JP4104204B2 - Coating method and coating equipment for deformed pipe inside and outside - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in the inner and outer surface coating of a deformed pipe forming a water pipe.
[0002]
[Prior art]
The individual pipes that form pipes for water supply etc. are mainly made of ductile cast iron, but the pipes are usually buried in the ground, so the corrosive atmosphere such as the surrounding groundwater on the outer surface of the pipes Need to protect the surface from. In addition, since pipes are loaded and unloaded at the time of storage and transportation before arrival at the laying site, external coating is required so as not to damage each other's outer surface due to collision and abrasion between the pipes. On the other hand, the inner surface of the pipe is constantly in contact with the drinking water that passes through it, so it is necessary to have an inner surface coating that is sufficiently durable in contact with water and that does not cause red rust and reach the customer. It becomes. Thus, as a coating for pipes, it goes without saying that adhesion and corrosion resistance to the metal base of the pipe are essential conditions, and further, an inner surface coating film that is strongly required to have durability against long-term water passage, impact resistance, If the flexibility is divided into two types of outer coatings that are particularly required, and the inner and outer surfaces are separated and applied separately to ensure the required performance, the original purpose of painting will not be fully achieved. There are special circumstances.
[0003]
On the other hand, in view of the configuration of the pipeline, the buried pipeline is bent along the bend of the road, and sometimes rarely branches and gathers to form a simple straight line, so the pipeline is also a standard pipe. It must be formed of straight pipes and deformed pipes (bend pipes) that join the straight pipes with appropriate coating on the inner and outer surfaces.
[0004]
The internal coating of straight pipes often uses a cement mortar lining method, and in recent years, epoxy resin powder coatings have also been installed. As for the outer surface coating, in recent years, the application of the powder coating has been promoted at a rapid pitch in the same manner as the inner surface coating because of spraying using a solvent-based coating, dipping (dipping), brush coating, and the like. In any case, since the straight pipe can be rotated on the roller and the inner surface or the outer surface can be evenly rotated, it is easy to become familiar with the mechanization and automation of coating. For example, Japanese Patent Application Laid-Open No. 07-034884 (inner surface by the present applicants). There are many conventional techniques such as Japanese Patent Application Laid-Open No. 07-77634 (solvent paint on the inner surface of the receiving port).
[0005]
On the other hand, because the tube shaft itself is made of a curved line, it is difficult to paint the deformed pipe with roller rotation as a requirement. Conventionally, the inner surface coating is rarely made of cement lining, and the construction is mainly done with powder paint. A method of applying a solvent-type paint is commonly used for painting. As shown in FIG. 5, the flow of this method is as follows. After heating the entire deformed tube to the temperature specified for each type of paint at around 200 ° C., the inner surface is coated by a known technical means such as electrostatic coating. If present, post-heating is performed to form a complete inner surface coating film. Here, after heat-dissipating and cooling the deformed tube to near room temperature, external coating is performed by spraying with a coating gun, dipping in a paint tank, or brushing by an operator's manual work. Cooling the surface to be coated is a condition for solvent-based coating. As is well known, solvent-based paint liquefies resin materials using an organic solvent such as toluene, so when the temperature of the surface to be coated is high This is because the coating film is cracked and a uniform coating film cannot be formed.
[0006]
[Problems to be solved by the invention]
The following problems have been pointed out in the conventional method of combining the inner surface coating with a powder coating and the outer surface coating with a solvent-based coating.
(1) In the case of a solvent-type paint, the resin component is liquefied with a solvent, so that a uniform and tough coating film cannot be formed in close contact with a metal surface unless the solvent is vaporized and dried after coating. The restriction that the coating cannot be completed unless a long curing and drying time (for example, 24 hours) is maintained is the first problem faced as a productivity limit.
(2) As long as organic solvents (such as toluene) are required as a component requirement, it is natural that there are concerns about the deterioration of the workplace environment and the health problems of workers, which imposes legal restrictions on handling as specific chemical substances. It is a target. Ventilation and restrictions on the amount of use are based on the premise of soaring building and equipment costs, compulsory maintenance, and other complicated management. Failure to do so will lead to serious occupational health accidents. In addition, since paint is a kind of hazardous material, it is absolutely necessary to pay full attention to fire during storage, storage and handling.
