JPH0351209B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a method of manufacturing heat shrinkable tubes used for coating various piping and cable connections, and other various types of tubes and rods for corrosion protection or heat retention. In particular, the present invention relates to a method for continuously manufacturing a heat-shrinkable tube using a crosslinked resin and having an adhesive layer formed inside.

Conventional technology Traditionally, corrosion protection and heat insulation have been used for the joints of lining steel pipes in oil, gas, water, and chemical plants, and the joints of protective steel pipes for power cables and communication cables, by shrinking them when heated. Heat-shrinkable tubes that can tightly cover connecting parts and the like are being used. Various synthetic resins are used for such heat-shrinkable tubes, but recently cross-linked synthetic resins such as cross-linked polyethylene are often used.

By the way, as a method for continuously manufacturing cross-linked heat-shrinkable tubes, a method described in Japanese Patent Publication No. 19356/1983 is known. In this method, an uncrosslinked resin compound is extruded and coated on a metal tube such as an aluminum tube with many small through holes formed in the tube wall, and then the coated tube is connected to a crosslinking chamber, an expansion chamber, and a cooling chamber. After crosslinking in the crosslinking chamber, the resin tube on the metal tube is expanded by controlling the internal and external pressure of the tube in the expansion chamber, and the resin tube is cooled in the expanded state in a cooling chamber and then rolled up. be.

On the other hand, as mentioned above, heat-shrinkable tubes are mainly used to cover various types of pipes, rods, and their connections, so when covering them, the heat-shrinkable tube is glued to the object to be covered. To do this, an adhesive layer is often formed on the inner surface of the heat shrink tube. Conventionally, the method of forming an adhesive layer on the inner surface of a heat-shrinkable tube for this purpose is to manufacture the heat-shrinkable tube itself and then apply an adhesive to the inner surface of the heat-shrinkable tube in a separate process. It was common. In addition, some methods apply double-layer extrusion when manufacturing heat-shrinkable tubes, and in the extrusion process, the adhesive layer as the inner layer material is simultaneously extruded with the resin of the heat-shrinkable tube itself as the outer layer material. Are known.

Problems to be Solved by the Invention The above-mentioned conventional method for continuously manufacturing cross-linked heat-shrinkable tubes uses a metal tube as a core and extrusion coats resin onto the metal tube. It is necessary to remove the metal tube, which inevitably lowers work efficiency, and the use of metal tubes increases costs, and furthermore, it is difficult in practice to wind up the metal tube with it inserted. Therefore, this method is impractical and difficult to actually apply to the continuous production of crosslinked heat-shrinkable tubes.

On the other hand, among the conventional methods for forming an adhesive layer on the inner surface of a heat-shrinkable tube, the process of applying the adhesive layer in a separate process from the manufacturing process of the heat-shrinkable tube requires a large number of steps and increases manufacturing costs. In addition, with the method of applying two-layer extrusion to form the inner adhesive layer at the same time as manufacturing the heat-shrinkable tube, the extruder, die, etc. There was a problem that the cost had to be high.

In any case, it has heretofore been difficult to continuously manufacture heat-shrinkable tubes made of crosslinked resin and having an adhesive layer on the inner surface at low cost and with high workability.

This invention has been made against the background of the above circumstances, and provides a method for continuously manufacturing heat-shrinkable tubes having an adhesive layer on the inner surface and made of cross-linked resin at low cost and with high workability. The purpose is to

Means for Solving the Problems The continuous manufacturing method for crosslinked heat-shrinkable tubes of the present invention includes:
The uncrosslinked resin, which is the material for crosslinked heat-shrinkable tubes, is continuously extruded into a hollow tube from between an extrusion die and a mandrel into a crosslinked tube, and pressure fluid is continuously applied to the inner surface of the extruded tube. Then, the tube is continuously guided from the outlet of the bridging cylinder into a diameter expanding die having a tapered inner surface to expand its diameter, and the adhesive is applied inside the bridging cylinder or the diameter expanding die. The method is characterized in that an adhesive layer is formed by spraying on the inner surface of the tube, and the diameter-expanded tube is continuously guided into the cooling cylinder from the enlarged end of the diameter-expanding die.

Function The uncrosslinked resin that is the material for crosslinked heat-shrinkable tubes is
A hollow tube is continuously extruded from between the extrusion die and the mandrel into the crosslinking cylinder, and is continuously heated and crosslinked within the crosslinking cylinder, and then the crosslinked tube expands from the crosslinking cylinder into a tapered shape. It is continuously guided into a diameter-expanding die having an inner surface, and then continuously guided into a cooling cylinder from the enlarged end of the diameter-expanding die. Here, since pressure fluid is blown into the inner surface of the extruded pipe, the pipe crosslinked with the crosslinked cylinder is moved into the diameter expansion die by the fluid pressure in the diameter expansion die before it reaches a low temperature. The diameter is expanded along the inner surface which expands in shape, and then the expanded diameter is continuously cooled in a cooling cylinder to obtain a heat-shrinkable tube.

Particularly in the cross-linking cylinder or in the diameter-expanding die, an adhesive (usually hot melt adhesive) is sprayed onto the inner surface of the extruded tube to form an adhesive layer, which is then placed inside the cooling cylinder. It is cooled and hardened. Therefore, a crosslinked heat-shrinkable tube having an adhesive layer on the inner surface is continuously produced.

Note that here, since the adhesive is sprayed onto the inner surface of the extruded tube inside the crosslinking cylinder or inside the diameter expanding die, the extruder itself can be used without making any changes to the extruder for normal single-layer extrusion. Can be used.

Embodiment FIG. 1 shows an example of an apparatus for carrying out the manufacturing method of the present invention.

First, to explain the apparatus shown in FIG. 1, a mandrel 2 is provided concentrically inside a generally cylindrical extrusion die 1 whose axis is perpendicular to the extrusion die. A continuous annular extrusion port 3 is formed at the bottom between the mandrel 1 and the mandrel 2. The extrusion port 3 is connected to an extruder (not shown) via a resin passage 4, and the uncrosslinked resin 15 is extruded into a hollow tube shape by the extrusion pressure from the extruder. There is. Further, a pressure fluid supply path 6 for supplying pressure fluid from the outside to the inner surface of the tube 5 made of resin extruded from the extrusion port 3 is formed through the mandrel 2 in parallel with the axial direction. Further, a through hole 16 is formed in the mandrel 2 along its axial direction, and an adhesive supply pipe 17 for introducing adhesive from the outside is fitted into the through hole 16. The adhesive supply pipe 17 has a plurality of adhesive injection holes 17A formed at its tip.
The injection hole 17A is located inside the bridge cylinder 7, which will be described later.

A bridging cylinder 7 having an inner diameter substantially equal to the outer diameter of the extrusion outlet 3, that is, the inner diameter of the extrusion die, is disposed in front of the extrusion outlet 3 in the extrusion direction, that is, at the bottom in FIG. The crosslinking tube 7 is provided with a heater 8 for ensuring a temperature for thermal crosslinking. Further, at the end of the bridge cylinder 7 on the extrusion port 3 side, a friction modifier supply port 9 is formed for supplying a friction modifier from the outside to the inner surface of the bridge cylinder 7. As described above, a plurality of injection holes 17A are located at the tip of the adhesive supply pipe 17 in the bridging cylinder 7, and the opening direction of these injection holes 17A faces toward the inner surface of the bridging cylinder 7. There is.

Below the bridging cylinder 7, a diameter expanding die 10 having an inner surface 10A whose diameter expands downward in a tapered manner is connected to the bridging cylinder 7. A cooling cylinder 11 having an inner diameter equal to the inner diameter of the enlarged end of the enlarged diameter die 10 is disposed at the lower end (enlarged end) of the die 10 in a state connected to the enlarged end of the enlarged diameter die 10 . Note that this cooling cylinder 11 has a water-cooled or air-cooled structure.

Furthermore, a guide 12 is provided below the cooling cylinder 11 for guiding the tube 5 hanging downward from the cooling cylinder 11 in a direction that flattens the cross-sectional shape. , guide 1
A pair of pressing rollers 13 are provided for further pressing the tube 5, which has been flattened by the tube 2, from both sides. Note that a winding roller (not shown) is provided below or to the side of the pressure roller 13.

Next, a method for manufacturing a crosslinked heat-shrinkable tube, for example a heat-shrinkable tube made of crosslinked polyethylene, using the above-described apparatus will be described.

The uncrosslinked resin 15 kneaded and extruded by an extruder (not shown) passes through a resin passage 4 from an extrusion port 3 between an extrusion die 1 and a mandrel 2 to a crosslinking tube 7.
It is continuously extruded into a hollow tube. Pressure fluid, preferably made of an inert gas, is blown into the inner surface of the extruded tube 5 from the pressure fluid supply path 6. Further, a friction modifier is supplied between the outer surface of the extruded tube 5 and the inner surface of the bridge tube 7 through the friction modifier supply port 9. Basically, any of liquid, solid (fine particle powder), or gas may be used as this friction modifier.The liquid is silicone oil or other lubricating oil, and the solid is boron nitride (BN). Powder, molybdenum disulfide (MoS ₂ ) powder, etc. can be used, and as the gas, an inert gas can be used. However, it may not be preferable to use an oil-based lubricant, and in that case, it is preferable to use a gas such as an inert gas as a friction modifier.

The tube 5 made of uncrosslinked resin extruded into the crosslinking cylinder 7 as described above is not affected by its own weight or the pressure roller 13.
The material is lowered in the crosslinking tube 7 by the take-up rotational force of the winder and the winding force of a winder (not shown), during which heating crosslinking is performed. At this time, the tube 5 tries to be pressed against the inner surface of the bridging tube 7 due to the pressurizing force of the pressure fluid, but the friction reducing agent causes a gap between the inner surface of the bridging tube 7 and the outer surface of the extruded tube 5. Frictional resistance is relaxed, and the extruded tube descends smoothly without seizing. Furthermore, inside the bridging cylinder 7, the adhesive supply pipe 1 is attached to the inner surface of the extruded pipe 5.
An adhesive such as a hot-melt adhesive is sprayed from the injection holes 17A of 7, thereby forming an adhesive layer 18 on the inner surface of the tube 5.

The pipe 5 crosslinked as described above and having the adhesive layer 18 formed on its inner surface subsequently passes through the diameter expanding die 10, but since it is still at a high temperature during this passage, the pressure applied by the pressure fluid described above is applied. is expanded along the inner surface 10A of the diameter-expanding die 10,
The diameter is expanded. Subsequently, the diameter-expanded tube is cooled to near room temperature within the cooling cylinder 11, and becomes a heat-shrinkable tube. Further, as the adhesive layer 18 is cooled, the hot melt adhesive layer 18 is hardened. After this, guide 1
2, the tube 5 is deformed into a flat shape, and then pressed from both sides by pressure rollers 13 into a folded state, and then wound up by a winder (not shown).
Here, since the internal space of the tube 5 is gas-sealed by being pressed by the pressure roller 13, the pressure caused by the pressure fluid as described above acts effectively for diameter expansion. Become.

In the above embodiment, the adhesive is sprayed onto the inner surface of the extruded tube 5 in the bridging tube 7, but it may be sprayed in the diameter-enlarging die 10 as the case may be.

Furthermore, in the embodiment described above, the adhesive supply pipe 17 for introducing adhesive from the outside is inserted into the through hole 16 formed separately from the pressure fluid supply path 6 of the mandrel 2. Of course, as shown in FIG. 2, the adhesive supply pipe 17 may be inserted concentrically with a gap G provided inside the pressure fluid supply path 6.

Effects of the Invention According to the method of the present invention, it is possible to continuously manufacture heat-shrinkable tubes made of a cross-linked resin and having an adhesive layer formed on the inner surface, and it is therefore possible to continuously manufacture a heat-shrinkable tube made of a cross-linked resin and having an adhesive layer formed on the inner surface. Ideal for continuous production of shrink tubes. Furthermore, unlike the conventional method of manufacturing cross-linked heat-shrinkable tubes by extrusion coating on metal tubes, the method of the present invention does not require the final extraction of the metal tubes, so it has good workability and is low in cost. Moreover, unlike the conventional method of forming an adhesive layer by two-layer extrusion, it does not use a special and complicated two-layer extruder, so there is no particular increase in equipment costs. It can be applied to the production of layered crosslinked heat shrinkable tubes.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a longitudinal cross-sectional view showing the main parts of another example of the apparatus for carrying out the method of the present invention. be. 1...Extrusion die, 2...Mandrel, 3...
...Extrusion port, 5...Extruded pipe, 6...Pressure fluid supply path, 7...Bridging cylinder, 10...Diameter expansion die, 1
1... Cooling cylinder, 17... Adhesive supply pipe, 18...
adhesive layer.

Claims (1)

[Claims] 1. Continuously extrude uncrosslinked resin, which is the material of the crosslinked heat-shrinkable tube, into a crosslinked tube from between an extrusion die and a mandrel into a hollow tube, and apply pressure fluid to the inner surface of the extruded tube. The tube is continuously blown in, and then the tube is continuously guided from the outlet of the bridging cylinder into a diameter-expanding die that has a tapered inner surface to expand its diameter, and then bonded inside the first-stage bridging cylinder or inside the diameter-expanding die. A cross-linking type heating device characterized in that an adhesive is sprayed onto the inner surface of the tube to form an adhesive layer, and the diameter-expanded tube is continuously guided from the enlarged end of a diameter-expanding die into the cooling cylinder. Continuous manufacturing method for shrink tubes.