JP3373911B2 - Heat shrinkable sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable sheet for external corrosion protection of steel pipes, corrosion protection of joints of lining pipes, scratches of linings, etc. (EN) Provided is an extremely excellent heat-shrinkable sheet capable of preventing the floating of parts.

[0002]

2. Description of the Related Art Conventionally, as a shrinking material for preventing corrosion of a connecting portion such as a pipe, for example, as shown in FIG. 1, a heat shrinkable film 1 which stretches only in the flow direction and shrinks only in that direction.
1. A heat-shrinkable sheet C in which an adhesive layer 31 is laminated on one surface of 1.
However, it is mainly used.

[0003]

However, a heat-shrinkable sheet stretched only in the flow direction shrinks in the flow direction, but expands in the width direction due to heat during shrinking work, and the sheet is covered with a pipe or the like. The force that floats from the wearing surface works. As a result, the terminal portion C1 of the sheet C floats as shown in FIG. 1, and after the pipe is buried, there is a risk that dirt and sand may enter the inside from the terminal portion and the anticorrosion function may be lost.

[0004]

Therefore, the present inventors have found that such a problem can be solved by adopting a specific laminated heat-shrinkable sheet, and arrived at the present invention.

That is, according to the present invention, at least one layer of a one-way heat-shrinkable film capable of heat-shrinking only in the flow direction is laminated on one surface of a two-way heat-shrinkable film capable of heat-shrinking in the flow direction and the width direction. And a heat-shrinkable sheet having an adhesive layer on the two-way heat-shrinkable film side of the heat-shrinkable sheet.

The bidirectional heat-shrinkable film which can be heat-shrinked in the machine direction and the transverse direction used in the present invention is obtained by stretching in the machine direction and the transverse direction, and the stretching ratio is usually 10 to 10 in the machine direction. 70%, 5 to 70 in width direction
%, Preferably 15-40% in the flow direction and 10 in the width direction.
It is desirable to set it to ˜30%. If the stretching ratio is less than 5%, it is difficult to obtain the effect, and if the stretching ratio exceeds 70%, the film may be excessively displaced inward and the protected area may be reduced.

In the present invention, the one-way heat-shrinkable film laminated on the two-way heat-shrinkable film and capable of heat-shrinking only in the flow direction is obtained by stretching only in the flow direction, and the stretching ratio is the same as above. Can be

At least one layer of such a one-way heat-shrinkable film can be provided. The thickness of these heat-shrinkable films is not particularly limited, but is usually 300 to 2000.
μm, preferably about 500 to 1500 μm.

The material of each heat-shrinkable film is not particularly limited, and examples thereof include polyethylene, polypropylene and EV.
A and the like can be mentioned, and in particular, crosslinked polyethylene, crosslinked polypropylene and the like are preferably used from the viewpoints of durability, heat resistance and impact strength.

The method for obtaining the heat-shrinkable sheet of the present invention is not particularly limited. For example, at least one unstretched film is laminated on a film stretched in the width direction, and then the laminated film is stretched in the machine direction. It is obtained by stretching.

In the present invention, it is preferable to provide an adhesive layer on the two-way heat-shrinkable film side of the heat-shrinkable sheet. Such an adhesive layer enables adhesion to the surface of an adherend such as a pipe. The adhesive layer is not particularly limited, but for example, a hot melt melt type, a mastic type, a butyl rubber type pressure sensitive adhesive can be preferably used. The thickness is not particularly limited, but usually 200
˜2000 μm, preferably about 400 to 1500 μm.

Next, an example of the present invention will be described with reference to the drawings. As shown in FIG. 2, the heat-shrinkable sheet A of the present invention is a bidirectional heat-shrinkable film 1 capable of heat-shrinking in the flow direction and the width direction.
The one-way heat-shrinkable film 2 capable of heat-shrinking only in the flow direction is laminated on one surface, and the adhesive layer 3 is provided on the other surface. When the heat-shrinkable sheet A is heated, a force that curls inward acts, and as shown in FIG. 3, floating does not occur from the surface of the polyethylene lining steel pipe 4 in the terminal portion A1.

[0013]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 A cross-linked polyethylene film having a thickness of 0.4 mm was stretched in the width direction at stretching ratios of 5%, 30%, and 50%, respectively.
Next, this width-direction stretched film and an unstretched cross-linked polyethylene film having a thickness of 0.4 mm were laminated by pressing with a press of four sheets. The laminated film was stretched by 30% in the machine direction to obtain a heat-shrinkable sheet having a thickness of 1.2 mm. A butyl rubber-based pressure-sensitive adhesive layer was provided on the film side of the heat-shrinkable sheet stretched only in the direction of flow so as to have a thickness of 1000 μm to obtain a heat-shrinkable sheet of the present invention.

The three types of heat-shrinkable sheets obtained were mixed with 700
As a result of being wound around the steel pipe A and being heat-shrinked by the gas burner, no floating occurred at the end portion of any of the sheets.

Comparative Example A heat-shrinkable sheet obtained in the same manner as in Example 1 except that the sheet was not stretched in the width direction was subjected to the same test. As a result, floating occurred at the end portion of the sheet. did.

[0016]

INDUSTRIAL APPLICABILITY The heat-shrinkable sheet of the present invention is a one-way heat-shrinkable film in which at least one layer is heat-shrinkable on one surface of a bidirectional heat-shrinkable film which can be heat-shrinked in the flow direction and the width direction. By laminating the flexible film, there is an effect that the force of curling inward when heat-shrinking works, and the floating does not occur in the terminal portion.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a conventional heat-shrinkable sheet and a usage example thereof.

FIG. 2 is a cross-sectional view showing a heat-shrinkable sheet of the present invention.

FIG. 3 is an explanatory diagram showing a usage example of the heat-shrinkable sheet of the present invention.

[Explanation of symbols]

1 Two-way heat-shrinkable film capable of heat shrinking in the flow direction and width direction One-way heat-shrinkable film capable of heat shrinking only in the flow direction 3 Adhesive layer

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-4-327932 (JP, A) JP-A-2-14127 (JP, A) JP-A-59-71851 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 B29C 63/00-65/82

Claims (2)

(57) [Claims] 1. A heat shrinkage comprising at least one layer of a unidirectional heat-shrinkable film capable of heat shrinking only in the flow direction, which is laminated on one surface of a bidirectional heat-shrinkable film capable of heat shrinking in the flow direction and the width direction. Sex sheet. 2. A heat-shrinkable sheet comprising an adhesive layer provided on the two-way heat-shrinkable film side of the heat-shrinkable sheet according to claim 1.