(3) As described above, the temperature of the deformed pipe is increased to use the powder coating for the inner surface coating, and if necessary, post-heating is also performed after the coating. In order to apply the outer surface coating with the solvent-based coating, Once it must cool to near room temperature, the loss time during that time is hard to ignore. This is the biggest cause of a decrease in productivity, a significant reduction in product turnover, and a significant reduction in processing capacity per unit time and area. Combined with quality control, it is the source of dramatically reducing the overall production efficiency of the factory.
(4) On the other hand, although the outer surface coating and the inner surface coating are related to each other for a single pipe, they are applied for different purposes, so the content of the paint itself is quite different. 5528 “Ductile cast iron tube inner surface epoxy resin powder coating” JDPA Z 2010 “Ductile cast iron tube synthetic resin coating” has a coating range. In particular, inner coatings are primarily required to have long-term durability against water, and outer coatings are required to have impact resistance. Each ingredient range is defined separately. In the case of epoxy resin powder coatings (for example, bisphenol A type), the softening point, epoxy equivalent, type of curing agent, for example, polyhydric phenol curing agent, the ratio of hydroxyl group to epoxy equivalent, etc. It becomes a condition to dominate.
[0007]
In addition, as specified in the above regulations, the paint color is also gray on the inner surface and black on the outer surface, so if the black outer paint protrudes into the light inner paint range, the appearance of the product will be significantly impaired and the appearance will be reduced. It becomes the object of rework in the inspection. Conventionally, when external coating is applied by spraying or brushing with solvent-based paint, the outer coating has been easily wiped off even if it protrudes over the inner coating, but both the inner and outer surfaces are easily maintained. When changing to powder coating, it was difficult to wipe off easily, especially when the outer coating wraps around the inner coating and the colors are mixed together, which is a cause of significant loss of product value. It is conceivable to use a masking material to prevent this wraparound, but the conventional masking material is an adhesive sheet that is not intended to use powder paint in the first place. If diverted as a masking material for powder coating, if the temperature of the surface to be coated is high, naturally it will be easily peeled off due to its poor heat resistance, and the adhesive will remain on the coating film, sticking to the surface and will not be able to withstand use. The result is expected.
[0008]
An object of the present invention is to provide a specific method and apparatus for solving various problems newly caused by switching from external coating with a solvent-type coating to powder coating in coating the inner and outer surfaces of a deformed pipe.
[0009]
[Means for Solving the Problems]
According to the present invention, the inner and outer surfaces of the deformed pipe are coated with an epoxy resin-based powder coating on the inner surface of the deformed pipe 1 preheated to a predetermined temperature and cured to form the inner surface coating film 11. The conical trapezoidal masking material 2 composed of the conical surface 21 having flexibility and heat resistance is fitted to the opening portions 12 and 13 on the end face, and all the opening portions are sealed to be necessary for curing. The problem is solved by applying an epoxy resin-based powder coating for the outer surface to the outer surface of the deformed tube 1 maintaining the residual heat and curing it to form the outer surface coating film 14 having different functions only on the outer surface. To do.
[0010]
Moreover, as a frustoconical masking material 2 which is fitted into the opening surfaces 12 and 13 of the end face of the deformed tube 1 on which the inner surface coating film 11 is formed and is sealed among the painting tools used in this method, a short diameter is used. A structure in which the upper surface 22, the lower surface 23 having a long diameter, and the skeleton 24 that specifies the height H are formed of a rigid material, and the conical surface 21 that connects the end surfaces of the upper surface 22 and the lower surface 23 to each other is formed of a heat-resistant flexible material. It is. More specifically, the rigid material is made of metal, plastic (including foamed product), or wood, and the heat-resistant flexible material has a rubber hardness of 70 or less and a silicon rubber, a fluorine rubber or a thickness of 1 to 5 mm. A configuration in which a conical surface with a gradient of 10 to 40 ° is formed of a material selected from any of ethylene propylene rubber is a desirable form.
[0011]
With this coating method, the masked material 2 is applied to the openings at both ends without waiting until the irregular tube is heated to a specific temperature required for inner surface coating to finish the inner surface powder coating and then cooled to room temperature. The conical surface 21 is fitted and the end surface is closed and hermetically sealed, the remaining heat is retained, and the outer surface is continuously applied to coat the inner and outer surfaces by a consistent process. In this case, since the skeleton 24 of the masking material 2 to be applied is formed of a rigid material, the inclination angle of the conical surface is specified, and the sealing surface has heat resistance and flexibility. It absorbs the dimensional error (diameter, roundness) allowed in the opening of the metal and adheres tightly to reliably block the communication between the inner and outer surfaces. Separate internal and external paint surfaces are formed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a front view showing an embodiment of the present invention, and FIG. 2 is a flowchart showing a procedure of the method. FIG. 3 is a cross-sectional view of the main part showing a state where the outer surface coating and the inner surface coating are separately applied. In these drawings, first, the deformed tube 1 having the inner surface coating film 11 formed on the basis of the known prior art is lifted from the ground with a hoist 3 or the like by a hoist 31 locked to a flange 15 at one end thereof, and opened in the vertical direction. The conical surface 21 of the masking material 2 is fitted into the openings 12 and 13 at both ends of the deformed pipe. When the deformed tube is a clove tube or a cross tube, there are 3 to 4 end opening portions into which the masking material 2 is fitted, but they are fitted so as to seal all the opening portions.
