JP4781975B2 - Application method of water-based paint - Google Patents
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- JP4781975B2 JP4781975B2 JP2006304195A JP2006304195A JP4781975B2 JP 4781975 B2 JP4781975 B2 JP 4781975B2 JP 2006304195 A JP2006304195 A JP 2006304195A JP 2006304195 A JP2006304195 A JP 2006304195A JP 4781975 B2 JP4781975 B2 JP 4781975B2
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Description
本発明は水性塗料の塗装方法に関する。 The present invention relates to a method for applying a water-based paint.
自動車の車体塗装では、一般に下塗り塗装（電着塗装）、中塗り塗装、上塗り塗装（ベース塗装及びクリヤ塗装）の順で行なわれている。その中塗り及びベース塗装には従来から溶剤型塗料が広く採用されてきたが、近年は環境負荷軽減の観点から、低溶剤型ないしは無溶剤型の塗料への置換が求められている。そのような塗料としては、水性塗料、粉体塗料、パウダースラリー塗料などが既に実用化されているが、塗装作業性の向上という観点から水性塗料への置換が進みつつある。 In automobile body painting, generally, undercoating (electrodeposition coating), intermediate coating, and topcoating (base coating and clear coating) are performed in this order. In the past, solvent-based paints have been widely used for intermediate coating and base coating, but in recent years, replacement with low-solvent type or solvent-free type paints has been demanded from the viewpoint of reducing environmental burden. As such paints, water-based paints, powder paints, powder slurry paints and the like have already been put into practical use, but replacement with water-based paints is progressing from the viewpoint of improving coating workability.
ところで、ウェットオンウェットにより、水性塗料による塗装に続いて溶剤型塗料のクリヤ塗装を行なった後に塗膜の焼付け乾燥を行なうと、水性塗料による塗膜に残存する水分によって突沸現象を生じ、ピンホールなどの塗膜欠陥が発生する。このような塗膜欠陥の発生を抑制するには、水性塗料による塗装後にその塗膜中の水分を蒸発させるプレヒート工程を組み込めばよいが、そのためのエネルギーが別途必要になるため、プレヒート工程を要しない水性塗料塗装技術の開発が要望されている。 By the way, when the paint film is baked and dried by wet-on-wet followed by clear coating of the solvent-based paint following the paint with the water-based paint, a bumping phenomenon occurs due to moisture remaining in the paint film with the water-based paint, and pinholes are generated. Such coating film defects occur. In order to suppress the occurrence of such coating film defects, it is sufficient to incorporate a preheating process that evaporates the moisture in the coating film after coating with a water-based paint, but this requires additional energy for that purpose. There is a demand for the development of water-based paint coating technology that does not.
これに対して、特許文献１には、水性塗料の噴霧粒子の平均粒子径を２５μｍ以下にするとともに、該水性塗料による塗膜の固形分が４０質量％以上の状態でクリヤ塗装をすることが開示されている。これは、上記平均粒子径を小さくすることにより、塗装段階で当該水性塗料からの水分の蒸発を促して塗膜の固形分を高め、プレヒート工程を不要にするというものである。
しかし、水性塗料の噴霧粒子の平均粒子径を小さくすると、水分の蒸発が促進されるものの、被塗物に塗着した塗料の粘度が高くなる問題がある。すなわち、塗着した塗料の流動性が低下し、かえってクリヤ塗装後の塗膜の平滑性ないしは表面外観が悪化するという問題である。 However, if the average particle diameter of the spray particles of the water-based paint is reduced, the evaporation of moisture is promoted, but there is a problem that the viscosity of the paint applied to the article to be coated is increased. That is, there is a problem that the fluidity of the applied paint is lowered and the smoothness or surface appearance of the coated film after clear coating is deteriorated.
そこで、本発明は、上記塗膜の平滑性を損なうことなく、上記水性塗料による塗膜の固形分を高め、プレヒート工程を簡略（乾燥温度の低減又は乾燥時間の短縮）に或いは省略できるようにすることを課題とする。 Therefore, the present invention increases the solid content of the coating film by the water-based paint without impairing the smoothness of the coating film, so that the preheating process can be simplified (reduction of drying temperature or shortening of drying time) or can be omitted. The task is to do.
本発明は、このような課題に対して、水性塗料の噴霧粒子の平均粒子径を小さくするとともに、該水性塗料の粘度を低くするようにした。 In the present invention, the average particle diameter of the spray particles of the water-based paint is reduced and the viscosity of the water-based paint is lowered in response to such a problem.
請求項１に係る発明は、水性塗料を噴霧式塗装機によって被塗物に吹き付ける水性塗料の塗装方法であって、
上記塗装機に供給する塗料の粘度を０．０５９Ｐａ・ｓ以下とし、
上記塗装機による噴霧塗粒の平均粒子径を１０μｍ以下とし、
塗着時の塗膜粘度が１０Ｐａ・ｓ以上、該塗着時から１分経過後の塗膜の固形分が７０質量％以上、並びに塗膜の乾燥後の膜厚が１μｍ以上４０μｍ以下となるようにすることを特徴とする。
The invention according to claim 1 is a coating method of a water-based paint in which a water-based paint is sprayed on an object to be coated by a spray type coating machine,
The viscosity of the paint supplied to the coating machine is 0.059 Pa · s or less,
The average particle size of the spray coating particles by the coating machine is 10 μm or less,
The coating film viscosity at the time of coating is 10 Pa · s or more, the solid content of the coating film after 1 minute from the coating time is 70% by mass or more, and the film thickness after drying of the coating film is 1 μm or more and 40 μm or less. It is characterized by doing so.
