JP3731340B2 - Biaxially oriented polyester film - Google Patents

Description

（ただし、式中のＲ₁は
【化２】

【化３】

などの脂肪族炭化水素基、脂環族炭化水素基、芳香族炭化水素基から選ばれた一種もしくは二種以上の基を表して、
また、式中のＲ₂は
【化４】

などの脂肪族炭化水素基、脂環族炭化水素基、芳香族炭化水素基から選ばれた一種もしくは二種以上の基を表す。）
かかる好ましいイミド系化合物（Ｂ）は、例えば、特開平８―１５７６４２号公報や第２５５８３３９号公報などに代表されるように、テトラカルボン酸および／またはその酸無水物と、脂肪族一級モノアミンおよび／または芳香族一級モノアミン、さらに／または脂肪族一級ジアミンおよび／または芳香族一級ジアミンよりなる群から選ばれる一種もしくは二種以上の化合物を脱水縮合することにより得られた化合物を挙げることができる。
【００２４】
テトラカルボン酸および／またはその酸無水物としては、例えば、エチレンテトラカルボン酸、１, ２, ３, ４―ブタンテトラカルボン酸、シクロペンタンテトラカルボン酸、ピロメリット酸、１, ２, ３, ４―ベンゼンテトラカルボン酸、３, ３', ４, ４'―ビフェニルテトラカルボン酸、２, ２', ３, ３'―ビフェニルテトラカルボン酸、３, ３', ４, ４'―ベンゾフェノンテトラカルボン酸、２, ２', ３, ３'―ベンゾフェノンテトラカルボン酸、ビス（２, ３―ジカルボキシフェニル）メタン、ビス（３, ４―ジカルボキシフェニル）メタン、１, １' ―ビス（２, ３―ジカルボキシフェニル）エタン、２, ２'―ビス（３, ４―ジカルボキシフェニル）プロパン、２, ２'―ビス（２, ３―ジカルボキシフェニル）プロパン、ビス（３, ４―ジカルボキシフェニル）エーテル、ビス（２, ３―ジカルボキシフェニル）エーテル、ビス（３, ４―ジカルボキシフェニル）スルホン、ビス（２, ３―ジカルボキシフェニル）スルホン、２, ３, ６, ７―ナフタレンテトラカルボン酸、１, ４, ５, ８―ナフタレンテトラカルボン酸、１, ２, ５, ６―ナフタレンテトラカルボン酸、２, ３, ６, ７―アントラセンテトラカルボン酸、１, ２, ７, ８―フェナントレンテトラカルボン酸、３, ４, ９, １０―ペリレンテトラカルボン酸、４, ４'―（ｐ−フェニレンジオキシ）ジフタル酸、４, ４'―（ｍ−フェニレンジオキシ）ジフタル酸、２, ２'―ビス[（２, ３―ジカルボキシフェノキシ）フェニル]プロパン等および／またはその酸無水物等が用いられる。
【００２５】
脂肪族一級モノアミンとしては、例えば、炭素数２〜２２の飽和または不飽和の直鎖、分岐または脂環系のモノアミンが用いられ、具体的には、エチルアミン、ブチルアミン、ペンチルアミン、ヘキシルアミン、ヘプチルアミン、オクチルアミン、ノニルアミン、デシルアミン、ウンデシルアミン、ドデシルアミン、トリデシルアミン、テトラデシルアミン、ペンタデシルアミン、ヘキサデシルアミン、ヘプタデシルアミン、オクタデシルアミン、ノナデシルアミン、エイコシルアミン、ヘネイコシルアミン、ドコシルアミン、シクロヘキシルアミン、メチルシクロヘキシルアミン、ジメチルシクロヘキシルアミン、ジエチルシクロヘキシルアミンおよびこれらの構造異性体などが用いられる。
【００２６】
芳香族一級モノアミンとしては、例えば、非置換あるいは炭素数１〜２２のアルキル置換の一級アニリンが用いられ、具体的には、アニリン、トルイジン、エチルアニリン、プロピルアニリン、ブチルアニリン、ペンチルアニリン、ヘキシルアニリン、ヘプチルアニリン、オクチルアニリン、ノニルアニリン、デシルアニリン、ウンデシルアニリン、ドデシルアニリン、トリデシルアニリン、テトラデシルアニリン、ペンタデシルアニリン、ヘキサデシルアニリン、ヘプタデシルアニリン、オクタデシルアニリン、ノナデシルアニリン、エイコシルアニリン、ヘネイコシルアニリン、ドコシルアニリンおよびこれらの構造異性体等が用いられる。
【００２７】
脂肪族一級ジアミンとしては、例えば、炭素数１〜１２のメチレン基で結合された一級ジアミンや脂環基を有するジアミンが用いられ、具体的には、エチレンジアミン、トリメチレンジアミン、テトラメチレンジアミン、ペンタメチレンジアミン、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、ウンデカメチレンジアミン、ドデカメチレンジアミン、１, ３―ビスアミノシクロヘキサン、ジアミノジシクロヘキシルメタン、ｍ−キシレンジアミンおよびこれらの構造異性体などが用いられる。
【００２８】
芳香族一級ジアミンとしては、例えば、ベンジジン、ジメチルベンジジン、ジアミノジフェニルメタン、ジアミノジトリルメタン、ジアミノジフェニルエタン、ジアミノジフェニルプロパン、ジアミノジフェニルブタン、ジアミノジフェニルエーテル、ジアミノジフェニルスルホン、ジアミノジフェニルベンゾフェノン、ｏ, ｍ, ｐ―フェニレンジアミン、トリレンジアミン、キシレンジアミン等およびこれらの例示した芳香族一級ジアミンの炭化水素基を構造単位に有する芳香族一級ジアミン等が用いられる。
【００２９】
本発明のイミド系化合物（Ｂ）は、数平均分子量が５００から１００００の範囲にあり、好ましくは１０００から５０００の範囲であり、さらに好ましくは１５００から３０００の範囲である。数平均分子量が５００より小さいと、製膜時にブリードアウトしやすくなり、異物の少ないフィルムを得ることが困難であり、好ましくない。また、数平均分子量が１００００より大きいと、フィルター濾圧を低減する効果が小さくなり、好ましくない。
【００３０】
本発明において、イミド系化合物（Ｂ）をポリエステル（Ａ）に添加する時期は、特に限定されないが、ポリエステルの重合前、例えば、エステル化反応前に添加してもよいし、重合後に溶融押出前に添加してもよい。また、溶融押出前に、ポリエステルとイミド系化合物あるいはポリエーテルイミド系化合物をペレタイズしてもよい。
【００３１】
本発明のポリエステルフィルムで用いられるイミド系化合物（Ｂ）のガラス転移温度は、特に限定されないが、７０から２５０℃の範囲にあることが好ましい。さらに好ましくは、１００から２３０℃の範囲であり、より好ましくは、１２０から２００℃の範囲である。イミド系化合物あるいはポリエーテルイミド系化合物のガラス転移温度が７０℃より小さかったり、また、２５０℃より大きかったりすると、ポリエステルフィルムの製膜において溶融成形性に劣ったりして、実用性がないので、ガラス転移温度は７０〜２５０℃の範囲が好ましい。
【００３２】
本発明のポリエステルフィルムで用いられるイミド系化合物（Ｂ）の溶解度パラメーターとポリエステル（Ａ）の溶解度パラメーターとの差が、特に限定されないが、４（ＭＰａ）^1/2以下であることが好ましい。さらに好ましくは、３（ＭＰａ）^1/2以下、より好ましくは、２（ＭＰａ）^1/2以下である。イミド系化合物（Ｂ）の溶解度パラメーターとポリエステル（Ａ）の溶解度パラメーターとの差が、４（ＭＰａ）^1/2より大きいと、溶融状態においてポリエステルとイミド系化合物あるいはポリエーテルイミド系化合物を均一に混合させることが困難であったりするので、４（ＭＰａ）^1/2以下であることが好ましい。本発明でいう溶解度パラメーターとは、原子団寄与法による計算値であり、例えば、Ｖａｎ Ｋｒｅｖｅｌｅｎ, “Ｐｒｏｐｅｒｔｉｅｓ ｏｆ Ｐｏｌｙｍｅｒｓ”, Ｔｈｉｒｄ ｃｏｍｐｌｅｔｅｌｙ Ｒｅｖｉｓｅｄ Ｅｄｉｔｉｏｎ, Ｅｌｓｅｖｉｅｒ（１９９０）に記載の方法で計算できる。各原子団のパラメーターに関しては、各種提案されており、いずれの方法で計算してもよいが、Ｈｏｆｔｙｚｅｒ―Ｖａｎ Ｋｒｅｖｅｌｅｎ, Ｈｏｙ, Ｓｍａｌｌ, Ｆｅｄｏｒｓらの方法を好ましく用いることができる。
