JP2004262987A

JP2004262987A - Method for producing acrylonitrile-containing copolymer and resin composition

Info

Publication number: JP2004262987A
Application number: JP2003052415A
Authority: JP
Inventors: Yuichi Matsumoto; 祐一松本; Kaname Sato; 要佐藤
Original assignee: Asahi Kasei Chemicals Corp
Current assignee: Asahi Kasei Chemicals Corp
Priority date: 2003-02-28
Filing date: 2003-02-28
Publication date: 2004-09-24

Abstract

【課題】アクリロニトリル含有率が比較的高い共重合体を製造するときに、成形品の黄色味が極めて少なく、かつ、透明性などの外観品質に優れる樹脂組成物を得る。
【解決手段】アクリロニトリル単量体２５〜６０重量％、芳香族ビニル系単量体４０〜７５重量％及び、他の共重合可能なビニル化合物単量体０〜３５重量％の単量体混合液１００重量部と、反応に不活性な有機溶剤０〜５０重量部、重合開始剤との混合物からなる原料液を、反応槽の上部気相部へスプレーノズル等を用いて散布し、強制攪拌反応槽へ連続的に供給して重合せしめ、外部凝縮器を通して反応槽内の単量体等蒸気を凝縮させ、該凝縮液を原料単量体又は原料液の一部と混合して連続的に反応槽へ供給するに際し、該反応槽の底部から重合体液面レベルの１／３以下の高さ範囲で、少なくとも１ヶ所以上の注入口から供給することを特徴とするアクリロニトリル含有共重合体の製造方法。
【選択図】なしAn object of the present invention is to obtain a resin composition having an extremely low yellowish tint and excellent appearance such as transparency when producing a copolymer having a relatively high acrylonitrile content.
A monomer mixture of 25 to 60% by weight of an acrylonitrile monomer, 40 to 75% by weight of an aromatic vinyl monomer, and 0 to 35% by weight of another copolymerizable vinyl compound monomer. A raw material liquid composed of a mixture of 100 parts by weight, 0 to 50 parts by weight of an organic solvent inert to the reaction, and a polymerization initiator is sprayed onto the upper gas phase of the reaction tank using a spray nozzle or the like, and a forced stirring reaction is performed. It is continuously supplied to the tank to polymerize it, the vapor of the monomer and the like in the reaction tank is condensed through an external condenser, and the condensate is mixed with the starting monomer or a part of the starting liquid to continuously react. A method for producing an acrylonitrile-containing copolymer, wherein the acrylonitrile-containing copolymer is supplied from at least one inlet at a height range of 1/3 or less of the polymer liquid level from the bottom of the reaction tank. .
[Selection diagram] None

