JP3813011B2 - Method and apparatus for collecting polymer solids - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、乳化重合などで得られる重合体ラテックスから重合体固形物を回収するための回収方法及びその装置に関するものであり、詳しくは第一槽である凝固槽及び第二槽以降の一つ以上の熟成槽内に、滞留した凝固スラリー及び熟成スラリーの付着を防止し、かつ粉体特性の優れた重合体固形物の回収方法及びその装置に関するものである。
【０００２】
【従来の技術】
一般に、乳化重合法で製造された重合体ラテックスから重合体固形物を回収するには、まず第一槽としての凝固槽にて重合体ラテックスと凝固剤水溶液を添加し、該凝固槽において重合体ラテックスを凝固させ、更に第二槽以降の一つ以上の熟成槽にて熟成を行うことが必要である。かかる重合体ラテックスから重合体固形物を回収する最も一般的な回収方法として、図２に示すように重合体ラテックスと凝固剤水溶液とを連続的に第一槽である凝固槽の液相部に供給して凝析を行い、引き続き第二槽以降の一つ以上の熟成槽にて凝固スラリーを熟成させ、脱水、乾燥を経て重合体固形物を得る回収方法が知られている。
【０００３】
しかしながらこの回収方法及び装置では、重合体ラテックスと凝固剤水溶液との接触状態が悪く凝固槽への凝集不十分な凝固スラリーの付着が著しく、加えて熟成槽での熟成スラリーの付着も激しい。その結果、凝固槽及び熟成槽内において凝固スラリー及び熟成スラリーの合一が原因であるブロッキングによる工程上のトラブルが多発し、工業的に極めて不利となる。
【０００４】
また、この方法で得られる重合体固形物の粉体は、脱水性が悪く、微粉量が多く、嵩比重も低く、微粉による作業環境の悪化、粉塵による爆発性増大等の問題も生じやすい。
【０００５】
更に、重合体ラテックスから重合体固形物を回収する方法及びその装置において、槽内の付着発生を改良する回収方法及び装置は種々検討されてきている。例えば図３に示すように、凝固槽において凝固剤水溶液を液表面にシャワー状にスプレー流下させた後、オ−バ−フロ−方式による重合体固形物を回収する方法及びその装置がある。しかしながら、この回収方法及びその装置は凝固槽内の気相界面付近の凝固スラリーの付着は低減され改良効果が認められるものの、第二槽以降の一つ以上の熟成槽に気相部分が存在し、気液界面付近の熟成スラリーの槽壁への付着が著しく、工程上のトラブルが生じやすく充分とは言えない。
【０００６】
【発明が解決しようとする課題】
前記したごとく重合体ラテックスから重合体固形物を回収するにあたっては、従来の回収方法及びその装置では、重合体固形物の粉体特性の向上並びに凝固槽での凝固スラリーの付着及び熟成槽内での熟成スラリーの付着防止を満足させる回収方法及び装置とはいえないのが実状である。
【０００７】
本発明は、前記の従来技術を背景になされたもので重合体ラテックスから重合体固形物を回収するに際し、凝固スラリー及び熟成スラリーが凝固槽及び熟成槽内に付着することを防止し、最終的には粉体特性の優れた重合体固形物を得ることを目的とするものである。
【０００８】
【課題を解決するための手段】
本発明者らは、上記問題点を解決することを目的として鋭意検討した結果、重合体ラッテクスから重合体固形物を回収するに際し、特定の条件を有する凝固槽と熟成槽と凝固スラリーを移送させる装置を組合せることによって凝固槽及び熟成槽内に凝固スラリー及び熟成スラリーを付着させることなく、かつ粉体特性の優れた重合体固形物を回収できる方法及び装置を見出したものである。
即ち、本発明は重合体ラテックスから重合体固形物を回収する方法において、気相部を有した凝固槽内の液表面全体及び槽壁に凝固剤水溶液をシャワー状にスプレー流下せしめると共に、重合体ラテックスを連続的に凝固槽内の液表面に滴下させることにより凝固スラリーを生じさせ、凝固スラリーを回転容積型ポンプで満液型熟成槽に移送させ凝固スラリーを熟成させて回収する回収方法であり、好ましくは、凝固スラリーを発生させる方法としては、凝固槽の気相部に設けた一つ以上の凝固剤水溶液供給用のスプレーノズルから凝固剤水溶液をシャワー状に凝固槽内の液表面全体及び槽壁にスプレー流下せしめると共に、凝固槽の気相部に設けた一つ以上の重合体ラテックス供給用ノズルから凝固槽内の液表面に滴下させて発生させ、かつ、凝固槽最下部に設けられた凝固スラリー移送口から凝固スラリーを移送させて回収する回収方法であり、
更には、凝固槽の気相部に設けた凝固剤水溶液供給用のスプレー用ノズルが充円錐スプレーノズルであり、そのスプレーノズルの噴霧角度θが真下向き３０゜≦θ≦１８０゜であり、かつそのスプレーノズルを用いてスプレー流下する槽璧側の液表面からの最高高さＨが０＜Ｈ≦０．２５Ｄ（凝固槽の内径）の範囲で凝固剤水溶液をシャワー状に凝固槽液表面及び槽壁にスプレー流下せしめる回収方法である。
【０００９】
また、重合体ラテックスから重合体固形物を回収する装置として凝固槽と一つ以上の熟成槽と凝固スラリー移送装置からなり、該凝固槽は気相部を有し、この気相部に一つ以上の凝固剤水溶液供給用のスプレーノズルと一つ以上の重合体ラテックス供給用ノズルを設け、かつ、凝固槽最下部に凝固スラリー移送口を設けた槽であり、また熟成槽としては満液型熟成槽であり、更に凝固槽最下部の凝固スラリー移送口から満液型熟成槽に凝固スラリーを移送する装置として回転容積型ポンプを設けることを特徴とする回収装置、更に好ましくは凝固槽の気相部に設けた凝固剤水溶液供給用のスプレーノズルが充円錐スプレーノズルであり、かつそのスプレーノズルの噴霧角度θが真下向き３０゜≦θ≦１８０゜である回収装置が好ましい。
