JPH02212692A - Manufacture of composite pipe - Google Patents

Abstract

PURPOSE:To provide a hot water feeding pipe which has high adhesion strength by a method wherein a long metallic beltform sheet is bent as it is conveyed to form it in a tubular shape, and after beltform selvage parts extending from the two side edge parts of the sheet are welded together, the inner peripheral surface of a metallic pipe is covered with resin. CONSTITUTION:A long metallic beltform sheet 11 unreeled from a reel stand 10 is caused to pass a pipe making machine 20 formed with a plurality of rolls in the shape of a hand drum in cross section, and a section is orderly bent to process the sheet from an U-shape to a tubular shape. Beltform selvage parts 12 and 12' are processed to erect them externally of a pipe from the two side edges of the sheet 11 by means of a selvage molder 30. Thereafter, beltform selvage parts 12 and 12' are welded together to form a metallic pipe 14. Meanwhile, the sheet 11 is inserted in a metallic pipe 14, and silane denatured polyorefin resin 15 is pressed against the inner peripheral surface of the metallic pipe 14 from the tip part of a resin extrusion mold 70 for coverage to produce a lining tube. Further, the outer peripheral surface of the lining tube is covered with silane denatured polyorefin resin 15' to manufacture a composite pipe 16.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a composite pipe mainly used for drain pipes and hot water supply pipes.

(Prior art) Conventionally, for example, Japanese Patent Application Laid-Open No. 61-95921 discloses a method in which long metal strips are sequentially curved to have a U-shaped cross section to a circular tube shape, and the side edges of the sheets are overlapped and welded. However, a manufacturing apparatus has been disclosed that manufactures a composite tube by forming a metal tube and then extrusion coating the inner peripheral surface of the metal tube with a synthetic resin layer having excellent water resistance and heat resistance.

(Problems to be Solved by the Invention) However, according to the above-mentioned prior art, when a metal tube is heated to a high temperature during, for example, an arc welding process, the inner and outer surfaces of the welded part of the metal tube are Along the line, scale or oxide film may be formed from the welded part, and in such cases, the adhesion with the synthetic resin layer extruded on the inner circumferential surface of the pipe is inhibited, and sufficient Adhesive strength may not be obtained, and when used as a hot water supply pipe, the resin layer coated on the welded part may peel off or form blisters, and the peeling or blisters may grow and damage the pipe. There was a problem in that the interior was blocked and fluid transport was hindered.

(Means for Solving the Problems) The method for manufacturing a composite pipe of the present invention has been made in order to solve the above-mentioned problems, and consists of continuously transporting a long metal sheet and sequentially bending it. After changing the cross section from a U-shape to a circular tube shape, forming band-like ears facing each other from both side edges of the sheet in the direction outside the tube, and welding substantially the tips of the ears together to form a metal tube. The gist of the present invention is to continuously manufacture a lining pipe by melt-coating at least the inner peripheral surface of the metal pipe with a water-crosslinkable silane-modified polyolefin resin.

In the present invention, first, a metal belt-shaped elongated sheet is sequentially curved and processed from a U-shaped cross section to a circular tube shape, and from both side edges of the circular sheet, a pair of belt-shaped ears are formed. erected toward the outside of the pipe.

The ears are erected close to each other so that the ears face each other, and have a height of 1.0 mm or more, preferably 1.0 mm or more, and preferably 1.0 mm or more.
25 hours.

Next, after arc welding the ears together, the welded ears are bent along the outer circumferential surface so that the outer circumferential surface of the metal tube meets the road surface, thereby forming a metal tube.

The welded ears do not necessarily need to be bent, but if they are bent, the internal pressure strength of the circular tube will be greater and the appearance will be better.

Further, the welding is performed at approximately the tip of the ear portion, at a location approximately 10 nnn or more away from the peripheral edge of the long belt-shaped sheet having a circular tubular shape.

By doing so, it is possible to prevent scale and oxide film from forming on the inner circumferential surface of the metal tube without adversely affecting the inner circumferential surface of the metal tube.

The ears need not both be of the same height, but may be of different heights. In this case, first, the ears are welded together, and then the taller ear is bent along the tip of the lower ear so that they are at the same height. It is bent along the outer circumferential surface so that

In the present invention, while forming a metal tube using the above method, a resin extrusion mold is inserted into the metal tube from a position before it becomes a metal tube, and a water-crosslinkable silane-modified polyolefin resin is applied to the inner peripheral surface of the metal tube. Melt coat and form composite tube.

Furthermore, in the present invention, not only the inner surface but also the outer surface of the metal tube may be coated with a resin.

The water-crosslinkable silane-modified polyolefin resin in the present invention refers to, for example, a polyolefin resin modified with a silane compound and brought into contact with water, preferably hot water, to cause crosslinking between molecules.

The above-mentioned silane modification can be performed using, for example, polyolefin resin 100
0.1 to 10 parts by weight of a silane compound and 0.001 to 3 parts by weight of a radical generator are added to the parts by weight, and the process is carried out in an extruder.

As the silane compound, compounds containing hydrolyzable organic functional groups such as methoxy and ethoxy groups, such as vinyltrimethoxysilane and vinyltriethoxysilane, are suitable.

Further, as the radical generator, dicumyl peroxide, t-butyl peroxide, etc. are suitable.

Examples of the polyolefin resin used in the present invention include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene/vinyl acetate copolymer, ethylene/propylene copolymer, polypropylene, polybutene, etc. It will be done.

