JPH08216314A - Heat-shrinkable double-layer tube and sheet for covering metal, and method for covering metal with them - Google Patents

Abstract

PURPOSE: To simply and surely obtain a strong adhesion on a surface of a metallic article without using an adhesive by a method wherein an outer surface is made of a heat-shrinkable resin, and an inner surface is made of a thermoplastic resin having an adhesive power and a melting point lower than that of the outer heat-shrinkable resin. CONSTITUTION: A heat-shrinkable double-layer tube 1a or a heat-shrinkable double-layer sheet is composed of a resin layer 2 of a resin having a heat shrinkability as an outer surface and a resin layer 3 of a resin having a melting point lower than that of the outer heat-shrinkable resin as an inner surface. A metallic article is covered with the heat-shrinkable double-layer tube 1a or sheet and heated to the thermally shrinking temperature of the resin as the outer surface. The outer resin layer 2 shrinks to bring the heat-shrinkable double-layer tube 1a or sheet into close contact with the metallic article as well as into pressure contact with the metallic surface thereof. Almost simultaneously with this action, the resin as the inner surface reaches its melting point. The inner resin layer 3 melts to adhere to the metallic surface. When this is cooled in this state, the inner resin layer 3 is bonded to the metallic surface and set integrally with the outer resin layer 2 to securely cover the metallic article.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable multi-layer tube and sheet used for forming a strong resin film on the outer surface of metal products such as metal pipes and metal rods, and multi-layer tubes thereof. The present invention relates to a metal coating method using a multilayer sheet.

[0002]

As a method for forming a resin film on the surface of a metal product such as a pipe, a method using a paint is generally used, but a method using a heat shrinkable tube is known as a simple method. The heat-shrinkable tube is obtained by subjecting a tube made of vinyl chloride, polyethylene or the like to a diametrical stretching process, covering it with a product and then heating it to shrink the product in the diametrical direction and adhere to the product. However, since most of these tubes are a single layer, they are only in contact with the surface of the metal product and are not bonded. It is necessary to further raise the temperature for heat bonding. However, when the temperature is raised, the entire resin may be melted and bubbles may be generated, which is similar to the powder coating method. Further, if the entire resin is melted, the orientation originally possessed by the resin film is lost, which is also unfavorable in terms of film strength.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, in the prior art, since the metal surface and the coating resin are not firmly adhered to each other, even if a part of the coating is damaged, water is soaked in the entire surface or easily peeled off. It cannot be expected to be durable. Further, in order to improve durability, it is necessary to apply an adhesive between the metal surface and the resin, but it is difficult to apply it in the working process. Due to such circumstances, there is a demand for a metal coating method that is a method that uses a heat-shrinkable sheet easily and that can obtain strong adhesion.

[0004]

In order to solve the above-mentioned problems, the present invention has a heat-shrinkable resin having a relatively high melting point as the resin on the outer surface, and a resin of the same kind as the resin on the outer surface as the resin on the inner surface, Alternatively, it is a thermoplastic resin that firmly adheres to the resin on the outer surface, and its melting point is 2 degrees Celsius higher than the melting point of the resin on the outer surface.
A multi-layer tube or sheet is manufactured by using 0 to 60 degrees lower.

The tube can be manufactured at the lowest cost by using a two-layer coextrusion tubular molding machine.
In the production of the sheet, the tube produced by the tubular forming machine may be opened, or the multi-layer sheet produced by the two-layer T-die method may be produced by a stretching method using a stenter stretching machine. it can.

The first method for coating the surface of a metal product by using the heat-shrinkable multilayer tube of the product of the present invention is to first add a pipe-shaped or rod-shaped metal product to the tubular product of the present invention. After passing through and putting it in the heating device as it is, and heating to the shrinking temperature of the resin on the outer surface at the melting point of the resin on the inner surface or more, the tube contracts and adheres to the metal surface, and the resin on the inner surface which has melted rises in temperature. Because it is pressed against a metal surface,
Complete thermal bonding of metal and resin is achieved. The heating temperature only needs to exceed the melting point of the resin on the inner surface, and must not exceed the melting point of the resin on the outer surface. After that, if the product is allowed to cool or is forcedly cooled, a resin-coated product having a complete wall can be obtained.

