JPH0691754A - Process for diameter-contracting plastic pipe and rod - Google Patents

Abstract

PURPOSE:To develop a technology to eliminate problems such as that the continuous drawing is impossible, the generation of cracks, or the coefficient of diameter-contraction is too small, etc., when a plastic pipe or rod for which a shape memory property is given is diameter-contraction-drawn by a drawing machine equipped with divided hole-type rolls. CONSTITUTION:Between two or more drawing stands 2 which are tandem arranged, heating furnaces 3 are provided, and a plastic pipe or rod 1 is diameter- contraction-drawn while the material temperature of the plastic pipe or rod 1 is kept to be uniform, and it is quenched after the completion of the diameter- contraction-drawing. Therefore, at the same time when a diameter-contraction process is performed, a material with a high elastic modulus and high strength can be manufactured.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method of reducing diameter in the production of heat-expanded diameters (the diameters of which are expanded by heating, the same applies hereinafter), and the plastics used as materials, which have high elastic modulus and high strength. The present invention relates to a method of reducing the diameter for giving the same.

[0002]

2. Description of the Related Art Recently, many methods for lining the inner surface of a tubular body have been proposed which utilize the shape memory property of resin. See, for example, JP-A-3-96785 and JP-A-4-59228. Such an inner surface lining method reduces the diameter of a plastic pipe having a shape memory property by reducing the diameter so that it can be easily inserted, and then inserts it into the pipe to be lined and then heats it. This is a method of restoring the original shape and lining the inner surface of the pipe.

The diameter reduction of the plastic pipe at this time is
Since it is accompanied by axial contraction at the time of heating recovery, it is preferable to suppress axial stretching as much as possible, and as a method therefor, in the above-mentioned publication, a method of reducing the diameter by a rolling mill equipped with a plurality of hole rolls is divided. Is proposed. However, in such a conventional technique, rolling cannot be continued,
There are problems such as cracking and small diameter reduction ratio, and it is necessary to investigate the cause.

[0004]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a method for reducing the diameter of plastic pipes or rods which solves the problems of the prior art. On the other hand, by stretching the plastic greatly,
It is known to increase the strength, but the stretching at that time needs to be performed within an appropriate temperature range. Attempts were made to carry out this stretching by means of a rolling mill equipped with a plurality of hole-type rolls, but sufficient improvements could not be achieved.

Japanese Unexamined Patent Publication (Kokai) No. 2-50818 discloses a method of rolling a polymer material, in which heat-retaining furnaces are installed in front of and behind the rolling mill to perform rolling while keeping the material temperature constant, for example, 100 to 140 ° C. However, this is related to the rolling of the film, and the idea is to extend the rollable range time, that is, increase the number of passes by heat retention. See FIG. 1 of the same publication.

[0006]

In fact, the above-mentioned Japanese Unexamined Patent Publication No.
In Japanese Patent No. 96785 and Japanese Unexamined Patent Publication No. 4-59228, heating is not mentioned at all, and heating is excluded from the whole description. Therefore, as a result of repeated studies on the causes of the problems of the above-mentioned conventional techniques, the present inventors have found that the problems as described above, which are observed during the diameter reduction process, are deprived of heat by the rolls during the rolling, or the stand. It occurs because the temperature of the material is reduced due to the influence of the ambient temperature during that time and rolling at the proper temperature cannot be performed. It was found that the diameter-reduced shape was retained by rapid cooling as shape-fixing processing after the diameter-reduction processing.

The present invention is a method of rolling and reducing the diameter of plastic pipes and rods while maintaining the material temperature at an appropriate level in a rolling mill equipped with a plurality of hole type rolls. In addition, the present invention also includes two tandemly arranged
A heating furnace is installed between the above rolling stands, each rolling stand is provided with a rolling mill having a hole-shaped roll, and the heating furnace is used, and more preferably, the hole-shaped roll is also preheated to obtain a plastic. This is a method for reducing the diameter of a plastic pipe or rod, which is characterized in that the diameter of the pipe or the rod is reduced while the temperature of the material is kept constant, and after the diameter reduction rolling, the material is rapidly cooled.

[0008]

Next, the function and effect of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic explanatory view of a tandem rolling mill for carrying out the diameter reduction processing method according to the present invention, and FIG. 2 is an explanatory view of the arrangement of split rolls in each rolling stand. In the figure, for example, a plastic pipe or rod 1 which has been preliminarily given a shape memory property and is molded.
In the illustrated example, four rolling stands 2 are sent to a continuous rolling line in which a tandem is arranged, and a diameter reduction process is performed.
A heating furnace 3 is installed between the rolling stands. The final rolling stand 2 is subsequently provided with a rapid cooling device 5 including, for example, a double water tank. The rapid cooling device may be provided between the third and fourth rolling stands. As a result, for example, immediately after completion of the diameter-reducing rolling, the material is rapidly cooled to about room temperature.

