JP4171226B2 - Flash-off device for water-based painting - Google Patents

Description

【００４２】
実験１−１
表１に示す条件で、上段の乾燥用ノズル（以下、単に上段ノズルともいう。）２１１、乾燥用中段スリット（以下、単に中段スリットともいう）２１２および乾燥用下段スリット（以下、単に下段スリットともいう）２１３をそれぞれ組み合わせ、図４に示す車体各部位における面風速を設定した結果を、図５および図６に示す。図５には、上段ノズル２１１と下段スリット２１２とを組み合わせたテスト２、下段スリット２１３のみのテスト４及び上段ノズル２１１のみのテスト５の結果を示し、図６には、上段ノズル２１１と下段スリット２１３とを組み合わせたテスト２及び全て２１１，２１２，２１３を組み合わせたテスト３の結果を示す。
【００４３】
図５の結果から、上段ノズル２１１のみ（テスト５，◆印）又は下段スリット２１３のみ（テスト４，×印）に比較して、テスト２（△印）、すなわち上段ノズル２１１と下段スリット２１３を組み合わせた条件の場合の方が、車体各部位における平均面風速が１．５ｍ／ｓ以上と大きくかつ均一となり、車体全体として速く乾燥することが理解される。
【００４４】
また図６の結果から、上段ノズル２１１、中段スリット２１２および下段スリット２１３を用いた場合（テスト３，■印）には、車体の外板部位の一部において面風速が大きい値が得られるが、車体内板部位には効果は認められないことが理解される。したがって、同図の上段ノズル２１１と下段スリット２１３とを組み合わせた条件（テスト２，▲）の場合と大きな差はなく、中段スリット２１２は必要に応じて省略できる。
【００４５】
実験１−２
上記実験１−１によって、上段ノズル２１１と下段スリット２１３との組み合わせが平均面風速の点から好ましいことが確認されたが、次に、この上段ノズル２１１と下段スリットを組み合わせた条件において、下段スリット２１３の幅とピッチとの最適条件を求めるために、これら幅とピッチとを変化させた場合の車体各部位における面風速を比較した。
【００４６】
ここで比較した下段スリット２１３としては、表１に示すように、テスト１が１５ｍｍ×２４０ｍｍのスリット開口でピッチを３３３ｍｍ、テスト７が７．５ｍｍ×２４０ｍｍのスリット開口でピッチを１６７ｍｍ、テスト８が２２．５ｍｍ×２４０ｍｍのスリット開口でピッチを５００ｍｍとした。これらテスト１，７，８の面風速の測定結果を図７に示す。同図において、テスト１を×印、テスト７を◆印、テスト８を●印で示す。
【００４７】
この図７に示す結果から、テスト１（×印）の下段スリット２１３の寸法、すなわちスリット開口が１５ｍｍ×２４０ｍｍ、ピッチが３３３ｍｍの場合が、車体各部位における平均面風速が最も大きくかつ内外板毎の平均面風速が均一となり、車体全体として速く乾燥することが理解される。
【００４８】
実験１−３
上記実験１−１及び１−２によって、上段ノズル２１１と下段スリット２１３を組み合わせたものであって、下段スリット２１３の開口が１５ｍｍ×２４０ｍｍでピッチが３３３ｍｍの条件が、平均面風速の点から好ましいことが確認されたが、次に、この条件において車体までの距離の最適条件を求めるために、下段スリット２１３から車体までの距離Ｌのみを２５０ｍｍ、３００ｍｍ、３５０ｍｍの３種類に変化させたときの、車体各部位における面風速を比較した。
【００４９】
ここで比較した下段スリット２１３として、テスト１が車体との距離を３００ｍｍ、テスト９が車体との距離を２５０ｍｍ、テスト１０が車体との距離を３５０ｍｍとしたものである。これらテスト１，９，１０の面風速の測定結果を図８に示す。同図において、テスト１を×印、テスト９を▲印、テスト１０を△印で示す。
【００５０】
図８に示す結果から、テスト１の下段スリット２１３と車体との距離が３００ｍｍの場合が、車体各部位における平均面風速が最も大きく、車体全体として速く乾燥することが理解される。
【００５１】
実験１−４
上記実験１−１乃至１−３によって、上段ノズル２１１と下段スリット２１３とを組み合わせた所定条件の場合が平均面風速の点から好ましいことが確認されたが、さらに、上段ノズル２１１と下段スリット２１３からそれぞれ吹き出される風量バランスの最適条件を求めるために、上段ノズル２１１及び下段スリット２１３の風量を変化させた場合における、車体各部位における面風速を比較した。
【００５２】
ここで、テスト１では上段ノズル２１１と下段スリット２１３の風量比を１：１、テストＡでは２：１の条件とした。これらテスト１及びＡの面風速の測定結果を図９に示す。同図において、テスト１を●印、テストＡを▲印で示す。
【００５３】
図９に示す結果から、テストＡの風量バランスでは、車体各部位における平均面風速のばらつきが大きいが、テスト１のように上段ノズル２１１と下段スリット２１３との吹き出し風量比を１：１とした場合は、車体各部位における平均面風速は均一となり、車体各部位での乾燥速度に差がなく良好となることが理解される。
【００５４】
（２）熱風循環装置による塗着固形分の測定
上記のフラッシュオフ装置を用いて、上述のテスト７の条件にて、車体の各部位におけるフラッシュオフ前後の水系ベース塗料の塗着固形分を測定した。
【００５５】
なお、実験条件として、コンベア速度を１．６ｍ／ｍｉｎとし、水系ベース塗料を内板部については手吹き、外板部についてはロボット塗装とし、水系ベース塗料を塗装してからフラッシュオフ終了までの時間を３４〜４１分とし、フラッシュオフ工程は静置室による自然冷却とした。水系ベース塗装の塗着固形分の測定は、アルミ箔を車体各部位に張り付けてこれに塗装し、フラッシュオフ前後での重量変化を測定した。
【００５６】
実施例１
アルミ箔を車体の８部位（前述１０部位中、フード端裏部とトランクヒンジ部を除く）に張り付け、内板部は手吹き、外板部はロボットにて水系ベース塗料を塗装した。次いで、コンベア速度１．６ｍ／ｍｉｎにて車体を移動させながら、本発明に係る熱風循環装置２１に入れて、水系ベース塗装の仮乾燥を行った。尚、熱風循環装置内の温度は５０℃、湿度は９．５ｇ／ｋｇとし、フラッシュオフ時間は３分間（熱風循環装置内通過時間）、水系ベース塗料を塗装してからフラッシュオフを終了するまでの時間は３５分間とした。
【００５７】
このとき、熱風循環装装置に入る直前に車体各部に張り付けたアルミ箔のうちの１枚を取り外して固形分を測定するとともに、熱風循環装置を出た直後に車体各部に張り付けた残りのアルミ箔を取り外して固形分を測定した。熱風循環装置の前後における塗着固形分（重量％）の測定結果を表２に示す。
【００５８】
表２に示すように、実施例１では、熱風循環装置に入る直前の水系ベース塗装の塗着固形分は、外板水平部で４４．１％、外板垂直部で５１．４％、内板については５３．１％であるのに対し、フラッシュオフ終了後の固形分は、前述の車体８部位について、７８．９〜８５．２％となり、全ての部位が７０％以上であった。
【００５９】
実施例２
実施例１において、熱風循環装置の湿度を１９．５ｇ／ｋｇ、水系ベース塗料を塗装してからフラッシュオフを終了するまでの時間を４１分間とした以外は、実施例１と同じ条件にして、熱風循環装置の前後における水系ベース塗装の塗着固形分を測定した。この結果を表２に示す。
【００６０】
表２に示すように、本実施例２では、熱風循環装置に入る直前の水系ベース塗装の固形分は、外板水平部で４６．４％、外板垂直部で４０．８％、また内板については５４．８％であるのに対し、フラッシュオフ終了後の固形分は、車体８部位について、７２．６〜８５．９％と、全ての部位が７０％であった。
【００６１】
実施例３
実施例１において、熱風循環装置内の温度を４０℃、フラッシュオフ時間を４．８分間（通過時間）、水系ベース塗料を塗装してからフラッシュオフを終了するまでの時間を３４分間とした以外は、実施例１と同じ条件にして、熱風循環装置の前後における水系ベース塗装の塗着固形分を測定した。この結果を表２に示す。
【００６２】
