JP2004331785A

JP2004331785A - Manufacturing method for (meth)acrylic resin emulsion

Info

Publication number: JP2004331785A
Application number: JP2003128690A
Authority: JP
Inventors: Seiji Tanimoto; 征司谷本
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2003-05-07
Filing date: 2003-05-07
Publication date: 2004-11-25

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a (meth)acrylic resin emulsion remarkably excellent in stability of the emulsion (co)polymerization and operationability of the polymerization and also excellent in film strength, mechanical stability, and solvent resistance. <P>SOLUTION: In the manufacturing method for the (meth)acrylic resin emulsion, which comprises emulsion (co)polymerizing at least one kind of monomer selected from acrylate monomers and methacrylate monomers, using a vinyl alcohol type polymer having a functional group containing an active hydrogen as a dispersant and employing a redox polymerization initiator consisting of a peroxide and a reducing agent, an iron compound (1), the monomer (2), and the vinyl alcohol type polymer (3) are charged at the initial stage of the polymerization and the peroxide is added into the system continuously or intermittently to carry out the emulsion (co)polymerization. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ビニルアルコール系重合体を分散剤とし、（メタ）アクリル酸エステル系単量体を乳化（共）重合する（メタ）アクリル樹脂系エマルジョンの製法に関する。詳しくは、乳化（共）重合の安定性、重合の操作性に顕著に優れ、さらには得られるエマルジョンの皮膜強度、耐溶剤性、機械的安定性にも優れる（メタ）アクリル樹脂系エマルジョンの製法に関する。
【０００２】
【従来の技術】
従来、（メタ）アクリル酸エステル系単量体を乳化重合したエマルジョンは塗料、紙加工および繊維加工などの分野で広く用いられている。これらの単量体の乳化重合においては、乳化重合の安定性の観点から通常、アニオン系あるいはノニオン系界面活性剤が安定剤として用いられる。しかし、界面活性剤を安定剤とするエマルジョンは機械的安定性に乏しい欠点があり、セメント、モルタル等の混和剤用途など、高い機械的安定性を必要とされる用途には使用し得ない問題点があった。
上記問題点を解決する目的で、重合度５００以下、好ましくは３００以下のポリビニルアルコール（ＰＶＡ）を保護コロイドとする、あるいはＰＶＡ及び連鎖移動剤の存在下に乳化重合するといった手法が提案（特許文献１、特許文献２）され、エマルジョンの機械的安定性の改善が試みられた。しかしながら、このようなＰＶＡを使用したのでは、ＰＶＡ保護コロイドの特長が十分に発現せず、機械的安定性を完全に満足できず、また、エマルジョン皮膜の強度にも劣る欠点があった。メルカプト基を有するＰＶＡ系重合体を乳化分散安定剤に用いることが提案（特許文献３、特許文献４、特許文献５）されている。この場合、通常用いられる開始剤、例えば、過硫酸カリウム、過硫酸アンモニウム、過酸化水素単独あるいは各種還元剤との組合せによるレドックス開始剤等では、該ＰＶＡ系重合体へのグラフト効率が低く、十分実用的な安定性の確保が難しいという問題があり、また、該ＰＶＡ系重合体のメルカプト基とのレドックス反応によってのみラジカルを発生する臭素酸カリウム等の開始剤では、重合安定性の向上は認められるが、ＰＶＡ系重合体のメルカプト基が消費された時点で、いわゆるＤｅａｄ−Ｅｎｄとなり重合のコントロール及び完結が難しいという問題点があった。重合を開始して以降、熟成を開始するまでの間にポリビニルアルコールを添加してエマルジョンを製造する方法が開示（特許文献６）されているが、この方法では、乳化重合を開始させるときに乳化剤を使用しているために、各種用途に使用する場合に乳化剤がマイグレーションを起こし、物性に悪影響を及ぼすという問題があった。（メタ）アクリル酸エステル系単量体、ジエン系単量体等の単量体及び水溶性高分子保護コロイドを連続的または断続的に添加して重合する方法が提案（特許文献７）され、機械的安定性等が改善されている。しかしながら該手法は、各種単量体、保護コロイド、重合開始剤など多くの物質を重合系中に添加する必要があり、重合の操作性に劣るばかりでなく、不均一系である乳化重合においては、攪拌翼の形状、攪拌速度、重合スケール（重合槽の容量）など種々の因子に大きく影響され、再現性良くエマルジョンを得ることが難しいという欠点があった。アクリル酸エステル系単量体をＰＶＡの存在下に粒子径０．５μｍ以下に乳化分散し、重合させる方法が提案（特許文献８）され、重合安定性などが改善されている。しかし、該手法では、ホモミキサーなど強制乳化装置が必須となり、また重合中、水相の酸素濃度を０．３ｐｐｍ以下に抑えるという厳しい条件下での重合が必要とされるなど、汎用的に用いることは困難である。また、けん化度の低いＰＶＡを用いる必要があったことから、耐溶剤性に劣る問題点もあった。
以上の様に、これまで、ＰＶＡ系重合体を保護コロイドとした（メタ）アクリル酸エステル系樹脂エマルジョンの提案が各種なされているが、乳化重合の安定性、重合の操作性を完全に満足し、得られるエマルジョンの皮膜強度、耐溶剤性、機械的安定性等の物性にも優れ、汎用的に使用可能なものは見られないのが現状であった。
【０００３】
【特許文献１】
特開平４−１８５６０６号公報（特許請求の範囲）
【特許文献２】
特開平４−１８５６０７号公報（特許請求の範囲）
【特許文献３】
特開昭６０−１９７２２９号公報（特許請求の範囲）
【特許文献４】
特開平６−１２８４４３号公報（特許請求の範囲）
【特許文献５】
特開平７−２７８２１２号公報（特許請求の範囲）
【特許文献６】
特開平８−２４５７０６号公報（特許請求の範囲）
【特許文献７】
特開平１１−３３５４９０号公報（特許請求の範囲）
【特許文献８】
特開２０００−２５６４２４号公報（特許請求の範囲）
【０００４】
【発明が解決しようとする課題】
本発明は、このような事情のもとで、乳化（共）重合の安定性、重合の操作性に顕著に優れ、さらには得られるエマルジョンの皮膜強度、耐溶剤性、機械的安定性にも優れる（メタ）アクリル樹脂系エマルジョンの製法を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
本発明者らは、前記の好ましい性質を有する水性エマルジョンの製法を開発すべく鋭意研究を重ねた結果、活性水素を含有する官能基を分子内に有するビニルアルコール系重合体を分散剤とし、過酸化物と還元剤からなるレドックス系重合開始剤を用い、アクリル酸エステル系単量体およびメタクリル酸エステル系単量体から選ばれる少なくとも一種の単量体を乳化（共）重合する際に、（１）鉄化合物、（２）前記単量体および（３）前記ビニルアルコール系重合体を重合初期に仕込み、前記過酸化物を連続的あるいは断続的に添加して乳化（共）重合することを特徴とする（メタ）アクリル樹脂系エマルジョンの製法が上記目的を満足するものであることを見出し、本発明を完成するに到った。
【０００６】
【発明の実施の形態】
本発明の製法に用いられる、活性水素を含有する官能基を分子内に有するビニルアルコール系重合体（活性水素基含有ＰＶＡと略記することがある）は、分子内に活性水素を含有する官能基を有するビニルアルコール系重合体であれば特に制限はないが、中でも、分子内に１級アミノ基、２級アミノ基、アセトアセチル基、メルカプト基およびジアセトンアクリルアミド基から選ばれる１種以上の官能基を有するビニルアルコール系重合体が、好ましく用いられる。分子内に１級アミノ基、２級アミノ基、アセトアセチル基、メルカプト基、ジアセトンアクリルアミド基から選ばれる１種以上の官能基を有するビニルアルコール重合体は従来公知の方法により合成される。
