JP4176492B2 - Coating method - Google Patents

Description

【００２２】
ここでｎ＝０〜８で示されるものが好適である。
【００２３】
エポキシ樹脂（ｉ）は、一般に１８０〜２，５００、好ましくは２００〜２，０００であり、さらに好ましくは４００〜１，５００の範囲内のエポキシ当量を有することができ、また、一般に少なくとも２００、特に４００〜４，０００、さらに特に８００〜２，５００の範囲内の数平均分子量を有するものが適している。
【００２４】
かかるエポキシ樹脂の市販品としては、例えば、ジャパンエポキシレジン（株）からエピコート８２８ＥＬ、同左１００２、同左１００４、同左１００７なる商品名で販売されているものが挙げられる。
【００２５】
変性剤：
変性剤として用いる多価ポリオール（ａ_２）は、例えば、１分子中に少なくとも２個のアルコール性水酸基を含有する化合物であり、具体的には、例えば、エチレングリコール、プロピレングリコール、1,3−ブチレングリコール、1,4−ブタンジオール、1,6−ヘキサンジオール、ジエチレングリコール、ジプロピレングリコール、シクロヘキサン−1,4−ジメチロール、ネオペンチルグリコール、ポリプロピレングリコール、ポリエチレングリコール、トリエチレングリコール、水素化ビスフェノールＡなどのジオール類；グリセリン、トリメチロールエタン、トリメチロールプロパンなどのトリオール類；ペンタエリスリトール、α−メチルグルコキシドなどのテトロール類；ソルビトール、ジペンタエリスリトールなどのヘキソール類；シュークロースなどのオクトール類が挙げられる。
変性剤としては、上記の多価ポリオール（ａ_２）にエピクロルヒドリンを反応させて得られる多価ポリオールのエポキシ化合物（ａ_３）も用いることができる。
【００２６】
さらにプロピレンオキシド変性ビスフェノールＡジグリシジル、エチレングリコールオキシド変性ビスフェノールＡジグリシジル等も変性剤として用いることができる。変性剤として用いる環状エステル化合物（ａ_４）は、下記の式 （１）
【００２７】
【化２】

式（１）
（式中、Ｒ＝ＨまたはＣＨ_３、ｎは３〜６）で示され、具体的には、例えば、δ−バレロラクトン、ε−カプロラクトン、ζ−エナラクトン、η−カプリロラクトン、γ−バレロラクトン、δ−カプロラクトン、ε−エナラクトン、ξ−カプリロラクトンが挙げられ、特に好ましくはε−カプロラクトンである。
【００２８】
上記付加反応において、式（１）の環状エステル化合物（ａ_４）は開環し、エポキシ樹脂中の２級水酸基と反応し、１級水酸基を付与するとともに、ラクトンに基因するメチレン鎖部分はエポキシ樹脂に可塑性を付与する。
【００２９】
エポキシ樹脂（ａ_１）と反応させる変性剤の量、即ち、多価ポリオール（ａ_２）、多価ポリオールのエポキシ化合物（ａ_３）、環状エステル化合物（ａ_４）から選ばれる少なくとも１種類の変性剤の量は、厳密に制限されるものではないが、アミン付加エポキシ樹脂（Ａ）中に、多価ポリオール（ａ_２）と多価ポリオールのエポキシ化合物（ａ_３）と環状エステル化合物（ａ_４）から選ばれる少なくとも１種類ノ変性剤が５〜４０重量％、好ましくは１０〜３５重量％を占めるように調節するのが好ましい。
【００３０】
次に、ポリフェノール化合物（ａ_５）は、例えば、パラ−オクチルフェノール、ビスフェノールプロパン、ビスフェノールメタン、レゾルシン、ピロカテコール、パラ−ｔｅｒｔ−ブチルフェノール、ビスフェノールスルホン、ビスフェノールエーテル、パラ−フェニルフェノール等、ビス（４−ヒドロキシフェニル）−２，２−プロパン、ビス（４−ヒドロキシフェニル）−１，１−エタン、ビス（４−ヒドロキシフェニル）−１，１−イソブタン、４，４′−ジヒドロキシベンゾフェノン、ビス（４−ヒドロキシ−３−ｔ−ブチルフェニル）−２，２−プロパン、ビス（２−ヒドロキシナフチル）メタン、１，５−ジヒドロキシナフタレンが挙げられ、これらはそれぞれ単独で又は２種以上組合せて用いることができる。
【００３１】
製造方法は、反応釜にエポキシ樹脂（ａ_１）、多価ポリオール（ａ_２）と多価ポリオールのエポキシ化合物（ａ_３）と環状エステル化合物（ａ_４）から選ばれる少なくとも１種類ノ変性剤、ポリフェノール化合物（ａ₅）を配合した後、さらに有機溶剤、ジメチルベンジルアミン、トリブチルアミン、トリエチルアミンなどの塩基性アミノ化合物触媒、及びテトラエチルアンモニュウムブロマイド、テトラブチルアンモニュウムブロマイド、テトラエチルアンモニュウムヒドロキシド、トリフェニルエチルホスホニュウムアイオダイドなどを加えて変性エポキシ樹脂を作成する。
【００３２】
変性エポキシ樹脂を製造するにおける触媒量としては、エポキシ樹脂（ａ_１）、多価ポリオール（ａ_２）と多価ポリオールのエポキシ化合物（ａ_３）と環状エステル化合物（ａ_４）から選ばれる少なくとも１種類ノ変性剤、及びポリフェノール化合物（ａ₅）の固形分合計に基づいて、１〜10,000ｐｐｍ配合し、約５０℃〜約２００℃の温度で約３０分〜約１０時間加熱することによって行うことができる。
【００３３】
次に、上記の変性エポキシ樹脂にアミノ基含有化合物（ａ₆）を付加してアミン付加エポキシ樹脂（Ａ）が製造される。
【００３４】
前記の変性エポキシ樹脂に反応するアミノ基含有化合物（ａ₆）は、エポキシ樹脂にアミノ基を導入して、該エポキシ樹脂をカチオン化するためのカチオン性付与成分であり、エポキシ樹脂と反応する活性水素を少なくとも１個含有するものが用いられる。
【００３５】
上記のアミノ基含有化合物（ａ₆）としては、モノメチルアミン、ジメチルアミン、モノエチルアミン、ジエチルアミン、モノイソプロピルアミン、トリイソプロピルアミン、モノブチルアミン、ジブチルアミンなどのモノ−もしくはジ−アルキルアミン；
モノエタノールアミン、ジエタノールアミン、モノ（２−ヒドロキシプロピル）アミン、ジ（２−ヒドロキシプロピル）アミン、トリ（２−ヒドロキシプロピル）アミン、モノメチルアミノエタノール、モノエチルアミノエタノールなどのアルカノールアミン；エチレンジアミン、プロピレンジアミン、ブチレンジアミン、ヘキサメチレンジアミン、テトラエチレンペンタミン、ペンタエチレンヘキサミン、ジエチルアミノプロピルアミン、ジエチレントリアミン、トリエチレンテトラミンなどのアルキレンポリアミン及びこれらのポリアミンのケチミン化物；エチレンイミン、プロピレンイミンなどのアルキレンイミン；ピペラジン、モルホリン、ピラジンなどの環状アミンなどが挙げられる。
【００３６】
これらのアミノ基含有化合物（ａ₆）は、変性エポキシ樹脂のエポキシ基と、約３０℃〜約１５０℃の温度で３０分〜１５０分間程度の条件下で反応させてもよいが、一般には、上記のアミンのうち第１級アミンやＮ−ヒドロキシアルキル第２級アミンを使用する場合には、このものをあらかじめケトン、アルデヒドもしくはカルボン酸と、１００〜２３０℃程度で加熱反応させてアルジミン、ケチミン、オキサゾリンもしくはイミダゾリンに変性し、このものを変性エポキシ樹脂中のエポキシ基と、約８０℃〜約２００℃の温度で約１時間〜約５時間反応させることが好ましい。
【００３７】
また、これらのアミノ基含有化合物（ａ₆）の使用量は、アミン付加エポキシ樹脂（Ａ）のアミン価が２０〜８０ｍｇＫＯＨ／ｇ、好ましくは２５〜７０ｍｇＫＯＨ／ｇとなるような範囲内が好ましい。また、アミン付加エポキシ樹脂（Ａ）の重量平均分子量は約１，０００〜約１０，０００の範囲内にあることが好ましい。
【００３８】
また、上記のようにして得られたアミン付加エポキシ樹脂（Ａ）のガラス転移温度は−１０〜６０℃の範囲である。
【００３９】
本発明でのガラス転移温度は、示差熱分析装置（セイコー電子工業社製熱分析装置”ＤＳＣ−５２００型”により昇温速度１０℃／分で測定）により実測した値である。
【００４０】
ブロック化ポリイソシアネート（Ｂ）
本発明において、架橋剤として使用されるブロック化ポリイソシアネート（Ｂ）は、ポリイソシアネート種としては、芳香族ポリイソシアネート化合物又は脂環式ポリイソシアネート化合物のポリイソシアネート化合物（ｂ_１）に、ブロック剤としては、オキシム系化合物、脂肪族アルコール類、芳香族アルキルアルコール類、エーテルアルコール類の中から選ばれる少なくとも１種類のブロック剤（ｂ_２）を反応させてなるブロック化ポリイソシアネート硬化剤（Ｂ）である。
【００４１】
芳香族ジイソシアネート化合物は、例えば、１，３−および／または１，４−フェニレンジイソシアネート、２，４−および／または２，６−トリレンジイソシアネート（ＴＤＩ）、粗製ＴＤＩ、２，４’−および／または４，４’−ジフェニルメタンジイソシアネート（通常、「ＭＤＩ」と呼ばれる）、４，４’−ジイソシアナトビフェニル、３，３’−ジメチル−４，４’−ジイソシアナトビフェニル、３，３’−ジメチル−４，４’−ジイソシアナトジフェニルメタン、クルードＭＤＩ、１，５−ナフチレンジイソシアネート、４，４’，４”−トリフェニルメタントリイソシアネート、ｍ−およびｐ−イソシアナトフェニルスルホニルイソシアネートなどが挙げられる。
【００４２】
なかでもジフェニルメタン−２，４'−ジイソシアネート、ジフェニルメタン−４，４'−ジイソシアネート（通常、「ＭＤＩ」と呼ばれる）、クルードＭＤＩが好適である。
【００４３】
