JP2003294174A - Resin lining steel pipe and manufacture method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin lining steel pipe good at adhesion between the steel pipe and an inner resin lining layer and to be used as piping for water supply, hot water supply, air-conditioning, fire fighting, drainage or the like, and also to provide a manufacture method. <P>SOLUTION: The resin lining steel pipe has an adhesive layer on an inner surface of the steel pipe, further has a plastic layer inside of the adhesive layer, and is characterized in that initial shearing adhesion force between the steel pipe and the plastic layer is 1.0 MPa or more, and that preferably there are an epoxy primer layer and a surface treatment layer between the steel pipe and the adhesive layer. A manufacture method for the resin lining steel pipe is characterized by inserting a plastic pipe of an outside diameter smaller than an inside diameter of the steel pipe and contracting the steel pipe at a contraction percentage of 1 to 50% to bring the plastic pipe into close contact. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-lined steel pipe used for piping such as water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. TECHNICAL FIELD The present invention relates to a resin-lined steel pipe having excellent properties and a manufacturing method thereof.

[0002]

2. Description of the Related Art With the improvement of urban living environment, hot water supply facilities are spreading from buildings to detached houses. In addition, the district cooling and heating system is being spread from the viewpoint of energy saving. Therefore, the durability of pipes that transport high-temperature fluids such as hot water is emphasized. As piping materials for transporting water and the like, in addition to steel pipes such as forged steel pipes and electric resistance welded steel pipes, thermoplastic resin pipes such as polyvinyl chloride, polyethylene, polypropylene and polybutene are used alone. Since steel pipes have greater mechanical strength than these resin pipes, they have excellent impact resistance during construction and excellent compression resistance even when they are buried under a road with heavy traffic, and even when the temperature of the fluid to be transported is high. By comparison, the compressive strength is sufficiently large and excellent, and it is difficult to burn like a resin pipe, so it is excellent even when used for indoor applications without spreading due to fire.

However, in applications where it is necessary to prevent turbidity of fluid due to corrosion of steel and prevention of blockage of pipelines, resin pipes that do not corrode are used. A composite pipe of resin and steel, in which a resin pipe is inserted into the inner surface of a steel pipe to prevent corrosion, is known as a pipe line having both good points. For example, composite pipes of steel and soft polyvinyl chloride that utilize inexpensive polyvinyl chloride are widely used as water supply pipes and drainage pipes, and composite pipes of steel and hard polyvinyl chloride are widely used as hot water supply pipes.

However, there is also a problem that dioxin is generated during incineration and disposal of the composite pipe residual material generated in the field piping work. Therefore, as a composite pipe used for a water supply pipe, a hot water supply pipe, a drainage pipe, and the like, one not using polyvinyl chloride has been desired.

Therefore, Japanese Patent Laid-Open No. 2001-9912 and Japanese Patent Laid-Open No. 2001-9913 utilize the shape memory property of a polyolefin resin or a cross-linked polyolefin resin, which does not cause the problem of dioxin generation, and reduce the diameter smaller than the inner diameter of the steel pipe. There is disclosed a method of lining the inner surface of the polyolefin resin pipe or the cross-linked polyolefin resin pipe by heating and restoring it.

However, when the inner surface of a polyolefin resin pipe or a crosslinked polyolefin resin pipe is lined by the method disclosed in JP 2001-9912 A or JP 2001-9913 A, a polyolefin resin or a crosslinked polyolefin resin is compared with polyvinyl chloride. Since the heat shrinkage is much larger than that of steel, the outer diameter of the polyolefin resin pipe or cross-linked polyolefin resin pipe tends to be smaller than the inner diameter of the steel pipe in the final cooling step of the manufacturing process. A large peeling force works at the interface of the pipe. Therefore, peeling stress is constantly working at the interface between the steel pipe and the polyolefin resin pipe or cross-linked polyolefin resin pipe, and even when adhesive is used to prevent peeling, water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. over a long period of time. When used for piping, the adhesive at the adhesive interface between the steel pipe and the polyolefin resin pipe or cross-linked polyolefin resin pipe deteriorates, weakening the adhesive force, and the shrinkage stress inherent in the polyolefin resin pipe and cross-linked polyolefin resin pipe causes the polyolefin resin pipe and cross-linked polyolefin resin pipe to shrink. There is a problem that the resin pipe is separated from the inner surface of the steel pipe.

[0007]

In view of the above problems, the present invention provides a pipe for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc., which has excellent adhesion between the steel pipe and the inner resin lining layer for a long period of time. A resin-lined steel pipe to be used and a method for producing the same are provided.

[0008]

Means for Solving the Problems The inventors have focused on a polyolefin resin or a crosslinked polyolefin resin which does not have the problem of dioxin generation. In addition, since these resins have much larger heat shrinkage than steel compared to polyvinyl chloride, we have devised not to use shape memory. That is, in the method of performing the inner surface lining by heating and restoring the plastic pipe whose diameter is smaller than the inner diameter of the steel pipe, the outer diameter of the plastic pipe tends to be smaller than the inner diameter of the steel pipe in the final cooling step of the production. A large peeling force works at the interface between the steel pipe and the plastic pipe.
Therefore, in the present invention, on the contrary, by squeezing the steel pipe, the inner surface of the plastic pipe is lined, and by further providing an adhesive layer, an epoxy primer layer or a chemical conversion coating between the steel pipe and the plastic pipe, a long period of time is provided. It has been found that a resin-lined steel pipe having excellent adhesiveness between the steel pipe and the inner surface resin lining layer can be used for pipes for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. ) A steel pipe or a steel pipe whose outer surface is galvanized has an adhesive layer on the inner surface and further has a plastic layer on the inner side, and the initial shear adhesive force between the steel pipe and the plastic layer is 1.0 MPa or more. A resin-lined steel pipe characterized in that Here, the initial shear adhesive strength means the adhesive strength between the steel pipe and the plastic layer after bonding and before passing water. If the initial shear adhesive strength is less than 1.0 MPa, the resin lining may peel off during use. Therefore, the initial shear adhesive strength needs to be 1.0 MPa or more.
The above is preferable.

