JP3886098B2 - Sludge dewatering agent and sludge dewatering method - Google Patents

Description

一般式（１）
Ｒ１、Ｒ２はメチルあるいはエチル基、Ｒ３は炭素数１〜３のアルキルまたアルコキシ基あるいはベンジル基、Ｘ１は陰イオンをそれぞれ表わす
【化２】

一般式（２）
Ｒ４、Ｒ５はメチルあるいはエチル基、Ｒ６は炭素数１〜３のアルキルまたアルコキシ基あるいはベンジル基、Ｘ２は陰イオンをそれぞれ表わす
【化３】

一般式（３）
Ｒ７は水素またはメチル基、Ｍは陽イオンをそれぞれ表わす
【０００７】
請求項２の発明は、分子の重量平均分子量が２００万〜１５００万であることを特徴とする請求項１あるいは２に記載の汚泥脱水剤である。
【０００８】
請求項３の発明は、前記両性高分子が、水に非混和性の有機溶剤と油溶性乳化剤存在下で、有機溶剤を連続相、両性高分子水溶液を非連続相とする油中水型エマルジョンからなることを特徴とする請求項１〜３に記載の汚泥脱水剤である。
【０００９】
請求項４の発明は、有機汚泥に対し無機凝集剤を添加しｐＨを３以上、５未満に調整した後、請求項１〜３に記載の両性高分子を添加、混合した後、脱水機により脱水することを特徴とするの汚泥の脱水方法である。
【００１０】
【発明の実施の形態】
本発明の多官能性単量体とアニオン性単量体及びノニオン性単量体共存下で、メタクリレ−ト系四級アンモニウム塩基含有単量体とアクリレ−ト系四級アンモニウム塩基含有単量体とを特定の割合で重合することにより合成される両性高分子は、具体的には以下のような操作により合成することができる。すなわち、多官能性単量体、アニオン性単量体、ノニオン性単量体、メタクリレ−ト系四級アンモニウム塩基含有単量体及びアクリレ−ト系四級アンモニウム塩基含有単量体が共存する水溶液を調製し、ｐＨを２〜５にした後、公知の重合法で重合する。重合法としては、水溶液重合、油中水型エマルジョン重合、油中水型分散重合、塩水中分散重合などによって重合した後、水溶液、分散液、エマルジョンあるいは粉末など任意の製品形態にすることができる。最も好ましい形態としては、乾燥工程が不要であり、濃度を高められ、溶解時間も短い油中水型エマルジョン重合品が適している。
【００１１】
油中水型高分子エマルジョンの製造方法としては、カチオンン性単量体、あるいはカチオン性単量体と共重合可能な単量体からなる単量体混合物を水、少なくとも水と非混和性の炭化水素からなる油状物質、油中水型エマルジョンを形成するに有効な量とＨＬＢを有する少なくとも一種類の界面活性剤を混合し、強攪拌し油中水型エマルジョンを形成させた後、重合することにより合成する。
【００１２】
分散媒として使用する炭化水素からなる油状物質の例としては、パラフィン類あるいは灯油、軽油、中油などの鉱油、あるいはこれらと実質的に同じ範囲の沸点や粘度などの特性を有する炭化水素系合成油、あるいはこれらの混合物があげられる。
【００１３】
油中水型エマルジョンを形成するに有効な量とＨＬＢを有する少なくとも一種類の界面活性剤の例としては、ＨＬＢ３〜１１のノニオン性界面活性剤であり、その具体例としては、ソルビタンモノオレ−ト、ソルビタンモノステアレ−ト、ソルビタンモノパルミテ−トなどがあげられる。これら界面活性剤の添加量としては、油中水型エマルジョン全量に対して０．５〜１０重量％であり、好ましくは１〜５重量％である。
【００１４】
重合後は、転相剤と呼ばれる親水性界面化成剤を添加して油の膜で被われたエマルジョン粒子が水になじみ易くし、中の水溶性高分子が溶解しやすくする処理を行い、水で希釈しそれぞれの用途に用いる。親水性界面化成剤の例としては、カチオン性界面化成剤やＨＬＢ９〜１５のノニオン性界面化成剤であり、ポリオキシエチレンアルキルエ−テル系などである。
【００１５】
重合濃度としては、水溶液重合ならば８〜１５重量％であり、好ましくは１０〜１２重量％であり、油中水型エマルジョン重合あるいは油中水型分散重合なら２０〜５０重量％であり、好ましくは２５〜４０重量％であり、塩水中分散重合なら１５〜３５重量％、好ましくは２０〜３０重量％である。重合温度としては、０〜８０℃であり、好ましくは２０〜５０℃、最も好ましくは２０〜４０℃であり、単量体の組成、重合法、開始剤の選択によって適宜重合温度を設定する。
【００１６】
使用するメタクリレ−ト系四級アンモニウム塩基含有単量体の例としては、メタクロイルオキシエチルトリメチルアンモニウム塩、メタクロイルオキシエチルトリエチルアンモニウム塩、メタクロイルオキシエチルジメチルエチルアンモニウム塩、メタクロイルオキシエチルジメチルベンジルアンモニウム塩などが上げられる。また、アクリレ−ト系四級アンモニウム塩基含有単量体の例としては、アクロイルオキシエチルトリメチルアンモニウム塩、アクロイルオキシエチルトリエチルアンモニウム塩、アクロイルオキシエチルジメチルエチルアンモニウム塩、アクロイルオキシエチルジメチルベンジルアンモニウム塩などが上げられる。ノニオン性単量体の例しては、アクリルアミドあるいはメタアクリルアミドである。更にアニオン性単量体の例としては、アクリル酸あるいはメタアクリル酸である。
【００１７】
最も重要なメタクリレ−ト系四級アンモニウム塩基含有単量体とアクリレ−ト系四級アンモニウム塩基含有単量体の比率について説明すると、本発明の特徴としてアクリレ−ト系四級アンモニウム塩基含有単量体の比率を高めることである。