表２に示すように、実施例３では、熱風循環装置に入る直前の水系ベース塗装の固形分は、外板水平部で３８．６％、外板垂直部で３４．７％、また内板については４５．０％であるのに対し、フラッシュオフ終了後の固形分は、車体８部位について、８１．９〜８４．８％と、全ての部位が７０％以上であった。
【００６３】
比較例
実施例１において、熱風循環装置内の温度を７０℃、フラッシュオフ時間を２分間（通過時間）、水系ベース塗料を塗装してからフラッシュオフを終了するまでの時間を３７分間とした以外は実施例１と同じ条件にして、熱風循環装置の前後における水系ベース塗装の塗着固形分を測定した。この結果を表２に示す。
【００６４】
表２に示すように、この比較例では、熱風循環装置に入る直前の水系ベース塗装の固形分は、外板水平部で５１．８％、外板垂直部で３８．９％、また内板については５４．２％であり、上記実施例１〜３とほとんど同様であったのに対し、フラッシュオフ終了後の固形分は、車体８部位の中で、バックピラーヒンジ部が６３．４％、バックピラー下端部が６７．５％と、７０％以下の部位が２カ所もあった。
【００６５】
参考例１
実施例１において、水系ベース塗料を塗装してからフラッシュオフを終了するまでの時間を６５分とした以外は実施例１と同じ条件にして、熱風循環装置の前後における水系ベース塗装の塗着固形分を測定した。この結果を表２に示す。
【００６６】
表２に示すように、参考例１では、熱風循環装置に入る直前の水系ベース塗装の固形分は、外板水平部で４８．４％、外板垂直部で５０％、また内板については８５．３％であるのに対し、フラッシュオフ終了後の固形分は、車体８部位について８０．４〜８６．７％と、全ての部位で８０％以上であった。
【００６７】
参考例２
実施例１において、熱風循環装置内の温度を６０℃、フラッシュオフ時間を２．５分間（熱風循環装置内通過時間）、水系ベース塗料を塗装してからフラッシュオフを終了するまでの時間を５５分とした以外は実施例１と同じ条件にして、熱風循環装置の前後における水系ベース塗装の塗着固形分を測定した。この結果を表２に示す。
【００６８】
表２に示すように、参考例２では、熱風循環装置に入る直前の水系ベース塗装の固形分は、外板水平部で４４．５％、外板垂直部で４６．４％、また内板については８３％であるのに対し、フラッシュオフ終了後の固形分は、車体８部位について８３．９〜８７．９％と、全ての部位で８０％以上であった。
【００６９】
【表２】

【００７０】
以上の結果から、本発明においてはフラッシュオフ工程を出た後、クリヤー塗装が施される直前の車体の内外板に塗装された水系ベースの固形分が７０％以上あれば、完成塗膜としての品質に問題がないことが確認されている。
【００７１】
また、フラッシュオフ工程の熱風循環装置内の温度については４０〜５０℃、フラッシュオフ時間（熱風循環装置内通過時間）については３〜５分間が好ましいことが確認された。
【００７２】
ちなみに、３〜５分間でフラッシュオフ処理を行う場合、温度を高くすることによっても水系ベース塗装の固形分を７０％以上とすることができるが、車体温度が高温となるためクーリング装置による冷却が必要となり、エネルギー消費の観点からは好ましくない。また、温度を高くしてフラッシュオフ時間を３分間より短くすると、比較例１に見られるように、車体の一部において水系ベース塗装の固形分が７０％以下の部位が出てしまうため、好ましくない。
【００７３】
なお、参考例１および２に示したように、実施例１乃至３に比べて水系ベース塗装からフラッシュオフまでを１．５倍以上の時間をかけて処理する場合には、車両の各部位の全てにおいて水系ベース塗装の固形分が８０％以上となり塗膜品質上全く問題はないが、生産性を考慮すると実用的ではない。
【００７４】
実ライン検証結果
表３に実ラインにおける検証結果を示す。この検証は、コンベアスピード４．６ｍ／ｍｉｎ、ブース内温度２３℃、熱風循環装置パスタイム３分、クーリング装置パスタイム０．６４分の条件で行った。同表に示す検証実験Ｎｏ．５およびＮｏ．６（従来のフラッシュオフ装置の湿度状態２０ｇ／ｋｇと、それより７ｇ／ｋｇ低い１３ｇ／ｋｇ）の結果より、内板部において顕著に固形分ＮＶの上がり方が向上していることが解った。
【００７５】
【表３】

【００７６】
なお、以上説明した実施形態は、本発明の理解を容易にするために記載されたものであって、本発明を限定するために記載されたものではない。したがって、上記の実施形態に開示された各要素は、本発明の技術的範囲に属する全ての設計変更や均等物をも含む趣旨である。
【図面の簡単な説明】
【図１】本発明に係るフラッシュオフ装置の実施形態と、比較例としての従来のフラッシュオフ装置とを示す平面図である。
【図２】本発明に係る熱風循環装置の実施形態を示す断面図である。
【図３】本発明に係る熱風循環装置の実施形態を示す側面図である。
【図４】本発明の実施例において風速測定の部位を示す平面図及び側面図である。
【図５】本発明の実施例における風速測定の結果（その１）を示すグラフである。
【図６】本発明の実施例における風速測定の結果（その２）を示すグラフである。
【図７】本発明の実施例における風速測定の結果（その３）を示すグラフである。
【図８】本発明の実施例における風速測定の結果（その４）を示すグラフである。
【図９】本発明の実施例における風速測定の結果（その５）を示すグラフである。
【符号の説明】
１…水系塗料塗装工程
２…フラッシュオフ工程
２１…熱風循環装置
２１１…乾燥用ノズル（熱風噴出口）
２１２…乾燥用中段スリット（熱風噴出口）
２１３…乾燥用下段スリット（熱風噴出口）
２２…静置室
３…クリヤー塗料塗装工程[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flash-off device used as a water-based base paint temporary drying device in a wet-on-wet coating system of a water-based paint, particularly a water-based base paint and a clear paint applied thereon. More specifically, the present invention relates to a flash-off device that can reduce the temperature rising energy and the cooling energy of an object to be coated by shortening the length of the flash-off zone as compared with the conventional case.
[0002]
[Prior art]
Conventionally, a clear paint is applied wet-on-wet on an aqueous base paint, and for that purpose, a so-called flash-off device is used to temporarily dry the aqueous paint before performing the clear paint. Yes.
[0003]
