JP4576644B2 - Aromatic liquid crystalline polyester and method for producing the same - Google Patents

Description

（但し、Ｒ¹は水素原子、ホルミル基、アセチル基、プロピオニル基またはベンゾイル基を表わし、Ｒ²は水素原子、メチル基、エチル基、プロピル基、ベンジル基またはフェニル基を表わす。）
【化６】

（但し、Ｒ¹とＲ²の定義は、式（Ｉ）におけるそれぞれの定義と同じである。式（Ｉ）と式（ＩＩ）におけるＲ¹は、互いに同一でも異なってもよく、式（Ｉ）と式（ＩＩ）におけるＲ²は、互いに同一でも異なってもよい。）
ここで流動温度とは、毛細管型レオメーターで測定され、４℃／分の昇温速度で加熱溶融された樹脂を、荷重１００ｋｇｆ／ｃｍ²のもとで、内径１ｍｍ、長さ１０ｍｍのノズルから押し出した時に、溶融粘度が４８，０００ポイズを示す温度（℃）をいう。
また、本発明は、〔２〕熱処理して得られた芳香族液晶性ポリエステルを、加熱溶融して造粒する前記〔１〕記載の芳香族液晶性ポリエステルの製造方法に係るものである。
さらに、本発明は、〔３〕前記〔１〕または〔２〕に記載の方法で製造されてなり、下記の繰り返し単位（Ａ）を繰り返し単位全体の７５〜２５モル％、下記の繰り返し単位（Ｂ）を繰り返し単位全体の２５〜７５モル％含み、対数粘度が４．０ｄｌ／ｇ以上であり、流動温度が３２０℃以下であり、流動温度より２５℃以上高い温度で測定されるメルトテンションが３．０ｇ以上である芳香族液晶性ポリエステルに係るものである。
【化７】

【化８】

また、本発明は、〔４〕前記〔１〕または〔２〕記載の方法で製造されてなり、流動温度において剪断速度１００ｓｅｃ^-1もしくは１０００ｓｅｃ^-1で測定した溶融粘度（粘度１）に対する、流動温度より２０℃高い温度において粘度１と同じ剪断速度で測定した溶融粘度（粘度２）の比の値（粘度２／粘度１）が、０．２０〜０．８０である芳香族液晶性ポリエステルに係るものである。
【００１２】
【発明の実施の形態】
次に本発明を詳細に説明する。
本発明の芳香族液晶性ポリエステルの製造方法は、下記式（Ｉ）で表わされる化合物を８０〜２０モル％、好ましくは７５〜２５モル％、下記式（ＩＩ）で表わされる化合物を２０〜８０モル％、好ましくは２５〜７５モル％の割合で反応槽に仕込み、２７０〜３５０℃で重縮合反応させて、生成した芳香族液晶性ポリエステルの流動温度が２１０℃以上、好ましくは２２０℃以上、かつ重縮合反応温度より３０℃以上、好ましくは３５℃以上低い温度、に達した時点で、反応槽の内容物である該芳香族液晶性ポリエステルを溶融状態で回収して固化させた後、３ｍｍ以下の粒径の粒子に粉砕し、固相状態のまま不活性気体雰囲気下２００℃〜３１０℃で熱処理することを特徴とする。固相状態のまま熱処理する時間としては、１〜２４時間が好ましい。
【化９】

（但し、Ｒ¹は水素原子、ホルミル基、アセチル基、プロピオニル基またはベンゾイル基を表わし、Ｒ²は水素原子、メチル基、エチル基、プロピル基、ベンジル基またはフェニル基を表わす。）
【化１０】

（但し、Ｒ¹とＲ²の定義は、式（Ｉ）におけるそれぞれの定義と同じである。式（Ｉ）と式（ＩＩ）におけるＲ¹は、互いに同一でも異なってもよく、式（Ｉ）と式（ＩＩ）におけるＲ²は、互いに同一でも異なってもよい。）
更に、本発明の芳香族液晶性ポリエステルの製造方法は、上記で粉末状で得られる芳香族液晶性ポリエステルを加熱溶融下に、造粒することを特徴とする。造粒の形態は、ペレット状が好ましい。
【００１３】
本発明における式（Ｉ）においては、ベンゼン核がハロゲンやアルキル基等で置換されたものも含むものとする。
上記式（Ｉ）で表わされる化合物の例としては、４−ヒドロキシ安息香酸、４−ホルモキシ安息香酸、４−アセトキシ安息香酸、４−プロピオニルオキシ安息香酸、４−ヒドロキシ安息香酸メチル、４−ヒドロキシ安息香酸プロピル、４−ヒドロキシ安息香酸フェニル、４−ヒドロキシ安息香酸ベンジル、４−アセトキシ安息香酸メチル、４−アセトキシ安息香酸フェニルなどが挙げられ、特に４−ヒドロキシ安息香酸または４−アセトキシ安息香酸が好ましい。
【００１４】
さらに、上記式（Ｉ）で表わされる化合物の例としては、３−クロロ−４−ヒドロキシ安息香酸、２−クロロ−４−ヒドロキシ安息香酸、２，３−ジクロロ−４−ヒドロキシ安息香酸、３，５−ジクロロ−４−ヒドロキシ安息香酸、２，５−ジクロロ−４−ヒドロキシ安息香酸、３−ブロモ−４−ヒドロキシ安息香酸およびこれらのアセチル化物などの核置換化合物を、ガスバリア性を向上する目的で併用することもできる。
【００１５】
本発明における式（ＩＩ）においては、ナフタレン核がハロゲンやアルキル基等で置換されたものも含むものとする。
上記式（ＩＩ）で表わされる化合物の例としては、６−ヒドロキシ−２−ナフトエ酸、６−アセトキシ−２−ナフトエ酸、６−ヒドロキシ−２−ナフトエ酸メチル、６−ヒドロキシ−２−ナフトエ酸フェニル、または６−アセトキシ−２−ナフトエ酸メチルなどが挙げられ、特に６−ヒドロキシ−２−ナフトエ酸、６−アセトキシ−２−ナフトエ酸が好ましい。また、上記式（ＩＩ）で表わされる化合物の例として、６−ヒドロキシ−５−クロロ−２−ナフトエ酸、６−ヒドロキシ−７−クロロ−２−ナフトエ酸、６−ヒドロキシ−４，７−ジクロロ−２−ナフトエ酸およびこれらのアセチル化物などの核置換化合物を、ガスバリア性を向上する目的で併用することもできる。
【００１６】
本発明においては、得られる芳香族液晶性ポリエステルの物性や加工性（製膜性）に重大な影響を与えない範囲で、３−ヒドロキシ安息香酸、３−ホルモキシ安息香酸、３−アセトキシ安息香酸、３−プロピオニルオキシ安息香酸、３−ヒドロキシ安息香酸メチル、３−ヒドロキシ安息香酸プロピル、３−ヒドロキシ安息香酸フェニル、３−ヒドロキシ安息香酸ベンジル、３−アセトキシ安息香酸メチル、４’−ヒドロキシビフェニル−４−カルボン酸、４’−アセトキシビフェニル−４−カルボン酸等を併用することができる。
【００１７】
本発明の芳香族液晶性ポリエステルを製造する際には先ず、上記の式（Ｉ）で表わされる化合物および式（ＩＩ）で表わされる化合物からなる混合物を反応槽中で重縮合反応させるが、これらの化合物の重合槽への仕込みは一括方式でも、回分方式でも良い。
式（Ｉ）で表わされる化合物または式（ＩＩ）で表わされる化合物としてフェノール性水酸基を有する化合物を用いる場合には、それらをより重縮合反応し易い化合物に変える反応（例えば無水酢酸などの酸無水物を用いるエステル化反応）を重縮合反応に先立って、該重縮合反応を行うのとは別の、または同一の反応槽で行った後、引き続き重縮合反応を行うことが好ましい。上記の式（Ｉ）で表わされる化合物または式（ＩＩ）で表わされる化合物としてフェノール性水酸基を有する化合物を用いる場合には、該フェノール性水酸基の好ましくは当量以上、より好ましくは１．１〜１．３倍当量の量の無水酢酸などの酸無水物を、上記の式（Ｉ）で表わされる化合物および式（ＩＩ）表わされる化合物からなる混合物とともに反応槽に仕込み、エステル化反応を行った後、重縮合反応させることがより好ましい。
その際、アセチル化反応槽の材質は、チタン、ハステロイＢ等の耐腐食性の材料の使用が可能である。また、ポリエステルが高い色調（Ｌ値）を必要とする場合はグラスライニングされたＳＵＳ製等の反応槽等を使用することが好ましい。
【００１８】
本発明における重縮合反応は、不活性気体、例えば窒素雰囲気下に、常圧、減圧、またはそれ等の組み合わせで行うことができるが、不活性気体雰囲気下に常圧下に行うことが好ましい。プロセスは回分式、連続式、またはそれ等の組み合わせを採用できる。
本発明における重縮合反応の温度は、２７０〜３５０℃の範囲であり、好ましくは２８０〜３３０℃である。温度が２７０℃より低いと反応の進行が遅く、３５０℃を越えると分解等の副反応が起こりやすい。反応槽が多段に分かれていたり、仕切られている場合には、最終部分の反応温度が本発明で言うところの重縮合反応温度である。
【００１９】
重縮合反応の時間は反応条件等により適宜決められるべきであるが、該反応温度において０．５〜５時間が好ましい。多段階の反応温度を採用しても構わないし、場合により、反応途中で、あるいは最高温度に達したら直ぐに反応生成物である芳香族液晶性ポリエステルを溶融状態で抜出し、回収することができる。
【００２０】
該溶融重縮合反応は、通常無触媒下でも十分進行するが、必要に応じて触媒として、Ｇｅ、Ｓｎ、Ｔｉ、Ｓｂ、Ｃｏ、Ｍｎ等の酸化物、酢酸塩等の化合物を使用することもできる。食品包装用フィルムに使用する場合は、触媒成分の除去等が必要な場合があり無触媒が好ましい。
【００２１】
反応槽の形状は、公知のものを用いることができる。縦型の反応槽の場合、多段のパドル翼、タービン翼、モンテ翼、ダブルヘリカル翼が好ましく、横型の反応槽では、１軸または２軸の攪拌軸に垂直に、種々の形状の翼、例えばレンズ翼、眼鏡翼、多円平板翼等が設置されているものが良い。また、翼にねじれを付けて、攪拌性能や送り機構を向上させたものも良い。
反応槽の加熱は、熱媒、気体、電気ヒーターにより行うが、均一加熱という目的で攪拌軸、翼、邪魔板等も加熱することが好ましい。
【００２２】
該芳香族液晶性ポリエステルの製造方法においては、重縮合反応により得られる芳香族液晶性ポリエステルの流動温度が、２１０℃以上かつ重縮合反応温度より３０℃以上低い温度、であることが重要であり、得られる芳香族液晶性ポリエステルの流動温度が、２２０℃以上かつ重縮合温度より３５℃以上低い温度、であることが好ましい。
流動温度が、２１０℃未満では、芳香族液晶性ポリエステルの分子量が十分でなく、成形加工上、物性上問題がある。また固相重合等の後処理を施すにしても、芳香族液晶性ポリエステル同士の融着や副生物が大量に生じ、経済的にも好ましくない。流動温度が、重縮合反応温度に近いと、ポリエステルの粘度が高くなり、回収が困難となるばかりか、攪拌混合性も悪くなり、不均一加熱のため、ポリマーの熱安定性に影響を及ぼすことがある。
また、工業的には、バッチ重合方式では、重合槽の洗浄はコストを増大させるため、重合槽の連続使用が有利であり、溶融抜き出し条件が特に重要である。反応釜の洗浄方法としては、特開平５−２９５９２号、特開平５−２９５９３号公報に記載されたグリコール類および／またはアミン類による洗浄法が挙げられる。
【００２３】
該芳香族液晶性ポリエステルを溶融状態で取出す場合、不活性気体雰囲気中、例えば窒素雰囲気中で実施するのが、得られるポリマーの色調の点で好ましいが、水分が少ない場合は空気中でも良い。該芳香族液晶性ポリエステルを溶融状態で取出す際、重合槽は、窒素等の不活性ガス雰囲気下、または窒素等の不活性ガス雰囲気により、好ましくは０．１〜２ｋｇ／ｃｍ²Ｇ、さらに好ましくは０．２〜１ｋｇ／ｃｍ²Ｇで加圧して行うことが、抜出し時のポリマーの流動温度の上昇を抑える上で好ましい。
【００２４】
本発明の芳香族液晶性ポリエステルを溶融状態で取出す機構としては、公知の押出機、ギヤポンプが挙げられるが、単なるバルブだけでも良い。取出されたものは通常、しばらくすると固化するので、目的に応じて、ストランドカッターやシートカッターでカットしたり、粉砕することができる。また、大量かつ短時間処理する手段としては、特開平６−２５６４８５号公報に記載された定量供給装置を経てダブルベルトクーラーで冷却する方法等が挙げられる。
【００２５】
溶融状態で回収された芳香族液晶性ポリエステルは、未反応原料を除去したり、分子量を上げ物性を上げる意味から固相重合を実施する。
得られた芳香族液晶性ポリエステルを公知の粉砕機で粉砕し、３ｍｍ以下、好ましくは０．５ｍｍ以下、更に好ましくは０．１〜０．４ｍｍの平均粒径（Ｒｏｓｉｎ−Ｒａｍｍｌａｒ法）の粒子（粉末）にし、固相状態のまま不活性気体雰囲気下熱処理する固相重合を実施することが好ましい。平均粒子径が３ｍｍを越えると、表面層と内部との間で、重合速度、未反応原料の反応の結果生じた副生物の拡散時間が異なることから、分子量分布を広げたり、除去すべきものを十分除去できないために発泡やガス発生の原因となる場合があり、好ましくない。
【００２６】
固相重合時の昇温速度、最高処理温度は、芳香族液晶性ポリエステル粒子を融着させないように選ぶ必要がある。融着を起こした場合、表面積が減少し、重縮合反応や低沸点成分の除去が遅くなり好ましくない。固相重合の最高処理温度としては、融着させないで、２００〜３１０℃の範囲、より好ましくは２３０〜３００℃の範囲で不活性気体雰囲気下に処理することが効果的である。２００℃未満の温度では、反応が遅く、処理時間がかかり不経済であり、３１０℃を越えると、粉体粒子同士が融着したり、溶融したりするため固相状態が保持できないので好ましくない。
【００２７】
固相重合装置としては、既知の乾燥機、反応機、混合機、電気炉等を用いることができるが、上記の趣旨から、密閉度の高いガス流通式の装置が好ましい。不活性気体としては、窒素、ヘリウム、アルゴン、炭酸ガスから選ばれるものが好ましく、さらに好ましくは窒素である。不活性気体の流量は、固相重合装置の容積、粉末の粒径、充填状態等を勘案して決められるが、固相重合槽１ｍ³当たり２ｍ³／ｈｒ〜８ｍ³／ｈｒ、より好ましくは３ｍ³／ｈｒ〜６ｍ³／ｈｒである。
不活性気体の流量が２ｍ³／ｈｒ未満では重合速度が遅く、８ｍ³／ｈｒを越えると、粉末の飛散が起こる場合がある。
【００２８】
本発明の製造方法で得られる芳香族液晶性ポリエステルは、下記の繰り返し単位（Ａ）を繰り返し単位全体の２０〜８０モル％、下記の繰り返し単位（Ｂ）を繰り返し単位全体の８０〜２０モル％含み、対数粘度が４．０ｄｌ／ｇ以上であり、流動温度が３２０℃以下であり、流動温度より２５℃以上高い温度で測定されるメルトテンションが３．０ｇ以上を示す芳香族液晶性ポリエステルであり、溶融時に光学異方性（液晶性）を示し、溶融成形性、耐薬品性、機械物性に優れるという特徴を有している。
本発明の芳香族液晶性ポリエステルは、好ましくは、下記の繰り返し単位（Ａ）２５〜７５モル％、下記の繰り返し単位（Ｂ）７５〜２５モル％からなる芳香族液晶性ポリエステルである。
【化１１】

