JP2006144038A - Resin lining steel pipe and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin lining steel pipe used as piping for water supply, hot water supply, air-conditioning, fire fighting, drainage or the like, even in the case a polyolefin resin or a crosslinking polyolefin resin in which the penetration of oxygen as a corrosion factor is high is applied as inside lining, which is usable instead of the conventional resin lining steel pipe obtained by inside-lining polyvinyl chloride to an inside-outside hot dip metal plated steel pipe without requiring complicated stages and special equipment, and in which the adhesion between the steel pipe and the inside resin lining layer is excellent over a long period, and to provide a method for producing the same. <P>SOLUTION: In the resin lining steel pipe, the inside of a steel pipe is provided with an adhesive layer, the further inside thereof is provided with a polyolefin resin layer or a crosslinked polyolefin resin layer, the steel pipe is beforehand subjected to substrate treatment, as the substrate treatment, a chemical conversion treatment coating of phosphate subjected to crystal grain refining treatment is applied, preferably, the space between the steel pipe and the adhesive layer is provided with an epoxy primer layer, and the outside of the steel pipe is provided with a metal sprayed coating. The production method uses the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin-lined steel pipe used for piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, and the like, and more specifically, without requiring a complicated process or special equipment. Instead, it can be used in place of conventional resin-lined steel pipes with inner surface lining of polyvinyl chloride on inner and outer surface hot-dip metal-plated steel pipes, even when polyolefin resin or cross-linked polyolefin resin with large oxygen permeability, which is a corrosive factor, is used. The present invention relates to a resin-lined steel pipe having excellent adhesion between the steel pipe and the inner surface resin-lined layer over a long period of time, and a method for manufacturing the same.

  In addition to steel pipes such as forged steel pipes and ERW steel pipes, thermoplastic resin pipes such as polyvinyl chloride, polyethylene, polypropylene and polybutene are used alone as pipe materials for transporting water and the like. Steel pipes have higher mechanical strength than these resin pipes, so they have excellent impact resistance during construction and compression resistance even when buried under heavy traffic roads, and even when the temperature of the fluid being transported is high. Compared to, the pressure strength is sufficiently large and excellent, and unlike resin tubes, it is difficult to burn, so even if it is used for indoor applications, it is excellent without being spread by fire.

  However, resin pipes that do not cause corrosion are used in applications that require prevention of turbidity of fluid due to corrosion of steel and prevention of blockage of pipes. As a piping material having both of the good points, a composite pipe of resin and steel obtained by inserting a resin pipe into the inner surface of a steel pipe to prevent corrosion is known. For example, steel and soft polyvinyl chloride composite pipes using inexpensive polyvinyl chloride are widely used as water supply pipes and drain pipes, and steel and hard polyvinyl chloride composite pipes are widely used as hot water supply pipes.

  However, when a polyvinyl chloride material is used, there is also a problem that dioxins are generated at the time of incineration disposal of the composite pipe residue generated in the local piping work. Accordingly, it has been desired that a composite pipe used for a water supply pipe, a hot water supply pipe, a drain pipe, etc. does not use polyvinyl chloride. Therefore, a resin-lined steel pipe has been proposed which is used for piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc., which is internally lined with a polyolefin resin or a cross-linked polyolefin resin that does not have the problem of generating dioxins instead of polyvinyl chloride.

  However, among the resin-lined steel pipes that are used as indoor pipes or outdoor exposed pipes, polyolefin resin or cross-linked polyolefin resin is applied to steel pipes that have been hot-plated with a metal that sacrifices and protects against iron like conventional polyvinyl chloride. When inner lining is used, polyolefin resin and cross-linked polyolefin resin have much larger permeability of oxygen, which is a corrosive factor than polyvinyl chloride, so when used for piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. It was found that the inner surface resin lining layer was peeled off from the steel pipe because the molten metal plating was corroded and the adhesive interface between the steel pipe and the inner surface resin lining layer was deteriorated and the adhesive strength was weakened.

  Therefore, in order to prevent peeling, for example, molten metal plating is applied to the inner surface as disclosed in Japanese Patent Application Laid-Open No. 2003-294174 (Patent Document 1) and International Publication WO 2004-011231 (Patent Document 2). There is a steel pipe whose inner surface is lined with a polyolefin resin or a cross-linked polyolefin resin on a steel pipe whose outer surface is plated with molten metal. However, in order to perform the molten metal plating only on the outer surface of the steel pipe, a complicated process and special equipment are required, and the cost for manufacturing and equipment increases. On the other hand, it is possible to use a conventional molten metal plating facility to temporarily apply the molten metal plating to the inner and outer surfaces of the steel pipe, and then remove the molten metal plating only on the inner surface of the steel pipe. Difficult to remove. Moreover, it is conceivable that only the inner surface of the steel pipe is pickled and removed, but this also requires a complicated process and special equipment.

  As described above, the method of performing the molten metal plating only on the outer surface of the steel pipe requires a complicated process and special equipment, and the cost for manufacturing and equipment increases. Furthermore, as mentioned above, polyolefin resin and cross-linked polyolefin resin have much larger oxygen transmission than polyvinyl chloride. Therefore, in order to suppress the peeling of the inner resin lining layer due to the progress of corrosion on the inner surface of the steel pipe, Although it is necessary to apply a chemical conversion coating, there is a problem that a complicated process and special equipment are also required to apply a chemical conversion coating only to the inner surface of a steel pipe.