(2) The resin-lined steel pipe according to (1) above, wherein the plastic layer is a polyolefin resin or a crosslinked polyolefin resin.

(3) The adhesive layer is made of synthetic rubber, maleic anhydride-modified polyolefin, ethylene / maleic anhydride copolymer, ethylene / maleic anhydride / acrylic acid copolymer, ethylene / maleic anhydride / acrylic acid. Consists of one or more of an ester copolymer, an ethylene / acrylic acid copolymer, an ethylene / acrylic acid ester copolymer, an ethylene / methacrylic acid copolymer, an ethylene / vinyl acetate copolymer, and an ionomer. The resin-lined steel pipe according to any one of (1) and (2) above.

(4) An epoxy primer layer is provided between the steel pipe and the adhesive layer.
The resin-lined steel pipe according to (3).

(5) The resin-lined steel pipe according to any one of (1) to (4), wherein the steel pipe is a steel pipe that has been preliminarily pretreated, and has an undertreatment layer on the inner surface of the steel pipe.

(6) The resin-lined steel pipe according to (5) above, wherein a chemical conversion treatment film of phosphate is applied as the base treatment.

(7) The resin according to any one of (1) to (6) above, wherein the outer surface of the resin-lined steel pipe has a primary rust preventive coating, a zinc rich paint coating, or a polyolefin coating instead of galvanizing. Lining steel pipe.

(8) When manufacturing the resin-lined steel pipe, an adhesive layer is formed on the inner surface of a steel pipe with or without base treatment, or an epoxy primer layer is applied and then adhered to the inner surface of the steel pipe. A layer is formed, a plastic pipe having an outer diameter smaller than the inner diameter of the steel pipe is inserted, and the plastic pipe is tightly adhered by squeezing the steel pipe. (1) to (6) Production method.

(9) In the production of the resin-lined steel pipe, a steel pipe having a base treatment or no base treatment, or a steel pipe having an epoxy primer layer formed thereon has an outer surface having an outer diameter smaller than the inner diameter of the steel pipe. Inserting a plastic pipe having an adhesive layer into the above, and squeezing the steel pipe to bring the plastic pipe into close contact, and heating at a melting point of the adhesive layer or more and less than the melting point of the plastic pipe. A method for producing the resin-lined steel pipe described.

(10) The method for producing a resin-lined steel pipe according to any one of (8) to (9), wherein, when the steel pipe is drawn, the outer diameter of the steel pipe is drawn at a drawing ratio of 1 to 50%.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The resin-lined steel pipe of the present invention is
First, the inner surface of the steel pipe is degreased and cleaned by pickling or blasting. The outer surface of this steel pipe may be plated with hot-dip galvanizing or the like, and the outer diameter is 10 to 2000 mm.
About 20 to 170 mm is usually used. After that, a plastic pipe having an outer diameter smaller than the inner diameter of the steel pipe by about 1 to 50% and further longer than the length of the steel pipe by 1 to 50% is inserted into the steel pipe, and the outer diameter of the steel pipe is reduced by 1 to 50%.
By roll drawing or die drawing, it becomes possible to obtain a resin-lined steel pipe in which a resin is lined with good adhesion to the inner surface of the steel pipe. The plastic pipe protruding from the end of the steel pipe is cut.

As the plastic pipe used in the present invention, a plastic pipe made of a polyolefin resin or a crosslinked polyolefin resin is used. As the polyolefin resin, ethylene homopolymer, or ethylene-α-olefin copolymer obtained by copolymerizing ethylene and α-olefin such as propylene, 1-butene, 1-hexene, 1-octene, or a mixture thereof. To the extent that the performance of the present invention is not impaired, an antioxidant, an ultraviolet absorber, a flame retardant, a pigment, a filler, a lubricant, an additive such as an antistatic agent, and a mixture of other resins are used as necessary. .

As the crosslinked polyolefin resin, one obtained by crosslinking the above polyolefin resin with a radical generator or one obtained by water crosslinking (silane crosslinking) the above silane-modified polyolefin resin is used. Examples of the radical generator include dicumyl peroxide, benzoyl peroxide, di-t-butyl peroxide, 2,
An organic peroxide such as 5-dimethyl-2,5-di (t-butylperoxy) hexane is used. In addition to the above organic peroxides, azo compounds such as azoisobutyronitrile can also be used. The silane modification is carried out by graft reacting the above-mentioned polyolefin resin with an ethylenically unsaturated silane compound 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 is an ethylenically unsaturated hydrocarbon group or a hydrocarbon oxy group, R'is an aliphatic saturated hydrocarbon group, Y is a hydrolyzable organic group, and n is 0 to 2). Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane and the like are used. This silane modification may be carried out in advance using an extruder or the like, or may be carried out in the kneading machine 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 during extrusion molding and / or after molding. In the case of a silane-modified polyolefin resin, it is desirable to use a silanol condensation catalyst together in order to improve the crosslinking rate. This may be compounded at the time of molding or applied after molding. As the silanol condensation catalyst, dibutyltin dilaurate, dioctyltin dilaurate, cobalt naphthenate, toluenesulfonic acid, etc. can be used. The cross-linked polyolefin resin used in the present invention, as long as the performance of the present invention is not impaired, if necessary, antioxidants, ultraviolet absorbers, flame retardants, pigments, fillers, lubricants, additives such as antistatic agents, and the like, and Other resins can be added.

