JP2004223429A - Method for corrosion prevention of cast iron pipe, and cast iron pipe subjected to corrosion prevention - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To paint the outside surface of a cast iron pipe with a metallic layer containing zinc formed on its surface and to provide corrosion prevention of the cast iron pipe for a long period of time right after painting. <P>SOLUTION: The outside surface of the cast iron pipe with the metallic layer containing the zinc formed on its surface is painted with a water-base emulsion paint which is composed of a copolymer obtained by using a reactive surfactant (A) as an emulsifier and a dicyclopentadiene derivative (B) and alkoxylsilyl group-containing monomer (C) as a crosslinkable monomers and by copolymerizing the dicyclopentadiene derivative (B) and a vinyl group monomer (D) copolymerizable with the alkoxylsilyl group-containing monomer (C) and is composed of a water dispersion resin in which the component (A) occupies 0.1 to 4.0 mass% in the copolymer, the component (B) 0.01 to 20.0 mass% in the copolymer, and the component (C) 0.01 to 5.0 mass% in the copolymer and in which the minimum film forming temperature (MFT) of the copolymer is 20 to 60°C. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２２】
【化２】

上記ジシクロペンタジエン誘導体の具体例としては、ジシクロペンテニルアクリレート、ジシクロペンテニルメタアクリレート、ジシクロペンテニルオキシエチルアクリレート、ジシクロペンテニルオキシエチルメタアクリレート等があげられる。なかでも、反応性、硬化性等の点で、ジシクロペンテニルオキシエチルアクリレートが好ましい。その含有割合は、共重合体（固形分）１００質量部中に０．０１〜２０．０部に設定することが必要である。特に０．０５〜１０．０部に設定することが好ましい。すなわち、その含有割合が０．０１部未満では耐溶剤性、耐水性が劣り、２０．０部以上では経済性が劣る。
【００２３】
上記特定の水分散樹脂における架橋性モノマーとしてのアルコキシシリル基含有単量体（Ｃ）とは、下記の構造式（３）で表されるアルコキシシリル基含有単量体をいう。これが含有されることで、本発明の防食方法に用いられる塗料は、架橋により高分子化し、緻密で強靭な皮膜を形成する。この架橋システムは脱水縮合反応であり、塗装後に水の揮発が進むにつれて反応し、ジシクロペンタジエン誘導体（Ｂ）に比べ反応速度が速い特長を持つ。
【００２４】
【化３】

上記アルコキシシリル基含有単量体（Ｃ）の具体例としてはビニルトリメトキシシラン、ビニルトリエトキシシラン、ビニルトリプロポキシシラン、ビニルメチルジエトキシシラン、ビニルメチルジプロポキシシラン、ビニルトリス（β−メトキシエトキシ）シラン、γ−メタクリロキシプロピルトリメトキシシラン、γ−メタクリロキシプロピルトリエトキシシラン、γ−メタクリロキシプロピルトリプロポキシシラン、γ−メタクリロキシプロピルメチルジメトキシシラン、γ−メタクリロキシプロピルメチルジエトキシシラン、γ−メタクリロキシプロピルメチルジプロポキシシラン、γ−メタクリロキシプロピルジメチルメトキシシラン、γ−メタクリロキシプロピルジメチルエトキシシラン等があげられる。
【００２５】
これらは単独でもしくは２種以上併せて用いられ、その含有割合は、共重合体（固形分）１００質量部中に０．０１〜５．０部に設定することが必要である。特に０．０５〜３．０部に設定することが好ましい。すなわちその含有割合が０．０１部未満では耐溶剤性が劣り、５．０部以上では重合安定性や造膜性が劣る。
【００２６】
本発明によれば、架橋性モノマーとして、ジシクロペンタジエン誘導体（Ｂ）とアルコキシシリル基含有単量体（Ｃ）との二者を用いることによって、エマルション合成時の最低造膜温度（ＭＦＴ）のばらつきを生じることなく、アルコキシシリル基含有単量体（Ｃ）による速硬化にもとづき塗装鋳鉄管搬出時の初期白錆の発生を抑制できるとともに、ジシクロペンタジエン誘導体（Ｂ）による架橋密度の向上にもとづき長期防錆性、耐溶剤性、耐ブロッキング性を達成することができる。
【００２７】
上記特定の水分散樹脂における重合性ビニル基単量体（Ｄ）は、アクリル樹脂の主骨格を成す成分であるが、反応性界面活性剤（Ａ）を乳化剤として、ジシクロペンタジエン誘導体（Ｂ）、アルコキシシリル基含有単量体（Ｃ）と共重合可能なものであれば、特に限定するものではない。