【０００７】
例えば、１級または２級アミノ基を有するビニルアルコール系重合体の場合、
（１）アクリルアミド、メタクリルアミド、Ｎ−ビニルホルムアミド、Ｎ−ビニルアセトアミド等の、１級または２級アミノ基を有するエチレン性不飽和単量体、または加水分解等により１級または２級アミノ基を生成しうる官能基を有するエチレン性不飽和単量体と、酢酸ビニル等のビニルエステル類とを共重合させた後、けん化する方法、
（２）アリルグリシジルエーテルなどのエポキシ基を有する単量体と酢酸ビニル等のビニルエステル類からなる重合体のエポキシ基に、アミノ基を有するメルカプタンをＮａＯＨ等を触媒として付加反応させた後、けん化する方法や、
（３）従来公知のポリビニルアルコールの水酸基と反応しうる官能基を分子内に有し、かつ、１級または２級アミノ基を有する化合物をビニルアルコール系重合体に反応させる方法、
（４）メルカプト基を有するビニルアルコール系重合体の存在下で、１級または２級アミノ基を有するエチレン性不飽和単量体を重合する方法（この方法ではポリビニルアルコール系ブロックポリマーが得られる）、
等の方法によって得られる。
分子内にアセトアセチル基を有するビニルアルコール系重合体の場合、（５）通常、従来公知のビニルアルコール系重合体にジケテンを付加させる後反応によって得られる。
分子内にメルカプト基を有するビニルアルコール系重合体は、チオ酢酸の存在下でビニルエステルを重合させた後、けん化することで分子内にメルカプト基を有するビニルアルコール系重合体が得られる。
また、ジアセトンアクリルアミド基を有するビニルアルコール系重合体の場合、（６）ビニルエステルとジアセトンアクリルアミドを共重合させた後、けん化することでジアセトンアクリルアミド基を有するビニルアルコール系重合体が得られる。
活性水素基含有ＰＶＡの活性水素基含有量は特に制限されないが、通常０．３〜１５モル％、好ましくは０．５〜１０モル％、より好ましくは０．７〜７モル％である。活性水素基含有量がこの範囲にある時、耐溶剤性により優れるエマルジョンが得られる。
【０００８】
該活性水素基含有ＰＶＡの粘度平均重合度（以下重合度と略す）は、各種の状況に応じて選定すればよく、特に制限はないが、１００〜８０００であることが好ましい。より好ましくは２００〜２５００、さらに好ましくは３００〜２０００である。重合度が上記範囲にある時、乳化重合の操作性、安定性がさらに向上する。一方、けん化度も特に制限されないが、通常７０モル％以上であり、好ましくは７０〜９９モル％、より好ましくは７５〜９９モル％、さらにより好ましくは８０〜９８モル％、特に好ましくは８０〜９５モル％、最適には８３〜９５モル％である。けん化度が７０モル％未満の場合には、ビニルアルコール系重合体本来の性質である水溶性が低下する懸念が生じる。
【０００９】
該活性水素基含有ＰＶＡは本発明の効果を損なわない範囲で共重合可能なエチレン性不飽和単量体を共重合したものでも良い。このようなエチレン性不飽和単量体としては、例えば、アクリル酸、メタクリル酸、フマル酸、（無水）マレイン酸、イタコン酸、アクリロニトリル、メタクリロニトリル、トリメチル−（３−アクリルアミド−３−ジメチルプロピル）−アンモニウムクロリド、アクリルアミド−２−メチルプロパンスルホン酸およびそのナトリウム塩、エチルビニルエーテル、ブチルビニルエーテル、塩化ビニル、臭化ビニル、フッ化ビニル、塩化ビニリデン、フッ化ビニリデン、テトラフルオロエチレン、ビニルスルホン酸ナトリウム、アリルスルホン酸ナトリウム、Ｎ−ビニルピロリドンが挙げられる。また、チオール酢酸、メルカプトプロピオン酸などのチオール化合物の存在下で、酢酸ビニルなどのビニルエステル系単量体を重合し、得られた重合体をけん化することによって得られる末端変性物を用いることもできる。
また、ここで、ビニルエステルとしては、蟻酸ビニル、酢酸ビニル、プロピオン酸ビニル、ピバリン酸ビニルなどが挙げられるが、一般に酢酸ビニルが好ましく用いられる。
【００１０】
また本発明において分散剤に用いる活性水素基含有ＰＶＡの使用量は特に制限されないが、用いる単量体１００重量部に対して、１〜２０重量部、好ましくは２〜１５重量部、より好ましくは２．５〜１０重量部である。活性水素基含有ＰＶＡの使用量が１重量部未満であると、重合安定性が低下する恐れがあり、一方、２０重量部を越える場合には得られるエマルジョンの粘度が高くなり、操作性に劣る懸念が生じる。
【００１１】
本発明の（メタ）アクリル樹脂系エマルジョンの製法において、分散質を構成する重合体は、アクリル酸エステル系単量体およびメタクリル酸エステル系単量体から選ばれる少なくとも１種の単量体を（共）重合したものである。該単量体としては、アクリル酸メチル、アクリル酸エチル、アクリル酸ｎ−プロピル、アクリル酸ｉ−プロピル、アクリル酸ｎ−ブチル、アクリル酸ｉ−ブチル、アクリル酸ｔ−ブチル、アクリル酸２−エチルヘキシル、アクリル酸ドデシル、アクリル酸オクタデシル等のアクリル酸エステル類、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ｎ−プロピル、メタクリル酸ｉ−プロピル、メタクリル酸ｎ−ブチル、メタクリル酸ｉ−ブチル、メタクリル酸ｔ−ブチル、メタクリル酸２−エチルヘキシル、メタクリル酸ドデシル、メタクリル酸オクタデシル等のメタクリル酸エステル類などが挙げられる。
【００１２】
また、上記分散質を構成する重合体は、本発明の効果を損なわない範囲で共重合可能な他の単量体を共重合したものでも構わない。このような単量体としては、エチレン、プロピレン、イソブチレンなどのオレフィン；塩化ビニル、フッ化ビニル、ビニリデンクロリド、ビニリデンフルオリドなどのハロゲン化オレフィン；蟻酸ビニル、酢酸ビニル、プロピオン酸ビニル、ピバリン酸ビニルなどのビニルエステル系単量体；アクリル酸、メタクリル酸などのカルボキシル基含有単量体；トリアリルシアヌレート、トリアリルイソシアヌレート、ジアリルフタレートなどの多官能性単量体；スチレン、α−メチルスチレン、ｐ−メチルスチレンスルホン酸およびそのナトリウム塩またはカリウム塩等のスチレン系単量体；ブタジエン、イソプレン、クロロプレン等のジエン系単量体などが挙げられる。これら他の単量体の使用量は全単量体に対し３０重量％以下が好ましく、さらには２０重量％以下が好ましい。
【００１３】
本発明の製法では、重合初期に、鉄化合物を、とくにその全量を添加することが、乳化重合の操作性をより優れたものにすることから重要である。鉄化合物としては特に制限されないが、塩化第一鉄、硫酸第一鉄、塩化第二鉄、硝酸第二鉄および硫酸第二鉄から選ばれる少なくとも１種の鉄化合物が好ましく用いられ、中でも塩化第一鉄、硫酸第一鉄が特に好ましく用いられる。
【００１４】
鉄化合物の使用量は特に制限されないが、通常使用する全単量体に対して１ｐｐｍ〜５０ｐｐｍ、より好ましくは５ｐｐｍ〜３０ｐｐｍである。鉄化合物の使用量がこの範囲内にあるとき、重合操作性が良好である。鉄化合物はその全量を重合初期に仕込んで用いることが好適である。
【００１５】
本発明の製法では、過酸化物と還元剤からなるレドックス系重合開始剤を用いる。過酸化物としては特に制限されないが、過酸化水素、過硫酸アンモニウム、過硫酸カリウムおよびｔ−ブチルヒドロパーオキシドなどが用いられ、特に過酸化水素が好ましく用いられる。過酸化物は、連続的あるいは断続的に添加することが必要である。連続的あるいは断続的に添加することにより、重合操作性が向上する。
【００１６】
過酸化物として過酸化水素を用いる場合、過酸化水素の０．１〜５％水溶液、好ましくは０．２〜３％水溶液、さらに好ましくは０．２５〜２％水溶液を用いることにより、重合の操作性が向上する。また、単量体１００重量部に対して、過酸化物を純分で０．０１〜１重量％用いた場合、重合の安定性が向上する。
【００１７】
また、過酸化物として過酸化水素が用いられる場合、還元剤としては酒石酸、Ｌ−アスコルビン酸、ロンガリット、あるいはこれらの金属塩が好適に用いられる。また、過酸化物として、過硫酸アンモニウム、過硫酸カリウムが用いられる場合、還元剤としては亜硫酸水素ナトリウム、炭酸水素ナトリウムなどが好適に用いられる。還元剤の添加方法は特に制限されないが、重合初期に全量を添加する方法が、重合操作性の観点から好適である。
還元剤の使用量も特に限定されないが、通常、過酸化物に対して、０．０５〜３当量、好ましくは０．１〜２当量、より好ましくは０．３〜１．５当量である。
【００１８】
上記還元剤のうち、酒石酸系が好ましく用いられ、詳しくは酒石酸および／またはその金属塩である。酒石酸としては右旋性のＬ（＋）酒石酸、左旋性のＤ（−）酒石酸、これら対掌体のラセミ化合物であるＤＬ酒石酸があり、特に制限されないが、これらの中でもＬ（＋）酒石酸を用いた場合、乳化重合操作性が顕著に良好であり、好ましく用いられる。また、酒石酸の金属塩を用いることも可能であり、金属の種類は特に制限されないが、酒石酸ナトリウムが好適に用いられる。中でもＬ（＋）酒石酸ナトリウムが好ましく用いられる。Ｌ（＋）酒石酸ナトリウムを用いた場合、重合操作性が最適となる。
【００１９】
