JP3946589B2 - Powder coating composition for pipes - Google Patents

Description

［式中、Ｒ^１〜Ｒ^４は、Ｈ又は炭素原子数１〜９のアルキル基である］
で表される２価フェノール類（ａ２）及びエピハロヒドリンから誘導されるエポキシ樹脂と、ビスフェノ−ルＦ（ａ１）との伸長反応により得られるエポキシ樹脂であることを特徴とする管用粉体塗料組成物である。
【００１０】
本発明で固形エポキシ樹脂（Ａ）として配合されるエポキシ樹脂は、従来型のビスフェノールＡ型固形エポキシ樹脂と比較して溶融粘度が低い。そのため、低温度領域における流れ性に優れているので、低温焼き付け条件での硬化が可能であり、また、硬化時に金属管表面や内部に含まれる水分から発生したガスの放散を促進し、ピンホール発生を抑制する。
さらに、従来型のビスフェノールＦ型固形エポキシ樹脂と比較して、可撓性及び耐衝撃性に優れた塗膜を得ることが出来る。
【００１１】
【発明の実施の形態】
以下、本発明を更に詳細に説明する。
本発明において、固形エポキシ樹脂（Ａ）として用いられるエポキシ樹脂は、原料として、ビスフェノールＦと、一般式（Ｉ）：
【化６】