【化１２】

【００２９】
本発明の芳香族液晶性ポリエステルにおいては、上記の繰り返し単位（Ａ）の割合が、８０モル％を越えると、加熱によって溶融しない部分が存在する場合が多いため、溶融加工性が著しく悪くなり、２０モル％未満でも、繰り返し単位（Ｂ）が８０モル％を越え、加工温度が３２０℃を越えるため、加工性の点で好ましくない。上記の範囲で、より低温での成形（製膜）が可能となり、特に厚さ２０μｍ以下の酸素バリア性、水蒸気バリア性に優れる薄膜フィルムを得ることも可能となり、該芳香族液晶性ポリエステルは、バランスの取れた物性および加工性を示す。
従来法の、例えば減圧１段重合では、取り出し時に配管への付着、滞留時の増粘等の問題を生ずるため、製膜に適した十分な分子量で取り出すことが難しいことがあり、本発明で言うメルトテンションを所望の値に設定しにくいと考えられる。本発明の製造方法では、溶融重縮合（プレ重合）と、メルト抜出し後の粉砕粉末の固相重合を併用することにより、安定的に所望のメルトテンションにまで高めることが可能となり、製膜上好ましい。
【００３０】
本発明の芳香族液晶性ポリエステルは、次式で定義される対数粘度（ηｉｎｈ）が４．０ｄｌ／ｇ以上であり、好ましくは６．０ｄｌ／ｇ以上、より好ましくは８．０ｄｌ／ｇ以上、更に好ましくは１０．０ｄｌ／ｇ以上のものが、高メルトテンションを与える点で好ましい。またηｉｎｈは、成形性等から見て好ましくは２０ｄｌ／ｇ以下、さらに好ましくは１５ｄｌ／ｇ以下である。ηｉｎｈが４．０ｄｌ／ｇ未満のものは、メルトテンションが小さく製膜性に問題があったり、機械的強度に問題があったりする。
【数１】
ηｉｎｈ＝（ｌｎ（ηｒｅｌ））／Ｃ
（式中、ηｒｅｌは相対粘度と呼ばれるもので、毛細管中の一定標線間を溶媒が落下する時間に対する、同標線間をポリマー溶液が落下する時間の比の値（ポリマー溶液が落下する時間／溶媒が落下する時間）である。Ｃは、ポリマー溶液の濃度で、単位は、ｇ／ｄｌである。本発明においては、溶媒として、３，５−ビス（トリフルオロメチル）フェノールを用い、ポリマー濃度０．１ｇ／ｄｌ、温度６０℃でウベローデ粘度計にて測定した。）
【００３１】
本発明の芳香族液晶性ポリエステルは、流動温度が３２０℃以下、好ましくは２３０〜２９５℃、さらに好ましくは２４０〜２９０℃である。該流動温度が３２０℃を越えると、加工温度が３５０℃を越えることがあり、好ましくない。ここで流動温度（以下「ＦＴ」と略称することがある。）とは、毛細管型レオメーター（例えば島津製作所製高化式フローテスターＣＦＴ−５００型）で測定され、４℃／分の昇温速度で加熱溶融された樹脂を、荷重１００ｋｇｆ／ｃｍ²のもとで、内径１ｍｍ、長さ１０ｍｍのノズルから押し出した時に、溶融粘度が４８，０００ポイズを示す温度（℃）をいう。
【００３２】
本発明の芳香族液晶性ポリエステルは、流動温度より２５℃以上高い温度で、キャピラリー内径２．１ｍｍ、長さ８ｍｍ、ピストン速度５ｍｍ／分の条件で測定されるメルトテンションが３．０ｇ以上を示すものであり、好ましくは６．０ｇ以上、さらに好ましくは１２．０ｇ以上である。芳香族液晶性ポリエステルの組成にも依存するが、ＭＴが３．０ｇ未満の場合は、インフレーション製膜における安定製膜温度域が狭くなったり、フロストラインが安定しなくなったりする場合が多い。ＭＴは、好ましくは３０ｇ以下、より好ましくは２５ｇ以下であり、製膜性の観点からは、ＭＴの温度依存性が小さい方が好ましい。
【００３３】
本発明の芳香族液晶性ポリエステルは、好ましくは、異方性溶融相を形成し始める温度（流動温度）において、剪断速度１００ｓｅｃ^-1もしくは１０００ｓｅｃ^-1で測定した溶融粘度（粘度１）に対する、流動温度より２０℃高い温度において粘度１と同じ剪断速度で測定した溶融粘度（粘度２）の比の値（粘度２／粘度１）が、０．２０〜０．８０、好ましくは０．２５〜０．７０であり、従来の芳香族液晶性ポリエステルのそれ（０．１６以下）より大きな値を示すことが好ましい。該芳香族液晶性ポリエステルは、溶融粘度の温度依存性が小さく、加工時の成形安定性は良くなる方向になる。
【００３４】
本発明に用いられる芳香族液晶性ポリエステルの通常の成形加工時の使用形態は、粉末または２軸押出機等で加熱溶融下にペレット状に造粒した後のペレット（造粒ペレット）であるが、より好ましくは、造粒ペレットである。
本発明の芳香族液晶性ポリエステルの造粒後のペレットの流動温度（ＦＴ１）は、固相重合後の粉末（アドバンストポリマーと略記することがある。）段階での流動温度（ＦＴ０）より低下する傾向を示す。この傾向は、固相重合法を使用する従来の芳香族液晶性ポリエステルと比べて低下の度合いが大きい。この差異は、固相重合条件の差異による結晶化度の違い等がその要因と考えられる。該芳香族液晶性ポリエステルの成形温度を低下させ、成形加工性を向上させるためには、ＦＴ１が［（ＦＴ０）−５］℃より低いことが好ましく、［（ＦＴ０）−１０］℃より低いことが更に好ましい。
【００３５】
芳香族液晶性ポリエステルを加熱溶融下にペレット状に造粒してペレット化する方法としては、公知の方法を用いることができる。重合槽から溶融状態で、溝付きの平行ローラーに供給し、ストランド状（紐状）に賦形し、ストランドカッター等で切断する方法もある。芳香族液晶性ポリエステル粉末を造粒してペレットを製造する方法としては、一般に使用されている一軸または二軸の押出機を用い溶融混練し、空冷または必要に応じて水冷した後、通常用いられるペレタイザー（ストランドカッター）でペレットに賦形する。溶融均一化と賦形が目的のため、汎用の混練機が使用できるが、Ｌ／Ｄの大きいものが溶融均一化の観点からは好ましい。溶融混練に際しては、混練装置のシリンダー設定温度（ダイヘッド温度）は２００〜３５０℃の範囲が好ましく、より好ましくは２３０〜３３０℃、更に好ましくは２４０〜３２０℃である。
【００３６】
本発明に使用する芳香族液晶性ポリエステルには、所望により無機充填剤を添加することができる。このような無機充填剤としては、炭酸カルシウム、タルク、クレー、シリカ、炭酸マグネシウム、硫酸バリウム、酸化チタン、アルミナ、モンモリロナイト、石膏、ガラスフレーク、ガラス繊維、炭素繊維、アルミナ繊維、シリカアルミナ繊維、ホウ酸アルミニウムウィスカ、チタン酸カリウム繊維等が例示される。これらの無機充填剤は、フィルムの透明性や機械強度を著しく損なわない範囲で用いることができる。
【００３７】
本発明に使用する芳香族液晶性ポリエステルに、必要に応じて、さらに、有機充填剤、酸化防止剤、熱安定剤、光安定剤、難燃剤、滑剤、帯電防止剤、無機もしくは有機系着色剤、防錆剤、架橋剤、発泡剤、蛍光剤、表面平滑剤、表面光沢改良剤、またはフッ素樹脂などの離型改良剤などの各種の添加剤を製造工程中あるいはその後の加工工程において添加することができる。
【００３８】
本発明の芳香族液晶性ポリエステルよりなるフィルムの成形方法は特に制限するものではなく、周知の方法で行うことができる。例えば、Ｔダイから溶融樹脂を押し出し、巻き取るＴダイ法や、環状ダイスを設置した押し出し機から溶融樹脂を円筒状に押し出し、冷却、巻き取るインフレーション製膜法によりフィルムを得ることもできるし、射出成形法や押し出し法で得られたシートをさらに一軸延伸してフィルムを得ることもできる。
【００３９】
これらの中で、該芳香族液晶性ポリエステルフィルムの成形（製膜）方法として、好適なインフレーション製膜について説明する。即ち、該芳香族液晶性ポリエステルは、環状スリットのダイを備えた溶融混錬押出機に供給され、シリンダー設定温度好ましくは２００〜３２０℃、さらに好ましくは２１０〜３１０℃、特に好ましくは２２０〜３１０℃で溶融混錬され、押出機に環状スリットから筒状フィルムを上方または下方に押し出される。環状スリットの間隔は、通常は０．２５〜２ｍｍ、好ましくは０．５〜１．５ｍｍ、更に好ましくは０．７〜１．２ｍｍであり、環状スリットの直径は、通常２０〜１０００ｍｍ、好ましくは２５〜６００ｍｍである。
【００４０】
溶融押出された筒状の溶融樹脂フィルムに、長手方向（ＭＤ）にドラフトをかけると共に、この筒状フィルムの内側から空気または不活性ガス、例えば窒素ガス等を吹き込むことにより長手方向に直角な横手方向（ＭＤ）にフィルムを膨張延伸させる。
【００４１】
本発明の芳香族液晶性ポリエステルからなるフィルムのインフレーション製膜において、好ましいＴＤ延伸倍率即ちブロー比は、１．５〜１５であり、更に好ましくは、２．５〜１５である。また、好ましいＭＤ延伸倍率即ちドロー比は、１．５〜６０であり、更に好ましくは、２．５〜５０である。ここで、ブロー比は、（円筒型のフィルムの直径）／（ダイスの直径）で求められ、ドロー比は、（環状スリットの面積）／（フィルムの断面積）から求められる。インフレーション製膜時の設定条件が上記の範囲外であると、厚さが均一で皺のない強度のある芳香族液晶性ポリエステルフィルムを得ることが困難になる。
【００４２】
膨張させたフィルムは、通常、その円周を、空気または不活性ガス、例えば窒素ガス等で冷却した後、ニップロールを通過させて引き取る。インフレーション製膜に際しては、芳香族液晶性ポリエステルの組成に応じて、筒状の溶融体フィルムが均一な厚みで表面が平滑な状態に膨張するような条件を選択することができる。
【００４３】
本発明の芳香族液晶性ポリエステルからなるフィルム層の厚みには特に制限はないが、好ましくは１〜５００μｍ、より好ましくは５〜２００μｍ、更に好ましくは５〜５０μｍである。
【００４４】
【実施例】
以下、実施例により本発明を詳しく説明するが、これによって本発明の範囲が限定されるものではない。なお、各物性は次に示す方法により測定した。
【００４５】
［物性の測定法］
流動温度（ＦＴ）：溶融流動性を表わす指標であり、毛細管式レオメーター（（株）島津製作所製、高化式フローテスターＣＦＴ５００型）で測定され、４℃／分の昇温速度で加熱溶融されたサンプル樹脂（約２ｇ）を１００ｋｇ／ｃｍ²の荷重下で内径１ｍｍ、長さ１０ｍｍのノズルから押し出した時に、溶融粘度が４８０００ポイズ（４８００Ｐａ・Ｓに相当する）を示す温度（℃）を、流動温度（ＦＴ）とした。
【００４６】
溶融粘度：キャピログラフ１Ｂ型（東洋精機製作所製）を用いて、キャピラリーの内径は、０．５ｍｍ、長さは１０ｍｍのものを使用し、試料約１０ｇを仕込み、所定温度下に所定の剪断速度（１００ｓｅｃ^-1，１０００ｓｅｃ^-1）で溶融粘度を測定した。
【００４７】
メルトテンション（溶融張力）：キャピログラフ１Ｂ型（東洋精機製作所製）を用いて、試料約１０ｇを仕込み、キャピラリーの内径２．０９５ｍｍ、長さは８．０ｍｍ、ピストンの押出し速度は５．０ｍｍ／分、速度可変巻取機で自動昇速しながら試料を糸状に引き取り、破断したときの張力（ｇ）を測定した。
【００４８】
光学異方性：サンプル樹脂の溶融状態における光学異方性は、加熱ステージ上に置かれた粒径２５０μｍ以下のサンプル樹脂粉末を偏光下、２５℃／分で昇温して、肉眼観察または透過光量をＸＹレコーダーに記録することにより行った。
【００４９】
酸素透過度：ＪＩＳ Ｋ７１２６ Ｂ法に準拠して、ＯＸ−ＴＲＡＮ２／２０型（Ｍｏｄｅｒｎ Ｃｏｎｔｒｏｌ社製）を用い、温度２３．５℃、相対湿度６４％の条件で測定した。単位はｃｃ／ｍ²・２４ｈｒ・ａｔｍである。
【００５０】
水蒸気透過度：ＪＩＳ Ｚ０２０８（カップ法）に準拠して温度４０℃、相対湿度９０％の条件で測定した。単位はｇ／ｍ²・２４ｈｒ・ａｔｍである。
なお、酸素ガス透過率と水蒸気透過率は、膜厚みを２５μｍに換算して求めた。
