JPH0720668B2 - Heat shrinkable tube and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-shrinkable tube for coating electric parts and the like that are easily placed in a high temperature state, and a method for manufacturing the same.

(Prior Art) Conventionally, as shown in the sectional view of FIG. 1, an electric component 1 such as a capacitor covered with a heat-shrinkable tube 2 for insulation has been widely used. Further, these electric parts are likely to be placed in a high temperature state even after being coated, and at that time, the coated heat-shrinkable tube 2 is further shrunk to expose the shoulder portion 11 as shown in the sectional views of FIGS. There was an easy drawback. And
In order to improve this, it has been proposed to use a heat-shrinkable tube having a small heat shrinkage in the longitudinal direction at 100 ° C. (JP-A-55-53407) (Problems to be solved by the invention) However, the above-mentioned conventional method is still insufficient to prevent the exposure of the shoulder portion when it is placed in a high temperature state. It was

(Means for Solving Problems) The present inventors have found that, in the soldering process and the like, the electric components have an unexpectedly high temperature (150 to 200 ° C.) and the coated heat-shrinkable tube further shrinks. The present invention has been achieved by paying attention to the high-temperature shrinkage characteristics of the heat-shrinkable tube, and the gist thereof is (1) the transverse heat shrinkage ratio V _{130 at} 130 ° C is 37 to 50.
%, The longitudinal heat shrinkage ratio P ₁₃₀ is 5 to 15%, and the transverse heat shrinkage ratio V ₁₃₀ → ₂₀₀ is V ₁₃₀ for each temperature from 130 ° C to 200 ° C.
Heat shrinkable tube characterized by the above (2) An internal pressure is applied to a raw tube obtained by melting and extruding a synthetic resin from an annular die to produce the original tube while maintaining an outer diameter equal to or larger than an outer diameter of the annular die, 1.58 to 2 times in the radial direction of the raw tube at a temperature above the softening point and below 130 ° C, and in the vertical direction
A method for producing a heat-shrinkable tube, which comprises stretching at 1.05 to 1.18 times.

Exist in.

1 is a partially cutaway front view showing the condenser in a state where the heat-shrinkable tube is well covered, and FIGS. 2 to 4 are partially cutaway front views showing the shoulder exposed at a high temperature. 5 and 5 are front sectional views showing an example of an apparatus for producing the heat-shrinkable tube of the present invention.

When the lateral heat shrinkage ratio V _{130 at} 130 ° C is less than 37%, it is difficult to surely cover the shoulder portion of the capacitor, while those exceeding 50% are difficult to manufacture.

If the heat shrinkage P ₁₃₀ in the vertical direction at 130 ° C is less than 5%, it is difficult to manufacture. If it exceeds 15%, the shoulder portion cannot be surely covered by shrinking too much during shrinkage coating.

The greatest feature of the present invention is that the lateral heat shrinkage V ₁₃₀ → ₂₀₀ at each temperature from 130 ° C. to 200 ° C. is equal to or higher than the lateral heat shrinkage V ₁₃₀ at 130 ° C. By this,
The reason why it is effective to prevent exposure of the shoulder is not clear, but since it retains the contracting force in the lateral direction even at high temperature, it is considered that the shoulder does not expose even if it tries to contract further in the longitudinal direction. .

This tendency is particularly remarkable in the polyvinyl chloride heat-shrinkable tube, and therefore the polyvinyl chloride heat-shrinkable tube will be described below as an example.

Even if the lateral heat shrinkage V ₁₃₀ → _{200 at} high temperature is too large, in the case of a polyvinyl chloride heat shrinkable tube, cracks may occur in the tube in relation to the strength at that temperature. It is preferably (V ₁₃₀ +5)% or less at 180 ° C, (V ₁₃₀ +10)% or less at 180 ° C, and (V ₁₃₀ +15)% or less at 200 ° C.

In addition, the longitudinal heat shrinkage ratio P ₁₃₀ → ₂₀₀ is
Since it is difficult to reduce the heat shrinkage ratio in the longitudinal direction at ₁₃₀ ° C to less than P _{130 in} terms of manufacturing, P ₁₃₀ or more is preferable, and if it is too large, the shrinkage stress in the lateral direction may be overcome and the shoulder may be exposed. It is preferably (P ₁₃₀ +20)% or less at 150 ° C, (P ₁₃₀ +40)% or less at 180 ° C, and (P ₁₃₀ +50)% or less at 200 ° C.

In the conventional heat-shrinkable tube, in the conventional heat-shrinkable tube, the inside of the raw tube 21 which is flexible at high temperature immediately after being extruded from the annular die 3 shown in FIG. Therefore, the diameter is reduced by the pulling force. It is considered that the radial shrinkage strain at the time of high-temperature extrusion remains as a diameter-expanding component at high temperature in the heat-shrinkable tube, and the heat shrinkage ratio in the lateral direction is reduced accordingly.

Therefore, the lateral heat shrinkage ratio V ₁₃₀ at high temperature according to the present invention →
To get a heat shrink tube where ₂₀₀ is V ₁₃₀ or above,
In the extrusion process before the stretching process shown in FIG. 3, when the melt-extruded raw tube 21 is taken from the annular die 3,
The inner pressure may be taken from the air supply pipe 4 communicating with the central portion of the annular die by the nip roll 6 so that the outer diameter is not reduced or slightly expanded, and cooled and solidified by the cooling device 5. This diameter expansion is preferably 1.2 times or less so that the lateral shrinkage at high temperature does not become too large.

At this time, it is preferable to adjust so that the longitudinal heat shrinkage P ₁₃₀ → _{200 at} a high temperature does not become much larger than P ₁₃₀ by taking up the tension in the longitudinal direction at a stretch ratio of 2 times or less without applying tension. Immediately after extrusion, put the tube on the belt conveyor to reduce the tension to 0
₁₃₀ → ₂₀₀ becomes almost equal to P _130, and there is no risk of exposing the shoulders of electrical parts under high temperature conditions, which is preferable.

