Water impervious heat shrinkable tube

A water impervious heat shrinkable rubber or plastic tube wherein a laminated metal foil layer consisting of a metal foil film having a thickness of 0.01 mm to 0.1 mm and, laminated on each surface thereof, an electrically insulating or semiconducting rubber or plastic sheet extends along the entire or partial length of the tube and over the entire periphery of the tube, the two longitudinal edges of the laminated metal foil layer overlapping in a predetermined width and the laminated metal foil layer being so arranged in the tube that the thickness of the inner tube layer inside the laminated metal foil layer is smaller than the thickness of the outer tube layer outside the laminated metal foil layer.

BACKGROUND OF THE INVENTION 
The present invention relates to a water impervious heat shrinkable tube 
which is impermeable to water. 
A heat shrinkable rubber or plastic tube is obtained by, for example, a 
method wherein a rubber or plastic such as polyethylene, polyvinyl 
chloride, polyester, or ethylene propylene rubber is melted and extruded 
in a tubular form, the obtained tube is irradiated with an electron beam 
to be crosslinked; and the crosslinked tube is stretched at a temperature 
which is lower than the melting point of the rubber or plastic used and 
higher than the softening point thereof. According to another method, a 
sheet of a rubber or plastic as mentioned above is irradiated with an 
electron beam to be crosslinked, stretched by a desired multiple of its 
initial length, wound to a desired thickness around a mandrel having a 
desired diameter, and then made into an integral tubular form by heating 
at a temperature higher than the melting point of the rubber or plastic 
used. 
A heat shrinkable rubber or plastic tube prepared in this manner (to be 
referred to as a heat shrinkable tube hereinafter) is capable of 
returning, when heated, to its original shape seen prior to stretching. 
Utilizing this property, a tight rubber or plastic covering may be formed 
on a desired object. For this reason, heat shrinkable tubes have been 
recently used in various fields. 
However, when a heat shrinkable tube is used in water for a long period of 
time, water permeate through the rubber or plastic covering. Therefore, 
such a heat shrinkable tube may not be used where a high water 
impermeability is required. 
Meanwhile, power cables are required to be water impermeable in order to 
prevent insulation degradation due to formation of a water-tree in an 
insulator which is caused by water permeation into the cables. In order to 
form a protective layer at a joint of power cables, a method is generally 
adopted wherein a heat shrinkable rubber or plastic tube is fitted around 
a cable joint and is heated to be shrunk. However, for the same reason as 
described above, the joint thus prepared does not have satisfactory water 
impermeability. 
As a means for improving the water impermeability of a heat shrinkable 
tube, the present inventors have previously proposed a heat shrinkable 
tube wherein a metal foil film which is almost completely impervious to 
water is so laminated on the inner surface of the tube that the metal foil 
film extends along the entire circumference of the tube. 
The heat shrinkable tube previously proposed by the present inventors has 
the configuration shown in FIGS. 1 and 2. Referring to FIGS. 1 and 2, two 
or more metal foil films 2 extend along the entire circumference of the 
tube with their longitudinal edges 2a overlapped each other in a 
predetermined width to follow the shrinkage of a heat shrinkable material 
layer 1. However, a water impervious heat shrinkable tube of this type has 
a large number of lapped portions, resulting in a complex configuration 
and a complex manufacturing process. In addition to this, depending upon 
the positions of the metal foil films 2 formed in the heat shrinkable tube 
1, the metal foil films 2 form rough wrinkles which make gaps in the 
longitudinal direction of the tube 1 when the tube 1 is shrunk. Thus, the 
metal foil films 2 may not be tightly fitted on the cable joint. 
