【発明の詳細な説明】[Detailed description of the invention]
本発明は自動車車体に経済的に強力にして美し
い仕上り塗装を与えるための防錆塗膜を付与する
塗装方法に関する。
近時、高速道路の発達により自動車の走行速度
が増加するに伴い、走行中自車あるいは対向車が
飛散させる砂れきの衝撃による塗膜の損傷（所謂
チツピング現象）、更にはそれに加えて冬期の寒
冷地において凍結防止のため散布する岩塩などの
腐蝕性凍結防止剤に起因する腐蝕（所謂塩害）の
問題が重大になつている。
自動車車体、特に車体の下廻り部分の防錆は、
上記の如きチツピング現象および塩害による塗膜
損傷の発生などの腐蝕性環境の悪化、必要耐要年
数の増大、高速走行により更に加えられた安全性
への要求などから、ますます強く求められてきて
おり、防錆効果の向上は業界の重要問題の一つで
ある。
自動車車体の防錆対策は種々研究されてきた。
このための塗料および塗装面では粉体塗料および
粉体電着塗料が開発され、これらを用いて得られ
る塗膜は極めて強靭でしかも厚膜が得られるため
上記要求に対して極めて有効なことが認められて
いる。これらを使用する方法としては、リン酸亜
鉛などの化成処理を施した車体に、まず粉体塗装
または粉体電着塗装を施し、次いでこれを焼付
け、架橋硬化せしめてから、前記塗装で塗装され
ていない車体部分を通常のイオン性電着塗料で電
着塗装し、更にこれを焼付け、架橋硬化せしめる
方法（リバース塗装方法）がある。
この塗装方法は前段の粉体塗装面または粉体電
着塗装面と後段の電着塗装面の境界部に薄膜の境
界部を生じさせ、これが防錆力を低下させる欠点
を有していた。
かかる問題点を解決する方法として特公昭56−
2159号公報の発明がある。この発明によれば先ず
最も高度の防錆性が要求される自動車車体の下廻
り部位を粉体電着塗装しその後形成された塗膜を
架橋硬化せずに、次に通常の電着塗装を行なう方
法（ウエツトリバース塗装方法）が提案された。
かかるウエツトリバース塗装方法によれば前段の
粉体電着塗装により形成される塗膜は硬化され
ず、このため電気絶縁性がとぼしいままの状態で
後段の電着塗装を行なうため、リバース塗装方法
では境界線として明瞭に現出する粉体電着塗装に
より薄膜に塗着した部分が、逆に薄膜なるが故に
それだけ大きな導電性を有し、このため電着塗装
による塗膜が前段の粉体電着塗装による塗膜上に
塗着されるのでリバース塗装方法での境界部の防
錆力を低下させる問題は解決される。
しかしながら、上述したウエツトリバース塗装
方法でも、特公昭56−2159号公報の実施例にも見
られるように、粉体電着塗装により得られる塗膜
の厚さと、後段の電着塗装によつて得られる塗膜
の厚さには差異があり、これが塗膜段差となつて
現出する欠点を有していた。即ち、粉体電着塗膜
部と電着塗膜部の境界部に段差を生ずることは避
けられなかつた。この段差は粉体電着塗料浴の液
面に相当する。この段差は、後の上塗り塗装後の
美観を損う原因となることが判つた。
本発明者等は上記ウエツトリバース塗装方法に
おける仕上り塗装後の美観上の欠点を解決せんと
して鋭意研究した結果本発明方法を見出したので
ある。従つて本発明は上記特公昭56−2159号の防
錆塗装方法の改良にある。よつて上記特公昭56−
2159号明細書の記載はここに引用して組入れるも
のとする。例えば上記特公昭56−2159号で使用す
る粉体電着塗料およびアニオン性またはカチオン
性電着塗料およびそれらの塗装方法は本発明にお
いてもそのまま使用される。
本発明者等の研究によれば、上記ウエツトリバ
ース塗装方法における前段の粉体電着塗料を用い
て自動車車体の下廻り部位を塗装する際、自動車
車体の吃水線部位に後述する如く一定速度以上の
撹拌流を当てることにより前述した粉体電着塗膜
と電着塗膜の段差は解消し、かつ境界部の性能は
充分に維持されることを見出したのである。
即ち本発明によれば自動車車体の下廻り部位を
粉体電着塗料浴中に浸漬し、自動車車体の下廻り
部位を粉体電着防錆塗装するに際し、自動車車体
の吃水線部位に後述する如く一定速度以上の撹拌
流を当てることからなる自動車車体の防錆塗装方
法を提供する。
一般に粉体電着塗装を行なう場合塗装浴中の粉
体／バインダー樹脂の比を2.8／１としたとき、
塗装条件によつて多少の差異はあるが、一般に形
成される塗膜中の粉体／バインダー樹脂の比は
2.8／１〜４／１となり、塗膜中のバインダー樹
脂に対する粉体の割合は浴組成中の粉体の割合よ