従来、ベルトプレスなどの脱水には、ニ重結合にメチル基が結合して疎水性がやや高まったメタクリレ−ト系四級アンモニウム塩基含有単量体が、脱水ケ−キの含水率が低下し、有用であるとされ、メタクリレ−ト系四級アンモニウム塩基含有単量体とアクリレ−ト系四級アンモニウム塩基含有単量体の両方を含有する両性高分子においても、メタクリレ−ト系四級アンモニウム塩基含有単量体を多く共重合する傾向があった。しかし、単にメタクリレ−ト系四級アンモニウム塩基含有単量体の比率を増加しただけでは解決できない汚泥がある。その場合、架橋結合の導入など検討されてきた。メタクリレ−ト系四級アンモニウム塩基含有単量体は、アクリレ−ト系四級アンモニウム塩基含有単量体に較べ、重合反応性がやや低下し、そのため架橋剤を共存しても効率良く架橋結合が導入できない場合が多かった。
【００１８】
そのため、本発明においてはアクリレ−ト系四級アンモニウム塩基含有単量体の比率を多くする。すなわちメタクリレ−ト系四級アンモニウム塩基含有単量体の構成単位をａモル％で表わし、アクリレ−ト系四級アンモニウム塩基含有単量体の構成単位をｂモル％で表わすと、ａが５〜２０、ｂが２０〜４０である。また、両者の比率は０．９＞ｂ／（ａ＋ｂ）＞０．５である。さらにこのとき、アニオン性単量体の構成単位をｃモル％とすると、ｃは５〜２０であり、アニオン性単量体構成単位とカチオン性単量体の構成単位合計のモル％との比率は、０．５＞ｃ／（ａ＋ｂ）＞０．１である。
【００１９】
本発明の両性高分子を合成する場合使用する重合開始剤は、ラジカル重合開始剤を用いる。その例としてアゾ系、過酸化物系、レドックス系いずれでも重合することが可能である。油溶性アゾ系開始剤の例としては、２、２’−アゾビスイソブチロニトリル、１、１’−アゾビス（シクロヘキサンカルボニトリル）、２、２’−アゾビス（２−メチルブチロニトリル）、２、２’−アゾビス（２−メチルプロピオネ−ト）などがあげられ、水混溶性溶剤に溶解し添加する。水溶性アゾ系開始剤の例としては、２、２’−アゾビス（アミジノプロパン）二塩化水素化物、２、２’−アゾビス〔２−（５−メチル−２−イミダゾリン−２−イル）プロパン〕二塩化水素化物、４、４’−アゾビス（４−シアノ吉草酸）などがあげられる。またレドックス系の例としては、ペルオキシ二硫酸アンモニウムあるいはカリウムと亜硫酸ナトリウム、亜硫酸水素ナトリウム、トリメチルアミン、テトラメチルエチレンジアミンなどとの組み合わせがあげられる。さらに過酸化物の例としては、ペルオクソ二硫酸アンモニウム、過酸化水素、ベンゾイルペルオキサイド、ラウロイルペルオキサイド、オクタノイルペルオキサイド、サクシニックペルオキサイド、t-ブチルペルオキシ２−エチルヘキサノエ−トなどをあげることができる。
【００２０】
使用する架橋剤は、Ｎ、Ｎ−メチレンビスアクリルアミド、エチレングリコ−ルジ（メタ）アクリレ−ト、ペンタエリスリト−ルテトラ（メタ）アクリレ−トなどの多不飽和単量体、あるいはＮ、Ｎ−ジメチルアクリルアミドあるいはＮ、Ｎ−ジエチルアクリルアミドなどの熱架橋性単量体である。これら架橋剤の両性高分子中での含有量は、全高分子構成単位に対して０．０００１〜０．０２モル％であり、好ましくは０．０００１〜０．００２モル％である。０．０００１モル％未満では、脱水剤として架橋の効果が発現しにくく、０．０２モル％より高いと高分子がゲル化など水不溶性になりやすく使用できない。
【００２１】
架橋剤による高分子が架橋した物性の変化を表わす指標としては、高分子純分０．５％濃度、１規定食塩水中における回転粘度計で測定した粘性による。本発明の場合、他の重合条件がすべて同様で架橋剤無添加時を基準として、架橋剤を全単量体に０．０００１モル％添加すると、前記粘度が２０％低下する。架橋剤の添加量が０．００００５モル％であると、前記粘度は５〜１０％しか低下しない。添加量が０．０００２〜０．００１モル％では前記粘度は２０〜５０％低下する。また、架橋剤が０．０２モル％より多いとゲル化、不溶化が起こりやすい。しかし、この添加量は一つの目安であり、重合条件によって変化する。従って、重合条件によって適宜添加量を適性に決めることが必要である。
【００２２】
本発明の両性高分子からなる汚泥脱水剤の分子量としては、重量平均分子量として２００万〜１５０００万であり、好ましくは３００万〜１０００万である。２００万未満では、凝集性が不足し、脱水不良となり、１５００万より高いと粘性が増加し過ぎ、分散性が悪くなり脱水性能が低下する。
【００２３】
適用可能な汚泥は、製紙排水、化学工業排水、食品工業排水などの生物処理したときに発生する余剰汚泥、あるいは都市下水の生汚泥、混合生汚泥、余剰汚泥、消化汚泥などの有機汚泥であるが、最も適する汚泥は、食品工業排水の生物処理汚泥である。
【００２４】
前記汚泥は、本発明の架橋性単量体、アクリレ−ト系四級アンモニウム塩基含有単量体、メタクリレ−ト系四級アンモニウム塩基含有単量体、（メタ）アクリル酸及びアクリルアミドからなる両性高分子単独でも処理可能であるが、無機凝集剤を併用するとさらに効果が発現し、効率的な汚泥脱水が実施できる。無機凝集剤の例としては、硫酸アルミニウム、塩化第二鉄、ポリ塩化アルミニウム、ポリ塩化鉄などがあげられ、これら無機凝集剤を先に汚泥に添加、混合後、本発明の両性高分子を添加混合し、脱水機に送る。無機凝集剤の添加量としては、汚泥固形分に対し重量で５００ｐｐｍ〜１００００ｐｐｍ程度であり、好ましくは１０００〜５０００ｐｐｍである。
【００２５】