【００３３】
本発明のポリエステルフィルムで用いられるイミド系化合物（Ｂ）の含有量は、特に限定されないが、０．０１から３０重量％の範囲にある。さらに好ましくは、０．１から２０重量％の範囲であり、より好ましくは、０．５から１０重量％の範囲である。イミド系化合物あるいはポリエーテルイミド系化合物の含有量が０．０１重量％未満であると、濾圧低減効果や機械特性の向上などの本発明の効果が小さく、また、３０重量％より大きいと、機械強度が向上しなかったり、フィルム表面特性が悪化したりするので、０．０１から３０重量％の範囲にあることが好ましい。
【００３４】
本発明のイミド系化合物（Ｂ）は、特に限定されないが、ポリエステル（Ａ）との溶融成形性や取り扱い性などの点から、例えば、１, ２, ３, ４―ブタンテトラカルボン酸、ピロメリット酸、ビス（３, ４―ジカルボキシフェニル）エーテル、ベンゾフェノンテトラカルボン酸、ビフェニルテトラカルボン酸等および／またはその酸無水物等のテトラカルボン酸成分の群から選ばれる一種もしくは二種以上の化合物と、エチレンジアミン、ヘキサメチレンジアミン、キシレンジアミン、ジアミノジフェニルメタン、ジアミノジフェニルエーテル、ジアミノジフェニルベンゾフェノン、フェニレンジアミン等のジアミン成分の群から選ばれる一種もしくは二種以上の化合物を脱水縮合した縮合体が例示される。その中で、芳香族系構造単位およびメチレン基を含む脂肪族系構造単位により、ポリエステルとの溶融成形が可能になる最適なガラス転移温度を有するイミド系化合物（Ｂ）を設計でき、また、例えば、カルボニル炭素を含む構造単位を有するイミド系化合物（Ｂ）は、ポリエステル（Ａ）との溶解度パラメーターの差が小さく、特に、溶融成形性に優れる。
【００３５】
本発明のポリエステルフィルムのヘイズは、特に限定されないが、０．１から２０％の範囲であることが好ましい。さらに好ましくは、０．１から１０％の範囲であり、より好ましくは０．１から５％の範囲である。ポリエステルフィルムのヘイズを０．１％未満にすることは、工業的に極めて困難であり、必ずしも必須要件ではない。また、ヘイズが２０％より大きいと、イミド系化合物やポリエーテルイミド系化合物がポリエステルフィルム中で効果的に分散していなかったり、異物が存在していたりするので、０．１から２０％の範囲であることが好ましい。
【００３６】
本発明のポリエステルフィルムの弾性率の長手方向と幅方向の和は、特に限定されないが、８〜１９．５ＧＰａの範囲である。さらに好ましくは１０〜１９．５ＧＰａ、より好ましくは１２〜１９．５ＧＰａである。ポリエステルフィルムの弾性率の長手方向と幅方向の和が８ＧＰａ未満であると、例えば、磁気記録媒体用などに用いる場合、ベースフィルムの弾性率が不足すると、走行時の磁気ヘッドやガイドピンから受ける張力のため、磁気テープに伸びが生じ、電磁変換特性（出力特性）に悪影響を与えたりして、実用上使用に耐えないことがあり、また、弾性率の和が３０ＧＰａより大きいポリエステルフィルムは、工業的に製造が困難である。
【００３７】
本発明のポリエステル（Ａ）の固有粘度は、特に限定されないが、０．５５〜３．００（ｄｌ／ｇ）の範囲であることが好ましい。さらに好ましくは、０．６０〜２．００（ｄｌ／ｇ）、より好ましくは、０．８０〜１．７５（ｄｌ／ｇ）、特に好ましくは１．００〜１．５０（ｄｌ／ｇ）である。ポリエステル（Ａ）の固有粘度が大きいと、イミド系化合物（Ｂ）を添加することにより、押出機での剪断発熱の抑制やフィルター濾圧の低減を効果的に実現できる。その結果、弾性率などの機械特性や表面欠点などの少ない優れたポリエステルフィルムを得ることができる。ポリエステル（Ａ）の固有粘度が０．５５（ｄｌ／ｇ）未満であると、添加したイミド系化合物の効果が発現されず、弾性率などの機械特性に劣ったり、オリゴマー量などによる表面欠点が増加したりし、また、３．００（ｄｌ／ｇ）より大きいと、工業的に押出してポリエステルフィルムを製造することが困難であるので、固有粘度は０．５５〜３．００（ｄｌ／ｇ）の範囲であることが好ましい。
【００３８】
本発明のポリエステルフィルムにおいて、具体的には、押出機にてポリマーを溶融押出した後、フィルター濾過して製膜したポリエステルフィルムにおいて、イミド系化合物（Ｂ）を含有したポリエステルのフィルター濾圧が、ポリエステル（Ａ）単独の場合に比べて、特に限定されないが、フィルター濾圧の低減度が１０％以上であることが好ましい。イミド系化合物を添加しても、フィルター濾圧低減度が１０％未満であると、本発明の目的とする弾性率などの機械特性に優れ、表面欠点やオリゴマー含有量の少ない高品質のポリエステルフィルムを得ることができないので、フィルター濾圧の低減度が１０％以上であることが好ましい。
【００３９】
本発明においては、特に限定されないが、イミド系化合物（Ｂ）の他に、例えば、主鎖にメソゲン基を有する共重合ポリエステルをポリエステル（Ａ）に添加することも濾圧低減および品質向上の点から有効である。該共重合ポリエステルは、主鎖にメソゲン基を有する溶融成形性があるポリエステルである。例えば、芳香族オキシカルボニル単位、芳香族ジオキシ単位、芳香族ジカルボニル単位、アルキレンジオキシ単位などから選ばれた構造単位からなる異方性溶融相を形成するポリエステルなどである。
【００４０】
本発明のポリエステルフィルムは、本発明を阻害しない範囲内で、熱安定剤、酸化防止剤、紫外線吸収剤、帯電防止剤、難燃剤、顔料、染料、脂肪酸エステル、ワックスなどの有機滑剤などが通常添加される程度添加されてもよい。また、表面の易滑性や耐磨耗性、耐スクラッチ性等を付与するために、クレー、マイカ、酸化チタン、炭酸カルシウム、カリオン、タルク、湿式または乾式シリカ、コロイド状シリカ、リン酸カルシウム、硫酸バリウム、アルミナおよびジルコニア等の無機粒子、アクリル酸類、スチレン等を構成成分とする有機粒子等を添加したり、ポリエステル重合反応時に添加する触媒等によって析出する、いわゆる内部粒子を含有していてもよいし、界面活性剤を含有していてもよい。
【００４１】
本発明のポリエステルフィルムの製造方法は、押出機にてポリマーを溶融押出した後、フィルター濾過して製膜するポリエステルフィルムの製造方法において、溶融押出前にポリエステル（Ａ）中に、数平均分子量が５００〜１００００のイミド系化合物（Ｂ）を添加・混合して製膜することを特徴とするものである。さらに詳しくは、押出機にてポリマーを溶融押出した後、フィルター濾過して製膜するポリエステルフィルムの製造方法において、溶融押出前にポリエステル（Ａ）中に、数平均分子量が５００〜１００００のイミド系化合物（Ｂ）を添加・混合することにより、ポリエステル（Ａ）単独でフィルター濾過する場合と比較して、固有粘度の高いポリエステル原料の溶融粘度を大幅に低減させて、フィルター濾圧、剪断発熱、および、押出トルクを大幅に低下させることにより、溶融押出時の固有粘度の低下が小さく、低オリゴマーで、機械強度に優れたポリエステルフィルムを得ることである。本発明のポリエステルフィルムの製造に用いるイミド系化合物（Ｂ）の数平均分子量は、５００〜１００００の範囲にあり、好ましくは１０００〜５０００の範囲であり、さらに好ましくは１５００〜３０００の範囲である。数平均分子量が５００より小さいと、例えば、製膜時にブリードアウトしやすくなり、異物の少ないフィルムを得ることが困難であり、また、数平均分子量が１００００より大きいと、フィルター濾圧を低減する効果等が小さくなるので、イミド系化合物（Ｂ）の数平均分子量は、５００〜１００００の範囲が好ましい。
【００４２】
