JPH0557839A - Cover metal member - Google Patents

Abstract

PURPOSE:To reduce the consumption of covering polyolefin and contrive to improve efficiency by a method wherein polyolefin layer consists of first polyolefin layer prepared by mixing and kneading pigments, the mixing ratio of which is constant irrespective of color to bring out, and specified second polyolefin layer prepared by mixing 3nd kneading pigments, the mixing ratio of which is controlled in accordance with the color to bring out. CONSTITUTION:As the colored polyolefin layer coveringly formed on the surface of metal pipe 1, first polyolefin layer 15 prepared by mixing and kneading pigments, the mixing ratio of which is constant irrespective of color to bring out, and second polyolefin layer 14, in which the pigment concentrations are controlled within the range of 0.5-3.0wt.% and, at the same time, the covering coating thickness of which is set to be 5-30% of the total thickness, are equipped. When coloring is changed, only the changing operation of the second polyolefin layer 14 is performed, resulting in reducing the amount of resin to be discharged and suppressing the lowering of efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal member coated with a polyolefin, particularly a metal tube, which is excellent in adhesion to the surface of a metal member and whose outer surface can be easily changed in color.

[0002]

2. Description of the Related Art Polyolefin has not only excellent corrosion resistance to acids, alkalis and certain organic solvents, but also electrical insulation and easy processability. For this reason, it is widely used for pipe linings, electric wire coatings, and coatings for electric machinery. Polyolefin-coated metal pipes are widely used for laying and burying ground surfaces such as gas pipes, crude oil or oil transfer pipes, cable protection pipes, and water pipes.

A polyolefin-coated metal tube of this type is manufactured by using a coating apparatus as shown in FIG. 4, for example, as disclosed in Japanese Patent Laid-Open No. 58-74336. This device
An extruder 5 for accommodating a primer coating device 2, a heating device 3, and an adhesive modified polyolefin used for strengthening the adhesion between the metal tube and the coating polyolefin in the line
The crosshead die 4 having the extruder 6 for containing the coating polyolefin, the cooling device 9, and the cutting device 10 are arranged in this order. As shown in FIG. 5, the polyolefin-coated metal pipe obtained by this apparatus has a primer layer 17 and an adhesion-modified polyolefin layer 1 on the surface of the steel pipe 1.
6. The colored color coating polyolefin layer 14 is formed in order. The adhesion-modified polyolefin layer 16 is usually 0.03 to 0.
3 mm, the coating polyolefin layer 14 to be colored is usually 1
It is formed to about 4 mm.

The coating polyolefin layer 14 is not mixed with the pigment, as specified by the customer and in order to impart weather resistance, to a color pellet obtained by mixing and kneading an organic or inorganic pigment and polyolefin and granulating. Natural pellets are mixed in a desired ratio, and the mixture is melted and kneaded in an extruder for coloring. When changing the coloring color of the coating polyolefin layer 14, it goes without saying that the color pellets mixed and kneaded with the above-mentioned pigments are changed, but the colored resin clogged in the extruder 6 and the die 4 is once completely discharged. Must. The resin discharged here may be crushed and pelletized again and reused, but in general, it is discarded from the viewpoint of cost, resulting in a waste of the coating polyolefin. In addition, the production is temporarily stopped during the discharging work, which causes a problem of reduced efficiency.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to suppress a decrease in efficiency when changing a coloring color, reduce waste of a coating polyolefin, and improve efficiency. To aim.

[0006]

In order to achieve the above object, the coated metal member of the present invention is a coated metal member in which a colored polyolefin layer is formed by coating on a metal member, and the polyolefin layer has a colored color. First, the first polyolefin layer in which pigments are mixed and kneaded in a fixed ratio and the second polyolefin layer in which pigments whose mixing ratio is adjusted according to the coloring color are mixed and kneaded are provided. The pigment concentration is adjusted in the range of 0.5 to 3.0% by weight, and the coating film thickness is 5 to 30% of the total polyolefin layer.

The metal member may have any shape such as a tube shape or a plate shape, and is particularly useful for a metal tube. The material of the metal member is not particularly limited, but is, for example, steel, copper, brass, aluminum or the like.

The polyolefin as the main component of the first coating polyolefin layer and the second polyolefin layer is, for example, polyethylene (low to high density), polypropylene,
It can be selected from homopolymers such as poly-1-butene, poly-1-hexene, poly-4-methyl-pentene, poly-1-octene and poly-1-decene and copolymers thereof.

As the pigment for the first coating polyolefin layer, an inexpensive and weather-resistant pigment such as carbon black, which is an inorganic synthetic pigment, is preferable. The first coating polyolefin layer determines the color with the second coating polyolefin layer, so there is no need for coloring. However, the second coating polyolefin layer is a thin film, and in order to ensure the weather resistance as a whole, it is preferable to add a pigment such as carbon black.

As the pigment added to the second coating polyolefin layer, various organic and inorganic pigments are used depending on the coloring color. Since the second coating polyolefin layer is formed into a thin film, a predetermined color cannot be obtained unless the pigment concentration is increased. However, due to the deterioration of the physical properties of the polyolefin itself, taking both factors into consideration, the pigment concentration should be 0.5
~ 3.0% by weight.

The layer thickness also plays a role in determining the color. The thicker the film, the easier it is to obtain a predetermined color, but the efficiency of color change and the waste of the second coating polyolefin layer cannot be alleviated. Therefore, the film thickness of the second coating polyolefin layer Is 5 to 30% of the total thickness of the coating polyolefin layer.

In the coated metal member of the present invention, a primer layer or a chromate layer or both layers can be interposed between the metal member and the first coating polyolefin layer. It is also preferable to interpose an adhesive modified polyolefin layer between these layers and the coating polyolefin layer to strengthen the adhesiveness.

[0013]

In the coated metal member of the present invention, the coating polyolefin layer always mixes and kneads the first polyolefin layer in which pigments such as carbon black are mixed and kneaded regardless of the change in coloring color, and the pigment for coloring color. The second polyolefin layer is provided, and when the coloring color is changed, the change operation of only the second polyolefin layer is performed, so that the amount of resin discharged is reduced and the decrease in efficiency is suppressed.

[0014]

The present invention will be described in detail below with reference to the illustrated embodiments.

The apparatus used in manufacturing the following examples is a coating apparatus as shown in FIG. 1, for example.
This device includes a primer coating device 2, a heating device 3, a crosshead die 4, a cooling device 9 and a cutting device 10 in a line.
Have a configuration in which they are arranged in order. The crosshead die 4 includes an extruder 5 for accommodating an adhesive modified polyolefin that forms an adhesive modified polyolefin layer 16 used to strengthen the adhesion between the metal tube and the covering polyolefin, and a covering polyolefin. Of these, an extruder 6 for accommodating a polyolefin forming a first coating polyolefin layer 15 in which a pigment such as carbon black is mixed and kneaded.
And an extruder 7 for accommodating the polyolefin for forming the second coating polyolefin layer 14 in which pigments for coloring color are mixed and kneaded.

As shown in FIG. 2, this coating apparatus coextrudes the adhesive modified polyolefin, the first coating polyolefin, and the second coating polyolefin from each manifold 11, 12, 13 of the crosshead die 4. Then, as shown in FIG. 3, on the surface of the metal tube 1, the primer layer 17,
The adhesion-modified polyolefin layer 16, the coating polyolefin layer 15, and the colored color coating polyolefin layer 14 are simultaneously formed by coating. Example 1 Hereinafter, a coated metal member according to the present invention was manufactured using the apparatus shown in FIG.

