JP4765145B2 - Process for producing polyphenylene ether - Google Patents

Description

（式中、Ｒ¹ 、Ｒ² 、Ｒ³ 、Ｒ⁴ は、各々独立に水素、アルキル基、置換アルキル基、ハロゲン基、フェニル基、又は置換フェニル基である。）
【０００７】
代表的なポリフェニレンエーテルは、ポリ（２，６−ジメチル−１，４−フェニレン）エーテル、ポリ（２−メチル−６−エチル−１，４−フェニレン）エーテル、ポリ（２，６−ジエチル−１，４−フェニレン）エーテル、ポリ（２−エチル−６−ｎ−プロピル−１，４−フェニレン）エーテル、ポリ（２，６−ジ−ｎ−プロピル−１，４−フェニレン）エーテル、ポリ（２−メチル−６−ｎ−ブチル−１，４−フェニレン）エーテル、ポリ（２−エチル−６−イソプロピル−１，４−フェニレン）エーテル、ポリ（２−メチル−６−クロロエチル−１，４−フェニレン）エーテル、ポリ（２−メチル−６−ヒドロキシエチル−１，４−フェニレン）エーテル等のホモポリマーを挙げられる。また、２，６−ジメチルフェノールに共重合体成分として２，３，６−トリメチルフェノールおよびｏ−クレゾールの１種あるいは両方を組み合わせたランダム共重合体又はブロック共重合体等が挙げられる。
【０００８】
また、本発明のポリフェニレンエーテルには、本発明の主旨に反さない限り、従来ポリフェニレンエーテルに存在させてもよいことが提案されている他の種々のフェニレンエーテルユニットを部分構造として含んでいてもよい。例えば、特開平１−２９７４２８号公報及び特開昭６３−３０１２２２号公報に記載の２−（ジアルキルアミノメチル）−６−メチルフェニレンエーテルユニットや、２−（Ｎ−アルキル−Ｎ−フェニルアミノメチル）−６−メチルフェニレンエーテルユニット等や、ポリフェニレンエーテル樹脂の主鎖中にジフェノキノン等が少量結合したものが挙げられる。さらに、炭素−炭素二重構造を持つ化合物により変性されたポリフェニレンエーテル（例えば特開平２−２７６８２３号公報、特開昭６３−１０８０５９号公報、特開昭５９−５９７２４号公報）も含むことができる。
【０００９】
本発明におけるポリフェニレンエーテルの重合方法は、例えば、特公昭４２−３１９５号公報、特公昭４５−２３５５５号公報、特公昭６１−８０９２号公報等に例示されるように、フェノール化合物を銅、マンガン又はコバルトからなる群から選ばれる金属の塩と各種アミンとの組み合わせからなる触媒を用いて酸化重合される。この中で好ましい金属の塩として、具体的には、塩化第１銅、塩化第２銅、臭化第１銅、臭化第２銅、硫酸第１銅、硫酸第２銅、酢酸第１銅、酢酸第２銅、プロピオン第１銅、ラウリン酸第２銅、パルミチン酸第１銅、安息香酸第１銅等の銅塩が挙げられる。また、組合せ成分として上記金属塩を直接添加する代わりに、金属又は金属酸化物及び無機酸、有機酸又はこれら酸の水溶液の形で添加し、その反応系内で、上記金属塩又はその水和物を形成させ使用することも可能である。
【００１０】
本発明におけるポリフェニレンエーテルの重合溶媒は、実質的に水と均一混合しない溶媒でかつポリフェニレンエーテルの良溶媒であり、例えば、ベンゼン、トルエン、キシレン等の芳香族炭化水素、ニトロベンゼン等のニトロ化合物等が挙げられる。また、該良溶媒にポリフェニレンエーテルの貧溶媒であるメタノール、エタノール等のアルコール類、ヘキサン、ヘプタン等の脂肪族炭化水素類、アセトン、メチルエチルケトン等のケトン類、酢酸エチル等のエステル類等を任意の割合および組成で混合し重合溶媒として用いることもできる。重合溶媒中の貧溶媒の割合が多くなると重合中にポリフェニレンエーテルが析出してくる沈澱重合となるが、本発明では重合後にポリフェニレンエーテルが析出しない溶液重合が溶液の移送や反応停止工程あるいは触媒分離工程等におけるハンドリングの点で好ましい。また、重合溶媒に用いられるポリフェニレンエーテルの良溶媒は、乾燥工程での残存溶媒除去のしやすさの点でトルエンが最も好ましい。
【００１１】
本発明のポリフェニレンエーテル反応溶液は、目的の粘度まで反応が進行した時点で、キレート剤を含む水溶液と接触混合させ、水相側に金属触媒のキレート化合物を抽出し反応を終了させる。ここで、キレート剤は金属触媒と水溶性錯体を形成する化合物であれば特に限定はされないが、例えば、エチレンジアミン４酢酸のアルカリ金属塩やニトリロトリ酢酸のアルカリ金属塩等が挙げられる。
【００１２】
キレート剤量ならびにキレート剤水溶液量は反応液中に含まれる金属触媒とキレート化合物を形成させるに十分な量であり、かつ金属触媒がキレート剤化合物を形成したときに水溶液から金属触媒のキレート化合物が析出しない量であれば特に限定される物ではないが、金属触媒に対するキレート剤は、通常１〜１０倍モル量、好ましくは１．１〜５倍モル量である。また、キレート剤水溶液量は、反応液重量に対、通常０．０１〜１倍量、好ましくは０．０５〜０．２５倍量である。
【００１３】
ポリフェニレンエーテル反応溶液とキレート剤水溶液との接触時間あるいは接触温度も金属触媒を抽出するに十分な時間あるいは温度であればよく、通常１分以上３０℃以上であればよいが、好ましくは３０分〜１８０分の接触時間で、５０℃〜８０℃の接触温度で行われる。
【００１４】
キレート剤を含む水溶液には公知の水溶性還元剤を混合しておいてもかまわない。ここで水溶性還元剤とは亜二チオン酸塩、チオ硫酸塩、亜燐酸塩等が挙げられる。
【００１５】
次いで、該ポリフェニレンエーテル反応溶液は、該水溶液と静置分離や遠心分離等の工業的に用いられる方法によって液液分離される。分離された該水溶液は、金属触媒のキレート化合物、キレート化合物の他に重合溶媒、重合時に添加されたアミン類や助触媒、水溶性還元剤、及び水溶性還元剤の酸化物等が含まれた水溶液である。液液分離の温度は３０℃〜１００℃の温度であれば特に限定はされない。また、該水溶液にキレート剤が金属触媒のキレート化合物に対し過剰量含まれている場合は、分離後のキレート剤水溶液の一部を再度反応停止工程にリサイクル使用することもできる。
【００１６】
