JPS6321127A - Continuous manufacture of crosslinked heat-shrinkable tube - Google Patents

Abstract

PURPOSE:To prevent resin in a crosslinking tube from seizing without using lubricating oil by a method wherein the resin is extruded into the crosslinking tube in the form of a tube while an extruder die and a mandrel are vibratingly reciprocated in extrusion direction. CONSTITUTION:Uncrosslinked resin 15 is extruded through a resin passage 4 from an extrusion port 3 into a crosslinking tube 7 in the form of a hollow tube. Pressure fluid is blasted from a pressure fluid feeding passage 6 to the inner surface side of the extruded tube 5. In addition, the reciprocative vibration in extrusion direction is given to an extruder die 1 and a mandrel 2 with a vibrator 9. The tube 5 extruded in the crosslinking tube 7 lowers in the crosslinking tube 7 and is subjected to crosslinking by heating during its lowering movement. At this time, the tube 5 tends to bring into contact with the inner surface of the crosslinking tube 7 by pressure. However, vibration is given to the tube 5 relative to the inner surface of the crosslinking tube 7 owing to the vibration given to the extruder die 1 and the mandrel 2, resulting in smoothly lowering the tube 5 with no seizure to the inner surface of the crosslinking tube 7. In succession, the tube 5 is stretched along the inner surface 10A of a divergent die 10 and, after that, cooled down near to room temperature in a cooling tubular body 1 in order to obtain a heat-shrinkable tube.

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, there have been various methods for corrosion protection and heat insulation of the joints of lining steel pipes in oil, gas, water, JCI, chemical plants, etc., and the joints of protective steel pipes of electric power cables and communication cables.
Heat-shrinkable tubes, which can be shrunk by heating to tightly cover the connecting portions, have been 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 onto a metal tube such as an aluminum tube with many small through holes formed in the tube wall, and then the coated tube is continuously placed in a crosslinking chamber, expanded seedlings, and cooled seedlings. After being stretched and straightened in a cross-linking chamber, the resin tube on the metal tube is expanded by controlling the internal and external pressure of the tube in the expansion stage, and the resin tube is cooled in the expanded state in a cooling stage and wound up. It's a method.

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

On the other hand, in order to manufacture pipes made of general cross-linked resin,
When extruding uncrosslinked resin into a tube and continuously heating and crosslinking it in a crosslinking cylinder, the purpose is to reduce friction between the extruded tube and the inner surface of the crosslinking cylinder to prevent resin seizure. However, with some types of lubricating oil, the components contained in the lubricating oil react with the crosslinking agent in the resin, making it impossible to obtain a lubricating effect. There is a problem in that the components in the lubricating oil may deteriorate the resin. Furthermore, when lubricating oil is used, the lubricating oil is not sufficiently distributed over the entire inner surface of the chestnut paper, which inevitably causes so-called oil depletion and seizure, and furthermore, the lubricating oil must be managed. Because it will be,
There is a strong desire for a method that can prevent seizure during crosslinking without using lubricating oil.

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 of cross-linked heat-shrinkable tubes of the present invention involves hollowing uncrosslinked resin, which is a material for cross-linked heat-shrinkable tubes, from between an extrusion die and a mandrel into a cross-linked tube. In addition to continuously extruding the extruded tube, the extrusion die and mandrel are vibrated reciprocally in the extrusion direction, and pressure fluid is continuously blown into the inner surface of the extruded tube. It is characterized in that it is continuously guided from the outlet of the bridging cylinder into a diameter-expanding die having an inner surface that expands in a tapered shape, and then continuously guided into the cooling cylinder from the enlarged end of the diameter-expanding die. .

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

In particular, in the method of the present invention, the extrusion die and mandrel are reciprocated in the extrusion direction, and the resin is extruded into the crosslinking cylinder from between the extrusion die and the mandrel in a tubular shape. Relative vibration is also applied between the tube and the inner surface of the cross-linked cylinder, and the vibration prevents the extruded resin from burning on the inner surface of the cross-linked cylinder.

In other words, when continuously manufacturing pipes made of cross-linked resin 1
The resin tends to seize with the inner surface of the cross-linked tube, and especially when pressure fluid is blown into the inner surface of the extruded tube as in the method of this invention, the resin tends to seize between the inner surface of the cross-linked tube and the extruded tube. As a result of being pressed, the frictional resistance between the outer surface of the extruded tube and the inner surface of the cross-linked tube increases, which tends to cause seizure, which makes it difficult to move the extruded tube smoothly and prevents continuous production. However, due to the relative vibration applied between the extruded pipe and the inner surface of the cross-linked cylinder, the resin in the extruded pipe may be locally localized at the same position on the inner surface of the cross-linked cylinder due to frictional resistance. As a result, the resin is prevented from burning on the inner surface of the crosslinked tube, allowing the extruded tube to move smoothly and preventing any interference with the crosslinked heat shrink tube. This allows for continuous production without any problems. In this way, the vibration applied to the extrusion die and mandrel prevents seizure within the crosslinked cylinder, so there is no need to use lubricating oil to prevent seizure, and there are disadvantages when using lubricating oil. That is, for example, it is possible to eliminate inconveniences such as the reaction of the lubricating oil components with the crosslinking agent or the occurrence of seizure due to lack of oil.

EXAMPLE The accompanying drawings show an example of an apparatus for carrying out the manufacturing method of the present invention.

