JP3689252B2 - Low-toxicity pre-coated metal sheet with excellent corrosion resistance and coating adhesion - Google Patents

Description

【００４０】
（式中、Ｘはハロゲンで置換されていてもよいフェニレン基又はシクロヘキシレン基を表し、ｎは０．５〜１２．０である。）
【００４１】
ラクトン化合物又はアルキレンオキサイドの付加量は、該エポキシ樹脂約９５〜６０重量部に対して約５〜４０重量部程度である。特に、該エポキシ樹脂約９０〜７０重量部に対してラクトン化合物又はアルキレンオキサイドは約１０〜３０重量部が好ましい。
【００４２】
上記一般式で表されるエポキシ樹脂のなかで、Ｘがｐ−フェニレン基であり、ｎが２〜９のものが好ましい。ハロゲンとしては、例えば臭素、塩素などがあげられる。この置換基の数は通常、１〜３個程度で、その位置はフェニレン基もしくはシクロヘキシレン基のいずれの位置でもよい。
【００４３】
ラクトン化合物としては、例えばβ−プロピオラクトン、ブチロラクトン、γ−バレロラクトン、γ−カプロラクトン、δ−バレロラクトン、δ−カプロラクトン、ε−カプロラクトンなどが挙げられるが、これらのなかで特にε−カプロラクトンが好ましい。アルキレンオキサイドとしては、例えばエチレンオキサイド、プロピレンオキサイド、スチレンオキサイド、グリシジルメタクリレート、エピクロルヒドリンなどがあげられるが、特にエチレンオキサイドが好ましい。
【００４４】
２級の水酸基を少なくとも１個有するエポキシ樹脂にラクトン化合物又はアルキレンオキサイドを付加させたものの配合割合は、ポリオール成分中、約１０〜７０重量％の割合であるが、特に約１０〜６０重量％の範囲で用いるのが好ましい。配合割合が１０重量％未満では耐汚染性のうち、特に耐からし汚染性が悪くなることがある。また、７０重量％を超えると耐からし汚染性はよくなるが、硬度が非常に低下してしまうことがある。
【００４５】
本発明に使用する樹脂に用いられる（３）のブロック化物としては、少なくとも２個のＮＣＯ基を有する化合物、例えば、トリメチレンジイソシアネート、テトラメチレンジイソシアネート、ヘキサメチレンジイソシアネート、ペンタメチレンジイソシアネート、１，２−プロピレンジイソシアネート、２，３−ブチレンジイソシアネート、１，３−ブチレンジイソシアネート、２，４，４−又は２，２，４−トリメチルヘキサメチレンジイソシアネート、ドデカメチレンジイソシアネート、２，６−ジイソシアナートメチルカプロエートなどの脂肪族ジイソシアネートや、例えば１，３−シクロペンタンジイソシアネート、１，４−シクロヘキサンジイソシアネート、１，３−シクロヘキサンジイソシアネート、３−イソシアナートメチル−３，５，５−トリメチルシクロヘキシルイソシアネート、４，４’−メチレンビス（シクロヘキシルイソシアネート）、メチル−２，４−シクロヘキサンジイソシアネート、メチル−２，６−シクロヘキサンジイソシアネート、１，２−ビス（イソシアナートメチル）シクロヘキサン、１，４−ビス（イソシアナートメチル）シクロヘキサン、１，３−ビス（イソシアナートメチル）シクロヘキサン、トランス−シクロヘキサン−１，４−ジイソシアネートなどのシクロアルキレン系ジイソシアネートや、例えばｍ−フェニレンジイソシアネート、ｐ−フェニレンジイソシアネート、４，４’−ジフェニルジイソシアネート、１，５−ナフタ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、２，４−又は２，６−トリレンジイソシアネート、４，４’−トルイジンジイソシアネート、ジアニシジンイソシアネート、４，４’−ジフェニルエーテルジイソシアネートなどの芳香族ジイソシアネートや、例えばω，ω’−ジイソシアネート−１，３−ジメチルベンゼン、ω，ω’−ジイソシアネート−１，４−ジメチルベンゼン、ω，ω’−ジイソシアネート−１，４−ジエチルベンゼン、α，α，α’，α’−テトラメチルメタキシリレンジイソシアネート、α，α，α’，α’−テトラメチルパラキシリレンジイソシアネートなどの芳香脂肪族ジイソシアネートや、例えばトリフェニルメタン−４，４’，４”−トリイソシアネート、１，３，５−トリイソシアネートベンゼン、２，４，６−トリイソシアネートトルエン、ω−イソシアネートエチル−２，６−ジイソシアナートカプロエートなどのトリイソシアネートや、例えば４，４’−ジフェニルジメチルメタン−２，２’，５，５’−テトライソシアネートなどのテトライソシアネートのブロック化物や、ダイマー、トリマー、ビュウレット、アロファネート、カルボジイミド、ポリメチレンポリフェニルポリイソシアネート（クルードＭＤＩ、ｃ−ＭＤＩ、ポリメリックＭＤＩ）、クルードＴＤＩ、等のイソシアネート化合物からの誘導体のブロック化物や、あるいはこれらと活性水素化合物との反応により得られる末端にＮＣＯ基を有するプレポリマーのブロック化物が挙げられる。
【００４６】
プレコート金属板として用いる場合、耐候性が要求されるので、前述のＮＣＯ基を有する化合物のなかでもヘキサメチレンジイソシアネート、３−イソシアナートメチル−３，５，５−トリメチルシクロヘキシルイソシアネート、１，４−ビス（イソシアナートメチル）シクロヘキサン、１，３−ビス（イソシアナートメチル）シクロヘキサン、４，４’−メチレンビス（シクロヘキシルイソシアネート）、α，α，α’，α’−テトラメチルメタキシリレンジイソシアネートなどのイソシアネート化合物を用いるのが好ましい。
【００４７】
これらのイソシアネート化合物と活性水素化合物との反応により得られる末端にＮＣＯ基を有するプレポリマーは、前記イソシアネート単量体と活性水素化合物とをイソシアネート基が過剰の状態で反応させることにより得られる。このプレポリマーを製造するのに用いられる活性水素化合物としては、例えばエチレングリコール、プロピレングリコール、１，２−ブチレングリコール、１，３−ブチレングリコール、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、ネオペンチルグリコール、ネオペンチルグリコールヒドロキシビバリン酸エステル、トリエチレングリコール、水添ビスフェノールＡ、キシリレングリコール、１，４−ブチレングリコールなどの２価アルコール、例えばグリセリン、トリメチロールエタン、トリメチロールプロパン、１，２，６−ヘキサントリオールなどの３価アルコール、例えばペンタエリスリトールなどの４価アルコールなどの低分子量ポリオールや、上記ポリオールのプロピレンオキサイドあるいはエチレンオキサイド付加物などのポリエーテルポリオールや、前述の低分子量ポリオールとジカルボン酸とを反応させて得られるポリエステルポリオールや、これらのポリエステルポリオールを製造する際に脂肪酸変性したものなどの高分子量ポリオールが挙げられる。これらのポリオールは単独あるいは混合して使用してもよい。
【００４８】
プレポリマーは、一般にはＮＣＯ基／ＯＨ基の当量比が約２．０〜１５、好ましくは約４〜８で、通常４０〜１４０℃、好ましくは７０〜１００℃で反応を行った後、必要ならば未反応のイソシアネート単量体を通常行われている薄膜蒸留法又は抽出法などで取り除くことにより得ることができる。この反応には、錫系、鉛系、亜鉛系、鉄系などの有機金属触媒を用いてもよい。
【００４９】
前述のイソシアネート単量体又はそれらのプレポリマーのブロック化物は、イソシアネート単量体又はそれらのプレポリマーを公知の方法によりブロック剤と反応させることによって得られる。この反応に用いられるブロック剤としては、イソシアネートのブロック化に使用されうることが知られているブロック剤、例えばフェノール系、ラクタム系、活性メチレン系、アルコール系、メルカプタン系、酸アミド系、イミド系、アミン系、イミダゾール系、尿素系、カルバミン酸塩系、イミン系、オキシム系、あるいは亜硫酸塩系などのブロック剤がいずれも使用されうるが、とりわけフェノール系、オキシム系、ラクタム系、イミン系などのブロック剤が有利に使用される。ブロック剤の具体例としては、次のものが挙げられる。
【００５０】
フェノール系ブロック剤： フェノール、クレゾール、キシレノール、ニトロフェノール、クロロフェノール、エチルフェノール、ｐ−ヒドロキシジフェニル、ｔ−ブチルフェノール、ｏ−イソプロピルフェノール、ｏ−ｓｅｃ−ブチルフェノール、ｐ−ノニルフェノール、ｐ−ｔ−オクチルフェノール、ヒドロキシ安息香酸、ヒドロキシ安息香酸エステルなど。
【００５１】
ラクタム系ブロック剤： ε−カプロラクタム、δ−バレロラクタム、γ−ブチロラクタム、β−プロピオラクタムなど。
【００５２】
活性メチレン系ブロック剤： マロン酸ジエチル、マロン酸ジメチル、アセト酢酸エチル、アセト酢酸メチル、アセチルアセトンなど。
【００５３】
アルコール系ブロック剤： メタノール、エタノール、ｎ−プロピルアルコール、イソプロピルアルコール、ｎ−ブチルアルコール、イソブチルアルコール、ｔ−ブチルアルコール、ｎ−アミルアルコール、ｔ−アミルアルコール、ラウリルアルコール、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エチルエーテル、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メチルエーテル、ジスチレングリコールモノエチルエーテル、プロピレングリコールモノメチルエーテル、ベンジルアルコール、メトキシメタノール、グリコール酸、グリコール酸メチル、グリコール酸エチル、グリコール酸ブチルなどのグリコール酸エステル、乳酸、乳酸メチル、乳酸エチル、乳酸ブチルなどの乳酸エステル、メチロール尿素、メチロールメラミン、ジアセトンアルコール、エチレンクロルヒドリン、エチレンブロムヒドリン、１，３−ジクロロ−２−プロパノール、ω−ハイドロパーフルオロアルコール、アセトシアンヒドリンなど。
【００５４】
メルカプタン系ブロック剤： ブチルメルカプタン、ヘキシルメルカプタン、ｔ−ブチルメルカプタン、ｔ−ドデシルメルカプタン、２−メルカプトベンゾチアゾール、チオフェノール、メチルチオフェノール、エチルチオフェノールなど。
【００５５】
酸アミド系ブロック剤： アセトアニリド、アセトアニシジド、アセトトルイド、アクリルアミド、メタクリルアミド、酢酸アミド、ステアリン酸アミド、ベンズアミドなど。
【００５６】
イミド系ブロック剤： コハク酸イミド、フタル酸イミド、マレイン酸イミドなど。
【００５７】
アミン系ブロック剤： ジフェニルアミン、フェニルナフチルアミン、キシリジン、Ｎ−フェニルキシリジン、カルバゾール、アニリン、ナフチルアミン、ブチルアミン、ジブチルアミン、ブチルフェニルアミンなど。
【００５８】
イミダゾール系ブロック剤： イミダゾール、２−エチルイミダゾールなど。
【００５９】
尿素系ブロック剤： 尿素、チオ尿素、エチレン尿素、エチレンチオ尿素、１，３−ジフェニル尿素など。
【００６０】
カルバミン酸塩系ブロック剤： Ｎ−フェニルカルバミン酸フェニル、２−オキサゾリドンなど。
【００６１】
イミン系ブロック剤： エチレンイミン、プロピレンイミンなど。
【００６２】
オキシム系ブロック剤： ホルムアミドキシム、アセトアルドキシム、アセトキシム、メチルエチルケトキシム、ジアセチルモノオキシム、ベンゾフェノンオキシム、シクロヘキサノンオキシムなど。
【００６３】
亜硫酸塩系ブロック剤： 重亜硫酸ソーダ、重亜硫酸カリなど。
【００６４】
前述のイソシアネート単量体又はそれらのプレポリマーとブロック剤との反応の具体的な方法としては、例えばイソシアネート単量体又はそれらのプレポリマーとブロック剤とをＮＣＯ基／ブロック剤中の活性水素基の当量比＝約０．９〜１．０、好ましくは約０．９５〜１．０で反応させる方法、イソシアネート単量体とブロック剤とをＮＣＯ基／ブロック剤中の活性水素基の当量比＝約１．１〜３．０、好ましくは約１．２〜２．０で反応させた後、これに前述のプレポリマーの製造に用いられるような低分子量ポリオール、高分子量ポリオール、水あるいは低級アミンを反応させる方法、あるいはイソシアネート単量体と低分子量ポリオール、高分子量ポリオール、水あるいは低級アミンをＮＣＯ基／活性水素基の当量比＝約１．６〜１０．０、好ましくは約２．０〜７．０で反応させた後、これにブロック剤を反応させる方法などがあげられる。上記の各反応は、活性水素基を持たない溶媒中（例として、ベンゼン、トルエン、キシレン等の芳香族系溶剤、ソルベッソ−１００、ソルベッソ−２００などの石油系溶剤、酢酸エチル、酢酸ブチルなどのエステル系溶剤、例えばアセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノンなどのケトン系溶剤、例えばテトラヒドロフランなどのエーテル系溶剤など）あるいはこのような溶媒の不存在下に、公知の方法で行われる。反応に際しては、例えば３級アミン、有機金属などの公知の触媒を使用してもよい。
【００６５】
本発明に用いられる成膜性樹脂原料は、前述のポリオール（１）及び（２）とブロック化物（３）であり、ポリオールとブロック化物の配合割合はＯＨ基／再生ＮＣＯ基の当量比が約１／２〜２／１、特に１／０．８〜１／１．２が好ましい。
【００６６】
次に、下塗り層で使用する非クロム系防錆剤について説明する。本発明では、下塗り層を形成する塗料中にリン酸イオン源とバナジン酸イオン源を含有させることにより、リン酸イオンだけでは不足するオキシダイザー機能をバナジン酸イオンにより補う。すなわち、本発明を構成する非クロム系防錆剤は、水及び酸素の存在する環境下で、リン酸イオンを放出するリン酸イオン源と、水及び酸素の存在する環境下でバナジン酸イオンを放出するバナジン酸イオン源である。
【００６７】
本発明の下塗り層の防錆力を発現させるには、下塗り層中にリン酸イオンとバナジン酸イオンが共存すればよく、下塗り層を形成する塗料中にリン酸イオン及びバナジン酸イオンがそのまま存在しても、あるいは下塗り層を形成する塗料が水及び酸素の存在する環境下でリン酸イオンとバナジン酸イオンを放出する物質を含んでもよい。リン酸イオンは水溶液中において単独で存在することが少なく、種々の形態、例えば縮合体として存在するが、そのような場合でも本明細書中の「リン酸イオン」の概念に含まれるものと理解される。また、バナジン酸イオンとは縮合バナジン酸イオンも含む概念と理解される。リン酸イオン源及びバナジン酸イオン源は主として防錆顔料として提供され、リン化合物、バナジウム化合物、及び必要により網目修飾イオン源とガラス状物質の一方又は両方を含有する混合物を焼成し粉砕することにより得られる。
【００６８】
防錆顔料に使用するリン化合物は、オルトリン酸、縮合リン酸、種々の金属のオルトリン酸塩又は縮合リン酸塩、五酸化リン、リン酸塩鉱物、市販の複合リン酸塩顔料、又はこれらの混合物が挙げられる。ここで言うオルトリン酸塩の中には、その一水素塩（ＨＰＯ₄ ^2- の塩）、二水素塩（Ｈ₂ ＰＯ₄ ^- の塩）も含むものとする。また縮合リン酸塩の中にも水素塩を含むこととする。また縮合リン酸塩にはメタリン酸塩も含み、通常のポリリン酸塩、ポリメタリン酸塩も含むものとする。リン化合物の具体例としてはリン酸塩鉱物、例えばモネタイト、トルフィル石、ウィトロック石、ゼノタイム、スターコライト、ストルーブ石、ラン鉄鉱等や、市販の複合リン酸塩顔料、例えばポリリン酸シリカ等や、複合リン酸、例えばピロリン酸、メタリン酸や、複合リン酸塩、例えばメタリン酸塩、テトラメタリン酸塩、ヘキサメタリン酸塩、ピロリン酸塩、酸性ピロリン酸塩、トリポリリン酸塩や、あるいはこれらの混合物が挙げられる。リン酸塩を形成する金属種は特に限定的でなく、アルカリ金属、アルカリ土類金属、その他の典型元素の金属種及び遷移金属が挙げられる。好ましい金属種の例としては、マグネシウム、カルシウム、ストロンチウム、バリウム、チタン、ジルコニウム、マンガン、鉄、コバルト、ニッケル、亜鉛、アルミニウム、鉛、スズ等が挙げられる。この他にバナジル、チタニル、ジルコニル等、オキソカチオンも含まれる。特に好ましいのはカルシウム、マグネシウムである。アルカリ金属の多量の使用は好ましくない。アルカリ金属のリン酸塩を用いた場合、焼成生成物が水に溶解しすぎる傾向にある。しかしながら、アルカリ金属のリン酸塩を使用した場合において、水への溶解性の制御を防錆剤製造時あるいはその他の時点で実施できれば使用してもよい。そのような制御は例えば、水への溶解性の防止のためのマトリックス材（特に、ガラス状物質）の使用、あるいはコーティング等、種々の態様が挙げられる。