[0013]
Since the conical surface 21 is flexible, even if there is some variation in the roundness and size of the opening of the deformed tube, the inclined surface is slightly deformed and attached, and the inner surface is tightly sealed and sealed. And In addition, although 10-40 degrees is suitable for an inclination angle, it is the aspect which can recommend the range of 20-30 degrees especially.
[0014]
With the masking material 2 mounted, in the example shown in this figure, the outer coating film 14 having the desired performance is sprayed by the coating gun 4 to form the outer coating film 14. At this time, the tube temperature required for the outer coating is If surplus heat after the inner surface coating can be used, it is possible to construct a coating line with extremely high energy efficiency. In any case, it is clear that time, labor and energy are significantly reduced if the inner and outer surfaces are treated with a continuous coating line.
[0015]
FIG. 3 is a longitudinal front view showing the main part of the present invention, and in this case, a part of the inner surface paint has already circulated to the outer surface at the stage of inner surface coating, and an excess coating has protruded. It is accepted that it will not cause any trouble. The masking material 2 is fitted in close contact with the end corners of the inner surface coating film 11, and the outer surface coating film 14 is applied to the outer surface including the inner coating film partially protruding by the coating gun 4 to form the outer surface coating film 14. State.
[0016]
Although the masking material 2 is an important requirement of the present invention, the performance to be provided by the masking material can be organized into the following six items.
(1) Heat resistance: The tube temperature (140 to 190 ° C.) at the time of external coating should be able to endure even if it is in close contact with the tube for several minutes to ten and several minutes.
(2) Sealing property: The tube end surface is sealed flexibly so as to prevent the outer paint from wrapping around the inner surface.
(3) Damage to the inner coating film: The inner coating film should not be damaged by masking.
(4) Workability: The masking material can be easily attached and detached, and should not be detached during painting.
(5) Cleanability: The paint fine powder or fusion adhered on the conical surface after use can be easily removed.
(6) Reusability: Must be able to withstand repeated use.
[0017]
A longitudinal front view of the embodiment of the masking material 2 is shown in FIG. 4 (A) and a half plan view is shown in FIG. 4 (B). Since the masking material has a truncated cone shape, it can be specified by the minor axis and the height H of the upper surface 22 and the lower surface 23. The hollow skeleton that specifies these is made of a rigid material such as metal, plastic (including foamed products), and wood. It is made of a lightweight and heat-resistant material. Further, the conical surface 21 surrounding the side surface of the skeleton is a flexible and elastic material excellent in heat resistance, specifically silicon rubber, SEP, fluorine rubber or ethylene propylene rubber (particularly peroxide vulcanization type), etc. Use materials. As this elastic material, it is desirable to use a film having a rubber hardness of 70 or less (JIS K 6301) and a thickness of 1 to 5 mm, and particularly preferably 2 to 4 mm for the reasons of (2) and (3) described above. With this hollow structure, it is possible to cope with the dimensional tolerance of the inner diameter of the pipe, and it is easy to follow the inner shape of the deformed pipe so as to satisfy the required performance.
[0018]
Masking material 2 that satisfies the requirements of the above six items, specifically, as Example 1, skeleton: polyacetal, elastic material: silicon rubber (thickness 2 mm, hardness 70 degrees, inclination angle 20 °), skeleton as Example 2: Urethane foam, elastic material: fluoro rubber (thickness 2 mm, hardness 60 degrees, inclination angle 30 °), as Example 3, skeleton metal plate (stainless steel plate (SUS304), plate thickness 1.2 mm), elastic material: silicon rubber (thickness) 2mm, hardness 70 degrees, inclination angle 20 degrees), the actual deformed pipe is coated with the powder coating for the outer surface and the powder coating for the inner surface used for normal work, and the actual line is painted The durability was confirmed by the assumed procedure. That is, (1) the deformed tube is heated to 200 ° C. and powder coating is performed on the inner surface of the tube.