【００５１】
実施例１
（繰り返し構造単位中の（Ａ）／（Ｂ）＝７３／２７（モル％）に相当する。）
（１）溶融重合
ジムロート冷却管、窒素導入管と内温測定用の熱電対を取り付けたト型連結管、イカリ型攪拌翼を有し、フラスコ外側にも熱電対を取り付けた３リットル四ツ口セパラブルフラスコを用いて、この重合槽に４−ヒドロキシ安息香酸１２０７．３ｇ（８．７４モル）、６−ヒドロキシ−２−ナフトエ酸６０８．４ｇ（３．２３モル）、および無水酢酸１３４５ｇ（１３．２モル）を投入し、窒素気流下、マントルヒーターにてフラスコ外温を１５０℃まで昇温し、２００ｒｐｍで攪拌しながら、還流下約３時間アセチル化反応を行った。アセチル化反応に引き続き、１℃／分で昇温し３１０℃で保持し、溶融重縮合を行った。この間に重縮合反応で副生する酢酸を留去し続けた。重合途中３１０℃到達から３０分後にサンプリングし、流動温度を測定したところ、２３０℃であった。同３５分後、撹拌を停止させ、ポリマーを溶融状態で容易に取出すことができた。重合槽および攪拌翼への付着は殆どなかった。得られたポリエステルはしばらくすると固化した。収量は１５６５ｇ（理論収量に対して、９７．８％）であった。
得られたポリエステルを３〜５ｃｍ角程度の大きさにした後、粉砕機を用い、平均粒径１ｍｍ以下に粉砕した後、流動温度（ＦＴ）を測定した所、２３９℃であった。このポリマー（プレポリマー）は溶融時に光学異方性を示した。
【００５２】
（２）固相重合
このプレポリマーをアルミ製トレーに入れ、窒素雰囲気炉に仕込み、窒素雰囲気下に、室温から１８０℃まで３時間で昇温し、同温度で２時間保持した後、さらに約７．５時間かけて２７０℃まで昇温し、同温度で５時間保持し、放冷した後取出し、ＦＴが２８７℃の芳香族液晶性ポリエステル（アドバンストポリマー）の粉末を得た。ここでの重量減少は、１．５％であった。
【００５３】
（３）造粒
得られたアドバンストポリマーを、池貝機販（株）製ＰＣＭ−３０二軸押出機にて、ダイヘッド温度は３００℃に設定し、スクリュー回転数８０ｒｐｍで溶融混練を行い、ＦＴが２６４℃の芳香族液晶性ポリエステルペレットを得た。この樹脂ペレットの２９５℃（ＦＴ＋３１℃）におけるメルトテンションは、７．７ｇであり、６０℃で測定した対数粘度（ηｉｎｈ）は、５．５ｄｌ／ｇであった。溶融粘度は表１に示す。
【００５４】
実施例２
（繰り返し構造単位中の（Ａ）／（Ｂ）＝７３／２７（モル％）に相当する。）
（１）溶融重合
実施例１（１）と同様にして、４−ヒドロキシ安息香酸１２０７．３ｇ（８．７４モル）、６−ヒドロキシ−２−ナフトエ酸６０８．４ｇ（３．２３モル）、および無水酢酸１３４５ｇ（１３．２モル）を仕込み、アセチル化（１５０℃、還流下約３時間）後、１℃／分で昇温し３１０℃保持し、副生する酢酸を留去し続けながら、溶融重合を行った。３１０℃到達後１５分で撹拌を停止させ、ポリマーを溶融状態で容易に取出した。重合槽および攪拌翼への付着は殆どなかった。得られたポリエステルはしばらくすると固化した。収量は１５７０ｇ（理論収量に対して、９８．１％）であった。得られたポリエステルを３〜５ｃｍ角程度の大きさにした後、粉砕機を用い、平均粒径１ｍｍ以下に粉砕した後、流動温度（ＦＴ）を測定した所、２１０℃であった。このポリマー（プレポリマー）は溶融時に光学異方性を示した。
【００５５】
（２）固相重合
実施例１（２）と同一条件で固相重合処理し、放冷した後取出し、ＦＴが２８８℃の芳香族液晶性ポリエステル（アドバンストポリマー）の粉末を得た。ここでの重量減少は、３．３％であった。
【００５６】
（３）造粒
実施例１（３）と同じ装置を使用し、ダイヘッド温度を３００℃に設定し、スクリュー回転数８０ｒｐｍで溶融混練を行って、ＦＴが２６５℃の芳香族液晶性ポリエステルペレットを得た。この樹脂ペレットの３０５℃（ＦＴ＋４０℃）におけるメルトテンションは、９．１ｇであり、６０℃で測定した対数粘度（ηｉｎｈ）は、５．６ｄｌ／ｇであった。溶融粘度は表１に示す。
【００５７】
実施例３
（繰り返し構造単位中の（Ａ）／（Ｂ）＝７３／２７（モル％）に相当する。）
（１）溶融重合
実施例１（１）と同様にして、４−ヒドロキシ安息香酸１２０７．３ｇ（８．７４モル）、６−ヒドロキシ−２−ナフトエ酸６０８．４ｇ（３．２３モル）、および無水酢酸１３４５ｇ（１３．２モル）を仕込み、アセチル化（１５０℃、還流下約３時間）後、１℃／分で昇温し３１０℃で保持し、その間副生する酢酸を留去し続けながら、溶融重合を行った。３１０℃到達後６０分後にサンプリングし、流動温度を測定した所、２４６℃であった。同９０分後、撹拌を停止させ、ポリマーを溶融状態で容易に取出すことができた。重合槽および攪拌翼への付着は殆どなかった。得られたポリエステルはしばらくすると固化した。収量は１５７３ｇ（理論収量に対して、９８．３％）であった。
同様の操作を７回繰り返し、得られたポリエステルを３〜５ｃｍ角程度の大きさにした後、粉砕機を用い、平均粒径１ｍｍ以下に粉砕した後、流動温度（ＦＴ）を測定した所、２４８℃であった。このポリマー（プレポリマー）は溶融時に光学異方性を示した。
【００５８】
（２）固相重合
このプレポリマーをアルミ製トレーに入れ、固相重合条件を「室温から１８０℃まで３時間で昇温し、同温度で２時間保持した後、さらに約８．３時間かけて２８０℃まで昇温し、同温度で５時間保持」に変更した以外は、実施例１（２）と同様に固相重合し、放冷した後取出し、ＦＴが３５７℃の芳香族液晶性ポリエステル（アドバンストポリマー）の粉末を得た。ここでの重量減少は、１．２％であった。
【００５９】
（３）造粒
得られたアドバンストポリマーを、実施例１（３）と同じ装置を使用し、ダイヘッド温度は３４０℃に設定し、スクリュー回転数１００ｒｐｍで溶融混練を行い、ＦＴが２７７℃の芳香族液晶性ポリエステルペレットを得た。この樹脂ペレットの３０７℃（ＦＴ＋３０℃）におけるメルトテンションは、２２．７ｇであり、６０℃で測定した対数粘度（ηｉｎｈ）は、１１．１ｄｌ／ｇであった。溶融粘度は表１に示す。
【００６０】
（４）インフレーション製膜
得られた芳香族液晶性ポリエステルペレットをラボプラストミル（東洋精機製作所製）に３０ｍｍφの二軸押出機を設置し、ヘッド部に２５ｍｍφ、ダイギャップ０．７５ｍｍのインフレーションダイを取り付け、シリンダー設定温度２３０〜２５５℃、シリンダーのスクリュウ回転数８０回転、ダイヘッド設定温度２５５℃、引き取り速度３０ｍ／分で製膜し、折幅１２０ｍｍのフィルムを得た。
バブルも安定し、膜厚は４〜９μｍであり、フィルム外観は比較的良好であった。引き取り速度１０ｍ／分以上で製膜可能なダイヘッド設定温度は、２５５〜２８５℃であった。
【００６１】
実施例４
（繰り返し構造単位中の（Ａ）／（Ｂ）＝３０／７０（モル％）に相当する。）
（１）溶融重合
実施例１（１）と同様にして、４−ヒドロキシ安息香酸４２８．８ｇ（３．１０モル）、６−ヒドロキシ−２−ナフトエ酸１３５９．７ｇ（７．２０ モル）および無水酢酸１１５９．７ｇ（１１．４モル）を仕込み、アセチル化（１５０℃、還流下約３時間）後、１℃／分で昇温し３２０℃で保持し、その間副生する酢酸を留去し続けながら、溶融重合を行った。３２０℃保持後４５分で撹拌を停止させ、ポリマーを溶融状態で容易に取出した。このポリマーのＦＴは、２４７℃であり、溶融時に光学異方性を示した。得られたポリエステルの収量は１５５７ｇ（理論収量に対して、９７．２％）であった。
【００６２】
固相重合
このプレポリマーをアルミ製トレーに入れ、固相重合条件を「室温から２０８℃まで３時間で昇温し、さらに８時間４０分かけて２６０℃まで昇温し、５時間保持」に変更した以外は実施例１（２）と同様に固相重合し、粉末のＦＴが２８１℃の芳香族液晶性ポリエステル（アドバンストポリマー）を得た。ここでの重量減少は、１．０％であった。
【００６３】
（３）造粒
得られたアドバンストポリマーを、実施例１（３）と同じ装置を使用し、、ダイヘッド温度は３１０℃に設定し、スクリュー回転数１５０ｒｐｍで、溶融混練を行って、ＦＴが２６０℃の芳香族液晶性ポリエステルペレットを得た。この樹脂ペレットの２９０℃（ＦＴ＋３０℃）におけるメルトテンションは、４．７ｇであり、６０℃で測定した対数粘度（ηｉｎｈ）は、４．４ｄｌ／ｇであった。
溶融粘度は表１に示す。
【００６４】
実施例５
（繰り返し構造単位中の（Ａ）／（Ｂ）＝６０／４０（モル％）に相当する。）
（１）溶融重合
実施例４（１）と同様にして、４−ヒドロキシ安息香酸９４７．０ｇ（６．９モル）、６−ヒドロキシ−２−ナフトエ酸８６０．３ｇ（４．６ モル）および無水酢酸１２８３．７ｇ（１２．６モル）を仕込み、アセチル化（１５０℃、還流下約３時間）後、１℃／分で昇温し３２０℃で保持し、その間副生する酢酸を留去し続けながら、溶融重合を行った。３２０℃保持後４５分で撹拌を停止させ、ポリマーを溶融状態で容易に取出した。このポリマーのＦＴは、２１６℃であり、溶融時に光学異方性を示した。得られたポリエステルの収量は１５６３ｇ（理論収量に対して、９７．７％）であった。
【００６５】
（２）固相重合
このプレポリマーをアルミ製トレーに入れ、固相重合条件を「室温から１９０℃まで３時間で昇温し、さらに８時間２０分かけて２４０℃まで昇温し、５時間保持」に変更した以外は実施例１（２）と同様に固相重合し、粉末のＦＴが２４０℃の芳香族液晶性ポリエステル（アドバンストポリマー）を得た。ここでの重量減少は、０．９％であった。
【００６６】
（３）造粒
得られたアドバンストポリマーを、実施例１（３）と同じ装置を使用し、、ダイヘッド温度は２８０℃に設定し、スクリュー回転数１５０ｒｐｍで、溶融混練を行って、ＦＴが２３０℃の芳香族液晶性ポリエステルペレットを得た。この樹脂ペレットの２６０℃（ＦＴ＋３０℃）におけるメルトテンションは、３．０ｇであり、６０℃で測定した対数粘度（ηｉｎｈ）は、４．９ｄｌ／ｇであった。
溶融粘度は表１に示す。
【００６７】
比較例１
（１）減圧重合
実施例１と同様に、繰り返し構造単位中の（Ａ）／（Ｂ）モル比＝７３／２７（モル％）に相当する４−ヒドロキシ安息香酸１２０８．９ｇ（８．７６モル）６−ヒドロキシ−２−ナフトエ酸６０９．１ｇ（３．２４モル） 、無水酢酸１３４６．４ｇ（１３．２１モル）を櫛型攪拌翼付きの重合槽に仕込み、窒素ガス雰囲気下で攪拌しながら、１５０℃まで昇温し、還流下約３時間アセチル化反応を行った。アセチル化反応に引き続き、副生する酢酸を留去し続けながら、１℃／分で昇温し、重合槽外温を３３０℃で保持し、溶融重縮合を行った。その後、重合槽外温を３３０℃で保持しながら、４０分かけて最終到達圧迄減圧操作を実施し、２ｔｏｒｒで５分維持した後、撹拌を停止させ、ポリマーを取リ出した。
重合槽および攪拌翼への重合物の付着が見られた。収量は１５５１ｇ（理論収量に対して、９７．１％）であった。得られたポリエステルを粗砕機を用い粉砕を試みたが、ファイバライズするため、実施例１と比べ、粉砕速度が遅かった。平均粒径３ｍｍ以下フィルターを通過したものについて、流動温度（ＦＴ）を測定した所、２６１℃であった。
【００６８】
（２）造粒
得られたポリマーを、実施例１（３）と同様に、、ダイヘッド温度は２６０℃に設定し、スクリュー回転数８０ｒｐｍで溶融混練を行って、ＦＴが２６３℃の芳香族液晶性ポリエステルペレットを得た。この樹脂ペレットの３０５℃（ＦＴ＋４２℃）におけるメルトテンションは、２．８ｇであり、６０℃で測定した対数粘度（ηｉｎｈ）は、５．５ｄｌ／ｇであった。溶融粘度は表１に示す。
【００６９】
【表１】

