することもできる。さらに、ポリアミド樹脂（Ａ）の重縮合時に分子量調節剤として少量のモノアミン、モノカルボン酸を加えてもよい。
【００１１】
ポリアミド（Ａ）は、溶融重縮合法により製造される。例えば、メタキシリレンジアミンとアジピン酸からなるナイロン塩を水の存在下に、加圧状態で昇温し、加えた水および縮合水を除きながら溶融状態で重合させる方法により製造される。また、メタキシリレンジアミンを溶融状態のアジピン酸に直接加えて、常圧下で重縮合する方法によっても製造される。この場合、反応系を均一な液状状態で保つために、メタキシリレンジアミンをアジピン酸に連続的に加え、その間、反応温度が生成するオリゴアミドおよびポリアミドの融点よりも下回らないように反応系を昇温しつつ、重縮合が進められる。
【００１２】
ポリアミド（Ａ）の数平均分子量は、１００００〜５００００であることが好ましく、１５０００〜４５０００であればさらに好ましい。なおここでいう数平均分子量とはポリアミド（Ａ）の末端アミノ基濃度［ＮＨ_２］（μ当量／ｇ）と末端カルボキシル基濃度［ＣＯＯＨ］（μ当量／ｇ）を塩酸又は水酸化ナトリウム水溶液を用いた中和滴定により求め、次式で算出したものである。
数平均分子量＝２００００００／（［ＣＯＯＨ］＋［ＮＨ_２］）
【００１３】
数平均分子量が１００００未満では溶融粘度が低すぎるため、ポリアミド（Ａ）とスメクタイト（Ｂ）を、押し出し機を用いて溶融混練する時にスメクタイトに十分な剪断応力がかからず、その層間の広がりや分散が不十分になるため好ましくない。また数平均分子量が５００００より大きいと逆に溶融粘度が高すぎるため、通常の装置ではポリアミド（Ａ）とスメクタイト（Ｂ）を溶融混練することができない。
またポリアミド（Ａ）の数平均分子量を表す指標として相対粘度を用いることができる。相対粘度とはポリアミド１ｇを９６％硫酸１００ｍｌに溶解して、キャノンフェンスケ型粘度計等を用いて２５℃で測定した値を表す。本発明のポリアミド（Ａ）の相対粘度は１．６〜４．４の範囲となる。
【００１４】
また、ポリアミド（Ａ）を得るには、前述のジアミン成分およびジカルボン酸成分を、反応モル比（反応したジアミンのモル数／反応したジカルボン酸のモル数）が０．９９０〜１．０００の範囲で重縮合させることが好ましい。反応モル比は、より好ましくは０．９９１〜０．９９９、特に好ましくは０．９９２〜０．９９８の範囲である。反応モル比が１．０００より大きい場合、過剰な末端アミノ基が、ヘーズ上昇、押出時のゲル発生等に寄与することから、安定した透明性を有する二軸延伸フィルムを作製することができない。０．９９０を下回る場合は、ポリアミド（Ａ）の分子量が小さく、粘度が小さいため、スメクタイトの分散不良が生じやすいだけでなく、フィルムやボトル等への成形時にドローダウンや厚みムラ等の不具合を生じるため好ましくない。ここで、反応モル比（ｒ）は次式で求められる。
ｒ＝（１−ｃＮ−ｂ（Ｃ−Ｎ））／（１−ｃＣ＋ａ（Ｃ−Ｎ））
式中、ａ：Ｍ_１／２
ｂ：Ｍ_２／２
ｃ：１８．０１５
Ｍ_１：ジアミンの分子量（ｇ／ｍｏｌ）
Ｍ_２：ジカルボン酸の分子量（ｇ／ｍｏｌ）
Ｎ：末端アミノ基濃度（当量／ｇ）
Ｃ：末端カルボキシル基濃度（当量／ｇ）
【００１５】
ポリアミド（Ａ）は、末端アミノ基濃度が１〜６０μ当量／ｇであることが好ましく、より好ましくは５〜５５μ当量／ｇ、特に好ましくは１０〜５０当量／ｇである。末端アミノ基濃度が６０μ当量／ｇより高い場合、ポリアミド樹脂組成物（Ｃ）からなる二軸延伸フィルムのヘーズが上昇する。末端アミノ基濃度を特定値に規定することで、ヘーズの上昇が抑えられ、安定した透明性を有することができるため、得られた商品の工業的価値、商業的価値を高めることができる。
ポリアミド（Ａ）の末端カルボキシル基濃度は、上記数平均分子量および反応モル比を満たす値であればよい。
【００１６】
ポリアミド（Ａ）には、溶融成形時の加工安定性を高めるため、あるいはポリアミド樹脂の着色を防止するためにリン化合物を添加することができる。リン化合物としてはアルカリ金属又はアルカリ土類金属を含むリン化合物が好適に使用され、例えば、ナトリウム、マグネシウム、カルシウム等のアルカリ金属又はアルカリ土類金属のリン酸塩、次亜リン酸塩、亜リン酸塩が挙げられるが、特にアルカリ金属又はアルカリ土類金属の次亜リン酸塩を使用したものがポリアミドの着色防止効果に特に優れるため好ましく用いられる。リン化合物の濃度はポリアミド（Ａ）中のリン原子濃度として５００ｐｐｍ以下、好ましくは３５０ｐｐｍ以下、更に好ましくは２００ｐｐｍ以下である。リン原子濃度が５００ｐｐｍを超えても着色防止効果に変化はなく、むしろこれを利用して得られる二軸延伸フィルムのヘーズが上昇するため好ましくない。
【００１７】
なお、ポリアミド（Ａ）の水分率は０．２重量％未満であることが成形加工上有利である。ポリアミド（Ａ）の水分率が０．２重量％以上である場合、スメクタイトの分散性が低下するだけでなく、分子量の低下やゲル状ブツが生じやすくなるので乾燥してから使用することが望ましい。ポリアミド（Ａ）の乾燥は、公知の方法により行うことができる。例えば、ベント付きの押出機でポリアミドを溶融押出する際にシリンダー内部を真空ポンプにより減圧にすることでポリマー中の水分を除去する方法、ポリアミド樹脂をタンブラー（回転式真空槽）中に仕込み、減圧下でポリマーの融点以下の温度で加熱して乾燥する方法等が挙げられるが、これに限定されるものではない。
【００１８】
本発明においてポリアミド樹脂組成物（Ｃ）１００重量部中のポリアミド（Ａ）の含有量は、８０〜９９．９重量部であることが好ましく、より好ましくは８５〜９９重量部である。ポリアミド含有量が８０重量部未満では、二軸延伸フィルムの透明性が損なわれるため好ましくない。また、９９．９重量部より大きいと、充分な量のスメクタイトを配合することができず、ガスバリア性を向上できないので好ましくない。
【００１９】
本発明で使用するスメクタイト（Ｂ）は、０．２５〜０．６の電荷密度を有する２−八面体型や３−八面体型の層状珪酸塩であり、２−八面体型としては、モンモリロナイト、バイデライト、ノントロナイト等、３−八面体型としてはヘクトライト、サポナイト等が挙げられる。これらの中でも、モンモリロナイトは高膨潤性を有し、浸透膨潤が起こり層間が広がりやすいため、ポリアミド樹脂組成物（Ｃ）中で分散しやすく、好ましい。
【００２０】
本発明においてスメクタイト（Ｂ）を配合する場合、上記層状珪酸塩をそのまま利用してポリアミド（Ａ）と混合することができるが、有機膨潤化剤を予め層状珪酸塩に接触させて、層状珪酸塩の層間を拡げたものを用いることがポリアミド中におけるスメクタイトの分散が良好になるため好ましく行われる。この場合、スメクタイトに有機膨潤化剤が含まれたスメクタイト組成物をポリアミド（Ａ）に混合することになるが、本発明では有機膨潤化剤の含有量がスメクタイト組成物中において５０重量％以下であるものを使用することが好ましい。有機膨潤化剤の含有量が５０重量％より大きいと、ポリアミド樹脂組成物（Ｃ）からなるフィルムのヘーズが上昇するため好ましくない。
【００２１】
有機膨潤化剤として、第４級アンモニウム塩が好ましく使用できるが、より好ましくは、炭素数１２以上のアルキル基またはアルケニル基を少なくとも一つ以上有する第４級アンモニウム塩が用いられる。有機膨潤化剤の具体例としては、例えばトリメチルドデシルアンモニウム塩、トリメチルテトラデシルアンモニウム塩、トリメチルヘキサデシルアンモニウム塩、トリメチルオクタデシルアンモニウム塩、トリメチルエイコシルアンモニウム塩等のトリメチルアルキルアンモニウム塩；トリメチルオクタデセニルアンモニウム塩、トリメチルオクタデカジエニルアンモニウム等のトリメチルアルケニルアンモニウム塩；トリエチルドデシルアンモニウム塩、トリエチルテトラデシルアンモニウム塩、トリエチルヘキサデシルアンモニウム塩、トリエチルオクタデシルアンモニウム等のトリエチルアルキルアンモニウム塩；トリブチルドデシルアンモニウム塩、トリブチルテトラデシルアンモニウム塩、トリブチルヘキサデシルアンモニウム塩、トリブチルオクタデシルアンモニウム等のトリブチルアルキルアンモニウム塩；ジメチルジドデシルアンモニウム塩、ジメチルジテトラデシルアンモニウム塩、ジメチルジヘキサデシルアンモニウム塩、ジメチルジオクタデシルアンモニウム塩、ジメチルジタロウアンモニウム塩等のジメチルジアルキルアンモニウム塩；ジメチルジオクタデセニルアンモニウム塩、ジメチルジオクタデカジエニルアンモニウム塩等のジメチルジアルケニルアンモニウム塩；ジエチルジドデジルアンモニウム塩、ジエチルジテトラデシルアンモニウム塩、ジエチルジヘキサデシルアンモニウム塩、ジエチルジオクタデシルアンモニウム等のジエチルジアルキルアンモニウム塩；ジブチルジドデシルアンモニウム塩、ジブチルジテトラデシルアンモニウム塩、ジブチルジヘキサデシルアンモニウム塩、ジブチルジオクタデシルアンモニウム塩等のジブチルジアルキルアンモニウム塩；メチルベンジルジヘキサデシルアンモニウム塩等のメチルベンジルジアルキルアンモニウム塩；ジベンジルジヘキサデシルアンモニウム塩等のジベンジルジアルキルアンモニウム塩；トリドデシルメチルアンモニウム塩、トリテトラデシルメチルアンモニウム塩、トリオクタデシルメチルアンモニウム塩等のトリアルキルメチルアンモニウム塩；トリドデシルエチルアンモニウム塩等のトリアルキルエチルアンモニウム塩；トリドデシルブチルアンモニウム塩等のトリアルキルブチルアンモニウム塩；４−アミノ−ｎ−酪酸、６−アミノ−ｎ−カプロン酸、８−アミノカプリル酸、１０−アミノデカン酸、１２−アミノドデカン酸、１４−アミノテトラデカン酸、１６−アミノヘキサデカン酸、１８−アミノオクタデカン酸等のω−アミノ酸などが挙げられる。中でもトリメチルドデシルアンモニウム塩、トリメチルテトラデシルアンモニウム塩、トリメチルヘキサデシルアンモニウム塩、トリメチルオクタデシルアンモニウム塩、ジメチルジドデシルアンモニウム塩、ジメチルジテトラデシルアンモニウム塩、ジメチルジヘキサデシルアンモニウム塩、ジメチルジオクタデシルアンモニウム塩、ジメチルジタロウアンモニウム塩が挙げられ、これらの有機膨潤化剤は、単独で、あるいは複数種類の混合物として使用することができる。
【００２２】
本発明においてポリアミド樹脂組成物（Ｃ）中のスメクタイト（Ｂ）の含有量は、ポリアミド（Ａ）８０〜９９．９重量部に対して、０．１〜１０重量部であることが好ましく、より好ましくは０．５〜８重量部、特に好ましくは０．８〜６重量部である。スメクタイト含有量が０．１重量部未満では、ガスバリア性の向上効果が現れない。また１０重量部より大きいと、ポリアミド樹脂組成物中にスメクタイトを均一に分散させることが困難であり、かつそれに見合ったガスバリア性の向上効果が期待できない。また得られるフィルムもヘーズが高く実用的ではない。
【００２３】
ポリアミド（Ａ）とスメクタイト（Ｂ）を溶融混練する方法については、ポリアミド樹脂の溶融重合中にスメクタイトを添加し攪拌する方法、単軸もしくは二軸押出機等の通常用いられる種々の押出機を用いて溶融混練する方法等が挙げられるが、これらのなかでも混練性に優れる点から二軸押出機を用いる方法が好ましい。その際の溶融混練温度は２２０〜３００℃、滞留時間は１２００秒以下に調整して行うことが好ましい。溶融混練温度が２２０℃を下回る場合、層状珪酸塩の分散不良が生じやすくなり、３００℃を越える場合及び滞留時間が１２００秒を越える場合は、ポリアミドの熱分解による分子量の低下やゲルが生じやすくなるため好ましくない。
【００２４】
本発明において、ポリアミド樹脂組成物（Ｃ）中に含有されるスメクタイト（Ｂ）は局所的に凝集することなく均一に分散していることが好ましい。ここでいう均一分散とは、スメクタイト（Ｂ）がポリアミド樹脂組成物（Ｃ）中において平板状に分離し、該スメクタイト間の層間距離の５０％以上が５ｎｍ以上、好ましくは６ｎｍ以上であることをいう。ここで言う層間距離とは平板状物の重心間距離を意味し、この距離が大きい程、スメクタイトの分散状態が良好と言える。層間距離が５ｎｍ以上のものが５０％未満であると、得られる二軸延伸フィルムのヘーズが高く、かつガスバリア性の向上効果が得られず、好ましくない。
【００２５】
前記ポリアミド樹脂組成物（Ｃ）の溶融粘度は、剪断速度１００／秒、温度２７０℃の条件下で、８０〜３０００Ｐａ・ｓであることが好ましく、より好ましくは１００〜２０００、特に好ましくは１５０〜１５００である。溶融粘度が８０未満では溶融粘度が低すぎるため、二軸延伸フィルムやボトル等への成形時にドローダウンや厚みムラ等の不具合を生じるため好ましくない。一方、３０００より大きいと溶融粘度が高すぎるため一般的な装置では二軸延伸フィルムやボトル等への成形が困難である。
【００２６】
前記ポリアミド樹脂組成物（Ｃ）は、水分率が０．２重量％未満であることが成形加工上有利である。水分率が０．２重量％以上であると、フィルム製造時に分子量の低下やゲル状ブツが生じやすく、さらにドローダウン等が起こりやすくなるので好ましくないので、その際は乾燥してから使用することが望ましい。ポリアミド樹脂組成物（Ｃ）の乾燥は、公知の方法により行うことができる。例えば、ベント付きの押出機でポリアミドを溶融押出する際にシリンダー内部を真空ポンプにより減圧にすることでポリマー中の水分を除去する方法、ポリアミド樹脂をタンブラー（回転式真空槽）中に仕込み、減圧下でポリマーの融点以下の温度で加熱して乾燥する方法等が挙げられるが、これに限定されるものではない。
【００２７】
また、前記ポリアミド樹脂組成物（Ｃ）には、目的を損なわない範囲で、ナイロン６、ナイロン６６、ナイロン６，６６、ポリエステル、ポリオレフィン等の他の熱可塑性樹脂をブレンドできる。また、ガラス繊維、炭素繊維などの無機充填剤、ガラスフレーク、タルク、カオリン、マイカなどの板状無機充填剤、各種エラストマー類などの耐衝撃性改質材、結晶核剤、脂肪酸アミド系、脂肪酸金属塩系化合物等の滑剤、銅化合物、有機もしくは無機ハロゲン系化合物、ヒンダードフェノール系、ヒンダードアミン系、ヒドラジン系、硫黄系化合物、リン系化合物等の酸化防止剤、熱安定剤、着色防止剤、ベンゾトリアゾール系等の紫外線吸収剤、離型剤、可塑剤、着色剤、難燃剤などの添加剤、酸素補足能を付与する化合物であるコバルト金属を含む化合物やポリアミド樹脂のゲル化防止を目的としたアルカリ化合物等の添加剤を添加することができる。
【００２８】
本発明の二軸延伸フィルムの製造方法において、前記ポリアミド樹脂組成物（Ｃ）から二軸延伸フィルムを製造する際は、下記式（１）乃至（６）を満足するように逐次二軸延伸する方法を採用することが好ましい。
【数３】

