JPH0547387B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a heating mandrel that uses a heat pipe to achieve rapid uniform heating and rapid cooling from a heated state, and a heating mandrel that uses this heating mandrel to heat the The present invention relates to a method for manufacturing a shrink tube.

Conventional technology Conventional heating mandrels used in the processing of synthetic resin products are made by forming a metal rod of iron, aluminum, copper alloy, etc. with excellent thermal conductivity to a predetermined outer diameter, and then heating it in a constant temperature bath. Either by heating the mandrel inside the mandrel, or by providing a heating means such as an electric heater at one end of the mandrel, and heating the one end with the electric heater etc. as necessary for heating, and transmitting the heat to the other end, the entire mandrel is heated. It was common to heat the

Problems to be Solved by the Invention However, in the case of the conventional heating mandrel described above, due to its large overall heat capacity, it takes a long time to heat it uniformly by placing it in a thermostatic oven. When heating one end of the mandrel with an electric heater, even if a material such as copper with high thermal conductivity is used, it takes a long time for the heat to be transferred to the entire mandrel and the entire length of the mandrel is heated. There is a drawback that the temperature distribution in the longitudinal direction tends to be non-uniform, such as when the temperature at the distal end side away from the electric heater becomes lower than the temperature at the proximal end side close to the electric heater, resulting in a temperature gradient. In addition, the temperature difference between the base end and the tip of this heating mandrel increases in proportion to the length of the heating mandrel, so the temperature may vary depending on the processing content performed using this heating mandrel. In order to keep the difference within an acceptable range, it was necessary to shorten the overall length of the mandrel to reduce the temperature difference between both ends.

In addition, in the case of the conventional heating mandrel, it not only takes time to heat the entire body above a certain temperature, but also has a large heat capacity, so it is necessary to quickly cool it down from a heated state. For example, when a thermoplastic resin product is heated and molded using this mandrel, the molded product is cooled to solidify.
Conventional mandrels have had the problem that once they are heated, they do not cool down easily and take a long time to cool down.

In addition, when manufacturing a semiconductive heat shrinkable tube used for shielding the conductor connection part of a plastic insulated power cable, for example, the heat shrinkable tube is placed on the cable core in advance during the connection work. After the conductor is connected, it is moved onto the connection part and heat-shrinked. However, a high shrinkage rate is required to bring the large-diameter conductor connection part and the small-diameter conductor part into close contact with each other. this is,
If the semiconductive heat-shrinkable tube does not completely adhere to the conductor portion when it is heat-shrinked, corona discharge may occur, so it is necessary to increase the shrinkage rate of the semiconductive heat-shrinkable tube. However, since the material of the semiconductive heat-shrinkable tube contains a large amount of conductive substances such as carbon powder and other fillers, it is necessary to increase the stretching ratio when forming it into a film and stretching it after crosslinking. It was difficult to do so.

Therefore, the present applicant has already filed an application for a method for producing a semiconductive heat-shrinkable tube with a high shrinkage rate (Japanese Patent Laid-Open No. 62-281714). This manufacturing method is
A resin compound mixed with a conductive substance is formed into a film, and this film is cross-linked and stretched to form a stretched film.The stretched film is then wrapped multiple times around a mandrel, heated above the melting point of the film, and melted and integrated. This product is made into a cylindrical body, which is subjected to secondary stretching by expanding its diameter under heating, and then cooled in the secondary stretched state to produce a semiconductive heat-shrinkable tube with a high shrinkage rate. It is.

However, in this conventional method of manufacturing a semiconductive heat-shrinkable tube with a high shrinkage rate, in order to wrap and heat the primary stretched film multiple times, a conventional heating processing mandrel, that is, a solid metal rod, is used. Because of this, it takes time for heat to be transferred to the entire length of the mandrel, and the temperature at the distal end of the mandrel, which is far from the heated part, is lower than that at the proximal end of the mandrel, which is directly heated. Because it cannot be heated evenly and there is a temperature difference between the base and tip, the mandrel cannot be made very long, and as a result, the length of the heat-shrinkable tube that can be processed at one time is limited.
The problem was that it was limited to short lengths of about 2 meters or less, resulting in low productivity and high costs. Furthermore, since a mandrel, which is a solid metal rod, is used, there is a problem in that it takes time to cool down the heated mandrel. Therefore,
Conventionally, a cylindrical body is wound around a mandrel, heated and melted into one body, and then removed from the mandrel, reinstalled on the diameter expansion jig, and then expanded in diameter under heating and subjected to secondary stretching. Ta. Therefore, it takes time and effort to remove the cylindrical body from the mandrel and attach it to the diameter expanding jig, which poses problems in terms of workability and productivity.