【００７０】
【発明の効果】
本発明の芳香族液晶性ポリエステルの製造方法は、重合後段に減圧下に重縮合する公知の製造方法に比べ、高分子量の液晶性ポリエステルをより安定的に得ることができる。本製造方法で得られる芳香族液晶性ポリエステルは、溶融粘度の温度依存性も小さく、加工温度範囲が広い傾向を示し、同一組成では高分子量化によりメルトテンションを上げることが可能となり、製膜加工に適したメルトテンションを有する材料の製造が可能となる。該全芳香族液晶性ポリエステルよりなるフィルムは、包装材料用として十分な耐熱性を有すると共に低温加工性を有し、ガスバリア性に優れたフィルムであり、フィルム外観も良好であり、食品包装、薬品包装、化粧品包装、電子材料包装など各種包装用途のフィルム用の樹脂材料、各種容器用途等のブロー用の樹脂材料、射出成形用材料として使用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aromatic liquid crystalline polyester excellent in film moldability (film forming property) and suitable for a film, and a method for producing the same.
[0002]
[Prior art]
In recent years, films made from various polymers have become indispensable for daily life. For example, various films such as a high strength film, a high elasticity film, an oxygen barrier film, a conductive film, a heat resistant film, and a light barrier film have been developed. Among them, a film having oxygen barrier properties or water vapor barrier properties is penetrating into our lives as a packaging material regardless of industrial use or consumer use.
[0003]
  Conventionally, stretched films of polyolefin such as polyethylene and polypropylene, stretched films of polyethylene terephthalate (hereinafter abbreviated as PET), polyvinylidene chloride (hereinafter abbreviated as PVDC) films, saponified ethylene-vinyl acetate. Copolymer (hereinafter abbreviated as EVOH) films and the like have been developed and used as single-layer or multi-layer films of two or more layers depending on the purpose and application.
  In order to maintain gas barrier properties, multilayering is often necessary, which is one of the factors that increase manufacturing costs. Recently, in the field of food packaging such as retort pouches, there is a tendency to perform high-temperature and short-time treatment in order to improve the efficiency of sterilization, and a packaging material having high heat resistance is required. Currently, PET films and the like on which silica, alumina and the like are vapor-deposited have been developed, but there are still problems in waste separation and incineration methods in the future. Polyethylene naphthalate (hereinafter abbreviated as PEN) -based packaging materials (containers) with improved heat resistance and oxygen barrier properties of PET films have been developed (for example, JP-A-8-113631 and JP-A-8-92467). High gas barrier properties (oxygen permeability of 1 cc / m)²・ 24hr · atm or less) Insufficient gas barrier properties.
  In addition, for EVOH which is excellent in oxygen barrier property but poor in water vapor barrier performance, the problem of water vapor barrier property is being solved by making a multilayer film laminated with polyolefin or the like excellent in water vapor barrier property, There remains a problem with heat resistance.
[0004]
In these fields, a resin material for a film (high gas barrier material) is desired which is inexpensive and heat resistant and has a high water vapor barrier property and high oxygen barrier property, assuming a future distribution at normal temperature. As materials having an oxygen barrier property and a water vapor barrier property, liquid crystal polymers, particularly thermotropic liquid crystal polyesters (hereinafter sometimes abbreviated as LCP), have attracted attention, and the formation of films has been studied. For example, a liquid crystalline copolymer polyester (Japanese Patent Publication No. 8-2974) and other semi-aromatic liquid crystals made of PET / p-hydroxybenzoic acid (hereinafter sometimes abbreviated as POB) having an aliphatic chain as a main chain. A film of a conductive polyester (Japanese Patent Publication No. 6-53383) and a film of a wholly aromatic liquid crystalline polyester (Japanese Patent Laid-Open Nos. 7-323506 and 7-251438) have been reported. In these studies, molecular orientation occurs in the flow direction (MD), which is a characteristic of LCP, and anisotropy in mechanical strength with the direction (TD) perpendicular to the flow direction (MD). It was difficult to obtain a thin film having an LCP thickness of 50 μm or less.
[0005]
In addition, the processing temperature of wholly aromatic LCP often exceeds 300 ° C, and the fully aromatic liquid crystalline polyester having heat resistance exceeding 250 ° C under load deflection temperature (TDUL) has a higher processing temperature of 350 ° C or higher. Requires expensive processing machines with special specifications. Film formation methods from wholly aromatic polyesters that form an optically anisotropic melt upon melting include, for example, inflation film formation and film formation by T-die in Japanese Patent Publication Nos. 62-58378 and 63-33450. Although the methods are described, all of them require a processing temperature of 340 ° C. or more, and there is still room for improvement in terms of the processing temperature.
[0006]
On the other hand, suspension polymerization methods, interfacial polymerization methods, solution polymerization methods, bulk melt polymerization methods, and the like are known as production methods for obtaining aromatic polyesters. It has problems such as washing of coalescence and drainage load. Mass production is generally used as a method for producing polyesters obtained by copolymerizing different kinds of aromatic hydroxycarboxylic acids and aromatic liquid crystalline polyesters obtained from aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids, and aromatic diols. ing. Bulk polymerization is economical, but the equilibrium constant of the polycondensation reaction of polyester is smaller than that of polyamide. Therefore, in order to proceed with the polycondensation reaction, the reaction temperature is increased or the reaction is carried out under reduced pressure. It is necessary to take a method of removing the substance.
[0007]
When the molecular weight is increased by using the low-pressure polymerization method, it may be difficult to continuously recover the polymer if the molecular weight is increased until the desired melt tension is exhibited due to the melt viscosity at the time of taking out the polymer. Because of the high temperature treatment, there is a problem of contamination of the polymer staying in the polymerization kettle or the outlet. Aromatic liquid crystalline polyesters with relatively low melting temperatures often react under reduced pressure in the latter stage, so there is a problem that it is difficult to obtain a high molecular weight resin in a stable state. (JP-A-8-192421). If unreacted raw materials or low-boiling compounds generated during polymerization remain in the aromatic liquid crystalline polyester, they may vaporize during molding, contaminating the environment, or gradually generating from the molded product and destroying the product mechanism. is there. If the unreacted raw material or the low boiling point compound is vaporized at the time of inflation film formation, there is a problem that the formation of bubbles is hindered and film formation becomes difficult.
As a method for stably producing a heat-resistant polyester, the present inventors have taken a method of taking out a polyester in a molten state after melt polycondensation (Japanese Patent Laid-Open No. 2-69517), or a combination of this and a solid phase polymerization method. A method for producing an aromatic polyester (Japanese Patent Laid-Open No. 2-69518) is proposed.
[0008]
A fully aromatic liquid crystalline polyester having a molecular weight sufficient to exhibit mechanical strength and capable of being molded at a low temperature (320 ° C. or lower) is disclosed in Japanese Patent Publication No. 63-3888, and a semi-aromatic liquid crystalline polyester is It is described in JP-A 61-102234. As a film forming method using this, a method for forming a film at a high shear rate is disclosed in JP-A-2-3430, and a film forming method using a ring die or the like is described in US Pat. No. 4,975,312 and WO9015706. Although described, any of them shows a method of relaxing the anisotropy peculiar to liquid crystal polyester by a special molding method. Since these use expensive 6-hydroxy-2-naphthoic acid at present, a thin film having a thickness of 25 μm or less, preferably 15 μm or less, is usually required because of cost requirements.
Japanese Patent Application Laid-Open No. 2-3430 describes a method of forming an inflation film at a high shear rate using melt strength measured under a certain condition as an important index for film formation as one of technical factors. A film having a thickness of 16 μm to 22 μm is exemplified, but problems remain in thinning. The LCP resin film material having high gas barrier properties and low temperature workability of 320 ° C. or less still has many problems in practical use.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing an aromatic liquid crystalline polyester suitable for a film having sufficient strength as a packaging material, low-temperature processability, and excellent gas barrier properties, and an aromatic obtained by this production method The object is to provide a liquid crystalline polyester.
[0010]
[Means for Solving the Problems]
The present inventors have intensively studied a method for producing an aromatic liquid crystalline polyester comprising two or more types of aromatic hydroxycarboxylic acid units and a high molecular weight of the resin, and the aromatic liquid crystal having a higher molecular weight than that of the conventional method. A production method capable of stably producing a reactive polyester has been found, and by increasing the molecular weight, the melt tension (hereinafter sometimes abbreviated as MT) can be increased, and the temperature dependence of the melt viscosity of the resin can be reduced. The present inventors have found that the present invention can be accomplished and have completed the present invention.
[0011]
  That is, the present invention provides [1] 80-20 mol% of a compound represented by the following formula (I) and 20-80 mol% of a compound represented by the following formula (II) in a reaction tank. When the flow temperature of the aromatic liquid crystalline polyester produced by polycondensation reaction at 350 ° C. reaches 210 ° C. or higher and 30 ° C. or lower than the polycondensation reaction temperature, the fragrance as the contents of the reaction vessel Aromatic liquid crystalline polyester, which is recovered in a molten state and solidified, then pulverized into particles having a particle size of 3 mm or less, and heat-treated at 200 ° C. to 310 ° C. in an inert gas atmosphere in a solid state. This relates to a method for producing polyester.
[Chemical formula 5]