As the method for producing the plastic pipe used in the present invention, the resin is extruded into a pipe shape 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, and then cooled. , Fix the shape. The thickness of the plastic pipe can be arbitrarily set as necessary 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. further,
In order to improve the adhesive strength with the adhesive layer, a commercially available primer may be applied, an oxidation treatment, and a surface roughening may be applied to the outer surface, if necessary, after the plastic pipe is molded.

Further, since the steel pipe and the plastic pipe do not have much adhesiveness, it is desirable to have an adhesive layer between them. In particular, the adhesive layer is made of synthetic rubber, maleic anhydride modified polyolefin, or ethylene / maleic anhydride. 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 copolymer It has been found that the use of one or two or more of a polymer, an ethylene / vinyl acetate copolymer, and an ionomer exerts a significantly superior adhesive force as compared with other ones. As the adhesive made of synthetic rubber, for example, a mixture of styrene-butadiene rubber, polyterpene resin and an organic solvent is used. Further, as the polyolefin of the adhesive composed of the maleic anhydride-modified polyolefin, for example, a low crystalline ethylene polymer or the like is used.

The application of the adhesive layer is carried out by applying the adhesive layer to the inner surface of the steel pipe by spin coating, spray coating or ironing in the case of an adhesive made of synthetic rubber. Furthermore, in order to improve the adhesive force, the steel pipe may be heated by hot air heating, high-frequency induction heating, or the like after being subjected to roll drawing or die drawing. In addition, in the case of an adhesive made of other materials, 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 plastic pipe is used, and the adhesive layer is co-extruded and covered during molding of the plastic pipe, Using a T-die, the adhesive layer is extruded and coated after molding the plastic pipe. Further, in order to develop the adhesive force, the steel pipe is subjected to roll drawing or die drawing, and then heated by hot air heating, high frequency induction heating or the like at a temperature higher than the melting point of the adhesive layer and lower than the melting point of the plastic pipe. 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, the thickness is 10 μm or more and 1.5 mm or less.

Further, it is desirable to have an epoxy resin powder primer layer between the steel pipe and the adhesive layer because good water resistance adhesion can be obtained. As the epoxy resin powder primer layer, for example, a mixture 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, and the like are used. Although these epoxies can be used alone,
The respective resins may be mixed and used according to the purpose. As the pigment, fine particle powders of extender pigments such as silica, barium sulfate and calcium carbonate and coloring pigments such as titanium oxide and carbon black are used. When the amount of these pigments added is in the range of 3 to 50 parts by weight with respect to 100 parts by weight of epoxy, good water-resistant adhesion can be obtained. As the additive, an acrylic oligomer or fine powder silica can be used.

As the curing agent, dibasic acids such as dicyandiamide and decanedicarboxylic acid, hydrazines such as adipic acid dihydrazide, acid anhydrides such as tetrahydrophthalic anhydride, and bisphenol A are added to bisphenol A diglycidyl ether. The phenol-based curing agent and the amine adducts obtained by adding diamidodiphenylmethane to the diglycidyl ether of bisphenol A can be used.
When a dibasic acid, a hydrazine or a phenolic curing agent is used as the curing agent, the amount of the curing agent is determined by the ratio of the epoxy equivalent of the epoxy and the active hydrogen equivalent of the curing agent. As the equivalent ratio, the epoxy equivalent is 1.0 and the active hydrogen equivalent is 0.
6 to 1.2 is good.

When dicyandiamide is used as the curing agent, modified imidazole is added as a curing accelerator in order to reduce the curing temperature. As the modified imidazole, for example, 2-methylimidazole, 2-phenylimidazole and the like 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 modified imidazole as a curing accelerator. As a typical epoxy resin powder coating material having the above composition, there is Powdax E (manufactured by Nippon Paint Co., Ltd.).

The epoxy resin powder primer layer is applied by coating the inner surface of the steel pipe with the epoxy resin powder primer layer at room temperature by electrostatic spray coating and then heating the steel pipe by hot air heating or high frequency induction heating. May be preheated, and an epoxy resin powder primer layer may be electrostatically spray-coated or fluidized-suction coated on the inner surface to cure the epoxy resin powder primer layer by post-heating. According to the above method, the preheating temperature of the steel pipe is about 60 to 230 ° C, and the postheating temperature is 160 to 230 ° C.
The degree is good. The thickness of the epoxy resin powder primer layer is preferably about 40 to 250 μm. If the film thickness is less than 40 μm, the film coating limit of the powder coating material may be exceeded, and a continuous film is not formed, so that the water resistant adhesive strength of the resin lining layer is reduced. From the viewpoint of workability and economy, the upper limit of the film thickness is preferably about 250 μm.

Further, it is desirable to apply a chemical conversion treatment film as a base treatment of the steel pipe because good water resistance adhesion can be obtained.
As the chemical conversion treatment liquid, a commercially available product is used, but for example, a mixture of zinc phosphate, phosphate, phosphoric acid, zinc nitrate, calcium nitrate, nitrate, sodium nitrite and water (zinc calcium phosphate) is used. The chemical conversion treatment method is
The chemical conversion treatment liquid may be applied by a dipping method, a steel pipe injection method, or any other suitable method, followed by heating and drying. The amount of the chemical conversion coating deposited is preferably about ² to 10 g / m ² . If the adhered amount is less than 2 g / m ² or more than 10 g / m ² , the water resistant adhesive strength of the resin lining layer is reduced.

