JPH0347179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a heat-shrinkable tube.

(Prior art) Examples of means for continuously manufacturing heat-shrinkable tubes include US Pat. No. 3,370,112 and Japanese Patent Publication No. 38-26581
No. and Special Publication No. 55-6045 are known.

First, the method shown in U.S. Patent No. 3,370,112 involves heating a crystalline polymer resin tube with an internally pressurized state in a heating bath to a temperature above the crystal melting point, passing it through a sealing die in the heated state, and drawing it into a decompression chamber. This is a method of obtaining a heat-shrinkable tube by guiding the tube into a molded tube equipped with a cooling device, cooling and fixing the tube while expanding its diameter by the pressure difference between them.

(Problem to be Solved by the Invention) The biggest problem when expanding the diameter of a tube using such a differential pressure is the method of maintaining the reduced pressure. The contact area with the tube changes, the friction between the two is greatly influenced, and the elongation in the length direction due to the transaction force of the expanded diameter tube changes, resulting in a product that is often not uniform and has a small amount of elongation.

Japanese Patent Publication No. 38-26581 proposes a method of suppressing the longitudinal elongation of the tube as much as possible by using, for example, an endless belt engaged with a slide fastener as a conveyance means. However, other drawbacks have been pointed out in this method, such as the use of the endless belt reduces cooling efficiency and complicates the apparatus.

In addition, the method disclosed in Japanese Patent Publication No. 55-6045 uses an expansion control cooling tube having through holes in the tube wall based on the idea of solving the above problem by performing the tube diameter expansion and cooling in a series. This method expands the diameter of the tube. However, in this case, the heating medium attached as a lubricant as usual on the surface of the heat-shrinkable tube whose diameter has been expanded to the inner diameter of the expansion control cooling pipe described above,
It is pushed out through the pipe wall through-hole, and as a result, the frictional resistance between the diameter-expansion control cooling pipe wall and the diameter-expanding tube increases, and the tube may sink into the through-hole, furthering this increase in frictional resistance. There are other problems. This problem is particularly serious when a tube with a thin wall is used or when the diameter expansion magnification is large.

(Means for Solving the Problems) As a result of intensive studies to solve these problems, the inventors have decompressed the outside of the tube in the direction of movement of the tube in order to provide a differential pressure when expanding the diameter of the tube. They discovered that by dividing the tube into two decompression chambers and carrying out the process separately, the longitudinal elongation of the tube can be suitably suppressed and the diameter can be expanded stably, and this invention has been completed.

That is, this invention consists of a case in which a thermoplastic resin tube under heat softening is sealed from one side with an unexpanded diameter tube on the introduction side and an enlarged diameter tube on the take-off side, and is equipped with appropriate pressure reducing means. The tube is introduced into the enlarged diameter part of the tube, which constitutes a cooling sizing part in which the outer periphery of the enlarged tube is inscribed and cooled, and the pressure on the outside of the tube is reduced in the enlarged diameter part of the tube, resulting in a continuous flow due to the differential pressure between the inside and outside. In the method for manufacturing a heat-shrinkable tube, the diameter of the tube is enlarged, the diameter of the tube is cooled and fixed in the cooling sizing part, and the tube is pulled out to the other side. When contacting, the casing is expanded so that two decompression chambers are formed before and after the sizing part, and separate decompression means are provided in both decompression chambers, so that the degree of decompression in the decompression chamber on the withdrawal side is equal to or equal to that on the introduction side. This method of manufacturing a heat-shrinkable tube is characterized in that the diameter of the tube is expanded by setting the diameter to exceed this value.