クルードＭＤＩは、ジフェニルメタン−４，４'−ジイソシアネートとジフェニルメタン−２，４'−ジイソシアネートとポリメチレンポリフェニルポリイソシアネートとを主成分とする混合物であり、市販品として、コスモネートＭ−５０、同Ｍ−２００、同Ｍ−１００、同Ｍ−３００等（以上、いずれも三井化学社製）；スミジュール４４Ｖ１０、同４４Ｖ２０、同４４Ｖ４０等（以上、いずれも住友バイエルウレタン社製）；ルプラネートＭ−１２、同Ｍ−１２Ｓ、同Ｍ−２０、同Ｍ−２０Ｓ等（以上、いずれもドイツ国、ＢＡＳＦ社製）；モンデュアＭＲ（ＬＩＧＨＴ）等（バイエル社製）などを挙げることができる。
【００４４】
脂環式ポリイソシアネート化合物は、イソホロンジイソシアネート（ＩＰＤＩ）、ジシクロヘキシルメタン−４，４’−ジイソシアネート（水添ＭＤＩ）、シクロヘキシレンジイソシアネート、メチルシクロヘキシレンジイソシアネート（水添ＴＤＩ）、ビス（２−イソシアナトエチル）−４−シクロヘキセン−１，２−ジカルボキシレート、２，５−及び／又は２，６−ノルボルナンジイソシアネートなどが挙げられる。
【００４５】
他に、上記のポリイソシアネート化合物の変性物には、変性ＭＤＩ（ウレタン変性ＭＤＩ、カルボジイミド変性ＭＤＩ、トリヒドロカルビルホスフェート変性ＭＤＩ）、ウレタン変性ＴＤＩ、ビウレット変性ＨＤＩ、イソシアヌレート変性ＨＤＩ、イソシアヌレート変性ＩＰＤＩなどのポリイソシアネートの変性物；およびこれらの２種以上の混合物［たとえば変性ＭＤＩとウレタン変性ＴＤＩ（イソシアネート基含有プレポリマー）との併用］が含まれる。
【００４６】
ブロック化剤は、ポリイソシアネート化合物のイソシアネート基に付加してブロックするものであり、そして付加によって生成するブロックポリイソシアネート化合物は常温において安定で且つ約１００〜２００℃、好ましくは１２０〜１５０℃に加熱した際、ブロック剤を解離して遊離のイソシアネート基を再生しうるものであることが望ましい。また解離するブロック剤としては分子量が小さい程、形成した加熱減量が少なく、またそのことにより乾燥炉の低ヤニ・ススに寄与する。
【００４７】
このようなブロック剤は、例えば、メチルエチルケトオキシム、シクロヘキサノンオキシムなどのオキシム系化合物；ｎ−ブタノール、２−エチルヘキサノールなどの脂肪族アルコール類；フェニルカルビノール、メチルフェニルカルビノールなどの芳香族アルキルアルコール類；エチ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チルエーテル、ジエチレングリコールモノエチルエーテルなどのエーテルアルコール類；ε−カプロラクタム、γ−ブチロラクタムなどのラクタム化合物；フェノール、パラ−ｔ−ブチルフェノール、クレゾールなどのフェノール系化合物；ｎ−メチルアセトアミド、ｎ−エチルアセトアミド、ｎ−メチルプロピオンアミド、ｎ−メチルホルムアミドなどの低分子量アミド化合物等が挙げられる。
【００４８】
なかでもオキシム系化合物、脂肪族アルコール類、芳香族アルキルアルコール類、エーテルアルコール類が、つきまわり性と防錆鋼板の電着適性の面から、本発明の目的とするカチオン電着塗料には好ましい。
上記のブロック剤の配合量としては、イソシアネートのＮＣＯ基に対して１：１〜１：１．３で反応させることが好ましい。比率が１．３を越えるとブロック剤が残存して塗膜の防食性を低下させ、１．０未満ではＮＣＯ基が残存して塗料組成物の安定性を損なうので好ましくない。
【００４９】
本発明の塗膜形成方法に用いるカチオン電着塗料のブロック化ポリイソシアネート硬化剤（Ｂ）には、ポリイソシアネート化合物として、芳香族ポリイソシアネート化合物、又は脂環式ポリイソシアネート化合物のポリイソシアネート化合物から選ばれる少なくとも１種類と、ブロック剤として、オキシム系化合物、脂肪族アルコール系、芳香族アルキルアルコール系、エーテルアルコール類の中から選ばれる少なくとも１種類の組み合わせが好ましい。
【００５０】
上記のカチオン電着塗料は、アミン付加エポキシ樹脂（Ａ）及びブロック化ポリイソシアネート硬化剤（Ｂ）を必須成分として含有するものであり、さらに必要に応じて、有機錫化合物、着色顔料、体質顔料、防錆顔料、有機溶剤、水、中和剤、顔料分散剤、塗面調整剤などの塗料添加物を含有することができる。
【００５１】
上記有機錫化合物は、ブロック化ポリイソシアネート（Ｂ）のブロック化剤の解離を促進し硬化触媒として働くものであり、例えば、ジブチル錫オキサイド、ジオクチル錫オキサイドなどの有機錫酸化物；ジブチル錫ジラウレート、ジオクチル錫ジラウレート、ジブチル錫ジアセテート、ジオクチル錫ジベンゾエート、ジブチル錫ジベンゾエートなどのジアルキル錫の脂肪酸または芳香族カルボン酸塩等を挙げることができ、なかでも低温硬化性の点からジアルキル錫芳香族カルボン酸塩が好適である。
有機錫化合物の含有量は、厳密に規定されるものではなく、塗料組成物に要求される性能等に応じて広範囲にわたって変えることができるが、通常、塗料組成物中の樹脂固形分１００重量部あたり０〜８重量部、好ましくは０．０５〜５重量部の範囲内となるようにするのが好適である。
【００５２】
カチオン電着塗料は、電着塗装によって所望の基材表面に塗装することができる。電着塗装は、一般には、固形分濃度が約５〜４０重量％となるように脱イオン水などで希釈し、さらにｐＨを５．０〜９．０の範囲内に調整した電着浴を、通常、浴温１５〜３５℃に調整し、負荷電圧１００〜４００Ｖの条件で被塗物を陰極として、通電時間は３０秒間〜５分、極面積比（Ａ/Ｃ）:８／１〜１／８、極間距離は１０ｃｍ〜３００ｃｍで通電することによって行うことができる。
電着塗膜の膜厚は、特に制限されるものではないが、一般的には、１０〜４０μｍ、好ましくは１５〜３０μｍの範囲内とすることができる。また、塗膜の焼き付け硬化温度は、一般に約１００〜約２００℃、好ましくは約１２０〜約１７０℃の範囲内が適している。
【００５３】
本発明の特定の基体樹脂と特定の硬化剤を用いたカチオン電着塗料による塗膜形成方法は、電着塗装時において、通電開始から１分後の塗膜抵抗値を４００ｋΩ・ｃｍ^２〜８５０ｋΩ・ｃｍ^２、好ましくはを４８０ｋΩ・ｃｍ^２〜６５０ｋΩ・ｃｍ^２の範囲とすることが容易であり、そのことによって通電時間が９０秒間〜１５０秒間の短時間での電着塗装にて、袋構造や内板部の膜厚が得られる高いつきまわり性と、防錆鋼板の電着適性（ｇ材塗装性）の両立が可能となった。
【００５４】
【発明の効果】
本発明によれば、特定の基体樹脂と特定の硬化剤を用い、好ましくは、両成分のガラス転移温度を一定の範囲内とした樹脂成分を用いたカチオン電着塗料によって、短時間（９０秒間〜１５０秒間）の電着塗装において高つきまわり性と、防錆鋼板の電着適性（ｇ材塗装性）、及び防食性に優れる塗装物品が得られる。
さらに上記のカチオン電着塗料の電着塗装において通電開始から１分後の塗膜抵抗値を４００ｋΩ・ｃｍ^２〜８５０ｋΩ・ｃｍ^２の範囲とすれば、容易に高つきまわり性と、防錆鋼板の電着適性（ｇ材塗装性）の両立が可能となる。
理由としては、カチオン電着塗料の構成成分であるエマルションは、エマルションのコア部（中心部分）に硬化剤が、シェル部（表層部分）に基体樹脂の成分となって、基体樹脂のアミノ基を中和することによってエマルションの粒子を形成している。ここで特定の基体樹脂と特定の硬化剤を用いて、好ましくはガラス転移温度が一定の範囲とすることによって、１．通電開始から早い時間に塗膜抵抗が形成されるため、外板に費やされた電流が内板の塗膜形成に費やすことができ、つきまわり性が向上する。２．コア部（中心部分）に硬化剤が、通電時のスパークに耐えうる硬さを有しており、塗膜破壊を起しにくく、またガス穴が発生しても、シェル部（表層部分）の軟らかさがピンホールを補修することから、防錆鋼板の電着適性（ｇ材塗装性）に優れる。と考えられる。
上記の塗膜形成方法によると、短時間電着塗装が可能であるため生産性の向上、ラインの省スペース化、省エネルギー性にも優れ、かつ高つきまわり性であることから、袋部や内板部では防食性に優れ、かつ外板面では防錆鋼板のピンホール発生のない、仕上り性に優れた塗装物品を得ることができる。
【００５５】
【実施例】
以下、実施例を挙げて本発明をさらに具体的に説明するが、本発明の範囲はこれら実施例のみに限定されるものではない。以下、「％」は「重量％」を意味するものとする。
【００５６】
基体樹脂の製造例
製造例１
温度計、撹拌機、還流冷却器、窒素ガス吹込口を取り付けた反応容器に、窒素ガス吹込下でプロピレンオキシド変性ビスフエノールＡジグリシジルエーテル（注１）５２５部、ビスフエノールＡ ３４２部、及び有効成分８０％のモノエタノールアミンとメチルイソブチルケトンとのケチミンのメチルイソブチルケトン溶液３６部を仕込み、１６０℃でエポキシ基が消失するまで反応させた。
さらに、このものにエポキシ当量が約１９０のビスフエノールジグリシジルエーテル ６６５部及び有効成分８０％のモノエタノールアミンとメチルイソブチルケトンとのケチミンのメチルイソブチルケトン溶液２３２部を加え、１４０℃でエポキシ基濃度が０．２７ミリモル/ｇになるまで反応させた。これによって数平均分子量約１５００のエポキシ樹脂液が得られた。
次にエチレングリコールモノブチルエーテル３６５部で希釈冷却し、１００℃になったところで有効成分８０％のジエチレントリアミンのメチルイソブチルケトンジケチミンのメチルイソブチルケトン溶液１６７部を加え、１００℃で粘度上昇が停止するまで反応させ、固形分が８０％の基体樹脂Ｎｏ．１を得た。基体樹脂Ｎｏ．１のガラス転移温度は、２３℃であった。
（注１） プロピレンオキシド変性ビスフエノールＡジグリシジルエーテル（三洋化成社製、商品名、グリシエールＢＰＰ−３５０、エポキシ当量約３４０）。