また、本発明の汚泥処理方法は、汚泥のｐＨを５未満に調節して両性高分子からなる汚泥脱水剤を添加する。上記無機凝集剤を添加すると汚泥ｐＨが低下してくる傾向があるが、低下しない場合は、有機あるいは無機酸を添加してｐＨを下げると効率的である。また、本発明の両性高分子の添加量は、汚泥固形分に対し重量で０．１〜１．０％であり、好ましくは０．２〜０．５％である。本発明の汚泥脱水剤及び汚泥脱水方法は、脱水機はベルトプレス、スクリュ−プレス、フィルタ−プレスなどに適用できるが、特にベルトプレスに適している。
【００２６】
【実施例】
以下、実施例および比較例によって本発明をさらに詳しく説明するが、本発明はその要旨を超えない限り、以下の実施例に制約されるものではない。
【００２７】
（合成例−１）
攪拌機および温度制御装置を備えた反応槽に沸点１９０°Ｃないし２３０°Ｃのイソパラフィン１２６．０ｇにソルビタンモノオレート６．０ｇ及びポリリシノ−ル酸／ポリオキシエチレンブロック共重合物０．６ｇを仕込み溶解させた。別に脱イオン水８３．２ｇとアクリル酸（ＡＡＣと略記）６０％水溶液２３．６ｇを混合し、これを３５％水酸化ナトリウム水溶液２２．４ｇで当量中和した。中和後、アクリロイルオキシエチルトリメチルアンモニウム塩化物（以下ＤＭＱと略記）８０％水溶液１２６．７ｇ、メタクリロイルオキシエチルトリメチルアンモニウム塩化物（以下ＤＭＣと略記）８０％水溶液３４．０ｇ、アクリルアミド（ＡＡＭと略記）５０％水溶液６５．１ｇ及びＮ，Ｎ−メチレンビスアクリルアミド（ＭＢＡと略記）０．１％水溶液０．５ｇを混合し溶解させ、ｐＨを４．０１に調節し、油と水溶液を混合し、ホモジナイザーにて１０００ｒｐｍで１５分間攪拌乳化した。この時の単量体組成は、ＤＭＱ／ＤＭＣ／ＡＡＣ／ＡＡＭ＝４０／１０／１５／３５（モル％）、また全単量体に対しＭＢＡは０．０００２５モル％である。
【００２８】
得られたエマルジョンにイソプロピルアルコール１０％水溶液０．５５ｇ（対単量体０．０２５重量％）を加え、単量体溶液の温度を２５〜２８℃に保ち、窒素置換を３０分行った後、２、２’−アゾビス〔２−（５−メチル−２−イミダゾリン−２−イル）プロパン〕二塩化水素化物の１０％水溶液０．３５ｇ（対単量体０．０２重量％）を加え、重合反応を開始させた。反応温度を２６±２℃で８時間重合させ反応を完結させた。重合後、生成した油中水型エマルジョンに転相剤としてポリオキシエチレントリデシルエ−テル１０．０ｇ（対液２．０重量％）を添加混合して試験に供する試料（試料−１）とした。また静的光散乱法による分子量測定器（大塚電子製ＤＬＳ−７０００）によって重量平均分子量を測定した。結果を表１に示す。
【００２９】
（合成例２）
合成例１と同様な操作により、それぞれＤＭＱ／ＤＭＣ／ＡＡＣ／ＡＡＭ＝３０／２０／１５／３５（試料−２）、４５／１５／２０／２０（試料−３）、５５／２５／２０／０（試料−４）、１０／５／５／８０（試料−５）（いずれもモル％）からなる組成の油中水型両性高分子エマルジョンを合成した。結果を表１に示す。
【００３０】
（比較合成例）
Ｎ，Ｎ−メチレンビスアクリルアミドを添加しないで重合した他は、合成例１と同様な操作により、比較−１〜比較−５を合成した。
【００３１】
【実施例１〜５】
都市下水混合生汚泥（ｐＨ６．８９、全ｓｓ分４０、３００ｍｇ／Ｌ）２００ｍＬをポリビ−カ−に採取し、ポリ塩化第二鉄を対汚泥固形分２３００ｐｐｍ添加しビ−カ−移し変え攪拌５回行った。この時の汚泥ｐＨは、４．７２であった。次ぎに表１の本発明における両性高分子、試料−１〜試料−５を対汚泥固形分４０００ｐｐｍ添加し、ビ−カ−移し変え攪拌１０回行った後、Ｔ−１１７９Ｌの濾布（ナイロン製）により濾過し、４５秒後の濾液量を測定した。また濾過した汚泥をプレス圧２Ｋｇ／ｍ2で１分間脱水する。その後、濾布剥離性とケ−キ自己支持性（脱水ケ−キの硬さ、含水率と関係）を目視によりチェックし、ケ−キ含水率（１０５℃で２０ｈｒ乾燥）を測定した。結果を表２に示す。
【００３２】
【比較例１〜９】
表２の比較合成例の試料、比較−１〜比較−５の両性高分子を用いた試験、また、無機凝集剤を併用しないで試料−１、試料−３のみをそれぞれ用いた試験、さらに無機凝集剤の添加量を体汚泥固形分１２００ｐｐｍ添加し、汚泥のｐＨを６．２０に調節し、試料−１、試料−３を添加した試験を実施例１〜５と同様な試験操作により行った。結果を表２に示す。
【００３３】
【実施例６〜１０】
食品加工廃水余剰汚泥（ｐＨ６．６５、全ｓｓ２４、０００ｍｇ／ｍＬ）２００ｍＬをポリビ−カ−に採取し、ポリ塩化第二鉄を対汚泥固形分１６００ｐｐｍ添加しビ−カ−移し変え攪拌５回行った。この時の汚泥ｐＨは、４．２２であった。次ぎに表１の本発明における両性高分子、試料−１〜試料−５を対汚泥固形分５０００ｐｐｍ添加し、ビ−カ−移し変え攪拌１０回行った後、Ｔ−１１７９Ｌの濾布（ナイロン製）により濾過し、４５秒後の濾液量を測定した。また濾過した汚泥をプレス圧２Ｋｇ／ｍ2で１分間脱水する。その後、濾布剥離性とケ−キ自己支持性（脱水ケ−キの硬さ、含水率と関係）を目視によりチェックし、ケ−キ含水率（１０５℃で２０ｈｒ乾燥）を測定した。結果を表３に示す。
【００３４】
【比較例１０〜１８】
表２の比較合成例の試料、比較−１〜比較−５の両性高分子を用いた試験、また、無機凝集剤を併用しないで試料−３、試料−５のみをそれぞれ用いた試験、さらに無機凝集剤の添加量を体汚泥固形分７００ｐｐｍ添加し、汚泥のｐＨを６．１０に調節し、試料−３、試料−５を添加した試験を実施例１１〜２０と同様な試験操作により行った。結果を表３に示す。
【００３５】
【表１】