(Function) In this invention, when the enlarged diameter tube is inscribed in the cooling sizing part within the casing of the enlarged diameter part, which will be described in detail later, the casing is arranged so that two decompression chambers are formed before and after the sizing part. By expanding the tube diameter and installing separate decompression means in both decompression chambers and setting the degree of decompression in the decompression chamber on the withdrawal side to be equal to or higher than that on the introduction side, the tube diameter can be expanded. As a result, the pulling friction force of the enlarged diameter tube becomes stable and fluctuations in the amount of elongation are suppressed, and the reduced pressure in the drawing-side decompression chamber is made larger than that on the introducing side. It is also possible to generate a force for moving the tube in the take-up direction, thereby reducing the tube tensile force and further promoting the above-mentioned suppression of elongation.

(Example) Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of the method for continuously expanding the diameter of a heat-shrinkable tube according to the present invention, and 1 is an illustration of the unexpanded tube 13.
A is a winding reel for feeding out, and the tube 13 is internally pressurized and fed into the pressurizing tank 4 via two and three guide rolls 2 and 3. The pressurized tank 4 is filled with a liquid heating medium, and while the tube 13 passes between the guide rolls 5 and 6, it is heated and softened, and at the same time, the tube 13 is slightly expanded in diameter in response to the internal pressurization.

Silicone oil or glycerin is most commonly used as the liquid heat medium for heating, but other materials can also be used as long as they are fluid at room temperature. It is desirable that this has as low a viscosity as possible during cooling.

The preheated unexpanded tube 13a is guided by guide rolls 7 and introduced into the expanded diameter section 8. This enlarged diameter part 8 is shown enlarged in FIG. 2, and in the figure, 9 is a horizontal cylindrical case, and the enlarged diameter tube 13 has a take-up hole 10 on the take-up side with a diameter substantially equal to that of the case. and the other end introduction side is an unexpanded diameter tube 13
A sealing die 11a having an introduction hole 11 approximately equal to the diameter of a is attached.

A cooling sizing section 12 corresponding to the diameter of the enlarged diameter tube 13 is provided in the axial direction in the case 9, and decompression chambers 14 and 15 (described later) are formed to expand in the radial direction on both sides of the cooling sizing section 12. has been done. Decompression means 16, 17 are connected to each decompression chamber 14, 15 via pipes 14a, 15a.

Each pressure reducing means 16, 17 may be a vacuum trap 18, a vacuum gauge 19, and a vacuum pump 20 arranged in this order as shown in the figure. In addition, 12 in the figure
a is a cooling medium circulation path. For the expanded diameter portion 8 having such a configuration, the above-mentioned unexpanded diameter tube 13a
are guided through the introduction hole 11 so as to be taken up sequentially from the take-up hole 10, and here the pressure reducing means 16, 1
Drive 7.

The unexpanded diameter tube 13a is expanded in diameter as shown in the figure, cooled while being inscribed in the cooling sizing section 12, and taken off as an expanded diameter tube 13.

By inscribing the enlarged diameter tube 13 in the sizing part 12, the inside of the case 9 is divided into two decompression chambers 14 and 15 with the sizing part 12 in front and back (hereinafter also referred to as first and second decompression chambers). ).

In this case, since the heating medium exists between the sizing section 12 and the enlarged diameter tube 13, it always moves with the movement of the tube and functions as a lubricant. Also, here, let's assume that the first decompression chamber 1
By setting the degree of decompression in the second decompression chamber 15 so as to exceed the decompression degree of No. 4, a differential pressure is generated between the first decompression chamber and the second decompression chamber, and the second decompression chamber always flows from the first decompression chamber side to the second decompression chamber. It is preferable to generate a tensile force that moves the enlarged diameter tube 13 to the side, thereby reducing the resistance between the outer wall of the tube and the inner wall of the cooling sizing, and suppressing elongation in the length direction. Further, by providing the cooling sizing section 12 with a slight taper to enlarge the diameter toward the tube take-up side, this resistance can be further reduced, and the elongation of the tube in the length direction can be further suppressed.

Furthermore, the existence of this second decompression chamber 15 means that the take-up hole 1
The function is to appropriately prevent a decrease in pressure caused by air leakage between the tube 13 and the expanded diameter tube 13, and to maintain a stable expanded diameter state.