【００６９】
防錆顔料に用いるバナジウム化合物は、原子価が０、２、３、４又は５であるバナジウムのいずれか又は２種以上を有する化合物であり、これらの酸化物、水酸化物、種々の金属の酸素酸塩、バナジル化合物、ハロゲン化物、硫酸塩、金属粉などが挙げられる。これらは、加熱時又は水の存在下で分解して酸素と反応し高級化する。例えば金属粉又は２価の化合物は、最終的に３、４、５価のいずれかの化合物に変化する。５価のバナジウム化合物を１つの成分として含むものが好ましい。０価のもの、例えばバナジウム金属粉は、上記の理由で使用可能であるが、酸化反応が不十分等の問題があるので実用上好ましくない。５価のバナジウム化合物はバナジン酸イオンを有し、リン酸イオンと加熱反応しヘテロポリマーを作りやすい。バナジウム化合物の具体例としては、バナジウム（II）化合物、例えば酸化バナジウム（II）、水酸化バナジウム（II）、バナジウム（III)化合物、例えば酸化バナシウム（III)、バナジウム（IV）化合物、例えば酸化バナジウム（IV）、ハロゲン化バナジル等、バナジウム（Ｖ）化合物、例えば酸化バナジウム（Ｖ）、バナジン酸塩、例えば種々の金属のオルトバナジン酸塩、メタバナジン酸塩又はピロバナジン酸塩、ハロゲン化バナジル等、又はこれらの混合物が挙げられる。バナジン酸塩の金属種はリン酸塩で示したものと同じものが挙げられる。これはバナジウムの酸化物と種々の金属の酸化物、水酸化物、炭酸塩等とを６００℃以上に焼成して作ってもよい。この場合もアルカリ金属は溶解性の故にあまり好ましくないが、リン酸塩において説明した適当な処理をして溶解性を制御すれば、これらの使用も差し支えない。またハロゲン化物、硫酸塩も同様である。
【００７０】
本発明の下塗り層におけるリン酸イオン源とバナジン酸イオン源の配合量は、下塗り層の塗料全固形分１００重量部に対して、リン酸イオン源とバナジン酸イオン源の両者を合わせて０．１〜５０重量部、好ましくは０．５〜２０重量部である。０．１重量部未満だと、十分な防錆効果が発現されず、５０重量部を超えると、硬化後の塗膜の凝集力が低下し、十分な塗膜強度が得られない。また、配合するリン酸イオン源とバナジン酸イオン源との比は、Ｐ₂ Ｏ₅ とＶ₂ Ｏ₅ のモル比に換算して１：３〜１００：１とするのが好ましい。
【００７１】
防錆顔料に用いる網目修飾イオンとは、リン化合物とバナジウム化合物との焼成生成物が形成する網目構造を変性するため添加される金属イオン種を意味し、具体的には種々の金属イオン種、例えばアルカリ金属イオン、アルカリ土類金属イオン、その他の典型元素の金属イオン及び遷移金属イオンが挙げられる。好ましい網目修飾イオンの例としては、リン酸の金属塩が挙げられる。網目修飾イオン源としては、上記金属種の酸化物、水酸化物、炭酸塩、硝酸塩、有機酸塩、ケイ酸塩、ホウ酸塩、硫酸塩あるいは塩化物等が例示され、最も好ましくは酸化物、水酸化物、炭酸塩である。上記金属イオン種の中でアルカリ金属を用いた場合、あるいは上記イオン源として硫酸塩又は塩化物を用いた場合には、これらの化合物が水に溶解しすぎる傾向にある。このような場合でも、前述のごとく適当な措置、例えばマトリックス材の使用あるいは粒子のコーティング等を行って水への溶解性を制御すればよい。網目修飾イオンを使用する場合、その配合量は、下塗り層に用いる防錆剤の全ての金属陽イオン（Ｍ）の量が、Ｍがとりうる酸化物（ＭＯ、Ｍ₂ Ｏ₃ 、Ｍ₃ Ｏ₄ 、ＭＯ₂ 又はＭ₂ Ｏ）の形で表して、Ｖ₂ Ｏ₅ とＰ₂ Ｏ₅ のモル数の和の３倍以下とするのが好ましい。網目修飾イオン源の添加で防錆力発現期間の増大が期待できるが、モル比で３倍を超えると効果が飽和し、不経済である。
【００７２】
防錆顔料で用いるガラス状物質とは、マトリックス形成性ガラス、例えばケイ酸塩ガラス、ホウ酸塩ガラスのみならず、これらに金属元素、例えば、網目修飾イオンを含むものを含む。これに該当するガラス状物質は、シリカ（石英）ガラス、ケイ酸塩ガラス、例えばソーダ石灰ケイ酸塩ガラス、鉛−ケイ酸塩ガラス、アルミノケイ酸塩ガラス、ホウケイ酸塩ガラス、鉛−ホウ酸塩ガラス（通称ハンダガラス）、アルミノ−ホウリン酸塩ガラス、アルミノ−ホウ酸塩ガラス、アルミノ−リン酸塩ガラス、等が挙げられる。好ましいガラス状物質の例としては、ソーダ石灰系（Ｃガラス）、例えば日本ガラス繊維製ガラスフレーク（ＣＣＦ−１５０）、アルミノケイ酸塩ガラス（Ｅガラス）、例えば日本ガラス繊維製ガラスフレーク（ＣＥＦ−１５０）、ホウケイ酸塩ガラス、例えばコーニング社製のパイレックスが挙げられる。ガラス状物質の微粉末の１ｇを水１００ｍｌに分散・懸濁した時の液の導電率が５００μＳ／ｃｍ以下のものが好適である。５００μＳ／ｃｍを超えると防錆能が低下する。
【００７３】
ガラス状物質を使用する場合、その配合量は、有機樹脂とリン酸イオン源及びバナジン酸イオン源の含有量の合計１００重量部に対し、５００〜５００００重量部とするのが好ましい。５００重量部未満では、防錆力を発現する期間のさらなる増大が期待できず、５００００重量部を超えると、防錆力及び塗装作業性が低下する。
【００７４】
リン化合物、バナジウム化合物、及び更に必要に応じガラス状物質、網目修飾イオン源からなる混合物を焼成して、冷却後粉砕することにより、本発明に使用する防錆顔料が得られる。混合物中には必要に応じて他の無機物質、例えばマトリックス材等を混合してもよい。焼成は上記成分からなる混合物の焼成生成物の溶融温度（Ｔ１）以上の温度、具体的には６００℃以上、好ましくは１０００℃以上、更に好ましくは上記Ｔ１とガラス状物質の溶融温度の高い方の温度以上で行なわれる。この温度未満であると、反応が不十分となり、各成分が単に混合された状態で残る。このような場合、下塗り層の防錆性能が悪化する。リン化合物とバナジウム化合物の配合量は、Ｐ₂ Ｏ₅ ／Ｖ₂ Ｏ₅ のモル比に換算して０．３〜１００、好ましくは１〜１０である。網目修飾イオン源の添加量は、下塗り層に用いる防錆剤の全ての金属陽イオン（Ｍ）の量が、Ｍがとりうる酸化物（ＭＯ、Ｍ₂ Ｏ₃ 、Ｍ₃ Ｏ₄ 、ＭＯ₂ 又はＭ₂ Ｏ）の形で表して、Ｖ₂ Ｏ₅ とＰ₂ Ｏ₅ のモル数の和の３倍以下、好ましくは０〜２．０倍となるように添加する。Ｍがとりうる酸化物の形は、Ｍが１価金属の場合はＭ₂ Ｏ、Ｍが２価金属の場合はＭＯ、Ｍが３価金属の場合はＭ₂ Ｏ₃ 、Ｍが４価の場合はＭＯ₂ 、更にＭが２価、３価の混合原子価（例えばＭｎは焼成した条件で２価、３価をとりやすい）ものはＭ₃ Ｏ₄ で代表して表すこととする。ガラス状物質はリン化合物、バナジウム化合物及び網目修飾イオン源の合計５〜５００倍、好ましくは１０〜１００倍の量で配合する。上記範囲を超えると十分な防錆性は得られない。
【００７５】
本発明のプレコート金属板の下塗り層に使用する成膜性樹脂原料は、そのままでも、加熱により十分に成膜されるが、塗料化に際し、上述のポリオール及びブロック化物以外に、有機溶媒、例えば酢酸エチル、酢酸ブチル、アセト酢酸メチル、２−エトキシエチルアセテートなどのエステル系、キシレン、トルエンなどの芳香族系、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノンなどのケトン系、ジエチレングリコールジメチルエーテルなどのエーテル系、ソルベッソ−１００、ソルベッソ−２００などの石油系といった有機溶媒、着色顔料や体質顔料、分散剤、例えばシリコン系、アミン系、ポリエーテル系、ポリエステル系、ヒマシ油系、合成ワックス系、ペントナイト系などの分散剤、消泡剤、レベリング剤、揺変剤、安定剤、例えばベンゾトリアゾール系、ヒンダードアミン系、ヒンダードフェノール系などの安定剤、反応触媒、例えば錫系、鉛系、亜鉛系、鉄系などの反応触媒、紫外線防止剤などを、必要に応じて加えてもよい。
【００７６】
各成分を配合して調製した塗料を、予め下地処理層を形成した金属板に塗布後、到達板温（ＰＭＴ）約１５０〜３５０℃、加熱時間約２０〜１２０秒程度で加熱することにより、ブロック化物中に含まれるブロック剤が解離してＮＣＯ基を再生し、この再生ＮＣＯ基がポリオール中のＯＨ基と反応して硬化した下塗り層の塗膜が得られる。この塗膜の厚さは３０μｍ以下が好適であり、３０μｍ超では塗膜の加工性が劣る。
【００７７】
本発明の下塗り層は、１つとしてもよいが、２つ以上とすることで大きな効果を示す。すなわち下塗り層形成用の塗料は、金属板上に１コートして使用してもよいが、２コート以上のプライマーとして使用する場合に更に有効である。
【００７８】
下塗り層形成用塗料の塗布、乾燥、焼付けは、下地処理層の場合と同様に、任意の公知の方法を利用して行うことができる。
【００７９】
本発明のプレコート金属板は、下塗り層を形成した金属板の上に、着色した皮膜層を有することを特徴としている。この着色皮膜層は、金属板に意匠性を付与し、この上に更に塗装を施さなくても使用できる被覆金属板を得るために必須の層である。
【００８０】
この皮膜層は、着色のために必要な顔料や染料等を含む。顔料としては、有機系、無機系、両者の複合系にかかわらず公知のものを使用することができ、チタン白、アルミナ白、亜鉛黄、シアニンブルー、等のシアニン系顔料、カーボンブラック、鉄黒、べんがら、黄色酸化鉄、モリブテートオレンジ、ハンサイエロー、ピラゾロンオレンジ、アゾ系顔料、紺青、縮合多環系顔料、等が例示できる。この他に、金属片・粉末、パール顔料、マイカ顔料、樹脂ビーズ等、意匠性や導電性等の機能性を付与するための添加物を加えてもよい。
【００８１】
染料としては、アゾ染料、アントラキノン染料、インジゴイド染料、硫化染料、フタロシアニン染料、ジフェニルメタン及びトリフェニルメタン染料、その他ニトロ染料、アクリジン染料等、公知のものが用いられる。
【００８２】
着色皮膜層のバインダーとしては、有機系、無機系のバインダーが使用できる。有機系のバインダーとしては、ポリオレフィン樹脂、アクリル樹脂、ウレタン樹脂、エポキシ樹脂、ポリエステル樹脂、塩化ビニル樹脂、フッ素系樹脂、ブチラール樹脂、ポリカーボネート樹脂、フェノール樹脂等を使用できる。これらの混合物や共重合物も使用できる。また、これらに加えて、イソシアネート樹脂、アミノ樹脂、シランあるいはチタンカップリング剤等を架橋剤や補助成分として併用することができる。
【００８３】
本発明によるプレコート金属板は、成形加工された後、そのまま使用されることを前提としているので、この着色層は、折り曲げやプレス成形に際して割れや剥離が無いことを求められる。このような観点からは、ポリエステル樹脂をメラミン樹脂で架橋する樹脂系、ポリエステル樹脂をウレタン樹脂（イソシアネート、イソシアネート樹脂）で架橋する樹脂系、塩化ビニル樹脂系、フッ素樹脂系（溶剤可溶型、アクリル樹脂との分散混合型）が望ましい。樹脂は水系、溶剤系、粉体系、無溶剤系のどのような形態でもよい。
【００８４】
また、着色層には、着色に直接関わらない顔料や添加物成分、例えば硫酸バリウム、炭化カルシウム、カオリンクレー等の顔料や、消泡剤、レベリング剤、分散補助剤等の添加剤や、ポリエチレン系、ポリプロピレン系、エステル系、パラフィン系、フッ素系などの有機ワックス成分、二硫化モリブデン等の無機ワックス成分等や、塗料粘度を下げるための希釈剤、溶剤、水等を加えることができる。
【００８５】
樹脂中の着色成分の量は特に限定されず、必要な色や隠蔽力によって決定すればよい。例えば、黒に着色するためにカーボンブラックを配合する場合には、固形分換算の顔料重量濃度で１〜５％入れれば十分であり、例えば白に着色するためにチタン白を配合する場合には、固形分換算の顔料重量濃度で３０〜５５％程度が必要である。
【００８６】
着色皮膜層は、ロールコーター、カーテンコーター、静電塗装、スプレー塗装、浸漬塗装等の公知の方法で下塗り層の上に塗装され、その後、熱風、誘導加熱、近赤外線、遠赤外線等の加熱によって乾燥、硬化される。着色皮膜層の樹脂が電子線や紫外線などの放射線によって硬化するタイプのものであれば、電子線照射、紫外線照射によって硬化される。これらの併用であってもよい。着色皮膜層の種類に応じた乾燥、硬化方式を選択することができる。乾燥、焼き付け板温も、皮膜層の種類に応じて決定される。一般的なプレコート金属板（塗装金属板）の連続生産ラインにおいては、この板温は１５０〜２５０℃である。
【００８７】
着色皮膜層の膜厚は特に限定されないが、均一な着色外観を得るためには、５μｍ以上の乾燥膜厚があることが望ましい。更に望ましくは８μｍ以上がよい。膜厚の特別な上限はないが、塗装金属板の製造ラインで連続的にコイルで塗装する場合には、１回の塗装で乾燥膜厚が５０μｍ程度であることが多い。この上限は、主に「ワキ」と呼ばれる塗装中の揮発分が塗膜中から系外に揮発する際に塗膜の粘度が上がりすぎている場合に起こる欠陥の発生によって支配されることが多い。切り板に断続的に塗装しながら製造する場合には、焼き付けを緩やかな条件で行うことが可能であり、この上限乾燥膜厚は２００μｍ程度まで上がる。また、スプレー塗装などで１枚ごとに処理する場合には、更にこの上限膜厚は上がる。
【００８８】
本発明のプレコート金属板は、その両面又は片面に、上述の下地処理層及び下塗り層と、その上の着色皮膜層を有するものである。着色皮膜層は、プレコート金属板を加工して得られる最終製品において表面に現れない裏側の面には施されないことが多く、その場合、その裏側の面には下地処理層に続いてサービスコートが施される。本発明のプレコート金属板におけるサービスコートには、公知のいずれのものを採用しても差し支えない。
【００８９】
【実施例】
以下、本発明を実施例により詳細に説明する。ただし、本発明はこれらの実施例に限定されるものではない。なお、断り無く示した部あるいは％はそれぞれ重量部もしくは重量％を示す。
【００９０】
ここではまず、以下の参考例１〜１７において、下記の実施例で使用した下塗り層のための成膜性樹脂原料用ポリオール（参考例１〜７）とブロック化物（参考例８〜１３）、及び防錆剤（参考例１４〜１７）の調製を説明し、次に本発明の実施例と比較例を説明する。
【００９１】
〔参考例１〕
水添ビスフェノールＡ ３６４．９部（１．５２モル）、アジピン酸４４１．６部（３．０２モル）を反応容器に仕込み、２２０℃に加熱して窒素ガスを吹き込み、生成する縮合水を留去しながら反応させ、酸価２５０．０となったところでトリメチロールプロパン（以下、ＴＭＰという）３０４．１部（２．２７モル）を仕込み、同様に縮合水を留去しながら反応させ酸価２．６、水酸基価１８７．２、官能基数５、数平均分子量１４７８のポリエステルポリオールを得た。このポリエステルポリオール６００部と下記式のエポキシ樹脂８０重量部に対してε−カプロラクトン２０重量部を付加させたもの（プラクセルＧ−４０２（ダイセル化学工業（株）製）、水酸基価１１９、エポキシ当量１２５０）４００部とをシクロヘキサノン１５００部に溶解し、固形分４０％の溶液とした。この溶液の性状を表１に示した。
【００９２】
【化２】

