JP4158855B2 - Method for producing high-purity biphenyltetracarboxylic dianhydride - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、高純度ビフェニルテトラカルボン酸二無水物（以下ＢＰＤＡと言う。）の製造法に関する。詳しくは、不溶性微粒体含有量のきわめて少ない高純度ＢＰＤＡの製造法に関する。
【０００２】
【従来の技術】
ＢＰＤＡは、耐熱性樹脂として注目されている芳香族ポリイミドの製造用原料として、有用な化合物である。ＢＰＤＡを用いた芳香族ポリイミドは、ＢＰＤＡと芳香族ジアミンとの重合反応によって製造する方法、ＢＰＤＡと芳香族ジアミンの常温付近の低温での重合によって得られるポリアミック酸を閉環イミド化する方法、のいずれかによって製造することができる。
【０００３】
ＢＰＤＡを用いた芳香族ポリイミドは、電子材料分野において使用される用途が大きい。近年、電子材料製品の機能高度化に伴い、これにフィルムやワニスとして使用される芳香族ポリイミドにも同様に高性能が要求されるようになった。特に、芳香族ポリイミドの特徴である耐熱性、絶縁性、ガスバリヤー性などに関しても、より高性能化を目指して種々の改良検討が行なわれている。例えば、ＢＰＤＡを用いた芳香族ポリイミドの代表的な用途として、ガス分離膜、フレキシブルプリント基板などがあるが、これらの用途分野においても、膜機能の高度化、基板の高機能化に伴う検討課題として、膜、成形品の欠陥改良の要求が強くなってきた。
【０００４】
従来から、有機化合物はその用途によっては、不溶性微粒体の含有を極端に嫌う場合がある。例えば、芳香族ポリイミドの原料となるＢＰＤＡに、これらの製造過程、その他の原因で不溶性微粒体が混入していると、当然ながらそのまま、製品ポリマーに残ることとなる。不溶性微粒体としては、(a) 製造過程で混入するもの、および、(b) 有機化合物製造後にこれを取り扱う過程で混入するものがある。上記(a) の具体例には、触媒、触媒の担体に由来するもの、金属粉、パッキング粉などの製造機器に由来するものなどがあり、上記(b) の具体例には、製品を取り扱う雰囲気中に浮遊している粉塵などの微粉末がある。
【０００５】
本発明者らは、芳香族ポリイミドの特定の特性と、粒径が特定の範囲にある不溶性微粒体含有量との間に、理由は不明であるが、何等かの相関があることを見出した。即ち、この粒径範囲の不溶性微粒体の含有量を一定レベル以下にすると、上述の芳香族ポリイミドの特定の特性を大幅に向上させることができる。例えば粒子の大きさが５〜３０μｍの範囲の不溶性微粒体含有量が、１ｇ当たり１×１０4 個以上混入していると、種々の欠陥が発生する。芳香族ポリイミドの用途が、繊維向けである場合には、紡糸の際に糸切れの原因になり、また、用途がフィルムの場合には、フィッシュアイ、ピンホールなどの原因になり、さらに、用途がワニスの場合には塗膜にフィッシュアイが発生し、用途がガス分離膜の場合には分離特性が低下する。これらは、いずれも製品価値を著しく低下させる欠点である。
【０００６】
これら不溶性微粒体に由来する欠点を排除するために、一般に、芳香族ポリイミドを製造する工程中に、フィルターを設置して不溶性微粒体を除去する方法がとられる。このフィルターの寿命は、フィルターの材質、使用条件などにもよるが、多くの場合に被処理液中の不溶性微粒体含有量に支配される。不溶性微粒体の含有量が多いと、寿命は短命となり、生産性や歩留りが低下する、高価なフィルターの頻繁な交換が必要である、などにより製造コストの上昇は免れない。従って芳香族ポリイミドの製造に用いる原料は、不溶性微粒体の含有量の少ないものであることが強く望まれている。
【０００７】
