JP4801599B2 - Manufacturing method of anticorrosion water pipe - Google Patents

Description

This invention is a method for producing a corrosion-resistant water pipe, and in particular, it can maintain a high anti-corrosion performance over a long period of time and has excellent impact resistance because it does not adversely affect water quality and can be thickly coated. In addition, the present invention relates to a method for producing a corrosion-proof coated water pipe that can be painted simultaneously on the inner and outer surfaces, and is immediately ready for use by rapid cooling after painting .

  Conventionally, in coated metal pipes used for water supply or sewerage, two-part liquid epoxy resin paint or epoxy resin powder paint is used for inner surface coating, and outer surface coating is generally liquid. Synthetic resin paints are used.

  Patent Document 1 (Japanese Patent Laid-Open No. 2003-11253) discloses a metal tube coated with an epoxy resin powder coating material in which an epoxy resin component is specified.

  When using epoxy resin powder paint for inner surface coating, the epoxy resin powder paint does not contain solvent and is applied to preheated metal tubes, so it takes less time to dry, There is no concern of adversely affecting water quality. Therefore, the epoxy resin powder coating is suitable for inner surface coating.

JP 2003-11253 A

  However, when a two-part liquid epoxy resin paint is used on the inner surface as described above, the liquid epoxy resin paint generally contains a solvent. There are concerns about adversely affecting

  In contrast, in the case of an epoxy resin powder coating, as described above, it does not contain a solvent, and since it is applied to a preheated metal tube, it does not take time to dry, and the water quality This is suitable for inner surface coating because there is no concern that it will adversely affect the surface, but when this is applied to the outer surface, it is unsuitable because the coating film is hard and impact resistance is low.

  On the other hand, generally used liquid synthetic resin paints are difficult to coat thickly, take time to dry, have low anticorrosion properties, and are embedded in corrosive soil for a short period of time. In some cases, metal pipes corrode and finish their life in a short time.

  Conventionally, the inner and outer surfaces of the pipe cannot be simultaneously coated with the same paint, and the outer surface is generally coated after the inner surface is coated.

Accordingly, the object of the present invention is that it can be applied with a thick coating without adversely affecting the water quality, so that high anticorrosion performance can be maintained over a long period of time, and it has excellent impact resistance, and at the same time the inner and outer surfaces are simultaneously coated. It is another object of the present invention to provide a method for producing a corrosion-proof coated water pipe that can be painted and that can be used immediately by being rapidly cooled after painting .

  Therefore, the inventor of the present application has made extensive studies in order to achieve the above object. As a result, the following findings were obtained.

  Since the thermoplastic saturated polyester resin powder coating does not contain a solvent and does not contain harmful substances such as environmental hormones, it does not adversely affect water quality. Moreover, according to the thermoplastic saturated polyester resin powder coating, the inner and outer surfaces of the pipe can be coated at the same time. Furthermore, if the coating is rapidly cooled after coating, it can be used immediately.

  The present invention has been made on the basis of the above findings, and is characterized by the following.

According to the first aspect of the present invention, a metal pipe is subjected to a surface finishing treatment, and then, zinc or zinc-aluminum is thermally sprayed on an outer surface of the metal pipe subjected to the surface finishing treatment, and then the metal pipe is Preheated to a temperature in the range of 280 ° C. to 300 ° C., and then on the inner and outer surfaces of the preheated metal tube, the particle size is 40 mesh, the melting point is in the range of 230 ° C. to 240 ° C., and the density is 1.28 to 1 The thermoplastic saturated polyester resin powder in the range of .30 is coated at the same time on the inner and outer surfaces so that the film thickness is in the range of 0.3 mm to 1.0 mm, and the metal tube is coated at 100 ° C./min to 200 ° C. It is characterized by cooling at a cooling rate in the range of / min. And thus forming a coating film made of a thermoplastic saturated polyester resin on the inner and outer surfaces of the metal pipe .

  According to the present invention, it is possible to maintain a high anti-corrosion performance for a long period of time without affecting the water quality and enabling a thick coating, and it is excellent in impact resistance. In addition, it can be used immediately after coating by rapid cooling.

Next, one embodiment of the anticorrosion paint water pipe manufactured by the method of the present invention will be described.

The anticorrosion-coated water pipe manufactured by the method of the present invention is applied to the inner and outer surfaces of a metal pipe such as a cast iron pipe or an iron pipe within a thickness range of 0.3 mm to 1.0 mm made of thermoplastic saturated polyester resin powder. It consists of a film formed.

  If the film thickness is less than 0.3 mm, coating film defects such as pinholes are likely to occur, and the desired anticorrosive effect cannot be obtained. On the other hand, if the film thickness exceeds 1.0 mm, paint dripping occurs and the appearance deteriorates. In addition, the impact resistance of the coating film decreases. In addition, the outer diameter of the pipe is increased, affecting the pipe joining by the joint. Therefore, in this invention, the film thickness of the thermoplastic saturated polyester resin powder is set in the range of 0.3 mm to 1.0 mm. Preferably, it is in the range of 0.5 mm to 0.8 mm.