【００９３】
〔参考例２〕
参考例１で得られたポリエステルポリオール８００部と下記式のエポキシ樹脂８０重量部に対してε−カプロラクトン２０重量部を付加させたもの（プラクセルＧ−７０２（ダイセル化学工業（株）製）、水酸基価１４０、エポキシ当量２７１０）の２００部をシクロヘキサノン１５００部に溶解し、固形分４０％の溶液とした。この溶液の性状を表１に示した。
【００９４】
【化３】

【００９５】
〔参考例３〕
１，６−ヘキサンジオール２０５．８部（１．７４モル）、ジメチルイソフタレート６７０．１部（３．４５モル）と酢酸亜鉛０．１ｇを反応容器に仕込み、２２０℃に加熱して窒素ガスを吹き込み、生成するメタノールを留去しながら反応させ、メタノールが１２１ml留出したところでＴＭＰ３４７．２部（２．５９モル）を仕込み、同様にメタノールを留去しながら反応させ、酸価１．４、水酸基価１９３．６、官能基数５、数平均分子量１４３８のポリエステルポリオールを得た。このポリエステルポリオール６００部と参考例１のプラクセルＧ−４０２ ４００部をシクロヘキサノン１５００部に溶解し、固形分４０％の溶液とした。この溶液の性状を表１に示した。
【００９６】
〔参考例４〕
３−メチル−１，５−ペンタンジオール２４５．３部（２．０８モル）、アジピン酸５４１．６部（３．７１モル）を反応容器に仕込み、２２０℃に加熱して窒素ガスを吹き込み、生成する縮合水を留去しながら反応させ、酸価２８０．０となったところでＴＭＰ３７２．９部（２．７８モル）とジブチルチンジラウレート０．１部を仕込み、同様に縮合水を留去しながら反応させ酸価１．６、水酸基価２１６．０、官能基数５、数平均分子量１２８９のポリエステルポリオールを得た。このポリエステルポリオール８００部と参考例１のプラクセルＧ−４０２ ２００部をシクロヘキサノン１５００部に溶解し、固形分４０％の溶液とした。この溶液の性状を表１に示した。
【００９７】
〔参考例５〕
エチレングリコール１５１．８部（２．４５モル）、コハク酸５５０．０部（４．６６モル）を仕込み、参考例１と同様な条件で反応し酸価が４２０．０となったところでペンタエリスリトール１５９．３部（１．１７モル）を仕込み、エステル化反応を続け、酸価が１６５．０となったところで、更にペンタエリスリトール１５９．３部（１．１７モル）とＴＭＰ１５７．０部（１．１７モル）を仕込み、縮合水を留去し、酸価３．８、水酸基価４４７．８、官能基数７、数平均分子量８７０のポリエステルポリオールを得た。このポリエステルポリオール８００部と参考例１のプラクセルＧ−４０２ ２００部をシクロヘキサノン１５００部に溶解し、固形分４０％の溶液とした。この溶液の性状を表１に示した。
【００９８】
〔参考例６〕
ビスヒドロキシエチルテレフタレート３２５．９部（１．２８モル）、セバシン酸５１３．８部（２．５４モル）を仕込み、参考例１と同様な条件で反応し、酸価が１８４．４となったところでＴＭＰ２５６．７部（１．９１モル）を仕込み、縮合水を留去してゆき、酸価８．０、水酸基価１６８．３、官能基数５、数平均分子量１５９１のポリエステルポリオールを得た。このポリエステルポリオール８００部と参考例１のプラクセルＧ−４０２ ２００部をシクロヘキサノン１５００部に溶解し、固形分４０％の溶液とした。この溶液の性状を表１に示した。
【００９９】
〔参考例７〕
エチレングリコール１８３．４部（２．９５モル）、コハク酸６６４．７部（５．６３モル）を仕込み、参考例１と同様な条件で反応し酸価が４２０．０となったところでＴＭＰ１８９．４部（１．４１モル）を仕込み、エステル化反応を続け、酸価１７０．０となったところで更にエチレングリコール１８３．４部（２．９５モル）を仕込み縮合水を留去し、酸価１．５、水酸基価２１５．５、官能基数３、数平均分子量７７６のポリエステルポリオールを得た。このポリエステルポリオール８００部と参考例２のプラクセルＧ−７０２ ２００部をシクロヘキサノン１５００部に溶解し、固形分４０％の溶液とした。この溶液の性状を表１に示した。
【０１００】
〔参考例８〕
１，３−ビス（イソシアナートメチル）シクロヘキサン２４１．６部をソルベッソ−１００ ４００．０部に溶解し、メチルエチルケトキシム１８０．６部を１時間で滴下する。滴下終了後更に１時間７５〜８０℃に加熱する。次にジブチル錫ジラウレート０．６部とポリエステルポリオール（アジピン酸８７６．６部、エチレングリコール１８６．３部、ＴＭＰ ２０１．２部、ジプロピレングリコール４０２．３部を常法により縮合させて得られる酸価３．５、水酸基価１７２．０、固形分１００％）１７７．０部を加え７５〜８０℃で６時間反応させる。かくして再生イソシアネート基含量８．５％、固形分６０％のブロック化物溶液を得た。この溶液の性状を表２に示した。
【０１０１】
〔参考例９〕
２リットルの４つ口フラスコにＴＭＰ−３−イソシアナートメチル−３，５，５−トリメチルシクロヘキシルイソシアネート付加体の溶液（タケネートＤ−１４０Ｎ（武田薬品工業（株）製）、固形分７５％、イソシアネート含量１０．７８％、酢酸エチル溶液）を８０１．２部及びセロソルブアセテート３１６．１部を仕込み、窒素ガス雰囲気下で、内温が６０〜７０℃を保つようにメチルエチルケトキシムの１８２．７部を徐々に滴下し、添加完了後、約４時間上記温度に保つと、固形分６０％、再生イソシアネート基含量６．６４％のブロック化物溶液を得た。この溶液の性状を表２に示した。
【０１０２】
〔参考例１０〕
ω，ω′−ジイソシアネート−１，３−ジメチルベンゼン３０７．５部をソルベッソ−１００ ５１９．１部及びメチルエチルケトン１２９．７部に溶解し、メチルエチルケトキシム２３７．２部を約２時間で滴下する。滴下終了後更に１時間７５〜８０℃に加熱する。次にジブチル錫ジラウレート０．３部と参考例８に用いたポリエステルポリオールの２３２．４部を加えて７５〜８０℃で６時間反応させる。かくして再生イソシアネート基含量８．０２％、固形分５５％のブロック化物溶液を得た。この溶液の性状を表２に示した。
【０１０３】
〔参考例１１〕
２リットルの４つ口フラスコにＴＭＰ−ヘキサメチレンジイソシアネート付加体（タケネートＤ−１６０Ｎ（武田薬品工業（株）製）、固形分７５％、イソシアネート含量１３．２％）を７６０．７部及びセロソルブアセテート３２５．６部を仕込み、窒素ガス雰囲気下で、内温が６０〜７０℃を保つようにメチルエチルケトキシムの２１３．７部を徐々に滴下し、添加完了後、約２時間上記温度に保つと、固形分６０％、再生イソシアネート基含量７．７７％、のブロック化物溶液を得た。この溶液の性状を表２に示した。
【０１０４】
〔参考例１２〕
４，４′−メチレンビス（シクロヘキシルイソシアネート）２２８．６部をトルエン１６０．０部及びシクロヘキサノン１６０．０部に溶解し、メチルエチルケトキシム１２６．５部を約１時間で滴下する。滴下終了後更に１時間７５〜８０℃に加熱する。次に１，１，３，３−テトラｎ−ブチル−１，３−ジアセトキシジスタノキサン０．４８部とポリエステルポリオール（参考例８に用いたポリエステルポリオールと同じ）１２３．９２部を加え７５〜８０℃で８時間反応させる。かくして再生イソシアネート基含量７．６％、固形分６０％のブロック化物溶液を得た。この溶液の性状を表２に示した。
【０１０５】
〔参考例１３〕
２リットルの４つ口フラスコに撹拌機、温度計、窒素ガス導入管、還流冷却用コンデンサーを取り付け、ＴＭＰとα，α，α′，α′−テトラメチルメタキシリレンジイソシアネートとの付加体（室温で固形状物、イソシアネート含量１３．３％）を５００部、酢酸エチル４２７．１部及び１，１，３，３−テトラｎ−ブチル−１，３−ジアセトキシジスタノキサン０．１９部を仕込み、窒素ガス雰囲気下で、内温６０〜７０℃を保つようにメチルエチルケトキシムの１４０．５部を徐々に滴下してゆき、添加完了後、約４時間上記温度に保つと、固形分６０％、再生イソシアネート基含量６．２０％のブロック化物溶液を得た。この溶液の性状を表２に示した。
【０１０６】
〔参考例１４〕
表３に示す成分を混合することにより防錆剤１４ａ〜１４ｄを得た。
【０１０７】
〔参考例１５〕
表４に示す成分を、併せて表４に示す条件で焼成、冷却、粉砕することにより防錆剤１５ａ〜１５ｉを得た。
【０１０８】
〔参考例１６〕
表５に示す成分を、併せて表５に示す条件で焼成、冷却、粉砕することにより防錆剤１６ａ〜１６ｅを得た。
【０１０９】
〔参考例１７〕
表６に示す成分を混合したあと、１４０℃で溶融し、冷却、粉砕することにより防錆剤１７ａ〜１７ｄを得た。
【０１１０】
〔実施例１〜５７、比較例１〜３９〕
亜鉛めっき付着量が片面当たり２０ｇ／ｍ² で両面がめっきされた厚み０．６ｍｍの電気亜鉛めっき鋼板（下記の表中では「ＥＧ」と表記）と、亜鉛めっき付着量が片面当たり６０ｇ／ｍ² で両面がめっきされた厚み０．６ｍｍの溶融亜鉛めっき鋼板（下記の表中では「ＧＩ」と表記）とを、ＦＣ−３６４Ｓ（日本パーカライジング社製）の２重量％濃度の６０℃の水溶液中に１０秒間浸漬することで脱脂を行い、水洗後、乾燥した。次いで、表７〜９に示す組成（各成分の含有量は重量部数で表される）の下地処理剤をメッキ鋼板にロールコーターにて塗布し、熱風乾燥炉で乾燥し、そして板を水冷して、表７〜９に示した付着量の下地処理層を形成した。乾燥時の到達板温は１５０℃とした。なお、乾燥時の到達板温を７０℃、２２０℃として同様の評価をしたが、いずれも到達板温が１５０℃の場合と同じ塗膜（下地処理層）が得られた。
【０１１１】
下地処理層に用いた水性樹脂のアクリルオレフィンは、東亜合成社製「ＡＰ−１０５８（１２）」及び東邦化学社製「ハイテックＳ−７０２４」の混合物、ウレタンは旭電化社製「ボンタイターＨＵＸ−３２０」、エポキシは昭和高分子社製「ポリゾール８５００」であった。タンニン酸としては、「タンニン酸ＡＬ」（富士化学工業社製）、「ＢＲＥＷＴＡＮ」（オムニケム社製）、及び「ＴＡＮＡＬ１」（オムニケム社製）を使用した。微粒シリカとしては、日産化学工業社製の「スノーテックスＮ」（下記の表中では「ＳＴ−Ｎ」と表記）と「スノーテックスＮＳ」（下記の表中では「ＳＴ−ＮＳ」と表記）を使用した下地処理層用塗料の塗布には、水を溶媒とする固形分２０％の溶液を使用した。
【０１１２】
下塗り層については、第１０〜１２に示すポリオール及びブロック化物（表中の「ポリオール」と「ブロック化物」の欄中の各数字は、各ポリオール及びブロック化物を調製した参考例の番号を示している）をＮＣＯ／ＯＨ当量比が１．０となるように仕込み、次いで表１０〜１２に示す防錆剤のリン化合物とバナジウム化合物との混合物（表中の「防錆剤」の欄中の各符号は、表３〜６にまとめて掲げられた防錆剤の符号を示している）を１２．０部仕込み、更に触媒として１，１，３，３−テトラｎ−ブチル−１，３−ジアセトキシジスタノキサン０．０３部を添加してペイントコンディショナーにより十分混練し、プレコート金属板プライマー用エナメル溶液を得た。このように、この溶液（下塗り層形成用溶液）は、成膜性樹脂としてポリオールとブロック化物とによって形成される樹脂を含むとともに、非クロム系防錆剤を含む。
【０１１３】
こうして調製した溶液を、下地処理層を形成した鋼板の両面に、乾燥膜厚にして５μｍとなるようにバーコーターで塗布し、熱風オーブンで到達板温２１０℃、到達時間４５秒間の条件で焼き付け、そして水冷して下塗り層を形成した。
【０１１４】
なお、比較例の一部においては、表１２から明らかなように、ポリオールとブロック化物とから形成される樹脂以外のもの、あるいは表３〜６に示した以外の各種防錆剤を使用した。すなわち、下塗り層の比較樹脂としては、メラミンアルキド樹脂（日本ペイント社製オルガセレクト１００）、及びエポキシナイロン樹脂（東亜合成社製ＦＳ７５ＳＺ改）を使用した。また、下塗り層の比較防錆剤として、ストロンチウムクロメート、第２リン酸マグネシウム、２ＣａＯ・Ｖ₂ Ｏ₅ 焼成物、Ｍｎ₂ Ｏ₃ ・Ｖ₂ Ｏ₅ 焼成物を使用した。
【０１１５】
続いて、形成した下塗り層の上に、日本ペイント社製ＦＬ１００ＨＱ（ポリエステル樹脂系、色は白）を塗布し、熱風を吹き込んだ誘導加熱炉で到達板温が２２０℃となるように硬化乾燥させ、そして板を水冷して、上層皮膜層を形成した。反対面（裏面）はすべて、メラミンアルキド系塗料を、乾燥膜厚にして７μｍとなるようバーコーターにて塗布し、到達板温２３０℃、到達時間４５秒間の条件で焼き付けた。
【０１１６】
下塗り層と上層皮膜層で用いた塗料と形成した塗膜の膜厚は、表１０〜１２に要約して示される。
【０１１７】
このようにして作製したプレコート鋼板について以下の評価を行った。なお、各評価は表側（着色皮膜層を形成した側）で行った。
１．塗膜密着性
塗装後の板を、塗装面に１ｍｍ角の碁盤目をカッターナイフで入れ、塗装面が凸となるようにエリクセン試験機で７ｍｍ押し出した後に、テープ剥離試験を行った。碁盤目の入れ方、エリクセンの押し出し方法、テープ剥離の方法についてはＪＩＳ−Ｋ５４００．８．２、及びＪＩＳ−Ｋ５４００．８．５記載の方法に準じて実施した。また、テープ剥離後の評価はＪＩＳ−Ｋ５４００．８．５記載の評価の例の図によって行い、評点１０点のときに○、９点のときに○−、６点以上９点未満のときに△、６点未満の時に×と評価した。更に、ＪＩＳ−Ｋ５４００．８．２０記載に従い、プレコート鋼板を沸騰水に浸漬した後、取り出して２４時間放置後に前述の方法で碁盤目エリクセン、テープ剥離を実施し、同様に評価した。
【０１１８】
２．折り曲げ加工性試験
塗装後の板を１８０°折り曲げ加工後に、加工部の塗膜を１０倍ルーペで観察し、塗膜の割れの有無を調べた。また、加工部に粘着テープを貼り付け、これを勢い良く剥離したときの塗膜の残存状態を目視にて観察した。折り曲げ加工は２０℃雰囲気中で、０．６ｍｍのスペーサーを間に挟んで実施した。塗膜割れの評価は、塗膜割れのない時を○、塗膜に若干の割れがある時を△、塗膜に目視でも明確な割れのある時を×として評価した（塗膜割れ試験）。また、テープで剥離後の塗膜残存状態の評価は、全く剥離せずにめっき鋼板上に残存している場合を○、塗膜が一部剥離している場合を△、折り曲げ加工部のほぼ全面にわたって剥離が認められる場合を×と評価した。更に、ＪＩＳ−Ｋ５４００．８．２０記載に従い、塗装鋼板を沸騰水に浸漬した後、取り出して２４時間放置後に前述の折り曲げ加工を実施し、同様に塗膜の剥離と加工部のテープ剥離試験後の塗膜残存状態を評価した（テープ剥離試験）。
【０１１９】
３．耐食性
塗装後の板に対しＪＩＳ−Ｋ５４００．９．１記載の方法で塩水噴霧試験を実施した。試験時間は電気亜鉛めっき鋼板の場合には１２０時間、溶融亜鉛めっき鋼板の場合には２４０時間とした。クロスカット部の塗膜の評価方法は、クロスカット片側の最大膨れ幅が１ｍｍ未満の場合に○、１ｍｍ以上２ｍｍ未満の場合に○−、２ｍｍ以上３ｍｍ未満の場合に△、３ｍｍ以上の場合に×と評価した。また、切断時の返り（バリ）が塗装鋼板の評価面側にくるように（上バリとなるように）作製した平板についても、前述の塩水噴霧試験を実施し、端面からの塗膜の膨れ幅を観察した。端面部の評価方法は端面からの膨れ幅が３ｍｍ以内の場合には○、３ｍｍ以上４ｍｍ未満の場合には○−、４ｍｍ以上５ｍｍ未満の場合には△、５ｍｍ以上の場合には×と評価した。
【０１２０】
４．毒性
毒性については、クロムを含有しているものを「有り」、クロム未使用のものを「低毒性」（下記の表では「−」で表示される）とした。
【０１２１】
評価結果を表１３〜１５に示す。本発明によるプレコート金属板（実施例１〜５７）の塗膜密着性、折り曲げ加工性（塗膜割れ試験）、折り曲げ加工密着性（テープ剥離試験）、耐食性は、比較例の下地処理も下塗り層もクロメート系のプレコート鋼板（比較例３７〜３９）と比べてほぼ同等以上の性能を有している。
【０１２２】
これに対し、下地処理層のタンニン酸含有量が少なすぎる場合（比較例２４、２５）及び、下地処理層の付着量が少なすぎる場合（比較例２８、２９）は、耐食性に大きく劣り、不適である。逆に、下地処理層の付着量が多すぎる場合（比較例３０、３１）は塗膜の密着性が低下し、ひいては耐食性が低下して、やはり不適である。また、下塗り層の膜厚が厚すぎる場合（比較例３２、３３）は、折り曲げ加工性が大きく劣り、不適である。なお、比較例３４〜３９については環境上有毒であるクロムを使用しているため、これも不適である。
【０１２３】
一方、比較例１〜１６では、下塗り層の樹脂としては本発明のものを使用しているが、防錆剤として適切なものを使用していないため、何らかの問題が生じている。すなわち、比較例１〜９及び１３はバナジン酸イオン源のみ含有し、比較例１０、１４はリン酸イオン源のみ含有するために、十分な耐食性が得られていない。比較例１１、１５は、ストロンチウムクロメートを使用しているために、耐食性には優れるが、毒性がある。比較例１２、１６は、防錆剤を添加していないので、耐食性が得られていない。
【０１２４】
更に、比較例１７と１８は、下塗り層の防錆剤としては本発明のものを使用しているが、樹脂として適切なものを使用していないため、耐食性に劣る。比較例１９〜２３は、下塗り層の樹脂、防錆剤ともに適当でなく、耐食性あるいは毒性に問題が生じている。
【０１２５】
【表１】

