JP2021062363A - Coating method with use of powdered paint - Google Patents

Abstract

To provide a coating method with use of powdered paint by which an inner surface can be coated with good efficiency and uniformly in a simpler manner in a pipe body comprising two parts having inner surfaces with irregularities of relatively different sizes.SOLUTION: In a coating method for coating an inner surface of a pipe body with powdered paint, the pipe body P comprises a socket 1 provided at one end in a pipe axis X direction, a spigot 2 provided at the other end in the pipe axis X direction, and a straight pipe part 3 which extends along the pipe axis X direction between the socket 1 and the spigot 2. An inner surface 1a of the socket 1 has a relatively larger irregularity compared to an inner surface 2a of the spigot 2 and an inner surface 3a of the straight pipe part 3. This method includes a process in which the inner surface 1a of the socket 1 is coated with a first powdered paint 13p, and a process in which the inner surface 2a of the spigot 2 and the inner surface 3a of the straight pipe part 3 are coated with a second powdered paint 14p. An average particle diameter of the first powdered paint 13p is smaller than an average particle diameter of the second powdered paint 14p.SELECTED DRAWING: Figure 2

Description

The present invention relates to a coating method using a powder coating material.

A pipe body such as a ductile cast iron pipe is used to flow a fluid such as water and sewage. The inner surface of the tube is painted with a powder paint to protect the inner surface. The tube body is required not only to be coated efficiently, but also to have a uniform coating film in order to more reliably protect the inner surface.

For example, a ductile cast iron pipe has a socket that can accept other ductile cast iron pipes and a straight pipe portion that communicates with the socket. The ductile cast iron pipe is connected to the other ductile cast iron pipe by accepting the other ductile cast iron pipe at the socket. A rubber ring or lock ring is provided on the inner surface of the ductile iron pipe socket in order to prevent fluid from leaking at the connecting portion or other ductile cast iron pipes from coming out. The rubber ring or lock ring, etc. Unevenness is formed to provide the above. Therefore, the ductile cast iron pipe is formed so that the unevenness of the inner surface of the receiving port is larger than the unevenness of the inner surface of the straight pipe portion.

When the inner surface of a ductile cast iron pipe as described above is painted by spraying a powder paint, there is a problem that it is difficult to form a coating film having a uniform thickness on the inner surface of a socket having large irregularities. In particular, since the socket accepts other ductile cast iron pipes, the dimensional tolerance of the thickness of the coating film applied is also severely limited. Therefore, as disclosed in Patent Document 1, for example, it has been attempted to form a uniform coating film on the inner surface of a socket having large irregularities by devising the injection shape of the powder coating material.

Japanese Unexamined Patent Publication No. 2003-53220

However, the method of Patent Document 1 requires improvement of the apparatus itself, and also requires complicated work such as optimizing the coating conditions. Therefore, in reality, the inner surface of the socket is not painted with powder paint, but is manually painted by a worker with liquid paint.

The present invention has been made in view of the above problems, and in a pipe body having two portions having inner surfaces having relatively different sizes of unevenness, the inner surface is coated efficiently and uniformly by a simpler method. It is an object of the present invention to provide a coating method using a powder coating material, which is possible.

The coating method of the present invention is a coating method in which the inner surface of a tubular body is coated with a powder paint, and the tubular body is provided at one end in the tubular axis direction and the other end in the tubular axial direction. The socket is provided with a straight pipe portion extending along the pipe axis direction between the socket and the socket, and the inner surface of the socket is the inner surface of the insertion port and the inner surface of the straight pipe portion. The method has a step of painting the inner surface of the socket with the first powder paint, and the inner surface of the insertion port and the inner surface of the straight pipe portion are second. It includes a step of coating with a powder coating material, and is characterized in that the average particle size of the first powder coating material is smaller than the average particle size of the second powder coating material.

Further, it is preferable that the average particle size of the first powder coating material is 20 to 50 μm, and the average particle size of the second powder coating material is 70 to 80 μm.

Further, it is preferable that the step of painting the inner surface of the socket with the first powder coating material includes charging the first powder coating material and electrostatically coating the inner surface of the socket.

Further, the step of painting the inner surface of the socket with the first powder coating material includes painting so that the thickness of the coating film formed on the inner surface of the socket is 150 to 250 μm. In the step of painting the inner surface of the mouth and the inner surface of the straight pipe portion with the second powder paint, the thickness of the coating film formed on the inner surface of the insertion port and the inner surface of the straight pipe portion is 300 μm or more. It is preferable to include painting in.

Further, in the step of painting the inner surface of the socket with the first powder paint, the discharge portion for discharging the first powder paint is directed from the socket to the insertion port along the pipe axis direction. Discharging the first powder coating material from the discharging portion at a first discharging angle with respect to the first direction while moving the first powder coating material relative to the inner surface of the receiving port in the first direction. The discharge portion for discharging the first powder coating material is moved relative to the inner surface of the socket in the second direction from the insertion port to the socket along the pipe axis direction. The first powder coating material is discharged from the discharge unit at a second discharge angle with respect to the second direction, and both the first discharge angle and the second discharge angle are sharp angles. Is preferable.

Further, it is preferable that the first discharge angle is larger than the second discharge angle.

Further, the gel time of the first powder coating material at 170 ° C. is preferably 90 to 250 seconds.

According to the present invention, in a tube body having two portions having inner surfaces having relatively different sizes of unevenness, the inner surface can be coated efficiently and uniformly by a simpler method. A painting method using a paint can be provided.

It is sectional drawing of the exemplary pipe body to which the coating method of this embodiment is applied. It is a schematic diagram which shows the exemplary coating apparatus used in the coating method of this embodiment. It is a figure which shows typically the state which the powder paint is discharged from the 1st ejection part in the exemplary coating apparatus used in the coating method of this embodiment, and (a) is a figure which shows the state which the 1st ejection part is ejected. A state in which the powder coating material is discharged while moving relative to the first direction is shown, and (b) is a state in which the powder coating material is discharged while the first discharging portion moves relative to the second direction. Is shown.

Hereinafter, a coating method using a powder coating material according to an embodiment of the present invention will be described with reference to the accompanying drawings. However, the embodiments shown below are merely examples, and the coating method using the powder coating material of the present invention is not limited to the following embodiments.

The coating method of the present embodiment is a coating method of coating the inner surface of the pipe body with a powder paint. Examples of the pipe body to which the coating method of the present embodiment can be applied include cast iron pipes such as known ductile cast iron pipes. However, the tube body to which the coating method of the present embodiment can be applied is not particularly limited as long as it has the structure of the tube body P described below, and is a tube body formed of another material. It doesn't matter if there is.

As shown in FIG. 1, the pipe body P is formed in a tubular shape with both ends open in the pipe axis X direction, and functions as a flow path through which a fluid such as water and sewage flows. The tubular body P is connected to another tubular body P to form a longer flow path. In the illustrated example, the tube body P is formed in a substantially cylindrical shape in which the tube axis X extends substantially linearly. However, the shape of the tube body P is not particularly limited as long as the fluid can flow inside the tube body P, the tube axis X may be curved, or a tube having another shape such as a substantially square tube shape. It may be formed in a shape.