【００５７】
製造例２
製造例１と同様な反応装置に窒素ガス吹込下でエポキシ当量約３００のエチレンオキシド変性ビスフエノールＡジグリシジルエーテル（注２）４５０部、及びビスフエノールＡ ３４２部、及び有効成分８０％のモノエタノールアミンのメチルイソブチルケトンケチミン（メチルイソブチルケトン溶液）３６部を仕込み、１６０℃でエポキシ基が消失するまで反応させた。
さらに、このものにエポキシ当量が約１９０のビスフエノールＡジグリシジルエーテル６６５部、及び有効成分８０％のモノエタノールアミンとメチルイソブチルケトンとのケチミンのメチルイソブチルケトン溶液２３２部を仕込み、１４０℃でエポキシ基濃度が０．２９ミリモル/ｇになるまで反応させた。これによつて数平均分子量約１，５００のエポキシ樹脂液が得られた。
次にこのものをエチレングリコールモノブチルエーテル３５０部で希釈冷却し、１００℃になつたところで有効成分８０％のジエチレントリアミンのメチルイソブチルケトンジケチミンのメチルイソブチルケトン１６７部を加え、１００℃の粘度上昇が停止するまで反応させ、固形分が８０％の基体樹脂Ｎｏ．２を得た。基体樹脂Ｎｏ．２のガラス転移温度は、２８℃であった。
（注２） エチレンオキシド変性ビスフエノールＡジグリシジルエーテル［三洋化成社製、商品名：グリシエールＢＰＥ−３００、エポキシ当量約３００］。
【００５８】
製造例３
攪拌機、温度計、窒素導入管および還流冷却器を取りつけたフラスコに、ビスフェノールＡとエピクロルヒドリンとの反応によって得られた数平均分子量３７０、エポキシ当量１８５のエポキシ樹脂５１８部を仕込み、ビスフェノールＡ ５７部、及びジメチルベンジルアミン０．２部を加え、１２０℃でエポキシ当量が２５０となるまで反応させた。
ついでε−カプロラクトン２１３部、及びテトラブトキシチタン０．０３部を加え、１７０℃に昇温し、この温度を保ちながら経時でサンプリングを行ない、赤外吸収スペクトル測定にて未反応ε−カプロラクトン量を追跡し、反応率が９８％以上になった時点でビスフェノールＡ １４８部とジメチルベンジルアミン０．４部をさらに加え、１３０℃でエポキシ当量９３６となるまで反応させた。ついでメチルイソブチルケトン２５７．４部、ジエチルアミン２５．６部、ジエタノールアミン６８．３部を加え８０℃で２時間反応後、メチルエチルケトンで希釈し、固形分が８０％の基体樹脂Ｎｏ．３を得た。基体樹脂Ｎｏ．３のガラス転移温度は、３８℃であった。
【００５９】
製造例４
反応容器にイソホロンジイソシアネート２２２部を仕込み反応温度を外部冷却により３０〜４０℃に保ちながら、メチルエチルケトオキシム１１３．１部を徐々に滴下して部分ブロックポリイソシアネートを合成した。
次に、製造例３で得た基体樹脂Ｎｏ．３ ５００部に、上記の部分ブロックイソシアネート８３．７部加え、窒素気流下に１００℃で赤外吸収スペクトル測定にてイソシアネート基の吸収がなくなるまで反応させた後、ジエチレングリコールモノブチルエーテルで希釈し、固形分が８０％の基体樹脂Ｎｏ．４を得た。基体樹脂Ｎｏ．４のガラス転移温度は、４４℃であった。
【００６０】
製造例５
エピコート８２８ＥＬ（ジャパンエポキシレジン（株）製、商品名、エポキシ樹脂）１０１０ｇに、ビスフェノールＡ ３９０ｇ及びジメチルベンジルアミン０．２ｇを加え、１３０℃でエポキシ当量８００になるまで反応させた。次に、ジエタノールアミン１６０ｇ及びジエチレントリアミンのケチミン化物６５ｇを加え、１２０℃で４時間反応させた後、ブチルセロソルブ３５５ｇを加え、アミン価６７、固形分が８０％の基体樹脂Ｎｏ．５を得た。基体樹脂Ｎｏ．５のガラス転移温度は、９０ ℃であった。
【００６１】
硬化剤の製造
製造例６
反応容器中に、コスモネートＭ−２００（注３） ２７０部及びメチルイソブチルケトン２５部を加え７０℃に昇温した。この中に２，２−ジメチロールブタン酸１５部を徐々に添加し、ついでエチレングリコールモノブチルエーテル１１８部を滴下して加え、７０℃で１時間反応させた後、６０℃に冷却し、プロピレングリコール１５２部を添加した。この温度を保ちながら、経時でサンプリングし、赤外線吸収スペクトル測定にて未反応のイソシアナト基の吸収がなくなったことを確認し、固形分が８０％の硬化剤Ｎｏ．１溶液を得た。ガラス転移温度は、５ ℃であった。（注３）コスモネートＭ−２００ ：商品名、三井化学社製、クルードＭＤＩ
【００６２】
製造例７
反応容器中に、トリレンジイソシアネート１７４部を加え７０℃に昇温した。この中に２，２−ジメチロールブタン酸１５部を徐々に添加し、ついでエチレングリコールモノブチルエーテル１１８部を滴下して加え、７０℃で１時間反応させた後、６０℃に冷却し、プロピレングリコール１５２部を添加した。この温度を保ちながら、経時でサンプリングし、赤外線吸収スペクトル測定にて未反応のイソシアナト基の吸収がなくなったことを確認し、固形分が８０％の硬化剤Ｎｏ．２を得た。ガラス転移温度は、１０ ℃であった。
【００６３】
製造例８
反応容器中に、イソホロンジイソシアネート２２２部及びメチルイソブチルケトン９９部を加え、５０℃に昇温した。この中にメチルエチルケトキシム１７４部をゆっくり加えた後、６０℃に昇温した。この温度を保ちながら、経時でサンプリングし、赤外線吸収スペクトル測定にて未反応のイソシアネートの吸収がなくったことを確認し、有機溶剤にて固形分を調整し、固形分８０％の硬化剤Ｎｏ．３を得た。ガラス転移温度は、８ ℃であった。
【００６４】
製造例９
ヘキサメチレンジイソシアネート５０部に、メチルケトオキシム３０部及びトリメチロールプロパン１０部を４０〜６０℃で滴下した後、８０℃で１時間加熱し、この温度を保ちながら、経時でサンプリングし、赤外線吸収スペクトル測定にて未反応のイソシアネートの吸収がなくったことを確認し、有機溶剤にて固形分を調整し、固形分８０％の硬化剤Ｎｏ．４を得た。ガラス転移温度は、−１９℃であった。
【００６５】
カチオン電着塗料用のエマルションの製造例
製造例１０ ＥＭ Ｎｏ．１
基体樹脂Ｎｏ．１ ８７．５部（樹脂固形分で７０部）、硬化剤Ｎｏ．１ を３７．５ｇ（樹脂固形分で３０ｇ）、及び１０％酢酸を１３部を配合し、均一に攪拌した後、脱イオン水を強く攪拌しながら約１５分間を要して滴下し、カチオン電着塗料用のエマルションである固形分３４％のＥＭ Ｎｏ．１を得た。
【００６６】
製造例１１〜１８ ＥＭ Ｎｏ．２〜Ｎｏ．９
表１の配合内容として、製造例１０と同様の操作にてカチオン電着塗料用のエマルションである固形分３４％のＥＭ Ｎｏ．２〜Ｎｏ．９を得た。
【００６７】
【表１】

【００６８】
顔料分散ペーストの製造
製造例１９
固形分６０％のエポキシ系４級アンモニウム型分散用樹脂 ５．８３部（固形分３．５部）、酸化チタン１４．５部、精製クレー７．０部、水酸化ビスマス １．０部、有機錫１．０部、カーボンブラック０．４部、脱イオン水２０．１部を加え、ボールミルにて２０時間分散したあと取出し、固形分５５％の顔料分散ペースト（固形分 ２７．４部）を得た。
【００６９】
実施例及び比較例
実施例１
エマルションＮｏ．１（基体樹脂Ｎｏ．１、硬化剤Ｎｏ．１） ２９４部（固形分１００部）に、顔料分散ペーストＮｏ．１を４９．８部（固形分２７．４部）、脱イオン水 ２９３．２部を加え、固形分２０％のカチオン電着塗料Ｎｏ．１（固形分 １２７．４）を製造した。
【００７０】
実施例２〜６
表２の配合内容とする以外は、実施例１と同様にしてカチオン電着塗料Ｎｏ．２〜Ｎｏ．６を得た。
【００７１】
比較例１〜３
表３の配合内容とする以外は、実施例１と同様にしてカチオン電着塗料Ｎｏ．７〜Ｎｏ．９を得た。
【００７２】
塗装試験
上記実施例及び比較例で得た各カチオン電着塗料中に、パルボンド＃３０２０（日本パーカラジジング社製、商品名、リン酸亜鉛処理剤）で化成処理した、０．８×１５０×７０ｍｍの冷延鋼板、亜鉛メッキ鋼板を用いて、下記の試験内容に従って、塗膜試験に供した。
【００７３】
カチオン電着塗料Ｎｏ．１〜Ｎｏ．６（実施例）の塗料配合、塗料特性、試験結果を表２に示す。
【００７４】
【表２】

【００７５】
カチオン電着塗料Ｎｏ．７〜Ｎｏ．９（比較例）の塗料配合、塗料特性、試験結果を表３に示す。
【００７６】
【表３】

【００７７】
（注４）つきまわり性：冷延鋼板（化成処理）によって図１のような４枚ボッ
クス法つきまわり性試験の治具を作成し、図２のような配線にて、浴温２８℃で、表中の電圧にて９０分間、又は１５０秒間、電着塗装を行った。その後、１７０℃−２０分間の焼付け乾燥を行い、外板（Ａ面）膜厚、内板（Ｇ面）膜厚、Ｇ面膜厚／Ａ面膜厚（％）を評価した。
【００７８】
（注５）防錆鋼板の電着適性（ｇ材塗装性）：亜鉛メッキ鋼板（化成処理）を電着浴のカソードとして浸漬し、浴温度２８℃で、表中の電圧にて、９０分間、又は１５０秒間電着塗装した。その後、１７０℃−２０分間の焼付け乾燥を行い、試験板１０×１０ｃｍ中のピンホールの数をかぞえる。
○：ピンホールの発生なく良好な仕上がり性、
△：ピンホールが３〜５個発生、
×：１０個以上発生した
【００７９】
（注６）防食性：冷延鋼板（化成処理）を用いてカチオン電着塗装を行った試験板に、素地に達するようにナイフでクロスカット傷を入れ、これをＪＩＳ Ｚ−２３７１に準じて８４０時間耐塩水噴霧試験を行った。ナイフ傷からの傷、フクレ幅によって以下の基準で評価した。
◎：錆、フクレの最大幅がカット部より２ｍｍ未満（片側）、
○：錆、フクレの最大幅がカット部より３ｍｍ未満（片側）、