In an extreme case, as shown in FIG. 3, the metal foil films 2 form rough 
wrinkles 3 in the longitudinal direction of the tube 1 upon shrinkage 
thereof. This results in the formation of small gaps 5 which extend on the 
outer circumferential surface of a cable 4 in the longitudinal direction 
thereof. Then, a problem arises in that when water permeation is caused 
from the ends of the coated portion of the cable or from a damaged portion 
thereof, water thus introduced permeates along the longitudinal direction 
of the cable. In addition, when such wrinkles are formed, the outer 
surface of the cable becomes nonuniform, providing a poor outer 
appearance. 
SUMMARY OF THE INVENTION 
In order to solve this problem, the present inventors have made extensive 
studies. As a result of such studies, it has been found effective to 
specifically control the thickness and position of a laminated metal foil 
layer to be formed integrally with a heat shrinkable tube. 
The present invention thus provides a water impervious heat shrinkable 
rubber or plastic tube wherein a laminated metal foil layer consisting of 
a metal foil film having a thickness of 0.01 mm to 0.1 mm and, laminated 
on each surface thereof, an electrically insulating or semiconducting 
rubber or plastic sheet extends along the entire or partial length of said 
tube and over the entire periphery of said tube, the two longitudinal 
edges of said laminated metal foil layer overlapping in a predetermined 
width and said laminated metal foil layer being so arranged in said tube 
that the thickness of the inner tube layer inside said laminated metal 
foil layer is smaller than the thickness of the outer tube layer outside 
said laminated metal foil layer. When the tube shrinks upon being heated, 
the metal foil film forms only small wrinkles and shrinks so that the 
covering layer is tightly fitted and provides an excellent outer 
appearance. 
An adhesive layer is formed as the innermost layer of the water impervious 
heat shrinkable tube of the present invention as needed. In a water 
impervious heat shrinkable tube with such an adhesive layer formed 
thereon, even if the metal foil film in the tube forms rough wrinkles 
instead of small wrinkles and gaps are formed between the covering layer 
and the cable or the like along the longitudinal direction thereof, the 
adhesive layer flows to fill such gaps, so that excellent water impervious 
performance is provided. 
According to the present invention, a laminated metal foil layer is used 
which comprises a metal foil film having a thickness of 0.01 to 0.1 mm and 
electrically insulating or semiconducting rubber of plastic films formed 
on both surfaces of the metal foil film. Furthermore, according to the 
water impervious heat shrinkable tube of the present invention, the 
thickness of the inner tube layer inside the laminated metal foil layer is 
smaller than that of the outer tube layer outside the laminated metal foil 
layer. These features of the tube facilitate formation of small wrinkles 
in the metal foil film upon shrinkage thereof, and also result in an 
excellent outer appearance of the tube. If an adhesive layer is formed as 
the innermost layer of the tube of the present invention, the adhesive 
layer flows to further improve the water impervious performance of the 
tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 4 to 6 show a water impervious heat shrinkable tube according to an 
embodiment of the present invention. Referring to FIGS. 4 to 6, reference 
numeral 8a denotes an inner heat shrinkable material layer and 8 denotes 
an outer heat shrinkable material layer. A laminated metal foil layer 9 
(coated metal foil--FIG. 4) including a metal foil film of copper, 
aluminum or lead and rubber or plastic films is interposed between the 
layers 8 and 8a. Two longitudinal edges of the laminated metal foil layer 
9 overlap for a predetermined distance in the circumferential direction of 
the tube to form an overlap portion 9a. Thus, the laminated metal foil 
layer 9 extends along the entire circumferential direction of the tube. 
The laminated metal foil layer 9 is obtained by laminating on both surfaces 
of a metal foil film electrically insulating or semiconducting rubber or 
plastic films. When such a combination of a metal foil film and rubber 
films or a combination of a metal foil film and plastic films is used, the 
laminated metal foil layer may easily be formed integrally with the heat 
shrinkable material layers during the manufacture of a tube. 
The metal foil film to be used in the present invention has a thickness of 
0.01 to 0.1 mm. When the thickness of the metal foil film is less than 
0.01 mm, the metal foil film may break or crack upon shrinkage of the 
tube. On the other hand, when the thickness of the metal foil film exceeds 
0.1 mm, the wrinkles formed in the metal foil film upon shrinkage of the 
tube become too large, so that the advantageous effects of the present 
invention are impaired. 
