JP2017077505A - Powder coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating method capable of serviceably using even recovery powder of the high mixed color ratio just after changing a color, and inconspicuous in contamination of a coating surface.SOLUTION: In a powder coating method for executing a color changing coating of a B color by using powdered paint of the B color thereafter, by cleaning a coating line of sticking an A color, when changing a color to the B color from the A color in powdered paint, a finish coating surface is formed by spraying new powder of the B color or a low mixed color recovery powder of the mixed color ratio of a predetermined value or less on a coating object to a surface of a primer coating surface of executing coating by spraying recovery powder of the B color recovered after changing the color on the coating object W, and contamination of the primer coating surface is hidden by a beautiful finish coating surface.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a powder coating method capable of obtaining a clean painted surface in which contamination (color mixing) is not conspicuous even when powder coating is performed using recovered powder after color change.

  Powder coating does not contain organic solvents and is used in many ways as an environmentally friendly coating. At first, it was used in many products mainly for outdoor use such as guardrails, gates, and fences. Many products are also used in places. It is also widely used for automotive parts, one of the key industries in Japan. For example, it is used for painting body parts of automobiles, in addition to paints such as wipers, aluminum wheels, brake pads, oil filters, and coil springs. In particular, it has recently been adopted for school children's chairs and desks due to its non-polluting characteristics.

  Powder coating does not contain organic solvents, is non-polluting, and can reuse overspray powder that has not adhered to the object to be coated, but color change is a problem compared to solvent coating.

  In the case of solvent paint, for example, even if B color is mixed into A color a little, if B color is dissolved in A color, B color is hardly felt, but powder of paint powder of another color When the body paint is mixed, the mixed powder paint is cured as it is and appears on the coating film as contamination.

  Therefore, in powder coating, the coating booth must be thoroughly cleaned so that contamination does not occur during color change, and there is a method for performing cleaning work during color change in a short time. Patent Document 1 and the like.

JP 2011-224414 A

  However, in order to prevent contamination during color change, it is necessary to clean not only the paint booth but also every corner of the dust collector's cyclone and duct, so that the paint line can be used for a long time. I have to stop.

  Even if the painting line is stopped for a long time and it is sufficiently cleaned, it is difficult to completely clean the painting line, and the color before color change is inevitably mixed in the collected powder.

  In particular, immediately after the color change, the paint before the color change on the coating film tends to have small spots.

  Contamination gradually decreases with time after the color change. For example, when the color of a powder coating is changed from A to B, immediately after the color change, the color mixing ratio of the A color is high in the collected powder of the B color, and the color mixing of the A color with the passage of time. The ratio is getting lower and lower.

  For this reason, especially when aesthetics are required as an object to be coated, use of a recovered powder with a high color mixing ratio causes noticeable contamination and harms the aesthetics. The powder may be discarded without being used, and there is a problem that the advantage of the powder coating that the overspray powder can be recovered and used is hindered.

  In addition, there is a limit to stopping the painting line for a long time and thoroughly cleaning the painting line in order to reduce the color mixture ratio of the collected powder immediately after the color change. There is a problem of lowering.

  Therefore, an object of the present invention is to provide a powder coating method in which recovered powder having a high color mixing ratio immediately after color change can be used without waste, and contamination on the coated surface is not noticeable.

  In order to solve the above-mentioned problems, the present invention sprays a powder coating material from a coating gun to the object to be coated in the powder coating booth, coats the object with the powder coating material, and adheres to the object to be coated. The over-spray powder that was not collected was collected, and when the powder coating to be used was changed from A color to B color on the coating line where powder collection was performed using the collected recovered powder, the A color adhered. In a powder coating method that cleans the painting line and then uses the B color powder coating to perform the B color change coating, the B color recovered powder collected after the color change is sprayed onto the object to be coated. The top coat surface is formed by spraying a new B color powder or a low color mixture recovered powder having a color mixture ratio of a predetermined value or less on the surface of the undercoating surface subjected to the above.

  According to the present invention, a new B color powder or a low color mixture ratio with a color mixture ratio of a predetermined value or less is applied to the surface of the undercoating surface where the B color recovered powder collected after the color change is sprayed on the object to be coated. Because the top coat surface is formed by spraying the powder onto the object to be coated, even if the recovered powder immediately after color change with a color mixture ratio exceeding the specified value is used for painting the undercoat paint surface, the contamination that appears on the undercoat paint surface is It is covered with the top coat surface and can be made inconspicuous.

  Therefore, there is an effect that it is possible to use a collected powder immediately after color change without waste and to obtain a clean coating film with no noticeable contamination.