The above-mentioned polyolefin resin itself has almost no adhesive property with metal, so by modifying it with silane, for example,
A method is adopted in which a functional group is formed within the resin molecule to improve adhesion to the metal tube.

The metal strip-like elongated sheet referred to in the present invention may be made of steel, copper, aluminum, etc., but it is preferable to use one made of aluminum or steel from the viewpoint of adhesiveness.

In the present invention, in order to improve the adhesiveness between the metal tube and the resin layer, a metal surface treatment step may be provided before coating with the resin layer.

(Function) The method for manufacturing a composite pipe of the present invention involves sequentially curving long metal strip sheets to form a circular tube shape in cross section, and forming strips that are erected from both side edges of the sheet so as to face each other toward the outside of the tube. Since the metal tube is formed by welding the ears of the metal tube together, no scale or oxide film is formed on the inner circumferential surface of the metal tube, which has a negative effect on adhesion, and the water bridges coated on the inner circumferential surface of the metal tube are not formed. The silane-modified polyolefin resin firmly adheres to metal pipes.

(Example) Examples of the present invention will be described below.

The method for manufacturing a composite pipe of the present invention is carried out, for example, by a manufacturing apparatus shown in FIG.

The metal strip-shaped long sheet 11 pulled out from the reel stand 10 is a plurality of rolls (not shown) each having a drum-shaped cross section.
The sheet 11 is processed into a U-shape by passing through a pipe-making machine 20 that sequentially curves its cross section, and then the sheet 11 is shaped like a drum, as shown in FIGS. 2 and 3, for example. A plurality of pairs of rolls 2L 21', 22.2 having a cross section of
2' and 23.23', opposing band-shaped ears 12.12'' with a height of 20+++ m are formed outside the tube from both side edges of the sheet 11, as shown in FIG. It is processed into a circular tubular object 13 that stands upright in the direction.

Next, after approximately the tip of the ear portion 12.12゛ of the circular tube-shaped object 13 is welded by the welding machine 50, the ear portion 12.12゛, which has been set upright, is bent by the ear bending machine 60. The metal tube 14 is formed by bending one side along the outer peripheral surface so as to overlap.

Thereafter, a resin extrusion mold 40 connected to an extruder (not shown) is placed in a position before the sheet 11 is welded with a welding machine 50 to form a metal tube, and the sheet is bent into a substantially U-shape. 11 into the metal tube 14, and the silane-modified polyolefin resin 15 is pressed from the tip of the resin extrusion mold 70 onto the inner peripheral surface of the metal tube 14 to coat it, thereby producing a lining tube.

Further, the outer circumferential surface of the lining tube is coated with silane-modified polyolefin resin 15'' to produce a composite tube 16 having resin layers on the inner and outer circumferential surfaces of the metal tube 14, as shown in FIG.

A belt-shaped long sheet 11 made of aluminum with a yaw thickness of 1.5 mm is sequentially curved to form a circular tubular cross section, and ears 12 with a height of 20 mm are provided on both side edges of the sheet 11. ．．
12" to form a metal tube 14 with a diameter of 80 mm. After extrusion coating the inner peripheral surface of the metal tube 14 with silane-modified low-density polyethylene resin 15, the ear portion 12.12" of the metal tube 14 is welded. The metal tube 14 was bent so as to be flush with the outer circumferential surface.The outer circumferential surface of the metal tube 14 was then coated with a 20-valent thick silane-modified low-density polyethylene resin 15' to form the composite tube 1.
6 was manufactured.

'' The composite pipe 16 was cut into a length of 50 cm as a sample, and hot water at 90°C and room temperature water at 25°C were added to the sample.
5000 tests in which water was passed alternately for 30 minutes each
Although the test was repeated several times, no peeling or blistering was observed in the 15 layers of silane-modified low-density polyethylene resin on the inner peripheral surface.

Misfortune 4 In Experimental Example-I, a composite pipe was manufactured in the same manner as Experimental Example-1, except that a 1.5 mm thick steel strip-shaped long sheet was used. The water flow test was repeated 5,000 times using the same method, but no peeling or blistering was observed in the resin layer on the inner peripheral surface.

(Effects of the Invention) As described above, the method for manufacturing a composite pipe of the present invention prevents the formation of scale or oxide film on the inner circumferential surface of the metal tube, which has a negative effect on adhesion. Since the coated water-crosslinkable silane-modified polyolefin resin firmly adheres to the metal pipe, it is possible to provide a hot water supply pipe with excellent adhesive strength.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the method for manufacturing a composite pipe of the present invention, FIG. 2 is a plan view showing an embodiment of the selvedge forming machine of the present invention, and FIG. A cross-sectional view along the line ■■, FIG. 4 is a cross-sectional view showing a circular tubular article manufactured according to the present invention,
FIG. 5 is a cross-sectional view of a composite tube manufactured according to the present invention. 11--Long strip sheet, 12.12'-Ear portion, 13
-Cylindrical object, 14-metal tube, 15.15'-silane modified polyolefin resin, I6-composite tube.

Claims (1)

[Claims] 1. Continuously transporting a long sheet of metal, the sheet is sequentially curved to form a U-shaped cross section into a circular tube shape, and opposing band ears are erected from both side edges of the sheet toward the outside of the tube. After forming a metal tube by welding substantially the tips of the ears together, at least the inner peripheral surface of the metal tube is fused and coated with a water-crosslinkable silane-modified polyolefin resin to continuously produce a lining tube. A method for manufacturing a composite pipe characterized by: