JP3890908B2 - Organic hydrophilic coating composition and aluminum material for heat exchanger having hydrophilic film - Google Patents
Organic hydrophilic coating composition and aluminum material for heat exchanger having hydrophilic film Download PDFInfo
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Description
【０００１】
【産業上の利用分野】
この発明は、アルミニウム又はアルミニウム合金からなるアルミニウム材を始めとして、熱伝導性に優れた銅又はその合金からなる銅材、プラスチック材等の硬質材料の表面に親水性皮膜を形成するための有機親水性塗料組成物、及びこの有機親水性塗料組成物により形成された親水性皮膜を有する熱交換器用アルミニウム材に関する。
【０００２】
【従来の技術】
建物や自動車等で用いられる空調機器等の熱交換器においては、熱伝導性及び加工性に優れているアルミニウム又はアルミニウム合金からなる種々の熱交換器用アルミニウム材、例えばフィン材やチューブ材等が用いられている。
【０００３】
そして、このような熱交換器用アルミニウム材については、例えばフィン材の場合、熱交換器の熱交換効率を高める目的や、熱交換器、ひいては空調機器の小型化を進める目的等のため、フィン相互間の間隔をできるだけ狭くしたり、通風抵抗をできるだけ小さくするためにフィンにルーバーと称される切り目を入れることが行われている。
【０００４】
このため、冷房時等において、空気中の水分がフィン表面等の熱交換表面で凝縮し、この凝縮した凝縮水が水滴として熱交換表面に溜まり、熱交換面積を減少せしめて熱交換効率を低下させ、あるいは、フィン相互間にブリッジを形成して通風抵抗を増加させ、結果として熱交換器の熱交換効率を大きく低下させる原因になっていた。
【０００５】
そこで、従来においても、この問題を解決するため、フィン材やチューブ材等の熱交換器用アルミニウム材の表面に親水性塗料組成物を用いて親水性皮膜を設け、フィン材やチューブ材等の表面の水濡れ性を高めて水滴の生成を可及的に防止し、これによって凝縮水による水滴の生成を抑制することが提案されており、例えば熱交換器用アルミニウム材がフィン材である場合、プレコートフィン材として供給されている。
【０００６】
しかしながら、従来の親水性塗料組成物としては、一般に、水ガラスやシリカ等の無機系のものが使用されており、フィン材等の成形時に金型の摩耗が激しく、また、冷房運転の際における不快臭の発生等が問題になっていた。
そこで、近年においては、このような金型摩耗や不快臭発生等の問題がないポリビニルアルコール系樹脂、ポリアクリルアミド系樹脂、ポリアクリル酸系樹脂、セルロース系樹脂等の水溶性の親水性樹脂を含む有機親水性塗料組成物が提案されており（特開昭63-173,632号、特開平5-302,042号、特開平9-14,889号等の各公報）、これらのうちポリビニルアルコール系樹脂は、合成繊維の原料としてその基礎研究や用途研究が進んでいて広範な品質（重合度、鹸化度、変性等）のものを比較的低コストで入手できることから、好適に使用されている。
【０００７】
ところで、このような熱交換器用アルミニウム材の表面に形成される親水性皮膜には、単に良好な親水性を有するということだけでなく、冷房運転時には長時間に亘って水に濡れる環境に晒されることから、水に濡れても膨潤したり溶解することのない優れた耐水性が不可欠であり、無機親水性塗料組成物の場合には原料として用いられるシリカが親水性を有し、かつ、水に不溶であることから問題はないが、有機親水性塗料組成物の場合、例えばポリビニルアルコール系樹脂を主成分とする場合には、熱処理、アセタール化、多価金属等との反応等により、形成される親水性皮膜に適度な耐水性を付与することが必要であり、しかも、このようにして親水性皮膜に耐水性を付与するとそれに反比例して不可避的に親水性が低下し、親水性と耐水性の両性能を同時に改善することは困難であるとされている。
【０００８】