  General synthetic resin paints have a solid content (component that becomes a coating film) as low as 30% to 50%. If thickly applied, inconveniences such as paint sag occur, so thick coating is difficult. In the case of a polyester resin powder, the solid content is almost 100%, and it can be applied ten times or more thicker than a general synthetic resin paint.

Next, the manufacturing method of the anticorrosion coating water pipe of this invention is demonstrated.

The anticorrosion coated water pipe manufactured by the method of the present invention is obtained by subjecting a metal pipe such as a cast iron pipe or an iron pipe to a surface finish treatment, preheating the metal pipe subjected to the surface finish treatment, and then preheating the metal pipe. By simultaneously coating thermoplastic saturated polyester resin powder on the inner and outer surfaces of the pipe making and cooling the metal pipe, thus forming a coating film made of thermoplastic saturated polyester resin on the inner and outer faces of the metal pipe Manufactured.

  The preheating temperature of the metal pipe is in the range of 270 ° C to 320 ° C. When the preheating temperature is less than 270 ° C., the powder does not completely melt, so that the original effect of the coating film cannot be obtained. Moreover, the impact resistance is reduced. On the other hand, if it exceeds 320 ° C., the resin of the paint is thermally deteriorated and the original effect of the coating film cannot be obtained. Moreover, it discolors and an external appearance worsens. Therefore, in the present invention, the preheating temperature of the metal pipe is set in the range of 270 ° C. to 320 ° C. Preferably, the temperature is in the range of 280 ° C to 300 ° C.

  The film thickness of the thermoplastic saturated polyester resin powder is as described above.

  The cooling rate of the metal pipe is in the range of 40 ° C./min to 200 ° C./min. The effect of the coating film is brought about by crystallization of the thermoplastic saturated polyester resin by rapid cooling. However, if the cooling rate is less than 40 ° C./min, the resin is difficult to crystallize, so that a desired effect cannot be obtained. On the other hand, even if it exceeds 200 ° C./min, the effect of crystallization of the resin does not change, and the cooling equipment is increased in size and is wasted. Therefore, in the present invention, the cooling rate of the metal pipe is set within the range of 40 ° C./min to 200 ° C./min. Preferably, it is in the range of 100 ° C./min to 200 ° C./min.

  As described above, the thermoplastic saturated polyester resin is crystallized by rapid cooling, and thus the rapid cooling is essential because the original performance is exhibited.

  The particle size of the paint is preferably 40 mesh, the melting point is 230 ° C. to 240 ° C., and the density is 1.28 to 1.30 in order to obtain the original performance.

  In order to further improve the outer surface anticorrosion performance, after spraying zinc or zinc-aluminum as a primer, thermoplastic saturated polyester resin powder coating is preferably performed thereon. Thereby, even if the coating film is damaged, it is possible to prevent the progress of corrosion of the pipe body by the sacrificial anode reaction of zinc or zinc-aluminum.

  Next, the present invention will be further described with reference to examples.

  A ductile cast iron pipe with a diameter of 75mm, a wall thickness of 7.5mm, and a length of 4000mm is preheated to 300 ° C in a heating furnace. A saturated polyester powder coating was simultaneously applied to the inside and outside of the tube. The thermoplastic saturated polyester powder coating is composed of a polyester polymer composed of a thermoplastic polyethylene terephthalate copolymer having an isophthalic acid component of 8 to 20 mol% and an intrinsic viscosity of 0.7 to 1.0. 40 mesh, melting | fusing point was 230 degreeC, and the density was 1.28. In this way, after the powder coating was simultaneously applied to the inner and outer surfaces of the tube, the tube was immediately cooled with water at a cooling rate of 100 ° C./min to produce an inner and outer surface thermoplastic saturated polyester powder coated tube.

In FIG. 1, the process drawing of the manufacturing method of the anticorrosion coating water pipe of this invention is shown.

As described above, according to the anticorrosion-coated water pipe manufactured by the method of the present invention, the use of the thermoplastic saturated polyester powder coating does not adversely affect the water quality and can be thickly coated. The anticorrosion performance could be maintained for a long time. In addition, it has excellent impact resistance, and because the same paint can be used on the inner and outer surfaces of the pipe, the inner and outer surfaces can be painted simultaneously, and the pipe coating time has been greatly reduced. Furthermore, since it is ready for use immediately after being painted, it is convenient for storage and shipment after pipe production.

It is process drawing of the manufacturing method of the anticorrosion coating water pipe of this invention.

Claims (1)

The metal pipe is subjected to a surface finishing treatment, and then zinc or zinc-aluminum is sprayed on the outer surface of the metal pipe subjected to the surface finishing treatment, and then the metal pipe is within a range of 280 ° C. to 300 ° C. Thermoplastic with a particle size of 40 mesh, a melting point of 230 ° C to 240 ° C, and a density of 1.28 to 1.30 on the inner and outer surfaces of the preheated metal tube Saturated polyester resin powder is coated simultaneously on the inner and outer surfaces so that the film thickness is in the range of 0.3 mm to 1.0 mm, and the metal pipe is cooled at a cooling rate in the range of 100 ° C./min to 200 ° C./min. And a coating film made of a thermoplastic saturated polyester resin is formed on the inner and outer surfaces of the metal pipe.

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