尚、式（１）〜（６）において
Ｔｇ：ポリアミド樹脂（Ａ）のガラス転移温度
Ｔ ：延伸温度
ｔ1：ｘ軸延伸に要する時間
ｔ2：ｘ軸延伸を始めてからｙ軸延伸を始めるまでの経過時間
ｔ3：ｘ軸延伸を始めてからｙ軸延伸が終了するまでの経過時間
ｘ0：延伸前のフィルムのｘ軸方向長さ
ｘ ：延伸後のフィルムのｘ軸方向長さ
ｙ0：延伸前のフィルムのｙ軸方向長さ
ｙ ：延伸後のフィルムのｙ軸方向長さ
ここで、ｘ軸とｙ軸は直交する。ｘ軸方向がＭＤ方向（シート押出方向）の時は、ｙ軸方向はＴＤ方向（シートの幅方向）を意味し、ｘ軸方向がＴＤ方向の時は、ｙ軸方向はＭＤ方向を意味する。
【００２９】
本発明の二軸延伸フィルムの製造方法において、延伸温度は、式（１）で表される範囲（Ｔｇ〜Ｔｇ＋８５℃）であることが好ましく、より好ましくはＴｇ＋５℃〜Ｔｇ＋７５℃の範囲である。延伸温度がポリアミド樹脂（Ａ）のガラス転移温度Ｔｇより低い場合、フィルムを延伸するのに極めて高い応力を必要とし、しばしばフィルムは破断するか、フィルムのヘーズが上昇し、透明性が損なわれるので好ましくない。延伸温度がガラス転移温度＋８５℃より高い場合、ポリアミド樹脂組成物（Ｃ）の結晶化速度が速まるためフィルムの延伸が困難となり、また、ヘーズが上昇しフィルムの透明性が損なわれるので好ましくない。ｘ軸延伸時の温度とｙ軸延伸時の温度は同じであっても異なっても良いが、ｙ軸延伸時の温度がｘ軸延伸時の温度より低いと、延伸応力が著しく大きくなるので均一に延伸するのが困難となり、しばしば破断の原因となる。
【００３０】
本発明の二軸延伸フィルムの製造方法では、式（２）で表される条件で延伸することが好ましい。ｔ２＝０は同時二軸延伸を意味するものであるが、同時二軸延伸ではフィルムのヘーズが上昇し、透明性に優れた二軸延伸フィルムを作製できないため好ましくない。
【００３１】
本発明の二軸延伸フィルムの製造方法において、延伸速度は、式（３）及び式（４）で表される範囲であることが好ましい。ｘ軸方向の延伸速度（式（３）に定義）とｙ軸方向の延伸速度（式（４）に定義）は同じであっても異なってもヘーズが低く透明性のよいフィルムを作成することができる。式（３）で表される延伸速度が１００％／秒未満、または式（４）で表される延伸速度が５０％／秒未満では、フィルムのヘーズが上昇し二軸延伸フィルムの透明性を損なうため好ましくない。
【００３２】
本発明の二軸延伸フィルムの製造方法において、延伸倍率は、式（５）及び式（６）で表される範囲であることが好ましい。より好ましくは２００％以上、特に好ましくは２５０％以上の範囲である。ｘ軸方向の延伸倍率（式（５）に定義）とｙ軸方向の延伸倍率（式（６）に定義）は同じであっても異なってあってもヘーズが低く透明性のあるフィルムを作成することができる。延伸倍率が１５０％未満では二軸延伸フィルムのヘーズが高く、二軸延伸フィルムの透明性が得られないので好ましくない。
【００３３】
本発明の二軸延伸フィルムの製造方法において、延伸時の予熱時間は、０〜１８０秒が好ましい。より好ましくは１０〜１５０秒、特に好ましくは２０〜１２０秒の範囲である。予熱時間が１８０秒を超えるとヘーズが上昇し二軸延伸フィルムの透明性が損なわれるため好ましくない。
【００３４】
本発明の二軸延伸フィルムは、ポリアミド樹脂組成物（Ｃ）からなる層のＣｕＫα線によるＸ線回折測定を行った際のＸ線回折パターンにおいて、回折角２θが１５°〜２５°の範囲で２つの強いピークが観察され、かつその２つのピークのうち、低角側のピーク強度をＰとし、高角側のピーク強度をＱとした場合、次式で求められる相対強度比が６０以下であることが好ましく、５〜５０の範囲内であればより好ましい。相対強度比が６０より大きい場合、ガスバリア性の改善効果は得られるが、ヘーズが高くなり実用性に欠けるため好ましくない。
相対強度比＝（Ｑ／Ｐ）×１００
前述のθは波長λのＸ線が面間隔ｄの格子面によって回折されるときの角度でブラッグ角（入射角、反射角とも呼ばれる）を示し、２θは回折角と呼ばれる。
【００３５】
なお前述のＸ線回折測定におけるピーク位置は、測定により得られたプロファイルをＳａｖｉｔｚｋｙとＧｏｌａｙの平滑化法により平滑化処理後、Ｓｏｎｎｅｖｅｌｔ−Ｖｉｓｓｅｒ法によってバックグラウンド除去を行い、Ｒａｃｈｉｎｇｅｒ法を用いてＫα２線の除去を行って得られた強度データの二次微分を取り、その極小値をピーク位置として求める。ピーク強度ＰおよびＱは、バックグラウンドの位置からピーク位置までの高さを計算して求めたものを採用する。
【００３６】
本発明において、低角側のピークに対応する面間隔ｄはおよそ４．７Å、高角側のピークに対応する面間隔ｄはおよそ４．２Åである（表４、表６参照）。一般に結晶構造は格子面と面間隔などにより表現されるが、参考文献（Ｔ．Ｏｈｔａ ｅｔ ａｌ．ＰＯＬＹＭＥＲ，１９９２，Ｖｏｌ．３３，Ｎｏ．８，１６２０−１６２２）によれば、ポリメタキシリレンアジパミドの結晶構造は格子面（１００）で面間隔ｄが４．７２Å、格子面（０１０）で面間隔ｄが４．２０Å、格子面（１１０）で面間隔ｄが４．１７Åとなっている。
【００３７】
このことから、本発明においても、低角側のピークは格子面（１００）、高角側のピークは格子面（０１０）および（１１０）を表しているものと考えられる。格子面（１００）は水素結合によって結びついた面、すなわちポリメタキシリレンアジパミドの折り畳み構造を示していると言われている。格子面（０１０）および（１１０）はポリメタキシリレンアジパミドの折り畳み構造以外の構造を示している。相対強度比が６０より大きいということは、ポリメタキシリレンアジパミド中で、格子面（０１０）および（１１０）の結晶構造が多く、結晶構造が乱れていることを示す。
【００３８】
メタキシリレンジアミンを７０モル％以上含むジアミン成分と、炭素数４〜２０のα，ω−直鎖脂肪族ジカルボン酸を７０モル％以上含むジカルボン酸成分とを重縮合して得られるポリアミド（Ａ）の場合は、低角側のピーク強度Ｐに対する高角側のピーク強度Ｑの比（相対強度比＝（Ｑ／Ｐ）×１００）が６０以上であっても、ヘーズが上昇し透明性が損なわれることはない。
【００３９】
しかし、ポリアミド（Ａ）とスメクタイト（Ｂ）を溶融混練してなるポリアミド樹脂組成物（Ｃ）からなる二軸延伸フィルムの場合は、スメクタイトが結晶の核となることから、分散したスメクタイトを中心として球晶が発達しやすく、ヘーズが上昇し、フィルムが白化する。特に格子面（０１０）および（１１０）が多く存在すると、これらはラメラ、およびそれからなる球晶の生長出発点となることから、スメクタイトの結晶核効果と相まって、ポリメタキシリレンアジパミド結晶中に球晶が多く存在し、球晶の生長が促進されることから、それに伴いヘーズが上昇しているものと思われる。
【００４０】
そこで本発明の方法ではポリアミド樹脂組成物（Ｃ）からなる二軸延伸フィルム中の格子面（０１０）および（１１０）で表される結晶構造を抑制し、選択的に格子面（１００）で表される結晶構造を増加させることで、結晶性を制御し、配向度の増加、球晶生長の抑制等ができる。それに伴い、延伸時の白化を防止し、ヘーズの低い透明性の優れる二軸延伸フィルムが作製できるものである。
【００４１】
本発明のフィルムの製造方法は特に制限はなく、ポリアミド樹脂組成物を溶媒に溶かした後、乾燥させ溶媒を除去する方法、単軸延伸、二軸延伸する方法などの公知公用の方法を用いて製造することができるが、工業的に製造が容易であり、生産性に優れることから、逐次二軸延伸が特に好ましい。
【００４２】
また、本発明においては、二軸延伸方法として、Ｔダイ法、あるいはリング状ダイにより筒状に押し出し後、空冷または水冷するチューブラー法等の公知の各方法で作製したシートを、テンター法、チューブラー法などの公知の方法を適用して延伸することができる。
【００４３】
本発明の二軸延伸フィルムは、そのままで使用してもよく、また、特定方向の物理的特性を向上させるためにさらに任意の方向に延伸しても良い。また延伸後のフィルムに熱的安定性をさらに付与するために、必要により該フィルムを熱処理することができる。
【００４４】
本発明の二軸延伸フィルムのヘーズは、１０％／２０μｍ以下であり、良好な透明性を示す。
また、本発明の二軸延伸フィルムの酸素透過係数は、２３℃／６０％ＲＨ（相対湿度）で０．５（mlmm/m²dayMPa）未満であり、ガスバリア性も良好である。
このように、本発明の二軸延伸フィルムは、酸素バリア性、透明度に優れ、酸素バリア性、透明性が必要な包装資材用二軸延伸フィルムとして、好適な材料とすることができる
【００４５】
本発明の二軸延伸フィルムは、機械物性の向上効果を付与するためなどの目的で熱可塑性樹脂と多層フィルムにすることができる。熱可塑性樹脂として特に制限はなく、例えば、低密度ポリエチレン、中密度ポリエチレン、高密度ポリエチレン等のポリエチレン類、プロピレンホモポリマー、プロピレン−エチレンブロックコポリマー、プロピレン−エチレンランダムコポリマー等のポリプロピレン類、エチレン−ブテン共重合体、エチレン−ヘキセン共重合体、エチレン−オクテン共重合体、エチレン−酢酸ビニル共重合体、エチレン−メチルメタクリレート共重合体、プロピレン−α−オレフィン共重合体、ポリブテン、ポリペンテン、アイオノマー樹脂等の各種ポリオレフィン類、ポリスチレン、ポリエチレンテレフタレート等のポリエステル樹脂、ナイロン６、ナイロン６６等のポリアミド樹脂等が挙げられる。多層構造の場合、必要に応じて変性ポリオレフィン樹脂等からなる接着性樹脂層を各樹脂層間に積層しても良い。多層フィルムは公知の公知の方法で製造でき、例えば、Ｔダイ法、インフレーション法等の共押出法、無延伸又は延伸フィルムを押出ラミネートやドライラミネート等により積層する方法でも良い。
【００４６】
本発明の二軸延伸フィルムは、優れた透明性、ガスバリア性を付与する包装材料として、例えば、単層あるいは他の樹脂を積層した多層構造のラップ、あるいは各種形状のパウチ、容器の蓋材等に利用できる。該二軸延伸フィルムを利用して得られた包装容器は、ガスバリア性に優れ、かつ透明性に優れたものであり、また、種々の物品を収納することができる。例えば、炭酸飲料、ジュース、水、牛乳、日本酒、ウイスキー、焼酎、コーヒー、茶、ゼリー飲料、健康飲料等の液体飲料、調味液、ソース、醤油、ドレッシング、液体だし、マヨネーズ、味噌、すり下ろし香辛料等の調味料、ジャム、クリーム、チョコレートペースト等のペースト状食品、液体スープ、煮物、漬物、シチュー等の液体加工食品に代表される液体系食品やそば、うどん、ラーメン等の生麺及びゆで麺、精米、調湿米、無洗米等の調理前の米類や調理された炊飯米、五目飯、赤飯、米粥等の加工米製品類、粉末スープ、だしの素等の粉末調味料等に代表される高水分食品、乾燥野菜、コーヒー豆、コーヒー粉、お茶、穀物を原料としたお菓子等に代表される低水分食品、その他農薬や殺虫剤等の固体状や溶液状の化学薬品、液体及びペースト状の医薬品、化粧水、化粧クリーム、化粧乳液、整髪料、染毛剤、シャンプー、石鹸、洗剤等、種々の物品を収納することができる。
【００４７】
【実施例】
以下、実施例等により本発明を具体的に説明するが、本発明はこれらの実施例に限定されない。尚、実施例等において、ポリアミド樹脂組成物、二軸延伸フィルム等の評価方法は、下記の方法によった。
（１）ポリアミド樹脂の末端アミノ基濃度
ポリアミド樹脂０．３〜０．５ｇを精秤し、フェノール／エタノール＝４／１容量溶液３０ｃｃに２０〜３０℃で撹拌溶解した。完全に溶解した後、三菱化学（株）製自動滴定装置を用いて、Ｎ／１００塩酸水溶液で中和滴定して求めた。
（２）ポリアミド樹脂の末端カルボキシル基濃度
ポリアミド０．３〜０．５ｇを精秤し、ベンジルアルコール３０ｍｌに窒素気流下１６０〜１８０℃でポリアミドを攪拌下に溶解した。ポリアミドが完全に溶解した後、窒素気流下８０℃まで冷却し、攪拌しながらメタノール１０ｍｌを加え、Ｎ／１００水酸化ナトリウム水溶液で中和滴定して求めた。
（３）ポリアミド樹脂の相対粘度
ポリアミド１ｇを精秤し、９６％硫酸１００ｃｃに２０〜３０℃で撹拌溶解した。完全に溶解した後、速やかにキャノンフェンスケ型粘度計に溶液５ｃｃを取り、２５℃±０．０３℃の恒温槽中で１０分間放置後、落下時間（ｔ）を測定した。また、９６％硫酸そのものの落下時間（ｔ０）も同様に測定した。ｔ及びｔ０から次式により相対粘度を算出した。
相対粘度＝（ｔ）／（ｔ０）
（４）水分率
三菱化学（株）製微量水分測定装置ＣＡ−０５を用いて、窒素雰囲気下、２３５℃、５０分の条件で測定を行った。
（５）ヘーズ
二軸延伸フィルムについて日本電色工業（株）製、色差・濁度測定器ＣＯＨ−３００Ａを使用し、ＡＳＴＭ Ｄ１００３に準じて二軸延伸フィルムのヘーズを測定した。
（６）酸素透過係数
二軸延伸フィルムについてＡＳＴＭ Ｄ３９８５に準じて測定した。測定はモダンコントロール社製、型式：ＯＸ−ＴＲＡＮ １０／５０Ａを使用し、２３℃、相対湿度６０％の雰囲気下にて行った。
（７）Ｘ線回折
測定は理学社製ミニフレックスを使用した。Ｘ線源にはＣｕＫαを用い、散乱スリットは４．２度、受光スリットは０．３ｍｍ、管電圧３０ｋＶ管電流１５ｍＡ、走査範囲は２〜５０度、サンプリング幅は０．０２度、走査速度５度／分の条件で測定した。
尚、本実施例、比較例で使用した層状珪酸塩の商品名は以下の通りである。
モンモリロナイト： 白石工業（株）製「ＮＥＷ−Ｄオルベン」（膨潤化剤として、ジメチルジオクタデシルアンモニウムを４２ｗｔ％含有）
【００４８】
以下の実施例及び比較例において、ポリアミド（Ａ）としては、メタキシリレンジアミンとアジピン酸から合成したナイロンＭＸＤ６（ポリアミドＡ１及びポリアミドＡ２）を使用した。これらのポリアミドの性状を表１に示す。
【００４９】
【表１】