更にまた、このような親水性皮膜が設けられた熱交換器用アルミニウム材、例えばプレコートフィン材については、熱交換器製造工程でプレス成形加工の際に、プレス成形前に揮発型プレスオイルを塗布するプレスオイルの塗布とプレス成形後に塗布した揮発型プレスオイルを加熱下に乾燥させて除去するプレスオイルの除去とが行われるが、このプレスオイルの除去の際の加熱乾燥（通常、１４０〜２００℃で数分から十数分間の加熱）により親水性皮膜の親水性が低下し、結果として製造された熱交換器が充分な熱交換効率を発揮し得なくなる場合がある。
【０００９】
この問題を解決するために、例えば有機親水性塗料組成物中に界面活性剤のような補助的な親水性付与剤を添加することも行われているが、このような補助的な親水性付与剤の添加では、熱交換器を使い始めてしばらくの間は良好な親水性が得られるものの、使用途中に界面活性剤等の親水性付与剤が凝縮水中に徐々に溶出し、次第に親水性が低下して長期に亘って親水性を持続させることが困難であるという問題がある。
【００１０】
【発明が解決しようとする課題】
そこで、本発明者らは、プレコートフィン材等の親水性皮膜を有する熱交換器用アルミニウム材について、初期親水性だけでなく、長期に亘って親水性を持続させる長期親水性に優れており、しかも、耐水性にも優れた親水性皮膜を形成し得る有機親水性塗料組成物の開発について鋭意検討した結果、樹脂成分としてポリビニルアルコール系樹脂及びポリエチレングリコール系樹脂を主成分とし、これに特定の硝酸化合物を添加した有機親水性塗料組成物が、初期親水性、長期親水性及び耐水性のいずれにおいても優れた性能を発揮する親水性皮膜を形成することを見出し、本発明を完成した。
【００１１】
従って、本発明の目的は、アルミニウム材を始めとして銅材等の種々の硬質材料の表面に初期親水性、長期親水性及び耐水性において優れた性能を発揮する親水性皮膜を形成し得る有機親水性塗料組成物を提供することにある。
また、本発明の他の目的は、このような有機親水性塗料組成物により形成された親水性皮膜を有するプレコートフィン材等の熱交換器用アルミニウム材を提供することにある。
【００１２】
【課題を解決するための手段】
すなわち、本発明は、樹脂成分としてポリビニルアルコール系樹脂及びポリエチレングリコール系樹脂を主成分とする有機親水性塗料組成物であり、１価又は２価の元素を有する硝酸化合物を含有する有機親水性塗料組成物である。
また、本発明は、アルミニウム又はアルミニウム合金からなり、本体表面の一部又は全部には請求項１〜４のいずれかの有機親水性塗料組成物を用いて形成された親水性皮膜を有するプレコートフィン材等の熱交換器用アルミニウム材である。
【００１３】
本発明において、有機親水性塗料組成物の樹脂成分を構成するポリビニルアルコール系樹脂については、好ましくはその鹸化度が９７モル％以上、より好ましくは９７．５〜９９．５モル％の完全鹸化タイプのポリビニルアルコール（ＰＶＡ）であり、また、その平均重合度が５００〜２５００、より好ましくは１５００〜２５００のＰＶＡである。鹸化度が９７モル％より低いと、親水性と耐水性が共に悪化するという問題があり、また、平均重合度については、５００より低いと親水性と耐水性が共に悪化し、反対に、２５００より高くなると粘土上昇が著しくなって必要な浴濃度を確保できなくなる場合が生じる。
【００１４】
このようなポリビニルアルコール系樹脂には、上記ＰＶＡ以外に、例えば、酢酸ビニルの重合時に少量（例えば５重量％以下）のアリルグリシジルエーテル（例えば、ナガセ化成工業社製商品名：デナコールEX-III）を共重合させ、水酸基の一部がエポキシ基で置換されたもの、あるいは、同じく酢酸ビニルの重合時にクロトン酸、アクリル酸、無水マレイン酸、イタコン酸、ＭＭＡ等のカルボキシル基を有するモノマーを共重合させることによって主鎖中にカルボキシル基を導入した変性ポリビニルアルコール等も含まれる。
【００１５】
また、ポリビニルアルコール系樹脂と共に有機親水性塗料組成物の樹脂成分を構成するポリエチレングリコール系樹脂については、好ましくはその重量平均分子量が１０００〜２００００、好ましくは４０００〜１１０００のポリエチレングリコール（ＰＥＧ）、エチレングリコール・プロピレングリコール共重合体等が挙げられる。
【００１６】