JP 2003-294174 A International Publication No. WO2004-011231

  In view of the above-mentioned problems, the present invention can be applied to conventional inner and outer surface molten metal-plated steel pipes even when lining a polyolefin resin or a cross-linked polyolefin resin, which has a large oxygen permeability as a corrosion factor, instead of polyvinyl chloride. Resin lining that can be used in place of internally lined resin-lined steel pipes and has excellent adhesion between the steel pipe and internal resin lining layer over a long period of time, such as pipes for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. A steel pipe and a method for manufacturing the steel pipe are provided.

  The inventors of the present invention have used a metal that sacrifices and protects against iron for resin-lined steel pipes that are internally lined with polyolefin resin or crosslinked polyolefin resin that does not have the problem of generating dioxin instead of polyvinyl chloride, and are used as indoor pipes or outdoor exposed pipes. Invented not to line the inner surface of the outer surface hot-plated steel pipe. In other words, polyolefin resin and cross-linked polyolefin resin have much greater penetration of oxygen, which is a corrosive factor, than polyvinyl chloride, so when used for piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. Since the molten metal plating is corroded and the adhesive interface between the steel pipe and the inner surface resin lining layer is deteriorated and the adhesive force is weakened, the inner surface resin lining layer is peeled off from the steel pipe.

  The present invention uses a steel pipe coated with a phosphate chemical conversion film that has been subjected to grain refinement treatment instead of an inner and outer surface hot-dip metal-plated steel pipe, and a polyolefin resin layer or a cross-linked polyolefin resin layer is attached to the inner surface via an adhesive layer. By lining, providing an epoxy primer layer if necessary, and providing a metal spray coating on the outer surface, oxygen is a corrosive factor instead of polyvinyl chloride without requiring complicated processes and special equipment. Even when polyolefin resin or cross-linked polyolefin resin with high permeation is lined internally, it can be used in place of conventional resin-lined steel pipes with inner surface lining of polyvinyl chloride for inner and outer surface hot-dip metal-plated steel pipes. For water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. piping with excellent adhesion between the inner surface and the resin lining layer Those are plastic lined steel pipe is made by finding that it is possible, and has as its gist is as follows.

(1) A steel pipe having an adhesive layer on the inner surface of the steel pipe and further having a polyolefin resin layer or a cross-linked polyolefin resin layer on the inner side, and the steel pipe is pretreated in advance. A resin-lined steel pipe, characterized in that a phosphate chemical conversion coating is applied and a metal spray coating is provided on the outer surface of the steel pipe.

(2) The adhesive layer is a maleic anhydride modified polyolefin, an itaconic anhydride modified polyolefin, an ethylene / maleic anhydride copolymer, an ethylene / maleic anhydride / acrylic acid copolymer, an ethylene / maleic anhydride / acrylic acid ester. A copolymer, an ethylene / acrylic acid copolymer, an ethylene / acrylic acid ester copolymer, an ethylene / methacrylic acid copolymer, an ethylene / vinyl acetate copolymer, or an ionomer, and The resin-lining steel pipe according to (1), wherein the melting end temperature of the adhesive layer is higher than the use temperature of the polyolefin resin layer or the crosslinked polyolefin resin layer and lower than the melting start temperature.

(3) The resin-lined steel pipe according to (1) or (2), wherein an epoxy primer layer is provided between the steel pipe and the adhesive layer.
(4) When manufacturing the resin-lined steel pipe, a polyolefin having a base treatment on the steel pipe or a base treatment on the steel pipe and then an epoxy primer layer, and having an adhesive layer on the outer surface smaller than the inner diameter of the steel pipe A resin pipe or a cross-linked polyolefin resin pipe is inserted into the steel pipe, the polyolefin pipe or cross-linked polyolefin resin pipe is brought into close contact with the inner surface of the steel pipe by squeezing the steel pipe, and the melting point of the adhesive layer is higher than the melting end temperature and the polyolefin resin pipe or cross-link The method for producing a resin-lined steel pipe according to any one of (1) to (3), wherein the bonding is performed by heating at a temperature lower than a melting start temperature of the polyolefin resin pipe.

(5) When the steel pipe is squeezed, the steel pipe is squeezed so that the outer diameter of the polyolefin resin pipe or the crosslinked polyolefin resin pipe is reduced by 0.5 to 10%. It is in the manufacturing method of a resin lined steel pipe.

  According to the present invention, instead of the inner and outer surface hot-dip metal-plated steel pipe, a steel pipe coated with a phosphate chemical conversion film subjected to grain refinement treatment is used, and a polyolefin resin layer or a cross-linked polyolefin resin layer is interposed via an adhesive layer. The inner surface lining is provided with an epoxy primer layer as required, and the outer surface is provided with a metal spray coating, so that oxygen, which is a corrosive factor, can be used instead of polyvinyl chloride without the need for complicated processes or special equipment. Even when polyolefin resin or cross-linked polyolefin resin with large permeation of the inner surface is lined, it can be used in place of the conventional resin-lined steel pipe with inner surface lining of polyvinyl chloride on the inner and outer surface molten metal-plated steel pipe. Piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. with excellent adhesion between steel pipe and inner resin lining layer It is possible to provide a resin lining steel pipe used in the.

  In producing the resin-lined steel pipe of the present invention, first, the surface of the steel pipe is degreased and cleaned by pickling or blasting. The outer diameter is about 10 to 2000 mm, usually about 20 to 170 mm. Next, as a base treatment for steel pipes, applying a chemical conversion treatment film of phosphate that has been refined with crystal grains and enhanced adhesion, it can be applied to piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. over a long period of time. Even if it is used, the inner surface resin lining layer will not peel off from the steel pipe, and even if the inner surface resin lining layer shrinks further in a cold region and the peel force increases, the chemical conversion coating film cannot withstand it and breaks down. I found that there was nothing.