ＢＰＤＡは、ビフェニルテトラカルボン酸（以下ＢＴＣと言う。）を１５０〜２５０℃の温度範囲に加熱し、脱水閉環反応させることによって得ることができるが、この工程のみでは、純度、不純物、着色などの観点から、満足できる製品は得られない。そこで、ＢＴＣを加熱して脱水閉環させることによって得られる粗ＢＰＤＡを、減圧下、２５０〜４００℃の温度に加熱して揮発させ、次いで、この揮発したＢＰＤＡの蒸気を冷却し、精製結晶として回収する方法が提案されている（特許文献１参照）。
しかしながら、この方法では、芳香族ポリイミド製造用原料に要求される水準にまで不溶性微粒体含有量を低下させることができないことがあり、不溶性微粒体含有量の極めて少ない高純度ＢＰＤＡを安定して製造する方法の開発が望まれていた。
【０００８】
【特許文献１】
特開平４−３７０７８号公報
【０００９】
【発明が解決しようとする課題】
本発明者らは、上記現状に鑑み、ポリイミドの製造に好適な不溶性微粒体含有量の少ない高純度ＢＰＤＡの工業的有利な製造法を提供すべく鋭意検討の結果、芳香族ポリイミドの特定の特性と、大きさが５〜３０μｍの不溶性微粒体の含有量との間に、理由は不明であるが、何等かの相関があること、及び前述の揮発−冷却方法によりＢＰＤＡを精製結晶として回収するに際して、この大きさの不溶性微粒体の含有量を芳香族ポリイミド製造用原料に要求される水準まで低下させるには、粗ＢＰＤＡの原料であるＢＴＣに不溶性微粒体含有量の少ないものを用いることが必要であることを見出し、本発明を完成した。
【００１０】
【課題を解決するための手段】
本発明によれば、不溶性微粒体を含有するビフェニルテトラカルボン酸を脱水閉環反応させてビフェニルテトラカルボン酸二無水物とし、次いでこれを、減圧下、加熱して揮発させ、揮発分を冷却して精製結晶として回収する方法において、大きさが５〜３０μｍの不溶性微粒体の含有量が１ｇ当り７×１０4 個以下のビフェニルテトラカルボン酸を脱水閉環反応に供することによって、大きさが５〜３０μｍの不溶性微粒体の含有量が１ｇ当り２×１０3個以下の高純度ビフェニルテトラカルボン酸二無水物を製造することができる。
【００１１】
以下、本発明を詳細に説明する。
本発明において、対象とする不溶性微粒体は、大きさが５〜３０μｍの範囲のものである。これらの大きさ、個数などは、粒径画像処理装置、例えば三菱化学（株）製のＧＸ−１０などの微粒子を拡大・計数することができる装置によって、容易に確認、計数することができる。精製ＢＰＤＡ中のこの大きさの不溶性微粒体は、原料のＢＴＣに由来するものの他に、製造過程や製造後の製品の取扱い過程で混入したものである。本発明者らの知見によれば製造過程や製品の取扱いに細心の注意を払っても、なおかつ精製ＢＰＤＡ中には相当量の不溶性微粒体が含有されているので、これを減少させるには原料のＢＴＣとして不溶性微粒体の含有量の少ないものを用いることが必要である。
【００１２】
ＢＴＣは、通常は、ｏ−フタル酸ジメチルの脱水二量化反応で得られたビフェニルテトラカルボン酸テトラメチルを、酸触媒の存在下、水性媒体中で加水分解して得られる。また、無水フタル酸をハロゲン化して得られる４−ハロフタル酸を、水性媒体中で、アルカリ・還元剤・Pd触媒の存在下、脱ハロゲン二量化反応させ、ビフェニルテトラカルボン酸テトラアルカリ金属塩を得、これを鉱酸で中和することによっても得ることができる。このようにして得られたＢＴＣは、実質上全て３，４，３´，４´−異性体である。
【００１３】
本発明ではこれらのいずれの方法で得られたＢＴＣも脱水閉環反応に用いることができるが、ＢＴＣは大きさが、５〜３０μｍの不溶性微粒体の含有量が１ｇ当り７×１０4 個以下でなければならない。通常は不溶性微粒体の含有量が１ｇ当り５×１０3 ないし７×１０4 個であるＢＴＣを脱水閉環反応に用いる。そのためには、ＢＴＣの製造に用いる液体原料、溶媒は、フィルターを通し、不溶性微粒体を除去する必要がある。また、固形の触媒などを除去した反応液も同様にフィルターを通し、最終的に得られる不溶性微粒体の含有量が１ｇ当り７×１０4 個以下になるように、調整しなければならない。この際使用されるフィルターは、条件によっても異なるが、例えば孔径１μｍフィルターを、１段または複数段直列に組合せて用いる。