すなわち、本発明者は、プレヒート工程の簡略化ないしは省略を課題として塗装方法を研究した結果、塗粒（噴霧式塗装機による塗料の噴霧粒子）の乾燥効率を下式のように塗粒の重量に対する塗粒の表面積の比で定義できることを見出した。そして、重量を塗粒の体積で近似すると、結局、乾燥効率はその粒子径に反比例すると定義付けることができる。 That is, as a result of studying the coating method with the aim of simplifying or omitting the preheating process, the present inventor has determined that the drying efficiency of the paint granules (spray particles of paint by a spray coater) is the weight of the paint grains as shown in the following formula. It was found that the ratio can be defined by the ratio of the surface area of the coated grain to the surface. When the weight is approximated by the volume of the coated grain, it can be defined that the drying efficiency is inversely proportional to the particle diameter.
乾燥効率∝(塗粒の表面積)／(塗粒の重量)
∝(粒子径)２／(粒子径)３
∝１／(粒子径)
そこで、固形分４８質量％の水性塗料を用いて上記定義式を検証した。その結果、図１に示すように、塗粒の平均粒子径を５０μｍ（従来の塗装方法の平均的な粒子径）から１０μｍまで小さくすると、塗着時（塗装機による塗料の吹付け終了時）の塗膜の固形分が５５質量％から８０質量％以上にまで上昇することがわかった。固形分８０質量％は、当該水性塗料による塗膜のプレヒートによる目標固形分である。
Drying efficiency ∝ (surface area of the granule) / (weight of the granule)
∝ (particle diameter) 2 / (particle diameter) 3
∝1 / (particle diameter)
Therefore, the above formula was verified using a water-based paint having a solid content of 48% by mass. As a result, as shown in FIG. 1, when the average particle size of the coating particles is reduced from 50 μm (average particle size of the conventional coating method) to 10 μm, at the time of coating (at the end of spraying of the paint by the coating machine) It was found that the solid content of the coating film increased from 55% by mass to 80% by mass or more. The solid content of 80% by mass is a target solid content by preheating of the coating film with the water-based paint.
一方、上記平均粒子径の微小化は乾燥効率の向上に有効であるものの、塗装機に供給する塗料の粘度を粒子径が大きいときと同じように設定すると、被塗物に塗着した塗料の粘度が高くなって、その流動性が低下してしまう。 On the other hand, miniaturization of the average particle size is effective for improving the drying efficiency, but if the viscosity of the coating material supplied to the coating machine is set in the same way as when the particle size is large, the coating material applied to the coating object Viscosity increases and its fluidity decreases.
そこで、本発明では、上記平均粒子径を１０μｍ以下にするとともに、塗装機に供給する塗料の粘度を従来よりも低い０．０５９Ｐａ・ｓ以下として、塗着した塗料の良好な流動性を確保した。この場合、塗料の粘度を低くすると、流動性の確保に有利になるだけでなく、塗装機によって塗料を噴霧したときの塗料の微粒化が容易になるという効果が得られる。 Therefore, in the present invention, the average particle diameter is set to 10 μm or less, and the viscosity of the paint supplied to the coating machine is set to 0.059 Pa · s or less, which is lower than the conventional one, to ensure good fluidity of the applied paint. . In this case, if the viscosity of the paint is lowered, not only is it advantageous for ensuring fluidity, but also an effect that the paint is easily atomized when the paint is sprayed by a coating machine can be obtained.
そうして、このような設定において、塗着時の塗膜粘度が１０Ｐａ・ｓ以上、塗膜の乾燥後の膜厚が４０μｍ以下となるようにすることにより、塗膜のタレ（流れ）を抑制して平滑性の高い塗膜を形成できるようにした。また、塗着時から１分経過後の塗膜の固形分を７０質量％以上とすることにより、仮にウェットオンウェットを行なってもピンホール等の欠陥を生じ難いようにした。換言すれば、当該塗膜への重ね塗りを行なう場合であっても、プレヒート工程を簡略に或いは省略できるようにようにした。また、上記平滑性を高める観点から、塗膜の乾燥後の膜厚は１μｍ以上が好ましい。 Thus, in such a setting, the coating film viscosity at the time of coating is 10 Pa · s or more, and the film thickness after drying of the coating film is 40 μm or less, thereby reducing the sagging (flow) of the coating film. It was suppressed so that a highly smooth coating film could be formed. Further, by setting the solid content of the coating film after 1 minute from the coating to 70% by mass or more, defects such as pinholes are hardly generated even if wet-on-wet is performed. In other words, the preheating process can be simplified or omitted even in the case of overcoating the coating film. Moreover, from the viewpoint of improving the smoothness, the film thickness after drying of the coating film is preferably 1 μm or more.
請求項２に係る発明は、請求項１において、
上記塗装機による上記噴霧塗粒の平均粒子径を５μｍ以下とすることを特徴とする。
The invention according to claim 2 is the invention according to claim 1,
An average particle diameter of the spray coating particles by the coating machine is 5 μm or less.