As shown in the lower diagram of FIG. 1, a conventionally used flash-off device 200 is provided following the stationary chamber 11 after the aqueous base coating, and an IR device 201 that dries the paint with an infrared electric heater, The apparatus includes a hot air circulation device 202 that dries the paint by hot air blow, a cooling device 203 that cools the vehicle body with cold air, and a stationary chamber 204. Then, after the vehicle body to which the water-based base coating is applied passes through the stationary chamber 11, the vehicle body outer plate is heated by an infrared electric heater disposed so as to face the outer periphery of the vehicle body cross section. Subsequently, hot air of about 80 ° C. is blown out toward the outer plate of the vehicle body from a plurality of hot air blow nozzles arranged so as to face the outer periphery of the cross section of the vehicle body, thereby heating the inner and outer plates of the vehicle body. The humidity in the hot air circulation device at this time is about 14.5 to 24.5 g / kg (water content in 1 kg of dry air).
[0004]
The entire vehicle body is heated and dried by heat transfer from the IR device 201 and the hot air circulation device 202, and the temperature is raised to about 90 ° C. at the vehicle body outer plate portion and to about 70 ° C. at the vehicle body inner plate portion. Thereafter, the vehicle body is cooled to about 30 ° C. or less by the cooling device 203, and the clear paint is applied when the applied solid content of the aqueous base paint that does not affect the coating film quality becomes 70% or more. In the conventional flash-off zone, for example, when the conveyor speed of the vehicle body is 4.5 to 5.0 m / min, the processing time by the IR device 201 for heating the vehicle body outer plate is about 1 minute, and the vehicle body inner plate is also heated. The processing time by the hot air circulation device 202 is about 2 minutes, and the processing time by the cooling device 203 is about 2 minutes. Therefore, the processing time of about 5 minutes is required in the entire flash-off zone.
[0005]
[Problems to be solved by the invention]
As described above, in the conventional flash-off device 200 described above, in order to establish a wet-on-wet coating system of the water-based base coating and the clear coating, the vehicle is first used as a temporary drying device after the water-based base coating is applied. An IR device 201 (far-infrared electric heater) is used for heating the outer plate, a hot air circulation device 202 is then used for the inner plate of the vehicle body, and a cooling device 203 is used to cool the heated vehicle body. It was.
[0006]
Particularly, since the far-infrared electric heater 201 and the hot air blowing nozzle of the hot air circulation device 202 are used to raise the temperature of the vehicle body, the temperature of the inner and outer plates of the vehicle body becomes high and the cooling device 203 needs to be cooled for a long time. . Further, the temperature rise by the body part is performed in different zones, such as using an IR device (far infrared electric heater) for raising the temperature of the outer plate of the vehicle body and using a hot air circulation device 202 for raising the temperature of the inner plate of the vehicle body. Therefore, there is a problem that the entire flash-off device 200 is long and a long processing time is required.
[0007]
Further, in the conventional processes such as the IR device 201, the hot air circulation device 202, and the cooling device 203, the temperature of the vehicle body does not affect the coating film quality when the next clear coating is performed after the entire vehicle body is heated and temporarily dried. There is a problem that the energy cost becomes high because it is necessary to cool to the bottom.