本発明のポリエステルフィルムは、単膜でもよいが、これに他のポリマー層、例えば、ポリエステル、ポリオレフィン、ポリアミド、ポリ塩化ビニリデンおよびアクリル系ポリマーを直接、あるいは接着剤などの層を介して積層してもよい。特にポリエステル層を表層に積層する場合、積層部に粒子を含有することにより、走行性、易滑性および平滑性に優れたフィルムとすることができ、特に表面特性が重要な磁気記録媒体用のベースフィルムとしては好ましい。
【００４３】
本発明のポリエステルフィルムは、必要に応じて、熱処理、成形、表面処理、ラミネート、コーティング、印刷、エンボス加工、エッチングなどの任意の加工を行ってもよい。
【００４４】
本発明のポリエステルフィルムは、特に限定されないが、公知の方法により一軸または二軸に配向されたフィルムであることが、機械強度や電気特性に対する効果の点から好ましい。
【００４５】
本発明のポリエステルフィルムは、特に限定されないが、通常、厚みが１０００μｍ以下であり、好ましくは１〜５００μｍ、さらに好ましくは３〜２５０μｍの範囲である。
【００４６】
本発明のポリエステルフィルムの用途は、特に限定されないが、磁気記録媒体用、電気絶縁用、包装用、感熱転写リボン用、感熱孔版印刷用などに用いられる。
【００４７】
本発明のポリエステルフィルムの製造方法の例について説明するが、これに限定されるものではない。ここでは、ポリエステル（Ａ）として、ポリエチレンテレフタレートを用いた例を示すが、用いるポリエステルにより製造条件は異なる。
【００４８】
まず、常法に従い、テレフタル酸とエチレングリコールからエステル化し、または、テレフタル酸ジメチルとエチレングリコールをエステル交換反応により、ビスーβ―ヒドロキシエチルテレフタレート（ＢＨＴ）を得る。次にこのＢＨＴを重合槽に移行しながら、真空下で２８０℃に加熱して重合反応を進める。ここで、固有粘度が０．５程度のポリエステルを得る。この時、所定量のイミド系化合物を添加しておいてもよい。得られたポリエステルをペレット状で減圧下において固相重合する。固相重合する場合は、あらかじめ１８０℃以下の温度で予備結晶化させた後、１９０〜２５０℃で１ｍｍＨｇ程度の減圧下、１０〜５０時間固相重合させる。また、フィルムを構成するポリエステルに粒子を含有させる方法としては、エチレングリコールに粒子を所定割合にてスラリーの形で分散させ、このエチレングリコールをテレフタル酸と重合させる方法が好ましい。粒子を添加する際には、例えば、粒子を合成時に得られる水ゾルやアルコールゾルを一旦乾燥させることなく添加すると粒子の分散性がよい。また、粒子の水スラリーを直接所定のポリエステルペレットと混合し、ベント式２軸混練押出機を用いて、ポリエステルに練り込む方法も有効である。粒子の含有量、個数を調節する方法としては、上記方法で高濃度の粒子のマスタを作っておき、それを製膜時に粒子に実質的に含有しないポリエステルで希釈して粒子の含有量を調節する方法が有効である。
【００４９】
次に、該ポリエチレンテレフタレートと数平均分子量が５００〜１００００の範囲であるイミド系化合物（Ｂ）をブレンドした原料や、これらを一旦溶融させて、均一混合させた原料を、１８０℃で３時間以上真空乾燥した後、固有粘度が低下しないように窒素気流下あるいは真空下で２８０℃に加熱された押出機に供給し、公知の方法により製膜する。この時、押出機での剪断速度は２０秒―¹以上、好ましくは５０秒―¹以上と高い方がイミド系化合物が押出機内でよく分散し、本発明の効果が大きくなり好ましいが、剪断速度を３００秒―¹以上に大きくすると、剪断発熱によりポリマーが熱分解するので好ましくない。また、異物や変質ポリマーを除去するために公知のフィルター、例えば、焼結金属、多孔性セラミック、サンド、金網などの素材からなるフィルターを用いることが好ましい。また、必要に応じて、定量供給性を向上させるためにギアポンプを設けてもよい。スリット状のダイからシート状に押出し、キャスティングロール上で冷却固化させて未延伸フィルムを作る。また、積層フィルムの場合は、２台以上の押出機、マニホールドまたは合流ブロックを用いて、溶融状態のポリエステルを積層したシートを押出し、キャスティングロール上で冷却して未延伸フィルムを作る。
【００５０】
次に、この未延伸フィルムを二軸延伸し、二軸配向させる。延伸方法としては、逐次二軸延伸法または同時二軸延伸法を用いることができる。ここでは、最初に長手方向、次に幅方向の延伸を行う逐次二軸延伸法を用いる。未延伸フィルムを８０〜１５０℃の加熱ロール群で加熱し、長手方向に２〜７倍に１段もしくは２段以上の多段で延伸し、２０〜５０℃の冷却ロール群で冷却する。長手方向延伸速度は１０００〜５００００％／分の範囲で行うのが好ましいが、特に限定されない。続いて、幅方向の延伸方法としては、例えば、テンターを用いる方法が一般的である。幅方向の延伸倍率は２〜７倍、延伸速度は１０００〜２００００％／分、温度は８０〜１５０℃の範囲で行うのが好ましいが、特に限定されない。さらに必要に応じて、再縦延伸および／または再横延伸を行う。その場合の延伸条件としては、長手方向の延伸は、温度８０〜１８０℃、延伸倍率１．１〜２．０倍、幅方向の延伸方法としてはテンターを用いる方法が好ましく、温度８０〜１８０℃、延伸倍率１．１〜２．０倍で行うのが好ましいが、特に限定されない。続いて、この延伸フィルムを緊張下または幅方向に弛緩しながら熱処理する。この場合の熱処理温度は、１５０℃〜２５０℃、好ましくは１８０〜２００℃で、時間は０．２〜３０秒の範囲で行うのが好ましいが、特に限定されない。
【００５１】
［物性の測定方法ならびに効果の評価方法］
（１）固有粘度
オルトクロロフェノール中、２５℃で測定した溶液粘度から下式から計算される値を用いる。すなわち、
ηｓｐ／Ｃ＝[η]＋Ｋ[η]２・Ｃ
ここで、ηｓｐ＝（溶液粘度／溶媒粘度）ー１、Ｃは溶媒１００ｍｌあたりの溶解ポリマ重量（ｇ／１００ｍｌ、通常１．２）、Ｋはハギンス定数（０．３４３とする）である。また、溶液粘度、溶媒粘度はオストワルド粘度計を用いて測定した。
【００５２】
（２）数平均分子量
東レリサーチセンターに分析依頼し、ゲルパークロマトグラフィー（ＧＰＣ）により測定した。
【００５３】
（３）ガラス転移温度Ｔｇ
ＤＳＣ（示差走査熱量計：セイコー電子工業製）を用いて測定した。ＤＳＣの測定条件は次の通りである。すなわち、試料５ｍｇをＤＳＣ装置にセットし、３００℃の温度で５分間溶融した後、液体窒素中で急冷する。この試料を１０℃／分で昇温し、ガラス転移温度Ｔｇを検知した。
【００５４】
（４）ヘイズ
ＪＩＳ―Ｋ―６７１４に従い、ヘイズメーター（スガ試験機製）を用いて測定した。テトラリンに浸した状態で内部ヘイズを測定し、下式により２５μｍ換算で表した。
【００５５】
ヘイズ（％）＝フィルム内部ヘイズ（％）×（２５（μｍ）／フィルム厚み（μｍ））
（５）弾性率
テンシロン型引張試験機（オリエンテック社製）に幅１０ｍｍ、チャック間距離１００ｍｍになるようにサンプルをセットし、２３℃、６５％ＲＨの雰囲気下で引張速度２００ｍｍ／分で引張試験を行い、求めた。
【００５６】
（６）オリゴマー量
ポリマー１００ｍｇをオルトクロロフェノール１ｍｌに溶解し、液体クロマトグラフィー（モデル８５００ＶＡＲＩＡＮ社製）で測定した。ポリマーに対する重量％で表した。
【００５７】
（７）フィルター濾圧およびフィルター濾圧の低減度
実験装置を図１に示す。ギアポンプ（三菱重工製、１．６ｃｃ／回転）、フィルター（日本精線製、リーフディスクフィルター−ＮＦ−１４０：６５ｍｍ径、８０μｍカット焼結フィルター１枚）および圧力計を備えた東芝製３０ｍｍ小型単軸押出機（Ｌ／Ｄ＝２２）を用い、下記条件でフィルター前後の圧力ＰａおよびＰｂを測定した。なお、Ｔｍは、ＤＳＣ（示差走査熱量計）で検知した溶融温度のピークである。
【００５８】