As shown in FIG. 1, the tubular body P includes a first tubular portion A and a second tubular portion B. As will be described in detail below, the inner surface of the first pipe portion A has a relatively large unevenness as compared with the inner surface of the second pipe portion B. The coating method of the present embodiment can be suitably applied to the tubular body P having at least two portions having inner surfaces having relatively different sizes of irregularities. Explaining the illustrated pipe body P in detail, the pipe body P includes a receiving port 1 provided at one end in the pipe axis X direction, an insertion port 2 provided at the other end in the pipe axis X direction, and a receiving port 1. A straight pipe portion 3 extending along the pipe axis X direction is provided between the pipe and the insertion port 2. In the illustrated example, the receiving port 1 constitutes the first pipe portion A, and the insertion port 2 and the straight pipe portion 3 form the second pipe portion B.

The receiving port 1 is formed in a tubular shape, and is a portion inside which the receiving port 1 receives the insertion port 2 of another tubular body P. When the receiving port 1 of the tubular body P receives the insertion port 2 of the other tubular body P, the tubular body P and the other tubular body P are connected. The receiving port 1 is formed so as to have an internal space larger than the outer shape of the insertion port 2 in order to receive the insertion port 2 of another tube body P. In the illustrated example, the receiving port 1 is formed in a substantially cylindrical shape extending along the pipe axis X direction, and has an inner diameter larger than the outer diameter of the insertion port 2. An opening 1b into which an insertion port 2 of another pipe body P is inserted is provided at one end of the receiving port 1 in the pipe axis X direction, and a straight pipe portion is provided at the other end of the receiving port 1 in the pipe axis X direction. A step portion 1c that defines a boundary with 3 is provided. By providing the step portion 1c at the other end of the receiving port 1, when the insertion port 2 of the other tubular body P is received inside the receiving port 1, the insertion port 2 goes straight beyond the step portion 1c. Invasion into the pipe portion 3 is restricted.

As shown in FIG. 1, the inner surface 1a of the receiving port 1 has a relatively large unevenness as compared with the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. Here, the relatively large unevenness means that, for example, the difference in height between the convex portion and the concave portion is larger than that of the comparison target. In the illustrated example, on the inner surface 1a of the receiving port 1, a rubber ring (not shown) that suppresses fluid leakage to the outside at the connecting portion between the pipe bodies P and P, and another rubber ring (not shown) from the pipe body P and another In order to provide a lock ring (not shown) for suppressing the tube body P from coming out, a plurality of convex portions 1d protruding from the inner surface 1a toward the tube axis X continuously in the circumferential direction of the inner surface 1a, and a plurality of convex portions 1d. A plurality of concave portions 1e formed between the convex portions 1d of the above are provided. The rubber ring and the lock ring are attached to the inner surface 1a of the receiving port 1 by fitting into the recess 1e. The receiving port 1 fits into the insertion port 2 of another tube body P via a rubber ring and a lock ring provided on the inner surface 1a. However, the receiving port 1 may have at least an inner surface 2a of the insertion port 2 and an inner surface 1a having an unevenness relatively larger than that of the inner surface 3a of the straight pipe portion 3, and is limited to the illustrated example. There is no such thing.

The insertion port 2 is a site that is received inside the receiving port 1 of another tube body P. When the insertion port 2 of the tube body P is received by the receiving port 1 of the other tube body P, the tube body P and the other tube body P are connected. The insertion port 2 is formed in a tubular shape, and the inside thereof communicates with the inside of the straight pipe portion 3. In the illustrated example, the insertion port 2 is formed in a substantially cylindrical shape extending along the pipe axis X direction, has an inner diameter substantially the same as the inner diameter of the straight pipe portion 3, and has an inner diameter smaller than the inner diameter of the receiving port 1. have. The insertion port 2 has an uneven inner surface 2a that is relatively smaller than the inner surface 1a of the receiving port 1. In the illustrated example, the inner surface 2a of the insertion port 2 has substantially the same smoothness as the inner surface 3a of the straight pipe portion 3, and is formed to be smoother than the inner surface 1a of the receiving port 1.

One end side of the insertion port 2 communicates with the straight pipe portion 3, and the other end side of the insertion port 2 is provided with an opening 2b. The outer surface of the insertion port 2 is provided with a protrusion 2c that prevents the tube body P from coming out of another tube body P. The protrusion 2c of the insertion port 2 is formed in the socket 1 of the other tubular body P when the tubular body P tries to come out from the other tubular body P when the tubular body P and the other tubular body P are connected. It abuts on a lock ring (not shown) provided on the inner surface 1a to prevent the tubular body P from coming out of another tubular body P.

The straight pipe portion 3 constitutes the main body portion of the pipe body P, and is configured such that a fluid flows inside the receiving port 1 and the insertion port 2. As shown in FIG. 1, the straight pipe portion 3 is formed in a tubular shape, and communicates with the receiving port 1 on one end side and communicates with the insertion port 2 on the other end side. In the illustrated example, the straight pipe portion 3 is formed in a substantially cylindrical shape extending along the pipe axis X direction, has an inner diameter substantially the same as the inner diameter of the insertion port 2, and has an inner diameter smaller than the inner diameter of the receiving port 1. have. The straight pipe portion 3 has an inner surface 3a having irregularities that are relatively smaller than the inner surface 1a of the receiving port 1. In the illustrated example, the inner surface 3a of the straight pipe portion 3 has substantially the same smoothness as the inner surface 2a of the insertion port 2, and is formed to be smoother than the inner surface 1a of the receiving port 1.

Next, the coating apparatus 10 used in the coating method of the present embodiment will be described with reference to FIG. However, the following coating device 10 is an example, and the coating method of this embodiment may be carried out using a known coating device other than the coating device 10.

As shown in FIG. 2, the coating device 10 includes a rotating device 11 that relatively rotates the tubular body P, and a discharging device 12 that discharges powder coating material. The painting device 10 paints the inner surface of the pipe body P by discharging the powder paint toward the inner surface of the pipe body P by the discharge device 12 while the pipe body P is relatively rotated by the rotating device 11. The coating apparatus 10 is a heating apparatus (not shown) such as a gas furnace or an electric furnace for preheating the tubular body P so that the powder coating material adhering to the inner surface of the tubular body P is cured on the inner surface thereof. ) May be provided.

The rotating device 11 supports the tube body P and rotates the tube body P relative to the tube axis X. As shown in FIG. 2, the rotating device 11 includes a rotating roller 11a for relatively rotating the tubular body P around the pipe axis X, a support base 11b for rotatably supporting the rotating roller 11a, and a rotating roller 11a. It is equipped with a drive device (not shown) such as a rotating motor. The rotating device 11 rotates the pipe body P around the pipe axis X over a predetermined range (for example, the entire circumference) while the discharge device 12 discharges the powder coating material toward the inner surface of the pipe body P. Thereby, in the coating apparatus 10, the inner surface of the pipe body P can be coated with the powder coating material over a predetermined range (for example, the total length) along the inner peripheral surface. The speed at which the tubular body P is rotated by the rotating device 11 is not particularly limited, and can be appropriately set according to the required coating film thickness and the like.