[0008]
For this reason, the length of the flash-off zone is shortened compared to the conventional case, the energy cost for carrying out temporary drying in water-based paint is reduced, and a wet-on-wet paint system with a clear paint is established to form a coating film. Ensuring appearance quality has been a challenge.
[0009]
The present invention has been made in view of such a conventional problem, and in a flash-off device used when performing wet-on-wet coating of a water-based paint and a clear paint applied thereon, In order to shorten the length and accelerate the drying of the inner and outer panels at the same time in a short time, the arrangement of hot air outlets for each part of the body is optimized with nozzles and slits, and the overall energy cost of temporary drying is reduced. The purpose is to do.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned problems, the present inventors have used only the hot air outlet provided in the hot air circulation device to paint the inner plate portion of the vehicle body while suppressing the temperature rise of the outer plate portion. In order to accelerate the drying of the water-based paint, the arrangement of hot air outlets (nozzles or slits) for each part is optimized, the temperature, humidity and processing time in the processing equipment are specified, At the same time, it has been found that by maximizing the moisture drying capacity in the paint throughout the entire body, the length of the flash-off zone can be shortened and processing can be performed for a short time. In the case of existing equipment), it was possible to reduce the temperature of hot air, and when it was the same as the conventional hot air temperature corresponding to the area at the time of new installation, it was found that the process length could be shortened and the present invention was achieved.
[0011]
For this purpose, a plurality of hot air blowing nozzles for drying the inner plate of the vehicle body are arranged at the upper position of the hot air circulation device, and a plurality of hot air blowing slits for drying the outer plate of the vehicle body are arranged at the lower position and / or middle position of the hot air circulation device. When the hot air is blown out to each part of the vehicle body, the wind speed is high, and the variation in the wind speed in each part of the vehicle body is reduced.As a result, the flash-off process or the hot air temperature can be reduced in a short time. It was confirmed that it was possible.
[0012]
That is, the flash-off device for water-based coating of the present inventionThe waterIn a flash-off device provided between a water-based paint coating process for coating a water-based paint and a clear paint coating process for applying a clear paint wet-on-wet on the water-based paint film, the coating on which the water-based paint has been applied. A hot air circulation device having a hot air outlet for blowing hot air on the coating is provided.The hot air outlet of the hot air circulation device is a plurality of drying nozzles and slits that simultaneously blow hot air against the object coated with the water-based paint that passes through the hot air circulation device, and the hot air circulation device The plurality of drying nozzles are provided at the upper position of the hot air circulation device facing the left and right window openings of the vehicle, which is the object to be coated, and from the left and right window openings to the inner plate of the vehicle body when the vehicle passes. Hot air is blown toward the inside of the vehicle to generate a convection circulation airflow, and the plurality of drying slits of the hot air circulation device are located at the lower position of the hot air circulation device opposite to the left and right lower surfaces of the vehicle being coated. When the vehicle passes, hot air is blown toward the outer plates on the left and right lower surfaces of the vehicle to generate an ascending airflow along the outer surface of the vehicleIt is characterized by that.
[0014]
Moreover, the flash-off device for water-based coating according to the present invention has a plurality of drying slits of the hot air circulation device as described in claim 2.A drying slit is provided at the middle position of the hot air circulation device facing the left and right side surfaces of the vehicle being coated, and blows hot air toward the outer plates on the left and right side surfaces of the vehicle when the vehicle passes.It is characterized by that.
[0016]
Furthermore, the flash-off device for water-based paint of the present invention isClaim 3As described, the time for the coated material to pass through the hot air circulation device is 3 to 5 minutes, the temperature in the hot air circulation device is 50 to 60 ° C., and the humidity in the hot air circulation device is 9.5 to 19 0.5 g / kg (water content in 1 kg of dry air).
[0017]
Moreover, the flash-off device for water-based paint of the present invention isClaim 4As described, the temperature of the inner plate and the outer plate of the article to be coated immediately before being put into the clear paint coating process is 30 ° C. or less.
[0018]
Furthermore, the flash-off device for water-based paint of the present invention isClaim 5As described, the coating solid content of the coating film immediately before being put into the clear paint coating process is 70% or more. Moreover, the flash-off device for water-based paint of the present invention isClaim 6As described, a cooling device is further provided between the hot air circulation device and the clear paint coating process.
[0019]
[Action]
Hereinafter, the present invention will be described in more detail.
The first object of the present invention is to shorten the length of the flash-off zone and promote drying in a short time in a flash-off device for establishing a wet-on-wet coating system of water-based coating and clear coating. Or, it is to reduce the energy cost of the entire temporary drying by lowering the temperature of the hot air.
[0020]
In the conventional flash-off device, in order to dry the vehicle body, the outer plate and the inner plate of the vehicle body are dried at a high temperature in different zones by using different devices. Therefore, since the whole vehicle body is heated at a high temperature for a long time, it is essential to use a powerful cooling device. On the other hand, in the present invention, the vehicle body outer plate and the inner plate are simultaneously dried using only the hot air outlet provided in the hot air circulation device. Specifically, a hot air blowing nozzle mainly for drying the inner plate of the vehicle body is used at the upper position of the hot air circulation device, and a plurality of hot air blowing slits for mainly drying the outer plate of the vehicle body are further provided at the lower position and / or middle position of the hot air circulation device. Is provided.
[0021]
The hot air from the hot air blowing nozzle arranged at the upper position generates an air flow inside the vehicle body, and this air flow is convectively circulated so that it can be processed at a lower temperature and / or dried in a shorter time than before. Become.
[0022]
Further, since hot air from the hot air blowing slit arranged at the lower position generates an updraft along the outer surface of the vehicle body, it can be similarly processed at low temperature and / or dried in a short time.
[0023]
Thus, by blowing hot air at the same time using the nozzle at the upper position of the present invention and the slit at the lower position and / or the middle position, variation in the wind speed at each part in the vehicle body is reduced, and the inner plate portion Since the wind speed of the is increased, drying in a short time becomes possible.