フィルター濾圧の低減度Ｒについては、下式で算出した。
【００５９】
Ｒ＝［（Ｐ₀―Ｐ₁）／Ｐ₀］×１００
Ｐ₀：イミド系化合物を添加しない場合の濾圧（圧力差：Ｐａ―Ｐｂ）
Ｐ₁：イミド系化合物を添加した場合の濾圧（圧力差：Ｐａ―Ｐｂ）
【００６０】
【実施例】
次の実施例に基づき、本発明の実施形態を説明する。
【００６１】
参考例１
１, ２, ３, ４―ブタンテトラカルボン酸４６．８ｇと、ヘキサデシルアミン４８．２ｇ、さらにｍ−キシレンジアミン１３．６ｇ、をフラスコ中でジメチルホルムアミドを溶媒として混合、２６０℃まで徐々に昇温しながら攪拌し、縮合された水およびジメチルホルムアミドを留去した。その後、さらに攪拌しながら徐々に減圧して、完全に留去を完了させ、フラスコ底に残留したイミド系化合物Ａを得た。
【００６２】
参考例２
ｍ−キシレンジアミンの代わりに、ヘキサメチレンジアミン４６．４ｇを用いるほかは、参考例１と同様の方法により、残留したイミド系化合物Ｂを得た。
【００６３】
参考例３
ｍ−キシレンジアミンの代わりに、ジアミノジフェニルメタン１９．８ｇを用いるほかは、参考例１と同様の方法により、残留したイミド系化合物Ｃを得た。
【００６４】
参考例４
ビス｛４−［３−（４−アミノフェノキシ）ベンゾイル］フェニル｝エーテル５６８ｇと、ビス（３, ４―ジカルボキシフェニル）エーテル二無水物３１０ｇ、ｎ―オクチルアミンおよびｍ−クレゾールを混合して反応させ、窒素雰囲気下に撹拌しながら１５０℃まで徐々に昇温して、メタノールに排出した。その後、さらに減圧乾燥して、残留したイミド系化合物Ｄを得た。
【００６５】
参考例５
窒素雰囲気下で、ｍ−フェニレンジアミン３２．４ｇ、イソキノリン１ｇ、ｍ−クレゾール２００ｇを入れ、５０℃に加熱して溶解させた。ここに、２, ２'―ビス[（２, ３―ジカルボキシフェノキシ）フェニル]プロパン二無水物２０８ｇを加え、５０℃で３０分、その後１８０℃に加熱し、発生する水をトラップにて受けて系外に除去し、２時間攪拌を続けた。その後、さらに減圧乾燥して、残留したイミド系化合物Ｅを得た。
【００６６】
実施例１（表１，２）
固有粘度０．８（ｄｌ／ｇ）のポリエチレンテレフタレート（滑り剤として平均粒径２００ｎｍの酸化アルミナを０．０７５重量％含有、チップオリゴマー量０．３重量％）に対して、参考例１で得たイミド系化合物Ａ５．０重量％添加したポリエステル組成物を１８０℃で１０時間乾燥（３Ｔｏｒｒ）した後、９０ｍｍの単軸押出機に供給し、温度２８５℃で混練溶融して、異物を高精度金属焼結フィルターを用いて濾過し除去後、１１０ｍｍ幅のフィルム成型用Ｔダイ口金から溶融体シートを押出し、２５℃に保たれた冷却ドラムに静電荷を印可させながら密着冷却固化し、未延伸フィルムを得た。このとき、フィルター濾圧の低減度は、１４％であった。
【００６７】
この未延伸フィルムをロール式延伸機にて長手方向に段階的に、温度９５℃で４倍延伸した。続いて、テンターを用いて、幅方向に温度１０５℃で４倍延伸し、定長下で温度２１０℃で１０秒間熱処理して、厚さ１２μｍの二軸配向フィルムを得た。
【００６８】
この二軸配向フィルムの特性は、表２に示したとおり、磁気記録媒体用や電気絶縁用などの各種用途のフィルムとして優れた特性を有していた。
【００６９】
実施例２、３（表１，２）
原料のポリエステルとして、固有粘度が異なるポリエチレンテレフタレート（固有粘度１．０（ｄｌ／ｇ）：チップオリゴマー量０．２８重量％、固有粘度１．４（ｄｌ／ｇ）：チップオリゴマー量０．２６重量％）を用いること以外は実施例１と同様にして製膜し、二軸配向フィルムを得た。フィルター濾圧低減度や得られた二軸配向フィルムの特性は表２に示した通りであるが、固有粘度が高い原料を用いると、イミド系化合物の効果がより顕著になって、実施例１の場合よりフィルター濾圧低減度や弾性率などに優れた高品質のフィルムが得られた。
【００７０】
実施例４〜７（表１，２）
使用するイミド系化合物の含有量、数平均分子量を変更し、実施例２と同様に製膜し二軸配向フィルムを得た。フィルター濾圧低減度や得られた二軸配向フィルムの特性は表２に示した通りであるが、本発明の構成をもつイミド系化合物を使用すると、フィルター濾圧低減度や弾性率などに優れた高品質のフィルムが得られた。
【００７１】
実施例８〜１１（表１，２）
使用するイミド系化合物（Ｂ）の種類をそれぞれイミド系化合物Ｂ〜Ｅに変更して、実施例２と同様に製膜し二軸配向フィルムを得た。フィルター濾圧低減度や得られた二軸配向フィルムの特性は表２に示した通りであるが、本発明の構成をもつイミド系化合物を使用すると、フィルター濾圧低減度や弾性率などに優れた高品質のフィルムが得られた。
【００７２】
比較例１〜３（表３，４）
イミド系化合物を使用しないこと以外は、それぞれ実施例１〜３と同様にして製膜し二軸配向フィルムを得た。フィルター濾圧低減度や得られた二軸配向フィルムの特性は表４に示した通りであるが、フィルター濾圧低減度が小さく、弾性率などの機械特性に劣り、また、オリゴマー量も多いことなどのため、高品質のフィルムを得ることが困難であり、磁気記録媒体用や電気絶縁用などの用途には実用上使用に耐えない。
【００７３】
比較例４，５（表３，４）
参考例１で得たイミド系化合物Ａの数平均分子量を変更し、実施例２と同様に製膜し、二軸配向フィルムを得た。イミド系化合物が本発明の構成を満たさない場合、使用しても効果が十分に発現せず高品質のフィルムを得ることが困難であり、磁気記録媒体用や電気絶縁用などの用途には実用上使用に耐えない。
【００７４】
【表１】

