JP2004002758A - Resin for dispersing pigment and aqueous pigment dispersion containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin for dispersing a pigment useful for preparing an aqueous pigment dispersion having low viscosity even if the concentration of the pigment is high, excellent in color forming properties and forming a coating film having excellent finish appearance. <P>SOLUTION: The resin for dispersing the pigment comprises a copolymer which comprises (A) a polymerizable unsaturated monomer having a sulfonic acid group, (B) a nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain, (C) a (meth)acrylic ester type polymerizable monomer having two tertiary alkyl groups in one molecule thereof (C-1) and/or (meth)acrylic ester type polymerizable monomer having one tertiary alkyl group and one secondary hydroxyl group in one molecule thereof (C-2) and (D) other ethylenically unsaturated monomer. <P>COPYRIGHT: (C)2004,JPO

Description

【００４０】
式中、Ｘは水素又はメチル基である、
で示されるモノマー等が挙げられ、また、モノマー（Ｃ−２）の具体例としては、下記式（３）
【００４１】
【化４】

【００４２】
式中、Ｘは水素又はメチル基であり、Ｒ^１及びＲ^２はそれぞれ炭素数１〜６のアルキル基を表し、ただしＲ^１とＲ^２の合計炭素数は７である、
で示されるモノマー等が挙げられる。
【００４３】
以上に述べたモノマー（Ｃ−１）及び（Ｃ−２）はそれぞれ単独で使用することができ又は両者を併用してもよい。
【００４４】
その他のエチレン性不飽和モノマー（Ｄ）
その他のエチレン性不飽和モノマー（Ｄ）は、以上に述べたモノマー（Ａ）、モノマー（Ｂ）及びモノマー（Ｃ）と共重合可能なモノマーで、これらのモノマー（Ａ）、モノマー（Ｂ）及びモノマー（Ｃ）以外の重合性不飽和モノマーであって、顔料分散用樹脂に望まれる特性に応じて適宜選択して使用される。
【００４５】
そのようなモノマー（Ｄ）の具体例としては、例えば、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ｎ−プロピル（メタ）アクリレート、イソプロピル（メタ）アクリレート、ｎ−ブチル（メタ）アクリレート、イソブチル（メタ）アクリレート、ｔｅｒｔ−ブチル（メタ）アクリレート、２−エチルヘキシル（メタ）アクリレート、ｎ−オクチル（メタ）アクリレート、ラウリル（メタ）アクリレート、ステアリル（メタ）アクリレート、シクロヘキシル（メタ）アクリレート、イソボルニル（メタ）アクリレート、トリデシル（メタ）アクリレート等のＣ_１〜Ｃ_２４の直鎖状又は環状アルキル（メタ）アクリレートモノマー；２−ヒドロキシエチル（メタ）アクリレート、ヒドロキシプロピル（メタ）アクリレート、ヒドロキシブチル（メタ）アクリレートなどの水酸基含有重合性不飽和モノマー（典型的にはヒドロキシアルキル（メタ）アクリレートモノマー）；メタクリル酸、アクリル酸などのカルボキシル基含有重合性不飽和モノマー；アクリルアミド、メタクリルアミド；３−エチル−３−（メタ）アクリロイルオキシメチルオキセタン、３−メチル−３−（メタ）アクリロイルオキシメチルオキセタン、３−ブチル−３−（メタ）アクリロイルオキシメチルオキセタンなどのオキセタン環含有（メタ）アクリレート；２−（２′−ヒドロキシ−５′−メタクリロイルオキシエチルフェニル）−２Ｈ−ベンゾトリアゾールなどの紫外線吸収性重合性不飽和モノマー；４−（メタ）アクリロイルオキシ−１，２，２，６，６−ペンタメチルピペリジンなどの紫外線安定性重合性不飽和モノマー；スチレン、α−メチルスチレン、ビニルトルエンなどの芳香族ビニル化合物；（メタ）アクリロニトリル、酢酸ビニルなどを挙げることができる。これらの重合性不飽和モノマーは１種のみ又は２種以上を組合せて使用することができる。
【００４６】
本発明に従う顔料分散用樹脂は、例えば、着色水性ベースコート用塗料の作成に用いられる場合、硬化剤成分、例えばアミノ樹脂やブロック化されてもよいポリイソシアネート化合物と反応し、架橋塗膜中にとりこまれることが塗膜性能上望ましく、そのため、上記モノマー（Ｄ）は、その成分の少なくとも一部として水酸基含有重合性不飽和モノマーを含有することが望ましい。
【００４７】
上記水酸基含有重合性不飽和モノマーの具体例としては、上記の２−ヒドロキシエチル（メタ）アクリレート、ヒドロキシプロピル（メタ）アクリレート、２，３−ジヒドロキシブチル（メタ）アクリレート、４−ヒドロキシブチル（メタ）アクリレート、ポリエチレングリコールモノ（メタ）アクリレート等の、多価アルコールと（メタ）アクリル酸とのモノエステル化物；上記多価アルコールと（メタ）アクリル酸とのモノエステル化物にε−カプロラクトンを開環重合した化合物等を挙げることができる。なかでも、４−ヒドロキシブチル（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［前記モノマー（Ｂ）以外のもの］、及び多価アルコールと（メタ）アクリル酸とのモノエステル化物にε−カプロラクトンを開環重合した化合物が反応性などの点から好適である。例示した上記化合物はそれぞれ単独で又は２種以上を組み合わせて使用することができる。水酸基含有重合性不飽和モノマーは、一般に、得られる共重合体の水酸基価が１５〜７５ｍｇＫＯＨ／ｇ、好ましくは２５〜７０ｍｇＫＯＨ／ｇ、さらに好ましくは３５〜６０ｍｇＫＯＨ／ｇの範囲内となるような量で使用することが望ましい。
【００４８】
また、本発明の顔料分散用樹脂は主として水系に用いることを目的としており、該樹脂の水分散性を確保するため、親水性の前記（Ｂ）モノマーに加えて、さらに必要に応じて、上記のその他のエチレン性不飽和モノマー（Ｄ）の少なくとも一部としてカルボキシル基含有重合性不飽和モノマーを用いることができる。
【００４９】
本発明の顔料分散用樹脂は、以上に述べたスルホン酸基を含有する重合性不飽和モノマー（Ａ）、非イオン性重合性不飽和モノマー（Ｂ）、特定の分岐鎖を有するモノマー（Ｃ）及びその他のエチレン性不飽和モノマー（Ｄ）を共重合することによって得られる。共重合に際してのこれらのモノマー（Ａ）、（Ｂ）、（Ｃ）及び（Ｄ）の使用割合は厳密に制限されるものではなく、形成される共重合体に望まれる物性等に応じて変えることができるが、一般には、モノマー（Ａ）、（Ｂ）、（Ｃ）及び（Ｄ）の合計量を基準にして下記の範囲内とすることができる。
【００５０】
モノマー（Ａ）：０．１〜１０重量％、好ましくは０．５〜７重量％、さらに好ましくは１〜４重量％、
モノマー（Ｂ）：５〜５０重量％、好ましくは７．５〜４０重量％、さらに好ましくは１０〜３０重量％、
モノマー（Ｃ）：１〜３０重量％、好ましくは３〜２５重量％、さらに好ましくは５〜２０重量％、
モノマー（Ｄ）：１０〜９３．９重量％、好ましくは２８〜８９重量％、さらに好ましくは４６〜８４重量％。
【００５１】
上記モノマー（Ａ）、（Ｂ）、（Ｃ）及び（Ｄ）の共重合は、それ自体既知の方法、例えば、有機溶剤中での溶液重合法、水中でのエマルション重合法などの方法により行なうことができるが、なかでも溶液重合法が好適である。溶液重合法による共重合法としては、例えば、前記モノマー（Ａ）、（Ｂ）、（Ｃ）及び（Ｄ）とラジカル重合開始剤の混合物を、有機溶媒に溶解もしくは分散せしめ、通常、約８０℃〜約２００℃程度の温度で、１〜１０時間程度撹拌しながら加熱して重合させる方法を挙げることができる。
【００５２】
共重合時に使用し得る有機溶媒としては、例えば、ヘプタン、トルエン、キシレン、オクタン、ミネラルスピリット等の炭化水素系溶剤；酢酸エチル、酢酸ｎ−ブチル、酢酸イソブチル、エチレングリコールモノメチルエーテルアセテート、ジエチレングリコールモノブチルエーテルアセテート等のエステル系溶剤；メチルエチルケトン、メチルイソブチルケトン、ジイソブチルケトン、シクロヘキサノン等のケトン系溶剤；メタノール、エタノール、イソプロパノール、ｎ−ブタノール、ｓｅｃ−ブタノール、イソブタノール等のアルコール系溶剤；ｎ−ブチルエーテル、ジオキサン、エチレングリコールモノメチルエーテル、エチレングリコールモノブチルエーテル、プロピレングリコールモノメチルエーテル、プロピレングリコールモノプロピルエーテル、プロピレングリコールモノブチルエーテル、ジプロピレングリコールモノメチルエーテル、ジプロピレングリコールモノブチルエーテル、トリプロピレングリコールモノメチルエーテル等のエーテル系溶剤；コスモ石油社製のスワゾール３１０、スワゾール１０００、スワゾール１５００等の芳香族石油系溶剤等を挙げることができる。これらの有機溶剤は１種のみ又は２種以上を組合せて使用することができる。重合反応時において、上記有機溶剤は、モノマー成分の合計量１００重量部に対して、通常、４００重量部以下となる範囲で使用される。
【００５３】
前記ラジカル重合開始剤としては、例えば、シクロヘキサノンパーオキサイド、３，３，５−トリメチルシクロヘキサノンパーオキサイド、メチルシクロヘキサノンパーオキサイド等のケトンパーオキサイド類；１，１−ビス（ｔｅｒｔ−ブチルパーオキシ）−３，３，５−トリメチルシクロヘキサン、１，１−ビス（ｔｅｒｔ−ブチルパーオキシ）シクロヘキサン、ｎ−ブチル−４，４−ビス（ｔｅｒｔ−ブチルパーオキシ）バレレート等のパーオキシケタール類；クメンハイドロパーオキサイド、２，５−ジメチルヘキサン−２，５−ジハイドロパーオキサイド等のハイドロパーオキサイド類；１，３−ビス（ｔｅｒｔ−ブチルパーオキシ−ｍ−イソプロピル）ベンゼン、２，５−ジメチル−２，５−ジ（ｔｅｒｔ−ブチルパーオキシ）ヘキサン、ジイソプロピルベンゼンパーオキサイド、ｔｅｒｔ−ブチルクミルパーオキサイド等のジアルキルパーオキサイド類；デカノイルパーオキサイド、ラウロイルパーオキサイド、ベンゾイルパーオキサイド、２，４−ジクロロベンゾイルパーオキサイド等のジアシルパーオキサイド類；ビス（ｔｅｒｔ−ブチルシクロヘキシル）パーオキシジカーボネート等のパーオキシカーボネート類；ｔｅｒｔ−ブチルパーオキシベンゾエート、２，５−ジメチル−２，５−ジ（ベンゾイルパーオキシ）ヘキサン等のパーオキシエステル類等の有機過酸化物系重合開始剤；２，２´−アゾビスイソブチロニトリル、１，１−アゾビス（シクロヘキサン−１−カルボニトリル）、アゾクメン２，２’−アゾビスメチルバレロニトリル、４，４´−アゾビス（４−シアノ吉草酸）等のアゾ系重合開始剤を挙げることができる。これらのラジカル重合開始剤の使用量は、特に限定されるものではないが、通常、重合性モノマーの合計量１００重量部あたり、０．１〜１５重量部、特に０．３〜１０重量部の範囲内であることが望ましい。
