JPH0737074B2 - Cross-linking type heat shrink tube continuous production equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat shrinkable pipe manufacturing apparatus used for coating various pipes and cables, as well as for connecting various pipes and rods to prevent corrosion or heat retention. In particular, the present invention relates to an apparatus for continuously producing a heat-shrinkable tube using a crosslinkable resin.

Conventional technology Conventionally, shrinkage is caused by heating for corrosion protection and heat retention of the connection parts of lining steel pipes used in oil, gas, water or chemical plants, and the connection parts of protective steel pipes of power cables or communication cables. It is practiced to use a heat-shrinkable tube capable of covering the connection portion and the like in a close contact state. Conventionally, various synthetic resins have been 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 producing a cross-linked heat-shrinkable tube, a method described in Japanese Patent Publication No. 47-19356 is known. In this method, an uncrosslinked resin compound is extrusion-coated on a metal pipe such as an aluminum pipe having a large number of through-holes formed on the pipe wall, and then the coated pipe is continuously connected to a crosslinking chamber, an expansion chamber and a cooling chamber. Through the cross-linking chamber, the internal and external pressures of the tube are controlled in the expansion chamber to expand the resin tube on the metal tube, and the expanded tube is cooled in the cooling chamber and wound. is there.

Problems to be Solved by the Invention In the above-mentioned conventional method, since the metal tube is used as the core and the resin is extrusion-coated on the metal tube, it is necessary to finally remove the metal tube, and therefore workability is improved. There is a problem that it is unavoidable that the cost is low and the cost is high due to the use of the metal tube. Furthermore, it is often difficult in practice to wind the metal tube while inserting it. It has been difficult to apply it to a continuous production of a heat shrink tube which is realistic and practical.

Further, in general, in the production of a cross-linking type heat-shrinkable tube, in order to impart heat-shrinkability to the tube, after the completion of cross-linking, the diameter is expanded (expanded) in a temperature range lower than the cross-linking temperature and higher than the softening temperature, and then the softening temperature It is necessary to cool the diameter to a sufficiently low temperature as it is, but when the conventional method as described above is performed, the temperature of the resin heated to a high temperature in the crosslinking chamber is still close to the crosslinking temperature even in the expansion chamber. In some cases, the resin may be retained and the resin may be crosslinked even during expansion, so that sufficient heat shrinkability may not be given. Furthermore, when the above-mentioned conventional method is carried out, the cooling efficiency of the cooling chamber is unavoidably lowered due to the heat effect from the expansion chamber, and therefore the length of the cooling chamber must be sufficiently long. There was also a problem that the total length would be longer and the equipment cost would be higher.

The present invention has been made in view of the above circumstances. In practice, a bridge-type heat-shrinkable tube can be manufactured at low cost and with high workability without causing various problems as in the case of using a metal tube as a core as described above. A heat-shrinkable tube that can be continuously manufactured and has good thermal stability and surely sufficient heat-shrinkability can be stably manufactured, and the length of the entire device can be made small. It is an object of the present invention to provide a device whose cost is low.

Means for Solving Problems A continuous manufacturing apparatus for a crosslinked heat-shrinkable tube according to the present invention comprises a mandrel and a die for extruding an uncrosslinked resin as a material for a crosslinked heat-shrinkable tube into a hollow tubular tube having a circular cross section. In the extruding head, a pressure fluid blowing means for injecting a pressure fluid to the inner surface side of the resin pipe extruded from the extruding head, a cross-linking cylinder for bridging the resin pipe extruded from the extruding head, and the cross-linking cylinder. A diameter-expanding die for expanding the diameter of the crosslinked resin tube by the pressure of the pressure fluid, and a cooling tube for cooling the resin tube coming out of the diameter-expanding die, and a resin tube near the inlet of the diameter-expanding die. It is characterized in that temperature control means for maintaining the temperature range lower than the crosslinking temperature and higher than the softening point temperature is provided.

The uncrosslinked resin, which is the material for the crosslinked heat-shrinkable tube, is continuously extruded into a hollow tubular shape with a circular cross-section from between the die of the extrusion head and the mandrel into the crosslinked tube, and then continuously in the crosslinked tube. Is thermally crosslinked, and then the crosslinked resin pipe is continuously guided from the bridge cylinder into the diameter expansion die, and continuously from the tip (expansion end) of the diameter expansion die into the cooling cylinder. . Here, since the pressure fluid is blown into the inner surface side of the extruded resin pipe, the resin pipe cross-linked in the cross-linking cylinder is expanded by the fluid pressure in the diameter expansion die, and then expanded in diameter. In this state, the heat-shrinkable tube is obtained by being continuously cooled in the cooling cylinder.

