JP3980496B2 - Production method and use of (meth) acrylic acid water-soluble polymer - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、（メタ）アクリル酸系水溶性重合体の製造方法並びに該製造方法で得られた（メタ）アクリル酸系水溶性重合体の用途に関する。
【０００２】
【従来の技術】
（メタ）アクリル酸系水溶性重合体の製造方法としては従来より多数提案されている。次亜リン酸（塩）存在下での（メタ）アクリル酸系水溶性重合体の製造方法についても多数提案されている。例えばＵＳ２，７８９，０９９号（特許文献１）、特開昭５０−１５８８１号（特許文献２）、特開昭５５−１２７４１３号（特許文献３）に製法が開示されている。また、次亜リン酸（塩）存在下で得られた（メタ）アクリル酸系水溶性重合体の用途についても多数提案されている。
【０００３】
例えば、特開昭５１−７６１８４号（特許文献４）、特開昭５５−１１０９２号（特許文献５）、特開昭５５−１４９００号（特許文献６）、特開昭５９−１９３９０９号（特許文献７）、特開昭６０−１７４７９３号（特許文献８）、特開昭６１−２２０７９４号（特許文献９）、特開昭６１−２９３５９９号（特許文献１０）、特開昭６２−２０７８８８号（特許文献１１）、特開昭６２−２１４１８６号（特許文献１２）等にスケール防止剤又は腐蝕抑制剤としての用途が開示されている。しかし、上記した従来の製法では次亜リン酸（塩）および／またはその変性物が製品中に多量残留するため、低純度の水溶性重合体しか得られなかった。
【０００４】
また、重合触媒として銅を併用する製法は、銅が最終製品中に残留するため、毒性面から不安の残るものであった。
【０００５】
また、これら従来の製法は、次亜リン酸（塩）の効率が悪く、高価な次亜リン酸（塩）を多量用いる必要があるため、低コスト水溶性重合体の製造には限界があった。
【０００６】
更には、従来の製法は比較的低濃度で重合を行うため、高濃度の水溶性重合体溶液を得るためには、溶媒を蒸発させる必要があるため、低コスト水溶性重合体は得られなかった。また、これら従来の製法で得られた水溶性重合体のスケール防止能及び腐蝕抑制能も充分でなく、改良が望まれていた。
【０００７】
【特許文献１】
米国特許第２，７８９，０９９号明細書
【０００８】
【特許文献２】
特開昭５０−１５８８１号公報
【０００９】
【特許文献３】
特開昭５５−１２７４１３号公報
【００１０】
【特許文献４】
特開昭５１−７６１８４号公報
【００１１】
【特許文献５】
特開昭５５−１１０９２号公報
【００１２】
【特許文献６】
特開昭５５−１４９００号公報
【００１３】
【特許文献７】
特開昭５９−１９３９０９号公報
【００１４】
【特許文献８】
特開昭６０−１７４７９３号公報
【００１５】
【特許文献９】
特開昭６１−２２０７９４号公報
【００１６】
【特許文献１０】
特開昭６１−２９３５９９号公報
【００１７】
【特許文献１１】
特開昭６２−２０７８８８号公報
【００１８】
【特許文献１２】
特開昭６２−２１４１８６号公報
【００１９】
【発明が解決しようとする課題】
本発明は、次亜リン酸（塩）存在下で（メタ）アクリル酸系水溶性重合体を得るに際し、従来の製法が有していた上記問題点を解消するものである。更には次亜リン酸（塩）存在下で得られた従来の（メタ）アクリル酸系水溶重合体の性能不充分を解消するものである。
【００２０】
【課題を解決するための手段】
本発明の（（メタ）アクリル酸系水溶性重合体の製造方法は、上記の課題を解決するために、（メタ）アクリル酸系水溶性単量体を水溶液重合して（メタ）アクリル酸系重合体を製造するに際し、重合後の反応液中の重合体の単量体換算濃度が３８〜７２重量％となるのに必要な（メタ）アクリル酸系水溶性単量体、重合開始剤及び次亜リン酸（塩）を水性媒体中に逐次導入して重合した後、中和することを特徴としている。
【００２１】
また、上記中和は、水酸化ナトリウムを用いて行うことが好ましい。
【００２２】
また、次亜リン酸（塩）は、（メタ）アクリル酸系水溶性単量体１モル当り０．００１〜０．５モル量用いることが好ましい。
【００２３】
また、上記重合開始剤は、過硫酸塩であることが好ましく、該重合開始剤の量は、（メタ）アクリル酸系水溶性単量体１モル当り、０．００１〜０．１モル量用いることが好ましい。
【００２４】
上記の製造方法で得られる（メタ）アクリル酸系水溶性重合体は、無機顔料分散剤として使用することができる。
【００２５】
【発明の実施の形態】
本発明は、水性媒体中に、重合後液中の重合体の単量体換算濃度が３８〜７２重量％となるのに必要な（メタ）アクリル酸系単量体、重合開始剤及び次亜リン酸（塩）を逐次導入して重合することを特徴とする（メタ）アクリル酸系水溶性重合体の製造方法並びに該製造方法により得られた（メタ）アクリル酸系水溶性重合体の無機顔料分散剤、スケール防止剤及び金属の腐蝕抑制剤としての用途に関する。
【００２６】
本発明では、（メタ）アクリル酸系単量体、重合開始剤及び次亜リン酸（塩）（以下添加成分と称す。）を水性媒体中に逐次導入する。
【００２７】
添加成分のいずれか一つの成分あるいは全ての成分を全量初期仕込みとした場合、本願発明のような（メタ）アクリル酸系水溶性重合体は得られないものである。
【００２８】
添加成分はそれぞれ独立にあるいは混合して水性媒体中に導入される。添加成分が固体である場合、固体状のまま導入するもできまた水あるいはアルコール、ケトンなどの有機溶媒に溶解して導入することができる。
【００２９】
逐次導入の方法としては添加成分を連続的に導入することもあるいは分割的に導入することもまた可能である。
【００３０】