液液分離されたポリフェニレンエーテル反応溶液は、ポリフェニレンエーテル回収工程に送ることもできるが、再度、水を加えて接触混合させた後、液液分離により反応溶液と水相を分離することにより反応溶液中に残る金属触媒のキレート化合物残渣を取り除くことが好ましい。該反応溶液と水は混合後、静置分離や遠心分離等の工業的に用いられる方法によって液液分離される。ポリフェニレンエーテル反応溶液と水との接触時間は、通常１〜６０分、好ましくは２〜１０分でおこなわれる。混合温度は、通常３０〜１００℃、好ましくは５０℃〜８０℃でおこなわれる。添加水量に特に規定はないが、反応液重量に対して、通常０．０１〜１倍量、好ましくは０．０５〜０．２５倍量である。本操作で分離された水はキレート剤水溶液と混合し反応停止工程に用いることができ、また反応停止工程で分離されたキレート剤水溶液と混合して回収処理することもできる。
【００１７】
また、水の代わりにキレート剤水溶液で再度反応溶液と接触混合し反応溶液中に残る金属触媒のキレート化合物残渣を取り除くこともできるが、この場合は分離されたキレート剤水溶液は反応停止工程で再度使用することが好ましい。
【００１８】
液液分離後のポリフェニレンエーテル反応溶液は、貧溶媒と接触させてポリフェニレンエーテルを固形物として析出させる。本発明におけるポリフェニレンエーテル貧溶媒としては、例えば、メタノール、エタノール等のアルコール類、アセトン等の脂肪族ケトン類が挙げられる。これらのうちでは、貧溶媒性の最も良好な、メタノールとするのが最も好ましい。また、場合によっては、貧溶媒中にポリフェニレンエーテルの前述の重合溶媒あるいは水が、ポリフェニレンエーテルの析出を妨げない範囲で存在していてもかまわない。
【００１９】
析出されたポリフェニレンエーテルは、連続又はバッチで遠心分離機や真空ろ過等により、重合溶媒及び貧溶媒を含む混合物から固液分離される。回収されたポリフェニレンエーテルは製品化のための乾燥工程に送られる。
【００２０】
反応溶液と分離された上記キレート剤水溶液は濃縮することによって好結果をもたらす場合があり、金属触媒回収工程の前にキレート剤水溶液の濃縮をおこなうこともできる。キレート剤水溶液中に含まれる触媒であるアミン類は水との共沸により留去し、留去液から上記アミンを液液分離あるいは重合溶媒等の有機溶媒で抽出する事により回収でき、留去された水はポリフェニレンエーテル製造工程で水が使用される任意の工程にリサイクル使用が可能である。
【００２１】
ここで、アミン分離を効率的におこなう方法として、塩基性化合物をキレート剤水溶液や留去水に添加する方法を採用することができる。該塩基性化合物は、触媒として使用されたアミン類より塩基性が高い物であればよいが、ナトリウム、カリウム、及びカルシウム等のアルカリ金属あるいはアルカリ土類金属の水酸化物、炭酸塩、又は炭酸水素塩が好ましく用いられる。また、金属濃度およびキレート剤濃度を高くすることに伴い、その後の金属触媒の回収工程やキレート剤の回収工程での回収率向上をもたらし、更には、最終的に系外に抜きだされる排水量を削減する効果もある。
【００２２】
反応溶液から分離されたキレート剤水溶液に溶解している金属触媒のキレート化合物は、アルカリ金属の硫化物と混合することにより、金属硫化物として析出させる。該アルカリ金属の硫化物とは、硫化ナトリウム、硫化カリウム、多硫化ナトリウムが例示され、好ましくは硫化ナトリウムが用いられる。硫化物の添加形態は固体あるいは水溶液のいずれでもかまわないが、好ましくはポンプ流量で添加量制御が容易な水溶液状態が好ましい。この場合、水溶液濃度は硫化物溶解度以下ならば特に規定はない。
【００２３】
本発明方法においては、金属触媒のキレート化合物含有のキレート剤水溶液に、アルカリ金属の硫化物を添加し、金属触媒を硫化物として析出させる際に、アルカリ金属の硫化物の添加量は、該キレート剤水溶液の酸化還元電位により制御される。即ち、金属触媒のキレート化合物を溶解したキレート剤水溶液に、アルカリ金属の硫化物を添加していくと酸化還元電位が当量点を越えたところで、該キレート剤水溶液中の金属触媒のキレート化合物は消失する。酸化還元電位値に対してアルカリ金属の硫化物の添加量を制御する方法により、アルカリ金属の硫化物濃度変動および／またはキレート剤水溶液に溶解している金属触媒濃度の変動に関わらず安定的にアルカリ金属の硫化物を添加することができる。
【００２４】
析出温度は水溶液が凍結あるいは沸騰しない温度であればかまわないが、通常２０〜７０℃、好ましくは３０〜５０℃でおこなわれる。また析出時間は両溶液が均一に混合される条件であればよく、通常１〜１２０分、好ましくは５〜６０分で行われる。
【００２５】
金属触媒の析出をおこなう槽の気体排出先はアルカリ水溶液によるスクラバーにするのが好ましい。該キレート剤水溶液にアルカリ金属の硫化物を混合すると硫化水素が発生が避けられないので、発生する硫化水素を捕獲する目的で気体排出先をアルカリ水溶液によるスクラバーとするのが好ましい。アルカリ水溶液とはアルカリ金属あるいはアルカリ土類金属の水酸化物、炭酸塩、炭酸水素塩が挙げられる。またブロアー等により発生硫化水素を強制的にスクラバー内に導入する方式が好ましく用いられる。
【００２６】
析出した金属触媒の硫化物は固液分離機によりろ液と分離する必要があるが、本発明方法で得られる金属触媒の硫化物は微細粒子でありきわめて取り扱いにくい性状で析出するため、プリコートろ過方式、好ましくはプリコート回転式連続真空ろ過方式を用いる。プリコートろ過はろ過面に助剤層を形成させ、捕獲された金属触媒硫化物を助剤層の表面層と共に取り除くことにより常に新しいろ過面が現れるため、本発明方法で得られる金属触媒の硫化物の固液分離に最適である。助剤は珪藻土、パーライト、カーボン、セルローズ、活性炭素、酸性白土などがあり適宜選択使用されればよいが、好ましくは珪藻土が用いられる。
【００２７】
金属触媒の硫化物スラリー液を直接プリコートフィルタ−により固液分離することもできるが、金属触媒の硫化物スラリー液に予めろ過助剤を混合するボディフィードもおこなうことができる。
【００２８】
該スラリー液中の金属触媒の硫化物濃度は、通常０．１〜１０ｗｔ％、好ましくは０．５〜２ｗｔ％にする。上記範囲より濃度が低下すると必要ろ過面積が大きくなるため過大な装置が必要となり、上記範囲より濃度が増加すると金属触媒の硫化物がプリコート面に均一に付着しなくなる問題、あるいは新規ろ過面形成（助剤層の表面層を捕獲金属触媒と共に削り取る）時に助剤層の表面削除量が多くなる問題が生ずる。金属触媒の硫化物の固液分離前に上記濃度以上に金属触媒の硫化物スラリー液濃度が高くなった場合は、水あるいは固液分離後の金属触媒の硫化物スラリー液のろ液による希釈を行うことにより上記濃度範囲にスラリー液濃度をコントロールすることができる。また固液分離の温度は金属触媒析出温度と同じ範囲であれば特に限定はされない。
【００２９】