First, to explain the illustrated device, a mandrel 2 is provided concentrically inside an extrusion die 1 having a cylindrical shape as a whole and whose axis is perpendicular.
A continuous annular extrusion port 3 is formed at the bottom 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 extrusion □
The uncrosslinked resin 15 is extruded in the form of a hollow tube by the extrusion pressure applied thereto.

Further, a pressurized fluid supply path 6 for supplying pressurized fluid from the outside to the inner surface side of the tube 5 made of resin extruded from the extrusion port 3 is formed through the mandrel 2 along the axial direction. Furthermore, a vibrator 9 is provided at the upper end of the recordable extrusion die 1 for imparting reciprocating vibration to the extrusion die 1 and the mandrel 2 along the extrusion direction (the width direction).

A bridge tube 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 port 3 in the extrusion direction, that is, at the bottom in the figure. 7 is provided with a heater 8 for ensuring a temperature for thermal crosslinking.

Below the bridging cylinder 7, a diameter expanding die 10 having an inner surface 10A whose diameter expands downward in a tapered manner is disposed in a state 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. , a pair of pressing rollers 1 for further pressing the tube 5 which has been flattened by the guide 12 from both sides.
3 are arranged. 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) is continuously extruded into the crosslinking cylinder 7 through the resin passage 4 from the extrusion port 3 between the extrusion die 1 and the mandrel 2 into the crosslinking cylinder 7. be done. 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 reciprocating vibration in the extrusion direction is applied to the extrusion die 1 and the mandrel 2 by a vibrator 9.

The pipe 5 made of uncrosslinked resin extruded into the cross-linked cylinder 7 as described above is pushed into the cross-linked cylinder 7 by its own weight, the take-up rotational force of the pressure roller 13, the winding force of each winding unit (not shown), etc.
During this period, thermal crosslinking is applied. At this time, the tube 5 tries to be pressed against the inner surface of the chestnut and the connecting portion 7 due to the pressurizing force of the pressure fluid, but as mentioned above, the tube 5 is cross-linked due to the motion applied to the extrusion die 1 and the mantle 2. A relative motion is applied to the inner surface of the tube 7, so that the tube 5 descends smoothly without its resin burning onto the inner surface of the bridging tube 7.

The crosslinked tube 5 then passes through a diameter expanding die 10,
Since the temperature is still high during this passage, the inner surface 10A of the diameter-expanding die 10 is
It is stretched along and expanded in diameter. Subsequently, the diameter-expanded tube is cooled to near the lowest 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 3 into a folded state, and then wound up by a winder (not shown). Furthermore, since the internal space of the tube 5 is gas-sealed by being pressed by the pressure roller 13 as described above, the pressurizing force by the pressure fluid described above is applied to the tube 5.
This will effectively work to expand the diameter of.

Here, the frequency and amplitude of the imaging applied to the extrusion die 1 and the mandrel 2 are not particularly limited, but it is usually sufficient to apply vibrations with a frequency of about 500 tlZ to 5000 Hz and an amplitude of 1 m or less. In addition, in the actual manufacturing equipment,
Constructed so that the frequency and/or amplitude of vibration can be changed continuously or stepwise, and adjusted to the optimal frequency and/or amplitude depending on the type of resin, the thickness and diameter of the extruded tube, the running speed of the tube, etc. It is desirable to do so.

Furthermore, although the method of the present invention is basically capable of preventing seizure by using only vibration without using lubricating oil, in some cases, a suitable lubricating oil may be selected and used in combination. Of course, it is possible to further enhance the anti-seizure effect. In this case, for example, a supply port (not shown) may be provided between the bridge tube 7 and the die 1, and the extruded tube 5 and the inner surface of the bridge tube 7 may be connected to each other. It is sufficient to supply lubricating oil between them. Further, a gas such as an inert gas, a lubricant, or a solid lubricant powder such as boron nitride (BN) may be supplied from the above-mentioned supply port to further improve the anti-seizure effect.

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 tube without particularly using lubricating oil. Therefore, it is particularly 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 deteriorating due to the reaction between the components in the lubricating oil and the crosslinking agent. There is no loss of anti-seizure effect, and there is no risk of seizure 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 handling of the metal tubes, so it is easy to work with, and the cost is low, making it practical for mass production. It can be applied to the production of cross-linked heat shrinkable tubes on a large scale.

[Brief explanation of the drawing]

The drawing is a schematic longitudinal sectional view showing an example of an apparatus for carrying out the method of the present invention. 1... Extrusion die, 2... Mandrel, 3...
... Extrusion port, 5... Extruded pipe, 6... Pressure fluid supply path, 7... Bridge tube, 9... Oscillator,
]O... Diameter expanding die, 11... Cooling cylinder.

Claims (1)

[Claims] The uncrosslinked resin, which is the raw material for the crosslinked heat-shrinkable tube, is continuously extruded into a hollow tube from between the extrusion die and the mandrel into the crosslinking tube, and during extrusion, the extrusion die and mandrel are moved in the extrusion direction. The extruded tube is vibrated reciprocatingly, pressure fluid is continuously blown into the inner surface of the extruded tube, and the extruded tube is continuously guided from the outlet of the bridge tube into a diameter expanding die having an inner surface that expands in a tapered shape. A continuous manufacturing method for a crosslinked heat-shrinkable tube, characterized in that the tube is then continuously guided from the enlarged end of the diameter-expanding die into the cooling cylinder.