The second method is a method used when coating a long product and it is difficult to pass it through the tubular product of the present invention. The sheet-shaped product of the present invention is wound so that the shrinking direction is perpendicular to the lengthwise direction, the seams are heat-sealed, and then placed in a heating device in the same manner as in the first method.
When heat-sealing the seam, if the inner surface and inner surface of the multilayer sheet are pressed and heated together, the thermoplastic resin on the inner surface is first melted and eliminated, and then the resin on the outer surface is welded to each other. Even if the resin on the inner surface is melted inside the heating device, the seam does not separate.

In any of the above cases, if the metal product is preheated to about 50 to 60 ° C. before being covered with the product of the present invention, the time required for the heat shrinking step can be shortened. Regarding the temperature difference between the resin melting point on the outer surface and the resin melting point on the inner surface, considering the difficulty of temperature control in the heating step,
It is desirable that the difference is as large as possible. On the other hand, when the tube is produced by the tubular method, the production becomes difficult if the difference is too large. Therefore, the temperature difference is preferably 20 ° C to 60 ° C.

[0009]

The multi-layer tube and sheet according to the present invention have a heat-shrinkable resin on the outer surface and a thermoplastic resin having a relatively low melting point on the inner surface. When heated to the heat shrinking temperature of the resin, the resin on the outer surface shrinks so that the multilayer tube or sheet adheres to the metal product and presses the metal surface. Around this time, when the resin used on the inner surface reaches the melting point, the resin on the inner surface is melted and pressure-bonded to the metal surface. When the next cooling step is started in this state, the resin on the inner surface is adhered to the metal surface and solidified, and the resin on the outer surface is also integrated to obtain a strong coating. In this way, the shrinkage of the resin on the outer surface,
The melting of the resin on the inner surface and the melting of the resin on the inner surface are simultaneously performed within a certain temperature range. In the process of raising the material temperature, the contraction action of the resin on the outer surface and the melting action of the resin on the inner surface may be mixed with each other.

[0010]

EXAMPLE In the first example, as the resin 2 on the outer surface, a polypropylene resin Show Allomer FG manufactured by Showa Denko KK was used.
110A, melting point 140 ° C., resin 3 on the inner surface is Adtex ET182 manufactured by Showa Denko KK, melting point 98 ° C.
Using a two-layer coextrusion tubular molding machine, a heat-shrinkable multi-layer tube 1a having an outer surface resin thickness of 100 μ and an inner surface resin thickness of 30 μ and a finished outer diameter of 85 mm was produced.

Next, as the metal product 4, a side of 60 mm,
On the outside of an aluminum square pipe with a wall thickness of 3 mm and a length of 2 m,
When the heat-shrinkable multi-layer tube 1a manufactured as described above was placed in a heating furnace and the temperature was raised to 110 ° C., the tube contracted and adhered to the aluminum square pipe.
At this time, the internal Adtex ET182 has a melting point of 98.
Since the temperature was above 0 ° C, the temperature was sufficient to adhere to the aluminum surface. After that, the product was taken out and allowed to cool, whereby an aluminum square pipe whose surface was strongly covered with a resin layer of polypropylene resin was obtained. Since the resin layer and the aluminum surface are strongly bonded, it was difficult to peel them off with a knife.

In Example 2, a vinyl chloride resin TK-800 manufactured by Shin-Etsu Chemical Co., Ltd. was used as the resin 2 on the outer surface.
H, melting point of 130 ° C., Adex ET182 manufactured by Showa Denko KK, melting point of 98 ° C. is used as the resin 3 on the inner surface, and these are two-layer co-extruded using a tubular molding machine to obtain a resin thickness of 150 μ on the outer surface, Resin thickness 50μ
Thus, a heat-shrinkable multi-layer tube having a finished outer diameter of 120 mm was manufactured.

Next, a steel pipe having a diameter of 100 mm and a wall thickness of 5 mm is preheated to about 50 ° C.
When the heat-shrinkable tube 1a manufactured as described above was put on a heating furnace and the temperature was raised to 105 ° C., the tube contracted and adhered to the steel pipe. At this time, since the melting point of the resin ET182 on the inner surface was higher than 98 ° C, the temperature was at a temperature at which it was sufficiently adhered to the steel surface. After that, the product was taken out and allowed to cool to obtain a steel pipe whose surface was strongly covered with a resin layer of vinyl chloride resin. Since the resin layer and the steel surface are strongly bonded, it was difficult to peel them off with a knife.

In Example 3, as the resin 2 on the outer surface, polyethylene resin Shorex F5 manufactured by Showa Denko KK was used.
010, melting point 135 ° C., resin 3 on the inner surface is Adtex ET184M manufactured by Showa Denko KK, melting point 83 ° C.
Using a two-layer coextrusion tubular machine, the outer surface of the resin has a thickness of 200 μ and the inner surface of the resin has a thickness of 50 μm.
μ, folding diameter 800 mm, double-sided manufacturing, width 800 mm
A heat-shrinkable multilayer sheet 1b was obtained.

Next, diameter 60 mm, wall thickness 1 mm, length 3
The heat-shrinkable sheet 1b manufactured as described above is vertically covered on the outer side of an aluminum pipe of m, and the side surface is heat-sealed to form a tubular shape.
When the temperature was raised to ℃, the sheet contracted and adhered to the aluminum pipe. At this time, the inner Adtex ET18
Since 4M had a melting point of more than 83 ° C, it was a temperature at which it was sufficiently adhered to the aluminum surface. Then take out the product,
As a result of allowing to cool, an aluminum pipe whose surface was firmly covered with a resin layer of polyethylene resin was obtained. Since the resin layer and the aluminum surface are strongly bonded, it was difficult to peel them off with a knife.

[0016]

When the multi-layer tube or multi-layer sheet of the present invention is used, the step of coating the surface of the metal product with the resin is carried out by covering the metal product with the multi-layer tube or multi-layer sheet and heating to a certain temperature. Since it is completed only by the step of cooling, the processing device is simple and can be manufactured with inexpensive equipment.

Since the multi-layer tube and the multi-layer sheet according to the present invention have an adhesive thermoplastic resin on the inner surface,
Even if the adhesive is not used again on the surface of the metal product, it is possible to easily and securely obtain strong adhesion. This strong adhesion has the effect of dramatically improving the water resistance and corrosion resistance as well as the physical strength of the resin coating.

[Brief description of drawings]

FIG. 1 is a partial perspective view of a heat-shrinkable multilayer tube of the present invention.

FIG. 2 is a partial perspective view of the heat-shrinkable multilayer sheet of the present invention.

FIG. 3 is a partial perspective view of a metal pipe coated with a heat-shrinkable multilayer tube.

[Explanation of symbols]

 1a Heat-shrinkable multi-layer tube 1b Heat-shrinkable multi-layer sheet 2 Resin layer on outer surface 3 Resin layer on inner surface 4 Metal product

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Claims (4)

[Claims] 1. A heat-shrinkable multilayer tube for metal coating, the outer surface of which is a heat-shrinkable resin, and the inner surface of which is made of a thermoplastic resin having a lower melting point than that of the heat-shrinkable resin of the outer surface. . 2. A heat-shrinkable multi-layer sheet for metal coating, the outer surface of which is a heat-shrinkable resin, and the inner surface of which is made of a thermoplastic resin having a lower melting point than the heat-shrinkable resin of the outer surface. . 3. The multi-layer tube according to claim 1 is covered with a metal product and heated to a temperature not lower than the shrinking temperature of the heat-shrinkable resin tube on the outer surface to a temperature not higher than the melting point to shrink the resin on the outer surface, and at the same time to remove the resin on the inner surface. A metal coating method for thermally bonding a metal product. 4. The multi-layer sheet according to claim 2, covering the outer surface of the metal product, heat-sealing the seam of the sheet, and then heating the outer surface to a temperature not lower than the shrinking temperature and not higher than the melting point of the heat-shrinkable resin. The metal coating method of shrinking the resin and heat-bonding the resin on the inner surface to the metal product.