The excellent water impermeability of the water impervious heat shrinkable 
tube of the present invention may be facilitated also by applying first an 
adhesive on a cable joint or the like to be coated, and then a water 
impervious heat shrinkable tube having no adhesive layer as shown in FIG. 
4. Alternatively, as shown in FIG. 7, such excellent water impermeability 
may be obtained by a water impervious heat shrinkable tube having an 
adhesive layer 10 as its innermost layer. 
In view of the installation procedure, a water impervious heat shrinkable 
tube with an adhesive layer 10 as its innermost layer as shown in FIG. 7 
is preferable for the following reasons. With such a tube, the number of 
installation steps is smaller; and variations in the water impermeability 
in the longitudinal direction of a cable or the like to be coated are 
smaller, irrespective of the installation technique used, than in the case 
wherein an adhesive layer is formed on a cable or the like to be coated. 
When the adhesive layer 10 is formed as the innermost layer of the tube of 
the present invention, the adhesive layer 10 may be formed along the 
entire length of a water impervious heat shrinkable tube. However, such an 
adhesive layer 10 may alternatively be formed only in a portion of a water 
impervious heat shrinkable tube along its longitudinal direction, where 
only such a portion is to be treated for watertightness. 
The water impermeability of a water impervious heat shrinkable tube along 
the longitudinal direction thereof is improved over that in the case of a 
water impervious heat shrinkable tube having an adhesive layer along its 
entire length if an adhesive free absorption region 11, free of the 
adhesive layer 10, is formed at least at an end of the tube. 
FIGS. 9A, 9B, 10A and 10B show respective configurations of water 
impervious heat shrinkable tubes with such adhesive free absorption 
regions. 
The effect obtainable with an adhesive free absorption region will now be 
described. 
In a water impervious heat shrinkable tube with adhesive free absorption 
regions 11 as shown in FIGS. 9B and 10B, after coating a joint 13 of 
cables 12, the adhesive free absorption regions 11 are formed to prevent 
flow of an adhesive or compound outside the joint 13, as shown in FIG. 11. 
For this reason, the water impermeability of the water impervious heat 
shrinkable tube along the longitudinal direction thereof is further 
improved. Furthermore, when the tube is shrunk upon application of heat or 
is in use, the adhesive may not flow outside the joint to adhere to other 
objects, thereby preventing impairment of the outer appearance. 
The adhesive free absorption regions 11 may be formed inside the adhesive 
layer 10 along the longitudinal direction of the tube as shown in FIG. 
10B. In this case, the adhesive compound may not flow inward along the 
longitudinal direction thereof to improve water-tightness of the tube 
portion having the adhesive layer 10. 
As for the position of the adhesive layer 10 in the heat shrinkable tube 
along the longitudinal direction thereof, it is so formed that at least 
part of the adhesive layer 10 overlaps the position of the laminated metal 
foil layer 9 so that gaps formed by wrinkles upon shrinkage of the metal 
foil layer are filled by the adhesive layer 10 to maintain excellent water 
impermeability. 
The metal foil film to be used in a water impervious heat shrinkable tube 
of the present invention may be a metal foil film of copper, aluminum or 
lead. In particular, lead is most preferable since it has excellent 
resistance to mechanical fatigue against mechanical strain, excellent 
corrosion resistance, and excellent chemical resistance. 
A plastic material to be laminated on both surfaces of a selected metal 
foil film may be selected from high-, medium- or low-density polyethylene, 
polypropylene, polybutene-1, polymethylpentene, an ethylene-ethylacrylate 
copolymer, an ethylene-vinyl acetate-vinyl chloride graft copolymer, 
chlorinated polyethylene and the like. Meanwhile, if a rubber material is 
used to be laminated on both surfaces of a selected metal foil film, such 
a rubber material may be selected from isoprene rubber, a chloroprene 
rubber, a styrene-butadiene rubber, and the like. Such a plastic or rubber 
material may be an electrically insulating material or a semiconducting 
material which is rendered semiconducting by the addition of a conductive 
material such as carbon black to such an electrically insulating material 
in a suitable amount. 