(However, R¹Represents a hydrogen atom, formyl group, acetyl group, propionyl group or benzoyl group;²Represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, a benzyl group or a phenyl group. )
[Chemical 6]

(However, R¹And R²The definition of is the same as each definition in Formula (I). R in formula (I) and formula (II)¹May be the same or different from each other, and R in the formulas (I) and (II)²May be the same or different. )
  Here, the flow temperature is a resin measured by a capillary rheometer and heated and melted at a heating rate of 4 ° C./min.²When extruding from a nozzle with an inner diameter of 1 mm and a length of 10 mm, MeltThe temperature (° C.) at which the melt viscosity shows 48,000 poise.
  The present invention also provides [2〕heatAromatic liquid crystalline polyester obtained by treatment is granulated by heating and meltingTheRuAs described in [1] aboveThe present invention relates to a method for producing an aromatic liquid crystalline polyester.
  Furthermore, the present invention is [3] produced by the method described in [1] or [2] above, wherein the following repeating unit (A) is 75 to 25 mol% of the entire repeating unit,belowRepeat unit (B)Of the entire repeating unitA fragrance containing 25 to 75 mol%, having a logarithmic viscosity of 4.0 dl / g or more, a flow temperature of 320 ° C. or less, and a melt tension measured at a temperature 25 ° C. or more higher than the flow temperature of 3.0 g or more. This relates to the group liquid crystalline polyester.
[Chemical 7]

[Chemical 8]

  Further, the present invention is [4] manufactured by the method described in [1] or [2].The flowShear rate 100 sec at dynamic temperature^-1Or 1000 sec^-1Melt viscosity (viscosity 1) measured byAgainst, Melt viscosity (viscosity 2) measured at the same shear rate as viscosity 1 at a temperature 20 ° C. higher than the flow temperature) Ratiovalue(Viscosity 2 / Viscosity 1)However, it relates to an aromatic liquid crystalline polyester of 0.20 to 0.80.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail.
In the method for producing the aromatic liquid crystalline polyester of the present invention, the compound represented by the following formula (I) is 80 to 20 mol%, preferably 75 to 25 mol%, and the compound represented by the following formula (II) is 20 to 80 mol%. The flow rate of the aromatic liquid crystalline polyester produced by charging the reaction vessel at a ratio of mol%, preferably 25 to 75 mol%, and polycondensation reaction at 270 to 350 ° C. is 210 ° C. or higher, preferably 220 ° C. or higher. And when the temperature reaches 30 ° C. or more, preferably 35 ° C. or more lower than the polycondensation reaction temperature, the aromatic liquid crystalline polyester as the contents of the reaction vessel is recovered in a molten state and solidified, and then 3 mm It is characterized by being pulverized into particles having the following particle size and heat-treated at 200 ° C. to 310 ° C. in an inert gas atmosphere in a solid state. The heat treatment time in the solid state is preferably 1 to 24 hours.
[Chemical 9]

(However, R¹Represents a hydrogen atom, formyl group, acetyl group, propionyl group or benzoyl group;²Represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, a benzyl group or a phenyl group. )
Embedded image