［式中、Ｒ^１〜Ｒ^４は、Ｈ又は炭素原子数１〜９のアルキル基である］
で表される２価フェノール類（ａ２）とが用いられているエポキシ樹脂であり、例えば下記の（１）〜（３）に示される製造方法で得ることができる。
（１）ビスフェノ−ルＦ（ａ１）と、前記２価のフェノ−ル類（ａ２）と、エピハロヒドリンとから誘導する。
（２）前記（１）で誘導されるエポキシ樹脂とビスフェノ−ルＦ（ａ１）とを伸長反応させる。
（３）原料として前記２価フェノール類（ａ２）が用いられていない従来のビスフェノ−ルＦ型エポキシ樹脂（ｘ１）と、前記２価フェノール類（ａ２）と、さらに任意成分としてビスフェノ−ルＦ（ａ１）とを伸長反応させる。
【００１２】
前記２価フェノ−ル類（ａ２）としては、例えば、ハイドロキノン、カテコール、レゾルシン、プロピルジヒドロキシベンゼン、ジプロピルジヒドロキシベンゼン、ブチルジヒドロキシベンゼン、ジブチルジヒドロキシベンゼン、オクチルジヒドロキシベンゼン、ジオクチルジヒドロキシベンゼン、ノニルジヒドロキシベンゼン、ジノニルジヒドロキシベンゼン、トリメチルハイドロキノン等が挙げられる。これらの化合物は、１種類でも用いることもできるし、２種類以上を併用することも可能である。これらの中でも、得られる粉体塗料の硬化性、塗膜物性が良好である点から、ハイドロキノン、トリメチルハイドロキノン、ターシャリーブチルジヒドロキシベンゼン、ジターシャリーブチルジヒドロキシベンゼンが好ましい。
【００１３】
前記ターシャリーブチルジヒドロキシベンゼン及びジターシャリーブチルジヒドロキシベンゼンを更に詳述すると、例えば、ブチルジヒドロキシベンゼンとしては、２−ターシャリーブチルハイドロキノン、２−ターシャリーブチルレゾルシン、４−ターシャリーブチルレゾルシン、５−ターシャリーブチルレゾルシン、３−ターシャリーブチルカテコール、４−ターシャリーブチルカテコール等が挙げられ、ジブチルジヒドロキシベンゼンとしては、３，５−ジ−ターシャリーブチルハイドロキノン、２，４−ジ−ターシャリーブチルレゾルシン、２，５−ジ−ターシャリーブチルレゾルシン、４，５−ジ−ターシャリーブチルレゾルシン、４，６−ジ−ターシャリーブチルレゾルシン、３，４−ジ−ターシャリーブチルレゾルシン、４，５−ジ−ターシャリーブチルレゾルシン等が挙げられる。これらの中でも、ブチルジヒドロキシベンゼンとしてハイドロキノン構造を有するものが特に好ましく、２−ターシャリーブチルハイドロキノンが更に好ましい。
【００１４】
前記エピハロヒドリンとしては特に限定されるものではないが、例えば、エピクロルヒドリン、β−メチルエピクロルヒドリン、エピブロモヒドリン、β−メチルエピブロモヒドリン等が挙げられる。これらの中でも、反応性の点からエピクロルヒドリンが好ましい。
【００１５】
前記（１）の具体的な製造方法としては、特に制限されるものではないが、例えば、前記ビスフェノールＦ（ａ１）と前記２価フェノ−ル類（ａ２）の全水酸基の１当量に対し、エピハロヒドリンを０．３〜１０当量添加し、塩基の存在下に、４０〜１００℃で常圧または、減圧下で、必要に応じて溶媒を用いて、反応を行うことができる。
また、前記ビスフェノールＦ（ａ１）と前記２価フェノ−ル類（ａ２）との反応比率は、９９／１〜７０／３０（質量比）が好ましく、特に９８／２〜７２／２８が好ましい。
前記溶媒としては、例えば、イソプロピルアルコール、ブタノール等のアルコール類、ジオキサン等のエーテル類、ジメチルスルフォキシド、１，３−ジメチルイミダゾリジノン等の非プロトン性極性溶媒を挙げることができる。
前記塩基としては、特に限定されるものではないが、水酸化カリウム、水酸化ナトリウム、水酸化バリウム、酸化マグネシウム、炭酸ナトリウム、炭酸カリウム等が挙げられる。この中でも水酸化カリウム及び水酸化ナトリウムが好ましい。また、これらの塩基は水溶液、固形のいずれでも好適に用いられる。
【００１６】
次いで、前記（２）の具体的な製造方法としては、例えば、前記（１）で誘導されるエポキシ樹脂とビスフェノールＦ（ａ１）とを触媒存在下で、１２０〜２２０℃で加熱攪拌して反応させる。ここで用いる触媒は、特に限定されるものではないが、例えば、オニウム塩、ホスフィン類、アルカリ金属水酸化物等が挙げられる。
また、前記エポキシ樹脂と前記ビスフェノールＦ（ａ１）との反応比率は、得られたエポキシ樹脂（Ａ）中のビスフェノールＦ（ａ１）と前記フェノール類（ａ２）の比率が９９／１〜７０／３０となるように調整することが好ましい。
【００１７】
次いで、前記（３）の具体的な製造方法としては、例えば、従来のビスフェノールＦ型エポキシ樹脂（ｘ１）と、前記２価フェノ−ル類（ａ２）とを、任意にビスフェノ−ルＦ（ａ１）を加えて、触媒存在下で、１２０〜２２０℃で加熱攪拌して行う。
ここで、従来のビスフェノールＦ型エポキシ樹脂（ｘ１）としては、原料として、ビスフェノールＦが用いられており、且つ、前記２価フェノール類（ａ２）が用いられていないものであれば特に制限はなく、例えば、ＥＰＩＣＬＯＮ８３０、ＥＰＩＣＬＯＮ８３０Ｓ（大日本インキ化学工業（株）製エポキシ樹脂）等を挙げることができる。前記触媒としては、特に限定されるものではないが、例えば、オニウム塩、ホスフィン類、アルカリ金属水酸化物等が挙げられる。
また、（ｘ１）、（ａ２）及び（ａ１）の反応比率は、得られたエポキシ樹脂（Ａ）中のビスフェノールＦ（ａ１）と前記フェノール類（ａ２）の比率が９９／１〜７０／３０となるように調整することが好ましい。
【００１８】
前記のようにして得られたエポキシ樹脂は、特に制限されるものではないが、耐ブロッキング性、粉体塗料化の容易さの点から、エポキシ当量が５００g／eq〜２０００g／eqであり、環球法（５℃／分昇温法）による軟化点が７０〜１３０℃であるものが好ましい。特に、これらの効果が顕著である点から、エポキシ当量が６００g／eq〜１３００g／eqであり、環球法（５℃／分昇温法）による軟化点が８０〜１０５℃であることが好ましい。
【００１９】
また、前記エポキシ樹脂の製造方法（１）〜（３）のうち、（３）の製造方法は、所望のエポキシ当量及び分子量の調節、或いは、ビスフェノールＦ（ａ１）や前記２価フェノ−ル類（ａ２）の樹脂中への導入量を容易に調整できる点から好ましい。
【００２０】
また、本発明の管用粉体塗料組成物には、固形エポキシ樹脂（Ａ）として、前記エポキシ樹脂の他に、さらに、防食性を付与するため、本発明の効果を損なわない範囲で、ビフェニル型エポキシ樹脂、ナフタレン型エポキシ樹脂、ジヒドロキシベンゼン型エポキシ樹脂、ジシクロペンタジエンフェノール型エポキシ樹脂等、低溶融粘度の固形のエポキシ樹脂を併用してもよい。
【００２１】
次に、硬化剤（Ｂ）としては、特に限定されず、イミダゾール系化合物、イミダゾリン系化合物、ジシアンジアミド、ポリカルボン酸ヒドラジド及びその誘導体、フェノール樹脂及びその誘導体等が挙げられる。なかでも、イミダゾール系化合物、イミダゾリン系化合物またはポリカルボン酸ヒドラジド及びその誘導体を単独または併用して用いることが塗膜の防食性、可撓性、密着性および強度が著しく良好となる点から好ましい。
【００２２】
ここで用いられるイミダゾール系化合物としては、特に限定されるものではないが、例えばイミダゾール、メチルイミダゾール、ドデシルイミダゾール、ヘプタデシルイミダゾール、フェニルイミダゾール等やそれらの１−シアノエチル化物、１−シアノエチル化物・トリメリット酸混合物、イソシアヌル酸付加物等が挙げられる。また、イミダゾリン系化合物としては、メチルイミダゾリン、ドデシルイミダゾリン、ヘプタデシルイミダゾリン、フェニルイミダゾリン等が挙げられる。これらは、単独でも、あるいは２種以上組み合わせて使用することができる。
