JPH11276949A - Coating of inside/outside surfaces of special shaped tube, and coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve environmental problems and inefficiency and to eliminate energy loss for solvent type coating material and to prevent defective appearance of a product for powdery coating material in the case of coating the outside surface of a special shaped tube. SOLUTION: After an epoxy resin base powdery coating material for inside surface is applied on the inside surface of the special shaped tube 1 preheated to a prescribed temperature and is hardened to form an inside surface coating film 11, the tube is hung and supported and conical masking materials 2 each consisting of a conical surface 21 having flexibility and heat resistance are inserted into openings 12, 13 at both the ends thereof to seal both the openings 12, 13, and an epoxy resin base powdery coating material for outside surface is applied on the outside surface of the special shape tube 1 having residual heat required for hardening and is hardened to separately apply the outside surface coating film 14 having a different function to the outside surface only. Since the conical surface has flexibility and absorbs dimensional casting errors (diameter, roundness) allowed for the special shaped tube and is closely adhered to the inside surface to surely cut off the communication between the outside and inside surfaces, action of the outside coating infiltrating to the inside surface is entirely interrupted to form the inside and outside coating surfaces applied in a completely separate manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the inner and outer surface coating of a deformed pipe for forming a water pipe or the like.

[0002]

2. Description of the Related Art Ductile cast iron is mainly used for individual pipes forming pipes for water supply and the like, but pipes are usually buried underground, so that the outer surface of pipes is It is necessary to protect the surface from corrosive atmospheres such as groundwater. Also, since the pipes need to be loaded and unloaded at the time of storage and transportation before arriving at the laying site, it is necessary to coat the outer surfaces so as not to damage the outer surfaces of the pipes due to collision or scraping of the pipes. On the other hand, the inner surface of the pipe is in constant contact with the drinking water that passes through it, so it is necessary to have an inner surface coating that has sufficient durability in contact with the water flow, does not cause red rust, etc., and may not reach the demand destination Becomes As described above, it is needless to say that adhesion and anticorrosion of the pipe to the metal substrate are indispensable conditions for the coating for the pipe, but the inner coating film, which is required to have higher durability for long-term water flow, and impact resistance, It is classified into two types of outer surface coatings that are particularly required for flexibility, and if the inner and outer surfaces are not distinguished and applied separately to ensure the required performance, the original purpose of coating will not be sufficiently fulfilled. There is a special circumstance.

[0003] On the other hand, from the viewpoint of the configuration of the pipeline, the pipeline to be buried is bent along the bend of the road, and it is rare that the branch is sometimes branched and assembled to form a simple straight line. It must be formed of straight pipes that are pipes and deformed pipes (bend pipes) that join the straight pipes, and the inner and outer surfaces of each pipe must be appropriately coated.

In many cases, the inner surface of a straight pipe is coated by a cement mortar lining method. In recent years, an epoxy resin powder coating has also been applied. In addition, application of powder coatings has been progressing at a rapid pace in recent years in the same manner as in the case of internal coatings, from the methods of spraying, dipping (dipping), and brushing using solvent-based coatings for external coating. In any case, since the straight pipe can be rotated on the rollers to rotate the inner surface or the outer surface evenly, it is easy to adapt to the mechanization and automation of coating. For example, Japanese Patent Application Laid-Open No. 07-034 by the present applicants.
No. 884 (powder paint on the inner surface) and JP-A-07-7763
There are many conventional technologies such as No. 4 (solvent-type paint on the inner surface of the receptacle).

[0005] On the other hand, the deformed pipe is difficult to paint with the requirement of roller rotation because the pipe axis itself is formed of a curve. Conventionally, the inner surface coating is rarely performed by cement lining, and is mainly performed by powder coating. The method of applying a solvent type paint for the outer surface coating has become common. In the flow of this method, as shown in FIG. 5, after heating the entire deformed pipe to a temperature specified for each type of paint of about 200 ° C., the inner surface is coated by a known technique such as an electrostatic coating method. If present, post-heating is performed to form a complete inner coating. Here, once the deformed pipe is radiated and cooled to near normal temperature, the outer surface is applied by spraying with a coating gun, dipping in a paint tank, or brushing manually by an operator. As is well known, the cooling of the surface to be coated is a condition of the solvent-based coating, because the solvent-based coating uses an organic solvent such as toluene to liquefy the resin material, so when the temperature of the surface to be coated is high, This is because a crack or the like of the coating film occurs and a uniform coating film cannot be formed.