【００１４】
このＢＴＣを、常圧または減圧下、例えば１０2 〜１０5 Ｐａの範囲で、１５０〜２５０℃の温度に加熱して脱水閉環させ、粗ＢＰＤＡとする。この場合、原料のＢＴＣは、水湿潤状態のものも使用でき、その際には、昇温途中で付着水が、さらには結晶水も蒸発によって除かれ、続いて、脱水閉環反応が起こる。これら一連の反応は、付着水、結晶水および脱水閉環反応によって生成する水を、反応系外にパージしながら行なうと、反応速度が向上するので、常圧で不活性ガスを通しながら、または、減圧下で行なうのが好ましい。
脱水閉環反応に要する時間は、加熱速度、加熱温度、減圧度および付着水の有無などによって異なるが、通常、０．５〜１０時間の範囲で選ぶことができる。
【００１５】
また別法として、ＢＴＣを例えば２〜１０重量倍の無水酢酸やデカリンなどの液状媒体中で１００℃ないし液状媒体の沸点の温度範囲に加熱して脱水閉環反応させて粗ＢＰＤＡとすることもできる。
粗ＢＰＤＡの揮発操作は、減圧下で、加熱しつつ行うのが好ましい。加熱温度が低すぎるとＢＰＤＡを効率よく揮発させることができず、高すぎるとＢＰＤＡが熱分解するので、いずれも好ましくない。本発明者らの実験によれば、４０００Pa以下の減圧下、好ましくは２７００Pa以下の減圧下、３００〜４００℃、好ましくは３００〜３５０℃の温度とするのがよいことが分かった。
【００１６】
不溶性微粒体含有量の多い粗ＢＰＤＡを揮発精製する場合には、大半の不溶性微粒体が蒸留釜に残渣として残るので、回分式で操作を行なう場合には、揮発精製操作を繰り返すに従い、被揮発精製物中の不溶性微粒体が増加する。従って、不溶性微粒体含有量の多い粗ＢＰＤＡを用いた場合には、蒸留釜の残渣を頻繁に抜き出す必要があり、生産性、歩留りが極端に低下する。しかし本発明方法のように不溶性微粒体含有量が１ｇ当り７×１０4個以下のＢＴＣを脱水閉環して得た粗ＢＰＤＡは不溶性微粒体含有量が少ないので、回分式で揮発精製操作を行なう場合にも、蒸留釜の残渣を頻繁に抜き出す必要がなく、生産性、歩留りが共に向上する。
粗ＢＰＤＡを揮発させる場合の速度が大きいと、不溶性微粒体が揮発する蒸気に同伴されて揮発精製した製品に混入するので、適切な揮発速度を選ぶべきである。
【００１７】
揮発したＢＰＤＡの冷却温度は、通常、２００℃以下、好ましくは１００℃以下である。この冷却方法は、種々の方法によることができるが、通常、揮発操作を行う容器、例えば、蒸発釜などの容器の気相部に直結するガス管先端に配置したドラム式回転冷却器により行うのが好ましい。ドラム式回転冷却器に付着したＢＰＤＡは、適当なかきとり装置によって、連続的に容易にかきとられ、フレークとして回収される。
【００１８】
このようにして得られたＢＰＤＡは、５〜３０μｍの大きさの不溶性微粒子の含有量が１ｇ当り２×１０3 個以下の高純度であり、芳香族ポリイミド製造用原料として好適であり、耐熱性、絶縁性、ガスバリヤー性などに優れた芳香族ポリイミドを得ることができる。
そして、上記の高純度ＢＰＤＡを原料とした芳香族ポリイミドから製造したガス分離膜は、膜欠陥が極めて少なく、従来品に較べ格段に優れた分離特性を発揮する。更に、好ましくは、不溶性微粒子の含有量が１ｇ当り１×１０2 個以下のＢＰＤＡと芳香族ジアミンとの反応によって得られるフィルムは、ガスバリヤー性が著しく向上する。これに対して、不溶性微粒子の含有量が１ｇ当り２×１０4 個のＢＰＤＡと芳香族ジアミンとの反応によって得られるフィルムは、絶縁性に乏しくフレキシブルプリント基板として使用することができなかった。
【００１９】
【実施例】
次に、本発明を実施例により詳細に説明するが、本発明はその趣旨を超えない限り、以下の記載例に限定されるものではない。
なお、以下の例において、溶媒の準備、サンプルの調整、不溶性微粒体の計数は、次の手順によった。
＜溶媒の準備＞
クラス１００のクリンベンチ内で、試薬グレードのＮ−メチルピロリドンを、目の粗さが０．２μｍのフィルターを通し、大きさが０．２μｍ以上の不溶性微粒体を除去した。