【００２３】
また、ポリカルボン酸ヒドラジド及びその誘導体としては、特に限定されるものではなく、例えば、ポリカルボン酸ヒドラジドとしては、コハク酸ジヒドラジド、アジピン酸ジヒドラジド、セバチン酸ジヒドラジド、イソフタル酸ジヒドラジド等が挙げられる。その誘導体としては、例えば、Ｎ−シクロヘキシル−β−アミノプロピオンヒドラジド、Ｎ−フェニル−β−アミノプロピオンヒドラジド、Ｎ−ブチル−β−アミノプロピオンヒドラジド、Ｎ−ベンジル−β−アミノプロピオンヒドラジド等のＮ−置換−β−アミノプロピオンヒドラジド類が挙げられる。
【００２４】
また、フェノール樹脂及びその誘導体としては、常温で固形であれば特に限定されず、例えば、フェノールホルムアルデヒド樹脂、クレゾールホルムアルデヒド樹脂、ビスフェノールＡホルムアルデヒド樹脂やそれらとトリアジンとの反応物、ビスフェノール類とビスフェノール型エポキシ樹脂との反応物等が挙げられる。中でも、粉体塗料としての貯蔵安定性、流動性の向上から、軟化点７０〜１３０℃のものが好ましい。例えば、フェノライトＴＤ−２０９０（大日本インキ化学製：軟化点１２０℃）、フェノライトＶＨ−４１７０（大日本インキ化学製：軟化点１０５℃）、フェノライトＫＨ−６１１５（大日本インキ化学製：軟化点１１５℃）が挙げられる。
【００２５】
また、本発明の管用粉体塗料組成物には、必要に応じて硬化促進剤を併用しても良い。硬化促進剤としては、特に限定されるものではないが、例えば、コハク酸、アジピン酸、サリチル酸、スベリン酸、セバチン酸等の有機酸が挙げられる。
【００２６】
充填剤（Ｃ）としては、特に限定されず、通常広く使用される体質顔料又は着色剤を使用することが出来る。体質顔料としては、例えば、硫酸バリウム、タルク、炭酸カルシウム、炭酸バリウム、シリカ、マイカ、アルミナなどが挙げられ、単独あるいは２種類以上組み合わせて使用することができる。また、着色剤としては酸化チタン、酸化鉄、ベンガラ、カーボンブラック、フタロシアニングリーン、フタロシアニンブルー、キナクリドンレッドなどを配合することができる。これらの体質顔料又は着色材の使用量は特に限定されるものではないが、粉体塗料中１０〜５０重量％となる範囲であることが好ましい。
【００２７】
また、本発明の管用粉体塗料組成物には、必要に応じて流展剤、ワキ防止剤、アエロジル等の添加剤を配合することも出来る。
【００２８】
かかる材料を用いての粉体塗料化は、通常の方法にて行うことができる。例えば、上述した固形エポキシ樹脂（Ａ）、硬化剤（Ｂ）及び充填剤（Ｃ）、更に必要に応じその他の添加剤などを粗粉砕、配合し、この配合物をヘンシェルミキサーなどを用いて充分に粉砕、混合した後に、加熱されたニーダーや押し出し機を用いて溶融混練し、冷却後粉砕、分級して得られる。
【００２９】
この様にして得られる本発明の管用粉体塗料組成物の平均粒子径は、塗着効率が良好となる点から１０μｍ以上であることが好ましく、塗装表面の平滑性が良好となる点から１５０μｍ以下であることが好ましい。
【００３０】
また、被塗物である管としては、特に限定されないが、直管、異形管形状の鋳鉄管、鋼管等、及びその付属品類等が挙げられる。
【００３１】
管内表面への塗装方法としては、特に制限されないが、吹き付け塗装、静電吹き付け塗装、遠心投射法、流動浸漬塗装等の方法が挙げられ、塗膜の膜厚は０．１〜１．５ｍｍであることが防食、ピンホール防止性の点から好ましい。
【００３２】
【実施例】
以下に本発明を実施例により詳述するが、本発明はこれに限定されるものではない。
合成例１
温度計、適下ロート、冷却管、撹拌機、邪魔板を備えた、下部に分液コック付きの２リットルのセパラブルフラスコに、ビスフェノールＦ２６２ｇ、ハイドロキノン８８ｇ、エピクロルヒドリン２２２ｇ、イソプロピルアルコール１４６ｇ及びメチルイソブチルケトン１４６ｇを仕込み、撹拌し、溶解させ、４０℃に加熱した。その後滴下ロートより、２０％水酸化ナトリウム水溶液５１２ｇを２時間かけて適下した。適下終了後６０分間撹拌を続け、反応を完結させた。次に、メチルイソブチルケトン４８６ｇを追加し、３０分間撹拌後、停止・静置し、下層の食塩水を分液し除いた。次に、水２４３ｇ、メチルイソブチルケトン１４６ｇを仕込み、３０分間攪拌後、停止・静置し、下層を分液し除いた。その後、脱水、イソプロパノール回収、濾過を経てメチルイソブチルケトンを蒸留回収させてエポキシ樹脂（ａ）を得た。エポキシ樹脂（ａ）のエポキシ当量は９７０ｇ／ｅｑ、軟化点は８５℃であった。
【００３３】
合成例２
攪拌機、温度計、冷却器を備えた、２リットルの四つ口フラスコに、市販のビスフェノールＦ型エポキシ樹脂（ＥＰＩＣＬＯＮ ８３０−Ｓ、大日本インキ化学工業社製、エポキシ当量＝１７０g/eq）１４００ｇ、ビスフェノールＦ５３２ｇ、２−ターシャルブチルハイドロキノン６８ｇと、５０％テトラメチルアンモニウムクロライド０．２ｇを入れ攪拌をし、１４０℃まで約２時間かけ昇温し、更に１４０℃で５時間分攪拌しエポキシ樹脂（ｂ）を得た。得られたエポキシ樹脂（ｂ）は、エポキシ当量＝９４７g/eq、軟化点＝９４℃であった。
【００３４】
合成例３
ビスフェノールＦを除き、２−ターシャルブチルハイドロキノン５１０ｇとする以外は、合成例２と同様の工程操作を用いエポキシ樹脂（ｃ）を得た。得られたエポキシ樹脂（ｃ）は、エポキシ当量＝９３５g/eq、軟化点＝９６℃であった。
【００３５】
合成例４
温度計、適下ロート、冷却管、撹拌機、邪魔板を備えた、下部に分液コック付きの２リットルのセパラブルフラスコに、ビスフェノールＦ３７５ｇ、エピクロルヒドリン２０５ｇ、イソプロピルアルコール１５０ｇ、メチルイソブチルケトン１５０ｇを仕込、撹拌、溶解させ、４０℃に加熱した。その後滴下ロートより、２０％水酸化ナトリウム水溶液４８７ｇを２時間かけて適下した。適下終了後６０分間撹拌を続け、反応を完結させた。次に、メチルイソブチルケトン５００ｇ追加し３０分間撹拌後、停止・静置し、下層の食塩水を分液し除いた。次に、水２５０ｇを仕込、３０分間攪拌後、停止・静置し、下層を分液し除いた。その後、脱水、イソプロパノール回収、濾過を経てメチルイソブチルケトンを蒸留回収させてエポキシ樹脂（ｄ）を得た。エポキシ樹脂（ｄ）のエポキシ当量は９０２ｇ／ｅｑ、軟化点は８５℃であった。
【００３６】
合成例５
市販の液状ビスフェノールＦ型エポキシ樹脂（ＥＰＩＣＬＯＮ ８３０Ｓ、大日本インキ化学工業社製、エポキシ当量＝１７０ｇ／ｅｑ）１４００ｇ及び、ビスフェノールＦ６００ｇを用い、２−ターシャルブチルハイドロキノンを用いなかった以外は合成例２と同様にして反応を行い、エポキシ樹脂（ｅ）を得た。得られたエポキシ樹脂（ｅ）は、エポキシ当量＝９２０g/eq、軟化点＝９７℃であった。
【００３７】
実施例１〜４及び比較例１〜４
合成例１〜５から得られた固形エポキシ樹脂（ａ）〜（ｅ）と市販の固形のビスフェノールＡ型エポキシ樹脂（ＥＰＩＣＬＯＮ ４０５０、大日本インキ化学工業製、エポキシ当量＝９２０ｇ／ｅｑ、軟化点９７℃）（以下、樹脂（ｆ）という。）を、それぞれ、硬化剤、充填剤、添加剤とともに、下記の表１、２に記載の割合で配合し、ヘンシェルミキサーを用いて充分に粉砕、混合した。その後Ｂｕｓｓ社製 コ・ニーダーＰＣＳ−３０を用い溶融混練し、混練物は冷却後粉砕、分級して粒径２０〜５０μｍの粉体塗料を得た。なお、実施例１〜４及び比較例１〜４で得られた粉体塗料は、それぞれ、塗料１〜８として、以下の試験例に供した。
【００３８】
【表１】

