JP3065711B2 - Heat-shrinkable article, method for producing the same, and composite 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 article having a novel structure, a method for producing the same, and a composite sheet which can be used for the manufacture of the heat-shrinkable article.

[0002]

2. Description of the Related Art Coatings for the purpose of moisture proofing, waterproofing, gas leak prevention and the like are provided on connecting portions of power cables, communication cables, etc., and connecting portions of steel pipes for pipelines for transporting gas, oil and the like. As this coating method, a method of arranging a heat-shrinkable article on a cable connecting portion and heating and shrinking the article is often used.

As the heat-shrinkable articles used in the above-mentioned coating method, there are known heat-shrinkable articles obtained by imparting heat shrinkage to a sheet or tube mainly composed of rubber or plastic. By the way, in recent years,
There is a strong demand for improved reliability of such a coating method. For example, for the coating of a cable connection portion, improvement in water blocking (waterproof or moistureproof) is expected. For this reason, a heat-shrinkable article having a structure in which a metal foil is interposed between heat-shrinkable layers has been proposed (Japanese Patent Application Laid-Open No. 59-62142, Japanese Utility Model Publication No. 63-63).
No. 12996).

[0004]

However, in this heat-shrinkable article, heat shrinkage of the heat-shrinkable layer may be suppressed or uniform heat shrinkage may not be obtained due to the presence of the metal foil. When non-uniform shrinkage occurs, there is a concern that an excessive stress acts on the metal foil at a boundary between a portion having a large degree of shrinkage and a portion having a small degree of shrinkage, thereby causing breakage.
Further, when used for coating a different diameter article having a large diameter portion and a small diameter portion continuous with the large diameter portion, the heat-shrinkable layer follows the different diameter shape near the boundary between the large diameter portion and the small diameter portion (step difference). When the metal foil shrinks by heat (to form a portion), the metal foil cannot follow and sometimes breaks, causing a substantial loss of water barrier.

Accordingly, the present invention provides a heat-shrinkable article which is less likely to suppress heat shrinkage and non-uniform shrinkage of the heat-shrinkable layer even though it has a metal layer, and is applicable to articles of different diameters. Provided is a composite sheet that can be used for a production method, production of the article, and the like.

[0006]

Means for Solving the Problems The inventor of the present invention has conducted intensive studies to solve the above-mentioned problems of the prior art, and as a result, used a metal layer having a function of deforming into a wavy shape by heating, and using this as a heat-shrinkable layer. The present inventors have found that the intended purpose is achieved by intervening in the present invention, and have completed the present invention.

That is, the heat-shrinkable article according to the present invention comprises a metal layer and heat-shrinkable layers provided on both sides of the metal layer, and both layers are deformed in a wave shape by heating due to a shape memory function. Characterized in that:

FIGS. 1 and 2 show an example of a heat-shrinkable article according to the present invention. The heat-shrinkable article is a sheet-like article having heat-shrinkable layers 2 and 3 provided on both sides of a metal layer 1 which is deformed by heating. Shows a tube. These heat-shrinkable articles can be provided with an adhesive layer on the surface to improve the adhesion to the object to be coated.

In the tubular heat-shrinkable article shown in FIG. 2, the metal layers overlap at a predetermined width at both ends in the circumferential direction. The overlapping width is set so that when the heat-shrinkable article is thermally shrunk on the object to be coated, the overlapping state of both ends in the circumferential direction of the metal layer is maintained.
If there is no overlap when heat-shrinking, the permeation of water tends to occur from this portion. The same effect can be obtained by winding the metal layer a plurality of times (for example, winding the metal layer a plurality of times in the circumferential direction).

[0010] In this heat-shrinkable article, the heat-shrinkage temperature of the heat-shrinkable layer and the wavy deformation temperature of the metal layer are set to be substantially the same. Therefore, when a predetermined temperature is reached by heating, heat shrinkage of the heat shrinkable layer and wavy deformation of the metal layer occur. The metal layer becomes flexible due to the wavy deformation, and the resistance of the heat-shrinkable layer to the heat-shrinking force is reduced, so that uniform shrinkage of the layer can be ensured. Further, the wavy deformation of the metal layer has an effect of improving the followability of the heat-shrinkable layer to the heat shrinkage. For example, when heat shrinking is used for coating a different diameter article having a large diameter portion and a small diameter portion continuous with the large diameter portion, the heat shrinkage of the heat shrinkable layer is caused by a step near the boundary between the large diameter portion and the small diameter portion. However, in the heat-shrinkable article of the present invention, since the metal layer can cope with this by reducing or losing its wavy height, there is no possibility of causing inconvenience such as breakage. Lower. Of course, the water shielding is improved by the presence of the metal layer.