【００１０】
以下、本発明について詳細に説明する。
本発明の重合体ラテックスと凝固剤水溶液とは以下に示されるものである。
重合体ラテックスとしては、一般的には乳化重合で製造される熱可塑性樹脂であればよいが、特にポリブタジエン、スチレン−ブタジエン、アクリロニトリル−ブタジエン等のジエン系ゴムラテックス、スチレン、α−メチルスチレン等の芳香族ビニル単量体の重合体ラテックス、アクリロニトリル、メタクリロニトリル等のビニルシアン単量体の重合体ラテックス、ブチルアクリレ−ト等のアクリル酸エステル単量体、メチルメタクリレ−ト等のメタクリル酸エステル単量体の重合体ラテックス等が挙げられる。また、これら各単量体群から選ばれた１種以上の単量体の共重合体ラテックスも挙げられ、これらの一般的に知られている共重合体ラテックスとしてＡＳ（アクリロニトリル−スチレン）ラテックスがある。更に、上記ジエン系ゴムラテックスに芳香族ビニル単量体、ビニルシアン単量体、アクリル酸エステル単量体及びメタクリル酸エステル単量体等から選ばれた１種以上の単量体をグラフト重合した重合体ラテックスも挙げられ、これらの一般的に知られている重合体ラテックスとしてはＭＢＳ（メチルメタクリレート−ブタジエン−スチレン）ラテックス、ＡＢＳ（アクリロニトリル−ブタジエン−スチレン）ラテックス、ＡＡＳ（アクリル酸アルキルエステル−アクリロニトリル−スチレン）ラテックスがある。
【００１１】
凝固剤水溶液とは、特に限定されず公知のものを使用できる。即ち凝固剤水溶液の例としては、塩酸、硫酸、硝酸等の無機酸、ギ酸、酢酸等の有機酸及び塩化カルシウム、硫酸マグネシウム、硫酸アルミニウム等の無機塩の水溶液、酢酸カルシウム、酢酸アルミニウム等の有機酸塩の水溶液等が挙げられ、１種または２種以上併用することもできる。また、無機及び有機酸塩純分としての添加量は重合体ラテックスに含まれる乳化剤量にもよるが、通常は重合体ラテックスの固形分１００重量部当たり１〜１０重量部の範囲が適当である。
【００１２】
本発明において用いる重合体ラテックスの回収装置とは、図１に示されるような気相部を有する凝固槽と、一つ以上の満液型熟成槽を備えた熟成槽からなる。ここで凝固槽とは、気相部と液相部を合わせた槽を指し、満液型熟成槽とは気相部を有さない液相部からなる槽のことである。
【００１３】
該回収装置における第一槽である凝固槽とは以下に提示する条件を満たすものである。即ち、凝固槽は、気相部と液相部を合わせた槽からなり、かつ凝固槽の気相部に一つ以上の凝固剤水溶液供給用のスプレーノズルと、気相部に一つ以上の重合体ラテックス供給用のノズルを有し、更に凝固槽最下部に凝固スラリー移送口を一つを備えたものである。
【００１４】
凝固剤水溶液供給用スプレーノズルは、充円錐スプレーノズルで噴霧角度θは３０゜≦θ≦１８０゜のものが好ましく、更に好ましくは噴霧角度６０゜≦θ≦１２０゜のノズルが良い。その噴霧角度は真下に向かった角度として設置されるものである。また、スプレーノズルの個数は特に限定されるものではないが、より好ましくは２〜４個である。
【００１５】
また、スプレーノズルの位置は、スプレーノズルを用いて凝固剤水溶液を凝固槽壁にスプレー流下する槽壁側の液表面からの最高高さＨが０＜Ｈ≦０．２５Ｄの範囲を満たしている位置に設けることが好ましい。但し、Ｄは凝固槽の内径（直径）を言う。
Ｈ≦０、すなわち凝固剤水溶液供給用スプレーノズルより供給される凝固剤水溶液が凝固槽壁にスプレーされないと、本発明の効果となる凝固槽内の凝固スラリーの付着防止が達成されない。また、Ｈ＞０．２５Ｄであると、直接接触する重合体ラテックスと凝固剤水溶液の割合が減少し凝固スラリーの凝集能力が低下し効率が悪い。
【００１６】
重合体ラテックス供給用のノズルは、凝固槽気相部に設けられていればノズル形状、個数は特に限定されるものではない。そのノズル口の高さは、液表面に近い方が好ましく、少なくとも液表面から０．２５Ｄ以下であることが好ましく、更には０．１２５Ｄ以下であることが好ましい。
【００１７】
凝固スラリー移送口は、凝固槽内に凝固スラリーが滞留しないために凝固槽最下部に設け、第二槽である熟成槽へ凝固スラリーを容易に移送するためのものである。
【００１８】
なお凝固槽での凝固温度は、重合体ラテックスの種類及び濃度により一概には決められないが、例えばＡＢＳラテックスでは温度３０〜８０℃であり、また凝固槽内の凝固スラリーの平均滞留時間は１〜１０分である。
【００１９】
本発明の熟成槽としては、一つ以上の満液型の熟成槽を備えた槽からなる。熟成槽の数については特に限定させるものではないが、回収装置規模と生産効率を考慮し好ましくは２〜５槽がよい。
【００２０】
さらに、第二槽以降の熟成槽における熟成温度は凝固温度よりも高く、且つ熟成槽が複数の場合は前槽よりも温度を高くして行う必要がある。なお熟成温度が凝固温度よりも低い場合は、本発明が目的とする粉体特性の優れた重合体固形物を得ることが困難となる。
【００２１】
熟成槽内の凝固スラリーの平均滞留時間については特に限定されるものではなく、熟成槽の数と生産効率を考慮し好ましくは１槽５〜１５分が良い。
【００２２】
