JPS604053B2 - Coating method for articles with different diameters - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of coating a strange product with a heat-shrinkable material.

Heat-shrinkable materials have conventionally been used to cover various articles such as fluid transport pipes for gas, oil, etc., cables, and the like.

Although this heat-shrinkable material is easy and convenient to coat, it sometimes causes the following inconveniences when covering articles with different diameters.

For example, in order to cover steel pipes of different diameters that have a large diameter part and a small light part adjacent to it with a heat shrinkable tube, the inner diameter before heat shrinking is larger than the large light part of the steel pipe, and the inner diameter of the steel pipe when heat shrinking is It must be able to shrink to the same size as the small diameter part, but as shown in Figure 1, this heat shrinkable tube 1 is placed on a steel pipe 2 of a different diameter, and then heated with a burner etc. to heat shrink it. In this case, the left half of the tube 1 that covers the large diameter part of the steel pipe 2 undergoes less thermal contraction than the right half, and the residual shrinkage stress in the left half becomes excessive, causing cracks at the left end of the tube. Openings 3 may occur and a good coating layer may not be formed.

Additionally, if a protrusion comes into contact with the left half of the tube during heat shrinking, cracks will easily occur due to excessive residual shrinkage stress or stress concentration, and these cracks will rapidly grow and propagate inside the tube, causing damage to the steel tube. In some cases, the anti-corrosion function may be lost. The present invention relates to a method for coating a dissimilar article that has good adhesion to each part of the dissimilar article and can effectively prevent the occurrence of cracks in the large diameter part, and the present invention relates to a method for coating a dissimilar article that has a large diameter part and a small light part adjacent to the large diameter part. A first heat-shrinkable material is disposed on the outer circumferential surface of the large-diameter part and the small-diameter part of the article, and the first heat-shrinkable material is placed on the corresponding outer circumferential surface of the large-diameter part of the different-diameter article of the first heat-shrinkable material. This method is characterized in that a second heat-shrinkable material that is separate and has a smaller heat shrinkage rate than the second heat-shrinkable material is disposed, and then both heat-shrinkable materials are heated to cause them to heat-shrink at the same time.

Both the first heat-shrinkable material and the second heat-shrinkable material used in the present invention are materials that can be heat-shrinkable, in other words, materials that can be thermally expanded (stretched), such as polyvinyl chloride, polyethylene, etc. , thermoplastic plastics such as polypropylene and fluorocarbon resins, synthetic rubbers such as silicone rubber and ethylene-propylene copolymer rubber, natural rubbers, or mixtures thereof, with additives such as anti-aging agents and colorants added as desired. It can be obtained by a method such as molding this into a sheet or tube shape, crosslinking the plastic or rubber as desired, then thermally expanding this molded product, and rapidly cooling it while maintaining this expanded state. The first heat-shrinkable material and the second heat-shrinkable material in the present invention may have the same or different components, but the heat shrinkage rate of the second heat-shrinkable material is set to be smaller. be done.

This means that when heating and heat-shrinking both heat-shrinkable materials on the outer circumferential surface of a different diameter article, the corresponding outer circumferential surface of the large-diameter portion of the different-diameter article of the first heat-shrinkable material, which tends to cause tearing, is transferred to the second heat-shrinkable material. The second heat-shrinkable material is reinforced with a heat-shrinkable material to prevent the first heat-shrinkable material from tearing, and the residual shrinkage stress of the second heat-shrinkable material is made as small as possible after the heat-shrinkage. This is important to prevent cracks from occurring in the material. In the present invention, the heat shrinkage rate of the second heat-shrinkable material is set to be smaller than that of the first heat-shrinkable material for the above-mentioned reasons, but the close contact of the first heat-shrinkable material to articles of different diameters Considering the strength, adhesion strength between heat-shrinkable materials, etc., the heat-shrinkage rate (A%) of the first heat-shrinkable material is 50 to 75%, and the heat-shrinkage rate (B%) of the second heat-shrinkable material. is preferably a value that satisfies the following formula.

A-B = 20 to 60 (%) The coating method according to the present invention uses the above-mentioned two types of heat-shrinkable materials having different heat shrinkage rates. A first heat-shrinkable material with a large heat shrinkage rate is arranged on the outer peripheral surface of the light part, and a second heat-shrinkable material with a smaller heat shrinkage coefficient is arranged on the corresponding outer peripheral surface of the large diameter part of the first heat-shrinkable material. Place the shrinkable material.

These two types of heat-shrinkable materials are used separately. Moreover, an adhesive layer can also be provided on the surface of the heat-shrinkable material.

Both heat-shrinkable materials thus placed on the outer circumferential surface of the alien product are then heated with a burner or the like and are simultaneously heat-shrinked.