Description

【０００１】
【発明の属する技術分野】
本発明はアクリロニトリル含有共重合体の改良された連続塊状又は溶液重合方法、及び成形加工時の黄色味が従来製法による同じアクリロニトリル含有率の共重合体と比べて極めて少なく、かつ透明性等の外観特性に優れる樹脂組成物に関する。さらに詳しくは、アクリロニトリル含有共重合体を製造するに際し、反応槽内で発生する重合熱や攪拌混合熱を重合体液の蒸発潜熱等により効率的に除去するプロセスにおいて、反応槽内で発生する蒸発ガスを反応槽外の熱交換器で凝縮し、該凝縮液を反応槽下部液相へ戻すに際して、該反応槽の最低部から重合体液面レベルの１／３以下の高さ範囲で、少なくとも１ヶ所以上の注入口から供給することによって、強制攪拌条件下で重合体液中にアクリロニトリル単量体が一様に分散している条件下で反応せしめ、該共重合体中のアクリロニトリル組成分布を均一化し、成形加工時の黄色味が少なく、かつ、透明性等の外観特性に優れる熱可塑性樹脂の製造方法、並びに熱可塑性樹脂組成物に関するものである。
【０００２】
【従来の技術】
スチレン−アクリロニトリルを主成分とする共重合体、いわゆるＳＡＮ樹脂は、その優れた耐薬品性、剛性、成形性などの諸性質を有することから、幅広い分野で使用されている。これらの共重合体の製造方法としては、乳化重合、懸濁重合、塊状重合、溶液重合等の各種の重合方法によって製造することができる。しかしながら、乳化重合の場合は乳化剤を使用するために、重合生成物の透明性、着色変色の点で外観品質上の問題があり、また、アクリロニトリルが水に溶解し易いために均一な組成の重合生成物を得ることが困難である。懸濁重合の場合にも、分散剤等を使用して水系で重合を行う為に上記と同様の問題が発生する。さらに水系を媒体とするために、重合反応温度の制御は優れているが、連続的に重合することが容易ではなく、そのために非水系重合方法に比べ生産性に劣る。また、これらの重合方法では、設備から排出される排水などによる水質汚濁などの問題もあり、近年では、環境問題、製造コストなどの観点から、連続塊状、溶液重合が注目されている。
【０００３】
塊状、溶液重合の場合は、原料単量体単独または原料単量体を有機溶剤に溶解して重合を行うが、重合後において溶媒や未反応単量体を除去して重合体を得るため、分散剤などによる重合生成物の着色変色や透明性の問題や、アクリロニトリルが水に溶解し易いため均一な組成の重合生成物が得られないという問題点が発生しない。また、回収される溶剤や単量体は、再利用するために排出することがない利点がある。従って、スチレン−アクリロニトリル系共重合体の工業的製造には、塊状重合、溶液重合が採用され、しかも、連続的に実施されることが多い。
【０００４】
しかしながら、工業的生産規模で連続的に塊状重合または溶液重合を行う場合には、高転化速度で重合を行うと、反応熱、攪拌熱などの発生熱の除去が困難になり生産性に制約を受ける。また、ＳＡＮ樹脂の重合において、アクリロニトリルの含有量が多いアゼオトロープ組成を大きく超える組成では、均一組成での重合が困難になり、樹脂製品の色調や透明性等の外観品質に優れる樹脂を得ることが難しくなる。これらの問題点を解決するため、単量体と溶剤などの蒸発潜熱を利用する重合方法（例えば、特許文献１、特許文献２）が開示されている。更に、ＳＡＮ樹脂を連続塊状又は溶液重合で製造する場合に、反応熱等を単量体の蒸発潜熱で除去し、かつ、アクリロニトリル／スチレン組成比一定の重合体を得る方法（例えば、特許文献３）や強制攪拌反応槽を用いた重合法が提案されている。
【０００５】
蒸発潜熱を利用する方法では、気相部と重合体液の気液界面からの蒸発による除熱、または必要に応じて、蒸発した溶剤と未反応単量体を反応槽外部の凝縮器で冷却し、反応槽内へ環流することにより効率的に除熱できるため、高転化速度での重合が可能になるので工業的生産規模の重合法として好ましい。
このような蒸発潜熱を利用した除熱の場合、重合体液中の各成分の蒸気圧差により、蒸発ガス中には原料液より低沸点成分が多く含まれ、凝縮液と重合体液との間に組成差が発生する。例えば、スチレン−アクリロニトリル単量体と芳香族系有機溶剤からなる原料液では、反応槽内で発生する蒸発ガス中のアクリロニトリル濃度が必然的に原料液中のアクリロニトリル濃度より高くなる。従って、蒸発ガスを凝縮してアクリロニトリル濃度の高い凝縮液を反応槽に戻すと均一組成での重合が困難になり、スチレン−アクリロニトリル系共重合体のアクリロニトリル組成分布が広くなる。
【０００６】
特に、アゼオトロープ組成近傍若しくはそれ以上のアクリロニトリル含有濃度の高いスチレン−アクリロニトリル系共重合体を製造する場合、該凝縮液中のアクリロニトリル濃度は原料液に比べて著しく高くなり、反応槽に戻すと均一組成での重合が益々困難になる。更に具体的には、高アクリロニトリル含有凝縮液を反応槽中に戻して重合すると、スチレン−アクリロニトリル系共重合体のアクリロニトリル組成分布において、分布が広がり、かつ、アクリロニトリル含有量の高い共重合体の割合が増える。（「アクリロニトリル含有量の高い側に分布が広がる」とは、アクリロニトリル含有量の高い共重合体の割合が増えるということである。傾向が強くなって、それによって得られた共重合体を成形加工した時に黄色味が少なく、かつ、透明性等の外観品質に優れる樹脂製品が得られなかった。
【０００７】
従来、スチレン−アクリロニトリル系共重合体の製造方法において、反応槽の液面から発生する単量体蒸気をコンデンサーで凝縮、液化させつつ反応器内に還流する際、凝縮液中に原料液の一部又は芳香族ビニル系単量体を追加補充することにより、アクリロニトリル含有比をさげて重合体液の組成を均一化する方法（例えば、特許文献４）が開示されているが、この方法では重合転化速度を３０重量％／ｈｒ以内に保持させるという制限条件があり生産性において必ずしも充分でなかった。
【０００８】
また、重合器のコンデンサーから環流する凝縮液を、大気圧における沸点が１２０℃以下である凝縮液成分の濃度が合計６５重量％以上になるように調整して、これを重合器の気相部にスプレーして戻す方法（例えば、特許文献５）が開示されているが、この方法では蒸発潜熱による除熱能力は良いものの、気相部のアクリロニトリル濃度が極めて高くなり、外観品質に優れる樹脂製品が得られなかった。
【０００９】
【特許文献１】
特開昭４８−１７５８４号公報
【特許文献２】
特開昭４９−７３９３号公報
【特許文献３】
特開昭５８−２９８０７号公報
【特許文献４】
特開平５−２５５４４８号公報
【特許文献５】
特開２０００−２２６４１７号公報
【００１０】
【発明が解決しようとする課題】
アゼオトロープ組成近傍若しくはそれ以上の比較的アクリロニトリル含有率の高い、アクリロニトリル含有共重合体を製造するに際しては、反応槽内で発生する重合熱や攪拌熱を重合体液の蒸発潜熱等によって除去し、かつ、反応槽内で発生する蒸発ガスを反応槽外部の熱交換器で凝縮し該凝縮液を反応槽に戻すプロセスにおいて、重合体液と該凝縮液との混合によって生じるアクリロニトリル含有率差（組成差）が均一組成での重合を困難にし、スチレン−アクリロニトリル系重合体のアクリロニトリル組成分布が広がり、アクリロニトリル含有量の高い共重合体の割合が増え、得られた共重合体を成形加工したときの黄色度が増加し、かつ、透明性等の外観品質も劣化し製品価値が著しく損なわれた。すなわち、本発明の課題は、アクリロニトリル含有共重合体の製造方法により、アクリロニトリル含有率が比較的高い共重合体を製造するときに、成形品の黄色味が極めて少なく、かつ、透明性などの外観品質に優れる樹脂組成物を得ることにある。
【００１１】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意検討を重ねた結果、成形加工したときの黄色度が増加し、かつ、透明性等の外観品質が劣化する要因は、重合体液の組成差、更に具体的には、重合体液中におけるアクリロニトリル含有率（濃度）の不均一性によるものであり、次の方法により、上記課題が解決されることを見出した。即ち、本発明は、
１．アクリロニトリル単量体２５〜６０重量％、芳香族ビニル系単量体４０〜７５重量％及び、他の共重合可能なビニル化合物単量体０〜３５重量％（単量体合計で１００重量％とする）の単量体混合液１００重量部と反応に不活性な有機溶剤０〜５０重量部、重合開始剤からなる原料液を、反応槽の上部気相部へスプレーノズル等を用いて散布し、反応槽の攪拌軸に取り付けたトルク計と回転数から計測される攪拌動力（ＫＷ）を、攪拌を受ける反応槽内の重合体液の容量（ｍ^３）で除して得られる攪拌所要動力が２〜２０ＫＷ／ｍ^３である強制攪拌反応槽へ連続的に供給して重合せしめ、反応槽上部の気相空間部に開口する配管から外部凝縮器を通して反応槽内の単量体等蒸気を凝縮させ、該凝縮液を原料単量体又は原料液の一部と混合して連続的に反応槽へ供給するに際し、該反応槽の底部から重合体液面レベルの１／３以下の高さ範囲で、少なくとも１ヶ所以上の注入口から供給することを特徴とするアクリロニトリル含有共重合体の製造方法。
【００１２】
２．アクリロニトリル含有共重合体において、液体クロマトグラフ測定による、下記の式（Ｉ）で定義されるアクリロニトリル組成分布を示すＷ値が、下記の式（ＩＩ）を満足する範囲であることを特徴とする請求項１記載のアクリロニトリル含有共重合体の製造方法。
Ｗ＝Ａ／ｈ（Ｉ）
式（Ｉ）中、Ａは液体クロマトグラフによる溶出曲線上アクリロニトリル組成分布積算面積、ｈは同分布のピーク高さを示す。
Ｗ＜０．９２×ＡＮ＋１４（ＩＩ）
式（ＩＩ）中のＡＮは、アクリロニトリル含有共重合体中のアクリロニトリル含有量（重量％）を示す。
【００１３】