【００５０】
実施例１
ポリアミドＡ１ ９７重量部と、モンモリロナイト（白石工業（株）製、商品名「ＮＥＷ Ｄ ＯＲＢＥＮ」）３重量部とをドライブレンドした後、該混合物を供給速度６ｋｇ／時間でシリンダー径３７ｍｍの二軸押出機に供給した。シリンダー温度２４０℃、スクリュー回転数５００ｒｐｍの条件で溶融混練を行い、溶融ストランドを冷却エアーにて冷却、固化した後、ペレタイズした。
上記で得られたペレットを供給速度１．２ｋｇ／時間でシリンダー径２０ｍｍのＴダイ付き二軸押出機に供給した。シリンダー温度２５０℃、スクリュー回転数１００ｒｐｍの条件で溶融混練を行った後、Ｔダイを通じてフィルム状物を押出し０．７ｍ／分の速さで引き取りながら７２℃の冷却ロール上で固化し、厚さ２８０μｍのシートを得た。
さらにこのシートを東洋精機製二軸延伸機にて延伸温度１１０℃、予熱３０秒、延伸速度１００％／秒（ｘ軸方向、ｙ軸方向とも）、ｘ軸延伸に要する時間（ｔ１）が３．６秒、ｘ軸延伸を始めてからｙ軸延伸を始めるまでの経過時間（ｔ２）が２．４秒、ｘ軸延伸を始めてからｙ軸延伸が終了するまでの経過時間（ｔ３）が６．０秒の条件下で３．６×３．６倍に逐次延伸後、熱処理した。熱処理は、延伸後のフィルムを２０ｃｍ四方の穴のあいた２枚のステンレス版に挟みクランプで固定後、２４０℃に設定した精密恒温器ＤＦ６２中で５秒間保持することによって行った。得られた二軸延伸フィルムの評価結果を表２に示す。
【００５１】
実施例２
ｔ１を２．０秒、ｔ２を１．４秒、ｔ３を３．４秒とし、延伸速度をｘ軸方向、ｙ軸方向とも１８０％／秒とした以外は、実施例１と同様に二軸延伸フィルムを作成した。結果を表２に示す。
【００５２】
実施例３
ポリアミドＡ２ ９７重量部と、モンモリロナイト（白石工業（株）製、商品名「ＮＥＷ Ｄ ＯＲＢＥＮ」）３重量部とをドライブレンドした後、該混合物を供給速度１２ｋｇ／時間にてシリンダー径３７ｍｍの二軸押出機に供給した。シリンダー温度２７０℃、スクリュー回転数３００ｒｐｍの条件で溶融混練を行い、溶融ストランドを冷却エアーにて冷却、固化した後、ペレタイズした。
上記で得られたペレットを供給速度１．２ｋｇ／時間にてシリンダー径２０ｍｍのＴダイ付き二軸押出機に供給した。シリンダー温度２５０℃、スクリュー回転数１００ｒｐｍの条件で溶融混練を行った後、Ｔダイを通じてフィルム状物を押出し０．７ｍ／分の速さで引き取りながら７２℃の冷却ロール上で固化し、厚さ２８０μｍのシートを得た。
さらにこのシートを東洋精機製二軸延伸機にて延伸温度１２０℃、予熱３０秒、延伸速度１８０％／秒、ｔ１が２．０秒、ｔ２が１．４秒、ｔ３が３．４秒の条件下で３．６×３．６倍に二軸延伸し、２４０℃で５秒間熱処理した。得られた二軸延伸フィルムの評価結果を表２に示す。
【００５３】
【表２】