り増加する。このため粉体電着塗膜は厚く塗着す
る。しかるに本発明に従つて吃水線部位に撹拌流
を当てると、撹拌流を受けている部位の塗膜中の
粉体／バインダーの比は小さくあることが判つ
た。この比は撹拌流量圧力、その方向により差異
はあるが、一般に0.5／１〜2.8／１となる。この
ため撹拌流を受けた部位の膜厚は粉体量の減少に
り低下し、次の電着塗膜との段差が小さくなるこ
とが判つた。ここに上記膜圧低下はあるが、塗膜
中には粉体が存在しているため粉体固有の塗膜性
能も発揮されることが判つた。
以下に本発明方法を更に詳細に説明する。
粉体電着塗膜浴は一般に浴液組成を可及的均一
に保ち、かつ消費された塗料成分を浴外で補給す
るため循環ポンプにより浴液の一部を取り出し、
塗料成分補給後これを浴中に戻し、循環させる方
法が採用されている。このため浴の自動車車体出
口方向に浴液取出口を設け、車体入口方向に循環
流を導入する導入口を設けて浴液を循環ポンプで
循環させているのが通常である。一般にこの循環
により生ずる浴液流速は0.1ｍ／秒〜0.01ｍ／秒
で比較的静かな浴の長さ方向の流れを生ずる。
かかる塗装浴において本発明によれば塗装浴両
側で浴液面、即ち自動車車体吃水線近くに複数個
の噴射ノズルを設け、上記循環流または浴液を車
体側面に向けて噴出させ、自動車車体の吃水部位
に撹拌流を当てるようにする。本発明で使用する
撹拌流は撹拌流速が自動車車体との接触点で３ｍ
以上、好ましくは５ｍ／秒以上になるようにす
る。これらの条件より小さい流速ではその段差を
充分に解消し得ないことがあつて好ましくない。
噴射ノズルの数は自動車車体の下廻り部位の粉
体電着塗装中、その吃水部位全体に前記流速で充
分な撹拌流（例えば200mm〜500mmの幅の）を作る
のに充分な数とすればよい。例えば自動車車体移
動速度0.13ｍ／秒で移動させるとき通電時間20
秒、車体長５ｍとすれば８ｍの浴中の吃水部位に
15個〜38個の噴射ノズルを設ければ充分である。
かくすると噴射ノズルによつて形成された撹拌流
のため、塗装浴中の合成樹脂粉末、顔料等の沈
澱、フロキユレーシヨン等も防止することがで
き、また塗装浴液全体を循環させるものとは別に
合成樹脂粉体の濃度分布の差異が車体吃水部位で
生ずるのを防止し、かつ急激な段差を生ぜしめ
ず、仕上り塗装の美観を損うことがなくなる。
以下実施例を示す。部および％は重量基準であ
る。
浴液の調整方法
粉体電着塗装浴液は次の如くして作つた。
水稀釈性カチオン性樹脂は、エピコート＃1001
（商標名：エポキシ樹脂、シエル社製品）488部、
ジエタノールアミン105部、イソプロピルアルコ
ール250部を80℃〜85℃で３時間還流下に反応さ
せて、液状のアミノエボキシ樹脂を得た。
また合成樹脂微粉体としてはエピコート＃1004
（シエル社製）40部、アダクトＢ−1065（フエバ
社製）30部、酸化チタンＲ−550（石原産業社
製）29部およびカーボンブラツクMA−100（三
菱化成社製）１部を粉体塗料製造の常法により、
エクストルーダーで溶融混練し衝撃式粉砕機で粉
砕し平均粒型７μのエポキシ樹脂を主体とする微
粉体を得た。
バインダーとしての前記カチオン性樹脂143部
に氷酢酸6.2部および脱イオン水500部を加え、デ
イソルバーで充分撹拌し、次いで前記微粉体の
280部を加えデイソルバーで30分間撹拌混合し、
分散させた後固形分15％になるまで脱イオン水で
稀釈した。
この溶液の特数はPH5.2Po／Bi比は2.8／１であ
つた。
カチオン電着浴は次の如くにして調整した。
エピコート＃1004 336部、エピコート＃1001
143部、エチルセロソルブ140部を混合撹拌し完全
に溶解させた。50℃に昇温し、ジエタノールアミ
ン59部、イソプロピルアルコール20部の溶液を１
時間かけで撹拌下に投入した。投入後80〜85℃に
３時間保持した。アダクトＢ−1065 202部、エチ
ルセロソルブ100部の溶液を、上記に撹拌下に30
分かけて投入し、更に１間30分、80〜85℃に保持
し、アミノエポキシイソシアネート樹脂を得た。
前記カチオン性樹脂を用いて電着塗料製造の常
法により中和剤として酢酸、顔料として酸化チタ
ンおよびカーボンブラツクを使用して製造し純水
で所定濃度まで稀釈してカチオン性電着浴を得
た。その浴液の特数はPH5.4、灰分25％、中和度
75％、加熱残分13％であつた。
実施例 １
粉体電着塗料浴を自動車車体のドアの下辺から
30cmまで浸漬するよう建浴した。浴液量は60tで