また本発明の製法では、鉄化合物、単量体、活性水素基含有ＰＶＡを重合初期に仕込むことが重要である。とくにこれらの全量を重合初期に仕込むことが好適である。該手法をとることにより、重合の操作性が向上するのみならず、乳化重合の安定性が顕著に向上する。ここで、重合初期とは、重合開始直前または直後を言う。
【００２０】
本発明の製法においては、連鎖移動剤を重合初期に添加することで、さらに重合安定性を向上させることが可能となる。連鎖移動剤としては、乳化重合時に連鎖移動をおこす化合物であれば特に制限されないが、例えば、メタノール、エタノール、ｎ−プロパノール、ｉ−プロパノール、ｎ−ブタノール、ｉ−ブタノールなどのアルコール類、アセトン、メチルエチルケトン、シクロヘキサノン、アセトフェノン等のケトン類、アセトアルデヒド、プロピオンアルデヒド、ｎ−ブチルアルデヒド、フルフラール、ベンズアルデヒド等のアルデヒド類、２−メルカプトエタノール、３−メルカプトプロピオン酸、ｎ−ドデシルメルカプタン、ｔ−ドデシルメルカプタン、ラウリルメルカプタン、ｎ−ブチルメルカプタン、ｔ−ブチルメルカプタン、２−エチルヘキシルチオグリコレート、チオグリコール酸オクチル等のメルカプタン類などが挙げられる。このうちメルカプタン系の連鎖移動剤が好適である。
連鎖移動剤の添加量は特に制限されないが、全単量体１００重量部に対して、０．０１〜５０重量部、好ましくは０．１〜３０重量部である。
【００２１】
本発明の製法では、エマルジョンの固形分濃度は特に制限されないが、通常、２０〜７０重量％、好ましくは３０〜６５重量％、さらに好ましくは４０〜６０重量％である。固形分濃度が２０重量％未満の場合、エマルジョンの放置安定性が低下し、２相に分離する恐れがあり、７０重量％を越える場合、重合時の安定性が低下する懸念が生じる。
【００２２】
本発明の製法で得られるエマルジョンは、マロン式機械的安定性測定装置により室温２０℃において０．５ｋｇ／ｃｍ^２の荷重下、１０００ｒｐｍで１０分間試験を行った後、６０メッシュ（ＡＳＴＭ式標準フルイ）ステンレス製金網でろ過した場合、ろ過残渣がエマルジョンの固形分に対して０．３重量％以下であることが好適であり、好ましくは０．２重量％以下であり、さらに好ましくは０．１重量％以下である。ろ過残渣が前記範囲にあるとき、エマルジョンは機械的安定性が良好であると言える。
【００２３】
上記の方法で得られるエマルジョンはそのままで用いることができるが、必要があれば、本発明の効果を損なわない範囲で、従来公知の各種エマルジョンを添加して用いることができる。また、本発明により得られるエマルジョンには、通常使用される添加剤を添加することができる。この添加剤の例としては、有機溶剤類（トルエン、キシレン等の芳香族類、アルコール類、ケトン類、エステル類、含ハロゲン系溶剤類等）、可塑剤、沈殿防止剤、増粘剤、流動性改良剤、防腐剤、防錆剤、消泡剤、充填剤、湿潤剤、着色剤等が挙げられる。
【００２４】
本発明の製法により得られるエマルジョンは、皮膜強度、機械的安定性に優れ、さらには耐溶剤性に優れるため、塗料、水硬性物質の混和剤、打継ぎ材、各種接着剤、含浸紙用、不織製品用のバインダー、塗料、紙加工および繊維加工、コーティング剤などの分野で好適に用いられる。
【００２５】
【実施例】
次に、実施例および比較例により本発明をさらに詳細に説明する。なお、以下の実施例および比較例において「部」および「％」は、特に断らない限り重量基準を意味する。
実施例１
還流冷却器、温度計、窒素吹込口、イカリ型攪拌翼を備えた２リットルガラス製重合容器に、イオン交換水７５０ｇ、ＰＶＡ−１（重合度５００、けん化度８８モル％、末端にメルカプト基１．５×１０^−５当量／ｇを含有）４０ｇを仕込み、９５℃で完全に溶解した。６０℃に冷却後、メタクリル酸メチル２６６ｇ、アクリル酸ブチル２６６ｇを仕込み、１２０ｒｐｍで攪拌しながら窒素置換を行った。その後、塩化第一鉄０．００５８ｇ、Ｌ（＋）酒石酸ナトリウム（ＴＡＳ）の１０％水溶液２５ｇを添加した。次に、過酸化水素（ＨＰＯ）の０．５％水溶液１００ｇを３時間かけて添加し、乳化重合を行った。過酸化水素添加開始５分後に発熱が見られ、乳化重合の開始を確認した。その後、外温を５０〜５５℃に保って重合を進めたところ、重合温度は５８〜６２℃で推移し、操作性良く重合が進行した。過酸化水素水溶液の添加終了後、１時間熟成し、重合反応を完結したのち冷却した。その結果、固形分濃度３９．８％のエマルジョンを得た。
得られたエマルジョンを次の方法により評価した。その結果を表１に示す。
【００２６】
（エマルジョンの評価）
（１）重合操作性
重合開始からの重合温度の推移を測定し、重合熱による温度上昇の程度を観察し、重合のコントロールが容易か否かを判断した。重合推移温度の幅が小さいほど重合のコントロールが容易であることを示す。
（２）乳化重合安定性
得られたエマルジョンを、６０メッシュ（ＡＳＴＭ式標準フルイ）のステンレス製金網を用いろ過した。ろ過後、金網上の残渣を採取し、重量を測定した。エマルジョン固形分１ｋｇあたりの残渣量を表１に示す。
（３）皮膜強度
得られたエマルジョンを室温２０℃、６５％ＲＨ下で、ポリエチレンテレフタレート（ＰＥＴ）フィルム上に流延し、７日間乾燥させて厚さ５００μｍの乾燥皮膜を得た。得られた乾燥皮膜を２０℃、６０％ＲＨ下で１週間調湿したのち、皮膜引張り強度（引張り速度：５ｃｍ／ｍｉｎ）を測定した。
（４）皮膜の耐溶剤性
得られた水性エマルジョンを２０℃、６５％ＲＨ下で、ＰＥＴフィルム上に流延し、７日間乾燥させて５００μｍの乾燥皮膜を得た。この皮膜を直径２．５ｃｍに打ち抜き、それを試料として２０℃のアセトンに２４時間浸漬した場合の、皮膜の溶出率および吸液率を求めた。
溶出率（％）＝｛１−（浸漬後の皮膜絶乾重量）／（浸漬前の皮膜絶乾重量）｝×１００
吸液率（％）＝｛（浸漬後の皮膜重量）／（浸漬前の皮膜絶乾重量）｝×１００
・浸漬前の皮膜絶乾重量；浸漬前の皮膜重量（含水）−｛浸漬前の皮膜重量（含水）×皮膜含水率（％）／１００｝
・皮膜含水率；皮膜（２０℃のアセトンに浸漬するサンプルとは別のサンプル）を、１０５℃で絶乾し、皮膜の含水率をあらかじめ求める。
・浸漬後の皮膜絶乾重量；浸漬後の皮膜を１０５℃で絶乾した重量。
・浸漬後の皮膜重量；浸漬後の皮膜をアセトンから引き上げた後、皮膜についたアセトンをガーゼで拭き取った後秤量。
【００２７】
（５）機械的安定性
得られた水性エマルジョンを、マロン式機械的安定性測定機を用い、室温２０℃において、０．５ｋｇ／ｃｍ^２の荷重下１０００ｒｐｍで１０分間試験を行った後、６０メッシュ（ＡＳＴＭ式標準フルイ）ステンレス製金網を用いてろ過し、水性エマルジョンの固形分重量に対するろ過残渣重量の割合（％）を測定した。ろ過残渣重量の割合が少ないほど機械的安定性が優れていることを示す。
なお、固形分濃度およびろ過残渣重量の測定は次のとおりである。
固形分濃度測定法
得られたエマルジョン約３ｇをアルミ皿にとり、精秤後、１０５℃の乾燥機で２４時間乾燥し、水分を揮発させた。その後の乾燥物の重量を測定し、重量比から固形分濃度を算出した。
ろ過残渣重量の測定法
ろ過残渣を１０５℃の乾燥機で２４時間乾燥し、水分を揮発させ、乾燥物の重量をろ過残渣重量とした。
【００２８】
比較例１
還流冷却器、滴下ロート、温度計、窒素吹込口、イカリ型攪拌翼を備えた２リットルガラス製重合容器に、イオン交換水を７５０ｇ、ＰＶＡ−１を４０ｇ仕込み、９５℃で完全に溶解した。次に窒素置換を行い、１２０ｒｐｍで撹拌しながら、６０℃に調整した後、塩化第一鉄０．００５８ｇ、Ｌ（＋）酒石酸ナトリウムの１０％水溶液２５ｇを添加した。その後、メタクリル酸メチル２６６ｇとアクリル酸ブチル２６６ｇの混合液を滴下ロートから２時間目標で連続的に添加し、併せて０．５％過酸化水素水溶液１００ｇを３時間目標で連続的に添加を開始した。外温を５５℃に保って重合を行っていたところ、１時間後、重合系がゲル化したため、試験を中止した。
【００２９】
比較例２
実施例１において塩化第一鉄を用いなかった他は、実施例１と同様の仕込みで過酸化水素水溶液の添加を開始した。過酸化水素添加開始１５分後に発熱、乳化重合が開始したため、外温を５０℃に調整し、過酸化水素の添加を続けたところ、重合温度が６５℃に達したため、過酸化水素の添加を中断した。しかし、発熱は止まらず、重合温度が７０℃に達したため、重合のコントロールが出来ないと判断し、試験を中止した。
【００３０】
実施例２
実施例１において、さらにｎ−ドデシルメルカプタンを２．６ｇ重合初期に仕込んだ他は、実施例１と同様に乳化重合を行った。得られたエマルジョンの評価を併せて表１に示す。
【００３１】
比較例３
比較例１において、さらにｎ−ドデシルメルカプタンを２．６ｇ重合初期に仕込んだ他は、比較例１と同様に乳化重合を試みた。しかし、重合開始１時間３０分後に重合系がゲル化し、試験を中止した。
【００３２】
比較例４
比較例２において、さらにｎ−ドデシルメルカプタンを２．６ｇ重合初期に仕込んだ他は、比較例２と同様に乳化重合を試みた。しかし、比較例２同様、発熱をコントロールすることが不可能であり、試験を中止した。
【００３３】
比較例５
実施例１においてＰＶＡ−１の代わりに、メルカプト基を含有しないＰＶＡ−２（重合度５００、けん化度８８モル％）を用いた他は、実施例１と同様に乳化重合を行った。得られたエマルジョンの評価を併せて表１に示す。