【００５４】
実施例４
延伸倍率を、４．０×２．５倍、ｔ１を２．２秒、ｔ２を１．６秒、ｔ３を３．０秒とした以外は、実施例３と同様に二軸延伸フィルムを作成した。結果を表３に示す。
また、得られたフィルムのＸ線回折におけるピーク強度を表４に示す。
【００５５】
実施例５
延伸倍率を、３．０×３．０倍、ｔ１を１．７秒、ｔ２を１．１秒、ｔ３を２．８秒とした以外は、実施例３と同様に二軸延伸フィルムを作成した。結果を表３に示す。
【００５６】
実施例６
熱処理条件を、２００℃で３０秒間とした以外は、実施例４と同様に二軸延伸フィルムを作成した。結果を表３に示す。
【００５７】
【表３】

【００５８】
【表４】

【００５９】
比較例１
延伸速度をｘ軸方向、ｙ軸方向とも６０％／秒、ｔ２を４．３秒ととした以外は、実施例１と同様に二軸延伸フィルムを作成した。結果を表５に示す。
【００６０】
比較例２
延伸速度をｘ軸方向、ｙ軸方向とも８０％／秒、ｔ２を３．２秒とした以外は、実施例１と同様に二軸延伸フィルムを作成した。結果を表５に示す。
【００６１】
比較例３
延伸速度をｘ軸方向、ｙ軸方向とも５０％／秒とし、同時二軸延伸した以外は、実施例１と同様に二軸延伸フィルムを作成した。結果を表５に示す。また、得られた二軸延伸フィルムのＸ線回折におけるピーク強度を表６に示す。
【００６２】
【表５】

【００６３】
【表６】

【００６４】
比較例４
実施例３と同様に作成したシートを東洋精機製二軸延伸機にて延伸温度８０℃、予熱３０秒、延伸速度１８０％／秒の条件下で延伸倍率を３×３倍として延伸を試みたが、フィルムが破断し延伸は不可能であった。
【００６５】
以上の実施例及び比較例で説明したように、本発明の範囲内でポリアミド樹脂組成物（Ｃ）を二軸延伸した実施例１乃至６は、透明性に優れ、得られた製品のガスバリア性も優れたものであった。一方、延伸速度が式（３）を満たしていない比較例１及び比較例２ではフィルムのヘーズが上昇し、透明性に劣っていた。式（２）、式（３）を満たしていないで比較例３ではフィルムのヘーズが上昇し、透明性に劣っていた。式（１）を満たしていない比較例４はフィルムが破断し、フィルムを得ることができなかった。
【００６６】
実施例７
シリンダー径が４５ｍｍの押出機から直鎖状低密度ポリエチレン（Ｉ層を構成する。三井化学（株）製、商品名：ウルトゼックス２０２２Ｌ、以下ＬＬＤＰＥと略記することがある）、シリンダー径が３０ｍｍの押出機から実施例３で得られたポリアミド樹脂組成物（Ｃ）ペレット（II層を構成）をそれぞれ、２００〜２１０℃、２４０〜２７０℃で押出し、層構成がＩ層／II層／Ｉ層の順になるようにフィードブロックを介して多層溶融状態を形成させ、円筒ダイ−水冷インフレーション法により、多層フィルムを作製した。得られた多層フィルムを、チューブラー法にて、延伸温度１２０℃、予熱３０秒、延伸速度１８０％／秒、ｔ１が２．０秒、ｔ２が１．４秒、ｔ３が３．４秒の条件下で３．６×３．６倍に二軸延伸し、２４０℃で５秒間熱処理した。得られた多層二軸延伸フィルムの評価結果を表７に示す。なお、相対強度比は多層フィルムよりＩ層だけ取り出しＸ線回折を行った結果を示す。
【００６７】
実施例８
シリンダー径が４５ｍｍの押出機から直鎖状低密度ポリエチレン（Ｉ層を構成する。三井化学（株）製、商品名：ウルトゼックス２０２２Ｌ、以下ＬＬＤＰＥと略記することがある）、シリンダー径が３０ｍｍの押出機から実施例３で得られたポリアミド樹脂組成物（Ｃ）ペレット（II層を構成）をそれぞれ、２００〜２１０℃、２４０〜２７０℃で押出し、層構成がＩ層／II層／Ｉ層の順になるようにフィードブロックを介して多層溶融状態を形成させ、Ｔダイを通じてフィルム状物を押出し多層フィルムを作製した。さらにこのフィルムを東洋精機製二軸延伸機にて延伸温度１２０℃、予熱３０秒、延伸速度１８０％／秒、ｔ１が２．０秒、ｔ２が１．４秒、ｔ３が３．４秒の条件下で３．６×３．６倍に二軸延伸し、２４０℃で５秒間熱処理した。得られた多層二軸延伸フィルムの評価結果を表７に示す。なお、相対強度比は多層フィルムよりＩ層だけ取り出しＸ線回折を行った結果を示す。
【００６８】
実施例９
シリンダー径が４５ｍｍの押出機からポリエチレンテレフタラート（Ｉ層を構成する。日本ユニペット（株）製、商品名ＰＥＴ５４３Ｃ：、以下ＰＥＴと略記することがある）、シリンダー径が３０ｍｍの押出機から実施例３で得られたポリアミド樹脂組成物（Ｃ）ペレット（II層を構成）をそれぞれ、２６０〜２９０℃、２４０〜２７０℃で押出し、層構成がＩ層／II層／Ｉ層の順になるようにフィードブロックを介して多層溶融状態を形成させ、Ｔダイを通じてフィルム状物を押出し多層フィルムを作製した。さらにこのシートを東洋精機製二軸延伸機にて延伸温度１２０℃、予熱３０秒、延伸速度１８０％／秒、ｔ１が２．０秒、ｔ２が１．４秒、ｔ３が３．４秒の条件下で３．６×３．６倍に二軸延伸し、２４０℃で５秒間熱処理した。得られた多層二軸延伸フィルムの評価結果を表７に示す。なお、相対強度比は多層フィルムよりＩ層だけ取り出しＸ線回折を行った結果を示す。
【００６９】
比較例５
実施例８で得た多層フィルムを東洋精機製二軸延伸機にて延伸温度１２０℃、予熱３０秒、延伸速度１１０％／秒、ｔ２が０秒の条件下で３．６×３．６倍に二軸延伸し、２４０℃で５秒間熱処理した。得られた多層二軸延伸フィルムの評価結果を表７に示す。なお、相対強度比は多層フィルムよりＩ層だけ取り出しＸ線回折を行った結果を示す。
【００７０】
【表７】

【００７１】
以上の実施例及び比較例で説明したように、本発明の範囲内でポリアミド樹脂組成物（Ｃ）を含む多層フィルムを二軸延伸した実施例７乃至９は、透明性に優れ、ガスバリア性も優れたものであった。一方、式（２）を満たしていないで比較例５ではフィルムのヘーズが上昇し、透明性に劣っていた。
【００７２】
【発明の効果】
本発明のポリアミド樹脂組成物から得られる二軸延伸フィルム、それからなる包装容器は、優れたガスバリア性を有し、かつ透明性に優れるものであり、従来のもの以上にその商品価値は高く、工業的に優れたものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biaxially stretched film having gas barrier properties and a method for producing the same. Specifically, the present invention relates to a biaxially stretched film made of a polyamide resin composition in which a specific amount of smectite is dispersed.
[Prior art]
[0002]
Polyamide is excellent in mechanical performance and processability and has a relatively high gas barrier property. Therefore, it is not only used as an injection molding material for automobiles and electrical and electronic parts, but also as a packaging material for foods, beverages, chemicals, and electronic parts. Widely used. Among polyamides, polymetaxylylene adipamide (hereinafter sometimes referred to as “nylon MXD6”) obtained by polycondensation from a diamine component mainly composed of metaxylylenediamine and a dicarboxylic acid component mainly composed of adipic acid, It shows low permeability compared to other polyamides for gaseous substances such as oxygen and carbon dioxide, so it is recommended for use as a material for packaging materials such as films and bottles that require gas barrier properties. ing. However, in recent years, there has been an increasing demand for packaging materials that can maintain the freshness of foods, beverages, and the like for a longer period of time, and nylon MXD6 is also required to have further improved gas barrier performance.
[0003]
As one method for improving the gas barrier performance of polyamide, a method of kneading a polyamide resin and a layered silicate using an extruder or the like is disclosed (for example, see Patent Document 1). According to these methods, since layered silicate can be mixed and dispersed in nylon MXD6, there is a description that the molded article such as a film has improved gas barrier properties and good whitening resistance. However, the whitening resistance can only be applied to limited resins such as lactams. For example, in a polyamide obtained from a polycondensation reaction between xylylenediamine and an aliphatic dicarboxylic acid, the haze of an unstretched film is practical. Even in a certain range, the haze increases when processed into a biaxially stretched film, and thus a biaxially stretched film satisfying both gas barrier properties and transparency could not be obtained. In addition, a method for obtaining a polyamide composite material having good transparency by mixing a polyamide monomer and a clay mineral, followed by polymerization and adding a deterioration preventing agent or a colorant and continuing the polymerization is disclosed (for example, Patent Documents). 2). However, the above-described method can be applied only to a limited resin such as lactam, and has a problem that it cannot be applied to, for example, a polyamide obtained from a polycondensation reaction between xylylenediamine and an aliphatic dicarboxylic acid.
[0004]
[Patent Document 1]
JP-A-2-305828
[Patent Document 2]
Japanese Patent No. 2572234
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a biaxially stretched film that solves the above problems, has good gas barrier properties, and is excellent in transparency.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention comprise a polyamide resin composition obtained by melt-kneading a polyamide having specific properties and a smectite composition treated with an organic swelling agent. The biaxially stretched film selectively imparted with a specific crystal structure was found to be excellent not only in gas barrier properties but also in transparency that could not be solved in the past, and completed the present invention. .
[0007]
That is, the present invention polycondenses a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 70 mol% or more of an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. A biaxially stretched film comprising a polyamide resin composition (C) obtained by melt-kneading polyamide (A) and smectite (B) obtained in the above, or comprising at least one layer comprising a polyamide resin composition (C). From the polyamide resin composition (C), the polyamide (A) in the polyamide resin composition (C) is in the range of 80 to 99.9 parts by weight, the smectite (B) is in the range of 0.1 to 10 parts by weight. In the X-ray diffraction pattern of CuKα ray of the layer to be formed, the intensity ratio (relative intensity ratio) between the highest intensity peak observed in the diffraction angle 2θ range of 15 ° to 25 ° and the next highest intensity peak. ( Q / P ) × 100) is 60 or less (however, P Is the peak intensity on the low angle side of the peak, Q Is a high-angle side peak intensity), and a packaging container using at least a part of the biaxially stretched film.
Further, the present invention polycondenses a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 70 mol% or more of an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. A biaxially stretched film comprising a polyamide resin composition (C) obtained by melt-kneading the polyamide (A) and smectite (B) obtained in this manner, or comprising at least one layer comprising the polyamide resin composition (C) is produced. The present invention relates to a method for producing a biaxially stretched film, characterized by sequentially biaxially stretching under production conditions that simultaneously satisfy the following formulas (1) to (6).
[Expression 2]