本発明において、上記ポリビニルアルコール系樹脂とポリエチレングリコール系樹脂の配合割合は、ポリビニルアルコール系樹脂が３０〜１５０ｇ／リットル、好ましくは５０〜１００ｇ／リットルであり、また、ポリエチレングリコール系樹脂が３〜４０ｇ／リットル、好ましくは５〜２０ｇ／リットルである。ポリビニルアルコール系樹脂の配合割合が３０ｇ／リットルより少ないと親水性に必要な膜厚を確保できず、また、１５０ｇ／リットルより多い塗料組成物では粘度が高くなり過ぎて塗装作業性が著しく低下する。そして、ポリエチレングリコール系樹脂の配合割合が３ｇ／リットルより少ないと所望の親水性が得られ難くなり、また、４０ｇ／リットルより多くなると形成された親水性皮膜の密着性が低下する。
【００１７】
本発明においては、このような樹脂成分を有する塗料組成物中に、１価又は２価の元素を有する硝酸化合物、好ましくは水素や、リチウム、カリウム、ナトリウム等のアルカリ金属等の１価の元素や、マグネシウム、カルシウム等のアルカリ土類金属や、亜鉛等の２価の元素を有する硝酸化合物を所定の割合で添加する。
この硝酸化合物の添加割合は、硝酸イオン濃度が０．１〜１６ｇ／リットル、好ましくは０．３〜６ｇ／リットルとなる割合であり、この硝酸イオン濃度が０．１ｇ／リットルより低いと所望の親水性が得られ難くなり、反対に、１６ｇ／リットルより高くなると一旦改善された親水性が再び低下して所望の親水性が得られなくなる。
【００１８】
本発明の有機親水性塗料組成物は、樹脂成分としてのポリビニルアルコール系樹脂及びポリエチレングリコール系樹脂と１価又は２価の元素を有する硝酸化合物とを必須成分として含むものであり、必要により、貯蔵中の腐敗防止を目的に有機銅系、有機ヨード系、イミダゾール系、イソチアゾリン系、ピリチオン系、トリアジン系、銀系等の抗菌・抗黴作用を有する防腐剤や、タンニン酸、没食子酸、フイチン酸、ホスフィン酸等の防錆剤や、ポリアルコールのアルキルエステル類、ポリエチレンオキサイド縮合物等のレベリング剤や、相溶性を損なわない範囲で添加されるポリアクリルアミド、ポリビニルアセトアミド等の充填剤や、酸化チタン、フタロシアニン化合物等の着色剤や、アルキル硫酸エステル塩、アルキルスルホコハク酸塩系等の界面活性剤等を添加することができる。
【００１９】
本発明の有機親水性塗料組成物を調製するに際しては、特に制限はないが、ポリビニルアルコール系樹脂が比較的水に溶け難いので、好ましくは、先ずポリビニルアルコール系樹脂を常温の水に５〜１０分間分散させた後、８０〜９０℃で３０〜６０分間加熱し、溶解させた後に所定の濃度となるように水を加え、次いで攪拌下にポリエチレングリコール系樹脂を添加して溶解させ、その後に硝酸化合物を、好ましくは水で希釈した硝酸化合物水溶液として、添加して混合する。
【００２０】
そして、本発明の有機親水性塗料組成物を種々の硬質材料の表面に塗布する方法については、特に制限はなく、例えば、通常良く用いられるロールコーターを用いる方法や、塗布量管理に便利なグラビアロールを用いる方法や、厚塗りするのに便利なナチュラルコート方式や、塗布面を綺麗に仕上げるのに有利なリバースコート方式等を採用することができる。
【００２１】
例えば、本発明の有機親水性塗料組成物を用い、チューブ材やフィン材等の熱交換器用アルミニウム材の表面に親水性皮膜を形成する際には、先ず、ロールコーター等を用いてアルミニウム材の表面に塗料組成物を塗布し、次いで例えばフローターオーブン等により高温通風下での加熱、好ましくは１０〜３０ｍ／分の高温通風下に２００〜３００℃の高温で１０〜１５秒間の加熱を行う。
【００２２】
本発明の有機親水性塗料組成物を用いて硬質材料の表面に形成される親水性皮膜の膜厚については、硬質材料の種類や用途等により異なり、特に制限はないが、例えばプレコートフィン材である場合、通常０．０５〜５μｍ、好ましくは０．１〜２μｍ、より好ましくは０．５〜１．５μ程度であるのがよい。
【００２３】
本発明の有機親水性塗料組成物を用いて形成される親水性皮膜は、塗料組成物中の樹脂成分であるポリビニルアルコール系樹脂やポリエチレングリコール系樹脂のポリマー側鎖の水酸基が硝酸イオンでマスキングされ、これによって、例えばプレコートフィン材の場合、熱交換器製造工程でプレスオイル除去ための加熱乾燥が行われ、ポリビニルアルコール系樹脂の結晶化が進んでも、ポリマー側鎖の水酸基どうしの水素結合が抑制され、結果として初期親水性だけでなくて長期親水性にも優れた性能が発揮されるほか、結晶化の進行による優れた耐水性をも発揮すると考えられる。