[0024]
By the way, the conventional flash-off device is 80m at a high temperature of 80-90 ° C.³In contrast to the provisional drying process with a large air volume of / min level, the flash-off device of the present invention is 40 m at 50 to 60 ° C.³Since the drying process can be performed with a small air volume of / min level and the temperature of the vehicle body can be significantly reduced as compared with the conventional one, it is not always necessary to install a cooling device exclusively.
[0025]
In the flash-off device of the present invention, although not particularly limited, the temperature in the hot air circulation device is 50 to 60 ° C., and the humidity is 9.5 to 19 g reduced from the conventional flash-off device by 5 to 10 g / kg. 5 g / kg is preferred. Under these conditions, the passage time of the hot air circulation device is preferably about 3 minutes. If the temperature or humidity in the hot air circulation device is out of this range, the flash-off process takes time, the solid content of the water-based paint film just before clear coating does not reach 70%, or the body temperature It may become too high and adversely affect the quality of the coating film.
[0026]
In the flash-off device of the present invention, it is possible only with the hot air circulation device, but the vehicle body temperature just before entering the clear painting process after leaving the flash-off device is 43 ° C. or more as in the case where the outdoor temperature in summer is high. In such a case, the vehicle body temperature may not become 30 ° C. or less immediately before the clear paint is actually applied. In such a case, it is preferable to cool the vehicle body using a cooling device with a cooling time of about 0.5 min. This is because it is not preferable in terms of coating film quality if the clear paint is applied in a state where the temperature of the vehicle body is 30 ° C. or higher.
[0027]
Incidentally, the temperature in the hot air circulating apparatus in the conventional flash-off apparatus is about 80 ° C., the humidity is about 5 g / kg higher than that in the present invention, and the processing time is about 3 minutes.
[0028]
【The invention's effect】
According to the present invention, since hot air is simultaneously blown from a plurality of drying nozzles and slits to a wet object coated with a water-based paint, the length of the flash-off zone is longer than that of a conventional flash-off device. Can be shortened. This can improve productivity, save space in the painting process, and reduce the number of vehicle stocks.
[0029]
Further, the flash-off device of the present invention can dry the inner and outer plates of the vehicle body at the same time and has excellent drying properties of the inner plate, so that the energy cost for carrying out the temporary drying in the water-based coating can be greatly reduced. Furthermore, since wet-on-wet coating with clear paint can be established, it is possible to ensure excellent coating quality.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view showing a layout of a water-based coating flash-off device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a hot air circulation device according to the embodiment, and FIG. 3 is a side view showing the hot air circulation device. FIG.
[0031]
FIG. 1 shows an example in which the flash-off device of the present invention is applied to a top coat. Hereinafter, a top coat system for applying a water-based base paint and a clear paint by wet on wet is applied to the inner and outer plates of the vehicle body. The present invention will be described with reference to embodiments.
[0032]
The body to be coated is transported at a constant speed from the left to the right in the figure by the floor conveyor, and then transported to the top coat drying furnace. In this figure, the water-based paint is applied in the top coating process. The final stage of the water-based paint coating process 1, the flash-off process 2 according to the present embodiment, and the first stage of the clear coating process 3 for applying the clear paint are shown. In order to explain the effect of the flash-off device according to the present embodiment, the top view of the figure shows a plan view of the present embodiment, and the bottom view shows a plan view of a conventional flash-off device.
[0033]
The water-based paint coating process 1 is provided in a painting booth in which room air is controlled with a constant flow, and in this process, the water-based base paint is painted on the inner and outer plates of the vehicle body. The stationary chamber 11 at the final stage is a chamber without air flow, and the vehicle body is conveyed as it is. The vehicle body in this example moves at a conveyor speed of 4 to 5 m / min.
[0034]
In the next stage of the water-based paint coating process 1, a flash-off process 2 is provided, in which a hot air circulation device 21 and a stationary chamber 22 according to the present invention are provided. In this example, under the condition of the conveyor speed of 4 to 5 m / min described above, the hot air circulation device 21 passes through the stationary chamber 22 for 3 to 4 minutes and the stationary chamber 22 for 0.5 to 0.7 minutes.
[0035]
The hot-air circulation device 21 of this example is formed as a tunnel-shaped furnace body as shown in FIGS. 2 and 3, and as shown in FIG. 2, at the upper position facing the upper part of the left and right window openings of the vehicle B. A drying nozzle 211 for blowing hot air toward the inner plate in the vehicle interior when the vehicle passes, and an intermediate drying slit 212 for blowing hot air toward the outer plates on the left and right side surfaces of the vehicle body B are provided. Further, drying lower slits 213 for blowing hot air toward the outer plates on the left and right lower side surfaces of the vehicle are provided.
[0036]
The drying nozzle 211, the drying middle slit 212, and the drying lower slit 213 are provided in the intake duct 214 provided on the left and right side walls of the furnace body along the longitudinal direction of the furnace body as shown in FIG. The air sucked by the intake fan 215 shown in FIG. 2 is heated to a predetermined temperature by the heater 216 and then supplied to the intake duct 214. In addition, exhaust ducts 217 for exhausting the air in the furnace body are provided at the upper portions of the left and right side walls of the furnace body. As shown in FIG. 3, from the exhaust opening 218 formed in the exhaust duct 217, FIG. The air in the furnace (hot air) sucked in by the exhaust fan 219 shown is exhausted out of the system.
[0037]
A stationary chamber 22 is provided in the next stage of the hot air circulation device 21. The stationary chamber 22 has a furnace body similar to the hot air circulation device 21 shown in FIG. It is a room that is not supplied.