【００２０】
＜サンプルの調整＞
まず、クラス１００のクリンベンチ内で、サンプル約１ｇを洗浄・乾燥済のガラス瓶に精秤し、これに上記Ｎ−メチルピロリドン２００ｍｌ加えたのち、この混合物を超音波洗浄器に入れ、約３時間にわたり洗浄器を作動させ、サンプルを溶解させた。次いで、この溶液を目の粗さが０．４μｍのフィルターを通し、不溶性微粒体を濾別した。
＜不溶性微粒体の計数＞
クラス１０００のクリンルーム内で、粒径画像処理装置｛三菱化学（株）製、ＧＸ−１０｝を用いて、フィルター上の不溶性微粒体の数を測定した。測定した不溶性微粒体の数をサンプル重量で補正し、サンプル１．０ｇ当りの個数に換算した。
【００２１】
［実施例１］
攪拌機、ジャケット、コンデンサー、温度計、不活性ガス供給口を備えた縦型筒状反応器に、大きさが５〜３０μｍの不溶性微粒体を１ｇ当り２×１０4 個含むＢＴＣ１００重量部を仕込んだ。反応器内容物を攪拌しながら、常圧下、２１５℃に加熱し、２ｍ3 ／時の速度で窒素ガスを通し、生成する水をパージしつつ、脱水閉環反応を１０時間継続し、粗ＢＰＤＡを得た。続いて、３００℃に昇温し、この温度で５時間保持し、粗ＢＰＤＡを溶融させた。
【００２２】
粗ＢＰＤＡの溶融液を、ジャケットを備えた縦型筒状蒸発釜に移送し、３０５℃、２３０Ｐａの条件下で、蒸発（揮発）させた。蒸発したＢＰＤＡは、蒸発釜の気相部に直結するガス配管先端に配したドラム式回転冷却器表面に接触させ、冷却析出させた。ドラム表面に付着したＢＰＤＡの結晶は、かきとり装置によって連続的にかきとり、フレークとして回収した。このフレークを粉砕後、精製ＢＰＤＡ８０重量部が得られた。
この精製ＢＰＤＡ中の大きさが５〜３０μｍの不溶性微粒体を計数したところ、１ｇあたり４００個であり、原料のＢＴＣ中の不溶性微粒体のものに較べて大幅に少なくなっていた。
【００２３】
［実施例２］
実施例１において、原料のＢＴＣを、大きさが５〜３０μｍの不溶性微粒体を１ｇ当り５×１０4 個含むＢＴＣに代えた他は、実施例１におけると同様の手順でＢＴＣの脱水閉環及び得られた粗ＢＰＤＡの揮発−冷却を行った。
得られたＢＰＤＡ中の大きさが５〜３０μｍの不溶性微粒体は、１ｇ当り１０００個であり、原料のＢＴＣ中の不溶性微粒体に較べて大幅に少なくなっていた。
【００２４】
［比較例１］
実施例１において、原料のＢＴＣを、大きさが５〜３０μｍの不溶性微粒体を１ｇ当り１．５×１０5 個含むＢＴＣに代えた他は、実施例１におけると同様の手順でＢＴＣの脱水閉環及び得られた粗ＢＰＤＡの揮発−冷却を行った。
得られたＢＰＤＡ中の大きさが５〜３０μｍの不溶性微粒体は、１ｇ当り３５００個であり、目標値の１ｇ当り２×１０3 個を越えていた。
【００２５】
【発明の効果】
本発明は、次のような特別に有利な効果を奏し、その産業上の利用価値は、極めて大である。
１．本発明方法で得られる大きさが５〜３０μｍの不溶性微粒体の含有量が１ｇ当り２×１０3 個以下の高純度のＢＰＤＡは、これを芳香族ジアミンと反応させてポリイミドを製造した際、耐熱性、絶縁性、ガスバリヤー性などに優れ、ガス分離膜に加工した場合には、膜欠陥の少ない製品が得られる。
２．本発明方法によれば、粗ＢＰＤＡの揮発−冷却を回分式で行なう場合にも、蒸留釜の残渣を頻繁に抜き出す必要がなく、生産性、歩留りが大幅に向上する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing high-purity biphenyltetracarboxylic dianhydride (hereinafter referred to as BPDA). Specifically, the present invention relates to a method for producing high-purity BPDA with a very low content of insoluble fine particles.