【００５４】
上記重合反応において、モノマー成分や重合開始剤の添加方法は特に制約されるものではないが、重合開始剤は重合初期に一括仕込みするよりも重合初期から重合後期にわたって数回に分けて分割滴下することが、重合反応における温度制御、ゲル化物のような不良な架橋物の生成の抑制、などの点から好適である。
【００５５】
このようにして得られる共重合体の分子量は、特に制限されるものではないが、水分散安定性、顔料分散性、粘度、ＶＯＣ、樹脂の色数（着色度）などの面から、通常、重量平均分子量で５００〜１００，０００、特に１，０００〜７０，０００、さらに特に３，０００〜５０，０００の範囲内にあることが好ましい。
【００５６】
また、該共重合体は、一般に、１５〜７５ｍｇＫＯＨ／ｇ、好ましくは２５〜７０ｍｇＫＯＨ／ｇ、さらに好ましくは３５〜６０ｍｇＫＯＨ／ｇの範囲内の水酸基価を有することが好ましく、さらに一般に、３〜１００ｍｇＫＯＨ／ｇ、好ましくは５〜７０ｍｇＫＯＨ／ｇ、さらに好ましくは１０〜４０ｍｇＫＯＨ／ｇの範囲内の酸価を有することができる。
【００５７】
以上に述べた如くして製造される共重合体からなる本発明の顔料分散用樹脂は、水性顔料分散体の作製に用いられるので、顔料への濡れ性と分散安定化を両立できるものであることが必要である。本発明の顔料分散用樹脂を構成するモノマー（Ａ）成分は、顔料分散用樹脂の顔料への吸着を向上させることができ、特に酸化チタンなどの無機顔料への濡れ性の向上と樹脂の分散安定性の向上の両面で有利に働くことができる。また、本発明の顔料分散用樹脂を構成するモノマー（Ｂ）成分は、顔料分散用樹脂の連続相（水性媒体）への溶解性の向上に寄与し、特に顔料分散用樹脂の分散安定性の向上に有利に働くことができる。さらに、本発明の顔料分散用樹脂を構成するモノマー（Ｃ）成分は、顔料分散用樹脂を用いて得られる水性塗料による塗膜の光沢やつやなどの仕上り外観を著しく向上させるのに役立つ。
【００５８】
したがって、本発明の顔料分散用樹脂は、顔料、水性媒体などと共に水性顔料分散体を調製するのに極めて有用である。
【００５９】
水性顔料分散体
本発明の水性顔料分散体は、以上に述べた顔料分散用樹脂に、顔料、水性媒体、及び必要に応じて、その他の顔料分散樹脂、分散助剤、塩基性中和剤、その他の添加剤などを配合することにより調製することができる。
【００６０】
上記顔料としては、例えば、アルミニウム粉、銅粉、ニッケル粉、ステンレス粉、クロム粉、雲母状酸化鉄、酸価チタン被覆マイカ粉、酸化鉄被覆マイカ粉、光輝性グラファイト等の光輝性顔料；ピンクＥＢ、アゾ系やキナクリドン系等の有機赤系顔料、シアニンブルー、シアニングリーンなどの有機青系顔料、ベンゾイミダゾロン系、イソインドリン系及びキノフタロン系等の有機黄色系顔料；酸化チタン、チタンイエロー、ベンガラ、カーボンブラック、黄鉛、酸化鉄、及び各種焼成顔料等の無機着色顔料等が挙げられる。また、体質顔料を含んでもよい。これらの顔料は、それ自体既知の表面処理、例えば酸・塩基処理、カップリング剤処理、プラズマ処理、酸化／還元処理などが施されたものであってもよい。これらのうち、特に酸化チタンなどの無機顔料が好適である。
【００６１】
これらの顔料の配合割合は、特に制限されるものではないが、通常、顔料分散用樹脂１００重量部あたり、１０〜３，０００重量部、特に１５〜２，０００重量部、さらに特に１５〜１，５００重量部の範囲内にあることが、顔料分散性、分散安定性、得られる顔料分散体の着色力の面などから好ましい。
【００６２】
水性媒体としては、水、または水に水溶性有機溶媒などの有機溶媒を溶解してなる水−有機溶媒混合溶液などを挙げることができる。ここで用いる有機溶媒としては、例えばメチルアルコール、エチルアルコール、イソプロピルアルコール、プロピレングリコールモノプロピルエーテル、エチレングリコールモノブルエーテル、プロピレングリコールモノメチルエーテル、プロピレングリコールモノブチルエーテル、ジプロピレングリコールモノメチルエーテル、ジプロピレングリコールモノブチルエーテル、トリプロピレングリコールモノメチルエーテル、３−メチル３−メトキシブタノールなどの水溶性有機溶媒；キシレン、トルエン、シクロヘキサノン、ヘキサン、ペンタンなどの難溶性又は不溶性有機溶剤などが挙げられる。該有機溶剤は１種のみ又は２種以上混合して使用できる。有機溶剤としては水溶性有機溶媒を主体とするものが好適である。また、水と有機溶媒との混合割合は特に制限はないが、有機溶媒の含有量は混合溶液の５０重量％以下、特に３５重量％以下が望ましい。水性媒体の配合割合は、特に制限されるものではないが、通常、顔料分散用樹脂１００重量部あたり、５０〜５，０００重量部、特に１００〜３，０００重量部、さらに特に１００〜２，０００重量部の範囲内にあることが顔料分散時の粘度、顔料分散性、分散安定性及び生産効率などの面から好ましい。
【００６３】
必要に応じて用いられる他の顔料分散用樹脂としては、例えば、（メタ）アクリル酸などのカルボキシル基含有重合性不飽和モノマーと、２−ヒドロキシエチル（メタ）アクリレートなどの水酸基含有重合性不飽和モノマーと、その他の重合性不飽和モノマーとをラジカル重合開始剤の存在下に共重合して得られるアクリル樹脂などを挙げることができる。該アクリル樹脂としては、重量平均分子量が約２，０００〜１５０，０００、特に５，０００〜１００，０００、酸価が５〜１５０ｍｇＫＯＨ／ｇ、特に１５〜１００ｍｇＫＯＨ／ｇ、水酸基価が１０〜１６０ｍｇＫＯＨ／ｇ、特に３０〜１２０ｍｇＫＯＨ／ｇの範囲内にあるものが好ましい。
【００６４】
本発明の顔料分散用樹脂（Ｉ）と他の顔料分散用樹脂（ＩＩ）の使用割合（固形分）は、通常、樹脂（Ｉ）１００重量部あたり、樹脂（ＩＩ）５〜３００重量部、特に２０〜１５０重量部の範囲内が適当である。
【００６５】
塩基性中和剤は、顔料分散用樹脂がカルボキシル基を有する場合、これを中和し、顔料分散用樹脂を水溶化ないしは水分散化するために使用されるものであって、その具体例としては、例えば、水酸化アンモニウム、水酸化ナトリウム、水酸化カリウムなどの無機塩基；アミノメチルプロパノール、アミノエチルプロパノール、ジメチルエタノールアミン、トリエチルアミン、ジエチルエタノールアミン、ジメチルアミノプロパノール、アミノメチルプロパノールなどのアミン類を挙げることができる。これらの塩基性中和剤の配合量は、顔料分散用樹脂を水溶化ないしは水分散化するのに必要な量以上であり、通常、顔料分散用樹脂中のカルボキシル基の中和当量が０．３〜１．５、特に０．４〜１．３となるような割合であることが好適である。
【００６６】
必要に応じて用いられる分散助剤としては、例えば、ＢＹＫ−Ｃｈｅｍｉｅ社のＤｉｓｐｅｒｂｙｋ１８４やＤｉｓｐｅｒｂｙｋ１９０などを挙げることができ、また、その他の添加剤としては、消泡剤、防腐剤、防錆剤、可塑剤などを挙げることができる。これらの配合量は、顔料の分散性やペーストの安定性、レットダウン安定性や塗膜性能を考慮すると、いずれも顔料分散用樹脂１００重量部に対して５０部以下であることが望ましい。
【００６７】
水性顔料分散体は、以上に述べた各成分を、例えば、ペイントシェーカー、サンドミル、ボールミル、ＬＭＺミル、ＤＣＰパールミルなどの分散機を用いて均一に混合、分散させることにより調製することができる。
【００６８】
水性塗料組成物
上記の如くして調製される水性顔料分散体は、塗料用バインダ樹脂、及び必要に応じて、水性媒体、ポリマー微粒子、硬化触媒、塩基性中和剤、紫外線吸収剤、紫外線安定剤、塗面調整剤、酸化防止剤、流動性調整剤、シランカップリング剤等の添加剤等を配合し、水性媒体中に安定に分散せしめることによって水性塗料組成物とすることができる。
【００６９】
上記塗料用バインダ樹脂としては、水溶性ないしは水分散性塗料の分野で通常使用できる基体樹脂と硬化剤の組合せが包含され、基体樹脂としては、例えば、水酸基含有アクリル樹脂、水酸基含有ポリエステル樹脂、エポキシ基含有共重合体樹脂、カルボキシル基含有高酸価樹脂などが挙げられ、硬化剤としては、例えば、アミノ樹脂、ブロック化されていてもよいポリイソシアネート化合物などを挙げることができ、これらは１種のみ又は２種以上組合せて使用することができる。
【００７０】
上記水酸基含有アクリル樹脂としては、例えば、２−ヒドロキシエチル（メタ）アクリレートなどの水酸基含有重合性不飽和モノマーと、その他の重合性不飽和モノマーとをラジカル重合開始剤の存在下に共重合して得られる、重量平均分子量が約２，０００〜１００，０００程度、特に５，０００〜５０，０００の範囲内にあるものが好ましい。
【００７１】
上記水酸基含有ポリエステル樹脂としては、例えば、エチレングリコール、ブチレングリコール、１，６−ヘキサンジオール、トリメチロールプロパン、ペンタエリスリトールなどの多価アルコールと、アジピン酸、イソフタル酸、テレフタル酸、無水フタル酸、ヘキサヒドロ無水フタル酸、無水トリメリット酸などの多価カルボン酸成分との縮合反応によって得られる、重量平均分子量が約１，０００〜１００，０００、特に１，５００〜７０，０００の範囲内にあるものが好ましい。
【００７２】
硬化剤として用いられる上記アミノ樹脂としては、メラミン樹脂が一般的で、なかでもメチロール化メラミン樹脂やメチロール化メラミン樹脂のメチロール基の少なくとも一部を炭素数１〜４の１価アルコールでエーテル化してなるメラミン樹脂が好適であり、特に水溶性ないしは水分散性を有するものが適しているが水不溶性のものも使用できる。
【００７３】
上記メラミン樹脂の市販品としては、例えば、ユーバン２０ＳＥ−６０、ユーバン２２５（以上、いずれも三井化学社製、商品名）、スーパーベッカミンＧ８４０、スーパーベッカミンＧ８２１（以上、いずれも大日本インキ化学工業社製、商品名）などのブチルエーテル化メラミン樹脂；スミマールＭ−１００、スミマールＭ−４０Ｓ、スミマールＭ−５５（以上、いずれも住友化学社製、商品名）、サイメル３０３、サイメル３２５、サイメル３２７、サイメル３５０、サイメル３７０（以上、いずれも三井サイテック社製、商品名）、ニカラックＭＳ１７、ニカラックＭＳ１５（以上、いずれも三和ケミカル社製、商品名）、レジミン７４１（モンサント社製、商品名）等のメチルエーテル化メラミン樹脂；サイメル２３５、サイメル２０２、サイメル２３８、サイメル２５４、サイメル２７２、サイメル１１３０（以上、いずれも三井サイテック社製、商品名）、スマミールＭ６６Ｂ（住友化学社製、商品名）等のメチル化とイソブチル化との混合エーテル化メラミン樹脂；サイメルＸＶ８０５（三井サイテック社製、商品名）、ニカラックＭＳ９５（三和ケミカル社製、商品名）等のメチル化とｎ−ブチル化との混合エーテル化メラミン樹脂などを挙げることができる。
