JPH0118862B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a waterproof heat-shrinkable tube having a water-blocking function. Heat-shrinkable tubes are made by melt-extruding plastic tubes made of polyethylene, vinyl chloride, polyester, etc., and then introducing cross-linking into the tubes.
It is then obtained by stretching at a temperature below its melting temperature and above its softening temperature. Such heat-shrinkable plastic tubes can form a tight coating layer on objects by heating, so they have been used in various fields in recent years, although they are difficult to use for long periods of time under water. Since it allows water to pass through, the water-blocking effect during long-term use cannot be said to be perfect. By the way, in recent years, as a protective layer for cable connections, the method of covering the aforementioned heat-shrinkable rubber or plastic tube and heating and shrinking it has been adopted as a standard method, but for the reasons mentioned above, its water-shielding effect deteriorates over time. The decline was seen as a problem. As a result of intensive studies to solve this problem, the inventors have installed at least two metal foils in the middle of the heat-shrinkable tube in the thickness direction so as to cover the entire circumference of the tube. By arranging the foil so that the side edges of the metal foil overlap by a desired width, the coating layer is formed without substantially impairing the inherent heat shrinkability of the heat-shrinkable tube, resulting in an excellent water-shielding layer. They found that it was possible to maintain the functionality and completed this invention. That is, the present invention provides an intermediate layer of a heat-shrinkable tube that extends along the entire circumferential direction of the tube over the entire length or part of the tube, and includes at least two sheets of metal foil such that both side edges thereof face each other. This waterproof heat-shrinkable tube is characterized by having metal foil layers arranged so as to have a desired width overlap. FIG. 1 shows a heat-shrinkable tube according to an embodiment of the present invention, in which 1 is an inner layer heat-shrinkable tube, 1' is an outer layer heat-shrinkable tube, and 2, 2... are integrated between these inner and outer heat-shrinkable tubes. Copper, aluminum,
It is a metal foil layer made of lead or the like, and the adjacent edges of the metal foils 2, 2, . . . overlap 2' in the circumferential direction of the tube with a suitable width. In the illustrated example, the metal foils 2, 2 are divided into four pieces in the circumferential direction of the tube, but they may be at least two pieces or more. Also metal foil 2, 2
Practically speaking, it is most preferable for the overlap width between the two to be about 5 mm. Next, the metal foils 2, 2, . . . may have a length extending over the entire length of the tube as shown in FIG. 2, or may be partial only in a portion where the water-shielding effect is desired to be improved as shown in FIG. The metal foils 2, 2, . . . can be more efficiently integrated into the inner and outer heat-shrinkable tubes 1, 1' by using plastic laminated on both surfaces in advance. Next, FIG. 4 shows another embodiment of the present invention, in which the metal foil 2a is corrugated 2a' so as to have elasticity in the circumferential direction of the tube. This corrugating process 2a' significantly improves the followability of the tube when it contracts in the circumferential direction. The metal foil used in this invention preferably has a thickness of approximately 0.01 to 0.1 mm; below the lower limit, cracks are likely to occur during heat shrinking of the tube, and above the upper limit, the heat shrinkability of the shrink tube is significantly inhibited. This is not good either way. Plastics to be laminated to this metal foil include low, medium, and high density polyethylene, polypropylene, polybutene-1, polymethylpentene,
Ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate-vinyl chloride graft copolymer,
Examples include chlorinated polyethylene, isoprene rubber, chloroprene rubber, and styrene-butadiene rubber. Furthermore, as the heat-shrinkable tubes for the inner and outer layers of the main body,
Used materials include high-pressure polyethylene, vinyl chloride, saturated polyester, crosslinked polyethylene, ethylene-propylene rubber, silicone, chloroprene rubber, fluororesin, etc., and have a heat shrinkage rate of at least 20% or more. In order to integrate the metal foil and the heat-shrinkable tube, it is necessary to heat-seal them. In this case, it is preferable to use the same material as the tube body, for example, if polyethylene is used, It is desirable to take measures such as laminating polyethylene on the metal foil. As is clear from the above description and the examples below, in this invention, the metal foil is arranged in a state in which the metal foil is divided into at least two parts in the entire circumferential direction of the heat-shrinkable tube during heat shrinkage and heat cycle during use. Therefore, it appropriately follows the shrinkage deformation of the heat-shrinkable tube and does not significantly impede heat-shrinkability. Furthermore, since both side edges of each metal foil are arranged to overlap with each other by a desired width, the water-shielding function can be maintained at a high level, and its practical effect is truly great. The present invention will be specifically explained below using examples. Examples 1 to 4 Four pieces of double-sided laminated tape with a width of 70 mm having the configuration shown below in the left column were placed between two layers of a heat-shrinkable tube made of material in the right column, each having a wall thickness of 1 mm and an inner diameter of 80 mm, covering the entire circumference of the tube and having both side edges of 5 mm. The tubes were embedded in an overlapping state to form a heat-shrinkable tube, and a butyl rubber adhesive layer was provided on the inner surface of the tube.