In the equations (1) to (6)
Tg: Glass transition temperature of polyamide resin (A)
T: Stretching temperature
t1: Time required for x-axis stretching
t2: Elapsed time from starting x-axis stretching to starting y-axis stretching
t3: Elapsed time from the start of x-axis stretching to the end of y-axis stretching
x0: length in the x-axis direction of the film before stretching
x: length of the stretched film in the x-axis direction
y0: length in the y-axis direction of the film before stretching
y: length in the y-axis direction of the stretched film
Here, the x axis and the y axis are orthogonal. When the x-axis direction is the MD direction (sheet extrusion direction), the y-axis direction means the TD direction (sheet width direction), and when the x-axis direction is the TD direction, the y-axis direction means the MD direction. .
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is described in detail below. The polyamide (A) used in the present invention polymerizes a diamine component mainly composed of metaxylylenediamine and a dicarboxylic acid component mainly composed of an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. It is a polyamide obtained by doing.
[0009]
The diamine component used in the present invention contains metaxylylenediamine at 70 mol% or more, preferably 75 mol% or more, more preferably 80 mol% or more. When the amount of metaxylylenediamine in the diamine component is less than 70 mol%, the gas barrier property of the polyamide (A) is lowered, which is not preferable. Examples of diamine components that can be used in addition to metaxylylenediamine in the present invention include tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, Aliphatic diamines such as dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis ( Aminomethyl) cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis (4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminomethyl) Caroline, alicyclic diamines such as bis (aminomethyl) tricyclodecane, diamines having aromatic rings such as bis (4-aminophenyl) ether, paraphenylenediamine, paraxylylenediamine, bis (aminomethyl) naphthalene, etc. However, the present invention is not limited to these examples.
[0010]
The dicarboxylic acid component used in the present invention contains an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms in an amount of 70 mol% or more, preferably 75 mol% or more, more preferably 80 mol% or more. If the α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the dicarboxylic acid component is less than 70 mol%, the crystallinity of the polyamide (A) is lowered and the gas barrier property of the polyamide (A) is lowered. It is not preferable. Examples of the α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms used in the present invention include succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecanedioic acid, Aliphatic dicarboxylic acids such as dodecanedioic acid can be exemplified, but among these, adipic acid is preferred. In the present invention, aromatic dicarboxylic acids exemplified by terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid and the like can be added as dicarboxylic acids other than the α, ω-linear aliphatic dicarboxylic acid. Furthermore, a small amount of monoamine or monocarboxylic acid may be added as a molecular weight regulator during the polycondensation of the polyamide resin (A).
[0011]
The polyamide (A) is produced by a melt polycondensation method. For example, it is manufactured by a method in which a nylon salt composed of metaxylylenediamine and adipic acid is heated in the presence of water in a pressurized state and polymerized in a molten state while removing added water and condensed water. Further, it is also produced by a method in which metaxylylenediamine is directly added to molten adipic acid and polycondensed under normal pressure. In this case, in order to keep the reaction system in a uniform liquid state, metaxylylenediamine is continuously added to adipic acid, and during this time, the reaction system is raised so that the reaction temperature does not fall below the melting point of the generated oligoamide and polyamide. The polycondensation proceeds while warming.
[0012]
The number average molecular weight of the polyamide (A) is preferably 10,000 to 50,000, and more preferably 15,000 to 45,000. The number average molecular weight here means the terminal amino group concentration of the polyamide (A) [NH. ₂ ] (Μ equivalent / g) and terminal carboxyl group concentration [COOH] (μ equivalent / g) were determined by neutralization titration using hydrochloric acid or aqueous sodium hydroxide solution, and calculated by the following equation.
Number average molecular weight = 2000000 / ([COOH] + [NH ₂ ])
[0013]
When the number average molecular weight is less than 10,000, the melt viscosity is too low, so that when the polyamide (A) and the smectite (B) are melt-kneaded using an extruder, the smectite is not subjected to sufficient shearing stress, This is not preferable because the dispersion becomes insufficient. On the other hand, if the number average molecular weight is larger than 50,000, the melt viscosity is too high, so that polyamide (A) and smectite (B) cannot be melt-kneaded with a normal apparatus.
Relative viscosity can be used as an index representing the number average molecular weight of polyamide (A). The relative viscosity is a value obtained by dissolving 1 g of polyamide in 100 ml of 96% sulfuric acid and measuring it at 25 ° C. using a Canon Fenceke viscometer or the like. The relative viscosity of the polyamide (A) of the present invention is in the range of 1.6 to 4.4.
[0014]
Moreover, in order to obtain polyamide (A), the above-mentioned diamine component and dicarboxylic acid component have a reaction molar ratio (number of moles of reacted diamine / number of moles of reacted dicarboxylic acid) of 0.990 to 1.000. It is preferable to carry out polycondensation with. The reaction molar ratio is more preferably in the range of 0.991 to 0.999, particularly preferably in the range of 0.992 to 0.998. When the reaction molar ratio is larger than 1.000, excessive terminal amino groups contribute to haze increase, gel generation at the time of extrusion, and the like, and thus a biaxially stretched film having stable transparency cannot be produced. If it is less than 0.990, the molecular weight of the polyamide (A) is small and the viscosity is small, so that not only smectite dispersion failure is likely to occur, but also problems such as drawdown and thickness unevenness during molding into films and bottles, etc. Since it occurs, it is not preferable. Here, the reaction molar ratio (r) is obtained by the following equation.
r = (1-cN-b (CN)) / (1-cC + a (CN))
Where a: M ₁ / 2
b: M ₂ / 2
c: 18.015
M ₁ : Molecular weight of diamine (g / mol)
M ₂ : Molecular weight of dicarboxylic acid (g / mol)
N: Terminal amino group concentration (equivalent / g)
C: Terminal carboxyl group concentration (equivalent / g)
[0015]
The polyamide (A) preferably has a terminal amino group concentration of 1 to 60 μeq / g, more preferably 5 to 55 μeq / g, and particularly preferably 10 to 50 equivalents / g. When the terminal amino group concentration is higher than 60 μequivalent / g, the haze of the biaxially stretched film made of the polyamide resin composition (C) increases. By defining the terminal amino group concentration to a specific value, an increase in haze can be suppressed and stable transparency can be obtained, so that the industrial value and commercial value of the obtained product can be increased.
The terminal carboxyl group concentration of the polyamide (A) may be a value satisfying the number average molecular weight and the reaction molar ratio.
[0016]
A phosphorous compound can be added to the polyamide (A) in order to increase the processing stability during melt molding or to prevent the polyamide resin from being colored. As the phosphorus compound, a phosphorus compound containing an alkali metal or an alkaline earth metal is preferably used. For example, an alkali metal or alkaline earth metal phosphate such as sodium, magnesium, calcium, hypophosphite, phosphorus Acid salts may be mentioned, but those using alkali metal or alkaline earth metal hypophosphites are particularly preferred because they are particularly excellent in the anti-coloring effect of polyamide. The density | concentration of a phosphorus compound is 500 ppm or less as a phosphorus atom density | concentration in a polyamide (A), Preferably it is 350 ppm or less, More preferably, it is 200 ppm or less. Even if the phosphorus atom concentration exceeds 500 ppm, there is no change in the anti-coloring effect. Rather, the haze of the biaxially stretched film obtained by using this increases, which is not preferable.
[0017]
In addition, it is advantageous in terms of molding processing that the moisture content of the polyamide (A) is less than 0.2% by weight. When the moisture content of the polyamide (A) is 0.2% by weight or more, not only the dispersibility of the smectite is lowered, but also the molecular weight is lowered and the gel-like stuff tends to be generated. . The polyamide (A) can be dried by a known method. For example, when melt-extruding polyamide with a vented extruder, the inside of the cylinder is depressurized with a vacuum pump to remove the water in the polymer, and the polyamide resin is charged into a tumbler (rotary vacuum tank) and decompressed. Although the method of drying by heating at the temperature below the melting point of a polymer below etc. is mentioned, it is not limited to this.
[0018]
In the present invention, the content of the polyamide (A) in 100 parts by weight of the polyamide resin composition (C) is preferably 80 to 99.9 parts by weight, and more preferably 85 to 99 parts by weight. If the polyamide content is less than 80 parts by weight, the transparency of the biaxially stretched film is impaired. On the other hand, when the amount is larger than 99.9 parts by weight, a sufficient amount of smectite cannot be blended, and the gas barrier property cannot be improved.
[0019]
The smectite (B) used in the present invention is a 2-octahedron or 3-octahedral layered silicate having a charge density of 0.25 to 0.6. As the 2-octahedron type, montmorillonite is used. Examples of 3-octahedron types such as beidellite and nontronite include hectorite and saponite. Among these, montmorillonite is preferable because it has high swellability, and osmotic swelling occurs and the interlayer is likely to spread, and thus is easily dispersed in the polyamide resin composition (C).
[0020]
When the smectite (B) is blended in the present invention, the layered silicate can be mixed with the polyamide (A) using the layered silicate as it is, but the organic swelling agent is previously brought into contact with the layered silicate to form the layered silicate. It is preferable to use a material having an expanded interlayer because the smectite is well dispersed in the polyamide. In this case, the smectite composition containing the organic swelling agent in smectite is mixed with the polyamide (A). However, in the present invention, the content of the organic swelling agent is 50% by weight or less in the smectite composition. It is preferred to use some. When the content of the organic swelling agent is more than 50% by weight, the haze of the film made of the polyamide resin composition (C) increases, which is not preferable.
[0021]
As the organic swelling agent, a quaternary ammonium salt can be preferably used. More preferably, a quaternary ammonium salt having at least one alkyl group or alkenyl group having 12 or more carbon atoms is used. Specific examples of the organic swelling agent include trimethyl alkyl ammonium salts such as trimethyl dodecyl ammonium salt, trimethyl tetradecyl ammonium salt, trimethyl hexadecyl ammonium salt, trimethyl octadecyl ammonium salt and trimethyl eicosyl ammonium salt; trimethyl octadecenyl Trimethyl alkenyl ammonium salts such as ammonium salt and trimethyl octadecadienyl ammonium; triethyl alkyl ammonium salts such as triethyl dodecyl ammonium salt, triethyl tetradecyl ammonium salt, triethyl hexadecyl ammonium salt and triethyl octadecyl ammonium; tributyl dodecyl ammonium salt and tributyl tetra Decyl ammonium salt, tributyl hexadecyl ammonium salt Tributylalkylammonium salts such as tributyloctadecylammonium; dimethyldialkylammonium salts such as dimethyldidodecylammonium salt, dimethylditetradecylammonium salt, dimethyldihexadecylammonium salt, dimethyldioctadecylammonium salt, dimethylditallowammonium salt; Dimethyldialkenylammonium salts such as octadecenylammonium salt and dimethyldioctadecadienylammonium salt; diethyls such as diethyldidodecylammonium salt, diethylditetradecylammonium salt, diethyldihexadecylammonium salt, diethyldioctadecylammonium salt Dialkyl ammonium salt; dibutyl didodecyl ammonium salt, dibutyl ditetradecyl ammonium salt, Dibutyl dialkyl ammonium salts such as butyl dihexadecyl ammonium salt and dibutyl dioctadecyl ammonium salt; methyl benzyl dialkyl ammonium salts such as methyl benzyl dihexadecyl ammonium salt; dibenzyl dialkyl ammonium salts such as dibenzyl dihexadecyl ammonium salt; Trialkylmethylammonium salts such as dodecylmethylammonium salt, tritetradecylmethylammonium salt, trioctadecylmethylammonium salt; trialkylethylammonium salts such as tridodecylethylammonium salt; trialkylbutylammonium salts such as tridodecylbutylammonium salt 4-amino-n-butyric acid, 6-amino-n-caproic acid, 8-aminocaprylic acid, 10-aminodecanoic acid, 12-amino Ω-amino acids such as dodecanoic acid, 14-aminotetradecanoic acid, 16-aminohexadecanoic acid, 18-aminooctadecanoic acid and the like. Among them, trimethyldodecyl ammonium salt, trimethyl tetradecyl ammonium salt, trimethyl hexadecyl ammonium salt, trimethyl octadecyl ammonium salt, dimethyl didodecyl ammonium salt, dimethyl ditetradecyl ammonium salt, dimethyl dihexadecyl ammonium salt, dimethyl dioctadecyl ammonium salt, dimethyl Examples include ditallow ammonium salts, and these organic swelling agents can be used alone or as a mixture of plural kinds.
[0022]
In the present invention, the content of smectite (B) in the polyamide resin composition (C) is preferably 0.1 to 10 parts by weight with respect to 80 to 99.9 parts by weight of the polyamide (A). Preferably it is 0.5-8 weight part, Most preferably, it is 0.8-6 weight part. When the smectite content is less than 0.1 parts by weight, the effect of improving the gas barrier properties does not appear. On the other hand, if it is larger than 10 parts by weight, it is difficult to uniformly disperse the smectite in the polyamide resin composition, and an improvement effect of gas barrier properties corresponding to it cannot be expected. Also, the obtained film has high haze and is not practical.
[0023]
As for the method of melt-kneading polyamide (A) and smectite (B), various commonly used extruders such as a method of adding smectite during melt polymerization of polyamide resin and stirring, a single-screw or twin-screw extruder, etc. are used. Among these, a method of using a twin screw extruder is preferred from the viewpoint of excellent kneadability. The melt kneading temperature at that time is preferably 220 to 300 ° C., and the residence time is preferably adjusted to 1200 seconds or less. When the melt kneading temperature is lower than 220 ° C., poor dispersion of the layered silicate tends to occur, and when it exceeds 300 ° C. and when the residence time exceeds 1200 seconds, the molecular weight is lowered or gel is likely to be generated due to the thermal decomposition of the polyamide. Therefore, it is not preferable.
[0024]
In the present invention, the smectite (B) contained in the polyamide resin composition (C) is preferably uniformly dispersed without locally agglomerating. Here, the uniform dispersion means that the smectite (B) is separated into a flat plate shape in the polyamide resin composition (C), and 50% or more of the interlayer distance between the smectites is 5 nm or more, preferably 6 nm or more. Say. The interlayer distance referred to here means the distance between the centers of gravity of the flat plate-like objects, and it can be said that the larger the distance, the better the smectite dispersion. When the distance between the layers is 5 nm or more and less than 50%, the resulting biaxially stretched film has a high haze and an effect of improving the gas barrier property cannot be obtained, which is not preferable.
[0025]
The melt viscosity of the polyamide resin composition (C) is preferably 80 to 3000 Pa · s, more preferably 100 to 2000, and particularly preferably 150 to 250 ° C. under conditions of a shear rate of 100 / sec and a temperature of 270 ° C. 1500. If the melt viscosity is less than 80, the melt viscosity is too low, which causes problems such as draw-down and uneven thickness at the time of forming into a biaxially stretched film or a bottle. On the other hand, if it is larger than 3000, the melt viscosity is too high, so that it is difficult to form a biaxially stretched film, a bottle or the like with a general apparatus.
[0026]
The polyamide resin composition (C) preferably has a moisture content of less than 0.2% by weight in terms of molding. If the moisture content is 0.2% by weight or more, it is not preferable because it tends to cause a decrease in molecular weight or gel-like spots during film production, and further tends to cause drawdown. Is desirable. The polyamide resin composition (C) can be dried by a known method. For example, when melt-extruding polyamide with a vented extruder, the inside of the cylinder is depressurized with a vacuum pump to remove the water in the polymer, and the polyamide resin is charged into a tumbler (rotary vacuum tank) and decompressed. Although the method of drying by heating at the temperature below the melting point of a polymer below etc. is mentioned, it is not limited to this.
[0027]
Further, the polyamide resin composition (C) can be blended with other thermoplastic resins such as nylon 6, nylon 66, nylon 6,66, polyester, polyolefin and the like within a range not impairing the purpose. In addition, inorganic fillers such as glass fibers and carbon fibers, plate-like inorganic fillers such as glass flakes, talc, kaolin and mica, impact resistance modifiers such as various elastomers, crystal nucleating agents, fatty acid amides, fatty acids Lubricants such as metal salt compounds, copper compounds, organic or inorganic halogen compounds, hindered phenols, hindered amines, hydrazines, sulfur compounds, phosphorus compounds and other antioxidants, heat stabilizers, anti-coloring agents, For the purpose of preventing gelation of compounds and polyamide resins containing benzotriazole-based UV absorbers, mold release agents, plasticizers, colorants, flame retardants, cobalt metal which is a compound that provides oxygen scavenging ability Additives such as alkali compounds can be added.
[0028]
In the method for producing a biaxially stretched film of the present invention, when the biaxially stretched film is produced from the polyamide resin composition (C), the biaxially stretched film is sequentially stretched so as to satisfy the following formulas (1) to (6). It is preferable to adopt the method.
[Equation 3]