【００７４】
硬化剤として使用できる前記ブロック化されていてもよいポリイソシアネート化合物は、フリーのイソシアネート基を有するポリイソシアネート化合物及びイソシアネート基がブロック化されたポリイソシアネート化合物の両者を包含する。
【００７５】
フリーのイソシアネート基を有するポリイソシアネート化合物としては、例えば、ヘキサメチレンジイソシアネート、トリメチルヘキサメチレンジイソシアネートの如き脂肪族ジイソシアネート類；水素添加キシリレンジイソシアネート、イソホロンジイソシアネートの如き環状脂肪族ジイソシアネート類；トリレンジイソシアネート、４，４′−ジフェニルメタンジイソシアネートの如き芳香族ジイソシアネート類；トリフェニルメタン−４，４′，４″−トリイソシアネート、１，３，５−トリイソシアナトベンゼン、２，４，６−トリイソシアナトトルエン、４，４′−ジメチルジフェニルメタン−２，２′，５，５′−テトライソシアネートなどの３個以上のイソシアネ−ト基を有するポリイソシアネート化合物の如き有機ポリイソシアネートそれ自体、またはこれらの各有機ポリイソシアネートと多価アルコール、低分子量ポリエステル樹脂もしくは水等との付加物、あるいは上記した各有機ポリイソシアネート同志の環化重合体、更にはイソシアネート・ビウレット体等を挙げることができる。
【００７６】
フリーのイソシアネート基を有するポリイソシアネート化合物の市販品としては、例えば、バーノックＤ−７５０、バーノック−８００、バーノックＤＮ−９５０、バーノックＤＮ−９７０、バーノックＤＮ−１５−４５５（以上、いずれも大日本インキ化学工業社製）、デスモジュールＬ、デスモジュールＮ、デスモジュールＨＬ、デスモジュールＮ３３９０（以上、いずれも住友バイエルウレタン社製、商品名）、タケネートＤ−１０２、タケネート−２０２、タケネート−１１０、タケネート−１２３Ｎ（以上、いずれも武田薬品工業社製、商品名）、コロネートＥＨ、コロネートＬ、コロネートＨＬ、コロネート２０３（以上、いずれも日本ポリウレタン工業社製、商品名）、デュラネート２４Ａ−９０ＣＸ（旭化成工業社製、商品名）等が挙げられる。
【００７７】
イソシアネート基がブロックされたポリイソシアネート化合物としては、上記したフリーのイソシアネート基を有するポリイソシアネート化合物のイソシアネート基を、オキシム、フェノール、アルコール、ラクタム、マロン酸ジエステル、アセト酢酸エステル又はメルカプタン等の公知のブロック剤でブロックしたものが挙げられる。これらの代表的な市販品の例としては、バーノックＤ−５５０（大日本インキ化学工業社製、商品名）、タケネートＢ−８１５−Ｎ（武田薬品工業社製、商品名）、アディトールＶＸＬ−８０（ドイツ国、ヘキスト社製、商品名）、コロネート２５０７（日本ポリウレタン工業社製、商品名）、デスモデュールＮ３５００（住友バイエルウレタン社製、商品名）等が挙げられる。
【００７８】
前記必要に応じて使用される水性溶媒としては、前記顔料分散体を製造する際に必要に応じて使用される水性媒体として説明したものの中から適宜選んで用いることができる。
【００７９】
前記ポリマー微粒子は、本発明の塗料組成物中で溶解せず微粒子として分散するポリマーであり、通常、平均粒子径が０．０１〜１μｍ、特に０．０５〜０．８μｍの範囲内のものが好適である。該ポリマー微粒子は、粒子内部が架橋されていても又はされていなくてもよいが、内部架橋されたものが望ましい。該ポリマー微粒子としては、塗料分野において、塗料の流動性調整剤としてそれ自体既知のものを使用できる。
【００８０】
前記硬化触媒としては、硬化剤としてブロック化されていてもよいポリイソシアネート化合物を用いる場合には、ジブチル錫ジアセテート、ジブチル錫ジオクテート、ジブチル錫ジラウレートなどの有機金属触媒；トリエチルアミン、ジエタノールアミン等などのアミン類などを好適に使用することができ、硬化剤としてメラミン樹脂などのアミノ樹脂を用いる場合には、パラトルエンスルホン酸、ドデシルベンゼンスルホン酸、ジノニルナフタレンスルホン酸などのスルホン酸化合物やこれらのスルホン酸化合物のアミン中和物などを好適に使用することができる。
【００８１】
前記紫外線吸収剤としては、例えば、ベンゾフェノン系、ベンゾトリアゾール系、シアノアクリレート系、サリシレート系、蓚酸アニリド系などの化合物を挙げることができ、前記紫外線安定剤としては、ヒンダードアミン系化合物などを挙げることができる。
【００８２】
本発明の水性塗料組成物は、着色顔料、メタリック顔料、干渉色顔料などの各種顔料を配合した着色塗料組成物（メタリック塗料、干渉色塗料も包含する）として使用することができ、なかでも自動車塗装用上塗り塗料（着色ベースコート）として好適に使用することができる。
【００８３】
本発明の塗料組成物は、常法により各種の被塗物に塗装することができ、通常、約８０〜約１８０℃の温度で、１０〜６０分間程度焼付けることにより硬化塗膜を形成することができる。短時間焼付けする場合には、例えば、素材到達最高温度が約１８０℃〜約２５０℃となる条件で約２０秒〜６０秒間焼付けることによっても硬化塗膜を形成することができる。
【００８４】
本発明の塗料組成物を塗装することができる被塗物は、特に限定されるものではなく、例えば、鋼板、アルミニウム、錫などの金属基材；モルタル、セメント、プラスチックス、ガラスなどのその他基材；これらの基材に表面処理及び／又は塗膜形成を施したものなどを挙げることができるが、なかでも、金属基材、特に鋼板を基材としたものや、プラスチックスを基材としたものを好適に使用することができる。
【００８５】
上記鋼板としては、冷延鋼板、溶融亜鉛メッキ鋼板、電気亜鉛メッキ鋼板、アルミニウムメッキ鋼板、ステンレス鋼板、銅メッキ鋼板、錫メッキ鋼板、鉛−錫合金メッキ鋼板（ターンシート）；鉄−亜鉛、アルミニウム−亜鉛、ニッケル−亜鉛などの亜鉛合金メッキ鋼板などを挙げることができる。また、表面処理を施した鋼板としては、上記鋼板に燐酸塩処理やクロム酸塩処理などの化成処理を施した鋼板を挙げることができる。
【００８６】
また、塗膜形成を施した被塗物としては、基材に必要に応じて表面処理を施し、その上にプライマー塗膜を形成したもの、該プライマー塗膜の上に中塗り塗膜を形成したものなどを挙げることができる。
【００８７】
本発明の塗料組成物を自動車塗装用上塗り塗料として使用する場合、被塗物の代表例としては、化成処理した鋼板にプライマ−を電着塗装し、必要に応じて中塗り塗料を塗装したもの、各種プラスチック基材（必要に応じて、表面処理、プライマ−塗装、中塗り塗装等を行ったもの）、これらのものが組み合わさった複合部材等が挙げられる。
【００８８】
上記電着塗装のための塗料としては、アニオン型及びカチオン型のいずれでもよいが、防食性の良好なカチオン型が望ましい。カチオン電着塗料としてはそれ自体既知のものを用いることができ、例えば、樹脂成分として水酸基及びカチオン性基を有する基体樹脂とブロックポリイソシアネート化合物などの硬化剤を含むものなどを好適に使用することができる。
【００８９】
本発明の水性塗料組成物は、被塗物上への１コート１ベーク用の着色塗膜形成用組成物、被塗物上への２コート１ベーク（２Ｃ１Ｂ）、２コート２ベーク（２Ｃ２Ｂ）、３コート１ベーク（３Ｃ１Ｂ）、３コート２ベーク（３Ｃ２Ｂ）又は３コート３ベーク（３Ｃ３Ｂ）方式などにおける上塗着色ベース塗料組成物などとして好適に使用することができる。
【００９０】
本発明の塗料組成物を自動車の上塗着色塗料として使用する場合、例えば、電着塗膜などのプライマ塗膜上に、又はプライマ塗膜上に塗装された未硬化もしくは硬化された中塗塗膜上に、例えば、静電霧化塗装（ベル型等）、エアスプレー塗装等の手段により、乾燥膜厚が通常、約１０〜約６０μｍとなるように塗装し、数分間室温に放置するか、約５０〜約８０℃の範囲で数分間強制乾燥するか、約１２０〜約１８０℃程度の温度で通常、約１０〜約６０分間焼付けることによって上塗着色塗膜を形成することができる。また、上記のように塗装された未硬化又は硬化された上塗着色塗膜上に、上塗クリヤ塗料を例えば静電霧化塗装（ベル型等）、エアスプレー塗装等の手段により、乾燥膜厚が通常、約２０〜約１００μｍとなるように塗装し硬化させることによって上塗り複層塗膜を形成することもできる。
【００９１】
上記上塗着色塗膜上に塗装される上塗クリヤ塗料としては、架橋性官能基（例えば、水酸基、エポキシ基、カルボキシル基、アルコキシシラン基など）を有するアクリル樹脂、ビニル樹脂、ポリエステル樹脂、アルキド樹脂、ウレタン樹脂などの少なくとも１種の基体樹脂と、この基体樹脂を架橋硬化させるためのアルキルエーテル化したメラミン樹脂、尿素樹脂、グアナミン樹脂、ブロック化されてもよいポリイソシアネート化合物、エポキシ樹脂、カルボキシル基含有化合物などの少なくとも１種の架橋剤とからなる上塗クリヤ塗料が好適であり、基体樹脂と架橋剤との配合比率は、両者の合計に基づいて、通常、基体樹脂成分が５０〜９０重量％、架橋剤成分が１０〜５０重量％であることが望ましい。これらの上塗りクリヤ塗料組成物の形態としては、特に制限されるものではなく、有機溶剤型、非水分散液型、水溶液型、水分散液（スラリー）型、ハイソリッド型、粉体型など任意の形態のものを使用することができる。
【００９２】
【実施例】
以下、製造例、実施例及び比較例を挙げて本発明をさらに具体的に説明する。なお、特に断らない限り「部」及び「％」は、それぞれ「重量部」及び「重量％」を意味する。
【００９３】
顔料分散用樹脂の製造
実施例１
撹拌機、温度計及び還流冷却管を備えた通常のアクリル樹脂反応槽に、エチレングリコールモノブチルエーテル３８部及びイソブチルアルコール１２部を仕込み、加熱撹拌して９５℃に保持した。この中に、メチルメタクリレート４６部、ｎ−ブチルアクリレート１５部、２−ヒドロキシエチルアクリレート１０部、「ＮＦバイソマーＳ２０Ｗ」（第一工業製薬（株）製、商品名、メトキシポリエチレングリコールモノメタクリレートの５０％水希釈品、分子量約２０８０）４０部、２−アクリルアミド−２−メチルプロパンスルホン酸１．５部、「イソステアリルアクリレート」（大阪有機化学社製、商品名、モノマー（Ｃ−１）に該当）７．５部、アゾビスイソブチロニトリル１部及びイソブチルアルコール５部からなる混合物を３時間かけて滴下した。滴下終了後、９５℃で３０分間熟成し、次に、エチレングリコールモノブチルエーテル２０部及びアゾビスイソブチロニトリル０．５部からなる追加触媒混合液を１時間かけて滴下した。ついで９５℃で１時間熟成したのち冷却し、固形分５０％の顔料分散用樹脂（Ａ−１）溶液を得た。
【００９４】
実施例２〜５及び比較例１、２
上記実施例１において、後記表１に示す配合とする以外は実施例１と同様の操作を行い、本発明の顔料分散用樹脂溶液（Ａ−２）〜（Ａ−５）ならびに比較用の顔料分散用樹脂溶液（ＡＣ−１）及び（ＡＣ−２）を得た。これらの顔料分散用樹脂溶液の固形分及び顔料分散用樹脂の樹脂酸価を下記表１に示す。なお、下記表１における（注１）は、下記の意味を有する。また、表１において「ＮＦバイソマーＳ２０Ｗ」の量は固形分量で示す。
（注１）「アクリットＭ−２０１」：大成化工社製、商品名、モノマー（Ｃ−２）に該当する。
【００９５】
【表１】

