WO2006054731A1

WO2006054731A1 - Steel pipe with resin lining and process for producing the same

Info

Publication number: WO2006054731A1
Application number: PCT/JP2005/021309
Authority: WO
Inventors: Shinichi Funatsu; Hiroyuki Mimura; Yoshihisa Kariyazono
Original assignee: Nippon Steel Corporation
Priority date: 2004-11-16
Filing date: 2005-11-15
Publication date: 2006-05-26
Also published as: JP2006144038A; TWI298774B; TW200624701A

Abstract

A steel pipe with resin lining that can be used in place of conventional resin lined steel pipes produced by subjecting a molten metal plated steel pipe having its internal and external surfaces furnished with plating layers to internal surface lining with polyvinyl chloride and that excels in the adhesion between steel pipe and resin lining so as to be serviceable in, for example, a piping for water supply, hot-water supply, air conditioning, fire control, drainage, etc. over a period longer than in the prior art; and a process for producing the steel pipe with resin lining. There is provided a steel pipe with resin lining characterized in that at least an internal surface of steel pipe is furnished with a chemical treatment coating composed of phosphate crystals of ≤ 10 μm particle diameter, and that further a resin layer of polyolefin resin or crosslinked polyolefin resin is bonded via an adhesive layer to the internal surface of the steel pipe, and that thereafter the external surface of the steel pipe is furnished with a sprayed layer of a metal or alloy baser than iron. Further, there is provided a process for producing the steel pipe with resin lining.

Description

Description Resin-lined steel pipe and its manufacturing method Technical Field

The present invention relates to a resin-lined steel pipe suitable for pipes for water supply, hot water supply, air conditioning, fire extinguishing, drainage, and the like, and a method for manufacturing the same. Background art

Steel pipes such as forged steel pipes and electric steel pipes are more resistant to mechanical strength, impact resistance during construction, and under heavy traffic roads than thermoplastic resin pipes such as polyvinyl chloride, polyethylene, polypropylene, and polybutene. Excellent compression resistance when buried, high pressure strength when transporting high-temperature fluid, and excellent combustion resistance. On the other hand, steel pipes have poorer corrosion resistance than resin pipes, so it is necessary to use resin pipes that do not cause corrosion in applications where steel corrosion is a problem, or to prevent fluid turbidity and blockage of pipes.

For this reason, resin-lined steel pipes are used for applications where mechanical properties and corrosion resistance are required, and have the advantages of both steel pipes and resin pipes. For example, a resin pipe made of inexpensive polyvinyl chloride is used as a water supply pipe or a drain pipe, and a resin lined steel pipe in which a resin pipe made of hard polyvinyl chloride is bonded to the inner surface of a steel pipe as a hot water pipe.

However, since polyvinyl chloride generates dioxin during incomplete combustion, incineration and disposal of residual materials generated during local piping work can be a problem. Therefore, instead of polyvinyl chloride, water pipes, hot water pipes, drain pipes, etc. are bonded to the inner surface with resin pipes made of polyolefin resin or cross-linked polyolefin resin that do not cause the problem of dioxin generation. Resin-lined steel pipes have been proposed.

Conventionally, resin-lined steel pipes used as indoor pipes or outdoor exposed pipes are made by melting a metal or alloy that sacrifices and protects iron, such as zinc or a zinc alloy, on the inner and outer surfaces to improve the corrosion resistance of the outer surface. Polyvinyl chloride was lined on the broken steel pipe. However, when lining the inner and outer surfaces of a steel pipe with a hot-dip galvanized polyolefin resin or cross-linked polyolefin resin, which has a much greater permeability of oxygen, which is a corrosive factor compared to polyvinyl chloride, when used for a long time Corrosion of the molten zinc plating layer. As a result, the adhesive interface between the steel pipe and the resin pipe deteriorates and the adhesive strength weakens, and the resin pipe peels from the inner surface of the steel pipe.

In order to prevent such peeling of the resin layer from the inner surface of the resin-lined steel pipe, the inner surface of the steel pipe that has been subjected to molten metal plating only on the outer surface without applying molten metal plating is used on the inner surface of the polyolefin resin or cross-linked polyolefin. For example, JP 2003-29474 A and International Publication W02004-01 123 1 have proposed resin-lined steel pipes bonded with plastic resin. However, applying molten metal to only the outer surface of the steel pipe requires complicated processes and special equipment, which increases the manufacturing and equipment costs. It is also conceivable to remove the molten metal plating on the inner surface of the steel pipe after applying the molten metal plating to the inner and outer surfaces of the steel pipe. However, it is difficult to completely remove the molten metal plating by blasting. It is also conceivable to pickle only the inner surface of the steel pipe and remove the molten metal plating, but this also requires complicated processes and special equipment.

As described above, the method of applying the molten metal plating only to the outer surface of the steel pipe requires a complicated process and special equipment, which increases the cost of manufacturing and equipment. Furthermore, 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, it is necessary to apply a chemical conversion coating to the steel pipe as a base treatment, but the chemical conversion coating is applied only to the inner surface of the steel pipe. After all, there were problems when complicated processes and special equipment were required.

In the present invention, even when a resin pipe made of a polyolefin resin or a cross-linked polyolefin resin having a high permeability of oxygen, which is a corrosive factor, is used instead of polyvinyl chloride, the resin layer from the inner surface of the steel pipe is lined. It is an object to prevent peeling. Disclosure of the invention

The gist of the present invention is as follows.

(1) At least the inner surface of the steel pipe is provided with a chemical conversion film made of a phosphate crystal having a particle size of 10 m or less, and a resin layer made of a polyolefin resin or a crosslinked polyolefin resin is formed on the inner surface of the steel pipe. A resin-lined steel pipe, wherein a thermal spray layer made of a metal or an alloy that is lower than iron is provided on the outer surface of the steel pipe after being adhered through an adhesive layer.