【００３４】
実施例３
実施例２においてＰＶＡ−１の代わりに、Ｎ−ビニルアセトアミドと酢酸ビニルを共重合した後、けん化することにより得たポリビニルアルコールＰＶＡ−３（１級アミノ基２モル％、重合度５００、けん化度８８モル％）を用いた他は、実施例２と同様に乳化重合を行った。得られたエマルジョンの評価を併せて表１に示す。
【００３５】
実施例４
実施例２においてＰＶＡ−１の代わりに、ポリビニルアルコールにジケテンを固気反応により反応させることにより得たポリビニルアルコールＰＶＡ−４（アセトアセチル基５モル％、重合度１０００、けん化度８８モル％）を用いた他は、実施例２と同様に乳化重合を行った。得られたエマルジョンの評価を併せて表１に示す。
【００３６】
実施例５
実施例２においてＰＶＡ−１の代わりに、酢酸ビニルとジアセトンアクリルアミドを共重合した後、けん化して得たポリビニルアルコールＰＶＡ−５（ジアセトンアクリルアミド基３モル％、重合度１０００、けん化度８８モル％）を用いた他は、実施例２と同様に乳化重合を行った。得られたエマルジョンの評価を併せて表１に示す。
【００３７】
実施例６
還流冷却器、温度計、窒素吹込口、イカリ型攪拌翼を備えた２リットルガラス製重合容器に、イオン交換水を７５０ｇ、ＰＶＡ−１を４０ｇ仕込み、９５℃で完全に溶解した。６０℃に冷却後、メタクリル酸メチル２６６ｇ、アクリル酸ブチル２６６ｇを仕込み、１２０ｒｐｍで攪拌しながら窒素置換を行った。その後、塩化第一鉄０．００５８ｇ、亜硫酸水素ナトリウム（ＳＨＳ）の１０％水溶液１０ｇを添加した。次に、過硫酸カリウム（ＫＰＳ）の０．５％水溶液５０ｇを３時間かけて添加し、乳化重合を行った。過硫酸カリウム添加開始１０分後に発熱が見られ、乳化重合の開始を確認した。その後、外温を５０〜５５℃に保って重合を進めたところ、重合温度は５６〜６５℃で推移した。過硫酸カリウム水溶液の添加終了後、１時間熟成し、重合反応を完結したのち冷却した。その結果、固形分濃度３９．７％のエマルジョンを得た。得られたエマルジョンの評価を併せて表１に示す。
【００３８】
実施例７
還流冷却器、温度計、窒素吹込口、イカリ型攪拌翼を備えた２リットルガラス製重合容器に、イオン交換水を７５０ｇ、ＰＶＡ−１を４０ｇ仕込み、９５℃で完全に溶解した。６０℃に冷却後、メタクリル酸メチル２６６ｇ、アクリル酸ブチル２６６ｇを仕込み、１２０ｒｐｍで攪拌しながら窒素置換を行った。その後、塩化第一鉄０．００５８ｇ、Ｌ（＋）酒石酸ナトリウムの１０％水溶液２５ｇを添加した。次に、過酸化水素の７％水溶液７ｇを３時間かけて添加し、乳化重合を行った。過酸化水素添加開始３分後に発熱が見られ、乳化重合の開始を確認した。その後、外温を５０〜５５℃に保って重合を進めたところ、重合温度は５５〜６５℃で推移した。過酸化水素水溶液の添加終了後、１時間熟成し、重合反応を完結したのち冷却した。その結果、固形分濃度３９．８％のエマルジョンを得た。得られたエマルジョンの評価を併せて表１に示す。
【００３９】
実施例８
還流冷却器、温度計、窒素吹込口、イカリ型攪拌翼を備えた２リットルガラス製重合容器に、イオン交換水を７５０ｇ、ＰＶＡ−１を４０ｇ仕込み、９５℃で完全に溶解した。６０℃に冷却後、メタクリル酸メチル３９９ｇ、アクリル酸ブチル１３３ｇ、ｎ−ドデシルメルカプタン２．６ｇを仕込み、１２０ｒｐｍで攪拌しながら窒素置換を行った。その後、塩化第一鉄０．００５８ｇ、Ｌ（＋）酒石酸ナトリウムの１０％水溶液２５ｇを添加した。次に、過酸化水素の０．５％水溶液１００ｇを３時間かけて添加し、乳化重合を行った。過酸化水素添加開始５分後に発熱が見られ、乳化重合の開始を確認した。その後、外温を５０〜５５℃に保って重合を進めたところ、重合温度は５８〜６２℃で推移し、操作性良く重合が進行した。過酸化水素水溶液の添加終了後、１時間熟成し、重合反応を完結したのち冷却した。その結果、固形分濃度３９．８％のエマルジョンを得た。得られたエマルジョンの評価を併せて表１に示す。
【００４０】
比較例６
還流冷却器、滴下ロート、温度計、窒素吹込口、イカリ型攪拌翼を備えた２リットルガラス製重合容器に、イオン交換水を７５０ｇ、ＰＶＡ−１を４０ｇ仕込み、９５℃で完全に溶解した。次に窒素置換を行い、１２０ｒｐｍで撹拌しながら、６０℃に調整した後、塩化第一鉄０．００５８ｇ、Ｌ（＋）酒石酸ナトリウムの１０％水溶液２５ｇ、ｎ−ドデシルメルカプタン２．６ｇを添加した。その後、メタクリル酸メチル３９９ｇとアクリル酸ブチル１３３ｇの混合液を滴下ロートから２時間で連続的に添加、併せて０．５％過酸化水素水溶液１００ｇを３時間で連続的に添加を行った。添加後、１時間熟成を行った後、系を冷却していたところ、系がゲル化したため、試験を中止した。
【００４１】
実施例９
還流冷却器、温度計、窒素吹込口、イカリ型攪拌翼を備えた２リットルガラス製重合容器に、イオン交換水を７５０ｇ、ＰＶＡ−１を４０ｇ仕込み、９５℃で完全に溶解した。６０℃に冷却後、メタクリル酸メチル１３３ｇ、アクリル酸ブチル３９９ｇ、ｎ−ドデシルメルカプタン２．６ｇを仕込み、１２０ｒｐｍで攪拌しながら窒素置換を行った。その後、塩化第一鉄０．００５８ｇ、Ｌ（＋）酒石酸ナトリウムの１０％水溶液２５ｇを添加した。次に、過酸化水素の０．５％水溶液１００ｇを３時間かけて添加し、乳化重合を行った。過酸化水素添加開始５分後に発熱が見られ、乳化重合の開始を確認した。その後、外温を５０〜５５℃に保って重合を進めたところ、重合温度は５８〜６２℃で推移し、操作性良く重合が進行した。過酸化水素水溶液の添加終了後、１時間熟成し、重合反応を完結したのち冷却した。その結果、固形分濃度３９．７％のエマルジョンを得た。得られたエマルジョンの評価を併せて表１に示す。
【００４２】
実施例１０
実施例２においてイカリ型攪拌翼の代わりに、３段パドル型攪拌翼を用いた他は、実施例２と同様に乳化重合を行い、安定にエマルジョンを得た。得られたエマルジョンの評価を併せて表１に示す。
【００４３】
比較例７（特開平１１−３３５４９０号公報に記載の方法）
ＰＶＡ−２の４０ｇをイオン交換水４００ｇに添加して９５℃に加熱、溶解した水溶液を２０℃に冷却し、メタクリル酸メチル２６６ｇおよびアクリル酸ブチル２６６ｇからなる単量体混合物を混合、撹拌して、単量体乳化物を得た。別途、還流冷却器、滴下ロート、温度計、窒素吹込口、３段パドル型撹拌翼を備えた２リットルガラス製重合容器に、イオン交換水３５０ｇおよびエタノール１０ｇを装入して温度を８０℃に昇温し、８０℃を維持した状態で、過硫酸アンモニウム０．５ｇをイオン交換水１０ｇに溶解した開始剤溶液を添加した。２分後に重合容器に前記単量体乳化物の添加を開始し、４時間かけて添加を終了した。添加終了後、さらに２時間撹拌を継続し、熟成を行った後、冷却してエマルジョンを得た。得られたエマルジョンの評価を併せて表１に示す。
【００４４】
比較例８（特開平４−１８５６０６号公報に記載の方法）
温度計、イカリ型攪拌翼、還流冷却器、窒素吹き込み口および滴下ロートを備えた内容量２リットルの重合容器中でＰＶＡ−６（重合度１００、けん化度８８モル％）８０ｇをイオン交換水６８０ｇに添加して、９５℃に加熱、攪拌して溶解し、その後７０℃に冷却、窒素置換を行った。別の容器にメタクリル酸メチル２００ｇ、アクリル酸ブチル２００ｇ、アクリル酸６ｇを混合し、窒素置換を行った。０．５％過硫酸カリウム水溶液１０ｇと混合単量体の４０ｇを重合容器に添加して初期重合を行い、ついで残りの混合単量体を３時間にわたって滴下した。その間、０．５％過硫酸カリウム水溶液１５ｇを同時に連続添加した。滴下終了後、さらに１時間熟成を行った後、冷却し、１０％アンモニア水でｐＨ７．５に調整した。得られたエマルジョンの評価を併せて表１に示す。
【００４５】
【表１】

【００４６】
【発明の効果】
本発明の方法は、乳化（共）重合時の安定性だけでなく、重合の操作性に顕著に優れており、得られるエマルジョンは、皮膜強度、機械的安定性に加えて、耐溶剤性に優れている。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a (meth) acrylic resin-based emulsion in which a vinyl alcohol-based polymer is used as a dispersant and a (meth) acrylate-based monomer is emulsion (co) polymerized. More specifically, a method for producing a (meth) acrylic resin-based emulsion which is remarkably excellent in stability of emulsion (co) polymerization and operability of polymerization, and further excellent in film strength, solvent resistance and mechanical stability of the obtained emulsion. About.
