JPH0439033A - Manufacture of composite pipe of metal and resin - Google Patents

Abstract

PURPOSE:To obtain a composite pipe having high adhesion strength between a metallic layer and a resin-layer by applying pressurized atmosphere to the inner peripheral surface of the composite pipe immediately after extruding of resin and coating with said resin. CONSTITUTION:A resin-coating device 70 has a resin-flowing tube 72, and a mandrel 73 is provided concentrically in said tube Resin 16 is extruded cylindrically from the gap between the tapered part of the tip of the resin-flowing tube 72 and the outer peripheral surface of the tip-core 74 of the mandrel 73, and the inner surface of the metallic pipe 14 after melding is covered therewith, thereby obtaining a composite pipe 15. Then, when compressed air is blown into the mandrel 73 from a compressed air-blowing tube 80, since the inner part of the composite pipe 15 at the prescribed distance downstream from molten resin 16-extruding part, is kept under pressurized atmosphere, the composite pipe with strong resin-adhesion force may be obtained without lengthening the tip-core 74.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention aims to improve corrosion resistance and chemical resistance of at least one metal pipe used for transferring fluids such as water supply and drainage. This invention relates to a method of manufacturing a composite pipe whose inner surface is lined with resin.

<Prior art> Conventionally, as a method for continuously manufacturing metal/resin composite pipes, as shown in JP-A-62-198447, both side edges of a band-shaped metal material (metal hoop material) A known method is to butt them together to form a circular tube, continuously weld the butt portions, and then extrude and coat the inner surface of the tube with resin.

In this manufacturing method, a metal tube is manufactured by abutting both side edges of a band-shaped metal material to form a circular tube shape, and joining the abutted portions by a welding means such as arc welding.

Then, a resin extrusion die is inserted inside the metal tube from the opening of the tube that is in the process of being formed, and the molten resin is extruded from the tip of the tube in a region downstream of the welding point, and the tip formed at the tip of the extrusion die is The resin is pressed against the inner surface of the metal tube using the outer circumferential surface of the core part, and the inner surface of the tube is coated with the resin.

<Problems to be Solved by the Invention> By the way, one of the factors that influences the durability of a metal/resin composite pipe is the adhesive strength between the metal layer and the resin layer.

The adhesive force is greatly influenced by the pressure with which the molten resin is pressed against the metal surface and the time period during which the pressure is applied.

In the composite tube obtained by the above-described conventional manufacturing method, the adhesive force between the metal layer and the resin layer is almost determined by the length of the outer peripheral surface of the extruded tip core.

In other words, the adhesive force of the resin layer to the metal layer increases as the pressing force increases and the pressing time increases, but in order to satisfy this condition in conventional manufacturing methods, the length of the mold tip core section must be increased. Therefore, it is necessary to lengthen the length. And the line speed is high (I see, the length of the mold tip core part required to obtain the same adhesive force is longer).

However, as the length of the mold tip core becomes longer, the resin flow path becomes longer in proportion, resulting in undesirable results such as an increase in back pressure and roughening of the product surface.

The present invention was made to solve these problems, and its purpose is to improve the adhesive strength between the metal layer and the resin layer without increasing the length of the mold tip core. It is an object of the present invention to provide a method for manufacturing a metal/resin composite pipe that allows a composite pipe to be obtained.

<Means for Solving the Problems> In order to achieve the above object, the method for manufacturing a metal/resin composite pipe of the present invention involves manufacturing a pipe by continuously welding a band-shaped metal material into a circular pipe shape. At the same time, the method for manufacturing a composite tube in which the inner surface of a tube obtained by welding is coated with a resin by extrusion is characterized by applying a pressurized atmosphere to the inner peripheral surface of the composite tube immediately after the extrusion coating of the resin.

<Operation> Immediately after extrusion, the resin extruded onto the inner surface of the metal tube is pressurized by air pressure and pressed against the metal surface.

That is, by pressurizing the resin with air pressure instead of pressing the resin against the inner surface of the metal tube with the outer periphery of the mold tip core, it becomes possible to take a longer pressurizing time and achieve the desired purpose.

<Example> Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of a continuous treatment process that is an embodiment of the method of the present invention.