本発明で用いられる（メタ）アクリル酸系単量体とはアクリル酸、メタクリル酸、アクリル酸塩及びメタクリル酸塩を５０ｗｔ％以上、好ましくは７０ｗｔ％以上含有する重合性単量体を意味する。（メタ）アクリル酸塩としては、（メタ）アクリル酸のナトリウム、カリウム、リチウムなどのアルカリ金属塩；アンモニア、モノメチルアミン、ジメチルアミン、トリメチルアミン、ジエチルアミン、モノエタノールアミン、ジエタノールアミン、トリエタノールアミンなどのアルカリ性物質を用いて中和して得られた無機あるいは有機のアンモニウム塩などを挙げることができる。中でもアクリル酸の使用が特に好ましい。重合開始剤としては特に制限がなく、多種類の触媒が使用できる。例えば、過硫酸ナトリウム、過硫酸カリウムなどの過硫酸塩；過酸化水素、２，２′−アゾビス（２−アミジノプロパン）塩酸塩、４，４′−アゾビス−４−シアノバレリン酸等の水溶性アゾ化合物；過酸化ベンゾイル、過酸化ラウロイル、過酢酸等の有機過酸化物；アゾビスイソブチロニトリル、２，２′−アゾビス（４−メトキシ−２，４−ジメチルバレロニトリル）等の油溶性アゾ化合物などが用いられるが、中でも安価で開始剤効率が高い過硫酸塩が特に好ましい。これら重合開始剤は（メタ）アクリル酸系水溶性単量体１モル当り、０．００１〜０．１モル量用いるのが好ましい。
【００３１】
次亜リン酸（塩）としては、次亜リン酸、次亜リン酸のナトリウム、カリウム、リチウムなどのアルカリ金属塩；アンモニア、モノメチルアミン、ジメチルアミン、トリメチルアミン、ジエチルアミン、モノエタノールアミン、ジエタノールアミン、トリエタノールアミンなどのアルカリ性物質を用いて中和して得られた無機あるいは有機のアンモニウム塩などを挙げることができる。中でも安価で工業的に入手しやすい次亜リン酸ナトリウムが特に好ましい。これら次亜リン酸（塩）は（メタ）アクリル酸系水溶性系単量体１モル当り０．０１〜０．５モル量用いるのが好ましい。本発明では、水性媒体中に前記添加成分を逐次導入して重合される。水性媒体とは水あるいは水と水に溶解可能な無機又は有機溶媒との混合溶媒を意味する。無機又は有機の溶媒使用は分子量調節に役立つが、最終製品とするためには、これら溶媒を除去する必要があるため、特殊な場合を除いては使用しない方が好ましい。
【００３２】
本発明では、重合後液中の重合体の単量体換算濃度が３８〜７２重量％とすることが必要である。好ましくは４０〜６０重量％である。３８重量％未満の低い単量体換算濃度で反応しても、本願発明のように高純度、低コスト且つ安全性の高い（メタ）アクリル酸系水溶性重合体は得られないものである。
【００３３】
又、３８重量％未満の低い単量体換算濃度で反応しても、本願発明品のように無機顔料分散剤、スケール防止剤及び金属腐蝕抑制剤として格段に優れた効果を奏する（メタ）アクリル酸系水溶性重合体は得られないものである。７２重量％を超える高い単量体換算濃度での製造は、重合系の粘度が著しく高くなり、実質上製造は困難となる。尚、本発明における重合後液中の重合体単量体換算濃度とは実質上重合が完結した時点における液中の重合した（メタ）アクリル酸系水溶性単量体分を重量％で表記したものである。また、発明の効果を損わない範囲で（メタ）アクリル酸系水溶性単量体、重合開始剤及び次亜リン酸（塩）のうち少くとも１つあるいはすべての成分の少量を初期仕込として重合することは勿論可能である。
【００３４】
その他の製造条件については特に制限はなく通常の重合条件が適用される。例えば、重合温度は２０〜１５０℃好ましくは７０〜１１０℃とすることができる。また、重合時の系のｐＨについて０．５〜１３．５好ましくは１〜１２の範囲とすることができる。また、重合時にＬ−アスコルビル酸（塩）、（重）亜硫酸（塩）、鉄などの還元剤の存在下に製造することも勿論可能である。
【００３５】
本発明では、発明の効果を損わない範囲で（メタ）アクリル酸系水溶性単量体以外の他の単量体を（メタ）アクリル酸系水溶性単量体と共に使用することは勿論可能である。このような単量体としては、例えば（メタ）アクリルアミド、ｔ−ブチル（メタ）アクリルアミドなどのアミド系単量体；（メタ）アクリル酸エステル、スチレン、２−メチルスチレン、酢酸ビニルなどの疎水性単量体；ビニルスルホン酸、アリルスルホン酸、メタリルスルホン酸、スチレンスルホン酸、２−アクリルアミド−２−メチルプロパンスルホン酸、３−アリロキシ−２−ヒドロキシプロパンスルホン酸、スルホエチル（メタ）アクリレート、スルホプロピル（メタ）アクリレート、２−ヒドロキシスルホプロピル（メタ）アクリレート、スルホエチルマレイミドあるいはそれ等の１価金属、２価金属、アンモニア、有機アミンによる部分中和物や完全中和物などの不飽和スルホン酸系単量体；３−メチル−３−ブテン−１−オール（イソブレノール）、３−メチル−２−ブテン−１−オール（ブレノール）、２−メチル−３−ブテン−２−オール（イソプレンアルコール）、２−ヒドロキシエチル（メタ）アクリレート、ポリエチレングリコールモノ（メタ）アクリレート、ポリプロピレングリコールモノ（メタ）アクリレート、ポリエチレングリコールモノイソプレノールエーテル、ポリプロピレングルコールモノイソプレノールエーテル、ポリエチレングリコールモノアリルエーテル、ポリプロピレングリコールモノアリルエーテル、グリセロールモノアリルエーテル、α−ヒドロキシアクリル酸、Ｎ−メチロール（メタ）アクリルアミド、グリセロールモノ（メタ）アクリレート、ビニルアルコールなどの水酸基含有不飽和単量体；ジメチルアミノエチル（メタ）アクリレート、ジメチルアミノプロピル（メタ）アクリルアミドなどのカチオン性単量体；（メタ）アクリロニトリルなどのニトリル系単量体；（メタ）アクリルアミドメタンスルホン酸、（メタ）アクリルアミドメタンスルホン酸メチルエステル、２−（メタ）アクリルアミド−２−メチルプロパンホスホン酸などの含リン単量体；イタコン酸、マレイン酸、シトラコン酸、フマール酸などのジカルボン酸系単量体；クロトン酸などを挙げることができる。
【００３６】
これら共重合可能な単量体の使用量は全単量体に対して３０モル％未満とするのが好ましい。
【００３７】