【００２８】
このような重合性ビニル基単量体としては、例えば、アクリル酸、メタクリル酸、クロトン酸、イタコン酸、マレイン酸、無水マレイン酸、フマル酸等の不飽和カルボン酸類、ビニルスルホン酸、スチレンスルホン酸、スルホエチルアクリレート、スルホエチルメタクリレート等のスルホン酸基含有単量体、ヒドロキシエチルアクリレート、ヒドロキシエチルメタクリレート、ヒドロキシプロピルアクリレート、ヒドロキシプロピルメタクリレート、アリルアルコール、カプロラクトン変性ヒドロキシアクリレート、カプロラクトン変性ヒドロキシメタクリレート、ビスヒドロキシエチルフタレートのモノアクリレート、ビスヒドロキシエチルフタレートのモノメタクリレート等の水酸基含有単量体、２−アクリロキシエチルアシッドフォスフェート、２−メタクリロキシエチルアシッドフォスフェート、２−アクリロキシプロピルアシッドフォスフェート、２−メタクリロキシプロピルアシッドフォスフェート、２−アクリロキシ−３−クロロプロピルアシッドフォスフェート、２−メタクリロキシ−３−クロロプロピルアシッドフォスフェート、２−アクリロキシフェニルエチルフェニルリン酸、２−メタクリロキシフェニルエチルフェニルリン酸等の酸性リン酸エステル系単量体、メチルアクリレート、エチルアクリレート、ｎ−プロピルアクリレート、ｎ−ブチルアクリレート、イソブチルアクリレート、ｔ−ブチルアクリレート、２−エチルヘキシルアクリレート、シクロヘキシルアクリレート、イソボルニルアクリレート等のアクリル酸エステル類、メチルメタクリレート、エチルメタクリレート、ｎ−プロピルメタクリレート、ｎ−ブチルメタクリレート、イソブチルメタクリレート、ｔ−ブチルメタクリレート、２−エチルヘキシルメタクリレート、シクロヘキシルメタクリレート、イソボルニルメタクリレート等のメタクリル酸エステル類、スチレン、ビニルトルエン、α−メチルスチレン等の芳香族単量体、酢酸ビニル等のビニルエステル類、塩化ビニル、塩化ビニリデン等のハロゲン含有単量体、ビニルエーテル類、アクリロニトリル、メタクリロニトリル等のシアノ基含有単量体、Ｎ，Ｎ−ジメチルアミノエチルアクリレート、Ｎ，Ｎ−ジメチルアミノエチルメタクリレート、Ｎ−メチロールアクリルアミド、４−ビニルピリジン、ビニルイミダゾール、アクリルアミド、メタクリルアミド等の窒素含有単量体、アクリル酸グリシジル、メタクリル酸グリシジル等のグリシジル基含有単量体等があげられる。これらは単独でもしくは２種以上併せて用いられる。
【００２９】
上記特定の水分散樹脂の最低造膜温度（ＭＦＴ）は２０〜６０℃に設定する必要があり、３０〜５０℃に設定することが好ましい。最低造膜温度（ＭＦＴ）をこのような範囲に規定することで、塗装時に６０〜９０℃に予熱された鋳鉄管にエマルション塗料を塗装するときにエマルション粒子の造膜不良を起こすことがなく、また塗装された管と管とがブロッキングを起こしにくくなる。反対に２０℃以下では耐ブロッキング性が劣り、６０℃以上では造膜性が劣る。
【００３０】
本発明にもとづくこのような分散樹脂は一液硬化型分散樹脂となるが、その製造に際しては、公知の重合開始剤、連鎖移動剤、アルカリ調整剤等を使用して、目的の分子量、粘度、粒子径に仕上げることができる。
【００３１】
また、本発明の一液硬化型分散樹脂を塗料化する際には、公知の、アクリル酸のアルカリ塩等の分散剤、シリコン系、鉱物油系等の消泡剤、繊維素系、ポリアクリル酸系等の増粘剤等の添加剤、酸化チタン、カーボンブラック、酸化鉄等の着色顔料や、炭酸カルシウム、沈降性硫酸バリウム、珪酸アルミニウム等の体質顔料や、リン酸アルミ、リン酸亜鉛、メタホウ酸バリウム等の防錆顔料等の顔料、造膜助剤としての有機溶剤などを使用することができる。
【００３２】
【実施例】
以下、本発明を実施例により詳細に説明する。
（実施例１）
表１の通り、反応性界面活性剤（Ａ）としてポリオキシエチレンノニルプロペニルフェニルエーテル硫酸エステルアンモニウム塩を１．０部使用し、ジシクロペンタジエン誘導体（Ｂ）としてのジシクロペンテニルオキシエチルアクリレート２．５部と、アルコキシシリル基含有単量体（Ｃ）としてのγ−メタクリロキシプロピルトリメトキシシラン０．５部と、ビニル基単量体（Ｄ）としてのメチルメタクリレート６３．０部、２−エチルヘキシルアクリレート３３．０部、アクリル酸１．０部の混合物の合計９６．０部とを共重合させた。そして、これにより合成した固形分５０％のエマルション１００部に、４．０部のカーボンブラックペーストと、造膜助剤としての３．０部のチッソ社製のＣＳ−１２とを添加して、目的とする塗料を得た。
【００３３】
【表１】

（実施例２〜８）
反応性界面活性剤（Ａ）、ジシクロペンタジエン誘導体（Ｂ）、アルコキシシリル基含有単量体（Ｃ）、ビニル基単量体（Ｄ）の配合割合を表１に示すように変更し、また実施例４においてはビニル基単量体（Ｄ）の構成成分を表１に示すように変更して、固形分を合成した。そして、この合成した固形分５０％のエマルション１００部に、４．０部のカーボンブラックペーストと３．０部のＣＳ−１２とを添加し目的とする塗料を得た。
（比較例１）
表２に示すように、反応性界面活性剤（Ａ）の使用量を０．０５部に変更した。そして、それ以外は実施例１と同様にして、塗料を得た。
【００３４】
【表２】

（比較例２）
表２に示すように、反応性界面活性剤（Ａ）の使用量を５．０部に変更した。そして、それ以外は実施例１と同様にして、塗料を得た。
（比較例３）
表２に示すように、反応性界面活性剤（Ａ）は使用せず、それに代えて水溶性高分子界面活性剤１．０部と非反応性界面活性剤１．０部とを使用した。そして、それ以外は実施例１と同様にして、塗料を得た。
（比較例４）
表２に示すように、ジシクロペンタジエン誘導体（Ｂ）を使用せず、それに代えてメチルメタクリレートを２．５部増量した。そして、それ以外は実施例１と同様にして、塗料を得た。