  Moreover, it discovered that joining strength improved, so that the crystal | crystallization of the phosphate of a chemical conversion treatment film was finer. As the chemical conversion treatment solution, for example, a mixture (zinc calcium phosphate treatment solution) composed of phosphoric acid, nitric acid, zinc oxide, calcium carbonate and water and adjusted in pH with sodium hydroxide is used. Since zinc calcium phosphate is excellent in heat resistance, it is suitable for the present invention involving heating during production. These addition amounts are 8-15 g / L as phosphate ions, 30-60 g / L as nitrate ions, 2-4 g / L as zinc ions, 5-10 g / L as calcium ions, and pH is 2.0-2. In the range of 5, good water-resistant adhesion can be obtained. A typical zinc calcium phosphate treatment solution corresponding to the above composition is Palbond P (manufactured by Nippon Parkerizing Co., Ltd.).

The chemical conversion coating is preferably applied by dip coating or spray coating the chemical conversion treatment liquid on the surface of the steel pipe, and then washing and washing the steel pipe with water and heating and drying with hot air heating or high frequency induction heating. Adhesion amount of the chemical conversion film 1 to 10 g / m ² about good. If the adhesion amount is less than 1 g / m ² , the chemical conversion coating does not completely cover the iron surface, so that the water-resistant adhesive strength of the inner surface resin lining layer is reduced. On the other hand, if the amount of adhesion exceeds 10 g / m ² , brittle secondary crystal grains grow in the chemical conversion film, so that the adhesion and water-resistant adhesion of the inner surface resin lining layer are reduced.

  Before applying the chemical conversion coating, the crystal grain refining treatment is a treatment liquid in which, for example, titanium colloid is dispersed in water in the range of 1 to 5 g / L on the surface of the steel pipe (typically, Preparen Z (Japan By dip coating or spray coating, and / or by adding, for example, basic nickel carbonate as nickel ions to the chemical conversion solution in the range of 0.2 to 1.0 g / L. Do. Titanium or nickel serves as a nucleus for precipitation of phosphate crystal grains, and finely adheres to the iron surface to refine the crystal grains, increasing the contact area between the crystal grains and iron and improving the adhesion. If the crystal grain refinement process is not performed, crystal grains with a size of more than 10 μm are generated. However, if the crystal grain refinement process is performed, the crystal grain size is refined to 10 μm or less. It improves more. If the amount of addition is less than the lower limit, the effect of crystal grain refinement will be reduced, and if it exceeds the upper limit, the economy will deteriorate.

  Thereafter, a polyolefin resin pipe or a crosslinked polyolefin resin pipe having an outer diameter smaller than the inner diameter of the steel pipe and longer than the length of the steel pipe is inserted into the steel pipe, and the outer diameter of the polyolefin resin pipe or the crosslinked polyolefin resin pipe is reduced by 0.5 to 10%. A polyolefin resin pipe or a cross-linked polyolefin resin pipe is brought into close contact with the inner surface of the steel pipe by roll drawing, tapping drawing or die drawing so that the diameter of the steel pipe is reduced. When the diameter reduction ratio of the polyolefin resin pipe or the cross-linked polyolefin resin pipe is less than 0.5%, the expansion force for increasing the outer diameter of the polyolefin resin pipe or the cross-linked polyolefin resin pipe with respect to the inner diameter of the steel pipe is reduced. For this reason, the force to adhere to the inner surface of the steel pipe is weakened, and the adhesive force of the inner surface resin lining layer is reduced. If the diameter reduction ratio of the polyolefin resin pipe or the cross-linked polyolefin resin pipe is more than 10%, the polyolefin resin pipe or the cross-linked polyolefin resin pipe is deformed, resulting in poor adhesion to the inner surface of the steel pipe.

  Examples of polyolefin resins include ethylene homopolymers, ethylene-α-olefin copolymers obtained by copolymerizing ethylene and α-olefins such as propylene, 1-butene, 1-hexene, and 1-octene, or mixtures thereof. As long as the performance of the present invention is not impaired, a mixture in which an additive such as an antioxidant, an ultraviolet absorber, a flame retardant, a pigment, a filler, a lubricant, an antistatic agent, and other resins and the like are mixed is used. .

  As the crosslinked polyolefin resin, one obtained by crosslinking the polyolefin resin using a radical generator, or one obtained by water-crosslinking (silane crosslinking) the silane-modified polyolefin resin is used. Examples of the radical generator include organic peroxides such as dicumyl peroxide, benzoyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di (t-butylperoxy) hexane. use.

In addition to the above organic peroxides, azo compounds such as azoisobutyronitrile can also be used. Silane modification is performed by graft reaction of the ethylenically unsaturated silane compound to the polyolefin resin in the presence of a radical generator. Here, the ethylenically unsaturated silane compound is represented by the following general formula.
RSiR ' _n Y _3-n
(Wherein R represents an ethylenically unsaturated hydrocarbon group or hydrocarbon oxy group, R ′ represents an aliphatic saturated hydrocarbon group, Y represents a hydrolyzable organic group, and n represents 0 to 2).

  Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, or the like is used. This silane modification may be performed in advance with an extruder or the like, or may be performed in the kneader part of the molding machine by introducing each raw material component from the hopper during molding. The cross-linking reaction is performed by heat treatment, water treatment or the like at the time of extrusion molding and / or after molding. In the case of a silane-modified polyolefin resin, it is desirable to use a silanol condensation catalyst in combination in order to improve the crosslinking rate. This may be blended during molding or applied after molding. As the silanol condensation catalyst, dibutyltin dilaurate, dioctyltin dilaurate, cobalt naphthenate, toluenesulfonic acid and the like can be used. The crosslinked polyolefin resin used in the present invention is an additive such as an antioxidant, an ultraviolet absorber, a flame retardant, a pigment, a filler, a lubricant, an antistatic agent, and the like, as long as the performance of the present invention is not impaired. Other resins can be added.

  As a method for producing a polyolefin resin pipe or a cross-linked polyolefin resin pipe used in the present invention, the resin is extruded into a pipe shape by using an extruder or the like from a round die having an outer diameter smaller than the inner diameter of the steel pipe to be lined, Then, it is cooled and the shape is fixed. The thickness of this polyolefin resin pipe or cross-linked polyolefin resin pipe can be arbitrarily set as required and is not particularly limited, but is usually 0.3 mm or more and 10 mm or less, preferably 0.5 mm or more and 5 mm or less. Is used. Furthermore, in order to improve the adhesive strength with the adhesive layer, a commercial primer application, oxidation treatment, or surface roughening may be applied to the outer surface as necessary after molding the polyolefin resin pipe or the crosslinked polyolefin resin pipe.

  Since the steel pipe and the polyolefin resin pipe or the cross-linked polyolefin resin pipe are not very adhesive, it is desirable to have an adhesive layer between them. In particular, the adhesive layer comprises maleic anhydride modified polyolefin, itaconic anhydride modified polyolefin, ethylene / maleic anhydride copolymer, ethylene / maleic anhydride / acrylic acid copolymer, ethylene / maleic anhydride / acrylic acid ester copolymer Combining, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid copolymer, ethylene / vinyl acetate copolymer, or ionomer, melting end temperature Has been found to exhibit significantly better adhesive strength than other materials by forming it with a material that is less than the melting start temperature of the polyolefin resin pipe or the crosslinked polyolefin resin pipe and exceeds the operating temperature.

  As the polyolefin of the adhesive layer made of maleic anhydride-modified polyolefin, for example, a low crystalline ethylene polymer having a melting end temperature of 100 ° C. is used. When the melting end temperature is equal to or higher than the melting start temperature of the polyolefin resin pipe or the cross-linked polyolefin resin pipe, it is necessary to perform heating for expressing the adhesive force at a temperature higher than the melting start temperature of the polyolefin resin pipe or the cross-linked polyolefin resin pipe. Therefore, the polyolefin resin pipe or the cross-linked polyolefin resin pipe is softened and the expansion force is lost, and the shrinking force due to recrystallization is generated in the cooling process, and the force to adhere to the inner surface of the steel pipe is weakened. Adhesive strength decreases. Further, when the melting end temperature is equal to or lower than the use temperature of the polyolefin resin pipe or the cross-linked polyolefin resin pipe, since the adhesive layer is completely melted during use, the adhesive force of the inner surface resin lining layer is lowered.

  The adhesive layer is applied by using a two-layer round die having an outer diameter smaller than the inner diameter of the steel pipe to be lined on the outer surface of the polyolefin resin pipe or the outer surface of the crosslinked polyolefin resin pipe. The adhesive layer is coextruded and coated, or a round die or a T die is used to extrude and coat the adhesive layer after molding a polyolefin resin pipe or after forming a crosslinked polyolefin resin pipe.

  Furthermore, in order to develop adhesive force, after steel pipe is roll-drawn, tapping-drawn or die-drawn, it is higher than the melting end temperature of the adhesive layer by hot air heating or high-frequency induction heating, etc. and below the melting start temperature of polyolefin resin pipe or cross-linked polyolefin resin pipe Heat with. When the heating temperature is lower than the melting end temperature of the adhesive layer, the adhesive layer is not completely melted, so that the adhesive force of the inner surface resin lining layer is not exhibited.

  If the heating temperature is equal to or higher than the melting start temperature of the polyolefin resin pipe or cross-linked polyolefin resin pipe, the polyolefin resin pipe or cross-linked polyolefin resin pipe softens and loses its expansion force. As a result, the force to adhere to the inner surface of the steel pipe is weakened and the adhesive force of the inner surface resin lining layer is reduced. The thickness of the adhesive layer can be arbitrarily set as necessary, and is not particularly limited, but is usually 1 μm or more and 3 mm or less, preferably 10 μm or more and 1.5 mm or less.

  It is desirable to have an epoxy primer layer between the steel pipe and the adhesive layer because good water-resistant adhesion can be obtained. As the epoxy primer layer, for example, a mixture (epoxy resin powder primer) composed of epoxy, pigment, additive and curing agent is used. As the epoxy, for example, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, phenol novolac type or cresol novolac type glycidyl ether, or the like is used.

  These epoxies can be used alone, but the respective resins can be mixed and used according to the purpose. As the pigment, fine powders of extender pigments such as silica, barium sulfate and calcium carbonate, and colored pigments such as titanium oxide and carbon black are used. The amount of these pigments to be added is in the range of 3 to 50 parts by weight with respect to 100 parts by weight of the epoxy, and good water-resistant adhesion can be obtained. An acrylic oligomer, fine powder silica, etc. can be used for an additive.