(However, R¹And R²The definition of is the same as each definition in Formula (I). R in formula (I) and formula (II)¹May be the same or different from each other, and R in the formulas (I) and (II)²May be the same or different. )
Furthermore, the method for producing an aromatic liquid crystalline polyester of the present invention is characterized in that the aromatic liquid crystalline polyester obtained in powder form is granulated while being heated and melted. The form of granulation is preferably a pellet.
[0013]
The formula (I) in the present invention includes those in which the benzene nucleus is substituted with a halogen, an alkyl group or the like.
Examples of the compound represented by the above formula (I) include 4-hydroxybenzoic acid, 4-formoxybenzoic acid, 4-acetoxybenzoic acid, 4-propionyloxybenzoic acid, methyl 4-hydroxybenzoate, and 4-hydroxybenzoic acid. Examples thereof include propyl acid, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, methyl 4-acetoxybenzoate, phenyl 4-acetoxybenzoate, and 4-hydroxybenzoic acid or 4-acetoxybenzoic acid is particularly preferable.
[0014]
Furthermore, examples of the compound represented by the formula (I) include 3-chloro-4-hydroxybenzoic acid, 2-chloro-4-hydroxybenzoic acid, 2,3-dichloro-4-hydroxybenzoic acid, 3, For the purpose of improving gas barrier properties, a nuclear substitution compound such as 5-dichloro-4-hydroxybenzoic acid, 2,5-dichloro-4-hydroxybenzoic acid, 3-bromo-4-hydroxybenzoic acid and acetylated compounds thereof. It can also be used together.
[0015]
In the formula (II) in the present invention, a compound in which a naphthalene nucleus is substituted with a halogen, an alkyl group or the like is included.
Examples of the compound represented by the above formula (II) include 6-hydroxy-2-naphthoic acid, 6-acetoxy-2-naphthoic acid, 6-hydroxy-2-naphthoic acid methyl, 6-hydroxy-2-naphthoic acid. Examples include phenyl or methyl 6-acetoxy-2-naphthoate, and 6-hydroxy-2-naphthoic acid and 6-acetoxy-2-naphthoic acid are particularly preferable. Examples of the compound represented by the formula (II) include 6-hydroxy-5-chloro-2-naphthoic acid, 6-hydroxy-7-chloro-2-naphthoic acid, 6-hydroxy-4,7-dichloro. Nuclear substitution compounds such as -2-naphthoic acid and acetylated compounds thereof can be used in combination for the purpose of improving gas barrier properties.
[0016]
In the present invention, 3-hydroxybenzoic acid, 3-formoxybenzoic acid, 3-acetoxybenzoic acid, as long as the physical properties and processability (film forming property) of the obtained aromatic liquid crystalline polyester are not seriously affected. 3-propionyloxybenzoic acid, methyl 3-hydroxybenzoate, propyl 3-hydroxybenzoate, phenyl 3-hydroxybenzoate, benzyl 3-hydroxybenzoate, methyl 3-acetoxybenzoate, 4′-hydroxybiphenyl-4- Carboxylic acid, 4′-acetoxybiphenyl-4-carboxylic acid and the like can be used in combination.
[0017]
  When producing the aromatic liquid crystalline polyester of the present invention, first, the above formula (I)Compound represented byandformulaA mixture composed of the compound represented by (II) is subjected to a polycondensation reaction in a reaction vessel, and these compounds may be charged into the polymerization vessel in a batch system or a batch system.
  Formula (I)Compound represented byOrformula(II)Compound represented byIn the case of using a compound having a phenolic hydroxyl group as a compound, a reaction (for example, an esterification reaction using an acid anhydride such as acetic anhydride) that converts them into a compound that is more easily subjected to a polycondensation reaction is performed prior to the polycondensation reaction. It is preferable to carry out the polycondensation reaction subsequently after the condensation reaction is carried out in a different or the same reaction vessel. Formula (I) aboveCompound represented byOrformula(II)Compound represented byWhen a compound having a phenolic hydroxyl group is used as an acid anhydride such as acetic anhydride in an amount of preferably at least equivalent, more preferably 1.1 to 1.3 times equivalent of the phenolic hydroxyl group, (I)Compound represented byandformula(II) It is more preferable to carry out a polycondensation reaction after charging into a reaction vessel together with a mixture of the compounds represented and performing an esterification reaction.
  At this time, the material of the acetylation reaction tank can be a corrosion-resistant material such as titanium or Hastelloy B. Moreover, when polyester requires a high color tone (L value), it is preferable to use a glass-lined reaction vessel made of SUS or the like.
[0018]
The polycondensation reaction in the present invention can be carried out under an inert gas, for example, a nitrogen atmosphere at normal pressure, reduced pressure, or a combination thereof, but is preferably carried out under an inert gas atmosphere under normal pressure. The process can be batch, continuous, or a combination thereof.
The temperature of the polycondensation reaction in this invention is the range of 270-350 degreeC, Preferably it is 280-330 degreeC. If the temperature is lower than 270 ° C., the reaction proceeds slowly, and if it exceeds 350 ° C., side reactions such as decomposition tend to occur. When the reaction tank is divided into multiple stages or partitioned, the reaction temperature of the final part is the polycondensation reaction temperature referred to in the present invention.
[0019]
The time for the polycondensation reaction should be appropriately determined depending on the reaction conditions and the like, but is preferably 0.5 to 5 hours at the reaction temperature. A multi-stage reaction temperature may be employed. In some cases, the aromatic liquid crystalline polyester as a reaction product can be extracted in a molten state and recovered during the reaction or as soon as the maximum temperature is reached.
[0020]
The melt polycondensation reaction usually proceeds sufficiently even in the absence of a catalyst, but if necessary, an oxide such as Ge, Sn, Ti, Sb, Co, Mn, or a compound such as acetate may be used as a catalyst. it can. When used for a film for food packaging, it may be necessary to remove the catalyst component, etc., and no catalyst is preferred.
[0021]
A well-known thing can be used for the shape of a reaction tank. In the case of a vertical reaction vessel, multi-stage paddle blades, turbine blades, Monte blades, and double helical blades are preferable, and in a horizontal reaction vessel, blades of various shapes, for example, perpendicular to one or two stirring axes, A lens wing, a spectacle wing, a multi-flat plate wing or the like is preferably installed. Moreover, the thing which attached the twist to the wing | blade and improved stirring performance and a feed mechanism is good.
The reaction tank is heated with a heat medium, gas, or an electric heater, but it is preferable to heat the stirring shaft, blades, baffle plate and the like for the purpose of uniform heating.
[0022]
In the method for producing the aromatic liquid crystalline polyester, it is important that the flow temperature of the aromatic liquid crystalline polyester obtained by the polycondensation reaction is 210 ° C. or higher and 30 ° C. lower than the polycondensation reaction temperature. The flow temperature of the obtained aromatic liquid crystalline polyester is preferably 220 ° C. or higher and 35 ° C. or lower than the polycondensation temperature.
When the flow temperature is less than 210 ° C., the molecular weight of the aromatic liquid crystalline polyester is not sufficient, and there are problems in terms of molding and physical properties. Even if post-treatment such as solid phase polymerization is performed, fusion of aromatic liquid crystalline polyesters and a large amount of by-products are generated, which is not preferable economically. If the flow temperature is close to the polycondensation reaction temperature, the viscosity of the polyester will be high and recovery will be difficult, and the stirring and mixing properties will also be poor, which will affect the thermal stability of the polymer due to uneven heating. There is.
Further, industrially, in the batch polymerization method, since the cleaning of the polymerization tank increases the cost, continuous use of the polymerization tank is advantageous, and the melt extraction condition is particularly important. Examples of the method for washing the reaction kettle include those using glycols and / or amines described in JP-A-5-29592 and JP-A-5-29593.
[0023]
When the aromatic liquid crystalline polyester is taken out in a molten state, it is preferable to carry out in an inert gas atmosphere, for example, in a nitrogen atmosphere, from the viewpoint of the color tone of the obtained polymer. When taking out the aromatic liquid crystalline polyester in a molten state, the polymerization tank is preferably in an inert gas atmosphere such as nitrogen or an inert gas atmosphere such as nitrogen, preferably 0.1 to 2 kg / cm.²G, more preferably 0.2-1 kg / cm²It is preferable to pressurize with G in order to suppress an increase in the flow temperature of the polymer at the time of withdrawal.
[0024]
As a mechanism for taking out the aromatic liquid crystalline polyester of the present invention in a molten state, known extruders and gear pumps may be mentioned, but only a simple valve may be used. The taken-out material usually solidifies after a while, so that it can be cut or pulverized with a strand cutter or a sheet cutter depending on the purpose. Moreover, as a means to process in large quantities for a short time, the method etc. which cool with a double belt cooler through the fixed supply apparatus described in Unexamined-Japanese-Patent No. 6-256485 are mentioned.
[0025]
The aromatic liquid crystalline polyester recovered in the molten state is subjected to solid-phase polymerization in order to remove unreacted raw materials or increase molecular weight and physical properties.
The obtained aromatic liquid crystalline polyester is pulverized by a known pulverizer, and particles having an average particle diameter (Rosin-Rammar method) of 3 mm or less, preferably 0.5 mm or less, more preferably 0.1 to 0.4 mm (Rosin-Rammar method) It is preferable to carry out solid phase polymerization in which the powder is heat-treated in an inert gas atmosphere in the solid state. When the average particle diameter exceeds 3 mm, the polymerization rate and the diffusion time of by-products generated as a result of the reaction of unreacted raw materials differ between the surface layer and the inside. Since it cannot be removed sufficiently, it may cause foaming and gas generation, which is not preferable.
[0026]
It is necessary to select the heating rate and the maximum processing temperature during solid phase polymerization so as not to fuse the aromatic liquid crystalline polyester particles. When fusing occurs, the surface area decreases, and the polycondensation reaction and the removal of low-boiling components are slow, which is not preferable. As the maximum processing temperature for solid-phase polymerization, it is effective to perform the treatment in an inert gas atmosphere in the range of 200 to 310 ° C., more preferably in the range of 230 to 300 ° C. without fusing. If the temperature is lower than 200 ° C., the reaction is slow and the processing time is uneconomical, and if it exceeds 310 ° C., the powder particles are fused or melted, so that the solid state cannot be maintained. .
[0027]
As the solid-phase polymerization apparatus, known dryers, reactors, mixers, electric furnaces and the like can be used. From the above-mentioned purpose, a gas flow type apparatus having a high sealing degree is preferable. As the inert gas, a gas selected from nitrogen, helium, argon, and carbon dioxide gas is preferable, and nitrogen is more preferable. The flow rate of the inert gas is determined in consideration of the volume of the solid phase polymerization apparatus, the particle size of the powder, the filling state, etc.^Three2m per^Three/ Hr ~ 8m^Three/ Hr, more preferably 3 m^Three/ Hr-6m^Three/ Hr.
The flow rate of inert gas is 2m^ThreeIf less than / hr, the polymerization rate is slow, 8 m^ThreeIf it exceeds / hr, powder scattering may occur.
[0028]
  The aromatic liquid crystalline polyester obtained by the production method of the present invention comprises 20 to 80 mol% of the following repeating unit (A),belowRepeat unit (B)Of the entire repeating unitAroma containing 80 to 20 mol%, logarithmic viscosity of 4.0 dl / g or more, flow temperature of 320 ° C. or less, and melt tension measured at a temperature 25 ° C. or more higher than the flow temperature of 3.0 g or more It is a group liquid crystalline polyester, has optical anisotropy (liquid crystallinity) when melted, and has excellent characteristics such as melt moldability, chemical resistance and mechanical properties.
  Aromatic liquid crystalline polyester of the present inventionIsPreferably, the repeating unit (A) below is 25 to 75 mol%,belowIt is an aromatic liquid crystalline polyester composed of 75 to 25 mol% of the repeating unit (B).
Embedded image