(2) The adhesive layer is made of maleic anhydride modified polyolefin, anhydrous anhydride modified polyolefin, ethylene / maleic anhydride copolymer, ethylene / maleic anhydride / acrylic acid copolymer, ethylene / anhydride copolymer. One of the following: oleic acid / acrylic acid ester copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid copolymer, ethylene / vinyl acetate copolymer, ionomer The resin-lined steel pipe according to (1) above, wherein the melting end temperature of the adhesive layer is higher than 15 ° C and lower than the melting start temperature of the resin layer. .

(3) The resin-lined steel pipe according to the above (1) or (2), which has an epoxy primer layer between the inner surface of the steel pipe and the adhesive layer.

(4) Thermal spray layer is zinc, zinc-aluminum mixture, zinc, aluminum The resin-lined steel pipe according to any one of the above (1) to (3), wherein the resin-lined steel pipe is any one of rum alloys.

(5) The resin-lined steel pipe according to (4) above, wherein the sprayed layer is a zinc-aluminum mixture or a zinc-aluminum alloy containing 30% or less of aluminum.

(6) The punching shear adhesive force between the steel pipe of the resin-lined steel pipe with the thermal spray layer on the outer surface and the inner resin layer is 10 to 40% greater than that of the resin-lined steel pipe with no thermal spray layer on the outer surface. The resin-lined steel pipe according to any one of (1) to (5) above, wherein

(7) The steel pipe is subjected to a base treatment to form a chemical conversion film made of phosphate crystals having a particle size of 10 m or less, and has an outer diameter smaller than the inner diameter of the steel pipe, and is made of a polyolefin resin or a crosslinked polyolefin. An adhesive layer is provided on the outer surface of a resin pipe made of a resin, the resin pipe is inserted into the steel pipe, and the resin pipe is tightly adhered to the inner surface of the steel pipe via the adhesive layer by squeezing the steel pipe. The resin-lined steel pipe is manufactured by heating and bonding at a temperature equal to or higher than the melting end temperature of the layer and lower than the melting start temperature of the resin pipe, and spraying a metal or alloy lower than iron on the outer surface of the steel pipe. Manufacturing method.

(8) The method for producing a resin-lined steel pipe according to the above (7), wherein after the chemical conversion treatment film is formed on the inner surface of the steel pipe, an epoxy primer layer is provided.

(9) The method for producing a resin-lined steel pipe according to the above (7) or (8), wherein the steel pipe is narrowed so that the outer diameter of the resin pipe is reduced by 0.5 to 10%.

(10) The resin-lined steel pipe according to any one of the above (7) to (9), wherein any one of zinc, a zinc-aluminum mixture, zinc, and an aluminum alloy is thermally sprayed on the outer surface of the steel pipe. Production method. (11) The method for producing a resin-lined steel pipe according to (10) above, wherein the outer surface of the steel pipe is sprayed with a zinc / aluminum mixture or a zinc / aluminum alloy containing 30% or less of aluminum. BEST MODE FOR CARRYING OUT THE INVENTION

A method for producing the resin-lined steel pipe of the present invention will be described. Degrease a steel pipe with an outer diameter of 10 to 2000 mm, preferably 20 to 170 mm, pickle it, and clean it by blasting if necessary. Next, a chemical conversion coating is formed on the inner surface of the steel pipe. The phosphate crystals of this chemical conversion coating must be made fine with a particle size of 10 ^ m or less in order to improve the joint strength between the steel pipe and the resin pipe made of polyolefin resin or cross-linked polyolefin resin. When the grain size of phosphate crystals is 10 m or less, the adhesion is improved by more than 3 times compared to the case where the grain size exceeds 10 m.

This makes it possible to prevent the resin layer from peeling off from the inner surface of the steel pipe even when used for piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. over a long period of time. Even if it shrinks and the peel force increases, the chemical conversion coating is not destroyed.

Deposition amount of the chemical conversion coating to the inner surface of the steel pipe is l to 10 g / m ² is not preferable. If the amount of the chemical conversion coating is less than 1 g / m ² , the chemical conversion coating may not completely cover the inner surface of the steel pipe, and the water-resistant adhesive strength of the resin layer on the inner surface of the steel pipe may be reduced. In addition, if the amount of chemical conversion coating is more than 10 g / m ² , brittle secondary grains may grow on the chemical conversion coating, reducing the adhesion between the inner surface of the steel pipe and the resin layer and the water-resistant adhesive strength. There are things to do.

In order to make the crystal grains of the chemical conversion coating finer, before the chemical conversion treatment, the metal that makes the phosphate crystal grains fine is attached to the steel pipe, or when the chemical conversion treatment is performed, the steel pipe Gold that refines phosphate grains The genus should be deposited first. The treatment for depositing metal to refine the phosphate crystal grains on the steel pipe and the treatment for precipitation may be used in combination. The crystal grain refinement treatment and chemical conversion treatment may be performed on at least the inner surface of the steel pipe, but may be performed on both the inner surface and the outer surface.

First, a process for attaching a metal that refines phosphate crystal grains to a steel pipe will be described. For example, a treatment liquid (preparation Z (manufactured by Nihon Parkerizing Co., Ltd.)) in which titanium colloid is dispersed in water in the range of 1 to 5 g / L, for example, is dip-coated or sprayed on the surface of the steel pipe. Paint.