The present invention is configured as described above, and since the second heat-shrinkable material is disposed on the corresponding outer peripheral surface of the large and light portion of the different article of the first heat-shrinkable material, the first heat-shrinkable material can be reinforced with the second heat-shrinkable material, and furthermore, it is designed to prevent direct action of heat on a predetermined portion of the first heat-shrinkable material disposed on the larger portion of the dissimilar article, which is likely to cause cracks during heat-shrinking work. So,
During this operation, the first heat-shrinkable material does not separate, and since the two heat-shrinkable materials are separate, a wrinkle-free coating layer can be formed on the outer peripheral surface of the article with different diameters.

Further, after the heat shrinking work, the first heat shrinkable material covering the small part of the different pot article and the second heat shrinkable material covering the large part of the article have a residual shrinkage stress of 4. So,
Even if these are touched by protrusions, cracks will not occur.

Hereinafter, the present invention will be explained in more detail by way of examples with reference to the drawings.

Although the first heat-shrinkable material and the second heat-shrinkable material in each example were both made of crosslinked polyethylene, the present invention is not limited thereto. Example 1 As shown in Fig. 2, the outer circumferential surface of a steel pipe 2 having an outer diameter of 10 mm, a large diameter portion on the 30 side, and a small diameter portion adjacent thereto, has an inner diameter of 105 willow, a wall thickness of 1 mm, and heat is applied in the radial direction. Shrinkage rate is 60%
A tube-shaped first heat-shrinkable material 4 is placed.

Next, on the corresponding outer peripheral surface of the large diameter portion of the steel pipe 2 of the first heat-shrinkable material 4, a second tube-shaped material having an inner diameter of 11, a wall thickness of 1, and a heat shrinkage rate of 25% in the radial direction is made. A heat-shrinkable material 5 is placed.

Thereafter, both heat-shrinkable materials 4 and 5 are heated with a burner to heat-shrink them, and are brought into close contact with the steel pipe 2, as shown in FIG.

In order to find out the presence or absence of fissures in the portion of the first heat-shrinkable material 4 corresponding to the large part of the steel pipe 2, the second heat-shrinkable material 5 was removed. No cracking occurred, and the steel pipe 2 was firmly adhered to the steel pipe 2.

For comparison, when only the first heat-shrinkable material was placed on the outer circumferential surface of a steel pipe and heat-shrinked, a tear occurred in a portion corresponding to the large diameter portion of the steel pipe.

Example 2 Using a steel pipe 2 with the same dimensions as used in Example 1,
As shown in FIG. 4, the outer peripheral surface of the steel pipe 2 has an inner diameter of 105
A tubular first heat-shrinkable material 4 having a wall thickness of one wall and a heat shrinkage rate of 60% in the light direction is arranged.

Next, on the corresponding outer peripheral surface of the large part of the steel pipe 2 of the first heat-shrinkable material 4, a second tube-shaped material having an inner diameter of 11 mm, a wall thickness of 1 rib, and a heat shrinkage rate of 25% in the radial direction is made. A heat-shrinkable material 5 is placed. Note that at this time, the second heat-shrinkable material 5 is
It is arranged so as to protrude slightly from the end of the heat-shrinkable material 4. Thereafter, both heat-shrinkable materials 4 and 5 are heated with a burner to heat-shrink them, and the steel pipe 2 is heated as shown in FIG.
Closely contact.

In order to find out whether or not there was a split in the part of the first heat-shrinkable material 4 corresponding to the large collar of the steel pipe 2, the second heat-shrinkable material 5 was removed. No cracking occurred, and the steel pipe 2 was firmly adhered to the steel pipe 2.

In this example, the second heat-shrinkable material 5 was arranged so that its end slightly protruded from the end of the first heat-shrinkable material 4; It is suitable when the heat shrinkage rate of No. 4 is particularly large (60% or more).

For comparison, when only the first heat-shrinkable material was placed on the outer circumferential surface of a steel pipe and heat-shrinked, a tear occurred in a portion corresponding to the large diameter portion of the steel pipe.

As is clear from the above Examples and Comparative Examples, according to the present invention, it is possible to form a good coating layer on articles of different diameters without causing any tearing of the heat-shrinkable material during heat-shrinking work.

[Brief explanation of the drawing]

Fig. 1 is a front view showing the state after coating steel pipes of different diameters by the sub-column method, and Figs. 3 and 5 are cross-sectional views showing the first heat-shrinkable material and the second heat-shrinkable material arranged as shown in FIGS. 2 and 4. FIG. 3 is a cross-sectional view showing the state after heat shrinkage. 2... Steel pipe "4... First heat-shrinkable material,
5...Second heat-shrinkable material. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A first heat-shrinkable material is disposed on the outer circumferential surfaces of the large-diameter part and the small-diameter part of a different-diameter article having a large-diameter part and a small-diameter part adjacent thereto, and A second heat-shrinkable material that is separate from the first heat-shrinkable material and has a smaller heat shrinkage rate than the first heat-shrinkable material is placed on the corresponding outer peripheral surface, and then both heat-shrinkable materials are heated to simultaneously heat-shrink. A method for coating articles with different diameters, the method comprising: