JPH0516234A - Manufacture of heat-shrinkable tube - Google Patents

Abstract

PURPOSE:To manufacture a heat-shrinkable tube having a high shrinkage factor and excellent in fusion properties by secondarily stretching a stretched tape to integrally fuse the same to an extrusion molded tube having a smooth surface in a non-crosslinked state. CONSTITUTION:A stretched tape W1 composed of a thermoplastic resin subjected to stretching processing after crosslinking is wound around the outer periphery of a heating mandrel 12 to be covered with a non-crosslinked extrusion molded tube W2 and thereafter the heating mandrel 12 is raised in temp. to soften the molded tube W2. At this point of time, a press tape T low in thermal elongation is wound around the extrusion molded tube W2 and the heating mandrel 12 is raised in temp. to integrally fuse the stretched tape W1 and the extrusion molded tube W2 in a molten state to form a cylindrical body W3. After the cylindrical body W3 is once cooled, the press tape T is removed and the heating mandrel 12 is again raised in temp. to heat the cylindrical body W3 to its melting temp. to expand the diameter thereof so as to obtain a predetermined diameter dimension.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a heat-shrinkable tube having a high shrinkage rate and a high fusion property.

[0002]

2. Description of the Related Art Rubber / plastic insulated cable 1 is
In general, as shown in the cross section of FIG. 7, an inner conductive layer 3, an insulator 4, and an outer conductive layer 5 are sequentially formed concentrically outside the central conductor 2. In such a rubber / plastic insulated cable 1, when laying a long line, the cable length is limited in terms of manufacturing, transportation, and laying. Therefore, it is necessary to connect the cables on site.

As shown in FIG. 8, the cables are connected to each other at this site. As shown in FIG. 8, the coatings on the ends of the cables 1 and 1 to be connected are removed to expose the conductors 2, and the ends of the cables are abutted against each other. After the conductor connecting sleeve 6 is put on the outer circumferences of both conductors 2 in this state, an inner conducting semi-conductive tube 7 which replaces the inner semi-conducting layer 3 is put on the outer side of the conductor connecting sleeve 6, and Insulating tape made of uncrosslinked thermoplastic resin is wound around the outside in multiple layers, and the cable 1
1. An insulating layer 8 which replaces the insulator 4 is formed, and an outer conducting semiconductive tube 9 which replaces the external semiconducting layer 5 is covered on the outer side of the insulating layer 8. The inner conductive semi-conductive tube 7 and the outer conductive semi-conductive tube 9 are preliminarily covered on the outer circumference of one cable 1 at the time of cable connection, and after the conductor connection sleeve 6 is attached, the conductor After the insulating layer 8 is formed, the outer conductive semi-conductive tube 9 is moved to the outside of the connection sleeve 6 and contracted to be closely attached to the outer periphery. Close to the outer circumference.

Therefore, in many cases, the inner conductive semi-conductive tube 7 is a heat-shrinkable tube in order to be closely attached to the outer side of the conductor connecting sleeve 6, and the inner conductive semi-conductive tube 7 is Insulating layer 8 formed on the outside
It is necessary to prevent dust and foreign matter from entering the interface with and to fuse the interface so that protrusions, peeling, or voids (air bubbles) are not formed, and to prevent the occurrence of electric field irregularities.
Similarly, the outer conductive semi-conductive tube 9 needs to be fused at the interface with the insulating layer 8 so that dust or foreign matter is not mixed in, peeled off, or voids are generated. Therefore, the inner conductive semi-conductive tube 7 is a heat-shrinkable tube having a high shrinkage ratio, and the outer peripheral surface in contact with the insulating layer 8 is smooth and the insulating layer 8 is
And need to be easily fused. Similarly, the outer conductive semi-conductive tube 9 is a heat-shrinkable tube having a high shrinkage ratio,
In addition, it is necessary that the inner peripheral surface in contact with the insulating layer 8 be smooth and be easily fused with the insulating layer 8.