(2) After the painting is finished, when the tube temperature is lowered to 165 ° C., a masking material is attached to the receiving port and the insertion port.
(3) After the tube is lifted, the outer surface is painted when the tube temperature reaches 160 ° C.
(4) After painting, remove the masking material, and when the tube temperature reaches room temperature, lower the deformed tube from the hanger. The field test was completely successful, and when it was incorporated into the actual line and performed continuously, the exterior coating and the interior coating were accurately painted within the prescribed range, and the appearance was excellent and the appearance was excellent. It was confirmed that the product value was retained.
[0019]
【The invention's effect】
In the coating of the inner and outer surfaces of deformed pipes, conventionally, after the inner surface coating with powder coating was completed, the outer surface coating that requires different performance was used for solvent-based coatings, so various problems, especially occupational health, workplace environment, He was struggling with inefficiencies such as waiting, and the negative effects of energy loss. If the external surface coating is switched to the powder coating to solve this problem, a new problem caused by this switching will be faced, in particular, the appearance defect of the product. The present invention brings about an effect that it is possible to surely solve various problems newly caused by switching from external coating with a solvent-based coating to powder coating and enjoy only the advantages. By practicing the present invention, it is possible to lay out a dedicated line for painting with a large number of deformed pipes and to continuously apply the coating mechanically and semi-automatically, which is evaluated as a requirement to further promote labor saving.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of the present invention.
FIG. 2 is a flowchart showing the procedure of the present invention.
FIG. 3 is a partially longitudinal front view showing the main part of the present invention.
FIG. 4 is a partially longitudinal front view (A) and a half plan view (B) of a masking material of the present invention.
FIG. 5 is a flowchart showing a procedure of the prior art.
[Explanation of symbols]
1 Modified pipe 2 Masking material 3 Hoist 4 Paint gun
11 Internal coating
12 opening
13 opening
15 Flange
14 External coating
21 Conical surface
22 Top view
23 Bottom
24 skeleton
31 Suspension H Masking material height

Claims (3)

In the coating method of the inner and outer surfaces of the deformed pipe for forming a pipe for water service etc., the inner surface coating film 11 was formed by applying and curing the epoxy resin-based powder coating on the inner surface of the deformed pipe 1 preheated to a predetermined temperature. after, sealed all opening is fitted a masking material 2 forming the profiled tube 1 frustoconical shape having a conical surface 21 which is a sealing surface of the opening 12, 13 of the end face by Tsu支, said The tube temperature required for curing the outer surface powder coating is different from the epoxy resin type outer surface powder coating different from the inner surface powder coating by the residual heat accompanying the heating during the formation of the inner surface coating film 11. Applying and curing to the outer surface of the deformed tube 1 in a maintained state, the outer surface coating film 14 having a function different from the inner surface coating film 11 is formed only on the outer surface of the deformed tube 1 by the powder coating for the outer surface. The masking material 2 seals the openings 12 and 13. When the conical surface 21 is fitted into the deformed tube 1 having a tube temperature necessary for curing the powder coating for the outer surface generated with the residual heat, the heat-resistant flexible material has heat resistance and sealing properties. A method for painting the inner and outer surfaces of a deformed pipe, characterized by being made of a material . A frustoconical masking material 2 which is used in the coating method for the inner and outer surfaces of the deformed pipe according to claim 1 and is fitted into the opening of the end face of the deformed pipe 1 on which the inner surface coating film 11 is formed and sealed. The upper surface 22, the lower surface 23 having a long diameter, and the skeleton 24 that specifies the height H are formed of a rigid material, and the conical surface 21 that connects the end surfaces of the upper surface 22 and the lower surface 23 to each other is used for the outer surface. The inner and outer surfaces of the deformed tube made of the masking material 2 formed by a heat-resistant flexible material having heat resistance and sealing properties when fitted into the deformed tube 1 having a tube temperature necessary for curing the powder coating material Painting equipment.    In Claim 2, the rigid material is made of metal, plastic, or wood, and the heat-resistant flexible material is any one of silicon rubber, fluorine rubber, or ethylene propylene rubber having a rubber hardness of 70 or less and a thickness of 1 to 5 mm. A coating device for the inner and outer surfaces of a deformed pipe, wherein a conical surface having a gradient of 10 to 40 ° is formed of the selected material.

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