Next, the chemical conversion treatment will be described. In the chemical conversion treatment, the chemical conversion solution is dip-applied on the inner and outer surfaces of the steel pipe or spray coated on at least the inner surface of the steel pipe, and then the steel pipe is washed with water and hot water, heated and dried by hot air heating, high-frequency induction heating, etc. A treatment film is formed. As a 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 to pH with sodium hydroxide is used. In particular, since zinc calcium phosphate is excellent in heat resistance, it is suitable for the present invention that involves heating during production. The preferred ranges of these addition amounts are 8-15 g / L for phosphate ions, 30-60 g / L for nitrate ions, 2-4 g / L for zinc ions, and 5-10 g / L for calcium ions. The pH is 2.0 to 2.5, which provides good water tightness. Palpond P (manufactured by Nihon Parkerizing Co., Ltd.) is a typical zinc phosphate treatment solution corresponding to this composition.

In addition, by adding basic nickel carbonate, for example, in the range of 0.2 to 1.0 g ZL as a nickel ion, the phosphate crystal grains are refined in the steel pipe. Even if the treatment to attach the metal to be removed is omitted, the grain size of the phosphate crystals in the chemical conversion coating should be 10 ^ m or less. can do. Such addition of nickel can also be performed when chemical conversion treatment is performed after the treatment of attaching a metal for refining phosphate crystal grains to a steel pipe.

Titanium colloid and nickel used for grain refinement process become the core of phosphate crystal grain precipitation during chemical conversion, and titanium colloid adheres densely to the surface of the steel pipe, and nickel is dense on the surface of the steel pipe. To crystallize the crystal grains. This increases the contact area between the phosphate crystal grains and the steel pipe and improves the adhesion.

If the titanium colloid used for the grain refinement treatment is less than 1 g / L or the nickel ion is less than 0.2 g / L, the effect of grain refinement may be reduced. On the other hand, if the titanium colloid used for grain refinement is more than 5 g Z L or the nickel ion is more than 1.0 g Z L, the economic efficiency may deteriorate.

It is preferable to provide an epoxy primer layer after the chemical conversion coating is formed on at least the inner surface of the steel pipe. When an epoxy primer layer is provided between the inner surface of the steel pipe and the adhesive layer, good water-resistant adhesion can be obtained over a long period of time when a resin-lined steel pipe is used. The epoxy primer layer can be formed, for example, by applying a mixture (epoxy resin powder primer) composed of an epoxy, a pigment, an additive and a curing agent, and curing it by heating. As the epoxy, for example, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, phenol nopolac-type or cresol nopolac-type glycidyl ether, or the like is used.

These epoxies can be used alone, but each resin can be mixed and used according to the purpose. As pigments, fine powders of extender pigments such as silica, barium sulfate and calcium carbonate, and colored pigments such as titanium oxide and force pump racks are used. these By adding the pigment in an amount of 3 to 50 parts by weight with respect to 100 parts by weight of the epoxy, good water-resistant adhesion can be obtained. As the additive, acryl oligomer, fine powder silica or the like can be used.

Hardeners include dibasic acids such as dicyandiamide and decanedicarboxylic acid, hydrazines such as adipic acid dihydrazide, acid anhydrides such as tetrahydrofuranic anhydride, bisphenol to diglycidyl ether of bisphenol A A phenolic curing agent to which A has been added or amine adducts to which diamide diphenylmethane has been added to diglycidyl ether of bisphenol A can be used. When dibasic acid or hydrazine phenolic curing agent is used as the curing agent, the amount of curing agent is determined by the ratio of epoxy equivalent of epoxy to active hydrogen equivalent of curing agent. As the equivalent ratio, the active hydrogen equivalent is preferably in the range of 0.6 to 1.2 with respect to the epoxy equivalent of 1.0.

When dicyandiamide is used as the curing agent, modified imidazole is added as a curing accelerator to reduce the curing temperature. As this modified imidazole, for example, 2-methylimidazole 2-phenol imidazole and the like can be used. In this case, the curing agent is blended 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. can get. Similarly, when using a phenolic curing agent, it is effective to use modified imidazole as a curing accelerator. As a representative epoxy resin powder coating material corresponding to this composition, there is PUDAX E (manufactured by Nippon Paint Co., Ltd.).

The epoxy primer layer is formed by coating the inner surface of the steel tube with the chemical conversion coating on the inner surface of the steel tube at room temperature to 80 ° C by electrostatic spraying or fluid suction, and then heating the steel tube with hot air or high-frequency induction. It is good to carry out heating and heating to about 140-220 ° C and curing. This epo The thickness of the xyprimer layer is preferably 40 to 600 m. If the film thickness of one epoxy liner is less than 40 m, it may be less than the film-forming limit of the powder coating, and it will not be a continuous film, reducing the water-resistant adhesion between the inner surface of the steel pipe and the resin layer. Sometimes. From the viewpoint of workability and economy, the upper limit of the film thickness of the epoxy primer is preferably 600 m or less.

A chemical conversion film is formed, and if necessary, a resin tube made of a polyolefin resin or a crosslinked polyolefin resin is brought into close contact with the inner surface of the steel tube provided with an epoxy primer layer via an adhesive layer. Polyolefin resins include ethylene homopolymers, ethylene monoolefin copolymers obtained by copolymerizing ethylene and propylene, 1-butene, 1-hexene, 1-octene, and other CK-olefins, or A mixture in which an antioxidant, an ultraviolet absorber, a flame retardant, a pigment, a filler, a lubricant, an additive such as an antistatic agent, and other resins are mixed with these mixtures can be used.

As the cross-linked polyolefin resin, a cross-linked polyolefin resin using a radical generator or a water-cross-linked (silane cross-linked) silane-modified polyolefin resin is used. Examples of radical generators include organic peroxides such as dicumyl peroxide, benzoyl peroxide, di-t-butyl baroxide, 2,5-dimethyl-2,5-di (t-butyl peroxide) hexane, and the like. Oxides can be used.