（比較例５）
表２に示すように、アルコキシシリル基含有単量体（Ｃ）を使用せず、それに代えてメチルメタクリレートを０．５部増量した。そして、それ以外は実施例１と同様にして、塗料を得た。
（比較例６）
表２に示すように、メチルメタクリレートと２−エチルヘキシルアクリレートの配合量の変更によりＭＦＴを０℃に設定した。そして、それ以外は実施例１と同様にして、塗料を得た。
（比較例７）
表２に示すように、メチルメタクリレートと２−エチルヘキシルアクリレートの配合量の変更によりＭＦＴを８５℃に設定した。そして、それ以外は実施例１と同様にして、塗料を得た。
【００３５】
実施例１〜８、比較例１〜７で作成した塗料を用いて塗料安定性（機械安定性）、耐溶剤性、付着性、初期白錆発生性、防錆性、ブロッキング性の比較評価を行い、その結果を表３に示した。
【００３６】
【表３】

表３における各々の評価は、以下の方法で実施した。
【００３７】
なお、各評価試験の試験片は、次のようにして作成した。すなわち、予め亜鉛溶射された呼び径１００ｍｍの鋳鉄管を３００ｍｍの長さに輪切りし、熱風乾燥炉で表面温度６０℃に予熱した後、実施例１〜６、比較例１〜７のエマルション塗料を、乾燥膜厚が１００μｍとなるように吹付け塗装し、室温で放冷した管体を試験片とした。
（エマルションの機械安定性）
各々のエマルションの機械安定性を、下記の試験条件のもとで、マーロンテスターを用いて評価した。
【００３８】
試験条件
荷 重 ９８Ｎ／ｃｍ^２（１０ｋｇｆ／ｃｍ^２）
回転数 １０００ｒｐｍ
試験温度 ２０℃
試験時間 １０分
試 料 ５０．０ｇ
評価基準
凝集物量 ０．０１ｇ以下 ◎
０．０１〜０．０５ｇ ○
０．０５〜０．１ｇ △
０．１ｇ以上 ×
（耐溶剤性）
耐溶剤性は塗装皮膜の緻密性の指標となるものであるが、試験片を塗装後７日間室温で乾燥した後、ミネラルスピリット２ｍｌを滴下し、３０秒後に表面のミネラルスピリットをウエスで拭き取り、塗膜の軟化、膨潤の程度を評価した。
【００３９】
評価基準
塗膜の軟化が無く硬度の変化も無い ◎
塗膜の軟化は無いが硬度がやや低い ○
塗膜がやや軟化している △
塗膜の軟化が大きい ×
（付着性）
試験片を塗装後７日間室温で乾燥した後、カッターで２ｍｍ格子２５分割の傷を入れ、傷の部分にセロハンテープを貼り付けたうえでこれを剥離し、塗膜が残存した升目の数をカウントして、付着性を評価した。
（初期白錆発生性）
初期白錆発生性は成膜スピードの指標となるものであるが、塗装後３０分間室温で放冷した試験片に霧吹きでイオン交換水を吹付け、次に室温で結露環境に設定した密閉されたボックスに入れて１６時間放置し、その後の塗膜状態を評価した。
【００４０】
評価基準
白錆の発生が無い ◎
白錆の発生が極僅かに認められる ○
白錆の発生が認められる △
白錆の発生が多い ×
（防錆性）
塗装後７日間室温で乾燥した試験片を、塩水噴霧試験機で７２時間試験し、その後の塗膜状態を評価した。
【００４１】
評価基準
白錆の発生が無い ◎
白錆の発生が極僅かに認められる ○
白錆の発生が認められる △
白錆の発生が多い ×
（耐ブロッキング性）
塗装後２４時間室温で乾燥した試験片同士を井桁状に積み、６０℃で６時間加熱した後のブロッキング状態を評価した。
【００４２】
評価基準
管同士の接点での塗膜の剥離が無い ◎
管同士の接点での塗膜の剥離面の大きさが直径１ｍｍ未満 ○
管同士の接点での塗膜の剥離面の大きさが直径１ｍｍ以上３ｍｍ未満 △
管同士の接点での塗膜の剥離面の大きさが直径３ｍｍ以上 ×
（評価結果）
上記表３の結果から明らかなように、実施例１〜８は、いずれも、塗料安定性、耐溶剤性、付着性、初期白錆発生性、防錆性、耐ブロッキング性に優れた塗膜を形成したものであった。
【００４３】
一方、比較例１は、反応性界面活性剤（Ａ）が少な過ぎたため、エマルション機械安定性すなわち塗料安定性が不良であり、塗料自体が実用性に欠けるものであった。このため、試験片に塗装できるものではなかった。
【００４４】
比較例２は、逆に反応性界面活性剤（Ａ）が多過ぎたため、塗料安定性は良好であったものの、成膜スピードが遅く、このため初期白錆発生性が不良であり、又防錆性も劣っていた。
【００４５】
比較例３は、反応性界面活性剤（Ａ）を使用せず、それに代えて非反応性界面活性剤を使用し、しかも水溶性高分子界面活性剤を併用していることから、エマルション粒子の保水性は良好なものの、成膜スピードが遅く、このため初期白錆発生性が不良であり、また防錆性も劣っていた。
【００４６】
比較例４、５は、各々ジシクロペンタジエン誘導体（Ｂ成分）とアルコキシシリル基含有単量体（Ｃ成分）とのいずれか一方を使用していないため、架橋密度が不足し、このため耐溶剤性、耐ブロッキング性が劣っていた。
【００４７】
比較例６は、塗膜のＭＦＴが低く、このため耐ブロッキング性が不良であり、耐溶剤性も劣っていた。
比較例７は、エマルションのＭＦＴが高く、このため成膜性が不十分で、初期白錆発生性、防錆性が不良であった。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for preventing corrosion of a cast iron pipe and a cast iron pipe subjected to corrosion protection, and more particularly to a method for preventing corrosion of a cast iron pipe having a zinc-containing metal layer formed on a surface thereof and a cast iron pipe subjected to corrosion protection.
