JP2003097769A - Lining synthetic resin, and method for manufacturing synthetic resin lining metallic pipe using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a synthetic resin lining metallic pipe with good durability by stably adhering a synthetic resin lining pipe coated with a synthetic resin layer to the inner face of a metallic pipe without a need of a pressurizing step. SOLUTION: This synthetic resin pipe is used for lining the inside of a metallic pipe, and both ends of said synthetic resin pipe are closed, so that the inside of the pipe is in a pressurizing condition. In this manufacturing method of a synthetic resin lining metallic pipe, while said synthetic resin pipe is inserted in a metallic pipe, said synthetic resin pipe is heated, expanded and adhered on the inner face of the metallic pipe, so as to adhere the outer peripheral face of the synthetic resin pipe and the inner face of the metallic pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin pipe for producing a lining metal pipe, which is a pipe material used for water supply, hot water supply, drainage, etc. and has excellent corrosion resistance in which the inner surface of the metal pipe is coated with synthetic resin. The present invention also relates to a method for producing a synthetic resin lining metal tube using the same.

[0002]

2. Description of the Related Art As one of the methods for producing a synthetic resin lining metal tube in which a layer of synthetic resin such as vinyl chloride resin is formed on the inner surface of a metallic tube A method is known in which a tube is inserted through an adhesive, and the tube is heated by a heating device to expand the diameter of the synthetic resin tube and adhere it to the inner surface of the metal tube. As an example, so as not to create an air pocket between the metal tube and the synthetic resin tube,
A method in which a synthetic resin pipe is expanded from the center to both ends by sequentially heating from the center in the longitudinal direction of the pipe to both ends of the pipe using a V-shaped heating device (JP-A-6-
No. 328565).

However, in the above manufacturing method,
There is a problem in that the adhesive force is partially reduced due to variations in the temperature of the heating device and peeling occurs later. Further, especially in polyolefins such as polyethylene and polypropylene, the glass transition temperature is lower than room temperature,
It is difficult to provide the heat expansion property, and for the lining process, it is necessary to pressurize the inside of the synthetic resin pipe in the heating device, which has a demerit that the facility is complicated and the productivity is reduced. The present invention has been made in view of the above problems, and an object thereof is to stabilize the quality of adhesive strength and the like, and a synthetic resin pipe that does not require internal pressure in a lining heating step, and The present invention provides a method for producing a synthetic resin lining pipe using.

[0004]

According to a first aspect of the present invention, there is provided a synthetic resin pipe used for lining the inside of a metal pipe, wherein both ends of the synthetic resin pipe are closed so that the inside of the pipe is under pressure. It is a characteristic synthetic resin tube for lining.

The synthetic resin is not particularly limited, and may be a known thermoplastic resin. As such, for example, low-density polyethylene, high-density polyethylene, modified polyethylene, polyolefin such as polypropylene,
Although hard vinyl chloride and the like can be mentioned, polyolefin is particularly suitable for the present invention in that it is difficult to impart heat-expandability and is excellent in environment as a lining resin.

[0006] The size of the synthetic resin pipe is appropriately selected depending on the metal pipe to be lined, but the outer diameter is slightly smaller than the inner diameter of the metal pipe to be lined, so that the pipe can be easily inserted into the metal pipe. It is preferable. Specifically, 90 to 99% of the inner diameter of the metal tube is preferable,
It is more preferably 95 to 97%. The wall thickness needs to be designed depending on the application, but is preferably 0.5 to 3.0 mm. As a method for manufacturing the synthetic resin pipe, a general extrusion molding method is used.

Further, it is preferable that an adhesive layer is provided on the outer peripheral surface of the synthetic resin pipe, since it is easier to line the inside of the metal pipe thereafter, and the adhesive strength of the lining layer is increased.

Although the above-mentioned adhesive is not limited, a hot-melt type adhesive is preferable in that it can be easily adhered by heating and the strength can be secured. As the hot melt adhesive, maleic anhydride modified polyolefin, ethylene-maleic anhydride copolymer resin, ethylene-maleic anhydride-acrylic acid ester copolymer resin, ethylene-methacrylic acid copolymer resin, ethylene-vinyl acetate copolymer resin Resin etc. are mentioned. The thickness of the adhesive layer is 20 μm
˜1 mm, preferably 100 to 200 μm.

As a method for laminating the adhesive layer on the outer peripheral surface of the pipe, a synthetic resin and a hot melt type adhesive are mixed in an extrusion die.
A method of layer extrusion molding, a method of applying an adhesive by a crosshead mold, brush coating or the like on each line during a series of extrusion molding or after molding a synthetic resin tube, and the like.

As a method of closing both ends of the synthetic resin pipe, there are a method of sealing with a cap or the like, a method of flattening both ends and fusion bonding. Further, as a method for putting the inside of the synthetic resin pipe in a pressurized state, the end portion is closed by the above method while introducing compressed air by a compressor to make it longer than the length of the metal pipe, and then the end portion is crushed. There is a method of increasing the internal pressure. Their schematic diagrams are shown in FIGS.

The internal pressure of the synthetic resin tube is limited to the expected performance and the processing method, but 0.05 MPa to 10 MPa is preferable in that it is less likely to burst during heating of the lining molding.