【００２４】
【発明の実施の形態】
以下、実施例及び比較例に基づいて、本発明の好適な実施の形態を具体的に説明する。
【００２５】
実施例１〜７及び比較例１〜５
鹸化度９７．５〜９９．５モル％及び平均重合度１７００のポリビニルアルコール（ＰＶＡ）６重量％と、重量平均分子量８５００のポリエチレングリコール（ＰＥＧ）１．２重量％と、表１に示す化合物を表１に示すアニオン濃度で含む各実施例及び比較例の親水性塗料組成物を調製した。
得られた各実施例及び比較例の親水性塗料組成物について、その初期親水性と長期親水性とを以下の方法で測定し、評価した。
【００２６】
〔親水性の評価〕
アルミニウム材（AA3102、厚さ0.15mm）を常法により脱脂し、次いで洗浄した。
得られた脱脂洗浄後のアルミニウム材について、クロメート処理剤（日本ペイント社製：アルサーフ407/47）を用い、浸漬法により燐酸クロメート下地処理を施し、流水中で１分間洗浄し、５０℃で１０分間乾燥して、アルミニウム材の表面にクロム（Cr）１００mg／ｍ2の耐食性皮膜を形成せしめ、親水性の評価のための試験片を調製した。
【００２７】
得られた試験片の表面に、ロールコーターを用いて各実施例及び比較例の親水性塗料組成物を塗布し、熱風乾燥炉を用いて２５５℃、１２秒の条件で焼付けを行い、試験片の表面に膜厚０．９〜１ｇ／ｍ2の親水性皮膜を形成した。
このようにして親水性皮膜を設けた試験片にプレスオイル（出光興産社製AF-2C）を塗布し、１８０℃、３時間の条件で加熱乾燥した後、直後の初期親水性と、水に１００時間浸漬後の長期親水性とを測定した。
【００２８】
初期親水性及び長期親水性の測定は、水平に設置した試験片の親水性皮膜上に純水２μＬを滴下し、形成された水滴の接触角を接触角計（協和界面科学社製：CA‐A）を用いて測定し、また、親水性の評価は、評価点５：接触角＜１０°、評価点４：接触角１０〜１６°、評価点３：接触角１７〜２５°、評価点２：接触角２６〜３５°、及び評価点１：接触角＞３５°の評価基準で行い、合格域は評価点≧３とし、また、総合評価では初期親水性及び長期親水性の各評価が共に評価点≧３の場合とした。
結果を表１に示す。
【００２９】
また、耐水性については、上記長期親水性測定後の試験片についてその親水性皮膜を観察したところ、各実施例及び比較例共に膨潤・溶解が認められず、また、親水性皮膜の上に垂らした水を指で擦って調べても、皮膜剥れが認められず、いずれも合格であった。
【００３０】
【表１】
【発明の効果】
本発明の有機親水性塗料組成物によれば、アルミニウム材等の硬質材料の表面に初期親水性、長期親水性及び耐水性において優れた性能を発揮する親水性皮膜を形成することができる
また、本発明のプレコートフィン材等の熱交換器用アルミニウム材は、その表面に初期親水性、長期親水性及び耐水性において優れた性能を有する親水性皮膜が設けられており、これを用いて形成された熱交換器は長期に亘って優れた熱交換効率を発揮する。[0001]
[Industrial application fields]
The present invention provides an organic hydrophilic material for forming a hydrophilic film on the surface of a hard material such as an aluminum material made of aluminum or an aluminum alloy, a copper material made of copper or an alloy thereof excellent in thermal conductivity, or a plastic material. The present invention relates to an aluminum material for heat exchangers having a hydrophilic coating film and a hydrophilic coating formed by the organic hydrophilic coating composition.