これにより、表面が平滑な塗膜を得る上でさらに有利になる。 This is further advantageous in obtaining a coating film having a smooth surface.
請求項３に係る発明は、請求項１又は請求項２において、
塗装ブース内の温度を５０℃以下とすることを特徴とする。
The invention according to
The temperature in the painting booth is 50 ° C. or lower.
これにより、噴霧された塗粒の粘度が過度に上昇することを防止し、塗着した塗料の流動性を確保して平滑な塗膜を得る上で有利になる。塗装ブース内の温度は３０℃以下が好ましい。 This is advantageous in preventing the viscosity of the sprayed coating particles from excessively increasing and securing the fluidity of the applied paint to obtain a smooth coating film. The temperature in the painting booth is preferably 30 ° C. or lower.
請求項４に係る発明は、請求項１乃至請求項３のいずれか一において、
塗装ブース内の相対湿度ＲＨを９０％以下とすることを特徴とする。
According to a fourth aspect of the present invention, in any one of the first to third aspects,
The relative humidity RH in the painting booth is 90% or less.
すなわち、塗装ブース内の相対湿度ＲＨが高すぎると、噴霧された塗粒からの水分の蒸発が進まなくなる。そこで、当該相対湿度ＲＨを９０％以下とするものである。 That is, when the relative humidity RH in the coating booth is too high, the evaporation of moisture from the sprayed coating particles does not proceed. Therefore, the relative humidity RH is set to 90% or less.
請求項５に係る発明は、請求項１乃至請求項４のいずれか一の水性塗料の塗装方法をウェットオンウェットにおける下層塗膜の形成に用いることを特徴とする。
The invention according to
すなわち、上述の如く塗粒の平均粒子径を１０μｍ以下とし、塗着時から１分経過後の塗膜の固形分が７０質量％以上となるようにしたから、ウェットオンウェットにおいてプレヒート工程の簡略化ないしは省略が可能になる。 That is, as described above, the average particle size of the coated particles is set to 10 μm or less, and the solid content of the coating after 1 minute from the time of coating is set to 70% by mass or more. It can be changed or omitted.
請求項６に係る発明は、請求項５において、
上記水性塗料の塗装方法による塗着時から１分経過後の当該下層塗膜の固形分が８０質量％以上となるようにすることを特徴とする。
The invention according to claim 6 is the invention according to
The solid content of the lower layer coating film after 1 minute from the time of application by the coating method of the water-based paint is 80% by mass or more.
従って、上層塗膜形成後の焼付け乾燥時にピンホール等の表面欠陥を生ずることを防止する上でさらに有利になる。 Therefore, it is further advantageous in preventing the occurrence of surface defects such as pinholes during baking and drying after the formation of the upper layer coating film.
請求項７に係る発明は、請求項５又は請求項６において、
上記下層塗膜の表面粗さＲａが０．３μｍ以下である状態で上層塗膜を形成する塗装を行なうことを特徴とする。
The invention according to claim 7 is the invention according to
The coating is performed to form the upper layer coating film in a state where the surface roughness Ra of the lower layer coating film is 0.3 μm or less.
従って、上層塗膜の平滑性を高める上で有利になる。 Therefore, it is advantageous in improving the smoothness of the upper layer coating film.
請求項８に係る発明は、請求項５乃至請求項７のいずれか一において、
上記下層塗膜の粘度が１０００Ｐａ・ｓ以上である状態で上層塗膜を形成する塗装を行なうことを特徴とする。
The invention according to claim 8 is the invention according to any one of
The upper layer coating film is coated in a state where the viscosity of the lower layer coating film is 1000 Pa · s or more.
従って、上層塗膜の平滑性を高める上で有利になる。 Therefore, it is advantageous in improving the smoothness of the upper layer coating film.
以上のように本発明によれば、噴霧式塗装機に供給する水性塗料の粘度を０．０５９Ｐａ・ｓ以下、該塗装機による噴霧塗粒の平均粒子径を１０μｍ以下とし、塗着時の塗膜粘度が１０Ｐａ・ｓ以上、該塗着時から１分経過後の塗膜の固形分が７０質量％以上、並びに塗膜の乾燥後の膜厚が１μｍ以上４０μｍ以下となるようにしたから、塗膜のタレを招くことなく、被塗物に塗着した塗料の良好な流動性を確保し、且つ塗膜の乾燥効率を高めることができ、平滑性の高い塗膜を得ることができる。 As described above, according to the present invention, the viscosity of the water-based paint supplied to the spray type coating machine is 0.059 Pa · s or less, the average particle diameter of the spray coating particles by the coating machine is 10 μm or less, and the coating at the time of coating is performed. Since the film viscosity is 10 Pa · s or more, the solid content of the coating film after 1 minute from the time of application is 70% by mass or more, and the film thickness after drying of the coating film is 1 μm or more and 40 μm or less, Without causing sagging of the coating film, good fluidity of the paint applied to the object can be ensured, the drying efficiency of the coating film can be increased, and a highly smooth coating film can be obtained.
また、ウェットオンウェットを行なう場合であっても、プレヒート工程の簡略化ないしは省略が可能になり、省エネルギー及び作業効率の向上に有利になる。 Further, even when wet-on-wet is performed, the preheating process can be simplified or omitted, which is advantageous for energy saving and work efficiency.