あつた。通常の浴液循環は4t／分にあるよう循環
ポンプを設置して行なつた。
更に本発明による吃水線部位での撹拌流を作る
ため、別のポンプにてノズル噴射を行なつて、浴
全域の表面、即ち自動車車体の吃水部位に、自動
車車体の接触点で５ｍ／秒の流速の表面撹拌流を
作つた。ノズル口と車体との距離劣は40cmであ
り、各ノズルの口径２cm2で浴の両側に80個を等間
隔で設置した。ノズル口の液深は10cmとした。
塗装に供する自動車車体は予めリン酸亜鉛化成
処理を施した後、純水で充分清浄になるよう水洗
し、150℃で水切り乾燥を行なつた。
この車体のドアの下辺より30cm上部まで浸漬す
るよう車体の下廻り部分を粉体電着塗装浴に浸漬
した後車体を陰極として直流を通電せしめて粉体
電着塗装を行なつた。
粉体電着条件は、電圧400V、通電時時間40
秒、浴液温度27℃、極間距離（最小）40cm、極比
は車体外板浸漬部分面積と対極の比で約１／１の
面積比であつた。
車体を浴より引き上げた後充分水洗を行なつて
からカチオン性電着塗装浴に全没し、電着塗装し
た。電着条件は電圧250V、通電時間（通電開始
より出槽まで）210秒、浴液温度28℃、極間距離
（最小）45cm、極比は外板面に対して対極が２倍
であつた。出槽後充分水洗を行なつてから80〜
100℃で水切り乾190℃で20分焼付けて架橋硬化さ
せた。
比較例 １
実施例１において、車体吃水部位、即ち浴液表
面でのノズルによる撹拌流を施さずに、他は実施
例１と同じ条件で車体下廻り部位を粉体電着塗装
した。
実施例１および比較例１で得た車体は常法によ
り外板部のみ中塗り後上塗りを施し、試験に供し
た。試験結果を対比させまとめると第１表のとお
りであつた。
The present invention relates to a coating method for applying a rust-preventing coating to an automobile body to provide an economically strong and beautiful finish. In recent years, as the speed of automobiles has increased due to the development of expressways, paint films have been damaged by the impact of debris thrown by the own vehicle or oncoming vehicles while driving (the so-called chipping phenomenon), and in addition to this, the cold weather in winter has increased. The problem of corrosion (so-called salt damage) caused by corrosive antifreeze agents such as rock salt that are sprayed on land to prevent freezing has become serious. Rust prevention for automobile bodies, especially the lower part of the car body,
Due to the deterioration of the corrosive environment such as the above-mentioned chipping phenomenon and the occurrence of paint film damage due to salt damage, the increase in required service life, and the increased safety requirements due to high-speed driving, there is an increasing demand for Therefore, improving the rust prevention effect is one of the important issues in the industry. Various rust prevention measures for automobile bodies have been studied.