△：錆、フクレの最大幅がカット部より３〜４ｍｍ（片側）、
×：錆、フクレの最大幅がカット部より４ｍｍ以上
【００８０】
【図面の簡単な説明】
【図１】 ４枚ボックスつきまわり性の塗装試験に用いる治具である。
【図２】 ４枚ボックスつきまわり性の塗装試験の結線図である。
【符号の説明】
１０．Ｈ面
１１．Ａ面
１２．Ｃ面
１３．Ｅ面
１４．Ｇ面
１５．８ｍｍφの穴を空ける
２０．浴槽
２１．カチオン電着塗料
２２．陽極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating film forming method using a cationic electrodeposition paint containing a specific base resin and a specific blocked polyisocyanate curing agent, and the coating film forming method includes electrodeposition in a short time of 90 seconds to 150 seconds. A coated article excellent in throwing power in coating, electrodeposition suitability of the rust-proof steel sheet (g material coating property), and corrosion resistance can be obtained.
[0002]
[Prior art and problems]
[Patent Document 1]
2001-1987 publication
[Patent Document 2]
No. 2002-275690
[Patent Document 3]
No. 2002-60680
Cationic electrodeposition paints are widely used as undercoating paints for conductive metal products such as automobile bodies that require these performances because of the excellent coating workability and good corrosion resistance of the formed coating film. However, in recent years, in order to increase the strength of automobile bodies from the standpoint of improving collision safety, the structure where multiple reinforcing members overlap each other is difficult to conduct electricity and the current density decreases, so the coating is difficult to deposit and becomes unpainted. Causes corrosion resistance to decrease. Therefore, it is conceivable that the coating voltage is increased and the inner plate is thickened.
[0003]
Further, from the viewpoint of cost reduction of an automobile body, a galvanized steel sheet (g material) is often used as a rust-proof steel sheet. In addition, electrodeposition coating in a short time (90 seconds to 150 seconds) has been required from the viewpoint of energy saving, space saving, and productivity improvement of the coating line.
[0004]
In light of the above issues, in order to obtain a high throwing power on the bag portion and inner plate surface of the coating object, it is necessary to perform electrodeposition coating at a high voltage. Sparks generated during the electrodeposition coating of the steel sheet (g material) remained as pinholes after baking of the coating film, resulting in a decrease in finish.
[0005]
In a conventional invention, a method for adjusting a cationic electrodeposition paint that suppresses the occurrence of gas pinholes on a galvanized steel sheet and provides a coating with high throwing power. Electrodeposition coating film forming method in which a cationic electrodeposition paint whose electric conductivity during painting is adjusted to 1000 to 1500 μS / cm is used within ± 5 ° C. of the paint setting temperature, and electrodeposition coating is performed at the above electrodeposition paint setting temperature. Invention related to [Patent Document 1].
[0006]
It is a cationic electrodeposition paint having a uniform coating property that can secure the inner plate thickness (μm) without increasing the thickness of the outer plate thickness (μm), and having good finish of the galvanized steel sheet. In cationic electrodeposition coating, the polarization resistance value (a) per unit film thickness is 120 to 300 kΩ · cm.²/ Μm, and coating film formation characterized by using a cationic electrodeposition paint having a paint deposition amount (b) in the range of 50 to 150 mg / C per unit of electricity and applying an effective voltage (V) of 230 V or less Invention related to the method [Patent Document 2]. Cationic electrodeposition coating composition with improved throwing power and gas pin resistance, comprising a resin component containing an amine-modified epoxy resin and a block polyisocyanate curing agent, and an organic acid and a metal salt of the organic acid as a neutralizing agent An invention relating to a cationic electrodeposition coating composition in which the total amount of an organic acid contained as a neutralizing agent and the equivalent ratio of the organic acid to the metal salt of the organic acid are adjusted [Patent Document 3]. Etc.
