JP4439779B2 - Biaxially stretched film - Google Patents

Description

又は一般式（２）：
【化６】

で表される化合物が好ましい。一般式（１）と（２）において、Ｒ¹およびＲ²はそれぞれ独立して、炭素数が１〜１０の脂肪族基、炭素数が３〜１０の脂環式基、及び炭素数が６〜１０の芳香族基からなる群から選ばれる有機基、好ましくは、メチレン基、エチレン基、プロピレン基、ブチレン基又はこれらの構造異性体、例えば、イソプロピレン基、イソブチレン基を表す。Ｒ³は炭素数が１〜１０の脂肪族基、炭素数が３〜１０の脂環式基、及び炭素数が６〜１０の芳香族基からなる群から選ばれる有機基、好ましくは、メチル基、エチル基、プロピル基、ブチル基、又はこれらの構造異性体、例えば、イソプロピル基、イソブチル基を表す。一般式（１）及び（２）の化合物としては、３，９−ビス（１，１−ジメチル−２−ヒドロキシエチル）−２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカン、５−メチロール−５−エチル−２−（１，１−ジメチル−２−ヒドロキシエチル）−１，３−ジオキサン等が特に好ましい。
【００１０】
環状アセタール骨格を有するジカルボン酸としては、一般式（３）：
【化７】