Embedded image

[0029]
In the aromatic liquid crystalline polyester of the present invention, if the proportion of the above repeating unit (A) exceeds 80 mol%, there are many portions that do not melt by heating, so the melt processability is remarkably deteriorated, Even if it is less than 20 mol%, since the repeating unit (B) exceeds 80 mol% and the processing temperature exceeds 320 ° C., it is not preferable in terms of workability. Within the above range, molding (film formation) at a lower temperature is possible, and it is also possible to obtain a thin film having excellent oxygen barrier properties and water vapor barrier properties particularly having a thickness of 20 μm or less. Shows balanced physical properties and processability.
In the conventional one-step polymerization, for example, reduced pressure one-stage polymerization, problems such as adhesion to the pipe at the time of removal and thickening at the time of retention may occur, and it may be difficult to take out with a sufficient molecular weight suitable for film formation. It is considered that the melt tension is difficult to set to a desired value. In the production method of the present invention, by using both melt polycondensation (prepolymerization) and solid-phase polymerization of the pulverized powder after melt extraction, it is possible to stably increase the melt tension to a desired value. preferable.
[0030]
  The aromatic liquid crystalline polyester of the present invention has a logarithmic viscosity (ηinh) defined by the following formula of 4.0 dl / g or more, preferably 6.0 dl / g or more, more preferably 8.0 dl / g or more. More preferably, 10.0 dl / g or more is preferable in terms of providing high melt tension. Further, ηinh is preferably 20 dl / g or less, more preferably 15 dl / g or less in view of moldability and the like.. ηWhen the inh is less than 4.0 dl / g, the melt tension is small, there is a problem in film forming property, and there is a problem in mechanical strength.
[Expression 1]
    ηinh = (ln (ηrel)) / C
(In the formula, ηrel is called relative viscosity.,hairBetween certain marked lines in the narrow tubeSolventTime to fallTime for the polymer solution to fall between the same marked linesRatio ofThe value of the(Polymer solutionTime for falling/solventTime for falling). C is the concentration of the polymer solution, and the unit is g / dl. In the present invention, 3,5-bis (trifluoromethyl) phenol is used as a solvent, and measurement is performed with an Ubbelohde viscometer at a polymer concentration of 0.1 g / dl and a temperature of 60 ° C.It was.)
[0031]
The aromatic liquid crystalline polyester of the present invention has a flow temperature of 320 ° C. or lower, preferably 230 to 295 ° C., more preferably 240 to 290 ° C. If the flow temperature exceeds 320 ° C, the processing temperature may exceed 350 ° C, which is not preferable. Here, the flow temperature (hereinafter sometimes abbreviated as “FT”) is measured with a capillary rheometer (for example, Koka type flow tester CFT-500 manufactured by Shimadzu Corporation), and the temperature rises at 4 ° C./min. Resin melted by heating at a speed of 100 kgf / cm²The temperature (° C.) at which the melt viscosity shows 48,000 poise when extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm.
[0032]
The aromatic liquid crystalline polyester of the present invention exhibits a melt tension of 3.0 g or more measured at a temperature higher by 25 ° C. or more than the flow temperature at a capillary inner diameter of 2.1 mm, a length of 8 mm, and a piston speed of 5 mm / min. It is preferably 6.0 g or more, more preferably 12.0 g or more. Although depending on the composition of the aromatic liquid crystalline polyester, when the MT is less than 3.0 g, the stable film forming temperature range in the inflation film formation is often narrowed or the frost line is not stable in many cases. MT is preferably 30 g or less, more preferably 25 g or less. From the viewpoint of film forming properties, it is preferable that the temperature dependence of MT is smaller.
[0033]
  Aromatic liquid crystalline polyester of the present inventionIsPreferably, at a temperature at which an anisotropic melt phase starts to be formed (flow temperature), a shear rate of 100 sec.^-1Or 1000 sec^-1Melt viscosity (viscosity 1) measured byAgainst, Melt viscosity (viscosity 2) measured at the same shear rate as viscosity 1 at a temperature 20 ° C. higher than the flow temperature) Ratiovalue(Viscosity 2 / Viscosity 1)However, it is 0.20-0.80, Preferably it is 0.25-0.70, and it is preferable to show a bigger value than that (0.16 or less) of the conventional aromatic liquid crystalline polyester. The aromatic liquid crystalline polyester is less dependent on the temperature of the melt viscosity and tends to improve the molding stability during processing.
[0034]
The normal liquid crystal polyester used in the present invention is used at the time of normal molding processing, but it is a pellet (granulated pellet) after being granulated into pellets by heating or melting with a powder or a twin screw extruder or the like. More preferably, it is a granulated pellet.
The pellet flow temperature (FT1) after granulation of the aromatic liquid crystalline polyester of the present invention is lower than the flow temperature (FT0) at the stage of solid-phase polymerization after powder (sometimes abbreviated as advanced polymer). Show the trend. This tendency is greatly reduced as compared with the conventional aromatic liquid crystalline polyester using the solid phase polymerization method. This difference is considered to be caused by a difference in crystallinity due to a difference in solid-state polymerization conditions. In order to lower the molding temperature of the aromatic liquid crystalline polyester and improve the molding processability, FT1 is preferably lower than [(FT0) -5] ° C, and lower than [(FT0) -10] ° C. Is more preferable.
[0035]
As a method for granulating the aromatic liquid crystalline polyester into a pellet form by heating and melting, a known method can be used. There is also a method in which a molten state is supplied from a polymerization tank to a grooved parallel roller, shaped into a strand (string), and cut with a strand cutter or the like. As a method for producing pellets by granulating aromatic liquid crystalline polyester powder, it is usually used after melt-kneading using a commonly used single-screw or twin-screw extruder, air cooling or water cooling as necessary. Shape into pellets with a pelletizer (strand cutter). A general-purpose kneader can be used for the purpose of melt homogenization and shaping, but a large L / D is preferable from the viewpoint of melt homogenization. In the melt-kneading, the cylinder setting temperature (die head temperature) of the kneading apparatus is preferably in the range of 200 to 350 ° C, more preferably 230 to 330 ° C, still more preferably 240 to 320 ° C.
[0036]
If desired, an inorganic filler can be added to the aromatic liquid crystalline polyester used in the present invention. Such inorganic fillers include calcium carbonate, talc, clay, silica, magnesium carbonate, barium sulfate, titanium oxide, alumina, montmorillonite, gypsum, glass flakes, glass fibers, carbon fibers, alumina fibers, silica alumina fibers, boron. Examples include aluminum oxide whiskers and potassium titanate fibers. These inorganic fillers can be used as long as the transparency and mechanical strength of the film are not significantly impaired.
[0037]
If necessary, the aromatic liquid crystalline polyester used in the present invention may further include an organic filler, an antioxidant, a heat stabilizer, a light stabilizer, a flame retardant, a lubricant, an antistatic agent, an inorganic or organic colorant. Various additives such as rust preventives, crosslinking agents, foaming agents, fluorescent agents, surface smoothing agents, surface gloss improvers, or mold release improvers such as fluororesins are added during the manufacturing process or in subsequent processing steps. be able to.
[0038]
The method for forming the film comprising the aromatic liquid crystalline polyester of the present invention is not particularly limited, and can be performed by a known method. For example, it is possible to obtain a film by a T-die method of extruding and winding a molten resin from a T-die, or an inflation film forming method of extruding a molten resin into a cylindrical shape from an extruder provided with an annular die, cooling and winding, A sheet obtained by an injection molding method or an extrusion method can be further uniaxially stretched to obtain a film.
[0039]
Among these, as a method for forming (film formation) of the aromatic liquid crystalline polyester film, a suitable inflation film formation will be described. That is, the aromatic liquid crystalline polyester is supplied to a melt kneading extruder equipped with a die having an annular slit, and a cylinder set temperature is preferably 200 to 320 ° C, more preferably 210 to 310 ° C, and particularly preferably 220 to 310. It is melt-kneaded at a temperature of 0 ° C., and the cylindrical film is extruded upward or downward from an annular slit into an extruder. The interval between the annular slits is usually 0.25 to 2 mm, preferably 0.5 to 1.5 mm, more preferably 0.7 to 1.2 mm, and the diameter of the annular slit is usually 20 to 1000 mm, preferably 25-600 mm.
[0040]
A transverse hand perpendicular to the longitudinal direction is created by drafting the melt-extruded tubular molten resin film in the longitudinal direction (MD) and blowing air or an inert gas such as nitrogen gas from the inside of the tubular film. The film is expanded and stretched in the direction (MD).
[0041]
In the inflation film-forming of the film comprising the aromatic liquid crystalline polyester of the present invention, the preferable TD stretch ratio, that is, the blow ratio, is 1.5 to 15, more preferably 2.5 to 15. Moreover, preferable MD draw ratio, ie, draw ratio, is 1.5-60, More preferably, it is 2.5-50. Here, the blow ratio is obtained from (diameter of cylindrical film) / (diameter of die), and the draw ratio is obtained from (area of annular slit) / (cross-sectional area of film). If the setting conditions at the time of inflation film formation are outside the above range, it becomes difficult to obtain an aromatic liquid crystalline polyester film having a uniform thickness and no wrinkle strength.
[0042]
The expanded film is usually cooled by air or an inert gas such as nitrogen gas, and then taken through a nip roll. In the inflation film formation, conditions can be selected such that the cylindrical melt film expands to a uniform thickness and a smooth surface according to the composition of the aromatic liquid crystalline polyester.
[0043]
Although there is no restriction | limiting in particular in the thickness of the film layer which consists of aromatic liquid crystalline polyester of this invention, Preferably it is 1-500 micrometers, More preferably, it is 5-200 micrometers, More preferably, it is 5-50 micrometers.
[0044]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this does not limit the scope of the present invention. Each physical property was measured by the following method.
[0045]
[Measurement method of physical properties]
  Flow temperature (FT): an index representing melt fluidity,hair100 kg / cm of sample resin (about 2 g) measured with a capillary type rheometer (manufactured by Shimadzu Corporation, Koka Type Flow Tester CFT500 type) and heated and melted at a heating rate of 4 ° C./min.²When extruding from a nozzle with an inner diameter of 1 mm and a length of 10 mm under the load of, MeltTemperature (° C) at which the melt viscosity shows 48000 poise (corresponding to 4800 Pa · S)The flow temperature (FT)Whendid.
[0046]
Melt viscosity: Capillograph type 1B (manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used. The capillary had an inner diameter of 0.5 mm and a length of 10 mm. About 10 g of a sample was charged, and a predetermined shear rate ( 100 sec^-1, 1000sec^-1) To measure the melt viscosity.
[0047]
Melt tension (melt tension): Capillograph 1B type (manufactured by Toyo Seiki Seisakusho) was used to prepare about 10 g of sample, capillary inner diameter was 2.095 mm, length was 8.0 mm, and piston extrusion speed was 5.0 mm / min. The sample was taken up into a thread shape while being automatically increased by a variable speed winder, and the tension (g) when the sample was broken was measured.
[0048]
Optical anisotropy: The optical anisotropy in the molten state of the sample resin is that the sample resin powder having a particle size of 250 μm or less placed on the heating stage is heated at 25 ° C./min under polarized light and observed with the naked eye or transmitted. This was done by recording the amount of light on an XY recorder.
[0049]
Oxygen permeability: Based on JIS K7126 B method, OX-TRAN 2/20 type (manufactured by Modern Control) was used and measured under conditions of a temperature of 23.5 ° C. and a relative humidity of 64%. Unit is cc / m²• 24 hr · atm.
[0050]
Water vapor transmission rate: Measured under conditions of a temperature of 40 ° C. and a relative humidity of 90% in accordance with JIS Z0208 (cup method). Unit is g / m²• 24 hr · atm.
The oxygen gas permeability and water vapor permeability were determined by converting the film thickness to 25 μm.
[0051]
Example 1
(This corresponds to (A) / (B) = 73/27 (mol%) in the repeating structural unit.)
(1) Melt polymerization
A 3 liter four-neck separable flask equipped with a Dimroth condenser tube, a nitrogen connection tube and a toroidal connecting tube fitted with a thermocouple for measuring the internal temperature, a squid type stirring blade, and a thermocouple attached to the outside of the flask. In this polymerization tank, 1207.3 g (8.74 mol) of 4-hydroxybenzoic acid, 608.4 g (3.23 mol) of 6-hydroxy-2-naphthoic acid, and 1345 g (13.2 mol) of acetic anhydride were added. The flask was heated to 150 ° C. with a mantle heater under a nitrogen stream, and subjected to acetylation under reflux for about 3 hours while stirring at 200 rpm. Subsequent to the acetylation reaction, the temperature was raised at 1 ° C./min and maintained at 310 ° C. to perform melt polycondensation. During this time, acetic acid by-produced by the polycondensation reaction was continuously distilled off. Sampling was performed 30 minutes after reaching 310 ° C. during the polymerization, and the flow temperature was measured to be 230 ° C. After 35 minutes, stirring was stopped and the polymer could be easily taken out in a molten state. There was almost no adhesion to the polymerization tank and the stirring blade. The obtained polyester solidified after a while. The yield was 1565 g (97.8% based on the theoretical yield).
The obtained polyester was made into a size of about 3 to 5 cm square, pulverized to an average particle size of 1 mm or less using a pulverizer, and then measured for flow temperature (FT), which was 239 ° C. This polymer (prepolymer) exhibited optical anisotropy when melted.
[0052]
(2) Solid phase polymerization
This prepolymer is placed in an aluminum tray, charged in a nitrogen atmosphere furnace, heated in a nitrogen atmosphere from room temperature to 180 ° C. over 3 hours, held at the same temperature for 2 hours, and then about 7.5 hours. The temperature was raised to 270 ° C., held at the same temperature for 5 hours, allowed to cool, and then taken out to obtain an aromatic liquid crystalline polyester (advanced polymer) powder having an FT of 287 ° C. The weight loss here was 1.5%.
[0053]
(3) Granulation
The obtained advanced polymer is melted and kneaded with a PCM-30 twin-screw extruder manufactured by Ikegai Machine Sales Co., Ltd. with a die head temperature of 300 ° C. and a screw rotation speed of 80 rpm, and an FT of 264 ° C. is aromatic. Liquid crystalline polyester pellets were obtained. The melt tension of this resin pellet at 295 ° C. (FT + 31 ° C.) was 7.7 g, and the logarithmic viscosity (ηinh) measured at 60 ° C. was 5.5 dl / g. The melt viscosity is shown in Table 1.
[0054]
Example 2
(This corresponds to (A) / (B) = 73/27 (mol%) in the repeating structural unit.)
(1) Melt polymerization
In the same manner as in Example 1 (1), 1207.3 g (8.74 mol) of 4-hydroxybenzoic acid, 608.4 g (3.23 mol) of 6-hydroxy-2-naphthoic acid, and 1345 g of acetic anhydride (13 .2 mol) was charged and acetylated (150 ° C., about 3 hours under reflux), then heated at 1 ° C./min and maintained at 310 ° C., and melt polymerization was performed while acetic acid produced as a by-product was continuously distilled off. . Stirring was stopped 15 minutes after reaching 310 ° C., and the polymer was easily taken out in a molten state. There was almost no adhesion to the polymerization tank and the stirring blade. The obtained polyester solidified after a while. The yield was 1570 g (98.1% based on the theoretical yield). The obtained polyester was made into a size of about 3 to 5 cm square, pulverized to an average particle diameter of 1 mm or less using a pulverizer, and then measured for flow temperature (FT), which was 210 ° C. This polymer (prepolymer) exhibited optical anisotropy when melted.
[0055]
(2) Solid phase polymerization
A solid phase polymerization treatment was performed under the same conditions as in Example 1 (2), the mixture was allowed to cool, and then taken out to obtain an aromatic liquid crystalline polyester (advanced polymer) powder having an FT of 288 ° C. The weight loss here was 3.3%.
[0056]
(3) Granulation
Using the same apparatus as in Example 1 (3), the die head temperature was set to 300 ° C., melt kneading was performed at a screw rotation speed of 80 rpm, and aromatic liquid crystalline polyester pellets having an FT of 265 ° C. were obtained. The melt tension of this resin pellet at 305 ° C. (FT + 40 ° C.) was 9.1 g, and the logarithmic viscosity (ηinh) measured at 60 ° C. was 5.6 dl / g. The melt viscosity is shown in Table 1.
[0057]
Example 3
(This corresponds to (A) / (B) = 73/27 (mol%) in the repeating structural unit.)
(1) Melt polymerization
In the same manner as in Example 1 (1), 1207.3 g (8.74 mol) of 4-hydroxybenzoic acid, 608.4 g (3.23 mol) of 6-hydroxy-2-naphthoic acid, and 1345 g of acetic anhydride (13 2 mol), acetylation (150 ° C., about 3 hours under reflux), heated at 1 ° C./min and held at 310 ° C., while acetic acid generated as a by-product was continuously distilled off, went. Sampling was conducted 60 minutes after reaching 310 ° C., and the flow temperature was measured. After 90 minutes, stirring was stopped and the polymer could be easily taken out in a molten state. There was almost no adhesion to the polymerization tank and the stirring blade. The obtained polyester solidified after a while. The yield was 1573 g (98.3% based on the theoretical yield).
The same operation was repeated 7 times, and the obtained polyester was made into a size of about 3 to 5 cm square, then pulverized to an average particle diameter of 1 mm or less using a pulverizer, and then the flow temperature (FT) was measured. It was 248 ° C. This polymer (prepolymer) exhibited optical anisotropy when melted.
[0058]
(2) Solid phase polymerization
This prepolymer was put in an aluminum tray, and the solid-state polymerization conditions were: “Raise the temperature from room temperature to 180 ° C. in 3 hours, hold it at the same temperature for 2 hours, and then raise the temperature to 280 ° C. over about 8.3 hours. In the same manner as in Example 1 (2), except that it was changed to “keep at the same temperature for 5 hours”, solid-state polymerization was carried out, the mixture was allowed to cool, and then taken out. An FT of 357 ° C. aromatic liquid crystalline polyester (advanced polymer) A powder was obtained. The weight loss here was 1.2%.
[0059]
(3) Granulation
The obtained advanced polymer was used in the same apparatus as in Example 1 (3), the die head temperature was set to 340 ° C., melt kneading was performed at a screw rotation speed of 100 rpm, and an aromatic liquid crystalline polyester pellet having an FT of 277 ° C. Got. The melt tension of this resin pellet at 307 ° C. (FT + 30 ° C.) was 22.7 g, and the logarithmic viscosity (ηinh) measured at 60 ° C. was 11.1 dl / g. The melt viscosity is shown in Table 1.
[0060]
(4) Inflation film formation
The obtained aromatic liquid crystalline polyester pellets were installed in a Laboplast mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a 30 mmφ twin screw extruder, an inflation die of 25 mmφ and a die gap of 0.75 mm attached to the head, and a cylinder set temperature 230 The film was formed at ˜255 ° C., a cylinder screw rotation speed of 80, a die head set temperature of 255 ° C., and a take-off speed of 30 m / min to obtain a film having a folding width of 120 mm.
The bubble was stable, the film thickness was 4-9 μm, and the film appearance was relatively good. The die head set temperature capable of forming a film at a take-up speed of 10 m / min or more was 255 to 285 ° C.
[0061]
Example 4
(This corresponds to (A) / (B) = 30/70 (mol%) in the repeating structural unit.)
(1) Melt polymerization
In the same manner as in Example 1 (1), 428.8 g (3.10 mol) of 4-hydroxybenzoic acid, 1359.7 g (7.20 mol) of 6-hydroxy-2-naphthoic acid and 1159.7 g of acetic anhydride ( 11.4 mol), acetylation (150 ° C., about 3 hours under reflux), heated at 1 ° C./min and held at 320 ° C., while acetic acid generated as a by-product was continuously distilled off while melt polymerization Went. Stirring was stopped 45 minutes after maintaining at 320 ° C., and the polymer was easily taken out in a molten state. The polymer had an FT of 247 ° C. and exhibited optical anisotropy when melted. The yield of the obtained polyester was 1557 g (97.2% based on the theoretical yield).
[0062]
Solid state polymerization
This prepolymer was put in an aluminum tray, and the solid-state polymerization conditions were changed to “temperature rising from room temperature to 208 ° C. over 3 hours, then heating up to 260 ° C. over 8 hours and 40 minutes and holding for 5 hours”. Was solid-phase polymerized in the same manner as in Example 1 (2) to obtain an aromatic liquid crystalline polyester (advanced polymer) having a powder FT of 281 ° C. The weight loss here was 1.0%.
[0063]
(3) Granulation
The obtained advanced polymer was used in the same apparatus as in Example 1 (3), the die head temperature was set to 310 ° C., melt kneading was performed at a screw rotation speed of 150 rpm, and an FT of 260 ° C. aromatic liquid crystal Polyester pellets were obtained. The melt tension of this resin pellet at 290 ° C. (FT + 30 ° C.) was 4.7 g, and the logarithmic viscosity (ηinh) measured at 60 ° C. was 4.4 dl / g.
The melt viscosity is shown in Table 1.
[0064]
Example 5
(This corresponds to (A) / (B) = 60/40 (mol%) in the repeating structural unit.)
(1) Melt polymerization
In the same manner as in Example 4 (1), 947.0 g (6.9 mol) of 4-hydroxybenzoic acid, 860.3 g (4.6 mol) of 6-hydroxy-2-naphthoic acid and 1283.7 g of acetic anhydride ( 12.6 mol), acetylation (150 ° C., about 3 hours under reflux), heated at 1 ° C./min and held at 320 ° C., while acetic acid generated as a by-product was continuously distilled off while melt polymerization Went. Stirring was stopped 45 minutes after maintaining at 320 ° C., and the polymer was easily taken out in a molten state. The polymer had an FT of 216 ° C. and exhibited optical anisotropy when melted. The yield of the obtained polyester was 1563 g (97.7% based on the theoretical yield).
[0065]
(2) Solid phase polymerization
This prepolymer was put in an aluminum tray, and the solid-state polymerization conditions were changed to "Raise the temperature from room temperature to 190 ° C in 3 hours, further raise the temperature to 240 ° C over 8 hours and 20 minutes and hold for 5 hours" Was solid-phase polymerized in the same manner as in Example 1 (2) to obtain an aromatic liquid crystalline polyester (advanced polymer) having a powder FT of 240 ° C. The weight loss here was 0.9%.
[0066]
(3) Granulation
The obtained advanced polymer was used in the same apparatus as in Example 1 (3), the die head temperature was set at 280 ° C., melt kneading was performed at a screw rotation speed of 150 rpm, and an FT of 230 ° C. aromatic liquid crystal Polyester pellets were obtained. The melt tension of this resin pellet at 260 ° C. (FT + 30 ° C.) was 3.0 g, and the logarithmic viscosity (ηinh) measured at 60 ° C. was 4.9 dl / g.
The melt viscosity is shown in Table 1.
[0067]
Comparative Example 1
(1) Vacuum polymerization
In the same manner as in Example 1, 1208.9 g (8.76 mol) 6-hydroxy-4-hydroxybenzoic acid corresponding to (A) / (B) molar ratio = 73/27 (mol%) in the repeating structural unit. 2-Naphthoic acid 609.1 g (3.24 mol) and acetic anhydride 1346.4 g (13.21 mol) were charged into a polymerization vessel equipped with a comb-shaped stirring blade, and the temperature was raised to 150 ° C. while stirring in a nitrogen gas atmosphere. The mixture was warmed and subjected to acetylation reaction under reflux for about 3 hours. Subsequent to the acetylation reaction, while acetic acid produced as a by-product was continuously distilled off, the temperature was raised at 1 ° C./min, and the polymerization tank external temperature was maintained at 330 ° C. to perform melt polycondensation. Thereafter, while maintaining the temperature outside the polymerization tank at 330 ° C., the pressure was reduced to the final pressure over 40 minutes. After maintaining at 2 torr for 5 minutes, the stirring was stopped and the polymer was taken out.
Adhesion of the polymer to the polymerization tank and the stirring blade was observed. The yield was 1551 g (97.1% based on the theoretical yield). Although the obtained polyester was pulverized using a pulverizer, the pulverization rate was slower than that of Example 1 because fiberization was performed. About what passed the filter with an average particle diameter of 3 mm or less, it was 261 degreeC when the flow temperature (FT) was measured.
[0068]
(2) Granulation
Similarly to Example 1 (3), the obtained polymer was melt-kneaded at a die head temperature of 260 ° C. and a screw rotation speed of 80 rpm to obtain aromatic liquid crystalline polyester pellets having an FT of 263 ° C. It was. The melt tension of this resin pellet at 305 ° C. (FT + 42 ° C.) was 2.8 g, and the logarithmic viscosity (ηinh) measured at 60 ° C. was 5.5 dl / g. The melt viscosity is shown in Table 1.
[0069]
[Table 1]