【０１２６】
【表２】

【０１２７】
【表３】

【０１２８】
【表４】

【０１２９】
【表５】

【０１３０】
【表６】

【０１３１】
【表７】

【０１３２】
【表８】

【０１３３】
【表９】

【０１３４】
【表１０】

【０１３５】
【表１１】

【０１３６】
【表１２】

【０１３７】
【表１３】

【０１３８】
【表１４】

【０１３９】
【表１５】

【０１４０】
【発明の効果】
以上の説明から明らかなように、本発明のプレコート金属板は、環境上有毒であるクロムを使用せずに、塗膜の密着性、耐食性に優れているとともに、塗膜の加工性にも優れたものである。従って、本発明によって、人の手に触れたり、食品が接触する可能性のある家電製品などに有利に用いることができる工業的価値の極めて高いプレコート金属板の提供が可能となった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly corrosion-resistant pre-coated metal plate used for home appliances, building materials, and the like, and more specifically, relates to a highly corrosion-resistant pre-coated metal plate provided with a coating film containing no toxic chromium.
[0002]
[Prior art]
For example, steel sheets for home appliances, building materials, automobiles, etc. will use pre-coated steel sheets pre-coated with a colored organic coating instead of the conventional post-painted products that have been painted after the steel sheet is formed. It has become. This pre-coated steel sheet is obtained by coating an organic colored film on a steel sheet or plated steel sheet that has been subjected to rust prevention treatment, and has the characteristics of having good workability and good corrosion resistance while having an aesthetic appearance. .
[0003]
For example, Japanese Patent Application Laid-Open No. 8-168723 discloses a technique for obtaining a precoated steel sheet having excellent workability, contamination resistance, and hardness by defining the structure of the film. Japanese Patent Application Laid-Open No. 3-100180 discloses a precoated steel sheet having improved end face corrosion resistance by using a specific chromate treatment solution. These pre-coated steel sheets have corrosion resistance, workability, and paint adhesion due to the combined effect of the plating film, chromate-treated film, and chrome-based anticorrosive pigment, and the coating after processing is omitted. The purpose is to improve productivity and quality.
[0004]
As described above, since the precoated steel sheet is required to have corrosion resistance, at present, the primer mainly contains a chromium-based rust preventive pigment and is subjected to a chromate treatment as a primer undercoat. The hexavalent chromium contained in the chromate-treated film and the chromium-based pigment has a water bath property, and when it is eluted, it has a property of repairing scratches on the film generated on the film. Therefore, especially in rust-proofing applications for zinc-based plated steel sheets, chromate-treated films have been used exclusively as corrosion-resistant films. The chromate treatment also has the effect of increasing the adhesion of the primer to the underlying steel plate.
[0005]
However, due to the toxicity problem of hexavalent chromium that can be eluted from the chromate-treated film and the organic film containing the chromium-based rust-preventive pigment, recently there has been a growing demand for non-chromium rust-proof treatment and non-chromium organic film.
[0006]
On the other hand, as disclosed in JP-A-52-43830, JP-A-52-128979, JP-A-56-80454, JP-A-56-113383, etc. Primers containing molybdate, phosphate, barium metaborate and the like have been reported as pollution-free paints.
[0007]
In addition, as disclosed in JP-A-5-84466, etc., there is also a method of applying a primer containing a phosphate-based rust preventive pigment and silica after iron-based plating is applied to the original plate.
[0008]
[Problems to be solved by the invention]
However, even when molybdate, phosphate, barium metaborate, or the like is included in the primer layer, the corrosion resistance is not comparable to that containing a chromium-based anticorrosive pigment. Further, the method of applying a phosphate-based anticorrosive pigment and a primer containing silica after applying iron-based plating to the original plate has the complexity of applying iron-based plating.
[0009]
Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a pre-coated metal plate including a non-chromium pre-coated steel plate having excellent adhesion and corrosion resistance and low toxicity.
[0010]
[Means for Solving the Problems]
  The high corrosion resistance pre-coated metal plate of the present invention has a coating layer containing an organic resin and tannin or tannic acid as a base treatment layer on at least one side of the metal plate, and on this base treatment layer,
  (A) (1)HydroxylA polyester polyol having at least 3 functional groups, (2) an epoxy resin having at least one secondary hydroxyl group added with a lactone compound or an alkylene oxide, and (3) a blocked product of organic polyisocyanate or organic polyisocyanate; An organic resin obtained from a film-forming resin raw material containing a prepolymer blocked product having an NCO group at the end obtained by reaction with an active hydrogen compound, and
  (B) a phosphate ion source that releases phosphate ions in an environment where water and oxygen are present; and a vanadate ion source that releases vanadate ions in an environment where water and oxygen are present;
A coating layer containing a primer layer, and a colored coating layer as an upper coating layer on the primer layer.And
  The phosphate ion source includes orthophosphoric acid, condensed phosphoric acid, orthophosphoric acid metal salts including monohydrogen salts and dihydrogen salts, condensed metal phosphates including hydrogen salts, metaphosphates, polyphosphates and polymetaphosphates. Salt, phosphorus pentoxide, monetite, tolufilite, witrockite, xenotime, starcolite, struvite, orbite, polyphosphate silica, pyrophosphate, metaphosphate, tetrametaphosphate, hexametaphosphate, pyrophosphate Selected from the group consisting of acid pyrophosphate, tripolyphosphate, and mixtures thereof, and the metal species in the metal orthophosphate and metal phosphate are magnesium, calcium, strontium, barium, titanium, zirconium, manganese, iron, Selected from cobalt, nickel, zinc, aluminum, lead and tin, the above metaphosphoric acid , Tetrametaphosphoric acid salts, hexametaphosphate, pyrophosphate, cationic acidic pyrophosphate and tripolyphosphate, the metal species, vanadyl, selected from titanyl and zirconyl cation,
  The vanadate ion source includes vanadium (II), vanadium (III), vanadium (IV) or vanadium (V) oxide, hydroxide, vanadate, vanadyl halide, halide and sulfate, and vanadium. Selected from metal powder, the vanadate is orthovanadate, metavanadate, pyrovanadate or a mixture thereof, and the metal species in the vanadate and sulfate are magnesium, calcium, strontium, barium, Selected from titanium, zirconium, manganese, iron, cobalt, nickel, zinc, aluminum, lead and tin,
It is characterized by that.
[0011]
The base treatment layer preferably contains 0.2 to 50 parts by weight of tannin or tannic acid with respect to 100 parts by weight of the organic resin as a solid content.
[0012]
When 10 to 500 parts by weight of fine silica is contained in the ground treatment layer as a solid content, the rust prevention action (corrosion resistance) is further promoted.
[0013]
In the coating layer of the undercoat layer, the phosphate ion source and the vanadate ion source are combined in an amount of 0.1 to 50 parts by weight with respect to 100 parts by weight of the total solid content.
[0014]
  The phosphate ion source and vanadate ion source of the undercoat layer may be rust preventive pigments. Further, as the rust preventive pigment, a mixture containing a phosphorus compound and a vanadium compound is calcined and pulverized, or in addition to the phosphorus compound and the vanadium compound, it contains at least one of a network-modifying ion source and a glassy material as necessary. Baked and pulverized mixture,SaidPhosphate ionsourceas well asSaidVanadate ionsourceCan be used.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
As the metal plate used for the pre-coated metal plate of the present invention, various metal plates (including plated metal plates) can be used. Typical examples are hot-rolled steel plates, cold-rolled steel plates, and electrogalvanized plates. Steel plate, hot dip galvanized steel plate, alloyed hot dip galvanized steel plate, zinc alloy plated steel plate, aluminum plated steel plate, chrome plated steel plate, nickel plated steel plate, copper plated steel plate, etc., stainless steel plate, aluminum plate, copper plate, aluminum alloy A known metal plate such as a plate can be applied. This metal plate can be subjected to ordinary treatments such as washing with water and alkaline degreasing before the base treatment.
[0016]
The base treatment layer used for the precoated metal sheet of the present invention is characterized by containing tannin or tannic acid based on an organic resin. This organic resin is obtained by curing or cross-linking the aqueous resin by applying a rust preventive coating agent comprising a composition containing an aqueous resin and tannin or tannic acid in water to the base metal material and then drying. The water-based resin here includes, in addition to water-soluble resins, water-insoluble resins (water-dispersible resins) that are insoluble in water but can be in a state in which insoluble resins are finely dispersed in water, such as emulsions and suspensions. . Examples of the resin that can be used as the aqueous resin include polyolefin resins, acrylic olefin resins, polyurethane resins, polycarbonate resins, epoxy resins, polyester resins, alkyd resins, phenol resins, and other heat resins. A curable resin can be exemplified, and a crosslinkable resin is more preferable. Two or more of these aqueous resins may be mixed or polymerized for use. Particularly preferred resins are acrylic olefin resins, polyurethane resins, and mixed resins thereof.
[0017]
Tannin or tannic acid exhibits a binder effect between the surface of the original metal plate and the film layer formed on it in the presence of an organic resin, dramatically improving the adhesion of the film and thus improving the corrosion resistance. Let The tannin or tannic acid is not particularly limited, and may be Hamametatannin, pentaploid tannin, gallic tannin, Milobatan tannin, dibibi tannin, Argarobila tannin, Valonia tannin, catechin tannin, and the like. Commercially available products such as “tannic acid: AL” (manufactured by Fuji Chemical Industry Co., Ltd.) can be used.
[0018]
The content of tannin or tannic acid is preferably 0.2 to 50 parts by weight in terms of solid content with respect to 100 parts by weight of the organic resin. If the amount is less than 0.2 parts by weight, the adhesion of the coating film and the rust prevention effect are not ensured. If the amount exceeds 50 parts by weight, the rust prevention effect is lowered, or the resin gels in the state of the coating solution. May occur.
[0019]
When fine silica is further added to the ground treatment layer, the rust prevention effect (corrosion resistance) is further promoted. Moreover, in addition to corrosion resistance, drying, scratch resistance, and coating film adhesion are also improved.
[0020]
In the present invention, the fine silica is a general term for silica having such a characteristic that when it is dispersed in water, it has a fine particle size and can stably maintain a water dispersion state and does not allow semipermanent sedimentation. It is. The fine silica is not particularly limited as long as it has few impurities such as sodium and is weakly alkaline. For example, commercially available silica such as “Snowtex N” (manufactured by Nissan Chemical Industries, Ltd.) and “Adelite AT-20N” (manufactured by Asahi Denka Kogyo Co., Ltd.) can be used.
[0021]
The content of fine silica is preferably 10 to 500 parts by weight with respect to 100 parts by weight of the aqueous resin in terms of solid content. If it is less than 10 parts by weight, the effect of addition is small, and if it exceeds 500 parts by weight, the effect of improving the corrosion resistance is saturated, which is uneconomical. A more preferable content of fine silica is 10 to 400 parts by weight.
[0022]
In addition to this, the base treatment layer may contain other components as necessary. Examples of such components include pigments, surfactants, rust inhibitors, and foaming agents.
[0023]
Examples of the pigment include titanium oxide (TiO₂), Zinc oxide (ZnO), zirconium oxide (ZrO), calcium carbonate (CaCO)_Three), Barium sulfate (BaSO)_Four), Alumina (Al₂O_Three), Kaolin clay, carbon black, iron oxide (Fe₂O_Three, Fe_ThreeO_FourInorganic pigments such as) and various colored pigments such as organic pigments can be used.
[0024]
Moreover, you may mix | blend a silane coupling agent with a base-treatment layer in order to further improve coating-film adhesiveness. Examples of the silane coupling agent include γ-aminopropyltrimethoxysilane, γ-aminopropylethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylsilane, N- [2- (vinylbenzyl). Amino) ethyl] -3-aminopropyltrimethoxysilane and the like.
[0025]
In order to form a base treatment layer on a metal plate, a base treatment agent (coating agent) containing the above components in water is prepared, applied to a metal material, and the coating film is heated and dried. When the resin is crosslinkable or curable, it is crosslinked and cured by this heating. As heating temperature, 50-250 degreeC is good. If it is less than 50 ° C., the evaporation rate of water is slow and sufficient film forming properties cannot be obtained, so that the rust prevention power is insufficient. If it exceeds 250 ° C., thermal decomposition of the aqueous resin occurs, so that there is a problem that the SST property and water resistance are lowered and the appearance is also yellowed. The heating temperature is more preferably 70 to 160 ° C. In hot air drying, a drying time of 1 second to 5 minutes is preferable.
[0026]
The amount of adhesion of the ground treatment layer after drying is 10 mg / m²The above is preferable. 10 mg / m²If it is less than 1, the rust preventive power is insufficient. On the other hand, if the amount of adhesion is too large, it is not only uneconomical for the base treatment layer, but also the coating film adhesion is lowered. The upper limit of the film thickness is 3000 mg / m²The following is good.
[0027]
The method for applying the ground treatment layer is not particularly limited, and generally known coating methods such as roll coating, air spray, airless spray, and immersion can be employed.
[0028]
The drying and baking of the ground treatment layer may be performed by a known method such as a hot air furnace, an induction heating furnace, a near infrared furnace, or a combination thereof. Further, depending on the type of aqueous resin to be used, it can be cured by energy rays such as ultraviolet rays and electron beams. Alternatively, natural drying may be performed without using these forced dryings, or the metal plate may be preheated in advance, and may be naturally dried after being applied to the metal plate.
[0029]
The undercoat layer used for the precoated metal sheet of the present invention is also called a primer layer. The undercoat layer in the present invention is formed from an undercoat paint having a low toxicity and excellent corrosion resistance, characterized by containing a phosphate ion source and a vanadate ion source as a non-chromium-based rust preventive agent, based on an organic resin. The RTECS (a collection of chemical toxicity data by public authorities in the United States) states that vanadium pentoxide and phosphate are lower than chromic acid in both acute and chronic toxicity.
[0030]
The organic resin for the undercoat layer is a film-forming resin raw material for a paint applied to a metal plate, (1) a polyester polyol having at least 3 functional groups, and (2) an epoxy resin having at least one secondary hydroxyl group. A compound or an alkylene oxide added, and (3) a block product of an organic polyisocyanate or a block product of a prepolymer having an NCO group at the terminal obtained by a reaction between an organic polyisocyanate and an active hydrogen compound.
[0031]
The precoat metal plate is required to have high workability because the coating film is processed together with the metal. In the present invention, a polyester polyol having at least 3 functional groups, an epoxy resin having at least one secondary hydroxyl group added with a lactone compound or an alkylene oxide, and a blocked product of organic polyisocyanate or organic polyisocyanate And a block product of an active hydrogen compound are used in combination to obtain a coating film having good bending resistance, high hardness, and excellent chemical resistance and stain resistance.
[0032]
The polyester polyol (1) having at least 3 functional groups used in the resin used in the present invention can be obtained by esterifying a dicarboxylic acid, glycol, and a polyol having at least 3 OH groups.
[0033]
Examples of the dicarboxylic acid used for producing the polyester polyol include succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, dimer acid, and the like. Aliphatic systems such as phthalic acid, phthalic anhydride, isophthalic acid, isophthalic acid dimethyl ester, terephthalic acid, terephthalic acid dimethyl ester, 2,6-naphthalenedicarboxylic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, cyclohexanedicarboxylic acid And aromatic and alicyclic ones such as cyclohexanedicarboxylic acid dimethyl ester, methylhexahydrophthalic anhydride, hymic anhydride, and methylhymic anhydride.
[0034]
Examples of the glycol include ethylene glycol, diethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, dipropylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, hydroxy Neopentyl glycol ester of bivalic acid, triethylene glycol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl- 1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, polycaprolactone diol, polypropylene glycol, polytetramethylene ether glycol, polycarbonate diol, 2-n-butyl-2-ethyl-1 Aliphatic compounds such as 3-propanediol and 2,2-diethyl-1,3-propanediol, such as cyclohexanedimethanol, cyclohexanediol, 2-methyl-1,1-cyclohexanedimethanol, xylylene glycol, bis Aliphatic or aromatic compounds such as hydroxyethyl terephthalate, 1,4-bis (2-hydroxyethoxy) benzene, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct It is done.
[0035]
Examples of the polyol having at least three OH groups include glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, pentaerythritol, diglycerin, and ethylene oxide adducts using these polyols as initiators. And propion oxide adducts or ε-caprolactone adducts.
[0036]
The above esterification reaction is carried out by charging an excess polyol component from the acid component and distilling off the condensate by a usual method. However, since the product is polyfunctional, gelation occurs if the reaction is advanced too much. Therefore, it is usually preferable to stop at an acid value of 0.1 to 50, particularly 1 to 20. As a specific production method, for example, dicarboxylic acid is charged in excess of the number of moles of glycol, condensed water is distilled off while blowing nitrogen gas at a temperature of 180 to 260 ° C., and the reaction is carried out to a predetermined acid value. A polyester product having COOH groups at both ends is obtained, and then a polyol having at least three OH groups is charged so that the end of the polyester product becomes an OH group. Is 50 or less, preferably in the range of 1-20. Also, when using a dimethyl ester of dicarboxylic acid, charge more than the number of moles of glycol and distill off the condensate under the same conditions as above to obtain a polyester product having methyl ester groups at both ends, then at least 3 A polyol having an OH group is charged and subjected to a transesterification reaction under the same conditions as described above to obtain a polyester polyol.
[0037]
In the case of using an acid anhydride in combination, first, dicarboxylic acid is charged in less than the number of moles of glycol, and the condensate is distilled off under the same conditions as above to obtain a polyester product having OH groups at both ends, and then dicarboxylic acid. An anhydride is added, and a polyesterification product having COOH groups at both ends is obtained by this ring-opening reaction. Next, a polyol having at least three OH groups is charged, and the reaction is performed in the same manner as described above to obtain a polyester. The method of obtaining a polyol is mention | raise | lifted. The polyester polyol used in the present invention is particularly preferably one having a functional group number of 3 to 7, particularly 4 to 6, a number average molecular weight of 600 to 3500, and a hydroxyl value of 80 to 460. When the number of functional groups is less than three, the hardness of the cured coating film is lowered and the chemical resistance is deteriorated. On the other hand, if it exceeds 7 functionalities, the bending resistance of the coating film may deteriorate. When the number average molecular weight is less than 600, the gloss of the cured coating film is deteriorated, and when it exceeds 3500, the viscosity becomes high, which may cause a problem in coating workability and may deteriorate the stain resistance. When the hydroxyl value is less than 80, the chemical resistance and stain resistance of the cured coating film may be deteriorated. Moreover, when the hydroxyl value exceeds 460, the bending resistance of the coating film may deteriorate.
[0038]
The epoxy resin having at least one secondary hydroxyl group (2), which is the other component of the polyol component used in the present invention, is added with a lactone compound or alkylene oxide, and is represented by the following general formula. Examples thereof include those obtained by adding a lactone compound or alkylene oxide to an epoxy resin by means known per se.
[0039]
[Chemical 1]