ＤＭＣ：メタアクリロイルオキシエチルトリメチルアンモニウム塩化物
ＤＭＱ：アクリロイルオキシエチルトリメチルアンモニウム塩化物
ＡＡＣ：アクリル酸、ＡＡＭ：アクリルアミド、
分子量：単位は万、液性状；ＥＭ：油中水型エマルジョン、ＡＱ：水溶液
【００３６】
【表２】

無機凝集剤添加量：ｐｐｍ（対汚泥固形分）
濾液量：ｍＬ、ケ−キ含水率：重量％、
【００３７】
【表３】

濾液量：ｍＬ、ケ−キ含水率：重量％、
無機凝集剤添加量：ｐｐｍ（対汚泥固形分）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sludge dewatering agent and a sludge dewatering method, and more specifically, a sludge dewatering agent comprising an amphoteric polymer having a specific cationic structural unit, an anionic structural unit and a nonionic structural unit, and an inorganic material for organic sludge. The present invention relates to a method for dewatering sludge comprising adding a flocculant and adjusting the pH to 3 or more and less than 5, then adding and mixing the amphoteric polymer, and then dehydrating with a dehydrator.
[0002]
[Prior art]
Conventionally, a cationic polymer dehydrating agent has been used alone for sludge dehydration, but in recent years, with the increase in sludge generation and sludge deterioration, conventional cationic polymer dehydrating agents have The treatment state is not always satisfactory in terms of the amount of treatment, the moisture content of the dehydrated cake, the SS recovery rate, the peelability of the cake from the filter cloth, and improvements are required. In order to improve the drawbacks of these conventional cationic polymer dehydrating agents, various amphoteric polymer dehydrating agents have been proposed, but these amphoteric polymer dehydrating agents are not always satisfactory. For example, (1) an amphoteric polymer dehydrating agent having a tertiary amino group (Japanese Patent Laid-Open No. Sho 62-205112), (2) an amphoteric polymer dehydrating agent containing a quaternary ammonium group (Japanese Patent Laid-Open No. Sho 53-149292) ), (3) amphoteric polymer dehydrating agents containing tertiary and quaternary (Japanese Patent Laid-Open No. 3-18900) and the like are disclosed. However, the amphoteric polymer dehydrating agent (1) is superior in cohesiveness compared to the conventional cationic polymer dehydrating agent and forms a large coagulation floc, but has a high pH such as digested sludge of sewage and human waste. For sludge, the performance is significantly reduced due to the dissociation state of the tertiary amino group, and it is easily affected by changes in sludge properties such as sludge concentration including pH, and stable treatment cannot be performed. There are disadvantages such as inferior to the conventional cationic polymer dehydrating agent in terms of the stability of the product in a powder or solution state. In addition, the amphoteric polymer dehydrating agent (2) has better product stability than the amphoteric polymer dehydrating agent containing a tertiary amino group and agglomeration compared to the conventional cationic polymer dehydrating agent. Although there is power, there are many points that need to be improved, such as a large amount of required addition, a high moisture content of the cake, and poor peelability of the cake from the filter cloth. On the other hand, although the amphoteric polymer dehydrating agent (3) has improved the disadvantages of the dehydrating agents (1) and (2), it is still satisfactory in terms of the required addition amount and the moisture content of the cake. It is not at a level that can be achieved, and improvements are required for practical use.
[0003]
Under such circumstances, improvement of amphoteric polymer dehydrating agents is also being promoted. For example, an amphoteric polymer containing both quaternary ammonium bases of dialkylaminoethyl acrylate and dialkylaminoethyl methacrylate has also been proposed, and JP-A-3-293100 contains both, An amphoteric polymer dehydrating agent containing 1 to 5 mol% of methacrylate is disclosed. JP-A-7-256299 discloses an amphoteric polymer dehydrating agent having a high methacrylate content and a high cationic group content, and JP-A-7-256300 discloses an acrylate content. An amphoteric polymer dehydrating agent having a high anionic group content is disclosed.
[0004]
Furthermore, in recent years, amphoteric polymers having a cross-linked treatment in the molecule have been widely studied. When the organic sludge is dehydrated by a belt press or a filter press, such a crosslinked polymer often exhibits an effect in order to obtain good peelability. From the viewpoint of polymerization reaction, methacrylate is slightly less reactive than acrylate, and especially when synthesizing amphoteric polymers that have been subjected to crosslinking treatment in the presence of a crosslinking agent, Disadvantageously, the polymerization reaction proceeds more rapidly with acrylate, so that a crosslinking reaction occurs.
[Problems to be solved by the invention]
The object of the present invention is to develop a dewatering agent capable of realizing a cohesive state having good drainage and filter cloth peelability when developing a sludge dewatering agent for belt presses or filter presses. A polymerization method for efficiently synthesizing an amphoteric polymer having a cationic group composed of an acrylate quaternary ammonium base-containing monomer and a methacrylate quaternary ammonium base-containing monomer in a molecule. And providing a method for efficiently dewatering organic sludge using the amphoteric polymer dehydrating agent.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a methacrylate-based quaternary ammonium base-containing monomer in the presence of a polyfunctional monomer, an anionic monomer and a nonionic monomer. It was found that by amply polymerizing the acrylate quaternary ammonium base-containing monomer at a specific ratio, it was possible to efficiently synthesize an amphoteric polymer having a cross-linking bond in the molecule. . That is, the invention of claim 1 of the present invention is composed of 5 to 30 mol% of structural units represented by the following general formula (1), 10 to 50 mol% of structural units represented by the general formula (2), and general formula (3). 5 to 20 mol% of the structural unit represented, 0 to 80 mol% of the (meth) acrylamide structural unit, and 0.0001 to 0.02 mol% of the crosslinkable monomer structural unit with respect to the total amount of the polymer, and When the molar percentages of the structural units represented by the general formulas (1) to (3) are a, b and c, a, b and c are 0.9> b / (a + b)> 0.5 . 0.5> c / (a + b)> 0.1 is a sludge dehydrating agent comprising an amphoteric polymer, characterized in that the relationship is satisfied.
[Chemical 1]

General formula (1)
R1 and R2 are methyl or ethyl groups, R3 is an alkyl, alkoxy or benzyl group having 1 to 3 carbon atoms, and X1 is an anion.

General formula (2)
R4 and R5 represent a methyl or ethyl group, R6 represents an alkyl, alkoxy or benzyl group having 1 to 3 carbon atoms , and X2 represents an anion.