[0038]
The flash-off process 2 of this example is composed of the hot air circulation device 21 and the stationary chamber 22 described above, and a coating booth that is a clear paint coating process 3 is provided in the next stage of the stationary chamber 22. In the upper diagram of FIG. 1, a zone 23 is shown between the stationary chamber 22 and the clear paint coating process 3, but this zone 23 is omitted when a new top coat process is provided. The chamber 22 and the clear coating process can be directly connected. In such a case, the length of the flash-off process 2 can be shortened. Further, when the existing flash-off process 2 is modified, the zone 23 can be constituted only by the furnace body and can be a part of the stationary chamber 22. Even in such a case, the space itself of the flash-off process 2 is not reduced, but the energy cost required for the IR device and the cooling device can be reduced as compared with the conventional flash-off device shown in the lower diagram of the figure. Incidentally, a cooling device for cooling the vehicle body can be provided in the zone 23, and can be used as a countermeasure process in the case where the vehicle body temperature does not fall sufficiently, such as in summer.
[0039]
【Example】
(1)Measurement of wind speed in the furnace of hot air circulation system
In order to obtain the optimum conditions for the upper drying nozzle 211, the drying middle slit 212, and the drying lower slit 213 for blowing hot air, a confirmation test using an actual vehicle was performed using the hot air circulation device 21 of the flash-off device. First, as shown in FIG. 4, 10 parts of the vehicle body, that is, 5 parts of the center of the hood, the center of the roof, the trunk vertical wall, the rear door skin, and the rear fender are the parts for measuring the wind speed on the outer plate of the vehicle body. The trunk hinge part, the back pillar hinge part, the side step part, and the lower part of the back pillar are the parts for measuring the wind speed on the inner plate of the vehicle body.
[0040]
The wind speed was measured by installing an anemometer (for example, a hot-wire anemometer) in each of the above parts. The diameter of the upper drying nozzle 211 is 65 mm, the pitch is 333 mm, the opening of the drying middle slit 212 is 15 mm × 240 mm, the pitch is 167 mm, and the width of the opening of the lower drying slit 213 is 7. Three types of 5 mm, 15 mm and 22.5 mm, one type of 240 mm in length, and two types of pitches of 167 mm and 333 mm were used. The distance between the drying lower slit 213 and the vehicle body (see distance L shown in FIG. 2) was set to three types: 250 mm, 300 mm, and 350 mm. Furthermore, the air speed, air volume, and the like of the upper drying nozzle 211, the drying middle slit 212, and the drying lower slit 213 were set under the conditions of Tests 1 to 10 shown in Table 1.
[0041]
[Table 1]

[0042]
Experiment 1-1
Under the conditions shown in Table 1, an upper drying nozzle (hereinafter also simply referred to as an upper nozzle) 211, a drying middle slit (hereinafter also simply referred to as a middle slit) 212, and a lower drying slit (hereinafter also referred to simply as a lower slit). 5) and FIG. 6 show the results of setting the surface wind speed at each part of the vehicle body shown in FIG. FIG. 5 shows the results of Test 2 in which the upper nozzle 211 and the lower slit 212 are combined, Test 4 only for the lower slit 213, and Test 5 only for the upper nozzle 211, and FIG. 6 shows the upper nozzle 211 and the lower slit. The results of Test 2 combining 213 and Test 3 combining all 211, 212, 213 are shown.
[0043]
From the result of FIG. 5, compared with only the upper nozzle 211 (test 5, ◆ mark) or only the lower slit 213 (test 4, x mark), test 2 (Δ mark), that is, the upper nozzle 211 and the lower slit 213 Under the combined condition, it is understood that the average surface wind speed at each part of the vehicle body is as large and uniform as 1.5 m / s or more, and the entire vehicle body dries faster.
[0044]
Further, from the results of FIG. 6, when the upper nozzle 211, the middle slit 212, and the lower slit 213 are used (test 3, ■ mark), a large surface wind speed is obtained in a part of the outer plate portion of the vehicle body. It is understood that no effect is recognized on the inner plate part of the vehicle body. Accordingly, there is no significant difference from the condition (test 2, ▲) in which the upper nozzle 211 and the lower slit 213 are combined, and the middle slit 212 can be omitted if necessary.
[0045]
Experiment 1-2
The experiment 1-1 confirmed that the combination of the upper nozzle 211 and the lower slit 213 is preferable in terms of the average surface wind speed. Next, under the condition of combining the upper nozzle 211 and the lower slit, the lower slit In order to obtain the optimum conditions for the width and pitch of 213, the surface wind speeds at various parts of the vehicle body when these width and pitch were changed were compared.
[0046]
As shown in Table 1, the lower slit 213 compared here is a test 1 with a slit opening of 15 mm × 240 mm and a pitch of 333 mm, a test 7 with a slit opening of 7.5 mm × 240 mm, a pitch of 167 mm, and a test 8 of The pitch was 500 mm with a slit opening of 22.5 mm × 240 mm. The measurement results of the surface wind speeds of these tests 1, 7, and 8 are shown in FIG. In the figure, test 1 is indicated by a cross, test 7 is indicated by a ♦, and test 8 is indicated by a ●.
[0047]
From the results shown in FIG. 7, when the dimension of the lower slit 213 of Test 1 (x mark), that is, the slit opening is 15 mm × 240 mm and the pitch is 333 mm, the average surface wind speed at each part of the vehicle body is the largest and the inner and outer plates It is understood that the average surface wind speed becomes uniform and the entire vehicle body dries quickly.
[0048]
Experiment 1-3
According to the above experiments 1-1 and 1-2, the condition that the upper nozzle 211 and the lower slit 213 are combined and the opening of the lower slit 213 is 15 mm × 240 mm and the pitch is 333 mm is preferable from the viewpoint of the average surface wind speed. Next, in order to find the optimum conditions for the distance to the vehicle body under these conditions, only the distance L from the lower slit 213 to the vehicle body was changed to three types of 250 mm, 300 mm, and 350 mm. The surface wind speed at each part of the car body was compared.
[0049]
As the lower slit 213 compared here, Test 1 has a distance of 300 mm, Test 9 has a distance of 250 mm, and Test 10 has a distance of 350 mm. The measurement results of the surface wind speed of these tests 1, 9, and 10 are shown in FIG. In the figure, test 1 is indicated by a cross, test 9 is indicated by a triangle, and test 10 is indicated by a triangle.