[0002]
[Prior art]
Conventionally, emulsions obtained by emulsion polymerization of (meth) acrylate monomers have been widely used in fields such as paints, paper processing, and fiber processing. In the emulsion polymerization of these monomers, an anionic or nonionic surfactant is usually used as a stabilizer from the viewpoint of the stability of the emulsion polymerization. However, emulsions using surfactants as stabilizers have the disadvantage of poor mechanical stability, and cannot be used for applications requiring high mechanical stability, such as admixtures such as cement and mortar. There was a point.
For the purpose of solving the above problems, a method has been proposed in which polyvinyl alcohol (PVA) having a polymerization degree of 500 or less, preferably 300 or less is used as a protective colloid, or emulsion polymerization is carried out in the presence of PVA and a chain transfer agent (Patent Documents) 1, Patent Document 2), and attempts have been made to improve the mechanical stability of the emulsion. However, the use of such PVA has drawbacks in that the features of the PVA protective colloid are not sufficiently exhibited, mechanical stability cannot be completely satisfied, and the strength of the emulsion film is poor. It has been proposed to use a PVA-based polymer having a mercapto group as an emulsion dispersion stabilizer (Patent Document 3, Patent Document 4, Patent Document 5). In this case, a commonly used initiator such as potassium persulfate, ammonium persulfate, or a redox initiator using hydrogen peroxide alone or in combination with various reducing agents has a low grafting efficiency to the PVA-based polymer and is sufficiently practical. In addition, there is a problem that it is difficult to secure the overall stability, and with an initiator such as potassium bromate that generates a radical only by a redox reaction with a mercapto group of the PVA-based polymer, an improvement in polymerization stability is observed. However, when the mercapto group of the PVA-based polymer is consumed, there is a problem that it becomes so-called Dead-End, and it is difficult to control and complete the polymerization. A method for producing an emulsion by adding polyvinyl alcohol between the start of polymerization and the start of ripening is disclosed (Patent Document 6). In this method, an emulsifier is used when emulsion polymerization is started. There is a problem in that the emulsifier causes migration when used for various purposes due to the use of the, and adversely affects physical properties. A method of continuously or intermittently adding and polymerizing a monomer such as a (meth) acrylate-based monomer or a diene-based monomer and a water-soluble polymer protective colloid has been proposed (Patent Document 7). The mechanical stability and the like have been improved. However, this technique requires various substances such as various monomers, protective colloids, and polymerization initiators to be added to the polymerization system, which not only deteriorates the operability of the polymerization, but also results in a heterogeneous emulsion polymerization. However, there is a drawback that it is difficult to obtain an emulsion with good reproducibility due to various factors such as the shape of the stirring blade, the stirring speed, and the polymerization scale (capacity of the polymerization tank). A method of emulsifying and dispersing an acrylate monomer to a particle size of 0.5 μm or less in the presence of PVA and polymerizing the same has been proposed (Patent Document 8), and the polymerization stability and the like have been improved. However, in this method, a forced emulsification apparatus such as a homomixer is essential, and during polymerization, polymerization under severe conditions of suppressing the oxygen concentration of the aqueous phase to 0.3 ppm or less is required, and is generally used. It is difficult. Further, since it was necessary to use PVA having a low degree of saponification, there was a problem that the solvent resistance was poor.
As described above, various (meth) acrylate resin emulsions using a PVA-based polymer as a protective colloid have been proposed. However, the emulsion polymerization stability and the operability of the polymerization are completely satisfied. At present, the emulsion obtained has excellent physical properties such as film strength, solvent resistance and mechanical stability, and none of them can be used for general purposes.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 4-185606 (Claims)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 4-185607 (Claims)
[Patent Document 3]
JP-A-60-197229 (Claims)
[Patent Document 4]
JP-A-6-128443 (Claims)
[Patent Document 5]
JP-A-7-278212 (Claims)
[Patent Document 6]
JP-A-8-245706 (Claims)
[Patent Document 7]
JP-A-11-335490 (Claims)
[Patent Document 8]
Japanese Patent Application Laid-Open No. 2000-256424 (Claims)
[0004]
[Problems to be solved by the invention]
Under such circumstances, the present invention is remarkably excellent in stability of emulsion (co) polymerization, operability of polymerization, and also in film strength, solvent resistance and mechanical stability of the obtained emulsion. It is an object of the present invention to provide a method for producing an excellent (meth) acrylic resin emulsion.
[0005]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to develop a method for producing an aqueous emulsion having the above-mentioned preferable properties. As a result, a vinyl alcohol-based polymer having a functional group containing active hydrogen in the molecule was used as a dispersant, and When a redox-based polymerization initiator composed of an oxide and a reducing agent is used to emulsify (co) polymerize at least one monomer selected from an acrylate-based monomer and a methacrylate-based monomer, 1) charging an iron compound, (2) the monomer and (3) the vinyl alcohol-based polymer at the initial stage of polymerization, and adding the peroxide continuously or intermittently to perform emulsion (co) polymerization. The inventors have found that a method for producing a (meth) acrylic resin-based emulsion, which is a feature, satisfies the above object, and have completed the present invention.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The vinyl alcohol polymer having an active hydrogen-containing functional group in the molecule (sometimes abbreviated as active hydrogen group-containing PVA) used in the production method of the present invention is a functional group containing an active hydrogen in the molecule. There is no particular limitation as long as it is a vinyl alcohol-based polymer having the following. Among them, one or more functional groups selected from primary amino group, secondary amino group, acetoacetyl group, mercapto group and diacetone acrylamide group in the molecule A vinyl alcohol polymer having a group is preferably used. A vinyl alcohol polymer having at least one functional group selected from a primary amino group, a secondary amino group, an acetoacetyl group, a mercapto group, and a diacetone acrylamide group in the molecule is synthesized by a conventionally known method.
[0007]
For example, in the case of a vinyl alcohol polymer having a primary or secondary amino group,
(1) An ethylenically unsaturated monomer having a primary or secondary amino group such as acrylamide, methacrylamide, N-vinylformamide, N-vinylacetamide, or a primary or secondary amino group by hydrolysis or the like. After copolymerizing an ethylenically unsaturated monomer having a functional group that can be generated and vinyl esters such as vinyl acetate, a method of saponifying,
(2) An addition reaction of a mercaptan having an amino group with an epoxy group of a polymer composed of a monomer having an epoxy group such as allyl glycidyl ether and a vinyl ester such as vinyl acetate using NaOH or the like as a catalyst is followed by saponification. How to do
(3) a method in which a compound having a functional group capable of reacting with a hydroxyl group of a conventionally known polyvinyl alcohol in a molecule and having a primary or secondary amino group is reacted with a vinyl alcohol-based polymer;
(4) A method of polymerizing an ethylenically unsaturated monomer having a primary or secondary amino group in the presence of a vinyl alcohol-based polymer having a mercapto group (this method yields a polyvinyl alcohol-based block polymer) ,
And the like.
In the case of a vinyl alcohol polymer having an acetoacetyl group in the molecule, (5) it is usually obtained by a post-reaction after adding diketene to a conventionally known vinyl alcohol polymer.
A vinyl alcohol polymer having a mercapto group in the molecule is obtained by polymerizing a vinyl ester in the presence of thioacetic acid and then saponifying to obtain a vinyl alcohol polymer having a mercapto group in the molecule.
In the case of a vinyl alcohol polymer having a diacetone acrylamide group, (6) a vinyl alcohol polymer having a diacetone acrylamide group can be obtained by copolymerizing a vinyl ester and diacetone acrylamide and then saponifying the copolymer. .
The active hydrogen group content of the active hydrogen group-containing PVA is not particularly limited, but is usually 0.3 to 15 mol%, preferably 0.5 to 10 mol%, more preferably 0.7 to 7 mol%. When the content of the active hydrogen group is in this range, an emulsion having better solvent resistance can be obtained.