【００３９】
【表２】

【００４０】
試験例１
得られた塗料１〜８の貯蔵安定性、硬化塗膜の外観、硬化性、耐衝撃試験、エリクセン試験、塩水噴霧試験、耐水性の評価を以下の基準に従って行った。その結果を表３、４に示す。
なお、硬化塗膜の外観、硬化性および耐水性は、ショットブラストにより酸化スケールを除去した１５０ｍｍ×７０ｍｍ×７．０ｍｍのダクタイル鋳鉄片を試験片として、１６０〜１８０℃に加熱した試験片の表面に得られた粉体塗料を吹き付け塗装したのち放冷して、膜厚２５０〜３５０μｍ前後の塗膜を形成して評価を行った。表３、４の予熱温度とは、塗装直前の温度である。
また、耐衝撃試験及び塩水噴霧試験は、１５０ｍｍ×７０ｍｍ×２．０ｍｍの鋼板を、エリクセン試験は、９０ｍｍ×９０ｍｍ×１．２ｍｍの鋼板を試験片として、同様にそれぞれ２５０〜３５０μｍの塗膜を形成し、１５０℃×１０分の後加熱をした後、評価を行った。
【００４１】
（貯蔵安定性）
高さ１０ｍｍ・５０ｍｍφのガラスシャーレーに、作成した粉体塗料を５ｇ敷き、２０ｇ・４０ｍｍφのおもしを置き、４０℃で１週間保存し、形状の変化を確認した。
ブロッキングなし：○、ブロッキングあり：×
（硬化塗膜の外観）
塗膜表面の平滑度を目視で確認した。
平滑性あり：○、平滑性不良：×
（硬化性)
塗膜面をアセトンによる溶剤ラビングすることで硬化性を調べた。
良好：○、硬化性不足：×
（耐衝撃試験）
ＪＩＳ Ｋ ５４００-１９９０の８・３・２（デュポン式衝撃試験）により、５００ｇでの耐衝撃高さを確認した。単位（ｃｍ）
（エリクセン試験）
ＪＩＳ Ｚ ２２４７のＡ法により、塗膜にクラックが入るまでの最大押し出し量を確認した。単位（ｍｍ）
（塩水噴霧試験）
塗膜面に基材に達する傷を入れ、３５℃で５％ＮａＣｌ水溶液を１０００時間連続噴霧した後の塗膜の状態、および傷口にナイフをいれてのクリープ試験を行い、剥離幅を確認した。
剥離幅１ｍｍ未満：○、剥離幅３〜４ｍｍ：×、剥離幅４〜５ｍｍ：××
（耐水性）
試験片を水中に６ヶ月間浸漬した後の塗膜の状態を確認した。
状態異常なし：○、異常有り：×
【００４２】
【表３】

【００４３】
【表４】

【００４４】
このように、本発明の実施例１〜４の塗料は、貯蔵安定性、硬化塗膜の外観、硬化性、耐衝撃試験、エリクセン試験、塩水噴霧試験、耐水性のすべての項目で良好な結果が得られた。これに対し、比較例１〜４の塗料は、特に予熱条件を１５０℃としたときの結果がよくなかった。
【００４５】
実施例５、６及び比較例５
上記の塗料1及び塗料２（実施例５、６）、及び塗料７（比較例５）を用い、それぞれ、直径１００ｍｍ×長さ４ｍのダクタイル鋳鉄管を表５に記載の予熱条件で予熱し、鋳鉄管を毎分５００ｒｐｍで回転させながら内面に吹き付け塗装を行い、膜厚４００〜５００μｍ前後の塗膜を形成し、塗膜外観の観察、ピンホール発生の有無、硬化性の確認を行った。
なお、ピンホール発生の有無の確認は目視にて行った。
○：ピンホールなし、×：ピンホール発生
その結果を表５に示す。
【００４６】
【表５】