以下、本発明の実施形態を図面に基いて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
＜塗膜構成＞
図２に本実施形態に係る塗装鋼板の塗膜構成を示す。同図において、１はＳＰＣ鋼板、２は電着塗装した下塗り塗膜、３は水性塗料による中塗り塗膜、４は水性塗料によるベース塗膜、５は溶剤系クリヤ塗料によるクリヤ塗膜である。
<Coating composition>
The coating-film structure of the coated steel plate which concerns on FIG. 2 at this embodiment is shown. In the figure, 1 is an SPC steel plate, 2 is an electrodeposition-coated undercoat, 3 is a water-based intermediate coating, 4 is a water-based base coating, and 5 is a solvent-based clear coating. .
＜塗装方法＞
リン酸亜鉛処理したＳＰＣ鋼板１に電着塗装を行ない、焼付け乾燥処理を施して下塗り塗膜２を形成する。この下塗り塗膜２の上に噴霧式塗装機を用いて水性塗料を均一に塗装することにより、中塗り塗膜３を形成する。次にこの中塗り塗膜３の上に噴霧式塗装機を用いウェットオンウェットにて別の水性塗料を均一に塗装することにより、ベース塗膜４を形成する。最後にベース塗膜４の上に噴霧式塗装機を用いウェットオンウェットにて溶剤系クリヤ塗料を均一に塗装し、焼付け乾燥を行なうことにより、クリヤ塗膜５を形成する。
<Coating method>
Electrodeposition coating is performed on the zinc phosphate-treated SPC steel sheet 1 and baking and drying treatment is performed to form an undercoat coating film 2. An
本発明の特徴とするところは、上記水性塗料による中塗り塗膜及びベース塗膜４の形成にあたって、次の塗装条件を採用した点にある。 The feature of the present invention is that the following coating conditions are adopted in forming the intermediate coating film and the base coating film 4 by the water-based paint.
Ａ．噴霧式塗装機に供給する水性塗料の粘度を０．０５９Ｐａ・ｓ以下とする。 A. The viscosity of the water-based paint supplied to the spray coater is set to 0.059 Pa · s or less.
Ｂ．噴霧式塗装機による噴霧塗粒の平均粒子径を１０μｍ以下、好ましくは５μｍ以下とする。 B. The average particle diameter of spray-coated grains by a spray-type coating machine is 10 μm or less, preferably 5 μm or less.
Ｃ．被塗物に対する塗着時の塗膜粘度は１０Ｐａ・ｓ以上となるようにする。 C. The coating film viscosity at the time of application to the object is set to 10 Pa · s or more.
Ｄ．塗着時から１分経過後の塗膜の固形分は７０質量％以上、好ましくは８０質量％以上になるようにする。 D. The solid content of the coating after one minute has elapsed from the time of application is 70% by mass or more, preferably 80% by mass or more.
Ｅ．塗膜の乾燥後の膜厚は１μｍ以上４０μｍ以下となるようにする。 E. The film thickness after drying of the coating film is set to 1 μm or more and 40 μm or less.
Ｆ．塗装ブース内の温度を５０℃以下とする。 F. The temperature in the painting booth is 50 ° C. or lower.
Ｇ．塗装ブース内の相対湿度ＲＨを９０％以下とする。 G. The relative humidity RH in the painting booth is 90% or less.
また、クリヤ塗装は、ベース塗膜４の表面粗さＲａが０．３μｍ以下である状態で、そして、ベース塗膜４の粘度が１０００Ｐａ・ｓ以上である状態で行なう。 Further, the clear coating is performed in a state where the surface roughness Ra of the base coating film 4 is 0.3 μm or less and in a state where the viscosity of the base coating film 4 is 1000 Pa · s or more.
＜塗装条件の評価試験＞
試験片に塗装条件を種々に変えて塗装を行ない、塗装条件の評価を行なった。
<Evaluation test for coating conditions>
The test piece was painted with various coating conditions, and the coating conditions were evaluated.
試験片はリン酸亜鉛処理した厚み０．７ｍｍ、縦１００ｍｍ、横３００ｍｍのＳＰＣ鋼板である。下塗り塗膜用の塗料には、日本ペイント社製商品記号PN1020Mの電着塗料を採用し、乾燥後の２０μｍとなるように電着塗装した後、１５０℃で３０分の乾燥を行なった。 The test piece is an SPC steel plate treated with zinc phosphate and having a thickness of 0.7 mm, a length of 100 mm, and a width of 300 mm. As the paint for the undercoat film, an electrodeposition paint having a product symbol of PN1020M manufactured by Nippon Paint Co., Ltd. was adopted. After the electrodeposition was applied so as to be 20 μm after drying, drying was performed at 150 ° C. for 30 minutes.
中塗り塗膜の形成には次の配合の水性塗料を採用した。すなわち、下記配合のうちの前四者を混合した後、これにウレタン会合型増粘剤を添加して混合攪拌し、中塗り用の水性塗料とした。 A water-based paint having the following composition was employed for forming the intermediate coating film. That is, after mixing the former four of the following blends, a urethane associative thickener was added thereto and mixed and stirred to obtain an aqueous coating for intermediate coating.