上記の固液分離後のろ液はキレート剤の他、種々雑多な化合物が溶解した水溶液であるため、そのままではリサイクル使用が難しい。そのためろ液に無機酸を加えて一旦キレート剤を析出させ、キレート剤を固液分離し、次いで、無機水酸化物により再度キレート剤の水溶液としてリサイクル使用する。具体的には、金属触媒の硫化物を除いたろ液は、塩酸、臭化水素酸、燐酸、亜燐酸、硫酸又は亜硫酸等に例示される無機酸あるいは無機酸水溶液と混合させて、ｐＨ値を４．０以下、好ましくは３．０以下にし、キレート剤をプロトン化された固形物とする。この際、水溶液中のキレート剤濃度は高いほど固体として析出するので、キレート剤収率は高くなるため、キレート剤濃度は、通常５ｗｔ％以上、好ましくは７ｗｔ％以上がよい。キレート剤の析出はバッチ式、連続式いずれの方法によっても行うことができる。また、ｐＨ値の調節は、ｐＨ計で測定しながら無機酸添加量を制御する方法が好ましく用いられる。キレート剤の析出温度は、通常２０〜７０℃、好ましくは３０〜５０℃で行われ、析出時間は両溶液が均一に混合する条件であればよく、通常１〜１２０分、好ましくは５〜６０分で行われる。
【００３０】
一旦、固形化されたキレート剤は固液分離をおこない、ろ液と分離する。固液分離方法は、通常の遠心分離、真空ろ過、加圧ろ過方法を適宜選択すればよく、回分式あるいは連続式いずれの方式を採用することができる。また、固液分離温度に関しても特に規定はないが、好ましくはキレート剤の析出温度範囲内で行うのがよい。
【００３１】
ろ液と分離したキレート剤は、水酸化ナトリウムおよび水酸化カリウム等に代表される無機水酸化物の水溶液と混合し再度水溶液とする。このとき無機水酸化物の量は、固形化されたキレート剤が溶解する以上であればよく、好ましくはキレート剤に対し２配位以上、より好ましくは３配位以上の量であれば良く、またキレート剤溶解後のキレート剤水溶液濃度に関してもキレート剤溶解度以下の濃度であれば特に限定される物ではない。その際のキレート剤水溶液のｐＨ値は、通常７．１〜１４．０、好ましくは７．５〜１２．０の範囲にする。
【００３２】
固液分離後のキレート剤の溶解は、固体のキレート剤を独立の槽に移送しアルカリ水溶液と接触混合させて溶解する方法、または固液分離機内で固体のキレート剤とアルカリ水溶液を混合して溶解する方法のいずれの方法を用いてもかまわない。また、固液分離機内で溶解する場合、アルカリ水溶液導入時間に対しキレート剤の溶解時間が短い場合は、ろ液を固液分離機内に複数回循環させ固体キレート剤を溶解させる方法を採用することができる。
【００３３】
溶解温度および溶解時間は、キレート剤が完全に溶解する温度および時間を設定すればよく、通常１０〜７０℃で、１〜６０分、好ましくは３０〜５０℃で、５〜３０分の条件で行われる。また、得られたキレート剤水溶液は、濃度調節を行うか、あるいはそのままの状態で、再度反応停止工程にリサイクルされる。
【００３４】
【実施例】
以下に具体例により本発明を説明するが、これらの実施例に限定されるものではない。
【００３５】
実施例１
〔ポリフェニレンエーテルの重合〕
臭化第二銅２２ｇ、ジブチルアミン４００ｇ、トルエン９８００ｇの触媒溶液中に、空気をモノマー１ｋｇ当たり１０ＮＬ／分で供給しながら、２，６−ジメチルフェノール２３５０ｇをトルエン５４００ｇに溶かした溶液を６０分かけて滴下し、４０℃で重合をおこなった。モノマー滴下した後の１２０分後にエチレンジアミン４酢酸４ナトリウムを５６ｇ溶解した水溶液１８００ｇを攪拌しながら反応液に加え反応を停止し、重合器から反応液を抜き出した。反応液を７０℃で２時間窒素雰囲気で攪拌した後、連続式遠心分離機で反応液と水溶液を分離した。次に、分離後の反応液に純水１８００ｇを加え、７０℃で５分間攪拌した後、連続式遠心分離機で反応液と水溶液を分離した。上記操作により得られた２種の水溶液を混合したのち、金属触媒回収操作をおこなった。
【００３６】
〔金属触媒回収〕
水溶液を単蒸留によって銅濃度０．６０重量％まで濃縮後、ＯＲＰ計により酸化還元電位を測定しならがら、硫化ナトリウム水溶液１０ｗｔ％水溶液を滴下していった。黒色の硫化銅が硫化ナトリウム添加と共に析出しはじめ、初期青色を呈していた水溶液は次第に黄色く変色していった。硫化ナトリウム水溶液添加量に対するＯＲＰ計指示値変化の傾きが変わるところで硫化ナトリウム水溶液の添加を停止した。このとき硫化ナトリウム添加量は銅モル数に対して１．１５倍モルであった。このときのＯＲＰ計指示値を硫化ナトリウム水溶液添加の基準とした。水溶液濃縮度を変え銅濃度０．２〜１．７２重量％とし、硫化ナトリウム水溶液濃度を８〜１２％と種々変化させ上記滴定操作をおこなった結果、硫化ナトリウム添加量変動値は銅モル数に対して１．２１±０．７倍モルであり、硫化ナトリウム添加量は、銅濃度および硫化ナトリウム濃度変動によらず安定に添加する事ができた。
【００３７】
比較例１
水溶液を単蒸留によって銅濃度０．６０重量％まで濃縮後、ｐＨ計によりｐＨ値を測定しならがら、硫化ナトリウム水溶液１０ｗｔ％水溶液を滴下していった以外は実施例１と同様な方法で実験をおこなった。硫化ナトリウム水溶液添加量に対するｐＨ計指示値変化は明確でなく硫化ナトリウム水溶液の添加終点の判定ができなかった。
【００３８】
実施例２
実施例１の方法に従って硫化銅スラリー液（硫化銅濃度０．９ｗｔ％）を調整し、ろ過面に珪藻土（ラジオライト＃６００）の助剤層を形成させた吸引ろ過器（プリコートフィルター）によって、４０℃に温度調節されたスラリー液にろ過面を浸し−０．０５ＭＰａで減圧しながら４０秒吸引ろ過した。スラリー液からろ過面を離し、更に１２０秒吸引を続けた後吸引を停止した。
ろ過面に硫化銅は均一に吸着されており、また珪藻土助剤層を１ｍｍ厚削ることにより新たな珪藻土助剤層の平滑な表面が現れ、良好なプリコートフィルター性が示された。
【００３９】
実施例３
硫化銅スラリー液の硫化銅濃度を２．５ｗｔ％とした以外は実施例２と同様の方法により実験をおこなった。
ろ過面から硫化銅の若干の剥離が見られ、また珪藻土助剤層を２ｍｍ厚削ることにより新たな珪藻土助剤層の平滑な表面が現れ、良好なプリコートフィルター性が示された。
【００４０】
比較例２
ろ過面を厚み１０ｍｍのフエルト層とした吸引ろ過器を用いた以外は実施例２と同じ方法を用いた。
多量の硫化銅がろ過面から剥離せず残ってしまった。また、フエルト層内部に硫化銅が進入しており、ろ過特性が悪いことが示された。
【００４１】
比較例３
ろ過面を厚み１ｍｍのポリプロピレン布（透気性１２cm³/cm² ・ｓ）とした吸引ろ過器を用いた以外は実施例２と同じ方法を用いた。