Powder coatings and powder electrodeposition coatings have been developed for paints and painted surfaces for this purpose, and the coatings obtained using these are extremely tough and thick, making them extremely effective in meeting the above requirements. It recognized. The method for using these is to first apply powder coating or powder electrodeposition coating to a car body that has been subjected to a chemical conversion treatment such as zinc phosphate, then bake this to crosslink and harden it, and then apply the coating. There is a method (reverse painting method) in which parts of the car body that are not coated are electrodeposited with a normal ionic electrodeposition paint, and then this is baked to crosslink and harden. This coating method has the disadvantage that a thin film boundary is formed at the boundary between the first powder-coated surface or the powder electrodeposition-coated surface and the second-stage electrodeposition coated surface, which reduces the rust-preventing ability. As a way to solve such problems,
There is an invention in Publication No. 2159. According to this invention, the lower part of the automobile body where the highest degree of rust prevention is required is first coated with powder electrodeposition, then the formed coating film is not cross-linked and cured, and then regular electrodeposition is applied. A method (wet reverse painting method) was proposed.
According to such a wet reverse coating method, the coating film formed by the powder electrodeposition coating in the first stage is not cured, and therefore the second stage electrodeposition coating is performed while the electrical insulation is still poor. In contrast, the area coated with a thin film using powder electrodeposition coating, which clearly appears as a boundary line, has a high conductivity because it is a thin film. Since it is applied onto a coating film formed by electrodeposition, the problem of reducing the antirust ability at the boundary in the reverse coating method is solved. However, even with the above-mentioned wet reverse coating method, as seen in the examples of Japanese Patent Publication No. 56-2159, the thickness of the coating film obtained by powder electrodeposition coating and the subsequent electrodeposition coating There is a difference in the thickness of the resulting coating film, which has the disadvantage of appearing as a step difference in the coating film. That is, it was unavoidable that a step would be formed at the boundary between the powder electrodeposition coating part and the electrodeposition coating part. This level difference corresponds to the liquid level of the powder electrodeposition paint bath. It was found that this difference in level caused the appearance to deteriorate after the top coat was applied. The inventors of the present invention discovered the method of the present invention as a result of intensive research aimed at solving the aesthetic defects of the above-mentioned wet reverse coating method after finishing. Therefore, the present invention is an improvement of the rust-preventing coating method disclosed in Japanese Patent Publication No. 56-2159. Therefore, the above-mentioned special public service 1976-
The description of specification No. 2159 is hereby incorporated by reference. For example, the powder electrodeposition paints, anionic or cationic electrodeposition paints, and their coating methods used in the above-mentioned Japanese Patent Publication No. 56-2159 can be used as they are in the present invention. According to the research of the present inventors, when painting the lower part of an automobile body using the powder electrodeposition paint in the first stage of the wet reverse painting method, the water line area of the automobile body is painted at a speed higher than a certain level as described below. It was discovered that by applying a stirring flow of , the above-mentioned difference in level between the powder electrodeposition coating film and the electrodeposition coating film was eliminated, and the performance of the boundary area was sufficiently maintained. That is, according to the present invention, when the lower part of an automobile body is immersed in a powder electrodeposition paint bath and the lower part of the automobile body is coated with a powder electrodeposited anti-rust coating, a certain amount of water is applied to the water line area of the automobile body as described below. To provide a method for anti-corrosion coating of an automobile body, which comprises applying an agitation flow at a speed higher than that of the vehicle body. Generally, when performing powder electrodeposition coating, when the ratio of powder/binder resin in the coating bath is 2.8/1,