[0002]
[Prior art]
BPDA is a useful compound as a raw material for producing an aromatic polyimide, which is attracting attention as a heat resistant resin. Aromatic polyimide using BPDA is either a method of producing by a polymerization reaction of BPDA and aromatic diamine, or a method of ring-closing imidization of polyamic acid obtained by polymerization of BPDA and aromatic diamine at a low temperature near room temperature. Can be manufactured.
[0003]
Aromatic polyimide using BPDA has a large application in the field of electronic materials. In recent years, with the advancement of functions of electronic material products, high performance has been required for aromatic polyimides used as films and varnishes as well. In particular, various improvements have been studied for higher performance with respect to heat resistance, insulation, gas barrier properties, and the like, which are characteristics of aromatic polyimide. For example, typical applications of aromatic polyimides using BPDA include gas separation membranes and flexible printed circuit boards. In these fields of application, however, there are issues to be addressed as membrane functions become more sophisticated and substrates become more functional. As a result, there is an increasing demand for improving defects in films and molded products.
[0004]
Conventionally, depending on the use of an organic compound, the inclusion of insoluble fine particles may be extremely disliked. For example, if insoluble fine particles are mixed in BPDA, which is a raw material for aromatic polyimide, due to these production processes and other reasons, it naturally remains in the product polymer as it is. As the insoluble fine particles, there are (a) those mixed in the production process, and (b) those mixed in the process of handling the organic compound after production. Specific examples of (a) above include catalysts, those derived from catalyst carriers, those derived from manufacturing equipment such as metal powder and packing powder, etc., and examples of (b) above deal with products. There is fine powder such as dust floating in the atmosphere.
[0005]
The present inventors have found that there is some correlation between the specific characteristics of the aromatic polyimide and the content of insoluble fine particles having a particle size in a specific range for unknown reasons. . That is, when the content of the insoluble fine particles in this particle size range is set to a certain level or less, the specific characteristics of the above-mentioned aromatic polyimide can be greatly improved. For example, if the content of insoluble fine particles having a particle size in the range of 5 to 30 μm is mixed at 1 × 10 4 or more per 1 g, various defects occur. If the use of aromatic polyimide is for fibers, it may cause thread breakage during spinning, and if the application is film, it may cause fish eyes, pinholes, etc. When varnish is used, fish eyes are generated in the coating film, and when the application is a gas separation membrane, the separation characteristics are deteriorated. These are all disadvantages that significantly reduce the product value.
[0006]
In order to eliminate the disadvantages derived from these insoluble fine particles, generally, a method of removing the insoluble fine particles by installing a filter during the process of producing the aromatic polyimide is taken. The life of this filter depends on the material of the filter, the use conditions, etc., but is often governed by the content of insoluble fine particles in the liquid to be treated. When the content of the insoluble fine particles is large, the lifetime is short, the productivity and the yield are lowered, and the expensive filter needs to be frequently replaced. Therefore, it is strongly desired that the raw material used for the production of the aromatic polyimide has a low content of insoluble fine particles.