ルチル型二酸化チタン分散ペースト １３０重量部
（ビックケミー社製Disperbyk190分散剤含有ペースト，樹脂固形分７５質量％）
アクリルエマルション １６５重量部
（日本ペイント社製，樹脂固形分３０質量％）
ウレタンエマルション ６５重量部
（アビシア社製，樹脂固形分３０質量％）
硬化剤 ３５重量部
（三井サイテック社製商品名サイメル327(メラミン樹脂，樹脂固形分９０質量％））
ウレタン会合型増粘剤 １重量部
（旭電化工業社製商品名アデカノールUH-814N(有効成分３０質量％)）
130 parts by weight of rutile type titanium dioxide dispersion paste (Disperbyk 190 dispersant-containing paste manufactured by Big Chemie, resin solid content 75% by mass)
165 parts by weight of acrylic emulsion (manufactured by Nippon Paint Co., Ltd., resin
65 parts by weight of urethane emulsion (Avisia Co., Ltd., resin
35 parts by weight of curing agent (trade name Cymel 327 (melamine resin, resin
Urethane associative thickener 1 part by weight (trade name Adecanol UH-814N (
ベース塗膜の形成には日本ペイント社製商品記号AR2000の水性塗料を採用した。また、中塗り及びベースの塗装には、アネスト岩田社製の塗装ガンLPH-100-144LVGを採用し、エア圧４．８ｋｇ／ｃｍ２とし、塗装ブース内の温度は２５℃、湿度は７０％とした。 For the formation of the base coating film, a water-based paint of Nippon Paint Co., Ltd. product symbol AR2000 was adopted. In addition, the coating gun LPH-100-144LVG manufactured by Anest Iwata is used for the intermediate coating and base coating, the air pressure is 4.8 kg / cm 2 , the temperature in the coating booth is 25 ° C, and the humidity is 70%. It was.
クリヤ塗膜の形成には日本ペイント社製商品記号Ｏ−１６００の溶剤型クリヤ塗料を採用した。そうして、クリヤ塗装にはベル型回転噴霧式塗装機（回転数３００００ｒｐｍ，吐出速度１５０ｃｃ／分，シェーピングエアの流速１５０ＮＬ／分）を採用し、塗装後に１４０℃で２０分の焼付け乾燥処理を施した。 For the formation of the clear coating film, a solvent-type clear coating of product symbol O-1600 manufactured by Nippon Paint Co., Ltd. was employed. Then, a bell-type rotary spray coater (rotation speed of 30000 rpm, discharge speed of 150 cc / min, shaping air flow rate of 150 NL / min) is adopted for clear coating, and baking and drying treatment at 140 ° C. for 20 minutes after coating. gave.
[評価用諸元（因子）の測定（判断）]
後に示す表１〜５における緒元の内容は以下の通りである。
[Measurement (determination) of specifications (factors) for evaluation]
The contents of the specifications in Tables 1 to 5 shown below are as follows.
塗料吐出量；塗装ガンからの塗料の吐出量である。 Paint discharge amount: The amount of paint discharged from the paint gun.
塗粒の粒子径；ガラス板上にシリコンオイルを塗布し、その上に瞬間的に塗料を吹き付けた。その後、顕微鏡（ニコン社製EPIPHOT）にてシリコンオイル上の塗粒の粒子径を測定し、測定数５０の平均値をとった。 Particle size of coated particles: Silicon oil was applied on a glass plate, and the paint was instantaneously sprayed thereon. Thereafter, the particle diameter of the coated particles on the silicon oil was measured with a microscope (Nikon Corporation EPIPHOT), and an average value of 50 measurements was taken.
塗料粘度；塗装ガンに供給される塗料の粘度である。 Paint viscosity: The viscosity of the paint supplied to the paint gun.
初期固形分，塗膜固形分；質量既知のアルミ箔に塗料を塗布し、その直後にアルミ箔を塗料が乾燥しないように折り畳んでこのアルミ箔とウェット塗膜との合計質量（ウェット質量）を測定した。その後、１４０℃で２０分の乾燥を行ない、得られたアルミ箔とドライ塗膜との合計質量（ドライ質量）を測定し、次式により固形分(質量％)を求めた。初期固形分は塗装ガンに供給される塗料の固形分である。塗膜固形分は塗装ガンから噴霧された塗料を用いて測定したものであり、試験片に塗着した塗膜の固形分に対応する。 Initial solid content, coating film solid content; paint is applied to aluminum foil of known mass, and immediately after that, the aluminum foil is folded so that the paint does not dry, and the total mass (wet mass) of this aluminum foil and wet coating film is calculated. It was measured. Thereafter, drying was performed at 140 ° C. for 20 minutes, the total mass (dry mass) of the obtained aluminum foil and the dry coating film was measured, and the solid content (mass%) was determined by the following formula. The initial solid content is the solid content of the paint supplied to the paint gun. The solid content of the coating film is measured using the paint sprayed from the coating gun, and corresponds to the solid content of the coating film applied to the test piece.
固形分＝(ドライ質量−アルミ箔質量)／(ウェット質量−アルミ箔質量)×１００
表面粗さ；ミツトヨ社製表面粗さ測定器(Mitutoyo S-3000)を用いＲａ（算術平均粗さ）を測定した（ｎ＝３）。
Solid content = (dry mass−aluminum foil mass) / (wet mass−aluminum foil mass) × 100
Surface roughness: Ra (arithmetic average roughness) was measured using a surface roughness measuring instrument (Mitutoyo S-3000) manufactured by Mitutoyo Corporation (n = 3).