In the present embodiment, the coating device 10 is configured to be coated with powder paint along the inner peripheral surface of the tube body P by rotating the tube body P around the tube axis X by the rotating device 11. ing. However, the coating device 10 does not necessarily have to include the rotating device 11, and for the purpose of coating with powder paint along the inner peripheral surface of the pipe body P, for example, the discharge device 12 described later is discharged. The portion may be configured to rotate around the pipe axis X, or the discharge portion may be configured to discharge the powder coating material into a predetermined range in the circumferential direction of the inner surface of the pipe body P.

The discharge device 12 discharges the powder coating material from the inside of the pipe body P toward the inner surface of the pipe body P in order to paint the inner surface of the pipe body P. As shown in FIG. 2, the discharge device 12 includes a first discharge device 13 and a second discharge device 14 that discharge powder coating materials different from each other. The first discharge device 13 and the second discharge device 14 are configured to discharge the first powder coating material 13p and the second powder coating material 14p, respectively. However, the discharge device 12 does not necessarily have to include two discharge devices. For example, one discharge device is configured to alternately discharge the first powder coating material 13p and the second powder coating material 14p. It may be configured so that the same powder coating material is discharged by one or more discharge devices.

The first discharge device 13 is used to paint the inner surface 1a (inner surface of the first pipe portion A) of the receiving port 1 of the pipe body P with the first powder coating material 13p. For that purpose, the first ejection device 13 is configured to eject the first powder coating material 13p from the inside of the receiving port 1 of the tubular body P toward the inner surface 1a of the receiving port 1. As shown in FIG. 2, the first discharge device 13 includes a first discharge portion 13a such as a nozzle that discharges the first powder coating material 13p toward the inner surface 1a of the receiving port 1, and a first discharge device 13. The first powder paint supply pipe 13b such as a lance that supplies the first powder paint 13p to the portion 13a and the first discharge portion 13a along the pipe shaft X direction are connected to the pipe shaft X direction of the receiving port 1. A first drive device 13c that is relatively moved over a predetermined range (for example, the total length from the opening 1b to the step portion 1c) and a first powder coating material 13p are accommodated, and the first powder coating material 13p is first. The powder coating material supply pipe 13b and the first powder coating material supply device 13d for supplying to the first discharge unit 13a are provided. The first discharging device 13 moves the inner surface 1a of the receiving port 1 by the first driving device 13c so that the first discharging portion 13a is relatively moved over a predetermined range in the pipe axis X direction of the receiving port 1. It can be coated with the first powder coating material 13p over a predetermined range in the pipe axis X direction.

As shown in FIGS. 3A and 3B, the first discharging device 13 receives the first discharging portion 13a for discharging the first powder coating material 13p along the pipe axis X direction. A first direction X1 from 1 toward the insertion port 2 (FIG. 3A, also referred to as "outward path") and a second direction X2 from the insertion port 2 toward the socket 1 along the pipe axis X direction (FIG. 3 (a), for example, "outward route"). It may be configured to move relative to the inner surface 1a of the socket 1 in both FIG. 3B, for example, also referred to as “return path”). In this case, the first discharge device 13 moves the first discharge portion 13a relative to the first direction X1 while the first discharge angle θ1 from the first discharge portion 13a to the first direction X1. Can be configured to eject the first powder coating 13p. Further, the first discharge device 13 moves the first discharge portion 13a relative to the second direction X2, and at a second discharge angle θ2 from the first discharge portion 13a to the second direction X2. It may be configured to eject the first powder coating 13p. The first discharge device 13 may paint the same place on the outward route and the return route (reciprocating coating), or may paint different locations on the outward route and the return route (outward route coating, return coating).

The first discharge angle θ1 and the second discharge angle θ2 may be set so that at least the first powder coating material 13p advances toward the inner surface 1a of the socket 1, and is not particularly limited. However, it is preferable that both of them have an acute angle. Since both the first discharge angle θ1 and the second discharge angle θ2 are acute angles, the inner surface 1a of the receiving port 1 having relatively large irregularities can be uniformly painted. For example, if the first discharge angle θ1 and the second discharge angle θ2 are obtuse angles (when the first discharge portion 13a is discharged to the opposite side with respect to the traveling direction), the first powder coating material 13p is discharged. The moving speed of the first discharging portion 13a is subtracted from the speed, and the spraying angle of the first powder coating material 13p becomes close to the direction perpendicular to the inner surface 1a of the receiving port 1, but the first discharging angle θ1 By setting both the second discharge angle θ2 and the second discharge angle θ2 as acute angles, the first powder coating material 13p can be more reliably sprayed along the direction inclined from the direction perpendicular to the inner surface 1a of the socket 1. It is considered that this is because the first powder coating material 13p can easily enter the uneven corner portion of the inner surface 1a of the receiving port 1.

The first discharge angle θ1 and the second discharge angle θ2 may be an acute angle in order to uniformly coat the inner surface 1a of the receiving port 1, and are not particularly limited, but the first discharge angle θ1 is It is preferable that the angle is set so as to be larger than the second discharge angle θ2. Since the first discharge angle θ1 is larger than the second discharge angle θ2, the inner surface 1a of the receiving port 1 can be painted more uniformly. This is because there is a difference in inclination between the side wall on the first direction X1 side and the side wall on the second direction X2 side of the recess 1e existing on the inner surface 1a of the receiving port 1, and the difference in inclination is the discharge angles θ1 and θ2. It is considered that the difference between the above is corresponding and the first powder coating material 13p can enter the corners of the unevenness.

The first discharge angle θ1 may be set to be larger than the second discharge angle θ2 in order to paint the inner surface 1a of the receiving port 1 more uniformly, and is not particularly limited. From the viewpoint of coating the inner surface 1a of the receiving port 1 more uniformly, it is preferably in the range of 60 to 70 °, and more preferably in the range of 60 to 65 °. Further, the first powder coating material 13p may be discharged from the first discharge portion 13a so as to spread at the first spread angle α1 with the first discharge angle θ1 as the center. The first spread angle α1 is not particularly limited, but is preferably smaller than the second spread angle α2, which will be described later, from the viewpoint of coating the inner surface 1a of the socket 1 more uniformly. It is more preferably in the range of ~ 30 °, and even more preferably in the range of 15-25 °.

The second discharge angle θ2 may be set to be smaller than the first discharge angle θ1 in order to paint the inner surface 1a of the receiving port 1 more uniformly, and is not particularly limited. From the viewpoint of coating the inner surface 1a of the receiving port 1 more uniformly, it is preferably in the range of 45 to 60 °, and more preferably in the range of 50 to 55 °. Further, the first powder coating material 13p may be discharged from the first discharge portion 13a so as to spread at the second spread angle α2 about the second discharge angle θ2. The second spread angle α2 is not particularly limited, but is preferably larger than the first spread angle α1 from the viewpoint of coating the inner surface 1a of the socket 1 more uniformly, and is 30 to 50. It is more preferably in the range of °, and even more preferably in the range of 40 to 50 °.

In the example shown in FIGS. 3A and 3B, the first discharge device 13 is shown so that the discharge angle and the spread angle can be changed by one first discharge unit 13a. However, two discharge portions having different discharge angles and spread angles may be provided, and the two discharge portions may be used properly according to the traveling directions X1 and X2.

In the present embodiment, the first discharge device 13 relatively moves the first discharge portion 13a along the pipe axis X direction by the first drive device 13c, so that the pipe on the inner surface 1a of the receiving port 1 It is configured to discharge the first powder coating material 13p over a predetermined range in the axis X direction. However, the first discharge device 13 does not necessarily have to be configured to move the first discharge portion 13a along the pipe axis X direction, and the first discharge device 13 does not necessarily have to be configured to move the first discharge portion 13a along the pipe axis X direction. For the purpose of discharging the powder coating material 13p, for example, the position of the first discharging portion 13a in the pipe axis X direction may be fixed and the pipe body P may be moved along the pipe axis X direction. However, the discharge portion may be provided so as to extend over a predetermined range in the pipe axis X direction.

The first discharge device 13 is a known electrostatic coating device (for example, a triboelectric coating device) for charging the first powder coating material 13p and coating the inner surface 1a of the socket 1 with electrostatic powder. (Not shown) may be provided. The electrostatic coating device includes, for example, a charging device (for example, a coating gun) for charging the first powder coating material 13p. The first powder coating material 13p is charged by a charging device and adheres to the inner surface 1a of the socket 1 by an electrostatic force. The first discharge device 13 can coat the inner surface 1a of the receiving port 1 more efficiently and more uniformly by performing electrostatic powder coating with the first powder coating film 13p.

The second discharge device 14 is used to paint the inner surface 2a of the insertion port 2 of the pipe body P and the inner surface 3a of the straight pipe portion 3 (inner surface of the second pipe portion B) with the second powder coating material 14p. Be done. For that purpose, the second discharge device 14 is a second powder from the inside of the insertion port 2 and the straight pipe portion 3 of the pipe body P toward the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. It is configured to discharge body paint 14p. As shown in FIG. 2, the second discharge device 14 is a second discharge device such as a nozzle that discharges the second powder coating material 14p toward the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. The portion 14a, the second powder paint supply pipe 14b such as a lance for supplying the second powder paint 14p to the second discharge portion 14a, and the second discharge portion 14a along the pipe axis X direction are inserted. The second drive device 14c that moves the mouth 2 and the straight pipe portion 3 relative to each other over a predetermined range (for example, the total length from the opening 2b to the step portion 1c) in the pipe axis X direction, and the second powder coating material 14p. It is provided with a second powder coating material supply device 14d for accommodating and supplying the second powder coating material 14p to the second powder coating material supply pipe 14b and the second discharge portion 14a. The second discharge device 14 is inserted by the second drive device 14c so that the second discharge portion 14a is relatively moved over a predetermined range in the pipe axis X direction of the insertion port 2 and the straight pipe portion 3. The inner surface 2a of 2 and the inner surface 3a of the straight pipe portion 3 can be coated with the second powder coating material 14p over a predetermined range in the pipe axis X direction.

Similar to the first discharge device 13, the second discharge device 14 inserts the second discharge portion 14a for discharging the second powder coating material 14p from the receiving port 1 to the insertion port 2 along the pipe axis X direction. Insertion in both the first direction X1 toward (see FIG. 2) and the second direction X2 (see FIG. 2) from the insertion port 2 toward the socket 1 along the tube axis X direction. It may be configured to move relative to the inner surface 2a of the mouth 2 and the inner surface 3a of the straight pipe portion 3. In this case, the second discharge device 14 moves the second discharge portion 14a relative to each of the first direction X1 and the second direction X2, and the second discharge portion 14a to the second powder coating material. It may be configured to discharge 14p. The second discharge device 14 may paint the same place on the outward path (first direction X1) and the return path (second direction X2) (reciprocating painting), or paint different places on the outward path and the return path. It may be (outward painting, inbound painting). The discharge angle and spread angle for discharging the second powder coating material 14p from the second discharge portion 14a are such that the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 are coated with the second powder coating material 14p. As long as it can be done, it is not particularly limited, and it may be the same as or different from the discharge angle and the spread angle in the first discharge device 13.

In the present embodiment, the second discharge device 14 moves the second discharge portion 14a along the pipe axis X direction by the second drive device 14c, whereby the inner surface 2a of the insertion port 2 and the straight pipe are used. The second powder coating material 14p is discharged over a predetermined range of the inner surface 3a of the portion 3 in the pipe axis X direction. However, the second discharge device 14 does not necessarily have to be configured to move the second discharge portion 14a along the pipe axis X direction, and the second discharge device 14 does not necessarily have to be configured to move the second discharge portion 14a along the pipe axis X direction. For the purpose of discharging the powder coating material 14p, for example, the position of the second discharging portion 14a in the pipe axis X direction may be fixed and the pipe body P may be moved along the pipe axis X direction. However, the discharge portion may be provided so as to extend over a predetermined range in the pipe axis X direction.

Here, the powder coating means a powder coating, and more specifically, a powder coating containing only a coating film-forming component without containing an organic solvent or water in the coating. .. The first powder coating material 13p and the second powder coating material 14p used in the coating method of the present embodiment are not particularly limited, and for example, after adhering to the inner surface of the tubular body P, heat is applied. A known epoxy resin powder coating material having a property of being cured by the above can be used. As for the first powder coating material 13p and the second powder coating material 14p, as will be described in detail later, if the average particle size of the first powder coating material 13p is smaller than the average particle size of the second powder coating material 14p. The material is not particularly limited, and may be formed of the same material or different materials.

For example, the epoxy resin powder coating material contains an epoxy resin that is solid at room temperature, a curing agent for the epoxy resin, and various pigments, additives, and the like, if necessary.

Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin and other bisphenol type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, novolak type epoxy resin, cyclic aliphatic epoxy resin and glycidylamine type. Examples thereof include resins, heterocyclic epoxy resins, and polyfunctional epoxy resins. Among them, from the viewpoint of safety, a bisphenol F type epoxy resin synthesized from bisphenol F and epichlorohydrin is preferably adopted.

The curing agent is not particularly limited as long as it has the property of curing the epoxy resin, but is not particularly limited, but is an amine compound, an amide compound, an imidazole compound, an imidazoline compound, a hydrazide compound, and an acid anhydride. , Phenolic resins and derivatives thereof and the like. Among them, from the viewpoint of corrosion resistance, flexibility, adhesion and strength of the coating film, modified aromatic amine adduct mainly composed of aniline, imidazole / imidazoline compound mainly composed of ethylenediamine and benzonitrile, hydrazine and dibase are used. Hydrazide, which is the main component, and acid anhydride, which is mainly composed of trimellitic acid and ethylene glycol, are preferably used.