In addition to the above organic peroxides, azo compounds such as azoisoptyronitrile can also be used. Silane modification is performed by grafting an ethylenically unsaturated silane compound to the above-mentioned polyolefin resin in the presence of a radical generator. Here, the ethylenically unsaturated silane compound is represented by the following general formula. RS iR ' _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, etc. are used. The silane modification of the polyolefin resin may be performed in advance with an extruder or the like, or may be performed in the kneader portion of the molding machine by adding each raw material component from the hopper during molding. The cross-linking reaction is performed by heat treatment, water treatment, etc. during extrusion molding and after Z or molding. In the case of a silane-modified polyolefin resin, it is preferable to use a silanol condensation catalyst in combination in order to improve the crosslinking rate, and it may be blended during molding or applied after molding. As the styrene condensation catalyst, dibutyltin dilaurate, dioctyltin dilaurate, cobalt naphthenate, toluenesulfonic acid, or the like can be used. The crosslinked polyolefin resin used in the present invention can be added with additives such as antioxidants, ultraviolet absorbers, flame retardants, pigments, fillers, lubricants, antistatic agents, and other resins as necessary. wear.

As a method for producing a resin pipe made of a polyolefin resin or a crosslinked polyolefin resin used in the present invention, a resin is extruded from a round die having an outer diameter smaller than the inner diameter of a steel pipe to be lined using an extruder or the like. Molded into a cylindrical shape, then cooled to fix the shape.

The thickness of the resin tube can be arbitrarily set as required, and is not particularly limited, but is usually in the range of 0.3 to 10 mm, preferably 0.5 to 5 mm. Furthermore, in order to improve the adhesive strength between the resin layer and the adhesive layer, after the resin tube is molded, a commercial primer is formed on the outer surface as necessary. Application, oxidation treatment, or surface roughening may be applied.

Since the adhesion between the inner surface of the steel pipe and the resin layer made of polyolefin resin or cross-linked polyolefin resin is not very good, an adhesive layer is provided between the chemical conversion coating and the resin layer, and the steel pipe and the resin pipe are bonded to each other. It is necessary to make them close together. The thickness of the adhesive layer can be arbitrarily set as required, and is not particularly limited, but is usually 1 m to 3 mm, and 10 n! It is preferable to be set to ~ 1.5 mm.

Adhesive layer is 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, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid copolymer, ethylene'vinyl acetate copolymer, or ionomer. .

The melting end temperature of the adhesive layer needs to be lower than the melting start temperature of the polyolefin resin or cross-linked polyolefin resin. For example, when the adhesive layer is made of maleic anhydride-modified polyolefin, a low crystalline ethylene polymer having a melting end temperature of 100 ° C. is used as the polyolefin. When the melting end temperature of the adhesive layer is equal to or higher than the melting start temperature of the resin tube made of the polyolefin resin or the cross-linked polyolefin resin, it is necessary to perform the heating for expressing the adhesive force at a temperature higher than the melting start temperature of the resin tube. In this case, the resin tube softens and the expansion force is lost, and in the cooling process, a shrinking force is generated by recrystallization, and the force to adhere to the inner surface of the steel tube is weakened, and the inner surface of the steel tube and the resin layer are reduced. Adhesive strength may be reduced. If the melting end temperature of the adhesive layer is 15 ° C or less, which is the standard operating temperature for resin-lined steel pipes, the adhesive layer melts completely during use. Adhesive strength decreases. To apply the adhesive layer to the outer surface of the resin pipe, use a double-layer round die having an outer diameter smaller than the inner diameter of the steel pipe to be lined, and extrude the polyolefin resin or cross-linked polyolefin resin from the inner die to remove the resin pipe. This can be done by molding and extruding the adhesive from the outer die at the same time. Alternatively, after forming a resin pipe made of a polyolefin resin or a crosslinked polyolefin resin using a round die, the adhesive layer may be extruded and coated using a round die or a T die.

The outer diameter of the resin pipe made of polyolefin resin or cross-linked polyolefin resin is preferably smaller than the inner diameter of the steel pipe, and the length of the resin pipe is preferably longer than the length of the steel pipe. After that, the resin pipe is inserted into the steel pipe, and the steel pipe is roll-squeezed so that the outer diameter of the resin pipe is reduced by 0.5 to 10%. Adhere. At this time, if the diameter reduction ratio of the resin pipe is less than 0.5%, the expansion force for increasing the outer diameter of the resin pipe becomes smaller than the inner diameter of the steel pipe. For this reason, the force to make the resin pipe adhere to the inner surface of the steel pipe is weakened, and the adhesive force of the resin lining layer to the inner surface of the steel pipe is reduced. On the other hand, when the diameter reduction ratio of the resin pipe is more than 10%, the resin pipe is deformed and the adhesion to the inner surface of the steel pipe is deteriorated.

After the steel pipe is shrunk and the resin pipe is brought into close contact with the inner surface, in order to further develop the adhesive force, hot air heating, high frequency induction heating, etc., the melting temperature of the adhesive layer is exceeded, whether it is a polyolefin resin or a crosslinked polyolefin resin. The resin tube is heated below the melting start temperature. When the heating temperature is lower than the melting end temperature of the adhesive layer, the adhesive layer does not melt completely, and thus the adhesive force of the inner surface resin lining layer is difficult to develop.

In addition, if the heating temperature is equal to or higher than the melting start temperature of a resin tube made of a polyolefin resin or a crosslinked polyolefin resin, the resin tube softens. As a result, the expansion force is lost, and in the cooling process, a shrinking force is generated by recrystallization, and the force to adhere to the inner surface of the steel pipe is weakened, and the adhesive force between the inner surface of the steel pipe and the lining resin layer is reduced.