[0040]
(In the formula, X represents a phenylene group or a cyclohexylene group which may be substituted with halogen, and n is 0.5 to 12.0.)
[0041]
The addition amount of the lactone compound or alkylene oxide is about 5 to 40 parts by weight with respect to about 95 to 60 parts by weight of the epoxy resin. In particular, the lactone compound or alkylene oxide is preferably about 10 to 30 parts by weight with respect to about 90 to 70 parts by weight of the epoxy resin.
[0042]
Among the epoxy resins represented by the above general formula, those in which X is a p-phenylene group and n is 2 to 9 are preferable. Examples of the halogen include bromine and chlorine. The number of the substituents is usually about 1 to 3, and the position may be any position of the phenylene group or the cyclohexylene group.
[0043]
Examples of the lactone compound include β-propiolactone, butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone, among which ε-caprolactone is particularly preferable. preferable. Examples of the alkylene oxide include ethylene oxide, propylene oxide, styrene oxide, glycidyl methacrylate, and epichlorohydrin, and ethylene oxide is particularly preferable.
[0044]
The blending ratio of the epoxy resin having at least one secondary hydroxyl group added with a lactone compound or alkylene oxide is about 10 to 70% by weight, particularly about 10 to 60% by weight in the polyol component. It is preferable to use within a range. When the blending ratio is less than 10% by weight, among the stain resistance, the stain resistance is particularly bad and the stain resistance may be deteriorated. On the other hand, if it exceeds 70% by weight, the rust resistance and stain resistance are improved, but the hardness may be extremely lowered.
[0045]
Examples of the blocked product (3) used in the resin used in the present invention include compounds having at least two NCO groups such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2- Propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, 2,6-diisocyanate methyl caproate Aliphatic diisocyanates such as 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl 3,5,5-trimethylcyclohexyl isocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, trans-cyclohexane-1,4-diisocyanate and other cycloalkylene diisocyanates such as m-phenylene diisocyanate, p- Phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4- or 2,6-to Aromatic diisocyanates such as diisocyanate, 4,4′-toluidine diisocyanate, dianisidine isocyanate, 4,4′-diphenyl ether diisocyanate, for example, ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate -1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene, α, α, α ′, α′-tetramethylmetaxylylene diisocyanate, α, α, α ′, α′-tetramethyl Araliphatic diisocyanates such as paraxylylene diisocyanate, for example triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatebenzene, 2,4,6-triisocyanate toluene, ω- Isocyanatoethyl-2,6-diiso Triisocyanates such as cyanate caproate, blocked products of tetraisocyanates such as 4,4′-diphenyldimethylmethane-2,2 ′, 5,5′-tetraisocyanate, dimers, trimers, burettes, allophanates, Blocked derivatives of isocyanate compounds such as carbodiimide, polymethylene polyphenyl polyisocyanate (crude MDI, c-MDI, polymeric MDI), crude TDI, or NCO at the end obtained by reaction of these with active hydrogen compounds Examples thereof include a blocked product of a prepolymer having a group.
[0046]
When used as a pre-coated metal plate, weather resistance is required. Therefore, among the above-mentioned compounds having an NCO group, hexamethylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,4-bis Isocyanate compounds such as (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 4,4′-methylenebis (cyclohexyl isocyanate), α, α, α ′, α′-tetramethylmetaxylylene diisocyanate Is preferably used.
[0047]
The prepolymer having an NCO group at the terminal obtained by the reaction of these isocyanate compound and active hydrogen compound can be obtained by reacting the isocyanate monomer with an active hydrogen compound in an excess of isocyanate groups. Examples of active hydrogen compounds used to produce this prepolymer include ethylene glycol, propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, Dihydric alcohols such as neopentyl glycol, neopentyl glycol hydroxybivalate, triethylene glycol, hydrogenated bisphenol A, xylylene glycol, 1,4-butylene glycol, such as glycerin, trimethylolethane, trimethylolpropane, 1 Low molecular weight polyols such as trihydric alcohols such as 1,2,6-hexanetriol, tetrahydric alcohols such as pentaerythritol, propylene oxide of the above polyols or the like Examples include polyether polyols such as tylene oxide adducts, polyester polyols obtained by reacting the aforementioned low molecular weight polyols with dicarboxylic acids, and high molecular weight polyols such as those modified with fatty acids when these polyester polyols are produced. It is done. These polyols may be used alone or in combination.
[0048]
The prepolymer generally has an NCO group / OH group equivalent ratio of about 2.0 to 15, preferably about 4 to 8, and usually after reaction at 40 to 140 ° C., preferably 70 to 100 ° C. Then, it can be obtained by removing the unreacted isocyanate monomer by a thin film distillation method or an extraction method which is usually performed. In this reaction, an organometallic catalyst such as tin, lead, zinc, or iron may be used.
[0049]
The aforementioned isocyanate monomers or their prepolymers are blocked by reacting the isocyanate monomers or their prepolymers with a blocking agent by a known method. As a blocking agent used in this reaction, a blocking agent known to be used for blocking of isocyanate, for example, phenol, lactam, active methylene, alcohol, mercaptan, acid amide, imide Any blocking agent such as amine, imidazole, urea, carbamate, imine, oxime, or sulfite can be used, especially phenol, oxime, lactam, imine, etc. These blocking agents are advantageously used. Specific examples of the blocking agent include the following.
[0050]
Phenol-based blocking agent: phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, p-hydroxydiphenyl, t-butylphenol, o-isopropylphenol, o-sec-butylphenol, p-nonylphenol, pt-octylphenol, Hydroxybenzoic acid, hydroxybenzoic acid ester and the like.
[0051]
Lactam blocking agents: ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam and the like.
[0052]
Active methylene blocking agent: diethyl malonate, dimethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone and the like.
[0053]
Alcohol-based blocking agent: methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol Glycolic acid esters such as monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, distyrene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol, methoxymethanol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate Lactic acid esters such as lactic acid, methyl lactate, ethyl lactate, butyl lactate, Lumpur urea, methylol melamine, diacetone alcohol, ethylene chlorohydrin, ethylene epibromohydrin, 1,3-dichloro-2-propanol, .omega. hydro perfluoro alcohol, aceto cyanohydrin.
[0054]
Mercaptan-based blocking agents: butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol and the like.
[0055]
Acid amide blocking agent: Acetanilide, acetanisidide, acetolide, acrylamide, methacrylamide, acetic acid amide, stearic acid amide, benzamide and the like.
[0056]
Imide-based blocking agent: Succinimide, phthalic imide, maleic imide and the like.
[0057]
Amine-based blocking agents: diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine and the like.
[0058]
Imidazole-based blocking agents: imidazole, 2-ethylimidazole and the like.
[0059]
Urea-based blocking agent: urea, thiourea, ethylene urea, ethylene thiourea, 1,3-diphenyl urea, and the like.
[0060]
Carbamate block agent: phenyl N-phenylcarbamate, 2-oxazolidone and the like.
[0061]
Imine block agent: Ethyleneimine, propyleneimine, etc.
[0062]
Oxime-based blocking agents: formamidoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexanone oxime, etc.
[0063]
Sulphite blocking agent: sodium bisulfite, potassium bisulfite, etc.
[0064]
Specific examples of the reaction of the aforementioned isocyanate monomer or their prepolymer with a blocking agent include, for example, an isocyanate monomer or their prepolymer and a blocking agent with NCO groups / active hydrogen groups in the blocking agent. Equivalent ratio of about 0.9 to 1.0, preferably about 0.95 to 1.0, equivalent ratio of isocyanate monomer and blocking agent to NCO group / active hydrogen group in blocking agent = About 1.1 to 3.0, preferably about 1.2 to 2.0, and then reacted with a low molecular weight polyol, high molecular weight polyol, water or lower Method of reacting amine, or equivalent ratio of NCO group / active hydrogen group of isocyanate monomer and low molecular weight polyol, high molecular weight polyol, water or lower amine = approximately 1.6 to 0.0, preferably after reaction with about 2.0 to 7.0, to which a method of reacting a blocking agent. Each of the above reactions is carried out in a solvent having no active hydrogen group (for example, aromatic solvents such as benzene, toluene and xylene, petroleum solvents such as Solvesso-100 and Solvesso-200, ethyl acetate and butyl acetate). Ester solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, ether solvents such as tetrahydrofuran, etc.) or in the absence of such a solvent. In the reaction, for example, a known catalyst such as a tertiary amine or an organic metal may be used.
[0065]
The film-forming resin raw material used in the present invention is the aforementioned polyols (1) and (2) and the blocked product (3), and the mixing ratio of the polyol and the blocked product is such that the equivalent ratio of OH groups / regenerated NCO groups is about. 1/2 to 2/1, particularly 1 / 0.8 to 1 / 1.2 is preferable.
[0066]
Next, the non-chrome rust preventive used in the undercoat layer will be described. In the present invention, by containing a phosphate ion source and a vanadate ion source in the coating material forming the undercoat layer, an oxidizer function that is insufficient only by phosphate ions is compensated by vanadate ions. That is, the non-chromium-based rust preventive agent constituting the present invention contains a phosphate ion source that releases phosphate ions in an environment where water and oxygen are present, and vanadate ions in an environment where water and oxygen are present. Vanadate ion source to be released.
[0067]
In order to develop the rust preventive power of the undercoat layer of the present invention, phosphate ions and vanadate ions may be present in the undercoat layer, and phosphate ions and vanadate ions are present as they are in the paint forming the undercoat layer. Alternatively, the paint forming the undercoat layer may contain a substance that releases phosphate ions and vanadate ions in an environment where water and oxygen are present. Phosphate ions are rarely present alone in an aqueous solution and exist in various forms, such as condensates, but even in such cases, it is understood that they are included in the concept of “phosphate ions” in this specification. Is done. The vanadate ion is understood as a concept including a condensed vanadate ion. Phosphate ion source and vanadate ion source are mainly provided as anticorrosive pigments, by firing and pulverizing a mixture containing a phosphorus compound, a vanadium compound, and optionally a network-modifying ion source and / or a glassy substance. can get.
[0068]
Phosphorus compounds used for rust preventive pigments are orthophosphoric acid, condensed phosphoric acid, orthophosphates or condensed phosphates of various metals, phosphorus pentoxide, phosphate minerals, commercially available complex phosphate pigments, or these A mixture is mentioned. Some orthophosphates mentioned here include their monohydrogen salt (HPO)._Four ^2-Salt), dihydrogen salt (H₂PO_Four ^-Salt). In addition, hydrogen phosphate is included in the condensed phosphate. Further, the condensed phosphate includes metaphosphate, and includes ordinary polyphosphate and polymetaphosphate. Specific examples of the phosphorus compound include phosphate minerals such as monetite, tolufilite, witrockite, xenotime, starcolite, struvite, orbite, and commercially available complex phosphate pigments such as silica polyphosphate. Complex phosphates such as pyrophosphate, metaphosphate, complex phosphates such as metaphosphate, tetrametaphosphate, hexametaphosphate, pyrophosphate, acidic pyrophosphate, tripolyphosphate, or mixtures thereof Is mentioned. The metal species forming the phosphate is not particularly limited, and examples thereof include alkali metal, alkaline earth metal, metal species of other typical elements, and transition metals. Examples of preferable metal species include magnesium, calcium, strontium, barium, titanium, zirconium, manganese, iron, cobalt, nickel, zinc, aluminum, lead, tin and the like. In addition, oxo cations such as vanadyl, titanyl, zirconyl and the like are also included. Particularly preferred are calcium and magnesium. The use of a large amount of alkali metal is not preferred. When an alkali metal phosphate is used, the fired product tends to dissolve too much in water. However, when an alkali metal phosphate is used, it may be used if the solubility in water can be controlled at the time of production of the rust inhibitor or at other times. Such control includes various modes such as the use of a matrix material (particularly, a glassy substance) for preventing solubility in water, or coating.
[0069]
The vanadium compound used for the rust preventive pigment is a compound having any one or more of vanadium whose valence is 0, 2, 3, 4 or 5, and these oxides, hydroxides, various metals Examples include oxyacid salts, vanadyl compounds, halides, sulfates, and metal powders. These are decomposed by heating or in the presence of water and react with oxygen to be upgraded. For example, a metal powder or a divalent compound finally changes to a trivalent, tetravalent, or pentavalent compound. What contains a pentavalent vanadium compound as one component is preferable. Zero-valent vanadium metal powder, such as vanadium metal powder, can be used for the above reasons, but is not practically preferred because of problems such as insufficient oxidation reaction. The pentavalent vanadium compound has vanadate ions, and easily reacts with phosphate ions to form a heteropolymer. Specific examples of vanadium compounds include vanadium (II) compounds such as vanadium (II) oxide, vanadium (II) hydroxide, vanadium (III) compounds such as vanadium (III) oxide, vanadium (IV) compounds such as vanadium oxide. (IV), vanadyl halides, vanadium (V) compounds such as vanadium oxide (V), vanadates such as orthovanadates, metavanadates or pyrovanadates of various metals, vanadyl halides, etc., or These mixtures are mentioned. The metal species of vanadate are the same as those shown for phosphate. This may be made by firing a vanadium oxide and various metal oxides, hydroxides, carbonates or the like at 600 ° C. or higher. In this case as well, alkali metals are not so preferred because of their solubility, but their use can be used if the solubility is controlled by appropriate treatment as described for phosphate. The same applies to halides and sulfates.
