JPS5852968Y2 - heat shrinkable sheet - Google Patents

Description

[Detailed description of the invention] This invention is a sheet made of a heat-shrinkable polymer material, especially a sheet body formed in a sheet shape, whose ends are joined to each other to form a cylindrical body, and then a built-in heating device is formed. This invention relates to the structure of the end portion of a sheet-like body made for the purpose of heating an electrical conductor to heat-shrink the sheet body.

BACKGROUND ART Conventionally, materials called heat-shrinkable tubes or heat-shrinkable sheets made of rubber or plastic have been used to prevent corrosion of connecting parts of long pipe bodies, long electric cables, and the like.

These materials are mainly made by heating a crystalline crosslinked polymer substance, such as crosslinked polyethylene, to a temperature above its crystal melting point, then elastically deforming it, and then cooling it below its crystal melting point while maintaining that deformed state to freeze the strain inside the molded body. It is made in a fixed manner, and the material has the property of returning to its original shape when it is heated above the crystal melting point during construction.

Usually, tube-shaped materials are used, but if they are damaged during construction or use, they cannot be easily inserted through long-distance lines even if you try to replace them. The method used is to prepare a sheet-like material, wrap it around a tube, connect both ends to form a tube, and then shrink the material.

However, when using this method, the strength of the joint was lower than that of a tube formed in advance into a complete tube, and a decrease in anticorrosion performance was unavoidable.

As a countermeasure to this problem, the present inventors investigated a heat-shrinkable sheet with a structure in which both ends of the sheet are divided into two pieces, as shown in Figure 1, and found that it was considerably improved compared to a simple overlapping structure. Admitted.

However, in the case of this structure, hot-melt adhesive is inserted in advance between the layers of the overlapping part and melts and adheres when heated, but the entire tube shrinks during adhesion, so the overlapping part However, there was a drawback in that the entire structure was slippery and easily fell off.

In addition, if slippage occurs in this area, the tightening force of the entire tube to the attached pipe body will be insufficient, so the tube will not fit well with the pipe body after shrinking, and the pre-coated inside of the tube will In many cases, it was not possible to cause the adhesive for bonding tubular shapes to flow sufficiently, resulting in unnecessary voids and the like, which impaired the anticorrosion effect.

This invention was developed to eliminate these drawbacks, and its purpose is to ensure that the joints at both ends of the heat-shrinkable sheet do not slip or fall off, not only during installation but also during heat-shrink processing. It is an object of the present invention to provide a heat-shrinkable sheet that can be joined and can impart sufficient clamping force and anticorrosion effect to objects to which it is attached.

The structure and usage of the heat-shrinkable sheet of the present invention will be explained in detail below with reference to FIGS. 2 to 4.

In the figure, reference numeral 1 indicates a sheet main body portion 2 and two joining tongue pieces 3, 4 and 5 formed at both ends of the main body portion 2, respectively.
A heat-shrinkable polymeric material sheet consisting of 6, 4' and 5
′ is a folded retaining portion formed to be able to be hooked to each other when joined to the tongue pieces 4 and 5 located on opposite sides of the sheet body 2, and 7 is each of the tongue pieces 3 and 6. A heat-melt adhesive applied to the inner surface, 8 a heat-melt watertight mixture applied to a predetermined position on the inner surface of the sheet body excluding the sheet edges, and 9 a heat-melt watertight mixture applied in the width direction so as not to inhibit the heat shrinkability of the sheet. This is a heating wire that is wrapped in a sequentially folded pattern.

The heat-shrinkable polymer sheet 1 is used by wrapping it around a tube (not shown) and engaging the folded retaining portions 4' and 5' of the tongues 4 and 5, respectively, as shown in Figure 4. , the upper and lower surfaces of the latch part are sandwiched between the tongue pieces 3 and 8 via the adhesive 7 to form an overlapping part for joining, and then heated and contracted by applying electricity to a heating wire to tightly fit it onto the tube body. This is a problem in which a covering layer is formed in an adhered state.

Next, an embodiment of the present invention will be described. Example width: 700 mm, length: 2000 mm, thickness: 150 mm
(7) Heat-shrinkable films made of cross-linked polyethylene were laminated and thermally welded, and heating wires of 0.08 mm2 were inserted inside the film during the lamination process to produce a heat-shrinkable polymer material sheet with a thickness of 1.5 mm.

Next, each of the 120 mm ends of the sheet is divided into two parts in the thickness direction to form two tongue pieces 3.4 and 5, 6. The film was folded back as shown in the figure, pressure was applied under heating, and the film was cooled as it was to form folded retaining parts 4' and 5'.

Further, a hot-melt adhesive 7 and a watertight mixture 8 were applied to each inner surface of the tongue piece 3.6 not provided with the folded engagement portion and to the inner surface of the sheet main body, respectively.

The sheet thus obtained is wrapped around a 60OA steel pipe, and the tongues at both ends are overlapped and engaged with each other as shown in FIG. Pieces 3 and 5 were fixed so that they were in close contact with each other.

In this state, electricity was applied to the heating wire built into the sheet to cause the sheet to undergo thermal contraction, and at the same time, the bonded portion was heated to melt the adhesive and the honey-like mixture, and then cooled.

When we cut open the formed coating layer and observed the state of the tongue joint, we found that the hot-melt adhesive applied to the inner surfaces of the tongues 3 and 6 completely filled the tongue joint space. When buried, a watertight structure was formed, and the tongues were completely and firmly connected to each other.

Furthermore, the watertight mixture coated on the sheet body flowed completely between the sheet and the steel pipe, and was fully functioning with no gaps or voids.

In the above explanation, an example was explained in which the folded engagement part is formed by folding and thermoforming the tip of the tongue, but of course, if necessary, a separately made strip may be welded to the tongue to form the folded retaining part. Needless to say, it is okay to do so.

Further, it is more preferable that the folded portion is formed into a folded shape and then crosslinked by means such as radiation irradiation.

As mentioned above, this device forms two or more joining tongues at each end of a sheet made of a heat-shrinkable polymeric material, and at least one of the two tongues can be engaged with each other during joining. Since the folded retaining part is provided, the sheets can be firmly joined with sufficient tightening force without slipping or falling off at the joint, not only during installation but also during heat shrinkage. This greatly contributes to improving the anti-corrosion performance of pipe joints.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram illustrating a heat-shrinkable polymer sheet before improvement of the present invention, Fig. 2 is a schematic diagram illustrating a heat-shrinkable sheet according to the present invention, and an enlarged cross-section of the main part of Fig. 3. FIG. 4 is a schematic cross-sectional view showing the bonded state of the heat-shrinkable sheet shown in FIG. 3. 1: sheet made of heat-shrinkable polymer material, 2: sheet main body,
3, 4, 5, 6: tongue piece, 4/, s/: folded retaining part, 7: adhesive, 8: watertight mixture.

Claims (1)

[Scope of utility model registration request] A sheet made of a heat-shrinkable polymer material that has a heating electrical conductor built in so as not to inhibit the shrinkability of the heat-shrinkable sheet, and the sheet has two or more joining tongues at each end thereof. and at least one of each of the two tongues has a folded retaining portion that can be hooked to each other during joining.