Band-shaped metal sheet 11 set in uncoiler 10
are sequentially drawn out and supplied to the surface treatment tank 20. This surface treatment tank 20 is used to treat the metal sheet 11 in order to improve the adhesion between the metal sheet 11 and the resin coated on the metal sheet 11.
0 It is not suitable for surface treatment.

The surface-treated metal sheet 11 is then led to a forming device 30 where it is bent into a U-shaped cross-section.

The metal sheet 12 having a U-shaped cross section formed by this forming device 30 is heated by a heating device 40, and then formed by a circular tube forming machine 50 so that its cross section becomes closer to a perfect circle. A metal sheet 1 with a perfectly circular cross section, with parts facing each other or overlapping each other
3 is obtained.

Then, this metal sheet 13 having a perfect circular cross section is transferred to a welding machine 6.
0, the side edges are welded together to form the metal tube 14.

A part of the resin coating device 70 is inserted into the above-mentioned circular tube forming machine 50. As shown in detail in a vertical cross-sectional view in FIG. 2, this resin coating device 70 includes a main body portion 71 located within a metal sheet 12 having a tJ-shaped cross section immediately before being molded into a perfect circular cross section; A resin flow pipe 72 is supported by the main body 71 in a cantilever manner and extends in the direction of conveyance of the metal sheet.

A mandrel 73 is provided concentrically inside the resin flow tube 72, and a tapered portion whose diameter gradually increases toward the tip side is formed at the tip of the resin flow tube 72. It faces the outer peripheral surface of the tip core 74 of 73 with a predetermined gap therebetween. Then, the resin 16 is extruded into a cylindrical shape from this gap, and the metal tube 14 after welding is
The composite tube 15 is thereby obtained.

In the above configuration, in the embodiment of the present invention, the mandrel 7
A compressed air blowing pipe 80 is formed in the interior of the compressed air blowing pipe 80 . Only the central portion of the distal end surface of the distal core 74 extends downstream within the composite pipe 15 by a predetermined distance to form an extended portion 74a, and the compressed air blowing pipe 80 described above has one end connected to an external compressor. An air source (not shown) is connected to the tip core 74 at the other end.
It communicates with the inside of the composite pipe 15 from the extension part 74a. Further, a composite pipe 1 is provided at the tip of the extending portion 74a of the tip core 74.
A packing 81 that seals the inside of 5 is fixed.

With such a configuration, when compressed air is blown from the compressed air blowing pipe 80, the inside of the composite pipe 15 between the tip core 74 and the packing 81, in other words, the composite at a predetermined distance downstream from the extrusion part of the molten resin 16. The inside of the tube 15 is
It will be placed under a pressurized atmosphere.

Note that on the downstream side of the resin coating device 70, if necessary,
As shown in FIG. 1, a metal tube outer surface coating device 91, a cooling device 92, and a winding device or cutting device 93 are arranged in this order.

With the above device, an aluminum alloy sheet is used as the metal sheet and silane-modified polyethylene is used as the resin.
The results of manufacturing a composite pipe by blowing compressed air from the compressed air blowing pipe 80 were as follows. Note that welding was performed by TIG arc welding using helium gas as a shield.

The pressurization conditions were as follows: air pressure 3 kg/cj, pressurization time (
When the extrusion was carried out for 3 minutes (time required for the part to reach the packing 81- after extruding the resin), the adhesive strength of the resin of the obtained composite pipe was 12 kgf/cm. In addition, the pressurization conditions were set to air pressure 1. When the pressure was changed to 5 kg/cd and the pressurization time was 3 minutes, the adhesive strength of the resin of the resulting composite pipe was 7 kg.
f/cm, and it was confirmed that the resin adhesive strength was improved by blowing compressed air.

FIG. 3 is a longitudinal cross-sectional view showing the main structure of another embodiment of the present invention.

This example is an example in which the resin coating device 170 does not have a tip core. That is, although the resin coating device 170 includes a main body portion 171, a resin flow pipe 172, and a mandrel 173, the tip portion 174 of the mandrel 173 does not protrude toward the inner circumference of the metal tube 14, and the resin flow pipe It remains within 172. A compressed air blowing pipe 180 is formed on the mandrel 173 as in the previous example, and an extending portion 174a extending a predetermined distance toward the downstream side is formed on the tip end 174 of this mandrel. A packing 181 that similarly seals the inside of the composite tube 15 is fixed to the tip of the extending portion 174a.