That is, as long as the tube is continuously expanded in diameter in a stable steady state as shown in the figure, the first decompression chamber 14 and the second decompression chamber 15 are separated by the expansion tube, so they cannot be separated. Decompression control is possible and the working conditions are stable. In addition, if for some reason there is a part of the unexpanded tube that cannot be expanded to the specified size, the incompletely expanded part is not in contact with the cooling sizing part, so it is not cooled and fixed, and the second depressurization at the subsequent stage is performed. The diameter is expanded depending on the degree of pressure reduction in the chamber, and a stable expanded diameter tube can be obtained. In the figure, 21 is an end seal diaphragm, which is in contact with the enlarged diameter tube 13 and prevents air from leaking from the outside of the second decompression chamber, and also scrapes off the heating medium adhering to the surface in the cooling cleaning tank. to facilitate cleaning. The expanded diameter tube 13, which has been expanded in diameter and cooled and fixed as described above, is
It is led to a cooling tank 22 in the figure, where it is completely cooled and the heating medium adhering to the surface is washed and removed, pulled by transaction rolls 23 and 24, and wound onto a take-up reel 25. In this case, it is preferable to provide an air blower either before or after the trading rolls 23, 24 to remove the cooling water adhering to the cooling tank.

(Example) The present invention will be specifically explained below with reference to Examples.

Example 1 Low density polyethylene (Japan Petrochemical Co., Ltd. W-
2000) 100 parts anti-aging agent (Irganox manufactured by Ciba Geigy)
1010) Using a mixture consisting of 1 part composition, a tube with an inner diameter of 4.0φ and a wall thickness of 0.4 mm was obtained using an extruder.
A crosslinked tube was obtained by irradiation with an electron beam of 20 Mrad. Using this tube, the diameter was continuously expanded using the method described above. The diameter expansion conditions are as follows.

Heating medium (120℃) Glycerin introduction hole diameter 6.5mm Tube internal pressure 0.07Kg/cm ² First vacuum chamber pressure reduction degree 280mmHg Second vacuum chamber pressure reduction degree 140mmHg Cooling sizing inner diameter First vacuum chamber side 8.5mmφ Second vacuum chamber side 9.5mmφ ( (Tapered) End seal diaphragm inner diameter 8.3mmφ Take-up speed 3m/min The resulting heat-shrinkable tube has an inner diameter of 8.2 to 8.5mm
When this heat-shrinkable tube, which had a diameter of 0.22 to 0.19 mm and a wall thickness of 0.22 to 0.19 mm, was immersed in a silicone oil bath at 120°C for 30 seconds, it shrunk to the size before expansion, and the shrinkage rate in the length direction was 1 to 2%. .

Example 2 Low density polyethylene (same as above, W-200) 70 parts ethylene propylene rubber (manufactured by Japan Synthetic Rubber Co., Ltd.)
EP-11) Using a mixture consisting of 30 parts hydrated alumina, 40 parts anti-aging agent (Irgaritx 1010, manufactured by the same company), 1 part carbon, 2 parts zinc white, 5 parts dicumyl peroxide, 2.7 parts sulfur, and 0.3 parts, the inner diameter was 10 mmφ. An extruded cross-linked tube with a wall thickness of 3 mm was used to expand its diameter in the same manner as in Example 1.

The diameter expansion conditions were as follows.

Heating medium (125℃) Glycerin introduction hole inner diameter 19mmφ Tube internal pressure 0.5Kg/cm ² First vacuum chamber pressure reduction degree 300mmHg Second pressure reduction chamber pressure reduction degree 180mmHg Cooling sizing inner diameter 38mmφ End seal diaphragm inner diameter 36mmφ Take-up speed 1.0m/min Obtained The heat shrink tube has an inner diameter of 34 to 35 mmφ and a wall thickness.
It was 1.1 to 1.2 mm. When this heat-shrinkable tube was immersed in a 120° C. silicone oil bath for 30 minutes in the same manner as in Example 1, it shrunk to its original size before diameter expansion, and the shrinkage rate in the length direction was 2 to 3%.