[0007]
As described above, although there are many methods for achieving both the throwing power and the electrodeposition suitability of the rust-proof steel plate (galvanized steel plate) in the cationic electrodeposition coating, in a short time (the energization time is 90 seconds to 150 seconds), There has been no invention that can achieve both throwing power and suitability for electrodeposition of a rust-proof steel sheet and has good corrosion resistance.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to meet these problems, the present inventors have found that the object can be achieved by the following means, and have completed the present invention.
[0009]
That is, the present invention
1. Coating method using a cationic electrodeposition paint containing the following amine-added epoxy resin (A) and blocked polyisocyanate curing agent (B),
Amine-added epoxy resin (A): epoxy resin (a₁) And a polyhydric polyol (a₂) And polyhydric polyol epoxy compounds (a₃) And a cyclic ester compound (a₄At least one modifier selected from the group consisting of polyphenol compounds (a₅) And an amino group-containing compound (a₆)
Blocked polyisocyanate curing agent (B): at least one polyisocyanate compound selected from aromatic polyisocyanate compounds or alicyclic polyisocyanate compounds (b)₁) And at least one blocking agent (b) selected from oxime compounds, aliphatic alcohols, aromatic alkyl alcohols, and ether alcohols.₂)
2. Item 1. The glass transition temperature of the amine-added epoxy resin (A) is in the range of −10 to 60 ° C., and the glass transition temperature of the blocked polyisocyanate curing agent (B) is in the range of −10 to 50 ° C. A method of forming a coating film according to
3. Furthermore, the coating-film formation method using the cationic electrodeposition coating material of 1 or 2 containing a bismuth compound as a rust preventive agent,
4). At the time of electrodeposition coating, the coating resistance after 1 minute from the start of energization is 400 kΩ · cm²~ 850kΩ · cm²The method for forming a coating film according to any one of items 1 to 3, wherein the cationic electrodeposition paint is
The present invention relates to a coated article coated by the coating film forming method according to any one of items 5.1 to 4.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention uses a specific base resin and a specific curing agent, and is preferably an electrodeposition coating in a short time (90 seconds to 150 seconds) by a cationic electrodeposition paint in which the glass transition temperatures of both components are within a certain range. In the coating film forming method with high throwing power that can easily attach the film thickness to the bag structure part and inner plate part, the electrodeposition suitability of the rust-proof steel sheet (g material paintability), and excellent corrosion resistance I found it.
[0011]
Furthermore, the above cationic electrodeposition paint has a coating resistance value of 400 kΩ · cm after one minute from the start of energization in electrodeposition coating.²~ 850kΩ · cm², Preferably 480 kΩ · cm²~ 650kΩ · cm²If it is within the range, it is possible to easily achieve both high throwing power and suitability for electrodeposition (g material paintability) of the rust-proof steel plate.
[0012]
Throwing power is evaluated by the 4-box method. That is, as shown in FIG. 1, a box in which four cold rolled steel sheets treated with zinc phosphate are arranged in parallel at intervals of 20 mm is used. In addition, a steel plate AB surface to EF other than the GH surface steel plate are provided with a hole of 8 mmφ at the bottom. Electrodeposition coating is performed using a wiring diagram as shown in FIG. 2, and evaluation is performed based on the values of the thickness of the A surface closest to the counter electrode and the thickness of the G surface farthest from the counter electrode.
[0013]
According to the coating film forming method of the present invention, in the electrodeposition coating in which the energization time is 90 seconds to 150 seconds in the electrodeposition coating, the G face film thickness (μm) / A face film thickness (μm) = 30 to 100%, preferably G Thickness of surface thickness (μm) / A surface thickness (μm) = 50 to 100% can be obtained.
[0014]
Regarding the electrodeposition suitability (g material coating property) of the rust-proof steel plate, a voltage having the above throwing power, for example, a voltage of 200 V or more, preferably 250 V or more, more preferably 300 V or more is applied to the object to be coated. However, there are no pinholes on the paint surface.
[0015]
As described above, in order to obtain throwing power and suitability for electrodeposition of a rust-proof steel plate, it is essential to use a cationic electrodeposition paint using a specific base resin and a specific curing agent, and further, the base resin and the curing In the agent, the glass transition temperature is within a specific range, and more preferably, the coating resistance value 1 minute after the start of energization of the cationic electrodeposition coating is within a certain range, thereby improving throwing power and rust prevention. It has been found that the electrodeposition suitability of the steel sheet is further improved.
[0016]
Below, the amine addition epoxy resin (A) used as a specific base resin used for a cationic electrodeposition coating and the blocked polyisocyanate curing agent (B) used as a curing agent will be described.
[0017]
  Amine-added epoxy resin (A):
  Epoxy resin (a₁) And a polyhydric polyol (a₂) And polyhydric polyol epoxy compounds (a₃) And a cyclic ester compound (a₄At least one modifier selected from the group consisting of polyphenol compounds (a₅) And an amino group-containing compound (a₆).In order to further improve the throwing power of the coating film, the amine-added epoxy resin (A) obtained by reacting part of the block polyisocyanate curing agent (B) with the amine-added epoxy resin (A) is used as a base resin. It is preferable to use it.
[0018]
Epoxy resin (a₁) Is particularly preferably an epoxy resin obtained by a reaction between a polyphenol compound and an epihalohydrin, for example, epichlorohydrin, from the viewpoint of the anticorrosive property of the coating film.
[0019]
As the polyphenol compound that can be used for the formation of the epoxy resin, those similar to the conventional ones can be used. Bis (4-hydroxyphenyl) -2,2-propane (bisphenol A), 4,4-dihydroxybenzophenone Bis (4-hydroxyphenyl) methane (bisphenol F), bis (4-hydroxyphenyl) -1,1-ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert- Butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone (bisphenol S), A phenol novolak, a cresol novolak, etc. can be mentioned.
[0020]
Moreover, as an epoxy resin obtained by reaction of a polyphenol compound and epichlorohydrin, the following formula induced | guided | derived from bisphenol A is mentioned especially,
[0021]
[Chemical 1]

[0022]
Here, those represented by n = 0 to 8 are preferred.
[0023]
The epoxy resin (i) can generally have an epoxy equivalent weight in the range of 180 to 2,500, preferably 200 to 2,000, more preferably 400 to 1,500, and is generally at least 200, Particularly suitable are those having a number average molecular weight in the range of 400 to 4,000, more particularly 800 to 2,500.
[0024]
Examples of such commercially available epoxy resins include those sold by Japan Epoxy Resins Co., Ltd. under the trade names of Epicoat 828EL, 1002 on the left, 1004 on the left, and 1007 on the left.
[0025]
Denaturant:
Polyhydric polyol used as a modifier (a₂) Is, for example, a compound containing at least two alcoholic hydroxyl groups in one molecule. Specifically, for example, ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, Diols such as 1,6-hexanediol, diethylene glycol, dipropylene glycol, cyclohexane-1,4-dimethylol, neopentyl glycol, polypropylene glycol, polyethylene glycol, triethylene glycol, hydrogenated bisphenol A; glycerin, trimethylolethane, Triols such as trimethylolpropane; Tetrols such as pentaerythritol and α-methyl glucooxide; Hexols such as sorbitol and dipentaerythritol; Octols such as sucrose .
As the modifier, the above-mentioned polyhydric polyol (a₂) And an epoxy compound of a polyhydric polyol obtained by reacting epichlorohydrin (a)₃) Can also be used.
[0026]
Furthermore, propylene oxide-modified bisphenol A diglycidyl, ethylene glycol oxide-modified bisphenol A diglycidyl, and the like can also be used as a modifier. Cyclic ester compound (a₄) Is the following formula (1)
[0027]
[Chemical 2]

Formula (1)
(Where R = H or CH₃, N is represented by 3-6), specifically, for example, δ-valerolactone, ε-caprolactone, ζ-enalactone, η-caprolactone, γ-valerolactone, δ-caprolactone, ε-enalactone, ξ-Caprolactone is exemplified, and ε-caprolactone is particularly preferable.
[0028]
In the above addition reaction, the cyclic ester compound of formula (1) (a₄) Opens and reacts with the secondary hydroxyl group in the epoxy resin to give the primary hydroxyl group, and the methylene chain portion attributed to the lactone imparts plasticity to the epoxy resin.
[0029]
Epoxy resin (a₁The amount of the modifier to be reacted with, that is, the polyhydric polyol (a₂), An epoxy compound of a polyhydric polyol (a₃), Cyclic ester compound (a₄The amount of at least one modifier selected from (1) is not strictly limited, but in the amine-added epoxy resin (A), a polyhydric polyol (a₂) And polyhydric polyol epoxy compounds (a₃) And a cyclic ester compound (a₄It is preferable to adjust so that at least one kind of denaturing agent selected from the group consisting of 5) to 40% by weight, preferably 10 to 35% by weight.