[0070]
【The invention's effect】
The method for producing an aromatic liquid crystalline polyester of the present invention can obtain a high molecular weight liquid crystalline polyester more stably than a known production method in which polycondensation is performed under reduced pressure after polymerization. The aromatic liquid crystalline polyester obtained by this production method has a low temperature dependency of melt viscosity and tends to have a wide processing temperature range. With the same composition, it becomes possible to increase the melt tension by increasing the molecular weight, and film forming processing is possible. It is possible to produce a material having a melt tension suitable for the above. The film made of the wholly aromatic liquid crystalline polyester is a film having sufficient heat resistance for packaging materials, low-temperature processability, excellent gas barrier properties, good film appearance, food packaging, chemicals It can be used as a resin material for films for various packaging applications such as packaging, cosmetic packaging and electronic material packaging, a resin material for blows for various container applications, and an injection molding material.

Claims (6)

Only the compound represented by the following formula (I) and the compound represented by the following formula (II) are used as raw material monomers, and the compound represented by the following formula (I) is represented by 80 to 20 mol%, represented by the following formula (II). The compound was charged into the reaction vessel at a rate of 20 to 80 mol%, and subjected to a polycondensation reaction at 270 to 350 ° C. without reducing the pressure in the reaction vessel. When the temperature reaches 30 ° C. or more lower than the polycondensation reaction temperature, the aromatic liquid crystalline polyester as the contents of the reaction vessel is recovered in a molten state and solidified, and then particles having a particle size of 3 mm or less And a heat treatment at 200 ° C. to 310 ° C. in an inert gas atmosphere in a solid phase state.

(However, R ¹ represents a hydrogen atom, a formyl group, an acetyl group, a propionyl group, or a benzoyl group, and R ² represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, a benzyl group, or a phenyl group.)

(However, the definitions of R ¹ and R ² are the same as those in formula (I). R ¹ in formula (I) and formula (II) may be the same as or different from each other, and formula (I And R ² in formula (II) may be the same or different.
Here, the flow temperature is a resin measured by a capillary rheometer and heated and melted at a heating rate of 4 ° C./min from a nozzle having an inner diameter of 1 mm and a length of 10 mm under a load of 100 kgf / cm ^2. when extruded, molten viscosity refers to a temperature (℃) showing a 48,000 poise. The aromatic liquid crystalline polyester obtained by the heat treatment, the production method of the aromatic liquid crystalline polyester according to claim 1, wherein the heat-melting to be characterized by granulation to Rukoto. As the compound represented by formula (I), 4-hydroxybenzoic acid, a compound represented by Formula (II), using 6-hydroxy-2-naphthoic acid, an equivalent amount or more of acetic anhydride phenolic hydroxyl groups that they have after acetylation, aromatic method for producing a liquid crystalline polyester according to claim 1 or 2 which comprises carrying out the polycondensation reaction. Glass-lined reaction when acetylating with acetic anhydride using 4-hydroxybenzoic acid as the compound represented by formula (I) and 6-hydroxy-2-naphthoic acid as the compound represented by formula (II) The method for producing an aromatic liquid crystalline polyester according to claim 1 or 2, wherein a polycondensation reaction is carried out after reacting using a tank (acetylation tank) and transferring to a polymerization tank. It is manufactured by the method in any one of Claims 1-4, The following repeating unit (A) is 75-25 mol% of the whole repeating unit, The following repeating unit (B) is 25-25 of the whole repeating unit. It contains 75 mol%, has a logarithmic viscosity of 4.0 dl / g or more, a flow temperature of 320 ° C. or less, and a melt tension measured at a temperature 25 ° C. or more higher than the flow temperature of 3.0 g or more. Aromatic liquid crystalline polyester.

It is produced by the method according to any one of claims 1 to 4, for the melt viscosity (viscosity 1) measured at a shear rate of 100 sec ^-1 or of 1,000 sec ^-1 at the flow dynamic temperature at 20 ° C. higher temperature than the flow temperature An aromatic liquid crystalline polyester having a ratio (viscosity 2 / viscosity 1) of melt viscosity (viscosity 2 ) measured at the same shear rate as that of viscosity 1 is 0.20 to 0.80.