JP2015229152A - Powder coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating method for applying powder paint A homogeneously to the inner face of even either a cylindrical coated object 1 of a small internal diameter or a cylindrical coated object 1 having a complicated inner surface shape, thereby to form a coating film 2 of the powder paint A on the inner face of the cylindrical coated object 1.SOLUTION: A cylindrical coated object 1 is being closed, while leaving at least one opening, in the other openings, and an electrically charged powder paint A is filled from an opened opening into the cylindrical coated object 1. After this, the filled charging powder paint A is dropped from the opening so that the powder paint A caused to stick to the inner surface of the coated object 1 by electrostatic force may be left as a coating film 2.

Description

  The present invention relates to a powder coating method for forming a coating film of a powder paint on the inner surface of a cylindrical object to be coated.

  In recent years, electrostatic coating has been used as a coating method using a powder coating.

  There are three main types of painting methods that use static electricity.

  Solvent-type electrostatic coating in which paint is diluted with solvent and applied with static electricity, or water-based (water-soluble) type electrostatic in which economical aqueous (water-soluble) paint is diluted instead of solvent and applied with static electricity In addition to coating, there is electrostatic powder coating in which a coating resin is pulverized into particles without dispersing the coating in a solvent and water system, and the coating particles are charged.

  Of these coating methods using static electricity, electrostatic powder coating is capable of recovering and reusing overspray powder, and in recent years, the transition from solvent coating to powder coating is progressing.

  Electrostatic powder coating begins with road materials such as fences and guardrails, and is applied to automobile parts such as refrigerators, washing machines, microwave ovens, fire extinguishers, wipers, coil springs, brake pads, and aluminum wheels used at home. Many are used. Overseas, it is also used for top clear painting of passenger cars.

  In recent years, electrostatic powder coating is also used for exterior panels and oil heater panels that require partitioning and weather resistance as interior and exterior buildings. It is also used for steel furniture, elementary school chairs and desks because of its non-polluting point.

  In electrostatic powder coating, for example, a powder coating is made into particles having an average of 20 to 30 μm, adhered to an object to be coated with static electricity, and then melted and cured in a baking and drying furnace to form a coating film. Is the method.

  Generally, there are two types of spray guns used for electrostatic powder coating. One is a corona gun system that boosts the voltage to a high voltage and applies it to the electrode for coating. The other is to contact the non-conductive resin and the powder paint to charge the paint particles and apply the paint. This is a triboelectric gun method.

  Further, as another method, as in Patent Document 1, the powder paint is flowed in a fluidized tank, and a corona electrode is arranged near the perforated plate on the bottom surface, and the powder paint is atomized at the upper part where it flows. In the vicinity of the fluidized tank, for example, electrostatic fluidized immersion coating that performs painting while rotating an object to be coated such as a rotor of a motor, or a powder coating that is rubbed into the fluidized tank as in Patent Document 2 Applying an electric charge to the powder coating material and immersing the coating material in the powder coating in the fluid tank, or rotating the coating material near the atomizing part above the fluidized powder coating material. There is also a method of painting.

Japanese Patent Laid-Open No. 06-28597 Japanese Unexamined Patent Publication No. 2012-11340

  By the way, for example, when coating the inner surface of a cylindrical object such as a pipe elbow or nipple by electrostatic powder coating, the powder coating sprayed from the electrostatic powder coating gun is used. There is a method of passing the inner surface of a cylindrical object to be coated and attaching a powder paint to the inner surface of the object to be coated.

  When painting the inner surface of a cylindrical object such as a pipe elbow or nipple with an electrostatic powder coating gun, if the inner diameter of the cylindrical object is large, the inside of the cylindrical object In addition, it is possible to paint by inserting a gun tip.

  However, when the inner diameter of the cylindrical object to be coated is small, the gun tip cannot be inserted, and if the gun point is too close to the cylindrical object to be coated, there is a gap between the gun tip electrode and the object to be coated. There is a risk of sparks.

  Further, if the gun tip and the object to be coated are separated too much, the powder paint does not reach the inner part of the cylindrical object to be coated, resulting in poor painting.