[0006]

The following problems have been pointed out in the prior art method of combining the inner surface coating with a powder coating and the outer surface coating with a solvent type coating. In the case of the solvent-type paint, the resin component is liquefied by the solvent, so that a uniform and tough coating film cannot be formed in close contact with the metal surface without evaporating and drying the solvent after coating. The limitation 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 the limit of productivity. As long as organic solvents (for example, toluene) are required for components, it is natural that there will be concerns about the deterioration of the work environment and the health problems of workers. is there. Restrictions on ventilation and usage are premised on soaring costs of buildings and equipment, forced maintenance, and other complicated management. Failure to do so may lead to serious occupational health accidents. In addition, since paint is a kind of dangerous substance, it is an absolute requirement to pay close attention to fire when storing, storing, handling and using. As mentioned above, the temperature of the deformed pipe is increased in order to use the powder coating for the inner surface coating, and the post-heating is also performed after the coating if necessary.
Once it has to be cooled to near normal temperature, the loss time during that time is not negligible. This is the largest cause of lowering the productivity, significantly lowering the product turnover rate, and greatly reducing the processing capacity per unit time and area. Together with quality control, it is the root of drastically reducing the production efficiency of the entire factory. On the other hand, although the outer surface coating and the inner surface coating are in a front-to-back relationship with respect to one pipe, they are applied to fulfill different purposes, so that the composition of the paint itself is considerably different.
The coating range is defined in ISG 5528 “Epoxy resin powder coating on the inner surface of ductile cast iron pipe” and JDP A2010 “Ductile cast iron pipe synthetic resin coating”. In particular, the inner coating is required to be resistant to long-term water penetration, and the outer coating is mainly required to have impact resistance.Therefore, even with the same epoxy powder coating, the mixing ratio of raw materials and The component ranges are each defined separately. In the case of an epoxy resin-based powder coating (for example, bisphenol A type), the properties of the formed coating film are determined by the softening point, epoxy equivalent, and type of curing agent, such as the ratio of hydroxyl group to epoxy equivalent for a polyhydric phenol curing agent. Is the condition that governs

[0007] Further, as described in the above-mentioned regulations, since the coating color is gray on the inner surface and black on the outer surface, if the black outer coating protrudes within the range of the light-colored inner coating, the appearance of the product is remarkably improved. Damaged and subject to rework in visual inspection. Conventionally, when the outer surface is applied by spraying or brushing by applying a solvent type paint, it is easy to wipe off the outer surface even if it protrudes above the inner surface and easily retain a beautiful appearance, but both the inner surface and the outer surface In the case of changing to powder coating, it is difficult to easily wipe off the color, especially when the outer coating wraps around the inner coating and the colors are mixed, which is a very unsightly cause and significantly impairs the product value.
It is conceivable to use a masking material to prevent this wraparound.However, the conventional masking material has been used in the form of an adhesive sheet which is not intended to use powder paint in the first place. If it is diverted as a masking material for powder coating, if the temperature of the surface to be coated is high, it is naturally easy to peel off due to poor heat resistance, the adhesive remains in the coating film, it is sticky and can not withstand use at all The result is expected.

[0008] The present invention relates to the coating of the inner and outer surfaces of a deformed pipe,
It is an object of the present invention to provide a specific method and apparatus for solving various problems newly generated by switching from exterior coating using a solvent type coating to powder coating.

[0009]

According to the present invention, a method for coating the inside and outside of a deformed pipe according to the present invention is to apply an epoxy resin-based powder coating for the inside to the inside of a deformed pipe 1 which has been preheated to a predetermined temperature, and to cure the inside of the pipe. 11, the deformed tube 1 is hung and the conical surface 21 having flexibility and heat resistance is provided to the openings 12, 13 and the like on the end surfaces.
A truncated cone-shaped masking material 2 is fitted and all openings are sealed, and an epoxy resin-based powder coating for the outer surface is applied to the outer surface of the deformed tube 1 maintaining the residual heat required for curing and cured. The problem is solved by performing a procedure of forming the outer surface coating film 14 having different functions only on the outer surface.

[0010] Among the coating tools used in this method, a truncated cone-shaped masking material 2 which is fitted into the opening surfaces 12 and 13 of the end surface of the profiled pipe 1 on which the inner coating film 11 is formed and sealed. Forming a skeleton 24 for specifying the upper surface 22 of the minor axis, the lower surface 23 of the major axis, and the height H from a rigid material,
A requirement is that the conical surface 21 connecting the end surfaces of the upper surface 22 and the lower surface 23 is formed of a heat-resistant flexible material. 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 thickness of 1 to 5 mm, such as silicon-based rubber, fluorine-based rubber, or the like. A desirable configuration is one in which a conical surface having a gradient of 10 to 40 ° is formed from a material selected from any of ethylene propylene rubber.

