JPH0380611B2 - - 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, it relates to a method for continuously manufacturing heat-shrinkable tubes using crosslinked resin.

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.

Problems to be Solved by the Invention The above-mentioned conventional method uses a metal tube as a core and coats the metal tube with resin by extrusion, so it is necessary to remove the metal tube at the end, which reduces workability. In addition, the use of a metal tube increases the cost, and furthermore, it is often difficult in practice to wind the metal tube with the metal tube inserted, so this method is unrealistic. However, it has been difficult to actually apply it to the continuous production of cross-linked heat-shrinkable tubes.

On the other hand, when extruding uncrosslinked resin into a tube shape and continuously heating and crosslinking it in a crosslinking cylinder in order to manufacture a pipe made of general crosslinked resin, the crosslinking cylinder has an inner wall surface made of stainless steel, etc. However, in this case, the resin of the extruded tube is likely to seize on the inner surface of the cross-linked tube, so it is generally necessary to reduce the friction between the extruded tube and the inner surface of the cross-linked tube. In order to reduce the risk of resin seizure, lubricating oil is supplied during this period, but with some types of lubricating oil, the components contained in the lubricating oil may There have been problems in that the lubricating effect may no longer be obtained due to reaction with the crosslinking agent, or the components in the lubricating oil may deteriorate the resin. Also, when lubricating oil is used, the lubricating oil is not sufficiently distributed over the entire inner surface of the bridge cylinder.
Seizing may occur due to so-called oil shortage, and lubricating oil must also be managed, so there is a strong desire for a method that can prevent seizing during crosslinking without using lubricating oil. There is.

This invention was made against the background of the above circumstances, and it is possible to produce cross-linked heat-shrinkable tubes continuously at low cost and with high workability, without causing the problems described above when using metal tubes as cores. The object of the present invention is to provide a method that can be manufactured in a cost-effective manner and that can prevent the resin from seizing inside the crosslinked cylinder without particularly using lubricating oil.

Means for Solving the Problems The continuous manufacturing method for crosslinked heat-shrinkable tubes of the present invention includes:
A lining layer made of a material with high mold releasability from the resin and a low coefficient of friction is formed on the inner surface of the uncrosslinked resin, which is the material of the crosslinked heat shrinkable tube, between the extrusion die and the mandrel. The pipe is continuously extruded into a hollow tube shape into a cross-linked tube, and pressure fluid is continuously blown into the inner surface of the extruded tube, and the extruded tube has an inner surface that expands in a tapered shape from the outlet of the cross-linked tube. It is characterized in that it is continuously guided into a diameter-expanding die, and then continuously guided into a 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.

In particular, in the method of the present invention, since a lining layer made of a material that has a high degree of deformation from the resin and a small coefficient of friction is formed on the inner surface of the crosslinked tube, the resin of the tube extruded into the crosslinked tube is crosslinked. Seizure on the inner surface of the cylinder is prevented. That is, when continuously manufacturing a pipe made of cross-linked resin, if the inner surface of the cross-linked cylinder is metal, the resin tends to seize with the inner surface of the cross-linked cylinder, and especially during extrusion as in the method of this invention, When pressure fluid is injected into the inner surface of the pipe, the extruded tube is pressed against the inner surface of the bridged cylinder, which increases the frictional resistance between the outer surface of the extruded tube and the inner surface of the bridged cylinder, which tends to cause seizure. This tends to make it difficult for the extruded tube to move smoothly, which may impede continuous production. is prevented from sticking to the inner surface of the crosslinked cylinder, the extruded tube moves smoothly, and crosslinked heat-shrinkable tubes can be continuously manufactured without any problems. Since the lining layer on the inner surface of the cross-linked cylinder prevents seizure inside the cross-linked cylinder,
In particular, there is no need to use lubricating oil to prevent seizure, and there are disadvantages when using lubricating oil, such as seizure occurring due to the components of the lubricating oil reacting with the crosslinking agent or running out of oil. can be resolved.

Embodiment FIGS. 1 and 2 show an example of an apparatus for carrying out the manufacturing method of the present invention.

First, to explain the apparatus shown in FIGS. 1 and 2, a mandrel 2 is provided concentrically inside an extrusion die 1 having a cylindrical shape as a whole and arranged so that its axis is perpendicular. A continuous annular extrusion port 3 is formed in the lower part between the extrusion die 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. In addition, mandrel 2 has
A pressure fluid supply path 6 for supplying pressure fluid from the outside is formed through the inner surface of the tube 5 made of resin extruded from the extrusion port 3 along the axial direction.