[0007]
BPDA can be obtained by heating biphenyltetracarboxylic acid (hereinafter referred to as BTC) to a temperature range of 150 to 250 ° C. and subjecting it to a dehydration ring-closing reaction, but only in this step, purity, impurities, coloring, etc. From the point of view, a satisfactory product cannot be obtained. Therefore, the crude BPDA obtained by heating and dehydrating and ring-closing BTC is volatilized by heating to a temperature of 250 to 400 ° C. under reduced pressure, and then the vapor of the volatilized BPDA is cooled and recovered as purified crystals. Has been proposed (see Patent Document 1).
However, this method may not be able to reduce the insoluble fine particle content to the level required for the raw material for producing aromatic polyimide, and can stably produce high-purity BPDA with extremely low insoluble fine particle content. Development of a method to do this has been desired.
[0008]
[Patent Document 1]
JP-A-4-37078
[Problems to be solved by the invention]
In view of the above situation, the present inventors have intensively studied to provide an industrially advantageous production method of high-purity BPDA with a low content of insoluble fine particles suitable for the production of polyimide. And the content of insoluble fine particles having a size of 5 to 30 μm, the reason is unknown, but there is some correlation, and BPDA is recovered as purified crystals by the above-mentioned volatilization-cooling method. At this time, in order to reduce the content of insoluble fine particles of this size to the level required for the raw material for producing aromatic polyimide, it is necessary to use BTC, which is a raw material for crude BPDA, having a low content of insoluble fine particles. As a result, the present invention was completed.
[0010]
[Means for Solving the Problems]
According to the present invention, biphenyltetracarboxylic acid containing insoluble fine particles is subjected to dehydration ring-closing reaction to form biphenyltetracarboxylic dianhydride, which is then heated to volatilize under reduced pressure, and the volatile matter is cooled. In the method of recovering as purified crystals, the content of insoluble fine particles having a size of 5 to 30 μm is 7 × 10 4 or less per 1 g of biphenyltetracarboxylic acid, and the size is 5 to 30 μm. High-purity biphenyltetracarboxylic dianhydride having an insoluble fine particle content of 2 × 10 3 or less per gram can be produced.
[0011]
Hereinafter, the present invention will be described in detail.
In the present invention, the target insoluble fine particles have a size in the range of 5 to 30 μm. These sizes, numbers, etc. can be easily confirmed and counted by a particle size image processing apparatus, for example, an apparatus capable of enlarging and counting fine particles such as GX-10 manufactured by Mitsubishi Chemical Corporation. The insoluble fine particles of this size in the purified BPDA are mixed in the production process and the handling process of the product after production in addition to those derived from the raw material BTC. According to the knowledge of the present inventors, even if careful attention is paid to the manufacturing process and the handling of the product, and since a considerable amount of insoluble fine particles are contained in the purified BPDA, the raw material is used to reduce this. It is necessary to use a BTC having a low content of insoluble fine particles.
[0012]
BTC is usually obtained by hydrolyzing tetramethyl biphenyltetracarboxylate obtained by dehydration dimerization reaction of dimethyl o-phthalate in an aqueous medium in the presence of an acid catalyst. In addition, 4-halophthalic acid obtained by halogenating phthalic anhydride is subjected to dehalogenation dimerization reaction in an aqueous medium in the presence of an alkali, a reducing agent, and a Pd catalyst to obtain a biphenyltetracarboxylic acid tetraalkali metal salt. This can also be obtained by neutralizing with a mineral acid. The BTCs thus obtained are essentially all 3,4,3 ′, 4′-isomers.
[0013]
In the present invention, BTC obtained by any of these methods can be used for the dehydration ring-closing reaction, but BTC has a size of insoluble fine particles having a size of 5 to 30 μm of 7 × 10 4 or less per 1 g. There must be. Usually, BTC having an insoluble fine particle content of 5 × 10 3 to 7 × 10 4 per gram is used for the dehydration ring-closing reaction. For this purpose, the liquid raw material and solvent used for the production of BTC need to pass through a filter to remove insoluble fine particles. Similarly, the reaction solution from which the solid catalyst has been removed must be passed through a filter and adjusted so that the final content of insoluble fine particles is 7 × 10 4 or less per gram. The filter used at this time varies depending on the conditions, but for example, a filter having a pore diameter of 1 μm is used in combination of one stage or a plurality of stages in series.
