JP3617219B2 - Polyester film having excellent thickness uniformity and method for producing the same - Google Patents

Description

（ただし、Ｒ１ 、Ｒ２ はそれぞれフェニル基、シクロアルキル基もしくはこれらの水素の一つを炭化水素基で置換した基、Ｐ１ 、Ｐ２ はそれぞれ下記構造式（２）、（３）、（４）のいずれかで表される基、Ｑはアルキレン基、フェニレン基、−Ｓ−基、−ＳＯ_２ −基、−Ｏ−基、−ＣＨ_２ −基、−ＣＯ−基もしくはこれらの基を含有する２価の基、ｎは１〜２０の自然数）
【化６】

【化７】

【化８】

このようなイミド系化合物は、例えば１，２，３，４−ブタンテトラカルボン酸および／またはその無水物と、脂肪族１級モノアミンまたは芳香族１級モノアミン、さらに脂肪族１級ジアミンまたは芳香族１級ジアミンを脱水縮合させることにより製造することができる。ここで、脂肪族１級モノアミンとしては、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などが用いられる。また、芳香族第１級モノアミンとしては、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、ドコシルアニリン等が用いられる。
【００１０】
一方、脂肪族１級ジアミンとしては、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−キシリ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。芳香族１級ジアミンとしては、ベンジジン、ジメチルベンジジン、ジアミノフェニルメタン、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、キシレンジアミンを用いることができる。
【００１１】
これらより成るイミド系化合物は、１種のみ用いても良く、また、２種以上を併用して用いても良い。
【００１２】
該イミド化合物のブレンド量は、０．１〜２０重量％であり、好ましくは０．３〜１０重量％であり、さらに好ましくは１〜５重量％である。ブレンド量が０．１重量％未満では十分な厚みむら低減効果や高速製膜速度が得られず、また、２０重量％を超えると厚みむら低減効果や高速製膜速度が得られないばかりかブリードアウトの問題や、取扱い性、耐熱性の点等で劣るため好ましくない。
【００１３】
本発明フィルムの長手方向の厚みむらは、５％以下、好ましくは３％以下、さらに好ましくは１％以下であるのが良い。さらに本厚みむらの波形をフーリエ解析した際の、０．１５以上０．４５（１／ｍ）以下の波数におけるスペクトル強度和Ｐｗ１の、全波数帯域におけるスペクトル強度和ＰｗＴにおける比、Ｐｗ１／ＰｗＴが０．２０以下、好ましくは０．１５以下と小さいことが好ましく、比較的繰返し周期の長い厚み均一性の優れたポリエステルフィルムがよい。さらに、厚みむらの波形をフーリエ解析した際の、１．００以上２．００（１／ｍ）以下の波数におけるスペクトル強度和Ｐｗ２の、全波数帯域におけるスペクトル強度和ＰｗＴにおける比、Ｐｗ２／ＰｗＴが０．１５以下、好ましくは０．１０以下と小さいことが好ましく、比較的繰返し周期の短い厚み均一性の優れたポリエステルフィルムが良い。さらにＰｗ１／ＰｗＴが０．２０以下、かつ、Ｐｗ２／ＰｗＴが０．１５以下と比較的繰返し周期の長いものと、周期の短いものの両方とも厚み均一性に優れたポリエステルフィルムが良い。
【００１４】
本発明においてポリエステル樹脂にイミド系化合物を配合させる方法は、押出機などにより該化合物を直接混練、押し出すことにより製造する方法、また、ベースとなるポリエステル樹脂の溶融重合終了時に該化合物を配合、吐出して製造することもできる。また、一旦高濃度の該化合物を含有するポリエステル原料を得た後、これを適宜他のポリエステル原料とブレンド、配合することにより、希望濃度の該化合物を含有するポリエステル組成物を得ることもできる。
【００１５】