ろ布に多量の硫化銅がろ過面から剥離せず残ってしまった。また、ろ液に硫化銅が多量に漏洩し、ろ過特性が悪いことが示された。
【００４２】
【発明の効果】
本発明の方法によれば、金属触媒のキレート化合物含有水溶液に、アルカリ金属の硫化物を添加するに際し、該金属触媒のキレート化合物含有水溶液の酸化還元電位を測定することにより、該アルカリ金属の硫化物の添加量を制御することができるので、アルカリ金属の硫化物の品質等の変化があっても、金属触媒を１００％回収することができ、しかも硫化水素の発生を最小減とすることができるとの効果を奏するものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing polyphenylene ether. Specifically, the present invention relates to a method for producing polyphenylene ether in which the polymerization of polyphenylene ether is stopped and the metal catalyst is stably separated and recovered.
[0002]
[Prior art]
Polyphenylene ether can be polymerized in the presence of oxygen in an aromatic solvent or a mixed solvent of an aromatic solvent and a non-solvent using an oxidative coupling polymerization catalyst containing copper, manganese, or cobalt. It is done. After the reaction, the polyphenylene ether solution is charged with an aqueous solution of a chelating agent to form a metal catalyst chelate compound to stop the reaction, and then the polyphenylene solution and the metal catalyst chelate compound-containing aqueous solution are separated to remove the metal catalyst. The solution is put into a poor solvent for polyphenylene ether to solidify the polyphenylene ether. Next, the solid-liquid separated polyphenylene ether after solidification is sent to a drying step to obtain a powdery polyphenylene ether. On the other hand, the separated metal catalyst chelate compound-containing aqueous solution is precipitated by adding an alkali metal sulfide, and the metal catalyst sulfide is precipitated as a solid, and the solid-liquid separator is used to remove the metal catalyst. Is made. The chelating agent is recovered from the aqueous chelating agent solution from which the metal catalyst has been removed, and the recovered chelating agent is recycled again.
[0003]
[Problems to be solved by the invention]
However, in an actual plant, the amount of the alkali metal sulfide added is stable due to fluctuations in the concentration of the metal contained in the chelate compound-containing aqueous solution of the metal catalyst or the quality of the added alkali metal sulfide. It was difficult to control the amount of the product added. That is, if the addition amount is small, the metal catalyst is not sufficiently solidified and insufficiently separated, whereas if the addition amount is too large, hydrogen sulfide is generated in the subsequent treatment process of the aqueous solution. It was.
[0004]
Further, since the sulfide of the solidified metal catalyst obtained by the method of the present invention is in the form of fine particles and is extremely difficult to handle, the filter cloth is clogged or leaked to the filtrate side in a normal solid-liquid separator. They also had problems and were forced to sacrifice poor productivity.