３．芳香族ビニル単量体がスチレンであり、他の共重合可能なビニル単量体がアルキルアクリレートであることを特徴とする、請求項１〜２何れか記載のアクリロニトリル含有共重合体の製造方法。
４．請求項１〜３の製造方法で得られたアクリロニトリル含有共重合体。
５．請求項１〜３の製造方法で得たれたアクリロニトリル含有率が２５重量％以上のアクリロニトリル含有共重合体において、成形加工された製品プレートにおける黄色度、即ちＹＩ値（合計厚みが１０ｍｍ以上となるよう製品プレートを重ねて、日本工業規格；Ｋ７１０５−１９８１に準拠したイエローインデックス測定値；ＹＩ値）が、下記の式（ＩＩＩ）を満足する範囲であることを特徴とするアクリロニトリル含有共重合体。
ＹＩ＜０．００６４×ＡＮ^{１．９９４}＋２（ＩＩＩ）
式（ＩＩＩ）中のＡＮは、アクリロニトリル含有共重合体中のアクリロニトリル含有量（重量％）を示す。
【００１４】
以下、本発明を更に詳細に説明する。本発明におけるアクリロニトリルの使用量は、単量体合計中２５重量％〜６０重量％、好ましくは３０重量％〜６０重量％である。アクリロニトリルが６０重量％を越えると得られる共重合体の黄色味が著しく強くなり、かつ、透明性等の外観品質が悪くなり商品価値が低下する。アクリロニトリルが２５重量％未満の場合は、黄色味や外観品質が低下することは少ない。
【００１５】
芳香族ビニル系単量体としては、例えば、スチレン、α−メチルスチレン、３，５−ジメチルスチレン、４−メトキシスチレン、２−ヒドロキシスチレンなどの置換基を有する置換スチレン、α−ブロムスチレン、２，４−ジクロロスチレンなどのハロゲン化スチレン、１−ビニルナフタレンなどが挙げられ、一般的にはスチレンを用いるが、２種以上を混合して用いることもできる。
これらの芳香族ビニル単量体の使用量は、単量体合計中４０重量％から７５重量％、好ましくは、４０重量％〜７０重量％である。芳香族ビニル単量体が４０重量％未満であると、得られる共重合体の黄色味が著しく強くなり、かつ、透明性等の外観品質が悪くなり商品価値が低下する。芳香族ビニル単量体が７５重量％を越えると、黄色味や外観品質が低下することは少ない。
【００１６】
アクリロニトリルと芳香族ビニル系単量体と共重合可能な他のビニル化合物としては、例えば、メチルメタクリレート、エチルメタクリレート、メチルアクルレート、エチルアクリレート、ブチルアクリレート（ＢＡ）などのアクリル酸エステル類、アクリル酸、メタクリル酸、無水マレイン酸、イタコン酸等の不飽和カルボン酸またはその無水物、Ｎ−フェニルマレイミド、Ｎ−シクロヘキシルマレイミドなどのマレイミド化合物などが挙げられ、特にエチルアクリレート、ブチルアクリレートが好ましく、これらの２種以上を混合して用いることもできる。これらのビニル化合物の使用量は、単量体合計中０重量％〜３５重量％、好ましくは、０重量％〜３０重量％である。３５重量％を越えると、得られる共重合体の熱的特性や力学特性が低下する。
【００１７】
溶液重合の場合、用いられる有機溶剤は、反応に不活性である有機溶剤であり、反応槽内における未反応単量体及び／又は、重合し生成する共重合体と有機溶剤とが重合温度の反応槽内の組成において均一相となる有機溶剤であればいずれの有機溶剤でも使用できる。
この有機溶剤としては、例えば、エチルベンゼン、トルエン等の芳香族炭化水素類、その他、クロロホルム、ジクロルメチレン、四塩化炭素などのハロゲン化炭化水素類、メチルエチルケトン、メチルプロピルケトン、ジエチルケトン、メチルイソブチルケトン、ジプロピルケトン、メチルアミルケトン、シクロヘキサノン、メチルシクロヘキサノン、アセチルアセトン等のケトン類、その他、アセトニトリル、ジメチルホルムアミドなどが挙げられる。好ましくは、エチルベンゼン、トルエン等の芳香族炭化水素、メチルエチルケトン、メチルイソブチルケトン等のケトン類である。また、これらは単独または２種以上の混合物として使用できる。有機溶剤の使用量は、通常、単量体混合物の総量１００重量部に対して、０〜５０重量部が好ましい。有機溶剤の使用量が５０重量部を越えると、得られる共重合体の収率が低下し、製造コストが高くなって好ましくない。
【００１８】
本発明において必要に応じて添加する重合開始剤には、公知の重合開始剤が使用でき、例えば、ｔ−ブチルパーオキシ３，３，５−トリメチルヘキサノエート、ｔ−ブチルパーオキシ−２−エチルヘキサノエート、ｔ−ブチルパーオキシラウレート、１，１，３，３−テトラメチルブチルパーオキシ−２−エチルヘキサノエート等のパーオキシエステル類、ジ−オクタノイルパーオキサイド、ジ−ラウロイルパーオキサイドなどのジアシルパーオキサイド類などの有機過酸化物、２，２−アゾビスイソブチロニトリル、２，２−アゾビス（２−メチルブチロニトリル）、ジメチル２，２’−アゾビス（２−メチルプロピオネート）、２−（カルバモイルアゾ）−イソブチロニトリル、４，４’−アゾビス（４−シアノペンタン酸）、２，２’−アゾビス（２，４−ジメチルバレロニトリル）、２，２−アゾビス（４−メトキシ−２，４ジメチルバレロニトリル）、２，２’−アゾビス［２−（ヒドロキシメチル）プロピオニトリル］、１，１−アゾビス（シクロヘキサン−１−カルボニトリル）などのアゾ系重合開始剤があげられる。
【００１９】
本発明における、連続重合を行わせる重合装置は、強制攪拌型反応槽であり、反応系ができる限り均一に近い状態にするため攪拌翼をもちいるが、その攪拌翼は通常、パドル型翼、ピッチパドル型攪拌翼、ヘリカル型攪拌翼、ダブルヘリカル型攪拌翼、リボン型攪拌翼、タービン型攪拌翼、スクリュー型攪拌翼、錨型攪拌翼、マックスブレンド型攪拌翼、フルゾーン型攪拌翼等が用いられる。
さらに、該反応槽に設置される攪拌軸に取り付けられるトルク計と回転数から計算される攪拌動力（ＫＷ）を、攪拌を受ける反応槽内の重合体液の容量（ｍ^３）で除して得られる攪拌強度を用いて反応液内の攪拌の目安とする。反応系内での強制攪拌による重合体液の組成均一化は、少なくとも攪拌強度２ＫＷ／ｍ^３以上で攪拌することが必要である。また、２０ＫＷ／ｍ^３を越えると攪拌熱で温度制御が困難になり好ましくない。
【００２０】
以下に図面を示して本発明を更に詳細に説明する。図１は、本発明の実施に用いる反応槽とその付属品の一例を示す概念図である。１は反応槽であり、攪拌翼による渦の発生を抑えるためにその壁面に邪魔板がついてもよく、２は単量体と有機溶剤の混合物である原料液の入口配管、３は反応槽上部の気相部への原料液散布用スプレー、４は蒸気抜き出し量調節弁であり、反応槽内部の圧力を一定に保ち、結果として重合温度を一定に保つ、５は反応槽の外部に設置された凝縮器であり、反応槽より抜き出された蒸気を凝縮させる。６は原料液の一部を凝縮液に加えるための配管、７は原料液と凝縮液を均一混合する混合器、８は凝縮液及び加えられた供給液を反応槽に戻すポンプ、９は反応槽下部の液相部への供給配管、１０ａ〜１０ｃはストップ弁、１１は攪拌機の攪拌翼、１２は攪拌機モーター、１３は重合体液の出口配管、１４は気相部、１５は重合体液、１６は重合体液の液面レベルを示す。
【００２１】
本発明において、反応槽内で発生する蒸発ガスを反応槽外の熱交換器で凝縮し、重合体液中の未反応原料液よりもアクリロニトリル濃度の高い凝縮液を、反応槽下部液相へ戻す時に、当該凝縮液を原料液の一部と混合してアクリロニトリル濃度を下げてから、反応槽底部から重合体液面レベルの１／３以下の高さ範囲で、少なくとも１ヶ所以上の注入口から反応槽内の重合体液中に戻す。
重合体液面レベルの１／３を越えた高さ範囲で当該混合液を重合体液へ戻して重合すると、得られる共重合体中のアクリロニトリル組成分布が広がり、かつ、アクリロニトリル含有量の高い共重合体の割合が増えて好ましくない。原料液の一部と混ぜて凝縮液を戻す時の混合液中におけるアクリロニトリル濃度は、原料液のアクリロニトリル濃度以上であり、原料液と凝縮液における２液のアクリロニトリル濃度の中間濃度以下が好ましい。中間濃度を超えて当該混合液を反応槽内の重合体液に戻すと、得られる共重合体中のアクリロニトリル組成分布が広がり、かつ、アクリロニトリル含有量の高い共重合体の割合が増えて好ましくない。
【００２２】
反応槽内の液相最上部、即ち気液界面は、蒸発ガスの気相部壁面での凝縮により、高濃度のアクリロニトリル含有凝縮液が壁面を伝って滴下し、常時、液相中で最もアクリロニトリル濃度が高い状態となっている。気液界面におけるアクリロニトリルの高濃度化を抑制するために、通常、原料液を反応槽上部の気相部壁面へスプレー散布したり、攪拌翼を使用して反応槽内の重合体液を強制攪拌して、アクリロニトリル濃度の均一化を施しているが、これだけでは充分ではない。
【００２３】
従来製法より成形加工時の黄色味が少なく、かつ、透明性等の外観特性に優れるアクリロニトリル含有共重合体を得るためには、強制攪拌条件下において反応槽内の気液界面のアクリロニトリル濃度と気液界面以外の反応液中のアクリロニトリル濃度とがバランスするよう、凝縮液を原料液の一部と混ぜてアクリロニトリル濃度を調整し、反応槽液相の最底部から重合体液面レベルの１／３以下の高さ範囲で、少なくとも１ヶ所以上の注入口から供給することが必要である。具体的には、製造する該共重合体のアクリロニトリル含有率に応じて、蒸気凝縮液器５で発生した凝縮液と原料液との混合液を供給配管９に通じて、反応槽に設置されたストップ弁１０ａ〜１０ｃの開閉によって、所定の注入位置から供給することによって達成される。
本発明において、反応槽から抜き出される重合体液から、未反応単量体、有機溶剤を除去して共重合体を回収する方法としては、反応液を予熱して減圧下でフラッシングする方法が好ましい。
【００２４】
【実施例】
以下に実施例及び比較例により本発明をさらに詳細に説明する。尚、本発明はこれらの実施例などにより何ら限定されるものではない。最初に本発明で用いた分析および評価方法について説明する。