本発明におけるポリエステルフィルムの製造方法の一例を示すが、必ずしもこれに限定されるものではない。ポリエステル原料を乾燥後、公知の押出機に供給して溶融し、異物を濾過して除去後、フィルム成型用Ｔダイ口金から溶融体シートを押出して、該溶融体シートに静電荷を印可させながら冷却ドラムに密着冷却させてキャストシートを得る。もちろん溶融体であることは必要であるが、該ポリエステル樹脂の融点以下の過冷却状態であっても良い。静電印可電圧は１〜５万Ｖ、印可電流は１０〜１０００ｍＡ程度であり、これは使用する条件により最適値は異なる。また使用する電極形状は特に限定はしないが、ワイヤー電極、テープ電極、ブレード電極、針状電極、凹面電極、ドラム電極及びそれらの複数の組合わせ電極でも、さらに他の密着性向上手段との併用でも良く、本発明の場合、特に０．１ｍｍ程度の細線からなるシングルあるいはダブルワイヤー電極またはテープ電極が好ましい。ワイヤー電極の場合は、ワイヤー張力は可能な限り大きくしておくのが良い。電極位置は、溶融体シートが冷却ドラムに接する直前でしかもドラムに接する側とは反対面がよいが、必ずしもこれに限定されない。印可時の雰囲気ガスは、基本的には空気であるが、イオン化し易いガスを介在させても良い。また、冷却ドラム上に水などの表面張力の大きな液体を０．１μｍ程度薄く介在させておくと、本発明の効果は大きくなるので好ましい。もちろん電極には押出時に飛散するオリゴマーなどの低分子化合物が付着し易いので、加熱したり、常時洗浄したり、常に新しい電極を供給したりしてもよい。もちろん静電印可する幅は、溶融体シート幅の内側に限定しないと、ドラムに放電する。
【００１６】
かくして得られたキャストシートを長手方向および／または幅方向に、好ましくはそれぞれの方向に多段階で二軸に延伸する。この後必要に応じて熱処理して二軸延伸フィルムを製膜しても良い。二軸延伸は逐次延伸あるいは同時延伸のいずれでもよく、延伸倍率は特に限定されるものではないが、通常は長手方向、幅方向それぞれに２〜７倍が適当である。あるいは二軸延伸後、再度長手方向および／または幅方向に延伸してもかまわない。このようにして得られたポリエステルフィルムの長手方向の厚みむらは５（％）以下と厚み均一性の優れたポリエステルフィルムになる。
【００１７】
【特性の測定法】
なお、本発明で用いた測定法につき以下に示す。
【００１８】
（１）固有粘度（［η］）
ｏ−クロロフェノールを溶媒として、２５℃で測定した値である。
【００１９】
（２）厚みむら
アンリツ社製フィルムシックネステスタＫＧ６０１Ａおよび電子マイクロメータＫ３０６Ｃを用い、縦方向に３０ｍｍ幅、１０ｍ長にサンプリングしたフィルムを連続的に厚みを測定する。長手方向の場合１０ｍ長、幅方向の場合全幅での厚み最大値Ｔｍａｘ （μｍ）、最小値Ｔｍｉｎ （μｍ）から、Ｒ＝Ｔｍａｘ −Ｔｍｉｎ を求め、Ｒと１０ｍ長の平均厚みＴａｖｅ （μｍ）から、厚みむら（％）＝（Ｒ／Ｔａｖｅ ）×１００として求めた。この全体の厚みむらが、２％未満のものを「○」、２％以上５％未満のものを「△」、５％を超えるものを「×」とした。
【００２０】
（３）フィルムの長手方向厚みむらのフーリエ解析
上述の長手方向厚みむら測定時に、電子マイクロメータからの出力をアナログ／デジタルコンバータ（Ａ／Ｃコンバータ）を介して、数値化処理し、コンピュータに取り込んだ。この際、電子マイクロメータの出力電圧と、Ａ／Ｃコンバータの入力電圧の適正化のため、必要に応じて、電子マイクロメータとＡ／Ｃコンバータの間にプリアンプを設けてもよい。本発明においては、電子マイクロメータの出力を、自作のプリアンプを介して、カノープス電子（株）製Ａ／Ｃコンバータ「ＡＤＸ−９８Ｅ」および専用トリガユニット「ＡＤＴ−９８Ｅ」に接続し、日本電気（株）製のパーソナルコンピュータ「ＰＣ−９８０１ＶＭ」にデータを取り込んだ。データの取り込みソフトウェアは自作したものを用いた。データの取り込みは、１０ｍ長の厚みむら測定中に、０．１９５秒の間隔で１０２４点サンプリングした（３ｍ／分で搬送測定しているため０．１９５秒×１０２４×３ｍ／分÷６０秒／分＝９．９８ｍで、９．９８ｍの厚みむらデータを取り込み）。もちろん、これらの機器に限定される必要はなく、同様の機能を持つ機器は多数存在する。このように取り込んだデータを上述のコンピュータにおいて、自作のソフトウエアを用い、高速フーリエ変換（ＦＦＴ）処理を施した。この際、流れ方向の変数に、フィルムの製膜速度と測定時の搬送速度から換算した。製膜時間（秒）を取ると、ＦＦＴ処理により、周波数（Ｈｚ）に対する強度分布が得られ、また、流れ方向の変数に、フィルムの長さ（ｍ）を取ると、ＦＦＴ処理により、波数（１／ｍ）に対する強度分布が得られる。ＦＦＴ処理については、例えば、「技術者の数学１」初版（共立出版（株）共立全書５１６）などにＦＦＴ処理の手法について記載があるなど公知の処理である。ここで、取り込んだデータに下記のようにフーリエ変換処理を施し、スペクトル強度和を求めた。
【００２１】
【数１】