第一槽である凝固槽から第二槽である熟成槽に凝固スラリーを定量的に移送するには凝固スラリー移送装置を備えることが好ましい。
凝固スラリーを移送する装置としてはポンプがあり、その種類は多種多様である。例えば、エアー駆動式ダイアフラム型ポンプは凝固スラリー流動に脈動があり凝固槽の凝固スラリー液量が変動し、液面レベル変動が大きく定量性に欠けると同時に、凝固槽内に凝固スラリーの付着が発生し好ましくない。また、誘導渦式インペラー型ポンプは脈動はないが流量がポンプの回転数と比例関係になく、少量の流動変動における制御が困難であり、定量性に欠け好ましくない。
【００２３】
回転容積型ポンプは、流量がポンプの回転数と比例関係になるため定量性がよく脈動がないため、凝固槽の凝固スラリー液量が安定し、液面レベル変動がなく好ましい。なお、回転容積型ポンプであれば特に限定はなくスクリュー型、チューブ型、ローター型等が挙げられる。ポンプの回転数については、特に限定しないが、凝固槽で得られた凝固スラリー粒子を破砕させない程度であれば良く、好ましくは１００〜４００ｒｐｍで運転できる吐出能力を有するサイズを選定する必要がある。
【００２４】
ここで、ポンプの定量性とは、原料である重合体ラテックスや、凝固剤水溶液の供給量に変動があっても凝固槽の凝固スラリー液量が一定に保たれ、液面レベルが一定であるようにポンプの吐出量が調整可能であることを指す。
【００２５】
そして、凝固槽の液面レベル検知、即ち凝固槽の液量コントロールは、凝固槽の液面にレベル計を設け、レベル計からの信号により、移送ポンプの出力をインバ−タ−制御を行い、凝固槽の液量コントロ−ル、即ち液面コントロ−ルをするという方法を用いて検知した。
【００２６】
また、本発明の重合体固形物の回収装置における凝固槽及び熟成槽の攪拌翼については、スラリーを均一に混合しうるものであれば特に限定されるものではなく、多段パドル翼、ファウドラー翼、タービン翼、ブルマージン翼、マックスブレンド翼、フルゾーン翼等が挙げられる。これらのうち、攪拌翼に凝固スラリー及び熟成スラリーの付着防止という点から平板翼であるマックスブレンド翼がより好ましい。また付着防止効果向上の目的で攪拌翼にテフロンコーティング等の表面加工処理を施しても良い。
【００２７】
凝固槽及び熟成槽の攪拌翼の回転数は特に限定されるものではないが、せん断によるスラリー粒子の粒子破砕を少なくするために、攪拌翼の先端速度が１．０〜２．０（ｍ／ｓ）で行うことが好ましい。
【００２８】
また、凝固槽及び熟成槽内の邪魔板についてその形状、槽壁−邪魔板間隔は、槽内のスラリーを均一に混合しうるものであれば特に限定されるものではなく、その形状はオーバル、板状、丸状等が挙げられる。これらのうち、邪魔板に凝固スラリー及び熟成スラリーの付着防止という点から形状は丸状、槽壁と邪魔板の間隔は槽内径の５〜２０％と離れていることがより好ましい。また付着防止効果向上の目的でテフロンコーティング等の表面加工処理を施しても良い。
【００２９】
本発明において用いる重合体ラテックスの回収装置において、凝固槽及び熟成槽の容量は特に限定されるものではないが、工業的生産規模と生産効率を考慮し好ましくは、１槽が０．１〜１０ｍ3 の範囲、更に好ましくは、０．５〜５ｍ3 にあるものを用いると良い。
【００３０】
熟成槽を経たスラリーは、ベルトフィルター或いは遠心分離機によって脱水、洗浄することができる。脱水されたウエットケーキはロータリドライヤー、フラッシュドライヤー、流動乾燥機、棚式乾燥機等によって乾燥し重合体固形物を得ることができる。例えば、ＡＢＳラテックスから得られたスラリーの乾燥条件は一般的に窒素または空気雰囲気下において温度８０〜１４０℃の熱風を送り込み、ウエットケーキの揮発物が２．０％以下になるまで乾燥する。
【００３１】
【実施例】
以下に、実施例により本発明の方法を具体的に説明するが、これらは本発明の範囲を限定するものではない。また、実施例については図１の回収装置を用いて行った。なお、実施例及び比較例中の諸物性は以下の方法にて測定した。
（１）凝固スラリー粒子保持性：移送ポンプ通過前後の凝固スラリーをコールター社ＬＳ−２３０粒度分布測定装置を用いて測定し、凝固スラリー粒子保持率＝〔（移送ポンプ通過後の凝固スラリーの５０％粒子径）／（移送ポンプ通過前の凝固スラリーの５０％粒子径）〕×１００（％）を用いて評価した。
○：凝固スラリー粒子保持率が９５％以上
△：凝固スラリー粒子保持率が８５％以上９５％未満
×：凝固スラリー粒子保持率が８５％未満
なお、凝固スラリーの５０％粒子径とは、粒度分布の積算分布における５０％積算値の粒子径を言う。
【００３２】
また、含水率、嵩比重及び粒度分布の測定用準備試料として、熟成スラリーを遠心機〔国産遠心機（株）製〕によって１分間脱液し、純水で２５秒間洗浄し、その後２分間脱水して約２ｋｇの湿潤状重合体固形物を得て以下の測定に用いた。
（２）含水率：上記で得た湿潤状重合体固形物２ｇを温度１００℃で６時間熱風乾燥して乾燥重量（ＷＤ）を測定し、含水率＝〔（２−ＷＤ）／２）〕×１００（％）の式を用いて求めた。
（３）嵩比重：上記で得た湿潤状重合体固形物５０ｇを温度８０℃で１６時間熱風乾燥して重合体粉体を得、これをＪＩＳ Ｋ６７２１に基づいて測定した。
（４）粒度分布：上記で得た湿潤状重合体固形物１００ｇを温度８０℃で１６時間熱風乾燥して重合体固形物の粉体を得、この粉体をコールター社ＬＳ−２３０粒度分布測定装置を用いて測定し、２００ｍｅｓｈパス量の頻度体積割合（％）を求めた。