[0014]
The BTC is heated to a temperature of 150 to 250 ° C. under normal pressure or reduced pressure, for example, in the range of 10 2 to 10 5 Pa, and dehydrated and closed to obtain crude BPDA. In this case, the raw material BTC can be used in a wet state. In this case, adhering water and further crystal water are removed by evaporation in the course of temperature rising, and then a dehydration ring-closing reaction occurs. These series of reactions are carried out while purging the adhering water, crystal water and water generated by the dehydration ring closure reaction outside the reaction system, so that the reaction rate is improved, so that an inert gas is passed at normal pressure, or It is preferable to carry out under reduced pressure.
The time required for the dehydration ring-closing reaction varies depending on the heating rate, heating temperature, degree of reduced pressure, and the presence or absence of attached water, but can usually be selected in the range of 0.5 to 10 hours.
[0015]
As another method, BTC can be heated to a temperature range of 100 ° C. to the boiling point of the liquid medium in a liquid medium such as 2 to 10 times by weight of acetic anhydride or decalin to obtain a crude BPDA. .
The volatilization operation of the crude BPDA is preferably performed while heating under reduced pressure. If the heating temperature is too low, BPDA cannot be volatilized efficiently, and if it is too high, BPDA is thermally decomposed. According to the experiments by the present inventors, it has been found that the temperature should be set to 300 to 400 ° C., preferably 300 to 350 ° C. under a reduced pressure of 4000 Pa or less, preferably 2700 Pa or less.
[0016]
When crude BPDA with a high content of insoluble fine particles is volatilely purified, most of the insoluble fine particles remain as residues in the distillation kettle. The insoluble fine particles in the purified product increase. Therefore, when crude BPDA with a high content of insoluble fine particles is used, it is necessary to frequently extract the residue of the distillation pot, and the productivity and yield are extremely lowered. However, the crude BPDA obtained by dehydrating and ring-closing BTC having an insoluble fine particle content of 7 × 10 4 or less per gram as in the method of the present invention has a low content of insoluble fine particles, and thus the volatile purification operation is carried out batchwise. Even in this case, it is not necessary to frequently extract the residue of the still, and both productivity and yield are improved.
If the speed at which the crude BPDA is volatilized is large, the insoluble fine particles are entrained in the vapor that volatilizes and are mixed into the volatile purified product, so an appropriate volatilization rate should be selected.
[0017]
The cooling temperature of the volatilized BPDA is usually 200 ° C. or lower, preferably 100 ° C. or lower. This cooling method can be performed by various methods, but is usually performed by a drum-type rotary cooler disposed at the tip of a gas pipe directly connected to a gas phase portion of a container for performing a volatilization operation, for example, an evaporation kettle or the like. Is preferred. The BPDA adhering to the drum type rotary cooler is easily and continuously scraped by a suitable scraper and recovered as flakes.
[0018]
The BPDA thus obtained has a high purity of insoluble fine particles of 5 to 30 μm in size of 2 × 10 3 or less per gram, is suitable as a raw material for producing aromatic polyimide, In addition, an aromatic polyimide having excellent insulation and gas barrier properties can be obtained.
And the gas separation membrane manufactured from the aromatic polyimide which used said high purity BPDA as a raw material has very few membrane defects, and exhibits the separation characteristic outstandingly excellent compared with the conventional product. Further, preferably, a film obtained by the reaction of BPDA having an insoluble fine particle content of 1 × 10 2 or less per gram and an aromatic diamine has a markedly improved gas barrier property. On the other hand, the film obtained by the reaction of 2 × 10 4 BPDA and aromatic diamine with an insoluble fine particle content per gram was poor in insulation and could not be used as a flexible printed board.
[0019]
【Example】
EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not limited to the following description examples, unless the meaning is exceeded.
In the following examples, solvent preparation, sample preparation, and insoluble fine particle counting were performed according to the following procedure.