Although there are some differences depending on the coating conditions, the powder/binder resin ratio in the coating film that is generally formed is
The ratio is 2.8/1 to 4/1, and the ratio of powder to binder resin in the coating film is higher than the ratio of powder in the bath composition. For this reason, the powder electrodeposition coating is applied thickly. However, it has been found that when a stirring flow is applied to the water line region according to the present invention, the powder/binder ratio in the coating film at the region receiving the stirring flow is small. Although this ratio varies depending on the stirring flow pressure and its direction, it is generally 0.5/1 to 2.8/1. For this reason, it was found that the film thickness at the area that received the stirring flow decreased due to the decrease in the amount of powder, and the difference in level from the next electrodeposited coating became smaller. It has been found that although there is the above-mentioned reduction in film pressure, since powder is present in the coating film, the coating film performance inherent to powder is also exhibited. The method of the present invention will be explained in more detail below. In powder electrodeposition coating baths, a part of the bath liquid is generally removed using a circulation pump in order to keep the bath liquid composition as uniform as possible and to replenish the consumed paint components outside the bath.
After replenishing the paint components, a method is adopted in which they are returned to the bath and circulated. For this reason, it is common practice to provide a bath liquid outlet in the direction of the outlet of the automobile body, and to provide an inlet for introducing a circulation flow in the direction of the inlet of the car body, so that the bath liquid is circulated by a circulation pump. Typically, this circulation results in a bath liquid flow rate of 0.1 m/sec to 0.01 m/sec, resulting in relatively quiet longitudinal flow of the bath. According to the present invention, in such a coating bath, a plurality of injection nozzles are provided on both sides of the coating bath near the bath liquid level, that is, near the water line of the automobile body, and the circulating flow or the bath liquid is ejected toward the side surface of the automobile body. Apply agitation current to the area of hiccups. The stirring flow used in the present invention has a stirring flow velocity of 3 m at the point of contact with the automobile body.
The speed is preferably set to 5 m/sec or more. A flow rate lower than these conditions is not preferable because it may not be possible to sufficiently eliminate the difference in level. The number of injection nozzles may be a sufficient number to create a sufficient agitation flow (e.g., 200 mm to 500 mm wide) at the flow rate throughout the wet area during powder electrodeposition coating of the underside of an automobile body. . For example, when moving a car body at a speed of 0.13 m/sec, the energization time is 20
Second, if the car body length is 5m, it will be a stifling area in a bath of 8m.
It is sufficient to provide between 15 and 38 injection nozzles.
In this way, because of the agitation flow formed by the injection nozzle, precipitation and flocculation of synthetic resin powder, pigments, etc. in the coating bath can be prevented, and the entire coating bath liquid can be circulated. Apart from this, it also prevents differences in the concentration distribution of the synthetic resin powder from occurring in wet areas of the car body, and also prevents sudden steps from occurring and impairing the aesthetic appearance of the finished coating. Examples are shown below. Parts and percentages are by weight. Method for preparing bath solution The powder electrodeposition coating bath solution was prepared as follows. Water-dilutable cationic resin is Epicote #1001
(Trade name: epoxy resin, Ciel product) 488 parts,
105 parts of diethanolamine and 250 parts of isopropyl alcohol were reacted under reflux at 80°C to 85°C for 3 hours to obtain a liquid aminoepoxy resin. Also, as a synthetic resin fine powder, Epicoat #1004
(manufactured by Ciel Corporation) 40 parts, Adduct B-1065 (manufactured by Hueva Corporation) 30 parts, titanium oxide R-550 (manufactured by Ishihara Sangyo Co., Ltd.) 29 parts, and Carbon Black MA-100 (manufactured by Mitsubishi Kasei Corporation) 1 part as powder. By the conventional method of paint manufacturing,
The mixture was melt-kneaded with an extruder and pulverized with an impact pulverizer to obtain a fine powder mainly composed of epoxy resin with an average particle size of 7 μm. Add 6.2 parts of glacial acetic acid and 500 parts of deionized water to 143 parts of the cationic resin as a binder, stir thoroughly with a desolver, and then dissolve the fine powder.