【表２】

【表３】

【表４】

【００７５】
【発明の効果】
本発明のポリエステルフィルムは、ポリエステル（Ａ）と、数平均分子量が５００〜１００００のイミド系化合物（Ｂ）からなり、該フィルムの弾性率などの機械特性を向上させるとともに、フィルムの表面欠点オリゴマーなどを低減させて品質向上を図ったものであり、磁気記録媒体用、電気絶縁用、包装用、感熱転写リボン用、感熱孔版印刷用などの各種フィルム用途に広く活用が可能である。
【図面の簡単な説明】
【図１】本発明のフィルター濾圧およびフィルター濾圧の低減度の評価に用いる押出装置の一例を示した概略図である。
【符号の説明】
１：３０ｍｍ小型単軸押出機
２：短管
３：ギアポンプ
４：フィルター
５：ブリード口
６：フィルター上流部圧力計
７：フィルター下流部圧力計
８１：押出機供給部熱電対
８２：押出機圧縮部熱電対
８３：押出機計量部熱電対
８４：ギアポンプ部熱電対
８５：フィルター部熱電対
８６：ホッパー[0001]
BACKGROUND OF THE INVENTION
The present invention is a film in which the physical properties and quality of a conventional polyester film are greatly improved. Specifically, it has a high elastic modulus, toughness, low surface defects, low oligomer content, and excellent electrical properties. The present invention relates to a polyester film and a method for producing the same.
[0002]
[Prior art]
Polyester film uses various properties such as magnetic recording media, electrical insulation, packaging, and various industrial materials by utilizing its excellent mechanical properties, thermal properties, electrical properties, surface properties, and heat resistance. It is used for. In improving the quality of these applications, for example, improvement of mechanical properties such as elastic modulus is required. Conventionally, as one method for increasing the elastic modulus of a polyester film, a method for increasing the degree of molecular orientation by improving stretching conditions and the like is generally performed. As another method, for example, as represented by International Publication WO87-05919, Japanese Patent Application Laid-Open No. 57-25354, etc., a compound having a high elastic modulus such as liquid crystalline polyester is added to non-liquid crystalline polyester. There is a method to reinforce and reinforce.
[0003]
[Problems to be solved by the invention]
However, if the molecular orientation is excessively increased in order to increase the elastic modulus, film tearing during stretching cannot be avoided, and there is a limit to the improvement in practical elastic modulus. In addition, when a film having a high intrinsic viscosity is extruded to form a film having excellent mechanical properties, an increase in the filtration pressure when passing through the filter is increased, making extrusion difficult. In order to avoid this drawback, when the temperature of the filter part is increased, the degree of polymerization is reduced due to the thermal decomposition of the polymer and the intrinsic viscosity is lowered. As a result, only a low quality film can be obtained with low mechanical strength. There was a problem. In particular, for example, in the case of a magnetic recording medium, it is necessary to remove foreign substances in the polymer as much as possible and to smooth the film surface. It was difficult to obtain a film having a smooth surface and excellent mechanical strength.
[0004]
In addition, the method of reinforcing and strengthening with liquid crystalline polyester has a remarkable effect when the form of liquid crystalline polyester can be controlled to be fibrous, and the shape of liquid crystalline polyester fiber is reduced in the film forming process. Therefore, there is a problem that it is not always effective.
[0005]
An object of the present invention is to provide a high-quality polyester film that is excellent in mechanical strength such as elastic modulus and has a small surface defect and oligomer content.
[0006]
Another object of the present invention is to significantly reduce the melt viscosity of a polyester raw material having a high intrinsic viscosity during melt extrusion, thereby greatly reducing the filtration pressure, shear heat generation, and extrusion torque. It is an object of the present invention to provide a method for producing a polyester film that has a low decrease in intrinsic viscosity at the time of melt extrusion, a low oligomer, and excellent mechanical strength without remodeling the film forming apparatus.
[0007]
[Means for Solving the Problems]
The polyester film of the present invention that meets the above-mentioned purpose is composed of polyester (A) and an imide compound (B) having a number average molecular weight of 500 to 10,000. A biaxial film having a content of the imide compound (B) of 0.01 to 30% by weight and a sum of the elastic modulus in the longitudinal direction and the width direction of the polyester film of 8 to 19.5 GPa. Oriented polyester film It is characterized by being.
[0008]
The polyester film of the present invention further includes one or more preferred embodiments described below.
[0009]
(A) The glass transition temperature of the imide compound (B) is 70 to 250 ° C.
[0010]
(B) The difference between the solubility parameter of the imide compound (B) and the solubility parameter of the polyester (A) is 4 (MPa). ^1/2 The following.
[0012]
(D) The polyester film has a haze of 0.1 to 20%.
[0014]
(F) The intrinsic viscosity of the polyester (A) is 0.55 to 3.00 (dl / g).
(G) In a polyester film formed by melt-extruding a polymer with an extruder and then filtered and formed into a film, when the filter filtration pressure of the polyester containing the imide compound (B) is polyester (A) alone In comparison, the degree of reduction in filter filtration pressure is 10% or more.
[0016]
The polyester film production method of the present invention is a method for producing a polyester film in which a polymer is melt-extruded by an extruder and then filtered and formed into a film. An imide compound (B) having an average molecular weight of 500 to 10,000 is added and mixed to form a film.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Details of the present invention will be described below.
[0018]
The polyester (A) constituting the polyester film of the present invention is, for example, a polyester mainly composed of aromatic dicarboxylic acid, alicyclic dicarboxylic acid or aliphatic dicarboxylic acid and diol.
[0019]
Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid. Acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and the like can be used. Among them, terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid can be preferably used. . As the alicyclic dicarboxylic acid component, for example, cyclohexane dicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. These acid components may be used alone or in combination of two or more. Furthermore, oxyacids such as hydroxyethoxybenzoic acid may be partially copolymerized.
[0020]
Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2′-bis (4 '-Β-hydroxyethoxyphenyl) propane or the like can be used. Among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol or the like can be used, and particularly preferably. , Ethylene glycol, etc. It is possible to have. These diol components may be used alone or in combination of two or more. In addition, polyester contains other compounds such as monomellitic compounds such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, 2,4-dioxybenzoic acid, lauryl alcohol, and phenyl isocyanate. The copolymer may be copolymerized within a linear range.
[0021]
The polyester (A) of the present invention is not particularly limited, but is selected from the group consisting of polyethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, and modified products thereof in terms of mechanical strength, productivity, and handleability. It is preferable that it is at least one kind.
[0022]
The imide-based compound (B) of the present invention is not particularly limited as long as it is melt moldable, but for example, those containing a structural unit represented by the following general formula are preferable.
[0023]
[Chemical 1]

(However, R in the formula ₁ Is
[Chemical 2]

[Chemical 3]

Represents one or more groups selected from an aliphatic hydrocarbon group such as, an alicyclic hydrocarbon group, an aromatic hydrocarbon group,
R in the formula ₂ Is
[Formula 4]