〔ポリマー中アクリロニトリル含有率の測定〕
装置：熱分解ガスクロマトグラフＧＣ−１７Ａ（島津製作所製）
熱分解装置ＰＹＲ−２Ａ（島津製作所）
カラム：溶融シリカキャピラリーカラムＤＢ−１７
検出器：水素炎イオン化検出器
方法：ポリマー試料０．６〜０．８ｍｇ秤量し、熱分解炉にて加熱分解処理。
その後、気化物質をガスクロマトグラフに導入してアクリロニトリル含有量を測定した。
【００２５】
〔アクリロニトリル組成分布の分析〕
装置：高速液体クロマトグラフＬＣ−６Ａ（島津製作所製）
カラム：ＺＯＲＢＡＸＣＮ（移動相；ＴＨＦ）
検出器：２５４ｎｍ出力；０．４Ｖ／ＡＵ
方法：樹脂ペレット０．５ｇをＴＨＦ４０ｇに溶解し、２０μｌ注入。クロマトグラフによる溶出曲線から、アクリロニトリル組成分布の積算面積をＡとし、同分布のピーク高さをｈとして、アクリロニトリル組成分布を表すＷ値；
Ｗ＝Ａ／ｈ（Ｉ）
を算出した。式（Ｉ）より得られたＷ値を共重合体中のアクリロニトリル組成分布の指標とすると、同じアクリロニトリル含有量（重量％）でＷ値がより小さければ、共重合体中のアクリロニトリル組成分布幅が狭いことを示す。
【００２６】
実験結果から得られた共重合体のアクリロニトリル含有量（重量％）とＷ値の関係を図２に示す。図２に示される様に、共重合体中のアクリロニトリル含有量（重量％）が増すと一定の比率でＷ値が増加し、アクリロニトリル組成分布幅が広がり、かつ、アクリロニトリル含有量の高い共重合体の割合が増えることが明らかになった。更に、本発明により、従来法では得られない、下記の式（ＩＩ）を満足するようなアクリロニトリル組成分布幅の狭い、アクリロニトリル含有共重合体を得ることができた。
Ｗ＜０．９２×ＡＮ＋１４（ＩＩ）
式（ＩＩ）中のＡＮは、共重合体中のアクリロニトリル含有量（重量％）を示す。実験結果を表１，２にまとめた。
【００２７】
〔イエローインデックスの評価方法〕
規格：日本工業規格Ｋ７１０５−１９８１準拠
方法：型締力３０トン−射出成形機（名機製作所製）、肉厚１／８インチの平板プレート金型を用いて、成形温度２２０℃で平板プレートを成形。得られた平板プレートを４枚重ねてイエローインデックスを測定した。
測定装置：スペクトラフラッシュ５００（データーカラーインターナショナル社製）
ＹＩ（イエローインデックス）値の換算方法
ＹＩ＝〔１００（１．２８Ｘ−１．０６Ｚ）〕／Ｙ
ＹＩ：黄色度（ＹＩ値が大きいほど、樹脂成形品の黄色味が強くなる。）
Ｘ，Ｙ，Ｚ：標準Ｃ光源における３刺激値（赤，緑，青）
【００２８】
実験結果から得られた共重合体のアクリロニトリル含有量（重量％）とＹＩ値の関係を図３に示す。図３に示される様に、共重合体中のアクリロニトリル含有量（重量％）が増すと一定の比率でＹＩ値が増加することが明らかになった。更に、本発明により、従来法では得られない、下記の式（ＩＩＩ）を満足するような、成形加工された時に黄色味の少ないアクリロニトリル含有共重合体を得ることができた。
ＹＩ＜０．００６４×ＡＮ^{１．９９４}＋２（ＩＩＩ）
式（ＩＩＩ）中のＡＮは、共重合体中のアクリロニトリル含有量（重量％）を示す。
実験結果を表１，２にまとめた。
【００２９】
〔くもり度（Ｈａｚｅ）の評価方法〕
規格：ＡＳＴＭＤ１７４６
方法：イエローインデックスと同様の方法で得られた平板プレート１枚をサンプルとし、須賀試験器（株）製のＳＭ−３にて、くもり度（Ｈａｚｅ，透過散乱光の強度）を測定した。
【００３０】
【実施例１】
〔反応槽〕図１に示す
・反応槽容量１９０ｌ
・攪拌翼：マックスブレンド攪拌翼
〔反応条件〕
・原料液中の単量体組成ＳＴ／ＡＮ＝７５／２５重量％
（ＳＴ；スチレンＡＮ；アクリロニトリル）
・溶剤量（エチルベンゼン）２０重量部
・重合開始剤（２，２−アゾビス（２−メチルブチロニトリル））０．０５重量部
・重合温度１４０℃
【００３１】
原料液は、反応槽上部気相部へスプレー散布する配管２と蒸気凝縮器５で発生する凝縮液と混合するための配管６に分けて反応槽へ供給した。更に該凝縮液と原料液の混合液を反応槽下部液相へ供給するために、ストップ弁１０ｃを開けて残りの１０ａと１０ｂは閉止した。表１に原料フィード組成とフィード流量、反応槽内での重合温度、蒸発ガスの凝縮器出口での組成、並びに、原料液と凝縮液の混合液を反応槽液相部へ戻す際の供給弁と供給する混合液の組成他を重合条件として示した。
重合運転中は反応槽容量に対する重合体液の充填率が５５〜６５容積％の範囲を維持するようにし、原料液供給量と同量の重合体液を連続的に抜き出した。重合時の反応槽内における攪拌機の攪拌所要動力、並びに、重合転化速度を表２に示した。反応槽から抜き出した重合体液を、揮発分を除去するため予め２３０℃に加温されたプレート式熱交換器を通じつつ、１．５ｋＰａの高真空タンク中にフラッシング処理した。
【００３２】
得られたポリマーを液体クロマトグラフによって、アクリロニトリル組成分布を測定したところ、Ｗ値が３３であった。更に、射出成形機において成形温度２２０℃で成形した平板プレートにてイエローインデックスを測定したところ、ＹＩ値が４．１であり黄色味が非常に少ないものであった。また、該平板プレートの透明性はＨａｚｅ＝１％未満で非常に良好であった。高い重合転化率でかつロスが少なく効率よく得られた。結果を表２にまとめた。
【００３３】
【実施例２】
凝縮液と原料液の混合液を反応槽下部液相へ供給するために、ストップ弁１０ｂを開けて残りの１０ａと１０ｃは閉止し、それ以外は全て実施例１と同一条件で重合運転を実施した。その結果、得られたポリマーのＷ値は３４、成形加工された平板プレートの黄色度を示すＹＩ値は４．８であり黄色味が少なく、透明性もＨａｚｅ＝１％未満で非常に良好であった。
【００３４】
【比較例１】
凝縮液と原料液の混合液を反応槽下部液相へ供給するために、ストップ弁１０ａを開けて残りの１０ｂと１０ｃは閉止し、それ以外は全て実施例１と同一条件で重合運転を実施した。その結果、得られたポリマーのＷ値は４０であり、アクリロニトリル含有共重合体中のアクリロニトリル含有量２５重量％での式（ＩＩ）より算出されるＷ値３７を超えていた。そして、成形加工された平板プレートのＹＩ値は６．５であり実施例１，２に比べ黄色度が強く、透明性もＨａｚｅ＝３％となり、実施例１，２に比べ悪化した。
【００３５】
【実施例３，４】
原料液中の単量体組成をＳＴ／ＡＮ＝６９／３１（重量％）として、実施例１，２と同様に重合運転を実施した。実施例３では凝縮液と原料液の混合液をストップ弁１０ｃから、実施例４ではストップ弁１０ｂから反応槽下部液相へ供給した。その結果、表２に示したように得られたポリマーはＷ値が低い、アクリロニトリル組成分布が狭いポリマーであった。更に、成形加工された平板プレートでの黄色味が少なく、透明性もＨａｚｅ＝１％未満で非常に良好であった。
【００３６】
【比較例２】
凝縮液と原料液の混合液を反応槽下部液相へ供給するために、ストップ弁１０ａを開けて残りの１０ｂと１０ｃは閉止し、それ以外は全て実施例３，４と同一条件で重合運転を実施した。その結果、得られたポリマーのＷ値は４５であり、アクリロニトリル含有共重合体中のアクリロニトリル含有量３０重量％での式（ＩＩ）より算出されるＷ値４１．６を超えていた。そして、成形加工された平板プレートのＹＩ値は８．２であり実施例３，４に比べ黄色度が強く、透明性もＨａｚｅ＝５％となり、実施例３，４に比べ悪化した。
【００３７】
【実施例５，６】
原料液中の単量体組成をＳＴ／ＡＮ＝５０／５０（重量％）として、実施例１，２と同様に重合運転を実施した。実施例５では凝縮液と原料液の混合液をストップ弁１０ｃから、実施例６ではストップ弁１０ｂから反応槽下部液相へ供給した。その結果、表２に示したように得られたポリマーはＷ値が低い、アクリロニトリル組成分布が狭いポリマーであった。更に、成形加工された平板プレートでの黄色味が少なく、透明性もＨａｚｅ＝１％未満で非常に良好であった。
【００３８】
【比較例３】
凝縮液と原料液の混合液を反応槽下部液相へ供給するために、ストップ弁１０ａを開けて残りの１０ｂと１０ｃは閉止し、それ以外は全て実施例５，６と同一条件で重合運転を実施した。その結果、得られたポリマーのＷ値は６０であり、アクリロニトリル含有共重合体中のアクリロニトリル含有量４０重量％での式（ＩＩ）より算出されるＷ値５０．８を超えていた。そして、成形加工された平板プレートのＹＩ値は１５．５であり実施例５，６に比べ黄色度が強く、透明性もＨａｚｅ＝８％となり、実施例５，６に比べ悪化した。
【００３９】
【実施例７，８】
原料液中の単量体組成をＳＴ／ＡＮ／ＢＡ＝４５／４５／１０（重量％）として、実施例１，２と同様に重合運転を実施した。実施例７では凝縮液と原料液の混合液をストップ弁１０ｃから、実施例８ではストップ弁１０ｂから反応槽下部液相へ供給した。その結果、表２に示したように得られたポリマーはＷ値が低い、アクリロニトリル組成分布が狭いポリマーであった。更に、成形加工された平板プレートでの黄色味が少なく、透明性もＨａｚｅ＝１％未満で非常に良好であった。
【００４０】
【比較例４】
凝縮液と原料液の混合液を反応槽下部液相へ供給するために、ストップ弁１０ａを開けて残りの１０ｂと１０ｃは閉止し、それ以外は全て実施例７，８と同一条件で重合運転を実施した。その結果、得られたポリマーのＷ値は５６であり、アクリロニトリル含有共重合体中のアクリロニトリル含有量４０重量％での式（ＩＩ）より算出されるＷ値５０．８を超えていた。そして、成形加工された平板プレートのＹＩ値は１４．５であり実施例７，８に比べ黄色度が強く、透明性もＨａｚｅ＝７％となり、実施例７，８に比べ悪化した。
【００４１】
【表１】