And, in particular, in the apparatus of the present invention, since the temperature control means for maintaining the temperature of the resin pipe in the temperature range lower than the crosslinking temperature and higher than the softening temperature is provided near the entrance of the diameter expansion die, the crosslinking The temperature of the pipe, which has come out of the cylinder and introduced into the diameter-expanding die, immediately becomes lower than the crosslinking temperature, so that it is possible to reliably prevent the heat-shrinkability from decreasing due to the progress of crosslinking during the diameter-expansion or after the diameter-expansion.

Further, as described above, by providing the temperature control means near the inlet of the expanding die, the cooling cylinder is not affected by the high temperature of the bridge cylinder, so that the cooling efficiency in the cooling cylinder is improved and therefore the cooling efficiency is improved. It is possible to shorten the length of the cylinder.

Further, in this type of continuous manufacturing apparatus, friction between the outer surface of the resin pipe extruded from the extrusion head and the inner surface of the cross-linking cylinder, the diameter expansion die, and the cooling cylinder is reduced to prevent seizure between them. Oil is often used as a friction modifier (lubricant) in order to facilitate continuous withdrawal of the resin pipe, but the viscosity of the oil generally decreases at low temperatures, and the friction relaxing effect decreases. Therefore, if the cooling cylinder is long, the low-viscosity region of the oil becomes long and the frictional resistance becomes large, which may make it difficult to continuously draw out the resin pipe.However, in the device of the present invention, the length of the cooling cylinder is set as described above. Because it can be shortened,
The low-viscosity region of the oil becomes short, and there is less risk of difficulty in drawing out the resin pipe.

Embodiment FIG. 1 shows an example of the continuous production apparatus of the present invention.

In FIG. 1, an extrusion head 3 having a generally cylindrical extrusion die 1 arranged so that its axis is vertical and a mandrel 2 concentrically arranged inside the extrusion die 1 are used. And a continuous annular extrusion port 3A is formed at the lower end between the extrusion die 1 and the mandrel 2. The extrusion port 3A is connected to an extruder body (not shown) through the resin passage 4, and the uncrosslinked resin 15 is extruded in a hollow tubular state by the extrusion pressure from the extruder body. There is. Mandrel 2 again
A pressure fluid supply passage 6 for supplying a pressure fluid from the outside to the inner surface side of the resin pipe 5 made of resin extruded from the extrusion port 3A is formed so as to penetrate therethrough in the axial direction. Further, a friction modifier supply port 9 for supplying the friction modifier from the outside to the outer surface of the resin pipe 5 is formed in the lower portion of the extrusion die 1.

In front of the extrusion port 3A in the extrusion direction, that is, in the lower part in the drawing, a bridge cylinder 7 having an outer diameter of the extrusion port 3A, that is, an inner diameter substantially equal to the inner diameter of the extrusion die 1, is arranged. The cylinder 7 is provided with a heater 8 for ensuring a temperature for thermal crosslinking. And this bridge cylinder 7
And the lower end of the extrusion die 1 are connected via a first heat insulating portion 21 for blocking heat conduction between them, for example, a low heat conductive material such as ceramic.

Below the bridging cylinder 7, a diameter expansion die 10 having an inner surface 10A whose diameter smoothly expands downward is disposed, and the upper end of the diameter expansion die 10 and the lower end of the bridging cylinder 7 are The second heat insulating portion 22 for blocking heat conduction between the two is connected through a low heat conductive material such as ceramic. And again, in the upper part of the diameter expansion die 10, that is, near the entrance,
Temperature control means 24, for example, a cooling water jacket, is provided for controlling the temperature of the resin pipe 5 to a temperature range lower than the crosslinking temperature and higher than the softening point temperature.

Further, below the expanding diameter die 10, that is, below the expanding end portion, a cooling cylinder 11 having an inner diameter equal to the inner diameter of the expanding end of the expanding diameter die 10 is arranged. This cooling tube
11 is a water-cooled or air-cooled structure. And cooling tube
The upper end of 11 and the lower end (enlarged end) of the diameter expansion die 10 are connected via a third heat insulating portion 23 for blocking heat conduction between them, for example, a low thermal conductivity material such as ceramics. .

Further, below the cooling cylinder 11, a mouthpiece 12 for deforming the cross-sectional shape of the resin pipe 5 guided downward from the cooling cylinder 11 into a flat shape.
Is provided on the lower side of the mouthpiece 12, and a pair of rollers 13A, 1A for applying downward pulling drive while further pressing the resin tube 5 flatly deformed by the mouthpiece 12 from both sides.
A take-up machine 13 composed of 3B is arranged. The take-off machine
A take-up roller (not shown) is provided below or on the side of 13.

A method for producing a cross-linked heat-shrinkable tube, for example, a heat-shrinkable tube made of cross-linked polyethylene, using the above apparatus will be described below.