Represents one or two or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. )
Such preferred imide compounds (B) include, for example, tetracarboxylic acid and / or acid anhydrides thereof, aliphatic primary monoamines and / or as represented by JP-A-8-157642 and 2558339. Examples thereof include compounds obtained by dehydration condensation of one or more compounds selected from the group consisting of aromatic primary monoamines, and / or aliphatic primary diamines and / or aromatic primary diamines.
[0024]
Examples of the tetracarboxylic acid and / or acid anhydride thereof include ethylene tetracarboxylic acid, 1, 2, 3, 4-butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, pyromellitic acid, 1, 2, 3, 4 -Benzenetetracarboxylic acid, 3, 3 ', 4, 4'-biphenyltetracarboxylic acid, 2, 2', 3, 3'-biphenyltetracarboxylic acid, 3, 3 ', 4, 4'-benzophenone tetracarboxylic acid 2,2 ′, 3,3′-benzophenonetetracarboxylic acid, bis (2,3-dicarboxyphenyl) methane, bis (3,4-dicarboxyphenyl) methane, 1,1′-bis (2,3 -Dicarboxyphenyl) ethane, 2,2'-bis (3,4-dicarboxyphenyl) propane, 2,2'-bis (2,3-dicarboxyphenyl) propane, bis (3,4-dicarboxyl Nyl) ether, bis (2,3-dicarboxyphenyl) ether, bis (3,4-dicarboxyphenyl) sulfone, bis (2,3-dicarboxyphenyl) sulfone, 2,3,6,7-naphthalenetetra Carboxylic acid, 1, 4, 5, 8-naphthalene tetracarboxylic acid, 1, 2, 5, 6-naphthalene tetracarboxylic acid, 2, 3, 6, 7-anthracene tetracarboxylic acid, 1, 2, 7, 8- Phenanthrenetetracarboxylic acid, 3, 4, 9, 10-perylenetetracarboxylic acid, 4, 4 '-(p-phenylenedioxy) diphthalic acid, 4, 4'-(m-phenylenedioxy) diphthalic acid, 2, 2′-bis [(2,3-dicarboxyphenoxy) phenyl] propane and / or its acid anhydride is used.
[0025]
As the aliphatic primary monoamine, for example, a saturated or unsaturated linear, branched or alicyclic monoamine having 2 to 22 carbon atoms is used, and specifically, ethylamine, butylamine, pentylamine, hexylamine, heptyl. Amine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, eicosylamine, heneicosylamine, Docosylamine, cyclohexylamine, methylcyclohexylamine, dimethylcyclohexylamine, diethylcyclohexylamine, and structural isomers thereof are used.
[0026]
As the aromatic primary monoamine, for example, an unsubstituted or alkyl-substituted primary aniline having 1 to 22 carbon atoms is used. Specifically, aniline, toluidine, ethylaniline, propylaniline, butylaniline, pentylaniline, hexylaniline. , Heptylaniline, octylaniline, nonylaniline, decylaniline, undecylaniline, dodecylaniline, tridecylaniline, tetradecylaniline, pentadecylaniline, hexadecylaniline, heptadecylaniline, octadecylaniline, nonadecylaniline, eicosylaniline , Heneicosylaniline, docosylaniline, and structural isomers thereof are used.
[0027]
As the aliphatic primary diamine, for example, a primary diamine bonded with a methylene group having 1 to 12 carbon atoms or a diamine having an alicyclic group is used. Specifically, ethylene diamine, trimethylene diamine, tetramethylene diamine, pentane is used. Methylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 1,3-bisaminocyclohexane, diaminodicyclohexyl methane, m-xylene diamine and these These structural isomers are used.
[0028]
Examples of the aromatic primary diamine include benzidine, dimethylbenzidine, diaminodiphenylmethane, diaminoditolylmethane, diaminodiphenylethane, diaminodiphenylpropane, diaminodiphenylbutane, diaminodiphenyl ether, diaminodiphenylsulfone, diaminodiphenylbenzophenone, o, m, p —Phenylenediamine, tolylenediamine, xylenediamine, and the like, and aromatic primary diamines having the hydrocarbon group of these exemplified aromatic primary diamines as structural units are used.
[0029]
The imide compound (B) of the present invention has a number average molecular weight in the range of 500 to 10,000, preferably in the range of 1000 to 5000, and more preferably in the range of 1500 to 3000. When the number average molecular weight is less than 500, bleeding out tends to occur at the time of film formation, and it is difficult to obtain a film with few foreign matters, which is not preferable. On the other hand, if the number average molecular weight is larger than 10,000, the effect of reducing the filter filtration pressure is reduced, which is not preferable.
[0030]
In the present invention, the timing of adding the imide compound (B) to the polyester (A) is not particularly limited, but it may be added before the polymerization of the polyester, for example, before the esterification reaction, or after the polymerization and before the melt extrusion. You may add to. Further, before melt extrusion, the polyester and the imide compound or the polyetherimide compound may be pelletized.
[0031]
The glass transition temperature of the imide compound (B) used in the polyester film of the present invention is not particularly limited, but is preferably in the range of 70 to 250 ° C. More preferably, it is the range of 100-230 degreeC, More preferably, it is the range of 120-200 degreeC. If the glass transition temperature of the imide-based compound or the polyetherimide-based compound is lower than 70 ° C. or higher than 250 ° C., the melt moldability is inferior in the formation of the polyester film, so there is no practicality. The glass transition temperature is preferably in the range of 70 to 250 ° C.
[0032]
Although the difference between the solubility parameter of the imide compound (B) used in the polyester film of the present invention and the solubility parameter of the polyester (A) is not particularly limited, 4 (MPa) ^1/2 The following is preferable. More preferably, 3 (MPa) ^1/2 Or less, more preferably 2 (MPa) ^1/2 It is as follows. The difference between the solubility parameter of the imide compound (B) and the solubility parameter of the polyester (A) is 4 (MPa). ^1/2 If it is larger, it may be difficult to uniformly mix the polyester and the imide compound or the polyetherimide compound in the molten state, so 4 (MPa) ^1/2 The following is preferable. The solubility parameter referred to in the present invention is a calculated value by the atomic group contribution method, and can be calculated by, for example, the method described in Van Krevelen, “Properties of Polymers”, Third complete Revised Edition, Elsevier (1990). Various parameters for each atomic group have been proposed and may be calculated by any method, but methods such as Hoftyzer-Van Krevelen, Hoy, Small, and Fedors can be preferably used.
[0033]
The content of the imide compound (B) used in the polyester film of the present invention is not particularly limited, but is in the range of 0.01 to 30% by weight. Ru . More preferably, it is in the range of 0.1 to 20% by weight, and more preferably in the range of 0.5 to 10% by weight. When the content of the imide-based compound or the polyetherimide-based compound is less than 0.01% by weight, the effects of the present invention such as a filtration pressure reducing effect and an improvement in mechanical properties are small, and when the content is more than 30% by weight, Since the mechanical strength does not improve or the film surface characteristics deteriorate, it is preferably in the range of 0.01 to 30% by weight.
[0034]
The imide-based compound (B) of the present invention is not particularly limited, but for example, 1, 2, 3, 4-butanetetracarboxylic acid, pyromellitic from the viewpoint of melt moldability with the polyester (A) and handleability. One or more compounds selected from the group of tetracarboxylic acid components such as acids, bis (3,4-dicarboxyphenyl) ether, benzophenonetetracarboxylic acid, biphenyltetracarboxylic acid and / or acid anhydrides thereof; Examples thereof include condensates obtained by dehydration condensation of one or more compounds selected from the group of diamine components such as ethylenediamine, hexamethylenediamine, xylenediamine, diaminodiphenylmethane, diaminodiphenyl ether, diaminodiphenylbenzophenone, and phenylenediamine. Among them, an imide-based compound (B) having an optimum glass transition temperature that can be melt-molded with a polyester can be designed by an aromatic structural unit and an aliphatic structural unit containing a methylene group. The imide-based compound (B) having a structural unit containing carbonyl carbon has a small difference in solubility parameter from the polyester (A), and is particularly excellent in melt moldability.
[0035]
The haze of the polyester film of the present invention is not particularly limited, but is preferably in the range of 0.1 to 20%. More preferably, it is in the range of 0.1 to 10%, and more preferably in the range of 0.1 to 5%. Setting the haze of the polyester film to less than 0.1% is extremely difficult industrially and is not necessarily an essential requirement. On the other hand, if the haze is greater than 20%, the imide-based compound or the polyetherimide-based compound is not effectively dispersed in the polyester film, or foreign matter is present. It is preferable that
[0036]
Although the sum of the longitudinal direction and the width direction of the elastic modulus of the polyester film of the present invention is not particularly limited, 19.5 In the range of GPa Ru . More preferably, it is 10 19.5 GPa, more preferably 12- 19.5 GPa. When the sum of the elastic modulus in the longitudinal direction and the width direction of the polyester film is less than 8 GPa, for example, when used for a magnetic recording medium, if the elastic modulus of the base film is insufficient, it is received from the magnetic head or guide pin during traveling. Due to the tension, elongation occurs in the magnetic tape, which may adversely affect the electromagnetic conversion characteristics (output characteristics), may not be practically used, and the polyester film having a sum of elastic modulus greater than 30 GPa Difficult to manufacture industrially Ru .
[0037]
The intrinsic viscosity of the polyester (A) of the present invention is not particularly limited, but is preferably in the range of 0.55 to 3.00 (dl / g). More preferably, it is 0.60-2.00 (dl / g), More preferably, it is 0.80-1.75 (dl / g), Most preferably, it is 1.00-1.50 (dl / g). is there. When the intrinsic viscosity of the polyester (A) is large, the suppression of shear heat generation in the extruder and the reduction of the filter filtration pressure can be effectively realized by adding the imide compound (B). As a result, an excellent polyester film with less mechanical properties such as elastic modulus and surface defects can be obtained. When the intrinsic viscosity of the polyester (A) is less than 0.55 (dl / g), the effect of the added imide-based compound is not exhibited, the mechanical properties such as the elastic modulus are inferior, and the surface defects due to the amount of the oligomer and the like are present. In addition, if it exceeds 3.00 (dl / g), it is difficult to produce a polyester film by industrial extrusion, so the intrinsic viscosity is 0.55 to 3.00 (dl / g). ) Is preferable.
[0038]
In the polyester film of the present invention, specifically, in the polyester film formed by melt-extruding the polymer with an extruder and then filtered and formed into a film, the filter filtration pressure of the polyester containing the imide compound (B) is Although it does not specifically limit compared with the case of polyester (A) independent, It is preferable that the reduction degree of filter filtration pressure is 10% or more. Even if an imide-based compound is added, if the filter filtration pressure reduction degree is less than 10%, it is excellent in mechanical properties such as elastic modulus, which is the object of the present invention, and has high surface quality and low oligomer content. Therefore, it is preferable that the degree of reduction of the filter filtration pressure is 10% or more.
[0039]