The inner surface of the resin-lined steel pipe may have a primary rust-preventive coating, a zinc-rich paint coating, or a polyolefin coating instead of zinc plating. As the primary rust-preventive coating, a commercially available alkyd-based or epoxy-based coating or the like is applied to a thickness of about 20 to 30 μm. As the zinc-rich paint coating, general commercially available organic or inorganic zinc-rich paint or the like is applied to a thickness of about 65 to 85 μm. Further, in order to improve the anticorrosion property, a commercially available clear paint or white rust preventive paint may be applied after the zinc rich paint is applied. Further, as the polyolefin coating, first, the outer surface of the steel pipe is degreased and cleaned by blasting or pickling. Then, the modified polyolefin adhesive and the polyolefin resin are sequentially coated.

As the modified polyolefin adhesive, ethylene homopolymer, or ethylene and propylene, 1-
An ethylene-α-olefin copolymer obtained by copolymerizing an α-olefin such as butene, 1-hexene or 1-octene, or a modified polyolefin obtained by modifying a mixture of these with maleic anhydride or itaconic anhydride is used. When the addition rate of this maleic anhydride is in the range of 0.05 to 0.5% by weight, good adhesive strength can be obtained.

These modified polyolefin adhesives are extruded and coated on the outer surface of the steel pipe using a round die or a T die.
The thickness of this modified polyolefin adhesive is 80-400μ
When it is about m, good adhesive strength can be obtained.

Next, as the polyolefin resin, an ethylene homopolymer, or ethylene and propylene, 1-
Butene, 1-hexene, homopolymer of ethylene-α-olefin copolymerized α-olefin such as 1-octene, or a mixture thereof, if necessary, an antioxidant,
A mixture obtained by mixing an ultraviolet absorber, a flame retardant, a pigment, a filler, a lubricant, an additive such as an antistatic agent, and other resins is used.

These polyolefin resins are extrusion-coated and laminated on the outer surface of a steel pipe coated with a modified polyolefin adhesive using a round die or a T-die, and a modified polyolefin adhesive is used with a two-layer round die or a two-layer T die. A method of co-extrusion coating with a polyolefin resin can also be used. When the thickness of this polyolefin resin is about 1 to 10 mm, good anticorrosion property is obtained.

Further, it is desirable to have a chemical conversion treatment film and an epoxy resin powder primer between the steel pipe and the modified polyolefin adhesive because good water resistance adhesion can be obtained. As the chemical conversion treatment liquid, a commercially available one is used, but for example, an aqueous solution of zinc calcium phosphate is used. The chemical conversion treatment method is
The chemical conversion treatment liquid may be dropped onto the outer surface of the steel pipe by ironing, brushing, brushing or any other suitable method, followed by heating and drying. The amount of this chemical conversion coating deposited is 2 to 10 g
/ M ² is good. If the amount of adhesion is less than 2 g / m ² or more than 10 g / m ² , the water resistant adhesive strength of the polyolefin coating decreases.

As the epoxy resin powder primer, for example, a mixture of epoxy, pigment, additive and curing agent is used. Applying epoxy resin powder primer
It is advisable to preheat a steel pipe coated with a chemical conversion coating by high-frequency induction heating, hot air heating, or the like, and apply an epoxy resin powder primer to the surface thereof by electrostatic spray coating, fluidized-bed coating or any other suitable method. The thickness of this epoxy resin powder primer is preferably about 40 to 250 μm. If the film thickness is less than 40 μm, the water resistant adhesive strength of the polyolefin coating decreases. From the viewpoint of workability and economy, the upper limit of the film thickness is preferably about 250 μm.

The present invention will be described in detail based on examples. (Example 1) Outer diameter 5 degreased with a commercially available alkaline degreaser
0.8 mm, thickness 3.3 mm, length 3930 mm outer surface hot-dip galvanized steel pipe inner surface is grit blasted to remove rust, and then an adhesive made of synthetic rubber is poured onto the inner surface of the steel pipe by the rotation method. It was applied to form an adhesive layer.
The thickness of the adhesive layer was 50 μm.

After that, a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7%. A resin was lined on the inner surface of the steel pipe with good adhesion, and the polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 2 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreasing agent
The inner surface of the steel pipe with the outer surface of mm having a hot-dip galvanized surface is grit blasted to remove rust, and then the surface temperature of the steel pipe is adjusted to 80 ° C. by heating the epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.) with hot air. An inner surface of the heated steel pipe was coated by an electrostatic spraying method using an electrostatic coating machine, and the surface temperature of the steel pipe was post-heated to 180 ° C. by heating with hot air to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Next, an adhesive made of synthetic rubber was cast on the inner surface of the steel pipe and applied by a rotating method to form an adhesive layer. The thickness of the adhesive layer was 50 μm.

After that, a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm was inserted into the steel pipe, and the outer diameter of the steel pipe was drawn by a roll at a drawing ratio of 4.7%. A resin was lined on the inner surface of the steel pipe with good adhesion, and the polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 3 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreasing agent
The inner surface of the steel pipe with the hot dip galvanized outer surface of mm is pickled to remove rust, and then a commercially available chemical conversion treatment solution consisting of zinc calcium phosphate is injected into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited is 6
It was g / m ² . Next, an adhesive made of synthetic rubber was cast on the inner surface of the steel pipe and applied by a rotating method to form an adhesive layer. The thickness of the adhesive layer was 50 μm.