The material of a heat shrinkable tube of the present invention is 
preferably polyethylene, polyvinyl chloride, saturated polyester, 
crosslinked polyethylene, ethylene-propylene rubber, silicone rubber, 
chloroprene rubber, fluoroplastic, or the like. Such a material must have 
a shrinking rate of at least 20% with respect to its original size upon 
being formed into a tube. 
In order to integrally form the laminated metal foil layer and the heat 
shrinkable tube, they must be heat sealed. It is preferable that the 
rubber or plastic laminated on the metal foil film is the same or of a 
similar type as the material used for the tube. For example, if 
polyethylene is used as the material of the tube, polyethylene is 
preferably laminated on the two surfaces of the metal foil film. 
The material of the heat shrinkable tube may be electrically insulating or 
semiconducting. If the heat shrinkable tube is semiconducting, the plastic 
or rubber material to be laminated on the metal foil film may also be 
semiconducting. In this case, a heat shrinkable tube including a metal 
foil film may be handled as a conductive tube. 
Furthermore, the inner layer of the tube inside the laminated metal foil 
layer may be semiconducting, while the outer layer of the tube outside the 
laminated metal foil layer may be electrically insulating. A water 
impervious heat shrinkable tube using such a semiconducting material may 
be fitted directly on a shield of an insulating reinforcing element such 
as a joint of a high-voltage cable or on a shield of a cable, without use 
of an intermediate adhesive layer. In this case, the metal foil layer in 
the tube is electrically connected to such a shield. Therefore, the metal 
foil layer does not electrically float and cause partial discharge. The 
cable joint or the like is not therefore damaged due to discharge. 
Moreover, workers such as cable joint splicers who may directly touch a 
water impervious heat shrinkable tube are not exposed to the danger of 
electric shock or the like. 
Similar effects can also be obtained if a heat shrinkable tube material is 
electrically insulating and if the following measures are taken. A 
semiconducting material is selected as the laminating material on the 
metal foil film. Furthermore, as shown in FIGS. 12 and 13, one side edge 
22 of a laminated metal foil layer 9 along the peripheral direction 
thereof is exposed to the inner surface of the tube, and such an exposed 
portion of the metal foil layer 9 is brought into direct contact with a 
shield of a cable joint or the like without the use of an intermediate 
adhesive layer. If an adhesive layer is semiconducting, it may be 
interposed between the exposed portion of the metal foil layer and the 
shield of a cable or a cable joint. 
As may be apparent from the above description and the following description 
of Examples, a water impervious heat shrinkable tube of the present 
invention allows complete prevention of water permeation in the radial 
direction or from an end of the tube, allows also slight permeation of 
water therethrough, and has a smooth surface. 
The present invention will now be described by way of Examples. 
EXAMPLES 1 to 4 and COMATIVE EXAMPLES 1 and 2 
Water impervious heat shrinkable tubes of the configurations given in Table 
1 below were prepared. Samples as shown in FIG. 14 were prepared from 
these tubes. The samples were immersed in warm water at 60.degree. C. and 
were left submerged in water for 30 days. The samples were later taken out 
of the water, and the respective amounts of permeated water were measured. 
The obtained results and results of visual observation of the outer 
appearance of the tubes after shrinkage are shown in Table 1. 
Referring to FIG. 14, reference symbol A denotes a copper pipe of 35 mm 
outer diameter with one end sealed, on which polyethylene B is coated. Two 
such copper pipes were aligned with their open ends facing each other. 
After placing a desiccant (silica gel) C inside the pipes, the open ends 
were inserted inside a water impervious heat shrinkable tube D. This model 
sample was heated to be tested. 