[0002]
[Prior art]
Cast iron pipes are widely used as water and sewer pipes, and require long-term anticorrosion performance because they are buried and used underground. Therefore, the outer surface of the tube is generally coated with an epoxy resin paint or a zinc rich paint. However, in recent years, a system has been used in which a thermal spray coating such as zinc is formed for the purpose of VOC countermeasures and further improvement of rust prevention due to environmental measures, and a water-based emulsion paint is further applied for the purpose of durability and protection of the thermal spray coating. (Patent Document 1).
[0003]
[Patent Document 1]
JP-A-10-264301
[Problems to be solved by the invention]
However, sprayed metal represented by zinc is very active for the purpose, and the water-based emulsion paint to be overcoated is porous and has high water permeability and oxygen permeability. The fact is that it has not been prevented. For this reason, when the aqueous emulsion paint is applied as a thin film or when used in a severe environment such as scattering of sea salt particles, zinc is greatly consumed and white rust tends to occur.
[0005]
Regarding the method of coating and drying the outer surface of the cast iron pipe, a method in which the metal-sprayed cast iron pipe is preheated to about 60 to 90 ° C. by hot air circulation, hot water immersion, or the like, and then finished by spray coating of a top coat paint is generally used. Yes, it is transported out several tens of minutes after the top coat. However, in this state, it cannot be said that the aqueous emulsion paint has completely formed a film, and when exposed directly to moisture such as rainfall, white rust is particularly noticeable.
[0006]
Further, cast iron pipes as products are often stored in a cross yard or a bale stack in the stockyard, and the peeling of the coating film and the damage due to blocking at the contact portion between the pipes tend to occur easily. In particular, when a solvent-type paint is used as a repair coating or a cosmetic paint at the time of product shipment, the emulsion coating film swells with the solvent, and peeling and scratching due to blocking are further increased.
[0007]
The present invention has been made in view of such circumstances, the initial white rust generation is good by completing the film formation in a short time after coating, and by forming a dense and tough film, Even if the cast iron tube is exposed to severe conditions, it can suppress the elution of zinc and have good rust prevention properties, and can form a film with good tube-to-tube blocking resistance and good solvent resistance. In this way, an object of the present invention is to prevent corrosion of a cast iron pipe.
[0008]
[Means for Solving the Problems]
The present inventors can apply a specific water-based emulsion paint to the outer surface of a cast iron pipe having a zinc-containing metal layer formed on the surface, thereby completing the film formation in a short time after the coating, and have a dense and anticorrosive property. It has been found that a solvent-resistant coating can be formed, and that the cast iron pipe carried out outdoors can suppress the elution of zinc and prevent the occurrence of white rust even when exposed to severe conditions, and completed the present invention. is there.
[0009]
That is, in the method for preventing corrosion of a cast iron tube of the present invention, a dicyclopentadiene derivative (B) and an alkoxysilane are provided on the outer surface of a cast iron tube on which a zinc-containing metal layer is formed, using a reactive surfactant (A) as an emulsifier. Using the silyl group-containing monomer (C) as a crosslinkable monomer, a vinyl group monomer (D) copolymerizable with the dicyclopentadiene derivative (B) and the alkoxysilyl group-containing monomer (C) is copolymerized. Wherein the component (A) is 0.1 to 4.0% by mass in the copolymer, the component (B) is 0.01 to 20.0% by mass in the copolymer, Component (C) occupies 0.01 to 5.0% by mass of the copolymer, and an aqueous emulsion paint using a water-dispersed resin having a minimum film-forming temperature (MFT) of 20 to 60 ° C as a vehicle. Is to be painted.
[0010]
The anticorrosion-treated cast iron tube of the present invention is characterized in that a reactive surfactant (A) is used as an emulsifier, a dicyclopentadiene derivative (B) and an alkoxysilyl are formed on the outer surface of a cast iron tube on which a zinc-containing metal layer is formed. Using the group-containing monomer (C) as a crosslinkable monomer, a vinyl group monomer (D) copolymerizable with the dicyclopentadiene derivative (B) and the alkoxysilyl group-containing monomer (C) is copolymerized. (A) component is 0.1 to 4.0% by mass in the copolymer, component (B) is 0.01 to 20.0% by mass in the copolymer, Component (C) occupies 0.01 to 5.0% by mass of the copolymer, and an aqueous emulsion paint using a water-dispersed resin having a minimum film-forming temperature (MFT) of 20 to 60 ° C. as a vehicle is used. A coating film is formed.
[0011]
According to the present invention, the metal layer is zinc, and the whole is 100% by mass, zinc is 70 to 95% by mass, and a zinc-aluminum alloy or pseudo alloy of 5 to 30% by mass of aluminum is 100% by mass as a whole. It is preferable that the sprayed metal layer is formed of any one of a zinc-aluminum-magnesium alloy or a pseudo alloy of 60 to 94% by mass of zinc, 5 to 30% by mass of aluminum, and 1 to 10% by mass of magnesium. .
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The cast iron pipe used in the present invention is widely used for water supply and sewerage, and its inner surface is coated with cement lining, powdered with epoxy resin, acrylic resin, polyester resin or the like before or after the outer surface anticorrosion coating process. Is protected.
[0013]
The present invention relates to a method for preventing corrosion of the outer surface of a cast iron tube. The outer surface of the cast iron tube is untreated or surface-treated by sand blasting, shot blasting or the like, and then zinc, zinc-aluminum alloy or pseudo- An alloy, zinc-aluminum-magnesium alloy or pseudo-alloy thermal spray coating layer is formed. The composition of the zinc-aluminum alloy or pseudo alloy is preferably 70 to 95% by mass of zinc and 5 to 30% by mass of aluminum, with the whole being 100% by mass. Further, the composition of the zinc-aluminum-magnesium alloy or pseudo alloy is preferably 60 to 94% by mass of zinc, 5 to 30% by mass of aluminum, and 1 to 10% by mass of magnesium, with the whole being 100% by mass.
[0014]
The cast iron tube thus pretreated is preheated to a tube temperature of 60 to 90 ° C. by a heating method such as hot water immersion or hot air circulation, and then the aqueous emulsion paint according to the present invention is dried to a film thickness of 80%. １５０150 μm, preferably 100-120 μm. Then, after 20 to 40 minutes, it is carried out outdoors and stored in the stockyard. Further, when the pipe is shipped, if the pipe is stained or scratched, the surface layer is coated with a weak solvent type acrylic resin enamel.
[0015]
The water-dispersible resin in the aqueous emulsion paint used in the present invention comprises a reactive surfactant (A) as an emulsifier, a dicyclopentadiene derivative (B) and an alkoxysilyl group-containing monomer (C) as a crosslinkable monomer. A copolymer obtained by copolymerizing the vinyl monomer (D) copolymerizable with the dicyclopentadiene derivative (B) and the alkoxysilyl group-containing monomer (C), Component (A) is 0.1 to 4.0% by mass in the copolymer, component (B) is 0.01 to 20.0% by mass in the copolymer, and component (C) is 0.01 to 4.0% by mass in the copolymer. It is a water-dispersed resin occupying 5.0% by mass and having a minimum film formation temperature (MFT) of 20 to 60 ° C. for the copolymer.
[0016]
According to the present invention, by using such a specific water-dispersed resin, it is possible to form a film having a high film-forming speed, a high density, and a high crosslinking density. As a result, rust prevention and solvent resistance can be improved, and even if the cast iron pipe carried out outdoors after coating is exposed to severe conditions, the elution of zinc is suppressed and the generation of white rust is prevented. be able to.
[0017]
The reactive surfactant (A) in the above specific water-dispersed resin refers to a surfactant having a double bond capable of radical polymerization in one molecule, and is copolymerized with other monomers to form polymer particles. Immobilized on the surface to improve the dispersion stability of the particles. Therefore, after the emulsion polymerization, it does not easily remain in the water-dispersed resin as a low-molecular emulsifier, and has the characteristics of a soap-free emulsion.
[0018]
Examples of the reactive surfactant as such an emulsifier include anionic or nonionic reactive surfactants. Specific examples thereof include sulfate salts of polyoxyethylene allyl glycidyl nonyl phenyl ether, and alkyl allyl. Sulfosuccinic acid sodium salt, bis (polyoxyethylene polycyclic phenyl ether) methacrylated sulfate ester salt, polyoxyethylene allyl glycidyl nonyl phenyl ether, polyoxyethylene nonyl propenyl phenyl ether, polyoxy ethylene nonyl propenyl phenyl ether sulfate ammonium salt, And polyoxyethylene allyloxymethyl alkyl ether sulfate ammonium salt.
[0019]
These are used singly or in combination of two or more, and the content thereof is 0.1 to 4.0 parts by mass in 100 parts by mass of the copolymer (solid content) (hereinafter simply abbreviated as “parts”). It is necessary to set to. In particular, it is preferable to set the amount to 0.5 to 3.0 parts. If the content of the reactive surfactant is less than 0.1 part, it becomes difficult to synthesize and maintain the stability of the water-dispersed resin. On the other hand, when the amount is 4.0 parts or more, the dispersion resin is stabilized, but the film forming speed is delayed. Accordingly, the white rust resistance in a short time after coating is reduced, and the water resistance and corrosion resistance are reduced, so that long-term white rust resistance cannot be obtained.
[0020]
The dicyclopentadiene derivative (B) as a crosslinkable monomer in the specific aqueous dispersion resin is represented by the following general formula (2) derived from dicyclopentadiene represented by the following structural formula (1). Refers to a dicyclopentadiene derivative. By containing this, the paint used in the anticorrosion method of the present invention is polymerized by crosslinking, and forms a dense and tough film. Moreover, since it crosslinks using oxygen in the air as a catalyst, it is extremely stable in a paint state and does not cause a change in the minimum film formation temperature (MFT) of the emulsion as compared with the case where other crosslinking monomers are used. .