Thereafter, a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7%. A resin was lined on the inner surface of the steel pipe with good adhesion, and the polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 4 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreasing agent
The inner surface of the steel pipe with the hot dip galvanized outer surface of mm is pickled to remove rust, and then a commercially available chemical conversion treatment solution consisting of zinc calcium phosphate is injected into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited is 6
It was g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of synthetic rubber was cast on the inner surface of the steel pipe and applied by a rotating method to form an adhesive layer. The thickness of the adhesive layer was 50 μm.

After that, a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm was inserted into the steel pipe, and the outer diameter of the steel pipe was drawn by a roll at a drawing ratio of 4.7%. A resin was lined on the inner surface of the steel pipe with good adhesion, and the polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 5 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreasing agent
After the steel pipe of mm was pickled and rust-free, the steel pipe was immersed in a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of synthetic rubber was cast on the inner surface of the steel pipe and applied by a rotating method to form an adhesive layer. The thickness of the adhesive layer was 50 μm.

Thereafter, a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm was inserted into the steel pipe, and the outer diameter of the steel pipe was drawn by a roll at a drawing ratio of 4.7%. A resin was lined on the inner surface of the steel pipe with good adhesion, and the polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 6 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreaser.
After the steel pipe of mm was pickled and rust-free, the steel pipe was immersed in a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of synthetic rubber was cast on the inner surface of the steel pipe and applied by a rotating method to form an adhesive layer. The thickness of the adhesive layer was 50 μm.

Thereafter, a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm was inserted into the steel pipe, and the outer diameter of the steel pipe was drawn by a roll at a drawing ratio of 4.7%. A resin was lined on the inner surface of the steel pipe with good adhesion, and the polyethylene resin pipe protruding from the end of the steel pipe was cut. The inner surface of the resin-lined steel pipe was degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then a commercially available organic zinc-rich paint was applied to a thickness of 75 μm. It was coated with a thickness of 30 μm.

Example 7 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreaser.
After the steel pipe of mm was pickled and rust-free, the steel pipe was immersed in a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of synthetic rubber was cast on the inner surface of the steel pipe and applied by a rotating method to form an adhesive layer. The thickness of the adhesive layer was 50 μm.

Thereafter, a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm was inserted into the steel pipe, and the outer diameter of the steel pipe was drawn by a roll at a drawing ratio of 4.7%. A resin was lined on the inner surface of the steel pipe with good adhesion, and the polyethylene resin pipe protruding from the end of the steel pipe was cut.

After degreasing the outer surface of the above-mentioned inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and grit blasting to remove rust, a commercially available chemical conversion treatment solution containing zinc calcium phosphate is dropped and applied by an ironing method, and high frequency is applied. The steel pipe surface temperature was heated to 110 ° C. by induction heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Immediately thereafter, a maleic anhydride-modified polyethylene adhesive and a polyethylene resin were coextrusion coated with a two-layer round die. The thickness of the maleic anhydride-modified polyethylene adhesive and the polyethylene resin are 100 μm and 1.5, respectively.
It was mm.

Example 8 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreasing agent
The inner surface of the steel pipe having an outer surface of mm of which hot-dip galvanizing was performed was subjected to grit blast treatment to remove rust. Next, an adhesive made of maleic anhydride-modified polyethylene was used, having an outer diameter of 42.4 mm,
At the time of molding a polyethylene resin pipe having a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer round die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled by a reduction ratio of 4.7%, so that the resin was lined on the inner surface of the steel pipe with good adhesion and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 9 Outer diameter 50.8 mm, thickness 3.3 mm, length 3930 degreased with a commercially available alkaline degreasing agent
The inner surface of the steel pipe with the outer surface of mm having a hot-dip galvanized surface is grit blasted to remove rust, and then the surface temperature of the steel pipe is adjusted to 80 ° C. by heating the epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.) with hot air. An inner surface of the heated steel pipe was coated by an electrostatic spraying method using an electrostatic coating machine, and the surface temperature of the steel pipe was post-heated to 180 ° C. by heating with hot air to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Next, an adhesive composed of maleic anhydride-modified polyethylene was coated on the outer surface by a coextrusion method using a two-layer round die at the time of molding a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm, An adhesive layer was formed. The thickness of the adhesive layer was 200 μm.

Thereafter, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin with good adhesion on the inner surface of the steel pipe, and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 10 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an adhesive made of maleic anhydride-modified polyethylene was used to have an outer diameter of 42.4 mm and a thickness of 1.5.
When a polyethylene resin pipe having a length of 40 mm and a length of 40 mm was formed, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer is 200μ
It was m.

Thereafter, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 11 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive consisting of maleic anhydride-modified polyethylene was coated on the outer surface by a coextrusion method using a two-layer round die at the time of molding a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm. Layers were formed. The thickness of the adhesive layer is 2
It was 00 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin with good adhesion to the inner surface of the steel pipe, and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 12 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreaser.
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of maleic anhydride-modified polyethylene was used, which had an outer diameter of
At the time of molding a polyethylene resin pipe having a thickness of 4 mm, a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, followed by heating with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 13 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of maleic anhydride-modified polyethylene was used, which had an outer diameter of 42.
At the time of molding a polyethylene resin pipe having a thickness of 4 mm, a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was drawn by a roll at a drawing ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion and then to heat with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut. The inner surface of the resin-lined steel pipe was degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then a commercially available organic zinc-rich paint was applied to a thickness of 75 μm. It was coated with a thickness of 30 μm.

