JP2003300247A - Heating method for thermoplastic resin pipe low in polarity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating method for a thermoplastic resin pipe low in polarity for uniformly heating the thermoplastic resin pipe in a short heating time to dispense with or to facilitate the cleaning of the inner and outer surfaces of the pipe. <P>SOLUTION: Both end parts of the pipe made of a thermoplastic resin low in polarity are closed hermetically and a pressure releasing valve is attached to one end part of the pipe so as to open the pipe under definite pressure or more. The resin pipe is filled with a liquid having polarity and irradiated with electromagnetic microwaves to heat the liquid to heat the resin pipe from the inner wall surface thereof. After or during the irradiation with electromagnetic microwaves, the pipe is irradiated with infrared rays to be heated from the outer wall surface thereof. It is more preferable that the liquid is water. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of heating a thermoplastic resin tube having low polarity such as polyethylene, polybutene, polypropylene.

[0002]

2. Description of the Related Art Conventionally, a thermoplastic resin tube having a low polarity such as polyethylene, polybutene, polypropylene, etc. is often heated for secondary processing such as bending. As a heating method, the tube is placed in a far-infrared heating furnace, the tube is heated from the outer surface by irradiating with far-infrared rays, or the entire tube is immersed in a constant temperature oil tank containing a liquid such as glycerin, and the tube is There was a method of heating from inside and outside the tube wall.

[0003]

In order to carry out the secondary processing, it is necessary to heat the whole tube until the temperature of the whole tube becomes uniform and constant. However, heating by far infrared rays may cause low thermal conductivity of the resin. Therefore, there is a problem that local heating unevenness may occur, and a poorly heated portion and a portion that is overheated and melted may coexist at the same time. If gentle heating is performed to prevent this, there is a problem that the heating time is extremely long.

On the other hand, when a pipe having a low polarity of a thermoplastic resin is used for the piping, an adhesive connection cannot be made. Therefore, a mechanical connection method or a heat fusion method is usually used. In particular, the heat fusion method has excellent seismic resistance and is a method often used for piping with pipes made of these materials.However, in the method of heating the entire pipe in a constant temperature oil bath, the fat and oil component that is the heating medium should be used. However, if they remain on the inner and outer surfaces of the pipe, there is a problem that the heat fusion connection of the pipes to be performed thereafter may be impossible or the reliability of the connection may be deteriorated. Therefore, in this method, a cleaning operation for completely removing the medium after heating is indispensable, and it is necessary to treat the removed heating medium with a lot of time, and it may take time other than heating,
The cost was high.

Particularly, in a thermoplastic resin pipe having a large diameter and a long length, which has been frequently used in recent years, the above-mentioned problems are conspicuously observed due to the large pipe wall thickness, and particularly the heating time is long. Therefore, there is a problem that there is no suitable heating method.

The present invention solves the problems of the above-mentioned conventional heating methods, and provides a heating method for a thermoplastic resin tube having low polarity, in which heating is uniform, the heating time is short, and cleaning of the inner and outer surfaces of the tube is unnecessary or easy. It was made for the purpose of doing.

[0007]

A method for heating a thermoplastic resin tube having a low polarity according to the present invention for solving the above problems is to seal both ends of a thermoplastic resin tube having a low polarity and A pressure release valve that opens at a certain pressure or more is attached to the end, and the resin pipe is filled with a polar liquid and irradiated with microwave electromagnetic waves, and the liquid pipe is heated to heat the resin pipe from the pipe inner wall surface side. A method for heating a thermoplastic resin tube having low polarity, which comprises irradiating far infrared rays during or after irradiation of microwave electromagnetic waves to heat from the outer wall surface side of the tube.

(Function) In the present invention, both ends of a thermoplastic resin tube having a low polarity are sealed, and a pressure release valve that opens at a certain pressure or more is attached to one end of the tube, and a polar tube is provided inside the resin tube. The resin pipe is heated from the inner wall surface side of the pipe by heating the liquid by irradiating it with microwave electromagnetic waves filled with a liquid having, so that only the liquid filled in the pipe is heated by irradiating the microwave electromagnetic waves. Since this temperature is transmitted to the inner wall surface of the tube, the tube is heated uniformly. In addition, heating is accelerated and heating time can be shortened by adjusting the irradiation intensity of microwave electromagnetic waves. Further, the action of the pressure release valve prevents the pipe from being deformed due to excessive internal pressure. Furthermore, while heating or after heating a thermoplastic resin tube having low polarity by the above heating method, it is possible to further shorten the heating time by heating from the outer wall surface side of the tube by far-infrared irradiation, and to reduce temperature unevenness. Become.