Among the pigments, coloring pigments include, for example, carbon black, titanium oxide, iron oxide, yellow iron oxide and the like. Among the pigments, the extender pigment includes, for example, barium sulfate, silica, calcium carbonate and the like.

The first powder coating material 13p and the second powder coating material 14p are prepared so that the average particle size of the first powder coating material 13p is smaller than the average particle size of the second powder coating material 14p. That is, in order to paint the inner surface 1a (inner surface of the first pipe portion A) of the socket 1 having relatively large irregularities, the first powder coating material 13p having a relatively small average particle size is used, and is relative to each other. A second powder coating material 14p having a relatively large average particle size for coating the inner surface 2a of the insertion port 2 having small irregularities and the inner surface 3a of the straight pipe portion 3 (inner surface of the second pipe portion B). Is used. By using the first powder coating material 13p having a relatively small average particle size for coating the inner surface 1a of the socket 1 having a relatively large unevenness, the inner surface 1a of the socket 1 having a relatively large unevenness can be made uniform. Can be painted. This is because when the relatively small first powder coating material 13p is discharged from the ejection device, the first powder coating material 13p is dispersed relatively uniformly and easily penetrates into the corners of the unevenness. It is considered to be. On the other hand, by using the second powder coating material 14p having a relatively large average particle size for coating the inner surface 2a of the insertion port 2 having relatively small irregularities and the inner surface 3a of the straight pipe portion 3, relatively The inner surface 2a of the insertion port 2 having small irregularities and the inner surface 3a of the straight pipe portion 3 can be efficiently painted. This is because when the relatively large second powder coating material 14p is ejected from the ejection device, the second powder coating material 14p is relatively straight on the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. Since it is suppressed from floating inside the tubular body P and flowing out toward the openings 1b and 2b on both sides of the tubular body P, the inner surface 2a and the straight pipe portion of the insertion port 2 have a good yield. It is considered that this is due to adhesion to the inner surface 3a of 3.

The term "particle size" of the powder coating material is used in the meaning of a commonly used term. For example, a sphere when the particles constituting the powder coating material are assumed to have the same volume as the particles. Means the diameter of. The average particle size of the powder coating material can be measured by a known particle size measuring device.

The sizes of the first powder coating material 13p and the second powder coating material 14p are particularly limited as long as the average particle size of the first powder coating material 13p is smaller than the average particle size of the second powder coating material 14p. It is not done, and it can be appropriately selected according to the size of the unevenness on the inner surface of the tubular body P to be coated. Among them, for example, the average particle size of the first powder coating material 13p is preferably 20 to 50 μm. By setting the average particle size of the first powder coating material 13p to 20 μm or more, the inner surface 1a of the socket 1 can be coated more efficiently. Further, by setting the average particle size of the first powder coating material 13p to 50 μm or less, the inner surface 1a of the socket 1 can be coated more uniformly. Further, for example, the average particle size of the second powder coating material 14p is preferably 70 to 80 μm. By setting the average particle size of the second powder coating material 14p to 70 μm or more, the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 can be coated more efficiently. Further, by setting the average particle size of the second powder coating material 14p to 80 μm or less, the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 can be coated more uniformly.

The first powder coating material 13p may have a property of being cured by heat after adhering to the inner surface of the tubular body P, and is not particularly limited, but has a gel time of 90 to 250 at 170 ° C. It is preferably prepared to be within the range of seconds. When the gel time of the first powder coating material 13p is 90 seconds or more, the inner surface 1a of the socket 1 can be uniformly coated. This is because the time required for the first powder coating material 13p to cure becomes longer, so that the first powder coating material 13p is applied to the inner surface 1a of the socket 1 before the first powder coating material 13p is cured. It is considered that this is because it becomes easier to enter the corners of the unevenness of. From the same viewpoint, the gel time of the first powder coating material 13p is more preferably 135 seconds or more, and even more preferably 180 seconds or more. Further, when the gel time of the first powder coating material 13p is 250 seconds or less, the coating efficiency is improved and the uniformity of the coating film is improved. From the same viewpoint, the gel time of the first powder coating material 13p is more preferably 235 seconds or less, and even more preferably 220 seconds or less.

The second powder coating material 14p may have a property of being cured by heat after adhering to the inner surface of the tubular body P, and is not particularly limited, but has a gel time of 50 to 250 at 170 ° C. It is preferably prepared to be within the range of seconds. When the gel time of the second powder coating material 14p is within the range of 50 to 250 seconds, the coating efficiency is improved and the uniformity of the coating film is improved. From the same viewpoint, the gel time of the second powder coating material 14p is more preferably 70 to 235 seconds or less, and even more preferably 90 to 220 seconds or less.

The gel time generally means the time after the specified dose of the powder coating material is melted until it cannot be deformed under the specified conditions. For gel time, for example, 2 g of powder paint is placed on a hot plate heated to 170 ° C and melted, and at this time, a part of the paint is pulled up by 10 cm using a metal rod, the stringing state is confirmed, and the paint is applied. It can be set to the time when the thread can be cut in 10 cm or less without pulling the thread. The gel time can be controlled by the type and amount of the curing agent, the degree of polymerization of the epoxy resin, and the like.

As shown above, in the coating apparatus 10 of the present embodiment, the first powder coating material 13p having a relatively small average particle size is used for coating the inner surface 1a of the socket 1 having relatively large irregularities, and is relative to the coating apparatus 10. By using a second powder coating material 14p having a relatively large average particle size for coating the inner surface 2a of the insertion port 2 having small irregularities and the inner surface 3a of the straight pipe portion 3, the inner surface of the tubular body P can be efficiently coated. Also, the inner surface can be painted uniformly. Further, by adjusting the discharge angle of the powder coating material as described above and / or by adjusting the gel time of the powder coating material as described above, the inner surface of the tubular body P can be made more efficient and more uniform. The inner surface can be painted. For the purpose of efficiently and uniformly coating the inner surface of the tubular body P, the average particle size of the first powder coating material 13p is larger than the average particle size of the second powder coating material 14p. Not only by making it smaller, for example, by adjusting the discharge angle of the powder coating material as described above regardless of the difference in the average particle size of the first powder coating material 13p and the second powder coating material 14p. And / or, by adjusting the gel time of the powder coating material as described above, the inner surface of the tubular body P can be efficiently and uniformly coated.

Next, a coating method using the powder coating material of the present embodiment will be described. Hereinafter, the coating method of the present embodiment will be described by taking as an example a method of coating the inner surface of the pipe body P using the coating apparatus 10 described above, but the coating method of the present invention has the same effect as the following. If it is possible to achieve the effect, it may be carried out using a coating device having another structure. Further, although a plurality of steps and procedures will be described below, the steps and procedures may be carried out in an order different from the order of the explanations, and some steps and procedures may be carried out at the same time.

As shown in FIG. 2, the coating method of the present embodiment includes a step of coating the inner surface 1a of the receiving port 1 (inner surface of the first pipe portion A) with the first powder coating material 13p, and the insertion port 2. It includes a step of painting the inner surface 2a and the inner surface 3a of the straight pipe portion 3 (the inner surface of the second pipe portion B) with the second powder coating material 14p.