The present invention was made against the above-mentioned technical background, and includes a heat pipe type heating mandrel that enables rapid uniform heating and rapid cooling, and can have a longer overall length; The purpose of the present invention is to provide a method for manufacturing a heat-shrinkable tube that utilizes the characteristics of the heat-shrinkable tube.

Means for solving the problem Claim 1 as a means for solving the above problem
The described heat pipe type heating mandrel has a heat pipe function by enclosing a condensable working fluid inside a sealed metal pipe having a predetermined outer diameter while exhausting non-condensable gas. A metal pipe is characterized in that a processed part is provided in a predetermined range of the middle part of the metal pipe to coat the outer periphery of the material to be heated, and a heating part and a cooling part are provided at the ends of the sealed metal pipe other than the processed part. There is.

Further, the heat pipe type heating mandrel according to claim 2 is provided with clampers provided at both ends of the processed portion of the hermetically sealed metal pipe for fixing the heated material adhered to the outer periphery of the processed portion in an airtight state; It is characterized by providing a ventilation path for supplying gas under pressure between the sealed metal pipe and the material to be heated.

Furthermore, the method for manufacturing a heat-shrinkable tube according to claim 3 includes wrapping a primarily stretched resin film in multiple layers around the outer periphery of the heat pipe type heating mandrel according to claim 1 or 2; is heated above the melting point by applying heat to the heating part of the heat pipe type heating mandrel, and is melted and integrated to form a cylindrical body, and then this cylindrical body and the heat pipe are heated under heating. Gas is forced into the space between the cylindrical heating mandrel and the cylindrical body to expand it, and the cylindrical body is stretched for a second time, and when the cylindrical body is expanded to a predetermined diameter, heat is removed from the cooling section and the cylindrical body is cooled. This method is characterized in that a heat-shrinkable tube having a desired diameter and a high elongation ratio can be obtained.

Function: In the heat pipe type heating mandrel according to claim 1, during heating, the mandrel is set so that the heating part side is lower, and the heating part is heated by a heating means such as an electric heater. In the heated mandrel, the heating part becomes the evaporation part of the heat pipe, and the working fluid sealed inside is heated and evaporated.
The vapor of this working fluid moves inside the mandrel, and the processed part excluding the heated part of the entire length of the mandrel becomes a condensation part, and the latent heat of vaporization is released within the mandrel. and is rapidly heated to a uniform temperature. As a result, the material to be heated attached to the outer periphery of the processing portion is heated uniformly in a short time. Further, the vapor of the working fluid that has radiated heat condenses and returns to the liquid phase working fluid, and is returned to the heating section by the capillary action or the action of gravity and is heated again.

In addition, when cooling a heated mandrel, set the mandrel so that the cooling part side is higher, and then cool it by cooling means such as blowing cold air on the cooling part with a blower, so that the cooling part acts as a condensing part. However, the heat from the high-temperature processing area is transported by the vapor of the working fluid and transferred to the condensing section where it is radiated and rapidly cooled, and the heated material attached to the outer periphery of the processing area is also cooled in a short time. .

In addition, the heat pipe type heating mandrel according to claim 2 is provided by fixing both ends of the material to be heated, which is attached to the outer periphery of the processing section, with clampers provided at both ends of the processing section. Thermal contraction of the material to be heated is prevented, and when gas is pressurized between the material to be heated and the mandrel through the ventilation passage in a heated state, the material to be heated expands.

Furthermore, by adopting the method for manufacturing a heat-shrinkable tube according to claim 3, the heat pipe type heating mandrel can be heated uniformly over the entire length of the mandrel in a short period of time during heating, and similarly rapidly cooled during cooling. be done. Moreover, the total length of the mandrel, which is capable of uniform heating, rapid heating, and rapid cooling, is long enough to allow the vapor of the heated and evaporated working fluid to condense and return to the evaporator, although it depends on the posture of the mandrel during use. This greatly increases the length of heat-shrinkable tubes that can be manufactured.