[0005]
[Means for Solving the Problems]
As a result of intensive studies in view of the above circumstances, the present inventors have completed the present invention. That is, the present invention stops the polymerization by contacting a polyphenylene ether solution obtained by polymerization in the presence of a catalyst in a water-insoluble polymerization solvent of polyphenylene ether with an aqueous chelating agent solution to form a metal catalyst chelate compound. The metal catalyst chelate compound-containing aqueous solution is separated from the polyphenylene ether solution, and an alkali metal sulfide is added to the metal catalyst chelate compound-containing aqueous solution to precipitate the metal catalyst as a sulfide from the aqueous solution as a solid. In the method for producing polyphenylene ether, the alkali metal sulfide is measured by measuring the oxidation-reduction potential of the aqueous solution containing the chelate compound of the metal catalyst when the alkali metal sulfide is added to the aqueous solution containing the chelate compound of the metal catalyst. Of polyphenylene ether to control the amount of sulfide added It is the law.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The polyphenylene ether in the present invention is a homopolymer, random copolymer or block copolymer having a repeating unit of the general formula (1).

(In the formula, R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen, an alkyl group, a substituted alkyl group, a halogen group, a phenyl group, or a substituted phenyl group.)
[0007]
Representative polyphenylene ethers include poly (2,6-dimethyl-1,4-phenylene) ether, poly (2-methyl-6-ethyl-1,4-phenylene) ether, poly (2,6-diethyl-1). , 4-phenylene) ether, poly (2-ethyl-6-n-propyl-1,4-phenylene) ether, poly (2,6-di-n-propyl-1,4-phenylene) ether, poly (2 -Methyl-6-n-butyl-1,4-phenylene) ether, poly (2-ethyl-6-isopropyl-1,4-phenylene) ether, poly (2-methyl-6-chloroethyl-1,4-phenylene) And homopolymers such as ether and poly (2-methyl-6-hydroxyethyl-1,4-phenylene) ether. In addition, a random copolymer or a block copolymer obtained by combining one or both of 2,3,6-trimethylphenol and o-cresol as a copolymer component with 2,6-dimethylphenol can be used.
[0008]
In addition, the polyphenylene ether of the present invention may include other various phenylene ether units that have been proposed to be present in the polyphenylene ether as a partial structure, unless they are contrary to the gist of the present invention. Good. For example, 2- (dialkylaminomethyl) -6-methylphenylene ether unit described in JP-A-1-297428 and JP-A-63-301222, and 2- (N-alkyl-N-phenylaminomethyl) Examples include -6-methyl phenylene ether unit or the like, or a small amount of diphenoquinone or the like bonded to the main chain of polyphenylene ether resin. Further, polyphenylene ethers modified with a compound having a carbon-carbon double structure (for example, JP-A-2-276823, JP-A-63-108059, JP-A-59-59724) can also be included. .
[0009]
Examples of the polymerization method of polyphenylene ether in the present invention include, as exemplified in Japanese Patent Publication No. 42-3195, Japanese Patent Publication No. 45-23555, Japanese Patent Publication No. 61-8092, etc. Oxidative polymerization is carried out using a catalyst comprising a combination of a metal salt selected from the group consisting of cobalt and various amines. Among these, as preferred metal salts, specifically, cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous sulfate, cupric sulfate, cuprous acetate And copper salts such as cupric acetate, cuprous propion, cupric laurate, cuprous palmitate, cuprous benzoate, and the like. Further, instead of directly adding the metal salt as a combination component, it is added in the form of a metal or metal oxide and an inorganic acid, an organic acid or an aqueous solution of these acids, and the metal salt or hydration thereof is added in the reaction system. It is also possible to form and use.
[0010]
The polymerization solvent for polyphenylene ether in the present invention is a solvent that does not substantially uniformly mix with water and is a good solvent for polyphenylene ether, such as aromatic hydrocarbons such as benzene, toluene, and xylene, nitro compounds such as nitrobenzene, and the like. Can be mentioned. In addition, the good solvent may be an alcohol such as methanol or ethanol which is a poor solvent for polyphenylene ether, aliphatic hydrocarbons such as hexane or heptane, ketones such as acetone or methyl ethyl ketone, esters such as ethyl acetate, etc. They can be mixed in proportions and compositions and used as a polymerization solvent. When the proportion of the poor solvent in the polymerization solvent is increased, precipitation polymerization in which polyphenylene ether is precipitated during the polymerization occurs, but in the present invention, solution polymerization in which polyphenylene ether does not precipitate after polymerization is a solution transfer, reaction stop process or catalyst separation. It is preferable in terms of handling in the process. The good solvent of polyphenylene ether used as the polymerization solvent is most preferably toluene from the viewpoint of easy removal of the residual solvent in the drying step.
[0011]
When the reaction proceeds to the target viscosity, the polyphenylene ether reaction solution of the present invention is contact-mixed with an aqueous solution containing a chelating agent, and the metal catalyst chelate compound is extracted on the aqueous phase side to complete the reaction. Here, the chelating agent is not particularly limited as long as it is a compound that forms a water-soluble complex with a metal catalyst, and examples thereof include an alkali metal salt of ethylenediaminetetraacetic acid and an alkali metal salt of nitrilotriacetic acid.
[0012]
The amount of the chelating agent and the amount of the chelating agent aqueous solution are sufficient to form a chelating compound with the metal catalyst contained in the reaction solution, and when the metal catalyst forms the chelating agent compound, the chelating compound of the metal catalyst is removed from the aqueous solution. Although it will not specifically limit if it is the quantity which does not precipitate, The chelating agent with respect to a metal catalyst is 1-10 times mole amount normally, Preferably it is 1.1-5 times mole amount. The amount of the chelating agent aqueous solution is usually 0.01 to 1 times, preferably 0.05 to 0.25 times the amount of the reaction solution.
[0013]
The contact time or contact temperature between the polyphenylene ether reaction solution and the chelating agent aqueous solution may be a time or temperature sufficient to extract the metal catalyst, and usually 1 minute or more and 30 ° C. or more, preferably 30 minutes to It is carried out at a contact temperature of 50 ° C. to 80 ° C. with a contact time of 180 minutes.