【００４７】
このように、本発明の実施例５，６の塗料は、塗膜外観がよく、ピンホールが発生せず、硬化性も良好であった。これに対し、比較例５の塗料は、予熱条件を１５０℃としたときの結果が不良であった。
【００４８】
【発明の効果】
本発明によれば、低温焼き付け条件下における硬化性及び機械物性に優れ、なおかつ貯蔵安定性に優れる管用粉体塗料組成物を提供できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a powder coating composition for pipes suitable for coating inner and outer surfaces of metal pipes, and more specifically, for pipes having excellent curability and mechanical properties under low-temperature baking conditions for metal pipes and excellent storage stability. The present invention relates to a powder coating composition.
[0002]
[Prior art and problems to be solved by the invention]
Metal pipes that are widely used for fluid transportation, such as water and sewage pipes, industrial water pipes, and gas pipes, are usually painted on the inside and outside surfaces to prevent corrosion caused by embedding in the soil or corrosion caused by fluids. .
Such coating is required to have excellent physical properties such as corrosion resistance, adhesion, water resistance, chemical resistance and mechanical properties. In particular, since the sizes and shapes of the objects to be coated have been diversified in recent years, it is important to obtain good film properties. Among them, painting using an epoxy powder coating is widely used because it has excellent physical properties and many achievements.
[0003]
Coating with an epoxy powder coating is, for example, preheating a metal tube as an object to be coated above the curing temperature of the epoxy powder coating, and spraying the epoxy powder coating on the inner and outer surfaces to form a coating film. Has been done.
For example, bisphenol A type epoxy resins are generally used as epoxy powder coatings for metal tubes because of their good balance of physical properties, but in order to ensure sufficient anticorrosion and long-term reliability, It is necessary to make it thicker than powder coating. For this reason, in order to sufficiently cure after coating, it is necessary to preheat the article to be coated at a temperature higher than the curing temperature of the epoxy resin, that is, 200 ° C. or higher.
[0004]
In recent years, it has been desired to lower the preheating temperature due to the problem of energy cost reduction. However, when the preheating temperature is lowered, there is a problem that a coating film having good physical properties cannot be obtained.
For example, when bisphenol A type epoxy resin is used as an epoxy powder coating for metal pipes, in a curing system in which the current preheating temperature of 200 ° C. or higher is reduced to 150 to 180 ° C., the appearance of the coating film is poor or the curing is poor. This causes problems such as deterioration of physical properties of the coating film and generation of pinholes.
[0005]
In order to prevent the occurrence of these problems, it is necessary to improve the flowability and curability of the powder coating material.
As means for improving the flowability and curability of the powder coating, for example, the following methods (1) to (3) are known.
(1) A method in which a polyfunctional novolac type epoxy resin is used in combination with a solid bisphenol A type epoxy resin as an epoxy resin used as a main component of a powder coating.
(2) A method of using a solid bisphenol F type epoxy resin as an epoxy resin used as a main component of a powder coating.
(3) A method of using an epoxy resin having a lower molecular weight than solid bisphenol A type epoxy resin.
[0006]
However, when the methods (1) and (2) are applied, although the curability is improved, the crosslink density increases due to the novolac type epoxy resin or the bisphenol F type epoxy resin, and the cured product (coating film). Has the disadvantage of becoming brittle. In addition, when the method (3) is applied, the flowability is improved, but the powder coating is likely to be blocked, which is a serious problem in the storage management of the coating.
[0007]
Therefore, it is desired to develop a powder coating for a metal tube that improves both flowability and curability and that provides good coating properties even when the preheating temperature is lowered.
That is, the problem to be solved by the present invention is that epoxy resin tube powder that can be baked onto a metal tube or the like at a lower temperature than before, has excellent curability, physical properties of the coating film, and excellent storage stability. The object is to provide a body paint composition.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have used a specific solid epoxy resin (A), so that the curability under a low-temperature baking condition of 200 ° C. or less, preferably 180 ° C. or less, and a coating film The inventors have found a powder coating composition for metal tubes that has excellent physical properties and excellent storage stability of the coating.
[0009]
That is, the present invention is a powder coating composition for a tube comprising a solid epoxy resin (A), a curing agent (B) and a filler (C) as essential components,
The solid epoxy resin (A) is
Bisphenol F (a1 ), general formula (I):
[Chemical formula 5]

[Wherein R ^{1 to} R ⁴ are H or an alkyl group having 1 to 9 carbon atoms]
A powder coating composition for pipes, characterized in that it is an epoxy resin obtained by an extension reaction of an epoxy resin derived from a dihydric phenol (a2) and an epihalohydrin represented by the formula: and bisphenol F (a1) . It is.
[0010]
The epoxy resin blended as the solid epoxy resin (A) in the present invention has a lower melt viscosity than the conventional bisphenol A type solid epoxy resin. For this reason, it has excellent flowability in the low temperature region, so it can be cured under low-temperature baking conditions, and it promotes the diffusion of gas generated from the moisture contained in the surface of the metal tube and the interior during the curing. Suppresses the occurrence.
Furthermore, compared with the conventional bisphenol F type solid epoxy resin, a coating film excellent in flexibility and impact resistance can be obtained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail.
In the present invention, the epoxy resin used as the solid epoxy resin (A) includes, as raw materials, bisphenol F and general formula (I):
[Chemical 6]