[0002]
[Prior art]
In heat exchangers such as air conditioners used in buildings and automobiles, various aluminum materials for heat exchangers made of aluminum or aluminum alloy having excellent thermal conductivity and workability, such as fin materials and tube materials, are used. It has been.
[0003]
For such an aluminum material for heat exchangers, for example, in the case of fin materials, the fin mutual material is used for the purpose of increasing the heat exchange efficiency of the heat exchanger and for the purpose of promoting the miniaturization of the heat exchanger and thus the air conditioner. In order to make the interval between them as narrow as possible or make the draft resistance as small as possible, cuts called louvers are made in the fins.
[0004]
For this reason, during cooling, moisture in the air condenses on the heat exchange surface such as the fin surface, and this condensed condensed water accumulates on the heat exchange surface as water droplets, reducing the heat exchange area and reducing the heat exchange efficiency. Alternatively, a bridge is formed between the fins to increase the ventilation resistance, and as a result, the heat exchange efficiency of the heat exchanger is greatly reduced.
[0005]
Therefore, conventionally, in order to solve this problem, a hydrophilic coating is provided on the surface of a heat exchanger aluminum material such as a fin material or a tube material using a hydrophilic coating composition, and the surface of the fin material or the tube material or the like is provided. It has been proposed to prevent the generation of water droplets as much as possible by increasing the wettability of the water, thereby suppressing the generation of water droplets by condensed water. For example, when the aluminum material for heat exchanger is a fin material, pre-coating It is supplied as a fin material.
[0006]
However, as a conventional hydrophilic coating composition, generally, an inorganic type such as water glass or silica is used, and the mold is severely worn during molding of a fin material or the like, and in the cooling operation. The generation of unpleasant odors has become a problem.
Therefore, in recent years, water-soluble hydrophilic resins such as polyvinyl alcohol resins, polyacrylamide resins, polyacrylic resins, and cellulose resins that do not have such problems as mold wear and unpleasant odors are included. Organic hydrophilic coating compositions have been proposed (JP-A 63-173,632, JP-A 5-302,042, JP-A 9-14,889, etc.). Of these, polyvinyl alcohol resins are synthetic fibers. As a raw material, the basic research and application research are progressing, and a wide range of qualities (degree of polymerization, degree of saponification, modification, etc.) can be obtained at a relatively low cost.
[0007]
By the way, the hydrophilic film formed on the surface of such an aluminum material for heat exchangers is not only having good hydrophilicity, but also exposed to an environment wetted with water for a long time during cooling operation. Therefore, excellent water resistance that does not swell or dissolve even when wet with water is essential, and in the case of an inorganic hydrophilic coating composition, silica used as a raw material has hydrophilicity, and water In the case of an organic hydrophilic coating composition, for example, when a polyvinyl alcohol resin is a main component, it is formed by heat treatment, acetalization, reaction with a polyvalent metal, etc. It is necessary to impart appropriate water resistance to the hydrophilic film, and in addition, imparting water resistance to the hydrophilic film in this way inevitably decreases the hydrophilicity in inverse proportion to the hydrophilic film. Improving both performance aqueous simultaneously is considered difficult.
[0008]
Furthermore, for aluminum materials for heat exchangers provided with such a hydrophilic film, for example, pre-coated fin materials, volatile press oil is applied before press molding at the time of press molding in the heat exchanger manufacturing process. The press oil is applied and the volatile press oil applied after the press molding is removed by drying under heating, and the press oil is removed by heating. In some cases, the hydrophilicity of the hydrophilic film is lowered by heating for several minutes to several tens of minutes, and as a result, the manufactured heat exchanger may not be able to exhibit sufficient heat exchange efficiency.
[0009]
In order to solve this problem, for example, an auxiliary hydrophilicity imparting agent such as a surfactant is added to the organic hydrophilic coating composition. With the addition of the agent, good hydrophilicity can be obtained for a while after starting to use the heat exchanger, but hydrophilicity imparting agents such as surfactants gradually elute into the condensed water during use, and the hydrophilicity gradually decreases. Thus, there is a problem that it is difficult to maintain hydrophilicity for a long time.