It is a schematic plan view which shows a part of coating line of embodiment of this invention. It is the schematic which shows the whole coating line of embodiment of this invention. (A) is a schematic diagram showing the state of a painted surface before baking, in which undercoating and topcoating are applied using highly mixed color recovered powder, and (b) is a state after baking the painted surface of (a) It is a schematic diagram which shows. (A) is a schematic diagram showing the state of the painted surface before baking, in which the undercoating is applied using a highly mixed color recovered powder, and the top coating is applied using a new powder thereon, (b) is ( It is a schematic diagram which shows the state after baking the coating surface of a). It is sectional drawing which shows another example of a powder coating material tank.

  Embodiments of the present invention will be described below.

FIG. 1 is an overall view of a coating line to which the powder coating method of the present invention is applied.
As shown in FIGS. 1 and 2, the object to be coated W is supported in a suspended manner in two rows so as to face the conveyor 2, and is transported through the coating booth 1 from the inlet side to the outlet side, and is being transported. The powder coating is sprayed from four coating guns 3 ₁ to ₈ installed in two rows on the left and right sides of the painting booth 1. The left and right paint guns 3 ₁ to ₈ are installed so as to move up and down by a reciprocator 16.

  As shown in FIG. 2, the overspray powder that has not adhered to the workpiece W in the painting booth 1 is supplied to the recovery cyclone 5 by the recovery duct 4, and the recovered cyclone 5 separates the recovered powder and air, The recovered powder is recovered from the discharge port below the recovery cyclone 5. A pinch valve 6 and a selection device 7 are provided at the discharge port of the recovery cyclone 5 to remove dust 8 mixed in the recovered powder.

  The recovered powder that has passed through the selection device 7 is sent to the recovered powder coating tank 10 through the flexible tube 9.

  The recovered powder paint tank 10 is divided into a first tank 10a and a second tank 10b. The recovered powder recovered in the recovery cyclone 5 is stored in the first tank 10a, and a new powder paint tank 11 is stored in the second tank 10b. The fresh powder is replenished by the injector 12.

  The first tank 10a and the second tank 10b of the recovered powder paint tank 10 are provided with levelers (not shown) for monitoring the amount of powder paint in the tank, and the amount of powder paint in the first tank 10a is large. Then, when the recovered powder in the first tank 10a is sent to the second tank 10b and the amount of the powder paint in the first tank 10a and the second tank 10b decreases, the second powder is supplied from the new powder paint tank 11 via the injector 14. The tank 10b is replenished with new powder, and the amount of powder paint in the first tank 10a and the second tank 10b is adjusted.

  For example, when the color of the powder coating is changed from A color (black) to B color (white), the recovered color of B color (white) after color change is changed to A color (black) before color change. In order to avoid mixing, the painting booth 1, the recovery cyclone 5, and the inside of the duct are cleaned by air blow or the like.

  Even if this cleaning is performed, the A color (black) before color change is inevitably mixed with the B color (white) recovered powder immediately after color change.

  For example, when the color mixing ratio in which A color (black) is mixed with B color (white) recovered powder immediately after color change is 1/1000, A color (black) is mixed with the lapse of coating time. The color mixture ratio gradually decreases.

  When the workpiece W is, for example, a partition, the required color mixture ratio is 1 / 10,000 or less, so that the color mixture ratio immediately after the color change is 1 / 1,000. When painting with powder, contamination (color mixing) is conspicuous, resulting in poor coating.

  FIG. 3 (a) is a schematic diagram of the case where a high color mixture recovered powder having a high color mixing ratio is used for undercoating and then a top color coating is continuously performed using a high color mixing recovered powder having a high color mixing ratio. Even if the A-color (black) powder coating appears as spots on both the undercoating surface and the top-coating surface, and it is baked after painting, the white coating is applied as shown in FIG. A poorly painted film with black spots remaining on the surface.

  For this reason, conventionally, after the color change, if the color mixture ratio required for the partition which is the workpiece W is 1 / 10,000, the color mixture ratio is a low color mixture ratio of 1 / 10,000 or less. The high color mixture recovered powder until then could not be used and had to be discarded.