【００３３】
（５）ポンプ定量性：以下の三段階で評価した。
○：凝固スラリー流動に脈動が無く、凝固槽の液面変動がない。
△：凝固スラリー流動に脈動が無く、凝固槽の液面変動が液量の５％以下。
×：凝固スラリー流動に脈動が有り、凝固槽の液面変動がある。
（６）スラリーの付着状況：以下に示すような目視判定にて行った。
○：槽内全体に付着全くなし
△：槽壁、攪拌翼、邪魔板に若干の付着有り
×：槽内全体に著しく付着有り
【００３４】
実施例１
重合体ラテックスとしては、スチレン、アクリロニトリルをポリブタジエンにグラフト共重合したブタジエン５０重量部、スチレン３７．５重量部、アクリロニトリル１２．５重量部よりなるグラフト共重合体ラテックスを原料とした。この重合体ラテックスの固形分濃度は３２％である。また、塩化カルシウム濃度が１．４％で１５％塩酸によりｐＨを２．４に調整した凝固剤水溶液を、凝固槽壁にスプレー流下する槽壁側の液表面からの最高高さＨが０．１５Ｄなるように充円錐スプレーノズル二つを用いて、液表面全体及び槽壁に流下せしめると共に、前記の重合体ラテックスを凝固槽の液表面より０．１０Ｄの高さの気相部に設けた重合体ラテックス供給用ノズル口より連続的に添加した。この時、凝固槽の凝固温度は６５℃とし、重合体ラテックスと凝固剤水溶液の比率は１．０：０．８とした。
【００３５】
スプレーノズルは、Lechler 社製の充円錐ノズルで噴霧角１２０°のものを使用した。更に凝固槽内の凝固スラリー液量は、移送ポンプの吐出量をインバーター制御により槽内容積の６５％になるように設定した。この時の移送ポンプのスクリュー回転数は２５０〜３００ｒｐｍであった。
【００３６】
凝固槽で得られた凝固スラリーは、凝固スラリー移送装置である回転容積型ポンプ〔（モーノポンプ：兵神装備（株）〕を経て熟成槽で熟成した。なお、熟成槽での熟成温度は段階的に軟化温度まで上げ、その後熟成スラリーを脱水、乾燥して重合体固形物を得た。評価結果を表１に示す。
【００３７】
実施例２
凝固剤水溶液の塩と酸種を表１に示すように変えた他は、実施例１と同様にして重合体固形物を得た。評価結果を表１に示す。
【００３８】
実施例３
塩を用いず、酸種を表１に示すように変えた他は、実施例１と同様にして重合体固形物を得た。評価結果を表１に示す。
【００３９】
比較例１
凝固剤水溶液を凝固槽壁にスプレー流下する槽壁側の液表面からの最高高さＨがＨ＝０．２５Ｄであり、凝固スラリー移送ポンプをエアー駆動式ダイアフラム型ポンプに変えた他は、実施例２と同様にして重合体固形物を得た。評価結果を表２に示す。
【００４０】
比較例２
凝固スラリー移送ポンプを誘導渦式インペラー型ポンプに変えた他は、実施例２と同様にして重合体固形物を得た。評価結果を表２に示す。
【００４１】
比較例３
凝固剤水溶液を凝固槽壁にスプレー流下する槽壁側の液表面からの最高高さＨがＨ＜０に変えた他は、実施例２と同様にして重合体固形物を得た。評価結果を表２に示す。
【００４２】
比較例４
重合体回収装置を図２に示すような満液圧送回収装置に変え、かつ移送ポンプを用いない他は、実施例２と同様にして重合体固形物を得た。評価結果を表２に示す。
【００４３】
比較例５
重合体回収装置を図３に示すようなオーバーフロー回収装置に変え、かつ移送ポンプを用いない他は、実施例１と同様にして重合体固形物を得た。評価結果を表２に示す。
【００４４】
【表１】
【表２】
【発明の効果】
本発明によれば、従来の回収装置に比べて重合体固形物が凝固槽、熟成槽内に付着発生することが防止され、凝固スラリー移送装置としての回転容積型ポンプを設けることで凝固槽で生成された凝固スラリーの粒子が、破砕されることなく定量的に熟成槽に移送され、ブロッキング等の工程上のトラブルが無く、最終的に粉体特性の優れた重合体固形物を安定して得ることができる。
【図面の簡単な説明】
【図１】本発明の実施例１、２、３及び、比較例１、２、３で用いた回収装置を示す図面である。
【図２】本発明の比較例４で用いた回収装置を示す図面である。
【図３】本発明の比較例５で用いた回収装置を示す図面である。
【符号の説明】
１ 凝固水溶液
２ 重合体ラテックス
３ 凝固槽
４ 移送ポンプ
５ 熟成槽
６ 熟成槽
７ 熟成槽
８ 凝固水溶液供給用スプレーノズル
９ 重合体ラテックス供給用ノズル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recovery method and apparatus for recovering a polymer solid from a polymer latex obtained by emulsion polymerization or the like, and more specifically, a coagulation tank as a first tank and one after a second tank. The present invention relates to a method and an apparatus for recovering a polymer solid that prevents adhesion of the coagulated slurry and the aging slurry staying in the aging tank and has excellent powder characteristics.