The raw tube 21 thus obtained is heated and softened to a temperature of a softening point to 130 ° C. by a hot water shower 7 or a heater in a state where pressurized air is enclosed in the tube between the nip roll 6 and the take-up roll 8. 1.58 in radial direction
The heat-shrinkable tube 2 of the present invention can be obtained by stretching 2 to 2 times and 1.05 to 1.18 times in the machine direction.

(Effects of the Invention) As described above, according to the heat-shrinkable tube and the method for manufacturing the same of the present invention, it is possible to surely cover the electric component up to the shoulder portion during the covering operation, and the electric part after the covering is kept at a high temperature. A heat-shrinkable tube having excellent characteristics such that the shoulder is not exposed even when the tube is placed in the heat-shrinkable tube.

(Examples and Comparative Examples) A composition (specific gravity: 1.35) in which 100 parts by weight of polyvinyl chloride having an average degree of polymerization P of 1000 was mixed with 15 parts by weight of a plasticizer and 3 parts by weight of a lead-based stabilizer was prepared from an annular die under the following conditions. It was melt-extruded at about 200 ° C. and cooled with water to obtain the following original tubes A, B and C having an outer diameter of 5 mm.

Raw Tube A (Example): Outer Diameter of Mouth 4.2 mm, Lip Spacing
Extrusion rate 4.0 kg / hour from 0.5 mm annular die, take-up speed 2
At an internal pressure (positive pressure to the outside air) of 200 mmAq at 0 m / min, the diameter was expanded to 5 mm, and the product was taken up and cooled with water at 20 ° C.

Raw tube B (Example): Outer diameter of base is 5 mm, lip interval is 0.4
Extrusion rate of 4.0 kg / hour, take-up speed of 20 m /
Min, while keeping the internal pressure 180mmAq and keeping the outer diameter 5mm, 20 ℃
It was water cooled.

Raw tube C (comparative example): Outer diameter of cap is 6 mm, lip spacing is 0.3
Extrusion rate 4.0 kg / hour, take-up speed 20 m from 5 mm annular die
/ Min, without internal pressure (communication with the outside air), the diameter was reduced to 5 mm and the diameter was reduced, then the water was cooled at 20 ° C.

Next, the original tubes A, B and C were stretched 1.1 times in the longitudinal direction at a stretching temperature of 100 ° C. by using the stretching device shown in FIG. 5 so that the outer diameter was 9 mm and the wall thickness was 0.09 mm. The film was stretched in the transverse direction to obtain heat-shrinkable tubes A, B and C corresponding to the original tubes A, B and C. The shrinkage rate at each temperature is shown in Table 1.

The heat shrinkage ratio is that when immersed in an oil bath at each temperature for 1 minute.

The obtained heat-shrinkable tubes A, B, and C were cut to a length of 13 mm, inserted into a condenser having an outer diameter of 8 mm and a height of 11 mm, and heated in a hot air tunnel at 250 ° C for 5 seconds. The coated capacitor was contracted and adhered well, and a coated capacitor as shown in FIG. 1 was obtained.

After leaving the coated capacitor in a gear oven at 200 ° C. for 1 minute, it was observed to evaluate whether the shoulder 11 was exposed as shown in FIGS. 100 each
Tested one by one, Table 2 shows the number of exposed shoulders out of 100.

As is clear from Table 2, heat-shrinkable tubes A, B, C
In both cases, the transverse heat shrinkage ratio V _{130 at} 130 ° C is 44%.
And within the range of 37 to 50%, and the thermal shrinkage ratio P _{130 in the} longitudinal direction is also within the range of 10 to 11% and 5 to 15%, so that heating can produce good results as shown in Fig. 1. A coated capacitor is obtained.

The heat shrinkage in the transverse direction at 150 ° C to 200 ° C is 47% to 53% for the heat shrinkable tube A and 44% for the heat shrinkable tube B.
Since V ₁₃₀ = 44% or more, V ₁₃₀ → ₂₀₀ meets the condition of V ₁₃₀ or more, and even if left in an atmosphere of 200 ° C for 1 minute, no shoulder is exposed.

On the other hand, the heat-shrinkable tube C has a transverse heat shrinkage of 15 to 200 ° C of 42 to 33%, which is smaller than V ₁₃₀ = 44%. All 100 pieces are shouldered as shown in Fig. 2-4.
Exposure occurs.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing a condenser in a state in which a heat-shrinkable tube is satisfactorily covered, and FIGS. 2 to 4 are partially cutaway front view showing a shoulder exposed at a high temperature, FIG. 5 is a front sectional view showing an example of an apparatus for producing the heat-shrinkable tube of the present invention. 1 ... Electrical parts, 2 ... Heat shrink tube

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Claims (2)

[Claims] 1. A lateral heat shrinkage ratio V _{130 at} 130 ° C. of 37 to 5
0%, the longitudinal heat shrinkage ratio P ₁₃₀ is 5 to 15%, and the transverse heat shrinkage ratio V ₁₃₀ → ₂₀₀ is V ₁₃₀ for each temperature from 130 ° C to 200 ° C.
The heat-shrinkable tube characterized by the above 2. A raw tube obtained by melting and extruding a synthetic resin from an annular die is subjected to internal pressure to produce the raw tube while maintaining an outer diameter equal to or larger than the outer diameter of the annular die, and the raw tube is softened to 130 ° C. or higher. A method for producing a heat-shrinkable tube, which comprises stretching 1.58 to 2 times in the radial direction and 1.05 to 1.18 times in the longitudinal direction under the following temperature.