The shrunk portion of the heat shrinkable tube D had dimensions of l1 =50 
mm and l2 =150 mm. The amount of water which had permeated the tube was 
measured in the following manner. After the sample had been immersed in 
water for 30 days, the weight of the desiccant measured before immersion 
in water was subtracted from that of the desiccant measured after 
immersion. The values shown are respectively mean values for three 
samples. 
A comparison of Examples and Comparative Examples in Table 1 reveals that 
the amount of water which had permeated into a water impervious heat 
shrinkable tube of the present invention was about 1/300 to 1/750 of that 
of a heat shrinkable tube consisting of the same heat shrinkable material 
alone and excluding a water impervious metal foil layer (Comparative 
Example 1). 
These results indicate that the tube of the present invention has excellent 
water impermeability both in the direction of thickness of the tube and in 
the longitudinal direction of the tube. 
In a heat shrinkable tube wherein a water impervious metal layer is so 
formed that the thickness of the portion outside the heat shrinkable layer 
is smaller than that of the portion inside the heat shrinkable layer, as 
in Comparative Example 2, four laminated metal foil layers were arranged 
so that their longitudinal edges overlapped each other by 10 mm, 
respectively. In this tube, as illustrated in FIG. 3, the wrinkles of the 
metal foil layer became too large locally; the outer surface was rough, 
and the amount of water permeation was only slightly lower than in 
Comparative Example 1. Thus, no effect of the laminated metal foil layer 
was exhibited. In this case, the water permeation is considered 
attributable mainly to water which permeates into the tube along the 
longitudinal direction thereof. 
EXAMPLES 4 and 5 
In order to examine the effect of a water impervious heat shrinkable tube 
having an adhesive flow absorption region for an adhesive layer, water 
impervious heat shrinkable tubes having configurations as indicated in 
Table 2 below were prepared to provide samples as shown in FIGS. 15A and 
15B. After being immersed in warm water at 60.degree. C., the samples were 
subjected to a gas leakage test of 30 days (720 hrs), two each at an 
internal pressure of 0.5 kg/cm.sup.2 (G) and at an external pressure of 
1.0 kg/cm.sup.2 (G). Referring to FIGS. 15A and 15B, reference numeral 28 
denotes a copper pipe having gas leakage holes 27, one sealed end and one 
open end 29. FIG. 15A shows a water impervious heat shrinkable tube 23, 
having an adhesive layer 25 along the entire inner surface thereof and a 
laminated metal foil layer 24 at its center, coated on a copper pipe 28 
having gas leakage holes 27. FIG. 15B shows a water impervious heat 
shrinkable tube 23 having adhesive flow absorption regions inside at ends 
thereof. With a tube of Example 5 wherein the adhesive layer is formed 
along the entire length of the tube, gas leakage occurred at a pressure of 
1.0 kg/cm.sup.2 (G). However, in a tube of Example 6 including the 
adhesive flow absorption regions at the two ends thereof, gas leakage did 
not occur. 
In practice, the pressure which may be established inside the tube by a 
load fluctuation in a general cable joint or the like is about 0.2 
kg/cm.sup.2 (G). When the water impervious heat shrinkable tube of Example 
5 is used for a power cable joint or the like, it provides an excellent 
watertightness. However, the water impervious heat shrinkable tube of 
Example 6 having adhesive flow absorpotion regions provides an even better 
watertightness. 
As may be seen from the Examples and Comparative Examples, a water 
impervious heat shrinkable tube of the present invention provides 
excellent water impermeability not only in the direction of thickness 
thereof but also in the longitudinal direction thereof and thus allows 
formation of a covering with a smooth surface and of high product quality. 
As was demonstrated in the Examples and Comparative Examples, the water 
impermeability of a tube of the present invention is several hundred times 
greater than that of a conventional tube without a water impervious metal 
foil layer. A high-voltage crosslinked polyethylene insulating power 
cable, for example, is known to be significantly degraded in electrical 
resistivity due to water immersion after use for a long period of time. 