[0002]
[Prior art]
In general, in order to recover a polymer solid from a polymer latex produced by an emulsion polymerization method, first, a polymer latex and a coagulant aqueous solution are added in a coagulation tank as a first tank, and the polymer is added in the coagulation tank. It is necessary to coagulate the latex and further perform aging in one or more aging tanks after the second tank. As the most common recovery method for recovering polymer solids from such polymer latex, as shown in FIG. 2, the polymer latex and the coagulant aqueous solution are continuously placed in the liquid phase part of the coagulation tank, which is the first tank. There is known a recovery method in which a coagulated slurry is supplied, coagulated, subsequently aged in one or more aging tanks after the second tank, and dehydrated and dried to obtain polymer solids.
[0003]
However, in this recovery method and apparatus, the contact state between the polymer latex and the aqueous coagulant solution is poor, and adhesion of the coagulated slurry insufficiently aggregated to the coagulation tank is remarkable, and in addition, the maturation slurry adheres to the maturation tank. As a result, in the coagulation tank and the aging tank, troubles in the process due to blocking caused by coalescence of the coagulated slurry and the aging slurry frequently occur, which is extremely disadvantageous industrially.
[0004]
In addition, the solid polymer powder obtained by this method has poor dehydration, a large amount of fine powder, a low bulk specific gravity, and problems such as deterioration of the working environment due to the fine powder and increase in explosiveness due to dust.
[0005]
Furthermore, in the method and apparatus for recovering polymer solids from polymer latex, various recovery methods and apparatuses for improving the occurrence of adhesion in the tank have been studied. For example, as shown in FIG. 3, there is a method and apparatus for recovering polymer solids by an overflow method after spraying a coagulant aqueous solution onto a liquid surface in a shower form in a coagulation tank. However, although this recovery method and its apparatus reduce the adhesion of coagulated slurry near the gas phase interface in the coagulation tank and an improvement effect is recognized, there is a gas phase part in one or more aging tanks after the second tank. Further, the aging slurry in the vicinity of the gas-liquid interface is remarkably attached to the tank wall, so that troubles in the process are likely to occur and it cannot be said that it is sufficient.
[0006]
[Problems to be solved by the invention]
As described above, in recovering the polymer solid from the polymer latex, in the conventional recovery method and its apparatus, the improvement of the powder characteristics of the polymer solid, the adhesion of the coagulated slurry in the coagulation tank, and the aging tank Actually, it cannot be said that the recovery method and apparatus satisfy the prevention of adhesion of the aging slurry.
[0007]
The present invention has been made based on the background of the above-described prior art, and prevents the solidification slurry and the aging slurry from adhering in the coagulation tank and the aging tank when the polymer solid is recovered from the polymer latex. An object of the present invention is to obtain a polymer solid having excellent powder characteristics.
[0008]
[Means for Solving the Problems]
As a result of intensive studies aimed at solving the above-mentioned problems, the present inventors have transferred a coagulation tank, an aging tank, and a coagulated slurry having specific conditions when recovering polymer solids from the polymer latex. The present inventors have found a method and an apparatus capable of recovering polymer solids having excellent powder characteristics without causing the coagulation slurry and the aging slurry to adhere to the coagulation tank and the aging tank by combining the apparatuses.
That is, the present invention relates to a method for recovering polymer solids from a polymer latex, in which a coagulant aqueous solution is sprayed in the form of a shower on the entire liquid surface in a coagulation tank having a gas phase portion and the tank wall. It is a recovery method in which coagulated slurry is generated by continuously dropping latex onto the liquid surface in the coagulation tank, and the coagulated slurry is transferred to a full liquid type aging tank by a rotary positive displacement pump, and the coagulated slurry is aged and recovered. Preferably, as a method for generating the coagulation slurry, the coagulant aqueous solution is sprayed from one or more spray nozzles for supplying the coagulant aqueous solution provided in the gas phase portion of the coagulation tank, and the entire liquid surface in the coagulation tank and The spray is allowed to flow down on the tank wall, and is dropped from one or more polymer latex supply nozzles provided in the gas phase of the coagulation tank to the liquid surface in the coagulation tank. A recovering process for recovering the solidified slurry was transferred from the solidified slurry transfer port provided at the bottom coagulation bath,
Furthermore, the spray nozzle for supplying the coagulant aqueous solution provided in the gas phase part of the coagulation tank is a full cone spray nozzle, and the spray angle θ of the spray nozzle is 30 ° ≦ θ ≦ 180 ° directly downward, and When the maximum height H from the liquid surface on the side of the tank wall where the spray flows down using the spray nozzle is in the range of 0 <H ≦ 0.25D (inner diameter of the coagulation tank), This is a recovery method that allows spray to flow down the tank wall.
[0009]
In addition, as a device for recovering polymer solids from the polymer latex, it comprises a coagulation tank, one or more aging tanks and a coagulated slurry transfer device, and the coagulation tank has a gas phase part, The above-mentioned spray nozzle for supplying the coagulant aqueous solution and one or more polymer latex supply nozzles are provided, and the coagulation slurry transfer port is provided at the bottom of the coagulation tank. A recovery device, further comprising a rotary positive displacement pump as a device for transferring the coagulated slurry from the coagulation slurry transfer port at the bottom of the coagulation vessel to the full liquid type maturation vessel, more preferably a gas in the coagulation vessel. A recovery device in which the spray nozzle for supplying the aqueous solution of the coagulant provided in the phase section is a full cone spray nozzle, and the spray angle θ of the spray nozzle is directly downward 30 ° ≦ θ ≦ 180 ° is preferable.
[0010]
Hereinafter, the present invention will be described in detail.
