JPS5948909B2 - Multilayer heat shrinkable tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer heat-shrinkable tube suitable for covering articles of different diameters.

2. Description of the Related Art Conventionally, a single-layer heat-shrinkable tube 1 as shown in FIG. 1 has been used to cover various articles such as pipes for transporting fluids such as gas and petroleum, cables, and the like.

Although this single-layer heat-shrinkable tube is easy and convenient to coat, it may cause the following inconveniences when covering articles with different diameters. For example, in order to cover a steel pipe with a different diameter that has a large diameter part and an adjacent small diameter part with the conventional heat shrinkable tube described above, the inner diameter before heat shrinking is larger than that of the large diameter part of the steel pipe, and when the inner diameter is The inner diameter must be able to shrink to the same size as the small diameter part of the steel pipe, but as shown in Fig. 2, this single-layer heat-shrinkable tube 1 is placed on a steel pipe 2 of a different diameter, and then heated with a burner etc. When the left half of the tube 1, which covers the large diameter portion of the steel pipe 2, undergoes heat shrinkage, the heat shrinkage of the left half of the tube 1, which covers the large diameter portion of the steel pipe 2, is smaller than that of the right half, and therefore the residual shrinkage stress in the left half becomes excessive. As a result, a split portion 3 may occur at the left end of the tube, and a good coating layer may not be formed. In addition, if a protrusion or the like touches the left half of the tube after heat shrinking, cracks will easily occur due to excessive residual shrinkage stress or stress concentration, and these cracks will quickly grow and propagate inside the tube, causing the steel tube to become damaged. In some cases, the anti-corrosion function may be lost.

The present invention relates to a multi-layer heat-shrinkable tube that solves the above-mentioned problems of the conventional single-layer heat-shrinkable tube. The tubular coating material layer is formed by integrally bonding tubular covering material layers, each of which has an axial dimension smaller than that of the base material layer.

Both the base material layer and the coating material layer in the present invention are made of a material that can impart heat shrinkability, in other words, thermal expansion (
Stretching) Processable materials such as thermoplastic plastics such as polyvinyl chloride, polyethylene, polypropylene, and fluororesin, synthetic rubbers such as silicone rubber, ethylene-propylene copolymer rubber, natural rubber, or mixtures thereof, and optionally anti-aging agents. It can be obtained by adding additives such as colorants, forming the tube into a tube, crosslinking it if desired, then thermally expanding the tube in the radial direction, and rapidly cooling it while maintaining this expanded state. .

The base material layer and the covering material layer are bonded and integrated by a method such as adhesion or fusion so that the covering material layer becomes the outer layer. Further, the base material layer and the covering material layer may be made of the same or different materials, but the thermal shrinkage rate of the covering material layer in the radial direction is set to be smaller than that of the base material layer.

This means that when heat-shrinking a multilayer heat-shrinkable tube 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 base material layer, which is likely to cause tearing, is placed on the covering material layer. This is important in order to prevent the base material layer from splitting by reinforcing it, and to minimize the residual shrinkage stress in the covering material layer after heat shrinkage to prevent cracks from occurring in the covering material layer. be. In the present invention, the thermal shrinkage rate of the coating material layer is set to be smaller than that of the base material layer for the above reasons, but considering the adhesion strength of the base material layer to the article, the adhesion strength between both layers, etc. , the heat shrinkage rate (A%) of the base material layer is 50 to 75%.
The thermal shrinkage rate (B%) of the coating material layer is preferably set to a value that satisfies the following formula.

Hereinafter, examples of the present invention will be explained with reference to the drawings.

In the multi-layered heat-shrinkable tube 4 shown in FIG. A tubular covering material layer 6 having a short axial dimension and a smaller radial heat shrinkage rate than the base layer 5 is integrally bonded via an adhesive layer 7. Note that an adhesive layer may be provided on the inner circumferential surface of the base layer if desired. Before coating steel pipes of different diameters using this multi-layer heat-shrinkable tube, the tube 4 is coated with its coating material layer 6 on the steel pipe 2, as shown in FIG.
2 corresponding to the large diameter part of the tube 4, and then the tube 4
The material is heat-shrinked.

During this heat shrinking work, the left end of the base material layer 5 is reinforced by a covering material layer 6 with a low heat shrinkage rate that is integrally bonded on the outer circumferential surface, and heat is not directly applied. The dehiscence phenomenon at the left end of the town does not occur. In addition, the coating material layer 6 and the steel pipe 2 after heat shrinkage
Since the residual shrinkage stress in the right half of the base material layer 5 covering the small diameter portion of the base material layer 5 is small, no cracks will occur even if a protrusion or the like touches it.

In the multilayer heat-shrinkable tube of the present invention, the axial dimension (length) of the covering material layer is set to be smaller than that of the base material layer.

This is because when the multi-layered heat-shrinkable tube of the fourth aspect of the present invention is heat-shrinked on an article with a different diameter, a predetermined portion of the outer peripheral surface of the base material layer corresponding to the large diameter portion of the article is reinforced with a covering material layer. This is because if the coating material layer has the same dimensions as the base material layer, the heat shrinkage of the base material layer portion corresponding to the small diameter part of the article will be hindered by the coating material layer with a small heat shrinkage rate, and the coating material layer of the small diameter part will This is not desirable because it is not carried out sufficiently. In the example shown in FIG. 5, a tubular covering material layer 6 integrally bonded to the outer peripheral surface of one end of the tubular base material layer 5 is made to protrude from an open end 8 of the base material layer 5.

If the covering material layer 6 is made to protrude from the open end 8 of the base material layer 5 in this way, direct action of heat on the open end 8 during heat shrinking work can be more effectively prevented, so that the base material layer 5 The effect of preventing the occurrence of the tearing phenomenon at the open end 8 of is further improved. 6 and 7 show examples of tubes suitably used depending on the shape of articles with different diameters, and FIG. ，
6'', and FIG. 7 shows a multi-layered heat-shrinkable tube in which a tube-shaped covering material layer 6 is integrally bonded to the outer peripheral surface of a substantially central portion of a tube-shaped base material layer 5. In yet another example, fasteners 9 are attached to the tubular base material layer 5 along its axial direction.

This tube 4 can be unfolded into a sheet by sliding the locking tool 0 of the fastener 19, so that articles of different diameters can be easily placed in the area to be covered.
The present invention is configured as described above, and a tubular covering material layer is provided on a predetermined portion of the outer circumferential surface of the tubular base material layer, and the heat shrinkage rate in the radial direction and the dimension in the axial direction are both smaller than that of the base material layer. Since the tubes are integrally bonded, it is possible to prevent both the occurrence of cracks in the tube during heat shrinking work and the occurrence of cracks after heat shrinking work.

[Brief explanation of drawings]

Figure 1 is a perspective view of a conventional single-layer heat-shrinkable tube;
The figure is a front view of steel pipes of different diameters covered with the tube shown in Figure 1, and Figures 3 and 5 to 7 are cross-sectional views showing examples of the multilayer heat-shrinkable tube according to the present invention. , FIG. 4 is a front view of a steel pipe having a different diameter covered with the tube shown in FIG. 3, and FIG. 8 is a front view of another example of the present invention. 4...Multi-layered heat-shrinkable tube, 5...
- Tube-shaped base material layer, 6...tube-shaped covering material layer.

Claims (1)

[Claims] 1. A multi-layer consisting of a heat-shrinkable tubular base material layer and a tubular covering material layer whose heat shrinkage rate and axial dimension are both smaller than that of the base material layer bonded to a predetermined portion of the outer peripheral surface of the heat-shrinkable base material layer. Mold heat shrinkable tubing.