[0030]
  Next, a polyphenol compound (a₅)Para-OctylphenorubySphenol propane, bisphenol methane, resorcin, pyrocatecholLe, paTert-butylphenol, bisphenolsulfone, bisphenol ether, para-phenylphenol, bis (4-hydroxyphenyl) -2,2-propane, bis (4-hydroxyphenyl) -1,1-ethane, bis (4- Hydroxyphenyl) -1,1-isobutane, 4,4′-dihydroxybenzophenone, bis (4-hydroxy-3-tert-butylphenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, 1,5 -Dihydroxynaphthalene, which are each singly orCombine two or moreCan be used.
[0031]
The manufacturing method is as follows.₁), Polyhydric polyol (a₂) And polyhydric polyol epoxy compounds (a₃) And a cyclic ester compound (a₄) At least one kind of denaturant selected from polyphenol compounds (a_Five), Organic solvent, basic amino compound catalysts such as dimethylbenzylamine, tributylamine, triethylamine, and tetraethylammonium bromide, tetrabutylammonium bromide, tetraethylammonium hydroxide, triphenylethylphosphonium iodide, etc. To make a modified epoxy resin.
[0032]
As the amount of catalyst in producing the modified epoxy resin, epoxy resin (a₁), Polyhydric polyol (a₂) And polyhydric polyol epoxy compounds (a₃) And a cyclic ester compound (a₄At least one type of denaturant selected from the group consisting of polyphenol compounds (a_Five) Based on the total solid content of 1) to 10,000 ppm and heated at a temperature of about 50 ° C. to about 200 ° C. for about 30 minutes to about 10 hours.
[0033]
Next, the amino group-containing compound (a₆) Is added to produce an amine-added epoxy resin (A).
[0034]
Amino group-containing compound (a₆) Is a cationic component for introducing an amino group into an epoxy resin to cationize the epoxy resin, and one containing at least one active hydrogen that reacts with the epoxy resin is used.
[0035]
The above amino group-containing compound (a₆) As mono- or di-alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, triisopropylamine, monobutylamine, dibutylamine;
Alkanolamines such as monoethanolamine, diethanolamine, mono (2-hydroxypropyl) amine, di (2-hydroxypropyl) amine, tri (2-hydroxypropyl) amine, monomethylaminoethanol, monoethylaminoethanol; ethylenediamine, propylenediamine , Butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, diethylenetriamine, triethylenetetramine and other polyalkylene amines and ketiminates of these polyamines; ethyleneimine, propyleneimine and other alkyleneimines; piperazine, Examples thereof include cyclic amines such as morpholine and pyrazine.
[0036]
These amino group-containing compounds (a₆) May be reacted with the epoxy group of the modified epoxy resin at a temperature of about 30 ° C. to about 150 ° C. for about 30 minutes to 150 minutes. When N-hydroxyalkyl secondary amine is used, it is preliminarily reacted with a ketone, aldehyde or carboxylic acid at about 100 to 230 ° C. to be modified to aldimine, ketimine, oxazoline or imidazoline. Preferably, the product is reacted with the epoxy groups in the modified epoxy resin at a temperature of about 80 ° C. to about 200 ° C. for about 1 hour to about 5 hours.
[0037]
These amino group-containing compounds (a₆) Is preferably within a range such that the amine value of the amine-added epoxy resin (A) is 20 to 80 mgKOH / g, preferably 25 to 70 mgKOH / g. The weight average molecular weight of the amine-added epoxy resin (A) is preferably in the range of about 1,000 to about 10,000.
[0038]
Moreover, the glass transition temperature of the amine-added epoxy resin (A) obtained as described above is in the range of −10 to 60 ° C.
[0039]
The glass transition temperature in the present invention is a value measured by a differential thermal analyzer (measured at a heating rate of 10 ° C./min with a thermal analyzer “DSC-5200 type” manufactured by Seiko Denshi Kogyo Co., Ltd.).
[0040]
Blocked polyisocyanate (B)
In the present invention, the blocked polyisocyanate (B) used as the cross-linking agent is an aromatic polyisocyanate compound or a polyisocyanate compound of an alicyclic polyisocyanate compound (b) as the polyisocyanate species.₁) And at least one blocking agent (b) selected from oxime compounds, aliphatic alcohols, aromatic alkyl alcohols and ether alcohols.₂Is a blocked polyisocyanate curing agent (B).
[0041]
Aromatic diisocyanate compounds include, for example, 1,3- and / or 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate (TDI), crude TDI, 2,4′- and / or Or 4,4′-diphenylmethane diisocyanate (usually referred to as “MDI”), 4,4′-diisocyanatobiphenyl, 3,3′-dimethyl-4,4′-diisocyanatobiphenyl, 3,3′- Dimethyl-4,4′-diisocyanatodiphenylmethane, crude MDI, 1,5-naphthylene diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, m- and p-isocyanatophenylsulfonyl isocyanate It is done.
[0042]
Of these, diphenylmethane-2,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate (usually referred to as “MDI”), and crude MDI are preferred.
[0043]
Crude MDI is a mixture mainly composed of diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, and polymethylene polyphenyl polyisocyanate. As commercial products, Cosmonate M-50 and M -200, M-100, M-300, etc. (all of which are manufactured by Mitsui Chemicals); Sumijour 44V10, 44V20, 44V40, etc. (all of which are manufactured by Sumitomo Bayer Urethane Co., Ltd.); Luplanate M-12 , M-12S, M-20, M-20S, etc. (all of which are manufactured by BASF, Germany); Mondur MR (LIGHT), etc. (manufactured by Bayer).
[0044]
The cycloaliphatic polyisocyanate compounds are isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4′-diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis (2-isocyanatoethyl). ) -4-cyclohexene-1,2-dicarboxylate, 2,5- and / or 2,6-norbornane diisocyanate.
[0045]
In addition, examples of the modified polyisocyanate compound include modified MDI (urethane modified MDI, carbodiimide modified MDI, trihydrocarbyl phosphate modified MDI), urethane modified TDI, biuret modified HDI, isocyanurate modified HDI, isocyanurate modified IPDI, and the like. Modified polyisocyanates; and mixtures of two or more thereof [for example, combined use of modified MDI and urethane-modified TDI (isocyanate group-containing prepolymer)].
[0046]
The blocking agent is to block by adding to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound produced by the addition is stable at room temperature and heated to about 100 to 200 ° C, preferably 120 to 150 ° C. In this case, it is desirable that the blocking agent can be dissociated to regenerate free isocyanate groups. Further, the smaller the molecular weight of the dissociating blocking agent, the smaller the heat loss formed, and this contributes to the reduction of the drying furnace.
[0047]
Such blocking agents include, for example, oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol. Ether ethers such as ethylene glycol monopropyl ether, ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; lactam compounds such as ε-caprolactam and γ-butyrolactam; phenolic compounds such as phenol, para-t-butylphenol and cresol; n -Low molecular weight amide compounds such as -methylacetamide, n-ethylacetamide, n-methylpropionamide, n-methylformamide, etc. The
[0048]
Of these, oxime compounds, aliphatic alcohols, aromatic alkyl alcohols, and ether alcohols are preferable for the cationic electrodeposition coating material of the present invention in terms of throwing power and electrodeposition suitability of the rust-proof steel sheet. .
As a compounding quantity of said blocking agent, it is preferable to make it react by 1: 1-1: 1.3 with respect to the NCO group of isocyanate. If the ratio exceeds 1.3, the blocking agent remains to reduce the anticorrosive property of the coating film, and if it is less than 1.0, the NCO group remains to impair the stability of the coating composition.
[0049]
  The blocked polyisocyanate curing agent (B) of the cationic electrodeposition paint used in the coating film forming method of the present invention is selected from an aromatic polyisocyanate compound or a polyisocyanate compound of an alicyclic polyisocyanate compound as the polyisocyanate compound. And at least one combination selected from oxime compounds, aliphatic alcohols, aromatic alkyl alcohols, and ether alcohols as a blocking agent.preferable.
[0050]
The cationic electrodeposition coating composition contains an amine-added epoxy resin (A) and a blocked polyisocyanate curing agent (B) as essential components, and further contains an organic tin compound, a coloring pigment, and an extender pigment as necessary. Further, paint additives such as a rust preventive pigment, an organic solvent, water, a neutralizer, a pigment dispersant, and a coating surface conditioner can be contained.
[0051]
The organotin compound promotes dissociation of the blocking agent of the blocked polyisocyanate (B) and functions as a curing catalyst. Examples thereof include organotin oxides such as dibutyltin oxide and dioctyltin oxide; dibutyltin dilaurate, Examples include dialkyltin fatty acids or aromatic carboxylates such as dioctyltin dilaurate, dibutyltin diacetate, dioctyltin dibenzoate, and dibutyltin dibenzoate. Acid salts are preferred.