In addition, if the liquid having the above-mentioned polarity is water, the heating medium can be removed by simply wiping it off after the heating is completed, so that the cleaning treatment is not necessary.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front view of an example of a heating device that realizes the method for heating a thermoplastic resin pipe of the present invention.

In the heating device M, the resin tube 1 filled with the liquid is placed between the high frequency electromagnetic wave transmitting electrodes 21 and 22 which are arranged to face each other, and the high frequency electromagnetic wave oscillator connected to the electrodes 21 and 22. Signal from 2, frequency 2500MHz
The microwave electromagnetic wave described above is emitted to irradiate the resin tube 1 to heat the liquid therein. Further, although not shown in the figure, for safety against the risk that the pressure inside the resin pipe 1 becomes abnormally high due to a pressure valve failure or the like and the resin pipe 1 and the sealing lids 11 and 11 ′ are damaged, the device M is It is desirable that the periphery is covered with a wall or the like.

The heating device M is safe in the event of a rupture accident of the resin pipe 1 and the like, if the heating device M is large enough to store the entire resin pipe 1. Further, the lengths of the electrodes 21 and 22 are not necessarily required to cover the entire resin pipe 1 as long as the resin pipe 1 can be heated uniformly. That is, the electrode 21,
If the electrode 22 itself is movable or the resin tube 1 itself is movable, the lengths of the electrodes 21 and 22 can be shortened.
For example, even if the short electrodes 21 and 22 are arranged so as to face each other with the resin pipe 1 sandwiched therebetween and a part of the resin pipe 1 is heated, the electrode 2 may be heated to uniformly heat the entire resin pipe.
With the resin pipes 1 and 22 facing each other with the resin pipe 1 sandwiched therebetween, the resin pipes 1 and 22 are moved along the pipe axis of the resin pipe 1, or are rotated around the resin pipe 1 as necessary to move along the axial direction. It may be done like this.

At both ends of the thermoplastic resin tube 1 having low polarity,
The sealing lids 11 and 11 'are fixed. A pressure release valve 12 that opens at a constant pressure is attached to the sealing lid 11,
The inside of the resin tube 1 is filled with a highly polar liquid.

Examples of the thermoplastic resin having low polarity include, for example, polyolefin resins such as polyethylene, polypropylene and polybutene. Examples of the highly polar liquid include alcohols such as ethyl alcohol and methyl alcohol; ketones such as acetone and methyl ethyl ketone; water and the like. Among them, ease of handling, safety, and cost advantage Water is most often used.

The sealing lids 11 and 11 'may be formed by fixing an ordinary plate-like body made of metal, (fiber reinforced) resin or the like so as not to come off against the internal pressure of the resin pipe 1. The fixing method is not particularly limited, for example, in the case of this example,
As shown in FIG. 2, the rubber ring 113 whose outer diameter is slightly smaller than the inner diameter of the resin pipe 1 and whose outer peripheral side is thicker than the inner peripheral side is a metal small disc 1 having an outer diameter smaller than the rubber ring.
11 and a large metal disc 11 having an outer diameter larger than that of the resin pipe 1.
It is made coaxial with and sandwiched between the two metal disks 111, 11
The two are connected to each other with a bolt 114 or the like, mounted on the pipe end surface of the resin pipe 1, and by rotating the bolt 114 or the like,
The structure may be such that the distance between the small circular plate 111 and the large circular plate 112 is reduced, and the rubber ring 113 between them is pushed outward to be in close contact.

The pressure relief valve 12 may be a conventional safety valve. That is, when the medium is heated and the internal pressure of the resin pipe 1 rises, the pressure release valve 12 may maintain the pressure below a certain level and prevent the resin pipe 1 from being deformed.

The high-frequency electromagnetic wave transmitter 2 and the high-frequency electromagnetic wave transmitting electrodes 21 and 22 may be ordinary oscillators and electrodes. Of course, since the size of the tube irradiated with the electromagnetic wave is large and the weight thereof is also large, it goes without saying that the electromagnetic wave output and the electrode size must be appropriately selected and determined depending on the planned heating time and the like.