The polymer latex and coagulant aqueous solution of the present invention are shown below.
The polymer latex may generally be a thermoplastic resin produced by emulsion polymerization, but in particular, diene rubber latex such as polybutadiene, styrene-butadiene, acrylonitrile-butadiene, styrene, α-methylstyrene, etc. Polymer latex of aromatic vinyl monomers, polymer latex of vinyl cyan monomers such as acrylonitrile and methacrylonitrile, acrylic acid ester monomers such as butyl acrylate, and methacrylic acid esters such as methyl methacrylate Monomer polymer latex and the like. In addition, a copolymer latex of one or more monomers selected from each of these monomer groups is also exemplified, and AS (acrylonitrile-styrene) latex is generally used as the copolymer latex. is there. Furthermore, the diene rubber latex was graft-polymerized with one or more monomers selected from an aromatic vinyl monomer, a vinyl cyan monomer, an acrylate monomer, and a methacrylate monomer. Polymer latex is also mentioned, and these generally known polymer latexes include MBS (methyl methacrylate-butadiene-styrene) latex, ABS (acrylonitrile-butadiene-styrene) latex, AAS (acrylic acid alkyl ester-acrylonitrile). -Styrene) latex.
[0011]
The aqueous coagulant solution is not particularly limited, and known ones can be used. That is, examples of the aqueous coagulant solution include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, organic acids such as formic acid and acetic acid, and aqueous solutions of inorganic salts such as calcium chloride, magnesium sulfate, and aluminum sulfate, and organic acids such as calcium acetate and aluminum acetate. Examples thereof include an aqueous solution of an acid salt, and one or more of them can be used in combination. Moreover, although the addition amount as a pure inorganic and organic acid salt depends on the amount of the emulsifier contained in the polymer latex, it is usually in the range of 1 to 10 parts by weight per 100 parts by weight of the solid content of the polymer latex. .
[0012]
The polymer latex recovery apparatus used in the present invention comprises a coagulation tank having a gas phase portion as shown in FIG. 1 and an aging tank provided with one or more full-type aging tanks. Here, the solidification tank refers to a tank in which the gas phase part and the liquid phase part are combined, and the full liquid type aging tank is a tank composed of a liquid phase part having no gas phase part.
[0013]
The coagulation tank which is the first tank in the recovery apparatus satisfies the conditions presented below. That is, the coagulation tank is composed of a tank in which the gas phase part and the liquid phase part are combined, and one or more spray nozzles for supplying a coagulant aqueous solution are provided in the gas phase part of the coagulation tank, and one or more in the gas phase part. It has a nozzle for polymer latex supply, and further has one coagulation slurry transfer port at the bottom of the coagulation tank.
[0014]
The spray nozzle for supplying the coagulant aqueous solution is preferably a full cone spray nozzle having a spray angle θ of 30 ° ≦ θ ≦ 180 °, more preferably a nozzle having a spray angle of 60 ° ≦ θ ≦ 120 °. The spray angle is set as an angle directed directly below. The number of spray nozzles is not particularly limited, but more preferably 2 to 4.
[0015]
In addition, the position of the spray nozzle is such that the maximum height H from the liquid surface on the tank wall side where the aqueous solution of the coagulant is sprayed down to the coagulation tank wall using the spray nozzle satisfies the range of 0 <H ≦ 0.25D. It is preferable to provide the position. However, D means the inner diameter (diameter) of the coagulation tank.
If H ≦ 0, that is, if the coagulant aqueous solution supplied from the coagulant aqueous solution supply spray nozzle is not sprayed on the coagulation tank wall, the prevention of adhesion of the coagulated slurry in the coagulation tank, which is the effect of the present invention, is not achieved. Further, if H> 0.25D, the ratio between the polymer latex and the aqueous coagulant solution in direct contact decreases, and the coagulation slurry coagulation ability decreases, resulting in poor efficiency.
[0016]
No particular limitation is imposed on the shape and number of the nozzles for supplying the polymer latex as long as they are provided in the gas phase section of the coagulation tank. The height of the nozzle opening is preferably close to the liquid surface, preferably at least 0.25D or less, more preferably 0.125D or less from the liquid surface.
[0017]
The coagulation slurry transfer port is provided at the lowermost part of the coagulation tank so that the coagulation slurry does not stay in the coagulation tank, and is for easily transferring the coagulation slurry to the aging tank as the second tank.
[0018]
The coagulation temperature in the coagulation tank is not generally determined depending on the type and concentration of the polymer latex. For example, in the case of ABS latex, the temperature is 30 to 80 ° C. The average residence time of the coagulation slurry in the coagulation tank is 1 -10 minutes.
[0019]
The aging tank of the present invention comprises a tank provided with one or more full liquid aging tanks. The number of aging tanks is not particularly limited, but 2 to 5 tanks are preferable in consideration of the recovery device scale and production efficiency.
[0020]
Further, the aging temperature in the aging tanks after the second tank is higher than the solidification temperature, and when there are a plurality of aging tanks, the temperature needs to be higher than that of the previous tank. When the aging temperature is lower than the coagulation temperature, it is difficult to obtain a polymer solid having excellent powder characteristics as intended by the present invention.
[0021]
The average residence time of the solidified slurry in the aging tank is not particularly limited, and is preferably 1 to 5 to 15 minutes in consideration of the number of aging tanks and production efficiency.
[0022]
In order to quantitatively transfer the solidified slurry from the solidification tank as the first tank to the aging tank as the second tank, it is preferable to include a solidified slurry transfer device.
There is a pump as an apparatus for transferring the coagulated slurry, and there are various types. For example, air-driven diaphragm pumps have pulsation in the flow of coagulation slurry, the amount of coagulation slurry in the coagulation tank fluctuates, liquid level fluctuations are large and lack quantitativeness, and at the same time adhesion of coagulation slurry occurs in the coagulation tank It is not preferable. In addition, the induction vortex impeller pump has no pulsation, but the flow rate is not proportional to the number of rotations of the pump, it is difficult to control in a small amount of flow fluctuation, and it is not preferable because of lack of quantitativeness.