[Wherein R ^{1 to} R ⁴ are H or an alkyl group having 1 to 9 carbon atoms]
The divalent phenol represented by (a2) is an epoxy resin used, and can be obtained by, for example, the production methods shown in the following (1) to (3).
(1) Derived from bisphenol F (a1), the divalent phenols (a2), and epihalohydrin.
(2) The epoxy resin derived in (1) and bisphenol F (a1) are subjected to an extension reaction.
(3) Conventional bisphenol F-type epoxy resin (x1) in which the dihydric phenols (a2) are not used as raw materials, the dihydric phenols (a2), and bisphenol F as an optional component (A1) is subjected to an extension reaction.
[0012]
Examples of the divalent phenols (a2) include hydroquinone, catechol, resorcin, propyldihydroxybenzene, dipropyldihydroxybenzene, butyldihydroxybenzene, dibutyldihydroxybenzene, octyldihydroxybenzene, dioctyldihydroxybenzene, nonyldihydroxybenzene, Examples include dinonyl dihydroxybenzene and trimethylhydroquinone. These compounds can be used alone or in combination of two or more. Among these, hydroquinone, trimethylhydroquinone, tertiary butyl dihydroxybenzene, and ditertiary butyl dihydroxybenzene are preferable from the viewpoint of good curability and coating film physical properties of the obtained powder coating material.
[0013]
The tertiary butyl dihydroxybenzene and ditertiary butyl dihydroxybenzene will be described in more detail. For example, as butyl dihydroxybenzene, 2-tertiary butyl hydroquinone, 2-tertiary butyl resorcin, 4-tertiary butyl resorcin, 5-tertiary Examples include dibutyl diresorbenzene, 3,5-di-tertiary butyl hydroquinone, 2,4-di-tertiary butyl resorcin, and the like. 2,5-di-tertiary butyl resorcin, 4,5-di-tertiary butyl resorcin, 4,6-di-tertiary butyl resorcin, 3,4-di-tertiary butyl resorcin, 4, - di - tertiary butyl resorcin, and the like. Among these, those having a hydroquinone structure as butyldihydroxybenzene are particularly preferred, and 2-tertiary butyl hydroquinone is more preferred.
[0014]
The epihalohydrin is not particularly limited, and examples thereof include epichlorohydrin, β-methylepichlorohydrin, epibromohydrin, β-methylepibromohydrin, and the like. Among these, epichlorohydrin is preferable from the viewpoint of reactivity.
[0015]
Although it does not restrict | limit especially as a specific manufacturing method of said (1), For example, with respect to 1 equivalent of all the hydroxyl groups of the said bisphenol F (a1) and the said bivalent phenol (a2), Epihalohydrin is added in an amount of 0.3 to 10 equivalents, and the reaction can be performed in the presence of a base at 40 to 100 ° C. under normal pressure or reduced pressure using a solvent as necessary.
The reaction ratio between the bisphenol F (a1) and the divalent phenols (a2) is preferably 99/1 to 70/30 (mass ratio), particularly preferably 98/2 to 72/28.
Examples of the solvent include alcohols such as isopropyl alcohol and butanol, ethers such as dioxane, aprotic polar solvents such as dimethyl sulfoxide and 1,3-dimethylimidazolidinone.
Although it does not specifically limit as said base, Potassium hydroxide, sodium hydroxide, barium hydroxide, magnesium oxide, sodium carbonate, potassium carbonate etc. are mentioned. Of these, potassium hydroxide and sodium hydroxide are preferred. These bases are preferably used either in an aqueous solution or in a solid form.
[0016]
Next, as a specific production method of (2), for example, the epoxy resin derived in (1) and bisphenol F (a1) are reacted by heating and stirring at 120 to 220 ° C. in the presence of a catalyst. Let The catalyst used here is not particularly limited, and examples thereof include onium salts, phosphines, alkali metal hydroxides, and the like.
The reaction ratio between the epoxy resin and the bisphenol F (a1) is such that the ratio of the bisphenol F (a1) and the phenol (a2) in the obtained epoxy resin (A) is 99/1 to 70/30. It is preferable to adjust so that.
[0017]
Next, as a specific production method of the above (3), for example, a conventional bisphenol F-type epoxy resin (x1) and the divalent phenols (a2) are optionally combined with bisphenol F (a1). ) Is added and heated and stirred at 120 to 220 ° C. in the presence of a catalyst.
Here, the conventional bisphenol F type epoxy resin (x1) is not particularly limited as long as bisphenol F is used as a raw material and the dihydric phenols (a2) are not used. For example, EPICLON 830, EPICLON 830S (Epoxy resin manufactured by Dainippon Ink & Chemicals, Inc.) can be used. The catalyst is not particularly limited, and examples thereof include onium salts, phosphines, alkali metal hydroxides, and the like.
The reaction ratio of (x1), (a2) and (a1) is such that the ratio of bisphenol F (a1) to the phenols (a2) in the obtained epoxy resin (A) is 99/1 to 70/30. It is preferable to adjust so that.
[0018]
The epoxy resin obtained as described above is not particularly limited, but has an epoxy equivalent of 500 g / eq to 2000 g / eq from the viewpoint of blocking resistance and ease of forming a powder coating material. A softening point of 70 to 130 ° C. by the method (5 ° C./minute temperature raising method) is preferable. In particular, from the standpoint of these effects, the epoxy equivalent is preferably 600 g / eq to 1300 g / eq, and the softening point by the ring-and-ball method (5 ° C./minute temperature raising method) is preferably 80 to 105 ° C.
[0019]
Of the production methods (1) to (3) for the epoxy resin, the production method (3) is for adjusting the desired epoxy equivalent and molecular weight, or using bisphenol F (a1) and the divalent phenols. This is preferable because the amount of (a2) introduced into the resin can be easily adjusted.
[0020]
Moreover, in addition to the said epoxy resin as a solid epoxy resin (A), in addition to the said epoxy resin, in addition to the said epoxy resin, the powder coating composition for pipes of this invention WHEREIN: In the range which does not impair the effect of this invention, A solid epoxy resin having a low melt viscosity such as an epoxy resin, a naphthalene type epoxy resin, a dihydroxybenzene type epoxy resin, a dicyclopentadiene phenol type epoxy resin may be used in combination.
[0021]
Next, the curing agent (B) is not particularly limited, and examples thereof include imidazole compounds, imidazoline compounds, dicyandiamide, polycarboxylic acid hydrazide and derivatives thereof, phenol resins and derivatives thereof. Of these, the use of an imidazole compound, an imidazoline compound, polycarboxylic acid hydrazide, or a derivative thereof alone or in combination is preferable from the viewpoint that the corrosion resistance, flexibility, adhesion, and strength of the coating film are remarkably improved.
[0022]
Although it does not specifically limit as an imidazole type compound used here, For example, imidazole, methyl imidazole, dodecyl imidazole, heptadecyl imidazole, phenyl imidazole, etc., those 1-cyanoethylated compounds, 1-cyanoethylated compounds, trimellit An acid mixture, an isocyanuric acid adduct, etc. are mentioned. Examples of the imidazoline compound include methyl imidazoline, dodecyl imidazoline, heptadecyl imidazoline, phenyl imidazoline, and the like. These may be used alone or in combination of two or more.
[0023]
The polycarboxylic acid hydrazide and its derivatives are not particularly limited, and examples of the polycarboxylic acid hydrazide include succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide and the like. Examples of the derivatives include N-cyclohexyl-β-aminopropion hydrazide, N-phenyl-β-aminopropion hydrazide, N-butyl-β-aminopropion hydrazide, N-benzyl-β-aminopropion hydrazide and the like. Substituted -β-aminopropion hydrazides are mentioned.
[0024]