  Curing agents include dibasic acids such as dicyandiamide and decanedicarboxylic acid, hydrazines such as adipic acid dihydrazide, acid anhydrides such as tetrahydrophthalic anhydride, and phenolic curing agents in which bisphenol A is added to diglycidyl ether of bisphenol A. Also, amine adducts obtained by adding diamide diphenylmethane to diglycidyl ether of bisphenol A can be used. When dibasic acids, hydrazines or phenolic curing agents are used as the curing agent, the amount of the curing agent is determined by the ratio of the epoxy equivalent of epoxy to the active hydrogen equivalent of the curing agent. As an equivalent ratio, an active hydrogen equivalent of 0.6 to 1.2 is good with respect to an epoxy equivalent of 1.0.

  When dicyandiamide is used as the curing agent, modified imidazole is added as a curing accelerator in order to reduce the curing temperature. As this modified imidazole, for example, 2-methylimidazole or 2-phenylimidazole can be used. In this case, when the curing agent is added in an amount of 3 to 10 parts by weight of dicyandiamide and 0.1 to 3 parts by weight of modified imidazole with respect to 100 parts by weight of epoxy, good water-resistant adhesion can be obtained. Similarly, when a phenolic curing agent is used, it is effective to use a modified imidazole as a curing accelerator. As a representative epoxy resin powder coating material corresponding to the above composition, there is Powderx E (manufactured by Nippon Paint Co., Ltd.).

  The epoxy primer layer is applied to the inner surface of the steel pipe at normal temperature to about 80 ° C., after the epoxy primer layer is electrostatic spray-painted or fluidly sucked, and then heated to about 140-220 ° C. by hot air heating or high-frequency induction heating. -It should be done after curing. The thickness of the epoxy primer layer is preferably about 40 to 600 μm. If the film thickness is less than 40 μm, it may be less than the film-forming limit of the powder coating material, so that it does not become a continuous film, so the water-resistant adhesive strength of the inner surface resin lining layer is reduced. From the viewpoint of workability and economy, the upper limit of the film thickness is preferably about 600 μm.

  A metal spray coating is applied to the outer surface of the inner surface resin-lined steel pipe instead of the conventional molten metal plating. As the metal spray coating, for example, zinc, aluminum, zinc / aluminum alloy, and aluminum / magnesium alloy, which are metals that sacrifice and prevent iron, are used. In applying the metal spray coating, first, the outer surface of the steel pipe is degreased and cleaned by blasting. At this time, it has been found that the adhesion of the metal sprayed coating is not lowered because the adhesion to the iron is large even if the phosphate chemical conversion coating that has undergone grain refinement treatment on the outer surface of the steel pipe remains. It was.

  Thereafter, the metal sprayed coating is applied to the outer surface of the steel pipe by gas flame spraying, electric arc spraying, or electric plasma spraying. The thickness of the metal spray coating is preferably about 100 to 400 μm. If the film thickness is less than 100 μm, the corrosion resistance is lower than that of conventional molten metal plating. This is because, due to the difference in density between the two, it is generally said that the normal thickness of 85 μm of the molten metal plating is equivalent to the thickness of the metal spray coating of 100 μm. However, in molten metal plating, there is always an alloy layer containing iron at the interface with the steel pipe that is inferior in corrosion resistance, and the pure metal layer with excellent corrosion resistance is thinner than the metal sprayed coating, so the thickness of the metal sprayed coating is 100 μm. Corrosion resistance may be improved from the metal plating thickness of 85 μm. From the viewpoint of workability and economy, the upper limit of the film thickness is preferably about 400 μm. Further, in order to improve the corrosion resistance, a white rust preventive paint or a sealing agent may be applied as necessary after applying the metal spray coating.

Hereinafter, the present invention will be specifically described based on examples.
Example 1
A steel pipe surface with an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm is degreased with a commercially available alkaline degreasing agent, pickled and derusted, and then a treatment liquid in which titanium colloid is dispersed in water (Nippon Parkerizing) Steel pipes were sequentially dipped in a preparene Z) and zinc calcium phosphate treatment solution (Palbond P, manufactured by Nihon Parkerizing Co., Ltd.) and dried by hot air heating to form a chemical conversion coating. The adhesion amount of the chemical conversion film was 4 g / m ² and the average particle size was about 5 μm. Next, using a two-layer round die, an adhesive made of maleic anhydride-modified polyethylene on the outer surface at the time of molding a polyethylene resin pipe (melting start temperature 120 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm ( A melting end temperature of 100 ° C. was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

  Thereafter, the polyethylene resin pipe is inserted into the steel pipe, and after the steel pipe is roll-drawn so that the outer diameter of the polyethylene resin pipe is reduced by 1.4%, the polyethylene resin pipe is brought into close contact with the inner surface of the steel pipe, The whole was heated to 115 ° C. in a hot air heating furnace and bonded. The polyethylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe is degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then zinc (85%) / aluminum (15%) alloy is sprayed to a thickness of 100 μm by an electric arc method. Furthermore, a 10 μm thick rust preventive paint was applied.