Further, in the heating device M, it is desirable to use, for example, an earth leakage breaker (not shown) as a power source in case the liquid in the resin tube 1 leaks.

(Example 1) Next, a polyethylene pipe (manufactured by Sekisui Chemical Co., Ltd., designated ESLON PE pipe S, inner diameter 300)
mm, outer diameter 355 mm, length 4 m), an example of an embodiment in which water is used as the liquid is shown.

Sealing lids 11 and 11 'were attached to both ends of the pipe 1, and the sealing lids 11 and 11' were fixed to the resin pipe 1 by the method shown in FIG. 2 so as not to come off. A pressure reducing valve 12 (diameter 20 mm, release pressure 1.0 MPa or less) and a temperature measuring terminal (not shown) of a general thermocouple type thermometer were attached to the sealing lid 11, and the resin tube 1 was filled with water. .

Between the opposing high-frequency electromagnetic wave transmitting electrodes 21, 2
The distance 2 was 450 mm, and the resin tube 1 filled with water was placed in the middle. The high frequency electromagnetic wave transmitter 2 was connected and the high frequency electromagnetic wave was irradiated at a frequency of 2500 MHz and an output of 4.5 kW.

When the temperature of the water in the resin pipe 1 reaches 95 ° C., the irradiation intensity of the microwave electromagnetic wave is adjusted by a method such as intermittent so that the water temperature keeps this temperature, and the outer surface temperature of the resin pipe 1 is adjusted. It continued until it reached 90 degreeC. When the outer surface temperature of the resin pipe 1 reaches 90 ° C., irradiation of microwave electromagnetic waves is stopped, the resin pipe 1 is taken out of the heating device M, and immediately the sealing lids 11, 1 are closed.
1'was removed and the water inside was drained.

The heater is placed in a far infrared heating furnace without any space, and the heating temperature of the far infrared heating furnace is set between 160 ° C. and 200 ° C., in the case of this example, 175 ° C., and the outer surface of the resin pipe 1 is set. Heated until the temperature reached 125 ° C. The tube surface temperature was uniformly around 125 ° C. The water remaining in the tube was completely evaporated when heated in the heating furnace, and neither wiping nor cleaning was necessary.

In this state, secondary processing such as bending of the pipe is performed. When the set temperature is high, the outer surface of the tube is melted to cause uneven heating, and when the set temperature is low, it takes too long heating time and may not reach a temperature suitable for secondary processing.

The time required for the temperature of the outer surface of the tube to reach 125 ° C. by the above method was about 4 hours. This heats the same polyethylene tube only in the same far infrared heating furnace,
The time required for the temperature of the entire tube to reach 125 ° C is approximately 13
Compared with time, it is a great reduction.

[0026]

As described above, according to the method for heating a thermoplastic resin pipe of the present invention, the heating of the pipe is uniform, the heating time is short, and cleaning of the inner and outer surfaces of the pipe is unnecessary or easy.

[Brief description of drawings]

FIG. 1 is a front view illustrating an example of a heating device that realizes a heating method of the present invention, omitting a method of fixing a pedestal of a resin pipe and a sealing lid.

FIG. 2 is a cross-sectional view showing an example of a method of fixing a sealing lid on a tube end.

[Explanation of symbols]

1 Thermoplastic resin tube 11, 11 'sealed lid 111 small disk 112 large disk 113 rubber ring 114 bolts and nuts 12 Pressure release valve 2 high frequency oscillator 21, 22 High frequency electromagnetic wave transmission electrode M heating device

Claims (2)

[Claims] 1. A thermoplastic resin tube having a low polarity is sealed at both ends, and a pressure release valve that opens at a certain pressure or more is attached to one end of the tube to fill the resin tube with a polar liquid. Microwave resin to irradiate microwaves to heat the liquid to heat the resin tube from the inner wall surface side of the tube, and to irradiate far infrared rays during or after irradiation of microwave electromagnetic waves to heat from the outer wall surface side of the tube. And a method of heating a thermoplastic resin tube having low polarity. 2. The method for heating a thermoplastic resin tube having low polarity according to claim 1, wherein the liquid having the polarity is water.