[0010]
[Problems to be solved by the invention]
Therefore, the present inventors have not only the initial hydrophilicity, but also the long-term hydrophilicity to maintain the hydrophilicity for a long period of time for the aluminum material for heat exchangers having a hydrophilic film such as a pre-coated fin material, As a result of diligent research on the development of an organic hydrophilic coating composition capable of forming a hydrophilic film having excellent water resistance, the resin component is mainly composed of polyvinyl alcohol resin and polyethylene glycol resin, and specific nitric acid. The present inventors have found that an organic hydrophilic coating composition to which a compound is added forms a hydrophilic film exhibiting excellent performance in any of initial hydrophilicity, long-term hydrophilicity and water resistance, and has completed the present invention.
[0011]
Accordingly, an object of the present invention is to form an organic hydrophilic material capable of forming a hydrophilic film exhibiting excellent performance in initial hydrophilicity, long-term hydrophilicity and water resistance on the surface of various hard materials such as an aluminum material and a copper material. It is in providing a conductive coating composition.
Another object of the present invention is to provide an aluminum material for a heat exchanger such as a pre-coated fin material having a hydrophilic film formed from such an organic hydrophilic coating composition.
[0012]
[Means for Solving the Problems]
That is, the present invention is an organic hydrophilic coating composition mainly comprising a polyvinyl alcohol-based resin and a polyethylene glycol-based resin as resin components, and an organic hydrophilic coating containing a nitric acid compound having a monovalent or divalent element. It is a composition.
Moreover, this invention consists of aluminum or an aluminum alloy, The precoat fin which has a hydrophilic membrane | film | coat formed in part or all of the main body surface using the organic hydrophilic coating composition in any one of Claims 1-4 It is aluminum material for heat exchangers, such as material.
[0013]
In the present invention, the polyvinyl alcohol resin constituting the resin component of the organic hydrophilic coating composition is preferably a completely saponified type having a saponification degree of 97 mol% or more, more preferably 97.5 to 99.5 mol%. Polyvinyl alcohol (PVA), and the average degree of polymerization is 500 to 2500, more preferably 1500 to 2500. When the degree of saponification is lower than 97 mol%, there is a problem that both hydrophilicity and water resistance are deteriorated. On the other hand, when the average degree of polymerization is lower than 500, both hydrophilicity and water resistance are deteriorated. If it is higher, the clay rises remarkably and the required bath concentration may not be ensured.
[0014]
In addition to the above PVA, for example, a small amount (for example, 5% by weight or less) of allyl glycidyl ether (for example, trade name: Denacol EX-III, manufactured by Nagase Kasei Kogyo Co., Ltd.) Copolymerized with a part of the hydroxyl group substituted with an epoxy group or a monomer having a carboxyl group such as crotonic acid, acrylic acid, maleic anhydride, itaconic acid, MMA, etc. This also includes modified polyvinyl alcohol having a carboxyl group introduced into the main chain.
[0015]
Moreover, about the polyethyleneglycol-type resin which comprises the resin component of an organic hydrophilic coating composition with a polyvinyl alcohol-type resin, Preferably the weight average molecular weight is 1000-20000, Preferably it is 4000-11000 polyethyleneglycol (PEG), ethylene And glycol / propylene glycol copolymers.
[0016]
In the present invention, the blending ratio of the polyvinyl alcohol resin and the polyethylene glycol resin is 30 to 150 g / liter, preferably 50 to 100 g / liter for the polyvinyl alcohol resin, and 3 to 40 g for the polyethylene glycol resin. / Liter, preferably 5 to 20 g / liter. If the blending ratio of the polyvinyl alcohol resin is less than 30 g / liter, the film thickness necessary for hydrophilicity cannot be secured, and if the coating composition exceeds 150 g / liter, the viscosity becomes too high and the coating workability is remarkably lowered. . When the blending ratio of the polyethylene glycol resin is less than 3 g / liter, it is difficult to obtain desired hydrophilicity, and when it exceeds 40 g / liter, the adhesion of the formed hydrophilic film is lowered.
[0017]
In the present invention, in the coating composition having such a resin component, a nitric acid compound having a monovalent or divalent element, preferably a monovalent element such as hydrogen, an alkali metal such as lithium, potassium, or sodium. Alternatively, an alkaline earth metal such as magnesium or calcium, or a nitric acid compound having a divalent element such as zinc is added at a predetermined ratio.