In the step of painting the inner surface 1a of the receiving port 1 with the first powder coating material 13p, first, the tubular body P is heated to a predetermined temperature. The heating temperature of the tubular body P is the temperature at which the first powder coating material 13p is cured through the heat transferred when the first powder coating material 13p comes into contact with or adheres to the inner surface 1a of the socket 1 (for example,). It is set to 150 ° C. or higher). In the present embodiment, the tube body P preheated by the heating device is mounted on the rotating device 11. However, the tubular body P may be heated when at least the first powder coating material 13p comes into contact with or adheres to the inner surface 1a of the socket 1, for example, the tubular body P is heated after being mounted on the rotating device 11. May be done. Further, the timing of heating the pipe body P in this step is to heat the pipe body P in the step of painting the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 with the second powder coating material 14p, which will be described in detail later. It may be the same as the timing.

Next, the first powder coating material 13p is applied to a predetermined range (for example, the total length) in the circumferential direction of the inner surface 1a of the receiving port 1 of the pipe body P and a predetermined range (for example, from the opening 1b to the step portion 1c) in the pipe axis X direction. It is sprayed toward (the total length of). In the present embodiment, the first powder coating material 13p is sprayed onto the inner surface 1a of the receiving port 1 by being discharged from the inside of the receiving port 1 toward the inner surface 1a of the receiving port 1 by the first discharging device 13. Be done. At this time, since the tubular body P is preheated to a predetermined temperature, the first powder coating material 13p that comes into contact with or adheres to the inner surface 1a of the receiving port 1 is placed on the inner surface 1a of the receiving port 1 through the transferred heat. And is deposited on the inner surface 1a of the socket 1. When the first powder coating material 13p is discharged by the first discharging device 13, the tubular body P is relatively rotated around the pipe axis X by the rotating device 11, so that the first powder coating material 13p is produced. It is deposited over a predetermined range in the circumferential direction of the inner surface 1a of the receiving port 1. Further, the first discharge portion 13a of the first discharge device 13 is relatively moved along the pipe axis X direction of the receiving port 1, so that the first powder coating material 13p is transferred to the inner surface 1a of the receiving port 1. It is deposited over a predetermined range in the X direction of the tube axis.

The discharge speed and the discharge amount of the first powder coating material 13p to be discharged toward the inner surface 1a of the receiving port 1 of the tubular body P are not particularly limited, and are appropriately set according to the required coating film thickness. can do. The relative rotation speed of the tubular body P and the relative movement speed of the first discharge portion 13a of the first discharge device 13 are also not particularly limited and can be appropriately set according to the required film thickness.

In the step of painting the inner surface 1a of the receiving port 1 with the first powder coating material 13p, as shown in FIGS. 3A and 3B, the first discharging portion for discharging the first powder coating material 13p While moving 13a relative to the inner surface 1a of the receiving port 1 in the first direction X1 from the receiving port 1 toward the insertion port 2 along the pipe axis X direction, the first discharging portion 13a to the first Discharge the powder coating material 13p at the first discharge angle θ1 with respect to the first direction X1 and the first discharging portion 13a for discharging the first powder coating material 13p along the pipe axis X direction. The first powder coating material 13p is moved from the first ejection portion 13a to the second direction X2 while moving relative to the inner surface 1a of the receiving port 1 in the second direction X2 from the insertion port 2 toward the receiving port 1. However, it may include discharging at the second discharge angle θ2. At this time, the same place may be painted on the outward route (first direction X1) and the return route (second direction X2) (reciprocating painting), or different places may be painted on the outward route and the return route (outward route). Painting, return painting).

As described above, it is preferable that both the first discharge angle θ1 and the second discharge angle θ2 are acute angles. Since both the first discharge angle θ1 and the second discharge angle θ2 are acute angles, the inner surface 1a of the receiving port 1 having relatively large irregularities can be painted more uniformly. The first discharge angle θ1 and the second discharge angle θ2 are preferably set so that the first discharge angle θ1 is larger than the second discharge angle θ2. Since the first discharge angle θ1 is larger than the second discharge angle θ2, the inner surface 1a of the receiving port 1 having relatively large irregularities can be painted more uniformly.

As described above, the first discharge angle θ1 is preferably in the range of 60 to 70 °, preferably in the range of 60 to 65 °, from the viewpoint of coating the inner surface 1a of the receiving port 1 more uniformly. Is more preferable. Further, when the first powder coating material 13p is discharged, the first spread angle α1 centered on the first discharge angle θ1 is from the viewpoint of coating the inner surface 1a of the socket 1 more uniformly. It is preferably smaller than the second spread angle α2, more preferably in the range of 10 to 30 °, and even more preferably in the range of 15 to 25 °.

As described above, the second discharge angle θ2 is preferably in the range of 45 to 60 °, preferably in the range of 50 to 55 °, from the viewpoint of coating the inner surface 1a of the receiving port 1 more uniformly. Is more preferable. Further, when the first powder coating material 13p is discharged, the second spread angle α2 centered on the second discharge angle θ2 is from the viewpoint of painting the inner surface 1a of the socket 1 more uniformly. It is preferably larger than the first spread angle α1, more preferably in the range of 30 to 50 °, and even more preferably in the range of 40 to 50 °.

In the present embodiment, the pipe body P is rotated around the pipe axis X, and the first discharge portion 13a of the first discharge device 13 is moved along the pipe axis X direction to obtain the first powder. The paint 13p is deposited over a predetermined range in the circumferential direction of the inner surface 1a of the receiving port 1 and in the pipe axis X direction. However, the present embodiment is not limited to this, and the first discharge portion 13a of the first discharge device 13 is rotated around the pipe axis X, and the pipe body P is moved along the pipe axis X direction. By another method, the first powder coating material 13p may be deposited over a predetermined range in the circumferential direction of the inner surface 1a of the receiving port 1 and the pipe axis X direction. Further, the first powder coating material 13p may be deposited on at least a part of the inner surface 1a of the socket 1, and for example, the first powder coating material 13p may be deposited on a portion other than the portion on which the first powder coating material 13p is deposited. Other powder coating materials different from the powder coating material 13p may be deposited.

Finally, the tubular body P is cooled by natural cooling or the like, and the painting of the inner surface 1a of the receiving port 1 is completed. The timing for cooling the pipe body P in this step is to cool the pipe body P in the step of painting the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 with the second powder coating material 14p, which will be described in detail later. It may be the same as the timing.