[0014]
A known water-soluble reducing agent may be mixed in the aqueous solution containing the chelating agent. Examples of the water-soluble reducing agent include dithionite, thiosulfate, and phosphite.
[0015]
Next, the polyphenylene ether reaction solution is liquid-liquid separated from the aqueous solution by an industrially used method such as static separation or centrifugation. The separated aqueous solution contained a metal catalyst chelate compound, a chelating compound, a polymerization solvent, amines and cocatalysts added during polymerization, a water-soluble reducing agent, and an oxide of a water-soluble reducing agent. It is an aqueous solution. The temperature of the liquid-liquid separation is not particularly limited as long as it is 30 ° C to 100 ° C. In addition, when the aqueous solution contains an excessive amount of the chelating agent relative to the chelate compound of the metal catalyst, a part of the separated chelating agent aqueous solution can be recycled again in the reaction stopping step.
[0016]
The liquid-liquid separated polyphenylene ether reaction solution can also be sent to the polyphenylene ether recovery step, but after adding water again and contact mixing, the reaction solution is separated from the reaction solution and the aqueous phase by liquid-liquid separation. It is preferable to remove the metal catalyst chelate compound residue remaining therein. The reaction solution and water are mixed and then liquid-liquid separated by an industrially used method such as stationary separation or centrifugation. The contact time between the polyphenylene ether reaction solution and water is usually 1 to 60 minutes, preferably 2 to 10 minutes. The mixing temperature is usually 30 to 100 ° C, preferably 50 to 80 ° C. The amount of added water is not particularly limited, but is usually 0.01 to 1 times, preferably 0.05 to 0.25 times the weight of the reaction solution. The water separated in this operation can be mixed with the aqueous chelating agent solution and used in the reaction stopping step, or can be recovered by mixing with the aqueous chelating agent solution separated in the reaction stopping step.
[0017]
In addition, the metal catalyst chelate compound residue remaining in the reaction solution can be removed by contacting and mixing with the reaction solution again with an aqueous chelating agent solution instead of water, but in this case, the separated aqueous chelating agent solution is again used in the reaction stopping step. It is preferable to use it.
[0018]
The polyphenylene ether reaction solution after liquid-liquid separation is brought into contact with a poor solvent to precipitate polyphenylene ether as a solid. Examples of the polyphenylene ether poor solvent in the present invention include alcohols such as methanol and ethanol, and aliphatic ketones such as acetone. Of these, methanol is most preferable because of its poor solvent resistance. In some cases, the aforementioned polymerization solvent or water of polyphenylene ether may be present in the poor solvent as long as it does not interfere with the precipitation of polyphenylene ether.
[0019]
The precipitated polyphenylene ether is solid-liquid separated from the mixture containing the polymerization solvent and the poor solvent by a centrifuge or vacuum filtration continuously or batchwise. The recovered polyphenylene ether is sent to a drying process for commercialization.
[0020]
The chelating agent aqueous solution separated from the reaction solution may give good results by concentrating, and the chelating agent aqueous solution may be concentrated before the metal catalyst recovery step. The amines that are catalysts contained in the chelating agent aqueous solution are distilled off by azeotropy with water, and the amine can be recovered from the distillate by liquid-liquid separation or extraction with an organic solvent such as a polymerization solvent. The water thus used can be recycled for any process where water is used in the polyphenylene ether production process.
[0021]
Here, as a method for efficiently carrying out amine separation, a method of adding a basic compound to an aqueous chelating agent solution or distilled water can be employed. The basic compound may be any compound having a higher basicity than the amines used as the catalyst, but hydroxides, carbonates or carbonates of alkali metals or alkaline earth metals such as sodium, potassium and calcium. Hydrogen salts are preferably used. In addition, as the metal concentration and chelating agent concentration are increased, the recovery rate in the subsequent metal catalyst recovery process and chelating agent recovery process is improved, and the amount of wastewater that is finally discharged out of the system. There is also an effect of reducing.
[0022]
The metal catalyst chelate compound dissolved in the chelating agent aqueous solution separated from the reaction solution is precipitated as a metal sulfide by mixing with an alkali metal sulfide. Examples of the alkali metal sulfide include sodium sulfide, potassium sulfide and sodium polysulfide, and sodium sulfide is preferably used. The addition form of sulfide may be either a solid or an aqueous solution, but an aqueous solution state in which the addition amount can be easily controlled with a pump flow rate is preferable. In this case, there is no particular limitation as long as the aqueous solution concentration is not higher than the solubility of sulfide.
[0023]
In the method of the present invention, when an alkali metal sulfide is added to a chelating agent aqueous solution containing a chelate compound of a metal catalyst and the metal catalyst is precipitated as a sulfide, the amount of the alkali metal sulfide added is It is controlled by the redox potential of the aqueous agent solution. That is, when an alkali metal sulfide is added to an aqueous chelating agent solution in which the chelating compound of the metal catalyst is dissolved, the chelating compound of the metal catalyst in the aqueous chelating agent solution disappears when the oxidation-reduction potential exceeds the equivalence point. To do. By controlling the amount of alkali metal sulfide added relative to the oxidation-reduction potential value, it is possible to stabilize regardless of fluctuations in the alkali metal sulfide concentration and / or the metal catalyst concentration dissolved in the chelating agent aqueous solution. Alkali metal sulfides can be added.
[0024]
The precipitation temperature may be any temperature at which the aqueous solution does not freeze or boil, but is usually 20 to 70 ° C, preferably 30 to 50 ° C. Moreover, the precipitation time should just be the conditions by which both solutions are mixed uniformly, and is normally performed for 1 to 120 minutes, Preferably it is 5 to 60 minutes.
[0025]
The gas discharge destination of the tank in which the metal catalyst is deposited is preferably a scrubber using an alkaline aqueous solution. Since generation of hydrogen sulfide is unavoidable when alkali metal sulfide is mixed in the chelating agent aqueous solution, it is preferable to use a scrubber made of an alkaline aqueous solution as a gas discharge destination for the purpose of capturing the generated hydrogen sulfide. Examples of the aqueous alkali solution include alkali metal or alkaline earth metal hydroxides, carbonates, and hydrogen carbonates. A method of forcibly introducing the generated hydrogen sulfide into the scrubber by a blower or the like is preferably used.