[0050]
From the results shown in FIG. 8, it is understood that when the distance between the lower slit 213 of the test 1 and the vehicle body is 300 mm, the average surface wind speed at each part of the vehicle body is the highest, and the entire vehicle body dries fast.
[0051]
Experiment 1-4
From the above experiments 1-1 to 1-3, it was confirmed that the case of the predetermined condition in which the upper nozzle 211 and the lower slit 213 are combined is preferable from the viewpoint of the average surface wind speed, but further, the upper nozzle 211 and the lower slit 213. In order to obtain the optimum condition for the balance of the amount of air blown from each, the surface wind speed at each part of the vehicle body when the air amounts of the upper nozzle 211 and the lower slit 213 were changed was compared.
[0052]
Here, in Test 1, the air volume ratio between the upper nozzle 211 and the lower slit 213 was 1: 1, and in Test A, the air ratio was 2: 1. The measurement results of the surface wind speeds of Tests 1 and A are shown in FIG. In the figure, test 1 is indicated by ● and test A is indicated by ▲.
[0053]
From the results shown in FIG. 9, in the air volume balance of test A, the variation in the average surface wind speed in each part of the vehicle body is large, but the ratio of the blown air volume between the upper nozzle 211 and the lower slit 213 is 1: 1 as in test 1. In this case, it is understood that the average surface wind speed at each part of the vehicle body is uniform, and the drying speed at each part of the vehicle body is not different and is good.
[0054]
(2)Measurement of coating solid content by hot air circulation device
Using the above-described flash-off device, the solid content of the water-based base paint applied before and after the flash-off in each part of the vehicle body was measured under the conditions of the test 7 described above.
[0055]
As experimental conditions, the conveyor speed was set to 1.6 m / min, the water-based base paint was manually blown for the inner plate portion, and the outer plate portion was robot-coated. The time was 34 to 41 minutes, and the flash-off process was natural cooling in a stationary room. The solid content of the water-based base coating was measured by applying an aluminum foil to each part of the car body and painting it, and measuring the weight change before and after the flash-off.
[0056]
Example 1
Aluminum foil was attached to 8 parts of the car body (excluding the back part of the hood and the trunk hinge part in the above 10 parts), the inner plate part was manually blown, and the outer plate part was painted with a water base paint by a robot. Subsequently, while moving the vehicle body at a conveyor speed of 1.6 m / min, the hot-air circulation device 21 according to the present invention was put in, and the aqueous base coating was temporarily dried. The temperature inside the hot air circulation device is 50 ° C., the humidity is 9.5 g / kg, and the flash-off time is 3 minutes (passing time in the hot air circulation device). The time was 35 minutes.
[0057]
At this time, one of the aluminum foils attached to each part of the vehicle body just before entering the hot air circulation device is removed to measure the solid content, and the remaining aluminum foil attached to each part of the vehicle body immediately after leaving the hot air circulation device Was removed and the solid content was measured. Table 2 shows the measurement results of the coating solid content (% by weight) before and after the hot air circulation apparatus.
[0058]
As shown in Table 2, in Example 1, the solid content of the water-based base coating immediately before entering the hot air circulation device was 44.1% at the outer plate horizontal portion, 51.4% at the outer plate vertical portion, The solid content after the end of the flash-off was 78.9 to 85.2% for the above-described 8 parts of the vehicle body, and 70% or more for all the parts.
[0059]
Example 2
In Example 1, except that the humidity of the hot air circulation device was 19.5 g / kg and the time from the application of the water-based base coating to the end of the flash-off was 41 minutes, the same conditions as in Example 1 were used. The coating solid content of the water-based base coating before and after the hot air circulation device was measured. The results are shown in Table 2.
[0060]
As shown in Table 2, in Example 2, the solid content of the water-based base coating immediately before entering the hot air circulation device was 46.4% in the horizontal portion of the outer plate, 40.8% in the vertical portion of the outer plate, While the plate was 54.8%, the solid content after the end of the flash-off was 72.6 to 85.9% for the vehicle body 8 part, and 70% for all parts.
[0061]
Example 3
In Example 1, the temperature in the hot air circulating apparatus was 40 ° C., the flash-off time was 4.8 minutes (passing time), and the time from application of the water-based base coating to completion of the flash-off was 34 minutes. Were the same conditions as in Example 1 and measured the solid content of the aqueous base coating before and after the hot air circulating apparatus. The results are shown in Table 2.
[0062]
As shown in Table 2, in Example 3, the solid content of the water-based base coating immediately before entering the hot air circulation device was 38.6% in the outer plate horizontal portion, 34.7% in the outer plate vertical portion, and the inner plate However, the solid content after completion of the flash-off was 81.9 to 84.8% for the vehicle body 8 parts, and all the parts were 70% or more.
[0063]
Comparative example
In Example 1, the temperature inside the hot air circulating device was set to 70 ° C., the flash-off time was set to 2 minutes (passing time), and the time from application of the water-based base coating to completion of the flash-off was set to 37 minutes. Under the same conditions as in Example 1, the solid content of the aqueous base coating was measured before and after the hot air circulation apparatus. The results are shown in Table 2.
[0064]
As shown in Table 2, in this comparative example, the solid content of the water-based base coating immediately before entering the hot air circulation device is 51.8% in the outer plate horizontal portion, 38.9% in the outer plate vertical portion, and the inner plate Was 54.2%, which was almost the same as in Examples 1 to 3 above, but the solid content after the end of the flash-off was 83.4% in the back pillar hinge portion in the 8 parts of the vehicle body. The lower end of the back pillar was 67.5%, and there were also two sites of 70% or less.
[0065]
Reference example 1
In Example 1, the same conditions as in Example 1 were applied except that the time from application of the aqueous base paint to the end of the flash-off was 65 minutes, and the aqueous solid base coating applied before and after the hot air circulation device. Minutes were measured. The results are shown in Table 2.
[0066]
As shown in Table 2, in Reference Example 1, the solid content of the water-based base coating immediately before entering the hot air circulation device is 48.4% at the outer plate horizontal portion, 50% at the outer plate vertical portion, and for the inner plate In contrast to 85.3%, the solid content after the end of the flash-off was 80.4 to 86.7% for the 8 parts of the vehicle body, and 80% or more in all parts.