Furthermore, a metal or alloy is sprayed on the outer surface of the resin-lined steel pipe to form a sprayed layer. As the thermal spray layer, for example, zinc, zinc, an aluminum mixture, or a zinc aluminum alloy that sacrifices and protects iron and is a base metal than iron is used.

In the case of a zinc / aluminum mixture or a zinc / aluminum alloy, the aluminum content in the sprayed layer is preferably 30% or less. If the aluminum content of the sprayed layer exceeds 30%, red glaze may occur at an early stage from the chuck jaws of the threading machine that is generated when the steel pipe is threaded in the local piping work. This is presumably because the large barrier reaching the steel pipe generated by the chuck claws of the threading machine does not fully exhibit the barrier action of aluminum.

The thickness of the sprayed layer formed on the outer surface of the resin-lined steel pipe is preferably 100 to 400. If the thickness of the sprayed layer is less than 100 m, the corrosion resistance may be lower than with conventional molten metal plating. This is because the porosity of the sprayed layer is larger than that of the melted layer and the density is small. The normal thickness of 85 μm of the melted layer corresponds to the thickness of the sprayed layer of 100 / m. However, in fusion welding, there is an alloy layer containing iron that is inferior in corrosion resistance at the interface with the steel pipe, and the number of pure metal layers that are excellent in corrosion resistance is reduced. Therefore, if the thickness of the sprayed layer is 100 m, the corrosion resistance may be improved compared to the 85 mm thick welded layer. Also, from the viewpoint of workability and economy, the upper limit of the thickness of the sprayed layer should be about 400 m. Furthermore, in order to improve the corrosion resistance, a thermal spray layer may be provided, and then, if necessary, an anti-white paint or a sealing agent may be applied.

Before spraying metal on the outer surface of a resin-lined steel pipe to form a sprayed layer In addition, the outer surface of the steel pipe is preferably degreased and cleaned by blasting to make it rough. At this time, even if a chemical conversion film consisting of phosphate crystal grains formed by the base treatment remains before lining the resin tube, the adhesion between the phosphate crystal grains and iron is large, It was found that the adhesion of the sprayed layer to the outer surface of the resin-lined steel pipe was not hindered. After that, any one of the above zinc, zinc, aluminum / nitrogen mixture, or zinc 'aluminum alloy is gas frame sprayed, electric arc sprayed or electric plasma sprayed on the outer surface of the resin-lined steel pipe. At this time, the temperature of the resin-lined steel pipe rises to about 90 ° C. This temperature rise is thought to reduce the strain generated in the adhesive layer and resin layer during the cooling process after bonding by heating in order to bond the resin tube to the inner surface of the steel tube before spraying. As a result, when metal is thermally sprayed on the outer surface of a resin-lined steel pipe, the punching shear adhesive force between the steel pipe and the inner surface resin layer is improved by 10 to 40% compared to before spraying. Example

Hereinafter, the present invention will be specifically described based on examples.

(Example 1)

The inner and outer surfaces of a steel pipe having an outer diameter of 50.8 min, a thickness of 3.3 mm, and a length of 3930ππη were degreased with a commercially available alkaline degreasing agent, and pickled and removed. After that, the steel pipe is immersed in a treatment solution (preparene Z, manufactured by Nihon Parkerizing Co., Ltd.) and zinc calcium phosphate treatment solution (Palpond P, manufactured by Nihon Pariki Rising Co., Ltd.), and heated with hot air. It was dried to form a chemical conversion coating. The amount of chemical conversion coating deposited was 4 g / m ^{2 as} measured by gravimetric method with chromic acid stripping, and the average grain size of phosphate crystals was about 5 mm as observed with a scanning electron microscope. .

Next, using a double-layered round die, the outer diameter is 42.4 mm by the coextrusion method. A polyethylene resin tube with a thickness of 1.5 mm and a length of 4040 mm was formed (melting start temperature 120 ° C), and at the same time, an adhesive made of maleic anhydride-modified polyethylene (melting end temperature 100 ° C) was applied to the polyethylene resin tube. The outer surface was coated with an adhesive layer. The thickness of the adhesive layer was 200 m.

Thereafter, the polyethylene resin pipe was inserted into the steel pipe, the steel pipe was roll-drawn so that the outer diameter of the polyethylene resin pipe was reduced by 1.4%, and the polyethylene resin pipe was brought into close contact with the inner surface of the steel pipe. Thereafter, the entire resin-lined steel pipe was heated to 5 ° C in a hot-air heating furnace, and a polyethylene resin pipe was bonded to the inner surface of the steel pipe. The polyethylene resin pipe that protruded from the end of the resin-lined steel pipe was cut. The outer surface of this resin-lined steel pipe was degreased with a commercially available Al-powered degreasing agent and treated with a glint blast to remove it. Then, while rotating the resin-lined steel pipe on the turner roll, an electric arc method is used to apply a zinc (72%) and aluminum (28%) mixture on the outer surface of the resin-lined steel pipe so that the thickness becomes ΙΟΟΙΟΟ. Sprayed. In addition, white paint was applied to the outer surface of the sprayed layer to a thickness of 10 m.

(Example 2)

As in Example 1, chemical conversion coatings were formed on the inner and outer surfaces of the steel pipe. Next, an epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe at room temperature by electrostatic spraying, and the whole was heated to 155 ° C in a hot air heating furnace. One primer layer was formed. The thickness of the epoxy primer layer was 100 im.

Further, in the same manner as in Example 1, a polyethylene resin pipe was lined on the inner surface of the steel pipe, and the polyethylene resin pipe protruding from the end was cut. After degreasing and removing the outer surface of this resin-lined steel pipe in the same manner as in Example 1, zinc, zinc (72%) · aluminum (28%) mixture, or zinc (85%), Aluminum (15 %) The alloy was sprayed, and white paint was applied by spraying.

