JP3908328B2 - Method and apparatus for manufacturing insertion pipe - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a method and an apparatus for manufacturing an insertion pipe used in an insertion method for inserting a polyethylene pipe into a pipe for repairing an existing pipe.
[0002]
[Prior art]
In the insertion method, the plastic tube is heated and softened, and is crushed by a roller or the like to reduce the diameter. After being inserted into the existing tube at a temperature below the shape recovery temperature, the shape is recovered by heating above the shape recovery temperature. JP-A-7-77291 discloses a method of reducing the diameter of a crosslinked polyethylene pipe in the vicinity of a pseudo-melting point where the tensile stress rapidly decreases as the temperature rises, and then the resin material recovers its shape as the temperature rises. A method of cooling to below the shape recovery temperature is disclosed.
[0003]
Japanese Patent Application Laid-Open No. 4-29834 discloses an inserter by extruding a plastic tube having a circular cross section from an extrusion die, cooling and solidifying it once for shape memory, and then reducing the diameter in a softened state by reheating. A method for manufacturing a production pipe in one line is disclosed.
[0004]
[Problems to be solved by the invention]
As described above, the insertion pipe heats and softens the plastic pipe prior to the diameter reduction processing. The heating is usually performed by heating the plastic pipe from the outside using high-temperature air or steam, and the temperature rises. The temperature rises to near the pseudo melting point where the tensile stress drops sharply. This causes a problem that is easy to do.
[0005]
The first object of the present invention is to provide an insertion pipe manufacturing method and apparatus that do not cause the above-mentioned problems.
It is also desirable that the insertion pipe has no shape memory property in a reduced diameter shape and has a good recovery property to a circular cross section after the diameter reduction. In this regard, cross-linked polyethylene pipes have the advantages of good resilience, excellent shape retention and little creep deformation, but once cooled and solidified, the pipes extruded from the extrusion dies are reheated to reduce the diameter. Therefore, it is not adopted in the method of manufacturing the insertion pipe in one line. The reason for this is that if the crosslinking is performed in a state where the resin is heated to a temperature at which the resin reaches the vicinity of the pseudo melting point and softens, the shape memory before processing is lost and a problem that the circular cross section cannot be restored occurs.
[0006]
A second object of the present invention is a method of cooling and solidifying a pipe extruded from an extrusion die and then reheating it to reduce the diameter. After the diameter reduction, the insert having good recoverability when heated to a shape recovery temperature or higher. It is intended to provide a manufacturing method for obtaining an action pipe.
[0007]
[Means for solving problems]
In order to achieve the first object, the present inventors made a polyethylene pipe (here, the polyethylene pipe includes a polyethylene pipe having a crosslinking degree of 65% or more, the same applies to the following polyethylene pipe) as the outer layer portion. As a result of various experiments conducted to obtain a temperature that can be softened without melting, for example, a range of 100 to 125 ° C. is suitable for a medium density polyethylene tube and 100 to 130 ° C. for a crosslinked polyethylene tube. Part melting was observed.
[0008]
In the first invention, a polyethylene pipe is heated in two stages. That is, a preliminary heating stage in which the temperature is uniformly increased in the thickness direction to a temperature at which the outer layer portion of the polyethylene pipe is not melted, and a stage in which the temperature is increased to 100 to 130 ° C. (hereinafter referred to as the pseudo melting point) after the preliminary heating. It consists of
[0009]
That is, in the first invention, the polyethylene pipe is heated and heated to near the pseudo melting point where the tensile stress rapidly decreases as the temperature rises, and then the diameter is reduced, and then the shape recovery temperature is maintained while maintaining the reduced diameter. in insertion pipe manufacturing method of the cooling to the heating process of a polyethylene tube prior to diameter reduction process, the steps of preheating the polyethylene tube to 80 to 98 ° C., after preheating, a temperature of at least the surface by the heating means 100 The apparatus for carrying out this method is characterized by comprising a step of heating to ˜130 ° C., and an apparatus for preheating the polyethylene pipe to 80 to 98 ° C. reduced by crushing and second heating device for heating to a temperature of at least the surface of the polyethylene pipe reaches 100 to 130 ° C., the polyethylene tube was raised A device for processing, characterized by comprising the cooling device for cooling the reduced diameter polyethylene tube to below the shape recovering temperature.
[0010]
As a method for preheating the polyethylene tube to 80 to 98 ° C., it is desirable to immerse it in hot water or raise the temperature with steam. This is because the temperature can be easily raised without unevenness in the thickness direction, and when immersed in hot water, it is not heated above 100 ° C. Moreover, in the polyethylene pipe containing a crosslinking agent, crosslinking can be caused by this step.