The addition ratio of the nitrate compound is such that the nitrate ion concentration is 0.1 to 16 g / liter, preferably 0.3 to 6 g / liter, and if the nitrate ion concentration is lower than 0.1 g / liter, the desired concentration is obtained. On the other hand, it becomes difficult to obtain hydrophilicity, and conversely, if it exceeds 16 g / liter, once improved hydrophilicity is lowered again, and the desired hydrophilicity cannot be obtained.
[0018]
The organic hydrophilic coating composition of the present invention comprises a polyvinyl alcohol resin and a polyethylene glycol resin as resin components and a nitric acid compound having a monovalent or divalent element as essential components. Organic copper, organic iodine, imidazole, isothiazoline, pyrithione, triazine, silver and other antiseptic / antifungal preservatives, tannic acid, gallic acid, phytic acid Rust preventives such as phosphinic acid, leveling agents such as polyalcohol alkyl esters, polyethylene oxide condensates, etc., fillers such as polyacrylamide and polyvinylacetamide added to the extent that compatibility is not impaired, and titanium oxide , Colorants such as phthalocyanine compounds, alkyl sulfate esters, alkylsulfosuccinic acid It can be added a surfactant system, or the like.
[0019]
In preparing the organic hydrophilic coating composition of the present invention, there is no particular limitation. However, since the polyvinyl alcohol resin is relatively hardly soluble in water, it is preferable that the polyvinyl alcohol resin is first dissolved in water at room temperature for 5-10. After dispersing for 30 minutes, heat at 80 to 90 ° C. for 30 to 60 minutes, and after dissolving, add water to a predetermined concentration, then add and dissolve the polyethylene glycol resin under stirring, The nitric acid compound is added and mixed, preferably as an aqueous nitric acid compound solution diluted with water.
[0020]
And there is no restriction | limiting in particular about the method of apply | coating the organic hydrophilic coating composition of this invention to the surface of various hard materials, For example, the method of using the roll coater used normally, and the gravure convenient for coating amount management A method using a roll, a natural coating method that is convenient for thick coating, a reverse coating method that is advantageous for beautifully finishing a coated surface, and the like can be employed.
[0021]
For example, when forming a hydrophilic film on the surface of an aluminum material for a heat exchanger such as a tube material or a fin material using the organic hydrophilic coating composition of the present invention, first, using a roll coater or the like, The coating composition is applied to the surface, and then heated under high-temperature ventilation, for example, with a floater oven or the like, preferably under high-temperature ventilation of 10 to 30 m / min at a high temperature of 200 to 300 ° C. for 10 to 15 seconds.
[0022]
The film thickness of the hydrophilic film formed on the surface of the hard material using the organic hydrophilic coating composition of the present invention varies depending on the type and use of the hard material and is not particularly limited. In some cases, it is usually 0.05 to 5 μm, preferably 0.1 to 2 μm, more preferably about 0.5 to 1.5 μm.
[0023]
In the hydrophilic film formed using the organic hydrophilic coating composition of the present invention, the hydroxyl group of the polymer side chain of the polyvinyl alcohol resin or polyethylene glycol resin which is a resin component in the coating composition is masked with nitrate ions. Thus, for example, in the case of a pre-coated fin material, heat drying for removing press oil is performed in the heat exchanger manufacturing process, and even if crystallization of the polyvinyl alcohol resin progresses, hydrogen bonding between hydroxyl groups in the polymer side chain is suppressed. As a result, it is considered that not only the initial hydrophilicity but also the long-term hydrophilicity are exhibited, and the excellent water resistance due to the progress of crystallization is also exhibited.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.
[0025]
Examples 1-7 and Comparative Examples 1-5
6% by weight of polyvinyl alcohol (PVA) having a saponification degree of 97.5 to 99.5 mol% and an average polymerization degree of 1700, 1.2% by weight of polyethylene glycol (PEG) having a weight average molecular weight of 8500, and the compounds shown in Table 1 The hydrophilic coating compositions of Examples and Comparative Examples containing the anion concentrations shown in Table 1 were prepared.
About the obtained hydrophilic coating composition of each Example and a comparative example, the initial hydrophilicity and long-term hydrophilicity were measured and evaluated by the following method.
[0026]
[Evaluation of hydrophilicity]
An aluminum material (AA3102, thickness 0.15 mm) was degreased by a conventional method and then washed.