Here, as described above, the average particle size of the first powder coating material 13p is smaller than the average particle size of the second powder coating material 14p. That is, in the coating method of the present embodiment, in order to coat the inner surface 1a (inner surface of the first pipe portion A) of the receiving port 1 having a relatively large unevenness, the first powder having a relatively small average particle size is used. Body paint 13p is used. By using the first powder coating material 13p having a relatively small average particle size for coating the inner surface 1a of the socket 1 having a relatively large unevenness, the second powder coating material 14p having a relatively large average particle size is used. It is possible to paint the inner surface 1a of the receiving port 1 having a relatively large unevenness with a uniform thickness as compared with the case of using. This is because when the relatively small first powder coating material 13p is discharged from the first discharging device 13, the first powder coating material 13p is relatively uniformly dispersed and penetrates into the corners of the unevenness. It is thought that this is due to the ease of use. By coating the inner surface 1a of the receiving port 1 with the first powder coating material 13p, the thickness of the formed coating film becomes uniform, and the inner surface 1a of the receiving port 1 can be effectively protected. Further, since the receiving port 1 is fitted with the insertion port 2 of another tube body P, high dimensional accuracy is required for the inner diameter of the receiving port 1 with respect to the insertion port 2. By making the thickness of the coating film formed on the inner surface 1a of the receiving port 1 uniform, the required high dimensional accuracy can be satisfied.

The size of the first powder coating material 13p is not particularly limited as long as the average particle size of the first powder coating material 13p is smaller than the average particle size of the second powder coating material 14p. It can be appropriately selected according to the size of the unevenness of the inner surface 1a of 1. Among them, for example, the average particle size of the first powder coating material 13p is preferably 20 to 50 μm. By setting the average particle size of the first powder coating material 13p to 20 μm or more, the inner surface 1a of the socket 1 can be coated more efficiently. From such a viewpoint, the average particle size of the first powder coating material 13p is more preferably 34 μm or more, and even more preferably 38 μm or more. Further, by setting the average particle size of the first powder coating material 13p to 50 μm or less, the inner surface 1a of the socket 1 can be coated more uniformly. From such a viewpoint, the average particle size of the first powder coating material 13p is more preferably 46 μm or less, and even more preferably 42 μm or less.

As described above, the first powder coating material 13p is not particularly limited, but is preferably prepared so that the gel time at 170 ° C. is within the range of 90 to 250 seconds. When the gel time of the first powder coating material 13p is 90 seconds or more, the inner surface 1a of the socket 1 can be uniformly coated. From the same viewpoint, the gel time of the first powder coating material 13p is more preferably 135 seconds or more, and even more preferably 180 seconds or more. Further, when the gel time of the first powder coating material 13p is 250 seconds or less, the coating efficiency is improved and the uniformity of the coating film is improved. From the same viewpoint, the gel time of the first powder coating material 13p is more preferably 235 seconds or less, and even more preferably 220 seconds or less.

The thickness of the coating film formed by the step of painting the inner surface 1a of the receiving port 1 with the first powder coating material 13p is not particularly limited as long as it can protect the inner surface 1a of the receiving port 1. Will not be done. Among them, by setting the thickness of the coating film to 150 μm or more, the inner surface 1a of the socket 1 can be protected more reliably.

The step of painting the inner surface 1a of the receiving port 1 with the first powder coating material 13p may include charging the first powder coating material 13p and electrostatically coating the inner surface 1a of the receiving port 1. In the present embodiment, the first powder coating material 13p is negatively charged by a high voltage (for example, 40,000 to 80,000 volts) generated by the charging device of the electrostatic coating device, and the inner surface of the socket 1 is charged by the electrostatic force. It is attached to 1a. By using electrostatic coating when painting the inner surface 1a of the receiving port 1, the inner surface 1a of the receiving port 1 can be painted more efficiently and more uniformly.

In the step of painting the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 with the second powder coating material 14p, the pipe body P is first heated to a predetermined temperature. The heating temperature of the tubular body P is the second powder coating material through the heat transferred when the second powder coating material 14p comes into contact with or adheres to the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. The temperature at which 14p cures (for example, 150 ° C. or higher) is set. In the present embodiment, the tube body P preheated by the heating device is mounted on the rotating device 11. However, the tubular body P may be heated when at least the second powder coating material 14p comes into contact with or adheres to the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3, for example, the tubular body P rotates. It may be heated after being mounted on the device 11.

Next, the second powder coating material 14p is applied to a predetermined range (for example, the total length) in the circumferential direction of the inner surface 2a of the insertion port 2 of the pipe body P and the inner surface 3a of the straight pipe portion 3 and a predetermined range in the pipe axis X direction (for example). It is sprayed toward the opening 2b to the step 1c). In the present embodiment, the second powder coating material 14p is discharged from the inside of the insertion port 2 and the straight pipe portion 3 toward the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 by the second discharge device 14. By doing so, it is sprayed on the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. At this time, since the pipe body P is preheated to a predetermined temperature, the second powder coating material 14p that comes into contact with or adheres to the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 is transferred heat. Through, it is hardened on the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3, and is deposited on the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. When the second powder coating material 14p is discharged by the second discharging device 14, the tubular body P is relatively rotated around the pipe axis X by the rotating device 11, so that the second powder coating material 14p is discharged. It is deposited over a predetermined range in the circumferential direction of the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. Further, the second discharge portion 14a of the second discharge device 14 is relatively moved along the pipe axis X direction of the insertion port 2 and the straight pipe portion 3, so that the first powder coating material 13p is inserted into the insertion port. The inner surface 2a of 2 and the inner surface 3a of the straight pipe portion 3 are deposited over a predetermined range in the pipe axis X direction.

The discharge rate and discharge amount of the second powder coating material 14p to be discharged toward the inner surface 2a of the insertion port 2 of the pipe body P and the inner surface 3a of the straight pipe portion 3 are not particularly limited, and the required coating film is not particularly limited. It can be set as appropriate according to the thickness of. The relative rotation speed of the tubular body P and the relative movement speed of the second discharge portion 14a of the second discharge device 14 are also not particularly limited and can be appropriately set according to the required film thickness.

The step of painting the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 with the second powder paint 14p is the same as the step of painting the inner surface 1a of the socket 1 with the first powder paint 13p. It may include discharging the second powder coating material 14p from the second discharging portion 14a while moving the second discharging portion 14a relative to each of the first direction X1 and the second direction X2. .. At this time, the same place may be painted on the outward route (first direction X1) and the return route (second direction X2) (reciprocating painting), or different places may be painted on the outward route and the return route (outward route). Painting, return painting). Further, the ejection angle and the spreading angle for ejecting the second powder coating material 14p from the second ejection portion 14a are not particularly limited, and the first powder coating material 13p is ejected from the first ejection portion 13a. It may be the same as or different from the discharge angle and the spread angle at the time of processing.

In the present embodiment, the pipe body P is rotated around the pipe axis X, and the second discharge portion 14a of the second discharge device 14 is moved along the pipe axis X direction to obtain the second powder. The paint 14p is deposited over a predetermined range in the circumferential direction and the pipe axis X direction of the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. However, the present embodiment is not limited to this, and the second discharge portion 14a of the second discharge device 14 is rotated around the pipe axis X, and the pipe body P is moved along the pipe axis X direction. By another method, the second powder coating material 14p may be deposited over a predetermined range in the circumferential direction of the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 and the pipe axis X direction. Further, the second powder coating material 14p may be deposited on at least a part of the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3, for example, a portion where the second powder coating material 14p is deposited. In a portion other than the second powder coating material 14p, another powder coating material different from that of the second powder coating material 14p may be deposited.