(Example 3)

As in Example 2, a chemical conversion coating was formed on the inner and outer surfaces of the steel pipe, and an epoxy primer layer was further formed on the inner surface of the steel pipe. Next, in the same manner as in Example 1, a polyethylene resin tube was formed by a coextrusion method using a double-layered round die, and at the same time, an itaconic anhydride-modified polyethylene having a melting end temperature of 100 ° C., an ethylene / maleic anhydride copolymer. Polymer, ethylene / maleic anhydride / acrylic acid copolymer, ethylene / maleic anhydride / acrylic acid ester copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene 'methacrylic acid An adhesive layer made of a copolymer, ethylene / vinyl acetate copolymer, or ionomer was coated on the outer surface of a polyethylene resin tube to form an adhesive layer.

Further, in the same manner as in Example 1, a polyethylene resin pipe was lined on the inner surface of the steel pipe, and the polyethylene resin pipe protruding from the end was cut. The outer surface of this resin-lined steel pipe is degreased and degreased in the same manner as in Example 1, and then sprayed with a zinc (72%) / aluminum (28%) mixture by an electric arc method. Spray painted.

(Example 4)

As in Example 1, chemical conversion coatings were formed on the inner and outer surfaces of the steel pipe. Next, a two-layer round die was used to form a polypropylene resin tube (melting start temperature: 155 ° C) with an outer diameter of 42.4 mm, a thickness of 1.5 M, and a length of 4040 mm by the coextrusion method. An adhesive layer made of a modified polypropylene (melting end temperature: 145 ° C) was coated on the outer surface of the polypropylene resin tube to form an adhesive layer. The thickness of the adhesive layer was 200 ^ m. Thereafter, the polypropylene resin tube was inserted into the steel tube, and the polypropylene resin tube was brought into close contact with the inner surface of the steel tube in the same manner as in Example 1. Thereafter, the entire resin-lined steel pipe was heated to 150 ° C. in a hot air heating furnace, and a polypropylene resin pipe was bonded to the inner surface of the steel pipe. The polypropylene resin pipe protruding from the end of the resin-lined steel pipe was cut. The outer surface of the resin-lined steel pipe was degreased and degreased in the same manner as in Example 1, and then sprayed with zinc (72%) 'aluminum (28%) mixture by an electric arc method. Spray painted.

(Example 5)

As in Example 2, a chemical conversion coating was formed on the inner and outer surfaces of the steel pipe, and an epoxy primer layer was formed on the inner surface of the steel pipe. Further, in the same manner as in Example 4, a polypropylene resin pipe was lined on the inner surface of the steel pipe, and the polypropylene resin pipe protruding from the end was cut. The outer surface of the resin-lined steel pipe was degreased and degreased in the same manner as in Example 1, and then sprayed with zinc (72%) 'aluminum (28%) mixture by electric arc method, Spray painted

(Example 6)

As in Example 1, chemical conversion coatings were formed on the inner and outer surfaces of the steel pipe. Next, a double-layer round die was used to form a cross-linked polyethylene resin tube (melting start temperature 120 ° C) with an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 dragons by co-extrusion. At the same time, an adhesive made of maleic anhydride-modified polyethylene (melting end temperature: 100 ° C.) was coated on the outer surface of the crosslinked polyethylene resin tube to form an adhesive layer. The thickness of the adhesive layer was 200 m.

Thereafter, the crosslinked polyethylene resin tube was inserted into the steel tube, and the crosslinked polyethylene resin tube was brought into close contact with the inner surface of the steel tube in the same manner as in Example 1. So Thereafter, the entire resin-lined steel pipe was heated to 115 ° C in a hot-air heating furnace, and a crosslinked polyethylene resin pipe was bonded to the inner surface of the steel pipe. Resin lining The cross-linked polyethylene resin pipe protruding from the end of the steel pipe was cut. The outer surface of this resin-lined steel pipe was degreased and degreased in the same manner as in Example 1, and then sprayed with a zinc (72%) 'aluminum (28%) mixture by an electric arc method. Spray painted.

(Example 7)

As in Example 2, a chemical conversion coating was formed on the inner and outer surfaces of the steel pipe, and an epoxy primer layer was formed on the inner surface of the steel pipe. Further, in the same manner as in Example 6, a cross-linked polyethylene resin pipe was lined on the inner surface of the steel pipe, and the cross-linked polyethylene resin pipe protruding from the end was cut. The outer surface of this resin-lined steel pipe is degreased and degreased in the same manner as in Example 1, and then sprayed with a zinc (72%) / aluminum (28%) mixture by an electric arc method, and further, a white anti-whitening paint Spray painted.

(Comparative Example 1)

Using a double-layered round die, a co-extrusion method was used to form a polyvinyl chloride tube (melting start temperature 120 ° C) with an outer diameter of 42.4mni, a thickness of 1.5mm, and a length of 4040M. A polymer adhesive (melting end temperature 100 ° C) was coated on the outer surface of the polyvinyl chloride tube to form an adhesive layer. The thickness of the adhesive layer was 200 2 m. Next, a polyvinyl chloride pipe was inserted into a steel pipe with an outer diameter of 50.8 mm, a thickness of 3.3 mm, and a length of 3930 mm, which was galvanized (85 m thick) on the inner and outer surfaces. The steel pipe was roll-drawn so that the outer diameter was reduced by 1.4%, and the polyvinyl chloride pipe was brought into close contact with the inner surface of the steel pipe. Thereafter, the entire resin-lined steel pipe was heated to 115 ° C in a hot-air heating furnace, and a polyvinyl chloride pipe was bonded to the inner surface of the hot-dip galvanized steel pipe. Poly salt that protrudes from the end of a resin-lined steel pipe The vinyl chloride tube was cut, and the outer surface was spray-coated with white-white paint to a thickness of 10 ^ m.