[0070]
The blending amount of the phosphate ion source and vanadate ion source in the undercoat layer of the present invention is 0. The combined amount of both the phosphate ion source and vanadate ion source is 100 parts by weight of the total solid content of the undercoat layer. 1 to 50 parts by weight, preferably 0.5 to 20 parts by weight. If it is less than 0.1 part by weight, a sufficient rust preventive effect will not be exhibited, and if it exceeds 50 parts by weight, the cohesive strength of the cured coating film will be reduced, and sufficient coating film strength will not be obtained. The ratio of the phosphate ion source and vanadate ion source to be blended is P₂O_FiveAnd V₂O_FiveThe molar ratio is preferably 1: 3 to 100: 1.
[0071]
The network-modifying ions used in the rust-preventing pigment mean metal ion species added to modify the network structure formed by the fired product of the phosphorus compound and vanadium compound. Specifically, various metal ion species, Examples thereof include alkali metal ions, alkaline earth metal ions, metal ions of other typical elements, and transition metal ions. Examples of preferable network modifying ions include metal salts of phosphoric acid. Examples of the network-modifying ion source include oxides, hydroxides, carbonates, nitrates, organic acid salts, silicates, borates, sulfates, and chlorides of the above metal species, most preferably oxides. , Hydroxides and carbonates. When an alkali metal is used among the metal ion species, or when a sulfate or chloride is used as the ion source, these compounds tend to be excessively dissolved in water. Even in such a case, it is sufficient to control the solubility in water by taking appropriate measures as described above, for example, using a matrix material or coating particles. When using a network-modifying ion, the amount of the metal cation (M) of the rust inhibitor used in the undercoat layer is an oxide (MO, M) that M can take.₂O_Three, M_ThreeO_Four, MO₂Or M₂O) in the form of V₂O_FiveAnd P₂O_FiveIt is preferable to make it 3 times or less of the sum of the number of moles. The addition of the network-modifying ion source can be expected to increase the period of development of rust prevention, but if the molar ratio exceeds 3 times, the effect is saturated and it is uneconomical.
[0072]
The glassy substance used in the rust preventive pigment includes not only matrix-forming glasses such as silicate glass and borate glass, but also those containing metal elements such as network modifying ions. Such glassy substances are silica (quartz) glass, silicate glass, such as soda lime silicate glass, lead-silicate glass, aluminosilicate glass, borosilicate glass, lead-borate. Examples thereof include glass (commonly called solder glass), alumino-borophosphate glass, alumino-borate glass, and alumino-phosphate glass. Examples of preferred glassy materials include soda lime (C glass), for example, Japanese glass fiber glass flakes (CCF-150), aluminosilicate glass (E glass), for example, Japanese glass fiber glass flakes (CEF-150). ), Borosilicate glass, for example, Pyrex manufactured by Corning. A liquid having a conductivity of 500 μS / cm or less when 1 g of a fine powder of glassy material is dispersed and suspended in 100 ml of water is preferable. When it exceeds 500 μS / cm, the rust preventive ability decreases.
[0073]
When using a glass-like substance, it is preferable that the compounding quantity shall be 500-50000 weight part with respect to a total of 100 weight part of content of an organic resin, a phosphate ion source, and a vanadate ion source. If the amount is less than 500 parts by weight, it is not possible to expect further increase in the period during which the rust-preventing power is exhibited.
[0074]
A rust preventive pigment used in the present invention is obtained by firing a mixture of a phosphorus compound, a vanadium compound, and, if necessary, a glassy substance and a network-modifying ion source, followed by cooling and pulverization. If necessary, other inorganic substances such as a matrix material may be mixed in the mixture. Firing is performed at a temperature equal to or higher than the melting temperature (T1) of the fired product of the mixture composed of the above components, specifically 600 ° C or higher, preferably 1000 ° C or higher, more preferably the higher melting temperature of T1 and the glassy material. At a temperature higher than Below this temperature, the reaction becomes insufficient and the components remain in a simply mixed state. In such a case, the rust prevention performance of the undercoat layer is deteriorated. The compounding amount of the phosphorus compound and the vanadium compound is P₂O_Five/ V₂O_FiveThe molar ratio is 0.3 to 100, preferably 1 to 10. The amount of addition of the network modifying ion source is such that the amount of all metal cations (M) of the rust preventive used in the undercoat layer is an oxide that M can take (MO, M₂O_Three, M_ThreeO_Four, MO₂Or M₂O) in the form of V₂O_FiveAnd P₂O_FiveIt is added so as to be 3 times or less, preferably 0 to 2.0 times the sum of the number of moles. The form of oxide that M can take is M when M is a monovalent metal.₂MO is when O and M are divalent metals, and M when M is a trivalent metal.₂O_Three, If M is tetravalent, MO₂Further, when M is a divalent or trivalent mixed valence (for example, Mn is easily divalent or trivalent under firing conditions), M is_ThreeO_FourIt will be represented as a representative. The glassy substance is blended in a total amount of 5 to 500 times, preferably 10 to 100 times that of the phosphorus compound, vanadium compound and network modifying ion source. If it exceeds the above range, sufficient rust prevention properties cannot be obtained.
[0075]
The film-forming resin raw material used for the undercoat layer of the precoated metal sheet of the present invention can be sufficiently formed by heating as it is, but in forming a paint, in addition to the above-described polyol and blocked product, an organic solvent such as acetic acid is used. Esters such as ethyl, butyl acetate, methyl acetoacetate and 2-ethoxyethyl acetate, aromatics such as xylene and toluene, ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethers such as diethylene glycol dimethyl ether, Solvesso-100 , Organic solvents such as petroleum-based solvents such as Solvesso-200, colored pigments and extender pigments, dispersants such as silicon-based, amine-based, polyether-based, polyester-based, castor oil-based, synthetic wax-based, and pentonite-based dispersants , Antifoaming agent, leveling agent, thixotropic , Stabilizers such as benzotriazoles, hindered amines, hindered phenols, etc., reaction catalysts such as tin, lead, zinc, iron, etc., UV inhibitors, etc. May be added.
[0076]
By applying a paint prepared by blending each component to a metal plate on which a base treatment layer has been formed in advance, by heating at a plate temperature (PMT) of about 150 to 350 ° C. and a heating time of about 20 to 120 seconds, The blocking agent contained in the blocked product is dissociated to regenerate the NCO group, and the regenerated NCO group reacts with the OH group in the polyol to cure the undercoat layer. The thickness of the coating film is preferably 30 μm or less, and if it exceeds 30 μm, the processability of the coating film is poor.
[0077]
The number of the undercoat layer of the present invention may be one, but a great effect can be obtained by using two or more undercoat layers. That is, the coating for forming the undercoat layer may be used by coating one on the metal plate, but is more effective when used as a primer having two or more coats.
[0078]
The application, drying, and baking of the undercoat layer-forming coating material can be performed using any known method as in the case of the base treatment layer.
[0079]
The precoated metal sheet of the present invention is characterized by having a colored film layer on a metal sheet on which an undercoat layer is formed. This colored coating layer is an indispensable layer for giving a design property to a metal plate and obtaining a coated metal plate that can be used without further coating.
[0080]
This coating layer contains pigments and dyes necessary for coloring. As the pigment, known ones can be used regardless of organic type, inorganic type, or a combination of both, and cyanine pigments such as titanium white, alumina white, zinc yellow, cyanine blue, carbon black, iron black, etc. , Bengara, yellow iron oxide, molybdate orange, hansa yellow, pyrazolone orange, azo pigment, bitumen, condensed polycyclic pigment, and the like. In addition to these, additives such as metal pieces / powder, pearl pigments, mica pigments, resin beads, and the like for imparting functionality such as design and conductivity may be added.
[0081]
As the dye, known dyes such as azo dyes, anthraquinone dyes, indigoid dyes, sulfur dyes, phthalocyanine dyes, diphenylmethane and triphenylmethane dyes, other nitro dyes and acridine dyes are used.
[0082]
As the binder for the colored coating layer, organic or inorganic binders can be used. As the organic binder, polyolefin resin, acrylic resin, urethane resin, epoxy resin, polyester resin, vinyl chloride resin, fluorine resin, butyral resin, polycarbonate resin, phenol resin, and the like can be used. Mixtures and copolymers of these can also be used. In addition to these, an isocyanate resin, an amino resin, a silane, a titanium coupling agent, or the like can be used in combination as a crosslinking agent or an auxiliary component.
[0083]
Since the precoated metal sheet according to the present invention is premised on being used as it is after being molded, the colored layer is required to be free from cracking and peeling during bending and press molding. From such a viewpoint, a resin system in which a polyester resin is crosslinked with a melamine resin, a resin system in which a polyester resin is crosslinked with a urethane resin (isocyanate, isocyanate resin), a vinyl chloride resin system, a fluororesin system (solvent soluble type, acrylic) A dispersion mixed type with a resin) is desirable. The resin may be in any form of water, solvent, powder, and solventless.
[0084]
In addition, pigments and additive components that are not directly related to coloring, such as pigments such as barium sulfate, calcium carbide, kaolin clay, additives such as antifoaming agents, leveling agents, dispersion aids, and polyethylene An organic wax component such as polypropylene, ester, paraffin, and fluorine, an inorganic wax component such as molybdenum disulfide, a diluent, a solvent, water and the like for decreasing the viscosity of the paint can be added.
[0085]
The amount of the coloring component in the resin is not particularly limited, and may be determined depending on the necessary color and hiding power. For example, when carbon black is blended in order to color black, it is sufficient to add 1 to 5% in terms of the solid pigment weight concentration. For example, when titanium white is blended to color white The pigment weight concentration in terms of solid content needs to be about 30 to 55%.
[0086]
The colored film layer is applied on the undercoat layer by a known method such as roll coater, curtain coater, electrostatic coating, spray coating, dip coating, etc., and then heated by hot air, induction heating, near infrared, far infrared, etc. Dry and harden. If the resin of the colored coating layer is of a type that is cured by radiation such as an electron beam or ultraviolet rays, the resin is cured by electron beam irradiation or ultraviolet irradiation. These may be used in combination. A drying and curing method can be selected according to the type of the colored coating layer. The drying and baking plate temperature is also determined according to the type of the coating layer. In a continuous production line of a general pre-coated metal plate (painted metal plate), the plate temperature is 150 to 250 ° C.
[0087]
The film thickness of the colored coating layer is not particularly limited, but it is desirable that there is a dry film thickness of 5 μm or more in order to obtain a uniform colored appearance. More desirably, it is 8 μm or more. Although there is no special upper limit of the film thickness, when continuously coating with a coil in a production line of a coated metal plate, the dry film thickness is often about 50 μm by one coating. This upper limit is often governed mainly by the occurrence of defects that occur when the viscosity of the coating is too high when the volatile components in the coating called “WAKI” volatilize out of the coating system. . In the case of manufacturing while intermittently painting the cut plate, baking can be performed under mild conditions, and the upper limit dry film thickness is increased to about 200 μm. In addition, when processing one by one by spray coating or the like, the upper limit film thickness further increases.
[0088]
The pre-coated metal plate of the present invention has the above-mentioned base treatment layer and undercoat layer on both sides or one side, and a colored coating layer thereon. In many cases, the colored coating layer is not applied to the back side surface that does not appear on the surface in the final product obtained by processing the pre-coated metal plate. In this case, the back side surface is provided with a service coat following the base treatment layer. Applied. Any known service coat may be adopted as the service coat in the pre-coated metal sheet of the present invention.
[0089]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to these examples. In addition, the part or% shown without notice shows a weight part or weight%, respectively.
[0090]
Here, first, in the following Reference Examples 1 to 17, polyols for film forming resin raw materials for the undercoat layer used in the following Examples (Reference Examples 1 to 7) and blocked products (Reference Examples 8 to 13), And preparation of rust preventives (Reference Examples 14 to 17) will be described, and then Examples and Comparative Examples of the present invention will be described.
[0091]
[Reference Example 1]
Charge hydrogenated bisphenol A 364.9 parts (1.52 mol) and adipic acid 441.6 parts (3.02 mol) to a reaction vessel, heat to 220 ° C. and blow nitrogen gas to distill the generated condensed water. When the acid value reached 250.0, 304.1 parts (2.27 mol) of trimethylolpropane (hereinafter referred to as TMP) was charged, and the reaction was conducted while distilling off the condensed water. A polyester polyol having 2.6, a hydroxyl value of 187.2, a functional group number of 5 and a number average molecular weight of 1478 was obtained. One obtained by adding 20 parts by weight of ε-caprolactone to 600 parts by weight of this polyester polyol and 80 parts by weight of an epoxy resin of the following formula (Placcel G-402 (manufactured by Daicel Chemical Industries)), hydroxyl value 119, epoxy equivalent 1250 ) 400 parts was dissolved in 1500 parts of cyclohexanone to give a 40% solids solution. The properties of this solution are shown in Table 1.
[0092]
[Chemical 2]