[0011]
The present method and apparatus may use a polyethylene pipe cooled to room temperature, or may be applied to a polyethylene pipe on a line that has been extruded from an extrusion die and once cooled and solidified for shape memory. In this case, the cooling temperature is desirably 60 ° C. or less for the reason described later. When the cooling temperature exceeds 60 ° C., the recoverability when the diameter-reduced polyethylene pipe is heated and restored to a circular cross section is deteriorated.
[0012]
According to experiments conducted by the present inventors in order to achieve the second object, it was found that 80 to 100 ° C. is appropriate for crosslinking of the resin.
[0013]
Therefore, in the third invention for achieving the second object, the polyethylene pipe having a circular cross section extruded from the extrusion die is once cooled and solidified, and then re-approximated to near the pseudo melting point where the tensile stress rapidly decreases as the temperature rises. In the method for reducing the diameter of a crosslinked polyethylene pipe that is reduced in diameter after heating, the step of heating the polyethylene pipe for diameter reduction is a first step of raising the temperature of the polyethylene pipe to 80 to 100 ° C. with hot water or steam to cause crosslinking. And a second step of raising the temperature to near the pseudo-melting point where the tensile stress decreases rapidly as the temperature rises.
[0014]
According to the present invention, the polyethylene pipe after crosslinking in the above temperature range is not memorized even if the diameter is reduced after the temperature is further raised to the vicinity of the pseudo melting point. In addition to having good resilience, it is possible to prevent melting of the outer pipe layer as described above by heating the polyethylene pipe in two stages.
The present inventors have also found that when the cooling temperature of the polyethylene pipe extruded from the extrusion die exceeds 60 ° C., the recoverability deteriorates, and it is necessary to cool to 60 ° C. or less in order to improve the recoverability. It was.
[0015]
Accordingly, the fourth invention is a cross-linked polyethylene pipe which is once cooled and solidified after the polyethylene pipe having a circular cross section extruded from the extrusion die is cooled and then reheated to near the pseudo melting point where the tensile stress decreases rapidly as the temperature rises. In the diameter reduction processing method, the cooling temperature of the polyethylene pipe having a circular cross section extruded from the extrusion die is set to 60 ° C. or less.
[0016]
In each of the above inventions, the polyethylene tube is heated until it reaches the vicinity of the pseudo melting point prior to the diameter reduction processing, for example, using a hot air dryer. In this case, so as not to hit directly hot polyethylene pipes, for such polyethylene pipe is polyethylene tube is covered with a hood is as uniform as possible heating is desirable.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an insertion pipe manufacturing apparatus, in which an extrusion die 1, a cooling device 3 that cools once to store a shape of a polyethylene tube 2 having a circular cross section extruded from the extrusion die 1, and hot water is filled and cooled. the polyethylene pipe 2 which is cooled by the device 3 and the first heating device 4 for preheating consists of a heater and a fan (not shown in the figure), a second heating device for heating the polyethylene pipe 2 which is pre-heated in the heating device 4 A hot air dryer 5, a roller and the like, a diameter reducing device 6 for reducing the diameter of the heated polyethylene pipe 2, and a cooling device for cooling the diameter-reduced polyethylene pipe 2 and stabilizing the shape in the reduced diameter state. 7, consists diameter polyethylene tube 2 the winding wound-up device 8 Prefecture, local heating of hits hot air directly to a polyethylene tube during heating of the polyethylene pipe 2 by hot air The polyethylene pipe as evenly heated without Rukoto hood is covered.
[0018]
EXAMPLE Using the apparatus shown in FIG. 1, a polyethylene tube 2 containing a cross-linking agent extruded from an extrusion die 1 is cooled to 60 ° C. or less by a cooling device 3 and then to a first heating device 4 (hot water temperature 98 ° C.). After passing through for 3 minutes and raising the temperature to 80 to 98 ° C. and crosslinking, it was sent to the hot air dryer 5 and heated to 100 to 130 ° C. Thereafter, the polyethylene 2 having a circular cross section is crushed and reduced in diameter by the diameter reducing device 6 as shown in FIG. Winded up.
[0019]
【The invention's effect】
The present invention is configured as described above and has the following effects.