A primer layer made of a thermosetting epoxy resin is formed on a steel metal tube from which the surface oxide coating is removed by shot blasting, and an adhesive modified polyethylene is formed on the primer layer by coextrusion of a crosshead die 4. And high density polyethylene in which carbon black was mixed and kneaded at a concentration of 2% by weight as the first coating polyolefin, and 0.9% by weight of a green pigment mainly containing cadmium yellow and titanium oxide as the second coating polyolefin. Three layers of high density polyethylene mixed and kneaded at the concentrations were coated. After that, the metal tube covered with the cutting device 10 was cut into a desired length. The obtained polyolefin multi-coated metal tube 8 comprises a metal tube 1 having a diameter of 27.2 mm, 0.3 mm adhesive modified polyethylene, 0.9 mm high density polyethylene for the first coating layer, and high density polyethylene for the second coating layer. Polyethylene 0.
It has a structure in which a film thickness of 6 mm is sequentially laminated. With respect to the obtained polyolefin-coated metal tube, the coloring color on the outer surface was compared with the product color in the conventional manufacturing method. The results are shown in Table 1. The colored colors in the table were evaluated as follows. The black color on the inside penetrates the color and affects the color ... × It is as good as the color in the conventional manufacturing method.

A polyethylene fin-coated metal tube manufactured in the same manner as in Example 1 and having a film thickness of the first coating high-density polyethylene 1.1 mm and the second coating high-density polyethylene 0.4 mm was prepared as in Example 1. The same survey was conducted. The results are shown in Table 1. Comparative Example 1

A polyethylene fin-coated metal tube manufactured in the same manner as in Example 1 and having a film thickness of the first coating high-density polyethylene 1.3 mm and the second coating high-density polyethylene 0.2 mm was prepared as in Example 1. The same survey was conducted. The results are also shown in Table 1. Comparative example 2

In Example 1, the same investigation as in Example 1 was conducted on a polyolefin-coated metal tube in which the pigment concentration of the second high-density polyethylene for coating was 0.4% by weight.
The results are also shown in Table 1. Conventional example

A second polyolefin for the tint color coating was formed without forming the first coating polyolefin. The second coating polyolefin is a high density polyethylene prepared by mixing and kneading cadmium yellow and a green pigment mainly composed of titanium oxide at a concentration of 0.3% by weight, and having a film thickness of 1.
Coated with 5 mm. This one had no color problems.

As is clear from Table 1, the polyolefin-coated metal pipes of Examples 1 and 2 had a good coloring, but as in Comparative Example 1, the second pipe was out of the scope of the present invention. When the film thickness of the high-density polyethylene for coating is thinned, or when the pigment concentration of the second polyethylene for coating is lowered beyond the range of the present invention as in Comparative Example 2, the black color inside penetrates and affects the color. Exert. The conventional example does not have a color problem, but as described above, when changing the coloring color,
This will reduce the efficiency of the changing work and waste the coating polyolefin.

[0023]

As described above, according to the present invention, the coloring color of the coating polyolefin is exhibited only in the outermost layer, and the coloring color of the second coating polyolefin layer is obtained by mixing and kneading the pigment for this coloring color. I made a change, so
It is possible to suppress a decrease in efficiency due to the changing work and reduce waste of the coating polyolefin.

[0024]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a polyolefin coating apparatus used in the present invention.

FIG. 2 is a cross-sectional view showing a state in which a metal pipe is coated with a crosshead die of the same device.

FIG. 3 is a sectional view showing an example of a polyolefin-coated metal tube according to an embodiment of the present invention.

FIG. 4 is a schematic view showing an example of a conventional polyolefin coating device.

FIG. 5 is a sectional view showing an example of a conventional polyolefin-coated metal tube.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal tube, 2 ... Primer coating device 3 ... Heating device, 4 ... Crosshead die 5,6,7 ... Extruder, 8 ... Coated polyolefin 9, Cooling device, 10 ... Cutting device 11, 12, 13 ... Manifold, 14 ... Second polyolefin layer for coating colored color 15 ... First polyolefin layer for coating 16 ... Adhesive modified polyolefin layer 17 ... Primer layer

Claims (1)

[Claims] 1. A coated metal member in which a colored polyolefin layer is formed on a metal member by coating, and the polyolefin layer has a colored color which is the same as that of the first polyolefin layer in which pigments are mixed and kneaded in a fixed ratio regardless of the colored color. The second polyolefin layer is prepared by mixing and kneading the pigment whose mixing ratio is adjusted according to the second polyolefin layer, the pigment concentration of the second polyolefin layer is adjusted in the range of 0.5 to 3.0% by weight, and the coating thickness is A covered metal member comprising 5 to 30% of the total polyolefin layer.