According to a fourth aspect of the present invention, the synthetic resin tube is inserted into a metal tube, and the synthetic resin tube is heated and expanded in the inserted state to be adhered to the inner surface of the metal tube and adhered to the inner surface of the metal tube. The method for producing a synthetic resin-lined metal tube according to claim 1.

As a means for expanding the synthetic resin tube by heating and adhering it to the inner surface of the metal tube, there is a method of expanding the synthetic resin tube together with the metal tube in a heating furnace for fusion.
As in the case of producing a vinyl chloride resin lining metal tube or the like, a method of using a hot air heating furnace of V-shaped type or diagonal type is preferably used (see FIGS. 1 and 2).

When an adhesive layer is provided on the outer peripheral surface of the synthetic resin pipe, the heating temperature is higher than the crystallization temperature of the synthetic resin used for the pipe and the adhesive melts. It is necessary to adjust the temperature. The heating temperature is preferably 140 to 160 ° C. in the case of polyethylene, for example. If the temperature is lower than 140 ° C., the residual strain generated when the diameter is increased from the initial outer diameter to the inner diameter of the metal tube is not relaxed due to temperature variations and the like, and there is a risk of defective adhesion.
On the other hand, when the temperature is higher than 160 ° C., polyethylene may start to flow due to its own weight, resulting in uneven thickness.

In addition, after heating, during cooling, it is better to keep the pressure applied until the temperature becomes lower than the crystallization temperature of the synthetic resin used in view of the stability of adhesion, so after the temperature has dropped, it is adjusted to the metal tube surface. A method of cutting both ends in this manner is preferable.

(Operation) The synthetic resin pipe for lining according to the present invention has both ends closed and a pressurized state, and therefore, the pipe is heated by crystallization temperature of the synthetic resin or higher during lining. Expands and can be attached and adhered to the inner surface of the metal tube. Furthermore, after sticking, at the time of cooling to at least lower than the crystallization temperature (preferably up to room temperature), both ends of the resin pipe are cut along with the surface of the metal pipe to obtain a lining metal pipe. .

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A polyethylene pipe having an outer diameter of 50.0 mm and a wall thickness of 1.5 mm is manufactured by using low density polyethylene as a synthetic resin, and a wall thickness of 0.2 m is obtained by a crosshead mold.
The modified polyethylene adhesive of m was applied to the outer peripheral surface of the synthetic resin tube. Both pipe ends are flat, but 0.2 MPa inside the pipe
The internal pressure of was maintained. This polyethylene pipe has an outer diameter of 60 m
It was inserted into a carbon steel metal tube having a thickness of 3.8 mm and a wall thickness of 3.8 mm, introduced into the V-shaped heating furnace shown in FIG. 3, and heated until the polyethylene reached 140 ° C. to be brought into close contact with the inner surface of the carbon metal tube. After the polyethylene pipe was cooled to 60 ° C., the pipe portions remaining at both ends were cut to obtain a polyethylene-lined metal pipe.

According to the present invention, since the inside of the synthetic resin pipe is in a pressurized state, the inner surface of the metal pipe can be easily lined without performing a pressing step. Therefore, in a hard vinyl chloride resin tube that can be heated and expanded, these linings can be performed more stably. Further, it becomes possible to easily perform the lining process on the inner surface of the metal tube even with polyolefin such as polyethylene or polypropylene which is difficult to be provided with the heat expansion property.

[0018]

[Brief description of drawings]

FIG. 1 is an explanatory view showing a lining process using a V-shaped hot air heating furnace.

FIG. 2 is an explanatory diagram showing a lining process using a diagonal hot-air heating furnace.

FIG. 3 is an explanatory view of the lining showing a state of sequentially heating from the center using a V-shaped hot air heating furnace.

FIG. 4 is a schematic view in which both ends of a synthetic resin pipe are capped and pressurized.

FIG. 5 is a schematic view of pressing a synthetic resin pipe with a flat seal.

FIG. 6 is a schematic view of pressurizing a synthetic resin pipe by a flat seal and deformation.

FIG. 7 is a schematic view showing a state in which a synthetic resin pipe is inserted into a metal pipe.

[Explanation of symbols]

A Laminated tube with synthetic resin tube inserted inside the metal tube 1 Conveyor 2 heating device 3 synthetic resin pipes 4 cap 5 valves 6 Seal part 7 Deformation part 8 metal tubes

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Claims (4)

[Claims] 1. A synthetic resin pipe for use in lining a metal pipe, wherein both ends of the synthetic resin pipe are closed so that the inside of the pipe is in a pressurized state. 2. The synthetic resin pipe for lining according to claim 1, wherein an adhesive layer is provided on the outer peripheral surface of the synthetic resin pipe. 3. The synthetic resin pipe for lining according to claim 1, wherein the resin used as the synthetic resin is polyolefin. 4. The synthetic resin pipe according to any one of claims 1 to 3 is inserted into a metal pipe, and in the inserted state, the synthetic resin pipe is heated and expanded and affixed to the inner surface of the metal pipe. A method for producing a synthetic resin-lined metal tube, characterized in that the surfaces are adhered.