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. As shown in detail in FIG. 2, on the inner surface of the bridge tube 7 is formed a lining layer 9 made of a material that has high mold releasability from resin and low frictional resistance. The material of this lining layer 9 is PTFE.
(Polytetrafluoroethylene; trade name Teflon)
Fluorine resins such as , ceramics, etc. are used. Further, the lining layer 9A may be formed by coating with the above-mentioned fluororesin or the like, or by separately molding the lining layer in advance and inserting it.

A diameter-expanding die 10 having an inner surface 10A whose diameter tapers downwardly is disposed below the bridge tube 7 and connected to the bridge tube 7. The above-mentioned lining layer 9 is also formed on the inner surface of this diameter-expanding die 10, as shown in detail in FIG. A cooling cylinder 11 having an inner diameter equal to the inner diameter of the enlarged end of the diameter-expanding die 10 is disposed at the lower end (enlarged end) of the diameter-expanding die 10 in a state connected to the enlarged end of the diameter-expanding die 10. has been done. 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 inert gas, is blown into the inner surface of the extruded tube 5 from the pressure fluid supply path 6.

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 is pressed against the inner surface of the bridging tube 7 by the pressurizing force of the pressure fluid, but as mentioned above, the inner surface of the bridging tube 7 does not have mold releasability from the resin, such as fluororesin. Since the lining layer 9 is made of a material that is large and has a small coefficient of friction, the pipe 5
The resin will not burn onto the inner surface of the bridge tube 7,
Descend smoothly.

The cross-linked pipe 5 then passes through the diameter-expanding die 10, but since it is still at a high temperature during this passage, it is expanded along the inner surface 10A of the diameter-expanding die 10 by the pressurizing force of the pressurized fluid mentioned above. and the diameter is expanded. The portion of this diameter expanding die 10 is the bridging tube 7
Unlike the above, heating is not performed, so there is almost no risk that the resin in the tube 5 will seize on the inner surface of the diameter expanding die 10, but it cannot be said to be perfect, so this implementation was carried out in preparation for the unlikely occurrence of seizing. In the example device, the diameter expanding die 1
A lining layer 9 similar to that formed on the inner surface of the bridge tube 7 is also formed on the inner surface of the bridge tube 7. Subsequently, the diameter-expanded tube is cooled to near room temperature within the cooling cylinder 11, and becomes a heat-shrinkable tube. After this, the tube 5 is deformed into a flat shape by the guide 12, and then pressed from both sides by the pressure rollers 13 into a folded state, and then wound up by a winder (not shown). Note that here, since the internal space of the tube 5 is gas-sealed by pressing the tube 5 with the pressure roller 13, the pressurizing force by the pressure fluid as described above is effective for expanding the diameter of the tube 5. It works.

In the illustrated embodiment, the lining layer 9 is formed not only on the inner surface of the bridging tube 7 but also on the inner surface of the diameter-expanding die 10; Therefore, the formation of the lining layer 9 on the inner surface of the diameter-expanding die 10 is not an essential component of the present invention.

Effects of the Invention According to the method of the present invention, heat-shrinkable tubes made of cross-linked resin can be smoothly and continuously manufactured while preventing seizure within the cross-linked cylinder without particularly using lubricating oil. Therefore, it is especially suitable for the continuous production of long heat-shrinkable tubes, and as mentioned above, it does not require the use of lubricating oil, which prevents the resin from degrading due to the reaction between the components in the lubricating oil and the crosslinking agent. There is no possibility that the anti-seizure effect will be lost, and there is no risk of seizing occurring due to lack of oil. Furthermore, unlike the conventional extrusion coating method on metal tubes, the method of the present invention does not require the final extraction of the metal tubes, so it is easy to work with and has low costs, making it suitable for mass production. It can be applied to the production of cross-linked heat shrinkable tubes on a large scale.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a vertical cross-sectional view showing an enlarged main part of FIG. 1...Extrusion die, 2...Mandrel, 3...
... Extrusion port, 5 ... Extruded pipe, 6 ... Pressure fluid supply path, 7 ... Crosslinked cylinder, 9 ... Lining layer, 10 ...
Expanding die, 11...cooling cylinder.

Claims (1)

[Claims] 1. A lining layer made of a material with high mold releasability from the resin and a low coefficient of friction is formed on the inner surface of the uncrosslinked resin, which is the material of the crosslinked heat-shrinkable tube, between the extrusion die and the mandrel. The extruded tube is continuously extruded into a hollow tube shape into the cross-linked tube, and pressure fluid is continuously blown into the inner surface of the extruded tube. 1. A continuous manufacturing method for a crosslinked heat-shrinkable tube, characterized by continuously guiding the tube into a diameter-expanding die having a diameter-expanding die, and then continuously guiding the tube from the enlarged end of the diameter-expanding die into a cooling cylinder.