Example 14 Degreased with a commercially available alkaline degreasing agent, outer diameter 50.8 mm, thickness 3.3 mm, length 393.
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of maleic anhydride-modified polyethylene was used, which had an outer diameter of
At the time of molding a polyethylene resin pipe having a thickness of 4 mm, a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

Thereafter, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin with good adhesion to the inner surface of the steel pipe, and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

The inner surface of the resin-lined steel pipe was degreased with a commercially available alkaline degreasing agent, grit blasted to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate was dropped and applied by an ironing method, and high frequency was applied. The steel pipe surface temperature was heated to 110 ° C. by induction heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Immediately thereafter, a maleic anhydride-modified polyethylene adhesive and a polyethylene resin were coextrusion coated with a two-layer round die. The thickness of the maleic anhydride-modified polyethylene adhesive and the polyethylene resin are 100 μm and 1.5, respectively.
It was mm.

(Example 15) Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent.
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of an ethylene / maleic anhydride copolymer is coated on the outer surface by a coextrusion method using a two-layer circular die when molding a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm. Then, an adhesive layer was formed. The thickness of the adhesive layer is 2
It was 00 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, followed by heating with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

(Example 16) Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent.
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive composed of an ethylene / maleic anhydride / acrylic acid copolymer was used, having an outer diameter of 42.
At the time of molding a polyethylene resin pipe having a thickness of 4 mm, a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the above-mentioned polyethylene resin pipe was inserted into the above-mentioned steel pipe, and the outer diameter of the steel pipe was subjected to roll drawing at a drawing ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, followed by heating with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 17 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent.
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive consisting of ethylene / maleic anhydride / acrylic acid ester copolymer is used to form a polyethylene resin pipe with an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm by using a two-layer circular die on the outer surface. It was coated by an extrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was roll-drawn at a drawing ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, followed by heating with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

(Example 18) Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent.
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of an ethylene / acrylic acid copolymer was used, which had an outer diameter of 42.4 mm and a thickness of 1.
At the time of molding a polyethylene resin pipe having a length of 5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer is 200
was μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7%, so that the resin was lined on the inner surface of the steel pipe with good adhesion and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 19 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive composed of an ethylene / acrylic acid ester copolymer is used, having an outer diameter of 42.4 mm,
At the time of molding a polyethylene resin pipe having a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer round die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% so that the inner surface of the steel pipe was lined with resin with good adhesion and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 20 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent.
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive composed of an ethylene / methacrylic acid copolymer was coated on the outer surface by a coextrusion method using a two-layer round die when molding a polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm. , An adhesive layer was formed. The thickness of the adhesive layer is 2
It was 00 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled by a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, followed by heating with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

Example 21 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of an ethylene / vinyl acetate copolymer was used, having an outer diameter of 42.4 mm and a thickness of 1.
At the time of molding a polyethylene resin pipe having a length of 5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer is 200
was μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, and then heated with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

(Example 22) Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent.
The inner surface of a steel pipe with a 0 mm outer surface coated with hot dip galvanized is pickled to remove rust, and then a commercially available chemical conversion treatment liquid consisting of zinc calcium phosphate is poured into the steel pipe and dried by heating with hot air to form a chemical conversion coating. Was formed. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an epoxy resin powder primer (Powderx E manufactured by Nippon Paint Co., Ltd.) was applied to the inner surface of the steel pipe preheated to 80 ° C. by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and hot air was applied. The surface temperature of the steel pipe was post-heated to 180 ° C. by heating to form an epoxy primer layer. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive made of an ionomer is used, having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 40.
At the time of molding a 40 mm polyethylene resin pipe, the outer surface was coated by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction rate of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, followed by heating with hot air. The steel pipe surface temperature by 11
Heated to 0 ° C. The polyethylene resin pipe protruding from the end of the steel pipe was cut.

(Example 23) Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
The inner surface of the 0 mm steel pipe was grit blasted to remove rust. Next, an adhesive made of maleic anhydride-modified polyethylene was used to give an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 404.
At the time of molding a 0 mm cross-linked polyethylene resin pipe, the outer surface was coated by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin with good adhesion on the inner surface of the steel pipe, and then the hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 24 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After the inner surface of the 0 mm steel pipe was grit blasted to remove rust, an epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.) was heated with hot air to bring the surface temperature of the steel pipe to 80 ° C.
The inner surface of the preheated steel pipe is coated by electrostatic spraying using an electrostatic coating machine, and the surface temperature of the steel pipe is adjusted to 1 by hot air heating.
It was post-heated to 80 ° C. to form an epoxy primer layer.
The thickness of the epoxy primer layer was 100 μm.
Next, an adhesive consisting of maleic anhydride-modified polyethylene was used, having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040 m.
The outer surface of the m cross-linked polyethylene resin pipe was molded by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7%, so that the inner surface of the steel pipe was lined with resin with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 25 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, an adhesive composed of maleic anhydride-modified polyethylene was applied to the outer diameter of 42.4 m.
m, thickness 1.5 mm, length 4040 mm, when forming a cross-linked polyethylene resin pipe, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the crosslinked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 26 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive composed of maleic anhydride-modified polyethylene was used, and the outer diameter was
At the time of molding a cross-linked polyethylene resin pipe having a thickness of 4 mm, a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer round die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 27 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreaser.
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. In addition, an adhesive consisting of ethylene / maleic anhydride copolymer was used with an outer diameter of 4
At the time of molding a cross-linked polyethylene resin pipe having a thickness of 2.4 mm, a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7%, so that the resin was lined on the inner surface of the steel pipe with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 28 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive made of an ethylene / maleic anhydride / acrylic acid copolymer was used, having an outer diameter of 42.4 mm, a thickness of 1.5 mm, and a length of 4040.
The outer surface was coated by a coextrusion method using a two-layer circular die at the time of molding a mm cross-linked polyethylene resin pipe to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7%, so that the inner surface of the steel pipe was lined with resin with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 29 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive made of ethylene / maleic anhydride / acrylic acid ester copolymer was used to form a cross-linked polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm by using a two-layer circular die on the outer surface. Coated by coextrusion method to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7%, so that the inner surface of the steel pipe was lined with resin with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 30 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive composed of ethylene / acrylic acid copolymer is used to have an outer diameter of 42.4.
mm, thickness 1.5 mm, length 4040 mm, the outer surface was coated by a coextrusion method using a two-layer circular die when forming a crosslinked polyethylene resin pipe to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 31 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive made of an ethylene / acrylic acid ester copolymer is coextruded by using a two-layer circular die on the outer surface when molding a crosslinked polyethylene resin pipe having an outer diameter of 42.4 mm, a thickness of 1.5 mm and a length of 4040 mm. Coated to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

