JPS58108127A - Manufacture of thermoplastic resin coated spiral metallic pipe - 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 for manufacturing a thermoplastic resin-coated spiral metal tube that has high corrosion resistance and sufficient water pressure resistance, using a metal plate coated on both sides with thermoplastic resin.

Coated metal pipes manufactured by the spiral caulking method include galvanized metal pipes, and although some results have been shown regarding these various properties, as the applications expand, products with even better corrosion resistance are needed. is being demanded.

In order to meet this demand, the present inventors first attempted to manufacture a general spiral metal tube using a metal plate coated with a synthetic resin and the spiral caulking method described above, and evaluated the results. .

Schematically, it is as shown in Fig. 1, and as the sheet metal plate is wound, the parts (arrows) where the sides meet each other are sequentially caulked by a caulking machine, as shown in Fig. 2. It is caulked as shown in the cross-sectional form.

However, the spiral metal tube coated with thermoplastic resin obtained by this aromatic property is subject to large processing strains in the area indicated by the arrow in Figure 2, and the coating layer in this area is likely to crack. The coating layer has the disadvantage of being inferior in corrosion resistance compared to other parts,69 and it cannot be used in areas where a high degree of corrosion resistance is required.

The present invention was developed and completed in order to solve the above-mentioned problems when manufacturing spiral metal tubes using metal plates coated with thermoplastic resin. The basic idea is to combine this with a commonly used heating device.

That is, in the case of manufacturing a spiral metal tube, when forming a spiral metal tube using a metal plate whose surface is coated with a hot-open Jll type shelving fat, the metal tube is crimped while caulking the parts that come into contact with each other. The present invention relates to a method for manufacturing a thermoplastic resin-coated spiral metal tube, which comprises forming a thermoplastic resin-coated spiral metal tube, melting the coating layer at the caulked portion intensively to integrate the thermoplastic resin, and then cooling.

The metal plate used in the present invention refers to a material that is normally used for pipe manufacturing, such as a steel plate or an aluminum plate.

As the thermoplastic resin used as the coating material for these metal plates, any commonly used thermoplastic resin can produce the desired effect. Very generally, when using a polyolefin resin such as polyethylene, it can be used as a general-purpose spiral metal tube because it is chemically stable.

The method of coating the surface of a metal plate using thermoplastic resin includes:
There are various methods other than roll lamination, press logging, etc., and the method used in the present invention may be any of these methods.

A metal plate coated with such a thermoplastic resin is caulked at its end by a spiral metal tube manufacturing apparatus having a caulking device to form a metal tube. The cross-section of the caulked portion of the metal tube obtained at this stage is as shown in FIG. 2, and up to this groove, it has the above-mentioned drawbacks.

In the present invention, the metal tube thus obtained is intensively heated at a temperature equal to or higher than the melting point of the thermoplastic resin using an appropriate heating means, thereby melting the resin at the caulked portion and forming the sixth
Il! It has mold.

In this case, the heating method is to use a known heating device such as an induction heater or a burner on the caulked portion of the metal tube as it rotates in the manufacturing line. The heating device must have at least enough heat output to melt the resin in the center of the caulked part, but this may vary depending on the speed of the spiral metal tube production line or the properties of the resin.
It is not preferable to apply too much heat in consideration of the thickness of the coating film, etc., because it will require the installation of an unnecessarily large-scale device in the next cooling process.

After the resin in the caulked portion has been completely melted as described above, cooling is performed next to solidify the molten resin to form a product. As the cooling means, a fan, spray, or other cooler using ordinary cooling fluid may be used.

By implementing the present invention having the above configuration,
Thermoplastic resin-coated spiral metal tubes have been difficult to put into practical use due to material deterioration in the bending process called crimping, but by adding heating means and cooling means during the manufacturing process, the corrosion resistance of the crimped parts has been improved. This makes it possible to produce a spiral metal tube that retains its properties to the same extent as other coating layers, making it extremely useful.

The effects of the present invention will be specifically explained below using Examples.

l! Example: Using a cold-rolled steel plate (α5 thickness, width 86 mm) coated on both sides with modified polyethylene with a thickness of approximately 200μ, an induction heater was used to form the KjD pipe using a spiral vibe forming machine while caulking. The coating layer at the crimp portion was melted and then cooled with water to solidify the molten resin.

A watertight test was conducted using this coated spiral steel pipe.
No water leakage was observed even at a water pressure of 0 K#/al.

In addition, 120 samples were cut out from this coated spiral steel pipe, including the caulked portion, and a salt water spray test was conducted for 1,000 hours. No rust was observed.

A sample with a width of 10 cm was cut out in a direction perpendicular to the caulked part, and a peel test was performed at a tensile rate of 501 cm in the direction indicated by the arrow in Figure 4. There was no peeling of the resin from the molten adhesive surface. The final maximum peel strength was approximately 9 (can).

For comparison, Example 1 was repeated except that the heat-melting process and the cooling process of the caulked part were omitted.

The watertightness test result of the spiral steel pipe thus obtained showed that water leaked from the caulked portion under a water pressure of 5V.

[Brief explanation of the drawing]

Figure 1'' is a schematic explanatory diagram showing the manufacturing process of the spiral metal tube, Figures 2 and 3 are cross-sectional views of the caulked part, and Figure 4 is an explanatory diagram showing the direction during the peel test.1 ...Thermoplastic resin coated metal plate, ?...Metal (-)
Plate, 5... Thermoplastic resin layer, 4... Calothermal device, 5
...Representative of cooling system Patent attorney Tadashi Sato

Claims (1)

[Claims] When manufacturing a spiral metal tube, when forming a spiral metal tube using a metal plate whose surface is coated with a thermoplastic resin, the metal tube is formed by caulking the parts that meet each other on the circumference, and the caulking part is A method for producing a thermoplastic 11J[l coated spiral metal tube, which comprises melting the coating layer intensively to integrate the thermoplastic resin, and then cooling it.