Even when the degree of vacuum in the first vacuum chamber was varied from 250 to 350 mm, heat-shrinkable tubes of the same size and the same shrinkage rate in the longitudinal direction were obtained.

Example 3 As a result of examining diameter expansion conditions using a cross-linked tube with the same composition and size as in Example 2 and setting the first and second vacuum chambers at the same degree of pressure reduction, it was found that a heat-shrinkable tube with the same characteristics as in Example 2 was used. The processing range pressure to obtain is
It was 250-300mmHg.

Example 4 A tube with an inner diameter of 1.0 mm and a wall thickness of 0.32 mm consisting of 100 parts of ethylene vinyl acetate copolymer (Ultracene UE630 manufactured by Toyo Soda Co., Ltd.), 2 parts of anti-aging agent (same as above, Irganox 1010) and 3 parts of pigment was extruded. Extrude using a machine and add 18 Mrad to this
A crosslinked tube was obtained by electron beam irradiation, and diameter expansion processing was similarly performed under the following diameter expansion conditions.

Heating medium (110℃) Inner diameter of glycerin inlet hole 2.1mmφ Tube internal pressure 1.3Kg/cm ² Degree of pressure reduction in first vacuum chamber 100mmHg Degree of pressure reduction in second vacuum chamber 30mmHg Cooling sizing inner diameter 3.0mmφ End seal diaphragm inner diameter 2.5mmφ Take-up speed 3m/min The heat shrinkable tube has an inner diameter of 2.2 to 2.3 mm, a wall thickness of 0.16 to 0.18 mm, and a shrinkage rate in the length direction of 1 to 2.
It was %.

(Effects of the Invention) As explained above, according to the present invention, shrinkage in the length direction can be appropriately suppressed over various compositions or tube sizes, and a heat-shrinkable tube that is homogeneous and has sufficient shrinkage characteristics can be stably produced. It is possible to obtain it by doing so.

The effect that the pressure reduction control for diameter expansion can be carried out extremely smoothly, product characteristics can be stabilized, and workability can be improved is extremely effective industrially.

[Brief explanation of drawings]

FIG. 1 is a schematic view of an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is an enlarged view of the main parts thereof. 1...Feeding reel, 4...Heating tank, 8...
Expanded diameter part, 12... Cooling sizing part, 13, 13
a...tube, 14, 15...first and second decompression chambers, 22...cooling tank, 25...winding section.

Claims (1)

[Claims] 1. A thermoplastic tube under heat softening from one side,
Cooling sizing, in which the inlet side of the tube is an unexpanded diameter tube, and the intake side is sealed with an expanded diameter tube, and the casing is equipped with an appropriate pressure reduction means, and the outer periphery of the expanded tube is inscribed and cooled. The tube is introduced into the enlarged diameter part of the tube, which reduces the pressure on the outside of the tube, and the diameter of the tube is continuously enlarged due to the pressure difference between the inside and outside.The diameter of the tube is then cooled in the cooling sizing part. In the method of manufacturing a heat-shrinkable tube that is fixed and pulled to the other side, when the enlarged diameter tube is inscribed in the cooling sizing part within the casing, two decompression chambers are formed before and after the sizing part. The tube diameter is expanded by expanding the casing, providing separate decompression means in both decompression chambers, and setting the degree of decompression in the decompression chamber on the withdrawal side to be equal to or higher than that on the introduction side. A method for producing a characteristic heat-shrinkable tube. 2. The method for manufacturing a heat-shrinkable tube according to the preceding item 1, wherein the diameter of the tube is expanded by slightly expanding the diameter of the cooling sizing portion in the tube withdrawal direction.