(Example 2)
A steel pipe surface with an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm is degreased with a commercially available alkaline degreasing agent, pickled and derusted, and then a treatment liquid in which titanium colloid is dispersed in water (Nippon Parkerizing) Steel pipes were sequentially dipped in a preparene Z) and zinc calcium phosphate treatment solution (Palbond P, manufactured by Nihon Parkerizing Co., Ltd.) and dried by hot air heating to form a chemical conversion coating. The adhesion amount of the chemical conversion film was 4 g / m ² and the average particle size was about 5 μm. Next, an epoxy resin powder primer (Nippon Paint Co., Ltd., Powderx E) was applied to the inner surface of the steel pipe at room temperature by an electrostatic spray method, and the whole was heated to 155 ° C. in a hot air heating furnace to form an epoxy primer layer. . The thickness of the epoxy primer layer was 100 μm. Furthermore, using a double-layer round die, an adhesive made of maleic anhydride-modified polyethylene (melting) on the outer surface during molding of a polyethylene resin pipe (melting start temperature 120 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm An end temperature of 100 ° C.) was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

  Thereafter, the polyethylene resin pipe is inserted into the steel pipe, and after the steel pipe is roll-drawn so that the outer diameter of the polyethylene resin pipe is reduced by 1.4%, the polyethylene resin pipe is brought into close contact with the inner surface of the steel pipe, The whole was heated to 115 ° C. in a hot air heating furnace and bonded. The polyethylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe is degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then zinc is sprayed to a thickness of 100 μm by an electric arc method. Further, a white rust prevention paint is formed to a thickness of 10 μm. Painted.

(Example 3)
A resin-lined steel pipe was obtained in the same manner as in Example 2 except that aluminum spray was used as the metal spray coating.

Example 4
A resin-lined steel pipe was obtained in the same manner as in Example 2 except that zinc (85%) / aluminum (15%) alloy spray was used as the metal spray coating.

(Example 5)
A resin-lined steel pipe was obtained in the same manner as in Example 2 except that aluminum (95%) / magnesium (5%) alloy spray was used as the metal spray coating.

(Example 6)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive made of itaconic anhydride-modified polyethylene (melting completion temperature: 100 ° C.) was used as the adhesive layer.

(Example 7)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive made of an ethylene / maleic anhydride copolymer (melting completion temperature: 100 ° C.) was used as the adhesive layer.

(Example 8)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive composed of an ethylene / maleic anhydride / acrylic acid copolymer (melting completion temperature: 100 ° C.) was used as the adhesive layer.

Example 9
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive made of an ethylene / maleic anhydride / acrylic acid ester copolymer (melting completion temperature: 100 ° C.) was used as the adhesive layer.

(Example 10)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive made of an ethylene / acrylic acid copolymer (melting completion temperature: 100 ° C.) was used as the adhesive layer.

(Example 11)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive made of an ethylene / acrylic acid ester copolymer (melting end temperature: 100 ° C.) was used as the adhesive layer.

(Example 12)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive made of an ethylene / methacrylic acid copolymer (melting end temperature: 100 ° C.) was used as the adhesive layer.

(Example 13)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive composed of an ethylene / vinyl acetate copolymer (melting completion temperature: 100 ° C.) was used as the adhesive layer.

(Example 14)
A resin-lined steel pipe was obtained in the same manner as in Example 4 except that an adhesive made of ionomer (melting end temperature: 100 ° C.) was used as the adhesive layer.

(Example 15)
A steel pipe surface with an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm is degreased with a commercially available alkaline degreasing agent, pickled and derusted, and then a treatment liquid in which titanium colloid is dispersed in water (Nippon Parkerizing) Steel pipes were sequentially dipped in a preparene Z) and zinc calcium phosphate treatment solution (Palbond P, manufactured by Nihon Parkerizing Co., Ltd.) and dried by hot air heating to form a chemical conversion coating. The adhesion amount of the chemical conversion film was 4 g / m ² and the average particle size was about 5 μm. Next, using a two-layer round die, an adhesive made of maleic anhydride-modified polypropylene on the outer surface at the time of molding a polypropylene resin pipe (melting start temperature 155 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm ( The melting end temperature (145 ° C.) was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

  Thereafter, the polypropylene resin pipe is inserted into the steel pipe, and after the steel pipe is roll-drawn so that the outer diameter of the polypropylene resin pipe is reduced by 1.4%, the polypropylene resin pipe is brought into close contact with the inner surface of the steel pipe, The whole was heated to 150 ° C. in a hot air heating furnace and bonded. The polypropylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe is degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then zinc (85%) / aluminum (15%) alloy is sprayed to a thickness of 100 μm by an electric arc method. Furthermore, a 10 μm thick rust preventive paint was applied.

(Example 16)
A steel pipe surface with an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm is degreased with a commercially available alkaline degreasing agent, pickled and derusted, and then a treatment liquid in which titanium colloid is dispersed in water (Nippon Parkerizing) Steel pipes were sequentially dipped in a preparene Z) and zinc calcium phosphate treatment solution (Palbond P, manufactured by Nihon Parkerizing Co., Ltd.) and dried by hot air heating to form a chemical conversion coating. The adhesion amount of the chemical conversion film was 4 g / m ² and the average particle size was about 5 μm. Next, an epoxy resin powder primer (Nippon Paint Co., Ltd., Powderx E) was applied to the inner surface of the steel pipe at room temperature by an electrostatic spray method, and the whole was heated to 155 ° C. in a hot air heating furnace to form an epoxy primer layer. . The thickness of the epoxy primer layer was 100 μm. Furthermore, using a double-layer round die, an adhesive made of maleic anhydride-modified polypropylene (melting) on the outer surface at the time of molding a polypropylene resin pipe (melting start temperature 155 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm (End temperature 145 ° C.) was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

  Thereafter, the polypropylene resin pipe is inserted into the steel pipe, and the steel pipe is roll-drawn so that the outer diameter of the polypropylene resin pipe is reduced by 1.4%, thereby bringing the polypropylene resin pipe into close contact with the inner surface of the steel pipe, The whole was heated to 150 ° C. in a hot air heating furnace and bonded. The polypropylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe is degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then zinc (85%) / aluminum (15%) alloy is sprayed to a thickness of 100 μm by an electric arc method. Furthermore, a 10 μm thick rust preventive paint was applied.