Finally, the pipe body P is cooled by natural cooling or the like, and the painting of the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 is completed.

Here, as described above, the average particle size of the second powder coating material 14p is larger than the average particle size of the first powder coating material 13p. That is, in order to coat the inner surface 2a of the insertion port 2 having relatively small irregularities and the inner surface 3a of the straight pipe portion 3 (inner surface of the second pipe portion B), the second powder having a relatively large average particle size Body paint 14p is used. By using the second powder coating material 14p having a relatively large average particle size for coating the inner surface 2a of the insertion port 2 having relatively small irregularities and the inner surface 3a of the straight pipe portion 3, the average particle size is relatively small. Compared with the case of using the first powder coating material 13p, the inner surface 2a of the insertion port 2 having relatively small irregularities and the inner surface 3a of the straight pipe portion 3 can be efficiently coated. This is because when the relatively large second powder coating material 14p is discharged from the second discharging device 14, the second powder coating material 14p is relatively straight on the inner surface 2a of the insertion port 2 and the straight pipe portion. Since it faces the inner surface 3a of 3, it is suppressed that it floats inside the tube P and flows out toward the openings 1b and 2b on both sides of the tube P, and the yield is good. It is considered that this is due to the adhesion to the inner surface 3a of the straight pipe portion 3.

The size of the second powder coating material 14p is not particularly limited as long as the average particle size of the second powder coating material 14p is larger than the average particle size of the first powder coating material 13p. It can be appropriately selected according to the size of the unevenness of the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3. Among them, for example, the average particle size of the second powder coating material 14p is preferably 70 to 80 μm. By setting the average particle size of the second powder coating material 14p to 70 μm or more, the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 can be coated more efficiently. From such a viewpoint, the average particle size of the second powder coating material 14p is more preferably 72 μm or more, and even more preferably 74 μm or more. Further, by setting the average particle size of the second powder coating material 14p to 80 μm or less, the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 can be coated more uniformly. From such a viewpoint, the average particle size of the second powder coating material 14p is more preferably 78 μm or less, and even more preferably 76 μm or less.

The thickness of the coating film formed by the step of painting the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 with the second powder coating material 14p is the inner surface of the inner surface 2a of the insertion port 2 and the inner surface of the straight pipe portion 3. The thickness is not particularly limited as long as it can protect 3a. Among them, by setting the thickness of the coating film to 300 μm or more, the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3 can be more reliably protected.

As described above, the second powder coating material 14p is not particularly limited, but is preferably prepared so that the gel time at 170 ° C. is within the range of 50 to 250 seconds. When the gel time of the second powder coating material 14p is within the range of 50 to 250 seconds, the coating efficiency is improved and the uniformity of the coating film is improved. From the same viewpoint, the gel time of the second powder coating material 14p is more preferably 70 to 235 seconds or less, and even more preferably 90 to 220 seconds or less.

As described above, in the coating method of the present embodiment, the inner surface having relatively large irregularities (inner surface 1a of the socket 1) is coated with the first powder coating material 13p having a relatively small average particle size. The step of coating the inner surface having relatively small irregularities (the inner surface 2a of the insertion port 2 and the inner surface 3a of the straight pipe portion 3) with the second powder coating material 14p having a relatively large average particle size. Includes. As a result, in the tubular body P having two portions having inner surfaces having relatively different sizes of unevenness, the inner surface can be efficiently and uniformly painted by a simpler method.

Further, in the coating method of the present embodiment, the step of additionally or alternatively coating the inner surface (inner surface 1a of the socket 1) having relatively large irregularities is a step of coating the discharge portion for discharging the powder coating material. While moving relative to the first direction X1, the powder coating material is discharged from the discharging portion at a sharp angle with respect to the first direction X1, and the discharging portion for discharging the powder coating material is relatively moved to the second direction X2. It may include discharging the powder coating material from the discharging portion at a sharp angle with respect to the second direction X2. As a result, in the tubular body P having two portions having inner surfaces having relatively different sizes of unevenness, the inner surface can be efficiently and uniformly painted by a simpler method.

Further, in the coating method of the present embodiment, the powder coating material for additionally or alternativeally coating the inner surface (inner surface 1a of the socket 1) having relatively large irregularities has a gel time at 170 ° C. It may be prepared to be in the range of 90 to 250 seconds. As a result, in the tubular body P having two portions having inner surfaces having relatively different sizes of unevenness, the inner surface can be efficiently and uniformly painted by a simpler method.

1 Receptacle 1a Inner surface of the socket 1b Opening 1c Step 1d Convex 1e Concave 2 Insertion 2a Inner surface of the insertion 2b Opening 2c Protrusion 3 Straight pipe 3a Inner surface of the straight pipe 10 Painting device 11 Rotating device 11a Rotation Roller 11b Support base 12 Discharge device 13 First discharge device 13a First discharge part 13b First powder paint supply pipe 13c First drive device 13d First powder paint supply device 13p First powder paint 14 Second discharge device 14a Second discharge part 14b Second powder paint supply pipe 14c Second drive device 14d Second powder paint supply device 14p Second powder paint A First pipe part B 2nd pipe part P pipe body X pipe shaft X1 1st direction X2 2nd direction α1 1st spread angle α2 2nd spread angle θ1 1st discharge angle θ2 2nd discharge angle

Claims (6)

It is a painting method that paints the inner surface of the tube with powder paint.
The pipe body extends along the pipe axis direction between a receiving port provided at one end in the pipe axis direction, an insertion port provided at the other end in the pipe axis direction, and the receiving port and the insertion port. Equipped with a straight pipe part,
The inner surface of the receiving port has a relatively large unevenness as compared with the inner surface of the insertion port and the inner surface of the straight pipe portion.
The above method
The step of painting the inner surface of the socket with the first powder paint and
Including a step of painting the inner surface of the insertion port and the inner surface of the straight pipe portion with a second powder coating material.
The average particle size of the first powder coating material is smaller than the average particle size of the second powder coating material.
Painting method. The average particle size of the first powder coating material is 20 to 50 μm.
The average particle size of the second powder coating material is 70 to 80 μm.
The coating method according to claim 1. The step of painting the inner surface of the socket with the first powder coating material comprises charging the first powder coating material and electrostatically coating the inner surface of the socket.
The coating method according to claim 1 or 2. The step of painting the inner surface of the socket with the first powder paint is
The discharge portion for discharging the first powder coating material is moved relative to the inner surface of the socket in the first direction from the socket to the insertion port along the pipe axis direction. Discharging the first powder coating material from the discharge unit at the first discharge angle with respect to the first direction,
The discharge portion for discharging the first powder coating material is moved relative to the inner surface of the socket in the second direction from the insertion port to the socket along the pipe axis direction. Including discharging the first powder coating material from the discharging portion at a second discharging angle with respect to the second direction.
Both the first discharge angle and the second discharge angle are acute angles.
The coating method according to any one of claims 1 to 3. The first discharge angle is larger than the second discharge angle.
The coating method according to claim 4. The gel time of the first powder coating material at 170 ° C. is 90 to 250 seconds.
The coating method according to any one of claims 1 to 5.

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