[0093]
[Reference Example 2]
One obtained by adding 20 parts by weight of ε-caprolactone to 800 parts by weight of the polyester polyol obtained in Reference Example 1 and 80 parts by weight of the epoxy resin of the following formula (Placcel G-702 (manufactured by Daicel Chemical Industries)), hydroxyl group 200 parts of a valence of 140 and an epoxy equivalent of 2710) were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. The properties of this solution are shown in Table 1.
[0094]
[Chemical 3]

[0095]
[Reference Example 3]
A reaction vessel was charged with 205.8 parts (1.74 moles) of 1,6-hexanediol, 670.1 parts (3.45 moles) of dimethyl isophthalate and 0.1 g of zinc acetate, heated to 220 ° C. and nitrogen gas. Then, the reaction was carried out while distilling off the produced methanol. When 121 ml of methanol was distilled off, 347.2 parts (2.59 mol) of TMP was added, and the reaction was carried out while distilling off methanol. A polyester polyol having a hydroxyl value of 193.6, a functional group number of 5, and a number average molecular weight of 1438 was obtained. 600 parts of this polyester polyol and 400 parts of Plaxel G-402 of Reference Example 1 were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. The properties of this solution are shown in Table 1.
[0096]
[Reference Example 4]
The reaction vessel was charged with 245.3 parts (2.08 moles) of 3-methyl-1,5-pentanediol and 541.6 parts (3.71 moles) of adipic acid, heated to 220 ° C. and blown with nitrogen gas. Reaction was performed while distilling off the condensed water to be formed. When the acid value reached 280.0, 372.9 parts (2.78 mol) of TMP and 0.1 part of dibutyltin dilaurate were added, and the condensed water was distilled off in the same manner. The polyester polyol having an acid value of 1.6, a hydroxyl value of 216.0, a functional group number of 5 and a number average molecular weight of 1289 was obtained. 800 parts of this polyester polyol and 200 parts of Plaxel G-402 of Reference Example 1 were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. The properties of this solution are shown in Table 1.
[0097]
[Reference Example 5]
When 151.8 parts (2.45 moles) of ethylene glycol and 550.0 parts (4.66 moles) of succinic acid were charged and reacted under the same conditions as in Reference Example 1 to give an acid value of 420.0, pentaerythritol 159.3 parts (1.17 mol) was charged, the esterification reaction was continued, and when the acid value reached 165.0, 159.3 parts (1.17 mol) of pentaerythritol and 157.0 parts of TMP (1 .17 mol) was added, and the condensed water was distilled off to obtain a polyester polyol having an acid value of 3.8, a hydroxyl value of 447.8, a functional group number of 7, and a number average molecular weight of 870. 800 parts of this polyester polyol and 200 parts of Plaxel G-402 of Reference Example 1 were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. The properties of this solution are shown in Table 1.
[0098]
[Reference Example 6]
Bishydroxyethyl terephthalate (325.9 parts, 1.28 mol) and sebacic acid (513.8 parts, 2.54 mol) were charged and reacted under the same conditions as in Reference Example 1 to give an acid value of 184.4. By the way, 256.7 parts (1.91 mol) of TMP was charged and condensed water was distilled off to obtain a polyester polyol having an acid value of 8.0, a hydroxyl value of 168.3, a functional group number of 5 and a number average molecular weight of 1591. 800 parts of this polyester polyol and 200 parts of Plaxel G-402 of Reference Example 1 were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. The properties of this solution are shown in Table 1.
[0099]
[Reference Example 7]
When 183.4 parts (2.95 mole) of ethylene glycol and 664.7 parts (5.63 mole) of succinic acid were charged and reacted under the same conditions as in Reference Example 1 and the acid value reached 420.0, TMP189. 4 parts (1.41 mol) was charged and the esterification reaction was continued. When the acid value reached 170.0, 183.4 parts (2.95 mol) of ethylene glycol was further charged to distill off the condensed water, and the acid value was reduced. A polyester polyol having 1.5, a hydroxyl value of 215.5, a functional group number of 3, and a number average molecular weight of 776 was obtained. 800 parts of this polyester polyol and 200 parts of Plaxel G-702 of Reference Example 2 were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. The properties of this solution are shown in Table 1.
[0100]
[Reference Example 8]
241.6 parts of 1,3-bis (isocyanatomethyl) cyclohexane are dissolved in 400.0 parts of Solvesso-100, and 180.6 parts of methyl ethyl ketoxime are added dropwise over 1 hour. After completion of dropping, the mixture is further heated to 75-80 ° C for 1 hour. Next, 0.6 parts of dibutyltin dilaurate and polyester polyol (adipic acid 876.6 parts, ethylene glycol 186.3 parts, TMP 201.2 parts, dipropylene glycol 402.3 parts are condensed by an ordinary method) 177.0 parts) (a valence of 3.5, a hydroxyl value of 172.0, a solid content of 100%) is added, and the mixture is reacted at 75-80 ° C. for 6 hours. Thus, a blocked product solution having a regenerated isocyanate group content of 8.5% and a solid content of 60% was obtained. The properties of this solution are shown in Table 2.
[0101]
[Reference Example 9]
TMP-3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate adduct solution (Takenate D-140N (manufactured by Takeda Pharmaceutical Company Limited)), solid content 75%, isocyanate in a 2 liter four-necked flask Content 80.78 parts of ethyl acetate solution) and 316.1 parts of cellosolve acetate, and 182.7 parts of methyl ethyl ketoxime was maintained in a nitrogen gas atmosphere so that the internal temperature was maintained at 60 to 70 ° C. When the addition was completed and the temperature was maintained for about 4 hours after the addition was completed, a blocked product solution having a solid content of 60% and a regenerated isocyanate group content of 6.64% was obtained. The properties of this solution are shown in Table 2.
[0102]
[Reference Example 10]
307.5 parts of ω, ω'-diisocyanate-1,3-dimethylbenzene are dissolved in 519.1 parts of Solvesso-100 and 129.7 parts of methyl ethyl ketone, and 237.2 parts of methyl ethyl ketoxime are added dropwise over about 2 hours. After completion of dropping, the mixture is further heated to 75-80 ° C for 1 hour. Next, 0.3 part of dibutyltin dilaurate and 232.4 parts of the polyester polyol used in Reference Example 8 are added and reacted at 75-80 ° C. for 6 hours. Thus, a blocked product solution having a regenerated isocyanate group content of 8.02% and a solid content of 55% was obtained. The properties of this solution are shown in Table 2.
[0103]
[Reference Example 11]
760.7 parts TMP-hexamethylene diisocyanate adduct (Takenate D-160N (manufactured by Takeda Pharmaceutical Co., Ltd.), solid content 75%, isocyanate content 13.2%) and cellosolve acetate in a 2 liter four-necked flask Charge 325.6 parts and gradually drop 213.7 parts of methyl ethyl ketoxime so that the internal temperature is kept at 60 to 70 ° C. in a nitrogen gas atmosphere. A blocked product solution having a solid content of 60% and a recycled isocyanate group content of 7.77% was obtained. The properties of this solution are shown in Table 2.
[0104]
[Reference Example 12]
228.6 parts of 4,4'-methylenebis (cyclohexyl isocyanate) are dissolved in 160.0 parts of toluene and 160.0 parts of cyclohexanone, and 126.5 parts of methyl ethyl ketoxime are added dropwise over about 1 hour. After completion of dropping, the mixture is further heated to 75-80 ° C for 1 hour. Next, 0.41 part of 1,1,3,3-tetra n-butyl-1,3-diacetoxy distanoxane and 123.92 parts of a polyester polyol (same as the polyester polyol used in Reference Example 8) were added and 75 parts were added. The reaction is allowed to proceed at ~ 80 ° C for 8 hours. Thus, a blocked product solution having a regenerated isocyanate group content of 7.6% and a solid content of 60% was obtained. The properties of this solution are shown in Table 2.
[0105]
[Reference Example 13]
A 2 liter four-necked flask is equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and adduct of TMP and α, α, α ', α'-tetramethylmetaxylylene diisocyanate (room temperature 500 parts of solid, isocyanate content 13.3%), 427.1 parts of ethyl acetate and 0.19 part of 1,1,3,3-tetra-n-butyl-1,3-diacetoxy distanoxane. In a nitrogen gas atmosphere, 140.5 parts of methyl ethyl ketoxime was gradually added dropwise so as to maintain an internal temperature of 60 to 70 ° C. After the addition was completed, the mixture was kept at the above temperature for about 4 hours. A blocked product solution having a regenerated isocyanate group content of 6.20% was obtained. The properties of this solution are shown in Table 2.
[0106]
[Reference Example 14]
Antirust agents 14a to 14d were obtained by mixing the components shown in Table 3.
[0107]
[Reference Example 15]
The components shown in Table 4 were fired, cooled and pulverized under the conditions shown in Table 4 to obtain rust preventives 15a to 15i.
[0108]
[Reference Example 16]
The components shown in Table 5 were fired, cooled and pulverized under the conditions shown in Table 5 to obtain rust inhibitors 16a to 16e.
[0109]
[Reference Example 17]
After the components shown in Table 6 were mixed, rust inhibitors 17a to 17d were obtained by melting at 140 ° C., cooling and pulverizing.
[0110]
[Examples 1 to 57, Comparative Examples 1 to 39]
Zinc plating coverage is 20g / m per side²Electrogalvanized steel sheet with a thickness of 0.6 mm plated on both sides (denoted as “EG” in the table below), and the amount of galvanized coating is 60 g / m per side²A hot-dip galvanized steel sheet with a thickness of 0.6 mm plated on both sides (indicated in the following table as “GI”) in an aqueous solution of FC-364S (manufactured by Nihon Parkerizing Co., Ltd.) at a concentration of 2% by weight at 60 ° C. Was degreased by dipping in 10 seconds, washed with water and dried. Next, a base treatment agent having the composition shown in Tables 7 to 9 (the content of each component is expressed in parts by weight) is applied to the plated steel plate with a roll coater, dried in a hot air drying furnace, and the plate is cooled with water. Thus, a base treatment layer having an adhesion amount shown in Tables 7 to 9 was formed. The ultimate plate temperature during drying was 150 ° C. In addition, although the same evaluation was made by setting the ultimate plate temperature at the time of drying to 70 ° C. and 220 ° C., the same coating film (primary treatment layer) as when the ultimate plate temperature was 150 ° C. was obtained.
[0111]
The acrylic resin of the water-based resin used for the base treatment layer is a mixture of “AP-1058 (12)” manufactured by Toa Gosei Co., Ltd. and “Hitech S-7024” manufactured by Toho Chemical Co., Ltd. The epoxy was “Polysol 8500” manufactured by Showa Polymer Co., Ltd. As tannic acid, “tannic acid AL” (manufactured by Fuji Chemical Industry Co., Ltd.), “BREWTAN” (manufactured by Omnichem), and “TANAL1” (manufactured by Omnichem) were used. As the fine silica, “Snowtex N” (referred to as “ST-N” in the following table) and “Snowtex NS” (referred to as “ST-NS” in the following table) manufactured by Nissan Chemical Industries, Ltd. For the application of the coating for the base treatment layer using, a solution having a solid content of 20% using water as a solvent was used.
[0112]
For the undercoat layer, the polyols and blocked products shown in Nos. 10 to 12 (each number in the column of “polyol” and “blocked product” in the table indicates the number of the reference example in which each polyol and blocked product was prepared). Are added so that the NCO / OH equivalent ratio is 1.0, and then a mixture of a phosphorus compound and a vanadium compound of a rust inhibitor shown in Tables 10 to 12 (in the column of “rust inhibitor” in the table) Each symbol indicates the symbol of the rust inhibitor listed in Tables 3 to 6), and 1,1,3,3-tetra-n-butyl-1,3 as a catalyst. -0.03 part of diacetoxy distanoxane was added and kneaded sufficiently with a paint conditioner to obtain an enamel solution for a pre-coated metal plate primer. Thus, this solution (undercoat layer forming solution) contains a resin formed of a polyol and a blocked product as a film-forming resin and also contains a non-chromium rust inhibitor.
[0113]
The solution thus prepared is applied to both surfaces of the steel sheet on which the base treatment layer is formed with a bar coater so as to have a dry film thickness of 5 μm, and baked in a hot air oven under conditions of an ultimate plate temperature of 210 ° C. and an arrival time of 45 seconds. And under water cooling to form an undercoat layer.