(Example 17)
A steel pipe surface with an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm is degreased with a commercially available alkaline degreasing agent, pickled and derusted, and then a treatment liquid in which titanium colloid is dispersed in water (Nippon Parkerizing) Steel pipes were sequentially dipped in a preparene Z) and zinc calcium phosphate treatment solution (Palbond P, manufactured by Nihon Parkerizing Co., Ltd.) and dried by hot air heating to form a chemical conversion coating. The adhesion amount of the chemical conversion film was 4 g / m ² and the average particle size was about 5 μm. Next, an adhesive made of maleic anhydride-modified polyethylene on the outer surface at the time of molding a cross-linked polyethylene resin pipe (melting start temperature 120 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm using a two-layer round die (A melting end temperature of 100 ° C.) was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

  Thereafter, the cross-linked polyethylene resin pipe is inserted into the steel pipe and the steel pipe is roll-squeezed so that the outer diameter of the cross-linked polyethylene resin pipe is reduced by 1.4%, thereby bringing the cross-linked polyethylene resin pipe into close contact with the inner surface of the steel pipe. After that, the whole was heated to 115 ° C. in a hot air heating furnace and bonded. The cross-linked polyethylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe is degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then zinc (85%) / aluminum (15%) alloy is sprayed to a thickness of 100 μm by an electric arc method. Furthermore, a 10 μm thick rust preventive paint was applied.

(Example 18)
A steel pipe surface with an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm is degreased with a commercially available alkaline degreasing agent, pickled and derusted, and then a treatment liquid in which titanium colloid is dispersed in water (Nippon Parkerizing) Steel pipes were sequentially dipped in a preparene Z) and zinc calcium phosphate treatment solution (Palbond P, manufactured by Nihon Parkerizing Co., Ltd.) and dried by hot air heating to form a chemical conversion coating. The adhesion amount of the chemical conversion film was 4 g / m ² and the average particle size was about 5 μm. Next, an epoxy resin powder primer (Nippon Paint Co., Ltd., Powderx E) was applied to the inner surface of the steel pipe at room temperature by an electrostatic spray method, and the whole was heated to 155 ° C. in a hot air heating furnace to form an epoxy primer layer. . The thickness of the epoxy primer layer was 100 μm. Furthermore, using a double-layer round die, an adhesive made of maleic anhydride-modified polyethylene on the outer surface at the time of molding a crosslinked polyethylene resin pipe (melting start temperature 120 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm ( A melting end temperature of 100 ° C. was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

  Thereafter, the cross-linked polyethylene resin pipe is inserted into the steel pipe and the steel pipe is roll-squeezed so that the outer diameter of the cross-linked polyethylene resin pipe is reduced by 1.4%, thereby bringing the cross-linked polyethylene resin pipe into close contact with the inner surface of the steel pipe. After that, the whole was heated to 115 ° C. in a hot air heating furnace and bonded. The cross-linked polyethylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe is degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then zinc (85%) / aluminum (15%) alloy is sprayed to a thickness of 100 μm by an electric arc method. Furthermore, a 10 μm thick rust preventive paint was applied.

(Comparative Example 1)
Using a double-layered round die, an adhesive made of an ethylene / vinyl acetate copolymer on the outer surface when molding a polyvinyl chloride pipe (melting start temperature 120 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm ( A melting end temperature of 100 ° C. was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm. Next, the polyvinyl chloride pipe was inserted into a steel pipe having an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm, the inner and outer surfaces of which were hot dip galvanized (thickness 85 μm). By rolling the steel pipe so that the outer diameter was reduced by 1.4%, the polyvinyl chloride pipe was brought into close contact with the inner surface of the steel pipe, and then the whole was heated to 115 ° C. and bonded in a hot air heating furnace. The polyvinyl chloride pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe was coated with a 10 μm thick antirust paint.

(Comparative Example 2)
Adhesive made of maleic anhydride-modified polyethylene (melting end temperature) on the outer surface when molding a polyethylene resin pipe (melting start temperature 120 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm, using a two-layer round die 100 ° C.) was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm. Next, the polyethylene resin pipe is inserted into a steel pipe having an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm, the inner and outer surfaces of which are hot dip galvanized (thickness 85 μm). After the steel pipe was roll-drawn so that the diameter was reduced by 1.4%, the polyethylene resin pipe was brought into close contact with the inner surface of the steel pipe, and then the whole was heated to 115 ° C. and bonded in a hot air heating furnace. The polyethylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe was coated with a 10 μm thick antirust paint.

(Comparative Example 3)
Adhesive (melting end temperature) made of maleic anhydride-modified polypropylene on the outer surface when forming a polypropylene resin pipe (melting start temperature 155 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm using a two-layer round die 145 ° C.) was coated by a coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm. Next, the polypropylene resin pipe is inserted into a steel pipe having an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm, the inner and outer surfaces of which are hot dip galvanized (thickness 85 μm). After rolling the steel pipe so that the diameter of the steel pipe was reduced by 1.4%, the polypropylene resin pipe was brought into close contact with the inner surface of the steel pipe, and then the whole was heated to 150 ° C. and bonded in a hot air heating furnace. The polypropylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe was coated with a 10 μm thick antirust paint.