[0008]
The viscosity average degree of polymerization (hereinafter abbreviated as degree of polymerization) of the active hydrogen group-containing PVA may be selected according to various situations, and is not particularly limited, but is preferably from 100 to 8,000. More preferably, it is 200 to 2500, still more preferably 300 to 2000. When the degree of polymerization is in the above range, the operability and stability of emulsion polymerization are further improved. On the other hand, the degree of saponification is not particularly limited, but is usually 70 mol% or more, preferably 70 to 99 mol%, more preferably 75 to 99 mol%, still more preferably 80 to 98 mol%, and particularly preferably 80 to 98 mol%. 95 mol%, optimally 83-95 mol%. When the degree of saponification is less than 70 mol%, there is a concern that the water solubility, which is an intrinsic property of the vinyl alcohol-based polymer, is reduced.
[0009]
The active hydrogen group-containing PVA may be obtained by copolymerizing a copolymerizable ethylenically unsaturated monomer within a range not to impair the effects of the present invention. Such ethylenically unsaturated monomers include, for example, acrylic acid, methacrylic acid, fumaric acid, (anhydride) maleic acid, itaconic acid, acrylonitrile, methacrylonitrile, trimethyl- (3-acrylamido-3-dimethylpropyl) ) -Ammonium chloride, acrylamide-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate , Sodium allyl sulfonate and N-vinylpyrrolidone. In addition, in the presence of a thiol compound such as thiolacetic acid and mercaptopropionic acid, it is also possible to use a terminal modified product obtained by polymerizing a vinyl ester monomer such as vinyl acetate and saponifying the obtained polymer. it can.
Here, examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like. In general, vinyl acetate is preferably used.
[0010]
In the present invention, the amount of the active hydrogen group-containing PVA used for the dispersant is not particularly limited, but is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and more preferably 100 parts by weight of the monomer used. 2.5 to 10 parts by weight. If the amount of the active hydrogen group-containing PVA is less than 1 part by weight, the polymerization stability may be reduced. On the other hand, if it exceeds 20 parts by weight, the viscosity of the obtained emulsion becomes high, resulting in poor operability. Concerns arise.
[0011]
In the method for producing a (meth) acrylic resin-based emulsion of the present invention, the polymer constituting the dispersoid includes at least one monomer selected from an acrylate-based monomer and a methacrylate-based monomer ( (Co) polymerized. Examples of the monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate Acrylates such as dodecyl acrylate, octadecyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-methacrylate Methacrylates such as -butyl, 2-ethylhexyl methacrylate, dodecyl methacrylate and octadecyl methacrylate;
[0012]
Further, the polymer constituting the dispersoid may be a polymer obtained by copolymerizing another copolymerizable monomer within a range that does not impair the effects of the present invention. Examples of such a monomer include olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride, vinyl fluoride, vinylidene chloride and vinylidene fluoride; vinyl formate, vinyl acetate, vinyl propionate and vinyl pivalate. Vinyl ester monomers such as acrylic acid and methacrylic acid; polyfunctional monomers such as triallyl cyanurate, triallyl isocyanurate and diallyl phthalate; styrene and α-methylstyrene And styrene monomers such as p-methylstyrenesulfonic acid and its sodium or potassium salt; and diene monomers such as butadiene, isoprene and chloroprene. The use amount of these other monomers is preferably 30% by weight or less, more preferably 20% by weight or less based on all monomers.
[0013]
In the production method of the present invention, it is important to add the iron compound in the early stage of the polymerization, particularly to the entire amount thereof, since the operability of the emulsion polymerization is further improved. The iron compound is not particularly limited, but at least one iron compound selected from ferrous chloride, ferrous sulfate, ferric chloride, ferric nitrate and ferric sulfate is preferably used, and among them, Ferrous iron and ferrous sulfate are particularly preferably used.
[0014]
The amount of the iron compound to be used is not particularly limited, but is usually 1 ppm to 50 ppm, more preferably 5 ppm to 30 ppm, based on all monomers usually used. When the amount of the iron compound used is within this range, polymerization operability is good. It is preferable to use the entire amount of the iron compound in the initial stage of the polymerization.
[0015]
In the production method of the present invention, a redox polymerization initiator comprising a peroxide and a reducing agent is used. The peroxide is not particularly limited, but hydrogen peroxide, ammonium persulfate, potassium persulfate, t-butyl hydroperoxide and the like are used, and hydrogen peroxide is particularly preferably used. The peroxide needs to be added continuously or intermittently. By continuously or intermittently adding, polymerization operability is improved.
[0016]
When hydrogen peroxide is used as the peroxide, a 0.1 to 5% aqueous solution of hydrogen peroxide, preferably a 0.2 to 3% aqueous solution, and more preferably a 0.25 to 2% aqueous solution is used, so that Operability is improved. When the peroxide is used in an amount of 0.01 to 1% by weight based on 100 parts by weight of the monomer, the stability of polymerization is improved.
[0017]
When hydrogen peroxide is used as the peroxide, tartaric acid, L-ascorbic acid, Rongalit, or a metal salt thereof is preferably used as the reducing agent. When ammonium persulfate or potassium persulfate is used as the peroxide, sodium hydrogen sulfite, sodium hydrogen carbonate, or the like is preferably used as the reducing agent. The method of adding the reducing agent is not particularly limited, but a method of adding the entire amount at the beginning of the polymerization is preferable from the viewpoint of polymerization operability.
The amount of the reducing agent used is also not particularly limited, but is usually 0.05 to 3 equivalents, preferably 0.1 to 2 equivalents, more preferably 0.3 to 1.5 equivalents to peroxide.
[0018]
Of the above reducing agents, tartaric acid is preferably used, specifically tartaric acid and / or a metal salt thereof. Examples of tartaric acid include dextrorotatory L (+) tartaric acid, levorotatory D (-) tartaric acid, and DL tartaric acid, which is a racemic compound of these enantiomers. When used, the emulsion polymerization operability is remarkably good, and it is preferably used. It is also possible to use a metal salt of tartaric acid, and the type of metal is not particularly limited, but sodium tartrate is preferably used. Among them, sodium L (+) tartrate is preferably used. When sodium L (+) tartrate is used, the polymerization operability is optimal.
[0019]
In the production method of the present invention, it is important to charge the iron compound, the monomer, and the active hydrogen group-containing PVA in the early stage of the polymerization. In particular, it is preferable to charge all of these in the early stage of polymerization. By employing this method, not only the operability of the polymerization is improved, but also the stability of the emulsion polymerization is significantly improved. Here, the initial stage of polymerization refers to immediately before or immediately after the start of polymerization.
[0020]
In the production method of the present invention, the polymerization stability can be further improved by adding the chain transfer agent at the beginning of polymerization. The chain transfer agent is not particularly limited as long as it is a compound that causes a chain transfer during emulsion polymerization. For example, alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, acetone, Ketones such as methyl ethyl ketone, cyclohexanone and acetophenone, aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, furfural and benzaldehyde, 2-mercaptoethanol, 3-mercaptopropionic acid, n-dodecylmercaptan, t-dodecylmercaptan and lauryl Mercaptans such as mercaptan, n-butyl mercaptan, t-butyl mercaptan, 2-ethylhexyl thioglycolate, and octyl thioglycolate are exemplified. Of these, mercaptan-based chain transfer agents are preferred.
The amount of the chain transfer agent to be added is not particularly limited, but is 0.01 to 50 parts by weight, preferably 0.1 to 30 parts by weight, based on 100 parts by weight of all monomers.
[0021]
In the production method of the present invention, the solid content of the emulsion is not particularly limited, but is usually 20 to 70% by weight, preferably 30 to 65% by weight, and more preferably 40 to 60% by weight. If the solid content is less than 20% by weight, the emulsion may have poor storage stability and may be separated into two phases. If it exceeds 70% by weight, the stability during polymerization may be reduced.
[0022]
The emulsion obtained by the production method of the present invention was subjected to a test at 1000 rpm for 10 minutes under a load of 0.5 kg / cm ^{2 at} a room temperature of 20 ° C. using a Malon mechanical stability measuring apparatus, and then a 60 mesh (ASTM standard screen) ) When filtered through a stainless steel wire mesh, the filtration residue is preferably not more than 0.3% by weight, preferably not more than 0.2% by weight, more preferably not more than 0.1% by weight, based on the solid content of the emulsion. % By weight or less. When the filtration residue is in the above range, it can be said that the emulsion has good mechanical stability.
[0023]
The emulsion obtained by the above method can be used as it is, but if necessary, conventionally known various emulsions can be added and used as long as the effects of the present invention are not impaired. In addition, commonly used additives can be added to the emulsion obtained by the present invention. Examples of the additives include organic solvents (aromatics such as toluene and xylene, alcohols, ketones, esters, and halogen-containing solvents), plasticizers, suspending agents, thickeners, Examples include a property improving agent, a preservative, a rust preventive, an antifoaming agent, a filler, a wetting agent, and a coloring agent.