The phenol resin and its derivative are not particularly limited as long as they are solid at room temperature. For example, phenol formaldehyde resin, cresol formaldehyde resin, bisphenol A formaldehyde resin and a reaction product thereof with triazine, bisphenols and bisphenol type epoxy Examples include a reaction product with a resin. Among these, those having a softening point of 70 to 130 ° C. are preferable from the viewpoint of improving storage stability and fluidity as a powder coating material. For example, Phenolite TD-2090 (Dainippon Ink Chemical Co., Ltd .: softening point 120 ° C.), Phenolite VH-4170 (Dainippon Ink Chemical Co., Ltd .: softening point 105 ° C.), Phenolite KH-6115 (Dainippon Ink Chemical Co., Ltd .: Softening point 115 ° C.).
[0025]
Moreover, you may use a hardening accelerator together with the powder coating composition for pipes of this invention as needed. The curing accelerator is not particularly limited, and examples thereof include organic acids such as succinic acid, adipic acid, salicylic acid, suberic acid, and sebacic acid.
[0026]
The filler (C) is not particularly limited, and extender pigments or colorants that are ordinarily widely used can be used. Examples of extender pigments include barium sulfate, talc, calcium carbonate, barium carbonate, silica, mica, and alumina, and these can be used alone or in combination of two or more. Further, as the colorant, titanium oxide, iron oxide, bengara, carbon black, phthalocyanine green, phthalocyanine blue, quinacridone red and the like can be blended. The amount of these extender pigments or colorants used is not particularly limited, but is preferably in the range of 10 to 50% by weight in the powder coating.
[0027]
Moreover, additives, such as a spreading agent, an anti-bacterial agent, and an aerosil, can also be mix | blended with the powder coating composition for pipes of this invention as needed.
[0028]
The powder coating using such a material can be performed by a usual method. For example, the above-mentioned solid epoxy resin (A), curing agent (B) and filler (C), and other additives, if necessary, are coarsely pulverized and blended, and this blend is sufficiently obtained using a Henschel mixer or the like. After being pulverized and mixed, the mixture is melt kneaded using a heated kneader or an extruder, pulverized and classified after cooling.
[0029]
The average particle diameter of the powder coating composition for pipes of the present invention thus obtained is preferably 10 μm or more from the viewpoint of good coating efficiency, and 150 μm from the viewpoint of good smoothness of the coating surface. The following is preferable.
[0030]
The pipe to be coated is not particularly limited, and examples thereof include a straight pipe, a deformed pipe-shaped cast iron pipe, a steel pipe, and accessories thereof.
[0031]
The coating method on the inner surface of the tube is not particularly limited, but examples thereof include spray coating, electrostatic spray coating, centrifugal projection method, fluidized immersion coating, etc., and the coating film thickness is 0.1 to 1.5 mm. It is preferable from the viewpoint of anticorrosion and pinhole prevention.
[0032]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.
Synthesis example 1
A 2-liter separable flask equipped with a thermometer, a suitable funnel, a condenser, a stirrer, and a baffle plate with a separatory cock at the bottom, 262 g of bisphenol F, 88 g of hydroquinone, 222 g of epichlorohydrin, 146 g of isopropyl alcohol and methyl isobutyl ketone 146 g was charged, stirred, dissolved and heated to 40 ° C. Thereafter, from a dropping funnel, 512 g of a 20% aqueous sodium hydroxide solution was appropriately applied over 2 hours. Stirring was continued for 60 minutes after completion of the proper condition to complete the reaction. Next, 486 g of methyl isobutyl ketone was added, and after stirring for 30 minutes, it was stopped and allowed to stand, and the lower layer saline was separated and removed. Next, 243 g of water and 146 g of methyl isobutyl ketone were charged, stirred for 30 minutes, stopped and allowed to stand, and the lower layer was separated and removed. Thereafter, methyl isobutyl ketone was recovered by distillation through dehydration, isopropanol recovery, and filtration to obtain an epoxy resin (a). The epoxy equivalent of the epoxy resin (a) was 970 g / eq, and the softening point was 85 ° C.
[0033]
Synthesis example 2
In a 2 liter four-necked flask equipped with a stirrer, a thermometer, and a condenser, 1400 g of a commercially available bisphenol F type epoxy resin (EPICLON 830-S, manufactured by Dainippon Ink and Chemicals, epoxy equivalent = 170 g / eq), Bisphenol F532g, 2-tertiarybutylhydroquinone 68g and 50% tetramethylammonium chloride 0.2g were added and stirred, heated to 140 ° C over about 2 hours, and further stirred at 140 ° C for 5 hours to obtain an epoxy resin ( b) was obtained. The obtained epoxy resin (b) had an epoxy equivalent = 947 g / eq and a softening point = 94 ° C.
[0034]
Synthesis example 3
Except for bisphenol F, an epoxy resin (c) was obtained using the same process operations as in Synthesis Example 2, except that 510 g of 2-tert-butylhydroquinone was used. The obtained epoxy resin (c) had an epoxy equivalent = 935 g / eq and a softening point = 96 ° C.
[0035]
Synthesis example 4
A 2 liter separable flask equipped with a thermometer, a suitable funnel, a condenser, a stirrer, and a baffle plate with a separator cock at the bottom is charged with 375 g of bisphenol F, 205 g of epichlorohydrin, 150 g of isopropyl alcohol, and 150 g of methyl isobutyl ketone. , Stirred, dissolved and heated to 40 ° C. Thereafter, 487 g of a 20% aqueous sodium hydroxide solution was appropriately applied from the dropping funnel over 2 hours. Stirring was continued for 60 minutes after completion of the proper condition to complete the reaction. Next, 500 g of methyl isobutyl ketone was added, stirred for 30 minutes, then stopped and allowed to stand, and the lower layer saline solution was separated and removed. Next, 250 g of water was charged, stirred for 30 minutes, stopped and allowed to stand, and the lower layer was separated and removed. Thereafter, methyl isobutyl ketone was recovered by distillation through dehydration, isopropanol recovery, and filtration to obtain an epoxy resin (d). The epoxy equivalent of the epoxy resin (d) was 902 g / eq, and the softening point was 85 ° C.
[0036]
Synthesis example 5
Synthesis Example 2 except that 1400 g of commercially available liquid bisphenol F type epoxy resin (EPICLON 830S, manufactured by Dainippon Ink and Chemicals, Epoxy equivalent = 170 g / eq) and bisphenol F 600 g were used and 2-tertiarybutyl hydroquinone was not used. In the same manner as above, an epoxy resin (e) was obtained. The obtained epoxy resin (e) had an epoxy equivalent of 920 g / eq and a softening point of 97 ° C.
[0037]
Examples 1-4 and Comparative Examples 1-4
Solid epoxy resins (a) to (e) obtained from Synthesis Examples 1 to 5 and a commercially available solid bisphenol A type epoxy resin (EPICLON 4050, manufactured by Dainippon Ink & Chemicals, epoxy equivalent = 920 g / eq, softening point 97 ° C.) (hereinafter referred to as resin (f)) together with a curing agent, a filler, and an additive, respectively, in the proportions shown in Tables 1 and 2 below, and sufficiently pulverized and mixed using a Henschel mixer did. Thereafter, it was melt-kneaded using a Co-kneader PCS-30 manufactured by Buss, and the kneaded product was pulverized and classified after cooling to obtain a powder coating material having a particle size of 20 to 50 μm. In addition, the powder coating material obtained in Examples 1-4 and Comparative Examples 1-4 was used for the following test examples as the coating materials 1-8, respectively.
[0038]
[Table 1]