In the present invention, although not particularly limited, in addition to the imide-based compound (B), for example, adding a copolyester having a mesogenic group in the main chain to the polyester (A) also reduces filtration pressure and improves quality. It is effective from. The copolyester is a melt-formable polyester having a mesogenic group in the main chain. For example, a polyester that forms an anisotropic melt phase composed of a structural unit selected from an aromatic oxycarbonyl unit, an aromatic dioxy unit, an aromatic dicarbonyl unit, an alkylenedioxy unit, and the like.
[0040]
As long as the polyester film of the present invention does not inhibit the present invention, organic stabilizers such as heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, pigments, dyes, fatty acid esters and waxes are usually used. It may be added to the extent that it is added. In addition, clay, mica, titanium oxide, calcium carbonate, carion, talc, wet or dry silica, colloidal silica, calcium phosphate, barium sulfate are used to impart surface slipperiness, abrasion resistance, scratch resistance, etc. In addition, inorganic particles such as alumina and zirconia, organic particles containing acrylic acid, styrene and the like as constituents may be added, or so-called internal particles that precipitate with a catalyst added during the polyester polymerization reaction may be contained. Further, a surfactant may be contained.
[0041]
The method for producing a polyester film of the present invention is a method for producing a polyester film in which a polymer is melt-extruded by an extruder and then filtered and formed into a film. The polyester (A) has a number average molecular weight before melt extrusion. 500 to 10,000 imide compounds (B) are added and mixed to form a film. More specifically, in a method for producing a polyester film in which a polymer is melt-extruded by an extruder and then filtered and formed into a film, an imide system having a number average molecular weight of 500 to 10,000 in the polyester (A) before melt extrusion. By adding and mixing the compound (B), the melt viscosity of the polyester raw material having a high intrinsic viscosity is greatly reduced as compared with the case where the filter is filtered with the polyester (A) alone. In addition, by significantly reducing the extrusion torque, the polyester film having a low oligomer and a low oligomer and excellent mechanical strength can be obtained. The number average molecular weight of the imide compound (B) used for the production of the polyester film of the present invention is in the range of 500 to 10,000, preferably in the range of 1000 to 5000, and more preferably in the range of 1500 to 3000. If the number average molecular weight is less than 500, for example, bleeding out is likely to occur during film formation, and it is difficult to obtain a film with less foreign matter. If the number average molecular weight is greater than 10,000, the filter filtration pressure is reduced. Therefore, the number average molecular weight of the imide compound (B) is preferably in the range of 500 to 10,000.
[0042]
The polyester film of the present invention may be a single film, but other polymer layers such as polyester, polyolefin, polyamide, polyvinylidene chloride and acrylic polymer are laminated directly or via a layer such as an adhesive. Also good. Particularly when the polyester layer is laminated on the surface layer, it is possible to obtain a film excellent in running property, slipperiness and smoothness by containing particles in the laminated portion, and particularly for a magnetic recording medium in which surface characteristics are important. It is preferable as a base film.
[0043]
The polyester film of the present invention may be subjected to any processing such as heat treatment, molding, surface treatment, laminating, coating, printing, embossing, etching, etc. as necessary.
[0044]
The polyester film of the present invention is not particularly limited, but is preferably a uniaxially or biaxially oriented film by a known method from the viewpoint of effects on mechanical strength and electrical characteristics.
[0045]
Although the polyester film of this invention is not specifically limited, Usually, thickness is 1000 micrometers or less, Preferably it is 1-500 micrometers, More preferably, it is the range of 3-250 micrometers.
[0046]
Although the use of the polyester film of the present invention is not particularly limited, it is used for magnetic recording media, electrical insulation, packaging, thermal transfer ribbons, thermal stencil printing, and the like.
[0047]
Although the example of the manufacturing method of the polyester film of this invention is demonstrated, it is not limited to this. Here, although the example using polyethylene terephthalate is shown as polyester (A), manufacturing conditions differ with polyester to be used.
[0048]
First, bis-β-hydroxyethyl terephthalate (BHT) is obtained by esterification from terephthalic acid and ethylene glycol or transesterification of dimethyl terephthalate and ethylene glycol according to a conventional method. Next, while transferring this BHT to the polymerization tank, the polymerization reaction is advanced by heating to 280 ° C. under vacuum. Here, a polyester having an intrinsic viscosity of about 0.5 is obtained. At this time, a predetermined amount of an imide compound may be added. The obtained polyester is solid-phase polymerized in a pellet form under reduced pressure. In the case of solid phase polymerization, preliminary crystallization is performed at a temperature of 180 ° C. or lower in advance, and then solid phase polymerization is performed at 190 to 250 ° C. under a reduced pressure of about 1 mmHg for 10 to 50 hours. Moreover, as a method for incorporating the particles into the polyester constituting the film, a method in which the particles are dispersed in a predetermined proportion in the form of a slurry in ethylene glycol and this ethylene glycol is polymerized with terephthalic acid is preferable. When adding the particles, for example, if the water sol or alcohol sol obtained at the time of synthesis is added without drying, the dispersibility of the particles is good. Also effective is a method in which a water slurry of particles is directly mixed with predetermined polyester pellets and kneaded into polyester using a vented twin-screw kneading extruder. As a method of adjusting the content and number of particles, a master of high-concentration particles is prepared by the above method, and this is diluted with polyester that is not substantially contained in the particles during film formation to adjust the particle content. The method to do is effective.
[0049]
Next, a raw material obtained by blending the polyethylene terephthalate and an imide-based compound (B) having a number average molecular weight in the range of 500 to 10,000, or a raw material obtained by once melting and uniformly mixing these at 180 ° C. for 3 hours or more After vacuum drying, it is supplied to an extruder heated to 280 ° C. under a nitrogen stream or under vacuum so that the intrinsic viscosity does not decrease, and a film is formed by a known method. At this time, the shear rate in the extruder is 20 seconds ¹ Or more, preferably 50 seconds ¹ The higher one is preferable because the imide compound is well dispersed in the extruder and the effect of the present invention is increased. ¹ A larger value is not preferable because the polymer is thermally decomposed by shearing heat generation. In addition, it is preferable to use a known filter, for example, a filter made of a material such as a sintered metal, a porous ceramic, sand, or a wire mesh, in order to remove foreign substances and altered polymers. Moreover, you may provide a gear pump as needed in order to improve fixed_quantity | feed_rate supply property. Extruded into a sheet form from a slit-shaped die and cooled and solidified on a casting roll to make an unstretched film. In the case of a laminated film, a sheet in which molten polyester is laminated is extruded using two or more extruders, manifolds, or merging blocks, and cooled on a casting roll to produce an unstretched film.
[0050]
Next, this unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. Here, a sequential biaxial stretching method in which stretching in the longitudinal direction and then in the width direction is performed first is used. The unstretched film is heated with a heating roll group at 80 to 150 ° C., stretched 2 to 7 times in the longitudinal direction in one or more stages, and cooled with a cooling roll group at 20 to 50 ° C. The longitudinal stretching speed is preferably in the range of 1000 to 50000% / min, but is not particularly limited. Subsequently, as a stretching method in the width direction, for example, a method using a tenter is common. The stretching ratio in the width direction is preferably 2 to 7 times, the stretching speed is 1000 to 20000% / min, and the temperature is preferably 80 to 150 ° C, but is not particularly limited. Further, if necessary, re-longitudinal stretching and / or re-lateral stretching is performed. As stretching conditions in that case, stretching in the longitudinal direction is preferably performed at a temperature of 80 to 180 ° C., a stretching ratio of 1.1 to 2.0 times, and as a stretching method in the width direction, a method using a tenter is preferable, and a temperature of 80 to 180 ° C. The stretching ratio is preferably 1.1 to 2.0 times, but is not particularly limited. Subsequently, this stretched film is heat-treated under tension or while relaxing in the width direction. In this case, the heat treatment temperature is 150 to 250 ° C., preferably 180 to 200 ° C., and the time is preferably 0.2 to 30 seconds, but is not particularly limited.
[0051]
[Methods for measuring physical properties and methods for evaluating effects]
(1) Intrinsic viscosity
The value calculated from the following equation from the solution viscosity measured at 25 ° C. in orthochlorophenol is used. That is,
ηsp / C = [η] + K [η] 2 · C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the weight of dissolved polymer per 100 ml of solvent (g / 100 ml, usually 1.2), and K is the Huggins constant (assuming 0.343). The solution viscosity and solvent viscosity were measured using an Ostwald viscometer.
[0052]
(2) Number average molecular weight
The analysis was requested from Toray Research Center, and measurement was performed by gel per chromatography (GPC).
[0053]
(3) Glass transition temperature Tg
It measured using DSC (Differential scanning calorimeter: Seiko Denshi Kogyo make). The DSC measurement conditions are as follows. That is, 5 mg of a sample is set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The sample was heated at 10 ° C./min, and the glass transition temperature Tg was detected.
[0054]
(4) Haze
According to JIS-K-6714, it measured using the haze meter (made by Suga Test Instruments). The internal haze was measured in a state immersed in tetralin, and expressed in terms of 25 μm according to the following formula.
[0055]
Haze (%) = Haze inside film (%) × (25 (μm) / film thickness (μm))
(5) Elastic modulus
Set the sample on a Tensilon type tensile tester (Orientec Co., Ltd.) so that the width is 10 mm and the distance between chucks is 100 mm. It was.
[0056]
(6) Amount of oligomer
100 mg of the polymer was dissolved in 1 ml of orthochlorophenol and measured by liquid chromatography (model 8500 Varian). Expressed in weight percent with respect to polymer.
[0057]
(7) Filter filtration pressure and degree of reduction of filter filtration pressure
The experimental apparatus is shown in FIG. 30mm small size unit made by Toshiba equipped with gear pump (Mitsubishi Heavy Industries, 1.6cc / rotation), filter (Nippon Seisen, Leaf Disc Filter-NF-140: 65mm diameter, one 80μm cut sintered filter) and pressure gauge Using a shaft extruder (L / D = 22), pressures Pa and Pb before and after the filter were measured under the following conditions. Tm is the peak of the melting temperature detected by DSC (differential scanning calorimeter).
[0058]