本発明の製法及び該製法で得られた製品が格段に優れた効果を奏するかは明確でないが次のように推察されている。
【００３８】
即ち、本発明の製法は、従来の製法より高濃度かつ特定の方法で重合を行うために次亜リン酸（塩）が効率的に作用する結果、少い次亜リン酸（塩）の使用並びに次亜リン酸（塩）および／またはその変性物含量の少く高純度な製品の製造を可能とならしめるものと考えられる。
【００３９】
また、本発明の製品は高純度のため、例えばスケール防止剤、金属の腐蝕抑制剤として使用した場合、次亜リン酸（塩）および／またはその変性物に基づく、初期スケール核形成が著しく抑制されるためであろうと推察される。また本発明の（メタ）アクリル酸系水溶性重合体は無機顔料分散剤としても優れた効果を発揮する。このような無機顔料としては、カオリン、クレー、炭酸カルシウム、サチンホワイト、二酸化チタン、水酸化アルミニウムなどの塗工紙用顔料；ベンガラ、水酸化マグネシウム、磁性粉、消石灰、セメント、シリカ、硫酸カルシウムなどの工業材料の分散剤として好適に使用される。
【００４０】
【実施例】
以下、実施例により、本発明を具体的に説明するが、本発明はこれらの実施例により限定されるものではない。尚、例中の部および％は重量部及び重量％を示す。
【００４１】
参考例１
容量５ｌのＳＵＳ３１６製セパラブルフラスコにイオン交換水３２１．９部を仕込み、１００℃に昇温し、窒素置換後、８０％アクリル酸水溶液５８７．５部、１５％過硫酸ナトリウム水溶液６８．７部（０．００６６モル／アクリル酸１モル）及び３０％次亜リン酸ナトリウム水溶液２１．９部（０．００９５モル／アクリル酸１モル）を各々、別々の滴下口より２時間かけて滴下した。この間、系の温度は終始系の沸点を維持した。更に同温度で１０分間の熟成を行い重合を完結し、重合後の液中のアクリル酸換算の濃度が４７％である（メタ）アクリル酸系水溶性重合体（１）を得た。（メタ）アクリル酸系水溶性重合体（１）を４８％水酸化ナトリウム水溶液を用いて中和（ｐＨ＝８）し、該して得た中和物の性能を以下のようにして評価した。
【００４２】
無機顔料分散能容量１ｌ（材質ＳＵＳ３０４、内径９０ｍｍ、高さ１６０ｍｍ）のビーカーに分散剤としての上記（メタ）アクリル酸系水溶性重合体（１）の中和物を０．２部及び水を加えて全量を１００部とした。ディゾルバー攪拌羽根（５０ｍｍφ）にて低速で攪拌下、カオリン（ジークライト工業社製、ＭＣ用ジーク）１００部を３分間で添加した。次いで、３０００ｒｐｍで１０分間分散した。
【００４３】
該して得られたカオリン５０％スラリーの粘度をＢ形粘度計で測定し、その結果を第１表および第２表に示した。
【００４４】
スケール防止能容量２２５ｍｌのガラスびんに水１７０部を入れ、塩化カルシウム２水塩１．５６％水溶液１０部及び（メタ）アクリル酸系水溶性重合体（１）の中和物の０．０２％水溶液１部（得られる炭酸カルシウム過飽和水溶液に対して１ｐｐｍ）混合し、さらに重炭酸ナトリウム３％水溶液１０部を加えて混合して得られた炭酸カルシウム５３０ｐｐｍの過飽和溶液を密栓して、７０℃で３時間加熱処理した。次いで冷却した後、沈殿物を０．２μメングランフィルターで濾過し、濾液をＪＩＳＫ０１０１に従って分析し、次式に従ってスケール抑制率（％）を算出した。
【００４５】
【数１】
Ａ：加熱処理前のＣａＣＯ3 濃度（＝５３０ｐｐｍ）
Ｂ：無添加試験後の濾液中のＣａＣＯ3 濃度（＝１９５ｐｐｍ）
Ｃ：試験後の濾液中のＣａＣＯ3 濃度得られた結果を第１表および第２表に示した。
【００４７】
金属の腐蝕抑制能容量５００ｃｃのＳＵＳ３１６製セパラブルフラスコに第５表に示した性状の合成水（姫路市水４倍濃縮に相当）４４５ｍｌをとり、そこへ腐蝕抑制剤として（メタ）アクリル酸系水溶性重合体（１）の中和物を合成水に対して固形分換算で６０ｐｐｍ添加し、水酸化ナトリウムを用いてｐＨを８．５に調整したのち、脱イオン水を加えて全量を４５０ｍｌとし、試験液を調製した。次いで、得られた試験液中に２５ｍｍ×４０ｍｍ×１ｍｍのＳＳ−４１製テストピース２枚を吊し、試験液上部に２５ｍｌ／分の空気を流しながら、４０℃で４０時間熱処理した。熱処理終了後、テストピース上の腐蝕生成物を除きテストピースの減量を測定した。結果は２枚のテストピースの減量の平均値をＭＤＤ（ｍｇ／ｄｍ2 ／ｄａｙ）換算し、第１表および第２表に示した。
【００４８】
参考例２
参考例１において、初期仕込のイオン交換水３２１．９部の代りにイオン交換水５５８．７部を用いた他は参考例１と同様にしてアクリル酸換算濃度が３８％である（メタ）アクリル酸系水溶性重合体（２）を得た。（メタ）アクリル酸系水溶性重合体（２）を参考例１と同様にして中和し、該して得た中和物の性能を参考例１と全く同様にして評価した。得られた結果を第１表および第２表に示した。
【００４９】
参考例３
参考例１において、初期仕込のイオン交換水３２１．９部の代りにイオン交換水８４．３部、８０％アクリル酸水溶性５８７．５部の代りに１００％アクリル酸４７０部、３０％次亜リン酸ナトリウム水溶液２１．９部の代りに３０％次亜リン酸水溶液６８．２部をそれぞれ用いた他は参考例１と同様にしてアクリル酸換算濃度が６８％である（メタ）アクリル酸系水溶性重合体（３）を得た。（メタ）アクリル酸系水溶性重合体（３）を参考例１と同様に中和し、該して得た中和物の性能を参考例１と全く同様にして評価した。得られた結果を第１表および第２表に示した。
【００５０】
参考例４
参考例１において８０％アクリル酸水溶液５８７．５部の代りに８０％メタクリル酸水溶液５８７．５部を用いた他は参考例１と同様にしてメタクリル酸換算濃度が４７％である（メタ）アクリル酸系水溶性重合体（４）を得た。（メタ）アクリル酸系重合体（４）を参考例１と同様に中和し、該して得た中和物の性能を参考例１と全く同様にして評価した。得られた結果を第１表および第２表に示した。
【００５１】
参考例５