General formula (3)
R7 represents hydrogen or a methyl group, and M represents a cation.
The invention according to claim 2 is the sludge dewatering agent according to claim 1 or 2, wherein the weight average molecular weight of the molecule is 2 million to 15 million.
[0008]
According to a third aspect of the present invention, the amphoteric polymer is a water-in-oil emulsion in which an organic solvent is a continuous phase and an aqueous amphoteric polymer aqueous solution is a discontinuous phase in the presence of an organic solvent immiscible with water and an oil-soluble emulsifier. The sludge dehydrating agent according to any one of claims 1 to 3, wherein
[0009]
In the invention of claim 4, after adding an inorganic flocculant to organic sludge and adjusting the pH to 3 or more and less than 5, after adding and mixing the amphoteric polymer according to claims 1 to 3, the dehydrator The method for dewatering sludge is characterized by dehydration.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the presence of the multifunctional monomer of the present invention, an anionic monomer and a nonionic monomer, a methacrylate-based quaternary ammonium base-containing monomer and an acrylate-based quaternary ammonium base-containing monomer The amphoteric polymer synthesized by polymerizing and at a specific ratio can be specifically synthesized by the following operation. That is, an aqueous solution in which a polyfunctional monomer, an anionic monomer, a nonionic monomer, a methacrylate quaternary ammonium base-containing monomer, and an acrylate quaternary ammonium base-containing monomer coexist After adjusting pH to 2-5, it superposes | polymerizes with a well-known polymerization method. As the polymerization method, after polymerization by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, salt water dispersion polymerization, etc., it can be made into any product form such as aqueous solution, dispersion, emulsion or powder. . The most preferred form is a water-in-oil emulsion polymerized product that does not require a drying step, has a high concentration, and has a short dissolution time.
[0011]
As a method for producing a water-in-oil polymer emulsion, a monomer mixture comprising a cationic monomer or a monomer copolymerizable with a cationic monomer is water, and at least carbon is immiscible with water. An oily substance composed of hydrogen, an amount effective to form a water-in-oil emulsion, and at least one surfactant having HLB are mixed and stirred vigorously to form a water-in-oil emulsion, followed by polymerization. To synthesize.
[0012]
Examples of oily substances composed of hydrocarbons used as a dispersion medium include paraffins, mineral oils such as kerosene, light oil, and middle oil, or hydrocarbon-based synthetic oils having characteristics such as boiling point and viscosity substantially in the same range as these. Or a mixture thereof.
[0013]
Examples of at least one surfactant having an amount effective to form a water-in-oil emulsion and HLB are HLB 3-11 nonionic surfactants, specific examples of which include sorbitan monooleate Sorbitan monostearate, sorbitan monopalmitate and the like. The amount of these surfactants to be added is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total amount of the water-in-oil emulsion.
[0014]
After the polymerization, a hydrophilic interfacial modifier called a phase inversion agent is added to make the emulsion particles covered with the oil film easy to become familiar with water, and to dissolve the water-soluble polymer therein. Dilute with and use for each application. Examples of hydrophilic interfacial chemicals include cationic interfacial chemicals and HLB 9-15 nonionic interfacial chemicals, such as polyoxyethylene alkyl ethers.
[0015]
The polymerization concentration is 8 to 15% by weight for aqueous solution polymerization, preferably 10 to 12% by weight, and 20 to 50% by weight for water-in-oil emulsion polymerization or water-in-oil dispersion polymerization. Is 25 to 40% by weight, and 15 to 35% by weight, preferably 20 to 30% by weight in the case of dispersion polymerization in brine. The polymerization temperature is 0 to 80 ° C., preferably 20 to 50 ° C., and most preferably 20 to 40 ° C. The polymerization temperature is appropriately set depending on the monomer composition, the polymerization method, and the selection of the initiator.
[0016]
Examples of the methacrylate-based quaternary ammonium base-containing monomer used include methacryloyloxyethyltrimethylammonium salt, methacryloyloxyethyltriethylammonium salt, methacryloyloxyethyldimethylethylammonium salt, and methacryloyloxyethyldimethylbenzyl. Ammonium salts are raised. Examples of acrylate quaternary ammonium base-containing monomers include acryloyloxyethyltrimethylammonium salt, acryloyloxyethyltriethylammonium salt, acryloyloxyethyldimethylethylammonium salt, acryloyloxyethyldimethylbenzyl. Ammonium salts are raised. Examples of nonionic monomers are acrylamide or methacrylamide. Further examples of anionic monomers are acrylic acid or methacrylic acid.
[0017]
The ratio of the most important methacrylate-based quaternary ammonium base-containing monomer to the acrylate-based quaternary ammonium base-containing monomer will be described as a feature of the present invention. It is to increase the body ratio.
Conventionally, for the dehydration of belt presses and the like, a methacrylate-based quaternary ammonium base-containing monomer having a slightly increased hydrophobicity due to a methyl group bonded to a double bond reduces the water content of the dehydration cake. The amphoteric polymer containing both the methacrylate-based quaternary ammonium base-containing monomer and the acrylate-based quaternary ammonium base-containing monomer is also useful for the methacrylate-based quaternary ammonium. There was a tendency to copolymerize many base-containing monomers. However, there are sludges that cannot be solved simply by increasing the ratio of the methacrylate-based quaternary ammonium base-containing monomer. In that case, introduction of cross-linking has been studied. The methacrylate-based quaternary ammonium base-containing monomer has a slightly lower polymerization reactivity than the acrylate-based quaternary ammonium base-containing monomer. There were many cases that could not be introduced.