塗膜厚；乾燥後の塗膜の厚さである。 Coating thickness: the thickness of the coating after drying.
ピンホール；塗膜のピンホールの有無は目視にて判断した。 Pinholes: The presence or absence of pinholes in the coating film was judged visually.
タレ；塗膜のタレの有無は目視にて判断した。 Sagging: The presence or absence of sagging of the coating film was judged visually.
仕上がり性；ＢＹＫ社製のWave Scan DOIを用い、試験片を水平にして塗装したとき、並びに垂直にして塗装したとき各々に関し、構造スペクトルWa(0.1〜0.3mm)、Wc(1.0〜3.0mm)及びWd(3.0〜10.0mm)で塗膜表面のうねりの程度を測定した。 Finishability: Structural spectrum Wa (0.1 to 0.3 mm), Wc (1.0 to 3.0 mm) for each of when the test piece was painted horizontally and painted vertically using a Wave Scan DOI manufactured by BYK And Wd (3.0 to 10.0 mm), the degree of undulation on the coating film surface was measured.
塗膜粘度；鋼板への塗着直後の塗膜をスパチュラにてかき取り、ＥＨ型粘度計にて測定した。 Coating film viscosity: The coating film immediately after application to the steel sheet was scraped with a spatula and measured with an EH viscometer.
[塗粒の粒子径の影響]
中塗り用及びベース用水性塗料の噴霧塗粒の平均粒子径を変化させて、中塗り及びベースの塗膜及びクリヤ塗膜に与える影響を調べた。結果を表１に示す。なお、表１欄外の「アルミムラ」は光輝材（アルミフレーク）の配向から生ずる光輝感のムラを意味する。この点は他の表も同じである。
[Effects of particle size of coated particles]
By changing the average particle size of the spray coating particles of the water-based paint for the intermediate coating and the base, the influence on the coating film and the clear coating film of the intermediate coating and the base was investigated. The results are shown in Table 1. Note that “aluminum unevenness” outside the column of Table 1 means unevenness in glitter caused by the orientation of the glitter material (aluminum flakes). This is the same for other tables.
表１の実施例１〜３及び比較例１〜３は、塗装ガンのエア圧を４．８ｋｇ／ｃｍ２の一定とし、塗料の吐出量を変化させることにより、塗粒の平均粒子径を変化させたものである。平均粒子径が小さくなるにつれて塗膜固形分が増大しており、図１の結果と符号している。換言すれば、比較例１〜３のように塗粒の平均粒子径が１０μｍを超えると、塗膜固形分が低くなる。その結果、比較例２，３では、クリヤ塗装後の焼付け乾燥において、中塗り塗膜及びベース塗膜に残存する水分によって突沸現象を生じ、ピンホールを発生しており、さらにウエットオンウェットによる混層を生じている。 In Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, the air pressure of the coating gun is kept constant at 4.8 kg / cm 2 , and the average particle diameter of the coated particles is changed by changing the discharge amount of the paint. It has been made. As the average particle size decreases, the solid content of the coating film increases, which is the result of FIG. In other words, when the average particle diameter of the coating particles exceeds 10 μm as in Comparative Examples 1 to 3, the solid content of the coating film becomes low. As a result, in Comparative Examples 2 and 3, in the baking and drying after the clear coating, the moisture remaining in the intermediate coating film and the base coating film caused a bumping phenomenon, and pinholes were generated. Has produced.
表面粗さをみると、表面粗さが０．３μｍ以下である実施例１〜３では、仕上がり性が良好である。これに対して、塗粒の平均粒子径が１０μｍを超えて１２μｍになった比較例１はＲａ１．４であり、仕上がり性が悪くなっている。なお、比較例２，３は平均粒子径が比較例１よりも大きいにも拘わらず、表面粗さＲａが小さくなっている。これは、粒子径が大きいため水分が飛ばず、試験片に塗着した塗料の流動性が良かったためであるが、上述の混層の問題を生じている。 Looking at the surface roughness, in Examples 1 to 3 in which the surface roughness is 0.3 μm or less, the finish is good. On the other hand, Comparative Example 1 in which the average particle diameter of the coating grains exceeds 10 μm and becomes 12 μm is Ra 1.4, and the finish is poor. In Comparative Examples 2 and 3, although the average particle diameter is larger than that of Comparative Example 1, the surface roughness Ra is small. This is because moisture does not fly because the particle diameter is large, and the fluidity of the paint applied to the test piece is good, but the above-mentioned mixed layer problem occurs.
そうして、比較例１〜３は、上記ピンホールを生じ、或いは中塗り塗膜やベース塗膜の表面粗さが大きいことにより、クリヤ塗装後の仕上がり性が、実施例に比べて悪くなっている。 Thus, in Comparative Examples 1 to 3, the pinhole is generated, or the surface finish of the intermediate coating film or the base coating film is large, so that the finish after the clear coating is worse than that of the example. ing.
以上から、塗粒の平均粒子径は１０μｍ以下、特に仕上がり性の観点から５μｍ以下であることが好ましいということができる。該平均粒子径の下限は１μｍを目安にすれば良い。 From the above, it can be said that the average particle diameter of the coated grains is preferably 10 μm or less, and particularly preferably 5 μm or less from the viewpoint of finish. The lower limit of the average particle diameter may be 1 μm.