[0005]

The semiconductive heat-shrinkable tube is made of a thermoplastic resin such as polyethylene or ethylene-ethyl acrylate copolymer as a base polymer, and a resin compound containing conductive carbon powder or the like. Is extruded into a tube having a predetermined wall thickness. Then, this semiconductive tube is manufactured by irradiating with an electron beam, for example, to crosslink it, and then expanding the diameter while heating it to the melting temperature, and the expansion ratio at this time is almost equal to the heat shrinkage ratio. Become.
However, since the extruded semi-conductive tube contains a large amount of conductive carbon powder etc., the elongation performance in the heated state is reduced and the tube has uneven wall thickness, so the diameter is being expanded. However, there is a problem that the tube cannot be made a heat-shrinkable tube having a high shrinkage rate even though the tube is easily damaged and the diameter cannot be expanded so much and thus the surface is smooth. Further, since the semiconductive tube is used after being electronically crosslinked, there is a problem in that the fusion degree with the insulating layer is poor when the degree of crosslinking is high.

Therefore, as a method for producing a high-contraction shrinkage semi-conductive heat-shrinkable tube, a resin compound containing conductive carbon powder and other fillers is extruded into a sheet,
This sheet is irradiated with, for example, an electron beam to be crosslinked, and then the sheet is cut into a tape having a predetermined width and is primarily stretched, and the primary stretched stretching tape is wound around the outer periphery of the heating mandrel in multiple layers. A cylindrical body is formed by heating and fusing the layers of the stretched tape together, and this cylinder is heated and the diameter is expanded (secondarily stretched) to obtain a semi-conducting heat-shrinkable tube with a high shrinkage ratio. The way is done.

However, in the method of manufacturing a semi-conductive heat-shrinkable tube using this stretched tape, the wall thickness can be equalized and a high shrinkage ratio can be obtained, but since the stretched tape is wound in a lap, unevenness is caused on the surface. However, there is a problem in that voids and peeling are likely to occur when fused to the insulating layer. Further, since the stretched tape has a high degree of cross-linking because it is used after being subjected to electronic cross-linking and then primary stretching, there is a problem in that the fusion property with the insulating layer is low.

The present invention has been made in view of the above circumstances, and has a high shrinkage ratio, at least one of the inner peripheral surface and the outer peripheral surface is smooth, and is a heat-shrinkable tube easily fused to an insulating layer. It is intended to provide a way.

[0009]

Means for Solving the Problems As a means for solving the above problems, the method of the first invention is such that a stretching tape of a thermoplastic resin, which has been stretched after crosslinking, is laid on the outer periphery of a heating mandrel. And then wound on the outside, covered with an uncrosslinked extruded tube made of the same material as the stretched tape, the temperature of the heating mandrel is raised, when the extruded tube is heated and softened, the extruded Wrap a holding tape with little thermal expansion around the outside of the forming tube, further raise the temperature of the heating mandrel to heat the stretched tape and the extruded forming tube to the melting temperature and fuse them together to form a cylindrical body and then cool. Then, after removing the pressing tape, the heating mandrel is heated again to heat the integrated cylindrical body to a melting temperature to expand the diameter to a predetermined size. To have.

In a second aspect of the invention, the outer periphery of the heating mandrel is covered with an uncrosslinked extruded tube of thermoplastic resin, and the heating mandrel is heated to soften the extruded tube. At this point, the outside is wrapped with a stretched tape that has been stretched after cross-linking, and the outside is wrapped with a holding tape with little heat expansion, and then the heating mandrel is further heated to raise the stretched tape and extrusion molding. After heating the tube to the melting temperature and fusing it integrally to form a cylindrical body, it is once cooled, after removing the holding tape, the heating mandrel is heated again to melt the integrated cylindrical body at the melting temperature. It is characterized by heating up to and expanding the diameter to a predetermined size.

[0011]

As described above, according to the first aspect of the present invention, the thermoplastic mandrel stretched tape is wound around the outer periphery of the heating mandrel and the outer circumference thereof is made of the same material as the stretched tape. After covering the uncrosslinked extruded tube, the temperature of the heating mandrel is raised, and when the extruded tube is heated and softened, a pressing tape with little thermal elongation is wrapped around the outside of the extruded tube and heated. When sagging is prevented and the temperature of the heating mandrel is further raised, the stretched tape and the extruded tube are melted and fused together to form a cylindrical body. After cooling this cylinder once, after removing the holding tape wound on the outside, the heating mandrel is heated again to heat the cylinder to the melting temperature and expand it to a predetermined size, The inner peripheral part of the has a large shrinkage ratio because the stretched tape is secondarily stretched, and the outer peripheral part of the cylindrical body to be fused to the insulator is smooth because it is formed by an extrusion molded tube and is not cross-linked. Therefore, it is easily fused.