In the present invention, the discarded mixed color ratio immediately after the color change is undercoat using a high color mixture recovered powder having a 1/1000 color mixing ratio, and the new powder or the mixed color ratio is 1/10, The top coating is performed with a low color mixture recovered powder of 000 or less.
In the coating line shown in FIG. 2, until the color mixing ratio of the recovered powder becomes 1 / 10,000 or less, the high-color-mixed recovered powder is drawn out from the first tank 10a of the recovered powder paint tank 10 by the injector 12, and the coating booth The high-color-collected powder is supplied to the four coating guns 3 ₁ , ₂ , ₅ , ₆ on the inlet side of ₁ , and undercoating is applied to the workpiece W. After that, the new powder is drawn out from the injector 13 of the new powder paint tank 11, and the new powder is supplied to the _four painting guns 3 ₃ , ₄ , ₇ , ₈ on the exit side of the painting booth 1, and the article W is overcoated. When painting, as shown in Fig. 4 (a), the undercoating surface where the contamination is conspicuous is covered with the top coating surface of the new powder, so the contamination of the undercoating surface is covered by the top coating surface of the new powder. When it becomes inconspicuous and is baked after painting, a clean coating film free from contamination can be obtained as shown in FIG.

After the color change, the operation time elapses and the color mixture ratio gradually decreases. For example, when a low color mixture recovered powder having a color mixture ratio required for the workpiece W of 1 / 10,000 or less is obtained, As shown by the broken line in the coating line shown in FIG. 2, the low-color-mixed recovered powder is drawn out from the second tank 10b of the recovered powder paint tank 10 by the injector 13, and the four coating guns 3 ₃ , ₄ , _The recovered powder may be supplied to ₇ and ₈ , and the top coating may be performed using the low-color-mixed recovered powder having a color mixture ratio of 1 / 10,000 or less.

  As described above, according to the present invention, by applying a top coat using a new powder or a low color mixture recovery powder having a color mixture ratio of an allowable concentration or less, a high color mixture recovery powder having a color mixture ratio of an allowable concentration or more Even when undercoating is performed, the conspicuous undercoating surface can be concealed by the overcoating surface, so that the recovered powder having a color mixture ratio exceeding the allowable concentration can be effectively used without being discarded.

  The allowable density of the color mixture ratio varies depending on the object to be coated W. As described above, in the case of partition, the allowable density of the color mixture ratio was 1 / 10,000, but the object to be painted W is like a mesh fence. In this case, the allowable density of contamination is not stricter than the partition, and the color mixture ratio is about 1/1000.

  Therefore, when cleaning the paint booth when changing colors, the cleaning time is lengthened or shortened according to the allowable concentration of contamination.In this invention, the undercoating surface above the allowable concentration of contamination is covered by the top coating. Since it can be hidden, the cleaning of the paint booth when changing colors can be made shorter than usual.

  For this reason, since the painting method of this invention can minimize the stop time of the painting line at the time of color change, it becomes possible to improve production efficiency.

  In the embodiment shown in FIG. 2, the recovered powder paint tank 10 is divided into a first tank 10a and a second tank 10b, and a new powder paint tank 11 is provided separately. However, as shown in FIG. 15 is divided into a recovered powder tank 15a to which recovered powder is supplied, a new powder tank 15b to which new powder is supplied, and a low color mixing tank 15c having a low color mixing ratio in which new powder and recovered powder are mixed. The powder coating material in the low color mixing tank 15c may be used for top coating while adjusting the density of the color mixing ratio.

1: Coating booth 2: Conveyor 3 ₁ to ₈ : Coating gun 4: Recovery duct 5: Recovery cyclone 6: Pinch valve 7: Selection device 8: Garbage 9: Flexible tube 10: Recovery powder paint tank 10a: First tank 10b : Second tank 11: New powder paint tank 12: Injector 13: Injector 14: Injector 16: Reciprocator 15: Paint tank 15a: Collected powder tank 15b: New powder tank 15c: Low color mixing tank W: Object to be coated

Claims (3)

  In the powder coating booth, powder paint is sprayed from the painting gun to the object to be coated, and the object to be coated is coated with the powder paint, and the overspray powder that has not adhered to the object is recovered and recovered. When changing the powder coating used from A to B in a coating line where powder coating is performed using powder, the coating line with the A color attached is cleaned, and then the B color powder is used. In the powder coating method of performing B color change painting using paint, the B color recovered powder collected after the color change is sprayed onto the surface of the object to be coated, and the surface of the undercoat painted surface is coated with B color. A powder coating method comprising forming a top coat surface by spraying new powder or low color mixture recovered powder having a color mixture ratio of a predetermined value or less onto an object to be coated.   2. The powder coating method according to claim 1, wherein the top coating surface is applied to a surface that places importance on the aesthetics of the object to be coated.   The paint tank that supplies powder paint to the coating gun is divided into a collection powder tank to which recovered powder is supplied, a new powder tank to which new powder is supplied, and a low color mixing tank with a low color mixing ratio that mixes new powder and recovered powder. The powder coating method according to claim 1, wherein the powder coating method is performed.

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