Each rolling stand 2 is provided with a hole-type roll 4, which is a divided roll as shown in FIGS. 2 (a) to 2 (d), respectively. It is installed at a 45 ° angle. That is,
The split-hole type roll 10 arranged at the position shown in FIG. 2 (a) in the first rolling stand 2 is composed of horizontal rolls 11 and 12 and vertical rolls 13 and 14. Reference numerals 15, 16, 17, and 18 indicate the vertical axis and the horizontal axis of each roll. Fig. 2 (b) shows an example of the arrangement of the hole type rolls 20 on the second rolling stand. Compared to the case of Fig. 2 (a), the horizontal rolls 11, 12 and the vertical rolls 13, 14 are 45 ° It is inclined. Similarly, in FIG. 2 (c), the hole roll 30 is that of the third rolling stand, and again the horizontal rolls 11 and 12 and the vertical rolls 13 and 14 are compared with the positions in FIG. 2 (b). It can be seen that is inclined by 45 °. In the last rolling stand 2, as shown in FIG. 2 (d), the hole type roll 40 is again inclined by 45 ° with respect to the horizontal rolls 11 and 12 and the vertical rolls 13 and 14 as compared with that in FIG. 2 (c). I can see it. Here, the case of the hole-type roll composed of four division rolls has been described, but the number is not particularly limited, and there is no problem even if it is composed of two, three, or five or more division rolls. In this case, the hole type rolls between the rolling stands are installed at different angles of 90 °, 60 ° and 36 °.

The hole-type roll 4 is constructed so that it can be heated to a predetermined temperature in advance, for example, by blowing hot air to heat it or by covering the entire stand with a heating furnace. Here, according to the present invention, by preheating the hole-shaped roll 4 by the heating furnace 3, it becomes possible to perform the diameter reduction rolling while keeping the material temperature of the plastic pipe or the rod to be diameter reduction rolled constant. As a result, the problems such as the inability to continue rolling, the occurrence of cracks, and the small diameter reduction ratio, which have been found in the prior art, are effectively eliminated.

The structure of the heating furnace 3 is not particularly limited, but may be one equipped with heating means for hot air or far infrared rays, for example. As already mentioned, in the production of heat-expanded pipes, when reducing the diameter of a plastic pipe or rod that has been previously processed and shaped to have shape memory properties with a rolling mill equipped with a plurality of hole-type rolls. , Usually at a glass transition temperature or higher. However, when the material temperature drops during rolling and becomes lower than the glass transition temperature, the deformation resistance of the material increases, and when rolling, damage to the material occurs and slippage occurs between the roll and material, making rolling difficult. May be.

Therefore, in the present invention, the diameter reduction processing is performed in the heated state, and the cooling is performed rapidly after the processing is completed.
According to this, not only does the diameter reduction process proceed smoothly and a large diameter reduction ratio can be achieved, but also the shape memory property is not adversely affected. As used herein, the "plastic having a shape memory property" includes polynorbornene, polyurethane known as a shape memory plastic,
There are polyester, blended materials with other plastics, and amorphous plastics such as acrylic, polycarbonate, polyvinyl chloride, and ABS. In the case of these materials, the heating condition may be a temperature in the rubber-like region above the glass transition temperature and below the flow region.

Further, when a polyolefin resin pipe capable of imparting a thermal expansion property depending on processing conditions is reduced in diameter by a rolling mill equipped with a plurality of hole type rolls, elastic recovery occurs when the temperature decreases. It will become large and the target diameter reduction ratio may not be obtained. Examples of the polyolefin resin mentioned here include polyethylene, polypropylene, polybutene and the like. On the other hand, when a method of rolling with a rolling mill equipped with a plurality of hole-shaped rolls is used as a method of significantly stretching plastic to obtain high elastic modulus and high strength, the material temperature decreases during rolling. As a result, the deformation resistance increases, and slippage occurs between the roll and the material, so there is a problem that rolling cannot be performed.

The material referred to here is polyethylene,
Examples include polypropylene, polyoxymethylene, polymethylene acrylate, nylon 6 and the like. In the case of these materials, the heating temperature may be 20 to 40 ° C. lower than the melting point to about the melting point, but is not particularly limited as long as the effect of the present invention is exhibited.

That is, according to the present invention, a heating furnace is installed between each rolling stand, and if necessary, the rolls are heated in advance, so that the rolling passage of the material has a uniform temperature, thereby reducing the temperature of the material. It is possible to reduce the diameter, and the rapid cooling immediately after that does not impair the shape memory property. Therefore, there is no damage to the material and the reduction of the target diameter reduction rate is achieved. Diameter processing is possible. Further, it can be largely stretched, and the plastic material as described above can be made to have a high elastic modulus and high strength. For example, when the axial stretch ratio is as small as 3 or less, the shape is fixed by quenching, but in order to realize high elastic modulus and high strength, 5 or more, or
If a large stretch ratio of 10 or more is taken, quenching is not necessary.

[0016]

【Example】

Example 1 A polyester resin known as a shape memory resin (ZEON Shape A-80, manufactured by Nippon Zeon Co., Ltd.) having an outer diameter of 60 mm,
After making into a tubular body with a wall thickness of 2 mm, it was heated to 80 ° C and placed on each rolling stand of the rolling line of Fig. 1 as shown in Figs. 2 (a) to (d).
As shown in Fig. 1, the multi-stage hole rolling mill line consisting of 5 units in tandem arranged by alternately shifting 45 ° hole rolling mills each having a substantially circular hole rolling type has the schedule shown in Table 1. The diameter was reduced by rolling.