[0023]
The rotary positive displacement pump is preferable because the flow rate is proportional to the number of rotations of the pump and has good quantitativeness and no pulsation, so that the amount of coagulated slurry liquid in the coagulation tank is stable and the liquid level does not fluctuate. In addition, if it is a rotary displacement type pump, there will be no limitation in particular, A screw type, a tube type, a rotor type etc. are mentioned. The number of revolutions of the pump is not particularly limited as long as the coagulated slurry particles obtained in the coagulation tank are not crushed, and it is preferable to select a size having a discharge capacity that can be operated at 100 to 400 rpm.
[0024]
Here, the quantitative property of the pump means that the amount of coagulation slurry liquid in the coagulation tank is kept constant and the liquid level is constant even if the supply amount of the raw material polymer latex or coagulant aqueous solution varies. Thus, the discharge amount of the pump can be adjusted.
[0025]
And the liquid level detection of the coagulation tank, that is, the liquid amount control of the coagulation tank is provided with a level meter on the liquid level of the coagulation tank, and the output of the transfer pump is controlled by the inverter by the signal from the level meter, Detection was performed using a method of controlling the liquid amount in the coagulation tank, that is, the liquid level control.
[0026]
Further, the stirring blades of the coagulation tank and the aging tank in the polymer solids recovery device of the present invention are not particularly limited as long as the slurry can be mixed uniformly, and include a multistage paddle blade, a fiddler blade, Examples include turbine blades, bull margin blades, max blend blades, and full zone blades. Among these, a Max Blend blade, which is a flat plate blade, is more preferable from the viewpoint of preventing the solidification slurry and the aging slurry from adhering to the stirring blade. Further, for the purpose of improving the adhesion prevention effect, the stirring blade may be subjected to a surface treatment such as Teflon coating.
[0027]
The number of revolutions of the stirring blades of the coagulation tank and the aging tank is not particularly limited, but the tip speed of the stirring blade is 1.0 to 2.0 (m / It is preferable to carry out in s).
[0028]
Further, the shape of the baffle plate in the coagulation tank and the aging tank, the space between the tank wall and the baffle plate is not particularly limited as long as the slurry in the tank can be uniformly mixed, and the shape is an oval, Examples include a plate shape and a round shape. Among these, it is more preferable that the shape is round from the viewpoint of preventing adhesion of the solidified slurry and the aging slurry to the baffle plate, and the distance between the tank wall and the baffle plate is 5 to 20% of the tank inner diameter. Further, surface treatment such as Teflon coating may be performed for the purpose of improving the adhesion preventing effect.
[0029]
In the polymer latex recovery apparatus used in the present invention, the capacities of the coagulation tank and the aging tank are not particularly limited, but in consideration of industrial production scale and production efficiency, one tank is preferably 0.1 to 10 m. Those in the range of 3 , more preferably 0.5 to 5 m 3 may be used.
[0030]
The slurry that has passed through the aging tank can be dehydrated and washed with a belt filter or a centrifuge. The dehydrated wet cake can be dried by a rotary dryer, a flash dryer, a fluid dryer, a shelf dryer or the like to obtain a polymer solid. For example, the drying conditions of the slurry obtained from ABS latex are generally dried by sending hot air at a temperature of 80 to 140 ° C. in a nitrogen or air atmosphere until the volatile matter of the wet cake is 2.0% or less.
[0031]
【Example】
Hereinafter, the method of the present invention will be described specifically by way of examples, but these do not limit the scope of the present invention. Moreover, about the Example, it carried out using the collection | recovery apparatus of FIG. Various physical properties in Examples and Comparative Examples were measured by the following methods.
(1) Solidified slurry particle retention: The solidified slurry before and after passing through the transfer pump was measured using a Coulter LS-230 particle size distribution measuring device, and the solidified slurry particle retention rate = [(50% of the solidified slurry after passing through the transfer pump) Particle size) / (50% particle size of coagulated slurry before passing through transfer pump)] × 100 (%).
○: Solidified slurry particle retention ratio is 95% or more Δ: Solidified slurry particle retention ratio is 85% or more and less than 95% ×: Solidified slurry particle retention ratio is less than 85% Note that the 50% particle size of the solidified slurry is a particle size distribution. The particle diameter of the 50% integrated value in the integrated distribution.
[0032]
In addition, as a preparation sample for measurement of moisture content, bulk specific gravity and particle size distribution, the aged slurry was drained for 1 minute with a centrifuge (manufactured by Kokusan Centrifuge Co., Ltd.), washed with pure water for 25 seconds, and then dehydrated for 2 minutes. About 2 kg of wet polymer solid was obtained and used for the following measurements.
(2) Moisture content: 2 g of the wet polymer solid obtained above was dried with hot air at a temperature of 100 ° C. for 6 hours, and the dry weight (WD) was measured. Moisture content = [(2-WD) / 2)] It calculated | required using the type | formula of x100 (%).
(3) Bulk specific gravity: 50 g of the wet polymer solid obtained above was dried in hot air at a temperature of 80 ° C. for 16 hours to obtain a polymer powder, which was measured based on JIS K6721.
(4) Particle size distribution: 100 g of the wet polymer solid obtained above was dried with hot air at a temperature of 80 ° C. for 16 hours to obtain a powder of polymer solid, and this powder was measured by Coulter LS-230 particle size distribution. It measured using the apparatus and calculated | required the frequency volume ratio (%) of the 200 mesh pass amount.
[0033]
(5) Quantitative determination of pump: Evaluated in the following three stages.