Add 280 parts and stir and mix for 30 minutes using a desolver.
After dispersion, it was diluted with deionized water to a solid content of 15%. The special feature of this solution was PH5.2.Po/Bi ratio was 2.8/1. The cationic electrodeposition bath was prepared as follows. Epicote #1004 336 copies, Epicote #1001
143 parts of ethyl cellosolve and 140 parts of ethyl cellosolve were mixed and stirred to completely dissolve. Raise the temperature to 50℃ and add 1 part of a solution of 59 parts of diethanolamine and 20 parts of isopropyl alcohol.
The mixture was added to the mixture over a period of time with stirring. After charging, the temperature was maintained at 80-85°C for 3 hours. A solution of 202 parts of Adduct B-1065 and 100 parts of ethyl cellosolve was added to the above while stirring for 30 minutes.
The mixture was added over a period of several minutes, and maintained at 80 to 85°C for an additional 1 to 30 minutes to obtain an aminoepoxy isocyanate resin. A cationic electrodeposition bath was obtained by using the above cationic resin and using acetic acid as a neutralizing agent and titanium oxide and carbon black as pigments by a conventional method for producing electrodeposition paints, and diluting it with pure water to a predetermined concentration. Ta. The special characteristics of the bath liquid are PH5.4, ash content 25%, and degree of neutralization.
75%, and the heating residue was 13%. Example 1 Powder electrodeposition paint bath is applied from the bottom of the door of an automobile body.
The bath was constructed so that the water could be immersed up to 30 cm. The amount of bath liquid was 60 tons. A circulation pump was installed to circulate the bath liquid at a rate of 4 t/min. Furthermore, in order to create an agitation flow at the water line area according to the present invention, a nozzle injection is performed using another pump to spray the entire surface of the bath, that is, the water stutter area of the car body, at a rate of 5 m/sec at the contact point of the car body. A surface agitation flow with a flow rate was created. The distance between the nozzle opening and the vehicle body was 40 cm, and each nozzle had a diameter of 2 cm 2 and 80 nozzles were installed at equal intervals on both sides of the bath. The liquid depth at the nozzle mouth was 10 cm. The car body to be painted was previously subjected to zinc phosphate chemical conversion treatment, washed with pure water until sufficiently clean, and drained and dried at 150°C. The lower part of the car body was immersed in a powder electrodeposition coating bath to a depth of 30 cm above the bottom edge of the door, and then a direct current was applied using the car body as a cathode to perform powder electrodeposition coating. Powder electrodeposition conditions are voltage 400V, time 40 when energized.
The temperature of the bath liquid was 27°C, the distance between the poles (minimum) was 40 cm, and the pole ratio was approximately 1/1 in terms of the area of the immersed part of the outer panel of the car body and the counter pole. After the car body was lifted from the bath, it was thoroughly rinsed with water, and then completely immersed in a cationic electrodeposition coating bath to perform electrodeposition coating. The electrodeposition conditions were: voltage 250V, current application time (from the start of current application to removal from the tank) 210 seconds, bath temperature 28℃, distance between electrodes (minimum) 45cm, and electrode ratio: the opposite electrode was twice that of the outer plate surface. . After taking out the tank, wash it thoroughly with water, and then
It was drained and dried at 100°C and baked at 190°C for 20 minutes to cure crosslinking. Comparative Example 1 In Example 1, the lower part of the car body was subjected to powder electrodeposition coating under the same conditions as in Example 1, except that no agitation flow was applied to the wet area of the car body, that is, the surface of the bath liquid, using a nozzle. The vehicle bodies obtained in Example 1 and Comparative Example 1 were subjected to a test by applying an intermediate coat and then a top coat to only the outer panel parts by a conventional method. The test results are compared and summarized as shown in Table 1.
【表】【table】
【表】【table】