参考例１で用いたのと同じ重合容器にイオン交換水３５．１部を仕込み、１００℃に昇温し、窒素置換後、４８％アクリル酸水溶液９７９．２部、４８％水酸化ナトリウム水溶液５４３．９部、３０％過硫酸ナトリウム水溶液３４．４部（０．００６６モル／アクリル酸ナトリウム１モル）及び３０％次亜リン酸ナトリウム水溶液２１．９部（０．００９５モル／アクリル酸ナトリウム１モル）を２時間かけて滴下した。尚４８％アクリル酸水溶液と４８％水酸化ナトリウム水溶液の滴下は、滴下口直前で混合しアクリル酸ナトリウム水溶液として重合系に導入した。他は各々、別々の滴下口より重合系に導入した。この間、系の温度は終始沸点を維持した。更に同温度で１０分間の熟成を行い重合を完結し、重合後の液中のアクリル酸ナトリウム換算の濃度が３８％である（メタ）アクリル酸系水溶性重合体（５）を得た。（メタ）アクリル酸系水溶性重合体（５）の性能を参考例１と全く同様にして評価した。得られた結果を第１表および第２表に示した。
【００５２】
参考例６
参考例１において、８０％アクリル酸水溶液５８７．５部、１５％過硫酸ナトリウム水溶液６８．７部及び３０％次亜リン酸ナトリウム水溶液２１．９部を５分毎に各々１／２４量ずつ分割的に重合系に導して反応した。参考例１と同様の熟成を行い、アクリル酸換算濃度が４７％である（メタ）アクリル酸系水溶性重合体（６）を得た。（メタ）アクリル酸系水溶性重合体（６）を参考例１と同様に中和し、該して得た中和物の性能を参考例１と同様に評価した。得られた結果を第１表および第２表に示した。
【００５３】
実施例１
参考例１で用いたのと同じ重合容器にイオン交換水２８５部を仕込み、１００℃に昇温し、窒素置換後、８０％アクリル酸水溶液５８７．５部、３７％アクリル酸ナトリウム水溶液２３６．９部、５０％３−アリロキシ−２−ヒドロキシプロパンスルホン酸ナトリウム（ＨＡＰＳ）水溶液８１３部、１５％過硫酸ナトリウム水溶液９７．６部（０．００６６モル／単量体１モル）及び３０％次亜リン酸ナトリウム水溶液３１．３部（０．００９５モル／単量体１モル）を各々、別々の滴下口より２時間かけて滴下した。参考例１と同様の熟成を行い重合後の単量体換算の濃度が４７％である（メタ）アクリル酸系水溶性重合体（７）を得た。（メタ）アクリル酸系水溶性重合体（７）を参考例１と同様に中和し、該して得た中和物の性能を参考例１と全く同様にして評価した。得られた結果を第１表および第２表に示した。
【００５４】
比較例１
参考例１において、３０％次亜リン酸ナトリウム水溶液２１．９部を初期仕込とした他は参考例１と同様にしてアクリル酸換算濃度が４７％である比較用（メタ）アクリル酸系水溶性重合体（１）を得た。比較用（メタ）アクリル酸系水溶性重合体（１）を参考例１と同様にして中和し、該して得た中和物の性能を参考例１と全く同様にして評価した。得られた結果を第３表および第４表に示した。
【００５５】
比較例２
参考例１において、初期仕込のイオン交換水３２１．９部の代りにイオン交換水１６７１．９部を用い且つ８０％アクリル酸水溶液５８７．５部、１５％過硫酸ナトリウム水溶液６８．７部及び３０％次亜リン酸ナトリウム２１．９部を全量初期仕込とし７０℃で反応した他は参考例１と同様にして重合して、アクリル酸換算濃度が２０％である比較用（メタ）アクリル酸系水溶性重合体（２）を得た。比較用（メタ）アクリル酸系重合体（２）を参考例１と同様にして中和し、該して得た中和物の性能を参考例１と全く同様にして評価した。得られた結果を第３表および第４表に示した。
【００５６】
比較例３
参考例１において、初期仕込のイオン交換水３２１．９部の代りにイオン交換水６６４．７部を用いた他は参考例１と同様にしてアクリル酸換算濃度が３５％である比較用（メタ）アクリル酸系水溶性重合体（３）を得た。比較用（メタ）アクリル酸系水溶性重合体（３）を参考例１と同様にして中和し、該して得た中和物の性能を参考例１と全く同様にして評価した。得られた結果を第３表および第４表に示した。
【００５７】
比較例４
参考例３において、初期仕込のイオン交換水８４．３部の代りにイオン交換水１９．８部を用いた他は、参考例３と同様にしてアクリル酸換算濃度が７５％である比較用（メタ）アクリル酸系水溶性重合体（４）を得た。比較用（メタ）アクリル酸系水溶性重合体（４）を参考例３と同様に中和し、該して得た中和物の性能を参考例３と全く同様にして評価した。得られた結果を第３表および第４表に示した。
【００５８】
比較例５
実施例１において、初期仕込のイオン交換水２８５部の代りにイオン交換水１１５５．２部を用いた他は実施例１と同様にして単量体換算濃度が３３％である比較用（メタ）アクリル酸系水溶性重合体（５）を得た。比較用（メタ）アクリル酸系水溶性重合体（５）を実施例１と同様に中和し、該して得た中和物の性能を実施例１と全く同様にして評価した。得られた結果を第３表および第４表に示した。
【００５９】
尚、（メタ）アクリル酸系水溶性重合体（１）〜（７）及び比較用（メタ）アクリル酸系水溶性重合体（１）〜（５）の分子量はいずれも２〜６万の範囲内にあり、ほぼ同等の分子量と見なせるものであった。
【００６０】
【表１】
【表２】
【表３】
【表４】
【表５】
【発明の効果】
本発明にかかる（メタ）アクリル酸系水溶性重合体の製造方法によれば、高純度で低コスト且つ安全性が高い（メタ）アクリル酸系水溶性重合体が工業的に容易に製造可能となる。更には、意外にも、スケール防止剤、腐蝕防止剤などのいわゆる水処理剤並びに無機顔料分散剤として使用した場合、従来品より格段に機能が優れるものである。
【００６６】
このように本発明は工業的利用価値が極めて高いものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a (meth) acrylic acid-based water-soluble polymer and uses of the (meth) acrylic acid-based water-soluble polymer obtained by the production method.
[0002]
[Prior art]
Many methods for producing a (meth) acrylic acid-based water-soluble polymer have been proposed. Many methods for producing a (meth) acrylic acid-based water-soluble polymer in the presence of hypophosphorous acid (salt) have also been proposed. For example, US 2,789,099 (Patent Document 1), Japanese Patent Application Laid-Open No. 50-15881 (Patent Document 2), and Japanese Patent Application Laid-Open No. 55-127413 (Patent Document 3) are disclosed. Many proposals have also been made regarding the use of (meth) acrylic acid-based water-soluble polymers obtained in the presence of hypophosphorous acid (salt).
[0003]
For example, JP-A-51-76184 (Patent Document 4), JP-A-55-11092 (Patent Document 5), JP-A-55-14900 (Patent Document 6), JP-A-59-193909 (Patent Document) Document 7), Japanese Patent Application Laid-Open No. 60-174793 (Patent Document 8), Japanese Patent Application Laid-Open No. 61-220794 (Patent Document 9), Japanese Patent Application Laid-Open No. 61-293599 (Patent Document 10), Japanese Patent Application Laid-Open No. 62-207888. (Patent Document 11), Japanese Patent Application Laid-Open No. 62-214186 (Patent Document 12), etc. disclose uses as a scale inhibitor or a corrosion inhibitor. However, in the conventional production method described above, hypophosphorous acid (salt) and / or a modified product thereof remains in the product in a large amount, so that only a low-purity water-soluble polymer can be obtained.
[0004]
In addition, the production method using copper as a polymerization catalyst is uneasy from the viewpoint of toxicity because copper remains in the final product.
[0005]
In addition, these conventional production methods have low efficiency of hypophosphorous acid (salt), and it is necessary to use a large amount of expensive hypophosphorous acid (salt), so there is a limit to the production of low-cost water-soluble polymers. It was.
[0006]
Furthermore, since the conventional production method performs polymerization at a relatively low concentration, it is necessary to evaporate the solvent in order to obtain a high-concentration water-soluble polymer solution, so a low-cost water-soluble polymer cannot be obtained. It was. In addition, the water-soluble polymers obtained by these conventional production methods are not sufficient in scale prevention ability and corrosion inhibition ability, and improvement has been desired.
[0007]
[Patent Document 1]
US Pat. No. 2,789,099 specification
[Patent Document 2]
Japanese Patent Laid-Open No. 50-15881
[Patent Document 3]
JP-A-55-127413 [0010]
[Patent Document 4]
Japanese Patent Laid-Open No. 51-76184
[Patent Document 5]
Japanese Patent Laid-Open No. 55-11092
[Patent Document 6]
Japanese Patent Laid-Open No. 55-14900
[Patent Document 7]
JP 59-193909 A
[Patent Document 8]
JP-A-60-174793 [0015]
[Patent Document 9]
Japanese Patent Laid-Open No. 61-220794
[Patent Document 10]
Japanese Patent Laid-Open No. 61-293599 [0017]
[Patent Document 11]
Japanese Patent Laid-Open No. 62-207888
[Patent Document 12]
Japanese Patent Laid-Open No. 62-214186
[Problems to be solved by the invention]
The present invention solves the above-described problems of conventional production methods when obtaining a (meth) acrylic acid-based water-soluble polymer in the presence of hypophosphorous acid (salt). Furthermore, the insufficient performance of the conventional (meth) acrylic acid-based water-soluble polymer obtained in the presence of hypophosphorous acid (salt) is eliminated.
[0020]
[Means for Solving the Problems]
In order to solve the above problems, the method for producing a ((meth) acrylic acid-based water-soluble polymer of the present invention is a (meth) acrylic acid-based polymer obtained by subjecting a (meth) acrylic acid-based water-soluble monomer to aqueous solution polymerization. In producing the polymer, a (meth) acrylic acid-based water-soluble monomer, a polymerization initiator, and a polymerization initiator, which are necessary for the monomer equivalent concentration of the polymer in the reaction solution after polymerization to be 38 to 72% by weight, It is characterized in that hypophosphorous acid (salt) is successively introduced into an aqueous medium and polymerized and then neutralized.
[0021]
The neutralization is preferably performed using sodium hydroxide.
[0022]
Hypophosphorous acid (salt) is preferably used in an amount of 0.001 to 0.5 mol per mol of (meth) acrylic acid water-soluble monomer.
[0023]
The polymerization initiator is preferably a persulfate, and the polymerization initiator is used in an amount of 0.001 to 0.1 mol per mol of (meth) acrylic acid water-soluble monomer. It is preferable.
[0024]
The (meth) acrylic acid-based water-soluble polymer obtained by the above production method can be used as an inorganic pigment dispersant.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a (meth) acrylic acid-based monomer, a polymerization initiator, and a hypochlorous acid, which are necessary for the monomer equivalent concentration of the polymer in the liquid after polymerization to be 38 to 72% by weight in an aqueous medium. A method for producing a (meth) acrylic acid-based water-soluble polymer, characterized by sequentially introducing phosphoric acid (salt) and polymerizing, and an inorganic (meth) acrylic acid-based water-soluble polymer obtained by the production method The present invention relates to uses as a pigment dispersant, a scale inhibitor, and a metal corrosion inhibitor.
[0026]
In the present invention, a (meth) acrylic acid monomer, a polymerization initiator, and hypophosphorous acid (salt) (hereinafter referred to as an additive component) are sequentially introduced into an aqueous medium.
[0027]
When any one or all of the additive components are initially charged, a (meth) acrylic acid-based water-soluble polymer as in the present invention cannot be obtained.
[0028]
The additive components are introduced into the aqueous medium independently or as a mixture. When the additive component is solid, it can be introduced as it is, or it can be dissolved in water or an organic solvent such as alcohol or ketone.
[0029]
As a sequential introduction method, the additive component can be introduced continuously or dividedly.