【００４２】
【表２】

【００４３】
【発明の効果】
本発明のアクリロニトリル含有共重合体の製造方法によれば、アクリロニトリル含有率が比較的高い共重合体を製造するときに、成形品の黄色味が極めて少なく、かつ、透明性などの外観品質に優れる樹脂組成物が、高い重合転化率でかつロスが少なく効率良く得られることとなり、その工業的意義が極めて大きい。
【図面の簡単な説明】
【図１】本発明の反応槽等の概略図。
【図２】実施例、比較例より得られる、ＡＮとＷ値との相関図。
【図３】実施例、比較例より得られる、ＡＮとＹＩ値との相関図。
【符号の説明】
１：反応槽
２：単量体と溶媒の混合物である原料液の入口配管
３：反応槽上部の気相部への原料液散布用スプレー
４：蒸気抜出し量調節弁
５：蒸気凝縮器
６：原料液の一部を凝縮液に加えるための配管
７：混合装置
８：凝縮液及び加えられた原料液を反応槽に戻すポンプ
９：反応槽下部の液相部への供給配管
１０ａ：ストップ弁
１０ｂ：ストップ弁
１０ｃ：ストップ弁
１１：攪拌機の攪拌翼
１２：攪拌機モーター
１３：重合体液出口配管
１４：気相部
１５：重合体液
１６：重合体液面レベル；ｈ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improved continuous bulk or solution polymerization method of an acrylonitrile-containing copolymer, and a yellowish tint at the time of molding is significantly less than that of a copolymer having the same acrylonitrile content by a conventional manufacturing method, and appearance such as transparency. The present invention relates to a resin composition having excellent characteristics. More specifically, in the process of producing the acrylonitrile-containing copolymer, in the process of efficiently removing the heat of polymerization and heat of stirring and mixing generated in the reaction tank by the latent heat of evaporation of the polymer liquid, the evaporative gas generated in the reaction tank Is condensed in a heat exchanger outside the reaction tank, and when the condensate is returned to the lower liquid phase of the reaction tank, at least one point is set within a height range of 1/3 or less of the polymer liquid level from the lowest part of the reaction tank. By supplying from the above-mentioned inlet, the reaction is performed under the condition that the acrylonitrile monomer is uniformly dispersed in the polymer liquid under the forced stirring condition, and the acrylonitrile composition distribution in the copolymer is uniformized, The present invention relates to a method for producing a thermoplastic resin having a small yellow tint during molding and excellent in appearance properties such as transparency, and a thermoplastic resin composition.
[0002]
[Prior art]
Copolymers containing styrene-acrylonitrile as a main component, so-called SAN resins, have been used in a wide range of fields because of their excellent properties such as excellent chemical resistance, rigidity and moldability. These copolymers can be produced by various polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization. However, in the case of emulsion polymerization, since an emulsifier is used, there is a problem in appearance quality in terms of transparency and discoloration of the polymerization product, and acrylonitrile is easily dissolved in water, so that polymerization of a uniform composition is performed. It is difficult to obtain the product. In the case of suspension polymerization, the same problem as described above occurs because polymerization is carried out in an aqueous system using a dispersant or the like. Further, since an aqueous medium is used as a medium, the control of the polymerization reaction temperature is excellent, but continuous polymerization is not easy, and therefore, the productivity is inferior to that of the non-aqueous polymerization method. In addition, these polymerization methods also have problems such as water pollution due to wastewater discharged from equipment, and in recent years, continuous bulk and solution polymerization have been attracting attention from the viewpoint of environmental problems and production costs.
[0003]
In the case of bulk, solution polymerization, the raw material monomer alone or the raw material monomer is dissolved in an organic solvent to carry out the polymerization, but after polymerization, the solvent or unreacted monomer is removed to obtain a polymer, The problems of discoloration and transparency of the polymerization product due to the dispersant and the like, and the problem that acrylonitrile is easily dissolved in water and a polymerization product having a uniform composition cannot be obtained do not occur. Further, there is an advantage that the recovered solvent and monomer are not discharged for reuse. Accordingly, bulk polymerization and solution polymerization are employed for industrial production of styrene-acrylonitrile copolymers, and are often carried out continuously.
[0004]
However, when performing bulk polymerization or solution polymerization continuously on an industrial production scale, if polymerization is performed at a high conversion rate, it becomes difficult to remove generated heat such as reaction heat and stirring heat, which limits productivity. receive. Further, in the polymerization of the SAN resin, if the content of acrylonitrile is much larger than the azeotropic composition, the polymerization with a uniform composition becomes difficult, and it is possible to obtain a resin having excellent appearance quality such as color tone and transparency of the resin product. It becomes difficult. In order to solve these problems, polymerization methods utilizing the latent heat of evaporation of monomers and solvents have been disclosed (for example, Patent Documents 1 and 2). Furthermore, when a SAN resin is manufactured by continuous bulk or solution polymerization, a method of removing a reaction heat and the like by latent heat of evaporation of a monomer and obtaining a polymer having a constant acrylonitrile / styrene composition ratio (for example, Patent Document 3) ) And a polymerization method using a forced stirring reactor.
[0005]
In the method using latent heat of vaporization, heat is removed by evaporating the gas phase and the polymer liquid from the gas-liquid interface, or, if necessary, the evaporated solvent and unreacted monomer are cooled in a condenser outside the reaction tank. Since it is possible to efficiently remove heat by refluxing into the reaction tank, polymerization at a high conversion rate becomes possible, which is preferable as a polymerization method on an industrial production scale.
In the case of heat removal using such latent heat of vaporization, the vapor gas contains more components having a lower boiling point than the raw material liquid due to the vapor pressure difference of each component in the polymer liquid, and the composition between the condensate and the polymer liquid is high. A difference occurs. For example, in a raw material liquid composed of a styrene-acrylonitrile monomer and an aromatic organic solvent, the concentration of acrylonitrile in the evaporative gas generated in the reaction tank is necessarily higher than the acrylonitrile concentration in the raw material liquid. Therefore, when the condensate having a high acrylonitrile concentration is returned to the reaction vessel by condensing the evaporative gas, polymerization with a uniform composition becomes difficult, and the acrylonitrile composition distribution of the styrene-acrylonitrile copolymer becomes wide.
[0006]
In particular, when producing a styrene-acrylonitrile copolymer having a high acrylonitrile content near or above the azeotrope composition, the acrylonitrile concentration in the condensate becomes significantly higher than that of the raw material liquid, and when returned to the reaction tank, a uniform composition is obtained. Polymerization becomes increasingly difficult. More specifically, when the high acrylonitrile-containing condensate is returned to the reaction tank and polymerized, the acrylonitrile composition distribution of the styrene-acrylonitrile copolymer is broadened, and the proportion of the copolymer having a high acrylonitrile content is increased. Increase. ("Distribution spreads to the side with higher acrylonitrile content" means that the proportion of the copolymer having higher acrylonitrile content is increased. The tendency becomes stronger, and the obtained copolymer is molded and processed. When this was done, no resin product having a low yellow tint and having excellent appearance quality such as transparency was obtained.
[0007]
Conventionally, in a method for producing a styrene-acrylonitrile copolymer, when a monomer vapor generated from the liquid surface of a reaction tank is condensed and liquefied by a condenser and refluxed into the reactor, one part of the raw material liquid is contained in the condensate. A method is disclosed in which the acrylonitrile content ratio is reduced to make the composition of the polymer liquid uniform by additionally replenishing a part or an aromatic vinyl monomer (for example, Patent Document 4). There was a limitation that the speed was kept within 30% by weight / hr, and the productivity was not always sufficient.
[0008]
Further, the condensate circulating from the condenser of the polymerization reactor is adjusted so that the concentration of the condensate component having a boiling point of 120 ° C. or less at atmospheric pressure is 65% by weight or more in total, and is adjusted to the gas phase of the polymerization reactor. (For example, Patent Document 5) is disclosed, but in this method, although the heat removal ability by the latent heat of evaporation is good, the acrylonitrile concentration in the gas phase becomes extremely high, and the resin product has excellent appearance quality. Was not obtained.
[0009]
[Patent Document 1]
JP-A-48-17584
[Patent Document 2]
JP-A-49-7393
[Patent Document 3]
JP-A-58-29807
[Patent Document 4]
JP-A-5-255448
[Patent Document 5]
JP 2000-226417 A
[0010]
[Problems to be solved by the invention]
When producing an acrylonitrile-containing copolymer having a relatively high acrylonitrile content near or higher than the azeotropic composition, the polymerization heat or stirring heat generated in the reaction tank is removed by the latent heat of evaporation of the polymer liquid, and the like, and In the process of condensing the evaporative gas generated in the reaction tank with a heat exchanger outside the reaction tank and returning the condensate to the reaction tank, the difference in acrylonitrile content (composition difference) caused by mixing of the polymer liquid and the condensate is reduced. The polymerization with a uniform composition becomes difficult, the acrylonitrile composition distribution of the styrene-acrylonitrile-based polymer is widened, the proportion of the copolymer having a high acrylonitrile content is increased, and the degree of yellowness when the obtained copolymer is molded is increased. In addition, the appearance quality such as transparency increased, and the product value was significantly impaired. That is, an object of the present invention is to provide a method for producing an acrylonitrile-containing copolymer, when producing a copolymer having a relatively high acrylonitrile content, the molded article has a very small yellow tint, and appearance such as transparency. An object is to obtain a resin composition having excellent quality.
[0011]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve the above-described problems, and as a result, the yellowness at the time of molding processing is increased, and the factors that deteriorate the appearance quality such as transparency are the difference in composition of the polymer liquid, More specifically, it is due to the non-uniformity of the acrylonitrile content (concentration) in the polymer solution, and it has been found that the above-mentioned problem can be solved by the following method. That is, the present invention
1. Acrylonitrile monomer 25 to 60% by weight, aromatic vinyl monomer 40 to 75% by weight, and other copolymerizable vinyl compound monomer 0 to 35% by weight (total 100% by weight of monomer) Spraying, using a spray nozzle or the like, a raw material liquid comprising 100 parts by weight of the monomer mixture, 0 to 50 parts by weight of an organic solvent inert to the reaction, and a polymerization initiator to the upper gas phase of the reaction tank. The stirring power (KW) measured from a torque meter attached to the stirring shaft of the reaction tank and the number of revolutions is converted into the capacity (m) of the polymer liquid in the reaction tank to be stirred. ³ ), The required power for stirring is 2 to 20 KW / m. ³ Is continuously supplied to the forced agitation reaction tank, which is polymerized, and vapors of monomers and the like in the reaction tank are condensed through an external condenser from a pipe opened in the gas phase space at the upper part of the reaction tank, and the condensate is discharged. When mixed with a part of the raw material monomer or the raw material liquid and continuously supplied to the reaction vessel, at least one or more locations within a height range of 1/3 or less of the polymer liquid level from the bottom of the reaction vessel. A method for producing an acrylonitrile-containing copolymer, which is supplied from an inlet.
[0012]
2. In the acrylonitrile-containing copolymer, a W value, which is determined by liquid chromatography and indicates an acrylonitrile composition distribution defined by the following formula (I), is in a range satisfying the following formula (II). Item 6. The method for producing an acrylonitrile-containing copolymer according to Item 1.
W = A / h (I)
In the formula (I), A indicates an integrated area of acrylonitrile composition distribution on an elution curve obtained by liquid chromatography, and h indicates a peak height of the distribution.
W <0.92 × AN + 14 (II)
AN in the formula (II) indicates the acrylonitrile content (% by weight) in the acrylonitrile-containing copolymer.
[0013]
3. The method for producing an acrylonitrile-containing copolymer according to any one of claims 1 to 2, wherein the aromatic vinyl monomer is styrene, and the other copolymerizable vinyl monomer is an alkyl acrylate.
4. An acrylonitrile-containing copolymer obtained by the production method according to claim 1.
5. In the acrylonitrile-containing copolymer having an acrylonitrile content of 25% by weight or more obtained by the production method according to any one of claims 1 to 3, the yellowness of the molded product plate, that is, the YI value (so that the total thickness becomes 10 mm or more) An acrylonitrile-containing copolymer characterized in that the product plates are stacked and the yellow index measurement value according to Japanese Industrial Standards; K7105-1981; YI value) is within the range satisfying the following formula (III).
YI <0.0064 × AN ^1.994 +2 (III)
AN in the formula (III) indicates the acrylonitrile content (% by weight) in the acrylonitrile-containing copolymer.
[0014]
Hereinafter, the present invention will be described in more detail. The amount of acrylonitrile used in the present invention is 25% by weight to 60% by weight, preferably 30% by weight to 60% by weight based on the total amount of the monomers. When the amount of acrylonitrile exceeds 60% by weight, the obtained copolymer has a remarkably strong yellow tint, and the appearance quality such as transparency is deteriorated, and the commercial value is reduced. When the amount of acrylonitrile is less than 25% by weight, the yellow color and appearance quality are hardly reduced.
[0015]
Examples of the aromatic vinyl monomer include a substituted styrene having a substituent such as styrene, α-methylstyrene, 3,5-dimethylstyrene, 4-methoxystyrene, and 2-hydroxystyrene, α-bromostyrene, Halogenated styrenes such as 1,4-dichlorostyrene and the like, 1-vinylnaphthalene and the like can be mentioned. Generally, styrene is used, but two or more kinds can be used in combination.
These aromatic vinyl monomers are used in an amount of 40 to 75% by weight, preferably 40 to 70% by weight, based on the total amount of the monomers. If the amount of the aromatic vinyl monomer is less than 40% by weight, the resulting copolymer will have a remarkably strong yellow tint, and will have poor appearance quality such as transparency, and will have low commercial value. When the amount of the aromatic vinyl monomer exceeds 75% by weight, the yellow color and appearance quality are hardly reduced.
[0016]
Other vinyl compounds copolymerizable with acrylonitrile and aromatic vinyl monomers include, for example, acrylates such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate (BA), and acrylic acid , Methacrylic acid, maleic anhydride, unsaturated carboxylic acids such as itaconic acid or anhydrides thereof, N-phenylmaleimide, maleimide compounds such as N-cyclohexylmaleimide, and the like.Especially, ethyl acrylate and butyl acrylate are preferable. Two or more kinds may be used as a mixture. The amount of these vinyl compounds to be used is 0% by weight to 35% by weight, preferably 0% by weight to 30% by weight based on the total amount of the monomers. If it exceeds 35% by weight, the thermal and mechanical properties of the resulting copolymer will be reduced.
[0017]
In the case of solution polymerization, the organic solvent used is an organic solvent that is inert to the reaction, and the unreacted monomer and / or the copolymer formed by polymerization and the organic solvent in the reaction vessel are at a polymerization temperature. Any organic solvent can be used as long as it has a homogeneous phase in the composition in the reaction tank.
Examples of the organic solvent include aromatic hydrocarbons such as ethylbenzene and toluene, halogenated hydrocarbons such as chloroform, dichloromethane, and carbon tetrachloride, methyl ethyl ketone, methyl propyl ketone, diethyl ketone, and methyl isobutyl ketone. , Dipropyl ketone, methyl amyl ketone, cyclohexanone, methyl cyclohexanone, ketones such as acetylacetone, acetonitrile, dimethylformamide and the like. Preferred are aromatic hydrocarbons such as ethylbenzene and toluene, and ketones such as methyl ethyl ketone and methyl isobutyl ketone. These can be used alone or as a mixture of two or more. Usually, the amount of the organic solvent used is preferably 0 to 50 parts by weight based on 100 parts by weight of the total amount of the monomer mixture. If the amount of the organic solvent exceeds 50 parts by weight, the yield of the obtained copolymer decreases, and the production cost increases, which is not preferable.
[0018]
Known polymerization initiators can be used as the polymerization initiator to be added as necessary in the present invention. Examples thereof include t-