[0114]
In addition, as is clear from Table 12, in some of the comparative examples, other than the resin formed from the polyol and the blocked product, or various rust preventives other than those shown in Tables 3 to 6 were used. That is, as a comparative resin for the undercoat layer, melamine alkyd resin (Orga Select 100 manufactured by Nippon Paint Co., Ltd.) and epoxy nylon resin (FS75SZ modified by Toagosei Co., Ltd.) were used. Moreover, as a comparative rust preventive for the undercoat layer, strontium chromate, dibasic magnesium phosphate, 2CaO · V₂O_FiveFired product, Mn₂O_Three・ V₂O_FiveA fired product was used.
[0115]
Subsequently, FL100HQ (polyester resin system, color is white) manufactured by Nippon Paint Co., Ltd. was applied on the formed undercoat layer, and cured and dried so that the ultimate plate temperature was 220 ° C. in an induction heating furnace blown with hot air. And the board was water-cooled to form an upper film layer. All the opposite surfaces (back surfaces) were coated with a melamine alkyd paint so as to have a dry film thickness of 7 μm with a bar coater, and baked under conditions of an ultimate plate temperature of 230 ° C. and an arrival time of 45 seconds.
[0116]
The film thicknesses of the paint used in the undercoat layer and the upper coating layer and the formed coating film are summarized in Tables 10-12.
[0117]
The following evaluation was performed on the pre-coated steel sheet thus produced. Each evaluation was performed on the front side (side on which the colored coating layer was formed).
1. Coating film adhesion
The coated plate was put into a 1 mm square grid with a cutter knife on the painted surface and extruded 7 mm with an Erichsen tester so that the painted surface became convex, and then a tape peeling test was performed. The method of placing the grid, the extrusion method of Erichsen, and the tape peeling method were carried out according to the methods described in JIS-K5400.88.2 and JIS-K5400.88.5. In addition, the evaluation after tape peeling is performed according to the example of evaluation described in JIS-K5400.88.5. When the score is 10 points, ○, when it is 9 points, when it is 6 points or more and less than 9 points Δ, when it was less than 6 points, it was evaluated as x. Further, according to the description of JIS-K5400.8.20, the precoated steel sheet was immersed in boiling water, then taken out and allowed to stand for 24 hours.
[0118]
2. Bending workability test
After the plate after coating was bent by 180 °, the coating film in the processed part was observed with a 10-fold magnifier to examine whether the coating film was cracked. Moreover, the adhesive tape was affixed on the process part, and the residual state of the coating film was observed visually when this was peeled off vigorously. The bending process was performed in an atmosphere of 20 ° C. with a 0.6 mm spacer interposed therebetween. The evaluation of coating film cracking was evaluated as ◯ when there was no coating film cracking, △ when there were some cracks in the coating film, and × when the coating film had clear cracks even visually (coating film cracking test). . Moreover, the evaluation of the coating film remaining state after peeling with the tape is ○ when the coating film remains on the plated steel sheet without peeling at all, Δ when the coating film is partially peeled, The case where peeling was observed over the entire surface was evaluated as x. Furthermore, according to JIS-K5400.8.20 description, after the coated steel sheet is immersed in boiling water, it is taken out and allowed to stand for 24 hours, and then the above-described bending process is performed. The coating film remaining state was evaluated (tape peeling test).
[0119]
3. Corrosion resistance
The salt spray test was implemented by the method of JIS-K5400.99.1 with respect to the board after coating. The test time was 120 hours for electrogalvanized steel sheets and 240 hours for hot dip galvanized steel sheets. The evaluation method of the coating film of the cross cut part is: ○ when the maximum swollen width on one side of the cross cut is less than 1 mm, ○ when 1 mm or more and less than 2 mm, △ when 2 mm or more and less than 3 mm, Δ when 3 mm or more X was evaluated. In addition, the above-mentioned salt spray test was performed on the flat plate prepared so that the return (burr) at the time of cutting was on the evaluation surface side of the coated steel sheet (so that it would be an upper burr), and the coating film swelled from the end surface. The width was observed. The evaluation method of the end face part is ○ when the swollen width from the end face is 3 mm or less, ○ when it is 3 mm or more and less than 4 mm, △ when it is 4 mm or more and less than 5 mm, and △ when it is 5 mm or more. did.
[0120]
4). toxicity
Regarding the toxicity, those containing chromium were designated as “present” and those not containing chromium were designated as “low toxicity” (indicated by “−” in the table below).
[0121]
The evaluation results are shown in Tables 13-15. Coating film adhesion, folding processability (coating crack test), folding process adhesion (tape peeling test), and corrosion resistance of the precoated metal sheet according to the present invention (Examples 1 to 57) are the same as those of the undercoat layer of the comparative example. Also, it has almost the same or better performance than the chromate-based precoated steel sheets (Comparative Examples 37 to 39).
[0122]
On the other hand, when the tannic acid content of the base treatment layer is too small (Comparative Examples 24 and 25) and when the amount of adhesion of the base treatment layer is too small (Comparative Examples 28 and 29), the corrosion resistance is greatly inferior. It is. On the contrary, when the adhesion amount of the ground treatment layer is too large (Comparative Examples 30 and 31), the adhesion of the coating film is lowered, and as a result, the corrosion resistance is lowered, which is also unsuitable. Moreover, when the film thickness of an undercoat layer is too thick (Comparative Examples 32 and 33), the bending workability is greatly inferior, which is inappropriate. Since Comparative Examples 34 to 39 use chromium which is environmentally toxic, this is also unsuitable.
[0123]
On the other hand, in Comparative Examples 1-16, although the thing of this invention is used as resin of undercoat, since a suitable thing is not used as a rust preventive agent, a certain problem has arisen. That is, since Comparative Examples 1-9 and 13 contain only a vanadate ion source and Comparative Examples 10 and 14 contain only a phosphate ion source, sufficient corrosion resistance is not obtained. Since Comparative Examples 11 and 15 use strontium chromate, they have excellent corrosion resistance but are toxic. Since the comparative examples 12 and 16 do not add a rust preventive agent, the corrosion resistance is not obtained.
[0124]
Furthermore, although Comparative Examples 17 and 18 use the thing of this invention as a rust preventive agent of undercoat, since the thing suitable as resin is not used, it is inferior to corrosion resistance. In Comparative Examples 19 to 23, neither the resin of the undercoat layer nor the rust inhibitor is suitable, and there is a problem in corrosion resistance or toxicity.
[0125]
[Table 1]

[0126]
[Table 2]

[0127]
[Table 3]

[0128]
[Table 4]

[0129]
[Table 5]

[0130]
[Table 6]

[0131]
[Table 7]

[0132]
[Table 8]

[0133]
[Table 9]

[0134]
[Table 10]

[0135]
[Table 11]

[0136]
[Table 12]

[0137]
[Table 13]

[0138]
[Table 14]

[0139]
[Table 15]

[0140]
【The invention's effect】
As is clear from the above description, the pre-coated metal sheet of the present invention is excellent in adhesion and corrosion resistance of the coating film, and excellent in processability of the coating film, without using environmentally toxic chromium. It is a thing. Therefore, according to the present invention, it is possible to provide a pre-coated metal plate having an extremely high industrial value that can be advantageously used for home appliances and the like that may be touched by human hands or that may come into contact with food.

Claims (8)

At least one surface of the metal plate has a coating layer containing an organic resin and tannin or tannic acid as a base treatment layer, and on this base treatment layer,
(A) (1) a polyester polyol having at least 3 hydroxyl functional groups, (2) an epoxy resin having at least one secondary hydroxyl group and a lactone compound or alkylene oxide added thereto, and (3) an organic polyisocyanate An organic resin obtained from a film-forming resin material containing a blocked product or a blocked product of a prepolymer having an NCO group at the end obtained by reaction of an organic polyisocyanate with an active hydrogen compound, and (B) water and oxygen A phosphate ion source that releases phosphate ions in an existing environment, and a vanadate ion source that releases vanadate ions in an environment where water and oxygen are present,
Has as a subbing layer coating layer containing, further on this undercoat layer, have a colored film layer as an upper layer film,
The phosphate ion source includes orthophosphoric acid, condensed phosphoric acid, orthophosphoric acid metal salts including monohydrogen salts and dihydrogen salts, condensed metal phosphates including hydrogen salts, metaphosphates, polyphosphates and polymetaphosphates. Salt, phosphorus pentoxide, monetite, tolufilite, witrockite, xenotime, starcolite, struvite, orbite, polyphosphate silica, pyrophosphate, metaphosphate, tetrametaphosphate, hexametaphosphate, pyrophosphate Selected from the group consisting of acid pyrophosphate, tripolyphosphate, and mixtures thereof, and the metal species in the metal orthophosphate and metal phosphate are magnesium, calcium, strontium, barium, titanium, zirconium, manganese, iron, Selected from cobalt, nickel, zinc, aluminum, lead and tin, the above metaphosphoric acid , Tetrametaphosphoric acid salts, hexametaphosphate, pyrophosphate, cationic acidic pyrophosphate and tripolyphosphate, the metal species, vanadyl, selected from titanyl and zirconyl cation,
The vanadate ion source includes vanadium (II), vanadium (III), vanadium (IV) or vanadium (V) oxide, hydroxide, vanadate, vanadyl halide, halide and sulfate, and vanadium. Selected from metal powder, the vanadate is orthovanadate, metavanadate, pyrovanadate or a mixture thereof, and the metal species in the vanadate and sulfate are magnesium, calcium, strontium, barium, Selected from titanium, zirconium, manganese, iron, cobalt, nickel, zinc, aluminum, lead and tin,
A precoated metal plate characterized by the above.   The precoated metal sheet according to claim 1, wherein the base treatment layer contains 0.2 to 50 parts by weight of tannin or tannic acid with respect to 100 parts by weight of an organic resin as a solid content.   The precoated metal sheet according to claim 1 or 2, wherein the ground treatment layer contains 10 to 500 parts by weight of fine silica as a solid content.   The undercoat layer according to any one of claims 1 to 3, comprising 0.1 to 50 parts by weight of both a phosphate ion source and a vanadate ion source in total with respect to 100 parts by weight of a total solid content. The precoat metal plate as described.   The precoated metal sheet according to any one of claims 1 to 4, wherein the phosphate ion source and the vanadate ion source are rust preventive pigments.   The precoated metal sheet according to claim 5, wherein the rust preventive pigment is obtained by firing and pulverizing a mixture containing a phosphorus compound and a vanadium compound. The anticorrosive pigment is state, and are not obtained by firing was crushed a mixture containing at least one of said phosphorus compound and a vanadium compound further network-modifier ion source and glassy material in addition to the network-modifying ion source, Selected from metal oxides, hydroxides, carbonates, nitrates, organic acid salts, silicates, borates, sulfates and chlorides, and the glassy materials are silica glass, soda lime silicate glass, lead - silicate glass, aluminosilicate glass, borosilicate glass, lead - borate glasses, alumino - borophosphate glasses, alumino - Ru is selected from phosphate glass - borate glasses and alumino The precoated metal sheet according to claim 6, wherein The anticorrosive pigment, characterized in that the mixtures of phosphate ion source and the vanadate ion source according to claim 5, wherein the precoated metal plate for coating.