The filter filtration pressure reduction degree R was calculated by the following equation.
[0059]
R = [(P ₀ -P ₁ ) / P ₀ ] × 100
P ₀ : Filtration pressure when no imide compound is added (pressure difference: Pa-Pb)
P ₁ : Filtration pressure when an imide compound is added (pressure difference: Pa-Pb)
[0060]
【Example】
Based on the following examples, embodiments of the present invention will be described.
[0061]
Reference example 1
4,6.8 g of 1,2,3,4-butanetetracarboxylic acid, 48.2 g of hexadecylamine, and 13.6 g of m-xylenediamine were mixed in a flask using dimethylformamide as a solvent, and the temperature was gradually raised to 260 ° C. The mixture was stirred while warming, and condensed water and dimethylformamide were distilled off. Thereafter, the pressure was gradually reduced with stirring to complete the distillation completely, and the imide compound A remaining at the bottom of the flask was obtained.
[0062]
Reference example 2
Residual imide compound B was obtained in the same manner as in Reference Example 1, except that 46.4 g of hexamethylenediamine was used instead of m-xylenediamine.
[0063]
Reference example 3
Residual imide compound C was obtained in the same manner as in Reference Example 1 except that 19.8 g of diaminodiphenylmethane was used instead of m-xylenediamine.
[0064]
Reference example 4
Reaction by mixing 568 g of bis {4- [3- (4-aminophenoxy) benzoyl] phenyl} ether with 310 g of bis (3,4-dicarboxyphenyl) ether dianhydride, n-octylamine and m-cresol The mixture was gradually heated to 150 ° C. with stirring in a nitrogen atmosphere and discharged into methanol. Thereafter, the remaining imide compound D was obtained by further drying under reduced pressure.
[0065]
Reference Example 5
Under a nitrogen atmosphere, 32.4 g of m-phenylenediamine, 1 g of isoquinoline, and 200 g of m-cresol were added and heated to 50 ° C. to dissolve. To this, 208 g of 2,2′-bis [(2,3-dicarboxyphenoxy) phenyl] propane dianhydride was added, heated at 50 ° C. for 30 minutes and then to 180 ° C., and the generated water was received by a trap. The mixture was removed from the system and stirred for 2 hours. Thereafter, the remaining imide compound E was obtained by drying under reduced pressure.
[0066]
Example 1 (Tables 1 and 2)
Obtained in Reference Example 1 with respect to polyethylene terephthalate having an intrinsic viscosity of 0.8 (dl / g) (containing 0.075% by weight of alumina oxide having an average particle diameter of 200 nm as a slipping agent and 0.3% by weight of chip oligomer). After the polyester composition added with 5.0% by weight of the imide compound A was dried at 180 ° C. for 10 hours (3 Torr), it was supplied to a 90 mm single screw extruder and kneaded and melted at a temperature of 285 ° C. After filtration and removal using a sintered metal filter, the melt sheet is extruded from a 110-mm-wide T-die die for film molding, solidified by cooling and solidifying while applying an electrostatic charge to a cooling drum maintained at 25 ° C., and unstretched A film was obtained. At this time, the reduction degree of the filter filtration pressure was 14%.
[0067]
This unstretched film was stretched 4 times at a temperature of 95 ° C. in a stepwise manner in the longitudinal direction using a roll-type stretching machine. Subsequently, using a tenter, the film was stretched 4 times in the width direction at a temperature of 105 ° C., and heat-treated at a temperature of 210 ° C. for 10 seconds under a constant length to obtain a biaxially oriented film having a thickness of 12 μm.
[0068]
As shown in Table 2, the biaxially oriented film had excellent properties as a film for various uses such as magnetic recording media and electrical insulation.
[0069]
Examples 2 and 3 (Tables 1 and 2)
Polyethylene terephthalate having a different intrinsic viscosity as a raw material polyester (intrinsic viscosity 1.0 (dl / g): chip oligomer amount 0.28 wt%, intrinsic viscosity 1.4 (dl / g): chip oligomer amount 0.26 wt. %) Was used in the same manner as in Example 1 to obtain a biaxially oriented film. The filter filtration pressure reduction degree and the characteristics of the obtained biaxially oriented film are as shown in Table 2. However, when a raw material having a high intrinsic viscosity is used, the effect of the imide compound becomes more remarkable. As a result, it was possible to obtain a high-quality film having excellent filter filtration pressure reduction and elastic modulus.
[0070]
Examples 4 to 7 (Tables 1 and 2)
The content of the imide compound to be used and the number average molecular weight were changed, and a film was formed in the same manner as in Example 2 to obtain a biaxially oriented film. The filter filtration pressure reduction degree and the characteristics of the obtained biaxially oriented film are as shown in Table 2, but when the imide compound having the structure of the present invention is used, the filter filtration pressure reduction degree and the elastic modulus are excellent. A high quality film was obtained.
[0071]
Examples 8 to 11 (Tables 1 and 2)
The type of imide compound (B) to be used was changed to imide compounds B to E, respectively, and a biaxially oriented film was obtained in the same manner as in Example 2. The filter filtration pressure reduction degree and the characteristics of the obtained biaxially oriented film are as shown in Table 2. However, when the imide compound having the structure of the present invention is used, the filter filtration pressure reduction degree and the elastic modulus are excellent. A high quality film was obtained.
[0072]
Comparative Examples 1 to 3 (Tables 3 and 4)
A biaxially oriented film was obtained in the same manner as in Examples 1 to 3 except that no imide compound was used. The filter filtration pressure reduction degree and the characteristics of the obtained biaxially oriented film are as shown in Table 4, but the filter filtration pressure reduction degree is small, the mechanical properties such as elastic modulus are inferior, and the oligomer amount is also large. Therefore, it is difficult to obtain a high-quality film, and it cannot be practically used for applications such as magnetic recording media and electrical insulation.
[0073]
Comparative Examples 4 and 5 (Tables 3 and 4)
The number average molecular weight of the imide compound A obtained in Reference Example 1 was changed, and a film was formed in the same manner as in Example 2 to obtain a biaxially oriented film. When the imide-based compound does not satisfy the configuration of the present invention, the effect is not sufficiently exhibited even if it is used, and it is difficult to obtain a high-quality film, and it is practical for applications such as magnetic recording media and electrical insulation. Unbearable for top use.
[0074]
[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0075]
【The invention's effect】
The polyester film of the present invention comprises a polyester (A) and an imide-based compound (B) having a number average molecular weight of 500 to 10,000, and improves mechanical properties such as the elastic modulus of the film, as well as surface defect oligomers of the film, etc. It is intended to improve quality and can be widely used for various film applications such as magnetic recording media, electrical insulation, packaging, thermal transfer ribbons, and thermal stencil printing.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an extrusion apparatus used for evaluating the filter filtration pressure and the degree of reduction of the filter filtration pressure according to the present invention.
[Explanation of symbols]
1: 30mm small single screw extruder
2: Short pipe
3: Gear pump
4: Filter
5: Bleed mouth
6: Pressure gauge on the upstream side of the filter
7: Pressure gauge downstream of the filter
81: Extruder supply unit thermocouple
82: Extruder compression section thermocouple
83: Extruder metering section thermocouple
84: Thermocouple for gear pump
85: Filter unit thermocouple
86: Hopper

Claims (6)

Polyester (A), a polyester film content of 0.01 to 30 wt% of the number average molecular weight of the imide compound of 500 to 10000 (B) Tona is, imide compound (B), a polyester A biaxially oriented polyester film characterized in that the sum of the elastic modulus in the longitudinal direction and the width direction of the film is 8 to 19.5 GPa . The biaxially oriented polyester film according to claim 1, wherein the imide compound (B) has a glass transition temperature of 70 to 250 ° C. The biaxially oriented polyester film according to claim 1 or 2, wherein the difference between the solubility parameter of the imide compound (B) and the solubility parameter of the polyester (A) is 4 (MPa) ^1/2 or less. The biaxially oriented polyester film according to any one of claims 1 to 3 , wherein the haze of the polyester film is 0.1 to 20%. The biaxially oriented polyester film according to any one of claims 1 to 4 , wherein the intrinsic viscosity of the polyester (A) is 0.55 to 3.00 (dl / g). In the polyester film formed by melt-extruding the polymer with an extruder and then filtered through a filter, the filter filtration pressure of the polyester containing the imide compound (B) is less than that of the polyester (A) alone. The biaxially oriented polyester film according to any one of claims 1 to 5 , wherein a reduction degree of the filtration pressure is 10% or more.

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