butylperoxy

3,3,5-trimethylhexanoate and t-butylperoxy-2-. Peroxyesters such as ethylhexanoate, t-butylperoxylaurate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di-octanoyl peroxide, di-lauroyl Organic peroxides such as diacyl peroxides such as peroxide, 2,2-azobisisobutyronitrile, 2,2-azobis (2-methylbutyronitrile),

dimethyl

2,2′-azobis (2- Methylpropionate), 2- (carbamoylazo) -isobutyronitrile, 4,4′-azobis (4-cyanopentanoic acid), 2,2′-a Bis (2,4-dimethylvaleronitrile), 2,2-azobis (4-methoxy-2,4 dimethylvaleronitrile), 2,2′-azobis [2- (hydroxymethyl) propionitrile], 1,1 Azo-based polymerization initiators such as -azobis (cyclohexane-1-carbonitrile).
[0019]
In the present invention, the polymerization apparatus for performing continuous polymerization is a forced stirring type reaction tank, and uses stirring blades in order to make the reaction system as uniform as possible.The stirring blades are usually paddle type blades. Pitch paddle type stirring blade, helical type stirring blade, double helical type stirring blade, ribbon type stirring blade, turbine type stirring blade, screw type stirring blade, anchor type stirring blade, max blend type stirring blade, full zone type stirring blade, etc. are used. Can be
Further, the stirring power (KW) calculated from the rotation speed and the torque meter attached to the stirring shaft installed in the reaction tank is changed to the capacity (m) of the polymer liquid in the reaction tank to be stirred. ³ ) Is used as a standard for stirring in the reaction solution. The homogenization of the composition of the polymer liquid by forcible stirring in the reaction system requires at least a stirring intensity of 2 KW / m ³ It is necessary to stir above. Also, 20KW / m ³ Exceeding the temperature makes stirring difficult to control the temperature, which is not preferable.
[0020]
Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a conceptual diagram showing an example of a reaction tank used for carrying out the present invention and its accessories. Reference numeral 1 denotes a reaction tank, which may be provided with a baffle plate on its wall in order to suppress generation of vortices due to stirring blades, 2 denotes an inlet pipe for a raw material liquid which is a mixture of a monomer and an organic solvent, and 3 denotes an upper part of the reaction tank. 4 is a control valve for controlling the amount of vapor withdrawn, and keeps the pressure inside the reaction tank constant and keeps the polymerization temperature constant. 5 is installed outside the reaction tank. For condensing the vapor extracted from the reaction tank. 6 is a pipe for adding a part of the raw material liquid to the condensed liquid, 7 is a mixer for uniformly mixing the raw liquid and the condensed liquid, 8 is a pump for returning the condensed liquid and the added liquid to the reaction tank, and 9 is a reaction tank. Supply piping to the liquid phase at the bottom of the tank, 10a to 10c stop valves, 11 a stirring blade of a stirrer, 12 a stirrer motor, 13 a polymer liquid outlet pipe, 14 a gas phase, 15 a polymer liquid, 16 Indicates the liquid level of the polymer liquid.
[0021]
In the present invention, when the evaporative gas generated in the reaction tank is condensed in a heat exchanger outside the reaction tank, and a condensate having a higher acrylonitrile concentration than the unreacted raw material liquid in the polymer liquid is returned to the lower liquid phase of the reaction tank. The condensate is mixed with a part of the raw material liquid to lower the acrylonitrile concentration, and then, from the bottom of the reaction tank, at least one-third of the level of the polymer liquid level, to the reaction tank through at least one injection port. Return to the polymer solution inside.
When the mixed liquid is returned to the polymer liquid in a height range exceeding one third of the liquid level of the polymer and polymerized, the acrylonitrile composition distribution in the obtained copolymer is widened and the copolymer having a high acrylonitrile content is obtained. Is unfavorable because the ratio increases. The acrylonitrile concentration in the mixed solution when the condensate is returned by mixing with a part of the raw material liquid is preferably equal to or higher than the acrylonitrile concentration of the raw material liquid and equal to or lower than the intermediate concentration of the acrylonitrile concentrations of the two liquids in the raw material liquid and the condensate. If the mixed solution is returned to the polymer solution in the reaction tank in excess of the intermediate concentration, the acrylonitrile composition distribution in the obtained copolymer is widened, and the proportion of the copolymer having a high acrylonitrile content is undesirably increased.
[0022]
At the top of the liquid phase in the reaction tank, that is, at the gas-liquid interface, a high concentration of acrylonitrile-containing condensate drops along the wall due to condensation of the evaporative gas on the gas phase wall, and the acrylonitrile in the liquid phase is always the most The concentration is high. In order to suppress the concentration of acrylonitrile from increasing at the gas-liquid interface, the raw material liquid is usually sprayed onto the gas phase wall at the top of the reaction tank, or the polymer liquid in the reaction tank is forcibly stirred using a stirring blade. Thus, the acrylonitrile concentration is made uniform, but this is not sufficient.
[0023]
In order to obtain an acrylonitrile-containing copolymer that has less yellowish color during molding than conventional production methods and has excellent appearance characteristics such as transparency, the acrylonitrile concentration and gas concentration at the gas-liquid interface in the reaction tank under forced stirring conditions Adjust the acrylonitrile concentration by mixing the condensate with a part of the raw material liquid so that the acrylonitrile concentration in the reaction solution other than the liquid interface is balanced, and adjust the acrylonitrile concentration from the bottom of the reaction tank liquid phase to 1/3 or less of the polymer liquid level. It is necessary to supply from at least one or more inlets within the height range. Specifically, according to the acrylonitrile content of the copolymer to be produced, a mixture of the condensate generated in the vapor condensate condenser 5 and the raw material liquid was passed through the supply pipe 9 and set in the reaction tank. This is achieved by supplying from a predetermined injection position by opening and closing the stop valves 10a to 10c.
In the present invention, as a method for removing the unreacted monomer and the organic solvent from the polymer solution withdrawn from the reaction tank to recover the copolymer, a method in which the reaction solution is preheated and flushing is performed under reduced pressure is preferable. .
[0024]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. It should be noted that the present invention is not limited by these examples and the like. First, the analysis and evaluation methods used in the present invention will be described.
(Measurement of acrylonitrile content in polymer)
Equipment: Pyrolysis gas chromatograph GC-17A (manufactured by Shimadzu Corporation)
Pyrolyzer PYR-2A (Shimadzu Corporation)
Column: Fused silica capillary column DB-17
Detector: Hydrogen flame ionization detector
Method: 0.6 to 0.8 mg of a polymer sample was weighed and subjected to a thermal decomposition treatment in a thermal decomposition furnace.
Thereafter, the vaporized substance was introduced into a gas chromatograph to measure the acrylonitrile content.
[0025]
(Analysis of acrylonitrile composition distribution)
Apparatus: High-performance liquid chromatograph LC-6A (manufactured by Shimadzu Corporation)
Column: ZORBAX CN (mobile phase; THF)
Detector: 254 nm output; 0.4 V / AU
Method: Dissolve 0.5 g of resin pellet in 40 g of THF and inject 20 μl. From a chromatographic elution curve, the integrated area of the acrylonitrile composition distribution is represented by A, and the peak height of the distribution is represented by h, a W value representing the acrylonitrile composition distribution;
W = A / h (I)
Was calculated. When the W value obtained from the formula (I) is used as an index of the acrylonitrile composition distribution in the copolymer, if the W value is smaller at the same acrylonitrile content (% by weight), the acrylonitrile composition distribution width in the copolymer becomes smaller. Indicates that it is narrow.
[0026]
FIG. 2 shows the relationship between the acrylonitrile content (% by weight) and the W value of the copolymer obtained from the experimental results. As shown in FIG. 2, when the acrylonitrile content (% by weight) in the copolymer increases, the W value increases at a constant ratio, the acrylonitrile composition distribution width increases, and the acrylonitrile content is high. It became clear that the ratio of the increase. Furthermore, according to the present invention, an acrylonitrile-containing copolymer having a narrow acrylonitrile composition distribution width satisfying the following formula (II), which cannot be obtained by the conventional method, could be obtained.
W <0.92 × AN + 14 (II)
AN in the formula (II) indicates the acrylonitrile content (% by weight) in the copolymer. The experimental results are summarized in Tables 1 and 2.
[0027]
[Evaluation method of yellow index]
Standard: Conforms to Japanese Industrial Standard K7105-1981