[0026]
The precipitated metal catalyst sulfide needs to be separated from the filtrate by a solid-liquid separator, but the metal catalyst sulfide obtained by the method of the present invention is a fine particle and precipitates with a property that is extremely difficult to handle. A system, preferably a precoat rotary continuous vacuum filtration system is used. Since precoat filtration forms an auxiliary layer on the filtration surface and removes the captured metal catalyst sulfide together with the surface layer of the auxiliary layer, a new filtration surface always appears, so the metal catalyst sulfide obtained by the method of the present invention It is most suitable for solid-liquid separation. The auxiliaries include diatomaceous earth, pearlite, carbon, cellulose, activated carbon, and acid clay, and may be appropriately selected and used, but diatomaceous earth is preferably used.
[0027]
The metal catalyst sulfide slurry liquid can be directly solid-liquid separated by a precoat filter, but a body feed in which a filter aid is mixed in advance with the metal catalyst sulfide slurry liquid can also be performed.
[0028]
The sulfide concentration of the metal catalyst in the slurry is usually 0.1 to 10 wt%, preferably 0.5 to 2 wt%. If the concentration falls below the above range, the required filtration area becomes large and an excessive apparatus is required. If the concentration increases from the above range, the metal catalyst sulfide does not adhere uniformly to the precoat surface, or the formation of a new filtration surface ( When the surface layer of the auxiliary layer is scraped off together with the capture metal catalyst, there arises a problem that the surface deletion amount of the auxiliary layer increases. If the sulfide slurry concentration of the metal catalyst is higher than the above concentration before the solid-liquid separation of the metal catalyst sulfide, dilute with water or the metal catalyst sulfide slurry after the solid-liquid separation with the filtrate. By carrying out, the slurry liquid concentration can be controlled within the above concentration range. The solid-liquid separation temperature is not particularly limited as long as it is in the same range as the metal catalyst deposition temperature.
[0029]
The filtrate after the solid-liquid separation is an aqueous solution in which various compounds other than the chelating agent are dissolved. Therefore, an inorganic acid is added to the filtrate to once precipitate a chelating agent, the chelating agent is solid-liquid separated, and then recycled again as an aqueous solution of the chelating agent with an inorganic hydroxide. Specifically, the filtrate from which the metal catalyst sulfide has been removed is mixed with an inorganic acid or an aqueous solution of an inorganic acid exemplified by hydrochloric acid, hydrobromic acid, phosphoric acid, phosphorous acid, sulfuric acid or sulfurous acid, and the pH value is adjusted. 4.0 or less, preferably 3.0 or less, and the chelating agent is a protonated solid. At this time, the higher the chelating agent concentration in the aqueous solution is, the higher the amount of the chelating agent that is precipitated, and thus the higher the chelating agent yield. The chelating agent can be deposited by either a batch method or a continuous method. In addition, the pH value is preferably adjusted by a method of controlling the amount of inorganic acid added while measuring with a pH meter. The precipitation temperature of the chelating agent is usually 20 to 70 ° C., preferably 30 to 50 ° C., and the precipitation time may be any condition as long as both solutions are uniformly mixed, and usually 1 to 120 minutes, preferably 5 to 60. Done in minutes.
[0030]
Once the solidified chelating agent is subjected to solid-liquid separation, it is separated from the filtrate. As a solid-liquid separation method, a normal centrifugal separation method, vacuum filtration method, or pressure filtration method may be selected as appropriate, and either a batch method or a continuous method may be employed. The solid-liquid separation temperature is not particularly limited, but it is preferably carried out within the range of the precipitation temperature of the chelating agent.
[0031]
The chelating agent separated from the filtrate is mixed with an aqueous solution of an inorganic hydroxide such as sodium hydroxide and potassium hydroxide to make an aqueous solution again. At this time, the amount of the inorganic hydroxide may be any amount as long as the solidified chelating agent dissolves, preferably two or more coordinations, more preferably three or more coordinations with respect to the chelating agent, Further, the concentration of the chelating agent aqueous solution after dissolution of the chelating agent is not particularly limited as long as it is a concentration equal to or lower than the solubility of the chelating agent. In this case, the pH value of the aqueous chelating agent solution is usually in the range of 7.1 to 14.0, preferably 7.5 to 12.0.
[0032]
Dissolution of the chelating agent after solid-liquid separation can be achieved by transferring the solid chelating agent to an independent tank and dissolving it by contact mixing with an alkaline aqueous solution, or by mixing the solid chelating agent and alkaline aqueous solution in a solid-liquid separator. Any method of dissolving may be used. In addition, when dissolving in a solid-liquid separator, if the dissolution time of the chelating agent is shorter than the alkaline aqueous solution introduction time, a method of circulating the filtrate multiple times in the solid-liquid separator and dissolving the solid chelating agent should be adopted. Can do.
[0033]
What is necessary is just to set the temperature and time for a chelating agent to melt | dissolve completely, and melt | dissolution temperature and melt | dissolution time should just set at 10-70 degreeC, 1-60 minutes, Preferably it is 30-50 degreeC, and the conditions for 5 to 30 minutes Done. Moreover, the obtained chelating agent aqueous solution is recycled to the reaction stopping step again while adjusting the concentration or in the same state.
[0034]
【Example】
The present invention will be described below by way of specific examples, but is not limited to these examples.
[0035]
Example 1
[Polyphenylene ether polymerization]
In a catalyst solution of 22 g of cupric bromide, 400 g of dibutylamine and 9800 g of toluene, a solution prepared by dissolving 2350 g of 2,6-dimethylphenol in 5400 g of toluene was supplied for 60 minutes while supplying air at 10 NL / min per 1 kg of monomer. Was added dropwise and polymerization was carried out at 40 ° C. 120 minutes after dropping the monomer, 1800 g of an aqueous solution in which 56 g of ethylenediaminetetraacetic acid 4 sodium salt was dissolved was added to the reaction solution while stirring to stop the reaction, and the reaction solution was extracted from the polymerization vessel. After stirring the reaction solution at 70 ° C. for 2 hours in a nitrogen atmosphere, the reaction solution and the aqueous solution were separated by a continuous centrifugal separator. Next, 1800 g of pure water was added to the separated reaction solution and stirred at 70 ° C. for 5 minutes, and then the reaction solution and the aqueous solution were separated using a continuous centrifuge. After mixing the two aqueous solutions obtained by the above operation, a metal catalyst recovery operation was performed.