In the second aspect of the invention, the outer periphery of the heating mandrel is covered with an uncrosslinked extruded tube of thermoplastic resin, and the heating mandrel is heated to soften the extruded tube by heating. At this point, on the outside, wrap a stretched tape that has been stretched after cross-linking and wrap a holding tape with little heat expansion around the outside to prevent heating sag, and then raise the heating mandrel further. Then, the drawn tape and the extruded tube are heated to a melting temperature to be fused and integrally formed into a cylindrical body, which is once cooled, and after the holding tape is removed, the heating mandrel is heated again to be integrated. When the cylindrical body thus heated is heated to a melting temperature and expanded to a predetermined size, the outer peripheral portion of the cylindrical body has a large shrinkage ratio because the stretched tape is secondarily stretched, and is fused to the insulator. That the inner peripheral portion of the cylindrical body, with a smooth because it is formed by extrusion tube, fused because uncrosslinked easily.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the method of the present invention is applied to the production of a semiconductive heat shrinkable tube used for coating a cable connecting portion will be described below with reference to FIGS.

FIG. 1 shows an example of an apparatus for producing a heat-shrinkable tube using a heat pipe type heating mandrel used for carrying out the method of the present invention.
Reference numeral 1 denotes a heating mandrel 12 on the outer side of which a material tube or the like is covered, and a detachable mount on the outer periphery of the heating mandrel 12 with a predetermined space, to melt and soften the material tube and blow air. At this time, the expansion tube 13 has an expansion restriction pipe 13 that restricts the expansion limit of the material tube so that the material tube has a predetermined outer diameter and prevents adhesion of dust and the like.

The heating mandrel 12 is a container 1 made of a metal pipe such as copper or copper alloy having excellent thermal conductivity.
A wick (not shown) is provided on the inner peripheral surface of 4,
The container 14 has a heat pipe function by enclosing only a condensable working fluid therein. Both ends of the container 14 are formed to have a small outer diameter and one end formed to have this small diameter. The portion (the left end in FIG. 1) is a heating / cooling portion 15 that is heated when the heating mandrel 12 is heated and cooled when it is cooled, and the central portion of the heating mandrel 12 has a constant outer diameter. Processing part 1
6 is formed.

A workpiece W such as a material tube is attached to the processing portion 16 of the heating mandrel 12 with the outer expansion regulating pipe 13 removed. An air blowing port 17 provided with a connector is provided at the end (right end in FIG. 1) of the heating mandrel 12 opposite to the heating / cooling unit 15. One end of this air blowing port 17 is An air passage 17a is formed which communicates with the air blowing port 17 and has the other end opened to the surface of the processed portion 16.

A high frequency coil 18 connected to a high frequency power source is provided in the heating / cooling section 15 of the heating mandrel 12.
When the heating mandrel 12 is heated, the high-frequency coil 18 is energized to induction-heat the heating / cooling unit 15. Further, when cooling the heating mandrel 12, the high-frequency coil 18 is removed and cold air is blown to the exposed heating / cooling section 15 to cool it.

On the other hand, the expansion control pipe 13 is formed of a transparent resin pipe such as polycarbonate having 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-sized air vent holes 19 are formed through the peripheral surface thereof. And
The expansion restricting pipe 13 is supported by ring-shaped clampers 20, 20 mounted so as to engage with the stepped portions of the heating mandrel 12 near the both ends formed in a small diameter, and is concentric with the outer periphery of the heating mandrel 12. It is installed in a shape. Further, on the surfaces of the clampers 20, 20 facing each other,
The expansion guide tapered recesses 20a are each formed in a mortar shape.

Further, the air compressor 2 is installed in the air blowing port 17 provided at the end of the heating mandrel 12.
The end portion of the pipe 22 connected to No. 1 is attached, and the connector 17 is provided at the other end of the ventilation path 17 a having one end opened to the surface of the processing portion 16.

The manufacturing apparatus 11 configured as described above is
When heating, set the heating mandrel 12 so that the heating / cooling unit 15 side becomes lower, and then the high frequency coil 1
When 8 is energized to perform induction heating, the heating / cooling section 15 serves as an evaporation section of the heat pipe, the processing section 16 serves as a condensation section, and the entire processing section 16 is rapidly and uniformly heated. Further, when the heated heating mandrel 12 is cooled, the heating mandrel 12 is set so that the heating / cooling unit 15 side becomes higher, and cold air is blown to the heating / cooling unit 15 to cool the heating / cooling unit 15. 15 serves as a condensing part, and the heat of the high-temperature working part 16 is carried to the vapor of the working fluid and radiated in the condensing part, whereby the entire working part 16 is rapidly cooled.