[0024]
The emulsion obtained by the production method of the present invention is excellent in film strength, mechanical stability, and also excellent in solvent resistance, so that it can be used for paints, admixtures of hydraulic substances, jointing materials, various adhesives, for impregnated paper, It is suitably used in fields such as binders for nonwoven products, paints, paper processing and fiber processing, and coating agents.
[0025]
【Example】
Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, “parts” and “%” mean on a weight basis unless otherwise specified.
Example 1
750 g of ion-exchanged water, PVA-1 (polymerization degree 500, saponification degree 88 mol%, mercapto group 1 (Containing 0.5 × 10 ⁻⁵ equivalents / g) and completely dissolved at 95 ° C. After cooling to 60 ° C., 266 g of methyl methacrylate and 266 g of butyl acrylate were charged and replaced with nitrogen while stirring at 120 rpm. Thereafter, 0.0058 g of ferrous chloride and 25 g of a 10% aqueous solution of sodium L (+) tartrate (TAS) were added. Next, 100 g of a 0.5% aqueous solution of hydrogen peroxide (HPO) was added over 3 hours to carry out emulsion polymerization. Five minutes after the start of the addition of hydrogen peroxide, heat generation was observed, confirming the start of emulsion polymerization. Thereafter, when the polymerization was promoted while maintaining the external temperature at 50 to 55 ° C, the polymerization temperature was changed to 58 to 62 ° C, and the polymerization proceeded with good operability. After completion of the addition of the aqueous hydrogen peroxide solution, the mixture was aged for 1 hour, and cooled after completing the polymerization reaction. As a result, an emulsion having a solid content of 39.8% was obtained.
The obtained emulsion was evaluated by the following method. Table 1 shows the results.
[0026]
(Evaluation of emulsion)
(1) Polymerization operability The transition of the polymerization temperature from the start of the polymerization was measured, and the degree of temperature rise due to the heat of polymerization was observed to determine whether the control of the polymerization was easy. The smaller the width of the polymerization transition temperature, the easier the polymerization control.
(2) Emulsion polymerization stability The obtained emulsion was filtered using a 60-mesh (ASTM standard sieve) stainless steel wire mesh. After filtration, the residue on the wire mesh was collected and weighed. Table 1 shows the residue amount per 1 kg of the solid content of the emulsion.
(3) Film Strength The obtained emulsion was cast on a polyethylene terephthalate (PET) film at room temperature of 20 ° C. and 65% RH, and dried for 7 days to obtain a dry film having a thickness of 500 μm. After the obtained dried film was conditioned for one week at 20 ° C. and 60% RH, the film tensile strength (tensile speed: 5 cm / min) was measured.
(4) Solvent Resistance of Film The obtained aqueous emulsion was cast on a PET film at 20 ° C. and 65% RH and dried for 7 days to obtain a dry film of 500 μm. The coating was punched out to a diameter of 2.5 cm, and the sample was immersed in acetone at 20 ° C. for 24 hours to determine the elution rate and liquid absorption of the coating.
Dissolution rate (%) = {1- (absolute dry weight of film after immersion) / (absolute dry weight of film before immersion)} × 100
Liquid absorption rate (%) = {(weight of film after immersion) / (dry weight of film before immersion)} x 100
-Absolute dry weight of the coating before immersion; weight of the coating before immersion (water content)-{weight of the coating before immersion (water content) x moisture content of the coating (%) / 100}
Film moisture content: The film (a sample different from the sample immersed in acetone at 20 ° C.) is completely dried at 105 ° C., and the moisture content of the film is determined in advance.
-Absolute dry weight of the film after immersion: The weight of the film after immersion absolutely dried at 105 ° C.
-Weight of the film after immersion: After lifting the film after immersion from acetone, the acetone on the film was wiped off with gauze, and then weighed.
[0027]
(5) Mechanical Stability The obtained aqueous emulsion was subjected to a test at 1000 rpm under a load of 0.5 kg / cm ² at room temperature of 20 ° C. for 10 minutes at a room temperature of 20 ° C. using a Malon-type mechanical stability measuring instrument. Filtration was performed using a mesh (ASTM-type standard sieve) stainless steel wire mesh, and the ratio (%) of the weight of the filtration residue to the weight of the solid content of the aqueous emulsion was measured. The smaller the ratio of the filtration residue weight, the better the mechanical stability.
In addition, the measurement of the solid content concentration and the filtration residue weight is as follows.
Solid content concentration measurement method About 3 g of the obtained emulsion was placed in an aluminum dish, precisely weighed, and dried in a dryer at 105 ° C for 24 hours to evaporate water. Thereafter, the weight of the dried product was measured, and the solid content concentration was calculated from the weight ratio.
Method for measuring filtration residue weight The filtration residue was dried with a dryer at 105 ° C for 24 hours to evaporate water, and the weight of the dried product was taken as the filtration residue weight.
[0028]
Comparative Example 1
750 g of ion-exchanged water and 40 g of PVA-1 were charged into a 2-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, a nitrogen inlet, and an squid-type stirring blade, and were completely dissolved at 95 ° C. Next, the atmosphere was adjusted to 60 ° C. while stirring at 120 rpm by purging with nitrogen, and then 0.0058 g of ferrous chloride and 25 g of a 10% aqueous solution of sodium L (+) tartrate were added. Thereafter, a mixture of 266 g of methyl methacrylate and 266 g of butyl acrylate is continuously added from the dropping funnel for 2 hours, and 100 g of 0.5% hydrogen peroxide aqueous solution is continuously added for 3 hours. did. While the polymerization was being carried out while maintaining the external temperature at 55 ° C., the test was stopped after 1 hour because the polymerization system gelled.
[0029]
Comparative Example 2
Except that ferrous chloride was not used in Example 1, the addition of an aqueous hydrogen peroxide solution was started in the same manner as in Example 1 except that ferrous chloride was not used. Exotherm and emulsion polymerization started 15 minutes after the start of hydrogen peroxide addition. The external temperature was adjusted to 50 ° C, and the addition of hydrogen peroxide was continued. The polymerization temperature reached 65 ° C. Interrupted. However, since the heat generation did not stop and the polymerization temperature reached 70 ° C., it was judged that the polymerization could not be controlled, and the test was stopped.
[0030]
Example 2
Emulsion polymerization was carried out in the same manner as in Example 1 except that 2.6 g of n-dodecyl mercaptan was further charged in the initial stage of polymerization. The evaluation of the obtained emulsion is also shown in Table 1.
[0031]
Comparative Example 3
Emulsion polymerization was attempted in the same manner as in Comparative Example 1, except that 2.6 g of n-dodecyl mercaptan was further charged in the initial stage of polymerization. However, the polymerization system gelled 1 hour and 30 minutes after the start of the polymerization, and the test was stopped.
[0032]
Comparative Example 4
Emulsion polymerization was attempted in the same manner as in Comparative Example 2 except that 2.6 g of n-dodecyl mercaptan was further charged in the initial stage of polymerization. However, as in Comparative Example 2, it was impossible to control heat generation, and the test was stopped.
[0033]
Comparative Example 5
Emulsion polymerization was carried out in the same manner as in Example 1 except that PVA-2 containing no mercapto group (polymerization degree: 500, saponification degree: 88 mol%) was used instead of PVA-1 in Example 1. The evaluation of the obtained emulsion is also shown in Table 1.
[0034]
Example 3
Polyvinyl alcohol PVA-3 obtained by copolymerizing N-vinylacetamide and vinyl acetate in place of PVA-1 in Example 2 and then saponifying (primary amino group 2 mol%, polymerization degree 500, saponification degree Emulsion polymerization was carried out in the same manner as in Example 2 except that 88 mol%) was used. The evaluation of the obtained emulsion is also shown in Table 1.
[0035]
Example 4
Polyvinyl alcohol PVA-4 (acetoacetyl group 5 mol%, polymerization degree 1000, saponification degree 88 mol%) obtained by reacting diketene with polyvinyl alcohol by a solid-gas reaction instead of PVA-1 in Example 2 was used. Emulsion polymerization was carried out in the same manner as in Example 2 except for using. The evaluation of the obtained emulsion is also shown in Table 1.
[0036]
Example 5
A polyvinyl alcohol PVA-5 obtained by copolymerizing vinyl acetate and diacetone acrylamide instead of PVA-1 in Example 2 and then saponifying (3 mol% of diacetone acrylamide group, polymerization degree 1000, saponification degree 88 mol) %), Except that emulsion polymerization was carried out in the same manner as in Example 2. The evaluation of the obtained emulsion is also shown in Table 1.
[0037]
Example 6
750 g of ion-exchanged water and 40 g of PVA-1 were charged into a 2-liter glass polymerization vessel equipped with a reflux condenser, a thermometer, a nitrogen inlet, and an squid-type stirring blade, and completely dissolved at 95 ° C. After cooling to 60 ° C., 266 g of methyl methacrylate and 266 g of butyl acrylate were charged and replaced with nitrogen while stirring at 120 rpm. Thereafter, 0.0058 g of ferrous chloride and 10 g of a 10% aqueous solution of sodium bisulfite (SHS) were added. Next, 50 g of a 0.5% aqueous solution of potassium persulfate (KPS) was added over 3 hours to carry out emulsion polymerization. Heat generation was observed 10 minutes after the start of the addition of potassium persulfate, and the start of emulsion polymerization was confirmed. Thereafter, when the polymerization was carried out while maintaining the external temperature at 50 to 55 ° C, the polymerization temperature changed from 56 to 65 ° C. After completion of the addition of the aqueous solution of potassium persulfate, the mixture was aged for 1 hour, and cooled after completing the polymerization reaction. As a result, an emulsion having a solid content of 39.7% was obtained. The evaluation of the obtained emulsion is also shown in Table 1.