In addition, when the primary stretched resin film is wrapped multiple times around the outer periphery of the mandrel and heated, the entire mandrel is uniformly heated in a short time, heated above the melting point and integrated, and is heated with a relatively low shrinkage rate. It becomes a cylindrical body which is a contraction tube. Next, when a fluid such as air is forced between this cylindrical body and the surface of the mandrel, the heated cylindrical body swells.
The diameter is expanded and secondarily stretched, and when the diameter is expanded to a predetermined diameter dimension, it is cooled and the expanded diameter state is fixed, thereby obtaining a secondarily stretched heat-shrinkable tube with a high shrinkage rate.

EXAMPLES Hereinafter, the heat pipe type heating mandrel of the present invention and the method for manufacturing a heat shrinkable tube using this heat pipe type heating mandrel will be described.
This will be explained based on FIGS. 6 to 6.

FIGS. 1 and 2 show an example of a heat shrink tube manufacturing apparatus using a heat pipe type heating mandrel of the present invention. A pipe-type mandrel 2 is detachably attached to the outer periphery of the mandrel 2 with a predetermined space, and when a cylindrical body in which a primary stretched film tape is melted and integrated is expanded and subjected to secondary stretching, It has a cylindrical expansion restriction pipe 3 that restricts expansion to a predetermined outer diameter.

The mandrel 2 is constructed by providing a container 4 (not shown) on the inner surface of a metal pipe made of copper or copper alloy with excellent thermal conductivity, and sealing only a condensable working fluid inside the container 4 to generate heat. It has the function of a pipe, and both ends of the container 4 are formed into a small diameter by constricting the outer diameter, and one end formed with this small diameter (the left end in Fig. 1) is used to heat the mandrel 2. The mandrel 2 has a heating/cooling part 5 that is heated at times and cooled when the heated mandrel 2 is cooled.The central part of the mandrel 2 is formed with a processed part 6 of a constant outer diameter. The end opposite to the cooling unit 5 (the first
An air inlet 7 equipped with a connector for connecting an air hose (not shown) from an air compressor or the like (not shown) is provided at the right end in the figure.
This air blowing port 7 has one end opened in the end face of the mandrel 2 and the other end opened in the surface of the processed portion 6, communicating with the mutually communicating ventilation passage 7a, and blows air to the outer periphery of the mandrel 2. (See Figure 2).

Further, a high frequency induction coil 9 connected to a high frequency power source 8 is detachably attached to the heating/cooling section 5 of the mandrel 2, and when heating the mandrel 2, the high frequency induction coil 9 is energized. The heating/cooling section 5 is heated by induction. Further, when cooling the mandrel 2, a blower 10 is installed in the heating/cooling section 5 exposed by removing the high frequency induction coil 9.
Cooling is performed by blowing cold air (see Figures 4 and 7). In addition, the total length of the mandrel 2 can be increased within a range that does not impair the isothermal properties, but when considering handling and workability,
For example, about 5 m is preferable.

On the other hand, the expansion regulating pipe 3 is a transparent resin pipe such as polycarbonate that has excellent mechanical strength and heat resistance, and its inner diameter matches the outer diameter of the semiconductive heat-shrinkable tube when completed. A large number of small diameter air vent holes 11 are formed through the surface. The expansion regulating pipe 3 is supported by ring-shaped clampers 12, 12 that are attached to engage with stepped portions near both ends formed in a small diameter of the mandrel 2, and is concentric with the outer periphery of the mandrel 2. It is installed in the shape. Further, each clamper 12 is connected to each fastening fitting 13 that is fitted and attached to the outer periphery of the small diameter portion at both ends of the mandrel 2.
By adjusting the adjustment bolt 14 of this fastening fitting 13, the mandrel 2
It moves forward and backward in the axial direction. Furthermore, expansion guide tapered concave surfaces 15 are formed in the shape of a mortar on the opposing surfaces of both the clampers 12, 12, respectively.

In addition, the reference numeral 16 in the figure is a tape of the primary stretched film, 16' is a cylindrical body made by melting and integrating the tape of the primary stretched film, 16'' is a heat-shrinkable tube made by secondarily stretching the cylindrical body, and 17 is a polyester film holding tape that has low elongation when heated and prevents sagging of the primary stretched film when heated.

By configuring as above, the manufacturing apparatus 1
At the time of heating, the mandrel is set so that the side of the heating/cooling section 5 is lowered, and then when the high frequency induction coil 9 is energized to heat the heating/cooling section 5, this heating/cooling section 5 becomes the evaporation section of the heat pipe. Therefore, the entire processing section 6 becomes a condensing section, and the latent heat of vaporization is released within this processing section 6. Therefore, due to this heat dissipation, the processed portion 6 is rapidly heated to a uniform temperature over its entire length.