[0018]
Therefore, in the present invention, the ratio of the acrylate quaternary ammonium base-containing monomer is increased. That is, when the structural unit of the methacrylic quaternary ammonium base-containing monomer is represented by a mol% and the structural unit of the acrylate quaternary ammonium base-containing monomer is represented by b mol%, a is 5 to 5%. 20, b is 20-40. The ratio between the two is 0.9> b / (a + b)> 0.5 . Further, at this time, assuming that the structural unit of the anionic monomer is c mol%, c is 5 to 20, and the ratio of the anionic monomer structural unit to the mol% of the total structural unit of the cationic monomer. Is 0.5> c / (a + b)> 0.1.
[0019]
A radical polymerization initiator is used as the polymerization initiator used when synthesizing the amphoteric polymer of the present invention. For example, any of azo, peroxide and redox polymers can be polymerized. Examples of oil-soluble azo initiators are 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylpropionate) and the like are dissolved in a water-miscible solvent and added. Examples of water-soluble azo initiators include 2,2′-azobis (amidinopropane) dichloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] And dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), and the like. Examples of redox systems include ammonium peroxydisulfate or potassium in combination with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, and the like. Examples of peroxides include ammonium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, and t-butylperoxy 2-ethylhexanoate. Can do.
[0020]
The crosslinking agent used is a polyunsaturated monomer such as N, N-methylenebisacrylamide, ethylene glycol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, or N, N- Thermally crosslinkable monomers such as dimethylacrylamide or N, N-diethylacrylamide. The content of these cross-linking agents in the amphoteric polymer is 0.0001 to 0.02 mol%, preferably 0.0001 to 0.002 mol%, based on all polymer structural units. If it is less than 0.0001 mol%, the effect of crosslinking as a dehydrating agent is difficult to be exhibited, and if it exceeds 0.02 mol%, the polymer tends to be insoluble in water such as gelation and cannot be used.
[0021]
The index representing the change in physical properties of the polymer crosslinked by the crosslinking agent is based on the viscosity measured with a rotational viscometer in a pure polymer 0.5% concentration and 1N saline solution. In the case of the present invention, when the other polymerization conditions are all the same and 0.0001 mol% of the crosslinking agent is added to all monomers on the basis of no addition of the crosslinking agent, the viscosity is reduced by 20%. When the addition amount of the crosslinking agent is 0.00005 mol%, the viscosity is reduced only by 5 to 10%. When the addition amount is 0.0002 to 0.001 mol%, the viscosity is reduced by 20 to 50%. Moreover, when there are more crosslinking agents than 0.02 mol%, gelatinization and insolubilization will occur easily. However, the amount added is only a guide and varies depending on the polymerization conditions. Therefore, it is necessary to appropriately determine the addition amount depending on the polymerization conditions.
[0022]
The molecular weight of the sludge dehydrating agent comprising the amphoteric polymer of the present invention is 2 million to 150,000,000, preferably 3 million to 10 million as a weight average molecular weight. If it is less than 2 million, the cohesiveness is insufficient, resulting in poor dehydration, and if it is higher than 15 million, the viscosity is excessively increased, the dispersibility is deteriorated, and the dehydration performance is lowered.
[0023]
Applicable sludge is surplus sludge generated during biological treatment such as papermaking wastewater, chemical industrial wastewater, food industry wastewater, or organic sludge such as raw sludge, mixed raw sludge, surplus sludge, digested sludge, etc. However, the most suitable sludge is biological treatment sludge from food industry wastewater.
[0024]
The sludge is an amphoteric polymer comprising the crosslinkable monomer of the present invention, an acrylate quaternary ammonium base-containing monomer, a methacrylate quaternary ammonium base-containing monomer, (meth) acrylic acid and acrylamide. Although treatment is possible with molecules alone, the combined use of an inorganic flocculant provides further effects and enables efficient sludge dewatering. Examples of inorganic flocculants include aluminum sulfate, ferric chloride, polyaluminum chloride, polyiron chloride, etc. These inorganic flocculants are first added to sludge, mixed and then the amphoteric polymer of the present invention is added. Mix and send to dehydrator. The amount of the inorganic flocculant added is about 500 ppm to 10000 ppm by weight with respect to the sludge solid content, preferably 1000 to 5000 ppm.
[0025]
Further, in the sludge treatment method of the present invention, the sludge dehydrating agent comprising an amphoteric polymer is added by adjusting the pH of the sludge to less than 5. When the inorganic flocculant is added, the sludge pH tends to decrease, but when it does not decrease, it is efficient to add an organic or inorganic acid to lower the pH. Moreover, the addition amount of the amphoteric polymer of this invention is 0.1-1.0% by weight with respect to sludge solid content, Preferably it is 0.2-0.5%. In the sludge dewatering agent and the sludge dewatering method of the present invention, the dehydrator can be applied to a belt press, a screw press, a filter press, and the like, and is particularly suitable for a belt press.