又は一般式（４）：
【化８】

で表される化合物が好ましい。一般式（３）及び（４）において、Ｒ³は前記と同様であり、Ｒ⁴及びＲ⁵はそれぞれ独立して炭素数が１〜１０の脂肪族基、炭素数が３〜１０の脂環式基、及び炭素数が６〜１０の芳香族基からなる群から選ばれる有機基、好ましくは、メチレン基、エチレン基、プロピレン基、ブチレン基又はこれらの構造異性体、例えば、イソプロピレン基、イソブチレン基を表す。Ｒ⁶およびＲ⁷はそれぞれ独立して水素原子、メチル基、エチル基、又はイソプロピル基、好ましくは水素原子あるいはメチル基を表す。一般式（３）及び（４）の化合物としては、３，９−ビス（１，１−ジメチル−２−カルボキシエチル）−２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカン、５−カルボキシ−５−エチル−２−（１，１−ジメチル−２−カルボキシエチル）−１，３−ジオキサン等が特に好ましい。
【００１１】
本発明に用いられるポリエステル樹脂は、環状アセタール骨格を有するジカルボン酸単位及び／又は環状アセタール骨格を有するジオール単位を導入することにより、二軸延伸フィルムに屈曲時の耐ピンホール性、耐衝撃性、透明性、耐熱性が付与できる。
【００１２】
本発明に用いられる樹脂を構成する環状アセタール骨格を有するジオール単位、又は環状アセタール骨格を有するジカルボン酸単位の含有割合は、それぞれジオール構成単位、ジカルボン酸構成単位の１〜１０モル％であり、好ましくは３〜１０モル％である。１モル％未満では屈曲時の耐ピンホール性、耐衝撃性、透明性が充分には得られないことがあり好ましくなく、１０モル％を超えると、樹脂の結晶性が確保できないことがあり好ましくない。上記割合で製造された二軸延伸フィルム用ポリエステル樹脂を二軸延伸して得られる二軸延伸フィルムは、良好な屈曲時の耐ピンホール性、耐衝撃性、透明性を示す。
【００１３】
本発明に用いられる樹脂を構成する環状アセタール骨格を有するジオール以外のジオールとしては、特に制限はされないが、エチレングリコール、トリメチレングリコール、１，４−ブタンジオール、１，５−ペンタンジオール、１，６−ヘキサンジオール、ジエチレングリコール、プロピレングリコール、ネオペンチルグリコール等の脂肪族ジオール類；ポリエチレングリコール、ポリプロピレングリコール、ポリブチレングリコール等のポリエーテル化合物類；１，３−シクロヘキサンジメタノール、１，４−シクロヘキサンジメタノール、１，２−デカヒドロナフタレンジメタノール、１，３−デカヒドロナフタレンジメタノール、１，４−デカヒドロナフタレンジメタノール、１，５−デカヒドロナフタレンジメタノール、１，６−デカヒドロナフタレンジメタノール、２，７−デカヒドロナフタレンジメタノール、テトラリンジメタノール、ノルボルネンジメタノール、トリシクロデカンジメタノール、ペンタシクロドデカンジメタノール等の脂環式ジオール類；４，４’−（１−メチルエチリデン）ビスフェノール、メチレンビスフェノール（ビスフェノールＦ）、４，４’−シクロヘキシリデンビスフェノール（ビスフェノールＺ）、４，４’−スルホニルビスフェノール（ビスフェノールＳ）等のビスフェノール類；前記ビスフェノール類のアルキレンオキシド付加物；ヒドロキノン、レゾルシン、４，４’−ジヒドロキシビフェニル、４，４’−ジヒドロキシジフェニルエーテル、４，４’−ジヒドロキシジフェニルベンゾフェノン等の芳香族ジヒドロキシ化合物；及び前記芳香族ジヒドロキシ化合物のアルキレンオキシド付加物等が例示できる。本発明の二軸延伸フィルムの機械的性能、経済性等の面から特にエチレングリコールが好ましい。ジオール構成単位中のエチレングリコール単位の割合を好ましくは８０〜９９モル％、より好ましくは９０〜９９モル％とすることで上記効果は一層顕著になる。
【００１４】
また本発明に用いられる樹脂を構成する環状アセタール骨格を有するジカルボン酸以外のジカルボン酸としては、特に制限はされないが、コハク酸、グルタル酸、アジピン酸、ピメリン酸、スベリン酸、アゼライン酸、セバシン酸、デカンジカルボン酸、ドデカンジカルボン酸、シクロヘキサンジカルボン酸、ノルボルナンジカルボン酸、トリシクロデカンジカルボン酸、ペンタシクロドデカンジカルボン酸等の脂肪族ジカルボン酸及びこれらのエステル形成性誘導体；テレフタル酸、イソフタル酸、フタル酸、２−メチルテレフタル酸、１，４−ナフタレンジカルボン酸、１，５−ナフタレンジカルボン酸、２，６−ナフタレンジカルボン酸、２，７−ナフタレンジカルボン酸、ビフェニルジカルボン酸、テトラリンジカルボン酸等の芳香族ジカルボン酸及びこれらのエステル形成性誘導体が例示できる。本発明の二軸延伸フィルムの機械的性能の面から芳香族ジカルボン酸及びそのエステル形成性誘導体が好ましく、経済性の面から特にテレフタル酸及びこのエステル形成性誘導体が好ましい。また、耐熱性の面から２，６−ナフタレンジカルボン酸及びそのエステル形成性誘導体が好ましい。ジカルボン酸構成単位中に占める芳香族ジカルボン酸単位の割合は、好ましくは８０モル％以上、より好ましくは９０モル％以上である。上記割合とすることにより、本発明の二軸延伸フィルムは耐熱性、機械的性能がより優れたものとなる。
【００１５】
本発明で用いられるポリエステル樹脂は、２８０℃で溶融して１５０〜２３０℃で定温結晶化した際の脱偏光強度法に基づく半結晶化時間の最小値が３００秒以下である。半結晶化時間が３００秒を超えると結晶性が小さくなり、二軸延伸フィルムを熱固定する際に球晶が大きくなって、透明性が損なわれたり、熱固定ができなくなったりすることがあり好ましくない。
【００１６】
本発明で用いられるポリエステル樹脂の極限粘度（フェノールと１，１，２，２−テトラクロロエタンとの質量比が６：４の混合溶媒中２５℃で測定）は好ましくは０．３〜１．５ｄｌ／ｇの範囲であり、より好ましくは０．５〜１．３ｄｌ／ｇ、更に好ましくは０．６〜１．１ｄｌ／ｇの範囲である。上記範囲とすることで、二軸延伸フィルムに強度と良好な成形性を付与することができる。
【００１７】
本発明で用いられるポリエステル樹脂には本発明の目的を損なわない範囲でブチルアルコール、ヘキシルアルコール、オクチルアルコール等のモノアルコール類やトリメチロールプロパン、グリセリン、ペンタエリスリトール等の３価以上の多価アルコール、安息香酸、プロピオン酸、酪酸等のモノカルボン酸を原料モノマーとして用いることもできる。
【００１８】
更に用途に応じて各種の成形助剤や添加剤、例えばフィラー、着色剤、補強剤、表面平滑剤、レベリング剤、硬化反応促進剤、光安定化剤、紫外線吸収剤、可塑剤、酸化防止剤、増量剤、つや消し剤、乾燥調節剤、帯電防止剤、沈降防止剤、界面活性剤、流れ改良剤、乾燥油、ワックス類、熱可塑性オリゴマー等を含むこともできる。
【００１９】
本発明で用いられるポリエステル樹脂を製造する方法に特に制限はなく、従来公知の方法を適用することが出来る。例えばエステル交換法、直接エステル化法等の溶融重合法または溶液重合法を挙げることが出来る。エステル交換触媒、エステル化触媒、エーテル化防止剤、また重合に用いる重合触媒、熱安定剤、光安定剤等の各種安定剤、重合調整剤等も従来既知のものを用いることが出来る。エステル交換触媒として、マンガン、コバルト、亜鉛、チタン、カルシウム等の化合物、またエステル化触媒として、マンガン、コバルト、亜鉛、チタン、カルシウム等の化合物、またエーテル化防止剤としてアミン化合物等が例示される。重縮合触媒としてはゲルマニウム、アンチモン、スズ、チタン等の化合物が例示される。また熱安定剤としてリン酸、亜リン酸、フェニルホスホン酸等の各種リン化合物を加えることも有効である。その他光安定剤、耐電防止剤、滑剤、酸化防止剤、離型剤等を加えても良い。また、直接エステル化法において、スラリー性改善のために水を加えても良い。
【００２０】
本発明で用いられるポリエステル樹脂から二軸延伸フィルムを得る方法としては特に制限されるものではないが、押し出し成形やカレンダー成形等の公知の方法でフィルムを製膜し、一方向に１．１〜７倍、好ましくは２〜６倍、特に好ましくは２．５〜５倍に延伸し、該方向と直角方向に１．１〜７倍、好ましくは２〜６倍、特に好ましくは２．５〜５倍に延伸する。フィルムの延伸手段としては、ロール延伸、長間隙延伸、テンター延伸などの方法が適用でき、また、延伸時の形状においてもフラット状、チューブ状等の方法が適用できる。更に、逐次二軸延伸、同時二軸延伸、一軸延伸あるいはこれらの組み合わせなどで行われる。これらの延伸におけるヒートセットは３０〜２４０℃の加熱ゾーンを１〜３０秒通すことにより行われる。
【００２１】
本発明の二軸延伸フィルムの厚さは好ましくは５〜３００μｍ、より好ましくは７〜１００μｍ、更に好ましくは１０〜５０μｍである。
【００２２】
本発明の二軸延伸フィルムを５００回屈曲させた後のピンホールの数は２．０個／ｍ²以下、好ましくは１．０個／ｍ²以下である。５００回屈曲させた後のピンホールの数が２．０個／ｍ²を超えると、ピンホールが出来易く、ガスバリア性が損なわれたり、機械的性能が損なわれたりすることがあり好ましくない。
【００２３】
本発明の二軸延伸フィルムの衝撃穴あけ試験での衝撃強度は５０００ｋｇ・ｃｍ／ｃｍ以上、好ましくは６０００ｋｇ・ｃｍ／ｃｍ以上、更に好ましくは７０００ｋｇ・ｃｍ／ｃｍ以上である。衝撃穴あけ試験での衝撃強度が５０００ｋｇ・ｃｍ／ｃｍ未満では衝撃強度が不足し、二軸延伸フィルムが破損することがあり好ましくない。
【００２４】
本発明の二軸延伸フィルム（厚さ１５μｍ）のヘーズは３％以下、好ましくは２％以下、更に好ましくは１％以下である。ヘーズが３％を超えると透明性が損なわれることがあり好ましくない。
【００２５】
本発明の二軸延伸フィルムは沸騰水中で３０分間熱水処理した後の収縮率が３％以下、好ましくは２％以下、更に好ましくは１％以下である。該収縮率が３％を越えると、耐熱性が不足することがあり好ましくない。
【００２６】
本発明の二軸延伸フィルムは耐ピンホール性、耐衝撃性、透明性、耐熱性が良好であり、食品をはじめ各種包装フィルム、磁気記録媒体用フィルム、コンデンサ用フィルムなどに好適に用いることができる。
【００２７】
【実施例】
以下実施例により本発明を更に具体的に説明する。但し本発明はこれらの実施例により限定するものではない。
【００２８】
実施例１〜６、参考例１、比較例１〜３
（１）樹脂の合成
充填塔式精留塔、分縮器、全縮器、コールドトラップ、攪拌翼、加熱装置、窒素導入管を備えた１５０リットル（Ｌ）のポリエステル製造装置に表１〜３に記載の量のモノマーを仕込み、酢酸マンガン四水和物をジカルボン酸成分に対して０．０３モル％加え、常圧、窒素雰囲気下で昇温した。２００℃まで昇温し、エステル交換反応を行った。ジカルボン酸成分の反応転化率を９０モル％以上とした後、ジカルボン酸成分に対して０．０２モル％の三酸化アンチモンと０．０６モル％のリン酸トリメチルを加え、昇温と減圧を徐々に行い、最終的に２７０〜３００℃、０．１ｋＰａ以下で重縮合反応を行った。徐々に反応物の粘度が上昇し、適度な溶融粘度になった時点で反応を終了し、ポリエステル樹脂を得た。
【００２９】
（２）二軸延伸フィルムの作製
得られたポリエステル樹脂を押し出し成形により、シリンダー温度２５０〜２８０℃、ダイ温度２５０〜２８０℃、ロール温度７５〜８０℃の条件で、厚さ約０．２ｍｍの未延伸シートを作製した。次に該未延伸シートをガラス転移温度より１０〜２０℃高い温度で３．６×３．６倍に同時二軸延伸を行った後、２１０〜２３０℃で１０〜３０秒間熱固定処理して、厚さ１５μｍの二軸延伸フィルムを得た。
【００３０】
（３）樹脂の評価
・極限粘度
混合溶媒（質量比：フェノール／１，１，２，２−テトラクロロエタン＝６／４）を用いて２５℃恒温下で測定した。
・半結晶化時間
樹脂ペレットを押し潰してシート状とし、カバーガラスにはさみ、２８０℃で３分間溶融した後、所定温度の結晶化浴に入れ脱偏光強度の経時変化を測定して、その温度での半結晶化時間を求めた。結晶化浴の温度を１５０〜２３０℃まで１０℃間隔で変化させて半結晶化時間を測定し、その中で最小の値をその樹脂の半結晶化時間とした。
【００３１】
（４）二軸延伸フィルムの評価
・耐ピンホール性
二軸延伸フィルムを理学工業（株）製ゲルボーフレックスで、５００回屈曲させた後、ゲルボーフレックスの軸方向を測定方向としてピンホールテスター（微弱電流測定法）でピンホールの数を測定した。測定回数は５回、測定電圧は１．０ｋＶで行った。
・衝撃穴あけ試験での衝撃強度
ＪＩＳ Ｐ８１３、ＡＳＴＭ Ｄ７８１に準じて測定した。測定機器は、東洋精機（株）製パンクチャー テスターを使用した。測定回数は５回、測定条件は、温度２３℃、相対湿度５０％で行った。
・ヘーズ
ＪＩＳ−Ｋ−７１０５、ＡＳＴＭ Ｄ１００３に準じ、測定装置は、日本電色工業社製の曇価測定装置（型式：ＣＯＨ−３００Ａ）を使用した。
・耐熱性
二軸延伸フィルムに５．０ｃｍ×５．０ｃｍの印をつけ、沸騰水中に３０分間入れて熱水処理を行った後、その間隔を測定した。収縮率を以下の式によりにより算出した。
収縮率（％）＝（１−熱水処理後の間隔／熱水処理前の間隔）×１００
これらの結果を表１〜３に示す。
【００３２】
尚、表中で使用した略記の意味は下記の通りである。
ＤＭＴ：テレフタル酸ジメチル
ＮＤＣＭ：２，６−ナフタレンジカルボン酸ジメチル
ＳＰＤ：３，９−ビス（１，１−ジメチル−２−カルボキシエチル）−２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカンを
ＤＯＤ：５−カルボキシ−５−エチル−２−（１，１−ジメチル−２−カルボキシキシエチル）−１，３−ジオキサン
ＥＧ：エチレングリコール
ＳＰＧ：３，９−ビス（１，１−ジメチル−２−ヒドロキシエチル）２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカン
ＤＯＧ：５−メチロール−５−エチル−２−（１，１−ジメチル−２−ヒドロキシエチル）−１，３−ジオキサン
【００３３】
表１
実施例番号 実施例１ 実施例２ 実施例３ 参考例１
モノマー仕込量（モル）
ジカルボン酸成分
ＤＭＴ ２９３．７ ３０４．５ ２８０．４ −
ＮＤＣＭ − − − ２３５．９
ジオール成分
ＥＧ ４８４．６ ５１１．６ ４５１．４ ３８９．２
ＳＰＧ １４．７ ６．１ ２５．２ １１．８
ポリエステル樹脂の評価
Ｔｇ（℃） ８７ ８５ ８９ １２５
ＩＶ（ｄｌ／ｇ） ０．６８ ０．６７ ０．７０ ０．６５
半結晶化時間（秒） １２５ ５７ ２４７ １９８
二軸延伸フィルムの評価
ヘーズ（％／１５μｍ） ０．３ ０．８ ０．２ ０．３
衝撃強度（ｋｇ・ｃｍ／ｃｍ）
７０００ ６０００ ７５００ ９０００
耐ピンホール性（個／ｍ2 ）
０．３ ０．７ ０．１ ０．５
収縮率（ＴＤ：％） ０．８ １．２ ０．５ ０．２
収縮率（ＭＤ：％） １．４ １．８ ０．８ ０．３
【００３４】
表２
実施例番号 実施例４ 実施例５ 実施例６
モノマー仕込量（モル）
ジカルボン酸成分
ＤＭＴ ３００．０ ２９７．２ ３０３．７
ＳＰＤ − １４．９ −
ＤＯＤ − − １５．２
ジオール成分
ＥＧ ４９５．０ ５０５．２ ５１６．２
ＤＯＧ １５．０ − −
ポリエステル樹脂の評価
Ｔｇ（℃） ８５ ８４ ８４
ＩＶ（ｄｌ／ｇ） ０．６５ ０．６９ ０．６８
半結晶化時間（秒） ７８ １７８ ２７７
二軸延伸フィルムの評価
ヘーズ（％／１５μｍ） ０．２ ０．５ ０．８
衝撃強度（ｋｇ・ｃｍ／ｃｍ）８５００ ５５００ ５５００
耐ピンホール性（個／ｍ2 ） ０．１ ０．８ ０．９
収縮率（ＴＤ：％） ０．４ １．２ ０．９
収縮率（ＭＤ：％） ０．６ １．６ １．３
【００３５】
表３

