JPS59158243A - Manufacture of metallic pipe coated with synthetic resin - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a synthetic resin-coated metal tube.

Conventionally, a resin coating layer of a thermoplastic resin such as polyethylene or polyvinyl chloride is removed from the outer surface of a metal tube using a crosshead die, and a tapered thread for connection is cut.

However, in this case, after forming the resin coating layer,
．． When performing thread cutting, depending on the adhesion between the metal tube and the resin coating layer, the thread cutting process becomes difficult, or the #'i' resin coating layer is damaged, resulting in a decrease in corrosion resistance. Additionally, when transporting or transporting metal pipes, the threads on the threads at the ends of the pipes may become crushed due to contact between the pipes, making it impossible to connect, and the pipes must be threaded again. There were also problems.

The present inventors used a metal tube (hereinafter referred to as a threaded metal tube) with male threads provided on the outer periphery of one or both ends of the tube, and by extrusion coating the outer surface of the metal tube with a synthetic resin. An attempt was made to improve the problems caused by the conventional thread cutting process after coating.

However, when the outer surface of a threaded metal tube is coated with a synthetic resin such as polyvinyl chloride resin by extrusion, when the molten resin is discharged from the rad die to the cross, a phenomenon in which it bulges in the radial direction (the so-called ballast effect) occurs, causing damage to the threaded portion. There was a problem in that the threaded portion could not be covered and protected because it spread out in the shape of a hole in the vicinity. This problem changed the structure of Ladogui to cross (
For example, some improvements have been made by lengthening the Guiland section, but this has not resulted in significant improvements.

As a result of extensive studies, the inventors of the present invention have found that the above-mentioned drawbacks can be improved by inserting and extruding a stopper with a flange and an insertion part into the end of a threaded metal tube. This led to the completion of the present invention.

The gist of the present invention resides in a method for producing a synthetic resin-coated metal tube, the outer diameter of which is approximately equal to the outer diameter of the metal tube, and characterized in that the outer surface of the metal tube is coated with a synthetic resin by extrusion.

The unexploded 8A will be explained below based on the drawings.

FIGS. 1 and 2 are explanatory diagrams showing the manufacturing process of the present invention.

It is a single-piece metal tube, and a male thread 2 is provided on the outer periphery of the end thereof. It may be provided at both ends of this two male threaded metal tube 1, or it may be provided with 5 taff only at one end.

It is a plug made of metal, synthetic resin, or inorganic material, and is formed from a collar part 31 and an insertion part 327, and the insertion part 32 is inserted into the end of the metal tube 1. The outer diameter of the collar portion 31 is approximately equal to the outer diameter of the metal tube 1. If the outer diameter of the flange 31 is smaller than the outer diameter of the metal tube 1, the Km resin will spread during extrusion coating and will not be coated, and if it is too large, it will be difficult to insert it into the mold and the resin extrusion conditions will be abrupt. This is because the coating changes to a uniform thickness, making it impossible to coat the wall with a uniform thickness.

In addition, when the axial length of the flange 31 has an outer diameter of 500 mm or less, it depends on the type of synthetic resin extruded and coated on the outer surface of the metal tube 1, but it is possible to obtain better adhesion near the threaded portion. In order to achieve this, it is preferable to set the diameter to 2 or more of the outer diameter of the metal tube 1. This is because as the length of the 3-piece flange becomes shorter, the adhesive force on the coating resin weakens and the thickness of the coating resin increases, causing a force that causes the resin coating layer to swell in the radial direction due to the lath effect. and,
This is because the coating layer spreads out in the form of a flake and may not be able to cover the plug 3 and the male thread 20 portion. Part 8 3
The longer the length of 1, the better the adhesion near the threaded part, but
From the viewpoint of cost and workability, the upper limit used is about 4 to 5 times the outer diameter of the metal tube 1. The insertion portion 32 only needs to be configured such that the plug body 3 is tightly fitted into the first metal, and when the outer diameter and axial length of the insertion portion 32 are coated by extrusion, The edge of No. 1 can be fixed as appropriate to prevent it from falling.

The metal tube 1 prepared as shown in FIG.
As shown in the figure, a synthetic resin-coated metal tube is obtained in which a resin coating 4 is formed on the outer surface of the metal tube 1, the cut portion 21 of the male thread, and the outer surface of the flange portion 31 of the cylindrical plug body 3. .

In order to improve adhesion during extrusion coating, it is preferable to apply an adhesive to the outer peripheral surfaces of the metal tube 1 and the plug 3. Further, it is preferable to apply a rust preventive agent to the male thread 2.

To connect the above synthetic resin coated metal pipes at the construction site,
As shown in Fig. 3, a cut is made in the resin coating layer 4 near the cut-up part 21 of the male thread, and the resin coating layer 4 at the end of the pipe is removed together with the cylindrical plug body for connection work. All you have to do is Incidentally, if the notch 5 is made at the manufacturing site, the connection work can be performed more easily.

In the above embodiment, the insertion part 32 of the cylindrical plug 3 was inserted into the inner surface of the metal tube 1, but as shown in FIG. It may be a cylindrical stopper 3' provided with an insertion part 33' that is screwed into the external threaded part 2, which is provided at the end of the pipe 1. Even if there is no '.

As described above, the method for producing a synthetic resin metal tube of the present invention involves extruding and coating the outer surface of the metal tube with a male thread on the outer periphery of the end. It is possible to obtain a synthetic resin-coated metal tube in which the screw portion is coated with good adhesion and the threaded portion is protected by the coating layer.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams partially omitting the manufacturing process of the present invention, FIG. 3 is a front view partially omitting the state in which the incision is provided, and FIG. 4 is a partially omitted front view showing a state in which a modified example of the stopper is inserted into a metal tube. l...Metal tube, 2...D/<male thread, 21...
Cut-up portion, 3, 3' to... Plug body, 31.31'... Flange portion, 32.32', 33'... Insertion portion, 4... Resin coating layer, 5... incision. Patent applicant Sekisui Chemical Co., Ltd. Representative Mototoshi Fujinuma

Claims (1)

[Claims] L: a flange whose outer diameter is approximately equal to the outer diameter of the metal tube;
A synthetic resin characterized in that the insertion part of a stopper consisting of an insertion part is inserted into an end of a metal tube provided with a male thread on the outer periphery, and the outer surface of the metal tube is coated with a synthetic resin by extrusion. Method for manufacturing coated metal pipes.