About the obtained aluminum material after degreasing and washing, a chromate treatment agent (manufactured by Nippon Paint Co., Ltd .: Alsurf 407/47) is used, and a phosphate chromate base treatment is applied by a dipping method, washed in running water for 1 minute, and treated at 50 ° C. for 10 minutes. After drying for a minute, a corrosion-resistant film of chromium (Cr) 100 mg / m 2 was formed on the surface of the aluminum material, and a test piece for hydrophilicity evaluation was prepared.
[0027]
The surface of the obtained test piece was coated with the hydrophilic coating composition of each Example and Comparative Example using a roll coater, and baked using a hot air drying oven at 255 ° C. for 12 seconds. A hydrophilic film having a film thickness of 0.9 to 1 g / m 2 was formed on the surface.
After applying the press oil (AF-2C manufactured by Idemitsu Kosan Co., Ltd.) to the test piece provided with the hydrophilic film in this way and heating and drying at 180 ° C. for 3 hours, the initial hydrophilicity immediately after and The long-term hydrophilicity after 100-hour immersion was measured.
[0028]
Initial hydrophilicity and long-term hydrophilicity are measured by dropping 2 μL of pure water onto the hydrophilic film of a horizontally installed test piece, and measuring the contact angle of the formed water droplet with a contact angle meter (Kyowa Interface Science Co., Ltd .: CA- A), and the hydrophilicity is evaluated by the following: evaluation point 5: contact angle <10 °, evaluation point 4: contact angle 10 to 16 °, evaluation point 3: contact angle 17 to 25 °, evaluation point 2: The contact angle is 26 to 35 °, and the evaluation point 1: The contact angle is> 35 °. The pass range is the evaluation point ≧ 3, and the overall evaluation includes initial hydrophilicity and long-term hydrophilicity. In both cases, the evaluation score ≧ 3.
The results are shown in Table 1.
[0029]
As for water resistance, when the hydrophilic film was observed on the test piece after the long-term hydrophilicity measurement, no swelling or dissolution was observed in each of the examples and comparative examples, and the test piece was suspended on the hydrophilic film. When the water was rubbed with a finger, no peeling of the film was observed, and both passed.
[0030]
[Table 1]
【The invention's effect】
According to the organic hydrophilic coating composition of the present invention, it is possible to form a hydrophilic film exhibiting excellent performance in initial hydrophilicity, long-term hydrophilicity and water resistance on the surface of a hard material such as an aluminum material. The aluminum material for heat exchangers such as the pre-coated fin material of the present invention is provided with a hydrophilic film having excellent performance in initial hydrophilic property, long-term hydrophilic property and water resistance on the surface thereof, and is formed using this. The heat exchanger exhibits excellent heat exchange efficiency over a long period of time.
Claims (6)
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| JP2001076984A JP3890908B2 (en) | 2001-03-16 | 2001-03-16 | Organic hydrophilic coating composition and aluminum material for heat exchanger having hydrophilic film |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3235886A1 (en) | 2016-04-22 | 2017-10-25 | Alcom Nikkei Specialty Coating Sdn. Bhd. | Organic hydrophilic coating composition and hydrophilic film, and aluminum material for heat exchanger |
| EP3275953A1 (en) | 2016-07-26 | 2018-01-31 | Alcom Nikkei Specialty Coating Sdn. Bhd. | Organic hydrophilic coating composition and hydrophilic film for aluminum material for a heat exchanger |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010059039A (en) * | 2008-08-05 | 2010-03-18 | Central Glass Co Ltd | Thin-pieced substance and coating composition |
| JP5466472B2 (en) * | 2009-10-14 | 2014-04-09 | 株式会社Ｕａｃｊ | Heat exchanger |
| JP2022161706A (en) * | 2021-04-09 | 2022-10-21 | 株式会社神戸製鋼所 | Aluminum fin material |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3235886A1 (en) | 2016-04-22 | 2017-10-25 | Alcom Nikkei Specialty Coating Sdn. Bhd. | Organic hydrophilic coating composition and hydrophilic film, and aluminum material for heat exchanger |
| EP3275953A1 (en) | 2016-07-26 | 2018-01-31 | Alcom Nikkei Specialty Coating Sdn. Bhd. | Organic hydrophilic coating composition and hydrophilic film for aluminum material for a heat exchanger |
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