Uncrosslinked resin that has been kneaded and extruded by an extruder (not shown)
15 is an extrusion die 1 and a mandrel 2 through the resin passage 4.
It is continuously extruded in the form of a hollow tube into the cross-linking cylinder 7 from the extrusion port 3A between the and. A pressure fluid, preferably an inert gas or the like, is blown into the inner surface of the extruded resin pipe 5 from the pressure fluid supply passage 6. A friction modifier is supplied through the friction modifier supply port 9 between the outer surface of the extruded resin pipe 5 and the inner surface of the bridge 7. As the friction modifier, basically any of liquid, solid (fine particle powder) and gas may be used. Silicon oil or other lubricating oil may be used as the liquid and boron nitride (BN) may be used as the solid.
Powder, molybdenum disulfide (MoS ₂ ) powder or the like can be used, and as the gas, an inert gas or the like can be used.

The resin tube 5 made of uncrosslinked resin extruded into the cross-linking cylinder 7 as described above is reinforced by its own weight, the take-up driving force of the take-up machine 13 and the take-up force of the take-up machine (not shown). It descends inside, and heat bridge | crosslinking is given in the meantime. At this time, the resin pipe 5 tends to be pressed against the inner surface of the bridge cylinder 7 due to the pressing force of the pressure fluid, but the frictional resistance between the inner surface of the bridge cylinder 7 and the outer surface of the extruded resin tube 5 is reduced by the friction modifier. Is extinguished, seizure does not occur between them, and the extruded resin pipe descends smoothly.

The cross-linked resin pipe 5 subsequently passes through the diameter-expanding die 10, but at this time, the temperature is controlled to exhibit plasticity, that is, the softening point or higher. It is expanded along the inner surface 10A of 10 and expanded in diameter. Then the expanded resin tube 5
Is cooled to near room temperature in the cooling cylinder 11 and becomes a heat-shrinkable tube. Subsequently, the contraction tube 5 passes through the mouthpiece 12, and is deformed from a circular state to an oval shape according to the change of the inner peripheral surface shape of the mouthpiece 12, and finally to a flat shape. At that time, the flattened resin pipe 5 is given a pulling force by the pulling machine 13,
Further, it is wound by a winder (not shown). Here, since the resin pipe 5 is flatly deformed as described above and further pressed by the take-up machine 13, the internal space of the resin pipe 5 is gas-sealed. It will work effectively due to the diameter.

Next, in the case of using the apparatus of the embodiment of the present invention shown in FIG. 1, the temperature distribution at each position in the resin extrusion direction
Shown in the figure. Further, for comparison, in the case of the comparative example in which the temperature control means 24 of the heat insulating parts 21, 22, 23 and the diameter expansion die 10 are not provided (however, the other points are the same as the configuration of the embodiment shown in FIG. 1). 3) shows the temperature distribution at each position in the resin extrusion direction.

As is clear from FIG. 3, in the case of the comparative example in which the heat insulating parts 21, 22, 23 and the temperature control means 24 of the diameter expansion die 10 are not provided, the resin is discharged from the stage before being extruded from the extrusion head 3. The temperature gradually rises due to the heat effect from the cross-linking cylinder 7, and then the temperature gradually rises even after entering the cross-linking cylinder 7 extruded from the extrusion head 3 to reach the cross-linking temperature range, and then the influence from the cooling cylinder 11 As a result, the temperature gradually drops through the diameter expansion die 10 and the cooling cylinder 11. Therefore, the bridge is not actually bridged between the inlet and the outlet of the bridge 7, but at a position slightly lowered from the inlet of the bridge 7.
Position P ₂ slightly lowered from the entrance of the diameter expansion die 10 from P ₁
Until then (this is referred to as an effective cross-linking portion), it is usual. If the lower end position P ₂ of the effective cross-linking portion is significantly lowered, the cross-linking proceeds while the diameter is being expanded in the diameter-expanding die 10 or after the end of the diameter expansion, so that sufficient heat shrinkability may not be obtained. is there. Further, the cooling cylinder 11 is affected by heat from the bridging cylinder 7 so that its cooling efficiency is low. Therefore, in order to cool the resin temperature to a sufficiently low temperature, the cooling cylinder 11 needs to be sufficiently long. Further, if the cooling cylinder 11 is long in this way, it means that the low viscosity region becomes long when oil (lubricating oil) is used as the friction modifier, so that there is also a problem that the friction resistance against the withdrawal of the resin pipe becomes large. Occurs. Further, as described above, the temperature rises due to the heat effect from the cross-linking cylinder 7 before the resin exits the outlet of the extrusion head 3, so that there is a problem that the resin is likely to be scorch (seizure) in the extrusion head 3.

