JPH07260085A - Corrosionproof covering method of metal pipe connecting part - Google Patents

Abstract

PURPOSE:To maintain good corrosionproofness extending over a long period with a simple work by providing a first adhesive layer on the whole circumference of a range where the metal of the connecting part of a coating metal pipe is exposed, and providing a heat shrinkage property member having a second adhesive layer on an inner surface, on the outer circumference of the first adhesive layer. CONSTITUTION:A first adhesive layer 21 is provided on the whole circumference of a range 1 in which metal of a step part formed by a bead part 7 and a lining end part 6a is exported. A heat shrinkage property member 3 having a second adhesive agent layer on its inner surface is provided on the outer circumference of the first adhesive material layer 21. Therefore, the lining end part 6a and the bead part 7 in which a space is generated are filled by the first adhesive agent layer 21 so as to prevent generation of space. It is thus possible to exhibit good corrosionproofness extending over a long period with a simple work. The first and second adhesive layers 22 may be formed of pressure sensitive adhesive agent so as to realize adhesion uniformly by only pressure at the time of shrinkage of the heat shrinkage property member 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion coating method for a metal pipe connecting portion, and more particularly to a method for anticorrosion coating with a heat-shrinkable tube or a sheet in a metal exposed region of a connecting portion of a coated metal tube.

[0002]

2. Description of the Related Art Metal pipes used as flow passages for gas, petroleum, chemical plants, water, etc. are coated with anticorrosion coating or anticorrosion tape in order to prevent corrosion.
Among them, the metal pipes buried in the ground and the metal pipes used as a flow path for dangerous substances such as gas are difficult to repair once the former is buried, and the latter are Long-term anticorrosion reliability is required because dangerous substances may leak from the corroded parts, which may lead to a serious accident.

Therefore, as a metal pipe satisfying this requirement, a metal pipe lined with a thick film polyethylene resin, polyurethane resin, epoxy resin or the like (lining pipe) is replaced with a conventional metal pipe covered with anticorrosion coating or anticorrosion tape. Instead, it is becoming popular. The connection of this metal pipe is performed as follows. First, the linings of the connected parts of the two metal pipes are peeled off, and then the connected parts are butted to each other and welded. Alternatively, in the case of a metal tube in which the connected portion is originally not covered and the metal is exposed so that it is suitable for welding work, the connected portion is butt-welded without welding for removing the lining of the connected portion. Since the connection portion thus formed has a region where the metal is exposed (hereinafter referred to as an exposed region), it is necessary to separately apply an anticorrosion coating to this exposed region. The anticorrosion coating for this purpose is covered with a heat-shrinkable tube or sheet (hereinafter referred to as a heat-shrinkable member) and then heat-shrinked to expose the anticorrosive layer made of the heat-shrinkable member to the exposed region. The method of setting is taken. A typical example of the heat-shrinkable member used in this case is a stretched cross-linked polyethylene film as a base material and a rubber-based or modified polyolefin-based adhesive material layer bonded to the inside thereof.

[0004]

By the way, when the anticorrosion coating is applied to the connection portion as described above, it is important that the anticorrosion coating and the exposed region are sufficiently in close contact with each other. However, FIG.
As shown in FIG. 5, in the conventional anticorrosion coating method, a void 4 is formed between the exposed region 1 and the heat-shrinkable member 3, and the anticorrosion property is deteriorated.
This is due to the heat-shrinkable member 3 as described above.
Even if the heat-shrinkable member 3 is covered, the heat-shrinkable member 3 receives shrinkage stress at the stepped portion formed at the welded portion (hereinafter referred to as the beat portion) 7 and the lining end portion 6a, and the This is because it floats. Therefore, as shown in FIG. 4, after the asphalt-based undercoat 8 is applied to the exposed region 1 in advance, the heat-shrinkable member 3 is provided thereon. However, even if the undercoat 8 is applied, the voids 4 can be made small to some extent, but the effect is still insufficient with the metal tube 5 that requires long-term corrosion resistance. Further, in order to completely fill the step difference with the undercoat 8, it is necessary to apply multiple layers and there is a problem in workability. The present invention has been made as a result of earnest studies in view of such a point, and provides a method for coating a metal pipe connecting portion with an anticorrosion coating capable of forming a connecting portion of the coated metal pipe 5 that exhibits excellent anticorrosion properties for a long period of time with a simple operation. The purpose is to do.

[0005]

According to the present invention, at least the metal-exposed region 1 of the connection portion of the coated metal tube 5 is used.
And the step of providing the heat-shrinkable member 3 having the second adhesive layer 22 on the inner surface on the outer periphery of the first adhesive layer 21. The above-mentioned problems have been solved by a method of coating a metal pipe connecting portion with anticorrosion.

As the heat-shrinkable member in the present invention, for example, a known number of heat-shrinkable films are laminated and thermocompression-bonded to each other, and an insulating plastic material is extruded into a tube shape and heated to a predetermined temperature. However, a heat-shrinkable tube or sheet formed by expanding the diameter to a predetermined size is preferably used. Further, the heat-shrinkable member may be a heat-shrinkable tube or a sheet having a function of generating heat by energization, such as a resistance heating element provided therein.

The material for the adhesive layer in the present invention is
Those mainly composed of pressure-sensitive and temperature-sensitive adhesives are preferably used. As the pressure-sensitive adhesive, a rubber-based adhesive made of natural rubber, synthetic polyisoprene rubber, butyl rubber, styrene-butadiene rubber, polyisoprene rubber, or various modified rubbers obtained by modifying these rubbers. It is preferably used. As the temperature-sensitive adhesive, a polyolefin-based adhesive made of modified polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-isobutyl acrylate copolymer, or polyamide containing polyamide as a main component. An adhesive such as a system is preferably used. In particular, a pressure-sensitive adhesive material represented by a rubber-based material is excellent in workability because it uniformly adheres to the heat-shrinkable member due to the contraction pressure when it contracts. In order to improve the adhesion between the first adhesive material layer and the second adhesive material layer, the same adhesive material such as temperature-sensitive material and pressure-sensitive material is used as the material of each adhesive material layer. It is preferable to select a material, and it is more preferable to select a material mainly containing the same kind of polymer such as butyl rubbers and modified polyethylenes.

The method of anticorrosion coating of a metal pipe connecting portion of the present invention is
For example, it can be implemented according to the following procedure.
First, the exposed area is cleaned by a conventional method such as keren, and if there are sharp projections or weld spatters on the beat portion, they are removed. The exposed area is then preheated and a first adhesive layer is provided over at least the exposed area.
At this time, in order to prevent the exposed region from appearing on the outer surface of the first adhesive layer, it is preferable to provide the lining end portion so as to be covered with the first adhesive layer. In addition, the first adhesive layer in the present invention is preferably provided by molding the adhesive into a sheet. This is because, for example, it is possible to make the first adhesive layer uniform in thickness while preventing the formation of voids and allowing the first adhesive layer to have a uniform thickness by a simple means such as roller application. Then, a heat-shrinkable member having a second adhesive layer on the inner surface is set on the outer periphery of the first adhesive layer and heat-shrinked.

[0009]

According to the method of anticorrosion coating of the metal pipe connecting portion of the present invention, the first adhesive layer 21 is provided on at least the entire periphery of the region 1 where the metal is exposed, and the second adhesive layer 22 is heat-shrinkable on the inner surface. By providing the elastic member 3 on the outer periphery of the first adhesive material layer 21, the lining end portion 6a and the beat portion 7 where the void 4 is normally formed are filled with the first adhesive material layer 21 and the void 4 is generated. Can be prevented. If a pressure-sensitive adhesive is used as the material for the adhesive layers 21 and 22, the heat-shrinkable member will be uniformly adhered by the contracting pressure when it contracts.

[0010]

EXAMPLES The present invention will be described in detail below based on examples. (Embodiment 1) FIG. 1 is a sectional view showing a connecting portion (exposed region 1: 300 mm) of a 600A polyethylene lining pipe coated with an anticorrosion coating by the following method.

(Corrosion preventive coating method) First, the exposed region 1 of the lined metal tube 5 is treated with a propane gas burner at about 60.
Preheated to ° C. Then, the butyl rubber that is attached to the release paper is mainly used, and the thickness is 1.5 mm, the width is 400 mm, and the length is 1.
A 900 mm adhesive sheet was wrapped around the exposed area 1 and the edges of the lining. Then, a roller was put on the release paper and the release paper was removed to form the first adhesive layer 21. After that, the second adhesive layer 22 mainly composed of butyl rubber having a length of 500 mm, a thickness of 0.6 mm and an inner diameter of 680 mm is attached to the inner surface to a thickness of 1.
The first adhesive layer 21 was covered with the heat-shrinkable member 3 made of crosslinked polyethylene and having a shrinkage rate of 5% and a thickness of 5 mm. Then, the heat-shrinkable member 3 is heated by a propane gas burner to shrink and adhere to the connecting portion, and the second adhesive layer 2 is formed on the first adhesive layer 21.
2 and the heat-shrinkable member 3 were formed.

When a part of the anticorrosion coating of the connection portion was peeled off and the adhesion with the exposed region 1 was confirmed, no void was confirmed around the beat portion 7 or the stepped portion generated at the lining end 6a. It was Further, a rectangular parallelepiped scratch having a width of 10 mm, a length of 600 mm, and a depth reaching the exposed region 1 was formed on the coating of the stepped portion and the stepless portion with a cutter knife, and one end of the scratch was peeled off. Was hung on a spring, and the adhesive strength by 180 ° peeling was measured. As a result, a good value of 4 to 6 kg / cm was obtained. This is the first adhesive layer 2 in this embodiment.
It is considered that since the first and second adhesive material layers 22 are made of the same kind of adhesive material, the adhesion between the first adhesive material layer 21 and the second adhesive material layer 22 is improved. Further, in this embodiment, since butyl rubber is used as the material of the adhesive layers 21 and 22, the adhesive layers 21 and 22 are uniformly adhered to each other only by the contraction pressure when the heat-shrinkable member 3 is heated and shrunk. Is good in terms of.