(Comparative Example 4)
Adhesive made of maleic anhydride-modified polyethylene on the outer surface at the time of molding a cross-linked polyethylene resin pipe (melting start temperature 120 ° C.) having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm, using a two-layer round die A temperature of 100 ° C.) was coated by a co-extrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm. Next, the cross-linked polyethylene resin pipe is inserted into a steel pipe having an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm, the inner and outer surfaces of which are hot dip galvanized (thickness 85 μm). The steel pipe was roll-drawn so that the outer diameter was reduced by 1.4%, thereby bringing the crosslinked polyethylene resin pipe into close contact with the inner surface of the steel pipe, and then the whole was heated to 115 ° C. and bonded in a hot air heating furnace. The cross-linked polyethylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this inner surface resin-lined steel pipe was coated with a 10 μm thick antirust paint.

  For the resin-lined steel pipes of Examples 1 to 18 and Comparative Examples 1 to 4, the shear adhesive force between the steel pipe and the resin pipe on the inner surface was measured. The shear adhesive force is measured by cutting the produced resin-lined steel pipe into a length of 20 mm, supporting only the steel pipe part using a jig, and extruding only the resin-lining layer on the inner surface under the condition of 10 mm / min. The shear adhesive strength was determined from the punching force at the time. Three samples were taken from each resin-lined steel pipe, and the average value was obtained. The unit of the shear adhesive force is MPa. The temperature during the measurement was uniformly 23 ° C. The shear adhesive strength after passing hot water of 40 ° C. or hot water of 90 ° C. through the resin-lined steel pipe for one year was also measured. Table 1 shows the conditions and measurement results of each example.

  The shear adhesive force after passing 40 ° C. warm water of Examples 1 to 18 for one year shows a value equivalent to that of Comparative Example 1 in which polyvinyl chloride is lined on the inner surface of a conventional inner and outer surface hot-dip galvanized steel pipe, It turns out that it is high compared with Comparative Examples 2-4. Moreover, the shear adhesive force after passing 90 degreeC hot water of Examples 1-18 for one year is a high value compared with the comparative example 1 which inner surface lined polyvinyl chloride to the conventional inner and outer surface hot-dip galvanized steel pipe. It can be seen that it is significantly higher than Comparative Examples 2 to 4, and can also be used for hot water supply piping over a long period of time.

Furthermore, a salt spray test was conducted on the resin-lined steel pipes of Examples and Comparative Examples in order to investigate the corrosion resistance of the outer surface. The salt spray test is performed by the method defined in JIS Z 2371 after cutting the manufactured resin-lined steel pipe to a length of 150 mm and attaching a ridge that reaches the steel pipe with a chuck claw of a screw cutter on the outer surface. The time until red rust was generated was measured. The measurement results are also shown in Table 1.
It can be seen that the time until red rust is generated from the heel portion of each of Examples 1 to 18 is longer than those of Comparative Examples 1 to 4 in which hot dip galvanizing is performed on the conventional outer surface, and is excellent in corrosion resistance.

From this table, for the resin-lined steel pipe of the present invention, a polyolefin resin or a cross-linked polyolefin resin having a large permeation of oxygen, which is a corrosive factor, is used instead of polyvinyl chloride without the need for complicated processes and special equipment. Even in the case of lining, it can be used in place of the conventional resin lining steel pipe with inner surface lining of polyvinyl chloride on the inner and outer surface molten metal plated steel pipe, and it has excellent adhesion between the steel pipe and the inner surface resin lining layer for a long period of time. Turned out to be.


Patent applicant: Nippon Steel Corporation
Attorney Attorney Shiina and others 1

Claims (5)

  The steel pipe has an adhesive layer on the inner surface, and further has a polyolefin resin layer or a cross-linked polyolefin resin layer on the inner side, and the steel pipe is a pre-treated steel pipe, and the grain refinement process was performed as the base process. A resin-lined steel pipe, which is provided with a chemical conversion coating of phosphate and has a metal spray coating on the outer surface of the steel pipe.   The adhesive layer is a maleic anhydride modified polyolefin, an itaconic anhydride modified polyolefin, an ethylene / maleic anhydride copolymer, an ethylene / maleic anhydride / acrylic acid copolymer, an ethylene / maleic anhydride / acrylic acid ester copolymer. , An ethylene / acrylic acid copolymer, an ethylene / acrylic acid ester copolymer, an ethylene / methacrylic acid copolymer, an ethylene / vinyl acetate copolymer, an ionomer, and the adhesive 2. The resin-lined steel pipe according to claim 1, wherein a melting end temperature of the layer is higher than a use temperature of the polyolefin resin layer or the crosslinked polyolefin resin layer and lower than a melting start temperature.   The resin-lined steel pipe according to claim 1 or 2, further comprising an epoxy primer layer between the steel pipe and the adhesive layer.   In producing the resin-lined steel pipe, a polyolefin resin pipe having an adhesive layer on the outer surface smaller than the inner diameter of the steel pipe, or a base treatment is applied to the steel pipe, or a base treatment is applied to the steel pipe and then an epoxy primer layer is applied. A cross-linked polyolefin resin pipe is inserted into the steel pipe, and the steel pipe is squeezed so that the polyolefin resin pipe or the cross-linked polyolefin resin pipe is brought into close contact with the inner surface of the steel pipe. The method for producing a resin-lined steel pipe according to any one of claims 1 to 3, wherein the bonding is performed by heating at a temperature lower than the melting start temperature.   5. The resin-lined steel pipe according to claim 4, wherein when the steel pipe is squeezed, the steel pipe is squeezed so that the outer diameter of the polyolefin resin pipe or the cross-linked polyolefin resin pipe is reduced by 0.5 to 10%. Production method.