[0036]
[Metal catalyst recovery]
The aqueous solution was concentrated by simple distillation to a copper concentration of 0.60% by weight, and a 10 wt% aqueous solution of sodium sulfide was added dropwise while measuring the oxidation-reduction potential with an ORP meter. Black copper sulfide began to precipitate with the addition of sodium sulfide, and the aqueous solution that had exhibited an initial blue color gradually turned yellow. The addition of the aqueous sodium sulfide solution was stopped when the slope of the change in the indicated value of the ORP meter with respect to the added amount of the aqueous sodium sulfide solution changed. At this time, the amount of sodium sulfide added was 1.15 times the mole of copper. The indicated value of the ORP meter at this time was used as a reference for adding the sodium sulfide aqueous solution. As a result of changing the concentration of the aqueous solution to a copper concentration of 0.2 to 1.72% by weight and varying the concentration of the sodium sulfide aqueous solution to 8 to 12% and performing the above titration operation, the sodium sulfide addition amount fluctuation value is in the number of moles of copper. On the other hand, it was 1.21 ± 0.7 times mol, and the amount of sodium sulfide added could be stably added regardless of fluctuations in copper concentration and sodium sulfide concentration.
[0037]
Comparative Example 1
The experiment was conducted in the same manner as in Example 1 except that the aqueous solution was concentrated to a copper concentration of 0.60% by weight and then the pH value was measured with a pH meter and a 10% by weight aqueous solution of sodium sulfide was added dropwise. I did it. The change in pH meter indicated value relative to the amount of sodium sulfide aqueous solution added was not clear, and the end point of addition of the sodium sulfide aqueous solution could not be determined.
[0038]
Example 2
By adjusting the copper sulfide slurry liquid (copper sulfide concentration 0.9 wt%) according to the method of Example 1, and using a suction filter (precoat filter) in which an auxiliary layer of diatomaceous earth (Radiolite # 600) is formed on the filtration surface, The filtration surface was immersed in a slurry liquid whose temperature was adjusted to 40 ° C., and suction filtration was performed for 40 seconds while reducing the pressure at −0.05 MPa. The filtration surface was separated from the slurry, and the suction was further stopped for 120 seconds.
Copper sulfide was uniformly adsorbed on the filtration surface, and a smooth surface of a new diatomaceous earth auxiliary layer appeared by cutting the diatomaceous earth auxiliary layer 1 mm thick, indicating good precoat filter properties.
[0039]
Example 3
An experiment was performed in the same manner as in Example 2 except that the copper sulfide concentration in the copper sulfide slurry was changed to 2.5 wt%.
Slight peeling of copper sulfide was observed from the filtration surface, and a smooth surface of a new diatomaceous earth auxiliary layer appeared by cutting the diatomaceous earth auxiliary layer 2 mm thick, indicating good precoat filter properties.
[0040]
Comparative Example 2
The same method as in Example 2 was used except that a suction filter having a felt layer with a filtration surface of 10 mm in thickness was used.
A large amount of copper sulfide remained without peeling from the filtration surface. In addition, copper sulfide entered the felt layer, indicating that the filtration characteristics were poor.
[0041]
Comparative Example 3
The same method as in Example 2 was used except that a suction filter having a 1 mm-thick polypropylene cloth (air permeability: 12 cm ³ / cm ² · s) was used.
A large amount of copper sulfide remained on the filter cloth without peeling off from the filtration surface. Moreover, it was shown that a large amount of copper sulfide leaked into the filtrate, and the filtration characteristics were poor.
[0042]
【The invention's effect】
According to the method of the present invention, when an alkali metal sulfide is added to a metal catalyst chelate compound-containing aqueous solution, the alkali metal sulfide is measured by measuring the oxidation-reduction potential of the metal catalyst chelate compound-containing aqueous solution. Since the amount of the product added can be controlled, the metal catalyst can be recovered 100% even when there is a change in the quality of the alkali metal sulfide, and the generation of hydrogen sulfide can be minimized. It has the effect of being able to do it.

Claims (5)

A polyphenylene ether solution obtained by polymerization in the presence of a catalyst in a water-insoluble polymerization solvent for polyphenylene ether is brought into contact with an aqueous chelating agent solution to form a metal catalyst chelate compound to terminate the polymerization, thereby chelating the metal catalyst. A method for producing polyphenylene ether, comprising separating a compound-containing aqueous solution from a polyphenylene ether solution and adding an alkali metal sulfide to the chelate compound-containing aqueous solution of the metal catalyst to precipitate the metal catalyst as a solid from the aqueous solution as a sulfide. In addition, when the alkali metal sulfide is added to the chelate compound-containing aqueous solution of the metal catalyst, the amount of the alkali metal sulfide added is measured by measuring the oxidation-reduction potential of the chelate compound-containing aqueous solution of the metal catalyst. controls and rotary type continuous to form a filter aid layer on the filtering surface Method for producing a polyphenylene ether, which comprises solid-liquid separation of sulfides of a metal catalyst by the air filtration system.  The method for producing polyphenylene ether according to claim 1, wherein the gas discharge destination of the tank in which the alkali metal sulfide is mixed with the chelate compound-containing aqueous solution is a scrubber made of the alkaline aqueous solution.  The method for producing a polyphenylene ether according to claim 2, wherein when the metal catalyst sulfide is solid-liquid separated by a continuous vacuum filtration method using a filter aid, the sulfide concentration of the metal catalyst is 2 wt% or less based on the total weight. .  The method for producing a polyphenylene ether according to claim 1, wherein the metal catalyst is a copper compound.  An inorganic acid is added to the filtrate obtained after solid-liquid separation of the sulfide of the metal catalyst, and the chelating agent is precipitated from the aqueous solution by adjusting the pH to 3 or less, so that the solidified chelating agent and the metal hydroxide The method for producing a polyphenylene ether according to claim 1, wherein the aqueous solution is mixed to dissolve the chelating agent.