The content of the organic tin compound is not strictly defined and can be varied over a wide range according to the performance required for the coating composition, but is usually 100 parts by weight of resin solids in the coating composition. It is suitable to be within the range of 0 to 8 parts by weight, preferably 0.05 to 5 parts by weight.
[0052]
The cationic electrodeposition paint can be applied to a desired substrate surface by electrodeposition coating. In general, the electrodeposition coating is performed by diluting with a deionized water or the like so that the solid content concentration is about 5 to 40% by weight, and further adjusting the pH within the range of 5.0 to 9.0. Usually, the bath temperature is adjusted to 15 to 35 ° C., and the coated object is a cathode under the condition of a load voltage of 100 to 400 V, the energization time is 30 seconds to 5 minutes, and the polar area ratio (A / C): 8/1 1/8, the distance between the electrodes can be carried out by energizing at 10 cm to 300 cm.
The film thickness of the electrodeposition coating film is not particularly limited, but is generally 10 to 40 μm, preferably 15 to 30 μm. In addition, the baking and curing temperature of the coating film is generally within the range of about 100 to about 200 ° C, preferably about 120 to about 170 ° C.
[0053]
The method of forming a coating film by cationic electrodeposition coating using a specific base resin and a specific curing agent of the present invention has a coating resistance value of 400 kΩ · cm after one minute from the start of energization at the time of electrodeposition coating.²~ 850kΩ · cm², Preferably 480 kΩ · cm²~ 650kΩ · cm²It is easy to be in the range of, and by this, high throwing power that the film thickness of the bag structure and the inner plate part can be obtained by electrodeposition coating in a short time of energization time of 90 seconds to 150 seconds, It became possible to achieve both electrodeposition suitability (g material paintability) of the rust-proof steel plate.
[0054]
【The invention's effect】
According to the present invention, a specific base resin and a specific curing agent are used, and preferably a cationic electrodeposition coating using a resin component having a glass transition temperature of both components within a certain range, for a short time (90 seconds). A coated article excellent in high throwing power, electrodeposition suitability of the rust-proof steel sheet (g material coating property), and corrosion resistance in electrodeposition coating for up to 150 seconds).
Furthermore, in the electrodeposition coating of the above cationic electrodeposition paint, the coating resistance value 1 minute after the start of energization is 400 kΩ · cm.²~ 850kΩ · cm²If it is in the range, it is possible to easily achieve both high throwing power and electrodeposition suitability (g material coating property) of the rust-proof steel plate.
The reason for this is that the emulsion, which is a constituent component of the cationic electrodeposition paint, has a curing agent in the core part (center part) of the emulsion and a component of the base resin in the shell part (surface part). The particles of the emulsion are formed by neutralization. Here, by using a specific base resin and a specific curing agent, preferably by setting the glass transition temperature within a certain range, Since the coating film resistance is formed at an early time from the start of energization, the current spent on the outer plate can be spent on forming the coating film on the inner plate, and the throwing power is improved. 2. The hardener in the core (center part) has a hardness that can withstand sparks when energized, and does not easily break the coating film. Even if gas holes occur, the shell part (surface layer part) Since the softness repairs the pinhole, it is excellent in the electrodeposition suitability (g material paintability) of the rust-proof steel plate. it is conceivable that.
According to the above-mentioned coating film forming method, since electrodeposition coating can be performed for a short time, the productivity is improved, the space of the line is saved, the energy saving property is excellent, and the throwing power is high. It is possible to obtain a coated article having excellent finish and having excellent corrosion resistance at the plate portion and no pinholes on the rust-proof steel plate on the outer plate surface.
[0055]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to only these examples. Hereinafter, “%” means “% by weight”.
[0056]
Production example of base resin
Production Example 1
In a reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas inlet, 525 parts of propylene oxide-modified bisphenol A diglycidyl ether (Note 1), 342 parts of bisphenol A and effective under nitrogen gas blowing 36 parts of a methyl isobutyl ketone solution of ketimine of 80% monoethanolamine and methyl isobutyl ketone was charged and reacted at 160 ° C. until the epoxy group disappeared.
Further, 665 parts of bisphenol diglycidyl ether having an epoxy equivalent weight of about 190 and 232 parts of a methyl isobutyl ketone solution of ketimine of 80% monoethanolamine and methyl isobutyl ketone were added to this, and the epoxy group concentration at 140 ° C. The reaction was continued until 0.27 mmol / g. As a result, an epoxy resin liquid having a number average molecular weight of about 1500 was obtained.
Next, dilute and cool with 365 parts of ethylene glycol monobutyl ether. When the temperature reaches 100 ° C., add 167 parts of methyl isobutyl ketone diketimine solution of diethylenetriamine of 80% active ingredient until the viscosity increase stops at 100 ° C. A base resin having a solid content of 80% was reacted. 1 was obtained. Base resin No. The glass transition temperature of 1 was 23 ° C.
(Note 1) Propylene oxide-modified bisphenol A diglycidyl ether (manufactured by Sanyo Kasei Co., Ltd., trade name, Glicier BPP-350, epoxy equivalent of about 340).
[0057]
Production Example 2
450 parts of ethylene oxide-modified bisphenol A diglycidyl ether (Note 2) having an epoxy equivalent of about 300 and 342 parts of bisphenol A and monoethanolamine having an active ingredient of 80% in the same reactor as in Production Example 1 36 parts of methyl isobutyl ketone ketimine (methyl isobutyl ketone solution) was charged and reacted at 160 ° C. until the epoxy group disappeared.
Further, 665 parts of bisphenol A diglycidyl ether having an epoxy equivalent of about 190 and 232 parts of a ketimine methyl isobutyl ketone solution of monoethanolamine and methyl isobutyl ketone having an active ingredient of 80% were added to this product, and the epoxy was heated at 140 ° C. The reaction was continued until the group concentration reached 0.29 mmol / g. As a result, an epoxy resin liquid having a number average molecular weight of about 1,500 was obtained.
Next, dilute and cool this with 350 parts of ethylene glycol monobutyl ether, and when it reaches 100 ° C., add 167 parts of methyl isobutyl ketone diketimine of 80% diethylenetriamine with an active ingredient, and stop the viscosity increase at 100 ° C. Until the solid content is 80%. 2 was obtained. Base resin No. The glass transition temperature of 2 was 28 ° C.
(Note 2) Ethylene oxide-modified bisphenol A diglycidyl ether [manufactured by Sanyo Chemical Co., Ltd., trade name: Glicier BPE-300, epoxy equivalent of about 300].
[0058]
Production Example 3
A flask equipped with a stirrer, thermometer, nitrogen inlet tube and reflux condenser was charged with 518 parts of an epoxy resin having a number average molecular weight of 370 and an epoxy equivalent of 185 obtained by the reaction of bisphenol A and epichlorohydrin, and 57 parts of bisphenol A. Then, 0.2 part of dimethylbenzylamine was added and reacted at 120 ° C. until the epoxy equivalent reached 250.
Next, 213 parts of ε-caprolactone and 0.03 part of tetrabutoxytitanium were added, the temperature was raised to 170 ° C., sampling was performed over time while maintaining this temperature, and the amount of unreacted ε-caprolactone was determined by infrared absorption spectrum measurement. When the reaction rate reached 98% or more, 148 parts of bisphenol A and 0.4 part of dimethylbenzylamine were further added and reacted at 130 ° C. until the epoxy equivalent was 936. Next, 257.4 parts of methyl isobutyl ketone, 25.6 parts of diethylamine, and 68.3 parts of diethanolamine were added, reacted at 80 ° C. for 2 hours, diluted with methyl ethyl ketone, and the base resin no. 3 was obtained. Base resin No. The glass transition temperature of 3 was 38 ° C.
[0059]
Production Example 4
Into the reaction vessel, 222 parts of isophorone diisocyanate was charged, and 113.1 parts of methyl ethyl ketoxime was gradually added dropwise while maintaining the reaction temperature at 30 to 40 ° C. by external cooling to synthesize a partially blocked polyisocyanate.
Next, the base resin No. 1 obtained in Production Example 3 was used. 3 Add 83.7 parts of the above partially-blocked isocyanate to 500 parts, react at 100 ° C. under nitrogen flow until there is no isocyanate group absorption by infrared absorption spectrum measurement, dilute with diethylene glycol monobutyl ether, The base resin No. 80% is 80%. 4 was obtained. Base resin No. The glass transition temperature of 4 was 44 ° C.
[0060]
Production Example 5
Bisphenol A (390 g) and dimethylbenzylamine (0.2 g) were added to Epicoat 828EL (trade name, epoxy resin, manufactured by Japan Epoxy Resin Co., Ltd.) 1010 g, and reacted at 130 ° C. until the epoxy equivalent was 800. Next, 160 g of diethanolamine and 65 g of a diethylenetriamine ketimine product were added and reacted at 120 ° C. for 4 hours, 355 g of butyl cellosolve was added, and base resin No. 60 having an amine value of 67 and a solid content of 80% was added. 5 was obtained. Base resin No. The glass transition temperature of 5 was 90 ° C.