  In addition, when there are openings at both ends of the cylindrical object, if the powder coating is passed with the openings at both ends open, the passing speed of the powder coating is high, and the powder coating It is difficult to sufficiently adhere to the inner surface of the cylindrical object.

  For this reason, the object to be coated is preheated before passing the powder paint, and the powder paint is melted to adhere to the inner surface of the object to be coated while the powder paint passes. In this case, if the preheating temperature distribution differs depending on the inner surface shape of the object to be coated, there is a problem that the film thickness becomes large and a uniform coating film cannot be obtained.

  In addition, since the powder coating that has passed through the preheated material starts to melt and becomes in a blocking or scaly state, the surface of the coating is liable to generate flaws and the recovered powder contains scaly powder. Due to the mixing, there is a problem in reusing the recovered powder.

  In view of this, the present invention provides a cylindrical object to be coated by uniformly adhering a powder coating to the inner surface of a cylindrical object having a small inner diameter or a cylindrical object having a complicated inner surface shape. It is an object of the present invention to provide a powder coating method for forming a coating film of a powder paint on the inner surface of an object.

  In order to solve the above problems, the present invention provides a cylindrical coating object in a powder coating method for forming a coating film of a powder coating material on the inner surface of a cylindrical object having at least one opening. Fill the cylindrical object to be coated with the electrostatic powder paint from the opening that has been opened and leave the other opening closed, and then fill the powder. The body paint is dropped from the opening to open, and the powder paint that adheres to the inner surface of the object to be coated by electrostatic force is left as a coating film.

  In the cylindrical object to be coated, the powder coating material charged with static electricity can be sprayed from the electrostatic coating gun and filled with the powder coating material.

  When filling powder coating material into a cylindrical object, the powder material may be filled into the cylindrical object while gradually separating from the opening of the cylindrical object to be opened. preferable.

  When the opening of the cylindrical object is closed, it may be closed by a lid member made of an insulating material.

  When the powder coating material filled in the cylindrical object is dropped from the opening that opens, the cylindrical object can be vibrated.

  When filling the cylindrical object to be coated with static electricity, it may be performed while rotating the object to be coated.

  According to this invention, the powder coating material charged with static electricity is filled into the cylindrical object to be coated from the opening to be opened, and then the filled powder coating material is dropped from the opening to be painted, Because the powder coating that adheres to the inner surface of the surface due to electrostatic force is left as a coating film, even if it is a cylindrical object with a small inner diameter or a cylindrical object with a complicated inner surface shape, A powder coating can be uniformly attached.

It is sectional drawing of the socket of the water supply hot water supply piping which is an example of the to-be-painted object of this invention. It is sectional drawing of the state in which the coating film was formed in the inner surface of the socket of the water supply hot-water supply piping which is an example of the to-be-painted object of this invention. (A) (b) (c) is sectional drawing which shows the state which fills the inside of the to-be-coated object of FIG. 1 with a powder coating material. It is sectional drawing which shows the state which removes an internal powder coating after filling the inside of the to-be-coated object of FIG. 1 with a powder coating. It is sectional drawing of the case of the lithium ion battery which is an example of the to-be-coated article of this invention. It is sectional drawing which shows the state before coat | covering the insulating coating film on the inner surface of the case of the lithium ion battery which is an example of the to-be-coated article of this invention. (A) (b) (c) (d) is sectional drawing which shows the state which fills the inside of the to-be-coated object of FIG. 6, and removes powder coating material after that. It is sectional drawing of the stainless steel pipe which is an example of the to-be-painted object of this invention. It is sectional drawing which shows the state which coat | covered the coating film on the inner surface of the stainless steel pipe which is an example of the to-be-coated article of this invention. It is sectional drawing which shows the state which filled the powder coating material into the bottom part of the stainless steel pipe | tube which is an example of the to-be-coated article of this invention. It is sectional drawing which shows the state which filled the powder coating material into the to-be-coated object further from the state of FIG. It is sectional drawing which shows the state which filled the inside of the to-be-coated object further from the state of FIG. 11 with the powder coating material. It is sectional drawing which shows the state which removes an internal powder coating, after filling the inside of the to-be-coated object of FIG. 8 with a powder coating.

  Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view of a socket for a hot water and hot water supply pipe. The socket is formed of a cylindrical body having both ends open, and a thread is formed on the inner surface. In the following, an embodiment in which a polyethylene resin coating film 2 is formed on the inner surface will be described.

  First, as shown to Fig.3 (a), the cylindrical to-be-coated article 1 which both ends open is stood on the upper surface of the earthed metal plate 3, and one opening part is obstruct | occluded.

  A cylindrical masking material 4 is placed on the outer surface of the cylindrical object 1, and an electrostatic coating gun 5 is installed above the cylindrical object 1. A muzzle with an inner diameter of 20 mm is installed at the tip of the electrostatic coating gun 5, and the inner diameter of the cylindrical object 1 is 12 to 20 mm, which is smaller than the diameter of the muzzle of the electrostatic coating gun 5.

  Therefore, since the muzzle of the electrostatic coating gun 5 cannot be inserted into the cylindrical object 1, the opening above the cylindrical object 1 is shown in FIG. 3 (a). Next, the muzzle of the electrostatic coating gun 5 is brought close to the inside of the cylindrical object 1 and the powder paint A is sprayed toward the inside of the cylindrical object 1 so that the powder is applied inside the closed cylindrical object 1. Paint A is deposited.

  Then, as the amount of the powder coating A deposited inside the cylindrical object 1 increases, as shown in FIGS. 3B and 3C, the electrostatic coating above the cylindrical object 1 is applied. The gun 5 is gradually raised, and the inside of the cylindrical object 1 is filled with the powder coating material A as shown in FIG.

  Thereafter, as shown in FIG. 4, the cylindrical masking material 4 and the metal plate 3 which are covered with the outer surface of the cylindrical object 1 filled with the powder coating material A are removed, and the cylindrical object is coated. When vibration is applied to the cylindrical object 1 by a shocker (vibrator) 8 disposed on the side surface of the object 1, the deposited powder falls from the opening below the cylindrical object 1.

  Even if the deposited powder falls from the opening below the cylindrical object 1, the powder coating A is uniformly attached to the inner surface of the cylindrical object 1 with a predetermined thickness by electrostatic force. It has become. Thereafter, the cylindrical object 1 with the powder coating material A attached to the inner surface is baked in a baking furnace to complete the coating.

  The film thickness of the powder coating A attached to the cylindrical object 1 can be adjusted by adjusting the voltage of the electrostatic coating gun 5, but as shown in Table 1, the particles of the powder coating A used This can be done by changing the diameter.

  Table 1 shows the film thickness after baking when four types of modified polyethylene resin powder coatings having an average particle size of 23 μm, 50 μm, 77 μm, and 100 μm were used and the coating was performed 10 times.

  Next, FIG. 5 is a cross-sectional view of a case of a lithium ion battery, which is made of a bottomed cylindrical aluminum material, whose upper surface is open, and from the opening of the inner surface to a height of 1/3 is modified PP (polypropylene). The upper 2/3 from the closed bottom is insulated by the resin coating film 2 and cannot be painted. The upper part of the outer surface of the opening of the case is also insulated by the coating film 2.

  An embodiment in which a cylindrical body made of a bottomed cylindrical aluminum material shown in FIG. 6 is used as an object to be coated 1 and an insulating coating film 2 is formed on the inner surface thereof as shown in FIG. 5 will be described.

  First, as shown in FIG. 7 (a), the cylindrical article 1 with the bottom closed is powdered from the closed bottom to the upper 2/3 with the opening up. In order to prevent the body paint A from adhering, a masking material 4 formed of silicon rubber is filled in the cylindrical object 1 and the electrostatic coating gun 5 is placed in the opening above the cylindrical object 1. The powder paint A is sprayed toward the inside of the cylindrical object 1 by bringing the muzzle close to the inside, and the powder paint A is deposited inside the cylindrical object 1.