[0021]
Embedded image

[0022]
Embedded image

Specific examples of the dicyclopentadiene derivative include dicyclopentenyl acrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl acrylate, dicyclopentenyloxyethyl methacrylate, and the like. Of these, dicyclopentenyloxyethyl acrylate is preferred in terms of reactivity, curability, and the like. It is necessary to set the content ratio to 0.01 to 20.0 parts in 100 parts by mass of the copolymer (solid content). It is particularly preferable to set the amount to 0.05 to 10.0 parts. That is, if the content is less than 0.01 part, the solvent resistance and water resistance are poor, and if it is 20.0 parts or more, the economic efficiency is poor.
[0023]
The alkoxysilyl group-containing monomer (C) as a crosslinkable monomer in the specific aqueous dispersion resin refers to an alkoxysilyl group-containing monomer represented by the following structural formula (3). By containing this, the paint used in the anticorrosion method of the present invention is polymerized by crosslinking, and forms a dense and tough film. This cross-linking system is a dehydration-condensation reaction, which reacts as the volatilization of water progresses after coating, and has a feature that the reaction rate is higher than that of the dicyclopentadiene derivative (B).
[0024]
Embedded image

Specific examples of the alkoxysilyl group-containing monomer (C) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldiethoxysilane, vinylmethyldipropoxysilane, and vinyltris (β-methoxyethoxy). Silane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltripropoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ- Examples thereof include methacryloxypropylmethyldipropoxysilane, γ-methacryloxypropyldimethylmethoxysilane, and γ-methacryloxypropyldimethylethoxysilane.
[0025]
These may be used alone or in combination of two or more, and the content ratio needs to be set to 0.01 to 5.0 parts in 100 parts by mass of the copolymer (solid content). In particular, it is preferable to set the amount to 0.05 to 3.0 parts. That is, if the content is less than 0.01 part, the solvent resistance is poor, and if it is 5.0 parts or more, the polymerization stability and the film forming property are poor.
[0026]
According to the present invention, by using two of the dicyclopentadiene derivative (B) and the alkoxysilyl group-containing monomer (C) as the crosslinkable monomer, the minimum film formation temperature (MFT) at the time of emulsion synthesis can be reduced. It is possible to suppress the generation of initial white rust at the time of carrying out the painted cast iron pipe based on the quick curing by the alkoxysilyl group-containing monomer (C) without causing variation, and to improve the crosslink density by the dicyclopentadiene derivative (B). Based on this, long-term rust prevention, solvent resistance, and blocking resistance can be achieved.
[0027]
The polymerizable vinyl group monomer (D) in the specific water-dispersed resin is a component constituting the main skeleton of the acrylic resin, and the reactive surfactant (A) is used as an emulsifier to prepare the dicyclopentadiene derivative (B). There is no particular limitation as long as it is copolymerizable with the alkoxysilyl group-containing monomer (C).
[0028]
Examples of such a polymerizable vinyl group monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, unsaturated carboxylic acids such as fumaric acid, vinyl sulfonic acid, and styrene sulfonic acid. , Sulfoethyl acrylate, sulfonic acid group-containing monomers such as sulfoethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, caprolactone-modified hydroxy acrylate, caprolactone-modified hydroxy methacrylate, bishydroxyethyl Hydroxyl-containing monomers such as monoacrylate of phthalate and monomethacrylate of bishydroxyethyl phthalate, 2-acryloxyethyl acid phosphate Acrylate, 2-methacryloxyethyl acid phosphate, 2-acryloxypropyl acid phosphate, 2-methacryloxypropyl acid phosphate, 2-acryloxy-3-chloropropyl acid phosphate, 2-methacryloxy-3-chloropropyl acid Acid phosphate monomers such as phosphate, 2-acryloxyphenylethylphenylphosphoric acid, 2-methacryloxyphenylethylphenylphenylphosphoric acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl Acrylates such as acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and isobornyl acrylate; methyl methacrylate Methacrylates such as methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, styrene, vinyl toluene, α-methyl Aromatic monomers such as styrene, vinyl esters such as vinyl acetate, halogen-containing monomers such as vinyl chloride and vinylidene chloride, vinyl ethers, cyano group-containing monomers such as acrylonitrile and methacrylonitrile, N, N Dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N-methylolacrylamide, 4-vinylpyridine, vinylimidazole, acrylamide, methacrylamide, etc. Containing monomers, glycidyl acrylate, glycidyl group-containing monomers such as glycidyl methacrylate and the like. These may be used alone or in combination of two or more.
[0029]
The minimum film forming temperature (MFT) of the specific water-dispersed resin needs to be set to 20 to 60 ° C, and is preferably set to 30 to 50 ° C. By defining the minimum film forming temperature (MFT) in such a range, when coating the emulsion paint on the cast iron pipe preheated to 60 to 90 ° C. at the time of coating, the film forming defect of the emulsion particles does not occur, In addition, the coated tubes are less likely to cause blocking. On the other hand, when the temperature is lower than 20 ° C., the blocking resistance is poor, and when the temperature is higher than 60 ° C., the film forming property is poor.
[0030]
Such a dispersion resin according to the present invention is a one-component curable dispersion resin.In the production thereof, a known polymerization initiator, a chain transfer agent, an alkali adjuster, and the like are used, and a target molecular weight, viscosity, Can be finished to particle size.
[0031]
When the one-component curable dispersion resin of the present invention is formed into a paint, a known dispersant such as an alkali salt of acrylic acid, a defoaming agent such as a silicone-based or mineral oil-based, a cellulose-based, or a polyacrylic-based resin can be used. Additives such as acid-based thickeners, coloring pigments such as titanium oxide, carbon black and iron oxide; extender pigments such as calcium carbonate, precipitated barium sulfate and aluminum silicate; aluminum phosphate and zinc phosphate; Pigments such as rust preventive pigments such as barium metaborate, and organic solvents as a film-forming aid can be used.
[0032]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
(Example 1)
As shown in Table 1, 1.0 part of ammonium polyoxyethylene nonylpropenyl phenyl ether sulfate was used as the reactive surfactant (A), and dicyclopentenyloxyethyl acrylate was used as the dicyclopentadiene derivative (B). 5 parts, 0.5 part of γ-methacryloxypropyltrimethoxysilane as an alkoxysilyl group-containing monomer (C), 63.0 parts of methyl methacrylate as a vinyl group monomer (D), 2-ethylhexyl A total of 96.0 parts of a mixture of 33.0 parts of acrylate and 1.0 part of acrylic acid was copolymerized. Then, 4.0 parts of carbon black paste and 3.0 parts of Chisso's CS-12 as a film forming aid were added to 100 parts of the emulsion having a solid content of 50% thus synthesized, The desired paint was obtained.
[0033]
[Table 1]

(Examples 2 to 8)
The proportions of the reactive surfactant (A), the dicyclopentadiene derivative (B), the alkoxysilyl group-containing monomer (C), and the vinyl group monomer (D) were changed as shown in Table 1, and In Example 4, the solid components were synthesized by changing the components of the vinyl group monomer (D) as shown in Table 1. Then, 4.0 parts of carbon black paste and 3.0 parts of CS-12 were added to 100 parts of the synthesized emulsion having a solid content of 50% to obtain a target paint.
(Comparative Example 1)
As shown in Table 2, the amount of the reactive surfactant (A) used was changed to 0.05 part. Other than that, it carried out similarly to Example 1, and obtained the coating material.
[0034]
[Table 2]

(Comparative Example 2)
As shown in Table 2, the amount of the reactive surfactant (A) used was changed to 5.0 parts. Other than that, it carried out similarly to Example 1, and obtained the coating material.
(Comparative Example 3)
As shown in Table 2, the reactive surfactant (A) was not used, and instead, 1.0 part of a water-soluble polymer surfactant and 1.0 part of a non-reactive surfactant were used. Other than that, it carried out similarly to Example 1, and obtained the coating material.
(Comparative Example 4)
As shown in Table 2, the dicyclopentadiene derivative (B) was not used, and instead, the amount of methyl methacrylate was increased by 2.5 parts. Other than that, it carried out similarly to Example 1, and obtained the coating material.
(Comparative Example 5)
As shown in Table 2, an alkoxysilyl group-containing monomer (C) was not used, and instead, 0.5 parts of methyl methacrylate was added. Other than that, it carried out similarly to Example 1, and obtained the coating material.
(Comparative Example 6)
As shown in Table 2, the MFT was set to 0 ° C. by changing the blending amounts of methyl methacrylate and 2-ethylhexyl acrylate. Other than that, it carried out similarly to Example 1, and obtained the coating material.
(Comparative Example 7)
As shown in Table 2, the MFT was set to 85 ° C. by changing the blending amounts of methyl methacrylate and 2-ethylhexyl acrylate. Other than that, it carried out similarly to Example 1, and obtained the coating material.
[0035]
Comparative evaluations of paint stability (mechanical stability), solvent resistance, adhesion, initial white rust generation, rust prevention, and blocking properties were performed using the paints prepared in Examples 1 to 8 and Comparative Examples 1 to 7. Table 3 shows the results.
[0036]
[Table 3]

Each evaluation in Table 3 was performed by the following method.
[0037]
In addition, the test piece of each evaluation test was created as follows. That is, a cast iron tube having a nominal diameter of 100 mm, which has been sprayed in advance with zinc, is cut into 300 mm lengths and preheated to a surface temperature of 60 ° C. in a hot-air drying oven, and then the emulsion paints of Examples 1 to 6 and Comparative Examples 1 to 7 are applied. A tube was spray-coated so as to have a dry film thickness of 100 μm, and allowed to cool at room temperature to obtain a test piece.
(Mechanical stability of emulsion)
The mechanical stability of each emulsion was evaluated using a Marlon tester under the following test conditions.
[0038]
Test conditions Load 98 N / cm ² (10 kgf / cm ² )
Rotation speed 1000rpm
Test temperature 20 ℃
Test time 10 minutes Sample 50.0g
Evaluation standard aggregate amount 0.01 g or less ◎
0.01-0.05g ○
0.05-0.1g △
0.1g or more ×
(Solvent resistance)
The solvent resistance is an index of the denseness of the coating film, but after drying the test piece at room temperature for 7 days after coating, 2 ml of mineral spirit is dropped, and after 30 seconds, the mineral spirit on the surface is wiped off with a rag, The degree of softening and swelling of the coating film was evaluated.
[0039]
Evaluation criteria No softening of coating film and no change in hardness ◎
There is no softening of the coating film, but the hardness is slightly low ○
The coating film is slightly softened △
Large softening of coating film ×
(Adhesiveness)
After the test specimen was dried at room temperature for 7 days after painting, a 2 mm grid 25-slice wound was made with a cutter, a cellophane tape was stuck to the wound part, and this was peeled off. Counting was performed to evaluate the adhesion.