However, if a water impervious heat shrinkable tube of the present 
invention is used to protect a joint or the like of such cables, the 
electrical resistivity of the cables is significantly improved. Thus, the 
water impervious heat shrinkable tube of the present invention provides a 
variety of practical applications. 
TABLE 1 
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Example 1 Example 2 Example 3 
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Configuration of 
PE(50.mu. )/Pb(50.mu. )/- 
PE(100.mu. )/Al(30.mu. )/- 
PET(50.mu. )/Cu(10.mu. )/- 
laminated metal 
PE(50.mu. ) (overall 
PE(100.mu. ) (overall 
PET(50.mu. ) (overall 
foil layer 
thickness: 0.15 mm) 
thickness: 0.23 mm) 
thickness: 0.15 mm) 
Material of heat 
Polyethylene 
Polyethylene 
Saturated polyester 
shrinkable layer 
Inner diameter of 
80 mm 80 mm 50 mm 
heat shrinkable 
tube 
Thickness of heat 
1.0 mm 1.0 mm 1.0 mm 
shrinkable tube 
(including metal 
foil layer) 
Positions of heat 
Outer layer of heat 
Outer layer of heat 
Outer layer of heat 
shrinkable material 
shrinkable material 
shrinkable material 
shrinkable material 
layer and metal 
layer: 0.70 mm; 
layer: 0.52 mm; 
layer: 0.65 mm; 
foil layer 
metal foil layer: 
metal foil layer: 
metal foil layer: 
0.15 mm; inner lay- 
0.23 mm; inner lay- 
0.15 mm; inner lay- 
er of heat shrink- 
er of heat shrink- 
er of heat shrink- 
able material lay- 
able material lay- 
able material lay- 
er: 0.15 mm 
er: 0.25 mm 
er: 0.20 mm 
Length of overlap 
10 mm (overlap 
10 mm (overlap 
10 mm (overlap 
portion of metal 
portion is heat 
portion is heat 
portion is heat 
foil layer 
sealed) sealed) sealed) 
Length of heat 
150 mm (no metal 
150 mm (no metal 
150 mm (no metal 
shrinkable tube 
foil layer at por- 
foil layer at por- 
foil layer at por- 
tions 20 mm from 
tions 20 mm from 
tions 20 mm from 
both ends of tube) 
both ends of tube) 
both ends of tube) 
Material of adhe- 
Natural rubber-type 
Butyl rubber-type 
Butyl rubber-type 
sive layer 
Thickness of adhe- 
0.6 mm 0.8 mm 0.6 mm 
sive layer 
Maximum shrinkage 
75% 75% 50% 
of heat shrinkable 
tube 
Outer appearance 
Smooth outer sur- 
Smooth outer sur- 
Smooth outer sur- 
after shrinkage 
face; only slight 
face; only slight 
face; only slight 
roughness roughness roughness 
Shrinkage of sample 
56% 56% 30% 
Amount of per- 
1.8 mg 2.3 mg 3.5 mg 
meated water 
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Comparative 
Comparative 
Example 4 Example 1 Example 2 
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Configuration of 
Conductive chloro- 
No metal foil layer 
PE(100.mu. )/Al(100.mu. )/- 
laminated metal 
prene rubber (100.mu. )/- 
PE(100.mu. ) (overall 
foil layer 
Al(30.mu. )/conductive 
thickness: 0.30 mm) 
chloroprene rubber 
(100.mu. ) (overall 
thickness: 0.23 mm) 
Material of heat 
Conductive chloro- 
Polyethylene 
Polyethylene 
shrinkable layer 
prene rubber 
Inner diameter of 
50 mm 80 mm 80 mm 
heat shrinkable 
tube 
Thickness of heat 
1.0 mm 1.0 mm 1.0 mm 
shrinkable tube 
(including metal 
foil layer) 
Positions of heat 