[0030]
The (meth) acrylic acid monomer used in the present invention means a polymerizable monomer containing 50 wt% or more, preferably 70 wt% or more of acrylic acid, methacrylic acid, acrylate and methacrylate. (Meth) acrylic acid salts include alkali metal salts such as sodium, potassium and lithium of (meth) acrylic acid; alkaline such as ammonia, monomethylamine, dimethylamine, trimethylamine, diethylamine, monoethanolamine, diethanolamine and triethanolamine Examples thereof include inorganic or organic ammonium salts obtained by neutralization with a substance. Of these, the use of acrylic acid is particularly preferred. There is no restriction | limiting in particular as a polymerization initiator, Many types of catalysts can be used. For example, persulfates such as sodium persulfate and potassium persulfate; water-soluble azo such as hydrogen peroxide, 2,2'-azobis (2-amidinopropane) hydrochloride, 4,4'-azobis-4-cyanovaleric acid Compound: Organic peroxide such as benzoyl peroxide, lauroyl peroxide, peracetic acid; oil-soluble azo such as azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) A compound or the like is used, and among them, a persulfate that is inexpensive and has high initiator efficiency is particularly preferable. These polymerization initiators are preferably used in an amount of 0.001 to 0.1 mol per mol of (meth) acrylic acid water-soluble monomer.
[0031]
Hypophosphorous acid (salt) includes alkali metal salts such as hypophosphorous acid, sodium, potassium and lithium of hypophosphorous acid; ammonia, monomethylamine, dimethylamine, trimethylamine, diethylamine, monoethanolamine, diethanolamine, Examples thereof include inorganic or organic ammonium salts obtained by neutralization with an alkaline substance such as ethanolamine. Of these, sodium hypophosphite, which is inexpensive and easily available industrially, is particularly preferable. These hypophosphorous acids (salts) are preferably used in an amount of 0.01 to 0.5 mol per mol of (meth) acrylic acid water-soluble monomer. In the present invention, polymerization is carried out by sequentially introducing the additive components into an aqueous medium. The aqueous medium means water or a mixed solvent of water and an inorganic or organic solvent that can be dissolved in water. The use of an inorganic or organic solvent is useful for adjusting the molecular weight. However, in order to obtain a final product, it is necessary to remove these solvents, so it is preferable not to use them except in special cases.
[0032]
In the present invention, the monomer equivalent concentration of the polymer in the post-polymerization solution needs to be 38 to 72% by weight. Preferably it is 40 to 60% by weight. Even if the reaction is performed at a low monomer equivalent concentration of less than 38% by weight, a (meth) acrylic acid-based water-soluble polymer with high purity, low cost and high safety cannot be obtained as in the present invention.
[0033]
In addition, even if the reaction is performed at a low monomer equivalent concentration of less than 38% by weight, (meth) acrylic is highly effective as an inorganic pigment dispersant, a scale inhibitor and a metal corrosion inhibitor as in the present invention product. An acid-based water-soluble polymer cannot be obtained. Production at a high monomer equivalent concentration exceeding 72% by weight significantly increases the viscosity of the polymerization system, making production substantially difficult. In addition, the polymer monomer equivalent concentration in the liquid after polymerization in the present invention is expressed by weight% of the polymerized (meth) acrylic acid-based water-soluble monomer content in the liquid when the polymerization is substantially completed. Is. In addition, a small amount of at least one or all of the (meth) acrylic acid-based water-soluble monomer, polymerization initiator and hypophosphorous acid (salt) is used as an initial charge within a range not impairing the effects of the invention. It is of course possible to polymerize.
[0034]
Other production conditions are not particularly limited, and normal polymerization conditions are applied. For example, the polymerization temperature can be 20 to 150 ° C., preferably 70 to 110 ° C. Further, the pH of the system during the polymerization can be in the range of 0.5 to 13.5, preferably 1 to 12. Of course, it can also be produced in the presence of a reducing agent such as L-ascorbic acid (salt), (bi) sulfurous acid (salt), and iron during polymerization.
[0035]
In the present invention, it is of course possible to use a monomer other than the (meth) acrylic acid-based water-soluble monomer together with the (meth) acrylic acid-based water-soluble monomer as long as the effects of the invention are not impaired. It is. Examples of such monomers include amide monomers such as (meth) acrylamide and t-butyl (meth) acrylamide; hydrophobic properties such as (meth) acrylic acid ester, styrene, 2-methylstyrene, and vinyl acetate. Monomer: vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, sulfoethyl (meth) acrylate, sulfone Unsaturated sulfones such as partially or completely neutralized products of propyl (meth) acrylate, 2-hydroxysulfopropyl (meth) acrylate, sulfoethylmaleimide or monovalent metal such as divalent metal, ammonia, organic amine Acid monomer; 3-methyl-3-butene-1-o (Isobrenol), 3-methyl-2-buten-1-ol (brenol), 2-methyl-3-buten-2-ol (isoprene alcohol), 2-hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) Acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol monoisoprenol ether, polypropylene glycol monoisoprenol ether, polyethylene glycol monoallyl ether, polypropylene glycol monoallyl ether, glycerol monoallyl ether, α-hydroxyacrylic acid, N- Hydroxyl-containing unsaturated monomers such as methylol (meth) acrylamide, glycerol mono (meth) acrylate, vinyl alcohol; dimethylaminoethyl (meth) Cationic monomers such as acrylate and dimethylaminopropyl (meth) acrylamide; nitrile monomers such as (meth) acrylonitrile; (meth) acrylamide methanesulfonic acid, (meth) acrylamide methanesulfonic acid methyl ester, 2- ( Examples thereof include phosphorus-containing monomers such as (meth) acrylamide-2-methylpropanephosphonic acid; dicarboxylic acid-based monomers such as itaconic acid, maleic acid, citraconic acid and fumaric acid; crotonic acid and the like.
[0036]
The amount of these copolymerizable monomers used is preferably less than 30 mol% with respect to the total monomers.
[0037]
It is not clear whether the production method of the present invention and the product obtained by the production method have outstanding effects, but it is presumed as follows.
[0038]
That is, in the production method of the present invention, hypophosphorous acid (salt) acts efficiently in order to carry out polymerization in a specific method at a higher concentration than the conventional production method, and as a result, less hypophosphorous acid (salt) is used. In addition, it is considered that it is possible to produce a high-purity product having a low content of hypophosphorous acid (salt) and / or a modified product thereof.
[0039]
In addition, since the product of the present invention has high purity, when used as, for example, a scale inhibitor or a metal corrosion inhibitor, initial scale nucleation based on hypophosphorous acid (salt) and / or a modified product thereof is remarkably suppressed. It is inferred that it will be. The (meth) acrylic acid-based water-soluble polymer of the present invention exhibits an excellent effect as an inorganic pigment dispersant. Examples of such inorganic pigments include pigments for coated paper such as kaolin, clay, calcium carbonate, satin white, titanium dioxide, aluminum hydroxide; bengara, magnesium hydroxide, magnetic powder, slaked lime, cement, silica, calcium sulfate, etc. It is suitably used as a dispersant for industrial materials.