  Then, as the accumulation amount of the powder coating A inside the cylindrical object 1 increases, as shown in FIG. 7B, the electrostatic coating gun 5 above the cylindrical object 1 is moved. The inside of the cylindrical object 1 is gradually filled with the powder paint A, and the powder paint A is also attached to the upper part of the outer surface of the opening of the cylindrical object 1.

  Thereafter, as shown in FIG. 7C, when the cylindrical object 1 filled with the powder coating A is turned over, the accumulated powder inside the cylindrical object 1 falls from the opening. . Even if the deposited powder falls from the opening below the cylindrical object 1, the inner surface of the cylindrical object 1 and the upper part of the outer surface of the opening of the object 1 are powdered by electrostatic force. The coating material A is in a state of being uniformly attached with a predetermined thickness. Thereafter, the object to be coated 1 is baked in a baking furnace, and the silicon rubber masking material 4 is removed. As shown in FIG. A case of a lithium ion battery in which the outer peripheral surface of the part is insulated by the coating film 2 is completed.

  FIG. 8 is a cross-sectional view of a stainless steel pipe having two branch pipes 1a and 1b on the lower side and a projecting wall 1c on the inner surface near the upper opening and closed at the lower end. As shown in FIG. 9, an embodiment in which a polyethylene resin coating film 2 is formed on the inner surface will be described.

  First, as shown in FIG. 10, after the openings of the branch pipes 1a and 1b are closed by the lid members 6 and 7, an electrostatic coating gun 5 with a long muzzle is inserted, and a powder is formed below the stainless pipe. The filling of the paint A is started.

  The filling of the powder coating A is started with the stainless steel tube facing sideways, as shown in FIG. 10, with the branch pipe 1a facing down, and the powder paint A is filled to a height at which the branch pipe 1a is filled. Then, as shown in FIG. 11, the stainless steel pipe is rotated so that the branch pipe 1b is at the bottom, and the powder paint A is filled into the branch pipe 1b.

  Thereafter, as shown in FIG. 12, the long muzzle of the electrostatic coating gun 5 is moved toward the opening of the stainless tube so that the inside of the stainless tube is filled with the powder coating A. The powder coating material A is filled inside.

  Thereafter, as shown in FIG. 13, when the lid members 6 and 7 closing the openings of the branch pipes 1a and 1b are removed and the opening of the stainless pipe filled with the powder coating A is directed downward, Deposited powder falls.

  Even if the deposited powder falls from the opening of the stainless steel tube, the powder coating A is uniformly attached to the inner surface of the stainless steel tube with a predetermined thickness by electrostatic force. Thereafter, the coating is completed by baking the stainless steel tube having the powder coating material A adhered to the inner surface in a baking furnace.

1: Object 1a: Branch pipe 1b: Branch pipe 1c: Projection wall 2: Coating film 3: Metal plate 4: Masking material 5: Electrostatic coating gun 6: Lid member 7: Lid member A: Powder paint

Claims (6)

  In a powder coating method for forming a coating film of a powder coating material on an inner surface of a cylindrical object to be coated having at least one opening, another opening leaving at least one opening of the cylindrical object to be coated With the part closed, the cylindrical object to be coated is filled with the powder paint charged with static electricity from the opening to be opened, and then the filled powder paint is dropped from the opening to be painted. A powder coating method characterized in that a powder coating that adheres to the inner surface of an object by electrostatic force is left as a coating film.   2. The powder coating method according to claim 1, wherein the powder coating material charged with static electricity is sprayed from an electrostatic coating gun to fill the cylindrical object to be coated with the powder coating material.   When filling powder paint into a cylindrical object to be coated, the powder paint is filled into the cylindrical object while being gradually separated from the opening of the cylindrical object to be opened. The powder coating method according to claim 2.   The powder coating method according to any one of claims 1 to 3, wherein the opening of the cylindrical object to be coated is closed with a lid member made of an insulating material.   The powder according to any one of claims 1 to 4, wherein the powder is filled with vibration when the powder coating material filled in the cylindrical object is dropped from the opening. Body painting method.   The powder coating method according to any one of claims 1 to 5, wherein the powder coating material charged with static electricity is filled in a cylindrical object to be coated while rotating the object to be coated. .

Images