The shape of the heat-shrinkable article according to the present invention is not limited to the one shown in the drawings, and any structure having a heat-shrinkable layer provided on both sides of a metal layer which is deformed in a wavy shape by heating may be used. A branch pipe having a plurality of small-diameter branch tubular portions at one end or both ends of the large-diameter tubular portion may be used.

Next, an example of a method for producing such a heat-shrinkable article will be described. This heat-shrinkable article is obtained by laminating heat-shrinkable sheets on both sides of a metal layer that is deformed into a wave shape by heating .
Above, this laminate is shaped into a wave, and then the waveform of the laminate is
It can be manufactured by a method in which the shape is lost or reduced and the metal layer is integrated with the heat-shrinkable sheet without being deformed in a wave shape .

The metal layer which is deformed in a wave shape by heating used in this manufacturing method includes, for example, aluminum foil, iron foil, copper foil,
Metal foils such as lead foils and titanium foils (the thickness is about 5-300
μm), a thermoplastic layer is laminated directly or indirectly via an adhesive on at least one surface of the thermoplastic resin layer, and the laminate is pressed into a corrugated mold to form a wave (hereinafter referred to as “corrugation”). Then, the composite sheet can be obtained by a method of eliminating or reducing (flattening) the corrugated shape by applying pressure at a temperature lower than the corrugating temperature. The corrugation height (vertical distance from the top to the bottom of the wave) at this time is about 0.3
It has been found that it is preferable to set it to 1 mm. Note that the wavy deformation temperature of the composite sheet is determined by the softening point or melting point of the thermoplastic.

The composite sheet thus obtained is composed of a metal layer and a plastic layer provided on at least one side thereof, and when heated to a temperature higher than the corrugating temperature, the plastic layer exhibits a shape memory function, Since the thin metal layer follows the thin metal layer, the whole is deformed like a wave. The plastic layer is made of polyethylene, polypropylene, ethylene-
It can be formed from a thermoplastic resin such as a vinyl acetate copolymer, polyvinyl chloride, modified polyolefin, etc., and its thickness is usually about 30 to 300 μm. In order to enhance the shape memory function of this thermoplastic, it is preferable to crosslink it after corrugating.

In the manufacturing method according to the present invention, first, a heat-shrinkable sheet is superimposed on both surfaces of a metal layer which is thus obtained and which is deformed in a wavy shape by heating. The heat-shrinkable sheet may be the same as a conventional heat-shrinkable sheet. For example, additives (antioxidant, colorant, flame retardant, filler, etc.) may be added to a heat-shrinkable thermoplastic resin, rubber or a mixture thereof. And the like, and then formed into a sheet, hot-stretched so that the stretch ratio becomes about 30 to 500%, and cooled by keeping the stretched state. In addition, thermoplastic or rubber is
Usually, it is crosslinked before hot stretching.

The mode of superimposition of the heat-shrinkable sheet and the metal layer which is deformed by heating is determined according to the desired shape of the heat-shrinkable article. For example, in the case of obtaining (a) a sheet-like heat-shrinkable article, a desired number of heat-shrinkable sheets may be superposed on both surfaces of a metal layer which is deformed in a wave shape by heating. In the case of obtaining a shrinkable article, a heat-shrinkable sheet, a metal layer and a heat-shrinkable sheet that are deformed in a wave shape by heating are wrapped a predetermined number of times on a heat-resistant core made of metal, fluororesin, or the like, Alternatively, a heat-shrinkable sheet may be overlaid on at least one side of the metal layer that is deformed in a wavy shape, and then wound around the core body a predetermined number of times.

After the metal layer deformed into a wave shape by heating and the heat-shrinkable sheet are overlapped in this way, the two are integrated without deforming the metal layer into a wave shape. This integration can be performed by a method using a hot-melt adhesive or a method in which a heat-shrinkable sheet is softened or melted and bonded by softening or melting. When the integration is performed by the former method, a hot-melt adhesive is disposed between the two when the two are overlapped.

In the manufacturing method according to the present invention, it is preferable that the two be integrated under a pressurized condition to suppress the corrugated deformation of the metal layer. This pressurization has the effects of promoting the integration of the two, improving the degree of adhesion between the two, and preventing the heat shrinkability of the heat shrinkable sheet from decreasing.