Method: Molding force: 30 tons-Injection molding machine (manufactured by Meiki Seisakusho), using a 1/8 inch thick flat plate mold, forming a flat plate at a molding temperature of 220 ° C. The obtained flat plates were stacked four times, and the yellow index was measured.
Measuring device: Spectra Flash 500 (manufactured by Data Color International)
Conversion method of YI (yellow index) value
YI = [100 (1.28X-1.06Z)] / Y
YI: Yellowness (the larger the YI value, the stronger the yellow tint of the resin molded product.)
X, Y, Z: tristimulus values for standard C light source (red, green, blue)
[0028]
FIG. 3 shows the relationship between the acrylonitrile content (% by weight) and the YI value of the copolymer obtained from the experimental results. As shown in FIG. 3, it was found that as the acrylonitrile content (% by weight) in the copolymer increased, the YI value increased at a constant rate. Furthermore, according to the present invention, it was possible to obtain an acrylonitrile-containing copolymer having a low yellowish color when formed and processed, which satisfies the following formula (III), which cannot be obtained by the conventional method.
YI <0.0064 × AN ^1.994 +2 (III)
AN in the formula (III) indicates the acrylonitrile content (% by weight) in the copolymer.
The experimental results are summarized in Tables 1 and 2.
[0029]
[Evaluation method of cloudiness (Haze)]
Standard: ASTM D1746
Method: One flat plate obtained in the same manner as in the Yellow Index was used as a sample, and the degree of cloudiness (haze, intensity of transmitted scattered light) was measured using SM-3 manufactured by Suga Test Instruments Co., Ltd.
[0030]
Embodiment 1
[Reaction tank] shown in FIG.
・ Reaction tank capacity 190l
・ Agitator: Max blend agitator
(Reaction conditions)
・ Monomer composition in raw material liquid ST / AN = 75/25% by weight
(ST; styrene AN; acrylonitrile)
・ Solvent amount (ethylbenzene) 20 parts by weight
・ Polymerization initiator (2,2-azobis (2-methylbutyronitrile)) 0.05 part by weight
・ Polymerization temperature 140 ° C
[0031]
The raw material liquid was supplied to the reaction tank separately in a pipe 2 for spraying the gas phase in the upper part of the reaction tank and a pipe 6 for mixing with the condensate generated in the vapor condenser 5. Further, in order to supply the mixed liquid of the condensed liquid and the raw material liquid to the lower liquid phase of the reaction tank, the stop valve 10c was opened and the remaining 10a and 10b were closed. Table 1 shows the raw material feed composition and feed flow rate, the polymerization temperature in the reaction tank, the composition of the evaporative gas at the outlet of the condenser, and the supply valve for returning the mixed liquid of the raw material liquid and the condensed liquid to the liquid phase of the reaction tank. And the composition of the mixture to be supplied are shown as polymerization conditions.
During the polymerization operation, the filling rate of the polymer liquid with respect to the capacity of the reaction tank was maintained in the range of 55 to 65% by volume, and the same amount of the polymer liquid as the raw material liquid was continuously discharged. Table 2 shows the power required for stirring by the stirrer in the reaction tank during polymerization and the polymerization conversion rate. The polymer liquid extracted from the reaction tank was subjected to a flushing treatment in a 1.5 kPa high vacuum tank while passing through a plate heat exchanger preheated to 230 ° C. to remove volatile components.
[0032]
The acrylonitrile composition distribution of the obtained polymer was measured by liquid chromatography, and the W value was 33. Further, when the yellow index was measured on a flat plate molded at a molding temperature of 220 ° C. using an injection molding machine, the YI value was 4.1, and the yellow tint was very small. The transparency of the flat plate was very good when Haze was less than 1%. It was obtained efficiently with high polymerization conversion and little loss. The results are summarized in Table 2.
[0033]
Embodiment 2
In order to supply the mixed liquid of the condensed liquid and the raw material liquid to the lower liquid phase of the reaction tank, the stop valve 10b is opened and the remaining 10a and 10c are closed, and all other operations are performed under the same conditions as in Example 1. did. As a result, the W value of the obtained polymer was 34, and the YI value indicating the yellowness of the formed flat plate was 4.8, the yellowness was small, and the transparency was very good with less than 1% Haze. there were.
[0034]
[Comparative Example 1]
In order to supply the mixed liquid of the condensed liquid and the raw material liquid to the lower liquid phase of the reaction tank, the stop valve 10a is opened and the remaining 10b and 10c are closed, and all other operations are carried out under the same conditions as in Example 1. did. As a result, the W value of the obtained polymer was 40, which exceeded the W value of 37 calculated from the formula (II) at an acrylonitrile content of 25% by weight in the acrylonitrile-containing copolymer. The YI value of the formed flat plate was 6.5, the yellowness was higher than in Examples 1 and 2, and the transparency was Haze = 3%, which was worse than Examples 1 and 2.
[0035]
Embodiments 3 and 4
The polymerization operation was carried out in the same manner as in Examples 1 and 2, except that the monomer composition in the raw material liquid was ST / AN = 69/31 (% by weight). In Example 3, the liquid mixture of the condensed liquid and the raw material liquid was supplied to the lower liquid phase of the reaction tank from the stop valve 10c through the stop valve 10c. As a result, as shown in Table 2, the obtained polymer was a polymer having a low W value and a narrow acrylonitrile composition distribution. Further, the molded flat plate had little yellowish tint, and the transparency was very good with Haze of less than 1%.
[0036]
[Comparative Example 2]
In order to supply the mixed liquid of the condensate and the raw material liquid to the lower liquid phase of the reaction tank, the stop valve 10a is opened and the remaining 10b and 10c are closed, and all other operations are performed under the same conditions as in Examples 3 and 4. Was carried out. As a result, the W value of the obtained polymer was 45, which exceeded the W value of 41.6 calculated from the formula (II) at an acrylonitrile content of 30% by weight in the acrylonitrile-containing copolymer. The YI value of the formed flat plate was 8.2, the yellowness was higher than in Examples 3 and 4, and the transparency was Haze = 5%, which was worse than Examples 3 and 4.
[0037]
Embodiments 5 and 6
The polymerization operation was carried out in the same manner as in Examples 1 and 2, except that the monomer composition in the raw material liquid was ST / AN = 50/50 (% by weight). In Example 5, the mixed liquid of the condensate and the raw material liquid was supplied from the stop valve 10c to the liquid phase in the lower part of the reaction tank from the stop valve 10b in Example 6. As a result, as shown in Table 2, the obtained polymer was a polymer having a low W value and a narrow acrylonitrile composition distribution. Further, the molded flat plate had little yellowish tint, and the transparency was very good with Haze of less than 1%.
[0038]
[Comparative Example 3]
In order to supply the mixed liquid of the condensed liquid and the raw material liquid to the lower liquid phase of the reaction tank, the stop valve 10a is opened and the remaining 10b and 10c are closed, and all other operations are performed under the same conditions as in Examples 5 and 6. Was carried out. As a result, the W value of the obtained polymer was 60, which exceeded the 50.8 W value calculated from the formula (II) at an acrylonitrile content of 40% by weight in the acrylonitrile-containing copolymer. The YI value of the formed flat plate was 15.5, the yellowness was higher than in Examples 5 and 6, and the transparency was Haze = 8%, which was worse than Examples 5 and 6.
[0039]
Embodiments 7 and 8
The polymerization operation was performed in the same manner as in Examples 1 and 2, except that the monomer composition in the raw material liquid was ST / AN / BA = 45/45/10 (% by weight). In Example 7, the mixed liquid of the condensed liquid and the raw material liquid was supplied to the lower liquid phase of the reaction tank from the stop valve 10c through the stop valve 10c. As a result, as shown in Table 2, the obtained polymer was a polymer having a low W value and a narrow acrylonitrile composition distribution. Further, the molded flat plate had little yellowish tint, and the transparency was very good with Haze of less than 1%.
[0040]
[Comparative Example 4]
In order to supply the mixed liquid of the condensed liquid and the raw material liquid to the lower liquid phase of the reaction tank, the stop valve 10a is opened and the remaining 10b and 10c are closed, and all other operations are performed under the same conditions as in Examples 7 and 8. Was carried out. As a result, the W value of the obtained polymer was 56, which exceeded the W value 50.8 calculated from the formula (II) at an acrylonitrile content of 40% by weight in the acrylonitrile-containing copolymer. The YI value of the formed flat plate was 14.5, the yellowness was higher than in Examples 7 and 8, and the transparency was Haze = 7%, which was worse than Examples 7 and 8.
[0041]
[Table 1]

[0042]
[Table 2]

[0043]
【The invention's effect】
According to the method for producing an acrylonitrile-containing copolymer of the present invention, when producing a copolymer having a relatively high acrylonitrile content, the molded article has a very small yellow tint, and is excellent in appearance quality such as transparency. The resin composition can be efficiently obtained with a high polymerization conversion rate and a small loss, and its industrial significance is extremely large.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a reaction tank and the like of the present invention.
FIG. 2 is a correlation diagram between AN and W value obtained from Examples and Comparative Examples.
FIG. 3 is a correlation diagram between AN and YI values obtained from Examples and Comparative Examples.
[Explanation of symbols]
1: Reaction tank
2: Inlet piping for raw material liquid, which is a mixture of monomer and solvent
3: Spray for spraying the raw material liquid on the gas phase at the top of the reaction tank
4: Steam extraction amount control valve
5: Steam condenser
6: Pipe for adding a part of the raw material liquid to the condensate
7: Mixing device
8: Pump for returning condensate and added raw material liquid to the reaction tank
9: Supply piping to the liquid phase at the bottom of the reactor
10a: Stop valve
10b: Stop valve
10c: Stop valve
11: Stirrer blade of stirrer
12: Stirrer motor
13: Polymer liquid outlet piping
14: Gas phase
15: Polymer liquid
16: polymer liquid level; h

Claims

Acrylonitrile monomer 25 to 60% by weight, aromatic vinyl monomer 40 to 75% by weight, and other copolymerizable vinyl compound monomer 0 to 35% by weight (total 100% by weight of monomer) A raw material solution comprising a mixture of 100 parts by weight of the monomer mixture of the above (1), 0 to 50 parts by weight of an organic solvent inert to the reaction, and a polymerization initiator, is sprayed into the upper gas phase of the reaction tank by a spray nozzle or the like. It is obtained by dividing the stirring power (KW) measured from the rotation speed and the torque meter attached to the stirring shaft of the reaction tank by the volume (m ³ ) of the polymer liquid in the reaction tank to be stirred. The power required for stirring is continuously supplied to a forced stirring reaction tank having a power of 2 to 20 KW / m ³ to polymerize the monomer, and the monomer in the reaction tank is passed through an external condenser through a pipe opened in a gas phase space above the reaction tank. Isocondensation of vapor and the condensate When the mixture is continuously supplied to the reaction tank after mixing with the reactor, the mixture is supplied from at least one injection port in a height range of 1/3 or less of the polymer liquid level from the bottom of the reaction tank. For producing an acrylonitrile-containing copolymer.

In the acrylonitrile-containing copolymer, a W value, which is determined by liquid chromatography and indicates an acrylonitrile composition distribution defined by the following formula (I), is in a range satisfying the following formula (II). Item 6. The method for producing an acrylonitrile-containing copolymer according to Item 1.
W = A / h (I)
In the formula (I), A represents the peak height of the acrylonitrile composition distribution integrated area h on the elution curve obtained by liquid chromatography.
W <0.92 × AN + 14 (II)
AN in the formula (II) indicates the acrylonitrile content (% by weight) in the acrylonitrile-containing copolymer.

The production of an acrylonitrile-containing copolymer according to any one of claims 1 to 2, wherein the aromatic vinyl monomer is styrene and the other copolymerizable vinyl monomer is an alkyl acrylate. Method.

An acrylonitrile-containing copolymer obtained by the production method according to claim 1.

In the acrylonitrile-containing copolymer having an acrylonitrile content of 25% by weight or more obtained by the production method according to any one of claims 1 to 3, the yellowness of the molded product plate, that is, the YI value (total thickness: An acrylonitrile-containing product characterized in that the product plates are stacked so that the thickness is 10 mm or more, and a yellow index measurement value according to Japanese Industrial Standards; K7105-1981; a YI value) is within a range satisfying the following formula (III). Copolymer.
YI <0.0064 × AN ^1.994 + 2 (III)
AN in the formula (III) indicates the acrylonitrile content (% by weight) in the acrylonitrile-containing copolymer.