【００９６】
水性顔料分散体の作製
実施例６〜１０及び比較例３、４
上記実施例１〜５及び比較例１、２で得た各顔料分散用樹脂溶液及び顔料と、さらに脱イオン水及び湿潤分散剤を用い、下記表２に示す組成配合にて、ディゾルバーにて３０分間分散して各水性顔料分散体（Ｂ−１）〜（Ｂ−５）ならびに（ＢＣ−１）及び（ＢＣ−２）を得た。なお、下記表２における（注２）〜（注４）は、それぞれ下記の意味を有する。
（注２）ＪＲ９０３：テイカ（株）社製、商品名、無機系チタン白顔料
（注３）ＳＮ−１２２ＮＳＫ：サンノプコ社製、商品名、消泡剤
（注４）ＢＹＫ−１８０：ビックケミー・ジャパン社製、商品名、湿潤分散剤
【００９７】
【表２】

【００９８】
塗料用基体樹脂の合成
合成例１
攪拌機、温度計、精留塔、窒素導入管、還流冷却器などを備えた反応槽に、イソフタル
酸３１７．８部、ヘキサヒドロフタル酸１９６．５部、アジピン酸３７２．６部、ネオペンチルグリコール２６８部、１，６−ヘキサンジオール２１７．８部、トリメチロールプロパン２６３．５部を仕込み、窒素ガス導入下で加熱攪拌して、１６０℃に達してから３時間かけて２３５℃まで昇温した。その後、同温度で１．５時間保持し、精留塔を還流冷却器に切り換え、トルエン１００部を導入し還流下にて反応を続けた。同温度で６時間反応させた後、減圧下トルエンを除去し、１７０℃まで冷却して無水トリメリット酸１２２．５部を添加した。そのまま１７０℃で３０分間保持した後、ブチルセロソルブ３２２部を添加してその後８０℃まで冷却した。次いでＮ，Ｎ−ジメチルアミノエタノール４部を加え、そのまま８０℃で３０分間保持した後、５０℃まで冷却し脱イオン水２２００部を加えて３０分間攪拌し、固形分濃度４５％のポリエステル樹脂溶液（Ｐ−１）を得た。
【００９９】
水性塗料組成物の製造
実施例１１
実施例６で得た水性顔料分散体（Ｂ−１）１３１．８部、合成例１で得たポリエステル樹脂溶液（Ｐ−１）１５３．５部、「ＭＳ−２５」（三和ケミカル（株）製、商品名、メチル・ｎ−ブチル混合エーテル化メラミン樹脂溶液）３７．５部及び「ＷＳ−３１４」（共栄社製、商品名、表面調整剤）０．８３部を加え、さらにジメチルエタノールアミン０．８部及び脱イオン水８８部を加えて、固形分約４４％、粘度３５〜４０秒（フォードカップ＃４／２０℃）、ｐＨ約８．５の着色水性塗料組成物を得た。
【０１００】
実施例１２〜１５及び比較例５、６
実施例１１において、配合組成を表３に示すとおりとする以外は実施例１１と同様に操作し、各着色水性塗料組成物を得た。
【０１０１】
これら各着色水性塗料組成物を用いて、下記試験塗板の作製方法に基づき各試験塗板を作製した。
【０１０２】
試験塗板の作製方法
リン酸亜鉛化成処理を施した厚さ０．８ｍｍの冷延ダル鋼板上に、エポキシ樹脂系カチオン電着塗料を乾燥膜厚が約２０μｍとなるように電着塗装し焼付けた電着塗膜上に、自動車用ポリエステル樹脂系中塗り塗料を乾燥膜厚が約２０μｍとなるように塗装し焼付けた。この塗装板を＃４００のサンドペーパーで水研、水切り乾燥し、石油ベンジンで脱脂した。ついでこの脱脂板上に、脱イオン水で粘度約２５秒（フォードカップ＃４／２０℃）に粘度調整した上記各着色水性塗料組成物を、エアスプレーを用い、乾燥膜厚が約３５μｍとなるように塗装し、室温で５分間放置後、電気熱風乾燥器にて１４０℃で３０分間焼付けて各試験塗板を作製した。
【０１０３】
これらの試験塗板について下記試験方法に基づいて種々の試験を行った。その試験結果を表３に併せて示す。
【０１０４】
試験方法
（＊１）光沢：「マイクロ−トリ−グロス光沢計」（ＪＩＳＺ８７４１）を用いて、各塗膜の６０度鏡面反射率を測定した。
（＊２）ＨＡＺＥ：「ＢＹＫマイクロヘイズメーター」（ＪＩＳＺ８７４１）を用いて、各塗膜のＨＡＺＥ値を測定した。数値が小さいほど良好であることを示す。
（＊３）塗膜外観：塗膜の仕上がり外観をツヤ感、肉持ち感から総合的に調査し次の基準で評価した（○：良好、△：不良、×：著しく不良）。
（＊４）耐候性：各試験塗板を、「スーパーキセノンウエザーメーター」（スガ試験機社製、耐候試験機）を用いて、ＪＩＳＫ５６００７−７に準じ促進耐候試験を行った。試験開始から１５００時間経過後の６０度光沢の保持率を調べた。数値が大きいほど耐候性が良好なことを示す。
【０１０５】
【表３】

【０１０６】
【発明の効果】
以上述べたとおり、本発明の顔料分散用樹脂を使用することによって、高顔料濃度においても濡れ性と分散安定性に優れ、低粘度で且つ発色性に優れた水性顔料分散体を得ることができる。また、この水性顔料分散体を使用することによって、顔料の発色性、塗膜の仕上がり外観ならびに耐候性、その他の物理的性質等の塗膜性能に優れ、しかも、顔料の分散安定性が良好で高顔料濃度化が可能な塗料組成物を得ることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pigment-dispersing resin suitable for a water-based coating, and particularly to an aqueous pigment dispersion containing the pigment-dispersing resin, which is suitably used for a water-based topcoat for automotive coating.
[0002]
[Prior art]
Heretofore, as a top coat for automotive coating, an amino resin, a poly (optionally blocked) resin may be added to a base resin (base polymer) component such as an acrylic resin, a polyester resin, and an alkyd resin having a functional group such as a hydroxyl group or a carboxyl group. Solvent-type compounds using a curing agent such as an isocyanate compound or an epoxy compound in combination have been widely used.
[0003]
In recent years, from the viewpoint of protection of the global environment, paints having a low volatile organic matter content (VOC) have been required. In the field of paints for automotive coatings, in particular, paints for colored base coats have a high emission VOC, so there is a strong demand for water-based coatings, and it is expected that the switch from solvent-based base coats to water-based base coats will proceed in the future.
[0004]
Problems associated with making the colored base coat paint water-based include, for example, (1) that the pigment dispersion resin blended in the water-based paint is not compatible with the binder component in the water-based paint; (2) the pigment dispersion resin And the dispersing agent does not uniformly disperse the pigment, causing the pigment to aggregate (flocculation or agglomeration). (3) The resin for dispersing the pigment or the dispersing agent in the water-based paint is not cured by baking and is coated. And performance degradation.
[0005]
Pigments used in colored basecoat paints generally have a hydrophobic surface and are hardly wetted by water, and pigment dispersing resins conventionally used in solvent-type colored paints have low solubility in water and have low solubility in aqueous media. Poor dispersion stability. Therefore, when designing the pigment dispersing resin in the water-based paint, it is important to achieve both the wettability of the pigment and the dispersion stability of the pigment dispersing resin in the aqueous medium.
[0006]
Regarding the wettability of the pigment, it is advantageous that the pigment dispersing resin has a low viscosity and a low molecular weight. For the dispersion stabilization, the formation of the steric repulsion layer on the pigment surface and the continuous phase ( It is said that it is advantageous to have good solubility in aqueous media). In addition, the interaction between the hydrophobic part of the pigment surface and the hydrophobic part of the pigment dispersing resin causes the wetting of the pigment dispersing resin on the pigment surface (the pigment dispersing resin has a group that causes weak aggregation in an aqueous system such as an alkyl group). It is considered that both the wettability of the pigment and the dispersion stability of the pigment dispersing resin are involved in the adsorption to the pigment.
[0007]
From the above viewpoints, pigment dispersing resins and auxiliaries for water-based paints or water-based inks have been developed. For example, in Patent Document 1, as a pigment dispersing resin, a monomer mixture containing a polymerizable unsaturated monomer having an acidic functional group such as (meth) acrylic acid as a part of a monomer component is polymerized. Although it has been proposed to use a linear anionic polymer having an acidic functional group, the polymer has high solubility in an aqueous medium, and is not suitable for stabilizing the dispersion of a pigment dispersion. In addition to being sufficient, there is a problem that the dispersion formed by using the dispersion has a remarkably high viscosity and is difficult to handle.
[0008]
Patent Documents 2, 3, and 4 disclose, as a pigment dispersing resin, a graft copolymer obtained by copolymerizing a carboxyl group-containing macromonomer. The graft copolymer is excellent in stabilizing the dispersion of the pigment because the trunk portion of the polymer is hydrophobic and the branch portion is hydrophilic, but is formed using the graft copolymer. Since the pigment dispersion has a high viscosity and a pigment dispersion having an increasingly higher pigment concentration is required from the viewpoints of cost and VOC reduction in the future, the above graft copolymer is also not satisfactory.
[0009]
Further, Patent Document 5, Patent Document 6, and Patent Document 7 disclose that a nonionic surfactant having a polyoxyalkylene chain is used as a pigment dispersant, but the surfactant is an aqueous pigment. Although it can be stably present in the dispersion, its adsorbability to the pigment is insufficient, particularly the letdown stability is poor, and the finished appearance of the coating film tends to be poor.
[0010]
In addition, at present, topcoat paints for automotive coatings not only have high durability, acid resistance, car wash abrasion resistance, chipping resistance, etc., but also more sharpness, transparency and color development than ever before. The finished appearance of the coating film such as properties is required.
[0011]
In order to meet these demands, the present inventors have first made a copolymerizable component containing a polymerizable unsaturated monomer containing an ionic functional group and a nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain. A pigment dispersing resin that is a polymer has been proposed (Patent Document 8, Patent Document 9, etc.). By using these pigment dispersing resins, it is possible to obtain an aqueous pigment dispersion having a low viscosity, excellent coloring properties, and excellent finished appearance of a coating film even at a high pigment concentration. However, in the case of dispersing an inorganic pigment such as titanium oxide, even when the above-mentioned pigment dispersing resin is used, problems may occur in the finish properties, weather resistance, and the like of the obtained coating film.
[0012]
[Patent Document 1] Japanese Patent Application Laid-Open No. 50-154328
[0013]
[Patent Document 2] Japanese Patent Application Laid-Open No. 1-182304
[0014]
[Patent Document 3] JP-A-7-316240
[0015]
[Patent Document 4] Japanese Patent Publication No. 10-502097
[0016]
[Patent Document 5] JP-A-9-255728
[0017]
[Patent Document 6] JP-A-9-267034
[0018]
[Patent Document 7] Japanese Patent Publication No. 8-19201
[0019]
[Patent Document 8] WO02 / 31010 pamphlet
[0020]
[Patent Document 9] JP-A-2003-12744
[0021]
[Problems to be solved by the invention]
An object of the present invention is to provide an aqueous pigment dispersion having excellent wettability and dispersion stability, low viscosity and excellent color development even at a high pigment concentration, and capable of obtaining an aqueous pigment dispersion having a good finished appearance of a coating film. It is to provide a resin.
[0022]
Another object of the present invention is to provide an aqueous pigment dispersion which is particularly suitable for dispersing an inorganic pigment such as titanium oxide and has a low viscosity and excellent coloring properties.
[0023]
Still another object of the present invention is to provide a water-based paint which has excellent curability and can form a coating film having excellent finish appearance such as coloring property and gloss.
[0024]
Other objects and features of the present invention will become apparent from the following description.
[0025]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, this time, a monomer having a sulfonic acid group, a nonionic hydrophilic monomer having a polyoxyethylene chain, etc., a monomer having a specific branched chain And found that a copolymer obtained by copolymerizing other ethylenically unsaturated monomers in the presence of a radical polymerization initiator was extremely suitable as a resin for dispersing a pigment in an aqueous coating material, and completed the present invention. Was.
[0026]
Thus, the present invention provides
(A) a polymerizable unsaturated monomer containing a sulfonic acid group,
(B) a nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain,
(C) (C-1) (meth) acrylate polymerizable monomer having two tertiary alkyl groups in one molecule and / or (C-2) tertiary alkyl group and secondary hydroxyl group in one molecule A (meth) acrylate-based polymerizable monomer having one each, and
(D) Other ethylenically unsaturated monomers
And a pigment dispersing resin characterized by being a copolymer of the above.
[0027]
The present invention also provides an aqueous pigment dispersion containing the pigment dispersing resin, the pigment, the aqueous medium, and, if necessary, a basic neutralizer and / or a dispersing aid.
[0028]
The present invention further provides an aqueous coating composition containing the above aqueous pigment dispersion.
[0029]
Hereinafter, the present invention will be described in more detail.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Pigment dispersion resin
The pigment dispersing resin provided by the present invention includes a polymerizable unsaturated monomer containing a sulfonic acid group (A) described below, a nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain (B), It is a copolymer of a monomer (C) having a branched chain and another ethylenically unsaturated monomer (D).
[0031]
Polymerizable unsaturated monomer containing sulfonic acid group (A)
The monomer (A) is a monomer component for introducing a sulfonic acid group as an ionic functional group into the pigment dispersing resin. Specifically, for example, (A) such as 2-acrylamido-2-methylpropanesulfonic acid (Meth) acrylamide-alkanesulfonic acid; and sulfoalkyl (meth) acrylates such as 2-sulfoethyl (meth) acrylate. These can be used alone or in combination of two or more. Among these, 2-acrylamido-2-methylpropanesulfonic acid is particularly preferred. The sulfonic acid group introduced into the resin by these monomers (A) particularly effectively acts on the pigment dispersion of the inorganic pigment.
[0032]
In the present specification, “(meth) acrylate” means acrylate or methacrylate.
[0033]
Nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain (B)
The monomer (B) is a monomer component that imparts hydrophilicity to the formed copolymer, and is a monomer having a polyoxyalkylene chain and a polymerizable unsaturated group in one molecule. Examples of the polyoxyalkylene chain include a polyoxyethylene chain, a polyoxypropylene chain, and a block chain of polyoxyethylene and polyoxypropylene.
[0034]
Suitably, the polyoxyalkylene chain has a molecular weight in the range of 200 to 3,000, preferably 300 to 2,500.
[0035]
As a typical example of the monomer (B), for example, the following formula (1)
CH₂= C (R³) COO (C_nH_2nO)_m-R⁴(1)
Where R³Represents a hydrogen atom or a methyl group;⁴Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m is an integer of 4 to 60, preferably 6 to 50;
n is 2 or 3, preferably 2, where m oxyalkylene units (C_nH_2nO) may be the same or different from each other,
The compound shown by these can be mentioned.
[0036]
Specific examples of such a monomer (B) include, for example, tetraethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate, ethoxytetraethylene glycol (meth) acrylate, and n-butoxytetraethylene glycol (meth) Acrylate, tetrapropylene glycol (meth) acrylate, methoxytetrapropylene glycol (meth) acrylate, ethoxytetrapropylene glycol (meth) acrylate, n-butoxytetrapropylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) ) Acrylate, methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) Rate and the like, which may be used alone or in combination. Among them, polyethylene glycol (meth) acrylate and polypropylene glycol (meth) acrylate are particularly preferable.
[0037]
Monomer (C) having a specific branched chain
The monomer (C) is a monomer component for introducing a tertiary alkyl group such as a tert-butyl group into the copolymer of the present invention, and has two tertiary alkyl groups in one molecule in the present invention. (Meth) acrylate polymerizable monomer (C-1) and / or (meth) acrylate polymerizable monomer (C-2) having one tertiary alkyl group and one secondary hydroxyl group in each molecule Use
[0038]
Specific examples of the monomer (C-1) include the following formula (2)
[0039]
Embedded image

[0040]
Wherein X is hydrogen or a methyl group;
And specific examples of the monomer (C-2) include the following formula (3)
[0041]
Embedded image

[0042]
Wherein X is hydrogen or a methyl group;¹And R²Represents an alkyl group having 1 to 6 carbon atoms, provided that R¹And R²Has a total carbon number of 7,
And the like.
[0043]
The monomers (C-1) and (C-2) described above can be used alone or in combination.
[0044]
Other ethylenically unsaturated monomers (D)
The other ethylenically unsaturated monomers (D) are monomers copolymerizable with the above-mentioned monomers (A), (B) and (C), and these monomers (A), (B) and A polymerizable unsaturated monomer other than the monomer (C), which is appropriately selected and used according to the properties desired for the pigment dispersing resin.
[0045]
Specific examples of such a monomer (D) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (Meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) C) such as acrylate and tridecyl (meth) acrylate₁~ C₂₄Linear or cyclic alkyl (meth) acrylate monomers; hydroxyl-containing polymerizable unsaturated monomers such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate (typically hydroxy Alkyl (meth) acrylate monomers); carboxyl group-containing polymerizable unsaturated monomers such as methacrylic acid and acrylic acid; acrylamide, methacrylamide; 3-ethyl-3- (meth) acryloyloxymethyloxetane, 3-methyl-3- ( Oxetane ring-containing (meth) acrylates such as (meth) acryloyloxymethyloxetane and 3-butyl-3- (meth) acryloyloxymethyloxetane; 2- (2'-hydroxy-5'-methacryloyloxyethylphenyl) -2 UV-absorbing polymerizable unsaturated monomers such as benzotriazole; UV-stable polymerizable unsaturated monomers such as 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine; styrene, α- Aromatic vinyl compounds such as methylstyrene and vinyltoluene; (meth) acrylonitrile, vinyl acetate and the like. These polymerizable unsaturated monomers can be used alone or in combination of two or more.
[0046]
The pigment dispersing resin according to the present invention reacts with a curing agent component, for example, an amino resin or a polyisocyanate compound which may be blocked, and is incorporated into a crosslinked coating film, for example, when used for preparing a colored aqueous base coat paint. It is desirable from the viewpoint of coating film performance that the monomer (D) desirably contains a hydroxyl group-containing polymerizable unsaturated monomer as at least a part of its components.
[0047]
Specific examples of the hydroxyl group-containing polymerizable unsaturated monomer include the above-mentioned 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) Monoester of polyhydric alcohol and (meth) acrylic acid such as acrylate and polyethylene glycol mono (meth) acrylate; ring-opening polymerization of ε-caprolactone to monoester of polyhydric alcohol and (meth) acrylic acid And the like. Among them, ε-caprolactone is used for 4-hydroxybutyl (meth) acrylate, polyethylene glycol mono (meth) acrylate [other than the monomer (B)], and a monoester of a polyhydric alcohol and (meth) acrylic acid. A compound obtained by ring-opening polymerization is preferred in terms of reactivity and the like. The above-mentioned compounds can be used alone or in combination of two or more. The amount of the hydroxyl group-containing polymerizable unsaturated monomer is generally such that the resulting copolymer has a hydroxyl value of 15 to 75 mgKOH / g, preferably 25 to 70 mgKOH / g, and more preferably 35 to 60 mgKOH / g. It is desirable to use it.
[0048]
Further, the pigment dispersing resin of the present invention is intended to be mainly used in an aqueous system. In order to ensure the water dispersibility of the resin, in addition to the hydrophilic monomer (B), if necessary, A carboxyl group-containing polymerizable unsaturated monomer can be used as at least a part of the other ethylenically unsaturated monomer (D).
[0049]
The pigment dispersing resin of the present invention comprises the above-mentioned polymerizable unsaturated monomer containing a sulfonic acid group (A), a nonionic polymerizable unsaturated monomer (B), and a monomer having a specific branched chain (C). And other ethylenically unsaturated monomers (D). The proportions of these monomers (A), (B), (C) and (D) used in the copolymerization are not strictly limited, and vary depending on the physical properties desired for the copolymer to be formed. However, in general, it can be within the following range based on the total amount of the monomers (A), (B), (C) and (D).
[0050]
Monomer (A): 0.1 to 10% by weight, preferably 0.5 to 7% by weight, more preferably 1 to 4% by weight,
Monomer (B): 5 to 50% by weight, preferably 7.5 to 40% by weight, more preferably 10 to 30% by weight,
Monomer (C): 1 to 30% by weight, preferably 3 to 25% by weight, more preferably 5 to 20% by weight,
Monomer (D): 10 to 93.9% by weight, preferably 28 to 89% by weight, more preferably 46 to 84% by weight.
[0051]
The copolymerization of the monomers (A), (B), (C) and (D) is carried out by a method known per se, for example, a method such as a solution polymerization method in an organic solvent and an emulsion polymerization method in water. Among them, a solution polymerization method is preferable. As a copolymerization method by a solution polymerization method, for example, a mixture of the above-mentioned monomers (A), (B), (C) and (D) and a radical polymerization initiator is dissolved or dispersed in an organic solvent. A method in which polymerization is performed by heating at a temperature of about 200C to about 200C with stirring for about 1 to 10 hours.
[0052]
Examples of the organic solvent that can be used in the copolymerization include hydrocarbon solvents such as heptane, toluene, xylene, octane, and mineral spirit; ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, and diethylene glycol monobutyl ether. Ester solvents such as acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and cyclohexanone; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, sec-butanol and isobutanol; n-butyl ether and dioxane , Ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol Ether solvents such as propyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monomethyl ether; aromatic petroleum solvents such as Swazole 310, Swazole 1000, and Swazole 1500 manufactured by Cosmo Oil; Solvents and the like can be mentioned. These organic solvents can be used alone or in combination of two or more. At the time of the polymerization reaction, the organic solvent is used in an amount of usually 400 parts by weight or less based on 100 parts by weight of the total amount of the monomer components.
[0053]
Examples of the radical polymerization initiator include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; 1,1-bis (tert-butylperoxy) -3 Peroxy ketals such as 1,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate; cumene hydroperoxide Hydroperoxides such as 2,5-dimethylhexane-2,5-dihydroperoxide; 1,3-bis (tert-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5 -Di (tert-butylperoxy) Dialkyl peroxides such as xane, diisopropylbenzene peroxide and tert-butylcumyl peroxide; diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide and 2,4-dichlorobenzoyl peroxide; bis ( peroxycarbonates such as tert-butylcyclohexyl) peroxydicarbonate; organic peroxides such as peroxyesters such as tert-butylperoxybenzoate and 2,5-dimethyl-2,5-di (benzoylperoxy) hexane. Oxide polymerization initiator: 2,2′-azobisisobutyronitrile, 1,1-azobis (cyclohexane-1-carbonitrile), azocumene 2,2′-azobismethylvaleronitrile, 4,4′- Azo Scan (4-cyanovaleric acid) azo-based polymerization initiators, and the like. The use amount of these radical polymerization initiators is not particularly limited, but is usually 0.1 to 15 parts by weight, particularly 0.3 to 10 parts by weight per 100 parts by weight of the total amount of the polymerizable monomers. It is desirable to be within the range.
[0054]
In the above-mentioned polymerization reaction, the method of adding the monomer component and the polymerization initiator is not particularly limited, but the polymerization initiator is divided and dropped several times from the initial stage of the polymerization to the latter stage of the polymerization, rather than batch charging in the early stage of the polymerization. This is preferable from the viewpoint of controlling the temperature in the polymerization reaction, suppressing the formation of a poor crosslinked product such as a gelled product, and the like.
[0055]
The molecular weight of the copolymer obtained in this manner is not particularly limited, but is usually selected from the viewpoints of water dispersion stability, pigment dispersibility, viscosity, VOC, and the number of colors (degree of coloring) of the resin. It is preferable that the weight average molecular weight is in the range of 500 to 100,000, particularly 1,000 to 70,000, and more particularly 3,000 to 50,000.
[0056]
In addition, the copolymer generally has a hydroxyl value in the range of 15 to 75 mg KOH / g, preferably 25 to 70 mg KOH / g, more preferably 35 to 60 mg KOH / g, and more generally 3 to 100 mg KOH / g. / G, preferably 5 to 70 mg KOH / g, more preferably 10 to 40 mg KOH / g.
[0057]
Since the pigment dispersing resin of the present invention comprising the copolymer produced as described above is used for producing an aqueous pigment dispersion, it is possible to achieve both wettability to the pigment and dispersion stabilization. It is necessary. The monomer (A) component constituting the pigment dispersing resin of the present invention can improve the adsorption of the pigment dispersing resin to the pigment, and particularly improves the wettability to an inorganic pigment such as titanium oxide and disperses the resin. It can work advantageously in both aspects of improving stability. Further, the monomer (B) component constituting the pigment dispersing resin of the present invention contributes to the improvement of the solubility of the pigment dispersing resin in the continuous phase (aqueous medium), and particularly, the dispersion stability of the pigment dispersing resin. It can work advantageously for improvement. Further, the monomer (C) component constituting the pigment dispersing resin of the present invention is useful for remarkably improving a finished appearance such as gloss and gloss of a coating film formed by using an aqueous paint obtained using the pigment dispersing resin.
[0058]
Therefore, the pigment dispersion resin of the present invention is extremely useful for preparing an aqueous pigment dispersion together with a pigment, an aqueous medium and the like.
[0059]
Aqueous pigment dispersion
The aqueous pigment dispersion of the present invention comprises the pigment dispersion resin described above, a pigment, an aqueous medium, and, if necessary, other pigment dispersion resins, a dispersing aid, a basic neutralizing agent, and other additives. It can be prepared by blending the above.
[0060]
Examples of the pigment include glittering pigments such as aluminum powder, copper powder, nickel powder, stainless steel powder, chromium powder, mica-like iron oxide, mica powder coated with titanium oxide, mica powder coated with iron oxide, and glittering graphite; EB, organic red pigments such as azo and quinacridone, organic blue pigments such as cyanine blue and cyanine green, organic yellow pigments such as benzimidazolone, isoindoline and quinophthalone; titanium oxide, titanium yellow, Examples include inorganic color pigments such as red iron oxide, carbon black, graphite, iron oxide, and various calcined pigments. Further, it may contain an extender pigment. These pigments may have been subjected to a surface treatment known per se, for example, an acid / base treatment, a coupling agent treatment, a plasma treatment, an oxidation / reduction treatment, or the like. Of these, inorganic pigments such as titanium oxide are particularly preferred.
[0061]
The blending ratio of these pigments is not particularly limited, but is usually 10 to 3,000 parts by weight, particularly 15 to 2,000 parts by weight, more preferably 15 to 2,000 parts by weight, per 100 parts by weight of the pigment dispersing resin. , 500 parts by weight is preferable from the viewpoints of pigment dispersibility, dispersion stability, coloring power of the obtained pigment dispersion, and the like.
[0062]
Examples of the aqueous medium include water and a water-organic solvent mixed solution obtained by dissolving an organic solvent such as a water-soluble organic solvent in water. Examples of the organic solvent used herein include methyl alcohol, ethyl alcohol, isopropyl alcohol, propylene glycol monopropyl ether, ethylene glycol monoble ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monomethyl ether. Water-soluble organic solvents such as butyl ether, tripropylene glycol monomethyl ether, and 3-methyl 3-methoxybutanol; and hardly soluble or insoluble organic solvents such as xylene, toluene, cyclohexanone, hexane, and pentane. These organic solvents can be used alone or in combination of two or more. As the organic solvent, a solvent mainly composed of a water-soluble organic solvent is preferable. The mixing ratio of water and the organic solvent is not particularly limited, but the content of the organic solvent is preferably 50% by weight or less, more preferably 35% by weight or less of the mixed solution. The mixing ratio of the aqueous medium is not particularly limited, but is usually 50 to 5,000 parts by weight, particularly 100 to 3,000 parts by weight, more preferably 100 to 2,000 parts by weight, per 100 parts by weight of the pigment dispersing resin. It is preferably in the range of 000 parts by weight from the viewpoints of viscosity at the time of pigment dispersion, pigment dispersibility, dispersion stability and production efficiency.
[0063]
Other pigment dispersing resins used as needed include, for example, a carboxyl group-containing polymerizable unsaturated monomer such as (meth) acrylic acid and a hydroxyl group-containing polymerizable unsaturated monomer such as 2-hydroxyethyl (meth) acrylate. An acrylic resin obtained by copolymerizing a monomer and another polymerizable unsaturated monomer in the presence of a radical polymerization initiator can be used. The acrylic resin has a weight average molecular weight of about 2,000 to 150,000, especially 5,000 to 100,000, an acid value of 5 to 150 mg KOH / g, particularly 15 to 100 mg KOH / g, and a hydroxyl value of 10 to 160 mg KOH. / G, particularly preferably in the range of 30 to 120 mgKOH / g.
[0064]
The use ratio (solid content) of the pigment dispersing resin (I) of the present invention and the other pigment dispersing resin (II) is usually 5 to 300 parts by weight of the resin (II) per 100 parts by weight of the resin (I), In particular, a range of 20 to 150 parts by weight is appropriate.
[0065]
When the pigment dispersing resin has a carboxyl group, the basic neutralizing agent is used to neutralize the carboxyl group and to make the pigment dispersing resin water-soluble or water-dispersible. Are, for example, inorganic bases such as ammonium hydroxide, sodium hydroxide and potassium hydroxide; amines such as aminomethylpropanol, aminoethylpropanol, dimethylethanolamine, triethylamine, diethylethanolamine, dimethylaminopropanol and aminomethylpropanol. Can be mentioned. The compounding amount of these basic neutralizing agents is not less than the amount necessary for solubilizing or dispersing the pigment dispersing resin in water or dispersing it in water. It is preferable that the ratio is 3 to 1.5, particularly 0.4 to 1.3.
[0066]
Examples of the dispersing aid used as necessary include, for example, Disperbyk 184 and Disperbyk 190 of BYK-Chemie, and other additives include an antifoaming agent, a preservative, a rust inhibitor, and a plasticizer. Agents and the like. In consideration of the dispersibility of the pigment, the stability of the paste, the let-down stability, and the performance of the coating film, the amount of each of these components is desirably 50 parts or less based on 100 parts by weight of the pigment dispersing resin.