In addition, when cooling the heated mandrel 2, the mandrel 2 is set so that the side of the heating/cooling part 5 is higher, and a blower 10 is installed in the heating/cooling part 5.
When cold air is blown, the heating/cooling section 5 acts as a condensing section, and the heat of the high-temperature processing section 5 is transferred to the vapor of the working fluid and transferred to the condensing section, where the heat is radiated, and the entire processing section 6 is heated. Cools quickly.

On the other hand, an example of manufacturing a semiconductive heat-shrinkable tube by a method for manufacturing a heat-shrinkable tube using the manufacturing apparatus 1 configured as described above will be described with reference to FIGS. 3 to 7. explain. The semiconductive heat-shrinkable tube is made of thermoplastic resins such as polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer, and silicone resin as the base polymer. conductive carbon powder is added to give it semiconductivity. In addition, fillers such as calcium carbonate and aluminum hydroxide, stabilizers, crosslinking agents such as peroxides, crosslinking aids, etc. are used as a resin compound. Then, this resin compound is extruded into a film using an extruder and then crosslinked. In addition to the above, the film may be formed by inflation molding, calender molding, or the like. Additionally, for crosslinking, an organic peroxide such as dicumyl peroxide is added to the resin formulation.
A method of crosslinking during extrusion molding, a method of crosslinking by irradiating the film with an electron beam after molding, etc. can also be used.

Then, the crosslinked film is heated at a temperature above the glass transition point and below the melting point, and uniaxially stretched as far as possible in the longitudinal direction without cutting to perform primary stretching, and after cooling, it is slitted into a predetermined shape. It is processed into a primary stretched tape 16 having a wide width.

The semiconductive heat shrinkable tube is manufactured using manufacturing equipment 1.
After removing the expansion regulating pipe 3, a primary stretched tape 16 made of a semiconductive film that has been primarily stretched to a predetermined width is placed around the outer periphery of the processed portion 6 of the heat pipe type heating mandrel 2 in a predetermined width. Wrap multiple times until the thickness is . At this time, in order to obtain a uniform thickness, for example, by wrapping the primary stretched tape 16 in a 1/2 wrap, any errors in the thickness of the primary stretched tape 16 are averaged out, and the thickness in the circumferential direction is also uniform. It can be wrapped around. Furthermore, a presser tape 17 is wrapped around the outer side of the primary stretched tape 16 which has been wrapped multiple times and pressed by 1/2, and this presser tape 17 suppresses foaming during heating. After preventing the stretched tape 16 from sagging when heated, the mandrel 2 is set so that its heating/cooling section 5 side is tilted downward, and the high frequency induction coil 9 attached to the outer periphery of the heating/cooling section 5 is energized. , the heating/cooling section 5 is heated by induction (see FIG. 3).

When the heating/cooling section 5 is heated, the mandrel 2
Since it has the function of a heat pipe, this heating/cooling part 5 serves as the evaporation part of the heat pipe, and the entire processed part 6 of the mandrel 2, that is, the primary stretching tape 16 is wrapped around it. The entire part becomes a condensation part. Therefore, the condensable working fluid sealed in the mandrel 2 is heated and evaporated in the lower heating/cooling section 5, rises as working fluid vapor, and becomes the condensing section of the mandrel 2. The latent heat of vaporization that has been transported is released throughout the processing section 6. The heat dissipated at this time uniformly heats the processed portion 6 of the mandrel 2. In addition, the vapor of the working fluid that has radiated heat condenses and returns to the liquid phase working fluid, which descends due to the capillary action of the wick provided on the inner surface of the mandrel 2 and the action of gravity.
The process of refluxing to the lower heating/cooling section 5, heating and evaporation is repeated, and the entire mandrel 2 is heated uniformly in a short period of time.

When the processed portion 6 of the mandrel 2 is heated to a temperature higher than the melting point of the primary stretched tape 16, the multiple rolled primary stretched tapes 16 are melted and integrated into a cylindrical body 16 with a uniform thickness. '. Since this cylindrical body 16' remains primarily stretched in a film state, its shrinkage rate upon heating is still small.

Once the cylindrical body 16' has been formed, the mandrel 2 is tilted in the opposite direction so that the side of the heating/cooling part 5 is higher, and then the high frequency induction coil 9 is removed and a blower is installed in the exposed heating/cooling part 5. Cool air is blown from 10 to cool the mandrel 2. When the heating/cooling section 5 is cooled by cold air, this heating/cooling section becomes a condensing section of the heat pipe, and the entire processed section 6 of the mandrel 2, which is at a higher temperature, becomes an evaporating section.
Therefore, the vapor of the working fluid that is heated and evaporated in the processing section 6 on which the cylindrical body 16' of the mandrel 2 is attached rises, radiates heat in the upper heating/cooling section 5, and condenses. The working fluid returns to a liquid phase, descends due to the capillary action of the liquid and the action of gravity, and is repeatedly heated and evaporated in the entire area of the high-temperature processing section 6, thereby rapidly cooling the entire mandrel 2. (See Figure 4).

When the mandrel 2 is cooled to a predetermined temperature and the cylindrical body 16' attached to the outer periphery of the processing section 6 has hardened to some extent, the presser tape 17 holding down the outer periphery of the cylindrical body 16' is removed. After leaving, the cylindrical body 16' is subjected to a secondary stretching process.

In the secondary stretching process of the cylindrical body 16', first, the holding tape 17 is removed and the cylindrical body 1 is stretched around the outer periphery of the processing section 6.
An expansion regulating pipe 3 is attached to the outer periphery of the mandrel 2, to which only the mandrel 6' is attached. At this time, a ring-shaped clamper 12 disposed concentrically with respect to the mandrel 2 is attached to each fastening fitting 1 of the expansion regulating pipe 3.
By pushing with the adjusting bolt 14 of No. 3, the cylindrical body 16' is compressed between the stepped portion of the small diameter portion of the mandrel 2 and the clamper 12, and both ends of the cylindrical body 16' are made airtight. Seal it. After that, the mandrel 2 is tilted and set so that the side of the heating/cooling part 5 is lowered, the high frequency induction coil 9 is attached to the heating/cooling part 5, and the processing part 5 of the mandrel 2 is heated by applying electricity (the fifth (see figure).

The heat pipe functions to uniformly heat the processed part 6 of the mandrel 2 in a short time, and when the cylindrical body 16' attached to the outer periphery of this processed part 6 is heated to a predetermined temperature and softened, this cylindrical Air is injected between the body 16' and the outer peripheral surface of the mandrel 2 to expand the softened cylindrical body 16'. Air from an air compressor or the like is blown in from an air inlet 7 provided at the end of the mandrel 2 opposite to the heating/cooling section 5, and is sent through an air passage 7a formed in the mandrel 2. Then, when air is pressurized between it and the outer peripheral surface of the mandrel 2, the cylindrical body 16' inflates.
At this time, the air in the expansion restriction pipe 3 is discharged through the air vent holes 11 formed in large numbers, so that the cylindrical body 16' comes into contact with the inner surface of the expansion restriction pipe 3 until the expansion is restricted. It is smoothly expanded and secondly stretched, and is formed into a predetermined outer diameter by coming into contact with the inner surface of the expansion restriction pipe 3 to restrict expansion. In addition, when the cylindrical body 16' expands, since the concave concave surfaces 15 for expansion guides are formed on the opposing surfaces of the clampers 12, 12 at both ends, both ends of the cylindrical body 16' expand. The expansion ratio in the vicinity gradually increases, and rupture of the cylindrical body 16' due to sudden expansion to a large diameter is prevented.
(See Figure 6).

After the cylindrical body 16' is expanded to a predetermined outer diameter through secondary stretching, the cylindrical body 16' is cooled while maintaining the supplied air at a constant pressure to harden the cylindrical body 16'.

Cooling is carried out by setting the mandrel 2 equipped with the expansion regulating pipe 3 so that the side of the heating/cooling part 5 is tilted upward, and then removing the high frequency induction coil 9 and applying the air flow from the blower 10 to the exposed heating/cooling part 5. This is done by blowing cold air (see Figure 7).

As the heat pipe functions and the mandrel 2 is cooled in a short time, the expanded cylindrical body 16'
The tube is cooled and hardened while being expanded to a predetermined outer diameter, and a heat-shrinkable tube 16'' with a high shrinkage rate is produced by secondary stretching.

After the heat-shrinkable tube 16'' has been sufficiently cooled and hardened, the expansion regulating pipe 3 is removed, and the portions in contact with the clamper 12 at both ends are cut off. The product is then cut to an appropriate length and used.In addition, in this example, a transparent polycarbonate pipe was used as the expansion regulating pipe 3, so the processing status at each stage can be checked from the outside. can.

In addition, although this example describes a case in which it is applied to a method for manufacturing a semiconductive heat-shrinkable tube, it can be similarly applied to other general methods for manufacturing a heat-shrinkable tube that do not contain a conductive substance. can.