The material of the semiconductive heat-shrinkable tube W4, that is, the materials of the stretched tape W1 and the extruded tube W2 are as follows: base polymer, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, A thermoplastic resin such as an ethylene-propylene copolymer or a silicone resin is used, to which conductive carbon powder is added in order to impart semiconductivity, and powdery calcium carbonate or aluminum hydroxide is also added. And the like, and a kneaded mixture is used as a resin mixture. Then, a sheet-shaped product of this resin composition is cut into a tape having a predetermined width, cross-linked by electron beam irradiation or the like, and then primary stretched to prepare a stretched tape W1. Further, the resin compound is extruded into a tube having a predetermined wall thickness to prepare an uncrosslinked semiconductive extruded tube W2. Therefore, the drawn tape W1 and the extruded tube W2 thus prepared have a large amount of conductive carbon powder, other fillers, and the like, and thus have low drawability during heating and are easily broken during expansion. .

Next, the case where the method of the first invention is applied to the production of an inner conductive semiconductive heat shrinkable tube used for coating a cable connecting portion will be described with reference to FIGS. 1 to 5. .

When manufacturing the semiconductive heat-shrinkable tube W4 for inner conduction, first, the expansion control pipe 1 of the manufacturing apparatus 11 is manufactured.
A thermoplastic resin drawing tape W1 which is stretched after crosslinking on the outer periphery of the heating mandrel 12 with No. 3 removed.
Is wound in multiple layers, and an uncrosslinked extruded tube W2 made of the same material as the stretched tape is placed on the outer side of the wound tape, and then the heating / cooling section 15 of the heating mandrel 12 is induction-heated by the high-frequency coil 18 The combined cooling unit 15 is heated to become the evaporation unit of the heat pipe, the working fluid enclosed therein is heated and evaporated, and becomes vapor of the working fluid and moves to the processing unit 16 which is the condensation unit of the heat pipe.
The heat transferred as latent heat of vaporization is released. as a result,
Due to the characteristics of the heat pipe, the entire processed portion 16 is uniformly heated, and the drawing tape W1 and the extruded tube W2 that are in close contact with the outer periphery thereof are uniformly heated. Then, when the extruded tube W3 softens, a pressing tape T having a small thermal expansion is wrapped around the extruded tube W3 to heat sag (state of FIG. 2).

After winding the holding tape T, the heating mandrel 12 is further heated to heat the drawing tape W1 and the extruded tube W2 to a melting temperature and fuse them together to form a cylindrical body W3. After that, it is once cooled and the pressing tape T is removed. Then, the expansion regulating pipe 13 is provided outside the heating mandrel 12 with the cylindrical body W3 covered.
Then, both ends of the cylindrical body W3 are clamped by the clampers 20, 20 between the surfaces of the heating mandrel 12 and sealed, and then the heating mandrel 12 is heated again to bring the cylindrical body W3 to the melting temperature. Heat (state of FIG. 3). Then, when the cylindrical body W3 is heated to the melting point, the compressor 21 is started and air is supplied from the air blowing port 17, and the air is press-fitted between the heating mandrel 12 and the cylindrical body W3. Expands. At this time, since the heating mandrel 12 is a heat pipe, the entire cylindrical body W3 is uniformly heated and uniformly softened, and as a result, the diameter can be increased at a high magnification. The air in the expansion control pipe 13 is discharged from the air vent hole 19 as the cylindrical body W3 expands.

When the diameter of the cylindrical body W3 is expanded to reach a predetermined diameter, the cylindrical body W3 comes into contact with the inner surface of the expansion regulating pipe 13 and the further expansion is regulated and held at the predetermined diameter (see FIG. 4). Status). When the cylindrical body W3 is expanded to a predetermined diameter in this way, the high-frequency coil 18 is removed from the heating / cooling unit 15, and the heating / cooling unit 15 side of the manufacturing apparatus 11 is set high again. Cooling air is blown to the combined cooling section 15 by a blower or the like to cool the heating mandrel 12. Therefore, since the heating / cooling unit 15 serves as the condensing unit of the heat pipe and the processing unit 16 serves as the heating unit of the heat pipe, the processing unit 16 and the air around it are rapidly cooled, and as a result, the diameter of the cylindrical body W3 is expanded. It is cooled in the cooled state, and fixed in the expanded state. Therefore, after cooling sufficiently, the air compressor 21 is stopped to stop the air supply, and the expansion regulating pipe 13 is removed. A heat shrinkable tube W4 is obtained (see FIG. 5).

Therefore, the semiconductive heat-shrinkable tube W4 for inner conduction manufactured by the method of the first invention comprises a stretched tape W1 which has been subjected to a primary stretching process after crosslinking and an uncrosslinked layer which is superposed thereon. The extruded tube W2 is heated by the heat pipe type heating mandrel 12 up to the melting point and integrally fused, so that the cylindrical body W3 is expanded by heating to be secondarily stretched. It is possible to make the inner conductive semi-conducting heat-shrinkable tube W4 which can be made large and which has a smooth outer peripheral surface on the side of the extruded tube W2 before fusion bonding and is not cross-linked. Therefore, if this inner conductive semi-conducting heat-shrinkable tube W4 is used for the inner semi-conducting layer for cable connection, it will be used as an insulating layer formed outside the inner conducting semi-conducting heat-shrinkable tube W4. No protrusions are formed at the interface of, and they can be closely fused without generating voids or peeling.

FIG. 5 shows a semiconductive heat-shrinkable tube for outer conduction manufactured by the method of the second invention.
The semiconductive heat-shrinkable tube W5 for external conduction is the first
It is manufactured by using the same manufacturing apparatus 11 as that used in the embodiment of the invention, and the manufacturing process will be described below in order. The material of the semiconductive heat-shrinkable tube W5 for outer conduction, that is, the material of the stretched tape W1 and the extruded tube W2 is polyethylene, ethylene-vinyl acetate copolymer, ethylene, as in the case of the above embodiment. −
A sheet-shaped resin compound prepared by adding conductive carbon powder for imparting semiconductivity and calcium carbonate as an extender to a base polymer of a thermoplastic resin such as ethyl acrylate copolymer is prescribed. After being cut into a tape having a width of 1 mm and further cross-linked by electron beam irradiation or the like, primary drawing is performed to prepare a drawn tape W1. Further, the resin compound is extruded into a tube having a predetermined wall thickness to prepare an uncrosslinked, semiconductive extruded tube W2. Therefore,
Prepared stretched tape W1 and extruded tube W
In No. 2, since a large amount of conductive carbon powder or the like was added, the stretchability during heating was reduced, and it was easy to break during diameter expansion.

Next, the case where the method of the second invention is applied to the production of the semiconductive heat-shrinkable tube for outer conductor used for coating the cable connecting portion will be described.

When manufacturing the semiconductive heat-shrinkable tube W5 for external conduction, first, the expansion control pipe 1 of the manufacturing apparatus 11 is manufactured.
The outer periphery of the heating mandrel 12 with 3 removed is covered with an uncrosslinked extruded tube W2 of thermoplastic resin, and then the heat pipe type heating mandrel 12 is heated to heat the extruded tube. When W2 softens, a stretched tape W1 which has been stretched after cross-linking is overlapped and wound on the outer side of the W2, and a holding tape T with little thermal elongation is further wound on the outer side thereof to prevent heat sag, and then heated. Extruded tube W2 by further heating the mandrel 12
Then, the drawing tape W1 is heated to the melting temperature, fused integrally to form a cylindrical body, and then once cooled, and the holding tape T is removed.

Then, after the expansion regulating pipes 13 are attached to the outside of the heating mandrel 12 with the cylindrical body covered to seal both ends of the cylindrical body, as in the case of the above-mentioned embodiment, the heating mandrel. When the temperature of 12 is raised again and the cylinder is heated to the melting temperature, the compressor 21 is started and air is supplied from the air blowing port 17, so that the cylinder expands. At this time, the entire cylindrical body is uniformly heated and uniformly softened, so that the diameter is expanded at a high magnification. When the diameter of the cylindrical body is expanded to reach a predetermined diameter, the expansion regulating pipe 13
The inner diameter is abutted against the inner surface, and the further expansion of the diameter is restricted and the diameter is maintained at a predetermined value. When the cylindrical body is expanded to a predetermined diameter in this way, the high-frequency coil 18 is removed from the heating / cooling unit 15, and the heating / cooling unit 15 side of the manufacturing apparatus 11 is set high again. Cooling air is blown to the combined cooling section 15 by a blower or the like to cool the heating mandrel 12. Therefore, the cylindrical body is cooled and fixed in the expanded state, and after sufficiently cooling in this state, the air compressor 21 is stopped to stop the air supply and the expansion regulating pipe 13 is removed. As shown in FIG. 6, a semi-conducting heat-shrinkable tube W5 having a high shrinkage ratio and having a high shrinkage ratio for outer conduction is obtained.

In the method of the second aspect of the present invention, a drawn tape W1 which has been subjected to a primary drawing process after crosslinking and an uncrosslinked extruded tube W2 which is superposed on the drawn tape W1 are heated by a heat pipe type heating mandrel 12. The cylindrical body heated to the melting point and integrally fused is subjected to secondary stretching by heating and expanding the diameter, so that the heat shrinkage rate can be increased,
It is possible to manufacture a semi-conductive heat-shrinkable tube W5 for outer conductor which has a smooth inner peripheral surface on the side of the extruded tube W2 and which is not cross-linked. Therefore, if it is used for cable connection, it is formed on the inside. No protrusions are formed between the insulating layer and the insulating layer, and it is possible to perform the tight fusion without generating peeling or voids.

Accordingly, if the extruded tube is formed outside, a heat-shrinkable tube for inner conduction is produced. If the extruded tube is formed inside, a heat-shrinkable tube for outer conduction is produced. it can.

[0033]

As described above, in the method for producing a heat-shrinkable tube of the present invention, the stretched tape is secondarily stretched under the two conditions of high shrinkage and fusion property required for the heat-shrinkable tube. In addition to having a high shrinkage ratio, this stretched tape and the extruded tube with a smooth flat surface were fused together in an uncrosslinked state to maintain the fusion property, so that a high shrinkage ratio and a fusion property were obtained. It is possible to manufacture an excellent heat-shrinkable tube having both of the above.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus used in the method of the present invention.

FIG. 2 is a diagram showing a pressing tape winding step of the method of the present invention.

FIG. 3 is a view showing a heating process of the same.

FIG. 4 is a diagram showing a diameter expanding process.

FIG. 5 is a perspective view of a semiconductive heat-shrinkable tube for inner conduction manufactured by the method of the first invention.

FIG. 6 is a perspective view of a semiconductive heat-shrinkable tube for outer conduction manufactured by the method of the second invention.

FIG. 7 is a cross-sectional view of a rubber / plastic insulated cable.

FIG. 8 is a cross-sectional view of a connecting portion between rubber / plastic insulated cables.

[Explanation of symbols]

11 ... Manufacturing apparatus, 12 ... Heating mandrel, 13 ...
Expansion control pipe, 15 ... Heating / cooling section, 16 ... Processing section, 17 ... Air blowing port, 17a ... Ventilation path, 18
... High frequency coil, 20 ... Clamper, 21 ... Air compressor, 22 ... Piping, T ... Pressing tape, W1 ... Stretching tape, W2 ... Extrusion tube, W3 ... Cylindrical body, W4 ... Semiconductive heat shrinkage for internal conduction Tube, semi-conductive heat shrink tube for outer conduction.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29L 23:22 4F

Claims (2)

[Claims] 1. A stretching tape of a thermoplastic resin, which has been stretched after crosslinking, is wrapped around the outer periphery of a heating mandrel, and an uncrosslinked extruded tube made of the same material as this stretching tape is covered on the outside of the winding tape. After that, the heating mandrel is heated, and at the time when the extruded tube is heated and softened, on the outside of the extruded tube, wrap a holding tape with little thermal expansion, and further raise the heating mandrel. The stretched tape and the extruded molded tube were heated to a melting temperature and fused together to form a cylindrical body, which was once cooled, and after the pressing tape was removed, the heating mandrel was heated again to be integrated. A method of manufacturing a heat-shrinkable tube, characterized in that the cylindrical body is heated to a melting temperature and expanded to a predetermined size. 2. The heating mandrel is covered with an uncrosslinked extruded tube of a thermoplastic resin, and then the heating mandrel is heated to soften the extruded tube by heating. Then, wind a stretched tape that has been stretched after cross-linking, and further wrap a holding tape with little heat expansion around the outside, then raise the heating mandrel further to bring the stretched tape and the extruded tube to the melting temperature. After heating and fusing together to form a cylindrical body, it is once cooled, the pressing tape is removed, the heating mandrel is heated again, and the integrated cylindrical body is heated to a melting temperature to a predetermined temperature. A method for manufacturing a heat-shrinkable tube, which is characterized by expanding the diameter.