According to the example shown in FIG. 3, the molten resin 16 passes through the resin flow pipe 172 and is forced out into the metal pipe 14 from the cylindrical opening between it and the tip 174 of the mandrel 173. It is pressed against the inner circumferential surface of the metal tube 14 by the pressure of compressed air supplied from the tube 180 into the tube.

Then, until the position where the packing 181 is installed, the resin 16
is pressed against the inner wall of the tube by compressed air.

In the example shown in Fig. 3, it is possible to coat the inner surface of a metal tube with an inner diameter larger than the extrusion diameter of the resin, so it is possible to manufacture composite tubes of multiple sizes with a single resin extrusion mold. It becomes possible. In addition, since there is no tip core, variations in wall thickness are reduced, and since there is no pressure distribution in the vertical direction to the surface when bonding metal and resin, circumferential variations in adhesive force are reduced. There is also.

However, when using the method shown in Figure 3, if the compressed air pressure is too high, the extruded resin may spread in the opposite direction to the pipe manufacturing direction. As shown, another seal 182 is arranged between the seal 181 and the resin extrusion part, and this
A discharge port of the compressed air blowing pipe 180 is provided on the downstream side of the
By configuring so that only a part of the compressed air flows to the upstream side through this packing 182, the packing 18
It is preferable that the pressure on the upstream side of 2 be lower than the pressure on the downstream side.

In addition, in the method of the present invention, various aluminum alloys, various steel plates, various copper alloys, etc. can be used as the metal sheet. Moreover, various types of arc welding, high frequency resistance welding, etc. are suitable for welding the respective side edges of such metal sheets. Furthermore, as the resin, modified polyolefins with excellent adhesion to metals, such as acid-modified polyethylene,
Silane-modified polyethylene or the like is suitable.

In addition, in the present invention, it is preferable to set the pressure on the inner surface of the composite tube immediately after resin extrusion to be as high as possible within the limit of the shielding force of the packing, but if the pressure is too high, the resin will be There is a risk of backflow occurring. Although higher adhesive strength can be obtained with longer pressure times, applying pressure on areas where the resin has completely solidified has little effect on improving adhesive strength (it is preferable to take this into consideration when making decisions). .

<Effects of the Invention> As explained above, according to the present invention, since the inner surface of the tube is placed under a pressurized atmosphere immediately after the resin is extruded into the metal tube, the length of the tip core is increased unlike the conventional method. In other words, the resin pressurization force and pressurization time can be set arbitrarily, without considering problems such as roughness of the product surface or back pressure during resin extrusion, and strong resin adhesion even at high line speeds. It became possible to obtain a composite tube with high strength.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a continuous treatment process that is an embodiment of the method of the present invention, FIG. 2 is a longitudinal cross-sectional view showing the detailed configuration of the resin coating device 70, and FIG. A vertical cross-sectional view showing the main part structure of another embodiment FIG. 4 is a longitudinal cross-sectional view showing the main part structure of still another embodiment to which the method of the present invention is applied. 10...Uncoiler 11...Metal sheet 12...Metal sheet 13...Metal sheet 13...Metal sheet 14...Metal tube 15... Composite pipe 16...Resin 20...Surface treatment tank 30...Forming device 40...Heating device 50...Circular tube forming machine 60...Welding machine 70... -Resin coating device 71...Body section 72...Resin flow pipe 73...Mandrel 74...Tip core 74a...9 -Extending portion 80...Compressed air blowing pipe 81...Packing 170...Resin coating device 171...Body portion 172...Resin flow pipe 173...Mandrel 174...Tip portion 174a...Extension Part 180... Compressed air blowing pipe 181... Packing 182... Packing

Claims (1)

[Claims] In a method for manufacturing a composite tube in which a tube is produced by continuously welding a band-shaped metal material into a circular tube shape, and at the same time, a resin is extruded and coated on the inner surface of the tube obtained by the welding, immediately after the resin is extruded and coated. A method for producing a metal/resin composite pipe, the method comprising: applying a pressurized atmosphere to the inner peripheral surface of the composite pipe.