Furthermore, in each embodiment, a case has been described in which a heating/cooling section 5 serving as both a heating section and a cooling section is provided at one end of the mandrel 2 for heat pipe heating. It is also possible to provide a manufacturing mandrel with a cooling section at the end.

Effects of the Invention As explained above, the heat pipe type heating mandrel of the present invention has a heat pipe function by sealing only a condensable working fluid inside the metal pipe mandrel. Since a heating section and a cooling section are provided at the ends of the mandrel, the long mandrel can be heated uniformly and rapidly over its entire length, and
A heated mandrel can be rapidly cooled in a short period of time.

Further, a method for manufacturing a heat shrink tube using the heat pipe type heating mandrel of the present invention includes 1
Next, the stretched film is wrapped multiple times around the outer periphery of a metal pipe mandrel that has a heat pipe function, and the metal pipe mandrel is heated to fuse and integrate the multiple wound film into a cylindrical body. After that, a fluid such as air is injected between the cylindrical body and the metal pipe mandrel under heating to cause the cylindrical body to be stretched for a second time to expand its diameter. By cooling the expanded diameter tube, a tube with a desired diameter and high elongation ratio is manufactured, so the mandrel functions as a heat pipe, making it possible to lengthen the mandrel. It becomes possible to uniformly heat the mandrel, and it is possible to manufacture a long, high-quality heat-shrinkable tube with a high shrinkage rate in the radial direction. In addition, the heat pipe function enables rapid heating and rapid cooling of long mandrels, which has the effect of improving productivity and significantly reducing costs.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment in which the heat pipe type heating mandrel of the present invention is applied to a heat-shrinkable tube manufacturing apparatus. Figure 1 is a half-sectional view of the manufacturing apparatus, and Figure 2 is a An enlarged view of the main parts in Fig. 1 and Figs. 3 to 7 show an embodiment of the method for manufacturing a heat-shrinkable tube of the present invention, and Fig. 3 shows heating a mandrel wrapped with a primary stretching tape. Figure 4 is a diagram showing the process of cooling the mandrel on which the cylindrical body has been formed, Figure 5 is a diagram showing the process of installing an expansion regulating pipe, and Figure 6 is a diagram showing the process of expanding the cylindrical body. FIG. 7 is a diagram showing a process of performing secondary stretching by cooling the tube to obtain a heat-shrinkable tube with a high shrinkage rate. DESCRIPTION OF SYMBOLS 1... Manufacturing equipment, 2... Heat pipe type mandrel, 3... Expansion regulating pipe, 5... Heating/cooling section, 7... Pressurized air inlet, 7a... Ventilation path, 9... High frequency induction coil, 10...Blower,
11... Air vent hole, 12... Clamper, 13...
...Fastening metal fitting, 15...Tapered concave surface for expansion guide,
16...Primary stretched tape, 16'...Cylindrical body, 1
6″...Heat shrink tube.

Claims (1)

[Claims] 1. A heat pipe function is provided by sealing a condensable working fluid inside a sealed metal pipe having a predetermined outer diameter with non-condensable gas exhausted, and the sealed metal pipe is provided with a heat pipe function. A heat pipe characterized in that a processed part is provided in a predetermined range of the intermediate part to which a material to be heated is applied on the outer periphery, and a heating part and a cooling part are provided on the end side of the closed metal pipe other than the processed part. Mandrel for formula heating. 2 Clampers are provided at both ends of the processed portion of the sealed metal pipe to fix the heated material attached to the outer periphery of the processed portion into an airtight body, and a gas is provided between the sealed metal pipe and the heated material. 2. The heat pipe type heating mandrel according to claim 1, further comprising an air passage for supplying the heat pipe under pressure. 3. By wrapping a primarily stretched resin film multiple times around the outer periphery of the heat pipe type heating mandrel, and heating the multiple wrapped resin film by applying heat to the heating part of the heat pipe type heating mandrel. After heating above the melting point and melting and integrating to form a cylindrical body, gas is pressurized between the cylindrical body and the heat pipe type heating mandrel under heating to expand the cylindrical body. A heat-shrinkable tube having a desired diameter and a high stretching ratio is obtained by performing secondary stretching and cooling the cylindrical body by removing heat from the cooling section in a state where the diameter is expanded to a predetermined thickness. A method for manufacturing a heat shrink tube using the heat pipe type heating mandrel according to claim 1 or 2.