<Preparation of solvent>
In a class 100 clean bench, reagent-grade N-methylpyrrolidone was passed through a filter having a mesh size of 0.2 μm to remove insoluble particles having a size of 0.2 μm or more.
[0020]
<Sample adjustment>
First, in a class 100 clean bench, about 1 g of a sample is precisely weighed into a cleaned and dried glass bottle, 200 ml of the above N-methylpyrrolidone is added thereto, and the mixture is placed in an ultrasonic cleaner for about 3 hours. The washer was turned on to dissolve the sample. Subsequently, this solution was passed through a filter having a coarseness of 0.4 μm to separate insoluble fine particles.
<Counting insoluble fine particles>
In a Class 1000 clean room, the number of insoluble fine particles on the filter was measured using a particle size image processing apparatus {manufactured by Mitsubishi Chemical Corporation, GX-10}. The number of insoluble fine particles measured was corrected with the sample weight and converted to the number per 1.0 g of the sample.
[0021]
[Example 1]
A vertical cylindrical reactor equipped with a stirrer, jacket, condenser, thermometer, and inert gas supply port was charged with 100 parts by weight of BTC containing 2 × 10 4 insoluble fine particles having a size of 5 to 30 μm per gram. . While stirring the reactor contents, heating to 215 ° C. under normal pressure, passing nitrogen gas at a rate of 2 m 3 / hour, purging the generated water and continuing the dehydration ring closure reaction for 10 hours, Obtained. Subsequently, the temperature was raised to 300 ° C. and held at this temperature for 5 hours to melt the crude BPDA.
[0022]
The melt of crude BPDA was transferred to a vertical cylindrical evaporation kettle equipped with a jacket and evaporated (volatilized) under the conditions of 305 ° C. and 230 Pa. The evaporated BPDA was brought into contact with the surface of a drum-type rotary cooler disposed at the end of a gas pipe directly connected to the gas phase portion of the evaporation kettle, and was cooled and deposited. The BPDA crystals adhering to the drum surface were continuously scraped by a scraper and recovered as flakes. After pulverizing this flake, 80 parts by weight of purified BPDA was obtained.
When the number of insoluble fine particles having a size of 5 to 30 μm in the purified BPDA was counted, it was 400 per 1 g, which was much smaller than that of the insoluble fine particles in the raw BTC.
[0023]
[Example 2]
In Example 1, except that BTC as a raw material was replaced with BTC containing 5 × 10 4 insoluble fine particles having a size of 5 to 30 μm per gram, the dehydration ring closure of BTC and the same procedure as in Example 1 were performed. The resulting crude BPDA was volatilized and cooled.
The number of insoluble fine particles having a size of 5 to 30 μm in the obtained BPDA was 1000 per 1 g, which was much smaller than the insoluble fine particles in the raw material BTC.
[0024]
[Comparative Example 1]
In Example 1, BTC was dehydrated in the same procedure as in Example 1 except that the BTC of the raw material was replaced with BTC containing 1.5 × 10 5 insoluble fine particles having a size of 5 to 30 μm per gram. Ring closure and volatilization-cooling of the resulting crude BPDA were performed.
The number of insoluble fine particles having a size of 5 to 30 μm in the obtained BPDA was 3500 per 1 g, exceeding 2 × 10 3 per 1 g of the target value.
[0025]
【The invention's effect】
The present invention has the following particularly advantageous effects, and its industrial utility value is extremely large.
1. When the content of insoluble fine particles having a size of 5 to 30 μm obtained by the method of the present invention is 2 × 10 3 or less per 1 g of high purity BPDA is reacted with an aromatic diamine to produce a polyimide, When it is processed into a gas separation membrane with excellent heat resistance, insulation and gas barrier properties, a product with few membrane defects can be obtained.
2. According to the method of the present invention, even when the volatilization / cooling of the crude BPDA is carried out batchwise, it is not necessary to frequently extract the residue of the distillation pot, and the productivity and yield are greatly improved.
Claims (5)
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| JP27783994A Division JP3625504B2 (en) | 1994-11-11 | 1994-11-11 | High purity biphenyltetracarboxylic dianhydride and process for producing the same |
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