[0067]
The aqueous pigment dispersion can be prepared by uniformly mixing and dispersing the above-mentioned components using a disperser such as a paint shaker, a sand mill, a ball mill, an LMZ mill, a DCP pearl mill and the like.
[0068]
Aqueous paint composition
The aqueous pigment dispersion prepared as described above contains a binder resin for paint, and, if necessary, an aqueous medium, polymer fine particles, a curing catalyst, a basic neutralizer, an ultraviolet absorber, an ultraviolet stabilizer, and a coating surface. An aqueous coating composition can be obtained by blending additives such as a regulator, an antioxidant, a fluidity modifier, and a silane coupling agent and stably dispersing the same in an aqueous medium.
[0069]
As the binder resin for the coating, a combination of a base resin and a curing agent which can be generally used in the field of water-soluble or water-dispersible coatings is included. Examples of the base resin include a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, and an epoxy resin. Examples include a group-containing copolymer resin and a carboxyl group-containing high acid value resin. Examples of the curing agent include an amino resin and a polyisocyanate compound which may be blocked. They can be used alone or in combination of two or more.
[0070]
As the hydroxyl group-containing acrylic resin, for example, a hydroxyl group-containing polymerizable unsaturated monomer such as 2-hydroxyethyl (meth) acrylate and another polymerizable unsaturated monomer are copolymerized in the presence of a radical polymerization initiator. Those obtained have a weight average molecular weight of about 2,000 to 100,000, particularly preferably in the range of 5,000 to 50,000.
[0071]
Examples of the hydroxyl-containing polyester resin include, for example, polyhydric alcohols such as ethylene glycol, butylene glycol, 1,6-hexanediol, trimethylolpropane, and pentaerythritol, and adipic acid, isophthalic acid, terephthalic acid, phthalic anhydride, and hexahydrohydric acid. Those having a weight average molecular weight of about 1,000 to 100,000, especially 1,500 to 70,000, obtained by a condensation reaction with a polycarboxylic acid component such as phthalic anhydride and trimellitic anhydride. Is preferred.
[0072]
As the amino resin used as a curing agent, a melamine resin is generally used. In particular, at least a part of the methylol group of the methylolated melamine resin or the methylolated melamine resin is etherified with a monohydric alcohol having 1 to 4 carbon atoms. The melamine resin is preferably a resin having water solubility or water dispersibility, but a water insoluble resin can also be used.
[0073]
Commercially available melamine resins include, for example, U-Van 20SE-60, U-Van 225 (all of which are manufactured by Mitsui Chemicals, trade name), Super Beckamine G840, and Super Beckamine G 821 (all of which are Dainippon Ink and Chemicals, Inc.) Butyl etherified melamine resin such as Sumimar M-100, Sumimar M-40S, Sumimar M-55 (all of which are trade names, manufactured by Sumitomo Chemical Co., Ltd.), Cymel 303, Cymel 325, Cymel 327; , Cymel 350, Cymel 370 (all, manufactured by Mitsui Cytec Co., Ltd., trade name), Nikarac MS17, Nikalac MS15 (all, manufactured by Sanwa Chemical Co., trade name), Regimin 741 (manufactured by Monsanto Co., trade name) Methyletherified melamine resin such as Cymel 235, Cymel 02, Cymel 238, Cymel 254, Cymel 272, Cymel 1130 (all of which are manufactured by Mitsui Cytec Co., Ltd., trade name), and mixed etherification of methylation and isobutylation of Sumamil M66B (trade name, manufactured by Sumitomo Chemical Co., Ltd.) Melamine resins; mixed etherified melamine resins of methylation and n-butylation such as Cymel XV805 (trade name, manufactured by Mitsui Cytec Co., Ltd.) and Niclac MS95 (trade name, manufactured by Sanwa Chemical Co., Ltd.).
[0074]
The blocked polyisocyanate compound that can be used as a curing agent includes both a polyisocyanate compound having a free isocyanate group and a polyisocyanate compound having a blocked isocyanate group.
[0075]
Examples of the polyisocyanate compound having a free isocyanate group include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate and isophorone diisocyanate; Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate; triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, Organic polyisoisomers such as polyisocyanate compounds having three or more isocyanate groups such as 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate Anate itself, or an adduct of each of these organic polyisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or a cyclized polymer of each of the above organic polyisocyanates, furthermore, an isocyanate / biuret compound, etc. Can be mentioned.
[0076]
Commercially available polyisocyanate compounds having a free isocyanate group include, for example, Vernock D-750, Vernock-800, Vernock DN-950, Vernock DN-970, Vernock DN-15-455 (all are Dainippon Ink and Chemicals, Inc.) Desmodur L, Desmodur N, Desmodur HL, Desmodur N3390 (all, trade names, manufactured by Sumitomo Bayer Urethane Co., Ltd.), Takenate D-102, Takenate-202, Takenate-110, Takenate -123N (all, manufactured by Takeda Pharmaceutical Co., Ltd., trade name), Coronate EH, Coronate L, Coronate HL, Coronate 203 (all, manufactured by Nippon Polyurethane Industry Co., Ltd., trade name), Duranate 24A-90CX (Asahi Chemical Industry) Product made by company ), And the like.
[0077]
As the polyisocyanate compound in which the isocyanate group is blocked, the isocyanate group of the polyisocyanate compound having a free isocyanate group described above, a known block such as oxime, phenol, alcohol, lactam, malonic diester, acetoacetate or mercaptan. And those blocked with an agent. Examples of these typical commercially available products include Burnock D-550 (trade name, manufactured by Dainippon Ink and Chemicals, Inc.), Takenate B-815-N (trade name, manufactured by Takeda Pharmaceutical Co., Ltd.), and Additol VXL-80. (Trade name, manufactured by Hoechst AG, Germany), Coronate 2507 (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.), Desmodur N3500 (trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.) and the like.
[0078]
The aqueous solvent used as needed can be appropriately selected from those described as the aqueous medium used as needed when producing the pigment dispersion.
[0079]
The polymer fine particles are polymers that are not dissolved in the coating composition of the present invention and are dispersed as fine particles, and usually have an average particle diameter of 0.01 to 1 μm, particularly 0.05 to 0.8 μm. It is suitable. The polymer particles may or may not be cross-linked inside the particles, but preferably are internally cross-linked. As the polymer fine particles, those known per se as a fluidity modifier for a paint in the field of paints can be used.
[0080]
As the curing catalyst, when a polyisocyanate compound which may be blocked as a curing agent is used, an organic metal catalyst such as dibutyltin diacetate, dibutyltin dioctate, dibutyltin dilaurate; an amine such as triethylamine, diethanolamine, etc. Are preferably used.When an amino resin such as a melamine resin is used as a curing agent, a sulfonic acid compound such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, An amine-neutralized acid compound or the like can be suitably used.
[0081]
Examples of the ultraviolet absorber include benzophenone-based, benzotriazole-based, cyanoacrylate-based, salicylate-based, and oxalic anilide-based compounds, and examples of the ultraviolet stabilizer include hindered amine-based compounds. it can.
[0082]
The aqueous coating composition of the present invention can be used as a colored coating composition (including metallic paint and interference color paint) containing various pigments such as colored pigments, metallic pigments and interference color pigments. It can be suitably used as a top coat for painting (colored base coat).
[0083]
The coating composition of the present invention can be applied to various objects to be coated by a conventional method, and usually forms a cured coating film by baking at a temperature of about 80 to about 180 ° C. for about 10 to 60 minutes. be able to. In the case of baking for a short time, a cured coating film can also be formed by baking for about 20 seconds to 60 seconds under the condition that the maximum temperature of the material reaches about 180 ° C. to about 250 ° C.
[0084]
The substrate to which the coating composition of the present invention can be applied is not particularly limited, and examples thereof include metal substrates such as steel plates, aluminum, and tin; and other substrates such as mortar, cement, plastics, and glass. Materials; those obtained by subjecting these base materials to surface treatment and / or coating film formation, and the like, among which metal base materials, particularly steel base materials, and plastics as base materials It can be suitably used.
[0085]
Examples of the steel sheet include cold-rolled steel sheet, hot-dip galvanized steel sheet, electro-galvanized steel sheet, aluminum-plated steel sheet, stainless steel sheet, copper-plated steel sheet, tin-plated steel sheet, lead-tin alloy-plated steel sheet (turn sheet); iron-zinc, aluminum And zinc alloy-plated steel sheets such as zinc and nickel-zinc. Examples of the steel sheet subjected to the surface treatment include a steel sheet obtained by subjecting the above steel sheet to a chemical conversion treatment such as a phosphate treatment or a chromate treatment.
[0086]
In addition, as an object to be coated, a substrate is subjected to a surface treatment as necessary, and a primer coating is formed thereon, and an intermediate coating is formed on the primer coating. And the like.
[0087]
When the coating composition of the present invention is used as a topcoat for automotive coating, a typical example of the object to be coated is a steel sheet which has been subjected to a chemical conversion treatment, which is coated with a primer and then coated with an intermediate coating as necessary. And various plastic base materials (subjected to surface treatment, primer coating, intermediate coating, etc., as required), and composite members obtained by combining these.
[0088]
The coating for the electrodeposition coating may be either an anionic type or a cationic type, but a cationic type having good anticorrosion properties is desirable. Known cationic electrodeposition paints can be used. For example, a resin containing a base resin having a hydroxyl group and a cationic group as a resin component and a curing agent such as a blocked polyisocyanate compound is preferably used. Can be.
[0089]
The aqueous coating composition of the present invention comprises a composition for forming a colored coating film for one coat and one bake on a substrate, and two coats and one bake (2C1B) on a substrate and two coats and two bake (2C2B). It can be suitably used as a top-coating colored base coating composition in a three-coat one-bake (3C1B), three-coat two-bake (3C2B) or three-coat three-bake (3C3B) system.
[0090]
When the coating composition of the present invention is used as a top coating color coating for automobiles, for example, on a primer coating such as an electrodeposition coating, or on an uncured or cured intermediate coating coated on the primer coating Then, for example, by applying a method such as electrostatic atomizing coating (bell type or the like), air spray coating, or the like, the dried film thickness is usually about 10 to about 60 μm, and left at room temperature for several minutes or A top-coating colored film can be formed by forcibly drying at 50 to about 80 ° C. for several minutes or baking at about 120 to about 180 ° C. for about 10 to about 60 minutes. Further, on the uncured or cured topcoat colored coating film coated as described above, a topcoat clear paint is applied by means of, for example, electrostatic atomization coating (bell type or the like), air spray coating, or the like to obtain a dry film thickness. Usually, an overcoating multilayer coating film can be formed by coating and curing to a thickness of about 20 to about 100 μm.
[0091]
Examples of the top clear coating material applied on the top coating film include acrylic resins having a crosslinkable functional group (for example, hydroxyl group, epoxy group, carboxyl group, alkoxysilane group, etc.), vinyl resin, polyester resin, alkyd resin, At least one kind of base resin such as urethane resin, and an alkyl etherified melamine resin, urea resin, guanamine resin, a polyisocyanate compound which may be blocked, an epoxy resin, and a carboxyl group-containing resin for crosslinking and curing the base resin; A top clear coating composition comprising at least one type of crosslinking agent such as a compound is suitable. The mixing ratio of the base resin and the crosslinking agent is usually 50 to 90% by weight based on the sum of the two, It is desirable that the crosslinker component is 10 to 50% by weight. The form of the clear top coating composition is not particularly limited, and may be any of an organic solvent type, a non-aqueous dispersion type, an aqueous solution type, an aqueous dispersion (slurry) type, a high solid type, and a powder type. Can be used.
[0092]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Production Examples, Examples, and Comparative Examples. Unless otherwise specified, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.
[0093]
Manufacture of resin for pigment dispersion
Example 1
An ordinary acrylic resin reaction tank equipped with a stirrer, thermometer and reflux condenser was charged with 38 parts of ethylene glycol monobutyl ether and 12 parts of isobutyl alcohol, and heated and stirred to be maintained at 95 ° C. Among them, 46 parts of methyl methacrylate, 15 parts of n-butyl acrylate, 10 parts of 2-hydroxyethyl acrylate, "NF Visomer S20W" (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 50% of methoxypolyethylene glycol monomethacrylate) Water-diluted product, molecular weight of about 2080) 40 parts, 2-acrylamide-2-methylpropanesulfonic acid 1.5 parts, "isostearyl acrylate" (trade name, manufactured by Osaka Organic Chemical Co., Ltd., corresponding to monomer (C-1)) A mixture consisting of 7.5 parts, 1 part of azobisisobutyronitrile and 5 parts of isobutyl alcohol was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was aged at 95 ° C. for 30 minutes, and then an additional catalyst mixed solution comprising 20 parts of ethylene glycol monobutyl ether and 0.5 part of azobisisobutyronitrile was added dropwise over 1 hour. Then, the mixture was aged at 95 ° C. for 1 hour and then cooled to obtain a pigment dispersing resin (A-1) solution having a solid content of 50%.
[0094]
Examples 2 to 5 and Comparative Examples 1 and 2
In the above-mentioned Example 1, the same operation as in Example 1 was carried out except that the formulation shown in Table 1 below was used, and the pigment-dispersing resin solutions (A-2) to (A-5) of the present invention and comparative pigments Dispersion resin solutions (AC-1) and (AC-2) were obtained. The solid content of these pigment dispersion resin solutions and the resin acid value of the pigment dispersion resin are shown in Table 1 below. Note that (Note 1) in Table 1 below has the following meaning. Further, in Table 1, the amount of “NF Bisomer S20W” is indicated by the solid content.
(Note 1) “Acryt M-201”: Corresponds to a product name, monomer (C-2), manufactured by Taisei Kako Co., Ltd.
[0095]
[Table 1]