（４）環状三量体含有量（［Ｃ３ ］）
ポリマー１００ｍｇをオルトクロロフェノール２ｍｌに溶解し、液体クロマトグラフィー（ＨＬＣ８０３Ｄ 東曹社製）で測定し、ポリマーに対する割合（重量％）で示した。
【００２２】
【実施例】
以下本発明を実施例により、さらに詳細に説明する。
【００２３】
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、さらにエチレンジアミン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撹拌し、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、さらに撹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化合物Ａを得た。
【００２４】
参考例２
エチレンジアミンの代わりに、ｍ−キシリレンジアミン１３．６ｇを用いる他は、参考例２と同様の方法により、残留したイミド化合物Ｂを得た。
【００２５】
参考例３
ヘキサデシルアミンのかわりに、ｐ−ドデシルアニリン５５．２ｇを用いる他は、参考例２と同様の方法により、残留したイミド化合物Ｃを得た。
【００２６】
実施例１
ポリエチレンテレフタレート（固有粘度０．６７、エステル交換触媒として酢酸マグネシウム、重合触媒として三酸化二アンチモン、安定剤として亜リン酸、滑り剤として平均粒径２００ｍμｍの酸化アルミナを０．０７５重量％を添加）１００重量％に対して、参考例１で得たイミド化合物Ａ０．５重量％を添加したポリエステル組成物を９０ｍｍの押出し機に供給し、温度２８５℃で混練溶融して、異物を２μｍカットの金属燒結体フィルムターを用いて濾過し除去後、１１００ｍｍ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、該溶融体シートに静電荷を印可させながら７０ｍ／ｍｉｎの高速で回転する冷却ドラムに密着冷却させてキャストシートを得た。静電印可は、溶融体シートが冷却ドラムに接する直前でしかもドラムに接する側とは反対面に行い、電極は直径０．１ｍｍのタングステンのワイヤーを用いた。この時の静電印可電圧は２．５万Ｖ、印可電流は２５ｍＡであった。かくして得られたキャストシートを長手方向に１１０℃で２倍延伸後、９５℃で３倍延伸するという多段階で長手方向に延伸した。一旦該フィルムのガラス転移温度以下に冷却した後、テンターに供給し９０℃で４．５倍幅方向に延伸し、一旦該フィルムのガラス転移温度以下に冷却した後に２２５℃と１５０℃で熱固定して、厚さ４μｍの二軸配向フィルムを得た。
【００２７】
かくして４００ｍ／ｍｉｎ以上の高速製膜で得られたフィルムの特性は表１のように、厚みむらに優れており、生産性・品質に優れたフィルムであった。
【００２８】
【表１】

実施例２〜５、比較例１〜２
イミド化合物の添加量を、ポリエステルチップ１００重量％に対して０、０．２、０．５、２、７、１２、２５重量％とする他は、実施例１と同様の方法でイミド化合物含有ポリエステル組成物を得、これを用いて二軸延伸フィルムを得た。これらの結果を表２に示す。この様に、添加量が少なすぎても、多すぎてもキャスト速度が上昇しないばかりか、得られたフィルムの厚みむらが改良出来ないことが判る。
【００２９】
【表２】

実施例６〜７
イミド化合物Ａの代りにイミド化合物Ｂ、Ｃを用いる他は、実施例１と同様の方法でイミド化合物含有ポリエステル組成物を得、これを用いて二軸延伸フィルムを得た。これらの結果を表３に示す。
【００３０】
【表３】