○: There is no pulsation in the solidified slurry flow, and there is no liquid level fluctuation in the solidification tank.
(Triangle | delta): There is no pulsation in a coagulation | solidification slurry flow, and the liquid level fluctuation | variation of a coagulation tank is 5% or less of liquid amount.
X: There is pulsation in the solidified slurry flow, and there is a fluctuation in the liquid level of the solidification tank.
(6) Slurry adhesion state: It was determined by visual judgment as shown below.
○: No adhesion on the entire tank Δ: Slight adhesion on the tank wall, stirring blade, baffle plate ×: Remarkably adhered on the entire tank [0034]
Example 1
As the polymer latex, a graft copolymer latex comprising 50 parts by weight of butadiene obtained by graft copolymerization of styrene and acrylonitrile onto polybutadiene, 37.5 parts by weight of styrene, and 12.5 parts by weight of acrylonitrile was used as a raw material. The solid concentration of this polymer latex is 32%. In addition, the maximum height H from the liquid surface on the side of the tank wall where the aqueous solution of the coagulant having a calcium chloride concentration of 1.4% and adjusted to pH 2.4 with 15% hydrochloric acid is sprayed to the wall of the coagulation tank is 0.00. Using two full-cone spray nozzles so as to be 15D, the whole liquid surface and the tank wall were allowed to flow down, and the polymer latex was provided in the gas phase part at a height of 0.10D from the liquid surface of the coagulation tank. The polymer latex was continuously added from the nozzle port for supplying the latex. At this time, the coagulation temperature of the coagulation tank was 65 ° C., and the ratio between the polymer latex and the coagulant aqueous solution was 1.0: 0.8.
[0035]
The spray nozzle used was a full cone nozzle manufactured by Lechler with a spray angle of 120 °. Furthermore, the amount of the coagulated slurry liquid in the coagulation tank was set so that the discharge amount of the transfer pump was 65% of the tank volume by inverter control. The screw speed of the transfer pump at this time was 250 to 300 rpm.
[0036]
The coagulation slurry obtained in the coagulation tank was aged in the maturation tank through a rotary positive displacement pump [(Mono pump: Hyojin Equipment Co., Ltd.) which is a coagulation slurry transfer device. The aging slurry was dehydrated and dried to obtain a polymer solid, and the evaluation results are shown in Table 1.
[0037]
Example 2
A polymer solid was obtained in the same manner as in Example 1 except that the salt and acid type of the aqueous coagulant solution were changed as shown in Table 1. The evaluation results are shown in Table 1.
[0038]
Example 3
A polymer solid was obtained in the same manner as in Example 1 except that the salt was not used and the acid species was changed as shown in Table 1. The evaluation results are shown in Table 1.
[0039]
Comparative Example 1
The maximum height H from the liquid surface on the tank wall side where the coagulant aqueous solution is sprayed down to the coagulation tank wall is H = 0.25D, and the solidification slurry transfer pump is changed to an air-driven diaphragm pump. In the same manner as in Example 2, a polymer solid was obtained. The evaluation results are shown in Table 2.
[0040]
Comparative Example 2
A polymer solid was obtained in the same manner as in Example 2 except that the coagulating slurry transfer pump was changed to an induction vortex impeller pump. The evaluation results are shown in Table 2.
[0041]
Comparative Example 3
A polymer solid was obtained in the same manner as in Example 2 except that the maximum height H from the liquid surface on the tank wall side where the aqueous solution of the coagulant was sprayed to the coagulation tank wall was changed to H <0. The evaluation results are shown in Table 2.
[0042]
Comparative Example 4
A polymer solid was obtained in the same manner as in Example 2 except that the polymer recovery apparatus was changed to a full-pressure pumping recovery apparatus as shown in FIG. 2 and no transfer pump was used. The evaluation results are shown in Table 2.
[0043]
Comparative Example 5
A polymer solid was obtained in the same manner as in Example 1 except that the polymer recovery apparatus was changed to an overflow recovery apparatus as shown in FIG. 3 and no transfer pump was used. The evaluation results are shown in Table 2.
[0044]
[Table 1]
[Table 2]
【The invention's effect】
According to the present invention, it is possible to prevent the polymer solid matter from adhering and generating in the coagulation tank and the aging tank as compared with the conventional recovery apparatus, and by providing a rotary positive displacement pump as a coagulation slurry transfer apparatus, The produced solidified slurry particles are quantitatively transferred to the aging tank without being crushed, and there are no troubles in the process such as blocking, and finally the polymer solids with excellent powder characteristics are stabilized. Obtainable.
[Brief description of the drawings]
FIG. 1 is a drawing showing a collection device used in Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 of the present invention.
FIG. 2 is a drawing showing a recovery device used in Comparative Example 4 of the present invention.
FIG. 3 is a view showing a recovery apparatus used in Comparative Example 5 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Coagulation
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP00060298A JP3813011B2 (en) | 1998-01-06 | 1998-01-06 | Method and apparatus for collecting polymer solids |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP00060298A JP3813011B2 (en) | 1998-01-06 | 1998-01-06 | Method and apparatus for collecting polymer solids |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11199630A JPH11199630A (en) | 1999-07-27 |
| JP3813011B2 true JP3813011B2 (en) | 2006-08-23 |
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| JP00060298A Expired - Fee Related JP3813011B2 (en) | 1998-01-06 | 1998-01-06 | Method and apparatus for collecting polymer solids |
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| JP (1) | JP3813011B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR100471601B1 (en) * | 2002-11-05 | 2005-03-11 | 주식회사 엘지화학 | Method for Preparing Powder of High Macromolecule Latex Resin |
| KR100837518B1 (en) | 2005-10-13 | 2008-06-12 | 주식회사 엘지화학 | Method for preparing of high molecule latex resin powder |
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| JPH11199630A (en) | 1999-07-27 |
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