In the equations (1) to (6)
Tg: Glass transition temperature of polyamide resin (A)
T: Stretching temperature
t1: Time required for x-axis stretching
t2: Elapsed time from starting x-axis stretching to starting y-axis stretching
t3: Elapsed time from the start of x-axis stretching to the end of y-axis stretching
x0: length in the x-axis direction of the film before stretching
x: x-axis direction length of the stretched film
y0: length in the y-axis direction of the film before stretching
y: length of the stretched film in the y-axis direction
Here, the x axis and the y axis are orthogonal. When the x-axis direction is the MD direction (sheet extrusion direction), the y-axis direction means the TD direction (sheet width direction), and when the x-axis direction is the TD direction, the y-axis direction means the MD direction. .
[0029]
In the method for producing a biaxially stretched film of the present invention, the stretching temperature is preferably in the range represented by Formula (1) (Tg to Tg + 85 ° C.), more preferably in the range of Tg + 5 ° C. to Tg + 75 ° C. If the stretching temperature is lower than the glass transition temperature Tg of the polyamide resin (A), extremely high stress is required to stretch the film, and the film often breaks or the haze of the film increases and transparency is impaired. It is not preferable. When the stretching temperature is higher than the glass transition temperature + 85 ° C., the crystallization speed of the polyamide resin composition (C) is increased, so that it is difficult to stretch the film, and haze is increased to deteriorate the transparency of the film. The temperature during x-axis stretching and the temperature during y-axis stretching may be the same or different. However, if the temperature during y-axis stretching is lower than the temperature during x-axis stretching, the stretching stress becomes significantly large and uniform. It is difficult to stretch and often causes breakage.
[0030]
In the manufacturing method of the biaxially stretched film of this invention, it is preferable to extend | stretch on the conditions represented by Formula (2). Although t2 = 0 means simultaneous biaxial stretching, simultaneous biaxial stretching is not preferable because the haze of the film increases and a biaxially stretched film excellent in transparency cannot be produced.
[0031]
In the method for producing a biaxially stretched film of the present invention, the stretching speed is preferably in the range represented by the formulas (3) and (4). Whether the stretching speed in the x-axis direction (defined in formula (3)) and the stretching speed in the y-axis direction (defined in formula (4)) are the same or different, create a film with low haze and good transparency. Can do. When the stretching speed represented by the formula (3) is less than 100% / second or the stretching speed represented by the formula (4) is less than 50% / second, the haze of the film increases and the transparency of the biaxially stretched film is increased. It is not preferable because it damages.
[0032]
In the method for producing a biaxially stretched film of the present invention, the stretch ratio is preferably in the range represented by the formulas (5) and (6). More preferably, it is 200% or more, and particularly preferably 250% or more. Create a transparent film with low haze regardless of whether the draw ratio in the x-axis direction (defined in equation (5)) and the draw ratio in the y-axis direction (defined in equation (6)) are the same or different. can do. When the draw ratio is less than 150%, the haze of the biaxially stretched film is high, and the transparency of the biaxially stretched film cannot be obtained.
[0033]
In the method for producing a biaxially stretched film of the present invention, the preheating time during stretching is preferably 0 to 180 seconds. More preferably, it is in the range of 10 to 150 seconds, particularly preferably 20 to 120 seconds. If the preheating time exceeds 180 seconds, the haze increases and the transparency of the biaxially stretched film is impaired.
[0034]
The biaxially stretched film of the present invention has a diffraction angle 2θ in the range of 15 ° to 25 ° in the X-ray diffraction pattern when the layer made of the polyamide resin composition (C) is subjected to X-ray diffraction measurement using CuKα rays. Two strong peaks are observed, and the peak intensity on the low angle side of the two peaks P And the peak intensity on the high angle side Q Is calculated by the following formula: Relative intensity ratio Is preferably 60 or less, more preferably in the range of 5-50. When the relative intensity ratio is larger than 60, an effect of improving the gas barrier property can be obtained, but it is not preferable because the haze increases and the practicality is lacking.
Relative intensity ratio = ( Q / P ) × 100
The above θ is an angle when the X-ray of wavelength λ is diffracted by the lattice plane with the surface interval d, and indicates a Bragg angle (also called an incident angle or a reflection angle), and 2θ is called a diffraction angle.
[0035]
The peak position in the above-mentioned X-ray diffraction measurement is obtained by smoothing the profile obtained by the measurement by the smoothing method of Savitzky and Golay, removing the background by the Sonnevert-Visser method, and using the Rachinger method for the Kα2 line. The second derivative of the intensity data obtained by removing is taken, and the minimum value is obtained as the peak position. Peak intensity P and Q Employs a value obtained by calculating the height from the background position to the peak position.
[0036]
In the present invention, the surface interval d corresponding to the low angle side peak is about 4.7 mm, and the surface interval d corresponding to the high angle side peak is about 4.2 mm (see Tables 4 and 6). In general, a crystal structure is expressed by a lattice plane and a plane interval, but according to a reference (T. Ohta et al. POLYMER, 1992, Vol. 33, No. 8, 1620-1622), polymetaxylylene adipa. The crystal structure of the imide has a lattice plane (100) with a face spacing d of 4.72 mm, a lattice plane (010) with a face spacing d of 4.20 mm, and a lattice plane (110) with a face spacing d of 4.17 mm. .
[0037]
Therefore, also in the present invention, it is considered that the low-angle peak represents the lattice plane (100) and the high-angle peak represents the lattice planes (010) and (110). The lattice plane (100) is said to indicate a plane connected by hydrogen bonds, that is, a folded structure of polymetaxylylene adipamide. The lattice planes (010) and (110) show structures other than the folded structure of polymetaxylylene adipamide. Relative intensity ratio That is greater than 60 indicates that the crystal structures of the lattice planes (010) and (110) are large in polymetaxylylene adipamide, and the crystal structure is disordered.
[0038]
Polyamide obtained by polycondensation of a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 70 mol% or more of an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms (A ), The peak intensity on the low angle side P Peak intensity on the high angle side for Q Ratio (relative intensity ratio = ( Q / P ) × 100) is 60 or more, haze is not increased and transparency is not impaired.
[0039]
However, in the case of a biaxially stretched film composed of a polyamide resin composition (C) obtained by melt-kneading polyamide (A) and smectite (B), since smectite becomes the nucleus of crystals, the dispersed smectite is the center. Spherulites tend to develop, haze increases, and the film whitens. In particular, when there are a lot of lattice planes (010) and (110), these serve as starting points for the growth of lamellae and spherulites composed of them, and this is coupled with the crystal nucleus effect of smectite in the polymetaxylylene adipamide crystals. Since there are many spherulites and the growth of spherulites is promoted, it is considered that the haze increases accordingly.
[0040]
Therefore, in the method of the present invention, the crystal structure represented by the lattice planes (010) and (110) in the biaxially stretched film made of the polyamide resin composition (C) is suppressed, and selectively expressed by the lattice plane (100). By increasing the crystal structure, the crystallinity can be controlled, the degree of orientation can be increased, and the growth of spherulites can be suppressed. Accordingly, whitening during stretching can be prevented, and a biaxially stretched film having low haze and excellent transparency can be produced.
[0041]
The method for producing the film of the present invention is not particularly limited, and a publicly known method such as a method of removing the solvent by dissolving the polyamide resin composition in a solvent and then removing the solvent, a method of uniaxial stretching, or a method of biaxial stretching are used. Although it can be produced, sequential biaxial stretching is particularly preferred because it is industrially easy to produce and has excellent productivity.
[0042]
Further, in the present invention, as a biaxial stretching method, a sheet produced by a known method such as a T-die method or a tubular method of extruding into a cylindrical shape by a ring die and then air-cooled or water-cooled, a tenter method, Stretching can be performed by applying a known method such as a tubular method.
[0043]
The biaxially stretched film of the present invention may be used as it is, or may be further stretched in any direction in order to improve physical properties in a specific direction. Moreover, in order to further give thermal stability to the film after extending | stretching, this film can be heat-processed if necessary.
[0044]
The haze of the biaxially stretched film of the present invention is 10% / 20 μm or less, and exhibits good transparency.
The biaxially stretched film of the present invention has an oxygen transmission coefficient of 0.5 (mlmm / m) at 23 ° C./60% RH (relative humidity). ² dayMPa) and gas barrier properties are also good.
As described above, the biaxially stretched film of the present invention is excellent in oxygen barrier properties and transparency, and can be a suitable material as a biaxially stretched film for packaging materials that requires oxygen barrier properties and transparency.
[0045]
The biaxially stretched film of the present invention can be made into a thermoplastic resin and a multilayer film for the purpose of imparting an effect of improving mechanical properties. There is no particular limitation on the thermoplastic resin, for example, polyethylenes such as low density polyethylene, medium density polyethylene, and high density polyethylene, polypropylenes such as propylene homopolymer, propylene-ethylene block copolymer, propylene-ethylene random copolymer, ethylene-butene Copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, propylene-α-olefin copolymer, polybutene, polypentene, ionomer resin, etc. Various polyolefins, polyester resins such as polystyrene and polyethylene terephthalate, polyamide resins such as nylon 6 and nylon 66, and the like. In the case of a multilayer structure, an adhesive resin layer made of a modified polyolefin resin or the like may be laminated between the resin layers as necessary. The multilayer film can be produced by a known method. For example, a coextrusion method such as a T-die method or an inflation method, or a method in which an unstretched or stretched film is laminated by extrusion lamination, dry lamination, or the like may be used.
[0046]
The biaxially stretched film of the present invention is a packaging material that imparts excellent transparency and gas barrier properties, for example, a single layer or a multi-layered wrap laminated with other resins, various shapes of pouches, container lids, etc. Available to: The packaging container obtained using the biaxially stretched film has excellent gas barrier properties and excellent transparency, and can store various articles. For example, carbonated drinks, juice, water, milk, sake, whiskey, shochu, coffee, tea, jelly drinks, health drinks, etc. Seasonings such as jams, creams, chocolate pastes and other paste-like foods, liquid soups, boiled foods, pickles, stewed and other liquid processed foods such as soba, udon and ramen, and raw noodles and boiled noodles , Representatives of pre-cooked rice such as polished rice, moistened rice, and non-washed rice, cooked cooked rice, processed rice products such as gomoku rice, red rice, rice bran, powdered soup, and powdered seasonings such as dashi stock High-moisture foods, dried vegetables, coffee beans, coffee powder, tea, low-moisture foods such as confectionery made from grains, and other solid and solution chemicals and liquids such as agricultural chemicals and insecticides And pasty medicines, lotions, makeup creams, cosmetic milky lotion, hair dressing, it is possible to house a hair dye, shampoo, soap, detergent or the like, various articles.
[0047]
【Example】
EXAMPLES Hereinafter, although an Example etc. demonstrate this invention concretely, this invention is not limited to these Examples. In Examples and the like, evaluation methods for polyamide resin compositions, biaxially stretched films and the like were based on the following methods.
(1) Terminal amino group concentration of polyamide resin
0.3-0.5 g of polyamide resin was precisely weighed and dissolved by stirring at 20-30 ° C. in 30 cc of phenol / ethanol = 4/1 volume solution. After complete dissolution, it was determined by neutralization titration with an aqueous N / 100 hydrochloric acid solution using an automatic titrator manufactured by Mitsubishi Chemical Corporation.
(2) Terminal carboxyl group concentration of polyamide resin
Polyamide 0.3-0.5 g was precisely weighed, and polyamide was dissolved in 30 ml of benzyl alcohol at 160-180 ° C. under nitrogen flow with stirring. After the polyamide was completely dissolved, it was cooled to 80 ° C. under a nitrogen stream, 10 ml of methanol was added with stirring, and neutralization titration with an N / 100 aqueous sodium hydroxide solution was performed.
(3) Relative viscosity of polyamide resin
1 g of polyamide was accurately weighed and dissolved in 100 cc of 96% sulfuric acid at 20-30 ° C. with stirring. After complete dissolution, 5 cc of the solution was quickly taken into a Cannon-Fenceke viscometer and allowed to stand in a thermostatic bath at 25 ° C. ± 0.03 ° C. for 10 minutes, and then the drop time (t) was measured. Further, the dropping time (t0) of 96% sulfuric acid itself was measured in the same manner. The relative viscosity was calculated from t and t0 according to the following formula.
Relative viscosity = (t) / (t0)
(4) Moisture content
Using a trace moisture measuring device CA-05 manufactured by Mitsubishi Chemical Corporation, measurement was performed under a nitrogen atmosphere at 235 ° C. for 50 minutes.
(5) Haze
About the biaxially stretched film, Nippon Denshoku Industries Co., Ltd. make, color difference / turbidity measuring device COH-300A was used, and the haze of the biaxially stretched film was measured according to ASTMD1003.
(6) Oxygen permeability coefficient
The biaxially stretched film was measured according to ASTM D3985. The measurement was carried out in an atmosphere of 23 ° C. and 60% relative humidity using a model manufactured by Modern Control Co., Ltd., model: OX-TRAN 10 / 50A.
(7) X-ray diffraction
The measurement used a Rigaku Corporation mini flex. CuKα is used as the X-ray source, the scattering slit is 4.2 degrees, the light receiving slit is 0.3 mm, the tube voltage is 30 kV, the tube current is 15 mA, the scanning range is 2 to 50 degrees, the sampling width is 0.02 degrees, and the scanning speed is 5 Measured under the condition of degree / minute.
In addition, the brand name of the layered silicate used by the present Example and the comparative example is as follows.
Montmorillonite: “NEW-D Orben” manufactured by Shiraishi Kogyo Co., Ltd. (containing 42 wt% dimethyldioctadecylammonium as swelling agent)
[0048]
In the following Examples and Comparative Examples, nylon MXD6 (polyamide A1 and polyamide A2) synthesized from metaxylylenediamine and adipic acid was used as the polyamide (A). Table 1 shows the properties of these polyamides.
[0049]
[Table 1]