実施例８
重合反応層から吐出する前の重合反応終了時に、イミド化合物Ａを１重量％加えて吐出して、固有粘度［η］＝０．５４（ｄｌ／ｇ）のポリエステル組成物を得た。該３ｍｍ径の立方体のポリエステルペレットを、回転型真空重合装置を用いて、１ｍｍＨｇの減圧下、２２５℃で３０時間加熱処理することにより固相重合を行ない、固有粘度［η］＝１．２０、環状三量体含有量０．２８重量％のポリエステルを得た。こうして得られたポリエステル組成物を用いて、２５０ｍｍ同志のタンデム押出し機に供給し、温度２９０℃で混練溶融したのち２段目の押出機で２６５℃まで冷却した後、異物を１５μｍカットの金属燒結体フィルムターを用いて濾過し除去後、２１００ｍｍ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、該溶融体シートに静電荷を印可させながら６３ｍ／ｍｉｎの高速で回転する冷却ドラムに密着冷却させてキャストシートを得た。静電印可は、溶融体シートが冷却ドラムに接する直前でしかもドラムに接する側とは反対面に行い、電極は直径０．０９ｍｍのタングステン合金のワイヤーを用いた。この時の静電印可電圧は２．２万Ｖ、印可電流は２３ｍＡであった。かくして得られたキャストシートを長手方向に１２０℃で１．８倍延伸後、１００℃で３．２倍延伸するという多段階で長手方向に延伸した。一旦該フィルムのガラス転移温度以下に冷却した後、テンターに供給し８５℃で４．５倍幅方向に延伸し、一旦該フィルムのガラス転移温度以下に冷却した後に２２５℃と１６５℃で熱固定して、厚さ７５μｍの二軸配向フィルムを得た。
【００３１】
固有粘度の高いポリエステルを溶融押出しても大きな剪断発熱はみられず、３５０ｍ／ｍｉｎ以上の高速で、しかも長手方向厚みむらが１％と小さく、フィルム中の環状三量体含有量も０．３３重量％と非常に少ないものであった。すなわち、生産性と品質に優れたフィルムであった。
【００３２】
【発明の効果】
本発明のポリエステルフィルムの製造方法を用いることにより、高速でキャストすることが可能であり、また二軸延伸性にも優れるばかりか、さらにかくして得られたフィルムの厚みむらが小さく、異物・ゲル化物の含まない高品質なフィルムが得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film and a method for producing the same, and more particularly to a polyester film having a small thickness unevenness and a method for producing the same at high speed.
[0002]
[Prior art]
Casting while applying static charge to reduce the thickness unevenness (improving thickness uniformity) and increase the casting speed in the casting process that adheres the molten polyester film to the cooled cooling body and gives a certain shape. This is a technique well known in Japanese Patent Publication No. 37-6142.
[0003]
[Problems to be solved by the invention]
However, even such a casting method that applies an electrostatic charge is not sufficient in terms of thickness uniformity and high-speed castability, and further improvement studies are necessary. For this purpose, a method for achieving high-speed casting by adding a conductive compound to the molten polymer and increasing the applied current by lowering the volume resistivity (for example, JP-A-51-70269) is studied. However, not only the high-speed cast as expected but also the thickness uniformity of the obtained film is inferior, and the electrical insulating properties of the film are also inferior. Also had the disadvantage that it could not be used. In addition, the thickness of the electrostatically applied electrode is changed to a wire electrode, a tape electrode, a blade electrode, a needle electrode, a concave electrode, a drum electrode, and a plurality of combined electrodes with these and / or other contact methods. Although unevenness has been improved and high-speed film formation has been studied, thickness uniformity and high-speed castability as expected were not obtained.
[0004]
[Means for Solving the Problems]
An object of the present invention is to provide a polyester film having small thickness unevenness, particularly in the longitudinal direction, and a method for producing the film at high speed with high productivity. Namely, in the manufacturing method of the polyester film which forms a film while applying an electrostatic charge to the melt of the polyester resin, the manufacturing method of the polyester film, wherein the polyester resin is a composite of the polyester resin and the imide compound Thus, a film having excellent thickness uniformity in which the thickness unevenness in the longitudinal direction of the film thus obtained is 5 (%) or less is provided.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The polyester film of the present invention can be obtained by forming a composite of a polyester resin and an imide compound. The composite includes any form such as blending / mixing, laminating, and copolymer. In the present invention, the blending / mixing form is particularly preferable.
[0006]
The polyester used in the present invention is not particularly limited. For example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, or a copolymerized polyester comprising two or more structural units. These are typical polyesters, and any of these may be used, and among these, polyethylene terephthalate is preferable from the viewpoint of productivity, heat resistance, and handleability when formed into a molded product such as a film. Further, the present polyester may be blended and blended with other polyesters such as liquid crystalline polyester, other polymer compounds represented by vinyl polymers such as polyamide, polyolefin, and polyvinylidene chloride. The liquid crystalline polyester is a polyester having a mesogenic group and exhibiting optical anisotropy when melted, and typical liquid crystalline polyester compounds are those represented by JP-A-7-233310 and the like. is there. In the present invention, the liquid crystalline polyester is particularly preferably a liquid crystalline polyester containing 40 to 90% by weight of a parahydroxybenzoic acid (HBA) component as a main mesogen.
[0007]
Polyester is a transesterification reaction between a dicarboxylic acid or its ester and a diol component, and then the product of this reaction is heated under reduced pressure to cause polycondensation while removing excess diol component. It is a produced polymer. As the reaction catalyst, conventionally known titanium compounds, lithium compounds, calcium compounds, magnesium compounds, antimony compounds, germanium compounds and the like can be used. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4 '-Diphenyl ether dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and the like can be used. Examples of the diol component include ethylene glycol, 1,2-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, , 2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, etc. Aliphatic, alicyclic, aromatic diols and the like can be used. These components may be used alone or in combination of two or more. Further, by subjecting this polyester to solid phase polymerization, the cyclic trimer can be reduced and the degree of polymerization can be increased. Solid phase polymerization is carried out by heating at a temperature in the range of 180 ° C. to the melting point for 5 to 50 hours under a nitrogen flow or under a vacuum of 1 torr or less.
[0008]
The imide compound used in the present invention is represented by the following general formula (1).
[0009]
[Chemical formula 5]