According to the manufacturing method and apparatus of claims 1 and 2 , since it is once heated to an intermediate temperature by preheating, then it is heated to near the pseudo melting point, and the temperature is raised in two stages. The amount of heating is small, and the outer layer of the polyethylene tube is less likely to melt compared to heating to the vicinity of the pseudo melting point at once.
[0020]
According to the manufacturing method of Claim 3 , an insertion pipe can be manufactured by 1 line, and productivity improves.
According to the manufacturing method of Claim 4, it becomes possible to perform shape memory completely with a pipe shape, and the restoring property when restoring the reduced diameter polyethylene pipe to a circular cross section is improved.
[0021]
According to the manufacturing method of claim 5 , the temperature can be easily raised without unevenness in the thickness direction.
According to the manufacturing method of claim 6 , by performing the crosslinking at 80 to 100 ° C., it is possible to manufacture an insertion pipe having good recoverability without losing shape memory before processing, and two-stage heating. By doing so, it is possible to prevent melting of the outer tube portion during heating.
[0022]
According to the manufacturing method of the seventh aspect , the insertion pipe can be manufactured in one line, and the resilience when the diameter-reduced polyethylene pipe is restored to a circular cross section is improved.
[0023]
When a hot air dryer is used to heat the polyethylene pipe as in the manufacturing method according to claim 8 , the polyethylene pipe can be heated relatively uniformly by covering the polyethylene pipe with a hood and blowing the hot air. it can.
[Brief description of the drawings]
FIG. 1 is a schematic view of a production apparatus according to the present invention.
FIG. 2 is a cross-sectional view of a pipe whose diameter has been reduced.
[Explanation of symbols]
1. Extrusion die 2. Plastic tube 3, 7. Cooling device 4. First heating device 5. Hot-air dryer 6. Diameter reduction device 8. Winding device

Claims (8)

Insertion pipe that heats a polyethylene pipe, raises the temperature to 100-130 ° C. , where the tensile stress decreases sharply as the temperature rises, then reduces the diameter, and then cools to a temperature below the shape recovery temperature while maintaining the reduced diameter in the method of manufacturing, a heating step of a polyethylene tube prior to diameter reduction process, the steps of preheating the polyethylene tube to 80 to 98 ° C., so that after preheating, a temperature of at least the surface by the heating means is 100 to 130 ° C. A method for manufacturing an insertion pipe, characterized in that the method comprises a step of heating to the insertion pipe. A first heating device for preheating the polyethylene tube to 80-98 ° C., a second heating device for heating the pre-heated polyethylene tube until at least the surface temperature reaches 100-130 ° C., and the temperature of the polyethylene a device for diameter reduction by crushing the tubes, reduced diameter polyethylene tube shape recovery temperature following to an apparatus for carrying out the production method of the insertion pipe according to claim 1, characterized in that the cooling device for cooling. The method for producing an insertion pipe according to claim 1, wherein the heating of the polyethylene pipe is performed on the polyethylene pipe after being extruded from an extrusion die and once cooled and solidified for shape memory. The method for producing an insertion pipe according to claim 3 , wherein the polyethylene pipe extruded from the extrusion die is cooled to 60 ° C. or lower. The method for manufacturing an insertion pipe according to any one of claims 1, 3 and 4 , wherein the preheating of the polyethylene pipe is performed using hot water or steam. In a method for reducing the diameter of a cross-linked polyethylene pipe, the polyethylene pipe having a circular cross section extruded from an extrusion die is once cooled and solidified, and then reheated to 100 to 130 ° C. where the tensile stress decreases rapidly as the temperature rises. a first heating step, the tensile stress an increase in temperature rapidly to the step of heating the polyethylene pipe for diameter reduction by a polyethylene tube was heated to 80 to 100 ° C. the hot water or steam to cause crosslinking A method for manufacturing an insertion pipe, characterized by comprising a second heating step in which the temperature is raised to 100 to 130 ° C. In a method for reducing the diameter of a cross-linked polyethylene pipe, the polyethylene pipe having a circular cross section extruded from an extrusion die is once cooled and solidified, and then reheated to 100 to 130 ° C. where the tensile stress decreases rapidly as the temperature rises. The method for producing an insertion pipe according to claim 6, wherein the cooling temperature of the polyethylene pipe having a circular cross section extruded from the extrusion die is 60 ° C. or less. The heating of the polyethylene pipe which is performed prior to the diametral reduction, is used a hot-air dryer, the time of heating the claims either hot air the polyethylene tube of claim 1, 3 or 7 hood so as not exposed to direct is covered The method for manufacturing the insertion pipe according to item.

Images