[0096]
Preparation of aqueous pigment dispersion
Examples 6 to 10 and Comparative Examples 3 and 4
Each of the resin solutions and pigments for dispersing the pigments obtained in Examples 1 to 5 and Comparative Examples 1 and 2, and further using deionized water and a wetting dispersant, were mixed with a dissolver in a composition shown in Table 2 below. After dispersing for 1 minute, each of the aqueous pigment dispersions (B-1) to (B-5) and (BC-1) and (BC-2) were obtained. Note that (Note 2) to (Note 4) in Table 2 below have the following meanings, respectively.
(Note 2) JR903: manufactured by Teika Co., Ltd., trade name, inorganic titanium white pigment
(Note 3) SN-122NSK: manufactured by San Nopco, trade name, defoamer
(Note 4) BYK-180: manufactured by BYK Japan KK, trade name, wetting and dispersing agent
[0097]
[Table 2]

[0098]
Synthesis of base resin for paint
Synthesis Example 1
A reactor equipped with a stirrer, thermometer, rectification tower, nitrogen inlet tube, reflux condenser, etc.
317.8 parts of acid, 196.5 parts of hexahydrophthalic acid, 372.6 parts of adipic acid, 268 parts of neopentyl glycol, 217.8 parts of 1,6-hexanediol, 263.5 parts of trimethylolpropane, and nitrogen The mixture was heated and stirred under the introduction of gas, and after the temperature reached 160 ° C, the temperature was raised to 235 ° C over 3 hours. Thereafter, the mixture was maintained at the same temperature for 1.5 hours, the rectification column was switched to a reflux condenser, 100 parts of toluene was introduced, and the reaction was continued under reflux. After reacting at the same temperature for 6 hours, toluene was removed under reduced pressure, cooled to 170 ° C., and 122.5 parts of trimellitic anhydride was added. After maintaining at 170 ° C. for 30 minutes as it was, 322 parts of butyl cellosolve was added, and then cooled to 80 ° C. Next, 4 parts of N, N-dimethylaminoethanol was added, and the mixture was kept at 80 ° C. for 30 minutes. After cooling to 50 ° C., 2200 parts of deionized water was added, and the mixture was stirred for 30 minutes. (P-1) was obtained.
[0099]
Production of aqueous coating composition
Example 11
131.8 parts of the aqueous pigment dispersion (B-1) obtained in Example 6, 153.5 parts of the polyester resin solution (P-1) obtained in Synthesis Example 1, "MS-25" (Sanwa Chemical Co., Ltd.) ), 37.5 parts of methyl / n-butyl mixed etherified melamine resin solution) and 0.83 part of “WS-314” (manufactured by Kyoeisha Co., Ltd., surface conditioner), and further dimethylethanolamine 0.8 parts and 88 parts of deionized water were added to obtain a colored aqueous coating composition having a solid content of about 44%, a viscosity of 35 to 40 seconds (Ford cup # 4/20 ° C), and a pH of about 8.5.
[0100]
Examples 12 to 15 and Comparative Examples 5 and 6
In Example 11, each colored aqueous coating composition was obtained in the same manner as in Example 11, except that the composition was changed as shown in Table 3.
[0101]
Using each of these colored water-based coating compositions, each test coated plate was prepared according to the following method for preparing a test coated plate.
[0102]
Preparation method of test coated plate
On a 0.8 mm thick cold-rolled dull steel plate that has been subjected to zinc phosphate conversion treatment, an epoxy resin-based cationic electrodeposition paint is electrodeposited and baked to a dry film thickness of about 20 μm. Then, a polyester resin intermediate coating for automobiles was applied and baked so as to have a dry film thickness of about 20 μm. The coated plate was subjected to water research, draining and drying with # 400 sandpaper, and degreased with petroleum benzene. Then, on the degreased plate, each of the colored water-based paint compositions whose viscosity was adjusted to about 25 seconds (Ford cup # 4/20 ° C.) with deionized water was dried to a dry film thickness of about 35 μm using an air spray. After coating at room temperature for 5 minutes and baking at 140 ° C. for 30 minutes in an electric hot air drier, each test coated plate was prepared.
[0103]
Various tests were performed on these test coated plates based on the following test methods. Table 3 also shows the test results.
[0104]
Test method
(* 1) Gloss: The 60-degree specular reflectance of each coating film was measured using a “micro-tri-gloss gloss meter” (JISZ8741).
(* 2) HAZE: The HAZE value of each coating film was measured using a “BYK micro haze meter” (JISZ8741). The smaller the value, the better.
(* 3) Appearance of the coating film: The finished appearance of the coating film was comprehensively investigated from the glossiness and the feeling of holding, and evaluated according to the following criteria (（: good, Δ: poor, ×: extremely poor).
(* 4) Weather resistance: Each test coated plate was subjected to an accelerated weather test according to JIS K56007-7 using "Super Xenon Weather Meter" (manufactured by Suga Test Instruments Co., Ltd., weather test machine). After a lapse of 1500 hours from the start of the test, the retention of the 60-degree gloss was examined. The larger the value, the better the weather resistance.
[0105]
[Table 3]

[0106]
【The invention's effect】
As described above, by using the pigment dispersing resin of the present invention, it is possible to obtain an aqueous pigment dispersion having excellent wettability and dispersion stability even at a high pigment concentration, having a low viscosity, and having excellent coloring properties. . In addition, by using this aqueous pigment dispersion, the coloring properties of the pigment, the finished appearance of the coating and the weather resistance, and other coating properties such as other physical properties are excellent, and the pigment has good dispersion stability. A coating composition capable of increasing the pigment concentration can be obtained.

Claims (16)

(A) a polymerizable unsaturated monomer containing a sulfonic acid group,
(B) a nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain,
(C) (C-1) (meth) acrylate polymerizable monomer having two tertiary alkyl groups in one molecule and / or (C-2) tertiary alkyl group and secondary hydroxyl group in one molecule A pigment dispersing resin, which is a copolymer of a (meth) acrylate polymerizable monomer having one each of the following, and (D) another ethylenically unsaturated monomer. The pigment dispersing resin according to claim 1, wherein the polymerizable unsaturated monomer (A) containing a sulfonic acid group is selected from the group consisting of (meth) acrylamide-alkanesulfonic acid and sulfoalkyl (meth) acrylate. The pigment dispersing resin according to claim 1, wherein the polymerizable unsaturated monomer (A) having a sulfonic acid group is 2-acrylamido-2-methylpropanesulfonic acid. The nonionic polymerizable unsaturated monomer (B) is represented by the formula (1)
^{_{CH 2 = C (R 3)}} COO (C n H 2n O) m -R 4 (1)
In the formula, R ³ represents a hydrogen atom or a methyl group, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m is an integer of 4 to 60, n is 2 or 3,
Here, the m oxyalkylene units (C _n H _2n O) may be the same or different from each other,
The pigment dispersing resin according to claim 1, which is a compound represented by the formula: The pigment dispersing resin according to claim 1, wherein the nonionic polymerizable unsaturated monomer (B) is selected from the group consisting of polyethylene glycol (meth) acrylate and polypropylene glycol (meth) acrylate. A (meth) acrylate polymerizable monomer (C-1) having two tertiary alkyl groups in one molecule is represented by the following formula:

Wherein X is hydrogen or a methyl group;
The pigment dispersing resin according to claim 1, which is a monomer represented by the following formula: A (meth) acrylate polymerizable monomer (C-2) having one tertiary alkyl group and one secondary hydroxyl group in one molecule is represented by the following formula:

In the formula, X is hydrogen or a methyl group, R ¹ and R ² each represent an alkyl group having 1 to 6 carbon atoms, provided that the total carbon number of R ¹ and R ² is 7.
The pigment dispersing resin according to claim 1, which is a monomer represented by the following formula: The pigment-dispersing resin according to claim 1, wherein the other ethylenically unsaturated monomer (D) contains a hydroxyl group-containing polymerizable unsaturated monomer as at least a part of its component. The pigment dispersing resin according to claim 1, wherein the other ethylenically unsaturated monomer (D) contains a carboxy group-containing polymerizable unsaturated monomer as at least a part of its component. The copolymer comprises 0.1 to 10% by weight of monomer (A) and 5 to 50% by weight of monomer (B) based on the total amount of monomers (A), (B), (C) and (D). The pigment dispersion resin according to claim 1, which is obtained by copolymerizing 1 to 30% by weight of a monomer (C) and 10 to 93.9% by weight of a monomer (D). The pigment dispersing resin according to claim 1, wherein the copolymer has a weight average molecular weight in the range of 500 to 100,000. The pigment-dispersing resin according to claim 1, wherein the copolymer has a hydroxyl value in a range of 15 to 75 mgKOH / g. An aqueous pigment dispersion comprising the pigment dispersing resin according to claim 1, a pigment, an aqueous medium and, if necessary, a basic neutralizing agent and / or a dispersing aid. The aqueous pigment dispersion according to claim 13, wherein the pigment is an inorganic pigment. An aqueous coating composition comprising the aqueous pigment dispersion according to claim 13. An article coated with the aqueous coating composition according to claim 15.