(However, R1 and R2 are each a phenyl group, a cycloalkyl group or a group obtained by substituting one of these hydrogens with a hydrocarbon group, and P1 and P2 are those represented by the following structural formulas (2), (3) and (4), respectively. A group represented by any one, Q is an alkylene group, a phenylene group, a —S— group, a —SO ₂ — group, a —O— group, a —CH ₂ — group, a —CO— group or a group containing these groups 2 Valent group, n is a natural number of 1-20)
[Chemical 6]

[Chemical 7]

[Chemical 8]

Such imide compounds include, for example, 1,2,3,4-butanetetracarboxylic acid and / or anhydrides thereof, aliphatic primary monoamines or aromatic primary monoamines, and aliphatic primary diamines or aromatics. It can be produced by dehydrating condensation of a primary diamine. Here, as the aliphatic primary monoamine, ethylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, Hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, eicosylamine, heneicosylamine, docosylamine, cyclohexylamine, methylcyclohexylamine, dimethylcyclohexylamine, diethylcyclohexylamine and the like are used. Examples of the aromatic primary monoamine include aniline, toluidine, ethylaniline, propylaniline, butylaniline, pentylaniline, hexylaniline, heptylaniline, octylaniline, nonylaniline, decylaniline, undecylaniline, dodecylaniline, tridecylaniline. Decylaniline, tetradecylaniline, pentadecylaniline, hexadecylaniline, heptadecylaniline, octadecylaniline, nonadecylaniline, eicosylaniline, heneicosylaniline, docosylaniline and the like are used.
[0010]
On the other hand, as aliphatic primary diamine, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine undecamethylenediamine, dodecamethylene Diamine, 1,3-bisaminocyclohexane, diaminodicyclohexylmethane, m-xylylenediamine and structural isomers thereof are used. Examples of the aromatic primary diamine include benzidine, dimethylbenzidine, diaminophenylmethane, diaminoditolylmethanediaminodiphenylethane, diaminodiphenylpropane, diaminodiphenylbutane, diaminodiphenyl ether, diaminodiphenylsulfone, diaminodiphenylbenzophenone, o, m, p- Phenylenediaminetolylenediamine and xylenediamine can be used.
[0011]
These imide compounds may be used alone or in combination of two or more.
[0012]
The blend amount of the imide compound is 0.1 to 20% by weight, preferably 0.3 to 10% by weight, and more preferably 1 to 5% by weight. If the blend amount is less than 0.1% by weight, a sufficient thickness unevenness reducing effect and a high speed film forming speed cannot be obtained, and if it exceeds 20% by weight, not only a thickness unevenness reducing effect and a high speed film forming speed can be obtained. It is not preferable because it is inferior in the problem of out, handling property, heat resistance and the like.
[0013]
The thickness unevenness of the film of the present invention in the longitudinal direction is 5% or less, preferably 3% or less, more preferably 1% or less. Furthermore, the ratio Pw1 / PwT of the spectral intensity sum PwT in the wave number range of 0.15 to 0.45 (1 / m) to the spectral intensity sum PwT in the entire wave number band when the waveform of the thickness unevenness is Fourier-analyzed is It is preferably 0.20 or less, preferably 0.15 or less, and a polyester film having a relatively long repeating cycle and excellent thickness uniformity is preferable. Furthermore, the ratio Pw2 / PwT of the spectral intensity sum Pw2 in the wave number of 1.00 or more and 2.00 (1 / m) or less to the spectral intensity sum PwT in the whole wave number band when the waveform of the thickness unevenness is Fourier analyzed is It is preferably 0.15 or less, preferably 0.10 or less, and a polyester film having a relatively short repetition period and excellent thickness uniformity is preferable. Further, a polyester film having excellent thickness uniformity is preferable for both Pw1 / PwT of 0.20 or less and Pw2 / PwT of 0.15 or less, both having a relatively long repetition period and those having a short period.
[0014]
In the present invention, the method of blending the imide compound with the polyester resin is a method of producing the compound by directly kneading and extruding the compound with an extruder or the like, and blending and discharging the compound at the end of the melt polymerization of the base polyester resin. Can also be manufactured. Alternatively, once a polyester raw material containing a high concentration of the compound is obtained, this can be appropriately blended and blended with other polyester raw materials to obtain a polyester composition containing the compound at a desired concentration.
[0015]