[0039]
[Table 2]

[0040]
Test example 1
The storage stability, appearance of the cured coating film, curability, impact resistance test, Erichsen test, salt spray test, and water resistance evaluation of the obtained paints 1 to 8 were performed according to the following criteria. The results are shown in Tables 3 and 4.
The appearance, curability and water resistance of the cured coating film are the surface of the test piece heated to 160-180 ° C. using a 150 mm × 70 mm × 7.0 mm ductile cast iron piece from which the oxide scale was removed by shot blasting. The obtained powder coating was sprayed and then allowed to cool to form a coating film having a thickness of about 250 to 350 μm for evaluation. The preheating temperature in Tables 3 and 4 is the temperature immediately before coating.
In addition, the impact resistance test and the salt spray test were performed using a steel plate of 150 mm × 70 mm × 2.0 mm, and the Eriksen test was performed using a steel plate of 90 mm × 90 mm × 1.2 mm as a test piece. After forming and post-heating at 150 ° C. for 10 minutes, the evaluation was performed.
[0041]
(Storage stability)
5 g of the prepared powder coating material was spread on a glass petri dish with a height of 10 mm and 50 mmφ, a weight of 20 g and 40 mmφ was placed, and stored at 40 ° C. for 1 week to confirm the change in shape.
Without blocking: ○, with blocking: ×
(Appearance of cured coating)
The smoothness of the coating film surface was confirmed visually.
Smoothness: ○, poor smoothness: ×
(Curable)
Curability was investigated by solvent rubbing the surface of the coating with acetone.
Good: ○, insufficient curability: ×
(Shock resistance test)
The impact resistance height at 500 g was confirmed according to JIS K 5400-1990 8.3.2 (DuPont impact test). Unit (cm)
(Eriksen test)
The maximum extrusion amount until cracks occurred in the coating film was confirmed by A method of JIS Z 2247. Unit (mm)
(Salt spray test)
Scratches reaching the substrate were put on the surface of the coating, and the state of the coating after continuous spraying of a 5% NaCl aqueous solution at 35 ° C. for 1000 hours and a creep test with a knife inserted into the wound were confirmed, and the peel width was confirmed. .
Peel width less than 1 mm: ○, Peel width 3-4 mm: x, Peel width 4-5 mm: xx
(water resistant)
The state of the coating film after the test piece was immersed in water for 6 months was confirmed.
No abnormal condition: ○, abnormal condition: ×
[0042]
[Table 3]

[0043]
[Table 4]

[0044]
Thus, the paints of Examples 1 to 4 of the present invention have good results in all items of storage stability, appearance of cured coating film, curability, impact resistance test, Erichsen test, salt spray test, and water resistance. was gotten. On the other hand, the coating materials of Comparative Examples 1 to 4 did not give good results when the preheating condition was 150 ° C.
[0045]
Examples 5 and 6 and Comparative Example 5
Using the above paint 1 and paint 2 (Examples 5 and 6) and paint 7 (Comparative Example 5), respectively, preheat ductile cast iron pipes having a diameter of 100 mm and a length of 4 m under the preheating conditions described in Table 5, The cast iron pipe was sprayed onto the inner surface while rotating at 500 rpm to form a coating film having a film thickness of about 400 to 500 μm, and the appearance of the coating film was observed, whether or not pinholes were generated, and the curability was confirmed.
In addition, the presence or absence of pinhole generation | occurrence | production was confirmed visually.
○: No pinhole, ×: Pinhole occurrence The results are shown in Table 5.
[0046]
[Table 5]

[0047]
Thus, the paints of Examples 5 and 6 of the present invention had a good coating film appearance, no pinholes, and good curability. On the other hand, the coating material of Comparative Example 5 had poor results when the preheating condition was 150 ° C.
[0048]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the powder coating composition for pipes which is excellent in sclerosis | hardenability and mechanical property on low temperature baking conditions, and is excellent in storage stability can be provided.

Claims (6)

It is a powder coating composition for pipes comprising a solid epoxy resin (A), a curing agent (B) and a filler (C) as essential components,
  The solid epoxy resin (A) is bisphenol F (a1), general formula (I):

[Wherein R ¹ ~ R ⁴ Is H or an alkyl group having 1 to 9 carbon atoms]
A powder coating composition for pipes, characterized in that it is an epoxy resin obtained by an extension reaction of an epoxy resin derived from a dihydric phenol (a2) and an epihalohydrin represented by the formula: and bisphenol F (a1). . Epoxy equivalent of the solid epoxy resin (A) is 500 to 2000 g / eq The powder coating composition for pipes according to claim 1, which has a softening point of 70 to 130 ° C. The powder coating composition for pipes according to claim 1 or 2, wherein the curing agent (B) is an amine-based curing agent. The powder coating composition for pipes according to claim 3, wherein the amine-based curing agent is an imidazole, a polycarboxylic acid hydrazide, or a derivative thereof. The powder coating composition for pipes according to claim 1 or 2, wherein the curing agent (B) is a phenol resin having a softening point of 70 to 130 ° C or a derivative thereof. The pipe according to any one of claims 1 to 5, wherein the dihydric phenol (a2) is one or more selected from the group consisting of hydroquinone, trimethylhydroquinone and 2-tertiarybutyl hydroquinone. Powder coating composition.