[0067]
Reference example 2
In Example 1, the temperature in the hot air circulating device is 60 ° C., the flash-off time is 2.5 minutes (passing time in the hot air circulating device), and the time from the application of the water-based base coating to the end of the flash-off is 55. The solid content of the aqueous base coating was measured before and after the hot air circulation apparatus under the same conditions as in Example 1 except that the content was the same. The results are shown in Table 2.
[0068]
As shown in Table 2, in Reference Example 2, the solid content of the water-based base coating immediately before entering the hot air circulation device is 44.5% in the horizontal portion of the outer plate, 46.4% in the vertical portion of the outer plate, and the inner plate. However, the solid content after the end of flash-off was 83.9 to 87.9% for the 8 parts of the vehicle body, and 80% or more for all parts.
[0069]
[Table 2]

[0070]
From the above results, in the present invention, after the flash-off process, if the solid content of the aqueous base painted on the inner and outer plates of the vehicle body immediately before the clear coating is applied is 70% or more, It has been confirmed that there is no problem in quality.
[0071]
Further, it was confirmed that the temperature in the hot air circulating apparatus in the flash-off process is preferably 40 to 50 ° C., and the flash off time (passing time in the hot air circulating apparatus) is preferably 3 to 5 minutes.
[0072]
By the way, when the flash-off process is performed in 3 to 5 minutes, the solid content of the water-based base coating can be increased to 70% or more by increasing the temperature. This is necessary and is not preferable from the viewpoint of energy consumption. In addition, when the temperature is increased and the flash-off time is shorter than 3 minutes, as seen in Comparative Example 1, a portion of the solid content of the aqueous base coating is 70% or less in a part of the vehicle body, which is preferable. Absent.
[0073]
In addition, as shown in Reference Examples 1 and 2, when processing from water-based base coating to flash-off over 1.5 times as compared with Examples 1 to 3, it is necessary to In all cases, the solid content of the water-based base coating is 80% or more and there is no problem in coating film quality, but it is not practical in consideration of productivity.
[0074]
Actual line verification results
Table 3 shows the verification results on the actual line. This verification was performed under the conditions of a conveyor speed of 4.6 m / min, a booth temperature of 23 ° C., a hot air circulation device pass time of 3 minutes, and a cooling device pass time of 0.64 minutes. Verification experiment No. shown in the same table. 5 and no. From the result of 6 (the humidity state of the conventional flash-off device is 20 g / kg and 13 g / kg which is 7 g / kg lower than that), it was found that the solid content NV is remarkably improved in the inner plate portion. .
[0075]
[Table 3]

[0076]
The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of a flash-off device according to the present invention and a conventional flash-off device as a comparative example.
FIG. 2 is a cross-sectional view showing an embodiment of a hot air circulation device according to the present invention.
FIG. 3 is a side view showing an embodiment of a hot air circulation device according to the present invention.
FIGS. 4A and 4B are a plan view and a side view showing a part of wind speed measurement in the embodiment of the present invention. FIGS.
FIG. 5 is a graph showing the result (part 1) of the wind speed measurement in the example of the present invention.
FIG. 6 is a graph showing the result (part 2) of the wind speed measurement in the example of the present invention.
FIG. 7 is a graph showing the results of wind speed measurement (part 3) in the example of the present invention.
FIG. 8 is a graph showing the result (part 4) of the wind speed measurement in the example of the present invention.
FIG. 9 is a graph showing the result (part 5) of the wind speed measurement in the example of the present invention.
[Explanation of symbols]
1 ... Water-based paint painting process
2 ... Flash-off process
21 ... Hot air circulation device
211 ... Drying nozzle (hot air outlet)
212 ... Middle slit for drying (hot air outlet)
213 ... Lower slit for drying (hot air outlet)
22 ... Still room
3 ... Clear paint painting process

Claims (6)

A flash-off device provided between a water-based paint coating process for coating a water-based paint and a clear paint coating process for applying a clear paint wet-on-wet on the water-based paint film, wherein the water-based paint is applied. A hot air circulation device having a hot air outlet for blowing hot air on the coated object ,
The hot air outlet of the hot air circulation device is a plurality of drying nozzles and slits that simultaneously blow hot air against an object coated with the water-based paint that passes through the hot air circulation device,
The plurality of drying nozzles of the hot air circulation device are provided at the upper position of the hot air circulation device facing the left and right window openings of the vehicle that is the object to be coated, and the vehicle body from the left and right window openings when the vehicle passes. Hot air is blown toward the inner plate of the vehicle to generate a convection circulation airflow inside the vehicle,
The plurality of drying slits of the hot air circulation device are provided at the lower position of the hot air circulation device facing the left and right lower surfaces of the vehicle that is the object to be coated, and when the vehicle passes, A flash-off device that blows hot air toward an outer plate to generate an updraft along the outer surface of the vehicle . The plurality of drying slits of the hot air circulation device are provided at the middle position of the hot air circulation device facing the left and right side surfaces of the vehicle, and direct hot air toward the outer plates on the left and right side surfaces of the vehicle when the vehicle passes. The flash-off device according to claim 1, further comprising a drying slit for spraying . It takes 3 to 5 minutes for the coated material to pass through the hot air circulation device, the temperature in the hot air circulation device is 50 to 60 ° C., and the humidity in the hot air circulation device is 9.5 to 19.5 g / kg ( The flash-off device according to claim 1 or 2 , which has a water content in 1 kg of dry air. The flash-off device according to any one of claims 1 to 3 , wherein a temperature of an inner plate and an outer plate of an object to be coated immediately before being put into the clear coating process is 30 ° C or lower. Wherein the coating solids of the coating film immediately before to be introduced into the clear coating paint process, flash-off device according to any one of claims 1 to 4 is 70% or more. The flash-off device according to any one of claims 1 to 5 , further comprising a cooling device between the hot air circulation device and the clear paint coating process.

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