Although an example of the manufacturing method of the polyester film in this invention is shown, it is not necessarily limited to this. After drying the polyester raw material, it is fed to a known extruder and melted, and after removing foreign matter by filtration, the melt sheet is extruded from a T-die die for film molding, and an electrostatic charge is applied to the melt sheet. A cast sheet is obtained by tightly cooling the cooling drum. Of course, it is necessary to be a melt, but it may be in a supercooled state below the melting point of the polyester resin. The electrostatic applied voltage is 1 to 50,000 V, and the applied current is about 10 to 1000 mA. The optimum value varies depending on the conditions used. Also, the electrode shape to be used is not particularly limited, but wire electrodes, tape electrodes, blade electrodes, needle electrodes, concave electrodes, drum electrodes, and combinations of these electrodes can be used in combination with other means for improving adhesion. However, in the case of the present invention, a single or double wire electrode or a tape electrode made of a fine wire of about 0.1 mm is particularly preferable. In the case of a wire electrode, the wire tension should be as large as possible. The electrode position may be a surface immediately before the melt sheet contacts the cooling drum and opposite to the side contacting the drum, but is not necessarily limited thereto. The atmosphere gas at the time of application is basically air, but a gas that is easily ionized may be interposed. In addition, it is preferable that a liquid having a large surface tension such as water is interposed on the cooling drum as thin as about 0.1 μm because the effect of the present invention is increased. Of course, since low molecular compounds such as oligomers scattered during extrusion are likely to adhere to the electrode, it may be heated, constantly washed, or always supplied with a new electrode. Of course, the width of electrostatic application is not limited to the inside of the melt sheet width, and the drum is discharged.
[0016]
The cast sheet thus obtained is stretched biaxially in multiple stages in the longitudinal direction and / or width direction, preferably in each direction. Thereafter, a biaxially stretched film may be formed by heat treatment as necessary. Biaxial stretching may be either sequential stretching or simultaneous stretching, and the stretching ratio is not particularly limited, but usually 2 to 7 times in each of the longitudinal direction and the width direction is appropriate. Or you may extend | stretch to a longitudinal direction and / or a width direction again after biaxial stretching. The polyester film thus obtained has a thickness unevenness of 5 (%) or less in the longitudinal direction, resulting in a polyester film having excellent thickness uniformity.
[0017]
[Measurement method of characteristics]
In addition, it shows below about the measuring method used by this invention.
[0018]
(1) Intrinsic viscosity ([η])
It is a value measured at 25 ° C. using o-chlorophenol as a solvent.
[0019]
(2) Unevenness of thickness Using a film thickest tester KG601A and an electronic micrometer K306C manufactured by Anritsu Corporation, the thickness of a film sampled 30 mm wide and 10 m long is measured continuously. R = Tmax−Tmin is obtained from the maximum thickness Tmax (μm) and the minimum value Tmin (μm) in the width direction in the case of 10 m in the longitudinal direction and in the full width, and from R and the average thickness Tave (μm) in the length of 10 m. Unevenness of thickness (%) = (R / Tave) × 100. When the overall thickness unevenness was less than 2%, “◯” was given, and when the thickness was 2% or more but less than 5%, “Δ”, and when it was more than 5%, “x” was given.
[0020]
(3) Fourier analysis of longitudinal thickness unevenness of film At the time of measuring the thickness unevenness in the longitudinal direction, the output from the electronic micrometer is digitized through an analog / digital converter (A / C converter) and taken into a computer. It is. At this time, a preamplifier may be provided between the electronic micrometer and the A / C converter as necessary to optimize the output voltage of the electronic micrometer and the input voltage of the A / C converter. In the present invention, the output of the electronic micrometer is connected to an A / C converter “ADX-98E” and a dedicated trigger unit “ADT-98E” manufactured by Kanopsu Electronics Co., Ltd. via a self-made preamplifier. Data was taken in to a personal computer “PC-9801VM” manufactured by Co., Ltd. The data acquisition software was self-made. Data acquisition was carried out by sampling 1024 points at intervals of 0.195 seconds during measurement of thickness unevenness of 10 m (0.195 seconds × 1024 × 3 m / min ÷ 60 seconds / since transport measurement was performed at 3 m / min) Min. = 9.98m, 9.98m thickness unevenness data is taken in). Of course, it is not necessary to be limited to these devices, and there are many devices having similar functions. Data taken in this way was subjected to a fast Fourier transform (FFT) process in the above-described computer using self-made software. Under the present circumstances, it converted into the variable of the flow direction from the film-forming speed | rate of a film, and the conveyance speed at the time of a measurement. When film forming time (seconds) is taken, intensity distribution with respect to frequency (Hz) is obtained by FFT processing, and when the film length (m) is taken as a variable in the flow direction, wave number ( An intensity distribution for 1 / m) is obtained. The FFT processing is a known processing, for example, the description of the FFT processing technique is described in “Engineer's Mathematics 1” first edition (Kyoritsu Publishing Co., Ltd. Kyoritsu Zensho 516). Here, the acquired data was subjected to Fourier transform processing as described below to obtain a sum of spectral intensities.
[0021]
[Expression 1]