(Initial white rust generation)
The initial white rust generation is an index of the film formation speed, but after spraying, ion-exchanged water is sprayed on the test specimen that has been allowed to cool at room temperature for 30 minutes, and then sealed at room temperature in a dew condensation environment. It was left in a box for 16 hours, and then the state of the coating film was evaluated.
[0040]
Evaluation criteria No white rust ◎
Very slight generation of white rust is observed ○
White rust is observed △
Many occurrences of white rust ×
(Rustproof)
A test piece dried at room temperature for 7 days after coating was tested for 72 hours with a salt spray tester to evaluate the state of the coating film thereafter.
[0041]
Evaluation criteria No white rust ◎
Very slight generation of white rust is observed ○
White rust is observed △
Many occurrences of white rust ×
(Blocking resistance)
Test pieces dried at room temperature for 24 hours after coating were stacked in a grid pattern, and the blocking state after heating at 60 ° C. for 6 hours was evaluated.
[0042]
There is no peeling of the coating film at the contact point between the evaluation standard tubes ◎
The size of the peeled surface of the coating film at the point of contact between the tubes is less than 1 mm in diameter.
The size of the peeled surface of the coating film at the contact point between the tubes is 1 mm or more and less than 3 mm.
The size of the peeling surface of the coating film at the point of contact between the tubes is 3 mm or more ×
(Evaluation results)
As is clear from the results in Table 3 above, all of Examples 1 to 8 were excellent in coating stability, solvent resistance, adhesion, initial white rust generation, rust prevention, and blocking resistance. Was formed.
[0043]
On the other hand, in Comparative Example 1, since the amount of the reactive surfactant (A) was too small, the mechanical stability of the emulsion, that is, the paint stability was poor, and the paint itself was lacking in practicality. For this reason, it could not be applied to the test piece.
[0044]
In Comparative Example 2, on the other hand, the coating stability was good because the amount of the reactive surfactant (A) was too large, but the film-forming speed was slow, and thus the initial white rust generation was poor, and The rust property was also poor.
[0045]
Comparative Example 3 did not use the reactive surfactant (A), but instead used a non-reactive surfactant and used a water-soluble polymer surfactant in combination. Although the water retention was good, the film formation speed was slow, so that the initial white rust generation was poor and the rust prevention was also poor.
[0046]
In Comparative Examples 4 and 5, since either one of the dicyclopentadiene derivative (component B) and the alkoxysilyl group-containing monomer (component C) was not used, the crosslink density was insufficient, and thus the solvent resistance was low. Properties and blocking resistance were inferior.
[0047]
In Comparative Example 6, the coating film had a low MFT, and thus had poor blocking resistance and poor solvent resistance.
In Comparative Example 7, the MFT of the emulsion was high, so that the film-forming properties were insufficient, and the initial white rust generation and rust prevention were poor.

Claims (4)

A reactive surfactant (A) is used as an emulsifier, and a dicyclopentadiene derivative (B) and an alkoxysilyl group-containing monomer (C) are cross-linked to the outer surface of a cast iron tube having a zinc-containing metal layer formed on the surface. A copolymer obtained by copolymerizing a vinyl group monomer (D) copolymerizable with the dicyclopentadiene derivative (B) and the alkoxysilyl group-containing monomer (C). Component (A) is 0.1 to 4.0% by mass in the copolymer, component (B) is 0.01 to 20.0% by mass in the copolymer, and component (C) is 0.1 to 4.0% by mass in the copolymer. A water-based emulsion paint containing a water-dispersible resin having a minimum film-forming temperature (MFT) of 20 to 60 ° C. as a vehicle, which occupies 0.01 to 5.0% by mass of the copolymer; Anticorrosion method. The metal layer
With zinc,
A zinc-aluminum alloy or pseudo-alloy of 70 to 95% by mass of zinc and 5 to 30% by mass of aluminum, with the whole being 100% by mass,
A zinc-aluminum-magnesium alloy or pseudo-alloy of 60 to 94% by mass of zinc, 5 to 30% by mass of aluminum, and 1 to 10% by mass of magnesium, with the whole being 100% by mass,
The method for preventing corrosion of a cast iron pipe according to claim 1, wherein the sprayed metal layer is formed by any one of the following. A reactive surfactant (A) is used as an emulsifier, and a dicyclopentadiene derivative (B) and an alkoxysilyl group-containing monomer (C) are cross-linked to the outer surface of a cast iron tube on which a zinc-containing metal layer is formed. As a copolymer obtained by copolymerizing the vinyl monomer (D) copolymerizable with the dicyclopentadiene derivative (B) and the alkoxysilyl group-containing monomer (C), Component (A) is 0.1 to 4.0% by mass in the copolymer, component (B) is 0.01 to 20.0% by mass in the copolymer, and component (C) is 0.01 to 4.0% by mass in the copolymer. It is characterized in that a coating film is formed by an aqueous emulsion paint using a water-dispersed resin having a minimum film-forming temperature (MFT) of 20 to 60 ° C. as a vehicle, occupying 5.0% by mass. Corrosion-resistant cast iron tube. The metal layer
With zinc,
A zinc-aluminum alloy or pseudo-alloy of 70 to 95% by mass of zinc and 5 to 30% by mass of aluminum, with the whole being 100% by mass,
A zinc-aluminum-magnesium alloy or pseudo-alloy of 60 to 94% by mass of zinc, 5 to 30% by mass of aluminum, and 1 to 10% by mass of magnesium, with the whole being 100% by mass,
The anticorrosion treated cast iron tube according to claim 3, wherein the sprayed metal layer is formed by any one of the following.