[0050]
Example 1
After dry blending 97 parts by weight of polyamide A1 and 3 parts by weight of montmorillonite (manufactured by Shiraishi Kogyo Co., Ltd., trade name “NEW D ORBEN”), the mixture was twin-screw extruded at a feed rate of 6 kg / hour and a cylinder diameter of 37 mm. Supplied to the machine. Melt kneading was performed under conditions of a cylinder temperature of 240 ° C. and a screw rotation speed of 500 rpm, and the molten strand was cooled and solidified with cooling air, and then pelletized.
The pellets obtained above were supplied to a twin-screw extruder with a T-die having a cylinder diameter of 20 mm at a supply rate of 1.2 kg / hour. After melt kneading under the conditions of a cylinder temperature of 250 ° C. and a screw rotation speed of 100 rpm, the film-like product is extruded through a T-die and solidified on a 72 ° C. cooling roll while being pulled at a speed of 0.7 m / min. A 280 μm sheet was obtained.
Further, this sheet was stretched at 110 ° C. by a Toyo Seiki biaxial stretching machine, preheated for 30 seconds, stretched at 100% / second (both in the x-axis direction and the y-axis direction), and the time required for x-axis stretching (t1) was 3 The elapsed time (t2) from the start of x-axis stretching to the start of y-axis stretching for 2.4 seconds is 2.4 seconds, and the elapsed time (t3) from the start of x-axis stretching to the end of y-axis stretching is 6. The film was sequentially stretched 3.6 × 3.6 times under the condition of 0 seconds, and then heat-treated. The heat treatment was performed by holding the stretched film between two stainless plates with a 20 cm square hole, fixing with a clamp, and holding in a precision thermostat DF62 set at 240 ° C. for 5 seconds. Table 2 shows the evaluation results of the obtained biaxially stretched film.
[0051]
Example 2
Biaxial as in Example 1, except that t1 was 2.0 seconds, t2 was 1.4 seconds, t3 was 3.4 seconds, and the stretching speed was 180% / second in both the x-axis direction and the y-axis direction. A stretched film was prepared. The results are shown in Table 2.
[0052]
Example 3
After dry blending 97 parts by weight of polyamide A2 and 3 parts by weight of montmorillonite (manufactured by Shiraishi Kogyo Co., Ltd., trade name “NEW D ORBEN”), the mixture was twin-screwed with a cylinder diameter of 37 mm at a feed rate of 12 kg / hour. Feeded to the extruder. Melt kneading was performed under conditions of a cylinder temperature of 270 ° C. and a screw rotation speed of 300 rpm, and the molten strand was cooled and solidified with cooling air, and then pelletized.
The pellets obtained above were supplied to a twin-screw extruder with a T-die having a cylinder diameter of 20 mm at a supply rate of 1.2 kg / hour. After melt kneading under the conditions of a cylinder temperature of 250 ° C. and a screw rotation speed of 100 rpm, the film-like product is extruded through a T-die and solidified on a 72 ° C. cooling roll while being pulled at a speed of 0.7 m / min. A 280 μm sheet was obtained.
Further, this sheet was stretched by a Toyo Seiki biaxial stretching machine at a stretching temperature of 120 ° C., a preheating of 30 seconds, a stretching speed of 180% / second, t1 of 2.0 seconds, t2 of 1.4 seconds, and t3 of 3.4 seconds. Under the conditions, the film was biaxially stretched 3.6 × 3.6 times and heat-treated at 240 ° C. for 5 seconds. Table 2 shows the evaluation results of the obtained biaxially stretched film.
[0053]
[Table 2]