[0040]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the part and% in an example show a weight part and weight%.
[0041]
Reference example 1
A 5L SUS316 separable flask was charged with 321.9 parts of ion-exchanged water, heated to 100 ° C., purged with nitrogen, 587.5 parts of 80% aqueous acrylic acid solution, and 68.7 parts of 15% aqueous sodium persulfate (0.0066 mol / acrylic acid 1 mol) and 21.9 parts of a 30% aqueous sodium hypophosphite solution (0.0095 mol / acrylic acid 1 mol) were respectively added dropwise from separate dropping ports over 2 hours. During this time, the temperature of the system maintained the boiling point of the system throughout. Further, aging was carried out at the same temperature for 10 minutes to complete the polymerization, and a (meth) acrylic acid-based water-soluble polymer (1) having a concentration in terms of acrylic acid in the liquid after polymerization of 47% was obtained. The (meth) acrylic acid water-soluble polymer (1) was neutralized (pH = 8) using a 48% aqueous sodium hydroxide solution, and the performance of the neutralized product thus obtained was evaluated as follows. .
[0042]
Into a beaker having an inorganic pigment dispersibility capacity of 1 l (material SUS304, inner diameter 90 mm, height 160 mm), 0.2 parts of the neutralized product of the (meth) acrylic acid-based water-soluble polymer (1) as a dispersant and water. In addition, the total amount was 100 parts. While stirring at a low speed with a dissolver stirring blade (50 mmφ), 100 parts of kaolin (manufactured by Siegrite Industrial Co., Ltd., Sieg for MC) was added over 3 minutes. Subsequently, it was dispersed at 3000 rpm for 10 minutes.
[0043]
The viscosity of the kaolin 50% slurry thus obtained was measured with a B-type viscometer, and the results are shown in Tables 1 and 2.
[0044]
Into a glass bottle with a scale prevention capacity of 225 ml, 170 parts of water was added, 10 parts of a 1.56% aqueous solution of calcium chloride dihydrate and 0.02% of the neutralized product of the (meth) acrylic acid water-soluble polymer (1) 1 part of an aqueous solution (1 ppm with respect to the resulting calcium carbonate supersaturated aqueous solution) was mixed, and further 10 parts of sodium bicarbonate 3% aqueous solution was added and mixed, and the supersaturated solution of 530 ppm calcium carbonate was sealed and sealed at 70 ° C. Heat-treated for 3 hours. After cooling, the precipitate was filtered through a 0.2 μm membrane filter, and the filtrate was analyzed according to JISK0101, and the scale inhibition rate (%) was calculated according to the following formula.
[0045]
[Expression 1]
A: CaCO 3 concentration before heat treatment (= 530 ppm)
B: CaCO 3 concentration in the filtrate after the additive-free test (= 195 ppm)
C: CaCO 3 concentration in the filtrate after the test The results obtained are shown in Tables 1 and 2.
[0047]
Into a SUS316 separable flask with a capacity of 500 cc for corrosion inhibition of metal, 445 ml of synthetic water having the characteristics shown in Table 5 (equivalent to 4 times concentration in Himeji city water) is taken, and (meth) acrylic acid is used as a corrosion inhibitor. A neutralized product of the water-soluble polymer (1) is added to synthetic water in an amount of 60 ppm in terms of solid content, pH is adjusted to 8.5 using sodium hydroxide, and then deionized water is added to make a total volume of 450 ml. A test solution was prepared. Next, two SS-41 test pieces of 25 mm × 40 mm × 1 mm were suspended in the obtained test solution, and heat-treated at 40 ° C. for 40 hours while flowing 25 ml / min of air over the test solution. After the heat treatment, the weight loss of the test piece was measured except for the corrosion products on the test piece. The results are shown in Tables 1 and 2 by converting the average value of weight loss of two test pieces into MDD (mg / dm 2 / day).
[0048]
Reference example 2
In Reference Example 1 , (meth) acrylic having an acrylic acid equivalent concentration of 38% is the same as Reference Example 1 except that 558.7 parts of ion-exchanged water is used instead of 321.9 parts of initially charged ion-exchanged water. An acid-based water-soluble polymer (2) was obtained. The (meth) acrylic acid water-soluble polymer (2) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 1 and 2.
[0049]
Reference example 3
In Reference Example 1 , in place of 321.9 parts of initially charged ion exchange water, 84.3 parts of ion exchange water, 470 parts of 100% acrylic acid instead of 587.5 parts of 80% aqueous solution of 80% acrylic acid, 30% hypochlorous acid A (meth) acrylic acid-based solution having an acrylic acid equivalent concentration of 68% in the same manner as in Reference Example 1 , except that 68.2 parts of a 30% aqueous hypophosphorous acid solution was used instead of 21.9 parts of the sodium phosphate aqueous solution, respectively. A water-soluble polymer (3) was obtained. The (meth) acrylic acid water-soluble polymer (3) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 1 and 2.
[0050]
Reference example 4
Except for using 80% 587.5 parts of methacrylic acid solution instead of 80% 587.5 parts of aqueous solution of acrylic acid is 47% methacrylic acid concentration in terms in the same manner as in Reference Example 1 Reference Example 1 (meth) acrylic An acid-based water-soluble polymer (4) was obtained. The (meth) acrylic acid polymer (4) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 1 and 2.
[0051]
Reference Example 5
In the same polymerization vessel as used in Reference Example 1 , 35.1 parts of ion-exchanged water was charged, the temperature was raised to 100 ° C., and after nitrogen substitution, 979.2 parts of a 48% aqueous acrylic acid solution and a 48% aqueous sodium hydroxide solution 543 were obtained. .9 parts, 34.4 parts of 30% aqueous sodium persulfate solution (0.0066 mol / mol 1 sodium acrylate) and 21.9 parts of 30% aqueous sodium hypophosphite solution (0.0095 mol / mol 1 sodium acrylate) ) Was added dropwise over 2 hours. The 48% acrylic acid aqueous solution and 48% sodium hydroxide aqueous solution were added dropwise immediately before the dropping port and introduced into the polymerization system as a sodium acrylate aqueous solution. Each of the others was introduced into the polymerization system through a separate dropping port. During this time, the temperature of the system maintained the boiling point throughout. Further, aging was carried out at the same temperature for 10 minutes to complete the polymerization, and a (meth) acrylic acid-based water-soluble polymer (5) having a sodium acrylate equivalent concentration of 38% in the liquid after polymerization was obtained. The performance of the (meth) acrylic acid water-soluble polymer (5) was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 1 and 2.