On the other hand, in the apparatus of the embodiment of the present invention, the heat conduction between the extrusion head 3, the bridging cylinder 7, the diameter expansion die 10 and the cooling cylinder 11 is blocked by the heat insulating parts 21, 22, 23. Therefore, it is possible to sufficiently eliminate the influence of heat between them, and it is possible to appropriately control the temperature of the diameter expansion die 10 by the temperature control means 24 near the inlet of the diameter expansion die 10. Therefore, as shown in FIG. 2, the temperature of the resin hardly rises until it exits the extrusion head 3, and the temperature rises sharply after entering the cross-linking cylinder 7 to reach the cross-linking temperature range. When it comes out and enters the diameter-expanding die 10, the temperature immediately drops and is controlled to a temperature lower than the crosslinking temperature and higher than the softening temperature, and subsequently when it enters the cooling cylinder 7, the temperature drops sharply to a required low temperature. Therefore, as in the case of the comparative example shown in FIG. 3, it is possible to sufficiently avoid the progress of cross-linking during the expansion of the diameter or after the expansion, and thus it is possible to secure a sufficient heat shrinkability. Also cooling tube
Since the cooling efficiency of 11 is also good, the length of the entire device can be shortened by shortening the cooling cylinder 11. Since the cooling cylinder 11 can be shortened in this way, the low-viscosity region at low temperatures becomes short even when oil (lubrication oil) is used as a friction modifier, so friction resistance is reduced and a pipe made of resin is pulled out. Can be performed smoothly and easily. further,
Since the temperature rise in the extrusion head 3 due to the heat effect from the cross-linking cylinder 7 is prevented, it is possible to effectively prevent the scorch from occurring before the cross-linking.

Here, the optimum temperature distribution when manufacturing a heat-shrinkable tube made of crosslinked polyethylene using the apparatus of the present invention is as follows. That is, the resin temperature at the extrusion head 3 is 125 ° C.
The cross-linking cylinder 7 is heated to about 250 ° C. and cross-linked. And 115 ° C (softening point) for expanding die 10
As described above, the temperature is cooled to about 150 ° C. or less to expand the diameter, and further cooled to 60 ° C. or less by the cooling cylinder 11.

Further, in the embodiment of FIG. 1, the friction modifier supply port 9 is formed above the first heat insulating part 21, but the friction modifier supply port 9 is formed below the first heat insulating part 21. You can leave it.

Further, in the embodiment shown in FIG. 1, in order to deform the resin pipe 5 coming out of the cooling cylinder 11 into a flat shape, a cap 12 surrounding the entire circumference of the resin pipe 5 is provided. It is not necessary to have a structure that surrounds.

EFFECT OF THE INVENTION Unlike the conventional apparatus for extrusion coating on a metal tube, the apparatus of the present invention does not need to use a metal tube as a core and does not need to finally withdraw the metal tube, and therefore has good workability. The cost is also low, and therefore, it is actually most suitable for continuous production of a long cross-linking heat-shrinkable tube on a mass production scale, and in particular, according to the apparatus of the present invention, during or after the expansion of the diameter of the resin pipe. Since it is possible to prevent the progress of cross-linking, it is possible to reliably and stably manufacture a heat-shrinkable tube having sufficient heat-shrinkability, and to shorten the cooling cylinder to reduce the length of the entire device. By making the length short, it is possible to reduce equipment installation costs and equipment costs.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an example of the device of the present invention, and FIG.
FIG. 1 is a diagram schematically showing the temperature distribution of the resin in the case of producing a cross-linking type heat-shrinkable tube using the apparatus of an example of the present invention shown in FIG. 1, and FIG. It is a diagram which shows typically the temperature distribution of resin at the time of manufacturing a mold heat-shrinkable tube. 1 ... Extrusion die, 2 ... Mandrel, 3 ... Extrusion head,
3A ... Extrusion port, 5 ... Extruded resin pipe, 6 ... Pressure fluid supply passage, 7 ... Crosslinking cylinder, 10 ... Expanding die, 24 ... Temperature control means.

Claims (1)

[Claims] 1. An extrusion head composed of a mandrel and a die for extruding an uncrosslinked resin, which is a material for a crosslinked heat-shrinkable tube, into a hollow tube having a circular cross section, and an inner surface side of the resin tube extruded from the extrusion head. A pressure fluid blowing means for blowing a pressure fluid into the inner wall, a bridge for bridging the resin pipe extruded from the extrusion head, and a diameter expansion for expanding the resin pipe crosslinked in the bridging barrel by the pressure of the pressure fluid. With a die
A temperature for holding a resin tube that cools the resin pipe coming out of the diameter expansion die, and for maintaining the resin tube near the inlet of the diameter expansion die in a temperature range lower than the crosslinking temperature and higher than the softening point temperature. A continuous manufacturing apparatus for a crosslinked heat-shrinkable tube, characterized in that a control means is provided.