However, this pressurization is not necessarily required. For example, when the superposition of the two is performed in the mode (b), the pressing can be omitted. When the two layers are integrated by heating as shown in (b), the metal layer has a wavy deformation function due to a rise in temperature. However, the metal layer is brought into a pressed state by the presence of the heat-shrinkable sheet on the outer periphery thereof. Therefore, the wavy deformation is suppressed even when there is no external pressure. In addition, even if the heat-shrinkable sheet is heated to a temperature equal to or higher than the heat-shrinkage temperature, the heat shrinkage of the sheet is suppressed by the core body, which may cause a disadvantage that the heat-shrinkability of the sheet is significantly reduced or lost. Absent.

In the heat-shrinkable article thus obtained, the heat-shrinkable layers 2 and 3 are thermally shrunk and the metal layer 1 is deformed in a wavy shape by heating, for example, as shown in FIG. The wave height after the deformation is lower than the wave height at the time of obtaining the metal layer, but the degree can be changed depending on various conditions.

[0021]

According to the present invention, the metal layer and the heat-shrinkable layer are both deformed in a wave-like manner by heating due to the shape memory function. Shrinkage can be improved. There is also an advantage that a heat-shrinkable article can be easily manufactured. (that's all)

[0022]

The present invention will be described in more detail with reference to the following examples.

Example 1 A 100 μm-thick polyethylene sheet was superimposed on both sides of a 100 μm-thick copper foil, and these were rolled together with a rubber roll and a metal roll (surface temperature of 150 ° C.) set so as to have a small gap. Laminate through the gap and then cool to room temperature.

The laminate is corrugated at room temperature using a shaping roll having a corrugated surface so that the corrugated height is about 0.5 mm, and then the polyethylene layer is irradiated with an electron beam. After cross-linking (gel fraction 50%), surface temperature 60
A composite sheet is obtained by passing through a pair of metal rolls at a temperature of up to 80 ° C. to be flat. This composite sheet is heated to a temperature of about 15
It was confirmed that the film deformed at 0 ° C. (the wave height after the deformation was about 0.5 mm, which was almost the same as that at the time of corrugating).

Next, a long heat-shrinkable sheet is wound around a cylindrical heat-resistant core body five times so that the longitudinal direction of the sheet is the circumferential direction of the core body. Roll the composite sheet once (overlap width at both ends of the sheet is 10 cm
Then, the same heat-shrinkable sheet is rolled five times, and the end of the roll is fixed with a heat-resistant adhesive tape. As the heat-resistant core, a stainless steel pipe having an outer diameter of 105 mm was subjected to release treatment by applying a silicone resin, and as the heat-shrinkable sheet, a long polyethylene sheet was crosslinked by electron beam irradiation (gel fraction: 40%). %)
This was subjected to a uniaxial stretching in the machine direction at a temperature of 50 ° C. so as to have a stretching ratio of 300%.

By heating at a temperature of 160 ° C. for about 30 minutes, the heat-shrinkable sheets and the heat-shrinkable sheet and the composite sheet are fused and integrated. After cooling to room temperature, the core and the adhesive tape are removed. , About 100mm inside diameter,
A heat-shrinkable tube having a thickness of 1.3 mm was obtained. Note that a butyl rubber adhesive layer having a thickness of 0.6 mm was provided on the inner peripheral surface of the tube.

This heat-shrinkable tube was placed on a connection portion of a communication cable having a water-proof structure having a diameter of 75 mm, and was heated by a burner and heat-shrinked to form a coating layer. Then, the coated part was immersed in pressurized water at 90 ° C. and 1 kg / cm ^2. However, even after 30 days, there was no permeation of water into the coated layer, indicating that the water shielding performance of the coated layer was sufficient. understood.

Further, when the coating layer was cut and the state of the composite sheet was visually observed, it was confirmed that the composite sheet was deformed in a wave shape (wave height: 0.2 to 0.3 mm) over the entire circumference.

Further, this heat-shrinkable tube is 95 m in diameter.
The large diameter portion and the small diameter portion were placed on an article having a cylindrical large diameter portion having a diameter of 50 m and a cylindrical small diameter portion having a diameter of 50 mm, which was heated by a burner and thermally contracted to cover the large diameter portion and the small diameter portion. Then, the outer heat-shrinkable layer was removed at the boundary between the large-diameter portion and the small-diameter portion, and the state of the composite sheet was observed. As a result, no break was observed.

Example 2 As a composite sheet, a 50 μm thick iron foil having a thickness of 1
00 μm polyethylene layer (gel fraction 50% by crosslinking)
And a 50 μm-thick ethylene-ethyl acrylate copolymer (ethyl acrylate content 60% by weight) -based hot melt adhesive layer provided on one of the polyethylene layers. When winding the composite sheet around the conductive core, the same operation as in Example 1 was performed except that the adhesive layer was on the outside, and a heat-shrinkable tube having an inner diameter of about 100 mm and a wall thickness of 1.25 mm was used. Obtained. The same test as in Example 1 was performed on this heat-shrinkable tube, and equivalent results were obtained.

Example 3 A 50 μm thick hot melt adhesive film made of denatured polyethylene on both surfaces of a 20 μm thick stainless steel foil (trade name: ADMER VE-30, manufactured by Mitsui Petrochemical Industries, Ltd.)
0) are overlapped, passed through a rubber roll set with a small gap and a metal roll (surface temperature: 150 ° C.), laminated, and then cooled to room temperature.

Next, the corrugated height is about 1 by the shaping roll.
mm at room temperature and then cross-link the denatured polyethylene by electron beam irradiation (gel fraction 3
5%), and then flattened between a pair of metal rolls having a surface temperature of 60 to 80 ° C. to obtain a composite sheet. It was confirmed that when heated, the composite sheet was deformed in a wave at a temperature of about 130 ° C. (the height of the wave after the deformation was about 1 mm, which was almost the same as that at the time of the corrugating process).

On the other hand, separately, a long polyethylene sheet having a thickness of 500 μm was irradiated with an electron beam to a gel fraction of 60 μm.
%, Stretched uniaxially at a temperature of 25 ° C. in the machine direction at a stretching ratio of 160%, cooled, and cooled to a thickness of 3%.
A heat-shrinkable sheet having a thickness of 30 μm and a heat shrinkage of 30% is obtained.

Then, a length of 1 m is provided on both sides of the composite sheet.
The heat-shrinkable sheets cut into pieces are superposed two by ^two , and heated and pressed by a press machine at a temperature of 150 ° C. and a pressure of 2 kg / cm ² for 15 minutes. A heat-shrinkable sheet having a thickness of 0.8 mm and a heat-shrinkage rate of 30% was obtained. At the time of this pressing operation, a fluororesin sheet was interposed as a release sheet between the press machine and a superposed body of these sheets. Then, an ethylene-vinyl acetate copolymer hot melt adhesive layer was provided on one side of the heat-shrinkable sheet.

The heat-shrinkable sheet was sushi-wound (with a winding inner diameter of about 300 mm) on the welded portion of a steel pipe having an outer diameter of 250 mm with the adhesive layer inside, and the end of the roll was fixed with a heat-resistant adhesive tape, and then burned. It was heated and adhered by heat shrinkage.

When this coating layer was cut and the state of the composite sheet was observed, it was observed that even in such a large diameter, the portion was not uniformly wrinkled in a part of the sheet but was uniformly wavy in the circumferential direction. .

Comparative Example A heat-shrinkable tube having a thickness of 1.1 mm and a heat shrinkage of 75% was obtained in the same manner as in Example 1 except that a copper foil having a thickness of 100 μm was used instead of the composite sheet. .

Example 1 of this heat-shrinkable tube
When the same test was performed, permeation of water was observed after 30 days. Moreover, in the coating test on the articles of different diameters, it was observed that the copper foil was broken at the boundary.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of the present invention.

FIG. 2 is a front view showing an example of the present invention.

FIG. 3 is an explanatory view schematically showing a state after heat-shrinking the heat-shrinkable article according to the present invention.

[Explanation of symbols]

 1 metal layer 2 heat shrinkable layer 3 heat shrinkable layer

Continuation of the front page (56) References JP-A-1-177384 (JP, A) JP-A-2-226617 (JP, A) JP-A-58-29659 (JP, A) JP-A-64-22425 (JP) , U) Japanese Utility Model 1-74125 (JP, U) Japanese Utility Model 1-79337 (JP, U) Japanese Utility Model 63-184573 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB Name) B32B 1/00-35/00

Claims (4)

(57) [Claims] And 1. A metal layer, Ri consists heat-shrinkable layer provided on both surfaces of the metal layer, they both layers of a shape memory function
Both are heat-shrinkable articles that are deformed into waves by heating . 2. The heat-shrinkable article according to claim 1, wherein the metal layer is a composite sheet composed of a thermoplastic layer provided on at least one surface of the metal layer. 3. A heat-shrinkable sheet is superimposed on both sides of a metal layer which is deformed into a wave shape by heating, and the laminate is formed into a wave shape, and then the corrugated shape of the laminate is reduced or reduced to form a metal layer. A method for producing a heat-shrinkable article, wherein the heat-shrinkable sheet is integrated with a heat-shrinkable sheet without being deformed in a wave shape. 4. A flat metal layer and a flat plastic layer, both of which are heated together by a shape memory function.
A composite sheet that is deformed in a wave-like manner .