【００３６】
【発明の効果】
本発明で用いられる樹脂から得られる二軸延伸フィルムは耐ピンホール性、耐衝撃性、透明性、耐熱性など、優れた性能を兼ね備えており本発明の工業的意義は大きい。[0001]
BACKGROUND OF THE INVENTION
The present invention uses a polyester resin having a diol unit having a cyclic acetal skeleton and / or a dicarboxylic acid unit having a cyclic acetal skeleton, and has good pinhole resistance, impact resistance, transparency, and heat resistance. It relates to film.
[0002]
[Prior art]
A biaxially stretched film obtained from a polyester resin typified by polyethylene terephthalate (hereinafter may be abbreviated as PET) has excellent transparency, mechanical properties, dimensional stability, heat resistance, chemical resistance, etc. Widely used for magnetic tape and food packaging.
[0003]
In recent years, for food packaging applications, particularly high demands have been placed on packaging films such as the contents appearing beautiful and the contents do not impair the taste during storage. However, the biaxially stretched PET film is excellent in transparency and gas barrier properties, but has poor flexibility and pinhole resistance, so that pinholes can be formed during transportation, etc. There was a problem that sometimes went out.
[0004]
Therefore, in order to improve pinhole resistance, it has been proposed to copolymerize a soft segment with polyester. Specifically, JP-A-7-330926 proposes a biaxially stretched film obtained from a polyester resin composed of polytetramethylene glycol, terephthalic acid and ethylene glycol having a low molecular weight. This biaxially stretched film has a problem that although the pinhole resistance is improved, the heat resistance is lowered. JP-A-8-41184 proposes a biaxially stretched film obtained from a polyester resin composed of polyoxytetramethylene glycol, naphthalenedicarboxylic acid and ethylene glycol having a low molecular weight. This biaxially stretched film has good pinhole resistance and heat resistance, but has a problem that transparency is impaired. Various studies have been made to impart pinhole resistance to biaxially stretched films obtained from PET and polyethylene naphthalate (hereinafter sometimes abbreviated as PEN), but pinhole resistance, impact resistance, transparency, A biaxially stretched film having heat resistance has not been proposed yet.
[0005]
[Problems to be solved by the invention]
In view of the above problems, the present invention is intended to provide a biaxially stretched film having pinhole resistance, impact resistance, transparency, and heat resistance.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that a biaxially stretched film obtained from a polyester resin modified with a dicarboxylic acid having a cyclic acetal skeleton and / or a diol having a cyclic acetal skeleton has a pinhole resistance. It was found that the property, the impact resistance, the transparency, and the heat resistance were good, and reached the present invention.
[0007]
That is, the present invention is a polyester resin having a dicarboxylic acid structural unit and a diol structural unit, wherein at least (a) 1 to 10 mol% of the dicarboxylic acid structural unit is a dicarboxylic acid unit having a cyclic acetal skeleton. Or (b) a biaxially stretched film using a polyester resin having the following physical properties (1) and (2), wherein 1 to 10 mol% of the diol structural unit is a diol unit having a cyclic acetal skeleton. Is.
(1) The intrinsic viscosity measured at 25 ° C. in a mixed solvent of phenol and 1,1,2,2-tetrachloroethane in a mass ratio of 6: 4 is 0.3 to 1.5 dl / g.
(2) The minimum value of the half crystallization time based on the depolarization intensity method when melted at 280 ° C. and crystallized at 150 to 230 ° C. is 300 seconds or less.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The polyester resin used for the biaxially stretched film of the present invention is (A) a dicarboxylic acid structural unit containing 1 to 10 mol% of a dicarboxylic acid unit having a cyclic acetal skeleton (a structural unit derived from a dicarboxylic acid having a cyclic acetal skeleton). And a diol structural unit having no cyclic acetal skeleton, (B) a dicarboxylic acid structural unit not having a cyclic acetal skeleton and a diol unit having a cyclic acetal skeleton (a structural unit derived from a diol having a cyclic acetal skeleton). Diol constituent unit containing 10 mol%, or (C) Diol constituent unit containing 1 to 10 mol% of a dicarboxylic acid constituent unit containing 1 to 10 mol% of a dicarboxylic acid unit having a cyclic acetal skeleton and a diol unit having a cyclic acetal skeleton A polyester resin consisting of
[0009]
The diol having a cyclic acetal skeleton constituting the resin used in the biaxially stretched film of the present invention has the general formula (1):
[Chemical formula 5]