(4) Cyclic trimer content ([C3])
100 mg of the polymer was dissolved in 2 ml of orthochlorophenol and measured by liquid chromatography (HLC803D manufactured by Tosoh Corporation), and the ratio (% by weight) relative to the polymer was indicated.
[0022]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0023]
Reference example 1
1,6.8,4-Butanetetracarboxylic acid (46.8 g), hexadecylamine (48.2 g), and ethylenediamine (6 g) were mixed in a flask using dimethylformamide as a solvent and stirred while gradually raising the temperature to 260 ° C. 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.
[0024]
Reference example 2
Residual imide compound B was obtained in the same manner as in Reference Example 2 except that 13.6 g of m-xylylenediamine was used instead of ethylenediamine.
[0025]
Reference example 3
Residual imide compound C was obtained in the same manner as in Reference Example 2, except that 55.2 g of p-dodecylaniline was used instead of hexadecylamine.
[0026]
Example 1
Polyethylene terephthalate (inherent viscosity 0.67, magnesium acetate as transesterification catalyst, antimony trioxide as polymerization catalyst, phosphorous acid as stabilizer, 0.075% by weight of alumina oxide with an average particle size of 200mμ as slipping agent) The polyester composition to which 0.5% by weight of the imide compound A obtained in Reference Example 1 is added to 100% by weight is supplied to a 90 mm extruder and kneaded and melted at a temperature of 285 ° C. After filtration and removal using a sintered film film, a melt sheet is extruded from a T-die die for film molding having a width of 1100 mm, and a cooling drum rotating at a high speed of 70 m / min while applying an electrostatic charge to the melt sheet. The cast sheet was obtained by closely cooling. Electrostatic application was performed immediately before the melt sheet was in contact with the cooling drum and on the surface opposite to the side in contact with the drum, and a tungsten wire having a diameter of 0.1 mm was used as the electrode. At this time, the electrostatic applied voltage was 25,000 V, and the applied current was 25 mA. The cast sheet thus obtained was stretched in the longitudinal direction in multiple stages, ie, stretched twice at 110 ° C. in the longitudinal direction and then stretched 3 times at 95 ° C. Once cooled to below the glass transition temperature of the film, supplied to a tenter and stretched in the 4.5-fold width direction at 90 ° C, and once cooled to below the glass transition temperature of the film, heat fixed at 225 ° C and 150 ° C Thus, a biaxially oriented film having a thickness of 4 μm was obtained.
[0027]
Thus, as shown in Table 1, the properties of the film obtained by high-speed film formation at 400 m / min or more were excellent in thickness unevenness, and were excellent in productivity and quality.
[0028]
[Table 1]

Examples 2-5, Comparative Examples 1-2
The imide compound was added in the same manner as in Example 1 except that the amount of imide compound added was 0, 0.2, 0.5, 2, 7, 12, 25% by weight based on 100% by weight of the polyester chip. A polyester composition was obtained and a biaxially stretched film was obtained using this. These results are shown in Table 2. Thus, it can be seen that if the addition amount is too small or too large, the casting speed does not increase and the thickness unevenness of the obtained film cannot be improved.
[0029]
[Table 2]