Outer layer of heat 
Single, heat 
Outer layer of heat 
shrinkable materi- 
shrinkable material 
shrinkable material 
shrinkable material 
al layer and metal 
layer: 0.52 mm; 
layer: 1.0 mm 
layer: 0.20 mm; 
foil layer 
metal foil layer: metal foil layer: 
0.23 mm; inner lay- 0.30 mm (4 metal 
er of heat shrink- foil films used); 
able material lay- inner layer of heat 
er: 0.25 mm shrinkable material 
layer: 0.50 mm 
Length of overlap 
10 mm (overlap 
-- 10 mm (overlap 
portion of metal 
portion is heat portion is heat 
foil layer 
sealed) sealed) 
Length of heat 
150 mm (no metal 
150 mm 150 mm (no metal 
shrinkable tube 
foil layer at por- foil layer at por- 
tions 20 mm from both 
tions 20 mm from both 
ends of tube) ends of tube) 
Material of adhe- 
Natural rubber-type 
Natural rubber-type 
Natural rubber-type 
sive layer 
Thickness of adhe- 
0.8 mm 0.6 mm 0.8 mm 
sive layer 
Maximum shrinkage 
50% 75% 75% 
of heat shrinkable 
tube 
Outer appearance 
Smooth outer sur- 
Smooth outer sur- 
Significant rough- 
after shrinkage 
face; only slight 
face after 
ness on outer sur- 
roughness shrinkage face; rough wrinkles 
in metal foil layer 
Shrinkage of sample 
29% 56% 56% 
Amount of per- 
4.2 mg 1440 mg 1200 mg 
meated water 
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TABLE 2 
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Example 5 Example 6 
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Configuration of 
PE(50.mu. )/Pb(50.mu. )/- 
PE(50.mu. )/Pb(50.mu. )/- 
laminated metal 
PE(50.mu. ) (overall 
PE(50.mu. ) (overall 
foil layer thickness: 0.15 mm) 
thickness: 0.15 mm) 
Material of heat 
Polyethylene Polyethylene 
shrinkable layer 
Inner diameter of 
70 mm 70 mm 
heat shrinkable 
tube 
Thickness of heat 
1.0 mm 1.0 mm 
shrinkable tube 
(including metal 
foil layer) 
Positions of heat 
Outer layer of heat 
Outer layer of heat 
shrinkable materi- 
shrinkable material 
shrinkable material 
al layer and metal 
layer: 0.70 mm; 
layer: 0.70 mm; 
foil layer metal foil layer: 
metal foil layer: 
0.15 mm; inner lay- 
0.15 mm; inner lay- 
er of heat shrink- 
er of heat shrink- 
able material lay- 
able material lay- 
er: 0.15 mm er: 0.15 mm 
Length of overlap 
10 mm 10 mm 
portion of metal 
foil layer 
Length of heat 
170 mm (no metal 
170 mm (no metal 
shrinkable tube 
foil layer at por- 
foil layer at por- 
tions 20 mm from 
tions 20 mm from 
both ends of tube) 
both ends of tube) 
Material of 
Butyl rubber-type 
Butyl rubber-type 
adhesive layer 
Thickness of 
0.8 mm 0.8 mm 
adhesive layer 
Position of 
Along entire length 
No adhesive mass 
adhesive layer 
of heat shrinkable 
layer at portions 
tube 20 mm from both ends 
of tube (flow absorp- 
tion regions) 
Air- Test Neither of 2 sam- 
Neither of 2 sam- 
tight- 
pressure: 
ples caused gas 
ples caused gas 
ness (in 
0.5 leakage leakage 
60.degree. C. 
kg/cm.sup.2 
warm (G) 
water) 
Test Sample 1: gas leaked 
Neither of 2 sam- 
pressure: 
after 420 hrs; ples caused gas 
1.0 Sample 2: gas leaked 
leakage 
kg/cm.sup.2 
after 456 hrs 
(G) 
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