Immediately before the final rolling, that is, a double cooling water tank is arranged between the fourth and fifth stages, and the polyester pipe reduced in diameter after the fourth rolling is cooled and fixed to fix the reduced diameter shape. I went. That is, the rolling mill at the fifth stage is installed not for reducing the diameter but for maintaining the shape. In addition, as a comparative example, an operation in which a diameter reduction rolling was performed without using a heating device was also performed.

On the other hand, as another comparative example, a heating furnace is installed between the first stage, the second stage, the second stage, the third stage, the third stage and the fourth stage, and hot air is blown. By rolling the rolls in advance, the diameter reduction processing was performed in the rolling line in which the rolling passage was set to 80 ° C. without providing a rapid cooling device.

As a result, when the heating furnace was not installed, cracks were found in the diameter-reduced pipe, but when the heating furnace was installed, no cracks were seen, and the outer diameter was 30 mm and the wall thickness was 2 mm. A diameter pipe was obtained. However, if rapid cooling to room temperature was not performed after rolling, after passing through the final roll, the outer diameter
It has expanded to 55 mm. However, in the example in which the rapid cooling device to room temperature was provided, there was no problem in shape memory.

Example 2 Medium-density polyethylene (Showa Denko, TR418X) was formed into a tubular body having an outer diameter of 60 mm and a wall thickness of 2 mm, heated to 120 ° C., and rolled using a rolling line shown in FIG. As shown in FIG. 2, a rolling stand having a substantially circular hole shape divided into four as shown in FIG. The diameter was reduced by rolling on the schedule shown in.

Immediately before the final rolling, that is, a double cooling water tank is arranged between the fourth and fifth stages, and the polyethylene pipe reduced in diameter after the fourth stage is cooled and fixed to fix the reduced diameter shape. I went. That is, the rolling mill at the fifth stage is installed not for reducing the diameter but for maintaining the shape. In addition, as a comparative example, an operation in which a diameter reduction rolling was performed without using a heating device was also performed.

On the other hand, as another comparative example, a heating furnace is installed between the first stage, second stage, second stage, third stage, third stage and fourth stage, and the rolls are heated in advance. As a result, diameter reduction processing was performed in the rolling line where the rolling passage was set at 120 ° C, without providing a rapid cooling device. As a result, when the heating furnace was not installed, a reduced diameter pipe with an outer diameter of 46 mm and a wall thickness of 2 mm was obtained, but when the heating furnace was installed, a reduced diameter pipe with an outer diameter of 39 mm and a wall thickness of 2 mm was obtained. Was obtained. As a result, it can be seen that the diameter reduction ratio is improved. Further, in the case where no cooling device was provided, the diameter increased to 50 mm after passing through the final roll.

(Example 3) Polypropylene (MF10.8, M _w = 542000) molded into a rod-shaped body having an outer diameter of 20 mm was heated to 150 ° C., and was divided into four as shown in FIG. Alternating the hole type roll rolling machine with the hole type by 45 ° alternately 4
With a multi-stage hole rolling machine with a tandem arrangement
An attempt was made to reduce the diameter by rolling according to the schedule shown in Table 3, but slipping occurred between the roll and the material during the rolling, and rolling could not be performed.

On the other hand, the first-second stage, the second-stage third stage,
When a rolling furnace was installed between the 3rd and 4th steps, and the rolls were heated in advance to reduce the rolling path to 150 ° C, we tried to reduce the diameter. We were able to. Polypropylene with reduced diameter has an elastic modulus
It had improved to 220MPa (initial 21MPa).

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

According to the present invention, it is possible to reduce the diameter of a plastic pipe or rod having a desired diameter reduction ratio without damaging the material. The thermally expanded pipe thus obtained can be used for various purposes such as inner surface lining of a steel pipe in a factory or rehabilitation of an existing buried pipe by a pipe-in-pipe method. Further, it is possible to manufacture a material having a high elastic modulus and a high strength.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a rolling line used in the present invention.

2 (a) to (d) are explanatory views showing roll arrangement of a hole-type roll rolling mill in each rolling stand of the rolling line of FIG.

[Explanation of symbols]

 1: Plastic pipe or rod 2: Rolling stand 3: Heating furnace 4: Roll 5: Rapid cooling device 10,20,30,40: Hole roll 11,12,13,14: Split roll 15,16,17,18 : Roll axis

Claims (2)

[Claims] 1. A heating furnace is installed between two or more rolling stands arranged in tandem, each rolling stand is equipped with a rolling mill having a hole-shaped roll, and the material temperature of a plastic pipe or rod is controlled by the heating furnace. The method for reducing the diameter of plastic pipes and rods is characterized in that the diameter of the plastic pipe and the rod is rapidly cooled after the diameter reduction rolling is completed. 2. The perforated roll is also heated.
The method described.