[0052]
Reference Example 6
In Reference Example 1 , 587.5 parts of 80% aqueous acrylic acid solution, 68.7 parts of 15% aqueous sodium persulfate aqueous solution and 21.9 parts of 30% aqueous sodium hypophosphite aqueous solution were divided into 1/24 parts each every 5 minutes. The reaction was led to the polymerization system. Aging was conducted in the same manner as in Reference Example 1 to obtain a (meth) acrylic acid-based water-soluble polymer (6) having an acrylic acid equivalent concentration of 47%. The (meth) acrylic acid-based water-soluble polymer (6) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 1 and 2.
[0053]
Example 1
In the same polymerization vessel as used in Reference Example 1 , 285 parts of ion-exchanged water was charged, the temperature was raised to 100 ° C., and after nitrogen substitution, 587.5 parts of an 80% aqueous acrylic acid solution and an aqueous 23% sodium acrylate solution 236.9. Part, 813 parts of 50% aqueous 3-allyloxy-2-hydroxypropanesulfonate (HAPS) solution, 97.6 parts of 15% aqueous sodium persulfate solution (0.0066 mol / monomer of 1 mol) and 30% hypophosphorous acid 31.3 parts of sodium acid aqueous solution (0.0095 mol / monomer of 1 mol) was added dropwise from a separate dropping port over 2 hours. Aging was carried out in the same manner as in Reference Example 1 to obtain a (meth) acrylic acid-based water-soluble polymer (7) having a monomer equivalent concentration after polymerization of 47%. The (meth) acrylic acid water-soluble polymer (7) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 1 and 2.
[0054]
Comparative Example 1
In Reference Example 1 , a comparative (meth) acrylic acid-based water-soluble solution having an acrylic acid equivalent concentration of 47% as in Reference Example 1 except that 21.9 parts of a 30% sodium hypophosphite aqueous solution was initially charged. A polymer (1) was obtained. The comparative (meth) acrylic acid-based water-soluble polymer (1) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 3 and 4.
[0055]
Comparative Example 2
In Reference Example 1 , 1671.9 parts of ion-exchanged water was used instead of 321.9 parts of initially charged ion-exchanged water, and 587.5 parts of 80% acrylic acid aqueous solution, 68.7 parts of 15% sodium persulfate aqueous solution, and 30 A comparative (meth) acrylic acid type polymerized in the same manner as in Reference Example 1 except that 21.9 parts of% sodium hypophosphite was initially charged and reacted at 70 ° C., and the acrylic acid equivalent concentration was 20%. A water-soluble polymer (2) was obtained. The comparative (meth) acrylic acid polymer (2) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 3 and 4.
[0056]
Comparative Example 3
In Reference Example 1 , a comparative example (methacrylic acid equivalent concentration of 35%) was used in the same manner as in Reference Example 1 except that 664.7 parts of ion-exchanged water was used instead of 321.9 parts of initially charged ion-exchanged water. ) Acrylic acid-based water-soluble polymer (3) was obtained. The comparative (meth) acrylic acid-based water-soluble polymer (3) was neutralized in the same manner as in Reference Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 1 . The obtained results are shown in Tables 3 and 4.
[0057]
Comparative Example 4
In Reference Example 3 , except that 19.8 parts of ion-exchanged water was used instead of 84.3 parts of initially charged ion-exchanged water, the same as in Reference Example 3 , the acrylic acid equivalent concentration was 75% (for comparison) A (meth) acrylic acid-based water-soluble polymer (4) was obtained. The comparative (meth) acrylic acid water-soluble polymer (4) was neutralized in the same manner as in Reference Example 3, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Reference Example 3 . The obtained results are shown in Tables 3 and 4.
[0058]
Comparative Example 5
In Example 1 , except that 1155.2 parts of ion-exchanged water was used in place of 285 parts of initially charged ion-exchanged water, the monomer equivalent concentration was 33% for comparison (meta) as in Example 1. An acrylic acid-based water-soluble polymer (5) was obtained. The comparative (meth) acrylic acid-based water-soluble polymer (5) was neutralized in the same manner as in Example 1, and the performance of the neutralized product thus obtained was evaluated in the same manner as in Example 1 . The obtained results are shown in Tables 3 and 4.
[0059]
The molecular weights of the (meth) acrylic acid-based water-soluble polymers (1) to (7) and the comparative (meth) acrylic acid-based water-soluble polymers (1) to (5) are all in the range of 20,000 to 60,000. The molecular weight was almost the same.
[0060]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
[Table 5]
【The invention's effect】
According to the method for producing a (meth) acrylic acid-based water-soluble polymer according to the present invention, a (meth) acrylic acid-based water-soluble polymer having high purity, low cost and high safety can be easily produced industrially. Become. Furthermore, surprisingly, when used as so-called water treatment agents such as scale inhibitors and corrosion inhibitors and inorganic pigment dispersants, the functions are far superior to conventional products.
[0066]
Thus, the present invention has extremely high industrial utility value.
Claims (7)
上記（メタ）アクリル酸系水溶性単量体として、アクリル酸またはメタクリル酸を含有する重合性単量体を用い、
重合後の反応液中の重合体の単量体換算濃度が３８〜７２重量％となるのに必要な（メタ）アクリル酸系水溶性単量体、および、全単量体に対して３０モル％未満（０モル％を除く）である不飽和スルホン酸系単量体、触媒として、銅（塩）を用いずに、重合開始剤及び次亜リン酸（塩）を水性媒体中に逐次導入して重合した後、中和することを特徴とする（メタ）アクリル酸系水溶性重合体の製造方法。When producing a (meth) acrylic acid polymer by polymerizing an aqueous solution of at least a (meth) acrylic acid water-soluble monomer as a monomer,
As the (meth) acrylic acid-based water-soluble monomer, a polymerizable monomer containing acrylic acid or methacrylic acid is used,
30 moles of the (meth) acrylic acid-based water-soluble monomer and the total monomer required for the monomer equivalent concentration of the polymer in the reaction solution after polymerization to be 38 to 72% by weight % (Excluding 0 mol%) of unsaturated sulfonic acid monomer, catalyst, and polymerization initiator and hypophosphorous acid (salt) are sequentially introduced into the aqueous medium without using copper (salt) Then, after the polymerization, neutralization is carried out, and a method for producing a (meth) acrylic acid-based water-soluble polymer.
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