[0061]
Hardener production
Production Example 6
In a reaction vessel, 270 parts of Cosmonate M-200 (Note 3) and 25 parts of methyl isobutyl ketone were added and heated to 70 ° C. To this, 15 parts of 2,2-dimethylolbutanoic acid was gradually added, and then 118 parts of ethylene glycol monobutyl ether was added dropwise, reacted at 70 ° C. for 1 hour, cooled to 60 ° C., and propylene glycol. 152 parts were added. While maintaining this temperature, sampling was carried out over time, and it was confirmed by infrared absorption spectrum measurement that there was no absorption of unreacted isocyanato groups. One solution was obtained. The glass transition temperature was 5 ° C. (Note 3) Cosmonate M-200: Trade name, manufactured by Mitsui Chemicals, Crude MDI
[0062]
Production Example 7
In the reaction vessel, 174 parts of tolylene diisocyanate was added and the temperature was raised to 70 ° C. To this, 15 parts of 2,2-dimethylolbutanoic acid was gradually added, and then 118 parts of ethylene glycol monobutyl ether was added dropwise, reacted at 70 ° C. for 1 hour, cooled to 60 ° C., and propylene glycol. 152 parts were added. While maintaining this temperature, sampling was carried out over time, and it was confirmed by infrared absorption spectrum measurement that there was no absorption of unreacted isocyanato groups. 2 was obtained. The glass transition temperature was 10 ° C.
[0063]
Production Example 8
In a reaction vessel, 222 parts of isophorone diisocyanate and 99 parts of methyl isobutyl ketone were added, and the temperature was raised to 50 ° C. To this was slowly added 174 parts of methyl ethyl ketoxime, and then the temperature was raised to 60 ° C. While maintaining this temperature, sampling was carried out over time, and it was confirmed by infrared absorption spectrum measurement that there was no absorption of unreacted isocyanate, and the solid content was adjusted with an organic solvent. 3 was obtained. The glass transition temperature was 8 ° C.
[0064]
Production Example 9
To 30 parts of hexamethylene diisocyanate, 30 parts of methyl ketoxime and 10 parts of trimethylolpropane were added dropwise at 40-60 ° C., then heated at 80 ° C. for 1 hour, sampled over time while maintaining this temperature, and infrared absorption spectrum It was confirmed by measurement that there was no absorption of unreacted isocyanate, and the solid content was adjusted with an organic solvent. 4 was obtained. The glass transition temperature was −19 ° C.
[0065]
Production example of emulsion for cationic electrodeposition coating
Production Example 10 EM No. 1
Base resin No. 1 87.5 parts (70 parts by resin solid content), curing agent No. 1 1 was mixed with 37.5 g (30 g in terms of resin solids) and 13 parts of 10% acetic acid. After uniformly stirring, the mixture was added dropwise over about 15 minutes with strong stirring of deionized water, EM No. 34% solid content emulsion for paint. 1 was obtained.
[0066]
Production Examples 11 to 18 EM No. 2-No. 9
As the content of the formulation in Table 1, an EM No. with a solid content of 34%, which is an emulsion for a cationic electrodeposition paint, by the same operation as in Production Example 10. 2-No. 9 was obtained.
[0067]
[Table 1]

[0068]
Manufacture of pigment dispersion paste
Production Example 19
Epoxy quaternary ammonium type dispersing resin having a solid content of 60% 5.83 parts (solid content 3.5 parts), titanium oxide 14.5 parts, refined clay 7.0 parts, bismuth hydroxide 1.0 part, organic Add 1.0 part of tin, 0.4 part of carbon black and 20.1 parts of deionized water, disperse in a ball mill for 20 hours, and then take out to obtain a pigment dispersion paste having a solid content of 55% (solid content: 27.4 parts). Obtained.
[0069]
Examples and Comparative Examples
Example 1
Emulsion No. 1 (base resin No. 1, curing agent No. 1) 294 parts (solid content 100 parts) were added to pigment dispersion paste No. 1 No. 1 was added 49.8 parts (solid content 27.4 parts) and deionized water 293.2 parts. 1 (solid content 127.4) was produced.
[0070]
Examples 2-6
Cationic electrodeposition paint No. 1 was prepared in the same manner as in Example 1 except that the content of blending in Table 2 was used. 2-No. 6 was obtained.
[0071]
Comparative Examples 1-3
Cationic electrodeposition paint No. 1 was prepared in the same manner as in Example 1 except that the contents of Table 3 were used. 7-No. 9 was obtained.
[0072]
Painting test
In each cationic electrodeposition paint obtained in the above Examples and Comparative Examples, 0.8 × 150 × 70 mm of chemical conversion treatment was performed with Palbond # 3020 (trade name, zinc phosphate treatment agent, manufactured by Nihon Parkerizing Co., Ltd.). A cold-rolled steel sheet and a galvanized steel sheet were used for the coating film test according to the following test contents.
[0073]
Cationic electrodeposition paint no. 1-No. Table 2 shows the paint composition, paint characteristics, and test results of No. 6 (Example).
[0074]
[Table 2]

[0075]
Cationic electrodeposition paint no. 7-No. Table 3 shows the paint composition, paint properties, and test results of 9 (Comparative Example).
[0076]
[Table 3]

[0077]
(Note 4) Throwing power: Four cold-rolled steel plates (chemical conversion treatment) as shown in FIG.
A jig for a throwing power test with a boxing method was prepared, and electrodeposition coating was performed for 90 minutes or 150 seconds at a bath temperature of 28 ° C. and a voltage in the table with wiring as shown in FIG. Then, baking baking of 170 degreeC-20 minutes was performed, and the outer plate (A surface) film thickness, the inner plate (G surface) film thickness, and the G surface film thickness / A surface film thickness (%) were evaluated.
[0078]
(Note 5) Electrodeposition suitability of rust-proof steel sheet (g material paintability): A galvanized steel sheet (chemical conversion treatment) is immersed as the cathode of the electrodeposition bath, bath temperature is 28 ° C., and the voltage in the table is 90 minutes. Alternatively, electrodeposition was applied for 150 seconds. Thereafter, baking and drying at 170 ° C. for 20 minutes are performed, and the number of pinholes in the test plate 10 × 10 cm is counted.
○: Good finish without pinholes,
Δ: 3 to 5 pinholes are generated,
X: 10 or more occurred
[0079]
(Note 6) Corrosion resistance: A test plate coated with cationic electrodeposition using cold-rolled steel sheet (chemical conversion treatment) is cross-cut with a knife so as to reach the substrate, and this is in accordance with JIS Z-2371. The salt spray resistance test was conducted for 840 hours. Evaluation was made based on the following criteria based on the damage from the knife scratch and the blister width.
A: The maximum width of rust and blisters is less than 2 mm (one side) from the cut part.
○: The maximum width of rust and swelling is less than 3 mm (one side) from the cut part.
Δ: The maximum width of rust and swelling is 3 to 4 mm (one side) from the cut part.
X: The maximum width of rust and blisters is 4 mm or more from the cut part
[0080]
[Brief description of the drawings]
FIG. 1 is a jig used in a coating test with a throwing ability with four boxes.
FIG. 2 is a connection diagram of a paint test with a throwing ability with a four-sheet box.
[Explanation of symbols]
10. H side
11. Side A
12 C side
13. E side
14 G side
Make a hole of 15.8mmφ
20. Bathtub
21. Cationic electrodeposition paint
22. anode

Claims (3)

A method of forming a film by electrodeposition coating a cationic electrodeposition coating containing an amine-added epoxy resin (A) and a blocked polyisocyanate curing agent (B) , wherein the amine-added epoxy resin (A) is an epoxy resin (a ₁ ), at least one modifier selected from a polyhydric polyol (a ₂ ), an epoxy compound (a ₃ ) of a polyhydric polyol, and a cyclic ester compound (a ₄ ), polyphenol compounds (a ₅₎ and Ri Na by reacting an amino group-containing compound (a _6), the glass transition temperature of the amine-added epoxy resin (a) is a base resin in the range of -10 to 60 ° C., the at least one polyiso blocked polyisocyanate curing agent (B) is selected from among aromatic polyisocyanate compounds, or alicyclic polyisocyanate compound Aneto compound (b _1), as a blocking agent, oxime compounds, aliphatic alcohols, aromatic alkyl alcohols, it at least one blocking agent selected from the group consisting of ether alcohols and (b ₂₎ is reacted The blocked polyisocyanate curing agent (B) has a glass transition temperature in the range of −10 to 50 ° C., and has a coating resistance value of 480 kΩ after one minute from the start of energization at the time of electrodeposition coating. A method for forming a coating film, characterized in that it is cm ^{2 to} 650 kΩ · cm ² and the energization time is in the range of 90 seconds to 150 seconds . The coating film according to claim 1, wherein the amine-added epoxy resin (A) is a base resin obtained by reacting a part of the blocked polyisocyanate curing agent (B) with the amine-added epoxy resin (A) according to claim 1. Forming method. The coated article painted by the coating-film formation method of Claim 1 or 2 .

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