Or general formula (2):
[Chemical 6]

The compound represented by these is preferable. In General Formulas (1) and (2), R ¹ and R ² are each independently an aliphatic group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and 6 carbon atoms. Represents an organic group selected from the group consisting of 10 to 10 aromatic groups, preferably a methylene group, an ethylene group, a propylene group, a butylene group, or a structural isomer thereof such as an isopropylene group or an isobutylene group. R ³ is an organic group selected from the group consisting of an aliphatic group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and an aromatic group having 6 to 10 carbon atoms, preferably methyl Represents a group, an ethyl group, a propyl group, a butyl group, or a structural isomer thereof, for example, an isopropyl group or an isobutyl group. Examples of the compounds of the general formulas (1) and (2) include 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 5-methylol-5-ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane and the like are particularly preferable.
[0010]
As the dicarboxylic acid having a cyclic acetal skeleton, the general formula (3):
[Chemical 7]

Or general formula (4):
[Chemical 8]

The compound represented by these is preferable. In the general formulas (3) and (4), R ³ is the same as above, R ⁴ and R ⁵ are each independently an aliphatic group having 1 to 10 carbon atoms and an alicyclic ring having 3 to 10 carbon atoms. An organic group selected from the group consisting of a formula group and an aromatic group having 6 to 10 carbon atoms, preferably a methylene group, an ethylene group, a propylene group, a butylene group, or a structural isomer thereof such as an isopropylene group, Represents an isobutylene group. R ⁶ and R ⁷ each independently represents a hydrogen atom, a methyl group, an ethyl group, or an isopropyl group, preferably a hydrogen atom or a methyl group. As compounds of the general formulas (3) and (4), 3,9-bis (1,1-dimethyl-2-carboxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 5-carboxy-5-ethyl-2- (1,1-dimethyl-2-carboxyethyl) -1,3-dioxane and the like are particularly preferable.
[0011]
The polyester resin used in the present invention introduces a dicarboxylic acid unit having a cyclic acetal skeleton and / or a diol unit having a cyclic acetal skeleton, whereby pinhole resistance when bent to a biaxially stretched film, impact resistance, Transparency and heat resistance can be imparted.
[0012]
The content ratio of the diol unit having a cyclic acetal skeleton constituting the resin used in the present invention or the dicarboxylic acid unit having a cyclic acetal skeleton is 1 to 10 mol% of the diol structural unit and the dicarboxylic acid structural unit, respectively. Is 3 to 10 mol%. If it is less than 1 mol%, pinhole resistance, impact resistance, and transparency at the time of bending may not be sufficiently obtained, and if it exceeds 10 mol%, the crystallinity of the resin may not be ensured. Absent. A biaxially stretched film obtained by biaxially stretching a polyester resin for a biaxially stretched film manufactured at the above ratio exhibits good pinhole resistance, impact resistance, and transparency when bent.
[0013]
The diol other than the diol having a cyclic acetal skeleton constituting the resin used in the present invention is not particularly limited, but ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1, Aliphatic diols such as 6-hexanediol, diethylene glycol, propylene glycol, and neopentyl glycol; polyether compounds such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; 1,3-cyclohexanedimethanol, 1,4-cyclohexanedi Methanol, 1,2-decahydronaphthalene diethanol, 1,3-decahydronaphthalene diethanol, 1,4-decahydronaphthalene diethanol, 1,5-decahydronaphthalene diethanol, 1,6- Cycloaliphatic diols such as cahydronaphthalene diethanol, 2,7-decahydro naphthalene diethanol, tetralin dimethanol, norbornene dimethanol, tricyclodecane dimethanol, pentacyclododecane dimethanol; 4,4 ′-(1 -Methylethylidene) bisphenol, methylene bisphenol (bisphenol F), 4,4'-cyclohexylidene bisphenol (bisphenol Z), bisphenols such as 4,4'-sulfonylbisphenol (bisphenol S); alkylene oxide addition of the bisphenols Products; aromatic dihydroxy compounds such as hydroquinone, resorcin, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenylbenzophenone; and Alkylene oxide adducts of serial aromatic dihydroxy compounds can be exemplified. Ethylene glycol is particularly preferred from the standpoints of the mechanical performance and economics of the biaxially stretched film of the present invention. The said effect becomes still more remarkable by making the ratio of the ethylene glycol unit in a diol structural unit preferably 80-99 mol%, more preferably 90-99 mol%.
[0014]
The dicarboxylic acid other than the dicarboxylic acid having a cyclic acetal skeleton constituting the resin used in the present invention is not particularly limited, but succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid , Decane dicarboxylic acid, dodecane dicarboxylic acid, cyclohexane dicarboxylic acid, norbornane dicarboxylic acid, tricyclodecane dicarboxylic acid, pentacyclododecane dicarboxylic acid and other aliphatic dicarboxylic acids and ester-forming derivatives thereof; terephthalic acid, isophthalic acid, phthalic acid Fragrances such as 2-methylterephthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetralindicarboxylic acid Dicarboxylic acids and their ester forming derivatives may be exemplified. Aromatic dicarboxylic acids and their ester-forming derivatives are preferred from the standpoint of mechanical performance of the biaxially stretched film of the present invention, and terephthalic acid and its ester-forming derivatives are particularly preferred from the economical standpoint. From the viewpoint of heat resistance, 2,6-naphthalenedicarboxylic acid and its ester-forming derivatives are preferred. The ratio of the aromatic dicarboxylic acid unit in the dicarboxylic acid structural unit is preferably 80 mol% or more, more preferably 90 mol% or more. By setting it as the said ratio, the biaxially stretched film of this invention becomes a thing with more excellent heat resistance and mechanical performance.
[0015]
The minimum value of the half crystallization time based on the depolarization intensity method when the polyester resin used in the present invention is melted at 280 ° C. and crystallized at 150 to 230 ° C. is 300 seconds or less. When the half crystallization time exceeds 300 seconds, the crystallinity decreases, and when the biaxially stretched film is heat-fixed, the spherulites become large, and the transparency may be impaired or heat-setting may not be possible. It is not preferable.
[0016]
The intrinsic viscosity of the polyester resin used in the present invention (measured in a mixed solvent having a mass ratio of phenol and 1,1,2,2-tetrachloroethane of 6: 4 at 25 ° C.) is preferably 0.3 to 1.5 dl. / G, more preferably 0.5 to 1.3 dl / g, still more preferably 0.6 to 1.1 dl / g. By setting it as the said range, intensity | strength and favorable moldability can be provided to a biaxially stretched film.
[0017]
In the polyester resin used in the present invention, monoalcohols such as butyl alcohol, hexyl alcohol and octyl alcohol and trihydric or higher polyhydric alcohols such as trimethylolpropane, glycerin and pentaerythritol, as long as the object of the present invention is not impaired. Monocarboxylic acids such as benzoic acid, propionic acid and butyric acid can also be used as raw material monomers.
[0018]
Furthermore, various molding aids and additives such as fillers, colorants, reinforcing agents, surface smoothing agents, leveling agents, curing reaction accelerators, light stabilizers, ultraviolet absorbers, plasticizers, antioxidants depending on applications. , Extenders, matting agents, drying regulators, antistatic agents, antisettling agents, surfactants, flow improvers, drying oils, waxes, thermoplastic oligomers, and the like.
[0019]
There is no restriction | limiting in particular in the method of manufacturing the polyester resin used by this invention, A conventionally well-known method is applicable. Examples thereof include a melt polymerization method such as a transesterification method and a direct esterification method, or a solution polymerization method. As the transesterification catalyst, esterification catalyst, etherification inhibitor, polymerization catalyst used in the polymerization, various stabilizers such as a heat stabilizer and a light stabilizer, polymerization regulators and the like, conventionally known ones can be used. Examples of the transesterification catalyst include compounds such as manganese, cobalt, zinc, titanium and calcium; examples of the esterification catalyst include compounds such as manganese, cobalt, zinc, titanium and calcium; and examples of the etherification inhibitor include amine compounds. . Examples of the polycondensation catalyst include compounds such as germanium, antimony, tin, and titanium. It is also effective to add various phosphorus compounds such as phosphoric acid, phosphorous acid, and phenylphosphonic acid as a heat stabilizer. Other light stabilizers, antistatic agents, lubricants, antioxidants, mold release agents and the like may be added. In the direct esterification method, water may be added to improve the slurry property.
[0020]
Although it does not restrict | limit especially as a method of obtaining a biaxially stretched film from the polyester resin used by this invention, A film is formed by well-known methods, such as extrusion molding and a calendering, and 1.1 ~ The film is stretched 7 times, preferably 2 to 6 times, particularly preferably 2.5 to 5 times, and 1.1 to 7 times, preferably 2 to 6 times, particularly preferably 2.5 to 5 times in the direction perpendicular to the direction. Stretch 5 times. As a film stretching means, methods such as roll stretching, long gap stretching, and tenter stretching can be applied, and a flat shape, a tube shape, or the like can also be applied to the shape during stretching. Furthermore, it is performed by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, or a combination thereof. The heat setting in these stretching is performed by passing a heating zone of 30 to 240 ° C. for 1 to 30 seconds.
[0021]
The thickness of the biaxially stretched film of the present invention is preferably 5 to 300 μm, more preferably 7 to 100 μm, and still more preferably 10 to 50 μm.
[0022]
The number of pinholes after the biaxially stretched film of the present invention is bent 500 times is 2.0 pieces / m ² or less, preferably 1.0 pieces / m ² or less. If the number of pinholes after bending 500 times exceeds 2.0 / m ² , pinholes are likely to be formed, gas barrier properties may be impaired, and mechanical performance may be impaired.
[0023]
The impact strength in the impact drilling test of the biaxially stretched film of the present invention is 5000 kg · cm / cm or more, preferably 6000 kg · cm / cm or more, more preferably 7000 kg · cm / cm or more. If the impact strength in the impact drilling test is less than 5000 kg · cm / cm, the impact strength is insufficient, and the biaxially stretched film may be damaged.
[0024]
The haze of the biaxially stretched film (thickness 15 μm) of the present invention is 3% or less, preferably 2% or less, more preferably 1% or less. If the haze exceeds 3%, the transparency may be impaired.
[0025]
The biaxially stretched film of the present invention has a shrinkage rate of 3% or less, preferably 2% or less, more preferably 1% or less after hydrothermal treatment for 30 minutes in boiling water. When the shrinkage rate exceeds 3%, heat resistance may be insufficient, which is not preferable.
[0026]
The biaxially stretched film of the present invention has good pinhole resistance, impact resistance, transparency, and heat resistance, and can be suitably used for food, various packaging films, films for magnetic recording media, capacitors, and the like. it can.
[0027]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
[0028]
Examples 1 to 6, Reference Example 1 , Comparative Examples 1 to 3
(1) Synthetic resin packed tower type rectification tower, partial condenser, full condenser, cold trap, stirring blade, heating device, 150 liter (L) polyester production apparatus equipped with nitrogen inlet tube The amount of the monomer described in 1) was charged, manganese acetate tetrahydrate was added in an amount of 0.03 mol% based on the dicarboxylic acid component, and the temperature was raised under normal pressure and a nitrogen atmosphere. The temperature was raised to 200 ° C. to conduct a transesterification reaction. After the reaction conversion rate of the dicarboxylic acid component is 90 mol% or more, 0.02 mol% of antimony trioxide and 0.06 mol% of trimethyl phosphate are added to the dicarboxylic acid component, and the temperature and pressure are gradually increased. Finally, a polycondensation reaction was performed at 270 to 300 ° C. and 0.1 kPa or less. When the viscosity of the reaction product gradually increased and reached an appropriate melt viscosity, the reaction was terminated to obtain a polyester resin.
[0029]
(2) Preparation of biaxially stretched film The obtained polyester resin is extruded to have a thickness of about 0.2 mm under conditions of a cylinder temperature of 250 to 280 ° C, a die temperature of 250 to 280 ° C, and a roll temperature of 75 to 80 ° C. An unstretched sheet was produced. Next, the unstretched sheet was simultaneously biaxially stretched 3.6 × 3.6 times at a temperature 10 to 20 ° C. higher than the glass transition temperature, and then heat-set at 210 to 230 ° C. for 10 to 30 seconds. A biaxially stretched film having a thickness of 15 μm was obtained.
[0030]
(3) Evaluation of Resin ・ Measured at a constant temperature of 25 ° C. using a mixed solvent of intrinsic viscosity (mass ratio: phenol / 1,1,2,2-tetrachloroethane = 6/4).
Semi-crystallization time Resin pellets are crushed into a sheet, sandwiched between cover glasses, melted at 280 ° C. for 3 minutes, then placed in a crystallization bath at a predetermined temperature, and the change in depolarization intensity with time is measured. The half crystallization time at was determined. The temperature of the crystallization bath was changed from 150 to 230 ° C. at intervals of 10 ° C., and the half crystallization time was measured, and the minimum value was taken as the half crystallization time of the resin.
[0031]
(4) Evaluation of biaxially stretched film ・ Pinhole resistance After pinning the biaxially stretched film with Rigaku Industry Co., Ltd. Gelboflex for 500 times, the pinhole tester with the axial direction of Gelbowflex as the measurement direction The number of pinholes was measured by (weak current measurement method). The number of measurements was 5 and the measurement voltage was 1.0 kV.
-Impact strength in impact drilling test Measured according to JIS P813, ASTM D781. As a measuring instrument, a puncture tester manufactured by Toyo Seiki Co., Ltd. was used. The number of measurements was 5 and the measurement conditions were a temperature of 23 ° C. and a relative humidity of 50%.
-Haze value measuring apparatus (model: COH-300A) manufactured by Nippon Denshoku Industries Co., Ltd. was used as a measuring apparatus according to Haze JIS-K-7105 and ASTM D1003.
-The heat-resistant biaxially stretched film was marked with 5.0 cm x 5.0 cm, and after being subjected to hot water treatment for 30 minutes in boiling water, the interval was measured. The shrinkage rate was calculated by the following formula.
Shrinkage rate (%) = (1−interval after hot water treatment / interval before hot water treatment) × 100
These results are shown in Tables 1-3.
[0032]
In addition, the meaning of the abbreviation used in the table | surface is as follows.
DMT: dimethyl terephthalate NDCM: dimethyl 2,6-naphthalenedicarboxylate SPD: 3,9-bis (1,1-dimethyl-2-carboxyethyl) -2,4,8,10-tetraoxaspiro [5.5 ] Undecane was converted to DOD: 5-carboxy-5-ethyl-2- (1,1-dimethyl-2-carboxyxyethyl) -1,3-dioxane EG: ethylene glycol SPG: 3,9-bis (1,1- Dimethyl-2-hydroxyethyl) 2,4,8,10-tetraoxaspiro [5.5] undecane DOG: 5-methylol-5-ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1 , 3-Dioxane
Table 1
Example No. Example 1 Example 2 Example 3 Reference Example 1
Monomer charge (mole)
Dicarboxylic acid component DMT 293.7 304.5 280.4 −
NDCM ---- 235.9
Diol component EG 484.6 511.6 451.4 389.2
SPG 14.7 6.1 25.2 11.8
Evaluation of polyester resin Tg (° C.) 87 85 89 125
IV (dl / g) 0.68 0.67 0.70 0.65
Half crystallization time (seconds) 125 57 247 198
Evaluation haze of biaxially stretched film (% / 15 μm) 0.3 0.8 0.2 0.3
Impact strength (kg · cm / cm)
7000 6000 7500 9000
Pinhole resistance (pieces / m2)
0.3 0.7 0.1 0.5
Shrinkage rate (TD:%) 0.8 1.2 0.5 0.2
Shrinkage rate (MD:%) 1.4 1.8 0.8 0.3
[0034]
Table 2
Example No. Example 4 Example 5 Example 6
Monomer charge (mole)
Dicarboxylic acid component DMT 300.0 297.2 303.7
SPD-14.9-
DOD--15.2
Diol component EG 495.0 505.2 516.2
DOG 15.0--
Evaluation of polyester resin Tg (° C.) 85 84 84
IV (dl / g) 0.65 0.69 0.68
Half crystallization time (seconds) 78 178 277
Evaluation haze of biaxially stretched film (% / 15 μm) 0.2 0.5 0.8
Impact strength (kg · cm / cm) 8500 5500 5500
Pinhole resistance (pieces / m2) 0.1 0.8 0.9
Shrinkage rate (TD:%) 0.4 1.2 0.9
Shrinkage rate (MD:%) 0.6 1.6 1.3
[0035]
Table 3