(Embodiment 2) A polyamide type temperature sensitive adhesive is used as a material for the first adhesive layer 21 and the second adhesive layer 22, and the exposed region 1 is subjected to the temperature sensitive adhesion by a propane gas burner. The exposed region 1 was coated with an anticorrosion coating in the same manner as in Example 1 except that the material was heated to about 120 ° C., which is higher than the melting temperature of the material.
In this example as well, no generation of voids was confirmed. When the adhesive strength was measured in the same manner as in Example 1, it was 8 to
A good value of 12 kg / cm was obtained.

(Embodiment 3) The same operation as in Embodiment 2 except that a temperature-sensitive adhesive made of maleic acid-modified polyethylene is used as a material for the first adhesive layer 21 and the second adhesive layer 22. The exposed area 1 was provided with an anticorrosion coating. In this example as well, no generation of voids was confirmed. Further, the adhesive strength was measured in the same manner as in the other examples and was 10 to 15 kg.
A good value of / cm was obtained.

(Comparative Example 1) The adhesive sheet used in Example 1 was cut into a width of 30 mm, and the beat portion 7 and the lining end portion 6 were cut.
The first adhesive layer 21 was wound only around a. Otherwise, in the same manner as in Example 1, the connection portion was provided with an anticorrosion coating. When a part of the anticorrosion coating of the connection portion was peeled off and the adhesion with the exposed region 1 was confirmed, a continuous width in the pipe circumferential direction along the end portion of the first adhesive material layer 21 as shown in FIG. 5 mm
Voids 4 were observed.

(Prior Art Example 1) The exposed region 1 was covered with the same heat-shrinkable tube as in Example 1 without providing the first adhesive layer 21. Then, the heat-shrinkable tube was heated by a propane gas burner to shrink and adhere to the connection part. When a part of the anticorrosion coating of the connection portion was peeled off and the adhesion with the exposed region 1 was confirmed, as shown in FIG. 3, the beat portion 7 and the lining end portion 6 were formed.
A continuous width 10 in the pipe circumferential direction along the stepped portion caused by a
Voids 4 of mm were observed.

[0017]

As described above, according to the method of anticorrosion coating of the metal pipe connecting portion of the first aspect, the first bonding is applied to the entire periphery of at least the metal-exposed region 1 of the connecting portion of the coated metal pipe 5. Since the material layer 21 is provided and the heat-shrinkable member 3 having the second adhesive material layer 22 on the inner surface is provided on the outer periphery of the first adhesive material layer 21, the lining end portion 6a and the beat portion 7 where the void 4 is usually generated are formed. Is filled with the first adhesive material layer 21, the voids 4 can be prevented from being generated, and a metal pipe connecting portion exhibiting excellent corrosion resistance over a long period of time can be formed by a simple operation. According to the method of coating a metal pipe connecting portion for corrosion protection according to claim 2,
Since the adhesive material layer 21 and the second adhesive material layer 22 are made of a pressure-sensitive adhesive material, the heat-shrinkable member is uniformly adhered only by the contraction pressure when the heat-shrinkable member contracts. Therefore, according to the anticorrosion coating method of the metal pipe connecting portion of the second aspect, it is possible to prevent the formation of voids by a simpler operation, and it is possible to form the metal pipe connecting portion exhibiting excellent anticorrosion properties for a long period of time. According to the anticorrosion coating method for the metal pipe connecting portion of claim 3, since the first adhesive material layer 21 and the second adhesive material layer 22 are made of the same kind of adhesive material, the adhesion between the layers becomes better. It is possible to prevent the formation of the voids 4 and form a metal pipe connecting portion that exhibits excellent anticorrosion properties for a longer period of time with a simple operation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state of a metal pipe connecting portion coated by an anticorrosion coating method of the present invention.

FIG. 2 is a cross-sectional view showing a state of a metal pipe connecting portion coated by the anticorrosion coating method of a comparative example.

FIG. 3 is a cross-sectional view showing a state of a metal pipe connecting portion coated by a conventional anticorrosion coating method.

FIG. 4 is a cross-sectional view showing a state of a metal pipe connecting portion coated by a conventional anticorrosion coating method.

[Explanation of symbols]

 1 Area where Metal is Exposed (Exposed Area) 21 First Adhesive Layer 22 Second Adhesive Layer 3 Heat Shrinkable Member 4 Void 5 Metal Tube 6 Lining 6a Lining End 7 Beat Part 8 Undercoat

Claims (3)

[Claims] 1. A first adhesive layer (2) is formed on the entire circumference of at least a metal-exposed region (1) of a connection part of a coated metal pipe (5).
1) and the heat-shrinkable member (3) having a second adhesive layer (22) on the inner surface thereof is provided with the first adhesive layer (2).
1) A step of providing the outer periphery of the metal pipe connecting portion. 2. The first adhesive layer (21) and the second adhesive layer (21)
The method of claim 1, wherein the adhesive layer (22) comprises a pressure-sensitive adhesive material. 3. The first adhesive layer (21) and the second adhesive layer (21)
The anticorrosion coating method for a metal pipe connecting portion according to claim 1 or 2, wherein the adhesive material layers (22) are formed of the same kind of adhesive material.