[Table] Comparative Examples 1 to 4 Comparative Example 1: Cross-linked polyethylene heat-shrinkable tube with a wall thickness of 1.5 mm and an inner diameter of 80 mm A piece of tape having the following configuration on the left column was used with a wall thickness of 1 mm and an inner diameter of 80 mm.
Tubes were obtained by laminating the inner surface of heat-shrinkable tubes made of the material in the right column, and a butyl rubber adhesive layer was applied to the innermost surface of each tube.

[Table] Stell The heat shrink tube of the above example and comparative example is 40 mm.
It was placed on a φ crosslinked polyethylene cylinder and heated and shrunk using infrared rays to integrate it. Then seal both terminals
Place in 90℃ warm water and heat cycle 20℃ at 90℃.
The condition of the metal tape and its water-blocking properties were examined and the results are shown in the table below.

[Table] As shown in the above table, it is clear that the water-blocking properties of the products of the present invention are significantly improved. Example 5 Next, the tape was coated with PE (50μ)/Pb (10μ or 50μ)/
The table shows the results of experiments in which PE (50μ) was used, the tube material was cross-linked polyethylene, and the wrap length of the tape was changed to embed it in a cross-linked polyethylene tube.

[Table] By overlapping the tapes as shown in the table above, the water-blocking properties of the heat-shrinkable tube are significantly improved. Further, if the Pb thickness is about 50μ, no cracks will occur and it is good. To prevent cracks in this ultra-thin lead tape, it is effective to use a corrugated process in which the metal foil is made elastic in the circumferential direction of the tube.The effects of the corrugated process are shown below. Waterproof tape PE (50μ) / Pb (10μ) / PE (50μ)
The tube material was made of cross-linked polyethylene.

[Table] As shown in the table above, corrugating the metal foil significantly improves its elasticity and eliminates the risk of cracks occurring in the metal foil during contraction.

[Brief explanation of drawings]

FIGS. 1 and 4 are sectional views of two embodiment tubes according to the present invention, and FIGS. 2 and 3 are perspective views of an example in which metal foil is provided over the entire length of the tube and partially. 1, 1'... Inner and outer layer heat shrink tube, 2, 2a
...metal foil, 2'...lap part, 2a'...corrugated processing.

Claims (1)

[Scope of Claims] 1. An intermediate layer of heat-shrinkable rubber or plastic tube extending along the entire circumferential direction of the tube over the entire length or part of the tube, and at least two metal foils are attached on both sides of the tube. 1. A waterproof heat-shrinkable tube comprising a metal foil layer arranged such that edges thereof face each other and overlap by a desired width. 2. The waterproof heat-shrinkable tube according to item 1 above, wherein the metal foil layer is made of a material laminated with plastic tape on both sides. 3. The waterproof heat-shrinkable tube according to item 1 above, wherein the metal foil layer is corrugated to give elasticity in the circumferential direction of the tube.