[0036]
【The invention's effect】
The biaxially stretched film obtained from the resin used in the present invention has excellent performance such as pinhole resistance, impact resistance, transparency and heat resistance, and the industrial significance of the present invention is great.

Claims (5)

A polyester resin having a dicarboxylic acid structural unit and a diol structural unit, wherein 1 to 10 mol% of the diol structural unit has a cyclic acetal skeleton represented by the following general formula (1) or general formula (2) unit der derived is, a unit of 90 to 99 mol% of the diol constituent units derived from ethylene glycol, 80 mol% or more of the dicarboxylic acid constitutional units are units derived from terephthalic acid, the following A biaxially stretched film having a shrinkage rate of 3% or less after hydrothermal treatment for 30 minutes in boiling water, using a polyester resin having the physical properties of (1) and (2).
(1) The intrinsic viscosity measured at 25 ° C. in a mixed solvent of phenol and 1,1,2,2-tetrachloroethane in a mass ratio of 6: 4 is 0.3 to 1.5 dl / g.
(2) The minimum value of the half crystallization time based on the depolarization intensity method when melted at 280 ° C. and crystallized at 150 to 230 ° C. is 300 seconds or less.

Wherein R 1 and R 2 are each independently a group consisting of an aliphatic group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and an aromatic group having 6 to 10 carbon atoms. Represents an organic group selected from

(Wherein R1 is the same as described above, and R3 comprises an aliphatic group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and an aromatic group having 6 to 10 carbon atoms. Represents an organic group selected from the group.)   A diol having a cyclic acetal skeleton is 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, or 5-methylol-5- The biaxially stretched film according to claim 1, which is ethyl-2- (1,1-dimethyl-2-hydroxyethyl) 1,3-dioxane. The biaxially stretched film according to claim 1 or 2, wherein 90 to 100 mol% of the dicarboxylic acid structural unit is a unit derived from terephthalic acid . The biaxially stretched film according to any one of claims 1 to 3 , wherein the diol unit other than the diol unit having a cyclic acetal skeleton is a unit derived from ethylene glycol. The biaxially stretched film according to any one of claims 1 to 4 , which has the following physical properties (1) to (3).
(1) The number of pinholes after the bending test is 2.0 pieces / m 2 or less.
(2) Impact strength in an impact drilling test is 5000 kg · cm / cm or more.
(3) The haze of a film having a thickness of 15 μm is 3% or less.