[0026]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated in more detail with an Example and a comparative example, this invention is not restrict | limited to a following example, unless the summary is exceeded.
[0027]
(Synthesis Example-1)
A reactor equipped with a stirrer and a temperature controller was charged with 6.0 g of sorbitan monooleate and 0.6 g of polyricinoleic acid / polyoxyethylene block copolymer dissolved in 126.0 g of isoparaffin having a boiling point of 190 ° C to 230 ° C. I let you. Separately, 83.2 g of deionized water and 23.6 g of a 60% aqueous solution of acrylic acid (abbreviated as AAC) were mixed and neutralized with 22.4 g of a 35% aqueous sodium hydroxide solution. After neutralization, 126.7 g of 80% aqueous solution of acryloyloxyethyltrimethylammonium chloride (hereinafter abbreviated as DMQ), 34.0 g of 80% aqueous solution of methacryloyloxyethyltrimethylammonium chloride (hereinafter abbreviated as DMC), and acrylamide (abbreviated as AAM) Mix and dissolve 65.1 g of 50% aqueous solution and 0.5 g of 0.1% aqueous solution of N, N-methylenebisacrylamide (abbreviated as MBA), adjust pH to 4.01, mix oil and aqueous solution, homogenizer And emulsified with stirring at 1000 rpm for 15 minutes. The monomer composition at this time is DMQ / DMC / AAC / AAM = 40/10/15/35 (mol%), and MBA is 0.00025 mol% with respect to all monomers.
[0028]
After adding 0.55 g of isopropyl alcohol 10% aqueous solution (0.025% by weight of monomer) to the obtained emulsion, keeping the temperature of the monomer solution at 25 to 28 ° C. and performing nitrogen substitution for 30 minutes, 2,5′-Azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride 10% aqueous solution 0.35 g (0.02% by weight of monomer) was added and polymerized. The reaction was started. The reaction was completed at a reaction temperature of 26 ± 2 ° C. for 8 hours to complete the reaction. After the polymerization, 10.0 g of polyoxyethylene tridecyl ether (2.0% by weight with respect to the liquid) was added to and mixed with the resulting water-in-oil emulsion as a phase inversion agent to prepare a sample for use in the test (Sample-1). . Moreover, the weight average molecular weight was measured with the molecular weight measuring device (DLS-7000 by Otsuka Electronics) by a static light scattering method. The results are shown in Table 1.
[0029]
(Synthesis Example 2)
DMQ / DMC / AAC / AAM = 30/20/15/35 (sample-2), 45/15/20/20 (sample-3), 55/25/20 / A water-in-oil amphoteric polymer emulsion having a composition of 0 (sample-4), 10/5/5/80 (sample-5) (both mol%) was synthesized. The results are shown in Table 1.
[0030]
(Comparative synthesis example)
Comparative-1 to Comparative-5 were synthesized in the same manner as in Synthesis Example 1 except that the polymerization was performed without adding N, N-methylenebisacrylamide.
[0031]
Examples 1-5
200 mL of municipal sewage mixed raw sludge (pH 6.89, total ss 40, 300 mg / L) was collected in a poly-bicker, and 2300 ppm of polyferric chloride was added to the sludge solids to the beaker. I went twice. The sludge pH at this time was 4.72. Next, the amphoteric polymer in the present invention shown in Table 1, Sample-1 to Sample-5, was added 4000 ppm to the sludge solid content, the beaker was transferred, stirred 10 times, and then T-1179L filter cloth (made of nylon). ) And the amount of filtrate after 45 seconds was measured. The filtered sludge is dehydrated at a press pressure of 2 kg / m @ 2 for 1 minute. Thereafter, the filter cloth peelability and cake self-supporting property (related to the hardness of the dewatered cake and the water content) were visually checked, and the cake water content (dried at 105 ° C. for 20 hours) was measured. The results are shown in Table 2.
[0032]
[Comparative Examples 1-9]
Samples of comparative synthesis examples in Table 2, tests using amphoteric polymers of Comparative-1 to Comparative-5, tests using only Sample-1 and Sample-3 without using inorganic flocculants, and inorganic A test in which the amount of flocculant added was 1200 ppm of body sludge solid content, the pH of the sludge was adjusted to 6.20, and Sample-1 and Sample-3 were added was performed by the same test operation as in Examples 1-5. . The results are shown in Table 2.
[0033]
Examples 6 to 10
Food processing wastewater surplus sludge (pH 6.65, total ss24,000 mg / mL) 200mL was collected in a poly-biker, ferric chloride was added to the sludge solid content 1600ppm, the beaker was transferred and stirred 5 times. It was. The sludge pH at this time was 4.22. Next, the amphoteric polymer in the present invention shown in Table 1, Sample-1 to Sample-5, was added 5000 ppm to the sludge solid content, the beaker was transferred, stirred 10 times, and then T-1179L filter cloth (made of nylon). ) And the amount of filtrate after 45 seconds was measured. The filtered sludge is dehydrated at a press pressure of 2 kg / m @ 2 for 1 minute. Thereafter, the filter cloth peelability and cake self-supporting property (related to the hardness of the dewatered cake and the water content) were visually checked, and the cake water content (dried at 105 ° C. for 20 hours) was measured. The results are shown in Table 3.
[0034]
[Comparative Examples 10-18]
Samples of comparative synthesis examples in Table 2, tests using amphoteric polymers of Comparative-1 to Comparative-5, tests using only Sample-3 and Sample-5 without using an inorganic flocculant, and inorganic A test in which the amount of flocculant added was 700 ppm of body sludge solid content, the pH of the sludge was adjusted to 6.10, and Sample-3 and Sample-5 were added was performed by the same test operation as in Examples 11-20. . The results are shown in Table 3.
[0035]
[Table 1]