[0054]
Example 4
A biaxially stretched film was prepared in the same manner as in Example 3 except that the draw ratio was 4.0 × 2.5, t1 was 2.2 seconds, t2 was 1.6 seconds, and t3 was 3.0 seconds. did. The results are shown in Table 3.
In addition, Table 4 shows the peak intensity in the X-ray diffraction of the obtained film.
[0055]
Example 5
A biaxially stretched film was prepared in the same manner as in Example 3 except that the draw ratio was 3.0 × 3.0 times, t1 was 1.7 seconds, t2 was 1.1 seconds, and t3 was 2.8 seconds. did. The results are shown in Table 3.
[0056]
Example 6
A biaxially stretched film was prepared in the same manner as in Example 4 except that the heat treatment conditions were set at 200 ° C. for 30 seconds. The results are shown in Table 3.
[0057]
[Table 3]

[0058]
[Table 4]

[0059]
Comparative Example 1
A biaxially stretched film was prepared in the same manner as in Example 1 except that the stretching speed was 60% / second in both the x-axis direction and the y-axis direction, and t2 was 4.3 seconds. The results are shown in Table 5.
[0060]
Comparative Example 2
A biaxially stretched film was prepared in the same manner as in Example 1 except that the stretching speed was 80% / second in both the x-axis direction and the y-axis direction, and t2 was 3.2 seconds. The results are shown in Table 5.
[0061]
Comparative Example 3
A biaxially stretched film was prepared in the same manner as in Example 1 except that the stretching speed was 50% / second in both the x-axis direction and the y-axis direction, and simultaneous biaxial stretching was performed. The results are shown in Table 5. In addition, Table 6 shows the peak intensity in X-ray diffraction of the obtained biaxially stretched film.
[0062]
[Table 5]

[0063]
[Table 6]

[0064]
Comparative Example 4
The sheet prepared in the same manner as in Example 3 was stretched at a stretching ratio of 3 × 3 under the conditions of a stretching temperature of 80 ° C., a preheating of 30 seconds, and a stretching speed of 180% / sec. However, the film was broken and could not be stretched.
[0065]
As described in the above Examples and Comparative Examples, Examples 1 to 6 in which the polyamide resin composition (C) is biaxially stretched within the scope of the present invention are excellent in transparency and have a gas barrier property of the obtained product. Was also excellent. On the other hand, in Comparative Example 1 and Comparative Example 2 in which the stretching speed did not satisfy the formula (3), the haze of the film increased and the transparency was inferior. In Comparative Example 3, the haze of the film increased and the transparency was inferior without satisfying the formulas (2) and (3). In Comparative Example 4 not satisfying the formula (1), the film was broken and the film could not be obtained.
[0066]
Example 7
Linear low-density polyethylene (which constitutes layer I, made by Mitsui Chemicals, Inc., trade name: ULTZEX 2022L, hereinafter abbreviated as LLDPE), cylinder diameter is 30 mm from an extruder with a cylinder diameter of 45 mm The polyamide resin composition (C) pellets (constituting the II layer) obtained in Example 3 from the extruder were extruded at 200 to 210 ° C. and 240 to 270 ° C., respectively, and the layer constitution was I layer / II layer / I layer. A multilayer melt state was formed through a feed block so as to be in the following order, and a multilayer film was produced by a cylindrical die-water cooling inflation method. The obtained multilayer film was subjected to a tubular method with a stretching temperature of 120 ° C., a preheating of 30 seconds, a stretching speed of 180% / second, t1 of 2.0 seconds, t2 of 1.4 seconds, and t3 of 3.4 seconds. Under the conditions, the film was biaxially stretched 3.6 × 3.6 times and heat-treated at 240 ° C. for 5 seconds. Table 7 shows the evaluation results of the obtained multilayer biaxially stretched film. In addition, relative intensity ratio shows the result of taking out only I layer from a multilayer film, and performing X-ray diffraction.
[0067]
Example 8
Linear low-density polyethylene (which constitutes layer I, made by Mitsui Chemicals, Inc., trade name: ULTZEX 2022L, hereinafter abbreviated as LLDPE), cylinder diameter is 30 mm from an extruder with a cylinder diameter of 45 mm The polyamide resin composition (C) pellets (constituting the II layer) obtained in Example 3 from the extruder were extruded at 200 to 210 ° C. and 240 to 270 ° C., respectively, and the layer constitution was I layer / II layer / I layer. A multilayer melt state was formed through a feed block so as to be in the following order, and a film-like product was extruded through a T die to produce a multilayer film. Furthermore, this film was stretched at a stretching temperature of 120 ° C., preheating for 30 seconds, a stretching speed of 180% / second, t1 of 2.0 seconds, t2 of 1.4 seconds, and t3 of 3.4 seconds with a biaxial stretching machine manufactured by Toyo Seiki. Under the conditions, the film was biaxially stretched 3.6 × 3.6 times and heat-treated at 240 ° C. for 5 seconds. Table 7 shows the evaluation results of the obtained multilayer biaxially stretched film. In addition, relative intensity ratio shows the result of taking out only I layer from a multilayer film, and performing X-ray diffraction.
[0068]
Example 9
Conducted from an extruder with a cylinder diameter of 45 mm, from polyethylene terephthalate (which constitutes layer I. Nippon Unipet Co., Ltd., trade name PET543C: hereinafter abbreviated as PET), and an extruder with a cylinder diameter of 30 mm The polyamide resin composition (C) pellet obtained in Example 3 (constituting the II layer) was extruded at 260 to 290 ° C. and 240 to 270 ° C., respectively, so that the layer constitution was in the order of I layer / II layer / I layer. A multilayer molten state was formed through a feed block, and a film-like product was extruded through a T die to produce a multilayer film. Further, this sheet was stretched by a Toyo Seiki biaxial stretching machine at a stretching temperature of 120 ° C., a preheating of 30 seconds, a stretching speed of 180% / second, t1 of 2.0 seconds, t2 of 1.4 seconds, and t3 of 3.4 seconds. Under the conditions, the film was biaxially stretched 3.6 × 3.6 times and heat-treated at 240 ° C. for 5 seconds. Table 7 shows the evaluation results of the obtained multilayer biaxially stretched film. In addition, relative intensity ratio shows the result of taking out only I layer from a multilayer film, and performing X-ray diffraction.
[0069]
Comparative Example 5
The multilayer film obtained in Example 8 was 3.6 × 3.6 times under the conditions of a stretching temperature of 120 ° C., a preheating of 30 seconds, a stretching speed of 110% / second, and a t2 of 0 second using a Toyo Seiki biaxial stretching machine. The film was biaxially stretched and heat treated at 240 ° C. for 5 seconds. Table 7 shows the evaluation results of the obtained multilayer biaxially stretched film. In addition, relative intensity ratio shows the result of taking out only I layer from a multilayer film, and performing X-ray diffraction.
[0070]
[Table 7]

[0071]
As described in the above Examples and Comparative Examples, Examples 7 to 9 obtained by biaxially stretching a multilayer film containing the polyamide resin composition (C) within the scope of the present invention are excellent in transparency and gas barrier properties. It was excellent. On the other hand, the film haze increased in Comparative Example 5 without satisfying the formula (2), and the transparency was poor.
[0072]
【The invention's effect】
A biaxially stretched film obtained from the polyamide resin composition of the present invention, and a packaging container comprising the same, has excellent gas barrier properties and excellent transparency, and has a higher commercial value than the conventional ones, industrial It is excellent.

Claims (9)

Polyamide obtained by polycondensation of a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 70 mol% or more of an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms (A ) And smectite (B) are melt-kneaded to form a polyamide resin composition (C), or a biaxially stretched film comprising at least one layer comprising a polyamide resin composition (C), the polyamide resin composition The polyamide (A) in (C) is in the range of 80 to 99.9 parts by weight, the smectite (B) is in the range of 0.1 to 10 parts by weight, and the layer made of the polyamide resin composition (C) is based on CuKα rays. in X-ray diffraction pattern, the peak intensity ratio of the diffraction angle 2θ is then high strength and highest intensity peaks observed in the range of 15 ° to 25 ° (relative intensity ratio = (Q / P) × 10 ) Is 60 or less (however, P is the peak intensity of the low angle side of the peak, Q is the peak intensity of the high angle side) biaxially oriented film, characterized in that. The polyamide (A) is obtained by polycondensing the diamine component and the dicarboxylic acid component at a reaction molar ratio in the range of 0.990 to 1.000 (number of moles of reacted diamine / number of moles of reacted dicarboxylic acid). The biaxially stretched film according to claim 1, wherein the terminal amino group concentration is in the range of 1 to 60 µequivalent / g. The biaxially stretched film according to claim 1, wherein the smectite (B) is separated into a flat plate shape in the polyamide (A), and 50% or more of the interlayer distance between the smectites is 5 nm or more. The biaxially stretched film according to claim 1, wherein the smectite (B) is montmorillonite. The biaxially stretched film according to claim 1, wherein the smectite (B) is treated with an organic swelling agent. 2. The biaxially stretched film according to claim 1, wherein the polyamide resin composition (C) has a melt viscosity of 80 to 3000 Pa · s under conditions of a shear rate of 100 / sec and a temperature of 270 ° C. 3. The biaxially stretched film according to claim 1, wherein the haze of the biaxially stretched film is 10% / 20 μm or less. Polyamide obtained by polycondensation of a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 70 mol% or more of an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms (A ) And smectite (B) melt-kneaded polyamide resin composition (C), or a method for producing a biaxially stretched film comprising at least one layer comprising a polyamide resin composition (C), A method for producing a biaxially stretched film, characterized by sequentially biaxially stretching under production conditions that simultaneously satisfy the following formulas (1) to (6).

In the formulas (1) to (6), Tg: Glass transition temperature of polyamide resin (A) T: Stretching temperature t1: Time required for x-axis stretching t2: Progress from starting x-axis stretching to starting y-axis stretching Time t3: Elapsed time from the start of x-axis stretching to the end of y-axis stretching x0: Length in the x-axis direction of the film before stretching x: Length in the x-axis direction of the film after stretching y0: Length of the film before stretching Length in y-axis direction y: Length in the y-axis direction of the stretched film Here, the x-axis and the y-axis are orthogonal to each other. When the x-axis direction is the MD direction (sheet extrusion direction), the y-axis direction means the TD direction (sheet width direction), and when the x-axis direction is the TD direction, the y-axis direction means the MD direction. . A packaging container using the biaxially stretched film according to claim 1 at least partially.