According to this coating method, the deformed pipe is heated to a specific temperature necessary for the inner surface coating as in the past, and after the inner surface powder coating is completed, without waiting for the temperature to drop to room temperature, the opening at both ends thereof is formed. The problem is solved by fitting the conical surface 21 of the masking material 2 to close and close the end surface, and subsequently applying the outer surface using the retained residual heat and coating the inner and outer surfaces by a consistent process. In this case, by forming the skeleton 24 of the masking material 2 to be applied from a rigid material, the inclination angle of the conical surface is specified, and the sealing surface has heat resistance and flexibility. Absorbs the dimensional errors (diameter, roundness) allowed in the opening of the, and firmly closes the connection between the inner and outer surfaces, so that the outer coating completely blocks the action of wrapping around the inner surface and paints beautifully Form separate inner and outer painted surfaces.

[0012]

FIG. 1 is a front view showing an embodiment of the present invention, and FIG. 2 is a flowchart showing a procedure of a method.
FIG. 3 is a cross-sectional view of a main part showing a state where the outer surface coating and the inner surface coating are separately applied. In these figures, first, the deformed pipe 1 on which the inner surface coating film 11 is formed based on a known conventional technique is lifted from the ground with a hoist 3 or the like by a hoist 3 or the like by a hanging tool 31 locked to a flange 15 at one end thereof, and is opened vertically. 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 pipe is a T-shaped pipe or a cross pipe, the opening at the end where the masking material 2 is fitted is 3 to
There are four places, but they are fitted so that all openings are sealed.

Since the conical surface 21 has flexibility, even if there is a slight variation in the roundness and dimensions of the opening of the deformed pipe, the inclined surface is slightly deformed and attached to the inner surface, so that the inner surface is surely adapted. Is sealed. It is to be noted that an appropriate inclination angle is 10 to 40 °, but a range of 20 to 30 ° is particularly recommended.

In a state where the masking material 2 is mounted, an external coating having desired performance is sprayed by a known means, in this example, a coating gun 4 to form the external coating 14, and at this time, the external coating necessary for the external coating is formed. As for the pipe temperature, if it is possible to utilize the surplus heat after performing the inner surface coating, it is possible to construct a coating line having extremely excellent energy efficiency. In any case, it is clear that the time, labor and energy can be significantly reduced if the inner and outer surfaces are treated by a continuous coating line.

FIG. 3 is a longitudinal sectional front view showing a main part of the present invention. In this figure, at the stage of inner coating, a part of the inner coating has already reached the outer surface and an excess coating has protruded. However, it is accepted that it does not cause any problems. The masking material 2 is fitted in close contact with the end corners of the inner coating film 11, and an outer coating material is applied by a coating gun 4 on the outer surface including the inner coating film that has partially protruded, thereby forming the outer coating film 1.
4 is formed.

Although the masking material 2 is an important requirement of the present invention, the performance to be provided by the masking material can be classified into the following six items. Heat resistance: It can withstand even a close contact with the tube for several minutes to more than ten minutes at the tube temperature (140 to 190 ° C.) at the time of outer coating. Sealability: Flexible sealing of the pipe end face to prevent the paint on the outside from entering the inside. Damage to the inner coating: The inner coating should not be damaged by masking. Workability: The masking material can be easily attached and detached and does not come off during painting. Cleanability: Easy removal of fine powder and fusion of paint on the conical surface after use. Reusability: To withstand repeated use.

FIG. 4A is a longitudinal sectional front view of the embodiment of the masking material 2, and FIG. Since the masking material has a truncated cone shape, the upper surface 22 and the lower surface 2
3 can be specified by the short major axis and the height H. The hollow skeleton for specifying these is made of a rigid material such as metal, plastic (including foamed product), wood, etc., which is lightweight and has heat resistance. In addition, the conical surface 21 surrounding the periphery of the side surface of the skeleton is made of a flexible and elastic material having excellent heat resistance, such as silicon rubber, SEP, fluorine rubber or ethylene propylene rubber (particularly, peroxide vulcanized type). Use the material. This elastic material has a rubber hardness of 70 or less (JIS K6301) and a thickness of 1 to 5 mm.
It is preferable to use a coating having a thickness of 2 to 4 mm for the reasons 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.