Then, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin with good adhesion on the inner surface of the steel pipe, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 32 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Further, an adhesive made of an ethylene / methacrylic acid copolymer was used to prepare an outer diameter of 42.
At the time of molding a cross-linked polyethylene resin pipe having a thickness of 4 mm, a thickness of 1.5 mm and a length of 4040 mm, the outer surface was covered by a coextrusion method using a two-layer round die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin on the inner surface of the steel pipe with good adhesion, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 33 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreaser.
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive composed of an ethylene / vinyl acetate copolymer is used, which has an outer diameter of 42.4.
mm, thickness 1.5 mm, length 4040 mm, the outer surface was coated by a coextrusion method using a two-layer circular die when forming a crosslinked polyethylene resin pipe to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin with good adhesion on the inner surface of the steel pipe, and then hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Example 34 Outer diameter 50.8 mm, thickness 3.3 mm, length 393 degreased with a commercially available alkaline degreasing agent.
After a 0 mm steel pipe was pickled to remove rust, the steel pipe was immersed in a commercially available chemical conversion treatment liquid containing zinc calcium phosphate and dried by hot air heating to form a chemical conversion coating. The amount of the chemical conversion coating deposited was 6 g / m ² . Next, epoxy resin powder primer (Powdax E made by Nippon Paint Co., Ltd.)
Is applied to the inner surface of the steel pipe preheated to 80 ° C by hot air heating by an electrostatic spraying method using an electrostatic coating machine, and the steel pipe surface temperature is postheated to 180 ° C by hot air heating to form an epoxy primer layer. Formed. The thickness of the epoxy primer layer was 100 μm. Furthermore, an adhesive made of an ionomer has an outer diameter of 42.4 mm and a thickness of 1.5.
When a cross-linked polyethylene resin pipe having a length of 40 mm and a length of 40 mm was formed, the outer surface was covered by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer is 20
It was 0 μm.

After that, the cross-linked polyethylene resin pipe was inserted into the steel pipe, and the outer diameter of the steel pipe was rolled at a reduction ratio of 4.7% to line the resin with good adhesion on the inner surface of the steel pipe, and then the hot air was blown. The surface temperature of the steel pipe was heated to 110 ° C. by heating. The crosslinked polyethylene resin pipe protruding from the end of the steel pipe was cut. Further, after degreasing the outer surface of this inner surface resin-lined steel pipe with a commercially available alkaline degreasing agent and performing grit blasting to remove rust, a commercially available alkyd paint was applied to a thickness of 25 μm.

Comparative Example 1 Outer diameter 34 mm, thickness 3.2 mm, length 4000 mm degreased with a commercially available alkaline degreasing agent
The inner surface of the steel pipe was treated with grit blast to remove rust. Next, an adhesive made of maleic anhydride-modified polyethylene was used, having an outer diameter of 26.1 mm, a thickness of 1.5 mm, and a length of 4,500 mm.
Polyethylene resin pipe molding (extruding polyethylene resin into a pipe shape at a die temperature of 220 ° C and then
At the time of production by stretching so as to reduce the diameter by 3%, the outer surface was coated by a coextrusion method using a two-layer circular die to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

Thereafter, the polyethylene resin pipe was inserted into the steel pipe, the surface temperature of the steel pipe was heated to 200 ° C. by high frequency induction heating to restore the shape of the polyethylene resin pipe, and the polyethylene resin pipe protruding from the end of the steel pipe was cut.

(Comparative Example 2) Outer diameter 34 mm, thickness 3.2 mm, length 4000 mm degreased with a commercially available alkaline degreasing agent.
The inner surface of the steel pipe was treated with grit blast to remove rust. Next, an adhesive made of maleic anhydride-modified polyethylene was used, having an outer diameter of 26.1 mm, a thickness of 1.5 mm, and a length of 4,500 mm.
In the case of the cross-linked polyethylene resin pipe molding (made by stretching the cross-linked polyethylene resin at a die temperature of 160 ° C. so as to reduce the diameter by 30% in the radial direction when extruded), a coextrusion method using a two-layer circular die on the outer surface Coated to form an adhesive layer. The thickness of the adhesive layer was 200 μm.

After that, the crosslinked polyethylene resin pipe is inserted into the steel pipe, the surface temperature of the steel pipe is heated to 200 ° C. by high frequency induction heating to restore the shape of the crosslinked polyethylene resin pipe, and the crosslinked polyethylene resin pipe protruding from the end of the steel pipe is removed. Disconnected.

With respect to the resin-lined steel pipes of Examples 1 to 34 and Comparative Examples 1 and 2, the shear adhesive force between the steel pipe and the resin pipe on the inner surface was measured. The shear adhesive strength is measured by cutting the produced resin-lined steel pipe to a length of 20 mm, supporting only the steel pipe portion with a jig, and only the inner resin lining layer
Punching was performed under the condition of 0 mm / min., And the pushing force at this time was regarded as the shear adhesive force. Three samples were taken and the average was calculated. The unit of shear adhesion is MPa. The temperature during the measurement test was uniformly set to 23 ° C. The shear adhesive strength after hot water of 60 ° C. or hot water of 95 ° C. was passed through the resin-lined steel pipe for one year was also measured. The measurement results are shown in Tables 1 to 4
Shown in. The initial shear adhesive strengths of Examples 1 to 34 are all 1.0 MPa or more, which is a preferable range of 2.0 MPa.
Showing a high value, which is significantly higher than those of Comparative Examples 1 and 2.

[0111]

[Table 1]

[0112]

[Table 2]

[0113]

[Table 3]

[0114]

[Table 4]

From these Tables 1 to 4, it was found that the resin-lined steel pipe of the present invention has excellent adhesion between the steel pipe and the inner surface resin lining layer for a long period of time.

[0116]

EFFECTS OF THE INVENTION By using the present invention, a resin having excellent adhesion between the steel pipe and the inner surface resin lining layer even when used for piping for water supply, hot water supply, air conditioning, fire extinguishing, drainage, etc. for a long period of time A lining steel pipe can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (31) Priority claim number Japanese Patent Application No. 2001-152120 (P2001-152120) (32) Priority date May 22, 2001 (May 22, 2001) (33) Priority claiming country Japan (JP) (72) Inventor Yasuhiro Sueuchi             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel shares             Company Kimitsu Works (72) Inventor Hiroyuki Mimura             1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel shares             Company Kimitsu Works F-term (reference) 3H111 AA01 BA02 BA15 BA34 CA52                       CB03 CB08 DB03 DB05 EA04                       EA15                 4F100 AB03B AB18A AK01D AK03C                       AK03D AK04C AK22C AK25C                       AK53E AK70C AL01C AL05C                       AL07C AN02C BA05 BA07                       CB00C CC00D DA11 DA11D                       EH71A EJ01D EJ05D EJ422                       EJ65E EJ68D GB07 JB02D                       JL00 JL13 JL13C YY00C                       YY00D YY002                 4F211 AD05 AD12 AG03 AG08 AH43                       SC03 SD04 SH22 SN02 SP02                       SP44

Claims (10)

[Claims] 1. A steel pipe, or a steel pipe whose outer surface is galvanized, has an adhesive layer on the inner surface, and further has a plastic layer on the inner side thereof, and the initial shear adhesive force between the steel pipe and the plastic layer is 1. Resin-lined steel pipe characterized by 0 MPa or more. 2. The resin-lined steel pipe according to claim 1, wherein the plastic layer is a polyolefin resin or a crosslinked polyolefin resin. 3. The adhesive layer comprises synthetic rubber, maleic anhydride modified polyolefin, ethylene / maleic anhydride copolymer, ethylene / maleic anhydride / acrylic acid copolymer, ethylene / maleic anhydride / acrylic acid ester. One or more of a copolymer, an ethylene / acrylic acid copolymer, an ethylene / acrylic acid ester copolymer, an ethylene / methacrylic acid copolymer, an ethylene / vinyl acetate copolymer, and an ionomer. The resin-lined steel pipe according to claim 1 or 2, which is characterized. 4. The resin-lined steel pipe according to claim 1, further comprising an epoxy primer layer between the steel pipe and the adhesive layer. 5. The resin-lined steel pipe according to any one of claims 1 to 4, wherein the steel pipe is a steel pipe that has been preliminarily preliminarily treated, and has an undertreatment layer on the inner surface of the steel pipe. 6. The resin-lined steel pipe according to claim 5, wherein a chemical conversion treatment film of phosphate is applied as the base treatment. 7. The resin-lined steel pipe according to claim 1, wherein the outer surface of the resin-lined steel pipe has a primary rust-preventive coating, a zinc rich paint coating, or a polyolefin coating instead of galvanizing. . 8. When manufacturing the resin-lined steel pipe, an adhesive layer is formed on the inner surface of a steel pipe with or without base treatment, or an epoxy primer layer is applied, and then the adhesive layer is formed on the inner surface of the steel pipe. 7. A plastic pipe having an outer diameter smaller than the inner diameter of the steel pipe is inserted, and the steel pipe is squeezed to tightly adhere the plastic pipe.
The method for producing a resin-lined steel pipe according to. 9. When manufacturing the resin-lined steel pipe, a steel pipe with or without base treatment, or with an epoxy primer layer, is applied to a steel pipe having an outer diameter smaller than the inner diameter of the steel pipe. 7. A plastic pipe having an adhesive layer is inserted, the steel pipe is squeezed to bring the plastic pipe into close contact, and heating is performed at a melting point of the adhesive layer or more and less than the melting point of the plastic pipe. Manufacturing method of resin-lined steel pipe. 10. The method for producing a resin-lined steel pipe according to claim 8, wherein, when the steel pipe is drawn, the outer diameter of the steel pipe is drawn at a drawing ratio of 1 to 50%.