[0038]
Example 7
750 g of ion-exchanged water and 40 g of PVA-1 were charged into a 2-liter glass polymerization vessel equipped with a reflux condenser, a thermometer, a nitrogen inlet, and an squid-type stirring blade, and completely dissolved at 95 ° C. After cooling to 60 ° C., 266 g of methyl methacrylate and 266 g of butyl acrylate were charged and replaced with nitrogen while stirring at 120 rpm. Thereafter, 0.0058 g of ferrous chloride and 25 g of a 10% aqueous solution of sodium L (+) tartrate were added. Next, 7 g of a 7% aqueous solution of hydrogen peroxide was added over 3 hours to carry out emulsion polymerization. 3 minutes after the start of the addition of hydrogen peroxide, heat generation was observed, confirming the start of emulsion polymerization. Thereafter, when the polymerization was carried out while maintaining the external temperature at 50 to 55 ° C, the polymerization temperature changed to 55 to 65 ° C. After completion of the addition of the aqueous hydrogen peroxide solution, the mixture was aged for 1 hour, and cooled after completing the polymerization reaction. As a result, an emulsion having a solid content of 39.8% was obtained. The evaluation of the obtained emulsion is also shown in Table 1.
[0039]
Example 8
750 g of ion-exchanged water and 40 g of PVA-1 were charged into a 2-liter glass polymerization vessel equipped with a reflux condenser, a thermometer, a nitrogen inlet, and an squid-type stirring blade, and completely dissolved at 95 ° C. After cooling to 60 ° C., 399 g of methyl methacrylate, 133 g of butyl acrylate, and 2.6 g of n-dodecyl mercaptan were charged, and nitrogen replacement was performed while stirring at 120 rpm. Thereafter, 0.0058 g of ferrous chloride and 25 g of a 10% aqueous solution of sodium L (+) tartrate were added. Next, 100 g of a 0.5% aqueous solution of hydrogen peroxide was added over 3 hours to carry out emulsion polymerization. Five minutes after the start of the addition of hydrogen peroxide, heat generation was observed, confirming the start of emulsion polymerization. Thereafter, when the polymerization was promoted while maintaining the external temperature at 50 to 55 ° C, the polymerization temperature was changed to 58 to 62 ° C, and the polymerization proceeded with good operability. After completion of the addition of the aqueous hydrogen peroxide solution, the mixture was aged for 1 hour, and cooled after completing the polymerization reaction. As a result, an emulsion having a solid content of 39.8% was obtained. The evaluation of the obtained emulsion is also shown in Table 1.
[0040]
Comparative Example 6
750 g of ion-exchanged water and 40 g of PVA-1 were charged into a 2-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, a nitrogen inlet, and an squid-type stirring blade, and were completely dissolved at 95 ° C. Next, the atmosphere was replaced with nitrogen and adjusted to 60 ° C. while stirring at 120 rpm. Then, 0.0058 g of ferrous chloride, 25 g of a 10% aqueous solution of sodium L (+) tartrate, and 2.6 g of n-dodecyl mercaptan were added. . Thereafter, a mixed solution of 399 g of methyl methacrylate and 133 g of butyl acrylate was continuously added from the dropping funnel over 2 hours, and 100 g of a 0.5% aqueous hydrogen peroxide solution was continuously added over 3 hours. After aging for 1 hour after the addition, the system was cooled, and the test was stopped because the system gelled.
[0041]
Example 9
750 g of ion-exchanged water and 40 g of PVA-1 were charged into a 2-liter glass polymerization vessel equipped with a reflux condenser, a thermometer, a nitrogen inlet, and an squid-type stirring blade, and completely dissolved at 95 ° C. After cooling to 60 ° C., 133 g of methyl methacrylate, 399 g of butyl acrylate, and 2.6 g of n-dodecyl mercaptan were charged, and nitrogen replacement was performed while stirring at 120 rpm. Thereafter, 0.0058 g of ferrous chloride and 25 g of a 10% aqueous solution of sodium L (+) tartrate were added. Next, 100 g of a 0.5% aqueous solution of hydrogen peroxide was added over 3 hours to carry out emulsion polymerization. Five minutes after the start of the addition of hydrogen peroxide, heat generation was observed, confirming the start of emulsion polymerization. Thereafter, when the polymerization was promoted while maintaining the external temperature at 50 to 55 ° C, the polymerization temperature was changed to 58 to 62 ° C, and the polymerization proceeded with good operability. After completion of the addition of the aqueous hydrogen peroxide solution, the mixture was aged for 1 hour, and cooled after completing the polymerization reaction. As a result, an emulsion having a solid content of 39.7% was obtained. The evaluation of the obtained emulsion is also shown in Table 1.
[0042]
Example 10
Emulsion polymerization was carried out in the same manner as in Example 2 except that a three-stage paddle-type stirring blade was used instead of the squid-type stirring blade, and an emulsion was obtained stably. The evaluation of the obtained emulsion is also shown in Table 1.
[0043]
Comparative Example 7 (Method described in JP-A-11-335490)
40 g of PVA-2 was added to 400 g of ion-exchanged water, heated to 95 ° C., the dissolved aqueous solution was cooled to 20 ° C., and a monomer mixture consisting of 266 g of methyl methacrylate and 266 g of butyl acrylate was mixed and stirred. Thus, a monomer emulsion was obtained. Separately, 350 g of ion-exchanged water and 10 g of ethanol were charged into a 2-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, a nitrogen inlet, and a three-stage paddle-type stirring blade, and the temperature was raised to 80 ° C. With the temperature raised and maintained at 80 ° C., an initiator solution in which 0.5 g of ammonium persulfate was dissolved in 10 g of ion-exchanged water was added. Two minutes later, the addition of the monomer emulsion to the polymerization vessel was started, and the addition was completed over 4 hours. After completion of the addition, stirring was further continued for 2 hours, aging was performed, and then cooling was performed to obtain an emulsion. The evaluation of the obtained emulsion is also shown in Table 1.
[0044]
Comparative Example 8 (Method described in JP-A-4-185606)
80 g of PVA-6 (polymerization degree: 100, saponification degree: 88 mol%) was replaced with 680 g of ion-exchanged water in a 2 liter polymerization vessel equipped with a thermometer, squid-type stirring blade, reflux condenser, nitrogen inlet, and dropping funnel. The mixture was heated to 95 ° C. and stirred to dissolve, then cooled to 70 ° C. and purged with nitrogen. In a separate container, 200 g of methyl methacrylate, 200 g of butyl acrylate, and 6 g of acrylic acid were mixed and replaced with nitrogen. 10 g of a 0.5% aqueous potassium persulfate solution and 40 g of the mixed monomer were added to the polymerization vessel to perform initial polymerization, and then the remaining mixed monomer was added dropwise over 3 hours. During that time, 15 g of a 0.5% aqueous potassium persulfate solution was simultaneously and continuously added. After completion of the dropwise addition, the mixture was further aged for 1 hour, cooled, and adjusted to pH 7.5 with 10% aqueous ammonia. The evaluation of the obtained emulsion is also shown in Table 1.
[0045]
[Table 1]

[0046]
【The invention's effect】
The method of the present invention is remarkably excellent not only in stability at the time of emulsion (co) polymerization, but also in operability of polymerization. The obtained emulsion has excellent solvent resistance in addition to film strength and mechanical stability. Are better.

Claims

Using a vinyl alcohol polymer having a functional group containing active hydrogen in the molecule as a dispersant, a redox polymerization initiator consisting of a peroxide and a reducing agent, and an acrylate monomer and a methacrylate ester When emulsifying (co) polymerizing at least one monomer selected from monomers, (1) an iron compound, (2) the monomer, and (3) the vinyl alcohol-based polymer are charged at an early stage of polymerization. A method for producing a (meth) acrylic resin emulsion, characterized in that the peroxide is continuously or intermittently added to the system and emulsion (co) polymerized.

The method for producing a (meth) acrylic resin-based emulsion according to claim 1, wherein a chain transfer agent is further charged at an early stage of polymerization.

The method for producing a (meth) acrylic resin emulsion according to claim 1 or 2, wherein the reducing agent is charged at an early stage of the polymerization.

The method for producing a (meth) acrylic resin-based emulsion according to any one of claims 1 to 3, wherein the peroxide is used in an amount of 0.01 to 1% by weight based on 100 parts by weight of the monomer. .

The method for producing a (meth) acrylic resin emulsion according to any one of claims 1 to 4, wherein the reducing agent is L (+) tartaric acid and / or sodium L (+) tartrate.

The method for producing a (meth) acrylic resin emulsion according to any one of claims 1 to 5, wherein an amount of the iron compound used is 1 ppm to 50 ppm based on all monomers.

The (meth) acrylic resin according to any one of claims 1 to 6, wherein the functional group containing active hydrogen is at least one functional group selected from an amino group, an acetoacetyl group, a mercapto group, and a diacetone acrylamide group. Production method of emulsion.