A masking material 2 which satisfies the requirements of the above six items, specifically, as Example 1, a skeleton: polyacetal,
Elastic material: silicon rubber (thickness: 2 mm, hardness: 70 degrees, inclination angle: 20 degrees), as Example 2, skeleton: urethane foam,
Elastic material: fluoro rubber (thickness 2 mm, hardness 60 degrees, inclination angle 30 °), skeletal metal plate (stainless steel plate (SUS304), plate thickness 1.2 mm) as Example 3, elastic material: silicon rubber (thickness 2 mm, Hardness 70 degrees, inclination angle 20
) Was applied to the actual deformed pipe using the powder coating for the outer surface and the powder coating for the inner surface used for normal work, and the durability was confirmed by the procedure assuming the coating on the actual line. That is, the deformed pipe is heated to 200 ° C., and powder coating is performed on the inner surface of the pipe. After the coating, when the tube temperature has dropped to 165 ° C., a masking material is attached to the receiving port and the insertion port. After the pipe is lifted, the outer surface is coated when the pipe temperature reaches 160 ° C. After painting, remove the masking material, and when the pipe temperature reaches room temperature, remove the deformed pipe from the hanging tool. The on-site test was completely successful, and when the coating work was carried out continuously by incorporating it into the actual line, the outer coating and the inner coating were accurately applied separately in a predetermined range, and exhibited excellent appearance and high appearance. It was confirmed that the product value was maintained.

[0019]

In the coating of the inner and outer surfaces of a deformed pipe, various problems, especially labor, have been conventionally achieved after the inner coating with a powder coating has been completed and the outer coating which requires different performance has been used for a solvent type coating. He was struggling with the inefficiencies of hygiene, the work environment, and waiting hours, and the negative effects of energy loss. If the outer surface coating is switched to powder coating to solve this problem, a new problem resulting from this switching, particularly, a problem of poor appearance of the product, is faced. The present invention has an effect that various problems newly generated due to switching from the outer surface coating by the solvent-based coating to the powder coating can be surely eliminated and only the advantages can be enjoyed. By practicing the present invention, it is possible to lay out a dedicated line for coating with a large number of deformed pipes suspended and to continuously apply the coating mechanically and semi-automatically, which is evaluated as a requirement for further promoting 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 a procedure of the present invention.

FIG. 3 is a partial longitudinal front view showing a main part of the present invention.

FIG. 4 is a partial longitudinal front view of the masking material of the present invention (A).
And a half-cut plan view (B).

FIG. 5 is a flowchart showing a procedure of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deformed pipe 2 Masking material 3 Hoist 4 Painting gun 11 Inner coating film 12 Opening 13 Opening 15 Flange 14 Outer coating film 21 Conical surface 22 Upper surface 23 Lower surface 24 Skeleton 31 Hanging tool H Height of masking material

Continued on the front page (72) Inventor Takaaki Exit 1-12-19 Kitahorie, Nishi-ku, Osaka-shi, Osaka Inside Kurimoto Ironworks Co., Ltd. (72) Inventor Masahiko Saito 1-112-19, Kitahorie, Nishi-ku, Osaka-shi, Osaka Inside Kurimoto Iron Works Co., Ltd. (72) Yoshisada Michiura 1-12-19 Kitahorie, Nishi-ku, Osaka City, Osaka Prefecture Inside Kurimoto Iron Works Co., Ltd. (72) Norio Nakamura 19-17 Ikedanakamachi, Neyagawa City, Osaka Prefecture Within Nippon Paint Co., Ltd. (72) Inventor Yuji Hashimoto 3-4-2-7 Ishibashi, Ikeda-shi, Osaka Co., Ltd. Inside Cotem (72) Inventor Daisuke Shibata 3-4-27, Ishibashi, Ikeda-shi, Osaka Co., Ltd. In the coatem

Claims (3)

[Claims] 1. A method for coating the inside and outside of a deformed pipe for forming a pipeline for water supply or the like, wherein an inner surface of the deformed pipe 1 preheated to a predetermined temperature is coated with an epoxy resin-based powder coating for an inner surface and cured to form an inner coating. After the membrane 11 is formed, a truncated cone-shaped masking material 2 composed of a conical surface 21 having flexibility and heat resistance is fitted into the openings 12 and 13 on the end surfaces of the deformed tube 1 by suspending the deformed tube 1, and all the shapes are inserted. An epoxy resin-based powder coating for the outer surface is applied to the outer surface of the deformed tube 1 whose opening is sealed and the residual heat required for hardening is maintained, and hardened to form an outer coating film 14 having different functions only on the outer surface. A method for coating the inside and outside of a deformed pipe, characterized in that: 2. A truncated cone-shaped masking material 2 which is fitted into an opening of an end face of a deformed pipe 1 on which an inner surface coating film 11 is formed and which is sealed when coating the inner and outer surfaces of the deformed pipe. Lower surface 23 and skeleton 24 for specifying height H
Is formed of a rigid material, and a conical surface 21 connecting the end surfaces of the upper surface 22 and the lower surface 23 to each other is formed of a heat-resistant flexible material. 3. The rubber material according to claim 2, wherein the rigid material is metal, plastic, or wood, and the heat-resistant flexible material has a rubber hardness of 70 or less and a thickness of 1 to 5 mm. A coating instrument for the inner and outer surfaces of a deformed pipe, wherein a conical surface having a gradient of 10 to 40 ° is formed from a material selected from rubber.