Examples 6-7
An imide compound-containing polyester composition was obtained in the same manner as in Example 1 except that the imide compounds B and C were used in place of the imide compound A, and a biaxially stretched film was obtained using this. These results are shown in Table 3.
[0030]
[Table 3]

Example 8
At the end of the polymerization reaction before being discharged from the polymerization reaction layer, 1% by weight of imide compound A was added and discharged to obtain a polyester composition having an intrinsic viscosity [η] = 0.54 (dl / g). The cubic polyester pellets having a diameter of 3 mm were subjected to solid phase polymerization by heat treatment at 225 ° C. for 30 hours under a reduced pressure of 1 mmHg using a rotary vacuum polymerization apparatus, and the intrinsic viscosity [η] = 1.20, A polyester having a cyclic trimer content of 0.28% by weight was obtained. The polyester composition thus obtained was supplied to a 250 mm tandem extruder, kneaded and melted at a temperature of 290 ° C., cooled to 265 ° C. with a second-stage extruder, and then subjected to 15 μm cut metal sintering. After filtration and removal using a body film tar, a melt sheet is extruded from a 2100 mm wide film molding T die die, and is attached to a cooling drum rotating at a high speed of 63 m / min while applying an electrostatic charge to the melt sheet. A cast sheet was obtained by cooling. The electrostatic application was performed immediately before the melt sheet was in contact with the cooling drum and on the surface opposite to the side in contact with the drum, and a tungsten alloy wire having a diameter of 0.09 mm was used as the electrode. At this time, the electrostatic applied voltage was 22,000 V, and the applied current was 23 mA. The cast sheet thus obtained was stretched 1.8 times in the longitudinal direction at 120 ° C., and then stretched in the longitudinal direction in multiple stages, ie, stretched 3.2 times at 100 ° C. Once cooled to below the glass transition temperature of the film, supplied to a tenter and stretched in the 4.5-fold width direction at 85 ° C, and once cooled to below the glass transition temperature of the film, heat fixed at 225 ° C and 165 ° C Thus, a biaxially oriented film having a thickness of 75 μm was obtained.
[0031]
Even when a polyester having a high intrinsic viscosity is melt-extruded, no large exothermic heat is observed, the speed is 350 m / min or higher, the thickness unevenness in the longitudinal direction is as small as 1%, and the cyclic trimer content in the film is also 0.33. It was very little with the weight%. That is, the film was excellent in productivity and quality.
[0032]
【The invention's effect】
By using the method for producing a polyester film of the present invention, it is possible to cast at a high speed, and it is excellent in biaxial stretchability. A high-quality film that does not contain any is obtained.

Claims (5)

In a method for producing a polyester film, in which an electrostatic charge is applied to a melt of a polyester resin, the polyester resin is a composite of a polyester resin and an imide compound , and the imide compound is represented by the following general formula (1 The method for producing a polyester film is characterized in that the amount of the imide compound added to and mixed with the polyester resin is 0.1 to 20% by weight with respect to the polyester resin .

(However, R ₁ and R ₂ are each a phenyl group, a cycloalkyl group or a group obtained by substituting one of these hydrogens with a hydrocarbon group, and P ₁ and P ₂ are structural formulas (2), (3), The group represented by any one of (4), Q is an alkylene group, a phenylene group, an —S— group, an —SO ₂ — group, an —O— group, a —CH ₂ — group, a —CO— group, or a group thereof; Divalent group containing n, n is a natural number of 1 to 20)

The thickness uniformity in the longitudinal direction of the film is 5 (%) or less, The polyester film excellent in thickness uniformity comprising the method for producing a polyester film according to claim 1 . The ratio of the spectral intensity sum Pw1 at a wave number of 0.15 or more and 0.45 (1 / m) or less to the spectral intensity sum PwT in the entire wave number band when the waveform of thickness unevenness is Fourier-analyzed, and Pw1 / PwT is 0. The polyester film having excellent thickness uniformity according to claim 2 , wherein the polyester film is 20 or less. The ratio of the spectral intensity sum Pw2 in the wave number of 1.00 or more and 2.00 (1 / m) or less to the spectral intensity sum PwT in the entire wave number band when the waveform of the thickness unevenness is Fourier-analyzed, and Pw2 / PwT is 0.00. The polyester film having excellent thickness uniformity according to claim 2 or 3 , wherein the polyester film has a thickness of 15 or less. Pw1 / PwT is 0.20 or less, and Pw2 / PwT is 0.15 or less, The polyester film excellent in thickness uniformity in any one of Claims 2-4 characterized by the above-mentioned.