[塗料粘度の影響]
塗装機に供給される水性塗料の粘度を変化させて、中塗り及びベースの塗膜及びクリヤ塗膜に与える影響を調べた。結果を表２に示す。
[Influence of paint viscosity]
By changing the viscosity of the water-based paint supplied to the coating machine, the influence on the intermediate coating, base coating and clear coating was investigated. The results are shown in Table 2.
表２の実施例１，２及び比較例１，２は、水性塗料を調製する時に添加する水の量を変えて塗料粘度を変化させたものである。従って、実施例１，２及び比較例１，２は、塗料の初期固形分も相異なる。 In Examples 2 and 1 and Comparative Examples 1 and 2 in Table 2, the viscosity of the paint was changed by changing the amount of water added when preparing the aqueous paint. Therefore, Examples 1 and 2 and Comparative Examples 1 and 2 also differ in the initial solid content of the paint.
塗料粘度が０．０５９Ｐａ・ｓ以下である実施例１，２は、塗装ガンによる噴霧の際に塗料が微粒化し易くなり、塗粒の平均粒子径が比較例に比べて小さくなっている。その結果、塗着後の塗膜固形分も高くなり、ピンホールの発生が見られなくなっている。また、塗料粘度が０．０５９Ｐａ・ｓ以下であるということは、塗粒が被塗物に塗着した際に塗粒が流動し易いということであり、塗膜の平滑性確保に有利になる。 In Examples 1 and 2 having a paint viscosity of 0.059 Pa · s or less, the paint tends to be atomized when sprayed with a coating gun, and the average particle diameter of the paint grains is smaller than that of the comparative example. As a result, the solid content of the coating film after coating increases, and the occurrence of pinholes is not observed. In addition, the fact that the viscosity of the paint is 0.059 Pa · s or less means that the coated particles are easy to flow when the coated particles are applied to the object to be coated, which is advantageous for ensuring the smoothness of the coating film. .
これに対して、塗料粘度が高い比較例１，２では、塗粒の平均粒子径が大きくなり、塗着後の塗膜粘度も低くなっている。そのため、塗膜の表面粗さが粗くなったり、或いは混層を生じている。 On the other hand, in Comparative Examples 1 and 2 having a high paint viscosity, the average particle diameter of the coated grains is large, and the coating film viscosity after coating is also low. Therefore, the surface roughness of the coating film becomes rough or a mixed layer is generated.
以上から、塗料粘度は０．０５９Ｐａ・ｓ以下であることが好ましいということができる。その下限は０．０４０Ｐａ・ｓ程度を目安にすれば良い。 From the above, it can be said that the paint viscosity is preferably 0.059 Pa · s or less. The lower limit may be about 0.040 Pa · s.
[塗膜粘度の影響]
水性塗料塗着時の塗膜粘度を変化させて、中塗り及びベースの塗膜及びクリヤ塗膜に与える影響を調べた。結果を表３に示す。
[Influence of film viscosity]
The effect on the intermediate coating, the base coating and the clear coating was examined by changing the coating viscosity at the time of applying the aqueous coating. The results are shown in Table 3.
表３の実施例１〜３及び比較例１，２は、塗装ガンの吐出量或いは塗料粘度を調節して水性塗料塗着時の塗膜粘度を変化させたものである。 In Examples 1 to 3 and Comparative Examples 1 and 2 in Table 3, the coating film viscosity at the time of applying the aqueous paint is changed by adjusting the discharge amount of the coating gun or the paint viscosity.
塗膜粘度が１０Ｐａ・ｓ以上である実施例１〜３では、塗膜固形分が多く、ピンホールやタレは発生しなかった。これに対して、塗膜粘度が低い比較例１，２では、塗膜固形分が少なく、ピンホールやタレの発生がみられ、仕上がり性も実施例に比べて劣っている。 In Examples 1 to 3 in which the viscosity of the coating film was 10 Pa · s or more, the coating film had a high solid content, and no pinholes or sagging occurred. On the other hand, in Comparative Examples 1 and 2 having a low coating film viscosity, the coating film solid content is small, pinholes and sagging are observed, and the finish is inferior to that of the Examples.
以上から、塗膜粘度は１０Ｐａ・ｓ以上であることが好ましいということができる。その上限は１００００Ｐａ・ｓ程度を目安にすれば良い。 From the above, it can be said that the viscosity of the coating film is preferably 10 Pa · s or more. The upper limit may be about 10,000 Pa · s.
[塗膜固形分の影響]
水性塗料塗着時から１分経過後の塗膜固形分を変化させて、中塗り及びベースの塗膜及びクリヤ塗膜に与える影響を調べた。結果を表４に示す。
[Effect of coating solids]
The effect on the intermediate coating, the base coating, and the clear coating was investigated by changing the solid content of the coating one minute after the water-based coating was applied. The results are shown in Table 4.
表４の実施例１〜３及び比較例１，２は、塗装ガンの吐出量或いは塗料粘度を調節して上記塗膜固形分を変化させたものである。 In Examples 1 to 3 and Comparative Examples 1 and 2 in Table 4, the coating film solid content is changed by adjusting the discharge amount of the coating gun or the paint viscosity.