(Comparative Example 2)

Using a double-layer round die, a polyethylene resin tube (melting start temperature 120 ° C) with an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm is formed by co-extrusion method, and at the same time made of maleic anhydride modified polyethylene An adhesive (melting end temperature 100 ° C) was coated on the outer surface of the polyethylene resin tube to form an adhesive layer. The thickness of the adhesive layer was 200 / im. Next, in the same manner as in Comparative Example 1, the polyethylene resin pipe was inserted into a steel pipe having inner and outer surfaces galvanized, and the polyethylene resin pipe was brought into close contact with the inner surface of the steel pipe. Thereafter, the entire resin-lined steel pipe was heated to 115 ° C in a hot air heating furnace, and a polyethylene resin pipe was bonded to the inner surface of the hot-dip galvanized steel pipe. The polyethylene resin tube that protruded from the end of the resin-lined steel tube was cut, and the outer surface was spray-coated with a white-white preventing paint as in Comparative Example 1.

(Comparative Example 3)

Using a double-layered round die, a polypropylene resin tube (melting start temperature: 155 ° C) with an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm is formed by coextrusion method. The adhesive (melting end temperature 145 ° C) was coated on the outer surface of the polypropylene resin tube to form an adhesive layer. The thickness of the adhesive layer was 200 ^ m. Next, in the same manner as in Comparative Example 1, the polypropylene resin tube was inserted into a steel tube having an inner and outer surface galvanized, and the polypropylene resin tube was brought into close contact with the inner surface of the steel tube. Thereafter, the entire resin-lined steel pipe was heated to 150 ° C in a hot air heating furnace, and a polypropylene resin pipe was attached to the inner surface of the hot-dip galvanized steel pipe. The polypropylene resin tube that protruded from the end of the resin-lined steel tube was cut, and the outer surface was spray-coated with white-white paint as in Comparative Example 1. (Comparative Example 4)

Using a double-layered round die, a co-extrusion method was used to form a cross-linked polyethylene resin tube (melting start temperature 120 ° C) with an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 mm, and simultaneously modified with maleic anhydride. An adhesive layer made of polyethylene (melting end temperature: 100 ° C) was coated on the outer surface of the cross-linked polyethylene resin tube to form an adhesive layer. The thickness of the adhesive layer was 200 m. Next, in the same manner as in Comparative Example 1, the cross-linked polyethylene resin pipe was inserted into a steel pipe whose inner and outer surfaces were melted with zinc, and the cross-linked polyethylene resin pipe was brought into close contact with the inner surface of the steel pipe. Thereafter, the entire resin-lined steel pipe was heated to 115 ° C in a hot air heating furnace, and a cross-linked polyethylene resin pipe was bonded to the inner surface of the hot-dip galvanized steel pipe. The cross-linked polyethylene resin tube that protruded from the end of the resin-lined steel tube was cut, and the outer surface was spray-coated with a white wrinkle-preventing coating as in Comparative Example 1.

The shear adhesive strength between the steel pipe and the inner resin pipe of the resin-lined steel pipes of Examples 1 to 7 and Comparative Examples 1 to 4 was measured. To measure the shear adhesive strength, cut the manufactured resin-lined steel pipe to a length of 20 mm, support only the steel pipe part using a jig, and push out only the resin-lined layer on the inner surface at l Omm / min. The shear adhesion force was obtained from the punching force at this time. Three samples were taken from each resin-lined steel pipe, and the average value was obtained. The unit of shear adhesion is MP a. The temperature during measurement was uniformly 23. Shear adhesion was also measured after passing 40 ° C hot water or 90 ° C hot water through a resin-lined steel pipe for 1 year. Table 1 shows the conditions and measurement results for each example.

The resin-lined steel pipes of Examples 1 to 7 are higher in shear adhesive strength after passing the initial and 40 ° C hot water for one year than in Comparative Examples 1 to 4, 90: Hot water passed for one year After that, the shear adhesive strength is remarkably higher than those of Comparative Examples 1 to 4. That is, the resin-lined steel pipe of the present invention has a conventional structure. It can be used for hot water supply pipes for a longer period of time than a resin-lined steel pipe lined with a polyvinyl chloride pipe on the inner surface of a hot-dip zinc plated steel pipe.

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 specified in JISZ 237 1 after cutting the manufactured resin-lined steel pipe to 150 dragon lengths and attaching a hook that reaches the steel pipe with the chuck claw of the threading machine on the outer surface. The time until the occurrence of red coral from the part was measured. The measurement results are also shown in Table 1.

The time from the heel portion of Examples 1 to 7 to the occurrence of red cocoon is longer than that of Comparative Examples 1 to 4 in which hot galvanizing is applied to the conventional outer surface, and the corrosion resistance is excellent. Recognize. '

table 1

Steel pipe inner surface Shear adhesive strength (MPa) Salt spray test (hours) Example Hot water 90 * C hot water on the outer surface of the steel pipe Remarks Red layer occurs Resin layer Adhesive layer Substrate treatment Initial 1 year 1 year