DMC: methacryloyloxyethyltrimethylammonium chloride DMQ: acryloyloxyethyltrimethylammonium chloride AAC: acrylic acid, AAM: acrylamide,
Molecular weight: 10,000 units, liquid properties; EM: water-in-oil emulsion, AQ: aqueous solution
[Table 2]

Addition amount of inorganic flocculant: ppm (to sludge solid content)
Filtrate volume: mL, cake water content: wt%,
[0037]
[Table 3]

Filtrate volume: mL, cake water content: wt%,
Addition amount of inorganic flocculant: ppm (to sludge solid content)

Claims (4)

5 to 30 mol% of structural units represented by the following general formula (1), 10 to 50 mol% of structural units represented by general formula (2), 5 to 20 mol% of structural units represented by general formula (3), ( The (meth) acrylamide structural unit 0-80 mol% and the crosslinkable monomer structural unit contain 0.0001-0.02 mol% with respect to the total amount of the polymer, respectively, and in the general formulas (1)-(3) When the mole% of the structural unit represented is a, b, c, respectively, a, b, c is 0.9> b / (a + b)> 0.5 , and 0.5> c / (a + b)> A sludge dehydrating agent comprising an amphoteric polymer, characterized by satisfying a condition of 0.1 .

General formula (1)
R1 and R2 are methyl or ethyl groups, R3 is an alkyl, alkoxy or benzyl group having 1 to 3 carbon atoms, and X1 is an anion.

General formula (2)
R4 and R5 are methyl or ethyl groups, R6 is an alkyl, alkoxy or benzyl group having 1 to 3 carbon atoms , and X2 is an anion.

General formula (3)
R7 represents hydrogen or a methyl group, and M represents a cation. The sludge dehydrating agent according to claim 1, wherein the amphoteric polymer has a weight average molecular weight of 2 million to 15 million. The amphoteric polymer comprises a water-in-oil emulsion in which an organic solvent is a continuous phase and an aqueous amphoteric polymer solution is a discontinuous phase in the presence of a water-immiscible organic solvent and an oil-soluble emulsifier. The sludge dewatering agent according to claim 1 or 2. An inorganic flocculant is added to organic sludge and the pH is adjusted to 3 or more and less than 5, and then the amphoteric polymer according to claim 1 is added and mixed, and then dehydrated by a dehydrator. Sludge dewatering method.