塗着１分後の塗膜固形分が７０質量％以上である実施例１〜３では、ピンホールや混層の発生がなかった。これに対して、塗膜固形分が低い比較例１，２では、ピンホール及び混層がみられた。 In Examples 1 to 3, in which the solid content of the coating film after 1 minute of coating was 70% by mass or more, no pinholes or mixed layers were generated. On the other hand, in the comparative examples 1 and 2 with a low coating-film solid content, the pinhole and the mixed layer were seen.
従って、塗着１分後の塗膜固形分は７０質量％以上であることが好ましく、仕上がり性の観点からさらに８０質量％以上が好ましいということができる。その上限は９５質量％程度を目安にすれば良い。 Accordingly, the solid content of the coating film after 1 minute of coating is preferably 70% by mass or more, and more preferably 80% by mass or more from the viewpoint of finish. The upper limit may be about 95% by mass.
[塗膜厚の影響]
水性塗料による塗膜厚を変化させて、中塗り及びベースの塗膜及びクリヤ塗膜に与える影響を調べた。結果を表５に示す。
[Effect of coating thickness]
The effect on the intermediate coating, base coating and clear coating was investigated by changing the coating thickness of the aqueous coating. The results are shown in Table 5.
中塗り及びベース各々の塗膜厚が１μｍ以上４０μｍ以下の実施例１〜５では、塗膜のタレはなく、発色性にも問題がなかったが、塗膜厚が０．５μｍの比較例１では発色性が悪く、塗膜厚が５０μｍの比較例２では塗膜のタレを生じている。塗膜厚が１μｍ以上であれば、発色性及び耐チッピングを確保することができる。 In Examples 1 to 5 in which the coating thickness of each of the intermediate coating and the base was 1 μm or more and 40 μm or less, there was no sagging of the coating film and there was no problem in color development, but Comparative Example 1 with a coating film thickness of 0.5 μm The color developability is poor, and the sagging of the coating occurs in Comparative Example 2 where the coating thickness is 50 μm. When the coating thickness is 1 μm or more, color developability and chipping resistance can be ensured.
従って、当該塗膜厚は１μｍ以上４０μｍ以下が好ましいということができる。 Therefore, it can be said that the coating film thickness is preferably 1 μm or more and 40 μm or less.
１ 鋼板
２ 下塗り塗膜
３ 中塗り塗膜
４ ベース塗膜
５ クリヤ塗膜
DESCRIPTION OF SYMBOLS 1 Steel plate 2
Claims (8)
上記塗装機に供給する塗料の粘度を０．０５９Ｐａ・ｓ以下とし、
上記塗装機による噴霧塗粒の平均粒子径を１０μｍ以下とし、
塗着時の塗膜粘度が１０Ｐａ・ｓ以上、該塗着時から１分経過後の塗膜の固形分が７０質量％以上、並びに塗膜の乾燥後の膜厚が１μｍ以上４０μｍ以下となるようにすることを特徴とする水性塗料の塗装方法。 A method of painting a water-based paint by spraying the water-based paint onto an object to be coated with a spray-type coating machine,
The viscosity of the paint supplied to the coating machine is 0.059 Pa · s or less,
The average particle size of the spray coating particles by the coating machine is 10 μm or less,
The coating film viscosity at the time of coating is 10 Pa · s or more, the solid content of the coating film after 1 minute from the coating time is 70% by mass or more, and the film thickness after drying of the coating film is 1 μm or more and 40 μm or less. A method of painting a water-based paint characterized by:
上記塗装機による上記噴霧塗粒の平均粒子径を５μｍ以下とすることを特徴とする水性塗料の塗装方法。 In claim 1,
A method for applying a water-based paint, characterized in that an average particle size of the spray-coated grains by the coating machine is 5 μm or less.
塗装ブース内の温度を５０℃以下とすることを特徴とする水性塗料の塗装方法。 In claim 1 or claim 2,
A method for painting a water-based paint, characterized in that the temperature in the painting booth is 50 ° C. or lower.
塗装ブース内の相対湿度ＲＨを９０％以下とすることを特徴とする水性塗料の塗装方法。 In any one of Claim 1 thru | or 3,
A method for painting a water-based paint, characterized in that the relative humidity RH in the painting booth is 90% or less.
上記水性塗料の塗装方法による塗着時から１分経過後の当該下層塗膜の固形分が８０質量％以上となるようにすることを特徴とする塗装方法。 In claim 5,
A coating method, characterized in that the solid content of the lower layer coating after one minute has elapsed from the time of application by the water-based coating method is 80% by mass or more.
上記下層塗膜の表面粗さＲａが０．３μｍ以下である状態で上層塗膜を形成する塗装を行なうことを特徴とする塗装方法。 In claim 5 or claim 6,
The coating method characterized by performing the coating which forms an upper layer coating film in the state whose surface roughness Ra of the said lower layer coating film is 0.3 micrometer or less.
上記下層塗膜の粘度が１０００Ｐａ・ｓ以上である状態で上層塗膜を形成する塗装を行なうことを特徴とする塗装方法。 In any one of Claims 5 thru | or 7,
The coating method characterized by performing the coating which forms an upper layer coating film in the state whose viscosity of the said lower layer coating film is 1000 Pa.s or more.
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