Time to

After passing water After passing water

Zinc / Aluminum

1 Zinc calcium phosphate 5. 0 4. 6 4. 2 2300

Mixture spraying

Zinc spraying 5. 0 4. 8 4. 6 770

7-Rainic acid modification

Zinc / Aluminum

H

2 5. 0 4. 8 4. 6 2300

Mixture spraying

Zinc / Aluminum

5. 0 4. 8 4. 6 2300

Alloy spraying

Itaic anhydride :! acid modification

5. 0 4. 8 4. 6

Polyethylene

Ethylene · None (Gumaleic acid

5. 0 4. 8 4. 6

Copolymer

Ethylene · Maleic anhydride-e. Liethylene 5. 0 4. 8 4. 6

Acrylic acid copolymer Zinc calcium phosphate +

Ethylene · Maleic anhydride · Eho. Xylene resin powder liner

5. 0 4. 8 4. 6

Acrylic acid I Stell copolymer

3 Invention Example Ethylene Acrylic acid

5. 0 4. 8 4. 6

Copolymer

Ethylene acrylate

Zinc / Aluminum 5. 0 4. 8 4. 6

Copolymer 2300

Mixture spraying

Ethylene methacrylic acid

5. 0 4. 8 4. 6

Copolymer

Ethylene · Vinyl acetate

5. 0 4. 8 4. 6

Copolymer

Ionoma-5. 0 4. 8 4. 6

4 Zinc calcium phosphate 5. 0 4. 6 4. 2

7-Rainic acid modification

Ho. Riff. D-pyrene zinc calcium phosphate +

5 ° riff lopyrene 5. 0 4. 8 4. 6

Jeho. Xi resin powder film

6 Calcium zinc phosphate 5. 0 4. 6 4. 2

7-Rainic acid modification

Cross-linked polyethylene zinc calcium phosphate +

7 Polyethylene 5. 0 4. 8 4. 6

Jeho. Xi resin powder film-ethylene · acetic acid! : 'Nil

1 Polyvinyl chloride 4.0 0 3. 6 1. 6

Copolymer

2 anhydrous 7 rain acid modification

Ho. Liethylene 4. 0 1. 8 0. 8

Ho. Liethylene

Hot-dip zinc soldering Hot-dip zinc plating 450 Comparative example Anhydrous 7-rain acid modification

3 Ho riff. D-pyrene 4. 0 1. 8

H ° Riff ° D-pyrene 0.8

7-Rainic acid modification

4 Cross-linked polyethylene 4. 0 1. 8

Ho. Reethylene ϋ. 8

Industrial applicability

The resin-lined steel pipe of the present invention can be used in place of a conventional resin-lined steel pipe in which polyvinyl chloride is lined on the inner surface of a molten metal-plated steel pipe having a plating layer on the inner and outer surfaces. In addition, according to the present invention, a resin-lined steel pipe with excellent adhesion between a steel pipe and a resin pipe that can be used for piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. for a longer period of time than before. And its manufacturing method can be provided

Claims

The scope of the claims

1. At least the inner surface of the steel pipe is provided with a chemical conversion film made of a phosphate crystal having a particle size of Ιθ ί m or less, and the inner surface of the steel pipe is a resin layer made of a polyolefin resin or a crosslinked polyolefin resin. A resin-lined steel pipe, wherein a thermal spray layer made of a metal or an alloy that is lower than iron is provided on the outer surface of the steel pipe after being adhered through an adhesive layer.

2. Adhesive layer is maleic anhydride modified polyolefin, anhydrous anhydride modified polyolefin, ethylene / maleic anhydride copolymer, ethylene / maleic anhydride / acrylic acid copolymer, ethylene Maleic anhydride / acrylic acid ester copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid copolymer, ethylene / vinyl acetate copolymer It is composed of one or more of a polymer and an ionomer, and the melting end temperature of the adhesive layer is higher than 15 ° C and lower than the melting start temperature of the resin layer. The resin-lined steel pipe according to claim 1.

3. The resin-lined steel pipe according to claim 1 or 2, further comprising an epoxy primer layer between the inner surface of the steel pipe and the adhesive layer.

4. The resin-lined steel pipe according to any one of claims 1 and 2, wherein the sprayed layer is any one of zinc, a zinc-aluminum mixture, zinc, and an aluminum alloy.

5. The resin-lined steel pipe according to claim 4, wherein the sprayed layer is a zinc-aluminum mixture or a zinc-aluminum alloy containing 30% or less of aluminum.

6. The punching shear adhesion between the steel pipe of the resin-lined steel pipe with the thermal spray layer on the outer surface and the inner resin layer is 10-40% larger than that of the resin-lined steel pipe without the thermal spray layer on the outer surface. It is characterized by The resin-lined steel pipe according to claim 1 or 2.

7. A base treatment is applied to the steel pipe to form a chemical conversion film made of phosphate crystals having a particle size of 10 ^ m or less, and has an outer diameter smaller than the inner diameter of the steel pipe. An adhesive layer is provided on the outer surface of a resin pipe made of a crosslinked polyolefin resin, the resin pipe is inserted into the steel pipe, and the resin pipe is sealed to the inner surface of the steel pipe through the adhesive layer by squeezing the steel pipe. A resin-lined steel pipe characterized by being heated and bonded at a temperature equal to or higher than a melting end temperature of the adhesive layer and lower than a melting start temperature of the resin pipe, and thermally spraying a metal or an alloy lower than iron on the outer surface of the steel pipe. Manufacturing method.

8. The method for producing a resin-lined steel pipe according to claim 7, wherein an epoxy primer layer is provided after the chemical conversion coating is formed on the inner surface of the steel pipe.

9. The method for producing a resin-lined steel pipe according to claim 7 or 8, wherein the steel pipe is squeezed so that the outer diameter of the resin pipe is reduced by 0.5 to 10%.

10. The method for producing a resin-lined steel pipe according to claim 7, wherein any one of zinc, a zinc-aluminum mixture, and a zinc ′ aluminum alloy is thermally sprayed on an outer surface of the steel pipe.

11. The method for producing a resin-lined steel pipe according to claim 10, wherein the outer surface of the steel pipe is sprayed with a zinc / aluminum mixture or a zinc / aluminum alloy containing 30% or less of aluminum.